JPS6111183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, foamed polystyrene molded articles have been either dried to remove moisture in the molded article after molding, or used as they are after molding. However, when such molded products are used at room temperature, dimensional shrinkage of 1% or more is observed in less than one year, which may cause problems in practical use. Furthermore, as the operating atmosphere temperature increases, the amount of dimensional shrinkage also increases.

To explain the shrinkage effect when foamed polystyrene is used in the fan casing used in conventional room coolers etc. in Figure 1, the gap 3 (clearance) between the fan casing 1 and the fan 2 is the air volume of the fan. , which has a large impact on noise. Therefore, if the gap 3 changes due to shrinkage of expanded polystyrene, both the air volume and the sound quality will change, causing problems. For example, if the inner diameter of the fan casing 1 is 408 mm and the diameter of the fan 2 is 400 mm, the gap 3 between them is initially 4 mm.

Assuming that the fan casing shrinks as shown in Figure 2, the gap will become 2 mm, half of the initial size, in about one year. Therefore, both the air volume and sound quality change. In order to prevent such problems, if a process such as that of the present invention is performed, the dimensional shrinkage rate will be reduced, and the problems encountered in the past will be eliminated.

That is, the present invention heats a foamed polystyrene molded product that has been foam-molded to a size larger than a desired size under normal pressure or reduced pressure for several hours or more to bring the pressure of the blowing agent gas in the cells of the molded product to the atmospheric pressure. By colliding with
The present invention relates to a method for stabilizing the dimensions of expanded polystyrene in which the dimensions of the molded article are forcibly shrunk to near desired dimensions.

To explain the present invention in detail below, a molded product made of expanded polystyrene gradually shrinks when left at room temperature after molding, and becomes stable after shrinking by 1% or more in about one year. Furthermore, as the ambient temperature increases, the shrinkage rate also increases.

This state is shown in FIG. In other words, this dimensional shrinkage over time is caused by the foaming agent (mostly lower aliphatic hydrocarbons) in the cells that have completed foaming.
However, after molding, it gradually escapes and diffuses into the atmosphere. When the gas pressure inside the cell balances with the atmospheric pressure, the contraction stops and the cell becomes dimensionally stable.

Therefore, by artificially balancing the blowing agent gas pressure within the cell with the atmospheric pressure before use, shrinkage during use can be minimized.

In the present invention, a foamed polystyrene molded product that has been foam-molded to a size larger than a desired size is heated for several hours or more under normal pressure or reduced pressure to bring the pressure of the blowing agent gas in the cells of the molded product to the same level as atmospheric pressure. The method relates to a method for stabilizing the dimensions of expanded polystyrene, in which the dimensions of the molded product are forcibly shrunk to near the desired dimensions by applying an impact, whereby the dimensional shrinkage rate is small, that is, from 0.1 to 0.1.
It is possible to limit the amount of dimensional shrinkage to 0.3%/year or less.

Hereinafter, the present invention will be further explained in detail with reference to the following specific examples.

Example In molding polystyrene foam, for the purpose of reducing dimensional shrinkage during use of polystyrene foam,
After molding the foamed polystyrene product, leave it in the air at 45 to 70℃ for 2 to 24 hours, or leave it under reduced pressure at room temperature to 65℃ for 2 to 24 hours.
Allowed to stand for ~24 hours to promote dimensional shrinkage.

The subsequent dimensional changes in the expanded polystyrene treated in this manner were extremely small. For example, as shown by the dotted line in Figure 2, 60°C x 7 days after molding.
When a product that had been heat treated for 15 hours was assembled on the 10th day after molding, the subsequent shrinkage rate was about 0.2%. However, as shown by the solid line in Figure 2, the untreated product shrank by about 0.65% in one year from the 7th day of molding. From the above, it can be seen that the treatment according to the method of the present invention is extremely excellent.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the state of the gap between the fan casing and the fan, shown to explain the shrinkage of conventional expanded polystyrene, and Figure 2 is the number of days after molding and shrinkage in the method of the present invention and the conventional method. It is a diagram showing the relationship with the rate.

Claims (1)

[Claims] 1 By heating a foamed polystyrene molded product that has been foam-molded to a size larger than the desired size under normal pressure or reduced pressure for several hours or more to bring the blowing agent gas pressure in the cells of the molded product to equilibrium with atmospheric pressure. . A method for stabilizing the dimensions of expanded polystyrene, the method comprising forcibly shrinking the dimensions of the molded article to near desired dimensions.