JPH0622927B2 - Foam molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for molding a foam, in which cooling is performed on a thermoplastic resin foam subjected to a heat expansion treatment by water cooling and vacuum cooling. It is about.

[Prior Art] Generally, in order to mold a foam, pre-expanded particles obtained by pre-expanding thermoplastic resin expanded particles are formed in a mold cavity formed by a mold including a stationary side mold and a moving side mold. Is forcedly sent together with pressurized air to fill. Then, after the steam is fed into the mold cavity through the steam chambers formed in the fixed side mold and the moving side mold to expand the pre-expanded particles by heat, cooling treatment such as water cooling and cooling is performed. This is applied to obtain a thermoplastic resin foam as a molded product.

In the conventional foam molding method, in the above-described cooling treatment, immediately after the heat expansion treatment, water cooling is performed for a few seconds, and then cooling or vacuum cooling is performed. In particular, in the method of performing vacuum cooling after performing water cooling, the cooling cycle can be shortened compared to the case of performing water cooling or air cooling alone, and only the method of water cooling that consumes a large amount of water is used. On the other hand, it has an advantage that it is not necessary to pay much attention to the use of water as a location condition of a foam molding factory (see Japanese Patent Publication No. 61-23102).

[Problems to be Solved by the Invention]

However, if water cooling is performed immediately after the heat expansion treatment as in the above-mentioned conventional case, the surface of the molded article is rapidly cooled and a skin is formed on the surface layer portion. For this reason,
Dispersion of steam and foaming gas remaining inside the molded product immediately after the heat expansion treatment is prevented, and in the vacuum cooling after water cooling, its cooling function (cooling function by vaporizing water) cannot be sufficiently drawn out, It has a drawback that the shortening of the cooling cycle is hindered. In addition, since the steam tends to contain water due to the prevention of steam emission, there is a drawback that drying and aging cannot be shortened.

[Means for Solving the Problems]

The method for molding a foam according to the present invention is, in order to solve the above problems, pre-expanded particles obtained by pre-expanding thermoplastic resin particles are filled into the mold cavity of the mold, and the pre-expanded particles are thermally expanded. After molding the thermoplastic resin foam by cooling, it is cooled and taken out from the mold cavity.
It is characterized in that vacuum cooling is performed at least before water-cooling the thermoplastic resin foam after being heated and expanded.

Since at least the thermoplastic resin foam after heat-expansion is water-cooled before being water-cooled, vacuum cooling may be continuously performed at the time of water-cooling, and further, even after water-cooling is completed, vacuum cooling may be performed. It is also possible to add as necessary.

[Work]

According to the above configuration, since the vacuum cooling is performed before the water cooling, the steam (water) and the foaming gas remaining in the thermoplastic resin foam (molded product) immediately after the heat expansion treatment are decompressed by the vacuum cooling. In addition to the smooth divergence, the divergence at this time cools to a certain extent, so that even if the subsequent cooling is performed with water, the cooling does not become abrupt, and the surface layer of the molded product immediately after the heat expansion treatment is not cooled. The formation of the epidermis can be suppressed. As a result, the cooling cycle can be shortened, the water content inside the molded article can be reduced, and the drying and aging can be shortened. Moreover,
When vacuum cooling is further performed after the above water cooling (or it is continued from the first vacuum cooling), the cooling function is fully exerted in the vacuum cooling due to the inhibition of skin formation as described above. As a result, it is possible to further accelerate the shortening of the cooling cycle, further reduce the water content in the molded article, and further shorten the drying and aging.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the method for molding a foam according to the present invention, as shown in FIG. 2, a foam molding die 1 used in this method includes a fixed side mold 2 provided in a fixed state and a movable side mold provided so as to be movable. 3 and 3. The stationary side mold 2 has a steam chamber 4 inside, and the movable side mold 3 has a steam chamber 5 inside.
5'is formed respectively, and a large number of core vents 2a ... 3a ... Are formed on the molding wall surfaces of the fixed mold 2 and the movable mold 3, respectively. Steam and the like can pass between the mold cavity 6 formed by mold matching with the mold 3 and the steam chambers 4, 5, 5 '. The steam for heat-expanding the pre-expanded particles filled in the mold cavity 6 is supplied to the steam chambers 4, 5, 5'by an introduction pipe (not shown).
It is designed to be guided inside. Further, nozzles 7 and 8 for ejecting cooling water are provided in the steam chambers 4 and 5.
Are extended downward from the upper part of each mold 2 and 3. The nozzles 7 and 8 are communicated with the cooling water supply pipes 11 and 12 via water cooling valves 9 and 10, respectively, and the steam chambers 4 and 5 are opened and closed by opening and closing the water cooling valves 9 and 10.
-The supply of cooling water into 5'and its stop can be switched. Further, communication pipes 13 and 14 for communicating between the inside of the steam chambers 4 and 5 and a vacuum (low pressure) generating device (not shown) are arranged below the molds 2 and 3, respectively. Vacuum valve 15 installed in
The switch 16 switches the vacuum (low pressure) state and the atmospheric pressure state in the steam chambers 4, 5, and 5 '. Further, the fixed side mold 2 is provided with a raw material charging device 17 for forcibly sending pre-expanded particles obtained by pre-expanding thermoplastic resin expanded particles into the mold cavity 6 together with pressurized air for filling. It is provided.

In order to perform the foam molding, after filling the pre-expanded particles in the mold cavity 6 with the raw material filling device 17, the steam chambers 4, 5, ...
Steam is fed into the mold cavity 6 through 5'to heat and expand the pre-expanded particles. Such steps are the same as conventional ones.

In the cooling of the molded product A after the heat expansion treatment, the cooling immediately after the heat expansion treatment is performed by vacuum cooling. For vacuum cooling, as shown in FIG. 1 (a), first, while maintaining the water cooling valves 9 and 10 in a closed state (in the figure, the black symbol indicates a closed state, the white symbol indicates an open state). The vacuum valves 15 and 16 are switched to the open state, and the inside of the steam chambers 4, 5, and 5'and the inside of the mold cavity 6 are brought into a vacuum state (a reduced pressure state). The degree of vacuum in this vacuum cooling is 300 mmHg to 750 mmHg.
Is desirable. Next, as shown in FIG. 7B, the water cooling valves 9 and 10 are switched to the open state while the vacuum valves 15 and 16 are maintained in the open state, and the steam chambers 4, 5, and 5 ′ are opened by the nozzles 7 and 8. Cooling water is introduced into the mold cavity 6 through the mold. That is, water cooling and vacuum cooling are used together. The cooling time depends on the shape and size of the molded product,
It is appropriately set depending on the material and the like. After that, as shown in FIG. 7C, the water cooling valves 9 and 10 are switched to the closed state, the ejection of the cooling water into the steam chambers 4, 5 and 5'and the mold cavity 6 is stopped, and the vacuum is resumed. Only cool. After such a series of cooling steps, as shown in FIG. 3D, the vacuum valves 15 and 16 are switched to the closed state to end the cooling cycle, and the fixed side mold 2 and the moving side mold 3 are opened. Then, the molded product A is taken out.

According to the above configuration, since the vacuum cooling is performed before the water cooling, the steam (water) and the foaming gas remaining inside the molded product A immediately after the heat expansion treatment are smoothly released by the reduced pressure by the vacuum cooling. At the same time, since it is cooled to some extent by the divergence at this time, rapid cooling does not occur even if the subsequent cooling is performed by water cooling, and a skin is formed on the surface layer portion of the molded product immediately after the heat expansion treatment. Can be suppressed. As a result, the cooling cycle can be shortened, the water content inside the molded article can be reduced, and the drying and aging can be shortened.

Furthermore, as in the present example, when vacuum cooling is continuously performed during and after water cooling from the first vacuum cooling, as described above, the skin formation of the molded article was suppressed, and In vacuum cooling after water cooling, the cooling function can be fully exerted to further shorten the cooling cycle, and the moisture content inside the molded product can be further reduced to further shorten drying and aging. Can be converted.

In the above example, the vacuum cooling was performed during and after water cooling after the first vacuum cooling, but the present invention is not limited to this, and only water cooling is performed after the first vacuum cooling (at atmospheric pressure). Water cooling) may be performed, and after that water cooling, vacuum cooling may be performed again.

The total molding time and the water content of the molded product were compared between the case where the molded product was actually obtained by the molding method of the present invention and the case where the molded product was obtained by the conventional method. The conditions at this time are as shown below.

Foam molding machine: ACE-12QS (manufactured by Sekisui Machinery Co., Ltd.).

Raw material: ESD (manufactured by Sekisui Plastics Co., Ltd.) 55 times pre-expanded granules used (0.01 kg /).

Molded product: External dimensions 450 mm (length) x 350 mm (width) x 18
0mm (height), maximum thickness 30mm.

The above are common conditions.

Conventional method: Water cooling for 5 seconds and vacuum cooling (60
0 mmHg) for 75 seconds.

Example: After vacuum cooling (500 mmHg) for 5 seconds, water cooling under atmospheric pressure for 5 seconds and then vacuum cooling (600 mmHg) for 48 seconds again.

In the above test, the total molding time of the conventional method is 1
05 seconds, that of the example was 84 seconds, the water content of the molded product obtained by the conventional method was 5%, and that of the example was 3.7%. Therefore, according to the method of the example, the total molding time was shortened by 21 seconds and the water content was reduced by 1.3%.

〔The invention's effect〕

As described above, the foam molding method according to the present invention is performed by filling the pre-expanded particles obtained by pre-expanding the thermoplastic resin particles into the mold cavity of the molding die and thermally expanding the pre-expanded particles to form the thermoplastic resin. After molding the foam, in the method of molding the foam which is cooled and taken out from the mold cavity, vacuum cooling is performed at least before water-cooling the thermoplastic resin foam after heat expansion. .

As a result, the cooling cycle can be shortened to shorten the total molding time, and at the same time, the moisture content inside the molded product can be reduced to shorten the drying and aging.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 (a) is an explanatory view showing a state where vacuum cooling is performed, and FIG. 1 (b) is a vacuum cooling and a water cooling. And (d) are explanatory views showing a state where and are simultaneously used, and (c) of the figure is an explanatory diagram showing a state of performing vacuum cooling, (d) of the same figure.
Is an explanatory view showing a state where the cooling step is finished, and FIG. 2 is a sectional view showing an internal structure of the foaming mold. 1 is a foam mold, 2 is a fixed mold, 3 is a movable mold, 4.5
5'is a steam chamber, 6 is a mold cavity, 7 is a nozzle, 9 is a water cooling valve, and 15 is a vacuum valve.

Claims (1)

[Claims] 1. A pre-expanded particle obtained by pre-expanding a thermoplastic resin particle is filled into a mold cavity of a mold, and the pre-expanded particle is thermally expanded to form a thermoplastic resin foam, which is then cooled. A method of molding a foam, which is characterized in that vacuum cooling is performed at least before water-cooling the thermoplastic resin foam after being heated and expanded, in the method of molding the foam taken out from the mold cavity.