JPS6350189B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for block molding expandable thermoplastic resins. Conventionally, when filling a mold with pre-foamed resin (hereinafter referred to as pre-expanded particles) of a foamable thermoplastic resin, filling is performed using an ejector-type feeder using compressed air. The disadvantages of the above-mentioned method of filling the preliminary grains using a feeder are that, for example, in block molding machines, the filling of the preliminary grains at the top of the mold tends to be insufficient, and in box-type molding machines, the filling of the preliminary grains at the side plate part tends to be insufficient. There are problems such as easy filling failure. If molding is carried out in this insufficiently filled state, for example, shrinkage occurs in the upper part of the molded product in the case of block molding, or at the end of the side plate part in the case of box molding, resulting in a decrease in product value. As a filling improvement method, in the case of block molding, a small cavity with a piston is provided on the upper side of the mold, and after filling, the preliminary grains in the small cavity are additionally filled into the upper part of the mold, thereby sufficiently improving the defect. However, the structure is complicated. A possible cause of insufficient filling is that with conventional feeders, the precipitated particles and air are fed into the mold together, so the precipitated particles fill the mold to the top and edges. When the mold is heated, there is no place for air to escape from the ceiling of the mold or the slits at the ends, and air tends to accumulate inside the mold.
It is thought that this hinders complete filling of the heat-generating grains. In the case of box-shaped molding, filling defects are also observed at the edges of side plates for the same reason. As a result of intensive research to solve these problems, the inventors of the present invention have developed a resin (pre-expanded granule) in which foamable thermoplastic resin is pre-foamed in a mold without using a conventional air-pressure feeder. Provide a hole to fill the
Furthermore, we have discovered that these problems can be solved by providing an exhaust blower device connected to the core side mold and/or the cavity side mold to suck and fill the precipitated particles, and have arrived at the present invention. be. That is, the present invention provides a method for molding a foamable thermoplastic resin block, which includes a filling hole for filling pre-explosion particles and an exhaust blower device in which a core side mold is connected to a cavity side mold. This is a molding method that uses a mold. The block molding method refers to the molding of particularly large molded bodies, as shown in the Examples, and is well known to those skilled in the art. The molding method of the present invention is a block molding method characterized in that the precipitated grains are suction-filled from the filling hole using the above-mentioned exhaust blower device without using a conventional pneumatic feeder, and after the suction-filling. ,
Furthermore, this molding method is characterized in that during cooling after hot molding, the molded product is cooled by suction and ventilation using the exhaust blower device. The present invention will be explained below using an example shown in FIG. 1 in which the present invention is applied to block molding. In order, first start the operation with the entire system closed. That is, both the cavity (abbreviation of cabinet) side mold 1 and the core side mold 2 are closed. The accessories around the mold, that is, the feeder valve 5, eject pin 6, cavity side drain valve 18, and core side drain valve 19 are in a closed state. The steam source valve 10, the cavity side steam valve 13, and the core side steam valve 14 are in a closed state. The cavity side cooling water valve 16 and the core side cooling water valve 17 are in a closed state. The exhaust blower 12 is stopped and the exhaust pipe main valve 11 is closed. As a second step, the exhaust blower 12 is started and made normal. Exhaust pipe main valve 1 as the third stage
1. Open the cavity side steam valve 13 and the core side steam valve 14 to exhaust the air inside the entire mold and reduce the pressure. In the fourth step, the feeder valve 5 is opened and the preliminary grains are filled into the mold. After filling is completed, close the open portions and move on to the next heating operation. As explained in the operating instructions above, the filling method for the precipitated grains has been changed from the conventional press-in method to the suction method, so filling problems caused by press-in air are eliminated, and only the air that accompanies the precipitated grains is passed through the mold slit. Since it is sufficient to suction and exhaust air through the mold, even if the upper part of the mold is almost full of particles, the mold will be completely filled. Another feature of the present invention is that by using the exhaust device, the molded product after heat molding can be cooled by suction cooling, thereby increasing the cooling efficiency. Taking conventional ordinary block molding as an example, the cooling method and time after hot molding are as follows, and the feature is that the cooling time is long. Water cooling time: 5 to 10 minutes Air cooling time: 10 to 20 minutes Water cooling is an operation in which heat is removed from the mold and molded object by spraying cooling water onto the mold. When the molded product is removed from the mold, expansion force remains inside the molded body, causing bulge, so the molded body is held in the mold until the expansion force disappears. In the method of the present invention, air cooling is performed using an exhaust device during water cooling and air cooling, and the water cooling time is 1 to 2 hours.
The time can be shortened by a great deal in minutes, and the amount of cooling water can be saved. Normally, during the cooling process, the mold temperature after water cooling will drop to the cooling water temperature for 1 to 2 minutes, but since the molded body is also a type of heat insulator, the temperature will not drop much below the surface of the molded body. Not yet. After water cooling 1-2
If the cooling operation is performed in minutes, the temperature of the mold will gradually rise and the cooling time will be extended. According to the present invention, the amount of cooling water can be saved by stopping water cooling after 1 to 2 minutes and then performing air cooling using an exhaust device during cooling. It has the advantage of being able to dry the moisture in the mold. As described above, the method of molding foamable thermoplastic resin using the mold of the present invention is extremely valuable in practice, and is suitable for general molding such as block molding and box molding of foamable thermoplastic resin. It can be applied to a variety of applications, and its effects can be particularly demonstrated in block molding. Further, the foamable thermoplastic resin referred to in the present application includes posttyrene, polyethylene, etc., and is particularly preferably used for foam molding of polystyrene resin. There are no particular restrictions on the exhaust system used in the present invention, but a normal exhaust blower can be used. Next, the present invention will be explained in more detail with reference to Examples. Example 1 Using the block molding mold shown in Figure 1, suction filling of expanded polystyrene pre-expanded granules was carried out under the following conditions.
The molded products shown in Table 1 were obtained by heat molding and cooling using suction cooling using an exhaust blower. Furthermore, a comparison of cooling effects is shown in Table 2. (B) Raw materials used: Styrofoam (B) Pre-expanded particle density: 0.012g/cc (C) Mold dimensions (mm): 1800 (height) x 900 (width) x 425
(Width) (d) Blower used; 20m ³ /min x 260mm water column

【table】

[Table] As shown in Table 1, those using the normal method are:
Compared to the case where the upper part of the molded body shrank, the appearance of the upper part of the molded body was very good in the method of the present invention. Furthermore, according to the cooling method of the present invention, the water cooling time can be significantly shortened compared to the conventional conventional method.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional and piping diagram showing one example of the configuration of a block molding machine to which the present invention is applied. 1...cabin side mold, 2...core side die, 3...cabin side frame, 4...core side frame, 5...feeder valve, 6...eject pin, 7...slit, 8...
Steam pipe, 9...exhaust pipe, 10...steam pipe main valve, 1...exhaust pipe main valve, 12...exhaust blower, 13...cabin side steam valve, 14...core side steam valve, 15...cooling water pipe,
16...cabin side cooling water valve, 17...core side cooling water valve, 18...cabin side drain valve, 19...core side drain valve, 20...precipitation particle filling hole.

Claims (1)

[Claims] 1. When filling a mold with pre-expanded particles of expandable thermoplastic resin and performing block molding, the pre-expanded particles are sucked and filled through the filling hole by an exhaust blower device connected to the core side mold and/or the cavity side mold. A method for molding a block of a foamable thermoplastic resin, characterized in that after hot molding, the mold is cooled with water, the exhaust blower device suctions and ventilates the molded product, and the molded product is held in the mold and cooled.