JPS62158024A - Manufacture of thin-walled foamed polystyrene molded part - Google Patents

Abstract

PURPOSE:To manufacture a foamed polystyrene molded part with the wall part, the thickness of which is smaller than the specified value, by a method wherein a cavity, which is formed by a cavity mold and a core mold, is evacuated and, after that or while the cavity is being sucked, specified primary foamed particles are loaded together with compressed air in the cavity. CONSTITUTION:First, while an evacuating device is put into actuation, a charging port 9 is opened so as to carry expandable polystyrene beads, the particle diameter of which is 0.1-0.35mm, with compressed air into a cavity in order to load the beads in the cavity. Secondly, molds are preheated by introducing heating medium such as steam, hot water or the like through heating and cooling medium inlets 7 and 12 into chambers 5 and 10. While the heating medium is kept on introducing, steam is introduced through steam blowing ports 4 into the cavity for main heating. After the finish of main heating, cooling medium such as water or the like is introduced in the chambers 5 and 10 in order to cool the molds. After the completion of cooling, the molds are opened and compressed air is blown through releasing air blowing ports 14 so as to release a molded part with the wall thickness of 0.6-1.2mm from a core mold 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applicable to single-foamed polystyrene molded products with a wall thickness of 0.
The present invention relates to a method of manufacturing a molded product having a thin wall portion of 6 to 1.2 mm.

Foamed polystyrene molded products are used for double-foamed polystyrene cups, cushioning materials, etc., and there is a strong demand for thin-walled molded products depending on the application.

Further, among the 2-foam polystyrene molded products, 2-foam polystyrene cups, for example, 9-foam polystyrene cups, are used in many fields including noodle cups, taking advantage of their characteristics of heat retention, hygiene, economy, etc.

Expanded polystyrene molded products are generally produced by primary foaming (pre-foaming) expandable polystyrene beads to a predetermined bulk specific gravity.
After ripening, it is filled into a mold and further heated and cooled to form the product.

Filling of raw materials has conventionally been carried out by entraining compressed air with primary foam particles.

(Problem that the invention attempts to solve) Flowers using foamed polystyrene molded products as cushioning material In this case, products have become smaller and thinner in recent years.

Although thinning is required, when manufacturing a device with a wall thickness of 1.2 arms or less, there is a problem in that it is difficult to uniformly fill the raw material beads.

The above requirements and problems are particularly noticeable in the 9-expanded polystyrene cup. The two expanded polystyrene cups will be explained below. Namely.

The biggest drawback of conventional expanded polystyrene cups compared to two-paper cups is that they are ``tight.'' for example,
In the same shape, the distance (stacking) occupied by a paper cup and one foamed polystyrene cup having a wall thickness of Z Ow is 5.8 mm and 16.4 mm, respectively. The move toward thinner foamed polystyrene cups has been an extension of conventional technology, but the smallest wall thickness currently on the market is up to 1.4 mto.
Anything smaller than this has not been possible due to material constraints and the filling technology is aimed at expanded polystyrene beads with relatively large particles.

Conventionally, filling of raw materials has been carried out using compressed air as mentioned above, but this filling method is difficult to use if the secondary foamed particles are fine particles or the gap to be filled is narrow.
It has the disadvantage that air is difficult to escape from the parting line, and is therefore prone to filling defects. Therefore, it has not been possible to reduce the thickness of single-foamed polystyrene molded products.

Therefore, it is an object of the present invention to provide a method for manufacturing a foamed polystyrene molded product having a wall thickness of +1.2m+n or less.

(Means for Solving the Problems) The present invention comprises foam-molding primary foamed polystyrene beads having a particle diameter of 0.1 to 0.35.
．． In a method for manufacturing a foamed polystyrene molded product having a wall thickness of 2 arms, a primary molding is applied to a cavity formed by a cavity mold and a core mold after reducing the pressure in the cavity or while suctioning the cavity. The present invention relates to a method for manufacturing a thin-walled foamed polystyrene molded product, which is characterized by filling expanded particles with compressed air.

The expandable polystyrene beads used in the present invention must have a particle size of 0.35 am or less, and the particle size is less than 0.10TI11.

This may cause clogging. Therefore, the particle size of the bifoamable polystyrene beads is preferably in the range of 0.1 to 0.35 m. The amount of easily volatile blowing agents such as propane and butane contained in the expandable particles is preferably 3.5 to 5.0% by weight, and if it is less than 3.5% by weight, one foaming is difficult. It is. Note that it is not necessary to use more than 500% by weight.

The expandable polystyrene beads are firstly expanded into particles and then subjected to molding. At this time, the degree of primary foaming becomes important in determining the weight of the molded product. As a means to achieve a predetermined foaming ratio.

Known ones can be applied. What is the foaming ratio?

It is determined by the intended weight fK of the molded product.

It is preferable that the bulk specific gravity falls within the range of 2509/l to 150 g/J. It is most suitable for producing thin-walled molded products that the aging after the primary foaming is completed so that the amount of blowing agent in the primary foamed particles is within the range of 2 to 5% by weight.

The production of expanded polystyrene molded articles is generally carried out by the following steps using such primary expanded particles.

(1) Mold clamping (2) Raw material filling (3) Preheating (4) Main heating (5) Cooling (6) Mold opening, mold release The present invention particularly requires step (2) of the above molding steps. This is an improvement.

The present invention will be explained using the drawings.

FIG. 1 is a cross-sectional view showing an example of a cup molding die used in foam molding of the present invention, and FIG. 2 is an enlarged view of section A in FIG. 1.

A cavity (inside the mold) 3 is formed in the cavity mold 1 and the core mold 2 when the molds are clamped. The cavity is adjusted so that the side wall thickness of the molded product is 0.6 to 1.2 tm. The cavity mold 1 is provided with a steam inlet 4 into the cavity 3, and an outer cylinder 6 is provided to form a chamber 5 on the outside of the cavity mold 1.

The outer cylinder 6 has a heating/cooling medium type lower and a heating/cooling medium outlet 8 to the chamber 5, and has a filling port 9 for filling the cavity 3 with primary foam particles. The filling port 9 is closed except when filling with primary foam particles. Also,
The core mold 2 includes a core 11 to form a chamber 10.
The core 11 has a heating/cooling medium inlet 12 and a heating/cooling medium outlet 13 to the chamber 10, and the core mold 2 has a mold release air inlet 14. Release air inlet.

The holes 9 are large enough that the primary foam particles do not pass through, for example, usually 0, 1
The hole has a diameter of about mm, but its shape is arbitrary.

When cavity mold 1 and core mold 2 are closed.

A crack (gap) 16 is formed in the parting line portion 15 of the cavity mold 1, and this crack 16
is connected to a decompression port 17 formed in the cavity mold 1. Cracking width is 0.1~0
．． 25 mm is preferred. The vacuum port is connected to a vacuum device for vacuuming or suctioning the cavity.

In the drawings, a crack 16 and a pressure reducing port 17 are shown, but a mold without these may be used in the foam molding of the present invention as the case may be. Further, in the two drawings, the cavity mold 1 and the core mold 2 are arranged like a square at the parting line portion 15, but in some cases, they may simply be horizontally opposed to each other. The cracks 16 are preferably formed over the entire circumference of the mold, but may be formed intermittently over the entire circumference depending on the case.

The present invention can be carried out using the mold shown in the drawings by the following secondary method.

First, as shown in Figure 9, the mold is closed (mold clamping process). In this case, the filling port 9 is closed. Next, the pressure reducing device is activated to bring the cavity into a reduced pressure state. The pressure inside the cavity is 400 mmHg
/cm" or less. Then, while operating the pressure reducing device, the filling port 9 is opened and the primary foamed particles are transported into the cavity with compressed air to perform filling. At this time, the inside of the cavity is suctioned. In many cases, the inside of the cavity is under reduced pressure, but in some cases, it may be under normal pressure as long as there is an airflow.

Depressurization or suction of the cavity by a decompression device.

The mold release air inlet 14 is connected to a pressure reducing device, through which the cavity 3 is depressurized or suctioned at the same time as the parting line portion 15 is depressurized or suctioned. In the case where cracking 16 is not formed in parting line portion 15.

Depressurization or suction of cavity 3 is done through mold release air inlet 1.
It is performed only from 4. Alternatively, the depressurization or suction from the mold release air inlet 14 may not be performed, and only the depressurization or suction from the parting line section 15 may be used. In this case, air etc. will not flow in from the mold release air inlet 14. Closed like this.

Furthermore, the vacuum or suction of the cavity 3 may be started at the same time as the filling of the primary expanded particles from the filling port 9 is started.

After filling is completed, the vacuum and suction are stopped.

The mold is then preheated. Preheating.

In chambers 5 and 10, a heating/cooling medium type lower and 1
This is done by introducing a heat medium such as steam or hot water from step 2. Furthermore, while the introduction of the heating medium is continued, steam is introduced into the cavity from the steam inlet 4 and heating is performed. After the main heating is completed, the introduction of the heat medium into the chambers 5 and 10 and the introduction of steam into the cavity 3 are stopped.

In chambers 5 and 10, a heating/cooling medium type lower and 1
2, a coolant such as water is introduced to cool the mold. After cooling is completed, the mold is opened, compressed air is blown from the mold release air inlet 14, and the molded product is released from the core mold 2. The trap is removed after cooling is complete.

The refrigerant in the chambers 5 and 10 is discharged before; simultaneously with or after the mold is opened. Furthermore, before opening the mold, the refrigerant in the chambers 5 and 10 may be discharged and allowed to cool.

Note that a pressure reducing device for reducing or suctioning the cavity 3 and a compressed air supply device for releasing the molded product are connected to the mold release air blowing port 14 in separate systems.

(Function) In the present invention, since the filling of the primary expanded particles of small-diameter expandable polystyrene beads into the cavity is carried out under full vacuum or suction, even if the primary expanded particles are fine particles, they can be filled well. It was. Since even narrow gaps can be filled uniformly, molded products having thin wall portions of 1.2 ain or less can be manufactured.

(Example) Next, the present invention will be explained in detail based on examples.

The present invention is not limited to this.

Example 1 Microparticle expandable polystyrene beads [HiBeads 78G (trademark) manufactured by Hitachi Chemical Co., Ltd. 2 particle size 0.177-0.29
7 mm) using a hot air-steam mixture as a heating medium.
The primary foaming was carried out until it reached 0.09/V (specific gravity 0.26/cc). This was aged at 24°C for 7 days, and the volatile content was 2. ．． 2
% of primary expanded particles were obtained. The particle size at this time is 0.25
It was ~0.50m. This is the side wall thickness 1.0+ynn
A 6.5-ounce cup was molded in a mold as shown in the drawing.

After the mold clamping is completed, the inside of the cavity is moved in 0.5 seconds.
The pressure was reduced to 0 mmHg. In this case, suction was simultaneously carried out from the parting line portion and the mold release air inlet. Thereafter, while performing the suction, the primary expanded particles were filled in for 1.5 seconds using compressed air of 4 kg/cUP. Thereafter, as described above, the mold was preheated with steam for 1.5 seconds, heated twice for 25 seconds, and cooled with water for 23 seconds, and then the mold was opened.

Compressed air was blown from the mold release air inlet to release the two expanded polystyrene cups from the mold. This cup cracks 8
It was a cabinet.

The obtained molded product had good appearance and particle fusion.

Comparative Example The procedure of Example 1 was followed except that the inside of the cavity was not depressurized or suctioned when filling the primary expanded particles.

As a result, only a molded product with a chipped cup bottom was obtained due to incomplete filling.

(Effects of the Invention) According to the present invention, a thin expanded polystyrene molded product having a wall thickness of 0.6 to 1.2 m can be manufactured using fine expandable polystyrene beads as a raw material.

[Brief explanation of drawings]

FIG. 1 shows a longitudinal sectional view showing an example of a mold for forming a cup used in the manufacturing method according to the present invention, and FIG.
FIG. Explanation of symbols 1... Cavity W 2... Core mold 3...
・Cavity 4...Steam inlet 5.
10...Chamber 6...Outer cylinder 7.12...
- Heating/cooling medium inlet 8.13... Heating/cooling medium outlet 9... Filling port 11... Core 14...
・Release air inlet 15...Parting line part 16...Cracking 17...Decompression port<,
,,, :,,;,' 2nd item

Claims (1)

[Scope of Claims] 1. Primary foamed particles of expandable polystyrene beads with a particle size of 0.1 to 0.35 mm are foam-molded to form particles of 0.6 to 1.2 mm.
In a method for manufacturing a foamed polystyrene molded product having a wall thickness of mm, a cavity formed by a cavity mold and a core mold is subjected to primary foaming after reducing the pressure in the cavity or while suctioning the cavity. A method for manufacturing a thin-walled expanded polystyrene molded product, characterized by filling particles by entraining them with compressed air. 2. The method for manufacturing a thin-walled polystyrene foam molded product according to claim 1, wherein the cavity is depressurized or suctioned from the parting line portion of the mold and/or the mold release air blowing port. 3. The method for producing a thin-walled polystyrene foam molded product according to claim 1 or 2, wherein the foamed polystyrene molded product is a foam polystyrene cup.