JP2589454B2 - Method for producing synthetic resin foam molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foamed synthetic resin article, and more particularly to a method of changing the steam supply pressure to keep the foaming pressure of raw material beads constant at a necessary optimum value. The present invention relates to a method for producing a synthetic resin foam molded article.

[0002]

2. Description of the Related Art The main structure of a conventional general synthetic resin foam molding apparatus has a structure as shown in the schematic diagram of the apparatus in FIG. That is, the foam molding space 51 partitioned into the volume shape of the molded body is formed from the pairing of the pair of convex molds 50a and concave molds 50b molded into a predetermined shape.
The dies 50a and 50b are formed of a gas permeable material, are respectively housed in master frames 52a and 52b, and have steam chambers 53a and 53b formed therein. Each steam chamber 53a, 53b has a discharge pipe 5 below it.
4a and 54b are attached, and the drain valves 55a and
5b makes it freely openable and closable. In addition, steam room 53
a and 53b are provided with steam supply pipes 56a and 56b, respectively.
7b. By adjusting the pressure regulating valve 57, the steam supply pressure to the steam chamber 53 is set. The opening of the pressure regulating valve 57 is adjusted through an air supply source 58.
This is performed by a three-way valve 59 and a semi-fixed air regulator 60. Reference numeral 61 denotes a pressure gauge for checking the air pressure.

[0003] With such an apparatus configuration, a manufacturing process of a synthetic resin foam molded article is performed as follows. First, the preformed (primary expanded) raw material beads 62 are filled into the foam molding space 51 manually or by using an auto feeder (automatic filling device) 63. After filling, while the drain valve 55 is open, the pressure regulating valve 57 is operated, the steam from the steam supply source 64 is supplied to the steam chamber 53 through the steam supply pipe 56, and the mold 50 is preheated (in the mold). Preheating step). next,
By closing only the drain valve 55b of one concave mold 50b and supplying steam only to the concave mold 50b, the air remaining in the grains of the raw material beads 62 is transferred to the steam chamber 50a on the other side. Send out (while heating step). Thereafter, both drain valves 55a, 55b are closed, and both steam chambers 53a,
Supply steam to 53b for a predetermined time and heat (110 ° to 150 °)
C) (Double-side heating step). If necessary, additional heating is performed (additional heating step). By the two-sided heating step and the additional heating step, the raw material beads 62 are foamed and filled in the foam molding space 51, and are molded into a shape according to the space area (foaming step). After the foam molding, water is sprayed (shower ring) into the steam chamber 53 and cooled (water cooling step). After discharging the water (draining step), the steam chamber is evacuated to remove the remaining water by utilizing the heat of vaporization to cool the foamed molded article (vacuum cooling step). Finally, both molds 50
a and 50b are separated from each other, and the foam molded body 66 is released and removed by the operation of the eject pin (extrusion rod) 65 (demolding step).

[0004] Reference numeral 67 denotes a foaming pressure detector mounted so as to face the foam molding space 51. by the way,
It has been found that the foaming pressure of the foamed molded article 66 is closely related to the steam supply pressure up to the heating step, as shown in a graph showing the relationship between each step and the foaming pressure in FIG.
That is, when the steam supply pressure is set high, the steam supply amount increases and the foaming pressure of the raw material beads increases, and when the steam supply pressure is set low, the foaming pressure decreases. Furthermore, when the foaming pressure increases, the cooling process also takes a long time, and it has been found that the steam supply pressure is closely related to the molding cycle time (the time required from the supply of the raw material to the demolding). Was done.

[0005]

However, in the above-mentioned conventional apparatus, in the heating step, the steam supply pressure to be supplied to the steam chamber 53 is set at one set value where the opening of the pressure regulating valve 57 is kept constant. I was Therefore, in order to improve the fusion between the foamed particles of the raw material beads 62, when the steam supply pressure is set to be high, the molding cycle becomes long, and when it is set to be low, the molding cycle becomes short, and the production quantity becomes short. However, there was a problem that the fusion was insufficient and many defective products were generated.

Further, in the conventional fixed type in which the set value of the steam supply pressure is one, even if the steam supply is stopped when the foaming pressure reaches a necessary foaming pressure (graph n in FIG. 2), There was also a problem that the foaming pressure reached an unnecessarily high level due to the residual heat of the mold (graph m in FIG. 2), resulting in a longer molding cycle.

Accordingly, the present invention has been made in view of such a problem, and the foaming pressure at the time of heating is suppressed to the minimum necessary by changing the steam supply pressure in the heating step, and is kept constant. Accordingly, the present invention provides a method for producing a synthetic resin foam molded article for the purpose of increasing the required energy efficiency and shortening the molding cycle.

[0008]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as follows. Raw material beads are filled in the foam molding space defined by the pair of molds, heated and foamed by supplying steam into the mold, and then cooled to remove the foam molded body. The method for producing a synthetic resin foam molded article described above is characterized in that the steam supply pressure into the mold is appropriately changed from the starting pressure in accordance with the change in the foaming pressure of the raw material beads in the foaming step.

Further, the present invention is characterized in that the foaming pressure is kept constant by changing the steam supply pressure as needed in accordance with the foaming pressure of the raw material beads. Further, the steam supply pressure is gradually reduced from the starting pressure to keep the foaming pressure constant.

[0010]

With this configuration, a change in the foaming pressure of the foam is detected in real time, and the steam supply pressure is appropriately varied based on this information, so that the foaming pressure is kept constant at an optimum value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the method for producing a synthetic resin foam molded article according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the apparatus configuration of the present embodiment, and FIG. 2 is a graph showing the relationship between the foaming pressure and the steam supply pressure in each step in comparison with a conventional example.

In the present embodiment, the same reference numerals as those used in the description of the above-described conventional example are given to the same components as those in the conventional example, and the detailed description thereof will be omitted. The characteristic part of the present invention is that in one molding cycle,
This is in the variable setting of the steam supply pressure in the double-sided heating step and the additional heating step as required, that is, the foaming step. That is, first, the supply of steam is started at a predetermined set pressure (start pressure), and the foaming pressure is detected in real time (every moment), and as the detected foaming pressure approaches the necessary optimum pressure, the steam supply pressure is increased. It will be gradually lowered. The steam supply pressure is changed as needed so that the foaming pressure is kept constant at the necessary optimum pressure as shown in the graph x. This optional adjustment may be set gradually lower as shown in the graph y, or may be set lower continuously, though not shown. Further, the steam supply pressure may be appropriately increased or decreased based on the detected change in the foaming pressure.

In an embodiment of the apparatus for performing such control, an electropneumatic regulator 3 is connected via a three-way solenoid valve 2 to an air supply pipe 1 for operating a pressure regulating valve 57 for adjusting the steam supply pressure. 3 is operated steplessly by the change of the electric signal, whereby the operating air pressure is varied to adjust the pressure regulating valve 57 steplessly (or stepwise). For this adjustment, the foaming pressure that changes over time is detected by the foaming pressure detector 67, this information is extracted as an electric signal (e), and the controller 3 controls the electropneumatic regulator 3 so that the optimal steam supply pressure is obtained. This is performed by controlling (f). This control may be either sequential control or so-called microcomputer control using a microcomputer.

In this embodiment, the control for stepwise decreasing the setting of the steam supply pressure is performed. However, the present invention is not limited to this. For example, the steam supply pressure may be reduced according to the change in the foaming pressure. Alternatively, it may be controlled so that the foaming pressure is kept constant at the optimum foaming pressure as much as possible.

Next, as another embodiment of the apparatus for changing the steam supply pressure, the structure shown in FIGS. 3A and 3B may be adopted. FIG. 3 (A) shows that instead of using the electropneumatic regulator 3 for controlling the pressure regulating valve 57, a plurality of three-way solenoid valves 5, 5,.
.. and semi-fixed regulators 6, 6,... Are connected in multiple stages. By operating the regulator 6, the air pressure for operating the pressure regulating valve 57 is changed stepwise as appropriate.

In FIG. 3B, instead of using the pressure regulating valve 57, a plurality of two-way solenoid valves 7, 7,.
Are directly attached to the steam supply pipe 56 in parallel. The steam supply pressure of the steam supply pipe 56 is appropriately changed by a combination of the operations of the valves 7 and 8.

Next, Table 1 below shows examples of specifications for forming polystyrene foam using the foam molding apparatus of this embodiment.

[0018]

[Table 1]

[0019]

[Effect] The present invention is configured as described above,
The foaming pressure can be set to the minimum necessary pressure, and unnecessary steam supply that has been performed so far can be eliminated, so that energy can be saved by reducing the amount of steam used.

Further, since the rise of the foaming pressure more than necessary is suppressed, the cooling time after foaming can be shortened, and the molding cycle can be shortened. As a result, there is an effect that the production efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a device configuration of the present embodiment.

FIG. 2 is a graph showing a relationship between a foaming pressure and a steam supply pressure in each step in comparison with a conventional example.

FIG. 3 is a schematic diagram showing another configuration example of a main part of the embodiment.

FIG. 4 is a graph showing a relationship between a molding step and a foaming pressure.

FIG. 5 is a schematic diagram showing a conventional apparatus configuration.

[Explanation of symbols]

1 ・ ・ ・ Air supply pipe 2 ・ ・ ・ Three-way solenoid valve 3 ・
..Electro-pneumatic regulator 4 ... Control device 5 ... 3-way solenoid valve 6 ...
・ Regulator 7 ・ ・ ・ 2-way solenoid valve 8 ・ ・ ・
Vacuum pressure reducing valve 50 ... mold 51 ... foam molding space 52 ... master frame 53 ...
Steam chamber 56 ・ ・ ・ Steam supply pipe 57 ・ ・ ・ Pressure regulating valve 58 ・ ・ ・ Air supply source 62 ・ ・ ・ Material beads 63 ・ ・ ・ Auto feeder 64 ・ ・ ・ Steam supply source 65 ・ ・ ・ Eject pin 66 ・ ・ ・Foaming molded article 67: Foaming pressure detector

Claims (1)

(57) [Claims] 1. A raw material bead (6) is formed in a foaming molding space (51) defined by matching a pair of molds (50).
In the method for producing a synthetic resin foam molded article in which the foamed article (66) is filled, heated and foamed by supplying steam into the mold, and then cooled, the foamed molded article (66) is removed from the mold . In response to the change in the foaming pressure of the raw material beads (62) , the steam supply pressure into the mold is changed to the starting pressure.
Wherein the foaming pressure is kept constant by changing the pressure appropriately .