JPS5951890B2 - Foam molding method for synthetic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for foam molding synthetic resins.

Conventional synthetic resin foam molding methods that use pre-foamed raw material beads, such as the molding of porous polystyrene resin products, involve supplying the raw material beads into a mold and then directing preheating steam to the opposing metal mold. The air is passed alternately from one side of the mold to the other to eliminate the air between the raw material beads in the mold and raise the mold and raw material beads to the required preheating temperature, and then the foaming material is placed in the mold. Since raw material beads are secondary-foamed and molded by supplying steam, a large amount of steam is required to preheat the mold, and depending on the shape of the mold, there may be areas where it is difficult for steam to enter. The air between the raw material beads in the mold was not completely removed by the steam and remained, resulting in insufficient foaming and fusing of the raw material beads.

The present invention was completed with the aim of forming a foam molding method for synthetic resin free of defects as described above. It is characterized by foam molding by supplying steam into a mold, and will be described in detail below using a multi-porous polystyrene molding using a horizontal porous synthetic resin molding machine as shown in the figure as an example. 1 and 1' are a pair of molds equipped with mating mold parts 2 and 2' in which a large number of small holes 5 and 5' are arranged for ventilation, and both molds 1 and 1' can be freely moved in and out of the molding machine. Opposed frame box 3
, 3' are installed so as to block the front openings of the molds 4 and 4', and chamber parts 4 and 4' are formed at the rear of each, 6 is a raw material supply device whose supply port is connected to one of the molds 1, and 7 is a raw material supply device. 9 is an extrusion rod for releasing the foamed molded product, the tip of which is inserted into the mold 1 so as to be freely retractable; 9 is a extrusion rod for returning the extrusion rod 7 whose base end is locked to the flange 8 of the extrusion rod 7; It's a spring. 10 has one end as mold 1
The connecting pipe is connected to the chamber part 4 of the main steam supply pipe 12 and the other end thereof is connected to the steam supply main pipe 12 via the on-off valve 11. A branch pipe 13 is connected to the connecting pipe 10, and the branch pipe 1
3 is connected to a vacuum source (not shown) via an on-off valve 14, and 16 is a discharge pipe with an on-off valve 15 connected to the bottom of the chamber section 4 of the mold 1, while 10' is one end. is a connecting pipe connected to the chamber part 4' of the mold 1', and the other end is connected to the main steam supply pipe 12 via an on-off valve 11', and the connecting pipe 10' has a branch pipe 13'. The branch pipe 13' is connected to a vacuum source (not shown) via an on-off valve 14'.

16' is a discharge pipe with an on-off valve 15' connected to the bottom of the chamber portion 4' of the mold 1'.

With this structure, the mating mold part 2 of the mold 1 is moved by the action of a cylinder (not shown) of the mold 1'.
', and then from each raw material supply device 6 to the molds 1 and 1.
The cavity formed between the mating mold parts 2 and 2' is filled with pre-foamed raw material beads and the mold is clamped.
The on-off valves 14, 14' of the branch pipes 13, 13' are connected to the vacuum source with the on-off valves 15, 15' of the branches 6, 16' closed.
When opened, the air in the chamber parts 4, 4' formed at the rear of both molds 1, 1' is discharged, and at the same time, the air is discharged through the small holes 5, 5' into the chamber parts 4, 4'. Mold 1, 1'
Since the air inside the molds is also properly removed without wasting steam supply, all the air remaining between the raw material beads in the molds 1 and 1' is also exhausted at the same time, and the air inside the molds 1 and 1' is maintained at a reduced pressure close to vacuum.

After doing this, the on-off valve 14 of the branch pipes 13, 13'
, 14' are closed and the on-off valves 11, 1 of the connecting pipes 10, 10' are closed.
1' is opened, the steam sent from the steam supply pipe 12 passes through the connecting pipes 10, 10' to the chamber part 4 of the molds 1, 1'.
, 4', the steam is supplied to the small holes 5, 4'.
5', the molds 1, 1' and the raw material beads enter the gap between the raw material beads filled in the cavity between the molds 1, 1' under reduced pressure in a very short time, and the molds 1, 1' and the raw material beads are In addition, the particles are uniformly heated to a predetermined temperature, secondary foaming is performed appropriately, and the harmful effects of residual air in the molds 1 and 1' on fusion are completely eliminated. The fusion was also performed well, and a homogeneous synthetic resin foam molding was formed between the mating mold parts 2 and 2', and during this time steam was released into the cavity part and chamber part 4 between the mold parts 1 and 1'. ，
Since the pressure inside the 4' is reduced and there is no residual air, the temperature drop is small and the heat transfer efficiency is high. efficient heating with a small amount of steam. After the foam molding is completed in this way, the on-off valves 11 and 1 of the connecting pipes 10 and 10' are
On-off valve 15, 1 of discharge pipe 16, 16' closes 1'
5' is opened to discharge the steam inside the molds 1 and 1' to the outside. death,
Thereafter, the pressure inside the chamber parts 4, 4' is reduced as necessary, and the molds 1, 1' are cooled by a conventional method.
When the mold is opened, the other end of the extrusion rod 7 comes into contact with a fixed plate (not shown), the tip of the extrusion rod 7 protrudes from the surface of the mating mold part 2, and the foam molded product is placed in the mating mold part of the mold 1. The molded product is extruded from Step 2 and released from the mold, and as described above, after supplying the raw material beads into the mold, the inside of the mold is brought into a reduced pressure state, and steam is supplied to form the molded product through foaming. The foamed particles are properly fused to each other, and the expansion coefficient of each part of the molded product is approximately equal due to uniform heating, so the molded product will not be partially damaged when released from the mold. It also has the advantage of being easy to perform without causing any damage or deformation. As is clear from the description of the above embodiments, the present invention is such that after the pre-foamed raw material beads are supplied into the mold, the pressure inside the mold is reduced and steam is supplied. This process is carried out after the air in the mold has been expelled, so the steam supply process conventionally used for the purpose of expelling air and preheating the mold is not necessary, and a small amount of steam can be used effectively. By using it to heat the foam for foam molding, the amount of steam used can be significantly reduced compared to conventional methods, which not only eliminates waste of thermal energy, but also produces high-quality products with uniform strength in each part. This is an extremely significant contribution to the industry as a synthetic resin foam molding method that has many advantages such as the ability to obtain products.

[Brief explanation of drawings]

The drawing is a partially cutaway front view showing the main parts of a porous synthetic resin molding machine that implements the method of the present invention. 1,1': Mold.

Claims (1)

[Claims] 1. A synthetic resin foam molding method, which comprises supplying pre-foamed raw material beads into a mold, reducing the pressure inside the mold, and then supplying steam into the mold for foam molding.