JPH11268068A - Low foam molding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perfectly return excessive foamable resin particles to a raw material hopper after a mold is filled with raw material particles comprising unfoamed foamable particles or low prefoamed particles. SOLUTION: The branch hose 50 branched from a hose 20 to be connected to a raw material hopper 10 so as to be allowed to communicate therewith is provided through the changeover valve 40 attached on the way of the hose 20 connecting the raw material hopper 10 and a raw material filling device 30 and the changeover device 40 is operated at a time of blow-back to return excessive foamed particles to the raw material hopper through the branch hose 50. Or, the raw material hopper 10 housing raw material particles comprising a foamable thermoplastic resin and the raw material filling device 30 attached to a mold are allowed to communicate with each other by the hose 20 and the changeover valve 40 is provided on the way of the hose 20 and the blow-back exclusive branch hose 50 branched from the hose 20 through the changeover valve 40 is provided to be connected to the raw material hopper 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam molding method and a foam molding apparatus, in which surplus raw material particles retained in a raw material filling device or the like can be blown back to a raw material hopper.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 62-27662 discloses a conventional foam molding method in which excess raw material particles retained in a raw material filler or the like are blown back to a raw material hopper. In the foam molding method, a hollow pipe is erected above a raw material outlet of a hopper, and excess foam particles are returned to the raw material hopper from the upper end of the pipe through the hollow pipe during blowback. I was trying to improve the return.

However, the blowback method is
It is used to manufacture buffer packaging materials and cold storage containers by molding with a general expansion ratio, for example, foaming in a bead mold.
It was foamed about 0 times. On the other hand, it has been proposed to use a low-foam molded product obtained by foaming in a bead mold as a building member or a frame material because it can be nailed. Therefore, when molding a low-expanded molded product using unexpanded or low-expanded (less than about 5 times) pre-expanded particles as raw material particles, the raw material is placed in the mold cavity using a normal hopper and a raw material filler. After filling the particles,
If excess raw material particles are blown back, there is a problem that the raw material cannot be completely returned to the hopper because the density of the raw material is high and heavy. In particular, it was difficult to blow back the raw material particles by automatic molding.

In the present invention, in particular, when foaming a foamed molded article having a low foaming degree, the raw material particles of a foamable thermoplastic resin composed of unfoamed or low-foamed prefoamed particles as a raw material are filled into a molding die. It is an object of the present invention to allow excess foamable resin particles accumulated in a filling device to be completely returned to a raw material hopper.

[0005]

According to the low foam molding method of the present invention which can achieve the above object, as described in the first aspect, a molding die is formed from a raw material hopper containing raw material particles made of an expandable thermoplastic resin. After feeding the raw material particles to the raw material filler attached to the mold and filling the raw material particles in the molding die, the excess air particles retained in the filling device and the like are returned by the pressure air to the raw material hopper side by the above. A method of blowing back excess raw material particles to a raw material hopper, comprising: a branch hose branched from the hose and connected to the raw material hopper through a switching valve attached in the middle of a hose connecting the raw material hopper and the raw material filling device. Is provided, and the switching valve is operated at the time of blowback so that excess foam particles are passed through the branch hose and returned to the raw material hopper.

According to the low foam molding method of the first aspect, a blow-back is performed by operating a switching valve by using a branch hose branched from the hose via a switching valve attached in the middle of the hose. In addition, the branch hose is dedicated to blowback, so that even heavy raw particles having high density due to low foaming can be blown back to the raw material hopper without difficulty.

In particular, even when the raw material particles have an expansion ratio of about 5 times or less, which is difficult to blow back by the conventional method, the blow back can be completely performed. Further, as a low-foam molding apparatus for performing the low-foam molding method, as described in claim 3, a raw material hopper containing raw material particles made of an expandable thermoplastic resin and a raw material filling device attached to a mold. And a switching valve is provided in the middle of the hose, and a branch hose dedicated to blowback branched from the hose via the switching valve is provided, and the branch hose is connected to the raw material hopper. It is characterized by:

In particular, according to the low-foaming molding apparatus, the switching valve provided in the middle of the hose and the branch hose branched from the hose via the switching valve are dedicated to blowback. A reasonable blowback can be realized for the raw material particles having the expansion ratio, and a blowback by automatic molding can be realized. As described above, according to the present invention which can solve the problems of the prior art, 3
Instead of a manual machine conventionally used to produce a low-fold foam molded product about twice as high, an automatic foam molding machine used in general foam molding can be used, but conventionally this is I couldn't. However, in the present invention, by enabling the use of this automatic foaming molding machine, it is possible to greatly reduce molding time in the automatic molding machine and to greatly improve molding efficiency such as taking multiple dies. In addition, since there is no need to have a person at the time of molding as in a manual machine, the number of personnel can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the low foam molding method according to the present invention will be described with reference to the drawings together with an apparatus used for carrying out the method. 10 is a raw material hopper,
The above-mentioned lid 12 is provided with an inlet 11 for raw material particles, and raw material particles made of expandable thermoplastic resin are fed into the raw material hopper 10 from the outside so that a certain amount of raw material particles can be stored by a level meter or the like. Is configured.

Reference numeral 20 denotes a hose having one end connected to the bottom outlet of the raw material hopper 10. The hose 20 is connected to the raw material hopper 10 attached to the mold A by connecting the other end to the raw material hopper 10. The raw material filling device 30 is communicated. Reference numeral 40 denotes a flow path switching valve provided in the middle of the hose 20. The branch hose 50 branches from the middle of the hose 20 via the switching valve 40. Through the material hopper 10. This branch hose 50 is designed to be used as a hose dedicated to blowback.

As the switching valve, a ball valve, an electromagnetic valve or the like is used. In order to perform the low-foaming molding of the present invention using such a low-foaming molding apparatus, the raw material filling device 30 on the molding die A side from the raw material hopper 10 through the hose 20 is used.
The raw material particles are sent to the mold A, and after filling the raw material particles into the mold A, the raw material particles staying in the filling device 30 are blown back to the raw material hopper 10 using the pressure air. In the present invention, at the time of the blowback, the flow path is changed to the branch hose 50 side by the switching operation of the switching valve 40, and the surplus raw material particles can be returned from the branch hose 50 to the upper part of the raw material hopper 10. The branch hose 50 is used as a blowback-only hose. Accordingly, even when the raw material particles are unfoamed or low-foamed (expansion ratio of about 5 or less), even if the density is high and heavy, the raw material particles can be returned to the raw material hopper 10 side with a blowback-only hose without difficulty.

The foaming mold to be used is set in a high-pressure molding machine for special EPS. Both the inner plate and the back plate have a mold thickness sufficient to withstand a maximum surface pressure of 4 kg / cm ² during molding. The thickness is required and may be set as appropriate according to the shape of the mold.
It is desirable to have twice the strength. In addition, it is desirable that the preheating time of the mold be set to be longer only at the beginning because of the increase in the thickness.

[0013] Since these dies have an increased thickness, a standard frame for mounting the dies may not be used in some cases. In this case, a dedicated frame or a frame obtained by adding a raised frame to a standard frame is used. For example, in this embodiment, the mold, the inner plate, and the back plate each use an aluminum material having a thickness of 12 mm compared to the conventional 6 mm, and a frame is used by adding a raised frame to a standard frame.

The material of the foaming mold is preferably made of pure aluminum from the viewpoint of strength, but may be an aluminum casting generally used in a foaming mold. In the low-foam molding according to the present invention, since it is difficult to release the molded product from the general foamed bead molded product, it is desirable to attach R1 or more to the corners and the top of the molded product, and the punching taper is necessarily 0.5 ° or more. Depending on the partial shape having a thickness of 30 mm or less, the taper may not be provided. Also,
It is desirable that the mounting position of the knockout pin be provided so as to correspond to the corner of the molded product.

It is needless to say that the surface of the mold is preferably subjected to Teflon processing. Furthermore, the raw material filling device may be a commonly used overfilling prevention type,
In order to avoid troubles inside the filling device, it is preferable to use a filling device having an outer diameter of 25 mm or less even if the filling does not prevent overfilling or the overfilling prevention type. The mounting location of the raw material filling device varies depending on the shape of the molded product, but it is desirable that the necessary number be mounted on the upper portion of the molded product as much as possible and the other filling devices be arranged in a well-balanced manner.

Since the raw material particles used in the present invention have a low expansion ratio, they are different from general expanded beads and are heavy.
In the conventional foam molding apparatus, a phenomenon may occur that the raw material does not return in the blowback step after the raw material is filled and the filling hose comes off, but in the case of the present invention, a branch hose dedicated for blowback is provided in the middle of the filling hose. There is no problem because the bypass is made and the raw material is returned to the raw material hopper. In addition, since the molded article body is heavy as a foam, it is desirable to install an automatic take-out machine for molded articles in order to prevent scratches after mold release.

The various conditions in the embodiment will be described below. When using so-called unfoamed beads that have not been prefoamed,
Since the bead diameter is very small, 0.5 to 1.4 mm, unlike ordinary foam molding, cracking must be set to 0 at the time of material filling, and the material filling pressure is adjusted between 4 to 6 kg / cm ² You can do it (equivalent to the conventional one).

In order to obtain a molded product which does not cause defective filling, it is preferable that the product has a thickness of 15 mm or more. In particular, if the thickness is 20 mm or more, a good molded product can be obtained without any problem. The steam pressure during molding may be set as appropriate for each raw material to be used, but is generally about 0.4 to 1.2 kg / cm ² . Performing one-side heating → reverse one-side heating → main heating is the same as in the related art.

It is conceivable that product swelling may occur due to the effect of residual foaming gas due to insufficient cooling in the molding process after molding. To suppress this, the surface pressure of the mold at the end of the cooling process is reduced to 1 kg / cm ² or less. And preferably 0.9
kg / cm ² or less (conventionally about 0.7 to 0.8). When multiple dies are taken, since the maximum foaming pressure during molding is about 4 kg / cm ^{2, the} number of dies can be appropriately set in consideration of the press pressure of the molding machine.

In the case of using expanded beads having a pre-expanded expansion ratio of about 5 times or less (for example, 2.2 times), the particle size of the beads becomes large, and in order to obtain a molded article which does not cause defective filling, a general method is used. 0.5 ~ cracking same as foam molding
It needs to be about 4 mm, but the others are the same as in the previous case of unfoamed. In any case, the cooling was allowed to cool (2 to 3).
Seconds) → water cooling (shower 300 seconds) → cooling (vacuum 300)
Seconds) and release.

As an example of a molded product, 860 × 100 × 3
It is a 0 mm plate. In addition, as a use of the molded product, a suitable product is provided as a building material such as a plate material and a frame material that can be nailed at a low expansion ratio.

[0022]

According to the low foam molding method and the low foam molding apparatus according to the present invention described above, even if the raw material particles have a high density and are heavy and are suitable for low foaming, the surplus raw material particles retained in the raw material filling device or the like can be removed. By operating the switching valve in the middle of the hose, the branch hose dedicated to blowback in the middle of the hose can be blown back to the raw material hose without difficulty, making it easy to automate the blowback method during low foam molding with a simple configuration. Become.

[Brief description of the drawings]

FIG. 1 shows a schematic diagram of an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 raw material hopper 20 filling hose 30 raw material filling device 40 switching valve 50 branch hose

Claims (3)

[Claims] (1) feeding raw material particles from a raw material hopper containing raw material particles made of an expandable thermoplastic resin to a raw material filling device attached to a molding die, filling the raw material particles into the molding die, and then filling the raw material particles; A method of blowing back the surplus raw material particles to the raw material hopper by back-flowing the pressurized air to the raw material hopper side with respect to the surplus raw material particles staying in the raw material hopper. Through a switching valve, a branch hose branched from the hose and connected to the raw material hopper is provided, and at the time of blowback, the switching valve is operated so that excess foam particles are returned to the raw material hopper through the branch hose. A low foam molding method characterized by performing the following. 2. The low foam molding method according to claim 1, wherein the raw material particles have an expansion ratio of about 5 times or less. 3. A raw material hopper accommodating raw material particles made of an expandable thermoplastic resin and a raw material filling device attached to a molding die are connected by a hose, and a switching valve is provided in the middle of the hose and the switching valve is provided. A low-foam molding apparatus characterized in that a branch hose dedicated to blowback branched from a hose is provided, and the branch hose is connected to and connected to a raw material hopper.