JP7024365B2 - A mold for molding a foamed synthetic resin by the bead method and a method for manufacturing a molded product of the foamed synthetic resin by the bead method. - Google Patents

Description

The present invention manufactures a mold for molding a bead method foamed synthetic resin used for a heat insulating container, a packaging material, etc., and a bead method foamed synthetic resin molded product for manufacturing a molded product of the foamed synthetic resin using the mold. Regarding the method.

In the bead method foamed synthetic resin molding, foamed beads of thermoplastic resin are filled in a molding space (cavity) formed by a pair of molds consisting of a core mold (convex mold) and a cavity mold (concave mold), and the foamed beads are formed. It is heated with steam, fused, cooled and dried to obtain a molded product having a required shape.
The bead method foamed synthetic resin molding mold, which is a pair of molds, is used inside and outside the mold in order to supply steam from the outside into the molding space and discharge steam from the inside of the molding space to the outside. A steam hole is required to communicate with the. Therefore, a large number of vent holes (core vent mounting holes) are formed in the direction orthogonal to the mold surface, and in these vent holes, for example, a large number of caps having an outer diameter of 10 mm and a total length (height) of 6 mm are formed. A core vent (vent fitting) having a slit or a small hole formed therein is generally attached so that the mold surface (molding surface) side is flush with each other (for example, FIG. 8A of Patent Document 1). And (b), and FIGS. 7 (a) and 7 (b)).

In addition to the bead method foamed synthetic resin molding die in which the steam holes are formed only by the core vent, the mold is used to efficiently and uniformly fill the difficult-to-fill portion of the molding chamber of the mold. A core vent and a drill hole are provided in the base portion, and the steam chamber and the molding chamber are communicated with each other along the direction in which the resin beads are guided from the hole for the raw material filler provided in the base portion to the tip of the difficult-to-fill portion of the mold. Some rectifying slits are extended (see, for example, Patent Document 2).
Further, in order to reduce the manufacturing cost of the mold, the core vent is not used, and the mold is communicated inside and outside the required portion of the three-dimensional mold formed by cutting and / or casting. In some cases, the mold itself is provided with a slit-shaped steam hole for passing the steam (see, for example, Patent Document 3).

Japanese Unexamined Patent Publication No. 2000-317968 Japanese Patent No. 6052463 JP-A-2015-227506

In the bead method foamed synthetic resin molding die of Patent Document 2, the opening ratio of the rectifying slit defined by the total opening area of the rectifying slit on the molding chamber side ÷ the total surface area on the molding chamber side × 100 is the effect of introducing / discharging the utility and the gold. From the aspect of mold strength, it is 3 to 40%.
Further, in Patent Document 3, a case is examined in which a slit-shaped steam hole has a steam hole opening ratio equivalent to that of a bead method foamed synthetic resin molding die in which a steam hole is formed only by a core vent, and steam is used. It is only stated that the hole opening ratio can be easily increased. In the bead method foamed synthetic resin molding die of Patent Document 3, for example, the opening ratio of the slit-shaped vapor holes in FIG. 3 is partial, and the average opening ratio of the entire slit-shaped steam holes formed in the mold is partial. Although it is not a reference example, it is about 1.4%.
In the bead method foamed synthetic resin molding die in which slit-shaped steam holes are formed as in Patent Documents 2 and 3, the main focus is on increasing the vapor hole opening ratio.

The inventors of the present application have developed a foamed synthetic resin manufactured by using a bead method foamed synthetic resin molding die in which various slit-shaped steam holes are directly formed (“a mold in which steam holes are provided by directly formed slits”). And the molded product of foamed synthetic resin manufactured by using the bead method foamed synthetic resin molding mold (“mold with steam holes by core vent”) in which the core vent is driven into the vent hole to provide steam holes. Was compared.
As a result, the mold provided with steam holes by the directly formed slit has an average opening ratio of steam holes (total opening area on the molding chamber side of the steam holes ÷ total surface area on the molding chamber side ×) as compared with the mold provided with steam holes by the core vent. It was found that even if 100) was lowered, there was no deterioration in fusion and no decrease in strength.
Therefore, by setting the average aperture ratio of the mold provided with steam holes by the directly formed slit to be low, energy saving can be achieved, the number of slit-shaped steam holes can be reduced, and / or the width of the slit-shaped steam holes can be reduced. It was found that the reduction makes the surface of the molded product more beautiful.

In view of the above background, the problem to be solved by the present invention is to save energy and to save energy in the production of a bead method foamed synthetic resin molded product using a mold having steam holes formed by a direct forming slit. It is to enhance the beauty of the surface.

As a result of diligent research to solve the above problems, the inventors of the present application have completed the present invention.

That is, the gist of the present invention is as follows.
[1] A molding space formed by a pair of molds consisting of a core mold and a cavity mold is filled with foamed beads made of a thermoplastic resin, and the foamed beads are heated with steam to be fused, cooled and dried, which is necessary. A bead method for obtaining a molded product of a foamed synthetic resin having a shape. The mold used for molding a foamed synthetic resin.
A slit-shaped steam hole formed directly in the mold itself for allowing the steam to pass through the inside and outside of the mold to the required portion of the three-dimensional mold formed by cutting and / or casting. Have,
A bead method foamed synthetic resin molding die characterized in that the average opening ratio of the slit-shaped steam holes is 0.5% or more and 1.0% or less.

[2] The foamed beads of the thermoplastic resin are filled in the molding space formed by the bead method foamed synthetic resin molding mold according to the above [1], and the foamed beads are heated by steam to be fused and cooled. A bead method for producing a molded product of a foamed synthetic resin having a required shape by drying and a method for manufacturing a molded product of a foamed synthetic resin.

According to the bead method foamed synthetic resin molding mold and the method for manufacturing a bead method foamed synthetic resin molded product according to the present invention, the following effects are exhibited.
(1) By using a mold having a steam hole by a direct forming slit, between the wall surface of the mold forming a vent hole and the core vent driven into the vent hole like a mold having a steam hole by a core vent. Since there is no contact thermal resistance and the wall thickness is not thin like the slit portion of the core vent, the area where the wall surface of the steam hole comes into contact with steam becomes large, so that the mold can be heated efficiently.
(2) In addition, since there is no dent on the surface opposite to the mold molding space where cooling water stays, the mold temperature does not drop more than necessary during vacuum cooling, so the mold temperature is raised. Can be maintained.
(3) Therefore, even if the average opening ratio of the slit-shaped steam holes is lowered, the fusion does not deteriorate or the strength does not decrease, and the mold can be heated to the required temperature with a small amount of steam. It is possible to make it 0.5% or more and 1.0% or less, and it is possible to save energy.
(4) Further, even if a resin having a low melting point is used for the purpose of saving energy, heat does not accumulate in the vicinity of the wall surface of the steam hole, so that the resin is less likely to stick.
(5) Further, by reducing the number of slit-shaped steam holes and / or reducing the width of the slit-shaped steam holes, the beauty of the surface of the molded product can be further enhanced.

It is a perspective view of the core mold of the bead method foam synthetic resin molding mold which concerns on embodiment of this invention. It is a perspective view of the cavity type of the mold for molding the foamed synthetic resin of the bead method which concerns on embodiment of this invention. It is also a plan view. It is an enlarged front view of the main part which shows the example of the slit-shaped steam hole formed in a mold. It is a perspective view which shows the state before driving the core vent in the core mold of the conventional bead method foam synthetic resin molding mold which used the core vent as a steam hole. It is a perspective view which shows the state before driving the core vent in the cavity mold of the conventional bead method foam synthetic resin molding mold which used the core vent as a steam hole. It is also a plan view. It is the enlarged front view of the main part which shows the example of the state which the core vent is driven into the vent hole of a mold.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
Since the "slit-shaped steam hole" of the present invention is a small gap-shaped steam hole directly formed in the mold itself, the surface on the molding space side thereof is used in a core vent or the like for driving into a vent hole formed in the mold. It does not include slit-shaped steam holes and the like that are previously formed in the above.

<Mold for molding foamed synthetic resin by bead method>
The bead method foamed synthetic resin molding die 1 which is a die provided with steam holes by a direct forming slit according to an embodiment of the present invention includes the core mold (convex mold) 2 shown in the perspective view of FIG. , The cavity type (concave type) 3 shown in the perspective view of FIG. 2A and the plan view of FIG. 2B, and is used by being attached to a general molding apparatus (not shown).
In the bead method foamed synthetic resin molding, the molding apparatus is used to fill the molding space formed by the core mold 2 and the cavity mold 3 with the foamed beads of the thermoplastic resin from the raw material filling port 5, and the foamed beads are steamed. A molded product of a foamed synthetic resin having a required shape is obtained by heating, fusing, cooling and drying, and then inserting and extruding the mold release pin through the mold release pin opening 6.
The foamed beads to be filled in the mold are a concept including pre-foamed beads obtained by pre-foaming the foamable beads.
The drainage piece 7 of FIGS. 2A and 2B is a component for providing a hole in the bottom portion of the molded product.

As the foamed synthetic resin used for the bead method foamed synthetic resin molding, for example, a foamed polyolefin resin or a foamed polystyrene resin is used.
When the foamed synthetic resin is a foamed polyolefin resin, a molded product having excellent strength and heat resistance as well as oil resistance and chemical resistance can be molded by using the bead method foamed synthetic resin molding mold 1. ..
Further, when the expanded synthetic resin is a expanded polystyrene resin, a lightweight and low-cost molded product having excellent heat insulating properties and shock absorption can be molded by using the bead method expanded synthetic resin molding mold 1.

The bead method foamed synthetic resin molding die 1 (core die 2 and cavity die 3), which is a die provided with steam holes by directly forming slits shown in FIGS. 1, 2A and 2B, is made of, for example, an aluminum alloy. Yes, it is formed into a three-dimensional shape by cutting and / or casting.
In the present invention, regarding the formation of a three-dimensional die, shaving and / or casting refers to a die as a single shaving, a die assembling a partially shaving portion, and a die as a single casting. It means a broad concept that includes a mold that is made by assembling a partially cast part, and a mold that is made by assembling a machined part and a cast part.

<Slit-shaped steam hole>
Further, in the core type 2 and the cavity type 3, slit-shaped steam holes 4, 4, ... For communicating steam inside and outside are directly formed at the required points thereof. Such slit-shaped steam holes 4, 4, ... Are formed by cutting with a machining center equipped with a metal saw as a tool, or by removing with a laser machine or a wire electric discharge machine.
The slit-shaped steam holes 4, 4, ... Are formed on the outer surface side and / or the inner surface side of the required points of the core type 2 and the cavity type 3.
Here, since the slit-shaped steam holes 4, 4, ... Arranged on the side surfaces of the core mold 2 and the cavity mold 3 are provided along the opening / closing direction of the mold, the molded product is molded in the mold. After that, when the mold is opened and the molded product is separated from the mold, the surface of the molded product bites into the steam holes 4, 4, ... It is difficult for the surface of the molded product to get caught and scratched.

The width A of the slit-shaped steam holes 4 shown in the enlarged front view of the main part of FIG. 3 is in the range of 0.1 mm to 0.7 mm, and the distance B between the slit-shaped steam holes 4 and 4 is in the range of 10 mm to 50 mm. Yes, the length of the slit-shaped steam hole 4 is in the range of 20 mm to 100 mm.
The intervals B of the steam holes 4 and 4 may be equal intervals or unequal intervals.
In the present invention, the average aperture ratio of the slit-shaped steam holes 4, 4, ... (total opening area on the molding chamber side of the steam holes 4, 4, ... ÷ total surface area on the molding chamber side x 100 (%)) is 0.5. % Or more and 1.0% or less.
The average aperture ratio is more preferably 0.6% or more and 0.9% or less, and most preferably 0.7% or more and 0.8% or less.

To show an example of the average aperture ratio, in a square area of 100 mm × 100 mm,
(1) There are three slit-shaped steam holes 4 having a width A of 0.35 mm and a length of 48 mm, and the average aperture ratio is 0.504%.
(2) There are three slit-shaped steam holes 4 having a width A of 0.4 mm and a length of 50 mm, and the average aperture ratio is 0.6%.
(3) There are four slit-shaped steam holes 4 having a width A of 0.4 mm and a length of 50 mm, and the average aperture ratio is 0.8%.
(4) There are six slit-shaped steam holes 4 having a width A of 0.3 mm and a length of 50 mm, and the average aperture ratio is 0.9%.
(5) There are six slit-shaped steam holes 4 having a width A of 0.35 mm and a length of 47 mm, and the average aperture ratio is 0.987%.
become.

Further, as shown in FIGS. 1, 2A and 2B, in the core type 2 or the cavity type 3 in which the slit-shaped steam holes 4, 4, ... Are formed, a recess is formed around the slit-shaped steam holes 4, 4, .... There is no. Therefore, there is no dent in which the cooling water stays on the surface opposite to the molding space formed by the core mold 2 and the cavity mold 3.

<Comparison experiment between a mold with steam holes by direct forming slit and a mold with steam holes by core vent>
Next, a comparison was made between a molded product of foamed synthetic resin manufactured using a mold provided with steam holes by a directly formed slit and a molded product of foamed synthetic resin manufactured using a mold provided with steam holes by a core vent. The results of the experiments conducted will be explained.

An example of the bead method foamed synthetic resin molding mold 1 (core mold 2 and cavity mold 3), which is a mold provided with steam holes by directly forming slits, is a perspective view of FIG. 1, a perspective view of FIG. 2A, and FIG. 2B. It is as shown in the plan view of.
Further, an example of the bead method foamed synthetic resin molding die 1'(core die 2'and cavity die 3'), which is a die provided with steam holes by the core vent, shows a state before the core vent is driven. It is as shown in the perspective view, the perspective view of FIG. 5A, and the plan view of FIG. 5B, and the same reference numerals as the perspective view of FIG. 1, the perspective view of FIG. 2A, and the plan view of FIG. 3B indicate the same parts or parts. ,
In the mold 1'provided with steam holes by the core vent, the vent holes 8, 8, ... Of the core mold 2'in FIG. 4 and the vent holes 8, 8, ... Of the cavity mold 3'in FIG. 5A are shown in FIG. A steam hole is formed by driving the core vents 9, 9, ... As shown in the enlarged front view of the main part.

(Examples and comparative examples)
Under the molding conditions shown in Table 1, in Examples 1 to 7 shown in Table 2, a molded product was manufactured using a mold provided with steam holes by a direct forming slit, and in Comparative Examples 1 to 7 shown in Table 2, a core vent was used. A molded product was manufactured using a mold provided with steam holes, and the molded product sizes of Example N and Comparative Example N (N = 1, 2, 3, ..., 7) were made the same.
The molded product of Example 3 and Comparative Example 3 is the lid of the heat insulating container, and the other molded products are the container body of the heat insulating container.

As shown in Table 2, the average opening ratio of the steam holes (total opening area on the molding chamber side of the steam holes ÷ total surface area on the molding chamber side × 100 (%)) was set smaller in the examples than in the comparative example.
That is, in Examples 1 to 7, the average aperture ratio of the steam holes (“directly formed slits”) is 0.65% to 1.00% for the cavity type and 0.59% to 0.77% for the core type. be.
On the other hand, in Comparative Examples 1 to 7, the average aperture ratio of the steam holes (“core vents”) was 1.27% to 1.94% for the cavity type and 1.05% to 1.90% for the core type. be.

(Experimental result: fusion rate)
The molded product was broken and the fusion rate was visually confirmed.
As a result, in all of Examples 1 to 7 and Comparative Examples 1 to 7, there was no deterioration in the fusion of the molded products.

(Experimental result: strength)
The strength of the molded product was measured by a strength tester using a TEAC TD-250T digital indicator and a pneumatic cylinder.
As a result, in all of Examples 1 to 7 and Comparative Examples 1 to 7, there was no decrease in the strength of the molded product.

From the above experimental results, the ratio (A / B) of the average aperture ratios of the examples and the comparative examples in Table 2 is 0.37 to 0.70 for the cavity type and 0.33 to 0.70 for the core type. A mold provided with steam holes by a directly formed slit can have a significantly lower average opening ratio of steam holes than a mold provided with steam holes by a core vent, and even if it is lowered, fusion is possible. It can be seen that there is no deterioration or decrease in strength.
Therefore, in the present invention, the average aperture ratio of the slit-shaped steam holes 4, 4, ... Is set to 0.5% or more and 1.0% or less.

The reason why the average opening ratio of steam holes can be lowered by using a mold having steam holes by directly forming slits is that the wall surface of the mold forming vent holes like a mold having steam holes by core venting. Since there is no contact heat resistance between the core vent and the core vent driven into the vent hole and the wall thickness (for example, 1.5 mm) is not thin like the slit part of the core vent, the area where the wall surface of the steam hole comes into contact with steam becomes large. This is thought to be due to the fact that the mold can be heated efficiently.
In addition, since there is no dent on the surface opposite to the mold molding space where cooling water stays, the mold temperature does not drop more than necessary during vacuum cooling, so the mold temperature can be kept high. ..

Therefore, even if the average opening ratio of the slit-shaped steam holes is lowered, the fusion does not deteriorate or the strength does not decrease, and the mold can be heated to the required temperature with a small amount of steam. Therefore, the average opening ratio is set to 0.5. By setting the percentage to 1.0% or more, energy saving can be achieved.
Further, even if a resin having a low melting point is used for the purpose of saving energy, heat does not accumulate in the vicinity of the wall surface of the steam hole, so that the resin is less likely to stick.
Further, by reducing the number of slit-shaped steam holes and / or reducing the width of the slit-shaped steam holes, the beauty of the surface of the molded product can be further enhanced.

All the descriptions of the above embodiments are examples, and the present invention is not limited thereto. Various improvements and changes can be made without departing from the scope of the present invention.

1,1'Bead method Foam synthetic resin molding mold 2,2'Core type 3,3' Cavity type 4 Slit-shaped steam hole 5 Raw material filling port 6 Release pin opening 7 Drain piece 8 Vent hole 9 Core vent A Slit-shaped steam hole width B Spacing between adjacent steam holes

Claims (2)

A molding space formed by a pair of molds consisting of a core mold and a cavity mold is filled with foamed beads made of a thermoplastic resin, and the foamed beads are heated with steam to be fused, cooled and dried to foam the required shape. Bead method for obtaining a molded product of synthetic resin The mold used for molding a foamed synthetic resin.
A slit-shaped steam hole formed directly in the mold itself for allowing the steam to pass through the inside and outside of the mold to the required portion of the three-dimensional mold formed by cutting and / or casting. Have,
A bead method foamed synthetic resin molding die characterized in that the average opening ratio of the slit-shaped steam holes is 0.5% or more and 1.0% or less. The molding space formed by the bead method foamed synthetic resin molding mold according to claim 1 is filled with foamed beads of a thermoplastic resin, and the foamed beads are heated with steam to be fused, cooled and dried. Bead method for manufacturing a molded product of a foamed synthetic resin having a required shape. A method for manufacturing a molded product of a foamed synthetic resin.

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