JPH08155999A - Bead foaming molding method and bead foamed molded form - Google Patents

Abstract

PURPOSE: To obtain a foamed molded form in which a thick part is sufficiently foamed and fusion-bonded and which has excellent external appearance by inserting a vapor introducing tube from the surface of the form where the appearance is not important, and introducing the vapor into foamed bead via the vapor injection hole of the tube. CONSTITUTION: A vapor introducing tube 15 is inserted from the lower side 14 of a mold, and heated vapor is introduced from a vapor source via the tube 15. Many vapor injection holes are formed at the tube 15. The tube 15 uses a tube of stainless steel or copper alloy having a diameter of about 2 to 30mm. Foamed bead 11 charged in the cavity of a mold 10 in this state is heated by the vapor introduced via the holes to be foamed and fusion-bonded to obtain a desired foamed form.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a bead foam molding method using beads of a thermoplastic resin containing a foaming agent, and a bead foam molding obtained by such a bead foam molding method.

[0002]

2. Description of the Related Art In order to mold various foamed resin molded products made of engineering plastics called high-performance resins, including thermoplastic resins such as polystyrene and polypropylene, resin particles containing a foaming agent in the material are used. Bead foam molding with some expanded beads is utilized.

In ordinary bead foaming molding, a required amount of foamed beads is filled in a mold, and heating steam is introduced to heat and expand the beads, and the foamed beads are partially melted and fused to each other. By doing so, the molding is performed.

In such bead foam molding, molded products having various expansion ratios can be obtained depending on the blending amount of the foaming agent.
There is a feature that it can reduce the weight. Further, a molded product having a relatively large volume can be obtained, and many uses are considered.

However, in the bead foam molding, a mold provided with a large number of slits for introducing steam is used.
Therefore, the traces of the slits remain, and the surface appearance of the molded product is often inferior.

In the conventional bead foam molding, as shown in FIG. 6, steam is introduced from the steam introduction slit 101 through the steam jackets 103 provided on both side surfaces of the mold 100 and heated to foam the expanded beads 102. There are many things. However, there is a problem that sufficient heating cannot be secured in a portion having a small vapor flow rate such as a partially thickened portion, and a sufficient foaming and fusion state cannot be obtained. If the heating time is simply lengthened or the steam flow rate is increased to cope with the problem, the molding cycle becomes long, which is against the demand for cost reduction, which is not preferable.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the drawbacks of the foam molding of beads according to the prior art, sufficiently expands and fuses the thick portion, and obtains a foam molded article having a good surface appearance. An object of the present invention is to provide a bead foam molding obtained by this.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to insert a steam introducing tube in a bead foam molding die from a surface where the appearance of a molded article is not considered, and to install one or a plurality of steam introducing tubes. A bead foam molding method for performing foam molding in which steam is introduced into the foam beads through the steam ejection holes and the foam beads are foamed by sufficiently spreading the steam, and a foam molded body foamed by the method. Will be resolved.

The vapor introducing tube may be a metal thin tube provided with a large number of vapor ejection holes around the metal thin tube, and an appropriate number of the vapor introducing tubes may be provided upright. Further, long and short metal thin tubes can be set upright, and steam can be introduced through the steam ejection holes at their tips.

[0010]

According to the bead foam molding method of the present invention,
Fill a predetermined amount of foamed resin beads in the mold cavity,
A steam introduction tube is inserted through an opening provided in a mold on the side that is not important in appearance, and steam is introduced through this steam introduction tube. The expanded beads are heated by the amount of heat of the steam thus introduced, and the surface of the beads is melted simultaneously with the foaming action of the foaming agent contained therein. As a result, the rise of the internal pressure of the cavity due to the foaming action and the molten state of the bead surface layer are combined to cause fusion between adjacent beads.

Further, in the bead foam molding method according to the present invention, the steam can be easily introduced to the deepest part of the expanded beads by the steam introduction tube. Therefore, even a molded product that partially includes a thick portion can be advantageously molded by shortening the molding cycle. The length of the steam introducing tube, the number of standing tubes, and the like can be appropriately changed depending on the desired shape and size of the molded body.

After the heating required for foaming and fusing has progressed, even if the steam introducing tube is removed, the fusing of the surface of the foam beads can proceed and be completely closed due to the residual heat.
There is no problem of strength reduction or deformation of the traces of the steam introduction tube. However, the trace of the opening formed on the mold surface for inserting the steam introduction tube may remain, so it is desirable to form it on a surface that poses no problem in appearance as much as possible.

Contrary to blocking the extraction mark of the steam introducing tube as described above, it is also possible to positively form the through hole by delaying the extraction timing of the steam introducing tube. By using the through-holes thus formed, a molded body containing the bead foam molded body can be molded by, for example, vacuum molding or vacuum pressure molding.

[0014]

The present invention will be disclosed below with reference to the accompanying drawings showing the embodiments. FIG. 1 is an explanatory view showing the basic principle of the bead foam molding method according to the present invention. The mold 10 is a bead foam molding mold. The mold cavity is filled with foam beads 11 in which a predetermined amount of a foaming agent is blended with a thermoplastic resin according to the purpose and application. The upper part 12 of the mold in this embodiment is not provided with a slit for introducing steam, and is provided with an appropriate number of small openings 13 for discharging steam, which are much smaller than the slit.

A steam introducing tube 15 is inserted from the lower side portion 14 of the mold in FIG. 1, and heating steam is introduced from a steam source (not shown) through the steam introducing tube 15. This steam introducing tube 15 is shown in FIG.
As shown in, a large number of steam ejection holes 16 are formed. In this case, the number of the steam ejection holes 16 may be, for example, about 1 to 3 near the tip portion, or a large number may be formed over an appropriate length as shown in the drawing. Further, the diameter of the steam ejection hole 16 can also be appropriately changed depending on the application, the steam conditions used, and the like.

As the vapor introducing tube 15 in this case, a tube made of stainless steel or a copper alloy and having a diameter of 2 to 30 mm can be used. Also, the diameter of the steam ejection hole 16 is
It can be about 0.1 to 3 mm. It is also possible to use a material having a high heat resistance other than metal, for example, a tube made of polytetrafluoroethylene.

FIG. 3 shows another embodiment, which is a mold 20.
No upper opening 22 is provided with a small opening for discharging steam. The steam introduced from the steam introducing tube 25 gives the retained heat amount to the foam beads 21 filled in the mold, and then is discharged to the outside from the lower part 24 of the mold 20.
Length of steam introducing tube 25, effective inner diameter, steam ejection hole 2
Sufficient foaming by considering the number and diameter of 6
Foam molding with fusion can be performed.

FIG. 4 shows still another embodiment,
Similar to the embodiment of FIG. 3, the upper portion 32 of the mold 30 is not provided with a small hole for discharging steam. The vapor introducing tube 35 inserted from the lower side portion 34 is deeply inserted until it reaches the cavity inner surface of the upper side portion 32. A foam molded article can be obtained by heating the foam beads 31 filled in such a state with steam to cause foam fusion.

As shown in FIG. 5, the foamed molded body 36 thus obtained is provided with a through hole 37 from which the vapor introducing tube 35 is removed. These through holes 37
By utilizing the foamed molded body 36 as a core material, it is possible to carry out secondary processing such as coating a sheet or film of a suitable material on the surface, for example, pressure molding or vacuum pressure molding.

Since it is clear that the surface appearance is inferior and the strength is inferior no matter what resin is used as the base material of the expanded beads, the exterior sheet is formed by vacuum forming or vacuum pressure forming as described above. It is significant to expand the application of the foam molding of beads.

In this case, the sheet exterior material to be used may be a plastic sheet other than those mentioned above, for example, an acrylic resin sheet which is rich in weather resistance and hardly scratches, or a flexible polyester elastomer sheet.

Further, in applications such as automobile interior materials where importance is attached to decorativeness, an exterior material which emphasizes softness can be used. When such a different sheet exterior material is used, good adhesion can be achieved by providing an adhesive layer such as hot melt on the side in contact with the foam beads.

[0023]

According to the bead foam molding method of the present invention, neither the steam introduction hole nor the steam discharge hole that leaves a trace on the surface of the molded product is formed on the side where the surface appearance is important. If it is unavoidable to form steam discharge holes,
Try to form a very small diameter discharge hole. As a result, the surface appearance of the foam-molded product is significantly improved.

Inside the bead foam molding as described above,
If it is not necessary to leave the through-hole by the steam introduction tube, by removing the steam introduction tube at the time when the foam fusion progresses and the steam heating is almost completed, the fusion due to the foam internal pressure and the residual heat is almost eliminated. It can be closed without leaving any traces. On the contrary, when it is desired to form the through hole by the steam introducing tube, it is possible to delay the removal of the steam introducing tube so as to take it out after the temperature of the molded body decreases.

The through hole formed in the molded body obtained by the molding method according to the present invention is advantageous when performing pressure-pressure molding or vacuum pressure-pressure molding.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a main part when a bead foam molding method according to the present invention is carried out.

FIG. 2 is an explanatory view showing a configuration example of a steam introducing tube when the bead foam molding method according to the present invention is carried out.

FIG. 3 is an explanatory view showing another configuration of a main part when the bead foam molding method according to the present invention is carried out.

FIG. 4 is an explanatory view showing still another configuration of the main part when the bead foam molding method according to the present invention is carried out.

5 is a perspective view showing the structure of a foam molded article obtained by the bead foam molding method shown in FIG. 4. FIG.

FIG. 6 is an explanatory view showing an aspect of bead foam molding in a bead foam molding method according to a conventional technique.

[Explanation of symbols]

 10, 20, 30 Mold body 11, 21, 31 Foamed beads 12, 22, 32 Upper part 13 Steam discharge opening 14, 24, 34 Lower part 15, 25, 35 Steam introduction tube 16 Steam ejection hole

Claims (6)

[Claims] 1. A bead foam molding mold (10, 20,
The steam introducing tube (15, 25, 35) is inserted from the surface of the molded product which does not give importance to the appearance of the molded product, and one or a plurality of steam ejection holes (1) provided in the steam introducing tube.
A method for foam-molding beads, characterized in that steam is introduced into the foam beads (11, 21, 31) via 6) and the foam is foamed by sufficiently spreading the steam. 2. The steam introducing tube (15, 25,
35) The method for foaming beads according to claim 1, wherein 35) is removed at an early stage to reduce or block the traces caused by the vapor introducing tube. 3. The steam introducing tube (15, 25,
35. The bead foam molding method according to claim 1, wherein the removal of 35) is delayed so that the traces of the vapor introducing tube remain as through holes. 4. The steam introducing tube (15, 25,
35) The bead foam molding method according to any one of claims 1 to 3, wherein 35) is a metal tube. 5. The steam introducing tube (15, 25,
35) is a non-metallic tube,
The bead foam molding method according to claim 1. 6. A bead foam molding die (10, 20,
The steam introducing tube (15, 25, 35) is inserted from the surface of the molded product which does not give importance to the appearance of the molded product, and one or a plurality of steam ejection holes (1) provided in the steam introducing tube.
The appearance of at least one surface is improved by introducing steam into the expanded beads (11, 21, 31) via 6) and performing foam molding to expand the expanded beads by sufficiently spreading the steam. A bead foam molding having a curved surface.