JPH0929750A - Foam molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a molding with clear surface and without deformation and to shorten a molding cycle by preventing the deformation of a porous electroforming mold at the time of molding in a foam molding machine using the porous electroforming mold as an inner mold. SOLUTION: The foam molding machine comprises a pair of molds 10, 20, wherein a porous electroforming mold 21 is provided on the inner surface of either one or both, a reinforcing member 22 is disposed on its rear surface, the open area ratio of the mold 21 per unit area is about 1 to 8%, the mean diameter of the vent holes is about 1 to 300μm, the open area ratio of the member 22 per unit area is about 10 to 98%, and further the product of the open area ratios of the electroforming mold and the member is in a range of about 0.5 to 8.0%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam molding apparatus, and in particular, in in-mold foam molding of a thermoplastic resin, it prevents transfer of the shape of the vent hole to the surface of the molded product and has a high designability. The present invention relates to an improved foam-molding device that makes it possible.

[0002]

2. Description of the Related Art In-mold foam molding of thermoplastic resin is usually
It is performed by filling pre-expanded particles of a thermoplastic resin in a molding chamber formed by a pair of molding dies and heating with steam. A vent hole for supplying steam into the molding chamber is formed on the inner surface of the molding die, and the steam from the heating source is supplied from the vent hole to heat-mold the filled thermoplastic resin pre-expanded particles. In this molding method, it is unavoidable that the shape of the vent hole is transferred to the molded product, and the appearance of the molded product is impaired in design.

In the foam molding apparatus of this type which is generally used at present, the vent holes are formed on the molding surface of the mold with a diameter of about 10 mm and a pitch of about 30 mm to 50 mm. Furthermore, in order to prevent pre-expanded particles from entering the vent holes and to reduce the influence of the transfer of the vent holes on the molded article to some extent, a narrow slit is formed in the vent holes. Steam is ejected into the molding chamber through the slit. Therefore, the actual aperture ratio per unit area in the commonly used foam molding die is 0.
It is usually between 5% and 2%.

As a foam molding method which avoids the influence of transfer due to the vent holes, it has been proposed to use a porous structure in a molding die. For example, JP-A-63-317323
In the publication, either one or both of a pair of molds is used as a mold having an air-permeable porous structure, and steam is blown into the mold through the air holes of the air-permeable porous structure. A method for forming a foam is shown in which the styrofoam beads that have been pre-expanded and are pre-expanded are heat-welded, in which porous electroforming and ceramic powder are used as the air-permeable porous structure. It is described that a bonded product or a product obtained by heating and curing a metal powder with a resin can be used. According to this molding method, if the steam is vented into the mold through the vent holes of the air-permeable porous structure, the surface of the molded article will be smooth.

Further, Japanese Unexamined Patent Publication No. 6-320634 discloses an in-mold foam molding mold comprising a first mold and a second mold, wherein the inner surface of the first mold and the second mold are At least one of the inner surface is described as a molding die for thermoplastic resin mold in-molding in which a breathable porous electroformed Naka mold is provided, and according to this molding die, a Naka breathable porous electroformed thing is used. It is described that, by using it, it is possible to obtain a molded product having a fine and complicated three-dimensional shape, and to obtain a molded product having an appearance without a vent hole mark. In addition, as the porous electroforming, a sheet-shaped one having a wall thickness of 10 μm or more can be used, and when a thin one is used, in order to prevent deformation of the Naka mold during molding, a conventional Naka mold is used. It may be used as it is, and a breathable porous electroformed Naka mold may be disposed on the Naka mold.

Further, the aperture ratio per unit area of porous electroforming which is actually used in a foam molding apparatus using a breathable porous electroformed Naka mold is about 0.1% to 10%, which is a strength factor. Considering the above, about 8% is the maximum.

[0007]

The present inventors have many achievements in foam molding of thermoplastic resins and have conducted many studies on the above-mentioned porous electroformed molds. Porous electroforming has a wall thickness of 10 μm to 4 m
Sheets of about m in size are easy to obtain, while thicker ones are difficult to manufacture. Therefore, when foam electroforming is carried out by using porous electroforming alone as a molding Naka die, In foam molding with a relatively low expansion ratio of ~ 20 times, since the central part of the porous electroforming mold deforms like a Tyco due to foaming pressure, some reinforcing member is placed on the back part as described in the previous application. I experienced that it was necessary to suppress the deformation.

Therefore, when the conventional Naka mold is used as it is as the reinforcing member and the porous electroformed mold is arranged thereon, as described above, the unit area of the conventional mold is reduced. Has an opening ratio of about 0.5% to 2%, the actual opening ratio on the molding surface of the porous electroforming mold is significantly reduced to about 0.0005% to 0.16% to obtain a good molded product. It has been found that it is not possible and that the time required for molding becomes long.

Accordingly, an object of the present invention is to provide a foaming mold that solves the above-mentioned disadvantages that occur when foaming is carried out using a mold having a porous electroforming mold inside.

[0010]

The present invention has been made to solve the above problems, and a reinforcing member is arranged on the back surface side of the porous electroforming mold to prevent deformation of the porous electroforming mold during molding. In the foam molding apparatus, a reinforcing material having a specific opening ratio is used as the reinforcing member.

That is, the foam molding apparatus according to the present invention is
A foam molding apparatus having a pair of molding dies, a porous electroforming mold provided on one or both of the inner surfaces thereof, and a reinforcing member arranged on the back surface thereof, wherein the aperture ratio per unit area of the porous electroforming mold is 1% to 8%, the average diameter of the ventilation holes is 1 μm to 300 μm, the aperture ratio per unit area of the reinforcing member is 10% to 98%, and
The product S of the aperture ratio of the porous electroforming mold and the aperture ratio of the reinforcing member S
Is about 0.5% to 8.0%.

When the foam molding apparatus according to the present invention is used, a high foaming pressure, particularly when foam molding with a relatively low expansion ratio of 3 to 20 times, a mixture or copolymer of polystyrene and polyphenylene ether, It prevents the deformation of the porous electroforming mold (that is, the deformation of the molded product) against the high vapor pressure required for foam molding of a copolymer of polystyrene and maleic anhydride, etc. It is possible to obtain a molded product with a high appearance and a high design. Further, since it is possible to maintain the same or higher opening ratio in the molding surface of the porous electroforming mold as a foam molding apparatus having a conventional vent hole, the molding cycle can also maintain the conventional time or can be further shortened, Productivity is also improved. Further, therefore, the quality of the molded product does not deteriorate.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a foam molding apparatus according to the present invention will be described below with reference to the drawings. FIG.
FIG. 2 is a sectional view showing an embodiment of a foam molding apparatus according to the present invention, FIG. 2 is a perspective view showing an embodiment of a reinforcing member,
FIG. 3 is a diagram illustrating a state in which a porous electroforming mold is arranged on the back surface of the reinforcing member shown in FIG.

The foam molding apparatus A has a first molding outer die 10 which is a fixed side, and a second molding outer die 20 which can be separated from the molding outer die 10 by a moving device (not shown). . A first molding Naka mold 11 is arranged on the molding side surface of the molding outer mold 10, and a diameter 10 is formed in the molding Naka mold 11.
Vent holes (steam holes) 12 of about mm are formed on the substantially entire surface at a pitch of about 35 mm. In addition, this molding mold 1
1 may be the same as that used in conventional foam molding equipment.

A molding inlet 13 is formed on one end side of the first molding outer die 10 and a drain port 14 is formed on the other end side thereof, and its side wall and the molding Naka mold are formed. A feeder 15 for supplying the thermoplastic resin pre-expanded particles is arranged so as to penetrate through 11. In the figure, 16
Is a support rod for preventing deformation of the first molding Naka mold 3 due to molding pressure during foam molding.

On the molding side surface of the second outer molding die 20, a porous electroformed Naka mold 21 which is a surface for forming a molded product and a reinforcing member 22 having a shape closely contacting the back surface of the porous electroformed Naka mold 21 are formed. Are placed. In the illustrated example, the reinforcing member 22
Is a portion in which the peripheral portion 22a is in close contact with the first molding Naka die 11 arranged in the first molding outer die 10, and a concave portion is formed from there to the central portion.
Of the molding mold 11 and the peripheral portion 22a of the reinforcing member 22
The molding chamber 30 is formed there by abutting against each other.

Further, similarly to the first molding outer die 10, a molding inlet 23 is formed on one end side of the second molding outer die 20, and a drain port 24 is formed on the other end side thereof. In addition, the support bar 1 is similarly provided on the back side of the reinforcing member 22.
6 are arranged. The reinforcing member 22 may be made of the same material as a Naka mold used in a conventional molding die (aluminum casting material, muku material, etc.), and the molding surface side of the reinforcement member 22 may be made of a conventional material. Similarly, the vent holes (vapor holes) 25 having a diameter of about 8 mm are formed on the substantially entire surface at a pitch of about 30 mm. Preferably, a large number of vent holes 25 may be provided within a range allowed by the strength. As shown in FIGS. 2 and 3, a concave groove 26 having a predetermined width and depth (preferably a width and a depth of about 2 to 10 mm) is formed on the surface of the reinforcing member 22 on the molding surface side. Is formed vertically and horizontally with a constant bitch,
As a result, the rectangular protrusions 27 are formed, and the aperture ratio per unit area on the molding surface side of the reinforcing member 22 is 10%.
% To 98%.

As described above, the sheet-like porous electric mold 21 is arranged on the molding surface side of the reinforcing member 22 so as to follow the shape thereof. In the present invention, the porous electroforming mold 21 has an average diameter of 1 μm through which vapor or air can pass.
Opening rate of 1 to 300 μm vent hole 21a per unit area
% To 8%, and the thickness thereof is about several tens of μm to 4 mm. The required thickness is calculated from the required strength and the receiving pitch, but the thicker it is, the higher the cost may be. Therefore, 100 μm to 1 m is preferable.
m.

The foam molding by the thermoplastic resin pre-expanded particles using the foam molding apparatus described above is basically performed by the same procedure as the conventional one, and a detailed description thereof will be omitted. In FIG. 3, S indicates a part of the thermoplastic resin pre-expanded particles supplied into the molding chamber 30. In the foam molding apparatus of the present invention, when the porous electroforming mold 21 and the reinforcing member 22 as described above are laminated as shown in FIG. 3, the substantial opening ratio of the porous electroforming mold 21 on the side facing the molding chamber 30 is: It is calculated as the product of both aperture ratios, and the value is
If the opening ratio of the molding surface of the conventional thermoplastic resin pre-expanded particles is about 0.5% or more, molding can be performed in the same molding cycle as before, and at the same time, the surface of the molded product Since the vent hole is not transferred and the back surface of the porous electroforming mold 21 is held by the reinforcing member 22, the molded product is not deformed.

Further, in the case of a molding apparatus using a conventional porous electroforming mold as a Naka mold, even if the porosity electroforming has an opening ratio of about 8%, no trace of the opening is left on the surface of the molded product. It is known that high quality molded products can be obtained, and thus the substantial aperture ratio may be about 8% at maximum. The opening ratio of the molding surface of the conventional thermoplastic resin pre-expanded particles in the foam molding device is at most 2% in consideration of the trace of the vent hole being transferred to the molded product.
Considering that it is up to a degree, the real aperture ratio is 2% ~
When it is 8%, it can be expected that the molding cycle is shortened more than ever. Even in this case, since the back surface of the porous electroforming mold is held by the reinforcing member, the molded product is not deformed.

That is, in the present invention, as the Naka-type, the open area per unit area is in the range of about 1% to 8%, and the average diameter of the vent holes is in the range of about 1 μm to 300 μm. , Aperture ratio per unit area is about 10%
˜98% of the reinforcing member is appropriately selected and combined, and the porous electroforming mold has a substantial aperture ratio of about 0.5% to 8.0.
By setting the content to be in the range of%, it is possible to obtain a foam-molded product having a beautiful appearance, high designability, and unnecessary deformation in a production cycle that is the same as or shorter than the production cycle of conventional foam-molding equipment. Become. The maximum aperture ratio of the reinforcing member is set to about 98% because the remaining 2% is the area required to support the porous electroforming mold from the back surface.

The resin species of the thermoplastic resin pre-expanded particles used in the foam molding apparatus of the present invention include, for example, propylene homopolymer, ethylene homopolymer, and ethylene-polymer.
Propylene copolymer, ethylene-butene copolymer,
Polyethylene resin such as ethylene-propylene-butene copolymer, propylene-butene copolymer, propylene-vinyl chloride copolymer, propylene-maleic anhydride copolymer, polyolefin resin such as polypropylene, polystyrene, polymethylstyrene, styrene-
Acrylonitrile copolymers, styrene-based resins such as styrene-maleic anhydride copolymers, mixed resins of styrene-based resins and polyphenyl ether-based resins, vinyl chloride-based resins, polyamide-based resins, and the like, but are not limited to such resins. There is no such thing. Among these thermoplastic resins, in the present invention, the above heat-resistant styrene resin can be particularly preferably used.

In addition, the pre-expanded particles can be supplied from the feeder into the molding chamber by the same method as in the conventional foam molding method, and the heating steam supply method and the heating temperature are the same as those in the conventional foam molding method. May be similar to.

[0024]

EXAMPLES Next, a molded article obtained by using the foam molding apparatus of the present invention will be described based on examples, but the present invention is not limited to the examples. Example 1 In-mold foam molding was performed using a foam molding apparatus having the shape shown in FIG. This molding device is the same device as the foam molding device described with reference to FIG. 1, but the molding side surfaces of the first molding naka mold 11 and the second molding outer mold 20 arranged in the first molding outer mold 10. The difference is that the molding surfaces of the porous electro-mold 21 are flat.

The molding die 11 has a diameter of 8 mm.
Vent holes (with slits) 12 are arranged at a pitch of 35 mm, and the reinforcing member 22 is a square of 5 mm square formed by processing a groove 26 having a width of 20 mm and a depth of 5 mm at a pitch of 5 mm as shown in FIG. Forming a protrusion 27 of the groove 26
A vent hole 25 having a pitch of 50 mm and a diameter of 8 mm was formed at the center of the. On top of this, the aperture ratio per unit area is about 3%
The average diameter of the vent holes 21a was about 200 μm, and the plate-shaped porous electroformed mold 21 having a thickness of 2 mm was attached.

Heat cell S2005 (product name of Sekisui Plastics Co., Ltd., foaming ratio: 5 times) as pre-expanded particles of heat-resistant styrene resin is charged into the molding chamber 30 through the feeder 15 in the above foam molding apparatus. did. Water vapor from the inlet 13 of the first outer mold 10 (vapor pressure 0.4 kg / cm
² G, temperature 75 ° C.) is introduced into the molding chamber 30 for 20 seconds, and then steam (vapor pressure 0.8 kg / cm ² G, temperature 93 ° C.) is introduced from the inlet 23 of the second outer mold 20. 1
After being introduced for 5 seconds, steam (vapor pressure: 3.2 kg / cm ² · G, temperature: 135 ° C.) was introduced into the molding chamber 30 from both inlets 13 and 23 for 20 seconds.

Next, after cooling water was introduced from both inlets 13 and 23 to cool it, the mold was opened to obtain an in-mold foam molded article.
When this molded product was visually observed, it was a good molded product having a smooth surface with no slit marks. The fusion rate measured by a destructive test was 90%. [Comparative Example] As a foam molding apparatus, in place of the reinforcing member 22 used in the foam molding apparatus of Example 1, a conventional molding mold (a vent hole having a diameter of 10 mm formed with a pitch of 30 mm) was used. The porous electroforming mold used in Example 1 (thickness: 2 mm, vent hole diameter: 200 μm, opening ratio: 3%) was attached thereto, and molded under the same conditions as in Example 1,
An in-mold foam molded product was obtained.

This molded body could not sufficiently supply steam at the time of molding, so that the surface of the molded body had irregularities. Further, when the fusion rate was measured by a destructive test, it was 90% in Example 1, whereas it was 50% in this molded product, which was not usable in actual use. The reason for this is that the opening ratio of the conventional molding mold is about 1.5%.
If a porous electroforming mold with an opening ratio of about 3% is brought into close contact with this, the actual opening ratio will be about 0.05%, and as a result, the amount of steam required for foam molding will be insufficient and sufficient foam molding cannot be performed. It is thought that the arrival rate has decreased.

[0029]

EFFECT OF THE INVENTION According to the foam molding apparatus of the present invention, not only a product with high designability can be obtained without leaving traces of vent holes on the surface of the obtained molded product, but also undesired deformation of the molded product. Moreover, it becomes possible to perform molding in a shorter molding cycle.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a foam molding apparatus according to the present invention.

FIG. 2 is a perspective view showing an example of a reinforcing member.

3 is a diagram illustrating a state in which a porous electroforming mold is arranged on the back surface of the reinforcing member shown in FIG.

FIG. 4 is a cross-sectional view showing a foam molding device used in Examples.

[Explanation of symbols]

A ... Foam molding device, 10 ... First molding outer mold, 20 ... Second
Molding outer mold, 30 ... Molding chamber, 21 ... Porous electroforming mold, 2
2 ... Reinforcement member

Claims (1)

[Claims] 1. A foam molding apparatus comprising a pair of molding dies, wherein a porous electroforming mold is provided on an inner surface of one or both of the molding dies, and a reinforcing member is arranged on the back surface thereof, wherein a unit area of the porous electroforming mold. The opening ratio per unit area is about 1% to 8%, the average diameter of the vent holes is about 1 μm to 300 μm, and the opening ratio per unit area of the reinforcing member is about 10%.
The expansion molding apparatus is characterized in that the product of the opening ratio of the porous electroforming mold and the opening ratio of the reinforcing member is in the range of about 0.5% to 8.0%.