JPH01110926A - Molding die - Google Patents

Abstract

PURPOSE:To obtain a mold capable of molding at favorable mold release conditions, by forming the planar part of the die from a metallic mirror surface body possessing a large number of fine vent holes. CONSTITUTION:This die 10 forms a planar part comprised of a vast area on its cavity part 11. A molding surface of the planer part is provided with a metallic mirror body 12. The mirror surface body 12 is provided on the cavity part 11 so as to cover the surface of a suction and exhaustion hole 13 bored in the cavity part 11. The mirror surface body 12 is formed of an electroformed plate having a large number of fine vent holes 12a. With this construction, molding of a product superior in transparency and gloss properties becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a molding die used for molding a product having a relatively wide flat area, and in particular, a mold for molding a product using a polypropylene sheet at a temperature below the melting point. The present invention relates to a mold for molding that is effective when performing such molding.

[Prior Art] Conventionally, various products such as containers and lids have been molded from thermoplastic resin sheets using compressed air and/or vacuum molding machines.

Among these various molded products, for example, containers are used for packaging foods, medicines, etc., and therefore, it is desired that they have good transparency in order to increase their commercial value. Furthermore, in order to speed up the molding cycle of the product, it is also necessary to improve cooling of the product after molding. On the other hand, when a product is molded using a mold with a large flat area, it is necessary to prevent the flat area of the product from undulating in order to increase the commercial value of the product.

However, when molding a thermoplastic resin sheet, especially a polypropylene sheet, at a temperature below its melting point,
It is difficult to use a mold with a large flat area to mold a container or lid material having a large flat area into a good shape without undulations. In other words, the air remaining between the sheet and the mold acts as a heat insulating layer, causing uneven cooling and solidification by the mold.

Distortion remains on the flat surface of the molded product, resulting in waving and making it impossible to obtain a good product.

In view of these conditions and problems, conventionally ceramic molds were used to eliminate residual air, porous molds,
Molds with molding surfaces coated with polytetrafiloethylene (trade name: Teflon) resin, molds with roughened molding surfaces, etc. are used.

[Problems to be Solved] However, when the above-mentioned various molds are used for molding products having a large planar area, the following problems occur.

In other words, although ceramic porous molds eliminate the waving of molded products, they also cause poor transparency of molded products due to rough surface transfer, as well as a reduction in molding cycles due to poor thermal conductivity and insufficient cooling. # There was a problem with nature.

In addition, although molds whose molding surfaces are coated with Teflon resin have excellent mold releasability, it is insufficient to eliminate waviness due to roughening the surface and improving slippage between the sheet and the mold, and transparency due to rough surface transfer. There was also the problem that the

Furthermore, molds whose molding surfaces have been roughened by shot blasting, paper coating, etc. (the molds most commonly used to prevent waviness in molded products with wide flat areas) are effective at eliminating waviness. Although it shows some effect, it is still not sufficient, and there are also problems in that the mold releasability is not very good and transparency is reduced due to rough surface transfer.

In addition, JP-A-60-152692 and JP-A-61-104820 are examples of molds using electroformed plates having porous air permeability.

No. 61-104849, etc., but all of these have complicated shapes with many curved surfaces and fine patterns (irregularities) on the surface.
This is a mold for molding a product that has been transferred, and there is no mention of a mold with a wide flat surface.

The present invention was made in view of the above-mentioned circumstances in the prior art, and eliminates the problem of waviness in the flat surface of products such as containers and lids that have a relatively wide flat surface without reducing transparency. The object of the present invention is to provide a molding die that can perform molding with good mold releasability.

[Means for Solving Problems] In order to achieve the above-mentioned object, the molding die of the present invention has a flat part with a relatively large area on the molding surface, and at least the flat part is provided with fine ventilation holes. The metal mirror surface body is preferably formed of an electroformed body.

[Example] Embodiments of the present invention will be described below based on the drawings.

1 and 2 show an embodiment of the mold of the present invention, with FIG. 1 showing a longitudinal sectional view of the whole, and FIG. 2 showing an enlarged sectional view of the main parts.

In these drawings, 10 is a molding die, which is used as a mold in a hot plate type or preheating type compressed air and/or vacuum forming machine. This mold 10 has a cavity portion 11 formed with a flat portion having a relatively wide area in order to mold products such as containers and lids having a relatively wide flat portion. A metal mirror body 12 is provided on the molding surface that comes into contact with the flat thermoplastic resin sheet. This metal mirror body 12 is provided so as to cover the surface of the air intake and exhaust hole 13 formed in the cavity portion 11 toward the molding surface. Note that 14 is a cooling pipe.

The metal mirror body 12 is made of a metal, for example, an electroformed plate (body), having a large number of fine ventilation holes 12a. The sheet contacting surface of this electroformed plate, that is, the surface excluding the fine ventilation holes, has a mirror surface roughness of 13 or less, preferably 0.8S or less, more preferably 0.5S or less. In this way, it becomes possible to mold a product with excellent transparency and gloss.

Further, the size of the fine ventilation holes is usually 5 to 300 l, preferably about 10 to 150 l if necessary, and the number of ventilation holes is usually 10 to 1000 pieces/cm2, and 30 to 500 if necessary. It is preferable that the number of particles/C is about 2.

Furthermore, this electroformed plate (metal mirror surface body 12) can be lined with a material having good air permeability and thermal conductivity, such as metal powder or a sintered body of metal fiber, if necessary.

The manufacturing method for electroformed plates with such minute ventilation holes is as follows:
This can be done by a known method (for example, Japanese Patent Application Laid-open No. 1986-
No. 152692, No. 61-253392), these known methods are all aimed at forming a mold for molding, and are based on the electroforming method (referred to as "metsuki" in a broad sense in the present invention). Although molds with various complicated shapes have been obtained, the present invention is different in that a mold with a wide flat surface is obtained.

Here, an example of the procedure for forming the itM board is schematically shown as follows.

That is, prepare a base material such as glass, resin-coated polished metal plate, epoxy resin, etc. (Fig. 3(a)), and coat the shiny surface (mirror surface) of this base material with a metal with good conductivity and a material with poor conductivity. For example, spray a mixture of pasty silver lacquer, butyl acetate, and vinyl chloride lacquer onto a substrate to form a layer of more than 10 layers, and dry this to coat the substrate. By changing the amount of vinyl chloride lacquer used during the treatment, the conductivity of the substrate surface can be freely set, and as a result, the size and number of microporous holes can be freely controlled.

Next, the metal materials are nickel and chrome.

It is electrolyzed in a plating liquid bath together with plating materials such as iron and copper to form a plating layer with many microscopic vents (Fig. 3 (b)). In this case, no surfactant is added to the plating liquid. , facilitating the formation of vent holes. Further, the diameter of the ventilation holes increases as the plating progresses, resulting in excellent air permeability and surface gloss. The thickness of the plated surface is usually about 2 to 2 ha.

Thereafter, this plating layer is easily peeled off from the base material via the spray layer, forming an electroformed plate.

As the plating material, it is preferable to use nickel. This makes it possible to obtain an electroformed plate that has one surface that is smooth and glossy, and that has a large number of fine ventilation holes.

In the above embodiment, a metal mirror surface body 1 having a large number of fine ventilation holes is used.
2, an example using an electroformed plate has been described, but it is of course possible to use something other than an electroformed plate. For example,
Polishing of the surface of a metal plate with multiple holes such as sintered metal, etc., where a large number of micro holes are drilled by drilling with a laser etc. on a metal plate, and the surface is polished before and/or after. There are things that have been done.

In addition, in the molding die of the present invention, the flat part formed by the metal mirror surface body 12 is a concept that includes a completely flat part and a substantially flat part with a large curved surface. In addition, a metal mirror body 1 having such a shape may be partially formed with letters, numbers, or even figures or patterns.
No. 2 is very easy to process, regardless of which of the materials and manufacturing methods described above are used.

Furthermore, although the non-planar portion in the molding die of the present invention may be formed in the same manner as the planar portion, it is preferable that it is made of a general material normally used for molds, such as aluminum, and In order to improve the mold releasability after molding, it is also possible to perform treatment using an fa type agent.

The molding die of the present invention having the above configuration is suitable for molding containers, lid materials, etc. from sheets with excellent transparency and gloss, especially transparent crystalline resin sheets such as polypropylene. There is. Also, the thickness is 1001L ~ 3+a
+s, usually suitable for forming sheets of about 120 μL to 2 cm.

Next, a molding example using the molding die of the present invention and a molding example using a conventional mold will be shown.

0 Example of molding using the mold of the present invention ■ Sheet Idemitsu Furayray FG-100 (highly transparent polypropylene sheet) 200 g/EVA sealant) 50 g Nora laminate sheet: Haze 12% ■ Lid material for molded product container, flat part 100 mmφ, height 8■■ Gold
The flat surface of the mold cavity is made of iltM board, and the other parts are made of aluminum with a Teflon resin coating on the surface.

■ Aging mold machine Hot plate air pressure forming machine, Vacuum pressure forming machine It has been found that it is possible to mold a lid material that does not have drops and does not cause undulation on the flat surface. Moreover, the mold releasability was also good. This results in
It is now possible to form a low melting point sealant layer on the mold surface.

Furthermore, it was found that productivity could be improved because cooling was sufficient and the molding cycle was quick.

0 Molding Example Using Conventional Mold ■ The molding conditions were the same as those of the present invention except that a mold in which the entire cavity (including the plane part) was made of aluminum whose surface was coated with Teflon resin was used.

■Results/See Fig. 4■ Discussion Although the mold releasability is good, the transparency is reduced and the height (
h) It was found that there remained a problem in that the lid material was molded with 2 mm undulations, making it unusable as a product.

[Effects of the Invention] As described above, according to the molding die of the present invention, it is possible to obtain a high-quality molded product without reducing transparency and causing no waviness defects in the plane part, and moreover, It also has the effect of maintaining good moldability.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of the first example mold of the present invention, and Fig. 2 is a longitudinal cross-sectional view of the first example mold of the present invention.
FIG. 3(a) is an enlarged sectional view of the main part of the figure. (b) and (C) are explanatory views when forming an electroformed plate, and FIG. 4 shows a cross-sectional view of a molded product using a conventional mold. 1: Mold ll: Cavity part 12: Metal mirror surface body 12a: Micro ventilation hole 13: Intake and exhaust hole
14: Cooling pipe

Claims (2)

[Claims] (1) A mold having a relatively wide flat area on its molding surface, wherein at least the flat area is formed of a mirrored metal body having a large number of fine ventilation holes. (2) The molding die according to claim 1, wherein the mirror-finished metal body is an electroformed body.