JPH0299228A - Bulging method for resin laminated aluminium foil - Google Patents

Abstract

PURPOSE:To give a large deformation to a forming blank by locally heating the contact part between the forming blank and the top surface of a punch and advancing the deformation of the forming blank. CONSTITUTION:The peripheral end part of the blank 1 is inserted and held between a die 3 and a blank holder 4 and the contact part 1a between the blank 1 and the top surface 2a of the punch is heated locally and the punch 2 is advance toward the die 3 and deforms the blank. This heating reduces the strength of the contact part 1a and decreases the deformation resistance in time of bulging. Consequently, the spreadability of the forming stock 1 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses resin-laminated aluminum foil, in which a resin film is laminated on at least one side of the aluminum foil, as a material for manufacturing packaging containers for foods, cosmetics, electronic parts, etc. This invention relates to a stretch-molding method for stretch-molding the same.

Conventional technology Until now, the most common wrinkle-free containers for the above-mentioned uses have been deep-drawn molded products using aluminum foil with a thickness of around 100 μm or synthetic resin molded products. There is.

However, the former deep-drawn product not only has poor productivity, but also has the disadvantage of being expensive due to the use of thick foil. Furthermore, the latter resin molded products have the inherent disadvantage of poor barrier properties against moisture, oxygen, light, and the like.

Therefore, in order to deal with these problems, recently, resin-laminated aluminum foil, which is made by laminating a resin film on an aluminum foil with a thickness of about 30 to 50 μm, is used, and this is continuously molded into a container of a predetermined depth by stretch molding. The method of molding is attracting attention.

In this case, the above-mentioned molding is required to make the critical molding height as high as possible.

As a measure to cope with such demands, it is of course extremely important to select and improve the molding material, but on the other hand, the molding method and molding conditions also have a dominant influence on the molding height. As for the selection of the forming method, vacuum forming, which applies stress uniformly to the entire molding material, or bulge forming using air or oil, etc., are preferable for the purpose of simply increasing the forming height, but both are suitable for production. The flexibility and freedom of shape selection are poor. Therefore, as a molding method with excellent productivity, the use of stretch molding using a punch is considered to be the most promising.

By the way, in order to achieve the highest possible molding height in stretch molding with a punch, it is generally necessary to have good spreading properties on the top surface of the punch, that is, on the top surface that is in contact with the molded blank. For this purpose, it is said that it is advantageous to make the top surface a surface with as low a coefficient of friction as possible and with good sliding properties. For example, when molding is performed using a punch made of tetrafluoroethylene resin, which has a lower coefficient of friction than when molding is performed using a stainless steel punch, Generally, a relatively high critical molding height can be obtained, and therefore it is easier to adapt to changes in container shape and depth, and the yield can also be improved.

Problems to be Solved by the Invention However, even when using a Teflon punch as described above, the maximum ideal limit forming height is not necessarily obtained, and further improvement is desired. be.

The present invention was made in view of this technical background, and an object of the present invention is to provide a stretch molding method that enables a higher molding height.

Means for Solving the Problems In order to achieve the above object, the present invention does not aim to increase the forming height by improving the material of the punch, but rather works directly on the forming blank to achieve good spread in the grain of the blank. This was done with the aim of giving it a sense of sexuality.

That is, the stretch molding processing method according to the present invention, when stretch-molding a molded blank made of resin-laminated aluminum foil using a molding device equipped with a punch, a die, and a wrinkle presser, reduces the contact portion of the molded blank with the top surface of the punch. The method is characterized in that the molded blank is locally heated to promote deformation of the molded blank.

FIG. 1 shows a molding apparatus for carrying out the present invention. In the same figure, (1) is a molded blank, (2) is a punch,
(3) is a die, and (4) is a wrinkle presser.

The molded base plate (1) is made by laminating a resin film made of vinyl chloride, polypropylene, polyethylene, nylon, etc. on one or both sides of an aluminum foil. When such a molded blank (1) is stretch-molded using the above-mentioned device, the peripheral end of the blank (1) is cut into a die (3).
) and the wrinkle presser (4), and push the punch (2) in the direction of the die (3) to deform the molded blank (1). Top surface (2
The contact portion (la) with a) is locally heated to promote deformation. This operation reduces the deformation resistance of the contact portion (la) and improves the spreadability of the molded blank (1).

That is, the strength of aluminum foil and resin film decreases as the temperature rises, so by locally heating the contact area (1a) of the base plate (1) with the punch top surface (2a), the strength of the aluminum foil and resin film decreases as the temperature increases. The strength of the contact area is reduced, and the deformation resistance during stretch molding is reduced.

The temperature-strength characteristics of aluminum foil are shown in FIG. 3, and the temperature-strength characteristics of a stretched nylon film under low elongation are shown in FIG. 4 as an example of the temperature-strength characteristics of a resin film.

A heating device for locally heating the contact portion (1a) of the molded blank (1) is preferably provided in the molding apparatus. The most suitable heating device is a heating device using an internal heat generation method, that is, a heating device using a method that directly acts on the aluminum foil in the base plate to cause an exothermic reaction inside the aluminum foil. Examples of such internal heating methods include high frequency heating methods such as high frequency induction heating, microwave heating methods, vibration heating methods, and ultrasonic heating methods.

The apparatus shown in FIG. 1 employs a high-frequency heating method, and for this purpose a high-frequency induction coil (5) is buried just inside the top surface (2a) of the punch (2). and,
By passing a high frequency current through the coil (5), the aluminum foil in the molded blank (1) is heated, and the heating can be stopped by stopping the current supply. By using a heating device using such an internal heat generation method, it is possible to easily control the start and stop of heating, and the contact part (1a) can be instantaneously heated, and since only the aluminum foil is heated, the heat capacity is small. It has some good advantages. Note that control such as starting and stopping heating may be performed using a computer. Further, the heating temperature is not particularly limited, but considering the temperature limit of the resin film, it is preferably set to about 150°C or less, and most preferably set to about 70 to 120°C.

FIG. 2 shows a modification of the punch (2') in the molding device, in which the shape of the top surface of the punch is changed. That is, a portion of the taper (
21), and a high-frequency induction coil (
5') is placed. With such a shape of the top surface of the punch, a molding height that is larger than that can be obtained.

The material of the punch (2) is not particularly limited in this invention, but by using a material made of Teflon with good slipperiness, a more preferable molding height can be achieved due to the synergistic effect with the present invention. .

Effects of the Invention As described above, when a molded blank made of resin-laminated aluminum foil is stretch-molded using a molding device equipped with a punch, a die, and a wrinkle presser, contact of the molded blank with the top surface of the punch is provided. Since the deformation of the molded blank is progressed by heating the part locally, it is possible to obtain a large deformation of the molded blank, making it possible to further increase the limit overhang molding height, and increasing the freedom of molding. , it is possible to improve the molding yield.

Example (Example 1) Molded blank: 25 μm thick polyester film (PET) / 40 μm thick aluminum foil / 70 μm thick
Double-sided resin laminated aluminum foil with μm polyvinyl chloride film (PVC).

Punch: Punch diameter 27 m1 Teflon die: Die diameter 341 MI Wrinkle press pressure crab 3 tons Using the molded blank and molding device having the above configuration, the molded blank was set in the molding device and wrinkle press pressure was applied. Note that the shape of the top surface of the punch and the arrangement of the high-frequency induction coil of the forming apparatus were the same as those shown in FIG.

Next, when performing stretch forming by pushing the punch while energizing the high-frequency induction coil or without energizing it, the temperature of the contact area of the molded blank with the top surface of the punch is varied as shown in Table 1 below. Stretch molding was performed by changing the punch speed to 75.750.7500 ms/min for each temperature, and the limit stretch molding height was investigated.

The results are shown in Table 1.

Table 1 (Example 2) The shape of the top surface of the punch was changed to one with a tapered part at the peripheral end as shown in Figure 2, and high frequency induction was added inside the tapered part and the central flat part as shown in the same figure. Stretch molding was performed under the same conditions as in Example 1 except that a coil was provided, and the limit height of stretch molding at that time was investigated. Note that the angle (θ) (shown in FIG. 2) between the taper part and the vertical line was set to 600. The results are shown in Table 2 below.

A cross-sectional view showing the second tabular example, FIG. 3 is a graph showing the temperature-strength characteristics of aluminum foil with a thickness of 100 μm, and FIG. 4 is a graph showing the temperature-strength characteristics of aluminum foil with a thickness of 1
It is a graph showing the temperature-strength characteristics of a 5 μm stretched nylon film under low elongation.

(1)...Molded blank, (1a)...Contact part with punch top surface, (2)...Punch, (2a)...Punch top surface, (3)...Dice, (4)...Wrinkle presser, (5
)...High frequency induction coil.

From the results of Example 1.2 above, it was confirmed that according to the present invention, it was possible to obtain a large deformation of the base material, and that the critical molding height could be further increased.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a stretch forming apparatus for carrying out the present invention, and Fig. 2 is a modified view of the stretch forming apparatus.

Claims (1)

[Claims] When a molded blank made of resin-laminated aluminum foil is stretch-molded using a molding device equipped with a punch, a die, and a wrinkle presser, the part of the molded blank that comes into contact with the top surface of the punch is locally heated. A stretch forming processing method characterized by progressing the deformation of.