JPH069713B2 - Cold stretch forming method for resin laminated aluminum foil - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resin-laminated aluminum foil in which a resin film is laminated on at least one side of an aluminum foil when manufacturing a packaging container for foods, cosmetics, electronic parts, etc. The present invention relates to a forming method for cold stretching using a punch.

2. Description of the Related Art Conventionally, the most common wrinkle-free container for the above-mentioned applications is a deep-drawing molded product using an aluminum foil having a thickness of about 100 μm, or a synthetic resin molded product. There is. However, the former deep-drawing molded product is not only poor in productivity, but also has a drawback that the cost is high because a thick foil is used. The latter resin molded product is
There is an inherent difficulty in that it is inferior in buyer properties such as water, oxygen and light.

Therefore, in order to address these problems, recently, a resin-laminated aluminum foil obtained by laminating a resin film on an aluminum foil having a thickness of about 30 to 50 μm is used, and this is continuously stretched to a predetermined depth by cold stretch forming. Attention has been paid to a method of molding into a container.

In this case, the above-mentioned molding is required to have the maximum molding height as high as possible. As a measure for coping 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 a selection of the molding method, vacuum molding in which stress is uniformly applied to the entire molding material or bulge molding with air or oil is preferable for the purpose of merely increasing the molding depth, but both are produced. And the flexibility of shape selection is poor. Therefore, it is most promising to adopt the stretch molding method using a punch as a molding method having excellent productivity.

By the way, in order to enable molding with as high a molding height as possible by bulging, it is generally necessary to provide the material with good spreadability on the top surface of the punch, that is, the crown surface in contact with the molding material. Therefore, it is said that it is advantageous to make the top surface a surface having a small friction coefficient and a good slipperiness. For example, a case of using a punch made of tetrafluoroethylene resin having a small friction coefficient, that is, a so-called Teflon (trade name ... the same hereinafter) punch is more preferable than a case of using a punch made of stainless steel. Generally, a relatively high limit forming height can be obtained, and therefore, it is possible to easily cope with a change in the container shape and the depth and improve the forming yield. This can be confirmed by the present inventors from the results of the following comparative molding test performed using the stainless steel punch and the Teflon punch.

[Molding test conditions]

Die: Pore diameter d2 = 57mm Shoulder radius rp = 7mm Gap: C = d2 / 2-d1 / 2 = 3.5mm Wrinkle holding force: Hn = 3 ton Forming plate: OPA 25μm / Al foil 40μm / PVC1
Resin-laminated aluminum foil (OPA: stretched polyamide resin film, PVC: vinyl chloride resin film) by lamination of 50 μm When a molding test was performed under the above conditions, the breaking height of the base plate when the punch (A) made of Teflon was used. The height is 14.5 mm,
The same height when using a stainless steel punch (B) is 1
It was 1.0 mm. Further, when a circle pattern having a diameter of 2.5 mm was previously printed on the base plate and the strain distribution after molding was measured, it was as shown in FIGS. 2 and 3.

Fig. 2 shows radial strain distribution curve (a) and circumferential strain distribution curve (b) when using a Teflon punch (A).
Fig. 3 shows a stainless steel punch (B).
Similarly, the distribution curves (a) and (b) of the strain in the radial direction and the strain in the circumferential direction in the case of using are shown. As shown in these figures, when the punch (A) made of Teflon is used, the amount of deformation of the base plate at the top surface portion thereof is larger than that when the punch (B) made of stainless steel is used. On the other hand, in the case of the stainless steel punch (B), the deformation amount is the largest in the vicinity of the punch shoulder portion, and the fracture occurs from this portion. Therefore, when a flat-head punch has a large diameter on the top surface, it is apparent that deep molding can be performed at least when a punch made of Teflon having a small friction coefficient is used.

The problem to be solved by the invention is that, when various molding tests are further conducted by the present inventors, particularly when the diameter of the die is smaller than a certain range, or when the punch shoulder radius becomes large, the ball head punch becomes large. When approaching, we have found that it is possible that the above common sense logic does not always fit. That is, as the diameter of the flat part of the top surface of the punch becomes smaller, the ratio of the deformation amount of the top surface to the forming depth becomes smaller, and finally it reverses, and the deformation amount of the punch shoulder part becomes the forming depth. It was found that the rate that contributes to the increase becomes large.

In practice, the shape of the forming punch is designed based on the shape of the container to be formed. Based on the prediction that the performance of the most preferable punch should be different in relation to its specific shape, the present inventors have conducted a number of experiments and researches, and as a result, the diameter of the top surface of the punch has been increased. In view of this, the inventors have found that the friction coefficient and the surface roughness have appropriate ranges, and have completed the present invention.
Thus, the present invention has an object to make the molding depth as large as possible in relation to the punch shape when the resin laminated aluminum foil is stretch-molded with a punch. Therefore, the coefficient of friction and the surface roughness of the top surface are specified.

Means for Solving the Problems The present invention is based on the premise that a resin-laminated aluminum foil having a resin film laminated on at least one surface of an aluminum foil is used as a forming blank and a punch having a punch diameter d1 of 20 mm or less is used. In addition, the case where the both sides of the resin film are brought into contact with the punch to perform stretch molding is applied.
Then, in this case, the coefficient of friction of the top surface of the punch, that is, the top surface in contact with the blank is set to μ: 0.08 to 0.2, and the surface roughness is set to Rmax: 0.5 to 2.0 μm. It is characterized by

The resin-laminated aluminum foil used as the base plate is generally one in which a resin film made of vinyl chloride resin, polypropylene resin, polyethylene resin or the like is laminated and integrated on one or both sides of an aluminum foil having a thickness of about 30 to 50 μm. In this case, the resin film surface side is brought into contact with the punch to perform stretch molding.

Further, in the present invention, the material of the punch is not particularly limited. A material made of a material that easily obtains the most appropriate surface friction coefficient and surface roughness within the specified range according to the pot diameter may be used. Also, the shape of the punch is not particularly limited. Therefore, in the case of a circular punch, the punch diameter d1 is evaluated by the diameter of the top surface portion, and whether the side surface or the peripheral surface portion is straight or slightly tapered is similarly evaluated. To be done. On the other hand, in the case of a punch having a corresponding shape used for forming an elliptical container, the punch diameter d1 referred to in the present invention depends on the flow of the top surface in the short axis direction, and the punch diameter d1 of the corresponding shape used for forming the rectangular cylindrical container. In the case of a punch, the punch diameter d1 is evaluated by the length on the shortest side thereof. In any case, the present invention is applicable to the case where the punch diameter evaluated above is 20 mm or less.

Regarding the coefficient of friction and the surface roughness of the top surface, which are important limiting elements of the present invention, the coefficient of friction μ of the punch top surface is 0.
When the surface roughness Rmax is less than 08 and the surface roughness Rmax is less than 0.5 μm, the amount of deformation of the top surface portion is large, and therefore, the effect of increasing the desired molding height cannot be obtained due to breakage at the portion. However, since it is preferable that the deformation amount of the punch top surface portion is large within a range not exceeding the deformation amount of the punch shoulder portion, the upper limit of the friction coefficient μ of the punch top surface is 0.2 and the surface roughness Rmax is The upper limit is set to 2.0 μm.

The most preferable coefficient of friction of the top surface is: μ: 0.1 to 0.1
5, and the surface roughness Rmax is 0.8 to 1.5 μm.

The friction coefficient defined in the present invention is a sliding friction coefficient measured by the Bowden formula, and when a punch is lubricated, it means a friction coefficient after the lubrication.

EFFECTS OF THE INVENTION According to the present invention, when a resin-laminated aluminum foil is stretch-molded by a punch, the slipperiness of the top surface of the punch is suppressed to be low when the punch diameter is small, particularly when the punch diameter is less than d1: 20 mm. Punch, side surface friction coefficient μ: 0.08-0.2, surface roughness Rmax
By using the one set in the range of 0.5 to 2.0 μm, it becomes possible to maximize the maximum forming height, which in turn makes it possible to increase the forming flexibility and the forming yield. There is an effect that can be done.

Examples Example 1 This example confirms that the appropriate coefficient of friction and surface roughness of the punch top surface differ depending on the change in punch diameter. Therefore, two types of punches, one made of Teflon and the other made of stainless steel, each having a different diameter, were prepared, and the resin-laminated aluminum foil was stretch-molded under the following molding conditions.

〔Molding condition〕

Die: Pore diameter d2 = 17 to 57 mm change Shoulder radius rp = 1 mm constant Gap: C = d2 / 2-d1 / 2 = 3.5 mm constant Molding base plate: OPA 25 μm / Al foil 40 μm / PVC1
Resin-laminated aluminum foil with a lamination of 50 μm The base plate was stretch-molded under the above-mentioned molding conditions, and the punch diameter and the molding height of the punch made of Teflon (A) and the punch made of stainless steel (B) were respectively determined. I investigated the relationship. The results are shown in Fig. 1. In the figure, a curve F shows a change in the limit forming height when a punch made of Teflon is used, and a curve S shows a change in the limit forming height when a punch made of stainless steel is used. As you can see from this figure,
With a punch diameter d1: about 20 mm as a boundary, a punch made of stainless steel has a higher forming height than a punch made of Teflon, that is, a punch having a relatively large friction coefficient and poor surface slipperiness. It turns out to be a thing.

Example 2 Then, the punch diameter was set to a constant value of d1: 12 mm, the surface friction coefficient and the surface roughness of the top surface portion were variously changed, and an overhang forming test was performed in the same manner as in Example 1 to perform punching. The relationship between the friction coefficient and the surface roughness of and the forming height was investigated.

As a result, it was as shown in Table 1 below.

As shown in the above table, the coefficient of friction on the top surface of the punch is μ:
In the range of 0.08 to 0.2, the surface roughness is Rmax 0.5.
It was confirmed that the maximum molding height was obtained in the range of up to 2.0 μm.

[Brief description of drawings]

Fig. 1 is a graph showing the results of examining the relationship between the change in punch diameter and the forming height in each case of Teflon punches and stainless steel punches, and Fig. 1 is the radial direction and circumference when using Teflon punches. FIG. 3 is a curve diagram showing the result of examining the strain distribution in the direction, and FIG. 3 is a curve diagram showing the result of similarly examining the strain distribution in the case of using a stainless steel punch.

Front page continuation (72) Inventor Susumu Takada 6-224 Kaiyamacho, Sakai City, Osaka Prefecture Showa Aluminum Co., Ltd. (56) References Japanese Patent Publication No. 45-36836 (JP, B1) Japanese Publication No. JP, B2)

Claims (1)

[Claims] 1. A resin film is laminated on at least one surface of an aluminum foil to form a resin-laminated aluminum foil as a base plate,
When a punch having a punch diameter d1 of 20 mm or less is used and the resin film surface side is brought into contact with the punch to perform stretch forming, the coefficient of friction of the top surface in contact with the blank of the punch is 0.08 to
0.2, and the surface roughness of the same surface is Rmax0.
A cold stretch forming method for a resin-laminated aluminum foil, wherein the above-mentioned forming is performed in a range of 5 to 2.0 μm.