JPH0455581B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field This invention is used to manufacture packaging containers for foods, cosmetics, electronic parts, etc., using resin-laminated aluminum foil, which has a resin film laminated on at least one side of the aluminum foil, and using a punch. The present invention relates to a forming method when performing cold stretch forming. Conventional technology Conventionally, the most common wrinkle-free containers for the above-mentioned uses have been deep-drawn 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 product has 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 formed into a predetermined depth by cold stretch forming. The method of forming containers is attracting attention. In this case, the above 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 improve the selection of molding materials, 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 is preferable for the purpose of simply deepening the forming depth, but neither of these methods are suitable. It has disadvantages of poor productivity and freedom of shape selection. 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 by stretch molding, it is generally necessary to give the material good spreadability at the punch and the top surface, that is, the top surface that contacts the molding material. Therefore, 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, it is better to shape using a punch made of tetrafluoroethylene resin, which has a smaller coefficient of friction, than to shape using a punch made of stainless steel. However, in general, a relatively high critical molding height can be obtained, and therefore it is easy to adapt to changes in container shape and depth, and the molding yield can also be improved. This could also be confirmed from the results of the following comparative molding test conducted by the present inventors using a stainless steel punch and a Teflon punch. [Forming test conditions] Punch: A...Made of Teflon (friction coefficient μ: 0.05 Surface roughness Rmax: 1.8μm B...Stainless steel (friction coefficient μ0.13 Surface roughness Rmax: 1.2μm Diameter d1 = 50mm Shoulder radius rp = 5mm Die: Hole diameter d2 = 57mm Shoulder radius rp = 7mm Gap: C = d2/2-d1/2 = 3.5mm Wrinkle holding force: Hn = 3 tons Molded blank: OPA 25μm/Al foil 40μm/PVC 150μm
Resin-laminated aluminum foil (OPA: oriented polyamide resin film, PVC: vinyl chloride resin film) was formed by laminating resin laminated aluminum foil (OPA: stretched polyamide resin film, PVC: vinyl chloride resin film). When a molding test was conducted under the above conditions, the breaking height of the blank plate when using Teflon punch A was
The height was 14.5 mm, and when stainless steel punch B was used, the height was 11.0 mm. Also, the diameter is 2.5 mm on the base plate in advance.
When a circle pattern of mm was printed and the strain distribution after molding was measured, it was as shown in FIGS. 2 and 3. Figure 2 shows the distribution curve A of radial strain and the distribution curve B of circumferential strain when Teflon punch A is used, and Figure 3 shows the same radial strain distribution curve B when stainless steel punch B is used. This figure shows uncurved curves A and B of directional strain and circumferential strain. As shown in these figures, when the punch A made of Teflon is used, the amount of deformation of the blank at its top surface is greater than when the punch B made of stainless steel is used. In contrast, in the case of the stainless steel punch B, the amount of deformation near the punch shoulder is large, and breakage occurs from this portion. Therefore, when using a flat head punch with a large top diameter, it is better to use a punch made of Teflon, which has a small coefficient of friction.
It is clear that deep molding is possible. Problems to be Solved by the Invention However, when the present inventors further conducted various molding tests, it was found that the diameter of the die is smaller than a certain range, or the shoulder radius of the die is still large, making it difficult to use a spherical die. We have discovered what can happen when the above common sense logic does not necessarily apply. In other words, as the diameter of the flat part of the top of the punch becomes smaller, the proportion of the amount of deformation at the top surface that contributes to the forming depth becomes smaller, and eventually this becomes reversed, and the amount of deformation at the punch shoulder becomes more important to the forming depth. It was found that the contribution rate to 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 most desirable performance of the punch would differ depending on the specific shape, the inventors conducted numerous experiments and research, and found that the shape of the top surface of the punch was The present inventors have discovered that there is an appropriate range for the coefficient of friction and surface roughness in relation to the above, and have completed the present invention.
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to increase the possible molding depth in relation to the shape of the punch when stretch-forming resin-laminated aluminum foil with a punch. Therefore, the friction coefficient and surface roughness of the top surface are specified. Means for Solving the Problems This invention is based on the premise that a molded blank is a resin-laminated aluminum foil in which a resin film is laminated on at least one side of the aluminum foil, and the punch diameter is d1 and the punch shoulder radius is rp. When I did,
The present invention is applicable to cases where stretch molding is performed using a punch with 2rp/d1≧0.7, that is, a punch head with a ball head or one close to it. In this case, the friction coefficient of the top surface of the punch, that is, the top surface that contacts the blank plate, is μ: 0.08 to 0.2, and the surface roughness is Rmax: 0.5.
It is characterized by being defined within the range of ~2.0 μm. Resin-laminated aluminum foil used as a base plate is generally made by laminating a resin film made of vinyl chloride resin, polypropylene resin, polyethylene resin, etc. on one or both sides of aluminum foil with a thickness of about 30 to 50 μm. Stretch molding is performed by bringing the resin film side into contact with a punch. Further, in the present invention, the material of the punch is not particularly limited, and it may be made of a material that can easily obtain the most appropriate surface friction coefficient and surface roughness within the specified range. Further, the shape of the punch is not particularly limited either. Therefore, in the case of a circular punch, the punch diameter d1 is evaluated by the diameter of its top surface, and it is the same whether the side surface or peripheral surface is straight or slightly tapered. be evaluated. On the other hand, in the case of a punch with a corresponding shape used for molding an elliptical container, the punch diameter d1 referred to in the present invention depends on the length of the top surface in the minor axis direction and the corresponding shape used for molding a rectangular cylindrical container. In the case of a punch, the punch diameter d1 is evaluated by the length of its shortest side. Therefore, in any case, the relationship between the punch diameter d1 and the punch shoulder radius rp evaluated above is
The present invention is applicable to the case where 2rp/d1≧0.7. Regarding the friction coefficient and surface roughness of the top surface, which are important limiting factors of this invention, if the friction coefficient μ of the punch top surface is less than 0.08 and the surface roughness Rmax is less than 0.5 μm, the amount of deformation of the top surface portion is large. Therefore, breakage occurs at this portion, making it impossible to enjoy the desired effect of increasing the molding height. However, the upper limit of the friction coefficient μ of the punch top is 0.2, and the upper limit of the friction coefficient μ of the punch top is 0.2, and the surface roughness
The upper limit of Rmax is defined as 2.0 μm. The most preferable friction coefficient of the top surface is approximately μ: 0.1 ~
0.15, and surface roughness Rmax: 0.8 to 1.5 μm. The above friction coefficient defined in this invention is:
This is the coefficient of sliding friction measured using the Bowden equation, and when the punch is lubricated, it refers to the coefficient of friction after the lubrication. Effects of the Invention According to the present invention, when stretch-molding resin-laminated aluminum foil with a punch, when the punch head is spherical or close to it, especially when the punch diameter is d1 and the punch shoulder radius is rp,
When 2rp/d1≧0.7, a punch with a rather low slipperiness on the punch top surface, that is, a top surface friction coefficient of μ: 0.08 to 0.2 and a surface roughness of Rmax0.5 to
By using a material set in the range of 2.0 μm, it is possible to maximize the limit molding height, which has the effect of increasing the freedom of molding and improving the molding yield. Examples Example 1 This example confirms that the appropriate friction coefficient and surface roughness of the top surface of the punch vary depending on the ratio of the punch shoulder radius rp to the punch diameter d1, that is, 2rp/d1. It is something to do. Therefore, two types of punches are available: one made of Teflon and one made of stainless steel, each with a different ratio of 2rp/d1.
Each type was prepared and stretch molding of resin-laminated aluminum foil was performed under the following molding conditions. [Forming conditions] Punch: A...Teflon (friction coefficient μ: 0.05, surface roughness Rmax: 1.8μm) B...Stainless steel (friction coefficient μ0.13, surface roughness Rmax: 1.2μm, diameter d1 = 50mm constant shoulder radius rp = 5 to 25 mm change 2rp/d1 = 0.2 to 1.0 change Die: Hole diameter d = 57 mm constant shoulder radius rp = 1 mm constant gap: C = d2/2 - d1/2 = 3.5 mm constant molded blank: OPA 25 μm / Al foil 40 μm /PVC150μm
Resin-laminated aluminum foil by lamination of a blank sheet was stretch-molded under the above-mentioned molding conditions, and the relationship between the punch diameter and molding height was investigated using Teflon punch A and stainless steel punch B, respectively. The results are shown in Figure 1. In the figure, a curve F shows a change in the maximum forming height when a Teflon punch is used, and a curve S shows a change in the maximum forming height when a stainless steel punch is used. As is clear from this figure, when the ratio 2rp/d1 between the punch diameter d1 and the punch shoulder radius rp is approximately 0.7, the stainless steel punch has a relatively higher friction coefficient than the Teflon punch. It can be seen that a higher molding height can be obtained when a larger punch with poor surface slipperiness is used. Example 2 Next, the punch diameter was fixed at d1: 12 mm, the punch shoulder radius was constant at rp: 5 mm, and the surface friction coefficient and surface roughness of the top surface were varied, and the other conditions were the same as in Example 1. A stretch molding test was conducted to investigate the relationship between the friction coefficient and surface roughness of the punch and the molding height. The results were as shown in Table 1 below.

【table】

[Table] As shown in the above table, if the friction coefficient of the top surface of the punch is in the range of μ: 0.08 to 0.2, the same surface roughness is
It was confirmed that the maximum molding height could be obtained when Rmax was in the range of 0.5 to 2.0 μm.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the change in the ratio of the punch shoulder radius to the punch and the molding height using a Teflon punch and a stainless steel punch, and Figure 2 is a graph showing the relationship between the change in the ratio of the punch shoulder radius and the molding height using a Teflon punch and a stainless steel punch. FIG. 3 is a curve diagram showing the results of examining the strain distribution in the radial direction and circumferential direction. FIG. 3 is a curve diagram showing the results of examining the strain distribution when a stainless steel punch is used.

Claims (1)

[Scope of Claims] 1. A punch that uses a resin laminated aluminum foil with a resin film laminated on at least one side of the aluminum foil as a base plate, and where 2rp/d1≧0.7 where the punch diameter is d1 and the punch shoulder radius is rp. When performing stretch forming using
The surface roughness of the same top surface is within the range of 0.08 to 0.2.
A cold stretch forming method for resin-laminated aluminum foil, characterized in that the forming is performed with Rmax set in the range of 0.5 to 2.0 μm.