JPH0141411B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field This invention relates to a method for producing an aluminum laminate material for cap seals such as food and beverage containers, and in particular, a method for producing an aluminum laminate material for producing cap seals with less warpage and elastic deformation after molding (so-called spring back). Regarding the method. In this specification, the term aluminum is used to include aluminum alloys. Conventional technology As material for cap seals such as food and drink containers,
Conventionally, soft foil (so-called O material) made by annealing 1N30 alloy, etc., has been used, but such soft foil has low strength, so the foil thickness is generally 30 to 100 μm.
It has become impossible to meet the recent demands for cost reduction, as it has no choice but to be relatively thick. Therefore, recently, aluminum laminate material, which is made by laminating a synthetic resin film on aluminum foil, has been developed as a material for cap seals, which aims to reduce the cost by thinning the aluminum foil itself and compensate for the decrease in strength due to the thinning of the aluminum foil. It is starting to be used. Problems to be Solved by the Invention When producing a cap seal using this aluminum laminate material, the laminate material after production is usually subjected to a punching process into cap seal-shaped pieces. After punching, the punched pieces often curled with the film inside. Therefore, if such a punched piece is used as a cap seal as it is, the cap seal will remain warped, and even if the punched piece is drawn as a blank material, this warp will cause spring back. This leads to drawbacks such as the size of the punch and the shape of the punch which differs from that of the drawing punch, which may cause processing problems in the next step. The present invention was made in view of the above circumstances, and an object of the present invention is to provide an aluminum laminate material for a cap seal that can reduce warpage of the cap seal itself and spring back after drawing by reducing the warpage of the punched piece. This was done as a. Means for Solving the Problems In order to achieve this objective, the inventor conducted various experiments and research, and as a result of elucidating the cause of the warpage of the punched pieces, the inventor found that the warpage was caused by aluminum in the manufacturing process of aluminum laminate materials. It has been discovered that this is due to the unevenness of residual stress based on the tensile force that is generally applied to the film to prevent wrinkles when laminated with a laminate material. Furthermore, it has been discovered that the warping of the punched pieces can be reduced by applying tensile strain within a certain range to the aluminum laminate material in a direction orthogonal to the tensile force applied to the resin film during lamination before punching. , this invention was completed. That is, this invention forms an aluminum laminate material by laminating and bonding a synthetic resin film on at least one side of an aluminum foil while applying a tensile force, and then, before punching into a cap seal shape, the resin film is attached to the laminate material before punching into a cap seal shape. The gist of this invention is a method for manufacturing an aluminum laminate material for a cap seal, which is characterized by imparting a tensile strain of 0.5 to 1.5% in a direction perpendicular to the direction of the tensile force. As the aluminum foil, a soft foil obtained by zero-treating a pure aluminum alloy such as 1N30 alloy is generally used, but the foil is not limited to these.
Further, the thickness of the aluminum foil is desirably 25 μm or less from the viewpoint of cost reduction effect. Examples of synthetic resin films include polypropylene (PP), polyester (PET), polyethylene (PE), and nylon. The synthetic resin film and aluminum foil may be laminated on only one side of the aluminum foil, or on both sides, or if laminated on both sides, the type of film is determined for each side. Alternatively, a plurality of films of the same type or different types may be laminated on top of the film. The lamination process of such a synthetic resin film and aluminum foil can be carried out by various methods including the well-known wet lamination method, dry lamination method, hot melt lamination method, or extrusion lamination method. However, in order to prevent the film from wrinkling during lamination, an appropriate tensile force is applied to the film. Immediately after lamination, the synthetic resin film has a larger residual stress than the aluminum foil as a result of being subjected to tensile force. The aluminum laminate material produced in this way is then subjected to a punching process into small pieces with a predetermined cap seal shape, but in this invention, before punching, the aluminum laminate material is , to the laminate material
The condition is to apply a tensile strain of 0.5 to 1.5%. This is to eliminate uneven residual stress caused by bonding and reduce warping of the punched piece, which in turn reduces warping as a cap seal and spring back after drawing. Here, if the tensile strain is less than 0.5%, the effect is poor, and if it exceeds 1.5%, conversely, large warpage occurs in the direction in which the tensile strain is applied, which is not preferable. For this reason, the range of tensile strain was limited to the above range. The tensile strain may be applied at any time after bonding the aluminum foil and the resin film before punching, or immediately after bonding or immediately before punching. The cap seal is manufactured by punching the aluminum laminate material and then using the punched piece as it is, or by shallow drawing the punched piece as a blank material. In addition, when drawing the punched piece, the drawing ratio is 1.3 to 2.0, and the wrinkle pressing pressure is 0.5.
It is preferable to carry out drawing forming under conditions of ~8.0 Kgf/cm ² and a clearance between the punch and die of 1.0 to 2.5 times the thickness of the material, since spring back after forming can be further suppressed. Effects of the Invention As explained above, this invention forms an aluminum laminate material by laminating a synthetic resin film on at least one side of an aluminum foil while applying a tensile force, and then punching it into a cap seal shape. The laminate material is characterized in that a predetermined tensile strain is imparted to the laminate material in a direction orthogonal to the tensile force direction of the resin film.
To produce an aluminum laminate material for a cap seal that can eliminate the imbalance of residual stress between the aluminum foil and the resin film that occurs during lamination due to the tensile strain, and that reduces warping when punched into a cap seal shape. be able to. Therefore, if this laminate material is used as a cap seal as it is after punching, the warpage of the cap seal itself can be reduced, while if it is drawn and formed after punching, spring back can be reduced, and it can also be used in the next process. It is possible to provide a cap seal with no problems in terms of quality. Examples Next, examples of the present invention will be shown in comparison with comparative examples. An aluminum laminate material was prepared by laminating a 6 μm thick polyester film on one side of a 20 μm thick soft aluminum foil treated with 1N30 alloy while applying a predetermined tensile force. Next, after applying or not applying tensile strain to this laminate material as shown in the table below in a direction perpendicular to the direction in which the tensile force is applied, the laminate material was punched into a cap seal shape with a diameter of 49 mm, and each punched piece was The amount of warpage (1/radius of curvature) was measured.
The results are shown in the same table.

[Table] As is clear from the above results, the punched pieces of aluminum laminate materials manufactured according to the present invention (Samples No. 2 to 4) were more effective than those to which no tensile strain was applied (Sample No. 1). It can be seen that the amount of warpage can be reduced. Furthermore, it can be seen that when a tensile strain is applied beyond the range of the present invention (sample No. 5), a large warpage occurs in the direction in which the tensile strain is applied. On the other hand, in order to confirm that there is a proportional relationship between the amount of warpage of the punched piece and the amount of springback after drawing, we prepared punched pieces with various amounts of warpage, and tested each punched piece under the same conditions. It was drawn and formed, and the amount of spring back at that time was examined. The amount of springback was evaluated based on the difference between the maximum diameter of the molded product after molding and the punch diameter. The results are shown graphically in the drawing. As is clear from the graph, as the amount of warpage decreases, the springback of the cap seal also decreases. Therefore, according to the aluminum laminate material manufactured according to the present invention, when a cap seal is manufactured by drawing a punched piece, the amount of springback can be reduced, and when the punched piece is used as it is as a cap seal, the amount of springback can be reduced. It was confirmed that this can naturally reduce the warpage.

[Brief explanation of drawings]

The drawing is a graph showing the relationship between the amount of warpage of the punched piece and the amount of springback of the cap seal.

Claims (1)

[Claims] 1. Form an aluminum laminate material by laminating and bonding a synthetic resin film on at least one side of an aluminum foil while applying a tensile force, and then apply the tensile force direction of the resin film to the laminate material before punching into a cap seal shape. A method for producing an aluminum laminate material for a cap seal, the method comprising applying a tensile strain of 0.5 to 1.5% in a direction perpendicular to the direction.