JP2003200949A - Metal cap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the re-capping durability of a metal cap. <P>SOLUTION: The internal surface of the metal cap 10 which closes a container 30 is coated with a plastic film 12. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal cap for plugging a container such as a glass bottle. [0002] Hitherto, for example, pill fur proof caps (hereinafter referred to as "PP caps") and screw caps made of, for example, aluminum or tin have been used to plug the mouth of a container such as a glass bottle. In the metal cap,
A varnish with a thickness of several microns is applied to the inner surface. This is because if the metal, which is the cap material, comes into direct contact with the outer periphery of the bottle mouth, the resistance will increase and a large force will be required for opening and re-opening. This is for the purpose of smoothing the stopper and protecting the inner surface of the cap by preventing the generation of rust. Further, the cap is required to seal a bottle made of, for example, glass, plastic or metal. For this purpose, an existing plastic packing is applied to the flat surface inside the cap, which comes into contact with the mouth of the bottle, from above the varnish film, or a plastic material (mainly polyethylene) in a flowing state is poured into the cap to close the cap. By rotating the plastic material to spread the plastic material evenly to form the packing, or by forming a packing part by a so-called mold method that is formed into an uneven shape that matches the bottle mouth, the bottle mouth and the cap To ensure a tight seal. However, in a metal cap coated with a varnish on the inner surface, frictional contact with the bottle occurs each time the metal cap is opened or re-opened, and in the case of a glass bottle, the surface condition of the bottle ( For example, by performing re-plugging ten times or more, the varnish is decomposed by frictional heat and the contact portion becomes black (so-called "blackening"). Then, the varnish comes off and the metal surface is exposed. This may increase the resistance at the time of re-plugging or cause rust, and sometimes it may not be possible to re-plug or open. For this reason, it has been a major problem for metal caps to improve re-plugging durability. [0005] Further, in the case of a cap provided with a packing, the steps of sticking and forming the packing are added to the cap manufacturing process, so that the items of quality maintenance are increased, and the cost is accordingly increased. Further, as a packing material, in many cases, foamed PVC must be used in a metal cap for a product to be filled at a high temperature, and an alternative product has been demanded due to environmental problems. Therefore, in order to solve the above-mentioned problems, the present invention is characterized in that a metal cap for plugging a container is covered with a plastic film. According to the metal cap of the present invention, by replacing the conventional varnish coating with a plastic film having excellent abrasion resistance, the inner surface of the cap is improved in re-plugging durability. Also, if an appropriate thickness is selected for the plastic film covering the inner surface of the cap, the flexible film itself can perform the same sealing function as the packing, so that there is no need to separately provide a packing as in the related art, The manufacturing process can be simplified and the cost can be reduced. Furthermore, by appropriately selecting the material of the plastic film that also functions as the packing, it can also be a measure against PVC.
It is also effective as a countermeasure for environmental problems. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a mouth 32 of a container 30 such as a glass bottle, which is capped with a metal cap 10.
2 and a partially enlarged cross section of the metal cap 10 are shown. The metal cap 10 includes a cylindrical portion 10a and a flat portion 10b that closes one end of the cylindrical portion 10a. A thread is formed on the outer peripheral portion of the mouth portion 32 of the container 30, and a thread groove is formed on the cylindrical portion 10a of the metal cap 10 corresponding to the thread. The mouth portion 32 of the container 30 is plugged with the metal cap 10 in a state where is screwed. The metal cap 10 is typically formed of a metal plate 11 of tin or aluminum, and its inner and outer surfaces are covered with plastic films 12 and 14, respectively. The plastic film 14 covering the outer surface of the metal cap 10 is not essential in the present invention, and may be omitted. When the plug is closed with the metal cap 10, the tip of the mouth 32 of the container 30 is pressed against the inner surface of the flat portion 10 b of the metal cap 10. Metal cap 10
Since the plastic film 12 on the inner surface of the container 30 has flexibility in the thickness direction, the sealing function is achieved when the mouth portion 32 of the container 30 is pressed. As a result, it is not necessary to separately provide a packing as in the related art, so that the manufacturing process can be simplified and the cost can be reduced. In addition, vinyl chloride is often used as a packing material, but if a material other than vinyl chloride is selected as the material of the plastic film 12, it will be a measure against PVC and also an environmental measure. Examples of the material of the plastic film 12 that covers the inner surface of the metal cap 10 include polyethylene, polyester, polyethylene terephthalate, and nylon.
Is not limited to a film of one kind of material, but may be a film obtained by laminating a plurality of films of different materials. The thickness of the plastic film 12 is, for example, 10 to 10.
It can be appropriately selected within the range of 400 μm, but is not necessarily limited to this numerical range. Next, a method of manufacturing the metal cap 10 will be described. First, a plastic film is attached to at least the inner surface of the tin or aluminum metal plate (the surface to be the inner surface of the metal cap 10). It is not essential to attach the plastic film to the outer surface of the metal plate (the surface corresponding to the outer surface of the metal cap 10), but it is reasonable to attach the film in the same manner from the viewpoint of workability. The attachment of the film is preferably performed by a so-called laminating method used for protecting paper, but may be performed by another method (for example, adhesion with an adhesive). Then, the metal plate to which the plastic film is bonded is formed into a cap by a mold. At the time of this molding, the slipperiness and strength of the film are required. On the outer surface side of the cap, a film having high slipperiness and high strength is required. On the other hand, the film on the inner surface side of the cap needs some strength, but also needs flexibility. In particular, when the film on the inner surface of the cap is used as a substitute for packing, flexibility is strongly required. The cap is formed by drawing a metal plate between a male die and a female die, and at this time, the gap between the die and the slipperiness of the metal plate surface are affected. If the gap is small, or if the surface of the metal plate has poor slipperiness, the metal plate or the film may be broken when narrowing. In the case of the metal cap 10 of the present embodiment, if the thickness of the plastic film 12 on the inner surface is about 10 to 30 μm, it can be molded with a gap under the same conditions as a conventional metal cap coated with a varnish (about 3 to 5 μm). However, when the thickness of the plastic film 12 is 30 μm or more, it is necessary to increase the gap and / or to increase the slipperiness of the surface. Here, the problem of tearing of the metal plate and the film was solved by widening the gap by a distance corresponding to about 90 to 95% of the film thickness. Next, a comparative test performed on the metal cap 10 of the present embodiment and a conventional metal cap will be described. Test 1 A PET (polyethylene terephthalate) film having a thickness of 12 μm is formed on the outer surface, and a PE film having a thickness of 100 μm is formed on the inner surface.
(Polyethylene) metal caps 10 to which films were attached were produced as test articles. On the other hand, an epoxy varnish with a thickness of 5 μm is applied to the outer surface and the inner surface and baked,
A metal cap coated with a surface lubricant before molding was used as a conventional product. A re-plug endurance test was performed on these test products and a conventional product, and a leak test was performed on the test products. The results are shown in [Table 1] below. In the endurance test for re-closing, two caps were used.
The glass bottle was resealed by tightening with a force of 0 kg · cm and then opened again to inspect the inner surface of the cap, and the number of times of reopening until the film or varnish on the inner surface was damaged or peeled was counted. In the leak test, a specified amount of water colored with methylene blue was placed in a glass bottle, the cap was closed with a force of 20 kg · cm, and the bottle was plugged. The method was performed by placing a glass bottle in a thermostat at 50 ° C. and leaving it for 48 hours to check for leakage. [Table 1]-Re-plug endurance test Test product (20 pieces) Average 45 times Minimum 32 times Conventional product (20 pieces) Average 18 times Minimum 12 times-Leak test test product (20 pieces) No leak [0019] Test 2 A metal cap having a 12 μm thick PET film adhered to the inner and outer surfaces, respectively, was prepared as a test product. On the other hand, as a conventional product, a metal cap generally used in the market (an aluminum cap having an inner surface and an outer surface which are coated with an adhesive layer, coated with a vinyl varnish, and baked thereon) was used. . Table 2 below shows the results of the re-plugging durability test performed on these test products and the conventional product. [Table 2] ・ Re-plug endurance test Test product (20 pieces) Average 45.0 times Minimum 38 times Conventional product (20 pieces) Average 13.6 times Minimum 10 times [ Test 3 ] 12 μm thick outer surface As a test product, a PET film was adhered, and a 12-μm-thick PET film was adhered on the inner surface, and a 70-μm-thick polyethylene film was further adhered on the PET film. On the other hand, a metal cap similar to the conventional product in Test 2 was used as the conventional product. Table 3 below shows the results of the re-plug endurance test performed on these test products and the conventional product. [Table 3]-Re-plug endurance test Test product (20 pieces) Average 46.8 times Minimum 37 times Conventional product (20 pieces) Average 13.2 times Minimum 9 times From the test results, it can be seen that the re-plugging durability of the test product is improved as compared with the conventional product. In this embodiment, a screw-type metal cap (a PP cap or a screw cap) has been described as an example. However, the present invention may be applied to a one-touch type metal cap. The material of the container may be glass, plastic, metal, or any other material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a mouth of a glass bottle capped with a metal cap and a partially enlarged sectional view of the metal cap. [Description of Signs] 10: metal cap, 10a: cylindrical portion, 10b: flat portion, 11: metal plate, 12: inner plastic film,
14 ... outer plastic film, 30 ... container, 32 ...
Mouth.

Claims (1)

Claims: 1. A metal cap, wherein an inner surface of a metal cap for plugging a container is covered with a plastic film.