JPH0555390B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a container lid with a liner that has impact-resistant sealing properties and stress-cracking resistance, and more specifically, an olefin resin liner that is press-molded within the shell of the container lid. This invention relates to improvements in impact resistance and stress cracking resistance. (Prior art) A lump of molten polyethylene is applied to the inside of a metal shell, this lump is pressed with a cooled plunger, the polyethylene is formed into a predetermined liner shape, and the liner is heated to the metal shell. Adhesive container lids have excellent hygienic properties, eliminate waste of liner forming material, and are easy to manufacture, so they have come to be widely used to seal the mouths of containers such as glass bottles. There is. (Problems to be Solved by the Invention) This container lid with a liner is related to the fact that the liner constituent material is thermoplastic olefin resin, and this liner is formed by press molding molten olefin resin within a shell. It has been found that liners made of vinyl chloride resin plastisol and liners made of synthetic rubber elastomer have drawbacks that are not found. One drawback is that this type of olefin resin liner has distortions during molding, and when this liner is actually used to seal filled bottles, it is susceptible to the effects of water vapor and heat. As a result, there is a strong tendency for environmental stress cracking to occur and a decrease in sealing performance to occur. Another serious drawback of this type of olefin resin liner is that even if it exhibits a satisfactory sealing property under static conditions, when an impact is applied to the mouth of the container with the container lid attached, the sealing performance becomes significant. This results in a decrease in Therefore, an object of the present invention is to provide a container lid that has an olefin resin liner formed on the inside of the shell by press molding on the spot and has excellent impact-resistant sealing properties and stress-cracking resistance. There is something to do. Another object of the present invention is to facilitate manufacturing operations, prevent the liner from coming off from the shell during manufacturing, transportation, etc., and provide excellent sealing even under any harsh usage conditions of the container lid. To provide a container lid with an olefin resin liner whose performance is maintained. (Means for Solving the Problems) According to the present invention, a metal shell having a top plate portion and a skirt portion hanging down from the periphery of the top plate portion;
In a container lid comprising an olefin resin liner applied to the inside of the top plate of the shell, the metal shell top plate includes a lacquer layer that is adhesive to the olefin resin and a lacquer layer that is non-adhesive to the olefin resin. The masking layer has a positional relationship such that the lacquer layer is in the center of the top plate, the masking layer is in a ring shape circumscribing the central lacquer layer, and the outermost portion circumscribing the ring-shaped masking layer is a ring-shaped lacquer layer. The outer peripheral edge of the ring-shaped masking layer is located on the outer peripheral side than the outer peripheral edge of the container opening, and the olefin resin liner is formed by stamping molten olefin resin inside the metal shell. The olefin resin liner has a thin central portion and a thick outer circumferential sealing portion formed by the olefin resin liner, and is substantially irremovably adhered to the top plate portion via the central lacquer layer and the ring-shaped lacquer layer. Provided is a container lid with a liner having impact-resistant sealing properties and stress-cracking resistance. (Function) In FIG. 1 showing the overall structure of the container lid of the present invention, this container consists of a metal shell, generally designated 1, and an olefin resin liner, generally designated 2. In this specific example, a metal shell (cap shell) 1 includes a top plate part 3 and a skirt part 4 hanging down from the periphery of the top plate part, and this skirt part 4 has perforations ( A pilfer roof mechanism 5 and a knurled groove 6 for gripping the cap are provided. In FIG. 2, which shows an enlarged cross-section of the joint between the liner 2 and the shell 1, an anti-corrosive undercoat 7 is applied to the entire inner surface of the shell 1, and an adhesive coating for olefin resin is applied on the entire surface of the inner surface of the shell 1. A lacquer 8 with a lacquer 8 is provided over the entire surface. On the inner peripheral part of the top plate part 3 and on the adhesive lacquer 8,
A ring-shaped masking layer 9 that is non-adhesive to the olefin resin is provided such that its outer peripheral edge is located outside the outer peripheral part 13 of the container opening 12. With this ring-shaped masking layer 9, the lacquer layer includes a circular central lacquer layer 8a, and an outermost ring-shaped lacquer layer 8 that circumscribes the masking layer.
It is divided into b. Returning again to FIG. 1, the liner 2 includes a thin central portion 10 and a thick outer circumferential sealing portion 11 formed by stamping the molten olefin resin inside the metal shell 1. The thick outer peripheral portion 11 is adapted to engage with the container opening 12. The olefin resin liner 2 is adhered to the shell top plate 3 through the adhesive lacquer layer 8 described above in a substantially unreleasable manner, and at least the container opening 1
The portion of the liner outer periphery 11 that engages with the outer periphery 13 of the liner 2 is maintained in a non-adhesive state via the masking layer 9. As mentioned above, in a liner manufactured by embossing molten olefin resin within a shell, the portion that engages with the outer periphery of the container mouth is the most critical for impact-resistant sealing and stress-cracking resistance. It has an impact. In the present invention, the portion of the liner that engages with the outer periphery of the container mouth is maintained in a non-adhesive state, and the non-adhesive portion is shaped like a ring including a portion corresponding to the outer periphery of the container mouth. This is based on the knowledge that by positioning and bonding both sides, impact-resistant sealing properties and stress-cracking resistance can be significantly improved. The exact reason for this is still unknown, but
According to the experimental facts of the present inventors, it is inferred that the reason is as follows. That is, by applying a shock to the mouth of the container with the container lid attached, or by heating the container,
Inspection of olefin resin liners that exhibited reduced sealing performance when the contents were brought into contact with steam
Without exception, such poorly sealed liners
Cracks or cuts are observed in the portion of the liner that engages the outer periphery of the container mouth. This seems to be because stress is concentrated in the part of the liner that engages with the outer periphery of the container mouth, and this part is subjected to the harshest conditions. Furthermore, when a molten olefin resin is supplied into a metal shell and molded into a liner by stamping it while cooling, the molding is performed while the resin is spread toward the outer periphery while cooling. It is thought that another important cause is that molecular orientation occurs or internal strain tends to remain in the outer peripheral part of the liner. In particular, when the metal shell is made of aluminum, which has high thermal conductivity, the above-mentioned drawbacks tend to occur even more significantly because the resin cools more rapidly. However, in accordance with the present invention, leaving this portion of the liner in a non-adhesive state prevents cracks or cuts in the portion of the liner that engages the outer periphery of the container mouth, even under environmental stress cracking and impact conditions. This is believed to be because by leaving this portion of the liner in an unbonded, ie, free state, stress concentration and internal strain are alleviated. Furthermore, in the present invention, the reason why the non-adhesive part is formed into a ring shape sandwiched between the adhesive parts is as follows. First of all, since the liner material of the present invention is formed by stamping molten olefin resin on the inside of a metal shell, the above structure makes it easier to release the liner material from the stamped liner material. This is because the molding workability of the liner material is improved, and secondly, since the liner material is bonded at the outer periphery, it is also possible to prevent the progress of peeling from the periphery of the liner material. At the same time, it is also possible to prevent foreign matter and residual sterilizing liquid from entering the non-adhered portion of the liner material. (Preferred embodiment of the invention) In the present invention, the olefin resin constituting the liner includes low-, medium-, or high-density polyethylene, crystalline polypropylene, ethylene-propylene copolymer, and ethylene-propylene-butene-1 copolymer. Although merging and the like are used, from the viewpoints of cushioning properties, flexibility, etc., a material mainly made of low-density polyethylene is most suitable. In addition, the olefin resin constituting the liner is preferably one that has excellent stress cracking resistance, and from this point of view, 70 to 90 parts by weight of low density polyethylene and 10 to 30 parts by weight of ethylene-propylene copolymer per 100 parts by weight of the whole. Parts by weight, styrene-isoprene-styrene.
It is best to use a thermoplastic resin composition comprising 1 to 5 parts by weight of a block thermoplastic copolymer or styrene-butadiene-styrene block copolymer and 0.1 to 0.8 parts by weight of a lubricant. Lacquers that have adhesive properties to olefin resins include epoxy-phenol resin paints,
For base paints such as epoxy-amino resin paints, epoxy-vinyl resin paints, epoxy-acrylic resin paints, vinyl-phenol resin paints, etc.
A paint is used in which an acid-modified olefin resin graft-modified with oxidized polyethylene, an ethylenically unsaturated carboxylic acid such as maleic anhydride or acrylic acid, or its anhydride is dispersed as an adhesion promoting component. Suitable examples of such adhesive lacquers are described in JP-A-54-71180 and JP-B-54-11836. As the non-adhesive masking layer, dry oil-modified alkyd resin, rosin, rosin-modified alkyd resin, rosin-modified phenolic resin, petroleum resin, etc. are used. The metal materials that make up the shell include tinplate,
In addition to steel plates such as galvanized steel plates, electrolytic chromic acid treated steel plates (tain-free steel), and aluminum plated steel plates, light metal plates such as aluminum are used. In the present invention, it is advantageous in terms of workability and precision to coat the adhesive lacquer on the front surface and provide a ring-shaped non-adhesive masking layer to divide the adhesive lacquer layer into a central portion and an outermost portion. brings the benefits of That is, while it is difficult to partially cover the acid-modified olefin resin-containing paint as an adhesive lacquer by printing, etc., the resin of the non-adhesive masking layer exemplified above can be partially covered by printing. Therefore, a non-adhesive region can be formed on the shell-constituting metal plate with high precision. In the container lid of the present invention, the metal shell can take any form such as a pill-proof cap, screw-on cap, lift-off cap, lug cap, or crown. The molding of the liner is easily carried out by a method known per se in which olefin resin is applied in the form of molten pellets to the inside of the shell and the pellets are pressed with a plunger, and at the same time the top plate of the liner is molded. Thermal bonding is also carried out. As shown in FIG. 1, the thick-walled sealing outer circumferential portion of the liner preferably has two or more ring-shaped protrusions and a ring-shaped recess between them, and the inner circumferential surface of the outermost ring-shaped protrusion and It is best to engage the outer periphery of the mouth of the container to achieve a seal. (Example) The present invention will be explained with the following example. Example 1 An ordinary vinyl paint was applied as a rust-preventing undercoat to an aluminum plate with a thickness of 0.24 mm and baked. An epoxy paint containing maleic acid-modified polyethylene is applied as an adhesive paint on top of this rust-preventing undercoat lacquer layer, and then baked. Furthermore, on top of this adhesive layer, a non-adhesive masking layer with outer diameter dimension A is applied. 24.5φmm (Example 1) and 23.5φmm, respectively
(Comparative example 1), a ring shape with an inner diameter dimension B of 19φmm,
After applying a dry oil-modified alkyd resin ink, each coated board was baked at 170°C for 10 minutes. Next, by molding the cap shell (pressing and perforating) so that the painted surface of each painted plate becomes the inner surface of the cap, the outer diameter is 28 mm.
It was molded into a pilfer-proof type cap (commonly known as 28mm PP cap) with a height of 16mm. Each cap shell obtained is heated using a high frequency heating device.
Heat to 190℃, extrude the resin shown in Table 1 from an extruder, put the molten resin particles (0.3g) cut with a rotary blade into the center of the inside of the heated cap shell, and immediately press it with a press mold to form a liner shape. A cap with a liner with a liner outer diameter of 26φmm was created by molding. Next, the molded caps were subjected to impact tests and stress cracking tests, and the results shown in Table 2 were obtained. The test method is as follows. Test (1) Cap impact test A bottle with a capacity of 132ml, commonly known as a 28mm PP cap with a threaded bottle opening (container opening outer diameter 24.1φmm), was
Pour 120 ml of diluted sulfuric acid made by diluting 40.5 g of concentrated sulfuric acid (98%) in 7.5 ml of water, then put 1.5 g of sodium bicarbonate into the bottle without touching the solution, and insert the sample cap into the bottle opening. After cutting and tightening the screws, completely dissolve the sodium bicarbonate. Immediately after that, heat treatment was performed for 2 minutes in 65℃ hot water and 4 minutes in 70℃ hot air, and after leaving it at room temperature for 24 hours, the third
As shown in the figure, each bottle is placed in a vertically erected cylinder at a falling distance of 400, 500, and 600 mm with the mouth facing down, and θ is placed at the bottom end of the cylinder.
A shock was applied to the test cap by allowing it to fall naturally against a steel block with a 10° sloped upper surface. After impact, the bottle was placed upside down with the mouth facing down, and leakage was observed after 24 hours. Test (2) Stress cracking test A bottle with a capacity of 132ml, commonly known as a 28mm PP cap with a threaded bottle opening (container opening outer diameter 24.1φmm), was tested.
Dilute 40.5 g of concentrated sulfuric acid (98%) in 7.57 g of water, add 120 ml of a solution containing 380 ml of surfactant (Ribonox), and then add 1.5 g of sodium bicarbonate to the bottle, taking care not to touch the solution. Place the test cap in a container, screw the sample cap onto the mouth of the bottle, and tighten the cap to completely dissolve the sodium bicarbonate. Immediately after that,
After heat treatment in hot water at 65°C for 2 minutes and in hot air at 70°C for 4 minutes, the temperature was returned to room temperature. After that, this test bottle was placed on its side in an oven at 50℃ for 1 hour.
After leaving it for 1 week, 2 weeks, 4 weeks, and 8 weeks,
The temperature was returned to room temperature, the test cap was opened, and the stress cracking state of the liner was observed using a stereoscopic microscope.

【table】

【table】

[Table] Example 2 An ordinary vinyl paint was applied as a rust-preventing undercoat lacquer to an aluminum plate with a thickness of 0.24 mm and baked. An epoxy paint containing maleic acid-modified polyethylene is applied as an adhesive paint on top of this rust-preventing undercoat lacquer layer, and then baked.Furthermore, on top of this adhesive layer, a non-adhesive masking layer with outer diameter dimension A is applied to each layer. 24.5 mm (Example 2), 27.5 mm (Comparative Example 2), and a ring shape with an inner diameter B of 19 mm were coated with drying oil-modified alkyd resin ink, and then heated at 170°C.
- Each painted board was created by baking for 10 minutes. Next, a cap shell was molded so that the painted surface of each coated plate became the inner surface of the cap, thereby forming a pilfer-proof type cap with an outer diameter of 28 mm and a height of 16 mm. Each cap shell obtained is heated using a high frequency heating device.
Molten resin particles (0.3g) heated to 190℃, extruded from an extruder as shown in Table 3, and cut with a rotary blade.
was put into the center of the inside of the heating cap shell, and immediately pressed with a press mold to form a liner shape, producing a cap with a liner having an outer diameter of 26 mm. Next, the molded caps were tested for the progress of peeling of the liner material and the amount of sterilizing solution remaining after the caps were sterilized was measured. The test method is as follows. Test (3) Progress test of peeling of liner material Caps prepared as in Examples were left in a thermostat at 40°C, and the progress of peeling of the liner material was examined. As a result, as shown in Table 4, in the cap of Example 2, no peeling of the liner material was observed at all, but in the cap of Comparative Example 2, progression of peeling of the liner material was confirmed as the time passed, and the liner material was rising from the cap. Note that the ratios shown in Table 4 indicate the ratio of the peeled area to the liner area. Test (4) Test for residual amount of hydrogen peroxide Place a cap in a 3% hydrogen peroxide solution, shake vigorously, take out the cap, place in distilled water, and rinse thoroughly with water. after that,
Twenty water-washed caps were placed in a glass bottle containing 100 ml of distilled water, and after vigorous stirring, the amount of hydrogen peroxide dissolved in the distilled water in the glass bottle was determined by the iodine method. As a result, as shown in Table 4, no residual hydrogen peroxide was observed in the cap of Example 2, but residual hydrogen peroxide was observed in the cap of Comparative Example 2. Therefore, Example 2 is advantageous when there is a step in which the cap is sterilized before use.

【table】

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a partially sectional side view of an example of a container lid with a liner of the present invention, FIG. 2 is an enlarged sectional view of the container lid of FIG. 1, and FIG. It is an explanatory view of an ivy impact test. The reference numbers are 1 for the metal shell, 2 for the olefin resin liner, 3 for the top plate, 4 for the skirt,
8 is an adhesive lacquer layer, 8a is a circular central lacquer layer, 8b is a ring-shaped lacquer layer, 9 is a non-adhesive masking layer, 10 is a thin central part of the olefin resin liner, and 11 is the olefin resin liner. Thick-walled outer circumference for sealing, 12 is a container opening, 13
indicates the outer periphery.

Claims (1)

[Scope of Claims] 1. A container lid consisting of a metal shell having a top plate portion and a skirt portion hanging from the periphery of the top plate portion, and an olefin resin liner applied to the inside of the top plate portion of the shell, comprising: The top plate of the metal shell has a lacquer layer that is adhesive to the olefin resin and a masking layer that is non-adhesive to the olefin resin. The ring-shaped masking layer is further provided in a positional relationship such that the outermost circumferential portion that circumscribes the ring-shaped masking layer becomes a ring-shaped lacquer layer, and the outer circumferential edge of the ring-shaped masking layer is further away from the outer circumferential edge of the container mouth. located on the outer peripheral side, the olefin resin liner has a thin center portion formed by stamping molten olefin resin inside a metal shell and a thick outer sealing peripheral portion; The olefin resin liner has a liner having impact-resistant sealing properties and stress-cracking resistance, which is bonded to the top plate section through the central lacquer layer and the ring-shaped lacquer layer in a substantially unpeelable manner. container lid.