JPH06547B2 - Synthetic resin container stopper - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a synthetic resin container stopper having particularly excellent sealing performance.

2. Description of the Related Art Conventionally, as a cap used for various bottles containing liquor, drinking water, etc., which is expensive and may cause hand damage when opened, a synthetic resin which is low cost and safe in recent years The container stopper molded in is widely used.

[Problems to be Solved by the Invention]

However, a container stopper formed of a synthetic resin has a problem in sealing property, and particularly has a poor sealing property for sealing a liquid having a gas whose internal pressure becomes high, such as soda water and tonic water. That is, when the internal pressure of the synthetic resin container stopper increases due to heat or the like, the top of the container stopper is pushed up by the internal pressure and lifts up, and the seal ring on the inner surface of the top is separated. The separated seal rings do not play their role, and the sealing property to the bottle mouth deteriorates. When deformed by internal pressure containing heat,
The deformation does not lose the restoring force and further deteriorates the sealing property. For this reason, various shapes of the seal ring have been devised and dealt with, but an effective one has not been considered yet. In order to prevent this sealing failure, it is necessary to increase the inner thickness of the container stopper to deal with it, and the fact is that a large and heavy one is put into practical use. As an example devised to eliminate this drawback, the container stopper body made of hard synthetic resin copes with the deformation, and the inner stopper made of semi-rigid synthetic resin is used as a sealing material, which is integrated into a container. There are some plugs configured, but the container stopper requires separate base materials, and the bothersome work of fitting both parts is required, and the container stopper main body may be formed due to improper fitting or a slight difference in size. It could not be a fundamental solution to prevent leakage such as a gap between the inner plug and the inner plug is likely to occur and the sealing is incomplete.

[Means for solving the problem]

The present invention solves such drawbacks and provides a synthetic resin container stopper that exhibits an excellent sealing effect even for a liquid having a high internal pressure. The present invention relates to a synthetic resin container stopper having a two-layer structure, characterized in that a water-absorbing resin is contained in the synthetic resin which is the inner layer of the two-layer structure synthetic resin container stopper. It is a container stopper. The water-absorbent resin includes starch-based resins, cellulose-based resins, and synthetic polymer-based resins such as polyacrylic acid-based resins, poval-based resins, and polyoxyethylene-based resins, but any of them may be selected. Considering the physical properties and the expansion coefficient, acrylic resin is preferable. The amount added to the synthetic resin is about 5 to 50 parts, preferably 1 part.
It is preferable to use it in the range of 0 to 20 parts. This is because if the amount of addition is small, the degree of foaming is small and the sealing property cannot be exhibited, and if it is too large, it absorbs too much water and causes a problem in strength, and also the sealing property is deteriorated. Further, since the synthetic resin of the inner layer facilitates expansion by the water-absorbing resin, a resin having low hardness, that is, a soft resin is suitable, and in consideration of being used for food, polyethylene, polyethylene-vinyl acetate polymerization is also taken into consideration. Resins, ethylene, propylene-based elastomers and others generally called thermoplastic elastomers are preferable. Among them, polyethylene-based resins are advantageous in terms of water absorption, and polyethylene-vinyl acetate copolymers are most preferable.

[Action]

As a method for obtaining this synthetic resin container stopper, a synthetic resin layer containing the water-absorbent resin is used as an inner layer and a relatively hard synthetic resin is used as an outer layer, and a container having a desired shape is formed by using two-color injection molding. By molding into a stopper, a container stopper having a perfect sealing property can be formed with two kinds of materials at one time, which is very advantageous in terms of cost. In addition, an integrated container stopper can be obtained without any worry of the seal portion falling off. In this way, when the synthetic resin container stopper having the synthetic resin containing the water absorbent resin on the inner layer side is plugged into the bottle mouth of the bottle filled with the contents, the water absorbent resin absorbs water to expand its volume,
It firmly adheres to the bottle mouth and exhibits perfect sealing performance. In order to promptly absorb water in the synthetic resin layer after the container stopper is plugged into the bottle mouth, it is desirable that the water absorbent resin is arranged on the surface as much as possible. A more effective sealing property can be obtained by adding an aliphatic solvent to the composition to form an organosol. The hardness of the synthetic resin layer is preferably less than 70 as measured by JIS hardness tester A, and optimally about 60. This is because water absorption is delayed when the hardness is high. However, this is also necessary depending on the application and is not particularly limited. The synthetic resin for the outer layer may be a thermoplastic synthetic resin such as polyethylene, polyalopylene, polyethylene terephthalate, polybutylene terephthalate, but is preferably a polyethylene resin from the viewpoint of moldability, economy, safety and the like. Further, the synthetic resin of the inner layer containing the water absorbent resin is not limited to the one provided on the entire surface, and may be provided only on the top of the container stopper,
Further, it is possible to further enhance the sealing effect by molding a liner shape projecting at a portion contacting the bottle mouth. In this way, when the container stopper obtained by molding into a desired container stopper by two-color injection molding or the like is plugged into the bottle mouth of the bottle filled with the contents, the synthetic resin layer expands 1.5 to 3 times in the thickness direction. Demonstrated excellent sealing performance. Both the new bottle mouth and the scratched bottle mouth were prepared, and the container stoppers were plugged into these bottles. However, none of the contents leaked and exhibited excellent sealing performance. This is because even with a damaged bottle mouth, unlike other seal liners, the seal expands and fills the scratched part after plugging, and because it seals ideally along the bottle mouth, it is excellent. It exhibits excellent sealing performance. In addition, it retains excellent sealability by always being able to respond to external shocks and deformations such as shaking and dropping after plugging.

【The invention's effect】

As described above, the present invention is completely different from the conventional method in which the liner is pressed by the capping pressure with the elastic seal liner to seal it, and after the plugging, the sealing part absorbs moisture and expands to completely seal the gap. Therefore, there is an ideal synthetic resin container stopper that exhibits excellent sealing performance even for scratched bottle mouths that have inevitably leaked in the past and especially for bottle mouths that are subject to internal pressure. can get.

Claims (3)

[Claims] 1. A synthetic resin container stopper having a two-layer structure, characterized in that a synthetic resin forming an inner layer of the container stopper contains a water-absorbing resin. 2. The synthetic resin container stopper according to claim 1, wherein the synthetic resin inner layer containing the water-absorbent resin is a thermoplastic elastomer or a polyethylene resin. 3. The synthetic resin container stopper according to claim 1 or 2, wherein the synthetic resin inner layer containing a water-absorbent resin is a polyethylene-vinyl acetate copolymer.