Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1990-04-05
1992-10-06
Robinson, Ellis P.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
428 359, 428 366, 428 367, 428520, 428522, 428913, 25218828, B32B 2704, B32B 2708
Patent
active
051530384
DESCRIPTION:
BRIEF SUMMARY
This is a continuation of PCT Application PCT/JP88/00449, filed Apr. 27, 1989.
DESCRIPTION
1. Technical Field
The present invention relates to a plastic multi-layer vessel, in which under conditions where water and heat act, that is, under heat sterilization conditions, and after the heat sterilization, the resistance against permeation of oxygen is very high and the amount of oxygen in the vessel is controlled to a very low level.
2. Background Art
Metal cans, glass bottles and various plastic vessels have heretofore been used as the packaging vessel, and in view of the light weight and high impact resistance and because of the low manufacturing cost, plastic vessels are widely used in various fields.
In case of a metal can or glass bottle, the amount of oxygen permeating into the vessel through the vessel wall is zero, but in case of a plastic vessel, the amount of oxygen permeating into the vessel through the vessel wall cannot be neglected and a problem rises by this permeation of oxygen with respect to the preservability of the content.
In order to solve this problem, there is adopted a method in which a multi-layer structure is imparted to a wall of a plastic vessel and a resin having a resistance against permeation of oxygen, such as an ethylene/vinyl alcohol copolymer, is used for at least one layer of this multi-layer structure.
An oxygen scavenger has been used from old for removing oxygen from the interior of a vessel, and a example of application of this oxygen scavenger to a vessel wall is disclosed in Japanese Examined Patent Publication No. 62-1824, and according to this known technique, a layer formed by incorporating an oxygen scavenger comprising a reducing agent as the main component into a resin having an oxygen permeability is laminated on a layer having an oxygen gas barrier property to form a packaging multi-layer structure.
An oxygen barrier resin such as an ethylene/vinyl alcohol copolymer is sensitive to the moisture, and the oxygen permeability tends to increase with adsorption of the moisture. As means for obviating this disadvantage, Japanese Unexamined Patent Publication No. 57-170748 discloses a method in which a resin layer in which a moisture-absorbing agent is incorporated is disposed in proximity to an ethylene/vinyl alcohol copolymer layer in a multi-layer plastic vessel, and Japanese Unexamined Patent Publication No. 61-11339 discloses a method to which a layer of a dispersion of highly water-absorbing resin particles in a thermoplastic resin medium is interposed between such gas barrier layer and moisture-resistant resin layer.
According to these prior techniques, the oxygen scavenger present in the vessel wall absorbs oxygen in the vessel to maintain a highly oxygen-free state in the vessel. However, when a plastic vessel which does not possess a completely oxygen-intercepting property as possessed by a metal foil or the like is placed under conditions in which water and heat simultaneously act, that is, under heat sterilization conditions, oxygen permeating through the vessel wall cannot be controlled to a low level.
In general, an oxygen barrier resin such as an ethylene/vinyl alcohol copolymer has a moisture-absorbing property and has such a property that the oxygen permeation coefficient increases with absorption of the moisture. Accordingly, there is ordinarily adopted a multi-layer structure in which inner and outer layers composed of a moisture-resistant resin such as an olefin resin are disposed on both the sides of an intermediate layer composed of an oxygen barrier resin. Under the above-mentioned conditions where water and heat simultaneously act, permeation of water through the olefin resin layer is caused, and by increase of the oxygen gas permeability in the oxygen barrier resin layer by absorption of the moisture and by increase of the oxygen permeability by elevation of the temperature, it is considered that the amount of oxygen in the vessel increases. According to another prior art, a moisture-absorbing and water-absorbing agent is incorporated in
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Koyama Masayasu
Oda Yasuhiro
Yamada Muneki
Dye Rena L.
Robinson Ellis P.
Toyo Seikan Kaisha Ltd.
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