Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1997-12-31
2002-06-25
Reddick, Judy M. (Department: 1713)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S035700, C428S036800, C525S057000
Reexamination Certificate
active
06410109
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a flexible resin composition having high gas-barrier properties and good heat-resistance and good moldability or formability and also to a molded or formed article making the best use of the gas barrier properties, heat resistance and flexibility each derived from the raw material resin composition. The molded or formed article according to the present invention has excellent gas barrier properties and heat resistance and also good flexibility so that it is useful as a sealing material, packaging film, container or the like. Owing good moldability or formability (particularly, extrusion formability), the resin composition of the present invention is useful as a component of the above-described molded or formed article.
The present invention also pertains to a closure for containers and a sealing element for the closure. The closure and sealing element according to the present invention are each formed of a material having suitable flexibility and also excellent gas barrier properties and oil resistance so that they have good mountability onto (or within) containers and hermetical sealing properties and also being excellent in long-term shelf stability and smell retention of the content.
2. Related Art of the Invention
A polyvinyl chloride resin having a plasticizer added thereto is used as a sealing material, packaging film, container or the like because of having excellent flexibility and gas barrier properties. The polyvinyl chloride resin however evolves gases such as hydrogen chloride upon disposal by incineration and there is a possibility of its bringing about adverse effects on the environment. In addition, since the plasticizer is apt to cause the bleed out, such a plasticizer-added resin used for a packaging film or container may potentially contaminate the contents. Moreover, it has not so high heat resistance.
Since an ethylene-vinyl alcohol copolymer has high barrier properties against various gases and organic liquids and does not emit harmful gases upon disposal by incineration different from a polyvinylidene chloride resin or polyvinyl chloride resin, its application to various fields such as food packaging has been developed. For example, the use of it as a food packaging material making use of high gas barrier properties is now actualized or under investigation. The ethylene-vinyl alcohol copolymer is however inferior in flexibility so that it is sometimes used as a composition with a soft resin such as polyolefin. The ethylene-vinyl alcohol copolymer, in general, has low affinity and inferior compatibility with other resins, so the original gas barrier properties and the like of the ethylene-vinyl alcohol copolymer tend to be markedly impaired in such a composition.
It is known that a resin composition composed of a polyolefin resin, an olefin-vinyl alcohol copolymer and a modified copolymer, which has been obtained by graft polymerizing an unsaturated carboxylic acid or derivative thereof to a hydrogenation product of a block copolymer having a polymer block of an aromatic vinyl compound and a conjugated diene polymer block, has excellent gas barrier properties and is therefore useful as a food packaging material (Japanese Patent Application Laid-Open No. HEI 1-313552). It is also known that a resin composition composed of a polyolefin resin, an ethylene-vinyl alcohol copolymer, a polyolefin modified with an unsaturated carboxylic acid or derivative thereof and a hydrogenation product of a block copolymer having a polymer block of an aromatic vinyl compound and a conjugated diene polymer block has excellent gas barrier properties and is therefore useful as a material for bottles, cups and the like (Japanese Patent Application Laid-Open No. HEI 3-277642). In such resin compositions containing a polyolefin resin and a vinyl alcohol copolymer, the above-described modified copolymer introduced from the hydrogenation product of a block copolymer having a polymer block of an aromatic vinyl compound and a conjugated diene polymer block; or the above-described modified polyolefin and the hydrogenation product of a block copolymer having a polymer block of an aromatic vinyl compound and a conjugated diene polymer block are considered to have effects for improving the compatibility between the polyolefin resin and the vinyl alcohol copolymer. In such resin compositions, however, heat resistance is not so high. When the molded or formed article available from such a resin composition is exposed to high temperature conditions for long hours, deterioration occurs and the surface of the article sometimes becomes sticky.
Incidentally, it is described in European Patent Application Publication No. 572,667 that a resin composition comprising 0.5 to 35 parts by weight of a block copolymer having a polymer block of an aromatic vinyl monomer and an isobutylenic polymer block and 100 parts by weight of a thermoplastic resin has improved impact resistance. In it, exemplified as the thermoplastic resin are polycarbonate, polyphenylene ether, polystyrene, polyolefin, polyester, polyvinyl chloride, styrene-methacrylate-acrylonitrile copolymer, methacrylate-styrene copolymer, acrylonitrile-styrene copolymer, polymethyl methacrylate, polyphenylene sulfide and polyvinyl acetate. An ethylene-vinyl alcohol copolymer is not included in the above examples. It is also described in said European Patent Application Publication that the above-described resin composition composed of a thermoplastic resin and a block copolymer has good thermal stability, impact resistance, solvent resistance and compatibility, but a description about gas barrier properties is not included. The gas barrier properties of the above-described resin composition is insufficient in some cases, depending on the application purpose.
In Japanese Patent Application Laid-Open No. HEI 7-118492, described is a thermoplastic resin composition comprising a polyolefin and a block copolymer which is composed of a polymer block of an aromatic vinyl monomer and an isobutylenic polymer block and has a hydroxyl group at least one end of the block copolymer. In Japanese Patent Application Laid-Open No. HEI 7-188509, described are a polymer composition obtained by adding, to a thermoplastic resin such as a polyolefin resin, a specific combination of block copolymers composed of a triblock copolymer which has a structure of a polymer block of an aromatic vinyl monomer—an isobutylenic polymer block—a polymer block of an aromatic vinyl monomer and a diblock copolymer which has a structure of a polymer block of an aromatic vinyl monomer—an isobutylenic polymer block (or a triblock copolymer having a structure of an isobutylenic polymer block—a polymer block of an aromatic vinyl monomer—an isobutylenic polymer block); and also a crown liner formed of said polymer composition. In the above Japanese patent applications, it is described that a composition having excellent flexibility and moldability or formability can be prepared, but the gas barrier properties of the resulting composition are insufficient in some cases, though depending on the application purpose. In these applications, there is no description about the incorporation of a vinyl alcohol copolymer.
As conventional molding materials for producing a closure (cap, stopper or the like) for containers and a sealing element (packing element) for the closure, a resin having suitable flexibility such as polyvinyl chloride resin and low-density polyethylene has generally be used. Also a resin composition having flexibility imparted by the addition of an elastomer or softener to a polyolefin resin such as high-density polyethylene or polypropylene has been employed as the molding material. However the closure or sealing element comprising a polyvinyl chloride resin may potentially contaminate the contents due to the bleed out of the remaining monomers and plasticizers under some conditions of the contents and the environment for use. Because the closure or the like comprising low-density polyethylene has poo
Ishiura Kazushige
Shachi Kenji
Kuraray Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Reddick Judy M.
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