Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1997-12-03
1999-11-02
Thibodeau, Paul
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
15624411, 428 367, 428349, 428212, 428220, 428516, B32B 2706, B32B 2732
Patent
active
059766514
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a laminate which is used suitably in the packaging field, particularly for the production of a container, and to a easily openable container produced using the same for the accommodation and packaging of foods, chemicals or the like which container is excellent in sealability and openability.
BACKGROUND ART
A plastic container for preserving and distributing foods by sealing them into the container and subjecting them to sterilization treatment at a high temperature is on the increase. Also, in some cases, consumers heat the same by means of a microwave oven in their use, and when the contents contain an oil, the temperature of the contents become high in some cases, so that it has been desired as the consumers' needs that the heat resistance and sealability in the cooking is excellent and, in addition, the openability is excellent. As a container excellent in sealability and easy openability, many proposals have been made for containers in which both sealability and easy openability have been attained by using a multilayer container and using the interface between layers of the multilayer container as an opening peel plane, without effecting the opening at the time of use by peeling the sealed portion which is generally effected (JP-A-50-37,598, JP-B-5-63,385 and JP-B-5-79,587). However, in these containers, the peeling layer is made of PE (polyethylene), and hence, they are disadvantageous in that 120.degree. C. is the upper limit as a high temperature treating condition; that particularly when they are filled with cooked foods containing a large amount of oils, swelling is seen in the peeling layer; that the seal with a lid material is broken because of the softening of the seal layer due to the high temperature; and the like.
For the purpose of overcoming these disadvantages, there is proposed a container having such a layer construction that a polypropylene resin is used as the innermost layer to increase the heat resistance as disclosed in JP-B-7-2,409, whereby the heat resistance has been enhanced as compared with the conventional container having a PE innermost layer. In such a construction, however, PE is still used as an intermediate layer for making peeling possible, and hence, the enhancement of heat resistance to some extent is found but there is such a disadvantage that since in the case of sterilization at a higher temperature (e.g., 130.degree. C.) the intermediate layer is softened and melted, the laminate strength between the intermediate layer and the surface layer is rapidly lowered and peel is caused during the sterilization and therefore the sealability is impaired. In addition, for the overall heat resistance of the container, it is necessary to use a material superior in heat resistance because the use of a usual PP results in a distortion.
The object of this invention is to provide a laminate which is suitably used in the production of an easily openable container in which the heat seal layer and the opening peel layer are made different, and which has heat resistance and oil resistance while keeping easy peelability of the opening peel layer.
DISCLOSURE OF INVENTION
The present inventors have eagerly made a study for achieving the above-mentioned object, and have consequently found that when a laminate to be used in the production of an easily openable container is given a specific layer construction, the above-mentioned problem can be solved, and based on this knowledge this invention has been completed.
That is to say, this invention is a laminate characterized by consisting of at least 4 layers and having (A) a seal layer which is a polypropylene having a melting point of at least 160.degree. C. as the first layer which is the innermost layer, (B) an adjacent layer consisting of a mixture of 20 to 90% by weight of a polypropylene and 80 to 10% by weight of a 4-methylpentene-1 resin as the second layer, (C) an intermediate layer consisting of a polypropylene having a melting point of at least 160.degree. C. and a melt index (JIS K
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Database WPI XP002062119 Sep. 10, 1996.
Akazawa Seigo
Tatsumi Yasuo
Yoshimoto Mamoru
Kruer Kevin R.
Sumitomo Bakelite Company Limited
Thibodeau Paul
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