Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Patent
1987-10-22
1989-09-05
Robinson, Ellis P.
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
428 354, 428212, 428213, 428214, 428220, 428335, 428349, 428482, 428483, 428500, 428515, 428517, 428518, 428520, 428522, 428523, 428913, 426127, 427 35, B32B 2708, B65D 8500
Patent
active
048637688
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an improvement of cylindrical laminated films which are used for heat shrinking packages of irregularly shaped fatty food as contents such as raw meat, processed meat or the like.
BACKGROUND ART
Heat shrinkable cylindrically laminated films comprising 3-5 layers, one of which is a polyvinylidene chloride type resin (hereinafter referred to as PVDC) as an oxygen gas barrier layer and having a total thickness of 40-80 are well known in the art. Typical laminated films which are currently commercially available include, for example, a laminated cylindrical film comprising 3 layers of an ethylene-vinyl acetate copolymer resin (hereinafter referred to as EVA) at the exterior side of the cylinder/a PVDC/a cross-linked EVA at the interior side of the cylinder according to Japanese Patent Application Publication No. 43024/83 (U.S. Pat. No. 3,741,253); a laminated cylindrical film comprising 3-5 layers of a specific polyolefin resin blend at the exterior side of the cylinder/a PVDC/a specific polyolefin resin blend at the interior side of the cylinder according to Japanese Patent Application Publication No. 40988/85 (U.S. Pat. No. 4,390,587); and a laminated cylindrical film comprising 4-5 layers of an EVA/a PVDC/an ionomer resin at the interior side of the cylinder according to Japanese Patent Application Publication No. 2192/80 (U.S. Pat. No. 4,161 ,562). These laminated cylindrical films have occupied the market share as the packaging materials used for packaging in tight irregularly shaped fatty foods as contents by heat shrinking by proposing as the sales point their unique advantages such as excellent appearance owing to their transparency, their heat shrinkability at low temperature which will not damage the freshness of contents, excellent handling and working properties and the like.
However, with the proceeding of the improvement of packaging efficiency by the introduction of high speed packaging technique using a rotary chamber vacuum packaging machine, new problems of quality have happened in the packaging field, which problems are those of quality of design and cannot be solved with the aforementioned packaging materials.
In other words, as the result of research of the present inventors, the applicability of the high speed packaging technique may be decided by the following three points; first of all, possibility of making a certain sealed part having oil resistance while shortening the time required for tight sealing of packing bags filled with contents under reduced pressure; secondly, securing the cruel treatment resistance of the films so as to resisting rough handling of packaged articles accompanied with the increase of packaging speed under severe conditions; and third, enhancement of oil resistance of interior and exterior layers, in particular, on the treatment at high temperature. In addition, these new quality requirements must be satisfied without damaging the conventional quality level and is also in a high level.
Specifically, referring to the cruel treatment resistance as an index of causing no failures such as pin hole or break of bag on handling of a package, the requirement level has been raised and a commercially available film comprising EVA/PVDC/crosslinked EVA which has been evaluated to have a toughness to ensure that the film can be used for direct packaging of meat with sharp bone at the initial application (see the effect of Japanese Patent Application Publication No. 43024/83) is now evaluated in the new market requirements to be insufficient in toughness owing to high incidence of failures such as pin hole or break of a sealed part during handling the film even if the content is changed to meat without bone so that sharp extrusion will not be detected in it on touching with hand.
However, these films are not easily modified or improved. The reason depends on that a PVDC layer as a core layer will be yellowed or deteriorated upon irradiation of electron rays and thus it is difficult to carry out crosslinking in a state of a lamin
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Ishio Tadashi
Matsumura Daisuke
Asahi Kasei Kogyo Kabushiki Kaisha
Loney Donald J.
Robinson Ellis P.
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