Plastic and nonmetallic article shaping or treating: processes – Carbonizing to form article – Agglomeration or accretion
Patent
1990-07-13
1994-03-22
Thurlow, Jeffery
Plastic and nonmetallic article shaping or treating: processes
Carbonizing to form article
Agglomeration or accretion
204165, 264510, 264566, 264570, 264173, 264DIG50, 4251748E, 425DIG2, 427458, 427540, 428 349, 4284758, B29C 7104, B29C 5910
Patent
active
052961702
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method for improving the internal surface of a multi-layer plastics film laminate in the form of a seamless tube for packing processed meat or like food, and more particularly to a method for treating the surface of the innermost polyolefin resin layer of a multi-layer plastics film laminate in the form of a seamless tube by subjecting the seamless tube to corona discharge treatment to improve the degree of close contact between the tube and the processed meat or the like to be enclosed therein.
BACKGROUND ART
Heretofore known are a variety of gas-barrier, multi-layer plastics film laminates useful as packaging materials for enveloping processed meat or like food. Among them are seamless tubes of gas-barrier, preferably heat-shrinkable, multi-layer plastics film laminate having a layer of olefin resin for contact with processed meat or the like to be enclosed therein. However, such seamless tubes of multi-layer plastics film laminate with the innermost polyolefin resin layer have drawbacks. Since the olefin resin layer has a poor property of closely contacting food, particularly ham, sausage or like processed meat, a gap is formed between the processed meat and the packaging material on heat-shrink packaging or after a time interval, followed by occurrence of the so-called release of gravy, water or the like from the processed meat into the gap. In that case, bacteria easily proliferate and the proliferation of bacteria renders the processed meat or the like less preservable.
To cope with the problem, various methods have been conventionally carried out which include, for example, applying to the olefin resin layer a substance capable of closely contacting processed meat or the like, forming the innermost layer capable of closely contacting meat, or treating the innermost layer by corona discharge to improve the degree of close contact with processed meat or the like. However, these methods have both advantages and disadvantages and thus remain to be improved.
DISCLOSURE OF THE INVENTION
The present invention has been accomplished to obviate said problem. An object of the invention is to provide a method for treating the surface of the innermost olefin resin layer of a multi-layer plastics film laminate in the form of a seamless tube to improve markedly the degree of close contact between the innermost layer and the processed meat or the like by applying corona discharge uniformly to the innermost layer.
The present invention provides a method for improving the internal surface of a gas-barrier, optionally heat shrinkable, multi-layer plastics film laminate in the form of a seamless tube having the innermost layer of olefin resin, the method comprising applying corona discharge employing at least two pairs of electrodes to the innermost layer from the outside of the tube having a gas sealed therein and pressed to a flat state avoiding the contact of opposed surface areas of innermost olefin resin layer with each other, said two pairs of electrodes being arranged such that one electrode of each pair is in contact with the outermost layer of the tube and the other of the same pair out of contact therewith while one electrode of one pair is kept in contact with the outermost layer of the tube with which one electrode of another pair is kept out of contact on the same side of the tube, so that the wetting tension of the innermost layer surface is increased to at least 35 dyne/cm by the corona discharge treatment.
According to the treating method of the invention, corona discharge is induced over the seamless gas-containing tube of a multi-layer film laminate from the outside of the tube by at least two pairs of electrodes provided in the above-specified arrangement while the tube is positively pressed to a flat state avoiding the mutual contact of opposed surface areas of innermost olefin resin layer, whereby the innermost layer is substantially evenly treated to increase the wet tensile strength of its surface. Reversely if corona discharge is applied
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Mori Nobuyuki
Nakamura Shoji
Sugimoto Noritsugu
Wada Fusazo
Gunze Kobunshi Corporation
Gunze Ltd.
Thurlow Jeffery
Vargot Mathieu
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