Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1996-03-26
2001-05-29
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S035700, C428S346000, C428S347000, C428S353000, C428S354000, C428S3550RA, C428S480000, C428S483000, C428S910000, C156S308200, C156S327000, C156S332000
Reexamination Certificate
active
06238788
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a multilayer packaging structure which: 1. is easily recycled, 2. has a relatively broad heat seal temperature, and 3. provides an easy open seal, even at very high heat seal temperatures. More specifically, the films of the present invention are preferably multilayer structures comprising: 1. a support film, such as polyester, 2. an acrylic interface layer; and 3. a heat seal outer layer.
BACKGROUND OF THE INVENTION
“Poly vinylidene chloride (“PVDC”) coated” polyester films are known and are often used as heat-sealable packaging films. However, halogenated films and coatings are increasingly coming under environmental attack and are being subjected to increasing government regulation. Also, such films generally have a rather narrow heat-sealing range (generally about 30-50° C.)—1. above this range, the package film has a tendency to tear, and 2. below this range, the packaged product may have a tendency to leak.
One possible solution to these problems is to replace the PVDC heat seal coating with other heat seal compositions. However, many heat seal compositions, such as copolyesters, can seal extremely tightly (depending upon the heat seal temperature) and thereby provide a package which is very difficult to open.
The present invention is an innovative solution to the above problems.
SUMMARY OF THE INVENTION
Overview
The present invention is directed to a novel and improved multilayer film comprising:
1. a copolyester heat seal layer;
2. an acrylic or acrylate interface layer; and
3. a support layer.
Once a heat sealing temperature is applied to the film, the peel strength of the heat seal will be advantageously limited by the interface layer. Hence, the film can be used in a wide range of heat seal applications, and the resulting heat seal will be effective in protecting the product, but not so strong as to frustrate consumers as they attempt to open the package.
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Chen Vivian
E. I. Du Pont de Nemours and Company
Kelly Patricia L.
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