Plastic packaging material

Details Plastic packaging material Plastic packaging material

1997-08-19

2001-02-20

Dye, Rena L. (Department: 1772)

Food or edible material: processes, compositions, and products

Packaged or wrapped product

C426S108000, C426S118000, C426S395000, C426S410000, C426S415000, C426S419000, C383S103000, C428S035200, C428S035500, C428S137000, C428S213000

Reexamination Certificate

active

06190710

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to plastic packaging materials generally, and more particularly to plastic packaging materials for packaging produce and horticultural products, as well as packaging techniques and packaged products.
BACKGROUND OF THE INVENTION
A great variety of plastic packaging materials is known in the art. The following patents and published patent applications are thought to be representative of the state of the art, particularly in the field of nylon-6 packaging materials, packaging for produce and control of humidity in packaging:
U.S. Pat. Nos. 5,492,705, 5,405,561, 5,037,459, 4,842,741, 3,876,738, and 3,682,028;
Japanese Patent Documents 05-329,947, 06-071,766, 05-316,943, 01-148,144, 57167,331, 01-167062, 03-059,196, 06-062,728, 04-074,529, 01-309,621, 05-
230,235, 05-168,400,
and 04-210,552;
European Patent Documents 358,038, 538,713, and 566,097;
PCT Patent Applications 8404529 and 9302130; and
Australian Patent 636,284.
SUMMARY OF THE INVENTION
The present invention seeks to provide an improved plastic packaging material which has a relatively high permeability to water vapor.
There is thus provided in accordance with a preferred embodiment of the present invention a plastic packaging material having a thickness of up to about 500 microns and a permeability to water vapor exceeding about 1.5 g mm m
−2
per day at 38° C. and 85-90% relative humidity (RH). The material allows for minimal or no condensation on its surface when used to package produce.
There is also provided in accordance with a preferred embodiment of the present invention a packaged produce including a plastic packaging material having a relatively high permeability to water vapor and providing an atmosphere for the packaged produce which comprises
4-20% O
2
, 0.5-17% CO
2
, and has a relative humidity of 85-100%.
There is additionally provided in accordance with a preferred embodiment of the present invention a method of preserving produce comprising:
providing a plastic packaging material of the type described hereinabove; and
at least partially enclosing the produce using the plastic packaging material, thereby to provide an environment for the produce which comprises approximately 4-20% O
2
, 0.5-17% CO
2
, and has a relative humidity of 85-100%.
In accordance with a preferred embodiment of the present invention, the composition of the plastic packaging material includes homopolymers or copolymers with chemical groups that are given to hydrogen bonding or association with water, for example homopolymers or copolymers containing amides, esters, anhydrides, or urethanes, or their derivatives, or containing acyl groups, carboxyl groups, or alcohol groups, or their derivatives.
Preferably, the plastic packaging material includes a polyamide such as nylon-6 or nylon-66 or copolyamides such as nylon-6/66 or nylon-6/12. For example, the material may be manufactured from a polymeric material that comprises a blend of nylon-6 or nylon-66, nylon 6/66, or nylon 6/12 with other polymeric and/or non-polymeric components.
In accordance with a preferred embodiment of the present invention, the raw material may be manipulated to increase the O
2
and CO
2
permeability of the film. For example, blends of nylon-6 and other components may be manufactured into a material having a porous character. Additionally or alternatively, the plastic packaging material may be manipulated after the film is formed, for example the plastic packaging material may be perforated. Preferably, the plastic packaging material may be macroperforated to have holes of approximately 1-10 mm diameter covering up to about 0.5% of the surface area of the material, or the plastic packaging material may be microperforated to have holes of approximately 0.05-1 mm diameter in a density of up to about 2000 holes per square meter of the material. Even more preferably, the plastic packaging material may be microperforated to have holes of approximately 0.3-0.8 mm diameter in a density of up to about 500 holes per square meter of the material.
In accordance with a preferred embodiment of the present invention, the raw material may be manipulated to tailor its permeability to water vapor, so as to either increase or decrease water vapor permeability. For example, blends of nylon-6 or nylon 6/66 with other raw materials may be processed to provide a film with a lower water vapor permeability or a higher water vapor permeability than a film processed from nylon-6 alone.
Additionally or alternatively, the packaging material may be manipulated by heat treatment or orientation processes to reduce its water vapor permeability.
Additionally or alternatively, the packaging material may be manipulated by steam treatment or other processes to increase its water vapor permeability.
In accordance with a preferred embodiment of the present invention, the raw material or resulting packaging material may be manipulated to absorb or degrade ethylene gas. For example, blends of polyamides with other materials which absorb or degrade ethylene may be employed in the manufacture of the packaging material, or the resulting packaging material may be coated or laminated with materials which absorb or degrade ethylene gas.
There is additionally provided in accordance with a preferred embodiment of the present invention a method for producing optimized packaging materials for packaging produce in an environment which is optimized in terms of gaseous composition and water condensation, the method including the steps of:
determining sensitivity of produce to at least carbon dioxide concentration and the presence of water condensation in an environment;
providing a plurality of package precursor materials having differing water vapor permeabilities;
selecting a package precursor material having a suitable water vapor permeability;
perforating a package material selected in the selecting step to an extent at least partially determined by the sensitivity of a product to at least carbon dioxide concentration in order to produce an optimized packaging material.
Thereafter, a packaging method may also include applying the optimized packaging material to the produce for packaging thereof.
In accordance with a preferred embodiment of the present invention, the step of perforating includes selecting the number of a preselected size perforations per unit of the optimized packaging material.
It is noted that throughout the specification and claims the term “produce” refers particularly but not exclusively to fruits, vegetables, flowers, plants, fungi, and other edible or inedible horticultural or botanical products which tend to spoil or otherwise have a limited shelf life.
It is further noted that throughout the specification and claims the term macroperforation refers to holes of approximately 1-10 millimeters (mm) diameter covering up to about 0.5% of a surface area.
It is further noted that throughout the specification and claims the term microperforation refers to holes of approximately 0.05-1 mm diameter in a density of up to about 2000 holes per square meter of a surface area.


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patent: 4-0

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