IL112151A - Plastic packaging material - Google Patents

Description

n**Bo^3 nD'tss; nam PLASTIC PACKAGING MATERIAL StfePac L.A. .X.1? pSSOD THE STERILIZING PACKAGING COMPANY OF nVj'ioo ηιτ'Ίχ^ minn L . A. , LTD .

S E OF ISRAEL/MINISTRY OF AGRICULTURE rns^pnn TWO/ ^ sum ru'io A' CULTURAL RESEARCH ORGANIZATION 'x^pnn npnon "7n:'a C: 20768 20768ste.pac HB-9412 26/12/94 FIELD OF THE INVENTION The present invention relates to plastic packaging materials generally and more particularly plastic packaging materials for food and horticultural products such as produce, as well as packaging techniques and packaged products.

BACKGROUND OF THE INVENTION A great variety of plastic packaging materials is known in the patent literature. 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. Patents: 5,037,459; 4,842,741; 3,876,738 Japanese Abstracts: 05-329,947; 06-071,766; 05-316,943; 01- 148,144; 57-167,331; 01-167062; 03-059,196; 06-062,728; 04- 074,529; 01-309,621; 05-230,235 European Patents: 358,038; 566,097 WO Published PCT Application 8,404,529; 9,302,130 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 1.5g mm m-2 per day at 38 degree C and 85 - 90% relative humidity. The material allows for minimal or no condensation on its surface when used to package produce or flowers .

There is also provided in accordance with a preferred embodiment of the present invention a packaged produce product including a plastic packaging material having a relatively high permeability to water vapor and providing an atmosphere for the packaged produce which comprises approximately 4 - 12% 02, 2 20% C02, 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 food products comprising: providing a plastic packaging material of the type described hereinabove; and at least partially enclosing the food product using the plastic packaging material, thereby to provide an environment for the food product which comprises approximately 4 - 12% 02, 2 20% C02, and has a relative humidity of 85 - 100%.

Preferably, the plastic packaging material is based on a polyamide such as nylon-6 or nylon-66. For example, the material may be manufactured from a polymeric material that comprises a blend of nylon-6 or nylon-66 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 02 and C02 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. Thus the plastic packaging material may be perforated 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 .

Microperforation or perforation may take place either in a continuous or in a batch process. For example, the perforation may be effected by contacting the material with one or more rollers, plates or other devices studded with appropriately sized and positioned pins or needles. Alternatively, the perforation or microperforation may be effected by use of laser technology. Perforation may occur during extrusion of the material downstream of a bubble collapsing frame or in tandem with a subsequent processing step such as printing or package forming.

In accordance with a preferred embodiment of the present invention, the raw material may be manipulated to tailor its permeability to water vapor. For example, blends of nylon-6 and other raw materials may be processed to produce a film with a lower 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.

In accordance with a preferred embodiment of the present invention, the raw material may be manipulated to absorb or degrade ethylene gas. For example,, blends of polyamides with other compounds which absorb or degrade ethylene may be employed in the manufacture of the packaging material.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawing in which: Fig. l is a simplified illustration of produce packaging in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED; EMBODIMENTS Reference is now made to Fig. 1, which illustrates produce packaging in accordance with a preferred embodiment of the present invention. In the illustrated embodiment, produce 10, such as bean sprouts, is enclosed within a bag 12 preferably composed of nylon-6 or a blend containing nylon-6. Alternatively a package or wrap other than a bag may be provided. The nylon-6 film may be extrusion blown or produced in any other conventional manner from raw materials which are commercially available, inter alia, under the trade name Capron 8209 from Allied Signal or under the trade name Ultramid B4 from BASF.

In accordance with a preferred embodiment of the present invention the nylon-6 material may be extrusion blended with nylon-6I/6T (for example SELAR PA 3426 commercially available from Dupont) to produce films of 20 and 30 micron thickness. The ratios may be between 80 - 99% nylon-6 and 1 - 20% nylon-6I/6T. The resulting films have reduced water vapor permeability relative to nylon-6 alone and retain the ability to minimize condensation.

Additionally in accordance with a preferred embodiment of the present invention the material may be a blend of nylon-6 and polyolefins and compatibilizers (for example Orgalloy LE 6000, commercially available from Elf Atochem) . Such blends can be' employed to produce films having reduced water vapor permeability relative to that of nylon-6 alone and are characterized by minimal moisture condensation on the film surface when used to package produce or other horticultural products.

Further in accordance with a preferred embodiment of the present invention the nylon-6 material may be extrusion blended with nylon-11 or nylon-12 to produce films having reduced water vapor permeability relative to that of nylon-6 alone and are characterized by minimal moisture condensation on the film surface when used to package produce or other horticultural products .

Additionally in accordance with a preferred embodiment of the present invention the polyamide material may be extrusion blended with porous additives, such as silica or diatomaceous earth to produce films having reduced water vapor permeability relative , to that of polyamide alone and are characterized by ethylene sorption and by minimal moisture condensation on the film surface when used to package produce or other horticultural products. The ratios may be between 88 - 99% polyamide and 0.5 12% porous additive.

Additionally in accordance with a preferred embodiment of the present invention, the films may be oriented during manufacture or in a subsequent processing step to provide films having reduced water vapor permeability relative to unoriented films produced of the same raw materials. The oriented material is characterized by minimal moisture condensation on the material surface when used to package produce or other horticultural products .

Further in accordance with a preferred embodiment of the invention, films of polyamide with or without the above described additives and compositions and having thicknesses of 5 - 100 microns may be passed through a heating tunnel to heat the film to temperatures of 100 - 200 degrees centigrade to provide films having reduced water permeability relative to polyamide that is not heat-treated and are characterized by minimal moisture condensation on the film surface when used to package produce or other horticultural products .

Additionally in accordance with a preferred embodiment of the present invention a polyamide material may be extrusion blended with soluble starch or salt additives and then passed through a water bath at 4 - 100 degree C to extract the soluble additive in order to produce films having increased 02 and C0 permeability relative to the base polyamide alone. The ratios may be between 88 - 99% polyamide and 1 - 12% soluble starch or salt additive. The bath water preferably is circulated, filtered and reintroduced to the bath on a continuous basis. Excess water is preferably removed from the film by passing it through a heating tunnel as described in the preceding paragraph.

Trays, baskets, containers, holders, bags, films or any other packaging material formed from films having a thickness generally in excess of 100 micron of nylon-6 or any other — 9 suitable polymer having water permeability exceeding 1.5 g mm m per day at 38 degrees C with or without the additives or compositions described above may be provided by extrusion or any other suitable manufacturing process.

Film and sheets manufactured from any of the materials listed above and/or by any of the techniques listed above may be unperforated, or they may be perforated or microperforated to increase the permeability of the film to 02 and C02 · For the purposes of the specification and claims, perforation refers to holes of approximately 1 - 10 mm diameter covering up to about 0.5% of the surface area of the material.

For the purposes of the specification and claims, microperforation refers to holes of approximately 0.05 - 1 mm diameter in a density of up to about 2000 holes per square meter of the material.

Reference is now made to the following examples which provide an indication of the scope of the present invention.

EXAMPLE I Nylon-6 extrusion blown film having a thickness of 40 microns was employed to package bean sprouts, mushroom, tarragon, chive and chickory lettuce. After 8 days of storage at 4 degrees C and a relative humidity of 90 - 97%, the sprouts were inspected and their weight loss was measured and compared with a control package of sprouts which had been stored under identical conditions in PVC film packaging.

The weight loss of the nylon-6 packaged sprouts was found to be less than of the control packaged sprouts. The nylon-6 packaged sprouts had a white color and were crisp, while the PVC packaged sprouts were brown and were not crisp.

The mushrooms were white and fresh after 18 days of storage in nylon-6 packaging. Visual observations of the tarragon, chive and chickory lettuce indicated that they stayed fresher longer in the nylon-6 packaging as compared to polyethylene packaging.

EXAMPLE II Nylon-6 extrusion blown film having a thickness of 20 microns and perforations 6 - 8 mm in diameter was used to package grapes. After 12 days of storage at.O degrees C and 7 days storage at 20 degrees C, the condition of the grapes was compared with control packages packaged in both perforated and non-perforated polyethylene. The grapes packaged in nylon-6 showed a higher percentage of healthy clusters and lower levels of decay than the control packages.

EXAMPLE III Nylon-6 extrusion blown film having a thickness of 20 microns and microperforations 0.8 mm in diameter was used to package snap beans (green beans). After 5 days of storage at 5 degrees C and 3 days storage at 20 degrees C, the condition of the beans was compared with control packages packaged in micro-perforated polyethylene. The beans packaged in nylon-6 showed less weight loss, less rusty spots and substantially no mold growth as compared with the control packages.

EXAMPLE IV Nylon-6 extrusion blown film having a thickness of 20 microns in both perforated and microperforated forms was used to package cucumbers. After 6 days of storage at 8 degrees C and 3 days storage at 20 degrees C, the condition of the cucumbers was evaluated and was found to be very good. The cucumbers packed in microperforated packages showed no chilling injury, while those in perforated packages showed very low chilling injury.

EXAMPLE V A blend of 20% nylon 6I/6T and 80% nylon-6 was extrusion blown into a film 20 microns thick, microperforated, and used to package cherry tomatoes. After a number of days, there was no condensation in the packages and the tomato quality was better than that of tomatoes packaged in alternative materials.

EXAMPLE VI A compatabilized blend of polyethylene and nylon-6 was extrusion blown into a film 20 micron thick, microperforated, and used to package sweet corn. After 14 days at l-ZdC, the corn was of high quality and showed minimal decay compared to corn packaged in polyvinylchloride film.

EXAMPLE VII 25 micron thick nylon-6 film, manufactured by a chill- roll cast process and then biaxially oriented by means tenter frame orientation equipment was used to wrap cut flowers.

EXAMPLE VIII micron thick nylon-66 film, manufactured by an extrusion blown film process, was perforated and then passed through a heating tunnel at 200 degrees C and was used to package mangos.

EXAMPLE IX 15 micron thick nylon-12 film, manufactured by extrusion in a chill-roll cast process and microperforated was used to package berries.

EXAMPLE X A copolymer of nylon-6 and nylon-66 is extruded into a film 20 microns thick via a blown film double-bubble process that imparts a high degree of orientation to the film. The film is then microperforated and used to package lettuce.

EXAMPLE XI A blend of nylon 610 and 8% soluble starch is extruded into a 30 micron thick film by a water quench cast film process. The soluble starch is extracted during the water quenching stage, leaving a porous film which is then passed through a heating tunnel and ultimately used to package green and red peppers.

EXAMPLE XII A mixture of 80% nylon-6 and 20% of a compatibilized blend of polyethylene and nylon-6 is extruded in a chill-roll cast processto produce a sheet 150 n th jc. This material is then perforated and thermoformed into trays to package cherries.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the invention is defined only by the claims which follow:

Claims (10)

112151/3 C L A I S

1. A method of preserving horticultural products comprising : providing a plastic packaging material having a thickness of up to about 500 microns and permeability to water -2 vapor exceeding about 1.5g mm m per day at 38 degrees C and 85- 90% relative humidity, whereby when the material is used to package produce and other horticultural products no condensation or minimal condensation appears on a surface of the material; and at least partially enclosing the horticultural product using the plastic packaging material, thereby to provide an environment for the horticultural product which comprises approximately 4 - 12% 0 , 2 - 20% CO , and has a relative 2 2 humidity of 85 - 100%.

2. A method according to claim 1 and wherein the plastic packaging material is based on a polyamide formulation.

3. A method according to claim 1 or claim 2 and wherein the plastic packaging material is perforated to have holes of approximately 1 - 10 mm diameter covering up to about 0.5% of the surface area of the material.

4. A method according to any of the preceding claims 1 3 and ^wherein said plastic packaging material is microperforated 1 12151/2 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.

5. A method according to any of claims 1 - 4 and wherein said product comprises horticultural products.

6. A method according to claim 3 or claim 4 and wherein the perforation takes place in a continuous process.

7. A method according to claim 3 or claim 4 and wherein the perforation takes place in a batch process.

8. A method according to any of claims 3, 4, 5 and 7 and wherein perforation occurs during extrusion of the material.

9. A method according to any of claims 3, 4, 6 and 7 and wherein perforation occurs during a subsequent processing step .

10. A method according to any of the preceding claims 1 9 substantially as illustrated and described hereinabove. Sanford T. Colb & Co. Advocates & Patent Attorneys C:20768 HB-9412