Plastic and nonmetallic article shaping or treating: processes – Disparate treatment of article subsequent to working,... – Effecting temperature change
Patent
1996-08-19
1999-04-06
Seidleck, James J.
Plastic and nonmetallic article shaping or treating: processes
Disparate treatment of article subsequent to working,...
Effecting temperature change
2642356, 2642358, 524494, 524423, 524425, 524430, B29C 7100
Patent
active
058913769
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing improved controlled permeability films and to improved films produced thereby.
Control of carbon dioxide (CO.sub.2) and/or oxygen (O.sub.2) concentration around stored products has been shown in the prior art to increase the storage life thereof. For example conditions for the optimal storage of horticultural commodities are influenced by factors which include crop species, cultivar, growing conditions, maturity, quality, temperature, relative humidity, packaging, and storage duration. Storage under controlled and modified atmosphere is influenced by the concentration of oxygen, carbon dioxide, ethylene, water vapour and other gases. Controlled atmosphere (CA) storage is achieved by externally supplying a gas stream of the required O.sub.2 and CO.sub.2 concentration into the storage cold room. Controlled atmosphere research into broccoli, for example, has shown that oxygen levels below approximately 1% and CO.sub.2 levels higher than approximately 15% independently induce offensive off-odours and off-flavours. Reported optimum O.sub.2 and CO.sub.2 concentrations for broccoli range from approximately 1 to 2.5% and approximately 5 to 10% respectively. Controlled atmosphere packaging achieves extended produce life because of effects such as slowing respiration and inhibiting pathogen growth.
It is also known in the prior art that CO.sub.2 and O.sub.2 atmospheres surrounding produce can be modified by utilizing the respiration behaviour of the produce where O.sub.2 is converted to CO.sub.2. With modified atmosphere (MA) packaging, produce is stored in polymeric film where the film permeability is exactly matched to the expected respiration behaviour as influenced by temperature and atmosphere changes to provide the optimum CO.sub.2 and O.sub.2 atmosphere. The accumulated O.sub.2 and CO.sub.2 concentration in such a package will be related to the rate at which O.sub.2 and CO.sub.2 is consumed or generated by the produce and the container permeability by a simple mass balance. The sensitivity of this balance to O.sub.2 and CO.sub.2 permeability and the possibility of producing commodity polymer films requires highly consistent and economic manufacturing of controlled permeability films.
Another use of controlled permeability films is for the storage of nematodes. As disclosed in co-pending application number PCT/AU92/00041, the entire disclosure of which is incorporated herein by reference, nematodes may be successfully packed for storage and transport using films according to the present invention.
In International Patent Application PCT/AU91/00346, to the applicants, the entire disclosure of which is incorporated herein by reference, there is disclosed a controlled permeability film including a film forming polymer and optionally including a dispersing polymer; and an inert porous filler optionally having a surface modifying agent coated thereon, the inert porous filler being present in an amount effective to reduce the ratio of the carbon dioxide permeability to the oxygen permeability of the film, and wherein the filler has a particle size greater than the intrinsic film thickness of the film forming polymer. A composite packaging article and a packaged produce product are also disclosed.
Such films of controlled permeability have been partially successful, however, their success has been limited by a continued difficulty in producing consistent film permeabilities throughout the film and difficulties in controlling film thickness.
Accordingly it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties related to the prior art.
Accordingly, in a first aspect of the present invention there is provided a controlled permeability film including; carbon dioxide (CO.sub.2) permeability to the oxygen (O.sub.2) permeability of the film, wherein the filler has a particle size greater than the intrinsic film thickness of the film forming polymer; the controlled permeability film being further modified to reduce the
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Carson Stewart Geoffrey
Christie Gregor Bruce Yeo
Christov Victor
Corrigan Penelope Anne
Gozukara Meltem Yesim
Commonwealth Scientific and Industrial Research Organisation
Rajguru U. K.
Seidleck James J.
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