Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1989-11-01
1991-09-17
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
25218624, 25218625, 25218633, 25218828, 252383, 252385, 428483, 428 366, 428 359, 428219, 428332, C08K 500, C08K 520, B32B 2718, B65D 8126
Patent
active
050496247
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to packaging of oxygen-sensitive foods and beverages.
BACKGROUND OF INVENTION
Among substances that are oxygen-sensitive we would particularly mention beers (especially lager beers), wines (especially white ones), fruit juices, some carbonated soft drinks, fruits, nuts, vegetables, meat products, baby foods, coffee, sauces, and dairy products. Almost all foods and beverages are sensitive to some degree.
One approach to oxygen-sensitive products has been the inclusion in the pack of a sachet containing a compound such as iron or a lower iron oxide or hydroxide. This material reacts with ("scavenges") oxygen packed with the product or transmitted through the wall of the package.
Another approach has been the inclusion of scavenger in the walls of the package. Where the walls comprise a polymer and are appreciably oxygen-permeable this has the advantage of scavenging at least a part of the oxygen before it reaches the package contents at all.
Some discussion of the conventional measurements and units of oxygen permeation is appropriate at this point. The measurement is made by exposing a package wall of area A to a partial pressure p of oxygen on the one side and to an essentially zero partial pressure of oxygen on the other. The quantity of oxygen emerging on the latter side is measured and expressed as a volume rate dV/dt, the volume being converted to some standard conditions of temperature and pressure. After a certain time of exposure (usually a few days) dV/dt is generally found to stabilise, and a P.sub.W value is calculated from the equation (1). the wall. (Analogy with magnetic permeance and electrical conductance would suggest that P.sub.W should be described as "permeance per unit area", but we are following the nomenclature in Encyclopaedia of Polymer Science and Technology, Vol. 2, Wiley Interscience, 1985, page 178.) The standard conditions for expressing dV/dt used generally and in this specification are 0.degree. C. and 1 atm (1 atm=101 325 N m.sup.-2). If the thickness of the area of wall is substantially constant over the area A with value T and the wall is uniform through the thickness (i.e. the wall is not a laminated or coated one) then the permeability of the material in the direction normal to the wall is calculated from the equation (2). approximation independent of t, p, and T although they are often appreciably dependent on other conditions of the measurement such as the humidity of the atmosphere on the oxygen-rich side and the temperature of the measurement.
For oxygen-scavenging walls, P.sub.W and P.sub.M are functions of t because the concentrations and activity of scavenger vary with time (particularly as the scavenger is consumed). This has not prevented us usually from measuring P.sub.W and P.sub.M reasonably accurately as a function of time (the changes in dV/dt being relatively gradual once the normal initial equilibration period of a few days is over). However, it should be recognised that, whereas after a few days' exposure to the measurement conditions a non-scavenging wall achieves a steady state in which dV/dt is equal to the rate of oxygen ingress to the wall, a scavenging wall achieves an (almost) steady state in which dV/dt is considerably less than the rate of oxygen ingress to the wall. This being the case, it is likely that P.sub.W calculated from (1) is a function of p as well as of t and that P.sub.M in (2) is a function of p and T as well as of t. P.sub.W and P.sub.M for scavenging walls are, strictly speaking, not true permeances and permeabilities at all (since permeation and scavenging are occurring simultaneously) but, rather, apparent ones. However, we have chosen to retain the conventional terms "permeance" and "permeability". So long as the conditions of the measurement are sufficiently specified they are suitable for characterising the walls in a manner relevant to the packaging user (i.e. in terms of the oxygen emerging from the wall).
All values of P.sub.W and P.sub.M hereinafter in this specificati
REFERENCES:
patent: 3586514 (1971-06-01), Vijlbrief
patent: 4041209 (1977-08-01), Scholle
patent: 4048361 (1977-09-01), Valyi
Chemical Abstracts, vol. 100, p. 60, 193165x.
Adams John F.
Cochran Michael A.
Folland Rickworth
Nicholas James W.
Robinson Melvin E. R.
CMB Foodcan plc
McDonald, Jr. T.
Michl Paul R.
LandOfFree
Packaging does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Packaging, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Packaging will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1917738