Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1994-04-28
2001-12-11
Krynski, William (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S516000, C524S300000
Reexamination Certificate
active
06329048
ABSTRACT:
FIELD OF THE INVENTION
The present invention is concerned with the over-wrapping of products which can be adversely affected from a quality standpoint with the infusion of unwanted odors and unwanted flavors or by the loss of characteristic, desired aromas and flavors.
BACKGROUND OF THE INVENTION
A constant problem in the packaging of commercial products, particularly those for human consumption, is how to protect the integrity of these products so that their desired flavor and aroma are not lost and unwanted odors and unpleasant flavors are not permitted to be transmitted into the product.
It is an object of the present invention to provide a packaging film material which retains the integrity of the flavor and aroma of a packaged product and excludes unwanted odors and flavors from being transmitted to the product.
It is another object of the present invention to provide a method for preventing the transmission of odors and flavors into or out of such a package.
SUMMARY OF THE INVENTION
The present invention relates to the packaging of a product capable of absorbing unwanted odors and unpleasant flavors, or a product containing desirable flavor and aroma characteristics, that are to be retained. The package employs an oriented film of a blend of polypropylene and a member selected from the group consisting of polymerized d-limonene, polymerized beta-pinene, or a polymerized synthetic approximation of d-limonene and beta-pinene and mixtures thereof, to exclude unwanted odors or flavors and to retain those that are desirable. The present invention is also concerned with a method for preventing the transmission of odors and flavors into or out of a product, when the product is packaged in an oriented film of a blend of polypropylene and a member selected from the group consisting of polymerized d-limonene, polymerized beta-pinene, a polymerized synthetic approximation of d-limonene and beta-pinene and mixtures thereof.
It is preferred that the film structures identified above include a heat-sealable skin layer comprising a polyolefin of comparatively low stereoregularity on at least one surface thereof.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is broadly directed to the improvement in the flavor or aroma barrier properties of polypropylene films. It has been discovered that the admixture of certain polyterpenes identified above, into polypropylene polymers will effectively block the transmission of flavors and odors through polypropylene polymer blend while other polyterpene admixtures are comparatively ineffective. An example of a polymerized polyterpene which has given ineffective results is polymerized alpha-pinene.
This is a surprising result in the face of past general teachings regarding the moisture barrier and gas barrier benefits that can arise from the use of the broad general class of polyterpenes and their blends with polypropylene.
Past disclosures have taught improvements in gas barrier characteristics, which pertain to the minimization of non-condensible gases; such as oxygen, nitrogen, and carbon dioxide, through the film. These are useful in such applications as gas flushing with nitrogen or carbon dioxide to protect the product inside a package from oxidizing and becoming stale.
Past disclosures have also taught improvements in moisture barrier which pertain to the migration of water and water vapor through the film. These are useful in the packaging of dry foods, such as crackers and potato chips, to maintain texture, etc.
What we have discovered is that application to pungent, aromatic oils is not encompassed in the past teaching. We have discovered a comparative few compounds which are effective in reducing the migration of aromatic oils when used in an admixture with polypropylene polymers. Oriented films made from these blends of polymers effectively prevent, for example, cigarette packages that are sold in gasoline station displays from picking up hydrocarbon odors, lemon-flavored cookies from losing their fresh-baked, lemon flavor and scent, etc. Oriented films with good moisture barrier and good gas barrier have not met these needs.
The base film of the present odor and flavor barrier structure is comprised of a combination of a homopolymer polypropylene, which is of comparatively high stereoregularity having a melting point range of from about 321°-333° F., interblended with from about 1 to about 20% by weight of the above identified polyterpene. A preferred range is from about 10 to 15% by weight of the added polyterpene. The basic structure of the aroma and flavor barrier film can be the same or similar to that described in U.S. Pat. No. 4,911,976 the disclosure of which is incorporated herein by reference in its entirety. In this patent the oriented multi-layer film structure comprises coextruded layers of
(a) a base layer comprising polypropylene of comparatively high stereo regularity and (b) a heat-sealable skin layer comprising a polyolefin of comparatively low stereo regularity on at least one surface of (a). The skin layers can contain a slip additive and/or an antiblock material chosen from those suitable for such products. The skin layer can range from about 0.5-5 microns. The preferred polypropylenes for the base layer are formed by polymerizing propylene in the presence of a stereo specific catalyst system. They can have a melt flow rate, measured by the ASTM-1238 technique, ranging from about 1 to about 25, preferably 2-4. The crystalline melting point is about 321°-333° F. The average molecular weight range is from about 25,000 to about 100,000. The density is from 0.90 to 0.92.
The comparatively low stereo regular polyolefin polymers contemplated as the skin materials of the multilayer system include, for example, ethylene-propylene-butene-1 terpolymers. Preferred terpolymers are ethylene-propylene-butene-1 terpolymers having 1-5 wt % ethylene and 1-15 wt % butene-1. The preferred polyterpenes have a molecular weight of from about 800 to about 15,000 M
n
.
The multi-layer films of the present invention can be prepared employing commercially available systems for coextruding resins. The polypropylene homopolymer of comparatively high stereo regularity blended with the selected polyterpene can be coextruded with an ethylene-propylene-butene-1 terpolymer. The polymers can be brought to the molten state and coextruded from a conventional extruder through a flat sheet die, the melt streams being combined in an adapter prior to being extruded from the die. After leaving the die orifice, the multi-layer film structure is chilled and the quenched sheet then reheated and stretched, e.g., 4-6 times in the machine direction (MD), and subsequently, for example, 4-12 times in the transverse direction (TD). The edges of the film can be trimmed and the film wound onto a core. The following examples will illustrate the invention.
REFERENCES:
patent: 3278646 (1966-10-01), Lambert, Jr.
patent: 4230767 (1980-10-01), Isaka
patent: 4293608 (1981-10-01), Isaka et al.
patent: 4911976 (1990-03-01), Park et al.
patent: 4921749 (1990-05-01), Bossaert et al.
patent: 5085943 (1992-02-01), Crighton et al.
patent: 5087667 (1992-02-01), Hwo
patent: 5089319 (1992-02-01), Bothe
patent: 5128183 (1992-07-01), Buzio
patent: 5151317 (1992-09-01), Bothe
patent: 5178960 (1993-01-01), Cook
patent: 5194474 (1993-03-01), Aoyama
patent: 308212 (1986-10-01), None
Balloni Riccardo
Heffelfinger Michael T.
Lockhart Mark W.
Peet Robert G.
Stetter Eileen A.
Krynski William
Mobil Oil Corporation
Simmons T. Dean
LandOfFree
Multi-layer barrier film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-layer barrier film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-layer barrier film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2580503