Non-wax packaging film

Details Non-wax packaging film Non-wax packaging film

2000-06-21

2003-03-04

Nolan, Sandra M. (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C426S127000, C426S130000, C426S415000, C428S349000, C428S516000, C428S520000, C428S903300

Reexamination Certificate

active

06528134

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to non-wax film structures useful in the packaging of food products, especially cheese. More specifically, the invention relates to polymeric film structures containing a hydrogenated aliphatic hydrocarbon additive useful in the packaging of food products, especially cheese.
BACKGROUND OF THE INVENTION
Wax packaging has been used over the years for food packaging, especially the packaging of cheese and processed cheese. For example, cheese manufacturers have utilized wax-coated cellophane to package 1-, 2-, 3- and 5-pound processed cheese loaves. In addition, machinery has been developed to form wax-coated cellophane film structures for pouches that are then inserted into corrugated boxes and filled with cheese at high temperatures.
Several issues have developed regarding the use of a typical wax-coated cellophane film structure for packaging food products such as cheese. First, wax coatings require a starch dusting (potato or corn powder depending on the final cheese product) to prevent “blocking” (i.e., fusing or sticking together) of the final structure in roll form. This is due to the soft nature of the wax. In addition, the starch aids in “cheese release” enabling the consumer to completely remove the wax coated cellophane structure from the cheese before consumption. These starch coatings tend to rub off of the film during machining causing an undesirable starch buildup on equipment. Secondly, due to the soft nature of wax coatings, they are temperature sensitive and require special storage conditions. Abnormally high temperature storage can cause complete blocking of finished rolls as the wax coating can activate during storage. In addition, at abnormally cold temperatures wax coatings can become brittle causing wax splitting and delaminating of the wax coating off of the cellophane substrate. Thirdly, as new processed cheese products have been developed, higher filling temperatures are being used by cheese manufacturers, and the need for a less heat sensitive sealant is desirable to aid in “cheese release.” It has now become desirable to find a replacement for cellophane and wax coatings.
Therefore there is a need to find a non-wax sealant film structure that would overcome the disadvantages of the wax-coated cellophane film structures of the prior art and yet meet the processing and packaging requirements of the food product, especially a cheese product.
Polymeric, sealant films are known in the art. Schuhmann, et al., U.S. Pat. No. 5,429,862 disclose a sealable film comprising a base layer comprising polypropylene and a hydrocarbon resin and at least one top layer comprising (ii) at least one top layer comprising (a) an ethylene/propylene copolymer having an ethylene content of not more than about 10% by weight, (b) a propylene/1-butene copolymer, (c) a propylene/ethylene/alpha-olefin terpolymer, or (d) a blend of two or more of (a), (b) and (c), wherein at least one of said base layer and said at least one top layer contains an anti-blocking agent or lubricant.
Schuhmann, et al., U.S. Pat. No. 5,851,640 disclose a multilayer film structure having a core layer and a sealable top layer and an intermediate layer between said core and sealable layer. The core layer comprises a propylene polymer; the sealable top layer comprises:
a copolymer of ethylene and propylene, ethylene and butylene, propylene and butylene, ethylene and an alpha-olefin having 5 to 10 carbon atoms, or propylene and an alpha-olefin having 5 to 10 carbon atoms, or
a terpolymer of ethylene and propylene and butylene, or ethylene and propylene and an alpha-olefin having 5 to 10 carbon atoms, or
a mixture of one or more of the above copolymers and terpolymers with polypropylene, or
a mixture of two or more of said copolymers, said terpolymers, or both of said copolymers and said terpolymers,
and the intermediate layer consists essentially of a propylene polymer.
Weiner, U.S. Pat. No. 4,275,120 discloses a multiple layer, heat-sealable film having a substrate layer consisting of a homopolymer of poly(propylene) or a copolymer of propylene and a blend compatible polyolefins and at least one heat sealable layer consisting of a blend poly(1-butene), and a copolymer of ethylene or propylene and a higher olefin.
Weiner, U.S. Pat. No. 4,291,092 discloses a multi-layer heat sealable film having a substrate layer consisting of a homopolymer of poly(propylene) or a copolymer of propylene and a blend compatible polyolefins and at least one heat sealable layer consisting of a blend of a copolymer of ethylene and a higher olefin and a copolymer of propylene and a higher olefin.
Weiner, U.S. Pat. No. 4,339,498 discloses a film comprising a core or substrate layer of propylene and a heat sealable surface layer which is present on either one or both sides of the substrate is:
(1) an interpolymer of 1-90 mole percent of propylene, 1-98 mole percent of an alpha-olefin having four or more carbon atoms and 1-98 mole percent of a different alpha-olefin having four or more carbon atoms;
(2) a copolymer of 50-97 mole percent of butene-1 and 3-50 mole percent of an alpha-olefin having more than four carbon atoms; or
(3) an interpolymer of 2-94 mole percent of ethylene, 1-93 mole percent of propylene, and 5-97 mole percent of an alpha olefin having four or more carbon atoms.
Schuhmann, et al., U.S. Pat. No. 5,554,245 disclose a process for producing a sealable film comprising:
(A) producing by coextrusion through a slot die a cast film comprising:
(i) a base layer comprising polypropylene and a hydrocarbon resin having a softening point of at least 140° C., and
(ii) at least one top layer comprising
(a) an ethylene/propylene copolymer having an ethylene content of not more than about 10% by weight,
(b) a propylene/1-butene copolymer,
(c) a propylene/ethylene/alpha-olefin terpolymer, or
(d) a blend of two or more of (a), (b) and (c), wherein said top layer comprises an antiblocking agent with an average particle size of 1 to 6 &mgr;m,
(B) chilling the cast film on a chill roll; and then
(C) orienting the film by biaxial stretching in the longitudinal and transverse directions.
Wilson, U.S. Pat. No. 5,419,934 discloses a three layered film, the three layers having two outer layers and an intermediate layer. The intermediate layer comprises a mixture of a first linear low density poly(ethylene) and a polyolefin wherein poly(propylene) is exemplified; and at least one of the two outer layers comprises a second linear low density poly(ethylene).
It is also known in the art that polymer sealant film structures provide a more consistent cheese release because a polymer film sealant has a higher melting point. Wax typically melts at the same temperature that processed cheese is filled at ~165° F. whereas, a polymer sealant melts at a significantly higher temperature. In addition, the higher melting point of a polymer sealant eliminates the need for starch, which is required for a wax coating, eliminating starch build up issues. A typical coextruded film, however, lacks the stiffness, “dead-fold”, pouch formation, and cutting qualities of a typical wax-coated cellophane structure. Due to the “memory” effect of polymers, it is difficult to maintain pouch formation during the filling of product. In addition, a coextruded film is more sensitive to the “shear” cutting employed on a typical processed cheese line during pouch formation. In summary, a typical wax structure cuts more consistently, is stiffer, has higher “dead-fold”, and tends to maintain pouch formation shape (less memory), all of which facilitates easier product filling.
Therefore, given the advantages and disadvantages of both the wax-cellophane film structure and the polymeric sealant film structures, there is a need to develop a polymeric sealant film structure which has the properties of high melt temperature, stiffness, dead-fold, pouch formation and cutting qualities.
An objective of this invention is to provide three layer cast coextruded film structures.
A further objective of this invention is to provide three layer cast c

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