Food or edible material: processes – compositions – and products – Packaged or wrapped product – Packaged product is animal flesh
Reexamination Certificate
1994-12-12
2001-09-11
Tran, Lien (Department: 1761)
Food or edible material: processes, compositions, and products
Packaged or wrapped product
Packaged product is animal flesh
C426S106000, C426S124000, C426S127000
Reexamination Certificate
active
06287613
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to packages for the packaging of bone-in meat products. More particularly, the present invention relates to a bag having a protective patch adhered directly thereto, the protective patch preventing, or reducing, puncture of the bag by exposed bone from a meat product within the bag.
BACKGROUND OF THE INVENTION
Heat-shrinkable thermoplastics are known to be useful as flexible packaging materials for vacuum packaging various foodstuffs, including meat. Such plastic materials, however, while generally suitable for packaging meat, understandably have difficulties in successfully packaging sharp or bony products. For example, attempts to package bone-in primal cuts of meat usually result in an unsatisfactorily large number of bag failures due to exposed bone puncturing the bag.
The use of cushioning materials such as paper, paper laminates, wax impregnated cloth, and various types of plastic inserts have proved to be less than totally satisfactory in solving the problem, as they require large expenditure of materials and labor, and are subject to shifting off of protruding bones. The preparation of special cuts of meat or close bone trim with removal of protruding bones has also been attempted. However, this is at best only a limited solution to the problem since it does not offer the positive protection necessary for a wide variety of commercial bone-in types of meat. Furthermore, removal of the bone is a relatively expensive and time-consuming procedure.
Some time ago, the use of a bag having a patch thereon, i.e., a “patch bag”, became a commercially-preferred manner of packaging a number of bone-in meat products. One of the first commercially-utilized patch bags utilized a heat shrinkable bag and a patch composed of two laminated VALERON™ high density polyethylene (“HDPE”) films, each film having been highly oriented in the machine direction. In the laminated patch, the machine direction of a first HDPE lamina was oriented about 90 degrees with respect to the machine direction of a second patch lamina.
The VALERON™ HDPE patch performed well in preventing punctures from exposed bone. However, upon packaging a meat product in a heat-shrinkable bag having such a patch thereon, the corners of the patch delaminated from the bag upon shrinkage of the bag, due to the fact that the patch would not shrink as the bag shrunk. Customers perceived the delamination of the patch corners from the bag to be highly undesirable. Furthermore, the highly oriented HDPE films were opaque white due to the formation of voids during the orientation process.
Thus, the need arose for a patch which would provide the patch bag with a desired level of puncture-resistance, while at the same time being heat-shrinkable so that there would be no substantial delamination at the corners of the patch. Furthermore, although for some uses it was desirable to use an opaque patch, for other uses it was desirable to provide a substantially translucent or transparent patch.
Although ethylene/vinyl acetate copolymer (“EVA”) was known to have the desired heat shrink properties for use in patches, it was discovered to lack the desired level of puncture-resistance obtainable using the VALERON™ HDPE patch. That is, EVA patches had to be much thicker than an HDPE patch in order to provide the same level of puncture-resistance. Furthermore, in addition to lacking the desired puncture-resistant character, EVA lacked abrasion-resistance, further diminishing its utility as the bulk polymer in the patch.
Surprisingly, linear low density polyethylene (LLDPE) was found to provide the combination of puncture-resistance, heat-shrinkability, abrasion-resistance, and even transparency, desired for use in a patch for patch bags. Within the last 10 years, patch bags having patches composed of LLDPE have come into widespread commercial use in the United States.
However, LLDPE has several drawbacks. For example, LLDPE is not easily processable as it causes high extruder back pressure if extrusion is attempted at relatively high speeds. Furthermore, because of its stiffness, LLDPE is difficult to orient, which necessitates that another polymer be blended with the LLDPE in order to permit the desired orientation of the LLDPE to provide a shrinkable patch. Furthermore, LLDPE will not heat-seal to itself, necessitating the use of another type of polymer if the patch is to be formed from a collapsed film tube, as is one of the most desirable processes for manufacturing patches.
Thus, it would be desirable to locate another polymer which can provide the combination of puncture-resistance and heat-shrinkability. Furthermore, it would be desirable that this other polymer also be capable of being manufactured as a substantially transparent film. Furthermore, it would be desirable if this other polymer was easier to extrude than LLDPE, had a stiffness low enough to avoid the need to blend a stiffness-reducing polymer therewith, and had the ability to be heat-sealed to itself.
SUMMARY OF THE INVENTION
The present invention is directed to the use of homogeneous ethylene/alpha-olefin copolymer in a patch for a patch bag. This homogeneous polymer has surprisingly been found to provide a combination of puncture-resistance and heat-shrinkability which is at least the equivalent of LLDPE. Furthermore, it has also surprisingly been found that this homogeneous polymer has about the same abrasion-resistance as LLDPE, and can be used to form a substantially transparent heat shrinkable patch. Thus, this homogeneous polymer has been discovered to provide an alternative to the use of LLDPE in patches for patch bags. At least some species of this homogeneous polymer are considerably easier to extrude than LLDPE. Furthermore, some species have a stiffness low enough to avoid the need to blend a stiffness reducing polymer therewith. Finally, at least some species of the polymer, when extruded into a tubular film, offer the further advantage of substantially better sealing to itself, relative to LLDPE.
As a first aspect, the present invention is directed to a patch bag comprising a heat-shrinkable patch adhered to a heat-shrinkable bag. The heat-shrinkable patch comprises a first heat-shrinkable film and the heat-shrinkable bag comprises a second heat-shrinkable film. The first heat-shrinkable film comprises a homogeneous ethylene/alpha-olefin copolymer.
Preferably, the patch bag further comprises an adhesive layer between the first heat-shrinkable film and the second heat-shrinkable film. Preferably, the homogeneous ethylene/alpha-olefin copolymer has a density of from about 0.87 to 0.94 g/cc, more preferably, 0.89 to 0.92. Preferably, the first heat-shrinkable film has a free shrink at 185° F. of from about 10 to 100 percent, more preferably 15 to 75 percent, and still more preferably, 20 to 60 percent. Preferably, the first heat-shrinkable film has a free shrink, at 185° F., of from about 40 to 120 percent of the free shrink of the second heat-shrinkable film; more preferably, from 40 to 100 percent.
Preferably, the homogeneous ethylene/alpha-olefin is present in the first heat-shrinkable film in an amount of from about 5 to 100 weight percent, based on the weight of the first heat-shrinkable film; more preferably, from about 15 to 85 weight percent.
The first heat-shrinkable film can comprise a first homogeneous ethylene/alpha-olefin copolymer while the second heat-shrinkable film comprises a second homogeneous ethylene/alpha-olefin copolymer. The first and second homogeneous ethylene/alpha-olefin copolymers can be the same or different.
Preferably, the first heat-shrinkable film comprises two outer layers and two inner layers, the two outer layers being substantially identical in chemical composition and thickness, and the two inner layers being substantially identical in chemical composition and thickness. In one preferred embodiment, each of the two outer layers comprises the homogeneous ethylene/alpha-olefin in an amount of from about 1 to 100 weight percent, based on the weight of the outer layers. Furtherm
Childress Blaine Clemons
Moffitt Ronald Dean
Oberle Timothy Theodore
Cryovac Inc
Hurley Jr. Rupert B.
Tran Lien
LandOfFree
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