NZ626761B2 - Easy-open cook-in packaged product - Google Patents
Easy-open cook-in packaged product Download PDFInfo
- Publication number
- NZ626761B2 NZ626761B2 NZ626761A NZ62676112A NZ626761B2 NZ 626761 B2 NZ626761 B2 NZ 626761B2 NZ 626761 A NZ626761 A NZ 626761A NZ 62676112 A NZ62676112 A NZ 62676112A NZ 626761 B2 NZ626761 B2 NZ 626761B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- layer
- ethylene
- copolymer
- film
- blend
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
- B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
- B65D65/38—Packaging materials of special type or form
- B65D65/40—Applications of laminates for particular packaging purposes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D75/00—Packages comprising articles or materials partially or wholly enclosed in strips, sheets, blanks, tubes or webs of flexible sheet material, e.g. in folded wrappers
- B65D75/002—Packages comprising articles or materials partially or wholly enclosed in strips, sheets, blanks, tubes or webs of flexible sheet material, e.g. in folded wrappers in shrink films
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D75/00—Packages comprising articles or materials partially or wholly enclosed in strips, sheets, blanks, tubes or webs of flexible sheet material, e.g. in folded wrappers
- B65D75/52—Details
- B65D75/58—Opening or contents-removing devices added or incorporated during package manufacture
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
- B65D81/34—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents for packaging foodstuffs or other articles intended to be cooked or heated within the package
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
- B65D81/34—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents for packaging foodstuffs or other articles intended to be cooked or heated within the package
- B65D81/3415—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents for packaging foodstuffs or other articles intended to be cooked or heated within the package specially adapted to be heated in hot water, e.g. boil pouches
- B65D81/3423—Packages shrinking in hot water, e.g. for boiling hams
Abstract
Disclosed herein is an easy-open packaged product for adhering to a cooked meat product, the packaging article comprises a multilayer film having a first layer that is a seal layer comprising at least one member selected from the group consisting of (i) ionomer resin that bonds to ethylene homopolymer with a bond strength of less than 36 grams per inch, (ii) polyamide, and (iii) polyester which is an inside layer of the package and a second layer that bonds to the first layer with a bond strength of at least 36 grams per inch. The second layer, or a third layer with the second layer being between the first layer and the third layer, comprises a tear-enhancing component comprising at least one member selected from the group consisting of an inorganic filler and an incompatible polymer blend. The layer comprising the filler and/or incompatible polymer blend allows the package to be torn open without delamination occurring between the seal layer and the tie layer. er with a bond strength of less than 36 grams per inch, (ii) polyamide, and (iii) polyester which is an inside layer of the package and a second layer that bonds to the first layer with a bond strength of at least 36 grams per inch. The second layer, or a third layer with the second layer being between the first layer and the third layer, comprises a tear-enhancing component comprising at least one member selected from the group consisting of an inorganic filler and an incompatible polymer blend. The layer comprising the filler and/or incompatible polymer blend allows the package to be torn open without delamination occurring between the seal layer and the tie layer.
Description
EASY-OPEN COOK-IN PACKAGED PRODUCT
Field
The present invention pertains to cook-in packaged products, particularly
cook-in packages comprising cooked meat products packaged under vacuum with a
film adhered to the meat product.
Background
For several decades, meat has been vacuum packaged in packaging articles
made from thermoplastic film. While fresh meat is frequently vacuum packaged,
vacuum packaging is also used for “cook-in” applications, i.e., with the meat being
cooked while it remains in the package. Cook-in films preferably have a tendency for
adhesion to the food product, thereby preventing "cook-out", i.e., "purge", which is
the collection of juices between the outer surface of the food product and the meat-
contact surface of the film, i.e., the surface in direct contact with the meat. This meat
adhesion characteristic of the meat contact layer serves to both prevent cook-out (and
thereby prevent an unattractive package or the need to strip the film from the meat
and repackage the meat), to increase product yield, and to prevent the meat from
losing juices which improve its edible character. As used herein, the term "adhere",
with respect to meat-adhesion, refers to a meat-contact surface of the film which
bonds to the contained meat product during cook-in, the bonding occurring to an
extent sufficient to substantially reduce or prevent accumulation of fluids between the
film and the contained meat product.
Some cook-in products have the package stripped from the product after
cooking (i.e., “cook-and-strip” packaging), other cook-in products remain in the cook-
in packaging article while shipped to the retailer or consumer (i.e., “cook-and-ship”
packaging). In order to increase the shelf life the product, the film can be provided
with a layer which is recognized as providing a barrier to atmospheric oxygen.
Cook-in meat packaging requires seal layers with relatively high melting
points, as the cook-in temperatures are capable of causing seals to fail during cooking
if the polymer of the seal layer has a low melting point. Moreover, as meat products
are relatively dense, and the packages relatively heavy, the film needs to be relatively
strong to withstand the processing, handling, and transport of the product. Cook-in
packaging articles generally have high puncture resistance and high impact strength.
As a result, cook-in meat packages are frequently difficult to open.
The opening of cook-in meat packaging articles is made more difficult by
the adhesion of the inside surface of the packaging article to the meat product during
cook-in, i.e., the adhesion described above. The opening of such tough packaging
requires more time and effort due to the toughness of the packaging article, and can
also result in damage to the product inside the package. The marketplace desires a
tough cook-in packaging article that can be opened quickly and easily, so that the
cooked meat product can be easily removed from the packaging article, without
damage to the product or injury to a person opening the package.
It is an object of the present invention to provide an improved or
alternative packaged product, or to at least provide the public with a useful choice.
Summary
It has been found that cook-in films tend to delaminate as they are stripped
from the meat product during the opening of the package and the removal of the meat
product from the package. The delamination has been found to be at the interface
between the seal layer and a tie layer which is adjacent the seal layer. This
delamination can result in pieces of film remaining on portions of the meat product.
Of course, this is undesirable because the meat product should be free of the film
when the meat is removed from the package.
Attempts were made to solve the delamination problem by selecting a tie
layer composition that bonds more strongly with the seal layer, so that the film would
not delaminate upon the opening of the package and the peeling of the film off of the
meat product. However, increasing the degree of adhesion between the seal layer and
the tie layer did not prove to be successful in overcoming the delamination problem.
It was surprisingly discovered that by making the film tear more easily
down the length of the package, the delamination problem could be eliminated. Thus,
it became apparent that the adhesion of the film to the meat product was not the
primary cause of film delamination during the opening of the package. Providing the
film with a lower tear force was accomplished by providing the film with at least one
layer comprising an incompatible polymer blend. By making the film easier to tear,
less stretching force had to be applied to the film in order tear the package open. It is
believed that it is the high stretching force required for a high force-to-tear film that
caused or enhanced the delamination problem. Thus, the delamination problem was
solved by providing a film with a reduced tear force. Of course, delamination could
still occur if the bond strength between the seal layer and the tie layer is low enough.
A first aspect is directed to a packaged product comprising an easy-open
packaging article including a multilayer film surrounding and adhering to a cooked
meat product. The packaging article has a heat seal of the inside surface of the film to
itself and a skirt extending outward from the heat seal with the skirt having a tear
initiator therein. The multilayer film comprises a first layer that is an inside seal
layer. The first layer comprises at least one member selected from the group
consisting of polyamide and polyester. The multilayer film further comprises a
second layer that bonds to the first layer with a bond strength of at least 36 grams per
inch. In the multilayer film, the second layer, or a third layer with the second layer
being between the first layer and the third layer, comprises a tear-enhancing
component comprising at least one member selected from the group consisting of an
inorganic filler and an incompatible polymer blend.
The filler is present in an amount of at least 5 weight percent, based on
layer weight, and the filler can comprise at least one member selected from the group
consisting of silicate, silica, siloxane, silicone resin, zinc sulfide, wollastonite,
microspheres, glass fiber, metal oxide, calcium carbonate, sulfate, aluminum
trihydrate, feldspar, perlite, gypsum, iron, fluoropolymer, crosslinked
polymethylmethacrylate, talc, diatomaceous earth, zeolite, mica, kaolin, carbon black,
and graphite. The second or third layer containing the filler (or any other layer
containing the filler) makes up at least 10 weight percent of the film, based on total
film weight.
The incompatible polymer blend comprises at least one member selected
from the group consisting of: (i) a blend of from 90 to 30 weight percent ethylene
homopolymer and/or ethylene/alpha-olefin copolymer with from 10 to 70 weight
percent ethylene/unsaturated ester copolymer having an unsaturated ester content of at
least 10 weight percent; (ii) a blend of ionomer resin with ethylene/unsaturated ester
copolymer, and/or polybutylene, and/or propylene homopolymer and/or propylene
copolymer; (iii) a blend of homogeneous ethylene/alpha-olefin copolymer with
recycled polymer blend comprising ethylene homopolymer, propylene homopolymer,
ethylene copolymer, propylene copolymer, polyamide, ethylene/vinyl alcohol
copolymer, ionomer resin, anhydride-modified ethylene/alpha-olefin copolymer,
and/or antiblock; (iv) a blend of from 10 to 75 weight percent ethylene/unsaturated
ester copolymer with from 90 to 15 weight percent polypropylene and/or
propylene/ethylene copolymer, and/or polybutylene, and/or modified ethylene/alpha-
olefin copolymer, and/or styrene homopolymer, and/or styrene/butadiene copolymer;
(v) a blend of ethylene/norbornene copolymer with ethylene/unsaturated ester
copolymer and/or polypropylene and/or polybutylene; (vi) a blend of from 90 to 15
weight percent ethylene/alpha-olefin copolymer with from 10 to 75 weight percent
polypropylene and/or polybutylene and/or ethylene/norbornene; (vii) a blend of from
90 to 25 weight percent homogeneous propylene homopolymer and/or homogeneous
propylene copolymer with from 10 to 75 weight percent homogeneous
ethylene/alpha-olefin copolymer and/or ethylene/unsaturated ester copolymer; (viii) a
blend of propylene homopolymer and/or propylene/ethylene copolymer and/or
polybutylene with ethylene/methyl acrylate copolymer and/or ethylene/acrylic acid
copolymer and/or ethylene/butyl acrylate copolymer; (ix) a blend of polyamide with
polystyrene and/or ethylene/alpha-olefin copolymer and/or ethylene/vinyl acetate
copolymer and/or styrene/butadiene copolymer; and (x) a blend of polyamide 6 and
polyamide 6I/6T. The at least one incompatible polymer blend is present in at least
one layer of the multilayer film. Preferably, the at least one incompatible polymer
blend makes up at least at least 10 weight percent of the film, or at least 20 weight
percent of the film, based on total film weight.
In an embodiment, the second layer comprises the tear-enhancing
component.
In a further embodiment, the second layer comprises a blend of (i) from 90 to 30
weight percent ethylene homopolymer and/or ethylene/alpha-olefin copolymer with
(ii) from 10 to 70 weight percent ethylene/unsaturated ester copolymer having an
unsaturated ester content of at least 10 weight percent. The ethylene homopolymer,
ethylene/alpha-olefin copolymer, and/or ethylene/unsaturated ester copolymer
together contain a grafted maleic anhydride content of at least 0.1 mole percent, based
on moles of ethylene/unsaturated ester copolymer. The ethylene/unsaturated ester
copolymer can be ethylene vinyl acetate copolymer or ethylene methyl acrylate
copolymer. The vinyl acetate content can be at least 10 wt. % percent based on
copolymer weight, at least 15 wt. %, at least 20 wt. %, or at least 25 wt. %, or at least
wt. %.
In an embodiment, the second layer is a tie layer and the third layer
comprises the incompatible polymer blend.
In an embodiment, the second layer bonds to the first layer at a bond
strength of 36 to 138 grams per inch. In another embodiment, the second layer bonds
to the first layer at a bond strength of at least 139 grams per inch. In another
embodiment, the second layer bonds to the first layer at a bond strength of from 139
to 680 grams per inch.
In an embodiment, the second layer is a first tie layer, the third layer
comprises the incompatible polymer blend, and the multilayer film further comprises
a fourth layer that is a second tie layer and a fifth layer that is an O -barrier layer, with
the fifth layer comprising at least one member selected from the group consisting of
saponified ethylene/vinyl acetate copolymer, polyvinylidene chloride, polyamide
6I/6T, polyamide MXD6, polyester, and polyacrylonitrile. The fourth layer is
between the third layer and the fifth layer. In a further embodiment, the multilayer
film further comprises a sixth layer that is a third tie layer and a seventh layer that is
an outside layer of the packaging article, with the sixth layer being between the fifth
layer and the seventh layer. The seventh layer can comprise any thermoplastic
polymer that provides the desired abuse properties. Such polymers include olefin
homopolymer, olefin copolymer, polyamide, polyester, and polyurethane. In a further
embodiment, the third layer comprises the incompatible polymer blend, and the
multilayer film further comprises an eighth layer that also comprises the incompatible
polymer blend, with the eighth layer being between the seventh layer and the sixth
layer, the eighth layer comprising at least one member selected from the group
consisting of the same group of incompatible polymer blend (i) through (x) above.
In an embodiment, the packaging article further comprises a skirt
extending outward from the first heat seal, the skirt having a tear initiator therein. In a
further embodiment, the skirt has a first lay-flat side and a second lay-flat side, and
the tear initiator comprises a first tear initiator through the first lay-flat side and a
second tear initiator through the second lay-flat side, with the first and second tear
initiators being coincident with one another, and the skirt further comprises (A) a first
grip-assister comprising a first passageway through the first lay-flat side of the skirt
and a first passageway through a second lay-flat side of the skirt, with the first
passageways being coincident with one another, and (B) a second grip-assister
comprising a second passageway through the first lay-flat side of the skirt and a
second passageway through the second lay-flat side of the skirt, with the second
passageways being coincident with one another, with the tear initiators being between
the first and second grip-assisters. In a further embodiment, the heat seal is a first
heat seal and the first lay-flat side of the skirt is heat sealed to itself at a second heat
seal, and the incompatible polymer blend is present in the film in an amount of from
40 to 60 weight percent, based on total film weight.
In an embodiment, the packaging article comprises a seamless tubing and
the heat seal is a first heat seal on a first end of the packaging article, with the
packaging article further comprising a closure on a second end of the packaging
article, the closure comprising a member selected from the group consisting of a heat
seal and a clip.
In an embodiment, the packaging article further comprises a skirt
extending outward from the first heat seal, the skirt having a tear initiator therein. In a
further embodiment, the skirt has a first lay-flat side and a second lay-flat side, and
the tear initiator comprises a first tear initiator through the first lay-flat side and a
second tear initiator through the second lay-flat side, with the first and second tear
initiators being coincident with one another. In a further embodiment, the skirt
further comprises (A) a first grip-assister comprising a first passageway through the
first lay-flat side of the skirt and a first passageway through a second lay-flat side of
the skirt, with the first passageways being coincident with one another, and a second
grip-assister comprising a second passageway through the first lay-flat side of the
skirt and a second passageway through the second lay-flat side of the skirt, with the
second passageways being coincident with one another, with the tear initiators being
between the first and second grip-assisters, and the heat seal is a first heat seal and the
first lay-flat side of the skirt is heat sealed to itself at a second heat seal, and the
incompatible polymer blend is present in the film in an amount of from 40 to 60
weight percent, based on total film weight.
In another embodiment, the heat seal is a first heat seal and the first lay-
flat side of the skirt is heat sealed to itself at a second heat seal which is outward of
the first heat seal.
In another embodiment, the skirt further comprises a first stabilizing slit on
a first side of the tear initiators and a second stabilizing slit on a second side of the
tear initiators, the first stabilizing slit comprising a first slit through the first lay-flat
side of the skirt and a first slit through the second lay-flat side of the skirt, the first
slits being coincident with one another, and the second stabilizing slit comprising a
second slit through the first lay-flat side of the skirt and a second slit through the
second lay-flat side of the skirt, the second slits being coincident with one another,
with the tear initiator and the first and second grip-assisters all being between the first
stabilizing slit and the second stabilizing slit. Stabilizing slits are used with heat-
shrinkable films as they reduce the tendency of the tear initiation slits to open up as
the film shrinks against the meat product, and they enhance the ability of a consumer
to detect and utilize the grip and tear easy open feature of the package.
In an embodiment, the at least one incompatible polymer blend is present
in at least one layer of the multilayer film, and the at least one incompatible polymer
blend makes up at least 30 to 70 weight percent of the film, based on total film
weight. In an embodiment, the at least one incompatible polymer blend is present in
at least one layer of the multilayer film, and the at least one incompatible polymer
blend makes up at least 40 to 60 weight percent of the film, based on total film
weight.
The term “comprising” as used in this specification and claims means
“consisting at least in part of”. When interpreting statements in this specification and
claims which include the term “comprising”, other features besides the features
prefaced by this term in each statement can also be present. Related terms such as
“comprise” and “comprised” are to be interpreted in similar manner.
Brief Description of the Drawings
is a schematic of a preferred heat-shrinkable packaging article in
lay-flat configuration, before the meat product is placed into the packaging article and
before the packaging article is shrunk around the meat product.
FIGs. 2A and 2B illustrate perspective views of a preferred embodiment of
a packaged product in accordance with the invention.
is a perspective view of a product packaged in a preferred
packaging article of the invention, with the packaging article being manually gripped
at the grip-assisters, in preparation for manual tearing open for removal of the
product.
is a perspective view of a product packaged of as the
packaging article is being torn open.
is a perspective view of a product packaged in a comparative
packaging article as the packaging article is being torn open, with the packaging
article undergoing delamination during the manual tearing of the packaging article.
is a perspective view of an alternative packaged product in
accordance with the invention.
is a perspective view of an alternative packaged product in
accordance with the invention.
is a schematic of a preferred process for making a heat-shrinkable
film for use in a preferred packaging article.
Detailed Description
As used herein, the phrase “packaged product” refers to a product that is
partially or entirely surrounded by a packaging article, such as a film. As used herein,
the term “meat” includes beef, pork, and poultry.
As used herein, the phrase “packaging article” refers to the article that
partially or entirely surrounds the meat product being packaged. The packaging
article can be a single piece of film sealed to itself, such as an end-seal bags and side-
seal bags (both of which are produced from seamless film tubing), or an L-seal bag.
An end-seal bag has an open top, folded side edges, and a transverse heat seal across
the bottom of the bag, and usually has a skirt below the transverse heat seal. End-seal
bags are produced by sealing across a seamless tubing and thereafter cutting the bag
free of the tubing. A side-seal bag has an open top, a folded bottom edge, and side
seals down each of the bag side edges, and usually has skirts outward of each of the
side seals. Side-seal bags are produced by making two transverse seals across a
seamless tubing, with the distance between the seals corresponding with the width of
the interior of the bag. Thereafter, the tubing is slit lengthwise down one folded side
edge to form the open bag top, with the bag then being cut free of the remainder of the
tubing. L-seal bags are made by folding a flat piece of film in half and sealing along
two sides to leave an open top, one folded side edge, one sealed side edge, and a
sealed bottom edge. Alternatively, the packaging article can be a pouch, which is
made from two separate pieces of film sealed to one another along three side edges,
leaving the fourth side edge unsealed. Finally, the packaging article can have
components in addition to the film, e.g., a tray, etc.
The phrase "cook-in" as used herein refers to the process of cooking a
product packaged in a material capable of withstanding exposure to long and slow
cooking conditions while containing the food product, for example cooking at 57°C to
121°C (i.e., 135°F-250°F) for 2-12 hours, preferably 57°C to 95°C (i.e., 135°F to
203°F) for 2-12 hours. Cook-in packaged foods are essentially pre-packaged, pre-
cooked foods which may be directly transferred to the consumer in this form. These
types of foods may be consumed with or without warming. Cook-in packaging
materials maintain seal integrity, i.e., any heat sealed seams should resist being pulled
apart during cook-in, and are conformable to the contained food product. In an
embodiment, conformability is enhanced by the film being heat-shrinkable so as to
shrink tightly against the product. Additional optional characteristics of films for use
in cook-in applications include delamination-resistance, low O -permeability, and
optical clarity.
As used herein, the phrase “lay-flat” is applied to a packaging article that
is made from a film tubing, etc. that can be placed in a flattened configuration. More
particularly, a segment of seamless tubing of film of defined length can be placed on a
flat horizontal surface and placed into a flattened configuration thereon. This tubing
has a first end, a second end, a first folded side edge, a second folded side edge, a first
lay-flat side (i.e., half of the film tubing), and a second lay-flat side (the other half of
the film tubing), a lay-flat width. The segment of seamless tubing also has a length
running in a machine direction and a width running in a transverse direction. If a heat
seal is made across the tubing to close the tubing near one end, with a skirt being
outward of the heat seal, the skirt also has a first lay-flat side and a second lay-flat
side.
As used herein, the term “heat seal” refers to a heat seal of a first region of
a film to a second region of the film, or a heat seal of a first region of the film to
region of a second film or to a region of a non-film portion of a packaging article.
Heat seals are generally made by applying enough heat with enough pressure for
enough time to cause the regions of the films to fuse, i.e., bond, to one another. Heat
seals can be made using equipment and processes such as are described in, for
example Canadian Patent No. 2,296,387, US Pub. No. 2007/0227102, US Patent No.
4,229,244, and US Patent No. 7,262,389, each of which is hereby incorporated, in its
entirety, by reference thereto.
As used herein, the phrase “outward of the heat seal” refers to a position
on a side of a heat seal that is away from the product, i.e., on the opposite side of the
heat seal from the product. Similarly, the phrase “inward of the heat seal” refers to a
position on the same side of the heat seal as position of the product relative to the heat
seal. The terms “skirt” and “header” are used interchangeably and refer to that
portion of a packaging article extending outward of the heat seal.
As used herein, the term “film” is inclusive of plastic web, regardless of
whether it is film or sheet. The film can have a total thickness of 0.25 mm or less, or
a thickness of from 1 to 10 mils, or from 1 to 5 mils, or from 1.2 to 5 mils, or from 1.3
to 4 mils, or from 1.4 to from 1.2 mils to 3 mils, or from 1.5 to 2.5 mils, or from 1.7
mils to 2.2 mils. If the film is heat-shrinkable, film thickness is determined before the
film undergoes shrinking.
As used herein, the phrase "outer layer" refers to any film layer having less
than two of its principal surfaces directly adhered to another layer of the film. Every
multilayer film has two outer layers, each of which has a principal surface adhered to
only one other layer of the multilayer film. As used herein, the phrase “inside layer”
refers to the outer film layer making up the inside layer of the packaging article which
is the seal layer and is also the layer in contact with the meat product. The other outer
layer of the packaging article is referred to as the “outside layer” and/or as the “outer
abuse layer” or “outer skin layer”, as it is the outside layer of the packaging article
and is the film layer furthest from the product, relative to the other layers of the
multilayer film. Likewise, the "outside surface" of a packaging article (i.e., bag) is the
surface away from the product being packaged within the article.
As used herein, the phrase “machine direction” refers to the direction in
which the film emerges from the die. Of course, this direction corresponds with the
direction the extrudate is forwarded during the film production process. The phrase
“machine direction” corresponds with “longitudinal direction”. Machine direction
and longitudinal direction are abbreviated as “MD” and “LD”, respectfully.
As used herein, the phrase “transverse direction” refers to a direction
perpendicular to the machine direction. Transverse direction is abbreviated as “TD”.
The multilayer film for use in the packaged product of the present
invention can be heat-shrinkable or non-heat-shrinkable. As used herein, “heat-
shrinkable” refers to a film exhibiting a total free shrink (i.e., machine direction shrink
plus transverse direction shrink) of greater than 10 percent at 85°C. Hot blown films
have a total free shrink at 85°C of up to 10 percent at 85°C. Films that are heat-
shrinkable are heated to their softening point and then oriented while in the solid state.
A preferred film for use in the present invention has a total free shrink at 85°C of
from 20 percent to 120 percent, or a total free shrink at 85°C of from 30 percent to
105 percent, or a total free shrink at 85°C of from 40 percent to 100 percent. Free
shrink is measured in accordance with ASTM D 2732, which is hereby incorporated,
in its entirety, by reference thereto.
As used herein, tear propagation is measured according to Elmendorf Tear
Strength Test - ASTM D 1922 Plastic Test Standard, which is hereby incorporated by
reference, in its entirety. This test measures the average force required to propagate
tearing through a specified length of plastic film. In an embodiment, the film exhibits
an Elmendorf tear strength in at least one direction (i.e., in at least the machine
direction or the transverse direction) of at least 0.7 Newton (“N”). The film can have
an Elmendorf tear strength of at least 0.7 N to 2 N, or 0.7 N to 1.5 N, or 0.9 N to 1.3
N, or 1 N to 1.2 N, or 0.95 N to 1.15 N. If the film is heat-shrinkable, the tear
strength is measured before shrinking. The film from which packaging article is made
is designed to be opened using a manual tearing operation.
The film can have a tear propagation in a machine direction, of at least 0.7
Newton, or 0.7 Newton to 2 Newtons, or 0.7 Newton to 1.5 Newtons, or 0.9 Newton
to 1.3 Newtons, or 1 Newton to 1.2 Newtons, or 0.95 Newtons to 1.15 Newtons. Tear
propagation resistance can be measured in accordance with ASTM D1938-08, which
is hereby incorporated by reference, in its entirety. If the film is heat-shrinkable, tear
propagation is measured before shrinking.
In an embodiment, the multilayer film exhibits a Peak Load Impact
Strength, determined using ASTM D 3763-95A, of at least 50 Newtons per mil; in
another embodiment from 50 to 250 Newtons per mil. Peak Load Impact Strength is
measured using ASTM D 3763-95A, which is hereby incorporated, in its entirety, by
reference thereto.
The first layer is the inside layer of the packaging article and serves as a
seal layer in that it is heat sealed to itself, and as a meat-contact and meat-adhesion
layer. The first layer comprises polyamide, polyester, and ionomer resin that bonds to
ethylene homopolymer with a bond strength of less than 36 grams per inch. The heat
seal must be capable of surviving the cook-in process.
Polyamides suitable for use in the first layer include polyamide 6,
polyamide 9, polyamide 10, polyamide 11, polyamide 12, polyamide 66, and
polyamide 6/66, polyamide 6/12, polyamide 6/69, polyamide 6I/6T, copolyamide
66/69/61, copolyamide 66/610, polyamide MXD6, polyamide MXDI, polyamide
66/610, amorphous polyamide, and polyether block amide copolymer, either alone or
blends of two or more of the above.
In an embodiment, the first layer comprises polyamide having a melting point of from
about 260°F to 400°F, or from about 275°F to 375°F, or from about 300°F to 360°F,
or from about 300°F to about 345° F. A blend of 50 wt % polyamide 12 with 50 wt.
% polyamide 6/12 is a preferred blend for use in the seal layer.
In an embodiment, the first layer has a thickness of from about 3 to 20
percent, based on the total thickness of the multilayer film, or from 5 to 18 percent, or
from 7 to 16 percent, or from 9 to 13 percent. In an embodiment, the first layer has a
thickness of from about 0.05 to 2 mils, or from 0.1 to 1 mil, or from 0.2 to 0.8 mil, or
from 0.2 to 0.4 mil, or from 0.2 to 0.3 mil.
As used herein, the phrase “ionomer resin that bonds to ethylene
homopolymer with a bond strength of less than 36 grams per inch” refers to metal
salts of copolymers of ethylene and methacrylic acid in which the methacrylic acid
mer content is relatively high and the degree of metal neutralization of the acid is
relatively high. Examples of such ionomer resins include Surlyn 1702 ionomer resin
and Surlyn 1705 ionomer resin, available from DuPont.
As used herein, the phrase "tie layer" refers to any film layer that serves to
adhere two film layers to one another, which layers would otherwise not adhere to one
another, or would not adhere to one another with sufficient bond strength. A tie-layer
polymer can be added to the composition of a second layer in order to cause the
second film layer to adhere to an adjacent first film layer. Similarly, a second layer
comprising a tie layer polymer can be inserted between a first layer and a third layer
that would otherwise not bond to one another with sufficient strength.
In the packaged product of the invention, the second layer of the
multilayer film is a tie layer. In other embodiments, the second, fourth, and sixth
layers are tie layers. Tie layers should have a relatively high degree of bonding to
relatively polar polymers, such as ethylene/vinyl alcohol copolymer, polyamide,
polyester, as well as relatively non-polar polymers, such as olefin polymers. The tie
layers can have a thickness of from 0.05 to 2 mils, or from 0.05 to 0.5 mil, or from 0.1
to 0.3 mil or from 0.12 to 0.17 mils. Tie layer polymers include anhydride-grafted
ethylene/alpha-olefin copolymer, anhydride-grafted ethylene/unsaturated ester
copolymer, anhydride-grafted ethylene/unsaturated acid copolymer, and
polyurethane.
In an embodiment, only one layer of the multilayer film comprises an
incompatible polymer blend. In another embodiment, two or more layers of the
multilayer film comprise an incompatible polymer blend. The incompatible polymer
blend allows the film to be easily torn in the machine direction (MD) down the length
of the package, or easily torn in the transverse direction (TD) across the width of the
packaging article. The incompatible polymer blend also allows the film to be easily
torn (in MD or TD) after the film has been shrunk around the product. The
incompatible polymer blend can be present in the film in an amount of at least 10
percent based on total film weight, or at least 20 percent based on total film weight, or
from 20 to 95 percent based on total film weight, or from 30 to 70 percent based on
total film weight, or from 40 to 60 percent based on total film weight.
Incompatible polymer blends include, but are not limited to, the group of
incompatible polymer blends (i) through (x) above. Incompatible polymer blends are
disclosed in U.S.S.N. 12/313,396, published as US 2009/0116768 A1, both
documents hereby being incorporated, in their entireties, by reference thereto.
Different incompatible polymer blends can be used in different film layers.
As used herein, the term "barrier", and the phrase "barrier layer", as
applied to films and/or film layers, are used with reference to the ability of a film or
film layer to serve as a barrier to one or more gases. The multilayer film used to
make the packaged product can optionally comprise a barrier layer. In the packaging
art, oxygen (i.e., gaseous O ) barrier layers can comprise, for example, at least one
member selected from the group consisting of hydrolyzed ethylene/vinyl acetate
copolymer (designated by the abbreviations "EVOH" and "HEVA", and also referred
to as “saponified ethylene/vinyl acetate copolymer” and “ethylene/vinyl alcohol
copolymer”), polyvinylidene chloride, amorphous polyamide, polyamide MXD6
(particularly MXD6/MXDI copolymer), polyester, polyacrylonitrile, etc., as known to
those of skill in the art.
In an embodiment, the multilayer film exhibits an O -transmission rate of
from 1 to 20 cc/m day atm at 23°C and 100% relative humidity, or from 2 to 15
cc/m day atm at 23°C and 100% relative humidity, or from 3 to 12 cc/m day atm at
23°C and 100% relative humidity, or from 4 to 10 cc/m day atm at 23°C and 100%
relative humidity. Alternatively, the multilayer film can exhibit an O -transmission
2 2 2
rate of from 21 cc/m day atm to 15,000 cc/m day atm, or from 500 cc/m day atm to
2 2 2
,000 cc/m day atm, or from 2000 cc/m day atm to 6,000 cc/m day atm. O -
transmission rate can be measured in accordance with ASTM-D-3985.
The outside layer of the packaging article contributes to the desired abuse
and gloss characteristics, and preferably comprises a polymer having relatively low
cost while providing these characteristics. Preferably, the outside layer has a
thickness of from about 0.1 to 3 mils; more preferably, from 0.1 to 2 mils; still more
preferably, from 0.1 to 0.5 mil; and yet still more preferably, from about 0.1 to 0.3
mil. The outside layer can comprise at least one member selected from the group
consisting of polyolefin (ethylene homopolymer and copolymer, high density
polyethylene, ethylene/alpha-olefin copolymer, linear low density polyethylene,
propylene homopolymer and copolymer, butene homopolymer and copolymer),
propylene/alpha-olefin copolymer, ethylene/unsaturated ester copolymer
(ethylene/vinyl acetate copolymer), ethylene/unsaturated acid copolymer, polyamide,
polyester, starch-containing polymer, polystyrene, and polyurethane.
Various multilayer film structures are suitable for use as the multilayer
film in the packaged product, such as the following layer arrangements, in which “/”
represents layer interface, “&” represents blended components in the same layer,
“IPB” represents incompatible polymer blend, and “barrier” represents O -barrier
layer:
seal / tie & IPB
seal / tie / IPB
seal / tie / IPB / tie / barrier
seal / tie / IPB / tie / barrier / tie / outer
seal / tie / IPB / tie / barrier / tie / IPB / outer
seal / tie & IPB / barrier / tie & IPB / outer
seal / tie & IPB / tie / barrier / tie & IPB / outer
seal / tie & IPB / barrier / tie / outer
seal / tie / barrier / tie & IPB / outer
seal / tie / barrier / tie / IPB / outer
In any of the layer arrangements above, the IPB-containing layers can alternatively
contain filler particles as described herein in order to provide the layer with enhanced
tear properties, i.e., allowing a machine-direction tear down the length of the
packaging article, or a transverse-direction tear across the width of the article, without
delamination of the film, which is adhered to the cooked meat product.
The phrase “tear initiator”, as used herein, refers to any one or more of a
variety of means that can be located in the skirt or header of a packaging article. The
tear initiator allows manual tearing force to be concentrated on a point or small region
of the film(s), so that tear initiation and tear propagation can be produced manually.
The tear initiators used in the packaging article include a cut through the film. The
cuts can be in the form of slits or notches. Slit-type tear initiators can be straight or
curved, with or without inflection points. A slit can be continuous or present as a line
of discontinuous cuts or perforations. The slit can extend to the edge of the skirt or
header, or have ends within the skirt or the header. A tear initiator can also be
provided by cutting only part way through the thickness of the film, providing a line
of weakness along which the remainder of the film thickness can be manually torn
through. Alternatively, the tear initiator can be a notch in a bag skirt or header of the
package. Tear initiators are illustrated and described in U.S.S.N. 12/313,396 ( see
U.S. Pub. No. 2009/0116768), to Huerta et al, entitled “Easy-Opening Packaging
Article Made From Heat-Shrinkable Film Exhibiting Directional Tear”, incorporated
by reference above.
In an embodiment, the first and second tear initiators on the respective first
and second lay-flat sides of the skirt or header are coincident with one another, i.e. the
tear initiators are aligned one directly on top of the other when the lay-flat sides of the
skirt or header are brought together. In this manner, manual tearing by grasping the
skirt or header produces two tears, i.e., one extending from each of the tear initiators
on each of the lay-flat sides of the skirt or header.
In an embodiment, the packaging article does not have a line of weakening
(e.g., scoring) along a tear path extending from the tear initiator. In this manner, the
film remains strong throughout the region in which the manual tearing is to take
place. In contrast to the tear path down the length of the packaging article, the one or
more tear initiator, or one or more portions of the tear initiators, can comprise a line of
weakness.
In an embodiment, the packaging article is also provided with one or more
grip-assisters as is also described and illustrated in U.S.S.N. 12/313,396. The grip-
assister can enhance the ease with which the film can be torn. The grip-assister can
be in one lay-flat side of the packaging article or in both lay-flat sides of the
packaging article. The grip-assister can be a hole in the skirt (and/or in the header),
an integral extension of the skirt or header, or a separate film tab fastened to the skirt
or header. The separate film tab can be made from a thermoplastic polymer, paper, or
other material, and can be heat-shrinkable or non-heat-shrinkable. The packaging
article can be provided with the combination of a tear-initiator and a grip-assister.
In an embodiment, the first heat seal is of a first region of the inside
surface to a second region of the inside surface. In another embodiment, the first heat
seal is of a first region of the inside surface to a first region of the outside surface.
The first heat seal can be straight or curved.
In an embodiment, the second heat seal is a curved seal. For example, a
transverse second heat seal that curves outwardly to provide an interior volume
longest in the center of the bag is a preferred transverse seal for the packaging of
products such as whole turkeys.
In an embodiment, no portion of the inside surface of the film is sealed to
itself along film edges defining the first and second tear initiators. That is, the inward
and outward ends of first and second tear initiators are between the first and second
heat seals. In an embodiment, the first and second tear initiators pass through the
second heat seal and to the bottom edge of the packaging article.
In an embodiment, the bottom edge of the packaging article is outward of
the second heat seal. In another embodiment, the second heat seal includes the
bottom edge of the packaging article. The first and second heat seals can be straight
or curved.
is a schematic of preferred packaging article 10 in lay-flat
configuration, before the meat product is placed into the packaging article and before
the packaging article is shrunk around the meat product. Packaging article 10 is an
end-seal bag made from a seamless tubing of film 22. Packaging article 10 has open
top 24, end seal 26, folded first side edge 28, folded second side edge 30, and bottom
edge 32. End seal 26 is a heat seal of a first region of the inside of the film tubing
(i.e., a first region of the inside surface of the film tubing) to a second region of the
inside of the film tubing. End seal 26 is curved in order that a rounded meat product
has a better fit with the interior volume within packaging article 10. Packaging article
also has skirt 34 between end seal 26 and bottom edge 32. Skirt 34 (also
commonly referred to as a “header”) has a pair of tear initiators 36, one through each
lay-flat side of skirt 34. Skirt 34 also has a first pair of grip-assisters 38 on a first side
of tear initiators 36 (one through each lay-flat side of skirt 34, with each tear initiator
being a plurality of spaced apart cuts along a line), and a second pair of grip-assisters
40 (one through each lay-flat side of skirt 34) on a second side of tear initiators 36.
Skirt 34 also has a supplemental heat seal 42 of a second region of the inside of the
film tubing to itself. Skirt 34 also has a first pair of stabilizing slits 44 on a first side
of tear initiators 36 (i.e., one stabilizing slit through each lay-flat side of skirt 34), a
second pair of stabilizing slits 46 on a second side of tear initiators 36 (i.e., one
stabilizing slit through each lay-flat side of skirt 34). Stabilizing slits 44 sand 46
serve to reduce stress on the tear initiators during film shrinkage, and to reduce the
kind of shrinkage of skirt 34 that makes tear initiators 36 and grip-assisters 38 and 40
difficult to detect and use. While each of tear initiators 36, stabilizing slits 44, and
stabilizing slits 46 can be a single continuous slit, preferably they are a series of
perforations or a series of short slits, e.g., 3 short slits each about 8 mm long in a line,
with the slits being separated by a distance of, for example, 4 millimeters. Grip-
assisters 38 and 40 are formed by curved slits that terminate before the film portion
(i.e., chad, illustrated, but unlabeled in separated from the remainder of the
film.
Optionally, at least a portion of skirt 34 is heatset, so that upon shrinking
the film around the product, the shrinkage and curl of skirt 34 is reduced. Reducing
the shrinkage of skirt 34 allows skirt 34, and the various features in skirt 34, such as
the tear initiators and grip-assisters, to be readily apparent and easily accessible to the
consumer.
FIGs. 2A and 2B illustrate a perspective view of a preferred packaged
product 48. Packaged product 48 has meat product 50 (see film cutaway exposing
meat product 50) surrounded by packaging article 52. Meat product 50 comprised a
water-added ham product. Packaging article 52 is shrunken tightly around meat
product 50.
When meat product 50 was placed into the packaging article, the
packaging article was as illustrated in described above. Thereafter, the
packaging article having meat product 50 therein was placed into a vacuum chamber
and the atmosphere was evacuated from within the packaging article, and the
packaging article was closed by a metal clip 54. Thereafter, packaged product 48 was
placed into an oven and cooked at 130°F for 1 hour, followed by continued cooking at
140°F for 1 hour, followed continued cooking at 150°F for one hour, followed by
continued cooking at 160°F until the internal temperature of meat product 50 reached
a temperature of 155°F. During cooking, the heat-shrinkable film from which the
packaging article was made shrunk tightly around meat product 50.
Packaging article 52 comprises heat seal 26 and header 34 outward of heat
seal 26. Within header 34 are a pair of tear initiators 36 (one tear initiator in each
lay-flat side of header 34) with first pair of grip-assisters 38 (one through each lay-flat
side of header 34) on a first side of tear initiators 36, and a second pair of grip-
assisters 40 (one through each lay-flat side of header 34) on a second side of tear
initiators 36. Skirt 34 also has a supplemental (i.e., second) heat seal 42 of a third
region of the inside of the film tubing to a fourth region of the inside of the film
tubing. Skirt 34 also has a first pair of stabilization slits 44 on a first side of tear
initiators 36 (i.e., one stabilization slit through each lay-flat side of skirt 34), and a
second pair of stabilization slits 46 on a second side of tear initiators 36 (i.e., one slit
line through each lay-flat side of skirt 34).
is a perspective view of a portion of packaged product 48 of
with a thumb 56 of a consumer’s right hand through first pair of grip-assisters 38 and
a finger 58 of the consumer’s left hand through second pair of grip-assisters 40.
Thumb 56 and finger 58 are in position to pull first pair of grip-assisters 38 away from
second pair of grip-assisters 40 away from one another, initially causing tear initiators
36 to spread open, with further pulling causing tears to initiate and propagate down
each lay-flat side of packaging article 52, as illustrated in described below.
is a perspective view of packaged product 48 of after
packaging article 52 is torn open. As can be seen in the pulling of grip-
assister pair 38 away from grip-assister pair 40 resulted in the initiation and
propagation of torn edges 54 from the pair of tear initiators. Two tears were made,
i.e., one tear down each side of packaging article 52. The tear down the backside of
packaged product 48 is not shown in However, each tear is down the length
of the shrunken packaging article 52, in the machine direction, i.e., in the direction in
which the film is made, and each of the tears is relatively straight. As is apparent in
packaging article 52 tears cleanly in that the multilayer film does not
delaminate during tearing even though the film adheres to the cooked meat product
during cooking. Moreover, the film separates cleanly from meat product 50, without
significant meat pull-off.
is a perspective view of comparative packaged product 48’ having
features corresponding with the features of the packaging article 52 illustrated in
FIGs. 1 through 4, described above. However, the multilayer film of comparative
packaging article 52’ differs from the multilayer film used to make packaging article
52, in that unlike the film used to make packaging article 52, the film used to make
packaging article 52’ does not have a layer comprising a tear-enhancing component
such as an incompatible polymer blend and/or a particulate filler. As is apparent in
the pulling of grip-assister pair 38 away from grip-assister pair 40 results in
the initiation and propagation of tearing, but as the film tears, the film exhibits an
undesirable delamination as is apparent from delaminated film portion 60.
Delamination can result in pieces of film remaining on the meat product after the
package is opened and the meat product removed from the packaging article. Of
course, that one or more pieces of delaminated film would remain on the meat product
is undesirable.
illustrates a perspective view of alternative preferred molded
packaged product 56. Packaged product 56 has meat product 50 surrounded by
packaging article 60. Meat product 50 was a water-added ham product. Packaged
product 56 was made by placing meat product 50 into the packaging article while the
packaging article was as illustrated in described above. The packaging article
having meat product 50 therein was then placed into a mold (not shown) with force
applied to conform packaging article 60 and meat product 50 into the shape of the
mold cavity. Thereafter, the packaging article having meat product 50 therein was
placed into a vacuum chamber and the atmosphere was evacuated from within the
packaging article, and the packaging article was then closed by heat sealing across the
open end thereof, resulting in packaging article 60. Excess film (not illustrated)
outward of the seal was cut off and discarded. Packaging article 60 was then shrunk
tightly around meat product 50 by passing the resulting packaged product 56 through
a hot water bath at a temperature of about 155°F in order to shrink the film around
meat product 58. Thereafter, the packaged product was placed into an oven and
cooked at 130°F for 1 hour, followed by continued cooking at 140°F for 1 hour,
followed continued cooking at 150°F for one hour, followed by continued cooking at
160°F until the internal temperature of the product achieved a temperature of 155°F.
The result was packaged product 56 of illustrates header 34 with its
pair of tear initiators 36 with first pair of grip-assisters 38 on a first side of tear
initiators 36, and a second pair of grip-assisters 40 on a second side of tear initiators
illustrates a perspective view of a preferred alternative packaged
product 62 which is similar to packaged product 56 of As with packaged
product 58 of packaged product 62 is also molded to a desired shape.
Packaged product 62 comprises packaging article 64 surrounding meat product 66.
Meat product 66 is a water-added ham product. When meat product 66 is placed into
packaging article 64, packaging article 64 is as illustrated in except that the
heat seal is about 0.5 inch from the bottom edge of the bag, and the packaging article
has no tear initiators, grip-assisters, etc, in the skirt. Packaging article 64 having meat
product 66 therein is placed into a mold with force applied to conform both packaging
article 64 and meat product 66 into the shape of the mold cavity. Thereafter,
packaging article 64 having meat product 66 therein is placed into a vacuum chamber
and the atmosphere is evacuated from within packaging article 64, and packaging
article 64 is closed by heat sealing across the open end thereof. After heat sealing
packaging article 64 closed, the excess film outward of the seal is cut off and
discarded.
Packaging article 64 is then shrunk tightly around meat product 66 by
passing the resulting packaged product 62 through a hot water bath at a temperature of
about 155°F in order to shrink the film around meat product 66. Thereafter, the
packaged product 62 is placed into an oven and cooked at 130°F for 1 hour, followed
by continued cooking at 140°F for 1 hour, followed continued cooking at 150°F for
one hour, followed by continued cooking at 160°F until the internal temperature of the
product achieves an internal temperature of 155°F. The result is the packaged product
62 of Packaged product 62 is designed to be opened by using a knife or
scissors to make a slit through the skirt and the end seal followed by manually
propagating tears from the slits down both sides of the package, down the full length
of the package, so that meat product 66 can be removed from packaging article 64.
is a schematic of a preferred process for making a heat-shrinkable
film for use in making a preferred packaging article. In solid polymer beads
(not illustrated) are fed to a plurality of extruders (for simplicity, only extruder 88 is
illustrated). Inside extruders 88, the polymer beads are forwarded, melted, and
degassed, following which the resulting bubble-free melt is forwarded into die head
90, and extruded through an annular die, resulting in tubing tape 92 which is
preferably from about 10 to 20 mils thick, and preferably has a lay-flat width of from
about 2 to 10 inches.
After cooling or quenching by water spray from cooling ring 94, tubing
tape 92 is collapsed by pinch rolls 96, and is thereafter fed through irradiation vault 98
surrounded by shielding 100, where tubing 92 is irradiated with high energy electrons
(i.e., ionizing radiation) from iron core transformer accelerator 102. Tubing 92 is
guided through irradiation vault 98 on rolls 104. Preferably, tubing 92 is irradiated to
a level of from about 40 to about 120 kGy, resulting in irradiated tubing 106, which is
then passed over guide roll 116, after which irradiated tubing 106 is passed into and
through hot water bath tank 118 containing hot water 120.
Irradiated tubing 106 is immersed in hot water 120 (preferably having a
temperature of about 185°F to about 210°F) for a period of about 10 to about 100
seconds, i.e., for a time period long enough to bring the film up to the desired
temperature for biaxial orientation. Thereafter, the resulting hot, irradiated tubing 122
is directed through nip rolls 124, and bubble 126 is blown, thereby transversely
stretching hot, irradiated tubular tubing 122 so that a heat-shrinkable, oriented film
tube 128 is formed.
Furthermore, while being blown, i.e., transversely stretched, nip rolls 130
have a surface speed higher than the surface speed of nip rolls 124, thereby resulting
in longitudinal orientation. As a result of the transverse stretching and longitudinal
drawing, oriented film tube 128 is produced, this blown tubing preferably having been
both stretched at a ratio of from about 1:1.5 to about 1:6, and drawn at a ratio of from
about 1:1.5 to about 1:6. More preferably, the stretching and drawing are each
performed at a ratio of from about 1:2 to about 1:4. The result is a biaxial orientation
of from about 1:2.25 to about 1:36, more preferably, from about 1:4 to about 1:16.
While bubble 126 is maintained between pinch rolls 124 and 130, oriented film tube
128 is collapsed by rollers 132, and thereafter conveyed through pinch rolls 130 and
across guide roll 134, and then rolled onto wind-up roll 136. Idler roll 138 assures a
good wind-up. This process can be carried out continuously in a single operation, or
intermittently, e.g., as a two-stage process, in which the extruded, irradiated tape is
wound up after irradiation, and, after a period of storage, unwound and subjected to
heating and orienting in order to arrive at oriented film tubing 128.
In an embodiment, skirt 408 further comprises at least one grip-assister for
assisting grip of the multilayer film during manual tearing, as disclosed in Pub. No.
US 2009/0116768 A1, which is hereby incorporated, in its entirety, by reference
thereto.
The invention is illustrated by the following example, which is provided
for the purpose of representation, and is not to be construed as limiting the scope of
the invention. Unless stated otherwise, all percentages, parts, etc. are by weight.
Example 1
A heat-shrinkable multilayer film for use in making a preferred packaging
article according to the present invention was produced by the process illustrated in
described above. The composition of this film, referred to herein as Film No.
1, is provided in Table 1, below. The first layer was an outer film layer that served as
the inside layer and seal layer of an end-seal bag made from the film. The second
layer was a tie layer between the first layer and the third layer. The third layer was a
layer that, together with the seventh layer (described below), comprised an
incompatible polymer blend in order to provide the film with a linear tear property in
the machine direction after shrinking. The fourth layer was a tie layer. The fifth layer
was an oxygen (i.e., O ) barrier layer, i.e., the layer that controlled the transmission
rate of atmospheric oxygen through the film. The sixth layer was a tie layer. The
eighth layer was a layer that, together with the third layer, comprised an incompatible
polymer blend in order to provide the film with a linear tear property in the machine
direction after shrinking. The seventh layer was an outer layer of the film that served
as an outside, abuse-resistant layer of the packaging article.
TABLE 1
Film No. 1 (working example)
Layer Layer
Number Layer Chemical Identity Thickness
(Layer (mils)
Function)
First blend of 50 wt % polyamide 6/12 and 0.28
(inside & seal) 50 wt % polyamide 12
Second 80% Plexar PX3227 blend of maleic anhydride modified 0.28
(tie) polyethylene and linear low density polyethylene
% Exact 4053 ethylene/butane copolymer
Third 70% Exceed 1012CJ ethylene/hexene copolymer 0.50
(incompatible 30% Escorene LD 713.934053 ethylene/vinyl acetate copolymer
polymer
blend)
Fourth 100% Plexar PX3227 blend of maleic anhydride modified 0.14
(tie) polyethylene and linear low density polyethylene
Fifth 100% Eval E 105A ethylene vinyl alcohol copolymer 0.16
(barrier)
Sixth 100% Plexar PX3227 blend of maleic anhydride modified 0.14
(tie) polyethylene and linear low density polyethylene
Eighth 70% Exceed 1012CJ ethylene/hexene copolymer 0.64
(incompatible 30% Escorene LD 713.934053 ethylene/vinyl acetate copolymer
polymer
blend)
Seventh 80% A-3018 ethylene/vinyl acetate copolymer 0.20
(outside) 20% Marlex 9006 ethylene/hexene copolymer
The various resins identified in Table 1, above, have the properties
provided immediately below, and were obtained from the sources provided below.
The comparative films set forth in Tables 2 and 3, below, also contained many of
these same resins.
Plexar PX3227 was blend of maleic anhydride-modified polyethylene
and linear low density polyethylene and had a density of 0.913 g/ cm , a melt index of
1.7 dg/min, a melting point of 124°C, and was obtained from Nippon Goshei.
Exact 4053 was a single site catalyzed ethylene/butene copolymer having
a density of 0.888 g/cm , a melt index of 2.2 dg/min, and was obtained from Exxon
Mobil.
Exceed 1012CJ was a single site catalyzed ethylene/hexene copolymer
and had a density of 0.912 g/cm , a melt index of 1.0 dg/min, and was obtained from
Exxon Mobil.
Escorene LD713.93 was an ethylene/vinyl acetate copolymer having a
vinyl acetate content of 14.4 wt %, a density of 0.933 g/cm , a melt index of 3.5
dg/min, and was obtained from Exxon Mobil.
Eval E 105A was an ethylene/vinyl alcohol copolymer having a density
of 1.14 g/ cm , a melt index of 5.5 dg/min, contained at least 44 mol % ethylene, and
was obtained from Evalca/Kuraray.
A-3018 was an ethylene/vinyl acetate copolymer containing 6.5 wt. %
vinyl acetate had a density of 0.929 g/cm , a melt index of 0.55 dg/min, and was
obtained from Westlake Chemicals.
Marlex 9006 was an ethylene/hexene copolymer having a density of
0.953 g/ cm , a melt index of 6.6 dg/min, and was obtained from Chevron Phillips
Chemical.
Film No. 1 was fully coextruded as a seamless tubing using the process
illustrated in described above. The seamless tubing was converted into end-
seal bags in accordance with described above. A water-added ham product
was packaged in the bags, under vacuum, with the open end of the bag having been
heat sealed closed or closed with a metal clip after the atmosphere was evacuated
from the bag.
Thereafter, packaged product 48 was placed into an oven and cooked at
130°F for 1 hour, followed by continued cooking at 140°F for 1 hour, followed
continued cooking at 150°F for one hour, followed by continued cooking at 160°F
until the internal temperature of the product achieved a temperature of 155°F. During
cooking, the heat-shrinkable film from which the packaging article was made shrunk
tightly around meat product 50. After cooking was complete, the packaged products
were allowed to cool to room temperature and then the packaged products were
placed in a refrigerator and brought to a temperature of 34°F. When the package was
opened, the packaging article tore cleanly down its length in the machine direction,
without film delamination, allowing the cooked meat product to be removed from the
package.
The machine direction tearing after shrinking without film delamination
was achieved with Film No. 1 for both (i) packages with headers and tear initiators as
illustrated in FIGs. 1-4 and 6, as well as for (ii) packages made without headers, i.e.,
as illustrated in The opening of packages as illustrated in was
performed using a knife, scissors, or other sharp implement. Once the cut was made
in the machine direction, a tear was manually propagated down the length of the
packaging article, without film delamination, allowing the cooked meat product be
removed from the package. In Film No. 1, the bond strength of the second layer to
the first layer was not measured but was believed to be 205 grams per inch because
the composition and thickness of the first and second layers is the same as the first
and second layers of Example 2, below, which was analyzed and determined to be
205 grams per inch.
Example 2 (Comparative)
The film of Example 2, i.e., Film No. 2, is a comparative film that had
been used for some time for cook-in packaging. Film No. 2 was a six-layer heat-
shrinkable film that was fully coextruded as a seamless tubing, i.e., made by the same
process used for the making of Film No. 1. The seamless tubing was converted into
end-seal bags. Various meat products were packaged in the bags, under vacuum, with
the open end of the bag having been heat sealed closed, or closed with a metal clip,
after the atmosphere was evacuated from the bag. The bag was then shrunk around
the meat product by passing the packaged product through a hot water bath having an
internal temperature of 155°F.
Table 2
Film No. 2 (Comparative)
Layer Layer
Number Layer Chemical Identity Thickness
(Layer (mils)
Function)
First blend of 50 wt % polyamide 6/12 and 0.28
(inside) 50 wt % polyamide 12
Second 80% Plexar PX3227 blend of maleic anhydride modified 0.28
(tie) polyethylene and linear low density polyethylene
% Exact 4053 ethylene/butane copolymer
Third 100% Plexar PX3227 blend of maleic anhydride modified 0.14
(tie) polyethylene and linear low density polyethylene
Fourth 100% Eval E 105A ethylene vinyl alcohol copolymer 0.16
(barrier)
Fifth 100% Plexar PX3227 blend of maleic anhydride modified 0.16
(tie) polyethylene and linear low density polyethylene
Sixth 80% A-3018 ethylene vinyl acetate copolymer 1.32
(outside) 20% T60119 high density polyethylene
Resins in Table 2 that are present in Table 1 are as identified in the
paragraphs below Table 1, above.
T60119 was a high density polyethylene having a density of 0.961 g/
cm and a melt index of 6.2 dg/min, and was obtained from Ineos.
A comparison of the film layers of Film No. 2 (i.e., the film of Example 2)
with the film layers of the Film No. 1 (i.e., the film of Example 1, above) reveals that
the first, second, third, fourth, fifth, and sixth layers of Film No. 2 substantially
correspond, in both polymeric composition and layer thickness, with the first, second,
fourth, fifth, sixth, and seventh layers, respectively, of Film No. 1. That is, six of the
eight layers of Film No. 1 correspond with the six layers of Film No. 2. The
difference between Film No. 1 and Film No. 2 was the presence third and eighth
layers of Film No. 1 that are not present in Film No. 2. However, the sixth layer (i.e.,
outside layer) of Film No. 2 was approximately as thick (i.e., 1.32 mils) as the
combined thickness of the third, seventh, and eighth layers of Film No. 1 (i.e., 0.50 +
0.20 + 0.64 = 1.34 mils), ensuring that the overall film thickness and film strength
was not a factor affecting the difference in tearing or delamination resistance. The
slight difference in the composition of the outside layers of Film No. 1 vs Film No. 2
is believed to have no bearing on the difference in the delamination results between
Film No. 1 and Film No. 2
As described above, the opening of a cooked meat product package made
from Film No. 1 occurred without film delamination. However, Film No. 2
delaminated upon the tearing open of the package. Analysis revealed that the
delamination of Film No. 2 occurred between the first layer and the second layer.
During the manual tearing of shrunken Film No. 2 in the opening of the package,
considerably more force was required to propagate the tears down each side of the
package. The higher force to propagate the tear is believed to exacerbate the film
delamination problem.
In stark contrast to the opening of the package made from Film No. 1, the
peeling of Film No. 2 from the cooked meat product resulted in a large area of
delamination beginning as the material was peeled past the point of the initial tear
initiator. Microscopic analysis of layer failure showed that the delamination occurred
between the first and second layers of Film No. 2. It is believed that the considerably
lower force required to propagate the manual tearing of Film No. 1, vs. Film No. 2, is
a significant factor in allowing a package made from Film No. 1 to be opened without
delamination. In Film No. 2, the bond strength of the third layer to the first layer was
measured and determined to be 205 grams per inch.
In addition, it has been discovered that Film No. 1 has increased endurance
of the seal to cook temperatures in the 200°F to 210°F range, relative to Film No. 2.
More particularly, when packaged products were cooked for 6 hours at 210°F,
packaging articles made from Film No. 1 exhibited 100% survival without
delamination, whereas only 71.9% of the packaging articles made from Film No. 2
survived cooking without delamination. Moreover, when packaged products were
cooked for 12 hours at 210°F, packaging articles made from Film No. 1 exhibited
100% survival without delamination, whereas only 53.1% of the packaging articles
made from Film No. 2 survived cooking without delamination. When packaged
products were cooked for 12 hours at 200°F, packaging articles made from Film No. 1
exhibited 100% survival cooking without delamination, whereas only 94% of the
packaging articles made from Film No. 2 survived cooking without delamination.
Example 3 (Working)
A heat-shrinkable multilayer film for use in making a packaging article
according to the present invention was produced in a manner as illustrated in
described above. The composition of this film, referred to herein as Film No. 3, is
provided in Table 3, below. The first layer was an outer film layer that served as the
inside layer and seal layer of an end-seal bag made from the film. The second layer
was a tie layer between the first layer and the third layer. The third layer was a layer
that comprised an incompatible polymer blend in order to provide the film with a
linear tear property in the machine direction after shrinking. The fourth layer was an
outer layer that served as the outside layer of the bag.
TABLE 3
Film No. 3 (working)
Layer Layer
Number Layer Chemical Identity Thickness
(Layer (mils)
Function)
First blend of 50 wt % polyamide 6/12 and 0.28
(inside & seal) 50 wt % polyamide 12
Second 100% Plexar PX3227 blend of maleic anhydride modified 0.15
(tie) polyethylene and linear low density polyethylene
Third 1.46
(incompatible 70% Exceed 1012CJ ethylene/hexene copolymer
polymer blend 28% Escorene LD 713.934053 ethylene/vinyl acetate copolymer
layer) 2% blue color concentrate in ethylene/methyl acrylate copolymer
Fourth 80% PE1651 ethylene vinyl acetate copolymer 0.51
(outside) 20% T60119
Resins in Table 3 that are present in Table 1 or Table 2 are as identified in
the paragraphs below Tables 1 and 2, above.
Blue Color Concentrate in ethylene/methacrylate copolymer had a density
of 0.951 g/cm , and was obtained from Colortech.
PE1651 ethylene vinyl acetate copolymer had a vinyl acetate content of
6.5% a density of 0.928 g/cm , a melt index of 0.5 dg/min, and was obtained from
Flint Hills Resources, LP.
Film No. 3 was fully coextruded as a seamless tubing using the process
illustrated in described above. The seamless tubing was converted into end-
seal bags and used to package a water-added ham product that was then cooked, as
described above for Film No. 1, with the film shrinking tightly around the produce.
After cooling and refrigeration, the package was opened and tore down it length in the
machine direction, without film delamination, allowing the cooked meat product to be
removed from the package.
Examples 4 through 40 (all are comparative examples, except Example 37)
Initial attempts to solve the delamination-during-tearing problem began
with a six layer film very similar to Film No. 2 as a starting point. Experiments were
run by modifying the polymeric composition of the second film layer, i.e., a tie layer
directly adhering to the seal layer, in an effort to locate a stronger bonding tie layer
that would not delaminate from the seal layer. Unless otherwise indicated in the
Comments in Table 5, the composition and thickness of the first, third, fourth, fifth,
and sixth layers of Films 4-42 is set forth in Table 4, below.
TABLE 4
Composition and Thickness of Layers 1, 3, 4, 5, 6 of Film Nos. 4 through 40
Layer Layer
Number Layer Chemical Identity Thickness
(Layer (mils)
Function)
First blend of 50 wt % polyamide 6/12 and 0.28
(inside & seal) 50 wt % polyamide 12
Second See Table 5 0.28
(tie)
Third 100% Plexar PX3227 blend of maleic anhydride modified 0.14
(tie) polyethylene and linear low density polyethylene
Fourth 100% Eval E 105A ethylene vinyl alcohol copolymer 0.16
(barrier)
Fifth 100% Plexar PX3227 blend of maleic anhydride modified 0.16
(tie) polyethylene and linear low density polyethylene
Sixth 80% A-3018 ethylene/vinyl acetate copolymer 1.32
(outside) 20% Marlex 9006 ethylene/hexene copolymer
Table 5, below, provides the polymeric composition of the second layer
for each of Film Nos. 4-40. In each of Film Nos. 4-40, the second layer had a
thickness of 0.28 mil. Delamination, where noted, occurred between the first and
second layers.
Table 5
Composition of Second Layer for Film Nos. 4-40
Bond
Film Composition of Second Strength
No. Layer (=First Tie Layer) Layer 1 to Comment
Layer 2
(gms/inch)
4 Bynel 41E687 139 Untested: assumed would delaminate;
bond strength ≤ 205 g/in
Bynel 41E850 157 Untested: assumed would delaminate;
bond strength ≤ 205 g/in n
6 Bynel CXA 21E787 195 Untested: assumed would delaminate;
bond strength ≤ 205 g/in
7 Plexar PX 3080 0.00 Untested: assumed would delaminate;
bond strength ≤ 205 g/in
8 EVAL E 105A 218 Delaminated
9 80% Infuse D9107.10 456 Delaminated
% Bynel CXA 41E710
Admer 2118A 36 Untested: assumed delamination;
bond strength ≤ 205 g/in
11 Arkema 18300 204 Untested: assumed delamination;
bond strength ≤ 205 g/in
12 80% Arkema 18300 77 Untested: assumed delamination;
% Exact 4011 bond strength ≤ 205 g/in
13 80% Infuse D9100.05 174 Untested: assumed delamination;
% Bynel CXA 41E710 bond strength ≤ 205 g/in
14 Bynel CXA 41E710 132 Delaminated
80% Plexar PX 3080 66 Untested: assumed delamination;
% Exact 4011 bond strength ≤ 205 g/in
16 80% Plexar PX3227 158 Untested: assumed delamination;
% Exact 4053 bond strength ≤ 205 g/in
17 90% Infuse D9107.10 115 Untested: assumed delamination;
% Bynel CXA 41E710 bond strength ≤ 205 g/in
18 75% Infuse D9107.10 188 Untested: assumed delamination;
% Bynel CXA 41E710 bond strength ≤ 205 g/in
19 90% Bynel CXA 21E787 330 Delaminated
% Infuse D9107.10
90% Affinity EG8100G 249 Delaminated
% Bynel CXA 41E710
21 90% Infuse D9100.05 154 Untested: assumed delamination;
% Bynel CXA 41E710 bond strength ≤ 205 g/in
22 85% Infuse D9100.05 83 Untested: assumed delamination;
% Bynel CXA 41E710 bond strength ≤ 205 g/in
Bond
Film Composition of Second Strength
No. Layer (=First Tie Layer) Layer 1 to Comment
Layer 2
(gms/inch)
23 100% Eval E 105A 241
Delaminated
ethylene vinyl alcohol
copolymer
24 20% Fusabond A ME-556D 96.8 Untested: assumed delamination;
80% Exact 4053 bond strength ≤ 205 g/in
Admer 2118A 171 Untested: assumed delamination;
bond strength ≤ 205 g/in
26 80% Admer 2118A 103 Untested: assumed delamination;
% Infuse D9107.10 bond strength ≤ 205 g/in
27 80% Admer 2118A 153 Untested: assumed delamination;
% Exact 4053 bond strength ≤ 205 g/in
28 80% Amplify TY 1052 H 89.4 Untested: assumed delamination;
% Exact 4053 bond strength ≤ 205 g/in
29 80% Fusabond A ME-556D 211 Untested: assumed delamination;
% Infuse D9107.10 bond strength just above 205 g/in
80% Fusabond A ME-556D 189 Untested: assumed delamination;
% Exact 4053 bond strength ≤ 205 g/in
31 90% Bynel CXA 21E787 361 Delaminated
% Infuse D9107.10
32 80% Bynel CXA 21E787 381 Delaminated
% Exact 4053
33 ADMER 2676A (PX099) 163.5 Delaminated
34 Admer 2675A 85.4 Delaminated
Bynel CXA 21E787 678 Delaminated
36 95% Bynel CXA 21E787 581 Delaminated
% Topas 9903D-10
37 95% Bynel 3861 508 Working Example; no delamination
% Topas 9903D-10 occurred while being stripped
38 Surlyn 1857 188 Delaminated
39 80% Topas 9903D-10 8.4 Delaminated
% Amplify TY 1052 H
40 80% Infuse D9107.10
456 Delaminated
% Bynel CXA 41E710
Bynel 41E687 was a maleic anhydride modified linear low density
polyethylene having a density of 0.910 g/ cm and a melt index of 1.7 dg/min, and
was obtained from DuPont.
Bynel 41E850 was a blend of a maleic anhydride modified polyethylene
and linear low density polyethylene, and had a density of 0.900 g/ cm and a melt
index of 1.0 dg/min, and was obtained from DuPont.
Bynel CXA 21E787 was a maleic anhydride modified ethylene
methacrylic acid copolymer having a density of 0.93 g/ cm and a melt index of 1.6
dg/min, and was obtained from DuPont.
Plexar PX 3080 was a maleic anhydride modified linear low density
polyethylene having a density of 0.91 g/ cm and a melt index of 1.8 dg/min, and was
obtained from LyondellBasell Industries.
Infuse D9107.10 was a polyethylene having a density of 0.866 g/ cm and
a melt index of 1.0 dg/min, and was obtained from Dow.
Bynel CXA 41E710 was a maleic anhydride modified linear low density
polyethylene having a density of 0.91 g/ cm and a melt index of 2.7 dg/min, and was
obtained from DuPont.
Admer 2118A was a maleic anhydride modified linear low density
polyethylene having a density of 0.91g/ cm and a melt index of 1.8 dg/min, and was
obtained from Mitsui.
Exact 4011 was a single site catalyzed ethylene/butene copolymer having
a density of 0.888 g/ cm and a melt index of 2.2 dg/min, and was obtained from
ExxonMobil.
Arkema 18300 was a linear low density polyethylene having a density of
0.91 g/ cm and a melt index of 1.8 dg/min, and was obtained from Arkema.
Infuse D9100.05 was a very low density polyethylene having a density of
o.877 g/ cm and a melt index of 1.0 dg/min, and was obtained from Dow.
Affinity EG8100G was a single site catalyzed substantially linear
ethylene/butene copolymer having limited long chain branching, having a density of
0.870 g/ cm and a melt index of 1.0 dg/min, and was obtained from Dow.
Fusabond A ME-556 D was a coextrusion adhesive resin having a
density of 0.93 g/ cm and a melt index of 1.8 dg/min, and was obtained from DuPont.
Amplify TY 1052 H was a maleic anhydride modified linear low density
polyethylene having a density of 0.875 g/ cm and a melt index of 1.25 dg/min, and
was obtained from Dow.
Admer 2676A was a maleic anhydride modified linear low density
polyethylene having a density of 0.92 g/ cm and a melt index of 4.4 dg/min, and was
obtained from Mitsui.
Topas 9903D-10 was an ethylene/norbornene copolymer having a density
of 0.974 g/ cm and a melt index of 1.0 dg/min, and was obtained from Topas
Advanced Polymers, Inc.
Bynel 3861 was a maleic anhydride modified ethylene/vinyl acetate
copolymer having a density of 0.980 g/ cm and a melt index of 2.0 dg/min, and was
obtained from DuPont.
Surlyn 1857 was a zinc neutralized ethylene/methyl acrylate copolymer
having a density of 0.94 g/ cm and a melt index of 4.0 dg/min, and was obtained
from DuPont.
Resins in Table 5 that are not identified immediately above are identified
following Table 1 or Table 2, above.
The results in Table 5 show that a wide variety of tie layer compositions
which bonded to the polyamide blend seal layer failed to solve the delamination
problem at the interface between the polyamide blend seal layer and adjacent tie layer.
Even when the bond strength between the layers was as high as 220 to 678 grams per
inch, delamination persisted in the absence of a layer containing an incompatible
polymer blend. More particularly, Comparative examples 8, 9, 19, 20, 23, 31, 32, 35,
36, and 40 each exhibited a bond strength of greater than 205 gm/inch, but none of
these films included a layer containing an incompatible polymer blend, and all of
these films delaminated upon testing.
However, working examples 1, 3, and 37 demonstrate that the
incompatible polymer blend solves the delamination problem when tearing the
packaging article open after the meat product is cooked and the film is shrunk around
the meat product and adhering to the meat product. The bond strengths for these
working examples were 205 grams per inch (Examples 1 and 3) and 508 grams per
inch (Example 37). However, the results in Table 5 support the conclusion that it was
the presence of the layer comprising the incompatible polymer blend, rather than the
bond strength, that prevented the delamination from occurring upon tearing the bags
open after the cooking of the meat product.
In comparative examples 4-7, 10-13, 15-18, 21-22, and 24-30, the bond
strength was less than 205 grams per inch, i.e., lower than the bond strength of
comparative example 2. As a result, these samples were not tested for delamination,
as it was assumed that these samples would delaminate because (i) none of these films
included a layer containing an incompatible polymer blend, and (ii) the bond strength
between the seal layer and the adjacent tie layer was lower than the bond strength of
the Comparative Example 2, which delaminated. Examples 14, 33, 34, 38, and 39
exhibited a bond strength of less than 205 grams per inch and were tested and did
delaminate, supporting the assumption that comparative examples 4-7, 10-13, 15-18,
21-22, and 24-30, if tested, would also have delaminated.
Although the present invention has been described with reference to the
preferred embodiments, it is to be understood that modifications and variations of the
invention exist without departing from the principles and scope of the invention, as
those skilled in the art will readily understand. Accordingly, such modifications are
in accordance with the claims set forth below.
Claims (15)
- Claim 1: A packaged product comprising an easy-open packaging article including a multilayer film surrounding and adhering to a cooked meat product, with the packaging article having a heat seal of the inside surface of the film to itself and a skirt extending outward from the heat seal with the skirt having a tear initiator therein, the multilayer film comprising: (A) a first layer that is an inside seal layer comprising a thermoplastic polymer comprising at least one member selected from the group consisting of polyamide and polyester; (B) a second layer that bonds to the first layer with a bond strength of at least 36 grams per inch; (C) wherein the second layer, or a third layer with the second layer being between the first layer and the third layer, comprises a tear-enhancing component comprising at least one member selected from the group consisting of an inorganic filler and an incompatible polymer blend, wherein: the filler is present in an amount of at least 5 weight percent, based on layer weight, and the filler comprises at least one member selected from the group consisting of silicate, silica, siloxane, silicone resin, zinc sulfide, wollastonite, microspheres, glass fiber, metal oxide, calcium carbonate, sulfate, aluminum trihydrate, feldspar, perlite, gypsum, iron, fluoropolymer, crosslinked polymethylmethacrylate, talc, diatomaceous earth, zeolite, mica, kaolin, carbon black, and graphite, and the second or third layer containing the filler makes up at least 10 weight percent of the film, based on total film weight; and the incompatible polymer blend comprises at least one member selected from the group consisting of: (i) a blend of from 90 to 30 weight percent ethylene homopolymer and/or ethylene/alpha-olefin copolymer with from 10 to 70 weight percent ethylene/unsaturated ester copolymer having an unsaturated ester content of at least 10 weight percent; (ii) a blend of ionomer resin with ethylene/unsaturated ester copolymer, and/or polybutylene, and/or propylene homopolymer and/or propylene copolymer; (iii) a blend of homogeneous ethylene/alpha-olefin copolymer with recycled polymer blend comprising ethylene homopolymer, propylene homopolymer, ethylene copolymer, propylene copolymer, polyamide, ethylene/vinyl alcohol copolymer, ionomer resin, anhydride-modified ethylene/alpha-olefin copolymer, and/or antiblock; (iv) a blend of from 10 to 75 weight percent ethylene/unsaturated ester copolymer with from 90 to 15 weight percent polypropylene and/or propylene/ethylene copolymer, and/or polybutylene, and/or modified ethylene/alpha-olefin copolymer, and/or styrene homopolymer, and/or styrene/butadiene copolymer; (v) a blend of ethylene/norbornene copolymer with ethylene/unsaturated ester copolymer and/or polypropylene and/or polybutylene; (vi) a blend of from 90 to 15 weight percent ethylene/alpha-olefin copolymer with from 10 to 75 weight percent polypropylene and/or polybutylene and/or ethylene/norbornene; (vii) a blend of from 90 to 25 weight percent homogeneous propylene homopolymer and/or homogeneous propylene copolymer with from 10 to 75 weight percent homogeneous ethylene/alpha-olefin copolymer and/or ethylene/unsaturated ester copolymer; (viii) a blend of propylene homopolymer and/or propylene/ethylene copolymer and/or polybutylene with ethylene/methyl acrylate copolymer and/or ethylene/acrylic acid copolymer and/or ethylene/butyl acrylate copolymer; (ix) a blend of polyamide with polystyrene and/or ethylene/alpha-olefin copolymer and/or ethylene/vinyl acetate copolymer and/or styrene/butadiene copolymer; and (x) a blend of polyamide 6 and polyamide 6I6T; and the incompatible polymer blend is present in at least one layer of the multilayer film, and the incompatible polymer blend makes up at least 20 weight percent of the film, based on total film weight.
- Claim 2: The packaged product according to Claim 1, wherein the second layer further comprises the tear-enhancing component.
- Claim 3: The packaged product according to Claim 2, wherein the second layer comprises a blend of (i) from 90 to 30 weight percent ethylene homopolymer and/or ethylene/alpha-olefin copolymer with (ii) from 10 to 70 weight percent ethylene/unsaturated ester copolymer having an unsaturated ester content of at least 10 weight percent, and wherein the ethylene homopolymer, ethylene/alpha-olefin copolymer, and/or ethylene/unsaturated ester copolymer together contain a grafted maleic anhydride content of at least 0.1 mole percent, based on moles of ethylene/unsaturated ester copolymer.
- Claim 4: The packaged product according to Claim 1, wherein the second layer is a tie layer and the third layer comprises the incompatible polymer blend.
- Claim 5: The packaged product according to Claim 4, wherein the second layer bonds to the first layer at a bond strength of 36 to 138 grams per inch.
- Claim 6: The packaged product according to Claim 4, wherein the second layer bonds to the first layer at a bond strength of at least 139 grams per inch.
- Claim 7: The packaged product according to Claim 4, wherein the film is heat- shrinkable and the second layer bonds to the first layer at a bond strength of from 139 to 680 grams per inch.
- Claim 8: The packaged product according to Claim 7, wherein the second layer is a first tie layer and the multilayer film further comprises fourth layer that is a second tie layer and a fifth layer that is an O -barrier layer, with the fifth layer comprising at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyvinylidene chloride, polyamide 6I/6T, polyamide MXD6,polyester, and polyacrylonitrile, and the fourth layer is between the third layer and the fifth layer.
- Claim 9: The packaged product according to Claim 8, wherein the multilayer film further comprises a sixth layer that is a third tie layer and a seventh layer that is an outside layer of the packaging article, with the sixth layer being between the fifth layer and a seventh layer, and the seventh layer comprising at least one member selected from the group consisting of olefin homopolymer, olefin copolymer, polyamide, polyester, and polyurethane.
- Claim 10: The packaged product according to Claim 9, wherein the third layer comprises the incompatible polymer blend, and the multilayer film further comprises an eighth layer that also comprises the incompatible polymer blend, with the eighth layer being between the seventh layer and the sixth layer, the eighth layer comprising at least one member selected from the group consisting of: (i) a blend of from 90 to 30 weight percent ethylene homopolymer and/or ethylene/alpha-olefin copolymer with from 10 to 70 weight percent ethylene/unsaturated ester copolymer having an unsaturated ester content of at least 10 weight percent; (ii) a blend of ionomer resin with ethylene/unsaturated ester copolymer, and/or polybutylene, and/or propylene homopolymer and/or propylene copolymer; (iii) a blend of homogeneous ethylene/alpha-olefin copolymer with recycled polymer blend comprising ethylene homopolymer, propylene homopolymer, ethylene copolymer, propylene copolymer, polyamide, ethylene/vinyl alcohol copolymer, ionomer resin, anhydride-modified ethylene/alpha-olefin copolymer, and/or antiblock; (iv) a blend of from 10 to 75 weight percent ethylene/unsaturated ester copolymer with from 90 to 15 weight percent polypropylene and/or propylene/ethylene copolymer, and/or polybutylene, and/or modified ethylene/alpha-olefin copolymer, and/or styrene homopolymer, and/or styrene/butadiene copolymer; (v) a blend of ethylene/norbornene copolymer with ethylene/unsaturated ester copolymer and/or polypropylene and/or polybutylene; (vi) a blend of from 90 to 15 weight percent ethylene/alpha-olefin copolymer with from 10 to 75 weight percent polypropylene and/or polybutylene and/or ethylene/norbornene; (vii) a blend of from 90 to 25 weight percent homogeneous propylene homopolymer and/or homogeneous propylene copolymer with from 10 to 75 weight percent homogeneous ethylene/alpha-olefin copolymer and/or ethylene/unsaturated ester copolymer; (viii) a blend of propylene homopolymer and/or propylene/ethylene copolymer and/or polybutylene with ethylene/methyl acrylate copolymer and/or ethylene/acrylic acid copolymer and/or ethylene/butyl acrylate copolymer; (ix) a blend of polyamide with polystyrene and/or ethylene/alpha-olefin copolymer and/or ethylene/vinyl acetate copolymer and/or styrene/butadiene copolymer; and (x) a blend of polyamide 6 and polyamide 6I6T.
- Claim 11: The packaged product according to Claim 10, wherein the packaging article further comprises a skirt extending outward from the first heat seal, the skirt having a tear initiator therein, and the skirt has a first lay-flat side and a second lay-flat side, and the tear initiator comprises a first tear initiator through the first lay-flat side and a second tear initiator through the second lay-flat side, with the first and second tear initiators being coincident with one another, and the skirt further comprises (A) a first grip-assister comprising a first passageway through the first lay-flat side of the skirt and a first passageway through a second lay-flat side of the skirt, with the first passageways being coincident with one another, and a second grip-assister comprising a second passageway through the first lay-flat side of the skirt and a second passageway through the second lay-flat side of the skirt, with the second passageways being coincident with one another, with the tear initiators being between the first and second grip-assisters, and the heat seal is a first heat seal and the first lay-flat side of the skirt is heat sealed to itself at a second heat seal, and the incompatible polymer blend is present in the film in an amount of from 40 to 60 weight percent, based on total film weight.
- Claim 12: The packaged product according to Claim 1, wherein the packaging article comprises a seamless tubing and the heat seal is a first heat seal on a first end of the packaging article, with the packaging article further comprising a closure on a second end of the packaging article, the closure comprising a member selected from the group consisting of a heat seal and a clip.
- Claim 13: The packaged product according to Claim 1, wherein the skirt has a first lay-flat side and a second lay-flat side, and the tear initiator comprises a first tear initiator through the first lay-flat side and a second tear initiator through the second lay- flat side, with the first and second tear initiators being coincident with one another, and the skirt further comprises (A) a first grip-assister comprising a first passageway through the first lay-flat side of the skirt and a first passageway through a second lay- flat side of the skirt, with the first passageways being coincident with one another, and (B) a second grip-assister comprising a second passageway through the first lay-flat side of the skirt and a second passageway through the second lay-flat side of the skirt, with the second passageways being coincident with one another, with the tear initiators being between the first and second grip-assisters.
- Claim 14: The packaged product according to Claim 13, wherein the heat seal is a first heat seal and the first lay-flat side of the skirt is heat sealed to itself at a second heat seal which is outward of the first heat seal.
- Claim 15: The packaged product according to Claim 13, wherein the skirt further comprises a first stabilizing slit on a first side of the tear initiators and a second stabilizing slit on a second side of the tear initiators, the first stabilizing slit comprising a first slit through the first lay-flat side of the skirt and a first slit through the second
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13/331,375 US20130156900A1 (en) | 2011-12-20 | 2011-12-20 | Easy-Open Cook-In Packaged Product |
| US13/331,375 | 2011-12-20 | ||
| PCT/US2012/070530 WO2013096400A1 (en) | 2011-12-20 | 2012-12-19 | Easy-open cook-in packaged product |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| NZ626761A NZ626761A (en) | 2016-09-30 |
| NZ626761B2 true NZ626761B2 (en) | 2017-01-05 |
Family
ID=
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