Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
1999-01-29
2002-07-16
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Composite
Of polyamide
C428S035200, C428S035700, C428S036700, C428S200000, C428S474400, C383S109000, C383S113000
Reexamination Certificate
active
06420046
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thermoplastic film that can be used to make a bag suitable for packaging coins or other objects; to the bag itself; and to a package containing coins or other objects.
BACKGROUND OF THE INVENTION
Coins such as the United States twenty five cent piece known as a “quarter” are typically packaged and transported by financial institutions in the US in canvas bags. In Europe and in some parts of Australasia, plastic bags are typically used. Clarity is sometimes an advantage, although some of the coin bags produced in Europe are white opaque. The canvas bag plus an appropriate closure is relatively expensive. The plastic system costs less than the canvas bag plus closure.
Plastic bags for storing and transporting coins is thus convenient in the sense that polyethylene bags can be made with a relatively high transparency, important when dealing with money, and with relatively low cost. However, commercial coin bags have an inadequate combination of resistance to tear propagation, and impact resistance. Quarters in particular have a rough, “serrated” edge which can cut bags open on impact. When dropped or thrown during transportation, loading or unloading, these bags will sometimes break open, and some of the contents will fall out of the bag. The body of the bag can be punctured or torn, or the seals can be breached by the coins. In packaging money, where accountability is essential and any loss must be accounted for, breakage and loss of contents can present a serious problem.
An improved packaging film for coins and other abusive materials should provide adequate performance in both of the physical properties discussed above: resistance to tear (as measured by tear propagation/mil, using a standard test: ASTM D 1938); and impact resistance (as measured by instrumented impact/mil, using a standard test: ASTM D 3763-95a). Other properties, such as heat sealability (so the film can be sealed together to make a bag or pouch), flexibility, i.e. relatively low tensile modulus (so a true bag can be made), and good clarity (for visual inspection of the bag contents) are also typically desirable in many packaging applications.
The inventors have developed a film, suitable for making into a bag for holding coins or other objects, exhibiting a good combination of resistance to tear and impact resistance.
SUMMARY OF THE INVENTION
In a first aspect, a multilayer film comprises a core layer comprising a polymer selected from the group consisting of nylon 6, nylon 66, nylon 6,66, and polyamide elastomer; first and second intermediate layers, each disposed on a respective opposite side of the core layer, comprising polymeric adhesive; a first outer layer, disposed on the first intermediate layer, comprising ethylene/alpha olefin copolymer having a density less than 0.940 grams/cubic centimeter; and a second outer layer, disposed on the second intermediate layer, comprising heat sealable polymer selected from the group consisting of ethylene/alpha olefin copolymer having a density less than 0.921 grams/cubic centimeter, ethylene/vinyl acetate copolymer, ethylene/alkyl (meth)acrylate copolymer, ethylene/(meth)acrylic acid copolymer, and ionomer; wherein the film has a tear propagation/mil value (ASTM D 1938) of at least 0.45 pound-inches/mil in the longitudinal direction, and at least 0.45 pound-inches/mil in the transverse direction, and an instrumented impact/mil value (ASTM D 3763-95a) of at least 0.5 joules/mil.
In a second aspect, a bag, having a first and second panel, a bag bottom, and a bag mouth, comprises a multilayer film comprising a core layer comprising a polymer selected from the group consisting of nylon 6, nylon 66, nylon 6,66, and polyamide elastomer; first and second intermediate layers, each disposed on a respective opposite side of the core layer, comprising polymeric adhesive; a first outer layer, disposed on the first intermediate layer, comprising ethylene/alpha olefin copolymer having a density less than 0.940 grams/cubic centimeter; and a second outer layer, disposed on the second intermediate layer, comprising heat sealable polymer selected from the group consisting of ethylene/alpha olefin copolymer having a density less than 0.921 grams/cubic centimeter, ethylene/vinyl acetate copolymer, ethylene/alkyl (meth)acrylate copolymer, ethylene/(meth)acrylic acid copolymer, and ionomer; wherein the film has a tear propagation/mil value (ASTM D 1938) of at least 0.45 pound-inches/mil in the longitudinal direction, and at least 0.45 pound-inches/mil in the transverse direction, and an instrumented impact/mil value (ASTM D 3763-95a) of at least 0.5 joules/mil.
In a third aspect, an article comprises a sealed bag having a first and second panel, a bag bottom, and a sealed bag mouth, wherein the bag comprises a multilayer film comprising a core layer comprising a polymer selected from the group consisting of nylon 6, nylon 66, nylon 6,66, and polyamide elastomer; first and second intermediate layers, each disposed on a respective opposite side of the core layer, comprising polymeric adhesive; a first outer layer, disposed on the first intermediate layer, comprising ethylene/alpha olefin copolymer having a density less than 0.940 grams/cubic centimeter; and a second outer layer, disposed on the second intermediate layer, comprising heat sealable polymer selected from the group consisting of ethylene/alpha olefin copolymer having a density less than 0.921 grams/cubic centimeter, ethylene/vinyl acetate copolymer, ethylene/alkyl (meth)acrylate copolymer, ethylene/(meth)acrylic acid copolymer, and ionomer; wherein the film has a tear propagation/mil value (ASTM D 1938) of at least 0.45 pound-inches/mil in the longitudinal direction, and at least 0.45 pound-inches/mil in the transverse direction, and an instrumented impact/mil value (ASTM D 3763-95a) of at least 0.5 joules/mil; and objects inside the sealed bag.
Definitions
“Tear Propagation” herein refers to the force required to propagate a tear from a tiny slit made by a sharp blade in a specimen of the film, measured by ASTM D 1938.
“Instrumented Impact” herein refers to the energy necessary to puncture a restrained specimen of film, measured by ASTM D 3763-95a.
“Adhesive” herein refers to polymeric adhesive, more preferably an olefin polymer or copolymer having an anhydride functionality grafted thereon and/or copolymerized therewith and/or blended therewith.
“Anhydride functionality” herein refers to any form of anhydride functionality, such as the anhydride of maleic acid, fumaric acid, etc., whether grafted onto a polymer, copolymerized with a polymer, or blended with one or more polymers, and is also inclusive of derivatives of such functionalities, such as acids, esters, and metal salts derived therefrom.
“Core layer” herein refers to the central layer of a multi-layer film. Where the film has an even number of layers, “core layer” refers to either of the two central layers of a film.
“Ethylene/alpha-olefin copolymer” (EAO) herein refers to copolymers of ethylene with one or more comonomers selected from C
4
to C
10
alpha-olefins such as butene-1 (i.e., 1-butene), hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures. This molecular structure is to be contrasted with conventional low or medium density polyethylenes which are more highly branched than their respective counterparts. EAO includes such heterogeneous materials as linear medium density polyethylene (LMDPE), linear low density polyethylene (LLDPE), and very low and ultra low density polyethylene (VLDPE and ULDPE); as well as homogeneous polymers (HEAO) such as TAFMER™ ethylene/alpha olefin copolymers supplied by Mitsui Petrochemical Corporation and metallocene-catalyzed polymers such as EXACT™ resins supplied by Exxon and AFFINITY™ resins supplied by the Dow Chemical Company. EAO includes long chain branched homogeneous ethylene/alpha-olefin copolymer. An EAO can for example have a density of between 0.916 and 0
Furrer William W.
Shah Gautam P.
Cryovac Inc.
Miggins Michael C.
Quatt Mark B.
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