Note: Descriptions are shown in the official language in which they were submitted.
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Child-Resistant Blister Package
BACKGROUND OF THE INVENTION
The present invention relates to improved child-resistant blister
packaging. More particularly, this invention relates to blister packaging
that includes a lidding component that comprises at least one nonwoven
layer selected from the group consisting of melt-spun continuous filament
nonwoven sheets and flash spun plexifilamentary sheets.
Blister packages are known in the art, for example as packaging for
pharmaceuticals and other materials. Blister packages include a blister
component having at least one cavity formed therein into which the
medicine or other packaged material is placed prior to being sealed to a
lidding or top web component. Blister components known in the art
include soft-tempered aluminum foils, hard-tempered aluminum foils,
multi-layer cold formable foils, and thermoformed films. Lidding
components known in the art include films, and combinat~ns of films,
paper, and/or foil. The lidding component generally has a heat-seal layer
applied to one side thereof which is used to heat seal the lidding
component to the blister component during the manufacture of the blister
package. When used for packaging pharmaceuticals and other materials
that are oxygen- and/or moisture-sensitive, the blister package should
have sufficient barrier properties to ensure a reasonable shelf-life for the
packaged materials. When used for packaging pharmaceuticals or other
materials that may be harmful to children, a blister package should also be
child-resistant so that a child cannot open the package, bite through it, or
otherwise damage the packaging in a way that exposes the packaged
pharmaceutical or other packaged material. At the same time, it is
generally desirable that an adult can open the blister package without
undue effort.
Examples of blister packages known in the art include peel-open,
tear-open, push-through, and peel off-push through packages. In a peel-
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open package, the lidding component is peeled away from the blister
component to reveal the packaged material. In a tear-open package, the
lidding and blister components contain a notch or perforation that extends
from an edge of the package in the direction of the cavity. The notch can
be made in an external edge of a package, or, for packages comprising
multiple blisters separated by perforations, the notch is preferably
contained internal to the package such that when an individual blister is
separated at the perforations from the rest of the blisters in the package,
the notch in the separated blister is on an exposed edge thereof. The
package is then torn at the notch and the tear is propagated until the
contents of the package are capable of being removed. In a push-
through package, the packaged material is pushed through the lidding
component by applying finger pressure to the exterior of the blister cavity.
In a peel off-push through package, the lidding component is a multi-layer
laminate that generally includes an outer paper layer bonded by an
intermediate adhesive layer to a film layer (e.g. polyester film), with the
film layer also being bonded by a peelable adhesive layer to a foil layer on
the side of the film opposite that which is bonded to the paper layer. The
foil layer generally has a heat-seal layer coated or otherwise applied to the
side of the foil opposite the film which provides a non-peelable seal when
heat-sealed to the blister component. To open the package, the lidding is
peeled between the film and the foil layers, leaving the foil layer attached
to the blister component. After peeling off the combined paper and film
lidding layers, the packaged material is pushed through the lidding layers)
that remains attached to the blister component. Generally the peelable
adhesive layer remains adhered to the film layer during peeling such that
only the foil layer remains attached to the blister component after peeling.
An example of a peel off-push through blister package is described in
Brunda, U.S. Patent No. 3,899,080. The blister package comprises a
peelable outer layer, for example film, cardboard, or paper that is adhered
by a peelable adhesive to a rupturable layer such as paper, selected
plastics, or metal foil.
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One challenge in the manufacture of blister packaging is to make a
package that is child resistant that can also be opened by an adult without
undue difficulty. Certain child-resistant blister packages known in the art
include peel-open packages that comprise a laminated paper-film lidding
component adhered to a plastic blister component by a peelable sealant.
Further child-resistance is obtained using peel off-push through packages,
which comprise the multi-layer lidding material described above. One
disadvantage of current peel off-push through packages is that paper-film-
foil laminates used in the lidding do not generally peel cleanly in one piece
and often tear at the perforation, making it difficult to initiate a new peel.
Some paper-film laminates and paper-film-foil laminates also have poor
puncture resistance and can be chewed through by a child. Another
disadvantage of using paper-film laminates or paper-film-foil laminates in
the lidding component is that it is not unusual to have problems with
moisture being sealed in the blister when moisture that is retained in the
paper forms steam at the high temperatures used in the heat-sealing
process.
Poore, British patent GB 2151581 describes push-through strip
packaging described as child-resistant that includes first and second
planar sheet materials with the packaged elements enclosed
therebetween. Neither of the planar sheet materials contains pre-formed
blisters, but rather the necessary accommodation of the packaged
elements is afforded by stretching of the material of each sheet as they
are sealed together. The first sheet is a laminate of a paper or a foil with a
tear-resistant biaxially oriented plastic material together with an adhesive
layer that is preferably a heat-sealable adhesive layer. The second sheet
preferably has a push through force of at least about 70 N and comprises
a laminate of paper or metal foil and a layer of plastic or other material
that
can provide adhesive properties, preferably a heat-sealable adhesive.
The package permits the removal of individual elements through the
second sheet by application of finger pressure.
Gerber published European Patent Application 0959020 describes
a peel off-push through type blister package that includes a cover sheet
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containing a metal foil-free push-through penetrable plastic layer, a
peelable release adhesive, and a non-penetrable cover layer. The cover
layer is peeled off the release adhesive in a first step and the packaged
material is pushed through the metal foil-free penetrable plastic layer.
Suitable cover layers include mono-films, film laminates containing
thermoplastics, papers or layered materials of thermoplastic paper.
Suitable papers include cellulose papers, security papers, and papers
made of synthetic fibers.
Carter, U.S. 4,947,620 describes a blister pack suitable for steam
sterilization that includes a lidding material of Tyvek~ nonwoven material
that is coated with an adhesive only on the areas of the lidding that are
bonded to the blister component. The Tyvek~ nonwoven material is
breathable and therefore such packaging is not suitable for packaging
pharmaceuticals and other materials that are oxygen or moisture sensitive.
There remains a need for improved child-resistant blister packaging
that protects materials packaged therein from moisture and/or oxygen that
is also economical to manufacture.
BRIEF SUMMARY OF THE INVENTION
In a first embodiment, the present invention is directed to a blister
package comprising a blister component having an inner surface and an
outer surface and a multi-layer lidding component having an inner surface
and an outer surface, wherein selected portions of the inner surfaces of
the blister and lidding components are adhered together to form at least
one cavity therebetween, the blister component comprising a first barrier
layer selected from the group consisting of polymeric films, coated
polymeric films, metal foils, and film-foil laminates, and the lidding
component comprising a second barrier layer and a nonwoven layer
comprising at least one melt-spun continuous filament nonwoven sheet.
A second embodiment of the present invention is a blister
package comprising a blister component having an inner surface and an
outer surface and a multi-layer lidding component having an inner surface
and an outer surface, wherein selected portions of the inner surfaces of
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the blister and lidding components are bonded together to form at least
one cavity therebetween, the blister component comprising a first barrier
layer selected from the group consisting of polymeric films, coated
polymeric films, metal foils, and film-foil laminates, and the lidding
component comprising a flash spun plexifilamentary sheet and a second
barrier layer comprising a sheet layer selected from the group consisting
of polymeric films, coated polymeric films, and metalized polymeric films.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic elevation view of a blister package.
Figure 2a is a schematic cross-sectional view of a lidding material
useful in blister packages of the present invention.
Figure 2b is a schematic cross-sectional view of a second
embodiment of a lidding material useful in blister packages of the present
invention.
Figure 3 is a schematic diagram of a process suitable for preparing
a blister package of the present invention.
Figure 4 is a portion of the product made by the process of Fig. 3,
showing multiple blister packages.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to an improved child-resistant blister
package that comprises a multi-layer lidding component and a blister
component. The multi-layer lidding component includes at least one
barrier layer and at least one nonwoven layer selected from the group
consisting of melt-spun continuous filament nonwoven sheets and flash
spun plexifilamentary sheets. The blister packages of the present
invention include peel-open, tear-open, and peel off-push through
packages. The use of a melt-spun continuous filament nonwoven sheet or
flash spun plexifilamentary sheet in the lidding results in a blister package
that is difFicult or impossible to open by pushing the packaged item
through the lidding or by chewing through the lidding, thus improving the
degree of child resistance compared to packages known in the art. The
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term "copolymer" as used herein includes random, block, alternating, and
graft copolymers prepared by polymerizing two or more comonomers and
thus includes dipolymers, terpolymers, etc.
The term "polyethylene" (PE) as used herein is intended to
encompass not only homopolymers of ethylene, but also copolymers
wherein at least 85% of the recurring units are ethylene units, and includes
"linear low density polyethylenes" (LLDPE) which are linear ethylenela-
olefin copolymers having a density of less than about 0.955 g/cm3, and
"high density polyethylenes" (HDPE), which are polyethylene
homopolymers having a density of at least about 0.94 g/cm3.
The term "polyester" as used herein is intended to embrace
polymers wherein at least 85% of the recurring units are condensation
products of dicarboxylic acids and dihydroxy alcohols with linkages
created by formation of ester units. Examples of polyesters include
polyethylene terephthalate) (PET), which is a condensation product of
ethylene glycol and terephthalic acid, and poly(1,3-propylene
terephthalate), which is a condensation product of 1,3-propanediol and
terephthalic acid.
The term "polyamide" as used herein is intended to embrace
polymers containing recurring amide (-CONH-) groups. One class of
polyamides is prepared by copolymerizing one or more dicarboxylic acids
with one or more diamines. Examples of polyamides suitable for use in
the present invention include poly(hexamethylene adipamide) (nylon 6,6)
and polycaprolactam (nylon 6).
The term "barrier layer" as used herein refers to a sheet layer,
including films and coatings that restrict the permeation of oxygen and/or
water vapor into a blister package that comprises the sheet layer. Barrier
layers suitable for use in the present invention preferably have a moisture
vapor transmission rate (MVTR) of less than 6 g/m2/24 hr measured
according to ASTM F1249 under the conditions of 38°C and 90% Relative
Humidity and/or an oxygen transmission rate of less than 28 cm3/m2/24 hr
measured according to ASTM D3985 under the conditions of 23°C, 100%
oxygen, and 100% Relative Humidity.
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The terms "nonwoven fabric", "nonwoven sheet", "nonwoven layer",
and "nonwoven web" as used herein refer to a structure of individual
fibers, filaments, or threads that are positioned in a random manner to
form a planar material without an identifiable pattern, as opposed to a
knitted or woven fabric. Examples of nonwoven fabrics include meltblown
webs, spunbond nonwoven webs, flash spun webs, carded webs,
spunlaced webs, and composite sheets comprising more than one
nonwoven web.
The term "machine direction" (MD) is used herein to refer to the
direction in which a nonwoven web is produced (e.g. the direction of travel
of the supporting surface upon which the fibers are laid down during
formation of the nonwoven web). The term "cross direction" (XD) refers to
the direction generally perpendicular to the machine direction in the plane
of the web.
The term "spunbond fibers" as used herein means fibers that are
melt-spun by extruding molten thermoplastic polymer material as fibers
from a plurality of fine, usually circular, capillaries of a spinneret with
the
diameter of the extruded fibers then being rapidly reduced by drawing and
then quenching the fibers.
The term "meltblown fibers" as used herein, means fibers that are
melt-spun by meltblowing, which comprises extruding a melt-processable
polymer through a plurality of capillaries as molten streams into a high
velocity gas (e.g. air) stream.
The term "spunbond-meltblown-spunbond nonwoven fabric"
("SMS") as used herein refers to a multi-layer composite sheet comprising
a web of meltblown fibers sandwiched between and bonded to two
spunbond layers. Additional spunbond and/or meltblown layers can be
incorporated in the composite sheet, for example spunbond-meltblown-
meltblown-spunbond webs ("SMMS"), etc.
The term "multiple component fiber" as used herein refers to a fiber
that is composed of at least two distinct polymeric components that have
been spun together to form a single fiber. The at least two polymeric
components are arranged in distinct substantially constantly positioned
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zones across the cross-section of the multiple component fibers, the
zones extending substantially continuously along the length of the fibers.
The term "bicomponent fiber" is used herein to refer to a multiple
component fiber that is made from two distinct polymer components, such
as sheath-core fibers that comprises a first polymeric component forming
the sheath, and a second polymeric component forming the core; and
side-by-side fibers, in which the first polymeric component forms at least
one segment that is adjacent at least one segment formed of the second
polymeric component, each segment being substantially continuous along
the length of the fiber with both polymeric components being exposed on
the fiber surface. Multiple component fibers are distinguished from fibers
that are extruded from a single homogeneous or heterogeneous blend of
polymeric materials. The term "multiple component nonwoven web" as
used herein refers to a nonwoven web comprising multiple component
fibers. The term "bicomponent web" as used herein refers to a nonwoven
web comprising bicomponent fibers. A multiple component web can
comprise single component and/or polymer blend fibers in addition to
multiple component fibers.
The term "plexifilamentary" as used herein, means a three-
dimensional integral network or web of a multitude of thin, ribbon-like, film-
fibril elements of random length and with a mean film thickness of less
than about 4 microns and a median fibril width of less than about 25
microns. In plexifilamentary structures, the film-fibril elements are
generally coextensively aligned with the longitudinal axis of the structure
and they intermittently unite and separate at irregular intervals in various
places throughout the length, width and thickness of the structure to form
a continuous three-dimensional network. A nonwoven web of
plexifilamentary film-fibril elements is referred to herein as a "flash spun
plexifilamentary sheet". Conventional flash spinning processes for forming
web layers of plexifilamentary film-fibril strand material are disclosed in
U.S. Pat. Nos. 3,081,519 (Blades et al.), 3,169,899 (Steuber), 3,227,784
(Blades et al.), 3,851,023 (Brethauer et al.), the contents of which are
hereby incorporated by reference.
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As used herein, the term "film" includes layers that are extruded
directly onto one of the other layers in the lidding or blister components, as
well as films that are formed in a separate film-forming step and then
laminated to one or more other layers.
The term "full-surface bonded nonwoven fabric" as used herein
refers to a nonwoven fabric that has been bonded by applying heat and
pressure to the nonwoven fabric between two substantially smooth
bonding surfaces. A full-surface bonded nonwoven fabric is bonded over
substantially 100% of its outer surfaces by fiber-to-fiber bonds. The use of
smooth bonding surfaces results in each side of the full-surface bonded
nonwoven fabric being substantially uniformly bonded. Full surface
bonded nonwoven fabrics are described in co-pending tJ.S. Patent
Application no. 60/529,997 (DuPont Docket no. TK-3820), filed on even
date herewith and incorporated herein by reference in its entirety.
Figure 1 illustrates a schematic elevation view of a blister package
according to the present invention. Lidding component 1 is heat-sealed to
a blister component comprising a plurality of cavities 2. The lidding and
blister components are heat-sealed in the shoulder areas 3 that separate
the individual cavities. The shoulder areas generally include perforations
(not shown) between the individual blisters or groups of individual blisters.
The blister component is formed from a forming web that comprises
at least one barrier layer, for example a polymeric film, coated polymeric
film, or metal foil. Forming webs suitable for forming the blister component
are known in the art. For example, the blister component can be prepared
by thermoforming cavities into a barrier film. Alternately, the blister
component can be formed from a soft-tempered or a hard-tempered foil
such as an aluminum foil layer. Films and foils suitable for forming the
blister component generally have a thickness between about 5.0 mils
(0.125 mm) and 15 mils (0.38 mm) for child-resistant packaging. For
example, a typical film thickness is about 10 mils (0.25 mm). The blister
component can be formed from a multi-layer sheet structure, for example
a multi-layer film or a film-foil laminate.
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Figure 2a is a cross-sectional view of an embodiment of a lidding
component suitable for use in peel-open, tear-open, and peel off-push
through blister packages of the present invention. Nonwoven layer 5,
which comprises at least one melt-spun continuous filament sheet or flash
spun plexifilamentary sheet, is bonded to barrier layer 7 by intervening
adhesive tie layer 6. Heat-seal layer 8 is adhered to the barrier layer on
the side of the barrier layer opposite the tie layer. A blister package is
formed by heat-sealing the lidding component to the blister component
with heat-seal layer 8. facing the blister component such that nonwoven
layer 5 forms one of the outer surfaces of the blister package. Tie layer 6
can form a peelable seal (e.g. in a peel off-push through package) or a
non-peelable seal (e.g. in a peel-open or tear-open package) between the
nonwoven layer and the barrier layer, depending on the desired method
for opening the blister package. A seal or bond is considered non-
peelable if the layers bonded by the non-peelable seal are not readily
opened by an adult by hand-peeling. Generally a seal having a peel
strength between about 3 to 4 Ib/in is preferred for a peelable seal. Peel
strengths less than about 3 Ib/in are generally peeled too easily to be
useful in child-resistant packages. Seals having a peel strength greater
than about 4 Ib/inch are generally considered to be non-peelable or
permanent seals. Peel strength can be measured according to ASTM F
88-0, which is hereby incorporated by reference, using the unsupported
method of clamping the sample described therein. Similarly, heat-seal
layer 8 can form a peelable seal (e.g. in a peel-open package) or a non-
peelable seal (e.g. in a peel off-push through or tear-open package)
between the barrier layer and the blister component. Examples of lidding
constructions according to Figure 2a include: (a) melt-spun continuous
filament nonwoven sheet/adhesive tie layer/metal foil/heat-seal layer, (b)
melt-spun continuous filament nonwoven sheet/adhesive tie layer/barrier
film (metalized or unmetalized, coated or uncoated)/heat-seal layer, and
(c) flash spun plexifilamentary sheet/adhesive tie layer/barrier film
(metalized or unmetalized, coated or uncoated) /heat-seal layer. The
barrier film can be a film that is laminated to the nonwoven sheet or can be
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a layer that is co-extruded with the adhesive tie layer onto the nonwoven
sheet.
Barrier layers suitable for use in the lidding component shown in
Figure 2a include foil sheets such as aluminum foil and laminated
structures comprising a foil layer such as film-foil laminates, as well as
mono-layer, multi-layer, and coated polymeric films, and metalized
polymeric films.
Examples of other materials useful as either the barrier layers
suitable for use in the lidding component, or as the blister component
include polyvinyl chloride) (PVC) used as a mono-layer film, PVC film
coated with poly(vinylidene chloride) (PVdC), PVC film laminated with
poly(chlorotrifluoroethylene) (PCTFE) film such as Aclar~ PCTFE film
available from Honeywell, Inc. (Morris Township, NJ), cyclo-olefin-
copolymer (COC) used as part of a laminated or co-extruded structure,
cold-formable foil such as PVC/aluminum/nylon laminated structures,
mono-layer aluminum foil, polypropylene (PP) used as a mono-layer film,
polyethylene terephthalate) (PET) used as a mono-layer film, and
polyethylene terephthalate) copolymers that have been modified with 1,4-
cyclohexanedimethanol, available from Eastman Chemicals (Kingsport,
TN) as PETG copolymers, used as a mono-layer film.
In one embodiment the barrier layer comprises a polymeric film
comprising a polymeric coating. For example, the barrier layer can
comprise a PVdC-coated polyester film such as PVdC-coated Mylar~
polyester films (e.g. M30 and M34 films, available from DuPont Teijin
Films). In another embodiment, the barrier layer comprises a polymeric
film that has been coated with a ceramic material. Ceramic materials
suitable for coating polymeric films include oxides, nitrides, or carbides of
silicon, aluminum, magnesium, chromium, lanthanum, titanium, boron,
zirconium, or mixtures thereof. Methods for depositing ceramic coatings
onto a substrate are known in the art, such as by deposition from the
vapor or gaseous phase under vacuum onto a film layer in thicknesses of
between about 5 to 500 nm. Suitable ceramic-coated films include films
made of a thermoplastic material, such as polyolefin films having a
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thickness of 23 to 100 pm or polyester films having a thickness of 12 to 80
pm, that have been coated with at least one 5 to 500 nm thick layer of
SiOX, where x is a number ranging from 1.1 to 2, or with AIyOZ, where the
ratio y/z is a number ranging from 0.2 to 1.5. Alternately, the barrier layer
can comprise a metalized film prepared using processes known in the art
such as vacuum deposition or sputter coating. In one embodiment, the
barrier layer is a metalized polyester film, for example a polyethylene
terephthalate) film, that has a layer of aluminum metal coated thereon;
preferably the metal layer is between about 10 Angstroms to 1000
Angstroms thick and the film is preferably at least 12 microns thick.
Metalized polyester films are known in the art and include aluminum-
coated polyester films such as Mylar~ MC2 aluminum-coated polyester
film (available from DuPont Teijin Films). When the barrier layer of the
lidding component comprises a ceramic-coated or a metalized polymeric
film, the film can be ceramic-coated or metalized on one or both sides.
The polymeric film is preferably ceramic-coated or metalized on one side
thereof and the lidding is preferably constructed such that the metalized or
ceramic-coated side of the film contacts adhesive tie layer 6 to avoid
flaking off of the metalized or ceramic layer onto the packaged material
when the package is opened. Metalized and ceramic-coated films
generally have better barrier properties than unmetalized and uncoated
films and therefore are preferred when higher barrier is required than can
be achieved with an un-metalized or uncoated film.
Figure 2b is a cross-sectional view of a second embodiment of a
lidding component suitable for use in peel-open and tear-open blister
packages of the present invention. The lidding component includes
nonwoven layer 5' and heat-seal layer 8'. In this embodiment, the heat-
seal layer is selected such that it is a barrier layer as well as being heat-
sealable, thus eliminating the need for separate barrier and heat-seal
layers. The nonwoven layer comprises at least one melt-spun continuous
filament nonwoven sheet or at least one flash spun plexifilamentary sheet.
When the heat-sealable barrier layer is applied as a coating on the
nonwoven layer, it completely coats the nonwoven layer to provide the
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desired barrier properties in the blister package. For example, PVdC at a
basis weight ranging from 5 g/m2 to 120 g/m2 coated on a nonwoven layer
provides sufficient barrier properties as well as functioning as a heat-seal
layer. Depending on the selection of the heat-sealable barrier layer and
the blister component, the heat seal can be peelable or non-peelable.
When it is desired to form a peel-open package, the heat-sealable barrier
layer and the blister component are selected such that the heat seal is
peelable. When it is desired to form a tear-open package, the heat seal is
preferably non-peelable. In one embodiment of the present invention
according to Figure 2b, a tear-open package is formed using a PVdC
blister component and a PVdC heat sealable barrier layer (heat seal is
non-peelable). In another embodiment of the present invention according
to Figure 2b, a peel-open package is formed using a PVC blister
component and a PVdC heat-sealable barrier layer, where the PVdC
formulation is selected to form a peelable seal with the PVC blister. The
lidding shown in Figure 2b optionally includes a non-peelable tie layer (not
shown) between the nonwoven layer and heat-seal/barrier layer. For
example the tie layer can be a polyester-based polyurethane composition
such as Adcote~ polyurethane adhesives available from Rohm & Haas
(Philadelphia, PA).
Melt-spun continuous filament nonwoven sheets suitable for use in
the nonwoven layer in the lidding component include spunbond nonwoven
webs and composite nonwoven fabrics that comprise at least one
spunbond nonwoven web. Spunbond webs suitable for use in the lidding
component of the blister package of the present invention can be prepared
using spunbonding methods known in the art. Alternately, the melt-spun
continuous filament nonwoven sheet can be formed from previously
collected continuous filaments that are laid down on a collecting surface,
for example as in the process described in Davies et al. U.S. Patent
3,595,731. Polymers suitable for forming the melt-spun continuous
filament nonwoven sheet include polyesters such as polyethylene
terephthalate) and poly(1,3-propylene terephthalate), polyamides such as
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nylon 6,6 and nylon 6, polyolefins such as polyethylene and
polypropylene, and copolymers thereof.
The melt-spun continuous filaments of the continuous filament
nonwoven sheet can be spun from a single polymer or from a
homogeneous or heterogeneous blend of two or more polymers.
Alternately, the melt-spun continuous filament nonwoven sheet can
comprise a multiple component spunbond nonwoven web. Multiple
component spunbond webs preferably comprise a polymeric component
that has a melting point that is lower than the melting points) of the other
polymeric components) to facilitate thermal bonding of the web.
Examples of suitable multiple component fiber cross-sections include
bicomponent fibers such as those having side-by-side or sheath-core
cross-sections. In one embodiment of the present invention, the melt-
spun continuous filament nonwoven sheet comprises multiple component
sheath-core spunbond fibers having a substantially concentric cross-
section wherein the melting point of the sheath component is at least
10°C, preferably at least 20°C, less than the melting point of
the core
component. Examples of suitable sheath/core polymer combinations are
polyethylene/polyester such as fibers comprising a linear low density
polyethylene sheath with a polyethylene terephthalate) core or a sheath
comprising a blend of LLDPE and HDPE with a PET core. In one
embodiment, the melt-spun continuous filaments comprise a polyester
copolymer sheath and a polyester core. For example, the sheath can
comprise a polyethylene terephthalate) copolymer and the core can
comprise polyethylene terephthalate). Polyethylene terephthalate)
copolymers suitable for use as the sheath component include amorphous
and semi-crystalline polyethylene terephthalate) copolymers. For
example, polyethylene terephthalate) copolymers in which between about
5 and 30 mole percent based on the diacid component is formed from di-
methyl isophthalic acid, as well as polyethylene terephthalate)
copolymers in which between about 5 and 60 mole percent based on the
glycol component is formed from 1,4-cyclohexanedimethanol are suitable
for use as the lowest-melting component in the multiple component fibers.
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Polyethylene terephthalate) copolymers that have been modified with 1,4-
cyclohexanedimethanol are available from Eastman Chemicals (Kingsport,
TN) as PETG copolymers. Polyethylene terephthalate) copolymers that
have been modified with di-methyl isophthalic acid are available from E.I.
du Pont de Nemours and Company (Wilmington, DE) as Crystar~
polyester copolymers.
Composite nonwoven fabrics comprising a spunbond nonwoven
web suitable for use in the lidding component include spunbond-meltblown
(SM) composite nonwoven fabrics, SMS composite nonwoven fabrics, and
composite nonwoven fabrics that include other combinations of spunbond
and/or meltblown nonwoven webs such as SMMS composite webs, etc.
The meltblown webs) used to prepare the composite nonwoven fabrics
can be single component or multiple component meltblown webs) and
can be prepared using methods known in the art.
The nonwoven layer used in the lidding component can comprise a
flash spun nonwoven sheet. Polymers suitable for forming flash spun
plexifilamentary sheets useful in the lidding component of the blister
package of the present invention include polyethylene, polypropylene, and
polyethylene terephthalate). One such flash spun plexifilamentary sheet
is Tyvek~ flash spun high density polyethylene, available from E.I. du
Pont de Nemours & Company (Wilmington, DE).
A particularly suitable lidding component can be obtained by
smooth-surface thermal bonding of a nonwoven web can be achieved by
heating the web between two smooth bonding surfaces to a temperature
sufficient to melt or soften the surfaces of the fibers on one or both sides
of the nonwoven web such that fiber-to-fiber thermal fusion bonds are
formed at the fiber cross-over points on one or both surfaces of the
nonwoven web, as disclosed in U.S. Serial No. 60/529,997 (DuPont
Docket no. TK-3820), filed on even date herewith and incorporated herein
by reference in its entirety.
Thermal calendering processes using a variety of roll configurations
are known in the art. The nonwoven layer can be calender bonded such
that one side of the nonwoven layer is thermally bonded, with the
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thermally bonded side forming one of the outer surfaces of the final blister
package. Alternately the nonwoven layer can be calendered such that
both sides of the nonwoven layer are thermally bonded. Examples of
other calendering processes suitable for bonding the nonwoven layer
include those disclosed in David, U.S. Patent No. 3,532,589, Janis, U.S.
Patent 5,972,147, and Lim et al., U.S. Patent No. 5,308,691, which are
each incorporated herein by reference.
In one embodiment, the nonwoven layer comprises a full-surface
bonded melt-spun multiple component continuous filament nonwoven
fabric or full-surface bonded flash spun plexifilamentary sheet that has
been thermally bonded on both sides in a smooth-calendering process.
Full-surface bonded melt-spun multiple component continuous filament
nonwoven fabrics have an improved combination of tensile and tear
strength for a given fabric thickness compared to comparable smooth-
calendered single component melt-spun nonwoven fabrics. Suitable full-
surface bonded melt-spun multiple component continuous filament
nonwoven fabrics include full-surface bonded bicomponent spunbond
webs such as a spunbond web comprising sheath/core fibers, wherein the
melting point of the sheath is at least 10°C less than the melting
point of
the core, that has been smooth-calendered and bonded on both sides.
Suitable sheath components include polyester copolymers, poly(1,4-
butylene terephthalate) (4GT), and poly(1,3-propylene terephthalate)
(3GT), and polyamides such as polycaprolactam (nylon 6). Suitable core
components include polyethylene terephthalate) and poly(hexamethylene
adipamide) (nylon 6,6). For example, the full-surface bonded
bicomponent spunbond web can comprise bicomponent fibers having a
polyester copolymer sheath and a polyethylene terephthalate) core.
The nonwoven layer preferably has a Spencer Puncture (measured
according to ASTM D3420, modified for 9/16 in. diameter probe) of at least
0.98 Joules, preferably at least 1.18 Joules, and more preferably at least
1.97 Joules; a tensile strength (measured according to ASTM D5035) in
both the machine direction and cross-direction of at least 20 Ib/in (35
N/cm), preferably at least 22 Ib/in (38.5 N/cm), and more preferably at
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least 25 Ib/in (43.8 N/cm); an elongation in both the machine direction and
cross-direction of at least 15%, preferably at least 18%, and more
preferably at least 20%; and an Elmendorf Tear (measured according to
ASTM D1424) in both the machine direction and the cross-direction of at
least .075 Ib (0.33 N), preferably at least 0.10 Ib (0.45 N), and more
preferably at least 0.20 Ib (0.89 N).
In one embodiment of the present invention the heat-seal layer
comprises a peelable sealant, thus providing a peel-open blister package.
Whether or not a particular heat-seal layer forms, a peelable seal may
depend on the nature of the layers to which it is sealed (e.g. the blister
component and barrier layer for the embodiment shown in Figure 2a or the
blister component and the nonwoven layer for embodiments shown in
Figure 2b). In a peel-open configuration, the package is opened by
peeling the multi-layer lidding component away from the blister
component, with the peeling occurring between the heat-seal layer and the
blister component. Peelable sealants suitable for use in the heat-seal
layer of the packages of the present invention include poly(vinylidene
chloride), or solvent-based sealants such as modified vinyl/acrylic sealants
available from Watson Rhenania (Pittsburgh, PA) such as JVHS-157-LT1
sealant, as well as extrudable sealants, for example blends of polyolefin
resins comprising primarily ethylene vinyl acetate or ethylene methyl
acrylate copolymers, such as Appeel~ resins, available from E.I. du Pont
de Nemours and Company (Wilmington, DE). The heat-seal layer can be
applied to the barrier layer of the lidding component using methods known
in the art including but not limited to roll coating, gravure coating, spray
coating, and extrusion coating. In a peel-open package, a non-peelable
adhesive tie layer is preferably used to join the nonwoven layer to the
barrier layer so that the nonwoven and barrier layers are strongly bonded
together, allowing the multi-layer lidding to be cleanly pulled away from the
blister component without delamination occurring between the nonwoven
and barrier layers. Non-peelable adhesive tie layers suitable for use in
lidding used in a peel-open package of the present invention include
solvent-based two-component dry-bond adhesive compositions such as
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polyester-based polyurethane adhesives, for example Adcote~
polyurethane-based adhesives available from Rohm & Haas (Philadelphia,
PA). In a dry-bond adhesive process, the adhesive is applied to either the
barrier layer or the nonwoven layer or both, and the two layers are bonded
together while the adhesive is "dry" or substantially free of solvent. If the
starting adhesive composition comprises a solvent, it is dried prior to
laminating the nonwoven layer to the barrier layer. Other adhesive
compositions which provide a non-peelable tie layer include extrudable
resins such as modified ethylene vinyl acetate, ethylene vinyl acetate, and
ethylene methyl acrylate based resins, for example Bynel~ and Nucrel~
modified ethylene vinyl acetate and modified ethylene methyl acrylate
resins, available from E.I. du Pont de Nemours and Company (Wilmington,
DE).
In another embodiment of a blister package of the present
invention, the blister package is a peel off push through package wherein
the outer nonwoven layer is adhered to a frangible barrier layer by a
peelable tie layer, and is peeled from the package to reveal the frangible
barrier layer through which the packaged material is pushed. A layer is
considered to be frangible if a packaged material can be removed by
rupturing the layer by applying pressure to the exterior of the blister
cavity.
Peeling may occur between the nonwoven layer and the adhesive tie layer
or between the adhesive tie layer and the barrier layer. The adhesive tie
layer is preferably selected such that it remains adhered to the nonwoven
layer and peels cleanly away from the barrier layer when the package is
opened without tearing or otherwise rupturing the barrier layer. That is,
the adhesive tie layer preferably has a high adherence to the nonwoven
layer and a relatively lower adherence to the frangible barrier layer. If
peeling occurs between the nonwoven layer and the adhesive tie layer,
the adhesive tie layer should also be a frangible layer. For example, in a
peel off push through package comprising a lidding component according
to Figure 2a, the adhesive tie layer is a peelable layer such that the
nonwoven layer can be peeled away from the barrier layer of the lidding
component, and wherein the combined barrier layer/heat-seal layer (for
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peeling between the adhesive tie layer and the barrier layer) or combined
adhesive tie layer/barrier layer/heat-seal layer (for peeling between the
nonwoven layer and tie layer) is frangible. Examples of frangible barrier
layers include metal foils (e.g. aluminum foil), frangible polymeric films
(e.g. biaxially-oriented poly(chlorotrifluoroethylene) films), frangible
metalized polymeric films, and frangible ceramic-coated polymeric films.
The frangible layers) are selected such that once the nonwoven layer (or
combined nonwoven/adhesive tie layer) is peeled away from the package,
the pharmaceutical or other packaged material can be pushed through the
frangible layer(s). The adhesive tie layer can be extruded or coated onto
one or both of the nonwoven layer (e.g. Tyvek~ flash spun high density
polyethylene or melt-spun continuous filament polyester-based spunbond
nonwoven) or frangible barrier layer and the nonwoven and barrier layer
bonded together by the intermediate tie layer. Examples of suitable
peelable tie layers include modified vinyl/acrylic compositions, such as
JVHS-157-LT1 modified vinyl/acrylic adhesive available from Watson
Rhenania (Pittsburgh, PA), or blends of polyolefin resins comprising
primarily ethylene vinyl acetate or ethylene methyl acrylate copolymers,
such as Appeel~ polyolefin resins, available from E.I. du Pont de Nemours
and Company (Wilmington, DE), and solvent-based modified acrylic
pressure sensitive adhesive, such as Adcote L74X105 from Rohm & Haas
(Philadelphia, PA). The heat-seal layer in a peel off-push through
package is selected such that it forms a non-peelable seal between the
blister component and the barrier layer in the lidding. Examples of
suitable permanent (non-peelable) sealants include modified vinyl/acrylic
compositions such as JVHS-157-2, or a modified polyester sealant such
as GNS01-014, both available from Watson Rhenania (Pittsburgh, PA).
When a tear-open package is desired, the adhesive tie layer and
heat-seal layer of Figures 2a and 2b are selected such that non-peelable
bonds/seals are formed between the barrier layer and the blister
component and between the nonwoven layer and the barrier layer. This
allows the package to be torn cleanly at a pre-formed notch in the package
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without peeling occurring between the various layers in the multi-layer
lidding component.
The blister package of the present invention can be manufactured
using methods known in the art. Figure 3 illustrates a process that is
suitable for forming a blister package of the present invention. The blister
cavities 10 are generally thermoformed into a forming web in-line just prior
to filling the cavities with the material 12 to be packaged. The lidding
component 14 is unwound from roll 15 and brought into contact with the
formed and filled blister component such that the heat-seal layer of the
lidding component contacts the blister component. The lidding and blister
components are heat sealed, typically using a heated platen 16 with or
without a pattern. Generally, some areas are not sealed to provide a
starting point for peeling off the lidding or selected layers of the lidding
prior to removing the product. If the lidding component is not pre-printed,
printing is generally done just before heat sealing (not shown). After heat
sealing, the individual blisters are generally perforated using methods
known in the art (not shown) so that they can be removed at point of use.
If the blister package is a tear-open package, notches are formed in the
individual blisters during the perforation step. The notches are preferably
contained internal to the package such that they are not exposed until the
individual blister is removed at point of use. The notch can also be formed
on one of the external edges of the blister package, however forming the
notches internal to the package decreases the likelihood that a child will
be able to tear open the package. Individual blister packages 18, which
can comprise multiple blisters (as shown in Figure 4) or a single blister,
are then cut from the continuous sheet of sealed blisters. It is important
that all materials maintain dimensional stability through the blister package
process due to the platen registry, the print registry and the perforation
registry.
The improved tear resistance provided by the continuous filament
or plexifilamentary nonwoven layer in the lidding component of the
packages of the present invention provides peel off-push through and
peel-open packages wherein the lidding or nonwoven layer peels cleanly
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away from the package without tearing, whereas packages known in the
art that utilize paper-film-foil laminates often do not provide a clean peel,
thus making it difficult for even an adult to open the package. The present
invention also reduces the number of processing steps required to
manufacture the lidding compared to the prior art by replacing three layers
(paper-adhesive-film) with a single nonwoven layer. Although the tear
resistance of the lidding component of the packages of the present
invention is improved compared to prior art lidding materials, they can also
be used in tear-open packages wherein the tear is initiated by a pre-
formed notch.
TEST METHODS
In the description above the following test methods are employed to
determine various reported characteristics and properties. ASTM refers to
the American Society for Testing and Materials.
Basis WeicLht is a measure of the mass per unit area of a fabric or
sheet and is determined by ASTM D-3776, which is hereby incorporated
by reference, and is reported in g/m2.
Spencer Puncture is a measure of the ability of a substrate to resist
puncture by impact. Spencer puncture is measured for nonwoven fabrics
and nonwoven/foil laminates using a bullet-shaped probe and is
determined by ASTM D3420 (modified for 9/16 inch diameter probe) with a
pendulum capacity of 5.4 Joules, which is hereby incorporated by
reference. It is reported in Joules. Spencer puncture was measured for
nonwoven/film laminates according to ASTM D3420 using a pointed probe
(modified for 9/16 inch diameter probe) with a pendulum capacity of 5.4
Joules, and is reported in units of Joules.
Tensile Strength is a measure of the force required to break the
material apart by pulling. For nonwoven fabrics and nonwoven/foil
laminates, tensile strength is determined according to ASTM D5035, which
is hereby incorporated by reference, and is reported in units of Ib/in or
N/cm. For nonwoven/film laminates, tensile strength was measured
according to ASTM D882, which is hereby incorporated by reference, and
is reported in units of psi.
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Elongation is a measure of the extent a substrate with stretch
before it breaks and is determined by ASTM D5035, which is hereby
incorporated by reference. It is reported in %.
Elmendorf Tear is a measure of the force required to propagate an
initiated tear from a cut or a nick. Elmendorf Tear is measured for
nonwoven fabrics and nonwoven/foil laminates according to ASTM D1424,
which is hereby incorporated by reference, and is reported in units of Ib or
N. Elmendorf Tear was measured for nonwoven/film laminates according
to ASTM 1922, and is reported in units of g/mm.
Graves Tear is a measure of the force required to initiate a tear and
is measured according to ASTM D1004, which is hereby incorporated by
reference, and is reported in units of Newtons.
Moisture Vapor Transmission rate (MVTR) was measured for
Example 2 using ASTM F1249, which is hereby incorporated by reference,
under the conditions of 38°C and 100% Relative Humidity, and is
reported
in units of g/m2/24 hr.
Oxyaen Transmission Rate was measured for Example 2 using
ASTM D3985, which is hereby incorporated by reference, at 23°C,
50%RH, and 100% oxygen, and is reported in units of cc/m2/24 hr.
EXAMPLE 1
This example demonstrates preparation of a blister package
comprising a lidding component according to Figure 2a, wherein the
nonwoven layer was a smooth-calendered full-surface bonded spunbond
nonwoven web and the barrier layer in the lidding was a metal foil.
A spunbond bicomponent nonwoven web was prepared in which
the fibers were continuous core/sheath fibers having a polyethylene
terephthalate) (PET) core component and a co-polyester sheath
component composed of 17 mole percent modified di-methyl isophthalate
PET copolymer.
The thermally calendered bicomponent spunbond web was then
laminated to a 0.93 mil (0.024 mm) thick soft-tempered aluminum foil
obtained from Alcoa (Pittsburgh, PA) using Adcote 503 A/Cat F solvent-
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based polyethylene terephthalate)-based polyurethane permanent
adhesive tie layer obtained from Rohm & Haas (Philadelphia, PA). An
Inta-Roto dry-bond coater/laminator (Model 'The Delaware') was used to
perform the lamination. The Adcote 503A/Cat F was mixed at a ratio of 62
percent by weight 503A, 3.5 percent by weight CatF, and 34.5 percent by
weight methyl ethyl ketone and the adhesive was applied using a reverse
gravure coating process. The bicomponent spunbond web was unwound
from a primary unwind and the adhesive was applied to the bicomponent
spunbond web using a reverse rotating gravure roll. Alternately, the
adhesive can be applied to the barrier layer. The gravure roll was
engraved with a 35 line per inch (13.8 line per cm) tri-helical pattern,
where a continuous triangular channel in the helical pattern circumvents
the gravure roll. The machine speed was 65 ft/min (19.8 m/min). Typical
line speeds used in a reverse gravure coating process are usually
between about 15 m/min to 305 m/min. The adhesive was applied at a dry
coating weight of about 8 g/m2. An adhesive tie layer dry coating weight
between about 3 g/m2 and 10 g/m2 is generally used, with a dry coating
weight between about 4 g/m2 and 8 g/m2 generally being preferred. A hot
air impingement dryer was used to dry the coated spunbond web to
remove the solvent present in the tie layer adhesive. Air heated to a
temperature of 74°C was forced through a slotted nozzle assembly onto
the adhesive-coated surface of the spunbond web evaporate the solvent.
After drying, the adhesive-coated spunbond nonwoven web layer
was laminated to the foil layer which was unwound from a roll and
contacted with the adhesive-coated side of the spunbond web in a nip
formed by two cylindrical calender rolls. One of the rolls was a rubber-
covered roll and the second roll was a steel roll heated to 82°C by
internal
water heating. The nonwoven web contacted the heated steel roll in the
nip and the aluminum foil contacted the rubber-surfaced roll. The
laminated substrate was then rewound on the rewinder.
A solvent-based peelable heat seal layer was then applied to the
aluminum foil side of the above-described spunbond nonwoven/aluminum
foil laminate using the reverse gravure coating process described above.
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The peelable heat seal composition used was a vinyl/acrylic solvent-based
sealant (JVHS-157-LT1, supplied by Watson-Rhenania, Pittsburgh, PA).
The heat-seal coating was applied at 5.2 g/m2 to the nonwoven/foil
laminate. Generally, heat seal coatings applied at a dry coating weight of
between about 4.8 to 5.6 g/m2 are preferred. After applying the sealant,
the coated material was dried using the same hot air impingement dryer
described above and an air temperature of 275°F (135°C) to
remove the
ethyl acetate solvent. After drying the laminate was rewound on the
rewinder. The multi-layer laminate can be used directly as a lidding
component to prepare a blister package or further processed by printing
on the nonwoven surface of the laminate prior to forming a blister
package. Properties of the lidding component are compared to a
conventional paper-film-foil laminate that is used in the art as lidding in
blister packages (CR-417, available from Hueck Foils (Wall, NJ) in Table I
below. The results demonstrate the significant improvement in Spencer
Puncture of the lidding of the present invention compared to the prior art
lidding material. The puncture resistance of the laminate prepared in
Example 1 was more than three times greater than the conventional
lidding material. Blister packages prepared according to the present
invention are expected to be much more difficult for a child to chew
through than conventional blister packages.
Blister packages were prepared according to the process shown in
Figure 3 using a Klockner Medipak CP-2 form-fill-seal blister packaging
machine. The forming web used to form the blister component was 10 mil
(0.254 mm) Pentapharm M570/01 polyvinyl chloride) film supplied by
Klockner Pentaplast of America (Gordonsville, VA). The platen used to
heat seal the lidding to the blister component was heated to a temperature
of 180°C to obtain a peel-open package. Numerous blister packages of
the present invention were peeled open and each sample peeled cleanly,
which represents a significant improvement compared to blister packages
known in the art that utilize a paper/film/foil laminate in the lidding which
are prone to tearing during peeling.
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Table 1. Properties of Lidding Component for Example 1
Example 1 Conventional Lidding
(nonwoven/foil) (paper/film/foil)
Basis Weight (g/m')102.7 72.5
MD Tensile Strength123.4 73.7
(N/cm)
XD Tensile Strength56.6 55.5
(N/cm)
MD Elongation (% 0.117 0.097
at 3
Ibs)
XD Elongation (% 0.25 0.2
at 3
Ibs)
MD Elmendorf Tear 1.16 1.11
(N)
XD Elmendorf Tear 0.98 0.89
(N)
Spencer Puncture 1.34 0.39
(J)
Thickness (mm) 0.144 0.093
EXAMPLE 2
This example demonstrates preparation of a lidding component
comprising a flash spun plexifilamentary sheet and a metalized polyester
film suitable for use in peel-open child-resistant blister packages.
A multi-layer laminated sheet was prepared using an extrusion
lamination process with an Egan Coater/Laminator. First, a permanent
adhesive tie layer was used to bond a layer of Tyvek~ flash spun high
density polyethylene sheet (Tyvek~ 1073D, basis weight 74.6 g/m2,
available from E.I. du Pont de Nemours and Company (Wilmington, DE) )
to a metalized polyethylene terephthalate) film (Mylar~ 7100 metalized
(aluminum) film having a thickness of 12 microns, available from DuPont-
Teijin Films). The permanent adhesive tie layer was Nucrel~ 1214
ethylene methyl acrylate resin. The Nucrel~ 1214 resin was extruded
between the nonwoven and film substrates by extruding onto the
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metalized side of the Mylar~ polyester film at a thickness of 0.5 mil and
subsequently contacting the extruded adhesive layer with the Tyvek~
flash spun sheet. The Nucrel~ copolymer was extruded using a single
screw extruder (with an exit temperature of 450°F (232°C)
through a
feedblock with a 40 inch (101.6 cm) wide (internally deckled to 28 inches
71.1 cm)) Cloeren edge bead reduction die having 30 mil gap operated at
321 °C and a backpressure of 500 psig (3447 kPa) to form a 0.5 mil
thick
adhesive layer. The air gap between the die exit and the nip (where the
extrudate contacts the metalized film) was 6 inches (15.2 cm) and the
lead-in was -0.5 inch (-1.27 cm). The line speed was 399 ft/min (122
m/min). The side of the metalized Mylar~ 7100 film that contacted the
Nucrel~ adhesive was corona treated in-line at 3 kW prior to extruding the
adhesive layer. The Tyvek~ flash spun sheet was laminated to the
adhesive-coated film and the assembly (Tyvek~ nonwoven/permanent
Nucrel~ adhesive/metalized Mylar~ film) was then passed over a chill roll
having a matte finish and operated at 10°C.
The above assembly was then extrusion coated with a layer of
peelable heat-sealable sealant on the film side of the metalized Mylar~
film using the Egan Coater/Laminator. The peelable sealant used was
Appeel~ 20D745 ethylene methyl acrylate copolymer sealant. The film
side of the metalized film was corona treated in-line at 3kW prior to coating
with the sealant. The line speed was 299 ft/minute (91 m/min), the
extruder exit temperature was 490°F (254°C), die width 40 in
(101.6 cm)
(internally deckled to 28 inches ( 71.1 cm)), air gap 6 inches (15.2 cm),
lead in of -0.5 inch (-1.27 cm), a Teflon~ fluoropolymer-coated pressure
roll and a matte finish chill roll, with a nip pressure of 60 psi (414 kPa).
The laminate structure can be processed on a blister packaging machine
as the lidding component to form a child-resistant blister package.
The properties of the lidding material are given in Table 2 below.
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Table 2 - Properties of Lidding Component Comprising Flash Spun Sheet
and Metalized Film
Property Example 2
Tensile Strength MD (psi) 8614
Tensile Strength XD (psi) 9120
Graves Tear Strength MD (N) 33.82
Graves Tear XD (N) 34.35
Elmendorf Tear MD (g/mm) 1990
Elmendorf Tear XD (g/mm) 2225
Spencer Puncture (J) 0.62
Oxygen Transmission Rate (cc/m'/2440.967
hr)
MVTR g/ m'/24 hr 0.324
27
