U.S. patent application number 10/175662 was filed with the patent office on 2003-12-25 for films having a desiccant material incorporated therein and methods of use and manufacture.
Invention is credited to Kaas, Roger, Merical, Rick.
Application Number | 20030235664 10/175662 |
Document ID | / |
Family ID | 29733938 |
Filed Date | 2003-12-25 |
United States Patent
Application |
20030235664 |
Kind Code |
A1 |
Merical, Rick ; et
al. |
December 25, 2003 |
Films having a desiccant material incorporated therein and methods
of use and manufacture
Abstract
Film structures, packages and methods of making the same are
provided wherein the film structures have a desiccant material
incorporated into a sealant layer of the films structures. More
specifically, the film structure further includes a barrier
material incorporated as an internal film layer within the film
structure. The film structure is utilized for a package to hold a
product that may be sensitive to the presence of moisture. The
product may preferably be diagnostic test strips useful in the
medical or pharmaceutical field.
Inventors: |
Merical, Rick; (Appleton,
WI) ; Kaas, Roger; (Sherwood, WI) |
Correspondence
Address: |
Stephen T. Scherrer
McDermott, Will & Emery
227 West Monroe Street
Chicago
IL
60606-5096
US
|
Family ID: |
29733938 |
Appl. No.: |
10/175662 |
Filed: |
June 20, 2002 |
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
A61B 2050/314 20160201;
A61B 50/30 20160201; B32B 15/04 20130101; B65D 81/267 20130101;
Y10T 428/1352 20150115; B32B 7/06 20130101; B32B 27/18 20130101;
A61B 2050/3004 20160201 |
Class at
Publication: |
428/35.7 |
International
Class: |
B65D 001/00 |
Claims
We claim:
1. A flexible film structure comprising: a barrier layer comprising
a barrier material that blocks the transmission of moisture through
the film structure; and a sealant layer comprising a desiccant
material.
2. The flexible film structure of claim 1 wherein said desiccant
material is a chemical desiccant material.
3. The flexible film structure of claim 1 wherein said desiccant
material is selected from the group consisting of calcium oxide,
magnesium sulfate, sodium phosphate di-basic, ammonium chloride,
potassium carbonate, potassium aluminum disulfate, magnesium
chloride, diammonium sulfate, sodium nitrate, calcium chloride,
calcium sulfate, sodium chloride, potassium bromide, molecular
sieves, clays and blends of these materials.
4. The flexible film structure of claim 1 wherein said barrier
material is selected from the group consisting of metal foil,
nylon, high density polyethylene or oriented polypropylene,
metallized oriented polypropylene, and oriented polyester.
5. The flexible film structure of claim 1 further comprising a
first tie layer of a polymeric material disposed between said
barrier layer and said sealant layer.
6. The flexible film structure of claim 5 wherein said first tie
layer of polymeric material comprises ethylene acrylic acid
copolymer.
7. The flexible film structure of claim 5 further comprising: an
outer layer of a polymeric material.
8. The flexible film structure of claim 7 wherein said outer layer
comprises a polymeric material selected from the group consisting
of PET, oriented polypropylene, polyethylene, nylon, foil, or
metallized substrates.
9. The flexible film structure of claim 7 further comprising a
second tie layer disposed between said outer layer and said barrier
layer.
10. The flexible film structure of claim 9 wherein said second tie
layer comprises ethylene acrylic acid copolymer.
12. A package comprising: a flexible film wherein said flexible
film comprises a barrier layer having a barrier material that
blocks the transmission of moisture through the film structure and
a sealant layer comprising a desiccant material; and a space inside
the package for a moisture-sensitive product.
13. The package of claim 12 wherein said desiccant material is a
chemical desiccant material.
14. The package of claim 12 wherein said desiccant material is
selected from the group consisting of calcium oxide, magnesium
sulfate, sodium phosphate di-basic, ammonium chloride, potassium
carbonate, potassium aluminum disulfate, magnesium chloride,
diammonium sulfate, sodium nitrate, calcium chloride, calcium
sulfate, sodium chloride, potassium bromide, molecular sieves,
clays and blends of these materials.
15. The package of claim 12 further comprising a second flexible
film wherein said second flexible film comprises a barrier layer
having a barrier material that blocks the transmission of moisture
through the second flexible film structure and a sealant layer
comprising a second desiccant material, wherein said first and
second flexible film structures are heat sealed together to form
the package having the space inside the package for said
moisture-sensitive product.
16. The package of claim 15 wherein said second desiccant material
is a chemical desiccant material.
17. The package of claim 12 further comprising: an outer layer of
polyethylene terephthalate; a first tie layer disposed between said
sealant layer and said barrier layer; and a second tie layer
disposed between said barrier layer and said outer layer.
18. A method of making a flexible film structure, comprising the
steps of: extruding a film layer comprising a blend of a polymeric
material and a desiccant material; and laminating said film layer
to a moisture barrier layer.
19. The method of claim 18 wherein said film layer is extruded via
a blown film extrusion process.
20. The method of claim 18 wherein said film layer is extruded via
a cast film extrusion process.
21. The method of claim 18 wherein said film layer is adhesive
laminated to said barrier material.
22. The method of claim 18 wherein said film layer is extrusion
laminated to said barrier material.
23. The method of claim 18 further comprising the steps of:
coextruding a tie layer with said film layer comprising the blend
of polymeric material and the desiccant material; and laminating
said tie layer and said film layer comprising the blend of
polymeric material and the desiccant material to said barrier
layer.
24. The method of claim 18 wherein said barrier layer comprises a
material selected from the group consisting of metal foil, nylon,
high density polyethylene, oriented polypropylene, metallized
oriented polypropylene, and metallized polyester.
25. A package having a space therein for a moisture-sensitive
product made from the film structure made from the method of claim
18 wherein said first layer is a heat sealant layer.
26. The package of claim 25 wherein said product comprises a
medical diagnostic test strip.
27. A method of making a flexible film structure, comprising the
steps of: extrusion coating a film layer comprising a blend of a
polymeric material and a desiccant material to a moisture barrier
film layer.
28. The method of claim 25 wherein said moisture barrier film layer
comprises a material selected from the group consisting of metal
foil, nylon, high density polyethylene, oriented polypropylene,
metallized oriented polypropylene, and metallized polyester.
29. The method of claim 25 wherein said film comprising the blend
of the polymeric material and the desiccant material is coextruded
with at least one other film layer.
30. A package having a space therein for a moisture-sensitive
product made from the film structure made from the method of claim
18 wherein said first layer is a heat sealant layer.
31. A package having a space therein for a moisture-sensitive
product made from the film structure made from the method of claim
27 wherein said first layer is a heat sealant layer.
32. The package of claim 31 wherein said product comprises a
medical diagnostic test strip.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a film having a desiccant
material incorporated therein. More specifically, the present
invention relates to a film structure having a desiccant material
within a sealant layer of the film structure wherein said film
structure is utilized as a package for a product that may be
sensitive to the presence of moisture. In addition, the present
invention relates to methods of manufacturing and methods of using
the film having a desiccant material incorporated therein.
BACKGROUND OF THE INVENTION
[0002] It is generally known to utilize plastic packaging to reduce
exposure of products to atmospheric conditions, such as to moisture
or oxygen, which may damage the products. For example, packaging
for foodstuffs is well known, in that moisture and oxygen may cause
the foodstuffs to become spoiled and inedible or otherwise
undesirable. In addition, many products in the medical field may
also be very sensitive to atmospheric moisture.
[0003] Typically, moisture-sensitive products may be encased in
thermoplastic material that is relatively impermeable to water
molecules. Specifically, many polymeric materials are utilized as
barriers to moisture transmission. For example, a film of high
density polyethylene (HDPE), or polyvinylidene chloride-methyl
acrylate (PVdC-MA) copolymer may be utilized to restrict the
movement of water molecules through the film. Oriented
polypropylene, metallized oriented polypropylene, or metallized
polyester would also be useful as moisture barrier material. In
addition, metal foil is known to prevent the transmission of oxygen
and/or moisture through polymeric packaging having a layer of metal
foil contained therein.
[0004] Although these moisture barrier polymers may be useful in
restricting the movement of moisture into a package, some moisture
molecules can still make their way into the package to
deleteriously affect the product contained therein. In addition,
even when barrier materials are effective at restricting the
transmission of water molecules through a package, certain features
of the package may still allow for the transmission of water
molecules. For example, where a barrier material is incorporated
into a central layer of a film structure and the film structure is
sealed to another film structure having a barrier material as a
central layer, the edges of the package may not be protected by the
barrier layers. This may allow moisture to make its way into a
package along the edges of a heat sealed package.
[0005] One solution to maintaining a particularly low or virtually
nonexistent level of moisture within a package is to incorporate
sachets of desiccant material into the internal space of the
package to remove the moisture from the headspace of the package. A
sachet may effectively maintain a very low level of moisture in
inside spaces of packages, but may have difficulty maintaining the
same consistent moisture levels after the package has been opened
and a product has been removed. For example, a typical package of
moisture-sensitive products may contain a plurality of the
products. A sachet of desiccant material incorporated into the
package may only guarantee that moisture level of the package is
maintained at a constant or minimal moisture level until the
package is opened and the first product is thereby removed. The
remaining products will be instantly exposed to atmospheric
moisture when the seal of the package is broken. Although the
sachet may remove some moisture from the headspace of the package
after the package is opened, the remaining moisture-sensitive
products, having already been exposed to moisture, may already be
damaged. This may be especially true in bulk packaged materials
where sachets are most often used. Desiccant materials are
typically incorporated into liddings of jars or in sachets of
multi-unite packages.
[0006] In addition, sachets of desiccant material may become
saturated with atmospheric moisture relatively quickly thereby
decreasing or eliminating their effectiveness. Moisture-sensitive
products, therefore, stand a greater chance of being damaged by
moisture in this case.
[0007] Moreover, the desiccant material contained in the sachets is
typically in powder or granular form and may leak or otherwise
spill from the sachets thereby contaminating the product or
products contained within the package. For example, if the
desiccant material contacts a food product or medical device, the
food product or medical device may become contaminated with the
desiccant material, which may be damaging to the health of an
individual that consumes the food product or uses the medical
device.
[0008] Additionally, although desiccant material is generally known
to reduce the moisture content within a package, typical desiccant
materials are "physical" desiccant materials, such as molecular
sieves, that bind water molecules within pore spaces of a material.
Typically, physical desiccant materials absorb water at all
humidity levels, but will cease to absorb water when interstices of
the physical desiccant material are filled. Therefore, physical
desiccant materials may be ineffective at high humidity levels.
[0009] An additional type of desiccant material may be hydrate
forming agents such as salts. Typical salts that may be utilized as
desiccant material are magnesium sulfate, sodium phosphate
di-basic, ammonium chloride, potassium carbonate, potassium
aluminum disulfate, magnesium chloride, diammonium sulfate, sodium
nitrate, calcium chloride, and calcium sulfate, although many
others are known as well. Typically, the drying capacity is greatly
influenced by the relative humidity within a package. Generally, no
water is taken up by the hydrate-forming agent until the relative
humidity reaches a value at which the first hydrate forms. In the
case of calcium chloride, for example, the first hydrate occurs at
less than about two percent relative humidity (R.H.). Water is then
taken up by the hydrate forming salt until the first hydrate is
completely formed by the salt. No further water is taken up by the
salt until the relative humidity reaches a second level where the
second hydrate forms. This process continues through as many
hydrates as the agent forms at which point the substance begins to
dissolve and a saturated solution is formed. The saturated solution
will then continue to take up water.
[0010] Although these salts may be effective at removing water
molecules from a quantity of gas that may be contained within the
headspace of a package, since the salt only binds the water
molecules within the salt, the water molecules may easily escape
back into the package. This is known as breathing, and may cause
deliquescence (water droplets and liquidization) inside the
package. Typically, this can happen if the salt becomes saturated
and if the temperature of the package increases, or if the pressure
of the package decreases, which may occur during shipment or
storage of the package.
[0011] In addition, salts may not allow moisture levels within a
package to fall to a level that is necessary to protect the
moisture-sensitive product that may be contained within the
package. Typically, since salts typically have different levels of
hydration, humidity levels may remain a certain level without
decreasing until the level of hydration changes.
[0012] However, these salts may be utilized to maintain certain
humidity levels within the headspace of a package. For example,
certain products may require that a certain level of moisture or
humidity be maintained within the package headspace. Headspace
humidity control for products can be manipulated by incorporation
of the appropriate hydrate forming agents.
[0013] Desiccant materials may also be used that form no hydrates,
such as common salt (NaCl) or potassium bromide (KBr). For example,
common salt will absorb no water at a relative humidity below about
75 percent. When 75 percent relative humidity is reached, a
saturated solution is formed which continue to take up water.
[0014] The present invention may utilize chemical desiccant
technology, which is more preferable because the moisture level
within a package may be maintained at an extremely low level.
Chemical desiccant materials chemically react with water molecules
to form a new product, wherein the water molecules are chemically
incorporated into the new product. For example, calcium oxide binds
water in the following reaction:
[0015] ti CaO+H.sub.2O.fwdarw.Ca(OH).sub.2
[0016] Because the reaction noted above requires very high energy
levels to reverse, it is, for all practical purposes, irreversible.
Chemical desiccant materials typically absorb water at all humidity
levels, and will continue to take up water at high relative
humidity levels. These chemical desiccant materials, therefore, may
reduce levels of moisture within the package headspace to zero or
near zero, which is often desired to maintain maximum dryness of
the product.
[0017] An example of a moisture-sensitive product that would
benefit from the present invention are medical diagnostic testing
equipment, such as diagnostic test strips. Medical diagnostic test
strips are typically used to test for the presence of particular
compounds in a biological fluid, such as blood or urine. For
example, diagnostic test strips may detect the presence of
narcotics or other substances.
[0018] A diagnostic test strip is typically dipped into a sample of
the biological fluid and if the individual has traces of narcotics
in the sample of the biological fluid then the diagnostic test
strip may change colors to indicate the presence of the
narcotics.
[0019] In addition, diagnostic test strips may be useful to detect
particular levels of naturally occurring compounds that may be
present within biological fluids. For example, high levels of
protein in blood and/or urine may indicate a disease state.
Diagnostic strips are useful to test not only for protein levels,
but a plurality of other indicators for levels of various disease
indicators. Diagnostic strips may also be utilized to detect
certain biological conditions, such as pregnancy.
[0020] Diagnostic strips, like the ones described above, are
typically extremely sensitive to moisture, and must be removed from
atmospheric conditions in order to work properly. In the medical
field, it is extremely important to get accurate readings using
diagnostic testing strips. An inaccurate reading may make it
difficult to diagnose a particular disease state, or may make a
doctor misdiagnose a particular disease-state entirely. In
addition, an inaccurate reading may jeopardize an individual that
may test positive for a particular narcotic, especially if the
positive result is a false reading. Therefore, it is of utmost
importance that diagnostic strips be as accurate as possible.
[0021] Therefore, diagnostic test strips are typically sealed away
from atmospheric conditions. For example, diagnostic test strips
are typically wrapped or otherwise contained within a material that
is impervious to moisture and oxygen that may cause damage to the
diagnostic test strips. A thick plastic or glass plastic package,
jar, vial or other container is typically used to house diagnostic
test strips prior to use. In addition, sachets of desiccant
material are typically incorporated into packaging for diagnostic
test strips. However, these packages suffer from the problems as
detailed above.
[0022] Other examples of typical packages or products that would
benefit from desiccant material are electrostatic shielding
packaging for electronic parts, such as printer cartridges, circuit
boards, televisions, DVDs, printers, modems, personal computers,
telecommunications equipment, etc., and in pharmaceutical and/or
nutriceutical packaging, such as inside pill bottle caps. Further,
other packaging that would benefit from desiccant material is
packaging for foods, such as cheese, peanuts, coffee, tea,
crackers, spices, flour, bread, etc. In addition, other products
that would benefit from desiccant material incorporated into the
packaging are shoes, boots, film products and cameras, and products
that may be shipped by sea, such as high-value wood like mahogany
that would be damaged if exposed to ambient humidity typically
found in cargo ships.
[0023] A need, therefore, exists for polymeric plastic packaging
that may be used in packaging to preserve products that may be
sensitive to atmospheric moisture. The packaging may comprise films
having a desiccant material incorporated directly into a sealant
layer of the film. In addition, films are needed that effectively
control the level of moisture within packaging without using
sachets or desiccant beads that may become ineffective over time,
or that may contaminate products contained within the packaging.
Moreover, films, methods of use and manufacture are needed to
overcome the additional disadvantages as noted above with respect
to sachets, beads or physical desiccants.
SUMMARY OF THE INVENTION
[0024] The present invention relates to multilayer plastic
polymeric flexible packaging films having a desiccant material
incorporated within a layer of the film. More specifically, the
present invention relates to a polymeric flexible film having a
desiccant material incorporated within a layer of the film that is
utilized as a package for a product that may be sensitive to the
presence of moisture. In addition, the present invention relates to
methods of manufacturing and using the polymeric film having a
desiccant material incorporated therein.
[0025] It is, therefore, an advantage of the present invention, to
provide a polymeric plastic packaging film having a desiccant
material incorporated therein for packages that may contain
moisture sensitive products. These products may be, for example,
foodstuffs and/or other products that may suffer from the
deleterious effects of moisture. Specifically, diagnostic strips
that are useful in health care may be packaged using a film having
a desiccant material contained within a layer of the film to
maintain the utility of the diagnostic strip. The desiccant
material is utilized to control the moisture level within a package
made by the film of the present invention. The desiccant materials
may be utilized as an alternative to high cost and marginally
effective desiccant sachets or beads that may ruin the product
within the package if the desiccant sachet breaks open or is
otherwise allowed to contaminate the product within the
package.
[0026] In addition, it is an advantage of the present invention to
provide a film having a desiccant material incorporated therein
that would eliminate the need to incorporate into high cost and
marginally effective sachets or beads of desiccant material that
may contaminate products contained within packages if the sachets
accidentally release the desiccant material into the package.
Moreover, sachets or beads may be unsightly and may take up space
within a package that could otherwise be used for product. If the
desiccant material within the sachets or beads are ingested, they
may become a health hazard. By the present invention, the desiccant
material is incorporated directly into the packaging film in a
rigid solid state in the packaging film substrate.
[0027] Moreover, it is an advantage of the present invention to
provide a film wherein the desiccant material is incorporated into
the sealant layer of the film and wherein the film is easily
extruded. In addition, many different types of desiccant materials
may be utilized, thereby allowing for particular relative humidity
levels within the packages.
[0028] The present invention further reduces packaging costs by
allowing for the use of thinner and, therefore, less expensive
barrier materials, such as aluminum foil. For example, many
flexible foil packages made using films of the present invention
can have barrier layers having thicknesses that may be reduced by
about 50% or more. Moisture can enter a package through a film
structure where two film structures are heat sealed together. The
present invention reduces the moisture absorption by blocking this
entry point.
[0029] Additional features and advantages of the present invention
are described in, and will be apparent from, the detailed
description of the presently preferred embodiments and from the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 illustrates a cross-section of a film of the present
invention comprising a desiccant material incorporated therein in
an embodiment of the present invention.
[0031] FIG. 2 illustrates a cross-section of a film structure
having a film layer comprising a desiccant material incorporated
therein in another embodiment of the present invention.
[0032] FIG. 3 illustrates a perspective view of a package made by
the film structure in an alternate embodiment of the present
invention.
[0033] FIG. 4 illustrates a cross-section of the package along line
IV--IV, in the alternate embodiment of the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0034] The present invention relates to films, film structures,
packages and methods of using and/or manufacturing the films, film
structures and packages of the present invention. Specifically, the
films comprise a desiccant material incorporated into the films as
an integrated component. More specifically, the desiccant material
is contained within a heat sealant layer of a film structure. The
film structure may be utilized to produce a package for a
moisture-sensitive product wherein said package has a first film
structure in face-to-face contact with a second film structure and
wherein said film structures are heat sealed together around the
edges of the package while the product is contained therein.
Although many types of moisture-sensitive products may be contained
within the packages made from the films or film structures of the
present invention, the packages made therefrom are especially
useful for packaging diagnostic test strips.
[0035] Now referring to the drawings, wherein like numerals refer
to like parts, FIG. 1 illustrates a film 1 of the present
invention. The film 1 may be made from a polymeric material, such
as a polyolefinic material. Preferably, the film may comprise
polyethylene selected from the group consisting of ultra low
density polyethylene, low density polyethylene, linear low density
polyethylene, medium density polyethylene, and high density
polyethylene, and may be made via any known method of making
polyethylene, such as via Ziegler-Natta catalysts, or single-site
catalysts, such as metallocene catalysts. Moreover, the film may
preferably comprise ethylene copolymers, such as ethylene
alpha-olefin copolymers, ethylene-methyl acrylate copolymer,
ethylene vinyl acetate copolymer, ethylene acrylic acid, ethylene
methyl acrylic acid copolymer, ionomer (Surlyn), and other like
polymers. In addition, the film may comprise polypropylene
homopolymer or copolymer, either alone or blended with polyethylene
or polyethylene copolymers, as noted above.
[0036] The film 1 may further comprise a desiccant material 10
blended therein, such as any known desiccant material that may
blend with polymeric resins that can be made into films.
Specifically, desiccant materials that may be useful for the
present invention include calcium oxide, magnesium sulfate, sodium
phosphate di-basic, ammonium chloride, potassium carbonate,
potassium aluminum disulfate, magnesium chloride, diammonium
sulfate, sodium nitrate, calcium chloride, calcium sulfate, sodium
chloride, potassium bromide, molecular sieves, clays, or any other
desiccant material apparent to one having ordinary skill in the
art. Chemical desiccant materials are preferred, such as calcium
oxide.
[0037] Chemical desiccant materials are preferred because chemical
desiccant materials irreversibly bind water molecules within the
crystalline product via a chemical reaction. The water molecules
typically cannot be released into the package at higher
temperatures or lower pressures. In addition, chemical desiccant
materials may more effectively remove humidity from the headspace
of a package made from the film 1. Hydrate-forming salts may also
be used, and may effectively maintain constant relative humidity
levels within the headspace of a package made from the film 1. For
example, magnesium sulfate may be blended with polyethylene or
another polymeric material to form a package that may maintain a
relative humidity level inside said package at about 35%. However,
other levels of humidity may be maintained depending on the
hydration levels or state of the magnesium sulfate within the
polymer material.
[0038] The desiccant material can be incorporated into the film 1
at a level of between about one weight percent and about 90 weight
percent. More preferably, the desiccant material can be
incorporated into the film 1 at a level of between about 20 weight
percent and about 60 weight percent. Most preferably, the desiccant
material can be incorporated into the film 1 at a level of about 30
weight percent.
[0039] Specifically, the film 1 may comprise a quantity of a
masterbatch of polymer and desiccant material. The masterbatch
comprises polyethylene having calcium oxide blended therein.
Specifically, the masterbatch comprises about 50 percent by weight
polyethylene and about 50 percent by weight calcium oxide. The
masterbatch is further blended into another polymeric material,
such as low density polyethylene, in a ratio of about 60 percent by
weight masterbatch and 40 percent by weight low density
polyethylene. Therefore, the film 1 may preferably have a desiccant
material content of about 30 weight percent in the film 1.
[0040] It should be noted that although the film 1 is illustrated
as a single independent layer, film 1 may be incorporated into a
multilayer structure such as via coextrusion with other film
layers, extrusion or coextrusion coating, adhesive lamination,
extrusion lamination or any other method of making multilayer film
structures having a sealant layer comprising a desiccant material
with other film layers.
[0041] FIG. 2 illustrates a film structure 100 of the present
invention, incorporating a film layer 110 having a desiccant
material incorporated therein, as detailed above with relation to
the film 1. Specifically, the film layer 110 may comprise a
polyolefinic material, such as polyethylene, as described above, or
polypropylene. Preferably, the polyolefinic material comprises
polyethylene. The desiccant material may comprise a chemical,
physical, or hydrate-forming desiccant material, although a
chemical desiccant material is preferred.
[0042] In addition, the film layer 110 may be between about 1 mils
and about 10 mils thick and may form a sealant layer or a product
contacting layer in a package made from the film structure 100.
More preferably, the film layer 110 may be between about 1 mils and
5 mils thick. Most preferably, the film layer 110 can be between
about 1.5 mils and about 3.5 mils thick.
[0043] The remaining film layers of a film structure of the present
invention may be any material that may be utilized to form a
package with the film layer 110 as a sealant layer or a product
contacting layer. Moreover, any number of layers may be
incorporated into the film structure 100 as may be needed to form a
package having desired characteristics. The preferred film
structure of the present invention includes the heat sealant layer
110, as noted above. The heat sealant layer 110 may be adhered to a
barrier layer 114 by a tie or adhesive layer 112. In addition, the
film structure 100 may comprise an outer layer 120 adhered to said
barrier layer via a second tie or adhesive layer 116 disposed
between said outer layer 120 and said barrier layer 114. Finally,
the presently preferred film structure 100 of the present invention
may comprise a primer layer or printed layer 118 disposed between
said outer layer 120 and said tie adhesive layer 116.
[0044] Preferably, tie or adhesive layer 112 may be a blend of low
density polyethylene (LDPE) and ethylene acrylic acid copolymer
(EAA). Barrier layer 114 may be made of a metal foil, such as
aluminum foil, nylon, high density polyethylene, polypropylene,
such as oriented polypropylene and metallized oriented
polypropylene, or metallized polyester, and may be any thickness
that may be necessary to reduce pin-holing and therefore reduce the
transmission of gases through the film structure 100. Preferably,
the barrier layer 114 may be about 0.35 mils when the barrier layer
114 is aluminum foil. Of course, the barrier layer may be other
thicknesses depending on the barrier material that is utilized. The
EAA of tie or adhesive layer 112 may aid in binding the
polyolefinic material of the heat sealant layer to the metal foil
layer 114. Film layer 116 may be a blend of LDPE and EAA and may be
similar, if not identical, to film layer 112. Film layer 118 may be
a primer layer and/or a printed layer. If the film layer 118 is a
printed ink or pigment layer, it may form a printed label or other
printed indicia on the film structure 100. Finally, film layer 120
may be an outer abuse layer, and may comprise polyethylene
terephthalate (PET), oriented polypropylene (OPP), polyethylene,
nylon, foil, metallized substrates, or any other material apparent
to one having ordinary skill in the art.
[0045] As stated above, the barrier layer 114 may be a metal foil
that may be any thickness to reduce the transmission of moisture
through the film. The number of pinholes present in a metal foil is
inversely related to the foil thickness. Therefore, a thicker foil
tends to have fewer pinholes. However, if the desiccant material of
the present invention is in the heat sealant layer 110, thinner
foil can be utilized in packages made from the film structure
100.
[0046] Metal foil is typically utilized to provide an effective
barrier against moisture transmission through a film structure.
However, metal foil can be relatively expensive and difficult to
process. Therefore, the desiccant sealant layer 110 is effective at
reducing or eliminating the transmission of moisture that may pass
through relatively thin metal foil. Desiccant films, therefore, add
significant protection to the inside space of a package made from
the film structure 100 in addition to the inherent barrier
protection provided by metal foil. Barrier layers may be relatively
thinner when a film structure incorporates a desiccant sealant
layer into the film structure, thereby saving on cost.
[0047] FIG. 3 illustrates a package 200 made from a film structure
of the present invention. Specifically, the package 200 is made
from the film structure 100, as illustrated with respect to FIG. 2,
described above. Specifically, the package 200 may comprise two
film structures that are heat sealed together via a heat seal 202
that is formed around a perimeter of the package 200.
Alternatively, the package 200 may comprise a single film structure
that is folded and heat sealed around the perimeter of the package
200. The package 200 may further comprise a space 204 to contain a
product 206. The product 206 may be sensitive to moisture, so that
a desiccant material contained within the film structure or film
structures reduces or eliminates the amount of water molecules
within the space 204. A preferable product contained within the
package 200 may be a diagnostic test strip useful in the medical
field. A single diagnostic test strip may be contained within the
package 200 so that when opened and the diagnostic test strip is
removed, there are no other test strips within the package 200 to
be contaminated by moisture.
[0048] FIG. 4 illustrates a cross-section of the package 200 along
line IV--IV, in an embodiment of the present invention. The
cross-section shows two film structures 210, 212 that are heat
sealed together at heat seals 202. The two film structures may be
identical, and may comprise the same film layers as described above
with respect to film structure 100. Specifically, the two film
structure 210, 212 may comprise a plurality of layers: a first
sealant layer 110 of a polyolefinic material and a desiccant
material; a second layer 112 of a blend of low density polyethylene
and ethylene acrylic acid copolymer; a third layer 114 of a foil
material; a fourth layer 116 of a blend of low density polyethylene
and ethylene acrylic acid copolymer; a fifth primer layer 118; and
a sixth layer 120 of PET. The product 206, such as a diagnostic
test strip, is contained within the package 200 in the space
204.
[0049] While foil can reduce or effectively eliminate water
transmission through film structures 210, 212 of the package 200,
it cannot completely eliminate the transmission of moisture through
the edges of the film structure. For example, FIG. 3 illustrates
the cross-section of the package 200 along line IV--IV. As shown,
the metal foil layer 114 of each film structure 210 and 212 are
displaced from the portions of the film structure 210 and 212 that
are heat sealed together. Therefore, there is an area 214 that is
not protected by the metal foil layer 114 that may transmit water
molecules into the space 204. If the desiccant material is
incorporated into the heat sealant layer 110, then the desiccant
material effectively blocks moisture from passing into the interior
space 204 of the package 200 thereby protecting the moisture
sensitive product contained therein.
[0050] The film layers of the film structure 100 may be made via
cast coextrusion, extrusion coating and/or extrusion lamination,
adhesive lamination, blown-film coextrusion or monolayer extrusion
or any other film making method generally known to those having
ordinary skill in the art. Preferably, the heat sealant layer may
be made by compounding the desiccant material into the polymeric
resin, and extruding or coextruding via blown extrusion, cast
extrusion into a monolayer film or a multilayer film. The remainder
of the film structure may be extrusion or adhesive laminated
together with the monolayer film or mulitilayer film. The desiccant
heat sealant layer can be laminated to the remainder of the film
structure, including the barrier layer of the film structure.
[0051] As noted in the above paragraph, several methods exist for
constructing an effective flexible package using the present
invention. These methods include, but are not limited to:
[0052] 1. Blown film monolayer extrusion or multilayer coextrusion
wherein the sealant film is extrusion laminated to a barrier
material. This method is preferred.
[0053] 2. Blown film monolayer extrusion or multilayer coextrusion
wherein the desiccant sealant film is adhesive laminated to a
barrier material with the use of adhesives and/or primers to bond
the desiccant sealant film to the barrier layer.
[0054] 3. Cast film monolayer extrusion or multilayer coextrusion
wherein the sealant film is extrusion laminated to a barrier
layer.
[0055] 4. Cast film monolayer extrusion or multilayer coextrusion
wherein the desiccant sealant film is adhesive laminated to barrier
materials with the use of adhesives and/or primers to bond the
desiccant sealant film to the barrier layer.
[0056] 5. Extrusion or coextrusion coating wherein the desiccant
sealant layer and/or an adhesive layer are extrusion or coextrusion
coated directly onto the barrier layer.
[0057] Of course, any other methods of making films, film
structures, and packages of the present invention may be utilized
as may be apparent to one having ordinary skill in the art.
Moreover, although film structures having barrier materials
incorporated therein as a barrier layer of the film structures are
preferred, other film structures such as those not having a barrier
material or barrier layer may also be produced as apparent to one
having ordinary skill in the art.
EXAMPLES
[0058] The following examples are illustrative of preferred
embodiments of the present invention, as described above, and are
not meant to limit the invention in any way.
Example 1
[0059] The following Table 1 illustrates preferred materials and
gauges for the film structure 100, as described above and
illustrated with respect to FIG. 2.
1 TABLE 1 Material Gauge PET 0.48 mils INK 0.1 mils LDPE/EAA blend
0.5 mils Foil 0.35 mils LDPE/EAA blend 0.5 mils LDPE/CaO blend 1.5
mils
Example 2
[0060] The following Table 2 illustrates preferred materials and
gauges for the film structure 100, as described above and
illustrated with respect to FIG. 2, in an alternate embodiment of
the present invention.
2 TABLE 2 Material Gauge PET 0.48 mils INK 0.1 mils LDPE/EAA blend
0.5 mils Foil 0.35 mils LDPE/EAA blend 0.5 mils LDPE/CaO blend 2.5
mils
Example 3
[0061] The following is a preferred embodiment of the package 200,
described above and illustrated with respect to FIG. 3. The package
may be made from film structures noted above, and preferably with
respect to Examples 1 and/or 2. Specifically, the package 200 may
be for diagnostic test strips. Each package may be about 5.25 in.
long and about 2.25 in. wide. The heat seals that are created
around the perimeter of the packages are about 0.25 in. wide.
Taking into consideration the heat seals, each package would have a
total exposed internal surface of about 16.6 in..sup.2
[0062] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications may be made without departing from the spirit and
scope of the present invention and without diminishing its
attendant advantages. It is, therefore, intended that such changes
and modifications be covered by the appended claims.
* * * * *