Abstrict 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.
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. |