Note: Descriptions are shown in the official language in which they were submitted.
CA 02486724 2004-11-02
BLISTER PACKAGE FOR ADHESIVE COMPOSITIONS
FIELD OF THE INVENTION
[0001] The present invention relates to packaging for storing and displaying
glue sticks and
other adhesive composition products, and more particularly to blister card
packaging for storing
and displaying such products while significantly increasing shelf life and
product stability.
BACKGROUND OF THE INVENTION
[0002] Many adhesive products are provided in primary containers formed of
plastics in
order to provide a relatively stable, durable, and user-friendly package. In
the case of glue sticks,
the primary package is generally cylindrical, having a circular horizontal
cross-sectional
geometry ("round" glue sticks). More recently, glue sticks have been sold
using a primary
package having a horizontal cross-section that is generally oval or ovaloid.
Such oval or ovaloid
packages are often referred to as "wide" glue sticks since they impart a wider
tip to the dispensed
glue stick or other adhesive composition contained in the package. In the
particular case of glue
sticks, there exist both round cylindrical and wide stick primary plastic
packaging that includes a
lower closed portion having means for advancing the product out of an opposite
dispensing
opening, and a cap for covering the dispensing opening. In either case, the
primary dispensing
package is customarily made of high-density polyethylene ("HDPE"~.
[0003) With the development of wide stick packaging, it has been found that
the shelf life of
the wide stick product is shorter than for round glue sticks. It is believed
that the wide stick
containers more readily permit the passing of air to the adhesive product
before, during, and after
use of the product. Passing air to the product results in undesirable aging of
the product, and
eventually deteriorates the product to the point that desirable properties
such as adhesion and
ease of application are lost. Additionally, some adhesive compositions are
hygroscopic making
it necessary to protect them from moisture degradation so that they retain
their usefulness over
prolonged periods; i.e. shelf life stability, until they are consumed.
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CA 02486724 2004-11-02
[0004] For the above reasons, it is desirable to prolong the shelf life of
glue sticks, whether
round or wide, as well as other adhesive compositions packaged in primary
packaging that is
susceptible to leakage and exposure to air.
[0005] It is further desirable to provide secondary packaging that protects
the adhesive
composition from exposure to air, gas and moisture due to failure of the
primary packaging.
SUMMARY OF THE INVENTION
[0006] It has now been found that the shortcomings of the existing primary
packaging for
glue sticks and similar adhesive composition consumer products can be overcome
by the novel
sandwich blister package of the present invention. In general, the sandwich
blister package of
this invention comprises a plastic film blister having at least one heat-
formed cavity, and. a
laminated blister card having a base layer and a foil layer overlying at least
a portion of the base
layer. Optionally, a sealing material forming a sealing layer is overlaying at
least a portion of the
foil layer, the sealing layer disposed so as to receive and securely seal the
blister against the foil
layer. Preferably, the laminated blister card has a base layer of paperboard
or corrugated paper, a
foil layer comprising aluminum, and a sealing layer comprising polyethylene.
In another
embodiment, the foil layer includes graphics superimposed upon and sealed to
the foil.
[0007) The invention further includes methods of using the plastic film
sandwich blister
package of the invention as a secondary package to reduce the loss of moisture
from the adhesive
composition resulting from the exposure of the primary container and its
adhesive contents to air.
As secondary benefit is that the blister isolates the primary package and
contents from exposure
to environmental conditions such as vapor humidity and liquid water. By
isolating the product in
a substantially airtight package, the present invention will significantly
lengthen the useful shelf
life of the product. In addition, the present invention provides a superior
secondary package for
display of the product for retail sale.
[0008] The plastic materials that can be used for the plastic f lm portion of
the bli ster
package of the invention are those which are resilient, heat formable and heat
sealable such as
polyvinyl chloride (PVC), polyvinylidine chloride, polyethylene,
polypropylene, polyolefin,
fluoroplastics, and combinations thereof. In one embodiment, PVC films having
a thickness of
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CA 02486724 2004-11-02
from between about 005 inches to about .008 inches provide the desired
packaging and
processing properties for use in the sandwich blister package of the invention
and are
commercially available. Additionally, PVC films can be readily heated to form
the cavities iFor
receiving and retaining product, retain the integrity of the formed cavities
after cooling, and are
heat sealable.
[0009] The metal foil used in the foil layer of the invention generally has a
thickness of from
about between .003 to about .005 inches, and is also commercially available.
The preferred type
of metal foil is aluminum, although foils of other metals, as well as foil
having multiple layers
that include plastics or other reinforcing materials, may be used.
[0010] The sealing layer overlaying the foil layer is comprised of a plastic
or adhesive that is
compatible with sealing to the blister. Where the blister is PVC, the
preferred method of sealing
is heat sealing, and accordingly, the sealing layer material includes PVC,
polyethylene, or
combinations thereof. The sealing material must provide a seal strong enough
to cause a fiber
tear of the paperboard when removed from the blister card. Preferably, the
sealing layer applied
to the foil layer is typically about .002 to about .020 inches thick.
[0011] Conventional packaging apparatus can be used to produce the sandwich
blister
package of the invention which generally comprises feeding a sheet of PVC
plastic film over a
heating plate having a plurality of spaced apertures formed therein;
concurrently applying heat
and vacuum to the PVC plastic sheet while it is held over the heating plate to
vacuum form a
plurality of spaced cavities in the PVC plastic sheet; advancing the PVC
plastic sheet and filling
the cavities with product; superimposing a sheet of blister card material
comprising a base layer,
a foil layer, and a sealing layer over the filled cavities; bonding the PVC
plastic blister sheet to
the sealing layer of the blister card, cutting the thusly bonded members to
obtain separate blister
cards of pre-set sizes, each containing a pre-determined quantity of product.
[0012] Other features and advantages of the present invention will be apparent
from the
following more detailed description of the preferred embodiment, taken in
conjunction with the
accompanying drawings which illustrate, by way of example, the principles of
the invention.
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CA 02486724 2004-11-02
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The blister package of the invention and a method for producing it will
become more
clear from the ensuing description when considered together with the
accompanying drawing
wherein like reference numerals identify like parts and wherein:
[0014] FIG. 1 is an exploded side elevation illustrating the elements of a
single unit of t:he
sandwich blister package of the invention;
[0015] FIG. 2 is a side elevation of the single unit sandwich blister package
of FIG. 1;
[0016] FIG. 3 is a side cross-sectional view of the single unit blister
package of FIG. 1 taken
along line 3-3 of FIG. 2;
[0017] FIG. 4 is a top plan view of another embodiment of the sandwich blister
package of
the invention, showing a foil layer having text superimposed thereon; and
[0018] FIG. 5 is a side perspective view of the single unit blister card of
FIG. 2.
DETAILED DESCRIPTION OF 'THE INVENTION
[0019) In order to accomplish the objects of the invention, the present
invention provides a
secondary package that provides an airtight enclosure for an adhesive product
that is contained in
a primary package. As shown in the preferred embodiment illustrated in FIG. l,
the secondary
package 10 is comprised of a plastic blister 12, and a blister card 20 , The
blister card 20
includes at least a base layer 22, a foil layer 24 overlaying at least a
portion of the base layer 22,
and a sealing layer 26 overlaying at least a portion of the foil layer 24. The
secondary package
is assembled as a sandwich wherein the blister 12 includes a cavity that
generally corresponds
to the size and shape of a product 30 such as an adhesive composition pre-
packaged in a primary
container. The blister 12 includes one or more cavities formed in the blister
12, and a
substantially flat perimeter portion 14 disposed for receiving and sealing
against the blister card
to form a moisture/vapor/gas impervious secondary package. When the blister
package 10 is
fully assembled and sealed, the product 30 is thus protected from
moisture/vapor/gas degradation
until the blister package 10 is unsealed to remove the product 30 to be
consumed.
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[0020] As shown in FIGS. 1 ~-5, the preferred embodiment of the blister
package 10 is a
moisture/vapor/gas impervious blister package 10 that comprises a blister 12
formed from a
sheet of plastic material such as polyvinylchloride ("PVC"), nylon, or other
resilient plastic. The
blister 12 may be formed by any known means, but is preferably formed by
heating PVC film in
a blister-forming packaging machine as further described herein. The blister
12 is configured so
as to closely conform to the shape and size of an adhesive composition product
13, so as to
minimize air content of the assembled package.
[0021] The blister card 20 is comprised of at least a base layer 22 and a foil
layer 24. The
card 20 is preferably a three-ply card comprising a lower base layer 22, a
laminated foil layer 24
overlaying at least a portion of the base layer 22, and a sealing layer 26
overlaying at least; a
portion of the foil layer 24.
[0022] The foil layer 24 is preferably comprised of a foil metal such as
aluminum, tin, or
combinations thereof. Alternatively, the foil layer can include a plastic or
resin such as polyester,
whether in combination with a metal foil or in place of the metal foil. The
foil layer 24 is
preferably between about 0.01 millimeters and 0.02 millimeters thick . Such
thin foils are
known to be easily punctured and have a tendency to easily tear. Therefore,
securely laminating
the foil layer 24 to the base layer 22 helps to strengthen the foil layer so
a.s to provide a
continuous foil barrier on the top surface of the base layer material.
Optionally, the foil layer 24
may be comprised of a second layer of a material laminated to the foil,
wherein the second layer
is a material that is tear-resistant and impervious to air. PVC, polyethylene,
and polyester for
example, can be used for this purpose, although other plastics will be known
to those skilled in
the art. In any case, the foil layer 24 imparts the desired moisture/vapor/gas
barrier protection
and is the layer overlaying the blister card base layer 22.
[0023] The sealing Layer 2E is preferably comprised of a heat-sealable plastic
composition
such as polyethylene, PVC, or other known heat-sealable plastic that is
compatible with the
flexible plastic film of the blister 12 and the foil layer 24 to form a
permanent bond with both the
blister 12 and the foil layer 24. The sealing layer 24 is preferably applied
to the foil layer 22
early in the packaging process since the resilient nature of the sealing layer
26 protects the
aluminum foil ply and can prevent it from being torn or punctured during
packaging.
CA 02486724 2004-11-02
[0024] FIG. 1 shows an exploded view of a single unit sandwich blister package
of the
invention. The package comprises a PVC plastic blister 12 having a cavity heat
formed therein
for receiving and retaining a product 13. A sealing layer 26 is superimposed
upon and bonded to
the top foil layer 24 of a blister card having a base layer 22, the base layer
22 and foil layer 24
laminated to form a blister card 20.
[0025] FIG. 2 shows the assembled sandwich blister package of FIG. 1, wherein
l:he
substantially flat perimeter edges of the blister 12 have been heat sealed to
the foil layer 24 of l:he
blister card by heating the sealing layer 26 so that it bonds to the blister
12 and to the foil layer
24. FIG. 3 shows a close-up side cross-sectional view of the assembled, heat-
sealed blister
package 10 of FIG. 2. Fog. 5 shows another side perspective view of the
assembled package.
[0026] As shown in FIG. 4, the assembled package of FIG. 2 can include
graphics and text
superimposed onto the foil layer 24 to form a package that is suitable for
display without further
modification. Graphics may include product names, ingredients, trademarks, and
any other
desirable artwork and text.
[0027] The preset invention further includes an assembly line method that can
be used to
continuously produce completed blister packages of the invention. PVC film for
the blister is
continuously supplied in sheet form from a roll of PVC film and led over a hot
plate having a
plurality of spaced apertures. The hot plate is kept at a temperature
sufficient to heat the PVC
sheet 10 so that it becomes softened and heat formable. 'Vhen the PVC sheet
has reached a
softened, heat formable state (usually within about 2 seconds to about 6
seconds) vacuum is
applied by conventional means to draw the softened PVC sheet film down into
apertures to
thereby form the cavities in the PVC sheet. The PVC sheet is then fed beneath
a product supply
means such as a product hopper where a product, such as a glue stick in a PVC
primary package
is deposited into each cavity. Sufficient distance from the cavity forming
operation and the
hopper is provided so that the cavities formed have time to cool, set and
become integral.
Usually, the cavities are set and cooled to maintain an integral self
supporting shape within about
2 seconds to about 6 seconds.
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[0028] Downstream from hopper, a blister card comprised of a base layer, a
foil layer
laminated to the base layer, and a sealing layer overlaying the foil layer is
provided to be
superimposed over the PVC sheet carrying the product in the formed cavities.
The blister card is
then heat sealed to the PVC sheet 10 such as by means of heat sealing platen
to obtain a sealed
blister secondary package assembly. Conventional knife blades and other
cutting means can then
be used to cut the blister package assembly into individual blister cards of
pre-set sizes. The
fully assembled blister cards arf; then fed to downstream stations for
packaging into bulk
containers or tertiary packages such as display cases.
EXAMPLES
[0029] The inventors were able to evaluate a series of experimental blister
packages,
designated herein as the "S series" and the ''L series". The samples each
included an Elmer's
round glue stick in its primary HDPE package, but with the cap removed,
packaged into a
secondary blister package. Each blister package included a glue stick laid on
a blister card, with
a plastic blister overlaying the glue stick and sealed to the blister card
using a polyethylene
sealing ring as the sealing layer. Each blister and card assembly was than
heat sealed at
temperatures of between about 240 to 300 degrees Fahrenheit for sufficient
dwell time to activate
the sealing layer and create an airtight and durable seal between the blister
card and the blister.
[0030] Each "S" series blister card included a paperboard backing having a
.003 to .005 inch
thick foil layer of aluminum foil on the exposed (top surface for contacting
the product and
plastic blister.
[0031 ] By contrast, each "L" series package included a plastic blister
overlay of the same
composition as the "S" series, and paperboard backing identical to that of the
"L" series, save :for
the absence of the foil top layer.
[0032] Each series of packages was then placed in a 50 degree Celcius oven for
2 weeks to
measure the total package weight loss. The results are listed in the tables
below. The displayed
weight loss is a total weight loss that includes the entire package and
product and therefore is not
limited to the product itself - however, given the identical package
components save for the foil
lacking in the "L" series, the majority of the weight loss can indeed be
attributed to moisture a.nd
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volatiles loss from the product. Calculated percentage weight loss for the
glue stick itself would
therefore, of course, be much greater.
[0033] To clearly compare the results, the inventors have provided a ratio of
the two weight
loss values to measure the performance impact of the different foil metal
layer. The "L" series,
which lacked the foil layer, lost 1.1.77 %, nearly four times (4X) as much
weight (presumably
mostly water) than the "S" series (2.83%).
S Series
Initial Aged Weight(g) Difference(g)(%)
Wt (g)
S-1 71.17 69.48 1.69 2.37
S-2 70.95 69.16 1.79 2.52
S-3 71.09 67.54 3.55 4.99
S-4 70.93 68.95 1.98 2.79
S-5 71.20 69.61 1.59 2.23
S-6 71.25 69.58 1.67 2.34
S-7 71.30 69.45 1.85 2.59
Average 2.83%
loss
(%)
=
L Series
Initial Wt Aged Weight(g)Difference (%)
(g)
L-1 72.98 65.01 7.97 10.92
L-2 72.79 64.08 8.74 12.01
L-3 72.53 64.28 8.25 11.37
L-4 72.08 63.09 8.99 12.47
L-5 72.29 63.55 8.74 12.09
L-6 72.06 63.42 8.64 11.99
L-7 72.51 64.12 8.39 11.57
Average loss (%) = 11.77%
[0034] The ratio of "L" average weight loss to "S" average weight loss as
approximately
4.16:1. Clearly, the foil layer constitutes a significant improvement over the
current secondary
blister packaging for glue sticks. It is fully expected that further testing
will show that the blister
package of the preset invention will significantly improve the useful shelf
life of the packaged
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glue stick products and similar adhesive composition products, and may triple
the current shelf
life of such products where the primary cause of product degradation is by
moisture loss.
[0035] While the invention has been described with reference to a preferred
embodiment, it
will be understood by those skilled in the art that various changes may be
made and equivalents
may be substituted for elements thereof without departing from the scope of
the invention. In
addition, many modifications may be made to adapt a particular situation or
material to the
teachings of the invention without departing from the essential scope thereof.
Therefore, it is
intended that the invention not be limited to the particular embodiment
disclosed as the best
mode contemplated for carrying out this invention, but that the invention will
include all
embodiments falling within the scope of the appended claims
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