Note: Descriptions are shown in the official language in which they were submitted.
A LOW-TACK, UV-CURED PRESSURE SENSITIVE ADHESIVE
SUITABLE FOR RECLOSABLE PACKAGES
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S. Provisional
Application Serial
No. 61/308,540 filed February 26, 2010, U.S. Provisional Application Serial
No. 61/407,406 filed
October 27, 2010, and U.S. Provisional Application Serial No. 61/407,409 filed
October 27, 2010.
FIELD
[0002] This disclosure relates generally to low-tack adhesives and, in
particular, to low-tack
adhesives suitable for packages.
BACKGROUND
[0003] Several types of closures or fasteners are available for reclosing a
previously opened
package. For example, it is common to use mechanical reclosable fasteners,
such as slider
zippers, clips, tabs, interlocking strips, and the like. These mechanical
closures can be bulky,
complex structures that require separate molding and fabrication steps prior
to being joined to
the package. Further, film rolls and other packaging materials incorporating
such fasteners can
be unwieldy and difficult to handle due to the added bulk from the fasteners.
Additionally,
such fasteners can add significant material and production costs to a package.
Mechanical
fasteners may also not form an airtight seal upon closure. For instance, when
in a closed
position, slider zippers can have an undesirable small air channel or gap due
to bridging of
interlocking flanges between an end-stop and the slider. These mechanical
fasteners can be
applied in form, fill, and seal operations, but such a process can require
complex manufacturing
steps to apply, interconnect, and align the features of each structure. For
these reasons,
mechanical reclosable fasteners can add undue complexity, cost, and expense
into the
manufacture of such packages.
[0004] Adhesive-based reclosable fasteners provide one alternative to the
mechanical
fasteners discussed above. Adhesive-based fasteners, however, present other
challenges in both
the manufacture and formation thereof. For example, thermoplastic elastomers
(TPE), which
are sometimes called thermoplastic rubber, have been used to form reclosable
pressure sensitive
adhesive (PSA) type fasteners. Some types of TPE copolymers (especially
certain styrenic block
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polymers) demonstrate high cohesive properties, and at the same time have low
tack levels or
a reduced tendency to adhere to unlike materials. TPEs can be effective at
forming reclosable
fasteners; however, such TPEs tend to have undesirably high cohesive
properties that render
them difficult for use as a reclosable fastener in packaging applications
because the TPE can
delaminate from the package substrate rather than peel at the cohesive
interface. Additionally,
the TPEs may need to be dissolved in a solvent so that the TPE can be printed
in a transverse or
machine web direction as an intermittent pattern onto the package substrate.
In some cases,
organic solvents suitable for use as a carrier with TPEs may not be acceptable
for contact with
food items. Pattern application of TPEs in the form of an aqueous dispersion
has been
contemplated; however, creating TPE dispersions in water that are suitable for
flexographic
or rotogravure printing processes is technically difficult to accomplish. Even
if a technically
feasible method for dispersing TPE in water were to be discovered, the high
cost of removing
the water carrier after the coating is applied may render pattern coating of
aqueous TPE
dispersions commercially infeasible for high volume consumer packaging
applications.
[0005] Other types of pressure-sensitive adhesives (PSAs) may be useful as
reclosable
fasteners for packages; however, common PSA reclosable fasteners generally
have high tack
levels. Tack is a property of an adhesive material that generally enables the
material to form a
bond with the surface of another material upon brief or light pressure. Tack
is often considered
as a quick stick, art initial adhesion, or a quick grab characteristic of a
material. Ordinary PSA
adhesives generally cannot be surface-printed onto materials that are intended
to be run on
commercial package forming equipment. Typical problems encountered when
attempting to
run PSA surface coated materials on packaging equipment include: blocking
where the
material does not unwind freely from a roll due to unacceptable back-side
adhesion; picking
where there is undesirable and unintended transfer of adhesive material to
equipment surfaces,
such as rollers, mandrels and filling tubes; poor tracking, such as the
inability of the material to
stay in proper alignment as it passes through the packaging machine; and
jamming where the
material is unable to slide over equipment surfaces and binds up.
[0006] PSA reclosable fasteners may also present concerns to a consumer
using a formed
package. If the package is used to contain a crumbly (i.e., a cookie, cracker,
and the like) or
shredded product (i.e., shredded cheese and the like), the high tack of most
PSAs may cause the
crumbs or shreds to stick to the PSA, which reduces the effectiveness of the
adhesive to form a
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sufficient closure due to contamination of the PSA surface from the food
product. A PSA
fastener that is sufficiently contaminated with product will generally not
form an adequate
closure seal because the crumbs that adhered to the PSA generally do not allow
the PSA to
adhere to the other side of the package.
[0007] Lower tack PSAs that function like cohesive materials generate other
concerns.
Lower tack adhesive can be difficult to adhere to a package surface due to the
low tack
properties. Thus, fasteners created with lower tack PSAs may result in
delamination of the PSA
from the package surface upon opening of the package.
SUMMARY
[00081 A low-tack, UV-cured pressure sensitive adhesive is provided having
at least one
UV-curable acrylic oligomer, at least one tack control component, and
optionally at least one
elastomeric material. In one aspect, the adhesive has an adhesive component
ratio (ACR) of the
UV-cured pressure sensitive adhesive defined by formula (A) where the weight
percent of the
UV-curable acrylic oligomer relative to the sum of the weight percents of the
tack control
component and the optional at least one elastomeric material is about 0.5 to
about 1.5
(wt% UV-curable acrylic oligomer) (A).
(wt% tack control component wt% elastomeric material)
The ACR is effective so that the reclosable UV-cured pressure sensitive
adhesive has a first peel
adhesion between opposing adhesive portions of about 200 grams per linear inch
(gpli) to about
900 gpli and up to five subsequent peel adhesions between opposing adhesive
portions each
about 30 percent to about 200 percent of the first peel adhesion and a first
subsequent peel
adhesion after fouling with debris at least about 50 percent of the first peel
adhesion. In another
aspect, a liquid mixture of the UV-curable acrylic oligomer, the tack control
component, and the
optional elastomeric material is compatible such that the liquid mixture
remains a stable liquid
that is homogeneous without phase separation for at least about 3 days at
about 70 to about
75 F.
BRIEF DESCRIPTION OF THE DRAWINGS
[00091 FIG. 1 is a perspective view of an exemplary flexible package having
an adhesive-
based reclosable fastener thereon illustrated in an open condition;
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[0010] FIG. 2A is a perspective view of a second embodiment of an exemplary
package
having an adhesive-based reclosable fastener thereon illustrated in a closed
condition;
[00111 FIG. 2B is a perspective view of the package in FIG, 2A, shown in an
open condition;
[0012] FIG. 3A is a perspective view of a third embodiment of an exemplary
rigid package
having an adhesive-based reclosable fastener thereon;
[0013] FIG. 3B is a perspective view of a fourth embodiment of an exemplary
package with a
pivotable cover, the package having an adhesive-based reclosable fastener
thereon;
[0014] FIG. 3C is a perspective view of a fifth embodiment of an exemplary
rigid package
having an adhesive-based reclosable fastener thereon;
[0015] FIG. 4 is a cross-sectional view of an exemplary adhesive-based
reclosable fastener;
[0016] FIG. 5A is a cross-sectional view of the adhesive-based reclosable
fastener illustrated
in an open condition and with a filled package;
[0017] FIG. 5B is a partial cross-sectional view of the adhesive-based
reclosable fastener of
FIG. 5A illustrated in a closed condition;
[0018] FIG. 6 is an exemplary process to apply the adhesive-based
reclosable fastener to a
package substrate;
[0019] FIG. 7 is an exemplary process to form a package using a adhesive-
based reclosable
fastener;
[0020] FIG. 8 is a cross-sectional view of another exemplary adhesive-based
reclosable
fastener; and
[0021] FIGS. 9 and 10 are exemplary processes to prepare packages with the
adhesive-based
reclosable fastener.
DETAILED DESCRIPTION
[00221 A low tack, adhesive-based reclosable fastener and packages
utilizing the fastener are
described herein. The fastener includes opposing layers, portions or patterns
of low-tack
adhesive that releasably adhere together to close the package. The fastener
secures to a package
substrate with a sufficient bond strength such that the opposing layers of
adhesive do not
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delaminate from the package substrate when opened even when the adhesive has
low tack. The
adhesive used to form the fastener also has a relatively high cohesive bond
strength, but at the
same time a relatively low tack so that it can function as an effective
reclosable fastener even
when exposed with crumbs, lint, particulate, or the like. The opposing layers
of adhesive can be
applied on a variety of substrates such as packaging materials including, for
example, film,
paperboard or other paper products, cardboard, foil, metal, laminates,
flexible, rigid, or semi-
rigid plastic products, or combinations thereof. Similarly, these materials
can be used to create
a variety of packages or containers, including, for example, flexible pouches
or bags, cartons or
boxes, sleeves, and clamshell packages, to name a few.
[00231 In one aspect, an adhesive-based reclosable fastener and/or package
substrate are
generally constructed or have a composition effective to minimize the adhesion
of the fastener
to undesired surfaces and still function at the same time as an effective
reclosable fastener that
does not delaminate. That is, the adhesive-based fastener and/or package
substrate has a
unique formulation or construction to achieve select tack and peel values so
that the adhesive-
based fastener can be opened and closed multiple times to seal the contents in
the package
during use by a consumer, but at the same time, not delaminate from the
opposing package
substrate panels. To this end, the reclosable fastener generally includes a UV-
cured adhesive
with relatively low tack levels to minimize adhesion to the unwanted surfaces,
a selected
bonding or opening peel strength sufficient to enable secure reclosure of the
package, and a peel
strength robust enough to enable repeated opening and reclosing of the
package. At the same
time, the fastener also has a strong bond to the package substrate so that the
adhesive does not
delaminate upon opening of the fastener to access the package. By one
approach, the reclosable
adhesive-based fastener may include specific blends of a UV-curable acrylic
oligomer and a tack
control agent. In other approaches, the reclosable adhesive-based fastener may
include specific
blends of at least one UV-curable acrylic oligomer, at least one tack control
agent, and at least
one elastomer (rubber) component.
[0024] In one approach, the UV-cured, adhesive-based reclosable fastener is
a UV-cured
pressure sensitive adhesive (PSA) exhibiting cohesive properties and low tack,
but, despite the
low tack, still forms a strong bond to the package substrate forming the
opposing package
panels. As generally understood, a cohesive-based material typically adheres
more readily to
like materials (i.e., self-adhesion) rather than to non-like materials.
Suitable adhesive materials
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used herein generally exhibit a relatively low tack to undesired surfaces, but
at the same time
still exhibit a good bond strength to desired surfaces (such as no
delaminating from the
opposing panels), and relatively good cohesive or self adhesion bond strength
to like surfaces to
hold a package or pouch closed, but still permit the package to be openable or
peelable by hand.
The selected adhesive-based materials also permit debonding or peeling from
such like
materials so that the adhesive layers may be repeatedly peeled apart without
substantial
damage to the adhesive material and/or any underlying package substrate. When
the adhesive
material is debonded or peeled apart, the selected adhesive materials have
sufficient internal
integrity and generally peel apart at an adhesive bonding interface
substantially cleanly without
substantial material picking, stringiness, delainination from the package
substrate, and/or other
substantial disfigurations of the material (i.e., globbing, pilling, etc.).
Advantageously, the
adhesive-based fasteners described herein maintain a peel adhesion where
opposing adhesive
strips contact each other with an average initial peel adhesion greater than
about 200 grams per
linear inch (gpli) and, in some cases, between about 200 gpli and about 900
gpli. Moreover, in
some instances, the adhesive-based fasteners retain greater than about 200
gpli and/or at least
about 30% to about 200% of the average initial peel adhesion after five
repeated seal and unseal
operations.
[00251 In another aspect, a package having the adhesive-based fastener
disposed thereon is
also constructed so that the bond or peel strength of the UV-cured, adhesive-
based reclosable
fastener to the package substrate is generally greater than the opening peel
strength between
the layers of the fastener itself. In this manner, the reclosable fastener
generally remains
adhered to the package substrate and does not pick, string, or delaminate from
the package
substrate when the package is opened by a consumer and the fastener is peeled
open. For
example and in one approach, a primary bond or peel strength of the adhesive
to the package
substrate is greater than about 600 gpli (in some cases, greater than about
900 gpli) and is
capable of withstanding multiple peel and re-seal cycles without detachment
from the film
substrate. In addition, the adhesive is cured so that it is capable of
withstanding more than 100
double rubs with methyl ethyl ketone (MEK) solvent.
[0026] Turning now to the figures, an exemplary package 10 having a UV-
cured, adhesive-
based reclosable fastener 12 is generally illustrated in FIGS. 1 to 3. The
package may include
both flexible packages, such as a pouches, bags, sachets, and the like as well
as more rigid
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=
packages, such as a boxes, cartons, envelopes and the like. In general, the
package includes a
plurality of walls that form a cavity therein configured to receive one or
more products, such as
food products. By some approaches, the package further includes opposing
panels of
packaging substrate configured to join together to restrict or block access,
to contain items,
and/or to preserve freshness. The adhesive-based fastener, as described above
including the
opposing adhesive portions, can be disposed on the opposing panels to provide
a reclosable
package. So configured, a user can separate the opposing panels and the
opposing adhesive
portions disposed thereon to access the one or more products in the cavity.
Then, the user can
join the opposing panels together, such as by shifting the panels toward each
other or pivoting
one or both of the panels with respect to the other, and applying slight
pressure to adhere the
opposing adhesive portions together, which recloses the package. These open
and reclose
operations can be repeated several times with minimal to no loss of bond
strength of the
fastener.
[00271 FIGS. 1 and 2 generally illustrate a flexible package utilizing the
adhesive-based
fastener 12. FIG. 1 shows the package 10 in an open condition, while FIG. 2A
generally
illustrates the package 10 in a closed or sealed condition. FIG. 3A generally
illustrates the
package 10 in the form of a more rigid hinged-type box suitable for containing
one or more
items, such as gum pieces. FIG. 313 is a box or carton having the adhesive-
based fastener 12, and
FIG. 3C shows an envelope or paper-based pouch utilizing the adhesive-based
fastener 12. It
will be appreciated that FIGS. 1-3 show examples of packages and other types,
sizes, and
configurations of the package may also be used as needed for a particular
situation.
[0028] In general, the packages 10 of FIGS. 1-3 are formed from one or more
portions,
panels, or pieces of material or substrate 14 formed into opposed front and
back panels, walls,
and the like (shown as panels 16 and 18 in the figures). The opposing walls
also have opposing
portions or patterns of adhesive 30 and 32 disposed thereon. As discussed
above, however, the
package can take a variety of forms having a variety of configurations or
openings therein
suitable for closure by the reclosable fastener 12, and specifically the
opposing portions or
patterns of adhesive 30 and 32.
[00291 In this exemplary form of FIGS 1 and 2, the package 10 may also
include a dead fold
20 along a bottom edge 22 thereof and transverse or side seals 24 along side
edges 26 thereof so
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that the package 10 forms a cavity 28 between the front pane116 and the back
panel 18 for
containing an item, such as a food item, comestible, or other material. The
package 10 may
further include a top seal 23 (FIG. 2A) above the adhesive-based reclosable
fastener 12, when
the package 10 is oriented in an upright position. It will be appreciated that
the form of package
is only an example of but one type of a package suitable for use with the
adhesive-based
reclosable fastener 12. As set forth above, other shapes, configurations,
materials, and
container/package types may also be combined with the adhesive-based
reclosable fastener 12.
The package 10 may further include other folds, seals, gussets, and/or flaps
as generally needed
for a particular application. The package 10 may also include a bottom seal at
the bottom edge
22 instead of a fold 20. Optionally, the package 10 may also include non-
reclosable peel seals 11
(shown, for example, in FIGS. 1 and 2A) either above or below the reclosable
fastener 12 as
generally provided in United States Application Serial Number 11/267,174.
Additionally, the
package 10 may also optionally include a rupturable line of weakness 13 (FIG.
2A) between the
reclosable fastener 12 and an upper end of the package 10, which, upon
complete rupturing, is
adapted to remove a portion of the upper end of the package 10 by providing a
removable
shroud 15 above the reclosable fastener 12 to provide a package opening, as
shown in FIG. 2B.
[0030] Referring now to FIG. 4, one form of the adhesive-based reclosable
fastener 12 is
illustrated that includes the opposing adhesive layers or adhesive portions 30
and 32 with one
of the layers 30 disposed on the front pane116 and the other layer 32 disposed
on the back panel
18. The fastener layers 30 and 32 are generally aligned with each other such
that facing outer
surfaces 34 and 36 of each fastener layer 30 and 32, respectively, oppose each
other and are
positioned to substantially contact each other in the closed or sealed
condition as the layers 30
and 32 are engaged together. The adhesive layers 30 and 32 are preferably
positioned at interior
or inner surfaces of the front panel 16 and the back panel 18, as shown in
FIGS. 4, 5A, and 5B.
Alternatively, with other package forms, the adhesive layers 30 and 32 can be
disposed on
opposing portions of a hinged container (FIG. 3A), on overlapping flaps (FIG.
3B), on a package
body and a cover flap (FIG. 3C), or other package surfaces as desired. As
shown, the shape,
pattern, and configuration of the layers 30 and 32 may vary as desired or
required by a
particular application. The adhesive portions 30 and 32 may also be provided
in intermittent
shapes, patterns, lines that may be regularly or irregularly spaced across the
package panels.
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[0031] Preferably, the opposing adhesive layers 30 and 32 can each be
supplied in the form
of a liquid coating mixture that may be heated and applied to the package
substrate at a warm
temperature, such as at about 160 F (71 C), but can be in the range of about
86 F (30 C) to about
190 F (88 C). After application of coating, the applied coating mixture, which
can contain an
added photoinitiator, can be exposed to UV treatment to cure (polymerize) the
coating and to
form the solid adhesive-based fastener 12 on the package substrate. In one
aspect, the applied
coating can have a thickness of about 0.0005 inches, but can be in the range
of about 0.0001
inches to about 0.005 inches; however, depending on package design,
configuration, and
requirements, a much thicker coating can be applied. By one approach, the
coating mixture
does not contain any or any substantial solvent that needs to be removed and
may be easily
applied to the package substrate on high speed coating and printing lines.
[0032] The first component of the adhesive is one or more UV-curable
acrylate or acrylic
oligomers. For instance, the UV-curable acrylic oligomer may be an acrylic or
methacrylic acid
ester having multiple reactive or functional groups (i.e., acrylic or
methacrylic oligomers). In
general, a functional group includes one UV reactive site. By one approach, UV
reactive sites
are most commonly carbon-carbon double bonds conjugated to another unsaturated
site such as
an ester carbonyl group. By one approach, the UV-curable acrylic oligomer is
an acrylic or
methacrylic acid ester of a multifunctional alcohol, which means the oligomer
has more than
one acrylated or methacrylated hydroxyl group on a hydrocarbon backbone of the
oligomer. By
one approach, the adhesive may include about 1% to about 90% by weight of the
UV-curable
acrylic oligomers and with functionalities of about 1.2 to about 6Ø In
another approach, the
UV-curable acrylic oligomers may have a functionality of about 2.0 to about
3Ø In other
approaches, the adhesive may include about 20% to about 70% by weight (in some
cases, about
33% to 60% by weight) of the acrylic oligomers.
[0033] In one form, the multifunctional UV-curable acrylic acid ester is an
acrylic acid ester
of a vegetable oil having a reactive functionality of 2.0 or greater. In
another aspect, the
UV-curable acrylic oligomer can comprise an epmddized soybean oil acrylate. In
general, the
amount of the UV-curable acrylic oligomers used, based on a preferred adhesive
component
ratio (ACR) (to be discussed herein), can impact the properties of the final
adhesive. For
instance, where the amount of the UV-curable acrylic oligomer is too low,
based on the
preferred ACR, the cure rate of the final adhesive is too slow. On the other
hand, where the
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amount of the UV-curable acrylic oligomer is too high, based on the preferred
ACR, the final
adhesive may be adequately cured, but can have inadequate self adhesion
properties to seal and
reseal.
[0034] The second component of the adhesive is a tack control agent. By one
approach, the
adhesive may include about 1% to about 65% by weight of the tack control
agent. In another
approach, the tack control agent can be present in amounts from about 20% to
about 65%. The
tack control agent can include a tackifying resin or a curable polymer/monomer
combination
that when cured can produce the desired levels of tack and self-adhering
properties appropriate
for the redosable fastener 12. In one aspect, the tack control agent can
comprise an aliphatic
urethane acrylated oligomer. Many other types of tack control agents suitable
for UV-curable
PSA adhesives may also be used in the reclosable adhesive system.
[0035] An optional third component of the adhesive is at least one
elastomeric or rubber
component. By one approach, the elastomeric component may include at least one
curable
acrylated (i.e., acrylic modified) or methacrylated esters of a hydroxy-
terminated elastomeric
polymer (i.e., an elastomeric polyol). This elastomeric component can include
acrylic-modified
polybutadiene, a saturated polybutadiene and/or a flexible polyurethane. In
one aspect, a
methacrylated polybutadiene can be provided. The elastomeric material can be
provided in
amounts of about 0% to about 20% when used in the adhesive. In one aspect, the
elastomeric
material is provided in amounts of about 5% to about 15%. Satisfactory
adhesives can be made
with the desired low tack, resealable properties as described herein without
the elastomer
component; however, it is believed that the elastomeric component aids in
achieving an optimal
coating performance. The optimal adhesive performance can be defined by
properties such as
self-adhesion, tack, viscosity, and cure rate, just to name a few. The
elastomeric component is
useful for adjusting peel strength properties, substrate adhesion strength,
increasing flexibility,
viscosity control, and cure rate modulation.
[00361 To achieve the balanced peel, tack, and bond to the package
substrate as described
herein, it was determined that the amounts of the three adhesive components
need to fall within
a specific adhesive component ratio (i.e., ACR) of the acrylate oligomer
relative to the
elastomeric and tack components. Preferably, the ACR for the adhesive is:
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(wt% of acrylate oligomer) = 0.5 to 1.5.
(wt% of elastomeric material + wt% of tack control agent)
In a preferred approach, the ACR can be in the range of about 0.8 to about
1.5.
100371 The range for the ACR of the three components in the formulation has
been found to
provide a unique adhesive formulation with a low tack property to non-like
substances (i.e.,
machine components, crumbs, food pieces, and the like), yet can seal to itself
with sufficient
bond or peel strength to maintain a seal therebetween as well as resist
contamination. The
adhesive in this specific ACR also provides for a resealable function that
does not significantly
reduce or lose its seal-peel-reseal qualities upon being subjected to repeated
open and close
operations. An ACR value below about 0.5 is generally undesired because the
adhesive would
require significantly large amounts of UV energy to cure. If the ACR is above
about 1.5, the
adhesive would cure quickly, but it would also have low (or no) peel strength,
unacceptable for
the adhesive closure herein. In addition to the desired range of the ACR, a
satisfactory adhesive
formulation in some cases may also have certain other parameters such as
mixture-stability of
the components, a certain viscosity of the formulation, a certain cure rate,
and/or a certain peel
strength.
[0038] Not only is the ACR of the adhesive components desired, but the
adhesive
components must also be compatible with each other such that they form a
stable flowable
liquid mixture. As used herein, the adhesive is considered stable when it (at
a minimum the
two or three main components) remains a homogeneous liquid, i.e., there is no
visible phase
separation of the components and no gel formation, while being held at room
temperature
(about 70 F-75 F) for up to three days.
[0039] In addition, the adhesive formulation can have a viscosity in the
range of about
10,000 to about 50,000 centipoise (cPs) or less when at room temperature, or
about 2,000 cPs or
less at about 160 F (71 C) and, in some cases, about 200 cPs or less at about
160 F (71 C). This
viscosity range provides for applying the adhesive to a film substrate using
conventional
printing, roll coating, slot-die application techniques or other suitable
application methods as
needed for a particular application.
[0040] To produce a sufficiently cured adhesive layer on the film
substrate, the adhesive can
be cured using UV light sources capable of delivering energy in the range of
about 100 mJ/cm2
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to about 800 mJ/cm2. This in turn helps to ensure that the adhesive has
sufficiently cured as
determined by an MEK rub resistance test value (ASTM D5402-06) of about 100
double rubs or
more (to be discussed in further detail herein).
[00411 The average initial peel strength of a properly cured adhesive can
be in the range of
about 200 gpli to about 900 gpli and, in some cases, about 280 gpli to about
800 gpli, and in
other cases, about 280 gpli to about 650 gpli, as measured by ASTM
D3330/D3330M ¨04
method F. The adhesive is also designed to retain its average peel after
repeated open and close
operations (i.e., adhesion retention). Preferably, the cured adhesive can
retain its average initial
peel adhesion between about 280 gpli and about 800 gpli up to at least five
repeated peel-reseal
cycles. This is called the adhesive retention valve. Preferably, the adhesion
retention value
upon peeling-resealing-peeling can be between about 30% to about 200%
retention of the initial
value. Upon contaminating the adhesive with crackers, the adhesion retention
value can be
between about 30% to about 150% of the initial value, where the cracker
contamination test
method is as described herein.
[0042] By some approaches, a UV photoinitiator can also be added to the
adhesive to aid in
initiating the curing process. The photoinitiator can be present in amounts of
about 0.1% to
about 5%. In one aspect, a photoinitiator can comprise a blend of benzophenone
derivatives
and a synergist compound. A synergist compound is a compound that interacts
with the
excited benzophenone molecules to form free radicals by electron transfer and
hydrogen
abstraction. One example is a mixture comprising
trimethylbenzoyldiphenylphosphine oxide,
a-hydroxyketones and benzophenone derivatives, where the synergist compound
includes the
first two compounds listed. In another example, the photoinitiator is a-
hydroxyketone by itself.
In another aspect, a photoinitiator can comprise onium salts or other acidic
materials activated
by UV light. The binder can be comprised of cationically reactive materials
such as epoxides,
vinyl esters and the like. Optionally, these can also be cross-linked with
resins functionalized
with carboxylic acid, hydroxyl, or other nucleophilic groups.
[00431 In one form, the package substrate 14 can be flexible sheet material
or film, which
may be formed of various plastic polymers, co-polymers, papers, foils or
combinations thereof.
The film substrate may be a multi-layer coextrusion and/or a laminate with
constructions to
enhance interfacial bonding with the UV-cured adhesive fastener 12. In
general, the polymeric
- 12 -
layers may include polyolef ins such as polyethylene (high, medium, low,
linear low, and/or
ultra low density polymers including metallocene or polypropylene (oriented
and/or biaxially
oriented)); polybutylene; ethylene vinyl acetate (EVA); polyamides such as
nylon; polyethylene
terephthalate; polyvinyl chloride; ethylene vinyl alcohol (EVOH);
polyvinylidene chloride
(PVDC); polyvinyl alcohol (PVOH); polystyrene; or combinations thereof, in
monolayer or
multi-layer combinations. In one aspect, the film substrate includes EVA. By
one approach, the
film substrate can have a film thickness between about 0.5 mils to about 5
mils thick. Examples
of suitable film substrate may be found in U.S. Publication Nos. 2008/0131636
and
2008/0118688.
[0044] By one approach, the package substrate 14 may be a single layer or a
multi-layer film.
An exemplary multi-layer film may include an inner heat sealable (sealant)
layer to which the
adhesive fastener 12 is bonded and one or more structural and/or functional
layers. In one
particular example, the package substrate 14 may include the inner sealant
layer and an outer
structural layer including one or more layers of high density polyethylene
and/or one or more
layers of nylon. The inner sealant layer may include various polymers and/or
blends of
polymers. By one approach, the package substrate 14 and/or the inner sealant
layer may
include blends of ethylene vinyl acetate (EVA), polyethylene (such as linear
low density
polyethylene-LLDPE), and one or more optional adhesion promoting filler
particles dispersed
throughout to be described in more detail below. For example, the inner
sealant layer may
include about 60% to about 80% EVA, about 5% to about 20% polyethylene, and
about 3% to
about 15% of the adhesion promoting filler particles or a filler composition
including the
particles. Such construction may form a polymeric dispersion in which the EVA
may be a
primary or continuous phase in which the polyethylene and filler/filler
composition is a
dispersed phase therein. With this approach, the adhesive-based fastener 12 is
applied to the
inner sealant layer, which forms the inner surface of the package 10. By
another approach, the
multi-layered film may include multiple layers such that about 85% of the
total film thickness is
high density polyethylene and about 15% of the film thickness is the sealant
layer.
[0045] By another approach, the package substrate may be a paperboard or
the like material
having a coating or polymer layer thereon. The coating or polymer layer may
include an
ethylene vinyl acetate (EVA), polyethylene, and blends thereof. This coating
or layer may
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include the fillers described above and may also include the fillers supplied
in the maleic
anhydride grafted linear low density polyethylene carrier (MA-LLDPE) as
described below.
[00461 In one form, the package substrate 14 has a construction to enhance
the primary bond
or an interfacial bonding between the adhesive and the package substrate 14.
To this end and
by one approach, the package substrate may include the adhesion promoting
filler particles
blended with at least a portion of the package substrate 14, such as, the
adhesion promoting
filler particles blended into the inner sealant layer of a film as described
above. By one
approach, the adhesion promoting filler particles may be micro- or nano-sized
fillers of clay,
calcium carbonate, montrnorillonite, microcrystalline silica, dohnite, talc,
mica, oxides, (silicon
oxides, aluminum oxides, titanium oxides, and the like) and other additives
and/or
combinations thereof, blended into at least the inner, sealant, or surface
layer(s) of the package
substrate to enhance the primary bonding of the adhesive fastener 12 to the
package substrate
14. In particular, an organoclay is used, and in one aspect the organoclay is
organically
modified montmorillonite or, in some cases, an exfoliated organoclay.
Organoclay is an
organically modified natural clay such as a montmorillonite clay that is
processed or treated
with surfactants such as quaternary ammonium salts. Montmorillonite is a
phyllosilicate group
of minerals that typically comprises a hydrated sodium calcium aluminum
magnesium silicate
hydroxide. While not wishing to be limited by theory, the organoclay-filled
substrate and, in
particular, the organically modified fillers can have the ability to aid in
producing operable and
reclosable adhesive-based closures that do not delaminate from the package
substrate 14 upon
being peeled open.
[00471 In some approaches, useful adhesion promoting filler particles have
a surface area
greater than about 100m2/gram and an aspect ratio greater than about 10. In
other approaches,
the organoclay used in the sealing layer typically comprises a plurality of
particles. In one
variation, the organoclay comprises a plurality of particles having at least
one spatial dimension
less than about 200 urn. In another variation, the organoclay comprises a
plurality of particles
having at least one spatial dimension less than about 100 urn. In another
variation, the
organoclay comprises a plurality of particles having at least one spatial
dimension less than
about 50 nut In still another variation, the organoclay comprises a plurality
of particles having
spatial dimensions greater than or equal to about 1 urn. In still another
variation, the
organoclay comprises a plurality of particles having spatial dimensions
greater than or equal to
- 14-
CA 02732720 2011-02-25
about 5 run. In another variation, the organoclay comprises platelets having
an average
separation between the platelets of at least about 20 angstroms. In yet
another variation, the
organoclay comprises platelets having an average separation of at least about
30 angstroms. In
still another variation, the organoclay comprises platelets having an average
separation of at
least about 40 angstroms. Typically, before combining with the thermoplastic
polymer, the
organoclay comprises platelets having an average separation between from about
20 to about 45
angstroms. Advantageously, upon combining with the substrate or at least the
sealant layer
thereof, the organoclay becomes dispersed throughout such that the average
separation is
maintained or, in some cases, increased.
[00481 Effectively dispersing the clay or other adhesion promoting filler
particles in
polyethylene and EVA used for the sealant layer can be a challenge due to
incompatibility of
clay fillers and certain polymers. Thus, supplying the adhesion promoting
filler particles using
a filler composition including the filler blended with a compatible carrier
helps aid in the
mixing and dispersing of the filler into the sealant layer of one form of the
package substrate 14.
By one approach, the adhesion promoting filler particles can be supplied in a
maleic anhydride
grafted linear low density polyethylene carrier (MA-LLDPE). By another
approach, the carrier
may be a blend of MA-LLDPE and unmodified polyethylene. While not wishing to
be limited
by theory, the maleic anhydride portion of the carrier has an affinity for the
filler particles, such
as clay, and the polyethylene portion of the carrier mixes well with other
polyethylene and
ethylene-like polymer components of the sealant layer or package substrate 14.
Exemplary clay
filler compositions may be obtained from PolyOne Corporation (Avon Lake,
Ohio). Without
wishing to be bound by theory, it is believed that the organically modified
clay particles, which
may be highly polar, and/or the maleic anhydride grafted linear low density
polyethylene
(MA-LLDPE) carrier resin present with the clay fillers serve to promote
adhesion of the cured
adhesive coating to the substrate surface by increasing the surface energy of
the substrate layer.
[0049] Additionally, it is also believed that on a microscopic level the
clay or other adhesion
promoting filler particles may impart an increased surface roughness to the
substrate, positively
affecting the coefficient of friction of the substrate and increasing the
available contact surface
area between the substrate and the adhesive, thereby providing more sites for
chemical and/or
mechanical bonding to occur. This will be discussed in more detail below with
respect to FIG.
8. By one approach, approximately 0.5% to about 20% by weight of the filler
composition in the
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CA 02732720 2011-02-25
sealant layer is expected to have a beneficial impact on the primary bond
strength of the
adhesive fastener 12 to the package substrate 14 so that the primary bond to
the substrate is
greater than the peel adhesion between the adhesive layers 30 and 32 such that
the fastener 12
does not delarninate upon opening. Additionally, the filler or particles may
roughen the surface
of the substrate layer enabling it to slide freely over metal surfaces of
packaging equipment
without binding, thus enabling the reduction or elimination of a migratory
slip additive in the
film. In some approaches, the inner sealing layer having the filler has a
higher degree of surface
roughness, such as an average roughness of about 1500 angstroms to about 5000
angstroms.
The sealing layer may also have a higher tensile modulus than layers without
the filler. In some
approaches, the inner sealant layer has a tensile modulus of about 500 to
about 2000 mPa.
100501 An optional component of the package substrate 14 can include a
migratory slip
additive, which helps to decrease coefficient of friction between the film and
other surfaces,
allowing the substrate to slide freely over metal surfaces or itself. In one
aspect, an erucamide
slip additive (i.e., an unsaturated fatty primary amide) can be provided. In
prior films, high
levels of slip additives have been used ranging from 2000 ppm to 7000 ppm;
however, it has
been discovered that at these high levels it is difficult for the adhesive 12
to bond to the low
energy surface of the film because the slip additive blocks surface sites
where adhesion can take
place. However, the addition of the filler allows for a much lower level of
the slip additive to be
used, such as less than about 1000 ppm. In other cases, the film has less than
about 700 ppm of
the slip additive or in yet other cases no slip additive. Since the use of the
filler reduces the
coefficient of friction between the film and other surfaces, an effect that
was previously
achieved with addition of the migratory slip additive, this allows for the
migratory slip additive
concentration to be lowered or eliminated. A lower migratory slip additive
level than typically
used can also help to increase the bonding of the cured coating to the
substrate both initially
and over time because there is less of the additive to interfere with the
bonding of the coating to
the substrate. While not wishing to be limited by theory, it is believed that
the fatty acid amides
in slip additives, which are low molecular weight components, can migrate or
bloom to the
surface of the film affecting the strength of the bond between the film's
surface and the adhesive
fastener 12. While corona treating or flame treating may initially bum off any
fatty acid amides
on the surface of the film resulting in an initial good bond strength of the
adhesive. Over time
additional fatty acid amides can migrate or bloom to the film surface, which
results in a reduced
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CA 02732720 2011-02-25
bond strength over an extended shelf life. Additionally, a high level of slip
additive may also
migrate or bloom to the surface of the adhesive portions, which may negatively
impact the
cohesive and bond strength therebetween.
100511 Additionally, prior to applying the adhesive to the package
substrate 14, the, substrate
can undergo a surface pretreatment to increase the surface energy, and/or
application of a
primer coat. For example, surface treatments may include corona treating,
plasma treating,
flame treating, and the like or chemical coatings, such as primers or adhesion
promoters may
also be used. A corona treatment can increase the surface energy of the
substrate which
improves the coating's ability to bond and remain bonded to the substrate. A
corona pretreat-
ment can include a cloud of ions that oxidize the surface and make the surface
receptive to the
coating. The corona pretreatment basically oxidizes reactive sites on the
polymer substrates. If
corona treating, ideally the surface energy after treatment should be about 36-
40 dynes/cm or
greater at the time of coating application.
[0052] Without wishing to be bound by theory, it is believed that the
corona treatment of the
substrate surface helps to provide for a strong bond between the coating layer
and the substrate
surface due to the increased surface energy of the substrate. In addition to
the corona treat-
ment, the combination of the corona treatment with a low concentration of a
slip additive and
the incorporation of a filler composition within the substrate film 14
together result in a strong
bond between the reclosable fastener and the substrate.
[0053] Turning to the coating process, the liquid coating formulation can
be heated to a
certain temperature in the range of about 86 F (30 C) to about 190 F (88 C)
and preferably
about 120 F (49 C) to about 160 F (71 C) such that the viscosity is low enough
for pattern
application by flexographic, rotogravure, or slot-die processes onto the
package substrate 14.
The package substrate 14, as discussed above, cart contain a filler throughout
(or at least
through certain portions or layers) and less than about 1000 ppm of a slip
additive in the
polymer film substrate. After the liquid coating material is applied to the
substrate it can be
UV-cured to form a solid reclosable adhesive fastener. In one aspect, the UV
radiation (about 10
run to about 400 run wavelength radiation) can be supplied at art energy level
between about
100 mJ/cm2 to about 800 mJ/cm2, and in other cases about 400 mJ/cm2 to about
730 mJ/cm2.
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CA 02732720 2011-02-25
[00541 As shown in the examples below, it has been discovered that UV-
curing is preferred
because in general other forms of curing (such as electron beam) do not
provide for the desired
bond and peel when using the ACR values described above. In one aspect of UV-
curing, a
photoinitiator comprising a blend of benzophenone derivatives and a synergist
compound can
be used in the coating formulation, which can result in the formation of free
radicals. In free
radical initiated polymerization systems, the curing reaction stops at the
moment the UV energy
source is withdrawn. An alternative mechanism for UV curing is cationic
initiated
polymerization. Cationic initiated polymerization systems, which use
photoinitiators, such as
oniuni salts or other UV activated acid catalysts to crosslink epoxides or
vinyl esters, differ from
free radical initiated systems in that the curing reaction continues even
after the source of UV
energy is withdrawn.
[0055] As mentioned above, the adhesive-based reclosable fastener 12
generally has a peel or
bond strength to permit the opposing layers 30 and 32 to be bonded together in
order to close or
re-seal the package 10. For example, a consumer may press the two opposing
layers into
engagement to seal or close the package as illustrated by the arrows 33 in
FIG. 4, and as shown
pressed together in FIG. 5B. By one approach, the bond between adhesive layers
30 and 32 is
generally sufficient to seal the layers 30 and 32 together and, in some cases,
form a hermetic
seal. As used herein, hermetic is understood to mean a generally air tight
seal. In one example,
the selected pressure sensitive adhesive (PSA) forming the layers 30 and 32
may exhibit an
initial cohesive or peel bond strength of about 200 g/inch to about 900
g/irtch (i.e., or grams per
lineal inch, gpli), and in some cases, between about 200 g/inch to about 400
g/irtch as measured
by the ASTM peel test D3330/D3330M-04 method F; however, the reclosable
fastener 12 may
have other peel strength values dependent on the particular application or
particular
measurement test. In one aspect, the preferred peel strength ranges from about
280 gpli to
about 800 gpli. Peel strengths greater than this level (i.e., greater than
about 900 gpli) are
generally too high when used with certain packages to be useful for a peelable
and resealable
package since the substrate may be damaged when the cohesive bonds are broken
at these high
strengths. The selected PSA may further have a subsequent peel bond strength
(adhesive
retention) preferably after five open/close operations of at least about 200
gpli, or in other cases
at least about 30% to about 200% of the initial peel, and, at a minimum, about
50 g/indi to
- 18 -
CA 02732720 2011-02-25
=
about 200 g/inch, where the subsequent peels comprise the seal-reseal action
that occurs after
the initial opening of the package 10 and separation of the reclosable
fastener 12.
[00561 The adhesive-based fastener 12 also preferably has a relatively low
tack level that
enables the fastener to minimize and, preferably, limit the adhesion of the
fastener 12 to
unwanted materials (i.e., contamination) and surfaces, such as food particles,
forming
equipment surfaces, rollers, and the like. By one approach, the adhesive may
have a tack level
to undesired surfaces not exceeding about 5 psi when preloaded with about 4.5
pounds using
the ASTM probe tack test D2979. By another approach, the PSA coating may have
a tack level
not exceeding about 15 psi when preloaded with about 10 pounds. However, the
tack level may
also vary depending on the particular PSA and application thereof and
measurement test used.
Using another metric, the adhesive-based fastener 12 exhibits a tack as
measured by a modified
version of a rolling ball test in ASTM D3121 where the adhesive tack permits
about 1 inch to
about 8 inches of ball travel. In some cases, up to about 14 inches of ball
travel. The modified
D3121 test is explained further below and in the examples.
[0057] Even with such relatively low tack levels to undesired surfaces, the
adhesive layers 30
and 32 still form a sufficiently strong primary bond with the package
substrate 14 forming the
front and back panels 16 and 18 so that the adhesive layers 30 and 32 are not
substantially
delaminated therefrom when the package 10 is opened. By one approach, the
primary bonding
strength of the adhesive layers 30 and 32 to the package substrate 14 at an
interface 38 thereof is
generally greater than the peel strength of the cohesive material itself. For
example, the
primary peel strength of the selected cohesive material to the film substrate
forming the front
and back panels 16 and 18 is greater than the peel force between layers 30 and
32 and generally
greater than about 600, in other cases greater than about 900 g/inch. In other
cases, greater than
about 1000 g/inch and, in yet other cases, greater than about 1200 g/inch. In
other instances,
the primary peel strength may range from about 600 to about 1200 g/inch (in
some cases, about
600 to about 900 gpfi). However, the peel strength may also vary depending on
the package
substrate 14, the PSA, and other factors,
[0058] In addition, it is further anticipated that interfacial, mechanical,
or chemical bonding
of the adhesive materials 30 and 32 to the substrate 14 may be enhanced
through particular
constructions of the substrate materials 14 to increase bonding surface energy
as generally
- 19-
CA 02732720 2011-02-25
discussed above. As discussed above, the substrate 14 may be a single layer or
a multi-layer
film, and, in such a case, it is preferred that at least an innermost layer of
the substrate film 14
forming the front and back panels 16 and 18 may be composed of a polymer blend
containing
ethylene vinyl acetate (EVA) and linear low density polyethylene (LLDPE).
Where an additive
or the adhesion promoting filler particles are also present, it is preferably
present in and
dispersed throughout at least this innermost layer (i.e., EVA /LLDPE blend
innermost layer).
Preferably the EVA is the predominant component of the blend, at about 65% to
about 90%, and
the LLDPE is a minor component of the blend, at about 5% to about 25%.
Preferably, the
substrate, innermost layer, and/or the blended EVA/LLDPE layer would have low
concentrations of migratory slip additives (commonly added to packaging
substrate in order to
obtain a coefficient of friction suitable to process the substrate on form,
fill, and seal machines).
It is appreciated that such additives may include amounts of fatty acid
amides, and it has been
discovered that such compounds can affect the bond strength of cohesive
materials to the
substrate. By one approach, therefore, the package substrate 14 may have less
than about 1000
ppm of fatty acid amides (i.e., migratory slip additives) throughout the
innermost layer or, in
some cases, throughout the entire substrate 14.
[0059] While not wishing to be limited by theory as mentioned above, it is
believed that fatty
acid amides, which are low molecular weight components, can migrate or bloom
to the surface
of the substrate affecting the strength of the bond between the substrate's
surface and the
cohesive materials. While corona treating or flame treating may initially burn
off any fatty acid
amides on the surface of the substrate resulting in an initial good bond
strength of the PSA, over
time additional fatty acid amides can migrate or bloom to the substrate
surface, which results in
a reduced bond strength over an extended shelf life. As a result, it is
desired to reduce the fatty
acid amide content in the substrate (either the inner most layers or the
entire substrate) to levels
below about 1000 ppm, which provides for both good initial bond strength and
good long term
bond strength because there are such small amounts of these impurities to
bloom to the
substrate surface over time. Alternatively, such substrate formulation
variations may also be
combined with use of other surface treatments (corona treating, plasma
treating, flame treating,
and the like) or other coatings as needed for a particular application.
[0060] By one approach, suitable flexible films forming the front and back
panels 16 and 18
may be a polyethylene based film about 0.5 mils to about 5 mils thick and, in
some cases, about
- 20 -
3 mils thick. Turning to FIG. 8 for a moment, one approach of a flexible film
forming the front
and back panels 16 and 18 is shown as a multi-layer, coextruded film including
a structural base
of one or more layers (two are shown) of a high density polyethylene 702
(HDPE) and an inner
or adhesive receiving layer (such as the above described sealant layer) of an
EVA/LLDPE heat
seal layer 704 filled with the adhesion promoting filler particles 706. With
this approach, the
adhesive fastener 12 is applied to the inner EVA/LLDPE heat seal layer 704,
which forms the
inner surface of the package 10.
[0061] As shown in FIG. 8, the adhesion promoting filler particles 706,
which may be
organoclay, is generally exaggerated in size for illustrative purposes, but is
expected to be
dispersed throughout the inner EVA/ LLDPE or sealant layer 704, and it is
expected that at least
some of the adhesion promoting filler particles (identified as filler 708 in
the drawing), for
example, may have at least a portion thereof exposed or protruding slightly
out of an outer
surface 710 of the EVA/LLDPE layer 704, as generally provided in Application
Serial Number
12/435,768. Alternatively, the adhesion promoting filler particles may not be
exposed at the
surface 708, but they may create a rougher outer surface, which increases the
surface area for
bonding to the adhesive. While not wishing to be limited by theory, the
adhesion promoting
filler particles 708 at the surface or exposed from the surface combined with
corona treatment
and/or the use of certain carriers for the filler may aid in the bonding of
the fastener to the
substrate, which may provide an effective primary bond to the substrate that
is greater than the
cohesive peel strength between the two adhesive layers 30 and 32. In general,
when the
cohesive peel force was less than approximately 600 g/inch to about 900 g/inch
between the
two adhesive layers 30 and 32, no delamination occurred during repeated peel/
reseal cycles
between the fastener and the substrate when the fillers and sealant
constructions described
herein were used. Thus, the primary bond of the adhesive layers 30 and 32 to
the substrate with
the adhesion promoting filler particles 706 therein is greater than about 600
gpli and, in some
cases, greater than about 900 gpli as discussed previously.
[0062] In other instances and while not wishing to be limited by theory,
the enhanced
primary bond between the adhesive and substrate may be due to a diffusion of
the liquid or
uncured adhesive into gaps, voids, or other spacing of the adhesion promoting
filler particles
(such as the spacing between the organoclay platelets) and, in particular,
into these gaps, void,
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CA 02732720 2011-02-25
or other spacing of the filler particles having at least a portion thereof
exposed at the surface of
the substrate. Upon subsequent polymerization, the diffused liquid adhesive
forms into a solid
adhesive that may be interlocked, tied or otherwise bound to the adhesion
promoting filler
particles to increase the primary bond to the substrate. In yet other
instances and again not
wishing to be limited by theory, the enhanced primary bond may also be due to
an affinity of
the polar portions of the adhesive to the polar filler particles. In general,
the filler particles are
more polar than the substrate and, thus, provide a greater bond thereto.
[0063] With the adhesive based fastener and substrates described herein, an
adhesive based
reclosable fastener can be repeatedly opened and closed without delamination
from the
opposing panels 16 and 18, can be achieved in a fastener that is stable over
time, and produces
generally repeatable results even after fouling or contamination with foreign
material, such as
food crumbs. Even if the adhesive-based fastener is contaminated with food
crumbs or edible
oils, the adhesive-based fasteners herein do not exhibit an unusable drop-off
in cohesive
properties.
[00641 By one approach, the adhesive fasteners herein maintain a cohesive
or self-adhesion
peel strength when contaminated with product, food crumbs, oils, and the like
between about
50 g/inch to about 900 g/irtch, and exhibit a residual adhesion or residual
cohesion after fouling
or contamination of at least about 20%, and in some cases about 30% to about
150% of the
cohesion peel levels prior to contamination. As used herein, adhesion
remaining or residual
cohesion is a measurement of the peel strength after direct contact of the
adhesive surface to
food particles, relative to the peel strength of a clean or uncontaminated
fastener, exhibited as
a percentage.
[0065] The reclosable fastener can be provided such that it can be peeled
and resealed at
least 5 to 10 times, and preferably more, yet still maintain its low tack and
resealable charac-
teristics. Furthermore, upon contact with itself, the reclosable fastener can
recover all or some
of its initial peel strength values. Depending on the final formulation of the
adhesive coating
used, the reclosable fastener can recover its peel strength in as little as
two to three minutes
between peel-reseal cycles. However, in some cases, shorter or longer time
periods may be
required to recover its peel strength between peel-reseal cycles. In some
aspects, the peel
-22 -
CA 02732720 2011-02-25
strength of the reclosable fastener can actually increase upon prolonged
contact between
opposing adhesive layers.
[00661 Turning back to FIGS. 4-5B, to close the package 10 a user's fingers
(or a machine
closing operation during package filing operations) squeezes the front and
back panels lband
18 together in the direction of arrows 33, as shown in FIG. 4, to engage the
opposing adhesive
layers 30 and 32 to form a cohesive bond therebetween to sealably close the
package 10. To
open the package 10, the user or a machine can peel back package portions 56
(FIG. 5B)
positioned above the fastener 12 in opposite directions 57 to peel the
adhesive layer 30 from
the adhesive layer 32. By one approach, the layers 30 and 32 are configured to
be closed and
re-opened multiple times and, in some cases, the layers 30 and 32 preferably
have sufficient
structural and bond integrity to be closed and opened about 5 to about 10
times or more.
However, particular layers and packages can be configured to be opened and
closed any
number of times depending on the particular configuration, coating weight, and
other
parameters of the cohesive layers and package substrate.
[00671 The package 10 having a reclosable fastener 12 can be used to store
a wide variety of
food and non-food items. Food items that may be stored can include snacks,
such as trail mix,
nuts, seeds, dried fruits, cereals, cookies, crackers, snack chips, chocolate,
confections, and the
like. The package 10 can also be used to store beverages, cheese, meat,
cereal, ground coffee
beans, desserts, pet food, and the like. Other possible applications of the
package 10 can include
packaging for various items that will benefit from resealability and permit
multiple openings.
This can include non-food items, such as potting soil, sandwich bags, first
aid kits, nuts and
bolts, office supplies, cleaning supplies, laundry supplies, disposable eating
utensils, CDs
and/or DVDs, toys, modeling supplies, art and craft supplies, electrical
supplies, and the like.
Many other examples are, of course, possible.
[0068] The adhesive fastener described herein can also be used for non-
packaging
applications, such as for consumer products that require a reusable fastener.
For example, the
adhesive fastener could be used as fasteners for disposable diapers, as
fasteners on articles like
athletic shoes, fasteners for jacket front openings, fasteners for pocket
closures, or other types of
clothing apparel, fasteners for office or school supplies such as folders and
portfolios, closures
on camping tents or backpacks, as repositionable labels or markers for posters
and maps for
- 23 -
CA 02732720 2011-02-25
educational supplies/classroom instructional materials, fasteners for arts and
crafts such as
scrap-booking, repositionable fasteners for board game pieces, or
repositionable strapping for
bundling goods during shipping that are easy to apply and remove.
[00691 Turning to FIGS. 6 and 7, an example of a suitable process 500 that
may be used to
apply a coating to a substrate having the reclosable fastener 12 thereon is
provided. A solvent
coating, printing, rotogravure, or flexographic printing process can be
provided to apply the
layers 30 and 32 to the substrate 14. It will be appreciated that other
application processes or
methods may also be used as needed for a particular application. By this
approach, the
substrate having the closure thereon can be a film wound up into a roll that
is later transferred
to a form, fill, and seal machine to form the package.
[00701 In this exemplary process 500, a supply of the substrate 14 may be
provided in a
large jumbo or roll 502 of base film, which may be a single layer or multi-
layer film having
EVA /LLDPE as the inner layer 504 to which the adhesives will be applied. The
film is then
unwound and directed to a first application station 506 where the adhesive
fastening layer can
be applied. For example, the liquid adhesive mixture may be applied to a first
engraved roll or
cylinder 510 that transfers the liquid PSA to a second or offset rubber roll
cylinder 512 having
an image or impression thereon 514 in the configuration, size, and shape of
the adhesive strip to
be applied to the film. The second cylinder 512 then transfers the PSA to the
moving film
substrate to form a first strip of the PSA containing material 516 on the web.
The liquid PSA can
have properties such as a viscosity between about 10,000 cPs to about 50,000
cPs at ambient
temperature (20-25 C), and less than about 2,000 cPs at about 70-75 C. When
applying the
liquid PSA coating, it can be preferred to apply the PSA coating at a
temperature of about 160 F
(71 C), but can be in the range of about 86 F (30 C) to about 190 F (88 C).
100711 After passing through an oven section 520 (which may be utilized to
apply mild
heating to assist with flow-out and leveling of the coating) the web 14 then
may be directed to
a UV-curing station 521 to cure the applied fastening layer. The UV station
521 can utilize
UV-light energy at about 10 nm to about 400 nm wavelength and between about
100 mJ/cm2
to about 800 mJ/cm2 energy dose and, in some cases, about 400 mJ/cm2 to about
730 mJ/cm2.
After the liquid coating layer has cured it is formed into the solid adhesive
fastener 12 upon the
package substrate 14. Then, if applicable to the particular form of package
substrate 14, the
- 24 -
CA 02732720 2011-02-25
substrate 14 may be wound up into an intermediate jumbo or roll 522 for
storage or transfer to
a subsequent package forming station, such as a form, fill, and seal process
600 as generally
illustrated in FIG. 7.
[0072] Referring now to FIG. 7, an exemplary form, fill, and seal machine
600 using the
intermediate roll 522 prepared from one form of the process 500 (which may be
singulated or
slit to an appropriate size prior to process 600) is illustrated to create one
example form of a
sealed package 602. In this example, a vertical bagger or flow wrapping
process is used that
wraps the substrate 14 around a filling tube 604. A first heat seal assembly
606 can form a first
machine-direction heat seal 607. A second transverse-direction heat seal
assembly 608 with an
integral trim tool can then form second and third transverse-direction heat
seals 609 and 611.
As shown in FIG. 7, the seal 609 is below an adhesive reclose fastener 613
created as described
above, but the seal 609 may also be above or both above and below the adhesive
reclose fastener
613. Finally, an integral trim tool within the transverse-direction heat seal
assembly 608 can cut
the substrate 14 between the adhesive reclose fastener 613 and the bottom seal
611 of an
adjacent package thereby separating the package that was just filled and
sealed from the
following package that is in the process of being filled. It will be
appreciated that the exemplary
processes of FIGS. 6 and 7 are only but one example of suitable methods of
forming and/or
filling packages having the UV-cured, adhesive reclosable fastener 12 thereon.
Other formation
methods may also be used as needed for a particular application.
[0073] Optionally, the coating mixture used to form the UV-cured, adhesive-
based
reclosable fastener 12 may include one or more additives or inert colorants to
change the
appearance of the fastener 12. For example and by one approach, the fastener
12 may include
titanium dioxide. Such optional additives may help identify the strips of
adhesive on the
opposing panels by making the adhesive more opaque, which may help make it
easier for a
consumer to re-seal the fastener because the consumer will be able to locate
the opposing
fastener strip easier.
[0074] In some aspects, a package can be created in accordance with a
method 800 and/or
a method 900 as generally shown in FIGS. 9 and 10. By one approach, as
generally shown in
FIG. 9, the low tack adhesive, configured as described above, is applied 802
to a package
substrate in a suitable pattern to dispose the adhesive-based fastener 20
thereon. The low tack
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CA 02732720 2011-02-25
adhesive is then cured 804, such as, for example, by UV-curing on the package
substrate. Once
the adhesive-based fastener 20 is applied and cured, the package substrate can
be formed 806
into the particular construction of the package 10, which can take any
suitable form, including
those shown in FIGS. 1-3. Once formed, the package 10 can then be filled, such
as with food:
products or the like. Alternatively, the package can, in some instances, be
formed first and have
the adhesive applied thereon.
100751 By another approach, as shown in FIG. 10, a method 900 of preparing
a package
substrate, which may be suitable for forming a more rigid package such as
those shown in
FIGS. 3A-3C, is shown. First, graphics, coatings, layers, and/or alphanumeric
content may be
printed or otherwise applied 902 on various inner or outer surfaces of the
package substrate,
which can be paperboard or the like. This can also include printing 902 an
overlacquer, a
polymer coating, or the like onto the package substrate as described above.
The overlacquer or
coating may include the filler as described above if needed to enhance bonding
of the adhesive
to the package. This application can be done via any suitable process,
including a slot-die
coating process, a flexo process, or a gravure process, for example. The
printing and/or coating
is then allowed to dry 906 so that the low tack adhesive, such as that
discussed above, can be
applied 906 to the substi ate by a suitable process, such as a slot-die
coating process, flexo
process, or a gravure process and the like. The low tack adhesive is then
cured 908. After
curing, the package substrate is then cut 910 into one or more blanks or other
package structure
by any suitable device, such as one or more dies, rotary dies, lasers, etc.,
and stored for future
use. When use is desired, the blanks are delivered 912 to the packaging line.
Alternatively, the
blanks can be formed in-line with the packaging line. On the packaging line,
the desired
package form is created 914 by folding the blanks about the various fold
lines, applying
permanent adhesive at overlapping portions, and adhering the overlapping
portions together.
Once the package is created, they can then be filled 916 with one or more
products, such as food
products, and closed for storage, shipping, and display. The filled packages
are then wrapped
918 in a clear overwrap film and assembled and sealed 920 with other wrapped
packages in an
outer master pouch or package. Multiple outer master pouches or packages are
packed 922 into
one or more cases and shipped to a customer, retail store, or the like.
Alternatively, the low tack
adhesive may be applied later in the process, such as after the die cut step
910, after the forming
step 914, and/or after the filling step 918 as needed for a particular
application.
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f00761 In another approach, the low tack reclosable adhesives described
herein may have
tack values (or at least a tack perception) and/or surface energy
substantially similar to that of
the packaging substrate without the low tack adhesive. For example, the low
tack reclosable
adhesive, when touched by the consumer, may have a tack level or at least a
perceived tack
level substantially the same as the uncoated substrate or film adjacent
thereto. By one
approach, this may be evidenced by a rolling ball tack test where tack values
of the low tack
adhesive are substantially the same as tack values of the uncoated film. For
example, values of
the rolling ball tack test (as described in the Exampks herein) for the low
tack adhesive may be
up to about 14 inches of ball travel. The uncoated film (that is, no adhesive)
may exhibit a
rolling ball tack value of about 16-17 inches (on average) of ball travel. In
some cases, the
rolling ball tack test results of the low tack adhesive may be only about 12
to about 17% lower
than the uncoated film.
[00771 In other approaches, the similarity of the surfaces of the adhesive
and uncoated film
may be evidenced by a surface energy of the low tack adhesive that may be
substantially similar
to the uncoated film. By one approach, for example, the surface energy of the
low tack adhesive
and the uncoated film may both be about 36 to about 38 dynes/cm, and, in other
cases, about 36
dynes/cm.
[00781 Advantages and embodiments of the fastener and package described
herein are
further illustrated by the following examples; however, the particular
conditions, processing
schemes, materials, and amounts thereof recited in these examples, as well as
other conditions
and details, should not be construed to unduly limit the fastener, package,
and methods. All
percentages are by weight unless otherwise indicated.
EXAMPLES
100791 Example 1
[00801 Various blends of acrylic oligomers, tack control agents and
elastomeric materials
were tested for compatibility and storage stability (stability being defined
as a mixture that does
not form gels or visibly separate after storing for up to 3 days at room
temperature). Table 1
below shows the combinations tested and the formulation levels used.
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10081] Table 1: Adhesive Formulations Tested for Stability
'Y. Component Provided in Final Adhesive Formulation
Adhesive
Acrylic Tack Tack Tack - Component Storage
Stability
Elastomer Elastomer
Oligomer Agent Agent Agent Ratio of
Liquid Blend
(ACR)
,
Observation after
Sample No. A B C D E F -
3 days
-
_
Stable, no visible
1
40 15 45 - - 0.67 gels, no phase
(Inventive)
, separation
Stable -but did
2
15 45 - 40 - 0 not cure because
(Comparative) -
too low ACR
Unstable, because
3 phases separated;
40 - 45 15 - - 0.67
(Comparative) components were
incompatible ,
Unstable, because
4
- - 45 15 40 0 phases separated
(Comparative)
and ACR too low
_
Stable, no visible
40 15 25 - - 20 0.67 gels, no phase
(Inventive)
separation
_
Unstable, because
6 phases separated;
40 15 - - - 45 0.67
(Comparative) components were
. incompatible
, 7 Unstable, because
60 - - - - 40 1.5
(Comparative) phases separated
,
Unstable, gel-like
8
- - - - 60 40 0 structure formed
(Comparative)
and ACR too low
The components are identified as follows:
A = acrylated epoxidized soybean oil (CN 111 US, Sartomer Company, Exton,
PA).
B = methacrylated polybutadiene (Ricacryl 3.500, Sartomer Company).
C = tackified aliphatic acrylate oligomer (CN 3001, Sartomer Company). This
component
comprises a blend of an aliphatic urethane acrylate and hydrocarbon tackifier
resins.
D = polybutadiene styrene copolymer (Ricon 184, Sartomer Company).
E = tackified aliphatic urethane acrylate oligomer (CN 3211, Sartomer
Company).
F = tackifier concentrate made with a light colored, low odor aromatic
resin (PRO 11236,
Sartomer Company).
Adhesive = (wt% Acrylic Oligomer)
Ratio (ACR) (wt% Elastomer + wt% Tackifier)
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CA 02732720 2011-02-25
[0082] Stability or compatibility of these adhesive components may be a
factor for
manufacture, shipping, in-plant storage, and use of the liquid coating
mixture. The stability
was judged visually by appearance and consistency of the observed formulation
after storage
over a period of 3 days (about, 72 hours). It was observed that Samples 1,2
and 5 in Table 1
provided visually satisfactory blends of the various adhesive components that
after 3 days
remained homogeneous, i.e., the components did not visibly separate or form
gels. Although
Sample 2 resulted in a stable formulation, this adhesive component had an
undesired ACR and
did not cure well (i.e., this can be seen from the MEK Rub Cure test in Table
3 below, for
similarly formulated Sample 10). However, Samples 1 and 5 provided stable
adhesive blends
that cured well and also had a desired ACR in the range of 0.5 to 1.5. The
other sample blends
either separated, became too viscous and/or gelled (i.e., Sample 8 became gel-
like after 3 days).
Sample 8 formed a gel, which indicated that the composition formed by the
aliphatic acrylate,
or component E, combined with the tackifier component F was not compatible.
[0083] Thus, to achieve a stable adhesive that is appropriate for use as
disclosed herein, the
stable adhesive generally needs to have one of the following and, in some
cases, more than one
of the following, and in other cases, all of the following factors: compatible
components,
curable, desired ACR, and all three component parts present (i.e., acrylic
oligomer, elastomer,
and a tack control agent).
[00841 Example 2
100851 Based on the initial adhesive compatibility results for the stable
formulations from
Example 1, these formulations were further refined to produce five
formulations of adhesive
coatings that were all stable for at least 24 hours as a blend of the
components indicated in
Table 2.
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CA 02732720 2011-02-25
[0086] Table 2: Revised Adhesive Formulations
% Component Provided in Final Adhesive Formulation
Adhesive Stability
Acrylic Tack Tack Tack
Elastomer Elastomer Component after 24
Oligomer Agent Agent Agent
Ratio (ACR) hours
Sample A
No.
9 40 15 45 0.67 Yes
15 45 40 0 Yes
11 40 15 20 25 0.67 Yes
12 50 45 5 1 Yes
13 45 45 10 0.82 Yes
[00871 The components A through F are as indicated above in Example 1.
Samples 9 and 10
correlate to Samples 1 and 2, respectively, from Example 1. Sample 11 is a
variation of Sample 5
from Example 1. The remaining sample formulations were new.
[00881 After the five adhesive formulations exhibited good compatibility
for at least one day,
the five samples were all combined with about 1% of a photoinitiator (Esacure
KTO 46,
Lamberti Spa, Italy) and then tested further. The photoinitiator was comprised
of a liquid
mixture of trimethylbertzoyldiphenyl phosphine oxide, a-hydroxyketones and
benzophenorte
derivatives. The samples were then coated onto film substrates comprising
ethylene vinyl
acetate copolymer (EVA), Metallocene low linear density polyethylene (LLDPE)
and about 12
percent of an organoclay composition (about 57-63% organically modified clay
and maleic
anhydride grafted linear low density polyethylene carrier, PolyOne
Corporation, McHenry, IL).
In particular, the substrate had about 77 wt% (EVA), about 10 wt% Metallocene
LLDPE, and
about 13 wt% organoclay composition. The samples were then cured after being
coated onto
the film substrates, where the curing was effected by application of UV
radiation with three
passes under a "D" bulb, which is a mercury with iron halide bulb. A single
pass under a
D bulb was approximately equivalent to 75 mJ/cm2 to 100 mJ/cm2. After the
coating was
cured, the cured adhesive layer was evaluated for the degree of cure and
effectiveness to bond
to the film.
-30 -
CA 02732720 2011-02-25
[00891 The degree of cure of the adhesive was tested using a solvent rub
resistance test
referred to as a methyl ethyl ketone (MEK) rub test, as per ASTM D5204. Good
cure results
were shown by an MEK rub value of 100 double rubs or more, which indicated
that the
adhesive was cured well and thus showed a resistance to the MEK rubbed/over
it. Poorly cured
adhesives did not show much resistance to the MEK (e.g., 10 double rubs or
less). MEK rub test
results can be seen in Table 3 below.
[0090] Tack and initial peel of the adhesives were also observed, and
reported subjectively.
The tackiness of the adhesive layer was observed upon touching and the level
of tack was
evaluated on a scale of Low (L), Medium (M), and High (H). Similarly, the
subjective force
required to peel apart the samples by hand was also evaluated on a scale of L,
M, and H. These
test results can be seen in Table 3.
[0091] Table 3: Test Results for Cure and Preliminary Adhesion for Table 2
Formulations.
MEK Rub Test
Sample No. Subjective Tack Test Subjective Peel Test
(# of double rubs)
9
>100
(Inventive)
-10 M-H M-H
(Comparative)
11
>100
(Inventive)
12 100
(Comparative) (Haze on surface)
13 , 100
M-H M-H
(Comparative) ((Haze on surface)
[0(921 All of the samples had at least moderate tackiness and peel
strength. Sample 10 had
the highest subjective tack and peel but the poorest cure, as evidenced by an
MEK rub test of
about 10, which showed that after about 10 rubs of MEK the adhesive was
removed from the
substrate. Samples 12 and 13 had a haziness upon performing the MEK rub test,
most likely
due to component D, the polybutadiene styrene copolymer, rising to the surface
when rubbed
with MEK. Therefore, although Samples 12 and 13 fall within the desired
adhesive ratio range,
component D does not appear to be compatible with the other two components and
thus is not
a satisfactory adhesive compound. It was desirable to find an adhesive with a
subjective tack
result of medium or lower, subjective peel force of medium or higher and an
MEK rub test of
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CA 02732720 2011-02-25
100 double rubs or greater without haze formation, which at a minimum, Samples
9 and 11
exhibited.
[00931 Example 3
[00941 The curing effectiveness of three different variations of an
adhesive formulation were
tested by applying the adhesive to the same film substrate as described in
Example 2 and then
curing in three different manners; a UV-curing step ("UV Cure") performed on
commercial
equipment, an electron beam (EB) curing step ("EB Cure") performed on a
similar commercial
system as the UV-cure but utilizing electron beam technology, and an EB cure
performed on
laboratory equipment ("EB Lab Cure"). Table 4 below shows the formulation of
the three
adhesives tested. The commercial EB system and lab EB system are both compared
due to the
varying energy levels supplied by each. The acrylic oligomer is CN 111 US, the
elastomer is
Ricacryl 3500 and the tackifier is CN 3001 as described in Example 1.
[00951 Table 4: Sample Adhesive Formulation
% Provided in Final Adhesive Formulation
Adhesive
Sample No. Acrylic Oligomer Elastomer Tack Agent Component Ratio
(ACR)
14
69.2 7.7 23.1 2.2
(Comparative)
45 15 40 0.81
(Inventive)
16
35 15 50 0.53
(Inventive)
[00961 The "UV Cure" comprised passing the coated sample under a UV-lamp at
about
ft/min in air and with about 2 to 4 passes, such that the sample was passed
under the length
of the UV-lamps 2 to 4 times. The energy provided by 1-pass of the UV lamp at
25 ft/min was
equivalent to about 100 mj/crn2. The "EB Cure" on a commercial system (Faustel
Corporation,
Germantown, WI) was performed under nitrogen gas at about 125 ft/min to about
250 ft/min
with only one pass and at about 2 Mrad to about 2.4 Mrad, and the "EB Lab
Cure" was also
performed under nitrogen requiring about 6 to 8 passes under the lab EB
system, which
operated at about 10 ft/min. Total cumulative dose for 6-8 passes through the
lab EB unit was
about 2 Mrad to about 4 Mrad. It is appreciated that a smooth surface finish
of the adhesive
fastener 12 is desired in some cases for a good adhesive to adhesive peel
strength. If the surface
- 32 -
CA 02732720 2011-02-25
of the adhesives 12 is lumpy, such as having a consistency of an orange peel,
the adhesive
fasteners 12 tend not to adhere together well. It was observed that all cured
coating samples
had comparably smooth and level surface finishes. After curing all of the
samples, the peel
strengths were tested per ASTM D3330/D3330M-04 method P, these results are
shown in
Table 5 below.
100971 Table 5: Peel Strength Results for Different Cure Processes (UV vs.
E-beam)
Peel Strength Results
Inventive Comparative
Peel Peel Peel
Strength Strength Strength
No. UV No. ES No. EB
Sample No. under UV under ED Under EB
Passes Passes Lab Passes
Cure Cure Lab Cure
Condition Condition Conditions
14
(Comparative) 200 gpli 2 0 gpli 1 100 gpli 6-8 passes
(Inventive) 480 gpli 3.5 0 gpli 1 200 gpli 6-8 passes
16
(Inventive) 680 gpli 4 0 gpli 1 200 gpli 6-8 passes
10098] Surprisingly, it was found that an ultraviolet curing treatment (UV
Cure)
outperformed both of the EB cures. The EB Cure performed on the commercial
line had no
adhesion at all, i.e., peel strength of 0 gpli_ The EB Lab Cure had some
adhesion, but the UV-
cured samples had the best adhesion overall.
[00991 In terms of the UV Cure results, Samples 15 and 16 had acceptable
ranges of peel
strengths (i.e., 480 gpli and 680 gpli, respectively) whereas Sample 14 had a
lower peel strength
(i.e., 200 gpli). The lower peel strength seen in Sample 14 is likely due to
the adhesive
formulation used with Sample 14, which did not fall within the desired range
of 0.5 to 1.5 (i.e.,
it had a ratio of 2.2).
[00100] While not wishing to be limited by theory, it is believed that a UV-
radiation cure in
ambient air (about 21% oxygen) provides a cure from the bottom of the sample
up toward its
surface due to the oxygen inhibition of free radical curing in adhesive
portions adjacent or near
the surface. The tacky components are more aliphatic in nature and therefore
are lower in
surface energy than, for example, the ester or urethane components. In some
cases, chemical
systems self-organize to the lowest possible energy state if allowed
sufficient time. In the
- 33 -
CA 02732720 2011-02-25
present case, it is believed that the slower cure rate of the UV process
allows sufficient time for
the tacky components of the coating to migrate toward the surface. In
contrast, the EB curing
process results in a much faster reaction cure rate, thus providing a more
random arrangement
of the polymer where it sets up cross-links within the growing polymer network
too quickly for
significant surface-energy driven self-ordering to develop. Thus, the EB cure
may have an
opposite cure pattern than the UV-radiation process, where EB curing commonly
takes place
in a nitrogen-purged environment and may cure faster at the surface and slower
near the
substrate. This can result in a completely different adhesive behavior based
solely on the
different cure methods. Ordinarily, such a rapid cure would be desirable,
however, when
curing the coating disclosed herein, such a fast cure is a disadvantage
because it does not allow
sufficient time to transpire in the process for the adhesive components to
become fully
organized.
[00101] While not wishing to be limited by theory, it is further believed that
the slower cure
time of the UV radiation curing allows for the growing polymer units to
arrange themselves,
such that polar units of the polymer favor the substrate and non-polar units
favor the surface,
where having the non-polar units near the surface of the substrate allows the
adhesive coating
to bond and stick to itself. This allows the adhesive components that are most
compatible with
the film substrate to congregate at the adhesive/substrate interface, thus
enhancing the
substrate adhesion, which may be one factor that aids in the absence of
delamination from the
substrate film.
[00102] Example 4
[001031 Two inventive adhesive-based reclosable fasteners, Samples 17 and 18,
were
prepared as indicated in Table 6. The two sample adhesives were compared to a
standard
pressure sensitive adhesive fastener (PSA-control, Sample 19) obtained from a
commercial
Nabisco Chips Ahoy Snack 'n Seal package using a standard PSA (Fasson 5700,
Avery
Dennison Corp., Pasadena, CA).
- 34 -
CA 02732720 2011-02-25
[001041 Table 6: Adhesive-based Fastener Formulations
% Component Provided in Final Adhesive Formulation
CN 111 US Esacure Adhesive
Ricacryl 3500 CM 3211
Samples (Acrylic KT046 Component
(Elastomer) (Tack Agent)
Oligomer) (Photoinitiator) Ratio (ACR)
17
35 12 50 3 0.56
(Inventive)
18
35 0 62 3 0.56
(Inventive)
100105] The substrate that was coated comprised about 77.2% EVA, about 10%
metallocene
LLDPE, and about 12.8% organoclay filler composition PolyOne 231-615
masterbatch. The
masterbatch comprises about 57% to about 63% organically modified clay and a
carrier that
contains MA-LLDPE and polyethylene. Sample 17 was cured at a UV-curing station
having an
average light energy of about 730 mj/cm2 and an average line speed of about
100 ft/tnin at an
average oven temperature of 130 F. Sample 18 was cured at the UV-curing
station having a
light energy of about 700 mJ/cm2 with a line speed of about 100 ft/min at an
oven temperature
of 160 F. The standard adhesive, PSA-control, was already provided in a final
form adhered to
a cookie package (Kraft Foods).
[001061 A crumb contamination test was performed on all three packages to see
if the food
particles would negatively impact the sealing of its respective adhesive. The
crumb test
procedure comprised the following steps: first, Triscuit crackers were
obtained and crushed
using a bottom of a glass jar. The breaking of the crackers in this fashion
created small particles
that would be consistent with what would be found in the bottom of a bag.
Next, a 2 inch
diameter ring fixture was placed onto the adhesive of the sample to be tested.
Approximately
grams of crumbs were placed into the ring on the sample. The sample and ring
were gently
agitated back and forth to settle the crumbs onto the adhesive surface of the
reclosable fastener.
The ring was removed from the sample and the crumbs were gently shaken off of
the sample
and disposed. The ring was replaced back on the substrate in its original
position and the area
exposed to the crumbs was visually rated for the quantity of crumbs retained.
A visual rating
scale of zero to 100 was used, where zero meant no visible retained crumbs and
100 meant the
total surface was covered with adhering crumbs. The results of the cracker
crumb test are
shown in Table 7.
- 35 -
CA 02732720 2011-02-25
[00107] Additionally, the peel strength of the adhesives was tested after
contaminating with
cracker crumbs. The peel strength was measured using a standard testing
procedure, ASTM
D3330/D3330M-04 method F, where the strength of the adhesive bond was tested
by peeling
one side away from the other and measuring the peel strength that was
required. An initial
peel strength, a subsequent peel strength after an initial contamination with
cracker crumbs,
and a second peel strength after a second round of contamination with cracker
crumbs, where
the sample was contaminated using the same procedure as the initial
contamination, were
measured. The results for the samples are presented in Table 7.
[001081 Table 7: Crumb Contamination Test Results
Initial peel Peel strength
%Peel strength Peel strength % Peel strength
Samples strength (no after first after second
retained after Contamination
retained after first
contamination) contamination contamination second rating
contamination
(gpli) (gpli) (gpli) contamination
17 315 167 53% 128 41% 0-10
18 116 161 138% 155 133% 0-10
19
(PSA- 499 196 39% 25 5% 60-80
Centro11
[00109] It can be seen from the results that the adhesivity (Le., peel
strength) of the PSA-
control, as measured per ASTM test 03330/D3330M-04 method F, dropped to about
5% of its
initial peel force value (i.e., from about 500 gpli to about 25 gpli) after
only two cracker crumb
exposures. In contrast, both of the adhesive-based Samples 17 and 18 retained
at least about
41% of its initial peel force value after two exposures to the cracker crumbs,
with Sample 18
actually showing an increase in peel force after contamination and after
repeated closures and
openings. Additionally, the visual crumb contamination ratings for the
adhesive-based samples
were 0 to 10, compared to values of 60 to 80 for the PSA-control.
[001101 A rolling ball tack test was also performed on uncontaminated Samples
17, 18, and
19, which was a modified version of ASTM1D3121 and followed the test method
parameters of
ASTM 133121, unless otherwise specified. The modified test measured how strong
the surface
of the coating adhered to non-like materials, such as the polar surface of a
rolling glass ball.
[001111 The rolling ball method included: releasing a glass ball which was
placed two inches
up the standard incline specified in the ASTM method and allowing the ball to
accelerate down
the incline and roll across a horizontal surface of the pressure sensitive
adhesive sample. The
-36 -
CA 02732720 2011-02-25
modified test version included using a glass ball instead of a metal ball, the
glass ball having a
diameter of about 1/8 inch, and using a shortened release point off of the
incline (i.e., as
indicated above, two inches up the incline). The relative tack was determined
by measuring the
distance the ball traveled across the adhesive before stopping, beginning from
the. end of the
ramp. A longer rolling ball travel distance indicated lower tack to the polar
surface of the glass
ball, and indicated that the coating has a lower tendency to stick to rollers
and metal surfaces on
packaging machines, compared to coatings with a shorter rolling ball travel
distance which
indicated a higher tack level. A longer rolling ball travel distance may also
correlate to a lower
tendency to adhere to food crumbs. In this measurement, the measurement was
limited to a
maximum of 4 inches because the maximum sample size available for testing was
4.0 inches x
4.0 inches. Results from the rolling ball tack test are shown at Table 8.
[0011.21 Table 8: Rolling Ball Tack Test Results
Samples Rolling Ball Distance (Inches)
17 >4
18 >4
19 1/ 8
(PSA-Control)
1001131 From the results, it can be seen that the two inventive Samples 17 and
18 had lower
surface tack than the control, as evidenced by the glass ball easily rolling
across the surface of
the reclosable fastener and off of the 4 inch long sample. On the contrary,
the glass ball stuck to
the PSA-control almost immediately upon contacting the PSA-control surface,
which was
indicative of a high tack surface of the coating.
[00114] Example 5
[001151 A peel repetition test was performed to test the reseal and peel
ability over multiple
repetitions. Approximately twenty samples were made; Samples 20 to 35 were
made using the
adhesive formulation of Sample 17 from Example 4, and Samples 36 to 38 were
made using the
adhesive formulation of Sample 18 from Example 4. Samples were produced on a
commercial
scale pilot coating line via the flexographic coating process. The liquid
adhesive coating system
was preheated to 160 F (71 C) and circulated through a chambered doctor blade
which was
mounted to art engraved chromium oxide ceramic roll. The engraved roll (which
was also
temperature-controlled to 160 F (71 C)) transferred the liquid adhesive
coating to a patterned
-37 -
CA 02732720 2011-02-25
rubber roll. The patterned rubber roll in turn transferred the patterned
coating to the moving
= substrate film (i.e., the process illustrated in FIG. 6). After exiting
the coating station, the film
traveled through a 60 ft. long oven section. A UV treater, consisting of 3
banks of UV lamps,
was located at the oven exit. The line configuration with the UV zone located
at the exit end of
the oven resulted in the maximum path length between the coating station where
the material
was applied and the UV curing station, which maximized the amount of time
available for the
liquid adhesive coating to flow-out and level, prior to being cured into a
cross-linked polymer
network. It is believed that, in some cases, a smooth and level coating
surface helps to achieve
the desired adhesive to adhesive peel force in the fully cured adhesive.
[001161 A series of experimental coating runs were performed. Line speed, oven
temperature, and the number of UV lamp banks were varied. The experimental
design and
experimental observations are summarized in Table 9 below. Visual surface
roughness, MEK
resistance, and separation of adhesive along the adhesive-to-adhesive bond
line of the sample
prior to testing were determined. In general, samples produced at 300 ft./min.
to 500 ft./min.
line speed had a rough surface appearance and low or no subjective peel force.
Instrumented
peel force measurement of these samples was for the most part not possible
because the joined
samples separated on their own accord before further tests could be carried
out. Samples
produced at 100 ft./min. had a smooth surface appearance and moderate adhesive
to adhesive
peel force. These samples were further characterized using instrumented peel
force testing as
summarized in Tables 10 and 11 to follow. Only the samples that did not
separate on their own,
as shown in Table 9, were tested in the repeated peel-reseal tests. These were
Samples, 21, 22,
29, 30,31, 32, 35,36 and 38.
-38 -
CA 02732720 2011-02-25
,
[001171 Table 9: Experimental Design Used to Produce Samples for Peel
Repetition Testing
Line Visual MEK Rub
Adhesive- Oven Joined
Sample
Based Speed Temperature No. of UV
adhesive Test (# of
No. (ft/min) lamp banks surface
double
samples
Sample No. CF) separated
appearance rubs)
. . , ,
20 17 (Ex. 4) 500 100 3 Very
15 Yes
Rough
21 17 (Ex. 4) 100 MO 1 Smooth 100+
No
22 17 (Ex. 4) 100 100 3 Smooth 100+
No
23 17 (Ex. 4) 500 100 1 Very 5
Yes
Rough
24 17 (Ex. 4) 300 100 2 Very
100+ Yes
Rough
25 17 (Ex. 4) 500 130 2 Very 60
Yes
Rough
26 17 (Ex. 4) 300 130 2 Very 100
Yes
Rough
27 17 (Ex. 4) 300 130 3 Very 100
Yes
Rough
,
28 17 (Ex. 4) 300 130 1 Very 20
Yes
Rough
29 17 (Ex. 4) , 100 160 1 Smooth 100+
.. No
30 17 (Ex. 4) 300 160 2 Slightly
100+ No
Rough
_
31 17 (Ex. 4) 100 160 2 Smooth
100+ No
32 17 (Ex. 4) 100 160 3 Smooth
100+ No
33 17 (Ex. 4) 500 160 1 Very 5
Yes
Rough
34 17 (Ex. 4) 500 160 3 Very
100 No
Rough
35 17 (Ex. 4) 100 130 2 , Smooth
100+ No
36 18 (Ex. 4) 100 160 3 Smooth
100 No
37 18 (Ex. 4) 500 160 3 Rough 100
Yes
38 18 (Ex. 4) 300 160 3 Rough
100 No
i
[00118] The first set of peel tests were performed using short intervals
between peels, i.e.,
about three minutes between a peel-reseal cycle. Table 10 includes results for
this test, where
the averages of two samples tested per condition are provided. These results
are compared to
Sample 19, the PSA-control from Example 4.
-39 -
CA 02732720 2011-02-25
[001191 Table 10: 3-Minute Delay Peel-Reseal Test Results
Peel Strength Value (gpli)
Peel Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample
No. 19 21 22 29 30 31 32 35 36 38
PSA-
__ Control
1 459.8 291.8 461.8 273.3 148.0 266.7 417.4 418.3
273.9 136.9
2 - 320.8 74.0 242.1 131.6 323 129.7 206.3 195.8
527.2 43.0
3 275.0 52.4 204.4 111.5 27.1 112.9 180.8 171.9
452.9 44.8
4 254.7 51.8 183.2 107.6 24.2 104.1 158.6 141.6 424.7 41.1
256.9 48.7 161.8 - 99.2 23.7 102.3 140.5 128.8 - 404.6
41.8
L
[001201 The second set of peel tests were performed using a longer duration
interval between
peels, i.e., about 24 hours between peel-reseal cycles, in order to understand
the impact of
longer adhesive-adhesive contact time, with the first peel taking place about
one week after the
samples were prepared_ The test results for the extended delay peel-reseal
samples are shown
at Table 11.
1001211 Table 11: 24-Hour Delay Peel-Reseal Test Results
Peel Strength Value (gpli)
Peel Sample Sample Sample Sample Sample Sample Sample Sample Sample Sample
No. 19 21 22 29 30 31 32 35 36 38
PSA-
Control
1 539.8 271.1 441.7 - 288.8 149.2 301.9 - 434.7 432.5
2773 124
2 521.6 202 362.1 238.5 116.2 147 327.6 338.7
447.4 107.3
3 514.6 233.1 349.6 248.3 115.8 226.3 297.6 321.6
478.5 106.5
4 550.3 218.2 314.8 222.2 95.5 239 286.5 289
493.9 116.8
5 567 231.9 285.9 236.9 95.9 224 299.9 280.4
487.5 125.1
[001221 The results show that the samples including adhesive formulation of
Sample 17 from
Example 4 do not exhibit as pronounced of a decrease in peel force that
typically occur with
repeated peels when the duration between peels was 24 hours (i.e., Samples 21,
22, 29, 30, 31, 32,
and 35 in this example). When the adhesive Sample 17 was allowed to remain in
contact with
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CA 02732720 2011-02-25
itself for about 24 hours between peels, the adhesive recovered up to about
85% of its original
peel force value, even after five peel-reseal cycles. Sample 30 had
significantly lower average
peel force values compared to the other test samples. Even though the joined
samples did not
separate on their own accord, it had poor surface smoothness due to the higher
line speed of
300 ft/min.
[00123] Furthermore, it was surprising to find that the samples including
adhesive
formulations of Sample 18 from Example 4 actually increased in peel force
value (i.e., Sample 36
in this example) with repeated peels at both the short and long time intervals
between peel test
cycles, similar to its contamination peel test results in Table 7, evidence of
a full recovery of peel
force after resealing. Only Sample 36 showed an increase in peel force value.
Sample 36 was
the sample cured using the slower line speed, which may have helped to provide
a level and
smooth sample surface (see Table 9), Sample 38 was made at a higher line speed
than Sample 36
resulting in a rougher surface, which may be why there was a decrease in peel
force value, as
well as a low initial peel force value.
[001241 In comparison, the PSA-control showed recovery behavior only when the
interval
between peels was long, i.e., 24 hours. At the shorter time interval, the
control actually dropped
in peel force, by about 40%.
[00125] Overall, for both peel-reseal tests, the best performers were Samples
22, 32, 35 and 36.
These four samples all correlated to adhesives made with similar processing
conditions. For
example, all four samples had slow line speeds of 100 ft/min, with at least
two or more banks of
UV lamps turned on. The adhesives that failed the peel-reseal tests likely did
not have
sufficient time to flow out and level prior to UV curing.
[001261 Example 6
[00127] An aging study was conducted using the adhesive Samples 17 and 18 of
Example 4,
Table 6 in order to understand the effects of longer adhesive to adhesive
contact time on peel
performance. Various properties of the adhesive were tested over a seven-week
period
including subjective initial peel force (i.e., low, medium, high), visual
appearance after peeling,
subjective tack or tendency to stick to fingers (i.e., none, low, medium,
high), coating durability
(i.e., MEK solvent resistance test ASTM D5204), and instrumented peel (i.e., 5
consecutive peels
- 41 -
CA 02732720 2011-02-25
repeated on same sample at intervals of about 3 minutes using ASTM 1)3330/
D3330M-04
method F; two samples were tested and averaged together) all at various
adhesive to adhesive
contact times. The adhesives were coated onto the same film substrates that
were used in
Example 2. Table 12 below shows the aging results for Sample 17-i Table 13
below shows the
aging results for Sample 18.
[001281 Table 12: Summary of Aging Study of Sample 17
_
Test
Day 0 Day 3 Week 1 Week 2 Week 3 Week 4 Week 5
Week 6 Week 7
Performed
,
Subjective
Initial Peel H H H H H H H H H
Force
Change in
No change No change No change No change Spotty Spotty Spotty
Spotty Spotty
aPPearance to adhesive to adhesive to adhesive to adhesive surface
surface surface surface surface
after
appearance appearance appearance appearance whitening whitening whitening
whitening whitening
peelnIg
Subjective
Low Low Low Low None None None None
None
Tack .. _
MEK Rub
(# of
>100 >100 >100 >100 >100 >100 >100 >100
>100
double
rubs) . 10 Peel
553 567 559 553 463 600 323 505 592
Avg. g/in
2*4 Peel
370 381 377 382 343 375 241 311 348
Avg. g/in . ,
3,v Peel
339 354 347 361 333 352 228 300 335
Avg. g/in
4th Peel
318 342 340 338 330 326 232 292 326
Avg. On .
5th Peel
311 322 326 323 311 297 226 277 317
Avg. g/M
-
Avg. Peel
Strength
378 393 390 391 356 390 250 337 384
g/in of 5
peels
,
- 42 -
CA 02732720 2011-02-25
[001291 Table 13: Effect of Adhesive/Adhesive Contact Time on Repeat
Peel Performance (Sample 18)
Test
Performed
Day 0 Day 3 Week 1 Week 2 Week 3
Week 4 Week 5 Week 6 Week 7
Subjective
Initial Peel H+ H H H H H H+ H+ H+
Force
Appearance
No change No change No change No change
change Surface Surface Surface Surface Surface
to adhesive to adhesive to adhesive to adhesive
after Damage
Damage Damage Damage Damage
peeling
appearance appearance appearance appearance
,
Subjective
Low Low Low Low None None None None None
Tack
MEK Rub
fit of
>100 >100 >100 >100 >100 >100 >100 >100
>100
double
rubs) . . . .
1, Peel
781 819 788 800 944 833 819 846 963
Avg. gun
2"d Peel
519 586 567 590 668 377 576 622 556
Avg. gum
3'd Peel
438 485 510 519 428 234 437 485 218
Avg. On
4th Peel
399 3% 407 409 102 107 322 229 105
Avg. On . .
5th Peel
386 358 343 361 64 66 251 134 73
Avg. gun -
Avg. Peel
Strength
505 529 523 536 441 323 481 463 383
On of 5
peels 1
[001301 It should be noted that the average peel strength value was an average
of five
repeated peels on the same sample that were consecutively peeled at intervals
of approximately
three minutes. Therefore, the first peel was determined and the peel strength
value recorded,
and the reclosable fastener sample was resealed. After three minutes had
passed, the reclosable
fastener was peeled apart again and the peel force strength was recorded. The
process was
repeated until five peels were performed.
[001311 The subjective peel force, subjective tack and MEK rub test results
were all good for
both Samples 17 and 18 regardless of the duration of the adhesive to adhesive
contact. The peel
force values (i.e., initial and subsequent peels on the same sample) remained
consistent for
Sample 17 regardless of the duration of adhesive to adhesive contact for the
range of zero days
to 7 weeks. Sample 17 showed a much more consistent peel-reseal cycle than
Sample 18. After
the initial peel of Sample 17, the loss in adhesive to adhesive bond strength
as represented by
-43 -
CA 02732720 2011-02-25
the loss in peel force upon subsequent peels was generally less than about 10%
per subsequent
peel, and was consistent regardless of the adhesive to adhesive contact time.
[001321 Beginning in week 3, there was a visible change in both Samples 17 and
18 (i.e.,
noticeable whitening and increase in opacity) upon peeling the aged samples.
It is believed that
this visible change is evidence of microscopic surface deformation of the
adhesive due to forces
acting on the adhesive surface during manual or instrumented peeling. The
surface
deformation did not affect the critical performance attributes of the adhesive
(i.e., tack or peel
strength). In the end, Sample 17 held up slightly better, with its peel
strength either increasing
over time, i.eõ recovering peel strength, or generally maintaining about a 10%
peel loss between
subsequent peels.
[00133] Example 7
[001341 The inventive adhesive-based redosable fastener Sample 17, from
Example 4, was
compared to three other inventive adhesive-based reclosable fasteners, Samples
39 to 41, having
the formulations as indicated in Table 14.
[001351 Table 14: Adhesive-based Fastener Formulations
% Component Provided in Final Adhesive Formulation
CN 111 US Ricacryle CN 3211 BR 144 CN 2302 Esacures
Adhesive
Samples (Acrylic 3500 (Tack (Acrylic (Acrylic KT046
Component
Ratio
Oligomer) (Elastomer) Agent) Oligomer) Oligomer) (Photoinitiator)
(ACR)
17 35 12 50 0 0 3 0.56
(Inventive)
39
27 0 50 20 0 3 0.94
(Inventive)
40 35 3 39 20 0 3 1.31
(Inventive)
41
15 0 45 20 17 3 1.16
(Inventive)
[001361 Component BR 144 is identified as an acrylic oligomer (BR 144, Bomar
Specialties
Company, Torrington, CT). Component CN 2302 is also identified as an acrylic
oligomer
(CN 2302, Sartomer Company). All three Samples, 39 to 41, have incorporated
the acrylic
oligomer BR 144, with Samples 39 and 40 having two acrylic oligomers and
Sample 41 having
three acrylic oligomers present in the formulation.
- 44 -
CA 02732720 2011-02-25
[001371 The adhesives were coated onto the same film substrates that were used
in
Example 2. Samples 39 to 41 were cured at a UV-curing station having an
average line speed
of about 25 ft/min and three passes under the UV lamps totaling about 400
inJ/cm2 to about
600 mJ/cm2.
[001381 Coating durability of the four adhesives was tested (i.e., MEK solvent
resistance test
ASTM D5204) as well as initial peel strength using ASTM D3330/ D3330M-04
method F.
A rolling ball tack test was also performed, which was a modified version of
ASTM D3121 as
described in Example 4, except the sample size available for testing was about
2.5 inches wide
by about 7 inches long. These results are indicated in Table 15.
1001391 Table 15: Test Results for Cure and Adhesion using Table 14
Formulations.
Average
MEK Rub Test Initial Peel Initial Peel Rolling Ball
Samples Initial Peel
(# of double Strength -1 Strength - strength
Distance
rubs) (gpli) 2 (gpli) (inches)
(gpli)
17 >100 184 191 188 1.5
39 >100 698 733 716 6.0
40 >100 341 333 337 >7.0
41 >100 336 289 313 >7.0
[001401 The initial peel strength, i.e., initial peel performed under
laboratory conditions,
increased for the new formulations by about 30%-300% compared to Sample 17,
having only
one acrylic oligomer component. The rolling ball tack distance increased for
the new
formulations by more than 300% compared to Sample 17.
[001411 From the results, it can be seen that the new formulations having two
or more acrylic
oligomers had an overall improved performance compared to Sample 17, as
evidenced by the
rolling ball test and the peel strength test. All samples had excellent cure
rates, evidenced by
the MEK rub test. In particular, all of the new sample formulations, i.e.,
Samples 39 to 41, had
lower surface tack than Sample 17 and, in particular, Samples 40 and 41 had an
even better low
surface tack as evidenced by the glass ball easily rolling across the surface
of the reclosable
fastener and off of the 7 inch long sample.
-45 -
CA 02732720 2011-02-25
[00142] Example 8
[00143] The four inventive adhesive-based reclosable fasteners of Example 7
were tested for
various repeat peel tests. The samples were initially peeled apart and opened,
the peel force
was measured in grams per linear inch (gpli) using ASTM test method
D33301D3330M-04
method F, then resealed for three minutes, and the peel repeated. This seal-
reseal was repeated
every three minutes until ten data points were obtained. The results are
presented below in
Table 16.
[00144] Table 16: Three Minute Peel Delay Test
Average Peel Strength (gpli)
Peel 17 39 40 41
Repetition (Inventive) (Inventive) (Inventive) (Inventive)
1 721.4 371 710 388.6
2 525.5 492.4 501.8 517.2
3 477.8 477.1 485.8 442.5
4 443.6 474.2 459.1 386.7
423 478.1 449.6 346.3
6 392.9 480.0 430.2 313.7
7 374.5 482.5 411.5 295.4
8 352.6 504.7 397.4 255.9
9 332.6 491.8 381.2 224.3
326.6 490.3 380.9 204.3
[00145] Example 9
[00146] A 24-hour delay repeat test was performed using the same four
inventive samples
from Example 7. The samples were initially peeled apart and opened, the peel
force required
being measured. Then the samples are resealed and allowed to sit for 24 hours
in a controlled
environment, i.e., 72F and 50% relative humidity (RH), until they were
repeeled and opened
again. This is repeated until a total of five data points have been gathered,
or for a period of
five days. The results are presented below in Table 17.
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CA 02732720 2011-02-25
[00147] Table 17: 24-Hour Peel Delay Test
Peel Force (gpli)
Initial Peel,
Samples Day 2 Day 3 Day 4 Day 5
Day 1
17
708.1 616.1 582.3 579.4 653.6
(Inventive)
39
555.5 641.6 690 752.4 653
(Inventive)
811.7 748.6 666 614.7 546.9
(Inventive)
41
469.2 513.6 516.8 503.2 479
(Inventive)
[00148] All four of the samples maintain their peel performance throughout the
five day test
period, without any sample falling below 400 gpli on any of the test days.
Samples 39 and 41
actually increase in peel force and recover the initial peel force or increase
in peel force during
the test period. Thus, allowing these samples to remain sealed for a period of
at least 24 hours
allows these samples to recover or increase in adhesivity.
[00149] Example 10
[00150] In Example 10, a similar test to Example 9 was performed using the
four samples
described in Example 7; however, after each peel opening the adhesive area was
contacted with
whole coffee beans, resealed, and allowed to remain closed for 24 hours, and
repeeled.
[00151] After each peel opening, whole coffee beans were placed on the
adhesive surface and
removed in less than five minutes. The samples were resealed and allowed to
sit for 24 hours in
a controlled environment, i.e., 72 F and 50% RH, until they were repeeled and
opened again.
This is repeated until a total of five data points have been gathered, or for
a period of five days.
The results are presented below in Table 18.
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CA 02732720 2011-02-25
[00152] Table 18: 24-Hour Peel Delay Test After Coffee Bean Contamination
,Average Peel Force (gpli)
Initial Peel,
Samples Day 2 Day 3 Day 4 Day 5
Day 1
17
695 507 422.1 344.3 271.5
(Inventive)
39
627.3 647 571.2 458.6 294.9
(Inventive)
770.4 548.3 412.1 327.3 230.4
(Inventive)
41
506.9 476.1 382 298.3 211.1
(Inventive)
[00153] Although the data shows a slight decrease in peel strength, the peel
values still
exceed 200 gpli after five peel/contamination cycles with whole coffee beans.
[00154] Example 11
[00155] A rolling ball tack test as described in Example 4 was performed on
film with no
adhesive for comparison to the tack values of the low tack adhesive. The
results are provided
below in Table 18. Roll #3 from Sample 1 took a fairly sharp turn shortly
after contacting the
film.
[00156] Table 18: Rolling Ball Tack Test On Uncoated Film
Sample 1 2
Roll #1 16.75 15.875
Roll #2 18 18
Roll #3 10.875 14.25
Roll #4 17.25 18.125
Roll #5 20.25 19.875
Roll #6 15
AVERAGE 16.35 17.23
-48 -
CA 02732720 2011-02-25
[00157] It will be understood that various changes in the details, materials,
and arrangements
of the package and process of formation thereof, which have been herein
described and
illustrated in order to explain the nature of the described package, may be
made by those skilled
in the art within the principle, and scope of the embodied method as expressed
in the appended
claims.
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