Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 3 ~ 4 2 3 2 4CAN9A
C.~nl.T;:-TOP CONTI~lNli:R CLOSURI~ SYSTEM
Back~round of the Invention
_ _ ... . . . _ .. _ . . _
1. Field of the Invention
. _ _ . _ . _
This invention relates to packaging, and
particularly to all improved package construction using a
pressure sensitiv~ adhesive tape material to i~prove the
opening characteristics of a disposable gable-top container
suitable for the packaging of liquids. More particu]arly,
this invention relates to a l-lank from which the container
i.s formed.
2. Description of the Prior Art
_ . _ _ . _ _ _ .
Containers for heverages such as mi]k, fruit
juices, and drinks are conventionally constructed from
hlanks of thermoplastic coated paperboard. The most wirlely
used of such containers have a rectanglllar cross-sectional
bocly surmounted by a gable-top closure incorporating an
extensible pouring spout. slanks from which the conta;ners
are constructed are divided into a plurality of panels
which are adapted to form the walls and closure members.
The panels are formed and separated by score lines at which
the blank is folded. Particular panels are intend~d to be
joined together in a lapped arrangement in the completed
container. Typically, those panels are pressed together and
heated or exposed to high frequency radiation to fuse the
adjoining thermoplastic surfaces and form a generally
strong seal. To finally seal the filled container, two or
more panels are finally joined and sealed to form a rib
along the top edge of the rooE panels. Exemplary of such
container blanks are those shown in ~lden U.S. Patent No.
2,750,095 and Wilcox U.S. Patent No. 3,245,603.
Containers of this type are opened for access to
the contents by a two-step toggle action process. First,
the gable edges of the roof panels at the front of the
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container are pushed outward and upward toward the rear of
the container by thumb pressure, breaking the seal between
the outside surfaces of the two lip pane]s, and breaking
the seal in the rib panels surmounting the roof above the
pouring spout. The gahle edges are forced backward past the
point at which the lip panels are joined, to nearly touch
the roof panels.
Second, the gable edges are pushed forward and
inward. The forces are communicated through spout panels to
the tip of the pouring spout, breaking the seal between the
lip panels and the underside of the roof panels and
snapping the spout outward to a pouring position.
In early models of gable-top containers, the
panels comprising the lips of the pouring spout were bonded
to the underside 3
of the roof panels. The resulting sealed spout was
difficult to open, generally requiring insertion of a tool
behind the lips to separate them from the roof underside.
The cardstock panels often tore or delaminated, producing
an unsightly and unsanitary container. In those cases where
an adhesive was applied to only those panels wllich were to
be joined, it was simple to eliminate adhesive from the
spout panels to reduce the forces required to open the
spout. The resulting container, of course, was not
effectively sealed and was subject to leakage.
An improvement in gable-top containers to provide
a hermetic seal for an extended shelf life package
consisted of coating the inner surface of the container
blank with a foil and an overcovering layer of
thermoplastic such as polyethylene. The panels to be sealed
are bonded by heating the thermoplastic surface coatings to
a softening or melting temperature, compressing the panels
together and cooling. I'he use of thermoplastic coatings or
foil adds some stiffness to the panels, and the contajner
is made resistant to wicking hy liquids. Ilowever, the
strong bonding of the lip panels results in buckling,
tearing and delamination of the cardstock upon opening the
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seal. Thlls, the spo-lt is difficult to open, and the opened
panels are unappealing in appearance.
Polyethylene has a low moclulus of elasticity, so
that the stiffness added by the coating is minimal.
As used in the food packaqing industry, the term
hermetic refers to a container designed and intended to be
secure against the entry of oxygen which degrades flavor.
The term is also used to designate cnntainers used for
aseptic filling and storage, i.e. containers sec~re against
the entry of microorganisms. The hermetic barrier of such
cartons typically comprises an aluminum or other barrier
film coating the inner surface, overcover~d with a
thermoplastic such as polyethylene. The carton wall -
thickness is thus increased, resulting in larger channe]s
where the edges of overlying panels have a stepped
relationship in the gable rib area, increasing the chance
for leakage.
Attempts to provide an easily opened spout seal
have included (a) perforations in the spout panels which
tear open to expose pouring lips, (b) improved contlol of
the sealing temperature, (c) the use of added scoreline
patterns to concentrate the opening forces, and (d) the use
of anti-adhesion agents, i.e. abhesives, to reduce the
required opening forces.
The use of perforations in the spout panels has
generally been unsatisfactory. Such perforations produce a
spout of reduced size, which requires special sealing
operations. The perforations are considered by some to be a
weak point in the carton, prone to develop leaks. This type
of carton spout requires external forces such as thumbnail
pressure to open, and this procedure is considered
unsanitary. The carton cannot be effectively closed, once
opened, and shaking of the carton results in spil~age.
Likewise, efforts to reduce temperature
variations in the sealing process have not produced a
satisfactory hermetic sealing gable-top container. Because
of narrow acceptable temperature range for obtaining the
-q 131~
desired adhesion, sea]ing variations persist in spite of
improved temperature control. Moreover, the reql~ired
opening forces generally e~ceed the panel strength, even
where minimal sealing is achieved.
The use of novel scoreline patterns generally has
not overcome the strong sealing forces of well-sealed
spouts and buckling of the spout panels is common.
One method for preventing the difficulty in
opening the completely bonded lip panels of polyethy]ene
coated gable-top containers is shown in Crawford et al,
U.S. Patent No. 3,116,002. In this reference, a thin
coating of a high molecular weight organo-siloxane gum is
applied to the lip panels as an abhesive, that is, to
prevent permanent adhesion to the panels in contact with
the lip panels.
Egleston et al, U.S. Patent No. 3,270,940
discloses the use of an anti-adhesive composition applied
to both the outside and inside surfaces of the youring lip
of a gable-top container. Abhesive agents disclosed include
cellulose plastic laminated to polyethylene, the latter
heat-bondable to the polyethylene surface of the cardstock
blank.
The release properties of abhesives are generally
affected by the heat sealing parameters and are
inconsistent. Containers designed for heLmetic use and
having adhesives in the spout sealing area often require
opening forces greater than the wall strength of the
panels, and the spout panels buckle during the opening
process.
Summary of the Invention
The present invention is directed to an
improvement in the formation of a package of paneled
flexible material to stiffen the package material adjacent
the sealed area to be opened. The result is a more
reliable, consistently openable hermetically sealed opening
for gaining access to the contents. The flexihle material
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may be cardstock plastic, or other material with a
thermoplastic inner surface coating which is sealed by
elevated temperature and pressure. The flexible material
may include a gas-impermeable film or foil layer. A blank
of the package material with scoreline-defined panels is
folded into the package shape and overlying panels are
sealed. A typical sealing process consists of heating with
hot air to a temperature which melts or fuses the
thermoplastic surface coatings, and compressing together
the panels to be joined.
A container body is provided having sides, a
bottom and a top suitable for the packaging of liquids.
The container body in the illustrated embodiment includes a
front body panel, a back body panel and first and second
side panels. sOttOm closure panel means is provided for
closing the bottom of the gable-top container. Connected to
the upper edges of the first and second side panels are the
first and second roof panels, respectively. When assembled,
the roof panels are oppositely disposed to converge
upwardly, and are connected at their top edges to form a
gable roof. The front edges of the roof panels have score
lines defining suhpanels which comprise first and second
roof wing panels. The wing panels form the rear portion of
the pouring spout.
Fi rst and second opposed, suhstantially
triangular end panels are connected to the upper edges of
the front and back body panels to extend upwardly
therefrom. The first triangular end panel, the first and
second under panels and the panels listed below form an
extensible pouring spout connected to the top of the
container body.
A first foldback panel is connected to the first
roof wing panel and to one lateral edge of the first
triangular end panel. A second foldback panel is connected
to the second roof wing panel and to the other lateral edge
of the first triangular end panel.
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A third ~o]dbacl~ panel is connected to the oth~r
end of the first roof panel and to one lateral rdge of the
second triangular end panel. A fourth foldback panel is
connected to the other lateral edge of the second
triangular end panel, and is adapted to be connected t~ the
second roof panel, opposite the second foldhack panel.
First and second gable rib panels are connected
to the upper edges of the first and second foldback panels,
respectively, and extend upwardly therefrom. These gable
rib panels are also connected to each other at a common
line, and comprise lips of the pouring spout from which the
container contents are discharged.
Third and fourth gable rib panels are connected
to the upper edges of the third and fourth foldback panels,
respectively, and extend upwardly therefrom.
First and second roof rib panels are connected to
the upper edges of the first and second roof panels,
respectively, and extend upwardly therefrom. Each roof rib
panel is connected at one side thereof to one of the first
and second gable rib panels.
First and second upper rib panels are connected
to the upper edges of the first and second rouf rib panels,
respectively, and extend upwardly therefrom.
At least one stiffening or reinforcement fillet
overlays a portion of, and is bonded to, the inner surface
of at least one of the following pouring spout panels:
(i) first gable rib panel,
(ii) second gable rib panel,
(iii) Eirst roof rib panel,
3n (iv) second roof rib panel,
(v) first triangular end panel,
(vi) first foldback panel,
(vii) second fo]dback panel,
(viii) first wing panel,
and (ix) second wing panel.
~7~ 13~
The fil]et comprises (a) a strip of material
resistant to deleterious effects of the conventional carton
sealing process, i.e. it will not melt, or otherwise
degrade at the temperature and pressure of the sealing
5 process, and (b) a layer of adhesive attached to one side
of the strip. The layer of adhesive adheres to the inner
surface of at least one of the above panel(s), strongly
bonding one side of the strip to the panel or panels. The
layer of adhesive ls preferably adapted to be partially
extruded from the fillet during the carton sealing process,
forming a bead of extruded adhesive along the edge of the
strip. This adhesive bead effectively bonds opposing
pouring spout panels together with the exposed portions of
the rib panels which become thermally bonded, provides a
hermetic seal. This bead, however, may be disrupted
without tearing, buckling or delamination of the panels.
The fillet extends along a major portion of the
force transmission line between the site where the opening
force is applied and the intersection of the panels which
receive the opening force. The fillet strengthens the panel
member to which it is bonded, so that the resistance of the
panel member to bending or buckling increases, and greater
opening forces are transmitted to the s~out tip.
Simultaneously, the fillet controls the force required to
break the hermetic seal between panel members, so that the
required opening force is less than the force which will
buckle or delaminate the panels. The sealing force is
controlled by: (a) controlling the area and specific
locations of the panels which will be suhject to
3Q thermoplastic heat-sealing, (b) controlling the adhesion
between the resistant strip and both panels, and (c)
controlling the thickness of the adhesive layer of the
fillet for optional extrusion from the fillet, to
adhesively join opposing panels in the pouring spout. In
opening the gable-top container from the sealed condition,
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1316~6
the force required is 1imited to a value below that which
will tear, delaminate, or crumple the pouring spout panels.
Brief Description of the Drawings
Figure l is a perspective view of the upper end
of a closed container formed from a blank according to one
embodiment of the present invention.
Figure 2 is a perspective view of the container
end of Figure 1 with a partially opened rib.
Figure 3 is a perspective view of the container
end of Figure 1 with its sealed rib fully open and the
spout panels in the closed position.
~- Figure 4 is a plan view of an embodiment of the
container blank according to the invention.
;~ 15 Figure 5 is a perspective view of a portion of a
reinforcement fillet attached to a container panel
according to the present invention. The cross-section of
the fillet and panel are expanded to show the laminar
construction.
Figure 6 is a cross-sectional view through the
closed upper closure along line 6-6 of Figure 1.
Figure 7~is a perspective view of the upper
portion of a gable-top container formed from one embodiment
of a blank according to the present invention.~ A portion
of the container is cut away to view panel mem~ets below
the roof and roof rib panels.~
` ~ Figur~es 8 through 12 are plan views of the
interior face of various embodiments of the present
invention.
~;~ 30
~ Detailed Des ipt on
:~ ~ Referring ~now to the drawings, the invention is
depicted with reference to a gable-top container in which
~ the invention is incorporated. A gable-top container is
`~ 35 formed from a blank of paperhoard or other suitable
material coated on the inner planar surface, or on both the
inner and outer surfaces with a thermoplastic material. The
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. , , ' ' .`' .
.
9 ~ 3 ~
container blank is adapted to be erected and have certain
panels sealed to each other by a container sealing process.
Typically, the sealing process consists of compressing
together the panels to be joined while those panels are at
an elevated temperature. Other alternative sealing
processes may also be utilized.
FIG. 1 shows a typical container 1 in a closed,
sealed condition as for storage of beverages and the like.
The container is self-sustaining in shape and is
hermetically sealed.
Container 1 is comprised of a series of panels,
including a container body having four body panels 2-5.
Front body panel 4 and second side body panel 5 are shown
in FIG. 1, while rear body panel 2 and first side body
panel 3, not shown, oppose panels 4 and 5, respectively,
forming a container of rectangular cross-section. Usually,
the cross-section is square. The bottom of the container 1
is closed. First roof panel 28 is connected to the upper
edge of first side panel 3. Second roof panel 30 is
connected to the upper edge of second side panel 5. When
the container is in the closed condition, the roof panels
28 and 30 converge upwardly to form a gable roof
construction. Roof rib panel 54 is attached to roof panel
30 and extends upwardly therefrom. Likewise, upper rib
panel 55 is attached to roof rib panel 54 and extends
upwardly therefrom.
First triangular end panel 29 is connected to the
upper edge of the front body panel q. When the container
is closed, end panel 29 is folded under the gable roof
formed by the two roof panels. Also shown are first roof
wing panel 40 and second roof wing panel 43. The ronf wing
panels 40 and 43 are subpanels of roof panels 28 and 30,
respectively. ~ second triangular end panel, not shown in
tllis figure, is usually adapted to remain folded under the
opposite gable roof, unless it is desired to open hoth
gable ends of the container.
FIG. 2 shows the container of FIG. 1 in which the
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spout has been partially opened. The first and second
foldback panels 41 and 42 and overlapping roof wing panels
40 and ~3 are typically pushed outward and backward with
thumb pressure to break the seal between the inner surfac~s
of the first and second upper rib panels ~9 and 55, and
between the outer surfaces of the first and second gahle
rib panels 50 and 52, the latter not visible in this
drawing. The gable rih panels are connected to the upper
edge of foldback panels 41 and ~2, and extend upwardly
therefrom.
FIG. 3 shows the container at the point where
foldback panels 41 and 42 have been pushed backward about
90 degrees from their sealed position. These panels are
roughly triangular in shape, each having one edge defined
by scoreline 35 or 36, where they are attached to a lateral
edge of first triangular end panel 29. First and second
gable rib panels 50 and 52 act as lips of the pouring
spout, and meet at a common gable rib score line 5t. The
upper terminus 51A of the common rib score line at the free
edge 53 of the pouring lip comprises the tip of the pouring
spout. First and second upper rib panels 49 and 55 extend
upwardly from the first and second roof rib panels 4~ and
54 to a level higher than the free upper edge 53 of gale
rib panels 50 and 52.
To complete the unsealin~ and opening of
container 1, foldback panels 41 and 42 are pushed backward
beyond the position shown in FIG. 3. The roof rib panels
and upper rib panels will fold along foldline 57. The
blank may or may not be scored at that location.
The gable rib panels are slightly longer than the
roof rib panels. Thus, after the panels are folded
backward, a subsequent forward and inward movement of wing
panels 40 and 43 transmits opening forces in a toggle-like
action along the wing panels and gable rib panels 50 and 52
toward the common line 51 between the qable rib panels. A
component of these forces extends outward and upward from
line 51 and from gable score lines 35 and 36 to pull the
gable rib panels 50 ancl 52 away from roof rib pane]s 54 and
Q~, the latter not visib]e in FIG. 3, and to pull foldhack
panels 41 and 42 away from roof wing panels ~0 and 43.
Likewise, triangular end panel 29 is forced outward, and
5 the distended panels create a pouring spout. The variol1s
score lines delineating the panels act as hinges for the
panels as they are unfolded.
The force required to distend the spout in this
fashion may be calculated theoretically. If the g~ble rib
panels are looked upon as a beam which is to be buckled in
the center, the force P required for bucking to occur may
be described as:
P = CEI/(L )
15 where: C = (pi~) = 9.87 for hinged ends.
E = modulus of elasticity of beam.
I = moment of inertia of the beam.
I = bh3/12 where b = width and
h = thickness of the beam.
and L = length oE the beam.
Analysis of the opening forces is complex. In general
however, the gable rib panels, foldhack panels, an~l roo~
rib panels must be relatively stiff to prevent the panels
from crumpling, and to transmit the applied opening forces
to common line 51. The sealing forces which bond the gable
rib panels to the roof rib panels are preferably only as
high as required to maintain the hermetic seal. Excessive
bonding forces will require greater stiffness in the spout
panels to prevent crumpling of the panels during the
opening process.
Certain features o~ this invention will produce a
liquid-proof spout seal which is easily opened without
tearing, delamination, or buckling of the spout panel
members. These features underlie the spout panel memhers
in FIG. 3, and are not visible in that figure. These
features include one or more Eillets 56, shown in ~IG. 4
and described in reference to the remainder of the figuLes.
131~
FIG. ~ illustrates an exemp]ary flat sheet
material blank of tllis invention for constructing a
gable-top container. The inner surface or face is shown,
and it is coated with a thermoplastic such as polyethylene.
S The outer surface may also be similarly coated. The sheet
material may include a gas impermeahle layer such as
aluminum foil. An appropriate pattern of score lines
divides blank lA into a plurality of panels and sub-panels
which are used as walls of the container and its closure
parts when the container is eLected.
The central portion of blank lA comprises four
body panels 2, 3, 4, and 5, having their lower edges along
bottom score line 13, and the;r upper edges along top score
line 31. These transverse score lines are shown as
extending from blank edge 6 to opposite blank edge 12 in
substantially parallel relationship across the face of the
blank. Vertical score lines 7, 8 a~d g transect the blank
to define the lateral edges of the body panel 2, 3, 4 and
5, and other panels above the body panels. These and other
score lines are not necessarily straight, but may be
slightly offset in certain sectors of the blank to improve
the fit of the various panels in the erected container.
In the example shown in FIG. 4, side seam flap 11
is connected to one lateral edge 10 of a body member for
sealing to the edge of another body member 2 by the
container sealing process. sottom closure means 26 is
shown as a group of bot~om closure panels 14 through 21
attached to the body members along bottom score line 13,
and extending downward therefrom. sottom closure score
lines 22 through 25 enable bottom closure panels 14, 16,
and 18-21 to be folded under closure panels ]5 and 17 and
sealed to provide a leakproof container bottom. Such a
closure means is well-known in the art. A separately
formed structure may alternatively be used to close the
bottom of the container. In fact, any closure means which
results in a satisfactorily tight seal may be used.
The gable top of the container is formed from a
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series of panels above top score line 31. First and second
roof panels 28 and 30 are connected to the upper edges of
the first and second side panels 3 and 5, respectively.
The roof panels are oppositely dispnsed and when erected,
converge upwardly to meet along score line 49 to form a
gable roof. Connected to the upper edge of the front panel
4 is a first substantially triangular end panel 29 whose
two lateral edges 35 and 36 formed by score lines extend
upwardly to score line 44. Similarly, second triangular
end panel 27 is connected to the upper edge of back panel
2, and has lateral edges 32 and 33 which extend upwardly to
score line 44.
On each side of triangular end panel 29 is a
foldback panel. First foldback panel 41 is connected to
triangular end panel 29 along edge 35, and to first roof
wing panel 40 along score line 8. ~anel 41 has a score
line 44 as its upper edge. Similarly, second foldback
panel 42 is connected to triangular end panel 29 along edge
36, and to second roof wing panel 43 along score line 9.
It has score line 44 as its upper edge.
Similarly, third and fourth foldback panels 39
and 38 are connected to triangular end panel 27 along
lateral edges 33 and 32, respectively. lhe third fo]dback
panel 39 is attached to the first rnof panel 28 along score
line 7, and the fourth fol~lback panel 38 is connected to
the second roof panel 30 by side seam flap 11 when the
container is erected.
Attached to the upper edge of each foldback panel
38, 39, 41 and 42 along score line 44 is a gable rib panel
45, 46, 50 and 52, respectively. Similarly, attached to
the upper edge of first and second roof panels 28 and 30
a~e first and second roof rib panels 48 and 54,
respectively. First and second gable rib panels 50 and 52
are connected to each other at a common score line 51, and
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third and fourth gable rib panels 46 and 45 are connected
to each other at common score line ~7. The uppermost end
51A of line 51 is the tip of the pouring spout of Lhe
erected container.
First gable rib panel 50 is connected to first
roof rib panel 48 at score line 8, and second gable rib
panel 52 is connected to second roof rib panel 54 at score
line 9.
First roof wing panel 40 comprises a triangular
portion of first roof panel 28 defined by score lines 34,
44 and ~, and is adjacent first foldback panel 41. Second
roof wing panel 43 comprises a triangular portion of second
roof panel 30 defined by score lines 37, 44 and 9 and is
adjacent second foldback panel 42. These roof wing panels
are more or less coextensive with the adjacent fol~back
panel when the erected container is closed.
A first upper rib panel 49 is connected to the
upper edge of the first roof rib panel 4~. Likewise, a
second upper rib panel 55 is connected to the upper edge of
the second roof rib panel 54. The score lines 60 and 61
separate the upper rib panels from the adjacent roof rib
panels, and are substantially continuous with the free
upper edge 53 of the first and second gable rib panels 50
and 52. The latter panels serve as lips of the pouring
spout of the erected container.
The score lines may be applied to blank lA
before or after the thermoplastic coating is appliecl to the
blank. The score lines may be applied to either surface or
both surfaces of the blank. For purposes of clearer
delineation of the various panels, score lines are shown in
the drawings on either or both o the inner and outer
surfaces of the blank and container.
In the embodiment shown in FIG. 4, two stiffening
fillets 56 overlie portions of the first and secon-1 gable
rib panels 50 and 52, and extend downwardly to overcover
portion of the first and second foldback panels 41 and 42
and small upper portions of first end panel 29.
-15 1 3 ~
As illustrated in an enlarged perspective view in
FIG. 4, each fillet 56 comprises a strip 66 of material
resistant to the container sealing process, and a layer 72
of adhesive. This adhesive layer 72 is attached to (a) a
first planar surface 67 of strip 66 and to (b) the inner
thermoplastic surface 62 of one or more of (i) the first
gable rib panel 50, (ii) the second gable rib panel 52,
(iii) the first roof rib panel 48, and (iv) the second roof
rib panel 54, (v) the first triangular end yanel, (vi) the
first fold back panel, (vii) the second fold back panel,
(viii) the first wing panel, and (ix) the second wing
panel.
The strip 66 of material is thus sealed to the
the-rmoplastic inner surface 62 of one or more of these
par-els.
Strip 66 may be formed from any solid material
which is resistant to any deleterious effect of the
container sealing process, and is sufficiently rigid so
that, together with adhesive layer 72, it provides
sufficient strength to reinforce the panel to achieve the
necessary stiffness. Thus, the bond strength between the
adhesive-free surface 68 of strip 66 to the thermoplastic
coating must be significantly less than the bond strength
between the strip 66 and the adhesive layer 72, or between
the adhesive layer 72 and the strip 66. Furthermore, strip
66 must not melt, extrude, or otherwise degrade at the
temperature and pressure conditions of the container
sealing process. Of course, a container sealing process of
significant compression of the panels at an elevated
temperature may tend to increase the area of intimate
contact and relieve elastic stresses, causing adhesive of
strip 66 to the thermoplastic inner surface 62. The
adhesive strength of this pressure-produced bond will be
significantly less than the adhesive strength of the
adhesive layer 72, however.
Material such as metallic foil, polyester film,
polycarbonate film are examples of strip materials which
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are unaffected by the temperatures used for sealing panels
coated with polyethylene. Such thermoplastic coatings are
typically sealed at temperatures o~ 250 to 400F (P,l and
205C).
The material of the strip may also be constructed
from unoriented polypropylene, such as that utilized as a
film backing in a pressure sensitive adhesive tape marketed
under the trademark "Y-8450" hy Minnesota Mining and
Manufacturing Company of St. Paul, Minnesota. A fillet
constructed of unoriented polypropylene exhibits severa]
advantages over strips constructed of other materials and
specifically polyester. Specifically, unoriented
polypropylene has a lower modulus of elasticity than
polyester (i.e. as low as 0.2 x 10 psl). Therefore, a more
compliant strip may be constructed which is better able to
conform to the scorelines between the pouring spout panels.
Thus, a notch, such as is shown in ~igures 9, 10 and 12 and
discussed hereinafter, is not required. I'his simplifies
the process of positioning and aligning the fillet on the
panels. The optimum temperature range per bonding the
unoriented polypropylene strip is 260' - 320'F. Unoriented
polypropylene is the preferred material for the stLip in
that it is dimensionally stable, even when subjected to the
elevated temperatures and pressures experienced when a
container is sealed. Oriented polypropylene, although
having increased tensive strength, has a tendency to return
to its unoriented state when exposed to temperatures (i.e.,
180`-200`F) below the sealing temperatures. This
distortion of oriented polypropylene results in huckling
3Q and separation of the polypropylene from a mounting
surface.
The strip 66 and adhesive layer 72 may be
preformed as a tape which is applied hy machine to the
blank lA.
For hermetic sealing containers, the modulus of
elasticity of strip 66 may be as low as 0.2 x loG psi (1.4
i ".
x 10~ kg/m2), but preferably for materials otht~r than
polypropylene is at least 0.4 x 10' psi (2.~ x 108 kg/m~).
The stiffness of the fillet 56 must be such that
the panel with the attached fillet has qreater stiffness
than a panel without the fillet. This relationship may be
expressed as follows:
E2>E1(h,) /(h~) 3
10 where: E, = modulus of elasticity of panel.
E2 = modulus of elasticity of panel ~ fillet.
h1 = thickness of panel.
h2 = thickness of panel + fillet.
It lS preferred that E~ be greater thall 0.2 x 10 poun-]s
per square inch (1.406 x 10~ kg per square meter) to
provide the desired stiffness.
The layer 72 is of such an adhesive type and
thickness that when the fillet 56 is compressed between
gable rib panel 50 and 52 and roof rib panels 48 and 54
during the first sealing process, a portion of the adhesive
of layer 72 extrudes from between the panel or panels and
strip 66 of resistant material. The extruded adhesive
fills channels otherwise open to leakage and effectively
seals the container. The adhesive used may be sealable by
pressure, heat, or other process.
FIG. 6 is an enlarged cross-sectional view
through the rib portion oE a container formed from this
invention, showing the panel members and fillet exaggerated
3Q in thickness for the sake of clarity. It is understood
that all of the panel members shown include a thermop]astic
coating on at least the inner surfaces, and preferably on
both the inner and outer surfaces. Additionally, the panel
members may include a film or foil of gas-impermeahle
material such as aluminum, overcovered by the thermoplastic
coating.
L 3 ~
First and second roof rib panels 48 and 54
oveLlie first and second gable rib panels 50 and 52. The
gable rib pane]s are separatecl from foldback panels 41 and
42 by scorelines 44, and the roof rib panels are likewise
separated from roof wing panels 40 and 43 by score~ines 44.
Upper rib panels 49 and 55 are separated by score lines 60
and 61 from the roof rib panels ~ and 54, and extend
upwardly therefrom. Eacll of the panels shown in the figure
includes a coating of thermoplastic on at least the inner
surface. Stiffening fillet 56 is shown attached to the
inner face of gable rib panels 50 and 52, and to an upper
portion of foldback panels 41 and 42. The fillet includes
resistant strip 66 and adhesive layer 72.
Fillet 56 may comprises a tape having a
relatively thick backing or strip 66 of a stiff material
whose bond to the thermoplastic surface of the panels is
weaker than its bond to adhesive layer 72. The adhesive
layer 72 may be thermoplastic in nature, hut preferably is
a pressure-sensitive adhesive. The latter affords easier
positioning during application to the blank lA, and does
not require the application of heat for positioning.
However, the thermal carton sealing process has been found
to significantly enhance the sealing strength of the
pressure-sensitive adhesives (PSA's) which were tested.
Typical pressure sensitive adhesives can be formed into
stable thick layers at room temperature, and will reaclily
extrude at the temperatures and pressures used to thermally
seal polyethylene. Thus, when an extruded bead of adhesive
is desired, PSA's appear to work well.
In FIG. 6, the container contents occupy the
space between panel 40 and panel 41, and the space between
panel 42 and panel 43.
When the first sealing process is thermal in
nature, the upper rib panels, the gable rib panels, and the
roof rib panels are heated to the softening or melting
point of the thermoplastic coating, and compressed together
as shown in FIG. 6. The upper rib panels are bonded on
-19- 1 3~
their inner sur~aces at interface 69, and gable rib panels
50 and 52 are preferably mutually bonded on their outer
surfaces at interface 70.
A further sealing feature may be produced if
desired. A thick layer 7~ of an extrudable adhesive may be
used in the fillet. Compression at an elevated temperature
during the carton sealing process extrudes the adhesive
from between the gable rib panels and strip 66, and the
extruded bead 79 of adhesive bon1s overlying panels 50 and
52 just above the upper edge 75 of strip 66. ~ similar
extrusion of adhesive is prodllced along the lateral edges
of strip 66 as well, both where the gable rib panels and
roof rib panels are joined, and along the exposed portion
of the common gable rib score line. A hermetic seal is
achieved where the adhesive extrudes, even when the bead of
extruded adhesive is minimal. The quantity of extruded
adhesive may be varied by controlling the type of adhesive,
the thickness of the adhesive layer, and the temperature
and pressure of the carton sealing process. The quantity
of extruded adhesive may be controlled to fill the small
channels 73 or channel 74 which typically develop along the
free upper edge 53 of the gable rib panels.
Furthermore, the space at the tip of the pouring
spout, that is, the space between common line 51 and the
corresponding line ~7 of the third and fourth gable rib
panels, usually not securely sealed in the prior art by the
first sealing process, may also be controllably filled with
a bead of extruded adhesive during the carton sealing
process to provide an aseptic or essentially hermetic seal.
This seal is especially enhanced by features to be later
described.
8ecause the bead bonding the gable rib panels to
the roof rib panels is relatively narrow, the seal may be
broken with minimal force to open the spout. The adhesion
of strip 66 to the container panel should preferably
produce a peel strength greater than 5Q oz. per inch of
width (612 grams per cm. width) at room temperature, so
-20 13~
that the fillet wi]l remain an integL-al part of the panel
to which it is attached, both before and after the spout
panels are unsealed and unfolded. The fi]let may he
adhesively attached to at least one of the pouring spout
5 panels listed above, depending upon what is desired for the
particular application. Fillets adhered to the roof rib
panels are somewhat less effective at transferring the
opening forces than fillets adhered to the gable rib
panels. However, the concomitant reduction in required
opening force enables fillets on the roof rib panels to
transfer the required forces.
In this invention, the thickness of adhesive
layer 72 is considerably greater than would be required for
merely bonding strip 66 to a panel. For example, while the
latter may be attained with a monomolecular layer of
adhesive, this invention generally requires an adhesive
layer exceeding 0.001 inch (0.0025 cm) in thickness for
achieving desired additional stiffness and leakproof
hermetic sealing. An adilesive layer of ~bout 0.002 inch
(0.005 cm) has proven optimal for certain pressure
sensitive adhesives used to seal polyethylene coated
containers. With other adhesives, a thickness of up to
0.004 inch (0.0102 cm) may be used. However, in
conjunction with a strip constructed of unoriented
polypropylene, an adhesive layer of approximately 0.003
inches (0.008cm) has been found to be preferred.
FIG. 7 shows a gable-top container 1 formed from
the blank of FIG. 4 and sealed according to the container
sealing process, and subsequently opened from the closed
and sealed condition. Second roof panel 30 and first roof
panel 28 converge upwardly so that their upper edges 44
meet or almost meet. Roof rib panels 48 and 54 are sealed
along approximately one-half of the length of the rib
structure, and enclose third and fourth gable rib panels 45
and 46. When the container is closed, common scoreline 47
between the third and fourth gable rib panels is somewhat
spaced from common scoreline 51. The void between those
-21- 1 3 ~
scorelines is a vertlcal channel which when filled with
adhesive will prevent leakage. First and second upper rib
panels 49 and 55 are joined by the container sealing
process. The spout panels of the rib structure are shown
to have been opened by first breaking the seal between the
upper rib panels 49 and 55, and then breaking the seal
between gable rib panels 50, 52 and roof rib panels 48, 54.
First trianglllar end panel 29, and first and second
foldback panels 41 and 4~ are folded outward to extend the
pouring spout.
Stiffening fillet 56 is shown at the inside of
the pouring spout, overlying and attached to a portion of
the inside surface of the first gable rib panel 50 and the
second gable rib panel 52, not visible in this view.
Conforming to a preferred embodiment, the fillet 56 also
extends downward over scoreline 44 to overcover a portion
of foldback panels 41 and 42. The advantages of such
extension will be later described.
Fillet 56 is shown as spaced from roof wing panel
40 and roof rib panel 48 to form side spacing 59, and also
spaced from the free upper edge 53 of gable rib panel 50 to
form lip spacing 58. During the first sealing process, a
portion of the adhesive is extruded from the adhesive layer
of the fillet 56 into channels 73, previously described,
resulting from spacings 58 and 59, to effectively seal
these areas from ]eakage. The surface 68 of the fillet 56
which has no adhesive layer is, of course, in contact with
roof rib panels 48 and 54 when the carton is sealed.
Fillet 56, being resistant to the container sealing
process, does not strongly adhere to the thermoplastic
surfaced roof rib panels, although the pressures and
temperatures typical of the first sealing process minimally
result in a close conformity of their surfaces which is
subsequently maintained by the tight seal of the rib panel
members. The seal between surface 68 and the overlying
panel, though not as tenacious as that of the opposite
adhesive coated side of the strip, nevertheless prevents
-22-
f.~
fluid leakage. ~ hermetic seal results from (a) the
thermoplastic heat seal between exposed portions of the
gable rib panels and opposing roof rib panels, or (h~ a
bead of adhesive extruded from beneath the strip, to be
described later, or ~c) a combination of the two.
FIGS. 8 through 12 show a portion of the blank
lA, including those panels which be~ome the pouring spout.
These figures depict various embodiments of fillet 56 in
terms of the particular panel area or areas covered
thereby.
In FIG. 8, a single fillet 56 overcovers all or a
portion of both gable rib panels 50 and 52. The uppermost
edge of fillet 56 may be generally continuous with the
upper free edge 53 of the gahle rib panels, but is
preferably spaced therefrom by less than 0.15 inches (0.38
cm) when a bead of extruded adhesive is to be a part of a
hermetic seal of the container. When the uppermost edge of
fillet 56 is lower than free edge 53 by more than 0.3
inches (0.76 cm), an excessive sealing area for the
thermoplastic carton sealing process may result. This
produces a strong seal which may require an excessive
opening force to break the seal. Also extruded adhesive
may not reach and fill the narrow channel which generally
forms ahove the edge 53. The narrow spacing 58 provides
space which in some cases is desirably filled with extruded
adhesive, minimi~ing the thermoplastic~to-thermoplastic
seal area and substituting an extruded adhesive seal. The
relatively narrow band of adhesive provides a tight seal
between the gable rib and roof rib panels which is
3n nevertheless openable with an acceptable opening force.
When the fillet or fillets 56 are adhesively
attached to both gable rib panels 50 and 52, and the
uppermost edge of the fillets extend above the upper free
edge 53 of the gable rib panels, the heat sealing process
will bond the exposed portions of the strips 66 on each
gable rib panel to each other. In addition, the amount of
adhesive extruded into the space above the strips 66 may be
-23-
1 3 ~
decreased. Tl-ereEore, it is general]y desirahle to limit
such upward extension of the fillet or fillets alove the
gable rib panels 50 and 52 to not more than 0.15 inches
(0.38 cm).
Each end of the fillet 56 may be spaced from the
roof rib panels q8 and 54 to form spaces ~9. The spacing
provides room for the panels to fold around the fillet at
scorelines 8 and 9. Preferably, the spacing 59 between
fillet 56 and the roof rib panels is not less tllan 0.01~1,
where W is the length of the first or second gable rib
panel 50 or 52. The maximum spacing 59 is controlled by
the length of fillet which will provide the desired
stiffness to the panels, and may be as great as 0.6w, where
w is as defined above.
FIG. 9 illustrates a fillet 56 overcovering a
portion of the gable rib panels S0 and 52, and extending
downwardly to overlie in bonded relationship a portion of
the first and second foldback panels 41 and 42. The fillet
also optionally overlies the upper portion of first
triangular end panel 29. The advantage of this downward
extension 71 is evident when the container sealing process
is one which affects the honding strength of the fillet
adhesive layer. In common heat sealing processes used to
seal polyethylene coated blanks, heat is directly applied
to the panels to be sealed, i.e., the rib panels. Panels
below the rib panels are only incidently heated and attain
a considerably lower temperature. The sealing temperature
is difficult to accurately control, and if the fillet
adhesive softens excessively, the fillet strip may slide
downward, not retaining its proper alignment on the gable
rib panel or panels. T11e portion of the fillet below the
gable rib panels will be much less affected because of the
lower temperature, and will maintain the original position
of the fillet. The high adhesion of adhesive layer 72 is
regained upon cooling.
The figure also shows the fillet as overlying
score line apex 6~ at the top of triangular end panel 29.
-2~- 131~
It has been discovered that enhanced sealing
results from cutting, notclling or slotting the strip 66
where it overcovers the common gahle rib scoreline 51,
especially the portion of the common line just below its
upper terminus 51A. Thus, strip 66 may include a cut
extending downwardly from the upper edge of the strip,
along at least a portion of the c~mmon line 51. This
enables adhesive from layer 72 and/or melted thermoplastic
polyethylene to extrude through the cut, notch or slot to
contact the opposite gable rib panels 45 and 46 at common
scoreline 47, and bond thereto. This difficult-to~seal
site is thus effectively sealed.
Fillet 56 is further shown in FIG. 9 with a notcl
65 extending downwardly from the upper edge of the strip,
along the common line 51 between the first gable rib panel
50 and the second gable rib panel 52. The notch may
optionally extend downwardly to expose apex 64, as further
shown in FIG. 10, or may extend downward as a slot through
the fillet to divide it into two fil~ets. When a notch or
slot exposes the common line 51, the edge of the fillet
strip may be separated ~rom a portion of the common line by
up to 0.3 inches (0.76 cm). When there are two fillets,
each overcovering a portion of one of the gable rib panels,
the maximum spacing of each fillet from common line 51 is
also 0.3 inches (0.76 cm). A greater spacing results in
insufficient stiffening of the panels in the vicinity of
common line 51, and in addition, the container sealing
process will bond an excessive portion of exposed gable rib
panel along line 51 to the corresponding roof rib par1el
with a thermoplastic-to-thermoplastic bond. Such a tight
bond at the point where the opening forces first act to
unseal the spout make such unsealing difficult. Greater
force is required, and with less reinforcement, the end of
the spout may crumple. When an aperture 76 exposes the
apex 64, as in FIG. 10, the edge 63 of the fillet is
preferably spaced from the apex by less than 0.3 inches
(0.76 cm).
-2~- 13~
Optiona]ly, the shape of fillet 56 may be such
that scorelines 35 and 36 are not covered thereby. ~he
forces required to open the seal are further reduced by so
doing.
~s shown in FIG. 11, a ~urther embodiment
comprises placement of fillets on one or both of the roof
rib panels 48 and 59. The size and shape of the fillets
are such that when the seal is closed, the fillets
generally correspond in coverage to those applied to the
gable rib panels. Thus, the upper edge 75 of each fillet
56 is no more than 0.3 inch (0.76 cm) from scoreline 60,
61, and preferably with 0.15 inch (0.38 cm). Likewise, it
is preferred that fillet edges 77 and 7~ are no more than
abol~t 0.3 inches (0.76 cm) from common line 51 when the
container spout is sealed. This ensures sealing of the
space between common fold]ines ~1 and 47.
FIG. 12 illustrates an embodiment whereby fillets
are attached to the inner surfaces of both the gable rib
panels and roof rib panels. In this embodiment, it is
imperative that the material from which the strips 66 are
made will not soften or melt under the container sealing
conditions to fuse the corresponding fillets together in a
strong bond. A limited degree of sealing is acceptable,
and may even be preferred. The previous discussion
regarding the desired fillet sizes and coverage also
applies.
When applied to a container blank which includes
a hermetic barrier, the container seal of this invention
may be adapted to provide a hermetically sealed container
under various conditions of cardstock thickness and
strength as well as container size.
EXAMPLE 1
Commercial hermetically sealed 0.5 gallon (1.9
liter) gable-top containers were manually opened. After
folding back the wing panels, simple forward hand pressure
on the roof rib panels resulted in buckling and distortion
-26- 1 3 ~
of the gable rib panels, without opening the tip of tlle
spout at the common fold line. In all cases, insertion of
a knife blade between the gable rib panels and roof rib
panels near the common fold line was re~uired to open the
spout.
Container blanks of the same material were sealed
by hand, using a LiquipaklM model 010 hand sealer.
Attempts to open the containers produced the same results
as were obtained with the commercially sealed containers.
An applied force of 15 pounds-force (6.~ kg-force) resulted
in tearing and buckling of the panels, without opening the
spout.
The opening force re~uired by a previously opened
hermetically sealed carton was determined to be abut 2.6
pounds-force (1.2 kg-force).
For the sake of comparison, a common milk carton
opened from the sealed condition with an applied force of
about 3.0 pound-force (1.36 kg-force), without te~ring of
the spout panels. This carton is sealed only to the extent
of preventing liquid leaks, and a hermetic barrier is not
provided.
E:XAMPI,E 2
Several types of fillet were applied to
polyethylene coated cardstock for determining the effect
upon panel stiffness and ease of container opening.
The container material was manufactured by
International Paper Company for hermetically sealed
cartons, and comprised paperboard having an aluminum film
bonded to the inside surface, and both sides then coated
with thermoplastic polyethylene.
The types of adhesive used in the fillets
included (a) ethylene-vinyl acetate (EVA) copolymer, (h)
medium density polyethylene ( MDPE ), and (c) a
pressure-sensitive adhesive (PSA).
The modulus oE elasticity was determined by
measuring the deflection caused by a weight placed on the
-27- 1 3 ~
center of a simple beam formed rom the cardstock.
Measurements were made on the cardstock itselE, on a pair
of gable rib panels from a blank, and from the entire outer
spout assembly comprising the gable rib panels, triangular
end panel, and foldback panels. The formula used to
calculate the modulus was:
E = fL /qba Y
where E = modulus of elasticity.
f = force applied, 0.11 pound (50 g) for most
tests.
a = thickness of beam.
b = width of beam, 1.0 inch (2.54 cm).
Y = deflection, inches (cm).
L = length of beam = 3.7 inches (9.4 cm).
-28-
1 3 ~
Tlle results were as fo]lows:
a Y E, Modulus,
Beam Material Thickness Deflection PSI(kg~cm )
,
5 Caldstock
(unreinforced) 0.027 in. 0.18 in. 393,0no
(0.069 cm) (0.46 cm) (2.76 x 108)
Cardstock with
transverse 0.027 in. 0.33 in. 28,000
scoreline.
(0.069 cm) (0.84 cm) (0.2 x 108)
(f = 10 g because of reduced modulus)
Cardstock with
fillet of 0.004 0.036 in. 0.090 in. 332,000
in. (0.010 cm)
polyester and (0.091 cm) (0.23 cm) (2.33 x 108)
0.002 in (0.005
cm) EVA adhesive
( ScotchpakT'~
26 tape)
Cardstock with
fillet of 0.002 0.032 in. 0.12 in. 390,000
in. (0.005 cm)
polyester and (0.079 cm) (0.30 cm) (2.7 x lOn)
0.003 in.
(0.0075 cm) PSA
Spout panels, 0.027 in 0.080 in. 885,000
not preflexed
(0.069 cm) (0.20 cm) (6.2 x 108)
Spout panels, 0.027 in. 0.21 in. 337,000
preflexed
(0.069 cm) (0.53 cm) (2.4 x lOa)
Polyester Film 400,000
(Literature
Value) (2.8 x lOg)
The results indicate that the modulus of
elasticity is approximately the same, i.e., 0.4 x 10~ psi
(2.8 x 108 kg/m2) for preflexed panels, either with or
without the added fillet.
Buckling forces were calculated from the data of
Table 2 using
-29-
~ 3 ~
Pcrit = CEh b/12L ,
where Pcrit is the forward-directed force at which
buckling will occur, lb-force;
C is pi '
E is the modulus of elasticity, approximately
0.4 x 106 psi;
h is thickness, 0.027 inches (0.069 cm);
b is width, 1.0 inch (2.54 cm); and
L is length, 3.7 inches (9.40).
The calculated force required to open (buckle the spout
tip) the unsealed spout of unreinforced cardstock was 0.5
pounds (0.23 kg.).
The force carried by both of the unreinforced
gable rib panels prior to buckling was calculated to be 1.9
pounds (0.86 kg.), using L = 1.85 inches. This leaves
1.9 - 0.5 = 1.4 pounds (0.64 kg.) of force for breaking the
bond at the tip of the spout.
~einforcement of the gable rib panels with a
0.002 inch (0.005 cm) thick polyester strip and 0.002 inch
(0.005 cm) layer of PSA adhesive provided a higher
calculated available force of 2.9 - 0.5 = 2.4 pounds for
breakiny the `oond at the spout tip. In this case, the net
panel thickness was 0.031 inches (0.079 cm.).
Reinforcing the gable rib panels with 0.004 inch
(0.010 cm) thick polyester and a 0.002 inch (0.005 cm)
layer 62 of EVA adhesive provided a calculated available
force of 4.6-0.5 = 4.1 pounds (2.09 kg.) for breaking the
bond at the spout tip. In this case, the net panel
thickness was 0.036 inches (0.142 cm). Thus, as a thicker,
stiffer reinforcement strip is added, the applied
forward-directed opening force available for opening the
spout tip greatly increases.
Measurements were made of the force required to
open a previously opened gable top hermetic sealing calton,
using a spring gauge. The average measured force of 2.4
-30-
1 3 ~
pounds (l.09 kg.) included the force required to buckle the
extreme tip of the unreinforced spout, that is, the common
fold line of the gable rib panels. Thus, the calculated
value of the force transmitted by the unreinforced spout
panels is only 1.9 pounds (0.~6 kg.), nearly equal to tlle
measured force o 2.4 pounds (1.09 kg) required to open the
previously opened carton. This demonstrates that the
greater joint strength of a sealed spout will result in
buckling of the cardstock when opening forces are applied
to the spout panels. On the other hand, when the gable rib
panels were reinforced with a fillet according to this
invention, the added stiffness provided an available
opening force qreater than 2.4 pounds to the common fold
line, and the containers were opened without bllckling or
delamination of the panels.
The effects of several variables upon ease of
opening were subjectlvely evaluated. Ease of opening was
enhanced by (a) an increase in gable rib area covered by
the fillet, (b) fillets of greater stiffness, (c) cutting,
notching or slotting the fillet strip 66 along the common
fold line between the gable rib panels, (d) ]eaving
uncovered the score line apex where the end panel touches
the common fold line, and (e) a reduction of gable rib area
which is permitted to thermally seal to the roof ribs.
EXAMPLE 3
Several types of adhesive tapes were evaluated
for use as fillets for ease of positioning in the spout,
adhesion to the gable rib panels, and opening
characteristics. The last are a function both of the
additional stiffness gained by the panels and the bonding
forces between the roof rib (or gable rib) panels and (a)
the fillet strip, (b) the exposed portion of the opposed
gable rib (or roof rib) panels, and (c) the extruded
adhesive, if present.
1 3 ~
The fillet configuration of FTG. 9 was utili%ed.
The notch 65 extended downwardly one half of the height of
the gable ribs, and the fillet extencled 1.0 inch (2.5 cm)
below the score line 44 separating the gable rib panels and
foldback panels 41 and 42.
The tapes included:
ScotchpakTM 26: 0.004 inch (0.01 cm) polyester backing
as the strip, with 0.002 inch (0.005 cm) EVA
adhesive.
ScotchpakTM 48: 0.0005 inch (0.0012 cm) polyester
backing with 0.004 inch (0.01 cm) MDPE adhesive.
ScotchtabrM: 0.002 inch (0.005 cm) polyester backing as
the strip, with 0.002 inch 90.005 cm) PSA
adhesive.
ScotchpakTM 26 with 0.00~ inch (0.0075 cm) PSA ad~esive
applied over the EVA adhesive.
Polyester/PSA: 0.002 inch (0.005 cm ) polyester film
backing as the strip, with 0.003 inch (O.nO76 cm)
PSA adhesive.
Control: No fillet.
The pressure-sensitive adhesive (PSA) used in
this test was a typical rubber-resin adhesive.
The results of the tests were as follows:
ScotchpakTM 26 with EVA adhesive was difficult to
position for sealinq, and required preliminary heat sealing
to provide a good seal. The sealed carton spout opened
easily without buckling or delamination.
ScotchpakTM ~8 with MDPE adhesive was difficult
to position and required preliminary heat sealing.
Insufficient stiffness was added by the fillet to
consistently transfer the required opening forces to the
spout tip. ScotchtabTM with PSA adhesive was easy to
position, and required heat sealing to strongly bond to the
panels. The sealed carton spout opened easily without
buckling or delamination.
-32- 13~
Scotchpak'M 26 with PSA adhesive was easy to
position, and heat-sealing provided a good seal. The
sealed spout opened easily without buckling or
delamination.
The control gable top carton spout, heat-sealed
according to the commercial process, could not be open--d
without buckling and delamination of the cardstock.
EXAMPLE 4
There are no standard tests for evaluating the
seal integrity of "hermetically sealed" containers.
However, a dye penetration test was performed on
"hermetically sealed" cartons both with and without a
fillet attached to the gable rib panels. Several
configurations of the fillet were tested. The dye
comprised 1.2 grams of Rhodamine B in 600 grams of
isopropyl alcohol. The dye solution was introduced into an
inverted carton having its gable-top sealed, and held for
10 minutes. The solution was then poured out and the
carton rinsed with water. The spout was opened and the
degree of dye penetration into the seal area was noted.
Containers formed from blanks without the fillets of this
invention and sealed conventionally to form "hermetic
seals" could not be opened without directly applying force
.o the inside of the spout. Tearing and delamination
resulted. All of the containers formed from blanks of this
invention were easily opened without significant tearing or
delamination of the spout panels. Little dye penetration
was noted in any of the opened container spouts, but the
penetration was greater in containers without the fillet or
fillets.
While the present invention has been particularly
set forth in terms of specific embodiments thereof, it will
be understood in view of the instant disclosl]re that
numerous variations upon the invention are enabled to those
skilled in the art, which variations yet reside within the
scope of the present teaching. Accordingly, this invention
-33-
is to be broadly construed, and limited only by the scope
and spirit of the claims now appended hereto.
EXAMPLE 5
An unoriented polypropylene adhesive tape was
evaluated as a stiffening filet in a one-half gallon gable
top container blank, which was then heat sealed with a
Liquipak Model 010 heat sealer.
The tape was applied to the inside of the spout
flush to the spout edge. ~rhe fillet was one and one-half
inches wide and three inches long and was centered on the
spout tip. No notch was cut in the fillet.
The tape had a 0.0035 inch thick unoriented
polypropylene backing and a 0.003 inch thick rubber/resin
pressure sensitive adhesive.
The carton was opened in the normal manner and a
spring gauge measured the opening force at 8.3 pounds. A
similar carton without the fillet would have a force in
excess of 12 pounds applied and would buckle and not open.
The polypropylene softned and filled the gaps and
channels in the spout. The polypropylene bonded
sufficiently to the polyethylene coating on the carton at
the back of the spout to provide a hermetic seal that was
easily separated during the spout opening. The hermetic
seal was determined by pouring an isopropyl alcohol dye
solution into the carton and examining the gable joint for
dye penetration. No dye penetration was observed.
EX~MPLE 6
An unoriented polypropylene adhesive tape was
evaluated as a stiffening filet in a one-half gallon gable
top container blank, which was then heat sealed with a
Liquipak Model 010 heat sealer.
The tape was applied to the inside of each side
of the carton in line with the spout edge. The fillets
were one-half of an inch wide and one-and-three-quarters of
an inch long.
1 3 ~ ;3
The tape had a n.oo3s inch thick unoriented
polypropylene backing and a 0.003 inch thick rubber/resin
pressure sensitive adhesive.
The carton was opened in the normal manner and a
spring gauge measured the opening force at 8.1 pounds. A
similar carton without the fillet would have a force in
excess of 12 pounds applied and would buckle and not open.
The polypropylene softned and filled the gaps and
channels in the spout. The polypropylene bonded
sufficiently to the polyethylene coatin~ on the carton at
the back of the spout to provide a hermetic seal that was
easily separated during the spout opening. The hermetic
seal was determined by pouring an isopropyl alcohol dye
solution into the carton and examining the gable joint for
dye penetration. No dye penetration was observed.
