Peelable seal on closure mechanism and method therefor

A peelable seal includes four layers. The first layer includes first and second alternating ribs. The first ribs comprise a first material, and the second ribs comprise a second material. The first material bonds well with the closure profiles. The second material bonds well with the third and fourth layers. The first material does not bond well with the second material. Thus, the bond strength is lower between the first and second ribs and between the third and fourth ribs than between the first and third ribs and the closure profiles and between the second and fourth ribs and the third and fourth layers. In this process, the strength of the peelable seal is controlled during the extrusion process rather than being subjected to the variations in the manufacturing process. Alternatively, the peelable seal includes six layers. The first and second layers bond well with the closure profiles. The third and fourth layers bond well with the fifth and sixth layers. The first layer does not bond well with the third layer and the second layer does not bond well with the fourth layer. Thus, the bond strength is lower between the first and third layers and between the second and fourth layers.

FIELD OF THE INVENTION 
The present invention generally relates to closure arrangements for 
polymeric packages and, in particular, to a closure arrangement having a 
peelable seal. 
BACKGROUND 
In many consumer packaging applications, it is important to prevent air or 
water from passing out of or into a package containing certain products. 
This is particularly true with respect to meat packages, cheese packages, 
and the like, for which the contained product must be kept in a constant 
environment to prevent spoilage. In order to preserve the product 
contained within such a package, the periphery of the package must be 
hermetically sealed. Hermetic seals can be provided by both permanent 
seals and temporary seals, known as peelable seals. Peelable seals are 
usable to provide a hermetic seal and, at the same time, provide a 
consumer with access to the contents of the package. A consumer breaks a 
peelable seal of a package by first grabbing onto opposing film faces to 
which peelable seal materials are adhered and then pulling the film faces 
apart. 
A common method of packaging foods, such as sliced luncheon meats and the 
like, is by use of a horizontal form, fill, and seal procedure. These 
procedures involve shaping a portion of film ("form"), placing the food 
article inside or upon the formed film portion ("fill"), completing the 
closure of the film portion around the food article and "sealing" open 
edges to complete the packaging process. 
In some implementations, one sealing station is used to seal all the edges 
of a package and, at the same time, make a peelable seal from a strip of 
peelable materials. The "sealing" stage of the form, fill, and seal 
procedure often involves using a resealable closure mechanism. The 
resealable closure mechanism and peelable seal are often produced as 
separate items from the package and are attached to and made integral with 
the package at a later point in the manufacturing process by a heat and 
pressure sealing process. In most implementations, the packages are made 
of polymeric materials, because these materials inhibit the migration of 
air and water from and into the package. 
To provide a peelable seal on a package with a resealable closure 
mechanism, the package typically uses permanent seals at its side edges 
and bottom edge and a peelable seal above or below the resealable closure 
mechanism at the mouth end of the package. In addition, the peelable seal 
may be arranged on either the flange/base portions of the closure 
mechanism or on the packaging film adjacent to the flange portions. 
The strength of the peelable seal is determined by the composition of the 
peelable material, temperature, pressure, dwell time of the seal bars, and 
the size of the peelable seal. The peelable seal needs to be strong enough 
to provide an adequate hermetic seal, but weak enough to allow the 
consumer to "peel" the peelable seal apart. Peelable seals are highly 
susceptible to small variations that might occur during manufacturing; 
i.e., the peelable seals have low manufacturing tolerances. Given these 
manufacturing variations, it is difficult to control the strength of the 
peelable seal. 
SUMMARY OF THE INVENTION 
In one aspect of the present invention, one example embodiment involves a 
closure arrangement for use with a polymeric package. The closure 
arrangement includes a first and second base strip. Each base strip has an 
inner and an outer surface. The outer surfaces are adapted for attachment 
to the polymeric package. The closure arrangement further includes a 
peelable seal. The peelable seal has a first and second layer. The first 
layer includes first and second alternating ribs. The first ribs comprise 
a first material, and the second ribs comprise a second material. The 
first ribs are attached to the first base strip. The second layer includes 
third and fourth alternating ribs. The third ribs comprise the first 
material, and the fourth ribs comprise the second material. The third ribs 
are attached to the second base strip. The peelable seal further includes 
a third and fourth layer. The third layer overlies the first layer and is 
attached to the second ribs of the first layer. The fourth layer overlies 
the second layer and is attached to the fourth ribs of the second layer. 
In another embodiment of the present invention, a closure arrangement 
includes a first and second base strip. Each base strip has an inner and 
an outer surface. The outer surfaces are adapted for attachment to the 
polymeric package. The closure arrangement further includes a peelable 
seal. The peelable seal has a first layer attached to the first base strip 
with a first bond strength therebetween and a second layer attached to the 
second base strip with a second bond strength therebetween. The peelable 
seal further has a third layer attached to the first layer with a third 
bond strength therebetween and a fourth layer attached to the second layer 
with a fourth bond strength therebetween. The peelable seal further has a 
fifth layer attached to the third layer with a fifth bond strength 
therebetween and a sixth layer attached to the fourth layer with a sixth 
bond strength therebetween. The first, second, fifth, and sixth bond 
strengths are greater than the third and fourth bond strengths. 
According to another aspect of the present invention, a method of 
manufacturing a polymeric package is provided. The method includes placing 
a first film panel adjacent to a second film panel, sealing a plurality of 
edges of the first film panel to corresponding edges of the second film 
panel, and placing a peelable seal between an unsealed edge of the first 
film panel and a corresponding unsealed edge of the second film panel. The 
peelable seal has a first and second layer. The first layer includes first 
and second alternating ribs. The first ribs comprise a first material, and 
the second ribs comprise a second material. The first ribs are attached to 
the first base strip. The second layer includes third and fourth 
alternating ribs. The third ribs comprise the first material, and the 
fourth ribs comprise the second material. The third ribs are attached to 
the second base strip. The peelable seal further includes a third and 
fourth layer. The third layer overlies the first layer and is attached to 
the second ribs of the first layer. The fourth layer overlies the second 
layer and is attached to the fourth ribs of the second layer. The method 
further includes heat sealing the peelable seal to both the first film 
panel and the second film panel and fusing the third and fourth layers of 
the peelable seal, forming a single, resulting layer that provides a 
hermetic seal. 
According to yet another aspect of the present invention, a method of 
manufacturing a polymeric package is provided. The method includes placing 
a first film panel adjacent to a second film panel, sealing a plurality of 
edges of the first film panel to corresponding edges of the second film 
panel, and using a peelable seal between an unsealed edge of the first 
film panel and a corresponding unsealed edge of the second film panel. The 
peelable seal has a first layer attached to the first base strip with a 
first bond strength therebetween and a second layer attached to the second 
base strip with a second bond strength therebetween. The peelable seal 
further has a third layer attached to the first layer with a third bond 
strength therebetween and a fourth layer attached to the second layer with 
a fourth bond strength therebetween. The peelable seal further has a fifth 
layer attached to the third layer with a fifth bond strength therebetween 
and a sixth layer attached to the fourth layer with a sixth bond strength 
therebetween. The first, second, fifth, and sixth bond strengths are 
greater than the third and fourth bond strengths. 
The above summary of the present invention is not intended to describe each 
illustrated embodiment or every implementation of the present invention. 
The figures and the detailed description that follow more particularly 
exemplify these embodiments.

DETAILED DESCRIPTION 
The present invention is believed to be applicable to a variety of 
packaging arrangements. The invention has been found to be particularly 
advantageous for use in sealing mechanisms for polymeric packages. An 
appreciation of various aspects of the invention is best gained through a 
discussion of an application example for such a packaging arrangement. 
According to an example embodiment of the present invention, a peelable 
seal is coextruded with a resealable closure mechanism to provide 
consistent and controlled strength of the peelable seal. FIGS. 1 and 2 
illustrate example types of packages 17, 24 that benefit from use of such 
peelable seals. 
FIG. 1 illustrates an example packaging arrangement in the form of a 
resealable, flexible package 17 having a zipper-type closure mechanism 26 
constructed in accordance with the present invention. The flexible package 
17 includes first and second opposed panel sections 15, 16 made from a 
flexible, polymeric film. For some manufacturing applications, the first 
and second panel sections 15, 16 are heat-sealed together along two edges 
25, 27 and meet at a fold line in order to form a three-edged containment 
section for a product within the interior of the package 17. The fold line 
comprises the bottom edge 29. Alternatively, two separate panel sections 
15, 16 of polymeric film may be used and heat-sealed together along the 
two edges 25, 27 and at the bottom 29. Access is provided to the interior 
of the package 17 through a mouth 31. In other implementations, the 
package 17 includes tear strings and/or notches at the mouth 31 to assist 
with opening the package 17. 
FIG. 2 is a perspective view depicting a rigid resealable package 24. The 
rigid resealable package 24 has the same basic features as the flexible 
resealable package 17 of FIG. 1. The package 24, however, has a flexible 
top side 21. The remaining five sides are either rigid, flexible, or a 
combination of rigid and flexible. 
A resealable closure mechanism 26 is illustrated in FIG. 1 at the opening 
of the flexible package 17. A similar closure mechanism 26' is illustrated 
in FIG. 2. Each closure mechanism 26 or 26' extends the width of the 
package 17 or 24. Each closure mechanism 26 or 26' can be one of a variety 
of closure mechanisms. In the particular embodiment illustrated in FIG. 3, 
the resealable closure mechanism 26 of FIG. 1 is shown in the specific 
form of a zipper-type mechanism. The resealable closure mechanism 26 
includes an elongated male closure profile 28 and an elongated female 
closure profile 30. The male closure profile 28 is comprised of a base 
strip 42 and an interlocking closure member 44. Base strip 42 is attached 
to the first package film 15. The female closure profile 30 is likewise 
comprised of a base strip 51 and an interlocking closure member 53. Base 
strip 51 is attached to the second package film 16. A resealable closure 
mechanism such as this is described in U.S. Pat. No. 5,486,051, hereby 
incorporated by reference. 
Still in reference to FIG. 3, a peelable seal, according to an example 
embodiment of the invention, is illustrated generally at 40. The peelable 
seal 40 includes a first peelable layer 32, a first sealant layer 33, a 
second peelable layer 34, and a second sealant layer 35. 
In the example embodiment illustrated in FIG. 3, the closure arrangement is 
manufactured using conventional extrusion and heat sealing techniques. In 
particular, the closure profiles 28, 30, the peelable layers 32, 34, and 
the sealant layers 33, 35 are coextruded through a die plate fed by a 
plurality of extruders. These extruders carry different molten materials 
for forming the closure profiles 28, 30, the peelable layers 32, 34, and 
the sealant layers 33, 35. As is well-known in the art, the die plate 
includes input ports, output ports, and channels connecting these input 
ports to output ports. The extruders feed the different molten materials 
to different input ports, and the channels are designed to configure the 
molten materials into the shapes of the closure profiles 28, 30, the 
peelable layers 32, 34, and the sealant layers 33, 35. 
Generally, the closure profiles 28, 30 are extruded from a polymeric resin 
such as polyethylene. The sealant layers 33, 35 are extruded from a 
material that heat-fuses easily during a typical heat and pressure seal 
process. For example, the sealant layers 33, 35 are extruded from a 
polyethylene resin. The first peelable layer 32 includes alternating first 
and second ribs 37, 38. The second peelable layer 34 includes alternating 
third and fourth ribs 37', 38'. The first and third ribs are extruded from 
a first material. The first material bonds well with the base strips 42, 
51 of the closure profiles 28, 30. For example, the first material 
comprises a polyethylene blend. By "bonds well," it is meant that the bond 
strength is greater than about six pounds per linear inch. The second and 
fourth ribs 38, 38' are extruded from a second material. The second 
material bonds well with the sealant layers 33, 35. For example, the 
second material comprises a polypropylene blend, a polybutylene blend, or 
a combination thereof. 
The bond strength between the first and second ribs 37, 38 and between the 
third and fourth ribs 37', 38' determines the strength of the peelable 
seal 40. The bond strength between the first and second ribs 37, 38 and 
between the third and fourth ribs 37', 38' is weak. By "weak," it is meant 
that the bond strength is typically from about 0.5 to 6 pounds per linear 
inch. This strength provides an adequate hermetic seal while still 
allowing the consumer to "peel" the peelable seal 40 apart. 
The die plate for the peelable layers 32, 34 is arranged and configured to 
extrude the first and second ribs 37, 38 and the third and fourth ribs 
37', 38' in a ribbed fashion, alternating ribs of the first material with 
ribs of the second material within the peelable layers 32, 34 as 
illustrated in FIG. 3. In this process, the first and third ribs 37, 37' 
are bonded to the base strips 42, 51, respectively, and the second and 
fourth ribs 38, 38' are bonded to the sealant layers 33, 35, respectively. 
This process causes the peelable layers 32, 34 to have a lower bond 
strength than the package films 15, 16, the closure profiles 28, 30, 
including base strips 42, 51, and the sealant layers 33, 35. The bond 
strength between the first rib 37 and the first base strip 42, between the 
third rib 37' and the second base strip 51, between the second ribs 38 and 
the first sealant layer 33, and between the fourth ribs 38' and the second 
sealant layer 35 is greater than six pounds per linear inch, while the 
bond strength between the first and second ribs 37, 38 and between the 
third and fourth ribs 37', 38' is no greater than six pounds per linear 
inch, typically about 0.5 to 6 pounds per linear inch. In one embodiment, 
the ribs 38, 38' may be omitted to provide air gaps between the ribs 37, 
37'. 
The bond strength of the peelable layers 32, 34 can be controlled by the 
length of time that the first and third ribs 37, 37' are in contact with 
the base strips 42, 51, respectively, and by the length of time the second 
and fourth ribs 38, 38' are in contact with the sealant layers 33, 35, 
respectively. Further control of the bond strength of the peelable seal 40 
is obtained by varying the melt temperature of each of the different 
materials of the closure profiles 28, 30, the peelable layers 32, 34, and 
the sealant layers 33, 35. This process allows the strength of the 
peelable seal 40 to be precisely controlled rather than subjecting the 
strength of the peelable seal 40 to the manufacturing tolerances of the 
heat and pressure seal process. 
After manufacturing, the closure profiles 28, 30 are interlocked, and the 
first sealant layer 33 is located opposite and adjacent to the second 
sealant layer 35. The closure arrangement is then attached to the package 
films 15, 16 by a conventional heat and pressure seal process. Attention 
is directed to FIG. 4. This process causes the package films 15, 16 to 
heat-fuse with the base strips 42, 51. This process further causes the 
first sealant layer 33 of FIG. 3 to heat-fuse with the second sealant 
layer 35 of FIG. 3 such that one fused layer 36 of FIG. 4 results, 
providing a hermetic seal. 
Attention is directed to FIG. 5. In yet another embodiment, the peelable 
seal 40 includes a first peelable layer 60, a second peelable layer 61, a 
first sealant layer 62, a third peelable layer 63, a fourth peelable layer 
64, and a second sealant layer 65. The closure profiles 28, 30, including 
the base strips 42, 51, and the sealant layers 62, 65 are comprised of the 
same material, such as polyethylene. The first and third peelable layers 
60, 63 are comprised of a polyethylene blend. The second and fourth 
peelable layers 61, 64 are also comprised of a polyethylene blend. This 
blend bonds well with polyethylene. In this embodiment, the bond strength 
of the peelable layers 60, 61, 63, 64 is controlled by varying the length 
of time each layer is in contact with its respective outer layer prior to 
tooling. For example, the first and third peelable layers 60, 63 are 
extruded with the closure profiles 28, 30, respectively. The second and 
fourth peelable layers 61, 64 are extruded with the sealant layers 62, 65, 
respectively. The first peelable layer 60 is combined with the second 
peelable layer 61 after tooling. Likewise, the third peelable layer 63 is 
combined with the fourth peelable layer 64 after tooling. 
This process results in a higher bond strength between the first peelable 
layer 60 and the male closure profile 28 and between the second peelable 
layer 61 and the first sealant layer 62 than between the first peelable 
layer 60 and the second peelable layer 61. Likewise, the bond strength 
between the third peelable layer 63 and the female closure profile 30 and 
between the fourth peelable layer 64 and the second sealant layer 65 is 
higher than between the third peelable layer 63 and the fourth peelable 
layer 64. The bond strengths between the first peelable layer 60 and the 
second peelable layer 61 and between the third peelable layer 63 and the 
fourth peelable layer 64 determine the strength of the peelable seal 40. 
This bond strength is no greater than six pounds per linear inch, 
typically about 0.5 to 6 pounds per linear inch. This strength provides an 
adequate hermetic seal while still allowing the consumer to "peel" the 
peelable seal 40 apart. The bond strength between the first peelable layer 
60 and the male closure profile 28 and between the second peelable layer 
61 and the first sealant layer 62 is greater than six pounds per linear 
inch. Likewise, the bond strength between the third peelable layer 63 and 
the female closure profile 30 and between the fourth peelable layer 64 and 
the second sealant layer 65 is greater than six pounds per linear inch. 
After manufacturing, the closure profiles 28, 30 are interlocked, and the 
first sealant layer 62 is located opposite and adjacent to the second 
sealant layer 65. The closure arrangement is then attached to the package 
films 15, 16 by a conventional heat and pressure seal process. Attention 
is directed to FIG. 6. This process causes the package films 15, 16 to 
heat fuse with the base strips 42, 51. This process further causes the 
first sealant layer 62 of FIG. 5 to heat-fuse with the second sealant 
layer 65 of FIG. 5 such that one fused layer 66 of FIG. 6 results, 
providing a hermetic seal. 
In yet another embodiment, the peelable seal 40 exists without the 
interlocking closure mechanisms 28, 30. In this embodiment, the peelable 
seal 40 is coextruded with the base strips 42, 51 and then heat-fused to 
the package films 15, 16 as described previously. 
The peelable seal 40 provides a hermetic seal at the mouth 31 of the 
package 17 of FIG. 1. The hermetic seal prevents air and water from 
penetrating the package films. This keeps the contents of the package in a 
constant environment to prevent spoilage. 
Prior to initially opening a package incorporating either the closure 
arrangement shown in FIG. 4 or the one shown in FIG. 6, the peelable seal 
40 is intact, the closure profiles 28, 30 are interlocked with each other, 
and the first and second films 15, 16 are connected at the mouth end 31 of 
the package 17 shown in FIG. 1. The first and second films 15, 16 are 
heat-fused together at the mouth end 31 of the package 17. Because the 
peelable seal 40 already provides a hermetic seal for the package, the 
first and second films 15, 16 may alternatively be disconnected from each 
other at the mouth end 31 of the package 17. 
To open the package 17, the first and second films 15, 16 are separated 
from each other by cutting them apart. Attention is directed to FIGS. 7 
and 8. Next, the interlocked closure profiles 28, 30 are detached from 
each other by grabbing onto the first and second films 15, 16 and pulling 
them apart. Finally, the peelable seal 40 is broken by continuing to pull 
the first and second films 15, 16 in opposite directions. In FIG. 7, the 
peelable seal 40 is broken between the first ribs 37 and the second ribs 
38, because of the weaker bond strength. Alternatively, the peelable seal 
40 is broken between the third ribs 37' and the fourth ribs 38'. In FIG. 
8, the peelable seal 40 is broken between the first peelable layer 61 and 
the second peelable layer 62, because of the weaker bond strength. 
Alternatively, the peelable seal 40 is broken between the third peelable 
layer 63 and the fourth peelable layer 64. 
The above specification and examples are believed to provide a complete 
description of the manufacture and use of particular embodiments of the 
invention. Many embodiments of the invention can be made without departing 
from the spirit and scope of the invention.