U.S. patent application number 10/570357 was filed with the patent office on 2007-04-12 for plastic container with rupturable seal.
Invention is credited to Nathan K. Hagen, Paul E. Hansen, John W. Rovang, Charlene M. Thill.
Application Number | 20070080078 10/570357 |
Document ID | / |
Family ID | 37910224 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070080078 |
Kind Code |
A1 |
Hansen; Paul E. ; et
al. |
April 12, 2007 |
Plastic container with rupturable seal
Abstract
A rupturable seal includes a first and second thermoplastic
polymer layer and a third continuous polymer layer between the
first and second polymer layers. The third polymer layer forms a
first physical polymer blend with the first layer, and forms a
second physical polymer blend with the second layer. The third
layer can include a continuous fibrous strip of nonwoven polymeric
microfibers, which may melt within a sealing region. Methods of
making such seals and multi-compartment containers comprising such
seals are disclosed. Applications for food storage and preparation
and other diverse end uses are disclosed.
Inventors: |
Hansen; Paul E.; (Lake Elmo,
MN) ; Rovang; John W.; (Savage, MN) ; Hagen;
Nathan K.; (Austin, TX) ; Thill; Charlene M.;
(Chanhassen, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Family ID: |
37910224 |
Appl. No.: |
10/570357 |
Filed: |
June 5, 2004 |
PCT Filed: |
June 5, 2004 |
PCT NO: |
PCT/US04/17722 |
371 Date: |
March 1, 2006 |
Current U.S.
Class: |
206/219 |
Current CPC
Class: |
B65D 81/3266
20130101 |
Class at
Publication: |
206/219 |
International
Class: |
B65D 25/08 20060101
B65D025/08 |
Claims
1. A rupturable seal, comprising: a first and second thermoplastic
polymer layer; and a third continuous polymer layer disposed
between the first and second polymer layers wherein the third
continuous polymer layer is devoid of through openings and
comprises a fibrous strip comprising nonwoven microfibers; wherein
the first and third polymer layers form a first physical polymer
blend; wherein the second and third polymer layers form a second
physical polymer blend; and wherein said blends are formed by
thermoplastic material melting and flowing into the interstices of
the microfiber strip.
2. (canceled)
3. The seal of claim 1, wherein the first and second physical
polymer blends define a sealing region of the rupturable seal, and
wherein the third continuous polymer layer comprises a distal
portion spaced away from the sealing region.
4. A container comprising the seal of claim 1.
5. A container according to claim 3, further comprising: a first
thermoplastic sheet sealed to a second member along at least one
permanent seal and at least one rupturable seal that defines a
first compartment within the container; and wherein the rupturable
seal is disposed between the first sheet and the second member to
form the rupturable seal.
6. The container of claim 5, wherein the second member comprises a
second thermoplastic sheet.
7. The container of claim 5, wherein the first thermoplastic sheet
comprises an inner thermoplastic layer and an outer strengthening
layer.
8. The container of claim 5, wherein the container comprises a
second compartment and wherein the rupturable seal separates the
first and second compartment.
9. A container according to claim 4, wherein the container holds a
food product.
10. A food storage article comprising the container of claim 8, and
further comprising a first food compartment sealed in the first
compartment and a second food component sealed in the second
compartment.
11. The food storage article of claim 10, wherein one of the first
and second compartments comprises an expandable portion.
12. A method of preparing food, comprising: providing the food
storage article of claim 10; and heating the food storage article
to an extent that vapor pressure in at least one of the first and
second compartments causes the rupturable seal to break.
13. The method of claim 12, wherein the pouch further comprises
edge seals around the periphery thereof that do not break when the
rupturable seal breaks.
14. A method of making a rupturable seal, comprising: providing
first and second transparent thermoplastic sheets; positioning a
continuous fibrous strip comprising nonwoven micro-fibers between
the first and second sheets to form a multilayer construction; and
applying sufficient heat and pressure to the multilayer
construction in a sealing region to form a rupturable seal that is
devoid of through openings.
15. The method of claim 14, wherein the applying step yields a
rupturable seal that is transparent.
16. The method of claim 14, wherein the fibrous strip is oversized
relative to the sealing region.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This international application claims priority as a
continuation-in-part to U.S. application Ser. No. 10/455,055,
"Nonwoven Plastic Pouch Separator", filed Jun. 5, 2003, pending,
and also claims priority to U.S. Provisional Application
60/511,064, "Plastic Pouch With Rupturable Seal For Food Storage
and Preparation", filed Oct. 13, 2003.
FIELD OF THE INVENTION
[0002] The invention relates to plastic containers such as pouches
that comprise at least one rupturable seal, used in many cases to
divide the container into a plurality of compartments. The
invention also relates to the application of such pouches in food
storage and preparation, and other applications.
BACKGROUND
[0003] Containers used for the storage of materials that react
together if allowed to come into contact with each other are known.
Such containers can include means, for example sealed boundaries or
barrier strips, and the like, to prevent contact between the
reactive materials until there is a need for the reaction product.
The seals and barrier strips can separate containers, particularly
plastic containers or packages, into a number of separate
compartments that can then isolate a variety of liquids or mobile
reactive components. Disruption of a barrier between compartments
provides a pathway for reactive components to intermix and react
together. Reaction may be encouraged by hand manipulation of a
flexible package.
[0004] The use of multi-compartment plastic packages is known for
containment of reactive materials including reactive liquid
monomers that require separation from activator materials that
convert the liquid monomers into cured resin materials. A typical
combination of reactive components comprises as a liquid epoxy
monomer separated from a stable mixture of a liquid polysulfide
polymer and an amine activator for the epoxy monomer. When mixed
together, these materials undergo exothermic reaction to produce a
heat-resistant, tough resinous product that finds use as an
electrical insulating material.
[0005] U.S. Pat. No. 2,932,385 (Bollmeier et al.) discloses a
multi-compartment plastic package suitable as a container that
keeps a liquid epoxy monomer composition separate from a liquid
polysulfide polymer. The package includes two sheets of a
thermoplastic film fusion bonded together along the outer edges of
the film and divided into compartments by heat-sealing a breaker
strip between the films so that it extends to the fused edges of
the films. A breaker strip is weaker physically than either of the
films, which allows it to break, under stress, before rupture of
the fused edge seals of the plastic package. U.S. Pat. No.
3,074,544 (Bollmeier et al.) describes several methods for forming
multicompartment packages using a variety of sealing strips.
[0006] Other references to multi-compartment plastic packages may
be found in, for example, U.S. Pat. No. 2,756,875 (Yochim), U.S.
Pat. No. 2,916,197 (Detrie et al.), U.S. Pat. No. 3,809,224
(Greenwood), U.S. Pat. No. 4,961,495 (Yoshida et al.), and U.S.
Pat. No. 5,287,961 (Herran). The '495 Yoshida reference discloses
that the compartments can be filled with medical and pharmaceutical
substances, and also mentions foods. U.S. Pat. No. 2,971,850
(Barton) discloses other materials that may be stored in
multi-compartment plastic containers, and identifies a
multi-compartment package including a rupturable membrane to
separate the components of an enzyme system. The package preserves
enzyme activity before rupture of the membrane and reaction between
the enzyme and an appropriate substrate material.
[0007] A need however remains for a rupturable seal forming
material to lower the cost, improve consistency, and increase the
efficiency of processes used for manufacturing multi-compartment
plastic storage bags and other containers having increased shelf
life. Such seals should ideally be suitable for food storage and
preparation applications, and various other end-use
applications.
BRIEF SUMMARY
[0008] The present application discloses an exemplary rupturable
strip seal, comprising micro-fibers such as melt-blown
micro-fibers, that separates by application of force, causing the
seal to rupture to allow admixture and/or interaction of the
contents previously isolated in separate compartments of a plastic
container. The rupturable seal can form a structure that
temporarily isolates the contents of a container from the outside
environment, or can provide a divider to seal compartments of a
plastic bag or pouch or similar container from each other. A
multi-compartment plastic bag or pouch provides suitable
containment for two or more materials that admix and/or react on
contact to yield useful products such as coating materials,
encapsulant materials, bonding materials, and the like.
[0009] The exemplary rupturable seal is particularly suitable for
food product applications. Different food components can be sealed
in the separate compartments of a multi-compartment plastic pouch,
which can then serve as a food storage article. In some cases the
food-filled pouch can be frozen for long-term storage until needed.
To prepare the food for consumption, the pouch can be placed in a
microwave oven where the food components are heated and cooked
separately from each other for a first time period as they are
exposed to microwave radiation. During the first time period, vapor
pressure (for example, due to steam) in at least one of the
compartments gradually increases to a level that causes the
rupturable seal to break, thus permitting admixture of the
different food components present in the compartments adjacent the
ruptured seal. The rupture of the seal marks the end of the first
time period and the beginning of a second time period, during which
the different food components are allowed to cook together in the
pouch as microwave radiation continues to bombard the pouch. The
microwave radiation is turned off at an appropriate time, marking
the end of the second time period. The pouch can then be opened
such as by tearing, cutting, or otherwise breaking the permanent
seals around the periphery of the pouch. In some cases methods
other than microwave cooking can be used to heat the pouch, such as
methods that utilize solar or infrared radiation, or methods that
use convection or conduction of heat such as placing the pouch in
boiling water or another heated fluid. In some cases the pouch can
comprise an expandable portion in which the cooked food contents
can collect such that the pouch sits upright on a flat surface,
permitting the user to eat the cooked food contents directly from
the opened pouch.
[0010] In some food or non-food applications, for example,
applications where heating is not desired, the pouch can be opened
by hand manipulation such as squeezing or pulling. Still other
applications may utilize a container comprising a molded plastic
base and a thin plastic cover sheet sealed to portions of the
plastic base to form isolated compartments therebetween.
[0011] Exemplary strip seals include substantially a single
material, such as a layer of meltblown plastic micro-fibers. This
differs from the description of breaker strips in U.S. Pat. No.
2,932,385 (Bollmeier et al.), which bond together two films on
opposite sides of a breaker strip consisting of a central fibrous
portion separating outer filmstrips. The outer filmstrips comprise
the same thermoplastic polymer as the two films bonded to them on
either side of a breaker strip. This produces a filmstrip-to-film
seal equally as strong as the seal formed by direct fusion sealing
of one film to another. The fibrous central layer provides a
weakened plane of the breaker strip, which splits along its central
plane when the films are jerked apart. With bursting of the breaker
strip, the two filmstrips remain separately attached to different
films that form the sides of a plastic package or container.
According to the '385 Bollmeier et al. reference, another example
of a breaker strip consists of a thin porous paper coated on both
surfaces with a thin continuous layer of polyethylene, which heat
seals to polyethylene films that form the outer envelope of a
multi-compartment package. The paper center of the breaker strip
remains porous and susceptible to leakage by premature rupture or
separation due to chemical attack. Either of these conditions
produces an opening between compartments. Premature rupture leads
to undesirable leakage between compartments.
[0012] As indicated above, previously known seals were composite
structures having a fibrous portion sandwiched between continuous
layers of barrier film of substantially the same chemical
composition as thermoplastic sheets of film used to form
multi-compartment bag structures. Exemplary strip seals disclosed
herein are uniform structures formed by cutting strips from fibrous
webs such as webs composed of melt blown micro-fibers. In some
embodiments, these webs can be characterized by effective fiber
diameters ranging from about 2.5 .mu.m to about 7 .mu.m. Effective
fiber diameter (EFD) is further defined below and for purposes of
this application is generally close to but slightly greater than
average fiber diameter. In some embodiments, the webs can comprise
fibers whose actual diameters range (on average) from a fraction of
a micrometer to about 10 or 20 .mu.m. One method for micro-fiber
formation uses a known process that disrupts high velocity streams
of a thermoplastic polymer to produce small diameter fibers
referred to herein as melt-blown micro-fibers.
[0013] Exemplary bags, pouches, or other containers can use sheets
of a composite film laminate having a surface of polyethylene, or
other thermoplastic heat-seal material, adjacent to a surface of
polyethylene terephthalate ("PET"), or other strengthening
material. These sheets are oriented or arranged such that the
heat-seal material of each opposing sheet is on the interior of the
pouch, and the strengthening material is on the exterior of the
pouch. A rupturable strip seal, used to separate two adjacent
compartments of a plastic pouch, can have fibers whose melting
point is higher than that of the thermoplastic heat-seal material
on the interior of the polymer sheets. In that case, where the heat
seal temperature is below the melting point of the micro-fibers,
bond formation between the strip seal and a thermoplastic polymer
sheet relies upon the thermoplastic material melting and flowing
into the interstices of the micro-fiber strip, forming physical
polymer blends of the micro-fibers and each thermoplastic material
to produce a bonded structure. On the other hand, where the heat
seal temperature is at or above the melting point of the
micro-fibers, all or a portion of the micro-fiber strip seal can
melt as the molten thermoplastic polymer sheet material flows into
the interstices of the micro-fiber strip, again forming a physical
polymer blend. In either case, a physical polymer blend of the
micro-fiber strip and the thermoplastic material on one side of the
strip is produced, and a physical polymer blend of the micro-fiber
strip and the thermoplastic material on the opposite side of the
strip is also produced. And in either case, air that initially
resides within the interstices of the micro-fiber strip is
substantially displaced from or otherwise driven out of the bonding
area. An exemplary embodiment of a multi-compartment pouch or other
container includes a strip seal of polypropylene micro-fibers
between layers of polyethylene. Polyethylene wets polypropylene
micro-fibers so there is no need to laminate compatible films of
polyethylene on either side of the polypropylene or alternatively
to add polyethylene fibers to the strip seal.
[0014] Although it is not necessary for the micro-fiber strip to
melt during sealing, a seal including thermoplastic polymer
micro-fibers, when incorporated into a pouch, has sufficient burst
strength, between about 0.1 kg/cm.sup.2 (1.45 psi) and about 1.25
kg/cm.sup.2 (17.5 psi), to prevent solid or liquid transfer across
the seal representing the impermeable barrier. However, the
micro-fiber strip seal can rupture under moderate hand stress
without damaging the thermoplastic sheets or breaking the edge
seals around the periphery of the bag.
[0015] An advantage of strip seals of melt blown polymer
micro-fibers is the high uniformity of an inert material that
provides barrier strip seals of greater reliability and consistency
than breaker strips described previously as including a central
layer of non-woven or paper material. The manufacture of such
breaker strips requires a complex process including at least one
additional step to laminate thermoplastic material on either side
of the non-woven or paper materials before the resulting breaker
strips may be bonded to thermoplastic polymer sheets during package
formation. Additional processing steps increase the probability of
inconsistent product performance leading to scrap and higher
manufacturing costs.
[0016] A melt blown polypropylene micro-fiber web is a readily
available material obtained by a one-step process that is more
controllable than processes used to produce laminates of polymer
films and non-woven or paper material. In addition, it is possible
to manufacture single layer melt blown polymer micro-fiber webs
having controlled levels of basis weight, fiber diameter, and
porosity. Single-layer strip seals have no internal planar
interfaces that could fail by premature rupture or separation
following chemical attack, for example. In cases where the sheet
materials are transparent, strip seals formed from melt blown
polymer micro-fiber webs can also advantageously provide a visual
indication of effective barrier seal formation when the sealed
junction changes from an opaque to a substantially transparent
condition. The transition from opaque to transparent provides an
observable signal of formation of a barrier seal that can provide
effective separation between compartments of a plastic package.
[0017] A multi-compartment plastic pouch or bag container can be
fabricated to include two opposed sheets of thermoplastic polymeric
film and at least one melt blown micro-fiber strip seal. Formation
of fused edges, by heat-sealing around the edges of the film sheets
forming the periphery of the bag produces a hermetically closed
interior space or envelope. A suitably positioned strip seal,
bonded between the two opposed sheets by application of heat and
pressure, divides the interior space into a first and second
adjacent compartment disposed on opposite sides of the strip seal,
and forms a barrier to material transfer between the first and
second compartments.
[0018] Moreover, the disclosed fibrous strip can provide a
rupturable seal when sandwiched with heat and pressure between a
first thermoplastic polymer layer having a first melting point and
a second thermoplastic polymer layer having a second melting point.
With adequate heat and pressure, material from the first
thermoplastic polymer layer flows at least partially into one side
of the fibrous strip, advancing into the interstices between
individual fibers of the strip. Likewise, material from the second
thermoplastic polymer layer preferably flows at least partially
into the opposite side of the fibrous strip, also advancing into
the interstices between individual fibers. This can occur when the
melting point of the fibers within the fibrous strip is greater
than that of the first and second thermoplastic polymer materials.
Exemplary rupturable seals are formed when the first and second
thermoplastic polymer materials contact each other through the
thickness of the fibrous strip to form physical polymer blends.
Depending upon bonding conditions, the portion of the fibrous strip
within the sealing region may still contain individual discernable
micro-fibers or may have melted. The presence of the individual
fibers (or melted fibers) produces a bond or seal that is weaker
than a seal directly between the first and second thermoplastic
polymer layers. Thus, an applied force can cause the seal to split
along the embedded fibrous strip, producing a controlled peel along
the length of the rupturable seal.
[0019] In some embodiments, a first thermoplastic material that
flows into a first major surface of the fibrous strip can be
considered to form a first boundary layer bonded to the first
polymer layer, and a second thermoplastic material that flows into
a second major surface of the fibrous strip can be considered to
form a second boundary layer bonded to the second polymer layer.
The fibers making up a sealing interlayer have a melting point
higher than the melting points of the first and second
thermoplastic materials and can comprise a plurality of
micro-fibers having an average effective fiber diameter from about
2.5 .mu.m to about 7 .mu.m. The first boundary layer includes a
first portion of the plurality of micro-fibers surrounded by the
first polymer material. The second boundary layer includes a second
portion of the plurality of micro-fibers surrounded by the second
polymer material. The rupturable seal can have a frangible
interface between the first boundary layer and the second boundary
layer. The rupturable seal parts at the frangible interface by
application of a force causing separation of the first boundary
layer from the second boundary layer.
[0020] These and other aspects of the invention will be apparent
from the detailed description below. In no event, however, should
the above summaries be construed as limitations on the claimed
subject matter, which subject matter is defined solely by the
attached claims, as may be amended during prosecution.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Throughout the specification reference is made to the
appended drawings, where like reference numerals designate like
elements, and wherein:
[0022] FIG. 1 is a plan view of a pouch comprising a rupturable
seal prior to filling the individual compartments with suitable
contents and edge sealing the pouch closed;
[0023] FIGS. 1a, 1b, and 1c are fragmentary plan views in the
vicinity of an edge of alternative embodiments to that of FIG.
1;
[0024] FIG. 2 is a sectional view along line 2-2 in FIG. 1;
[0025] FIG. 3 is a schematic close-up cross-sectional view of the
edge of a rupturable seal;
[0026] FIG. 4 is a plan view of a pouch similar to that of FIG. 1
but incorporating an expandable portion in one of the
compartments;
[0027] FIG. 5 is a plan view of multi-compartment pouch comprising
multiple rupturable seals forming more than two compartments;
[0028] FIG. 6 is a plan view of a multi-component pouch comprising
intersecting micro-fiber strip seals that form multiple rupturable
seals in a four-compartment pouch;
[0029] FIG. 7 is a plan view of a two-compartment pouch
incorporating a combination rupturable seal and permanent seal to
permit an enhanced mixing feature;
[0030] FIGS. 7a and 7b are fragmentary plan views of alternative
embodiments to that of FIG. 7;
[0031] FIG. 8 is a schematic sectional view of a container having a
molded rigid plastic base and a cover sheet bonded to each other
with at least one rupturable seal; and
[0032] FIG. 9 is a plan view of a single compartment pouch
incorporating a disclosed rupturable seal as an opening
thereof.
GLOSSARY
[0033] As used herein, the following terms shall have the meanings
shown unless otherwise indicated.
[0034] "Micro-fiber" refers to fibers whose average diameter is
about 20 .mu.m or less, preferably from about 1 .mu.m to about 10
.mu.m.
[0035] "Effective fiber diameter" is a calculated dimension, known
to one of ordinary skill in the art, derived from the pressure drop
across a micro-fiber web of known thickness, polymer density, and
basis weight.
[0036] "Rupturable seal", "barrier seal", and the like refer to an
airtight closure formed using at least one plastic sheet, which
closure can be opened without tearing the plastic sheet. In some
cases such a seal can comprise a composite structure comprising at
least two layers of thermoplastic polymer bonded to the sides of a
strip seal, as well as boundary layers produced by infusion of
molten thermoplastic polymer into spaces between micro-fibers
forming side portions of a strip seal.
[0037] "Strip seal," "separator strip seal," "microfibrous strip
seal," "sealing interlayer," "fibrous strip", and the like refer to
a collection of fibers formed into a long, thin porous layer or
layers, and in some cases can comprise a blown micro-fiber web,
converted into strip form for use in the formation of rupturable
seals between suitable layers of polymer film or film laminates.
This definition also includes strip seals (etc.) embedded between
layers of thermoplastic material, where the fibers of such strip
seals may have been partially or completely melted to form shapes,
other than fibers, capable of producing a physical blend with
another polymer.
[0038] A "boundary layer" forms on either side of a barrier seal
when molten polymer infuses into a strip seal to provide, on
cooling, a polymer-filled side portion of the strip seal.
[0039] "Frangible interface" refers to a central portion of a
rupturable seal. In some cases the frangible interface may reside
between boundary layers and may include micro-fibers substantially
free of thermoplastic polymer. This provides a relatively weak
interface that preferentially parts during forced separation of
opposing boundary layers. In some cases the frangible interface can
include portions wherein the first polymer contacts the second
polymer. In some cases, depending on the bonding temperature and
the dwell time under pressure, molten polymer can substantially
fill the internal space of a strip seal. A major portion of a
frangible interface may in some cases comprise a
micro-fiber-containing gap between boundary layers.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS
[0040] A multi-compartment plastic pouch or bag container, such as
that shown at 10 in FIGS. 1 and 2, may be fabricated to include two
opposed sheets 12, 14 of thermoplastic polymeric film and at least
one melt blown micro-fiber strip seal 16 or similar fibrous strip.
Depending upon the duration and pressure of bonding, layers of
polyethylene (or other suitable thermoplastic) fuse together at
temperatures between about 120.degree. C. and about 200.degree. C.
to form fused, permanent heat-sealed margins 18a, 18b, 18c around
the edges of the film sheets, producing a hermetically closed
interior space or envelope. In FIGS. 1 and 2, such a space is
created after formation of a final edge seal at the top of the
pouch opposite margin 18b. A suitably positioned strip seal 16,
bonded between the two film sheets 12, 14, divides the interior
space into first and second adjacent compartments 20, 22
respectively, and represents a barrier to material transfer from
the first to the second compartment. The bonded strip seal 16 forms
a rupturable barrier seal 16a along the strip seal and preferably
has a narrower width than that of the strip seal itself, as
indicated by the broken lines extending along strip seal 16 in FIG.
1. Note that the rupturable barrier seal 16a is not preserved at
those places where it overlaps a heat-sealed margin such as 18b,
thus ensuring that when a rupture occurs in the barrier seal 16a,
the peripheral edge seals remain intact and the interior space of
the pouch remains closed. The sizes and positions of the two
compartments depend upon the position of the strip seal inside the
plastic package. It will be appreciated that additional strip seals
can be positioned between the two film sheets to increase the
number of compartments in a bag container.
[0041] The region of overlap (labeled 15 in FIG. 1) at the end of
the strip seal 16, where a permanent edge seal such as 18b crosses
the strip seal, forms a seal that is not as weak as the central
portion of barrier seal 16a due to mechanical reinforcement by
being flanked on opposed sides by permanent edge seal 18b, but not
as strong as the permanent heat-sealed margins 18a, 18b, 18c due to
the presence of the embedded fibrous strip or strip seal 16. Such a
seal of intermediate strength at region 15 can be used
advantageously as a pressure relief mechanism. Thus, for example,
after closing compartments 20, 22 with a permanent top edge seal, a
first amount of pressure is applied to rupture barrier seal 16a. If
further pressure is then applied (or the temperature of the pouch
is increased), region 15 and its counterpart at the top of the
pouch 10 provide relatively small but predictable failure points so
that the pouch does not undergo a more energetic and less
predictable failure through sheets 12, 14 or one of the permanent
edge seals. The strength of the overlap region 15 can be adjusted
by changing the sealing conditions (temperature, pressure, dwell
time, and so forth) of the permanent heat-sealed margin 18b. It can
also be adjusted by selectively narrowing or widening portion(s) of
the fibrous strip or strip seal 16 and then before sealing the
upper and lower edge seals, aligning the narrowed or widened
portion(s) with the upper and lower edges of the pouch 10. This is
depicted in the fragmentary views of FIGS. 1a and 1b, producing
modified overlap regions 15a and 15b respectively.
[0042] FIG. 1c shows another fragmentary view of a portion of a
lower permanent edge seal 19 formed by, for example, heat sealing
film sheets such as 12, 14 described above. The edge seal may be
part of any of the container embodiments described herein, or may
be part of an otherwise conventional multi-compartment pouch or
other container, or even an otherwise conventional single
compartment pouch or container. But included in the seal is a piece
of fibrous strip or strip seal 17 large enough to span the width of
the edge seal and preferably, but not necessarily, extending
slightly beyond the seal into the sealed compartment 21. The sealed
strip is flanked on opposed sides by strong permanent seals, but is
rupturable. The strip seal 17 can thus provide a simple, low cost
pressure release mechanism for virtually any type of plastic
container.
[0043] Suitable film materials for multi-compartment plastic
packages may be selected from a group of polymer films and film
composites including a suitable heat-seal layer. Formation of the
barrier seals may use any of a wide range of thermoplastic polymers
to provide bonding layers melting below or close to the melting
point of the micro-fibrous strip seal. Suitable materials may be
selected from, for example, polyolefin polymers including
polyethylene and polypropylene, polyvinyl chloride, and ethylene
vinyl acetate and film composites including any of these materials
laminated with films of polymers that can provide additional
strength, such as polyethylene terephthalate (PET), that melts at
temperatures higher than those used during the bonding process. The
strengthing layer such as PET preferably forms an outer layer or
exterior of the pouch or other container, and is preferably
composed of a material whose melting point is also higher than that
of the thermoplastic material forming the interior of the pouch or
container. Alternative strengthening layers can comprise or be
substantially composed of, for example, polypropylene, nylon
(polyamide), polyethylene naphthalate and other polyesters,
fluoropolymers, and metal foils such as aluminum foil.
[0044] Manufacture of a blown micro-fiber polymer web preferably
relies upon a method of the type described by Van Wente in
Industrial and Engineering Chemistry Vol. 48, No. 8, 1956, p. 1342.
U.S. Pat. No. 3,978,185 (Buntin et al.) describes a similar but
improved method that reduces the amount of undesirable coarse
"shot" or "beads" of material larger than about 0.3 mm in diameter.
The manufacturing method has been shown to yield micro-fibers as
fine as 0.1 .mu.m to 1.0 .mu.m for various thermoplastic materials
including nylon (polyamide), polyolefins, polystyrene, poly(methyl
methacrylate), poly(ethylene terephthalate), and
polytrifluorochloroethylene. Fiber formation requires the use of an
apparatus that is essentially a ram-extruder that forces molten
material through a row of fine orifices and directly into two
converging, high velocity streams of heated air or other
appropriate gas. Air temperature and polymer-melt temperature have
separate adjustment, as do the velocities of the streams of air and
thermoplastic fluid materials.
[0045] A resin, ejected from an extruder nozzle at a temperature
between about 290.degree. C. (550.degree. F.) and 430.degree. C.
(800.degree. F.), enters a gas stream as molten strands of resin
that the gas stream attenuates into fibers. Fibers form at a point
that lies within the gas stream where cooling has progressed
sufficiently to solidify the resin material. Since the hot-melt
resin issues from the nozzle directly into the confluence of the
two air streams, the greatest amount of attenuation occurs at this
point of exit. Depending upon the exact temperatures and velocities
used, the fibers cool to a solid form after being carried by the
air stream a distance of about 2.5 cm away from the nozzle tip.
[0046] Newly formed fibers move away from the nozzle in a dispersed
turbulent stream at very high velocity. With typical air conditions
of about 315.degree. C. (600.degree. F.) and about 3.5 kg/cm.sup.2
(50 psi), this velocity might equal or exceed sonic velocity, i.e.
about 500 meters per second (1600 feet per second). A moving 16
mesh screen provides a surface that separates the air blast from
the fibers to provide a random deposit of fibers that may be
stripped from the screen as a (nonwoven) fiber mat for collection
on a wind-up reel, with or without being densified using press
rolls. Melt blown polymer webs, preferably polypropylene webs,
suitable for fabrication of strip seals as described herein
preferably have an effective fiber diameter (EFD) from about 1 to
20 .mu.m, preferably 2.5 .mu.m to 7 .mu.m, more preferably 4 .mu.m
to 6 .mu.m. Polymer webs or fibrous strips composed of a collection
of micro-fibers in a nonwoven layer have been found to be useful in
the disclosed applications, where the fibers have an average
(actual) diameter ranging from about 4 .mu.m in some embodiments to
about 12 .mu.m in other embodiments. An exemplary range for average
fiber diameter is considered to be about 1 to 20 .mu.m, more
preferably about 4 to 6 .mu.m.
[0047] Preferably, in its original condition before sealing, the
strip seal or fibrous strip is both (1) continuous and (2) porous.
By this we mean that the strip is (1) substantially devoid of
through-openings, yet is also (2) porous by virtue of
interconnected interstitial spaces between the fibers. The
continuous feature prevents or discourages softened thermoplastic
sheet material from flowing in direct paths across the strip, which
would form islands of uninterrupted thermoplastic material and
detract from the desired rupturable nature of the seal. The porous
feature however permits softened thermoplastic sheet material to
form serpentine or tortuous paths into at least the outer portions
of the strip seal, and if the micro-fibers of the strip do not melt
during sealing, then preferably across the thickness of the strip.
After sealing, the portion of the strip seal or fibrous strip that
extends out of the sealing area generally remains continuous and
porous, because it was not subjected to the full heat and pressure
in the sealing area. The portion of the strip within the sealing
zone generally remains continuous, and forms physical polymer
blends (i.e., interconnecting material structures) with the
adjacent thermoplastic layers whether or not the micro-fibers
remain intact or melt during the sealing process.
[0048] Preferred combinations of micro-fibers and thermoplastic
sheet materials are those that do not adhere well to each other
when placed in molten contact with one another. This is to avoid
the formation of an excessively strong seal bond if the bonding
conditions cause both the thermoplastic sheet material and the
micro-fibers in the fibrous strip to melt. Preferred combinations
of micro-fiber/thermoplastic materials include but are not limited
to: polypropylene/polyethylene, nylon/polyethylene,
PET/polyethylene, fluoropolymer/polyethylene,
fluoropolymer/polypropylene, nylon/polypropylene, and
PET/polypropylene, where the first material in each combination
refers to the composition of the micro-fibers, and the second
material refers to the composition of the thermoplastic material
layer that bonds to the fibrous strip.
[0049] A convenient package for separately storing reactive
materials, particularly fluid materials, as well as food
components, comprises at least two sheets of thermoplastic
polymeric film edge-bonded to each other along their peripheries.
As used herein, "two sheets" and the like can refer to a single
sheet folded over upon itself. Separation of the two components is
achieved by one or more rupturable seals, also referred to herein
as a strip seal that form barriers to movement of materials between
the isolated compartments within the package. The material of a
strip seal (i.e., the individual fibers making up the strip seal)
typically has a melting point close to or higher than the interior
thermoplastic film layers used to form the package. Controlled
heating of thermoplastic film layers against the strip seals
disclosed herein causes the film layers to at least initially melt
and flow into the sides of the micro-fiber strip seal at
temperatures higher than the melting point of the thermoplastic
film layers but close to or lower than the melting point of the
micro-fiber seal material. The micro-fiber strip seals may or may
not themselves then melt depending on the sealing conditions. Upon
cooling, the thermoplastic film layers bond to the micro-fiber
strip seal to provide a rupturable seal.
[0050] The rupturable seal formed by bonding plastic film to a
micro-fiber strip seal, as described above, has sufficient strength
to completely separate material of one compartment from material in
an adjacent compartment of a pouch, envelope, or other container
during normal handling, shipping, and storing operations. The
disclosed multi-compartment plastic pouches can maintain the
required seal, in a two-part container, or multiple seals in a bag
having more than two compartments, until there is a need to
intermix the separated materials. In some cases, it may be
appropriate to initiate the mixing process by gripping a portion of
film on opposed sides of a strip seal and jerking the films in
opposite directions, which ruptures the seal and allows material
migration through the open seal. Complete mixing of materials can
then be done by hand manipulation of the flexible plastic package.
In other cases, it may be appropriate to apply pressure by
squeezing one or more compartments to rupture the seal.
Alternatively, vapor pressure generated inside one or both adjacent
compartments, such as upon heating by microwave radiation or other
suitable energy form, can be used to break the rupturable seal
without the need to even touch the package. Fluid flow together
with bubbling action such as is present during cooking may then
suffice to adequately mix the materials after the seal between the
compartments is ruptured. From the description of the sequence of
actions for mixing the separated materials inside a bag container,
it should be apparent that the (permanent) edge seals between the
sheets of thermoplastic film are stronger than the rupturable
seal.
[0051] The formation of a heat seal between portions of
thermoplastic film sheets and a strip seal involves a series of
process steps including inserting a strip of micro-fiber web
between two sheets of film. This produces a sandwich construction
having a narrow strip of micro-fibers extending between two sheets
of film, each sheet having a width greater than that of the strip
of micro-fibers, so that the edges of the sheets overlap the edges
of the strip of seal-forming micro-fibers. Film sheets may be
bonded to the micro-fiber strip following positioning of the
sandwich construction between a pair of heated platens. One or both
platens can include individually controlled, heated rails aligned
with the strip seal, and can also if desired include heated rails
along parallel edges and across the width of the sheet sandwich.
The rails can be made of metal for good thermal conductivity, and
can also include an outer layer or covering of a heat stable
cushioning material such as a fluoropolymer or silicone rubber for
a more uniform distribution of applied pressure within the desired
sealing area or zone. The positioning and number of heated rails
depends upon the particular design of a multi-compartment packaging
container or pouch. After closing the heated platens around the
sheet construction, application of pressure causes the film layers
to bond to the strip seal and to fuse together along the edges and
across the width of the sheets. The platen press produces a bag or
pouch sealed along its parallel edges and along its base, and
having at least one barrier seal separating a number of
compartments. A multi-compartment bag, as described above, has an
opening to each compartment for addition of the materials for which
the temporary separation is desired. In FIG. 1, the openings for
compartments 20, 22 are shown at 24, 26, respectively. After
placing the materials in their respective compartments, the open
ends of the multi-compartment package may be sealed using a second
platen press that includes a heated rail to form a final edge seal.
The temperature for edge seal formation may be high enough to
produce a fused junction at the intersection between the edge seal
and the strip seal. Formation of fused junctions of this type
provides an advantage compared to previously known breaker seals
including paper tissue. A junction including a paper strip may
introduce a point of failure at temperatures that cause paper
charring.
[0052] One embodiment uses a platen press temperature typically in
a range from about 140.degree. C. to about 150.degree. C. This
temperature range is above the melting points of the thermoplastic
heat seal layers in contact with the strip seal, but below the
melting point of the melt blown micro-fiber strip seal itself. The
heating time is typically from two seconds to four seconds
depending upon the pressure applied to the plates of the platen
press. Suitable application of heat and pressure causes melting of
the thermoplastic layer and migration of molten polymer into the
interstices of the micro-fibers to produce boundary layers, on both
sides of the seal strip, containing molten polymer that solidifies
as it cools. Thermoplastic polymer flowing from one side of a strip
seal may make contact with polymer flowing from the opposite side.
Effective bonding between a strip seal and package films can leave
at least an internal portion of the strip seal free from
thermoplastic polymer to provide a frangible interface at which the
rupturable seal strip parts during application of force to the
plastic package causing separation of the boundary layers of the
strip seal.
[0053] A preferred embodiment uses top and bottom actively heated
metal rails associated with the rupturable bond, the rails having
no cushioning heat stable material thereon, and heated to a
temperature in the range from about 270-310.degree. F. This
temperature range is sufficient to quickly melt the thermoplastic
heat seal layers in contact with the strip seal. The heating time,
when both the top and bottom elements are heated, is typically from
0.5 to 2 seconds. A suitable application of pressure causes melting
of the thermoplastic layers and migration of the molten polymer
into the interstices of the sealing interlayer to initially occur.
As the sealing cycle continues, the molten thermoplastics penetrate
through the fibrous strip or strip seal, contacting each other
within the strip seal. In another case, the molten thermoplastics
may penetrate through the strip seal and cause the individual
micro-fibers thereof to melt, resulting in a completely melted
physical polymer blend, which forms the rupturable seal. In both of
the above cases the rupturable seal contains polymer material
(including polymer material from the inner thermoplastic sheet
layers and from the micro-fibers) throughout the entire thickness
and is substantially free from air in the heat sealed region. This
process may be done in a batch mode to form a single rupturable
seal, or it may be done in a step and repeat process forming a
continuous rupturable seal for use in a continuous container making
process.
[0054] An alternate process for forming a heat seal between
portions of thermoplastic film sheets and a strip seal involves a
series of steps of a continuous process including inserting a strip
of melt blown micro-fiber web between two sheets of film. This
produces a sandwich construction having a narrow strip of
micro-fibers extending between two sheets of film each having a
width greater than the strip of micro-fibers, so that the edges of
the sheets overlap the edges of the strip of seal-forming
micro-fibers. The film sheets bond to the micro-fiber strip during
movement of the sandwich construction between rollers aligned along
the strip seal and heated to an elevated temperature. The duration
of contact of the thermoplastic film sheets with the heated rollers
causes melting of the thermoplastic layer and migration of molten
polymer into the interstices of the micro-fibers at least enough to
produce boundary layers, on either side of the strip seal,
containing molten polymer that solidifies as it cools. The
thermoplastic boundary layers preferably contact each other, and
the micro-fiber layers may or may not melt in whole or in part in
the area of the seal.
[0055] Alternative means for heating the sealing region of the
disclosed rupturable seal (or permanent seals) include the use of
ultrasonic horns, induction heating, and radio frequency
heating.
[0056] The continuous sandwich construction formed as described
above may enter another heat sealing device that produces
peripheral seals by application of heat and pressure along the
edges of the overlapping sheets and across the sheet structure as
needed to provide plastic packages having two compartments
separated by a strip seal as shown, for example, in FIGS. 1 and 2.
One edge of each compartment remains open for charging of reactive
materials, food materials, or other desired materials to be
temporarily isolated, after which a heat sealer forms the final
fused edge seal that closes the compartments and isolates the
materials from each other until the rupturable seal is broken.
[0057] In the process of forming the rupturable seals and
containers with these seals, individual portions of the seal area
may be contacted multiple times by the heated sealing bars. Heating
may occur from one or both sides or may also be done in a manner in
which alternate sides of the seal are heated in separate contact
steps such as in a step and repeat process similar to that
previously described. In some cases, the formation of the
container, the filling of the container, and the final sealing of
the container can be done in one continuous process, this process
commonly known as form, fill, seal.
[0058] Melt blown micro-fiber webs used for forming the preferred
strip seals include non-woven, fibrous polymeric materials,
preferably a polypropylene homopolymer such as #3960 or the like,
having a melt flow rate from about 280-420 g/10 minutes at
230.degree. C. (available from Atofina, Houston, Tex.). Micro-fiber
webs typically have basis weights ranging from about 10 grams per
square meter (gsm) to about 30 gsm, preferably about 25 gsm when
using opposed sheet materials whose thermoplastic heat seal
(interior) layers each have a thickness of about 3.5 mils. The
ideal basis weight for a given application will depend on the
thickness of the thermoplastic polymer materials forming the
interior layers of the container, with smaller basis weights being
more suitable for thinner thermoplastic layers, and vice versa.
Preferred effective fiber diameters and actual fiber diameters are
as mentioned previously. Such strip seals introduce less of a bump
between packaging films and other seals, e.g. edge seals. A strip
seal between about 1 cm and 1.25 cm wide, having a basis weight of
15 gsm, has a thickness of about 100 .mu.m before sealing, and a
thickness of about 25 .mu.m (0.001 inch) after sealing.
[0059] The preferred nonwoven micro-fiber web material can become
compressed, typically by a factor of two or more, in the area of
the seal. This is depicted schematically in FIG. 3, where opposed
heat seal rails 40, 42 press against sheets 44, 46 and strip seal
or fibrous strip 48 (depicted schematically for ease of
illustration) in a sealing region 50 to form a rupturable seal as
described elsewhere in this application. The sheets 44, 46 each
preferably comprise an inner thermoplastic layer 44b, 46b
respectively, and an outer strengthening layer 44a, 46a
respectively. When the heat seal rails apply heat and pressure to
the construction, the fibrous strip 48, which is preferably a
nonwoven arrangement of micro-fibers, becomes compressed within the
sealing region 50. Molten thermoplastic polymer from inner layers
44b, 46b migrates into the fibrous strip from opposite sides, and
if the temperatures are low enough that strip 48 does not melt, the
thermoplastic materials form surface layers within the strip that
preferably contact each other as shown. Strip 48 is preferably
oversized with respect to the sealing region 50 so that a distal
portion 48a of the strip extends away from the fracturable seal and
into a defined compartment 52. This oversizing or extension of the
fibrous strip beyond the sealing region advantageously allows for
normal manufacturing tolerances in the positioning of the fibrous
strip relative to the heat seal rails. The distal portion 48a of
the strip is not in intimate contact with the thermoplastic layers
44b, 46b, unlike the central portion of strip 48 within the sealing
region 50. Whether or not fibrous strip 48 melts within the sealing
region 50 during sealing, the observed thickness t2 of the (melted
or intact) fibrous strip within the sealing region is typically
substantially less than the observed thickness of the distal
portion 48a, with relative thickness ratios of about 2 to 4 being
typical.
[0060] Where at least one (and preferably both) of sheets 44, 46 is
substantially transparent so that contents within the
compartment(s) can be viewed by the user, strip seals formed from
polymer micro-fiber nonwoven webs can also advantageously provide a
visual indication of effective barrier seal formation when the
sealed junction changes from an opaque to a substantially
transparent condition. Fibrous strips or strip seals tend to have
an opaque, typically white appearance prior to sealing. This
appearance is due in large part to the highly scattering nature of
the multitude of reflective surfaces formed by the individual
micro-fibers when surrounded by air. This appearance changes to
substantially transparent when the fibrous strip forms a successful
fracturable seal to a transparent sheet because the thermoplastic
material of the sheet substantially displaces the air in the
sealing region so that the fibers (or melted fiber shapes) of the
fibrous strip are now surrounded by the thermoplastic. Since the
thermoplastic typically has a refractive index much closer to that
of the micro-fibers, reflection at the micro-fiber surfaces is
greatly reduced, light scattering by the fibrous strip is reduced,
and light can more easily pass through the sealing region 50
characterized by the micro-fiber/thermoplastic material physical
polymer blend. A consequence of this is the closer in refractive
index the micro-fibers are to the thermoplastic material, the more
transparent the sealing region 50 becomes. The transition from
opaque to transparent provides an observable signal of formation of
a rupturable seal that can provide effective separation between
compartments of a plastic package. The sealing operation changes
the appearance of the construction from a completely opaque
(typically white) strip to a substantially clear central region
(corresponding to region 50 in FIG. 3 and to barrier seal 16a in
FIG. 1) bordered by at least one and usually two opaque regions
(corresponding to distal end 48a in FIG. 3 and to the portion of
strip 16 outside of seal 16a in FIG. 1).
[0061] The porosity of a melt blown micro-fiber web depends upon
basis weight and fiber diameter. These characteristics control the
rate of flow of molten polymer into the interstices between
micro-fibers, during the process of bonding packaging film sheets
to either side of a micro-fiber strip seal. After successful
formation of heat sealed container bags, the strength of a
rupturable barrier seal may be evaluated using a pressurized
bag-bursting machine. The test includes inflating the adjacent
compartments on opposite sides of a strip seal to an air pressure
at which the melt blown micro-fiber seal bursts. A preferred range
of seal strength is from about 0.21 kg/cm.sup.2 (3 psi) to about
0.63 kg/cm.sup.2 (9 psi).
[0062] The strength of the individual rupturable seal may also be
evaluated by conventional peel tests such as those described in
ASTM F 88-00 (Standard Test Method for Seal Strength of Flexible
Barrier Materials) or variations of this test. These test methods
are particularly useful when only the rupturable seal itself is
available for testing and not an entire pouch or container.
[0063] Package-forming polymer sheets suitable for use in forming
the disclosed bags and pouches include polymer films having a lower
melting point than the polymer used to form a melt blown
micro-fiber web. As a preferred example, a multi-compartment bag
uses a film laminate identified by the trade name SCOTCHPAK 29905
(also known as SCOTCHPAK ES241) available from 3M Company, St.
Paul, Minn. The film laminate consists essentially of an 86 .mu.m
(3.4 mil) thick layer of linear, low density polyethylene adjacent
to a 14 .mu.m (0.56 mil) thick layer of biaxially oriented
polyethylene terephthalate. Opposed sheets of the SCOTCHPAK 29905
film are positioned during formation of a multi-compartment pouch
so that the polyethylene layer of both sheets is the inner layer
that bonds to a strip seal during heating between about 120.degree.
C. and about 200.degree. C. to form the barrier seal.
[0064] Various fluid components may be enclosed in the separate
compartments of a multi-compartment package. For non-food
applications, a typical combination of reactive components
comprises as a first material a liquid polyol resin and as a second
material an isocyanate crosslinking agent. These materials react to
form a polyurethane encapsulating or blocking compound. A second
combination of reactive components comprises a liquid having
anhydride functionality and a suitable crosslinking agent. These
two components react to provide a polyester encapsulant material.
Component materials that react to form an epoxy resin may also be
stored in multi-compartment packages. In this case the package
separates a liquid, epoxy-functional, composition from a mixture of
a liquid polymer and amine activator prior to formation of the
epoxy resin. Activation of the reaction between resin-forming
components involves gripping the outer packaging films close to the
central area of one of the compartments and jerking the films apart
along the axis of the rupturable seal. This breaks the strip seal
by fiber separation in the frangible interface between the boundary
layers of the strip seal without damaging the permanent fused edge
seals of the package. Rupture of the frangible interface permits
the reactive contents of the package to combine. Homogeneous mixing
may require hand manipulation of the packaging envelope to promote
the resin-forming reaction. Removal of a corner of the package
provides an opening for release of the reacting mixture that may be
dispensed into a waiting mold or other cavity or container wherein
the reaction continues to completion. As an alternative to removing
a corner from a multi-compartment package, a nozzle closure may be
built into one of the film sheets used to produce the package.
[0065] Further non-food applications of the disclosed
multi-compartment packages include use as flexible container bags
for materials that react together to produce resins for a variety
of end uses including resins for application in telecommunications
systems, particularly as encapsulant materials. Chemical resistance
testing of a melt blown micro-fiber strip seal with different
encapsulating resin systems showed no damage to the seal during
oven-aging at an elevated temperature of 65.5.degree. C.
(150.degree. F.) with the multi-compartment package supporting a
weight of 1 kg.
[0066] As mentioned above, the preferred rupturable seal disclosed
herein is also particularly suitable for food product applications.
Different food components can be sealed in the separate
compartments of a multi-compartment plastic pouch, which can then
serve as a food storage article. In such cases, the material
selection of the strip seal and sheet materials can be conveniently
selected from among the many polymer materials known to be
acceptable in conventional food packaging applications. In some
cases the food-filled pouch can be frozen for long-term storage
until needed. To prepare the food for consumption, the pouch can be
placed in a microwave oven where the food components are heated and
cooked separately from each other for a first time period as they
are exposed to microwave radiation. During the first time period,
vapor pressure (for example, due to steam) in at least one of the
compartments gradually increases to a level that causes the
rupturable seal to break, thus permitting admixture of the
different food components present in the compartments adjacent the
ruptured seal. The rupture of the seal marks the end of the first
time period and the beginning of a second time period, during which
the different food components are allowed to cook together in the
pouch as microwave radiation continues to bombard the pouch. The
microwave radiation is turned off at an appropriate time, marking
the end of the second time period. The pouch can then be opened
such as by tearing, cutting, or otherwise breaking the permanent
seals around the periphery of the pouch. In some cases methods
other than microwave cooking can be used to heat the pouch, such as
methods that utilize solar or infrared radiation, or methods that
use convection or conduction of heat such as placing the pouch in
boiling water or another heated fluid. In some cases the pouch can
comprise an expandable portion in which the cooked food contents
can collect such that the pouch sits upright on a flat surface,
permitting the user to eat the cooked food contents directly from
the opened pouch.
[0067] In particular, FIG. 4 shows a pouch 30 which is similar to
pouch 10 except that it includes an expandable gusseted portion.
For simplicity of description, elements that correspond
substantially in structure and function to elements in FIGS. 1-2
are given the same reference number with the addition of a prime
symbol. Pouch 30 is shown prior to charging the compartments 20',
22' with the food or other contents, and prior to the final edge
seal operation that closes off openings 24', 26'. Unlike pouch 10
of FIG. 1 which uses substantially flat sheets, pouch 30
incorporates folds 32, 34 in one or both opposed sheets 12', 14' at
one of the compartments 22'. The folds permit the compartment 22'
to expand to receive a substantial portion of the combined contents
of compartments 20' and 22', thus forming a stable base at one end
of the pouch when the pouch is full. To maintain a good seal, the
strip seal 16', and therefore also the barrier seal 16a',
preferably do not intersect the folds.
[0068] In FIG. 5, a multi-compartment pouch 60 is shown in plan
view. Pouch 60 includes a plurality of fibrous strips arranged to
form a plurality of isolated compartments in a single pouch. Two
film sheets 62, 64 are joined together via a network of rupturable
seals 66a, 68a, 70a, 72a (formed along fibrous strips 66, 68, 70,
72 respectively) and permanent seals 74a-d formed by heat sealing
or other conventional means. These seals form isolated compartments
76, 78, 80, 82, 84, pairs of which can be fluidly joined together
by rupturing a selected rupturable seal as will be understood by
inspection of the drawing. Filling of the compartments with the
desired contents can be done before completing one or more of the
permanent seals, by direct injection into the compartments after
the pouch formation, or a combination thereof. Regions of overlap
86a-h are formed as shown and can function as pressure relief
mechanisms. Note that fibrous strips 66, 68, 70, 72 may or may not
be of identical construction. If not, strips of different basis
weight, fiber diameter, and so forth can be selected to provide
rupturable seals with a desired set of predetermined seal
strengths. An optional injection or dispenser nozzle, dip tube, or
other device shown generically at 88 is provided for compartment
78, but similar devices can be provided for the other compartments.
Alternatively, compartment 78 can in some embodiments remain empty
of any contents, but can serve as a final dispensing chamber or
outlet by breaking seal 68a only after breaking the other
rupturable seals and thoroughly mixing the previously separated
contents of compartments 76, 80, 82, and 84.
[0069] In FIG. 6, another multi-compartment pouch 90 is shown in
plan view. Pouch 90 is similar in many respects to pouch 60, but in
pouch 90 two fibrous strips are arranged to cross over each other.
Two film sheets 92, 94 are joined together via a network of
intersecting rupturable seals 96a, 98a (formed along fibrous strips
96, 98 respectively) and permanent seals 100a-d formed by heat
sealing or other conventional means. These seals form isolated
compartments 102, 104, 106, 108, pairs of which can be fluidly
joined together by rupturing a selected rupturable seal. Filling of
the compartments can be done as described above. Regions of overlap
110a-d are formed as shown.
[0070] FIG. 7 shows a plan view of a multi-compartment pouch 120
that includes a series combination of two rupturable seals and one
permanent seal separating two compartments to provide a unique
mixing capability. In pouch 120, opposed thermoplastic sheets are
joined together via a network of rupturable seals 122a, 124a
(formed along fibrous strips 122, 124 respectively), permanent
seals 124a-d along the periphery of the pouch, and permanent seal
124e connecting the rupturable seals, thus forming compartments
126, 128. Fluid communication between the compartments can be
established by selectively breaking one of the rupturable seals
(e.g., upper seal 122a, such as by exerting stabilizing pressure
with one's hand on the lower seal 124a while squeezing one of the
compartments with the other hand), then breaking the other
rupturable seal (e.g. lower seal 124a, such as by exerting
stabilizing pressure with one's hand on the upper seal 122a while
squeezing one of the compartments). A net circular flow of combined
fluid material can then be established between the chambers by
alternatively pinching off or otherwise substantially closing one
of the opened rupturable seals and then the other.
[0071] The embodiment of FIG. 7 requires placement and alignment of
two separate, relatively short fibrous strips. In alternative
embodiments, a single longer fibrous strip can be used as shown in
FIGS. 7a and 7b. In FIG. 7a, fibrous strip 140 has a central
narrowed portion 140a. For forming the seals between the
compartments, a straight heat seal bar whose (uniform) width is
intermediate that of the end portions of strip 140 and central
portion 140a is used. In this way, the fibrous strip is oversized
relative to the sealing region (vertical dashed lines) at the ends,
forming rupturable seals. But in the central region of portion
140a, the fibrous strip is undersized relative to the sealing
region so that a permanent seal is formed by direct contact of
thermoplastic sheet materials of the upper and lower sheets on at
least one side of the strip portion 140a. In FIG. 7b, fibrous strip
144 is uniform in width, but a heat seal bar of nonuniform width is
used to produce a nonuniform sealing region 146, again resulting in
a central permanent seal connected to rupturable seals on both ends
of the permanent seal.
[0072] In FIG. 8, a multi-compartment container 150 is shown in
schematic sectional view. Container 150 is similar to the other
disclosed embodiments, except that a relatively rigid molded
plastic base 152 is provided rather than a more compliant flexible
plastic sheet. A cover sheet 154 is bonded selectively to base 152
with seals 156a, 156b, 156c, any one or all of which can be
rupturable seals formed with the disclosed fibrous strips.
[0073] In FIG. 9, a single compartment pouch 160 is shown in plan
view. A rupturable seal 162a is provided along one edge, and
permanent seals 164a-c are provided along the other edges. Fibrous
strip 162, as in previously described embodiments, is oversized in
width so that a portion of the strip extends beyond the sealing
region corresponding to 162a. Rupturable seal 162a provides a
convenient opener so that contents of compartment 166 can be
accessed by a user.
Applications
[0074] Containers that incorporate the disclosed rupturable seals
can be used in a wide variety of end-use applications. Reactive
chemicals and food storage and preparation have already been
mentioned. The food applications can include not only frozen foods
to be heated in a microwave oven or otherwise, but also
shelf-stable foods and refrigerated foods. Food applications are
also intended to encompass beverage products. Other two- or
three-part reactive systems are also contemplated, covering such
categories as adhesives, coatings, and fillers.
[0075] Other applications are available in the medical field. For
example, a multi-compartment pouch can be designed such that when a
rupturable seal is broken, two or more components are mixed
together that will harden in a short period of time. Before
hardening, the pouch can be wrapped around a body part to create
support for an injured limb, for example, and then hardening into a
cast to provide support and protection. In a related example, a
similar but smaller multi-compartment pouch can be designed such
that after the components are mixed but before hardening, the pouch
is placed into the user's ear taking the shape as it hardens to be
used for hearing aide custom fit development. In another medical
application, specific amounts of medications can be mixed and
delivered in multi-compartment pouch to deliver desired
concentrations of medicine. In some cases such a pouch can
incorporate a hang tab and be used as an intravenous (IV) delivery
bag.
[0076] An application useful in the dental field is a mixing pad
replacement. By having pre-weighed amounts of reagents used for
cavity filling, a multi-compartment pouch can be utilized to allow
mixing within the pouch after the rupturable seal has been opened.
When fully mixed, the pouch can be opened and used for the intended
application. Another application useful in the dental field is for
making impressions. A multi-compartment pouch can hold the reagents
used to make dental impressions or the like. This would eliminate
the need for weighing reagents, since convenient individual
packages can be made.
[0077] Still other applications are in the field of indicators. In
these applications, the multi-compartment pouch can provide the
user with information on what conditions the pouch has been exposed
to, such as temperature or pressure. Rupture indicators made in
this way can inform the user of shock or temperature extremes. The
pouches can also be used as seam breakage indicators.
[0078] In the area of cosmetics, one useful application is for hair
coloring. The multi-compartment pouch can allow the components,
such as a developer and a color creme, to be held separate until
the time of use. The components can be mixed with ease within the
pouch compared to the current method of adding the color creme
component, contained in a tube, to the developer bottle and then
shaking the open bottle with a finger over the hole. The disclosed
multi-compartment pouches can also avoid the risk of handling the
color creme component alone, which can be a skin and eye irritant.
The pouch in such case can incorporate a spout for easy application
to hair. Facial mud is another useful cosmetic application. A
multi-compartment pouch can hold mud components, such as a liquid
(milk or water), clay, and a powder separate until the rupturable
seals are broken and the product can then be mixed and applied.
[0079] Still other applications of the disclosed containers with
rupturable seals include such things as: food or medicine mixes,
two-part hot or cold packs, analytical testing (resealable),
perishable two-component test mixtures, single use hand towel with
soap or disinfectant, single use dental whitening packs, two-part
cleaning compounds for dental or other applications, complete salad
components, baking components compartmentalized, wilderness food
packaging, meat/marinade combinations, meat/liquid flavorant/noodle
combinations, sauces mixed after ingredients are heated, two-part
juice pouches, endothemic chemical for cooling, pasta and sauce,
rice/chicken/vegetable combinations, heated cleaning solution into
cleaning cloth, carpet or spot cleaner with peroxide on one side,
customized cosmetics in two or more parts, special effects personal
care such as fizzing shampoos, peroxide/colorant hair color,
customizable hand lotions/fragrances, kaleidoscopes, instructional
toys utilizing color, self-contained chemistry experiment kits,
two-part slime toys such as Borax / white glue combinations,
chemical coolers and heaters, flotation devices, light sources,
automotive body fillers, curable paint systems, dissolvable bag
holding curing agent, custom pigment delivery, putty and body
filler, self-inflating seats, oxygen-generating components made
with oxygen-permeable sheet materials for live well fish, packaging
foam, packaging material such as where an acid and base combination
produces a gas, two-part foaming system, rupture indicator such as
for shock, temperature, and pressure, seam breakage indicator, and
microwave bag vent.
Compartment Design Features
[0080] The containers disclosed herein can incorporate a wide
variety of design features. For example, a pump spray device can be
incorporated into a multi-compartment pouch. In this case, a dip
tube and spray atomizer can be inserted into one of the
compartments to allow dispensing of a combined mixture. The dip
tube can extend to the bottom of one compartment so that when the
rupturable seal is opened, the two separated components can be
mixed becoming homogeneous and surrounding the dip tube. The
solution can then be dispensed using a spray atomizer pump similar
to hair spray dispensing but using a multi-component pouch.
[0081] Disclosed pouches or containers can likewise incorporate an
atomizer/venturi nozzle to dispense the mixed contents of a pouch.
A dip tube extends to the bottom of the pouch where an
atomizer/venture device is sealed around the applicator.
Pressurized air is connected to the nozzle, creating a siphoning of
the pouch contents through the atomizer allowing a uniform
application of the contents onto the chosen substrate.
[0082] Disclosed pouches or containers can incorporate pull handles
or tabs to assist with opening. For instance, two pull handles can
be secured on opposed sides of the pouch on or near the rupturable
seal. By pulling in opposing directions, the seal can be readily
opened to enable the separate contents to mix. The handles or tabs
can comprise heat sealable polyethylene film tabs bonded directly
to the outside of the pouch with a higher bond strength than that
of the rupturable seal itself.
[0083] Disclosed pouches or containers can include conventional
pressure relief valves. If the pouch contents are heated and
release steam, the pouch will begin to inflate. If pressure within
the pouch reaches a setpoint of the conventional relief valve, the
valve opens to permit steam to escape the pouch to maintain
pressure within a normal range to prevent the pouch from bursting.
Such a relief valve can be in addition to the weakened overlap
regions discussed above.
Experimental
[0084] A two-compartment bag, formed by heat sealing a strip seal
of melt blown polypropylene web down the center of a polyethylene
bag may be tested using either ASTM-F88-00 or ASTM-F2054-00 to
determine the strength of the resulting barrier seal. The first of
these tests (ASTM-F88-00) measures seal strength of flexible
barrier bags. Burst strength measurement uses internal
pressurization within restraining plates as described by the second
test method (ASTM-F2054-00).
A. Comparison of Blown Micro-Fiber (BMF) Barrier and Effective
Fiber Diameter (EFD)
[0085] For this comparison, the bag dimensions were: width of 19.7
cm, length of 11.4 cm. Bags including a lengthwise barrier strip
were manufactured on a Klockner-Ferromatik Bag Maker, Model LA III.
The process included platen press activation using a temperature
between about 135.degree. C. and about 150.degree. C., a dwell time
setting between about two seconds to about four seconds and a
machine pressure setting of 1.54-1.97 kg/cm.sup.2 (22-28 psi). Bags
of Examples 1-12 were burst using an ARO 2600 pressurized air burst
machine with a flow rate setting of 9.0. Examples 1-6 of Table 1
show that at a fixed temperature the barrier burst strength
increases with effective fiber diameter increase. TABLE-US-00001
TABLE 1 Burst Strength of BMF Webs Strip Seals of Examples 1-6
Example 1 2 3 4 5 6 Sealing 135 135 135 140.5 140.5 140.5
temperature .degree. C. EFD (microns) 4.7 4.5 4.0 4.7 4.5 4.0 Basis
weight 25 25 25 25 25 25 (g/m.sup.2) Barrier burst 0.22 0.12 0.10
0.45 0.30 0.22 strength (kg/cm.sup.2)
[0086] TABLE-US-00002 TABLE 2 Burst Strength of BMF Webs Seals of
Examples 7-12 Example 7 8 9 10 11 12 Sealing 140 140 146 146 146
146 temperature .degree. C. EFD (microns) 6-8 6-8 4.7 4.5 4.4 4.0
Basis weight 20 30 25 25 25 25 (g/m.sup.2) Barrier burst 0.74 0.50
0.49 0.44 0.41 0.34 strength (kg/cm.sup.2)
[0087] Examples 7-12 of Table 2 show that at a fixed temperature
the barrier burst strength increases with effective fiber diameter
increase and also with lowering of basis weight. Comparison between
the results of Table 1 and Table 2 indicate that barrier burst
strength increases as the sealing temperature increases.
B. Blown Micro-Fiber (BMF) Barrier Basis Weight Comparison
[0088] For this comparison (Examples 13-23), the bag dimensions
were: width of 25.4 cm, length of 26.7 cm. Bags were manufactured
on a Klockner-Ferromatik Bag Maker, Model LA III. The process
included platen press activation using a dwell time setting about
two seconds to about four seconds. The machine pressure setting was
1.54-1.97 kg/cm.sup.2 (22-28 psi). During bag manufacture feeding
of the strip seal web between film sheets could optionally be
machine fed, using a barrier strip unwinder, or hand fed. The bags
were burst using an ARO 2600 pressurized air burst machine.
[0089] Table 3 shows at a fixed temperature that the barrier seal
burst strength increases with effective fiber diameter increase and
also with lowering of basis weight of the micro-fiber web. Table 4
shows that bags formed using machine fed strip seal differed in
burst strength from those manufactured using a hand feeding
technique. The difference may be attributed to a difference in
strip seal tension during feeding. TABLE-US-00003 TABLE 3 Burst
Strength of BMF Webs Seals of Examples 13-16 Example 13 14 15 16
Sealing temperature .degree. C. 140 140 140 140 Basis weight 20 30
25 30 EFD (.mu.m) 6-8 6-8 5.0 5.0 Burst strength - hand fed 1.23
1.12 0.42 0.46 (kg/cm.sup.2)
[0090] TABLE-US-00004 TABLE 4 Burst Strength of BMF Webs Seals of
Examples 17-23 Example 17 18 19 20 21 22 23 Sealing temperature
.degree. C. 146 146 146 146 146 146 146 Basis weight 20 25 30 25 30
25 30 EFD (.mu.m) 4.7 4.7 4.7 4.5 4.5 4.0 4.0 Burst strength - hand
fed 0.5 0.29 0.23 -- -- -- -- (kg/cm.sup.2) Burst strength -
machine -- -- -- 0.45 0.40 0.52 0.51 fed (kg/cm.sup.2)
[0091] Samples in the following sections C through I were sealed
and tested in the following manner.
[0092] Heat sealing description: seals of the heat seal materials
were made with a Packrite (Racine, Wis.) model R robot jaw sealer
with 12 inch long sealing rails. The sealer was equipped with
heated top and bottom brass rails which had a sealing width of 3/16
of an inch. This device had a thermocouple feedback controlling
temperature of the sealing rails and a digital control of the
sealing time. Pressure was controlled by the air pressure on the
clamping cylinder. Specific sealing conditions will be listed for
each of the examples.
[0093] Rupturable seal testing: when peel values are reported for
the rupturable seals, they were generated by using a test method
similar to ASTM F 88-00, except that the peel test was performed
down the length of the rupturable seal and used a rail separation
rate of 5 inches/minute. Values reported for the rupturable seal
strength are the average of three separately bonded samples that
were peeled. Values for the control samples are a single individual
peel value.
[0094] Control materials, when noted, for each of the examples
refers to the listed heat seal material sealed directly to itself
without the listed fibrous strip in the sealing region.
C. Effect of Sealing Temperature on Rupturable Seal Strength
Conditions Used:
[0095] Heat seal (thermoplastic) film-SCOTCHPAK ES241, consisting
essentially of a 0.56 mil PET strengthening layer and a 3.44 mil
LLDPE heat seal (thermoplastic) layer. [0096] Fibrous strip
material--blown micro-fibers (BMF) of polypropylene (PP)
homopolymer substantially similar to Atofina #3960, but including
minor additives that are insignificant for purposes of the present
application. Effective fiber diameter was 4.4 microns and basis
weight was 25 grams per square meter (gsm). [0097] Sealing
conditions-- [0098] Dwell time=1.0 seconds [0099] Sealing
Pressure=40 PSI
[0100] Sealing Temperature=(variable) TABLE-US-00005 TABLE 5 Effect
of temperature on the peel value of the heat seal bond with the
nonwoven fibrous strip inserted into the bond line. Seal Temp.
Control Examples Example .degree. F. lb force lb force Comments 24
240 2.316 0.001 sealing region opaque 25 250 13.400 0.039 sealing
region opaque 26 260 Tear 0.116 sealing region opaque 27 270 Tear
0.145 sealing region clear 28 280 Tear 0.285 sealing region clear
29 290 Tear 0.416 sealing region clear 30 300 Tear 0.481 sealing
region clear 31 310 Tear 0.302 sealing region clear 32 320 Tear
0.237 sealing region clear 33 330 Tear 0.196 sealing region clear
34 340 Tear 0.148 sealing region clear 35 400 Tear 0.165 sealing
region clear
[0101] In is set of data, the seal force is initially very low as
the sealing temperature is not high enough to melt the
thermoplastic and form a bond. "Tear" means that the seal was so
strong that the sheet tore without any seal failure. This can be
seen from the control sample bond value. The published melt
temperature of the sealing resin is 255.degree. F. As the
temperature is increased, the seal force becomes higher as the
thermoplastic material flows better upon bonding. At a temperature
of 270.degree. F. the conditions allow the seal to become clear
(i.e., transparent, indicating a substantial absence of entrapped
air in the fracturable seal area) as the thermoplastic polymers
from each side of the seal make contact through the nonwoven
fibrous strip. Seal values continue to increase until the
thermoplastic material begins to flow too much at higher
temperatures and the sealing region line pressure begins to force
thermoplastic material out of the sealing region, forming two beads
at the edge of the sealing region or bond line, reducing the peel
value of the seal.
D. Effect of Sealing Dwell Time on Rupturable Seal Strength
Conditions Used:
[0102] Heat seal film--(same as section C) [0103] Fibrous strip
material--(same as section C) [0104] Sealing conditions-- [0105]
Dwell time--(variable) [0106] Sealing Pressure=40 psi or 80 psi
[0107] Sealing Temperature=300.degree. F. TABLE-US-00006 TABLE 6
Effect of sealing dwell time on rupturable seal strength, for 40
psi sealing pressure Dwell Time Peel force Example seconds lb force
36 0.5 0.1255 37 1.0 0.4805 38 2.0 0.516 39 5.0 0.5715 40 10.0
0.856
[0108] TABLE-US-00007 TABLE 7 Effect of sealing dwell time on
rupturable seal strength, for 80 psi sealing pressure Dwell Time
Peel force Example seconds lb force 41 0.5 0.401 42 1.0 0.859 43
2.0 0.7055 44 5.0 0.6995 45 10.0 0.7895
[0109] In this set of data, the seal strength (represented by peel
force) at the lowest dwell times is low due to insufficient dwell
time to effectively heat and melt the thermoplastic sealing layer.
At longer dwell times the seal strength reaches a relatively
consistent value which would allow it to function in a container
application.
E. Effect of Sealing Pressure on Rupturable Seal Strength
Conditions Used:
[0110] Heat seal film--(same as section D) [0111] Fibrous strip
material--(same as section D) [0112] Sealing conditions-- [0113]
Dwell time=2 seconds [0114] Sealing Pressure=(variable)
[0115] Sealing Temperature=300.degree. F. TABLE-US-00008 TABLE 8
Effect of sealing pressure on rupturable seal strength Pressure
Peel force Example psi lbs 46 20 0.4915 47 40 0.516 48 60 0.527 49
80 0.7055
[0116] Table 8 shows that seal strength increases modestly over the
range of pressures shown, with all of the rupturable seal strength
values being in a usable range.
F. Effect of Fibrous Strip Basis Weight on Rupturable Seal
Strength
Conditions Used:
[0117] Heat seal film--(same as section E) [0118] Fibrous strip
material--BMF of polypropylene homopolymer, type Atofina #3960.
[0119] Actual optically measured fiber diameter of 12 microns.
Stock basis weights of 5, 15, 20, and 30 gsm. Fibrous strip
materials were stacked to achieve the effective basis weights of
10, 40, and 60 gsm. [0120] Sealing conditions-- [0121] Dwell time=1
second [0122] Sealing Pressure=40 psi
[0123] Sealing Temperature=300.degree. F. TABLE-US-00009 TABLE 9
Effect of fibrous strip basis weight on rupturable seal strength
Peel Basis weight force Example grams/sq meter Lbs Comments 50 5
2.7865 clear seal region 51 10 1.439 clear seal region 52 15 1.257
clear seal region 53 20 0.8445 clear seal region 54 30 0.793 clear
seal region 55 40 0.057 opaque seal region 56 60 0 opaque seal
region
[0124] This data shows that at a low basis weight of fibrous strip
material, the peel value of the rupturable bond is too high. At
higher basis weights, there is a range where the peel value falls
into the usable range. As the basis weight increases even more, the
ability to make a transparent seal at a 1 second dwell time is
lost.
G. Effect of Different Thermoplastic Heat Sealing films on
Rupturable Seal Strength
Conditions Used:
[0125] Heat seal film--(see table) [0126] ES33--SCOTCHPAK ES33,
comprising 0.56 mil PET and 3.44 mil Primacor 3330 ethylene acrylic
acid copolymer [0127] ES26--SCOTCHPAKES26, comprising 3.80 mil PET
and 2.0 mil Elvax 3185 ethylene vinyl acetate [0128]
ES241--SCOTCHPAK ES241, as described in section C [0129]
Nylon/PE--3 mil nylon and 2.25 LLDPE [0130] Fibrous strip
material--(same as section E) [0131] Sealing conditions-- [0132]
Dwell time=(see table) [0133] Sealing Pressure=40 psi
[0134] Sealing Temperature=(see table) TABLE-US-00010 TABLE 10
Effect of different heat sealing films on rupturable seal strength.
Temperature Dwell time Peel value Example Film .degree. F. seconds
Control lb force 57 ES33 290 1 Tear 0.491 58 ES26 190 5 5.29 0.931
59 ES241 300 1 Tear 0.961 60 Nylon/PE 300 10 Tear 0.916
[0135] This data shows that an effective rupturable seal can be
made with a variety of thermoplastic heat seal films. Depending
upon the construction of the heat seal films, different sealing
conditions may need to be used to get the proper rupturable seal
peel value
H. Effect of Different Sealing Strip Materials on Rupturable Seal
Strength
Conditions Used:
[0136] Heat seal film--(same as section F) [0137] Fibrous strip
material--(various, see table) [0138] Sealing conditions-- [0139]
Dwell time=1.0 second [0140] Sealing Pressure=40 psi
[0141] Sealing Temperature=300.degree. F. TABLE-US-00011 TABLE 11
Effect of fibrous strip materials on rupturable seal strength.
Fibrous Strip Peel value Example material lb force Comments 61
Transweb-BMF Tears Polyethylene (PE) web, TM07-27-98-02 86 gsm
basis weight 62 Kimberly Clark 1.155 Meltblown PP, 20 gsm basis
weight, 4.7 micron EFD 63 PGI Airlaid 4104 13.234 51 gsm basis
weight; each microfiber has PET core, PE sheath 64 BBA Securon
0.753 15 gsm basis weight; 3-layer SMS "SMS" construction using PP
65 HTC 3180 easy 1.340 PP stitch 66 Pellon 1.523 polyamide
Wonderweb #807
[0142] Various purchased non-woven web materials were tested for
their ability to make a rupturable seal with a suitable seal
strength. Several were found. In Example 61 the seal is permanent
due to the same polymer in the fibrous strip and the thermoplastic
bonding layer. Example 63 also shows this effect with a high peel
value due to the PE in the fibrous strip construction. In Example
64, the fibrous strip had a 3-layer SMS (spun-bond/melt blown/ spun
bond), each layer being composed of polypropylene (PP). Other blown
micro-fibers and the SMS construction gave values in a suitable
peel value range.
I. Effect of Sealing Configuration on Rupturable Seal Strength
Conditions Used:
[0143] Heat seal film--(same as section H) [0144] Fibrous strip
material--(same as section G) [0145] Sealing conditions-- [0146]
Dwell time=(variable, see table) [0147] Sealing Pressure=40 psi
[0148] Sealing Temperature=300.degree. F. TABLE-US-00012 TABLE 12
Effect of sealer configurations on rupturable seal strength Dwell
Peel Time Control value Example seconds lb force lb force Comments
67 1 Tear 1.111 Heated upper and lower, one layer of tape on bottom
68 1 Tear 0.205 Heated upper and lower, one layer of tape on top
and bottom 69 2 Tear 0.95 Heated upper and lower, one layer of tape
on top and bottom 70 2 Tear 0.971 Heated upper and lower, two
layers of tape on bottom 71 1 Tear 0 Upper heat only, no tape top
or bottom. Sample flipped over, 1 second on each side 72 4 Tear
0.592 Upper heat only, 3 layers of tape on bottom. Sample flipped
over, 4 second on each side
[0149] In Table 12, a "layer of tape" refers to a layer of 3M 60
PTFE film (a 2 mil PTFE tape) used to cover the sealing rails. The
data in Table 12 shows that various heating rail configurations can
be used to produce a rupturable seal with reasonable peel values.
This includes heating the seal from one or both sides and having
one or both sealing rails covered with a tape layer.
Food Examples
[0150] In these examples, different combinations of food components
were charged into the adjacent compartments of two-compartment
plastic pouches. The pouches were constructed using film laminate
sheets similar to the SCOTCHPAK 29905 sheets described above, but
where the layer of linear, low density polyethylene was composed of
Dowlex 2035 LLDPE from Dow Chemical Co. Prior to charging the
compartments with food, the pouches were substantially of the
design depicted in FIGS. 1 and 2. A strip seal composed of a melt
blown polypropylene web, slit to about 12 mm in width, was also
used. The pouches were manufactured on a Klockner-Ferromatik Bag
Maker, Model LA III. Pouch dimensions were: width of about 25.4 cm
(10 inches), length of about 26.7 cm (10.5 inches) for "double
serving" size and about 16.5 cm (6.5 inches) for "single serving"
size. After the compartments, which were of substantially equal
size, were charged with the selected food components, the open end
of the pouch was edge sealed and the resulting food storage article
was placed in the freezer compartment of a conventional
refrigerator-freezer. Later, for testing, the completely frozen
food storage article was removed from the freezer and immediately
placed in a General Electric model JES1339WC001 Turntable microwave
oven having a power rating of 1.53 kW, and the oven was turned on
at the: "High" setting. The vapor pressure in the compartments was
allowed to increase, and the time at which the rupturable seal was
broken due to the internal vapor pressure was noted. In all cases,
the edge seals of the pouches remained intact and the food
components were allowed to cook together for a further period of
time after the barrier seal was ruptured.
F1. Cheese Ravioli/Red Sauce (Single Serving)
[0151] In this example, one compartment of the pouch was charged
with about 221 g of cheese-filled ravioli pasta, and the other was
charged with about 119 g of tomato sauce. These components cooked
separately for about 2 minutes and 27 seconds, at which time the
barrier seal was observed to rupture. The contents of the pouch
were then allowed to cook together for an additional 35 seconds, at
which time the microwave oven was turned off. The pouch was removed
from the oven and opened. The food was of good consistency and both
components were hot.
F2. Noodles/Diced Chicken and Vegetables (Single Serving)
[0152] In this example, one compartment of the pouch was charged
with about 119 g of frozen dough noodles, and the other was charged
with about 51 g of diced, pre-cooked chicken and about 61 g of
uncooked vegetables. These components cooked separately (noodles
separate from the chicken and vegetables) for about 1 minute and 51
seconds, at which time the barrier seal was observed to rupture.
The contents of the pouch were then allowed to cook together for an
additional 33 seconds, at which time the microwave oven was turned
off. The pouch was removed from the oven and opened. All components
of the food were hot. The vegetables had a good crunchy (non-soggy)
consistency, but the noodles were dried out and on the hard
side.
F3. Noodles/Diced Chicken, Vegetables, and White Sauce (Single
Serving)
[0153] In this example, one compartment of the pouch was charged
with about 119 g of frozen dough noodles, and the other was charged
with about 51 g of diced, pre-cooked chicken, about 61 g of
uncooked vegetables, and about 109 g of white sauce. These
components cooked separately (noodles separate from the chicken,
vegetables, and sauce) for about 1 minute and 52 seconds, at which
time the barrier seal was observed to rupture. The contents of the
pouch were then allowed to cook together for an additional 10
seconds, at which time the microwave oven was turned off. The pouch
was removed from the oven and opened. The food had hot and cold
spots. The noodles were dried out and on the hard side.
F4. Rice/Diced Chicken and Vegetables (Double Serving)
[0154] In this example, one compartment of the pouch was charged
with about 238 g of cooked rice and the other was charged with
about 102 g of diced, pre-cooked chicken and about 122 g of
uncooked vegetables. These components cooked separately (rice
separate from the chicken and vegetables) for about 5 minutes and
13 seconds, at which time the barrier seal was observed to rupture.
The contents of the pouch were then allowed to cook together for an
additional time, at which time the microwave oven was turned off.
The pouch was removed from the oven and opened. All components of
the food was hot. The vegetables had a good crunchy (non-soggy)
consistency, and the rice also had a good consistency.
F5. Rice/Diced Chicken, Vegetables, and White Sauce (Double
Serving)
[0155] In this example, one compartment of the pouch was charged
with about 238 g of cooked rice and the other was charged with
about 102 g of diced, pre-cooked chicken, about 122 g of uncooked
vegetables, and about 218 g of white sauce. These components cooked
separately (rice separate from the chicken, vegetables, and white
sauce) for about 6 minutes and 19 seconds, at which time the
barrier seal was observed to rupture. The contents of the pouch
were then allowed to cook together for an additional time, at which
time the microwave oven was turned off. The pouch was removed from
the oven and opened. The food had hot and cold spots.
[0156] Additional food examples were also performed. In one, cheese
was placed in one compartment and nacho chips were placed in the
other compartment. In another, cheese was placed in one compartment
and a large soft pretzel was placed in the other compartment. In
these cases the barrier seal again ruptured from the vapor pressure
within the compartment(s) without rupturing the edge seals of the
pouch. After cooking, all food components were well heated and the
resulting food products were of good quality and taste.
[0157] Various modifications and alterations of this invention will
be apparent to those skilled in the art without departing from the
scope and spirit of this invention, and it should be understood
that this invention is not limited to the illustrative embodiments
set forth herein.
* * * * *