Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MULTI-LAYERED BAGS WITH SHORTENED INNER LAYER
INVENTORS: Michael G. Borchardt, Kyle R. Wilcoxen, Robert W. Fraser,
Robert T. Dorsey, Shaun T. Broering, Jack A. MacPherson, Scott Binger,
Kenneth E. Cisek and Theodore J. Fish
BACKGROUND OF THE INVENTION
1. The Field of the Invention
[0001] The
present invention relates generally to thermoplastic films and bags
formed therefrom.
2. Background and Relevant Art
[0002]
Thermoplastic films are a common component in various commercial
and consumer products. For example, grocery bags, trash bags, sacks, and
packaging
materials are products that are commonly made from thermoplastic films.
Additionally, feminine hygiene products, baby diapers, adult incontinence
products,
and many other products include thermoplastic films to one extent or another.
[0003] The
cost to produce products including thermoplastic film is directly
related to the cost of the thermoplastic film. Recently the cost of
thermoplastic
materials has risen. In
response, many manufacturers attempt to control
manufacturing costs by decreasing the amount of thermoplastic material in a
given
product.
[0004] One
way manufacturers may attempt to reduce production costs is to
use thinner films or stretch the thermoplastic films, thereby increasing
surface area
and reducing the amount of thermoplastic film needed to produce a product of a
given
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size. Unfortunately, stretched or otherwise thinner thermoplastic films can
have
undesirable properties. For example, thinner thermoplastic films are typically
more
transparent or translucent. Additionally, consumers commonly associate thinner
films
with weakness. Such consumers may feel that they are receiving less value for
their
money when purchasing products with thinner films; and thus, may be dissuaded
to
purchase thinner thermoplastic films. As such, manufacturers may be dissuaded
to
stretch a film or use thinner films despite the potential material savings.
[0005] Accordingly, there are a number of considerations to be made in
thermoplastic films and manufacturing methods.
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BRIEF SUMMARY OF THE INVENTION
[0006] Implementations of the present invention solve one or more
problems
in the art with apparatus and methods for creating multi-layered bags with an
inner
bag that is shorter than the outer bag. The shortened inner bag can absorb
forces and
stretch to the size of the outer bag before the outer bag is significantly
strained. Once
stretched the inner bag can work in concert with the outer bag(s) to provide
strength.
Such implementations can provide an overall bag employing a reduced amount of
raw
material that nonetheless has maintained or increased strength parameters.
Alternatively, such implementations can use a given amount of raw material and
provide a bag with increased strength parameters.
[0007] For example, one implementation of a multi-layered
thermoplastic bag
with a shortened inner layer includes a first thermoplastic bag and a second
thermoplastic bag positioned within the first thermoplastic bag. Each of the
first and
second thermoplastic bags include first and second opposing sidewalls joined
together
along a first side edge, an opposite second side edge, and a bottom edge. At
least a
portion of the respective top edges of the first and second sidewalls and the
third and
fourth sidewalls are un-joined to define an opening. Additionally, the second
thermoplastic bag is shorter than the first thermoplastic bag such that the
bottom edge
of the second thermoplastic bag is spaced a distance from the bottom edge of
the first
thermoplastic bag.
[0008] Another implementation of the present invention includes a
multi-
layered bag comprising a first sidewall comprising a first layer of a
thermoplastic
material and an adjacent second layer of thermoplastic material. The multi-
layered
bag also includes a second sidewall comprising a first layer of a
thermoplastic
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material and an adjacent second layer of thermoplastic material. The first
layers of
the first and second sidewalls each have a first length. The second layers of
the first
and second sidewalls each have a second length that is less than the first
length. The
second sidewall is joined to the first sidewall along a first side edge, an
opposing
second side edge, and a bottom edge. Furthermore, at least a portion of
respective top
edges of the first and second sidewalls define an opening of the multi-layered
bag.
[0009] In addition to the forgoing, a method for forming a multi-
layered
thermoplastic bag within a shortened inner layer involves providing a first
thermoplastic film having a first width. The method also involves providing a
second
thermoplastic film having a second width, the second width being smaller than
the
first width. Additionally, the method involves folding the first and second
thermoplastic films in half along their widths. The method also involves
joining at
least two edges of the first thermoplastic film together to form a bag
configuration.
Similarly, the method involves joining at least two edges of the second
thermoplastic
film together to form a bag configuration. The method further involves joining
the
first and second thermoplastic films together.
[0010] Additional features and advantages of exemplary embodiments of
the
present invention will be set forth in the description which follows, and in
part will be
obvious from the description, or may be learned by the practice of such
exemplary
embodiments. The features and advantages of such embodiments may be realized
and
obtained by means of the instruments and combinations particularly pointed out
in the
appended claims. These and other features will become more fully apparent from
the
following description and appended claims, or may be learned by the practice
of such
exemplary embodiments as set forth hereinafter.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In order to describe the manner in which the above-recited and
other
advantages and features of the invention can be obtained, a more particular
description of the invention briefly described above will be rendered by
reference to
specific embodiments thereof which are illustrated in the appended drawings.
It
should be noted that the figures are not drawn to scale, and that elements of
similar
structure or function are generally represented by like reference numerals for
illustrative purposes throughout the figures. Understanding that these
drawings depict
only typical embodiments of the invention and are not therefore to be
considered to be
limiting of its scope, the invention will be described and explained with
additional
specificity and detail through the use of the accompanying drawings in which:
[0012] Fig. 1 illustrates a perspective view of a multi-layered
thermoplastic
bag with a shortened inner layer in accordance with one or more
implementations of
the present invention;
[0013] Fig. 2 illustrates a cross-sectional view of the multi-layered
thermoplastic bag of Fig. 1 taken along the section line 2-2 of Fig. 1;
[0014] Fig. 3 illustrates a perspective view of another multi-layered
thermoplastic bag with a shortened inner layer in accordance with one or more
implementations of the present invention;
[0015] Fig. 4 illustrates a cross-sectional view of the multi-layered
thermoplastic bag of Fig. 3 taken along the section line 4-4 of Fig. 1;
[0016] Fig. 5 illustrates a view of another multi-layered
thermoplastic bag
with a shortened inner layer in accordance with one or more implementations of
the
present invention;
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[0017] Fig. 6 illustrates a view of yet another multi-layered
thermoplastic bag
with a shortened inner layer in accordance with one or more implementations of
the
present invention;
[0018] Fig. 7 illustrates a view of still another multi-layered
thermoplastic bag
with a shortened inner layer in accordance with one or more implementations of
the
present invention;
[0019] Fig. 8 illustrates a view of another multi-layered
thermoplastic bag
with a shortened, incrementally stretched inner layer in accordance with one
or more
implementations of the present invention;
[0020] Fig. 9 illustrates a schematic view depicting a high-speed
manufacturing process for producing multi-layered thermoplastic bags having
shortened inner layers in accordance with one or more implementations of the
present
invention;
[0021] Fig. 10 illustrates a schematic view of the final steps of one
or more
implementations of the high-speed manufacturing process shown in Fig. 9;
[0022] Fig. 11 illustrates a schematic view of another high-speed
manufacturing process for producing multi-layered thermoplastic bags having
shortened inner layers in accordance with one or more implementations of the
present
invention; and
[0023] Fig. 12 illustrates a schematic view depicting yet another high-
speed
manufacturing process for producing multi-layered thermoplastic bags having
shortened inner layers in accordance with one or more implementations of the
present
invention.
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DETAILED DESCRIPTION
[0024] One or more implementations of the present invention include
apparatus and methods for creating multi-layered bags with an inner bag that
is
shorter than the outer bag. The shortened inner bag can absorb forces and
stretch to
the size of the outer bag(s) before the outer bag(s) is significantly
strained. Once
stretched the inner bag can work in concert with the outer bag(s) to provide
strength.
Such implementations can provide an overall bag employing a reduced amount of
raw
material that nonetheless has maintained or increased strength parameters.
Alternatively, such implementations can use a given amount of raw material and
provide a bag with increased strength parameters.
[0025] For example, in one or more implementations the combined layers
of
the multi-layered bag may use less material than a conventional bag, but
nonetheless
have maintained or increased strength parameters provided by the layers of the
bag
working in concert with each other. In particular, in one or more
implementations the
layers of the multi-layered bag are thinner and/or stretched to reduce the
amount of
thermoplastic material to form a bag of a given size. For instance, one or
more layers
of the multi-layered bag can be continuously stretched or incrementally
stretched to
thin the layer and/or increase or otherwise modify the strength parameters of
the
layers. Suitable stretching methods include machine direction orientation
("MDO"),
ring rolling, a structural elastic like film (SELF) process, embossing, or
other
methods.
[0026] As the multi-layered bags of the present invention include two
or more
layers, the layers can be provided with different aesthetic, material, or
strength
properties. For example, in one or more implementations the inner layer of the
multi-
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layered bag can include elastic characteristics that allow the inner layer to
stretch to
the outer layer(s). The inner layer can include elastic characteristics either
by material
choice or processing (e.g., SELFing or ring rolling). Thus, the inner layer
may
comprise the same or different material as the outer layer(s). The inner layer
may also
have higher or lower strength and/or abrasion resistance than the outer
layers.
[0027] In one or more implementations, the inner layer is joined or
bonded to
the outer layer(s) of the multi-layered bag. The joining of the inner layer to
the outer
layer(s) can control how much the inner layer may or may not stretch in use.
For
instance, to allow the inner layer to stretch freely and independently from
the outer
layer(s), the inner layer may be joined to the outer layer along only a hem
seal near
the top of the layers. Alternatively or additionally, the side edges of the
inner and
outer layers can be joined together. To prevent at least some stretching of
the inner
layer, the side walls of the inner layer can be laminated to the sidewalls of
the outer
layer(s). To allow an intermediate amount of stretching, only intermediate or
discrete
portions of the sidewalls of the inner layer can be laminated to the sidewalls
of the
outer layer(s).
[0028] Lamination of at least a portion of the inner layer to any
adjacent or
outer layers can be accomplished through one or more suitable techniques. For
example, bonding may be achieved by pressure only (for example ring rolling,
stainable network lamination, or embossing), or with a combination of heat and
pressure. Alternately, the film layers can be laminated by ultrasonic bonding.
Alternately, the films can be laminated by the application of adhesives to one
or more
layers. Treatment with a Corona discharge can enhance any of the above
methods.
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Prior to lamination, the separate layers can be flat film or can be subject to
separate
processes, such as stretching, slitting, coating and printing, and corona
treatment.
[0029] In one or more implementations, the lamination between the
inner
layer and adjacent or outer layer(s) of a multi-layer is relatively light such
that forces
acting on the multi-layer film are first absorbed by breaking the lamination
bonds
rather than, or prior to, tearing or otherwise causing the failure of the
layers of the
multi-layer bag. In particular, the bonds or bond regions of an inner layer
and
adjacent or outer layer(s) of multi-layer bags in accordance with one or more
implementations can act to first absorb forces via breaking of the bonds prior
to
allowing that same force to cause failure of the individual layers of the
multi-layer
bag. Such action can provide increased strength to the multi-layer bag. In one
or
more implementations, the bonds or bond regions include a bond strength that
is
advantageously less than a weakest tear resistance of each of the individual
films so as
to cause the bonds to fail prior to failing of the film layers. Indeed, one or
more
implementations include bonds that the release just prior to any localized
tearing of
the layers of the multi-layer bag. In particular, bonds formed by pressure
only may
have bond strengths less than the weakest tear resistance.
[0030] Thus, in one or more implementations, bonds or bond regions of
a
multi-layer film or bag can fail before either of the individual layers
undergo
molecular-level deformation. For example, an applied strain can pull the bonds
or
bond regions apart prior to any molecular-level deformation (stretching,
tearing,
puncturing, etc.) of the individual film layers. In other words, the light
bonds or bond
regions can provide less resistive force to an applied strain than molecular-
level
deformation of any of the layers of the multi-layer film or bag. The inventors
have
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surprisingly found that such a configuration of light bonding can provide
increased
strength properties to the multi-layer film or bag as compared to a film or
bag with a
monolayer equal thickness or a multi-layer film or bag in which the plurality
of layers
are tightly bonded together (e.g., coextruded).
[0031] One or more implementations of the present invention provide
for
tailoring the bonds or bond regions between layers of a multi-layer bag in
different
regions of the bag. For example, one or more implementations include modifying
or
tailoring one or more of bond strength, bond density, bond pattern, bond type
and/or
bond size of different sections of a multi-layer film or bag to deliver a bag
with zones
or sections with tailored strength and/or aesthetic characteristics.
[0032] As used herein, the terms "lamination," "laminate," and
"laminated
film," refer to the process and resulting product made by bonding together two
or
more layers of film or other material. The term "bonding," when used in
reference to
bonding of multiple layers of a multi-layer film, may be used interchangeably
with
"lamination" of the layers. According to methods of the present invention,
adjacent
layers of a multi-layer film are laminated or bonded to one another. In one or
more
implementations, the bonding purposely results in a relatively weak bond
between the
layers that has a bond strength that is less than the strength of the weakest
layer of the
film. This allows the lamination bonds to fail before the film layer, and thus
the film,
fails.
[0033] The term laminate does not include heated coextruded multilayer
films
comprising one or more tie layers. As a verb, "laminate" means to affix or
adhere (by
means of, for example, adhesive bonding, pressure bonding, ultrasonic bonding,
corona lamination, and the like) two or more separately made film articles to
one
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another so as to form a multi-layer structure. As a noun, "laminate" means a
product
produced by the affixing or adhering just described.
[0034] The individual layers (i.e., inner and outer layers) of the
multi-layer
bags of one or more implementations may each themselves comprise a plurality
of
laminated layers. Such layers may be significantly more tightly bonded
together than
the bonding provided between the inner and outer layers. Both tight and
relatively
weak lamination can be accomplished by joining layers by mechanical pressure,
joining layers with adhesives, joining with heat and pressure, joining the
layers by
heat, and combinations thereof. Adjacent sub-layers of an individual layer may
be
coextruded. Coextrusion results in tight bonding so that the bond strength is
generally
greater than the tear resistance of the resulting layers (i.e., rather than
allowing
adjacent layers to be peeled apart through breakage of the coextrusion bonds,
the film
will tear).
[0035] In one or more implementations, the light lamination or bonding
between layers of a multi-layer bag may be non-continuous (i.e., discontinuous
or
partial discontinuous). As used herein the terms "discontinuous bonding" or
"discontinuous lamination" refers to lamination of two or more layers where
the
lamination is not continuous in the machine direction and not continuous in
the
transverse direction. More particularly, discontinuous lamination refers to
lamination
of two or more layers with repeating bonded patterns broken up by repeating un-
bonded areas in both the machine direction and the transverse direction of the
film.
Or alternatively, random bonded areas broken up by random un-bonded areas.
[0036] As used herein the terms "partially discontinuous bonding" or
"partially discontinuous lamination" refers to lamination of two or more
layers where
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the lamination is substantially continuous in the machine direction or in the
transverse
direction, but not continuous in the other of the machine direction or the
transverse
direction. Alternately, partially discontinuous lamination refers to
lamination of two
or more layers where the lamination is substantially continuous in the width
of the
article but not continuous in the height of the article, or substantially
continuous in the
height of the article but not continuous in the width of the article. More
particularly,
partially discontinuous lamination refers to lamination of two or more layers
with
repeating bonded patterns broken up by repeating unbounded areas in either the
machine direction or the transverse direction.
[0037] As used herein, the term "flexible" refers to materials that
are capable
of being flexed or bent, especially repeatedly, such that they are pliant and
yieldable
in response to externally applied forces. Accordingly, "flexible" is
substantially
opposite in meaning to the terms inflexible, rigid, or unyielding. Materials
and
structures that are flexible, therefore, may be altered in shape and structure
to
accommodate external forces and to conform to the shape of objects brought
into
contact with them without losing their integrity. In accordance with further
prior art
materials, web materials are provided which exhibit an "elastic-like" behavior
in the
direction of applied strain without the use of added traditional elastic. As
used herein,
the term "elastic-like" describes the behavior of web materials which when
subjected
to an applied strain, the web materials extend in the direction of applied
strain, and
when the applied strain is released the web materials return, to a degree, to
their pre-
strained condition.
Film Materials
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[0038] As an initial matter, one or more layers of the films can
comprise any
flexible or pliable material comprising a thermoplastic material and that can
be
formed or drawn into a web or film. Each individual film layer may itself
include a
single layer or multiple layers. Adjuncts may also be included, as desired
(e.g.,
pigments, slip agents, anti-block agents, tackifiers, or combinations
thereof). The
thermoplastic material of the films of one or more implementations can
include, but
are not limited to, thermoplastic polyolefins, including polyethylene,
polypropylene,
and copolymers thereof Besides ethylene and propylene, exemplary copolymer
olefins include, but are not limited to, ethylene vinylacetate (EVA), ethylene
methyl
acrylate (EMA) and ethylene acrylic acid (EAA), or blends of such olefins.
Various
other suitable olefins and polyolefins will be apparent to one of skill in the
art.
[0039] Other examples of polymers suitable for use as films in
accordance
with the present invention include elastomeric polymers. Suitable elastomeric
polymers may also be biodegradable or environmentally degradable. Suitable
elastomeric polymers for the film include poly(ethylene-butene), poly(ethylene-
hexene), poly(ethylene-octene), poly(ethylene-propylene), poly(styrene-
butadiene-
styrene), poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-
styrene),
poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate),
poly(ethylene-
methylacrylate), poly(ethylene-acrylic acid), poly(ethylene butylacrylate),
polyurethane, poly(ethylene-propylene-diene), ethylene-propylene rubber, and
combinations thereof
[0040] In at least one implementation of the present invention, the
film can
include linear low density polyethylene. The term "linear low density
polyethylene"
(LLDPE) as used herein is defined to mean a copolymer of ethylene and a minor
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amount of an alkene containing 4 to 10 carbon atoms, having a density of from
about
0.910 to about 0.926 g/cm3, and a melt index (MI) of from about 0.5 to about
10. For
example, one or more implementations of the present invention can use an
octene co-
monomer, solution phase LLDPE (MI=1.1; p=0.920).
Additionally, other
implementations of the present invention can use a gas phase LLDPE, which is a
hexene gas phase LLDPE (MI=1.0; p=0.920). One will appreciate that the present
invention is not limited to LLDPE, and can include "high density polyethylene"
(HDPE), "low density polyethylene" (LDPE), and "very low density polyethylene"
(VLDPE). Indeed films made from any of the previously mentioned thermoplastic
materials or combinations thereof can be suitable for use with the present
invention.
[0041] One
will appreciate in light of the disclosure herein that manufacturers
may form the individual films or webs so as to provide improved strength
characteristics using a wide variety of techniques. For example, a
manufacturer can
form a precursor mix of the thermoplastic material including any optional
additives.
The manufacturer can then form the film(s) from the precursor mix using
conventional flat extrusion, cast extrusion, or coextrusion to produce
monolayer,
bilayer, or multilayered films.
[0042]
Alternative to conventional flat extrusion or cast extrusion processes, a
manufacturer can form the films using other suitable processes, such as, a
blown film
process to produce monolayer, bilayer, or multilayered films. If desired for a
given
end use, the manufacturer can orient the films by trapped bubble, tenterframe,
or other
suitable processes. Additionally, the manufacturer can optionally anneal the
films.
[0043] In one
or more implementations, the films of the present invention are
blown film, or cast film. Blown film and cast film is formed by extrusion. The
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extruder used can be a conventional one using a die, which will provide the
desired
gauge. Some useful extruders are described in U.S. Pat. Nos. 4,814,135;
4,857,600;
5, 076,988; 5,153,382, each of which are incorporated herein by reference.
Examples
of various extruders, which can be used in producing the films to be used with
the
present invention, can be a single screw type modified with a blown film die,
an air
ring, and continuous take off equipment.
[0044] In one or more implementations, a manufacturer can use multiple
extruders to supply different melt streams, which a feed block can order into
different
channels of a multi-channel die. The multiple extruders can allow a
manufacturer to
form a multi-layered film with layers having different compositions. In a
blown film
process, the die can be an upright cylinder with a circular opening. Rollers
can pull
molten plastic upward away from the die. An air-ring can cool the film as the
film
travels upwards. An air outlet can force compressed air into the center of the
extruded
circular profile, creating a bubble. The air can expand the extruded circular
cross
section by a multiple of the die diameter. This ratio is called the "blow-up
ratio."
When using a blown film process, the manufacturer can collapse the film to
double
the plies of the film. Alternatively, the manufacturer can cut and fold the
film, or cut
and leave the film unfolded.
[0045] Referring to Figs. 1 and 2, an implementation of multi-layered
thermoplastic bag 100 with a shortened inner layer is illustrated. While the
multi-
layered bags of one or more implementations are generally capable of holding a
vast
variety of different contents, the multi-layered bag 100 illustrated in Fig. 1
may be
intended to be used as a liner for a garbage can or similar refuse container.
The multi-
layered thermoplastic bag 100 can include a first layer or bag 101 including a
first
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sidewall 102 and a second sidewall 104. The first and second sidewalls 102,
104 can
be joined together along a first side edge 110, an opposing second side edge
112, and
along a bottom edge 114. The bottom edge 114 can extend between the first and
second side edges 110, 112. The first and second sidewalls 102, 104 may be
joined
along the first and second side edges 110, 112 and bottom edge 114 by any
suitable
process such as, for example, a heat seal. In one or more implementations, the
bottom
edge 114 or one or more of the side edges 110, 112 can comprise a fold.
[0046] To allow access to the interior volume of the multi-layered bag
100 at
least a portion of the top edges 120, 122 of the first and second sidewalls
102, 104
may be un-joined to define an opening 124. The opening 124 can be opposite the
bottom edge 114. When placed in a trash receptacle, the top edges 120, 122 of
the
first and second sidewalls 102, 104 may be folded over the rim of the
receptacle.
[0047] The multi-layered bag 100 also optionally includes a closure
mechanism located adjacent to the upper edges 120, 122 for sealing the top of
the
multi-layered bag 100 to form a fully-enclosed container or vessel. As shown
by
Figs. 1 and 2, the closure mechanism can comprise a draw tape 140. To
accommodate the draw tape 140 the first top edge 120 of the first sidewall 102
may be
folded back into the interior volume 106 and may be attached to the interior
surface of
the sidewall to form a first hem 142. Similarly, the second top edge 122 of
the second
sidewall 104 may be folded back into the interior volume and may be attached
to the
second sidewall 104 to form a second hem 144.
[0048] As shown by Fig. 2, in one or more implementations, the draw
tape
140 extends loosely through the first and second hems 142, 144 along the first
and
second top edge 120, 122. To access the draw tape 140, first and second
notches 146,
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148 (Fig. 1) may be disposed through the respective first and second top edges
120,
122. Pulling the draw tape 140 through the notches 146, 148 will constrict the
first
and second top edge 120, 122 thereby closing or reducing the opening 124. The
draw
tape closure may be used with any of the implementations of a reinforced
thermoplastic bag described herein. One will appreciate in light of the
disclosure
herein that the present invention is not limited to draw tape closure
mechanisms. In
alternative implementations, the closure mechanism can comprise flaps,
adhesive
tapes, a tuck and fold closure, an interlocking closure, a slider closure, a
zipper
closure or other closure structures known to those skilled in the art for
closing a bag.
[0049] As
previously mentioned, the multi-layered bag 100 further includes a
second layer or bag 150 (shown in dashes in Fig. 1). The second layer or bag
150 can
include a first sidewall 102a and a second sidewall 104a. The first and second
sidewalls 102a, 104a can be joined together along a first side edge 110a, an
opposing
second side edge 112a, and along a bottom edge 114a. The bottom edge 114a may
extend between the first and second side edges 110a, 112a. The first and
second
sidewalls 102a, 104a may be joined along the first and second side edges 110a,
112a
and bottom edge 114a by any suitable process such as, for example, a heat
seal. In
one or more implementations, the bottom edge 114a or one or more of the side
edges
110a, 112a can comprise a fold.
[0050] As
shown by Figs. 1 and 2, the second layer or bag 150 is positioned
within the first layer or bag 101. Such a configuration may be considered a
"bag-in-
bag" configuration. In other words the multi-layered bag 100 can include a
second
thermoplastic layer or bag 150 positioned within a first thermoplastic layer
or bag
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101. Each of the first and second layers or bags 101, 150 can include a pair
of
opposing sidewalls joined together along three edges as described above.
[0051] The multi-layered bag 100 can also be considered as a bag with
multi-
layered sidewalls. For example, the first sidewalls 102, 102a of the first and
second
layers or bags 101, 150 can be considered a first sidewall of the multi-
layered bag
100. Similarly, the second sidewalls 104, 104a of the first and second layers
or bags
101, 150 can be considered a second sidewall of the multi-layered bag 100.
[0052] Each of the sidewalls 102, 104, 102a, 104a (or in other words
each of
the inner and outer layers or bags 101, 150) can have a gauge or thickness
(i.e.,
average distance between the major surfaces) between about 0.1 mils to about
10
mils, suitably from about 0.1 mils to about 4 mils, suitably in the range of
about 0.1
mils to about 2 mils, suitably from about 0.1 mils to about 1.25 mils,
suitably from
about 0.9 mils to about 1.1 mils, suitably between about 0.2 mils to about 0.9
mils,
and suitably between about 0.3 mils to about 0.7 mils. Additionally, as shown
by Fig.
2, the sidewalls 102, 104 can have a thickness approximately equal to the
thickness of
the sidewalls 102a, 104a. In alterative implementations, the sidewalls 102,
104 may
be thinner than the sidewalls 102a, 104a. In yet further implementations, the
sidewalls 102, 104 may be thicker than the sidewalls 102a, 104a.
[0053] As shown in Figure 2, each of the sidewalls 102, 104, 102a,
104a can
have a uniform or consistent gauge. In alternative implementations, one or
more of
the sidewalls 102, 104, 102a, 104a can be rough or uneven. Further, the gauge
of one
or more of the sidewalls 102, 104, 102a, 104a need not be consistent or
uniform.
Thus, the gauge of one or more of the sidewalls 102, 104, 102a, 104a can vary
due to
product design, manufacturing defects, tolerances, or other processing issues.
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[0054] In particular, in one or more implementations one or more of
the
sidewalls 102, 104, 102a, 104a is incrementally stretched as explained in
greater
detail below. For example, in one or more implementations one or more of the
102,
104, 102a, 104a is incrementally stretched by one or more of MD ring rolling,
transverse direction TD ring rolling, SELFing, or other methods described in
U.S.
Patent Application No. 13/273,384 filed October 14, 2011 and entitled NON-
C ONTINUOUS LY LAMINATED MULTI-LAYERED BAGS, previously
incorporated by reference herein. Incrementally stretching one or more of the
sidewalls 102, 104, 102a, 104a can increase or otherwise modify one or more of
the
tensile strength, tear resistance, impact resistance, or elasticity of the
films, while also
reducing the basis weight of the film.
[0055] The sidewalls 102, 104, 102a, 104a can each comprise films of
thermoplastic material. In particular, the sidewalls102, 104, 102a, 104a can
comprise
any of the thermoplastic materials described hereinabove, or combinations
thereof. In
one or more implementations, the sidewalls 102, 104 can comprise the same
thermoplastic material as the sidewalls 102a, 104a. In alternative
implementations,
the sidewalls 102a, 104a can comprise a different thermoplastic material than
the
sidewalls 102, 104. For example, the material of the sidewalls 102a, 104a may
have a
higher tensile strength, tear resistance, puncture resistance, elasticity,
and/or abrasion
resistance than the material of the sidewalls 102, 104. Sidewalls 102a, 104a
made of
stronger and/or tougher material may help further protect the multi-layered
bag 100
against rupture and/or puncture.
[0056] In at least one implementation the inner bag 150 includes an
elastic
material that allows the inner bag 150 to expand to the size of the outer bag
101 when
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filled with objects, such as trash, or otherwise strained. For example, in one
or more
implementations the inner bag can comprise a PLASTOMER from Dow Chemical
Company, Midland, Mich., a FLEXIMER from Dow Chemical Company, Midland,
Mich., ethylene propylene diene monomer, polybutylene, poly(1-butene),
combinations thereof, or other materials with similar elastic characteristics.
In one or
more implementations the inner bag can comprise a material that has a tensile
yield
strength lower than the tensile yield strength of LLPDE with a density of
about 0.915
to about 0.925 g/cm3*
[0057] In addition to the forgoing, in one or more implementations the
sidewalls 102, 104, 102a, 104a can comprise the same color. In alternative
implementations, the color of the sidewalls 102a, 104a and the sidewalls 102,
104 can
differ. For example, in one or more implementations the sidewalls 102, 104 can
comprise a white, translucent thermoplastic material. The sidewalls 102a, 104a
can
comprise a pigmented (i.e., non-white) thermoplastic material. For example, in
one or
more implementations the sidewalls 102a, 104a can comprise a black
thermoplastic
material. In such implementations, the areas of the multi-layered bag 100
reinforced
by the sidewalls 102a, 104a can appear gray when view from the outside of the
multi-
layered bag 100. Thus, the differing color of the areas of the multi-layered
bag 100
reinforced by the inner layer 150 can serve to notify a consumer that such
areas of the
multi-layered bag 100 are reinforced. Furthermore, the difference in color can
also
serve to notify the consumer once the inner layer or bag 150 stretches to the
size of
the outer layer or bag 101, as the bottom of the outer layer or bag 101 will
change
from a white appearance to a grey appearance.
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[0058] The
individual films or layers (e.g., inner layer or bag 150 and outer
layer or bag 101) may each themselves comprise a plurality of film layers.
Such film
layers may be joined by mechanical pressure, adhesives, heat and pressure,
spread
coating, extrusion coating, and combinations thereof. In particular, one or
more of the
sidewalls 102, 104, 102a, 104a can comprise two, three, four, or more
coextruded,
continuously laminated, non-continuously laminated, or otherwise bonded
layers. For
ease in description, the sidewalls 102, 104, 102a, 104a are described and
shown
herein as single film layers. One will appreciate, however, that the present
invention
is not so limited, and the sidewalls 102, 104, 102a, 104a can each include
one, two,
three, or more layers.
[0059]
Additionally, as shown by Figs. 1 and 2, the multi-layered bag 100
includes multiple layers. Figs. 1 and 2 illustrate a multi-layered bag 100
with two
layers. One will appreciate in light of the disclosure herein that in
alternative
implementations one or more multi-layered bags of the present invention can
include
more than two layers. For
example, multi-layered bags of one or more
implementations can include 3, 4, 5, 6, or more layers.
[0060] In any
event, multi-layered bags of one or more implementations at
least one inner layer that is shorter than at least one adjacent or outer
layer. For
example, Figs. 1 and 2 illustrate that the multi-layered bag 100 includes a
second,
inner layer or bag 150 that is shorter than a first, outer layer 101. Thus,
the bottom
edge 114a of the second layer or bag 150 is spaced a distance 160 from the
bottom
edge 114 of the first layer or bag 101. Thus, the sidewalls 102, 104 the first
layer or
bag 101 can have a first length 162, while the sidewalls 102a, 104a of the
second
layer or bag 150 can have a second length 164 that is less than the first
length 162. In
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other words, each of the sidewalls of the multi-layered bag can include outer
layers
102, 104 with a first length 162 and inner layers 102a, 104a with a second
length 164
that is less than the first length 162.
[0061] The length 162 may have a first range of about 20 inches (50.8
cm) to
about 48 inches (121.9 cm), a second range of about 23 inches (58.4 cm) to
about 33
inches (83.8 cm), and a third range of about 26 inches (66 cm) to about 28
inches
(71.1 cm). In one implementation, the length 162 may be 27.375 inches (69.5
cm). In
alternative implementations, the length 162 may be shorter or longer than the
examples listed above.
[0062] Along similar lines, the length 164 may have a first range of
about 20
inches (50.8 cm) to about 48 inches (121.9 cm), a second range of about 23
inches
(58.4 cm) to about 33 inches (83.8 cm), and a third range of about 26 inches
(66 cm)
to about 28 inches (71.1 cm). In one implementation, the length 164 may be
27.375
inches (69.5 cm). In alternative implementations, the length 164 may be
shorter or
longer than the examples listed above. In any event, the length 164 may be
smaller
than the length 162.
[0063] In particular, as described above, the length 164 can be
shorter than the
length 162 by a distance 160 between the bottom edge 114a of the second layer
or bag
150 and the bottom edge 114 of the first layer or bag 101. The distance 160
can vary
based on the elasticity of the inner layer or bag 150 or other design factors.
In one or
more implementations, the distance 160 comprises between about 5% and 50% of
the
length 162. In alternative implementations, the distance 160 comprises about
5%,
10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45% of the length 162 of the outer layer
or
bag 101. In alternative implementations, the distance 160 can be greater than
50% of
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the length 162 of the outer layer or bag 101. One will appreciate in light of
the
disclosure herein that the shortened inner layer or bag 150 can allow for a
reduction in
material as compared with a conventional bag.
[0064] In one or more implementations, the inner layer or bag 150 is
joined or
bonded to the outer layer or bag 101 of the multi-layered bag 100. For
example, Fig.
2 illustrates that in one implementation the inner layer or bag 150 is joined
to the
outer layer or bag 101 only along the hems 142, 144. Thus, the inner layer or
bag 150
can expand or stretch freely relative to the outer layer or bag 101. In such
implementations, the inner layer or bag 150 can act independently of the outer
layer
or bag 101. In particular, the inner layer or bag 150 can act as a shock
absorber and
absorb forces associated with loading the multi-layered bag 100.
[0065] In alternative implementations, the inner layer or bag 150 can
additionally, or alternatively, be joined to the outer layer or bag 101 along
their
respective edges. For example, one or more of the first side edges 110, 110a
and the
second side edges 112, 112a of the respective inner and outer layers or bags
101, 150
can be joined by a heat seal, a fold, or other mechanism. In at least one
implementation the first side edges 110, 110a and the second side edges 112,
112a of
the inner and outer layers or bags 101, 150 are joined by heat seals, while
the bottom
edges 114, 114a comprise folds that are un-joined to each other. One will
appreciate
in light of the disclosure herein that heat seals or other mechanisms bonding
the first
side edges 110, 110a and the second side edges 112, 112a of the inner and
outer layers
or bags 101, 150 together can restrict or prevent at least some stretching of
the inner
layer or bag 150.
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[0066] In addition to the foregoing, in one or more implementations
one or
more of the sidewalls 102a, 104a of the inner layer or bag 150 can be
laminated to the
respective sidewalls 102, 104 of the outer layer or bag 101. For example, the
sidewalls 102a, 104a of the inner layer or bag 150 can be continuously bonded
to the
sidewalls 102, 104 of the outer layer or bag 101. For example, the inner and
outer
layers or bags 101, 150 can be co-extruded, joined shortly after extrusion
while still
tacky, adhesively bonded, or otherwise continuously bonded.
[0067] In alternative implementations the inner layer or bag 150 is
non-
continuously laminated to the outer layer or bag 101. For example, the inner
layer or
bag 150 can be non-continuously laminated to the outer layer or bag 101 using
any of
the methods, process, and techniques described in previously incorporated by
reference U.S. Patent Application No. 13/273,384 filed October 14, 2011 and
entitled
NON-CONTINUOUSLY LAMINATED MULTI-LAYERED BAGS. For example,
the inner layer or bag 150 can be non-continuously laminated to the outer
layer or bag
101 using a process selected from the group consisting of adhesive bonding,
ultrasonic bonding, embossing, ring rolling, SELFing, and combinations
thereof.
[0068] In at least one implementation, the lamination between the
inner and
outer layers or bags 101, 150 can have a bond strength that is less than a
weakest tear
resistance of each of the inner and outer layers or bags 101, 150 so as to
cause the
lamination to fail prior to failing of the inner and outer layers or bags 101,
150.
Indeed, one or more implementations include bonds that the release just prior
to any
localized tearing of the inner and outer layers or bags 101, 150. In
particular, the
lamination between the inner and outer layers or bags 101, 150 can act to
first absorb
forces via breaking of the bonds prior to allowing that same force to cause
failure of
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the inner and outer layers or bags 101, 150. Such action can provide increased
strength to the multi-layered bags of one or more implementations of the
present
invention.
[0069] Thus, in one or more implementations, strains applied to a
multi-
layered bag with a shortened inner layer can first be at least partially
absorbed or
softened by breaking of the bond(s) between the inner layer or bag and the
outer layer
or bag. Thereafter, the shortened inner bag can absorb forces and stretch to
the size of
the outer bag(s) before the outer bag(s) is significantly strained. Once
stretched the
inner bag can work in concert with the outer bag(s) to provide strength. Such
implementations can provide an overall bag employing a reduced amount of raw
material that nonetheless has maintained or increased strength parameters.
[0070] In addition to the foregoing, the bonds between the inner and
outer
layers can allow the inner layer or bag to act as a shock absorber by
debonding from
the outer layer or bag as articles, such as trash, are added to the bag. This
debonding
may allow the inner layer or bag to expand, stretch, or otherwise move
downward.
This debonding may also allow the inner layer or bag to separate in areas away
for the
added article and thus absorb some of the energy.
[0071] This is beneficial as it has been found that thermoplastic
films often
exhibit strength characteristics that are approximately equal to the strength
of the
weakest layer. Providing relatively weak bonding between the inner and outer
layers
or bags 101, 150 has surprisingly been found to greatly increase the strength
provided
by the inner layer or bag 150. As more explicitly covered in U.S. Patent
Application
No. 12/947,025 filed November 16, 2010 and entitled DISCONTINUOUSLY
LAMINATED FILM, incorporated by reference herein, the MD and TD tear values of
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non-continuously laminated films in accordance with one or more
implementations
can exhibit significantly improved strength properties, despite a reduced
gauge. In
particular, the individual values for the Dynatup, MD tear resistance, and TD
tear
resistance properties in non-continuously laminated films of one or more
implementations are unexpectedly higher than the sum of the individual layers.
Thus,
the non-continuous lamination of the inner and outer layers or bags 101, 150
can
provide a synergistic effect.
[0072] More specifically, the TD tear resistance of the non-
continuously
laminated films can be greater than a sum of the TD tear resistance of the
individual
layers. Similarly, the MD tear resistance of the non-continuously laminated
films can
be greater than a sum of the MD tear resistance of the individual layers.
Along
related lines, the Dynatup peak load of the non-continuously laminated films
can be
greater than a sum of a Dynatup peak load of the individual layers. Thus, the
non-
continuously laminated films can provide a synergistic effect. In addition to
the
foregoing, one or more implementations of a non-continuously laminated multi-
layered bag with a shortened inner layer can allow for a reduction in basis
weight
(gauge by weight) as much as 50% and still provide enhanced strength
parameters.
[0073] For example, Figs. 3 and 4 illustrate a multi-layered bag 200
with a
shortened inner layer or bag similar to the multi-layered bag 100 of Figs. 1
and 2,
albeit that the sidewalls 102a, 104a of the inner layer or bag 150 are
partially
discontinuously laminated to the sidewalls 102, 104 of the outer layer or bag
101. In
particular, a ribbed pattern 170 can non-continuously bond the inner layer or
bag 150
to the outer layer or bag 101 and provide desirable physical characteristics.
The
ribbed pattern 170 and associated bonds can be formed by passing the
respective
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sidewalls 102, 102a and 104, 104a together through TD intermeshing rollers and
shown and described in detail in previously incorporated by reference U.S.
Patent
Application No. 13/273,384 filed October 14, 2011 and entitled NON-
CONTINUOUSLY LAMINATED MULTI-LAYERED BAGS.
[0074] The ribbed pattern 170 can comprise a plurality of alternating
thin
linear ribs 171 and thick linear ribs 172 that may extend across the sidewall
102, 104,
102a, 104a substantially between the first side edges 110, 110a and second
side edges
112, 112a. As illustrated in Fig. 3, the ribs 171, 172 may be parallel and
adjacent to
one another. Additionally, as illustrated in Fig. 3, the ribbed pattern 170
may extend
from the bottom edge 114a toward the opening 124. To avoid interfering with
the
operation of the draw tape 140, the extension of the ribbed pattern 170 may
terminate
below the hem seals 142, 144, as illustrated by Fig. 3. In alternative
implementations,
the ribbed pattern 170 can extend from the bottom edge 114a to the top edges
of each
sidewall.
[0075] Fig. 4 further illustrates that the inner layer or bag 150 is
bonded to the
outer layer or bag 150. In particular, a first plurality of non-continuous
bonded
regions or bonds 174 can secure the first and second layers 102, 102a, 104,
104a of
the each sidewall together. Thus, the bonds 174 can comprise a pattern of
linear
bonds 174 extending between the first side edge 110 and the second side edge
112 of
each sidewall 102, 104.
[0076] As shown by Fig. 4, in one or more implementations, the bonds
174
can bond thick linear ribs 172 of the inner layer or bag 150 to thick linear
ribs 172 of
the outer layer or bag 101. Fig. 4 illustrates that the bonds 174 can secure
some, but
not all, of the thick linear ribs 172 of one layer to the thick linear ribs
172 of an
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adjacent layer. In particular, Fig. 4 illustrates that bonds 174 can secure
every other
thick linear rib 172 of adjacent layers together. In alternative
implementations, bonds
174 can secure each thick linear rib 172 of adjacent layers together.
Additionally, in
one or more implementations the thin linear ribs 171 may be unbounded.
[0077] One will thus appreciate that the multi-layered bags with
shortened
inner layers can allow the inner layer or bag 150 to freely stretch by having
the inner
layer or bag 150 joined to the outer layer or bag 101 only along an upper hem
seal.
Alternatively, the multi-layered bags with shortened inner layers can prevent
the inner
layer or bag 150 from stretching relative to the outer layer or bag 101 by
tightly
bonding the layers together. In still further implementations, the multi-
layered bags
with shortened inner layers can allow the inner layer or bag 150 to freely
stretch once
relatively light non-continuous bonds between the layers are broken. In
additional
implementations, multi-layered bags with shortened inner layers can allow
intermediate stretching of the inner layer or bag 150 by forming discrete
zones of non-
continuous lamination between the inner and outer layers or bags 101, 150.
[0078] For example, Fig. 5 illustrates a multi-layered bag 300 with a
shortened inner layer or bag similar to the multi-layered bag 200 of Figs. 3
and 4,
albeit that the ribbed pattern 170 non-continuously bonding the inner layer or
bag 150
to the outer layer or bag 101 is formed only in a top portion 180 of the bag
adjacent
the top of the bag 300. One will appreciate in light of the disclosure herein
that the
ribbed pattern 170 and associated bonds can reduce or prevent stretching (at
least
initially) of the top portion 180 while allowing the rest of the inner layer
or bag 150 to
stretch freely.
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[0079] Fig. 6 illustrates another multi-layered bag 400 with a
shortened inner
layer or bag. The multi-layered bag 400 can include a top portion 180, an
upper-
middle portion 184, a lower middle portion 186, and a bottom portion 192 with
a
ribbed pattern 170 non-continuously bonding the inner layer or bag 150 to the
outer
layer or bag 101. The portion with ribbed patterns 170 non-continuously
bonding the
inner layer or bag 150 to the outer layer or bag 101 are separated by portions
182,
186, 190 in which the inner layer or bag 150 is unbounded to the outer layer
or bag
101.
[0080] Thus, one or more implementations allow for the tailoring of
various
zones or sections of a multi-layered bag with non-continuous bonds or bonded
regions. In particular, different types, sizes, shapes, patterns,
concentrations, and/or
combinations of non-continuous bonds can provide different zones or sections
of a
multi-layered bag with strength and/or aesthetic properties optimal for the
particular
zone or section. Fig. 6 illustrates a multi-layered bag 400 with seven zones.
One will
appreciate that the present invention is not so limited and multi-layered bags
of one or
more implementations can include 0, 1, 2, 3, 4, 5, 6, or more zones or
sections with
tailored non-continuous bonds. Furthermore, the Figs. illustrate sections that
extend
along the width of the bag (i.e., bottom, middle, and upper), in alternative
implementations, the sections can extend across the height of the bag (i.e.,
left side,
middle, right side). In still further implementations the sections can
comprise a
combination of width-wise and length-wise extending sections. Alternatively,
the
sections are neither width-wise nor length-wise extending. For example, the
sections
can extend at an angle to the edges of the bag.
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[0081] The multi-layered bags 200, 300, 400 with non-continuous bonds
securing the inner layers or bags to the outer layers or bags shown in Figs. 3-
6 each
include a bond pattern 170 formed by TD ring rolling. One will appreciate that
the
present invention is not so limited. For example, non-continuous bonds between
the
inner layers and outer layers or bags can be formed using any of the processes
shown
and described in detail in previously incorporated by reference U.S. Patent
Application No. 13/273,384 filed October 14, 2011 and entitled NON-
CONTINUOUSLY LAMINATED MULTI-LAYERED BAGS. For example, Fig. 7
illustrates a multi-layered bag 500 with a shortened inner layer or bag
similar to the
multi-layered bag 300 of Fig. 5, albeit that the strainable network bonds 196
(i.e.,
bonds created by a SELFing process) arranged in diamond patterns non-
continuously
bond the bottom portion 192 of the inner layer or bag 150 to the outer layer
or bag
101.
[0082] One will appreciate in light of the disclosure herein that the
different
types of non-continuous bonds in the top and bottom portions or sections 182,
192 can
provide the different strength and aesthetic properties to the top and bottom
sections
182, 192. For example, the non-continuous bonds created by TD ring rolling can
provide the top section 182 with increased MD tear resistance, balanced MD and
TD
resistances, and/or increased the impact and/or puncture resistance.
Additionally, the
TD ring rolling of the top section 182 can result in reduced material
utilization. The
strainable network bonds 196 can provide the bottom section 192 with the
ability to
stretch around objects and prevent tears and rips. In other implementations,
the inner
and outer bags can be non-continuously laminated together through the use of
TD ring
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rolling, DD, ring rolling, SELFing, ultrasonic bonding, adhesive bonding, or
any
combination of such various bonding techniques.
[0083] In addition to non-continuous bonding, one or more layers of
the multi-
layered bags of one or more implementations can be incrementally stretched.
One
will appreciate that some types of non-continuous bonding described here can
incrementally stretch the layers as they are non-continuously bonded (i.e.,
ring rolling,
SELFing). One or more implementations of the present invention further include
incrementally stretching one or more layers independent of bonding. For
example,
Fig. 8 illustrates a multi-layered bag 600 with a shortened inner layer or bag
similar to
the multi-layered bag 100 of Figs. 1-2, albeit that the inner layer or bag 150
is
incrementally stretched. In particular, the inner layer or bag 150 includes a
strainable
network 198 formed by a SELFing process. As shown by Fig. 8, the strainable
network 198 is arranged in diamond patterns. The strainable network 198 can
provide
the inner layer or bag 150 with increased elasticity; thereby, allowing the
inner layer
or bag 150 to stretch to the size of the outer layer or bag 101 when strained.
[0084] Thus, one will appreciate in light of the disclosure herein
that a
manufacturer can tailor specific sections or zones of a multi-layered bag with
a
shortened inner layer or bag with desirable properties by MD, TD, DD ring
rolling,
SELF 'ing, or combinations thereof One will appreciate in light of the
disclosure
herein that one or more implementations can include bonded regions arranged in
other
patterns/shapes. Such additional patterns include, but are not limited to,
intermeshing
circles, squares, diamonds, hexagons, or other polygons and shapes.
Additionally,
one or more implementations can include bonded regions arranged in patterns
that are
combinations of the illustrated and described patterns/shapes.
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[0085] In another implementation, a pattern may be formed by
embossing, in
a process similar to ring rolling. Embossed patterns such as squares,
diamonds,
circles or other shapes may be embossed into a multi-layer bag. The embossed,
laminated film layers may be prepared by any suitable means by utilizing two
or more
layers of preformed web of film and passing them between embossing rollers.
The
method of embossing multiple layers of film can involve calendar embossing two
or
more separate, non-laminated layers with discrete "icons" to form bonded areas
or
icons, each icon having a bonded length and separated from adjacent icons by
an
equivalent un-bonded length. Such icons may be any desired design or shape,
such as
a heart, square, triangle, diamond, trapezoid, or circle.
[0086] As mentioned previously, numerous methods can be used to
provide
the desired degree of lamination in the bonded areas. Any of the described
ring
rolling techniques may be combined with other techniques in order to further
increase
the strength of the lamination bond while maintaining bond strength below the
strength of the weakest layer of the multi-layer film. For example, heat,
pressure,
ultrasonic bonding, corona treatment, or coating (e.g., printing) with
adhesives may be
employed. Treatment with a corona discharge can enhance any of the above
methods
by increasing the tackiness of the film surface so as to provide a stronger
lamination
bond, but which is still weaker than the tear resistance of the individual
layers.
[0087] Adjusting (e.g., increasing) the strength of the relatively
light
lamination bonding could be achieved by addition of a tackifier or adhesive to
one or
more of the skin plies of a multi-layer film, or by incorporating such a
component into
the material from which the film layer is formed. For example, the outer skin
sublayers of a given layer could contain from about 0 to about 50% of a
polyolefin
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plastomer tackifier such as a C4-C10 olefin to adjust bonding strength by
increasing
the tackiness of the surfaces of adjacent layers to be lightly laminated.
[0088] In one or more implementations, a component may be included to
decrease tackiness. For example, the outer skin sublayers could contain higher
levels
of slip or anti-block agents, such as oleamide (amide of oleic acid) or talc,
to decrease
tack. Similarly, these surfaces may include very low levels of or be
substantially void
of slip or anti-block agents to provide a relative increase in tackiness.
[0089] Implementations of the present invention can also include
methods of
forming multi-layered lightly-laminated film and bags including the same.
Figs. 9-12
and the accompanying description describe such methods. Of course, as a
preliminary
matter, one of ordinary skill in the art will recognize that the methods
explained in
detail herein can be modified. For example, various acts of the method
described can
be omitted or expanded, additional acts can be included, and the order of the
various
acts of the method described can be altered as desired.
[0090] To produce a bag having a ribbed pattern as described,
continuous
webs of thermoplastic material may be processed through a high-speed
manufacturing
environment such as that illustrated in Fig. 9. In the illustrated process
200,
production may begin by unwinding a first continuous web or film 101 of
thermoplastic sheet material from a roll 202 and advancing the web along a
machine
direction 206. The unwound web 101 may have a width 203 that may be
perpendicular to the machine direction 206, as measured between a first edge
203 and
an opposite second edge 203. The first thermoplastic film 101 may have an
initial
average thickness measured between a first surface 209 and a second surface
211. In
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other manufacturing environments, the film 101 may be provided in other forms
or
even extruded directly from a thermoplastic forming process.
[0091] The process 200 can also involve unwinding a second continuous
web
or film 150 of thermoplastic sheet material from a roll 204 and advancing the
web
along a machine direction 206. The second film 150 can comprise a
thermoplastic
material and/or a thickness that is similar or the same as the first film 101.
In
alternative one or more implementations, one or more of the thermoplastic
material
and/or thickness of the second film 150 can differ from that of the first film
101. As
shown in Fig. 9, the width 208 of the second film 150 can be less than the
width 203
of the first film 101. One will appreciate in light of the disclosure herein
that this can
provide a finished multi-layered bag with a shortened inner layer or bag as
shown and
described herein above.
[0092] To provide the first and second sidewalls of the finished bag,
the webs
101, 150 may be folded into a first half 222 and an opposing second half 224
about
the machine direction 206 (i.e., along the width of the films 101, 150) by a
folding
operation 220. When so folded, the first edge 210 may be moved adjacent to the
second edge 212 of the web. Accordingly, the width of the webs 101, 150
proceeding
in the machine direction 206 after the folding operation 220 may be a width
228 that
may be half the initial width 208. As may be appreciated, the portion mid-
width of
the unwound webs 101, 150 may become the outer edge of the folded web. In any
event, the hems may be formed along the adjacent first and second edges 210,
212
and the draw tape 232 may be inserted during a hem and draw tape operation
230.
[0093] To produce the finished bag, the processing equipment may
further
process the folded web. For example, to form the parallel side edges of the
finished
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bag, the web may proceed through a sealing operation 270 in which heat seals
272
may be formed between the outer edge 226 and the adjacent edges 210, 212. The
heat
seals may fuse together the adjacent halves 222, 224 of the folded web. The
heat
seals 272 may be spaced apart along the folded web and in conjunction with the
folded outer edge 226 may define individual bags. The heat seals may be made
with a
heating device, such as, a heated knife. A perforating operation 280 may
perforate
282 the heat seals 272 with a perforating device, such as, a perforating knife
so that
individual bags 290 may be separated from the web. In one or more
implementations,
the webs may be folded one or more times before the folded webs may be
directed
through the perforating operation. The webs 101, 150 embodying the finished
multi-
layered bags 284 may be wound into a roll 286 for packaging and distribution.
For
example, the roll 286 may be placed in a box or a bag for sale to a customer.
[0094] In one
or more implementations of the process which is illustrated in
Fig. 10, a cutting operation 288 may replace the perforating operation 280 in
Fig. 9.
Referring to Fig. 10, the web are directed through a cutting operation 288
which cuts
the webs at location 290 into individual bags 292 prior to winding onto a roll
294 for
packaging and distribution. For example, the roll 294 may be placed in a box
or bag
for sale to a customer. The bags may be interleaved prior to winding into the
roll 294.
In one or more implementations, the web may be folded one or more times before
the
folded web is cut into individual bags. In one or more implementations, the
bags 292
may be positioned in a box or bag, and not onto the roll 294. The bags may be
interleaved prior to positioning in the box or bag. These
manufacturing
implementations may be used with any of the manufacturing implementations
described herein, as appropriate.
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[0095] Fig. 11 illustrates another manufacturing process 200a for
producing a
multi-layered bag in accordance with one or more implementations of the
present
invention. The process 200a can be similar to process 200 of Fig. 11, except
that the
inner layer or film 150 can be non-continuously laminated to the outer layer
101. To
impart the ribbed pattern 170 (and optionally the bonds 174), the processing
equipment may include TD intermeshing rollers 242, 243 such as those described
herein above. Referring to Fig. 11, the folded webs 101, 150 may be advanced
along
the machine direction 206 between the TD intermeshing rollers 242, 243, which
may
be set into rotation in opposite rotational directions to impart the resulting
web pattern
150. To facilitate patterning of the webs 101, 150, the first roller 242 and
second
roller 243 may be forced or directed against each other by, for example,
hydraulic
actuators. The pressure at which the rollers are pressed together may be in a
first
range from 30 PSI (2.04 atm) to 100 PSI (6.8 atm), a second range from 60 PSI
(4.08
atm) to 90 PSI (6.12 atm), and a third range from 75 PSI (5.10 atm) to 85 PSI
(5.78
atm). In one or more implementations, the pressure may be about 80 PSI (5.44
atm).
[0096] In the illustrated implementation, the TD intermeshing rollers
242, 243
may be arranged so that they are co-extensive with or wider than the width 208
of the
folded webs 101, 150. In one or more implementations, the TD intermeshing
rollers
242, 243 may extend from proximate the outer edge 226 to the adjacent edges
210,
212. To avert imparting the ribbed pattern 170 onto the portion of the web
that
includes the draw tape 232, the corresponding ends 249 of the rollers 242, 243
may be
smooth and without the ridges and grooves. Thus, the adjacent edges 210, 212
and
the corresponding portion of the web proximate those edges that pass between
the
smooth ends 249 of the rollers 242, 243 may not be ribbed.
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[0097] In one or more implementations, the webs 101, 150 may be
stretched
to reduce their thickness as they passes between the rollers. Referring to
Fig. 11, the
webs 101, 150, when unwound from the rolls 202, 204, may have an average
thickness 260, measured between the first surface 216 and a second surface
218.
After passing between the TD intermeshing rollers 242, 243, the web may have
an
average thickness that is reduced.
[0098] One result of reducing the thickness of the web material is
that the
ribbed pattern 170 may be imparted into the web(s) 101, 150. The thermoplastic
material of the web may be stretched or worked during reduction such that the
initially planar web takes the new ribbed shape. In some implementations, the
molecular structure of the thermoplastic material may be rearranged to provide
this
shape memory. Furthermore, upon stretching, individual initially separate
layers of
the thermoplastic material of the web become non-continuously laminated
together at,
or proximate, the location of the ribs 172. In other words, at or adjacent the
ribs 172,
the adjacent layers 101, 150 are lightly bonded to one another, while adjacent
portions
are not bonded to one another.
[099] Referring to Fig. 11, another result of reducing the web
thickness is
that some of the web material may be stretched longitudinally along the TD
intermeshing rollers 242, 243 and perpendicular to the machine direction 206.
Also,
some of the web material may be compressed longitudinally along the TD
intermeshing rollers 242, 243. This action may widen the folded web from its
initial
width 228 to a larger width 258. To facilitate the widening of the web, the
adjacent
edges 210, 212 of the web may be located between the smooth ends 249 of the TD
intermeshing rollers 242, 243. The smooth ends 249 of the TD intermeshing
rollers
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242, 243 can maintain alignment of the web along the machine direction. The
processing equipment may include pinch rollers 262, 264 to accommodate the
growing width of the widening web.
[0100] The processed web may have varying thickness as measured along
its
width perpendicular of the machine direction. Because the ridges 246, 245 and
the
grooves 250, 251 on the TD intermeshing rollers 242, 243 may not be co-
extensive
with the width 228 of the folded webs 101, 150 only the thickness of that
portion of
the web which is directed between the ridges and the grooves may be reduced.
The
remaining portion of the web, such as, toward the adjacent edge 210, 212, may
retain
the web's original thickness. The smooth ends 249 of the TD intermeshing
rollers
242, 243 may have diameters dimensioned to accommodate the thickness of that
portion of the web which passes there between.
[0101] In alternative implementations, the film layers 101, 150 may
pass
through the TD intermeshing rollers 242, 243 prior to the folding process 220.
Furthermore, the TD intermeshing rollers 242, 243 can include smooth portions
249
on each end. In alternative implementations, the TD intermeshing rollers 242,
243
can include smooth portions 249 in the middle of the rollers or intermittent
smooth
portions.
[0102] In still further implementations, the TD intermeshing rollers
242, 243
can be replaced with other intermeshing rollers, such as MD or DD intermeshing
rollers, embossing rollers, SELFing rollers, or hybrid rollers combining one
of the
aforementioned types of rollers. Additionally, or alternatively, the process
can
include an ultrasonic horn or adhesive applicator that can bond the film
layers 101,
150 together. In still further implementations, one or more of the film layers
101, 150
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may pass through the intermeshing rollers or be otherwise stretched just after
being
unwound.
[0103] Fig.
12 illustrates another manufacturing process 200b for producing a
multi-layered bag with a shortened inner layer or bag. The process 200b can be
similar to process 200 of Fig. 11, except that the film layers 101, 150 are
folded in
half to form c-, u-, or j-folded films prior to winding on the rolls 202, 204.
Thus, in
such implementations, the films 101, 150 unwound from the rolls 202, 204 are
already
folded.
[0104]
Additionally, the manufacturing process 200b illustrates that each film
101, 150 can pass through a set of TD intermeshing rollers 242a, 243a, 242b,
243b to
incrementally stretch the films (and impart a ribbed pattern thereto) prior to
bonding,
or to impart one or more desired characteristics (such as elasticity). The
manufacturing process 200b can then include an insertion operation 296 for
inserting
the folded film 101 into the folded film 150. Insertion operation 296 can
combine the
folded films 101, 150 using any of the apparatus and methods described in U.S.
Patent
Application Nos. 13/225,757 filed September 6, 2011 and entitled METHID FOR
INSERTING A FIRST FOLDED FILM WITHIN A SECOND FOLDED FILM and
13/225,930 filed September 6, 2011 and entitled APPARATUS FOR INSERTING A
FIRST FOLDED FILM WITHIN A SECOND C-FOLDED FILM, each of which are
incorporated herein by reference in their entirety.
[0105]
Additionally, Fig. 12 illustrates that the film layers 101, 150 can then
pass through a lamination operation 298 to lightly bond or laminate the films
101, 150
together. Lamination operation 298 can lightly laminate the folded films 101,
150
together via adhesive bonding, pressure bonding, ultrasonic bonding, corona
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lamination, and the like. Alternatively, lamination operation 298 can lightly
laminate
the folded films 101, 150 together by passing them through machine-direction
ring
rolls, transverse-direction ring rolls, diagonal-direction ring rolls, SELF
'ing rollers,
embossing rollers, or other intermeshing rollers.
[0106] The present invention may be embodied in other specific forms
without departing from its spirit or essential characteristics. Thus, the
described
embodiments are to be considered in all respects only as illustrative and not
restrictive. The scope of the invention is, therefore, indicated by the
appended claims
rather than by the foregoing description. All changes that come within the
meaning
and range of equivalency of the claims are to be embraced within their scope.
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