U.S. patent application number 15/268914 was filed with the patent office on 2017-01-05 for enhanced flexible material and articles formed therefrom.
The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Shaun Thomas Broering, Karen Denise MCaffry.
Application Number | 20170001780 15/268914 |
Document ID | / |
Family ID | 47438705 |
Filed Date | 2017-01-05 |
United States Patent
Application |
20170001780 |
Kind Code |
A1 |
Broering; Shaun Thomas ; et
al. |
January 5, 2017 |
Enhanced Flexible Material And Articles Formed Therefrom
Abstract
A flexible film, and articles comprising the film, comprises
interleaved pluralities of each of first bands and second bands
disposed adjacent to the first bands. Both the first and second
bands have a length and a width; the first bands comprise a first
film basis weight and first and second regions. The first regions
and second regions being comprised of the same material
composition. The first regions undergo a substantially
molecular-level deformation and the second regions initially
undergo a substantially geometric deformation when the sheet
material is subjected to an applied elongation along at least one
axis. The second bands comprise a second film basis weight and a
plurality of corrugations disposed along the length of the band. In
this aspect the material may be described as having alternating
bands of structural-elastic-like film and ring-rolled film.
Inventors: |
Broering; Shaun Thomas; (Ft.
Thomas, KY) ; MCaffry; Karen Denise; (Cincinnati,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Family ID: |
47438705 |
Appl. No.: |
15/268914 |
Filed: |
September 19, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13179201 |
Jul 8, 2011 |
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15268914 |
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61363336 |
Jul 12, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B31B 70/00 20170801;
Y10T 428/24479 20150115; B32B 3/28 20130101; B31B 2160/10 20170801;
B32B 27/32 20130101; B65D 75/006 20130101; B31B 70/88 20170801;
B31B 2150/00 20170801; Y10T 428/24694 20150115; B65F 1/0006
20130101; B65D 33/00 20130101; Y10T 428/13 20150115 |
International
Class: |
B65D 75/00 20060101
B65D075/00 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. The method of claim 17 where the width of the second region is
less than 0.75 inches.
7. (canceled)
8. (canceled)
9. (canceled)
10. The method of claim 17 wherein the first regions of the first
bands are arrayed asymmetrically about the second bands.
11. The method of claim 17 wherein the first regions of the first
bands are arrayed symmetrically about the second bands.
12. The method of claim 17 wherein the basis weight of the first
bands is about 23 gsm and the basis weight of the second bands is
about 16 gsm.
13. The method of claim 17 further comprising third bands having
substantially the same basis weight as the first bands, the third
bands being substantially planar.
14. (canceled)
15. (canceled)
16. A method for forming a flexible film comprising a plurality of
first bands and a plurality of second bands, the plurality of first
bands interleaved with the plurality of second bands, wherein the
mechanical properties of the first band are essentially equal to
the mechanical properties of the second band; the method comprising
formation of each band to different degree of stretch as suitable
to obtain equal mechanical properties at lower basis weight than a
film made solely of the first band.
17. A method for forming a flexible film comprising a plurality of
first and second bands, wherein the first band comprises a first
film basis weight and first and second regions, the first regions
undergo a substantially molecular-level deformation and the second
regions initially undergo a substantially geometric deformation
when the sheet material is subjected to an applied elongation
across the width of the band, the second band comprises a second
film basis weight and a plurality of substantially continuous
corrugations disposed along the length of the band; the method
comprising forming said first and second bands simultaneously.
Description
FIELD OF THE INVENTION
[0001] The invention relates to physically enhanced flexible
polymeric films and articles comprised of such films. The invention
relates particularly to flexible polymeric films having enhanced
physical structures and properties, and articles made
therefrom.
BACKGROUND OF THE INVENTION
[0002] Polymeric films are well known in the art, as are articles
such as bags for storage and disposal made from such films.
Altering the geometry of a flat film while maintaining the basis
weight of the film is known to have the potential of imparting
elastic-like properties to the film and to articles made from the
altered film. The costs associated with such films and articles are
often directly related to the quantity of material present in the
final article and/or the basis weight of the films used. Films may
be drawn to reduce the film gauge and therefore the amount of
material used for a given unit area. Such drawing or gauge
reduction techniques may favorably impact the cost associated with
a finished article but often do so at a reduction in the
performance of the film and article due to the reduction in film
gauge and associated basis weight.
[0003] What is desired is a way of reducing the material
requirements for films and corresponding articles without
equivalent reductions in film and article performance.
SUMMARY OF THE INVENTION
[0004] In one aspect, a flexible film comprises interleaved
pluralities of each of first bands and second bands disposed
adjacent to the first bands. Both the first and second bands have a
length and a width, the first bands comprise a first film basis
weight and first and second regions. The first regions and a second
regions being comprised of the same material composition. The first
regions undergo a substantially molecular-level deformation and the
second regions initially undergo a substantially geometric
deformation when the sheet material is subjected to an applied
elongation along at least one axis. The first regions and the
second regions are visually distinct from one another. The second
regions include a plurality of raised rib-like elements and the
first regions are substantially free of rib-like elements. The
second bands comprise a second film basis weight and a plurality of
corrugations disposed along the length of the band. In this aspect
the material may be described as having alternating bands of
structural-elastic-like film and ring-rolled film.
[0005] In one aspect, a flexible bag comprises at least one sheet
of flexible sheet material assembled to form a semi-enclosed
container having an opening defined by a periphery. The sheet of
flexible material comprises interleaved pluralities of each of
first bands and second bands disposed adjacent to the first bands.
Both the first and second bands have a length and a width, the
first bands comprise a first film basis weight and first and second
regions. The first regions and a second regions being comprised of
the same material composition. The first regions undergo a
substantially molecular-level deformation and the second regions
initially undergo a substantially geometric deformation when the
sheet material is subjected to an applied elongation along at least
one axis. The first regions and the second regions are visually
distinct from one another. The second regions include a plurality
of raised rib-like elements and the first regions are substantially
free of rib-like elements. The second bands comprise a second film
basis weight and a plurality of corrugations disposed along the
length of the band. In this aspect the material and bag may be
described as having alternating bands of structural-elastic-like
film and ring-rolled film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic plan view of a portion of the material
of the bags of the present invention illustrating a symmetrical
pattern;
[0007] FIG. 2 is a schematic plan view of a portion of the material
of the bags of the present invention illustrating an asymmetrical
pattern;
[0008] FIG. 3A is a segmented, perspective illustration of the
polymeric film material of flexible bags of the present invention
in a substantially untensioned condition;
[0009] FIG. 3B is a segmented, perspective illustration of the
polymeric film material of flexible bags according to the present
invention in a partially-tensioned condition;
[0010] FIG. 3C is a segmented, perspective illustration of the
polymeric film material of flexible bags according to the present
invention in a greater-tensioned condition;
[0011] FIG. 4 is a schematic plan view of a portion of the material
of the bags of the present invention illustrating a symmetrical
pattern;
[0012] FIG. 5 is a schematic plan view of a portion of the material
of the bags of the present invention illustrating an asymmetrical
pattern;
[0013] FIG. 6 is a schematic plan view of a portion of the material
of the bags of the present invention illustrating a symmetrical
pattern;
[0014] FIG. 7 is a schematic perspective view of a bag according to
one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] As used herein, basis weight, refers to the weight per unit
are. Basis weight may be expressed in units of lbs/ft.sup.2, or
g/m.sup.2.
[0016] As utilized herein, the term "flexible" is utilized to refer
to materials which 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 which 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. Flexible bags of the type commonly
available are typically formed from materials having consistent
physical properties throughout the bag structure, such as stretch,
tensile, and/or elongation properties as well as material basis
weight.
[0017] Referring now to FIG. 3A, first bands 52 include a
"strainable network" of distinct regions. As used herein, the term
"strainable network" refers to an interconnected and interrelated
group of regions which are able to be extended to some useful
degree in a predetermined direction providing the first bands with
an elastic-like behavior in response to an applied and subsequently
released elongation. The strainable network includes at least a
first region 64 and a second region 66. First bands 52 include a
transitional region 65 which is at the interface between the first
region 64 and the second region 66. The transitional region 65 will
exhibit complex combinations of the behavior of both the first
region and the second region. It is recognized that every
embodiment of such first bands suitable for use in accordance with
the present invention will have a transitional region; however,
such bands are defined by the behavior of the first region 64 and
the second region 66. Therefore, the ensuing description will be
concerned with the behavior of the first bands in the first regions
and the second regions only since it is not dependent upon the
complex behavior of the first bands in the transitional regions
65.
[0018] First bands 52 have a first surface 52a and an opposing
second surface 52b. In the embodiment shown in FIG. 3A, the
strainable network includes a plurality of first regions 64 and a
plurality of second regions 66. In one embodiment, the first
regions 64 have a first axis 68 and a second axis 69, wherein the
first axis 68 is longer than the second axis 69. The first axis 68
of the first region 64 is substantially parallel to the
longitudinal axis "L" of the first bands 52 while the second axis
69 is substantially parallel to the transverse axis "T" of the
first bands 52. In one embodiment, the second axis of the first
region, the width of the first region, is from about 0.01 inches to
about 0.5 inches. In one embodiment from about 0.03 inches to about
0.25 inches. The second regions 66 have a first axis 70 and a
second axis 71. The first axis 70 is substantially parallel to the
longitudinal axis of the first bands 52, while the second axis 71
is substantially parallel to the transverse axis of the first bands
52. In one embodiment, the second axis of the second region, the
width of the second region, is from about 0.01 inches to about 2.0
inches. In one embodiment from about 0.125 inches to about 1.0
inches. In the embodiment of FIG. 3A, the first regions 64 and the
second regions 66 are substantially linear, extending continuously
in a direction substantially parallel to the longitudinal axis of
the first bands 52.
[0019] The first region 64 has an elastic modulus E1 and a
cross-sectional area A1. The second region 66 has a modulus E2 and
a cross-sectional area A2.
[0020] In the illustrated embodiment, the first bands 52 have been
"formed" such that the first bands 52 exhibits a resistive force
along an axis, which in the case of the illustrated embodiment is
substantially parallel to the longitudinal axis of the web, when
subjected to an applied axial elongation in a direction
substantially parallel to the longitudinal axis. As used herein,
the term "formed" refers to the creation of a desired structure or
geometry upon a first band that will substantially retain the
desired structure or geometry when it is not subjected to any
externally applied elongations or forces. A first band of the
present invention is comprised of at least a first region and a
second region, wherein the first region is visually distinct from
the second region. As used herein, the term "visually distinct"
refers to features of the first bands which are readily discernible
to the normal naked eye when the first bands or objects embodying
the first bands are subjected to normal use. As used herein the
term "surface-pathlength" refers to a measurement along the
topographic surface of the region in question in a direction
substantially parallel to an axis. The method for determining the
surface-pathlength of the respective regions can be found in the
Test Methods section of U.S. Pat. No. 5,518,801 issues to Chappell
et al. on Feb. 28, 1994. Methods for forming such first bands
useful in the present invention include, but are not limited to,
embossing by mating plates or rolls, thermoforming, high pressure
hydraulic forming, or casting. While the entire portion of the web
52 has been subjected to a forming operation, the present invention
may also be practiced by subjecting to formation only a portion
thereof, e.g., a portion of the material comprising the bag body
20, as will be described in detail below.
[0021] In the embodiment shown in FIG. 3A, the first regions 64 are
substantially planar. That is, the material within the first region
64 is in substantially the same condition before and after the
formation step undergone by web 52. The second regions 66 include a
plurality of raised rib-like elements 74. The rib-like elements may
be embossed, debossed or a combination thereof. The rib-like
elements 74 have a first or major axis 76 which is substantially
parallel to the transverse axis of the web 52 and a second or minor
axis 77 which is substantially parallel to the longitudinal axis of
the web 52. The length parallel to the first axis 76 of the
rib-like elements 74 is at least equal to, and in one embodiment
longer than the length parallel to the second axis 77.
[0022] In one embodiment, the ratio of the first axis 76 to the
second axis 77 is at least about 1:1 or greater, and in another
embodiment at least about 2:1 or greater.
[0023] The rib-like elements 74 in the second region 66 may be
separated from one another by unformed areas. In one embodiment,
the rib-like elements 74 are adjacent one another and are separated
by an unformed area of less than 0.10 inches as measured
perpendicular to the major axis 76 of the rib-like elements 74. In
one embodiment, the rib-like elements 74 are contiguous having
essentially no unformed areas between them.
[0024] The first region 64 and the second region 66 each have a
"projected pathlength". As used herein the term "projected
pathlength" refers to the length of a shadow of a region that would
be thrown by parallel light. The projected pathlength of the first
region 64 and the projected pathlength of the second region 66 are
equal to one another.
[0025] The first region 64 has a surface-pathlength, L1, less than
the surface-pathlength, L2, of the second region 66 as measured
topographically in a direction parallel to the longitudinal axis of
the web 52 while the web is in an untensioned condition. In one
embodiment, the surface-pathlength of the second region 66 is at
least about 15% greater than that of the first region 64. In one
embodiment at least about 30% greater than that of the first
region. In one embodiment at least about 70% greater than that of
the first region. In general, the greater the surface-pathlength of
the second region, the greater will be the elongation of the web
before encountering the force wall. Suitable techniques for
measuring the surface-pathlength of such materials are described in
the above-referenced and above-incorporated Chappell et al.
patent.
[0026] First bands 52 exhibit a modified "Poisson lateral
contraction effect" substantially less than that of an otherwise
identical base web of similar material composition. The method for
determining the Poisson lateral contraction effect of a material
can be found in the Test Methods section of the above-referenced
and above-incorporated Chappell et al. patent. In one embodiment,
the Poisson lateral contraction effect of webs suitable for use in
the present invention is less than about 0.4 when the web is
subjected to about 20% elongation. In one embodiment, the webs
exhibit a Poisson lateral contraction effect less than about 0.4
when the web is subjected to about 40, 50 or even 60% elongation.
In one embodiment, the Poisson lateral contraction effect is less
than about 0.3 when the web is subjected to 20, 40, 50 or 60%
elongation. The Poisson lateral contraction effect of such webs is
determined by the amount of the web material which is occupied by
the first and second regions, respectively. As the area of the
first bands occupied by the first region increases the Poisson
lateral contraction effect also increases. Conversely, as the area
of the first bands occupied by the second region increases the
Poisson lateral contraction effect decreases. In one embodiment,
the percent area of the first bands occupied by the first area is
from about 2% to about 90%. In one embodiment from about 5% to
about 50%.
[0027] For first bands 52, the direction of applied axial
elongation, D, indicated by arrows 80 in FIG. 3A, is substantially
perpendicular to the first axis 76 of the rib-like elements 74. The
rib-like elements 74 are able to unbend or geometrically deform in
a direction substantially perpendicular to their first axis 76 to
allow extension in web 52.
[0028] Referring now to FIG. 3B, as web of first bands 52 is
subjected to an applied axial elongation, D, indicated by arrows 80
in FIG. 3B, the first region 64 having the shorter
surface-pathlength, L1, provides most of the initial resistive
force, P1, as a result of molecular-level deformation, to the
applied elongation. In this stage, the rib-like elements 74 in the
second region 66 are experiencing geometric deformation, or
unbending and offer minimal resistance to the applied elongation.
In transition to the next stage, the rib-like elements 74 are
becoming aligned with (i.e., coplanar with) the applied elongation.
That is, the second region is exhibiting a change from geometric
deformation to molecular-level deformation. This is the onset of
the force wall. In the stage seen in FIG. 3C, the rib-like elements
74 in the second region 66 have become substantially aligned with
(i.e., coplanar with) the plane of applied elongation (i.e. the
second region has reached its limit of geometric deformation) and
begin to resist further elongation via molecular-level deformation.
The second region 66 now contributes, as a result of
molecular-level deformation, a second resistive force, P2, to
further applied elongation. The resistive forces to elongation
provided by both the molecular-level deformation of the first
region 64 and the molecular-level deformation of the second region
66 provide a total resistive force, PT, which is greater than the
resistive force which is provided by the molecular-level
deformation of the first region 64 and the geometric deformation of
the second region 66.
[0029] The resistive force P1 is substantially greater than the
resistive force P2 when (L1+D) is less than L2. When (L1+D) is less
than L2 the first region provides the initial resistive force P1,
generally satisfying the equation: P1=(A1.times.E1.times.D)/L1 When
(L1+D) is greater than L2 the first and second regions provide a
combined total resistive force PT to the applied elongation, D,
generally satisfying the equation:
PT=((A1.times.E1.times.D)/L1)+((A2.times.E2.times.|L1+D-L2|)/L2- ).
The maximum elongation occurring while in the stage corresponding
to FIGS. 3A and 3B, before reaching the stage depicted in FIG. 3C,
is the "available stretch" of the formed web material. The
available stretch corresponds to the distance over which the second
region experiences geometric deformation. The range of available
stretch can be varied from about 10% to 100% or more, and can be
largely controlled by the extent to which the surface-pathlength L2
in the second region exceeds the surface-pathlength L1 in the first
region and the composition of the base film. The term available
stretch is not intended to imply a limit to the elongation which
the web of the present invention may be subjected to as there are
applications where elongation beyond the available stretch is
desirable.
[0030] When the first bands are subjected to an applied elongation,
the first bands exhibit an elastic-like behavior as it extends in
the direction of applied elongation and returns to its
substantially untensioned condition once the applied elongation is
removed, unless the first bands are extended beyond the point of
yielding. The first bands are able to undergo multiple cycles of
applied elongation without losing their ability to substantially
recover. Accordingly, the web is able to return to its
substantially untensioned condition once the applied elongation is
removed. While the first bands may be easily and reversibly
extended in the direction of applied axial elongation, in a
direction substantially perpendicular to the first axis of the
rib-like elements, the web material is not as easily extended in a
direction substantially parallel to the first axis of the rib-like
elements. The formation of the rib-like elements allows the
rib-like elements to geometrically deform in a direction
substantially perpendicular to the first or major axis of the
rib-like elements, while requiring substantially molecular-level
deformation to extend in a direction substantially parallel to the
first axis of the rib-like elements.
[0031] The amount of applied force required to extend the web is
dependent upon the composition and cross-sectional area of the
first bands and the width and spacing of the first regions, with
narrower and more widely spaced first regions requiring lower
applied extensional forces to achieve the desired elongation for a
given composition and cross-sectional area. The first axis, (i.e.,
the length) of the first regions is in one embodiment greater than
the second axis, (i.e., the width) of the first regions in one
embodiment with a length to width ratio of from about 5:1 or
greater.
[0032] The depth and frequency of rib-like elements can also be
varied to control the available stretch of a web of first bands
suitable for use in accordance with the present invention. The
available stretch is increased if for a given frequency of rib-like
elements, the height or degree of formation imparted on the
rib-like elements is increased. Similarly, the available stretch is
increased if for a given height or degree of formation, the
frequency of the rib-like elements is increased. The selection of
rib-like element depth or frequency versus band 2 stretch (or basis
weight reduction) is chosen to balance overall film and article
mechanical properties. A method to closely approximate the required
formation required in band 1 versus band 2 is obtained by
mechanical property of each of the band in sufficient size for
testing. For formation using solid state formation method, this can
be obtained by changing the DOE for each band and relating this DOE
to overall film properties. A quasi-matched set of properties is
preferred. The resulting tooling can be designed using different
patterns and tooling heights in band 1 versus band 2. While not to
be limited, it is believed that the properties will matched best
and the most aesthetic design if the width of the second band is
limited to less than 0.75 inch and preferably less than 0.5 inch
width. Without being limited, it is believed that the best
properties will result in designs where the width of the second
band is less than 0.75 inches and preferably less than 0.5 inches
and the width of the second band does not exceed 60% of the width
the sum for the first band and the second band. If more than two
bands are included in the design, it is believed that the second
band should not exceed 60 of the width of the sum of all band
regions.
[0033] There are several functional properties that can be
controlled through the application of such materials to flexible
bags of the present invention. The functional properties are the
resistive force exerted by the first bands against an applied
elongation and the available stretch of the first bands before the
force wall is encountered. The resistive force that is exerted by
the first bands against an applied elongation is a function of the
material (e.g., composition, molecular structure and orientation,
etc.) and cross-sectional area and the percent of the projected
surface area of the first bands that is occupied by the first
region. The higher the percent area coverage of the first bands by
the first region, the higher the resistive force that the web will
exert against an applied elongation for a given material
composition and cross-sectional area. The percent coverage of the
first bands by the first region is determined in part, if not
wholly, by the widths of the first regions and the spacing between
adjacent first regions.
[0034] The available stretch of the web material is determined by
the surface-pathlength of the second region. The surface-pathlength
of the second region is determined at least in part by the rib-like
element spacing, rib-like element frequency and depth of formation
of the rib-like elements as measured perpendicular to the plane of
the web material. In general, the greater the surface-pathlength of
the second region the greater the available stretch of the web
material. As discussed above with regard to FIGS. 3A-3C, the first
bands 52 initially exhibit a certain resistance to elongation
provided by the first region 64 while the rib-like elements 74 of
the second region 66 undergo geometric motion. As the rib-like
elements transition into the plane of the first regions of the
material, an increased resistance to elongation is exhibited as the
entire first band then undergoes molecular-level deformation.
Accordingly, first bands of the type depicted in FIGS. 3A-3C and
described in the above-referenced and above-incorporated Chappell
et al. patent provide the performance advantages of the present
invention when formed into closed containers such as the flexible
bags of the present invention.
[0035] An additional benefit realized by the utilization of the
aforementioned first bands in constructing flexible bags according
to the present invention is the increase in visual and tactile
appeal of such materials. Polymeric films commonly utilized to form
such flexible polymeric bags are typically comparatively thin in
nature and frequently have a smooth, shiny surface finish. While
some manufacturers utilize a small degree of embossing or other
texturing of the film surface, at least on the side facing
outwardly of the finished bag, bags made of such materials still
tend to exhibit a slippery and flimsy tactile impression. Thin
materials coupled with substantially two-dimensional surface
geometry also tend to leave the consumer with an exaggerated
impression of the thinness, and perceived lack of durability, of
such flexible polymeric bags.
[0036] In contrast, first bands useful in accordance with the
present invention such as those depicted in FIGS. 3A-3C exhibit a
three-dimensional cross-sectional profile wherein the first bands
are (in an un-tensioned condition) deformed out of the predominant
plane of the first bands. This provides additional surface area for
gripping and dissipates the glare normally associated with
substantially planar, smooth surfaces. The three-dimensional
rib-like elements also provide a "cushiony" tactile impression when
the bag is gripped in one's hand, also contributing to a desirable
tactile impression versus conventional bag materials and providing
an enhanced perception of thickness and durability. The additional
texture also reduces noise associated with certain types of film
materials, leading to an enhanced aural impression.
[0037] The second bands are formed into a pattern of substantially
continuous corrugations along the length of the bands, that is,
substantially parallel to the major direction of the bands. The
corrugations are formed concurrently with the ribs of the first
bands. The corrugations are formed by ring-rolling the relevant
portion of the film. Ring-rolling the portion of the film
segmentally stretches and yields the film into a corrugated
structure while simultaneously reducing the basis weight of the
ring-rolled portion of the film and stretching or extending the
width of that portion. The stretch of the second band generally
results in plastic set of the film by 20 to 60%. This stretch
lowers the basis weight of the film in the second band by 62 to 83%
of the starting material.
[0038] The combination of interleaved first and second bands of
formed film provides the majority of the physical performance of an
identical base film which has been formed only with the structures
of the first bands. As the ring-rolled second bands are stretched
or expanded, the interleaved pattern yields the additional benefit
of providing a final film having substantially the same performance
while utilizing significantly less material.
[0039] The forming of the first and second bands are preferentially
performed simultaneously. If the forming depth for the first band
and the stretching length for the second band differ then tooling
must be designed to achieve the results simultaneously. Not to be
limited to the following examples, one option to achieve
simultaneous but differential forming strains is to use different
forming tooth heights for each of the bands. Other options such as
using different tooth pitch in the first band versus the second
band can also be practiced. It is also possible to perform
formation of the first band either first or second and the second
band either second or first in sequence.
[0040] In forming the materials of the invention, a sheet of film
may be processed between patterned plates, or a continuous web of
film may be processed between patterned rollers. In one embodiment,
the depth of engagement of the patterned features forming the first
bands differs from the depth of engagement of the patterned
features forming the second bands. In this embodiment, the depth of
engagement for the second bands is less than the depth of
engagement for the first bands. In one embodiment, the first bands
are formed with a depth of engagement of about 0.038'' (0.965 mm)
and the second bands are concurrently formed with a depth of
engagement of about 0.024'' (0.610 mm) or with a DOE difference of
about 0.014'' (0.356 mm). This variation in the depth of engagement
between the two bands is achieved by using a forming element having
individual forming features with different heights interacting with
a mating element having features of a uniform height. As an
example, the features associated with the first bands may have a
height of about 0.080'' (2.03 mm) while the features associated
with the second bands have a height of about 0.066'' (1.68 mm).
EXAMPLES
Example #1
[0041] A LLDPE film made from 89% Tuflin XHS 7091, 8% Fleximer ETSE
9068 and 3% white pigment masterbatch. The Tuflin and Fleximer are
from Dow Chemical, Midland, Mich. and the white pigment masterbatch
is from Ampecet, Tarrytown, N.Y. The film was blown into a 0.0009
inch thick film of 30 inch width. The film was slit to a 10 inch
width prior to solid state formation. The film was processed using
either a 0.040 inch pitch ring roll or a 0.040 inch pitch seven
tooth diamond SELF pattern as shown in USD518648S1. The mechanical
properties of the film were measured for tensile properties per
ASTM D882, tear properties per ASTM D1922, and dart drop per ASTM
D1709 (D4272,?). The mechanical properties from SELF and ring roll
films are exhibited in Table SRR. The properties of a film formed
via SELF pattern at a depth of 0.038 inch can be matched with ring
roll film with the exception of dart drop. The best property match
excluding dart drop is a ring roll film deformed to a depth of
0.024 inches.
TABLE-US-00001 TABLE SRR Ply Ply MD Tensile TD Direct Direct Strn
Energy Tensile Energy MD CD Pattern Peak At To Peak Strn At To Tear
Tear SELF/ DOE Load Break Break Load Break Break Index Index Dart
RR (in) (lbf) (%) (in * lbf) (lbf) (%) (in * lbf) (gf) (gf) g/mil
SELF 0.038 3.61 434 15.57 2.73 503.49 15.35 288 315 332 RR 0.020
4.99 498 21.03 4.99 596.03 25.92 385 259 169 RR 0.024 4.41 472
17.97 4.17 446.87 18.05 281 239 180 RR 0.028 3.57 413 13.76 4.15
456.15 17.60 278 173 158
Example #2
[0042] The same film as described in Example #1 was formed into the
hybrid SELF/RR design exhibited in FIGS. 6/7 and Figure MOD 5
Diamond. The tooling was fabricated with a difference in tool
height of 0.014 inches with the SELF band being deformed to the
greater degree. The results are in Table HYBRID.
Example #3
[0043] The same film as described in Example #1 was formed into the
hybrid SELF/RR design exhibited in Figure MOD 5 Diamond. The
tooling was fabricated with a difference in tool height of 0.011
inches with the SELF band being deformed to the greater degree. The
results are in Table HYBR.
TABLE-US-00002 TABLE HYBR MD TENSILE TD TENSILE MD TD Load Strain
Load Strain TEAR TEAR SELF RR at Peak at at Peak at Tear Tear DOE
DOE Growth yeild Load Break yeild Load Break Index Index Pattern
(inch) (inch) (%) Dart (lbf) (lbf) (%) (lbf) (lbf) (%) (gf) (gf)
Force 0.038 na NA 311 1.22 3.69 358.2 1.21 2.59 542.70 367.12
277.92 Flex 0.038'' MOD 4 0.038 0.024 12% 232 1.16 4.99 358.6 1.26
3.01 510.20 280.56 343.84 Diamond MOD 5 0.042 0.031 17% 351 1.15
3.94 406.5 1.32 2.95 489.29 269.8 257.3 Diamond 0.042''
[0044] As an example, a linear-low-density-polyethylene (LLDPE)
film having a base or nominal thickness of 0.0009 inches (0.0223
mm) and a nominal density of 0.918 g/cm.sup.2 may be formed with an
interleaved pattern of the disclosed bands. The bands are comprised
of formed second regions and corrugations as described above. The
pitch or spacing of the features across the width of the film is
about 0.040 inches (1 mm). The pattern comprises first bands of
four adjacent features of discontinuous features adjacent to second
bands of three adjacent substantially continuous features. At a
depth of engagement (DOE) of about 0.042 inches (1.07 mm), the film
exhibits about a 17% growth in area due to the formation process.
That is, a square meter of film subjected to the formation process
becomes about 1.17 square meters of film. As used herein, "depth of
engagement" refers to the extent which the forming elements overlap
during the formation of the films disclosed. A 0.042 inch depth of
engagement corresponds to an overlap between the two forming
elements of 0.042 inches.
[0045] The respective patterns of the first bands and second bands
may comprise a variety of patterns. Generally, the pattern of the
first bands comprises a set of substantially parallel features
along the length of the band. Each feature comprises a series of
ribs as described above. The position of the ribs in adjacent
features together with the unformed portions in the bands
determines the overall pattern of the bands.
[0046] In one embodiment, the ribs are disposed in a symmetric
pattern. In this embodiment, ribs are disposed symmetrically with
respect to the bands of continuous features. In symmetric patterns,
the actual pattern of ribs in any particular ribbed band may take
any form, the pattern in each other ribbed band is arrayed
symmetrically with respect to the corrugations of the ring-rolled
bands. FIGS. 1, 4, and 6 illustrate symmetric patterns.
[0047] In one embodiment the ribs are disposed in an asymmetric
pattern with respect to the ring rolled bands. In this embodiment
the patter of ribs in each ribbed band is not arrayed symmetrically
with respect to the ring rolled bands. The degree of asymmetry may
range from a simple shift of the pattern of ribs such that the
overall pattern of ribs in each ribbed band is similar or
substantially identical but the disposition of ribs is shifted
along the length of the band such that the pattern is not
symmetrical with regard to the ring rolled band. In another
embodiment, the pattern in each ribbed band may be identical with
regard to the ring rolled bands but not symmetrical. FIGS. 2, and 5
illustrate asymmetric patterns.
[0048] In one embodiment symmetric and asymmetric patterns may be
used in a single article. As asymmetric patterns reduce the force
necessary to extend the film, asymmetric patterns may be used in a
portion of the bag where easier extension is desired while
symmetric patterns may be used where extension but at a higher
level of force is desired.
[0049] Substantially identical base films formed with patterns
differing as to level of symmetry may have different physical
properties. As an example, otherwise identical films, one formed
with a symmetric pattern and the other formed with an asymmetric
pattern require different level of elongation force to extend each
of the films across the width of the formed bands as illustrated in
Table 1. The diamond pattern illustrated in FIG. 1 is considered to
be symmetric. The zig-zag pattern illustrated in FIG. 2 is
considered to be asymmetric.
TABLE-US-00003 Band Band One Two Low DOE DOE Force Sample Pattern
(inches) (inches) Growth Extension 1 5 bar diamond 0.042 0,031 17%
12.9% 2 5 bar zig-zag 0.042 0.031 17% 16.7% 3 5 bar diamond 0.046
0.033 19% 13.8% 4 5 bar zig-zag 0.046 0.035 22% 15.6% 5 5 bar
diamond 0.050 0.039 23% 13.1% 6 5 bar zig-zag 0.050 0.039 25%
16.8%
Table 2 provides comparative physical property data of otherwise
identical films formed with a uniform SELF patterns and alternative
SELF ring rolled composite patterns.
TABLE-US-00004 4 Broken Diamond SELF Diamond 4 Diamond Shift 5
Diamond 5 Zig Zag Criteria Target (FIG. 4) (FIG. 6) (FIG. 5) (FIG.
1) (FIG. 2) Max LFE 18% 13.0% 11.5% 10.4% 12.9% 16.7% (% Exp) Max 0
15% 15% 15% 17% 16% Growth w/parity Properties (% growth) Parity TD
1.21 1.3 1.28 1.29 1.32 1.35 Yield (lbf) TD Tear 277.92 298.88
275.36 307.52 257.3 219.2 (gf)
Test Methods:
Low Force Extension Test Method:
Materials Required:
[0050] 1) 8 inch wide (CD) web with at least 6 inches activated
with SELF or RR patterns. [0051] 2) 200 g weight and 25 g clamp.
[0052] 3) Electronic metric caliper affixed vertically to stand
beside the hanging material to be tested. [0053] 4)
3/4''.times.10'' stainless steel rod
Test Procedures:
[0053] [0054] 1) Cut the activated part of the web to 13 cm in the
MD and 20 cm in the CD. [0055] 2) Separate the film into one-ply
samples. [0056] 3) Lay the film with 13 cm MD perpendicular to your
body. [0057] 4) Lay the 3/8'' stainless steel rod in the CD and
loosely roll the sample in the MD until the 13 cm web is rolled.
[0058] 5) Slide the rod out one end so as to leave just the
rolled-up web at one end to be a 2 cm flat. [0059] 6) Staple the
end of the material at 1 cm to 1.5 cm from the end of the rolled
material. [0060] 7) Finish pulling the rod out from the material
roll. [0061] 8) Staple the other end at 1 cm to 1.5 cm from the
other end of the material roll. [0062] 9) Place the material roll
in the upper clamp so that the staple and any flat web is into the
clamp. [0063] 10) Hang the bottom clamp and weight onto the roll so
that the staple and web are into the clamp leaving only 15 cm of
exposed material between the upper and lower clamps. Before
allowing any extension of the web, set the caliper gauge to the 15
cm mark of the web and set to "0". [0064] 11) Place the weight and
slowly let the weight extend the web. [0065] 12) Slide the caliper
to the new extension length of the material and record the
measurement.
[0066] Various compositions suitable for constructing the flexible
bags of the present invention include flexible or pliable
thermoplastic material which may be formed or drawn into a web or
sheet. Examples of suitable thermoplastic material may include
polyethylene, such as, high density polyethylene, low density
polyethylene, very low density polyethylene, ultra low density
polyethylene, linear low density polyethylene, polypropylene,
ethylene vinyl acetate, nylon, polyester, ethylene vinyl alcohol,
ethylene methyl acrylate, ethylene ethyl acrylate, or other
materials, or combinations thereof, and may be formed in
combinations and in single or multiple layers. When used as a
garbage can liner, the thermoplastic material may be opaque but in
other applications may be transparent, translucent, or tinted.
Furthermore, the material used for the sidewalls may be a gas
impermeable material.
[0067] Once the desired materials are manufactured in any desirable
and suitable manner, comprising all or part of the materials to be
utilized for the bag body, the bag may be constructed in any known
and suitable fashion such as those known in the art for making such
bags in commercially available form. Heat, mechanical, or adhesive
sealing technologies may be utilized to join various components or
elements of the bag to themselves or to each other. In addition,
the bag bodies may be thermoformed, blown, or otherwise molded
rather than reliance upon folding and bonding techniques to
construct the bag bodies from a web or sheet of material. Two
recent U.S. patents which are illustrative of the state of the art
with regard to flexible storage bags similar in overall structure
to those depicted in FIG. 7 but of the types currently available
are U.S. Pat. No. 5,554,093, issued Sep. 10, 1996 to Porchia et
al., and U.S. Pat. No. 5,575,747, issued Nov. 19, 1996 to Dais et
al.
Representative Closures
[0068] Closures of any design and configuration suitable for the
intended application may be utilized in constructing flexible bags
according to the present invention. For example, drawstring-type
closures, tieable handles or flaps, twist-tie or interlocking strip
closures, adhesive-based closures, interlocking mechanical seals
with or without slider-type closure mechanisms, removable ties or
strips made of the bag composition, heat seals, or any other
suitable closure may be employed. Such closures are well-known in
the art as are methods of manufacturing and applying them to
flexible bags.
[0069] In one embodiment the bag comprises a second sheet of
flexible material disposed distal to the opening of the bag as a
reinforcing member along the bottom edge of the bag whether that
edge comprises a seamed edge or a folded edge. The second sheet may
be disposed inside or outside the bag itself. The second sheet may
be affixed to the first sheet over the entire area of the second
sheet or it may be affixed over only a portion of its area. In one
embodiment the second sheet is affixed only along the edges of the
second sheet.
[0070] As illustrated in FIG. 7, a bag 10 comprises a film material
having interleaved bands 20 and 30. The bag 10 further comprises a
bottom edge 11, side edges 16 and 18, a closure 14, an opening 12.
First bands 30 are illustrated as only partially comprising
features. The first bands 30 may comprise features across all or
only a portion of the width of the bag 10. Similarly, the bag 10
may comprise first and second bands 20 and 30, over all or only a
portion of the surface of the bag apart from the closure area
14.
[0071] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0072] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extent that any meaning or definition of
a term in this document conflicts with any meaning or definition of
the same term in a document incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
[0073] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *