U.S. patent application number 10/721807 was filed with the patent office on 2004-06-03 for multi-wall bag.
Invention is credited to Floyd, Thomas M. JR..
Application Number | 20040105600 10/721807 |
Document ID | / |
Family ID | 32397165 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040105600 |
Kind Code |
A1 |
Floyd, Thomas M. JR. |
June 3, 2004 |
Multi-wall bag
Abstract
A coated paper and a multi-wall bag formed from the coated paper
is provided. The coated paper uses a kraft stock paper having a
polyethylene layer applied to one surface. On top of the
polyethylene layer, a biaxially oriented thermoplastic layer is
provided such as polypropylene or polyester. Additionally, the
biaxially oriented thermoplastic layer may include a foil or metal
layer. The coated paper is resistant to water, greases, fats, and
oils and provides an improved printing surface for graphics and
enhances the strength of bag structures comprising the coated
paper.
Inventors: |
Floyd, Thomas M. JR.;
(Moore, SC) |
Correspondence
Address: |
ROBERTSON & MULLINAX, LLC
PO BOX 26029
GREENVILLE
SC
29616-1029
US
|
Family ID: |
32397165 |
Appl. No.: |
10/721807 |
Filed: |
November 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60429004 |
Nov 25, 2002 |
|
|
|
Current U.S.
Class: |
383/109 |
Current CPC
Class: |
B65D 33/02 20130101;
B65D 31/04 20130101; B65D 31/02 20130101; B65D 31/10 20130101; B65D
33/20 20130101 |
Class at
Publication: |
383/109 |
International
Class: |
B65D 030/08 |
Claims
That which is claimed is:
1. A multiple-ply bag comprising: a tubular multi-wall structure
having upper and lower ends, the upper and lower ends being
sealable; front and back walls joined at opposite bag sides by at
least two side gussets running the length of the bag; and, an outer
ply layer of said multi-wall bag having a base layer of a kraft
paper, a layer of polyethylene applied to an exterior side of said
kraft layer, and, an outermost layer of a biaxially oriented
thermoplastic polymer applied to the polyethylene layer, said
outermost layer further defining a printable surface.
2 An improvement in a multi-wall bag having at least an inner ply
and an outer ply, said improvement comprising said outermost ply
having a fiber layer of an about 40 to an about 60 pound basis
weight paper, an exterior side of the paper having about a 5 to
about a 15 pound layer of polyethylene applied to said paper, said
polyethylene layer being in further contact with an outermost layer
of an oriented thermoplastic polymer selected from the group
consisting of a polypropylene, a polyester, or a combination
thereof.
3. A multiple-ply bag comprising: a multi-wall structure having at
least two ply layers, said multi-wall structure further having
upper and lower ends being sealable; front and back walls joined at
opposite back sides by at least gussets running a length of the
bag; an exterior ply of said at least two ply layers comprising a
paper substrate; an extrusion coating of polyethylene on a first
side of said paper substrate; and, a film layer applied to said
polyethylene coating, said film layer defining a non-absorptive
printing surface which is selected from the group consisting of
biaxially oriented polypropylene films, biaxially oriented
polyethylene films, metallized films of biaxially oriented
polypropylene, and metallized films of biaxially oriented
polyester.
4. A multiple-ply bag comprising: an inner ply layer comprising a
paper having a laminated surface, the laminated surface defining an
innermost surface of the multiple-ply bag; a second ply layer of an
uncoated paper adjacent an uncoated surface of said inner ply; a
third ply layer of an uncoated paper positioned between said second
ply layer and a fourth ply layer, said fourth ply layer defining an
exterior ply of said multi-ply bag, said fourth ply layer further
defining a coating of a 5 to 15 lb. weight/3000 sq. ft. of
polyethylene and a film layer applied to a surface of said
polyethylene, said film layer comprising a biaxially oriented film
selected from the group consisting of a biaxially oriented
polypropylene film, a biaxially oriented polyethylene film, a
metallized film of biaxially oriented polypropylene, and a
metallized film of biaxially oriented polyester; wherein said
multiple-ply bag has increased burst resistance and improved tear
strength than a comparable four-ply bag without said film
layer.
5. The multiple-ply bag according to claim 4 wherein said fourth
ply layer comprises a paper having a fiber content of about a 35 to
about a 90 lb. basis weight.
6. The multiple-ply bag according to claim 4 wherein said fourth
ply has a film layer selected from the group consisting of
metallized films of biaxially oriented polypropylene and metallized
films of biaxially oriented polyester, said multiple-ply bag
further having a WVTR of about 0.01 g/100 in..sup.2/24 hrs. or
less.
7. The multiple-ply bag according to claim 4 wherein at least one
of said second and said third ply layers is provided by a converter
kraft paper.
8. The multiple-ply bag according to claim 4 wherein said second
ply and said third ply are provided by a converter kraft paper.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
application having application serial No. 60/429,004 filed Nov. 25,
2002, and which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] This invention is directed towards a multi-wall bag having a
tubular form comprising a plurality of overlapping,
paper-containing plies of flexibly shaped material. Such bags are
commonly used in packaging of pet food.
BACKGROUND OF THE INVENTION
[0003] This invention relates to stand-up pouches and multi-wall
bags for use in packaging granulated or powdered products such as
animal feed, chemicals, powdered milk, and other pourable types of
products. Bags and pouches within this industry are frequently
referred to as self-opening style (SOS) bags, pinched-bottom or
open-mouthed bags, and valve sacks which are hereinafter
collectively referred to as multi-wall bags. A multi-wall bag
frequently includes a tear open tab located at least partially
inside the bag and which is folded with the pinched closure between
the walls of the bag.
[0004] One form of a multi-wall bag may be seen in reference to
U.S. Pat. No. 3,687,356 assigned to St. Regis Paper Company and
which describes single-wall and multi-ply wall gusseted type bags.
Multi-wall bags of this basic construction have been widely used
for the packaging of animal feed, particularly dog and cat
food.
[0005] Recently, the exterior ply of multi-wall bags used within
the pet food packaging industry were treated with fluorocarbons
such as Scotch Guard.RTM. brand FC807 (3M) protectants designed to
provide grease/oil resistance to the exterior surface of the
outermost bag ply. The grease/oil barrier was achieved by adding
the fluorocarbon to the pulp prior to making the paper.
Additionally, clay-coated papers had additional fluorocarbon added
to the clay slurry prior to coating the paper. Such treatments
prevented grease and oil from sticking to the constituent paper
fibers. Such chemical treatment has been adequate to provide
grease/oil resistance to the bag's exterior surface while
permitting the application of graphics and printing using
conventional printing techniques.
[0006] Useful background information with respect to multi-wall bag
containers may be found in the publication entitled, Reference
Guide For The Paper Shipping Sack Industry, Copyright 1991,
published by the Paper Shipping Sack Manufacturer's Association,
Inc., of Tarrytown, N.Y., a 51-page guide which is incorporated
herein by reference. The reference guide discusses paper finishes
and treatments including use of fluoro-chemical agents to make
paper resistant to oil and grease. While fluorocarbon coating of
papers used to construct multi-wall bags has proven adequate within
the industry, there remains room for improvement and variation
within the art.
SUMMARY OF THE INVENTION
[0007] It is one aspect of one of the present embodiments of the
invention to provide a paper layer suitable for use as the
outermost ply of a single-ply or a multi-wall bag having improved
resistance properties to grease, fat, and oils of animal or plant
derivation and which exhibits excellent graphic printing
capabilities.
[0008] It is yet another aspect of at least one of the present
embodiments of the invention to provide a paper layer suitable for
use as an outermost ply of a single-ply or a multi-wall bag having
an outer ply layer of a coated paper which provides improved
resistance to water, has improved graphic printing capabilities,
and increased tear resistance and strength properties compared to
similar bags having an uncoated outer ply.
[0009] It is yet another aspect of at least one of the present
embodiments of the invention to provide a paper layer suitable for
use as a ply layer of a multi-wall bag in which the paper layer
provides for low water vapor transmission rates (WVTR).
[0010] It is yet another aspect of at least one of the present
embodiments of the invention to provide a multi-wall bag in which
the outer ply layer comprises a natural kraft or bleached paper
having a film layer of a biaxially oriented thermoplastic material
such as polypropylene or polyester positioned as an outermost
layer. An extruded thermoplastic layer, and/or a glue layer such as
a conventional tie resin, polyurethane adhesive, or polyester
adhesive, may be present between the paper and the film layer.
[0011] It is another aspect of at least one of the present
embodiments of the invention to provide for a multi-wall bag
construction having an outermost ply of a coated paper. The outer
ply of coated paper results in an overall greater bag strength and
brings about noted improvements in graphics, printing capabilities,
and water vapor transmission rates, and permits bag dimensions of
face width, tube length, and gusset width to be varied without
having to change the composition or characteristics of the various
ply layers which make up the bag. The added strength provided by
the exterior coated paper substrate enhances the strength of the
resulting bags such that standard variations in useful bag
dimensions all have adequate strength for conventional bag contents
such as pet food, cat litter, bird seed, and similar materials.
[0012] It is yet another aspect of at least one of the present
embodiments of the invention to provide a coated paper layer
suitable for use within a stand-up pouch container or a multi-wall
bag in which a coated paper provides the outermost ply, the coated
paper having an extruded structural layer of polyethylene to which
a barrier film layer is bonded. The barrier film layer provides
moisture resistance to the outer ply along with increased grease,
fat, and oil resistance. The coated paper further provides an
improved printing surface as compared to an untreated paper.
Additionally, the coated paper constituent layers provide a
structural reinforcement to the base paper such that when the
material is used as an outer ply for a multi-wall bag, the
resulting bag strength is increased in comparison to an outer ply
lacking the film and extruded layers.
[0013] It is yet another aspect of at least one of the present
embodiments of the invention to provide for a three-ply multi-wall
bag in which the outermost ply layer defines a coated paper layer
comprising an outer layer of a biaxially oriented polyester,
polypropylene, or other oriented thermoplastic film layer. The
resulting ply of coated paper permits a 3-ply bag strength which is
equivalent to or greater than that of a 4-ply multi-wall bag using
similar ply layers with an uncoated outer ply.
[0014] These and other features, aspects, and advantages of the
present invention will become better understood with reference to
the following description and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A fully and enabling disclosure of the present invention,
including the best mode thereof, to one of ordinary skill in the
art is set forth more particularly in the remainder of the
specification, including reference to the accompanying
drawings.
[0016] FIG. 1 is a perspective view of a single-ply, pinch-bottom
bag construction in accordance with the invention.
[0017] FIG. 2 is a perspective view of an alternative embodiment of
the invention showing a multi-wall 3-ply bag construction in which
the bag plies are successively stepped along the open end of the
bag.
[0018] FIG. 3 is a cross-section taken along line 3-3 of FIG. 1
providing details of a coated paper construction of one embodiment
of the present invention.
[0019] FIG. 4 is a cross-section similar to FIG. 3 setting forth an
alternative embodiment of a coated paper construction according to
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] Reference will now be made in detail to the embodiments of
the invention, one or more examples of which are set forth below.
Each example is provided by way of explanation of the invention,
not limitation of the invention. In fact, it will be apparent to
those skilled in the art that various modifications and variations
can be made in the present invention without departing from the
scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used on
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention cover such modifications and
variations as come within the scope of the appended claims and
their equivalents. Other objects, features, and aspects of the
present invention are disclosed in the following detailed
description. It is to be understood by one of ordinary skill in the
art that the present discussion is a description of exemplary
embodiments only and is not intended as limiting the broader
aspects of the present invention, which broader aspects are
embodied in the exemplary constructions.
[0021] In describing the various figures herein, the same reference
numbers are used throughout to describe the same material,
apparatus or process pathway. To avoid redundancy, detailed
descriptions of much of the apparatus once described in relation to
a figure is not repeated in the descriptions of subsequent figures,
although such apparatus or process is labeled with the same
reference numbers.
[0022] As used herein, the term "coated paper" refers to a paper
having a surface to which is adhered a biaxially oriented polyester
or polypropylene film layer. One or more intervening layers of an
extruded material or adhesive may also be present.
[0023] As seen in reference to FIGS. 1 and 2, an exemplary,
non-limiting embodiment of the present invention is directed to a
stand-up pouch or multi-wall bag having a pinched closure at one
end. As seen in reference to FIG. 1, the bag 10 defines at least
one pinch-closable end and is formed from a ply of paper 20 which
is folded to form a pinch closure. As seen in reference to FIG. 1,
bag 10 may be formed from a single paper ply 20. The bag has a
front wall 12 and an oppositely disposed rear wall 14, rear wall 14
extending above the front surface 12 at one end of the tube when
the bag is in its assembled condition as illustrated. As seen in
FIG. 1, the bag 10 defines a series of forward fold lines 22, 24,
26, and 28. Bag 10 further defines a pair of oppositely spaced
gussets 32 and 34 which are positioned between the respective front
and rear walls of bag walls 12 and 14.
[0024] In reference to FIG. 2, a multi-ply bag embodiment is
referenced having a rear wall 14 that comprises a plurality of
three plies including an outer ply 50 of a coated paper as
described herein, a second ply 52, and an innermost ply layer 54.
Ply layers 52 and 54 may be formed of natural kraft paper,
converter kraft, or other conventional paper stock. The
construction of single-wall and multi-wall gusseted type bags is
well known in the art as may be found in reference to U.S. Pat.
Nos. 3,687,356 and 6,599,016 which are incorporated herein by
reference.
[0025] Exemplary bags seen in FIGS. 1 and 2 may be constructed from
a coated paper in which the single ply or outermost ply comprises a
coated paper having an exterior surface of a biaxially oriented
film layer. As best seen in reference to FIG. 3, one embodiment of
a coated paper 20 is provided in which paper 20 comprises an
innermost paper substrate layer 40. Paper substrate layer 40 may be
in the form of a natural kraft, converter kraft, bleached paper, or
extensible kraft paper. Conventional paper weights for multi-wall
bags used in the pet food industry use kraft paper for inner ply
layers corresponding to a 40 to 60 pound weight paper. Along an
exterior surface of the coated paper 20, a 5 to 15 pound layer (per
3000 sq. ft. of paper stock) of a polyethylene 42 is extrusion
coated onto the paper. The polyethylene extruded layer 42 provides
a smooth surface to the coated paper while providing a bondable
surface for applying a subsequent film layer. Useful polyethylenes
for layer 42 include low density polyethylene (LDPE), linear low
density polyethylene (LLDPE), polyethylene-based adhesive tie
layers, polyethylene terepthalate (PET), as well as other polymers
as conventionally used to laminate paper or paperboard substrates.
Following application of the polyethylene layer 42, a biaxially
oriented thermoplastic material 44 such as polypropylene or
polyester film is applied. When polyester film is used, a useful
thickness of the biaxially oriented film layer is about 48 gauge,
although a range of about 30 gauge to about 98 gauge is believed
useful. In the case of biaxially oriented polypropylene, a film
thickness of about 55 gauge has been found useful, although it is
believed that a range of about 40 to about 100 gauge is also
useful. Applying a biaxially oriented polyester or polypropylene
film to a paper or laminated paper substrate may be carried out
using conventional techniques well known within the art.
[0026] In accordance with the present invention, it has been found
that polypropylene biaxially oriented films having a melting point
of between 325.degree. to 330.degree. F. prove useful. In addition,
it has been found that having an acrylic coating applied to the
exterior surface of the film, i.e., print ink receiving surface,
improves the film's surface receptivity to inks and hot melts.
Suitable polypropylene films, including films having acrylic
coatings are commercially available from AET Films, Inc. (New
Castle, Del.) and ViFan, a division of Vibac (Morristown, Tenn.).
Further, it has been noted that selection of a smooth finished
kraft paper such as machine glazed paper available from Longview
Fibre Company (Longview, Wash.), may reduce by up to 50 percent the
amount of the polyethylene extrusion coating required to achieve a
smooth surface for applying the subsequent film layer 44.
[0027] As seen in reference to FIG. 4, an alternative embodiment of
the present invention makes use of a paper layer 40 with an
extruded polyethylene layer 42 similar to that described above in
reference to FIG. 3. The biaxially oriented thermoplastic layer may
additionally include a foil or metal layer 48. By way of example,
an aluminum foil layer may have a thickness of about 1 to 2
angstroms with an optical density (OD) ranging from about 2.0 to
about 3.5. On top of the foil layer 48 is the biaxially oriented
thermoplastic layer 44 of polypropylene or polyester. Preferably,
metal layer 48 and the thermoplastic film layer 44 may be applied
in a single step using a vacuum metallized oriented polypropylene
sheet. Suitable metallized oriented polypropylene film is available
from AET Films, Inc. (New Castle, Del.) and ViFan (Morristown,
Tenn.).
[0028] In paper layer 40, seen in reference to FIGS. 3 and 4, the
polyethylene layer 42 provides a smooth, outer surface to the paper
layer 40. The smooth surface provided by layer 42 facilitates the
subsequent application of the polypropylene or polyester film 44
and which may include optional foil layer 48. As a result, film 44
provides a smooth, even exterior surface which facilitates
subsequent printing of bag graphics onto film layer 44 using, for
example, conventional flexo printing or gravure printing
techniques. In the described embodiments, there is no need for an
overprint varnish or separate oil/grease resistant coating to be
applied following printing.
[0029] In accordance with the present invention, it has been found
that the biaxially oriented thermoplastic coated kraft paper offers
several advantages with respect to the construction of a multi-wall
bag. Foremost, the biaxially oriented thermoplastic film layer has
been found to provide an improved printing surface as opposed to
kraft papers which have been treated with a fluorochemical agent.
The improved printing surface is achieved, in part, by providing a
smoother and non-abrasive printing surface. As a result, the
printing surface requires less ink to be applied while enhancing
the sharpness and contrast of the applied inks. Consequently, ink
printing costs are lowered. The resulting graphics are cleaner and
crisper since the absorptive paper layer does not directly interact
with or absorb the ink as occurs with fluorochemically treated
papers.
[0030] Similar properties are also achieved when using the metal or
foil layer embodiment. Again, an improved print quality is achieved
while at the same time using less ink. As set forth in Table 1A,
paper coated with the metal or foil layer also exhibits excellent
WVTR properties.
[0031] Additionally, the use of the coated paper as set forth in
the various embodiments offers additional advantages in printing
operations. To the extent different types of kraft papers may be
used on consecutive printing runs, there is no longer a need to
switch inks based upon the type of paper. When various types of
kraft paper are coated according to the present invention, the
resulting papers are all compatible with a single type of ink and
do not require time consuming and costly ink switching at the
printing stage.
[0032] Additionally, coated paper when used as an outer ply for a
multi-wall bag results in the outer ply having improved strength
properties and tear resistance compared to a similar bag made with
an uncoated kraft paper. For instance, when a kraft paper, rated at
a conventional 41 pounds, is coated as set forth above in reference
to FIG. 3, the resulting coated paper has a rating of between about
70 to about 80 pounds. Without the biaxially oriented film coating,
a 41 pound kraft paper when treated with a traditional calendaring,
clay coating, or metalizing process contributes only 15 to 20
pounds of strength under Uniform Freight Classification ICC Rule
40. This additional strength, a direct result of the biaxially
oriented film layer 44, allows a 25 pound bag of pet food which is
conventionally shipped in a 4-ply bag to be shipped in a 3-ply bag.
As a result, the material and shipping costs of the bag are
decreased while achieving the attendant improvements noted above
with respect to improved graphics and printability.
[0033] The use of the coated paper in a multi-wall bag construction
permits a converter kraft grade of interior ply layers to be used
while still meeting the requirements of ICC Rule 40. Heretofore,
compliance with ICC Rule 40 effectively excluded the use of less
expensive converter kraft grades in multi-wall bags in favor of the
more expensive and stronger natural kraft papers. The use of coated
paper in bag construction allows interior ply layers to be made of
converter kraft while still meeting the performance standards set
forth in ICC Rule 40.
[0034] Tables 1A and 1B below set forth test data with respect to
physical properties and performance data of polypropylene coated
bleached kraft papers and metallized polypropylene coated natural
kraft papers, along with various control kraft and metallized kraft
papers. With respect to the test results seen in Tables 1A and 1B,
the paper weight was determined according to TAPPI official test
method T-410. Porosity measurements were made according to TAPPI
official test method T-460. The tensile strength and tear
resistance determination of the paper were made using TAPPI test
methods T-494 and T-414 respectively. The Dart Impact data was
collected using ASTM 1709 methods. While not separately set forth,
the coated paper was noted to have excellent glueability properties
with respect to paper-paper, paper-film, and film-paper
adhesion.
[0035] As noted in Table 1A, the WVTR properties of the coated
paper are significantly improved compared to WVTR values for
conventional prior art outer ply construction. When incorporated
into a multiple wall bag, the coated paper enhances the freshness
of products sealed within the bag. In addition, decreasing vapor
loss also provides for improved odor control. The ability to
provide for grain and animal food products in a low odor release
bag can be important in retail environments where odors may be
absorbed by clothing merchandise or be objectionable to near food
dispensing areas.
[0036] As further noted in Tables 1A and 1B, the properties of the
coated paper have the indicated values for tear and strength
properties. As seen in reference to Table 1B, the single sheet and
samples 1 through 3 have a core fiber basis weight of about 50.
Following coating with the biaxially oriented polypropylene film,
the basis weight and strength increases as indicated in Table 1B
when compared to the comparison 1 natural kraft 50-pound basis
weight paper and the comparison 2 43-pound basis weight metallized
prior art paper. As provided for in Table 2, the overall
improvements in bag strength which result from use of the coated
paper on an exterior ply may be seen in comparison to control bags
without the coated paper enhancement.
1TABLE 1A MET PP/Extruded/ MET PP/Extruded/ Test Description
PP/Extruded/BL NK NK NK Basis Weight 70.715 72.738 68.0 (Llbs/3000
ft.sup.2) Porosity Avg.: Exceeds 1800 Exceeds 1800 Exceeds 1800
(Sec/100 cc Air) Std. seconds seconds seconds TAPPI T460 Dev.: Low:
High: 20.degree. Gloss Avg.: 34.3 0 @ 20.degree. and 60.degree. 0 @
20.degree. and 60.degree. (Degrees) Std. 1.83 Geometry Geometry
TAPPI T480 Dev.: Low: 31.8 High: 36.9 MD CD MD CD MD CD Tensile
Avg.: 36.38 19.22 49.51 22.65 46 28 (Lbf/in) Std. 1.74 1.38 3.10
1.96 TAPPI T494 Dev.: Low: 33.37 17.05 46.42 19.40 High: 37.60
20.55 53.65 24.65 TEA Avg.: 4.02 53.20 7.81 26.05 7.3 24
(Ftlbs/ft.sup.2) Std. 0.39 16.26 1.55 4.85 TAPPI T494 Dev.: Low:
3.39 25.48 6.51 21.38 High: 4.44 66.60 9.73 33.21 Tear Avg.: 159.6
148.5 125.5 187.7 137 134 (Grams) Std. 9.6 8.3 11.6 3.2 TAPPI T414
Dev.: Low: 148.0 141.4 114.5 182.7 High: 174.6 161.0 142.3 191.6
WVTR 0.48 0.01 0.01 (g/100 in.sup.2/24 hrs @ 100.degree. F. and
90.degree. RH) ASTM E-96-80
[0037]
2 TABLE 18 Basis Weight (before/after coating) Test Param Test
Discripto Test Test Units Impact Dart Drop Impact Ft.-lb force Std
Dev Mullen A NA Mullen A Avg lbs/sq in Mullen A Std Deviat lbs/sq
in Tear MD Tear Avg gms Tear Std Deviation gms CD Tear Avg gms Tear
Std Deviation gms Tensile MD Tens Energy Abs Av Ft-lb/sq ft Tens
Energy Abs St Ft-lb/sq ft Tens Ext Stif Avg lbs/inch Tens Ext Stif
Std De lbs/inch Tens Stretch Avg Percent Tens Stretch Std De
Percent Tensile Avg lbs/inch Tensile Std Deviatio lbs/inch CD Tens
Energy Abs Av Ft-lb/sq ft Tens Energy Abs St Ft-lb/sq ft Tens Ext
Stiff Avg lbs/inch Tens Ext Stif Std De lbs/inch Tens Stretch Avg
Percent Tens Stretch Std De Percent Tensile Avg lbs/inch Tensile
Std Deviatio lbs/inch WVTR Single Sheet Comparison ONTIC Metal
COMPARISON 2 Single Sheet COMPARISON 1 Sample 1 Vac Met ONTIC White
NK METAL Sample 2 Sample 3 C1S/Metallized 50/70 50 50/72 50/72
50/72 43 Test Methods ASTM 1709 0.2045 0.6547 0.029 0.165 101 46 79
67 32 14 2 16 7 4 TAPPI 159.6 133.1 125.5 137.68 136.18 49.6 T-414
om-88 9.6 11.6 6.53 5.05 1.03 148.5 125.7 187.7 138.14 131.62 46.98
8.3 3.2 3.77 4.56 1.92 TAPPI 4.02 7.81 4.69 2.2 T-494 om-88 0.39
1.55 0.64 0.78 3940 2770 221 115 6.51 1.6 1.29 9.73 0.16 0.26 36.38
49.51 39.2 22.5 1.74 3.1 1.4 3 53.2 26.05 19.4 4.51 16.26 4.85 1.05
1.24 1870 1250 129 65 21.38 6.5 3.79 33.21 0.27 0.81 19.22 22.65
32.1 13.3 1.38 1.96 1 1.2 ASTM F-372
[0038] The coated paper is useful for single-wall bags, multi-ply
bags, or stand-up pouches in which the outermost ply is of a coated
paper as described herein. The resulting bag has advantages in
terms of the mechanical packaging capabilities of the bag. The
exterior, i.e., printed surface of the bag/paper has an extremely
smooth and glossy texture. Suction belts and cups used on
mechanical packaging equipment are able to better grasp the bag.
The improved gripping results in bag processing in which the outer
face is not torn or damaged by the use of overly aggressive
handling techniques or application of excessive vacuum pressure to
the handling equipment.
[0039] The improved bag strength which results from inclusion of
the coated paper in the bag construction significantly increases
the tear resistance of the bag. Consumers will often grab a bag
along an upper seam or gusset wall. The coated paper provides
sufficient tear resistance to the bag that the integrity of the bag
is maintained during handling along key stress points. This
additional strength also facilitates the incorporation of handles
into the bag, such handles being known in the art.
[0040] Further, bags made with the biaxially oriented film-coated
paper are more resistant to punctures, tears, and abrasion of the
exterior layer. The exterior layer comprises the print surface upon
which packaging graphics are printed. As a result, the improved
strength and tear resistance maintains the shelf appeal of the
packaging. Consumers perceive visible tears or abrasions in bag
packaging as an indication of underlying weakness of the bag and/or
a compromise of the product's integrity. By reducing the incidence
of tears and abrasions in the bag exterior, retailers do not have
to discount or remove as much product as a result of damaged
packaging.
[0041] An additional benefit of providing a multi-wall bag having
the outer ply of the coated paper described herein is that the
resulting bags have shown improved resistance to external moisture
damage. Heretofore, conventional pet food bags and similar products
had an exterior ply layer which offered poor resistance to
moisture. As a consequence, exposure of the bag to rain or moisture
would greatly weaken the bag strength. Further, visible moisture
damage lessened the attractiveness of the bag graphics and was
frequently perceived by the consumers as indicative of potentially
spoiled or damaged goods. The use of the coated paper, described
herein as the exterior ply layer, substantially increases the
resistance of the bag to moisture. This resistance has positive
effects on the bag strength as well as the appearance of the bag
graphics.
[0042] The biaxially oriented coated paper described herein
provides a more stable outer ply for use in a multi-wall converting
process. Not only will the coated paper allow use of fewer plies,
or alternatively the use of lower basis weight paper for
intermediate plies, the reduction in ply numbers and/or basis
weight has advantages in the bag manufacturing process. The
increased stability of the outer ply allows higher bag machine and
tuber speeds to be utilized, increasing the efficiency of the
bag-making operation.
[0043] Additionally, the coated paper of the present invention
maintains stability during the converting process. For instance,
using conventional exterior ply paper, the conventional outer ply
becomes very brittle and difficult to convert following printing of
the outer ply. The increased brittleness is brought about by water
loss occurring during the printing/lamination process. In
comparison, the biaxially oriented coated paper of the present
invention exhibits minimal moisture loss during converting and
printing steps. As such, the outer ply material is easier to handle
and any associated natural kraft or bleached base paper in the
interior plies is likewise maintained in a good condition.
[0044] During printing production steps, the biaxially oriented
coated paper exhibits improvements in manufacturing efficiencies. A
significant time factor of printing on prior art paper involves the
drying of the paper following application of one or more ink
colors. Using the biaxially oriented coated paper reduces the ink
volume by a factor of two to three without loss of color intensity
or hues. Since printing occurs directly on the film side of the
paper, there is no to minimal absorption of the ink which reduces
drying requirements, uses less ink, and helps maintain favorable
moisture conditions by minimizing use of drying ovens. As a result,
the graphics printing can be done at a higher rate of speed and
using less inks than on a conventional outer ply paper of
conventional design.
[0045] The outer ply layer heretofore used within the bag industry
exhibits a tendency to crack when folded during a bag-making
operation. As a result, the gussets and bottom folds often exhibit
a poor appearance and undesirable shelf appeal. Additionally, the
crack impairs whatever barrier properties may have been present
within the conventional outer ply layer. The present invention's
use of a biaxially oriented polypropylene or polyester has been
found to greatly increase the flex characteristics of the paper. As
a result, folds and creases are additionally protected from
cracking and thereby increase both the appearance as well as the
barrier properties of the resulting multi-wall bags.
[0046] Additionally, the biaxially oriented films of the coated
paper described herein will readily receive an extruded or film
applied heat seal coating such as a low density polyethylene. As
such, the coated paper of the present invention becomes an ideal
substrate for stand-up pouches and other containers where heat
sealing may be used to seal the container. As previously noted, the
coated paper of the present invention also exhibits excellent
properties with respect to glueability.
[0047] Additionally, sealed multi-wall bags in which the exterior
ply comprises the coated paper of the present invention have
demonstrated improved properties with respect to control bags in
standard drop tests. Set forth in Table 2 is comparative data
between a conventional 4-ply metallized bag (37.5 lb. capacity)
having a fluorchemical outer ply treatment in comparison to a
similar multi-ply bag having the outermost ply of a coated paper
using the metallized biaxially oriented film (ONTICTM) as described
herein.
3TABLE 2 BAG COMPARISON Bag: 75 OPP/2-60 NK/Outer Ply Outer Ply
Old: 43 C1S/Metallized Outer Ply New: ONTIC Metal OLD NEW Test Test
4-PLY 4-PLY Parameter Test Test Units BAG BAG Mullen A NA Mullen A
Avg lbs/sq in 143 215 (bursting) D774M-97 Mullen A Std Dev. lbs/sq
in 9 12 Tear MD Tear Avg gms 127.3 173.26 Tear Std Deviation gms
6.08 8.92 CD Tear Avg gms 119.04 138.78 Tear Std Deviation gms 4.39
8.77 Tensile MD Tens Energy Abs Avg Ft-lb/sq ft 13.4 13.5 Tens
Energy Abs Std Ft-lbs/sq ft 1.83 1.09 Dev. Tens Ext Stif Avg
lbs/inch 10000 10500 Tens Ext Stif Std Dev. lbs/inch 273 411 Tens
Stretch Avg Percent 1.55 1.39 Tens Stretch Std Dev. Percent 0.17
0.18 Tensile Avg lbs/inch 96.6 102.5 Tensile Std Deviation lbs/inch
6.8 11.5 CD Tens Energy Abs Avg Ft-lb/sq ft 34.8 53.8 Tens Energy
Abs Std Ft-lb/sq ft 0.75 9.07 Dev. Tens Ext Stif Avg lbs/inch 4190
5950 Tens Ext Stif Std lbs/inch 201 233 Deviation Tens Stretch Avg
Percent 3.82 3.44 Tens Stretch Std Percent 0.43 0.35 Deviation T
nsile Avg lbs/inch 57.2 72.4 Tensile Std Deviation lbs/inch 2.9
2.8
[0048] Multi-wall bags made according to the exemplary embodiments
described above exhibit excellent resistance to grease migration
through the packaging. Grease barriers are important with respect
to packaged animal feed including dog food or cat food. It has been
found that multi-wall bags as referenced in Table 2 using the
biaxially coated paper will provide a grease barrier for 30 days
when tested using refined poultry fat maintained in the bags at
temperatures of 120.degree. F.
[0049] The improvements in overall bag strength brought about by
incorporation of the biaxially oriented film-coated paper results
in a bag packaging having three times the resistance to impact
damage compared to a conventional bag of 50 lb. natural kraft
paper. As a result, it is possible to eliminate one or more plies
from a multi-ply bag when the exterior bag layer is comprised of
the biaxially coated paper described herein. As a result, packaging
bags can be provided which are stronger than comparative bags, use
less material, offer improved print and graphic capabilities, have
improved resistance to abrasion and tearing of the bag exterior
surface, and offer improvements in terms of water vapor
transmission properties, water resistance properties, and grease
barrier properties. Such improvements, depending upon the bag size
and contents, may permit a single-wall bag or stand-up pouch of
superior performance to be constructed using biaxially oriented
film coated paper. As noted in Table 2, the burst strength (Mullen
A) of the bag is improved by about 33% in comparison to an
identical bag having an uncoated outer ply.
[0050] The ability to vary the dimensions of width, gusset size,
and tube length allow one to provide for a multi-ply bag having a
lower center of gravity and using the same materials as similar
volume bags but having a higher center of gravity. The lower center
of gravity places greater stress upon certain seams used to form
the bag. The inclusion of the coated paper as the outermost ply
provides sufficient bag strength that variations in bag dimensions
may be readily made without having to change the underlying
materials used to form the various ply layers.
[0051] While many of the above referenced embodiments discuss the
use of extrusion to apply various layers to the coated paper, it is
understood by one having ordinary skill in the art that one or more
of the applied layers coating the paper may be provided by the
application of films. The use of films to provide layers within a
coated paper or board structure is well known within the art.
[0052] Although preferred embodiments of the invention have been
described using specific terms, devices, and methods, such
description is for illustrative purposes only. The words used are
words of description rather than of limitation. It is to be
understood that changes and variations may be made by those of
ordinary skill in the art without departing from the spirit or the
scope of the present invention, which is set forth in the following
claims. In addition, it should be understood that aspects of the
various embodiments may be interchanged, both in whole or in part.
Therefore, the spirit and scope of the appended claims should not
be limited to the description of the preferred versions contained
therein.
* * * * *