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Patent 1228578 Summary

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(12) Patent: (11) CA 1228578
(21) Application Number: 451106
(54) English Title: SHIPPING BAG
(54) French Title: SAC D'EXPEDITION
Status: Expired
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 220/6
(51) International Patent Classification (IPC):
  • B65D 30/08 (2006.01)
(72) Inventors :
  • HARRISON, RAY E. (Canada)
  • MURRAY, CHARLES R. (Canada)
(73) Owners :
  • SMURFIT-STONE CONTAINER CANADA INC. (Canada)
(71) Applicants :
(74) Agent: BARLOW, CHARLES BRIAN
(74) Associate agent:
(45) Issued: 1987-10-27
(22) Filed Date: 1984-04-02
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract



Abstract
Shipping Bag
A thermoplastic heavy duty shipping bag having walls
formed of cross-laminated outer plies of uni-axially oriented
polyethylene and inner walls of low density polyethylene,
heat sealed thereto. The bag provides improved puncture and
snag resistance.


Claims

Note: Claims are shown in the official language in which they were submitted.



The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:

1. A thermoplastic shipping bag having a front wall and a
back wall, each wall comprising a cross-laminated ply
comprising at least two sheets of uni-axially oriented
polyethylene bonded together; said laminated plies heat
sealed one to the other to provide a heat seal area and
wherein interposed between said laminated plies in said heat
seal area are two layers of low density polyethylene
constituting distinct inner plies of the bag, said low
density polyethylene plies being heat sealed together and
serving as a bridge to permit the effective heat sealing of
the laminated plies to each other without significant loss
of draw-induced film strength in and around the heat sealed
area.

2. A bag as claimed in Claim 1 wherein said
cross-laminated ply comprises at least two sheets of
uni-axially oriented high density polyethylene bonded
together.

3. A bag as claimed in Claim 1 wherein said
cross-laminated ply comprises at least two sheets of
uni-axially oriented low density polyethylene bonded
together.

4. A bag as claimed in Claim 1 wherein said
cross-laminated ply comprises at least two sheets of
uni-axially oriented linear low density polyethylene bonded
together.

19

Description

Note: Descriptions are shown in the official language in which they were submitted.


I I

Sllippln~ sag - 1 C-I-L 671
This invention relates to thermoplastic shipping bags
and, particularly, to said bags for heavy duty use having
one or more plies of a uni-axially oriented cross-laminated
polyethylene.
Thermoplastic shipping bags are an economical means for
the packaging, transportation and storage of a wide variety
of products in granular, bead, pellet or powder form. These
bays may be either open ended, requiring separate provision
for closing, or fitted with a valved opening. The most
commonly used type of thermoplastic bags are manufactured
from film made by blown film processes using low density
polyethylene and rubber modified high density polyethylene
resins and coextruded versions of these resins and allied
copolymers. The film may be subsequently converted to bags
by a variety of sealing techniques. Some of these simple
thermoplastic films may be converted to bags by sewing but
this has the disadvantage of badly weakening the films and
introducing unwanted holes in the bag through which moisture
or other contaminants can enter or allow environmental
contaminants to exit. Other bags may be manufactured by the
multiple folding and gluing of the bag end, but this has
the serious disadvantage of requiring very expensive
converting equipment, as well as the use of expensive and
difficult to control two component glue systems.
cause of these drawbacks the use of heat sealing is
the desired method of manufacture of thermoplastic bags.
At the present, heat sealed thermoplastic bags are
commonly used for the packaging of low cost, non-hazardous
products. Their use for higher cost and hazardous products,
however, has been badly restricted because of the poor
juncture and snag resistance of the bags compared with
multi-wall paper or woven plastic backs of related composition
structures.
It is known in the art that the required level ox

357~3

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puncture and snag resistance can be built into a thermoplastic
film manufactured from linear ethylene polymers such as high
density polyethylene or linear low density polyethylene, by
uni-axially cold drawing such film and subsequently
laminating two of these layers in such a manner that the
draw-incluced orientation of one web typically is go to
that of the other web. Thus, the uni-axially oriented
sheets of polyethylene are laminated one to the other in
such a manner -that the directions of orientation cross each
other. The resulting composite laminated film, generally
known as a cross-plastic, cross-laminate, or cross-laminate
ply has high puncture and snag resistance compared to an
equivalent gauge non-oriented blown film. Films of this type
have thus been used for sewn and glued shipping bags for
high value and hazardous materials.
however, these materials have one serious drawback in
that they cannot reliably be heat sealed on conventional bag
making machinery to provide bags for heavy duty use. this
has seriously impeded their utility and acceptability in the
market place notwithstanding the aforementioned advantages
of heat sealed bags.
Surprisingly, we have now found that this unacceptable
heat seal drawback can be overcome to produce an improved
heavy duty shipping bag by interposing a double layer of low
density polyethylene, which has not been cold drawn (i.e.,
has not been uni-axially oriented), between the two cross-
laminated films to be heat sealed together to form the walls
of the bag. We have surprisingly found that these layers of
low density polyethylene in the heat seal area can be welded
to each other and to the cross-laminated film or ply without
heat build up sufficient to cause serious loss of cold
draw-induced film strength. Thus, an acceptable bridge
between the high strength cross laminated film and the Cody
of the heat seal is formed. this is to be contrasted with

:~2;~1357i~

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the fact that although two cross-laminated films in -the
absence of interposed low density polyethylene film could be
melted and fused together to produce welded bonds, the
cross-laminated film immediately adjacent to the welded mass
has its cold draw orientation destroyed by the heat from the
seal with consequent loss of film strength in this margin
area; whereby the seals so produced are weak and brittle in
the margin area, rendering them unacceptable for use in
Levi duty shipping bags.
It has thus now been found that a suitable thermoplastic
shipping bag having improved puncture and snag resistance can
now be reliably manufactured by heat sealing techniques
using suitably modified conventional equipment.
Thus, in its simplest form the invention provides a
thermoplastic shipping back having a front wall and a back
wall, each wall comprising a cross-laminated ply comprising
at least two sheets of uni-axially oriented polyethylene
bonded together, said laminated plies heat sealed one to the
other to provide a heat seal area and wherein interposed
between said laminated plies in said heat seal area are two
layers of low density polyethylene.
Each of the interposed layers of low density polyethylene
may constitute simply a sheet of polyethylene laminated to
a surface of a cross-laminated ply and being of sufficient
thickness in the heat seal area to effect an acceptable
bridge between the two laminated plies in this area to form
a scam. flowerer, these interposed layers of low density
polyethylene may extend beyond the heat seal area to
on represent a laminated layer on the full surface of each of
tune laminated plies. Thus, each of the cross laminate piles
comprisinc3 the walls of the shipping back have a layer of low
cleanest polyethylene laminated thereto. Such a structure,
of course, aloes not cletrclc~ from the requirement that the
laminated plies need only be heat sealed at designated heat

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seal areas. These areas constitute those parts of the jag,
generally parts of the periphery, where the front and back
walls are joined by heat sealing during manufacture.
Where the layers of low density polyethylene are
represented as outer laminated sheets on the cross-laminated
plies, each of -the sheets must be of sufficient thickness to
effect an acceptable bridge between the two cross-laminated
plies. We have found that a mere coating of low density
polyethylene on each of the cross-laminated plies is not
sufficient, and that a minimum thickness of 0.5 mix of low
density polyethylene is required, preferably ~1.5 mill
We have also found that each of the cross-laminated
plies constituting the walls of the bag must have a laminated
sweet of low density polyethylene to provide an acceptable
heat seal for heavy duty bag use. For reasons hereinafter
discussed, a single interposed layer of low density
polyethylene, represented either as a laminated sheet or as
a distinct ply, is not satisfactory. Thus, a double layer
of polyethylene is required.
In a much preferred form of a bag according to the
invention the interposed layers of low density polyethylene
represent full and distinct piles constituting part of the
walls of the bag.
accordingly, the invention further provides a bag as
herein before described wherein each of said layers of low
density polyethylene constitutes an inner ply of the bag.
In this preferred form of bag each of the walls
comprising a cross-laminated ply has an interposing ply of
low density polyethylene associated therewith. In this
arrangement, each of the interposing plies may be considered
as being an inner wall of the bag while the two cross-
laminated plies considered as being the two outer walls.
Accordingly, the invention further provides a thermos
plastic shipping bag comprising a front wall and a back wall

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- s - C-I-L 671
heat sealed thereto each of said walls comprising a
cross-laminated outer ply comprising at least two sheets of
uni-axially oriented polyethylene bonded together and heat
sealed thereto an inner wall formed of low density
polyethylene.
When a bag containing a fluid product is dropped a major
amount of the kinetic energy from the product is transmitted
to the bag wall upon impact as the walls prevent the product
lo) from flowing outward. This energy is absorbed by the bag
walls stretching. The peak force build-up in the bag walls
during this energy absorption is dependent on the elasticity
of the bag walls. If the peak force build-up on impact is
greater than the tensile yield strength of the bag walls the
bag will be permanently stretched. When this peak force is
greater than the ultimate tensile strength of the walls the
bag will rupture at the weakest points. when a heat seal
is introduced into a bag walLsthe ultimate tensile strength
of the heat seal at its weakest section should be greater
than the tensile yield strength of the bag walls to maximize
the impact strength of the heat seal.
In uni-axially oriented cross-l~minated cold drawn
films such as V~L~RO~ high density polyethylene the
yield tensile strength of tile film is hither than the ultimate
tensile strength of the plastic resin mass from. which it is
made. When the film is heat sealed the orientation of the
film is destroyed in the heat seal margin which results in a
drastic reduction in both the yield tensile strength and the
ultilnclte tensile strength.
I A laminated seal is understood in the art to be a
seal wherein the joining interfaces of the films can be
separated by the physical pulling apart of the bonded film
without the destruction of the film and thus effecting a
relatively clean separation. On the other hand a 'heat seal'
in the art is understood to be a seal produced under a
Trade Clark

78
- 6 - COLE 671
combination of pressure and heat, at or above the films'
crystalline melting points, applied to the films in order
that they are truly welded at their interfaces such that a
clean separation cannot be effected by physical or chemical
means.
We have surprisingly found that a heat seal as
hereinbeore defined when integrally formed with an adjacent
laminated seal has improved seal strength. Thus, by the term
'heat seal' as used in this specification and claims is
meant a heat seal as herein before defined having an adjacent
laminated seal integral therewith. the adjacent laminated
seal has a length of at least 2 no.
We have found that i31 order to prevent stress from
lo building up only in the heat sealed junction of the oriented
and non-oriented fits these layers must be laminated sealed
together adjacent the heat seal mass so that the stress is
also taken up by the adjacent multi-ply laminate. It will be
realized that film stretching is a two dimensional effect,
i.e. if a film is stretched only in one direction it tends
to neck down in the other if unrestrained. Therefore, if the
inner non-oriented layer is totally amounted to the less
elastic oriented outer layer it will take on the neck down
characteristics of the total laminate. While each pair of
oriented and non-oriented layers may be laminated one to the
other optionally the full lenc3th of the bag walls, it is
nonetheless necessary that laminations extend between the
layers in close proximity to the heat seal. A length of only
5-10 mm for the adjacent laminated seal integral with the
heat seal mass is the most desirable length. Further, we
have found that a single layer of non-oriented polyethylene
between the two oriented layers reduces the utility of this
invention since that laminated section of the seal between

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- 7 - C-I-L 671
the single ply and the double ply peels away under the
constant pressure exerted when bags are loaded and stacked.
By the term "thermoplastic", as used heroin is meant
S any -thermoplastics material capable of providing a film, ply
or layer of suitable thickness and strength for a heavy duty
skipping bag. Of particular use are thermoplastics of the
polyethylene and polybutadiene family of polymers. As
examples, high density and low density polyethylene and
1,2 polybutadienes may be mentioned.
The term "low density polyethylene" includes ethylene
homopolymers and copolymers, such as the linear low density
. . ._




. .

7~3

- 8 - C-I-L 671
polyethylene, vinyl acetate copolymers, and blends thereof.
The term "inner wall" is mean-t not to be restricted
solely to the actual or true inner wall of the bag which
contacts product when the bag is filled. The term also
includes the situation, ton example, where one or more plies
of non-oriented low density polyethylene constitute plies in
a multi-wall bag which plies may or may not be adjacent the
true inner wall. Similarly, the term "outer ply" is meant
lo not to be restricted solely to the most external ply.
Thus, it should be understood that the principles of
the invention are applicable also to the fabrication of bags
having walls individually comprising more than two plies.
Thus, the invention embraces bags having three plies, four
plies, etc. The important and essential feature is that
there must be either a laminated layer or at least one ply
of non-oriented low density polyethylene constituting each
of the inner surfaces ox the bag such thaw a eross-laminated
ply of polyethylene does not contact another cross-laminated
ply of polyethylene at a designated heat seal area of an
inner surface such as to weaken a heat seal.
In preferred embodiments of the bags according to the
invention as herein before and hereinafter defined the
interposed layer of low density polyethylene represented
either as a laminated sheet on the cross-laminated ply or as
a distinct inner ply or inner wall, is formed of blown linear
low density polyethylene. However, it is readily apparent
that cast films are also suitable for this application.
Preferably each of the cross-laminated plies comprises
at least two sheets of unwell oriented low density
polyethylene, more preferably linear low density polyethylene
and yet, more preferably, high density polyethylene.
Where the cross-laminated ply comprises sheets of
uni-axially oriented high density polyethylene, the sheets
may be bonded together, for example, with a layer of

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- 9 - C-I-L 671
non-oriented high density polyethylene. Where the laminated
ply comprises sheets of uni-axially oriented low, or
preferably, linear low density polyethylene, -these may be
bonded together with non-oriented low density polyethylene
or, preferably, linear low density polyethylene.
In one form, bags according to the invention comprise
two inner linings or walls of non-oriented low density
polyethylene film, heat sealed at their peripheries to plies
Lo of cross-laminated polyethylene film. The low density
polyethylene inner lining or wall may, however, be also
heat sealed to the cross-laminated ply intermittent over
other parts of their respective facing surfaces, provided
that there is not sufficient heat build-up to cause serious
15 loss of film strength in the cross-laminated ply. Generally,
the inner wall and cross-laminated outer ply are heat sealed
at and around all, or part of, their peripheries; these
being the principal heat seal areas. The arrangement and
positions of the heat seal areas will depend on the type of
20 shipping bag, and it is well within the skill ox the rut for
such areas to be identified.
While it is generally accepted that all polyethylene film
is generally uni-axially oriented to some degree, the term
"uni-axially oriented" when used with reference to
25 polyethylene in this specification and claims means
polyethylene film that has been blown and cold drawn to at
least a 2.5-fold extent, preferably to a 4-fold extent, but
also up to a 6-fold extent. The orienting and cross-
laminating of the films may be carried out according to
30 well-known methods.
A typical uni-axially oriented cross-laminated ply may
be made by extrudinc3 respective tubular haggle density

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- 10 - C-I-L 671
polyethylene or low density polyethylene film and cold
drawing this tubing down by a factor of four times in -the
machine direction to produce film with extremely high MD
tensile and To tear properties. The tubing is then
subsequently spirally split into sheeting whereby the film
orientation is typically at an angle of 45~ to the new web
machine direction. two sheets of this sheeting may then
be extrusion laminated with a thin layer of non-oriented
hlc3h density polyethylene or low density polyethylene as is
appropriate.
The cold drawn cross-laminated film may be made from low
density and high density polyethylene resins and blends
thereof, and can be used in a variety of thicknesses. One
particular blend of use in the practice of the invention
comprises linear low density and high density polyethylene
in the ratio of 9:1. Increasing the relative amount of
high density polyethylene in such a blend enhances the
puncture resistance and tensile strength of the film.
It is not necessary that all plies of the bag be made
of the same materials as those of use in the practice of the
invention. with the ability to introduce compatible but
dissimilar materials, specially designed awakes can ye produced
with plies allowing the packaging of fine powders, oil-bear.inc~
materials, materials that are hot at the point of packaging,
to
Thus, the bags according to the invention may also
comprise one or more plies formed of other thermoplastic
compatible packaging materials without detracting from the
principles of the invention.
lo Kit will be understood that the scope of the
invention as claimed also embraces those therrlloplastic backs

578

- 11 - C-I-L 671
wherein only a part of -the manufactured bag incorporates
the important and essential feature of the invention as
herein before set forth and wherein other parts of the bag
are joined in an alternative manner, for example, by hot
melt or adhesive bonding. The arrangement and positions of
those other parts joined in an alternative manner may be
readily selected by the skilled man.
A two-ply bag is the simplest embodiment of this
invention. However, in some instances it is advantageous to
have more than two inner plies of non-oriented film
constituting the inner layers of the bag, i.e., between the
front and back cross-laminated outer sides of the jag. An
example of this would be a bag of the simplest embodiment
with an additional thin true inner ply of linear low density
polyethylene in the form of a fine filter mesh to allow air
to be filtered from powdered products, as described in our
cop ending Canadian Application Serial No. 438,484, filed
October 6, 1983.
In other instances it may be preferred Jo have
additional plies of film outermost of the cross-laminatecl ply.
Such an outer ply could give the benefit resulting from
introducing blown low density polyethylene film between the
gusted surfaces of cross-laminated plies to give -the same
improvements in seal quality as created on the innermost
parts of the bag. The squarecl-off appearance of the final
packacJe resulting from this gusting improves its
performance for poulticing and stacking.
on additional benefit to be gained from such an outer
layer is tilt the surface can be suitably roughened my the
addition of high molecular weicJht granules to the film durinc3
Him extrusion; thus, imparting additional improved hanclliny
properties to the bag. As well, the inner surface of this
outer ply can be printed and the resulting message thus
I locked between plies to escape abrasion and distortion during

~2Z13~7~3

C-I-L 671
the handling of filled packages. It can readily be seen
that the utility of -this outer ply can be expanded by usinc3 a
laminate or coextrusion film to impart special properties
to the bag, i.e., oil barrier or grease resistant layers.
The utility of this invention thus lies in the fact
that by the introduction of a double layer of a non cold-
drawn low density polyethylene film between the mating
surfaces of two uni-axially oriented crisply polyethylene
Ellrns both open top and valved top type heavy duty shipping
bags, suitable for the packaging of expensive or hazardous
materials, can be reliably manufactured using commonly
available heat seal bag making equipment The resulting
heat seals induced by the technique according to the
invention have been found to have the strength required for
heavy-duty shipping bags.
Accordingly, in a further feature the invention
provides a thermoplastic shipping bag ox the open-top type
comprisinc3 a front side and a back side characterized in
that each of said front side and said back side comprises a
cross-laminated outer ply comprising at least two sheets of
uni-axially oriented polyethylene bonded together, and heat
sealed thereto, an inner wall wormed of low density
polyethylene.
An open-top shipping bay according to the invention may
be made by feeding a web of the uni-axially oriented cross-
laminated film in conjunction with an inner web of blown low
density polyethylene through commercial side-weld, heat
sealed or back scanned and bottom heat sealed bag maying
ecluipment-

One particularly useful type of thermoplastics shippinc3bag is that Nina as a valved bag. One SEIKO embodiment is
described in our United States Patent No. 3,833,166. These
bags possess the important commercial advantage of being
easily filled throucJh a valve structure with the sel~-closing

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of this valve structure after filling.
Accordingly, in a further feature the invention
provides a thermoplastic shipping bag of the valved bag type
comprising a front side and a back side joined together
around -the entire periphery of the bag and a filling aperture
characterized in that each of said front side and said back
side comprises a cross-laminated outer ply comprising at
least two sheets of uni-axially oriented polyethylene bonded
together, and heat sealed thereto, an inner wall formed of
low density polyethylene.
In a more preferred feature the invention provides a
thermoplastic valved bay of the type comprising a front side
and a back side joined together around -the entire periphery
lo of the bag, said front side consisting of a first panel and
a second panel, of greater combined width than the width of
said back side, said first panel at least partially
overlapping said second panel throughout the length of the
bag and said panels in their common axe being joined together
along a line substantially parallel with and at a distance
from one end of the bag, thus forming a tubular self-closing
filling sleeve having inner and outer walls and extending
transversely of the bag adjacent to said one end thereof,
with said first panel forming -the outer wall and said second
panel forming the inner wall of said filling sleeve, and
being also joined together along at least one line extending
from said first-mentioned line substantially to the
opposite end of the bag, said second panel consisting ox at
Least two plies that are non-coextensive with each other so
that at least the inner end portion of the inner wall of
said filling sleeve is formed of a number of plies that is
less than the total number of plies in said second panel,
characterized in that each of said frorlt side and said back
stale comprises a cr4ss-laminated outer ply comprising at
least two sheets of uni-axially oriented polyethylene bonder

I

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together, and heat sealed thereto, an inner wall formed of
low density polyethylene.
In a further feature the invention provides a thermos
plastic material suitably for use in a heavy duty shipping
bay which Material comprises a laminate of at least two sheets
of uni-axially oriented polyethylene bonded together, and a
sheet of low density polyethylene of at least 0.5 mix
thickness bonded thereto.
Preferably the sheet of low density polyethylene is at
least 1.5 mix thick and the uni-axially oriented polyethylene
is low density polyethylene, more preferably linear low
density polyethylene and yet more preferably high density
polyethylene.
Several embodiments of this invention will now be more
particularly described by way of example only with reference
to the accompanying drawings, in which:
Figure 1 it a front elevation Al view of an open-top bag
according to the invention;
Figure 2 is a sectional view along line II-II of Figure l;
Figure 3 is a front elevation Al view of a valved bag
according to the invention;
Figure 4 is a sectional view along the line IV-IV of
Figure 3;
Figure 5 is a diagrammatic view of a section through a heat
seal as herein before defined of use in the practice of
the invention;
Flyer 6 us a cross-sectional view of a preferrer laminate
of a thermoplastic material according to the invention,
Figures 1 and 2 show a generally rectangular two-ply
pillow-type bag 1 having an inner wall 2 formed of blown
linear low density polyethylene film I mill manufactured
fl-om'~045"1inear low density polyethylene resin tow Chemical
Co.), and an outer ply 3 ~3.5 mill of uni-axially oriented
cross-laminated linear low density polyethylene film,

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commercially available under the trade mark "VA~ERON"*.
The bag 1 has thus a two-ply back wall 4, and à two-
ply front wall 5 made up of first and second partially
overlapping panels 6 and 7. The outer ply 3 of back wall 4
is continuous with the outer wall 3 of front wall 5 except
where separated and joined together by heat sealing with
layer 2 in the overlapping panels 6 and 7. Thus, the walls 4
and 5 are integral and form a two-ply tube. One end of the
tube 8 is heat sealed to form a simple two-ply open-top bag.
The bag was made by feeding a web of 37" film 3 into a
longitudinal folding frame with a web of film 2 and foxing
a two-ply tube 18" wide with a 1" overlapping portion. The
four plies of the overlapping area were then heat sealed
longitudinally to consolidate the two-ply tubing which was
then passed to a transverse heat seal unit which made the
bottom seal 8. A 26" length of tube with the heat seal
present was cut from the web by a guillotine to form the
open top bag 1.
To test the strength of the heat seals, the bag 1 was
filled with 5C pounds of granular salt, heat sealed at its
open end by a "Dough Betty sealer, and drop tested on
each side, edge and butt from a height of 10 feet. There
was no rupture of any film or seal The open top of the
bag is generally heat sealed after filling with product to
produce an airtight and watertight package. Because it is
extremely difficult to exclude all air from the filled
package prior to the heat sealing operation, it it preferable
to perforate the walls of the bags with pinholes typically
0.025" in diameter to facilitate air release, the number of
holes required depending on the amount of air left in the bag
and the type of product being packaged. In those cases where
it is critical that the package retains its maximum value for
air tightness and moisture protection, the perforation holes
in the inner and outer plies are offset typically by I to
* trade mark

A

I

C-I-L 671
create an indirect path to air product mixes during the
venting period.
Although the inner ply 2 of the bag is described as a
single ply of sheeting it can be readily appreciated that
a two-ply tube of 1.5 mix could also be used instead. Indeed
ions tubing may be less expensive to manufacture the tube
could be a preferred option. Again, although the outer wall
is described as a linear low density polyethylene cross-
laminated film, high density polyethylene cross-laminated
film would be the preferred embodiment for applications where
extra heat resistance is required of -the package.
Egress 3 and 4 show a generally rectangular three-
ply pillow type bag lo having a front side 11 and a back side
12 joined together around the entire periphery of the bag.
Front side if consists of an inner wall 13 and an outer wall
14 formed of blown linear low density polyethylene (3 mix),
and a middle wall 15 of uni-axially oriented cross-laminated
linear low density polyethylene illume (3.5 molehill' Dow
Chemical Carson. sack side 12 is of an identical
construction.
Front side if has partially overlapping panels 16 and
17 heat sealed together loncJitudinally to form a three-ply
tube open only to form a self-closing filling sleeve 18~ The
tube is 'neat sealed at both ends lo to form a complete
valved back of the type illustrated in our tJnited States
Patent Noah. In the embodiment shown the bag has its
lateral edges 20 tucked in and heat sealed in the longitudinal
region 21 through twelve layers of film.
to will be noted that in all the heat seal arias the
uni-axially oriented cross-laminat~d film is never sealed to
itself but always has a double layer of non-oriented film
between mating sell surfaces oven in the twelveh-ply heat seal
ureas 19.
It is, of killers, desirable to have this tuckèd~in

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multiple seal area to give the filled bag a squared
configuration.
Again, it will be appreciated that tubing could be
substituted for sheeting in layers 13 and 14.
Besides the advantage of allowing the bag to be gusset
sealed, the outer ply can be reverse printed to jock the
print between plies I and 15 to protect it from abrasion in
transit. Additionally, a small amount (0.5~) of 40 mesh high
Lo molecular wicket high density polyethylene resin can be
incorporated in layer 14 during extrusion to produce a
pebbled surface to confer excellent handling properties on
the filled bags.
Figure 5 shows a polyethylene heat seal in a bag loaded
with product wherein the seal is under tension due to the
product acting in a manner tending to separate the plies.
The figure shows a polyethylene heat seal mass 50 resulting
from the fusion of part of the two oriented high density
polyethylene films 51 and the two non-oriented linear low
density polyethylene films 52. Integral with heat seal mass
50 at heat seal margin 54 are laminated seals 54, extending
along each of the two adjacent plies 51 and 52. There is
a relatively minor lamination seal 55 between the two plies
52.
The presence of the laminated seal integral with the
heat seal can be accomplished by the application of a
gradient heat seal bar unit to the films whereby the
lamination is effected at the same time as the heat seal.
Alternatively, it can be accomplished in a two stuck operation
wherein a laminated seal is first made, typically of a 1"
width, by joining the plies at a temperature lower than the
malting point of the cross laminated polyethylene (to prevent
destruction of the orientation), typically, 240F.
Subsequently, a side weld heat seal is made through the
laminated section by the application of temperature and

So

- 18 - C-I-L 671
pressure.
Figure 6 shows a laminate 110 of oriented high density
polyethylene sheets 111 and 112, each of 1.5 mix thickness,
extrusion laminated together in which -the direction of
orientation in the two sheets form a right angle to each
other. Laminated sealed to laminate 110 by extrusion
lamination is a linear low density polyethylene sheet 113,
(0.25 mix).
It is preferred that the low density polyethylene in
contact with the cross laminated ply has as low a melting
joint as possible and be as fluid as possible when melted.
'Issue characteristics are generally achieved using low density
polyethylene polymers with relatively low tensile yield
strength. It is, therefore, desirable that the inner layer
of the two-ply structure be a coextrusion with only a thin
layer, typically 0.25 mix thick, of low melt temperature,
high melt index film on the layer in direct contact with the
cross laminated film.
We have found that the thickness of the inner layers of
low density polyethylene required to produce an acceptable
heat seal will depend greatly on the elasticity of the cross
amount film to be used, i.e. the less elastic the cross
laminate film the thicker the low density polyethylene film
must be. Relative thicknesses of all the polyethylene
layers can be readily determined by the skilled man

Representative Drawing

Sorry, the representative drawing for patent document number 1228578 was not found.

Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date 1987-10-27
(22) Filed 1984-04-02
(45) Issued 1987-10-27
Expired 2004-10-27

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $0.00 1984-04-02
Registration of a document - section 124 $100.00 1997-05-22
Registration of a document - section 124 $100.00 1998-08-12
Registration of a document - section 124 $100.00 2002-02-07
Registration of a document - section 124 $100.00 2004-10-13
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
SMURFIT-STONE CONTAINER CANADA INC.
Past Owners on Record
AT PLASTICS INC.
HARRISON, RAY E.
MURRAY, CHARLES R.
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
Documents

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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Drawings 1993-09-27 2 69
Claims 1993-09-27 1 36
Abstract 1993-09-27 1 9
Cover Page 1993-09-27 1 14
Description 1993-09-27 18 854
Assignment 2002-02-07 19 803
Correspondence 2002-04-16 1 28