U.S. patent application number 10/845988 was filed with the patent office on 2005-11-17 for easy-open handle bag for medium to heavy duty applications.
This patent application is currently assigned to Curwood, Inc.. Invention is credited to Berbert, Otacilio Teixeira, Fuller, Scott A..
Application Number | 20050254731 10/845988 |
Document ID | / |
Family ID | 34941287 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050254731 |
Kind Code |
A1 |
Berbert, Otacilio Teixeira ;
et al. |
November 17, 2005 |
Easy-open handle bag for medium to heavy duty applications
Abstract
A bag for carrying medium to heavy loads comprising a body
formed from a flexible thermoplastic film, such that the body
comprises a first panel and an opposing second panel, a receptacle
cavity formed the first and second panels, an integral handle
opening, and an easy-open feature which extends longitudinally from
a top seal to an opposing bottom seal and positioned adjacent to a
first side seal of the body. The easy-open feature comprises at
least one of (i) at least one line of structural weakness in the
thermoplastic film, (ii) a reclosable fastener adhered to the
thermoplastic film, or (iii) a combination of (i) and (ii).
Inventors: |
Berbert, Otacilio Teixeira;
(Oshkosh, WI) ; Fuller, Scott A.; (Oshkosh,
WI) |
Correspondence
Address: |
BEMIS COMPANY, INC.
2200 BADGER AVENUE
OSHKOSH
WI
54904
US
|
Assignee: |
Curwood, Inc.
|
Family ID: |
34941287 |
Appl. No.: |
10/845988 |
Filed: |
May 14, 2004 |
Current U.S.
Class: |
383/7 ; 383/120;
383/203; 383/204; 383/37; 383/61.2; 383/63; 383/64; 383/66 |
Current CPC
Class: |
B65D 33/08 20130101;
B65D 33/2591 20130101; B65D 75/5805 20130101 |
Class at
Publication: |
383/007 ;
383/066; 383/203; 383/204; 383/061.2; 383/120; 383/063; 383/064;
383/037 |
International
Class: |
B65D 033/10 |
Claims
What is claimed is:
1. A flexible bag for medium to heavy duty packaging applications
comprising: (a) a body formed from a thermoplastic film which has
an inner surface and an outer surface relative to said bag, wherein
said body comprises: (i) a first panel; (ii) a second panel
opposite said first panel; (iii) wherein said first panel and said
second panel each have a perimeter having a first peripheral side
edge and an opposing second peripheral side edge, connected by a
peripheral top edge, and an opposing peripheral bottom edge; (b) a
plurality of seals which joins said first panel to said second
panel, wherein said plurality of seals comprises at least a first
side seal, a first top seal and an opposing bottom seal, wherein
said plurality of seals are connected to form a seal perimeter
between said first panel and said second panel; (c) a receptacle
cavity formed between said front panel and said rear panel and
delimited by said seal perimeter; (d) an integral handle opening
which extends transversely across said bag from said first
peripheral side edge to said opposing second peripheral side edge
of said perimeter of both said first panel or said panel; and (e)
an easy-open feature which extends longitudinally from said first
top seal to said opposing bottom seal in either of said first panel
or said second panel and is positioned adjacent to one of said
peripheral side edges of either said first panel or said second
panel; wherein said easy-open feature comprises at least one of:
(i) at least one line of structural weakness in either said inner
surface or said outer surface of said thermoplastic film, (ii) a
reclosable fastener affixed to said inner surface of said
thermoplastic film, (iii) a combination of (i) at least one line of
structural weakness in either said inner surface or said outer
surface of said thermoplastic film and (ii) a reclosable fastener
affixed to said inner surface of said thermoplastic film.
2. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said thermoplastic film
has an unrestrained linear thermal shrinkage in both the machine
direction and transverse direction of between 0-10% at 85.degree.
C. as measured in accordance with ASTM D-2732-96.
3. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said thermoplastic film
has a minimum tensile strength at break in the machine direction of
at least 3000 psi (2.times.10.sup.7 N/m.sup.2) as measured at a
rate of 12 inch/min. (30.5 cm/min.) in accordance with ASTM
D-882.
4. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said thermoplastic film
has a maximum elongation at break in the machine direction of
between 0-150% as measured at a rate of 12 inch/min. (30.5 cm/min.)
in accordance with ASTM D-882.
5. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said thermoplastic film
has a total thickness of between 2.0-7.0 mils (0.005-0.018 cm).
6. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said thermoplastic film
is a multilayer thermoplastic film.
7. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 6, wherein said multilayer
thermoplastic film comprises at least: (a) a first polymer layer;
(b) a second polymer layer; (c) a third polymer layer; and (d)
wherein said second polymer layer is positioned between said first
polymer layer and said third polymer layer.
8. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 7, wherein said first polymer layer
comprises a material selected from the group consisting of
polyester, polyamide, polyolefin and blends thereof.
9. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 8, wherein said first polymer layer
comprises a material selected from the group consisting of
polyester terephthalate, polyamide, polypropylene and blends
thereof.
10. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 9, wherein said first polymer layer
comprises either a biaxially-oriented polyester terephthalate or a
biaxially-oriented polyamide.
11. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 7, wherein said second polymer
layer comprises an adhesive material.
12. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 7, wherein said third polymer layer
comprises of a sealant material.
13. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said plurality of seals
further comprises a second top seal which is parallel to said first
top seal and positioned below said integral handle opening.
14. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said plurality of seals
further comprises a second side seal opposite said first side
seal.
15. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said body further
comprises: (a) a first side gusset; and (b) a second side gusset
opposite said first side gusset.
16. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said bag further
comprises a tear-initiation feature.
17. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said reclosable fastener
comprises a first interlocking member and a second interlocking
member.
18. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 17, wherein said first interlocking
member and second interlocking member each have an attachment
flange.
19. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said reclosable fastener
further comprises a slider device.
20. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said integral handle
opening is formed in a reinforced portion of both said first panel
and second panel.
21. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 1, wherein said bag further
comprises at least one removable thermoplastic inner package
disposed within and separate from said bag.
22. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 21, wherein said at least one
removable thermoplastic inner package comprises a freezer storage
package.
23. A flexible bag for medium to heavy duty packaging applications
comprising: (a) a body formed from a multilayer thermoplastic film
which has an inner surface and an outer surface relative to said
bag, wherein said body comprises: (i) a first panel; (ii) a second
panel opposing said first panel; (iii) wherein said first panel and
said second panel each have a perimeter having a first peripheral
side edge and an opposing second peripheral side edge, connected by
a peripheral top edge, and an opposing peripheral bottom edge; (b)
a plurality of seals which joins said first panel to said second
panel, wherein said plurality of seals comprises at least a first
side seal, a first top seal, and an opposing bottom seal, wherein
said plurality of seals are connected to form a seal perimeter
between said first panel and said second panel; (c) a receptacle
cavity formed between said front panel and said rear panel and
delimited by said seal perimeter; (d) an integral handle opening
which extends transversely across said bag from said first
peripheral side edge to said opposing second peripheral side edge
of said perimeter of both said first panel and said second panel;
(e) an easy-open feature which extends longitudinally from said
first top seal to said opposing bottom seal in either said first
panel or said second panel and is positioned adjacent to one of
said peripheral side edges of either said first panel or said
second panel, wherein said easy-open feature comprises at least one
of: (i) at least one line of structural weakness in either said
inner surface or said outer surface of said multilayer
thermoplastic film, (ii) a reclosable fastener affixed to said
inner surface of said multilayer thermoplastic film, (iii) a
combination of (i) at least one line of structural weakness in
either said inner surface or said outer surface of said multilayer
thermoplastic film and (ii) a reclosable fastener affixed to said
inner surface of said multilayer thermoplastic film; and (f)
wherein said multilayer thermoplastic film has a minimum tensile
strength at break in the machine direction of at least 3000 psi
(2.times.10.sup.7 N/m.sup.2) as measured at a rate of 12 inch/min.
(30.5 cm/min.) in accordance with ASTM D-882 and comprises: (i) a
first polymer layer of a material selected from the group
consisting of polyester, polyamide, polyolefin and blends thereof;
(ii) a second polymer layer of an adhesive material; (iii) a third
polymer layer of a sealant material; and (iv) wherein said second
polymer layer is positioned between said first polymer layer and
said third polymer layer.
24. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said thermoplastic film
has a maximum elongation at break in the machine direction of
between 0-150% as measured at a rate of 12 inch/min. (30.5 cm/min.)
in accordance with ASTM D-882.
25. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said multilayer
thermoplastic film has an unrestrained linear thermal shrinkage in
both the machine direction and transverse direction of between
0-10% at 85.degree. C. as measured in accordance with ASTM
D-2732-96.
26. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said first polymer
layer comprises a material selected from the group consisting of
polyester terephthalate, polyamide, polypropylene and blends
thereof.
27. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 26, wherein said first polymer
layer comprises either a biaxially-oriented polyester terephthalate
or a biaxially-oriented polyamide.
28. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said second polymer
layer comprises an adhesive material.
29. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said third polymer
layer comprises of a sealant material.
30. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said plurality of seals
further comprises a second top seal which is parallel to said first
top seal and positioned below said integral handle opening.
31. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said plurality of seals
further comprises a second side seal opposite said first side
seal.
32. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said bag further
comprises a tear-initiation feature.
33. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said reclosable
fastener comprises a first interlocking member and a second
interlocking member.
34. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 33, wherein said first interlocking
member and second interlocking member each have an attachment
flange.
35. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said reclosable
fastener further comprises a slider device.
36. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said integral handle
opening is formed in a reinforced portion of both said first panel
and second panel.
37. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said bag further
comprises at least one removable thermoplastic inner package
disposed within and separate from said bag.
38. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 37, wherein said at least one
removable thermoplastic inner package comprises a freezer storage
package.
39. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 23, wherein said body further
comprises: (a) a first side gusset; and (b) a second side gusset
opposite said first side gusset.
40. A flexible bag for medium to heavy duty packaging applications
comprising: (a) a body formed from a multilayer thermoplastic film
which has an inner surface and an outer surface relative to said
bag, wherein said body comprises: (i) a first panel; (ii) a second
panel opposing said first panel; (iii) wherein said first panel and
said second panel each have a perimeter having a first peripheral
side edge and an opposing second peripheral side edge, connected by
a peripheral top edge, and an opposing peripheral bottom edge; (iv)
a first side gusset; (v) a second side gusset opposite said first
side gusset; (b) a plurality of seals which joins said first panel
to said second panel, wherein said plurality of seals comprises at
least a first side seal, a top seal, and an opposing bottom seal,
wherein said plurality of seals are connected to form a seal
perimeter between said first panel and said second panel; (c) a
receptacle cavity formed between said front panel and said rear
panel and delimited by said seal perimeter; (d) an integral handle
opening which extends transversely across said bag from said first
peripheral side edge to said opposing second peripheral side edge
of said perimeter of both said first panel and said second panel;
(e) an easy-open feature which extends longitudinally from said
first top seal to said opposing bottom seal in either said first
panel or said second panel and is positioned adjacent to one of
said peripheral side edges of either said first panel or said
second panel, wherein said easy-open feature comprises at least one
of: (i) at least one line of structural weakness in either said
inner surface or said outer surface of said multilayer
thermoplastic film, (ii) a reclosable fastener affixed to said
inner surface of said multilayer thermoplastic film, (iii) a
combination of (i) at least one line of structural weakness in
either said inner surface or said outer surface of said multilayer
thermoplastic film and (ii) a reclosable fastener affixed to said
inner surface of said multilayer thermoplastic film; and (f)
wherein said multilayer thermoplastic film has a minimum tensile
strength at Break in the machine direction of at least 3000 psi
(2.times.10.sup.7 N/m.sup.2) as measured at a rate of 12 inch/min.
(30.5 cm/min.) in accordance with ASTM D-882 and comprises: (i) a
first polymer layer comprises a material selected from the group
consisting of polyester terephthalate, polyamide, polypropylene and
blends thereof; (ii) a second polymer layer of an adhesive
material; (iii) a third polymer layer of a sealant material; and
(iv) wherein said second polymer layer is positioned between said
first polymer layer and said third polymer layer.
41. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said thermoplastic film
has a maximum elongation at break in the machine direction of
between 0-150% as measured at a rate of 12 inch/min. (30.5 cm/min.)
in accordance with ASTM D-882.
42. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said multilayer
thermoplastic film has an unrestrained linear thermal shrinkage in
both the machine direction and transverse direction of between
0-10% at 85.degree. C. as measured in accordance with ASTM
D-2732-96.
43. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said plurality of seals
further comprises a second top seal which is parallel to said first
top seal and positioned below said integral handle opening.
44. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said first polymer
layer comprises either a biaxially-oriented polyester terephthalate
or a biaxially-oriented polyamide.
45. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said bag further
comprises a tear-initiation feature.
46. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said reclosable
fastener comprises a first interlocking member and a second
interlocking member.
47. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 46, wherein said first interlocking
member and second interlocking member each have an attachment
flange.
48. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said reclosable
fastener further comprises a slider device.
49. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said integral handle
opening is formed in a reinforced portion of both said first panel
and second panel.
50. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 40, wherein said bag further
comprises at least one removable thermoplastic inner package
disposed within and separate from said bag.
51. A flexible thermoplastic bag for medium to heavy duty packaging
applications according to claim 50, wherein said at least one
removable thermoplastic inner package comprises a freezer storage
package.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to thermoplastic
handle bags suitable for storing and transporting medium to heavy
loads, e.g., frozen foods such as chickens, turkeys, and the like
comprising an easy-open feature, and more particularly, to
thermoplastic handle bags having an easy-open feature adapted for
the removal of large or bulky medium to heavy loads contained
therein.
[0002] Thermoplastic bags having a handle opening and/or an
easy-open feature which support heavy granulated items such as salt
pellets, pet food, fertilizer, etc. are known in the art. U.S. Pat.
No. 6,231,232 to Warr is directed to synthetic bags primarily for
granulated contents which are capable of carrying loads of from 10
to 50 pounds and which include a hand-insertion slit below the top
seal of the bag that may serve as a handle. U.S. Pat. Nos.
5,482,376 and 5,601,369, both to Moseley et al. also disclose bags
adapted to hold pourable contents from 20 to 150 pounds. These bags
include a handle which is either attached or formed from the bag
and further disclose a curved line of perforations in the corner
portion of the bag which permits easy opening of the bag. U.S. Pat.
Nos. 5,482,376 and 5,601,369 both to Warr further disclose
thermoplastic bags designed for heavy-duty applications which
include a die-cut handle opening similar to that described in U.S.
Pat. No. 6,231,232 and an easy-open feature which comprises a line
of perforations which extends from the top edge to the side edge at
the corner of the bag. While these bags are capable of carrying
medium to heavy load and are easy to open, they are not suitable
for large or bulky items contained therein which require a
different means of removal from the package.
[0003] It is also known in the art that flexible bags may include
both a handle and an opening zone in the side of the package which
facilitates in the removal of bulky items contained therein. U.S.
Pat. No. 4,966,286 to Muckenfuhs; U.S. Pat. No. 5,036,978 to Frank
et al. and U.S. Pat. No. 5,054,619 to Muckenfuhs describe
thermoplastic packages which are suitable for storing and
transporting compressed flexible articles, such as disposable
absorbent products, e.g., diapers, bandages, sanitary napkins and
the like. These packages have a carrying handle and an easy-open
feature which consists of one or more arcuate lines of weakness in
a side panel or gusset of the bag. While these bags allow for easy
removal of relatively bulky contents, they will neither separately
support medium to heavy loads nor will the perforated tear lines of
the easy-open feature resist tearing or bursting during
transportation or storage of medium to heavy loads.
SUMMARY OF THE INVENTION
[0004] The present invention provides flexible bags that resists
tearing or bursting during the storage and transportation of medium
to heavy duty loads which may range in weight from about five
pounds to about fifty pounds or more. The present invention also
provides flexible bags formed from thermoplastic films which
include a handle opening and an easy-open feature. The present
invention further provides flexible bags suitable for supporting
medium to heavy duty loads which include an easy-open feature
suitable for removing large or bulky items contained therein.
[0005] Accordingly, one aspect of the present invention is directed
to flexible bags for medium to heavy duty packaging applications
which have a body formed from a thermoplastic film having an inner
surface and an outer surface relative to the bag. Preferably, the
flexible bags include a body formed from a thermoplastic film
having an unrestrained linear thermal shrinkage in both the machine
direction and the transverse direction of between 0-10% at
85.degree. C. as measured in accordance with ASTM D-2732-96, which
is hereby incorporated, in its entirety, by reference thereto.
Preferably, the thermoplastic film has a minimum tensile strength
at break in the machine direction of at least 3000 psi
(2.times.10.sup.7 N/m.sup.2) as measure at a rate of 12 inch/min.
(30.5 cm/min.) in accordance with ASTM D-882, which is hereby
incorporated, in its entirety, by reference thereto. Preferably,
the thermoplastic film has a maximum elongation at break in the
machine direction of between 0-150% as measure at a rate of 12
inch/min. (30.5 cm/min.) in accordance with ASTM D-882, which is
hereby incorporated, in its entirety, by reference thereto.
Preferably, the film has a total thickness of from about 2.0 to 7.0
mils (0.005 to 0.018 cm). Although the thermoplastic film may be a
monolayer film or a multilayer film, preferably the film is a
multilayer film. Preferably, the film is a multilayer film
comprising at least a first polymer layer, a second polymer layer,
and a third polymer layer. The first polymer layer of the
thermoplastic multilayer film comprises a material selected from
the group consisting of polyester, polyamide, polyolefin or blends
thereof, preferably, a material selected from the group consisting
of polyester terephthalate, polyamide, polypropylene or blends
thereof, and most preferably, either a biaxially-oriented polyester
terephthalate or a biaxially-oriented polyamide. The second polymer
layer of the thermoplastic multilayer film comprises an adhesive
material. The third polymer layer of the thermoplastic multilayer
film comprises a sealant material. Preferably, the second polymer
layer is directly adhered to the first and third polymer layer. For
certain packaging applications, it may be beneficial to include the
three-layer thermoplastic film as a substructure in a larger
multilayer flexible film in forming the body of a bag. In such a
configuration, the larger multilayer film incorporating three-layer
structure as a substructure may advantageously possess properties
and benefits resulting from the three-layer structure as discussed
herein, but may also possess additional properties and benefits
arising from the additional layers. Larger multilayer film
structures which incorporate three-layer structure as a
substructure may have at least one additional layer adhered to this
substructure by various methods known to those skilled in the art
which include thermal lamination, adhesive lamination, coextrusion
coating, coextrusion lamination.
[0006] The present invention is also directed to bags which include
a first panel and a second panel where each of the panels have a
perimeter which includes a first peripheral side edge and an
opposing second peripheral side edge, connected by a peripheral top
edge and an opposing peripheral bottom edge. The body also includes
a plurality of seals which joins the first panel to the second
panel. In one embodiment of the present invention, the plurality of
seals include a first side seal, a first top seal and an opposing
bottom seal. The first side seal, first top seal and opposing
bottom seal can be connected together to form a seal perimeter
between the first and second panels. Alternatively, the plurality
of seals may further include a first side seal and an opposing
second side seal, a first top seal and an opposing bottom seal. In
this regard, the first side seal and opposing second side seal, the
first top seal and opposing bottom seal can be connected together
to form a seal perimeter. In another embodiment, the plurality of
seals may still further include a first side seal and an opposing
second side seal, a first top seal, a second top seal and an
opposing bottom seal. Preferably, the second top seal is parallel
with the first top seal and positioned below the handle opening of
the bag extending transversely across the bag from the first
peripheral side edge to the second peripheral side edge. In this
particular embodiment, the first side seal and opposing second side
seal, the second top seal and opposing bottom seal can be connected
together to form a seal perimeter. The body of the bags are
provided with a receptacle cavity which is formed between the first
and second panels and defined by the seal perimeter. While the
flexible bags of the present invention need not necessarily include
side gussets, for some applications it may be beneficial to include
at least one of: a first side gusset and a second side gusset, a
bottom gusset, or a first side gusset, a second side gusset and a
bottom gusset.
[0007] As a second aspect, the present invention is directed to
flexible bags for medium to heavy duty packaging applications which
include an integral handle opening. The integral handle opening is
disposed in a pre-determined area below the peripheral top edge and
extends transversely across the bag from a first peripheral side
edge to a second peripheral side edge. The integral handle opening
may be formed in the first and second panels of the body of the bag
as either a hole, slit, cut and the like. Preferably, the
pre-determined area in the first panel and the second panel is a
reinforced portion of the body of the bag.
[0008] As a third aspect, the present invention is directed to
flexible bags for medium to heavy duty packaging applications
having an easy-open feature adapted such that large and/or bulky
items may be easily removed from the receptacle cavity of the bag.
Examples of large or bulky items include, but are not limited to,
fresh or frozen meat and poultry, such as turkey, chicken, duck and
the like. The easy-open feature extends longitudinally from the
peripheral top edge to the peripheral bottom edge in either the
first panel or the second panel and is positioned adjacent to
either the first peripheral side edge or the second peripheral side
edge of the body of the bag.
[0009] In one embodiment of the invention, the easy-open feature
may include at least one line of structural weakness in either the
inner surface or the outer surface of the thermoplastic film.
Preferably, the at least one line of structural weakness further
includes a tear-initiation feature. A tear-initiation feature may
be formed as a cut, notch or surface-roughening area and the like,
in the external surface of film positioned above the at least one
line of structural weakness. In this regard, the bag can be easily
opened by a relatively weak manual force at the tear-initiation
feature and in combination with the at least one line of structural
weakness obviating the need to cut the bag with a knife, scissors
or any other sharp implement.
[0010] Alternatively, the easy-open feature may be provided as a
reclosable fastener attached to the inner surface of the
thermoplastic film forming the body of the bag. Suitable reclosable
fastener, in general, are known and are taught, for example, in
U.S. Pat. Nos. 5,063,644; 5,301,394; 5,442,837; 5,964,532;
6,409,384; 6,439,770; 6,524,002; 6,527,444; 6,609,827; 6,616,333;
6,632,021; 6,663,283; 6,666,580; 6,679,027; and U.S. patent
application Nos. 2002/0097923; and 2002/0196987, each of which is
incorporated by reference herein.
[0011] Preferably, the reclosable fastener comprises a first
interlocking member and a second interlocking member. Preferably,
the first and second interlocking members each have an attachment
flange for securing each member to the inner surface of the
thermoplastic film forming the body of the bag. Preferably, the
reclosable fastener further comprises a slider device which
facilitates the manual operation of the fastener by engaging and
dis-engaging the first interlocking member with the second
interlocking member.
[0012] In another embodiment, the easy-open feature may include a
combination of both the at least one line of structural weakness in
either the inner surface or the outer surface of the thermoplastic
film and the reclosable fastener attached to the inner surface of
the thermoplastic film.
[0013] The present invention is also directed to flexible bags for
medium to heavy duty packaging applications which further comprises
at least one removable thermoplastic inner package disposed within
and separate from the bag. Preferably, the at least one removable
thermoplastic inner package comprises a freezer storage
package.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a partially schematic, front plan view of one
embodiment of a flexible bag according to the present invention
showing one example of an easy-open feature.
[0015] FIG. 2 is a partially schematic, front plan view of an
alternative embodiment of a flexible bag according to the present
invention showing another example of an easy-open feature.
[0016] FIG. 3 is a partially schematic, front plan view of still
another embodiment of a flexible bag according to the present
invention having an easy-open feature similar to that depicted in
FIG. 1.
[0017] FIG. 4 is a cross-sectional view of a thermoplastic film
which forms the body of the flexible bags according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] As used herein, the term "multilayer" refers to a plurality
of layers in a single film structure generally in the form of a
sheet or web which can be made from a polymer material or a
non-polymer material bonded together by any conventional means
known in the art, i.e., coextrusion, extrusion coating, and
lamination, vacuum vapor deposition coating, solvent coating,
emulsion coating, or suspension coating or combination of one or
more thereof. The multilayer film of the present invention may
include as many layers as desired, preferably, at least three
polymer layers.
[0019] As used herein, the phrase "thermoplastic" refers to a
polymer or polymer mixture that softens when exposed to heat and
returns to its original condition when cooled to room temperature.
In general, thermoplastic materials include, but are not limited
too, synthetic polymers such as polyamides, polyolefins, polyalkyl
acrylates, polyesters, ethylene/vinyl alcohol copolymers, and the
like. Thermoplastic materials may also include any synthetic
polymer that are cross-linked by either radiation or chemical
reaction during a manufacturing process operation.
[0020] As used herein, the term "polymer" refers to the product of
a polymerization reaction, and is inclusive of homopolymers,
copolymers, terpolymers, etc. In general, the layers of a film can
consist essentially of a single polymer, or can have still
additional polymers together therewith, i.e., blended
therewith.
[0021] As used herein, the term "copolymer" refers to polymers
formed by the polymerization of reaction of at least two different
monomers. For example, the term "copolymer" includes the
co-polymerization reaction product of ethylene and an
.alpha.-olefin, such as 1-hexene. The term "copolymer" is also
inclusive of, for example, the co-polymerization of a mixture of
ethylene, propylene, 1-propene, 1-butene, 1-hexene, and 1-octene.
As used herein, a copolymer identified in terms of a plurality of
monomers, e.g., "propylene/ethylene copolymer", refers to a
copolymer in which either monomer may copolymerize in a higher
weight or molar percent than the other monomer or monomers.
However, the first listed monomer preferably polymerizes in a
higher weight percent than the second listed monomer.
[0022] As used herein, the term "extrusion" refers to the process
of forming continuous shapes by forcing a molten polymeric material
through a die, followed by cooling.
[0023] As used herein, the term "coextrusion" refers to the process
by which the outputs of tow or more extruders are brought smoothly
together in a feed block, to form a multilayer molten mixture that
is fed to a die to produce a layered extrudate. Coextrusion can be
employed in film blowing, sheet and flat film extrusion, blow
molding, and extrusion coating.
[0024] As used herein, the term "biaxially-oriented" refers to a
polymer web which forms a film structure in which the web has been
elongated in two directions at elevated temperatures followed by
being "set" in the elongated configuration by cooling the material
while substantially retaining the elongated dimensions. This
combination of elongation at elevated temperature followed by
cooling causes an alignment of the polymer chains to a more
parallel configuration, thereby improving the mechanical properties
of the polymer web. Upon subsequently heating of certain
unrestrained, unannealed, biaxially-oriented sheet of polymer to
its orientation temperature, heat-shrinkage may be produced.
Following orientation, the biaxially-oriented polymer web is
preferably cooled and then heated to an elevated temperature, most
preferably to an elevated temperature which is above the glass
transition temperature and below the crystalline melting point of
the polymer. This reheating step, which may be referred to as
annealing or heat setting, is performed in order to provide a
polymer web of uniform flat width. In accordance with the present
invention, the biaxially-oriented polymer web may be used to form a
film layer is heated to an elevated temperature in order to provide
a packaging film with an unrestrained linear thermal shrinkage in
the machine direction of between 0-10% at 85.degree. C. as measured
in accordance with ASTM D-2732-96 test method, which is
incorporated herein by reference.
[0025] As used herein, the terms "joins" or "joining" are used in
its broad sense to mean either two formerly separate sheets
connected together, or integrally formed by, for example, folding
over a film or laminate to define an edge.
[0026] As used herein, the phrase "machine direction" refers to a
direction "along the length" of the film, i.e., in the longitudinal
direction the film is formed during extrusion. In contrast, the
"transverse direction" refers to the direction across the film or
perpendicular to the machine direction.
[0027] As used herein, terminology employing a "/" with respect to
the chemical identity of a copolymer (e.g., polyvinylidene
chloride/methyl acrylate copolymer), identifies the comonomers
which are copolymerized to produce the copolymer.
[0028] As used herein, the term "polyester" refers to homopolymers
or copolymers having an ester linkage between monomer units which
may be formed, for example, by condensation polymerization
reactions between a dicarboxylic acid and a glycol. The
dicarboxylic acid may be linear or aliphatic, i.e., oxalic acid,
malonic acid, succinic acid, glutaric acid, adipic acid, pimelic
acid, suberic acid, azelaic acid, sebacic acid, and the like; or
may be aromatic or alkyl substituted aromatic, i.e., various
isomers of phthalic acid, such as paraphthalic acid (or
terephthalic acid), isophthalic acid and naphthalic acid. Specific
examples of alkyl substituted aromatic acids include the various
isomers of dimethylphthalic acid, such as dimethylisophthalic acid,
dimethylorthophthalic acid, dimethylterephthalic acid, the various
isomers of diethylphthalic acid, such as diethylisophthalic acid,
diethylorthophthalic acid, the various isomers of
dimethylnaphthalic acid, such as 2,6-dimethylnaphthalic acid and
2,5-dimethylnaphthalic acid, and the various isomers of
diethylnaphthalic acid. The glycols may be straight-chained or
branched. Specific examples include ethylene glycol, propylene
glycol, trimethylene glycol, 1,4-butane diol, neopentyl glycol and
the like. In one example a preferred embodiment of this invention,
the first layer comprises polyethylene terephthalate copolymer and
most preferable, biaxially-oriented polyethylene terephthalate
copolymer.
[0029] As used herein, the term "adhesive" refers to a polymer
material serving a primary purpose or function of adhering two
surfaces to one another. In the present invention, the adhesive may
adhere one film layer surface to another film layer surface or one
area of a film layer surface to another area of the same film layer
surface. The adhesive may comprise any polymer, copolymer or blend
of polymers having a polar group thereon, or any other polymer,
homopolymer, copolymer or blend of polymers including modified and
unmodified polymers, e.g., grafted copolymers, which provide
sufficient interlayer adhesion to adjacent layers comprising
otherwise nonadhering polymers. Adhesive compositions of the
present invention may include, but are not limited to, modified and
unmodified polyolefins, preferably polyethylene, such as for
example, low-density polyethylene, linear low-density polyethylene,
medium-density polyethylene, and modified and unmodified copolymers
of ethylene with one or more alpha-olefins (.alpha.-olefins) such
as butene-1, hexene-1, octene-1, or the like as a comonomer.
[0030] As used herein, the term "polyolefin" refers to
homopolymers, copolymers, including e.g. bipolymers, terpolymers,
etc., having a methylene linkage between monomer units which may be
formed by any method known to those skill in the art. Suitable
examples of polyolefins include polyethylene, low density
polyethylene, linear low density polyethylene, very low density
polyethylene, ultra low density polyethylene, medium density
polyethylene, high density polyethylene, polyethylenes comprising
ethylene/.alpha.-olefin which are copolymers of ethylene with one
or more alpha-olefins (.alpha.-olefins) such as butene-1, hexene-1,
octene-1, or the like as a comonomer, linear low density
polyethylene, very low density polyethylene, ultra low density
polyethylene, ethylene/propylene copolymers, polypropylene,
propylene/ethylene copolymer, polyisoprene, polybutylene,
polybutene, poly-3-methylbutene-1, poly-4-methylpentene-1, ionomers
and the like.
[0031] As used herein, the phrase "ethylene/.alpha.-olefin" refers
to a modified or unmodified copolymer produced by the
co-polymerization of ethylene and any one or more .alpha.-olefin.
The .alpha.-olefin in the present invention may have between 3-20
pendant carbon atoms. The co-polymerization of ethylene and an
.alpha.-olefin may be produced by heterogeneous catalysis, i.e.,
co-polymerization reactions with Ziegler-Natta catalysis systems,
for example, metal halides activated by an organometallic catalyst,
i.e., titanium chloride, optionally containing magnesium chloride,
complexed to trialkyl aluminum and may be found in patents such as
U.S. Pat. No. 4,302,565 to Goeke, et al. and U.S. Pat. No.
4,302,566 to Karol, et al., both of which are hereby incorporated,
in their entireties, by reference thereto.
[0032] As used herein, the term "modified" refers to a chemical
derivative, e.g., one having any form of anhydride functionality,
such as anhydride of maleic acid, crotonic acid, citraconic acid,
itaconic acid, fumaric acid, etc., whether grafted onto a polymer,
copolymerized with a polymer, or blended with one or more polymers,
and is also inclusive of derivatives of such functionalities, such
as acids, esters, and metal salts derived therefrom.
[0033] As used herein, the term "polyamide" refers to homopolymers,
copolymers, or terpolymers having an amide linkage between monomer
units which may be formed by any method known to those skill in the
art. Useful polyamide homopolymers include nylon 6
(polycaprolactam), nylon 11 (polyundecanolactam), nylon 12
(polylauryllactam), and the like. Other useful polyamide
homopolymers also include nylon 4,2 (polytetramethylene
ethylenediamide), nylon 4,6 (polytetramethylene adipamide), nylon
6,6 (polyhexamethylene adipamide), nylon 6,9 (polyhexamethylene
azelamide), nylon 6,10 (polyhexamethylene sebacamide), nylon 6,12
(polyhexamethylene dodecanediamide), nylon 7,7 (polyheptamethylene
pimelamide), nylon 8,8 (polyoctamethylene suberamide), nylon 9,9
(polynonamethylene azelamide), nylon 10,9 (polydecamethylene
azelamide), nylon 12,12 (polydodecamethylene dodecanediamide), and
the like. Useful polyamide copolymers include nylon 6,6/6 copolymer
(polyhexamethylene adipamide/caprolactam copolymer), nylon 6/6,6
copolymer (polycaprolactam/hexamethylene adipamide copolymer),
nylon 6,2/6,2 copolymer (polyhexamethylene
ethylenediamide/hexamethylene ethylenediamide copolymer), nylon
6,6/6,9/6 copolymer (polyhexamethylene adipamide/hexamethylene
azelaiamide/caprolactam copolymer), as well as other nylons which
are not particularly delineated here.
[0034] As used herein, the term "sealant" refers to a layer which
is heat sealable to itself, i.e., be capable of fusion bonding by
conventional indirect heating means which generate sufficient heat
on at least one film contact surface for conduction to the
contiguous film contact surface and formation of a bond interface
therebetween without loss of the film integrity. Advantageously,
the bond interface must be sufficiently thermally stable to prevent
gas or liquid leakage therethrough. Suitable examples of sealants
for the present invention include, but are not limited to,
polyolefins, including polyethylenes, polypropylenes,
polybutylenes, ionomers, ethylene/.alpha.-olefin copolymers and
blends thereof.
[0035] As used herein, the term "surface-roughened" refers to
dimples, indentations, scratches, bores, holes, perforations, and
the like, on an external surface of a film. It will be recognized
by those skilled in the art, that the dimples, indentations,
scratches, bores, holes, perforations, and the like may have a
random or regular repeating arrangement. Generally, a predetermined
portion (less than the entire area) of a surface of the film is
treated in order to provide a surface-roughened portion. The
surface-roughened portion may be formed by mechanical means, e.g.,
subjecting the external surface of the film layer to knurling by a
roller formed with a plurality of circumferentially extending
projections as described, for example, in U.S. Pat. Nos. 4,543,279
and 4,778,058, which are incorporated herein by reference.
Alternatively, non-mechanical methods may be used which include
corona discharge, plasma discharge, ultrasonic wave, and optical
ablation.
[0036] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0037] Referring now to FIG. 1, bag 10 represents one example of a
flexible bag according to the present invention having one
embodiment of an easy-open feature. As shown, bag 10 is depicted as
comprising a body 11 which is formed from a thermoplastic film 12
having an inner surface 13a (See FIG. 4) and an outer surface 13b
(See FIG. 4) relative to the bag. It should be appreciated by a
person of ordinary skill in art that body 11 may comprise one or
more monolayer or multilayer thermoplastic films suitable for use
with medium to heavy duty packaging applications. The body 11 of
bag 10 comprises a first panel 14a and a second panel 14b (See FIG.
2) such that the panels, 14a and 14b, each have a perimeter 15 and
15' (See FIG. 2). Perimeter 15 includes a first peripheral side
edge 16a and an opposing second peripheral side edge 16b connected
by a peripheral top edge 16c and an opposing peripheral bottom edge
16d. Body 11 also includes a plurality of seals 17 comprising at
least a first side seal 17a, a first top seal 17b and an opposing
bottom seal 17c, all which join first panel 14a to second panel
14b. It should be appreciated by a person of ordinary skill in art
that the body 11 of bag 10 may be integrally formed by folding a
thermoplastic film 12 over onto itself and sealing first panel 14a
to second panel 14b (See FIG. 2) thus creating a seal perimeter 18
which is comprised of first side seal 17a, first top seal 17b and
opposing bottom seal 17c. Alternatively, body 11 may be fabricated
from more than one thermoplastic films which may include
thermoplastic film 12 by sealing the four peripheral edges of first
panel 14a and 14b (See FIG. 2) together thereby providing a seal
perimeter 18 having a first side seal 17a, a second side seal 17d
(See FIG. 2), a first top seal 17b and an opposing bottom seal
17c.
[0038] Body 11 further comprises an inner receptacle cavity 19 (not
shown) which is formed between first panel 14a and opposing second
panel 14b and defined by a seal perimeter 18, and an integral
handle opening 20 which extends transversely across the bag 10 from
the first peripheral side edges 16a to the second side edges 16b.
Integral handle opening 20 may be fabricated, for example, by
slitting or die cutting into first panel 14a and second panel 14b
at the same time such that the slit or cut in first panel 14a is in
registration with the slit or cut in second panel 14b. Body 11 also
includes an easy-open feature 21 which extends longitudinally from
the first top seal 17b to opposing bottom seal 17c and is disposed
adjacent to peripheral side edge 16a of the first panel 14a.
Easy-open feature 21, by way of example, is depicted as being at
least one line of structural weakness 21a in the first panel 14a
and may be formed in either the inner surface 13a (See FIG. 4) or
the outer surface 13b (See FIG. 4) of thermoplastic film 12.
Alternatively, the at one line of structural weakness 21a may be
formed in second panel 14b (see FIG. 2) in either inner surface 13a
(See FIG. 4) or outer surface 13b (See FIG. 4) of thermoplastic
film 12.
[0039] Formation of the at least one line of structural weakness
21a may be accomplished by methods disclosed in U.S. Pat. Nos.
3,626,143; 3,909,582; 4,778,058; 4,834,245; 5,001,325; 5,613,779;
5,630,308; and 6,427,420, which are hereby incorporated by
reference. These methods include e.g., forming grooves, scores,
scratches, cuts, slits or surface roughening e.g., with a laser, by
corona or plasma discharge, by contact with a rough surface roller
or roughened surface such as sand paper, emery paper, or by cutting
devices or blades. For example, the at least one line of structural
weakness may be provided by any of the methods disclosed in the
aforementioned documents, such as using a cutting device to form
the at least one line of structural weakness in a first moving web
or layer followed by lamination of the first moving web or layer to
a second moving web or layer with or without tear-initiation
features or the like. It will be appreciated that at least one line
of structural weaknesses 21a may be provided in a variety of shapes
including curves or sinusoidal and may also be provided either
continuously or intermittently along the inner surface 13a (See
FIG. 4) or the outer surface 13b (See FIG. 4) of thermoplastic film
12 of first panel 14a or second panel 14b. While at least one line
of structural weaknesses 21a may be provided having a depth of the
entire thickness of thermoplastic film 12, e.g., by intermittent
perforations or slits, it is preferred that the at least one line
of structural weaknesses has a depth of less than the entire
thickness of the panel that it is formed on. It will be appreciated
that the at least one line of structural weakness may be provided
in any length along either panel between from first top seal 17b to
opposing bottom seal 17c.
[0040] Referring now to FIG. 2, bag 20 represents another example
of an embodiment of the present invention. Bag 20 comprises a body
11 of a first panel 14a (See FIG. 1) and second panel 14b such that
second panel 14b has a perimeter 15' which includes a first
peripheral side edge 16a' and an opposing second peripheral side
edge 16b', connected by a peripheral top edge 16c' and an opposing
bottom edge 16d'. Body 11 includes a plurality of seals 17 which
joins first panel 14a to second panel 14b and comprises a first
side seal 17a and a second side seal 17d, a first top seal 17b and
a second top seal 17e, and a bottom seal 17c. In this particular
example, the seal perimeter 18 which defines receptacle cavity 19
(not shown) consists of first side seal 17a and second side seal
17d, second top seal 17e and bottom seal 17c. Body 11 also includes
integral handle opening 20 that is formed in a reinforced portion
27a (See FIG. 3) of the first panel 14a and in a reinforced portion
the second panel 27b of second panel 14b. It should be appreciated
by a person of ordinary skill in art that the reinforced portions
27a (See FIG. 3) and 27b may be fabricated from a patch of film
such as thermoplastic film 12 which is adhered to the portion
overlaying and surrounding handle opening 20. The film patch is
typically applied before the handle opening 20 is formed and may be
secured to first and second panels, 14a and 14b by an adhesive or
heat-fusing process. Body 11 of bag 20 also comprises a reclosable
fastener 21b as the easy-opening feature 21 which is positioned
adjacent to first side seal 17a and extends longitudinally from
first top seal 17b to opposing bottom seal 17c. Reclosable fastener
21b, may include, but is not limited to, a reclosable fastener
having interlocking members, preferably, interlocking members and a
slider device 26. Suitable reclosable fasteners, in general, are
known and are taught, for example, in U.S. Pat. Nos. 5,063,644;
5,301,394; 5,442,837; 5,964,532; 6,409,384; 6,439,770; 6,524,002;
6,527,444; 6,609,827; 6,616,333; 6,632,021; 6,663,283; 6,666,580;
6,679,027; and U.S. patent application Nos. 2002/0097923; and
2002/0196987, each of which is incorporated by reference herein. It
will be noted that the reclosable fastener 21b is not limited to
any particular number of interlocking members and/or slider device
structure. It will be appreciated that the reclosable fastener 21b
may be chosen which does not include a slider device 26 and/or
interlocking members.
[0041] Turning now to FIG. 3, bag 30 is still another embodiment of
flexible bags for medium to heavy duty packaging applications
according to the present invention. Bag 30 is depicted having a
body 11 comprising first panel 14a and second panel 14b (See FIG.
2), and a plurality of seals which includes a first top seal 17b, a
second top seal 17e and an opposing bottom seal 17c, a first side
seal 17a and opposing second side seal 17d. The easy-open feature
21 of body 11 of bag 30 comprises at least one line of structural
weakness that includes a tear-initiation feature 23.
Tear-initiation feature 23 is provided to further facilitate the
opening of the package by obviating the need to cut bag 30 at the
peripheral side of the easy-open feature 21. In this regard,
tear-initiation feature 23 may be formed as a cut, slit, notch,
score or surface-roughened area in thermoplastic film 12 at a
peripheral side edge which affords easy opening of bag 30 by a
relatively weak manual force. In this way, a tear begins at
tear-initiation feature 23 and then propagates in the direction of
the at least one line of structural weakness 21a.
[0042] FIG. 4 represents an across-sectional view of one embodiment
of a thermoplastic film suitable for forming a bag according to the
present invention. Thermoplastic film 12 is depicted as a
multilayer thermoplastic film having an inner surface 13a and an
outer surface 13b relative to the bag and comprising at least three
layers of a first polymer layer 12a, a second polymer layer 12b,
and a third polymer layer 12c, such that second polymer layer 12b
is positioned between first polymer layer 12a and third polymer
layer 12c. Preferably, first polymer layer 12a may include a
material selected from the group consisting of polyester,
polyamide, polyolefin or blends thereof, more preferably, polyester
terephthalate, polyamide, polypropylene or blends thereof, and most
preferably, biaxially-oriented polyester terephthalate or
biaxially-oriented polyamide. Preferably, first polymer layer 12a
comprises a biaxially-oriented polyester terephthalate having a
thickness of 0.48 mils (1.22 cm), a ultimate tensile strength in
the machine direction of 27000 psi, an elongation at break in the
machine direction of 110%, a modulus of 550 kpsi. It will be
appreciated that first polymer layer 12a may also be treated on at
least one surface with an anchor coating to improve the adhesion to
an adjacent layer. An example of a commercially available
biaxially-oriented polyester terephthalate is sold under the
trademark Mylar.RTM. LBT which is supplied by E.I. de Pont de
Nemours and Company, Wilmington, Del., U.S.A. Preferably, second
polymer layer 12b comprises an adhesive material. Preferably,
polymer layer 12b is a low density polyethylene having a melt index
of 1.9, a density of 0.922 and a melting point of 110.degree. C.,
such as that sold under the trademark Escorene.RTM. LD-134 and
available from ExxonMobil Chemical Company of Houston, Tex., U.S.A.
Preferably, polymer layer 12c comprises a sealant material such as
low density polyethylene. An example of a suitable low density
polyethylene having melt index of 4.1, a density of 0.923, and a
melting point of 112.degree. C., such as that sold under the
trademark Escorene.RTM. LD-201 and available from ExxonMobil
Chemical Company of Houston, Tex., U.S.A. It should be appreciated
by a person of ordinary skill in the art that one or more of the
polymer layers described hereinabove may also, if desired, include
well known additives such as processing aids, slip agents,
anti-blocking agents and pigments, printed indicia and mixtures
thereof.
[0043] Thermoplastic film 12 has an unrestrained linear thermal
shrinkage in both the machine direction and the transverse
direction of between 0-10% at 85.degree. C. as measured in
accordance with ASTM D-2732-96, a minimum tensile strength at break
in the machine direction of at least 3000 psi (2.times.10.sup.7
N/m.sup.2) as measured at a rate of 12 inch/min. (30.5 cm/min.) in
accordance with ASTM D-882, and a maximum elongation at break in
the machine direction of between 0-150% as measured at a rate of 12
inch/min. (30.5 cm/min.) in accordance with ASTM D-882. Preferably,
thermoplastic film 12 has a total thickness of between 2.0-7.0 mils
(0.005-0.018 cm).
[0044] Unless otherwise noted, the physical properties and
performance characteristics reported herein were measured by test
procedures similar to the following methods.
1 Density ASTM D-1505 Melting Point ASTM D-3418 Melt Index ASTM
D-1238 Percent Elongation at Break ASTM D-882 Tensile strength at
Break ASTM D-882 Modulus ASTM D-882 Unrestrained Linear Thermal
Shrinkage ASTM D-2732-96
[0045] Many modifications and other embodiments of the invention
will come to mind to one skilled in the art to which this invention
pertains having the benefit of the teachings presented in the
foregoing descriptions and the associated drawings. Therefore, it
is to be understood that the invention is not to be limited to the
specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
* * * * *