U.S. patent number RE33,376 [Application Number 07/434,636] was granted by the patent office on 1990-10-09 for non-foil composite structures for packaging juice.
This patent grant is currently assigned to International Paper Company. Invention is credited to Charles E. Gibbons, Cynthia L. Tanner, Allan A. Whillock.
United States Patent |
RE33,376 |
Gibbons , et al. |
October 9, 1990 |
Non-foil composite structures for packaging juice
Abstract
The present invention relates to a non-foil composite barrier
.Iadd.structure .Iaddend.for an improved container for citrus
juices and other liquids. The container utilizes a paperboard
barrier laminate for the containment of essential oils and the
prevention of losses of vitamin C. Also disclosed is a process of
making the laminate. The laminate makes use of .[.an inner.].
.Iadd.a buried .Iaddend.barrier layer of a heat-sealable ethylene
vinyl alcohol copolymer to enhance the barrier properties of the
laminate.
Inventors: |
Gibbons; Charles E. (Mobile,
AL), Tanner; Cynthia L. (Mobile, AL), Whillock; Allan
A. (Mobile, AL) |
Assignee: |
International Paper Company
(Purchase, NY)
|
Family
ID: |
27368878 |
Appl.
No.: |
07/434,636 |
Filed: |
November 13, 1989 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
373964 |
Jun 27, 1989 |
|
|
|
Reissue of: |
055629 |
May 29, 1987 |
04789575 |
Dec 6, 1988 |
|
|
Current U.S.
Class: |
428/34.2;
428/336; 428/345; 428/349; 428/511; 428/516; 428/537.5 |
Current CPC
Class: |
B32B
27/10 (20130101); Y10T 428/31895 (20150401); Y10T
428/31913 (20150401); Y10T 428/31993 (20150401); Y10T
428/1303 (20150115); Y10T 428/2826 (20150115); Y10T
428/265 (20150115); Y10T 428/2809 (20150115) |
Current International
Class: |
B32B
27/10 (20060101); B65D 085/00 () |
Field of
Search: |
;428/34.2,336,345,349,511,516,537.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
56-87038 |
|
Dec 1979 |
|
JP |
|
2117536 |
|
Feb 1983 |
|
GB |
|
Primary Examiner: Buffalow; Edith
Attorney, Agent or Firm: Zielinski; Walt Thomas Gitler;
Stewart L.
Parent Case Text
.Iadd.This is a continuation of copending application Ser. No.
07/373,964 filed on June 27, 1989 now abandoned. .Iaddend.
Claims
What is claimed is:
1. A container for liquids containing essential oils and flavors,
.Iadd.said container having an interior and an exterior,
.Iaddend.said container constructed from a laminate comprising:
(a) a paperboard substrate .Iadd.with inner and outer surfaces,
said inner surface being closer to the interior of the container
than said outer surface.Iaddend.;
(b) a 12 lb. outer layer of a heat-sealable low density
polyethylene polymer .[.coated on.]. .Iadd.exterior to .Iaddend.to
said outer surface of said paperboard substrate;
(c) .[.an inner.]. .Iadd.a coextruded .Iaddend.sandwich layer
comprising a 4.5 lb. tie layer, a 4.0 lb. heat-sealable ethylene
vinyl alcohol copolymer layer and a 4.5 lb. tie layer .[.extruded
on.]. .Iadd.interior to .Iaddend.said inner surface of said
paperboard substrate; and
(d) a product-contact layer of a 10 lb. heat-sealable low density
polyethylene polymer .[.coextruded onto.]. .Iadd.interior to
.Iaddend.said outer surface of said inner sandwich layer of tie
layer--ethylene vinyl alcohol copolymer--tie layer whereby said
laminate can be heat-sealed on conventional equipment at
temperatures ranging from 250.degree. F-500.degree. F.
2. The container as claimed in claim 1 wherein said outer layer of
low density polyethylene polymer is corona discharge treated to
enhance printability of said laminate.
3. The container as claimed in claim 1 wherein said outer layer of
low density polyethylene polymer is flame treated to enhance
printability of said laminate.
4. The container as claimed in claim 1 wherein said tie layer is
.[.a Plexar.]. .Iadd.an ethylene based copolymer with functional
groups.Iaddend..
5. A container for liquids containing essential oils and flavors,
.Iadd.said container having an interior and an exterior,
.Iaddend.said container constructed from a laminate comprising:
(a) a paperboard substrate .Iadd.with inner and outer surfaces,
said inner surface being closer to the interior of the container
than said outer surface.Iaddend.;
(b) a thin 0.8 mil thick outer layer of a heat-sealable low density
polyethylene polymer .[.coated on.]. exterior to said outer surface
of said paperboard substrate;
(c) .[.an inner.]. .Iadd.a coextruded .Iaddend.thin tie layer and a
0.2 to 0.7 mil thick layer of a heat-sealable ethylene vinyl
alcohol copolymer, .[.coextruded on.]. .Iadd.interior to
.Iaddend.said inner surface of said paperboard substrate,
.Iadd.said heat-sealable ethylene vinyl alcohol copolymer layer
being interior to said tie layer.Iaddend.; and
(d) a thin 0.7 mil thick .Iadd.product contact .Iaddend.layer of a
heat-sealable low density polyethylene polymer .[.coated on an
outer surface of.]. .Iadd.interior to .Iaddend.said .[.tie
material-.]. ethylene vinyl alcohol copolymer layer whereby said
laminate can be heat-sealed on conventional equipment at
temperatures ranging from 250.degree. F-500.degree. F.
6. The container as claimed in claim 5 wherein said outer layer of
low density polyethylene polymer is corona discharge treated to
enhance printability of said laminate.
7. The container as claimed in claim 5 wherein said outer layer of
low density polyethylene polymer is flame treated to enhance
printability of said laminate.
8. The container as claimed in claim 6 wherein said surface of said
inner layer of said heat-sealable ethylene vinyl alcohol copolymer
is corona discharge treated to enhance adhesion of said thin
heat-sealable LDPE layer.
9. The container as claimed in claim 7 wherein said surface of said
inner layer of said heat-sealable ethylene vinyl alcohol copolymer
is flame treated to enhance adhesion of said heat-sealable LDPE
layer.
10. A container for liquids containing essential oils and flavors,
.Iadd.said container having an interior and on exterior.Iaddend.,
constructed from a laminate comprising:
(a) a paperboard substrate .Iadd.with inner and outer surfaces,
said inner surface being closer to the interior of the container
than said outer surface.Iaddend.;
(.Iadd.b) .Iaddend.a thin 0.8 mil thick outer layer of a
heat-sealable low density polyethylene polymer .[.coated on.].
.Iadd.exterior to .Iaddend.said outer surface of said paperboard
substrate;
(c) an inner tie layer .[.of an ethylene acrylic acid coated on.].
.Iadd.interior to .Iaddend.said inner surface of said paperboard
substrate;
(d) a 0.2 to 0.7 mil thick ethylene vinyl alcohol copolymer layer
.[.coated on.]. .Iadd.interior to .Iaddend.said tie layer; and
(e) a thin 0.7 mil thick heat-sealable layer of low density
polyethylene polymer .[.coated on.]. .Iadd.interior to
.Iaddend.said .[.outer surface of said EVOH.]. .Iadd.ethylene vinyl
alcohol copolymer layer whereby said laminate can be heat-sealed on
conventional equipment at temperatures ranging from 250.degree. F-
500.degree. F.Iaddend..
11. The container as claimed in claim 10 wherein said outer layer
of low density polyethylene polymer is corona discharge treated to
enhance printability of said laminate.
12. The container as claimed in claim 10 wherein said outer layer
of low density polyethylene polymer is flame treated to enhance
printability of said laminate.
13. The container as claimed in claim 11 wherein said inner layer
of ethylene vinyl alcohol copolymer is corona discharge treated to
enhance adhesion of said subsequent heat-sealable LDPE coating.
14. The container as claimed in claim 12 wherein said inner layer
of ethylene vinyl alcohol copolymer is flame treated to enhance
adhesion of said subsequent heat-sealable LDPE coating. .Iadd.15.
The container as claimed in claim 5 wherein said tie layer is an
ethylene based copolymer
with functional groups. .Iaddend. .Iadd.16. The container as
claimed in claim 10 wherein said tie layer is an ethylene based
copolymer with functional groups. .Iaddend. .Iadd.17. A container
for liquids containinq essential oils and flavors, said container
having an interior and an exterior, said container constructed from
a laminate comprising:
(a) a paperboard substrate with inner and outer surfaces, said
inner surface being closer to the interior of the container than
said outer surface;
(b) a thin outer layer of a heat-sealable low density polyethylene
polymer exterior to said outer surface of said paperboard
substrate;
(c) a coextruded sandwich layer comprising a 4.5 lb. tie layer, a
4.0 lb. heat-sealable ethylene vinyl alcohol copolymer layer and a
4.5 lb. tie layer interior to said inner surface of said paperboard
substrate; and
(d) a product-contact layer of a heat-sealable low density
polyethylene poltmer interior to said outer surface of said inner
sandwich layer of tie layer--ethylene vinyl alcohol copolymer--tie
layer whereby said laminate can be heat-sealed on conventional
equipment at temperatures ranging from 250.degree. F- 500.degree.
F. .Iaddend. .Iadd.18. The container as claimed in claim 17 wherein
said outer layer of low density polyethylene polymer is corona
discharge treated to enhance printability of said
laminate. .Iaddend. .Iadd.19. The container as claimed in claim 17
wherein said outer layer of low density polyethylene polymer is
flame treated to enhance printability of said laminate. .Iaddend.
.Iadd.20. The container as claimed in claim 17 wherein said tie
layer is an ethylene based copolymer with functional groups.
.Iaddend. .Iadd.21. A container for liquids containing essential
oils and flavors, said container having an interior and an
exterior, said container constructed from a laminate
comprising:
(a) a paperboard substrate with inner and outer surfaces, said
inner surface being closer to the interior of the container than
said outer surface;
(b) a thin outer layer of a heat-sealable low density polyethylene
polymer exterior to said outer surface of said paperboard
substrate,
(c) a coextruded thin tie layer and a 0.2 to 0.7 mil thick layer of
a heat-sealable ethylene vinyl alcohol copolymer, interior to said
inner surface of said paperboard substrate, said heat-sealable
ethylene vinyl alcohol copolymer layer being interior to said tie
layer; and
(d) a thin product contact layer of a heat-sealable low density
polyethylene polymer interior to said ethylene vinyl alcohol
copolymer layer whereby said laminate can be heat-sealable on
conventional equipment at temperatures ranging from 250.degree. F-
500.degree. F. .Iaddend.
.Iadd.22. The container as claimed in claim 21 wherein said outer
layer of low density polyethylene polymer is corona discharge
treated to enhance printability of said laminate. .Iaddend.
.Iadd.23. The container as claimed in claim 21 wherein said outer
layer of low density polyethylene polymer is flame treated to
enhance printability of said laminate. .Iaddend. .Iadd.24. The
container as claimed in claim 22 wherein said surface of said inner
layer of said heat-sealable ethylene vinyl alcohol copolymer is
corona discharge treated to enhance adhesion of said thin
heat-sealable LDPE layer. .Iaddend. .Iadd.25. The container as
claimed in claim 23 wherein said surface of said inner layer of
said heat-sealable ethylene vinyl alcohol copolymer is flame
treated to enhance adhesion of said heat-sealable LDPE layer.
.Iaddend. .Iadd.26. The container as claimed in claim 21 wherein
said tie layer is an ethylene based copolymer with functional
groups. .Iaddend. .Iadd.27. A container for liquids containing
essential oils and flavors, said container having an interior and
on exterior, constructed from a laminate comprising:
(a) a paperboard substrate with inner and outer surfaces, said
inner surface being closer to the interior of the container than
said outer surface;
(b) a thin outer layer of a heat-sealable low density polyethylene
polymer exterior to said outer surface of said paperboard
substrate:
(c) an inner tie layer interior to said inner surface of said
paperboard substrate:
(d) a 0.2 to 0.7 mil thick ethylene vinyl alcohol copolymer layer
interior to said tie layer: and
(e) a thin heat-sealable layer of low density polyethylene polymer
interior to said ethylene vinyl alcohol copolymer layer whereby
said laminate can be heat-sealable on conventional equipment at
temperatures ranging from
250.degree. F- 500.degree. F. .Iaddend. .Iadd.28. The container as
claimed in claim 27 wherein said outer layer of low density
polyethylene polymer is corona discharge treated to enhance
printability of said aminate. .Iaddend. .Iadd.29. The container as
claimed in claim 27 wherein said outer layer of low density
polyethylene polymer is flame treated to enhance printability of
said laminate. .Iaddend. .Iadd.30. The container as claimed in
claim 28 wherein said inner layer of ethylene vinyl alcohol
copolymer is corona discharge treated to enhance adhesion of said
subsequent heat-sealable LDPE coating. .Iaddend. .Iadd.31. The
container as claimed in claim 29 wherein said inner layer of
ethylene vinyl alcohol copolymer is flame treated to enhance
adhesion of said subsequent heat-sealable LDPE coating. .Iaddend.
.Iadd.32. The container as claimed in claim 27 wherein said tie
layer is an ethylene based copolymer with
functional groups. .Iaddend. .Iadd.33. A container for liquids
containing essential oils and flavors, said container having an
interior and an exterior, said container constructed from a
laminate comprising:
(a) a paperboard substrate with inner and outer surfaces, said
inner surface being closer to the interior of the container than
said outer surface;
(b) a thin outer layer of a heat-sealable, low density polyethylene
polymer exterior to said outer surface of said paperboard
substrate;
(c) a 0.2 to 0.7 mil thick ethylene vinyl alcohol copolymer layer
interior to said inner surface of said paperboard substrate;
and
(d) a thin heat-sealable layer of low density polyethylene polymer
interior to said ethylene vinyl alcohol copolymer layer whereby
said laminate can be heat-sealed on conventional equipment at
temperatures ranging from 250.degree. F.- 500.degree. F. .Iaddend.
.Iadd.34. The container as claimed in claim 33 wherein said outer
layer of low density polyethylene polymer is corona discharged
treated to enhance printability of said
laminate. .Iaddend. .Iadd.35. The container as claimed in claim 33
wherein said outer layer of low density polyethylene polymer is
flame treated to enhance printability of said laminate. .Iaddend.
.Iadd.36. The container as claimed in claim 34 wherein said inner
layer of ethylene vinyl alcohol copolymer is corona discharged
treated to enhance adhesion of said subsequent heat-sealable low
density polyethylene polymer coating. .Iaddend. .Iadd.37. The
container as claimed in claim 35 wherein said inner layer of
ethylene vinyl alcohol copolymer is flame treated to enhance
adhesion of said subsequent heat-sealable low density polyethylene
polymer coating. .Iaddend. .Iadd.38. A container for liquids
containing essential oils and flavors, said container from a
laminate comprising:
(a) a paperboard substrate with inner and outer surfaces, said
inner surface being closer to the interior of the container than
said outer surface;
(b) a thin 0.8 mil thick outer layer of a heat-sealable low density
polyethylene polymer exterior to said outer surface of said
paperboard substrate;
(c) a 0.2 to 0.7 thick ethylene vinyl alcohol copolymer layer
interior to said inner surface of said paperboard substrate;
and
(d) a thin 0.7 mil thick heat-sealable layer of low density
polyethylene polymer interior to said ethylene vinyl alcohol
copolymer layer whereby said laminate can be heat-sealed on
conventional equipment at temperatures ranging from 250.degree. F.-
500.degree. F. .Iaddend. .Iadd.39. The container as claimed in
claim 38 wherein said outer layer of low density polyethylene
polymer is corona discharged treated to enhance printability of
said laminate. .Iaddend. .Iadd.40. The container as claimed in
claim 38 wherein said outer layer of low density polyethylene
polymer is flame
treated to enhance printability of said laminate. .Iaddend.
.Iadd.41. The container as claimed in claim 39 wherein said inner
layer of ethylene vinyl alcohol copolymer is corona discharged
treated to enhance adhesion of said subsequent heat-sealable low
density polyethylene polymer coating. .Iaddend. .Iadd.42. The
container as claimed in claim 40 wherein said inner layer of
ethylene vinyl alcohol copolymer is flame treated to enhance
adhesion of said subsequent heat-sealable low density polyethylene
polymer coating. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The invention relates to heat-sealable barrier laminates for the
containment of essential oils and the prevention of loss of vitamin
C in paperboard cartons, as well as to a process for making such
laminates. More particularly, this invention relates to barrier
laminates which are comprised of an improved heat-sealable non-foil
composite structure which retains the vitamin C in juice at
nutritional-claims levels throughout the normal expected shelf life
when the carton/package is made, as well as improving the retention
of citrus juice flavor oils therein.
Heat-sealable low-density polyethylenes are well known to be
components of current paperboard citrus juice cartons which provide
little barrier to absorption and/or transmission of citrus juice
essential flavor/aroma oils. Additionally, it is well known that
impermeable materials such as aluminum foil, polar materials such
as: polyamides, polyethylene terephthalates, polyvinylidene
chlorides,polyvinyl chlorides, etc., and highly crystalline
non-polar materials such as high-density polyethylene and
polypropylene provide varying degrees of barrier to the absorption
and/or transmission of non-polar citrus juice flavor oils such as
.[.d-Limonene,.]. .Iadd.d-limonene .Iaddend.et al. However, these
materials require a thick liquid contact, low density polyethylene
layer for heat sealability as well as an expensive tie layer to
provide consistent adhesion between the LDPE and the barrier
material. The thick (.Iadd.1.5 .Iaddend.mil) LDPE liquid contact
layer .[.(1.5 mil).]. generally required in such cartons also
absorbs citrus flavor/aroma oils, with resultant deleterious
effects on product quality.
The existing commercial structure for a paperboard carton for juice
and similar products has utilized an easily heat-sealable barrier
laminate composed of paperboard sandwiched between two layers of
low density polyethylene (LDPE). The LDPE is an inexpensive
heat-sealable moisture barrier. The conventional structure falters
in that the thick LDPE layer absorbs the essential oils of the
juice after short periods of time causing integrity decay of heat
seals, stress cracking of the layer and allows transmission of the
essential oils into the paperboard and to the atmosphere.
Additionally, the conventional structure provides virtually no
barrier resistance to oxygen, causing the juice to lose vitamin C
in large amounts.
One other conventional structure adds two additional layers to the
structure identified above, namely a foil layer and an additional
LDPE layer. The expensive foil layer increases barrier resistance
to the flow of oxygen, while the additional LDPE allows for
ultimate heat-sealability of the laminate. The improved
conventional structure has poor barrier properties relating to the
absorption of essential oils and aromas, since the interior
contacting layer is still a thick layer of LDPE.
The object of the present invention is to produce an improved juice
packaging heat-sealable laminate material for a juice carton which
does not transmit flavor/odor ingredients of citrus and other
juices.Iadd., .Iaddend.and .Iadd.which .Iaddend.exhibits an
improved cost-to-performance ratio relative to foil-lined
cartons.
SUMMARY OF THE INVENTION
The preferred embodiment of the present invention reveals an
improved non-foil composite structure providing a substantial
barrier to the loss of vitamin C and an almost complete barrier to
the loss of essential flavor oils over the shelf life period of the
carton (six weeks) and far beyond the six week period as well. The
preferred embodiment comprises from the outer atmosphere exposed
surface to the inner surface contacting the essential oils and/or
flavors (liquid juice): a first exterior layer of a low density
polyethylene polymer; a paperboard substrate; an interior laminate
coating comprising a Plexar tie layer an ethylene vinyl alcohol
copolymer (EVOH) layer, and another Plexar tie layer.Iadd.,
.Iaddend.and a second layer of a low density polyethylene polymer
coated onto the laminate coating layer of Plexar/EVOH/Plexar in
contact with the juice.Iadd., .Iaddend.rendering the laminate
heat-sealable.
A second embodiment of the present invention reveals a non-foil
composite structure, providing a substantial barrier to the loss of
vitamin C and an almost complete barrier to the loss of essential
flavor oils; which comprises from the outer atmosphere exposed
surface t the inner surface contacting the essential oils and/or
flavors (liquid juice.[.;.]. .Iadd.: .Iaddend.a thin layer of a low
density polyethylene polymer, a paperboard substrate, a tie layer
of Plexar or ethylene acrylic acid, an interior layer of an
ethylene vinyl alcohol copolymer (EVOH).Iadd., .Iaddend.and a thin
layer of a low density polyethylene polymer coated onto the
interior layer of EVOH, in direct contact with the juice, rendering
the laminate heat-sealable.
A third embodiment of the present invention reveals a non-foil
composite structure, providing a substantial barrier to the loss of
vitamin C and an almost complete barrier to the loss of essential
flavor oils.[.;.]. which comprises from the outer atmosphere
exposed surface to the inner surface contacting the essential oils
and/or flavors (liquid juice): a thin layer of a low density
polyethylene polymer, a paperboard substrate, an interior layer of
an ethylene vinyl alcohol copolymer (EVOH) and a thin layer of a
low density polyethylene polymer coated onto the interior layer of
EVOH, in direct contact with the liquid, rendering the laminate
heat-sealable.
The cartons constructed of the laminate of the present invention
enable significant flavor oil retention of the citrus juice
contained, and also significant prevention of loss of vitamin C,
.[.resulting.]. .Iadd.which results .Iaddend.in a substantial
extension of the shelf life thereof and .Iadd.which
.Iaddend.permits replacement of the costly aluminum foil
barrier.
The preferred ethylene vinyl alcohol copolymer is sold under the
product name EVAL EP resins and is available from EVAL Company of
America. The preferred tie layer is .[.a.]. Plexar 177 and is
available from .[.USI.]. .Iadd.Ouantum Chemical
.Iaddend.Corporation. .Iadd.Plexar 177 is a tradename for
ethylene-based copolymers modified with functional groups.
.Iaddend.
The present invention has produced a suitable container .[.which
has.]. .Iadd.with .Iaddend.excellent barrier properties utilizing
laminate .[.which.]. .Iadd.that .Iaddend.can be heat-sealed with
its exterior and interior layers being a non-polar constituent
(LDPE) and a like non-polar constituent (LDPE) from front to back.
The liquid juice components are insoluble in the polar EVOH
material, preventing flavor oil absorption and resulting swelling,
stress cracking, plasticization.Iadd., .Iaddend.and heat seal
degradation .[.as.]. .Iadd.that .Iaddend.occurs with a thick
.Iadd.layer of .Iaddend.LDPE .[.as the.]. .Iadd.in .Iaddend.contact
.[.layer.]. .Iadd.with the juice. .Iaddend.
The preferred laminates of the present invention not only exhibit
significant barrier properties to extend the shelf life of the
juice, but the laminates can be produced using conventional
extrusion equipment.
The preferred embodiments of the present invention are constructed
as follows:
Stepwise, the paperboard is flame treated on both sides. Second, a
layer of molten LDPE is then placed onto the paperboard substrate
by extrusion coating.
Thirdly, the web is turned over and a sandwich layer of EVOH
surrounded by Plexar tie layers, or one Plexar tie layer and EVOH,
or EVOH alone is coextruded onto the uncoated exposed side of the
paperboard substrate. This newly placed layer .[.is.]. .Iadd.may be
.Iaddend.corona discharge treated or flame treated to facilitate
adhesion of a subsequent food contact layer
.Iadd.LDPE.Iaddend..
Lastly, a layer of LDPE is extruded onto the interior sandwich
layer of Plexar-EVOH-Plexar, or Plexar-EVOH layer or EVOH layer.
The completed laminate can now be heat-sealed from front to back
(LDPE to LDPE) at conventional temperatures (250.degree. F to
500.degree. F).
The newly formed laminate can then be scored, cut into blanks,
folded and side-seam heat-sealed thereon for transport.
Once transported, the prepared blanks can be filled .[.onto.].
.Iadd.using .Iaddend.conventional equipment, such as a
.[.PurePak.RTM..]. .Iadd.form-fill-seal .Iaddend.machine made by
.[.Ex-Cell-O.]..Iadd.Pure-Pak, Inc. .Iaddend.The blanks are
formed.Iadd., .Iaddend.heat-sealed at the bottom, filled.Iadd.,
.Iaddend.and heat-sealed at the top .[.by.]. .Iadd.on .Iaddend.the
.[.PurePak.RTM..]. .Iadd.form-fill-seal .Iaddend.machine to
.[.complete.]. .Iadd.produce .Iaddend.the filled .[.carton.].
.Iadd.cartons.Iaddend..
The barrier laminates produced by the present invention not only
exhibit excellent barrier properties and can be easily
constructed.Iadd., .Iaddend.but also meet FDA .[.approval.].
.Iadd.requirements .Iaddend.for use in food packaging. EVAL Company
of America's EVAL EP is FDA approved for direct food contact and
the preferred ethylene vinyl alcohol copolymer of the invention.
Other EVOH's which heat seal at low temperatures (250.degree. F to
500.degree. F) and which can be cut on conventional
machinery.Iadd., .Iaddend.could also be used as the barrier
material.
Thus, until the advent of the present invention few suitable
containers for the containment of citrus juices have been developed
which retain the advantages of using paperboard as the base
material as well as have a relatively inexpensive barrier layer
(EVOH) which can be fabricated using conventional extrusion coating
equipment.
The present invention described herein is particularly useful as a
paperboard laminate employed in the manufacture of citrus juice or
other liquid product containers. Such containers make use of
heat-seals for seaming and closing.[.,.]..Iadd.; .Iaddend.for
example, cartons, folding square or rectangular containers or
boxes, and/or even fabricating cylindrical tubes.
The packaging material is printed, converted into flat blanks, side
seamed, and then formed, filled, and sealed using conventional
carton illing machines. Specifically, the preferred embodiment of
the new packaging material, as used to produce 10-ounce, quart,
half-gallon and three-quart .[.PurePak.RTM..]. .Iadd.gable-top
.Iaddend.cartons, comprises an exterior coating of 12 lbs.Iadd..,
.Iaddend.LDPE, paperboards of varying thickness (depending on
carton size), a coextruded sandwich layer of .[.4.5 lbs of an
adhesive tie material (Plexar 177), 4.0 lbs EVOH (EVAL), 4.5 lbs of
a tie layer material (Plexar 177).]. , and a product contact
coating layer of 10 lbs LDPE.
The second embodiment of the present invention comprises an
exterior coating of 0.8 mil LDPE, paperboards of varying thickness
(depending on carton size), 0.5 to 0.8 mil adhesive tie layer, 0.2
to 0.7 mil EVOH. and 0.7 mil LDPE (product-contact).
The third embodiment of the present invention comprises an exterior
coating of 0.8 mil LDPE, paperboards of varying thickness
(depending on carton size), 0.2 to 0.7 mil EVOH, and 0.7 mil LDPE
(product-contact).
Prior cartons containing aluminum foil are often expensive relative
to the performance problems they present when being
form-fill-sealed by the juice packager. Also, the usual thick (22
lb) or (1.5 mil) LDPE product-contact layer generally required in
such cartons absorbs citrus flavor/aroma oils, with subsequent
deleterious effects on product quality.
The present invention makes use of a relatively inexpensive layer
of EVOH, reducing loss of essential oils and vitamin C, while
functioning as an excellent barrier. Provided is a very thin (0.7
mil) product-contact layer of LDPE thereby reducing juice
absorption in the product-contact layer and resultant degradation
of the contact layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional elevation of an existing commercial
structure of a laminate;
FIG. 2 is a cross-sectional elevation of an existing commercial
structure of a laminate;
FIG. 3 is a cross-sectional elevation of an existing commercial
structure of a laminate;
FIG. 4 is a cross-sectional elevation of an existing commercial
structure of a laminate;
FIG. 5 is a cross-sectional elevation of the preferred embodiment
of the laminate of the present invention;
FIG. 6 is a cross-sectional elevation of an alternate embodiment of
the laminate of the present invention;
FIG. 7 is a cross-sectional elevation of an alternate embodiment of
the laminate of the present invention;
FIG. 8 is a block diagram representing the process for making the
preferred embodiment of the laminate of the present invention;
FIG. 9 is a block diagram representing the process for making the
alternate embodiment of the laminate of the present invention;
and
FIG. 10 is a block diagram representing the process for making the
alternate embodiment of the laminate of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The existing commercial structure for a paperboard carton for juice
and similar products has made use of an easily heat-sealed barrier
laminate composed of paperboard 4 (FIG. 1) sandwiched between two
thick layers of low density polyethylene (LDPE) 2,6 (1.5 mil). The
LDPE is an inexpensive heat-sealable material which acts to a
limited extent as a moisture barrier to prevent loss of essential
oils (flavor) and aroma. The problem encountered with the
conventional laminate structure has been that the essential oils of
the juice (namely - d-Limonene) have, after short periods of time,
been absorbed into the thick 1.5 mil LDPE layer causing heat seal
decay, stress cracking, and swelling while stripping the juice of
the essential oils. Additionally, the conventional structure (FIG.
1) provides virtually no barrier resistance to oxygen which causes
the juice to lose vitamin C in great quantities after a relatively
short period of time. To illustrate, the conventional paperboard
1/2 gallon juice carton will lose 60.5% of its essential oil
(d-Limonene) and 84% of its vitamin C content in a storage period
of six weeks (SEE TABLE 1).
One conventional existing paperboard carton (FIG. 2) utilizes two
extra layers in addition to the layers disclosed in FIG. 1 to add
greater barrier resistance to the passage of oxygen and resultant
loss of vitamin C. Expensive aluminum foil 14 has been added to the
laminate structure to increase the barrier's resistance to the flow
of oxygen. An additional thick layer of LDPE 16 is needed to allow
the laminate to be heat-sealed from front or back with the exterior
LDPE 8 layer. The structure of the barrier laminate (FIG. 2) has
poor barrier properties relating to the absorption of essential
oils and aromas, since the heat-sealable contacting layer is a
thick layer of low density polyethylene. The shelf storage life of
the juice carton made up of the barrier laminate of FIG. 2 still
exhibits a percentage loss of essential oils (d-Limonene) of 35.5%,
while greatly improving its barrier properties with respect to the
percentage loss of vitamin C, 24% (See Table 1). The addition of
the foil layer allows the laminate to exhibit excellent O.sub.2
barrier properties. Although the use of a foil layer is extremely
beneficial, the enormous increased expense makes the use of foil
economically less desirable.
FIGS. 3 and 4 disclose structures of barrier laminates described in
U.S. Pat. No. 4,513,036. FIG. 3 discloses a barrier laminate
comprising a sandwich of LDPE 18-paperboard 20-High .[.Density
Polyethylene.]. .Iadd.density polyethylene .Iaddend.(HDPE) 22-LDPE
24. The laminate disclosed exhibits large losses of essential oils
during its shelf life of six weeks, namely 60.5%, while also
exhibiting large losses of vitamin C during the six week period,
namely 87% (see Table 1). The economics and ease of fabrication of
the laminates of FIG. 3 are outweighed by the poor barrier
properties exhibited.
FIG. 4 discloses the preferred embodiment of U.S. Pat. No.
4,513,036, namely a barrier laminate comprising LDPE 26-Paperboard
28-Polypropylene 30-LDPE 32. The additional polypropylene layer 30
and to the barrier properties at relatively low additional costs.
The barrier properties still are extremely deficient in resistance
to the passage of oxygen and loss of vitamin C, namely 71% after
six weeks. The polypropylene laminate structure loses 39.5% of its
essential oils (d-Limonene) after six weeks (see Table 1).
Both embodiments disclosed in the patent cited above do not
adequately preserve the flavor/aroma and vitamin C content of the
juice. The structure of the existing commercial constructions have
all faced the same problem due to the necessity for heat sealing
the seams and closures while forming the carton blank and while
filling the cartons with juice or the like. The necessity of
forming a heat seal from the front to the back of the laminate has
resulted in the use of a thick exterior layer of LDPE and a thick
interior layer of LDPE, both non-polar compounds which exhibit
excellent heat-sealing characteristics to one another (see FIGS.
1-4).
Referring to FIG. 5, the preferred embodiment of the laminate of
the present invention is shown as comprising a paperboard substrate
36 of varying thickness which is most suitably high-grade
paperboard stock, for example, 282 lb Milk Carton Board, to which
is applied on one side a coating of low density polyethylene (LDPE)
34, in a coating weight ranging from about 9 to about 15 pounds per
ream. Any commercial extrusion coating grade LDPE is suitable for
use herein. On the back or interior portion of the laminate, namely
onto the paperboard layer 36, is coextruded a sandwich 44 of a 4.5
lb tie material (Plexar 177) 38/4.0 lb EVOH (EVAL) 40/4.5 lb tie
material (Plexar 177) 42. The EVOH being a barrier layer composed
of EVAL Company of America's EVAL EP resins. Extruded thereon is a
coating of 10 lbs LDPE 46.
Referring to FIG. 6, the alternate embodiment of the laminate of
the present invention is shown as comprising a paperboard substrate
54 of varying thickness which is suitably high grade paperboard
stock, i.e., 282 lb milk carton board, to which is applied on one
side a very thin 0.8 mil coating of low density polyethylene (LDPE)
52, in a coating weight range averaging 12 lbs per 3000 square
feet. Any commercial extrusion coating grade LDPE is suitable for
use herein. On the back or interior portion of the laminate, namely
onto the paperboard layer 54, a (Plexar 177) tie layer 56 and a
layer of 0.2 to 0.7 mil of EVOH 56 are applied by coextrusion. The
EVOH being a barrier layer composed of EVAL Company of America's
EVAL EP resins. Extrusion coated thereon is a very thin 0.7 mil
layer 58 of a non-polar LDPE.
Referring to FIG. 7, a third embodiment of the laminate of the
present invention is shown as comprising a paperboard substrate 66
of varying thickness which is suitably high grade paperboard stock,
i.e. 282 lb milk carton board, to which is applied on one side a
very thin 0.8 mil coating of LDPE 64, a 0.2 to 0.7 mil layer of
EVOH 68 is applied by extrusion coating. Extrusion coated thereon
is a thin layer 70 of a non-polar LDPE.
Referring now to FIG. 8, wherein a block diagram discloses the
method of forming the heat-sealable barrier laminate of FIG. 5.
The laminate can be easily fabricated. In Step A, the paperboard is
flame treated two sides. Step B, a molten layer of the LDPE 34 is
extrusion coated onto the paperboard substrate 36. Stop C, the LDPE
layer 34 is corona discharge or flame treated in preparation for
subsequent printing. Step D, the web is turned over to facilitate
Step E, which has a sandwich layer 44 of Plexar 38/EVAL 40/Plexar
42 coextruded onto the paperboard substrate 36. In Step F,
extrusion coating of a layer of LDPE 46 onto the sandwich layer 44
completes the laminate.
Referring now to FIG. 9, wherein a block diagram discloses the
method of forming the heat sealable barrier laminate of FIG. 6.
In Step A, the paperboard is flame treated on two sides. Step B, a
molten layer of LDPE 52 is extrusion coated onto the paperboard
substrate 54. Step C, the LDPE layer 52 is corona discharge or
flame treated to provide subsequent inner layer adhesion. Step D,
the web is turned over to facilitate Step E, which has a layer of
molten tie layer 56 and EVOH 56 coextruded onto the paperboard
substrate 54. Step F, the tie/EVOH layer 60 has its surface corona
discharge treated or flame treated to facilitate the adhesion of a
subsequent interior product-contact thin LDPE coating 62 to
complete the laminate.
Referring now to FIG. 10, wherein a block diagram discloses the
method of forming the heat-sealable barrier laminate of FIG. 7.
In Step A, the paperboard 66 is flame treated on two sides. Step B,
a layer of LDPE 64 is extrusion coated onto the paperboard
substrate 66. Step C, the LDPE layer 64 is corona discharge or
flame treated to provide subsequent inner layer adhesion. Step D,
the web is turned over to facilitate Step E, which has a layer of
molten EVOH 68 extrusion coated onto the paperboard substrate 66.
Step F, EVOH layer 68 is corona discharge treated or flame treated
to facilitate the adhesion of a subsequent interior product-contact
thin LDPE coating to complete the laminate.
Although specific coating techniques have been described, any
appropriate technique for applying the layers onto the paperboard
substrate can be suitably employed, such as extrusion, coextrusion,
or adhesive lamination .[.or.]. .Iadd.of .Iaddend.single and/or
multilayer films to paperboard to achieve the stated inventions of
this patent.
The unique barrier effect provided by the laminate of the present
invention to the % loss of essential oils and to the % loss of
vitamin C is clearly demonstrated by the following example outlined
in Table 1.
Standard .[.1/2.]. .Iadd.half .Iaddend.gallon juice containers were
prepared and filled with juice. A typical essential oil in the
juice was .[.d-Limonene.]. .Iadd.d-limonene.Iaddend.. The filled
cartons were stored for a test period of six weeks after which the
juice was analyzed to determine the percentage loss by weight of
the essential oil d-Limonene and the percentage loss by weight of
vitamin C.
All weights .Iadd.shown .Iaddend.in lbs are given .[.in.]. .Iadd.as
.Iaddend.lbs per 3000 square feet.
TABLE 1 ______________________________________ Test Sample % Loss
of 1/2 Gallon Juice % Loss of [Essential Oil] Container Essential
Oil Vitamin C ______________________________________
LDPE/BOARD/LDPE 60.5 84 (FIG. 1) LDPE/BOARD/LDPE/FOIL/ 35.5 24 LDPE
(FIG. 2) LDPE/BOARD/HDPE/LDPE 60.5 87 (FIG. 3) LDPE/BOARD/POLYPRO-
39.5 71 PYLENE/LDPE (FIG. 4) LDPE/BOARD/PLEXAR- 16.5 46
EVOH-PLEXAR/LDPE (FIG. 5)
______________________________________
It can be clearly seen that the container prepared from a laminate
of the present invention provides an almost complete barrier to the
loss of essential oils far greater than has been present in
existing structures. Additionally, the oxygen passage or percentage
loss of vitamin C has been greatly reduced over all prior laminates
not containing aluminum foil.
The effectiveness of the laminate of the present invention as a
barrier to migration of essential oils and flavors, as well as a
barrier to a loss of vitamin C permits a significant extension of
shelf life of .Iadd.juice products packaged in .Iaddend.containers
constructed therefrom.
* * * * *