U.S. patent application number 11/895457 was filed with the patent office on 2008-02-07 for nylon barrier board structure.
This patent application is currently assigned to BRPP, LLC. Invention is credited to Kevin Cable, Steven Frohock.
Application Number | 20080032075 11/895457 |
Document ID | / |
Family ID | 33416584 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080032075 |
Kind Code |
A1 |
Cable; Kevin ; et
al. |
February 7, 2008 |
Nylon barrier board structure
Abstract
A paperboard laminate useful for making gable top juice cartons
is provided. The laminate provides for a high melting point polymer
such as a semi-crystalline nylon to be applied directly to a board
surface as an oxygen barrier layer. An anti-scalping layer is also
provided by a polar polymer which is connected by a tie layer to an
outermost skin coat layer. Positioned between the skin coat layer
and the oxygen barrier layer are one or more bulk layers of
polyolefins. The resulting laminate affords a juice carton which
has good oxygen barrier and Vitamin C retention properties, is
resistant to overactivation during heat sealing, has minimal
scalping of d-limonene and essential oils, and has excellent bulge
resistance.
Inventors: |
Cable; Kevin; (Waynesville,
NC) ; Frohock; Steven; (Canton, NC) |
Correspondence
Address: |
J. BENNETT MULLINAX, LLC
P. O. BOX 26029
GREENVILLE
SC
29616-1029
US
|
Assignee: |
BRPP, LLC
Canton
NC
|
Family ID: |
33416584 |
Appl. No.: |
11/895457 |
Filed: |
August 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10431955 |
May 8, 2003 |
7276294 |
|
|
11895457 |
Aug 24, 2007 |
|
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Current U.S.
Class: |
428/34.2 |
Current CPC
Class: |
B32B 2307/7244 20130101;
B32B 2310/14 20130101; B32B 27/32 20130101; Y10T 428/31757
20150401; Y10T 428/31779 20150401; B32B 2323/046 20130101; Y10T
428/1303 20150115; Y10T 428/31783 20150401; B32B 27/08 20130101;
B32B 2439/00 20130101; Y10T 428/31739 20150401; B32B 27/34
20130101; B32B 2307/5825 20130101; B32B 27/10 20130101; Y10T
428/31743 20150401; Y10T 428/31725 20150401 |
Class at
Publication: |
428/034.2 |
International
Class: |
B32B 27/10 20060101
B32B027/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 7, 2004 |
US |
PCT/US2004/014305 |
Claims
1. A laminate structure comprising: a paperboard substrate having
an inner surface and an outer surface; a layer of a heat-sealable
polymer coated on the outer surface of the paperboard substrate; a
semi-crystalline polyamide polymer layer coated on the inner
surface of the paperboard substrate; a first tie layer coated on an
inner surface of the semi-crystalline polyamide polymer layer; at
least one layer of polyolefin polymer coated on an inner surface of
the first tie layer; a second tie layer positioned on an inner
surface of the at least one layer of polyolefin polymer; a polar
polymer scalping barrier layer selected from the group consisting
of a semi-crystalline nylon, an amorphous nylon, a polyester, and
combinations thereof on an inner surface of the second tie layer; a
third tie layer positioned on an inner surface of the polar polymer
scalping barrier layer; and, a heat-sealable polymer layer coated
on an inner surface of the third tie layer.
2. The laminate structure according to claim 1 wherein said
semi-crystalline polyamide polymer layer further comprises a nylon
selected from the group consisting of Nylon 4/6, Nylon 6/6, Nylon
6/12, Nylon 11, Nylon 12, and combinations thereof.
3. The laminate structure according to claim 1 wherein the polar
polymer scalping barrier layer is a high melting point
semi-crystalline polyamide.
4. The laminate structure according to claim 2 wherein said polar
polymer scalping barrier layer comprises a high melting point
semi-crystalline polyamide.
5. The laminate structure according to claim 1 wherein said
semi-crystalline polyamide polymer layer and said polar polymer
scalping barrier layer are Nylon 6.
6. The laminate structure according to claim 1 wherein said
semi-crystalline polyamide polymer layer and said polar polymer
scalping barrier layer is Nylon 6/6.
7. The laminate structure according to claim 1 wherein said at
least one layer of polyolefin polymer on an inner surface of the
first tie layer has a coating weight of about 12 to about 24
lbs/3,000 sq. ft.
8. A laminate structure consisting essentially of: a paperboard
substrate having an inner surface and an outer surface; a layer of
a heat-sealable polymer coated on the outer surface of the
paperboard substrate; a semi-crystalline polyamide polymer layer
coated on the inner surface of the paperboard substrate; a first
tie layer coated on an inner surface of the semi-crystalline
polyamide polymer layer; at least one layer of polyolefin polymer
coated on an inner surface of the first tie layer; a second tie
layer positioned on an inner surface of the at least one layer of
polyolefin polymer; a polar polymer scalping barrier layer selected
from the group consisting of a semi-crystalline nylon, an amorphous
nylon, a polyester, and combinations thereof on an inner surface of
the second tie layer; a third tie layer positioned on an inner
surface of the polar polymer scalping barrier layer; and, a
heat-sealable polymer layer coated on an inner surface of the third
tie layer.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. application Ser.
No. 10/431,955 filed on May 8, 2003, and PCT Application
PCT/US2004/014305 filed on May 7, 2004, both of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed towards a paperboard
laminate useful for making containers for citrus juices and
beverages, as well as dried food products. In addition, the
paperboard laminate is useful for making containers for liquid
non-food products such as fabric softeners. The present invention
uses two layers of Nylon 6 separated by a low density polyethylene
layer to provide a resulting laminated structure having good oxygen
barrier properties, abuse resistance, and protection of products
packaged therein against the loss of vitamins, flavor, and
essential oils. The innermost layer of Nylon 6 is applied directly
to the board substrate and provides an oxygen barrier which also
protects against overactivation of the board. An additional layer
of Nylon 6 provides an anti-scalping layer and is placed adjacent
the skin coat layer. The skin coat layer and the adjacent Nylon 6
layer are joined by an adhesive tie layer. The resulting laminate
provides for a board structure and carton which are resistant to
the creation of pin holes in the laminated layers which may occur
through overactivation of the board. Further, the resulting cartons
have excellent resistance to scalping. The resulting laminate
structure also provides for an assembled carton which, when filled
with an aqueous liquid, has good resistance to carton bulge over
the life of the carton.
BACKGROUND OF THE INVENTION
[0003] This invention relates to coated paperboard which may be
used within the beverage industry to provide containers for citrus
and fruit juices, milk, and other liquid and non-liquid food
products. A variety of coating layers are known to be used to
provide useful properties to the resulting paperboard laminate. For
instance, within the citrus juice industry paperboard cartons have
coatings designed to provide an oxygen barrier. The incorporation
of oxygen barriers into a laminate structure helps preserve Vitamin
C content against oxidative loss and contributes to a longer
product shelf life.
[0004] In addition, juice cartons are prone to scalping of
essential oils in the carton's contents by the skin or product
contact layer of the laminated board. As such, barrier coatings
which provide increased resistance to scalping are also
desirable.
[0005] Extruded nylon has been used as one layer of a
multi-component laminated structure for a barrier board. One such
barrier board which provides for oxygen barrier properties and
reduces essential oil loss is disclosed in Thompson et al, U.S.
Pat. No. 4,777,088.
[0006] Brown et al, U.S. Pat. No. 4,753,832, also discloses a nylon
oxygen barrier layer as part of a laminated structure. The Brown et
al layer provides a skin layer of glycol-modified polyethylene
terephathalate (PET-G).
[0007] Parks et al, U.S. Pat. No. 6,149,993, discloses a layer of
amorphous nylon as an oxygen barrier structure. Amorphous nylon has
relatively low strength as compared to Nylon-6 and other
semi-crystalline nylon structures. The Park et al reference
proposes that the oxygen barrier properties of amorphous nylon are
equivalent to the barrier properties of laminated structures
containing ethylene vinyl alcohol (EVOH).
[0008] An EVOH barrier laminated structure may be seen in reference
to the Gibbons et al, U.S. Pat. No. 4,701,360, in which EVOH is
provided as a heat-sealable oxygen barrier that offers resistance
to scalping when present as the skin layer of a board laminate.
[0009] While the art provides for a variety of laminated barriers
for cartons, there remains for room for variation and improvement
within the art.
SUMMARY OF THE INVENTION
[0010] It is one aspect of at least one of the present embodiments
of the invention to provide an improved, heat-sealable laminated
board structure for a juice carton which exhibits excellent oxygen
barrier properties. The oxygen barrier properties provide for the
retention of high Vitamin C levels. Juice cartons constructed from
the laminate board structure also offer good resistance to scalping
of essential oils.
[0011] It is yet another object of at least one of the present
embodiments to provide a heat-sealable paperboard laminated
structure which may be used for fruit or citrus juices, other
beverages, dry food products, and non-food liquid products such as
fabric softeners. The multi-layer laminated structure contains two
distinct, separated layers of a high melting temperature polyamide
such as Nylon 6 applied to the product side of a paperboard
substrate. The innermost layer of Nylon 6 provides an oxygen
barrier which is resistant to overactivation.
[0012] The outermost layer of Nylon 6 provides a barrier against
scalping of essential oils which further protects the extruded,
laminated layers during heat sealing steps associated with the
folding and filling of cartons.
[0013] It is yet another aspect of at least one of the present
embodiments of the invention to provide a laminated board structure
in which the extruded polymer layer prevents blistering and
pinholing of the laminated layers (overactivation) during heat
sealing of the cartons. In accordance with this invention, it has
been found that when a carton is heat sealed, the paperboard
substrate is often raised to a temperature in excess of the boiling
point of water. As such, moisture in the paperboard layer turns to
steam, the release of which may compromise the structural integrity
of the various laminated layers (board overactivation). The damaged
lamination layers provide undesirable pathways through the
laminated structure for oxygen and moisture. Several of the
embodiments described herein provide for laminated structures which
are resistant to overactivation.
[0014] Thus, in one embodiment of the present invention a
paperboard, coated with an outer heat-sealable polyolefin layer, is
provided as a coated base substrate upon which an inner, laminated
structure is extruded. The extruded, laminated structure, from the
exterior (gloss side) of the laminated structure to the interior of
the structure, comprises the following layers: [0015]
polyolefin/paperboard/Nylon 6/tie layer/polyolefin/tie layer/Nylon
6/tie layer/polyolefin.
[0016] It is yet another embodiment of at least one of the present
inventions to provide a laminated structure for paperboard cartons
in which an outer skin layer of a polyolefin or other heat-sealable
material is attached to an anti-scalping layer such as Nylon 6,
Nylon 6/6, amorphous nylon, or other polar polymer material using
an adhesive tie layer. The anti-scalping layer, when a high melting
polar polymer is used, also provides additional protection to the
paperboard against overactivation.
[0017] Cartons can be constructed from the laminates of the present
invention which provide excellent gas-barrier protection for food
and non-food products. Further, the resulting carton has been found
to offer a significant reduction in scalping of essential oils
which further extends the shelf life and quality of a juice
product.
[0018] These and other features, aspects, and advantages of the
present invention will become better understood with reference to
the following description and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] A fully and enabling disclosure of the present invention,
including the best mode thereof, to one of ordinary skill in the
art is set forth more particularly in the remainder of the
specification, including reference to the accompanying
drawings.
[0020] FIG. 1 is a schematic cross-section illustrating a barrier
board laminate according to the present invention;
[0021] FIG. 2 is a graphical representation of Vitamin C retention
in a carton constructed from a laminate in accordance with the
present invention;
[0022] FIG. 3 is a graph of d-limonene levels of orange juice in
cartons according to the present invention; and,
[0023] FIGS. 4A and 4B are graphical representations of the
respective bulge and normalized bulge properties of cartons
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] Reference now will be made in detail to the embodiments of
the invention, one or more examples of which are set forth below.
Each example is provided by way of explanation of the invention,
not limitation of the invention. In fact, it will be apparent to
those skilled in the art that various modifications and variations
can be made in the present invention without departing from the
scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used on
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention cover such modifications and
variations as come within the scope of the appended claims and
their equivalents. Other objects, features, and aspects of the
present invention are disclosed in the following detailed
description. It is to be understood by one of ordinary skill in the
art that the present discussion is a description of exemplary
embodiments only and is not intended as limiting the broader
aspects of the present invention, which broader aspects are
embodied in the exemplary constructions.
[0025] In describing the various figures herein, the same reference
numbers are used throughout to describe the same material,
apparatus or process pathway. To avoid redundancy, detailed
descriptions of much of the apparatus once described in relation to
a figure is not repeated in the descriptions of subsequent figures,
although such apparatus or process is labeled with the same
reference numbers.
[0026] An embodiment of the present invention may be provided by a
paperboard laminate having the structure as seen in reference to
FIG. 1. When the structure is assembled into a carton, the
structure has been found to provide excellent oxygen barrier
properties, good resistance to bulge, resistance to oxidative loss
of Vitamin C, and provides a skin coat layer which minimizes the
uptake of essential oils such as d-limonene.
[0027] The laminated structure 1, as seen in reference to FIG. 1,
may be provided by a conventional paperboard substrate. The
substrate used herein is a 23 point paperboard 10 having a basis
weight of 280 lbs/ream. A gloss or exterior surface 12 of the
paperboard 10 may be provided as a 16 lb/ream weight coating of low
density polyethylene (LDPE) applied following conventional flame
treatment of the paperboard substrate. Subsequent corona treatment,
as is conventional within the art, is used to achieve a surface
energy of about 42 to about 43 dyns which facilitates printability
of the gloss layer(s).
[0028] As seen in FIG. 1, an interior surface of the board has
extruded thereon, in sequence from the board to the outermost
product contact layer, a 5 lb. layer of Nylon 6 (layer 14); a 5 lb.
layer of an adhesive tie layer (layer 16); a 20 lb. layer of LDPE
(layer 18); a 3 lb. layer of an adhesive tie layer (layer 20); a 3
lb. layer of Nylon 6 (layer 22); a 3 lb. layer of an adhesive tie
(layer 24); and, a skin coat layer of 3 lb. of LDPE (layer 26). In
all examples set forth herein, the coating weights are per 3,000
sq. ft. of board surface.
[0029] The LDPE used on the gloss 12 and skin coat layer 26 is a
Chevron 4517 LDPE which may be extruded onto the board at a
temperature of about 600.degree. F. The possible operative
extrusion temperatures of LDPE are well known to one having
ordinary skill in the art and may be varied within the known
acceptable temperature ranges. The Nylon 6 is a B85QP (Honeywell)
material extruded at 580.degree. F., though a lower extrusion
temperature of about 500.degree. F. is recommended. The respective
tie layers are low density polyethylene Plexar.RTM. 175 (Quantum
Corp.) and may be extruded at a temperature of about 600.degree.
F.
[0030] The resulting laminate may be scored and cut into blanks
which may be subsequently folded. The side seams may be heat sealed
as is conventional within the art. The prepared blanks are then
ready to be filled with juice or other product and sealed using
conventional equipment and techniques.
[0031] While the structure seen in reference to FIG. 1 and
described in more detail above is given in reference to specific
polymers and tie layers, a variety of different polymers may be
used in accordance with the scope of the present invention. For
instance, suitable heat-sealable polyolefins may include
polypropylene, high density polyethylene, medium density
polyethylene, low density polyethylene, linear low density
polyethylene, and combinations thereof. Various additives may be
included in the polyolefins so as to achieve desired extrusion,
adhesion, or heat sealing properties. Coating weights for the gloss
side of the board may be between about 6 to about 20 lbs/ream. The
skin coat weights of the polyolefins may vary between about 2 to
about 28 lbs/ream. However, as noted below, a skin coat layer
selected from the lower end of the coating ranges is preferred so
as to minimize scalping of essential oils.
[0032] Positioned between the oxygen barrier layer 14 and the
anti-scalping layer 20 is a relatively thick 20 lb. layer of LDPE
(layer 18). The inclusion of a relatively thick layer of LDPE
within the laminated structure has been found useful in that the
added bulk material further minimizes the overactivation of board
during heat sealing. Additionally, the LDPE layer 18 also limits
water vapor loss of carton contents which is particularly important
for non-refrigerated liquids such as fabric softeners which must
have extended shelf lives in low humidity storage environments. The
bulk and density of the LDPE helps insulate the board substrate
during heat sealing operations and provides for a more rigid carton
which resists bulge. While a 20 lb. coating weight is used in the
example set forth below, the coating weight of the LDPE may range
from between about 10 to about 24 lbs/ream. Additionally, the
various polyolefins described above may also be used in place of
the low density polyethylene within layer 18. Likewise, similar
properties may be achieved by using multiple layers of polyolefin,
along with any necessary adhesive tie layers, so as to achieve the
similar benefits and attributes of the bulk polyolefin layer
18.
[0033] Paperboards suitable for use with the present invention may
include a range of paperboard stock having a basis weight of
between about 150 to about 300 lbs/ream.
[0034] The oxygen barrier layer 14, represented in FIG. 1 by the 5
lb. Nylon 6 layer, may include other extrudable polymers including
other semi-crystalline nylons or semi-crystalline polyamides such
as Nylon 4/6, Nylon 6/6, Nylon 6/12, Nylon 11, and Nylon 12,
aromatic containing polyamides, as well as Amorphous Nylon, EVOH,
blends of Amorphous Nylon/EVOH, PET, PET-G, other polyesters and
combinations thereof. The oxygen barrier layer may be present in a
coating weight of between about 3 to about 16 lbs/ream, the coating
weight varying depending upon the actual oxygen barrier material
selected. It is well within the skill level of one having ordinary
skill in the art to select and apply an appropriate amount of an
oxygen barrier material by conducting routine tests to determine
the effectiveness of the oxygen barrier. The high melting point
oxygen barriers such as the semi-crystalline nylons or
semi-crystalline polyesters are believed most useful in minimizing
overactivation of the board during heat sealing operations and are
preferably applied directly to a surface of the board.
[0035] The tie resins suitable for co-extrusion with the individual
laminated layers may include a variety of conventional tie resins
such as anhydride modified co-polymers available under the trade
name of Bynel.RTM. (DuPont Corp.) along with the Plexar.RTM. resins
noted above. Useful coating levels of tie layers include about 2 to
about 6 lbs/ream coating weight.
[0036] The anti-scalping layer, represented in FIG. 1 by the 3 lb.
layer of Nylon-6, may include other extrudable barrier layers or
films. In at least one embodiment of the present invention, it is
useful if the anti-scalping layer is selected from a polar polymer
or film having a high melting point. The high melting point further
minimizes transfer of heat from the skin coat side of the laminate
to the underlying board substrate, thereby minimizing
overactivation of the board and the resulting pin holes or
blistering of the oxygen barrier layers and laminated layers which
results from evolved steam. As such, the integrity of the oxygen
barrier layer(s) is maintained.
[0037] Amorphous nylon may also be used as the anti-scalping layer
22. Amorphous nylon provides excellent oxygen barrier properties to
the overall structure and works well in high humidity environments
such as those encountered in refrigerated juice cartons.
[0038] As set forth in the examples which follow, a structure as
seen in FIG. 1 (N6C) and comparative structures were evaluated with
respect to Vitamin C retention, d-limonene uptake (scalping), and
carton bulge. The comparative structures included quart size glass
containers (glass). Additionally, a commercially available control
structure having the designation VS+10 was also evaluated. The
VS+10 structure is as follows: [0039] 16# LDPE/23 point
280#board/5#Nylon-6/5#Plexar.RTM. 175 tie layer/26# LDPE
Example 1
[0040] A laminate according to the embodiment seen in reference to
FIG. 1 was prepared and converted into carton blanks as previously
described. The carton blanks were filled with orange juice under
refrigerated conditions and stored at 5.degree. C. for 49 days.
Vitamin C levels were determined on the intervals as seen in
reference to FIG. 2, using established protocols of starch-iodine
titration. Comparison tests from the glass and VS+10 containers
were also conducted. The results, set forth in FIG. 2, indicate
that the N6C laminate has Vitamin C retention properties better
than the VS+10 comparative structure. The Vitamin C data indicates
that the laminate constructed according to one aspect of the
present invention provides an effective oxygen barrier as reflected
by the improved Vitamin C levels. Oxidative loss of Vitamin C
within paperboard cartons is correlated with oxygen transmission
rates through the laminated structure, along with dissolved oxygen
and head space oxygen. The improvements in oxygen transmission are
believed attributable to the integrity of the oxygen barrier layers
and other laminate layers which are present during the heat sealing
steps.
[0041] As seen in reference to FIG. 3, the laminate of the present
invention also provides significant improvements with respect to
scalping of d-limonene, an essential oil. The measurements of
d-limonene are set forth as percent volume in FIG. 3 and were
derived using the Scott method for percent oil. As indicated in the
data in FIG. 3, the d-limonene loss is greatly improved compared to
the control VS+10 structure. The improvements in d-limonene loss
are attributable to the anti-scalping barrier of Nylon 6 material
which is secured to the skin coat layer by a tie layer. The polar
nature of the anti-scalping barrier limits the uptake of d-limonene
to the relatively thin skin coat layer 26 and adhesive tie layer
24. Further, d-limonene loss compares favorably to the glass
container indicating only a minimal amount of d-limonene loss
attributable to scalping. As reflected by the data in FIG. 3, the
majority of d-limonene loss occurs immediately following filling
and d-limonene levels are substantially stable thereafter. To the
extent an anti-scalping barrier such as Nylon-6 is used which also
has oxygen barrier properties, the overall oxygen barrier
properties of the resulting laminate are also enhanced.
[0042] As seen in reference to the data set forth in FIGS. 4A and
4B, bulge data for the control VS+10 structure and the N6C
structure of the present invention were measured and plotted. As
seen, the N6C carton is more resistant to bulge than the control
VS+10 structure. Carton bulge, as described in Applicant's commonly
assigned U.S. Pat. No. 6,372,317, and which is incorporated herein
by reference in its entirety and for all purposes, may be
controlled by reducing the rate of moisture transmission through
the carton board. Without being limited by theory, it is believed
that the improvements in carton bulge are attributable in part to
the improved integrity of the laminated layers which form the
carton. The ability of the resulting board structure to avoid
overactivation preserves the structural and functional integrity of
the laminated layers. Improved integrity minimizes both oxygen
transmission rates and water vapor transmission rates. The
reduction in water transmission rates is believed to correlate with
the noted improvements seen in carton bulge.
[0043] Additionally, the use of a high semi-crystalline nylon as
discussed in some embodiments as oxygen barrier layers and/or an
anti-scalping layer, imparts additional stiffness to the laminated
structure which also contributes to the overall bulge resistance of
the carton.
[0044] As set forth in Applicant's co-pending application having
Ser. No. 60/428,293, entitled Improved Flavor Barrier, and which is
incorporated herein by reference in its entirety, calcium carbonate
and other organic and inorganic fillers described may be
incorporated into skin coat 26 and tie layer 24 at a percent by
weight loading of at least about 10 to 20 percent. The inclusion of
a filler into the skin coat and tie layer resins will further
reduce the amount of d-limonene which is scalped by the polyolefin
polymers.
[0045] Although preferred embodiments of the invention have been
described using specific terms, devices, and methods, such
description is for illustrative purposes only. The words used are
words of description rather than of limitation. It is to be
understood that changes and variations may be made by those of
ordinary skill in the art without departing from the spirit or the
scope of the present invention, which is set forth in the following
claims. In addition, it should be understood that aspects of the
various embodiments may be interchanged, both in whole or in part.
Therefore, the spirit and scope of the appended claims should not
be limited to the description of the preferred versions contained
therein.
* * * * *