U.S. patent application number 11/301583 was filed with the patent office on 2007-06-14 for unsupported lap-sealable liner for composite container.
Invention is credited to Michael T. Drummond, David McKnight, Robert Thor Versluys.
Application Number | 20070131750 11/301583 |
Document ID | / |
Family ID | 38138288 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070131750 |
Kind Code |
A1 |
Drummond; Michael T. ; et
al. |
June 14, 2007 |
Unsupported lap-sealable liner for composite container
Abstract
An unsupported lap-sealable liner for a composite container
comprises a heat seal layer, a barrier web having a first surface
attached to the heat seal layer and having an opposite second
surface, and a sealable primer applied as an aqueous dispersion to
the second surface of the barrier web and then dried. The sealable
primer comprises a polymer having bonding affinity with wet
adhesive used for bonding the liner to a paperboard surface of a
composite container. The sealable primer furthermore is
heat-sealable to the heat seal layer such that the liner is
lap-sealable.
Inventors: |
Drummond; Michael T.;
(Laurinburg, SC) ; McKnight; David; (Florence,
SC) ; Versluys; Robert Thor; (Florence, SC) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Family ID: |
38138288 |
Appl. No.: |
11/301583 |
Filed: |
December 13, 2005 |
Current U.S.
Class: |
229/123.1 ;
229/5.82 |
Current CPC
Class: |
B32B 38/164 20130101;
B32B 37/1284 20130101; B32B 2037/243 20130101; B65D 77/2024
20130101; B31B 2105/001 20170801; B32B 37/20 20130101; B65D 3/22
20130101 |
Class at
Publication: |
229/123.1 ;
229/005.82 |
International
Class: |
B65D 43/02 20060101
B65D043/02; B65D 5/56 20060101 B65D005/56 |
Claims
1. A composite container, comprising: a tubular body wall
comprising paperboard material, the body wall defining an inner
paperboard surface facing toward an interior of the container; and
an unsupported liner free of paper layers and adhered to the inner
paperboard surface of the body wall via a wet adhesive interposed
between the liner and the inner paperboard surface, the liner
comprising a heat seal layer defining an innermost surface of the
container, a barrier web attached to a radially outer surface of
the heat seal layer, and a sealable primer applied as an aqueous
dispersion to a radially outer surface of the barrier web and then
dried, the sealable primer comprising a polymer having bonding
affinity with the wet adhesive and furthermore being heat-sealable
to the heat seal layer of the liner, the liner having opposite
edges that form a lap joint therebetween via heat sealing of the
heat seal layer to the sealable primer.
2. The composite container of claim 1, wherein the sealable primer
comprises a modified ethylene polymer.
3. The composite container of claim 1, wherein the sealable primer
is selected from the group consisting of modified ethylene
polymers, modified acrylic primers, acrylic heat seal coatings, and
vinyl primers/washcoats.
4. The composite container of claim 1, wherein the heat seal layer
comprises a layer of ionomer resin.
5. The composite container of claim 4, wherein the ionomer resin
comprises ethylene acid copolymer having acid groups partially
neutralized by zinc or sodium ions.
6. The composite container of claim 4, wherein the heat seal layer
further comprises a layer of high-density polyethylene coextruded
with the layer of ionomer resin.
7. The composite container of claim 1, wherein the barrier web
comprises metal foil.
8. The composite container of claim 1, wherein the barrier web
comprises metallized polymer film.
9. An unsupported, lap-sealable liner for a composite container,
the liner being free of paper layers and comprising: a heat seal
layer; a barrier web having a first surface attached to the heat
seal layer and having an opposite second surface; and a sealable
primer applied as an aqueous dispersion to the second surface of
the barrier web and then dried, the sealable primer comprising a
polymer having bonding affinity with wet adhesive used for bonding
the liner to a paperboard surface of a composite container, the
sealable primer furthermore being heat-sealable to the heat seal
layer whereby the liner is lap-sealable.
10. The unsupported, lap-sealable liner of claim 9, wherein the
sealable primer comprises a modified ethylene polymer.
11. The unsupported, lap-sealable liner of claim 9, wherein the
sealable primer is selected from the group consisting of modified
ethylene polymers, modified acrylic primers, acrylic heat seal
coatings, and vinyl primers/washcoats.
12. The unsupported, lap-sealable liner of claim 9, wherein the
heat seal layer comprises a layer of ionomer resin.
13. The unsupported, lap-sealable liner of claim 12, wherein the
ionomer resin comprises ethylene acid copolymer having acid groups
partially neutralized by zinc or sodium ions.
14. The unsupported, lap-sealable liner of claim 12, wherein the
heat seal layer further comprises a layer of high-density
polyethylene coextruded with the layer of ionomer resin.
15. The unsupported, lap-sealable liner of claim 9, wherein the
barrier web comprises metal foil.
16. The unsupported, lap-sealable liner of claim 9, wherein the
barrier web comprises metallized polymer film.
17. The unsupported, lap-sealable liner of claim 9, wherein the
heat seal layer comprises a blow or cast film and is adhesively
laminated to the barrier web.
18. The unsupported, lap-sealable liner of claim 9, wherein the
heat seal layer comprises an extrusion coating on the barrier
web.
19. A method of making an unsupported, lap-sealable liner for a
composite container, comprising the steps of: providing a barrier
web having opposite first and second surfaces; attaching a heat
seal layer to the first surface of the barrier web; and applying an
aqueous dispersion of a sealable primer to the second surface of
the barrier web and allowing the aqueous dispersion to dry such
that a layer of the sealable primer covers the second surface of
the barrier web, the sealable primer comprising a polymer having
bonding affinity with wet adhesive used for bonding the liner to a
paperboard surface of a composite container, the sealable primer
furthermore being heat-sealable to the heat seal layer whereby the
liner is lap-sealable.
20. The method of claim 19, wherein the heat seal layer comprises a
blow or cast sealant film, and the step of attaching the heat seal
layer comprises adhesively laminating the sealant film to the
barrier web.
21. The method of claim 19, wherein the step of applying the
aqueous dispersion comprises using a gravure roll to apply the
aqueous dispersion onto the barrier web.
22. The method of claim 19, wherein the step of attaching the heat
seal layer comprises extrusion coating the heat seal layer onto the
barrier web.
23. The method of claim 19, wherein the sealable primer is selected
from the group consisting of modified ethylene polymers, modified
acrylic primers, acrylic heat seal coatings, and vinyl
primers/washcoats.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to composite containers, and
particularly relates to liners for composite containers.
[0002] Traditionally, liners for composite containers have included
a layer of paper on the back side that faces outward toward the
paperboard body wall of the container. Such liners have been termed
"supported" liners because the paper layer serves as a structural
support for the liner, which imparts substantial tensile strength
to the liner and makes the handling of the liner during the
container manufacturing process relatively easy. The paper layer
also facilitates gluing the liner to the paperboard body wall.
[0003] While the paper layer thus serves useful purposes, it also
necessitates an "anaconda" fold seal of the liner so that the paper
layer is not exposed to the container contents at the edge of the
liner ply. The innermost surface of the liner comprises a sealant
material. The folded edge of the liner places the sealant on the
folded edge in contact with sealant on the opposite unfolded edge
of the liner ply, and the liner edges are sealed together by the
sealant.
[0004] Such supported liners tend to be quite thick, and the
anaconda fold seal represents three layers of the liner, such that
the fold seal is extremely thick. This extreme thickness of the
fold seal can create problems in forming a hermetic seal between a
container end and a membrane lid because the fold seal creates a
large bump on the container end. Accordingly, efforts have been
made to develop "unsupported" liners that do not have a paper
backing. Instead of the paper backing, the back side of current
unsupported liners comprises an extruded polymer layer. However,
this necessitates the use of a special adhesive for adhering the
liner to the paperboard body wall, because the types of wet
adhesives typically used for adhering conventional supported liners
are not suitable.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention addresses the above needs and achieves
other advantages, by providing an unsupported, lap-sealable liner
for a composite container, a method of making such a liner, and a
composite container incorporating the liner. The liner is
compatible with wet adhesives for attaching the liner to a
paperboard body wall of a container. Because the liner is
lap-sealable, the liner joint represents only two thicknesses of
the liner, and because the liner is unsupported, the liner is thin.
Therefore, the liner joint is much thinner than a fold seal of a
conventional supported liner.
[0006] In accordance with one embodiment of the invention, an
unsupported lap-sealable liner comprises a heat seal layer, a
barrier web having a first surface attached to the heat seal layer
and having an opposite second surface, and a sealable primer
applied as an aqueous dispersion to the second surface of the
barrier web and then dried. The sealable primer comprises a polymer
having bonding affinity with wet adhesive used for bonding the
liner to a paperboard surface of a composite container. The
sealable primer furthermore is heat-sealable to the heat seal layer
such that the liner is lap-sealable.
[0007] Various materials can be used for the sealable primer,
including but not limited to modified ethylene polymers, modified
acrylic primers, acrylic heat seal coatings, and vinyl primers or
washcoats. The heat seal layer forming the opposite surface of the
liner can comprise any of various heat seal materials including but
not limited to ionomer resins such as SURLYN.RTM. or TRANCEND.RTM.,
high-density polyethylene (HDPE), ionomer/HDPE coex, or the like.
The heat seal layer can be a separately manufactured film that is
adhesively laminated to the barrier web, or can comprise an
extrusion coating on the barrier web.
[0008] The barrier web can comprise a metal foil layer, a layer of
metallized polymer film (i.e., a polymer film on which a thin layer
of metal in substantially pure form, such as aluminum, is
vapor-deposited), a layer of barrier polymer such as ethylene vinyl
alcohol copolymer (EVOH), or combinations thereof.
[0009] A composite container in accordance with one embodiment of
the invention comprises a tubular body wall defining an inner
paperboard surface facing toward an interior of the container, and
an unsupported liner free of paper layers and adhered to the inner
paperboard surface of the body wall via a wet adhesive interposed
between the liner and the inner paperboard surface. The liner
comprises a heat seal layer defining an innermost surface of the
container, a barrier web attached to a radially outer surface of
the heat seal layer, and a sealable primer applied as an aqueous
dispersion to a radially outer surface of the barrier web and then
dried. The sealable primer comprises a polymer having bonding
affinity with the wet adhesive and furthermore being heat-sealable
to the heat seal layer of the liner, and the liner has opposite
edges that form a lap joint therebetween via heat sealing of the
heat seal layer to the sealable primer.
[0010] The invention also provides a method of making an
unsupported, lap-sealable liner for a composite container. The
method comprises the steps of providing a barrier web having
opposite first and second surfaces, attaching a heat seal layer to
the first surface of the barrier web, and applying an aqueous
dispersion of a sealable primer to the second surface of the
barrier web and allowing the aqueous dispersion to dry such that a
layer of the sealable primer covers the second surface of the
barrier web, the sealable primer comprising a polymer having
bonding affinity with wet adhesive used for bonding the liner to a
paperboard surface of a composite container, the sealable primer
furthermore being heat-sealable to the heat seal layer whereby the
liner is lap-sealable.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0011] Having thus described the invention in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0012] FIG. 1 is a perspective view of a composite container in
accordance with an embodiment of the invention, and including a
membrane lid sealed to a top end of the container and an overcap
for placement over the sealed membrane lid;
[0013] FIG. 2 is a cross-sectional view through the top end of the
container along line 2-2 in FIG. 1;
[0014] FIG. 3 is a cross-sectional view through the container body
wall along line 3-3 in FIG. 1, showing the liner lap joint;
[0015] FIG. 4 is a diagrammatic illustration of a liner
manufacturing process in accordance with one embodiment of the
invention; and
[0016] FIG. 5 is a diagrammatic illustration of a liner
manufacturing process in accordance with another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present inventions now will be described more fully
hereinafter with reference to the accompanying drawings, in which
some, but not all embodiments of the invention are shown. Indeed,
these inventions may 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
satisfy applicable legal requirements. Like numbers refer to like
elements throughout.
[0018] FIGS. 1-3 depict a container 10 in accordance with one
embodiment of the invention. The container 10 includes a tubular
container body 12 that may be formed by various methods and may
have various constructions. In general, the container body 12 can
be made by winding at least one structural body ply 14 about a
forming mandrel (not shown) and either adhering overlapping edges
of a single body ply to each other to form a tubular structure, or,
in the case of multiple body plies, winding the plies one upon
another and adhering opposing faces of the plies to one another to
form a tubular structure. The body ply or plies can be wound either
spirally or convolutely. The body ply or plies advantageously
comprise paperboard. The container body 12 may also include an
outer label ply 16 wrapped about an exterior surface of the
outermost body ply and adhered thereto. The label ply 16 may
comprise, for example, a thin non-structural ply of paper or
polymer film, and may include graphics and/or indicia printed or
otherwise provided on its exterior surface.
[0019] The container body 12 also includes a liner 18 adhered
against an inwardly facing surface of the innermost body ply 14.
The liner 18 is provided for forming a barrier substantially
impervious to moisture and/or gases such as oxygen. In the
packaging of food and drink products in particular, it is often
important to ensure that the container wall have a water vapor
transmission rate (WVTR) below a certain specified value, and/or to
ensure that the container wall have an oxygen transmission rate
(OTR) below a certain specified value. Depending upon the
requirements in a particular case, the material(s) that are
suitable for the liner 18 may vary
[0020] The present invention particularly concerns containers in
which the liner 18 is an unsupported, lap-sealable liner. By
"unsupported" is meant that the liner does not include any paper
layer as a backing. The liner 18 includes a web 20 of material that
forms the barrier to moisture and/or gases. The barrier web 20 can
comprise one or more layers of barrier material. Suitable barrier
materials include but are not limited to metal foil, metallized
polymer film (i.e., polymer film having a thin layer of
substantially pure metal vapor-deposited thereon), barrier polymers
such as ethylene vinyl alcohol copolymer (EVOH), polyvinylidene
chloride, polyethylene, and polypropylene, silicon dioxide or
aluminum oxide coatings, or combinations thereof. The liner 18
further comprises a heat seal layer 19 attached to the radially
inward surface of the barrier web 20. The heat seal layer 19 forms
the innermost surface of the container adjacent the container
contents. Various materials can be used for the heat seal layer,
including but not limited to ionomer resins such as SURLYN.RTM. or
TRANCEND.RTM. (ethylene acid copolymers having acid groups
partially neutralized by zinc or sodium ions), high-density
polyethylene (HDPE), and others. A coextruded heat seal layer
comprising a layer of ionomer resin and a layer of HDPE can also be
used.
[0021] The liner 18 also comprises a layer of sealable primer 21
that forms the radially outermost surface of the liner facing the
paperboard body wall of the container. The liner 18 is adhered to
the inner paperboard surface of the body wall ply or plies 14 by a
wet adhesive 23. The wet adhesive can comprise, for example, a PVA
type adhesive such as XR-6520M available from the H.B. Fuller
Company. The sealable primer comprises a material that has good
bonding affinity with the wet adhesive 23 and is also heat-sealable
to the heat seal layer 19 of the liner. Various materials are
suitable for the sealable primer, including modified ethylene
polymers, modified acrylic primers, acrylic heat seal coatings, and
vinyl primers or washcoats. Examples of suitable commercially
available materials include: Sovereign 87XW134 (water-based vinyl
primer) available from Sovereign Specialty Chemicals, Inc.; H.B.
Fuller SC8062 (solvent-based acrylic primer/heat seal coating)
available from H.B. Fuller Company; and MICA M1164 (water-based,
modified acrylic primer/heat seal coating) available from Mica
Corporation of Shelton, Conn.
[0022] Thus, as shown in FIG. 3, the joint between the edges of the
liner ply 18 can be an unfolded or lap joint. This means that the
joint has only two thicknesses of the liner 18. Additionally, the
unsupported liner 18 is substantially thinner than a conventional
supported liner. Accordingly, the lap joint of the unsupported
liner can be on the order of one-third to one-tenth the thickness
of an anaconda fold seal for a conventional supported liner.
[0023] The container 10 can also include a rolled bead 22 at a top
end of the container body 12, formed by rolling the top edge of the
wall of the container body 12 radially outwardly and then
downwardly toward a lower end of the container body. The bead 12
can be formed by providing a die of suitable configuration and
forcing the top end of the container body axially against the die
to roll an upper portion of the body outwardly and then downwardly.
The bead 12 is provided in part so that a removable and replaceable
overcap 24 can be snap-fit onto the top end of the container in
engagement with the bead. The overcap provides a way to re-close
the container after it has initially been opened.
[0024] The primary or original sealing of the top end of the
container, however, can be provided by a flexible membrane closure
26 that is bonded to the end surface of the bead 22 after the
container is filled. The membrane closure 26 can be of various
constructions, but generally includes at least a moisture and/or
gas barrier layer 28 and can include one or more further layers 30
if desired. To bond the membrane closure 26 to the bead, the
membrane closure includes on its under surface a sealant 32 that is
heat-sealable to the heat seal layer 19 of the liner. The greatly
reduced thickness of the liner lap joint relative to conventional
anaconda fold seals means that there is a much smaller profile
variance on the end of the bead. This potentially can allow the
thickness of the sealant layer 32 on the membrane to be reduced,
since a lesser amount of sealant is needed to fill in any gap
between the membrane and the bead created by the lap joint.
[0025] After the membrane closure 26 is bonded to the bead 22, the
overcap 24 is then placed over the membrane and engaged with the
bead. When the consumer wishes to open the sealed container, the
overcap 24 is removed and then the membrane closure 26 is peeled
off the bead as depicted in FIG. 1. The container is re-closed by
replacing the overcap.
[0026] The liner 18 can be manufactured in a number of ways. FIG. 4
depicts a first embodiment of a liner manufacturing process in
accordance with the invention. A barrier web 20 is withdrawn from a
barrier web roll 20a and advanced to a laminating adhesive
applicator 40 that applies laminating adhesive to one surface of
the barrier web. A heat seal film 19 is withdrawn from a heat seal
film roll 19a. The barrier web 20 with the laminating adhesive
applied thereto, and the heat seal film 19, are passed through a
laminating station 42 comprising a pair of rolls forming a nip
through which the barrier web and heat seal film pass such that
they are pressed together and adhered to each other via the
laminating adhesive. The resulting laminate is then advanced to a
primer coating station 44 at which the sealable primer is applied
to the surface of the barrier web 20 opposite from the heat seal
film. In the illustrated embodiment, the primer coating station
comprises a gravure roll 46 and a resilient backup roll 48 that
form a nip through which the laminate passes. The gravure roll 46
picks up aqueous dispersion of the primer from a reservoir 50 and
applies the dispersion to the laminate; excess liquid is removed
from the gravure roll by a doctor blade 47 and flows back into the
reservoir. Alternatively, the primer coating station can comprise
other types of coating devices such as a metered rod coater, a flow
coater, a reverse roll coater, a slot die coater, an air knife
coater, or the like.
[0027] After application of the aqueous primer composition, the
laminate is passed through a dryer 60 to dry the coating of primer.
The finished liner 18 is then wound into a roll 18a in a reel-up
70.
[0028] Variations can be made in the process depicted in FIG. 4.
For example, the laminating adhesive can be applied to the heat
seal film 19 rather than to the barrier web 20. The primer can be
applied to the barrier web 20 and dried prior to the laminating
step. The barrier web 20 provided in the roll 20a can already have
the primer applied thereto, such that the web is simply withdrawn
from the roll and laminated to the heat seal film.
[0029] Another embodiment of a liner manufacturing method in
accordance with the invention is shown in FIG. 5. A barrier web 20
is withdrawn from a roll 20a and advanced to an extrusion coater or
slot die coater 34 that includes an extrusion die or slot die 36
that extrudes a layer of heat seal material onto one surface of the
barrier web. The slot die 36 can be configured to coextrude more
than one layer of heat seal material onto the barrier web. For
instance, a layer of ionmer resin (e.g., SURLYN.RTM.) and a layer
of HDPE can be coextruded onto the web. A chill roll 38 may be
provided for cooling the coating after the extrusion coater. The
coated web is then advanced to a primer coating station 44 at which
the sealable primer is applied to the surface of the barrier web 20
opposite from the heat seal coating. In the illustrated embodiment,
the primer coating station comprises a gravure roll 46 and a
resilient backup roll 48 that form a nip through which the laminate
passes. The gravure roll 46 picks up aqueous dispersion of the
primer from a reservoir 50 and applies the dispersion to the
laminate; excess liquid is removed from the gravure roll by a
doctor blade 47 and flows back into the reservoir. Alternatively,
the primer coating station can comprise other types of coating
devices such as a metered rod coater, a flow coater, a reverse roll
coater, a slot die coater, an air knife coater, or the like.
[0030] After the application of the aqueous primer composition, the
web is advanced through a dryer 60 to dry the primer coating, and
then the finished liner 18 is wound into a roll 18a in a reel-up
70.
[0031] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Therefore, it is to be understood that the inventions are
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.
* * * * *