Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02534881 2006-02-07
WO 2005/016781 PCT/EP2004/009251
NCa 7501
'~FLE~II~LE T'ACI~AG~hIG AND ME~'HQD OF lVIAIVU~'ACTt;~"
FIELD ~F TNVENTIC3N
This invention relates to flexible packaging units intended. to be opened by
tearing and to means for controlling the opening by tearing. The invention
provides a
method of constructing a flexible packaging unit to facilitate controllable
opening
thereof by tearing. Further, the invention provides a flexible packaging unit
incorporating tear control mews for facilitating its controllable opeung.
EACTC~'rRC'UND t>F TF-IE INVEI~ITIC~N
Being able to control the opening of a flexible container such as a plastic
bag
or pouch is important to consumers, especially wlxere the contents are likely
to mess if
spilt. Means for controlling the direction of tearing of a tearable packaging
unit have
been previously proposed. In IJS 5,186,543 there is disclosed an eas~T-open
flexible
container having guide strips respectively located on either opposed side wall
and a
tear strip located at the apex of the container. Extending from the tear strip
to each
guide strip is an opposing tear area defined on each wall. Tearing is limited
to these
areas v~.~hen the consumer takes hold of and pulls the tear strip from anc
side to the
other. A drawback of this invention is that a special tear strip has to be
provided and
incorporated into the construction.
European patent EP 0471220 discloses a pouch having a thin-walled part for
easy
tearing, the thin wall part incorporating strings in the plastic film that
makes up the
wall; the strings being pullable to open the pouch. A drawback of this
invention too is
the requirement of providing special elements, in this case the strings,
adding
complexity to the manufacture thereof:
CONFIRMATION COPY
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EP 0325993 describes a bag having a tear strip that is defined by parallel
perforated
lines. The perforations are backed by a sealing strip to maintain the hermetic
integrity
of the bag's interior. Again, this invention has the dxawback of increasing
cozrzplexity
of manufacture.
EP 0423456 discloses a bag having zipper means rendering it reclosable and a
tear
strip for facilitating the initial opening. The tear strip can be located
internally and
exterz~tally at the apex of the bag. Protection against unwanted propagation
of the tear
towards the zipper elezxzents is achieved by providing the zipper elements
each with an
extended base portion to reinforce the fzlm of the walls and to keep the tear
frozrz
reaching down to tl~xem. This invention adds further to the material
requirements for
manufacture.
Them is a need for a bag ar other flexible container oonstruotion of simple,
yet having
zrzeans of preventing prapagatian of an initial tear in an undesired direction
or area.
An advantage of the present invention is to provide a container having a
bc~.nd~d tear
area in which tearing is confined in a construction that avoids havin'T a teL-
Grip. B~-
setting limits to the area available far tearing and defining such area
entirelw within a
wall of the container, the problem of the tear propagating off the top edge of
the
container, leaving the mouth not completely opened, is avoided.
An advantage of the present invention is to provide barrier rxzeans far
preventing the
tear frarn propagating to the tap edge of the container.
SUMMARY OF INVENTION
According to a fZrst aspect of the invention, there is provided a flexible
container
comprising opposed front and back walls sealed together proximate to their
edges to
3C1 define an internal space, a pair of tear-limiting strips applied to a
surface of each wall
or located within each wall so that the stzips on or within opposed walls
coincide
substantially, definiz~:g corresponding tear paths.
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NO 701
To be tear-limiting, the strips have substantially greater tear resistance
than the walls.
In a preferred form of the invention, the strips of each pair are spaced from
about
S O.lmm to aboczt 6zxzzn apart, preferably about 1mm-2mm and further
preferably froze
about 1.2mm to l.8zrzrrz.
1n a further preferred form of the invention, the strips of each pair are
located to be
substantially parallel to each other.
In an embadiznent, the strips comprise sealable strips.
In an embodiment, the strips are self adhesive.
In a still further preferred form of the invention, the strips are about 1 mm
to about
Smm in breadth, preferably from about l.Smm - 2.Smm,
Futtlzer according to the invention, the strips znay all be located on the
outer suefac~ ~ f
the v,Jalls. Alternatively, the strips are all located an the inner surface of
the walls. In
an embodiment, one pair of strips is located an an inner wall surface and the
other on
an outer wall surface. In another embodiment, one strip in each pair is
located on an
izmer surface and the other strip is located on an outer surface of each wall.
In the
event the wall is comprised of a laminate material, a strip zxzay be boated to
be on a
surface between laminate materials making up the wall material.
In preferred embodiments, the thickness of the strips is in th.e range from
about I2 -
100 znicrans, preferably about'~0-~0 rnicrozzs.
Further according to the invention, the strips are made of polypropylene (PP).
3fl Alteznatively, the strips may be made of polyethylene (PET).
-3-
CA 02534881 2006-02-07
WO 2005/016781 PCT/EP2004/009251
ITC? '501.
According to a second aspect of the invention, there is provided a
tlexibleAwalled
container having opposed back and front walls, each wall having a respective
top edge,
the twalls being sealed together proximate to the respective top edges
defining an
internal space between them, and tear barrier means provided on or within each
wall,
defining a tear path Located to be spaced from at least a part of the tap edge
thereof
In a preferred farm of the invention, the tear paths are defined by paired
spaced barrier
strips resistant to tearing.
Acaordixzg to a third aspect of the invention, a method of rxjanufacftxring a
flexible
walled container comprises the steps of providing first and second films,
providing
tear barrier material in strip farm, applying the tear barrier material in
paired strips to
each film so as to define a substantially coixxciding tear path on each and
arranging the
films in apposition to form a container comprising substantially aainciding
tear paths
1 ~ on each wall.
The invention further provides a method o~ manufacturing a sealable bag, the
method
comprising the steps of providing a flexible fxhn and forming it into a
container
defining an internal space bounded by respective front and back walls, and
applying a
2(1 tear barrier strip to the walls to define a bounded tear path on each of
the front and
back walls.
In all embodiments of the invention, the tear barrier is of substantially
greater tear
resistance than the flexible film to which it is applied.
BRTEF DESCRIPT101rT CF I~I~AW1NGS
Figure 1 presents in A a side view of an embodiment of a ffexible container of
tlae
invention arid in B a crass section of the container along line A-A'.
Figure z is a side view of an alternative embodiment of the invention.
_q._
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NO 701.
Figure 3 is a side view of a fiirther alternative embodiment of the invention.
Figure A~ is a schematic illustration of a process of manufacture of a
container
according to the inVent1013.
DETAILED DESCRIPTION OF EIvI$0r3IMENT~
The invention provides for the definition of substantially coinciding tear
paths on
opposing walls of a flexible packaging mit made of a tearable film, for
example a film
of plastics material or a laminate. The tear path is designed to facilitate
the opening of
1Q the container in a controllable manner by a consumer desirous of accessing
the
contents, Ey limiting the propagation of the opening tear to a defined path, a
cleaner
open may be obtained and the likelihood of spillage, waste and messing
reduced. The
packaging unit may be a pouch container ar a bag or the like.
1 S The tear paths are defined by applying tear limiting elements in the form
of barrier
strips in pairs to the surfaces of the container walls or to sheets in
laminated material
making up the walls. Preferably the strips are substantially parallel to each
other. The
barrier strips may be applied to the inner or outer surfaces of the container
and in an~~
combination. In a preferred embodiment, the strips are all applied to the
outer surfaces
20 at corresponding positions. However, they may also be applied to the
opposing inner
surfaces. Alternatively, one pair may be applied to an inner surface and the
other to
the outer surface of the opposing wall. In an embodiment, one strip in a pair
may be
applied to an outer surface while its partner may be applied to the inner
surface of the
same wall. Where the wall is constructed of a laminate material, one of more
of the
25 strips may be located between adjacent layers in th.e lalninats.
The strips are preferably spaced apart from about ~. lnnn to about 6tnin and
further
preferably from about 1 mm to about ~mrn. In a particularly preferred
embodiment, the
strips are spaced apart by about l.3mm to about l.8mzn.
CA 02534881 2006-02-07
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ICU 7SOI
By zzarrowing the spacing between fihe strips in each pair arid by making the
positioning of the pairs coincide on the opposing walls, a near perfect tear
line is
achievable with the tear paths on the opposing walls alzzz,ost exactly
superposed.
S The strips are comprised of tear tape that is sealable or preferably self
adhesive.
Each strip desirably may have a width in the range from about Imm to Snzzn,
preferably from about I .Smm to about 2.Smm. Desirably the strips have a
thicklzess in
the range from about 12 microns to lOfl microns, preferably from about 2Q to
about S4
microns. Factors such as strip thickness, strip width and grade of strip tape
material
I O will determine the strip tear resistance in comparison with the tear
resistance of the
film from which the container is fashioned.
In the case where the containers are to be retorted or subjected to a form. of
heat
treatment, the strips are preferably made of polyester or polyethylene (fET).
Where
I S the containers are intended to house a dry product and not be subjected to
a retort
stage, they may conveniently be made from polyproylene (IMP) tape. Polyester
tape
may however also be used, as may other suitable tape materials known in the
art.
The pouches may conveniently be of the doypacl~ type or be 3- or 4-sidedly
sealed
20 pouches. However, other pouch configurations may be employed. The pouch
material
may be fF, fET arid Iarninates compzxsing two or more affP, metallised foil,
e,g.
aluminium foil (Alu), poly-acryIamide (PA), PET, fibre sheeting, such as
paper, and
fE. Preferably it will be a 3-layer laminate of PET/Alu/PP for retorted
product
applications, and PETlP'P or PfIPE for dry product applications. further
layers may
2S be added, depending on the product application and processing and tlxe
degree of tear
resistance required in comparison with the 'tear-limiting strips to be
applied.
To facilitate the initiation of a tear, a notch may be formed at an edge of
the container
wall. Alternatively, a hole may be punched at a suitable location where the
opposed
30 walls are sealed together. The notch or hole is sealed around its edges to
maintain the
airtight integrity of the container. The tear limiting tape strip may be
applied to eaoh
side of the notches or punched holes.
,.C_
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1'10 '~5CI1
The flexible container ltl illustrated in Figure I has opposing walls 12, 14.
sealed
together at xegion 1G, proximate to top edges I $, 20. Below region I6 and
spaced from
tap edges 1 S, 20 is barrier strip 22, 24 applied externally to the wall 12,
14. Spaced
from barrier strip 22, ~4 is a second barrier strip 26, 2$. Between the upper
and lower
bal-rier strips is defined thus a tear area ~0, 32. A notch 34 is provided to
facilitate
initiation of a tear in the tear area. 'then a tear 36 is initiated ;n t~hr
~~p~ ~zn ;o ;+ ;
forced to propagate in that tear area defined by the barrier strips, and not
stray beyond.
The direction and extent of tearing is thus controllable.
Figure 2 illusta~ates in crass section an embodiment of laminated wall
sections to which
barrier strips are applied, according to the invention. I,i~e numerals are
applied to
denote like features appearing in figure I. In this exnbodinaent, tear barrier
strips 2~,
24, 25 and 28 are located internally in walls 12 and I4, being placed between
adjacent
layers of aluminium foil 3$ and polypropylene 40. An external layer 42 of
polyethylene PET is applied over the altuninium foil 3$. The layers are sealed
together at heat seal 44.
Figure 3 illustrates a further exemplary embodiment, in which the barrier
strips 22, 24,
26 and 28 are placed externally to the container, being applied as self
adhesive tape to
the outer polyethylene surfaces of layers 42.
A wall material for a tearable flexible container of the invention may be
manufactured
by providing a flexible film far forming a wall of the container, such as a
laminate of
2S alufoil and polyethylene, providing a tear barrier element having
substantially greater
tear resistance than the wall film, for example a polypropylene tape, locating
the
element on the film to define a tear path thereon, and fixing the element to
the film.
The barrier element in strip forzu may be adhered to the film through use of
an
adhesive, or may be thermally bonded to it.
3Q
Figure 4 illustrates a method of manufacturing a laminated flexible sheet
material foil
for use in farming the bag of figure I. In the illustrated exemplary
embodiment, the
CA 02534881 2006-02-07
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NU '75GI
walls 12, I4 are constructed of a laminated sheet comprising a foil ~.2 on a
polyethylene film 44. The tear barrier comprises polyethylene strips 22, 26
applied to
the foil ~~. The foil is preferably metallised and may for e~an~ple be an
al~zzz~inizun
foil {'talufoil").
S
In a preferred embodiment, as the Iamizxated sheet ~0 is moved by means of a
conveyor system, the barrier strips are of polyester and optionally covered by
a layer
4& of polypropylene extruded aver them. In figure ~, the polypropylene layer
4C is
applied by means of an e:~trusian hopper 48. Irregularities 50 iz~z layer ~~6
are smoothed
I O out by passing the layer under a eoxreeting roll 5~. The adhesive an the
strip is a self
adhesive material delivered in reel. No high tezx~perature treatznant is
needed far the
application which is done by simple contact by unwinding a tape while
unr~inding the
film. The strip and its applicator are obtainable frazxz the company PP Payne
of
Nottingham, England.
IS
An advantage of the invention is that it provides a highly reliable guided
tear in both
opposing walls of the container, along a bounded path leading from one edge to
another, be it from a side edge to the opposite side edge or from the top edge
to a side
edge or from a side edge to a defined part of the top edge.
2U
A further advantage is that the paclcage and the guide strips defining the
tear path are
all retartable.
~g_
