Note: Descriptions are shown in the official language in which they were submitted.
WO95/11170 2 1 7 ~ 4 9 9 PCT/AU94/00638
SELF-STANDING FLEXIBLE BAG
This invention relates to lightweight, flexible
plastic bags or pouches and in particular relates to such
bags usable as containers for liquid foods or food pastes,
and other liquids such as motor oil or household solvents
and cleaners.
Much of the recent development in this product area
has been in relation to self-standing pouches and
disposable infant feeding bottles such as described
below. However, a common and important difficulty is in
providing such flexible containers which are collapsible
to minimise shipping volume and waste volume, yet
self-supporting when both empty and full. Another
difficulty is with filling such a non-rigid container.
Both of these difficulties are addressed in the present
invention. The invention also addresses the trend to
minimising the use of difficult to recycle materials in
such containers, that is by minimising wall thicknesses,
whilst retaining adequate functionality. Ideally such
containers should be self-supporting for filling, stable
during use, yet easily collapsed when emptied by the user.
To illustrate some of the background to this
invention, we further consider the "baby bottle" marketed
in the U.S.A. by the Playtex company. This consists of an
open ended rigid plastic tube together with a screw-top
and rubber teat, and is supplied with a number of empty
collapsed, flat plastic bags. In use, one such bag is
loaded into the open tube and filled with infant formula.
The rubber teat and screw-top are then screwed down onto
the open end of the plastic bag. The infant can then
drink some or all of the contents held within the bag,
which collapses as it is emptied. This minimises or
eliminates the problem of "air-sucking" during drinking by
the infant and provides a more natural, consistent flow of
liquid.
When empty, the collapsed bag is then disposed of
and no bottle washing is required. Many parents prefer
39 this, as bottle washing with detergent causes concern
WO 95/11170 PCT/AU94/00638
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about residual chemicals from the detergent dissolving
into the formula and being consumed. Nevertheless, the
flat empty bags have no flange or flat`base and are quite
difficult to fit into the holder without leaking. They
can be messy to fill and do not lend themselves to
refrigeration storage without leaking when pre-filled from
a larger batch of formula.
More recently E.I. Du Pont De Nemours & Company in
their International Patent Application No. PCT/US90/02367
described an alternative baby bottle construction. The
main difference compared with the Playtex bottle was the
provision of a semi-rigid, cup-shaped disposable container
which replaces the flat plastic bag of the Playtex
design. This disposable container is provided with a
rigid annular flange at the mouth of the container and
thin side walls which are progressively collapsible and
which vary in thickness going from very thin near the base
to thicker near the flange.
The Du Pont container construction has the advantage
that it can be more easily placed in an outer rigid tube
because of its rigidity compared with the floppy bag of
Playtex. The flanged rim gives a further advantage by
providing a stable surface onto which the teat can be
sealed. Also, because it retains its shape when filled
with product, it is more suitable for marketing in
pre-filled form than a non-rigid bag. Furthermore, the
rigid flange at the rim is suitable for heat sealing with
removable foil or film making the package more user
friendly and attractive to consumers.
Whilst the Du Pont container has a number of
advantages over simple bags, it has aspects which can
cause difficulties. For example, the progressive change
in wall thickness can be difficult to control accurately
in the container manufacturing process. Furthermore, the
region where the thin side walls of the container meet the
base may be relatively weak and prone to crumpling. This
may be overcome by increasing the thickness of the base,
but there is the consequent disadvantage that more plastic
39 material must be used to produce the container.
WO9S/11170 2 1~ 4 4 ~ 9 PCT/AU94/00638
It is an object of the invention to provide a
container consisting of a flexible yet self-supporting
bag-like tube which reduces or ameliorates one or more of
the aforesaid disadvantages.
In one aspect the invention provides a flexible,
self-supporting shaped plastics bag having an open end
surrounded by a rigid flange, a tubular or frusto-conical
side wall depending from the flange to form a generally
tubular portion and a base joining the side wall through a
radiused portion, the side walls being provided with a
plurality of reinforcing ribs extending longitudinally
along the tubular portion and through the radiused
portion, characterised in that the thickness of said ribs
increases proqressively from the open end portion of the
container through the radiused portion at which the ribs
form elongated knuckles reinforcing the junction of the
side wall and the base and enabling the container to stand
on its base.
The container according to the invention may be used
for packaging a range of products including food pastes
such as vegetable or fruit puree or potable liquids such
as orange juice or milk or other materials such as oil or
water, as well as non-food liquid products such as
lubricating oils, shampoos and household chemicals.
The container may be formed from a mono- or
multi-layer sheet of plastics material by a cuspation
dilation method along the lines of that described in
Australian Patent No. 534392. If the container is formed
generally according to this method, it may be formed with
the aforesaid reinforcing ribs running longitudinally
along the tubular wall. We have found a way to extend
these ribs into the radiused portion joining the wall to
the base and this new property forms an important part of
our invention, as described hereinafter.
The cuspation dilation method described in
Australian Patent No. 534392 involved stretch-forming a
hollow article from a heated sheet of thermoplastics
material and comprised pressing against one face of the
39 sheet in a primary movement a plurality of tips carried
wos5/11170 PCT/AU91,~0~8
21~4499
symmetrically by a tool at a temperature lower than 50C
below the melting point of the sheet and comprising a
plunger having an axis extending in the direction of the
primary movement, each tip being constituted by an end of
a blade which blade is coplanar with the plunger axis and
pivoted to the plunger, and, while continuing the primary
movement, rotating the blades about their pivots while
maintaining each blade coplanar with the plunger axis to
symmetrically separate the tips in directions transverse
of the plunger and to bring the outer edge of each blade
from the tip progressively towards the rear into
engagement with the sheet.
When the preferred cuspation dilation (CD) process
is used to produce the present pouch-like containers, the
resultant ribs naturally taper in thickness, being almost
non-existent at the open end, then progressively
thickening to the base and corner knuckle. This is a very
desirable property for a deep tube of greater than 2.5
draw ratio, as the accumulated vertical buckling load on
the wall increases towards the bottom of a filled,
standing pouch.
The thick knuckles which reinforce the base-side
wall junction are new, and not seen in earlier CD
products. They are formed by changing the CD blade tip
geometry away from a relatively sharp tip, that is a tip
which chills a localised "blob" of thermoformed melt of
plastics material, to a radiused tip, which chills an
extended thick knuckle around the side wall corner and
into the base at each rib location.
It was previously considered undesirable to use
other than a sharp blade tip, as this was thought then to
allow "sledging" of the material over the blade end,
causing an uncontrolled thinning of the base during draw
down of the melt. This was seen to be caused by the
relatively strong "cable" of cooler ribbed material
chilled by each blade becoming strong enough to pull still
molten material around the blade tip from the base. The
sharp blade tip was found normally to anchor the melt
39 material and prevent this. However, it is has now been
WO95/11170 2 1 7 4 4 9 9 PCT/AU94/00638
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found possible, for example by the use of more flexible
plastics materials, together with the very thin walls
required for the present products, for an extended knuckle
to be formed without sledging occurring.
The material of the container may be a plastics
material which is a single or multiple-layer material
which may be resistant to oxygen permeation. A
multi-layer plastics material comprising a composite of
different layers of different plastics with desired
properties is particularly suitable. A softer
polypropylene, ethylene vinyl alcohol, polypropylene
copolymer composite may be suitable in such applications.
Other preferred materials leading to good flexibility in
the formed products of the present invention include low
density polyethylene, linear low density polyethylene,
thermoplastic polyurethane and plasticised polyvinyl
chloride.
The container of the invention is also provided with
regions of different thickness to allow the container to
progressively collapse under pressure differential, for
example arising from squeezing the side wall or applying
suction to remove the contents, but designed to allow the
container to also be free-standing and to maintain its
shape (whether or not it is filled with product) in the
absence of pressure differential. Preferably the side
wall have a film thickness in the range of 30 to 300
micrometers and the ribs have an average thickness in the
range of 80 to 600 micrometers and are spaced between 0.5
and 1.5 centimeters apart.
Preferably, the longitudinal ribs will be of the
order of 1.5 to 4 times the thickness of the tubular wall
film of the container. Typically rib thickness will be
150 micrometers to 300 micrometers and the wall film
thickness may be substantially constant, and preferably in
the range of 50 micrometers to 150 micrometers. The ribs
may typically have a width in the range lmm to 2mm.
The base of the container may generally have a
thickness in the range 50 micrometers to 500 micrometers.
39 The length of the container formed in accordance
WO95/11170 PCT/AU91~C~8
2174~9~ 6 -
with the present invention is preferably greater than 2.5
times the maximum transverse dimension of the open end.
Thus for a cylindrical container of 50cm diameter, the
length will preferably be at least 125cm.
The thickness of the flange will generally be
greater than that of the body of the container. Depending
on the physical properties of the plastics used, the
thickness of the flange will be chosen to ensure a degree
of rigidity thereof. In most instances, a thickness in
the range of 500 micrometers to lO00 micrometers will be
required for the flange.
Measurement of the suction achievable by a small
baby suggests that the container when used as a baby
bottle should be capable of collapsing when suction
creating a differential container/atmosphere pressure of l
kPa is applied through the teat.
Rigidity against bending/buckling during tilting to
pour or drink, is also important. This tendency to bend
and/or buckle is worst when the tube is partially empty.
The weight of the remaining liquid is concentrated in the
lower part of the container and this tends, on further
tilting, to collapse the already empty part of the tube
nearer to the open end, below the hand. The longitudinal
ribs in the containers of the present invention thus play
an important role in reducing this tendency, hence less
material can be used in this tubular pouch. This in turn
reduces the amount of rubbish generated from discarded
packaging.
The integral flange, unique for a plastic bag,
provides a means of attaching a sealed (for example,
heat-sealed film or foil) closure, to maintain a hermetic,
bacteria tight package and enabling convenient re-opening.
The integral flange also provides a means of reliably
clamping the bag into a wide range of dispensers, for
example baby bottle holders, without risk of leakage.
This invention is further described with reference
to the attached drawings wherein:-
Figure l shows a filled container;
39 Figure 2 shows an enlarged sectional view of a circled
woss/11170 2 1 7 ~ 4 9 ~ PCT/AU~ C~8
section of the container of Figure l;
Figure 3 shows a container with a seal and dispensingflange;
Figure 4 shows a container of rectangular cross section;
Figure 5 shows a plurality of filled containers in an
overpackage; and
Figures l and 2 illustrate a self-supporting
collapsible container and show it in a filled condition
containing nutritional, non-carbonated contents (15) and
sealed with a foil (6) of metal or plastic which is to be
highly resistant to oxygen permeation attached by a
peelable, heat, radio-frequency, ultrasonic or friction
weld (5) to the relatively thick (say lmm thick) ring
flange (9) to (13) of the hollow container. The container
has longitudinally extending ribs l formed in the side
wall of its tubular portion 3 and extending into radiused
portion 2 where the side wall merges with base 4. Ribs l
are relatively thick compared with the thickness of the
side wall between them and form knuckles around the
radiused portion 2 which enable the container to stand
without independent support, whether filled or unfilled.
Items (9) to (13) are an out-of-scale cross section
of the multi-layer material which also makes up the
relatively very thin walls and base (typically of say 50
to 200 micrometers total thickness) of the container.
These layers, bonded together, typically comprise an inner
layer (13) of clean, heat resistant, moisture containing
thermoplastic polymer, such as polypropylene or
polyethylene, two thin adhesive layers (ll) on each side
of an oxygen barrier layer (12) which is made of a
so-called high oxygen barrier thermoplastic polymer such
as ethylene vinyl alcohol or polyvinylidene chloride, or
other "oxygen barrier" thermoplastics, a scrap layer (lO),
containing recycled thermoplastic material and an optional
outer layer (9) which may be pigmented for colour or
opacity to light (as may any or all of the other aforesaid
layers).
The container shown in Figure 3 incorporates the
39 ribbing, knuckles and thin film features disclosed in
WO9S/11170 ~ PCT/AU94/00638
217~4~9
-- 8
relation to the containers at Figures l and 2. However it
is also provided with an optionally thicker walled member
51 shaped in the form of a pouring spout, with a step 52
providing a flange 53. The flange stiffens the container,
provides a more rigid means of gripping it in the hand
after it is opened and also provides a sealing area for
attachment of a sealing film 54 applied over the mouth of
the container. The film may be heat sealed to the flange
and may incorporate means to facilitate removal such as
the pull tab 55.
In Figure 4 a container of square cross section 15
is illustrated to show that the invention is equally
applicable to containers having a range of shapes. From
this illustration it can be seen that the longitudinal
ribs 61 extend into a radiused portion 62 joining the base
of the container to the tubular portion 63. The ribs form
knuckles at the radiused portion as detailed above in
relation to Figures l and 2.
Referring to Figure 5, a number of filled and sealed
containers 71 according to the invention are shown in a
multiple overpack 72. The overpack includes a number of
- openings top and bottom and designated 73 and 74
respectively to snugly receive the containers 71 in the
manner illustrated. The flanges 75 of the containers
serve to locate them in the overpack. An outer rigid or
semi-rigid cover or stretch film envelope 76 may
optionally be provided for additional light blocking or
dust protection.
The containers of the invention can be sold empty,
as a disposable pouch, such as for disposable baby bottles
to be fitted into rigid holders. For this use no oxygen
barrier would be needed. If sold as a filled and sealed
pack, for chilled storage and distribution, a polymer
oxygen barrier layer would also then not be required.
If a polymer layer for osygen barrier is
incorporated into the walls of the tube and if the pack is
then sterilised and aseptically filled with suitable heat
treated food, or filled first without sterility and then
39 heat or radiation treated as a sealed pack, then a shelf
WO 95/11170 2 17 4 4 9 9 PCT/AU94.'0~8
stable packed product will result, which will not need
chilled distribution or refrigerator storage.
If filled with liquid or semi-solid food, it may be
desirable to pack with a small inert gas overpressure,
typically less than 0.1 atmosphere, in order to provide
internal support from both the contents and gas pressure,
for handling and transportation of the filled packs.
Optionally, overpacking of the type shown in Figure 5,
could also be adopted, to help to ensure that the packages
reach the end user in good condition.
39
