U.S. patent application number 09/832481 was filed with the patent office on 2002-01-24 for multi-layer film structure for use with a high-speed pouch forming, filling and sealing machine.
Invention is credited to Basque, Roland, Pitre, Andre, Quintin, Yves.
Application Number | 20020009579 09/832481 |
Document ID | / |
Family ID | 23214429 |
Filed Date | 2002-01-24 |
United States Patent
Application |
20020009579 |
Kind Code |
A1 |
Quintin, Yves ; et
al. |
January 24, 2002 |
Multi-layer film structure for use with a high-speed pouch forming,
filling and sealing machine
Abstract
The multi-layer film structure having an inner sealing layer
which comprises metallocene resin, a core which includes
polypropylene copolymer and an outer layer and wherein the
multi-layer film structure has a thickness within a range between
about 50 and 70 microns (2.0-2.75 mil). By utilizing this thin film
with specific properties the sealers may be operated at lower
temperatures thereby resulting in an energy saving and they produce
seals having improved seal strength of 30% to 50% as compared with
known prior mono-layer polyethylene film. The seal initiation
temperature is reduced by 10.degree. C. to 15.degree. C. and the
film exhibits an improved machine direction tensile strength of 25%
to 40% and an improvement of 30% to 50% in puncture resistance as
compared with a 76 microns (3 mil) mono-layer polyethylene film.
This results in a reduction in the sealing cycle time and an
increase in the throughput of the machine. This results in a liquid
pouch having a substantial improvement in drop test performance,
puncture resistance and seal strength. The machine accomplishes
better seals with less energy, requires less downtime for roll
changes and maintenance and increase throughput.
Inventors: |
Quintin, Yves; (Saint-Bruno,
CA) ; Basque, Roland; (Brossard, CA) ; Pitre,
Andre; (Varennes, CA) |
Correspondence
Address: |
David M. Carter
Carter & Schnedler, P.A.
56 Central Avenue, Suite 101
P.O. Box 2985
Asheville
NC
28802
US
|
Family ID: |
23214429 |
Appl. No.: |
09/832481 |
Filed: |
April 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09832481 |
Apr 11, 2001 |
|
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|
09313112 |
May 17, 1999 |
|
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6237308 |
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Current U.S.
Class: |
428/213 ;
428/220; 428/516 |
Current CPC
Class: |
Y10T 428/2495 20150115;
Y10T 428/31913 20150401; B32B 27/32 20130101; Y10T 428/31938
20150401 |
Class at
Publication: |
428/213 ;
428/220; 428/516 |
International
Class: |
B32B 007/02; B32B
027/32 |
Claims
We claim:
1. A multi-layer film structure for use in packaging flowable dairy
products into flexible pouches comprising an inner sealing layer,
an outer layer, and a core sandwiched between said sealing layer
and said outer layer, wherein said sealing layer comprises about 40
to 100% weight percent of a metallocene resin having a density of
between about 0.902 and 0.9122, and about 0 to 60 weight percent of
a low density polyethylene or a mixture of low density polyethylene
and linear low density polyethylene, said outer layer comprises a
low density polyethylene or a mixture of low density polyethylene
and linear low density polyethylene, said core comprising a mixture
of about 20 to 90 weight percent of a polypropylene copolymer and
about 10 to 80 weight percent of a low density polyethylene or a
mixture of low density polyethylene and linear low density
polyethylene, said multi-layer film structure having a thickness
within a range between about 50 and 70 microns (2.0-2.75 mil).
2. A multi-layer film structure according to claim 1, wherein said
sealing layer represents about 10 to 30 weight percent of said
structure.
3. A multi-layer film structure according to claim 1, wherein said
core represents about 30 to 70 weight percent of said
structure.
4. A multi-layer film structure according to claim 1, wherein said
outer layer represents about 10 to 30 weight percent of said
structure.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of Application Ser. No.
09/313,112, filed May 27, 1999.
TECHNICAL FIELD
[0002] The present invention relates to a multi-layer film
structure comprised of an inner sealing layer, an outer layer and a
core sandwiched between the sealing layer and the outer layer, and
wherein the film structure is particularly for use in a high-speed
pouch forming, filling and sealing machine.
BACKGROUND ART
[0003] Traditionally, in North America, the film used for packaging
fluid milk or the like in flexible plastic pouches consists of a 76
microns (3 mil) mono-layer polyethylene film.
[0004] However, this standard film has some disadvantages which
should be overcome. For example, the packaging operation requires a
certain amount of electrical energy for the heat sealing operation
due to the thickness of the film. To generate this heat electrical
energy is dispensed. It is desirable to develop a process which
could decrease the energy consumption in order to make the
operation more economically feasible. Another problem involved with
the sealing operation is that some of the hardware, such as the
sealing element per se and the rubber and Teflon.TM. parts
associated with the sealing jaws have a relatively short useful
life, requiring frequent changes and again increasing the cost of
producing milk pouches.
[0005] Yet another problem resulting from the packaging of liquids
with a mono-layer polyethylene film is the amount of waste and
machine downtime due to film roll changes and seal breaks.
Packaging milk or other liquids with mono-layer polyethylene also
involves the use of a narrow sealing window which renders the
operation somewhat difficult. Finally, the seals obtained with this
type of film pouches, often exhibits weakness which can cause fluid
leakage.
[0006] Polymer film pouches made from a polyethylene film structure
and used for packaging flowable materials such as milk, are known
and examples of such are described in U.S. Pat. Nos. 5,288,531;
5,360,648; 5,364,486 and 5,508,051, all of which have issued to the
Down Chemical Company.
SUMMARY OF INVENTION
[0007] It is a feature of the present invention to provide a
thinner multi-layer coextruded film structure, which overcomes some
or all of the disadvantages of the prior art and incorporated in a
bag forming, sealing and filling machine to improve on its method
of operation and throughput.
[0008] It is another feature of the present invention to provide
fluid containing pouches that exhibit desirable properties as
compared to the pouches of the prior art.
[0009] It is another feature of the invention to provide a
multi-layer film structure which makes it possible to reduce the
material used as compared to the film of the prior art.
[0010] It is another feature of the present invention to provide a
multi-layer film structure for packaging liquid that can be sealed
at much lower seal initiation temperature.
[0011] It is another feature of the present invention to provide a
multi-layer film structure for packaging liquid that has a greater
machine direction tensile strength.
[0012] It is another feature of the present invention to provide a
pouch made with the multi-layer film structure according to the
invention that is improved in horizontal seal strength, exhibits
lower horizontal seal thinning, and minimizes post consumer
waste.
[0013] It is yet another feature of the present invention to
provide a lower gauge pouch having a higher stiffness enabling
pouring of liquid, and which exhibits a substantial improvement in
drop test performance and puncture resistance.
[0014] It is another feature of the present invention to provide a
multi-layer film structure for packaging liquid into pouches, which
ensures a reduction of the electrical energy required for sealing
due to lower heat initiation temperature and lower mass to be
sealed.
[0015] It is another feature of the present invention to provide a
multi-layer film structure for packaging consumable liquid products
into pouches which uses lower sealing temperature and thereby
improves the useful life of the jaw sealers, such as the rubber,
and electrical sealing heads, and resulting in overall energy
reduction.
[0016] It is another feature of the present invention to provide a
multi-layer film structure for packaging dairy products into
pouches that permits a substantial reduction of wastes and downtime
caused by film roll changes.
[0017] It is another feature of the present invention to provide a
multi-layer film structure for packaging liquid wherein sealing is
easier to operate due to a wider sealing window, and speed increase
is made possible as a result of a faster sealing cycle.
[0018] According to another feature of the present invention there
is provided a high-speed pouch forming, sealing and filling machine
and its method of operation and utilizing sealing heads which
operate at lower temperatures due to a decrease in the film
thickness as compared with 76 microns (3 mil) mono-layer
polyethylene film and thereby resulting in an electrical energy
saving and wherein the thin film permits the machine to obtain a
substantially higher yield with a film roll substantially the same
size as with the 76 microns (3 mil) film.
[0019] According to the above features, from a broad aspect, the
present invention provides a multi-layer structure for use in
packaging consumable liquid into flexible pouches comprising an
inner sealing layer, an outer layer, and a core sandwiched between
said sealing layer and said outer layer, wherein the sealing layer
comprises about 40% to 100% weight percent of a metallocene resin
having a density of between about 0.902 and 0.912, and about 0 to
60 weight percent of a low density polyethylene or a mixture of low
density polyethylene and linear low density polyethylene, the outer
layer comprises a low density polyethylene or a mixture of low
density polyethylene and linear low density polyethylene, the core
comprising a mixture of about 20 to 90 weight percent of a
polypropylene copolymer and about 10 to 80 weight percent of a low
density polyethylene or a mixture of low density polyethylene and
linear low density polyethylene, said multi-layer structure having
a thickness within a range between about 50 and 70 microns
(2.0-2.75 mil).
[0020] According to a still further broad aspect of the present
invention there is provided a high-speed pouch forming, sealing and
filling machine which comprises means to draw a multi-layer film
from a film roll over a pouch-former to form a plastic film tube
having an overlap vertical film edge. A vertical sealer is provided
and has a sealing head for heat fusing the overlap vertical film
edge to form a vertical seal. A filler tube extends into the
plastic film tube for injecting a consumable liquid product at a
filling location of the plastic film tube. A horizontal sealing
jaw, having an electrical thermal sealing element, is provided for
effecting a horizontal seal across the plastic film tube and spaced
below the filling location and for simultaneously severing the tube
to form a top transverse seal for a filled pouch and a bottom
transverse seal for a pouch being filled. The multi-layer film has
an inner sealing layer, an outer layer and a core sandwiched
therebetween. The characteristics of this film are described above.
The horizontal and vertical seals have an improved seal strength of
30% to 50% as compared with the 76 microns (3 mil) mono-layer
polyethylene film and a 10.degree. C. to 15.degree. C. reduction in
seal initiation temperature, an improved machine direction tensile
strength of 25% to 40% and an improvement of 30% to 50% in puncture
resistance, while reducing the sealing cycle time and increasing
the throughput of the machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The preferred embodiments of the present invention will now
be described with reference to the accompanying drawings in
which:
[0022] FIG. 1 is a schematic diagram illustrating basic component
parts of the improved high-speed pouch forming, sealing and filling
machine of the present invention;
[0023] FIG. 2a is an enlarged fragmented and partly sectioned view
showing the horizontal sealing jaws of a prior art machine and the
defect of seal thinning that occurs when using conventional 76
microns (3 mil) mono-layer polyethylene film;
[0024] FIG. 2b is an enlarged sectional view of the horizontal seal
of the pouch illustrated in FIG. 2a which better illustrates seal
thinning;
[0025] FIG. 3 is a sectional view illustrating the three-layer film
of the present invention; and
[0026] FIG. 4 is an enlarged fragmented sectional view showing a
top horizontal seal formed on a pouch and using the three-layer
film of the present invention and wherein film thinning is
eliminated.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] Referring now to the drawings and more particularly to FIG.
1 there is shown generally at 10 basic component parts of a
high-speed bag forming, sealing and filling machine constructed in
accordance with the present invention. These basic component parts
are only schematically illustrated and are well known in the art.
The improvement in the machine resides primarily in the vertical
sealer operating characteristics and the horizontal sealing jaws
characteristics, as will be described later. The sealers are
controlled to operate with a new multi-layer film whereby to
increase the throughput of the machine and provide filled pouches
having improved strength and wherein the seals are greatly improved
over those of the prior art thereby resulting in a machine which
can output more filled pouches, achieve a significant waste
reduction and less downtime as compared with prior art machines
using a 76 microns (3 mil) mono-layer polyethylene film. As
hereinshown the high-speed pouch forming, sealing and filling
machine comprises a film roll 11 provided with a multi-layer film
12 which is guided through guide rolls and tensor rolls 13 to a top
end of a pouch former 14 where the plastic film is guided and
folded to form a plastic film tube 15 having an overlap vertical
film edge 16. A filler tube 17 extends within the pouch former 14
and the tube 15 and has a liquid discharge end 17' positioned at a
filling location 18.
[0028] A vertical sealer 19 has a sealing head 20 provided with a
heating element 21 and a backing member 22 is disposed vertically
aligned behind the overlap vertical film edge 16. A vertical seal
is formed by fusing the overlapped edge 16 along the plastic tube
15 above the filling location 18. A horizontal sealing jaw assembly
23 is provided spaced at a predetermined distance below the filling
location 18 whereby to form a horizontal seal across the film tube
18 and at the same time sever the tube to form a sealed pouch 24
filled with a consumable liquid 25 therein. The pouch is then
released on a discharge conveyor means 26.
[0029] The horizontal sealing jaw assembly 23 is comprised of a
sealing head 27 provided with an electrical impulse sealing wire
element 28 to sever the film tube as well as to form a top
horizontal seal 29 for the pouch 24 and a bottom horizontal seal 30
for the next pouch being formed herein illustrated by reference
numeral 24'. The horizontal sealing jaw assembly 23 also has a
backing member 31 which is provided as a rubber or Teflon.TM. pad
32 to serve as a backing for the electrical impulse sealing wire
element 27. From time-to-time it is necessary to change the pad and
the wire element as they wear down. By operating at lower
temperature, 10.degree. C.-15.degree. C. lower than the prior art
discussed above, these elements have a longer life cycle and there
is less machine stoppages. The jaw assembly 23 may move in and out
in unison to form the seal or the backing member 31 may be
stationary and positioned close to the film with only the sealing
head 26 moving in and out. Other suitable sealing assemblies are
conceivable provided they can achieve the same results. The film
sheet 12 is drawn in continuous motion by a pair of draw rolls 33
in a manner well known in the art. So far we have described the
basic component parts of a well known pouch forming, sealing and
filling machine such as the Thimonnier M3200.TM. or a Prepak
IS-7.TM..
[0030] The present invention resides in the provision of a novel
multi-layer film structure in combination with the machine to
enhance the performance of the machine. This enhancement is
achieved by controlling the temperature of the sealing assemblies
19 and 23 wherein they operate at temperatures which are lower than
prior art machines. The draw rolls 33 are also operated at higher
speeds whereby to increase the throughput of the machine while
producing horizontal seals which are much superior than the
above-mentioned prior art machines and resulting in a production
having less post consumer waste and permitting the machine to
operate with less downtime previously caused by malfunction or
plastic film roll change.
[0031] In particular the high-speed bag forming, sealing and
filling machine as above described is utilized for the production
of milk pouches and such machines conventionally use a 76 microns
(3 mil) mono-layer polyethylene film which heretofore was the best
film product available for this use. FIGS. 2a and 2b illustrate one
of the more serious problems that these machines have been plagued
with in the production of such pouches and namely the formation of
seal thinning. As shown in FIG. 2a the pouch 24 has just been
formed with the horizontal seal 29 severed and the filled pouch 24
is being discharged under the influence of its own weight. As the
seal is formed the weight of the liquid 25 within the pouch 24
exerts a load on the horizontal seal and this causes seal thinning
in the region 35. Seal thinning is caused by the stretching of the
polyethylene in the area of the seal which causes the film to thin
out in this region. FIG. 2b better illustrates the seal thinning
area 35 and as hereinshown this produces a weakness in the pouch 24
in this thinner stretched area of the seal. As the pouch is dropped
on the discharge conveyor 26 it is subject to impact which could
burst the film in the seal thin region 35. Furthermore, as these
pouches are handled by consumers or during packaging pressures
applied against the liquid 25 within the pouch exerts a force on
the thin film region 35 which again could cause leakage. Weak seals
caused by seal thinning has long existed and no adequate solution
has been found to date to improve these machines and the film in
order to substantially overcome the above-mentioned problems. We
have now discovered that by producing a film which can
substantially eliminate seal thinning and improve on machine
performance that a superior pouch can be produced at a higher
machine throughput and at a lower cost by substantially eliminating
the above production problems.
[0032] In a preferred embodiment the multi-layer film of the
present invention is a three-layer film as schematically
illustrated in FIG. 3. The three-layer film has an inner sealing
layer 36, an outer layer 37 and a core layer 38 sandwiched
therebetween. The core may be of one of several layers of
polymers.
[0033] Seal thinning is substantially eliminated by the combination
of the m-polyethylene sealing layer and a core incorporating a
higher melting point polypropylene.
[0034] According to preferred embodiments, the sealing layer 36
represents about 10 to 30 weight percent of the structure, the core
38 represents about 30 to 70 weight percent of the structure, and
the outer layer 37 represents about 10 to 30 weight percent of the
structure.
[0035] Preferably, the sealing layer 36 is a metallocene resin
having a density within a range between about 0.902 and 0.905, and
the thickness "x" of the multi-layer structure is preferably about
65 microns.
[0036] In accordance with another embodiment, the multi-layer
structure has an inner layer 36 having a seal initiation
temperature between about 80.degree. and 90.degree. C.
[0037] The metallocene resin preferably consists of m-polyethylene.
For example, the sealing layer may comprise between about 70 and 95
weight percent metallocene polyethylene, more specifically between
about 75 and 85 weight percent metallocene polyethylene.
[0038] The preferred copolymer to be used in the core 38 consists
of high impact polypropylene copolymer having a melting point
differential with the m-polyethylene of at least 40.degree. C.
[0039] The invention also relates to a process for preparing the
multi-layer structure by providing a sealing composition comprising
about 40 to 100 weight percent of a metallocene resin having a
density between about 0.902 and 0.912, and about 0 to 60 weight
percent of a low density polyethylene or a mixture of low density
polyethylene and linear low density polyethylene, an outer layer
composition comprising a low density polyethylene or a mixture of
low density polyethylene and linear low density polyethylene, and a
core composition comprising a mixture of about 20 to 90 weight
percent of a polypropylene copolymer and about 10 to 80 weight
percent of a low density polyethylene or a mixture of low density
polyethylene and linear low density polyethylene, simultaneously
co-extruding in a blown or cast coextrusion line, the sealing
composition, the outer layer composition and the core composition,
and feeding the co-extruded compositions to a die under conditions
to provide a thickness between about 50 and 70 microns.
[0040] When compared to the traditional 76 microns (3 mil)
mono-layer film, the advantages of the film according to the
invention when used in vertical form, fill & seal machine, such
as shown in FIG. 1, for a liquid pouch application are as
follows:
[0041] Film:
[0042] a minimum of 25% improvement in yield (sq.inch per lbs)
[0043] a 10.degree. C. to 15.degree. C. lower seal initiation
temperature
[0044] 25% to 40% greater machine direction tensile strength
(Psi)
[0045] 30% to 50% improvement in puncture resistance (lbs/mil)
[0046] Pouch:
[0047] a 30% to 50% improvement in horizontal seal strength
(lb/inch)
[0048] a reduction of horizontal seal thinning from more than 20%
to less than 3% (typical seal thinning is greater than 20% for
mono-layer films in this application)
[0049] a minimum of 25% post consumer waste reduction
[0050] an improvement of 30% to 50% in stiffness, (% modulus in
Psi) which enables pouring of liquid at a lower gauge
[0051] a two to threefold improvement in drop test performance
[0052] Pouch filling and sealing application
[0053] a 20% to 40% reduction of energy required for sealing due to
the lower heat initiation temperature and the lower mass (33% less)
to seal through
[0054] an improvement in the useful life of consumable items
proportional to the energy reduction (rubber, Teflon.TM., sealing
element)
[0055] a minimum of 20% reduction of wastes and downtime caused by
film roll changes
[0056] easier operation due to a wider sealing window
[0057] increased speed made possible by a faster sealing cycle
[0058] FIG. 4 illustrates the improvement in the seal of the pouch
24" achieved with the multi-layer film of the present invention. As
can be seen seal thinning below the top horizontal seal 29' is
eliminated and results in a pouch which is free of seal defects and
which exhibits all of the above listed advantages of the pouch as
well as the machine. Although the three-layer film of the present
invention has been described with particular reference to a pouch
forming sealing and thinning machine such as a VFFS machine like a
Thimonnier M3200.TM. or Prepak IS-7.TM., it is conceivable that
this film may have other uses and the present invention is not
intended to limit the scope of its use in such machines.
[0059] The invention will now be illustrated by means of the
following table which is not intended to limit the scope of the
invention as defined in the appended claims.
1 DG 2 DG 10 Comp 1 Comp 2 Thickness (mil) 2.5 2.5 3.0 3.0 Film
Yield 13,400 13,400 10,200 10,200 Seal Initiation Temperature
(.ident.C) 80 80 95 95 Puncture (peak load in lb) 22 22 17 16
Horizontal Seal Strength (lb/inch) 9.4 9.1 7.0 6.8 Seal Thinning
2.1% 3.0% >20% >20% Stiffness (1% Modulus in lb) 170 170 100
103 Glopak Drop Test (# of times) 7-9 7-9 2-4 2-4
[0060] The above are typical values obtained from representative
samples, DG 2 and DG 10 are Glopak experimental multi-layer films.
Comp 1 and Comp 2 are competitive mono-layer films used in Canadian
dairies.
[0061] It is within the ambit of the present invention to cover any
obvious modifications provided these fall within the scope of the
appended claims.
* * * * *