Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1
COOLING RING, METHOD AND BLOWN FILM LINE
FOR MANAGING LOW-MOLECULAR DEPOSITS
The invention relates to a cooling ring, a method and a blown film line for
the
managing of low-molecular deposits on a plastic film production device.
More precisely, the invention relates to the management of low-molecular
deposits on a blown film line, in particular the management of low-molecular
deposits on a cooling ring of a blown film line. The invention thus relates to
a
cooling ring for a blown film line. The invention further relates to a method
for
operating such a cooling ring. Furthermore, the invention relates to a suction
device for a low-molecular deposit on a cooling ring of a blown film line as
well
as a method for operating such a suction device. Lastly, the invention relates
to a
blown film line as well as a method for operating a blown film line.
Blown film lines are known and proven in the prior art with respect to the
producing of films: An extruder, or in the case of multilayer films usually a
plurality of extruders, melts one or more different plastic granulate(s) and
compresses and homogenizes the granulates into plastic melt. The plastic melt
is
conveyed through a line to a pre-distributor of a die head and from there to a
spiral distributor of a die head. In the die head, a coil guides the incoming
plastic
melt(s) ¨ in multiple layers in the case of multiple melt flows ¨ into an
annular
gap and then along the annular gap to an annular nozzle, also simply referred
to
in the following as a nozzle. The film is extruded from the annular nozzle as
a
continuous film tube.
The film tube is still in melt form as it exits the nozzle. Compressed air
blown into
the interior of the film tube inflates the melt, which primarily leads to
transverse
stretching of the film tube. At the same time, longitudinal stretching is
usually
applied by means of a pair of take-off rollers so as to produce a biaxially
stretched plastic film.
A calibration unit, for example comprising a plurality of cylindrically
arranged
rollers, leads the film tube to a flat lay. The cross section of the film tube
is
qualitatively changed in the flat lay, namely from its at least approximately
Date Recue/Date Received 2023-10-16
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cylindrical shape into a flat double-layer film web; there is however no
change or
at least no significant change in the circumference.
Once the film tube has been laid flat, it can be redirected, whereby a
reversing
device is usually used in order to prevent or respectively spread out thick
spots in
the wound film during its subsequently winding.
Blown film lines may have different orientations: In the past, production
usually
took place vertically from top to bottom; i.e. in the effective direction of
gravity,
nowadays, however, production is usually from the bottom upward, thus against
the effective direction of gravity. The first blown film lines in the top-to-
bottom
direction of production thereby took advantage of gravitational force.
However,
due to circumstances such as thinner melts being developed and efforts under-
taken to increase throughput, difficulties arose with the stability of the
film tube
immediately after exiting the nozzle. The film is still molten at that point
and,
depending on the film material and throughput, not able to support the weight
of
the film tube continuing to come down in the effective direction of gravity,
which
can lead to the film bubble ripping. If the film bubble rips, the line needs
to be
restarted, meaning a significant expenditure of time and money. With the
bottom-upward production direction; i.e. against the effective direction of
gravity,
the film tube is pulled off on the far side from the nozzle, i.e. at the top,
by a
pair of rollers which takes up the weight of the film bubble at a point at
which
the film bubble has further cooled and can therefore bear this force.
Customary film materials for blown films are crystalline or semi-crystalline
materials, for example certain polyethylene or polypropylene compounds or even
certain polyamides and ethylene vinyl alcohols or ethylene vinyl acetates,
among
others. In multilayer films, the different layers consist of different
materials
having different properties such as printability, UV blocking properties or
diffusion barrier properties, for example. Blown films have a broad field of
application and are used for example as packaging film, including in medical
technology or for food packaging, agrofoils, bags, laminating films, etc.
To support the cooling of the film bubble, thermoregulated external air is
usually
passed against the film bubble, for which a cooling ring is provided behind
the
nozzle. The supporting air, i.e. the air introduced into the film bubble to
inflate
Date Recue/Date Received 2023-10-16
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the film bubble, can also be thermoregulated and guided in a flow, whereby new
cold air is continuously blown into the film bubble so as to also cool the
film
bubble from the inside. The cooling ring thus constitutes the first cooling
element
seen in the production direction of a blown film line. The cooling ring not
only
allows tempered air to be blown onto the exterior of the film bubble, the
cooling
ring also enables the exterior of the film bubble to be brought into contact
with a
liquid cooling fluid, e.g. water.
Should the produced film be as transparent as possible, it needs to be cooled
down very quickly after the nozzle in order to severely inhibit or even
prevent the
crystallization of the melt to the greatest extent possible. Further positive
effects
of rapid cooling include, for example, high gloss, high puncture and tear
resistance as well as good thermoforming properties.
Heat transfer from plastic to air is much worse than that from plastic to
water.
Using water as a cooling medium to extract heat from the film tube is
therefore
obvious and also known. This is most easily achieved when the production
direction is in the direction of gravity; i.e. downward, since the water
itself can
then follow gravity and there is no risk of water flowing onto the nozzle,
which
needs to remain hot. A cooling ring equipped to apply water to the exterior of
the
film bubble is also provided for this case.
Films are produced from plastics. Plastics have macromolecules. Macromolecules
thereby exhibit a repeat molecule, thus a repeat unit, which is repeated very
frequently in a chain. For example, polyethylene has C2H4 as a repeat unit and
is
produced from ethylene via polymerization. Ethylene is gaseous under normal
conditions. Polyethylene contains the repeat unit on an order of magnitude of
50,000 times. Polyethylene is solid at normal room temperatures. When such a
macromolecule is intensely heated, the solid body transitions into the liquid
state.
.. The melting point of most polyethylenes is thereby between approximately
130 C
and 145 C, the processing temperature for film extrusion is up to 300 C.
However, upon a sufficiently high enough degree of heating, chain degradation
also produces degradation products which can be in gaseous, liquid or solid
form
depending on the length of the resulting chain segment and the temperature.
Date Recue/Date Received 2023-10-16
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When such degradation products settle onto system components, they are
generally referred to as "low-molecular deposits" in this document.
In particular, paraffins CnH2n are also formed when polyethylene is heated to
processing temperature, with n being between 24 and 32. These paraffins are
gaseous at processing temperature, whereby they become solid when cooled to
room temperature by way of the liquid state.
The surfaces of a cooling ring are considerably colder during operation than
the
film material situated there in the production process. Therefore, degradation
products evaporating from the film material at this point in the production
process
commonly condense on the cooling ring surfaces situated in the immediate
vicinity of the film bubble, particularly on the closest cooling ring lip to
the film
bubble. Due to various possible effects, at least some of these condensates
can
get from the cooling ring lip to the film bubble where they lead to
undesirable
defects in the film, at least visually.
A cooling ring is described for example in DE 10 2015 016 825 Al.
The present invention is based on the task of providing an improvement or an
alternative to the prior art.
According to a first aspect, the task posed is solved by a cooling ring for a
blown
film line having a film tube guide, wherein the film tube guide has a central
passage with at least one cooling ring lip for a film tube running through the
cooling ring during operation of the blown film line as well as a cooling
fluid
guide configured to apply cooling fluid entering the cooling air guide to the
film
tube running through the cooling ring during operation of the blown film line,
whereby the cooling fluid guide comprises a cooling fluid nozzle for applying
the
cooling fluid and the cooling fluid nozzle is directed toward the passage,
wherein
the at least one cooling ring lip is thermally insulated from the cooling
fluid
running through the cooling ring during operation of the blown film line
and/or
the film tube running through the cooling ring during operation of the blown
film
line.
Date Recue/Date Received 2023-10-16
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The following clarifications are made with respect to terminology:
It is expressly pointed out that in the context of the present patent
application,
indefinite articles and indefinite numerical details such as "one...,"
"two...," etc.
should generally be understood as a minimum indication; i.e. as "at least
one...,"
"at least two...," etc., unless the context or the specific text of a certain
passage
indicates that only "exactly one...," "exactly two...," is intended at that
point.
Furthermore, all numerical details as well as details on method parameters
and/or
device parameters are to be understood in the technical sense; i.e. are to be
understood as having the usual tolerances. Neither does explicitly specifying
the
"at least" or similar limitation allow drawing the inference that simply
stating
"one;" i.e. without specifying "at least" or similar, means "exactly one."
A "blown film line" comprises one or more extruders. Plastic granulates can be
conveyed, melted and homogenized in each extruder. In the construction of a
blown film line, the actual extrusion follows the extruder.
In doing so, the melt is pressed through a tool with an annular nozzle. This
produces a molten tube which is usually inflated with air and at the same time
cooled from the outside, for example by cool air or a cooling fluid. Cooling
from
the inside can also come into play. The width and thickness of the film are
determined in this phase of the process, these being contingent on the size to
which the tube is inflated. Once the tube of film has cooled, it is flattened
by
squeegees and then automatically wound. Multiple layers of different plastic
films
can be placed on top of each other in one die head in order to combine the
properties of the different plastics into one film.
An "annular nozzle" is to be understood as a nozzle having a ring-shaped
outlet
cross section. In blown film production, plastic melt is formed into a film
tube via
.. an annular nozzle. The terms annular nozzle and nozzle are used
synonymously in
this document.
To be understood by "cooling fluid" herein is a fluid which is used to cool
the film
bubble. The cooling fluid can be gaseous, e.g. air, or liquid, e.g. water,
whereby
the water can be treated and/or provided with an additive.
Date Recue/Date Received 2023-10-16
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The "production direction" is the direction which the flow of material
follows. The
production direction can be and usually is different at different positions in
the
production line. Thus, the extruder(s) which melt and convey the material
is/are
horizontally positioned; i.e. essentially parallel to an installation site.
For example,
on a production hall floor, the production direction is horizontal from the
extruder
feed to a tool with a nozzle. The production direction is usually redirected
in the
tool to the vertical. The film tube is usually further guided vertically at
least until
haul-off in order to then also be redirected multiple times in any subsequent
stretching and reversing devices, whereby the production direction can assume
any angle. Subsequently, the film is usually led by different rollers to a
take-up
mechanism, whereby the production direction can also assume different angles
in
this section of a blown film line.
To be understood by a "cooling ring" is an annular device able to engage
around
a film tube and is in addition disposed to bring a cooling fluid into contact
with
the exterior of the film tube. To that end, the cooling ring has a "cooling
fluid
nozzle" through which the cooling fluid exits in order to reach the film
tube's
exterior. The cooling fluid nozzle of a cooling ring is usually likewise
annularly
arranged on the inner circumference of the cooling ring and constitutes a gap
through the cooling ring's closed surface on the inner circumference. The
cooling
fluid nozzle is limited by a "cooling ring lip." The cooling ring furthermore
has a
"cooling fluid guide," whereby the cooling fluid guide directs the cooling
fluid
from a cooling fluid source to the cooling fluid nozzle. A cooling ring may
have a
plurality of cooling ring nozzles with corresponding cooling ring lips and
cooling
.. fluid guides.
To be understood herein by a "coating" is a layer on a surface of a substrate,
wherein the material of the layer can differ from the material of the
substrate.
A coating can affect physical, electrical and/or chemical properties of
metallic
or semi-metallic components. A coating can in particular also have an
insulating effect, including thermally insulating.
To be understood as an "inlet" on a cooling ring is the region at the first
end of
the cooling ring, as viewed in the production direction, where the film tube
coming out of the nozzle enters the cooling ring during operation. An inlet
gap
Date Recue/Date Received 2023-10-16
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forms between the cooling ring inlet surface and the exterior of the film tube
during operation.
"Ambient pressure" or "ambient air pressure" refers to the air pressure
prevailing
in the environment of the respective component.
In the present document, "normal air pressure" is understood as being the
prevailing air pressure at the respective location without artificial
influence. The
air pressure at any given location in the earth's atmosphere is the
hydrostatic
pressure of the air that prevails at that location. This pressure results from
the
weight of the air column on the earth's surface or a body and therefore
depends
on the height of the respective location above sea level. Meant here by
"without
artificial influence" is the natural air pressure which prevails at the
respective
elevation above sea level in the absence of a negative or positive pressure
being
artificially created.
To be understood here by a "suction housing" is a housing which serves the
exhaust of gases, aerosols or even liquids or solids. To that end, the suction
housing has an opening pointing in the direction of the fluid or solid to be
drawn
off, whereby a negative pressure can be applied to the suction housing so that
an
air flow is created which draws off the fluid or the solid to be suctioned
through
the suction housing into a drain.
To be understood by "evaporation temperature" herein is the temperature at
which the phase transition of a substance into the gaseous phase occurs at the
respective air pressure.
To be understood by "degradation product" here is a substance which results
from the degrading of a macromolecule under thermal stress. Films are produced
from plastics. Plastics have macromolecules. Macromolecules thereby exhibit a
repeat molecule, thus a repeat unit, which is repeated very frequently in a
chain.
For example, polyethylene has C2H4 as a repeat unit and is produced from
ethylene via polymerization. Ethylene is gaseous under normal conditions.
Polyethylene contains the repeat unit on an order of magnitude of 50,000
times.
Polyethylene is solid at normal room temperatures. When such a macromolecule
is intensely heated, the solid body transitions into the liquid state. The
melting
Date Recue/Date Received 2023-10-16
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point of most polyethylenes is thereby between approximately 130 C and 145 C,
the processing temperature for film extrusion is up to 300 C. At such heating,
chain degradation produces degradation products which can be in gaseous,
liquid
or solid form depending on the length of the resulting chain segment and the
temperature. The degradation products have different evaporation temperatures
depending on chain length.
When such degradation products settle onto system components, they are
generally referred to as "low-molecular deposits" in this document
To be understood by "regulation" is a system process in which interaction
occurs
and with which a variable, which generally speaking is variable, is usually
kept
constant or approximately constant automatically.
The inventors have recognized that low-molecular deposits preferentially
accumulate on the cooling ring lip in cooling rings known from the prior art.
The low-molecular deposits form from degradation products condensing from
the film. They are usually at their maximum production process temperature at
the nozzle outlet. Thus, most degradation products are emitted at this point.
Seen in the production direction, the cooling ring is the first cooling
element
arranged in close proximity to the nozzle. The cooling ring itself is
relatively cold
due to the cooling fluid flowing through it and constitutes the coldest system
component at this point. On the cooling ring itself, the cooling lip is in
turn the
coldest component, which is why the most degradation products condense here.
Due to drafts of air, the low-molecular deposits resulting from the condensing
of
these degradation products can get onto the film bubble passing by during
operation, thereby forming undesirable defects. The effect is particularly
large
when producing highly transparent blown films in particular: On the one hand,
such visual defects are particularly noticeable on a highly transparent or
high-
gloss film. To make matters worse, the film bubble must be cooled particularly
quickly and thus intensively should crystallization in the film be minimized
or
even completely prevented, whereby the temperature of the cooling ring lip is
particularly low in this process. To even further complicate matters, the
selected
production direction in liquid-cooled blown film production is usually from
top to
bottom; i.e. in the direction of gravity, by virtue of cooling with a liquid
film
being so relatively simple to configure as the liquid can thereby follow the
force
Date Recue/Date Received 2023-10-16
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of gravity. In addition to the air flow, however, low-molecular deposits can
also
obey the law of gravity in this production direction and land on the film
bubble
from the cooling lip. Therefore, the present inventive cooling ring is based
on
the concept of not allowing the temperature of the cooling ring lip to become
as
low as is the case with known prior art cooling rings. Thermally insulating at
least one cooling ring lip from the cold cooling fluid has the potential of
having
the at least one cooling lip not being as cold as it would be without said
thermal
insulation, meaning fewer low-molecular deposits thereby depositing on the
cooling lip, whereby fewer corresponding defects also occur on the film
bubble.
In one embodiment of the first aspect of the invention, the at least one
cooling
ring lip is coated on surfaces having the cooling fluid running through the
cooling
ring during operation of the blown film line and/or on surfaces opposite from
the
film tube running through the cooling ring during operation of the blown film
line.
The coating can thereby act as thermal insulation in order to realize the
potential
of having the at least one cooling lip not being as cold as it would be
without the
coating and there thus being fewer low-molecular deposits on the cooling lip,
whereby fewer corresponding defects also occur on the film bubble.
According to a second aspect of the invention, the task posed is solved by a
cooling ring for a blown film line having a film tube guide, wherein the film
tube
guide has a central passage with at least one cooling ring lip for a film tube
running through the cooling ring during operation of the blown film line as
well as
a cooling fluid guide configured to apply cooling fluid entering the cooling
air
guide to the film tube running through the cooling ring during operation of
the
blown film line, whereby the cooling fluid guide comprises a cooling fluid
nozzle
for applying the cooling fluid and the cooling fluid nozzle is directed toward
the
passage, wherein the at least one cooling ring lip can be heated.
This cooling ring is likewise is based on the concept of not letting the
temperature of the cooling ring lip become as low as is the case with known
prior
art cooling rings. Being able to heat at least one cooling ring lip has the
potential
of enabling the at least one cooling lip to not be as cold as it would be
without
the heating option and there thus being fewer low-molecular deposits on the
cooling lip, whereby fewer corresponding defects also occur on the film
bubble.
Date Recue/Date Received 2023-10-16
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In one embodiment of the second aspect of the invention, the at least one
cooling ring lip is additionally thermally insulated against the cooling fluid
running
through the cooling ring during the operation of the blown film line and/or
the
film tube running through the cooling ring during the operation of the blown
film
line, which can thereby potentially intensify the effect of the at least one
cooling
lip not being as cold as it would be without the heating option and fewer low-
molecular deposits thereby depositing on the cooling lip, whereby fewer
corresponding defects also occur on the film bubble.
In a further embodiment of the second aspect of the invention, the at least
one
cooling ring lip is heated during operation of the blow molding line to at
least a
temperature corresponding to the evaporation temperature of the potential
degradation product of the processed film material at the highest evaporation
temperature.
Under certain circumstances, this can thereby achieve no degradation products
being deposited on the at least one cooling ring lip.
According to a third aspect of the invention, the task posed is solved by a
cooling
ring for a blown film line having a film tube guide, wherein the film tube
guide
has a central passage with at least cooling ring lip for a film tube running
through
the cooling ring during operation of the blown film line as well as a cooling
fluid
guide configured to apply cooling fluid entering the cooling air guide to the
film
tube running through the cooling ring during operation of the blown film line,
whereby the cooling fluid guide comprises a cooling fluid nozzle for applying
the
cooling fluid and the cooling fluid nozzle is directed toward the passage,
wherein
the cooling ring has an inlet at its end facing the nozzle, wherein the
cooling ring
is configured to generate and maintain an air pressure difference at the
inlet,
wherein the air pressure decreases radially outwardly.
This aspect of the invention is based on the consideration that should low-
molecular degradation products have deposited on the at least one cooling ring
lip, they should not end up on the film bubble. Generating and maintaining an
air
pressure difference at the inlet, whereby the air pressure decreases in the
radial
outward direction, creates an air flow to the outside; i.e. directed away from
the
Date Recue/Date Received 2023-10-16
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film bubble, so as potentially enable the realization that should low-
molecular
degradation products have formed on and flaked off of the at least one cooling
ring lip, they will not end up on the film bubble.
In one embodiment of the third aspect of the invention, the cooling ring is
configured to generate and maintain a higher air pressure at the inlet than
the
ambient air pressure, wherein the ambient air pressure corresponds to the
normal
air pressure at the site of the cooling ring's installation.
In other words, there is excess pressure at the inlet in this embodiment as
compared to the ambient pressure; i.e. particularly compared to the exterior
of
the cooling ring, which may under certain circumstances result in an outward
air
flow; i.e. directed away from the film bubble, so as potentially enable the
realization that should low-molecular degradation products have formed on and
flaked off of the at least one cooling ring lip, they will not end up on the
film
bubble.
In a further embodiment of the third aspect of the invention, the inlet has an
inlet start point at its end facing the nozzle as seen in the production
direction,
wherein the cooling ring is configured to generate and maintain a lower air
pressure on the radially outer edge of the inlet point than prevails at the
inlet.
In other words, there is a negative pressure on the exterior of the cooling
ring
compared to the air pressure at the inlet in this embodiment, whereby an
outward air flow may likewise result under certain circumstances; i.e.
directed
away from the film bubble, so as enable the potential realization that should
low-
molecular degradation products have formed on and flaked off of the at least
one
cooling ring lip, they will not end up on the film bubble.
In a further embodiment of the third aspect of the invention, the cooling ring
comprises a suction housing, wherein the suction housing is arranged at the
end
of the inlet start point facing the nozzle.
Applying a negative pressure to the suction housing, whereby an outward air
flow
may likewise result under certain circumstances; i.e. directed away from the
film
bubble, also enables the potential of achieving no low-molecular degradation
Date Recue/Date Received 2023-10-16
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products, should they have formed on and flaked off of the at least one
cooling
ring lip, ending up on the film bubble.
In a further embodiment of the third aspect of the invention, the suction
housing
is of annular shape.
Under certain circumstances, the annular design is able to achieve an outward
air
flow developing over the entire circumference; i.e. directed away from the
film
bubble, so as enable the potential realization that should low-molecular
degradation products have formed on and flaked off of the at least one cooling
ring lip, they will not end up on the film bubble, regardless of where on the
circumference of the at least one cooling ring lip they would have formed.
In a further embodiment of the third aspect of the invention, the at least one
cooling ring lip is thermally insulated from the cooling fluid running through
the
cooling ring during operation of the blown film line and/or the film tube
running
through the cooling ring during operation of the blown film line.
Combining the thermal insulating of the at least one cooling ring lip vis-à-
vis the
cooling fluid running through the cooling ring during the blown film line's
operation and/or the film tube running through the cooling ring during the
blown
film line's operation with the aforementioned features of the third aspect of
the
invention has the potential of amplifying the described effects of this aspect
of
the invention.
In a further embodiment of the third aspect of the invention, the at least one
cooling ring lip can be heated.
Combining the heatability of the at least one cooling ring lip with the afore-
mentioned features of the third aspect of the invention has the potential of
amplifying the described effects of this aspect of the invention.
In a further embodiment of the third aspect of the invention, the at least one
cooling ring lip is heated during the operation of the blow molding line to a
temperature below the evaporation temperature of the potential degradation
product of the processed film material at the highest evaporation temperature.
Date Recue/Date Received 2023-10-16
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Thus, although it is possible for some potential degradation products to
nevertheless condense on the cooling ring lip under certain circumstances,
heating can realize the effect that degradation products which are more easily
evaporated do not deposit on the cooling ring lip and that fewer of the
degradation products that can only evaporate at higher temperatures condense
on the cooling ring lip, whereby potentially able to be achieved is fewer low-
molecular degradation products, should they have formed on and flaked off the
at
least one cooling ring lip, reaching the film bubble.
In a further embodiment of the third aspect of the invention, the at least one
cooling ring lip is heated during the operation of the blow molding line to at
least
a temperature corresponding to the evaporation temperature of the potential
degradation product of the processed film material at the highest evaporation
temperature.
Heating to such a temperature has the potential to achieve preventing all the
degradation products from condensing on the cooling ring lip, whereby no low-
molecular components ending up on the film bubble and leading to defects is
able
.. to be achieved under certain circumstances.
According to a fourth aspect of the invention, the task posed is solved by a
method for operating a cooling ring as described above, wherein the heating
temperature is regulated.
Regulation enables potentially achieving an essentially constant cooling ring
lip
temperature, with the number of defects on the film bubble thus remaining at
an
essentially constant low or even film bubble defects being consistently
prevented.
According to a fifth aspect of the invention, the task posed is solved by a
blown
film line having an extruder for producing a melt flow, a die head, an annular
nozzle for producing a continuous film tube from the melt flow, a calibration
unit
as well as a flat lay, wherein the blown film line comprises a cooling ring as
described above.
Date Recue/Date Received 2023-10-16
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Such a blown film line enables the potential of producing a film with fewer
visual
defects than is possible with known prior art systems.
The previously described embodiments can be employed individually or also in
any combination with one another.
The invention will be described in greater detail below on the basis of
exemplary
embodiments referencing the figures. Shown therein:
Fig. 1 a perspective view of a blown film line having a general bottom-to-top
production direction
Fig. 2 a perspective view of a blown film line having a general top-to-bottom
production direction
Fig. 3 a schematic sketch of a detail of an inventive blown film line having a
general top-to-bottom production direction from the nozzle to behind
the calibration zone
Fig. 4 a perspective schematic sketch of a detail from a double-lip cooling
ring
The blown film line shown in Fig. 1 has a general bottom-to-top production
direction x. The extruder zone 100 of the blown film line is arranged at the
bottom; i.e. at ground level on the floor of a production hall. A plurality of
extruders 101 operate on a die head having an annular nozzle 110 (not shown in
the view). A film tube inflated via the annular nozzle exits from the annular
nozzle 110 so that a film bubble 600 is produced from the film tube. The
inflation
radially stretches the film tube. A cooling ring 700 follows the annular
nozzle 110
.. in the production direction x. Different implementations of cooling rings
700 with
varying numbers of lips are known. For example, cooling rings having one, two
or
even three cooling ring lips 704, 705 are also known. The film bubble 600 is
cooled in the cooling ring 700 from the outside by cooling fluid being brought
into
contact with the exterior of the film bubble 600 through a cooling fluid
nozzle
702, 703. A calibration zone 200 within which the external diameter of the
film
bubble 600 is calibrated follows in the production direction x. Following the
Date Recue/Date Received 2023-10-16
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calibration zone 200 in the production direction is a take-off zone 300 in
which
the film tube is squeezed and drawn off via a pair of rollers. The squeezing
confines the inflation pressure within the film bubble 600. When drawn off,
the
film bubble is stretched in the axial direction so that a biaxially stretched
consolidated film tube is produced after the take-off zone 300. A stretching
zone
400 follows the take-off zone 300 in the production direction x within which
the
consolidated film tube is further axially stretched. After the stretching
zone, the
flat film tube is redirected and guided back to the level of the extruder zone
100;
thus ground level on the floor of a production hall, where it is wound in a
winding
zone 500. The general bottom-to-top production direction x is typical for
blown
film lines in which the film bubble 600 is cooled with air.
The blown film line shown in Fig. 2 has a general top-to-bottom production
direction x. The extruder zone 100 of the blown film line is arranged at the
top;
i.e. above all the other system components. A plurality of extruders 101
operate
on a die head having an annular nozzle 110 (not shown in the view). A film
tube
inflated via the annular nozzle exits from the annular nozzle 110 so that a
film
bubble 600 is produced from the film tube. The inflation radially stretches
the film
tube. A cooling ring 700 follows the annular nozzle 110 in the production
direction
x. Different implementations of cooling rings 700 with varying numbers of lips
are
known. For example, cooling rings having one, two or even three cooling ring
lips
704, 705 are also known. The general top-to-bottom production direction x is
typical for blown film lines in which the film bubble 600 is cooled with a
liquid
cooling fluid, such as water, since a liquid cooling fluid film which is able
to
follow gravity in this production direction x is usually applied to the film
bubble
600. The film bubble 600 is cooled in the cooling ring 700 from the outside by
cooling fluid being brought into contact with the exterior of the film bubble
600
through a cooling fluid nozzle 702, 703. A calibration zone 200 in which the
external diameter of the film bubble 600 is calibrated follows in the
production
direction x. Following the calibration zone 200 in the production direction is
a
take-off zone 300 in which the film tube is squeezed and drawn off via a pair
of
rollers. The squeezing confines the inflation pressure within the film bubble
600.
When drawn off, the film bubble is stretched in the axial direction so that a
biaxially stretched consolidated film tube is produced after the take-off zone
300. A
stretching zone 400 follows the take-off zone 300 in the depicted embodiment
within which the consolidated film tube is further axially stretched, whereby
the
Date Recue/Date Received 2023-10-16
16
film tube is redirected to the stretching zone since the stretching zone 400
is
arranged next to but above the take-off zone 300 in this embodiment for
reasons
of space. After the stretching zone, the flat film tube is redirected and
guided
back to the level of take-off zone 300, thus ground level on the floor of a
production hall, where it is wound in a winding zone 500.
Fig. 3 shows a detail of an inventive blown film line from the nozzle 110 to
behind the calibration zone 200 as a schematic sketch. The film tube extruded
from the nozzle 110 is inflated into the film bubble 600 and initially passes
through a cooling ring 700 in which it is externally cooled with a cooling
fluid by
a cooling fluid being brought into contact with the exterior of the film
bubble 600.
The film bubble 600 then passes through the calibration zone 200 in which the
external diameter of the film bubble is calibrated.
Fig. 4 shows an enlarged detail of a double-lip cooling ring 700 in a
perspective
depiction. In its circular interior, the double-lip cooling ring 700 initially
exhibits
the film tube guide in the form of a central passage 700 for the film bubble
600.
A cooling fluid can exit through cooling fluid channels 708 to the central
passage
701 through a first cooling air nozzle 702 as well as a second cooling air
nozzle
703. The first cooling fluid nozzle 702 is limited by a first cooling ring lip
704
while the second cooling fluid nozzle 703 is limited by a second cooling ring
lip
705. The first cooling ring lip 704 is designed statically in the depicted
embodiment and constitutes the inlet 709 for the film bubble 600. In contrast,
the second cooling ring lip 705 is divided into segments along its
circumference
(segmentation not shown). The individual segments are articulated, for example
on a radially inner joint 706 (not depicted here). The film bubble 600 exits
the
cooling ring 700 at an exit collar 707.
The embodiments shown here only represent examples of the present invention
and should therefore not be construed as limiting. Alternative embodiments
entertained by those skilled in the art are equally included within the
protective
scope of the present invention.
Date Recue/Date Received 2023-10-16
17
List of reference numerals used
100 extruder zone
101 extruder
110 annular nozzle, nozzle
200 calibration zone
300 take-off zone
400 stretching zone
500 winding zone
600 film bubble
700 cooling ring, double-lip cooling ring
701 central passage
702 first cooling fluid nozzle
703 second cooling fluid nozzle
704 first cooling ring lip
705 second cooling ring lip
706 joint bearing
707 exit collar
708 cooling fluid channel
709 inlet
x production direction
Date Recue/Date Received 2023-10-16
