Field Of Invention
The present invention relates to an apparatus and a method for quenching plastic
film, more preferably polyolefinic film, particularly polypropylene film extruded in
form of hot melt from the extruder. However, the apparatus may be used for films
5 extruded using other materials such as HDPE, TPE, PC and ABS etc.
Background of Invention
A film of solid plastic materials can be prepared by several different methods. Such
methods include casting of films from solutions and the blown tubing technique
10 whereby a tube of polymer is extruded and is thereafter expanded by applying
pneumatic pressure to the interior of the tube so as to reduce the wall thickness of
the tube to desired size. Extrusion of molten polymer or plastic material through
small opening is often known as slot die extrusion.
15 It is well known that, in the manufacture of polyolefinic film, particularly
polypropylene film but also other materials such as HDPE, TPE, PC and ABS etc.,
the hot melt polymer is extruded into a water quench-bath where the film solidifies.
The solidified polypropylene film is then taken from the bath and passed over a
system of rollers before being fed to the hot air oven in which the film is drawn to
20 induce molecular orientation.
Many prior art documents disclose process of producing plastic films. US 3048895
patent discloses a process for production of film of plastic material such that it
passes through grooved rollers for lateral stretching. The molten material from the
25 extruder is directly dipped in a water tank to form a film which passes through the
grooved roller which results into the stretching of the film. However, this type of
the lateral stretching without a flexible member at the earlier phase of the
solidification results into the distortion of the flexible extruded film due to the
excess tension stresses developed at the molecular level of the film.
30
3
Further, in the US Patent 3048895, the molten material is directly dipped in the
water tank which increases the temperature of the nearby contact water or cooling
medium, such sudden increase in temperature will result in the distortion of the
film. There is no method of rapid cooling of the water disclosed in the Patent US
5 3048895 which is essential for production of desirable film from molten material.
Further, another US 2311755 (‘1755) patent discloses use of the curved guide
member in the coagulating bath where the partially converted gel web is stretched
in such a manner that the sheet wrapping material finally produced has very
10 desirable physical characteristics. The film passes about this guide in such a manner
that the central portion of the web is displaced in its line of travel to a greater extent
than the marginal portions of the web. Further, the patent (‘1755) disclosed a curved
member for removing shrinkage within the solidified film. The curved member is
placed inside the water tank and its position is close to the extruder die. Due to the
15 position of the member near the extruder die while applying tension in the direction
perpendicular to the motion of film, it can tear of the solidified film due to improper
solidification. However, the patent (‘1755) does not addresses the problem of quick
solidification of the extruded film due to the improper circulation of cooling
medium. In most processing operations, it is generally desirable to “set” the
20 polymer as soon as possible after it has been shaped; usually by cooling in a
quenching water bath after the extrusion die. And this is possible only when the
temperature of the water is maintained in the range of 19°C to 21°C ± 2°C with the
help of some cooling device through which water circulated continuously and
maintained its desired temperature such that the polymer molecules may not have
25 time to coil up (recoil) completely before the melt freezes.
Therefore, there is a requirement of quick solidification of the molten material
with the help of continuously circulated cooled water maintained at desired range
of temperature and a method of carrying solidified flexible film such that water
30 removal takes place effectively.
4
Further, the film which passes through the water tank is to be dried up using
efficient drying assembly which can be a set of wipers. However, in conventional
systems, the life and performance of the wipers is not adequate for efficient
5 removal of the water droplets. Drying method used for film drying should be
quick and compatible with the speed of modern machines operating at high speed.
Hence, there is a need of a suitable and convenient quenching method and a
device to produce a film from the molten material.
10
Objects of Invention:
Accordingly, some of the objects of the invention are as follows.
The main object of the present invention is to provide an apparatus for quick
15 solidification of molten film.
Another objective of this invention to provide an apparatus for drying the film
efficiently.
20 Further objective of the present invention is to provide a method for quenching
plastic film extruded in form of hot melt from the extruder.
Another objective of the present invention is to provide a method for drying the
film in a continuous line.
25 Yet another objective of the present invention is to increase the overall efficiency
of the system in continuous line.
Brief Description Of Figures:
5
Figures 1 shows the inventive device of the present invention used for the
solidification of a polyolefinic film particularly polypropylene film extruded
in form of hot melt from the extruder.
5 Figure 2 shows an arrangement of tray units and its specially designed
hemispherical cut edge.
Figure 3 shows a film guiding unit and combination of different rollers like
small roller, mid roller, and big roller.
10
Figure 4 shows a wiper and scrapper unit used to pull out the moisture
contents from the film.
Figure 5 shows perspective view of tank unit where the film just entered
15 into the tank and start forming the bubbles due to energy exchange.
Figure 6 show the cross section view of cooling pipe unit.
List of Parts:
20 1. Film
1A. Molten film
1B. Exit film
2. Tank unit
2A. Water inlet
25 2B. Water outlet
3. Tray unit
3A. Contact Bar
3B. Air gap sensor.
3C. Cooled water inlet roller
30 3D. Tray
3E. Hemispherical cut edge
6
3F. Circulating pipe
3G. Inner roller
4. Film guide unit
4A. Fixed point
5 4B. Small roller
4C. Big roller
4D. Mid roller
5. Wiper and scrapper unit
5A. Wiper or scrapper
10 5B. Semi-circular pipe
5C. Pipe Opening
6. Draw Roller unit
6A. First Roller
6B. Second Roller
15 6C. Upper set of rollers
6D. Lower set of rollers
7. Air Knife unit
7A. Suction pipe
8. Cooling pipe unit
20 9. Extruder die
10. Third Roller
11. Bubbles
Summary Of Invention:
25 The present invention relates to the solidification of a molten polyolefinic film,
particularly a polypropylene film (1), extruded in form of hot melt from an extruder
die (9). Molten film (1A) extruded from the extruder die (9) is solidified and cooled
normally with the help of water, air or contact with cold surface (highly polished
water-cooled chill rollers) or any other cooling medium before entering the
30 upcoming processing unit where further enhancement of mechanical properties
happens. In the present invention solidification and cooling of the molten film (1A)
7
is done with the help of water stored in a tank unit (2) and continuously circulating
through the cooling device to maintain its cooling temperature.
In present invention for cooling the molten film (1A), water is used as the preferred
5 quenching medium, however, the quenching medium can also be of any type such
as oil, soft soap, emulsion of oil and water, ethylene glycol etc. In the molten state,
and when not subjected to external stresses, polymer molecules tend to coil up. That
is, they prefer to exist in a random coil configuration. When external stresses are
applied (as occur during extrusion, moulding, and other shaping operations) the
10 molecules become distorted from their randomly coiled state and tend to become
oriented. In most processing operations it is generally desirable to “set” the polymer
as soon as possible after it has been shaped; usually by cooling in a water bath after
the extrusion die (9). In such circumstances, the polymer molecules may not have
time to coil up (recoil) completely before the melt freezes. This results in the effect
15 known as frozen-in orientation which can be easily achieved in the molten
polyolefinic film particularly polypropylene film extruded from the extruder die
(9).
The present invention is also used to remove water droplets or moisture from the
20 film surface after solidification and cooling by the chilled water present inside the
tank unit with the help of wiper and scrapper unit (5) overcoming the shortcomings
of the conventional system of drying. After passing from the wiper and scrapper
unit (5) for the final stage of water and moisture removal completely, solidified film
enters into the draw film assembly consisting of at least one pair of rollers, namely
25 a first roller (6A) and a second roller (6B) that are positioned vertically apart from
each other. An air knife unit (7) is provided between the two rollers, first roller and
second roller (6A, 6B) which forces the air out in a direction that is tangentially
downward and vertically opposite to the film flow direction due to which small
droplets of the water spread out from the film and help to increase the efficiency of
30 dryness of solidified film. The first roller (6A) and the second roller (6B) can be
8
made up of steel, rubber, brass, and any other materials which can be metallic, nonmetallic or combination of both.
The film then it passes through a specially designed third roller (10) having a
5 specific shape and peripheral profile which is used to remove the wrinkles and
shrinkage which occurs inside the film and entered the downstream processing units
which consist of a slitting unit, a holding and stretching unit, a hot air oven, and a
stretching and annealing unit.
10 Detail Description Of Invention:
As discussed earlier, the polyolefinic film, particularly the polypropylene film,
extruded in form of a hot melt from the extruder die which must be solidified and
cooled goes to up-next units for further processing to enhance the mechanical
properties. Figure 1 shows the apparatus of invention used for the solidification of
15 a polyolefinic film particularly polypropylene film extruded in form of hot melt
from the extruder. It consists of various units such as a tank unit (2), a tray unit (3),
a film guide unit (4), a wiper and scrapper unit (5), a draw roller unit (6), an air
knife unit (7), a cooling pipe unit (8), an extruder die (9) and a third roller (10).

20 Also, as discussed earlier, the molten film (1A) after the extrusion from the extruder
die (9) enters the water tank unit (2). Molten film (1A) can be of any thickness and
basically depends upon the opening at the die. Higher the thickness of the molten
film, more will be the rate of cooling required. Inside the water tank unit (2) chilled
water is continuously circulated whose temperature is maintained at around 19°C
25 to 21°C ± 2°C continuously with the help of cooling device and cooling pipe unit
(8). As the molten film (1A) enters the water tank unit (2) heat energy associated
with the molten film (1A) gets exchanged with the surrounded cooled water and
due to this exchange of energy between the molten film (1A) and the cooled water
in its immediate vicinity, the molten film (1A) starts changing its state from molten
30 to flexible solid.
9
To extract heat, water is taken as the coolant from the water tank unit (2) because it
is available in abundance and has a great value of specific heat capacity. Another
key reason to choose water as a heat absorber because it can be used for both open
cycle and closed cycle. Open cycle is the one in which same cooling medium does
5 not circulate again and again, while for closed cycle same cooling medium is
circulated again and again in a fixed close loop. Higher the value of specific heat
capacity (C), higher the heat interaction that takes place without any significant
amount of change in the temperature of water.
𝐶ௐ௔௧௘௥ = 4.18 𝑘𝐽/𝑘𝑔𝐾
10
As soon as the molten film (1A) enters into the tank (2), water starts boiling locally
around the interface of the molten film (1A) and water, and start forming bubbles
(11) in between a pair of trays (3D) which collectively termed as tray unit (3) due
to sudden transition of energy in between the film and water. The boiled water
15 which increases the temperature of the water to an extent in between the 60°C to
70°C ± 2°C is circulated back to the cooling device with the help of pair of trays
(3D) placed parallelly both side of the entered molten film (1A). The set of trays
(3D) gives the advantage of separation of boiled water from the tank unit (2) such
that temperature of the remaining water inside the tanks remain within the desirable
20 limit. As already mentioned before, boiling of the water takes place only at
immediate surrounding of the film/water interface so it is desirable for the pair of
trays (3D) to collect hot water from that inner side only where hemispherical cut
edges are produced. Hence small intermittent hemispherical cut edge (3E) as shown
in figure 2, is made on inner side of the pair of trays (3D) so that only high
25 temperature water is circulated back to the cooling device which increases the
coefficient of performance (C.O.P) of the water tank. Coefficient of performance
depends on the rate of heat extraction from the heat tank. Higher the temperature of
the water extracted from the tanks (2), higher will the rate of heat interaction. Hot
water is circulated back to the cooling device with the help of circulating pipe (3F)
30 attached at the ends of the trays. Circulating pipes (3F) are directly attached to the
10
separate chamber placed at the end of the tank (2). An air gap sensor is used to find
the water level present in the tanks from the hot water collecting trays (3D).
Example1: In case where the temperature of the water just around the area where
5 film enter into the tanks is 100°C while the average temperature of the tank is 19°C
to 21°C ± 2°C. Water near the film extracts the heat from the molten film and try
to transfer the heat to the complete water tank but if we extract the hot water as soon
as possible whose temperature at the time of extraction reaches the range of 60°C
to 65°C ± 2°C while if we doesn’t prevent the intermixing of the hot water with
10 cold water it will leads toward the overall increment in the temperature of the hot
water and hence result into the low rate of heat transfer from the tank unit.
𝐶𝑂𝑃௧௔௡௞ =
஽௘௦௜௥௘ௗ ா௙௙௘௖௧
௣௢௪௘௥ ௜௡௣௨௧

𝐶𝑂𝑃௧௔௡௞ =
ோ௔௧௘ ௢௙ ௛௘௔௧ ௘௫௖௧௥௔௖௧௘ௗ ௙௥௢௠ ௧௛௘ ௧௔௡௞
௣௢௪௘௥ ௜௡௣௨௧
15
From the above result we can easily understand that higher the rate of heat
extraction from the water tanks it leads towards the increment of its coefficient of
performance. Which result into the quick solidification of the molten film (1A) due
20 to higher temperature deference between the film (1) and the water.
Hence this special type of hemispherical cut edges (3E) and pair of trays (3D) are
some of the key features of the present invention which lead towards the overall
increment in efficiency of the inventive system.
25
It also helps system to maintain the quick solidification of the film as quenching
medium maintains its temperature within the desirable range which was one of the
major problems that occurs in the conventional systems.
11
Example 2: In case where the temperature of the water after extracting heat from
films reaches the range of 60°C to 65°C ± 2°C and if this water is extracted with
the help of the trays quickly then temperature inside the tank can be easily
maintained to be at19°C to 21°C ± 2°C while if this is not done this hot water mixed
5 with the cooled water of the tank and increases the overall temperature of the tank
in the range of 30°C to 35°C ± 2°C which result into the low rate of heat transfer.
Quick solidification refers to how fast the heat energy of the molten film is
transferred to the quenching medium. Higher the temperature difference between
10 the molten film and quenching medium, higher the heat interaction between the
molten film and quenching medium. Hence by adjusting the height of the trays (3D)
the amount of boiled and bubble water can be separated out as per the process
requirement and vertical adjustment allows to moments of film extruded from the
die. Height of the tray unit (3) is adjustable both in vertical and horizontal direction
15 with the help of mechanical arrangement such kind of arrangement can be of knob
fittings, screw pairs, linkage motion, electric driven, pneumatic driven etc. A
contact bar (3A) is provided just below the pair of trays (3D) which is used to break
down the bubbles (11) produced due to the sudden energy exchange in between
molten film (1A) and cooled water. When water is boiled, the heat energy is
20 transferred to the molecules of water, which begin to move more quickly.
Eventually, the molecules have too much energy to stay connected as a liquid.
When this occurs, they form gaseous molecules of water vapor, which float to the
surface as bubbles (11) and travel into the air. While reaching the surface it will
25 comes into contact with molten film and releases its energy to it and destroys the
surface of the molten film. Hence in order to prevent this problem, contact bar (3A)
is used to break the bubbles and when bubbles come in contact with the bar, it will
releases all its energy to the contact bar (3A) to prevent film (1) from bubble
damage. As a surprising effect of the present invention, since small bubbles are
30 formed, the energy released by the brakeage of the small bubbles is much smaller
12
than the energy released by uncontrolled breakage of large bubbles. The formation
of large bubbles is thus prevented.
Cooled water from the cooling device entered into the tank (2) with the help of
5 cooled water inlet roller (3C) which is connected to the cooling device with the help
of cooling pipe unit (8). Water coming from the water inter roller (3C) directly
comes in contact with molten film inside the quenching medium which is extruded
from the extruder die. Fig 6 is the perspective view of water inlet roller (3C) that
consists of inlet inner roller consist of series of holes and a sleeve fitted over the
10 roller and having a slot on its periphery over its complete length and free to rotate
in 360° with respect to the inner roller (3G). This arrangement is basically done to
prevent the excess flow pressure applied on the just solidified film (1) just below
the tray arrangement. After the initial sudden cooling of film (1) sustained with in
the water tank for a very short time period which depends on the line speed of the
15 subsequent unit after and before the system but with continuous flow line. Line
speed of the machine is depending upon the thickness of the molten film, higher the
thickness of the molten film, slower is the line speed while thinner the molten film,
higher the line speed of machine.
20 For this to be achieved, water tank unit (2) has film guide unit (4) which guide the
film (1) in between the tray unit (3) and wiper and scrapper unit (5). Film guide unit
(4) is pivoted completely around a fixed point (4A) to adjust the tension in the
running film. Film guiding unit (4) consists of pairs of small rollers (4B) is just to
support the film whose number is dependent upon the length of the tank and time
25 required to put the film in contact with water, more the time required for
solidification, more will be the length of the guide unit and hence more will be the
no of small roller (4B) . Film moves in zig zag manner to increase contact time with
water inside the tanks within the same length. In another embodiment shown in the
Fig. 4 big rollers (4C) is used just below the pair of trays (3D) to support the just
13
solidified film (1) by increasing the surface of contact. Another mid roller (4D) is
used to transfer the film is placed just below the wiper and scrapper unit (5).
The solidified flexible film then enters into the wiper and scrapper unit (5) such that
5 at least one wiper and scrapper unit (5) is present which is used for the removal of
water and moisture content present on the film (1), a pair of wipers is used to wipe
the water from the top and bottom surface of the film to the greater extent. Wiper
can be of any shape that is conventional, flat, or of hybrid geometry and made up
of rubber, elastomer, or any other synthetic elastic material. Fig. 5 shows a wiper
10 scrapper assembly consisting of pair of wipers or scrapper (5A) in between which
a film (1) is passed such that all the moisture drop on the surface of the film is easily
removed. As the film meets wiper all its moisture drop is collected in the semicircular pipe (5B) and transfer this water to the water tank unit (2) through the pipe
opening (5C) at the ends of the semi-circular pipe (5B).
15
Further, wipers are flexible enough to take shape of the moving film and apply very
less pressure on the film. The pressure applied by the wipers and scrapper (5) on
the film is in the range of 1.5 – 2.5 bars which is enough to take the water droplets
with it such that at higher speed also the film is sufficiently dried.
20
After passing through the wiper and scrapper unit (5), solidified flexible film (1),
which still has small amount of moisture on the surface of film (1) enters into the
draw roller unit (6) which consist of upper set of roller (6C) and lower set of roller
(6D) which consist of at least one pair of First roller (6A) and second roller (6B)
25 present vertically apart from each other. An air knife unit (7) is positioned between
the rollers (6A and 6B) which forces the air out tangentially to the film and in a
direction opposite to the travel direction of the solidified film . The solidified
flexible film (1) is stretched in between the upper set of rollers (6C) and lower set
of rollers (6D) arrangement consist of First roller (6A) and Second roller (6B) each.
14
First roller (6A) and Second roller (6B) can be made of steel, rubber, brass, and
any other materials which can be metallic non-metallic or combination of both.
The rotational speed of the upper set of rollers (6C) is less than the rotational speed
5 of lower set of rollers (6D) thereby making the film slack and forced air jet from
the air knife which create flapped vibration within the film (1) which is required for
the final removal of the moisture from the film surface. Both upper set of rollers
and lower set of rollers (6C and 6D) are driven by separate driving mechanism
which can be electric motor or any other rotary source. Before passing through the
10 air knife, the film passes through the pair of suction pipe (7A) having negative
pressure (vacuum) that helps to sucks the moisture present on the film. After passing
through draw roller unit (6) and air knife unit (7), film (1) then enters to the last
stage i.e., to the specially designed third roller (10) which is unique spiral helix
profile in shape and used to remove the final stage wrinkles and shrinkages
15 produced inside the film during solidification.
After wrinkles or shrinkage removal, the film enters into the downstream
processing units for further enhancement in mechanical properties which consist of
Slitting unit, Holding and Stretching unit, Hot Air-Oven, Stretching and Annealing
20 unit irrespective of absence of the and mentioned unit. Specially designed roller has
unique spiral helix profile on its surface such that it tries to move the fabric towards
the outer direction from the centre of the roller along its length. Helix is done in
such a way that half of the roller spiral helix is right hand side while half of the
spiral helix is left hand side. Overall efficiency of the present innovative system is
25 increased rapidly from the conventionally existing systems as disclosed in prior arts
in many aspects which can be a solidification of the film, dryness of the film,
circulation of the quenching medium, continuous operation of the system to flow
the line speed of up-next processing unit etc.
15
For example, in the conventional system due to improper circulation of the
quenching medium quick solidification of the film in not possible hence it required
more time for the solidification result in the slow line speed having the difference
of nearly 50 m/min. while in the conventional system there is no air knife and wiper
5 arrangement in the system which decreases the dryness efficiency of the system and
moisture contents remains on the surface of film while present invention consist of
sets of air knife and wiper arrangement to increase the efficiency of the system. Due
to the installation of pivoted film guide, line speed of the system also increases due
to unbroken travel of the film during the solidification.
10
Hence, all factors mentioned in the examples plays important roles to increase the
overall efficiency of the system nearly by 10-15 % in terms of line speed.
The invention also discloses a quenching method of polypropylene film and
15 removing of the moisture from the film surface after solidification and the
apparatus comprising the following sequential steps:
1) Polypropylene film (1) is extruded from the extruder die (9) in molten
from and entered to tank unit (2) wherein the said tank unit (2)
20 comprises a cooling fluid which solidifies the molten film (1A) by
taking out its energy and enhance its mechanical properties.
2) Hot water is being continuously circulated back to the cooling device
with the help of the Tray unit (2) and circulating pipe (3F).
3) After that just solidified film enters to film guide unit (4) which is
25 pivoting about the fixed point (4A) and consist of small roller (4B),
big roller (4C) and Mid roller (4D).
4) As the film passes through the series of the roller arrangements inside
the tank unit, it will get perfect solidification.
16
5) After that film enters the wiper and scrapper unit (5) where initial
moisture removal is done with the help of wiper and scrapper (5A)
and removed water is collected to the semi-circular pipe (5B).
6) After that film enters the draw roller unit (6) between the upper set of
5 rollers (6C) and lower set of rollers (6D) wherein upper set of rollers
(6C) is rotating with lower speed as compared to the lower set of
rollers (6D) which result into the slackness of the film.
7) For final removal of the moisture from the film surface. the said film
is being forced air jet from the air knife (7) which create flapped
10 vibration within the film (1).
8) Thereafter, the film is being passed through the specially designed
third roller (10) which is unique profile spiral helix in shape and used
to remove the final stage wrinkles and shrinkages produced inside the
film during solidification.
15 9) After that film enters the downstream processing units comprising of
various stations such as cutter and slitter, hot air oven and annealing
and stretching unit.
It is evident that the invention has the following embodiments.
20
In the preferred embodiment, the invention discloses an apparatus for quenching
of plastic film. The characterising aspect of the apparatus is that it comprises a
water tank unit (2), a tray unit (3) having a pair of trays (3D), a film guide unit
(4), a wiper and scrapper unit (5), a draw roller unit (6), an air knife unit (7), a
25 cooling pipe unit (8), an extruder die (9), a third roller (10), and a pair of trays
(3D), wherein a molten film (1A) extruded from said extruder die (9) travels
through said water tank unit (2) into a tray unit (3) followed by said film guide
unit (4) and through said wiper and scrapper unit (5), and through a pair of lower
rollers (6D) that form a part of said draw roller unit (6) that leads the film through
30 said air knife unit (7) and then through a set of upper rollers (6C) which are also a
17
part of said draw roller unit (6) to turn into a quenched film that is sent over said
third roller (10).
In another embodiment of the apparatus, chilled water is continuously circulated
5 inside said water tank unit (2) into which said plastic film in its molten state enters
and boils the water in its vicinity, said boiled water leading to said pair of trays
(3D) and circulated back to the cooling device.
In a further embodiment of the apparatus, hot water is continuously circulating
10 back to the cooling device with the help of the water tray unit (2) and a circulating
pipe (3F).
In yet another embodiment of the apparatus, said pair of trays (3D) have an
intermittent hemispherical cut edge (3E) on the inner side of each of the pair of
15 trays (3D) to ensure that water with only higher temperature is circulated back to
the cooling device.
In a still further embodiment of the apparatus, said trays (3D) are adjustable in
their height and width.
20
In a yet further embodiment of the apparatus, a bubble-breaking contact bar (3A)
is provided immediately below the said pair of trays (3D).
In another embodiment of the apparatus, a cooled water inlet roller (3C)
25 connected to cooling pipe unit (8) allows cooled water from the cooling device to
enter into the tank (2), wherein said inlet inner roller consist of series of holes and
a sleeve fitted over the roller and having a slot on its periphery over its complete
length and free to rotate in 360° with respect to the inner roller.
18
In still another embodiment of the apparatus, said film guide unit (4) is positioned
between said tray unit (3) and said wiper and scrapper unit (5), and is pivoted
completely around a fixed point (4A) to adjust the tension in the running film,
wherein said film guiding unit (4) consists of pairs of small rollers (4B).
5
In a further embodiment of the apparatus, big rollers (4C) are provided just below
the pair of trays (3D) to support the just solidified film (1), and a mid-roller (4D)
used to transfer the film is placed just below the wiper and scrapper unit (5).
10 In yet further embodiment of the apparatus, said wiper and scrapper unit (5) have
at least one pair of wipers and scrappers (5A) which are flat or of hybrid geometry
and made up of rubber, elastomer, or synthetic elastic material, and wherein the
moisture removed by said wiper or scrapper unit (5) is collected in a semi-circular
pipe (5B) and transferred back to the water tank unit (2) through the pipe opening
15 (5C) at the ends of the semi-circular pipe (5B).
In a still further embodiment of the apparatus, said wipers or scrapper unit (5)
applies pressure on said film in the range of 1.5 – 2.5 bars.
20 In another embodiment of the apparatus, each of said upper set of rollers (6C) and
lower set of rollers (6D) consist of at least one pair of first roller (6A) and second
roller (6B) present vertically apart from each other, and wherein said air knife unit
(7) is positioned between the first and second rollers (6A and 6B).
25 In yet another embodiment of the apparatus, said first roller (6A) and second
roller (6B) are made of steel, rubber, brass, and any other materials which can be
metallic non-metallic or combination of both.
In a further embodiment of the apparatus, the rotational speed of the upper set of
30 rollers(6C) is less than the rotational speed of lower set of rollers (6D).
19
In yet another embodiment of the apparatus, said upper set of rollers and lower set
of rollers (6C and 6D) are driven by separate driving mechanism which can be
electric motor or any other rotary source.
5
In another preferred embodiment of the invention, a method for quenching the
plastic film using the apparatuses disclosed previously is described. The
characterising features of the method are that it comprises the following steps :
a. extruding a polyolefin film (1A) through the extruder die (9) in molten
10 from and entering it into the water tank unit (2) having a cooling fluid,
thereby solidifying the molten film (1A);
b. continuously circulating hot water back to the cooling device with the
help of the tray unit (2) and a circulating pipe (3F);
c. sending the solidified film (1A) through a film guide unit (4) that is
15 pivotable about the fixed point (4A), and consisting of a small roller
(4B), a big roller (4C), and a mid-roller (4D), thereby further
solidifying said film (1A) ;
d. passing the solidified film (1A) through the wiper or scrapper unit (5),
whereby moisture from the film surfaces is removed, and collecting the
20 removed moisture in the semi-circular pipe (5B), thereby substantially
drying the film (1A);
e. passing the substantially dried film (1A) through the upper and lower
sets of rollers (6C and 6D) of the draw roller unit (6) in order to achieve
slackness of the film, wherein the upper set of rollers (6C) rotates at a
25 smaller speed than the lower set of rollers (6D);
f. removing the remaining moisture from its surface by using a forced air
jet from the air knife (7) which creates flapped vibration within the film
(1A);
g. sending the dried film (1A) over a third roller (10) having a spiral helix
30 shape, thereby removing wrinkles from the film;
20
h. optionally after removal the moisture, wrinkles and shrinkages, the film
is sent to next stage of downstream processing unit for further
enhancing the mechanical properties of the film if so desired.

5 In another embodiment of the method, in its step d, said wipers or scrapper unit
(5) applies pressure on said film in the range of 1.5 – 2.5 bars.
In a further embodiment of the method, in its step e, said upper set of rollers and
lower set of rollers (6C and 6D) are driven by separate driving mechanism which
10 can be electric motor or any other rotary source.
While the above description contains much specificity, these should not be
construed as limitation in the scope of the invention, but rather as an
exemplification of the preferred embodiments thereof. It must be realized that
15 modifications and variations are possible based on the disclosure given above
without departing from the spirit and scope of the invention. Accordingly, the
scope of the invention should be determined not by the embodiments illustrated,
but by the invention as a whole and in addition to appended claims and their legal
equivalents.

We claim:

1. An apparatus for quenching of plastic films characterised in that said apparatus
comprises a water tank unit (2), a tray unit (3) having a pair of trays (3D), a
film guide unit (4), a wiper and scrapper unit (5), a draw roller unit (6), an air
5 knife unit (7), a cooling pipe unit (8), an extruder die (9), a third roller (10),
and a pair of trays (3D), wherein a molten film (1A) extruded from said
extruder die (9) travels through said water tank unit (2) into a tray unit (3)
followed by said film guide unit (4) and through said wiper and scrapper unit
(5), and through a pair of lower rollers (6D) that form a part of said draw roller
10 unit (6) that leads the film through said air knife unit (7) and then through a set
of upper rollers (6C) which are also a part of said draw roller unit (6) to turn
into a quenched film that is sent over said third roller (10).
2. The apparatus as claimed in claim 1, wherein chilled water is continuously
15 circulated inside said water tank unit (2) into which said plastic film in its
molten state enters and boils the water in its vicinity, said boiled water leading
to said pair of trays (3D) and circulated back to the cooling device.
3. The apparatus as claimed in claims 1 and 2, wherein Hot water is continuously
20 circulating back to the cooling device with the help of the water tray unit (2)
and a circulating pipe (3F).
4. The apparatus as claimed in claims 1 to 3, said pair of trays (3D) have an
intermittent hemispherical cut edge (3E) on the inner side of each of the pair of
25 trays (3D) to ensure that water with only higher temperature is circulated back
to the cooling device.
5. The apparatus as claimed in claims 1 to 4, wherein said trays (3D) are
adjustable in their height and width.
22
6. The apparatus as claimed in claims 1 to 5, wherein a bubble-breaking contact
bar (3A) is provided immediately below the said pair of trays (3D).
7. The apparatus as claimed in claims 1 to 6, wherein a cooled water inlet roller
5 (3C) connected to cooling pipe unit (8) allows cooled water from the cooling
device to enter into the tank (2), wherein said inlet inner roller consist of series
of holes and a sleeve fitted over the roller and having a slot on its periphery
over its complete length and free to rotate in 360° with respect to the inner
roller.
10
8. The apparatus as claimed in claims 1 to 7, wherein said film guide unit (4) is
positioned between said tray unit (3) and said wiper and scrapper unit (5), and
is pivoted completely around a fixed point (4A) to adjust the tension in the
running film, wherein said film guiding unit (4) consists of pairs of small
15 rollers (4B).
9. The apparatus as claimed in claims 1 to 8, wherein big rollers (4C) is
provided just below the pair of trays (3D) to support the just solidified film
(1), and a mid-roller (4D) used to transfer the film is placed just below the
20 wiper and scrapper unit (5).
10. The apparatus as claimed in claims 1 to 9, wherein said wiper and scrapper
unit (5) have at least one pair of wipers and scrappers (5A) which are flat or
of hybrid geometry and made up of rubber, elastomer, or synthetic elastic
25 material, and wherein the moisture removed by said wiper or scrapper unit (5)
is collected in a semi-circular pipe (5B) and transferred back to the water tank
unit (2) through the pipe opening (5C) at the ends of the semi-circular pipe
(5B).
23
11. The apparatus as claimed in claims 1 to 10, wherein said wipers or scrapper
unit (5) applies pressure on said film in the range of 1.5 – 2.5 bars.
12. The apparatus as claimed in claims 1 to 11, wherein each of said upper set of
5 rollers (6C) and lower set of rollers (6D) consist of at least one pair of first
roller (6A) and second roller (6B) present vertically apart from each other,
and wherein said air knife unit (7) is positioned between the first and second
rollers (6A and 6B).
10 13. The apparatus as claimed in claims 1 to 12, wherein said first roller (6A) and
second roller (6B) are made of steel, rubber, brass, and any other materials
which can be metallic non-metallic or combination of both.
14. The apparatus as claimed in claims 1 to 13, wherein the rotational speed of
15 the upper set of rollers(6C) is less than the rotational speed of lower set of
rollers (6D).
15. The apparatus as claimed in claim 14, wherein said upper set of rollers and
lower set of rollers (6C and 6D) are driven by separate driving mechanism
20 which can be electric motor or any other rotary source.
16. A method for quenching the plastic film using the apparatus as claimed in
claims 1 to 15, characterised in that said method comprises the following
steps :
25 a. extruding a polyolefin film (1A) through the extruder die (9) in molten
from and entering it into the water tank unit (2) having a cooling fluid,
thereby solidifying the molten film (1A);
b. continuously circulating hot water back to the cooling device with the
help of the tray unit (2) and a circulating pipe (3F);
24
c. sending the solidified film (1A) through a film guide unit (4) that is
pivotable about the fixed point (4A), and consisting of a small roller (4B),
a big roller (4C), and a mid-roller (4D), thereby further solidifying said
film (1A) ;
5 d. passing the solidified film (1A) through the wiper or scrapper unit (5),
whereby moisture from the film surfaces is removed, and collecting the
removed moisture in the semi-circular pipe (5B), thereby substantially
drying the film (1A);
e. passing the substantially dried film (1A) through the upper and lower sets
10 of rollers (6C and 6D) of the draw roller unit (6) in order to achieve
slackness of the film, wherein the upper set of rollers (6C) rotates at a
smaller speed than the lower set of rollers (6D);
f. removing the remaining moisture from its surface by using a forced air jet
from the air knife (7) which creates flapped vibration within the film
15 (1A);
g. sending the dried film (1A) over a third roller (10) having a spiral helix
shape, thereby removing wrinkles from the film;
h. optionally after removal the moisture, wrinkles and shrinkages, the film is
sent to next stage of downstream processing unit for further enhancing the
20 mechanical properties of the film if so desired.

17. The method as claimed in claim 16, wherein in step d, said wipers or
scrapper unit (5) applies pressure on said film in the range of 1.5 – 2.5
bars.
25
18. The method as claimed in claims 16 and 17, wherein in step e, said upper
set of rollers and lower set of rollers (6C and 6D) are driven by separate
driving mechanism which can be electric motor or any other rotary source.