Field Of Invention
The present invention relates to an apparatus for removing moisture from
material used for extruding molten film in a raffia tapeline and a method for
removal of moisture from material being processed on raffia tape extrusion
5 line. The invention more particularly relates an apparatus for removal of
moisture content from polymeric granules by dehumidifier based air drying
system before being processed in tape extrusion line and integration of such
system with the raffia tape extrusion line. The invention also relates to a
raffia tapeline having integrated with the apparatus for removing the
10 moisture from the material to be used for extruding a film.
Background Of Invention
Polymeric film which are typically manufactured from resins, each with its own
unique physical properties that are differently suited to different applications.
15 Such film can be produced by film extrusion technique from the molten material
such as polypropylene, polyolefin more particularly termed as LDPE/ HDPE / PP
which are processed by amalgamation of the calcium carbonate filler masterbatch
and the reprocess granules with it. Besides all the different materials it can be
made from, a polymeric film can be clear, coloured, smooth, rough, functionally
20 embossed, opaque, or semi-transparent.
When these films are extruded in the tape extrusion line, they should flow
smoothly without any breaks to get an even output. Any foreign content like
moisture or air can create a hinderance to the flow of the film out of the extruder
25 unit as these foreign contents tend to create gaps in the die lip while coming out of
the extruder unit. Moreover, these gaps, when created, allow the external
surrounding air to enter into the die lip and can easily entraps more moisture. The
main cause of the moisture content is the hygroscopic nature of plastic resins
which is being introduced into the tape extrusion line for production of the film.
3
Most of the plastic resins look dry but due to the hygroscopic nature they attract
moisture from the surrounding air. So, although it is manufactured dry, by the
time it gets to the processor or is introduced in the tape extrusion line it will have
some moisture content. These resins containing moisture content, when processed
5 further in tape extrusion line, will eventually hinder the performance of the line.
This is due to the fact that the moisture which is entrapped into the film creates a
molecular gap in the film which thereby weakens the film. Further, the films so
produced tend to break at a point where moisture is entrapped.
10 In order to minimise the film breakage due to the moisture content, operator tends
to reduce the processing speed by around 10-15% resulting in decrease in
production up to 15%. Further, operator tends to reduce reprocess material content
up to 50-60% for lower processing speed which will eventually increase
production cost. Reprocessed material are materials in form of granules which are
15 made by recycling waste materials produced during the manufacturing of different
products. In the packaging industry, it can be the waste generated from the
manufacturing of tapes, fabrics or bags and other related products.
In addition to it, in the reprocessed material operator tends to add high amount of
20 calcium to lower the cost of production. As we know calcium is highly
hygroscopic in nature, thus it absorbs high amount of moisture which is difficult
to be removed.
A well-known art of conventional drying system is being used in in various
25 applications wherein an air drying technology of eliminating moisture content
from the material is used. Such systems are compact and can be integrated with
the hopper of the machine or if bulky can be installed as a standalone part. But
the main drawback of such system is that only drying of the plastic granules takes
place, there is no provision of eliminating humified air which is produced after
30 drying the granules. Such humid air gets circulated back into the dried granules.
4
So, operator has to provide an additional dehumidifier system which cannot be
integrated with the drying unit at the hopper section.
Providing an integrated system having dehumidifier drying system all together has
5 never been used in the raffia tape extrusion line for dehumidifying air drying of
the resins before being processed. Rather operator reduces the speed of the
machine or reduces the calcium content in the reprocessed material.
In one of the conventional systems, there is no dehumidifying unit present, rather
10 only drying of the granules take place as can be seen in figure 1A,

In another conventional system, dehumidifying air drying unit is being used as
stand-alone (unintegrated) drying system. Therefore, raw material is processed
somewhere else and then fed to the extrusion line. The problem with this kind of
15 system is that during transportation or handling, there are strong chances that
some moisture content is bound to be laid or entrapped within the raw material. It
may also be considered that over-drying of material, for too long or at too higher
temperatures is also potentially disastrous. If colour pigments are being used with
the processing material, the over drying of colour pigments and too long residence
20 time in the drying process can cause shifts in the colour, potentially causing it to
darken.
As can be seen from Figure 1, which shows a conventional system of tape raffia
extrusion line, plastic resins are stored in the pallet (1). The pallet (1) has plurality
25 of chambers for storing material such as polymeric material, calcium filler
masterbatch, reprocess materials, pigments, any kind of additives or combination
of. Through a first set of conduits (6), the stored material is then transferred to a
dosing unit (C), where the desired amount of masterbatch and filler as per the
process requirement is metered and mixed. The dosing unit (C) can be an optional
30 station and the metred material is filled in the container and is supplied to the
5
extrusion line. This unit is not integrated with the tapeline and metred material is
filled in the container and is supplied to the extrusion line. Now through pipe (7)
the material is transferred to a hopper unit (3) where the material or resins are
stored before being fed to the next station and supply of resins is done as per the
5 processing speed of the line. Further, the resins are directly transferred to extruder
unit (D) through a first passage (8). Here the resins are crushed and their state is
changed to molten material due to heat generated by the friction and pressure
caused during the crushing action by the rotation of the screw. The molten
material is made to exit from extruder unit (D) through a second passage (9) into a
10 die (5) from which a molten film(10) is extruded for further processing.
In the raffia tape extrusion line, the polymeric film particularly polypropylene
film is extruded in the form of hot melt from extruder die. The said polymeric film
is produced by processing the resins in adequate amount or as per the process
15 requirement.
The resins can be polymeric material, calcium filler masterbatch, reprocess
materials, pigments, any kind of additives or combination of which are separately
placed in a pallet. Due to the hygroscopic nature of the resins, the moisture in the
20 air is trapped by the resins, such trapping of moisture can happen during
manufacture or during storage.
The moisture content in the resins lowers down the processing performance of the
tape extrusion line so it is required to be removed before being feed into the
25 extrusion line. Various method of drying the resins can be selected wherein the
resins are treated or passed through the hot air closed chamber and moisture
content in the resins is removed. But the moisture content which is removed from
the resins is evaporated in the surrounding and forms a closed loop, whereby the
hot air will be laden with the moisture again and again which will eventually
30 lower the performance of the hot air to remove the moisture from the resins. For
6
instance, a system in a closed loop is capable of processing with an output of 500
kg/ hr and hot air which is circulating can absorb moisture of 4-5% in each cycle
form resins. During a course of time of about 4-5 hrs, the hot air now is laden with
20-25% of moisture which will eventually degrade the performance of the system.
5
Therefore, there is a requirement of a system of drying as well as dehumidifying
the resins in a closed chamber so that the moisture content is completely removed
before being feed into the tape extrusion line. For the same, a well-known
apparatus of dehumidifying air drying is introduced in the raffia tape extrusion
10 line to increase the performance of the machine.
Dehumidifying air dryers are designed to eliminate moisture in the plastic material
before processing. Air is forced through a desiccant bed to make it extremely dry.
This air is then heated to a specified temperature and fed into a drying hopper
15 containing the material to be dried. This hot dry air draws the moisture out of the
material; the saturated air is then fed out of the drying hopper and back through
the desiccant bed again to remove the moisture before the cycle begins again. This
desiccant has a limited ability to hold moisture before it needs to be regenerated
(dried out). Typically, plastics processors use regenerative or twin tower dryers
20 and, in this case, when the desiccant bed has reached its moisture retaining
capacity the airflow is automatically switched to the second desiccant bed to allow
the drying process to continue. At the same time, the first desiccant bed is
regenerated by heating to remove moisture, allowed to cool and it is then ready to
absorb moisture again.
25
In such method of production of molten film, hot gases as well as moisture
contents present in the molten material also escapes which causes breakage in the
film or if carried further will eventually degrades the properties of the tape
thereof.
30
7
Thus, there a need of a system that overcomes the above drawback of the
conventional system in tape extrusion line such that resins entering the extruder
unit are free from moisture content.
5 Objects of Invention:
The main object of the present invention is to provide an apparatus and a method
for dehumidifying air drying the resins before being processed in an automated
raffia tape extrusion line.
10 Another object of the present invention to provide a process where the material
can be processed at high speed in tape extrusion line.
Yet another object of the present invention is to provide a system to increase the
reprocess material content for given processing speed.
15
Further object of the present invention is to provide an automated system in tape
extrusion line to decrease the tape breakage rate.
Another object of the present invention is to increase the productivity by reduction
20 in tape breakage in an automated tape extrusion line.
A further object of the invention is to provide a raffia tapeline where the apparatus
for dehumidifying air drying the resins used for making an extruded film is
integrated into the tapeline.
25
Brief Description Of Figures:
Figure 1 shows the conventional system used in tape extrusion line.
Figure 1A shows another conventional method of drying polymeric granules in
30 tape extrusion line
8
Figure 2 shows the apparatus of the present invention used in tape extrusion line.
Figure 2A shows apparatus of invention as a system of dehumidifier dryer which
is integrated in raffia tape extrusion line to dry the plastic granules before being
5 processed into the raffia tape extrusion line.
Figure 3 shows one of the types of dehumidifier drying system with two desiccant
bed dryers using first desiccant bed for dehumidification
10 Figure 3A shows the same type of dehumidifier drying system with two desiccant
bed dryers using second desiccant bed for dehumidification
Figure 4 shows another type of dehumidifier drying system with desiccant wheel
dryer.
15
Summary of Invention:
The present invention describes an apparatus for removing moisture from material
used for extruding a film on raffia tapeline and a method for removal of moisture
from material being processed on raffia tape extrusion line. The invention also
20 describes a raffia tapeline that has the apparatus for moisture removal from the
material used for extruding a film integrated into it.
The present invention more particularly describes a method for removal of
moisture contents from polymeric granules by dehumidifier based air drying
system before being processed in tape extrusion line and integration of such
25 system with the raffia tape extrusion line. The apparatus of the invention deploys
a dehumidifier air drying system (B) comprising a drying unit (11) and a
dehumidifier unit (15). The drying unit (11) further comprises at least one loader
(12) into which resins are transferred and which is constructed in such a way that
it has a special anti-heat transfer coating and an insulation layer on its inside so
9
that the heat is not dissipated from the loader out into the environment. The
dehumidifier unit (15) supplies hot air as well as sucks the moisture laden air out
from the loader (12). A set of air transport conduits (13) is provided which
connects the dehumidifier unit (15) with the loader (12). The hot air conduit (13A)
5 from the set of the air transport conduits (13) carries the hot (dry) air into the
loader (12) while another conduit, the moisture laden air conduit (13B) sucks the
moisture laden air out of the loader (12). Both of the set of the air transport
conduits (13) are constructed from materials which can withstand high
temperature and pressure. The resins which are now dried are supplied to the
10 dosing unit (C) through third set of conduits (14). In this station, the desired
amount of masterbatch and filler as per the process requirement is metered and
mixed. Dosing unit (C) is a metering device for accurate mixing of additives,
masterbatches with base polymer. The dosing unit (C) can be optional station in
case when virgin material is used, or more precisely, material without any fillers is
15 used, for example 100% plastic resins. Through a pipe (7) the accurate amount of
mixed material which is metred by the dosing unit (C) is transferred to the hopper
unit (3) where the material or resins are stored before being fed to the next station
and supply of resins is done as per the processing speed of the line. Further, the
resins are directly transferred to extruder unit (D) through a first passage (8). Here
20 the resins are crushed and their state is changed to molten material due to heat
generated by the rotation of the screw. The molten material is made to exit
through a second passage (9) into the die (5) from which a molten film is extruded
for further processing. The obtained molten film (10) now flows smoothly without
any break. The dehumidifier air dryer units (B) are based on desiccant dryers
25 which is one of most effective technology. A desiccant dryer system operates as a
closed loop air circulation system where heated “dry” air is circulated over a
thermoplastic resin, which releases absorbed moisture into the passing air. This
“wet” air subsequently passes through a desiccant molecular sieve material. The
desiccant material is able to absorb moisture from the circulating air making it
30 “dry” again. There are two forms of desiccant systems described in the invention:
10
a desiccant bed system or a desiccant wheel system. Desiccant bed (20) is made
up of moisture absorbent agent such as silica gel which absorbs the moisture from
the cool air and supply the same in form of dry air to the first air heater (18) to
form a close loop. During operation of a desiccant bed dryer, the desiccant bed
5 becomes saturated with moisture that has been removed from the resin. After a
period of time, it becomes fully saturated and is no longer able to reduce moisture
in the passing air. To further dry the material, the saturated desiccant bed first
needs to release its absorbed moisture. The process of drying a desiccant bed is
called “regeneration”. In the wheel desiccant system, the desiccant wheel is
10 constantly rotating, allowing the unit to go through its drying, cooling and
regeneration process constantly. Because the desiccant wheel system (4) is
constantly running, it is more efficient and has a lower power consumption rate.
Unlike the desiccant bed system, this system does not have to shut off part of the
unit to regenerate the desiccant.
15 The invention also describes to a raffia tapeline that has the apparatus for moisture
removal from the material used for extruding a film integrated into it.
List of Parts:
1. Pallet
20 2. Regeneration filter
3. Hopper
4. Desiccant wheel system
5. Die
6. First set of conduits
25 7. Pipe
8. First passage
9. Second passage
10. Molten film
11. Air dryer or drying unit
11
12. Loader
13. Second set of conduits
14. Third set of conduits
15. Dehumidifier unit
5 16. Blower
17. Raffia tapeline
18. First air heater
19. Second air heater
20. First desiccant bed
10 21. Second desiccant bed
22. Return air cooler
23. First switch
24. Second switch
25. Process filter
15 26. Cooling cell
27. Process blower
28. Process heater
29. Regeneration heater
30. Regeneration blower
20 (A) Material storing region
(B) Dehumidifier air drying unit
(C) Dosing unit
(D) Extruder unit
(E) Quenching unit
25 (F) Cutting unit
(G) Pre stretching unit
(H) Hot air oven
(I) Annealing unit
(J) Winding machine
30
12
Detail Description Of Invention:
Figure 2 shows a raffia tapeline into which the apparatus of invention having a
dehumidifier air drying system (B) for extruding a molten film (10) through an
extruder unit (D) is integrated. The tapeline (17) has a pallet (1). The pallet (1) has
5 plurality of chambers for storing a number of materials such as polymeric
material, calcium filler masterbatch, reprocess materials, pigments, any kind of
additives or combination of, separately. Through a first set of conduits (6), the
stored material is transferred to the dehumidifier air drying unit (B). The
dehumidifier air drying unit (B) which forms the key part of the apparatus of
10 invention comprises a drying unit (11) The drying unit (11) further comprises at
least one loader (12) into which resins are transferred from the pallet (1). The
loader (12) can be placed in multiple numbers as per the requirement as each resin
type which is going to be processed in the tape extrusion line requires separate
loader for treatment.
15
The loader (12) is constructed in such a way that it has a special anti-heat transfer
coating and an insulation layer on its inside so that the heat is not dissipated from
the loader out into the environment. The anti-heat transfer coating may include the
special kind of paints which have low thermal conductivity and does not allow
20 heat to conduct from one surface to another. However, to insulate the heat inside
the loader (12) the insulation layer may be made from insulation materials such as
fiberglass, perlite, rock wool, and organic foams such as polyurethane or
expanded polystyrene which are thermal insulators and have low thermal
conductivities to help reduce heat flow.
25
The dehumidifying air drying unit (B) further comprises a dehumidifier unit (15)
which supplies hot air as well as sucks the moisture laden air out from the loader
(12). A set of air transport conduits (13) is provided which connects the
dehumidifier unit (15) with the loader (12). The hot air conduit (13A) from the set
30 of the air transport conduits (13) carries the hot (dry) air into the loader (12) while
13
another conduit, the moisture laden air conduit (13B) sucks the moisture laden air
out of the loader (12). Both of the set of the air transport conduits (13) are
constructed from materials which can withstand high temperature and pressure.
The resins which are now dried are supplied to the dosing unit (C) through third
5 set of conduits (14). In this station, the desired amount of masterbatch and filler as
per the process requirement is metered and mixed. Dosing unit (C) is a metering
device for accurate mixing of additives, masterbatches with base polymer. The
dosing unit (C) can be optional station in case when virgin material is used, or
more precisely, material without any fillers is used, for example 100% plastic
10 resins.
Now, through pipe (7) the accurate amount of mixed material which is metred by
the dosing unit (C) is transferred to the hopper unit (3) where the material or
resins are stored before being fed to the next station and supply of resins is done
15 as per the processing speed of the line. Further, the resins are directly transferred
to extruder unit (D) through a first passage (8). Here the resins are crushed and
their state is changed to molten material due to heat generated by the rotation of
the screw. The molten material is made to exit through a second passage (9) into
the die (5) from which a molten film is extruded for further processing. The
20 obtained molten film (10) now flows smoothly without any break.
Figure 2A, shows apparatus of invention as a system of dehumidifier dryers which
is integrated in raffia tape extrusion line to dry the plastic granules before being
processed into the raffia tape extrusion line.
25
Accordingly, the raffia tape extrusion line of the present invention comprises of
number of stations as mentioned herein below, which function in synchronised
manner with specific functionalities such as:
 Material storing unit (A) for storing polymeric material, calcium filler
30 masterbatch, reprocess materials, pigments, any kind of additives
14
 Dehumidifier air drying unit (B) for removal of moisture content from
material
 Dosing unit (C) for metering of the various material
 Extruder unit (D) for converting resins into molten film
5  Quenching unit (E) for simultaneous quenching and melt-drawing of the
molten polymer in the cooling device to form a film sheet
 Cutting unit (F) for slitting the film sheet into a plurality of relatively
narrow slit film tapes
 Optional pre stretching unit (G) containing rollers or godets for pre
10 stretching of the tapes
 Hot air oven (H) for stretching tapes at elevated temperature, by passing
the slit film tapes through a heating medium at a temperature just below
the softening temperature of the slit film tapes
 Annealing unit (I) for annealing and cooling the oriented slit film tapes
15
Now, the tapes obtained are wounded on the winding machine (J).
There are basically three basic types of industrial dehumidifiers: Refrigerant
(Compressor), Low-Grain Refrigerant (LGR), and Desiccant dehumidifiers (or
20 dryers), where in desiccant dehumidifiers are most efficient with longest life span.
The dehumidifier air dryer units (B) are based on desiccant dryers which is one of
most effective technology. A desiccant dryer system operates as a closed loop air
circulation system where heated “dry” air is circulated over a thermoplastic resin,
25 which releases absorbed moisture into the passing air. This “wet” air subsequently
passes through a desiccant molecular sieve material. The desiccant material is able
to absorb moisture from the circulating air making it “dry” again. There are two
forms of desiccant systems; a desiccant bed system (see Figure 3, 3A) or a
desiccant wheel system (see Figure 4).
15
Details of the desiccant bed system type dehumidifier air drying system is
illustrated from the Figure 3. The material from the pallet is fed into the loader
(12). The heated air from the first air heater (18) is supplied into the loader (12)
5 which dries the polymeric granules such that moisture from it is evaporated and is
sent back to the return air cooler (22) where the moisture laden air is cooled and
supplied to the first desiccant bed (20).
Desiccant bed (20) is made up of moisture absorbent agent such as silica gel
10 which absorbs the moisture from the cool air and supply the same in form of dry
air to the first air heater (18) to form a close loop. During operation of a desiccant
bed dryer, the desiccant bed becomes saturated with moisture that has been
removed from the resin. After a period of time, it becomes fully saturated and is
no longer able to
15 reduce moisture in the passing air. To further dry the material, the saturated
desiccant bed first needs to release its absorbed moisture. The process of drying a
desiccant bed is called “regeneration”. During regeneration process the air from
the atmosphere is made to enter the second air heater (19) and hot air from it is
flown into the idle second desiccant bed (21) which is laden with moisture such
20 that moisture is removed form it back into the atmosphere. Thus the process of
drying a moisture saturated desiccant bed (21) is achieved by passing heated
ambient air over the desiccant. Elevated temperature (>200 °C [392°F]) causes the
desiccant bed to release absorbed moisture.
25 For desiccant bed type dryers, while the saturated desiccant bed (21) is
regenerating, another dry desiccant bed (20) is switched into the closed loop and
is able to continue drying the material.
16
For desiccant bed dryers, once the bed (21) is sufficiently dry, it is cooled and
switched back through a first switch (23) and a second switch (24) into the closed
loop when the alternative bed is saturated with moisture as shown in figure 3A.
5 The figures 3, 3A shows only two desiccant dryers, however, there may be more
than two dryers in operation simultaneously to minimise the regeneration time
and drying process is continued without any hinderance.
Figure 4 illustrates another type of dehumidifier air drying system wherein heated
10 air is supplied into the loader (12) through process heater (28). The moisture laden
air is sent to process filter (25) such that fine impurities can be removed at first
stage. Now the moisture laden air is sent to cooling cell (26) where it is cooled as
more moisture condense at low temperature. The process blower (27) blows the
moisture laden air into the wheel desiccant system (4). In the wheel desiccant
15 system, the desiccant wheel is constantly rotating, allowing the unit to go through
its drying, cooling and regeneration process constantly. Because the desiccant
wheel system (4) is constantly running, it is more efficient and has a lower power
consumption rate. Unlike the desiccant bed system, this system does not have to
shut off part of the unit to regenerate the desiccant.
20
During regeneration process, the ambient air enters into the regeneration filter (2)
and into the regeneration heater (29) through the regeneration blower (30) such
that it dries the portion of the desiccant wheel system (4) to remove moisture into
the atmosphere.
25
The following examples are intended to illustrate and provide a better
understanding of the working of the system of the present invention and do not
restrict or limit the scope thereof.
17
In one of the experiments, the reprocessed material laden with 2-3% moisture by
weight is loaded in the loader (12) from the pallet (1) of raffia tape extrusion line
integrated with the dehumidifier drying system. These laden materials are
processed in dehumidifier drying system for 20mins at a temperature of 75-80
5 degree centigrade. The dried material is again tested for the moisture content, it is
observed that moisture is reduced from 2 -3% to only 0.02-.0.05 % by weight.
In all the above examples the moisture content for plastics can be determined by
Karl Fischer (refer ASTM D 6869) or by loss in weight method which is very well
10 known by person skilled in art.
In one of examples when in the conventional system of raffia tape extrusion line
without dehumidifier dryer system, the material containing 80% of polypropylene
and 10% reprocess material with the moisture or water content of about 0.5-0.8 %
15 by weight is processed, it was observed that the tape extrusion line can attain the
processing speed in the range of 550-600 meters per minute (mpm) whereas if
same percentage of polypropylene and reprocess material is processed in the
inventive system of the present invention of tape extrusion line, it can attain the
processing speed in the range of 700-750 mpm and thus increasing the production
20 rate by about 15%.
As an another example, now when in the conventional system of tape extrusion
line the material containing 75% of polypropylene with moisture content of 1-1.5
% by weight and 25% of calcium filler masterbatch is processed, it was observed
25 that the tape extrusion line can attain the processing speed in the range of 550-650
mpm whereas if same percentage of polypropylene and calcium filler masterbatch
is processed in the inventive system of tape extrusion line, the tape extrusion line
can attain the processing speed in the range of 700-750 mpm and thus increasing
the production rate by 12%.
30
18
Through further example, when in the conventional system of tape extrusion line
the material containing 50-60% reprocess material with high moisture content of
2-3% by weight is processed and is made to run at a speed of 550-600 mpm it was
observed that the process has an average of 8-10 breaks/ hour whereas if same
5 percentage of reprocess material is processed in the inventive system running at a
speed of 550-600 mpm it was observed that the moisture content is drastically
reduced to only 0.02% by weight and the overall process has an average of 4-5
breaks/ hour resulting into about 50% reduction in the breakage.
10 The method of removal of moisture content from polymeric granules in a raffia
tape extrusion line involve following steps:
a) Transferring the resins in the form of calcium carbonate filler masterbatch
and the reprocessed granules from pallet (1) to loader (12) of dryer unit
(11) through the first set of conduits (6).
15 b) Treating the resins stored in the loader (12) with hot air which is supplied
by the first heater (18).
c) Evaporating moisture back to the return cooler (22).
d) Supplying cooled moisture laden air to the first desiccant bed (20) to
remove moisture and supply back the dried air first heater (18)
20 e) Switching between the first and second desiccant bed (20, 21) by first and
second switch (23, 24) when one of the desiccant beds become fully laden
with moisture to carry the regeneration process.
f) Thus, the resins are completely dried and sent to the dosing unit (C) via
third set of conduits (14).
25
Another method of removal of moisture content from polymeric granules in a
raffia tape extrusion line involve following steps:
a. Transferring the resins in the form of calcium carbonate filler
masterbatch and the reprocessed granules from pallet (1) to loader (12)
30 of dryer unit (11) through the first set of conduits (6).
19
b. Treating the resins stored in the loader (12) with hot air which is
supplied by the process heater (28).
c. Removing the moisture laden air from the loader (12) and sending it to
the cooling cell (26) through process filter (25) and further to the
5 desiccant wheel system (4) via blower (27).
d. A close loop system is formed such that dried air from the desiccant
wheel system (4) is supplied back into the loader (12) via process
heater (28).
e. Simultaneously, regeneration of the desiccant wheel system (4) takes
10 places to remove the moisture from the desiccant wheel system (4).
f. Thus, the resins are completely dried and sent to the dosing unit (C)
via third set of conduits (14).
The method of formation of molten film (10) free from any defects involves
15 following steps:
a) Transferring the resins in the form of calcium carbonate filler masterbatch
and the reprocessed granules from pallet (1) to drying unit (11) through the
first set of conduits (6).
b) Treating the resins stored in the loader (12) with hot air which is supplied
20 by a dehumidifier unit (15) through second set of conduits (13).
c) Sucking with the help of the hot air supply unit (15) the moisture
generated in the loader (12) out of the loader (12) back into the hot air
supply unit (15).
d) Transferring the dried resins to the dosing unit (C) through a third set of
25 conduits (14).
e) Metering in the dosing unit (C) different types of resins as per the
requirement.
f) Supplying the mixed granular resins are supplied to the hopper (3) and
storing them there till they are supplied further.
20
g) Supplying the resins to the extruder unit (D) through a first passage (8)
where the shredding action takes place.
h) Flowing the molten material formed by the extruder screw out through a
die (5) in the form of a molten film (10).
5
The applicant states that there are a number of embodiments of the invention.
In the preferred embodiment, an apparatus is disclosed for removal of moisture
content from the material being processed for making an extruded film on a raffia
tapeline. The characterising feature of the apparatus that it has at least one
10 dehumidifier air drying unit (B) that has a drying unit (11) having at least one
loader (12) into which resins are transferred from a material storage unit (A), and
wherein said at least one loader (12) has an anti-heat transfer coating on its inside
made of heat resistant paints having low thermal conductivity, and a dehumidifier
unit (15) to supply hot air as well as sucks the moisture laden air out from the
15 loader (12), and wherein a set of air transport conduits (13) is provided to connect
the dehumidifier unit (15) with the loader (12).
In an embodiment of the apparatus, the anti-heat transfer coating is made from
materials selected from a group consisting of fiberglass, perlite, rock wool, and
20 organic foams such as polyurethane or expanded polystyrene.
In a further embodiment of the apparatus, a hot air conduit (13A) that forms a part
of said set of the air transport conduits (13) carries the hot (dry) air into the loader
(12) while a moisture laden air conduit (13B) sucks the moisture laden air out of
25 the loader (12), wherein both of the set of the air transport conduits (13) are
constructed from materials which can withstand high temperature and pressure.
In a still further embodiment of the apparatus, the dehumidifier air dryer units (B)
are of desiccant type having a closed loop air circulation system circulating heated
30 dry air over a thermoplastic resin from said material used for making film sheet.
21
In yet another embodiment of the apparatus, the dehumidifier unit (15) comprises
a first desiccant bed (20) and a second desiccant bed (21), and a first switch (23)
and a second switch (24) to control the path of said air circulation; a first air dryer
(18) and a second air dryer (19) are connected to said first switch (23), and
5 wherein heated air from said first air heater (18) is supplied into the loader (12)
which dries the polymeric granules of said material to make said film such that
moisture from it is evaporated and is send back to a return air cooler (22) where
the moisture laden air is cooled and supplied to said first desiccant bed (20).
10 In a still further embodiment of the apparatus, the desiccant bed (20) is made up
of moisture absorbent agent such as silica gel.
In another embodiment of the apparatus, the heated dry air has a temperature
greater than 200 °C.
15
In a further embodiment of the apparatus, the dehumidifier air dryer units (B)
have a desiccant wheel system (4) having a wheel type desiccant bed wherein
heated air is supplied into the loader (12) through a process heater (28) and
moisture laden air is sent to process filter (25) to remove fine impurities from said
20 batch material for film making, said moisture laden air is blown sent into the
wheel desiccant system (4) using a process blower (27).
In yet further embodiment of the apparatus, a regeneration blower (30) blows
ambient air into a regeneration filter (2) and into the regeneration heater (29) for
25 drying the portion of the desiccant wheel system (4) to remove moisture into the
atmosphere.
In another preferred embodiment of the invention a method for removal of
moisture from the material being processed for making an extruded film using the
30 apparatus as described earlier is disclosed. It comprises the steps of:
22
a) transferring resins in the form of calcium carbonate filler masterbatch
from the material being processed for making the film and the
reprocessed granules from pallet (1) to the loader (12) of the dryer unit
(11) through the first set of conduits (6);
5 b) treating the resins stored in the loader (12) with hot air supplied by the
first heater (18);
c) evaporating moisture back to the return cooler (22);
d) supplying cooled moisture laden air to the first desiccant bed (20) to
remove moisture and supplying back the dried air to the first heater
10 (18);
e) switching between the first and second desiccant bed (20, 21) using
the first and second switches (23, 24) when any one of the desiccant
beds becomes fully laden with moisture to carry out the regeneration
process;
15 f) sending the completely dried resins to the dosing unit (C) via the third
set of conduits (14).
In an embodiment of the method described above, all steps including c onwards
are replaced by the following steps:
20 c. removing the moisture laden air from the loader (12) and sending it to
the cooling cell (26) through process filter (25) and further to the
desiccant wheel system (4) via blower (27);
d. forming a closed loop system wherein dried air from the desiccant
wheel system (4) is supplied back into the loader (12) via the process
25 heater (28);
e. simultaneously regenerating the desiccant wheel system (4) to remove
the moisture from the desiccant wheel system (4);
f. sending the completely dried resins to the dosing unit (C) via the third
set of conduits (14).
30
23
In a final preferred embodiment of the invention a raffia tapeline for extruding
molten film is disclosed. It comprises:
- a material storing unit (A) for storing material used for making film sheet
such as polymeric material, calcium filler masterbatch, reprocess
5 materials, pigments, and any kind of additives;
- a dosing unit (C) for exact metering of the various material;
- an extruder unit (D) for converting resins into molten film;
- a quenching unit (E) for simultaneous quenching and melt-drawing of the
molten polymer in the cooling device to form said film sheet;
10 - a cutting unit (F) for slitting the film sheet into a plurality of relatively
narrow slit film tapes;
- an optional pre stretching unit (G) containing rollers or godets for pre
stretching of the tapes;
- a hot air oven (H) for stretching tapes at elevated temperature, by passing
15 the slit film tapes through a heating medium at a temperature just below
the softening temperature of the slit film tapes;
- an annealing unit (I) for annealing and cooling the oriented slit film tapes,
characterised in that the said raffia tapeline for extruding molten film is
integrated between said material storing unit (A) and said dosing unit (C)
20 with the apparatus for removal of moisture content from the material being
processed for making an extruded film as described above.
While the above description contains much specificity, these should not be
construed as limitation in the scope of the invention, but rather as an
25 exemplification of the preferred embodiments thereof. It must be realized that
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 appended claims and their legal equivalents.
30
24
We claim:
1. An apparatus for removal of moisture content from the material being
processed for making an extruded film on a raffia tapeline, characterised in
that said apparatus comprises :
5 - at least one dehumidifier air drying unit (B) that has a drying unit (11)
having at least one loader (12) into which resins are transferred from a
material storage unit (A), wherein said at least one loader (12) has an
anti-heat transfer coating on its inside made of heat resistant paints
having low thermal conductivity, and
10 - a dehumidifier unit (15) to supply hot air as well as for sucking the
moisture laden air out from the loader (12), wherein a set of air
transport conduits (13) is provided to connect the dehumidifier unit
(15) with the loader (12).
15 2. The apparatus as claimed in claim 1, wherein said anti-heat transfer coating
is made from materials selected from a group consisting of fiberglass,
perlite, rock wool, and organic foams such as polyurethane or expanded
polystyrene.
20 3. The apparatus as claimed in claims 1 and 2, wherein a hot air conduit (13A)
that forms a part of said set of the air transport conduits (13) carries the hot
(dry) air into the loader (12) while a moisture laden air conduit (13B) sucks
the moisture laden air out of the loader (12), wherein both of the set of the
air transport conduits (13) are constructed from materials which can
25 withstand high temperature and pressure.
4. The apparatus as claimed in claims 1 to 3, wherein the dehumidifier air
dryer units (B) are of desiccant type having a closed loop air circulation
system circulating heated dry air over a thermoplastic resin from said
30 material used for making film sheet.
25
5. The apparatus as claimed in claims 1 to 4, wherein said dehumidifier unit
(15) comprises a first desiccant bed (20) and a second desiccant bed (21),
and a first switch (23) and a second switch (24) to control the path of said
air circulation; wherein a first air dryer (18) and a second air dryer (19) are
5 connected to said first switch (23), and heated air from said first air heater
(18) is supplied into the loader (12) which dries the polymeric granules of
said material to make said film such that moisture from the said polymeric
material is evaporated and is sent back to a return air cooler (22) where the
moisture laden air is cooled and supplied to said first desiccant bed (20).
10
6. The apparatus as claimed in claim 5, wherein said desiccant bed (20) is
made up of moisture absorbent agent such as silica gel.
7. The apparatus as claimed in claim 4, wherein said heated dry air has a
15 temperature greater than 200 °C.
8. The apparatus as claimed in claims 1 to 4, wherein said dehumidifier air
dryer unit (B) has a desiccant wheel system (4) having a wheel type
desiccant bed wherein heated air is supplied into the loader (12) through a
20 process heater (28) and moisture laden air is sent to process filter (25) to
remove fine impurities from said batch material for film making, said
moisture laden air is blown sent into the wheel desiccant system (4) using a
process blower (27).
25 9. The apparatus as claimed in claim 8, wherein a regeneration blower (30)
blows ambient air into a regeneration filter (2) and into the regeneration
heater (29) for drying the portion of the desiccant wheel system (4) to
remove moisture into the atmosphere.
30 10. A method for removal of moisture from the material being processed for
making an extruded film using the apparatus as claimed in claims 1 to 9
comprising the steps of:
26
a) transferring resins in the form of calcium carbonate filler masterbatch
from the material being processed for making the film and the
reprocessed granules from pallet (1) to the loader (12) of the dryer unit
(11) through the first set of conduits (6);
5 b) treating the resins stored in the loader (12) with hot air supplied by the
first heater (18);
c) evaporating moisture back to the return cooler (22);
d) supplying cooled moisture laden air to the first desiccant bed (20) to
remove moisture and supplying back the dried air to the first heater
10 (18);
e) switching between the first and second desiccant bed (20, 21) using the
first and second switches (23, 24) when any one of the desiccant beds
becomes fully laden with moisture to carry out the regeneration
process;
15 f) sending the completely dried resins to the dosing unit (C) via the third
set of conduits (14).
11. The method as claimed in claim 10, wherein all steps including c) onwards
are preferably replaced by the following steps:
20 c) removing the moisture laden air from the loader (12) and sending it to
the cooling cell (26) through process filter (25) and further to the
desiccant wheel system (4) via blower (27);
d) forming a closed loop system wherein dried air from the desiccant
wheel system (4) is supplied back into the loader (12) via the process
25 heater (28);
e) simultaneously regenerating the desiccant wheel system (4) to remove
the moisture from the desiccant wheel system (4);
f) sending the completely dried resins to the dosing unit (C) via the third
set of conduits (14).
30
27
12. A raffia tapeline for extruding molten film comprising:
- a material storing unit (A) for storing material used for making film
sheet such as polymeric material, calcium filler masterbatch, reprocess
materials, pigments, and any kind of additives;
5 - a dosing unit (C) for exact metering of the various material;
- an extruder unit (D) for converting resins into molten film;
- a quenching unit (E) for simultaneous quenching and melt-drawing of
the molten polymer in the cooling device to form said film sheet;
- a cutting unit (F) for slitting the film sheet into a plurality of relatively
10 narrow slit film tapes;
- an optional pre stretching unit (G) containing rollers or godets for pre
stretching of the tapes;
- a hot air oven (H) for stretching tapes at elevated temperature, by
passing the slit film tapes through a heating medium at a temperature
15 just below the softening temperature of the slit film tapes;
- an annealing unit (I) for annealing and cooling the oriented slit film
tapes;
characterised in that the apparatus for removal of moisture content from the
material being processed for making an extruded film as claimed in claims 1
20 to 9 is integrated between said material storing unit (A) and said dosing unit
(C) of said raffia tapeline for extruding molten film.