WO2023067536A1

WO2023067536A1 - An apparatus and a method for removal of moisture content from the material being processed for making an extruded film on a raffia tapeline, and a raffia tapeline integrated with apparatus for moisture removal

Info

Publication number: WO2023067536A1
Application number: PCT/IB2022/060084
Authority: WO
Inventors: Gaurav LOHIA
Original assignee: Lohia Corp Limited
Priority date: 2021-10-22
Filing date: 2022-10-20
Publication date: 2023-04-27

Abstract

An apparatus and a method for removal of moisture content from the material being processed for making an extruded film on a raffia tapeline using dehumidifier based air drying system (B) is disclosed. The dehumidifier air drying system (B) comprises a drying unit (11) and a dehumidifier unit (15). The drying unit (11) comprises at least one loader (12) having anti-heat transfer coating and an insulation layer on its inside into which resins are transferred. The dehumidifier air dryer units (B) are based on desiccant dryers which operate as 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 "dry" again.

Description

AN APPARATUS AND A METHOD FOR REMOVAL OF MOISTURE CONTENT FROM THE MATERIAL BEING PROCESSED FOR MAKING AN EXTRUDED FILM ON A RAFFIA TAPELINE, AND A RAFFIA TAPELINE INTEGRATED WITH APPARATUS FOR MOISTURE REMOVAL

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 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 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. 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 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 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.

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 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.

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 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 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 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 drying the granules. Such humid air gets circulated back into the dried granules. 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 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 only drying of the granules take place as can be seen in figure 1 A,

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 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 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 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 station and the metred material is filled in the container and is supplied to the 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 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 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 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 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 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 lower the performance of the hot air to remove the moisture from the resins. For 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.

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 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 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 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. 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.

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.

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.

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.

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 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. 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 tape extrusion line

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 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

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.

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 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 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 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) 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 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 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 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 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 “dry” again. There are two forms of desiccant systems described in the invention: 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 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 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.

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

2. Regeneration filter

3. Hopper

4. Desiccant wheel system

5. Die

6. First set of conduits 7. Pipe

8. First passage

9. Second passage

10. Molten film

11. Air dryer or drying unit

12. Loader

13. Second set of conduits

14. Third set of conduits

15. Dehumidifier unit

16. Blower

17. Raffia tapeline

18. First air heater

19. Second air heater

20. First desiccant bed

21. Second desiccant bed

22. Return air cooler

23. First switch

24. Second switch

25. Process filter

26. Cooling cell

27. Process blower

28. Process heater

29. Regeneration heater

30. Regeneration blower

(A) Material storing region

(B) Dehumidifier air drying unit

(C) Dosing unit

(D) Extruder unit

(E) Quenching unit

(F) Cutting unit (G) Pre stretching unit

(H) Hot air oven

(I) Annealing unit

(J) Winding machine

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 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 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.

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 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. 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 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 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 used, for example 100% plastic 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 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 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. 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 masterbatch, reprocess materials, pigments, any kind of additives

• 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

• 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 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

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 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, 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).

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) 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 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 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 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. 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.

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 3 A.

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 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 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.

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. 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.

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 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 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 % 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 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 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%.

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 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.

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). 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) 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). 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) of dryer unit (11) through the first set of conduits (6). 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 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 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 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 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 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. 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).

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 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 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 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 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 dry air over a thermoplastic resin from said material used for making film sheet.

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 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).

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.

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 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 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 apparatus as described earlier is disclosed. It comprises the steps of: 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); 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 (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; 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: 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 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). In a final preferred embodiment of the invention a raffia tapehne 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 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; 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 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) 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 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.

Claims

Claims:

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 : 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 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).

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.

3. The apparatus as claimed in claims 1 and 2, wherein a hot air conduit (13 A) 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 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 material used for making film sheet.

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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 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).

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 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 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).

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.

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 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); 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 (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; f) sending the completely dried resins to the dosing unit (C) via the third set of conduits (14). The method as claimed in claim 10, wherein all steps including c) onwards are preferably replaced by the following steps: 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 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).

. 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; 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 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 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 to 9 is integrated between said material storing unit (A) and said dosing unit (C) of said raffia tapeline for extruding molten film.

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