Field of Invention:
This present invention relates to an apparatus and method to decontaminate a polymeric material composition having higher particulate impurities by filtering a melt through a multiple melt filtration system. The apparatus and method for decontamination deliver a filtered polymeric composition having reduced levels of particulate impurities. The filtered polymeric composition prepared is suitable for making slit film tape use in flexible woven packaging applications.
Background of invention:
Slit film tapes - also known as film bands, strips, slit film tapes, raffia tapes, tape yam and mono-axially oriented tapes - are defined as unidirectional oriented tapes with a high width-to-thickness ratio and produced by slitting sheet or films made from thermoplastics, followed by monoaxial stretching.
Slit film tapes made of polyolefins such as polypropylene (PP), high density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) and other similar polymeric materials have been in use for several industrial applications. The major areas of application of slit film tapes include woven sacks, large industrial sacks and packaging fabrics, geo-textiles, ropes and twines, and miscellaneous industrial woven fabrics. The polyolefin-based slit film tapes are made from films that are extrusion cast in a flat or tubular (blown) form. The majority of slit film tapes are made from cast films. The slit film tapes are typically formed by slitting sheets of extruded film. The slit-film tapes are then stretched by using one of the two known processes of stretching all slit tapes formed from a film together as a single group or stretching single slit-film tapes or stretching groups containing a number of tapes.
With increasing price of polyolefin resin there has been trend towards increasing the amount of filler in the slit film tape raw materials. In particular, there has been an increase in the use of the inorganic additives in the production of slit film tapes.

Inorganic or organic additives with suitable particulate geometry (granules, spheres, flakes etc.), typically known as fillers, are added to thermoplastics for modifying or enhancing physical and thermal properties, improving, and controlling of processing conditions and achieving an overall cost reduction. The most commonly used particulate fillers are industrial minerals such as talc, calcium carbonate, mica, kaolin, wollastonite, feldspar, and barite.
The most commonly used filler in the manufacture of polyolefin-based slit film tapes is calcium carbonate, which is introduced in the extrusion system using a commercially available calcium carbonate master batch that contains the mineral and the resin optionally processing additives or their combination. The calcium carbonate filler master batch enhances the thermal conductivity and the specific heat of poly olefin, reduces fibrillation tendency of the tape, and also improves the productivity of the tape making process due to higher specific gravity of the raw material mixture. With increasing price of polyolefin resin there has been trend towards increasing the amount of filler in the slit film tape raw materials. In particular, there has been an increase in the content of the calcium carbonate filler masterbatch in material composition for the production of slit film tapes.
However, with increase in the content of inorganic filler, the level of impurity increases in the molten melt of the material composition. Also, the high level of impurities may also be due to the uncrushed polymeric granules. These high levels of impurity, if not removed from the melt before sheet formation, causes holes or punctures in sheet film, and may also cause black specks or uneven distribution of material or higher breakage level during subsequent orientation process.
However, not only in the processing of recycled materials, but also when using virgin polymers, contaminations can occur during the storage or processing of the material. This may also adversely affect the melt quality due to which also the quality of the final extrusion product degrades. Examples of possible

contaminations are metal particles which are caused by wear and tear of the extruder, or degradation products of the processed material.
As a result of increasing demands on the quality of extrusion products, especially in the field of fiber and film extrusion, the filtration of polymer melts is widely used and state of the art. To remove unwanted particles out of the melt, different metal filter media are used. Some examples of typical filter media are different kinds of wire mesh, filters made of nonwoven metal fibers or sintered metal powder discs. By using this filter media, it is possible to remove foreign particles like solid particles as well as soft components so called "gels" from the melt. This ensures a high-quality extrusion result.
The conventional method of decontamination of polymeric material uses an apparatus or system for extrusion as shown in Figure-1. The conventional extruder system comprises of material hopper (2) which is mounted on the extruder unit (3). The material hopper (2) provides the polymeric material supply into the extruder screw (11) for crushing as well as for changing the state of polymeric material from granules to molten material. The extruder screw (11) is driven by the extruder drive unit (4). The extruder screw (11) is surrounded by an extrusion barrel (10) as a housing. The extrusion barrel (10) is further connected to the extruder unit (3) at the second end (15) while it is connected to the first filtration unit (5) at the first end (14). The molten material from the extruder screw (11) enters the first filtration unit (5) wherein the molten polymeric material is decontaminated, and impurities are removed. The melt pump (7) pushes the molten material into the extrusion die (9). The melt pump (7) is connected with the extrusion die (9) by a first spacer (16). The molten material from the extrusion die (9) come out in form of melt/ film (6) which is send for further processing into tapes.
Some of the filtration units are as disclosed in a Patent EP 3308941B1 ('8941) wherein an inlet valve, an outlet valve and a filter canister is present, in which a

cavity is formed that is closeable by means of a removable cover and into which a melt channel opens, wherein in the filter canister, a plurality of filter candles is arranged, each being formed by a filter carrier and a filter sock the filter carrier is fixed to the filter canister and comprises a wall with a plurality of openings, which wall defines an interior space that opens to a collector channel through an outlet, switching of the inlet and outlet line takes place during filter change . The patent ('8941) further discloses method of replacement of the clogged filter.
Another filtration system is disclosed in US 5958255 ('8255) wherein a filtering method and apparatus for continuously filtering a polymeric melt is provided. The patent ('8255) includes a plurality of filter chambers which are arranged in a melt flow path parallel to one another. Also, an intermediate filter is arranged parallel to the filter chambers. When one of the filter chambers is disconnected for the purpose of cleaning or replacing the filter element therein, the intermediate filter is connected synchronously in the melt flow path and, after the filter chamber is cleaned, or the filter element is exchanged, the flow is switched back through the filter chamber, and the intermediate filter is again disconnected.
The above said filtration units are used in wide applications but the main problem of such filtration systems is that during switching or replacement of filter, the difference of pressure drops between a cleaned and a clogged filter chamber and become directly noticeable as a pressure fluctuation in the melt flow. So, use of more efficient filtration system is desired to be used to get perfect results.
Also, the major problem of the conventional system is that filtration unit is only capable of carrying finer mesh of filter in order to filter the fine particles. Thus, when the molten material passes through this fine mesh the residence time increases which eventually lowers the performance of the system as more time is required to filter the molten material due to single stage filtration.

Also, in the above conventional system of using a single melt-filtration system is not adequate as at higher level of impurities greater clogging of filtration media takes place. Another reason for clogging is due to the hinderance created by the large impurities which comes in path of the fine impurities, which does not allow the fine impurities to filter and thereby clogging takes place. Also, if multiple filtration unit are placed the back pressure generated by the melt will be very high and it will be very difficult to transport the melt towards the die which eventually reduces the efficiency of the system.
Further, providing higher filtration area in available space is difficult. Hence, there is a requirement of providing apparatus and method for decontaminate a polymeric material composition with higher inorganic filler/impurities and deliver a filtered polymeric material composition having reduced levels of particulate impurities, for manufacturing slit film tape use in flexible woven packaging applications.
Objectives Of Invention:
The main objective of present invention is to provide apparatus and method for decontaminate a polymeric material composition with higher inorganic filler or impurities.
Another objective of invention is to deliver decontaminated molten polymeric material composition having substantially removed impurities for sheet formation.
Yet another objective of invention is to enable delivered molten polymeric composition to be processed into slit film tapes at higher productivity level.
Further objective of present invention is to deliver better filtered molten polymeric material at improved processing speed.
Summary Of Invention :

Accordingly, the present invention provides an apparatus that is capable of not only filtering a fluid medium, but also distributive mixing and dispersing the filtered fluid. The present invention also provides an apparartus that enables the aforementioned distributive mixing and filtering capabilities but at the same time does not increase the pressure drop of the fluid medium through the filter apparatus. The present invention therefore provides an apparatus that satisfies these needs for filtration of polymeric material.
As used herein the term "polymeric material" is inclusive of a composition comprising polyolefins such as polypropylene (PP), high density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) and other similar polymeric materials. It may also contain additional components which include additional resins, functionalizing agents and/or additives selected from flame retardants, mold release agents and other lubricants, antioxidants, thermal stabilizers, ultraviolet stabilizers, pigments, dyes, colorants, anti-static agents, conductive agents, fillers, and the like, or a combination of the foregoing additives. Selection of particular additives and their amounts may be performed by those skilled in the art based on their specific requirements. If the additives are mixed/blended with the polymeric material in the extrusion process, then the impurities must be decontaminated for delivering good quality melt to film forming die.
Any type of known extruder that can provide a homogenous melt of polymer and/or additional resins and additives, may be used. Useful types of extruders include, for example, a twin-screw counter-rotating extruder, a twin screw co-rotating extruder, a single screw extruder, a single screw reciprocating extruder, a kneader, a ring extruder, or the like or a combination of any of these. A single extruder or multiple extruders may be employed.
The present invention describes a novel and inventive apparatus for decontaminating polymeric material by filtration. The method of filtration of the

present invention discloses use of multistage filtration system or method to deliver a filtered polymeric material having reduced level of particulate or impurities.
The present invention describes an apparatus which comprises of an extruder unit wherein material is fed into it by the material hopper. Herein material defines as 'polymeric material' as described above. The extruder unit comprise of screw which drives and crushes the material to change its state from granules to molten form. The molten material is further transported to the first filtration unit wherein the impurities of larger size are filtered such as more than 100 microns or more than 80microns or preferably more than 60 microns.
Also, in one of the embodiments, the first filtration unit can filter the small impurities as well such as more than 60 microns, or more than 30 microns, or preferably more than 5 microns.
Further, the filtered molten material is made to passed through the melt pump which forces the molten material in the forward direction. The melt pump can be driven by separate melt pump motor to drive the molten material in the forward direction with ease and without any pressure drop and melt pump is efficient enough to counter the back pressure which is generated by the melt filtration unit. Further, the apparatus of the present invention has another filtration unit called as second filtration unit to filter the molten material further. The impurities of smaller size such as above 5 microns are filtered while passing through the second filtration unit. The material thus obtained is passed through the die to form a sheet/ film for further processing into tapes in the tape extrusion line.
The two-stage or multistage filtration method is beneficial since the time taken between the successive filtration is increase which ensure the proper filtration of impurities at greater processing speed.

Brief Description Of Figures
Figure 1 shows a schematic of the conventional system of filtration Figure 2 shows a schematic of apparatus of the invention. Figures 3, 3A, 3B, 3C, 3D shows types of filtration unit

List Of Parts:
1. Apparatus of invention
2. Material hopper
3. Extruder unit
4. Extruder drive unit or extruder drive 30
5. First filtration unit or first filter unit
6. Melt/film
7. Melt pump
8. Second filtration unit or 35 second filter unit
9. Sheet/film forming die or extrusion die or die
10. Extrusion barrel or barrel
11. Extruder screw 40
12. Melt pump drive
13. Extruder frame
14. First end
15. Second end

16. First spacer
17. Second spacer
18. First mesh
19. Handle
20. Second mesh
21. Hydraulic drive
22. Piston
23. First breaker plate
24. Second breaker plate
25. Continuous mesh
26. Container
27. Disk
28. First hydraulic cylinder
29. First dual mesh
30. Second dual mesh
31. Second hydraulic cylinder
32. Single plate

Detailed Description Of Invention with reference to drawings:
The apparatus(l) of the present invention consists of an extruder frame (13). The extruder frame (13) is constructed by fabrication method or by mechanical j oining of machined tubes with cross sections such as rectangular, square, or circular or any other shape such that it has enough strength to take the load of the

components mounted on it without bending or distortion. The extruder frame (13) supports the extruder drive unit (4)which is connected to the extruder unit (3). The connection between the extruder drive unit (4) and the extruder unit (3) be of any type such as using mechanical bolts, screws, or rivets. Further, the extruder unit (3) is provided with a material hopper (2) or a material conveying, and storage unit mounted on it. . The material hopper (2) is constructed out of sheet metal bending in circular fashion, to form a hollow region from inside for material filling and transfer. The walls of the material hopper (2) are strong enough to bear the extreme loading condition of the granules or the polymeric material. The extruder drive unit (4) which comprises of the set of gears, drive shafts, bearings can be selected as per the process requirement or as per the melt output required.
Further, the apparatus (1) of the present invention comprises of extrusion barrel
(10) which is connected to the extruder unit (3) at the second end (15). The connection between be of any type such as using mechanical bolts, screws, or rivets to form a leak proof joining. For leak proof joining, a gasket (not shown) can also be provided between the extruder unit (3) and extrusion barrel (10) second end (15). The extrusion barrel (10) consists of the rotating extruder screw
(11) which rotated by the extruder drive unit (4) and crushes the granules to form molten material and also provides a forward positive feed to the molten material.
Next, there is a first filtration unit (5) fitted at first end (14) of the extrusion barrel (10) which pre filters the molten material to delivers it to the melt pump (7) or a gear pump which then delivers the melt at uniform pressure into a second filtration unit (8) from where the decontaminated melt is delivered to the sheet/film forming die (9).
The arrangement of filtration Units are such that the first filtration unit (5) is capable of filtering the larger impurities such as of above 100 microns or above 80 microns or preferably above 60 microns whereas the second filtration unit (8) is

capable of filtering the smaller impurities such as of above 60 microns or above 30 microns or preferably above 5 microns.
In one of the embodiments, the first filtration unit (5) is capable of filtering smaller impurities such as of above 60 microns or above 30 microns or preferably above 5 microns and the second filtration unit (8) is capable of filtering the larger impurities such as of above 100 microns or above 80 microns or preferably above 60 microns.
In another embodiment, the first filtration unit (5) and the second filtration unit (8) can be altered and used in position in vise versa.
The melt pump (7) is driven by the melt pump drive (12) connected just below the melt pump (7) and is supported on the extruder frame (13). The melt pump (7) is connected with the first filtration unit (5) at one end and with the second filtration unit (8) at the other end. Between the melt pump (7) and second filtration unit (8), there is present a first spacer (16) which has a taper profile inside it to push the molten material into the second filtration unit (8) from melt pump (7) at greater speed. The main purpose of melt pump (7) is to provide an accurate metering device that eliminates surging of the extruder screw, also reduces back pressure and increases output of the complete line.
The second filtration unit (8) is however connected to the extrusion die (9) via a second spacer (17), the second spacer (17) can be of identical construction as of first spacer (16).
Although single screw extruders may be utilized, it is generally preferable to use single-screw extruders provided with an extrusion barrel (10) inside which an extruder screw (11) is provided with improved design to generate greater pumping capability through the melt filtration system.

The first melt filtration unit (5) of the apparatus of invention (1) is preferably located at the first end (14) of the extrusion barrel (10), and the location of the second filtration unit (8) is more preferably after the melt pump (7) or just before the extrusion die (9).such that the back pressure created by the second filtration unit (8) can be easily counter by the melt pump (7) for smooth melt flow without any pressure drop. Thus, in the apparatus(l) of the present invention, the position of the first melt filtration unit (5) and second filtration unit (8) can be altered.
Also, in the inventive apparatus (1) disclosed here, there is not needed to use multiple screens at single filtration unit as used in conventional system. Due to usage of multiple screens at the single filtration unit, the back pressure generated is higher when compared to conventional system. Thus, multiple stage filtration unit, preferably installed one before the melt pump (7) and another after the melt pump (7) will provide greater efficiency as the back pressure generated is less due to the more porous nature of the screen used and finer filtration of melt is done in the second stage.
One such example is disclosed here, for production of polymeric film (6) using conventional system wherein an extruder providing an output of 500-550 kg/hr and a single filtration unit is placed just after the output of the extruder with the multiple mesh with both finer and courser mesh one after the other. When the melt is flown into the filtration unit, it was observed that the back pressure increased from 650 psi to 1000 psi which eventually reduces the melt throughput from the extruder by 15-20%. The melt pump installed after the filtration unit carries the melt from the filtration unit and delivers to the die, in such situation it was observed that the throughput efficiency of the melt pump is reduced by 20-30% .
When the same polymeric film (6) is produced using the invention apparatus (1) wherein an extruder providing an output of 500-550 kg/hr and a multiple stage filtration unit are installed namely first filtration unit (5) and second filtration unit

(8) having courser mesh and finer mesh respectively. When the melt is flown into the first filtration unit (5), it was observed that the back pressure increased from 650 psi to 750 psi which eventually reduces the melt throughput from the extruder by 5-8% which is very less compared to conventional system. Further the melt pump (7) installed after the first filtration unit (5) carries the melt from it and delivers to the second filtration unit (8). In such case due to the courser mesh of the first filtration unit the efficiency of the melt pump does not reduces or reduces merely by 1-2%.
It is also preferable to minimize the residence time of the melt through the melt filtration unit (5, 8). Here, residence time is measured in terms of length of time that molten polymer spends in the first and second filtration unit (5,8). The melt filtration unit (5, 8) are designed to provide short residence times based on, the selection of the surface area of the filter, the type of filter, volume of the melt filtration housing and temperature of molten material supplied to the filtration unit. A higher filter surface area and a smaller housing volume provide shorter residence times. Also, higher the temperature of the supplied molten material lesser the friction created and thus lesser the residual time.
As an example, to filter particulate size of 10-15 microns, in a conventional system with single filtration unit, using mesh type twill dutch weave, the mesh count required is 200x1400 micrometers. It is observed that since the mesh is very fine so residence time during filtration of molten material is around 15-20 sees. Also, the mesh required to be changed after every 4 hours due to clogging of the impurities. However, when the same size particulate is be filtered in the apparatus of the present invention (1), with the two stage first and second filtration units (5, 8) using mesh type twill dutch weave in first filtration unit(5), the mesh count required is only 40x560 micrometer. It was also observed that since the mesh is course so residence time during first filtration unit (5) of molten material is around 3-5 sees and then the further filtration of the molten material is done passing through second filtration unit (8). The second filtration has finer mesh count of

200x1400 micrometers for filtering fine particulates takes residual time of 5-8 sees. Therefore, even the combine residual time in case of apparatus of the present invention is quite less than the conventional system.
In one embodiment, as shown in figure 2, a melt pump (7) or gear pump is used in combination with the extruder to provide sufficient flow rate and pressure of a flow of melt through the first and second filtration unit (5, 8). The melt pump (7), which is operated using a melt pump drive (12), also provides the capability to control and maintain an even flow of melt through the filtration unit (5, 8) resulting in a more uniform polymeric material. The most important criteria to choose the right melt pump are throughput (kg/hr), application (sheet, compounding, recycling, etc.), type of polymer (PET, PE, etc.), filler content (kind of filler and percentage), pressure range. For uniform flow with 650-700 kg/hr through put the ideal pump size should be 50/50 or can be 63/63.
Any suitable melt filtration unit or device that can remove particulate impurities from a melt mixture may be used. In one embodiment the melt is filtered through multiple melt filtration unit.
Suitable melt filtration unit include filters made from a variety of materials such as, but not limited to, sintered-metal, metal mesh or screen, fiber metal felt, ceramic, or a combination of the foregoing materials, and the like. Any geometry of melt filter may be used including, but not limited to, cone, pleated, candle, stack, flat, wraparound, screens, cartridge, pack disc, as well as a combination of the foregoing, and the like. There are many designs and sizes for wire mesh screens. Most screens are made from steel wire, with stainless steel available for special high-pressure or corrosive applications. A 20-mesh screen has 20 holes or wires per inch, while an 80-mesh screen has 80 holes or wires per inch. As the mesh increases, the hole size decreases, providing more filtration capacity and higher pressure drop, which reduces the extruder output per rpm. Finer filtration is

accomplished with smaller screen openings, such as 300 or higher mesh. The screen pack normally consists of more than one screen. If a 120-mesh screen is used by itself, the pressure build-up in front of the screen will blow holes through the screen pack at the breaker plate holes. To prevent polymer from blowing holes in the screen, coarse screens are placed between the fine screen and the breaker plate holes to support the fine screen. Assuming the polymer must be filtered through a 120- mesh screen, it is common to use a 20/60/120/60/20 screen pack, where the first 20- mesh and 60-mesh screens filter coarse particles, preventing them from accumulating on the 120-mesh screen, and the back 60- and 20- mesh support the 120-mesh screen. The selection of the geometry can vary depending on various parameters such as, for example, the size of the extruder and the throughput rate desired as well as the degree of particle filtration that is desired.
As an example, uniform flow with 550-650 kg/hr through put from the extruder with the L/D ratio of the extruder to be 25:1 to 35:1 for thermoplastic material and 12:1 to 20:1 for rubber material, the ideal mesh size used for first filtration unit (5) is 20-50 mesh such that the larger impurities is drained out easily and molten material with smaller impurities is passed through the second filtration unit (8) wherein the mesh size of 120-150 mesh or greater is used to filter the tiny impurities.
Exemplary materials of construction of mesh include stainless steels, titanium, nickel, as well as other metals alloys. Various weaves of wire fabric including plain, dutch, square, twill and combinations of weaves can be used wherein a square or twill weave can provide filtration down to 100 microns. Dutch weave filters out particles between 40 and 80 microns in diameter, while a dutch twill weave filters particles between 8 and 35 microns in diameter. The advantage of dutch weave is the precise wire separation, minimizing the pressure drop across the screen pack while removing smaller particle sizes from the melt.

In one of the embodiments, in filtration applications, more than one type of screen may be used to provide better filtration. Depending on the screen type and mesh size, one can remove particles from 500 micrometer to 5 micrometers.
The pore size of the melt filter may be 0.5 micrometer to 200 micrometers. The first and second melt filter may have same pore size of filter. In one embodiment, the second melt filter has finer/lower pore size filter than first melt filter system. The finer pore size in the second filtration unit (8) is beneficial as it can carry fine particles only and did not work additionally for the larger particles. However, the presence of larger particles will eventually hinder the path of the fine particles , which results in improper filtration. Thus, larger particles are removed from the molten material first by the first filtration unit (5) for further processing into second filtration unit (8).
Both first and second melt filtration units (5, 8) may operate on similar or different working principles. Such working principles of filtration can be for instance by use of manual first and second filtration unit (5, 8) wherein filters with first and second mesh (18, 20) are used with two breaker plates such as first breaker plate and second breaker plate (23, 24) connected to each other to form a single plate (32). A long handle (19) is connected to the single plate (32), which can be done by any kind of mechanical joining such as by bolting, riveting or by welding. When the second mesh (20) is clogged , the handle (19) is turned in the direction as shown in figure 3 such that the second mesh (20) comes out of the filtration zone and its place is taken by the first mesh (18). This system is inexpensive and works very well in a discontinuous operation as shown in figure 3.
As shown in figure 3A, another working principle of filtration can be by use of hydraulic first and second filtration unit (5, 8) wherein either a continuous or discontinuous operation of filtration takes place depending on the transferring of

the first mesh (18) out from first breaker plate (23) and thereby place is taken by the second mesh (20). For continuous filtration, when the active screen or first mesh (18) with first breaker plate (23) becomes contaminated or clogged, the hydraulic drive (21) is activated automatically . The hydraulic drive (21) with the help of piston (22) pushes the clean screen or second mesh (20) with second breaker plate (24) into the melt stream, and the dirty/clogged one exits from the other side. The dirty/clogged screen pack and breaker plate are removed and replaced with a clean screen pack and breaker plate. For discontinuous filtration, the mesh change takes place by manual actuation of the hydraulic drive (21), as it requires manual operator involvement so filtration system to be stopped.
As shown in figure 3B, yet another principle of filtration can be achieved by using Ribbon-type first and second filtration units (5,8), wherein the use of long or continuous filter screen material or mesh (25) moves through the polymer flow channel. The continuous mesh (25) is pulled by a hydraulic clamp (not shown) or pushed through the melt by the melt pressure. As the melt pressure increases, the continuous mesh (25) is pushed forward to provide clean screen for filtering. This is a semi-continuous process, with the melt pressure acting as the driving force to provide fresh screen. The mesh (25) is a continuous ribbon that is sealed in a container (26) to prevent polymer leakage by cooling the ribbon where it enters and exits to form a polymer seal. These systems provide continuous filtration with minimal moving parts and a simplified system. Throughput, pressure, and melt temperature variations are less.
As shown in figure 3C, further principle of filtration can be of double bolt filtration or back flush filtration wherein said first and second filtration units (5,8) comprise of two round bolts or hydraulic cylinders (28, 31) with first and second breaker plates (23, 24) and first and second dual mesh (29, 30) that move in and out of the melt stream. Options are available for the melt to flow through both bolts simultaneously and individually/sequentially. The first dual mesh (29) is

used while keeping the second dual mesh (30) as a spare to replace the first one when it becomes dirty/clogged. There is less filtration area, leading to more rapid screen plugging. First dual mesh (29) becomes dirty/clogged; the second hydraulic cylinder (31) or with a clean screen or second dual mesh (30) is slowly brought in line, allowing the air to escape from the bolt along with some polymer melt. This provides continuous operation and prevents trapped air in the bolt from exiting the die. The dirty/clogged screen or first dual mesh (29) is removed from first hydraulic cylinder (28) and replaced with a new screen pack (30). Melt is pumped through the second screen or mesh (30) until that screen becomes dirty/clogged. Once the second dual mesh (30) is dirty/clogged, the first hydraulic cylinder (28) with a new screen is slowly transferred back into line and the second dual mesh (30) is removed and cleaned.
Figure 3D shows yet another principle of filtration on which the first and second filtration units (5,8) operate. In this system, a rotating disk around which 10 to 12 screens are provided in a ring ; they are indexed (shown by arrow) in steps as small as one degree. As soon as screens become contaminated, indexing is turned in a rotating disc in circular fashion but very slowly step by step. Due to indexing or rotating of disc which has screens or mesh, the clean mesh is obtained after every degree of rotation such that molten material is not clogged due to presence of impurities., This provides constant melt pressure during operation through indexing the rotary disk (27) to supplying clean screens or mesh. The microprocessor control (not shown) determines the index rate by monitoring either the pressure before the screens or the pressure differential across the screens. Thus, to obtain constant pressure of the flow of molten material, the indexing rate or its degree of rotation can be changed automatically.
In one of the embodiments, the above defined filtration system can be used in as first filtration unit (5) or second filtration unit (8) or any combination thereof.

The temperature of the melt first and second filtration units (5, 8) is sufficient to maintain the material in a molten state and at a sufficiently low viscosity for the material to pass through the filter without excessive pressure drop. Generally suitable/optimal temperature is in the range of 260° C. to 380° C. The low viscosity of the molten material helps in the penetration into the mesh wherein the mesh is highly dense, and impurities are high. However, the low viscosity also helps in smooth movement of the molten material out of each filtration unit such that the extra force is not exerted by the extruder screw.
Operation of the melt filtering process in a continuous fashion is preferred, for long periods of continuous operative time which generally helps to minimize formation of gels and black specks formed during the start-up and shut-down operations and thereby enables a more steady-state process to be achieved. Processed materials obtained during the start-up and shut-down operations that are outside the desired level may be reprocessed to avoid wasted material. Also, if the process is not continuous or subjected to jerks, an uneven flow of the material will be observed. This may create clogs. Thus, in order to get a uniform flow, long continuous flow is required.
The filtered polymeric material obtained is substantially free of visible particulates. In one of the embodiments, the filtered polymeric material recovered from the extruder is substantially free of particulate impurities greater than 20 micrometers, or, more specifically, greater than 10 micrometers. Upon extrusion, the filtered polymeric material is passed through film forming die for further manufacturing of slit film tapes with higher productivity.
To decontaminate a polymeric material composition by filtering a melt through a multiple melt filtration system, the following steps are involved:
a) The granules or resins of polymeric material are feed into the material hopper (2) and transferred into the extruder unit (3).

b) The extruder screw (11) takes up the granules from second end (15) to first end (14) by rotation, wherein the rotational movement of extruder screw (11) is provided by the extruder drive unit (4)
c) Granules are crushed into molten material by extruder screw (11) and passed through first filtration unit (5).
d) In the first filtration unit (5), the molten material is made to passes through multiple or single mesh (18, 20, 29, 30)
e) The first filtration unit (5) works on one of the principles as can be seen from figures 3, 3A, 3B, 3C, and 3D
f) The filtered molten material is pumped further by the melt pump (7) into the second filtration unit (8)
g) In the second filtration unit (8), the molten material is made to passes through multiple or single mesh (18, 20, 29, 30)
h) The second filtration unit (8) works on one of the principles as can be
seen from figures 3, 3A, 3B, 3C, and 3D i) The filtered molten material from second filtration unit (8) is now
transferred to the extruder die (9) to form film (6) which is free from any
contamination.
It is evident from the foregoing discussion that the invention has a number of embodiments.
According to a preferred embodiment, the present invention discloses an apparatus(l) to decontaminate a polymeric material. The characterizing features of said apparatus comprises the following:
- an extruder frame (13);
- an extruder drive unit (4) supported by said extruder frame which is connected to an extruder unit (3);
- a material hopper (2) to receive granules or resins of polymeric material, said material hopper (2) being mounted on said extruder unit
(3);

- an extrusion barrel (10) to make molten material from said granules, wherein said extrusion barrel (10) is being connected to the extruder unit (3) at the second end (15) of said extrusion barrier (10);
- a first filtration unit (5) fitted at the first end (14) of said extrusion barrel (10),
- a melt pump (7) connected to the first filtration unit (5) at one end and the second filtration unit (8) at the other end and
- a second filtration unit (8) separated by a first spacer (16).
The molten material from said extrusion barrel (10) is filtered by said first filtration unit (5) and delivered to said melt pump (7) which then delivers the molten material at uniform pressure into said second filtration unit (8) from where the decontaminated molten material is delivered to a sheet/film forming die (9).
In another embodiment of the apparatus of invention, the extruder frame (13) is constructed of machined tubes with cross sections such as rectangular, square, or circular or any other shape. The connection between the extruder drive unit (4) and the extruder unit (3) is of a type selected from mechanical bolts, screws, or rivets.
In other embodiments of the apparatus of invention , the material hopper (2) has sheet metal walls bent in a circular fashion to form a hollow region from inside for material filling and transfer; the first filtration unit (5) is capable of filtering impurities of size of above 60-100 microns, and wherein said second filtration unit (8) is capable of filtering impurities of the size of 5-60 microns; and first filtration unit (5) and said second filtration unit (8) can be swapped with each other in their positions, altered and used in position in vise versa.
In yet other embodiments of the apparatus of invention, the melt pump (7) is driven by a melt pump drive (12) connected just below the melt pump (7) and

supported on the extruder frame (13). Also, the first spacer (16) has a taper profile inside it to facilitate pushing of the molten material into the second filtration unit (8) from melt pump (7).
In yet other embodiments of the apparatus of invention, the second filtration unit (8) is connected to said extrusion die (9) with a second spacer (17). The second spacer (17) may be of identical construction as said first spacer (16).
In a further embodiment of the apparatus of invention , the extrusion barrier (10) has a single extruder screw (11). Further, the first and second filtration units (5, 8) have filters made from materials consisting of sintered-metal, metal mesh or screen, fiber metal felt, ceramic, or a combination thereof, and the filters have a shape consisting of cone, pleated, candle, stack, flat, wraparound, screens, cartridge, pack disc, or a combination thereof.
In a yet further embodiment of the apparatus of invention , the first and second filtration units (5, 8) incorporate a periodic or continuous screen changing filter or batch filters. The pore size of said filter may be in the range between 0.5 micrometer to 200 micrometers. In respect of the pore size of the first and second filtration units (5, 8), they may either have same size or the second filtration unit (8) may have a smaller pore size than that of said first filtration unit (5).
In another embodiment of the apparatus of invention , each of said first and second filtration units (5, 8) have a first and second mesh (18, 20) housed respectively in a first breaker plate (23) and a second breaker plate (24) that are mounted close to each other, and wherein a handle (19) is provided to facilitate insertion and removal of first and second breaker plates (23, 24) into and from said first and second filtration units (5, 8). The insertion and removal of said first and second breaker plates (23, 24) may be activated using a hydraulic drive (21).

In a further embodiment of the apparatus of invention , each of said first and second filtration units (5, 8) have continuous filter screen material or mesh (25) that moves through the polymer flow channel, said continuous mesh (25) being pulled by a hydraulic clamp or pushed through the melt by the melt pressure. The mesh (25) may be in a form of a ribbon and sealed in a container (26), thereby preventing polymer leakage by cooling the ribbon where it enters and exits to form a polymer seal.
In a still further embodiment of the apparatus of invention, each of said first and second filtration units (5, 8) comprise two round bolts or hydraulic cylinders (28,31) with first and second breaker plates (23,24) and first and second dual mesh (29, 30) that move in and out of the melt stream is present. The molten material flows through both bolts (28, 31) simultaneously. First dual mesh (29) may be used while keeping the second dual mesh (30) as a spare to replace the first when it becomes dirty/clogged. Alternatively, both dual meshes (29, 30) are operated simultaneously.
In another embodiment of the apparatus of invention , each of said first and second filtration units (5, 8) comprise a rotating disk made of a plurality of screens enclosed within a ring. Here, the rate of rotation of said disk may be set to obtain a constant pressure of molten material.
The invention also discloses another preferred embodiment in which a method to decontaminate a polymeric material composition using an apparatus(l) of invention as disclosed in foregoing sections is described. The method has characterizing steps of:
a. feeding granules or resins of polymeric material into the material hopper (2) and transferring them to the extruder unit (3);

b. taking up said granules from second end (15) to first end (14) by rotation
of the extruder screw (11), wherein said rotational movement of extruder
screw (11) is being provided by the extruder drive unit (4);
c. crushing said granules into molten material by extruder screw (11) and
passing said molten material through the multiple or single mesh (18, 20,
29, 30) of first filtration unit (5);
d. pumping the filtered molten material by the melt pump (7) into the
second filtration unit (8);
e. passing the molten material through multiple or single mesh
(18,20,29,30) of the second filtration unit (8);
f transferring the contamination-free filtered molten material to the extrusion die (9) to form the film.
In another embodiment of the method of decontamination as disclosed herein, the first and second filtration units (5, 8) incorporate a periodic or continuous screen changing filter or batch filters. The pore size of said filters may be in the range between 0.5 micrometer to 200 micrometers. Further, the filters of said first and second filtration units (5, 8) may have same pore size, or alternatively, the second filtration unit (8) has a smaller pore size than that of said first filtration unit (5).
In another embodiment of the method of the present invention, each of said first and second filtration units (5, 8) have a first and second mesh (18, 20) housed respectively in a first breaker plate (23) and a second breaker plate (24) that are mounted close to each other, wherein a handle (19) is provided to facilitate insertion and removal of first and second breaker plates (23, 24) into and from said first and second filtration units (5, 8). The insertion and removal of said first and second breaker plates (23, 24) is activated using a hydraulic drive (21).
In yet another embodiment of the method of the present invention, each of said first and second filtration units (5, 8) have continuous filter screen material or mesh (25) that moves through the polymer flow channel, said continuous mesh

(25) are being pulled by a hydraulic clamp or pushed through the melt by the melt pressure, and wherein said mesh (25) may be in a form of a ribbon and sealed in a container (26), thereby preventing polymer leakage by cooling the ribbon where it enters and exits to form a polymer seal.
In a further embodiment of the method, each of said first and second filtration units (5, 8) comprise two round bolts or hydraulic cylinders (28,31) with first and second breaker plates (23,24) and first and second dual mesh (29, 30) that move in and out of the melt stream is present, wherein the molten material flows through both the bolts (28, 31) simultaneously. The first dual mesh (29) may be used while keeping the second dual mesh (30) as a spare to replace the first when it becomes dirty/clogged.
In yet another embodiment of the method of the present invention, each of said first and second filtration units (5, 8) comprise a rotating disk made of a plurality of screens enclosed within a ring. The rate of rotation of said disk is set to obtain a constant pressure of molten material.
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.

We Claim:
1. An apparatus (1) to decontaminate a polymeric material composition having
particulate impurities characterized in that said apparatus comprises:
- an extruder frame (13);
- an extruder drive unit (4) supported by said extruder frame which is connected to an extruder unit (3);
- a material hopper (2) to receive granules or resins of the polymeric material, said material hopper (2) being mounted on said extruder unit
(3);
- an extrusion barrel (10) to make molten material from said granules, said extrusion barrel (10) being connected to the extruder unit (3) at the second end (15) of said extrusion barrel (10);
- a first filtration unit (5) fitted at the first end (14) of said extrusion barrel (10),
- a melt pump (7) connected to the first filtration unit (5) at one end and the second filtration unit (8) at the other end and
- a second filtration unit (8) separated by a first spacer (16);
wherein the molten material from said extrusion barrel (10) is filtered by said first filtration unit (5) and delivered to said melt pump (7) which then delivers the molten material at uniform pressure into said second filtration unit (8) from where the decontaminated molten material is delivered to a sheet/film forming die (9).
2. The apparatus (1) as claimed in claim 1 wherein said extruder frame (13) is constructed of machined tubes with cross sections such as rectangular, square, or circular or any other shape.
3. The apparatus (1) as claimed in claims 1 and 2 wherein the connection between the extruder drive unit (4) and the extruder unit (3) is a type selected from mechanical bolts, screws, or rivets.

4. The apparatus (1) as claimed in claims 1 to 3, wherein said material hopper (2) has sheet metal walls bent in a circular fashion to form a hollow region from inside for material filling and transfer.
5. The apparatus (1) as claimed in claims 1 to 4, wherein said first filtration unit (5) is capable of filtering impurities of size of above 60-100 microns, and wherein said second filtration unit (8) is capable of filtering impurities of the size of 5-60 microns.
6. The apparatus (1) as claimed in claims 1 to 5, wherein said first filtration unit (5) and said second filtration unit (8) can be swapped with each other in their positions, altered and used in position in vise versa.
7. The apparatus (1) as claimed in claims 1 to 6, wherein said melt pump (7) is driven by a melt pump drive (12) connected just below the melt pump (7) and supported on the extruder frame (13).
8. The apparatus (1) as claimed in claims 1 to 7, wherein said first spacer (16) has a taper profile inside it to facilitate pushing of the molten material into the second filtration unit (8) from melt pump (7).
9. The apparatus (1) as claimed in claims 1 to 8, wherein said second filtration unit (8) is connected to said extrusion die (9) with a second spacer (17).
10. The apparatus (1) as claimed in claims 1 to 9, wherein said second spacer (17) is of identical construction as of said first spacer (16).
11. The apparatus (1) as claimed in claims 1 to 10, wherein said extrusion barrel (10) has a single extruder screw (11).

12. The apparatus (1) as claimed in claims 1 to 11, said first and second filtration units (5, 8) have filters made from materials consisting of sintered-metal, metal mesh or screen, fiber metal felt, ceramic, or a combination thereof.
13. The apparatus (1) as claimed in claims to 1 to 12, wherein said first and second filters are of a shape consisting of cone, pleated, candle, stack, flat, wraparound, screens, cartridge, pack disc, or a combination thereof.
14. The apparatus (1) as claimed in claims 1 to 13 wherein said first and second filtration units (5, 8) incorporate a periodic or continuous screen changing filter or batch filters.
15. The apparatus (1) as claimed in claim 14, wherein the pore size of said first and second filters is in the range between 0.5 micrometer to 200 micrometers.
16. The apparatus (1) as claimed in claims 1 to 15, wherein the filters of said first and second filtration units (5, 8) have same pore size.
17. The apparatus (1) as claimed in claims 1 to 15, wherein said second filtration unit (8) has a smaller pore size than that of said first filtration unit (5).
18. The apparatus (1) as claimed in claims 1 to 17, wherein each of said first and second filtration units (5, 8) have a first and second mesh (18, 20) housed respectively in a first breaker plate (23) and a second breaker plate (24) that are mounted close to each other, and a handle (19) is provided to facilitate insertion and removal of first and second breaker plates (23, 24) into and from said first and second filtration units (5, 8).

19. The apparatus (1) as claimed in claim 18, wherein the insertion and removal of said first and second breaker plates (23, 24) is activated using a hydraulic drive (21).
20. The apparatus (1) as claimed in claims 1 to 17, wherein each of said first and second filtration units (5, 8) have continuous filter screen material or mesh (25) that moves through the polymer flow channel, said continuous mesh (25) is being pulled by a hydraulic clamp or pushed through the melt by the melt pressure.
21. The apparatus (1) as claimed in claim 20, wherein said mesh (25) is in a form of a ribbon and sealed in a container (26), thereby preventing polymer leakage by cooling the ribbon where it enters and exits to form a polymer seal.
22. The apparatus (1) as claimed in claims 1 to 17, wherein each of said first and second filtration units (5, 8) comprise two round bolts or hydraulic cylinders (28,31) with first and second breaker plates (23, 24) and first and second dual mesh (29, 30) that move in and out of the melt stream.
23. The apparatus (1) as claimed in claim 22, wherein the molten material flows through both bolts (28, 31) simultaneously wherein first dual mesh (29) is used while keeping the second dual mesh (30) as a spare to replace the first when it becomes dirty/clogged.
24. The apparatus (1) as claimed in claim 22, wherein both dual meshes (29, 30) are operated simultaneously.
25. The apparatus (1) as claimed in claims 1 to 17, wherein each of said first and second filtration units (5, 8) comprise a rotating disk made of a plurality of screens enclosed within a ring.

26. The apparatus (1) as claimed in claim 25, wherein the rate of rotation of said disk is set to obtain a constant pressure of molten material.
27. A method to decontaminate a polymeric material composition having particulate impurities using an apparatus (1) as claimed in claims 1 to 26, characterized in that said method comprises the steps of:
a. feeding granules or resins of polymeric material into the material
hopper (2) and transferring them to the extruder unit (3);
b. taking up said granules from second end (15) to first end (14) by
rotation of the extruder screw (11), wherein said rotational movement
of extruder screw (11) being provided by the extruder drive unit (4);
c. crushing said granules into molten material by extruder screw (11) and
passing said molten material through the multiple or single mesh (18,
20, 29, 30) of first filtration unit (5);
d. pumping the filtered molten material by the melt pump (7) into the
second filtration unit (8);
e. passing the molten material through multiple or single mesh
(18,20,29,30) of the second filtration unit (8);
f transferring the contamination-free filtered molten material to the extrusion die (9) to form the film.
28. The method as claimed in claim 27, wherein said first and second filtration units (5, 8) incorporate a periodic or continuous screen changing filter or batch filters.
29. The method as claimed in claims 27 and 28, wherein the pore size of said filter is in the range between 0.5 micrometer to 200 micrometers.

30. The method as claimed in claims 27 to 29, wherein the filters of said first and second filtration units (5, 8) have same pore size.
31. The method as claimed in claims 27 to 30, wherein said second filtration unit (8) has a smaller pore size than that of said first filtration unit (5).
32. The method as claimed in claims 27 to 31, wherein each of said first and second filtration units (5, 8) have a first and second mesh (18, 20) housed respectively in a first breaker plate (23) and a second breaker plate (24) that are mounted close to each other, and a handle (19) is provided to facilitate insertion and removal of first and second breaker plates (23, 24) into and from said first and second filtration units (5, 8), which) is activated using a hydraulic drive (21).
33. The method as claimed in claims 27 to 31, wherein each of said first and second filtration units (5, 8) have continuous filter screen material or mesh (25) that moves through the polymer flow channel, said continuous mesh (25) is being pulled by a hydraulic clamp or pushed through the melt by the melt pressure, and said mesh (25) is in a form of a ribbon and sealed in a container (26), thereby preventing polymer leakage by cooling the ribbon where it enters and exits to form a polymer seal.
34. The method as claimed in claims 27 to 31, wherein each of said first and second filtration units (5, 8) comprise two round bolts or hydraulic cylinders (28,31) with first and second breaker plates (23,24) and first and second dual mesh (29, 30) move in and out of the melt stream, and the molten material flows through both bolts (28, 31) simultaneously wherein first dual mesh (29) is used while keeping the second dual mesh (30) as a spare to replace the first when it becomes dirty/clogged.