DESC:

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. Title of the Invention
PROCESS FOR CONTINUOUS COMPACTION OF DISENTANGLED HIGH MOLECULAR WEIGHT POLYMERIC MATERIAL
2. Applicant(s)
Name Nationality Address
RELIANCE INDUSTRIES LTD Indian 3RD FLOOR, MAKER CHAMBER-IV, 222, NARIMAN POINT, MUMBAI-400021, INDIA
3. Preamble to the description

The following specification particularly describes the invention and the manner in which it is to be performed

This is an application for a patent of addition to the Indian Patent Application No. 4329/MUM/2015 filed on 17th November, 2015, the entire contents of which are specifically incorporated herein by reference.
FIELD
The present disclosure relates to a process for continuous compaction of polymeric material.
DEFINITIONS
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.
Root Diameter: The root is the measure of the diameter of the shaft of an extruder screw.
Flight: An extruder screw is machined out of a solid rod and when finished, the extruder screw is like a shaft on which a helical screw is built. Each turn of the helix is called a flight and is like a thread of an Archimedean screw used for conveying materials.
Helix angle: The helix angle is the angle between the screw flight and the plane perpendicular to the axis of the screw.
Compression ratio of a screw is defined as the ratio of the channel depth (or alternatively channel volume) in the feed section to that in the metering section.
L/D (length over diameter) ratio is defined as the ratio of screw length over screw diameter.
The expression ‘DUHMWPE’ for the purpose of the present disclosure refers to disentangled ultrahigh molecular weight polyethylene’ (DUHMWPE) having molar mass in the range of 3 X 105 and 20 X 106 g/mole, crystallinity greater than 75%, heat of fusion greater than 180 J/g, and bulk density less than 0.3 g/cc. Also, DUHMWPE is characterized by increase in elastic modulus, represented by a ratio of G’/G0 (where G0 is the initial elastic modulus and G’ is the elastic modulus at any point on G’/G0 vs time curve) with time above the melt temperature of the DUHMWPE, when tested on strain controlled rheometer having parallel plate assembly, as disentangled polymer chains tend to entangle on application of shearing in sinusoidal test.
The term “Entangled Ultrahigh Molecular Weight Polyethylene” or UHMWPE used in the context of the present disclosure refers to homo-polymers or copolymers of ethylene having intertwined or entangled polymer chains. Entangled UHMWPE is characterized by molecular weight ranging between 3 x 105 and 20 x 106, bulk density greater than 0.30g/cc and heat of fusion less than 175 J/g.
The term ‘molecular weight’ as used in the present disclosure is the ‘weight average molecular weight’ (Mw), which is calculated by rheometry method. IN rheometry method Frequency sweep test of the samples is carried out by strain controlled rheometer (RDA-III from T. A. Instruments) using parallel plate geometry. The specimens used for the test were of 0.5 mm thick and were prepared by compression molding at 170 °C. The test conditions employed were as follows: strain 2%, temperature 190 oC and frequency sweep range as 0.002 to 100 rad/s. Orchestrator software was used to calculate Mw from the frequency sweep data so obtained.
BACKGROUND
Ultra-high molecular weight polyethylene (UHMWPE) is a very high molecular weight resin having exceptionally low coefficient of friction, extremely high impact resistance even at low temperature, abrasion and wear resistance and good long term mechanical properties. This combination of properties makes it suitable for manufacturing of high strength products for various applications. However, UHMWPE shows a very high melt viscosity and high chain entanglement due to linear, longer chain length which make it difficult to process in to finished product by conventional melt processing technique. Usually UHMWPE resin is processed by ram extrusion and compression molding.
Disentangled ultra-high molecular weight polyethylene (DUHMWPE) is a type of resin having a substantially low entanglement between the chains of the polymer. Once molded it also exhibits exceptionally low coefficient of friction, extremely high impact resistance even at low temperature, abrasion and wear resistance and good long term mechanical properties.
The high molecular weight and disentangled characteristics of DUHMWPE makes the polymer suitable for processing especially for solid state compaction process, however, conventional melt processing techniques result in extremely high melt viscosity and limit the polymer processability and thereby the end use applications.
Many attempts have been made in the past in relation to continuous processing of UHMWPE/DUHMWPE or their blend in melt, solid and solution states by conventional processing techniques. Conventional techniques suggest extrusion of DUHMWPE using a single screw extruder with a die head at an extrusion temperature equal to or above the melting temperature of the DUHMWPE thereby increasing the viscosity of the DUHMWPE. However, the extrudate at this temperature tends to lose the disentangled characteristics/properties.
WO2010063679 A1 suggests a process for making UHMWPE tape by extrusion of a mix of high molecular weight polyethylene (HMWPE) and UHMWPE through a wide slit extrusion die in the form of a gel prepared in suitable solvents. The MW of UHMWPE is of the order of 0.8 million g/mol. The design of the die is so modified as to include more than one inlet from the barrel through which the gel is supplied, one extrusion slit and a cavity made with multiple sections in width direction of the extrusion slit. The width of tape prepared by the above process is in the range of 30 to 100 mm. However, the process focuses on the use of wide slit extrusion die for extruding the mix and also does not disclose the extrusion of DUHMWPE or its blend.
WO1992011125 A1 suggests a continuous production of a high modulus article by forcing polyethylene close to or at its melt temperature using a single screw extruder. This is used to process a polymer of MW 0.75 to 6 million g/mol in which the elongation velocity gradient (EVG) should not exceed above 1.3 sec-1 for polyethylene (PE) having 0.50 to 1 million g/mol averages MW and 0.4 sec-1 for polyethylene having 5-6 million g/mol average MW. The polymer is lubricated with 2.5 to 7.5% of lubricant to avoid plug flow in passage. The extrudate is deformed and drawn in the direction of its elongation. The design of the passage of the die is conical in which the cross sectional area diminishes in the forward direction of plastic flow. However, the tensile modulus and the tensile strength of the articles so produced are 30 GPa and 550 MPa respectively.
WO2013034582 A1 suggests a melt extrusion technique for processing DUHMWPE having MW in the range of 0.5-4.0 million g/mol. The melt extrusion is carried out in the range 160-170° C using a capillary extruder at a very low extrusion speed of 0.5 to 5mm/min. However, the elastic modulus of the extrudate so produced is 1.4 MPa at the most.
Our co-pending patent application No. 4329/MUM/2015 dated 17/11/2015 discloses a process for continuous extrusion of entangled UHMWPE material. The application describes compaction of the polymer in the required form of tape/profile using an extruder without a die-head. The elimination of the die-head as part of extruder helps in overcoming the limitations of processing caused by very high melt viscosity and flow resistance of the polymer melt. The extrudate is drawn out through the opening from the space between the last two flights.
There remains a need for a process to produce an extrudate in the form of a continuous tape or profile that has better tensile strength and tensile modulus while, simultaneously, retaining the disentangled characteristics of the DUHMWPE after processing.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to overcome the limitations of extrusion of disentangled ultra-high molecular weight polyethylene or its blend caused by very high melt viscosity leading to low melt flowability.
Another object of the present disclosure is to provide a continuous compaction process for obtaining a DUHMWPE extrudate in the form of a continuous tape or profile that attains a relatively higher tensile strength and higher tensile modulus on hot stretching.
Still another object of the present disclosure is to provide an extrusion process wherein the extrudate significantly retains the disentangled characteristics of the polymer.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for continuous compaction of disentangled high molecular weight polymeric material or its blend with or without additives.
The process of continuous compaction of disentangled high molecular weight polymeric material or its blend is carried out by using an extruder without a die-head.
In one embodiment of the present disclosure, the extruder screw extends outside the extruder barrel to accommodate at least two extra flights for the extrudate to reach a conveyor for post processing operations.
The extruder screw in the metering zone can be characterized by a rough surface to facilitate smooth exit of the extrudate. The process of the present disclosure overcomes the limitations of obstruction in the polymer flow due to very high viscosity. The polymer or its blend, during extrusion, is compacted in conveying/plasticizing and compression/metering zones of the extruder at a temperature in the range of Tm to Tm ± 15° C, where Tm is the melt temperature of the disentangled high molecular weight polymeric material and ranges from 130° C to 150° C. The process of the present disclosure allows free exit of the extrudate of a defined shape without the use of a die-head.
The extruded disentangled high molecular weight polymeric material is obtained through the opening, from between the spacing between the last two consecutive flights at the distal end in the form of a tape or a profile. This spacing shapes the extruded material in the form of a tape or profile.
The compacted and extruded high molecular weight polymeric material maintains the disentangled characteristics of the polymer significantly due to less residence time of the extrudate in the compression/metering zones of the extruder maintained at a temperature of Tm to Tm ± 15° C.
The compacted material can further be subjected to hot stretching at a temperature in the range of temperature 125° C to 155° C in a hot stretching unit. The stretched extrudate so obtained has a tensile strength in the range of 1.2 GPa to 2 GPa, and tensile modulus in the range of 60 GPa to 100 GPa.
Typically, the disentangled high molecular weight polymer that is compacted using the process of the present disclosure is disentangled ultra-high molecular weight polyethylene or its blend.
Typically, the blend comprises a first polymer and a second polymer. The first polymer can be disentangled ultra-high molecular weight polyethylene. The second polymer can be at least one polymer selected from the group consisting of long chain branched polyethylene, copolymers of long chain branched polyethylene, linear polyethylene, ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene acrylic acid copolymer (EAA), ethylene-propylene diene copolymer (EPDM) and polypropylene copolymer (PPCP).
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
A process for continuous compaction of a disentangled high molecular weight polymeric material will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates an extruder with an extended extruder screw in accordance with the present disclosure.

LIST OF REFERENCE NUMERALS/LETTERS
Reference Numeral/Letter Reference
1 barrel
2 extruder screw
3 feed zone
4 conveying/plasticizing zone
5 compression/metering zone
6 drive mechanism
7 plurality of heaters
8 hopper
A direction of introducing the feed in to the hopper
B direction of material movement within the barrel
9a plurality of helical flights
9b plurality of helical flights outside the barrel
DETAILED DESCRIPTION
The disclosure will now be described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
Conventional techniques do not efficiently process disentangled high molecular weight polymeric material and the extrudate so obtained, may not retain the disentangled characteristics of the polymer. The present disclosure, therefore, envisages a continuous compaction process for the processing of disentangled high molecular weight polymeric material or its blend with or without additives under or above but close to the melt temperature of disentangled high molecular weight polymeric material by using an extruder without a die-head, to obtain an extrudate in the form of a continuous tape or profile that alleviates the drawbacks associated with the conventional processes. The extruded profile is found to be stretchable under hot condition just after extrusion and shows high tensile strength due to orientation of polymer chains in the profile. The extruder without the die-head facilitates free exit of the extrudate.
A process for continuous compaction of disentangled high molecular weight polymeric material or its blend is described herein in detail.
An extruder, without a die-head, is provided which comprises a barrel (1) with an opening at its distal end. An extruder screw (2) having a predetermined arrangement of flights (9a) arranged helically along the surface of the screw (2) is disposed in the inside of the barrel (1). The barrel (1) is internally divided into three zones – a feed zone (3), a conveying/plasticizing zone (4) and a compression/metering zone (5) arranged from its proximal end to the distal end. These three zones are configured to be maintained at predetermined temperatures with the help of a plurality of heaters (7) arranged on the barrel (1). The barrel (1) is preheated to maintain the zones at predetermined temperatures. Disentangled high molecular weight polymeric material or its blend to be compacted is fed in the feed zone (3) of the extruder through hopper (8). The fed material is then conveyed through the conveying/plasticizing zone (4) and the compression/metering zone (5) while compacting the polymeric material or its blend at the conveying/plasticizing zone (4) and the compression/metering zone (5). The screw (2) may have a rough surface at the compression/metering zone (5) till its distal end for a smooth exit of the extrudate from the space between the last two flights (9b) of the screw (2). Free exit of the extrudate of the compacted polymeric material or its blend is facilitated through the opening at the distal end in the form of a tape or profile.
The extruder screw (2) comprises a first constant root diameter in the feed zone (3), an increasing root diameter in the conveying/plasticizing zone (4) and a second constant root diameter in the compression/metering zone (5). The second constant root diameter is larger than the first constant root diameter. The extruder screw (2) is defined by a plurality of helical flights (9a) formed on its surface, disposed at an angle, also referred to as the helix angle f, along the length of the screw from the proximal end to the distal end. The annular space defined between the inner wall of the barrel (1) and the outer surface of the screw (2) reduces in the conveying/plasticizing zone (4) and compression/metering zone (5) to compact the polymeric material. In one embodiment, the extruder screw (2) has an extended length appearing outside the barrel so as to accommodate at least two helical flights (9b) outside the barrel (1). In an exemplary embodiment, the extruder screw has an overall L/D ratio in the range of 15 to 50 with the screw diameter in the range of 25-65mm. The compression ratio of the extruder screw is in the range of 2.5 to 4.5.
Surrounding the barrel (1) are a plurality of heaters (7) disposed along the length of the barrel (1) to provide heating means for the barrel (1) such that the temperature of the barrel (1) increases from the proximal end to the distal end. With the help of the heaters (7), the feed zone (3) is maintained at temperatures in the range of 30° C to 50° C; the conveying/plasticizing zone (4) at temperatures in the range of 100° C to 130° C to soften the polymeric material and the compression/metering zone (5) at temperatures in the range of Tm to Tm ± 15° C, where Tm is the melt temperature of the disentangled high molecular weight polymeric material and ranges from 130° C to 150° C.
In the conveying/plasticizing zone (4), the temperature is maintained below the melt temperature of the disentangled high molecular weight polymeric material due to which all the molecules retain the disentangled state. However, the temperature in the compression/metering zone (5) is maintained in the range of Tm to Tm ± 15° C, where Tm is the melt temperature. The disentangled polymeric material may be exposed to a slightly higher temperature than the melt temperature for a short residence time which does not significantly affect the disentangled state of the molecules. The extruded profile made of predominantly disentangled high molecular weight polymeric material or its blend, is suitable for hot stretching and attains higher tensile strength and tensile modulus when hot stretched.
A drive mechanism (6) which is functionally coupled to the extruder screw (2) is disposed at the proximal end of the barrel (1). The drive mechanism (6) brings about rotation of the extruder screw (2) with respect to the barrel (1). The drive mechanism (6) is so adjusted that the extruder screw (2) is maintained at rotational speed as required, preferably, in the range of 3 rpm to 50 rpm.
The spacing between the last two consecutive flights (9b) outside the barrel (1) shapes the extrudate in the form of a continuous tape or a profile which is further taken on a conveyor with the help of a winder.
The total residence time of the disentangled high molecular weight polymeric material or its blend in the extruder is maintained in the range of 20 seconds to 600 seconds.
In one embodiment of the present disclosure, the disentangled high molecular weight polymeric material is disentangled ultra-high molecular weight polyethylene (DUHMWPE) wherein, the weight average molecular weight of the DUHMWPE ranges from 3 x 105 to 20 x 106 g/mol and can be used with or without any additive. Further, the relative viscosity of the disentangled ultra-high molecular weight polyethylene is in the range of 3.4 to 61 dl/g and the melt temperature is in the range of 130° C to 150° C.
In an exemplary embodiment, the process includes feeding DUHMWPE powder with a weight average molecular weight of 5 x 106 g/mol through a hopper of the extruder into the feed zone. The temperature profile of the extruder is kept as follows: feed zone at 50° C in one heater, conveying/plasticizing zone at 110° C and 126° C in two heaters respectively, and the compression/metering zone at 128° C. The extruder screw speed is fixed at 15 rpm. The extruder is without a die-head and the extruder screw has an extended length appearing outside the barrel so as to accommodate at least two helical flights outside the barrel which facilitates the exit of the extrudate. In another embodiment of the present disclosure, the so obtained extrudates are hot stretched keeping the heating temperatures close to melt temperature of the disentangled ultra-high molecular weight polyethylene to obtain a tape having a tensile strength greater than or equal to1.2 GPa and a tensile modulus greater than or equal to 60 GPa.
In accordance with the present disclosure, the tensile strength of the hot stretched extrudate is in the range of 1.2 GPa to 2 GPa and the tensile modulus is in the range of 60 GPa to 100 GPa.
Though, the high molecular weight polymeric material can be processed with or without any additives primary and/or secondary antioxidants may be uniformly mixed with the material before processing to prevent thermo-oxidative degradation. In addition to the antioxidants, other additives such as coloring agents, plasticizers, modifiers, stabilizers, surfactants, binders and the like may also be uniformly mixed with the material before subjecting it to processing. The stabilizer can be selected from the group consisting of hindered phenolic antioxidant group compounds, and hydrolytically stable organic phosphites and phosphonites compounds.
In one exemplary embodiment of the present disclosure, 1 ppm to 5 thousand ppm of at least one antioxidant is mixed with DUHMWPE powder before feeding it through the hopper to prevent degradation of the polymer. A non-limiting example of the antioxidant is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate). In yet another exemplary embodiment of the present disclosure, 3 ppm to 5000 ppm of at least one lubricant is mixed with DUHMWPE powder before subjecting it to compaction. A non-limiting example of the lubricant is calcium stearate.
In a further embodiment of the present disclosure, the material to be compacted is a blend comprising a first polymer and a second polymer. The first polymer is disentangled ultra-high molecular weight polyethylene. The second polymer is at least one polymer selected from the group consisting of a long chain branched polyethylene, copolymers of long chain branched polyethylene, linear polyethylene, ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene acrylic acid copolymer (EAA), ethylene-propylene diene copolymer (EPDM) and polypropylene copolymer (PPCP).
The present disclosure is further described in the light of the following laboratory experiment which is set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiment can be scaled up to industrial/commercial scale and the results obtained can be extrapolated for industrial scale.
EXPERIMENTS:
EXPERIMENT 1: Continuous compaction of disentangled ultra-high molecular weight polyethylene:
The compaction of disentangled ultra-high molecular weight polyethylene (DUHMWPE) powder having weight average molecular weight ~5 x 106 g/mol, bulk density, 0.063 g/cm3, Tm ~145° C, crystallinity ~85%, heat of fusion ~202 J/g was carried out using a single screw extruder. Also, 1000 ppm of antioxidant (pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) was physically mixed in to DUHMWPE resin before processing in to the extruder. The specifications of the extruder are: screw diameter 30 mm, screw length 825 mm, L/D 27.5, compression ratio 3.5, pitch load 21.5 mm in the feed zone and 24 mm in compression/metering zone. The extruder was provided with four heaters in which temperature was maintained as follows: room temperature and 50° C in the feed zone, 126° C in the conveying/plasticizing zone and 128° C in the compression/metering zone. The screw speed was set as 15 rpm. Dried DUHMWPE powder was continuously fed through hopper into the feed zone. Once the feed zone of extruder is packed with polymer material, further addition of resin drives the material towards the conveying/plasticizing and compression/metering zones where the material was compacted with the help of the high compression ratio of the screw. The residence time of the DUHMWPE material in the extruder was 30 seconds. The compacted extruded tape with thickness of around 0.19 mm was obtained which was further taken on a conveyor with the help of guide rollers. The density of the extruded profile was measured as 0.97 g/cm3. The extruded material was hot stretched at successively at three different temperatures – 130° C, 145° C and 150° C. The tensile strength (TS) and the tensile modulus (TM) of the hot-stretched extruded tape were found to be 1.37 GPa and 62.42 GPa respectively.
In comparison to DUHMWPE, UHMWPE (entangled) is not suitable for hot-stretching as it shows high elasticity and thereby high shrinkage in the product on cooling due to high entanglement of polymeric chains. As entangled UHMWPE is not suitable for hot-stretching, the tensile strength and the tensile modulus of the unstretched extruded tape were measured. The tensile strength and the tensile modulus of the unstretched entangled UHMWPE were 0.048 GPa and 0.46 GPa respectively. The density of an unstretched extruded profile of entangled UHMWPE was found to be 0.95 g/cm3.
EXPERIMENT 2: Continuous compaction of a blend of disentangled ultra-high molecular weight polyethylene and linear low density polyethylene (LLDPE)
Another compaction process was conducted for a blend of disentangled ultra-high molecular weight polyethylene (DUHMWPE) powder (having the same characteristic properties as provided in Experiment 1) and linear low density polyethylene (LLDPE) using a single screw extruder of Experiment 1. The feed zone, the conveying/plasticizing zone, and the compression/metering zone of the extruder were maintained at a temperature of 50° C, 126° C, and 140° C respectively. The screw speed of the extruder screw was set at 20 rpm. A premix containing dried DUHMWPE powder (70 wt%) and linear low density polyethylene (LLDPE) (30 wt%) along with 1000 ppm calcium stearate and 1000 ppm pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) were first converted in to preform by pressing at room temperature. The preform was then continuously fed through a hopper into the feed zone. Once the feed zone of extruder is packed with the preform further addition of preform facilitates the movement of the preform towards the conveying/plasticizing where it is compacted and a blend of DUHMWPE and LLDPE was obtained which is further compacted in the compression/metering zone with the help of the high compression ratio of the screw. The residence time of the preform in the extruder was 40 seconds. Thereafter, compacted extruded tape with thickness of around 0.21 mm was obtained which was further taken on a conveyor with the help of guide rollers. The density of the extruded profile was measured as 0.99 g/cm3. The extruded material was hot stretched at successively at three different temperatures – 130° C, 145° C and 150° C. The tensile strength (TS) and the tensile modulus (TM) of the hot-stretched extruded tape were found to be 1.20 GPa and 60 GPa respectively.
Further, similar experiments were performed using DUHMWPE having weight average molecular weight of 2.5 x 106 g/mol, 6 x 106 g/mol, 7 x 106 g/mol, 10 x 106 g/mol, and 15 x 106 g/mol. The extrudate so obtained from these DUHMWPE using the compaction process of the present disclosure, after hot stretching, showed the tensile strength (TS) in the range of 1.2 GPa to 2 GPa, and the tensile modulus (TM) in the range of 60 GPa to 100 GPa.
Thus, from the above experiments it is evident that the process of the present disclosure is capable of compacting/extruding disentangled high molecular weight polymeric material and/or its blend to produce an extrudate with high tensile modulus and tensile strength while maintaining/retaining the disentangled characteristics.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The process of the present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? a process for continuous compaction and extrusion of disentangled high molecular weight polymeric material or its blend with or without additives to obtain an extrudate in the form of a continuous tape or profile that has a high tensile strength and tensile modulus;
? extrudate on further hot stretching can provide high strength oriented products; and
? an extrusion process wherein the extrudate significantly retains the disentangled characteristics of the high molecular weight polymeric material.
The foregoing description of the specific embodiments so fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM:
1. A process for continuous compaction of disentangled high molecular weight polymeric material or its blend, said process comprising:
extruding, without the help of a die-head, by conveying, through an extruder comprising an extruder screw rotating in a barrel, while maintaining a predetermined controlled temperature profile, said polymeric material, through a feed zone, a conveying/plasticizing zone and a compression/metering zone; compacting said polymeric material by extruder screw having compression ratio in the range of 2.5 to 4.5 and facilitating free exit of an extrudate in the form of a tape or profile, wherein said feed zone of the extruder is maintained at a temperature in the range of 30° C to 50° C, said conveying/plasticizing zone is maintained at a temperature in the range of 100° C to 130° C and said compression/metering zone is maintained at a temperature in the range of Tm to Tm ± 15° C, wherein Tm is the melt temperature of said disentangled high molecular weight polymeric material.
2. The process as claimed in claim 1, wherein said Tm is in the range of 130° C to 150° C.
3. The process as claimed in claim 1, wherein the residence time of said polymeric material in the extruder is in the range of 20 seconds to 600 seconds.
4. The process as claimed in claim 1, wherein said extrudate in the form of a tape or profile is shaped by the space formed between the last two flights at the exit of extruder.
5. The process as claimed in claim 1, wherein said disentangled high molecular weight polymeric material is disentangled ultra-high molecular weight polyethylene.
6. The process as claimed in claim 1, wherein said blend comprises a first polymer and a second polymer, wherein said first polymer is disentangled ultra-high molecular weight polyethylene and said second polymer is at least one polymer selected from the group consisting of long chain branched polyethylene, copolymers of long chain branched polyethylene, linear polyethylene, ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene acrylic acid copolymer (EAA), ethylene-propylene diene copolymer (EPDM) and polypropylene copolymer (PPCP), wherein said first polymer is present in an amount of at least 20 wt% of the blend.
7. The process as claimed in claim 1, wherein said extrudate is hot stretched to obtain a stretched extrudate in the form of tape/profile having a tensile strength in the range of 1.2 GPa to 2 GPa, and a tensile modulus in the range of 60 GPa to 100 GPa.
8. The process as claimed in claim 1, wherein said disentangled high molecular weight polymeric material contained in said extrudate retains its disentangled characteristics.
9. A tape made by the process as claimed in claim 1, having a tensile strength greater than or equal to 1.2 GPa and tensile modulus greater than or equal to 60 GPa.