FORM-2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(see section 10 and rule 13)
HIGH DENSITY, ORIENTED POLYETHYLENE PRODUCTS AND A PROCESS
FOR PREPARATION THEREOF
RELIANCE INDUSTRIES LIMITED
an Indian Company
of 3rd Floor, Maker Chamber-IV
222, Nariman Point, Mumbai-400021,
Maharashtra, India.
Inventors:
MATHUR AJIT BEHARI GANDHAM SATYA SRINIVASA RAO SATPATHY UMA SANKAR SARMA KRISHNA RENGANATH PATIL YOGESH P. PATEL NANUBHAI F. MEHTA GAURANG M. JASRA RAKSHVIR
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF INVENTION
The present invention relates to polyethylene products. More particularly, the present invention relates to high density, oriented polyethylene products.
BACKGROUND OF THE INVENTION
It is well understood that if very long chains are prepared in an orderly position, parallel to each other in a polymer matrix by suitable processing, it provides extremely high strength and modulus. Such an orientation in the polymer matrix is facilitated with a decrease in the molecular entanglement, thereby providing freedom to large macromolecules to orient them in the direction of applied stress.
Linear polyethylenes of molecular weight more than 1x10 g/mol are known to provide very high mechanical strength, but the increase in molecular weight limits their processability due to very high melt viscosity. Besides, UHMWPE produced by using conventional heterogeneous stereo-specific catalyst is generally available in highly entangled state. The entangled nature of the polymer further causes a decrease in the melt processability by conventional processing tools; thereby limiting the efficient preparation of oriented sheets or products with a very high strength. Extremely high strength and high modulus fibres of UHMWPE are, therefore, produced by gel spinning process as described in US Patent 4,344,908, 4,436,689 and US 2011/0207907A1. Here, initially, a very dilute solution of the polymer is prepared at elevated temperatures (>120°C) in high boiling hydrocarbon solvents such as decalin and paraffin oil. The dilute solution is then spun to produce fibers by employing non-solvents and the thus prepared fibers are further hot stretched to yield very highly oriented fibers of ultra-high tensile properties.
However, if UHMWPE is made available in a disentangled form, the process step of dissolution of the polymer in a solvent, for spinning purposes, is eliminated. Substantially disentangled UHMWPE has been synthesized by employing specific

catalysts and reaction methodologies. As disclosed in 2862/MUM/2011, UHMWPE is obtained by polymerizing ethylene with and without the comonomer i.e. alpha-olefin in the range of C3 to C8 in presence of a phenoxy imine Ti based single site catalyst. As disclosed in patent application number 361 /MUM/2012, desired molecular weight can be achieved by controlling the reaction kinetics and a range of polymers can also be prepared by using single site immobilized catalyst system. Here, the molecular weight of the resultant ultra-high molecular weight polyethylene ranges from 1 x 105 to 20 x 106 g/mol and the molecular weight distribution varies widely from 1.10 and above. Further, the bulk density of the polymer is below 0.30 g/cc which indicates a state of high level of disentanglement. Avoidance of heat cycles and heat aging is a way of stopping entanglement as the disentangled state is fundamentally a meta-stable state. However, one major drawback associated with the afore-stated processes is the static charge build-up. The static charge build-up of UHMWPE powder is nonpolar and of very low bulk density. Further, it escalates with an increase in temperature which adversely affects the compacting of the polymer powder. Additionally, such a static charge build-up can become a potential fire hazard. Said phenomenon, therefore, hinders the preparation of a highly compact sheet of polymer that can be further stretched to form highly oriented and high strength sheets or products. Thus the throughput of the process is also adversely affected. Solid state compacting of the polymer to form a sheet is described in the published PCT document number WO 2009/153318 Al. The process describes inclusion of an additional step of controlling the temperature of the polymer powder for avoiding building up of static charge of the powder particles.
A direct process of hot rolling of UHMWPE powder into a sheet is reported in US 8206810B1 and US 2011/0268962A1, where the temperature maintained for sheet making ranges from 16 °C below the melt temperature to 1 °C above the melt temperature of the polymer. The roller speed is 0.5 to 4.0 meters per minute. The sheet prepared is translucent which is further processed in the form of a high modulus tape. However, in the hot rolling process provided in US 8206810, the polymer powder is

allowed to fall on the heated rollers, which may become a reason of static charge build up.
Numerous studies have been carried out to improve various properties of the polymer. It has been reported that the thermal conductivity of the polymer increases with an increase in the chain orientation. In these studies, chain orientation has been achieved by various mechanical stretching techniques. However, said results are currently being studied for commercial exploitation feasibility. It is also known that addition of fillers or other additives in the polymer enhances the mechanical as well as thermal properties and selectively improves the required performance properties depending on the nature of the polymer. However, dispersion of solid inert or function additives in the polymer is difficult and also limits the stretching of UHMWPE in the form of a film or a tape. This becomes even more difficult when the loading level of the additives is high. However if made possible, the oriented products like sheet, film or tape can highly add value to the products of niche market segment.
US 2011/0268962A1 describes the ultra-high molecular weight polyethylene comprising refractory particles in nano form like zirconia calcium carbonate etc. Zirconia is reported to improve the derealization of stresses generated during impact and stop crack propagation in the matrix. The disentangled ultra-high molecular weight polyethylene sheet comprising compression moulded refractory particles is found to be hot stretchable with tensile strength of at least 1.0 GPa and tensile modulus of at least 40 GPa.
Dispersion of fillers and similar materials or other functional or non-functional additives is difficult in the oriented products of UHMWPE such as fibers, which may be used for various applications.
The present invention deals with highly oriented products of ultra-high molecular weight polyethylene such as sheets, films and tapes and overcomes the drawbacks of the prior art methods by providing single or multi-layered films, sheets or tapes of

ultra-high molecular weight and improved properties such as luminous transmittance, haze, density, crystallinity and hot stretchability, with or without fillers and additives.
OBJECTS
Some of the objects of the present invention which at least one embodiment is adapted to provide, are described herein below:
It is an object of the present invention to provide polyethylene products with improved properties.
It is another object of the present disclosure to provide a process for preparing polyethylene products with improved properties.
It is yet another object of the present disclosure to provide a process for preparing polyethylene products with improved properties, which is economical and environment friendly.
It is still another object of the present disclosure to provide a process for preparing polyethylene products with improved properties, which is continuous, simple and efficient.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for the preparation of high density oriented polyethylene products; said process comprising the following steps:
i. providing pre-dried, disentangled ultra-high molecular weight polyethylene (UHMWPE) powder;

ii. minimizing static charge build-up by cooling said UHMWPE powder to
obtain cooled UHMWPE powder; iii. compacting said cooled UHMWPE powder by feeding said cooled
UHMWPE powder at the nip of at least one pair of heated, polished
counter rotating roller compactor maintained at a pre-determined
temperature and at pre-determined rotations per minute (rpm) to obtain a
preform; and iv. slitting said preform followed by hot stretching at a pre-determined
temperature and stretching speed to obtain the high density oriented
polyethylene product, wherein said product is selected from the group consisting of sheets, films, fibers and tapes.
Typically, the process includes the step of adding at least one additive in the UHMWPE powder.
Typically, the process includes incorporating at least one additive along with the cooled UHMWPE powder, at the nip of said pair roller compactor.
Typically, the process includes admixing at least one additive in the preform before hot stretching.
Typically, the additive is at least one selected from the group consisting of calcium
carbonate, silica, alumina, kaolin, calcium sulphate, silicates, glass fiber, glass beads,
wollastonite, mica, talc, metals oxides, titanium dioxide, antimony oxide, nickel
oxide, chromium oxide, cobalt oxide, calcium oxide, magnesium oxide, iron oxide,
zinc oxide, metals, iron, zinc, bronze, copper, nickel, lead, aluminium, silver, gold,
silicon dioxide, metal sulphides, barium sulphide, molybdenum sulphide, zinc
sulphide, zirconium silicate, carbon black, carbon fiber, graphite powder, graphite
fiber, wood flour, cellulose, cotton, sisal, jute, synthetic, fibers, polyethylene
terephthalate, aromatic amide, aliphatic polyamide, boron fiber, polyacrylonitrile,
ceramic fiber, aluminium hydroxide, polytetrafluoroethylene,
polychlorotrifluoroethylene, pigments based on metal oxide, pigments based on metal

sulphides, cadmium red, cadmium orange and chromates, lead chromate, organic colorants, azo dyes, phathalocynin pigment, quinacridones, naphthalene derivatives, anthraquinone dye, organo metallic complexes, mix metal pigments, fluorescent pigments, halogen, phosphorous based flame retardants, fatty acid esters, ethoxylated alkylamines, optical whiteners, bis-benzoxazoles, gypsum, clay, sodium benzoate, sodium salts, aluminium salts, sorbitol based nucleating agents and synthetic hydrotelcite.
Typically, the pre-determined temperature is a temperature below the melt temperature of the UHMWPE powder.
Typically, the high density oriented polyethylene product is single-layered.
Typically, the high density oriented polyethylene product is multi-layered.
The present disclosure further provides a preform, prepared by the afore-stated process, having thickness ranging between 50 microns and 250 microns, density ranging between 0.50 g/cc and 1.5 g/cc, crystallinity ranging between 75% and 85%, luminous transmittance ranging between 80% and 100% and haze ranging between 10% and 30%.
The present disclosure even further provides a high density oriented polyethylene product, prepared by the afore-stated process, having tensile strength ranging between 0.5 GPa and 2.5 GPa and tensile modulus ranging between 200 GPa and 300 GPa.
BRIEF DESCRIPTION OF THE DRAWINGS:
The disclosure will now be explained in relation to the non-limiting drawings accompanys the provisional specification, in which:
Figure 1 illustrates the process of sheet making using a pair of heated rollers and a processing line of the film or tape of polyethylene; wherein 2 represents the feed hopper,

4 represents the heated rollers, and
6 represents the apparatus used for stretching.
Figure 2a illustrates series configurations of rollers to produce multi-layered sheets or films or tapes of polyethylene; wherein 8 represents the Feed Point 1,
10 represents the Feed Point 2, and
12 represents the multi-layered sheet.
Figure 2b illustrates parallel configurations of rollers to produce multi-layered sheets or films or tapes of polyethylene; wherein 8 represents the Feed Point 1,
10 represents the Feed Point 2, and
12 represents the multi-layered sheet.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with one aspect of the present invention there are provided polyethylene products including but not limited to sheets, films, fibers and tapes, that have improved properties such as orientation, luminous transmittance, haze, density, crystallinity, modulus stretchability and strength that enable their application in various arenas such as the automobile sector, the bottling industry, manufacturing of medical devices and the sports sector.
In accordance with another aspect of the present invention, there is provided a process for the preparation of polyethylene products with improved properties. In one of the embodiments of the present disclosure, the UHMWPE powder of disentangled nature can initially be dried at a temperature of 80 °C and for 2 hours. The UHMWPE powder may or may not contain traces of one or more residual solvents including without limitation, decalin, paraffin oil and acetone. The resultant dried powder is then admixed with antioxidants for increasing the in-process stability of the polymer

sheet. A typical antioxidant may be chosen from any of the commercially available antioxidants, added either before or after drying and the quantity may be as usual as for any commercial polyethylene grade. The admixture may further be optionally cooled, to any temperature below the melting point of the polymer or even below the ambient temperature, to minimize the static charge build-up. The cooled admixture is then fed at the nip of the two heated highly polished/ chrome plated counter rotating calendar rollers to effect compaction. Direct contact of the feed with a substantial surface of the heated rollers is thus minimized to prevent charge build-up. The gap between the rollers is adjusted in such a way that highly dense sheets of the polymer with uniform thickness along the width are formed, without altering the feed rate. The sheet width can be adjusted according to the length of the roller or available commercial calendar roll machine. The roller temperature may be maintained at about 45- 55 °C below the melt temperature of the polymer, a typical roller temperature being 95 °C. Even further, the roller(s) may be maintained at the same or different speeds, depending on the shearing necessary for processing the polyethylene to prepare polyethylene sheets. The shear action may also be enhanced by creating a temperature difference between the rollers or by keeping the diameter of the rollers different. A roller stack of 3 or more facilitates the compacting process while maintaining the roller temperature below the melt temperature of the polymer and also aids in the preparation of a multi-layered film. In case of more than 2 rollers' assembly, the rolling speed for compacting the polymer in the form of a sheet can be further increased to make the process more efficient. The compacting speed of the polymer can also be increased by aligning two pairs of rollers or their multiples where the sheet can travel between their nips in a sequence.
The process of formation of compacted sheets of UHMWPE having density (about > 0.9500 g/cc), through two or more calendar rolls sizing unit or two or more rolls revolving with different speeds for imparting shear, eliminates the major time consuming step of compacting the polymer powder in the form of a preform and pre-stretch rolling. Said process further makes the process of sheet forming continuous, as

compared to two or more steps, as the preforms prepared by hot compress process do not join in seamless manner.
The compact polymer sheet exiting the heated rollers, may be slit for further stretching, in the form of thin tapes of uniform width, depending on the required size and shape to achieve high strength and modulus. The sheet or slit tapes can directly be taken to hot stretching in the continuous process or can be wound on rollers and subsequently be taken for hot stretching. The process may thus be carried out in a continuous or discontinuous fashion depending on the requirements. The hot stretching of the tapes depends on the crystalline morphological state, molecular weight and temperature at which the sheet is prepared by calendar rolling. The sheet stretching ratio after calendar rolling ranges from 10 to 100. The hot stretched tapes so prepared have 1.5 GPa and above tensile strength and up to 250 GPa tensile modulus as per ASTM D882.
The process of preparing improved polyethylene products may further include a step of admixing pre-dried additives and stabilizers with the UHMWPE powder using suitable high speed mixing devices and processing aids to ensure good dispersion. The concentration of the additives in UHMWPE powder is above 0.05%. The additives may be selected from the group that includes but is not limited to calcium carbonate, silica, alumina, kaolin, calcium sulphate; silicates such as glass fiber and glass beads, wollastonite, mica and talc; metals oxides such as titanium dioxide, antimony oxide, nickel oxide, chromium oxide, cobalt oxide, calcium oxide, magnesium oxide, iron oxide and zinc oxide; metals such as iron, zinc, bronze, copper, nickel, lead, aluminium, silver and gold; silicon dioxide; metal sulphides such as barium sulphide, molybdenum sulphide and zinc sulphide; zirconium silicate; carbon black, carbon fiber, graphite (powder and fiber), wood flour, cellulose, cotton, sisal, jute: synthetic fibers such as polyethylene terephthalate, aromatic amide, aliphatic polyamide, boron fiber, polyacrylonitrile and ceramic fiber.; aluminium hydroxide, polytetrafluoroethylene, polychlorotrifluoroethylene, pigments based on metal oxide and metal sulphide such as cadmium red, cadmium orange and chromates (lead

chromate), organic colorants such as azo dyes, phathalocynin pigment, quinacridones, naphthalene derivatives, anthraquinone dye, organo metallic complexes, mix metal pigments and fluorescent pigments; halogen and phosphorous based flame retardants, fatty acid esters, ethoxylated alkylamines, optical whiteners like bis-benzoxazoles; gypsum, clay, sodium benzoate, and other sodium and aluminium salts, sorbitol based nucleating agents, synthetic hydrotelcite etc.
Further, the polymer sheets resulting from the process may be single or multi-layered. A multi-layered film of polymer is prepared by repeating the single layer film preparation process as many times for as many layers that are required, by setting up multiple rollers or multiple pairs of rollers in parallel, series or any other formation to impart effective compacting. The process of preparation of a multi-layered polymer film typically comprises the following steps:
i) compacting the polymer powder mixed with additives by continuous
feeding at the nip of the plurality of heated highly polished/ chrome plated
counter rotating calendar rollers. The additives may optionally be added to
one or more of the layers;
ii) adjusting the gap between the rollers such that it is suitable to achieve
highly dense sheet of required uniform thickness along its width; and iii) passing the resultant film through another set of rollers where another mixture of polymer with or without additive(s) is fed at the nip of the second set of heated highly polished/ chrome plated counter rotating calendar rollers in same way as done in the first set of rollers.
Use of more than one pair of rollers facilitates the feeding of the polymer powder at the nip of the second pair of rollers along with the sheet formed through the first pair of rollers. This provides a second layer of the polymer on the sheet. The number of layers can be increased in the same way by further adding pairs of rollers and feeding the polymer powder at the nip, while the various pairs of rollers can be placed in a typical sequence such as in parallel, in series, or any other fashion. This can also be made possible by feeding two or more separately prepared sheets at the nip of a pair of

rollers and passing them together between the rollers. The multi-layered product so obtained can attain the form of a thin sheet of very high strength and ultra-high modulus on further hot stretching and the additive in the sheet, if present in any of the layers, can define the multi-functionality of said polymer layers and of the overall product.
One or more of the layers in the single or multi-layered products may optionally contain functional or non-functional additives. However, the products that do not contain solid additives may also show favorable properties such as high/ low luminous transmittance and low haze.
A single layered or multi-layered sheet with or without additives are prepared at a temperature below the melt temperature of the polymer by using heated calendar rollers. The sheets can be further hot stretched below the melt temperature or the stretching temperature is set to a value below the melting temperature of the sheet or partly stretched sheet as the melting temperature of the sheet or tape increases with an increase in stretching. This is achieved by using different sets of heated rollers, godet rolls, oven or hot plates for stretching. Generally, the stretching speed is above 1.0 mm/min.
The afore-mentioned process used for preparing stretchable, oriented polyethylene products with improved properties such as high density, high crystallinity, ultra-high strength and ultra-high modulus may find applications such as impact resistant materials, ropes and nets. These ropes and nets may be used in various adventure sports such as rock climbing, wave jumping, aerobatics and ice climbing amongst others. Products containing additives such as carbon black can protect the matrix from ultra violet radiations and the product so prepared can be useful for electromagnetic radiation shielding.
In a particular embodiment of the invention the molecular weight of the polymer can be 5.14xl06 with roller speed as 10 meter/min, roller temperature can be 138 degree °C

the sheet thickness can be 200 micron, density can be 0.9510 g/cc (@ 24.5 °C) measured as per ASTM D 792, and crystallinity can be 77%(DSC).
In another embodiment of the invention the total luminous transmittance of the sheet can be 90% and haze can be 18%, when measured as per ASTM D 1009. However, one of the factors affecting these optical properties is the sheet thickness.
The present invention will now be further described with reference to the following examples which are to be regarded solely as illustrative and not as restricting the scope of the present invention.
Example 1: Preparation and characterization or disentangled polyethylene
The polymer powder used for making the polyethylene sheets was obtained by polymerizing ethylene with or without the comonomer i.e. alpha-olefm in the range of C3 and above using Ti based single site catalyst. The reaction pressure was maintained at anyone of sub-ambient, ambient and higher than ambient. The reaction temperature was 10 °C or above. The molecular weight distribution, RSV and bulk density of the polymer were 2 and above, 17 dl/g and above and 0.3 g/cc or below, respectively. A range of polymers were prepared by using single site immobilized catalyst system. RSV of the polymer was measured using ASTM-D 4020-la. The molecular weight was calculated using Mark-Houwink equation, M = K[η]α, where K and a are constants and K = 53700, α = 1.37; η - intrinsic viscosity. Bulk density of the polymer was measured by ASTM D-1895. The molecular weight distribution of the polymer samples was measured by melt rheometry using Rheometrics RDA-III from T A Instruments employing Orchestrator software. The UHMWPE powder was highly crystalline and richly disentangled. The samples were characterized by measuring their melting temperatures (Tm), crystallization temperatures (Tc), heat of fusion during melting (∆HTm) and heat of crystallization (AHTc) from the thermograms using Differential Scanning Calorimeter (Perkin Elmer, Pyrisl-DSC) which was calibrated with Indium. The density of the sheet was measured as per ASTM D 792 using measuring unit of Mettler Toledo.

Example 2: Preparation of polymer sheet by roller compaction 50 grams of UHMWPE powder (MW: 5.14M g/mol, MWD: 5.05, DSC crystallinity: 63%, Bulk density: 0.0486 g/cc) was dried in air oven at 80 °C and stabilized by mixing 5000 ppm of a primary anti-oxidant. This was then subjected to calendar rolling under different conditions of temperature and rolling speed. The calendar roll machine was of roller diameter: 155 mm and roller length: 230 mm. The powder was allowed to be fed directly at the rollers' nip gap. The sheet was wound on roller and the density of the samples was measured as per ASTM D792. Similarly polymer samples of different molecular weight were also calendar rolled in the form of continuous sheets. The density values (@24.5 °C) and crystallinity of the prepared sheets are given in Table 1.
Table 1. Sheet thickness, density and crystallinity of sheets prepared by roller compaction

Sr. No. Molecul ar
weight
of polymer
million, g/mol Speed,
Meter/mi n Temperature of rollers, °C Sheet
thickness,
microns Density,
g/cc Crystal li
nity (DSC),
%
1 5.14 0.30 125 40 0.9677 -
2 5.14 9.75* 138 150 0.9520 78
3 5.14 10.00 138 200 0.9510 77
4 5.14 0.20 100 50 0.9728 -
5 5.14 0.30 125 35 0.9790 -
6 3.3 0.2 125 180 0.9631 84
7 5.14 0.2 125 170 0.9636 78
8 9.4 0.2 125 180 0.9849 77
9 12.3 0.2 125 190 0.9709 77
*The sheet rolling was done using two pairs of rollers in continuous manner while maintaining the same temperature

Example 3; Preparation of polymer sheet by roller compaction
The luminuous transmittance and haze of the sheets of UHMWPE (MW: 5.14M g/mol, MWD: 5.2, DSC crystal Unity: 63%, Bulk density: 0.055 g/cc), prepared under different rolling conditions on a twin roll machine was measured using Spherical Hazemeter (Model EEL 57) of M/s Diffusion Systems Ltd. The data obtained is presented in Table 2.
Table 2. Thickness, luminous transmittance and haze of sheets prepared by roller compaction

S.No. Speed,
meter/min Temperature, °C Thickness, microns Luminous
transmittance, % Haze, %
1 0.2 125 35 90 18
2 0.2 110 40 90 15
3 0.2 100 50 89 27
4 0.3 125 40 90 19
Example 4: Preparation of polymer sheet by roller compaction and hot stretching
UHMWPE powder (MW: 5.0 x 106 g/mol, MWD: 5.0, RSV: 27.4 dl/g, bulk density: 0.0486 g/cc), stabilized with 5000 ppm of primary anti-oxidant, was poured between the two heated rollers (temperature: 125 °C) of two rolls sizing machine. The gap between the rollers was maintained at 0.15 mm and rotation was maintained at 0.32 meter/min. The width of the sheet was maintained at 90 mm by using Teflon spacers. The thickness of the sheet obtained was 200 microns. The film could be wound using suitable rollers. The width of the sheet was increased up to 160 mm by spreading the polymer powder between the rollers. The sheet so prepared was stretched 72 times in an oven maintained at 125 °C for providing a stretched tape of 0.02 mm thickness, 1.82 GPa tensile strength and 105 GPa tensile modulus. The same sheet when stretched 52 times under similar conditions provided a tape of 1.79 GPa tensile strength and 90 GPa tensile modulus.

Example 5: Preparation of polymer sheet by roller compaction and hot stretching
A sheet was prepared by calendar rolling UHMWPE powder at 125 °C. The polymer of molecular weight 5.4 million g/mol, bulk density 0.0489g /cc, DSC crystallinity 63%, was used. The sheet thickness was maintained at 150 microns. The sheet so prepared was hot stretched 72 times at 125 °C. The tensile strength and modulus of the stretched sample were found to be 1.86 GPa and 105 GPa, respectively.
Example 6: Preparation of polymer sheet by two stage hot stretching
A sheet of UHMWPE of molecular weight 3.3 million g/mol, RSV 20.4 dl/g, bulk density 0.070 g/cc, g/cc, DSC crystallinity 66%, prepared below the melt temperature, was hot stretched at the rate of 20 mm/min to about 183 times (including roller stretching) in two stages, maintaining the oven temperature as 125 °C and 137 °C in subsequent stages. The modulus value of the stretched sample was found to be 161 GPa.
*
Example 7: Preparation of polymer sheet by incorporating additives
100 grams of UHMWPE powder (MW: 5.4M g/mol) was dried in an air oven at 80 °C and stabilized by mixing 5000 ppm of the antioxidant Irganox 1010. The stabilized polymer powder was homogeneously mixed with 0.25 grams of carbon black (Ensaco 250G of M/s Timcal Graphite and Carbon) in a Brabender mixer. The polymer powder mixture so obtained was subjected to calendar rolling at 0.2 meter/min and while maintaining the roll temperature at 133 °C. The thickness of the resultant continuous sheet was 100 microns. The calendar roll machine was of roller diameter: 155 mm and Roller length: 230 mm. The polymer powder mixture was allowed to be fed directly on the rollers nip gap. The sheet was wound on the roller. The sheet so prepared was cut into tapes of width 1.27 cm and stretched in the oven in two stages i.e. at 137 °C up to and subsequently at 140 °C. The stretching speed was maintained as 20 mm/min. The tensile strength and tensile modulus of the stretched tape were found to be 1.80 GPa and tensile modulus 101 GPa.

Example 8: Preparation of polymer sheet by incorporating multiple additives
0.05 grams each of carbon black and titanium dioxide were mixed in 10 grams each of pre-dried UHMWPE powder (MW: 5.4 M g/mol). The homogeneously mixed powder samples were calendar rolled at 135 °C, keeping the speed as 0.2 meter/min. The mixed powder samples were allowed to fall separately on the top two rollers such that at the nip, a single two layered sheet having white color on one side due to titanium dioxide and black color on the other side due to carbon black was formed. The thickness of sheet was about 200 microns. The calendar roll mill machine used in Example 6 was used here.
Example 9: Preparation of multi-layered polymer sheets
Polymer sheets as prepared from the above mixed powder samples were prepared below 90 °C. separately at the roller speed of 0.2 meter/min using calendar roll machine. The sheets were then fed in the roll mill allowing them to be conveyed separately through converging rollers surface keeping the roller temperature at 135 °C. A single two layered sheet was obtained by direct powder feeding (as mentioned above). The two layered sheet so obtained was hot stretchable below the melt temperature (>140 °C) in the oven providing high strength film and tape when in pre-split form.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the 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.
The foregoing description of the specific embodiments will so fully reveal 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.
Having described and illustrated the principles of the present invention with reference to described embodiments, it will be recognized that the described embodiments can be modified in arrangement and detail without departing from the scope of such principles. It should also be understood that the compositions, processes or methods described herein above are not related or limited to any particular type of manufacturing set up. Without departing from the scope of this invention all standard processing additives, can be used in any of the embodiment.
Many modifications of the present invention will be apparent to those skilled in the art to which the present invention applies. Further, it may be desirable to use some of the above-described features without the corresponding use of other features.
TECHNICAL ADVANTAGES
The present disclosure provides a process for preparing polyethylene products which eliminates the processing step of making preforms which is needed for hot rolling to form high density sheets.
The present disclosure provides a process for preparing polyethylene products which may be performed in the absence of solvents.

The present disclosure provides a process for preparing polyethylene products which is fast and economical.
The present disclosure provides a process for preparing polyethylene products which may be continuous or discontinuous.
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 particular features of this disclosure, it will be appreciated that various modifications 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 modifications in the nature of the

disclosure or the preferred embodiments 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.

We Claim:
1. A process for the preparation of high density oriented polyethylene products;
said process comprising the following steps:
i. providing pre-dried, disentangled ultra-high molecular weight
polyethylene (UHMWPE) powder; ii. minimizing static charge build-up by cooling said UHMWPE powder to
obtain cooled UHMWPE powder; iii. compacting said cooled UHMWPE powder by feeding said cooled
UHMWPE powder at the nip of at least one heated, polished rotating
roller maintained at a pre-determined temperature and at pre-determined
rotations per minute (rpm) to obtain a preform; and iv. slitting said preform followed by hot stretching at a pre-determined
temperature and stretching speed to obtain the high density oriented
polyethylene product, wherein said product is selected from the group consisting of sheets, films, fibers and tapes.
2. The process as claimed in claim 1, which includes the step of adding at least one additive in said UHMWPE powder.
3. The process as claimed in claim 1, which includes incorporating at least one additive along with said cooled UHMWPE powder, at the nip of at least one roller.
4. The process as claimed in claim 1. which includes admixing at least one additive in the preform before hot stretching.
5. The process as claimed in claims 2-4, wherein said additive is at least one selected from the group consisting of calcium carbonate, silica, alumina, kaolin, calcium sulphate, silicates, glass fiber, glass beads, wollastonite. mica,

talc, metals oxides, titanium dioxide, antimony oxide, nickel oxide, chromium oxide, cobalt oxide, calcium oxide, magnesium oxide, iron oxide, zinc oxide, metals, iron, zinc, bronze, copper, nickel, lead, aluminium, silver, gold, silicon dioxide, metal sulphides, barium sulphide, molybdenum sulphide, zinc sulphide, zirconium silicate, carbon black, carbon fiber, graphite powder, graphite fiber, wood flour, cellulose, cotton, sisal, jute, synthetic fibers, polyethylene terephthalate, aromatic amide, aliphatic polyamide, boron fiber, polyacrylonitrile, ceramic fiber, aluminium hydroxide, polytetrafluoroethylene, polychlorotrifluoroethylene, pigments based on metal oxide, pigments based on metal sulphides, cadmium red, cadmium orange and chromates. lead chromate, organic colorants, azo dyes, phathalocynin pigment, quinacridones, naphthalene derivatives, anthraquinone dye, organo metallic complexes, mix metal pigments, fluorescent pigments, halogen, phosphorous based flame retardants, fatty acid esters, ethoxylated alkylamines, optical whiteners, bis-benzoxazoles, gypsum, clay, sodium benzoate, sodium salts, aluminium salts, sorbitol based nucleating agents and synthetic hydrotelcite.
6. The process as claimed in claim 1, wherein said pre-determined temperature is a temperature below the melt temperature of the UHMWPE powder.
7. The process as claimed in claim 1, wherein said high density oriented polyethylene product is single-layered.
8. The process as claimed in claim 1, wherein said high density oriented polyethylene product is multi-layered.
9. A preform prepared by the process as claimed in claim 1, having thickness ranging between 50 microns and 250 microns, density ranging between 0.50 g/cc and 1.5 g/cc, crystallinity ranging between 70% and 95%, luminous transmittance ranging between 80% and 100% and haze ranging between 10% and 30%.

10. A high density oriented polyethylene product prepared by the process as claimed in claim 1, having tensile strength ranging between 0.5 GPa and 2.5 GPa and tensile modulus ranging between 200 GPa and 300 GPa.
11. The process as claimed in claim 1, wherein at least one pair of heated, polished counter rotating rollers maintained at a pre-determined temperature and at predetermined rotations per minute (rpm) are used to obtain a preform.