DESC:FIELD
The present disclosure relates to a homogenized polymer composition.
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.
The term ‘Environmental stress cracking resistance’ (ESCR) as used in the context of the present disclosure refers to resistance towards external or internal crack formation in an article prepared from a polymer or polymer composition, caused by stress applied on the article under accelerated environmental conditions, the applied stress being less than short-term mechanical strength of the article prepared from the polymer or polymer composition. The term ‘Environmental stress cracking resistance’ as used in the context of the present disclosure includes but is not limited to resistance to brittle fracture, multiple cracks, creep rupture and stretched fibrils.
The term ‘disentangled ultrahigh molecular weight polyethylene’ (DUHMWPE) refers to homo-polymer(s) and copolymer(s) of ethylene having molar mass in the range of 3 X 105 and 20 X 106 g/mol, crystallinity greater than 75%, heat of fusion greater than 180 J/g, and bulk density in the range of 0.05 to 0.3 g/cc. The DUHMWPE is characterized by increase in elastic modulus, represented by a ratio of G’/G0 (G’ is the elastic modulus at any point in the curve and G0 is the initial elastic modulus) 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 ‘molecular weight’ as used in the present disclosure is the ‘weight average molecular weight’ (Mw), which is calculated by rheometry method provided herein below.
Determination of weight average Molecular weight (Mw) and molecular weight distribution (MWD) through Rheological Method: Frequency sweep test of the ethylene based polymer samples was 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 and MWD from the frequency sweep data so obtained.
Melt flow index (MFI) of lower polyethylenes was measured as per ASTM D1238.
The term ‘lower polyethylenes’ as used in the context of the present disclosure refers to polyethylene homopolymers and polyethylene copolymers having weight average molecular weight in the range of 40000 to < 3 X 105 g/mole. The term ‘lower polyethylenes’ as used in the present disclosure, refers to the polyethylenes having lower weight average molecular weight, typically as compared to that of the disentangled ultra-high molecular weight polyethylene (DUHMWPE). Typically, the lower polyethylenes encompass ethylene based homopolymers and ethylene based copolymers such as high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), ultra-low-density polyethylene (ULDPE), very low density polyethylene (VLDPE), and linear low density polyethylene (LLDPE). The polyethylene copolymers can have at least one co-monomer like butane, hexane and so on, in the concentration range of 0.2 to 10 mole %. The lower polyethylenes can have unimodal or bimodal molecular weight distribution.
The modality of a polymer refers to the form of molecular weight distribution (MWD) curve of the polymer, i.e., the appearance of the graph of the polymer weight fractions (on X- axis) as a function of their average molecular weights (on Y-axis). The term ‘unimodal molecular weight distribution’ of a polymer used in the context of the present disclosure refers to the graph related to the polymer having a single peak. The term ‘bimodal molecular weight distribution’ of a polymer used in the context of the present disclosure refers to the graph related to the polymer having two peaks.
The term ‘polymer blend’ as used in the present disclosure refers to a homogenized blend comprising at least two polymers. The term ‘polymer blend’ may alternatively be referred to as ‘polymer concentrate’.
Molecular level mixture is a mixture of two or more compounds in which the molecules of the respective compounds are mixed together at a molecular level. A polymer composition comprising at least two polymers is termed as a molecular level homogenized polymer composition if a film prepared from the composition (by compression molding, followed by hot stretching) does not show defects such as polymer lumps, polymer mass and the like upon evaluation under polarized optical microscope. Molecular level homogenized polymer compositions hereinafter will be referred as homogeneous composition or homogenized composition or composition or homogenized polymer composition or molecular level homogenized composition.
The term “processing tools” as used in present disclosure refers to tools used in the melt processing techniques such as injection molding, blow molding, extrusion, rotational -molding and on the like.

BACKGROUND
Semi-crystalline polymers, such as polyethylene and polypropylene, exist as compositions of crystalline segments that are regularly arranged and closely packed in a matrix of unordered, rubbery and amorphous segments. The crystalline phase and the amorphous phase in the polymer are chemically indistinguishable from each other; however, physically these phases appear as separate discrete phases in the polymer. Like other heterophasic structures, the cohesiveness of these two phases governs the strength of the polymer.
The crystalline phase is characterized by considerable secondary bonding within the phase. Long molecules in the crystalline phase form loops that initiate and terminate within the same crystalline unit. Such crystalline units are separated from each other by the weak amorphous phase. The amorphous phase is disorderly and contains too much free volume to permit any significant amount of secondary bonding between the molecules in the amorphous phase. Short molecules in the amorphous phase do not have sufficient length for adequate entanglement and therefore, provide little resistance to separation under stress.
If a molecular segment which initiates in one crystalline unit, crosses the amorphous region and, yet, has enough length to become securely locked in subsequent adjacent crystalline unit and so on, it successfully ties the crystalline units together and significantly contributes in enhancing the performance properties of the polymer. Such molecular segments are termed as “tie chains” and these tie chains help in securing a link between the crystalline units, thereby providing the desired strength. Increased mechanical properties such as high elongation, toughness, impact resistance, resistance to slow-crack growth and environmental stress cracking can be achieved by forming these tie chains. Semi crystalline polymers having a very high average molecular weight have a high presence of these tie chains acting as inter-crystalline linkages.
Incorporation of long polymer chains using ultra-high molecular weight polyethylene (UHMWPE) in lower polyethylenes can increase the concentration of tie chains and thereby enhance the mechanical properties of lower polyethylenes. R-UHMWPE is a thermoplastic polyethylene having a weight average molecular weight as high as 500 times as compared to the conventional polyethylene having weight average molecular weight of 40,000 g/mole to <3 x 105 g/mol. Regular UHMWPE (R-UHMWPE) has high chain entanglement. The long chains of R-UHMWPE result in large overlaps (high chain entanglement) within its molecules, and thereby increase resistance to shearing forces in the melt state.
The homogenization of R-UHMWPE with lower polyethylenes has been attempted through various routes to enhance the performance of lower polyethylenes. However, high level of homogenization has not been attained because of strong chain entanglement and because of the large difference in the melt viscosities of R-UHMWPE and lower polyethylenes. These factors prevent efficient mixing during processing and result in an inhomogeneous product.
Further, to attain high degree of tie chains and enhanced mechanical properties in lower polyethylene, it is required to add high concentration of ultra-high molecular weight polyethylene (UHMWPE). However, this may be detrimental to other properties of lower polyethylenes due to limited homogeneity.
Disentangled UHMWPE (DUHMWPE) has low entanglement within polyethylene chains as compared to R-UHMWPE. However, homogenization of the disentangled UHMWPE in lower polyethylenes is also difficult. Simple melt kneading of the mixture of these two polymers results in an inhomogeneous mixture because the DUHMWPE chains tend to get entangled on shearing above the melt temperature, which limits the homogenization of these two polymers. This may be because of partial entanglement of the disentangled chains of DUHMWPE above the melt temperature. In order to achieve high level of homogeneity sequential addition of DUHMWPE is attempted. However, the sequential addition limits processing of the composition by different processing tools.
Thus, there is felt a need to provide homogenized polymer composition of DUHMWPE and lower polyethylenes, and a simple and efficient method for its preparation.
OBJECTS
Some of the objects of the present disclosure, aimed to ameliorate one or more problems of the prior art or to at least provide a useful alternative, are listed herein below.
It is an object of the present disclosure to provide a homogenized polymer composition of DUHMWPE and lower polyethylenes.
It is another object of the present disclosure to provide a homogenized polymer composition of DUHMWPE and lower polyethylenes having enhanced mechanical and performance properties.
It is yet another object of the present disclosure to provide a homogenized polymer composition of DUHMWPE and lower polyethylenes having the desired processability.
It is still another object of the present disclosure to provide a process for the preparation of the homogenized polymer composition of UHMWPE and lower polyethylenes.
It is yet another object of the present disclosure to provide articles prepared from the homogenized polymer composition.
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
In one aspect, the present disclosure provides a homogenized polymer composition being homogenized at a molecular level. The homogenized polymer composition comprises
i. a polymer blend comprising at least one first polymer and at least one second polymer; wherein
a. the first polymer is selected from the group consisting of ethylene based homopolymer and ethylene based copolymer; and
b. the second polymer is disentangled ultra-high molecular weight polyethylene (DUHMWPE) having weight average molecular weight in the range of 3 x 105 to 20 x 106 g/mole;
ii. at least one third polymer selected from the group consisting of ethylene based homopolymer and ethylene based copolymer,
wherein, the molecules of the second polymer form tie chains in the composition.

The composition of the present disclosure is characterized by an environmental stress crack resistance (ESCR) in the range of 50 % to 800 % higher than ESCR of the third polymer.
The first polymer and the third polymer are independently selected from the group consisting of high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), ultra low density polyethylene (ULDPE), very low density polyethylene (VLDPE), and linear low density polyethylene (LLDPE).
The first polymer and the third polymer can be the same or different.
The ethylene based copolymer comprises at least one co-monomer selected from the group consisting of butene, hexene, and octene. The amount of the co-monomer in the ethylene based copolymer is in the range of 0.2 mole % to 10 mole %.
The first polymer and the third polymer have at least one molecular weight distribution independently selected from the group consisting of unimodal distribution and bimodal distribution.
The second polymer has a molecular weight higher than the molecular weight of the first polymer and the third polymer.
In the composition of the present disclosure (i) the weight of the first polymer is in the range of 0.095 % to 4 %, (ii) the weight of the second polymer is in the range of 0.005 % to 20 % and (iii) the weight of the third polymer is in the range of 76 % to 99.9 % with respect to the total weight of the composition.
The composition of the present disclosure further comprises at least one additive selected from the group consisting of colorants, fillers, stabilizers, flame retardants, anti-static agents, and reinforcing agents.
In a second aspect, the present disclosure provides a process for the preparation of a homogenized polymer composition being homogenized at a molecular level of the present disclosure. The process comprises the following steps.
The first polymer and the second polymer are mixed to obtain a first mixture. The first mixture is melt blended to obtain a polymer blend. The second polymer is disentangled ultra-high molecular weight polyethylene (DUHMWPE) having weight average molecular weight in the range of 3 x 105 to 20 x 106 g/mole.
The polymer blend is processed to obtain a polymer blend preform. In this step, the process conditions are so selected as to result in a preform selected from the group consisting of chips, pellets and granules.
The polymer blend preform is admixed with at least one third polymer to obtain a second mixture. The second mixture is homogenized by at least one method selected from the group consisting of melt blending, and extrusion to obtain the homogenized polymer composition.
The composition of the present disclosure is characterized by an environmental stress crack resistance (ESCR) in the range of 50 % to 800 % higher than ESCR of the third polymer. The molecules of the second polymer form tie chains in the composition.
The first mixture is melt blended at a temperature in the range of 150 oC to 250 oC for a time period in the range of 5 minutes to 150 minutes, and at a speed in the range of 10 rpm to 300 rpm.
The second mixture is melt blended at a temperature in the range of 150 oC to 250 oC for a time period in the range of 0.5 minute to 30 minutes, and at a speed in the range of 10 rpm to 300 rpm.
The second mixture is extruded at a temperature in the range of 150 oC to 250 oC and with a residence time in the range of 0.5 minute to 10 minutes.
The process of the present disclosure further comprises adding at least one additive selected from the group consisting of fillers, stabilizers, flame retardants, anti-static agents and reinforcing agents. The additive is added in at least one step selected from the steps of mixing, blending, processing, admixing, and homogenizing.
The process of the present disclosure further comprises adding at least one colorant. The colorant is added in at least one step selected from the steps of admixing and homogenizing.
The process of the present disclosure further comprises converting the molecular level homogenized polymer composition into a form selected from the group consisting of chips, flakes, granules, powder, filaments, and sheets.
In a third aspect, the present disclosure provides an article prepared from the homogenized polymer composition of the present disclosure. The article is selected from the group consisting of fiber, yarn, pipe, tape, film, and molded articles.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing in which:
Figure 1(a) illustrates an image of the stretched film of the polymer blend as prepared in Experiment 1A;
Figure 1(b) illustrates a polarizing microscope (POM) image of the stretched film of the polymer blend as prepared in Experiment 1A;
Figure 2(a) illustrates the morphology of the stretched film of HMHDPE as used in Experiment 1B, and Figure 2(b) illustrates the morphology of the stretched film prepared from the homogenized polymer composition of Experiment 1B;
Figure 3(a) illustrates a POM image of the stretched film prepared from the HMHDPE as used in Experiment 1B, and Figure 3(b) illustrates a POM image of the stretched film prepared from the homogenized polymer composition of Experiment 1B;
Figure 4(a) illustrates an image of the stretched film prepared in experiment 2C;
Figure 4(b) illustrates a POM image of the stretched film prepared in experiment 2C;
Figure 5(a) illustrates an image of the stretched film of the homogenized polymer composition prepared in Experiment 3B;
Figure 5(b) illustrates a POM image of the stretched film of the homogenized polymer composition prepared in Experiment 3B; and
Figure 6 illustrates a blow molded container prepared from the homogenized polymer composition of Experiment 6.
DETAILED DESCRIPTION
Mechanical and performance properties of a polymer can be enhanced by homogenizing that polymer with a long chain polymer. However, the preparation of homogenous polymer compositions of long chain polymers, such as UHMWPE, with lower polyethylenes is associated with various drawbacks.
The present disclosure envisages enhancement of mechanical and performance properties of a polymer by preparing a molecular level homogenized polymer composition of that polymer with a long chain polymer.
In one aspect, the present disclosure provides a homogenized polymer composition being homogenized at a molecular level. The composition comprises,
i. a polymer blend comprising at least one first polymer and at least one second polymer, wherein
a. the first polymer is selected from the group consisting of ethylene based homopolymer and ethylene based copolymer; and
b. the second polymer is disentangled ultra-high molecular weight polyethylene (DUHMWPE) having weight average molecular weight in the range of 3 x 105 to 20 x 106 g/mole;
ii. at least one third polymer selected from the group consisting of ethylene based homopolymer and ethylene based copolymer,
wherein, the molecules of the second polymer form tie chains in the molecular level homogenized polymer composition.
The composition of the present disclosure is characterized by an environmental stress crack resistance (ESCR) in the range of 50 % to 800 % higher than ESCR of the third polymer.
The molecular level homogenization of long chains of the second polymer in the third polymer is achieved by (i) first preparing a polymer blend of the first polymer and the second polymer using melt processing and (ii) finally admixing and homogenizing a suitable quantity of the polymer blend with the third polymer through melt process. The homogenized polymer composition of the present disclosure has long chains of the second polymer. By virtue of the characteristic make-up of the molecular level homogenized polymer composition, especially due to the presence of tie chains of the polymer having long chains, the inherent mechanical and performance properties of the third polymer are enhanced.
The first polymer and the third polymer are independently selected from the group consisting of high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), ultra low-density polyethylene (ULDPE), very low density polyethylene (VLDPE), and linear low density polyethylene (LLDPE).
The ethylene based copolymer comprises at least one co-monomer selected from the group consisting of butene, hexene, and octene. The amount of the co-monomer in the ethylene based copolymer is in the range of 0.2 mole % to 10 mole %.
The first polymer and the third polymer have at least one molecular weight distribution independently selected from the group consisting of unimodal distribution and bimodal distribution.
In accordance with the embodiments of the present disclosure, the first polymer and the third polymer can be the same or different.
In accordance with one embodiment of the present disclosure, the first polymer and the third polymer are different.
In accordance with another embodiment of the present disclosure, the first polymer and the third polymer are the same.
For the preparation of the molecular level homogenized polymer composition of the present disclosure, the ratio of the first and the second polymers in the polymer blend, and the quantity of the polymer blend admixed with the third polymer is such that desired amounts of the first polymer, the second polymer, and the third polymer are present in the composition. The inherent mechanical and performance properties of the composition are dependent of the amounts of each of the first polymer, the second polymer, and the third polymer. Further, requisite enhancement of the mechanical and performance properties of the third polymer can be achieved by choosing appropriate amounts of the first polymer, the second polymer, and the third polymer.
In the composition of the present disclosure, (i) the weight of the first polymer is in the range of 0.095 % to 4 %, (ii) the weight of the second polymer is in the range of 0.005 % to 20 % and (iii) the weight of the third polymer is in the range of 76 % to 99.9 % with respect to the total weight of the polymer composition.
The composition of the present disclosure further comprises at least one additive selected from the group consisting of colorants, fillers, stabilizers, flame retardants, anti-static agents and reinforcing agents.
In accordance with one embodiment of the present disclosure, the additive is at least one stabilizer selected from the group consisting of hindered phenolic antioxidant group compounds, and hydrolytically stable organic phosphites and phosphonites compounds. The amount of the antioxidant is in the range of 500 ppm to 25000 ppm.
In a second aspect, the present disclosure provides a process for the preparation of a homogenized polymer composition, being homogenized at a molecular level. The process comprises the following steps.
At least one first polymer and at least one second polymer are mixed to obtain a first mixture. The second polymer is DUHMWPE having molecular weight in the range of 3 x 105 to 20 x 106 g/mole.
The first mixture is melt blended to obtain a polymer blend. The first mixture is melt blended at a temperature in the range of 150 oC to 250 oC for a time period in the range of 5 minutes to 150 minutes, and at a speed in the range of 10 rpm to 300 rpm.
The polymer blend is processed to obtain a polymer blend preform. In this step, the process conditions are so selected as to result in a preform selected from the group consisting of chips, pellets, and granules.
The polymer blend preform is admixed with at least one third polymer to obtain a second mixture. The polymer blend and the third polymer are admixed in such a way that the quantity of the second polymer in the homogenized polymer composition is in the range of 50 ppm and 2,00,000 ppm.
The second mixture is homogenized by at least one method selected from the group consisting of melt blending, and extrusion to obtain the homogenized polymer composition.
The second mixture can be melt blended at a temperature in the range of 150 oC to 250 oC for a time period in the range of 0.5 minute to 30 minutes, and at a speed in the range of 10 rpm to 300 rpm.
The second mixture can be extruded at a temperature in the range of 150 oC to 250 oC and with a residence time in the range of 0.5 minute to 10 minutes.
The process of the present disclosure is simple. Further, the process of the present disclosure is efficient as the time required for formation of the molecular level homogenized polymer composition is short.
The homogenization of the third polymer with the polymer blend can be carried out in various processing tools related to injection molding, blow molding, extrusion, and rotational molding. Therefore, the process of the present disclosure is amenable to various processing techniques.
The process of the present disclosure further comprises adding at least one additive selected from the group consisting of fillers, stabilizers, flame retardants, anti-static agents and reinforcing agents. The additive is added in at least one step selected from the steps of mixing, blending, processing, admixing, and homogenizing.
The process of the present disclosure further comprises adding at least one colorant. The colorant is added in at least one step selected from the steps of admixing, and homogenizing.
An improvement in the properties of the third polymer, such as creep rupture and environmental stress cracking, is achieved by the preparation of a molecular level homogenized polymer composition, by diluting the third polymer with the polymer blend.
The molecular level homogenized polymer composition of the present disclosure has high processability.
The process of the present disclosure further comprises converting the molecular level homogenized polymer composition into a form selected from the group consisting of chips, flakes, granules, powder, filaments and sheets.
Further, by means of the process of the present disclosure, a dispersion of DUHMWPE in the lower polyethylene at molecular level can be achieved in a very short residence time, making the process suitable for use on fast processing line for high throughput.
In a third aspect, the present disclosure provides an article prepared by using the molecular level homogenized polymer composition of the present disclosure. The article can be selected from the group consisting of fiber, yarn, pipe, tape, film and molded articles. The molded articles prepared from the homogenized polymer composition of the present disclosure include blow molded articles and injection molded articles. Some examples of the molded articles prepared by using the homogenized polymer composition of the present disclosure are bottle, containers (of capacity from 10 ml to 500 liters) for packaging applications, automotive parts such as bumpers, tailgate outer panels, dash board, interior parts and the like; construction products such as parking decks, industrial door, partitions, panels and the like; and household appliance parts such as washing machine, dryers, dishwashers, refrigerators, small appliances, furniture and the like. Similar articles can be prepared by using the homogenized polymer composition of the present disclosure.
In accordance with one embodiment of the present disclosure, the article is a sheet.
In accordance with another embodiment of the present disclosure, the article is a blow molded container.
In accordance with one embodiment of the present disclosure, the ESCR of the lower polyethylenes is increased by more than 541% upon preparation of the homogenized polymer composition of the present disclosure.
The present disclosure is further described in light of the following laboratory scale experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
Experiment 1: Preparation of the polymer composition of the present disclosure using a batch mixer
1A] Preparation of the polymer blend
19.55 g of bimodal HMHDPE powder (butene content - not less than 2.0 mole%, Mw 1.12 x 105 g/mole, density - 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg), 3.45 g of DUHMWPE powder (bulk density 0.064 g/cc, Mw ~2 million g/mole, MWD 17.11, heat of fusion (?Hf) 202 J/g, and Tm 140 °C) and 0.345 g of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (as a primary stabilizer) were dry blended to obtain a first mixture.
The first mixture was then melt blended in a Brabender Plasticorder (batch mixer) at 190 °C for 80 minutes with the rotational speed fixed at 60 rpm to obtain a polymer blend. A 5 kg load was also placed on the kneader head to provide axial force to ensure efficient mixing of the two polymers. The molten polymer blend was processed to form polymer blend preforms in the form of fine chips.
Preparation of a film from the polymer blend
4.5 g of the fine chips of the polymer blend obtained as above were compression molded at 150 °C to form a film having 0.5 mm thickness using a compression press. The pressure in compression press was maintained as 0 kg/cm2 - 5 minute, 50 kg/cm2 - 5 min, 100 kg/cm2 - 10 min and 200 kg/cm2 - 10 min. The mold was cooled to 45oC under air and the molded film was taken out. 5x1 cm2 pieces of this film were cut and later stretched under tension at 125 °C using a universal tester equipped with an environmental chamber.
The film was viewed under polarizing microscopic (POM) view and the results obtained were analyzed.
Figure 1(a) illustrates an image of the stretched film of the polymer blend as prepared in Experiment 1A, and Figure 1(b) illustrates a Polarizing Microscope (POM) image of the stretched film of the polymer blend as prepared in Experiment 1A.
Inference
From the figures, it is observed that the film obtained from the polymer blend showed no imperfection and that two polymers are in a homogenized state.
1B] Preparation of the polymer composition from the polymer blend (using a batch mixer)
0.153 g of the polymer blend preform (chips) obtained from experiment 1A was dry blended with 23 g of bimodal HMHDPE (butene content - not less than 2.0 mole%, Mw 1.12x 105 g/mole, density 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg) and 5000 ppm of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to obtain a second mixture.
The second mixture was melt kneaded with the help of a Brabender Plasticorder at 190 °C and for 10 minutes with the rotational speed fixed at 60 rpm. A 5 kg load was also placed on the kneader head to provide axial force to ensure efficient mixing of the two polymers. After the completion of the melt blending, the molten polymer composition was obtained. The polymer composition was cooled, and chopped into fine chips.
1C] Preparation of a film from the polymer composition
The HMHDPE as used in experiment 1B and the polymer composition (chips) obtained in experiment 1B both were compression molded and further stretched individually into thin films using a procedure similar to that described in experiment 1A.
The films were analyzed under polarizing microscope (POM). Figures 2(a), 2(b), 3(a) and 3(b) illustrate a comparison between the morphologies of the stretched film made up of HMHDPE and the polymer composition prepared in Experiment 1B.
Figure 2(a) illustrates an image of the stretched film prepared from HMHDPE as used in experiment 1B and Figure 2(b) illustrates an image of the stretched film prepared from the polymer composition of experiment 1B. Figure 3(a) illustrates a POM image of the stretched film prepared from HMHDPE as used in Experiment 1B and Figure 3(b) illustrates a POM image of the stretched film prepared from the polymer composition of experiment 1B.
Inference
From the figures, it is clear that there are no imperfections in the film prepared from the polymer composition of the present disclosure. Thus, the polymer blend prepared in Experiment 1A was completely homogenized with the third polymer to obtain the polymer composition.

Experiment 2: Preparation of the polymer composition of the present disclosure using a twin screw extruder
2A] Preparation of the polymer blend
50g polymer blend was prepared using the process of Experiment 1A. The polymer blend was processed to obtain polymer blend preforms in the form of chips.
2B] Preparation of the polymer composition from the polymer blend (using a twin screw extruder)
47 g of the polymer blend preforms (chips) obtained in Experiment 2A, 7 kg HMHDPE with butene content - not less than 2.0 mole% (bimodal), (Mw 1.12 x 105 g/mole, density 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg), 1500 ppm of stabilizer (500 ppm – pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 1000 ppm – tris(2,4-ditert-butylphenyl) phosphite) were blended in a tumbler mixer for 10 minutes to obtain a second mixture.
The second mixture was extruded with the help of a twin screw extruder (TSE) to obtain a homogeneous polymer composition. The temperature profile of the extruder was set as 160 °C – 170 °C – 185 °C – 195 °C – 200 °C – 200 °C – 200 °C – 210 °C – 210 °C – 210 °C. The speed of the screw was 75 rpm and residence time was 185 seconds. The quantity of polymer blend chips fed to the extruder was such that the DUHMWPE content in the polymer composition was maintained as 1000 ppm. The extruded material was pelletized into 3 mm to 5 mm granules and dried for 2 hours at 80 °C.
2C] Preparation of a film from the polymer composition
The pellets of the polymer composition of experiment 2B were compression molded and subsequently stretched in a manner similar to experiment 1A. The stretched thin film was analyzed by visual inspection as well as by polarized light microscope (POM).
Figure 4(a) illustrates an image of the stretched film prepared in experiment 2C, and Figure 4(b) illustrates a POM image of the stretched film prepared in experiment 2C.
Inference
From the figures it is clear that there are no imperfections in the film. Thus, the polymer blend prepared in Experiment 2A was homogenized with the third polymer (Experiment 2B).
Experiment 3: Preparation of the polymer composition of the present disclosure using a micro-compounder
3A] Preparation of the polymer blend (using a micro-compounder)
The polymer blend was prepared using a twin screw DSM Xplore 15 ml micro compounder (Model 2005- MC15) as follows.
7.0 g HMHDPE powder with butene content - not less than 2.0 mole% (bimodal), 12 x 105 g/mole , density 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg) was mixed with 3.0 g of DUHMWPE powder (bulk density - 0.0554 g/cc, RSV – 24.67 dl/g, Mw 4.4 million g/ mole, MWD – 10.73, % crystallinity 95.7 (X–ray), Heat of fusion (?Hf) - 186 J/g and Tm 140°C ) and 1000 ppm of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate for 10 minutes to obtain a first mixture. The first mixture was fed into the barrel of a micro-compounder through hopper under nitrogen purge while maintaining a temperature profile of 190 °C – 210 °C – 210 °C and screw rotational speed as 50 rpm. After the polymer addition is completed in the micro-compounder, the hopper was replaced with a seal plug to close the micro-compounder. The mixing of two polymers in molten form was carried out for a period of 15 minutes under nitrogen atmosphere to obtain molten polymer blend. The molten polymer blend was extruded through nozzle and granulated into pellets of size 2 mm to 3 mm.
3B] Preparation of the polymer composition from the polymer blend
0.383g of the polymer blend preform (pellets) obtained in Experiment 3A, 23 g of bimodal HMHDPE (butene content - not less than 2.0 mole%, Mw 1.12 x 105 g/mole, density 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg) and 5000 ppm of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate were mixed to obtain a second mixture. The second mixture was melt kneaded in the mixer attached to Brabender Plasticorder at 190 oC and rotor rpm of 60 to obtain a polymer composition. The polymer composition was cut into pellets using a pelletizer.
3C] Preparation of a film from the polymer composition
The pellets of the material from experiment 3B were compression molded and further stretched into a thin film in a manner similar to Experiment 1A. The stretched thin film prepared was analyzed by visual inspection as well as by polarized light microscope (POM).
Figure 5(a) illustrates an image of the stretched film of the polymer composition prepared in experiment 3B, and Figure 5(b) illustrates a POM image of the stretched film of the polymer composition prepared in experiment 3B.
Inference
From figures 5(a) and 5(b), it is clear that there are no imperfections in the film. Thus, the polymer blend prepared in Experiment 3A was homogenized with the third polymer.
Experiment 4: Preparation of a polymer blend of HMHDPE and DUHMWPE in a Micro-compounder and further homogenization of the polymer blend in a twin screw extruder

4A] Preparation of a polymer blend of HMHDPE and DUHMWPE in Micro-compounder
7.0 g of pulverized HMHDPE powder with butene content - not less than 2.0 mole% (bimodal), (Mw 1.12x 105 g/mole, density 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg), 3 g of DUHMWPE powder (bulk density - 0.0554 g/cc, RSV – 24.67 dl/g, Mw ~3.53 million g/ mole, MWD – 10.73, % crystallinity 95.7 (X–ray), Heat of fusion (?Hf) - 186 J/g and Tm 140°C ), pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (500 ppm) and tris(2,4-ditert-butylphenyl) phosphite were compounded, and mixed thoroughly for 20 minutes in polyethylene bag under nitrogen atmosphere to obtain a first mixture.
The first mixture was fed into DSM Xplore Micro-compounder, (model 2005- MC15) through a hopper under nitrogen atmosphere. After addition of the polymer composition, the hopper was replaced with a seal plug to close the micro-compounder. The melt blending was carried out inside the micro-compounder keeping the temperature profile of 190 oC –210 oC –210 oC, screw rpm of 50 for a period of 30 minutes to obtain molten polymeric blend. The molten polymeric blend was extruded through a die in the form of strands and granulated into 2 mm to 3 mm granules.
4B] Preparation of the polymer composition from the polymer blend using a twin screw extruder
83.33 g of the polymer blend preform (granules) (obtained by the procedure as given in Experiment 4A), 5000 g of HMHDPE powder (Mw 1.12 x 105 g/mole, Density 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg), 2.5 g of primary antioxidant pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4hydroxyphenyl)propionate and 5 g of secondary antioxidant - tris(2,4-ditert-butylphenyl) phosphite (1000 ppm) were mixed in a tumbler mixer for 20 minutes to obtain a second mixture.
The second mixture was fed into a hopper of a twin screw extruder (TSE Omega 30 from M/s Steer) and extruded with a temperature profile of 165°C–185°C–195°C–195oC-200°C–200°C–200°C–210°C–210°C–210°C, with screw rpm of 50 and operating torque of 72 m/g. The extruded material was passed through a water trough and pelletized into 3 mm to 5 mm granules and dried for 2 hours at 80 °C in dry hot air oven.
4C] Preparation of a sheet from the polymer composition
The granules of polymer composition (obtained in Experiment 4B through TSE) and HMHDPE used in experiment 4B were compression molded individually into sheets to obtain the standard ESCR test specimen as per standard ASTMD1693. The compression molding conditions were kept at temperature 190 oC, pressure at 0 t – 1 minute, 15 t – 2 minutes, 30 t – 3 minutes on M/s Carver compression press (50 Tonnes). Total cycle time of 6 minutes was used for compression molding. The mold was cooled to 45 oC under air and molded sheet was taken out. The molded sheets were kept at room temperature for 48 hours and punched into standard test specimens using a pneumatic punch cutter (ASTM 1693).
4D] Evaluation of environmental stress crack resistance
The standard test specimens as prepared in experiment 4C were tested for their environmental stress crack resistance (ESCR) as per ASTM D1693-00. The results obtained for these two specimens (1 and 2) are given in Table 1.
(1) HMHDPE used in experiment 4B and
(2) The polymer composition obtained in experiment 4B

Table 1 Environmental Stress Cracking Resistance of specimens (1 and 2)
Specimen No. Sample ESCR* (h) Increase in ESCR (%)
1 HMHDPE used in experiment 4B 288 -
2 Polymer composition obtained in experiment 4B, prepared in accordance with the procedure of the present disclosure 1560 541
Inference
Table 1 indicates that the addition of 83.33g of the polymeric blend into 5000 g of HMHDPE (as used in experiment 4B) increases the ESCR of the polymer composition of experiment 4B by 541 %. The time of failure for 50 % of the samples of the polymer composition increases to 1560 hours as compared to 288 hours for HMHDPE.
The results of the aforestated experiments show that on compounding the DUHMWPE (through polymer blend as an additive) into a lower polyethylene, there is an improvement in the properties of the lower polyethylene.
Experiment 5: Preparation of the polymer blend with unimodal lower polyethylene and UHMWPE
19.55 g of unimodal HDPE powder (Mw 99573 g/mole, density 0.955 g/cc, MFI 1.0 g/10 min at 190 °C /2.16 kg), 6.9 g of DUHMWPE powder (bulk density - 0.055 g/cc, Mw ~3.53 million g/mole, MWD - 10.72, ?Hf - 186 J/g and Tm = 139 °C) and 0.115 g of pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (as a primary stabilizer) were mixed to obtain a first mixture.
This first mixture was then melt blended in a Brabender Plasticorder (batch mixer - kneader) at 190 °C for 80 minutes with the rotational speed fixed at 60 rpm to obtain a polymer blend. A 5 kg load was also placed on the kneader head to provide axial force to ensure efficient blending of the two polymers. The molten polymer blend was processed to form polymer blend preforms as fine chips. A compression molded and further hot stretched film of this polymer blend showed no imperfection and indicated that two polymers are in a homogenized state.
Experiment 6: Preparation of a molded article using the polymer composition of the present disclosure
6A] Preparation of a polymer blend
16.1 g of bimodal HMHDPE powder (butene content - not less than 2.0 mole %, Mw 1.12x 105 g/mole, density - 0.956 g/cc, MFI 0.30 g/10 min at 190 °C /2.16 kg), 6.9 g of DUHMWPE powder (bulk density 0.055 g/cc, Mw ~ 3.53 million g/mole, MWD - 10.72, ?Hf - 186 J/g and Tm = 139 °C), 0.184 g of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (as a primary stabilizer) and 0.046 g Tris(2,4-ditert-butylphenyl)phosphite (secondary stabilizer) were mixed to obtain a first mixture. The first mixture was melt blended in a Brabender Plasticorder (batch mixer) at 190 °C for 75 minutes with the rotational speed fixed at 60 rpm to obtain a polymer blend. A 5 kg load was placed on the kneader head to provide axial force to ensure efficient mixing of the two polymers. The molten polymer blend was processed to form polymer blend preforms in the form of fine chips.
6B] Preparation of the polymer composition
3.33 kg of the polymer blend preforms (chips) (obtained from experiment 6A), 200 kg of HMHDPE as a third polymer (Mw 1.59 x 105 g/mole, MFI 0.45 g/10 min at 5Kg/190oC, density: 0.945g/cc, 1-butane content >2mole%) along with primary stabilizer pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (500 ppm), secondary stabilizer tris(2,4-ditert-butylphenyl)phosphite (1000 ppm) was extruded with the help of a twin screw extruder (Omega TSE from M/s Steer Engineering Co. Ltd.) to obtain a polymer composition. The temperature profile of the extruder was set as 185 °C – 205 °C – 215 °C – 215 °C – 220 °C – 220 °C – 220 °C – 225 °C – 225 °C – 225 °C. The speed of the screw was 50 rpm with a feed rate of 2.5 to 3 Kg and Torque of 75. The quantity of polymer blend chips fed to the extruder was such that the DUHMWPE content in the polymer composition was maintained at 5000 ppm. The extruded material was pelletized into 3 mm to 5 mm granules and dried for 2 hours at 80 °C, which showed a MFI of 0.3 g / 10 min at 5 kg load and 190 °C.
6C] Preparation of blow molded containers using the polymer composition obtained in Experiment 6B.
The polymer composition as prepared in experiment 6B (granules) was blow molded in to 120 liters size (wt. 3.9 kg) chemical containers. The processing temperature and cycle time was 190 °C to 215 °C, and 207 seconds respectively. The molded product was produced with no surface defect. This indicates that the second polymer (DUHMWPE) added by using the polymer blend in the polymer composition was homogenized completely with the third polymer.
Colorant was mixed during the stage of preparation of the polymer composition to achieve a blue color of the container. The container obtained in experiment 6C is shown in Figure 6.
Experiment 7: Preparation of a polymer composition having disentangled UHMWPE (second polymer) content of 50 ppm
0.0076 g of the polymer blend preform (chips) (prepared as per the process of experiment 1A) was dry blended with 23 g of HMHDPE (butane-1 content - not less than 2.0 mole% (bimodal), Mw 1.84 x 105 g/mole, density 0.946 g/cc, MFI 0.30 g/10 min at 190 °C /5 kg) and 5000 ppm of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to obtain a second mixture.
The second mixture was melt kneaded in a Brabender Plasticorder as per the experimental condition used in experiment 1B. The obtained molten polymer composition was cooled, and chopped into fine chips. The polymer composition (chips) was compression molded and further a stretched film was obtained therefrom by a process similar to experiment 1C. The film was evaluated in POM. POM analysis showed that the polymer composition is homogenized completely with the third polymer.
Experiment 8: Preparation of a polymer composition having a second polymer in an amount of 200000 ppm
36.66 g of the polymer blend preform (chips) was prepared by a process similar to experiment 1A. The polymer blend was further dry blended with 23 g of HMHDPE (butane-1 content - not less than 2.0 mole% (bimodal), Mw 1.84x105 g/mole, density 0.946 g/cc, MFI 0.30 g/10 min at 190 °C /5 kg) and 5000 ppm of pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate to obtain a second mixture.
The second mixture was melt kneaded in Brabender Plasticorder as per the experimental conditions used in experiment 1B. The molten polymer composition thus obtained was cooled, and chopped into fine chips. The polymer composition (chips) was compression molded and further a stretched film was obtained by a process similar to experiment 1C. The film was evaluated in POM. The POM analysis showed that the polymer composition was homogenized completely with the third polymer.
The composition exhibits enhanced ESCR as compared to lower polyethylene. This enhancement in ESCR indicates an increase in tie chain concentration at molecular level.

TECHNICAL ADVANCEMENTS AND ECONOMIC SIGNIFICANCE
The molecular level homogenized polymer composition of the present disclosure has several technical advancements that include, but are not limited to, the realization of:
• the inherent mechanical and performance properties of lower polyethylenes are enhanced by preparation of a homogenized polymer composition of DUHMWPE with lower polyethylenes being homogenized at a molecular level; and
• a large scale process for preparing the molecular level homogenized polymer composition, being homogenized at a molecular level.
The foregoing description of the specific embodiments 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 homogenized polymer composition being homogenized at a molecular level, said composition comprising,
i. a polymer blend comprising at least one first polymer and at least one second polymer, wherein
a. said first polymer is selected from the group consisting of ethylene based homopolymer and ethylene based copolymer; and
b. said second polymer is disentangled ultra-high molecular weight polyethylene (DUHMWPE) having weight average molecular weight in the range of 3 x 105 to 20 x 106 g/mole;
ii. at least one third polymer selected from the group consisting of ethylene based homopolymer and ethylene based copolymer;
wherein, the molecules of said second polymer form tie chains in said composition; and
wherein, said composition is characterized by an environmental stress crack resistance (ESCR) in the range of 50 % to 800 % higher than ESCR of said third polymer.
2. The composition as claimed in claim 1, wherein said first polymer and said third polymer are independently selected from the group consisting of high density polyethylene (HDPE), high molecular weight high density polyethylene (HMHDPE), ultra low-density polyethylene (ULDPE), very low density polyethylene (VLDPE), and linear low density polyethylene (LLDPE).
3. The composition as claimed in claim 1, wherein said first polymer and said third polymer are the same or different.
4. The composition as claimed in claim 1, wherein said ethylene based copolymer comprises at least one co-monomer selected from the group consisting of butene, hexene, and octene; and the amount of said co-monomer in said ethylene based copolymer is in the range of 0.2 mole % to 10 mole %.
5. The composition as claimed in claim 1, wherein said first polymer and said third polymer have at least one molecular weight distribution independently selected from the group consisting of unimodal distribution and bimodal distribution.
6. The composition as claimed in claim 1, wherein said second polymer has molecular weight higher than the molecular weight of said first polymer and said third polymer.
7. The composition as claimed in claim 1, wherein (i) the weight of the first polymer is in the range of 0.095 % to 4 %, (ii) the weight of the second polymer is in the range of 0.005 % to 20 % and (iii) the weight of the third polymer is in the range of 76 % to 99.9 %, with respect to the total weight of the homogenized polymer composition.
8. The composition as claimed in claim 1 further comprises at least one additive selected from the group consisting of colorants, fillers, stabilizers, flame retardants, anti-static agents and reinforcing agents.

9. A process for the preparation of a homogenized polymer composition being homogenized at a molecular level, said process comprising the following steps,
i. mixing at least one first polymer and at least one second polymer to obtain a first mixture, wherein said second polymer is disentangled ultra-high molecular weight polyethylene (DUHMWPE) having weight average molecular weight in the range of 3 x 105 to 20 x 106 g/mole;
ii. blending the first mixture by melt blending to obtain a polymer blend;
iii. processing said polymer blend to obtain polymer blend preform;
iv. admixing said polymer blend preform with at least one third polymer to obtain a second mixture; and
v. homogenizing the second mixture by at least one method selected from the group consisting of melt blending and extrusion to obtain said homogenized polymer composition,
wherein said composition is characterized by an environmental stress crack resistance (ESCR) in the range of 50 % to 800 % higher than ESCR of said third polymer, and wherein the molecules of said second polymer form tie chains in said composition.

10. The process as claimed in claim 9 which further comprises adding at least one additive selected from the group consisting of fillers, stabilizers, fire retardants, anti-static agents and reinforcing agents; said additive being added in at least one step selected from steps (i) to (v).

11. The process as claimed in claim 9 or 10 which further comprises adding at least one colorant; said colorant being added in at least one step selected from steps (iv) and (v).

12. The process as claimed in claim 9, wherein in step (ii) said first mixture is melt blended at a temperature in the range of 150 oC to 250 oC for a time period in the range of 5 minutes to 150 minutes, and at a speed in the range of 10 rpm to 300 rpm.

13. The process as claimed in claim 9, wherein in step (v) said second mixture is melt blended at a temperature in the range of 150 oC to 250 oC for a time period in the range of 0.5 minutes to 30 minutes, and at a speed in the range of 10 rpm to 300 rpm.

14. The process as claimed in claim 9, wherein in step (v) said second mixture is extruded at a temperature in the range of 150 oC to 250 oC and with a residence time in the range of 0.5 minute to 10 minutes.

15. The process as claimed in claim 9, wherein in step (iii) the process conditions are so selected as to result in a preform selected from the group consisting of chips, pellets and granules.

16. The process as claimed in claim 9 further comprising converting said homogenized polymer composition into a form selected from the group consisting of chips, flakes, granules, powder, filaments and sheets.

17. An article prepared from said homogenized polymer composition as claimed in any of the claims 1 to 8, said article being selected from the group consisting of fiber, yarn, pipe, tape, film and molded articles.