WO2017077455A2

WO2017077455A2 - A process for preparation of high melt strength polyolefin composition

Info

Publication number: WO2017077455A2
Application number: PCT/IB2016/056581
Authority: WO
Inventors: Uma Sankar Satpathy; Satya Srinivasa Rao GANDHAM; Ajit Behari Mathur; Raksh Vir Jasra; Devesh Kumar SHUKLA; Yogini Maheshbhai AMIN; Amit Kumar Punamchand SHAH; Nanubhai Fuljibhai PATEL; Gaurang Manilal MEHTA; Ashishkumar Indravadan PAREKH
Original assignee: Reliance Industries Limited
Priority date: 2015-11-02
Filing date: 2016-11-02
Publication date: 2017-05-11
Also published as: WO2017077455A3

Abstract

The present disclosure relates to a process for preparing a high melt strength polyolefin composition. The process includes melt blending at least one polyolefin, ultra-high molecular weight polyethylene (UHMWPE) and at least one additive selected from a lubricant, a plasticizer, a filler, and a processing aid to obtain the high melt strength polyolefin. The additives facilitate dispersion of UHMWPE in the polyolefin, thereby improving the melt compatibility and phase separation of UHMWPE in the polyolefin matrix. The process of the 0 present disclosure is useful in preparing a polyolefin composition which has reduced melt flow index and increased melt viscosity to be suitably processed using processing techniques like thermoforming, blow molding, and the like.

Description

A PROCESS FOR PREPARATION OF HIGH MELT STRENGTH POLYOLEFIN COMPOSITION

FIELD

The present disclosure relates to a process for preparation of a polyolefin composition. DEFINITIONS

As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.

Direct process is a process for preparing a high melt strength polyolefin without any side reactions.

Entangled ultra-high molecular weight polyethylene: The term entangled ultrahigh molecular weight polyethylene used in the context of the present disclosure refers to a homo-polymer or copolymer of ethylene having a viscosity average molecular weight of 2 million and above and heat of fusion less than 200 J/g and bulk density more than 0.3 g/cc. Disentangled ultra-high molecular weight polyethylene: The term disentangled ultrahigh molecular weight polyethylene used in the context of the present disclosure refers to a homo- polymer or copolymer of ethylene having a viscosity average molecular weight of 2 million and above and heat of fusion more than 200 J/g and bulk density in the range of 0.03 g/cc to 0.3 g/cc. The term 'phr' in the present disclosure stands for "parts per hundred parts resin".

The melt flow index (MFI) is a measure of the ease of flow of the melt of a thermoplastic polymer. More precisely, MFI is the measure of the resistance to flow of polymer melt under defined set of conditions (unit: dg/min).

—Melt flow rate (MFR): Melt flow rate is a measure of the ability of the material's melt to flow under pressure. Melt flow rate is inversely proportional to viscosity of the melt at the conditions of the test, though it should be borne in mind that the viscosity for any such material depends on the applied force. Shear modulus or modulus of rigidity, denoted by G, or sometimes 5 or μ, is defined as the ratio of shear stress to the shear strain.

Shear stress is a stress resulting from the application of opposing forces parallel to a cross- sectional area of a polymer. Shear strain is the amount of the movement of one layer relative to an adjacent layer divided by the layer thickness. This may be expressed as an angle of shear, in radians.

Strain hardening refers to an increase in hardness and strength of a polymer caused by plastic deformation at temperatures lower than the re-crystallization range.

Extensional thinning is the reduction in the viscosity of a polymer with increasing stress. Resistance to sagging is the ability of a polymer to resist bending under its own weight or a given load.

Storage modulus (G') is a measure of the elasticity of a polymer melt.

Loss modulus or viscous modulus (G") is defined as the ability of the material to dissipate the energy of the polymer melt as measure by dynamic rheological test. The ratio of (G" / G') is the measure of material damping (Tan δ) i.e. higher the G' lower will be the Tan δ.

MFI is inversely related to molecular weight of the polymer and is used as indicator of melt strength enhancement of polyolefin (i.e. either PP or PE) during the course of its modification. In fact, the change in the melt strength as described in the present disclosure is indicated through the change in MFI. .

Tensile modulus is a measure of the rigidity of a polymer.

Tensile yield strength is the stress at which a polymer deforms plastically.

Tensile strength: The ability of a material to resist a force that tends to pull it apart. It is usually expressed in terms of the measure of the largest force that can be applied before a sample of the material breaks apart. BACKGROUND

Polyethylene (PE) and polypropylene (PP) are the most widely used commodity plastics. HDPE and PP possess a predominantly linear chain structure which results in low melt strength, low melt shear sensitivity, low strain hardening behavior, and high extensional thinning.

Ultra-high molecular weight polyethylene (UHMWPE) is a linear grade polyethylene having a viscosity average molecular weight greater than 2 million. UHMWPE offers high abrasion resistance, non-toxicity, high impact resistance, high toughness, high fatigue resistance, and high resistance to environmental stress cracking. Therefore, to alleviate the drawbacks associated with HDPE and PP, UHMWPE can be blended with PE and PP, to obtain a polyolefin composition having better mechanical properties such as high melt strength, and the like.

High melt strength polypropylene/polyethylene (HMS-PP/HMS-PE) compositions employing ultra-high molecular weight polyethylene (UHMWPE) are generally known in the art. However, the primary challenge associated with these compositions is the want of effective blending of UHMWPE and PE/PP that is industrially scalable.. Conventional melt processing cannot be used to achieve intimate mixing of UHMWPE and PE/PP (because of the vast mismatch between the viscosities of UHMWPE and PE/PP). Also, solution processing as a probable method is not industrially viable because of the requirement of large quantities of solvents.

Recently, a technique called solid-state shear pulverization was developed which brings about effective mixing of the blending components utilizing its exceptional ability to achieve intimate mixing free from kinetic limitations.

In spite of using solid-state shear pulverization for blending UHMWPE with PE/PP, the technique still proved short for effective mixing of UHMWPE with PE/PP.

Therefore, there remains a need in the art for a method to produce high melt strength polyolefin (i.e.HMS-PP/ PE) of reliable and /or improved quality which obviates the drawbacks associated with the conventional processes. OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.

It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide a process for obtaining a polyolefin that has high melt strength.

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 accordance with the present disclosure, a process for preparing high melt strength polyolefin composition is disclosed. The process comprises melt blending at least one polyolefin, ultra-high molecular weight polyethylene (UHMWPE) in the range of 0.5 phr to 45 phr , at least one polyolefin, and at least one additive selected from the group consisting of a lubricant , a plasticizer, a filler, and a processing aid, to obtain high melt strength polyolefin. The at least one polyolefin in the present disclosure is selected from the group consisting of homopolymers and copolymers of long chain branched polyethylene, linear polyethylene, ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), and high molecular weight high density polyethylene (HMHDPE) and polypropylene.

The lubricant is in an amount in the range of 0.5 phr to 20 phr of the at least one polyolefin, the plasticizer is in an amount in the range of 5 phr to 30 phr of the at least one polyolefin, the filler is in an amount in the range of 0.5 phr to 10 phr of the at least one polyolefin, and the processing aid is in an amount in the range of 5 phr to 40 phr of the at least one polyolefin.

Typically, the melt blending is achieved by extrusion.

Typically, the ultra-high molecular weight polyethylene is at least one of entangled ultra-high molecular weight polyethylene and disentangled ultra-high molecular weight polyethylene. Typically, the lubricant is at least one selected from the group consisting of silicone oil, paraffin wax, oxidized polyethylene, metal stearate, fatty acid amides, oleyl palmitamide, and polyethylene glycol.

Typically, the plasticizer is decalin and the filler is nano clay. Typically, the processing aid is at least one selected from the group consisting of high melt flow index polypropylene and high melt flow index high density polyethylene.

Typically, the melt flow index of the high melt strength polyolefin is less by at least six times the melt flow index of the at least one polyolefin.

Typically, the melt viscosity of the high melt strength polyolefin is at least five times the melt viscosity of the at least one polyolefin.

DETAILED DESCRIPTION

Polyolefins such as high density polyethylene (HDPE) and polypropylene (PP) possess a predominantly linear chain structure, and thereby possess low melt strength, low melt shear sensitivity, low strain hardening behavior, high extensional thinning and the like. Due to such behavior, HDPE and PP offer resistance to stretching during elongation of the molten PE or molten PP. Therefore, processing techniques such as thermoforming, blow molding, and the like cannot be employed on PE and PP for making finished products.

To increase their melt strength behavior, polyolefins such as HDPE and PP are blended with UHMWPE. However, the conventional processes result in an ineffective blending, resulting in a non-uniform dispersion of UHMWPE in the polyolefin. Further, the blending of UHMWPE with the polyolefin is associated with processing problems such as die blockage, melt fracture, wall slippage, small processing temperature window, and the like. The present disclosure, therefore, envisages an alternative process for preparing a high melt strength polyolefin for obviating the drawbacks associated with the conventional processes. In accordance with the present disclosure, a process for preparing high melt strength polyolefin composition is disclosed.

The process comprises melt blending at least one polyolefin, ultra-high molecular weight polyethylene (UHMWPE) in the range of 0.5 phr to 45 phr of the at least one polyolefin, and at least one additive selected from the group consisting of a lubricant, a plasticizer, a filler, and a processing aid, to obtain the high melt strength polyolefin. The at least one polyolefin is selected from the group consisting of homopolymers and copolymers of long chain branched polyethylene, linear polyethylene, ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), and high molecular weight high density polyethylene (HMHDPE) and polypropylene.

The lubricant is present in an amount in the range of 0.5 phr to 20 phr of the at least one polyolefin. The plasticizer is present in an amount in the range of 5 phr to 30 phr of the at least one polyolefin. The filler is in an amount in the range of 0.5 phr to 10 phr of the at least one polyolefin. The processing aid is present in an amount in the range of 5 phr to 40 phr of the at least one polyolefin.

In accordance with the embodiments of the present disclosure, the ultra-high molecular weight polyethylene is at least one of entangled ultra-high molecular weight polyethylene and disentangled ultra-high molecular weight polyethylene.

Dis-entangled UHMWPE simplifies the processing problems of UHMWPE, thereby facilitating uniform dispersion of the dis-entangled UHMWPE in the polyolefin.

In accordance with the embodiments of the present disclosure, the amount of entangled ultrahigh molecular weight polyethylene is in the range of 10 phr to 45 phr of the at least one polyolefin.

In accordance with the embodiments of the present disclosure, the amount of disentangled ultra-high molecular weight polyethylene is in the range of 0.5 phr to 10 phr of the at least one polyolefin.

In an embodiment of the present disclosure, the ultra-high molecular weight polyethylene is a combination of entangled ultra-high molecular weight polyethylene and disentangled ultrahigh molecular weight polyethylene in an amount in the range of 0.5 phr to 45 phr of theat least one polyolefin.

Ultra-high molecular weight polyethylene imparts elasticity and high melt strength to the polyolefin composition. The high strength polyolefin composition as prepared by the process of the present disclosure can be used in varied processes such as thermoforming, blow molding, and the like, to produce a variety of products having improved sagging resistance.

In accordance with the embodiments of the present disclosure, the lubricant is at least one selected from the group consisting of polyethylene glycol (PEG), silicone oil, paraffin wax, oxidized polyethylene, metal stearate, fatty acid amides, and oleamide. The lubricant enhances the dispersion of ultra-high molecular weight polyethylene in the polyolefin. Further, the lubricant effectively reduces the frictional drag, degradation of the high melt strength polyolefin, and its discoloration.

In accordance with an embodiment of the present disclosure, the plasticizer is decalin. The plasticizer modifies the macromolecular structure of the at least one polyolefin, to provide the desired melt properties to the high melt strength polyolefin composition.

In accordance with an embodiment of the present disclosure, the filler is a nanoclay. A preferable nanoclay is montmorillonite, typically, montmorillonite modified with a quaternary ammonium salt. The filler facilitates crystallization of ultra-high molecular weight polyethylene in the polyolefin, thereby, increasing the strength of the resultant polyolefin composition.

In accordance with an embodiment of the present disclosure, the processing aid at least one selected from the group consisting of high melt flow index (MFI) polypropylene and high melt flow index high density polyethylene. Adding of the processing aid increases the compatibility of ultra-high molecular weight polyethylene with the at least one polyolefin.

A preferred processing aid for modifying high density polyethylene as the polyolefin is high melt flow index (MFI) polypropylene.

The high melt strength polyolefin composition has a tensile strength in the range of 20 % to 30 % more as compared to that of the polyolefin and tensile modulus in the range of 35 % to 40 % more as compared to that of the polyolefin.

The present disclosure is further described in the light of the following laboratory experiments which are set forth for illustration purpose only, and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale, and the results obtained can be extrapolated to industrial scale. EXPERIMENTS

In the experiments -

Rheometric Dynamic Analysis (RDA) of polymer samples were carried out using a parallel plate assembly for low shear melt rheological evaluation on RDA III - AERS of TA instruments. The frequency sweep analyses were done at a strain of 3 % and at a temperature of 190° C in the frequency range of 0.1-500 rad/sec. The molecular weight averages (like M_n, M_w, M_z, M_z+1) and MWD data was synthesized using an orchestrator software of RDA with the rheological data.

MFR Measurements of the samples were carried out as per ASTM D1238 method at a temperature of 230° C and varying the dead load. The dead loads used were 2.16 kg, 5.0 kg, 10.0 kg and 21.6 kg. For this purpose, Ceast Melt Flow Indexer was used for the measurement.

Differential Scanning Calorimetry (DSC) Analysis

Polymer samples having size 5 mg were analyzed on DSC 2910 / Q2000 MDSC (M/s TA instruments, USA) by heating them from ambient to 250° C in N2 atmosphere with a heating rate of 10° C / min to record its melting temperature (T_m), initial crystallization temperature (Ti_c) and heat of melt fusion (AH_m) respectively. The heating and cooling medium was N₂. For this purpose a thermal analyzer of TA Instruments was used.

Batch preparation and Reactive extrusion process: Various batches comprising HDPE/PP, UHMWPE (4M MW-RIL) along with required amounts of antioxidant (Irganoxl010: 1500- 2000ppm), lubricant (Polyethylene glycol: PEG) and other additives in varying quantities were prepared by blending them together.

The extrusion of these various batches was carried out using a single screw bench scale extruder of screw diameter 25 mm and L/D ratio 25: 1. The temperatures in the four zones of the barrel was maintained as typically required for the extrusion of HDPE/PP containing entangled UHMWPE as an additive with an objective to improve melt strength as well as mechanical properties in the presence of lubricant with or without high MFI -PP with lower concentrations (2.5-5 wt%). More importantly, decalin is used here (5-15 %) as plasticizer to facilitate dispersion and melt compatibility between primary linear polyolefin matrix and UHMWPE under a typical temperature profile and rpm as summarized in Table- 1 A. Experiment-1 (Modification of HDPE with UHMWPE):

Different quantities of UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to 150 g of HDPE, and the mixture was melt processed using an extruder having the following configuration as provided in Table 1A:

Table 1A

The Experimental results are tabulated in Table-IB.

Table-IB

PP-

HD UHMWMontmo MFI Melt high PEG decali

Samples PE PE rillonite (g/ io Viscosity

MFI (g) n(g)

(g) (g) (g) min) (Pa-s)

(g)

PPS-0 150 0 0 1.0 0 0 19.45 1878

PPS-1 150 5 25 1.0 0 0 2.97 12608

PPS-2 150 5 50 1.0 0 0 1.53 23541

PPS-3 150 5 50 1.0 20 0.25 0.49 73091

PPS-4 150 5 50 1.0 25 0.25 0.51 74091

(*Load used for measuring MFI was 10 Kg; MFI and Melt viscosity was measured at 230° C) As summarized in Table-IB, different samples (PPS-0 to PPS-4) were prepared by adding different amounts of ultra-high molecular weight polyethylene, and decalin to 150 g of HDPE. The amounts of high melt flow index polypropylene for preparing the samples PPS-1 to PPS-4 were maintained constant, and the amounts of PEG for preparing the samples PPS-0 to PPS-4 were maintained constant. UHMWPE used in this experiment was entangled ultrahigh molecular weight polyethylene.

From Table- 1, it can be observed that:

- by adding higher amounts of UHMWPE, decalin, and montmorillonite to HDPE, the melt flow index of the samples PPS-3 and PPS-4 decreased, as compared to the other samples PPS-0 to PPS-2;

- by adding higher amounts of UHMWPE, decalin, and montmorillonite to HDPE, the melt viscosity of the samples PPS-3 and PPS-4 increased, significantly, as compared to the samples PPS-0 to PPS-2;and

- the melt viscosity of the samples PPS-0 to PPS-2 in the absence of decalin and montmorillonite was significantly lower compared to the samples PPS-3 and PPS-4.

From the above description, it can be concluded that the melt flow index of the samples decreases in the presence of decalin, because decalin facilitates:

- reduction in chain entanglement of ultra-high molecular weight polyethylene; and

- dispersion of ultra-high molecular weight polyethylene in HDPE. Further, thermal properties like melting temperature (T_m), heat of fusion (AH_m), and the initial crystallization temperature (T;_c) of the samples (PPS-0 to PPS-4) were determined by differential scanning calorimetry (DSC). The changes in the thermal properties of the samples (PPS-0 to PPS-4) are summarized in Table-2.

Table-2

PPS-4 130.0 189 119.05

DSC Condition: Sample Size: 5 mg, Heating Rate: 10° C/min, Temp Profile: RT-25⁰ C

It is observed that thermal characteristics for samples from PPS-0 to PPS-4, viz., melting temperature, the enthalpy of fusion and initial crystallization temperature (T;_c) changed by a certain degree after modification as compared to neat HDPE as shown in Table-2.

Moreover, with the increase in the amounts of decalin and montmoriUonite doses further increased the initial crystallization temperature as compared to the samples without decalin and montmoriUonite (PPS-0 to PPS-2) as shown in Table-2.

Conclusion: Blending UHMWPE with HDPE:

- increases the initial crystallization temperature of the samples;

- Promotes crystallization of HDPE by shortening the inducing time; and

- DSC results confirms no phase separation after modification

The initial crystallization temperatures of the samples before and after addition of ultra-high molecular weight polyethylene to HDPE were determined by differential scanning calorimetry (DSC). It is found that the crystallization temperature of the samples (i.e. PPS-1 to PPS-4) had increased as compared to virgin sample (PPS-0) with change of ultra-high molecular weight polyethylene doses in the composition as displayed in Table- 1 A and Table- 2, respectively. However, the change in crystallization temperature was maximum with PPS- 4 as shown in Table-2. This indicates that well dispersed ultra-high molecular weight polyethylene facilitates nucleation process during melt processing.

More importantly, the rheological measurements were carried out using dynamic frequency sweep mode at 190° C essentially to compare the difference in melt flow behaviors of neat HDPE and modified HDPE with UHMWPE , However, modified samples showed significant change in broadening of molecular weight distribution, rise in melt viscosity η ( Pa.s ), shear modulus (G), number average molecular weight (M_n), weight average molecular weight (M_w), Z-average molecular weight (Mz ) , Z+l-average molecular weight (M_z+i), shear, and molecular weight distribution (MWD) and significantly lowering in Tan5 (i.e. ratio of G' VG') respectively, which distinctly differentiate between neat and modified HDPE as shown in results summarized in Table-3 & Table-4 .

Table-3

Table-4

The result shows that the high molecular component (UHMWPE) can effectively elevate the melt viscosity @ close to zero shear. It is reported that Newtonian (zero shear) viscosity can successfully be used to model the effects of gravity-induced sag in commercial large - diameter pipe processing and an inverse relationship between zero shear viscosity and gravity-induced sag was found. Therefore, we concluded that with a small amount of UHMWPE, the zero shear viscosities of HDPE-UHMWPE composites could be elevated to desired level and consequently the issues of gravity-induced sag during pipe manufacturing could be effectively be avoided. Experiment-2:

Different quantities of UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to 150 g of HDPE and the mixture was melt processed in an extruder similar to Experiment- 1. The extruder used in this example had a similar configuration as that of the extruder described in Experiment- 1, but the temperatures in the four zones were different from those as exemplified in Experiment- 1. The temperatures were 150° C in the first zone, 230° C in the second zone, 250° C in the third zone, and 260° C in the fourth zone.

The amounts of HDPE, UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene taken during the experimentation are summarized in Table-5.

Table 5

Extrusion Condition: Temperature: 150-230-250-260° C; RPM: 90, MFI Measurement: Temp.:230° C and Load used: 10 kg From Table-5, it is observed that, the melt flow index of the POM-1 and the POM-4 is less than that of the POM-0 and the POM-3.

Rheological properties like melt viscosity (η), shear modulus (G) , and various molecular weights namely number average molecular weight (M_n), weight average molecular weight (M_w), Z-average molecular weight (M_z), Z+l -average molecular weight (M_z+1), and molecular weight distribution (MWD) of the samples (POM-0, POM-1 , POM-3, and POM-4) estimated from rheological plots are summarized in Table-6 Table-6

Referring to Table-6, it is observed that, the rheological properties i.e. melt viscosity and shear modulus of the samples POM- 1 and POM-4 are distinctly greater than that of POM-0 and POM-3.

Conclusion:

Results reveals that the quantity of UHMWPE in presence and absence of decalin influence the melt rheological properties of modified HDPE ( i.e increase in melt viscosity & shear modulus) and accordingly observed a rise in the molecular weight of the modified sample after modification.

Experiment-3:

Different quantities of UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to 150 g of HDPE and melt processed in an extruder to achieve maximum melt viscosity. The amounts of HDPE, UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene taken during the experimentation are tabulated in Table-7.

Table-7

From Table-7, it is observed that, after adding UHMWPE to HDPE, the MFI of the samples (PPS-0 to TPPS-4) decreased significantly from PPS-0 to TPPS-4.

Experiment-4:

Different quantities of UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to 150 g of HDPE and melt processed in an extruder to produce modified HDPE (high melt strength HDPE).

The amounts of HDPE, UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene taken during the experimentation are summarized in Table-8.

Table-8

HDPE-2 150 5 1.0 20 50 0.25 0.477

HDPE-3 150 5 1.0 20 50 1.0 0.518

Referring to Table-8, it can be observed that, the melt flow index of the samples (HDPE-1 to HDPE-3) did not change significantly in the presence and the absence of decalin.

Conclusion:

The presence or the absence of decalin does not affect the melt flow index of the modified HDPE.

Experiment-5:

Different quantities of UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to 150 g of HDPE and melt processed in an extruder to produce modified HDPE (high melt strength HDPE). The amounts of HDPE, UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene taken during the experimentation are summarized in Table-9.

Table-9

Referring to Table-9, it is observed that, the presence of UHMWPE reduced the melt flow index of the samples (HDPE-4 to HDPE-7) significantly. Further, it is observed that the presence of UHMWPE, decalin, and montmoriUonite reduced the melt flow index of the sample (HDPE-7) to a greater extent when compared to the other samples (HDPE-0 to HDPE-6).

Conclusion: The presence of UHMWPE, decalin, and montmoriUonite facilitates in the reduction of the melt flow index. Basically, reduction in the melt flow index signifies the enhancement in melt viscosity leading to produce high melt strength HDPE as found in the results of Table-9. On the other hand, MFI is inversely related to molecular weight of polymer and is used as indicator of melt strength enhancement of polyolefin (i.e. Polypropylene /PE) during the course of its modification.

Experiment-6:

Different quantities of UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to 150 g of HDPE and melt processed in an extruder to produce modified HDPE (high melt strength HDPE). The amounts of HDPE, UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene taken during the experimentation are summarized in Table- 10.

Table-10

Referring to Table- 10, it is observed that, the absence of montmoriUonite and decalin increases the melt flow index of the sample (HDPE-9). Further, it is observed that the absence of decalin and the presence of montmoriUonite were effective in reducing the melt flow index of the sample/s (HDPE-8). Conclusion:

Decalin can be an option but not indispensable in order to modify the macromolecular structure of HDPE, thereby obtaining the desired melt rheological characteristics of the modified HDPE.

Experiment-7 1kg of high melt strength HDPE was prepared by adding UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene to HDPE. After obtaining the modified HDPE, the modified HDPE (PPS-4) was molded to determine the mechanical properties like tensile modulus TM, tensile strength at yield, and tensile strength (TS). The mechanical properties of PPS-0 and PPS-4 are summarized in Table-11.

Table-11

Referring to Table-11, it is found that the tensile modulus, the yield strength, and the tensile strength (TS) of the sample (PPS-4) increased after blending UHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene with HDPE.

Hence, it can be concluded that on modifying HDPE, the tensile modulus, tensile yield strength, and tensile strength (TS) of the samples increase. Experiment-8:

Different quantities of DUHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene were added to HDPE and melt processed in an extruder to produce a modified HDPE (high melt strength HDPE). The amounts of HDPE, the DUHMWPE, polyethylene glycol, decalin, montmoriUonite, and high melt flow index polypropylene taken during the experimentation are summarized in Table- 12.

Table-12

Referring to Table-12, it is found that the MFI of HDPE- 13 reduced significantly at lower doses of the DUHMWPE.

Conclusion:

The DUHMWPE reduces the melt flow index of the samples, effectively, even while using lower doses of the DUHMWPE as compared to UHMWPE.

Experiment-9: PP was modified in the same process as described in Experiment- 1.

Homo-PP was modified alone and in combination with HDPE comprising 5 wt% based on primary plain homo PP alone or PP in combination with HDPE as an additive along with 0.1 wt % di(3,4-dimethylbenzylidene)sorbitol (i.e. Millad 3988) as nucleator, polyethylene glycol (PEG) as a lubricant, and montmoriUonite as a reinforcing agent. Detail composition is described in Table- 13. Properties like MFI, melt viscosity were measured before & after modification as shown in table- 13. Besides plain & modified PP samples were used to prepare molded samples to measure mechanical properties i.e. tensile strength & tensile modulus as summarized in the same Table- 13.

Table-13

Referring to Table-13, it is observed that the MFI of the samples reduced from MPP-0 to MPP-3, and the melt viscosity of the samples increased from MPP-0 to MPP-3.

It is found that the MFI reduction for the modified PP matrix is not significant when compared to the modified HDPE matrix. However, the tensile strength and the tensile modulus of the modified PP increased significantly as compared to modified HDPE.

Similarly, Polypropylene was modified using DUHMWPE as a potential additive. The properties of the modified polypropylene PP are summarized in Table-14. Table-14

Referring to Table- 13 and Table-14, it can be concluded that, modification of PP results in reduction of the melt flow index of the samples, effectively, by using lower doses of the DUHMWPE as compared to UHMWPE. It can be concluded that the tensile strength and the tensile modulus of the samples increase, significantly, on modification of PP, using lower doses of the DUHMWPE as compared to that of UHMWPE.

Experiment- 10: Polypropylene was modified with UHMWPE and DUHMWPE under conditions similar to Experiment 1. Modified samples of the polypropylene (PP-0 to PP-2) were molded to determine the mechanical properties like tensile modulus and tensile strength of the samples (PP-0 to PP-2). Effects of UHMWPE and the DUHMWPE on the samples are summarized in Table- 15.

Table-15

Referring to Table-15, it can be concluded that DUHMWPE increases the tensile strength (TS) and the tensile modulus (TM) of the samples, significantly, by using lower doses of the DUHMWPE as compared to higher doses of UHMWPE. This is due to the high degree of entanglement of UHMWPE, thereby affecting the dispersion of UHMWPE in the modified polypropylene .

The melt flow index of the high melt strength polyolefin prepared in Experiments 1 to 8 is reduced by at least 6 times of melt flow index of the polyolefin.

In accordance with the present disclosure, the melt flow index of the high melt strength polyolefin is reduced by at least 6 times and up to 40 times of the melt flow index of the polyolefin. The melt viscosity of the high melt strength polyolefin prepared in Experiments 1 to 8 is increased by at least 5 times of the melt viscosity of the polyolefin.

In accordance with the present disclosure, the melt viscosity of the high melt strength polyolefin is increased by at least 5 times and up to 40 times of the melt viscosity of the polyolefin.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for preparing high melt strength polyolefin that:

- uniformly disperses ultra-high molecular weight polyethylene in the polyolefin matrix having melt compatibility and without any phase separation;

- can provide modified polyethylene suitable to be processed using various processing techniques such as thermoforming, blow molding, and the like, to produce multifarious products having improved strain hardening, melt strength , sagging resistance etc. ; and

- is simple and economical.

The foregoing description of the specific embodiments so fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

A process for the preparation of high melt strength polyolefin composition, said process comprising melt blending at least one polyolefin, ultra-high molecular weight polyethylene (UHMWPE) in the range of 0.5 phr to 45 phr of said at least one polyolefin, and at least one additive selected from the group consisting of a lubricant, a plasticizer, a filler, and a processing aid to obtain said high melt strength polyolefin,

wherein said at least one polyolefin is selected from the group consisting of homopolymers and copolymers of long chain branched polyethylene, linear polyethylene, high density polyethylene (HDPE), ultra-low density polyethylene (ULDPE), very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high molecular weight high density polyethylene (HMHDPE), and polypropylene, - said lubricant is in an amount in the range of 0.5 phr to 20 phr of said at least one polyolefin,

said plasticizer is in an amount in the range of 5 phr to 30 phr of said at least one polyolefin,

said filler is in an amount in the range of 0.5 phrto 10 phr of said at least one polyolefin, and

said processing aid is in an amount in the range of 5 phr to 40 phr of said at least one polyolefin.

The process as claimed in claim 1, wherein the melt blending is achieved by extrusion.

The process as claimed in claim 1 , wherein said ultra-high molecular weight polyethylene is at least one of entangled ultra-high molecular weight polyethylene and disentangled ultra-high molecular weight polyethylene.

The process as claimed in claim 1 , wherein said lubricant is at least one selected from the group consisting of silicone oil, paraffin wax, oxidized polyethylene, metal stearate, fatty acid amides, oleoylpalmitamide, and polyethylene glycol.

The process as claimed in claim 1, wherein said plasticizer is decalin.

The process as claimed in claim 1, wherein said filler is a nanoclay.

7. The process as claimed in claim 1, wherein said processing aid is at least one selected from the group consisting of high melt flow index polypropylene and high melt flow index high density polyethylene.

8. The process as claimed in claim 1, wherein the melt flow index of said high melt strength polyolefin is less by at least six times the melt flow index of said at least one polyolefin.

9. The process as claimed in claim 1, wherein the melt viscosity of said high melt strength polyolefin is at least five times the melt viscosity of said at least one polyolefin.

10. High melt strength polyolefin composition prepared by the process as claimed in claim 1.