WO2018078571A1

WO2018078571A1 - Ethylene based disentangled polymers and a process for preparing them

Info

Publication number: WO2018078571A1
Application number: PCT/IB2017/056678
Authority: WO
Inventors: Mahuya BAGUI; Yogesh Popatrao PATIL; Viralkumar PATEL; Raksh Vir Jasra; Ajit Behari Mathur; Satya Srinivasa Rao GANDHAM; Devesh Kumar SHUKLA
Original assignee: Reliance Industries Limited
Priority date: 2016-10-27
Filing date: 2017-10-27
Publication date: 2018-05-03

Abstract

The present disclosure relates to an ethylene based disentangled polymer and a process for preparing the same, having predetermined modality. The process comprises polymerization of at least one olefinic monomer in the presence of a catalyst composition. The process for preparing ethylene based disentangled polymer having predetermined modality, includes the step of controlling the addition of a predetermined amount of a molecular weight regulator at appropriate stages of the polymerization reaction and for a predetermined period of time.

Description

ETHYLENE BASED DISENTANGLED POLYMERS AND A PROCESS FOR

PREPARING THEM

FIELD

The present disclosure relates to ethylene based disentangled polymers and a process for preparing them.

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. Ethylene based disentangled polymer: The term 'ethylene based disentangled polymer' refers to homo-polymer(s) or copolymer(s) of ethylene having molar mass in the range of 0.1 million to 25 million; 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 ethylene based disentangled polymer is characterized by increase in its elastic modulus, represented by a ratio of GVGo (G'is the elastic modulus at any point in the curve and Go is the initial elastic modulus) with time above the melt temperature of the ethylene based disentangled polymer when tested on strain controlled rheometer having parallel plate assembly as disentangled polymer chains tend to entangle on application of shearing in a sinusoidal test. The typical test results of change in the elastic modulus of the ethylene based disentangled polymer are illustrated in figure 1, wherein the elastic modulus is observed to increase with time when tested by strain controlled rheometer using 8 mm parallel plate geometry (with the test conditions as follows: Temperature: 180 °C, Frequency: 10 rad/sec, Strain: 0.5%). The sample of the ethylene based disentangled polymer (1 mm thick) for the test was prepared by compression molding at 125 °C and at a pressure of 200 bar. Modality: It refers to the form of molecular weight distribution (MWD) curve of the polymer, i.e., the appearance of the graph of the polymer weight fraction as a function of its molecular weight.

Molecular weight: Molecular weight is the mass of a molecule. The term 'molecular weight' used in the present disclosure is the weight average molecular weight (Mw) Determination of 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 8 mm 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 °C 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.

BACKGROUND A polymer with ease of processability along with balanced solid state properties is preferred for commercial acceptability. While tailoring a polymer to achieve desired solid state properties by increasing molecular weight, the processibility is sacrificed due to high melt viscosity. Conversely, on improving the melt processibility of a polymer by lowering its molecular weight, the solid state properties are adversely affected. One way to address this problem is by producing polymer fractions with two or more molecular weight ranges and homogenizing them at molecular level. However, the available homogenization techniques have their limitations, and they are highly energy intensive. It is also difficult to achieve complete homogenization, when the molecular weights of the polymer fractions are widely different from each other. Another method for producing polymers with polymer fractions having two or more molecular weight ranges and homogenizing them at molecular level is to grow the polymer chains of widely different molecular weights on the same catalyst composition site. Further, it is essential to achieve high degree of molecular level homogenization of the widely different molecular weight fractions during polymerization itself, while allowing the polymer chains of different molecular weights to grow on the same catalyst composition. Such polymers may find very wide acceptability due to very high performance to cost ratio.

There is, therefore, felt a need to provide a process for preparing an ethylene based disentangled polymer having predetermined modality with molecular level homogeneity of different molecular weight fractions having different molecular weight ranges in the polymer matrix. OBJECTS

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

An object of the present disclosure is to provide a process for preparing ethylene based disentangled polymer.

Another object of the present disclosure is to provide a process for preparing multimodal, specifically bimodal ethylene based disentangled polymer.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure. SUMMARY

In one aspect, the present disclosure provides ethylene based disentangled polymer a process for preparing ethylene based disentangled polymer, more specifically ethylene based disentangled polymer having predetermined modality. The process comprises polymerizing at least one olefinic monomer in the presence of a catalyst composition. The process includes the step of controlling the addition of a predetermined amount of a molecular weight regulator at appropriate stages of the polymerization reaction and for a predetermined period of time.

In second aspect, there is provided ethylene based disentangled polymer obtained by the process described herein above. In third aspect, there is provided a process for preparing a multimodal ethylene based disentangled polymer. The process for preparing the multimodal ethylene based disentangled polymer is at least two step reaction, and the molecular weight regulator is added in at least one of the steps of the polymerization reaction. The ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of the molecular weight regulator is in the range of 4: 1 to 100: 1. Each step of the polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes. In fourth aspect, there is provided a process for preparing a bimodal ethylene based disentangled polymer. The process for preparing the bimodal ethylene based disentangled polymer is a two-step reaction and the molecular weight regulator is added in any one of the step of the polymerization reaction. The ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of the molecular weight regulator is in the range of 4: 1 to 100: 1. Each step of the polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

In one embodiment, the process for preparing the bimodal ethylene based disentangled polymer is a two-step reaction, a first step and a second step, and the molecular weight regulator is added in the first step of the polymerization reaction.

In another embodiment, the process for preparing the bimodal ethylene based disentangled polymer is a two-step reaction, is a two-step reaction, a first step and a second step, and the molecular weight regulator is added in the second step of the polymerization reaction. In sixth aspect, there is provided a process for preparing an unimodal ethylene based disentangled polymer. The process for preparing the unimodal ethylene based disentangled polymer is a single step reaction and the molecular weight regulator is added at the start of the reaction. The ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of the molecular weight regulator is in the range of 4: 1 to 100:1. The polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

The molecular weight regulator used in the process is at least one selected from the group consisting of hydrogen, and metal alkyl, typically hydrogen. The catalyst composition comprises a pro-catalyst, a co-catalyst, and the polymerization takes place in a fluid medium. The fluid medium can be at least one fluid medium selected from the group consisting of pentane, hexane, cyclohexane, methyl cyclohexane, heptane, octane, decane, toluene, isopentane and mineral spirit. The pro-catalyst is a single Schiff base imine or phenoxy imine based homogeneous catalyst comprising titanium. The co-catalyst is an organoaluminum compound. In accordance with the embodiments of the present disclosure, the polymerization is carried out in a phase, selected from the group consisting of slurry phase and gas phase, using single or multiple reactor systems.

In accordance with the embodiments of the present disclosure, the polymerization is carried out in a mode selected from the group consisting of batch mode, continuous mode and semi continuous mode.

In fifth aspect, there is provided an ethylene based disentangled polymer. The ethylene based disentangled polymer of the present disclosure comprises one fraction having molecular weight in the range of 0.04 million g/mole to 1.44 million g/mole , and other fractions having molecular weight in the range of 1.45 million g/mole to 8.0 million g/mole.

The molecular weight of the unimodal ethylene based disentangled polymer is in the range of 0.05 g/mole 1.0 million g/mole.

In an embodiment of the present disclosure, the olefinic monomer is ethylene.

In another embodiment of the present disclosure, the olefinic monomer is a mixture of ethylene and at least one a-olefin selected from the group consisting of propylene, 1-butene, and 1-hexane.

The bimodal ethylene based disentangled polymer of the present disclosure is either polyethylene or ethylene co-polymer, wherein the co-monomer is at least one a-olefin selected from the group consisting of propylene, 1-butene, and 1-hexane. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The process of the present disclosure will now be described with the help of the accompanying drawing, in which:

Figure 1 illustrates a graph of variation of elastic modulus of ethylene based disentangled polymer with time. Figure 2(a) illustrates molecular weight distribution curves of the ethylene based polymer obtained in experiments 2 to 4 along with the molecular weight distribution curves of HDPE and DUHMWPE (comparative examples 7 and 8 respectively). Figure 2(b) illustrates molecular weight distribution curves of the ethylene based polymer obtained in experiments 5 and 6 along with the molecular weight distribution curves of HDPE and DUHMWPE (comparative examples 7 and 8 respectively).

Figure 2(c) illustrates molecular weight distribution curves of the ethylene based polymer obtained in experiments 1 and 4 along with the molecular weight distribution curves of HDPE and DUHMWPE (comparative examples 7 and 8 respectively); and

Figure 3 illustrates molecular weight distribution curves of the ethylene based polymer obtained in experiments 17 to 19 along with the molecular weight distribution curve of DUHMWPE (comparative examples 8). DETAILED DESCRIPTION

High molecular weight polymers possess the desired solid state properties. However, the processibility of such polymers is limited due to very high melt viscosity. Polymers having the desired solid state properties and high processibility are desired. The present disclosure envisages a process for preparing ethylene based disentangled polymer having a predetermined modality with molecular level homogeneity of different molecular weight fractions. Such polymers can have high ease of processability.

In one aspect, the present disclosure provides a process for preparing ethylene based disentangled polymer, more specifically ethylene based disentangled polymer having predetermined modality. The process comprises polymerizing at least one olefinic monomer in the presence of a catalyst composition, while controlling the addition of a predetermined amount of a molecular weight regulator at appropriate stages of the polymerization reaction and for a predetermined period of time.

In second aspect, there is provided ethylene based disentangled polymer obtained by the process described herein above. The ethylene based polymer produced using the process of the present disclosure can either be unimodal or multimodal, more specifically bimodal.

In third aspect, there is provided a process for preparing a multimodal ethylene based disentangled polymer. The process for preparing the multimodal ethylene based disentangled polymer is at least two step reaction and the molecular weight regulator is added in at least one of the steps of the polymerization reaction. The ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of the molecular weight regulator is in the range of 4: 1 to 100: 1. Each step of the polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

In fourth aspect, there is provided a process for preparing a bimodal ethylene based disentangled polymer. The process for preparing the bimodal ethylene based disentangled polymer is a two-step reaction and the molecular weight regulator is added in any one of the step of the polymerization reaction. The ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of the molecular weight regulator is in the range of 4: 1 to 100: 1. Each step of the polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

In one embodiment, the process for preparing the bimodal ethylene based disentangled polymer comprises the following steps:

In the first step, at least one olefinic monomer and the molecular weight regulator are introduced in a reactor containing a catalyst composition, to attain a pressure in the range of 1 bar to 20 bar to obtain a first mixture.

Next, the olefinic monomer is polymerized by agitating the first mixture at a temperature in the range of 10 to 65 °C, for a time period in the range of 5 to 150 minutes. After a predetermined time of agitating, gases are vented off from the reactor to obtain a first slurry.

In the next step, a fresh charge of the olefinic monomer is introduced into the reactor comprising the first slurry to attain a pressure in the range of 1 bar to 20 bar to obtain a second mixture. The olefinic monomer is polymerized by agitating the second mixture at a temperature in the range of 10 to 65 °C, for a time period in the range of 5 to 150 minutes to obtain a second slurry comprising the bimodal ethylene based disentangled polymer.

The bimodal ethylene based disentangled polymer is separated from the second slurry and dried. In another embodiment, the process for preparing the bimodal ethylene based disentangled polymer comprises the following steps:

In the first step, at least one olefinic monomer is introduced in a reactor containing a catalyst composition, to attain a pressure in the range of 1 bar to 20 bar to obtain a first mixture. Next, the olefinic monomer is polymerized by agitating the first mixture at a temperature in the range of 10 °C to 65 °C for a time period in the range of 5 minutes to 300 minutes to obtain a first slurry.

In the next step, a fresh charge of the olefinic monomer and the molecular weight regulator are introduced into the reactor comprising the first slurry to attain a pressure in the range of 1 bar to 20 bar to obtain a second mixture.

The olefinic monomer is polymerized by agitating the second mixture at a temperature in the range of 10 °C to 65 °C for a time period in the range of 5 minutes to 300 minutes to obtain a second slurry comprising the bimodal ethylene based disentangled polymer.

The bimodal ethylene based disentangled polymer is separated from the second slurry and dried.

In fifth aspect, there is provided a process for preparing an unimodal ethylene based disentangled polymer. The process for preparing the unimodal ethylene based disentangled polymer is a single step reaction and a molecular weight regulator is added at the start of the reaction. The ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of the molecular weight regulator is in the range of 4: 1 to 100: 1. The polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

The process for the preparation of the unimodal ethylene based disentangled polymer comprises the following steps: Initially, at least one olefinic monomer and a molecular weight regulator are introduced in a reactor containing a catalyst composition, to attain a pressure in the range of 1 bar to 20 bar to obtain a mixture. Next, the olefinic monomer is polymerized by agitating the mixture at a temperature in the range of 10 °C to 65 °C for a time period in the range of 5 minutes to 300 minutes to obtain a slurry comprising the unimodal ethylene based disentangled polymer.

The unimodal ethylene based disentangled polymer is separated from the slurry and dried. In an embodiment of the present disclosure, the olefinic monomer is ethylene.

In another embodiment of the present disclosure, the olefinic monomer is a mixture of ethylene and at least one a-olefin selected from the group consisting of propylene, butene, and hexane.

In accordance with the embodiments of the present disclosure, the ethylene based polymers could be either polyethylene or ethylene co-polymer, wherein co-monomer is at least one a- olefins selected from the group consisting of propylene, 1 -butene, and 1-hexene.

The terminating agent is at least one selected from the group consisting of hydrogen, and metal alkyl, preferably hydrogen.

Further, the catalyst composition of the present disclosure comprises a pro-catalyst, a co- catalyst and the polymerization takes place in a fluid medium. The pro-catalyst of the present disclosure is a single Schiff base imine or phenoxy imine based homogeneous catalyst represented by Formula I, and is a subject matter of patent application number WO2014170913.

Formula I The co-catalyst is at least one selected from the group consisting of triethylaluminum, tridecylaluminum, tri-n-butylaluminum, tri-isopropylaluminum, tri-isoprenylaluminum, tri- isobutylaluminum, ethyl aluminum sesquichloride, diethylaluminum chloride, di-isobutyl aluminum chloride, triphenylaluminum, tri-n-octylaluminum tri-n-decylaluminum, methylaluminoxane and polymethylaluminoxane.

Further, the molar ratio of the amount of the elemental aluminum to elemental titanium in the pro-catalyst can be in the range of 50: 1 to 1000:1.

In accordance with one embodiment, the molar ratio of the amount of the elemental aluminum to elemental titanium in the pro-catalyst composition is 225: 1. The fluid medium can be at least one selected from the group consisting of pentane, hexane, cyclohexane, methyl cyclohexane, heptane, octane, decane, toluene, isopentane and mineral spirit.

The bimodal ethylene based disentangled polymer of the present disclosure is characterized by a molecular weight in the range of 0.05 million g/mole to 8 million g/mole, the bulk density in the range of 0.05 to 0.12 g/cc, crystallinity in the range of 85-98%, melting point in the range of 138 °C to 142 °C and heat of fusion of greater than 190 J/g.

The ethylene based disentangled polymer of the present disclosure comprises one fraction having molecular weight in the range of 0.04 million g/mole to 1.44 million g/mole , and other fraction having molecular weight in the range of 1.45 million g/mole to 8.0 million. The molecular weight of the ethylene based disentangled polymer, wherein the modality is unimodal is in the range of 0.05 g/mole 1.0 million g/mole.

The bimodal ethylene based disentangled polymer of the present disclosure comprises a polymer fraction having high molecular weight, as well as, a polymer fraction having lower molecular weight. The different polymer fractions of are homogeneous, as they are developed on a single catalyst site. The fraction of the high molecular weight ethylene based polymer helps to maintain the desired physical properties of the polymer and the fraction of low molecular weight ethylene based polymer helps in easy processing of the polymer. The polymerization reaction of the present disclosure is carried out in at least one phase selected from the group consisting of slurry phase and gas phase using single or multiple reactor systems.

The polymerization reaction of the present disclosure is carried out in at least one mode selected from the group consisting of batch mode, continuous mode and semi continuous mode.

The present disclosure is further described in light of the following 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

Experiments 1 to 6: Process for preparing bimodal ethylene based disentangled polymer

Experiments 1 to 6 were carried out for the preparation of bimodal disentangled polyethylene in accordance with the present disclosure, wherein the hydrogen was added during the first stage polymerization reaction.

(i) First step

A reactor fitted with an agitator was charged with 500 mL hexane, 1.6 mL polymethylalummoxane (PMAO) solution (15 wt% solution of PMAO in toluene), and 9 mg pro-catalyst composition (Schiff base imine or phenoxy imine based homogeneous catalyst composition of formula I) to obtain a catalyst composition (Al/Ti ratio ~ 225) in hexane. Ethylene and hydrogen were introduced into the reactor, to attain a total pressure of 6 bar to obtain a first reaction mixture. The partial pressure of hydrogen used for experiments 1 to 6 is provided in Table 1. The first reaction mixture was polymerized at 55 °C for a time period mentioned in Table 1 with agitation, followed by venting off the gases from the reactor to obtain a slurry.

(ii) Second step

A new charge of ethylene was introduced into the reactor containing the slurry, till a pressure of 6 bar was reached to obtain a second reaction mixture. The second reaction mixture was polymerized at 55 °C, while agitating, to obtain a product mixture comprising the bimodal disentangled polyethylene. Bimodal disentangled polyethylene was separated and was dried.

The total time period of polymerization including the first step and the second step for experiments 1 to 6 was 180 minutes. Table 1 summarizes selected process parameters and properties of the bimodal disentangled polyethylene obtained in experiments 1 to 6. These properties of bimodal disentangled polyethylene are compared with the properties of disentangled ultra high molecular weight polyethylene (DUHMWPE) and commercial high density polyethylene (HDPE).

Table 1: Selected process parameters and properties of polyethylene obtained in experiments 1 to 6 with HDPE and UHMWPE

The bimodal disentangled polyethylene obtained by the process of the present disclosure exhibited the presence of high molecular weight polyethylene ranging from 22 wt% to 74 wt% and low molecular weight polyethylene in the range of 26 wt% to 78 wt%. The proportion of the high molecular weight polyethylene and the low molecular weight polyethylene was found to be dependent upon the time period of the first stage polymerization and the amount of the hydrogen.

It is observed that the amount of high molecular weight polyethylene decreased upon increasing the time of polymerization of the first stage, which is carried out in the presence of hydrogen. The amount of hydrogen also played a vital role in determining the molecular weight of the polyethylene. On decreasing the amount of hydrogen, the amount of the high molecular weight polyethylene increased. The bulk density of the polyethylene obtained in experiments 1 to 6 was found to be between 0.08 to 0.09 g/cc.

The solid state properties of the bimodal disentangled polyethylene obtained in experiments 1 to 6 are summarized in Table 2.

Table 2: Solid state properties of bimodal polymer obtained in experiment 1 to 6

Bimodal

disentangled polyethylene obtained in experiments 1 to 6 was observed to exhibit crystallinity ranging from 87.9 to 94.3, heat of fusion is in the range of 198.9 to 207.5 J/g. T_m was in the range of 138.9 to 140.9 °C, which indicated that polyethylene obtained by the process of the present disclosure was disentangled in nature. Figure 2(a), 2(b), and 2(c) illustrates the molecular weight distribution curves of polyethylene obtained in experiments 1 to 6 along with that of comparative examples 7 and 8 (HDPE and DUHMWPE).

Experiments 9 to 12: Process for preparing bimodal ethylene based disentangled polymer Experiments 9 to 12 were carried out for the preparation of bimodal disentangled polyethylene in accordance with the present disclosure, wherein the hydrogen was added in the second step.

(i) First step

A reactor fitted with an agitator was charged with 500 mL of hexane, 1.6 mL PMAO solution (15 wt% solution of PMAO in toluene), and 9 mg pro-catalyst composition (Al/Ti ratio ~ 225) to obtain a catalyst composition in hexane. Ethylene was introduced into the reactor to attain a pressure of 6 bar to obtain a first reaction mixture. Ethylene was polymerized by agitating the first reaction mixture at a temperature 55 °C. The gaseous mixture from the reactor was vented out to obtain a slurry. (i) Second step

The reactor was pressurized with ethylene and hydrogen to attain a total pressure of 6 bar to obtain a second reaction mixture. The partial pressure of hydrogen is provided in Table 3. Ethylene was polymerized by agitating the second reaction mixture at 55 °C for a time period provided in Table 3 to obtain a product mixture. Bimodal disentangled polyethylene was separated from the product mixture and was dried.

The total time period of polymerization including the first stage and the second stage for experiments 9 to 12 was 180 minutes.

Table 3 summarizes selected process parameters of bimodal disentangled polyethylene obtained in experiments 9 to 12 with disentangled ultra high molecular weight polyethylene (DUHMWPE of Exp. 8) and commercial high density polyethylene (HDPE of Exp.7).

Table 3: Selected process parameters and the properties of bimodal disentangled

polyethylene obtained in experiments 9 to 12 Exp. H₂ (bar) Time Bulk HMW LMW %, MW

(min.) of density %, (Mw) (Mw) D first stage (g/cc) million million

g/mole g/mole

9 1 90 0.10 71 (4.47) 29 (0.07) 190

10 1 120 0.11 51 (2.77) 49 (0.04) 272

11 1 135 0.11 84 (1.83) 16 (0.04) 93.7

12 1 150 0.09 93 (1.45) 07 (0.06) 36.5

7* 0.4 100

(0.20)

§** - - 0.12 100 (4.9) - 15.8

HMW- high molecular weight, LWD- low molecular weight, MWD- molecular weight

distribution

^Comparative example (HOPE)

^^Comparative example (DUHMWPE)

*^■*^■*^■ Total time of first stage polymerization and second stage polymerization - 180 minutes

The bimodal disentangled polyethylene obtained in experiments 9 to 12 comprises the high molecular weight polyethylene ranging from 51 wt% to 93 wt% and the low molecular weight polyethylene ranging from 07 wt% to 49 wt%. The proportion of the high molecular weight polyethylene and the low molecular weight polyethylene was found to be dependent on polymerization time in the presence or in the absence of hydrogen. The solid state properties of the bimodal disentangled polyethyelene obtained in experiments 9 to 12 are summarized in Table 4.

Table 4: Selected solid state properties of polyethylene obtained in experiment 9 to 12

Exp. Crystallinity (%) ΔΗ (J/g) T_m (°C)

9 91.6 200.1 141.4

10 92.3 213.4 140.7

11 92.9 207.9 139.7

12 94.3 205.9 139.5

7* 50-60 - -

§** 92.4 210.3 141.2 ^Comparative example - HDPE

^Comparative example - DUHMWPE

Polyethylene obtained in experiments 9 to 12 exhibited crystallinity ranging from 91.6% to 94.3%, heat of fusion in the range of 200.1 to 213.4 J/g and T_m in the range of 139.5 to 141.4 °C, which indicate polyethylene obtained by the process of the present disclosure is disentangled in nature.

Experiment 13 to 16: Process for preparing bimodal ethylene based disentangled polymer

Experiments 13 and 14 were performed using the experimental procedure of experiments 1 to 6, except the following material and parameters: Co-catalyst composition- PMAO was replaced with MAO (methylaluminoxane) 0.9 mL solution (11 wt% MAO in toluene), the amount of pro-catalyst composition - 5 mg, and

Al/Ti ratio - 200.

Experiments 15 and 16 were performed using the experimental procedure of experiments 9 to 12, except the following material and parameters:

Co-catalyst composition- PMAO was replaced with MAO (methylaluminoxane) 0.9 mL solution (11 wt% MAO in toluene), the amount of pro-catalyst composition - 5 mg, and

Al/Ti ratio - 200.

Table 5: Selected process parameters and the properties of polyethylene obtained in experiments 13 to 16

The bimodal disentangled polyethylene obtained in experiments 13 to 16 comprise high molecular weight polyethylene ranging from 42 wt to 82 wt and low molecular weight polyethylene ranging from 18 wt to 58 wt .

The solid state properties of the bimodal disentangled polyethylene obtained in experiments 13 and 15 are summarized in Table 6.

Table 6: Solid state properties of polymer fractions obtained in experiments 13 and 15 heat of

Sample Crystallinity (%) Tm (°C)

fusion (J/g)

13 89.4 202.3 140.4

15 93.7 209.9 139.9

50-60 - -

§** 92.5 190.1 141.7

^Comparative example HDPE

^Comparative example (DUHMWPE)

Experiments 17 to 19: Process for the preparation of unimodal disentangled polyethylene in accordance with the present disclosure.

Experiment 17 and 18 : A reactor fitted with an agitator was charged with 500 mL hexane, 1.6 mL polymethylaluminoxane (PMAO) solution (15 wt% solution of PMAO in toluene), and 9 mg pro-catalyst to obtain a catalyst composition (Al/Ti ratio ~ 225). Ethylene and hydrogen were introduced into the reactor to attain a total pressure of 6 bar to obtain a mixture. The partial pressure of hydrogen is provided in Table 7. The mixture was polymerized at 55 °C for 180 minutes to obtain a slurry comprising unimodal disentangled polyethylene. The unimodal disentangled polyethylene was separated and dried. Experiment 19: Further, for preparing the unimodal polyethylene of experiment 19, the experimental procedure of experiments 17-18 was followed except the following changes: The co-catalyst PMAO was replaced with MAO (l lwt solution of MAO in toluene), quantity of pro-catalyst was 5 mg, and Al/Ti ratio was 200.

Table 7: Selected process parameters and the properties of polymer fractions obtained in experiments 17 to 19

Sample H₂ (bar) Time Bulk Mw, MWD

(min.) density million

(g/cc) g mole

17 1 180 0.08 0.21 2.91

18 0.3 180 0.08 0.44 1.83

19 1 180 0.06 0.42 2.82

7* - - 0.4 0.15 12.6 §** - 180 0.12 4.9 15.80

Comparative example 7 (HDPE)

**Comparative example 8 (DUHMWPE)

The molecular weight of polyethylene obtained in experiments 17 to 19 is in the range of 0.21 to 0.44 million g/mole, and bulk density is in the range of 0.06 to 0.08 g/cc.

Table 7: Solid state properties of polymer fractions obtained in experiments 17 and 18

Figure 3 illustrates molecular weight distribution curves of polyethylene obtained in experiments 17 to 19 along with that of comparative examples 8 (DUHMWPE). From experiments 17-19, it is evident that on performing the polymerization in a single step using hydrogen, unimodal disentangled polyethylene is produced. Therefore, the process of the present disclosure provides a choice to prepare the disentangled polyethylene having predetermined modality.

Articles of different size and shapes were prepared by continuous molding process such as extrusion and cyclic molding process like injection molding from ethylene based disentangled polymer. The articles prepared were tape, film, pipe, and sheet.

A comparative bimodal polyethylene blend was prepared by mixing 48 wt% of polyethylene of comparative experiments 7 and 52 wt% polyethylene of experiment 8. The mixture was homogenized by heating under stirring. Before mixing, the two fractions were bought into disentangled state for better mixing. The mixing process required high shear work and temperature, thereby requiring significantly higher energy. Similar articles were prepared from the comparative bimodal polyethylene blend.

It was observed that the bimodal disentangled polyethylene of experiment 6 has a superior processability for extrusion and injection molding, as compared to the conventionally prepared comparative bimodal polyethylene blend. It was observed that the melt viscosity of the disentangled polyethylene of the present disclosure was lower, which is due to the higher residual chain disentanglement.

Further, the articles prepared using the bimodal disentangled polyethylene of experiment 6, were found to be tough, flexible and sturdy. On the contrary, the articles prepared using the comparative conventional bimodal polyethylene blend, were found to be hard and brittle.

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 producing an ethylene based disentangled polymer with a predetermined modality; and

• an ethylene based disentangled polymer with a predetermined modality that can be easily processed.

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 invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment 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

CLAIMS:

1. A process for preparing an ethylene based disentangled polymer having predetermined modality, said process comprising polymerization of at least one olefinic monomer in the presence of a catalyst composition, wherein said process includes the step of controlling the addition of a predetermined amount of a molecular weight regulator at appropriate stages of the polymerization reaction and for a predetermined period of time.

2. Ethylene based disentangled polymer prepared by the process as claimed in claim 1.

3. The process as claimed in claim 1, wherein said predetermined modality is multimodal, said polymerization reaction is at least two step reaction and said molecular weight regulator is added in at least one of the steps of said polymerization reaction, wherein the ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of said molecular weight regulator is in the range of 4: 1 to 100: 1, and each step of said polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

4. The process as claimed in claim 1, wherein said predetermined modality is bimodal, said polymerization reaction is a two-step reaction and said molecular weight regulator is added in any one of the step of said polymerization reaction, wherein the ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of said molecular weight regulator is in the range of 4: 1 to 100: 1, and each step of said polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

5. The process as claimed in claim 4, wherein said predetermined modality is bimodal, said polymerization reaction is a two-step reaction, a first step and a second step, and said molecular weight regulator is added in said first step of said polymerization reaction.

6. The process as claimed in claim 4, wherein said predetermined modality is bimodal, said polymerization reaction is a two-step reaction, a first step and a second step, and said molecular weight regulator is added in said second step of said polymerization reaction.

7. The process as claimed in claim 1, wherein said predetermined modality is unimodal, said polymerization reaction is one step reaction and is carried out in the presence of said molecular weight regulator, wherein the ratio of the partial pressure of at least one olefinic monomer being polymerized to the partial pressure of said molecular weight regulator is in the range of 4: 1 to 100:1, and polymerization reaction is carried out at a temperature in the range of 10 to 65 °C and at a pressure in the range of 1 bar to 20 bar for a time period in the range of 5 to 300 minutes.

8. The process as claimed in any one of claims 1, and 3 to 7, wherein said molecular weight regulator is at least one selected from the group consisting of hydrogen, and metal alkyl.

9. The process as claimed in claim 1, wherein said catalyst composition comprises a pro- catalyst, and a co-catalyst; wherein said pro-catalyst is Schiff base imine or phenoxy imine based homogeneous catalyst comprising titanium; and said co-catalyst is an organoaluminum compound.

10. The process as claimed in claim 1, and 3 to 7, wherein said polymerization takes place in at least one fluid medium selected from the group consisting of pentane, hexane, cyclohexane, methyl cyclohexane, heptane, octane, decane, toluene, isopentane and mineral spirit .

11. The process as claimed in claim 1, and 3 to 7, wherein said olefinic monomer is ethylene.

12. The process as claimed in claim 1, and 3 to 7, wherein said olefinic monomer is a mixture of ethylene and at least one a-olefin selected from the group consisting of propylene, butene, and hexane.

13. The process as claimed in claim 1, and 3 to 7, wherein said ethylene based polymers is at least one selected from the group consisting of polyethylene and ethylene co- polymer wherein co-monomer is at least one a-olefin selected from the group consisting of propylene, butene, and hexane.

14. An ethylene based disentangled polymer obtained by the process as claimed in any one of claims 3 to 6, wherein said ethylene based disentangled polymer comprises one fraction having molecular weight in the range of 0.04miHion g/mole to 1.44 million g/mole , and other fraction having molecular weight in the range of 1.45 million g/mole to 8.0 million g/mole.

15. An ethylene based disentangled polymer as claimed in claim 7, wherein said predetermined modality is unimodal, comprises one fraction having molecular weight in the range of 0.05 g/mole 1.0 million g/mole.

16. The process as claimed in any one of claims 1, and 3 to 7, wherein said polymerization is carried out in at least one phase selected from the group consisting of slurry phase and gas phase using single or multiple reactor systems.

17. The process as claimed in any of claims 1 and 3 to 7, wherein said process is carried out in at least one mode selected from the group consisting of batch mode, continuous mode, and semi continuous mode.