Claims:1. In a process for preparing dis-entangled ultra-high molecular weight polyethylene by polymerizing ethylene, in a reactor, in the presence of a catalyst composition provided in an organic liquid medium, said catalyst composition comprising a pro-catalyst and a co-catalyst; wherein said pro-catalyst is at least one selected from the group consisting of a transition metal-Schiff base imine ligand complexes, and said co-catalyst is an organo-aluminium compound;
the improvement comprising the employment of a stirrer having anchor type blades, in said reactor, to obtain dis-entangled ultra-high molecular weight polyethylene (DUHMWPE) having a yield greater than 10 kg of DUHMWPE per gram of said catalyst composition.
2. The process as claimed in claim 1, wherein said transition metal-Schiff base imine ligand complexes are represented by Formula (I),

Wherein, R1, R2, R4, R6, R8, R10 and R12 are independently selected from the group consisting of hydrogen, aryl, heteroaryl and halogen;
R5 and R9 are tertiary alkyl groups;
R7 and R11 are independently selected from the group consisting of hydrogen and tertiary alkyl group;
R3 is selected from the group consisting of hydrogen, halogen, alkoxy, aryloxy, carboxyl and sulphonic acid;
M is a transition metal selected from the group consisting of Hafnium (Hf), Manganese (Mn), Iron (Fe), Rhenium (Re), Tungsten (W), Niobium (Nb), Tantalum (Ta), Vanadium (V), and Titanium (Ti); and
X1 and X2 are independently selected from the group consisting of Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).
3. The process as claimed in claim 2, wherein R5 and R9 are tertiary butyl group, and R7 and R11 are hydrogen.
4. The process as claimed in claim 2, wherein R5, R7, R9, and R11 are tertiary butyl group.
5. The process as claimed in claim 2, wherein M is titanium.
6. The process as claimed in claim 1, wherein said organo-aluminium compound is at least one selected from the group consisting of methylaluminoxane, poly-methylaluminoxane, trimethylaluminium, triethylaluminium and diethylaluminium chloride.
7. The process as claimed in claim 1, wherein the molar ratio of the elemental aluminium of said co-catalyst and the elemental transition metal of said pro-catalyst is in the range of 200:1 to 250:1.
8. The process as claimed in claim 1, wherein said organic liquid medium is at least one selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, toluene and cyclohexane.
9. The process as claimed in claim 1, wherein the polymerization is carried out at an ethylene pressure in the range of 2 bar to 30 bar, and at a temperature in the range of 20° C to 70° C for a time period in the range of 1 hour to 10 hours.
10. The process as claimed in claim 1, wherein the polymerization of ethylene is carried out at a stirring speed in the range of 450 rpm to 700 rpm using said stirrer having said anchor type blades.
11. The process as claimed in claim 1, wherein the DUHMWPE is characterized by the following properties:
• molecular weight distribution in the range of 0.5 to 8.0;
• molecular weight greater than 2 million g/mole;
• crystallinity greater than 90 %;
• enthalpy in the range of 195 J/g to 260 J/g;
• melting temperature in the range of 139° C to 142° C;
• bulk density in the range of 0.05 g/cc to 0.2 g/cc; and
• porous and fibrous morphology. , Description:FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
AND
THE PATENTS RULES, 2003

COMPLETE
SPECIFICATION
(See section 10; rule 13)

A PROCESS FOR PREPARING DIS-ENTANGLED ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE (DUHMWPE)

RELIANCE INDUSTRIES LIMITED
an Indian Company of,
3rd Floor, Maker Chamber-IV
222, Nariman Point, Mumbai – 400021
Maharashtra, India.

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
This is an application for a patent of addition to the Indian Patent Application No. 1440/MUM/2013 filed on 17.04.2013 the entire contents of which are specifically incorporated herein by reference.
FIELD
The present disclosure relates to a process for preparing dis-entangled ultra-high molecular weight polyethylene.
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.
The term ultra-high molecular weight polyethylene (UHMWPE) used hereinafter in the specification refers to a polymer of ethylene having extremely long chains and molar mass of 2 million g/mol and above.
The term dis-entangled ultra-high molecular weight polyethylene (DUHMWPE) used hereinafter in the specification refers to a polymer of ethylene having extremely long chains and molar mass of 2 million g/mol and above, wherein the polyethylene chains have substantially low entanglement.
The term ‘reduced specific viscosity’ (RSV) used hereinafter in the specification refers to the ratio of the specific viscosity increment to the mass concentration of the polymer.
These definitions are in addition to those expressed in the art.
BACKGROUND
Ultra-high molecular weight polyethylene (UHMWPE) has properties such as high abrasion resistance and high impact strength, due to which UHMWPE continues to find increasing industrial and specialty applications, including the automotive and textile engineering, and medical sectors.
High molecular weight of UHMWPE leads to increased entanglement between the polymer chains and therefore limits the properties that can be achieved without such entanglements. Therefore, the preparation of dis-entangled ultra-high molecular weight polyethylene (DUHMWPE) is desired to extract the best out of UHMWPE. DUHMWPE can be used in the making of tapes, films, fibers, as an additive to enhance the performance of many polymers, films for packaging, and thermally conductive products.
Our published patent application No. 1440/MUM/2013 dated 17.04.2013 discloses a process for preparing a transition metal based pro-catalyst, a catalyst composition obtained therefrom, and a process for polymerizing olefins by employing the catalyst composition comprising the transition metal based pro-catalyst to prepare DUHMWPE. However, the conventional processes for the preparation of DUHMWPE are associated with certain drawbacks such as low yield.
There is, therefore, felt a need to provide a process for preparing DUHMWPE with high yield.
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 preparing dis-entangled ultra-high molecular weight polyethylene (DUHMWPE); and
Another object of the present disclosure is to provide a process for preparing DUHMWPE with high yield.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure provides a process for preparing dis-entangled ultra-high molecular weight polyethylene. The process is an improvement, wherein the improvement comprises polymerization of ethylene in a reactor by employing a stirrer having anchor type blades. The polymerization of ethylene is carried out in the presence of a catalyst composition provided in an organic liquid medium. The process of the present disclosure is capable of obtaining a yield greater than 10 kg of DUHMWPE per gram of the catalyst composition.
The catalyst composition comprises a pro-catalyst and a co-catalyst. The pro-catalyst is at least one selected from the group consisting of a transition metal-Schiff base imine ligand complex, and the co-catalyst is an organo-aluminium compound.

The transition metal-Schiff base imine ligand complexes are represented by Formula (I), wherein, R1, R2, R4, R6, R8, R10 and R12 are independently selected from the group consisting of hydrogen, aryl, heteroaryl and halogen; R5 and R9 are tertiary alkyl groups; R7 and R11 are independently selected from the group consisting of hydrogen and tertiary alkyl group; R3 is selected from the group consisting of hydrogen, halogen, alkoxy, aryloxy, carboxyl, and sulphonic acid; M is a transition metal selected from the group consisting of Hafnium (Hf), Manganese (Mn), Iron (Fe), Rhenium (Re), Tungsten (W), Niobium (Nb), Tantalum (Ta), Vanadium (V), and Titanium (Ti); and X1 and X2 are independently selected from the group consisting of Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).
The organo-aluminium compound can be at least one selected from the group consisting of methylaluminoxane, poly-methylaluminoxane, trimethylaluminium, triethylaluminium, and diethylaluminium chloride. Typically, the organo-aluminium compound is methylaluminoxane.
The molar ratio of the elemental aluminium of the co-catalyst and the elemental transition metal of the pro-catalyst can be in the range of 200:1 to 250:1.
The organic liquid medium can be at least one selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, toluene, and cyclohexane. Typically, the organic liquid medium is n-hexane.
The polymerization of ethylene can be carried out at a stirring speed in the range of 450 rpm to 700 rpm using the stirrer having anchor type blades.
The DUHMWPE prepared by the process of the present disclosure is characterized by molecular weight distribution in the range of 0.5 to 8.0, molecular weight greater than 2 million g/mole, crystallinity greater than 90 %, enthalpy in the range of 195 J/g to 260 J/g, melting temperature in the range of 139° C to 142° C, bulk density in the range of 0.05 g/cc to 0.2 g/cc, and porous and fibrous morphology.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
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 the molecular weight distribution of DUHMWPE obtained by the process of the present disclosure;
Figure 2 illustrates an SEM pattern of a DUHMWPE obtained by the process of the present disclosure;
Figure 3 illustrates an anchor type blade used for carrying out the stirring of the contents of the reactors in the process of present disclosure; and
Figure 4 illustrates the laminar flow of the contents of the reactor obtained by the use of the anchor type blades in the process of preparing DUHMWPE in accordance with the embodiments of the present disclosure.
DETAILED DESCRIPTION
Conventional processes for preparing dis-entangled ultra-high molecular weight polyethylene (DUHMWPE) are associated with the disadvantage of low yield.
The present disclosure therefore, envisages an improvement in the process for preparing DUHMWPE with high yield.
In accordance with the present disclosure, there is provided an improvement in the process for preparing dis-entangled ultra-high molecular weight polyethylene, wherein the improvement comprises polymerization of ethylene in a reactor provided with a stirrer having anchor type blades, for stirring the contents of the reactor during the polymerization process, in the presence of a catalyst composition provided in an organic liquid medium. The process of the present disclosure results in a yield greater than 10 kg of DUHMWPE per gram of the catalyst composition.
The catalyst composition of the present disclosure comprises a pro-catalyst and a co-catalyst. The pro-catalyst is at least one selected from the group consisting of a transition metal-Schiff base imine ligand complexes.
In an embodiment of the present disclosure, the transition metal-Schiff base imine ligand complexes are represented by Formula (I),

wherein, R1, R2, R4, R6, R8, R10 and R12 are independently selected from the group consisting of hydrogen, aryl, heteroaryl and halogen; R5 and R9 are tertiary alkyl groups; R7 and R11 are independently selected from the group consisting of hydrogen and tertiary alkyl group; R3 is selected from the group consisting of hydrogen, halogen, alkoxy, aryloxy, carboxyl, and sulphonic acid; M is a transition metal selected from the group consisting of Hafnium (Hf), Manganese (Mn), Iron (Fe), Rhenium (Re), Tungsten (W), Niobium (Nb), Tantalum (Ta), Vanadium (V), and Titanium (Ti); and X1 and X2 are independently selected from the group consisting of Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).
In another embodiment of the present disclosure, the transition metal-Schiff base imine ligand complex is represented by Formula (I), wherein R1, R2, R3, R4, R6, R7, R8, R10, R11 and R12 are hydrogen; R5 and R9 are tertiary butyl group; M is Titanium (Ti) and X1 and X2 are Chlorine (Cl).
In yet another embodiment of the present disclosure, the transition metal-Schiff base imine ligand complex is represented by Formula (I), wherein R1, R2, R3, R4, R6, R8, R10 and R12 are hydrogen; R5, R9, R7 and R11 are tertiary butyl group; M is Titanium (Ti); and X1 and X2 are Chlorine (Cl).
The transition metal-Schiff base imine ligand complex represented by Formula (I) is obtained by reacting a Schiff base imine ligand of Formula (II) with a transition metal halide compound.

The Schiff base imine ligand of Formula (II) is prepared by reacting an aromatic diamine of Formula III with a substituted salicylaldehyde of Formula (IVA/IVB).

The catalyst composition in its active form involves ionic interaction between the transition metal-Schiff base imine ligand complex and the organo-aluminium compound, where the transition metal-Schiff base imine ligand complex assumes partial cationic character and the organo-aluminium compound assumes partial anionic character.
The substituted salicylaldehyde can be an alkyl substituted salicylaldehyde. In a specific embodiment, the alkyl substituted salicylaldehyde is 3-tert-butyl salicylaldehyde. In another specific embodiment, the alkyl substituted salicylaldehyde is 3,5-di-tert-butyl salicylaldehyde.
The catalytic activity of the transition metal-Schiff base imine ligand complex represented by Formula (I) is attributed to the introduction of tertiary butyl substituents on the third and/or the fifth position of the phenyl ring of salicylaldehyde. The steric effect plays a key role in the ion separation between the cationic active species of the transition metal-Schiff base imine ligand complex and the anionic organo-aluminium compound. The introduction of the bulky alkyl group in the ligand influences the electronic and steric environment around the metal complex and results in enhanced catalyst productivity. The effective ion separation provides more space for polymerization and in addition, enhances the degree of unsaturation associated with the catalytically active cationic species of the transition metal-Schiff base imine ligand complex.
The co-catalyst is an organo-aluminium compound. The organo-aluminium compound can be at least one selected from the group consisting of methylaluminoxane, poly-methylaluminoxane, triethylaluminium, trimethylaluminum, and diethylaluminium chloride. In a particular embodiment, the organo-aluminium compound is methylaluminoxane. The preparation of DUHMWPE by the process of the present disclosure largely depends upon the organo-aluminium compound used. It is observed that methylaluminoxane (MAO) provides high yield of DUHMWPE. The MAO increases the polarity of the organic liquid medium with a better ion – pair separation, thus contributing to a higher rate of polymerization. Commercially available MAO contains residual trimethylaluminum (TMAL 15 – 30%), called “free TMAL” or “active aluminum”. The catalyst activity of the commercially available MAO, further, increases with the increase in the amount of TMAL.
In accordance with the embodiments of the present disclosure, the molar ratio of the elemental aluminium of the co-catalyst and the elemental transition metal of the pro-catalyst can be in the range of 200:1 to 250:1.
The organic liquid medium can be at least one selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, toluene, and cyclohexane. In an exemplary embodiment, the organic liquid medium is n-hexane. The organic liquid medium used for the preparation of DUHMWPE has a significant role in determining the yield of DUHMWPE. The nature of the organic liquid medium affects the polymerization system in two ways. First, the solubility of ethylene depends on the type of the organic liquid medium. Second, the polarity of the organic liquid medium strongly determines the solvation and ion separation of the catalyst composition. It is observed that n-hexane is the most preferred organic liquid medium which results in high yield of DUHMWPE.
In accordance with the present disclosure, a process for preparing the DUHMWPE is disclosed, the process comprising the steps described herein below:
In a reactor the pro-catalyst and the co-catalyst are added to the organic liquid medium to obtain a mixture thereof. The reactor is provided with a stirrer having anchor type blades (as shown in Figure 3), wherein the stirrer is used for stirring the mixture. More specifically, the mixture is stirred at a temperature in the range of 10° C to 30° C for a time period in the range of 1 hour to 5 hours to obtain the catalyst composition of the present disclosure. In a preferred embodiment, the reactor is a stainless steel type reactor, although other reactors may be conveniently used in the process of the present disclosure.
Thereafter, ethylene is introduced into the reactor containing the catalyst composition to initiate polymerization. Polymerization is carried out at an ethylene pressure in the range of 2 bar to 30 bar, at a temperature in the range of 20° C to 70° C for a time period in the range of 1 hour to 10 hours, while maintaining stirring at a stirring speed in the range of 450 rpm to 700 rpm to obtain a slurry comprising DUHMWPE. The DUHMWPE is separated from the slurry. The yield of DUHMWPE obtained by the process of the present disclosure is at least 10 kg of DUHMWPE per gram of the catalyst composition.
Prior to starting the polymerization reaction, the mixture comprising the pro-catalyst, the co-catalyst, and the organic liquid medium in the reactor has a low viscosity and can be stirred easily using the stirrer having anchor type blades (as shown in figure 3). When ethylene is introduced in the reactor containing the catalyst composition, ethylene undergoes polymerization, and slurry is obtained. The viscosity of the slurry increases with the increase in the amount of DUHMWPE formed in the slurry. The stirrer having anchor type blades facilitates in homogenizing the solid-liquid phases in the slurry effectively thus contributing to high yield of the polymer. The stirrer having anchor type blades can be used for effective stirring of the highly viscous flow of liquid; typically, the viscosity of the liquid/slurry being in the range 103 centipoise to 104 centipoise, which is a typical viscosity range for polymer reactions. The stirrer having anchor type blades generates laminar flow for polymer reactions with highly viscous flow. Figure 4 illustrates the laminar flow of the contents of the reactor obtained by the use of the anchor type blades in the process of preparing DUHMWPE in accordance with the embodiments of the present disclosure.
The DUHMWPE obtained by the process of the present disclosure is characterized by molecular weight distribution in the range of 0.5 to 8.0, preferably 5.0, molecular weight greater than 2 million g/mole, crystallinity greater than 90 %, enthalpy in the range of 195 J/g to 260 J/g, melting temperature in the range of 139° C to 142° C, bulk density in the range of 0.05 g/cc to 0.2 g/cc, preferably 0.09 g/cc, and porous and fibrous morphology.
The DUHMWPE obtained by the process of the present disclosure has a narrow molecular weight distribution. Further, it is observed that the interaction of the organo-aluminium compound with the transition metal-Schiff base imine ligand complex forms a cationic complex which regulates the molecular weight of the resulting polymer and terminates the polymerization reaction at the required stage. The molecular weight and molecular weight distribution (MWD) play important roles in the processing characteristics of the DUHMWPE, which ultimately influences the physical and mechanical properties of the polymer. For instance, in a melt spinning process, a low molecular weight polymer with a broad MWD is needed, whereas to produce fiber by solution spinning a very high molecular weight polymer with narrow MWD is required.
The DUHMWPE obtained by the process of the present disclosure is highly crystalline in nature and its crystallinity is higher than that of ultra-high molecular weight polyethylene (UHMWPE). The high crystallinity of DUHMWPE as compared to UHMWPE can be attributed to the highly disentangled state of the polymer chains.
The disentanglement of the polymer is observed by conducting a sheet formation test. The sheet can be drawn into very high strength films, tapes and fibers having strength of more than 1 GPa. The DUHMWPE is molded into different forms having high strength. The DUHMWPE obtained by the process of the present disclosure also has potential utility as an additive that can be used to enhance the performance of polymers, films for packaging, and thermally conductive products.
The present disclosure is further described in the 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. The experiments used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. These laboratory experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
Experimental Details:
Experiment 1:
The DUHMWPE was prepared by polymerization of ethylene in the presence of the transition metal-Schiff base imine ligand complex (of Formula I) as a pro-catalyst and methylaluminoxane as a co-catalyst. The substituents in the pro-catalyst were as follows, R1, R2, R3, R4, R6, R8, R10 and R12 were hydrogen; R5, R9, R7 and R11 were tertiary butyl groups; M was Titanium; and X1 and X2 were Chlorine. This pro-catalyst is herein after referred to as TMSBILC. A reactor was equipped with a stirrer having anchor type blades. To the reactor, n-hexane (0.5 lit), methylaluminoxane (0.35 ml) and TMSBILC (1.75 mg) were added, while stirring to obtain a mixture. The molar ratio of the elemental aluminium of methylaluminoxane and the elemental titanium of the TMSBILC was 225:1. Thereafter, ethylene was then introduced in the reactor. Polymerization was carried out at an ethylene pressure of 6 bar, at a temperature of 50° C for a period of 3 hours, while maintaining the stirring speed at 500 rpm, to obtain a slurry containing DUHMWPE. The DUHMWPE was separated from the slurry by vacuum filtration. The experimental conditions and characterization of the DUHMWPE obtained are listed in table 1 herein below.
Experiments 2 to 19:
Experiments 2 to 19 where carried out using similar procedure as described herein above with reference to experiment 1, but employing different stirrer types, varying pressure of ethylene, varying aluminium to titanium ratio, different co-catalysts, and different organic liquid media. The pro-catalyst used in all of the experiments 2 to 19 was TMSBILC. The details of the experiments 2 to 19 are summarized in table 1 below.

Exp. No./Variables 1 2 3

4 5 6
TMSBILC (mg) 1.75 1.75 1.75 3.5 3.5 3.5
Co-catalyst Name MAO MAO MAO MAO MAO MAO
Amount (ml) 0.35 0.35 0.35 0.7 0.7 0.7
Organic liquid medium Name n-hexane n-hexane n-hexane n-hexane Toluene Cyclohexane
Amount (liter) 0.5 0.5 0.5 0.5 0.5 0.5
Stirrer Type Anchor Anchor Anchor Anchor Anchor Anchor
Stirring speed (RPM) 500 500 500 500 500 500
Al/Ti ratio 225:1 225:1 225:1 220:1 220:1 220:1
Ethylene pressure (bar) 6 6 6 6 6 6
Polymerization temperature (°C) 50 50 50 50 50 50
Polymerization time (hrs.) 3 3 3 3 3 3
Yield (g) 107 116 112 214 91 127
Yield (Kg/g of TMSBILC) 61.1 66.3 64 61 26 36.3
BD (g/cc) 0.09 0.09 0.09 0.15 0.07 0.2
MW (Mg/mole) 4.4 4.51 4.55 4.5 5.9 4.6
RSV (dl/g) NA NA NA 24.8 31.1 25
Crystallinity (%) (XRD) 96.8 97.1 96.8 - - -
DSC - - -
Tm (°C) 142.9 142 141.7 - - -
Tc (°C) 117.4 117.8 118.1 - - -
?H (J/g) 211.1 201 200.5 - - -
Crystallinity (%) 72.3 68.9 68.7 - - -
RDA
Mn 4.03 x 105 - - - - -
MW 2.02 x 106 - - - - -
Mz 1.01 x 107 - - - - -
Mz+1 4.52 x 107 - - - - -
MWD 5.01 - - - - -
TABLE 1
TABLE 1 (CONTINUED …)
Exp. No./Variables 7 8 9 10
TMSBILC (mg) Amount (mg) 3.5 3.5 3.5 3.5
Co-catalyst Name MAO MAO MAO MAO
Amount (ml) 0.7 0.7 0.7 0.7
Organic liquid medium Name n-hexane n-hexane n-hexane n-hexane
Amount (liter) 0.5 0.5 0.5 0.5
Stirrer Type Anchor Anchor Anchor Anchor
Stirring speed (RPM) 500 500 500 500
Al/Ti ratio 220:1 220:1 220:1 220:1
Ethylene pressure (bar) 3 6 12 20
Polymerization temperature (°C) 50 50 50 50
Polymerization time (hrs.) 3 3 3 3
Yield (g) 86 214 225 300
Yield (Kg/g of TMSBILC) 24.6 61.1 64.3 86
BD (g/cc) 0.16 0.15 0.2 0.19
MW (Mg/mole) 3.86 4.5 3.71 4.34
RSV 22.7 24.8 22 24.7
TABLE 1 (CONTINUED …)
Exp. No./Variables 11 12 13 14 15
TMSBILC (mg) Amount (mg) 3.5 3.5 3.5 3.5 3.5
Co-catalyst Name MAO TEAL DEAC DEAC:MAO PMAO
Amount (ml) 0.7 0.7 0.7 0.7 0.7
Organic liquid medium Name n-hexane n-hexane n-hexane n-hexane n-hexane
Amount (liter) 0.5 0.5 0.5 0.5 0.5
Stirrer Type Anchor Anchor Anchor Anchor Anchor
Stirring speed (RPM) 500 500 500 500 500
Al/Ti ratio 220:1 220:1 220:1 220:1 220:1
Ethylene pressure (bar) 6 6 6 6 6
Polymerization temperature (°C) 50 50 50 50 50
Polymerization time (hrs.) 3 3 3 3 3
Yield (g) 214 2.2 8.6 56 65.8
Yield (Kg/g of TMSBILC) 61.1 0.6 2.4 16 18.8
BD (g/cc) 0.15 NA 0.078 0.143 0.17
MW (Mg/mole) 4.5 NA 3.1 3.7 5.3
RSV 24.8 NA 19.33 22 29.2
TABLE 1 (CONTINUED …)
Exp. No./Variables 16 17 18 19
TMSBILC (mg) Amount (mg) 3.5 3.5 3.5 3.5
Co-catalyst Name MAO MAO MAO MAO
Amount (ml) 0.7 0.7 0.7 0.7
Organic liquid medium Name n-hexane n-hexane n-hexane n-hexane
Amount (liter) 0.5 0.5 0.5 0.5
Stirrer Type Anchor Pitch Propeller Turbine
Stirring speed (RPM) 500 500 500 500
Al/Ti ratio 220:1 220:1 220:1 220:1
Ethylene pressure (bar) 6 6 6 6
Polymerization temperature (°C) 50 50 50 50
Polymerization time (hrs.) 3 3 3 3
Yield (g) 214 85 120 123
Yield (Kg/g of TMSBILC) 61.4 24.3 34.3 35.1
BD (g/cc) 0.15 0.091 0.11 0.13
MW (Mg/mole) 4.5 5.2 3.4 3.47
RSV 24.8 28 20.67 20.95
INFERENCES (EXPERIMENTS 1 TO 19):
Experiments 1 to 3 were performed with same pro-catalyst (TMSBILC), co-catalyst (MAO) and organic liquid medium (n-hexane) in the same amount to confirm reproducibility of the process of the present disclosure.
The DUHMWPE obtained (in experiments 1 to 3) was characterized for:
o Percentage of crystallinity (which was determined by XRD), wherein it was observed that the DUHMWPE obtained by the process of the present disclosure exhibit highly crystalline nature with crystallinity in the range of 96.8 % to 97.1 %.
o The following properties of the DUHMWPE (of the experiments 1 to 3) were determined by differential scanning calorimetry (DSC), wherein:
? the melting temperature (Tm), of the DUHMWPE was found to be in the range of 141.7° C to 142.9° C on first heating;
? the crystallization temperature (Tc) was found to be in the range of 117.4° C to 118.1° C;
? enthalpy (?H) of the DUHMWPE was found to be in the range of 200.5 J/g to 211.1 J/g; and
? the percentage crystallinity was found to be in the range of 68.7 % to 72.3 %.
Whereas, the molecular weight distribution (MWD) was determined only for DUHMWPE obtained in experiment 1 by Rheometric dynamic analyzer (RDA), wherein the MWD of the DUHMWPE (obtained in experiment 1) was found to be narrow. Figure 1 is a graph depicting the MWD of the DUHMWPE obtained in experiment 1.
Further, the morphology of the DUHMWPE (obtained in experiment 1) was observed using Scanning Electron Microscope (SEM), which is shown in figure 2. It is observed that the DUHMWPE obtained in experiment 1 has a porous and fibrous morphology.
Experiments 4 to 6 were performed to understand the effect of the organic liquid medium on ethylene polymerization, wherein three organic liquid media were used, namely, n-hexane, toluene, and cyclohexane in experiments 4, 5 and 6 respectively. The yield, reduced specific viscosity, molecular weight and bulk density of the DUHMWPE along with the experimental conditions are tabulated in table 1.
From table 1 it is evident that with n-hexane as the organic liquid medium, the yield of the DUHMWPE is highest as compared with the other two organic liquid media, whereas highest density of the DUHMWPE is obtained when cyclohexane is used and highest molecular weight of the DUHMWPE is obtained when toluene is used.
Experiments 7 to 10 were performed to study the effect of ethylene pressure on the polymerization of ethylene. The ethylene pressure was varied from 3 bar to 20 bar. The results are tabulated in table 1. It is evident that with the increase in ethylene pressure, the yield of DUHMWPE increases. Reduced specific viscosity (RSV), the bulk density, and the molecular weight remained more or less the same.
In experiments 11 to 15, the effect of the co-catalyst was studied, wherein MAO, TEAL, DEAC, DEAC and MAO in 1:1 proportion and PMAO were used in the experiments 11, 12, 13, 14, and 15 respectively. The results are tabulated in table 1. Highest yield of DUHMWPE was obtained with MAO as the co-catalyst as compared to others.
Further, experiments 16 to 19 were carried out using stirrer with different types of blades and their effect on ethylene polymerization was studied. The type of blades used and the results obtained along with the experimental conditions are tabulated in table 1. The stirrer with anchor type blades was found to be effective as compared to other blades. This is evident from the yield of the DUHMWPE, wherein when a stirrer with anchor type blade is used, the yield of TMSBILC is 61.4 Kg/g, which is significantly high.
In the published patent application No. 1440/MUM/2013 dated 17.04.2013 (from the same applicant), the maximum yield of DUHMWPE obtained was 6.7 kg of DUHMWPE per gram of the catalyst. However, as seen in Table 1, the yield of DUHMWPE as per the process of the present disclosure, which makes use of a stirrer having anchor type blades, is in the range of 24.3 kg to 86 kg of DUHMWPE per gram of the catalyst, which amounts to an increase in the yield in the range of 263 % to 1183 % as compared with the maximum yield obtained by the process of the aforementioned published patent application no. 1440/MUM/2013. Thus, it can be seen that the process of the present disclosure, which makes use of the stirrer having anchor type blades, shows an enormous increase in the yield of the DUHMWPE product.
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 to obtain dis-entangled ultra-high molecular weight polyethylene (DUHMWPE) with high yield of DUHMWPE.
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.