DESC:FIELD
The present disclosure relates to a catalyst system and a process for polymerizing olefins using the catalyst system.
DEFINITION
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.
Hybrid catalyst: Hybrid catalyst means single catalyst containing two different catalyst components.
Slurry phase polymerization reaction: The slurry phase polymerization reaction takes place in the presence of fluid medium.
Gas phase polymerization reaction: The gas phase polymerization reaction takes place in presence of seed bed (resin).
Isotacticity: Isotacticity of a stereospecific polymer means having identical steric configurations of the groups on each asymmetric carbon atom on the chain.
Stereo-rigid compound: Stereorigid compounds of the present disclosure are the metallocene compounds having indenyl ligands.
Nonstereo-rigid compound: Nonstereorigid compounds of the present disclosure are the metallocene compounds having substituted or un-substituted cyclopentadienyl ligands.
BACKGROUND
In olefin polymerization, the catalyst system plays an important role for carrying out the process. Generally, separate catalyst systems are used for homopolymerization and co-polymerization. Further, the homopolymerization and co-polymerization is carried out separately in two reactors. No attempt has been made to arrive at a catalyst system that enables the formation of a homopolymer and a copolymer in the same reactor and as a continuous process.
Therefore, there is a need to develop a catalyst system which can be used to prepare a homopolymer and a copolymer in the same reactor, in a continuous process.
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 a homo-polymer and co-polymer in a continuous process by using the same catalyst system.
Another object of the present disclosure is to provide a catalyst system for homo-polymerization and co-polymerization of olefins.
Still another object of the present disclosure is to provide a process for preparing a catalyst system for homopolymerization and co-polymerization of olefins.
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 supported hybrid metallocene catalyst system comprising a spherical magnesium alkoxide supported titanium pro-catalyst, at least one binding agent, and at least one of a stereorigid and a non-stereorigid metallocene compound.
The present disclosure also provides a process for preparing the supported hybrid metallocene catalyst system. The process step involves the preparation of spherical magnesium alkoxide supported titanium pro-catalyst by reacting at least one spherical magnesium alkoxide, at least one titanation fluid medium and at least one internal donor at different temperatures ranging from 40 oC to 80 oC for a time period ranging from 10 hours to 12 hours.
The so obtained spherical magnesium alkoxide supported titanium pro-catalyst is mixed with at least one binding agent to obtain a mixture. The mixture is treated with at least one of stereorigid and a non- stereorigid metallocene compound at a temperature ranging from 50 oC to 80 oC for a time period ranging from 2 to 4 hours to obtain the supported hybrid metallocene catalyst system. The supported hybrid metallocene catalyst system may optionally contain a masking agent.
The present disclosure further provides a process for the polymerization of olefins comprising a first stage of homopolymerization and a second stage of co-polymerization, carried out in a single reactor using the same catalyst system. In the present disclosure, the catalyst system in addition to spherical magnesium alkoxide supported titanium pro-catalyst, binding agent and a stereorigid and a non-stereorigid metallocene compound includes a masking agent, a co-catalyst, and an external donor for carrying out the polymerization reaction. The process involves the step of mixing at least one masking agent in a first fluid medium to obtain a first slurry; mixing the supported hybrid metallocene catalyst, at least one co-catalyst and at least one external donor in a second fluid medium to obtain a second slurry; polymerizing olefin using the first slurry and the second slurry at a temperature ranging from 60 oC to 80 oC under constant pressure ranging from 4 kg/cm2 to 8 kg/cm2 for a time period ranging from 1 to 4 hours to obtain a homopolymer; cooling said homopolymer and adding H2 to obtain the desired molecular weight homopolymer and adding at least one co-catalyst, hydrogen and a mixture of at least two olefins to the so obtained homopolymer at a temperature ranging from 50 oC to 80 oC for a time period ranging from 10 minutes to 30 minutes to obtain a co-polymer. The so obtained copolymer contains Rc (Rubber content) in the range of 25% to 35%, thereby confirming 65-75% of homogenous polypropylene matrix in the co-polymer. Thus, the co-polymer obtained has 65-75% of a homogeneous polymer matrix.
DETAILED DESCRIPTION
The inventors of the present disclosure envisage a supported hybrid metallocene catalyst system and a process for preparing a supported hybrid metallocene catalyst system. The present disclosure further envisages a process for homo-polymerization and co-polymerization of olefin using the supported hybrid metallocene catalyst.
In one aspect, the present disclosure provides a supported hybrid metallocene catalyst system comprising a magnesium alkoxide supported titanium pro-catalyst, at least one binding agent, and at least one of a stereorigid and a non-stereorigid metallocene compound.
The magnesium alkoxide used in the process of the present application is spherical magnesium alkoxide. The spherical magnesium alkoxide has the formula Mg [(OR1)2-x (OR2) x]. One of OR1 and OR2 is methoxy and the other one is selected from the group consisting of ethoxy, propoxy, butoxy and pentoxy. The methoxy content in the spherical magnesium alkoxide ranges from 0.01 to 8 wt%.
The binding agent is alkyl aluminum, which is selected from the group consisting of methylaluminoxane (MAO), triethyl aluminum (TEAL), tri-isobutyl aluminum (TIBAL) and diethylaluminum chloride (DEAC).
The metallocene compound is at least one of a stereo-rigid metallocene compound and a non-stereo-rigid metallocene compound and comprises at least one metal selected from titanium (Ti), zirconium (Zr) and hafnium (Hf) as a central metal atom. In one embodiment, the metallocene compound is at least one of selected from the group consisting of bis (n-ethyl cyclopentadienyl) titanium dichloride, bis (n-ethyl cyclopentadienyl) zirconium dichloride and rac-dimethylsilylbis (1-indenyl) zirconium chloride.
The amount of metallocene incorporated in the supported hybrid metallocene catalyst system of the present disclosure ranges from 0.05 to 2 wt %.
In an embodiment the supported hybrid metallocene catalyst system of the present disclosure further comprises at least one masking agent. The masking agent is at least one compound selected from the group consisting of 4-vinyl cyclohexene, 9-vinyl carbazole, and the like. The ratio of the amount of the masking agent and the catalyst system is in the range of 1500 to 6000 mmoles/mmoles (Specifically the ratio is the amount of masking compound : Ti in the catalyst system ratio).
The masking agent is used for deactivation of the metallocene component of the hybrid catalyst during homopolymerization. The metallocene component becomes inactive in the presence of the masking compound and only Ziegler Natta diester component of the hybrid catalyst is active during homo polymerization. During co-polymerization, in the presence of ethylene and hydrogen, the metallocene components get reactivated and participate in the ethylene propylene copolymerization reaction.
In an embodiment, when 4-vinyl cyclohexene or 9-vinyl carbazole is added as a masking compound during homo polymerization, the homo polymer is formed by the Zigler Natta component of the hybrid catalyst and the metallocene component becomes inactive in the presence of the masking compound. During copolymerization, when ethylene and hydrogen is added, metallocene becomes active during copolymerization.
In another aspect, the present disclosure provides a process for preparing a supported hybrid metallocene catalyst system, which is described herein below:
The process involves reacting at least one spherical magnesium alkoxide, at least one titanation fluid medium and at least one internal electron donor at a temperature in the range of 40 oC to 80 oC for a time period ranging from 10 hours to 12 hours to obtain a spherical magnesium alkoxide supported titanium pro-catalyst. The titanation fluid medium may be an equimolar mixture of titanium tetrachloride and chlorobenzene. The internal donor can be di-isobutyl phthalate.
The so obtained spherical magnesium alkoxide supported titanium pro-catalyst is mixed with at least one binding agent to obtain a mixture. In an embodiment, the binding agent /binder is added into supported titanium procatalyst followed by addition of metallocene component. The binding agent can be at least one selected from the group consisting of Triethylaluminium (TEAL), Methylaluminoxane (MAO), and Triisobutylaluminium (TiBA). The binding agent binds pro-catalyst and metallocene component to form a single hybrid catalyst. The binding agent is used for interaction between pro-catalyst and the metallocene component to form combined Ziegler Natta and metallocene catalyst of the present disclosure.
The so obtained mixture is then treated with at least one of stereo-rigid metallocene compound and a non-stereo-rigid metallocene compound at a temperature ranging from 50 oC to 80 oC for a time period ranging from 2 to 4 hours to obtain supported hybrid metallocene catalyst. The supported hybrid metallocene catalyst system further comprises at least one masking agent to obtain a supported hybrid metallocene catalyst with the masking agent.
The process for preparing the supported hybrid metallocene catalyst system is a three step process which is described herein below;-
Step I-Preparation of spherical magnesium alkoxide:
The spherical magnesium alkoxide has the formula Mg[(OR1)2-x(OR2)x], wherein, one of OR1 and OR2 is methoxy and the other one is selected from the group consisting of ethoxy, propoxy, butoxy and pentoxy, and the methoxy content in the spherical magnesium alkoxide ranges from 0.01 to 8% by weight. The magnesium alkoxide precursor is prepared by the process as disclosed in example 1 of US 8,633,124 B2.
The preparation of spherical magnesium alkoxide supported titanium pro-catalyst is conducted in a step-wise manner. The reaction mixture of spherical magnesium alkoxide, titanation fluid medium and internal donor, is heated first in the range to 40 °C to 65 °C for a period of 2 hours and then in the range of 65 °C to 80 °C for a period of 1 hour, further by maintaining the reaction temperature at 80 °C for a period of 7 hours. The vapors of the mixture produced during the reaction are condensed in a condenser, typically an overhead condenser. The hydrogen gas produced during the reaction is vented off and the mixture of alcohols left after the reaction is removed by filtration.
Step II-Preparation of pro-catalyst:
The solid spherical magnesium alkoxide supported titanium pro-catalyst so obtained, is dried, and stored in mineral oil. The pro-catalysts (titanium supported spherical magnesium alkoxide pro-catalyst) are prepared by the process as described in example 3 of US 8,633,124 B2.
Step III- Preparation of supported hybrid metallocene catalyst system:
The so obtained spherical magnesium alkoxide supported titanium pro-catalyst is mixed with at least one binding agent to obtain a mixture. The pro-catalyst is mixed with a binding agent in such a proportion that the ratio of aluminum to titanium is maintained typically at (250 ± 5):1
In a further step of the process for preparation of the catalyst system, the mixture is treated with at least one of a stereo-rigid metallocene compound and a non-stereo-rigid metallocene compound at a temperature ranging from 50 oC to 80 oC for a time period ranging from 2-4 hours to obtain the supported hybrid metallocene catalyst system. The ratio of the amount of the binding agent to titanium in the supported hybrid metallocene catalyst system ranges from 50-1500 mmole/mmole.
In yet another aspect, the present disclosure provides a process for homo-polymerization and co-polymerization of olefin using supported hybrid metallocene catalyst. The process of polymerization is described herein below:
The process of polymerization of olefins of the present disclosure comprises a first stage of homopolymerization and a second stage of co-polymerization, carried out in a single reactor using the same catalyst system.
The process comprises preparation of a first slurry and a second slurry. The first slurry is prepared by mixing at least one masking agent with a first fluid medium. The second slurry is prepared by mixing at least one supported hybrid metallocene catalyst system with at least one co-catalyst and at least one external donor in a second fluid medium. The co-catalyst used in the process of the present disclosure is alkyl aluminum such as triethyl aluminum. The first fluid medium and second fluid medium can be independently selected from the group consisting of hexane or decane. The external donor can be an organosilane. In an exemplary embodiment, the external donor is dicyclopentyldimethoxysilane. The molar ratio of aluminum to external donor can be (3.0 ±0.2):1.
The polymerization is carried out by introducing an olefin in the polymerization reactor containing the first slurry and the second slurry at a temperature in the range of 60 oC to 80 oC under constant pressure ranging from 4 kg/cm2 to 8 kg/cm2 for a time period ranging from 1 to 4 hours followed by addition of 50 to 60 mmole of hydrogen to obtain the homopolymer. The so obtained homopolymer is cooled and H2 is added to the cooled homopolymer. Hydrogen is used as a chain terminating agent in the polymerization reaction for controlling the molecular weight of the desired polymer.
In the process, at least one masking agent is mixed with a first fluid medium to obtain a first slurry. The first slurry is introduced into a polymerization reactor. The slurry and gas phase polymerization procees are suitable for the catalyst performance evaluation. In the slurry reactor, initially the mixture of hexane and 4-vinyl cyclohexene is added. Then the hybrid catalyst slurry is added. When propylene is fed into the reactor, the masking compound prevents the metallocene component of the hybrid catalyst to take part in the polymerization reaction. Homo polypropylene is formed only by the Ziegler Natta procatalyst component. When co-polymerization is carried out, in the presence of ethylene and hydrogen, the metallocene component of the hybrid catalyst become active.
The masking agent can be selected from 4-vinylcyclohexene and 9-vinyl carbazole. The masking compound restricts the metallocene’s catalytic activity during homo-polymerization of propylene. However, during co-polymerization of the so obtained homopolymer (homopolymer of propylene), with a mixture of propylene and ethylene, the metallocene remains active in the presence of hydrogen and ethylene.
The so obtained homopolymer is cooled and the excess/unreacted olefin is vented off. Further reaction of the homopolymer continues with co-polymerization, where at least one co-catalyst, hydrogen and a mixture of at least two olefins are added into the cooled homopolymer and the whole reaction mixture is heated at a temperature ranging from 50 oC to 80 oC for a time period ranging from 10 minutes to 30 minutes to obtain a co-polymer. The obtained co-polymer typically has 65-75% of a homogeneous polymer matrix. The olefin is at least one selected from ethylene, and propylene. In an exemplary embodiment, the homopolymerization of propylene and co-polymerization of propylene and ethylene is carried out. Co-polymerization of propylene with ethylene shows high dispersion of the ethylene moiety in the polypropylene.
The present disclosure is further illustrated herein below with the help of the following experiments. 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. Accordingly, the examples should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to an industrial/commercial scale.
Experimental details
Experiment 1
Step I-Preparation of spherical magnesium alkoxide:
Magnesium powder (55 g) was added to a mixture of ethanol and methanol (125 ml) in the presence of iodine (0.15 gm) as initiator at 40 °C with continuous stirring to obtain a reaction mixture. The reaction mixture was stirred while being heated at different temperature ranges in a step-wise manner - the reaction mixture was first heated in the range of 40 °C to 65 °C for a period of 2 hours and then in the range of 65 °C to 80 °C for a period of 1 hour and was further maintained at 80 °C for a period of 7 hours.
The vapors of the mixture produced during the reaction were condensed in an overhead condenser. The hydrogen gas produced during the reaction was vented off and the mixture of alcohols left after the reaction was removed by filtration. The filtrate was reused for further synthesis. A wet cake was obtained after removal of the filtrate. The wet cake was dried to obtain 250 g of white free flowing spheroidal magnesium alkoxide particles and was characterized for bulk density, methoxy content, ethoxy content, and surface area studies. The characterization of the spheroidal magnesium alkoxide particles obtained by the process of the present disclosure is summarized in Table 1.
Table 1- Characterization of spheroidal magnesium alkoxide particle:
Parameters Values
1. Methoxy content (wt %) 8.0
2. Ethoxy content (wt %) 70
3. Mean Particle size (microns) 25-35
4. Bulk density (g/ml) 0.59
5. Crushing strength (kg) 30.2
7. Circularity 0.72
8. Surface Area (m2/g) 10

Step II: Preparation of pro-catalyst (titanium supported magnesium alkoxide):
The spheroidal magnesium alkoxide (10 g) from step I was treated with an equal volume mixture of TiCl4 and chlorobenzene (115 ml). Di-isobutyl phthalate was added as an internal donor to obtain a reaction mixture. After three stage heating treatment (as described in step 1), the solid obtained was filtered and washed with 1 liter of isopentane and dried at 50 °C under a stream of nitrogen. The dried solid, i.e. titanium supported magnesium alkoxide pro-catalyst was yellow colored with 15 gm yield.
The so obtained yellow colored titanium supported magnesium alkoxide pro-catalyst was stored in Hydrobrite-380 mineral oil . The compositional analysis of the final product was carried out using the content of titanium (%), magnesium (%) and chlorine, ethoxy and internal donor concentration studies were also performed, which are summarized in Table-2.
Table 2-Characterization of pro-catalyst (titanium supported magnesium alkoxide):
Elements Value
Magnesium (wt %) 18.6
Titanium (wt %) 2.6
Chlorine (wt %) 60.5
Ethoxy (wt %) 0.32
DIBP (wt %) 9.2
Mean Particle size (micron) 23-25
Surface Area (m2/g) 260-280

Step III:
Preparation of supported hybrid metallocene catalyst using bis (n-ethyl cyclopentadienyl) titanium dichloride (non-stereorigid titanium metallocene)
Titanium supported magnesium alkoxide pro-catalyst (9 g slurry containing 30 wt% solid content); obtained from step II of experiment 1 was washed with hexane for removal of the mineral oil. The so obtained dry powder was suspended in 100 ml hexane followed by addition of Tri ethyl aluminum (0.5 ml) to obtain pro-catalyst slurry.
250 mg of bis (n-ethyl cyclopentadienyl) titanium dichloride metallocene was added in the pro-catalyst slurry and the so obtained mixture was stirred at 60 °C for 3 hours. After 3 hours, the mixture was cooled to 25 oC to 30 oC. The homogeneous solution was decanted. The residual catalyst left after decantation of homogenous solution was washed with a mixture of hexane/toluene and the supernatant slurry was decanted. This washing and decantation were repeated for 5-6 times to remove any unreacted compounds/components. After decantation, the residue was dried to obtain dried powder which was collected for further compositional analysis.
The remaining magnesium supported hybrid catalyst was stored in hexane for further polymerization experiments.

Experiment 2:
Preparation of supported hybrid metallocene catalyst using bis (n-ethyl cyclopentadienyl) zirconium dichloride (non-stereo-rigid zirconium metallocene)
A similar experiment as that of experiment 1 was carried out except that, in the step III of experiment 2, Bis (n-ethyl cyclopentadienyl) zirconium dichloride was used as non-stereo-rigid zirconium metallocene instead of Bis (n-ethyl cyclopentadienyl) titanium dichloride (non-stereorigid titanium metallocene).
Experiment 3:
Preparation of supported hybrid metallocene catalyst using rac-dimethylsilylbis (1-indenyl) zirconium dichloride
A similar experiment as that of experiment 1 was carried out except that, in the step III of experiment 3 rac-dimethylsilylbis (1-indenyl) zirconium dichloride was used instead of Bis (n-ethyl cyclopentadienyl) titanium dichloride (non-stereorigid titanium metallocene).
Compositional analysis of the supported hybrid metallocene catalysts of expt 1, expt 2 and expt 3 are given below in Table-3.-

Table-3
Composition analysis
Elements Supported hybrid metallocene catalyst (bis (n-ethyl cyclopentadienyl) titanium dichloride as metallocene

Expt 1 Supported hybrid metallocene catalyst Bis (n-ethyl cyclopentadienyl) Zirconium dichloride as metallocene
Expt 2 Supported hybrid metallocene catalyst rac-dimethylsilylbis (1-indenyl) Zirconium dichloride as metallocene

Expt 3
Values
Magnesium (% wt) 16.7 15.6 16.8
Titanium (% wt) 2.8 2.5 2.5
Zirconium (% wt) ----- 0.01 (125 ppm) 0.04 (450ppm)
Chlorine (% wt) 56.8 56.8 55.1

Experiments 2 and 3 show that Zr (wt%) is incorporated in the hybrid metallocene catalyst.
In experiment 3, stereorigid metallocene is used and it has higher Zr content as compared to non- stereorigid metallocene in expt-2.
Experiment 4:
Slurry phase polymerization of propylene using pro-catalyst (titanium supported magnesium alkoxide):
Solid titanium supported magnesium alkoxide pro-catalyst (0.08 g) obtained from step II of experiment 1, was mixed with triethyl aluminum co-catalyst (12 mmole) and dicyclopentyldimethoxysilane as an external donor (0.05). The pro-catalyst was mixed with co-catalyst in such proportions that aluminum: titanium ratio was maintained at (250±5):1. The mole ratio of aluminum (co-catalyst) to dicyclopentyldimethoxysilane (external donor) was maintained at (3.0 ±0.2):1, to obtain a Ziegler-Natta diester catalyst (pro-catalyst).
Slurry Polymerization:
This catalyst was employed to polymerize polypropylene in the slurry phase with hexane as the diluent under a constant polypropylene pressure of 5 kg/cm2 for 2 hours at 70 °C, followed by addition of 50 mmole of hydrogen to terminate the polymerization.

Experiment 5:
Slurry polymerization of propylene using titanium supported hybrid metallocene catalyst containing ((bis (n-ethyl cyclopentadienyl) titanium dichloride as metallocene) :
A similar experiment of slurry polymerization to that of experiment 4 was carried out except that the pro-catalyst titanium supported magnesium alkoxide was replaced by titanium supported hybrid metallocene catalyst containing ((bis (n-ethyl cyclopentadienyl) titanium dichloride as metallocene).
Experiment 6:
Slurry polymerization of propylene using titanium supported hybrid metallocene catalyst containing (Bis (n-ethyl cyclopentadienyl) zirconium dichloride as metallocene):
A similar experiment of slurry polymerization to that of experiment 4 was carried out except that the procatalyst titanium supported magnesium alkoxide was replaced by titanium supported hybrid metallocene catalyst containing (Bis (n-ethyl cyclopentadienyl) zirconium dichloride as metallocene).
Experiment 7
Slurry polymerization of propylene using titanium supported hybrid metallocene catalyst containing (rac-dimethylsilylbis (1-indenyl) zirconium dichloride as metallocene):
A similar experiment of slurry polymerization to that of experiment 4 was carried out except that the procatalyst (titanium supported magnesium alkoxide) was replaced by titanium supported hybrid metallocene catalyst containing (rac-dimethylsilylbis (1-indenyl) zirconium dichloride as metallocene)
The results of slurry polymerization of propylene using various catalysts are depicted in Table-4 below.
Table 4: Propylene Homo-polymerization using different catalyst
Properties of Polymer Propylene slurry polymerization using catalyst
Titanium supported Magnesium catalyst (Ziegler Natta diester catalyst)

Expt 4 Titanium supported hybrid metallocene catalyst ((bis (n-ethyl cyclopentadienyl) titanium dichloride as metallocene)
Expt 5 Titanium supported hybrid metallocene catalyst (Bis (n-ethyl cyclopentadienyl) Zirconium dichloride as metallocene)
Expt 6 Titanium supported hybrid metallocene catalyst (rac-dimethylsilylbis (1-indenyl) Zirconium dichloride as metallocene)
Expt 7
Productivity (kg PP/g catalyst) 8.5 1.9 4.6 6.6
MFI (g/10min) 2.5 0.3 2.5 1.4
Bulk density (g/ml) 0.49 0.48 0.5 0.5
Xylene soluble (wt %) 1.4 1.6 1.3 2.5
Melting temperature
(deg C) 161 159 160 NA
Isotacticity 94 NA NA NA

Zirconium based hybrid metallocene catalyst of expt 6 and expt 7 shows high productivity, high MFI than titanium based hybrid metallocene catalyst.
Further, stereorigid hybrid metallocene catalyst of expt 7 is found to have high productivity as compared to non- stereorigid hybrid metallocene catalyst of expt 6.
Procatalyst (Ziegler Natta diester catalyst) and metallocene catalyst, when both are used together, gives lower productivity. The hybrid catalyst synthesized contains both the components. Experiment-4 shows higher productivity as only diester procatalyst is used, whereas in expt-5,6,7, hybrid catalyst are synthesized which also contains the metallocene component along with the diester procatalyst. The productivity drops when a hybrid catalyst is used.
Experiment 8:
Use of a masking compound in slurry polymerization of propylene using supported titanium catalyst (Using 4-vinyl cyclohexene and 9-vinyl carbazole as masking compound):

And
4 vinyl cyclohexene 9 vinyl carbazole
Slurry Polymerization: The masking compound (4-vinyl cyclohexene/9 vinyl carbazole) was added to 2 liters hexane in the slurry polymerization reactor which was followed by addition of hybrid catalyst and then slurry phase propylene polymerization was carried out. The ratio of masking compound to titanium varied as 0, 1500, 3000, and 6000 (mmole/mmole).
Supported hybrid metallocene catalyst as described in step III of experiment 1 (0.08 g) was mixed with triethyl aluminum co-catalyst and dicyclopentyldimethoxysilane as an external donor. The catalyst was mixed in such proportions that the aluminum to titanium ratio was maintained at 250±5:1. The mole ratio of aluminum to external donor was maintained at (3±0.2):1. The catalyst was employed to polymerize propylene in the slurry phase reactor with hexane as the diluent under constant propylene atmospheric pressure.
Similar experiments were carried out to study the effect of masking compound in propylene slurry polymerization using various supported hybrid catalysts and the results are summarized in Tables 5 and 6 below:
Table 5- Effect of masking compound (4-vinyl cyclohexene) on slurry polymerization of propylene using catalyst
Effect of masking compound (4-vinyl Cyclohexene) on slurry polymerization of propylene using catalyst
Catalyst used 4-Vinyl Cyclohexene/Ti
ratio (mmole/mmole) Productivity (Kg PP /g cat) MFI-Melt Flow index (g/10 min) Bulk Density (g/ml) Xylene soluble (%)
Titanium supported Magnesium catalyst (Zeigler Natta diester catalyst)
(Expt 4) 0 10.5 1.1 0.5 1.3
1500 10.3 1 0.5 1.2
3000 9.4 0.99 0.5 1.4
6000 9.1 0.92 0.51 1.1
Supported hybrid metallocene catalyst Bis (n-ethyl cyclopentadienyl) Zirconium dichloride as metallocene
(Expt 6) 0 4.6 2.5 0.5 1.3
1500 2.1 2.2 0.48 1.6
3000 2 2.3 0.47 1.8
6000 1.9 1.8 0.47 1.7
Supported hybrid metallocene catalyst rac-dimethylsilylbis (1-indenyl) Zirconium dichloride as metallocene (Expt 7) 0 6.6 1.4 0.5 2.5
1500 6.4 1.2 0.48 2.6
3000 6.1 1.3 0.49 3

Using 4-vinylcyclohexene as a masking agent for homo polymerization of C3 was carried out with three different ratios. The result indicates that higher concentrations of masking component do not affect the PP productivity significantly.
Table 6- Effect of masking compound (9-vinyl carbazole) on slurry polymerization of propylene using catalyst
Effect of masking compound ( 9-vinyl carbazole) on slurry polymerization of propylene using catalyst
Catalyst of the present disclosure 9-Vinyl carbazole/Ti
ratio Productivity (Kg PP /g cat) MFI-Melt Flow index (g/10 min) Bulk Density (g/ml) Xylene soluble (%)
Titanium supported Magnesium catalyst (procatalyst)

Expt 4 0 8.5 2.5 0.5 1.3
1500 4.5 1.8 0.45 2.5
3000 4.1 2.3 0.43 2.3
6000 3.6 1.7 0.43 2.2
Supported hybrid metallocene catalyst Bis (n-ethyl cyclopentadienyl) Zirconium dichloride as metallocene

Expt 6 0 4.6 2.5 0.5 1.3
1500 2.1 1.9 0.43 1.8
3000 1.3 2 0.43 2
6000 0.5 1.9 0.43 2.1
Supported hybrid metallocene catalyst rac-dimethylsilylbis (1-indenyl) Zirconium dichloride as metallocene

Expt 7 0 6.6 1.4 0.5 2.5
1500 2.8 1.7 0.47 2.8
3000 1.9 1.9 0.46 2.5
6000 1.4 1.4 0.45 1.7

Using 9-vinylcarbazole as a masking agent, for polymerization of C3 was carried out with three different ratios. The result indicates that a higher concentration of the masking component affects the PP productivity significantly. Bulk density of the polypropylene and Isotacticity always remains the same in all the cases even at higher concentration of masking compounds. Isotacticity means (a stereospecific polymer) having identical steric configurations of the groups on each asymmetric carbon atom on the chain
These hybrid catalysts show higher hydrogen response than Ziegler Natta Diester catalyst which may be due to the presence of a zirconium metallocene moiety.
Better hydrogen response means less hydrogen is used to get the desired Melt Flow Index (MFI). When masking compound is used during homo polymerization, MFI reduces significantly in case of titanium supported pro-catalyst (as compared to the results with less concentration of the masking compound); where as in hybrid catalyst, MFI reduces only slightly in presence of masking compounds (as compared to the results with less concentration of the masking compound).
Polymerization conditions for experiment 8
• Al/Ti = 250 ± 10 (mmole/mmole)
• Al/Donor (Organosilane) = 3.0 ± 0.1 (mmole/mmole)
• H2 = 240 ± 10 ml
• Pressure = 5.0 ± 0.5 kg/cm2
• Temperature = 70 ± 2 °C
• Time = 2.0 hr
• 4-vinylcyclohexene or 9-vinyl carbazole = (5-20 ml)

The use of masking agent in co-polymerization of propylene with ethylene is crucial. The masking agent masks the metallocene moiety in the hybrid catalyst during propylene homo-polymerization and is subsequently reactivated with hydrogen and ethylene in the co-polymerization of ethylene and propylene polymerization.

Experiment 9:
Effect of concentration of tri alkyl aluminum as binder for synthesis of hybrid catalyst (Stereo-rigid Zr metallocene):
In 9 g titanium supported magnesium alkoxide pro-catalyst (30%) slurry obtained in step II of experiment 1; 0.3, 0.6 and 1.2 ml of tri-ethyl aluminum (neat) was added, followed by the addition of 250 mg of rac-dimethylsilylbis (1-indenyl) zirconium dichloride. The mixture was heated at 60 °C for 2-3 hours and the agitator speed was maintained at 400 rpm to obtain a reaction mixture. After the reaction was completed, the supernatant liquid was decanted and the catalyst was washed 5-6 times with toluene to remove any unreacted component. The hybrid catalyst formed was stored in hexane under nitrogen atmosphere. The composition of the hybrid catalyst obtained by the process of the present disclosure is summarized in Table-7.
Supported catalyst (or procatalyst) means transition metal component supported on magnesium alkoxide support where as hybrid catalyst means combination of supported magnesium alkoxide procatalyst and metallocene.
Table-7: Characterization of titanium supported hybrid metallocene catalyst:
S. No Tri alkyl aluminum conc. (ml) Mg
(Wt %) Ti
(Wt %) Zr
(Wt %) Cl
(Wt %) Al
(Wt %)
1 0.3 17.4 2.6 0.03
(350 ppm) 54.2 0.47
2 0.6 16.8 2.5 0.04
(425 ppm) 55.1 0.36
3 1.2 16.5 2.5 0.04
(450 ppm) 52.6 0.51
It is observed from Table 7 that as the amount of binding component (trialkyl aluminum) increases, the Zr wt% in the hybrid catalyst increases.
Catalyst compositional analysis and slurry polymerization studies:
Hybrid catalyst (0.07 g) obtained in experiment 9 was mixed with triethyl aluminum co-catalyst and dicyclopentyldimethoxysilane as an external donor. The catalysts were mixed in such proportions that the aluminum to titanium ratio was maintained at 250:1. The mole ratio of aluminum to external donor was maintained at (3.0 ±0.2) :1. The catalyst was employed to polymerize propylene in slurry phase with hexane as the diluent under a constant propylene pressure of 7 kg/cm2 for 2 hr. at 70 °C, followed by addition of 50 mmole of hydrogen to terminate the polymerization. Polymerization performance (productivity) and Product characteristics (MFI, Xylene solubles and bulk density ) are summarized in Table-8 below.
Table-8:
S. No Tri ethyl aluminum conc. (ml) in the catalyst (binder) Productivity (Kg PP/g cat) MFI (g/10 min) Bulk Density (g/ml) Xylene soluble (%)
1 0.3 6.6 1.4 0.50 2.5
2 0.6 7.2 1.0 0.48 2.5
3 1.2 6.0 1.4 0.48 3.4

From the results obtained in Table 8 it is observed that productivity, MFI and bulk density remains in the desirable range with increase in concentration of binder however xylene soluble percentage increases if binder is used in higher component i.e. isotacticity reduces.

Experiment 10:
Effect of hydrogen concentration, pressure, and temperature on stereo-rigid hybrid catalyst for propylene polymerization performance:
Preparation of supported hybrid metallocene catalyst: In 9 g magnesium alkoxide supported titanium catalyst (30%) slurry; 5 ml triethyl aluminum was added, followed by addition of 250 mg of rac-dimethylsilylbis (1-indenyl) zirconium dichloride metallocene to obtain a mixture. The mixture was heated at 60 °C for 3 hours and the agitator speed was maintained at 400 rpm. After 3 hours of the reaction, the supernatant liquid was decanted and the catalyst was washed 5-6 times with toluene and decanted to remove any unreacted component. The hybrid catalyst formed was stored in hexane in nitrogen (The hybrid catalyst does not dissolve in hexane and hence the hybrid catalyst forms catalyst slurry).
Characterization of the catalyst obtained in experiment 10 is summarized below in Table-9.
Table-9:
Elements Value
Magnesium (% wt) 16.8
Titanium (% wt) 2.4
Zirconium (% wt) 0.04 (450 ppm)
Chlorine (% wt) 54.2
A. Effect of hydrogen concentration
Slurry Polymerization: Hybrid catalyst (0.07 g) obtained in experiment 10 was mixed with triethyl aluminum co-catalyst and dicyclopentyldimethoxysilane as an external donor. The catalysts were mixed in such proportions that the aluminum to titanium ratio was maintained at 250:1 (the ratio of triethyl aluminum (mmole) to titanium (mmole) is maintained 250:1 which is standard ratio).The mole ratio of aluminum to external donor kept was maintained at (3.0 ±0.2) :1. The catalyst was employed to polymerize propylene in slurry phase with hexane as the diluent under a constant propylene pressure of 7 kg/cm2 for 2 hour at 70 °C., followed by using varying amounts of hydrogen, 240 ml (50 mmole), 480 ml (100 mmole) and 720 ml (150 mmole), to terminate the polymerization.
Polymerization performance and product characteristics are summarized in Table-10.
Table-10:
S. No Hydrogen Conc. ml Productivity (Kg PP/g cat) MFI (g/10 min) Bulk Density (g/ml) Xylene soluble (%)
1 240 7.5 1.0 0.48 2.4
2 480 6.6 2.9 0.51 0.8
3 720 6.5 4.0 0.51 0.7

From the results obtained in Table 10, it is observed that MFI of the polymer increases with increase in hydrogen concentration.
Polymerization conditions:
• Al/Donor (organosilane) = 3±0.2
• Temp = 70 ± 5 °C
• Pressure = 5 ± 0.5 atmospheres
• Al/Ti = 250 ± 10
• Amount of hydrogen = 240 or 480 or 720 (± 20 ml)
• Time = 2 hours
B. Effect of temperature
Slurry Polymerization: Supported hybrid metallocene catalyst (0.07 g) obtained in experiment 10 was mixed with triethyl aluminum co-catalyst and dicyclopentyldimethoxysilane as an external donor. The catalysts were mixed in such proportions that the aluminum to titanium ratio is maintained at 250:1. The mole ratio of aluminum to external donor was kept at (3 ±0.2):1. The catalyst was employed to polymerize propylene in slurry phase with hexane as diluent under a constant propylene pressure of 7 kg/cm2 for 2 hours at 60 °C, 70 °C, and 80 °C followed by the addition of 50 mmole of hydrogen to terminate the polymerization.
Polymerization productivity and product characteristics are summarized in Table-11.
Table-11:
S. No Temp (°C) Productivity (Kg PP/g cat) MFI (g/10 min) Bulk Density (g/ml) Xylene soluble (%)
1 60 3.7 1.4 0.49 2.2
2 70 7.6 1.4 0.50 2.5
3 80 4.5 2.5 0.42 1.1

From Table 11, it is observed that optimum temperature for propylene polymerization is 70°C.
Polymerization condition for experiment 10
• Al/Donor (Organosilane) = 3 ± 0.2 (mmole/mmole)
• Temp = 60, 70, 80 (± 5°C)
• Pressure = 5 ± 0.5 atm
• Al/Ti = 250 ± 10 (mmole/mmole)
• Amount of hydrogen = 240 ± 20 ml
• Time = 2 hours
C. Effect of external donor dosing on propylene homo-polymerization performance:
Slurry Polymerization: Supported hybrid metallocene catalyst (0.07 g) obtained in experiment 10 was mixed with triethyl aluminum as co-catalyst and dicyclopentyldimethoxysilane as an external donor. The catalysts were mixed in such proportions that the aluminum to titanium ratio was maintained at 250:1. The mole ratio of aluminum to external donor (Al/D) was maintained at (3.0 ±0.2) :1, (5 ±0.2):1 and (7±0.2):1. The catalyst was employed to polymerize propylene in slurry phase with hexane as diluent under a constant propylene pressure of 7 kg/cm2 for 2 hours at 70 °C, followed by addition of 50 mmole of hydrogen to terminate the polymerization. Polymerization productivity and Product characteristics are summarized in Table 12.
Table-12:
S. No Al/ D ratio (mmole/mmole) Productivity (kg PP/g cat) MFI (g/10 min) Bulk Density (g/ml) Xylene soluble (%)
1 (3.0 ±0.2):1 7.6 1.4 0.50 2.5
2 (5.0 ±0.2):1 5.2 1.9 0.50 1.0
3 (7.0 ±0.2):1 4.7 1.9 0.46 1.7
From the above table it is evident that the ratio of aluminum to external donor affects the productivity. With the mole ratio of aluminum to external donors of (5±0.2):1 and (7±0.2):1 the productivity is low as compared to at (3±0.2):1.. The ratio of Aluminum/ dicyclopentyldimethoxysilane is inversely proportional to the productivity of the polymerization process.
Polymerization conditions:
• Al/ Donor (Organosilane) = 3 or 5 or 7 (± 0.2)
• Temp = 70 ± 5 °C
• Pressure = 5 ± 0.5 atm
• Al/Ti = 250 ± 10
• Amount of hydrogen = 240 ± 20 ml
• Time = 2 hours

Experiment 11:
Gas phase propylene homo-polymerization and propylene with ethylene copolymerization by supported hybrid metallocene catalyst using 4-vinyl cyclohexene masking compound:
Supported hybrid metallocene catalyst: In 9 g magnesium alkoxide supported titanium catalyst (30%) slurry; 5 ml triethyl aluminum was added, followed by the addition of 250 mg of rac-dimethylsilylbis (1-indenyl) zirconium dichloride metallocene. The reaction was carried out at 60 °C for 2-3 hours and the agitator speed were maintained at 400 rpm. After the reaction was completed, the supernatant liquid was decanted and the catalyst was washed 5-6 times with toluene to remove any un-reacted component. The hybrid catalyst formed was stored in hexane under nitrogen.
Characterization details of the hybrid catalysts are summarized in Table-13.
Table-13:
Elements Value
Magnesium (% wt) 16.8
Titanium (% wt) 2.4
Zirconium (% wt) 0.04 (450 ppm)
Chlorine (% wt) 54.2
A. Gas Phase homo-polymerization of propylene using supported hybrid metallocene catalyst:
Supported hybrid metallocene catalyst (0.1 g) was mixed with tri-ethyl aluminum as a co-catalyst and dicyclopentyldimethoxysilane as an external donor. The catalysts were mixed in such proportions that the aluminum to titanium ratio was maintained at 250:1. 250:1 ratio is mmole/mmole of cocatalyst (added during polymerization) / titanium (present in hybrid catalyst). Aluminum to Titanium is the ratio of cocatalyst added during polymerization to Titanium ratio and not during synthesis of hybrid catalyst. The mole ratio of aluminum to dicyclopentyldimethoxysilane was maintained at (3±0.2):1. The catalyst was employed to polymerize propylene in gas phase reactor under a constant propylene pressure of 7 kg/cm2 for 1 hour at 70 °C followed by the addition of 50 mmole of hydrogen to terminate the polymerization.
Polypropylene resin was used as a seedbed in the gas phase reactor, as a fluidization media. 4-vinyl cyclohexene was used as the masking compound and the ratio of the masking compound/Ti ratio was maintained at 1500 mmole/mmole. The masking compound 4-vinyl cyclohexene was added to the reactor followed by addition of hybrid catalyst. After that the propylene was fed to the reactor. The masking compound masks metallocene component of hybrid catalyst and polyproylene PP (as homopolymer) was produced by pro-catalyst component of hybrid catalyst. Masking compound masks metallocene component of hybrid catalyst. The polymerization conditions are as given below-
Polymerization conditions:
• Al/Ti = 250 (mmole/mmole)
• Al/Donor = 3.0 ±0.2 (mmole/mmole)
• H2 = 500 ml
• Propylene Pressure = 7.0 ± 0.5 kg/cm2
• Temperature = 70 ± 2 oC
• Time = 1.0 hour
B. Gas Phase Co-polymerization of propylene with ethylene using supported hybrid metallocene catalyst:
After 1 hour of homo polymerization obtained in Step A of experiment 11, the polymerization reaction was stopped and the reactor was cooled to 45 °C and the excess propylene was vented. Modified triethyl aluminum and 200 ml of hydrogen was added and co-polymerization with ethylene-propylene mixture was started at 55°C by keeping C2/ (C2+C3) ratio about 0.35. The co-polymerization reaction was carried out for about 10 to 30 minutes. After 30 minutes the monomer consumption is minimal and ?T observed between reactor and heating/chilling medium starts reducing. This was the indication of completion of the co-polymerization reaction. The reactor was cooled to room temperature, i.e. 25 to 30 oC and the co-polymer was dried overnight. The obtained co-polymer typically was found to have 65-75% of a homogeneous polymer matrix. The copolymer formed, contains Rc (rubber content) equal to 25% to 35%, which means that the copolymer obtained contains 65-75% of homogenous PP matrix.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The process of the present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
? a simple process for preparing a supported hybrid metallocene catalyst;
? homopolymerization as well as co-polymerization of olefins can be done using a single supported hybrid metallocene catalyst in a continuous process;
? incorporation of metallocene compound in the supported hybrid metallocene catalyst is achieved up to 2%;
? incorporation of metallocene compound allows more dispersion of ethylene moiety in polypropylene;
? hetero-phasic polymers can be synthesized from the supported hybrid metallocene catalyst; and
? polymers (homopolymer as well as co-polymer) with controlled molecular weight.

The exemplary embodiments herein quantify the benefits arising out of this disclosure and the various features and advantageous details thereof are explained with reference to non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments 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 has 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.
Any discussion of documents, acts, materials, devices, articles and 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.
While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

,CLAIMS:1. A supported hybrid metallocene catalyst system comprising:
a) a magnesium alkoxide supported titanium pro-catalyst;
b) at least one binding agent; and
c) at least one of a stereorigid and a non- stereorigid metallocene compound.
2. A catalyst system as claimed in claim1, wherein the amount of said metallocene in said supported hybrid metallocene catalyst system ranges from 0.05 to 2 wt %.
3. A catalyst system as claimed in claim 1, wherein said magnesium alkoxide is spherical magnesium alkoxide.
4. The catalyst system as claimed in claim 1, wherein said spherical magnesium alkoxide has the formula Mg [(OR1)2-x (OR2) x], wherein one of OR1 and OR2 is methoxy and the other one is selected from the group consisting of ethoxy, propoxy, butoxy and pentoxy; wherein the methoxy content in said spherical magnesium alkoxide ranges from 0.01 to 8 wt%.
5. The catalyst system as claimed in claim 1, wherein said binding agent is an alkyl aluminum, which is selected from the group consisting of methylaluminoxane (MAO), tri-ethyl aluminum (TEAL), tri-isobutyl aluminum (TIBAL) and di-ethyl aluminum chloride (DEAC).
6. The catalyst system as claimed in claim 1, wherein said metallocene compound is selected from the group consisting of bis (n-ethyl cyclopentadienyl) titanium dichloride, bis (n-ethyl cyclopentadienyl) zirconium dichloride and rac-dimethylsilylbis (1-indenyl) zirconium dichloride.
7. The catalyst system as claimed in claim1, wherein said catalyst system further includes a masking agent.
8. The catalyst system as claimed in claim 7, wherein said masking agent is at least one compound selected from the group consisting of 4-vinyl cyclohexene and 9-vinyl carbazole.
9. The catalyst system as claimed in claim 7, wherein the ratio of the amount of said masking agent and said catalyst system is in the range of 1500 mmoles to 6000 mmoles.

10. A process for preparing a supported hybrid metallocene catalyst, said process comprising:
a) reacting at least one spherical magnesium alkoxide, at least one titanation fluid medium and at least one internal donor at a temperature ranging from 40 oC and 80 oC in a stepwise manner for a time period ranging from 10 to 12 hours to obtain a spherical magnesium alkoxide supported titanium pro-catalyst;
b) mixing said pro-catalyst with at least one binding agent to obtain a mixture;
c) treating said mixture with at least one metallocene compound at a temperature ranging from 50 oC to 80 oC for a time period ranging from 2 to 4 hours to obtain the supported hybrid metallocene catalyst; and
d) optionally, adding at least one masking agent to said supported hybrid metallocene catalyst to obtain a supported hybrid metallocene catalyst with the masking agent.
11. The process as claimed in claim 10, wherein said titanation fluid medium is an equimolar mixture of titanium tetrachloride and chlorobenzene, and said internal donor is at least one selected from the group consisting of di-isobutyl phthalate.
12. A process for homo-polymerizing and co-polymerizing olefins using a supported hybrid metallocene catalyst system, said process comprising;
i. mixing at least one masking agent with a first fluid medium to obtain a first slurry;
ii. mixing at least one said supported hybrid metallocene catalyst system with at least one co-catalyst and at least one external donor in a second fluid medium to obtain a second slurry;
iii. polymerizing at least one olefin using said first slurry and said second slurry at a temperature ranging from 60 oC to 80 oC under constant pressure ranging from 4 kg/cm2 to 8 kg/cm2 for a time period ranging from 1 hour to 4 hours to obtain a homopolymer followed by cooling said homopolymer and adding H2 to obtain the homopolymer of the desired molecular weight; and
iv. adding a co-catalyst and a mixture of at least two olefins to said homopolymer of the desired molecular weight at a temperature ranging from 50 oC to 80 oC for a time period ranging from 10 minutes to 30 minutes to obtain a co-polymer, wherein said co-polymer has 65-75% of the homopolymer matrix.
13. The process as claimed in claim 12, wherein said first fluid medium and said second fluid medium are independently selected from the group consisting of hexane, decane, and heptane.
14. The process as claimed in claim 12, wherein said co-catalyst is tri-alkyl aluminum.
15. The process as claimed in claim 14, wherein said co-catalyst istri-ethyl aluminum.
16. The process as claimed in claim 12, wherein said external donor is organosilane.
17. The process as claimed in claim 16, wherein said organosilane is dicyclopentyldimethoxysilane,