FORM-2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(see section 10 and rule 13)
A PROCESS FOR PREPARING HIGH MELT STRENGTH POLYOLEFINS
RELIANCE INDUSTRIES LIMITED
An Indian Company
of 3rd Floor, Maker Chamber-IV
222, Nariman Point, Mumbai-400021,
Maharashtra, India.
Inventors:
1. SATPATHY UMA SANKAR
2. BASARGEKAR RAJEEV S
3. MATHUR AJIT BEHARI
4. JASRA RAKSH VIR
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE DISCLOSURE:
The present disclosure relates to a process for preparing high melt strength polyolefins.
BACKGROUND:
Polyolefin compositions find their widespread applications in the manufacture of various articles and products due to their excellent solid state properties. Commercial polyolefins, for example polyethylene and polypropylene produced with Ziegler-Natta or metallocene catalysts have a linear molecular structure with a narrow molecular weight distribution. In spite of their excellent solid state properties, linear polyolefins shows relatively low melt strength and exhibits no strain hardening. The absence of strain hardening and low melt strength make linear polyolefins less suitable for applications like thermoforming, blow molding, extrusion, coating and foaming. Among polyolefins, polypropylene with their high melting point and high modulus are of particular interest for applications like extruding, forming and the like. The introduction of long chain branches (LCB) to the linear polyolefin chain and/or mixing high molecular weight polymer fractions in the linear polyolefin with low melt strength are known to improve the overall melt strength properties of the linear polyolefins.
EXISTING KNOWLEDGE:
The introduction of long chain branches to the linear polyolefins, particularly polypropylene is accomplished by means of various methods. Most of them includes either the use of a free radical initiator to crosslink the linear polypropylene chain or the use of co-monomers to graft the monomers on to the polypropylene backbone.
For introducing long chain branches, different methodologies are adapted at industrial scale, for example, grafting branches from a polymer backbone as disclosed in PCT Int. Appl. WO0047643, US6084030 and Macromolecules 2002, 35, 9246-9248; addition of a branching agent to during the polymerization as disclosed in

US5328956, PCT Int. Appl. WO9708216 and Res. 2004, 43, 2860-2870; addition of a chain transfer agent during the polymerization as disclosed in Macromolecules 2003, 36, 4692-4698, Macromol. Chem. Phys.1994, 195, 1381-1388; copolymerization of a monomer with a macro monomer as disclosed in J. Am. Chem. Soc., 1998, 120, 1082-1083, PCT. Int. Appl. WO9834970, 1998, PCT Int. Appl. WO 0107493, US6225432, US6455649, US6423793, US0127649, and US Patent Appl. 0054098.
Further, the long chain branched Polyolefins are also prepared through the copolymerization of an alkene-terminated macro monomer with a co-monomer by using single-site catalysts, for example, the processes as disclosed WO9834970, Macromolecules 1999, 32, 5723-5727, J. Am. Chem. Soc. 2002, 124, 15280-15285, Macromolecules 2003, 36, 9014-9019, Macromol. Mater. Eng. 2005, 290, 72-77. The single site catalyst allows control over the branch length and distribution.
Further to the above described methods known, the post reactor treatment of the linear polyolefins is the most widely accepted method for introducing long chain branching, for example the processes as disclosed in US4916198, J. Appl. Poly. Sci., 99, 250, 2005, Adv. Polym. Technol., 25, 208, 2006, Polymer, 47, 7962, 2006, Macromolecules, 35, 4602, 2002 and Eur. Polym. J., 44, 200, 2008.
Post reactor treatment usually includes electron beam irradiation as disclosed in Adv. Polym. Technol., 25, 208 (2006), and Macromol. Sci., Pure Appl. Chem. 1999, 36, 1759-1769; peroxide decomposition as disclosed in Polymer 2001, 42, 10035-10043; and reactive extrusion processes as disclosed in Polymer, 42, 10035, 2001, Angew. Makromol. Chem., 69, 107, 1978 and Angew. Makromol. Chem., 69, 107, 1978. Compared to the electron beam irradiation, the reactive extrusion has many merits, including simple operation, low cost and high productivity. For this reason, the preparation of long chain branched polyolefins by reactive extrusion processes has generated increasing interest over the past decades.

Lagendijk et al. (Polymer, 42, 10035 (2001) disclose a process for the preparation of long chain branched polypropylene (LCB-PP) by reactive extrusion in the presence of peroxydicarbonate (PODIC) with various structures. According to Lagendijk et al., all modified samples showed enhanced strain hardening, slightly lower melt flow index (MFI), increased extrudate swelling, and improvement in melt strength. According to Lagendijk et. al. the amount of the long chain branchings (LCB) can be controlled by the type and the amount of PODIC used for the modification process, thereby, indicating that the peroxide structure has a direct influence on the branching level of modified PPs. PP has a tendency to undergo [beta]-scission because of the nature of its molecular structure, and this competes with grafting and cross-linking reactions during the reactive extrusion process. The use of polyfunctional monomers can decrease the degradation and improve the degree of branching for polypropylene, as disclosed in Polymer, 47, 7962: 2006 and J. Appl. Polym. Sci., 61, 1395: 1996.
A polyfunctional monomer in the presence of free radicals produces more stable macro radical sites, which increase the likelihood of further reactions, because of a decrease of the probability of fragmentation. Rheological properties of a melt are strongly affected by the presence of long chain branches. Thus, rheology has proven to be a reliable and easy to implement method for the verification of the existence of long branches on the polymeric chain.
Long chain branching increase the possibility of entanglements in the polymeric melt, and thus affect its elasticity. Yu and coworkers confirm the branching chain structure of modified PPs by small-amplitude oscillatory shear experiments (probability fragmentation). The detection of the branching number is very difficult because the degradation, grafting, and cross-linking reactions take place simultaneously during the reactive extrusion process leading to a complex product. Compared to NMR and GPC, rheology is a more appropriate and reliable technique for verifying the existence of long chain branches on polymeric chains, especially for low level LCB. Tsenoglou and Gotsis (Macromolecules, 34, 4685: 2001) determined the extent of LCB based on the rheological characteristics. Garcia-Franco et al. (Eur. Polym. J., 44, 376 ; 2008)

suggested that the level of LCB on polyethylene can be quantified by small amplitude oscillatory shear experiments, with analysis predicated on the use of so-called Van Gurp-Palmen plots (Van Gurp plots).
Therefore, there always remains a need to provide an improved process for the preparation of high melt strength polyolefins which facilitate to achieve desired level of branching with control over its type and distribution on to the polyolefin matrix and also suits for commercialization in running polyolefin plants.
OBJECTS:
Some of the objects of the present disclosure are described herein below:
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.
Another object of the present disclosure is to provide a process for the preparation of high melt strength polyolefins.
Still another object of the present disclosure is to provide a simple, efficient and a cost effective process for the preparation of high melt strength polyolefins.
A yet another object of the present disclosure is to provide a process for the preparation of high melt strength polyolefins wherein an optimal amount of modifier is employed during the modification process, thereby obtaining high melt strength polyolefin products substantially free from modifier residues.
A yet another object of the present disclosure is to provide high melt strength polyolefins having substantially improved properties that include rheology, broadening of MW, processing window and the like.

Other objects and advantages of the present invention will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present invention.
DEFINITIONS:
As used the terms 'single acrylate monomer' and 'multi-functional acrylate monomer' in the context of the present disclosure refer to a monomer having only one acrylate site and to a monomer having two or more acrylate sites, respectively.
As used, the term "high melt strength polyolefin" in the context of the present disclosure refer to a modified polyolefin prepared by the reactive modification of a linear polyolefin via introducing long chain branching onto the main polyolefin chain. The introduction of long chain branching in the linear polyolefin molecules enhances entanglement density thereby turning melt behavior of the polyolefin from extensional thinning to extensional hardening i.e. enhancement in melt strength.
As used the term "Melt Flow Rate (MFR)" in the context of the present disclosure refers to the quantity of a melted polyolefin that will flow through an orifice at a specified temperature and under a specified load. The Melt Flow Rate is the measure of resistance to flow of polyolefin melt under defined set of conditions (unit: dg/min or g/10 min). Being a measure at low shear rate condition, MFR is inversely related to a molecular weight distribution of the polyolefin and is used as an indicator of melt strength enhancement of polyolefin during the course of its modification. High Melt Strength or enhancement in the melt strength of the modified polyolefin as described in the present disclosure is indicated through its reduced melt flow rate as compared to the melt flow rate of the linear polyolefin.
As used herein, the term "synergic composition" and "synergistic composition" refers to a composition comprising optimal amounts of a modifier and free radical initiators that provides the desired melt strength properties to a polyolefin matrix and the

achieved melt strength property is greater than the melt strength property achieved by using either a modifier or free radical initiators alone.
As used the term "compounding" in the context of the present disclosure refers to a reactive extrusion process wherein the polymer matrix is chemically reacted with at least one ingredient intimately mixed with said polymer matrix during a polymer extrusion process.
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.
SUMMARY
In accordance with one aspect, the present disclosure provides a process for preparing high melt strength polyolefin, said process comprising the following steps:
i. physically mixing a polyolefln matrix, at least one multifunctional monomer and at least one first free radical initiator optionally in combination with at least one second free radical initiator at ambient temperature to obtain a reaction mixture, wherein said first free radical initiator and said second free radical initiator being characterized with half-lives differing by at least one order of magnitude; and
ii. compounding the reaction mixture under pre-determined conditions to obtain polyolefin having melt strength characterized by a melt flow rate ranging between 0.5 and 30 dg/min.

Typically, the polyolefin is at least one polyolefm selected from the group consisting of polyethylene and, polypropylene.
Typically, the polyolefin is a homo-polymer or a copolymer of propylene with one or more olefins and/or dienes selected from the group consisting of ethylene. C4-C18 alpha-olefins and dienes.
Typically, the polyolefin is a linear homo-polymer of propylene having low melt strength characterized with a melt flow rate (MFR) in the range of from 3 to 12 dg/min.
Typically, the multifunctional monomer is an acrylate compound that includes at least one compound selected from the group consisting of diacrylates, triacrylates, tetraacrylates and pentaacrylates.
Typically, the multifunctional monomer is triacrylate, preferably pentaerythritol triacrylate.
Typically, the amount of the multifunctional monomer varies between 1000-10000 ppm, preferably between 1000 and 5000 ppm, more preferably between 1000 and 2500 ppm.
Typically, the half life of the first radical initiator varies in the range of 0.1 hr. to 0.99 hr.
Typically, the half life of the second free radical initiator varies in the range of 1 hr. to 10 hr.
Typically, the first free radical initiator is dicetyl peroxydicarbonate, said free radical initiator is present in an amount varying between 500 and 3000 ppm, preferably between 1000 and 3000 ppm, more preferably between 2000 and 3000 ppm.

Typically, the second free radical initiator is 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, said free radical initiator is present in an amount varying between 10 and 50 ppm, preferably between 10 and 20 ppm.
Typically, the method step (i) of the process of the present disclosure further comprises the addition of at least one additive, said additive being selected from the group of compounds consisting of stabilizers, lubricants and the like.
Typically, the additive is a stabilizer that includes at least one compound selected
from the group consisting of tetrakis-(methylene-(3,5-di(tert)-butyl-4-
hydroxycinnamate))methane, Tris(2,4-di-(tert)-butyl phenyl)phosphite and
Tetrakis(2,4-di-tert-butylphenyl)-4,4-biphenyldiphosphonite.
Preferably, the stabilizer is a mixture of tetrakis-(methylene-(3,5-di(tert)-butyl-4-hydroxycinnamate))methane in an amount varying between 500 and 2000 ppm and Tris(2,4-di-(tert)-butylphenyl)phosphite in an amount varying between 1000 and 2000ppm.
Preferably, the stabilizer is a mixture of tetrakis-(methyIene-(3,5-di(tert)-butyI-4-hydroxycinnamate))methane in an amount varying between 1000 and 2000 ppm and Tetrakis(2,4-di-tert-butyIphenyI)-4,4-biphenyIdiphosphonite in an amount varying between 500 and lOOOppm.
Typically, the compounding of the reaction mixture is a reactive extrusion process carried out using a twin screw extruder at screw rpm varying between 50 and 500, preferably between 100 and 300, more preferably between 150 and 250 and at a temperature varying between 100 and 300 °C, preferably between 180 and 250 °C, more preferably between 150 and 250 °C.

In accordance with another aspect of the present disclosure there is provided high melt strength polyolefin prepared in accordance with the process as disclosed in the present disclosure, said high melt strength polyolefin being characterized by a melt flow rate ranging between 0.5 dg/min and 30 dg/min, preferably between 0.50 and 25 dg/min, more preferably between 0.5 and 10 dg/min.
Typically, the polyolefin is at least one selected from the group consisting of polypropylene and polyethylene.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 of the accompanying drawings illustrates (A) Tan8; and (B) Molecular Weight and Molecular Weight Distribution of homo-polymer of propylene (homo-PP) (5MI) (a) before and (b) after reactive modification thereof carried out by using a combination of PETA (0.045wt%) and Parkadox (0.29 wt%), in accordance with the process of the present disclosure;
Figure 2 of the accompanying drawings illustrates Molecular Weight and Molecular Weight Distribution of homo-polymer of propylene (homo-PP_ (5MI) (a) before and (b) after reactive modification thereof carried out by using a combination of PETA (0.40 wt%) and Parkadox (0.20 wt%), in accordance with the process of the present disclosure;
Figure 3 of the accompanying drawings illustrates Molecular Weight and Molecular Weight Distribution of homo-polymer of propylene (3MI) (a) before and (b) after reactive modification thereof carried out by using a combination of PETA (0.35wt%) and Parkadox (0.15 wt%). in accordance with the process of the present disclosure;
Figure 4 of the accompanying drawings illustrates rheological plots for:

A. Overlay of Tan5 of (a) virgin homo-polymer of propylene, (b)
polypropylene modified with PARKADOX (o.25 wt%) and LUPEROX
(corresponding to Example-4B), and (c) polypropylene modified with a
composition comprising the combination of PETA, PARKADOX and
LUPEROX (corresponding to example-4A);
B. MW/MWD of (a) virgin homo-polymer of propylene, (b) polypropylene
modified with PARKADOX (0.25wt %) and LUPEROX (corresponding to
Example-4B) and (c) polypropylene modified with a composition comprising
the combination of PETA, PARKADOX and lUPEROX (corresponding to
example-4A); and
Figure 5 of the accompanying drawings illustrates DSC thermograms of the following:
(A) Modified Impact Copolymer Propylene (ICP-PP-) (MI 1.5 dg/min);
(B) Modified Homo-Polypropylene (5MI);
(C) Modified mixed Matrix of Homo-PP and ICP-PP (50:50 wt%); and
(D) Modified mixed matrix of Homo-PP and ICP-PP (80:20 wt%), wherein all the polymers being modified by using a composition comprising 0.25 wt% PETA and 0.3 wt% of PARKADOX.
DETAILED DESCRIPTION:
Accordingly, a process for preparing high melt strength polyolefin via reactive modification of linear polyolefin of low melt strength and poor process-ability is envisaged in the present disclosure wherein high mait strength is imparted by introducing long chain branching (LCB) onto the linear polyolefin chain. The reactive modification of the linear polyolefin matrix via introducing long chain branching is typically accomplished by using a synergic composition of modifiers and free-radical initiators.

The introduction of long chain branching to the linear polyolefin matrix considerably improves its melt strength. Branches are typically considered to be long chain branches when the branch length is at least 2.5 times of entanglement molecular weight ("the molecular weight between adjacent temporary entangle points) as defined by Eckstein and co-workers in Macromolecules 1998, 31, 1335-1340).
As described earlier, the use of modifiers for the modification of linear polyolefin, particularly the linear polypropylene to produce high melt polypropylene is known, however the reported methods disclose the use of a single modifier. When modifiers are used alone, they are particularly used in relatively higher concentrations, and due to temperature sensitivity and lower half life, they lead to the problems of coloration and/or residual modifier in the final polyolefin product.
Therefore, in order to overcome the problems allied with the usage of higher amount of modifiers, the inventors of the present disclosure envisages the use of a modifier in combination with optimal amounts of free radical initiators for the reactive modification of the linear polyolefins. The use of optimal amounts of free radical initiators significantly reduces the effective concentration of modifiers required for the reactive modification of the linear polyolefins , thereby, making the process more effective to achieve desired melt strength of the polyolefins.
In accordance with the present disclosure, there is provide a process for the preparation of high melt strength polyolefin, said process comprising the steps described herein below:
For preparing high melt strength polyolefin in accordance with the process of the present disclosure, a reaction mixture comprising pre-determined weight proportions of polyolefin matrix, at least one modifier and at least one first free-radical initiator optionally in combination with at least one second free radical initiator is prepared.

The obtained reaction mixture is then compounded under pre-determined reaction conditions to obtain high melt strength polyolefin.
The polyolefin matrix used in the process of the present disclosure includes at least one selected from the group consisting of polyethylene and polypropylene. In accordance with one of the embodiments of the present disclosure, the polyolefin matrix is polypropylene.
The polypropylene matrix employed in the process 0f the present disclosure is typically a linear polypropylene. The linear polypropylene is a homo-polymer of propylene having a weight average molecular weight Mw ranging between 500,000 to 1,500,000 g/mol and a melt flow rate ranging between 3-12 dg/min. Alternatively, the linear polypropylene is a copolymer of propylene with one or more olefins and/or dienes selected from the group consisting of ethylene and C4-C18 alpha-olefins or dienes, preferably ethylene. The co-polymer of propylene may be a random copolymer or a block copolymer, preferably a random copolymer of propylene with ethylene. In accordance with one of the embodiments 0f the present disclosure, the linear polypropylene is Impact Copolymer Polypropylene.
The linear polypropylene employed in the process of the present disclosure can be prepared by using any catalyst systems known in the field of propylene polymerization, preferably a Zeigler-Natta or a metallocene catalyst system.
The first free radical initiator used in the process of the present disclosure is typically chosen from free radical initiators having half life particularly varying between 0.1 hour and 0.99 hour. However, in order to accelerate the modification process, the second free radical initiator is also added to the reaction mixture. The second free radical initiator used in the process of the present disclosure is chosen from the free radical initiators having life half particularly varying between 1 hour and 10 hours.

The multifunctional monomer used in the process of the present disclosure is typically selected from the group of consisting of acrylates; allyl compounds, for example, allyl acrylate, allyl methacrylate, allyl methyl maleate and/or allyl vinyl ether; dienes, for example, butadiene, chloroprene, cyclohexadiene, cyclopentadiene, 2,3 dimethylbutadiene, heptadiene, hexadiene, isoprene and/or 1,4 pentadiene; divinyl compounds, for example, divinylaniline, divinylbenzene, p-divinylbenzene, divinylpentane and/or divinylpropane, and any combinations thereof.
In accordance with one of the embodiments of the present disclosure, the modifier is typically an acrylate containing monomer. The acrylate containing monomer may be hydrophilic, hydrophobic or combinations thereof. The acrylate containing monomer in accordance with the present disclosure is a single acrylate monomer; alternatively, the acrylate containing monomer is a multi-functional acrylate monomer.
In accordance with one of the embodiments of the present disclosure, the acrylate containing monomer is a multifunctional acrylate monomer selected from the group consisting of diacrylates, triacrylates, tetraacrylates, pentaacrylates and combinations thereof. Preferably, the multifunctional monomer is triacrylate. A suitable example of such acrylates includes pentaerythritol acrylate (PETA). The amount of the modifier, particularly pentaerythritol acrylate typically varies between 100-10000 ppm, preferably between 500 to 5000 ppm, more preferably between 500 ppm and 3000 ppm.
The first and the second free radical initiators employed in the process of the present disclosure may be selected from the group of compounds consisting of peroxides, per esters, peroxycarbonates and combinations thereof. The preferred free radical initiators in accordance with the present disclosure are chosen from peroxides.
Typically, the first free radical initiator is selected from the group of peroxides having half life varying between 0.1 hour and 0.99 hour. A suitable example of first free

radical initiator in accordance with the present disclosure is dicetyl peroxydicarbonate (PARKADOX241).
Typically, the second free radical initiator is selected from the group of peroxide having half life varying between 1 hour and 10 hours that includes at least one selected from the group consisting of 2,5-bis-(tert-butylperoxy)-2,5-dimethylhexane (Luperox 101), 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Trignox 101) and 3,6,9-triethyl-3,6,9-trimethyl-l,4,7-triperoxonane , and 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexene (L-130). In accordance with one of the embodiments of the present disclosure, the second free radical initiator is 2,5-bis-(tert-butylperoxy)-2,5-dimethylhexane.
In addition to the second free radical initiators as described above , the free radical initiators as disclosed in United States Patent 4707524, for example, Trigonox® 301 is also suitable for use in the process of the present disclosure.
The amount of the first free radical initiator, particularly dicetyl peroxydicarbonate as employed in the process of the present disclosure varies between 500 and 3000 ppm, preferably between 1000 to 3000 ppm. In accordance with one of the embodiments of the present disclosure, the amount of the first free radical initiator varies between 2000 to 3000 ppm. The amount of the second free radical initiator typically varies in the range of from 10 to 50 ppm. In accordance with one of the embodiments of the present disclosure, the amount of the second free radical initiator for the desired degree of modification varies between 10 and 20 ppm.
The mixing of the polyolefin matrix along with the modifier and the free radical initiators is typically accomplished in a batch mode by using a high speed mixer for a time period varying between 5 and 10 min, preferably between 2 and 3 min. The mixing is typically accomplished at ambient temperature.

The obtained reaction mixture is then compounded by employing a reactive extrusion process under pre-determined conditions of rpm, extrusion time and temperature to reactively modify the linear polyolefin and to obtain high melt strength polyolefins. The reactive extrusion process is a continuous process typically performed in a continuous reactor, mixer, kneader and extruder. In accordance with the process of the present disclosure, the reactive extrusion process is carried out in batch mode by using Bhusco kneader having batch size 0.50 to 2 kg in lab and in continuous mode in pilot scale by using a Co-rotary twin screw compounder (OMEGA 30) of M/s Steer Engineering (P) Ltd., Bangalore. The screw diameter of the extruder is typically 30 mm andL/Das 40:1.
The extrusion process is known to be temperature and shear sensitive, particularly in the circumstances when a synergic composition comprising the modifier and the free radical initiators are used for the reactive modification. The extrusion conditions in accordance with the process of the present disclosure are therefore well manipulated to achieve the target melt rheological properties in the polyolefins of high melt strength. The reactive extrusion in accordance with the process of the present disclosure is typically carried out at a temperature varying between 200-260 °C, preferably between 180-250 °C. To maintain a maximum suitability and sensitivity. the temperature profile for modification is well negotiated in the range 150-250 °C based on the half life of the free radical initiators used in the present process.
In continuation extrusion process, twin screw extruder rpm is also optimized to provide optimum residence time to the free radical initiators for an optimum grafting reaction of the modifier on to the polypropylene matrix. The rpm of extrusion in accordance with the process of the present disclosure varies between 50 and 300. In accordance with one of the embodiments of the present disclosure, the preferred rpm of extrusion varies between 50 and250, more preferably between 50 and 200 for a complete and kinetically balanced reaction.

Further to the modifiers and free radical initiators, the standard polymer additives can also be employed in the process of the present disclosure. The additives can be added at any convenient stage during the preparation of the high melt strength-long chain branched polyolefins. However, in accordance with a particular preferred method of the present disclosure, stabilizers/additives are mixed during the batch preparation of the reaction mixture.
The stabilizer suitable for the purpose of the present disclosure includes at least one
selected from the group consisting of tetrakis-(methylene-(3,5-di(tert)-butyl-4-
hydroxycinnamate))methane, Tris(2,4-di-(tert)-butylphenyl)phosphite and
Tetrakis(2,4-di-tert-butylphenyl)-4,4-biphenyldiphosphonite.
In accordance with one of the embodiments of the present disclosure, the stabilizer is a mixture of tetrakis-(methyIene-(3,5-di(tert)-butyl-4-hydroxycinnamate))methane (commonly known as IrganoxlOlO) in an amount varying between 500 and 15000 ppm and Tris(2,4-di-(tert)-butylphenyl)phosphite (commonly known as Irgafos -168) in an amount varying between 1000 and 2000 ppm, based on the total amount of the linear polypropylene used.
In accordance with another embodiment of the present disclosure, the stabilizer is a mixture of tetrakis-(methylene-(3,5-di(tert)-butyl-4-hydroxycinnamate))methane (IrganoxlOlO) in an amount varying between 1000 and 2000 ppm and Tetrakis(2,4-di-tert-butylphenyl)-4,4-biphenyldiphosphonite (commonly known as PEPQ) in an amount varying between 500 and 100 ppm, based on the total amount of the linear polyolefin matrix..
In addition to the above described antioxidants/stabilizers. normal doses of calcium stearate as a lubricant is also added during the preparation of the reaction mixture. The amount of the lubricant as added in the process of the present disclosure is 600 ppm. The combinations of stabilizers and lubricants as employed in the process of the

present disclosure facilitate to retain stability and integrity of branching even after multiple extrusion processes.
The reaction mixture prepared in accordance with the process of the present disclosure is a single shot recipe wherein all the components/ingredients are added together before starting the reactive extrusion process. The process of the present disclosure. therefore, does not require any installment wise addition of additives/antioxidants during the reactive extrusion process.
The molten and modified polyolefin as obtained after completion of the reactive extrusion process, in accordance with the present disclosure, is then cooled and palletized. The resultant long chain branched polyolefin displays a variety of improved properties, for example reduced melt flow rate (MFR), higher melt viscosity, broadening of molecular weight distribution (MWD) and processing window when compared to an othenvise similar polyolefin composition lacking the acryl ate-containing compound.
In accordance with another aspect of the present disclosure, there is provided high melt strength prepared in accordance with the process of the present disclosure. The high melt strength polyolefin includes at least one polyolefin selected from the group consisting of polyethylene and polypropylene, particularly polypropylene.
The high melt strength polypropylene is characterized with a melt flow rate (MFR) typically ranging between 0.5 g/10 min to 30 g/10 min., preferably between 0.50 g/10 min. to 25 g/10 min., more preferably between 0.5 g/10 min. to 20 g/10 min. The Melt flow rate of the high melt strength polypropylene is typically reduced from 10% to 60%, preferably from 20% to 60%, more preferably from 30% to 60%, when compared to the melt flow rate of the linear polypropylene. The MFR is determined by using a dead-weight piston Plastometer that extrudes polypropylene through an

orifice of specified dimensions at a temperature of 230° C and a load of 2.16 kg in accordance with ASTM Standard Test Method D-1238.
The high melt strength polypropylene prepared in accordance with the process of the present disclosure demonstrates improved process-ability when compared with the linear polypropylene with similar melt flow rate. This improved process-ability is reflected by a marginal reduction/retain in extrusion melt pressure, extruder torque, energy expenditure, and increases in the extrusion rates for processing of the long chain branched polypropylene. For example, high melt strength polypropylene extrudes at a reduced melt pressure (or without change in melt pressure) when compared to the linear polypropylene with similar melt flow rate. Typically, the melt pressure of the high melt strength polypropylene shows a reducing tendency in the range of 5-10%, under optimized synergic compositions when compared to the linear polypropylene with similar melt flow rate.
Without wishing to be limited by theory, the high melt strength polypropylene prepared in accordance with the process of the present disclosure displays a reduced melt pressure due to the presence of long chain branching. The lower melt pressure of the high melt strength polypropylene also results in a higher extrusion rate when compared to the linear polypropylene with similar melt flow rate. Typically, the high melt strength polypropylene is characterized with an extrusion rate increased by greater than 5%, preferably greater than 10%, more preferably greater than 20% when compared to the linear polypropylene having a similar melt flow rate.
The high melt strength polypropylene prepared in accordance with the process of the present disclosure is extruded at a reduced torque (same or 5-10 % reduction based on synergic composition) when compared to the linear polypropylene with similar melt flow rate. The extruder torque is a measure of the resistance the extruder motor experiences as it conveys the composition. The extruder torque is typically reduced by

greater than 5%, preferably greater than 10%, when compared to the linear polypropylene with similar melt flow rate.
The high melt strength polypropylene prepared in accordance with the process of the present disclosure is extruded at a reduced specific energy when compared to the linear polypropylene. The specific energy is an important factor in twin-screw extruder that refers to the amount of energy required to perform extrusion process. Typically, the high melt strength polypropylene is extruded at a specific energy lowered by greater than 5%. preferably greater than 10%, when compared to the linear polypropylene with equivalent melt flow rate.
The process for producing high melt strength polypropylene in accordance with the process of the present disclosure further comprises a method step of heating the high melt strength polypropylene using the optimum synergic composition of the modifier and the peroxides to introduce (3-structure into the tailor made high melt strength polypropylene. The introduction of p-structure into the high melt strength polypropylene improves its mechanical properties, particularly notched Izod impact to a higher side as compared to the linear polypropylene polymer. Particularly, the mixed matrix comprising linear polypropylene (Homo-PP) (5 MI) and Impact Copolymer Polypropylene (ICP-PP) (1.5 MI) when reactively extruded using optimum amounts of the first radical initiator, for example, dicetyl peroxydicarbonate and Pentaerythritol triacrylate (in combination with 10-20 ppm 2,5-bis-(tert-butyIperoxy)-2,5-dimethylhexane (LUPEROX101) shows B-structure formation which is further evidenced from the thermal characteristics evaluated by DSC.
The combination of the modifier and the free radical initiators makes the process of the present disclosure simple and more importantly quite effective for imparting the desired level branching even at much lower concentration of both the initiators and the modifier. Such minimization of doses facilitates to inhibit homo polymerization of the modifier during extrusion and consequently enhances the degree of branching via optimum melt grafting of said modifier on to the linear polyolefin matrix.

The high melt strength polyolefins prepared in accordance with the process of the present disclosure is further converted to end-use articles by any suitable process and is used to manufacture extruded articles such as foam, extruded and/or oriented sheets or fiJms, cast films, blown f)]ms, extrusion coated films, and the like. The use of the high melt strength polyolefins in various processes described may result in an improved manufacturing efficiency due to the improvements in a variety of factors for example melt pressure, torque and the like
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following 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.
Example-1:
In this experiment, high melt strength polypropylene via reactive extrusion of linear polypropylene carried out in the presence of a composition comprising a modifier and free radical initiators was prepared.
Reactive extrusion experiments were carried out in a Co-rotary twin screw compounder (OMEGA 30) of M/s Steer Engineering (P) Ltd., Bangalore. The screw diameter of the extruder was 30 mm and L/D as 40:1. The configuration of the screw was tailored for the reactive extrusion which has a loss in weight solids feeder and vacuum port (capacity 30 in Hg vacuum). Possible volatile products and solvent were removed through a vent port attached in the line.

In this example, a 5 kg batch of homo-polypropylene (homo-PP) (5MI) dispersed with Pentaerythritol triacrylate (PETA) (450 ppm), dicetyl peroxydicarbonate (hereinafter referred as PARKADOX) (2900 ppm) and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (hereinafter referred as LUPEROX101) along with standard doses of stabilizers and additives was prepared (referred to as Example-1). The mixing of the reactants was carried out using a high speed mixer for 2-3 minutes to ensure perfect dispersion and mixing of the reactants prior to the reactive extrusion process. The obtained reaction mixture was then extruded at a temperature in the range of 170-250 °C on a twin screw extruder under nitrogen environment. Extrusion was carried out at 170 rpm with a preset through put of 10 kg/h. The typical reaction conditions are summarized in Table-1.
fn another experiment (referred to as Reference Sample) a linear polypropylene without being dispersed with any modifiers and/or free radical initiators was extruded under similar extrusion conditions.
The modified polymer of example-1 and the linear polypropylene matrix extruded without using a composition of modifier and free radical initiators were characterized for melt rheology, die swell and thermal properties. The change in melt strength or the deformation behavior under shear or tensile mode can be measured as resistance of material in terms of force or by using indicators of polymer melt modification like elastic modulus (G')s Tan 8, melt viscosity and Melt Flow Rate (MFR). Dynamic rheological analyzer was used to determine the change in G'. Tan 5, melt viscosity (T|) at different frequencies. The Melt Flow Rate is determined by using a dead-weight piston Plastometer that extrudes polypropylene through an orifice of specified dimensions at a temperature of 230° C and a load of 2.16 kg in accordance with ASTM Standard Test Method D-1238.
The obtained results were summarized in Table-2. Rheological plots were shown in Figure-1 of the accompanying drawings.

TabJe-1: Process Condition; High melt strength-Long Chain Branched polypropylene (5MI) via reactive extrusion:

Exp. No. RPM Torque
{%) Melt Press.
(bar) Melt Temp
(°C) Specific Energy
(kw hr/ kg) Through
put (kg/h)
Reference Sample 170 67 18 245 0139 14
Example-1 170 68 19 240 0.138 17
Temperature profie
Irgafosl68:0.10%, : 31, 170, 200, 250, 250, 250, 250, 250, 250, 245; IrganoxlOlO: 05%, Cast: 0.06%, Batch Size: 5 kg.
Table-2: Rheological properties before and after modification of homo-PP (5 MI)

Exp. No. PETA
(wt %) Parkadox
(wt %) MFR
(dg/ min) Die
swelling
{%) (Pa-s) Tan
S Tc
(°C) MWD
Reference Sample Nil Nil 6.25 24 6822 4.70 115 3.52
Example-1A 0.045 0.29 3.40 81 8755 2.73 130 5.02
As clearly indicated from the results, a drop in melt temperature and marginal increase in melt pressure was observed for the modified polymer (Table-1). The melt flow rate (MFR) of the modified polymer dropped to 45-50 % (Table-2). This clearly indicates that the required recombination reaction of free radical initiators takes place and the modifier has supported the stability of these radicals thus facilitating the recombination. Further, though MFR dropped to 40-50%, melt pressure, torque and specific energy almost remained unchanged, however melt temperature decreased with increasing through put rate as shown in Table-1 which are incentives for the process indicating that fractional MFR polymer having long chain branching will possibly not require high energy during formation of reactive processing as compared to linear polymer of MFRJ >5dg/min.
From the results as tabulated in Table-2 and Figure-1 of the accompanying drawings it is clearly evidenced that in spite of lower doses of PETA (450 ppm) and PARKADOX (2900 ppm), their synergistic effect is found to impart long chain branching on to the polypropylene matrix.

The Modified polypropylene showed however, enhanced melt viscosity leading to high melt strength, lower melt flow rate (MFR), increased extrudate swelling, higher molecular weight, broadening of molecular weight distribution and processing window along with high through put without additional energy of consumption. The amount of long chain branches can be controlled by manipulating synergic composition and key process variables.
Example-2:
The mixing, kneading, extrusion, and palletization of 5kg homo-polypropylene (homo-PP) reaction mixture which was premixed thoroughly with 0.35 % PETA and 0.20% PARKADOX without LUPEROX101 in the presence of standard doses of stabilizers and additive was carried cert successfully on twin screw extruder as described in Example-1. The synergic composition as used in Example-2 comprises higher doses of the modifier and lower doses of peroxides. The modified polypropylene thus obtained was characterized in a way similar to the process of example-1 and the obtained results were summarized in Table-3. The properties of the modified polymer were also compared with the plain/unmodified linear polypropylene (referred to as Reference Sample) (refer to Table-3). From the results as tabulated in Table-3, it is clearly indicated that the modified polymer showed reduction in melt flow rate (MFR), higher melt viscosity, broadening in molecular weight distribution (MWD) and enhancement in Tc compared to tht; unmodified linear Homo-polypropylene (homo-PP). The properties of the modified polymer confirmed long chain branch formation with higher throughput rate and almost same process characteristics as described in example-1 and Table-1.
Rheological plot for molecular weight (MW) and molecular weight distribution (MWD) was shown in Figure-2 of the accompanying drawings.
Table-3: Rheological properties before and after modification of Homo-polypropylene (5MI), in accordance with the process of example-2.

Exp. No.
PETA
(wt%) Parkado
X
(wt%) MFR
(dg/m in) Die
swell
(%) η
(Pa-s) Tan
δ Tc
(°C) MWD
Reference
Sample
Homo-PP Nil Nil 6.06 24 6822 4.70 115 3.55
Example-2 0.40 0.20 2.86 79 8827 2.63 129 5.77
Example-3:
A 5kg batch of Homo-PP (3MI) was prepared by dispersing 0.35% PETA along with 0.15% PERKADOX at ambient temperature using high speed mixer. Standard doses of stabilizers and additives were used for making the batch. The reactive extrusion was carried out as described in example-1. In this experiment, PERKADOX dose was kept at lower concentration (0.15%) whereas PETA was 0.35%. This combination was found to be quite effective to convert linear polypropylene to long chain branched polypropylene (LCB-PP) retaining throughput 25 % higher. Other parameters like melt pressure, melt temperature, specific energy, torque and the like were marginally on a lower side as compared to the linear polypropylene matrix extruded under similar conditions with out using any modifiers and free radical initiators (reference sample). Rheological plots were shown in Figure-3 of the accompanying drawings and results are presented in Table-4.
Table-4: Rheological results before and after modification of Homo-PP (3MI)

Exp. No. PETA
(wt %) Parkadox
(wt%) MFR
(dg/min) Die swelli
(%) δη
(Pa-
s) Tan
5 G'/G" Tc
(°C) MWD
Reference
Sample
(Homo-PP Nil Mil 6.06 24 7273 4.70 111/ 718 117 3.50
Example-3 0.35 .0.15 2.94 69 8708 2.73 232/ 839 128 4.35
Example-4:
1 kg batch of homo-polypropylene (5MI) was dispersed with 800 ppm of PETA along with 0.3% w/w PARKADOX in combination with 20 ppm LUPEROX101. Standard

doses of stabilizers and additives were also added. Mixing was perfectly done prior to the reactive extrusion process and the batch was extruded using Bhussco-kneader similar to the process of example-preferred to as Experiment-4A). Another experiment (referred to as Example-4B) was also performed under similar conditions to prepare a modified polypropylene with only 0.3% PARKADOX for comparative study. The modified polymers (Example-4A and Example-4B) were characterized in a way similar to the process of example-1. The obtained results were tabulated in Table-5 and rheological plots were shown in Figure-4 of the accompanying drawings.
From the results as provided in Table-5, it is clearly understood that in spite of very low concentration of PETA in the synergic composition, the modification was very effective and MFR reduced by many folds when compared with only PARKADOX modified polymer (Example 4B) and only a few folds with respect to the plain/unmodified linear polypropylene (referred to as Reference Sample). MFR of samples was measured at 190 °C. Though MFR reduced significantly as reflected in rheological properties shown in Table-5, even torque reduced marginally with higher through put rate. Results distinctly demonstrate the synergic effect of the modifier and the peroxides which ultimately confirms long chain branched polypropylene (LCB-PP) formation.
Table-5: Rheological results before & after modification of Homo-PP (5MI)

Exp. no. PETA
(wt%) Parka dox
(wt%) MFR
(dg/min
@ 190
oC) MWD η
(Pa-s) Tan
∆ G'/G" Tc
(oC)
Reference Sample Nil Nil 8.85 4.02 2808 7.70 38/278 115
Example-4B Nil 0.30 19.25 3.06 875 5.40 16/86 130
Example-4A 0.08 0.30 2.12 5.15 5554 3.50 149/53 5 129
Temp.: 145-2 0.1%, Cast: 0 00-220-.06 %, r 250 ; Perc pm:90 xide: 20 pp m, Irgar 1OX1010: 0.05% Irgafos 1 68:

ExampIe-5:
Three different batches of Homo-PP (5MI) of 1.0 kg each were prepared using 0.25% modifier and 0.3% PARKADOX in combination with 20 ppm LUPEROX101 along with stabilizer and calcium stearate (Cast) as additives in the final formulation. Prepared batches were extruded in three different types of extruders having different screw configurations. The experiments were carried out in (1) Bhussco-kneader (referred to as BPP); (2) Kolsite (referred to as KPP); and (3) Co-rotary twin screw compounder under (OMEGA 30) of M/s Steer Engineering (P) Ltd,, Bangalore (referred to as MPP) having screw diameter of 30 mm and L/D as 40:1 under identical conditions. Results were shown in Table-6. Results showed that branching and degree of modification is influenced by the type of screw configuration available on the extruder. Therefore, the extruder's configuration needs to be tailored prior to the reactive extrusion process. Results also confirmed the formation of long chain branching during the modification process by using a synergic composition of the modifier and the free radical initiators.
Table-6

Expt. No. MFR
(gms/l0 min)
η
(Pa-s @ 230oC) Tc (°C)
BBP-5-0 7.50 1006 118
BPP-5-M 3.54 2193 128
KPP-5-0 6.2 1225 118
KPP-5-M 3.95 1992 126
MPP-5-0 6.25 1280 118
MPP-5-M 2.95 2800 128
PETA: 0.25%; PARKADOX: 0.3%; Matrix: Homo-PP 5 MI; Temp.: 170:220-240-240; rpm-90 BPP: Bhuscokneader; KPP: Kolsite; and MPP: Co-rotary twin screw compounder under (OMEGA 30) of M/s Steer Engineering (P) Ltd., Bangalore; O: original; and M:-modified.
Example-6:
In this experiment, two different sets of experiments were carried out. 1. First Set:

In this set, two individual batches of homo-PP (5MI) (referred to as Example-6A) and Impact copolymer polypropylene (ICP-PP) (referred to as Example-6B) (1.5 MI) of 500g each were prepared using 0.3% Parkadox and 0.25 % PETA along with normal doses of stabilizer.
2. Second Set:
In this set, two individual batches of 500 g each comprising a mixture of Homo-PP and ICP-PP in the ratio of 80/20 (referred to as Example-6C) and 50/50 (referred to as Example-6D) were prepared. To the batches, PETA and PARKADOX were added in the same amount as added in the first set of experiments. The batches thus prepared in the first set and in the second set were extruded on a Bhuscokneader in accordance with the process of example-1. The obtained modified polypropylenes were then characterized.
The obtained results were displayed in Table-7 and Figure-5 of the accompanying
drawings. The obtained results for the modified polypropylenes were also compared with the corresponding plain/unmodified linear polypropylene and Impact Copolymer Polypropylene.
From the results as provided in Table-7, it is clearly understood that in all the cases MFR reduced and Tc increased to 10-12 °C after modification as compared to the plain linear polypropylene. Interestingly, it was also found that the use of the synergic composition of PARKADOX and PETA also induce p-structure in the modified polypropylene which is more pronounced in the presence of 20-50% ICP-PP in the Homo-PP matrix as seen in Figure-5 of the accompanying drawings (No.-3 & No.-4). The p-structure was introduced when samples were exposed to second cycle heating in DSC. The second Tm peak appeared at 150 °C is responsible for p-structure. Overall results confirmed the formation of long chain branching and β-structure which indeed is an incentive to improve Izod Impact properties of molded products. However, such characteristic is essentially an additional merit to the process and of course to the formation of p-structure depending on the type of matrix and its

composition, and further would be influenced by feed composition of modifier and peroxide as well as process conditions.
Table-7: Thermal & Rheological data before & after modification

Exp. No PETA
(%) Parkad
ox (%) MFR
(dg/min) (Pas
@230 °C) Tc Matrix composition
(bywt)
Reference Sam pie-1 NIL NIL 7.5 1006 117 Homo-PP (5MI): 100%
Example-6A 0.25 0.30 3.53 2194 128 Homo-PP (5MI): 100%
Reference Sample-2 nil nil 2.15 3628 118 ICP-PP
100%
Example-6B 0.25 0.3 0.55 14149 126 ICP-PP 100%
Example-6C 0.25 0.30 3.70 2083 128 HPP:1CP-PP 50:50
Example-6D 0.25 0.3 4.18 1855 127 HPP: ICP-PP 80:20
Temp.: 160-2 rpm: 90; Bate! 0-220-2 l size ; i 50 °C,Irga 500g uoxl010:0 05%,Irga fosl68:0 l%,Cast:0.06%,
Example-7:
lkg homo-PP batch (5MI) was prepared under different feed compositions along with reference sample using normal doses of stabilizers and additives. Concentration of PETA and free radical initiators were varied. The prepared batches were extruded in a Buss-co-kneader as per the procedure followed in Example-1. The obtained results displayed in Table-8, showed that MFR reduced when a composition comprising PARKADOX (0.7 % by weight), 20 ppm LUPEROX101 and PETA (0.25% by weight) was used for the modification (Example-7C). The MFR was also reduced when only PETA (Example-7A) or only PARKADOX with ppm level of LUPEROX101 (Example-7B) was used for the modification. However, in case of Example-7B and Example-7C, the MFR reduction is almost same. In spite of reduction in MFR and long chain formation, torque remained unchanged rather reduced a bit which shows that extra energy was not required during modification of homo-PP to produce high melt strength polypropylene (HMS-PP).

Table-8: Modification of Homo-PP under different composition: Melt Rheology Results

Expt. No PETA
(%) Parkadox
(%) MFR
(dg/min) (Pa-s@230
°C) Tc
(oC) Torque
%
Reference Sample
(Homo-PP) NIL NIL 8.38 1006 117 70
Example-7A 0.25 NIL 5.94 1326 126 66
Example-7B NIL 0.7 5.80 1379 127 66
Example-7C 0.25 0.7 3.50 2198 128 66
Batch: 1 kg; Temp.: 160-210-220-250; rpm:90; Irganoxl010:0.05%,irgafosl68:0.1%,cast:0.06%
Example-8:
1 KG batch of homo-PP (12MI) was prepared using required amounts of PETA and PARKADOX containing 20 ppm of LUPEROX101 in the presence of normal doses of stabilizers and additives. Samples were prepared as described in example-1. Modified polypropylene sample showed lower MFR compared to plain and linear homo-PP. Results revealed that synergic composition of PETA and Parkadox is more effective as compared to individual formulation of PETA and Parkadox as shown in Table-8. Table-9

Exp.No PETA Parkadox
(%) MFR
(dg/min) n
(Pa-
s@230
oC) Tc
(°C) Tan
δ MWD
Reference Sample NIL NIL 12.15 1006 117 7.95 3.15
Example-8A 0.40 0.30 5.75 1357 126 4.57 4.15
Example-8B 0.25 0.25 4.77 1679 127 3.95 4.29
Irganoxl010:0.1% 220-250 °C, Batch:. Irgafos 500g. 68: 0.1%, C -ast: 0.06% rpm: 90 ;Temp. : 150 -210-
Example-9:
In this example, the effect of PARKADOX concentration at a fixed concentration of PETA is evaluated. For this, 500g batch of homo-PP (5MI) was prepared with Parkadox concentration varying from 0.08% to 1% at a fixed concentration of PETA (0.08%). Along with PETA and PARKADOX, 20 ppm of LUPEROXI01 and normal doses of stabilizers and additives were also added. Modified polymers were prepared as described in example-1. Results were summarized in Table-10. Modified polymers showed decrease in MFR and this effect is more pronounced at lower concentration of

PARKADOX. Further, the synergic effect is more when both PETA and PARKADOX are in lower doses as shown in Table-10.
Table-10: Variation of MFR & Melt Viscosity with change in Perkadox concentration

Expt.No PETA
(%) Parkadox
(%) MFR
(dg/min) η
(Pa-s@230 oC) Tc
(°C) Temp. profile
°C
Reference Sample NIL NIL 13.36 1006 117 160-210-220-250
Example-9A 0.08 nil 6.47 1357 126 160-210-220-250
Example-9B 0.08 0.05 6.25 1238 127 160-210-220-250
Example-9C 0.08 0.15 8.59 901 128 160-210-220-250
Example-9D 0.08 0.30 7.94 975 127 160-210-220-250
Example-9E 0.08 0.60 7.05 1098 127 160-210-220-250
Batch: 1.0kg, Irgan size : 1.0 kg oxl010:( ).l%;Irgafo 3168:0.1°/ o, Cast: 0.06% ; rpm : 90 ; Batch
TECHNICAL ADVANCEMENT:
The present disclosure related to a process for preparing high melt strength polyolefins has the following technical advancements:
(1) Using optimal amount of modifiers in combination with free radical initiators for reactively modifying the linear polyolefin of low melt strength,
(2) Low residual modifiers and/or free radical initiators in the final high melt strength polyolefin product, and
(3) No coloration defect in the final polyolefin product of high melt strength
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 invention, unless there is a statement in the specification specific to the contrary

The foregoing description of the specific embodiments will so fully reveal 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.

We Claim:
1. A process for preparing high melt strength polyolefin, said process comprising
the following steps:
i. physically mixing a polyolefin matrix, at least one multifunctional monomer and at least one first free radical initiator optionally in combination with at least one second free radical initiator at ambient temperature to obtain a reaction mixture, wherein said first free radical initiator and said second free radical initiator being characterized with half-lives differing by at least one order of magnitude; and
ii. compounding the reaction mixture under pre-determined conditions to obtain polyolefin having melt strength characterized by a melt flow rate ranging between 0.5 dg/min and 30dg/min.
2. The process as claimed in claim 1, wherein the polyolefin is at least one polyolefin selected from the group consisting of polyethylene and polypropylene.
3. The process as claimed in claim 1, wherein the polyolefin is a homo-polymer or a copolymer of propylene with one or more olefins and/or dienes selected from the group consisting of ethylene, C4-C18 alpha-olefins and dienes.
4. The process as claimed in claim 1, wherein the polyolefin is a linear homo-polymer of propylene having melt strength characterized with a melt flow rate ranging between 3 to 12 dg/min.
5. The process as claimed in claim 1, wherein the multifunctional monomer is an acrylate compound that includes at least one compound selected from the group consisting of diacrylates, triacrylates, tetraacrylates and pentaacrylates.
6. The process as claimed in claim 1, wherein the multifunctional monomer is a triacrylate, preferably pentaerythritol triacrylate.
7. The process as claimed in claim 1, wherein the amount of the multifunctional monomer varies between 1000 and 10000 ppm, preferably between 1000 and 5000 ppm, more preferably between 1000 and 2500 ppm.

8. The process as claimed in claim 1, wherein the half life of the first radical initiator varies in the range of 0.1 hr. to 0.99 hr.
9. The process as claimed in claim 1, wherein the half life of the second free radical initiator varies in the range of 1 hr. to 10 hr.
10. The process as claimed in claim 1, wherein the first free radical initiator is dicetyl peroxydicarbonate, said free radical initiator is present in an amount varying between 500 and 3000 ppm, preferably between 1000 and 3000 ppm, more preferably between 2000 and 3000 ppm.
11. The process as claimed in claim 1, wherein the second free radical initiator is 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane, said free radical initiator is present in an amount varying between 10 and 50 ppm, preferably between 10 and 20 ppm.
12. The process as claimed in claim 1, wherein the method step (i) further comprises the addition of at least one additive, said additive being selected from the group of compounds consisting of stabilizers, lubricants and the like.
13. The process as claimed in claim 12. wherein said additive is a stabilizer that includes at least one compound selected from the group consisting of tetrakis-(methylene-(3;5-di(tert)-butyl-4-hydroxycinnamate))methane, Tris(2,4-di-(tert)-butyl phenyl)phosphite and Tetrakis(2,4-di-tert-butylphenyl)-4,4-biphenyldiphosphonite.
14. The process as claimed in claim 12, wherein said stabilizer is a mixture of
tetrakis-(methylene-(3,5-di(tert)-butyl-4-hydroxycinnamate))methane in an amount varying between 500 and 2000 ppm and Tris(2,4-di-(tert)-butylphenyl)phosphite in an amount varying between 1000 and 2000 ppm.
15. The process as claimed in claim 12, wherein said stabilizer is a mixture of
tetrakis-(methylene-(3,5-di(tert)-butyl-4-hydroxycinnamate))methane in an
amount varying between 1000 and 2000 ppm and Tetrakis(2,4-di-tert-
butylphenyl)-4,4-biphenyldiphosphonite in an amount varying between 500
and 1000 ppm.

16. The process as claimed in claim 1, wherein the compounding of the reaction mixture is a reactive extrusion process carried out by using a twin screw extruder at screw rpm varying between 50 and 500, preferably between 100 and 300, more preferably between 150 and 250 and at a temperature varying between 100 and 300 °C preferably between 180 and 250 °C, more preferably between 150 and 250 °C.
17. A high melt strength poly olefin prepared in accordance with the process as claimed in any of the preceding claims, said high melt strength polyolefin being characterized by a melt flow rate ranging between 0.5 dg/min and 30 dg/min, preferably between 0.50 and 25 dg/min, more preferably between 0.5 and 10 dg/min, measured according to ASTM Standard Test Method D-1238.
18. The high melt strength polyolefin as claimed in claim 17, wherein the polyolefin is at least one polyolefin selected from the group consisting of polypropylene and polyethylene.