Thermoformable polyolefin compositions

FIELD

The present disclosure relates to thermoformable compositions. More particularly, the present disclosure relates, to a thermoformable composition and processes for preparation thereof.

DEFINITIONS OF TERMS USED IN THE SPECIFICATION

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

The change in the melt strength or the deformation behavior under shear or tensile mode can be measured as the resistance of the material in terms of force or by using the indicators of polymer melt modification like elastic modulus (G'), material dampening (Tan δ), melt viscosity (Mv or η) and the like.

Elastic modulus (G') is a measure of the elasticity and viscous modulus (G") is defined as the ability of a material to dissipate energy of a polymer melt as measured by dynamic rheological test. The ratio of G'VG' is the measure of material dampening (Tan δ), wherein higher the G' lower will be the Tan δ.

Enhancement of chain entanglement through incorporation of long chain branching and thus achieving high melt strength is possible through an increase in the molecular weight, the molecular weight distribution and the long chain branching. This can be monitored by determining the change in G' (increase), Tan δ (drop in value) and η (increase). Dynamic rheological analyzer has been used to determine the change in G\ Tan δ and melt viscosity (η) at different frequencies (rad/sec). The resistance of a polymer melt to deformation is the melt strength under the given set of conditions. Melt flow index (MFI) or melt flow rate (MFR) is a measure of the resistance to flow of the polymer melt under a defined set of conditions (unit: dg/-min or g/10 min). Being a measure at low shear rate condition, MFI is inversely related to the molecular weight of the polymer and is used as an indicator of the melt strength enhancement of polypropylene during the course of its modification. Change in the melt strength, as described in the embodiment is indicated through the changed MFI which drops with an increase in the molecular weight during incorporation of long chain branching. The measurement of the MFI was made as per ASTM D1238 using temperature as 230 °C and load as 2.16 Kgf.

Die swell is the ratio of the extrudate diameter to the die orifice diameter of a rheometer. This is an indicator of melt elasticity (as indicated by elastic modulus- G'), higher the die swell, higher will be the melt elasticity.

Commercial polymers have heterogeneity in terms of molecular weight (MW) and therefore molecular weight distribution (MWD) is also accounted for understanding the molecular properties. Due to this heterogeneity, molecular weight averages are calculated as the number average molecular weight (Mn), the weight average molecular weight (Mw), the average molecular weight (Mz), the average molecular weight (Mz+1) in an increasing order of molecular weight. The increase in Mz and Mz+1 are good indicators of the incorporation of high molecular weight fractions in the polymer matrix with the chain branching through recombination of ma6ro free radicals during modification.

The modification of polypropylene to achieve long chain branching is carried out using polyfunctional acrylate monomers, hence its bonding with polymer chains is established through infra-red analysis (FTIR) calculating carbonyl index (>C=O index) which is the ratio of carbonyl absorbance band (>C=O) and methyl absorbance band (-CH3) of polypropylene. >C=O index = A 1 ₇₃₅ / A ₈ 1.

Flexural modulus (FM) is a measure of the ratio of the stress to the corresponding strain in a three point bending mode, within the elastic limit of polymer in solid state and is determined as per ASTM D 790.

Izod impact is the Izod impact strength of a polymer in the solid state while clamping the notched test piece in cantilever position (vertical). The test is carried out as per ASTM D 256.

BACKGROUND

High melting point, low density, excellent chemical resistance, high tensile modulus coupled with low cost are the reasons behind polypropylene (PP) capturing a major market share in commodity plastics. However, commercial PP comprises highly linear chains with a relatively narrow molecular weight distribution that results in poor processing characteristics in processes where extensional stiffing is predominantly required such as foaming, thermo forming, extrusion coating, blow molding and the like. Therefore, modifications are needed to enhance the strain hardening behavior of the PP melt (manifestation of high melt strength). Although, maintaining a very broad (including bimodal) molecular weight distribution (MWD) can improve this behavior, strain hardening is most efficiently achieved by the addition of long chain branching (LCB).

PP with enhanced melt strength (modified PP) is prepared by various methods such as electron beam (EB) irradiation, reaction with low decomposition temperature peroxides and reactive extrusion with several peroxydicarbonates (PODIC).

US Patent No. 3970722 discloses a method for preparing a modified polypropylene by mixing crystalline propylene polymer, 0.1 to 5% organic peroxide and 0.1 to 7% modifying agent. The modifying agent may either be: (1) acrylic and methacrylic salts of Na, Ca, Mg, Zn, Al and Fe (III) or (2) compounds containing a phenol or benzyl group (e.g., 4-methacryloyl-oxymethylphenol).

Grafting low molecular weight side chains onto peroxygenated polyolefins is also known in the art. US Patent No. 6444722 discloses a process for making graft copolymers by treating the peroxygenated polyolefins in a substantially non-oxidizing atmosphere at a temperature of about 1 10° to 140° C. with at least one grafting monomer in a liquid form and at least one additive to control the molecular weight of the side chains. In US Patent No. 6774186, a free radical co-agent (a monomer) or a low molecular weight polymer having two or more functional groups with high response to free radicals is disclosed. Grafting short chain branches or functional groups onto semi crystalline polypropylene resins, however, has proven to be insufficient to enhance the melt strength of such resins. Poor melt strength of polypropylenes can be seen in properties such as, e.g., excess sag in sheet extrusion, rapid thinning of walls in parts thermoformed in the melt phase, low draw-down ratios in extrusion coating, poor bubble formation in extrusion foam materials and relative weakness in large-part blow molding. In addition, the use of free radical generators, such as organic peroxides, having a highly concentrated peroxide content (greater than 400 mmoles/kg) must be carefully controlled in order to keep the degradation (increased melt flow rate) of the polypropylene resin to a minimum. Accurately metering such low levels of peroxide in grafted propylene production is very difficult even when an organic peroxide master batch with low peroxide content is used.

In view of the afore-stated disadvantages associated with the prior art process, a need is felt to develop improved thermoformable propylene polymers and processes for preparation thereof.

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 provide a thermoformable composition with enhanced thermoformability.

It is another object of the present disclosure to provide thermoformable propylene polymers.

It is yet another object of the present disclosure to provide a simple and cost-effective process for preparing thermoformable compositions.

Other objects and advantages of the present disclosure 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 disclosure.

SUMMARY

The present disclosure provides a thermoformable composition prepared by melt kneading comprising a homogenous mixture of at least two polyfunctional aery late monomers in a polyolefin matrix having at least one organic peroxide in an amount less than 50 ppm, dispersed through said matrix.

Typically, the thermoformable composition is characterized by melt flow index (MFI) ranging between 0.10 g/ 10 min (g/min) and 10 g/10 min (g/min).

Typically, the thermoformable composition is characterized by elastic modulus (G') ranging between 500 and 4500 Pa, at a temperature ranging between 185 °C and 195 °C in melt state, with the frequency sweep mode ranging from 0.1 to 100 rad/s.

Typically, the thermoformable composition is characterized by material dampening (Tan δ) ranging between 0.5 and 1.5, at a temperature ranging between 185 °C and 195 °C in melt state, with the frequency sweep mode ranging from 0.1 to 100 rad/s. Typically, the thermoformable composition is characterized by melt viscosity (η) ranging between 2,000 and 50,000 Pa-s, at a temperature ranging between 185 °C and 195 °C in melt state, with the frequency sweep mode ranging from 0.1 to 100 rad/s.

Typically, the thermoformable composition further comprises at least one additive selected from the group consisting of stabilizers, acid neutralizers, nucleators, antioxidants and lubricants, uniformly dispersed throughout the polyolefin matrix. Typically, said polyolefin matrix comprises at least one base propylene polymer selected from the group consisting of homopolypropylenes, copolymers of propylene with C ₂ -C ₂ o alpha-olefin, random propylene copolymers and polypropylene block polymers; said base propylene polymer having a melt flow index (MFI) ranging between 1.0 g/10 minutes and 12.0 g/10 minutes.

Typically, said polyolefin matrix comprises a copolymer of propylene with at least one C ₂ -C ₂₀ alpha-olefin; said alpha olefin, in an amount ranging between 1% and 45% by weight of the copolymer, being selected from the group consisting of ethylene, 1- butene, 1-pentene, 1-hexene, methyl- 1-butene, methyl- 1-pentene, 1-octene and 1- decene.

Typically, said polyfunctional acrylate monomer is selected from the group consisting of pentaerythritol triacrylate (PET A), trimethylolpropane triacrylate (TMPTA), hexadecylmethacrylate (HDMA), octadecylmethacrylate (ODA) and butylmethacrylate (BMA), in an amount ranging between 0.1% and 2% by weight of the thermoformable composition.

Typically, said polyfunctional acrylate monomer comprises a combination of pentaerythritol triacrylate (PETA) and trimethylolpropane triacrylate (TMPTA).

Typically, said organic peroxide is at least one selected from the group consisting of diacyl peroxides, peroxyketals, peroxyesters, dialkyl peroxides and hydro peroxides. Typically, said organic peroxide is at least one selected from the group consisting of benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, l,l-di-t-butylperoxy-2,4- di-t-butylcyclohexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Luprox 101) and 3 ,6,9-triethyl-3 ,6,9-trimethyl- 1 ,4,7-triperoxonane.

Typically, said stabilizer is at least one selected from the group consisting of Tetrakismethylene, (3,5-di-t-butyl-4-hydroxyhydroconnamate)methane (Irganox- 1010), Tris (2,4-di-t-butylphenol) phosphate (Irgafosl68) and Tetrakis(2,4-di-t- butylphenol-4,4'-biphenylenediphosphonite (PEPQ).

Typically, said lubricant is calcium stearate.

The present disclosure further provides an article prepared from the thermoformable composition; said article being selected from the group consisting of thermoformable sheets, spare wheel covers, dash boards, interior trims, door liners, noise suppressors, front covers, instrument panels, seats, engine covers, wheel covers, refrigerator liners, mixer bodies, television back covers, fan bodies, washing machine liners and air conditioner parts.

The present disclosure even further provides a process for the preparation of a thermoformable composition; said process comprising the following steps:

i. mixing a polyolefin matrix with at least two polyfunctional acrylate monomers and at least one organic peroxide to obtain an admixture;

ii. homogenizing said admixture at a temperature ranging between 23 °C and 30 °C , in a high speed mixer at a speed ranging between 90 rpm and 300 rpm to obtain a homogenized admixture; and

iii. kneading said homogenized admixture in a kneader to reactively modify said homogenized admixture to obtain the thermoformable composition. Typically, the step of mixing further comprises mixing at least one additive selected from the group consisting of stabilizers, acid neutralizers, nucleators, antioxidants and lubricants.

Typically, said stabilizer is at least one selected from the group consisting of Tetrakismethylene, (3,5-di-t-butyl-4-hydroxyhydroconnamate)methane (Irganox- 1010), Tris (2,4-di-t-butylphenol) phosphate (Irgafosl68) and Tetrakis(2,4-di-t- butylphenol-4,4'-biphenylenediphosphonite (PEPQ).

Typically, said lubricant is calcium stearate.

Typically, said polyolefin matrix comprises at least one base propylene polymer selected from the group consisting of homopolypropylenes, copolymers of propylene with C ₂ -C ₂₀ alpha-olefin, random propylene copolymers and polypropylene block polymers; said base propylene polymer having a melt flow index (MFI) ranging between 1.0 g/10 minutes and 12.0 g/10 minutes.

Typically, said polyolefin matrix comprises a copolymer of propylene with at least one C ₂ -C ₂ o alpha-olefin; said alpha olefin, in an amount ranging between 1% and 45% by weight of the copolymer, being selected from the group consisting of ethylene, 1- butene, 1-pentene, 1-hexene, methyl- 1-butene, methyl- 1-pentene, 1-octene and 1- decene.

Typically, said polyfunctional acrylate monomer is selected from the group consisting of pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), hexadecylmethacrylate (HDMA), octadecylmethacrylate (ODA) and butylmethacrylate (BMA), in an amount ranging between 0.1% and 2% by weight of thermoformable composition.

Typically, said polyfunctional acrylate monomer comprises a combination of pentaerythritol triacrylate (PETA) and trimethylolpropane triacrylate (TMPTA). Typically, said organic peroxide is at least one selected from the group consisting of diacyl peroxides, peroxyketals, peroxyesters, dialkyl peroxides and hydro peroxide.

Typically, said organic peroxide is at least one selected from the group consisting of benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, l,l-di-t-butylperoxy-2,4- di-t-butylcyclohexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (Luprox 101) and 3,6,9-triethyl-3,6,9-trimethyl- 1 ,4,7-triperoxonane.

Typically, said homogenized admixture is fed into said kneader at a feed rate ranging between 8 and 15 kg/ hour. At the afore-stated feed rate range, the melt pressure in the melt pump drops by a value ranging between 7 and 10%. In one embodiment, at a feed rate of 8 kg/hour, the melt pressure of neat polymer has been found to be 140 bar. The drop in the melt pressure is an indicator of chain branching in the polymer, as branching is said to facilitate melt flowability at the set kneading conditions.

Typically, the step of kneading is carried out at a temperature ranging between 170 and 260 °C.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig. 1 (a) illustrates the reaction mechanism by which fragmentation of the polypropylene base polymer (PPBP) takes place in the absence of the polyfunctional acrylate monomers (PFAMs);

Fig 1 (b) illustrates the reaction mechanism by which chain elongation of the PPBP results due to the addition of the PFAMs;

Fig. 2 illustrates the comparison between the deep draw ability of thermoformed polypropylene impact copolymer (PP-ICP) prepared by the commercial process (no modifier), Figure 2 (a) and that prepared by the process of the present disclosure (PET+TMPTA), Figure 2 (b). Fig. 3 illustrates a thermoformed part of an automotive interior made of the modified polypropylene impact copolymer (PP-ICP) of the present disclosure.

I

DETAILED DESCRIPTION

Our co-pending patent application number 2860/MUM/2010 discloses a process for the preparation of high melt strength (HMS) polymers prepared by reactive blending of base propylene polymers with 0.1 to 1.0% of a polyfunctional acrylate monomer, in the presence of 10 to 50 ppm organic peroxide and 0.2 to 20% of at least one additive such as stabilizer, acid neutralizer, antioxidant and lubricant. Typically, the melt strength of the resultant HMS polymers is 30-60% greater than that of the base propylene polymers. Further, the melt flow index (MFI) of the polymers prepared by the process of 2860/MUM/2010 is found to range between 0.2 and 1.5 g/10 minutes.

After conducting further trials we found that incorporation of at least two polyfunctional acrylate monomers into the polymer matrix or base polymers demonstrated a further decrease in the MFI of the resultant polymers as compared to the polymers of 2860/MUM/2010, containing just a single polyfunctional acrylate monomer.

Therefore, in accordance with one aspect of the present disclosure there is provided a thermoformable composition comprising:

i. at least two polyfunctional acrylate monomers; and

ii. at least one organic peroxide

dispersed homogenously in a polyolefin matrix. The combination of monomers in the composition has demonstrated a significant synergistic effect.

The polyolefin matrix of the present disclosure in which the monomers and the peroxides(s) are dispersed, typically comprises at least one base propylene polymer selected from the group that includes but is not limited to homopolypropylenes, copolymers of propylene with C ₂ -C ₂ o alpha-olefin, random propylene copolymers and polypropylene block polymers. The MFI of the base propylene polymer ranges between 1.0 g/10 minutes and 12.0 g/10 minutes. The C ₂ -C ₂ o alpha-olefin which forms a copolymer with propylene is selected from the group that includes but is not limited to ethylene, 1-butene, 1-pentene, 1-hexene, methyl- 1-butene, methyl- 1-pentene, 1- octene and 1-decene and is present in an amount ranging between 1% and 45% by weight of the copolymer.

The organic peroxide of the present disclosure is present in an amount less than 50 ppm. Typically, the organic peroxide is at least one selected from the group that includes but is not limited to diacyl peroxides, peroxyketals, peroxyesters, dialkyl peroxides and hydro peroxides. The organic peroxide is at least one selected from the group that includes but is not limited to benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, l,l-di-t-butylperoxy-2,4-di-t-butylcyclohexane, 2,5-dimethyl-2,5-di- (tert-butylperoxy)hexane (Luprox 101) and 3,6,9-triethyl-3,6,9-trimethyl-l,4,7- triperoxonane. Peroxide in the range of 10-50 ppm performs the job of modification showing enhancement in melt viscosity and crystallization temperature confirming thermformable-PP formation. Further, the propylene polymer of the present disclosure has reduced yellowness due to the low content of the peroxide. As the propylene polymer of the present disclosure is siibstantially free of peroxide, there is no need of controlling the content of peroxide which is otherwise required in order to keep the degradation of the polypropylene resin to a minimum.

When the amount of peroxide is in excess, the peroxide free radical (R ) causes fragmentation of the polypropylene base polymer chain and thus, mars the objective of preparing thermoformable polypropylene polymers. This phenomenon of fragmentation has been demonstrated in Figure 1(a) where the polypropylene base polymer is represented by (PPBP) and the resultant unstable polypropylene macro free radical is represented by PPMFR. The PPMFR subsequently undergoes beta scission to yield fragments. When the polyfunctional acrylate monomers are included in the composition of the present disclosure, the monomers stabilize the unstable PPMFR and make available multiple reactive sites; thereby facilitating chain elongation. The effect of the addition of the polyfunctional acrylate monomers is demonstrated in Figure 1 (b) where the polyfunctional acrylate monomers are represented by PFAMs. The chain elongation of the PPBP buttresses the formation thermoformable polypropylene.

The polyfunctional acrylate monomer of the present disclosure is selected from the group that includes but is not limited to pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), hexadecylmethacrylate (HDMA), octadecylmethacrylate (ODA) and butylmethacrylate (BMA). Typically, the monomer is present in an amount ranging between 0.1% and 2% by weight of the thermoformable composition. In one embodiment of the present disclosure, the thermoformable composition comprises a combination of pentaerythritol triacrylate (PETA) and trimethylolpropane triacrylate (TMPTA) as the polyfunctional acrylate monomer. It has been found that inclusion of two polyfunctional acrylate monomers in place of one polyfunctional acrylate monomer, reduces the MFI of the polymer effectively; thereby increasing its thermoformability.

In addition to the polyfunctional acrylate monomer and the organic peroxide, the thermoformable composition of the present disclosure further comprises at least one additive that is uniformly dispersed throughout the polyolefin matrix. Typically, the additive is selected from the group that includes but is not limited to stabilizers, acid neutralizers, nucleators, antioxidants and lubricants. These additives may be included in amounts effective to impart the desired properties. Stabilizers or stabilization agents may be employed to help protect the polymer resin from degradation due to the exposure to excessive temperatures and/or ultraviolet light. The stabilizer of the present disclosure is at least one selected from the group that includes but is not limited to Tetrakismethylene, (3,5-di-t-butyl-4-hydroxyhydroconnamate)methane (Irganox-1010), Tris (2,4-di-t-butylphenol) phosphate (Irgafosl68) and Tetrakis(2,4- di-t-butylphenol-4,4'-biphenylenediphosphonite (PEPQ). In one embodiment, the lubricant is calcium stearate.

The thermoformable composition of the present disclosure has an MFI ranging between 0.10 g/10 min and 10.0 g/10 min. It is a known fact that that the melt flow index and thermoformability of a polymer are inversely proportional. Thus, the lower MFI values of the polymer of the present disclosure demonstrate high thermoformability. Further, other parameters of the thermoformable composition have been quantified such as the elastic modulus (G'), the material dampening (Tan δ) and the melt viscosity (r)).The elastic modulus (G') and the melt viscosity are directly proportional to the thermoformability whereas the material dampening (Tan 6) is inversely proportional to the thermoformability. Typically, the elastic modulus (G') of the thermoformable composition ranges between 500 and 4500 Pa, the material dampening (Tan δ) ranges between 0.5 and 1.5 and the melt viscosity (η) ranges between 2,000 and 50,000 Pa-s. The afore-stated parameters have been quantified under a temperature ranging between 185 °C and 195 °C in melt state, with the frequency sweep mode ranging from 0.1 to 100 rad/s. In one embodiment, the temperature at which quantification is carried out is 190 °C. The characterization data, therefore, buttresses the proposition that the polymer of the present disclosure has high thermoformability.

In accordance with another aspect of the present disclosure, an article prepared from the afore-stated thermoformable composition is provided. Typically, the article is selected from the group that includes but is not limited to thermoformable sheets, spare wheel covers, dash boards, interior trims, door liners, noise suppressors, front covers, instrument panels, seats, engine covers, wheel covers, refrigerator liners, mixer bodies, television back covers, fan bodies, washing machine liners and air conditioner parts.

In accordance with yet another aspect of the present disclosure, there is provided a process for the preparation of the thermoformable composition. The process initially includes mixing at least two polyfunctional acrylate monomers and at least one organic peroxide in a polyolefin matrix to obtain an admixture. The polyolefm matrix of the present disclosure typically comprises at least one base propylene polymer selected from the group that includes but is not limited to homopolypropylenes, copolymers of propylene with C ₂ -C ₂ o alpha-olefin, random propylene copolymers and polypropylene block polymers. The MFI of the base propylene polymer ranges between 1.0 g/10 minutes and 12.0 g/10 minutes. The C ₂ -C ₂ o alpha-olefin which forms a copolymer with propylene is selected from the group that includes but is not limited to ethylene, 1-butene, 1-pentene, 1-hexene, methyl- 1-butene, methyl- 1-pentene, 1- octene and 1-decene and is present in an amount ranging between 1% and 45% by weight of the copolymer. The polyfunctional acrylate monomer of the present disclosure is selected from the group that includes but is not limited to pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), hexadecylmethacrylate (HDMA), octadecylmethacrylate (ODA) and butylmethacrylate (BMA). Typically, the monomer is present in an amount ranging between 0.1% and 2% by weight of the thermoformable composition. In one embodiment of the present disclosure, the thermoformable composition comprises a combination of pentaerythritol triacrylate (PETA) and trimethylolpropane triacrylate (TMPTA) as the polyfunctional acrylate monomer. The organic peroxide of the present disclosure is present in an amount less than 50 ppm. Typically, the organic peroxide is at least one selected from the group that includes but is not limited to diacyl peroxides, peroxyketals, peroxyesters, dialkyl peroxides and hydro peroxides. The organic peroxide is at least one selected from the group that includes but is not limited to benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, l,l-di-t-butylperoxy-2,4-di-t-butylcyclohexane, 2,5-dimethyl-2,5-di- (tert-butylperoxy)hexane (Luprox 101) and 3,6,9-triethyl-3,6,9-trimethyl-l,4,7- triperoxonane. In addition to the polyfunctional acrylate monomer and the organic peroxide, the thermoformable composition of the present disclosure further comprises at least one additive that is uniformly dispersed throughout the polyolefin matrix. Typically, the additive is selected from the group that includes but is not limited to stabilizers, acid neutralizers, nucleators, antioxidants and lubricants. The stabilizer of the present disclosure is at least one selected from the group that includes but is not limited to Tetrakismethylene, (3,5-di-t-butyl-4-hydroxyhydroconnamate)methane (Irganox-1010), Tris (2,4-di-t-butylphenol) phosphate (Irgafosl68) and Tetrakis(2,4- di-t-butylphenol-4,4'-biphenylenediphosphonite (PEPQ). In one embodiment, the lubricant is calcium stearate.

The resultant admixture is further homogenized at a temperature ranging between 23 °C and 30 °C, in a high speed mixer. Typically, the speed of the step of homogenization ranges between 90 rpm and 300 rpm. The step of homogenization causes mere physical homogenization of the contents of the admixture.

In order to effect a deep-seated interaction, the resultant homogenized admixture is fed into said kneader at a feed rate ranging between 8 and 15 kg/ hour. The step of kneading causes a chemical reaction in the admixture, grafting of polyfunctional acrylate monomer onto the polymer chain which follows branching of the polymer chains that reduces the MFI and consequently increases the thermoformability of the resultant polymer composition. At the afore-stated feed rate range, the melt pressure in the melt pump drops by a value ranging between 7 and 10%. In one embodiment, at a feed rate of 8 kg/hour, the melt pressure of neat polymer has been found to be 140 bar. The drop in the melt pressure is an indicator of chain branching in the polymer, as branching is said to facilitate melt flowability at the set kneading conditions. The step of kneading is carried out at a temperature ranging between 170 and 260 °C.

The details of the disclosure will be further explained by way of examples which do not limit the scope of the disclosure. The individual reactants in the formulations as given in the examples are maintained in ppm and percentage by weight unless otherwise specified.

Example 1: Preparation of thermoformable propylene polymer as per the process of the co-pending patent application number 2860/MUM/2010

Batch size: 500 g of polypropylene impact copolymer (PP-ICP) Matrix;

30 ppm of peroxide; 0.35 %w/w, 1.0 % w/w, 2.0% w/w and 4.0 % w/w of pentaerythritol triacrylate (PETA) as a modifier;

0.05% w/w of Irganox-1010;

0.1% w/w of Irgafos-168; and

0.06% of calcium stearate.

50% of the PP-ICP was blended with a concentrate of trifunctional monomer (co- agent/ modifier) containing peroxide with thorough mixing. In the subsequent step the remaining part of polymer was added and mixed perfectly to form a uniform dispersion of the modifier. Irganox-1010 (0.05% w/w based on total matrix used for modification) and Irgafos-168 (0.1% w/w based on total matrix) were added as the primary and secondary antioxidants respectively, followed by 0.06% calcium stearate these were added to the whole mass and blended. The hand mixing operation was repeated several times to ensure proper mixing. The extrusion of PP-ICP containing reactants was carried out on a lab model Buss-co-kneader. The temperature in different zones of the extruder was maintained as Zone-l : 170 °C; Zone-2: 230 °C; Zone-3: 250 °C and Zone-4 (die zone): 260 °C with the screw rpm as 90. The extruded material was quenched and pelletized. The modified samples were characterized for MFI, MW, MWD and melt rheological characteristics.

Example 2: Preparation of thermoformable polypropylene polymer using TMPTA as a modifier

The process of Example 1 was repeated, except that TMPTA was used as the modifier in place of PETA. The modified samples were characterized for MFI, MW, MWD and melt rheological characteristics.

Several trials were later conducted where a minimum of 2 modifiers were used to form thermoformable propylene. The procedure is presented herein-below: Example 3: Preparation of thermoformable propylene polymer as per the process of the present disclosure, using a combination of PETA + TMPTA as a modifier.

500 g batch plain PP-ICP (MFI: 1.5 g/10 min) was used as base matrix for making the formulation as described in Example- 1, comprising 500 ppm of IrgaoxlOlO, 1000 ppm of Irgafosl68, 600 ppm of Cast, 0.25 % PETA, 0.25 % TMPTA and 15 ppm of LuperoxlOl . The prepared batch was extruded on a Buss-co-kneader with a temperature profile: Zone-1 : 170 °C; Zone-2: 230 °C; Zone-3: 250 °C; and Zone-4 (die zone): 260 °C at 90 rpm. The modified extrudate was then characterized for MFI and melt viscosity.

It was found that the MFI reduced significantly when a mixed modifier was used as compared to using a single modifier as discussed in Example 1. It was found that the requirement of a mixed modifier was much lower as compared to that of a single modifier, to achieve significant reduction in the MFI as per the summarized data shown in Table 1.

Table 1: Melt properties of PP-ICP before and after modification with single as well as mixed modifier

*Measured using MFI data

The results demonstrate a synergistic effect of the 2 modifiers.

Example 4: Thermoformability of the PP obtained by the process of the present disclosure The thermoformability of the PETA+TMPTA modified PP-IGP (invention of the present disclosure) and a known thermoformable PP-ICP sheet (prepared under identical processing conditions and having 2.5 mm thickness) was compared on a lab model machine for depth of draw. The details of the wooden mould used for the study are given below.

It was inferred that PETA+TMPTA modified PP-ICP sheet developed by the process of the present disclosure could be drawn successfully up to a depth of 300 mm as demonstrated in Figure 2 (b) whereas the commercial thermoformable PP-ICP sheet failed to show this level of deep drawability as shown in Fig 2 (a). The PETA+TMPTA modified sheet was successfully thermoformed and showed a good mold conformation w.r.t. the thickness uniformity.

Example 5: Applicability to homopolymer as well as copolymer.

Polypropylene impact copolymer (PP-ICP with MI: 1.50) and Homo-PP (5MI) were initially modified using PETA as the only modifier under optimum extrusion conditions as described in Example 1. The result was a 1 kg batch of propylene polymer comprising optimum levels of peroxide, 500 ppm of IrgaoxlOlO, 1000 ppm _ of Irgafosl68, 600 ppm Cast, 0.4 and 1.0 wt % modifier (PETA), prepared at a temperature profile of 170-230-250-260 °C under 90 rpm.

A similar set of experiments was carried out where a combination of 2 modifiers was used in place of a single modifier. Interestingly, for mixed modifier, change in MFI and melt viscosity was found to be more pronounced.

The extrudates obtained by both the processes were characterized for MFI and melt viscosity and the results are summarized in Table 2. Table-2: Melt properties before and after modification of PP-ICP (1.5MI) and Homo-PP (5MI)

* Measured using MFI data

Example 6: Preparation of thermoformable propylene polymer with and without modifier/s and peroxide

A control batch of propylene polymer was prepared that did not contain either the modifier or the peroxide. The MFI, Mv (using MFI data) and Tc of the batch were noted.

The afore-stated results were compared with the following:

(i) one modifier and one peroxide;

(ii) two modifiers and one peroxide in Table 3.

A 1 kg batch of propylene polymer was prepared where the temperature profile was maintained as 170-230-250-260 ⁰ at 90 rpm. The batch comprised 500 ppm of Irgaox- 1010, 1000 ppm of Irgafos 168 and 600 ppm of Cast.

For mixed matrix in the presence of ppm level peroxide, reduction in MFI and correspondingly enhancement in melt viscosity were found to be more pronounced when compared with single modifier.

Table-3:Melt rheological and thermal characteristic before and after modification of Homo-PP (5MI) Sample PETA wt% w/w Luperox MFI g / 10 Mv, Pa-s Tc, °C

101 (ppm) min

Blank nil Nil 7.42 1044 1 19

1 modifier, 0.20 15 4.18 1863 127 1 peroxide

2 modifiers, 0.1+0.1 15 2.65 3102 128 1 peroxide (PETA+TMPTA)

Example 7:

The modified PP-ICP (PETA+TMPTA) as prepared under optimum reactive processing conditions as given in Example 2 was extruded in the form of a sheet of 2.5 mm thickness and 1220 mm width. The square pieces of sheet of area 1200 mm x 1220 mm were clamped on a commercial machine. A wooden family mold was used for thermoforming an automotive part. The sheet temperature was brought close to 200 °C (as measured by an infra-red gun) and pre-blown before thermoforming. A depth of draw of 300 mm retaining the required texture was obtained. A thermoformed article made up of modified PP-ICP (PETA+TMPTA) for automotive interior is shown in Fig. 3.

"Whenever a range of values is specified, a value up to 10 % below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure".

The embodiments herein and the various features and advantageous details thereof are explained with reference to the 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 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.

TECHNICAL ADVANTAGES AND ECONOMICAL SIGNIFICANCE

The present disclosure provides a process for preventing homo-polymerization of the polyfunctional acrylate monomers during the extrusion process and consequently improving the grafting and branching efficiency along with having an overall impact on the process economy.

The process of the present disclosure provides broad processing parameters whilst trying to maintain satisfactory Optical and mechanical properties required for target end-product applications.

The present disclosure provides thermoformable polymers with optimum melt rheological characteristics and relatively broad molecular weight distribution to make the product compatible for thermoformability/ deep drawing. The present disclosure provides thermoformable propylene polymers with reduced yellowness.

The present disclosure provides long chain branched polypropylenes in which the _Λ integrity of the branch structure remains intact even after multiple thermal cycles.

Throughout this specification the ord "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.

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

While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications in the process or compound or formulation or combination of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.