FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
85
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
"IMPROVED THERMOPLASTIC POLYOLEFIN ALLOYS AND PROCESS FOR THEIR PREPARATION"
We, INDIAN PETROCHEMICALS CORPORATION LIMITED, a Government Company incorporated under the Companies Act, 1956, of P. O. Petrochemicals, District Vadodara 391 346, Gujarat, India.
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

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IMPROVED THERMOPLASTIC POLYOLEFIN ALLOYS AND PROCESS FOR THEIR PREPARATION
Field of Invention
5 The present invention relates to improved thermoplastic polyolefin alloys. In
particular, the present invention relates to compatibilized polypropylene copolymer blends prepared by melt blending in a co-rotating twin-screw extruder (or Buss-co kneader). The compatibilized blends of this invention exhibit very high notched Izod impact strength at moderate concentration of elastomer and a suitable compatibilizer
10 along with/without a natural filler. The present invention alos relates to process for preparing improved thermoplastic polyolefin alloys. Background of the Invention
Polymer blends have gained significant commercial growth in the last 2-3 decades outpacing the growth rate of existing polymers by at least 2-5%. Commercial
15 polymer blends are either designed or selected to have some degree of compatibility between the components to resist delamination and loss in ductility. Compatibility is to be viewed here as the ability for the polymer components to co-exist either as molecularly miscible or morphologically distinct phases but interfacially stabilized blends, without a tendency for delamination.
20 Compatibilization of highly immiscible commercial polymer pairs has thus far
been a technically more challenging task for the polymer blends technologists in the industry. Significant progress has, however, been made, in recent years in utilizing compatibilizers based on graft or block copolymer or other interfacial agents that effectively reduce the interfacial tension between the components to achieve useful
25 levels of ductility and delamination resistance, while at the same time stabilizing the morphology against processing effects. Interfacial compatibilization in commercial polymer blends is generally achieved through reactive extrusion in which the block or graft copolymer compatibilizer is generated in situ at the interface during the melt blending.
30 Many commercial polymer blends often include an elastomer to improve the
impact strength of the blends under conditions of stress concentration. The elastomeric dispersions are judiciously employed within the matrix phase or in the dispersed polymer phase or in both the phases, depending upon the requirement and the fracture behavior of the blend. An overwhelming factor in determining the impact strength of an
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immiscible or partially miscible blend is the degree and efficiency of interfacial compatibilization mat either is inherent in or has been designed into the blend system. If the interfacial adhesion or compatibilization is poor, the elastmer dispersion alone will not improve the toughness. Combining a high level of (notched) Izod impact
5 strength with moderate stiffness has been the primary thrust of this invention.
There have been several innovations in this area and many patents have been granted. US Patent No. 5,030,694 (1991) granted to Kelley, J. M., describes blends of ethylene-propylene copolymer and EPDM along with some organic peroxide exhibiting appreciable melt flow, impact strength and flexural modulus properties. EP Patent
10 No.132, 968 (1985) granted to Mitsui Petrochemical Industries Ltd., teaches blends of ethylene-propylene copolymer with a random ethylene-a-olefin copolymer rubber along with natural filler such as talc offering good impact as well as rigidity properties. GB 2,246,358 (1992) sanctioned to Nissan Motor Co. Ltd. and Mitsubishi Petrochemical Co. Ltd. describes the blends of ethylene-propylene copolymer with
15 EPR and talc exhibiting excellent flow, impact and flexural properties. EP 435,247 (1991) granted to Nippon Petrochemicals Co. Ltd. and Nippon Oil and Fats reveals blends of polypropylene and multi-phase propylene-vinyl monomer graft copolymer offering good moldability, heat as well as impact resistance. German Patent DE 3,520,151 (1986) granted to Dynamic Nobel, AG, describes blends of partially
20 crystalline EP polymer, polypropylene homo or copolymer and polyethylene along with organic peroxide exhibiting high impact and good weather resistance properties. JP 04,258,652 (1992) granted to Mitsui Toatsu Chemicals Inc., reveal the preparation of syndiotactic PP and ethylene-properties copolymer blends exhibiting high impact strength and transparency. Similar properties were exhibited by the blends of propylene
25 polymers and thermoplastic elastomers along with aromatic phosphorous compound metal salts described in JP 04,96,947 (1992) granted to Mitsui Toatsu Kagaku, K.K. JP 03,252,436 (1991) issued to Tonen Chemical Corporation and Toyota Motor Corporation describes blends of ethylene-propylene block copolymer, EPR, noncrystalline Nylon and modified PP exhibiting good heat and impact resistance
30 properties. JP 03,168,233 (1991) granted to Idemitsu Petrochemical Co. Ltd., describes a blend of PP and elastomer exhibiting improved impact strength and weather resistance. Japan Synthetic Rubber Co. Ltd., received a patent JP 02,191,656 (1990) for their blend of thermoplastic resins, rubbers, cross-linking monomers and other additives
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exhibiting appreciable impact strength. The same company was granted another patent JP 02,49,043 (1990) for their polyolefin blend with resistance properties. Innovations for high impact materials were also made with nonpolyolefinic materials. EP 297,517 (1989) granted to Idemitsu Petrochemical Co. Ltd., and Nippon Zeon Co. Ltd.,
5 describes blends of polycarbonate and graft copolymer obtained from vinyl/ polyfunctional vinyl monomers exhibiting good low temperature impact resistance and solvent resistance properties. US Patent No.4,673,722 (1987) issued to General Motors illustrates blends of Nylon withpolyurea offering appreciable impact strength.
In all the above patents, impact resistance was given paramount importance.
10 Need for high impact materials has been growing as their applications in several gadgets is ever growing with more and more industrialization and development of new and innovative machines etc. The present invention is carried out to fulfill the requirement for a cost- effective polyolefins blends with very high impact strength with adequate stiffness and heat deflection temperature. The blends disclosed in this
15 invention can be used in several applications, such as molded luggage, furniture, body panels and automotive components, to name a few. Objects of the Invention
It is an object of the present invention to provide compatibilized blends of polypropylene block copolymer with EPDM or EPR and enhance miscibility by using a
20 suitable compatibilizer.
It is another object of the present invention to provide compatibilized polyolefin blends or alloys using a twin-screw extruder or a Buss-co-kneader.
It is yet another object of the present invention to provide an alloy, with polypropylene copolymer, EPDM or EPR along with a suitable compatibilizer and
25 other additives that exhibits very high (notched) Izod impact strength i.e., 60-90 kg. cm/cm, flexural moduls: 6,000 -8,000 kg./ cm2, heat deflection temperature: 60-70°C, that would allow injection molding, compression molding, thermoforming and other conventional techniques to be applied for making end products.
It still another object of the present invention to provide a process for preparing
30 a cost effective polyolefin alloy that is suitable for making end products exhibiting very high (notched) Izod impact strength along with moderate flexural modulus. Summary of the Invention
The present invention relates to a process for the preparation of polypropylene
copolymer alloys with EPDM or EPR along with a suitable compatibilizer and with or
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without a filler, melt-blended in a co-rotating twin-screw extruder or a Buss-co-kneader all together or in separate batches, keeping the extruder temperature in the range of 125-240°C and the screw rotation speed in the range of 50-100 rpm.
In one embodiment of the invention, the polypropylene copolymer has a melt
5 flow index in the range of 1-4 g/ 10 min. when tested at 230 °C /2.16 kg. Load
(according to ASTM D 1238); and EPDM with ethylene content in the range of 55-65
wt% possessing specific gravity: 0.86-090, and Mooney viscosity in the range of 36-77
[ML(l+4)125°C];orEPR.
In one embodiment of the invention, the alloys consist of polypropylene
10 copolymer as a dominant phase in the concentration range of 50-95 wt%.
In another embodiment of the invention, the alloy consists of a compatibilizer
picked up from a group of two ionomers, styrene-ethylene/butylenes-styrene block
copolymer (SEBS), styrene- acrylonitrile copolymer (SAN) and polypropylene
copolymer grafted with maleic anhydride (PPBC-g- MAH) in the concentration I the
15 range of 5-30 wt%.
In another embodiment of the invention, the alloys also consist of a natural
filler, selected from the group consisting of calcium carbonate, talc and mica, of a
preferred particle size in the range of 10-30 microns and with a suitable adhesion
promoting surface treatment, in the concentration in range of 0-10 wt%.
20 In another embodiment of the invention, the alloys exhibit melt flow rate in the
range of 2-5 g/10 min. when tested according to ASTM D 1238.
In a further embodiment of the invention, the alloys exhibit an Izod impact
strength (notched specimen) in the range of 60-90 kg. cm/cm., when tested using
injection molded 3.2 mm thick specimens (cut from the mid portions of the tensile bar
25 of Type-I described in ASTM D638), and 50-70 kg. cm/cm when tested using 6.4 mm
thick specimens, according to ASTM D 256.
In yet another embodiment of the invention, the alloys exhibit flexural modulus in the range of 6,000/8,000 kg/cm2, when tested according to ASTM D 790.
In another embodiment of the invention, the alloys exhibit tensile strength in the
30 range of 150-200 kg/cm2, when tested according to ASTM D638, using injection molded specimens.
In another embodiment of the invention, the alloys show heat deflection
temperature in the range of 60-70°C with 4.6 kg the present invention to provide stress
and 45-55 °C with 18.2 kgf stress according to ASTM D648.
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Detailed Description of the Invention
A polyolefin polymer, viz., propylene ethylene block copolymer (PPBC) was the preferred matrix material for carrying out the present invention. It was obtained in the form of granules after adequately adding the stabilizers and antioxidants soon after
5 polymerization. The granules were dried at 80 ± 5 °C for two hours, preferably, in an oven with air circulation facility. An elastomer, ethylene propylene copoylmer rubber (EPR) or ethylene-propylene-diene monomer (EPDM), in a preferred form of granules, was also dried separately in an air circulating oven at a preferred temperature of 80 + 5 °C for a period of two hours. A compatibilizer selected from a group of two ionomers,
10 styrene-ethylene/ butylenes-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and polypropylene copolymer grafted with maleic anhydride (PPBC-g MAH) was also dried at the same above temperature for the same time. Similarly, a natural filler, picked up among a group of mica, talc and calcium carbonate, preferably with a particle size in the range of 10-30 microns, was also dried at the same
15 temperature, mentioned above, for the same time.
The object of melt blending, by means of a twin-screw extruder or Buss-co-kneader with a specially designed screw profile, is to break the elastomer into as fine particles as possible and to disperse them uniformly within the matrix of polypropylene block copolymer. This intimate associated with the presence of a suitable compatibilzer
20 would yield an alloy that would exhibit desired mechanical properties, especially enhanced impact strength.
Dried PPBC, elastomer, compatibilizer, with or without a filler, along with other ingredients were tunable - mixed in the composition given here : PPBC : 50-59 wt%, EPR/ EPDM: 5-50 wt%, compatibilizer (s) 5-30 wt%, filler : 0-10 wt% initiator,
25 sulfur and other additives viz., glycerin mon-stearate, Tinuvin- 770, Tinuvin -327, B-blend -225 and Chimmasorb, a combination of Tinuvin- 622 and Bcnzophenone 0.01-0-10 phr each. This tumble-mixed dry mixture was extruded in a co-rotating twin-screw extruder (or a Buss-co-kneader) with a preferred screw profile under the following conditions: temperature range : 125-240 °C, screw speed : 50-100 rpm, residence time :
30 0.5-5.0 min. The extrudate was dipped in cold circulating water and was chopped into
granules of length 3-4 mm.
The extrudated granules were dried and then injection molded into ASTM
standard test specimens for evaluating various performance properties such as tensile
strength, flexural modulus, notched Izod impact strength and heat deflection
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temperature. Injection molding was carried out using a computer-controlled injection molding machine having four heating zones operating in the range : 130-230 °C, injection pressure (applied in six stages) 60-100 kg/cm2, injection time (in six stages): 2-6 sec. With screw speed (in two stages) in the range : 90-105 rpm. The standard test
5 specimens, thus obtained were used for testing various mechanical properties of the alloys (mentioned above) following the ASTM standard test methods.
Other tests, such as melt flow index, crystallization kinetics (using Differential
Scanning Calorimeter) and filler content (using Thermogravimetric Analyzer) were
carried out using dry granules of the alloys. Dispersions of the elastomer and the filler
10 were studied using thin microtomed sections cut from the injection molded flexural
bars, using polarized optical microscope.
Rubber toughening is the most often used method of improving the impact resistance of polymers. In impact-modified materials, the composition of the constituents, their miscibility and the morphology influence the deformation and failure
15 mechanisms in the blend. Particle size of the elastomer, its dispersion and its adhesion, (if required by the use of a suitable compatibilizer), with the matrix are also the important factors determining the toughness of the blend.
In the case of PPBC blends with EPDMZEPR, the elastomer was found to reduce the crystallinity of PPBC and significantly influence its failure mechanism. Both
20 crazing and shear yielding, responsible mechanisms for plastic deformation in rigid polymers, found to be operating simultaneously in these blends. These two mechanisms are not mutually exclusive, but under certain conditions both operate simultaneously. They were found to be responsible for toughening the matrix materials, PPBC.
The present invention will now be described in greater detail by the following
25 examples, the purpose of which is merely to illustrate the invention and not limit the scope thereof.
Example -1
30 Dried Granules of polypropylene copolymer 60 wt% were mixed with dried
EPDM of concentration 20 wt%, a dried preferred compatibilizer, styrene-acrylonitrile copolymer (SAN) 5 wt%; PPBC grafted with maleic anhydride (PPBC-g-MAH) 5 wt% and a natural filler, preferably talc, 10 wt%, and all the constituents were tumble-mixed thoroughly. The dry mixture was extruded in a twin-screw extruder (or a Buss-
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co-kneader) with co-rotating screws, having a preferred screw profile with an objective of intimate mixing of the ingredients. The extruder was operated in the temperature range: 125-240 °C with screws rotating at a speed : 50-100 rpm. The extrudate strand (referred to as Alloy -A) was dipped in a trough of circulating cold water. The strand
5 was later dried and granulated.
Standard ASTM test specimens were prepared by injection molding the dry granules of Alloy-A, using FRK-85, Knockner-Windsor injection molding machine applying the molding conditions given below in Table -I.
Table-I 10
Typical Injection Molding Conditions for Preparing ASTM
Test Specimens of the Pory olefin alloys

No. Processing Parameters Unit Typical Value
1. Injection Pressure kg/cm"4 60-100
2. Injection Speed mm/sec. 7-12
3. Temperature maintained °C 130-230
4. Injection time sec. 2-6
5. Cooling time sec. 30-90
6. Screw speed rpm. 90-105
The performance properties of the alloys, injection molded under the above 15 conditions, are given below in Table-II. For each property reported here, at least six specimens were tested and the average value was calculated.
Table-II Typical Properties of Alloy - A

No. Property Unit ASTM AUoy-B
1. Melt flow index ' g/l0min. D1238 4.2
2. Tensile strength kg/cm2 D638 167
3. Tensile modules kg/cm2 D638 8,958
4. Flexural Strength kg/cm2 D790i 206
5. Flexural modules0 kg/cm2 D790 8,134
6. Notched Izod impact strength 3.2 mm thick specimen * kg cm/cm. D256 62
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6.4 mm thick specimen 55
7. Heat deflection temperatureAt 4.6 kgf stressAt 18.2 kgf stress °Ct D648 75 50
(* Middle portion of the injection molded ASTM standard tensile specimen was used)
Example-2
Moisture free granules of polypropylene copolymer 72 wt% were mixed with
dried elastomer preferably, EPR of concentration 23 wt% and a dried compatibilizer,
5 peferably, styrene-ethylene/butylenes-styrene block copolymer (SEBS) 5 wt%. All the constituents were thoroughly tumble mixed and then extruded in the same extruder under the same conditions mentioned above in Example-1. The extrude (referred to as Alloy B) was granulated and standard ASTM test specimens were prepared using the same injection molding machine under the same conditions mentioned in the above
10 example. The properties Alloy-B are presented in Table -HI.
Table-III Typical Properties of Alloy — B

*
No. Property Unit ASTM Alloy-B
1. Melt flow index g/l0min. D1238 2.34
2. Tensile strength kg /cm2 D638 160
3. Tensile modules kg/cm2 D638 7,964
4. Flexural Strength kg/cm2 D790 170
5. Flexural modules0 kg/cm2 D790 6,800
6. Notched Izod impact strength3.2 mm thick specimen *6.4 mm thick specimen kg cm/cm. D256 73 69
7. Heat deflection temperature At 4.6 kgf stress At 18.2 kgf stress °C D648 65 48
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(* Middle portion of the injection molded ASTM standard tensile specimen was used)
Example -3
Polypropylene copolymer, 45 wt%, polypropylene copolymer grafted with
maleic anhydride (PPCP-g-MAH), 45 wt%, and an elastomer; preferably BPDM, 10
5 wt%, were all weighed and dried. All the constituents were mixed thoroughly and then
extruded in the same above-mentioned extruder under the same extruding conditions.
The extrudate (referred to as Alloy-C) was granulated and standard ASTM test
specimens were injection molded as mentioned in the previous examples. The
properties of Alloy-C are given in Table - IV.
10 Table -IV
Typical Properties of Alloy - B

No. Property Unit ASTM AIloy-B
1. Melt flow index G/10min. D1238 7.2
2. Tensile strength Kg/cm2 D638 165
3. Tensile modules Kg/cm2 D638 7,758
4. Flexural Strength Kg/cm2 D790 180
5. Flexural modules0 Kg/cm2 D790 6,489
6. Notched Izod impact strength3.2 mm thick specimen *6.4 mm thick specimen Kg. Cm/cm. D256 76 63
7. Heat deflection temperatureAt 4.6 kgf stressAt 18.2 kgf stress °C D648 67 50
(* Middle portion of the injection molded ASTM standard tensile specimen was used)
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Claims:
1. A thermoplastic polyolefin alloy having high (notched) Izod impact strength
comprising a polypropylene block copolymer as a base polymer, an
elastomer and a compatibilizer.
5 2. Polyolefin alloys as claimed in claim 1 exhibiting izod impact strength in
the range: 60-90 kg. cm/cm, for notched specimens of thickness 3.2 mm, following the ASTM D256 test method using injection molded standard specimens.
3. Polyolefin alloy as claimed 1 and 2 wherein said polypropylene block
10 copolymer is a block copolymer of propylene and ethylene.
4. Polyolefin alloy as claimed in any preceding claim wherein said elastomer is
selected from a terpolymer made from ethylene propylene diene monomer
(E$PDM)/an ethylene propylene copolymer rubber (EPR).
5. Polyolefin alloy as claimed in any preceding claim wherein said
15 compatibilizer is selected from a group of two different ionomers, styrene-
ethyiene/butylene-styrene block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and polypropylene block copolymer grafted with maleic anhydride (PPBC-g-MAH).
6. Polyolefin alloy as claimed in any preceding claim wherein said
20 polypropylene block copolymer is present in an amount of 50 to 95 wt % of
said alloy.
7. Polyolefin alloy as claimed in any preceding claim wherein said elastomer is
present in a concentration range of 5 to 50 wt %.
8. Polyolefin alloy as claimed in any preceding claim wherein said
25 compatibilizer is present in an amount of from 5 to 30 wt %.
9. Polyolefin alloy as claimed in any preceding claim further including a natural filler.
10. Polyolefin alloy as claimed in claim 9 wherein said filler is selected from the group consisting of mica, talc and calcium carbonate.
30 11. Polyolefin alloy as claimed in claim 9 or 10 wherein said filler is present in
the concentration range of from 0-10 wt %.
12. A thermoplastic polyolefin alloy having high (notched) Izod impact strength
comprising a base polymer selected from a block copolymer of propylene
and ethylene (PPBC) in the concentration range of 50 to 59 wt%; an
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elastomer comprising, a terpolymer made from ethylene propylene diene
monomer (EPDM)/an ethylene propylene copolymer rubber (EPR) in the
concentration range of 5-50 wt %; a compatibilizer selected from the group
consisting of two different ionmers, styrene-ethylene/butyienes-styrene
5 block copolymer (SEBS), styrene-acrylonitrile copolymer (SAN) and
polypropylene block copolymer grafted with maleic anhydride (PPBC-g-
MAH) in a concentration range of 5 to 30 wt % and natural filler selected
from a group consisting of mica, talc and calcium carbonate in the
concentration range of 0 tol 0 wt %.
10 13. Polyolefin alloy as claimed in claim 12 when heated in differential, scanning
calorimeter at a uniform heating rate of 10°C/min. in nitrogen environment, exhibit 2 to 3 endothermic peaks in the range: 90-167°C.
14. Polyolefin alloy as claimed in claim 12 having exothermic major peak in the
temperature range of 115-25°C followed by a minor peak in the range of
15 113 to 125°C with total AH value in the range: 55 of 75 J/g, when heated in
differential scanning calorimeter at a uniform heating rate of 10°C/min. in nitrogen environment, up to 200°C and cooled after holding isothermally for 3 min.
15. Polyolefin alloy as claimed in claim 12 having melt flow indices in the
20 range: 2-5 g/10 min. when tested according to ASTM D1238 standard
method using dried granules.
16. Polyolefin alloy as claimed in claim 12 having tensile strength in the range
of 150 to 200 kg/cm2 when tested according to ASTM D638, using injection
molded test specimens.
25 17, Polyolefin alloy as claimed in claim 12 exhibiting tensile modulus in the
rangeof7,000 to 8,000 kg/cm2, when tested according to ASTM D638, using injection molded test specimens.
18. Polyolefin alloy as claimed in claim 12 exhibiting flexural strength in the
range of 160 to 200 kg/cm2, when tested according to ASTM D790, using
30 injection molded specimens.
19. Polyolefin alloy as claimed in claim 12 having flexural modules in the range
of 6,000 to 8,000 kg/cm2, when tested according to ASTM D790, using
injection molded specimens.
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20. Polyolefin alloy as claimed in claim 12 having heat deflection temperature
in the range of 60-70°C with 4.6 kgf stress when tested according to ASTM
D648, using injection molded test specimens.
21. Polyolefin alloy as claimed in claim 12 exhibiting heat deflection
5 temperature in the range: 45-55°C with 18.2 kgf stress when tested
according to ASTM D648, using injection molded test specimens.
22. A process for the preparation of a thermoplastic polyolefin alloy having
high (notched) Izod impact strength which comprises melt blending a
polypropylene block copolymer, a terpolymer and a compatibilizer, with or
10 without a natural filler.
23. A process as claimed in claim 22 wherein said melt blending is carried out in in a twin screw extruder or a Buss -co - kneader.
24. A process as claimed in claim 22 wherein said polypropylene block copolymer is a block copolymer of propylene and ethylene.
15 25. A process as claimed in any one of claims 22 to 24 wherein said elastomer
is selected from a terpolymer made from ethylene propylene diene monomer (EPDM)/an ethylene propylene copolymer rubber (EPR).
26. A process as claimed in any one of claims 22 to 25 wherein said
compatibilizer is selected from a group of two different ionomers, styrene-
20 ethylene/butylene-styrene block copolymer (SEBS), styrene-acrylonitrile
copolymer (SAN) and polypropylene block copolymer grafted with maleic anhydride (PPBC-g-MAH).
27. A process as claimed in any one of claims 22 to 26 wherein said
polypropylene block copolymer is present in an amount of 50 to 95 wt % of
25 said alloy.
28. A process as claimed in any one of claims 22 to 27 wherein said elastomer is present in a concentration range of 5 to 50 wt %.
29. A process as claimed in any one of claims 22 to 28 wherein said compatibilizer is present in an amount of from 5 to 30 wt %.
30 30. A process as claimed in any one of claims 22 to 29 further including a
natural filler. 31. A process as claimed in claims 30 wherein said filler is selected from the group consisting of mica, talc and calcium carbonate.
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Dated this the 18th day of July 2006
(H. SUBRAMANIAM) of SUBRAMANIAM, NATARAJ & ASSOCIATES ATTORNEY FOR THE APPLICANTS
32. A process as claimed in claim 31 wherein said filler is present in the concentration range of from 0-10 wt %.
33. A process as claimed in any one of claims 23 to 32 wherein said extruder temperature is maintain at in the range of 125 to 240°C.
34. A process as claimed in any one of claims 23 to 33 wherein the twin-screw extruder / Buss-co-kneader is operated with the screws rotating at a speed of 50-100 rpm.
35. A process as claimed in any one of claims 22 to 34 wherein the melt blending is carried out at a residence time of 0.5 to 5.0 min.
36. An article of manufacture whenever made of the polyoelfin alloy as claimed in any one of claims 1 to 21.

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ABSTRACT
A thermoplastic polyolefin alloy having high (notched) Izod impact strenght and process for it preparation are disclosed. The alloys of this invention comprises of a polypropylene block copolymer as a base polymer, an elastomer, a compatibilizer, and optionally a natural filler and is prepared by melt blending a twin-screw extruder (or Buss-co-kneader) the above ingredients. The polylefin alloys of this invention exhibit very high( notched) Izod impact strenght of 60 to 90 kg. cm/cm, flexural modulus of 6,000 to 8,000 kg/cm2, tensile strength at yield of 150 to 200 kg/cm2, and heat deflection temperature of 60 to 70oC with 4.6 kgf stress. The alloys also possess melt flow index of 2-5 g/10 min. when tested according to ASTM D1238 and allow injection molding, compressing molding, thermoforming and other conventional techniques to be applied for making end products that demand high inpact strenght.