Field of the invention
The present invention relates to one pot synthetic process for preparing controlled grafted polyolefinic elastomer with improved polarity.

Background and prior art

Olefinic polymers (polyolefins) have saturated backbone. Being a saturated backbone polymer, this class of polymers has some excellent properties. It has excellent resistance against O2, O3, thermal degradation, and UV radiation compared to diene polymers. Due to these excellent properties, polyolefinic elastomers find applications in automotive parts, many outdoor applications, seals, cable insulations, tubes and hoses etc. (Brydson J. A. "Rubbery Materials and Their Compounds" (l988), Elsevier Applied Science, London; b) Baldwin F. B., Verstrate G. (1972), Rubber. Chem. Technol., 45,709-882.

However, it has got some disadvantages too. Being nonpolar in nature, these polymers have poor compatibility towards polar polymers and polar fillers (Blow C. M., Hepburn C. Rubber Technology and Manufacture (1982), 2nd ed. London: Butterworth Science). Its bond-ability towards polar substrates is also poor. It has also very poor resistance to oils and fuels. These limit its applications. Chemical modification by incorporating polar group into these olefinic polymers will enhance its compatibility towards polar substrates and will improve their resistance to oils and fuels (Duin v M., Dikland H. (2007), Polym. Degrad. Stab. 92,2287-2293; Biswas A., Singha N. K., Bhowmick A. K. (2010), Eur. Polym. J., 46(2), 364-373; and Botros S. H., Moustafa A. F. (2002) J. Elast. Plast. 34 (1), 15-32).

This can be achieved via grafting reaction. A grafted polymer with polar functionality onto polyolefin may increase interaction with wide range of materials, which can make the grafted polyolefin suitable for many applications, e.g. in coating and adhesives, as thermoplastic elastomeric material, as compatibilizers for polymer blends and composites etc (Hoang T., Park J., Kim G., Oh S., Ha C., Cho W. (2000), J. Appl. Poly. Sci., 77, 2296-2304; (b) Oostenbrink A.J., Gaymans. R. J. (1992), Polymer, 33(14), 3086-3088).

Many attempts have been made to carry out clinical modification on polyolefin. These attempts were based on "free radical", "radiation", "graft from" and "graft onto" approaches (Moad G., Solomon D. H. "The Chemistry of Free Radical Polymerization" (l995),1st eds, Elsevier Science Ltd, Oxford; (b) Shenc J., Hu J. (1996), J. Appl. Polym. Sci. 60, 1499- 1503).
But all attempts suffered certain difficulties, like formation of homopolymer during modification, degradation of backbone chain, gelation with very ill-defined product etc (Moad G., Solomon D. H. "The Chemistry of Free Radical Polymerization" (l995),1st eds, Elsevier Science Ltd, Oxford; (b) Shenc J., Hu J. (1996), J. Appl. Polym. Sci. 60, 1499- 1503).
However, graft copolymerization via ionic polymerizations leads to well defined graft copolymers. But they need stringent reaction conditions and very complex reaction set up to carry out graft copolymerization reaction. Ionic polymerizations are applicable to a limited number of monomers only.

Recent advances in controlled radical polymerization (CRP) have overcome many of these difficulties ((a) Matyjaszewski K., Davis T. P. "Handbook of Radical Polymerization" (2002), Wiley-Interscience, 1st eds, A John Wiley &. Sons, Inc. Publication; (b) Matyjaszewski K. edited, "Controlled/Living Radical Polymerization Progress in ATRP, NMP and RAFT" (1997), ACS Symp. Ser., 685; (c) Kamigaito M., Ando T., Sawamoto, M. (2001), Chern. Rev., 101, 3689-3746).

Transition metal catalyzed controlled radical polymerization is a very promising technique among the different types of CRP known so far ((a) Kamigaito M., Ando T., Sawamoto, M. (2001), Chern. Rev., 101, 3689-3746; (b) Matyjaszewski K., Xia J. (2001), J. Chem. Rev., 101, 292-2990; (c) Coessens V., Pintauer T., Matyjaszewski, K.(2001), Prog. Polym. Sci., 26, 337-377).

In this polymerization, metal halides based on transition metal having two consecutive oxidation states catalyze the polymerization reaction in presence of a suitable initiator based on halo esters or aryl sulfonyl halides (Matyjaszewski K., Xia J. (2001), J. Chem. Rev., 101, 292-2990).
This process involves the reversible activation of alkyl halide or dormant polymer chain (Pn-X) by a metal halide followed by reversible deactivation of the active species by the same metal halide of higher oxidation state. A suitable ligand is used to tune the reaction kinetics and molecular weight along with the catalyst (Pan K., Jiang L., Zhang J., Dan Y. (2007), J. Appl. Polym. Sci., 105, 521-526; Jiang L., Pan K., Dan Y. (2006), Col. Polym. Sci., 285, 65-74, Wang Y., Pei X., He X., Yuan K. (2005), Eur. Polym. J. 41, 1326-1332; and Yamamoto K., Tanaka H., Sakaguchi M., Shimad S. (2003), Polymer, 44, 7661-7669).

This controlled radical polymerization (CRP) can be used to prepare a graft copolymer with high grafting percentage which cannot be achieved by conventional radical grafting polymerization. There are reports on the preparation of acrylates/methacrylates grafted polyolefin via transition metal catalyzed CRP, but all adopted a two step synthetic route (Wang X., Luo N., Ying S. (1999), Polymer, 40, 4515-4520). In the first step, active halide group was introduced in the olefinic polymers and in the second step the halide groups were used to initiate the polymerization using a catalyst in combination with a suitable ligand.

US 3988227 (Eldred R. J. “Oil-resistant EPDM Elastomer” (1976), US3988227) describes the preparation of a polar and oil resistant polyolefinic elastomer (EPDM), where EPDM and acrylic monomers were got crosslinked on high energy irradiation.

EP 0044683 (Cornell R. J. "Blends of oil-resistant elastomers and grafted EPDM-terpolymers"(1982), EP44683) and US 4397987 (Cornell R. J. “Nitrile rubber/EPDM graft- blends” (1983)) disclose the preparation of polar and oil resistant polymer blends of a polyolefinic elastomer (EPDM) by blending acrylonitrile butadiene polymer with methylethacrylate grafted polyolefinic elastomer (EPDM).

US 4761452 discloses the preparation of highly oil resistant polymer blend of polyolefinic elastomer (EPM, EPDM) and acrylic rubber (Itoh K., Fukushima M., Nakamura T. “Oil-resistant rubber composition” (1988), US 4761452).

US 3646168 and US 3492371 disclose the oil and ozone resistant elastomer blends comprising polyolefinic elastomer (EPDM) (Barrett R. E. “Oil and ozone resistant elastomer blends comprising EPDM rubber” (1972), US3646168; (b) Barrett R. E. “Oil and ozone resistant elastomer blends comprising EPDM rubber” (1970), US3492371).

US 4316971 discloses modified monoolefin copolymer elastomer with improved heat and oil resistance (Rim Y. S., Davison J. A., Nudenberg W. “Modified monoolefin copolymer elastomer with improved heat and oil resistance” (1982), US4316971)

US 5700872 (Wang J. H., Schertz D. M. “Process for making blends of polyolefin and poly(ethylene oxide)) relates a method to prepare a blend of modified polyolefin and modified poly(ethylene oxide) using a single pass reactive extruder. Simultaneous in situ grafting of methacrylate monomers to the melted polyolefin and poly(ethylene oxide) in presence of a free radical initiator during extrusion led to a miscible polymer blend of polyolefin and poly(ethylene oxide). This in situ grafting reaction was carried out via conventional free radical graft copolymerization, where formation of homopolymer of monomers and gelation are very common as explained in the introductory section. US 5700872 does not talk about the absence of homopolymer of (meth) acrylates or gelation during extrusion in the ultimate blend. This invention of US 5700872 was focused mainly on the preparation of a miscible blend of polyolefin and poly(ethylene oxide) where physical interaction was responsible to hold the two polymers together.

Conventional grafting of acrylates or methacrylates on polyolefins leads to undesirable gel formation causing reduction in mechanical properties and poor processing characteristics of the resultant grafted polymer. Formation of homopolymer, degradation of backbone chain, very ill-defined products etc. are the common drawbacks in case of conventional radical grafting process. Presence of homopolymer in grafted polyolefin causes reduction in mechanical and thermal properties, leads to phase separation and also exhibits poor processing characteristic. Therefore, the formation of homopolymer during modification is undesirable. The removal of homopolymer from the grafted polyolefin adds an additional step to the process and hence makes the entire process very laborious and expensive. The present process does not lead to gel formation. It is also very difficult to control the grafting length as well as grafting amount in the grafted polymer via conventional techniques.

These difficulties in the conventional radical grafting technique can be easily overcome by using controlled radical polymerization (CRP) technique. CRP techniques can be applied to graft material even from a surface. Among the different CRP techniques, reverse atom transfer radical polymerization (RATRP) is a simple and versatile living polymerization technique. It involves a thermal and conventional free radical initiator (e.g., AIBN, BPO etc.). The basic ingredients of RATRP are a suitable transition metal halide (e.g.; CuCl2, CuBr2 etc.) in its higher oxidation state, a suitable ligand to bind the catalyst and a thermal initiator like BPO/AIBN to initiate the polymerization reaction. In RATRP, combination of a suitable initiator and a suitable catalyst with a suitable ligand can tune the reaction kinetics and molecular weight. It can yield graft copolymer with high grafting percentage which is not achievable by any conventional radical grafting technique. There are reports on modification of polyolefins (e.g. EPDM, PE etc.) via conventional grafting process (Duin v M., Dikland H. (2007), Polym. Degrad. Stab. 92, 2287-2293; (b) Biswas A., Singha N. K., Bhowmick A. K. (2010), Eur. Polym. J., 46(2), 364-373; (c) Botros S. H., Moustafa A. F. (2002), J. Elast. Plast. 34 (1), 15-32). But none of them reported the preparation of grafted polyolefins with high grafting percentage and without compromising its mechanical and thermal properties.
Extensive literature survey was carried out using different internet search engines like, www.freepatentsonline.com; www.boliven.com; Scopus; World Intellectual Property Search (WIPS) web site; SciFinder and www.scholar.google.co.in. Some of the literature based on chemical modification of polyolefin and its mechanical property are explained in the prior art section.

Modification of polyolefinic elastomers via CRP was reported by few research groups but all adopted a two-step synthetic route. In its first step, polyolefins were modified to attach a halide group on it and in the second step the halide group was used as initiation site for grafting in presence of catalyst, ligand and monomer.
However, none of the patents discloses a single step synthetic process which leads to a controlled grafted polyolefin with improved polarity without formation of homopolymers. Hence there is a need to provide a single step process which provides a single step chemical process to obtain controlled polar modified olefinic elastomers. Unlike the process of prior art, present invention provides a controlled approach to modify polyolefins with controlled and predetermined grafting lengths.

Objectives of the invention
It is one of the objectives of the present invention is to overcome the drawbacks of the prior art.

It is another objective of the present invention is to provide one step process for synthesis of controlled grafted polyolefin with improved polarity.

Summary of the Invention
According to one aspect of the present invention, there is provided a one step process of preparing polar polyolefinic elastomers by graft copolymerization comprising the steps of:
i. adding ligand dissolved in small amount of pure solvent;
ii. adding purified suitable transition metal halide as catalyst to the ligand;
iii. dissolving polyolefin and thermal initiator in solvent and introducing to the reaction tube under continuous stirring;
iv. allowing nitrogen purging for several minutes through the reaction mixture;
v. emerging the reaction tube in an oil bath preheated at desired temperature;
vi. initiating the grafting reaction by adding (meth) acrylates;
vii. measuring the grafting percent gravimetrically by taking out aliquot in specific time intervals; and
vii. purifying the grafted polyolefins by re-precipitating from methanol.

According to another aspect of present invention, there is provided grafted polyolefinic elastomer manufactured by the process thereof.

Brief description of the accompanying drawings:

Figure 1 illustrates FT-IR spectra of pristine polyolefin and grafted polyolefins.
Figure 2 illustrates 1H NMR spectra of polyolefin-g-poly(methyl methacrylate).
Figure 3 illustrates 3D AFM images of a) pristine polyolefin, b) methacrylate grafted polyolefin.
Figure 4 illustrates Swelling index for pristine polyolefin and methacrylate grafted
polyolefins.

Detailed Description of invention

The present invention provides an in situ approach, which provides a single step synthesis of acrylate/methacrylate grafted polyolefin of high surface energy and improved mechanical properties without affecting its thermal properties.
The process of present invention is ‘single step’ as the present process is carried out without formation of homopolymers providing controlled grafted polyolefin with improved polarity unlike the prior art where grafted polyolefins are obtained with formation of homopolymers as well as gelation. The present process avoids this additional step which makes the entire process very laborious and expensive. The present process does not lead to gel formation.
Polyolefinic elastomers being highly nonpolar in nature are not compatible with polar polymers, different polar substrates and polar fillers. This invention discloses a one pot synthetic process to prepare controlled polar modified olefinic polymers with improved polarity and improved oil resistance property without formation of homopolymers of grafted monomers.
The extent of polarity on the polyolefins can be tuned by grafting more polar material. The extent of grafting as well as grafting length can be tuned as much as required by varying the concentration of different ingredients. The main advantage of the process of present invention over conventional metal catalyzed CRP is that this process does not use organic halide initiators and the easily oxidizable metal halide catalyst (Wang X., Luo N., Ying S. (1999), Polymer, 40, 4515-4520).
The process of present invention uses a suitable oxidized transition metal halide with a suitable ligand as catalyst system and a free radical initiator to initiate the polymerization reaction.
The polar modified polyolefinic elastomers provided by the process of the present invention can have improved polarity and improved resistance to oils and fuels. These modified elastomers can have commercial applicability in automotive parts, as compatibilizers in making polymer blends of polar and non polar nature and in coating and adhesive applications. These modified polyolefinic elastomers will also have better adhesion for bonding with metal or with other polar materials.
The process of present invention provides modified polar polyolefins prepared by using a thermal initiator, a suitable transition metal halide in combination with a suitable ligand in presence of different acrylates and methacrylates. A suitable solvent was used as reaction medium. The inventors of present invention have found that the different components used in the present process are important in controlling the graft length and grafting percentage and to avoid the formation of homopolymers.

Monomers (Acrylate/methacrylate) includes inhibitor free acrylates (such as butyl acrylate, 2-ethylhexyl acrylate etc.) and methacrylates (such as methyl methacrylate, bulyl methacrylate, glycidyl methacrylate etc).
Thermal initiator includes benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), dicumyl peroxide (DCP), 2, 2'-azobis(2-methylpropionitrile) di-tert-amyl peroxide.
Catalysts include copper, iron, nickel, rhodium and ruthenium halides (chloride and bromide) in its higher oxidation state are used to catalyze the polymerization.
Ligands in combination with transition metal halide form an efficient catalyst system. The ligand includes, nitrogen based ligands, such as 2, 2'-bypyridine (bpy), N, N, N', N", N"- pentamethyl diethylenetriamine (PMDETA), tris[2-(dimethylamino)ethyl]amine (Me6TREN), tris(2-pyridylmethyl)amine (TPMA) etc. and phosphorous based ligand such as triphenylphosphine (PPh3) etc.
Solvent includes toluene and xylene. It provides reaction medium for grafting reaction by solublizing polyolefinic elastomer into the solvent. In some cases small amount of acetone or diethyl carbonate was used as a co-solvent.
The term “improved polarity” as referred herein refers to incorporation of polar groups to polyolefinic elastomer via grafting reaction to enhance the polarity of the polyolefinic polymers. The term is used to refer these grafted polyolefinic polymers.
The term “improved oil resistance” as referred herein refers to oil resistance property of polyolefinic polymer which is improved after incorporation of polar group.
The term “swelling test” as referred herein refers to an experiment, which is performed to measure the affinity of the polyolefinic elastomer towards a particular solvent by measuring solvent uptake on immersion at a regular interval.
The term “pristine polyolefin” as referred herein refers to unmodified or neat polyolefinic elastomer.
The term “grafted polyolefin” as referred herein refers to modified polyolefinic elastomer via grafting of acrylates.
The term “controlled grafting” as referred herein refers to controlled grafting reaction which yields well-defined graft length.
The one step process of present invention is different from the two step process of prior art in view of the following distinguishing features.

Two step synthetic route of prior arts
1. In the first step, halide group is introduced to the polyolefin substrate by reaction between the olefinic polymer and an organic reagent. The halide functionalized polymer is isolated from the reaction mixture to use in the second step.
2. In the second step the halide functionalized polymer is used as an initiator to initiate the polymerization reaction in presence of monomers using a catalyst in combination with ligand. The combined steps result the grafted polyolefin.

One step synthetic route of present invention
1. In the single step process, all required ingredients are introduced to the reaction vessel all together and grafting reaction is carried out. This process results grafted polyolefins with predetermined molecular weight and grafting length.
2. The one pot synthetic process doesn’t produce homopolymer of grafted monomers. The extent of grafting as well as grafting length can be tuned as much as required by varying the concentration of different ingredients. It results in grafted polyolefin with enhanced polarity, improved oil resistance property without affecting its mechanical property and thermal property unlike conventional techniques like extrusion, melt mixing, blending etc.

Advantages of the process of present invention:
The main advantages of this present process are as follows:

1. In this single pot process, extent of grafting as well as grafting length can be well designed and well-defined.
2. A variety of monomers can be grafted on different polyolefinic elastomers.
3. The resultant controlled graft copolymers have improved polarity and improved resistance to oils and fuels.
4. During the graft copolymerization there is no gel formation.
5. This process does not permit the formation of homopolymer of starting materials.
6. This process is simple and elegant.

The present invention is illustrated by the non limiting workable examples.

Detailed description of the accompanying drawings:

Figure 1 illustrates structural characterization of the grafted copolymers was performed by using FT-IR analyses. The strong IR absorption peak at ~1730 cm-1 in the grafted polyolefins is attributed to the >C=O group of grafted part.
Figure 2 illustrates the 1H NMR spectra of polyolefin-g-PMMA showing the resonances for various protons of polyolefin-g-PMMA in 1H NMR spectrum.
Figure 3 illustrates 3D AFM images of pristine polyolefin and grafted polyolefin. AFM image analysis was utilized to study the surface morphology and surface roughness.

Figure 4 illustrates the swelling index of pristine polyolefin and grafted polyolefins. The swell index plots show the improvement in oil resistance for methacrylate grafted polyolefin.

The invention is now illustrated by way of non limiting examples.

Example 1

Single pot preparation process:
The graft co-polymerizations were carried out in a Schlenk tube. The purified catalyst was added to the Schlenk tube. The ligand was dissolved in a small amount of pure solvent and was then added to the catalyst. The mixture was then stirred until a homogeneous solution was obtained. Polyolefin and initiator were dissolved in a suitable solvent and were introduced to the reaction tube under continuous stirring. The reaction tube was then sealed with a rubber septum and nitrogen was allowed to pass through the reaction mixture to expel out oxygen present in the reaction mixture with continuous stirring. After several minutes of nitrogen purging, the reaction tube was then emerged in an oil bath preheated at desired temperature. The grafting reaction was started by adding acrylate/methacrylate. Grafting percentage was measured gravimetrically by taking out aliquot in specific time intervals. The grafted polyolefins were purified by re-precipitating from methanol.

For a specified amount of polyolefin, the amount of grafted monomer in the grafted polyolefin can be tuned by varying the molar ratio of monomer to initiator and subsequently the concentrations of catalyst and ligand respectively. Table 1 shows the amount of all required ingredients to prepare controlled grafted polyolefinic elastomer with improved polarity.
Table 1: Amount of chemical ingredients required for polar modification on polyolefinic elastomer.
Chemicals Amount
Polyolefin 0.5 - 5 g
Thermal Initiator 0.03 – 0.15 g
Catalyst 0.08 - 0.40 g
Ligand 0.13 - 0.50g
Monomer 1 - 5 mL
Solvent 10 - 100 mL

Example 2:
A control experiment was carried out taking (5 mL) polyolefin stock solution (prepared by dissolving in toluene) into a Schlenk tube already having a thermal initiator (4.78x10-5 mol), transition metal bromide (9.60x10-5 mol), N, N, N´, N´´, N´´- pentamethyl diethylenetriamine (PMDETA) (1.91x10-4 mol) and 0.5 mL acetone in it. The degassed reaction mixture with continuous stirring was placed in an oil bath preheated at desired temperature. The reaction mixture was allowed to react for several minutes and then was removed from the oil bath. The polymer was isolated from the reaction mixture and purified by re-precipitating from alcohol. It was assumed that during the control reaction some bromo (-Br) functionality will be incorporated on the polyolefin which can be used as a macroinitiator for transition metal catalyzed CRP of methyl methacrylate (MMA). To verify this, the isolated polyolefin was dissolved in toluene. MMA (0.057 mol) was added to the above polyolefin macroinitiator solution, metal bromide (1.14x10-4 mol) and PMDETA (1.72x10-4 mol) were added separately to the above reaction mixture. Nitrogen was passed through the reaction mixture for several minutes. The reaction mixture was then placed in an oil bath already heated at desired temperature. The reaction was run for 12 hrs.
Yield of the polymer was noted to be 5.1 g.

The increased weight in the resultant grafted polymer and FT-IR and 1H NMR analysis confirmed the successful incorporation of (meth)acrylates into the polyolefinic polymer. The Soxhlet extraction and re-precipitation method of the resultant grafted polymer confirmed there was no formation of homopolymer of grafted monomer.

Example 3:

Structural Characterization of Polyolefin-g-poly(meth)acrylate

The structural characterization of the grafted copolymers was performed by using FT-IR (Figure 1) and 1H NMR (Figure 2) analyses. The strong IR absorption peak at ~1730 cm-1 in the grafted polyolefins is attributed to the >C=O group of grafted part.
Figure 2 shows the 1H NMR spectra of polyolefin-g-poly(methyl methacrylate). The resonances for various protons of polyolefin-g-PMMA in 1HNMR spectrum are shown in Figure 2. The resonance at δ=5.2 ppm is attributed due to the unsaturated (=CH¬¬-) proton present in the grafted polyolefin. The resonance at δ=3.6 ppm is due to the –OCH3 protons of polymethyl methacrylate (PMMA) part of the grafted polyolefin. It indicated that PMMA was successfully grafted on polyolefin. The resonances at δ=0.9-2.4 ppm are mainly due to the methyl, methylene and methine protons present in the grafted polyolefin. The molar composition of PMMA present in the grafted polyolefin was calculated from the integrated area of –OCH3 protons and methyl protons of polyolefinic part.
Example 4:
Morphological study:
AFM image analysis was utilized to measure the surface morphology and surface roughness of the grafted polyolefins. Figure 3 shows the 3D AFM images of pristine polyolefin and grafted polyolefin. The sharp needles like extension present in the Figure 3b are due to the high modulus poly(methacrylate) grafted onto the polyolefin. The difference between root mean square roughness RMS (Rq) and roughness average (Ra) give the measurement for surface roughness. It was also observed that the Rq-Ra value was increased with the grafting of poly(meth)acrylate on the grafted polyolefin. Table 2 summarizes the calculated surface roughness parameters for polyolefin and grafted polyolefin.

Table 2: Quantitative surface roughness parameters of pristine polyolefin and grafted polyolefin.

Parameters
(nm) Pristine polyolefin Grafted polyolefin
*RMS (Rq) 1.27 3.99
*Ra 1.01 2.81
(Rq-Ra) 0.26 1.18

*Root mean square roughness RMS (Rq) and roughness average (Ra)

Example 5:

Polar grafted polyolefin:
The present process provides a route to synthesis of controlled graft copolymer of polyolefin with improved polarity and improved oil resistance property (Table 3). Figure 4 shows the swelling index of pristine polyolefin and grafted polyolefins. The improvement of oil resistance for methacrylate grafted polyolefin is well understood from the swell index plots.

Table 3: Surface energy parameters for polyolefin and grafted polyolefin.
Samples Grafting percentage
(%) Total surface energy
( ), ( )
Polar component
( ), ( )
Dispersive component
( ), ( )

Pristine polyolefin
----
20.19
2.69
17.50
Methacrylate grafted polyolefin-1
124
43.54
14.59
28.95
Methacrylate grafted polyolefin-2
60
35.92
9.87
26.05

The present process provides controlled grafted polyolefin with improved polarity and improved oil resistance property without deteriorating its mechanical and processing characteristics. The literature survey (as mentioned in the “Background and prior art” section”) indicates that by using conventional techniques it is not possible to tailor the extent of grafting or grafting length in the grafted polymers (Grigoryeva O. P., Karger-Kocsis J. z (2000), Eur. Polym. J., 36, 1419-1429; Papke N., Karger-Kocsis J. z (1999), J. Appl. Polym. Sci., 74, 2616–2624; Qu X., Shang S., Liu G., Zhang L. (2002), J. Appl. Polym. Sci., 86, 428–432; Duin v M., Dikland H. (2007), Polym. Degrad. Stab. 92,2287-2293; Biswas A., Singha N. K., Bhowmick A. K. (2010), Eur. Polym. J., 46(2), 364-373). Conventional process also leads to homopolymerization as well as gelation because of which it is not possible to make good films to carry out AFM analysis. Since the grafted samples are insoluble they are difficult to analyze via 1H NMR and GPC analyses. The conventional techniques also cannot be used to achieve higher grafting percentage unlike present invention as evident from Table 3.

Swelling index (SI) was calculated by using the following equation:

Where SI = swelling index (% of volume swell/l00)
W1 and W2 = weight of specimen before and after swelling respectively
pc and ps = density of the specimen and the test oil respectively.

The optimum swelling index and swelling time for the pristine polyolefinic elastomer was reduced significantly after grafting with (meth)acrylates. The optimum swelling index observed for two methacrylate grafted polyolefinic elastomers of different grafting percentages 124% and 60 % are shown in Figure 4.

We Claim:
1. A one step process of preparing polar polyolefinic elastomers by graft copolymerization comprising the steps of:
i. adding ligand dissolved in small amount of pure solvent;
ii. adding purified suitable transition metal halide as catalyst to the ligand;
iii. dissolving polyolefin and thermal initiator in solvent and introducing to the reaction tube under continuous stirring;
iv. allowing nitrogen purging for several minutes through the reaction mixture;
v. emerging the reaction tube in an oil bath preheated at desired temperature;
vi. initiating the grafting reaction by adding (meth) acrylates;
vii. measuring the grafting percent gravimetrically by taking out aliquot in specific time intervals; and
viii. purifying the grafted polyolefins by re-precipitating from methanol.

2. The process as claimed in claim 1, wherein the grafted polyolefins are prepared without formation of homopolymers.

3. The process as claimed in claim 1, wherein said thermal initiators are selected from benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), dicumyl peroxide (DCP) and 2, 2'-azobis(2-methylpropionitrile) di-tert-amyl peroxide.

4. The process as claimed in claim 1, wherein said transition metal halides are selected from chlorides and bromides of copper, iron, nickel, rhodium and ruthenium halides.

5. The process as claimed in claim 1, wherein said monomers are selected from inhibitor free acrylates (such as butyl acrylate, 2-ethylhexyl acrylate etc.) and methacrylates (such as methyl methacrylate, bulyl methacrylate and glycidyl methacrylate.

6. The process as claimed in claim 1, wherein said suitable ligand is nitrogen based ligands.

7. The process as claimed in claim 6, wherein said nitrogen based ligands is selected from 2, 2'-bypyridine (bpy), N, N, N', N", N"- pentamethyl diethylenetriamine (PMDETA), tris[2-(dimethylamino)ethyl]amine (Me6TREN), tris(2-pyridylmethyl)amine (TPMA).
8. The process as claimed in claim 1, wherein said solvent is selected from toluene and xylene.
9. The process as claimed in claim 1, wherein the grafting reactions were carried out at reaction temperatures of about 60 to 120ºC.

10. A grafted polyolefinic elastomer manufactured by the process of claim 1.

11. The grafted polyolefin as claimed in claim 10, wherein the said grafted polyolefinic elastomer has improved polarity and improved oil resistance property.

ABSTRACT

A one step process of preparing polar polyolefinic elastomers by graft copolymerization comprising the steps of adding ligand dissolved in small amount of pure solvent; adding purified suitable transition metal halide as catalyst to the ligand; dissolving polyolefin and thermal initiator in solvent and introducing to the reaction tube under continuous stirring; allowing nitrogen purging for several minutes through the reaction mixture; emerging the reaction tube in an oil bath preheated at desired temperature; initiating the grafting reaction by adding (meth) acrylates; measuring the grafting percent gravimetrically by taking out aliquot in specific time intervals; and purifying the grafted polyolefins by re-precipitating from methanol and a grafted polyolefinic elastomer manufactured by the process thereof.