POLYMERIZATION OF CRYSTALLINE COPOLYMERS OF OLEFINS AND CYCLIC OLEFINS

Abstract: A copolymerization process suitable for the preparation of high crystalline melting point cyclic olefin copolymers comprising contacting ethylene, and at least one cyclic olefin with an active polymerization catalyst comprising a Group 4 transition metal compound containing an asymmetrically substituted monocyclopentadienyl ancillary ligand, a bulky substituent-containing heteroatom ligand, the monocyclopentadienyl and heteroatom ligands being covalently bridged is disclosed. Ethylene/norbornene copolymers prepared in accordance with the invention exibited crystalline melting points of about 250 DEG C, and were prepared at high catalyst activity levels with feed ratios less than 6:1 of norbornene to ethylene.

Description: Polymerization of Crystalline Copolymers of Olefins and Cyclic Olefins Field of the Invention The invention relates to a polymerization process for the preparation of semi-crystalline copolymers of olefins and cyclic olefins without ring-opening metathesis. Specific catalysts suitable in the process include bridged, monocyclopentadienyl catalyst compounds with alumoxane or ionizing catalyst activators. Background The polymerization of cyclic olefins, either alone, or with copolymerizable monomers, particularly olefins, has been significantly advanced with the discovery of the effectiveness of metallocene catalysts for coordination polymerization. Crystalline homopolymers can be prepared from the use of stereorigid, chiral metallocenes that yield conformationally regular or stereospecific polymers. See, New Materials by Polymerization of Cyclic Olefins with Metallocene Catalysts, W. Kaminsky, Paper for METCON '93, Houston, Tx, May 26-28, 1993, p. 325-335. Copolymerization with α-olefins can result in elastomeric polymers due to disruption of the v-olefin ciystallinity caused by the olefin incorporation. See, U.S. patent 5,204,429. More recently it has been discovered that by careful selection of the ligand structure of the metallocene catalysts, copolymers having crystalline attributes can be prepared by copolymerizing olefins with the cyclic olefins. U.S. patent 5,324,801 describes a process for the preparation of cycloolefin copolymers having from 1 to 80% of at least one cyclic olefin comprising copolymerization with an acyclic olefin in the presence of sandwich structured metallocenes where the sandwiching ligands are connected or bridged so as to form a ring. Preferred copolymers are said to have incorporation ratios of 40:60 to 60:40 of the cyclic olefin to acyclic olefin. Using the sandwich metallocenes exhibiting Ci symmetry, with the preferred ligands being fluorenyl and cyclopentadienyl, copolymers of alternating sequence ethylene and either of norbornene or tetracycloclododecene were prepared having crystalline melting points of 235 °C to 335 °C and molar ratios ranging from 50:50 to 41:59, cyclic olefin to acyclic olefin. Due to transparency the polymers are said to be suitable as glass substitutes, and suitable in polymer alloys. Further product description appears in Cherdon, et al, Cycloolefin Copolymers: A New Class of Transparent Thermoplastics, A gew. Chem. 223, 121-133 (1994). Since these crystalline and semi-crystalline copolymers of ethylene, α-olefins, and cyclic olefins exhibit uniquely interesting physical properties, alternative means of preparing them, with potential improvements in ease of catalyst synthesis, increased polymerization efficiencies, increased cyclic olefin incorporation efficiencies and differing copolymer product characteristics are of great interest. Accordingly work was done to develop catalyst systems different from those previously discovered to be capable of such copolymerization processes. Summary of the Invention The invention thus is a copolymerization process suitable for the preparation of high crystalline melting point cydic olefin copolymers comprising contacting ethylene and at least one cyclic olefin, under suitable polymerization conditions, with an active polymerization catalyst comprising a Group 4 transition metal compound containing an asymmetrically substituted monocydopentadienyl ancillary ligand, a bulky substituent-containing heteroatom ligand, the monocydopentadienyl and heteroatom ligands being covalently bridged. Description and Examples The cyclic olefin copolymers for which the invention process is suitable indude those having both sequence regularity and conformational regularity. Sequence regularity means here essentially alternating sequences of cyclic olefin monomer and ethylene. Conformational regularity, or sterospecifidty, is the result of consistent molecular coordination geometries. These characterizing features assure that the copolymer can exhibit initial crystalline melting points from about 150 β C to 350 °C, particularly 200 °C to 300 °C, as measured by differential scanning calorimetry (DSC) conducted at a heating rate of 10 °C per minute from -50 to 350 °C. These copolymers typically have an intrinsic viscosity of 0.05 dl g to 20 dl/g as measured at 135 °C in decalin. Molecular weight distribution, or polydispersity (MWD), is typically narrow, ranging from about 1.1 up to 6.0, preferably 1.2 to 4.5, more preferably 2.0 to 4.0 as calculated from molecular weights measured by gel permeation chromatography (GPC) referenced to a known polyethylene standard in accordance with traditional methods. Although an MWD <2.0 is not typical in traditional Ziegler-Natta polymerization, the use of certain polymerization conditions for the copolymerization in accordance with this invention can result in polymerization analogous to "living" anionic polymerizations which are typified with MWD characterizations below 2.0. Ethylene is the preferred comonomer in that using the catalyst system of this invention, C3 and higher carbon number α-olefins are not typically capable of copolymerization sequences consistent with production of the semicrystalline polymers of the invention. This phenomena is notable, in the prior art relating to cyclic olefin copolymers, the C3 and higher carbon number α-olefins are typically said to be readily copolymerized in almost any incorporation ratio to the cyclic olefins. Suitable cyclic olefins indude those having at least 4 carbon atoms and one coordination polymerizable ethylenic unsaturation site. Such olefins indude those with multicyclic structures and those having additional hindered or masked ethylenic unsaturation not readily available to coordination addition reactions at the catalyst coordination site. These olefins are most usually hydrocarbyl but may indude low levels of non-carbon, heteroatoms when such are, again, hindered, shielded or masked so as to not be capable of coordination at the catalyst coordination site. Though these olefins preferably contain only unsubstituted ring members, substitution can be tolerated where by location or site there is insignificant disruption of the overall crystalline configuration of the copolymer composition made by the invention process. Preferably substitution will be with C^-Cg hydrocarbyl ligands not located on one of the ethylenically bonded carbon atoms. Preferred cyclic olefins indude cydobutene, cydopentene, cydooctene, norbornene, 5-methylnorbornene, 3-methylnorbornene, ethylnorbornene, phenylnorbornene, dimethylnorbornene, diethylnorbornene, dicydopentadiene, tetracydodododecene, methyltetracydododecene, and the like. Additionally suitable cyclic olefins indude those known in the art, exemplary description can be found in WO-94/17113 and U.S. patents 5,270,393 and 5,324,801, all of which are incorporated by reference for purposes of U.S. patent practice. The preferred heteroatom-containing, monocydopentadienyl Group 4 metal catalysts are in the dass compromising covalently bridged Group 4 metal-containing compounds having the generic formula: MRχR 2 J (T) Cp, where Ri and R2 are the same or different univalent ligands capable of ethylene insertion or capable of abstraction and replacement with a ligand capable of ethylene insertion; J is a Group 15 heteroatom which is covalently bridged to Cp through a connecting group T and which contains a univalent substituent sufiϊriently bulky to shield M from direct approach by the cyclic olefins; and Cp is an η5-cydopentadienyl ring derivative having substitution on ring atom members such that it is asymmetric to a line drawn between the bridging ring member and a point on the opposite side of the ring. Rl and R2 are identical or different and are a hydrogen atom, a halogen atom, a Ci.Cjo-ε kyl group, a group, a Cg_ CiQ-aryl group, a C(}.Cιo~ ar yl oχ y group, a C2-Cιo-alken l group, a C io-arylalkyl group, a Cg.CiO'^ kυ'yl group or a Cg.CiO" arylalkenyl group. J is the heteroatom containing ligand and indudes C3-C30 hydrocarbyl ligands such as isopropyl, tert-butyl, adamantyl, cydododecyl, etc., as the univalent, bulky ligand. Preferably the bulky univalent ligand will comprise a secondary, more preferably a tertiary carbon, bound to the heteroatom so as to provide broadest bulk for hindrance of the approach of cyclic olefins to the catalyst coordination site. Ligands described in WO 96/00244 are particularly suitable. The covalent bridging group T between J and Cp typically contains Group 13-15 elements having hydrogen and/or carbon or silicon element comprising ligands. Preferably T comprises methylene, ethylene or silylene, any of which can have alkyl, aryl, alkyaryl, preferably Cι-C20 > or silyl substituents. Specific examples indude monocydopentadienyl catalyst compounds having substitutions selected from known dasses of ligand groups readily synthesized analogously to those available in the literature. Description is given in 5,055,438, 5,096,867, 5,264,400, and WO 92/00333, among others, each is incorporated by reference for purposes of U.S. patent practice. In particular, a preferred compound is dimethylsilyl (3-teri-butylcydopentadienyl) (1-adamantylamido) hafnium dimethyl which pictorially exemplifies the dass of compounds suitable in this invention. Its diagram follows. Figure 1: As will be apparent from this description and diagram any alkyl substitution of Ci or higher carbon number, preferably C2 and higher, most preferably C3 and higher up to C30, preferably up to C20 > and most preferably up to Cχo > can be used in the 3-cydopentadienyl position. In addition disubstituted substitution patterns can be used where two adjacent R groups in the 3-cydopentadienyl and 2- cydopentadienyl positions can be the same or different group selected from hydrogen, C1-C30 hydrocarbyl, preferably C2-C20. most preferably C3-Cχo > such as alkyl, alkenyl, aryl, alkylaryl or arylalkyl radicals, induding those structures where two adjacent R substituents are bound together to form a further C1-C20 substituted or unsubstituted ring system, such as cydohexyl, indenyl, benzyindenyl, etc. The substituted cydopentadienyl derivatives may have ring positions 4 and/or 5 substituted, so long as they are substituted with such as to preserve the asymmetric substitution pattern. Any derivatives, such as 3-phenyl-indenyl and the like will be suitable. For darity the cydopentadienyl ring positions are to be numbered as shown above in determining asymmetry. In a like manner, J may be any known amido, phosphido, etc., heteroatom structure having a bulky substituent in the exocydic position of the heteroatom as exemplified by the pictured adamantyl group, preferably a C3-C30 hydrocarbyl substituted amido or phosphido group. Of the Group 4 tranition metals, hafnium and zirconium are particularly suitable when low molar ratios of cyclic olefin to ethylene are to be utilized, e.g., 3:1 to 15:1. Titanium catalysts tend to incorporate ethylene sequences in higher amounts, thus higher levels of cyclic olefin to ethylene will be suitable, e.g., molar ratios (cyclic olefin:ethylene) up to 80:1, or higher, will be preferable. The higher molar ratios can be achieved by using lower ethylene pressures and increased cyclic olefin content in the polymerization medium. See the process description below and in U.S. Patents 5,324,801 and 5,498,677 for further description. A compound capable of activating the Group 4 transition metal compound of the invention to an active catalyst state is used in the invention process to prepare the activated catalyst. Suitable activators indude the ionizing noncoordinating anion precursor and alumoxane activating compounds, both well known and described in the field of metallocene catalysis. An active, ionic catalyst composition comprising a cation of the Group 4 transition metal compound of the invention and a noncoordinating anion result upon reaction of the Group 4 transition metal compound with the ionizing noncoordinating anion precursor. This activation reaction is suitable whether the anion precursor ionizes the metallocene, typically by abstraction of Rj or R2, by any methods indusive of protonation, ammonium or carbonium salt ionization, metal cation ionization or Lewis add ionization. The critical feature of this activation is cationization of the Group 4 transition metal compound and its ionic stabilization by a resulting compatible, noncoordinating, or weakly coordinating (induded in the term noncoordinating), anion capable of displacement by the copolymerizable monomers of the invention. See, for example, EP-A- 0 277,003, EP-A- 0 277,004, U.S. patent 5,198,401, U.S. patent 5,241,025, U.S. patent 5,387,568, WO 91/09882, WO 92/00333, WO 93/11172, and WO 94/03506 which address the use of noncoordinating anion precursors with Group 4 transition metal catalyst compounds, their use in polymerization processes and means of supporting them to prepare heterogeneous catalysts. Activation by alumoxane compounds, typically, alkyl alumoxanes, is less well defined as to its mechanism but is none-the-less well known for use with Group 4 transition metal compound catalysts, see for example U.S. patent 5,096,867. The process of the invention is typically conducted in a reaction medium condudve to interaction of the catalyst and the monomers, one that facilitates their contact. Thus a slurry of supported catalyst in liquid cyclic olefin may serve as the reaction medium. Similarly a solution process using typical hydrocarbon solvents will be suitable, preferably the solvent is one of aromatic or cycloaliphatic hydrocarbon compounds, but linear or branched aliphatic compounds will also be suitable. Suitable solvents thus indude toluene, cydohexane, hexane; etc. The active catalyst may be supported in any manner suitable for the reaction process chosen, particularly when a slurry process is to be used. Numerous methods of support are known in the art for copolymerization processes for olefins, particularly for catalysts activated by alumoxanes, any is suitable for the invention process in its broadest scope. See, for example, U.S. patent 5,227,440. When using a Lewis add ionizing catalyst activator a particularly effective method is that described in WO 96/04319. The support method of this co-pending application describes the use of a Lewis add noncoordinating anion precursor (e.g., trisperfluorophenyl boron) which is covalently bound to siHca-containing supports through retained hydroxy groups which as an initially formed activator complex donates the hydroxyl hydrogens as protons for protonation of the Group 4 transition metal compound to catalytically active cations. The slurry or solution processes in which the contacting of catalyst and monomers is conducted can be done under conditions known to be suitable for the catalyst chosen. Thus, polymerization reaction temperatures can range from below about -20 °C up to about 300 °C, and at any temperature in between. Room temperature (20 °C) reactions are convenient but increases in activity are attainable at the higher temperature ranges. Thus, temperatures above 60 °C are suitable, as are those above 100 °C, or even at 120 °C and above given the stability of the monocydopentadienyl catalysts of the invention. The pressure of the polymerization is not critical as long as the appropriate ratios of cyclic olefin to ethylene are attained. Typically ethylene is introduced as a pressurized gas and can be maintained at about 0.1 to about 15 bar, preferably 0.5 to 2.0 bar. The polymerization process of the invention suitably uses the catalyst and activator in accordance with their known methods in the known amounts and under the known conditions. Thus, preactivation or in situ activation, and scavenging with alumoxane or alkyl aluminum, or combinations of them, known to those skilled in the art will be suitable in accordance with this invention. The description of processes in the references dted above are exemplary. Together with the examples of the invention, one of ordinary skill in the art will readily appredate suitable methods. It is believed that a catalyst structure as exemplified and described above acts to allow ready polymerization of the bulky cyclic olefins, but preferentially from the unhindered approaches to the metal coordination center and in a manner dictated by the steric constraints of the catalyst compound ligand system and both the shape of the cyclic olefin and the position in it of the polymerizable ethylenic unsaturation. This apparently leads to conformationally regular or stereospecific incorporation. Additionally, the bulk of a first cyclic olefin and the steric constraints of the catalyst ligand system during insertion likely acts to inhibit entry into the coordination center of the catalyst of an immediately subsequent cyclic olefin monomer. Thus insertion of a subsequent cyclic olefin is preceded by the insertion of ethylene which is not so sterically inhibited in entry and which acts when inserted to remove the initially inserted cyclic olefin from the coordination site. A subsequent cyclic olefin in turn is then not inhibited by the inserted ethylene and can readily enter and be inserted. A copolymer results having sequence segments that are essentially of alternating comonomers. This copolymer has insignificant, if any, diads comprising sequentially polymerized cyclic olefins. The below exemplified catalyst was used to prepare a high melting point, engineering polymer, of ethylene and norbornene, of the present invention. Amounts of greater than 40 mol. % norbornene were readily incorporated into the polymer backbone under the reported polymerization conditions. In contrast to the catalysts of U.S. patent 5,324,801 (see Background), which are known to be capable of making polypropylene, the contacting of propylene with the invention catalyst yielded essentially no measurable polypropylene polymer. Thus it was entirely unexpected to achieve copolymerization of cyclic monomers, since they are bulky like propylene. Similarly, polynorbornene is known to result from the use of similar biscydopentadienyl catalysts but could not be produced with the catalysts of this invention. Additionally, the inability to enchain two consecutive bulky monomers such as propylene or cyclic olefin enables the addition of cyclic olefin monomers in broad feed ratios, to ethylene, of from about 3:1 to 30:1 or more without sacrifice of the sought and highly preferred substantially alternating sequence, particularly with hafnium and zirconium compounds. Since the resulting polymer is essentially free of cydic-olefin diads a more defect free alternating sequence distribution copolymer results. These copolymers can have higher, and more predictable melting point temperatures at lower cyclic olefin-to-ethylene ratios. A copolymer with a melting point temperature of 235 °C was achieved at low feed ratio (7 : 1) of norbornene to ethylene in U.S. patent 5,324,801 . Yet at lower norbornene to ethylene ratios of less than 6:1 the process of this invention produced copolymers of crystalline melting points above 245 °C. See Table 2. This can be translated in industrial practice to a significant economic advantage in terms of cylic olefin conversion effidendes and related process advantages. The copolymers of the invention can be processed into polymer compositions useful in those applications where high crystalline melting point polymers, also known as engineering polymers, have previously found use. Specifically, thermally stable polymer compositions suitable for injection molding similar to polyamides and polyesters are possible, as are the uses known for the hard, thermally stable, transparent polymer compositions of polycarbonate. Thus, optical applications as disdosed in U.S. patent 5,324,801 are made possible in addition to those applications suggested by the technologies relevant to that of other engineering polymers and resins of similar glass transition temperature or melting point. Additionally, potential compatibilities of these polyolefin engineering polymer compositions make it possible to prepare polymer alloys comprising the invention product and other engineering polymers so as to prepare materials with modified use temperatures. The copolymers of the invention exhibit brittleness characteristics of rigid engineering plastics. This lack of impact toughness, or impact strength, can be improved by the indusion of elastomeric polymers in amounts of from 5-40 wt. %, more typically 10- 30 wt. %, and preferably 12-25 wt. %. Such elastomeric polymers can be essentially any exhibiting compatibility with copolymers of the invention. "Compatibility'' in the sense used here means capable of being blended with the invention copolymers, typically under melt processing or solution conditions, and subsequently being stably dispersed without significant problems of gross separation or stratification. Any elastomeric polymers known in the art to be suitable for impact modification of rigid thermoplastics will be suitable, particularly those comprising comonomers indusive of ethylene or cyclic olefins. Of particular importance will be the use of rubbery or elastomeric cyclic olefin copolymers, particularly those described in WO 94/17113 and WO 96/11983, see also U.S. Application Ser. Nos. 08/005,676, filed 1/19/93, and 08/539,487, filed 10/6/95. Additionally, polymers based on ethylene and vinyl-aromatic olefins, such as styrene and alkyl-substituted styrenes will be suitable. The following description and tables illustrate the invention examples (1 - 3) and provide comparative examples (4 - 6) illustrating the non-functional capabilities of similar catalysts tested during the development of the invention process. Examples Polymerization of ethylene/ norbornene was conducted in accordance with the following procedure under the conditions reported in Table 1, product properties are shown in Table 2. It is notable that only the process according to the invention in examples 1) through 3) was capable of preparing a high crystalline melting point polymer under the selected polymerization conditions, particularly at the low comonomer molar ratios. Under the described conditions, the bridged monocydopentadienyl catalyst system of comparative example 6), not exhibiting asymmetry in the cydopentadienyl ring, did not produce high melting temperature cyclic olefin copolymers. The glass transition temperature (Tg) is indicative of cyclic olefin incorporation, higher numbers correlate to greater incorporation. Thus comparative example 5) illustrates a comparable incorporation of cydic olefin as for the invention catalyst but no measurable crystalline melting point. Similarly, biscydopentadienyl catalyst systems exhibiting asymmetry in one cydopentadienyl group and a bulky substitution pattern in the other (comparative examples 4-5) did not produce copolymers having measurable crystalline melting point under comparable polymerization conditions. Example 1 Catalyst Activation 40.0 mg μ-Me2Si(3-teri-BuCp)(l-Adamantyl Amido)HfMe2 (prepared in accordance with the disdosure in WO 96/00244 was weighed out under inert atmosphere and N,N-Dimethylanilinium tetrakis-perfluorophenyl boron (DMAH) B(pfp)3 activator was added to give a slight molar excess of the transition metal complex. 2 mL of dry toluene was added by pipette and the mixture allowed to stand with occasional stirring until activation was complete (10 to 20 min.). The resulting mixture was septa sealed and ready for transfer to the reactor via canula. Reactor Conditions 0.8 liter of dry toluene was transferred to a dean, dry and N2 purged 2 liter autodave reactor using air sensitive technique. The solvent was stirred under a continued slow N2 purge (10 SLPM) while the reactor was equilibrated at 60 °C. Triisobutylaluminum (TIBA) was added as a scavenger by diluting 0.5 mL of a 1 M solution in toluene with additional toluene (10 to 20 mL) and transferring to the reactor via cannula through the purge port using standard air sensitive technique. 106 g norbornene was added to the reactor as a concentrated solution in toluene (86 wt.%) via cannula through the purge port using standard air sensitive technique. The N2 purge was shut off simultaneously as the reactor was sealed. 15 psig (1 bar) ethylene gas was added to the reactor until the solution was saturated. (Molar feed ratio Norbornene: Ethylene = 5.6:1.) The ethylene regulator and flow controller are set to maintain the 15 psig (1 bar) ethylene pressure with a 10 SLPM replenishing flow. The reactor was then quickly vented and the pre-activated catalyst was added to the reactor via cannula through the purge port. The port was then sealed and the ethylene pressure quickly returned to 15 psi (1 bar) by opening the flow controller. The mixture was stirred at 60 °C for 74 minutes. The reaction was quenched by rapid venting of the rector and its contents poured into one liter of rapidly stirring acetone. The resulting white solid polymer was washed, separated by filtration, and dried in a vacuum oven overnight (60 °C, -30 in. Hg (-1.0 atm)). 128.4 g of copolymer was obtained that had a melt temperature of 247 °C, M w = 39,685, MWD = 1.44. Note: All weight-average molecular weight (M w ) measurements were by gel permeation chromatography (GPC) and were based upon a polyethylene standard. Accordingly, the M w reported is comparable for the examples of the invention, but not accurate for determination of actual M w . Examples 2 - 6 The following examples (2 - 6) were conducted in a process similar to the one described for Example 1, but with the conditions shown in Table 1. The resulting copolymer products and the catalyst used to prepare them are described in Table 2. Example 7 An ethylene-nόrbornene copolymer (A) according to the invention was prepared with the catalyst system of Example 1 at 60°C, but with 938 mg of catalyst, 10,960 ml toluene, and 21 psi (144.8 kPa) ethylene pressure. An amount of 3766 g norbornene was provided to establish a molar ratio of nonbornene to ethylene of 5.6:1. The polymerization reaction was run for 1 hour. The yield was 1.01 kg copolymer for an activity of 1076 g/g-h. The copolymer exhibited a T m of 250°C, a T g of 112°C, M w of 57,000 (by GPC using a PE standard), and a molecular weight distribution (MWD) of 2.34. Table 2 : Catalyst & Copolymer Characteristics nm - DSC revealed no distinct feature characteristic of a glass transition temperature or melt transition. An E/NB (ethylene/norbornene) elastomer (B) made in accordance with the description in WO 94/17113 and having about 10 moles % NB, some ethylene crystallinity (T m = 60°C, MWD = 1.83) and M n equal to 43,800 was also blended (20 wt %) with the stereoregular alternating E NB of this Example 7 to compare its ability to toughen the brittle E/NB copolymer (A). The blending was accomplished under standard melt processing conditions at 250°C using a Brabender mixer for a period of 10 min. After the removal and cooling, the resulting blend was a rigid opaque solid with a hard shinny surface. The compression molded film was somewhat transparent and could not be torn by hand unless a notch was cut. The films were strong and did not break when folded repeatedly. Both the unmodified alternating E NB polymer (A) and the blend of it with the E/NB elastomer (B) were then tested under standardized conditions for both tensile at break and % strain at break. ( Blend w/(B) Tensile @ Break 2929 psi 6835 psi (20,195 kPa) (47,126 kPa) % Strain @ Break 5.0 8.9 I claim

Claims: CLAIMS: 1. A copolymerization process suitable for the preparation of high ciystalline melting point cyclic olefin copolymers comprising contacting ethylene and at least one cydic olefin, under suitable polymerization conditions, with an active polymerization catalyst comprising a Group 4 transition metal compound containing an asymmetrically substituted monocyclopentadienyl ancillary ligand, a bulky substituent-containing heteroatom ligand, the monocyclopentadienyl and heteroatom ligands being covalently bridged. 2. The process in accordance with Claim 1 wherein said Group 4 transition metal compound comprises zirconium. 3. The process in accordance with Claim 2 wherein said Group 4 transition metal compound comprises hafnium. 4. The process in accordance with Claims 1-3 wherein said bulky substituent-containing heteroatom ligand comprises a hydrocarbyl substituted amido ligand comprising a tertiary carbon bound to the nitrogen atom. 5. The process in accordance with Claims 1-3 wherein said bulky substituent-containing heteroatom ligand comprises a hydrocarbyl substituted amido ligand comprising a tertiary carbon bound to the nitrogen atom. 6. The process in accordance with Claim 1-3 wherein said bulky substituent-containing heteroatom ligand is 1-adamantyl amido. 7. The process in accordance with Claims 1-6 wherein the monocyclopentadienyl and heteroatom ligands are covalently bridged by a group comprising carbon or silicon. 8. The process in accordance with Claims 1-7 wherein said asymmetrically substituted monocyclopentadienyl ancillary ligand comprises in the 3-cyclopentadienyl position at least one C2-C20 alkyl or alkyl substituted silyl substituent. 9. The process in accordance with Claims 1-7 wherein said asymmetrically substituted monocyclopentadienyl ancillary ligand comprises a disubstituted substitution pattern where two adjacent R groups in the 3-cyclopentadienyl and 2- cyclopentadienyl positions are the same or different substitutent selected from hydrogen, C2-C1 alkyl-substituted silyl, C2-C20 hydrocarbyl, such as alkyl, alkenyl, aryl, alkylaryl or arylalkyl radicals, including those structures where the two adjacent K substituents are bound together to form a substituted or unsubstituted ring system. 10. The process in accordance with Claims 1-9 wherein said ethylene and at least one cydic olefin are contacted with said active polymerization catalyst by introduction into a polymerization medium of one or more feedstreams so as to establish a feedstream ratio of cyclic olefin to ethylene of less than or equal to about 6.0.

Inventors: HARRINGTON BRUCE ALLAN, HARRINGTON, BRUCE, ALLAN
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1996
Main classification: C08F10
IPC codes: C08F4, C08F210, C08F232