SYNDIOTACTIC/ATACTIC BLOCK POLYOLEFINS, CATALYSTS AND PROCESSES FOR PRODUCING THE SAME

Abstract: Metallocene catalysts useful for the preparation of syndiotactic/atactic block polyolefins have the general formula: R"(C4R'mC5C4R'n) XMeQ wherein X is a hetero-atom ligand with one or two lone pair electrons selected from the elements of Group VA or VIA which can be substituted or non-substituted; (C4Rm'C5C4R'n') is a fluorenyl or a symmetrically substituted fluorenyl or cyclopentadienyl ring; R' is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino or alkylsilylo radical, each R' may be the same or different and m and n independently are 0, 1, 2, 3 or 4, with the proviso that the bilateraly symmetry is maintained; R" is a structural bridge between X and the (C4R'mC5C4R'n) ring to impart stereorigidity; Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB, VB, or VIB metal as positioned in the Periodic Table of Elements; and Me can be in any of its theoretically possible oxidation states. Olefin monomers (particularly propylene) polymerised using those catalysts to form syndiotactic/atactic block polymers of high molecular weight and comprising at least 70 % of syndiotactic triads.

Description: SYNDIOTACTIC/ATACTIC BLOCK POLYOLEFINS, CATALYSTS AND PROCESSES FOR PRODUCING THE SAME FIELD OF THE INVENTION: The invention relates to a metallocene catalyst useful m preparing syndiotactic/atactic block polyolefms and to the polymers so obtained. The catalyst comprises a bridged monocyclopentadienyl metallocene in which the cyclopentadienyl ring is substituted symmetrically with respect to the active coordination positions. The invention further includes a process of preparing syndiotactic/atactic block polyolefms that comprises the use of the disclosed catalyst. The present invention also provides for a process for polymerizing olefms having three or more carbon atoms to produce polymers with syndiotactic /atactic stereochemical configurations. Tne catalyst and process of the invention are particularly useful in polymerizing propylene to form a syndiotactic/atactic block polypropylene. DESCRIPTION OF THE PRIOR ART: As known in the art, syndiotactic polymers have a unique stereochemical structure in which monomeric units having enantiomorphic configuration of the asymmetrical carbon atoms follow each other alternately and regularly in the macromolecular main chain. Syndiotactic polypropylene was first disclosed by Natta et al . in U . S . Patent Number 3,258,455. The Natta group obtained syndiotactic polypropylene by using a catalyst prepared from titanium trichloride and diethyl aluminum monochloride . A later patent to Natta et al . , U.S. Patent Number 3,305,538, discloses the use of vanadium tπacetylacetonate or halogenated vanadium compounds in combination with organic aluminum compounds for producing syndiotactic polypropylene . U S Patent Number 3,364,190 to Emnck discloses a catalyst system composed of finely divided titanium or vanadium trichloride, aluminum chloride, a trialkyl aluminum and a phosphorus-containing Lewis base as producing syndiotactic polypropylene U S Patent No 4,892,851 disclosed a metallocene catalyst for producing highly crystalline syndiotactic polyolefms As disclosed in these patent references and as known m the art, the structure and properties of syndiotactic polypropylene differ significantly from those of lsotactic polypropylene The isotactic structure is typically described as having the methyl groups attached to the tertiary carbon atoms of successive monomeric units on the same side of a hypothetical plane through the mam chain of the polymer, e g , the methyl groups are all above or below the plane Using the Fischer projection formula, the stereochemical sequence of isotactic polypropylene is described as follows Another way of describing the structure is through the use of NMR Bovey's NMR nomenclature for an isotactic pentad is rnmmm with each "m" representing a "meso" dyad or successive methyl groups on the same side n the plane As known in the art, any deviation or inversion in the structure of the chain lowers the degree of isotacticity and crystallmity of the polymer In contrast to the isotactic structure, syndiotactic polymers are those in which the methyl groups attached to the tertiary carbon atoms of successive monomeric units in the chain lie on alternate sides of the plane of the polymer Using the Fischer projection formula, the structure of a syndiotactic polymer is designated as T In NMR nomenclature, this pentad is described as rrrr in which each ' r" represents a "racemic" dyad, l e , successive methyl groups on alternate sides of the plane The percentage of r dyads in the chain determines the degree of syndiotacticity of the polymer. Syndiotactic polymers are crystalline and, like the isotactic polymers, are insoluble in xylene This crystallimty distinguishes both syndiotactic and isotactic polymers from an atactic polymer that is soluble in xylene Atactic polymer exhibits no regular order of repeating unit configurations m the polymer chain and forms essentially a waxy product While it is possible for a catalyst to produce all three types of polymer, it is desirable for a catalyst to produce predominantly syndiotactic or isotactic polymer with some atactic block fractions SUMMARY OF THE INVENTION The invention provides for a new syndiotactic/atactic block homopolyolef s and particularly a new syndiotactic/atactic block homopolypropylene The present invention also provides a catalyst and process for preparing syndiotactic/atactic block polyolefms, and more particularly syndiotactic /atactic block polypropylene The catalyst and process can each be adapted to produce a polymer with differing syndιo-/atactιc block ratios The catalyst comprises a metallocene, 1 e., a metal derivative of a cyclopentadiene , and an ionizing agent The metallocene compound contains only one substituted cyclopentadienyl ring and is of the general formula . R" (C 4 R' m C 5 C 4 R' n ) XMeQ wherein X s an hetero-atom ligand with one or two lone pair electrons and selected from the elements of Group VA or VIA and is preferably nitrogen, phosphorus, oxygen or sulfur, which can be substituted or non-substituted, (C 4 R m 'C 5 C 4 R n ' ) is a fluorenyl or a symmetrically substituted fluorenyl or cyclopentadienyl ring, R' is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino or alkylsilylo radical, each R' may be the same or different and m and n independently are 0, 1, 2, 3 or 4, with the proviso that the bilateraly symmetry is maintained;, R" is a structural bridge between the X and (C 4 R ' m C 5 C 4 R' n ) ring to impart stereorigidity and, preferably is a silyl or a hydrocarbyl biradical having at least one silicon or carbon atom to form the bridge; Q is a hydrocarbyl radical, such as an alkyl, aryl , alkenyl, alkylaryl or arylalkyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB, VB, or VIB metal as positioned in the Periodic Table of Elements, Me can be any of its theoretically possible oxidation states Preferred metals for the catalyst of the invention are Zr, Ti , Hf The term "symmetrically" shall mean that the local bilateral symmetry of the active polymerization sites is essentially maintained The present invention further provides a process for producing syndiotactic/atactic block polyolefms, particularly syndiotactic/atactic polypropylene. The process comprises utilizing at least one of the catalysts described by the above formula and introducing the catalyst into a polymerization reaction zone containing an olefm monomer In addition, a cocatalyst such as alumoxane may be introduced into the reaction zone. Further, the catalyst may also be pre-polymerized prior to introducing it into the reaction zone and/or prior to the stabilization of reaction conditions in the reactor. Metallocene catalysts are single site catalyst which, generally, produce polymer having narrow molecular weight distribution. While the present invention is mainly directed to α-olefin homopolymerization it is obvious that copolymerization with other olefins can be obtained. The present invention also provides for a new polymer comprising alternating blocks of syndiotactic and atactic sequences, preferably long syndiotactic and short atactic sequences, most preferably comprising a fraction of syndiotactic triads (rr) of at least 70% BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein Figure 1 shows the structure of a catalyst precursor 2 , 7 -bis- tert-butyl-fluorenyl-9-dime hylsylyl- tert-butyl -amido titani-um dichloride Figure 2 shows the "Η NMR spectrum of the 2 , 7 -bis- tert-butyl -fluorenyl-9-dimethylsilyl- tert-butyl -amido titaniumdichloπde DETAILED DESCRIPTION OF THE INVENTION The present invention provides for a new polymer comprising alternating blocks of syndiotactic and atactic sequences The polymer of the invention possesses particularly long sequences of syndiotactic species and short sequences of atactic species The syndio- /atactic ratio can easily be modified by changing the polymerization conditions and/or the catalyst structure within the invention For example, as shown below, increasing the polymerization temperature for a given catalyst decreases the syndio- /atactic ratio As also evidenced below, replacing a dimethylsilyl bridge by a d phenylsilyl bridge also decreases the syndιo-/atactιc ratio for identical polymerization conditions In the specific case of polypropylene, it has been noted that the new polymer has elastomeric properties. Without being bound by the theory, it may be considered that these properties are deriving from the combination of the crystalline syndiotactic part and the amorphous atactic part The polymer obtained has a molecular weight ranging from 100,000 to 1,000,000 depending on the polymerization conditions and on the catalyst used in the process For example, as shown below, replacing a dimethylsilyl bridge by a diphenylsilyl bridge results in increased molecular weight under identical polymerization conditions The present invention provides a catalyst and process for the production of syndiotactic/atactic block polyolefms, particularly polypropylene The catalysts of the present invention produce a polymer with a syndiotactic/atactic block microstructure The Applicants have now unexpectedly found that the catalyst of the invention can be used for the production of high molecular weight polyalphaolefin with stereoregular / stereoirregular block micro- structure When propylene or other alpha-olefins are polymerized using a catalyst consisting of a transition metal compound, the polymer product typically comprises a random mixture (reactor blend) of amorphous atactic and crystalline xylene insoluble fractions The crystalline fraction may contain either isotactic or syndiotactic polymer or a mixture of both The catalysts of the present invention have syndιo-/atactιc specificity and produce polymeric chains with differing syndιo-/atactιc block ratios The metallocene catalysts of the present invention may be described by the formula R" (C 4 R'- n C 5 C 4 R' n ) MeXQ wherein X is an hetero atom ligand with one or two lone pair electrons and selected from the elements of Group VA or VIA and is preferably nitrogen, phosphorus, oxygen or sulfur which can be substituted or not (C 4 R' m C 5 C 4 R' n ) is a fluorenyl ring, preferably substituted symmetrically, each R' is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino or alkylsilylo radical, each R' may be the same or different, m and n independently are 0, 1, 2, 3 or 4 , and with the proviso that the bilateral symmetry is maintained, R" is a structural bridge between the hetero atom X and (C R' m C 5 C 4 R' rι ) ring to impart stereorigidity, and preferably is a silyl or hydrocarbyl biradical having at least one silicon or carbon atom to form the bridge, Q is a hydrocarbyl radical, such as an alkyl, aryl, alkenyl, alkylaryl or arylalkyl radical having 1-20 carbon atoms or is a halogen, Me is a Group IIIB, IVB, VB , or VIB metal as positioned in the Periodic Table of Elements, the transion metal can adopt any of the possible oxidation states Preferred metals for the catalysts of the invention are Ti, Zr, Hf A particularly suitable metal is Ti (C 4 R ' 4 C 5 C 4 R' 4 ) comprises hydrocarbyl biradicals bonded to two adjacent carboR atoms in a cyclopentadienyl ring to form a fused ring In order to obtain syndiospeciflcity the cyclopentadienyl or fluorenyl rings in the metallocene catalysts must be substituted in an essentially symmetric manner with respect to the active coordination positions so that the metallocene exibits bilateral symmetry at least around the active coordination site It has been unexpectedly noted that if the original syndiospecific catalysts described m US patent No.4,892,851 the non-substituted cyclopentadienyl is replaced by a heteroatom ligand with one or two lone pair electrons and selected from elements of Group V A or VI A, the stereospecificty of catalyst will be periodically changed from syndiospeciflcity to aspecificity during the polymerization giving rise to the formation of atactic blocks within the predominantly syndiotactic chain Bilateral symmetry is defined as the condition m which there is no substituents or one or more substituents on one side and no substituents or one or more substituents on the other side in the same relative position such that a mirror image is formed from one side to another One preferred example of such a compound is 2,7 dι-tert-butyl-9- fluorenyl dimethyl silyl, tert-butyl amido titanium dichloride. An illustration of the ligands of this compound is shown below: Bilateral symmetry is illustrated by a plane bisecting the fluorenyl and the bridge resulting the right side of each ligand being a mirror image of its left side The numerical positions of the fluorenyl ring represent the position of possible substituents on the fluorenyl ring, 9 being the position of the bridge. Whilst not wishing to be bound by a theory and without intending to limit the scope of the present invention as indicated by the claims, it is believed that during the polymerization reaction the growing polymer chain migrates from one coordination position to the other after each monomer insertion as the catalyst simultaneously isomerizes and enchains sequences of polymer of the syndiotactic structure; occasionally this mechanism is disturbed by a haptocity change of the fluorenyl-transition metal bonding or through inversion of the chiral nitrogen center, leading to the loss of steπc control and formation of short sequences of atactic blocks whithin a predominantly syndiotactic polymer chain. This mechanism differs from that put forward for syndiospecific catalysts such as the active species formed from isopropylidene [cyclopentadιenyl-9-fluorenyl ] zirconium dichloride as disclosed in U.S. Patent no. 4,892,851 wherein the fluorenyl ring exhibits mainly pentahapto bonding, i.e., all five carbon atoms of the fluorenyl rings are coordinated with the zirconium atom. It is believed that the catalysts of the present invention demonstrate a reversible transformation of syndiospecific sites to atactic specific sites through a haptocity change related stereoregulation/stereoderegulation mechanism In theory, the steric condition for a preferred orientation of the growing chain, adoption of one of the two possible conformation, intermittently disappears and the coordination and insertion of either of the propylene prochiral faces at both lateral coordination positions becomes accidental This mechanism enchains atactic sequences m a predominantly syndiotactic polymer chain by a spontaneous change in haptocity of the bonding between the fluorenyl and the transition metal from pentahapto to tri- and possibly mono-hapto bonding which results in the loss of stereoregulatmg property of the sites This electro-dynamic behavior of the active species provides in effect a temporary transformation of enantiotopic equivalent sites to non-enantiotopic , non-equivalent environment at the lateral coordination positions, atactic sequences being formed whenever this occurs Theoretically only when both events, 1 e , periodic loss of stereoregularity and the stereospecific character of the catalyst occur simultaneously, is a syndiotactic/atactic blok homopolymer formed When catalysts of the present invention are used in polymerization of olefins, the polymer which results is of a syndιo-/atactιc microstructure as illustrated below In a preferred embodiment of the catalyst of the present invention (C R' m C 5 C 4 R' rι ) is preferably a substituted cyclopentadienyl ring with bulky substituents m 2 and 7 or positions ( combined 1,8 or 3,6 or 4,5 positions are also envisageble) such as tert-butyl and tπmethylsilyl , (C 4 R' m C 5 C 4 R' rl } is more preferably a substituted fluorenyl radical. Me is preferably titanium, zirconium or hafnium, more preferably zirconium or titanium and most preferably titanium, Q is preferably a halogen and is most preferably chlorine, and R' is preferably a silyl or hydrocarbyl biradical of at least one silicon or carbon atom which is coordinated with the heteroatom ligand and with (C 4 R' m C 5 C R' n ) , most preferably a silyl or hydrocarbyl biradical of at least one silicon or carbon atom being connected with heteroatom ligand and (C 4 R' m C 5 C 4 R' R n ) moiety Exemplary hydrocarbyl biradicals for the structural bridge include ethyl propyl, butyl pentyl , hexyl , heptyl , octyl , nonyl , decyl and the like Other hydrocarbyl radicals useful as the structural bridge in the present catalysts include linear alkyl radicals of 1 10 carbon atoms or branched alkyl radicals of 1 20 carbon atoms preferably one carbon atom which may be substituted or unsubstituted, preferably substituted Exemplary silyl biradicals for structural bridge include dimethylsilyl (which is preferred), diphenylsilyl of the general formula R 2 Sι=, with each R independently being any C 1 -C 20 hydrocarbyl or C x -C 2 o mono-, di- or trialkyl silyl radicals The catalyst may be prepared by any method known in the art Generally, the preparation of the catalyst complex consists of forming and isolating the substituted cyclopentadienyl or fluorenyl ligands which are then reacted with a halogenated metal to form the complex The preferred method is that disclosed in U S Patent nos 4,892,851 The catalyst may further be supported on an organic or inorganic carrier The synthesis process generally comprises the steps of (1) preparing the halogenated or alkylated metal compound, (2) preparing the ligand, (3) synthesizing the complex, and (4) purifying the complex The metallocene catalysts of the present invention are useful in many of the polymerization processes (solution, slurry or gas phase) known the art including many of those disclosed for the preparation of crystalline or amorphous polypropylene. When the catalysts of the present invention are used in these types of processes, the processes produce syndiotactic/atactic block polymers Further examples of polymerization processes useful the practice of the present invention include those disclosed U S Patent No 4,767,735 and European Patent Application Publication No 310,734, the disclosures of which are hereby incorporated herein by reference These preferred polymerization procedures include the step of prepolymerizmg the catalyst and/or precontactmg the catalyst with a cocatalyst and an olef monomer prior to introducing the catalyst into a reaction zone The ionizing agent is an alumoxane, an aluminum alkyl other Lewis acid or a combination thereof which will ionize a neutral metallocene compound to form a catiomc metallocene catalyst Examples of such ionizing agents are methyl alumoxane (MAO), triethyl aluminum (TEA1) and tris (pentafluorophenyl ) boron Other ionizing agents are disclosed in European Patent Publication Nos 277003 and 277004 which are hereby incorporated by reference The syndio- /atactic-specific catalysts of the present invention are particularly useful in combination with an aluminum alkyl cocatalyst or with an alumoxane, preferably with the latter In addition, a complex may be isolated between a metallocene catalyst as described herein and an aluminum cocatalyst m accordance with the teachings of European Patent Publication Number 226 463 As disclosed therein a metallocene is reacted with an excess of alumoxane in the presence of a suitable solvent A complex of the metallocene and alumoxane may be isolated and used as a catalyst the present invention The alumoxanes useful in combination with the catalysts of the present invention, either m the polymerization reaction or in forming the complex disclosed above, may be represented by the general formula (R-Al-0-)-, in the cyclic form and R (R-A1-0- ) n ALR 2 in the linear form wherein R is an alkyl group with one to five carbon atoms and n is an integer from 1 to about 20 Most preferably, R s a methyl group and the preferred alumoxane is methylalumoxane (MAO) The alumoxanes can be represented structurally as follows CH . n=15 -20 The alumoxanes can be prepared by various methods known in the art. Preferably, they are prepared by contacting water with a solution of trialkyl aluminum, such as trimethyl aluminum, m a suitable solvent such as a benzene Another preferred method includes the preparation of alumoxane in the presence of a hydrated copper sulfate as described in the U.S Patent Number 4,404,344 the disclosure of which is hereby incorporated by reference This method comprises treating a dilute solution of trimethyl aluminum in toluene with copper sulfate. The preparation of other aluminum cocatalysts useful in the present invention may be prepared by methods known to those skilled in the art The Examples given below illustrate the present invention and its various advantages and benefits in more detail. Example 1 The synthesis procedure was performed under an inert gas atmosphere using a Vacuum Atmospheres glovebox or Schlenk techniques . Step 1 Preparation of the 2,7 d - tert-butylfluorenyl-dimethylsilyl-chloπde (1) a) Aromatization of the fluorene. In a one liter flask equipped with magnetic stirring bar, nitrogen inlet and reflux condenser, there was added a solution of 0 1 mol 2 , 7-dι- tert-butylfluorene in 300 cc of dicthyl ether To this solution was added at room temperature dropwise 0.1 equimol of methyllithium in ether (1.6 molar) The reaction was completed after gas evolution stops The orange solution was used in the next step. b) Reaction w th dimethyldichlorosilane . The orange solution prepared step la was added dropwise to a solution of 0.1 mol of dimethyldichlorosilane m 200 cc of ether. The mixture was stirred for several hours at room temperature until the reaction was completed. Step 2 Preparation of tert-butyllithiumamide (2) . In a one liter flask equipped with magnetic stirring bar, nitrogen inlet and reflux condenser 0.1 mol of tert-butylamine was dissolved in 200 cc of d ethyl ether. The solution was cooled to -78 "C. One equimol of methyllithium in ether was added dropwise to the solution. The temperature was increased to room temperature slowly. The reaction mixture was stirred for several hours at room temperature until the formation of the title compound was complete. Step 3 preparation of 2 , 7-dι-tert-butylfluorenyl-dimethylsilyl- tert-butylamine (3) . The reaction products prepared in step 2 and step 3 were added together and stirred for several hours at room temperature. The LiCl formed as byproduct was filtered off and the ether filterate was subjected to evaporation. The title compound was obtained as a yellow oil. Step 4. Preparation of 2 , 7-dι- tert-butyl-dimethyl- tert-butylamido titanium dichloride (4) a) Formation of diamon : 0.25 mol of 3 was dissolved 200 cc of diethylether . To this solution was added dropwise 0.5 mol of methyllithium in ether. The solution became red. The reaction was stopped after gas evolution had stopped b) Reaction of the diamon with TιC14 The red powder obtained after evaporation of the ether from the solution resulting from step 4b was washed several times with pentane and then reacted with 0.25 mol of TιC14 in 200 cc pentane. The mixture was stirred for several hours at room temperature and filtered to separate the LiCl . Evaporation of the solvent led to the isolation of a brown powder. Recrystalization of the product from dichloromethane provided spectroscσpically pure product "4" (Cf Figure 2 HNMR) . Examples 2 and 3 2 , 7 -di- ter -butyl-fluorenyl-dimethylsilyl-te t-butylamido-zirconium dichloride ("5") and the corresponding hafnium derivative ("6") were formed by repeating example 1 while in step 4b respectively ZrC14 or HfCl4 were used instead of TiCl 4 . Examples 4 to 6 Examples 1 to 3 were repeated while using diphenyldichlorosilane instead of dimethyldichlorosilane m step lb. The following metallocenes were formed : 2 , 7-dι ert-butylfluorenyldiphenylsilyl ertbutylamido titaniumdichloride ("7") . 2, 7 -di ert-butylfluorenyldiphenylsilyl ertbutylamido zirconiumdichloride ( " 8 " ) . 2 , 7-dι ert-butylfluorenyldiphenylsilyl ertbutylamido hafniumdichlo ide { " 9 " } Examples 7-14 Propylene was polymerized using the metallocenes produced by examples 1 to 6 - Two liters of liquid propylene were introduced into a 4 liter bench reactor at room temperature. The metallocene was placed in three milliliters of a ll°o solution of MAO m toluene to form a solution which was added to the reactor and the temperature increased to 40 * C. The polymerization reaction was allowed to run for 60 minutes during which time the reactor was maintained at the temperature indicated Tab. 1 for each individual run. The reaction was terminated by venting the reactor of monomer. The catalyst activity in grams of polypropylene per grams of catalyst per hour was calculated. The molecular weight, molecular weight distrubution and 1 C NMR analysis of the polymer were determined. The results are shown in Table 1. Example 7 : polymerization of propylene with "4" at 60 'C. Figure 3 shows the 13 C NMR spectrum of the syndiotactic/atactic block polypropylene; signals at about 15.3, 17.5, 31.2 and 35.7 may be due to long-chain branching. Example 8 • polymerization of propylene with "4" at 80 "C Example 9 : polymerization of Propylene with "4" at 40 'C Example 10 : polymerization of propylene with "4" at 60 "C in 1 liter of cyclohexane Example 11 : copolymerization of propylene and ethylene with "4" at 60"C Example 12 : polymerization of propylene with "5" at 60 "C Example 13 : polymerization of propylene with "6" at 60 "C Example 14 : polymerization of propylene with "7" at 60 'C The pslymerization conditions and results are summarized Table 1. Table 1 : polymerization conditions and results with 4. 5. 6 and rr mr [CATA Polym. Temp. Catalyst Polymer Activity Mn fluff Mw fluff Mz fluff M D deg C fmq. fa) Q Q-h) W (KDa) (KDa) (%) <%) (% 180 160000 98 317 835 3.2 3.75 79.86 16. 150 75000 4.9 72.74 22. 86 27000 969 2.6 3.91 83.37 12. 124 52560 631 2.6 3.71 74.6 21. 150 50000 831 3.6 2.35 80.72 16. 250 66000 3.8 85.54 10. 2 952 45 18750 190 687 1630 3.6 6.03 72.08 21.

Claims: CLAIMS 1 Catalyst for the polymerization of olefins of general formula R" (C 4 R' m C 5 C 4 R' n ) XMeQ wherein X is an hetero-atom ligand with one or two lone pair electrons selected from the elements of Group VA or VIA which can be substituted or non-substituted; (C 4 R rrι , C 5 C 4 R rl ' ) is a fluorenyl or a symmetrically substituted fluorenyl or cyclopentadienyl ring; R' is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino or alkylsilylo radical, each R' may be the same or different and m and n independently are 0, 1, 2, 3- or 4, with the proviso that the bilateraly symmetry is maintained, R" is a structural bridge between X and the (C R' m C C 4 R ' rl ) ring to impart stereoπgidity; Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB, VB, or VIB metal as positioned n the Periodic Table of Elements, and Me can be in any of its theoretically possible oxidation states. 2. Catalyst according to claim 1 wherein (C 4 R' rn C 5 C 4 R' rl ) is a substituted fluorenyl radical, preferably symmetrically substituted. 3. Catalyst according to claim 2 wherein the substituent of the fluorenyl radical is 2,7 di- tert-butyl-9-fluorenyl . 4 Catalyst according to claims 1 to 3 wherein the heteroatom ligand is selected from the group consisting of N, P, O and S. 5. Catalyst according to claims 1 to 4 wherein Me is selected from the group consisting of Ti , Zr and Hf . 6. Catalyst according to claims 1 to 5 wherein R" is preferably a silyl or hydrocarbyl biradical having at least one silicon or carbon atom to form the bridge . Catalyst according to claim 6 wherein R" is di ethylsilyl . Catalyst according to any one of claims 1 to 7 , wherein Q is selected from the group consisting of alkyl, aryl , alkenyl, alkylaryl and arylalkyl radicals Process for polymerizing an olefm monomer to form a syndiotactic/atactic block polyolef comprising: a) selecting a catalyst according to any one of claims 1 to 8 b) introducing the catalyst into a polymerization reaction zone containing an olefm monomer and maintaining the reaction zone under polymerization reaction conditions, and c) extracting a syndiotactic/atactic block polymer Process according to claim 9 wherein the monomer is propylene. Syndiotactic/atactic block homopolymers of an -olefm having 3 or more carbon atoms Syndiotactic/atactic block polypropylene Syndiotactic/atactic block homopolymers according to claims 11 or 12 wherein the fraction of the syndiotactic triads is at least 70o Syndiotactic/atactic block copolymers of two α-olefms

Inventors: RAZAVI ABBAS, RAZAVI, ABBAS
Applicants: FINA RESEARCH, RAZAVI ABBAS, FINA RESEARCH S.A., RAZAVI, ABBAS
Application year: 1997
Main classification: C08F10
IPC codes: C08F4, C08F10, C08F110, C08F297