A PROCESS FOR POLYMERIZING OLEFINS

Abstract: The invention relates to a process for the polymerization of olefins by contacting olefins with a transition-metal catalyst and a co-catalyst, characterized in that the co-catalyst is a compound having the formula XR4, where X represents Si or Ge and R represents an alkyl, aryl, arylalkyl or alkylaryl group or the co-catalyst is a compound having the formula [XR5]<->[Y]<+>, where X represents Si, Ge, Sn or Pb, R represents hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and Y represents a cation.

Description: A PROCESS FOR POLYMERIZING OLEFINS The invention relates to a process for polymerizing olefins by bringing olefins into contact with a transition metal catalyst and a cocatalyst. In the polymerization of olefins, besides a transition-metal catalyst usually a co-catalyst is required to obtain an active catalyst system. Ziegler-Natta catalysts have been used for the polymerization of olefins since the Fifties. In order for these olefin polymerizations to proceed satisfactory with these Ziegler-Natta catalysts, co- catalysts need to be added. Usually aluminium- containing co-catalysts, such as, for example diethyl aluminium chloride, are used in combination with Ziegler-Natta catalysts. Recently other types of transition-metal catalysts, such as for example metallocene catalysts, have also been used for the polymerization of olefins. In order for olefin polymerizations with the aid of metallocene catalysts to proceed satisfactory, it is also necessary to use a co-catalyst. Aluminoxanes are used as co-catalysts in combination with metallocene catalysts. An example of an aluminoxane is methylaluminoxane (MAO) . A disadvantage of the use of aluminoxanes as co-catalysts in the polymerization of olefins with the aid of a metallocene catalyst is that a very large excess of the aluminoxane relative to the metallocene catalyst has to be applied in order for an active catalyst system to be obtained. As a result, the polyolefin produced contains a high concentration of aluminium, so that the aluminium will often need to be washed out of the polyolefin. The object of the invention is to provide co- catalysts suitable for use in combination with a transition-metal catalyst for the polymerization of olefins which do not have this disadvantage. The invention relates to a cocatalyst having the formula XR 4 , wherein X represents Si or Ge and R represents an alkyl, aryl, arylalkyl or alkylaryl group, or to a cocatalyst having the formula [XR 5 ] ~ [Y] + , wherein X represents Si, Ge, Sn or Pb and R represents hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and Y represents a cation. In this way an active catalyst system consisting of a transition-metal catalyst with one of the compounds according to the invention as co-catalyst is obtained which is suitable for the polymerization of olefins. When the compounds according to the invention are used as co-catalyst for the polymerization of olefins, the required quantity of co-catalyst relative to the transition-metal catalyst is much smaller than when an aluminoxane is used a co-catalyst. Lewis acids or ion complexes are also used as coatalysts in combination with metallocene catalysts. Examples of Lewis acids are boranes, such as tris (pentafluorophenyl) borane, and examples of ion complexes are borates, such as dimethylaniliniumtetrakis- (pentafluorophenyl) borate, triphenylcarbeniumtetrakis- (pentafluorophenyl) borate and trityltetrakis (3 , 5-trifluoromethylphenyl) borate . Boron-containing co-catalysts of this kind are described in for example EP-A-426 , 637 , EP-A-277,003 and EP-A-277, 004. Another advantage of the use of compounds according to the invention as co-catalysts in the polymerization of olefins is that the use of these compounds is generally cheaper than the use of aluminoxanes, boranes or borates. Compounds which are suitable as co-catalyst are compounds having the formula XR 4 and compounds having the formula [XR 5 ] " [Y] + . X is an atom from Group 14 of the Periodic Table of the Elements and can be chosen from the group comprising Si, Ge, Sn and Pb . Prefrably X is Si, as Si is non- toxic. Here and hereinafter the Periodic Table of the Elements is understood to be the Periodic Table on the inside cover of the Handbook of Chemistry and Physics, 70th edition, 1989/1990 (New IUPAC Notation) . The R groups may be identical or different and can be chosen from the group comprising hydrogen and alkyl , aryl, arylalkyl or alkylaryl groups. The R group is preferably a hydrocarbon group containing 1-20 carbon atoms. Examples of suitable R groups are methyl, ethyl, propyl, isopropyl, hexyl, decyl and phenyl . Also, two R groups may together form a bridged R 2 -group, for example a biphenyl-2,2' -diyl group and a diphenyl-2 , 2 ' - diylmethane group . Preferably, at least two R groups together form a bridged aryl group. More preferably the compound having the formula XR 4 or [XR S ] " [Y] + contains two of such bridged aryl groups . The cation Y is for example a Bronsted acid which can donate a proton, a cation of an alkali metal or a carbene. Examples of cations are Li + , K + , Na + , H + , triphenylcarbenium, anilinium, guanidinium, glycinium, ammonium or a substituted ammonium cation, in which at most three hydrogen atoms have been replaced by a hydrocarbyl radical having 1-20 carbon atoms, or a substituted hydrocarbyl radical having 1-20 carbon atoms , in which one or more of the hydrogen atoms has or have been replaced by a halogen atom, phosphonium radicals, substituted phosphonium radicals, in which at most three hydrogen atoms have been replaced by a hydrocarbyl radical having 1-20 carbon atoms or a substituted hydrocarbyl radical having 1-20 carbon atoms, in which one or more of the hydrogen atoms has or have been replaced by a halogen atom. The cation is preferably dimethylanilinium, triphenylcarbenium or Li + . Compounds having the formula XR 4 are known from, for example, 'The chemistry of organic silicon compounds, E.S. Patai et al . , Wiley and Sons, 1989' . Anionic organosilicates were demonstrated for the first time in Angew. Chem. Int. Ed. Engl . 1996, 35, no. 10. In this publication lithium (2, 2' - biphenyldiyltrimethylsilicate) .4THF, lithium (2 , 2 ' - biphenyldiyldimethylphenylsilicate) .4THF, lithium (2 , 2 ' - biphenyldiyldimethyl-t-butylsilicate) .4THF and lithium (pentaphenylsilicate) .4HMPA are mentioned. (THF is tetrahydrofuran and HMPA is hexamethylphosphorus triamide.) The possible use of these silicates as co- catalysts in the polymerization of olefins is neither mentioned nor suggested. The above-mentioned compounds having the formula XR 4 can for example be synthesized according to the synthesis methods described in the above-mentioned publications . The compounds according to the invention can also be used on a carrier as co-catalysts in the polymerization of olefins. Si0 2 , A1 2 0 3 , MgCl 2 and polymer particles, such as polystyrene spherules, can be mentioned as suitable carrier materials. These carrier materials can also be modified with for example silanes and/or aluminoxanes and/or aluminium alkyls . The supported co-catalysts can be synthesized prior to the polymerization, but they can also be formed in situ. Transition-metal catalysts are suitable as catalysts for the polymerization of olefins. Examples of such catalysts are described in US-A-5 , 096, 867 , WO- A-92/00333, EP-A-347 , 129 , EP-A-344 , 887 , EP-A-129 , 368 , EP-A-476,671, EP-A-468 , 651 , EP-A-416 , 815 , EP-A-351 , 391 , EP-A-351,392, EP-A-423 , 101 , EP-A-503 , 422 , EP-A-516 , 018 , EP-A-490,256, EP-A-485 , 820 , EP-A-376 , 15 , DE-A- 4,015,254, WO-A-96/13529, EP-A-530 , 908 , WO-A-94/11406 , EP-A-672,676 and WO-A-96/23010. Transition-metal catalysts containing metals from group 3 of the Periodic Table of the Elements and the lanthanides can also be used. Supported transition-metal catalysts can be used. Si0 2 , Al 2 0 3 , MgCl 2 and polymer particles, such as polystyrene spherules, can be mentioned as suitable carrier materials. These carrier materials can also be modified with for example silanes and/or aluminoxanes and/or aluminium alkyls. The supported transition-metal catalysts can be synthesized prior to the polymerization, but they can also be formed in situ. Preferably metallocene catalysts are used for the polymerization of olefins in combination with a cocatalyst according to the invention. Metallocene catalysts are characterized by the presence in the transition-metal catalyst of one or more π-bound ligands, such as cyclopentadiene ligands (Cp) or cyclopentadiene-related ligands, for example indene and fluorene . The use of a transition-metal catalyst in which the transition metal is in a reduced oxidation state, as described in WO-A-96/13529, is more preferred. The polymerisation of olefins, for example ethylene, propylene, butene, hexene, octene and mixtures thereof and combinations with dienes can be conducted in the presence of a transition-metal catalyst and the co-catalyst according to the invention. The catalyst system described above can also be used for the polymerization of vinylaromatic monomers, such as styrene and p-methylstyrene, for the polymerization of polar vinyl monomers, such as for example monomers containing alcohol, amine, alkyl halide, ether, amide, imine or anhydride groups, and for the polymerization of cyclic olefins, such as cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, norbornene, dimethanooctahydronaphthalene and substituted norbornenes. The amount of co-catalyst used relative to the amount of transition-metal catalyst (mol:mol) is normally 1:100-1000:1, preferably 1:5-250:1. The polymerizations can be carried out in the known manner and the use of the co-catalyst according to the invention does not necessitate any essential modification of these processes. The known polymerizations are carried out in suspension, solution, emulsion, gas phase or as bulk polymerization . When the co-catalyst is used in suspension or gas-phase polymerization it is to be preferred to use the transition-metal catalyst or the co-catalyst according to the invention on a support. It is also possible to use both the catalyst and the co-catalyst on a support. The polymerizations are carried out at temperatures between -50°C and +350°C. Preferably between 50°C and 250°C. The pressures used generally lie between atmospheric pressure and 250 Mpa; for bulk polymerizations more in particular between 50 and 250 MPa, for the other polymerization processes between 0.5 and 25 MPa. As dispersants and solvents substituted and unsubstituted hydrocarbons can for example be used, such as pentane, heptane and mixtures thereof. Aromatic, possibly perfluorinated hydrocarbons can also be considered. A monomer to be used in the polymerization can also be used as dispersant. The invention will be elucidated by means of the following non-restrictive examples. Example I a) Synthesis of bis-biphenylsilane 12.3 g biphenyl (80 mmol) was dilithiated in tetramethylethylenediamine (TMEDA) (24.1 ml, 160 mmol) by addition of n-butyllithium (100 ml, 160 mmol) at room temperature in about 5 minutes. When the addition was completed the reaction mixture was kept at 60°C for 90 minutes. After cooling down to -20°C, 2,2"- dilithiobiphenyl .2TMEDA was crystallised. The liquid was transferred to another vessel and the crystals were dissolved again in 150 ml diethylether . This solution was added at room temperature in about 45 minutes to a solution of tetrachlorosilane (4.6 ml, 40 mmol) in about 100 ml diethylether. When the addition was completed, the mixture was stirred for 1 day and refluxed for 2 days. After careful addition of water, the reaction mixture was worked up with IN HC1 to get rid of the TMEDA. After extraction of the water phase with diethylether the organic layer was washed once with water, dried on MgS0 4 , filtered and concentrated under reduced pressure. Crystallization from ethylacetate gave pure 9, 9 ' -spirobi (9H, 9-silafluorene) (which we address here as the bis-biphenylsilane) , which was investigated using 29 Si-, 1 H- and "C-NMR. b) Polymerisation 0.01 mmol of the metallocene catalyst bis (2- methylindenyl) dimethylzirconium was mixed in 100 ml pentamethylheptane at roomtemperature with 0.02 mmol bis-biphenylsilane during 1 minute. In a stainless steel bench rig of 1 1, 750 ml pentamethylheptane was introduced, followed by 0.2 mmol trioctylaluminium (Witco GmbH) . The reactor was heated to 80 °C and the ethylene pressure was equilibrated at 20 bar overpressure (21 bar) . In the next step the catalyst/cocatalyst mixture was introduced. The ethylene pressure was kept constant at 20 bars during the polymerisation. After 20 minutes the polymerization was stopped, the polymer was removed from the reactor and the yield was determined to be 3.63 g. Example II a) Reaction of bis-biphenylsilane with MeLi and iC β Hj j CL 1.31 mmol (436 mg) bis-biphenylsilane was mixed with 50 ml dry THF in a Schlenk flask of 100 ml. The Schlenk flask was put in a cold bath (dry ice/petrol) to cool the reaction mixture down to -65°C. The bis-biphenylsilane completely dissolved in THF. At -65°C 1,31 mmol (885 μl , 1.4 M) MeLi was added. During and after the addition, the reactionmixture stayed colourless. The Schlenk flask was left for 2 hours at -65°C, and during that time the reaction mixture remained colourless. After two hours of stirring, the reaction mixture was allowed to come slowly to room temperature and was stirred overnight. After stirring overnight, the reaction mixture had a very light yellow colour. Reaction mixture was brought to -65°C and 1,31 mmol (9,56 ml) (C 6 H 5 ) 3 CCL was added. After stirring overnight, the THF was evaporated and yellow crystals were formed. Dry petrol was added (three times) and then evaporated. Result: a yellow/white powder. Dry toluene was added to the powder and the slurry was stirred very well. The toluene fraction was filtered off and the toluene of the filtrate-fraction was evaporated to yield a yellow solid. The solid was washed with petrol and the petrol was evaporated to yield a light yellow solid. Yield: 774 mg .

Claims: C L A I M S 1. Process for the polymerization of olefins by contacting olefins with a transition-metal catalyst and a co-catalyst, characterized in that the co-catalyst is a compound having the formula XR 4 , where X represents Si or Ge and R represents an alkyl, aryl, arylalkyl or alkylaryl group. 2. Process for the polymerization of olefins by contacting olefins with a transition-metal catalyst and a co-catalyst, characterized in that the co-catalyst is a compound having the formula [XR 5 ] ' [Y] + , where X represents Si, Ge, Sn or Pb, R represents hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and Y represents a cation. 3. Process according to any one of Claim 1-2, characterized in that the transition-metal catalyst is a metallocene catalyst . 4. Process according to Claim 3, characterized in that the transition-metal catalyst contains a transition metal which is in a reduced oxidation state. 5. Proess according to any one of Claims 1-4, characterized in that at least two R groups together form a bridged aryl group. 6. The use of a compound having the formula XR 4 , where X represents Si or Ge and R represents an alkyl, aryl, arylalkyl or alkylaryl group, as co-catalyst in the polymerization of olefins 7. The use of a compound having the formula [XR 5 ] " [Y] + , where X represents Si, Ge, Sn or Pb, R represents hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and Y represents a cation, as co-catalyst in the polymerization of olefins. 8. Compound having the formula [XR 5 ] " [Y] + , where X represents Si, Ge, Sn or Pb, R represents hydrogen or an alkyl, aryl, arylalkyl or alkylaryl group and Y represents a cation, in which the compounds lithium (2, 2 ' -biphenyldiyltrimethylsilicate) .4THF, lithium (2, 2' -biphenyldiyldimethylphenyl- silicate) .4THF, lithium (2 , 2 ' -biphenyldiyldimethyl- t-butylsilicate) .4THF and lithium (pentaphenyl- silicate) .4HMPA are excluded.

Inventors: DE KEIJZER ADRIANUS HENRICUS J, KLUMPP GERHARD WILLEM, VAN TOL MAURITS FREDERIK HENDR, DE KEIJZER, ADRIANUS, HENRICUS, JOSEPH, FRANCISCUS, KLUMPP, GERHARD, WILLEM, VAN TOL, MAURITS, FREDERIK, HENDRIK
Applicants: DSM NV, KEIJZER ADRIANUS HENRICUS JOSE, KLUMPP GERHARD WILLEM, TOL MAURITS FREDERIK HENDRIK V, DE KEIJZER, ADRIANUS, HENRICUS, JOSEPH, FRANCISCUS, DSM N.V., KLUMPP, GERHARD, WILLEM, VAN TOL, MAURITS, FREDERIK, HENDRIK
Application year: 1997
Main classification: C08F4
IPC codes: C07F7, C08F4, C08F10