Soluble catalyst systems for preparing poly-1-alcenes with high molecular weight.

0001Catalyst systems for the polymerization of C₂- to C₁₀-Alk-1-enes, containing as active ingredients<ul id="ul0001" list-style="none"><li>a) a metallocene complex of the general formula I<chemistry id="chem0001" num="0001"><img file="EP0519237A2_D0001.tif" /></chemistry>in which the substituents have the following meaning:<ul id="ul0002" list-style="none"><li>M titanium, zirconium, hafnium, vanadium, niobium, tantalum</li><li>X halogen or C₁- to C8-alkyl</li><li>Y carbon, phosphorus, sulfur, silicon or germanium</li><li>ZC₁- to C8-alkyl, C₃- to C₁₀Cycloalkyl, C₆- to C₁₀-Aryl</li><li>R ', R² C.₁- to C₄-Alkyl, where R¹ and R² are the same or different</li><li>R³ to R⁶ Hydrogen, C₁- to C8-alkyl, where R³to R⁶ are identical or different, or where two adjacent radicals R³ and R⁴ as well as R⁵ and R⁶ each together represent 4 to 15 carbon atomic hydrocarbon ring systems,</li><li>and n represents 0, 1 or 2,</li></ul></li><li>b) and an open-chain or cyclic alumoxane compound of the general formula II or III<chemistry id="chem0002" num="0002"><img file="EP0519237A2_D0002.tif" /></chemistry>where R⁷ represents a C1-C4 alkyl group and m represents a number from 5 to 30.</li></ul>

0002The invention also relates to a process for the preparation of polymers of propylene with the aid of these catalyst systems and to the polymers obtainable hereafter.

0003In addition to the insoluble Ziegler-Natta catalysts, soluble catalyst systems can also be used for the polymerization of alk-1-enes. The latter are complex compounds of metals of subgroups IV and V. of the periodic table with organic ligands, which are used in conjunction with oligomeric aluminum compounds (EP-A 185 918, EP-A 283 739 and GB-A 2 207 136) . The complex compounds used in these catalyst systems mostly contain cyclopentadienyl groups as organic ligands, which form π bonds with the transition metal. Transition metal complexes which also have halogens bonded to the metal atom in addition to organic ligands are frequently used as catalysts.

0004EP-A 284 708 and 316 155 and EP-A 355 447 describe soluble catalyst systems for the polymerization of alk-1-enes, in which bis (cyclopentadienyl) complexes of metals of subgroup IV of the periodic table are used as complex compounds , wherein the two cyclopentadienyl rings are connected by an alkyl-substituted silicon, tin, or germanium atom or by sulfur atoms. It is also possible to use transition metal complexes in which the cyclopentadienyl rings are substituted by alkyl groups and which contain two halogens bonded to the transition metal as further ligands. Linear or cyclic alumoxane compounds of the general formula II or III are preferably used as the oligomeric aluminum compounds.

0005With the aid of such catalyst systems, polymers of propylene can be obtained which, among other things, are distinguished by a relatively narrow molar mass distribution. In contrast to polypropylene, which is produced by using insoluble Ziegler-Natta catalysts, the molar masses of the polypropylenes obtained in this way are at significantly lower values, so that they have numerous applications in which polymers with molar masses of more than 100,000 are used , cannot be used.

0006One way to increase the molecular weights of polyolefins is to lower the reaction temperature during the polymerization. In this way, for example, EP-A 355 447 propylene polymers with molecular weights of approximately 50,000 (M._w) available. With this measure, however, the increase in the molar masses is associated with a significant slowdown in the polymerization rate, that is to say a significant increase in the reaction time, so that the reduction in the reaction temperature impairs the economy of the production process.

0007The object of the present invention was therefore to remedy this disadvantage and to develop an improved soluble catalyst system with the aid of which polyalk-1-enes with high molar masses can be produced in the most economical manner possible.

0008Accordingly, the soluble catalyst systems defined at the outset have been found.

0009According to the invention, metallocene complexes of the general formula I are used, titanium, zirconium, hafnium, vanadium, niobium or tantalum being used as central atoms. The central atom in the metal complex of the general formula I to be used according to the invention is bonded on the one hand via π bonds to substituted cyclopentadienyl groups and on the other hand to further substituents X which are fluorine, chlorine, bromine or iodine or a C.₁- to C₈-Alkyl can be. Those metallocene complexes of the general formula I are preferably used in which M represents zirconium or hafnium and X represents chlorine or bromine.

0010In addition, the metal complex of the general formula I to be used according to the invention contains, in addition to the central atom and its substituents and the substituted cyclopentadienyl groups, a bridge member (Z)_nY, which connects the two cyclopentadienyl groups. Y is carbon, phosphorus, sulfur, silicon or germanium, Z is a C.₁- to C8-alkyl, C₃- to C₁₀Cycloalkyl or C₆- to C, o-aryl and n the numbers 0, 1 or 2.

0011In the metallocene complexes of the general formula I which are preferably used, Y represents carbon, sulfur or silicon, Z represents a C.₁-to C₄-Alkyl and n for the number 2.

0012Another important component of the metal complexes of general formula 1 to be used according to the invention are substituted cyclopentadienyl groups. These each contain residues R¹ or R²that are the same or different and for a C₁- to C₄Alkyl group, in particular for a methyl, ethyl, iso-propyl or a tert-butyl group. These cyclopentadienyl groups also have the substituents R.³ to R⁶ on, where R³ to R⁶ the meaning hydrogen or C₁- Have to C8-alkyl and are the same or different or where two adjacent radicals R³ and R⁴ as well as R⁵ and R⁶ together each represent 4 to 15 carbon atom hydrocarbon ring systems. Metallocene complexes of the general formula I whose cyclopentadienyl groups have such substituents R³ to R⁶ have where R³ and R⁵ for C₁- to C₄-Alkyl and R⁴ and R⁶ represents hydrogen or two adjacent radicals R³ and R⁴ as well as R⁵ and R⁶ together each represent 4 to 12 carbon atom hydrocarbon ring systems, for example an indenyl system. In terms of the number of carbon atoms in the hydrocarbon ring systems, the two carbon atoms in the cyclopentadienyl system, which act as linking points with the substituents R₃ to R₆ serve, counted, which, for example, in the event that R³ and R⁴ as well as R⁵ and R⁶ each represent a cyclohexyl radical, resulting in a total of two hydrocarbon ring systems, each with 6 carbon atoms.

0013Examples of particularly preferred metallocene complexes include

0014Dimethylsilanediylbis (-2-methylindenyl) zirconium dichloride,<ul id="ul0003" list-style="none"><li>Diethylsilanediylbis (-2-methylindenyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-ethylindenyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-isopropylindenyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-tert.butylindenyl) zirconium dichloride,</li><li>Diethylsilanediylbis (-2-methylindenyl) zirconium dibromide,</li><li>Dimethyl sulfide bis (-2-methylindenyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-methyl-5-methylcyclopentadienyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-methyl-5-ethylcyclopentadienyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-ethyl-5-isopropylcyclopentadienyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-methylindanyl) zirconium dichloride,</li><li>Dimethylsilanediylbis (-2-methylbenzindenyl) zirconium dichloride and</li><li>Dimethylsilanediylbis (-2-methylindenyl) hafnium dichloride.</li></ul>

0015Such complexes can be synthesized by methods known per se, the reaction of the appropriately substituted cycloalkenyl anions with halides of titanium, zirconium, hafnium, vanadium, niobium or tantalum being preferred. Examples of corresponding production processes are described, inter alia, in the Journal of Organometallic Chemistry, 369 (1989), 359-370.

0016In addition to the metallocene complex, the catalyst system according to the invention also contains linear or cyclic alumoxane compounds of the general formula 11 or 111<chemistry id="chem0003" num="0003"><img file="EP0519237A2_D0003.tif" /></chemistry>where R⁷ preferably represents methyl or ethyl groups and m preferably represents a number from 10 to 25.

0017These alumoxane compounds are usually prepared by reacting a solution of trialkylaluminum with water and are described, inter alia, in EP-A 284 708 and US Pat. No. 4,794,096.

0018As a rule, the alumoxanes obtained are mixtures of different lengths, both linear and cyclic chain molecules, so that m is to be regarded as the mean. The alumoxane compound may also contain trialkylaluminum compounds whose alkyl groups each have 1 to 8 carbon atoms, for example trimethyl, triethyl or methyldiethylaluminum.

0019In the polymerization of alk-1-enes with the aid of the catalyst system according to the invention, it is advantageous to use the metallocene complex a) and the alumoxane compound b) in amounts such that the atomic ratio between aluminum from the alumoxane b) and the transition metal from the metallocene complex a) in the range of 10: 1 to 10⁶: 1, especially in the range of 10: 1 to 10⁴: 1 lies. The two catalyst constituents can be introduced into the polymerization reactor individually or as a mixture in any order. A particularly reactive soluble catalyst system can be obtained if the metallocene complex a) and the alumoxane compound b) are mixed with one another 5 to 60 minutes, in particular 10 to 40 minutes before the actual polymerization. The catalyst activated in this way can then be used immediately.

0020These soluble catalyst systems can be used to prepare polymers of alk-1-enes. These include homopolymers and copolymers of C₂- to C,_O-Alk-1-enes understood, preferably ethylene, propylene, but-1-ene, pent-1-ene and hex-1-ene being used as monomers. The catalyst systems according to the invention are particularly suitable for the production of polypropylene and copolymers of propylene with minor proportions of other C.₂- to C₁₀-Alk-1-enes, especially ethylene and but-1-enes.

0021The preparation of these polymers can be carried out either batchwise or preferably continuously in the customary reactors used for the polymerization of alk-1-enes. Suitable reactors include continuously operated stirred kettles, it also being possible, if appropriate, to use a number of several stirred kettles connected in series.

0022The polymerization is carried out at pressures from 0.1 to 3000 bar and temperatures from -20 to 300 ° C. Pressures from 0.5 to 2500 bar and temperatures from + 10 to + 150 ° C. are preferred. The polymerization time is usually in the range from 0.5 to 10 hours.

0023Polymerization reactions using the catalyst systems of the invention can be carried out in the gas phase, in liquid monomers and in inert solvents. Polymerization in solvents, in particular in liquid hydrocarbons such as benzene or toluene, is preferably used. In this case, it is advantageous if 10- per liter of the solvent⁴ until 10-¹ mol aluminum used as alumoxane.

0024The average molecular weight of the polymers formed can be controlled using the methods customary in polymerization technology, for example by adding regulators such as hydrogen, or by changing the reaction temperatures.

0025The polymers produced with the aid of the catalyst systems according to the invention are notable for a high molar mass and a narrow molar mass distribution. They can still be produced at relatively high temperatures, as a result of which the polymerization time can be limited. Because of these properties, the polymers obtainable from the catalyst systems according to the invention are particularly suitable for the production of films and moldings.

Examples Production of polypropylene

example 1

0026350 ml of dried toluene were placed in a stirred autoclave with a useful volume of 1 l and then a solution of 0.45 g of methylalumoxane (average chain length m = 20) in 30 ml of toluene was added. 7.6 '10-3 mol aluminum were used per liter of the solvent. A solution of 15 mg of dimethylsilanediylbis (-2-methylindenyl) zirconium dichloride (corresponding to 31.2 '10-6 mol) in 15 ml of toluene was then added, so that the atomic ratio between aluminum and zirconium was 244: 1. This mixture was first stirred at 50 ° C. for 30 minutes and then propylene was injected at a pressure of 2 bar and polymerized for 4 hours and 40 minutes. The polymerization was carried out at a temperature of 50 ° C and a pressure of 2 bar. Then unused propylene was removed and a mixture of 1 l of methanol and 10 ml of concentrated hydrochloric acid was added to the reaction solution. The precipitated polymer was filtered off, washed with methanol and dried in vacuo.

0027This gave 45 g of polypropylene with a weight average (M_w) of 114200, a number average (M_n) of 41500 and a molecular weight distribution (<o>M</o>_w/<o>M</o>_n) of 2.75.

Example 2

0028The procedure was analogous to Example 1, with 350 ml of dried toluene likewise being introduced and a solution of 0.45 g of methylalumoxane (m = 20) in 30 ml of toluene then being added. A suspension of 0.5 mg of dimethylsilanediylbis [3,3 '- (2-methylbenzindenyl)] zirconium dichloride in 20 ml of toluene was then added, so that the atomic ratio between aluminum and zirconium was 8950: 1. Then the procedure was continued as described in Example 1.

002951.4 g of polypropylene with a weight average (M._w) of 142 896, a mean number (M_n) of 91917 and a molecular weight distribution of 1.55.

0030Pentad content, measured by means of ¹³C-NMR: fraction mmmm = 93.5%.