DE4009169A1 - METHOD FOR PRODUCING A POLYPROPYLENE MOLDING MATERIAL - Google Patents

Abstract

Polypropylene with a broad or bimodal molar mass distribution and good processing properties can be produced by two-stage polymerization in which, in the first reaction stage, polypropylene is both educt and suspension agent and the catalyst is a Ziegler catalyst.

Description

The invention relates to a method for Production of a polypropylene with wide or bimodal Molar mass distribution and good processing properties.

A catalyst system is known with which polypropylene is obtained with good isotacticity and high yield (see DE 32 41 999). The catalyst system consists of the following components (A), (B) and (C):

• A) a solid component containing magnesium, titanium, Halogen and an ester, the component being obtained is achieved by contacting a solution of (i) one Magnesium compound with (ii) a liquid Titanium compound in the presence of (D) at least one Electron donor and during or after the formation of the solid product (A) contacting (E) a Esters
• B) an organometallic compound of a metal of Groups I to III of the periodic table, and
• C) an organosilicon compound with a Si-O-C bond or Si-N-C bond.

However, the polymer obtained with this catalyst has due to its molecular weight distribution for a number of Processing processes, for example for extrusion of large moldings, unfavorable rheological Properties, especially a lack Melt resistance.

Attempts have been made by new ones Polymerization process this for processing reduce or eliminate unfavorable properties.  

A method is known for the production of polypropylene in a two-stage polymerization process using a highly isotactic catalyst with hexane as a suspending agent (cf. JP 59-1 72 507). In this process, a product with a viscosity (η) of 1.8 to 10 dl / g is produced in the first stage, and a polymer with a viscosity (η) of 0.6 to 1.2 dl / g in a second stage . The total viscosity of the end product is then 1.2 to 7 dl / g and the polydispersity M _w / M _{n of} the polymer is 7 to 20.

However, with an intrinsic viscosity of the polymer from the 2nd stage above 1.2 dl / g, a total polymer is obtained which does not have good processing properties and melt tension. The stated molecular weight distribution M _w / M _n of 6 to 20, on the other hand, proves to be insufficient for the production of outstanding products.

The described polymerization process in an inert Suspension medium also allows only moderate space-time Yields the reactors and requires a variety of technically complex processing steps for extraction of the polymer and for cleaning the reusable Suspension medium in a continuously operated Investment.

The task was therefore to find a process which polypropylene with wider or bimodal Molar mass distribution in high yield and good Processing properties generated.

It has been found that wider or polypropylene bimodal molecular weight distribution and good Processing properties through a two-stage Polymerization can be produced with propylene in the  serves as the starting material and suspending agent in the first reaction stage and a Ziegler catalyst is used as the catalyst.

The invention thus relates to a process for the preparation of a polypropylene by homopolymerization of propylene or copolymerization of propylene with ethylene or a 1-olefin with 4 to 10 C atoms in suspension at a temperature of 30 to 150 ° C and a pressure of 1 to 49 bar, in the presence of a catalyst consisting of a transition metal component (component A), which by reaction of a magnesium halide first with at least one electron donor and then with a tetravalent titanium compound of the formula TiX _m (OR ¹ ) _4-m , wherein R ^{1 is} an alkyl radical 2 to 10 carbon atoms, X is a halogen atom and m is a number from 0 to 4, obtained in the presence of an ester of an aromatic carboxylic acid, a halogen-free organoaluminum compound (component B) and an organosilicon compound as a stereoregulator (component C), characterized that the polymerization is carried out in two reaction stages, with d he monomer is both starting material and suspension medium and a polypropylene with a viscosity of 4 to 14 dl / g and a proportion of the total polymer of 20 to 80% by weight is produced and in the second reaction stage a polypropylene with a viscosity of 1 to 3 dl / g and a proportion of the total polymer of 80 to 20 wt .-%, and the total polymer has a viscosity of 1.5 to 6 dl / g and a polydispersity M _w / M _n of 10 to 50.

The polymerization is carried out in a so-called mass process carried out in two stages in which the monomer (mainly propylene) reactant and suspending agent at the same time.

In the first stage, a high molecular weight product with a viscosity (η) of 4 to 14 dl / g and a proportion of the total polymer of 20 to 80% by weight, preferably 55 to 80% by weight, is produced, in the second Step a low molecular weight product with a viscosity of 1 to 3 dl / g and a proportion of 80 to 20 wt .-%, preferably 45 to 20 wt .-%, so that the sum of both parts is always 100%. The viscosity of the overall polymer is then 1.5 to 6 dl / g, its polydispersity M _w / M _n (GPC measurement) 10 to 50, preferably 20 to 40.

To carry out the polymerization, highly active and highly stereospecific catalysts are preferably used, in particular a catalyst consisting of a transition metal component (component A), which by reaction of a magnesium halide first with at least one electron donor and then with a tetravalent titanium compound of the formula TiX _m (OR ¹ ) _{4 -m} , in which R ^{1 is} an alkyl radical having 2 to 10 carbon atoms, X is a halogen atom and m is a number from 0 to 4, is obtained in the presence of an ester of an aromatic carboxylic acid, a halogen-free organoaluminum compound (component B) and an organosilicon compound as a stereo regulator (component C).

Instead of component C, a combination of two can also be used different organosilicon compounds Si-O-C bonds as a stereo regulator (components C and D) be used.

An anhydrous is used for the production of component A. Magnesium halide such as magnesium chloride or Magnesium bromide, preferably magnesium chloride, is used.

The reaction product of the magnesium halide with the Electron donor is in in a manner known per se Presence of an inert solvent, for example by heating the magnesium halide in a solution of the reactant or by suspending of the Mg halide in the liquid reactant.  

The molar ratio of the magnesium halide used Electron donor compound is more than 2: 1. Preferred a molar ratio of 3 to 15: 1 is particularly preferred becomes a molar ratio of 4.5 to 8: 1.

As electron C ₁ -C ₂₀ -Monocarbonsäureester, C ₁ -C ₂₀ aliphatic carboxylic acids, C ₄ -C ₂₀ -Carbonsäureanhydride, C ₃ -C ₂₀ ketones, C ₂ -C ₁₆ aliphatic ethers, C ₃ -C ₂₀ -aliphatic carbonates, alcohols containing a C ₃ -C ₂₀ alkoxy group, alcohols containing a C ₃ -C ₂₀ aryloxy group, organosilicon compounds with a Si-OC bond in which the organic group has 1 to 10 carbon atoms, and organophosphorus compounds with a POC -Bond in which the organic group has 1 to 10 carbon atoms.

Examples of suitable electron donors are Methylpentanol, 2-ethylhexanol, 2-ethylhexanoic acid and Phthalic anhydride.

A reactor with stirrer, temperature control device and protective gas blanket (N ₂ , Ar) is used for the reaction. The reaction medium presented is expediently the dispersant used in the polymerization to meter the catalyst. Aliphatic or cycloaliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, cyclohexane, methylcyclohexane, isooctane and aromatic hydrocarbons such as benzene, toluene, xylene are suitable as such. Gasoline and hydrogenated diesel oil fractions that have been carefully cleaned of oxygen, sulfur compounds and moisture can also be used. The dispersant must not contain any compounds with double bonds. The reaction is carried out at a temperature of 0 to 200 ° C, preferably 30 to 150 ° C.

The response time depends on the Reactivity of the reactants 0.5 to 5 hours, preferably 1 to 3 hours. The solution obtained is then cooled.

The complex obtained in this way is immediately reacted with a tetravalent compound of the titanium of the formula TiX _m (OR 1) _4-m , in which R 1 is an alkyl radical having 2 to 10 carbon atoms, X is a halogen atom, preferably chlorine, and m is an integer on is 0 to 4, preferably 2 or 4. A mixture of several of these compounds can be used.

Preferred compounds are e.g. B. TiCl₄, TiCl₃ (OEt), TiCl₃ (O-iPr), TiCl₂ (OEt), TiCl₂ (O-iPr) ₂, TiCl₂ (O-CH₂C₆H₅) ₂, TiCl (O-iBu) ₃, Ti (OEt) ₄, Ti (O-Pr) ₄ or Ti (O-iPr) ₄.

Particularly preferred are TiCl₄, TiCl₂ (OEt) ₂ and Ti (OEt) ₄ or a mixture of these compounds.

In the reaction described above, the Compound of titanium in an amount of 0.1 to 2 mol, preferably 0.8 to 1.8 mol, based on one gram atom Magnesium of the complex.

The reaction temperature is 30 to 150 ° C, preferably 60 to 120 ° C, and the reaction time is up to 30 min several hours, preferably 1 to 5 hours.

The reaction takes place in the presence of an ester, in particular an ester of a C ₆ -C ₁₆ aromatic carboxylic acid with a C ₁ -C ₁₂ aliphatic hydroxy compound. Preferred compounds of this type are diesters of phthalic acid with a C ₁ -C ₁₀ aliphatic or aromatic alcohol, for example diethyl phthalate or diisobutyl phthalate.

The catalyst component A produced in this way is finally at a temperature of 0 to 100 ° C, preferably from 10 to 50 ° C, by repeated washing with an inert hydrocarbon of soluble Impurities such as metal or halogen compounds exempted.

Suitable halogen-free organoaluminum compounds (component B) are, in particular, branched, unsubstituted aluminum alkyls of the formula AlR ₃ , where R is an alkyl radical having 1 to 10 carbon atoms, such as B. aluminum trimethyl, aluminum triethyl, aluminum triisobutyl, aluminum tridiisobutyl. The reaction products of aluminum triisobutyl or aluminum diisobutyl hydride and isoprene, which are commercially available under the name aluminum isoprenyl, are also suitable. Aluminum triethyl and aluminum triisobutyl are particularly suitable.

The catalyst component C is an organosilicon compound of the formula R² _n Si (OR³) _4-n , wherein R² is a C₁-C₁₀ alkyl group, C₅-C₁₂ cycloalkyl group, C₆-C₂₀ aryl group, C₁-C₁₀ alkenyl group, C₁-C₁₀ haloalkyl group or C₁-C₁₀ amino group, R³ is a C₁-C₁₀ alkyl group, C₅-C₁₂ cycloalkyl group, C₆-C₂₀ aryl group, C₁-C₁₀ alkenyl group or C₂-C₁₆ alkoxyalkyl group and n is an integer and the R² groups or ( 4-n) OR³ groups can be the same or different.

Examples of (C) are organosilicon compounds such as Trimethylmethoxysilane, trimethylethoxysilane, Dimethyldimethoxysilane, dimethyldiethoxysilane, Diphenyldimethoxysilane, methylphenyldimethoxysilane, Diphenyldiethoxysilane, ethyltrimethoxysilane, Methyltrimethoxysilane, vinyltrimethoxysilane, Phenyltrimethoxysilane, γ-chloropropyltrimethoxysilane,  Methyltriethoxysilane, ethyltriethoxysilane, Vinyl triethoxysilane, butyltriethoxysilane, Phenyltriethoxysilane, γ-aminopropyltriethoxysilane, Chloropropyltriethoxysilane, cyclohexylmethyldimethoxysilane, Cyclohexylmethyldiethoxysilane, di-n-octyldimethoxysilane, Di-n-octyldiethoxysilane, i-octyltrimethoxysilane, i-octyltriethoxysilane, methylphenyldiethoxysilane, Dibutyldimethoxysilane, dibutyldiethoxysilane, Di-i-butyldimethoxysilane, di-i-butyldiethoxysilane, Di-t-butyldimethoxysilane, di-t-butyldiethoxysilane, t-butyltrimethoxysilane, t-butyltriethoxysilane, Di-p-toluyldimethoxysilane, di-p-toluyldiethoxysilane, Dicyclohexyldimethoxysilane, dicylohexyldiethoxysilane, Ethyl triisopropoxysilane, vinyl tributoxysilane, ethyl silicate, Butyl silicate, trimethylphenoxysilane, Methyltriallyloxysilane, vinyltris (β-methoxyethoxy) silane, Vinyl triacetoxysilane, dimethyltetraethoxyisilane and Phenyldiethoxydiethylaminosilane.

Among these are methyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenylmethyldiethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylmethyldiethoxysilane, vinyltriethoxysilane, phenyltrietoxysilutilysilane, phenyltriethoxysilane, phenyltrietoxysilane
preferred.

Are particularly preferred Diphenyldimethoxysilane, Diphenyldiethoxysilane, cyclohexylmethyldimethoxysilane, Cyclohexylmethyldiethoxysilane, phenyltrimethoxysilane and Phenyltriethoxysilane.

Two of these compounds (C and D) can also be used Combination can be used. The component D is then always different from component C.  

Component A is in the form of a suspension in one inert hydrocarbon, or after separating the Suspension medium dry for the polymerization of propylene used. The copolymerization of is also possible Propylene with ethylene and / or a 1-olefin with 4 to 10 Carbon atoms and one or more double bonds, for example 1-butene, isobutene, 1-hexene or 1,3-butadiene.

The first stage of the process according to the invention is described in liquid monomer carried out, both continuous as well as discontinuous Reaction management is possible.

The catalyst concentration is chosen as is customary for propylene polymerization. The concentration of component A is therefore 0.001 to 1 mmol / dm ³ , based on titanium, preferably 0.001 to 0.1 mmol / dm ³ .

Component B is used in a concentration of 0.001 to 5 mmol / dm ³ , preferably 0.1 to 5 mmol / dm ³ , component C in a concentration of 0.003 to 2 mmol / dm ³ , preferably 0.03 to 1.2 mmol / dm ³ .

If a combination of two organosilicon compounds (C and D) is used, both are initially introduced in a concentration of 0.003 to 2 mmol / dm ³ , preferably 0.03 to 1.2 mmol / dm ³ . The molar ratio of components C and D can vary from 1:99 to 99: 1. A ratio of 20:80 to 80:20 is preferred.

The polymerization is carried out in such a way that liquid propylene, a suspension of the solid Catalyst portion in an inert suspension medium and the other liquid catalyst components in one suitable reaction vessel are pumped in. This Reaction vessel can be an autoclave, a common one Reaction vessel or a tubular reactor in loop form,  whereby as usual by built-in stirrers or circulation pumps sufficient mixing is ensured.

The heat of reaction is removed by Jacket cooling, through internal cooling built into the vessels or also by evaporative cooling.

The liquid propylene itself, both as a monomer and as also serves as a suspending agent, can vary in amounts contain inert, low-boiling, dissolved components, such as B. propane or nitrogen, but the on Products made using this process have no significant value Have influence.

A reaction temperature of 40 to 100 ° C, preferably one of 50 to 85 ° C, maintained. The Pressure is 1 to 49, preferably 20 to 40 bar. The reaction time is 10 to 240 min, preferably 30 to 120 min.

Setting the desired molecular weight of the polymer in the first stage is done by adding hydrogen. The amount added is adjusted so that the resulting product has a melt index MFI 230/5 of 0.05 up to 5 g / 10 min.

Polymerization without molecular weight regulator is preferred in the first stage.

The amount of polymer produced in the first stage is based on the whole in the process resulting polymer, 20 to 80 wt .-%, preferably 55 to 80% by weight.

If one with small amounts of a 1-olefin other than Comonomer modified polypropylene can be produced  the comonomer is metered like the other starting materials. As other monomers, ethylene and 1-olefins come with 4 bis 10 carbon atoms in question, preferably ethylene and Butene, especially ethylene. The concentration of ethylene or 1-olefin in liquid propylene is 0 to 15 Mole%. The entire polymer consists of at least 95% by weight. made of polymerized propylene.

There are two to complete the second stage Practices possible, both without additional Auxiliaries such as high-boiling inert suspending agents are feasible. They differ in that Start of the second stage in one case none intermediate processing of the polymer suspension in Propylene takes place, while in the second case before the start second stage, the main part of the monomer is separated off and into the first stage is returned.

First of all, the process is without intermediate Processing described.

The polymer suspension formed in the first stage, the essentially the predominantly crystalline, isotactic Polypropylene, optionally with small amounts of a 1-olefin is modified, the active Catalyst components, liquid propylene, certain amounts contains hydrogen and optionally inert portions, is now transferred to the second reaction stage.

At the beginning of the second stage, hydrogen is now in the Suspension initiated until the equilibrium boiling pressure the suspension 1 to 20 bar, preferably 2 to 10 bar above the vapor pressure of propylene at the same Temperature. The propylene is then 0.1 to 10 mol%, preferably 1 to 8 mol%, hydrogen dissolved.  

Instead of pure hydrogen, you can also use a solution of hydrogen in propylene, as in the Processing of the polymer suspension at the end of the process occurs or in a separate process step can be manufactured.

The second reaction stage is carried out at a temperature of 40 to 100 ° C, preferably 50 to 85 ° C, performed. they takes 10 to 180 min, preferably 15 to 120 min.

After completing the second stage, the resultant Worked up polymer. This can be done by the resulting mixture of polymer and monomer in one or several stages to atmospheric pressure and that recycle residual monomer.

The work-up can also be carried out by filtration, Decantation or centrifugation in suitable, pressure-resistant units happen, e.g. B. in pressure filters, Sedimentation towers, centrifuges or decanters.

In the second process variant, after the first stage in an intermediate Process step separated a large part of the monomer and returned to the first stage. The separation takes place at least to the extent that the polymer formed is no longer surrounded by liquid monomer and the Total system pressure below that at the reactor temperature observable boiling pressure of the monomer or Monomer mixture has fallen.

The monomer can be separated off, for example, by Distill off or by sudden relaxation the polymer suspension, e.g. B. with a valve.

The polymer / gas mixture resulting after this step is now transferred to the second reaction stage.  

In this reaction stage, this is still hydrogen-free Polymer / monomer mixture hydrogen or a hydrogen-rich propylene / hydrogen mixture to the extent supplied that in the reactor from a monomer composition 50 to 99.8 mol%, preferably 90 to 99.8 mol%, olefin plus inert components and from 0.2 to 50 mol%, preferably 0.2 to 10 mol%, hydrogen is present. The Pressure in the second stage is 5 to 100 bar, preferably 10 to 64 bar, the temperature 40 to 100 ° C, preferably 50 to 85 ° C. Pressure and temperature are there combined so that no liquefaction in the reactor of the monomer / hydrogen mixture can take place.

The duration of the second stage is 10 to 180 min. preferably 15 to 120 min.

Throughout the duration is for an intense Mixing of the polymer / gas mixture to ensure Clumping of the polymer or adherence to the Avoid reactor wall. This can be done either through a intensive stirring in the reactor and / or by intensive Blow through the monomer / hydrogen mixture through the Reactor.

It is also possible to start before the second stage additionally meter the activator. Most of all, this is then advantageous if the polymerization in the first Level at a low molar ratio of activator to Catalyst, d. H. at low activator concentration is carried out.

After performing the second stage, the obtained Polymer / monomer / hydrogen mixture worked up. This happens, for example, by single or multi-stage Relaxation to atmospheric pressure and return of the gaseous components in the process.  

The polymer obtained by either method has excellent hardness and morphology. Its viscosity is 1.5 to 6 dl / g, its polydispersity M _w / M _n is 10 to 50, preferably 20 to 40.

Other excellent properties are the strong ones Change in its melt viscosity when the applied shear stress and its high Melt resistance.

For further processing, this is the invention polymer obtained with the usual additives (Stabilizers, lubricants, fillers, pigments etc.) Mistake. It can either be in extruders or kneaders Granulate form transferred or because of its good homogeneity without previous treatment in one Extruder or kneader directly in powder form for the Manufacture of plastic articles can be used. There its melt viscosity varies over a wide range can be used for the known processing methods is needed, it can be done by all common methods are processed.

The determination of the properties according to the polymers prepared in the following examples was in carried out individually according to the following methods: The melt index MFI 230/5 was measured according to DIN 53735 and given in g / 10 min.

The measurement of the ball indentation hardness (KDH) was carried out according to DIN 53456 on pressed plates, which were annealed for 3 h at 140 ° C under N ₂ , cooled in the course of 3 h and for temperature compensation 24 h at 23 ° C and 50% rel. Humidity has been stored in a climatic chamber. The KDH is given in N / mm ² .

The molecular weight distribution M _w / M _n was determined by gel permeation chromatography at 150 ° C. with 1,2-dichlorobenzene as the solvent.

The viscosity number (VZ) of the polymer was 0.1 weight percent solutions in decahydronaphthalene (Mixture of isomers) at 135 ° C in a capillary viscometer determined and given in dl / g.

The flowability of the polymer melt was determined on a Measuring extruder with a slot nozzle of 0.5 × 10 mm opening and measured a length of 100 mm. After performing the Bagley and Rabinowitsch-Weisenberg correction became the receive the specified values.

To determine the melt strength, the polymer was also melted in a measuring extruder and extruded through a die (10 × 1 mm) at a shear rate of 138 s ^-1 .

The extruded melt strand was received between two counter-rotating gears, which were mounted on a force measuring device together with the drive and tachometer. As the number of revolutions of the gearwheels increased linearly in time, the strand emerging from the nozzle was drawn off with a continuously increasing expansion speed. The tensile force of the thread was recorded on an Xy recorder as a function of the number of revolutions. The force at which the drawn-out melt strand breaks is called the thread break force F _a .

example 1 Manufacture of a solid titanium catalyst component

9.52 g (100 mol) of anhydrous magnesium chloride, 50 cm ^{3 of} decane and 46.8 cm ³ (300 mmol) of 2-ethylhexyl alcohol were reacted at 130 ° C. for 2 h, during which the magnesium chloride dissolved. 2.22 g (15.0 mmol) of phthalic anhydride were added to the solution. The mixture was further stirred at 130 ° C. for 1 h until the phthalic anhydride had dissolved. The solution obtained was cooled to room temperature and dropwise added to 400 cm ³ (3.6 mol) of titanium tetrachloride kept at -20 ° C. in the course of 1 hour, whereupon the mixture was heated to 110 ° C. in the course of 4 hours. When the temperature of 110 ° C was reached, 5.36 cm ³ (25.0 mmol) diisobutyl phthalate was added. The mixture was kept at this temperature with stirring for a further 2 h. The mixture was then filtered hot and the solid portion resuspended in 400 cm ^{3 of} titanium tetrachloride and reacted at 110 ° C. for 2 h. The solid was then collected by hot filtration and washed with decane and hexane at 100 ° C. until no free titanium compound could be detected in the washing solvents.

The solid catalyst component A thus obtained was in Form of a suspension kept in hexane. A part of Suspension was dried to determine the composition of the Examine catalyst. The analysis showed 2.5% by weight Titanium, 56.4 wt% chlorine, 17.5 wt% magnesium and 21.0 % By weight diisobutyl phthalate.

Polymerization

40 dm ^{3 of} liquid propylene were placed in a vessel with a volume of 70 dm ³ and 200 mmol of triethyl aluminum, 40 mmol of diphenyldimethoxysilane and 2.83 cm ^{3 of} the above contact suspension (≅0.04 mmol of Ti) were metered in successively. The contents of the kettle were then heated to 70 ° C. and held at this temperature for 60 minutes.

Hydrogen was then added until the internal pressure of the Reactor was 33.5 bar, and the polymerization for a further 60 min carried out.

5.7 kg of polymer were obtained with a VZ of 3.63 and an MFI of 9.9. His KDH was 86 and his polydispersity M _w / M _n 12.4.

The melt viscosity at 210 ° C. and 10 ⁴ Pa shear stress was 6 × 10 ³ iPa × s, at 4 × 10 ⁴ Pa it was 7 × 10 ² Pa × s. The thread breaking force at 210 ° C was 850 mN.

Example 2

The polymerization was carried out as described above, but only after 90 min of hydrogen was pressurized to a reactor pressure of 36.2 bar and the polymerization was continued for a further 30 min. 2.8 kg of polymer were obtained with a VN of 5.79 and an MFI of 1.9. Its KDH was 83 and its polydispersity M _w / M _n 39. The melt viscosity at 210 ° C. and 10 ⁴ Pa shear stress was 9 × 10 ⁴ Pa × s, at 4 × 10 ⁴ Pa it was 3 × 10 ³ Pa × s.

The thread breaking force at 210 ° C had a value of 2450 mN.

Example 3

The polymerization was carried out as in Example 2, but the first stage in the presence of 3 dm ^{3 of} hydrogen. 3.5 kg of polymer were obtained with a VZ of 4.06 and an MFI of 8.2. His KDH was 88, his polydispersity M _w / M _n = 23.2.

The melt viscosity at 210 ° C. and 10 ⁴ Pa shear stress was 9 × 10 ³ Pa × s, at 4 × 10 ⁴ Pa it was 1.2 × 10 ³ Pa × s.

The thread breaking force at 210 ° C had a value of 1030 mN.  

Example 4

10 dm ^{3 of} liquid propylene, 50 mmol of triethylaluminum, 10 mmol of diphenyldimethoxysilane and 0.7 cm ³ (0.0099 mmol of Ti) of the contact suspension described above were condensed in a 16 dm ³ reactor with stirrer (500 rpm). The reactor was then heated to 70 ° C. and the polymerization was carried out over 45 minutes. The monomers were then removed until the internal reactor pressure had dropped to 20 bar. After 80 dm ^{3 of} hydrogen had been injected, the polymerization was continued for 75 min, a reactor pressure of 25 bar being maintained by feeding in propylene. 1.3 kg of polymer were obtained with a VN of 3.89 and an MFI of 8.9.

His KDH was 92 and his polydispersity M _w / M _n = 20.2. The melt viscosity at 210 ° C. and 10 ⁴ Pa shear stress was 1 × 10 ⁴ Pa × s, at 4 × 10 ⁴ Pa it was 1.5 × 10 ³ Pa × s. The thread breaking force at 210 ° C had a value of 1380 mN.

Comparative example

2.5 dm ^{3 of} hydrogen were placed in a 16 dm ³ reactor and 10 dm ^{3 of} liquid propylene, 50 mmol of triethylaluminum, 10 mmol of diphenyldimethoxysilane and 0.7 cm ³ (0.0099 mmol of Ti) of the contact suspension described above were metered in. The polymerization was carried out over 120 min.

0.9 kg of polymer were obtained with a VZ of 2.68 and one MFI of 18.6.

His KDH was 86, his polydispersity M _w / M _n 6.8. The melt viscosity at 210 ° C. and 10 ⁴ Pa shear stress was 5 × 10 ³ Pa × s, at 4 × 10 ⁴ Pa it was 2 × 10 ³ Pa × s.

The thread break force at 210 ° C was 294 mN.

Claims (1)

Process for the preparation of a polypropylene by homopolymerizing propylene or copolymerizing propylene with ethylene or a 1-olefin with 4 to 10 C atoms in suspension at a temperature of 30 to 150 ° C and a pressure of 1 to 49 bar, in the presence of a Catalyst consisting of a transition metal component (component A) which, by reaction of a magnesium halide, first with at least one electron donor and then with a tetravalent titanium compound of the formula TiX _m (OR ¹ ) _4-m , in which R ^{1 is} an alkyl radical with 2 to 10 C Atoms, X is a halogen atom and m is a number from 0 to 4, was obtained in the presence of an ester of an aromatic carboxylic acid, a halogen-free organoaluminum compound (component B) and an organosilicon compound as a stereoregulator (component C), characterized in that the polymerization in two reaction stages is carried out, in the first reaction stage the monomer both starting material and Suspending agent is and a polypropylene with a viscosity of 4 to 14 dl / g and a proportion of the total polymer of 20 to 80 wt .-% is produced and in the second reaction stage a polypropylene with a viscosity of 1 to 3 dl / g and a proportion is produced on the total polymer of 80 to 20 wt .-%, and the total polymer has a viscosity of 1.5 to 6 dl / g and a polydispersity M _w / M _n of 10 to 50.