- 2 ~ 7'~7 The present invention relates to a process for the preparation of homopolymers and copolymers of eth-ylene.
Catalyst systems comprising a cyclopentadienyl compound of t;tanium or zirconium and an aluminum com-ponent of the alum;noxane type hav;ng ~he general for-mula Al20R4(Al(R)-O-)n for linear alum;noxane and (AltR)-O-)n+3 for cyclic alum;noxane have been des-cr;bed ~cf. German Offenlegungsschrift 3,127,133).
1~ Accord;ng to the examples, the aluminoxane employed as the co-catalyst component ;s employed in relat;vely large amounts. For an industr;al process, at a usage of about 1 mg/cm3 or 1 kgJm3, large amounts of the aluminoxane must be made ava;lable.
1~ A process ;s also kno~n for the preparat;on of the alum;noxan,e component, where;n the preferred ol;go-mer;c aLuminoxanes are prepared by reacting A~R3 with hydrated alum;num sulfate ;n hydrocarbons at temperatures preferably between 15 and 40C (cf. German O~fenlegungs-schr;ft 3,240,383). It also emerges from the examples that th;s preparation ;s time-consuming (10 to 40 hours are indicated in the examples), and that the res;dual so~id has to be separated off from the solution of the aluminoxane ;n the hydrocarbon. A~together, th;s means 2~ tha~ the a~um;noxane component must be prepared in a separate process stage.
Finally~ a process is also kno~n for the prepar-ation of f;l~ed polyolefins~ in ~hich inorganic sub-stances containing ~ater as the result of adsorption or absorpt;on are reacted ~ith aluminum trialkyls, and 3 cyclopentadienyl compound of titanium or ~irconium ;s used (cf. ~erman ~ffenlegungsschrift 3~240~382).
It has now been found that it is possible to obviate the aluminoxane synthesis ~hich has to be carried out separately and to prepare a h;gh~y act;ve catalyst system in one process stage ~ithin a short timea The invention relates, accordingly, to a
- 3 ~ 72~7 process for the polymerizat;on of ethylene or mixtures of ethylene containing up to 8X by ~eight of a 1-olefin o~
the formula R1-CH=CHz in ~hich R1 denotes a linear or branched alkyl radical having 1 to 12 carbon atoms in solution or in suspens;on at a temperature of 0 to 150C
and a pressure of 1 to 50 bar, ;n the presence of a m;xed catalyst composed of a transit;on metal component (compo-nent A) and an organo-aluminum compound (component B), the component B having been obtained by react;ng an inorganic material containing ~ater, as the result of adsorpt;on or absorption, with an aluminum trialkyl, ~hich comprises carrying out the polymerization in the presence of a mixed catalyst in ~hich the component B has been prepared by reacting ~ater ~ith an aluminum trialkyl in a molar ratio of aluminum trialkyl to ~ater of 4:1 to 0.25:1 in the presence of a finely divided solid based on silicon dioxide and/or aluminum oxide in a ratio by weight of ~ater to solid of 3:1 to 1:3 at a temperature of -20 to 100C, and the component A represents a transition 2û ~etal compound of the formula (cyclopentadienyl)2MeRHal in ~hich R is cyclopentadienyl~ a C1 to C6 alkyl radical or halogen, ~al denotes halogen and Me is titanium or zirconium.
An aluminum tr;alkyl is reacted ~ith ~ater in the presence of a solid for the preparation of the catalyst component B ~hich is to be used in accordance ~ith the invention.
The solid is a finely divided, porous material ~ased on si~icon dioxide and/or aluminu~ oxide~ Solids 3~ of this type are availabLe commercially. The aluminum trialkyl used is alum;num trimethyl or aluminum triethyl.
~ reactor equipped with a stirrer, a temperature control device and protective gas blanketing ~N~ or Ar), ~hich can also be the polymerization reactor~ is used for ~5 the reaction. The reaction medium initially taken is advantageously ~he dispersing agent ~hich is also used in the poly~eri7ation. Suitable dispersing agents are ali-phatic or cycloaliph3t;c hydrocarbons, such as butane, pentane, hexane, heptane, cyclohexane, methylcyclohexane
- 4 - ~ ~ ~7~7 or isooctane, and aromat;c hydrocarbons, such as benzene, toLuene or xylene; petroleum fractions and hydrogenated diesel oil fractions ~hich have been carefully freed from oxygen, sulfur compounds and moisture can also be used.
The d;spersing agent must not contain compounds having double bonds.
The finely divided, porous solid is then intro-duced in an amount of 10 to 1,000 mg/dm3, under a pro-tective gas and ~ith slo~ stirring, at a temperature of -Z0 to 100, preferably 15 to ~0, C. The intended amount of ~ater (0.03 to 3 cm3/dm3) is then added, and stirring is continued for a few minutes. The addition of the a~uminum trialkyl (aluminum trimethyl or aluminum tri-ethyl) is then effected ~ith slow stirring and blanketing ~ith protective gas. û.5 to 5 cm3/dm3 of the pure, liquid components are added. The co-catalyst component is formed by stirring for 10 to 60 minutes. The molar ratio of aluminum alkyl compound to water is 4 to 0.25, prefer-ab~y 0.5 to 3.
2~ The molecular weight of the aluminoxane component ~as determined by cryoscopic measurements in benzene as ~00 to 1,000 g~mole. This corresponds, in the case of methyl aluminoxane, to n-values between 11 and 15 for linear molecules and to n-values between 10 and 14 for cyclic molecule~.
~ f the reaction of the aluminum tr;alkyl ~ith the ~ater ~as carried out ;n the po~ymerizat;on kettle, the contents of the latter are then raised to the polymeriz-ation temperature. ~hen this temperature has been reached, the catalyst component A, which is a transition metal com-pound of the formuLa ~cyclopentadienyl)2MeRHal in which R is cyclopentadienyl, a C1 to ~6 alkyl radica~ or halogen, preferably chlorine, Me denotes titaniu~ or zir-conium and ~al is halogen, preferably chlorine, is added, and the polymerization is started by introducing the reactants.
The polymerizatiun of ethylene and the copolymeriz-ation of ethylene with ~ole~ines is carried out in solu-tion or in suspension~ continuousLy or discontinuously~ at ~'7~7 a temperature of O to 150C, preferably 50 to 100C. The pressure is 1 to 50 bar~ preferably 1.5 to 10 bar.
Polymers having a very w;de molecular ~e;ght d;s-tr;bution can be prepared by carrying out the polymeriz-ation in two or more stages, it being poss;ble to vary the polymerization temperature and/or the amount of reg-ulator (hydrogen) ;n the ;ndividual stages.
1-Olefins of the formula R1-CH=CH2 in ~hich R1 denotes a linear or branched alkyl radical having 1 to 12, preferably 1 to 6, carbon atoms are used for the co-polymerization with ethylene. Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene may be mentioned as examples. The m;xtures of ethyLene and the 1-olefines mentioned contain up to ~X by weight, in par-ticular up to 2Z by weight, of 1-olef;nes.
The molar ratio Al:Ti or Zr in the polymeri~ation is 5,000 to 20~000, preferably 8,000 to 15,000.
The polymerization is carried out with or without 2~ the addition oF hydrogen to regulate the molecular weight of the polymer. Amounts of hydrogen up to ~0% by volume in the gas phase are possible. The catalyst system according to the invention responds very readily to hyd-rogen, so that a smaller amount of hydrogen is required in order to reach a specific molecular we;ght than ~hen known catalyst systems are employed.
Both thermoplastic and elastomeric polymers hav-ing vary;ng average molecular ~eights and dens;ty can be prepared using these catalyst systems.
3~ The polymers obtained are characterized by the fo~lo~ing measurements: melt index ~MFI) as specified in ~IN 53~735 in coniunction with the explanatory notes for polyethylene, density ~d) as specified in DIN 53~479~
process A on the compression-molded sheet, reduced spe-cific viscosity (Y~) as specified in }S~/R 1191 and bulk density of the powder as specified in DIN 53,912.
~xample 1 1 dm3 of a petroleum fraction having a boiling range bet~een 1~D and t4D~ at room temperature were ~, initially taken in a 2 dm3 reactor, under a blanket of nitrogen. All the further operations were carried out under nitrogen blanketing. son mg of SiO2 and 0.29 cm3 of water ~ere introduced success;vely into the reactor ~ith slo~ stirring (4 r.p.m.). The mixture was then stirred for 20 minutes. 3.25 cm3 of aluminum trimethyl were then added and stirring was continued for a ~urther 30 minutes. The reactor ~as then brought to the poly-merization temperature of 85C. When the contents of the reactor had reached the temperature of ~5C, 0.004 mmole, corresponding to 0.91 mg, of (cyclopentadienyl)2-ZrCl2 ~as added under protective gas.
Immediately after~ards~ the speed of the stirrer uas raised to 100 r.p.m. and ethylene was injected up to 3 p, essure of 3 bar. This pressure ~as kept constant over a reaction time of 5 hours, by supplying furth~r ethylene at the rate at ~hich it was consumed by the po~ymeri~ationr After a reaction time of 5 hours the supply of ethylene was discontinued, the reactor ~as depressurized and the polymer suspension ~as discharged.
The polymer ~ias filtered off, ~ashed ~ith acetone and dried at 80C in vacuo for several hours.
150 9 of polyethylene having the following pro-~uct data ~ere obtained; MFI 190~5 = 0.4 9/10 minutes, MF} 180~21.~ = 5.3 g/lD minutes, VN = 250 cm3/g; bulk density of the powder 0~15 g/cm3; density = O.9oO g/cm3.
The productiv;ty of the catalyst after a reaction time of
5 hours at an ethylene partial pressure of 3 bar was 37.5 k~ of PE~mmole of Zr.
3~ Example 2 This test ~as carried out similarly to Example 1, but a different SiO2 ~as employed. 1 dm3 of petroleum fraction was initially taken in the 2 dm3 reactor, and 300 mg of SiO2 were introduced. 0.29 cm3 of ~ater ~ere then addedJ and the mixture was stirred for 20 minutes at room temperature. 3.25 cm3 of aluminum trimethyl ~ere then added and stirring ~as cont;nued for a further ~0 minutesu The reactor ~as brought to the polymeri~ation temperature of ~5~C. When ~2~7;2 97 this temperature had been reached, 0.004 mmole, corres-ponding to 0.91 mg, of (cyclopentadienyl)2ZrCl2 was added.
The polymerization was carried out as described ;n Example 1. 65 9 of polyethylene having the follo~ing product data ~ere obtained: VN = 260 cm3/g; density =
0.959 g/cm3. The cataLyst productivity after a reaction time of 5 hours and an ethylene partial pressure of 3 bar ~as 10.3 kg of PE/mmole of Zr.
Example 3 This test ~as carried out similarly to Example 1, but an Al203 ~as used instead of the SiO2 employed in Example 1. 1 dm3 of petroleum fraction ~as init;ally taken in a 2 dm3 rPactor, and 100 mg of the Al203 ~ere introduced w;th slo~ stirring. 0.2~ cm3 of water ~as then added and the mixture ~as stirred for 20 m;nutes at room temperature. After 2.25 cm3 of aluminum trimethyl had been added, stirring was continued for a further 20 minutes. The reactor was then brought to the polymer;z-ation temperature of 85C. After this temperature had been reached, 0.004 mmole, corresponding to 0.91 mg, of ~cyclopentadienyl)~ZrCl~ ~as added. The polymeriz-ation ~as carried out as described in Example 1. 85 9 of polyethylene having the followin3 product data were obtained: MFI 190/5 = 1.~ 9/10 minutes, VN = 200 c~3/g;
bulk density of the powder: 0.18 gtcm3. The catalyst productivity after a react;on time oF S hours at an ethylene pressure of 3 bar ~as 21.3 kg of PE/mmole of Zr.
Examp~e 4 Th;s test ~as carried out as described in Example 1~ but hydrogen ~as introduced into the reactor in order to regulate the mo~ecu~ar weight. The hydrogen content ;n the gas space of the reactor ~as approximately 1.~ mole %.
The polymerization ~as carried out for 5 hours at an ethylene partial pressure of 3 bar. 130 9 of poLyethyl-ene having the follo~ing product data ~ere obta;ned: MFI
190/5 = 1~ g/lD minutes, MFI 1~0/15 = 105 9/10 minutes, VN - 1~a cm3~g; bul~ dens;ty of the powder = 0.18 g/cm3;
densi~y = 0.9~ g~cm3. The cataLyst productiv;ty after a :~2~2~7 reaction time of 5 hours at an ethylene partial pressure of 3 bar was 32.5 kg of PE/mmole of Zr.
Example 5 The catalyst system in th;s test was prepared as described in Example 1. Before ethylene was injected, 100 cm3 of liquid 1-butene were injected into the reactor from a pressure lock. Ethylene was then injected up to a pressure of 3 bar, and the polymerization was carried out for 5 hours without the Further addition of 1-butene. When the polymerization was compLete, the reactor was depressurized and cooled to 50C. The con-tents of the reactor were then stirred into 5 dm3 of ace~one. The polymer was filtered off and dried at 60C
;n vacuo for several hours. 120 9 of copolymer hav;ng the following product data were obtained: MFI 19û/2.16 = 35 9/
1û minutes; VN = 100 cm3/9; density = 0.936 g/cm3. The catalyst productivity ~as 30 kg of polymer/mmole of Zr.
Example 6 _ This test ~as carried out in a 2 dm3 3-necked flask equipped ~ith a stirrer and inlet gas lines. 1 dm3 of a petroleum fraction having a boi~ing range between ~Oû
a~d 140C at room temperature was inieially taken under protective gas (Ar). A~l further operations were also carried out under protective gas. 500 mg of SiO2 2~ according to Example 1 and 0.29 cm3 of ~ater ~ere intro-duced successiveLy into the reactor ~ith slo~ s~irring C1~ r.p.m.~. The mixture was then stirred for 15 min-utes. 3.25 cm3 of alum;num tr;methyl ~ere then added and stirr;ng ~as cont;fiued for a further 30 m;nutes. The reactor was then brought to the polymer;zation temperature of 4ac. When the contents of the reactor had reached this temperature, 0.0~4 mmole~ correspond;ng to 0.~1 mg, of ~cyclopentadienyl~2~rCl2 was 3dded under protective gas.
Immediately after~ards the speed of the stirrer was raised to 50 r.p.m. 50 cm3 of 1,7-octadiene ~before use, this product was extracted by shaking with sodium hydroxide solut;on, washed ~ith water~ dried ~ith magnesium sulfate, distilled and stored over a 3 A molecul3r sieve under 7;Z9~
_ 9 _ protect;ve gas) ~as then added and 5 parts by volume of propene and 2 parts by volume of ethylene were subse-quently introduced into the petroleum fraction phase under normal pressure.
After a reaction time of 1 hour a product had been formed; this accumulated round the stirrer. This product, together with the contents of the reactor, was subjected to steam distillation in order to remove the petroleum fraction; it was then dried at 30C in vacuo.
This gave 30 g of an elastomeric molding composition which no longer dissolved in hydrocarbons (decahydronaphth-a~ene) at 150C. The catalyst productivity was 7.5 kg of polymer/mmole of 7r.