DE2521075C2 - Process for the production of polyethylene - Google Patents

Description

It has long been known that catalysts, consisting of an activated with aluminum alkyls, Solid containing titanium, magnesium and chlorine in the polymerization of -olefins, in particular of Ethylene, used as a dispersant in hydrocarbons, has a very high activity. In recent years are very many proposals for the production of polyethylene have become known, which are particularly with deal with the type of production of the solid used. A large part of these suggestions is Technically not usable because of the grain properties of the polyethylene produced with it does not meet the requirements for polymerization, conveyance and further processing. Others are ruled out because of the physical properties of the polyethylene produced moldings are not sufficient for many purposes. It is unusually difficult the various requirements for easy processability, high rigidity, high impact strength and to optimally meet thermal stability.

The object of the invention was to show a process for the production of polyethylene with which it succeeds in largely meeting the requirements mentioned.

The invention is a process for the production of polyethylene by continuous or discontinuous, single or multi-stage polymerization of ethylene, optionally together with up to 10 Mol% of -olefins with 3 to 6 carbon atoms, in Hydrocarbons as dispersants at pressures

ίο from 8 to 40 atmospheres and temperatures from 60 to 100 ⁰ C, optionally in the presence of hydrogen, using a catalyst which is activated with aluminum alkyls or reaction products of dialkyl aluminum hydrides with diolefins with 4 to 20 carbon atoms, containing titanium, magnesium and chlorine There is a solid that has been obtained by reacting metallic magnesium with a halogen-containing compound and a: - Another compound and subsequent reaction of the carrier thus obtained with a chlorine-containing Ti (IV) compound, which is characterized in that the solid is obtained in the manner has been prepared by reacting metallic magnesium with at least 2, preferably 2.2 to 10 moles of allyl chloride and 1.75 converted to 3 moles per g-atom of magnesium dialkyl ether at 30 to 100 ⁰ C, the solid is formed at least 24, preferably 65 up to 150 hours, optionally in the presence of hydrocarbons, at 30 to 140 ⁰ C, vorzu sometimes 50 to 80 ⁰ C, aged, the solid separated from the reaction mixture before or after aging after a ^{treatment, optionally in hydrocarbon suspension, at -50 to 120 0} C with at least 0.2, preferably 0.7 to 4, mol dialkyl sulfite per g atom of magnesium with 0.5 to 10, preferably 1 to 5, mol TiCl ₁ OR ^ where R is an alkyl radical, χ has a value from 2 to 4 and y has a value from 0 to 2 and x + y = 4, has reacted for 1 to 5 hours at 60 to 140 ^° C. per g atom of magnesium and has separated the solid from the reaction mixture.

Magnesium shavings, magnesium powder or magnesium powder, for example, can be used as metallic magnesium will. The magnesium becomes useful as in the preparation of the Grignard compounds

activated by small amounts of iodine. Ether is essential for the reaction. Dialkyl ethers are suitable with the same or different alkyl groups. The alkyl groups preferably have 2 to 4 carbon atoms, Diethyl ether is particularly suitable.

Other solvents such as B. Beczin or benzene can also be added.

it is preferred for the reaction of magnesium with allyl chloride and ether. Magnesium and allyl chloride and the ether slowly added dropwise or magnesium and allyl chloride and ether to drip. It is also possible to slowly add magnesium to an allyl chloride / ether mixture. In contrast to the production of Grignard compounds, it is important for the solid properties of the Magnesium chloride is not so beneficial to submit magnesium and ether and the allyl chloride slowly admit it. In order to achieve good solid properties, those specified in the claim formulation should be Molar ratios of the reactants are taken into account.

The temperature is 30 to 100 ⁰ C. Often, the reaction at atmospheric pressure is carried out under reflux. After combining the components, the reaction mixture is used to complete the

Implementation held at the reaction temperature for a few hours.

The solid reaction product, essentially, but not exactly in composition, magnesium chloride, must be subjected to thermal aging, without which you can get very dusty polyethylene would receive. The aging is expediently carried out in the presence of hydrocarbons Suitable hydrocarbons are here as in the following those for the polymerization of Ethylene are known as a dispersant. These are mainly aliphatic, cycloaliphatic and aromatic compounds With boiling points between 30 and J 60 ° C, for example, hexane, haptane, isooctane, Cyclohexane, benzene, toluene or gasoline fractions in the specified boiling range. You can use the reaction mixture simply dilute with hydrocarbon, whereby the degree of dilution is not critical Im In general, the reaction product: hydrocarbon dilution ratio is 1: 0.5 to 1: 5. At the same time as the dilution, one can use the others if there is a corresponding boiling point difference Separate components of the reaction mixture by distillation and ether, excess allyl chloride and formed Win diallyl. It is also possible to first remove the solid mechanically or by distillation from the reaction mixture to be separated and suspended in the hydrocarbon. You can also see the aging in Carry out the reaction mixture yourself or in the dry state. However, these methods are of minor importance Meaning. Aging takes place for at least 24, preferably 65 to 150, hours at 30 up to 140 ° C, preferably 50 to 80 ° C.

Aging is followed by a treatment with dialkyl sulfite, which is essential for high yields of polyethylene, based on the magnesium used. The reasons for this are unknown this was not done before aging. This can be done mechanically, by decanting, centrifuging or filtering. However, the volatile constituents can also be distilled off. The treatment is often carried out in hydrocarbon suspensions, with times of a few minutes to several hours being used -50 to 120 ^° C., preferably 20 to 90 ^° C., with at least 0.2, preferably 0.7 to 4, mol of dialkyl sulfite per g atom of magnesium In general, more dialkyl sulfite and a treatment time of more than 20 hours are of no use Advantages: The treatment time is usually between half an hour and 5 hours preferably holds an amount of the solid reaction product corresponding to 0.2 to 2 g atom of magnesium per liter. The alkyl groups in the dialkyl sulfite can be different, but they are preferably identical to one another and each contain 1 to 6, preferably 2 to 4, carbon atoms.

The titanium-containing solid component of the catalyst is obtained by reacting the aged and dialkyl sulfite-treated solid reaction product (essentially magnesium chloride) with TiCl ₁ C ¹ R ,, where χ assumes a value of 2 to 4, y a value of 0 to 2 and x + y = 4 is obtained. The reaction can without removal of the excess dialkyl sulfite effected, generally, especially when using more than 1 mole of dialkyl sulfite per g-atom of magnesium, but it is better to separate the solid before and z, B ₁ wash with hydrocarbons. The reaction can take place without a diluent, but it is preferred to work in a hydrocarbon suspension. Per g atom of magnesium is 0.5

to 10, preferably 1 to 5, MoI TiCI, ORj, used. The value of. χ is preferably 3 to 4 and that from / 0 to 1. The reaction takes place for 1 to 5 hours at 60 to 140 ^° C. The finished solid component is then removed by decanting, centrifuging or filtering

ίο separated and z. B. washed with hydrocarbons.

The alkoxide groups of the titanium compounds often contain 1 to 8, preferably 2 to 4, carbon atoms. These compounds are generally produced by reacting TiCU with Τ1ΟΓ4 in appropriate molar ratios. This means that any value of χ or y can be achieved. The values of χ and y are to be understood as average values of the total titanium component, so that fractions are also meant, not just TiCl ₄ , TiCl ₃ OR, TiCl ₂ OR ₂ , but also z. B-TiCI ₃ JORo ^ TiCl ₂₃ OR ,,, etc.

To activate the solid component, aluminum alkyls or reaction products of dialkyl aluminum hydrides are used used with diolefins with 4 to 20 carbon atoms The aluminum alkyls can each contain a hydrogen or a chlorine atom, but aluminum trialkyls are preferred. in the In general, the alkylresia have a chain length of 1 to 20, in particular 1 to 10, preferably 2 to 4.

Examples of alkyl groups are ethyl, propyl, isopropyl. Butyl, isobutyl, octya and dodecyl. For the preparation of the reaction products from dialkyl aluminum hydrides and diolefins isoprene is preferred. The use of aluminum triethyl is particularly advantageous or aluminum triisobutyl.

The aluminum component is mostly used in large excess, based on titanium in the solid, e.g. B. in a molar ratio of titanium to aluminum component of 1:10 to ί: 1000, preferably 1:20 to 1: 500. Can be reacted before the polymerization with the solid component in a hydrocarbon slurry at 0 to 100 ⁰ C, or both components be metered separately into the polymerization reactor, the Aiuminiumalkyl completely or partially.

The polymerization itself can be carried out in a known manner, continuously or discontinuously, in one or more stages be performed. The process is carried out at temperatures from 60 to 100 ° C. and at pressures from 8 to 40 Atmospheres. The molecular weight is generally regulated by adding hydrogen. In the case of the catalyst system according to the invention, this water regulation can be carried out particularly easily. the Pressure data are to be understood as total pressure data,

consisting of partial pressures of ethylene and hydrogen. The hydrogen partial pressure can be up to Make up 75% of the total pressure, but also be zero, the ethylene partial pressure corresponding to at least 25% until 100%. To influence the physical properties of polyethylene, especially for To increase the resistance to stress corrosion cracking, other α-olefins with 3 to 6 Add carbon atoms in amounts of up to 10 mol%, based on ethylene.

The polymerization in several stages is carried out in the batchwise procedure so that one the reaction conditions during the polymerization, in particular the composition of the gas phase,

gradually changes.

In continuous polymerization, for example, the hydrogen partial pressure in a polymerization reactor can be periodically changed in the manner of a square or sawtooth oscillation with a frequency in the order of magnitude of the average residence time, or the polymerization suspension can be run successively through two or more reactors with different reaction conditions permit. It is preferred to use two reactors with different hydrogen partial pressures, it being advantageous to use a solid as catalyst which was produced with TiCl ₄ . Particularly good results are achieved when the hydrogen partial pressure in the first reactor is at least five times as high as in the second. In this way it is possible to produce medium and high molecular weight polyethylene with very good processing properties.

When copolymerizing with other α-olefins is it is advantageous to add this only in the second stage or in the second reactor.

The process according to the invention gives polyethylenes in high yields, based on the amount used Magnesium, and with very good grain size distributions (no dust content). It's high density, shows good Processing properties, has a low ash content and leads to highly rigid products with good Impact strength and good thermal stability

Referred to in the examples melt index was determined according to DIN 53 735 at 190 ⁰ C and 5 kgf load of the flow factor is the quotient of the melt indices at 21.6 and 5 kp load.

example 1

A 1 liter three-necked flask equipped with a stirrer, dropping funnel and reflux condenser is charged with 12.2 g of magnesium, 90 ml of allyl chloride and 0.1 g of iodine. 150 ml of diethyl ether are added dropwise in 40 minutes with stirring (200 rpm) and gentle heating into the vessel which has been rinsed with ultrapure nitrogen. After 10 to 15 minutes, the reaction begins and the reaction mixture begins to boil. After the dropwise addition, the mixture is stirred at reflux temperature for a further 4 hours. The mixture is then made up to 500 ml with benzene and the mixture is stirred under reflux for a further 70 hours. 50 of the suspension, the solid is washed by repeated decantation and slurrying with isooctane at 70 ⁰ C ml. Finally, the suspension with isooctane is returned to 50 ml and treated with 2.5 ml Diäthylsulfit one hour at 70 ⁰ C. Subsequently 273 ml of titanium tetrachloride are added dropwise and the mixture for 2 hours at 95 ° C stirring. The solid is washed out again by decanting and slurrying at 95 ° C. and then suspended in 150 ml of isooctane.

The polymerization takes place in a 1 liter glass autoclave with 0.5 ml of solid suspension and 1 ml of aluminum triethyl in 700 ml of isooctane at 85 ° C., 6 ata H ₂ , 4 ata C2H4. After 1.5 hours, 134 g of uniformly granular polyethylene are obtained. The yield corresponds to 208 g per mg of titanium used. The polyethylene has a melt index of 26, the proportion of particles below 100 μm is 0.2%.

Example 2

50 ml of the solid suspension prepared in Example 1 and aged be treated in the manner described therein initially at 2O ⁰ C and then at 95 ⁰ C with isooctane to remove the ether, allyl chloride, Dialllyl and benzene, to at most 0.1% of the original liquid phase are present. Then 10 ml of diethyl sulfite are added to the 50 ml suspension, the mixture is stirred for one hour at 95 ° C. and the excess diethyl sulfite is removed at the same temperature by repeated decanting and slurrying with isooctane treated with titanium tetrachloride, but 5 hours at

is stirred in 95 ° C. Finally, as described washed out and made up to 150 ml

The polymerization takes place in a 5 liter autoclave with t ml of solid suspension, 5 ml of aluminum triethyl in 3.5 1 of isooctane. Polymerization is first carried out for 50 minutes at 7 ata H2 and 3 ata C2H4, then for 10 minutes at 0.05 ata H ₂ and 9.95 ata C ₂ H ₄ . 720 g of a coarse-grained polyethylene are obtained. The yield corresponds to 206 g per mg of titanium used. 95% of the polyethylene has a grain size between 0.5 and 0.6 m <r>, the melt index is 0.3, the flow factor 22.

Example 3

The solids production takes place including the treatment with diethyl sulfite as in the example! described, only 5 ml of diethyl sulfite are now used instead of 2.5 ml and the excess diethyl sulfite is removed as described in Example 2. 14 ml of titanium tetra-n-propoxide are added to the 50 ml suspension. After one hour stirring at 70 ⁰ C 16.5 ml of titanium tetrachloride are added dropwise and I hour at 7O ⁰ C further stirred Then, as washed in Example 1 and brought ml, the volume of the suspension to 150

The polymerization is carried out as in Example 1, but at 7 ata H ₂ and 3 ata C ₂ H ₄ . 221 g of uniformly fine-grained polyethylene, corresponding to a yield of 192 g per mg of titanium used, are obtained. The melt index is 19.

If the experiment is carried out under otherwise identical conditions, but with titanium tetraisopropoxide, then no 81 g of uniformly coarse-grained polyethylene with a melt index of 17.

Example 4

The solid preparation is carried out as only that the treatment with Diäthylsulfit 1 hour at 70 ⁰ C and the reaction with titanium tetrachloride is carried out for 3 hours at 70 ⁰ C in Example 2.

The polymerization is carried out in 2 stages in a 5 liter autoclave with 1 ml of solid suspension, 5 ml of aluminum triethyl in 3.51 of isooctane with the addition of 13 g of 1-butene. First stage: 50 minutes at 6.5 ata H ₂ , 3 /. a! a C ₂ H ₄ . Second stage: 14 minutes at 0.05 ata H ₂ , 9.95 ata C ₂ H ₄ . 1.116 g of polyethylene, corresponding to 320 g per mg of Ti, are obtained. The Sdimelzinciex is 0.43, the flow factor 23.

It is already known. Polymerization catalysts for «-olefins, their carrier on magnesium

fen (oxide) are based on the preparation of the catalyst, apart from the transition metal component, with inorganic or organic halogen compounds has been reacted. For example, see Derwent CPI 1974, Referat I518V-A (for BE-PS

ii 8 02 016) and Derwent CPI 1975, Referat 87926V / 51 (for JP-OS Sho 49-86481). However, the catalysts prepared accordingly did not show satisfactory activities and resulted, for. Part moreover

Polymers with unsatisfactory properties (cf. the activities given there are calculated

Table I and comparative experiment A). according to the formula:

Activity =

manufactured polyethylene (g)

Polymerization time (h) · transition metal used (mg) ■ partial pressure CjI Ij (bar) Table I.

example Monomer Polyni. activity Temp. inventive 1 Ethylene 85 ( 34.7 according to 3 the same 85 C 42.7 2 the same 85 C 49.0 4th the same 85 C 61.2 BL-: 8 02 016 I. Ethylene 90 C 2.0 Il the same 90 C 12.1 !!! ίΐρςρΐ 90 ( 2.3 IV the same 90 C 2.7 V the same 90 C " 5.0 Vl the same 90 C 9.7 VI the same 90 C 12.2 VIII the same 90 C " 2.8 IX the same 90 C 5.9 X the same 90 C 10.4 Xl the same 90 C 2.5 XII the same 70 '■ 2.0

Comparative experiment A
to Derwent Report CPI 1975. Ref. 87 926 V / 51

a) Preparation of the catalyst

4 g of magnesium were 1 hour at 150'C im Vacuum dried, then stirred with 23.6 g SiCU, 460 g of ethanol are added dropwise in 10 minutes and then a further 50 ml Ethanol mixed. The mixture was then refluxed for 3 hours, at 50 ml Hexane added and freed from the solvent '. The resulting white powder became at 1 hour

130 ° C. reacted with 50 ml of TiCl ₄ and then washed with hexane.

2. Preparation of the catalyst as above, but with the difference that after the addition of the Mg / SiCl mixture of this with ethanol distilled off again and the residue was maintained for 3 hours at 180 ⁰ C.

b) polymerization

The polymerization was carried out in 700 ml of isooctane at 85 ° C. and 10 bar total pressure with the addition of 1 ml Aluminum alkyl as carried out in the process according to the invention.

Table II AlR; H ₃ Time yield activity Schütt Fine Kji. onee., et / tes density proportion of Ti " (ban (Hi (G) (g / l) <100 -ι in
Wt% img) AlEt ₅ 4th 1.5 158 4.3 245 23 1 4.1 Bl (iBut); 4th 0.5 6th 0.5 - - 4.1 AlEt ₃ 4th 1.5 202 5.2 285 25th 2 4.3 AIEt ₃ 5 1.5 200 6.2 290 26th 4.3 Al-isopr. 4th 1.5 185 4.8 250 36 4.3 AKiBUt) ₃ 4th 1.5 9 0.7 - - 4.3

In addition to the consistently significantly lower activity of the catalyst, it had to be found that according to the said document produced polyethylene had completely unsatisfactory properties.

Claims (2)

Patent claims: 1. Process for the production of polyethylene by continuous or discontinuous, single or multi-stage polymerization of ethylene, optionally together with up to 10 mol% of α-olefins with 3 to 6 carbon atoms, in hydrocarbons as a dispersant at DrOkken from 8 to 40 atmospheres and temperatures of 60 to 100 ^° C., optionally in the presence of hydrogen, using a catalyst which is activated from one with aluminum alkyls or reaction products of dialkyl aluminum hydrides with diolefins having 4 to 20 carbon atoms. Titanium, magnesium and chlorine-containing solid, which has been obtained by reacting metallic magnesium with a halogen-containing compound and a further compound and subsequent reaction of the carrier thus obtained with a chlorine-containing Ti (IV) compound, characterized in that the solid is in such a way has been prepared by metalliscnes magnesium with at least 2 moles of allyl chloride and 1.75 to 3 moles per g-atom of magnesium dialkyl ether at 30 converted to 100 ⁰ C, the solid formed is aged for at least 24 hours at 30 to 140 ⁰ C, the separated before or after aging the reaction mixture after a solid made at -50 to 120 ⁰ C treatment with at least 0.2 moles per gram atom of magnesium dialkyl sulfite with 0.5 to 10 moles of TiCl _{1 n} oR where R is an alkyl radical, Af has a value of 2 to 4, y assumes a value of 0 to 2 and x + y = 4, ^{reacted per g atom of magnesium for 1 to 5 hours at 60 to 140 °} C. and the F has separated est material from the reaction mixture. 2. The method according to claim 1, characterized in that the solid with titanium tetrachloride produced and the polymerization carried out in two stages at different hydrogen partial pressures will.