A method of producing polyethylene

 

(57) Abstract:

Describes a method of producing polyethylene by polymerization of ethylene at elevated temperature and pressure in the presence of a catalyst consisting of zirconocene and socializaton - methylalumoxane. The polymerization of ethylene is carried out at a temperature of 120 - 140oC, a pressure of 4 to 8 bar in the presence of a catalyst containing as zirconocene a compound selected from the group including rat-dimethylsilane-bis-1-(2-methyl-4-phenylindane)-zirconiabased, rat-dimethylsilane-bis-1-(2-metalcrafter)zirconiated, rat-dimethylsilane-bis-1-(2-methyl-4,5-benzhydryl)zirconiated. The technical result - obtaining polyethylene at high temperatures with high molecular weight. table 1.

The present invention relates to a method for production of polyethylene at high temperatures.

Known methods for producing polyolefins using homogeneous catalytic systems consisting of a component of the transition metal type metallocene and component socializaton, for example, oligomeric aluminum compounds of the type alumoxane that at high activity give polymers and copolymers with narrow molecular the temperature using soluble metallocene was previously described in the patent Germany 31 50 270 at pressures above 100 bar and later described in EP 260 999 at pressures above 500 bar of ethylene. When polymerization within a few minutes form the polyethylene is low density. Still described catalysts, however, in the polymerization of ethylene at low pressure at temperatures above 100oC give polymers with low molecular weights.

This disadvantage has tried to eliminate, according to EP 303 519, by adding silicon compounds, however, strongly reduced activity of the polymerization.

According to EP 416 815, metallocene with special ligands used in the field of higher temperatures. However, above 100oC are formed polymers or copolymers with a broad molecular weight distribution with Mw/Mnmore than 3.

It is known that with increasing partial pressure, i.e. with the increase of monomer concentration increases the molecular weight of the resulting polymers. With this method, however, by increasing the monomer pressure up to 2000 bar can be increased molecular weight, however, the high pressure process requires a high financial cost.

In addition, for example, from the patent Germany 3 808 267 it is known that due to the use of guarracino it is possible to achieve high molecular weights. However, we have observed pony is ity of guarracino.

There is also known a method of producing polyolefins by polymerization or copolymerization of olefins at a temperature from -60oC to 200oC and a pressure of 0.5 to 100 bar, in the presence of a catalyst comprising at least one metallocene and at least one socializaton (EP 0 545 303 AI, 09.06.93). However, in the known method is also not achieved a high molecular weight of the obtained polymers.

The present invention is to develop a method which is carried out at temperatures above 100oC and in which there are no disadvantages of the prior art. Unexpectedly shown that this problem can be solved by using a specific metallocene catalyst systems.

The invention relates to a method for producing polyethylene by polymerization of ethylene at elevated temperature and pressure in the presence of a catalyst consisting of zirconocene and socializaton - methylalumoxane, while the polymerization of ethylene is carried out at a temperature of 100-150oC, a pressure of 4-8 bar in the presence of a catalyst containing as zirconocene a compound selected from the group including rat-dimethylsilane - bis-1-(2-methyl-4-phenylindane)zirconiated, rat )zirconiated.

Acetalization used according to the invention the catalyst is preferably alumoxane or other alyuminiiorganicheskikh connection. Alumoxanes preferably is a compound of formula (IIa) linear and/or formula (IIb) cyclic type:

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R represents C1-C6alkyl group, preferably methyl, ethyl, n-butyl or isobutyl, in particular methyl or butyl; and p represents an integer 4-30, preferably 10-25, and the residues R may be different. Especially preferred methylalumoxane and methylbutylamine with a ratio of methyl: butyl= 100:1 to 1:1, and butyl may represent n-butyl, isobutyl or a mixture of n-butyl/isobutyl, and the remnants have any, preferably statistical distribution.

Alumoxane may also have a three-dimensional structure [J. Am. Chem. Soc. 1993, 115, 4971-4984].

Alumoxane can be obtained in different ways.

One possibility is a gradual addition of water to dilute the solution trialkylamine or mixtures of different trialkylaluminium compounds, and the solution trialkylamine, preferably trimethylaluminum, enter into interaction with small portions of water. This exercise presumes when interacting insoluble alumoxane can be used as socializaton.

Another possibility of obtaining alumoxane on the media is that the media in inert conditions are suspended in a solution of at least one alkylamine and this suspension hydrolyzing with water.

In another method, a powder pentahydrate of copper sulfate suspended in toluene in a glass flask in an atmosphere of inert gas at about -20oC is mixed with so many trialkylamine that for every 4 atoms of aluminium accounted for approximately 1 mol CuSO45H2O. After slow hydrolysis with elimination of alkane, the reaction mixture was incubated for 24-48 h at room temperature, and, if necessary, the mixture is cooled so that the temperature did not rise above 30oC. and Then dissolved in toluene alumoxane filtered off from the copper sulfate and the toluene is distilled off in vacuum.

Next alumoxane get by reacting at a temperature of from -10oC to 100oC dissolved in an inert aliphatic or aromatic solvent trialkylamine with containing crystallization water aluminum salts. Preferably using heptane and toluene, as well as aluminum sulfate. At the same time the volume ratio between the solvent and ispolnitelnostj due to the removal of alkane, is 1-200 hours, preferably 10-40 hours

Of the aluminum salts used in particular salts with a high content of water of crystallization. Particularly preferred hydrate of aluminum sulfate, primarily Al2(SO4)318H2O and Al2(SO4)316H2O with a particularly high content of water of crystallization of 16 or 18 mol H2O/mol Al2(SO4)3.

Below is an example of getting methylalumoxane:

37,1 g Al2(SO4)318 H2O [0,056 mol, respectively, 1 mol H2O] are suspended in 250 cm3toluene, mixed with 50 cm3of trimethylaluminum (0.52 mol) and 20oC enter into interaction. After 30 h is approximately 1 mol of methane. Then the solid solution of aluminum sulfate is filtered off. By removing toluene gain of 19.7 g methylalumoxane. The output is 63% of theory. Some cryoscopic in benzene average molecular weight is 1170. The number of [Al(R')-O]-units according to the calculation to be up to 20.2. The average degree of oligomerization, therefore, is about 20.

Another option for obtaining alumoxane is in the interaction, either directly in nagoda solutions alumoxane have variable content of unreacted trialkylamine, Al(R)3that is in free form or in the form of an adduct.

Alumoxane applied either in solution or in suspension of the above-described method of obtaining.

Further suitable alyuminiiorganicheskikh compounds are compounds of the formula AlR21H AlR21Cl, Al2R31Cl and AlR1Cl2where R1represents C1-C6alkyl group, a C1-C6alkyl fluoride group, a C6-C18aryl group, a C6-C18ferrillo group or a hydrogen atom. Examples R1are methyl, ethyl, isopropyl, n-butyl, isobutyl or n-octyl.

Getting used according to the invention the catalyst can be accomplished by interaction of metallocene with alyuminiiorganicheskikh connection in different ways:

1. Alyuminiiorganicheskikh compound in a suitable solvent, such as pentane, hexane, heptane, toluene or dichloromethane, combine together with metallocene at a temperature of from -20oC to +120oC, preferably at 15-40oC, by intensive mixing. The molar ratio of Al:M1in this case is 1: 1 to 10 000:1, preferably 10:1 to 2000:1, and the reaction time is 5-g/DM3in the atmosphere of inert gas.

2. Insoluble or supported on a carrier alumoxane in suspension with a content of 1-40 weight. %, preferably 5-20 wt.% alumoxane, in an aliphatic, inert suspendium agent, as n-decane, hexane, heptane or diesel oil, is injected into the interaction of with a solution of metallocene in an inert solvent like toluene, hexane, heptane, diesel oil or dichloromethane, in a molar ratio of Al:M1=1:1 - 10 000:1, preferably 1:1 to 2000:1, at a temperature of -20oC - +120oC, preferably 15-40oC, during 5-120mm minutes, preferably 10-30 minutes, with vigorous mixing.

Received on p. 2 the catalyst is used either in suspension directly for polymerization, or it is separated by filtration or decantation and washed with an inert suspendium agent as toluene, n-decane, hexane, heptane, diesel oil, dichloromethane. The catalyst can be dried in vacuum and used in powder form or another to add to the polymerization system, together with the solvent, again resuspending in suspension in an inert suspendium agent, such as toluene, hexane, heptane or diesel oil.

As diesel oil m is SS="ptx2">

The catalyst can also be used supported on a carrier form. Application can be made by p. 2 by introducing interaction supported on a carrier of socializaton [for example, alumoxane] nenalezena on the media by metallocenes.

3. By introducing interaction supported on a carrier of metallocene with nenalezena on the media by acetalization [for example, alumoxanes].

4. By introducing into the interaction of the reaction mixture from metallocene and socializaton (for example, alumoxane) with the carrier; or

5. By introducing interaction nenalezena media metallocene with nenalezena on the media by socialization (for example, alumoxanes) in the presence of the media. As a carrier you can use inorganic oxide, preferably silica or polymeric materials.

Prepared according to p. p. 1, 2, 3, 4 or 5, the catalyst can be applied terpolymerization. For terpolymerization preferably used polymerizing olefins.

The polymerisation process is carried out periodically or continuously, in one or several stages. The temperature of polymerization is 100-150oC, preferably 120-150oC.

The total pressure in the polymerization system is 4-8 bar.

Depending on the melting temperature and solubility of the resulting polymer polymerization can be performed in solution or suspension, and the monomer or mixture of monomers or in the gas phase, preferably in solution.

Before addition of the catalyst in the polymerization process additionally, you can add another alkylamino compound, such as trimethylaluminum, triethylaluminum, triisobutylaluminum or isoprenaline, for passivation of a polymerization system in a concentration 1-0,001 mmol of aluminium per kg of the contents of the reactor. Moreover, these compounds can also be used additionally for regulirovanie is at temperatures above 100oC it is possible to obtain polymers with a narrow molecular weight distribution with a relatively high molecular weight.

In addition, in this way we obtain a high efficiency of the polymerization process at temperatures above 100oC, making possible the implementation of the homogeneous polymerization in solution, which compared with the traditional printed on the medium titanium catalysts for obtaining ethylene copolymers leads to a more homogeneous products. Proposed according to the invention catalysts are therefore preferably suitable for the production of LLDPE (linear low-density polyethylene).

Moreover, when copolymerization statistical embedding of co monomer due to colophony metallocene catalysts allows to carry out effective regulation of density in the copolymer, which reduces the consumption of expensive co monomer. The formed products of the fractionation does not show any enrichment of the comonomers in low molecular weight fractions, and show a uniform distribution of the side chains around the region of molecular weight of the copolymer. Thus, also at low densities, see ptx2">

Introduced notation:

CV = coefficient of viscosity, cm3/g; Mw= srednevekovaja molecular mass Mn= Brednikova molecular weight (determined by gel permeation chromatography [digital data in g/mol]), Mw/Mn= polydispersity, engineers 190/5 = melt flow index at 190oand a load of 5 kg according to DIN 53 735, SD = apparent density of the polymer powder, g/DM3.

The melting temperature, crystallization point, their width, and enthalpy of melting and crystallization, and glass transition temperature (Tg) determined by DSC measurements [10oC/min heating rate/cooling].

EXAMPLES

All glass apparatus is heated in a vacuum and rinsed with argon. All operations is carried out with exclusion of moisture and oxygen in the vessels Slanka. Used solvents each time subjected to fresh distilled in an atmosphere of argon over the alloy of Na/K and stored in vessels Slanka in the atmosphere of inert gas.

Synthesis of metallocene - rat.-dimethylsilane-bis-1-(2-methyl - 4-phenylindane)-zirconiabased is carried out according to patent application P 42 21 244.8. Synthesis of metallocene - rat.-dimethylsilane-bis-1- (2-metalcrafter)-zirconiabased the-4,5-benzhydryl)-zirconiabased - carried out according to the patent, the Federal Republic of Germany 41 39 595.

Methylalumoxane available in the form of about 10 wt.%-aqueous solution in toluene by the company Witco GmbH and contains, according to the definition of aluminum, 36 mg Al/ml. The average degree of oligomerization, according to the decrease in the freezing temperature in benzene, is n = 20.

Example 1

The dried reactor with a stirrer with a capacity of 1.5 DM3removal of oxygen is blown with nitrogen and filled with 0.9 DM3inert diesel oil (so Kip. 140 - 170oC). After purging with ethylene and heated to 120oC. in Parallel, the 0.3 mg rat. - dimethylsilane-bis-1,1'-(2-methyl-4-phenyl-indenyl)-zirconiabased dissolved in 10 ml methylalumoxane in toluene (12 mmol of aluminum) and pre-activate within 15 minutes, the Polymerization begins by dispensing a solution of catalyst and the pressure of ethylene is increased to 4 bar. After 1 h time of polymerization in the reactor lower pressure, is cooled and the suspension is released. After filtration and drying for 12 h in a vacuum drying Cabinet obtain 23 g of polyethylene, which corresponds to the estimated output at the contact time of 12 kg/(mmol Zr bar), with an apparent density of 0.205 kg/DM3and KV = 170 cm32

Repeat example 1, and for preparation of a solution of catalyst used 0.5 mg dimethylsilane-bis-1-(2-methyl - acenaphthyl)-zirconiabased. Get 16 grams of polyethylene, which corresponds to the calculated output 4.7 kg/(mmol Zr), with an apparent density of 0.190 kg/DM3and KV = 211 cm3/, Molecular weight distribution (according to GPC) is Mw/Mn= 2.5.

Example 3

Repeat example 1, and for preparation of a solution of catalyst used 0.4 mg rat.-dimethylsilane-bis-1-(2 - methyl-4,5-benzhydryl)zirconiated. Get 19 grams of polyethylene, which corresponds to the calculated output 6.9 kg/ (mmol Zr), with an apparent density = 0.210 kg/DM3and KV = 221 cm3/, Molecular weight distribution (according to GPC) is Mw/Mn= 2.4.

Example 4

Repeat example 1 at 140oC and a pressure of 7 bar of ethylene. After cooling, get a polyethylene, which corresponds to the output of 2.0 kg/(only Zr), with KV = 167 cm3/, Molecular weight distribution (according to GPC) is Mw/Mn= 2.3.

Example 5

The dried reactor with stirrer capacity of 16 DM3removal of oxygen is blown with nitrogen and filled 8 DM3inert the e ethylene up to 8 bar.

Parallel to this, 4 mg rat.-dimethylsilane-bis-1,1'-(2-methyl - 4-phenylindane)-zirconiabased dissolved in 10 ml methylalumoxane in toluene (12 mmol A1) and pre-activate within 15 minutes

Polymerization begins by dispensing a solution of the catalyst through the gateway device and the total pressure is maintained constant by the introduction of additional ethylene. After 0.5 h time of polymerization reaction is stopped with methanol in the reactor lower pressure, is cooled to 20oC and the suspension is released. Ambassador filtering and drying for 12 h in a vacuum drying Cabinet receive 408 g of polymer, which corresponds to the output 16 kg/(mmol Zrap) and KV=180 cm3/, engineers 190/5 is 4.26 deaths g/10 min at a density 0,934 g/cm3.

Comparative example 1

Repeat example 1, and for preparation of a solution of catalyst used 0.4 mg of bis-(n-butylcyclopentadienyl) zirconiated. After removing just a suspending agent get 4 g of polyethylene wax respectively output 0,98 kg/(mmol Zr) with KV=40 cm3/,

Comparative example 2

Repeat the comparative example 1 with 0.4 mg of bis-indenyl - zirconiabased. Get y example 3

Repeat example 2, described in EP 0 646 604 A1, at a temperature of 70oC. Obtained according to comparative example polyethylene, and the polyethylene of example 2 according to the invention were analyzed using IR spectroscopy. The results are shown in the table below.

A method of producing polyethylene by polymerization of ethylene at elevated temperature and pressure in the presence of a catalyst consisting of zirconocene and socializaton - methylalumoxane, characterized in that the polymerization of ethylene is carried out at a temperature of 100 - 150oC, a pressure of 4 to 8 bar in the presence of a catalyst containing as zirconocene a compound selected from the group including rat-dimethylsilane-bis-1-(2-methyl-4-phenylindane)-zirconiabased, rat-dimethylsilane-bis-1-(2-metalcrafter)-zirconiabased, rat-dimethylsilane-bis-1-(2-methyl-4,5-benzhydryl)-zirconiabased.

 

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