DE3345785A1 - Process for the preparation of polyethylene - Google Patents

Abstract

High-molecular-weight polyethylene is obtained with the aid of a catalyst comprising a) a zero-valent nickel compound and b) an adduct or mixture of a quinoid compound and a tertiary phosphine if the solvent used is one or more aliphatic hydrocarbons having a boiling point of between 60 and 150 DEG C.

Description

Process for the production of polyethylene

The invention relates to a process for the production of high molecular weight Polyethylene with the help of a nickel catalyst in special solvents.

From the German Offenlegungsschrift 29 23 206 it is known that ethylene to waxy polymers with the aid of a catalyst consisting of a) a zero-valent Nickel compound and b) an adduct and / or mixture of a quinoid compound and a tertiary phosphine in a mixed solvent of an aromatic To polymerize hydrocarbon and a hydroxyl group-containing solvent.

According to this prior art, the solvent has a great influence on the reaction process; only one of the solvent components is used alone, the catalyst is not active or has very little activity.

High molecular weight polyethylene (intrinsic viscosity in tetralin at 1400C > 0.8 dl / g) cannot be obtained in this way.

The object of the present invention is, with the help of the above described, easily accessible catalyst to high molecular weight polyethylene produce.

It has now been found, surprisingly, that this task can be carried out by others Solvent as the previously known solvent combination can be dissolved.

The invention therefore relates to a process for the production of high molecular weight Polyethylene consisting of the polymerization of ethylene with the aid of a catalyst of a-) a zero-valent nickel compound and b) an adduct and / or mixture from a quinoid compound and a tertiary phosphine, which is characterized is that the solvent is one or more: aliphatic hydrocarbons with a boiling point between 60 and 1500C used.

Suitable zero valent nickel compounds, quinoid compounds and tertiary phosphines can be found in the above-mentioned laid-open specification, the disclosure of which is hereby declared to be part of this description.

The polymerization is preferably at 60 to 16 (40C and 5 to 200 bar ethylene pressure carried out.

The boiling points of the aliphatic hydrocarbons are not critical and are only practical limits. The solvents can low Contain proportions of other solvents, for example get into the reaction mixture through the catalyst production. It is this however, no hydroxyl-containing solvents, so that the method is preferred is carried out in the absence of hydroxyl-containing solvents.

A preferred zero valent nickel compound is bis (cyclooctadiene) nickel (O). A preferred component B is an adduct or mixture of triphenylphosphine and p-benzoquinone used.

The polymerization can either be continuous or batchwise be performed.

The amount of nickel compound used is not critical. Typical Catalyst concentrations are between Ao 2 to 10 4 mol per liter. The amount of catalyst, based on ethylene, is in the range from 0.005 to 10 percent by weight, preferably 0.01 to 1 percent by weight.

For the polymerization of ethylene with the catalysts of the invention The following procedures are suitable: a) Submitting the solid, dissolved or suspended Catalyst (or its components), addition of ethylene; then heat up.

b) Submission of the ethylene, injection of the catalyst solution or suspension (or its components).

c) Continuous metering of the catalyst solution or suspension (or its components) under given desired polymerization conditions (Pressure, temperature) to ethylene.

Example The catalyst according to the invention from 2 mmol bis-cyclooctadiene-nickel- (O) and from 2 mmol of the triphenylphosphine p-benzoquinone adduct in 50 ml of toluene injected into the prepared autoclave, which contains 1 1 solvent. After 1 up to 3 hours of polymerization at an ethylene pressure of 100 bar, allowed to cool, The pressure in the autoclave is released and the solid polyethylene is isolated by filtration. That The filtrate is examined by gas chromatography. After removing the solvent The amount of oligomers can be weighed out in the rotary evaporator. The low-boiling ones The proportions are therefore in the given yields (sum of polymers and oligomers) or the calculated activities (mol converted ethene per mol nickel) are not taken into account.

The following table shows the reaction conditions and results refer to. The meanings are: A) type of solvent B) temperature / õC7 C) polyethylene yield (Percentage of oligomers) D) catalyst activity (mol ethene per mol Ni) E) Polyethylene melting point / õC7 F) Limiting viscosity tbin tetralin at 140 "C / dl / g7 G) Density 8 / g / cm37 Table Example A B C D E F G 1 Cyclo- 92-84 305 (0) 5446 135 3.40 0.970 hexane 2 n-hexane 100-101 123 (o) 2196 133 3.14 0.976

Claims (3)

Claims Process for the production of high molecular weight polyethylene by polymerization of ethylene with the help of a catalyst, consisting of a) a zero valent nickel compound and b) an adduct and / or mixture of a quinoid compound and a tertiary phosphine, characterized in that one as a solvent, one or more aliphatic hydrocarbons with a boiling point used between 60 and 150 ° C. 2. The method according to claim 1, characterized in that the catalyst from a) bis (cyclooctadiene) nickel (O) and b) an adduct or mixture of triphenylphosphine and p-benzoquinone. 3. The method according to claim 1, characterized in that the catalyst concentration 10 2 to 10 4 mol per liter and the amount of catalyst, based on ethylene, 0.005 to 10% by weight.