DE1143331B - Process for the production of high molecular weight polyethylene - Google Patents

Description

It is known, «-olefins at normal pressure or elevated pressure and temperatures between 20 and To polymerize 10OtC in the presence of a suspending agent using catalysts, the reaction of metal compounds of IV. to VI. Subgroup of the periodic system with organometallic compounds of II. and III. Subgroup of the periodic system (Belgian patents 533 362 and 534 792, "Angewandte Chemie" 67 [1955], pp. 541 to 547). That also uses low-valent vanadium chlorides together with aluminum trialkyls as catalysts be körinen, is from Belgian patent 543 259 known. The products obtained during the polymerization have their molecular weight and structure, depending on the production conditions and their properties are not homogeneous and of different value.

A process for the production of high molecular weight polyethylene has now been found in which ethylene is at temperatures between 20 and 150 ° C, preferably between 20 and 100 ° C, and pressures between 1 and 100 kg / cm ² in the presence of catalysts made from mixtures of chlorides of the vanadium of lower valency and aluminum trialkylene is polymerized and which is characterized in that vanadium oxide dichloride is used as the chloride of the vanadium of lower valency. In this way, polyethylene is obtained with a straight-chain structure, high tear strength and low elongation. Such polyethylenes also contain only a few double bonds. The molecular weight of such products is very high and mostly exceeds 1,500,000.

For the polymerization ^,! as mentioned, vanadium oxide dichloride is used. The production of this connection, for which no protection is sought, is advantageous for. B. by reducing vanadium oxytrichloride, dissolved in a hydrocarbon, with an organometallic compound. A dark purple to black, fine precipitate is formed. The vanadium oxydichloride precipitate, which has been carefully washed out repeatedly, suspended in an oxygen-free, hydrogenated hydrocarbon, is one component of the catalyst system.

Aluminum trialkyls serve as a further component. Aluminum compounds whose hydrocarbon chains have a maximum of about 20 carbon atoms, preferably up to about 10 carbon atoms per chain, can advantageously be used as aluminum trialkyls. The chain lengths of the hydrocarbons can have the same or different carbon numbers, furthermore processes for production
of high molecular weight polyethylene

Applicant:

Ruhrchemie Aktiengesellschaft,
Oberhausen (Rhld.) - Holten

. Dr. Otto Liethen, Duisburg-Beeck,

and Dr. Walter Rottig, Oberhausen (Rhld.) - Sterkrade, have been named as inventors

'They can have a straight or branched structure. '■'

The concentration of the catalyst during the polymerization can be relatively very low being held. It is sufficient if the concentration of both catalyst components is less than 0.02 mol / Liters of suspension liquid. Very good results are already with 0.01 mol / liter suspension liquid achieved.

Hydrocarbons are used as suspension liquid, z. B. pure and / or substituted and / or partially hydrogenated aromatics, naphthens, in particular however, aliphatic hydrocarbons (branched and / or straight-chain), which have been expediently carried out beforehand .a hydrating treatment and drying to a large extent are freed of oxygen, oxygen-containing compounds and moisture.

The polymerization is carried out at pressures between 1 and 100 kg / cm ² and at temperatures between 20 and 150.degree. C., preferably between 20 and 100.degree.

It was also found that in one

Molar ratio of vanadium oxide dichloride to aluminum trialkyl of 1: 1 and higher, the polymer yields remain practically the same, while with an excess of vanadium oxide dichloride over the aluminum trialkyl compound, the yields of polyethylene increase with increasing amount of aluminum trialkyl. If one uses instead of VOCI ₂ z. B. VOC1 _? so poses

it is found that, _{surprisingly, with increasing VOCl 3} excess, the conversion falls very sharply.

309 508/294

Polyethylenes obtained according to the procedure of the invention have an ultimate tensile strength at 120 ° C of about 400 kg / cm ^2, elongation values at 120 ⁰ C 550 to 730% and ZST values at 150 ° C, the 9000 to 14,000 g / cm ² lie. (The ZST values at 150 ° C denote the flow behavior of a thread in glycerine, given in g / cm ^2. )

If one now compares the polymers of the catalyst composition according to the invention with those the z. B. using titanium trichloride and aluminum trialkyl, so one provides established that, according to the invention, polymers with significantly higher molecular weights, ZST and tear strength values and much lower elongations can be obtained.

example

A clean and dry 5-1 glass comes with a Aluminum lid sealed airtight. The lid contained a stirrer, a thermometer connector, a gas inlet pipe and a discharge pipe.

After the air has been displaced from the reaction vessel with pure nitrogen or pure ethylene, 1.81 dry, hydrogenated hydrocarbons (diesel oil with a boiling point of 110 to 190 ° C or tetramerized Propylene) is filled in while passing a weak stream of ethylene and the hydrocarbon heated to 70 ° C by irradiation.

Now the aluminum trialkyl and then the vanadium oxydichloride were first suspended in a little Diesel oil, added. The reaction vessel was closed and the ethylene gas flow regulated so that a certain amount of exhaust gas was present. The reaction temperature was determined by air cooling or kept at 70 ° C by blasting. One observed the formation of polyethylene. After a certain reaction time, the attempt was stopped The polymer formed is suctioned off and the filter residue with a 2% hydrochloric acid-propanol solution Boiled under reflux for 1 hour.

After filtration and washing out of the filter residue with a water-alcohol mixture (10%) Alcohol), the polymer was dried at an elevated temperature in vacuo. For the way of working No protection is sought for cleaning the polymers.

The vanadium oxydichloride was obtained in the following way: When 6.93 g of vanadium oxytrichloride were reacted with 4.56 g of aluminum triethyl (molar ratio 1: 1) in 400 cm ^{3 of} a hydrogenated, oxygen-free diesel oil, a dark, violet to black, fine precipitate of Vanadium oxide dichloride, which was filtered after a formation time of 20 hours, ^{washed five times with 100 cm 3 of} diesel oil each time and taken up in 200 cm of diesel oil.

The titanium trichloride was obtained in a similar manner from 8.3 g of titanium tetrachloride and 5 g of aluminum triethyl (Molar ratio 1: 1). The following table shows the results of the tests:

Diesel oil (liter)

Tetramer propylene (liter)

VOCl ₂ (g)

Al (iC ₄ H ₉ ) ₃ (g)

A1 (C ₂ H ₅ ) ₃ (g)

Ti: Al

V: Al

d reaction temperature (° C)

Response time (minutes)

Intake of C ₂ H ₄ (liters)

Response time (minutes)

Intake of C ₂ H ₄ (liters)

Yield (g)

Molecular weight (Mv · ΙΟ " ³ ) *

% Ash in the crude product

% Ash after treatment

Mechanical properties Tensile strength: ff _Ä (120 ° C, in kg / cm ² ) **

Elongation at the point of rupture: δ 120 °

Flow properties: ZST 150 ° (g / cm ² )

Double bonds: ε · c

(RHC = CH ₂ ) ***

Branching: ε ■ c (-CH ₃ )

1.8

0.41

0.305 1:

70 300 446 360 483 558 750

230

850

2000

0.075 1.0

1.8

0.371 0.534

1: 1

70

300

295

333 1650 0.11 0.009

400

676

9500

0.034 0.61 1.8

0.371
1.068

1: 2

70

300

309

360

339

388

1800

0.125

0.010

416

732
12200

0.029
0.76

1.8

0.371
1.6

1: 3

300

295

343
1500
0.18
0.003

657
13500

0.03
0.61

1.8

0.742 0.534

2: 1 70 300 432 360 469 543

1500

0.11

0.003

550

0.032 0.74

* Mv = viscometrically determined molecular weight of a solution of the polymer in decahydronaphthalene at ** cr _Ä : See K. Frank "Examination book for rubber and plastics" 1955, p. 64. *** e ■ c = product of extinction coefficient e and concentration c , determined by infrared spectral analysis.

1.8

0.958 0.534

2.58: I 70 300 464

525 1550 0.15 0.0145

411

9000

0.033 0.76

135 ° C.

Claims (3)

Patent claims: 1. A process for the production of high molecular weight polyethylene by polymerization of ethylene at temperatures between 20 and 150 ° C, preferably between 20 and 100 ° C, and pressures between 1 and 100 kg / cm ² in the presence of catalysts made from mixtures of chlorides of the Vanadium of lower valency exist with aluminum trialkyls, characterized in that vanadium oxide dichloride is used as the chloride of vanadium of lower valency. 2. The method according to claim 1, characterized in that the catalysts used are vanadium oxydichloride and aluminum trialkyls used in a molar ratio of at least 1: 1. 3. The method according to claim 1 or 2, characterized in that the two catalyst components are used in a concentration that together is less than 0.02 mol / liter of suspension liquid, is preferably less than 0.01 mol / liter of suspension liquid. Considered publications:
Opened documents of Belgian patent No. 543 259. ι 309 508/294 1.63