Method for high pressure polymerization of ethylene
In a process for the polymerization of ethylene and optionally further monomers in a high-pressure reactor at from 120 to 350° C. and pressures of from 1000 to 4000 bar, hydrogen is intermittently introduced into the reactor.
1. A process for the polymerization of ethylene and optionally further monomers in a high-pressure reactor at from 120 to 350° C. and pressures of from 1000 to 4000 bar, wherein hydrogen is intermittently introduced into the reactor.
2. A process as claimed in claim 1 , wherein the polymerization is carried out in a tubular reactor having a length-to-diameter ratio of >1000:1.
3. A process as claimed in claim 1 , wherein the hydrogen is introduced into the reactor for from 10 seconds to 5 hours and the reactor is subsequently operated without addition of further hydrogen for a period of from 1 to 50 times the time of hydrogen addition.
4. A process as claimed in claim 1 , wherein the concentration of hydrogen, based on the amount of ethylene in the reactor, is in a range from 0.1 to 5000 ppm.
5. A process as claimed in claim 1 , wherein the polymerization is initiated by means of peroxides.
6. A process as claimed in claim 2 , wherein ethylene and optionally further monomers are fed into the reactor at a plurality of points along the tubular reactor.
7. A process as claimed in claim 1 , wherein the pressure in the reactor is from 1800 to 3500 bar.
8. A process as claimed in claim 1 , wherein the polymerization temperature is not above 310° C.
9. A process as claimed in claim 1 , wherein the high-pressure reactor is made of a nickel-containing steel.
10. A process as claimed in claim 1 , wherein the interior walls of the high-pressure reactor are coated with nickel or nickel-containing material.