| 摘要 |
Copolymers of propylene with 1-alkenes, obtainable by two-step polymerisation from the gas phase in an agitated fixed bed by means of a Ziegler-Natta catalyst system containing, as cocatalysts, an aluminium compound and an organosilicon compound in addition to a supported titanium-containing solids component, where a) in the first polymerisation step, propylene is polymerised together with a further alk-1-ene in the presence of hydrogen at a pressure of from 15 to 40 bar, a temperature of from 60 to 90@C and a mean residence time of the reaction mixture of from 0.7 to 5 hours, and the ratio between the partial pressure of the propylene and the partial pressure of the further alk-1-ene is in this case set at from 10:1 to 500:1, and the ratio between the partial pressure of the propylene and the partial pressure of the hydrogen is set at from 30:1 to 180:1, and subsequently b) in a second polymerisation step, propylene and a further alk-1-ene are polymerised onto the polymer obtained from the first polymerisation step in the presence of hydrogen at a pressure of from 5 to 25 bar, where this pressure is at least 3 bar below the pressure in the first polymerisation step, a temperature of from 40 to 90@C and a mean residence time of the reaction mixture of from 0.7 to 5 hours, where the ratio between the partial pressure of propylene and the partial pressure of the further alk-1-ene is set at from 0.3:1 to 10:1, the ratio between the partial pressure of propylene and the partial pressure of hydrogen is set at from 4:1 to 1:1, and the weight ratio between the monomers reacted in the first and second polymerisation steps is set at from 0.5:1 to 20:1. |
