| 摘要 |
1. A process for the continuous preparation of propylene-ethylene block copolymers, in which, in an agitated fixed bed comprising small polymer particles, in each case in the presence of hydrogen as a molecular weight regulator and in the absence of a liquid reaction medium, first (I) propylene is homopolymerized, from the gas phase, in a first polymerization zone, by feeding in a Ziegler-Natta catalyst comprising (1) a titanium (III) component and (2) a dialkyl-aluminum chloride component, with or without (3) a further catalyst component, and then (II) the product obtained in the first polymerization zone is fed, with or without additional catalyst components (1) and/or (2) and/or (3), into a second polymerization zone, where a mixture of propylene and ethylene is polymerized with the propylene homopolymer present in the product from the first polymerization zone, with the proviso that the overall atomic ratio of titanium from the titanium (III) component (1) to aluminum from the dialkyl-aluminum chloride component (2) is from 1:2 to 1:15, wherein a) in the first polymerization zone, the reaction is carried out under a total pressure of from 25 to 40 bar and at from 70 to 100 degrees C, with the proviso that the ratio of the partial pressure of propylene to that of hydrogen (P/H-I) is from 100:0.1 to 100:15, b) in the second polymerization zone, the reaction is carried out under a total pressure from 22 to 34 bar and at from 63 to 83 degrees C, whit the provisos that (i) the ratio of the partial pressure of propylene to that of ethylene is from 100:10 to 100:70, and (ii) the ratio of the partial pressure of propylene to that of hydrogen (P/H-II) is from 100:5 to 100:50, c) the total pressure in the first polymerization zone is kept not less than 5 bar higher that that in the second polymerization zone, d) the relationship between the ratio partial pressure of propylene partial pressure of hydrogen in the fist polymerization zone (P/H-I) and the ratio partial pressure of propylene partial pressure of hydrogen in the second polymerization zone (P/H-II) is set so that the ratio P/H-I:P/H-II is from 0.6 to 1400, and e) the weight ratio of propylene converted to polymer in the first polymerization zone to propylene/ethylene mixture converted to polymer in the second polymerization zone is from 100:40 to 100:15. |
