| 摘要 |
Ethylene is continuously polymerized with the aid of a Ziegler catalyst in two polymerization zones, the polyethylene formed in the first zone together with the catalyst being passed to the second zone wherein ethylene is polymerized with the catalyst from the first zone. The polyethylene prepared in the first zone has an intrinsic viscosity between 0.4 and 2, whilst the polyethylene prepared in the second zone has an intrinsic viscosity between 3 and 20. The product recovered from zone two comprises an admixture of these polyethylenes. The relative amounts of polyethylene formed in the two zones is such that the product has a flow parameter, A.S.T.M. 1238/57T, in the range of 1.4 to 2.5. If desired, polyethylene of I.V. 3-20 may be formed in the first zone and polyethylene of 0.4 to 2 in the second zone. In a modification, ethylene may be polymerized in one or both zones, in the presence of a minor proportion of propylene, or butene-1, i.e. a copolymer being formed containing up to 10% by weight of propylene or butene-1. A molecular weight modifier, e.g. hydrogen, may be used in either of the zones. The exemplified catalyst is gamma TiCl3 and AlEt2Cl. The polymerization is preferably carried out in an inert diluent, and effected continuously. |
