Multi-stage process for producing polyethylene
US5326835A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 20, 1992 |
| Grant date | Jul 5, 1994 |
| Priority date | — |
| Expiry date | Aug 20, 2012 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S526/905
- WIPO fieldMacromolecular chemistry, polymers
- WIPO sectorChemistry
Abstract
The invention concerns a multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in the presence of an ethylene polymerizing catalyst system in a multistep reaction sequence, in which the first reaction step is a liquid phase polymerization step and the second reaction step is formed by one or more gas-phase polymerization steps. According to the process of the invention in the first reaction step ethylene is polymerized in a loop reactor (10) in an inert low-boiling hydrocarbon medium the residence time being at least 10 minutes, reaction mixture is discharged from the loop reactor (10) and at least a substantial part of the inert hydrocarbon mixture is separated and the polymer is transferred into one or more gas-phase reactors (30), where the polymerization is completed in the presence of ethylene and optionally hydrogen and a comonomer. As an inert hydrocarbon medium in the loop reactor (10) propane can be used and the polymerization can be carried out also so that the mixture of inert hydrocarbon, monomer, hydrogen and optional comonomer is under supercritical conditions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.