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US5326835A
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Multi-stage process for producing polyethylene
Assignee: Borealis Holding AS
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Filing: 1991-12-20
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Granted: 1994-07-05
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Expires: 2011-12-20
Abstract
Abstract PCT No. PCT/FI91/00406 Sec. 371 Date Aug. 20, 1992 Sec. 102(e) Date Aug. 20, 1992 PCT Filed Dec. 20, 1991 PCT Pub. No. WO92/12182 PCT Pub. Date Jul. 23, 1992.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.
Inventors
- 👤 Antero Ahvenainen
- 👤 Kari Sarantila
- 👤 Henrik Andtsjo
- 👤 Jouni Takakarhu
- 👤 Ari Palmroos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:25
CPC Classifications
C; C08; C08F; C08F297/00; C08F297/06; C08F297/08; C08F297/083; B; B01; B01J; B01J19/00; B01J19/24; B01J19/2415; B01J19/2435; B01J8/00; B01J8/18; B01J8/24; C08F110/00; C08F110/02; C08F210/00; C08F210/16; Y; Y02; Y02P; Y02P20/00; Y02P20/50; Y02P20/54; Y10; Y10S; Y10S526/00; Y10S526/905
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
181 words
A multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in a multi-step reaction sequence, in which the first stage is a liquid phase polymerization step and the second step comprises one or more gas phase polymerization steps, said process comprising polymerizing ethylene in the first step in the presence of an ethylene polymerizing catalyst system, hydrogen and optional comonomer in a loop reactor in an inert low boiling hydrocarbon medium during a residence time which is at least 10 minutes and which is sufficiently long to produce polyethylene in an amount of 20-90% based on the total polymer produced in the process, discharging the resulting reaction mixture from the loop reactor, removing hydrogen, unreacted reactants, and the inert hydrocarbon medium from said reaction mixture, transferring the produced polymer from which hydrogen, unreacted reactants and the hydrocarbon medium has been removed into one or more gas phase reactors, and completing the polymerization in the gas phase reactor in the presence of ethylene and optionally hydrogen and comonomer to produce polyethylene having bimodal and/or broad molecular weight distribution.
Claim 2
Dependent Claim
181 words
A multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in a multi-step reaction sequence, in which the first stage is a liquid phase polymerization step and the second step comprises one or more gas phase polymerization steps, said process comprising polymerizing ethylene in the first step in the presence of an ethylene polymerizing catalyst system, hydrogen and optional comonomer in a loop reactor in an inert low boiling hydrocarbon medium during a residence time which is at least 10 minutes and which is sufficiently long to produce polyethylene in an amount of 20-90% based on the total polymer produced in the process, discharging the resulting reaction mixture from the loop reactor, removing hydrogen, unreacted reactants, and the inert hydrocarbon medium from said reaction mixture, transferring the produced polymer from which hydrogen, unreacted reactants and the hydrocarbon medium has been removed into one or more gas phase reactors, and completing the polymerization in the gas phase reactor in the presence of ethylene and optionally hydrogen and comonomer to produce polyethylene having bimodal and/or broad molecular weight distribution.
Claim 3
Dependent Claim
36 words
Method according to claim 1, wherein the polymer produced in the first step has a higher melt flow index, and the polymer produced in the second step has a lower melt flow index and lower density.
Claim 4
Dependent Claim
21 words
Method according to claim 1, wherein the ratio of hydrogen to ethylene in the first step is up to 1 mol/mol.
Claim 5
Dependent Claim
20 words
Method according to claim 1, wherein the inert hydrocarbon medium is propane, butane, pentane, hexane, heptane, octane, cyclohexane or cycloheptane.
Claim 6
Dependent Claim
14 words
Method according to claim 1, wherein the inert hydrocarbon medium is propane or isobutane.
Claim 7
Dependent Claim
12 words
Method according to claim 1, wherein the inert hydrocarbon medium is propane.
Claim 8
Dependent Claim
26 words
Method according to claim 1, wherein the first step polymerization is carried out at a temperature of about 75°-110° C. and a pressure of 40-90 bar.
Claim 9
Dependent Claim
18 words
Method according to claim 1, wherein the residence time in the first step is between about 1-2 hours.
Claim 10
Dependent Claim
16 words
Method according to claim 1, wherein hydrogen and the inert hydrocarbon medium is removed by flashing.
Claim 11
Dependent Claim
24 words
Method according to claim 1, wherein the polyethylene produced in the first step is 40-90% based on the total polymer produced in the process.
Claim 12
Dependent Claim
19 words
Method according to claim 7, wherein the low boiling hydrocarbon medium in the first step is propane or butane.
Claim 13
Dependent Claim
204 words
A multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in a multi-step reaction sequence, in which the first step is a liquid phase polymerization step and the second step comprises one or more gas phase polymerization steps, said process comprising polymerizing ethylene in the first step in the presence of an ethylene polymerizing catalyst system, hydrogen and optionally comonomer in a loop reactor in propane medium under supercritical conditions wherein the polymerization temperature and pressure are above the corresponding critical points of the mixture formed by propane, ethylene, hydrogen and optional comonomer and below the melting point of formed polymer, during a residence time of at least 10 minutes and sufficiently long to produce polyethylene in an amount of 20-90% based on the total polymer produced in the process, discharging the resulting reaction mixture from the loop reactor, removing hydrogen, unreacted reactants and the propane from the reaction mixture, transferring the polymer from which hydrogen, unreacted reactants and the propane have been removed into one or more gas phase reactors, and completing the polymerization in the gas phase reactor in the presence of ethylene and optionally hydrogen and comonomer to produce polyethylene having bimodal and/or broad molecular weight distribution.
Claim 14
Dependent Claim
204 words
A multi-stage process for producing polyethylene having a bimodal and/or broad molecular weight distribution in a multi-step reaction sequence, in which the first step is a liquid phase polymerization step and the second step comprises one or more gas phase polymerization steps, said process comprising polymerizing ethylene in the first step in the presence of an ethylene polymerizing catalyst system, hydrogen and optionally comonomer in a loop reactor in propane medium under supercritical conditions wherein the polymerization temperature and pressure are above the corresponding critical points of the mixture formed by propane, ethylene, hydrogen and optional comonomer and below the melting point of formed polymer, during a residence time of at least 10 minutes and sufficiently long to produce polyethylene in an amount of 20-90% based on the total polymer produced in the process, discharging the resulting reaction mixture from the loop reactor, removing hydrogen, unreacted reactants and the propane from the reaction mixture, transferring the polymer from which hydrogen, unreacted reactants and the propane have been removed into one or more gas phase reactors, and completing the polymerization in the gas phase reactor in the presence of ethylene and optionally hydrogen and comonomer to produce polyethylene having bimodal and/or broad molecular weight distribution.
Claim 15
Dependent Claim
28 words
Method according to claim 12, wherein the polymerization in the loop reactor is carried out at a temperature of about 85°-110° C. and a pressure of 60-90 bar.
Claim 16
Dependent Claim
16 words
Method according to claim 12, wherein hydrogen, unreacted reactants and the propane are removed by flashing.
Claim 17
Dependent Claim
23 words
Method according to claim 12, wherein the polyethylene produced in the first step is 40-90% of the total polymer produced in the process.
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