# US 11,897,975 B2 · Multi-stage process for producing a C2 to C8 olefin polymer composition > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,897,975 B2 - Document ID: US11897975B2 - Status: Granted - Kind: B2 - Application number: 17/273,325 - Filed: 2019-09-19 - Published: 2021-10-14 - Granted: 2024-02-13 - Earliest claimed: 2018-09-28 - Assignees: Borealis AG - Applicants: Borealis AG - Inventors: Klaus Nyfors; Vasileios Kanellopoulos; Erno Elovainio; Ravindra Tupe; Victor Sumerin - Web page: https://patentgrep.com/patent/US11897975B2 ## CPC - C08F 2/001: {Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer (C08F295/00, C08F297/00 take precedence)} - C08F 10/00: Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond - C08F 2/34: Polymerisation in gaseous state - C08F 4/022: {Magnesium halide as support anhydrous or hydrated or complexed by means of a Lewis base for Ziegler-type catalysts} - C08F 4/64: Titanium, zirconium, hafnium or compounds thereof - C08F 210/02: Ethene - C08F 210/06: Propene - C08F 210/14: Monomers containing five or more carbon atoms - C08L 23/06: Polyethylene - C08L 2205/025: containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure - C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS - C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06) ## Abstract The present invention relates to a multi-stage process for producing a C2 to C8 olefin polymer composition in a process comprising at least two reactors, wherein a pre-polymerized solid Ziegler-Natta catalyst is prepared by carrying out an off-line pre-polymerization of a solid Ziegler-Natta catalyst component with a C2 to C4 olefin monomer before feeding to the polymerization process. ## Claims ### Claim 1 A continuous multi-stage process for producing a C2 to C8 olefin polymer composition in at least two reactors, the continuous multi-stage process comprising the steps of: a) introducing a stream of a pre-polymerized solid Ziegler-Natta catalyst and a monomer of C2 to C8 olefin into a first polymerization reactor, thereby producing in a first polymerization a first C2 to C8 olefin polymer; b) withdrawing a stream comprising the first C2 to C8 olefin polymer from the first polymerization reactor and passing it into a second polymerization reactor; c) introducing a stream of a monomer of C2 to C8 olefin into the second polymerization reactor, thereby producing in a second polymerization a first polymer mixture comprising the first C2 to C8 olefin polymer and a second C2 to C8 olefin polymer produced in the second polymerization reactor; and d) withdrawing a stream comprising the first polymer mixture from the second polymerization reactor, thereby obtaining the C2 to C8 olefin polymer composition; wherein the pre-polymerized solid Ziegler-Natta catalyst is prepared by off-line pre-polymerization of a solid Ziegler-Natta catalyst component with a C2 to C4 olefin monomer before feeding to the continuous multi-stage process, and wherein the pre-polymerized solid Ziegler-Natta catalyst has a particle size distribution span ((d90-d10)/d50) of below 1.5. ### Claim 2 (depends on 1) The continuous multi-stage process according to claim 1, wherein the solid Ziegler-Natta catalyst component comprises: (a1) a compound of a transition metal (TM), which transition metal is selected from one of the groups 4 to 6 of the periodic table (IUPAC), (a2) a compound of a metal (M) which metal is selected from one of the groups 1 to 3 of the periodic table (IUPAC), (a3) optionally an internal donor (ID) and (a4) optionally a compound of a group 13 metal of the periodic table (IUPAC). ### Claim 3 (depends on 1) The continuous multi-stage process according to claim 1, wherein the solid Ziegler-Natta catalyst component is in the form of particles having a mean particle size ranging from 3 to 200 μm. ### Claim 4 (depends on 1) The continuous multi-stage process according to claim 1, wherein the off-line pre-polymerization is carried out in the presence of a co-catalyst (Co) and optionally in the presence of an external electron donor (ED); and/or wherein the off-line pre-polymerization is carried out with a total residence time of 5 to 55 minutes. ### Claim 5 (depends on 1) The continuous multi-stage process according to claim 1, wherein the off-line pre-polymerization degree is from 0.1 to 50 gpolymer/gcat. ### Claim 6 (depends on 1) The continuous multi-stage process according to claim 1, wherein the off-line pre-polymerization is carried out in a medium, wherein the medium is an oil or a hydrocarbon solvent. ### Claim 7 (depends on 1) The continuous multi-stage process according to claim 1, wherein the off-line pre-polymerization is carried out at a temperature in a range from 0 to 50° C. ### Claim 8 (depends on 1) The continuous multi-stage process according to claim 1, wherein pre-polymerized solid Ziegler-Natta catalyst has a particle size distribution span ((d90-d10)/d50) of below 1.2. ### Claim 9 (depends on 1) The continuous multi-stage process according to claim 1, wherein the first polymerization reactor in step a) is a loop reactor. ### Claim 10 (depends on 1) The continuous multi-stage process according to claim 1, wherein the process comprises at least one gas phase reactor. ### Claim 11 (depends on 1) The continuous multi-stage process according to claim 1, wherein the process comprises a further step e) of introducing the stream of step d) and a stream of a monomer of C2 to C8 olefin into a third polymerization reactor, thereby producing a second polymer mixture. ### Claim 12 (depends on 11) The continuous multi-stage process according to claim 11, wherein the process further comprises a step f) of withdrawing a stream comprising the second polymer mixture from the third polymerization reactor. ### Claim 13 (depends on 11) The continuous multi-stage process according to claim 11, wherein the process comprises two loop reactors and one gas phase reactor. ### Claim 14 (depends on 11) The continuous multi-stage process according to claim 11, wherein the process comprises one loop reactor and two gas phase reactors. ### Claim 15 (depends on 12) The continuous multi-stage process according to claim 12, wherein the process further comprises a step g) of introducing the second polymer mixture into a fourth polymerization reactor together with additional monomers selected from C2 to C8 olefins, thereby producing a third polymer mixture.