# US 11,078,305 B2 · Method of reducing the entrainment of polymer in the polymer-lean liquid phase of a separator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,078,305 B2 - Document ID: US11078305B2 - Status: Granted - Kind: B2 - Application number: 16/624,390 - Filed: 2018-06-22 - Published: 2020-04-23 - Granted: 2021-08-03 - Earliest claimed: 2017-06-29 - Assignees: Borealis AG - Applicants: Borealis AG - Inventors: Mohammad Al-Haj Ali - Web page: https://patentgrep.com/patent/US11078305B2 ## CPC - B01D 17/0208: {by sedimentation} - C08F 6/003: {from polymer solutions, suspensions, dispersions or emulsions without recovery of the polymer therefrom} - B01D 17/02: Separation of non-miscible liquids - B01D 19/0042: {modifying the liquid flow (B01D19/0021 takes precedence)} - C08F 2/01: characterised by special features of the polymerisation apparatus used - C08F 2/06: Organic solvent - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS ## Abstract The present invention relates to a method of reducing the entrainment of polymer in the polymer-lean liquid phase in a separator, comprising the steps of: (i) Selecting the diameter of the polymer droplets in the polymer solution entering the separator; (ii) Determining the traveling time of the polymer droplets in the separator; and (iii) Adjusting the residence time of the polymer-dense phase in the separator to be at least the traveling time of the polymer droplets, a solution polymerization process using said method for reducing the entrainment of polymer in the polymer-lean liquid phase in the separator and the use of said method for determining the minimum residence time of the polymer solution in the separator required to ensure efficient separation of a polymer solution into a polymer-lean phase and a polymer-rich phase. ## Claims ### Claim 1 A method of reducing entrainment of polymer in a polymer-lean liquid phase in a separator, comprising the steps of: setting a diameter range of polymer droplets in a polymer solution entering the separator; (ii) estimating a traveling time of the polymer droplets in the separator; and (iii) adjusting a residence time of the polymer solution in the separator to be at least the traveling time of the polymer droplets in the polymer-lean liquid phase; wherein the diameter range of the polymer droplets is set by selecting a hole size of a distributor inside the separator. ### Claim 2 (depends on 1) The method according to claim 1, wherein a diameter of the polymer droplets is at least 50 μm. ### Claim 3 (depends on 1) The method according to claim 1, wherein the traveling time is estimated from a termination velocity of the polymer droplets. ### Claim 4 (depends on 3) The method according to claim 3, wherein the termination velocity uT of the polymer droplets is calculated according to the following formula: u T = 4 ⁢ g ⁡ ( ρ d - ρ f ) ⁢ d p 3 ⁢ ρ f ⁢ CD ( I ) with a droplet density ρd being in a range of 700 to 900 kg/m3, a fluid density ρf being in a range of 350 to 700 kg/m3, a droplet diameter determined according to step (i) and a Drag Coefficient CD determined from a Reynolds number Re according to the following formula: CD = 24 Re ⁡ [ 1 + 0.173 ⁢ Re 0.657 ] . ( II ) ### Claim 5 (depends on 3) The method according to claim 3, wherein the termination velocity uT is at least 0.001 m/s. ### Claim 6 (depends on 1) The method according to claim 1, wherein the residence time of the polymer solution in the separator is adjusted by increasing a height of a polymer-rich phase of the polymer solution in the separator. ### Claim 7 (depends on 1) The method according to claim 1, wherein the polymer-lean liquid phase withdrawn from the separator is substantially free of polymer. ### Claim 8 (depends on 1) The method according to claim 1, wherein the separator is suitable to separate liquid-liquid two phase systems and vapour-liquid two phase systems. ### Claim 9 (depends on 1) The method according to claim 1, wherein the polymer is an alpha-olefin homo- or copolymer comprising a monomer and optionally at least one comonomer all selected from ethylene or C3 to C12 alpha-olefins. ### Claim 10 A process for producing a polymer comprising the steps of: (a) continuously polymerizing a monomer and optionally at least one comonomer in a solvent in a polymerization reactor to produce a polymer solution comprising the solvent, the polymer, unreacted monomer and optionally unreacted comonomer; (b) continuously withdrawing the polymer solution from the polymerization reactor; (c) heating the polymer solution; (d) reducing the pressure of the heated polymer solution by an amount sufficient to separate the polymer solution into a polymer-rich liquid phase comprising the polymer and a polymer-lean liquid phase comprising the solvent, the unreacted monomer and optionally the unreacted comonomer; (e) feeding the pressure-reduced polymer solution into a separator; (f) reducing the entrainment of the polymer in the polymer-lean liquid phase by: (i) setting a diameter range of polymer droplets in a polymer solution entering the separator; (ii) estimating a traveling time of the polymer droplets in the separator; and (iii) adjusting a residence time of the polymer solution in the separator to be at least the traveling time of the polymer droplets in the polymer-lean liquid phase; (g) withdrawing the polymer-rich liquid phase from separator and recovering the polymer from the polymer-rich liquid phase; and (h) withdrawing the polymer-lean liquid phase from the separator and directly recycling the polymer-lean liquid phase into the polymerization reactor. ### Claim 11 (depends on 10) The process according to claim 10, wherein the monomers and optional comonomers are selected from alpha-olefin monomers with 2 to 12 carbon atoms. ### Claim 12 A method for determining a minimum residence time of a polymer solution in a separator required to ensure efficient separation of a polymer solution into a polymer-rich phase comprising the polymer and a polymer-lean phase comprising solvent, unreacted monomer and optionally unreacted comonomer with the maximum fraction of polymer collected in the polymer-rich phase, the process comprising: setting a diameter range of polymer droplets in a polymer solution entering the separator; estimating a traveling time of the polymer droplets in the separator; and adjusting a residence time of the polymer solution in the separator to be at least the traveling time of the polymer droplets in the polymer-lean phase; wherein the diameter range of the polymer droplets is set by selecting a hole size of a distributor inside the separator. ### Claim 13 (depends on 12) The method according to claim 12, wherein the polymer solution is continuously withdrawn from a polymerization reactor, heated and expanded in order to reduce pressure before being introduced into the separator. ### Claim 14 (depends on 12) The method according to claim 12, wherein it is decided to use the separator for vapour-liquid separation or for liquid-liquid separation depending on the minimum residence time which depends on the weight average molecular weight and the optional comonomer content of the polymer in the polymer solution.