# US 2019/0314767 A1 · Porous hollow fiber membrane and method for producing porous hollow fiber membrane > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0314767 A1 - Document ID: US20190314767A1 - Status: Published application - Kind: A1 - Application number: 16/348,268 - Filed: 2017-10-26 - Published: 2019-10-17 - Earliest claimed: 2016-11-09 - Assignees: Asahi Kasei Kabushiki Kaisha - Applicants: Asahi Kasei Kabushiki Kaisha - Inventors: Yuki MIKI; Daisuke OKAMURA - Web page: https://patentgrep.com/patent/US20190314767A1 ## CPC - B01D 67/00165: {Composition of the coagulation baths} - B01D 67/00135: {Air gap characteristics} - B01D 67/00793: {Dispersing a component, e.g. as particles or powder, in another component} - B01D 69/02: characterised by their properties - B01D 69/08: Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08) - B01D 69/081: {characterised by the fibre diameter} - B01D 69/087: {Details relating to the spinning process} - B01D 69/1218: {Layers having the same chemical composition, but different properties, e.g. pore size, molecular weight or porosity} - B01D 69/148: {Organic/inorganic mixed matrix membranes} - B01D 71/027: {Silicium oxide} - B01D 71/34: Polyvinylidene fluoride - C08J 9/26: by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out - D01F 6/12: from polymers of fluorinated hydrocarbons - B01D 2323/082: Cooling - B01D 2323/21: Fillers - B01D 2325/0283: Pore size - B01D 2325/04: Characteristic thickness - B01D 2325/24: Mechanical properties, e.g. strength - C08J 2327/16: Homopolymers or copolymers of vinylidene fluoride - 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) - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - D01F: CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS ## Abstract Provided is a porous hollow fiber membrane made of a thermoplastic resin, wherein a membrane thickness is 0.050 mm or larger and 0.25 mm or smaller, and when a strength coefficient is defined as K=(compressive strength)/((membrane thickness)/(inside diameter/2))3, K=1.7 or more. ## Claims ### Claim 1 A porous hollow fiber membrane made of a thermoplastic resin, wherein a membrane thickness is 0.050 mm or larger and 0.25 mm or smaller, and when a strength coefficient is defined as K=(compressive strength)/((membrane thickness)/(inside diameter/2))3, K=1.7 or more. ### Claim 2 (depends on 1) The porous hollow fiber membrane according to claim 1, wherein a coefficient of variation in a thickness of a backbone forming a surface on the filtration side is 80% or less. ### Claim 3 (depends on 1) The porous hollow fiber membrane according to claim 1, wherein a pore ratio of the surface on the filtration side is 32% or more. ### Claim 4 (depends on 1) The porous hollow fiber membrane according to claim 1, wherein the thickness of the backbone forming a surface on the filtration side is 0.20 μm or larger and 20 μm or smaller. ### Claim 5 (depends on 1) The porous hollow fiber membrane according to claim 1, wherein the inside diameter is 0.75 mm or larger, the compressive strength is 0.30 MPa or more, and the porous hollow fiber membrane is in a hollow fiber form having a three-dimensional network structure. ### Claim 6 (depends on 1) The porous hollow fiber membrane according to claim 1, wherein the porous hollow fiber membrane consists of at least two layers. ### Claim 7 (depends on 1) The porous hollow fiber membrane according to claim 1, wherein the porous hollow fiber membrane consists of at least two layers, a pore ratio of a surface on the pre-filtration side is 32% to 60%, and a pore size is 500 nm or smaller. ### Claim 8 A hollow fiber membrane module having a hollow fiber membrane bundle and fixing parts at both ends of the hollow fiber membrane bundle, wherein: the end of one of the fixing parts seals a hollow part of the hollow fiber membrane, and the end of the other fixing part opens the hollow part; the hollow fiber membrane module is of external pressure type in which filtration is performed from the outside of the hollow fiber membrane where the hollow fiber membrane is exposed, to the inside thereof; and when a strength coefficient of the hollow fiber membrane is defined as K=(compressive strength)/((membrane thickness)/(inside diameter/2))3, K=1.7 or more. ### Claim 9 (depends on 7) A method for producing the porous hollow fiber membrane according to claim 7, wherein when a difference between a discharge temperature at a discharge port of a melt-kneaded product which is a starting material of the porous hollow fiber membrane and an internal temperature of a coagulation bath where the melt-kneaded product is coagulated is defined as ΔT, and a time required for the melt-kneaded product in a hollow form to pass through a free traveling part from the discharge port to the liquid surface of the coagulation bath is defined as free traveling time t, cooling rate ΔT/t is 180° C./s or more and 340° C./s or less. ### Claim 10 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein the free traveling time required for the melt-kneaded product in a hollow form to pass through a free traveling part from the discharge port of the melt-kneaded product to the liquid surface of a coagulation bath where the melt-kneaded product is coagulated is 0.50 seconds or longer. ### Claim 11 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein raw materials of the melt-kneaded product are three components of a thermoplastic resin, an inorganic fine powder and a solvent. ### Claim 12 (depends on 11) The method for producing the porous hollow fiber membrane according to claim 11, wherein the inorganic fine powder is silica. ### Claim 13 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein the thermoplastic resin is polyvinylidene fluoride (PVDF). ### Claim 14 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein a melt-kneaded product for use in the production of a layer including a surface on the filtration side in the porous hollow fiber membrane has a thermoplastic resin concentration of 35% by mass or higher and 48% by mass or lower. ### Claim 15 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein a melt-kneaded product for use in the production of a layer including a surface on the pre-filtration side in the porous hollow fiber membrane has a thermoplastic resin concentration of 20% by mass or higher and 35% by mass or lower. ### Claim 16 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein a solvent that satisfies a condition of parameter P represented by the following expression is used in the production of a layer including a surface on the pre-filtration side in the porous hollow fiber membrane: P=((σdm−σdp)2+(σpm−σpp)2+(σhm−σhp)2)0.5≤7.8 wherein σdm and σdp represent dispersion force terms of the solvent and polyvinylidene fluoride, respectively; σpm and σpp represent dipole bonding force terms of the solvent and polyvinylidene fluoride, respectively; and σhm and σhp represent hydrogen bond terms of the solvent and polyvinylidene fluoride, respectively. ### Claim 17 (depends on 9) The method for producing the porous hollow fiber membrane according to claim 9, wherein a solvent that satisfies a condition of parameter P represented by the following expression is used in the production of a layer including a surface on the filtration side in the porous hollow fiber membrane: P=((σdm−σdp)2+(σpm−σpp)2+(σhm−σhp)2)0.5>7.8 wherein σdm and σdp represent dispersion force terms of the solvent and polyvinylidene fluoride, respectively; σpm and σpp represent dipole bonding force terms of the solvent and polyvinylidene fluoride, respectively; and σhm and σhp represent hydrogen bond terms of the solvent and polyvinylidene fluoride, respectively. ### Claim 18 (depends on 1) A filtration method using the porous hollow fiber membrane according to claim 1. ### Claim 19 (depends on 18) The filtration method according to claim 18, wherein the filtration method is a suction filtration method. ### Claim 20 A method for filtering a medium to be filtered through a hollow fiber membrane module, comprising the steps of: dipping the hollow fiber membrane module having an exposed hollow fiber membrane in a tank having the medium to be filtered; and filtering the medium to be filtered from the outside to the inside of the hollow fiber membrane, wherein when a strength coefficient of the hollow fiber membrane is defined as K=(compressive strength)/((membrane thickness)/(inside diameter/2))3, K=1.7 or more.