# US 10,765,987 B2 · Air filter medium, air filter pack, and air filter unit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,765,987 B2 - Document ID: US10765987B2 - Status: Granted - Kind: B2 - Application number: 15/764,444 - Filed: 2016-09-30 - Published: 2018-09-20 - Granted: 2020-09-08 - Earliest claimed: 2015-09-30 - Assignees: Nitto Denko Corporation - Applicants: Nitto Denko Corporation - Inventors: Takashi Niki; Masaaki Mori; Shiho Wada; Atsushi Daimon - Web page: https://patentgrep.com/patent/US10765987B2 ## CPC - B01D 46/543: {using membranes} - B01D 39/1623: {of synthetic origin} - B01D 39/1692: {Other shaped material, e.g. perforated or porous sheets} - B01D 46/0005: {Mounting of filtering elements within casings, housings or frames (B01D46/2422 takes precedence)} - B01D 46/009: {Identification of filter type or position thereof, e.g. by transponders or bar codes} - B01D 46/52: Particle separators, e.g. dust precipitators, using filters embodying folded {corrugated or wound sheet} material - B01D 46/521: {using folded, pleated material} - B01D 63/14: Pleat-type membrane modules - B01D 71/36: Polytetrafluoroethylene - B01D 2239/065: More than one layer present in the filtering material - B01D 2239/1216: Pore size - B01D 2239/1225: Fibre length - B01D 2239/1233: Fibre diameter - B01D 2275/10: Multiple layers - 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) ## Abstract An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. An average fiber diameter of fibers included in the first porous PTFE membrane is 0.24 to 0.45 μm, an average fiber diameter of fibers included in the second porous PTFE membrane is 0.04 to 0.23 μm, the air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. ## Claims ### Claim 1 An air filter medium comprising a first porous PTFE membrane and a second porous PTFE membrane, wherein an average fiber diameter of fibers included in the first porous PTFE membrane is 0.24 to 0.45 μm, an average fiber diameter of fibers included in the second porous PTFE membrane is 0.04 to 0.23 μm, the air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. ### Claim 2 (depends on 1) The air filter medium according to claim 1, wherein an average fiber length of the fibers included in the first porous PTFE membrane is 53 to 274 μm, and an average fiber length of the fibers included in the second porous PTFE membrane is 3 to 50 μm. ### Claim 3 (depends on 1) The air filter medium according to claim 1, wherein a thickness of the first porous PTFE membrane is 7 to 36 μm, and a thickness of the second porous PTFE membrane is 1 μm or more and less than 7 μm. ### Claim 4 (depends on 1) The air filter medium according to claim 1, wherein a ratio of a thickness of the first porous PTFE membrane to a thickness of the second porous PTFE membrane is more than 1. ### Claim 5 (depends on 1) The air filter medium according to claim 1, wherein an average pore diameter of the first porous PTFE membrane is 3 to 30 μm, and an average pore diameter of the second porous PTFE membrane is 0.1 to 3 μm. ### Claim 6 (depends on 1) The air filter medium according to claim 1, further comprising an air-permeable fiber layer disposed, when viewed from the first porous PTFE membrane, on a side opposite to a side where the second porous PTFE membrane is disposed, wherein a mass per unit area of the air-permeable fiber layer is 30 to 260 g/m2. ### Claim 7 (depends on 1) The air filter medium according to claim 1, further comprising: a first air-permeable fiber layer disposed, when viewed from the first porous PTFE membrane, on a side opposite to a side where the second porous PTFE membrane is disposed, the first air-permeable fiber layer forming the first main surface; and a second air-permeable fiber layer disposed, when viewed from the second porous PTFE membrane, on a side opposite to a side where the first porous PTFE membrane is disposed, the second air-permeable fiber layer forming the second main surface, wherein the first air-permeable fiber layer and the second air-permeable fiber layer are each an embossed non-woven fabric, and an embossing pattern of the first air-permeable fiber layer is different from an embossing pattern of the second air-permeable fiber layer. ### Claim 8 (depends on 1) The air filter medium according to claim 1, wherein at least one selected from the first main surface and the second main surface is provided with an identification mark that allows distinguishing between the first main surface and the second main surface. ### Claim 9 (depends on 8) The air filter medium according to claim 8, wherein the identification mark comprises at least one selected from the group consisting of a letter, a figure, and a symbol. ### Claim 10 (depends on 1) The air filter medium according to claim 1, further comprising: a first air-permeable fiber layer disposed, when viewed from the first porous PTFE membrane, on a side opposite to a side where the second porous PTFE membrane is disposed, the first air-permeable fiber layer forming the first main surface; and a second air-permeable fiber layer disposed, when viewed from the second porous PTFE membrane, on a side opposite to a side where the first porous PTFE membrane is disposed, the second air-permeable fiber layer forming the second main surface, wherein at least one selected from the first air-permeable fiber layer and the second air-permeable fiber layer is colored, and a color of the first air-permeable fiber layer is different from a color of the second air-permeable fiber layer. ### Claim 11 (depends on 1) The air filter medium according to claim 1, wherein when poly-α-olefin in the form of polydisperse particles with an average particle diameter of 0.15 μm is passed through the air filter medium at a concentration of 20 to 40 g/m3 and a linear flow velocity of 5.3 cm/sec to measure change in pressure drop, an amount of poly-α-olefin collected by the air filter medium is 20 mg/m2/Pa or more at a time point where the pressure drop reaches 500 Pa. ### Claim 12 (depends on 1) The air filter medium according to claim 1, wherein when NaCl in the form of polydisperse particles with an average particle diameter of 0.5 μm is passed through the air filter medium at a concentration of 1 to 3 g/m3 and a linear flow velocity of 5.3 cm/sec to measure change in pressure drop, an amount of NaCl collected by the air filter medium is 8 mg/m2/Pa or more at a time point where the pressure drop reaches 500 Pa. ### Claim 13 (depends on 1) An air filter pack comprising the air filter medium according to claim 1, the air filter medium being pleated. ### Claim 14 (depends on 13) An air filter unit comprising the air filter pack according to claim 13 and a frame supporting the air filter pack.