EP0092819A2
Expired / Lapsed
EP
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Filter medium and process for preparing same
Assignee: Asahi Kasei Corp
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Filing: 1983-04-22
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Granted: —
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Expires: 2003-04-22
Abstract
Abstract A filter medium comprising one fibrous web or a plurality of piled and integrated fibrous webs is provided. The web or webs are composed mainly of ultrafine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 µ. The constituent fibers in each web are entangled with one another in various directions and satisfy the following requirements: (i) The fiber packing ratio a (%), defined by the formula: a = (p'/p) x 100 (p = true density of the fibers, p' = apparent density of the filter medium), is in the range of 20 ≥ α ≥ 3, (ii) the ratio S B /S A of the actually measured surface area S B (m 2 ) of the fibers per m 2 of the filter medium to the total surface area S A (m 2 ) expressed by the formula: S A = (9000πφw)/d (d mean single fiber denier, φ the means single fiber diameter (m) and W basis weight (g/m 2 ) of the filter medium) is in the range of and (iii) the number N of single fibers piled in the thickness direction of the filter medium, expressed by the formula: N = aℓ/100φ (a = fiber packing ratio (%), ℓ = thickness (µ) of the filter medium and φ = mean single fiber diameter of (µ)) is in the range of 1000 ≥ N ≥ 40. The filter medium is prepared by jetting high-pressure water to at least one surface of the fibrous web or webs, after or without a heat treatment thereof, from nozzles having a diameter of 0.05 to 0.5 mm and making a circular or reciprocating movement in parallel to the fibrous web or webs while moving the fibrous web or webs.
Inventors
- 👤 Masaaki Miyake
- 👤 Kunihiko Fukumori
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 23:38
CPC Classifications
B; B01; B01D; B01D39/00; B01D39/14; B01D39/16; B01D39/1607; B01D39/1623; D; D04; D04H; D04H1/00; D04H1/40; D04H1/44; D04H1/46; D04H1/492; D04H3/00; D04H3/08; D04H3/10; G; G21; G21F; G21F9/00; G21F9/02; B01D2239/00; B01D2239/04; B01D2239/0457; B01D2239/06; B01D2239/0604; B01D2239/0622; B01D2239/065; B01D2239/12; B01D2239/1233
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
250 words
A filter medium comprising one fibrous web or a plurality of piled and integrated fibrous webs, said web or webs being composed mainly of ultra-fine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 µ, wherein the constituent fibers are interlaced and entangled with one another in various directions and satisfy the following requirements: (i) the fiber packing ratio a (%), which is defined by the following formula, is in the range of 20 > a > 3: wherein p stands for the true density of the fibers and P' stands for the apparent density of the filter medium, (ii) the ratio S B /S A of the actually measured surface area S B (m 2 ) of the constituent fibers per m 2 of the filter medium to the total surface area S A (m 2 ) expressed by the following formula: S A = wherein d stands for the mean single fiber denier, φ stands for the mean single fiber diameter (m) and W stands for the basis weight (g/ m 2 ) of the filter medium, is in the range of and (iii) the number N of single fibers piled in the thickness direction of the filter medium, which is expressed by the following formula: wherein a stands for the fiber packing ratio (%), ℓ stands for the thickness (µ) of the filter medium and φ stands for the mean single fiber diameter (p), is in the range of 1000 > N > 40.
Claim 2
Dependent Claim
250 words
A filter medium comprising one fibrous web or a plurality of piled and integrated fibrous webs, said web or webs being composed mainly of ultra-fine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 µ, wherein the constituent fibers are interlaced and entangled with one another in various directions and satisfy the following requirements: (i) the fiber packing ratio a (%), which is defined by the following formula, is in the range of 20 > a > 3: wherein p stands for the true density of the fibers and P' stands for the apparent density of the filter medium, (ii) the ratio S B /S A of the actually measured surface area S B (m 2 ) of the constituent fibers per m 2 of the filter medium to the total surface area S A (m 2 ) expressed by the following formula: S A = wherein d stands for the mean single fiber denier, φ stands for the mean single fiber diameter (m) and W stands for the basis weight (g/ m 2 ) of the filter medium, is in the range of and (iii) the number N of single fibers piled in the thickness direction of the filter medium, which is expressed by the following formula: wherein a stands for the fiber packing ratio (%), ℓ stands for the thickness (µ) of the filter medium and φ stands for the mean single fiber diameter (p), is in the range of 1000 > N > 40.
Claim 3
Dependent Claim
79 words
A filter medium as set forth in claim 1, wherein the filter medium has a three-layer structure comprising a front layer in which the constituent fibers are interlaced and entangled mainly three-dimensionally and which has fine fluffs formed on the surface thereof, an intermediate layer in which the constituent fibers are interlaced and entangled mainly two-dimensionally and a back layer in which the constituent fibers are interlaced and entangled mainly three-dimensionally and which is denser than the front layer.
Claim 4
Dependent Claim
49 words
A filter medium as set forth in claim 1, wherein at least one surface of the filter medium is entirely covered with irregular fine depressions not uniform in the shape, which have a mean diameter of 0.05 to 2 mm and a mean depth of 0.05 to 0.5 mm.
Claim 5
Dependent Claim
43 words
A filter medium as set forth in claim 1, wherein the web composed mainly of ultra-fine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 p is a web of polyester continuous filaments obtained by a melt blow spinning method.
Claim 6
Dependent Claim
101 words
A process for the preparation of a filter medium, which comprises jetting high-pressure water to at least one surface of a fibrous web or a plurality of piled fibrous webs, after or without a heat treatment thereof, from nozzles having a diameter of 0.05 to 0.5 mm and making a circular or reciprocating movement in parallel to the fibrous web or webs while moving the fibrous web or webs, said web or webs being composed mainly of ultra-fine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 µ, and then drying the water jet-treated fibrous web or webs.
Claim 7
Dependent Claim
101 words
A process for the preparation of a filter medium, which comprises jetting high-pressure water to at least one surface of a fibrous web or a plurality of piled fibrous webs, after or without a heat treatment thereof, from nozzles having a diameter of 0.05 to 0.5 mm and making a circular or reciprocating movement in parallel to the fibrous web or webs while moving the fibrous web or webs, said web or webs being composed mainly of ultra-fine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 µ, and then drying the water jet-treated fibrous web or webs.
Claim 8
Dependent Claim
81 words
A process for the preparation of a filter medium according to claim 5, wherein the high-pressure water jet treatment is conducted on each of the front and back layers of the fibrous web or webs at least once, the frequency of the high-pressure water jet treatment on the front layer is higher than the frequency of the high-pressure water jet treatment on the back layer, and the jet pressure is highest at the first jet treatment and is then gradually reduced.
Claim 9
Dependent Claim
41 words
A process for the preparation of a filter medium according to claim 5, wherein a net member is interposed between the fibrous web or webs and the water jet nozzles at the high-pressure water jet treatment to finely disperse high-pressure water.
Claim 10
Dependent Claim
47 words
A process for the preparation of a filter medium according to claim 5, wherein the web composed mainly of ultra-fine combustible synthetic fibers having a single fiber diameter of 0.1 to 1.5 p is a web of polyester continuous filaments obtained by a melt blow spinning method.
References Cited (Backward Citations)
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