Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
261 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 from 0.1 to 1.5μ, wherein the constituent fibers are interlaced and entangled with one another in various directions and satisfy the following requirements: (i) the fiber packing ratio α (%), which is defined by the following formula, is in the range of 20≧α≧3: ##EQU8## wherein ρ stands for the true density of the fibers and ρ' stands for the apparent density of the filter medium, (ii) the ratio S B /SA 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: ##EQU9## 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 ##EQU10## (iii) the number N of single fibers piled in the thickness direction of the filter medium, which is expressed by the following formula: ##EQU11## wherein α 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 (μ), is in the range of 1000≧N≧40 and wherein at least one surface of the filter medium is entirely covered with irregular fine depressions not uniform in shape.
Claim 2
Dependent Claim
261 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 from 0.1 to 1.5μ, wherein the constituent fibers are interlaced and entangled with one another in various directions and satisfy the following requirements: (i) the fiber packing ratio α (%), which is defined by the following formula, is in the range of 20≧α≧3: ##EQU8## wherein ρ stands for the true density of the fibers and ρ' stands for the apparent density of the filter medium, (ii) the ratio S B /SA 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: ##EQU9## 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 ##EQU10## (iii) the number N of single fibers piled in the thickness direction of the filter medium, which is expressed by the following formula: ##EQU11## wherein α 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 (μ), is in the range of 1000≧N≧40 and wherein at least one surface of the filter medium is entirely covered with irregular fine depressions not uniform in shape.
Claim 3
Dependent Claim
78 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 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
32 words
A filter medium as set forth in claim 1, wherein the depressions have a mean diameter of from 0.05 to 2 mm and a mean depth of from 0.05 to 0.5 mm.
Claim 5
Dependent Claim
42 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 1.5μ is a web of polyester continuous filaments obtained by a melt blow spinning method.
Claim 6
Dependent Claim
11 words
A filter medium according to claim 1 comprising one fibrous web.
Claim 7
Dependent Claim
16 words
A filter medium according to claim 1 comprising a plurality of piled and integrated fibrous webs.