Filter cartridge
A filter cartridge formed by winding, in a twill construction, a band-shaped unwoven cloth, which contains thermoplastic fibers and at least a part of its fiber intersections are stuck thereon, so that a cylindrical shape can be obtained, wherein 1. two types of filtrating layers are used, 2. unwoven cloth having opening hole parts is used, 3. an end face seal part is provided on both end parts of the cartridge, 4. unwoven cloth having a tongue piece part is used, or 5. two or more pieced of unwoven cloth are wound simultaneously, whereby those characteristic of the filter cartridge such as liquid permeability, filterable life, and stability of filtration accuracy can be kept in balance with each other.
1. A filter cartridge comprising a first filtration layer and a second filtration layer wherein the second filtration layer has an initial 80% trapped particle diameter that is 0.05 to 0.9 times as large as an initial 80% trapped particle diameter in the first filtration layer, and the first filtration layer is prepared by winding a strip of filament nonwoven in a twill form around the second filtration layer so as to make a cylindrical form ad wherein the strip of filament nonwoven formed by a spun-laying method comprises thermoplastic fiber and the thermoplastic fiber is aligned with longitudinal edges of the strip to produce openings having a length oriented alone a length of the strip and a width oriented between longitudinal edges of the strip wherein the length of the openings is substantially greater than the width of the openings.
2. The filter cartridge as described in claim 1 , wherein the strip of filament nonwoven is turned into a pleated matter having 4 to 50 pleats and wound around a perforated cylinder in a twill form.
3. The filter cartridge as described in claim 2 , wherein at least a part of the pleats of the pleated matter is arranged in non-parallel.
4. The filter cartridge as described in claim 2 , wherein the pleated matter has a void rate of 60 to 95%.
5. The filter cartridge as described in claim 1 , wherein the first filtration layer of the filter cartridge has a void rate of 65 to 90%.
6. The filter cartridge as described in claim 1 ; wherein the thermoplastic fiber is a thermally adherent composite fiber comprising a low melting point resin and a high melting point resin, difference in melting point between both resins being 10° C. or more.
7. The filter cartridge as described in claim 6 , wherein the low melting point resin is a linear low density polyethylene and the high melting point resin is a polypropylene.
8. The filter cartridge as described in claim 1 , wherein fiber intersections in the strip of nonwoven are bonded by thermal compression bonding by means of a hot embossing roll.
9. A filter cartridge as described in claim 1 , wherein the strip of nonwoven has a width of 0.5 cm or more, and a product of a width cm and a mass per unit area (g/cm 2 ) of the strip of nonwoven is 200 or less.