Filter cartridge and process for producing the same

Abstract

An object of the present invention is to provide a filter cartridge having an high filtering accuracy, a long filter life and a good liquid-passing property, in which an initial trapped particle diameter little changes, a pressure loss is small and neither bubbling nor falling of the filter material is observed. Such a filter cartridge is obtained by a production process, which comprises winding a non-woven fabric strip comprising a thermoplastic fiber around a perforated cylinder in a twill form, wherein a non-woven fabric strip satisfies the following equation (A): log 10 Y< 3.75−0.6 (log 10 X )  (A) wherein X (cm 3 /cm 2 /sec) is an airflow amount of the non-woven fabric strip, and Y (g/m 2 ) is a basis weight thereof; or a production process, which comprises winding in a twill form, wherein a number (W) of winding a non-woven fabric strip around a perforated cylinder from one end to the other end is one to 10 per a length of 250 mm in the perforated cylinder.

What is claimed is:  
     
         1 . A filter cartridge which is prepared by winding a non-woven fabric strip comprising a thermoplastic fiber around a perforated cylinder in a twill form, wherein the non-woven fabric strip satisfies the following equation (A):  
         log   10   Y< 3.75−0.6( log   10   X)   (A)  
       wherein X (cm 3 /cm 2 /sec) is an airflow amount of the non-woven fabric strip measured in accordance with JIS L 1096-A (1990), and Y (g/m 2 ) is a basis weight thereof.  
     
     
         2 . A filter cartridge which is prepared by winding a long fiber non-woven fabric strip comprising a thermoplastic fiber around a perforated cylinder in a twill form, wherein the non-woven fabric strip satisfies the following equation (B):  
         log   10   Y< 3.75−0.75( log   10   X)   (B)  
       wherein X (cm 3 /cm 2 /sec) is an airflow amount of the non-woven fabric strip measured in accordance with JIS L 1096-A (1990), and Y (g/m 2 ) is a basis weight thereof.  
     
     
         3 . A filter cartridge which is prepared by winding a non-woven fabric strip comprising a thermoplastic fiber around a perforated cylinder in a twill form, wherein in winding in a twill form, a number (W) of winding the non-woven fabric strip from one end to the other end in a longitudinal direction of the perforated cylinder is one to 10 per a length of 250 mm in the perforated cylinder.  
     
     
         4 . The filter cartridge as claimed in  claim 3 , wherein when a 2-fold value (2W) of the winding number (W) is represented by a fraction having a denominator of two figures or less which is a non-reducible approximate value, the denominator is 4 to 40.  
     
     
         5 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein at least a part of fiber intersections of the non-woven fabric strip is thermally bonded.  
     
     
         6 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein the non-woven fabric strip has a width of 0.5 to 40 cm.  
     
     
         7 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein a product of a width (cm) and a basis weight (g/m 2 ) of the non-woven fabric strip is 10 to 200.  
     
     
         8 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein the non-woven fabric strip has a thickness of 0.02 to 1.20 mm.  
     
     
         9 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein the non-woven fabric strip is thermal compression bonded by means of a heat embossing roll having an embossing area rate of 5 to 25%.  
     
     
         10 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein the filter material of the filter cartridge has a void rate of 65 to 85%.  
     
     
         11 . The filter cartridge as claimed in  claim 1  or  3 , wherein the non-woven fabric strip is of a long fiber non-woven fabric.  
     
     
         12 . The filter cartridge as claimed in  claim 11 , wherein the long fiber non-woven fabric is produced by a spun bonding method.  
     
     
         13 . The filter cartridge as claimed in  claim 1  or  3 , wherein the non-woven fabric strip is of a melt blown non-woven fabric.  
     
     
         14 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein the thermoplastic fiber is a composite fiber comprising a low melting resin and a high melting resin, a difference of the melting points between these resins being 10° C. or more.  
     
     
         15 . The filter cartridge as claimed in any one of  claims 1  to  3 , wherein the thermoplastic fiber is a fiber formed from at least one thermoplastic resin selected from the group consisting of a polyester resin, a polyamide resin, a polyethylene resin and a polypropylene resin.  
     
     
         16 . A process for producing a filter cartridge, which comprises winding a non-woven fabric strip comprising a thermoplastic fiber around a perforated cylinder in a twill form, wherein the non-woven fabric strip satisfies the following equation (A):  
         log   10   Y< 3.75−0.6( log   10   X)   (A)  
       wherein X (cm 3 /cm 2 /sec) is an airflow amount of the non-woven fabric strip measured in accordance with JIS L 1096-A (1990), and Y (g/m 2 ), and Y (g/m 2 ) is a basis weight thereof.  
     
     
         17 . A process for producing a filter cartridge, which comprises winding a non-woven fabric strip comprising a thermoplastic fiber around a perforated cylinder in a twill form, wherein in winding in a twill form, a number (W) of winding the non-woven fabric strip from one end to the other end in a longitudinal direction of the perforated cylinder is one to 10 per a length of 250 mm in the perforated cylinder.