Water processing filter and manufacturing method therefor
A water-processing filter having a high dimensional accuracy and an improved filterability (such as a capability to remove turbidity components) is provided. The water-processing filter comprises (A) a hollow cylindrical filter which comprises (a1) a granular activated carbon having a median particle size of 30 to 80 μm and (a2) a fibrillated fibrous binder. The cylindrical filter (A) has an upstream outer surface having an arithmetical mean deviation of a waviness profile adjusted to not more than 30 μm and an arithmetical mean deviation of a primary profile adjusted to 35 to 45 μm. The cylindrical filter (A) may have a downstream inner surface having an arithmetical mean deviation of a waviness profile of not more than 30 μm and an arithmetical mean deviation of a primary profile of 35 to 45 μm. The cylindrical filter (A) may have a grounded outer surface. In a hollow space of the cylindrical filter (A), (B) a cylindrical filter comprising (b1) a granular activated carbon having a median particle size of 30 to 80 μm and (b2) a granular binder may be disposed.
1. A water-processing filter comprising (A) a hollow cylindrical filter which comprises (a1) a granular activated carbon having a median particle size of from 30 to 80 μm and (a2) a fibrillated fibrous binder, wherein the cylindrical filter (A) has an upstream outer surface having an arithmetical mean deviation of a waviness profile in accordance with JIS B 0601 of not more than 30 μm and an arithmetical mean deviation of a primary profile in accordance with JIS B 0601 of from 35 to 45 μm.
2. The water-processing filter according to claim 1 , further comprising (B) a hollow cylindrical filter disposed in a hollow space of the cylindrical filter (A), wherein the cylindrical filter (B) comprises (b1) a granular activated carbon having a median particle size of from 30 to 80 μm and (b2) a granular binder.
3. The water-processing filter according to claim 2 , wherein a density ratio of the cylindrical filter (A) relative to the cylindrical filter (B) is the cylindrical filter (A)/the cylindrical filter (B)=0.7/1 to 1.5/1.
4. The water-processing filter according to claim 2 , wherein a volume ratio of the cylindrical filter (A) relative to the cylindrical filter (B) is the cylindrical filter (A)/the cylindrical filter (B)=3/1 to 20/1.
5. The water-processing filter according to claim 1 , wherein the cylindrical filter (A) has a downstream inner surface having an arithmetical mean deviation of a primary profile of from 0.5 to 1.5 times as large as the arithmetical mean deviation of the primary profile of the outer surface.
6. The water-processing filter according to claim 1 , wherein the outer surface of the cylindrical filter (A) is ground without compression.
7. A method for producing a water-processing filter of claim 1 , the method comprising:
preparing a slurry by dispersing a mixture of (a1) a granular activated carbon and (a2) a fibrous binder in water,
filtering the slurry by suction to give (A1) a premolded product,
drying the premolded product (A1) to give (A2) a dried molded product, and
grinding an outer surface of the molded product (A2).
8. The method according to claim 7 , wherein, in the grinding, the outer surface of the molded product (A2) is ground at a grinding depth of from 5 to 200 times as large as a median particle size of the granular activated carbon (a1).
9. The method according to claim 7 , wherein the outer surface of the molded product (A2) is ground while the molded product (A2) is rotated.
10. The method according to claim 7 , further comprising:
thermoforming a mixture of (b1) a granular activated carbon and (b2) a granular binder to give (B) a cylindrical filter, and
inserting the cylindrical filter (B) into a hollow space of the cylindrical filter (A).