Filter structure and method for filtrating

Abstract

The invention provides a filter structure. A second porous film having a plurality of second holes is disposed on a first porous film having a plurality of first holes. The second holes are smaller than the first holes. The filter structure is dried by an easy and power-saving method such as compression.

1 . A filter structure, comprising:
 a first porous film having a plurality of first holes; and   a second porous film on the first porous film and having a plurality of second holes, wherein the second holes are smaller than the first holes.   
     
     
         2 . The filter structure as claimed in  claim 1 , wherein the first porous film capable to absorb water, and the second porous film is capable to filter objects bigger than the second holes. 
     
     
         3 . The filter structure as claimed in  claim 1 , wherein the first porous film directly contacts the second porous film. 
     
     
         4 . The filter structure as claimed in  claim 3 , wherein the range for the diameter of the first holes is between diameters of the second holes and 0.457 cm. 
     
     
         5 . The filter structure as claimed in  claim 3 , wherein the diameters of the second holes are smaller than the diameters of the intercepted solid particles. 
     
     
         6 . The filter structure as claimed in  claim 3 , wherein the first porous film comprises a polymer, non-woven fiber or synthetic fiber. 
     
     
         7 . The filter structure as claimed in  claim 6 , wherein the first porous film comprises a polyvinyl alcohol (PVA), polyurethane, polyacrylic acid, polyacrylamide, polyethylene or polystyrene. 
     
     
         8 . The filter structure as claimed in  claim 3 , wherein the second porous film comprises a polymer or ceramics. 
     
     
         9 . The filter structure as claimed in  claim 8 , wherein the second porous film comprises a polyvinyl alcohol (PVA), polyethersulfone, cellulose triacetate, polypropylene fiber or polyvinyl chloride. 
     
     
         10 . The filter structure as claimed in  claim 1 , wherein the first holes of the first porous film gradually become larger from the top to the bottom of the first porous film. 
     
     
         11 . The filter structure as claimed in  claim 1 , wherein the first porous film having the first holes gradually becoming larger from the top to the bottom of the first porous film is formed by stacking a plurality of porous films capable of absorbing water of different-sized holes. 
     
     
         12 . The filter structure as claimed in  claim 1 , further comprising a film capable of absorbing water disposed between the first porous film and the second porous film. 
     
     
         13 . The filter structure as claimed in  claim 12 , wherein the film capable of absorbing water directly contacts the first porous film and the second porous film. 
     
     
         14 . The filter structure as claimed in  claim 13 , wherein the range for the diameter of the first holes is between diameters of the second holes and 0.457 cm. 
     
     
         15 . The filter structure as claimed in  claim 13 , wherein the diameters of the second holes are smaller than the diameters of the intercepted solid particles. 
     
     
         16 . The filter structure as claimed in  claim 13 , wherein the film capable of absorbing water comprises a polymer, non-woven fiber or synthetic fiber. 
     
     
         17 . The filter structure as claimed in  claim 16 , wherein the film capable of absorbing water comprises a polyvinyl alcohol (PVA), polyurethane, polyacrylic acid, polyacrylamide, polyethylene or polystyrene. 
     
     
         18 . The filter structure as claimed in  claim 13 , wherein the first porous film comprises a metal, polymer, non-woven fiber or synthetic fiber. 
     
     
         19 . The filter structure as claimed in  claim 18 , wherein the first porous film comprises a polyvinyl alcohol (PVA), polyurethane, polyacrylic acid, polyacrylamide, polyethylene or polystyrene. 
     
     
         20 . The filter structure as claimed in  claim 13 , wherein the second porous film comprises a polymer, porous cellulose or ceramics. 
     
     
         21 . The filter structure as claimed in  claim 20 , wherein the second porous film comprises a polyvinyl alcohol (PVA), polyethersulfone, cellulose triacetate, polypropylene fiber or polyvinyl chloride. 
     
     
         22 . The filter structure as claimed in  claim 13 , wherein the first porous film has the capability of supporting the second porous film and absorbing water, and the second porous film is capable to filter objects bigger than the second holes. 
     
     
         23 . A method for filtrating, comprising:
 providing the filter structure as claimed in  claim 1 ; and   drifting down a mixed solution onto a top surface of the second porous film of the filter structure to intercept residue larger than the second holes in the mixed solution, and a liquid in the mixed solution passing through the second holes and allow the liquid to continue to flow downward.   
     
     
         24 . The method for filtrating as claimed in  claim 23 , further comprising:
 after the first porous film absorbs the liquid, compressing the first porous film by a compressing force to drain out the liquid and rinse the second porous film when the liquid flows back to the second porous film due to the compression to remove the residue blocking the second holes; and   removing the compressing force so that the compressed first porous film springs back to an original shape.   
     
     
         25 . The method for filtrating as claimed in  claim 23 , wherein the filter structure further comprises a film capable of absorbing water disposed between the first porous film and the second porous film, and the method further comprises:
 after the film capable of absorbing water absorbs the liquid, compressing the film capable of absorbing water by a compressing force to drain out the liquid and rinse the second porous film when the liquid flows back to the second porous film due to the compression to remove the residue blocking the second holes; and   removing the compressing force so that the compressed film capable of absorbing water springs back to an original shape.