Metal membrane filter, and method and apparatus for the production thereof

Abstract

The invention relates to a metal membrane filter ( 1 ) and to a method and apparatus for the production thereof. The metal membrane filter ( 1 ) has rectilinear, cylindrical filter pores ( 2 ), which are arranged statistically distributed on the metal membrane filter surface ( 3 ) in a density of from a single filter pore ( 2 ) per cm 2 up to 10 7 filter pores ( 2 ) per cm 2 . The average diameter of the filter pores ( 2 ) is uniform for all filter pores ( 2 ) and is from a few tens of nm up to several micrometres. The metal membrane filter ( 1 ) comprises a metal electro-deposited with rectilinear, cylindrical filter pores ( 2 ) or a correspondingly electro-deposited metal alloy.

1 . Metal membrane filter having rectilinear, cylindrical filter pores ( 2 ), which are arranged statistically distributed on the metal membrane filter surface ( 3 ) in a density of from a single filter pore ( 2 ) per square centimetre up to  107  filter pores ( 2 ) per square centimetre and which have an average diameter (d) of from a few tens of nanometres up to several micrometres, wherein the metal membrane filter ( 1 ) comprises a metal electro-deposited with rectilinear, cylindrical filter pores ( 2 ) or a correspondingly electro-deposited metal alloy.  
     
     
         2 . Metal membrane filter according to  claim 1 , 
 characterised in that 
 the metal membrane filter ( 1 ) comprises a nickel, copper, gold or platinum electro-deposited with rectilinear, cylindrical filter pores or correspondingly electro-deposited alloys thereof.  
   
     
     
         3 . Metal membrane filter according to  claim 1  or  claim 2 , 
 characterised in that 
 the filter pores ( 2 ) have on one side, the top side ( 4 ), a rounded-off or conical aperture-rim ( 5 ) and, on the reverse side ( 6 ) located opposite, a sharp-edged aperture-rim ( 7 ).  
 
 
     
     
         4 . Metal membrane filter according to one of the preceding claims, 
 characterised in that 
 the rectilinear, cylindrical filter pores ( 2 ) have a smooth internal wall structure ( 8 ).  
   
     
     
         5 . Method for the production of a metal membrane filter, comprising the following method steps: 
 production of a plastics membrane filter ( 9 ) having filter pores ( 2 ),    deposition, on one side of the plastics membrane filter ( 9 ), of an electrically conductive layer ( 10 ) to form a metal-coated plastics membrane filter ( 11 ),    flow, through the filter pores ( 2 ) of the metal-coated plastics membrane filter ( 11 ), of a liquid ( 12 ) that is inactive with respect to electro-deposition, from the uncoated to the coated side of the metal-coated plastics membrane filter ( 11 ); electrodeposition of a metal membrane filter body ( 13 ) onto the metal-coated plastics membrane filter ( 11 ),    dissolution of the plastics membrane filter ( 11 ) away from the metal membrane filter ( 1 ).    
     
     
         6 . Method according to  claim 5 , 
 characterised in that, 
 for production of a plastics membrane filter ( 9 ), a plastics film ( 14 ) is first irradiated with an ion beam ( 15 ).  
   
     
     
         7 . Method according to  claim 6 , 
 characterised in that 
 the plastics film ( 14 ) comprises a polybiphenolcarbonate.  
   
     
     
         8 . Method according to  claim 6  or  claim 7 , 
 characterised in that 
 the plastics film ( 14 ) has a thickness (D) of from 30 to 150 micrometres.  
 
 
     
     
         9 . Method according to one of  claims 6  to  8 , 
 characterised in that 
 the ion beam ( 15 ) comprises U 238  ions, which are accelerated to a kinetic energy of from 10 to 15 MeV/u and form discrete ion beam tracks ( 16 ) in the plastics film ( 14 ).  
 
 
     
     
         10 . Method according to  claim 9 , 
 characterised in that, 
 for production of the plastics membrane filter ( 9 ), the ion beam tracks ( 16 ) in the plastics film ( 14 ) are dissolved to form rectilinear, cylindrical filter pores ( 2 ) using a solution of 6M sodium hydroxide solution mixed with up to 10% methanol at room temperature.  
   
     
     
         11 . Method according to one of  claims 5  to  10 , 
 characterised in that 
 the deposition of an electrically conductive layer ( 10 ) on one side of the plastics membrane filter ( 9 ) to form a metal-coated plastics membrane filter ( 11 ) is carried out by means of powder deposition methods or sputtering.  
 
 
     
     
         12 . Method according to one of  claims 5  to  11 , 
 characterised in that, 
 on deposition of an electrically conductive layer ( 10 ) on one side of the plastics membrane filter ( 9 ), a metal or metal alloy is deposited which corresponds to the metal material of the metal membrane filter.  
 
 
     
     
         13 . Method according to one of  claims 5  to  12 , 
 characterised in that, 
 for flow, through the filter pores ( 2 ) of the metal-coated plastics membrane filter ( 11 ), of a liquid ( 12 ) that is inactive with respect to electro-deposition, from the uncoated to the coated side of the metal-coated plastics membrane filter, the liquid ( 12 ) that is inactive with respect to electro-deposition is subjected to a positive pressure on the uncoated side of the plastics membrane filter ( 9 ) of between 100 Pa and 1,000 Pa.  
 
 
     
     
         14 . Method according to one of  claims 5  to  13 , 
 characterised in that 
 water, sulphuric acid, sulphurous acid, ethylenediaminetetraacetic acid or mixtures thereof are used as the liquid ( 12 ) that is inactive with respect to electro-deposition.  
 
 
     
     
         15 . Method according to one of  claims 5  to  14 , 
 characterised in that, 
 on electro-deposition of a metal membrane filter body ( 13 ) of gold or a gold alloy onto the metal-coated plastics membrane filter ( 11 ), a gold sulphite bath containing from 10 mg to 15 mg of gold or gold alloy per cm 3  is used at a bath temperature of between 20 and 60° C.  
 
 
     
     
         16 . Method according to one of  claims 5  to  14 , 
 characterised in that, 
 on electro-deposition of a metal membrane filter body ( 13 ) of platinum or a platinum alloy onto the metal-coated plastics membrane filter ( 11 ), an acid or alkaline platinum bath containing from 1 mg to 20 mg of platinum or platinum alloy per cm 3  is used.  
 
 
     
     
         17 . Method according to one of  claims 5  to  14 , 
 characterised in that, 
 on electro-deposition of a metal membrane filter body ( 13 ) of copper or a copper alloy onto the metal-coated plastics membrane filter ( 11 ), a copper sulphate bath is used at a bath temperature of between 20 and 60° C. and at a current density of between 20 mA/cm 2  and 60 mA/cm 2 .  
 
 
     
     
         18 . Method according to one of  claims 5  to  14 , 
 characterised in that, 
 on electro-deposition of a metal membrane filter body ( 13 ) of nickel or a nickel alloy onto the metal-coated plastics membrane filter ( 11 ), a nickel sulphamate bath is used at a bath temperature of between 40 and 60° C. and at a current density of between 15 mA/cm 2  and 25 mA/cm 2 .  
 
 
     
     
         19 . Method according to one of  claims 5  to  18 , 
 characterised in that 
 the plastics membrane filter ( 9 ) is removed from the metal membrane filter body ( 13 ) by dissolving away the plastics material in dichloromethane.  
 
 
     
     
         20 . Method according to one of  claims 5  to  19 , 
 characterised in that, 
 after removal of the plastics membrane filter ( 9 ), the reverse side of the metal membrane filter ( 1 ) is mechanically polished.  
 
 
     
     
         21 . Apparatus for the production of a metal membrane filter ( 1 ), wherein the apparatus comprises a vessel ( 17 ) for accommodating an electro-deposition bath ( 18 ), which vessel ( 17 ) has a cover ( 19 ) having an anode ( 20 ) and has, in its bottom region ( 21 ), a holder ( 22 ), under cathode potential, for a metal-coated plastics membrane filter ( 11 ) and, upstream of the metal-coated plastics membrane filter ( 11 ), a pressure inlet ( 23 ) for a liquid ( 12 ) that is inactive with respect to electro-deposition, which pressure inlet ( 23 ) is connected to a pressure vessel ( 24 ) by way of a shut-off valve ( 25 ).  
     
     
         22 . Apparatus according to  claim 21 , 
 characterised in that 
 the anode ( 20 ) comprises gold, platinum, copper, nickel or alloys thereof.  
   
     
     
         23 . Apparatus according to  claim 21  or  claim 22 , 
 characterised in that 
 the apparatus ( 26 ) has a direct-current source for an adjustable cathode current density of between 10 mA/cm 2  and 100 mA/cm 2 .