Filtration Medias, Fine Fibers Under 100 Nanometers, and Methods

Abstract

An electrospinning fine fiber production methodology for generating a significant amount of fibers with diameters of less than 100 nanometers is provided. Also, a filter media composite comprising a substrate layer and an electrospun fine fiber layer having a increased efficiency relative to pressure drop and/or a controlled pore size distribution is provided. According to some embodiments nylon is electrospun from a solvent combination of formic and acetic acids.

1 . A filter media, comprising:
 a substrate layer of permeable media;   a fine fiber layer carried by the substrate layer, the fine fiber layer including a significant amount of fibers with a diameter of less than 100 nanometers.   
   
   
       2 . The filter media of  claim 1 , wherein the fine fiber layer is solvent bonded to the substrate layer. 
   
   
       3 . The filter media of  claim 1 , wherein the significant amount means that the fine fiber layer includes an average fiber diameter of less than 100 nanometers. 
   
   
       4 . The filter media of  claim 1 , wherein the significant amount means a mean fiber diameter of less than 100 nanometers. 
   
   
       5 . The filter media of  claim 1 , wherein the significant amount means at least 25% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers. 
   
   
       6 . The filter media of  claim 5 , wherein at least 50% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers. 
   
   
       7 . The filter media of  claim 5 , wherein at least 70% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers 
   
   
       8 . The filter media of  claim 6 , wherein at least 70% of the fibers have a diameter of between 50 and 100 nanometers. 
   
   
       9 . The filter media of  claim 5 , wherein the fine fiber comprises a polymer that is inherently hydrophobic and not water soluble. 
   
   
       10 . The filter media of  claim 9 , wherein the polymer comprises a nylon. 
   
   
       11 . The filter media of  claim 5 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has an efficiency of at least 90% for 0.75-1.00 micron sized particles, with less than 15% difference in pressure drop relative to the substrate layer alone. 
   
   
       12 . The filter media of  claim 11 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has an efficiency of at least 80% for 0.237-0.316 micron sized particles. 
   
   
       13 . The filter media of  claim 12 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has an efficiency of at least 85% for 0.237-0.316 micron sized particles. 
   
   
       14 . The filter media of  claim 12 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 50% of pore size distribution over a separation range of 6 micron. 
   
   
       15 . The filter media of  claim 14 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, have at least 60% of pore size distribution over a separation range of 6 micron. 
   
   
       16 . The filter media of  claim 15 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 40% of pore size distribution over a separation range of 4 micron. 
   
   
       17 . The filter media of  claim 16 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 45% of pore size distribution over a separation range of 4 micron. 
   
   
       18 . The filter media of  claim 17 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 25% of pore size distribution over a separation range of 2 micron. 
   
   
       19 . The filter media of  claim 11 , wherein the substrate layer has an efficiency without the fine fiber layer of an efficiency of less than 75% for 0.75-1.00 micron sized particles. 
   
   
       20 . The filter media of  claim 12 , wherein the substrate has an efficiency without the fine fiber layer of an efficiency of less than 40% for 0.237-0.316 micron sized particles. 
   
   
       21 . The filter media of  claim 20 , wherein, the substrate layer comprise a cellulose based porous filter media, the cellulose fiber based porous filter media having the following characteristics:
 (a) a Frazier Permeability of between about 1 and about 400 CFM @ 0.5″ WG;   (b) an average fiber diameter of between about 2 and about 50 microns;   (c) a base weight of between about 30 and about 200 lb/3000 ft 2 ;   (d) a pore size distribution generally between about 2 and about 50 micron; and   (e) a Mullen burst strength of between about 5 and about 70 psi.   
   
   
       22 . The filter media of  claim 21 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 10%. 
   
   
       23 . The filter media of  claim 21 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 5%. 
   
   
       24 . The filter media of  claim 21 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 1%. 
   
   
       25 . A filter media, comprising:
 a substrate layer of permeable media;   an electrospun fine fiber layer carried by the substrate layer, the combination of the substrate layer and the fine fiber layer apart from other layers, if any, having an efficiency of at least 90% for 0.75-1.00 micron sized particles with the combination of the fine fiber layer and substrate layer having less than a 15% difference in pressure drop relative to the substrate layer alone.   
   
   
       26 . The filter media of  claim 25 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, have an efficiency of at least 80% for 0.237-0.316 micron sized particles. 
   
   
       27 . The filter media of  claim 26 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, have an efficiency of at least 85% for 0.237-0.316 micron sized particles. 
   
   
       28 . The filter media of  claim 27 , wherein the substrate has an efficiency without the fine fiber layer of an efficiency of less than 40% for 0.237-0.316 micron sized particles. 
   
   
       29 . The filter media of  claim 25 , wherein the substrate has an efficiency without the fine fiber layer of an efficiency of less than 75% for 0.75-1.00 micron sized particles. 
   
   
       30 . The filter media of  claim 25 , wherein, the substrate layer comprise a cellulose based porous filter media, the cellulose fiber based porous filter media having the following characteristics:
 (a) a Frazier Permeability of between about 1 and about 400 CFM @ 0.5″ WG;   (b) an average fiber diameter of between about 2 and about 50 microns;   (c) a base weight of between about 30 and about 200 lb/3000 ft 2 ;   (d) a pore size distribution generally between about 2 and about 50 micron; and   (e) a Mullen burst strength of between about 5 and about 70 psi.   
   
   
       31 . The filter media of  claim 30 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 5%. 
   
   
       32 . The filter media of  claim 31 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 1%. 
   
   
       33 . The filter media of  claim 31 , wherein at least 50% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers. 
   
   
       34 . The filter media of  claim 25 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 50% of pore size distribution over a separation range of 6 micron. 
   
   
       35 . The filter media of  claim 25 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, having at least 60% of pore size distribution over a separation range of 6 micron. 
   
   
       36 . The filter media of  claim 25 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 40% of pore size distribution over a separation range of 4 micron. 
   
   
       37 . The filter media of  claim 36 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 45% of pore size distribution over a separation range of 4 micron. 
   
   
       38 . The filter media of  claim 25 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 25% of pore size distribution over a separation range of 2 micron. 
   
   
       39 . A filter media with controlled pore size distribution, comprising:
 a substrate layer of permeable media;   an electrospun fine fiber layer carried by the substrate layer, the combination of the substrate layer and the fine fiber layer apart from other layers, if any, having at least 50% of pore size distribution over a separation range of 6 micron.   
   
   
       40 . The filter media of  claim 39 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, having at least 60% of pore size distribution over a separation range of 6 micron. 
   
   
       41 . The filter media of  claim 39 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 40% of pore size distribution over a separation range of 4 micron. 
   
   
       42 . The filter media of  claim 41 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 45% of pore size distribution over a separation range of 4 micron. 
   
   
       43 . The filter media of  claim 41 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 25% of pore size distribution over a separation range of 2 micron. 
   
   
       44 . The filter media of  claim 39 , wherein, the substrate layer comprise a cellulose based porous filter media, the cellulose fiber based porous filter media having the following characteristics:
 (a) a Frazier Permeability of between about 1 and about 400 CFM @ 0.5″ WG;   (b) an average fiber diameter of between about 2 and about 50 microns;   (c) a base weight of between about 30 and about 200 lb/3000 ft 2 ;   (d) a pore size distribution generally between about 2 and about 50 micron; and   (e) a Mullen burst strength of between about 5 and about 70 psi.   
   
   
       45 . The filter media of  claim 44 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 10%. 
   
   
       46 . The filter media of  claim 45 , wherein at least 50% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers. 
   
   
       47 . The filter media of  claim 46 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 5%. 
   
   
       48 . The filter media of  claim 46 , wherein the fine fiber layer modifies the pressure drop across the substrate layer by less than 1%. 
   
   
       49 . A method of forming filter media, comprising:
 dissolving a polymer in a solvent to form a polymer solution;   electrospinning fine fibers from the polymer solvent from an electrode under an electrostatic field;   depositing the fine fibers onto a substrate layer; and   selecting at least one solvent and at least one polymer to generate a significant amount of fibers with a diameter of less than 100 nanometers.   
   
   
       50 . The method of  claim 49 , wherein selecting at least one solvent includes selecting a dissolving agent for the polymer and adjusting at least one of the conductivity and the surface tension with a control agent. 
   
   
       51 . The method of  claim 50 , wherein the control agent is a solvent different than the dissolving agent. 
   
   
       52 . The method of forming filter media of  claim 49 , wherein the method includes:
 containing the polymer solution in a receptacle;   dipping the electrode into the polymer solution and emitting fibers at several spinning locations from the electrode over a span;   running the substrate transverse to the span to collect the emitted fibers.   
   
   
       53 . The method of forming filter media of  claim 52 , further comprising solvent bonding the fine fibers to the substrate layer. 
   
   
       54 . The method of  claim 49 , wherein the spinning locations are in a generally linear array across the electrode along an edge of the electrode. 
   
   
       55 . The method of  claim 54 , wherein the linear array includes a plurality of rows spinning locations. 
   
   
       56 . The method of  claim 52 , wherein a plurality of electrodes are arranged with respective spans transverse to the running of the substrate, the electrodes spaced between inlet and outlet ends of a electrospinning region, the substrate running through the inlet end to the outlet end. 
   
   
       57 . The method of  claim 49 , further comprising spacing the substrate layer is spaced between about 4 and about 10 inches from the electrode, and controlling the relative humidity between about 30% and 50%. 
   
   
       58 . The method of  claim 57  wherein the polymer comprises a nylon and wherein the at least one solvent comprises an acid, the solvent ratio of polymer to solvent being controlled between about 8% and about 20%. 
   
   
       59 . The method of  claim 58 , wherein the at least one solvent includes a combination of acetic acid and formic acid. 
   
   
       60 . The method of  claim 59 , wherein the at least one solvent has a greater proportion of acetic acid than formic acid. 
   
   
       61 . A filter media made by the method of  claim 49 , comprising:
 a substrate layer of permeable media;   a fine fiber layer including a electrospun polymer carried by the substrate layer, the fine fiber layer including a significant amount of fibers with a diameter of less than 100 nanometers.   
   
   
       62 . The filter media of  claim 61 , wherein the significant amount means that the fine fiber layer includes an average fiber diameter of less than 100 nanometers. 
   
   
       63 . The filter media of  claim 61 , wherein the significant amount means a mean fiber diameter of less than 100 nanometers. 
   
   
       64 . The filter media of  claim 61 , wherein the significant amount means at least 25% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers. 
   
   
       65 . The filter media of  claim 61 , wherein at least 50% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers. 
   
   
       66 . The filter media of  claim 61 , wherein at least 70% of the fibers in the fine fiber layer have a diameter of less than 100 nanometers 
   
   
       67 . The filter media of  claim 61 , wherein at least 80% of the fibers have a diameter of between 50 and 100 nanometers. 
   
   
       68 . The filter media of  claim 61 , comprising:
 a substrate layer of permeable media;   an fine fiber layer including a electrospun polymer carried by the substrate layer, the combination of the substrate layer and the fine fiber layer apart from other layers, if any, having an efficiency of at least 90% for 0.75-1.00 micron sized particles, and wherein the combination of the fine fiber layer and the substrate layer have less than a 10% difference in pressure drop relative to the substrate layer alone.   
   
   
       69 . The filter media of  claim 68 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, have an efficiency of at least 80% for 0.237-0.316 micron sized particles. 
   
   
       70 . The filter media of  claim 69 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, have an efficiency of at least 85% for 0.237-0.316 micron sized particles. 
   
   
       71 . The filter media of  claim 70 , wherein the substrate has an efficiency without the fine fiber layer of an efficiency of less than 40% for 0.237-0.316 micron sized particles. 
   
   
       72 . The filter media of  claim 68 , wherein the substrate has an efficiency without the fine fiber layer of an efficiency of less than 75% for 0.75-1.00 micron sized particles. 
   
   
       73 . The filter media of  claim 68 , wherein, the substrate layer comprise a cellulose based porous filter media, the cellulose fiber based porous filter media having the following characteristics:
 (a) a Frazier Permeability of between about 1 and about 400 CFM @ 0.5″ WG;   (b) an average fiber diameter of between about 2 and about 50 microns;   (c) a base weight of between about 30 and about 200 lb/3000 ft 2 ;   (d) a pore size distribution generally between about 2 and about 50 micron; and   (e) a Mullen burst strength of between about 5 and about 70 psi.   
   
   
       74 . The filter media of  claim 68 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 50% of pore size distribution over a separation range of 6 micron. 
   
   
       75 . The filter media of  claim 68 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 60% of pore size distribution over a separation range of 6 micron. 
   
   
       76 . The filter media of  claim 68 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 40% of pore size distribution over a separation range of 4 micron. 
   
   
       77 . The filter media of  claim 76 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 45% of pore size distribution over a separation range of 4 micron. 
   
   
       78 . The filter media of  claim 77 , wherein the combination of the substrate layer and the fine fiber layer apart from other layers, if any, has at least 25% of pore size distribution over a separation range of 2 micron.