Expanded composite filter media including nanofiber matrix and method

Abstract

A composite filter media includes an expanded substrate media carrying fine fibers, wherein the fine fibers are extended with the expanding substrate media, thereby improving dust holding capacity and slowing down pressure drop increase.

1 . A method of making a filter media, comprising:
 depositing fine fibers on a surface of a substrate having a first thickness, the fine fibers having an average diameter of less than 1 micron; and   expanding the substrate to a second thickness greater than the first thickness carrying the fine fibers therewith.   
     
     
         2 . The method of  claim 1 , further comprising forming the substrate, wherein multi-component fibers having a low melt polymer component and a high melt polymer component are compressed to form the substrate having the first thickness. 
     
     
         3 . The method of  claim 2 , wherein depositing fine fibers comprises electrospinning the fine fibers and depositing the fine fibers directly on the surface of the substrate, wherein some of the fine fibers are attached to some of the multi-component fibers proximate the surface of the substrate. 
     
     
         4 . The method of  claim 3 , electrospinning the fine fibers involves depositing the fine fibers on the surface of the substrate to obtain a fine fiber coverage between about 0.012 g/m 2  and 0.025 g/m 2 . 
     
     
         5 . The method of  claim 3 , wherein expanding comprises heating the filter media, wherein the multi-component fibers of the substrate relax and reorient, thereby expanding the substrate to the second thickness and forming an undulating surface; wherein the fine fibers are extended as the fine fibers move with the multi-component fibers carrying the fine fibers, wherein the fine fibers are integrated into 3-dimensional matrix with multi-component fibers of the undulating surface. 
     
     
         6 . The method of  claim 5 , wherein heating comprises heating the filter media to about a melting temperature of the low melt polymer component, wherein the low melt polymer component melts or softens, wherein some of the fine fibers are embedded in the melted or softened low melt polymer component. 
     
     
         7 . The method of  claim 1 , wherein the second thickness is at least 1.5 times the first thickness after expansion. 
     
     
         8 . The method of  claim 1 , wherein the second thickness is at least double the first thickness after expansion. 
     
     
         9 . The method of  claim 1 , further comprising laminating a filter layer such that the fine fibers are sandwiched between the substrate media and the filter layer, wherein the filter media comprising the substrate media, fine fibers and the filter layer is heated, wherein the substrate and filter layer expand and the fine fibers are extended. 
     
     
         10 . The method of  claim 1 , further comprising laminating multiple layers of the substrate carrying the fine fibers and a filter layer, such that each layer of the fine fibers is sandwiched between the substrates or between the substrate and the filter layer; wherein the laminated layers are heated, wherein the substrates and the filter layer expand, and fine fibers are extended and integrated within undulating surfaces of the substrates. 
     
     
         11 . A filter media comprising:
 a substrate of first fibers having an average fiber diameter of greater than 1 micron carrying fine fibers having an average fiber diameter of less than 1 micron, the substrate having an undulating surface such that the fine fibers are integrated into 3-dimensional matrix with the first fibers of the undulating surface.   
     
     
         12 . The filter media of  claim 11 , wherein the substrate is an expanded scrim comprising multi-component fibers, the expanded scrim having a first unexpanded state, the scrim in the first unexpanded state having a generally flat surface and a thickness less than that of the expanded scrim, the undulating surface being formed during an expansion from the first expansion state to the expanded scrim. 
     
     
         13 . The filter media of  claim 12 , wherein the multi-component fibers include a first component and a second component, wherein the first component has a higher melting temperature than the second component; wherein the fine fibers are attached to the multi-component fibers of the undulating surface via the second component. 
     
     
         14 . The filter media of  claim 13 , wherein the first component is formed of a high melt polyester and the second component is formed of a low melt polyester; wherein the fine fibers are electrospun polyamide nanofibers. 
     
     
         15 . The filter media of  claim 12 , wherein the scrim carries the fine fibers on or proximate a surface level in the first unexpanded state, wherein the first fibers are reoriented in the expanded scrim, the first fibers carrying and extending the fine fibers therewith; wherein fine fibers are integrated beyond the surface level to a greater depth in the expanded scrim than in the unexpanded state. 
     
     
         16 . The filter media of  claim 15 , wherein the filter media including the expanded scrim has a higher dust holding capacity and a slower pressure drop increase than the filter media including the scrim in the first unexpanded state. 
     
     
         17 . The filter media of  claim 11 , further including a scrim, wherein the fine fibers are laminated between the substrate and the scrim. 
     
     
         18 . The filter media of  claim 11 , wherein the filter media comprises multiple layers of the substrate carrying the fine fibers; and further comprising a scrim; wherein the each layer of the fine fibers are sandwiched between layers of the substrate or the substrate and the scrim. 
     
     
         19 . The filter media of  claim 18 , wherein each layer of the substrate is formed of a multi-component scrim comprising a multi-component fibers, the multi-component fibers including a high melt component and a low melt component; wherein the fine fibers are formed of electrospun polymer nanofibers; wherein the electrospun polymer nanofibers and the high melt component has a higher melting temperature than the low melt component; wherein the multi-component scrim is expanded from an unexpanded state via heating; wherein the low melt component melts or softens during heating and bonds with the fine fibers; wherein the fine fibers are extended as the multi-component scrim expands. 
     
     
         20 . The filter media of  claim 10 , wherein the substrate is formed of a multi-component fiber scrim having an average fiber diameter between about 1 and 40 microns and a base weight between about 0.5 and 15 oz/yd 2 ; wherein the fine fibers have an average fiber diameter between about 0.01 and 0.5 microns; and each layer of the fine fibers has a fine fiber coverage between about 0.012 g/m 2  and 0.025 g/m 2 ; wherein the filter media has a Frazier air permeability between about 100 and 200 CFM, and a MFP dust holding weight of about 400-600 mg/100 cm 2  with a final pressure drop of about 1.5 inch W.G.