Filtration media

Abstract

A filtration media with improved filtration, strength, tear resistance and air permeability in the form of a relatively thin and lightweight wet-laid fibrous web that has a wet Mullen ratio of 60% to 75% to ensure that the media is flexible enough to be formed into a fluted structure, and strong enough to retain the fluted structure when wound into a roll and to permit further processing without the media becoming too brittle. The filtration media comprises a blend of cellulose and synthetic fibers having a basis weight of 81% to 87% of a basis weight of the media and a resin binder having a basis weight of 13% to 19% (preferably about 16%) of the basis weight of the media.

We claim: 
     
         1 . A filtration media comprising a blend of fibers having a basis weight of 81% to 87% of a basis weight of the media and a resin binder having a basis weight of 13% to 19% of the basis weight of the media, the blend of fibers comprising cellulose fibers having a basis weight of about 82.5% to about 96% of the basis weight of the media and synthetic fibers having a basis weight of about 4% to about 17.5% of the basis weight of the media, the cellulose fibers comprising about 32% to about 66% by weight of the media softwood pulp of a type that when formed into a handsheet with a caliper of less than 23 mils, the handsheet has an air permeability of 100-175 cfm, and the media has a wet Mullen Ratio of 60% to 75%. 
     
     
         2 . The filtration media of  claim 1 , wherein the cellulose fibers further comprise hardwood pulp having a basis weight of about 13% to about 41% of the media. 
     
     
         3 . The filtration media of  claim 2 , wherein the synthetic fibers are polyester fibers having a denier of 1 to 3 and a length of ¼ to ½ inch. 
     
     
         4 . The filtration media of  claim 1 , wherein the resin comprises a phenolic resin binder with a crosslinking agent. 
     
     
         5 . The filtration media of  claim 1 , wherein the media has a tear resistance of at least 50 g/16 ply in the machine direction and at least 60 g/16 ply in the cross direction. 
     
     
         6 . The filtration media of  claim 1 , wherein the caliper of the media is about 10 to 12 mils. 
     
     
         7 . The filtration media of  claim 1 , wherein the basis weight of the media is 35 to 45 pounds/3000 square feet. 
     
     
         8 . The filtration media of  claim 1 , wherein the media has an air permeability of at least 25 cfm. 
     
     
         9 . The filtration media of  claim 1 , wherein the media has a pressure drop of less than 350 Pa for dust loading of 30 mg/cm 2  when testing with SAE fine dust at a concentration of 200 mg/m 3  and a face velocity of 5 cm/sec. 
     
     
         10 . The filtration media of  claim 1 , wherein the media has a removal efficiency of at least 20% when measured in accordance with ASTM-125-89, where dust has been substituted for latex particles. 
     
     
         11 . The filtration media of  claim 1 , wherein the media comprises pores having a maximum pore size of 43 to 63 microns and an average pore size between 10 and 20 microns. 
     
     
         12 . The filtration media of  claim 3 , wherein the hardwood pulp is eucalyptus. 
     
     
         13 . A filtration media comprising a blend of fibers having a basis weight of 81% to 87% of a basis weight of the media and a resin binder having a basis weight of 13% to 19% of the basis weight of the media, the media having a wet Mullen Ratio of 60% to 75%, the blend of fibers comprising softwood pulp in an amount of about 32% to about 66% by weight of the media, the softwood pulp being of a type that when formed into a handsheet with a caliper of less than 23 mils, the handsheet has an air permeability of 100-175 cfm. 
     
     
         14 . The filtration media of  claim 13 , wherein the resin comprises a phenolic resin binder with a crosslinking agent. 
     
     
         15 . The filtration media of  claim 14 , wherein the blend of fibers further comprises synthetic fibers having a basis weight of about 4% to about 17.5% of the basis weight of the media and hardwood pulp having a basis weight of about 13% to about 41% of the media. 
     
     
         16 . The filtration media of  claim 14 , wherein the synthetic fibers are polyester fibers having a denier of 1 to 3 and a length of ¼ to ½ inch. 
     
     
         17 . The filtration media of  claim 16 , wherein the caliper of the media is about 10 to 12 mils and the basis weight of the media is about 35 to 45 pounds/3000 square feet. 
     
     
         18 . The filtration media of  claim 16 , wherein the media comprises pores having a maximum pore size of 43 to 63 microns and an average pore size between 10 and 20 microns.