Formed filter element

Abstract

A filter medium for use in filtering a mobile fluid made from at least a bicomponent fiber. Other fibers, particles, or other materials can also be entrained in the filter medium. The filter medium has a substantial thickness compared to filters of the prior art. The fiber length and diameter dimensions are selected to obtain desired filter characteristics including thickness, basis weight, pore size, filtration efficiency, pressure drop, burst strength, and manufacturing efficiency. Further, a multilayer filter medium can be provided with ease. Each layer can have a different composition, pore size, basis weight, and so forth, thus providing the ability to build multiple functionality into the filter media of the invention.

1 . A filter medium comprising:
 a bicomponent fiber; and   a particle, the particle comprising at least one of a metal oxide, a metal, a ceramic, a zeolite, a carbon, an ion exchange resin, or a nanotube,   wherein the filter medium has a basis weight at least about 500 gram/meter 2 , a permeability of about 0.5 to 200 fpm inclusive, a thickness equal to or greater than 8 millimeters, and a solidity of less than about 25%.   
     
     
         2 . The filter medium of  claim 1 , wherein the bicomponent fiber is about 20 to 95 wt % inclusive of the filter medium. 
     
     
         3 . The filter medium of  claim 2 , further comprising, about 80 to 5 wt % inclusive of a glass fiber having a fiber diameter of about 0.1 to 8.0 microns inclusive and aspect ratio of greater than about 1:100. 
     
     
         4 . The filter medium of  claim 3  wherein the filter medium has a thickness greater than about 5 centimeters. 
     
     
         5 . The filter medium of  claim 3  wherein the bicomponent fiber has a diameter of about 5 to 50 micrometers inclusive and a length of about 0.1 to 20 millimeters inclusive. 
     
     
         6 . The filter medium of  claim 3  wherein the bicomponent fiber has a diameter of about 10 to 20 micrometers inclusive and a length of about 0.2 to 15 millimeters inclusive. 
     
     
         7 . The filter medium of  claim 3  wherein the bicomponent fiber comprises a core material disposed within a sheath material. 
     
     
         8 . The filter medium of  claim 7  wherein the core material has a higher melting point than the sheath material. 
     
     
         9 . The filter medium of  claim 8  wherein the core material has a melting point of about 200° C. to 260° C. inclusive and the sheath material has a melting point of about 80° C. to 200° C. inclusive. 
     
     
         10 . The filter medium of  claim 7  wherein the sheath material comprises a polyolefin, a polyester, a polyvinyl acetate, a polyvinyl chloride, a polyvinyl butyral, an acrylic resin, a polyamide, a polyvinylidene chloride, a polystyrene, a polyvinyl alcohol, a polyurethane, a cellulosic resin, a styrene-butadiene copolymer, an acrylonitrile-butadiene-styrene copolymer, a KRATON® rubber available from Kraton Polymers U.S. LLC of Houston, Tex., or a copolymer blend or a mixture thereof. 
     
     
         11 . The filter medium of  claim 3 , further comprising a binder. 
     
     
         12 . The filter medium of  claim 11  wherein the binder is a latex. 
     
     
         13 . The filter medium of  claim 11  wherein the binder comprises an acrylic, ethylene vinyl acetate, a polyvinyl alcohol, an ethylene vinyl alcohol, a polyvinyl pyrrolidone, a polyvinyl chloride, or a copolymer or a blend thereof. 
     
     
         14 . The filter medium of  claim 11  wherein the binder is solvent borne. 
     
     
         15 . The filter medium of  claim 14  wherein the binder comprises a phenolic resin, a polyvinyl acetate, a polyvinyl alcohol, an acrylic resin, a methacrylic resin, a polyurethane, a polycyanoacrylate, an epoxy, a melamine resin, a polycaprolactone, or a blend or a copolymer thereof. 
     
     
         16 . The filter medium of  claim 3 , further comprising a thermoplastic fiber. 
     
     
         17 . The filter medium of  claim 16  wherein the thermoplastic fiber comprises a polyester, a polyamide, a polypropylene, a copolyetherester, a polyetherketoneketone, a polyetheretherketone, a liquid crystalline polymer, or a copolymer or a mixture thereof. 
     
     
         18 . The filter medium of  claim 17  wherein the thermoplastic fiber comprises a polyester comprising poly(ethylene terephthalate). 
     
     
         19 . The filter medium of  claim 3  further comprising an antioxidant, a stabilizer, a lubricant, a toughener, a dispersing aid, a binder, a surface active agent, an acid, a catalyst, or a mixture thereof. 
     
     
         20 . The filter medium of  claim 3  further comprising an inorganic fiber. 
     
     
         21 . The filter medium of  claim 20  wherein the inorganic fiber comprises a carbon, a metal, a metal oxide, or a combination thereof. 
     
     
         22 . The filter medium of  claim 3  further comprising a fiber comprising one or more naturally occurring cotton, linen, wool, cellulosic or proteinaceous polymers. 
     
     
         23 . The filter medium of  claim 3  wherein the particle is the carbon, the carbon comprising activated charcoal. 
     
     
         24 . The filter medium of  claim 3  wherein the particle has an average particle size of 3 millimeters or less. 
     
     
         25 . The filter medium of  claim 3  wherein the filter medium has an average pore size of 0.1 to 50 micrometers inclusive. 
     
     
         26 . The filter medium of  claim 3  wherein the filter medium has an efficiency of greater than about 50% as measured by ASTM-1215-89 using 0.78μ monodisperse polystyrene spherical particles at 20 fpm. 
     
     
         27 . The filter medium of  claim 3  wherein the filter medium has a Di-octyl Phthalate (DOP) efficiency in filtering 2 μm aerosol particles of at least about 95%. 
     
     
         28 . The filter medium of  claim 3  wherein the filter medium has a burst strength of at least 10 psid. 
     
     
         29 . The filter medium of  claim 3  wherein the filter medium has a tensile strength of at least 20 psi and an elongation at break of between about 1.0 and 10.0%. 
     
     
         30 . The filter medium of  claim 3  wherein a pressure drop across the filter medium at 60 psi applied air pressure is less than about 2.0 psi after 200 hours of filtration at 60 psi of air containing oily particles. 
     
     
         31 . The filter medium of  claim 3  wherein a pressure drop across the filter medium at 60 psi applied air pressure is less than about 10.0 psi after 8000 hours of filtration at 60 psi of air containing oily particles. 
     
     
         32 . The filter medium of  claim 3  wherein an oil carryover is less than about 2.0 ppm after 1000 hours of filtration at 60 psi of air containing oily particles. 
     
     
         33 . The filter medium of  claim 3  wherein an oil carryover is less than about 3.0 ppm after 4000 hours of filtration at 60 psi of air containing oily particles. 
     
     
         34 . The filter medium of  claim 3  wherein an oil carryover is less than about 5.0 ppm after 8000 hours of filtration at 60 psi of air containing oily particles. 
     
     
         35 . The filter medium of  claim 3  wherein a discharge temperature is less than about 93° C. after 8000 hours of filtration at 60 psi of air containing oily particles. 
     
     
         36 . The filter medium of  claims 2  further comprising about 80 to 5 wt % inclusive of a first glass fiber having a diameter of about 0.1 to 8.0 microns inclusive and a second glass fiber having a fiber diameter of about 8.0 to 13.0 microns inclusive. 
     
     
         37 . The filter medium of  claim 2  further comprising about 80 to 5 wt % inclusive of a first glass fiber having a diameter of less than about 1.0 micron and a second glass fiber having a diameter of more than 1.0 micron. 
     
     
         38 . The filter medium of  claim 2  further comprising about 80 to 5 wt % inclusive of a first glass fiber having a diameter of about 0.1 to 2.0 microns inclusive and a second glass fiber having a fiber diameter of about 2.6 to 8.0 microns inclusive. 
     
     
         39 . The filter medium of  claim 2  further comprising about 80 to 5 wt % inclusive of a first glass fiber having a diameter of about 0.5 to 0.8 microns inclusive and a second glass fiber having a diameter of about 2.6 to 3.0 microns inclusive. 
     
     
         40 . A process to form a filter medium, comprising the steps of:
 blending a first mixture of fibers comprising a bicomponent fiber to form a first aqueous slurry;   applying the first aqueous slurry to a support to form a first wet layer;   removing sufficient water from the first wet layer to make a first formed layer;   blending a second mixture of fibers to form a second aqueous slurry, wherein the composition of the second mixture of fibers differs from the composition of the first mixture of fibers;   applying the second aqueous slurry to the first formed layer to form a second wet layer;   removing sufficient water to form a second formed layer; and   heating the first and second formed layers to a temperature sufficient to melt one component of the bicomponent fiber.   
     
     
         41 . The process of  claim 40  wherein the water is removed from the first and second wet layers by a vacuum means. 
     
     
         42 . The process of  claim 40  wherein the fibers are substantially dried during the heating step. 
     
     
         43 . The process of  claim 40  wherein one or more of the first and second mixture of fibers comprises about 20 to 95 wt % inclusive of a bicomponent fiber; and about 80 to 5 wt % inclusive of a glass fiber. 
     
     
         44 . The process of  claim 43  wherein the glass fiber has a diameter of about 0.1 to 8.0 microns inclusive and aspect ratio of greater than about 1:100. 
     
     
         45 . The process of  claim 43  wherein the glass fiber comprises a first glass fiber having a diameter of about 0.1 to 8.0 microns inclusive and a second glass fiber having a fiber diameter of about 8.0 to 13.0 microns inclusive. 
     
     
         46 . The process of  claim 43  wherein the glass fiber comprises a first glass fiber having a diameter of about 0.1 to 2.0 microns inclusive and a second glass fiber having a fiber diameter of about 2.6 to 8.0 microns inclusive. 
     
     
         47 . The process of  claim 40  wherein the filter medium after the heating step has a thickness equal to or greater than 8 millimeters. 
     
     
         48 . The process of  claim 40  wherein the filter medium after the heating step has a thickness greater than about 5 centimeters. 
     
     
         49 . The process of  claim 40  wherein the bicomponent fiber has a diameter of about 5 to 50 micrometers inclusive and a length of about 0.1 to 20 millimeters inclusive. 
     
     
         50 . The process of  claim 40  wherein the bicomponent fiber comprises a core material disposed within a sheath material, the core material having a melting point of about 200° C. to 260° C. inclusive and the sheath material having a melting point of about 80° C. to 200° C. inclusive. 
     
     
         51 . The process of  claim 50  wherein the sheath material comprises a polyolefin, a polyester, a polyvinyl acetate, a polyvinyl chloride, a polyvinyl butyral, an acrylic resin, a polyamide, a polyvinylidene chloride, a polystyrene, a polyvinyl alcohol, a polyurethane, a cellulosic resin, a styrene-butadiene copolymer, an acrylonitrile-butadiene-styrene copolymer, KRATON® rubbers available from Kraton Polymers U.S. LLC of Houston, Tex., or a copolymer or a mixture thereof. 
     
     
         52 . The process of  claim 40 , further comprising adding a binder to one or more of the first and second aqueous slurries. 
     
     
         53 . The process of  claim 52  wherein the binder is a latex binder, the latex binder comprising an acrylic, an ethylene vinyl acetate, a polyvinyl alcohol, an ethylene vinyl alcohol, a polyvinyl pyrrolidone, a polyvinyl chloride, or a copolymer or a blend thereof. 
     
     
         54 . The process of  claim 52  wherein the binder is solvent borne, the binder comprising a phenolic resin, a polyvinyl acetate, a polyvinyl alcohol, an acrylic resin, a methacrylic resin, a polyurethane, a polycyanoacrylate, an epoxy, a melamine resin, a polycaprolactone, or a copolymer or blend thereof. 
     
     
         55 . The process of  claim 40 , further comprising adding a thermoplastic fiber to one or more of the first and second aqueous slurries, the thermoplastic fiber comprising a polyester, a polyamide, a polypropylene, a copolyetherester, a polyethylene terephthalate, a polybutylene terephthalate, a polyetherketoneketone, a polyetheretherketone, a liquid crystalline polymer, and mixtures thereof. 
     
     
         56 . The process of  claim 55  wherein the thermoplastic fiber comprises a polyester comprising poly(ethylene terephthalate). 
     
     
         57 . The process of  claim 40  further comprising adding an antioxidant, a stabilizer, a lubricant, a toughener, a dispersing aid, a surface active agent, an acid, a catalyst, or a mixture thereof. 
     
     
         58 . The process of  claim 40  further comprising adding an inorganic fiber to one or more of the first and second aqueous slurries, the inorganic fiber comprising a carbon, a metal, a metal oxide, or a combination thereof. 
     
     
         59 . The process of  claim 40  further comprising adding a fiber to one or more of the first and second aqueous slurries, the fiber comprising one or more naturally occurring cotton, linen, wool, cellulosic or proteinaceous polymers. 
     
     
         60 . The process of  claim 40  further comprising adding a particle to one or more of the first and second aqueous slurries, the particle comprising a metal oxide, a metal, a ceramic, a zeolite, a carbon, an ion exchange resin, a nanotube, or a mixture thereof. 
     
     
         61 . The process of  claim 60  wherein the particle is the carbon, the carbon comprising activated charcoal. 
     
     
         62 . The process of  claim 60  wherein the particle has an average particle size of 3 millimeters or less. 
     
     
         63 . The process of  claim 40 , further comprising adding an additive to one or more of the first and second slurries after the heating step, the additive comprising a surface finish compound, a compound to change the surface energy of one or more fibers, an acid, a base, a fluorocarbon, a flame retardant compound, a catalyst, an antistatic compound, or a combination thereof. 
     
     
         64 . The process of  claim 63  wherein the additive is added by means of dipping the filter medium in a solvent having the additive dispersed therein. 
     
     
         65 . The process of  claim 63  wherein the additive is added by a spraying means. 
     
     
         66 . The process of  claim 40 , further comprising adding an additive to one or more of the first and second slurries, the additive comprising a surface finish compound, a compound to change the surface energy of one or more fibers, an acid, a base, a fluorocarbon, a flame retardant compound, a catalyst, an antistatic compound, or a combination thereof. 
     
     
         67 . The process of  claim 40 , further comprising heating the first formed layer prior to applying the second aqueous slurry to the first formed layer. 
     
     
         68 . A method of removing an impurity from a fluid stream comprising:
 contacting a stream containing an impurity with a filter medium comprising a bicomponent fiber, wherein the filter medium has a basis weight at least about 500 gram/meter 2 , a permeability of about 0.5 to 200 fpm inclusive, a thickness equal to or greater than 8 millimeters, and a solidity of less than 25%; and   passing the stream through the filter medium such that the impurity is removed from the fluid stream.   
     
     
         69 . The method of  claim 68  wherein the filter medium comprises a particle of at least one of metal oxide, a metal, a ceramic, a zeolite, a carbon, an ion exchange resin, or a nanotube. 
     
     
         70 . The method of  claim 68  wherein the filter medium has a thickness of greater than 5 centimeters. 
     
     
         71 . The method of  claim 68  wherein the stream is a gas or a liquid. 
     
     
         72 . The method of  claim 71  wherein the stream is the gas and the gas is air. 
     
     
         73 . The method of  claim 71  wherein the stream is the liquid and the liquid is water. 
     
     
         74 . The method of  claim 68  wherein the stream comprises gasoline, diesel fuel, motor oil, or a combination thereof. 
     
     
         75 . The method of  claim 68  wherein the impurity is a particle. 
     
     
         76 . The method of  claim 75  wherein the impurity particle comprises dust, soot or smoke. 
     
     
         77 . The method of  claim 75  where the impurity particle is an aerosol. 
     
     
         78 . The method of  claim 77  wherein the aerosol is an oil. 
     
     
         79 . The method of  claim 77  wherein the aerosol is aqueous. 
     
     
         80 . The method of  claim 77  wherein between about 700 and 20,000 ppm of the aerosol per million parts by volume of the stream is present in the stream prior to contact with the filter medium. 
     
     
         81 . The method of  claim 68  wherein the impurity is a compound. 
     
     
         82 . The method of  claim 81  wherein the compound comprises a toxin, a carcinogen, a teratogen, a mutagen, or a lachrymator. 
     
     
         83 . The method of  claim 68  wherein the stream passes through the filter medium at a rate of 0.5 to 200 fpm inclusive.