Filter element

Abstract

A filter element adapted for attachment to a respirator face piece which includes front and rear walls of filter material, a breather tube, and a porous inner layer which maintains the front and rear walls in a spaced-apart relationship over substantially their entire area and which functions to evenly distribute air flow across the available filter element surface area.

What is claimed is: 
     
       1. A filter element comprising (A) substantially coextensive front and rear walls joined to each other along their peripheral edges and defining an interior space between them; the front and rear walls each comprising at least one layer of a filter material, and the rear wall, including said layer of filter material, having an opening that provides access to the interior space defined by the front and rear walls,   (B) a porous layer contained between the front and rear walls .Iadd.within the interior space .Iaddend.substantially coextensive with the walls, which maintains the walls .[.is.]. .Iadd.in .Iaddend.a spaced-apart relationship over substantially their entire area, and which contributes no more than 50% of the total pressure drop across the filter element, .Iadd.said porous layer comprising material selected from the group consisting of woven webs, nonwoven webs, loose fibers, fiber batts, loose particulate material, particulate material bonded together in a porous matrix, or combinations thereof, .Iaddend.and   (C) a breather tube having one end that communicates through said opening with the .Iadd.porous layer within the .Iaddend.interior space between the front and rear walls, and adapted at its other end for securing the filter element to a respirator face piece,   the air being drawn through the front and rear walls into the porous layer within the space between the front and rear walls, and from the interior space through the breather tube into a respirator face piece.Iadd.. .Iaddend.   
     
     
       2. The filter element of claim 1 wherein said front and rear walls and said porous layer are joined together along their peripheral edges. 
     
     
       3. The filter element of claim 1 wherein said filter element is round. 
     
     
       4. The filter element of claim 1 further comprising flexible cover layers disposed over the exterior surface of the filter element. 
     
     
       5. The filter element of claim 4 wherein said cover layers comprise polyolefin. 
     
     
       6. The filter element of claim 1 wherein said at least one layer of filter material comprises material selected from the group consisting of nonwoven microfiber webs, fibrillated film webs, air-laid webs, carded webs, or combinations thereof. 
     
     
       7. The filter element of claim 6 wherein said at least one layer of filter material comprises material selected from the group consisting of polyolefin, polycarbonate, polyester, polyurethane, polyamide, glass, cellulose, carbon, alumina, or combinations thereof. 
     
     
       8. The filter element of claim 1 wherein said at least one layer of filter material comprises a plurality of layers of electrically charged, nonwoven, blown microfiber web. 
     
     
       9. The filter element of claim 8 wherein said electrically charged, nonwoven, blown microfiber web comprises polyolefin. 
     
     
       10. The filter element of claim 8 wherein said electrically charged, nonwoven, blown microfiber web comprises polypropylene. 
     
     
       11. The filter element of claim 1 wherein said at least one layer of filter element comprises sorbent particle-loaded fibrous web. 
     
     
       12. The filter element of claim 11 wherein said sorbent particle-loaded fibrous web is selected from the group consisting of alumina-particle-loaded or carbon-loaded web. .[.13. The filter element of claim 1 wherein said porous layer comprises material selected from the group consisting of woven webs, nonwoven webs, loose fibers, fiber batts, loose particulate material, particulate material bonded together in a 
     
     
        porous matrix, or combination thereof..]. 14. The filter element of claim .[.13.]. .Iadd.1 .Iaddend.wherein said porous layer comprises material selected from the group consisting of polyolefin, polycarbonate, polyurethane, polyester, polyamide, glass, cellulose, carbon, alumina or 
     
     
        combinations thereof. 15. The filter element of claim .[.13.]. .Iadd.1 .Iaddend.wherein said particulate material bonded together in a porous 
     
     
        matrix comprises sorbent particles. 16. The filter element of claim 15 wherein said porous matrix comprises sorbent carbon particles bonded 
     
     
        together with polyurethane resin. 17. The filter element of claim .[.13.]. .Iadd..Iaddend.wherein said porous layer comprises .Iadd.a 
     
     
        .Iaddend.nonwoven web. 18. The filter element of claim 17 wherein said non-woven web is selected as from a group consisting of glass filter paper, air-laid web, carded web, fibrillated film web, sorbent 
     
     
        particle-loaded fibrous web, or combinations thereof. 19. The filter element of claim 17 wherein said non-woven web comprises a blend of staple 
     
     
        and binder fibers bonded together at points of fiber intersection. 20. The filter element of claim 17 wherein the fiber diameter of said nonwoven web is no less than about 10 microns and the solidity of said nonwoven web is 
     
     
        no greater than about 11%. 21. The filter element of clahn 18 wherein said 
     
     
        air-laid web comprises polyester. 22. The filter element of claim 18 
     
     
        wherein said carded web comprises polyester. 23. The filter element of claim 18 wherein said sorbent-particle-loaded fibrous web is selected from the group consisting of alumina-particle-loaded or carbon particle-loaded 
     
     
        web. 24. The filter element of claim 1 wherein said porous layer is 0.2 cm 
     
     
        to 4.0 cm thick. 25. The filter element of claim 24 wherein said porous 
     
     
        layer is 0.3 cm to 1.3 cm thick. 26. The filter element of claim 1 wherein 
     
     
        said of the breather tube is cylindrical in shape. 27. The filter element of claim 26 wherein the inner diameter of the breather tube is 1.0 to 4.0 
     
     
        cm. 28. The filter element of claim 27 wherein diameter of the breather 
     
     
        tube is 1.5 to 3.5 cm. 29. The filter element of claim 1 wherein said .[.nonwoven web comprises the front and rear walls and the porous layer.]. .Iadd.front and rear walls and said porous layer comprise nonwoven 
     
     
        webs..Iaddend. 30. A filter element comprising (A) substantially coextensive front and rear walls joined to each other along their peripheral edges and defining an interior space between them; the front and rear walls each comprising at least one layer of filter material, and the rear wall, including said layer of filter material having an opening that provides access to the interior or space defined by the front and rear walls,   (B) a porous layer contained between the front and rear walls .Iadd.within the interior space .Iaddend.which is substantially coextensive with the walls, which maintains the walls in a spaced-apart relationship substantially their entire area, and which contributes no more than 50% of the total pressure drop across the filter element, .Iadd.said porous layer comprising material selected from the group consisting of woven webs, nonwoven webs, loose fibers, fiber batts, loose particulate material, material bonded together in a porous matrix, or combinations thereof, .Iaddend.and   (C) a breather tube having one end that communicates through said opening with the .Iadd.porous layer within the .Iaddend.interior space between the front and rear walls, and adapted at its other end for securing the filter element to a respirator face piece.Iadd., .Iaddend.   .Iadd.the air being drawn through the front and rear walls into the porous layer within the interior space between the front and rear walls, and from the interior space through the breather tube into a respirator face piece, .Iaddend.   wherein said filter element will permit no more than 1.5 mg penetration of silica dust having a geometric means particle diameter of 0.4-0.6 micrometer through said filter element over a 90 minute period at an air flowrate of 16 liters per minute, a pressure drop across said filter element before the 90 minute period of no more than 30 mm H 2  O, and a pressure drop across the filter element after the 90 minute period of not   
     
     
        more than 50 mm H 2  O. 31. A filter element comprising (A) substantially coextensive front and rear walls joined to each other along their peripheral edges and defining an interior space between them; the front and rear walls each comprising at least one layer of a filter material, and the rear wall, including said layer of filter material, having an opening that provides accesss to the interior space defined by the front and rear walls,   (B) a porous layer contained between the front and rear walls within the iterior space which is substantially coextensive with the walls, which maintains the walls in a spaced-apart relationship over substantially their entire area, and which contributes no more than 50% of the total pressure drop across the filter element, .Iadd.said porous layer comprising material selected from the group consisting of woven webs, nonwoven webs, loose fibers, fiber batts, loose particulate material, particulate material bonded together in a porous matrix, or combinations thereof, .Iaddend.and   (C) a breather tube having one end that communicates through said opening with the .Iadd.porous layer within the .Iaddend.interior space between the front and rear walls, and adapted at its other end for securing the filter element to a respirator face piece .Iadd.   the air being drawn through the front and rear walls into the porous layer within the interior space between the front and rear walls, and from the interior space through the breather tube into a respirator face piece, .Iaddend.   wherein said filter element will permit   (i) no more than about 3.0 percent penetration of 0.3 micrometer diameter particles of dioctyl phthalate contained in a stream at a concentration 100 micrograms/l, at a flow rate of 42.5 liters per minute, and   (ii) no more than 1.5 mg penetration of silica dust having a geometric means particle diameter of 0.4-0.6 micrometer through said filter element over a 90 minute period at an air flowrate of 16 liters per minute, a pressure drop across said filter element before the 90 minute period of no more than 30 mm H 2  O, and a pressure drop across the filter element   
     
     
        after the 90 minute period of not more than 50 mm of H 2  O. 32. The filter element of claim 32 wherein said penetration of 0.3 micrometer 
     
     
        diameter particles of dioctyl phthalate is about 0.03 percent. 33. A filter element comprising (A) substantially coextensive front and rear walls joined to each other along their peripheral edges and defining an interior space between them; the front and rear walls each comprising at least one layer of a filter material, and the rear wall, including said layer of filter material, having an opening that provides access to the interior space defined by the front and rear walls,   (B) a porous layer contained between the front and rear walls .Iadd.within the interior space .Iaddend.which is substantially coextensive with the walls, which maintains the walls in a spaced-apart relationship over substantially their entire area, and which contributes no more than 50% of the total pressure drop across the filter element, .Iadd.said porous layer comprising material selected from the group consisting of woven webs, nonwoven webs, loose fibers, fiber batts, loose particulate material, particulate material bonded together in a porous matrix, or combinations thereof, .Iaddend.and   (C) a breather tube having one end that communicates through said opening with the .Iadd.porous layer within the .Iaddend.interior space between the front and rear walls, and adapted at its other end for securing the filter element to a respirator face piece,   .Iadd.the air being drawn through the front and rear walls into the porous layer within the space between the front and rear walls, and from the interior space through the breather tube into a respirator face piece, .Iaddend.   wherein said filter element will permit no more than 1.5 mg penetration of lead fume penetration, through said filter element over a 312 minute period at an air flowrate of 16 liters per minute, a pressure drop across said filter element before the 312 minute period of no more than 30 mm of H 2  O, and a pressure drop across the filter element after the 312   
     
     
        minute period of not more than 50 mm of H 2  O. 34. One or more filter elements of claim 1 in combination with a respirator comprising a face 
     
     
        piece. 35. One or more filter elements of claim 30 in combination with a 
     
     
        respirator comprising a face piece. 36. One or more filter elements of 
     
     
        claim 31 in combination with a respirator comprising a face piece. 37. One or more filter elements of claim 33 in combination with a respirator comprising a face piece. .[.38. A method of filtering air comprising drawing air to be filtered through either the front or rear wall of a filter element comprising (A) substantially coextensive front and rear walls joined to each other along their peripheral edges and defining an interior space between them; the front and rear walls each comprising at least one layer of a filter material, and the rear wall, including said layer of filter material, having an opening that provides access to the interior space defined by the front and rear walls,   (B) a porous layer contained between the front and rear walls which is substantially coextensive with the walls, which maintains the walls in a spaced-apart relationship over substantially their entire area, and which contributes no more than 50% of the total pressure drop across the filter element, and   (C) a breather tube having one end that communicates through said opening with the interior space between the front and rear walls, and adapted at its other end for securing the filter element to a respirator face piece,   the air being drawn into the interior space between the front and rear walls, and from the interior space through the breather tube into a   
     
     
        respirator face piece..]. 39. The filter element of claim 1 wherein said front and rear walls are joined to each other along their peripheral edges 
     
     
        by ultrasonic welding. 40. The filter element of claim 1 wherein the front and rear walls comprise electrically charged, nonwoven, blown micro fiber web joined to each other along their peripheral edges by ultrasonic welding, and the porous layer comprises nonwoven web comprising a blend of 
     
     
        staple fibers bonded together at points of fiber intersection. 41. The filter element of claim 40 further comprising flexible cover layers disposed over the exterior surface of said filter element.