Laminated edge filter structure and method of making

Abstract

The present invention relates to a filter element having a non-porous extrusion laminated strip formed on at least one edge and at least one side of a membrane. The strip is used to provide a means for ensuring a good bond between the filter element and the material into which it is potted. The strip is formed by the use of one or more extrusion heads that apply molten or softened polymer to one or both of the surfaces of the filter in a width and height desired. The strip is then subjected to pressure such as through a nip to at least partially embed the polymer strip into the filter pores so as to create a strong mechanical bond between the strip and the filter element. Additionally, it allows for the simultaneous formation of more than one membrane with the edge lamination at the same time.

What we claim:  
     
         1 ) A membrane having a porous structure having at least one lateral edge, the at least one lateral edge having a first and a second major surface and at least the first major surface of at least one lateral edge contains a non-porous extruded strip of plastic material.  
     
     
         2 ) The membrane of  claim 1  wherein the strip contains a dye for color coding of the product.  
     
     
         3 ) The membrane of  claim 1  wherein the strip is formed of a material dissimilar from the material of the membrane.  
     
     
         4 ) The membrane of  claim 1  wherein the strip is formed of a material selected from the group consisting of polyethylene, polypropylene, PVDC, EVA copolymers, polyamides, acrylics, methacrylics, perfluorinated thermoplastics and PTFE and the membrane is made of a material selected from the group consisting of nitrocellulose, cellulose acetate, polysulphones, polyethersulphones, polyarylsulphones, polyvinylidene fluoride, polyolefins, ultrahigh molecular weight polyethylene, polyethylene, polypropylene, nylons, polyamides, PTFE, thermoplastic fluorinated polymers and polycarbonates and wherein the strip and membrane are made of different materials.  
     
     
         5 ) The membrane of  claim 1  wherein the strip is partially embedded into the porous structure.  
     
     
         6 ) A filter comprising at least one membrane having a porous structure and at least one lateral edge, the at least one of the lateral edge having a first and a second major surface and at least one of the at least one lateral edge containing a non-porous extruded strip of plastic material wherein the strip is formed by a process comprising the steps of selecting a membrane, selecting a material for the strip, heating the material for the strip to a temperature at or above its melting pointing point and applying the material to at least one major surface of at least lateral edge of the membrane.  
     
     
         7 ) The filter of  claim 6  wherein the strip is formed of a material selected from the group consisting of polyethylene, polypropylene, PVDC, EVA copolymers, polyamides, acrylics, methacrylics, perfluorinated thermoplastics and PTFE and the membrane is made of a material selected from the group consisting of nitrocellulose, cellulose acetate, polysulphones, polyethersulphones, polyarylsulphones, polyvinylidene fluoride, polyolefins, ultrahigh molecular weight polyethylene, polyethylene, polypropylene, nylons, polyamides, PTFE, thermoplastic fluorinated polymers and polycarbonates and wherein the strip and membrane are made of different materials.  
     
     
         8 ) The filter of  claim 6  wherein the strip is partially embedded into the porous structure of the membrane.  
     
     
         9 ) The filter of  claim 6  further comprising a cartridge for the membrane and a first endcap having an inlet to the housing and a second endcap having an outlet from the housing and the strip is formed on the first major surface of both lateral edges and is bonded respectively to the first and second endcaps such that all fluid entering the inlet must pass through the membrane before reaching the outlet.  
     
     
         10 ) A filter comprising a cartridge having a first and a second end, a first endcap and second endcap, the first endcap containing an inlet to the cartridge and the second endcap containing an outlet from the cartridge and at least one membrane having a porous structure and two lateral edges, each lateral edge having a first and a second major surface and at least the first major surface of each lateral edge contains a non-porous extruded strip of plastic material and wherein the strips are bonded to the first and second endcaps to form an integral, fluid tight seal between the lateral edges of the membrane and the endcaps such that all fluid entering the inlet must pass through the membrane before reaching the outlet.  
     
     
         11 ) The filter of  claim 10  further comprising a porous core downstream of the membrane and attached to the outlet so as to be in fluid communication with the outlet.  
     
     
         12 ) The filter of  claim 10  wherein the membrane is pleated.  
     
     
         13 ) The filter of  claim 10  wherein the strip is partially embedded into the porous structure of the membrane.  
     
     
         14 ) The filter of  claim 10  wherein the cartridge, endcaps and strips are formed of a material selected from the group consisting of polyethylene, polypropylene, PVDC, EVA copolymers, polyamides, acrylics, methacrylics, perfluorinated thermoplastics and PTFE, the membrane is made of a material selected from the group consisting of nitrocellulose, cellulose acetate, polysulphones, polyethersulphones, polyarylsulphones, polyvinylidene fluoride, polyolefins, ultrahigh molecular weight polyethylene, polyethylene, polypropylene, nylons, polyamides, PTFE, thermoplastic fluorinated polymers and polycarbonates and wherein the cartridge, endcaps and strips and the membrane are made of different materials.  
     
     
         15 ) The filter of  claim 10  wherein the cartridge, endcaps and strips are formed of a material selected from the group consisting of polyethylene, polypropylene, PVDC, EVA copolymers, polyamides, acrylics, methacrylics, perfluorinated thermoplastics and PTFE, the membrane is made of a material selected from the group consisting of nitrocellulose, cellulose acetate, polysulphones, polyethersulphones, polyarylsulphones, polyvinylidene fluoride, polyolefins, ultrahigh molecular weight polyethylene, polyethylene, polypropylene, nylons, polyamides, PTFE, thermoplastic fluorinated polymers and polycarbonates and wherein the cartridge, endcaps and strips are formed of the same material and the membrane is formed of a material dissimilar to that of the cartridge, endcaps and strips.  
     
     
         16 ) The filter of  claim 10  wherein the strip contains a dye for color coding of the product.  
     
     
         17 ) The filter of  claim 10  wherein the at least one membrane is two or more membranes.  
     
     
         18 ) The filter of  claim 10  wherein the at least one membrane is two or more membranes and the two or more membranes are formed of different materials.  
     
     
         19 ) The filter of  claim 10  wherein the at least one membrane is three membranes.  
     
     
         20 ) The filter of  claim 10  wherein the at least one membrane is selected from the group consisting of microporous membranes, ultrafiltration membranes, nanofiltration membranes, or reverse osmosis membranes.  
     
     
         21 ) A process for the formation of a sealing edge on a membrane comprising the steps of selecting a membrane, selecting a material for the sealing edge, heating the material to a temperature at or above its melting pointing point and applying the material to one or more portions of the membrane.  
     
     
         22 ) The process of  claim 21  wherein the material is heated in an extruder and the material is applied to the membrane from an extrusion die of the extruder.  
     
     
         23 ) The process of  claim 21  further comprising applying a pressure to the material after it has been applied to the one or more portions of the membrane.  
     
     
         24 ) The process of  claim 21  wherein the material is heated in an extruder and the material is applied to the membrane from an extrusion die of the extruder wherein the die has two or more openings spaced apart from each other.  
     
     
         25 ) The process of  claim 21  further comprising applying a pressure to the material after it has been applied to the one or more portions of the membrane and wherein the pressure is applied by one or more nip rollers.  
     
     
         26 ) An apparatus for forming a non-porous plastic strip on one or more locations of a porous membrane comprising a roll for membrane for the apparatus, one or more tension rollers, one or more guide rollers, a lamination roll, an extrusion die capable of applying one or more strips of heated non-porous plastic material onto one or more selected portions of the membrane surface, a pressure roll to partially embedded into the membrane, one or more guide rollers, one or more tension rolls and a wind up roll.  
     
     
         27 ) The apparatus of  claim 26  further comprising a slitter located between the pressure roll and the wind up roll, said slitter having one or more knives for cutting the membrane.  
     
     
         28 ) The membrane of  claim 1  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material.  
     
     
         29 ) The filter of  claim 6  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material.  
     
     
         30 ) The filter of  claim 10  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material.  
     
     
         31 ) The membrane of  claim 1  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material and the surface modification is selected from the group consisting of energy and mechanical modifications.  
     
     
         32 ) The filter of  claim 6  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material and the surface modification is selected from the group consisting of energy and mechanical modifications.  
     
     
         33 ) The filter of  claim 10  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material and the surface modification is selected from the group consisting of energy and mechanical modifications.  
     
     
         34 ) The membrane of  claim 1  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material and the surface modification is selected from the group consisting of heat, corona discharge, ozone, plasma, laser, ultrasonic and combinations thereof.  
     
     
         35 ) The filter of  claim 6  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material and the surface modification is selected from the group consisting of heat, corona discharge, ozone, plasma, laser, ultrasonic and combinations thereof.  
     
     
         36 ) The filter of  claim 10  wherein at least the first surface of at least one lateral edge had been surface modified before the application of the non-porous extruded strip of plastic material and the surface modification is selected from the group consisting of heat, corona discharge, ozone, plasma, laser, ultrasonic and combinations thereof.  
     
     
         37 ) The membrane of  claim 1  wherein the membrane is circular in shape and has one lateral edge.  
     
     
         38 ) The filter of  claim 6  wherein the at least one membrane is circular in shape and has one lateral edge.  
     
     
         39 ) The membrane of  claim 1  wherein the membrane is rectangular in shape and has more than one lateral edge.  
     
     
         40 ) The filter of  claim 6  wherein the at least one membrane is rectangular in shape and has more than one lateral edge.