Process for producing a microporous polymeric filter membrane with adjacent non-porous edge layers and a pleated filter element formed from the membrane

Claim 2

A process for preparing an organic polymeric microporous filter membrane having a first porous film area and a second adjacent film area wherein the pore size of the second film area is less than the pore size of the first film area, the process comprising: (a) preparing a first casting solution of an amount of a film forming polymer in a first solvent system; (b) preparing a second casting solution of an amount of the film forming polymer in a second solvent system; (c) simultaneously casting the first and second casting solution onto a casting surface to provide, respectively, a first cast area and a second adjacent cast coated area in contact therewith; (d) simultaneously contacting the cast areas with a quenching bath comprising a non-solvent system for the polymer for a time sufficient to form the appropriate micropors in the cast coated areas to thereby form, respectively, the first and second film areas; wherein the amount of polymer and the solvent and non-solvent systems are each individually selected to provide the second film area with a pore size less than the first film area.

Claim 3

The process of claim 1, wherein the second porous area is substantially non-porous.

Claim 4

A process for preparing a hydrophilic organic polymeric microporous filter membrane having an elongated porous filtration area longitudinally bordered by two edge areas, wherein the porosity of the edge areas are less than the pore size of the filtration area, the process comprising: (a) preparing a first casting solution of an amount of film forming polymer in a first solvent system; (b) preparing a second casting solution of an amount of the film forming polymer in a second solvent system; (c) simultaneously casting the first and second casting solutions onto a casting surface to provide, respectively, an elongated cast area bordered by two edge cast areas, each edge cast area adjacent to and in contact with the longitudinal edge of the elongated cast area; (d) simultaneously contacting the cast areas with a quenching bath comprising a non-solvent system for the polymer for a time sufficient to form the appropriate micropores in the cast areas to thereby form respectively, the filtration and edge areas; wherein the amount of polymer and the solvent and the non-solvent systems are each individually selected to provide the edge area with a pore size less than the filtration area.

Claim 5

A process for preparing a hydrophilic organic polymeric microporous filter membrane having an elongated porous filtration area longitudinally bordered by two edge areas, wherein the porosity of the edge areas are less than the pore size of the filtration area, the process comprising: (a) preparing a first casting solution of an amount of film forming polymer in a first solvent system; (b) preparing a second casting solution of an amount of the film forming polymer in a second solvent system; (c) simultaneously casting the first and second casting solutions onto a casting surface to provide, respectively, an elongated cast area bordered by two edge cast areas, each edge cast area adjacent to and in contact with the longitudinal edge of the elongated cast area; (d) simultaneously contacting the cast areas with a quenching bath comprising a non-solvent system for the polymer for a time sufficient to form the appropriate micropores in the cast areas to thereby form respectively, the filtration and edge areas; wherein the amount of polymer and the solvent and the non-solvent systems are each individually selected to provide the edge area with a pore size less than the filtration area.

Claim 6

The process of claim 3, wherein the edge area is substantially non-porous.

Claim 7

The process of claim 3, wherein the film forming polymer is nylon.

Claim 8

The process of claim 5, wherein: (a) the solvent systems comprise a mixture of at least one solvent and one non-solvent for the polymer, the amount of non-solvent being no greater than an amount required to induce nucleation of the solution to obtain a visible precipitate, said solvent being formic acid and said non-solvent being selected from the group consisting of methanol, methyl formate, water and glycerol; and (b) the non-solvent system is a mixture of methanol and water or formic acid and water.

Claim 9

A process for preparing a hydrophilic organic polymeric microporous filter membrane having an elongated porous filtration area longitudinally bordered by substantially non-porous areas, the process comprising: (a) preparing the filter membrane having the elongated porous filtration area; and (b) collapsing the pores along the longitudinal borders of the filtration area.

Claim 10

A process for preparing a hydrophilic organic polymeric microporous filter membrane having an elongated porous filtration area longitudinally bordered by substantially non-porous areas, the process comprising: (a) preparing the filter membrane having the elongated porous filtration area; and (b) collapsing the pores along the longitudinal borders of the filtration area.

Claim 11

The process of claim 7, wherein the organic polymer is nylon.

Claim 12

The process of claim 7, wherein the organic polymer is polyhexamethylene adipamide.

Claim 13

The process of claim 7, further comprising forming the membrane into a cylinder having the substantially non-porous areas at each end of the cylinder.

Claim 14

The process of claim 7, further comprising pleating the membrane transversely to its length and forming the pleated membrane into a cylinder having the substantially non-porous areas at each end of the cylinder.

Claim 15

A process for producing a filter element comprising: (a) preparing the cylindrical pleated membrane by the process of claim 11, and (b) applying preformed end caps to the membrane by: (i) heating an inside face of a thermoplastic end cap to a temperature sufficient to soften but not liquify a sufficient amount of the end cap to form a thermoplastic seal with the non-porous area at each end of the cylinder; (ii) embedding all of the edges of one end of the cylinder into the softened end cap; (iii) hardening the softened end cap material thereby forming a thermoplastic sealing relationship between the sealing surface of the end cap and the non-porous area to thereby form a leak-proof seal.

Claim 16

A process for producing a filter element comprising: (a) preparing the cylindrical pleated membrane by the process of claim 11 and (b) applying preformed end caps to the membrane by: (i) heating an inside face of a thermoplastic end cap to a temperature sufficient to at least soften a sufficient amount of the end cap to form a thermoplastic seal with the non-porous area at each end of the cylinder; (ii) embedding all of the edges of one end of the cylinder into the softened end cap; (iii) hardening the at least softened end cap material thereby forming a thermoplastic sealing relationship between the sealing surface of the end cap and the non-porous area to thereby form a leak-proof seal.

Claim 17

The process of claim 13, wherein the end caps are hydrophobic.