Process for producing reinforced microporous membrane

DETAILED DESCRIPTION OF THE INVENTION The inner and outer membranes of the reinforced laminated filtration membrane of this invention are produced from an organic polymeric microporous membrane.
Such membranes are well known in the art.
By the use of the term "microporous membrane" as used herein, it is meant a porous single layer membrane having a pore size of at least 0.
05 microns or larger or an initial Bubble Point (IBP), as that term is used herein, in water of less than 120 psi.
A maximum pore size useful for this invention is about 1.
2 microns or an IBP of greater than about 8 psi.
Preferably, but not necessarily, this membrane is substantially symmetrical and isotropic.
By "symmetrical" it is meant that the pore structure is substantially the same on both sides of the membrane.
Asymmetric membranes, i.
e.
membranes having one side formed with a very tight thin layer which is supported by a much more porous open structure, may also be utilized in this invention.
By the use of the term "isotropic" it is meant the membrane has a uniform pore structure throughout the membrane.
Preferably, the microporous membranes are hydrophilic.
By the use of the term "hydrophilic" in describing the membranes, it is meant a membrane which adsorbs or absorbs water.
Generally, such hydrophilicity is produced by a sufficient amount of hydroxyl (OH--), carboxyl (--COOH), amino (--NH.
sub.
2) and/or similar functional groups on the surface of the membrane.
Such groups assist in the adsorption and/or absorption of the water onto the membrane.
Such hydrophilicity is particularly useful in the filtration of aqueous fluids.
Preferred microporous membranes are those produced from nylon.
The term "nylon" is intended to embrace film forming polyamide resins including copolymers and terpolymers which include the recurring amido grouping.
While, generally, the various nylon or polyamide resins are all copolymers of a diamine and a dicarboxylic acid, or homopolymers of a lactam and an amino acid, they vary widely in crystallinity or solid structure, melting point, and other physical properties