Patent ID: 8104624

Claim:
A method for making a multi-polymeric solution having a known cloud point for production of a hollow-fiber membrane, comprising: determining a cloud point for a sample system comprising water and, in known amount ratios, polyethersulfone (PES), a polar solvent, a first polyvinylpyrrolidone (PVP), and a second PVP by conducting a series of trials comprising successively increasing water concentration in the sample system until the cloud point in the sample system is reached, wherein the trial immediately prior to the achievement of the cloud point defines a water amount at near-cloud point conditions in the sample system; preparing a multipolymeric solution comprising a volume of water, a volume of polar solvent, PES, the first PVP, and the second PVP, all present in the same percentage of ingredients at which the sample system reached near-cloud point conditions, comprising mixing a portion of the volume of polar solvent and the entire volume of water; dissolving the first PVP in the mixture of water and polar solvent; dissolving the second PVP in the solution of the first PVP, water, and solvent, wherein the molecular weight of said second PVP is less than the molecular weight of said first PVP; adding a portion of the remaining volume of the polar solvent; dissolving the PES in the mixture of water, polar solvent, and the first PVP and second PVP; adding the remaining volume of the polar solvent; agitating the mixture for 5 to 50 hours at a temperature between 10° C. to 50° C., to form a multi-polymeric solution for the production of a hollow-fiber membrane.