Patent ID: 8210361

Claim:
A method of producing a thermally, heat and chemically stable asymmetric ultrafiltration polyimide membrane with water permeability (Q) from Q=80*10 −4 cm/sec atm to Q=320*10 −4 cm/sec atm, comprising the steps of preparing a 10-15% forming solution of (co)polyimidoacid based on dianhydride of aromatic tetracarbonic acid and aromatic diamine in amide solution, introducing in the prepared solution of (co)polyamidoacid, a catalyst of thermal imidization-azole in the quantity of 1.5-2.5 mol per 1 monomeric link of (co)polyamidoacid, and then successively with mixing, introducing reagents: tertiary amine and anhydride of lower monocarbonic aliphatic and aromatic acids in the quantity of 0.4-1.0 mol per 1 monomeric link of (co)polyamidoacid, and during this performing a partial controlled chemical imidization of (co)polyamidoacid of 10-40%, mixing and degassing the solution of produced (co)polyimidoamidoacid, and after this performing a wet formation of the membranes by casting of a layer of forming solution of polyimidoamidoacid by a die with a regulated gap on a forming plate, immersing the plate into a deposition bath with an aqueous solution containing up to 60% of aliphatic one-atom alcohol, retaining the formed membrane in at least 20-60% solution of a high boiling oil in organic solvent for filling pores of the membrane with oil, drying the membrane and heating to 160-200° C. with the speed of temperature elevation 10°/min for obtaining complete imidization of (co)polyimidoamidoacid.