Patent ID: 8216342

Claim:
A process for the production of membranes, which contain at least one solid layer on one side of a porous substrate, which comprises treating, with synthesis solution forming the solid layer, that side of the substrate which is to be coated, wherein, in the production of the solid layer on the porous substrate, the substrate itself is partly or completely filled with an inert fluid and the space which is in contact with that side of the porous substrate which is not to be coated is filled with an inert fluid, the pressure and/or the temperature of the fluid being chosen so that contact of the synthesis solution with that side of the porous substrate which is not to be coated is substantially prevented, wherein the fluid is gaseous, and wherein the pressure of the fluid during the production of the solid layer is kept at a value which corresponds to the solution where the contact angle formed by the synthesis solution and substrate material is less than 90° or wherein the pressure of the fluid during the production of the solid layer is kept at a value which corresponds to not more than the pressure of the synthesis solution where the contact angle made by synthesis solution and substrate material is greater than 90° and wherein the inert fluid is nitrogen and wherein the space filled with the synthesis solution is sealed from the space filled with the fluid.