Abstract: A process for the preparation of semipermeable membranes with improved acid and base stability including: (a) coating a base and acid stable ultrafiltration (UF) membrane support polymer, with a high molecular weight amphoteric polyelectrolyte coating polymer optionally in solution, the amphoteric polyelectrolyte containing both cationic and anionic groups and in addition primary and secondary amine groups, the solution optionally containing a latent internal crosslinker compound that is a polyfunctional compound that crosslinks the coating polymer only during a curing step at elevated temperatures and basic pH; (b) draining or washing the coated support; and (c) reacting the coating with a solution of an external crosslinking compound that is a polyfuntional compound, not overly reactive so as not to be hydrolyzed prematurely in solution, the time of exposure to the external crosslinking compound being sufficient to ensure its diffusion into the bulk of the coating, so that the crosslinking is effected not o

Abstract: A gradient mixer for the preparation of immobilized pH-gradient (IPG) gels, which includes a positive displacement syringe dispensing device (4,5) driven by a controlled speed motor (1); a mixer driven by a magnetic stirrer (6); a temperature controlled circulating air oven for the mixer/dispensing syringes (7); a cassette into which mixed solutions of acidic/basic gels are dispensed and the IPG gel is shaped (9); and a second temperature controlled circulating air oven for the cassette (8).

Abstract: Immobilized buffered gels obtained from hydroxy group containing natural or synthetic polymers and acid or basic di- or triazine derivatives are useful and highly effective media, e.g. in form of membranes, for preparative isoelectric focusing electrophoresis for separating high molecular compounds, such as proteins or peptides, from biological mixtures.

Abstract: Immobilized buffered gels obtained from hydroxy group containing natural or synthetic polymers and acid or basic di- or triazine derivatives are useful and highly effective media, e.g. in form of membranes, for preparative isoelectric focusing electrophoresis for separating high molecular compounds, such as proteins or peptides, from biological mixtures.

Abstract: The present invention relates to semipermeable mosaic polymer membranes of asymmetric structure and with a macroscopic distribution of the mosaic-forming anionic and cationic charges (sites). The membranes can be prepared by casting a polymer solution of an optionally charged matrix-forming polymer and at least one precursor polymer, incompatible with the matrix-forming polymer, in a selected solvent, into a film, forming a skin on one side of the film, precipitating the skinned film to form the asymmetric membrane and charging it by chemical reactions to introduce or complete their mosaic structure. These membranes have good permeability for electrolytes, such as salts of mono- or polyvalent inorganic acids, while retaining low molecular weight organic solutes.

Abstract: A process and apparatus for the continuous separation of electrically charged macromolecular compounds, such as proteins, by forced-flow membrane electrophoresis is provided.Said process is conducted in an electrophoretic cell comprising a membrane compartment, divided by a micro- or ultrafiltration membrane into a feed and permeate cell, and electrode compartments being partitioned from the membrane compartment with ion-exchange membranes, which are impermeable to the macromolecular compounds, and have virtually no permeability to salts.The electrophoretic process comprises the steps of recycling a mixed solution of the charged compounds which are dissolved in a separation buffer through the feed cell, subjecting of the solution to a pressure-driven membrane separation, applying an electric field across the membranes and the solution to cause electrophoretic migration of the charged compound and to separate them, and withdrawing the charged compounds thus separated.

Abstract: Semipermeable composite membranes composed of a porous substrate and at least two layers of film-forming polymers coated thereon are provided, which comprise a first layer of monomeric or polymeric diazonium salts, which have been reacted with themselves and with an at least difunctional compound, and a second layer, which is chemically bonded to the first one, of a cross-linked, ionically charged hydrophilic polymer.The membranes show good mechanical, physical and chemical stabilities and are useful in reverse osmosis and ultrafiltration processes, particularly for desalting solutions of low molecular weight organic compounds.

Abstract: Semipermeable composite membranes which comprise a porous substrate of a homo- or copolymer on the basis of acrylonitrile are provided, which have been cross-linked, and at least two layers of film-forming polymers coated thereon, a first layer of monomeric or polymeric diazonium salts which have been reacted with themselves and with an at least difunctional compound, and a second layer, which is chemically bonded to the first one, of a cross-linked, ionically charged hydrophilic polymer.The membranes show good mechanical, physical and chemical stabilities, preferably solvent stability, and are useful in reverse osmosis and ultrafiltration processes, particularly for desalting solutions of low molecular weight organic compounds.

Abstract: Composite membranes are provided comprising an underlying membrane selected from the group consisting of microfiltration, ultrafiltration and reverse osmosis membranes; and a coating thereon comprising at least one member selected from the group consisting of polyaromatic polymers and sulfonated poly(haloalkylenes), which has been subjected to a post-coating crosslinking treatment. These coated membranes are useful for various separation processes, especially in the food industry.

Abstract: A process for preparing a microporous membrane, which comprises casting the membrane from a solution comprising a mixture of at least one pore-forming polymer and at least one film-forming polymer, and a solvent for the mixture of polymers, wherein the at least one pore-forming polymer is one which if cast alone would contract to form either large pores or a non-uniform distribution of material.