Abstract: Semipermeable composite membranes containing on one surface of a porous support a superficial thin film having semipermeable properties. The film contains polyvinyl alcohol (PVA)/polyvinyl alcohol-copolymers (PVA-copolymers) modified by at least radicals containing ionizable groups are provided. The modification steps comprise e.g. reacting PVA/PVA-copolymer films with(a) a monomeric organic compound containing at least two functional groups,(b) a linear or branched polyfunctional oligomer or polymer, and(c) a compound containing cross-linking and ionizable groups.The novel membranes show good mechanical, temperature and pH-stabilities and are suitable, for example, for separating monovalent ions of low ionic weight from polyvalent ions of low or high ionic weight or for separating ionic compounds from non-ionic compounds or from ionic compounds which have a different molecular weight or opposite charge.

Abstract: Dynamic membranes are obtained by coating on a porous polymeric substrate containing functional groups a chemically reactive hydrophilic polymer from a dilute aqueous solution under pressure and crosslinking said polymer present on the porous substrate as thin layer with low molecular polyfunctional compounds. The new membranes show good solvent and compaction resistance and resistance to separation of the individual layers. They can be used in ultrafiltration and reverse osmosis processes.

Abstract: Semipermeable composite membranes suitable for separating organic compounds of low moelcular weight from aqueous, inorganic salts containing solutions are provided. These membranes are obtained by coating one side of a membrane support with an aqueous solution containing dissolved therein an organic, film-forming, hydrophilic polymer, and a cross-linking agent (1) and optionally ionic monomeric compounds to form at least one polymer layer, contacting the still wet polymer layer(s) interfacially with an organic solution of a cross-linking agent (2), containing at least two functional groups, drying the resultant product for a time sufficient to form the composite membrane comprising the membrane support and an asymmetrical coacting consisting of polymer layer(s) and a thin semipermeable cross-linked film, containing ionic groups resting on the top of said layer and being integrally attached thereto.

Abstract: Semipermeable membranes of a porous polymeric substrate whose external and all internal surfaces (pores) are encapsulated by a semipermeable thin film of a hydrophilic polymer are provided. The encapsulating film consists of at least one layer of said polymer which is cross-linked/stabilized by polyfunctional compounds containing at least two functional (reactive) groups. The membrane substrate is optionally pretreated--before the encapsulation step--with polyfunctional compounds. The new membranes can be used in ultrafiltration and reverse osmosis processes. They are solvent-, pressure- and temperature-resistant and show good separation capacities, e.g. for separating organic compounds from salt solutions.

Abstract: Semipermeable composite membranes suitable for separating organic compounds of low molecular weight from aqueous, inorganic salts containing solutions are provided. These membranes are obtained bycoating one side of a membrane support with an aqueous solution containing dissolved therein an organic, film-forming, hydrophilic polymer, and a cross-linking agent (1) and optionally ionic monomeric compounds to form at least one polymer layer,contacting the still wet polymer layer(s) interfacially with an organic solution of a cross-linking agent (2), containing at least two functional groups,drying the resultant product for a time sufficient to form the composite membrane comprising the membrane support and an asymmetrical coating consisting of polymer layer(s) and a thin semipermeable crosslinked film, containing ionic groups resting on the top of said layer and being integrally attached thereto.

Abstract: Semipermeable composite membranes containing on one surface of a porous support a superficial thin film having semipermeable properties. The film contains polyvinyl alcohol (PVA)/polyvinyl alcohol-copolymers (PVA-copolymers) modified by at least radicals containing ionizable groups are provided. The modification steps comprise e.g. reacting PVA/PVA-copolymer films with(a) a monomeric organic compound containing at least two functional groups,(b) a linear or branched polyfunctional oligomer or polymer, and(c) a compound containing cross-linking and ionizable groups.The novel membranes show good mechanical, temperature and pH-stabilities and are suitable, for example, for separating monovalent ions of low ionic weight from polyvalent ions of low or high ionic weight or for separating ionic compounds from non-ionic compounds or from ionic compounds which have a different molecular weight or opposite charge.

Abstract: Semipermeable membranes of modified styrene polymers are obtained by modifying styrene polymers containing reactive groups(A) through chemical reaction with(a) a monomeric compound containing at least two functional groups,(b) a polyfunctional oligomer of polymer, and(c) a compound containing at least one, preferably two groups capable of reaction with (b), provided that the reactive groups are amino, hydroxyl or mercapto groups,(B) through chemical reaction with components (b) and (c), provided that the reactive groups are halogen atoms, aldehyde, cyanate or thiocyanate groups, or(C) through chemical reaction with hydroxylamine and components (a), (b) and (c), provided that the reactive group is a nitrile group.The new membranes can be used in reverse osmosis and ultrafiltration processes. They show good permeability (flux) and rejection characteristics as well as good solvent, compaction and temperature resistance. Their range of molecular cut-offs lies preferably between about 200 and 2000.

Abstract: Semipermeable membranes of modified polysulfones are provided which comprises repeating units of the formula--M.sub.1 --R.sub.1 --M.sub.2 --R.sub.2 --SO.sub.2 --R.sub.3 --(1)wherein M.sub.1 and M.sub.2 are independently a valence bond, --O-- or --NH--, R.sub.1 is a valence bond or a group of the formula ##STR1## with the proviso that if R.sub.1 is a valence bond, only one of M.sub.1 and M.sub.2 can be --O--, R.sub.2 and R.sub.3 are independently a group of the formula ##STR2## the aryl radicals R.sub.1, R.sub.2 and R.sub.3 are optionally further substituted, R.sub.4 is a valence bond, --O--, alkylene of 1 to 4 carbon atoms optionally substituted or interrupted by cycloalkyl(ene) or aryl(ene) of at most 7 carbon atoms, or alkylidene of 2 to 4 carbon atoms, R.sub.5 to R.sub.10 are independently hydrogen, or --R.sub.11 NH.sub.2, ##STR3## or --R.sub.

Abstract: Semipermeable membranes of modified polysulfones are provided which comprises repeating units of the formula--M.sub.1 --R.sub.1 --M.sub.2 --R.sub.2 --SO.sub.2 --R.sub.3 --(1)wherein M.sub.1 and M.sub.2 are independently a valence bond, --O-- or --NH--, R.sub.1 is a valence bond or a group of the formula ##STR1## with the proviso that if R.sub.1 is a valence bond, only one of M.sub.1 and M.sub.2 can be --O--, R.sub.2 and R.sub.3 are independently a group of the formula ##STR2## the aryl radicals R.sub.1, R.sub.2 and R.sub.3 are optionally further substituted, R.sub.4 is a valence bond, --O--, alkylene of 1 to 4 carbon atoms optionally substituted or interrupted by cycloalkyl(ene) or aryl(ene) of at most 7 carbon atoms, or alkylidene of 2 to 4 carbon atoms, R.sub.5 to R.sub.

Abstract: Dynamic membranes are obtained by coating on a porous polymeric substrate containing functional groups a chemically reactive hydrophilic polymer from a dilute aqueous solution under pressure and crosslinking said polymer present on the porous substrate as thin layer with low molecular polyfunctional compounds. The new membranes show good solvent and compaction resistance and resistance to separation of the individual layers. They can be used in ultrafiltration and reverse osmosis processes.

Abstract: Semipermeable membranes of polyacrylonitrile or copolymers of acrylonitrile and other ethylenically unsaturated monomers are chemically modified through reaction with (a) hydroxylamine and (b) a poly functional ionic colorless cyclic carbonic acid imide-halide capable of reaction with amidoxime groups, and optionally containing ionic groups. The new membranes show good compaction and solvent resistance and are stable over a broad temperature and pH range. They are suitable for reverse osmosis and especially ultrafiltration processes.