Processes for manufacturing continuous laterally graded porous membranes are disclosed. Such processes utilize freeze casting techniques with a continuous varying solids loading method to make laterally graded porous membranes. Also disclosed are laterally graded porous membranes.

The present invention relates to a hydrophilic polyimide including at least one type of building blocks [A-B] and [A-C], and represented by the formula -[A-B].sub.n-[A-C].sub.m— (I), wherein: the n-bracketed building blocks and the m-bracketed building blocks are randomly distributed over the polyimide chain; repeat unit A results from a monomer comprising two carboxylic anhydride moieties, repeat unit B is hydrophilic and results from a first hydrophilic monomer comprising two primary amine moieties and at least one further hydrophilic moiety different from the primary amines, and repeat unit C is hydrophilic and results from a second hydrophilic monomer comprising two primary amine moieties and at least one further hydrophilic moiety different from the primary amines; wherein: n and m represent independently an integer from 0 to about 1000; wherein n+m is an integer from about 10 to about 1000.

The present invention also relates to a porous membrane comprising the same, a method of producing the hydrophilic polyimide and the porous membrane, a liquid phase separation system comprising the porous membrane, and a liquid phase separation method.

A process for separating hydrogen from a gas mixture having hydrogen and a larger gas molecule is comprised of flowing the gas mixture through a carbonized polyvinylidene chloride (PVDC) copolymer membrane having a hydrogen permeance in combination with a hydrogen/methane selectivity, wherein the combination of hydrogen permeance and hydrogen/methane selectivity is (i) at least 30 GPU hydrogen permeance and at least 200 hydrogen/methane selectivity or (ii) at least 10 GPU hydrogen permeance and at least 700 hydrogen/methane selectivity. The carbonized PVDC copolymer may be made by heating and restraining a polyvinylidene chloride copolymer film or hollow fiber having a thickness of 1 micrometer to 250 micrometers to a pretreatment temperature of 100° C. to 180° C. to form a pretreated polyvinylidene chloride copolymer film and then heating and restraining the pretreated polyvinylidene chloride copolymer film to a maximum pyrolysis temperature from 350° C. to 750° C.

The present invention provides a hollow fiber membrane including a cellulose acetate-based polymer, in which when an inner surface of the hollow fiber membrane is observed under an atomic force microscope, a plurality of groove-like recesses oriented in a lengthwise direction of the hollow fiber membrane are observed, an average length of the recesses is greater than or equal to 200 nm and less than or equal to 500 nm, an average width of the recesses is greater than or equal to 15 nm and less than or equal to 50 nm, and an aspect ratio defined as a ratio of the average length to the average width of each of the recesses is greater than or equal to 6 and less than or equal to 22.

Disclosed are a ceramic membrane for water treatment using oxidation-treated SiC and a method for manufacturing the same. An object of the present invention is to manufacture a ceramic membrane for water treatment, which can be sintered at a low temperature of 1,050° C. or less, in which a SiO.sub.2 oxide layer formed during an oxidation process induces volume expansion so as to prevent defects due to the contraction of a coating layer during general sintering. The ceramic membrane for water treatment using the oxidation treated SiC includes a porous ceramic support layer; and a SiC layer formed on the porous ceramic support layer and including SiC particles on which a SiO.sub.2 oxide layer formed on a surface thereof.

Described are porous polymeric membranes that include two opposing sides and that have a variable pore structure through a thickness of the membrane; filter components and filters that include this type of porous polymeric membrane; methods of making the membranes, filter components, and filters; and methods of using the polymeric filter membrane, filter component, or filter.

Disclosed herein are membranes having a first surface, a second surface opposing the first surface, a skin at the first surface having visible pores when viewed at a magnification of 10,000 and a pore size gradient, wherein pore size increases from the second surface to the skin.

A porous membrane has a thickness of 150 m or greater. The pore diameters of a first surface are smaller than the pore diameters of a second surface. The average value of the pore diameters of the first surface is 60 nm or less, and the coefficient of variation of the pore diameters is 10% or greater and 50% or less.

Microporous polyamide-imide membranes and methods for making them are disclosed. The microporous membrane includes polyamide-imide polymer, wherein the membrane has an HFE bubble point, and an IPA flow-time. The microporous membrane has an HFE bubble point from about 25 psi to about 200 psi and has an IPA flow-time from about 400 second to about 40,000 seconds. Another microporous polyamide-imide membrane includes a polyamide-imide polymer, wherein the membrane has a HFE bubble point from about 25 psi to about 200 psi. The membrane is asymmetric- and has a tight layer with a thickness of 10 microns. Filter and purification devices incorporating such devices are also disclosed.

Hydrophobic poly(4-methyl-1-pentene) hollow fiber membrane for retention of anesthetic agents with an inner and an outer surface and between inner and outer surface an essentially isotropic support layer with a sponge-like, open-pored, microporous structure free of macrovoids and adjacent to this support layer on the outer surface a dense separation layer with a thickness between 1.0 and 3.5 m. The membrane has a porosity in the range of greater than 35% to less than 50% by volume and a permeance for CO.sub.2 of 20-60 mol/(h.Math.m.sup.2.Math.bar), a gas separation factor (CO.sub.2/N.sub.2) of at least 5 and a selectivity CO.sub.2/anesthetic agents of at least 150. The process for producing this membrane is based on a thermally induced phase separation process in which process a homogeneous solution of a poly(4-methyl-1-pentene) in a solvent system containing components A and B is formed, wherein component A is a strong solvent and component B a weak non-solvent for the polymer component. After formation of a hollow fiber the hollow fiber is cooled in a liquid cooling medium to form a hollow fiber membrane. The concentration of the polymer component in the solution may be in the range from 42.5 to 45.8 wt.-% and the hollow fiber leaving the die runs through a gap between die and cooling medium with a gap length in the range of 5-30 mm.