Canadian Patents & Development Ltd.

University of Ottawa

Canadian Patents & Dev. Limited

Srinivasa Sourirajan

William L Thayer

Oleh Kutowy

Takeshi Matsuura

William A Adams

Brian Conway

Geeta Chowdhury

Adam J Bennett

Thomas A Tweddle

Lucien Pageau

Arthur G Baxter

Pierre Blais

Bhupender S Minhas

Branko Kunst

Brian Farnand

The present invention relates to film composite membranes for use as battery separators or coatings on electrodes.

Thin film composite membrane as battery separator

There is provided a method of manufacturing cellulose membranes with pore radii less than 30.times.10.sup.-10 m, suitable for reverse osmosis applications. The method comprises dissolving a cellulosic material in a DMSO/PF solvent at a temperature about 125.degree. C. for about 90 min., cooling and casting the solution at room temperature, evaporating the solvent at a temperature of 140.degree.-180.degree. C. and gelling the resulting membrane in a protic solvent, e.g. ethanol or water.

Reverse osmosis membrane of cellulosic material

A cellulose acetate membrane is provided, capable of separating gaseous hydrogen from a gaseous mixture of hydrogen and hydrocarbon, by casting a 0.02 to 0.05 cm cellulose acetate film into an atmosphere at 20.degree. to 40.degree. C. and a relative humidity of 30 to 70%, from a casting solution at 0.degree. to 20.degree. C. and comprising 10 to 20 wt % cellulose acetate, 60 to 80 wt % acetone, 0.5 to 0.2 wt % magnesium perchlorate, balance water, then evaporating the solvent to form a membrane from the film, then gelling the membrane in ice cold water, then shrinking the membrane at 60.degree. to 90.degree. C. to produce a water wet membrane having an average pore radius less than 7 .ANG., then replacing the water in the membrane sequentially at the laboratory temperature (about 20.degree. to 25.degree. C.) first with aqueous alcohol (isopropyl plus water) and secondly with nonaqueous alcohol (isopropyl), then replacing the alcohol in the membrane with a nonaqueous, readily volatile organic solvent (hexane), and finally evaporating the nonaqueous solvent at laboratory temperature (about 20.degree. to 25.degree. C.) to produce a membrane having a pore radius in the range 1.5 to 5.0 .ANG. and a standard deviation in the range 0.5 to 5.5 .ANG., according to the definition of Gaussian normal distribution.

Method of manufacturing a cellulose acetate membrane and the membrane so

A gelation shrinkable, polymer casting solution, that has been cast on the internal surface of a tubular support is gelled using pressure gelation by supporting the tubular support with one end higher than the other and pumping gelation liquid upwardly along the tube at a velocity in the range of the order of 10 to 100 cm/second and at a pressure of at least 10 kPa gauge at all points of contact between the gelation liquid and polymer casting solution. This achieves asymmetricity of the pore structure and ensures that the cast polymer solution is continuously in contact with the tubular support as a gelled membrane. If the tubular support is a porous, tubular support, then preferably the pressure gelation is continued until gelation liquid has passed through the cast polymer solution and the porous support removing solvent and any additives from the cast polymer solution.

Method of gelling a gelation shrinkable, polymer casting solution

An ultrafiltration and reverse osmosis module comprising a tubular casing having a plurality of tubular membrane assemblies spaced therein by spacing plates, in stepped end portions of the casing bore, and held therein by sealing plates clamped to flanges on the ends of the casing. The tubular membrane assemblies are sealed around bores in the spacing plates and boxes in the sealing plates by 'O'-rings and are held against collapse by sleeves in the ends of the tubular membrane assemblies.

Ultrafiltration and reverse osmosis tubular membrane module

Polysulfone cast films, including polyethersulfone cast films, are partially gelled with mineral acid prior to or during the conventional water gelation to control the porosity of and improve the productivity of reverse osmosis and ultrafiltration membranes thus produced. The partial gelation may be carried out prior to the water gelation by contacting the cast film with the mineral acid in a gaseous or aqueous form and the gaseous form may be diluted with air. The partial gelation may, in different embodiments, be carried out simultaneously with the conventional gelation by dissolving the mineral acid in the gelation liquid.

Method of gelling cast, polysulfone membranes

An improvement in the method of casting a reverse osmosis or ultrafiltration polymeric membrane on a wall of porous support having a first, high pressure side under service conditions, and a second, low pressure side under service conditions, wherein the first side is coated wih a cellulose ester casting solution to at least partially impregnate the support, solvent carrier of the casting solution is partially evaporated to leave a residue, and then residues adjacent the first and second sides are gelled with a gelation liquid comprising a monohydric alcohol. The improvement comprises gelling the residue adjacent the first side with a gelation liquid which is separate from that used to gel the residue adjacent the second side, and the monohydric alcohol mole fractions of the separate gelation liquid, and their temperatures during gelation, are chosen so that relatively larger pores are formed towards the second side of the porous support. The method is particularly useful for casting tubular, polymeric membranes anchored to the inner surface of a porous, tubular support and where the relatively larger pores are adjacent the outer surface of the porous support.

Method of casting a reverse osmosis or ultrafiltration polymeric membrane

A reverse osmosis method of concentrating fruit juices wherein a major portion of the fruit juice sugars are removed in a reverse osmosis first stage from the fruit juice at about room temperature and a pressure in the range 500 to 1500 psi, using porous cellulose acetate membrane material, while flavor compounds are removed in a reverse osmosis second stage from the separated water in liquid form therefrom at a temperature in the range 0.degree. C. to about room temperature and a pressure substantially in the range 50 to 1000 psi using asymmetric, porous, polymeric membrane material which is non-polar relative to the membrane material of the first stage as determined by .delta..sub.d of the solubility parameter of the membrane materials. The membrane material of the second stage is preferably at least as polar as the membrane material of the first stage and is preferably of a material selected from the group consisting of cellulose acetate propionate, cellulose acetate butyrate, ethyl cellulose, aromatic polyamide, aromatic polyhydrazide and aromatic polyamide-polyhydrazide copolymer. Preferably the fruit juice fed to the first stage is at a temperature in the range 15.degree. to 30.degree. C. and the separated water fed to the second stage is at a temperature in the range 5.degree. to 10.degree. C.

Method of concentrating natural fruit juices by reverse osmosis

An apparatus for casting tubular polymeric membranes for reverse osmosis and ultrafiltration which includes a plurality of upwardly extending casting tubes, a manifold with branch outlets for mounting the casting tubes to extend upwardly therefrom, a casting bob assembly comprising a centering sleeve with a screw threaded bore and cylindrical extension, a casting bob screwed into the centering sleeve and having casting solution outlet ports to an annular gap between the casting bob and the casting sleeve, the annular gap being adjustable by screwing the casting bob into and out of the centering sleeve, and a transport sleeve which is pressed on to the casting bob and the cylindrical extension of the centering sleeve for transporting the assembly from one casting tube to another between casting operations and a flexible sleeve and a hose clamp for releasably securing the transport sleeve in a lower end of each casting and sealing the lower ends of each casting tube to a branch outlet.

Apparatus for casting tubular, polymeric membranes for reverse osmosis

The present invention relates to the production of a novel membrane having a larger number of small sized pores therein such that the product rate in a reverse osmosis separation using said membrane is substantially increased for a particular separation factor. The invention is predicated upon the concept that the performance of a membrane in reverse osmosis separation is primarily dependent upon two interrelated factors, namely the structure of the polymer solution from which the film is cast and the evaporation rate during the period of evaporation of the organic solvent from the cast film. The present invention thus provides processes in which the solvent structure of the solution and the evaporation rate of the solution from the cast film is adjusted towards an optimum for producing a large number of small pores in the surface layer of the membrane to increase substantially the product rate at a given separation factor.

Growing community of inventors

Ottawa, Canada

Srinivasa Sourirajan