Abstract: The tubular extrusion of a thermoplastic nonderivatized cellulose solution about a mandrel and through a long air gap in excess of 304 mm is facilitated by use of a mandrel which is extensible from the extrusion die. On extrusion start-up, the mandrel extends a short length from the die. For steady-state operation, the mandrel is extended its full length from the die. Also disclosed is a mandrel structure to facilitate the introduction of a nonsolvent liquid into the interior of the extruded tube at a high location on start-up of extrusion and at a lower location during steady-state operation. The mandrel also includes a sizing portion having circumferential grooves which gather gas bubbles that may evolve at the interface between the extruded tube and the sizing portion. Vertical channels in the sizing portion connect these grooves and provide the passage of gas bubbles into a volume below the mandrel.

Abstract: The use together of (1) an aromatic compound containing a benzene ring bearing at least two substituents selected from the group consisting of hydroxy groups, primary amino groups and secondary amino groups and (2) a sulphur-containing compound containing an --SH group or an anion or precursor thereof, not being a carbocyclic arenethiol, is effective in stabilising solutions of polysaccharides such as cellulose in tertiary amine N-oxides against thermal degradation. Such solutions are useful for the manufacture of extruded articles such as fibers and films.

Abstract: In a method for forming a cellulose tube suitable for use as a food casing or as cellophane film, in which a solution of nonderivatized cellulose, tertiary amine N-oxide and water is extruded through an air gap of at least five inches, and into a water bath, such that a wet cellulose tube is formed. The wet tube is inflated from about 55% to 140% or more and dried thereby substantially retaining its work-to-rupture characteristics, especially when compared to viscose-derived tubes.

Abstract: In a method for forming a cellulose tube suitable for use as a food casing, in which a solution of nonderivatized cellulose, tertiary amine N-oxide and water is extruded through a die gap and the extruded tube is downwardly drawn through an air gap while being internally cooled and then is passed into a water bath, the tube transverse direction tensile strength being increased by drawing the extruded tube through an air length of at least about five inches and exposing the exterior surface of the extruded tube to cooling air in the air gap.

Abstract: The present invention provides a method for making medical devices, especially stents, catheters, cannulas, plugs and constrictors, by treatment of ionically crosslinkable polymer compositions with crosslinking ions.

Abstract: A method and an apparatus for processing food into a tubular shape is provided in which a die for processing the food includes a guide plate having a material outlet and a cylindrical feed pin having a water outlet at its center co-axially housed in the material outlet. The guide plate and feed pin cooperatively define a ring-like opening. Food material is extruded out of the ring-like opening in a tubular shape. Simultaneously, hot water is expelled out of the water outlet of the feed pin, flows into and fills a hollow inside the tubular food material. The hot water in the hollow prevents the wall of the tubular food material from collapsing and also accelerates coagulation of the food material. Food material is thus continuously processed into a tubular shape. An extruding die for performing the described method is also provided.

Abstract: Method for the preparation of cellulose sheet by extrusion of a heated solution of cellulose in a tertiary amine-oxide, which method includes using an extrusion die with an extrusion orifice, characterised in that, immediately below the extrusion orifice there is provided an inlet for cooling gas to cool the extruded sheet. The method according to the invention is especially suitable for the preparation of cellulose tubular films.

Abstract: A method of making a porous polymeric material by heating a mixture comprising polyvinylidene fluoride and a solvent system initially comprising a first component that is a latent solvent for polyvinylidene fluoride and a second component that is a non-solvent for polyvinylidene fluoride wherein, at elevated temperature, polyvinylidene fluoride dissolves in the solvent system to provide an optically clear solution. The solution is then rapidly cooled so that non-equilibrium liquid-liquid phase separation takes place to form a continuous polymer rich phase and a continuous polymer lean phase with the two phases being intermingled in the form of bicontinuous matrix of large interfacial area, and cooling is continued until the polymer rich phase solidifies. The polymer lean phase is removed from the solid polymeric material.

Abstract: A nozzle assembly for forming hollow fibers, particularly a "Z-fiber" having longitudinally oriented trabeculae with the fiber wall, is provided. The nozzle assembly contains a replaceable nozzle cap, a replaceable seal-guide, and a retractable central bore used to supply core material for the hollow fibers. The Z-fibers are particularly useful in enabling cells, solutes, or the like, to enter the fiber wall and move longitudinally into the center of the fiber wall.

Abstract: In a method for forming a cellulose tube suitable for use as a food casing, in which a solution of nonderivatized cellulose, tertiary amine N-oxide and water is extruded through a die gap and the extruded tube downwardly flowed through an air length while being internally cooled, and passed into a water bath, the tube transverse direction tensile strength is substantially increased by drawing the extruded tube through an air length of at least about six inches.

Abstract: A dialysis membrane in the form of a hollow fiber with a continuous internal cavity is made of cellulose acetate or a cellulose acetate derivative. The hollow fiber is made by using a gas to form the internal hollow cavity. A dialysis membrane in the form of a hollow fiber with a continuous hollow cavity may be made in a process using a spinning solution containing an organic carboxylic acid. Modification agents can be added to the solution and the solution extruded through a spinneret suitable for manufacturing hollow fibers, while an internal medium is introduced simultaneously into the internal cavity of the forming hollow fiber. The precipitation of the dialysis membrane thus formed and an ordinary further aftertreatment take place subsequently in a precipitation bath. The hollow fiber is made by using a gas as the internal medium to form the internal cavity.

Abstract: Extrusion of hollow membranes is improved by coextruding a coating fluid layer about the extrudate of heated polymer solution with its interior lumen forming extrudate. The coating fluid is disposed between the forming hollow fiber and a cooling fluid, and controls the rate of heat transfer to afford superior control over the structure and form of the hollow fiber produced in the invention. The coating fluid is typically the same material as the cooling fluid, and often is the same material as the solvent for the polymer in the heated polymer solution.

Abstract: A method of making a porous polymeric material by heating a mixture of a thermoplastic polymer and a cationic or non-ionic surfactant having a hydrophilic-lipophilic balance range of 4.0 to 6.0 to a temperature and for a time sufficient for the polymer and surfactant to mutually dissolve. The mixture is then cooled to a temperature so that non-equilibrium liquid-liquid phase separation takes place to form a bi-continuous matrix of the polymer and surfactant so that the polymer and surfactant form two intermingled separate phases of large interfacial surface area. The surfactant is then removed from the polymer. The porous polymeric material produced by the above method has a lacey or filamentous structure consisting of a plurality of polymer strands connected together at spaced apart locations along each strand.

Abstract: A process is provided which allows economical production of polyolefin separation membranes having various structures, porosities and pore sizes. The process involves using a melt blend solution consisting of a polyolefin such as polypropylene or polyethylene and a diluent selected from the group consisting of natural soybean oil, pure linoleic acid, or a mixtures of oleic acid, linoleic acid and palmitic acid.

Abstract: A process for the production of a porous organic material, in particular an organic semi-permeable membrane, provided with a plurality of separate passageways, comprising dissolving a polymer in a solvent, using a drawplate comprising needles having a shape conjugate with that of the passageways and external dimensions comprising between 0.7 and 1.2 times those of said passageways and an extrusion orifice of a conjugate fome to that of the extrudate and of internal dimensions comprising between 0.8 and 1.2 times those of said extrudate, injecting around the needles a solution having a viscosity greater than 500 millipascal-second, introducing into the interior of the conduits of the drawplate a centering fluid which is a non-solvent with respect to the polymer and able to precipitate the polymeric solution, causing the extrudate to travel from the output of the drawplate a distance da in a gaseous atmosphere which is non-precipitating with respect to the polymeric solution such that 500.times.e<da<0.

Abstract: The process for production of polyacrylonitrile hollow threads with a stable, asymmetric pore structure by a dry-wet-spinning process with glycerine-based core liquids, definite draw and after treatment conditions and a treatment with alcohols and drying.

Abstract: A method for the manufacture of a hollow fiber membrane by mixing polypropylene, an organic filler capable of uniformly dispersing in the polypropylene in a fused state and easily dissolving in an extractant being used, and a crystal seed forming agent. The resulting mixture, in a molten state, is discharged in the shape of a hollow fiber through an annular spinning nozzle and into contact with a liquid made of said organic filler or a compound similar thereto. This results in cooling and solidifying the hollow fiber, which is then forwarded into contact with an extractant incapable of dissolving polypropylene, to remove the organic filler and form the membrane.

Abstract: A process for the production of a porous organic material, in particular a semi-permeable membrane, comprising a plurality of separate passageways, including dissolving a polymer in a solvent, using a drawplate having needles of a shape conjugate with those of the passageways and of external dimensions between 0.7 and 1.2 times those of the passageways and an extrusion orifice of a shape conjugate those of the extrudate and of internal dimensions comprising between 0.8 and 1.2 times those of the extrudate, injecting around the needles a solution having a viscosity greater than 500 mPa.s and introducing a centering fluid into the interior of these needles, recovering the extrudate at the output of the drawplate in a precipitating medium in such a manner that the extrudate travels in the medium a distance such that 800.times.

Abstract: This invention relates to a novel composition useful for preparing a semi-permeable cellulose ester gas separation membrane, which composition includes a mixture of a cellulose ester, a solvent selected from the group consisting essentially of glycerol acetate, glycerol diacetate, glycerol triacetate, and mixtures thereof, and optionally the non-solvent glycerol. This invention also relates to a process of fabricating a cellulose ester gas separation membrane from said composition.

Abstract: A dope for forming membranes and the resulting asymmetric gas separation membranes are disclosed, the membranes having graded density skins which exhibit improved permeability characteristics and increased failure pressure strength. The membranes are produced from a process utilizing membrane forming dopes of complexing solvent systems formulated from two non-solvents and one or more solvents. The non-solvents are chosen one each, from non-solvents grouped according to non-solvent strength, i.e., one strong non-solvent and one weak non-solvent which are combined with one or more solvents in an acid:base complex solvent system for dissolving high weight percent total solids of membrane forming polymers. The process for forming the membranes is also disclosed.

Abstract: A process for the preparation of a membrane comprising bisphenol-based polycabonate wherein at least 25 percent by weight of the bisphenol moieties are tetrahalogenated wherein the halogen is Cl or Br, and the membrane prepared by such process.

Abstract: Isotropic microporous polysulfone membranes can be prepared by using a particular combination of casting solution and precipitation solution formulations, and casting conditions. Both hollow fiber and flat membranes can be prepared in this manner. The membranes are skinless and are characterized by uniform porosity throughout the membrane.

Abstract: A method is provided of manufacturing a skinless, nylon microporous hollow fiber membrane. The method comprises the steps of providing a nylon polymer dope solution and a quench liquid capable of solidifying and forming micropores in an extruded nylon polymer dope solution to produce a skinless, microporous nylon membrane. The quench liquid is placed into a vessel and a tube is provided which has a top and a bottom outlet. The bottom outlet of the tube is partially submerged in the quench liquid, the tube vertically extending therefrom. A spinneret is provided which has an outlet adjacent the top of the tube. The chemical quench liquid is raised in the tube until it is in substantial contact with the spinneret outlet. The nylon polymer dope solution is extruded in the form of a hollow fiber through the spinneret outlet directly into the quench liquid.

Abstract: An asymmetric microporous hollow fiber for hemodialysis is made up of 90 to 99% by weight of a first hydrophobic polymer and 10 to 1% by weight of a second hydrophilic polymer. The fiber has a water adsorbing capacity of 3 to 10% and is produced by extruding a solution containing 12 to 20% by weight of the first polymer and 2 to 10% by weight of the second polymer, the rest being a solvent to give a continuous hollow structure with a wall, causing a precipitation liquor to act on said structure in an outward direction through the wall thereof with the full precipitation thereof and the concurrent dissolution and washing out of a part of said first polymer from said extruded structure and then washing out the dissolved out part of the pore-forming substance and the other organic components. Thereafter the fiber so produced is fixed in a washing bath.

Abstract: A process is disclosed for the production of biaxially oriented liquid crystal films. The process includes:(i) forming an anisotropic dope from a polymerization solution of rigid rod heterocyclic liquid crystalline polymers such as poly{[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl] 1,4-phenylene}, its cis isomer or mixtures thereof, and poly{[benzo(1,2-d:4,5-d')bisoxazole-2,6-diyl] 1,4-phenylene}, its cis isomer or mixtures thereof, and a solvent such as polyphosphoric acid;(ii) extruding the dope to form a film;(iii) imparting biaxial orientation to the film to increase the transverse strength thereof;(iv) solidifying the biaxially oriented film; and(v) washing the solidified film to remove the solvent. Also disclosed is a liquid crystal film produced by the above process.

Abstract: A process for preparing aromatic polyamide fibers wherein an aromatic diamine and an aromatic diacidchloride are dissolved in an amide polymerization solvent containing an inorganic salt, a partial polymerization is effected at a low temperature to form an optically anisotropic liquid crystalline prepolymer dope, and the liquid crystalline prepolymer dope is subjected to a molecular orientating polymerization in a polymerization accelerating-precipitation solvent to provide aromatic polyamide fibers free of a crystal defect layer perpendicular to the fiber axis and having high strength and high degree of molecular orientation.

Abstract: A process for forming high free volume, asymmetric gas separation membranes having graded density skins and macrovoid-free morphology from a solvent system comprising a Lewis acid, Lewis base, and a Lewis acid:base complex which dissolve hydrophobic polymers. The dopes have high total solids, high viscosity and low coagulation (g) values which enhance rapid gelation without the formation of macrovoids and which minimize densification. The dope solvent system complexes are readily disassociated by the coagulation medium and the component molecules are miscible in the medium which provides for rapid desolvation of the formed membrane thus providing a membrane having low residual solvent retention.

Abstract: A microporous nylon hollow fiber is prepared by extruding a nylon spinning solution through an annular slit of an orifice into a quench liquid while simultaneously introducing a core liquid into the inside hollow portion of the extruded spinning solution where the weighted densities of the spinning solution, quench liquid and the core liquid are regulated such that the average of the density of the core liquid and the spinning solution is about equal to the density of the quench liquid.

Abstract: Directly spinning highly oriented staple fibers of para-aramids using a dry-jet wet-spinning process in which the filaments in the gap between the spinneret and the coagulating fluid are attenuated with a liquid jetted symmetrically about the filaments at a rate sufficient to break the filaments intermittently to form staple length fibers that taper along their length from an enlarged head.

Abstract: A porous regenerated cellulose hollow fiber is obtained by a micro-phase-separation method. The hollow fiber is characterized in that the viscosity average molecular weight is at least 5.times.10.sup.4, each of the average pore diameter D.sub.1 on the inner wall surface of the hollow fiber and the average pore diameter D.sub.2 on the outer wall surface is 0.02 to 10 .mu.m, the in-plane porosity Pr on the outer wall surface is at least 10%, and the hollow fiber comprises a wall thickness portion having pores piercing therethrough between the inner wall surface and outer wall surface and a hollow portion extending continuously over the entire fiber length.

Abstract: A quench bath, for quenching and solidifying an extruded hollow porous fiber of a liquid polymer solution in a chemical quenching solution, includes a shallow quench bath of a length for the generally horizontal part of the extruded fiber travel in the bath. A vertical extension tube with its lower end beneath the surface of the bath liquid holds a spinneret through which the fiber is extruded. The spinneret is sealed in the tube above the height of the liquid in the shallow bath. A vacuum drawn in the tube raises the liquid up to the spinneret. Also, the vacuum may be drawn by disposing the spinneret in a sealing piston which is raised through the tube to draw the vaccum in the tube behind the piston.

Abstract: A process for preparing collagen tubes includes extruding an aqueous gel containing about 1.5% native collagen through a cylindrical spinneret equipped with a central concentric tube designed to receive a part of a coagulation bath, followed by coagulation of the internal and external walls of the tube, leaving the spinneret in a coagulation bath constituted by about 70% acetone and 30% ammonia, followed by drying. Following drying, the collagen tube may be subjected to reticulation by dehydration carried out at about 80.degree. C. under a pressure of about 0.1 mm of Hg (vacuum) for about 24 hours. The reticulated collagen tube may eventually be subjected to a treatment which permits the introduction of azide groups onto the molecule without requiring that the collagen be coupled to any external molecule.

Abstract: Processes for producing semipermeable membranes in the form of hollow fibers are disclosed including extruding a solution of a block copolymer including at least one hydrophilic polymer and at least one hydrophobic polymer while simultaneously injecting a gaseous or vaporous center medium into the center bore of the hollow fiber extrudate, including coagulating the extrudate so formed therefrom. The preferred process includes using air or the components of air as the center medium and employing a polyethyleneoxide-polycarbonate block copolymer to form the hollow fiber membranes.

Abstract: A skinless hollow fiber of a cellulose ester material is formed by providing an aqueous coagulation bath having a tube-in-ring jet immersed therein and extruding a spinning solution comprising at least one cellulose ester material and a solvent therefor directly into the bath through an annulus surrounding the tube of said tube-in-ring jet while simultaneously allowing a portion of the liquid in the bath to be autogenously aspirated through an opening in the tube, located below the surface of the liquid in the bath, and through the tube thereby forming a lumen in the extruded fiber and then drying the extruded fiber.

Abstract: Pharmaceutical compositions are provided which contain hollow fine tube drug delivery systems. The compositions comprise a pharmaceutically suitable carrier, preferably in the form of a capsule, tablet, suspension, or suppository, and at least one drug delivery system which consists essentially of (1) a polymeric tube having a membrane outer sheath and a hollow core, and (2) at least one drug compound contained within the core, said system contained in the composition in an amount sufficient to deliver a therapeutic amount of the drug contained therein at a predetermined rate over a predetermined period of time. By varying the polymer, the permeability of the outer sheath, the drug, the drug concentration in the hollow core of the tube, the tube diameter, the tube length, the tube core diameter, and the sealing of the tube ends, a wide variety of drug therapeutic amounts, rates and dosing times can be achieved.

Abstract: Monofils and bristles which comprise at least 90% by weight of acrylonitrile units and have a linear density of more than 2.5 tex possess a relative solution viscosity of 1.7 to 6.0, a tear strength of at least 20 cN/tex and an initial modulus of more than 700 cN/tex.The manufacturing process is distinguished by a wet stretch of the spun filaments by at least 1:4, drying under tension and a subsequent hot stretch of at least 1:2, the overall stretch being at least 1:8, preferably 1:10 to 1:20.The monofils and bristles according to the invention are suitable in particular for producing filament-reinforced composite materials.

Abstract: Process for preparing poly-piperazinamide, anisotropic shaped articles comprising the preparation of the polymer solution in a polar organic solvent, the transformation of the solution into shaped bodies by spreading or spinning, the gelation of the shaped articles by phase inversion, and, optionally, the heat treatment of the gellified shaped articles.

Abstract: Hollow chitosan fibres for use in ultrafiltration processes are described, and which can be plasticized by the addition of glycerin such that they contain this latter in a quantity variable between 0.5 and 5% by weight with respect to the polymer. Said fibres are prepared by the wet spinning of acid chitosan solutions, using an alkali solution as the external fibre coagulant and a gaseous phase containing a basic gaseous component as the internal fibre coagulant.

Abstract: Aromatic polyimide hollow fibers having an enhanced mechanical strength are produced by a process comprising the steps of: preparing a spinning dope solution of at least one aromatic polyimide having 90 molar % or more of a recurring unit of the formula (I). ##STR1## wherein R is a divalent aromatic radical, in a phenolic solvent; converting the dope solution into at least one filamentary stream thereof; and introducing the filamentary dope solution stream into a coagulating liquid having a coagulating rate coefficient of 1.5 microns/sec for the dope solution, to provide rigid hollow filaments.

Abstract: A process is disclosed for the production of asymmetrical hollow filament membranes suitable for ultrafiltration and/or microfiltration, in which a spinning solution composed of a polyamide or a mixture of polyamides and/or copolyamides, formic acid and a coagulating core liquid, is extruded into a coagulating setting bath liquid, and the hollow filaments are stretched after leaving the setting bath, in the wet state. The pH-value-difference between core liquid and setting bath liquid should be at least 3. The spinning solution contains, in particular, 15 to 25% by weight polyamide, 5 to 20% by weight polyethylene glycol, up to 10% by weight customary additive and formic acid. Preferred embodiments include a stretching ratio amounting to between 1:1.5 and 1:2.5, and having core liquid and setting bath liquid chosen from various combinations of caustic soda, glycol, formic acid or polyethylene glycol.

Abstract: A method for the manufacture of a hollow fiber which comprises extruding a cellulosic spinning dope through an annular spinning nozzle directly into a non-coagulative liquid layer in a bath filled in the upper layer with a coagulative liquid relative to said spinning dope and in the lower layer with a non-coagulative liquid of a halogenated hydrocarbon and, at the same time, introducing a non-coagulative liquid relative to said spinning dope into the inner center of the tubularly extruded thread of spinning dope, and subsequently passing the resultant tubular fiber of spinning dope through said coagulative liquid thereby coagulating and regenerating the fiber.

Abstract: A liquid composition for the manufacture of a membrane, comprising a reaction product a cuprammonium cellulose with an ammonium or alkali metal salt of a polymer containing 10 to 70 equivalent percent of a carboxyl group and having a number-averaged molecular weight in the range of from 500 to 200,000, and a membrane is obtained by molding the composition in the form of a film, immersing the shaped article thus obtained in a dilute sulfuric acid solution thereby coagulating and regenerating it, subsequently immersing the shaped article in an strong alkali solution thereby expelling said ammonium or alkali metal salt of the polymer therefrom and forming therein fine pores substantially corresponding to the molecular weight of said salt.

Abstract: A process for producing a porous, film-like or fibrous structure of an aromatic polyester, which comprises(1) forming a substantially non-oriented film-like or fibrous structure by melt-molding an aromatic polyester blend composed of(A) an aromatic polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic diol and/or an alicyclic diol as a main glycol component, and(B) at least one low-molecular-weight compound selected from the group consisting of imide compounds and isocyanurate compounds being compatible, but substantially non-reactive, with the aromatic polyester and having a molecular weight of not more than 1,000,the amount of the low-molecular-weight compound being present in an amount of 10 to 300 parts by weight per 100 parts by weight of the aromatic polyester, and(2) extracting at least a major part of the low-molecular-weight compound from the resulting substantially non-oriented film-like or fibrous structure with an organic solvent which can dissolve the low-mo

Abstract: A wholly aromatic polyester composition comprising(a) 100 parts by weight of a wholly aromatic polyester containing as a main component at least one compound selected from the group consisting of aromatic dicarboxylic acids, aromatic dihydroxy compounds and aromatic hydroxycarboxylic acids, and(b) from 5 to 300 parts by weight of a low-molecular-weight compound being substantially non-reactive with the wholly aromatic polyester and having a boiling point of at least about 200.degree. C. under atmospheric pressure and a molecular weight of not more than 1,000.The wholly aromatic polyester composition is produced advantageously by polycondensing in the molten state the polyester-forming starting mixture in the presence of the low-molecular-weight compound.A film-like or fibrous article of a wholly aromatic polyester may be produced by extracting the low-molecular-weight compound from a film-like or fibrous article of the wholly aromatic polyester composition.

Abstract: A regenerated cellulose hollow fiber exhibiting a good cellulose II crystalline structure and an exchanged wet strength/wet elongation ratio is prepared by a process wherein: a dope comprised of cellulose ester in a non-volatile organic solvent is extruded through a circular slit defined between inner and outer tubes of a spinning nozzle having a double tube structure, while a core liquid is forced through the inner tube of said nozzle; the hollow fibrous extrudate is coagulated in a coagulating bath; the coagulated hollow fibrous extrudate is drawn 1.05 to 2.00 times its original length; and then, the drawn hollow fiber still containing a core liquid in the hollow is treated with an aqueous caustic alkali solution containing at least 0.5% by weight of a water soluble metal salt, thereby hydrolyzing the cellulose ester into cellulose.

Abstract: A method of manufacturing a microporous hollow fiber having a high permeability to water characterized in that a spinning solution of (A) polyacrylonitrile, (B) an acrylonitrile copolymer, or (C) an admixture of (A) and (B) in an organic solvent is extruded from an annular slit, while simultaneously extruding an organic core liquid which is a solvent for (A), (B) and (C) or a swelling agent capable of swelling them from an orifice encircled by the annular slit and introducing the extruded spinning solution with the core liquid into an aqueous coagulating bath to coagulate the spinning solution to form the hollow fiber.

Abstract: There is provided a hollow fiber membrane of ethylene-vinyl alcohol copolymer which is produced by a process comprising extruding a spinning solution of an ethylene-vinyl alcohol copolymer in a solvent selected from the group consisting of dimethylsulfoxide, dimethylacetamide, pyrrolidone, N-methylpyrrolidone and mixtures thereof through a hollow fiber spinneret while a liquid coagulant is introduced into a central aperture of said spinneret, passing the spun fiber through a gaseous atmosphere in a manner such that the fiber is drawn 0.5 to 20 times its extrusion rate and then coagulating said fiber in a coagulating bath at a temperature within the range satisfying the following relationship:when 15.ltoreq.C.ltoreq.40, 1/4C+20.ltoreq.T.ltoreq.1/4C+57wherein C denotes the copolymer concentration of the spinning solution (wt. %) and T denotes the coagulation temperature (.degree.C.).

Abstract: Hollow fibers, particularly useful as semipermeable membranes in separatory devices such as blood dialyzers, having a non-uniform cross-sectional area along the length thereof. The fibers have recurring points of maximum outside diameter and minimum outside diameter and such points may recur on a regular basis or at random. Fiber wall thicknesses may be substantially uniform or non-uniform. Methods and apparatus for making the fibers are disclosed.

Abstract: Process for production of a hollow fiber semipermeable membrane which can selectively separate the components of solution or gas mixtures, which consists essentiallly of dissolving cellulose triacetate and an organic acid and optionally a polyether in N-methyl-2-pyrrolidone to give a spinning solution having fixed contents of cellulose triacetate and organic acid and polyether (if any), and extruding the spinning solution through a spinneret into a gaseous atmosphere and immersing the spun fibers in an aqueous coagulation bath. The hollow fiber semipermeable membrane has excellent permeability and excellent separation characteristics with good life and hence is useful for various techniques such as dialysis, ultrafiltration, reverse osmosis, and separation of gases.

Abstract: A hollow fiber membrane made of an ethylene-vinyl alcohol copolymer is provided, which is characterized in that, when observed in a dry state with an electron microscope, the hollow fiber membrane has at least one dense, active layer (or skin layer) on the inside and/or outside surface thereof and further a three-layered structure comprising two layers respectively contacting the inside and outside surfaces and each consisting of a plurality of particles bonded together and having particle sizes of 0.01 to 2 microns and a substantially particle-free homogeneous layer lying between the two layers.