Hollow fibers of cuprammonium cellulose and a process of the manufacture of same

Abstract

An improved dialyzing hollow fiber of cuprammonium regenerated cellulose, showing a substantially similar network structure of fine gap passage routes having a max. gap size of 200 A when .[.seen.]. .Iadd.observed .Iaddend.at .[.its.]. any cross-section and .[.logitudinal.]. .Iadd.longitudinal .Iaddend.section, having skinless structure at its inside and outside surface of the hollow fiber and representing a superior water permeability.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A dialyzing hollow fiber of cuprammonium regenerated cellulose .[.having a smooth, skinless inner and outer wall surface and said wall having distributed throughout its thickness a netlike structure of passage routes, the routes having a diameter of not greater than 200, and said fiber having been prepared by the steps of extruding.]. .Iadd.that in artificial kidney use causes substantially no clotting of blood and achieves an improved ultrafiltration rate obtained by .Iaddend.a spinning .Iadd.process using a duplicate orifice, said process comprising extruding .Iaddend.a spinning liquor of .[.cuprommonium.]. .Iadd.cuprammonium .Iaddend.regenerated cellulose .[.to form a hollow core extrudate.]. .Iadd.through an outer ring-shaped orifice .Iaddend.and simultaneously .[.therewith passing.]. .Iadd.extruding .Iaddend.a non-coagulating organic solvent through .[.the hollow core; passing the resulting extrudate through a gaseous atmosphere whereby the weight of said extrudate causes.]. .Iadd.an inner concentric core orifice, .Iaddend.stretching .[.to substantially reduce the outer diameter thereof;.]. .Iadd.the resultant extrudate, .Iaddend.coagulating the .[.hollow core.]. extrudate .[.by contacting said extrudate with.]. .Iadd.in .Iaddend.a solution containing aqueous sodium hydroxide .[.to form a hollow core fiber having a smooth, skinless inner and outer wall;.]..Iadd., regenerating the coagulated extrudate with an acid, .Iaddend.and rinsing and drying the resulting .Iadd.hollow .Iaddend.fiber.Iadd. , said hollow fiber having the following characteristics: (1) a smooth skinless inner and outer wall surface,   (2) said wall having distributed throughout its thickness a network structure of passage routes,   (3) the said routes having a diameter of not greater than 200 Å,   (4) the outer diameter of the fiber being not greater than 1000μ,   (5) the wall thickness being not greater than 450μ; and   (6) the wall having substantially no pin holes. .[.   
     
     
       2.  The fiber of claim 1 wherein the outer diameter is no greater than 1,000μ..]. .[.3. The fiber of claim 1 wherein the wall thickness is not 
     
     
        greater than 450μ..]. 4. A process for the manufacture of a dialyzing hollow fiber having distributed throughout its thickness a .[.net-like.]. .Iadd.network .Iaddend.structure of passage routes.Iadd., said hollow fiber in artificial kidney use causing substantially no clotting of blood and achieving an improved ultrafiltration rate, .Iaddend.which comprises the steps of extruding a spinning liquor of .[.cuprommonium.]. .Iadd.cuprammonium .Iaddend.regenerated cellulose .[.to form a hollow core extrudate and simultaneously therewith passing a non-coagulating organic solvent.]. through .[.the hollow.]. .Iadd.an outer ring-shaped orifice;   and simultaneously extruding a non-coagulating organic solvent through a concentric .Iaddend.core .Iadd.orifice to form a composite core-and-sheath liquid string; .Iaddend.   passing the resulting extrudate through a gaseous atmosphere whereby .Iadd.solely .Iaddend.the weight of said extrudate causes stretching to substantially reduce the outer diameter thereof;   coagulating the .[.hollow core.]. extrudate by contacting said extrudate with a solution containing aqueous sodium hydroxide to .[.from.]. .Iadd.form .Iaddend.a hollow .[.core.]. fiber having a smooth, skinless inner and outer wall;   regenerating the hollow fiber with an acid; and rinsing and drying the   
     
     
        resulting fiber. 5. The process according to claim .[.4.]. .Iadd.7 .Iaddend.wherein the non-coagulating organic solvent is selected from the group consisting of aromatic hydrocarbons, aliphatic .[.hydrocarbon.]. 
     
     
        .Iadd.hydrocarbons .Iaddend.and halogenated hydrocarbons. 6. The process according to claim .[.4.]. .Iadd.7 .Iaddend.wherein the sodium hydroxide 
     
     
        is present in the solution in an amount from 5% to 15% by weight. 7. The process of claim 4 wherein the fiber is dried at a temperature of up to 150° C. .Iadd.8. The fiber of claim 1, a wherein the fiber is dried at a temperature of up to 150° C..Iaddend. .Iadd.9. The fiber of claim 1 wherein the degree of polmerization of the cellulose ranges from 400 to 500..Iaddend. .Iadd.10. The fiber of claim 8 wherein the concentration of aqueous sodium hydroxide solution is less than 20% by weight..Iaddend. .Iadd.11. The fiber of claim 10, wherein the concentration of aqueous sodium hydroxide solution is between 5 and 15% by weight..Iaddend. .Iadd.12. The fiber of claim 8 wherein the drying temperature ranges from 100° C. to 140° C..Iaddend. .Iadd.13. The fiber of claim 10, wherein said contacting with a sodium hydroxde solution is for a time period short enough to avoid a skin core structure..Iaddend. .Iadd.14. The process of claim 4, wherein the sodium hydroxide is present in the solution in an amount of less than 20% by weight, and said contacting with a sodium hydroxide solution is for a time period short enough to avoid a skin core structure..Iaddend.