Abstract: A flame retardant composition comprises an organic polymer containing one of the inorganic compounds with phosphorus and nitrogen, or either of them in the form of finely powdered crystal. The inorganic compounds are coated with an inactive material.

Abstract: Carbon fibers are prepared by spinning a copolymer of a carboxyl group-containing unsaturated monomer and at least 85 mol% acrylonitrile, washing the filaments with water, stretching the filaments in hot acid water having a pH below 3.5, and heating the resultant fibers to cause carbonization or graphitization.

Abstract: An acrylonitrile polymer composition obtained by uniformly mixing an acrylonitrile polymer, water and acrylonitrile is heated at the autogeneous pressure or above and the resulting melt is shaped into a desired form. The shaping processability is improved thereby.

Abstract: The invention relates to new ionogenic hydrogels based on partially hydrolyzed polymers containing, in the starting material, at least 60, advantageously at least 80% (mol.) of acrylonitrile units, said hydrogels being characterized by a weakly ampholytic, character and by a multiblock structure of polymeric chains with continuous sequences of acrylonitrile units in an amount of from 2 to 95% (molar), alternating with continuous sequences of hydrophylic units consisting of a major amount of acrylic acid and a minor amount of acrylamide units, the sequences or blocks of acrylonitrile units forming together polyacrylonitrile domains detectable by X-ray analysis. In water-swelled condition the hydrogels consist of two distinct but inseparable phases, one of them said polyacrylonitrile, the other said amorphous hydrophilic, highly solvated chains with predominating acrylic acid units.

Abstract: Flame resistant acrylic fibers are produced by, in a solution polymerization of a mixture consisting of 30-80% by weight of acrylonitrile, 20-70% by weight of vinyl chloride or vinylidene chloride and 0-15% by weight of the other unsaturated monomer in a solvent of dimethylformamide, adding a polymer (referred to as blendmer) consisting of acrylonitrile, vinyl chloride or vinylidene chloride and an anionic monomer and zinc salt of an aromatic sulfonic acid prior to starting of the polymerization, subjecting the resulting mixture to the solution polymerization, removing unreacted monomers from the formed polymer solution, adding sulfur dioxide and adding water to adjust water content, spinning the thus formed spinning solution into an aqueous solution of dimethylformamide.

Abstract: Process for producing a flame retardant acrylic fiber by wet-spinning a halogen-containing acrylic spinning solution containing antimony oxide particles dispersed therein, wherein an acrylic fiber having a high degree of flame retardancy and improved fiber properties, such as transparency, luster and brightness of colors of dyed products, is produced in an industrially advantageous manner by regulating the water content in the hydrogel fiber obtained by hot stretching after wet-spinning within a range of 50-130% based on the fiber-forming polymer.

Abstract: This invention relates to a process for the production of dyed filaments or fibres of acrylonitrile polymers, wherein carbon black pigments are added to the polymer before the spinning process and the filament containing carbon black pigments are dyed. By this process it is possible to save considerable amounts of dye-stuff.

Abstract: Acrylic fibers of a fiber-forming first acrylonitrile polymer containing at least 50% acrylonitrile, a flame retardant amount of a halogen-containing vinyl monomer, and any balance of a halogen-free vinyl monomer having heterogeneously dispersed therein a small amount of an incompatible, halogen-free, second acrylonitrile polymer containing at least 70% acrylonitrile and one or more halogen-free vinyl monomers. The fibers are prepared by wet-spinning an intimate mixture of the polymers separately dissolved in aqueous inorganic solutions of the same salt following conventional procedures but including a hot-wet relaxation of the stretched wet-gel filaments prior to drying.

Abstract: A process for producing flame-resistant filaments by preparing a hot solution of a halogen-containing acrylonitrile polymer composition in an inert organic solvent for the composition, extruding the solution to form filaments and removing the solvent from the filaments. Corrosive attack of the solution on metallic equipment used in the process is greatly reduced by incorporating both water and specified phosphorus compounds in the solution.

Abstract: Novel antiflaming fibers having excellent dyeability and heat resistance are prepared from a matrix-polymerized resin which comprises polymerizing acrylonitrile in the matrix of a vinyl chloride resin. A vinyl chloride resin and/or an acrylonitrile resin can be added in a specific amount to the matrix-polymerized resin when dissolved in a spinning solvent. Substantially the same fibers are also prepared from blended polymers which comprise blending a specific vinyl chloride resin and a specific acrylonitrile resin in the specific proportion, by employing the coagulation bath of an aqueous solution of calcium chloride.

Abstract: The invention relates to a process for the production of high-shrinkage wet-spun acrylic fibres having good fibre strength and high densities by fixing the unstretched fibres with saturated steam and then stretching in a ratio of from 1:3,5 to 1:5.

Abstract: Method of preparing films of acrylonitrile polymer exhibiting very high tensile strength, stiffness, optical clarity, and outstanding gas barrier properties. Method entails extruding a hot, concentrated solution of said polymer in a solvent therefor that is water-soluble, e.g., dimethyl sulfoxide, onto a film-supporting surface, e.g., a flat surface, or a drum, which, preferably, has a low energy surface such as provided by wetting the surface with aqueous dimethyl sulfoxide, or coated with polytetrafluoroethylene, or other suitable means to thereby form a film. The resulting film is then contacted with an aqueous medium, e.g., water to remove the solvent (e.g., dimethyl sulfoxide) and partially replace it with water, this treatment being effected under conditions that will prevent the film from curling or puckering. The resulting film is composed essentially of acrylonitrile polymer and water, and is ignition resistant.

Abstract: Process for producing an acrylonitrile polymer in a substantially melted state by polymerizing a monomer mixture composed mainly of acrylonitrile in the presence of water under a pressure above the autogenous pressure at a temperature of from 80.degree. to 120.degree. C so as to attain a polymerization rate of at least 45%.

Abstract: A semipermeable composite membrane which shows only a small reduction of water permeability even when it is subjected to one time hot water treatment or drying treatment is provided according to the method of the present invention. Said semipermeable composite membrane consists of a porous substance and a reinforcing material embedded therein. Said porous substance has a porous region of network structure at least in one part thereof and numbers of voids in said porous region. Said reinforcing material is a fabric in case of flat type membrane or a braid having a central hollow portion in case of hollow fiber type membrane which is embedded in the wall of the membrane. Said method comprises impregnating said reinforcing material with a polymer solution and treating the impregnated reinforcing material with a coagulating liquid.

Abstract: A method for preventing or eliminating water-absorption whitening of a molded article containing an acrylonitrile polymer or copolymer which comprises immersing the molded article into an aqueous medium containing a salt.

Abstract: The invention relates to modacryl filaments and fibers made from copolymers insoluble in acetone of acrylonitrile and from 20 to 45 weight % of vinylidene chloride, containing from 0 to 1.5 weight % of unsaturated organic sulfonic acids or the salts thereof, and from 0 to 10 weight % of further copolymerizable compounds, which copolymers have a K value according to Fikentscher of from about 60 to about 90, and a process for the manufacture thereof. These modacryl filaments and fibers are especially distinguished by their permanent brilliance and permanent transparence; these properties are maintained even on contact with water having a temperature above 80.degree. C.

Abstract: The invention relates to modacryl filaments and fibers made from copolymers insoluble in acetone of acrylonitrile and from 20 to 45 weight % of vinylidene chloride, containing from 0 to 1.5 weight % of unsaturated organic sulfonic acids or the salts thereof, and from 0 to 10 weight % of further copolymerizable compounds, which copolymers have a K value according to Fikentscher of more than about 95 and a process for the manufacture thereof. These modacryl filaments and fibers are especially distinguished by their permanent brilliance and permanent transparence; these properties are maintained even on contact with water having a temperature above 80.degree. C.

Abstract: An improved splice is provided which is useful in joining segments of a substantially flat band (e.g., a flat tow) of an acrylic fibrous material in an end to end relationship. A fabric surrounds and is sewn to an end of each band segment and extends beyond the end of the band to form a fabric extension. A pair of fabric extensions are sewn in an overlapping opposing relationship in the absence of any substantial overlap of the acrylic fibrous material of each band segment within the splice. The resulting splice is substantially flat in configuration and the band may be continuously passed in the direction of its length through the thermal stabilization zone without impairment of movement resulting from the presence of the splice. The usual exothermic heat of reaction which is evolved during the cyclization portion of the thermal stabilization reaction effectively is dissipated from within the splice without harm.

Abstract: An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

Abstract: In a process for the production of flame retardant acrylic synthetic fibers by mixing a spinning solution of a acrylonitrile polymer with an emulsion of a polymer of a vinyl halide and/or vinylidene halide, and wet-spinning the resulting mixed solution, the improvement which comprises using, as said emulsion, an emulsion obtained by polymerizing a vinyl halide and/or vinylidene halide in an aqueous medium in the presence of certain water-soluble polymer.

Abstract: Filamentary vinyl polymer compositions are commonly prepared according to a procedure which includes the following steps:A. polymerizing a vinyl monomer in a concentrated aqueous inorganic salt solution to produce a vinyl polymer solution;B. spinning the resulting vinyl polymer solution through a spinnerette into a coagulating bath containing an aqueous solution of the same inorganic salt as that employed in the polymerization step, the concentration of inorganic salt in the coagulating bath being maintained at a level which affords precipitation of the vinyl polymer to form a coherent filamentary gel;C. washing the vinyl polymer filamentary gel so produced;D. recovering the concentrated aqueous inorganic salt solution from the washing and coagulation steps by concentrating the combined effluents thereof; andE. recycling the recovered concentrated aqueous inorganic salt solution into the polymerizing step.

Abstract: Halogen-containing acrylic fibers are improved in flame retardancy when a diorganotin oxide compound is incorporated therein.

Abstract: The novel improved process of the invention for spin-dyeing of acid-modified polymers or copolymers of acrylonitrile with basic dyestuffs wherein the spinning solutions of the polymers contain the basic dyestuffs in form of their free dyestuff bases as anhydro or carbinol bases is conducted with completely transparent spinning solutions avoiding clogging and mechanical abrasion of the spinning nozzles and yields filaments and fibers which do not show matting effects but have a high tinctorial strength and good and improved fastnesses to rubbing, to light and to wet-processing.

Abstract: The invention relates to wet-spun modacrylic filaments with improved coloristic properties based on a polymer mixture, which comprises at least one acrylonitrilevinyl chloride copolymer and a chlorine-containing copolymer containing sulphonic acid ester groups or sulphuric acid ester groups.

Abstract: The invention relates to dry-spun modacrylic filaments with improved coloristic properties based on a polymer mixture, which comprises at least one acrylonitrile-vinyl chloride copolymer and a chlorine-containing copolymer containing sulphonic acid ester groups or sulphuric acid ester groups.

Abstract: There are disclosed a process for preparing acrylic fibers of improved hot-wet properties and improved elastic recovery by finely dispersing in the spin dope prior to spinning a solution of a polycarbonate resin in a solvent immiscible with the spin dope. The acrylic fibers so produced contain elongated fibrils of the polycarbonate resin of 0.05 to 5.0 microns diameter and up to several centimeters long.

Abstract: Acrylic synthetic fibers having excellent touch and luster properties are produced, wherein such fibers are prepared from a copolymer comprising 30 weight % or more of acrylonitrile, 70 weight % and less of vinyl chloride and/or vinylidene chloride and from 0 to 10 weight % of other polymerizable vinyl monomers. The copolymer also contains at least one metallic compound which is present in an amount of from 0.1 to 8.0 parts per 100 parts of copolymer and, additionally, at least one cellulose derivative which is present in an amount from 1.0 to 8.0 parts per 100 parts of the copolymer. Fibers produced from such copolymer have the touch and luster very similar to natural animal hair.

Abstract: A method for obtaining delustered polyacrylonitrile fibers, wherein fibers are formed from a spinning solution, that is, being a mixture of two copolymer solutions, one of them being polyacrylonitrile and the other a ter grafted copolymer of acrylonitrile and styrene on rubber such as butadiene or butadiene-styrene rubber-ABS-copolymer.

Abstract: High nitrile polymer articles having improved impact strength and dimensional stability are prepared by stretching in more than one direction a solvent-free, thermoformed polymer article having less than 0.5 percent water and then heat setting the oriented article while in a restrained position at orientation temperatures for about 5 seconds to 2.5 minutes.

Abstract: A method of manufacturing acrylic fibers free from delustering in boiling water, comprises the steps of forming a spinning solution by dissolving in a solvent of acetone, acetonitrile, dimethylformamide and mixtures thereof, (a) a copolymer consisting of (1) 30 - 80% acrylonitril and (2) 70 - 20% vinyl chloride or vinylidenechloride, or (b) a tripolymer consisting of (1), (2) and (3) 3.0% or less by weight of ethylenically unsaturated monomer having hydrophilic groups, and adding one or more compound selected from the group of (1) homopolymer or copolymer of glycidyl methacrylate and (2) specific organic tin compounds, and spinning said spinning solution into a first bath consisting of 60% or less said organic solvent-water and leading said yarn in a 2nd bath consisting of 61 - 85% said organic solvent-water and then in a 3rd and more bath consisting of less than 60% said organic solvent-water and drying, drawing out and annealing said yarn by ordinary methods.

Abstract: An improved process is provided for the production of stabilized acrylic fibers and films. Certain stabilization promoting agents are incorporated in a solution of an acrylic polymer prior to extruding the same to form a fibrous material or film wherein the pendant nitrile groups present in the acrylic polymer are substantially uncyclized, and the acrylic fibrous material or film having a minor quantity of the stabilization promoting agent incorporated therein is heated in an oxygen-containing atmosphere until a stabilized fibrous material or film is formed which is capable of undergoing carbonization. The stabilization promoting agents employed in the present process are mineral acids, sulfonic acids, certain carboxylic acids, and Lewis acids. The resulting stabilized fibrous material or film is non-burning, and may be utilized as a fire resistant fiber, fabric, or film, or optionally carbonized or carbonized and graphitized to form a carbonaceous fibrous material or film.

Abstract: An improved process for the wet-spinning of acrylic polymers is disclosed, wherein a spinning solution of an acrylic polymer in an organic solvent, such as dimethylacetamide or dimethylformamide, is extruded through a spinneret into a coagulating bath consisting essentially of water and an organic solvent in a ratio between 30:70 and 60:40 by weight, and wherein the filaments thus obtained are washed, stretched and heat treated, and wherein the coagulating bath contains from 0.03% to 3% by weight of acid corresponding to said organic solvent and has a pH value greater than 5, and preferably between 6.5 and 8. The spinning solvent is preferably dimethylacetamide containing free acetic acid to an extent of less than 0.1% by weight, the acetic acid if necessary being added to the coagulating bath to bring its concentration up to values between 0.03% and 3% by weight. The pH value greater than 5 is obtained by the addition to the coagulating bath of ammonium hydroxide, an alkali metal hydroxide, or dimethylamine.

Abstract: An improved process is provided for the formation of metal ion containing carbon fibers which particularly are suited for utilization in electron shielding applications. An acrylic fibrous material is formed having substantially uniformly dispersed therein a halide of a transition metal. The metal halide (e.g. a chloride) present within the fibrous material is (1) converted to an oxide, (2) the fibrous material containing the metal oxide is heated in an oxygen-containing atmosphere until thermally stabilized, and (3) the thermally stabilized fibrous material is carbonized or carbonized and graphitized at a more highly elevated temperature in an appropriate atmosphere. The resulting product comprises ions of a transition metal substantially uniformly dispersed in an amorphous carbon or graphitic carbon matrix. The halide of a transition metal may be incorporated into the acrylic precursor by co-spinning and/or padding prior to thermal stabilization.

Abstract: There is disclosed an improvement in the continuous melt extrusion of a refractory polymer and its melt assistant by which a porous plug of the composition being extruded is formed between the compressing zone and the melting zone of the extruder so as to prevent loss of vaporized melt assistant by backward escape through the feed inlet.

Abstract: A naturally crimped polyacrylonitrile fiber having an asymmetrical cross section, the cross section having at least two large oblong lobes, the angle between at least two of these lobes being less than 90.degree., the fiber having an outer structure which has a relatively high density and has a variable thickness, this outer structure enclosing an inner structure which is porous and less dense than the outer structure.The process for producing crimped polyacrylonitrile fibers comprises spinning a solution of a polyacrylonitrile polymer into a cold bath at a temperature of less than 30.degree.C.

Abstract: Acrylic fibers have a decreased tendency to accumulate static charges when the spinning solution from which the fibers are spun has incorporated therein a polymer of tetrohydrofuran, which polymer remains durably adhered to the formed fiber.

Abstract: The present invention relates to a process for producing high shrinking acrylic fibers which have excellent antipilling properties and dyeing characteristics. This process involves dissolving an acrylonitrile polymer in an inorganic solvent to prepare a spinning solution containing the inorganic solvent in a concentration of 40-70%, subjecting the spinning solution to a wet-spinning by extruding through spinnerette orifices into two coagulating baths, while maintaining the linear velocity ratio of free extrusion at 1 or higher and maintaining a jet stretch ratio of 1.5 or higher, stretching the formed swollen gel fibers to 3-7 times the length in hot water or in a heated steam medium at 80.degree.-120.degree.C, drying the stretched fibers, then subjecting the fibers to a secondary stretch of 1.05 to 1.60 times the length, wherein the first coagulating bath has an inorganic solvent concentration of 50-70% of that in the spinning solution.

Abstract: An improved process for drawing a continuous length of an acrylic multifilament fibrous material is provided. Prior to drawing at an elevated temperature by continuous passage through a suitable drawing zone the surface of the fibrous material is coated with powdered graphite (e.g. colloidal graphite) via contact with a dipersion containing the graphite paticles which serve to improve the drawing properties of the same. The process is suited for the hot drawing of a continuous length of an acrylic multifilament fibrous material (e.g. a substantially untwisted tow) which is intended for subsequent thermal stabilization, and cabonization to form a carbonaceous fibrous material.

Abstract: The present invention relates to a process for producing an anti-pilling acrylic fiber which has excellent level dyeing properties. This process involves dissolving an acrylonitrile in an inorganic solvent to prepare a spinning solution, wherein the inorganic solvent in the spinning solution is 40-70%, subjecting the spinning solution to wet-spinning by extrusion through spinneret orifices into a coagulation bath containing an inorganic solvent in an amount of 50-70% of that in the spinning solution, while maintaining the linear velocity ratio of free extrusion at 1 or higher and the jet stretch ratio 1.5 or higher, stretching the formed gel fibers 3-7 times the length in hot water or in a heated steam medium at 80.degree.-120.degree.C, drying the stretched fibers and then subjecting the fibers to a relaxation treatment in a hot air current at a temperature of 150.degree.C or lower or in a wet heat atmosphere at a temperature of 120.degree.C or lower.

Abstract: A method is provided for fabricating asymmetric acrylic hollow fibers for use in separatory processes as a selective membrane. The fibers are highly permeable and exhibit a high degree of selectivity in discriminating mixtures into their various components. The fibers are formed by extruding an acrylic polymer solution through an annular orifice while simultaneously injecting a coagulating fluid into the bore of the fiber extrudate as it is formed. The extrusion may be directly into a coagulating bath maintained at a temperature of from 60.degree. to 80.degree.C. or alternatively the freshly extruded fiber may be first passed through an air space (evaporation zone) and thence into the coagulating bath. Following coagulation, the fibers are water washed to remove residual solvent.

Abstract: A process for reducing the extractable HCN content of packaging materials prepared from molten nitrile polymers which process comprises having styrene oxide in intimate contact with the molten nitrile polymer during the forming steps used to prepare the packaging materials.

Abstract: Continuous process for preparing a spinning solution of acrylic polymeric material. Process utilizes acrylic polymers obtained in a bulk polymerization slurry, and comprises adding a solvent such as dimethylacetamide to the slurry in such quantity as to be insufficient to attack and dissolve the polymer, bringing the resulting mixture to a temperature not exceeding 170.degree.C, such temperature being such as to not result in any appreciable attack of the polymer by the solvent, removing unreacted monomer by vacuum adiabatic evaporation, and then heating to a temperature not exceeding 170.degree.C, such temperature being sufficiently high to result in solvent attack and dissolution of the polymer.

Abstract: Solutions of polymers or copolymers containing up to 100% of acrylonitrile units and from 0 to 50 mol percent of units of one or more comonomers copolymerizable with acrylonitrile into nitric acid-soluble polymers is wet spun in a coagulating bath containing a constant surplus of neutralizing agents in an amount ranging from about 0.05 to about 5% by weight which neutralizing agents are sufficient to convert the nitric acid into nitrates and to make the filaments leaving the coagulating bath free of nitric acid. The coagulating bath is maintained at a temperature at least about 5.degree. C above the temperature at which the solution of the same concentration is saturated with respect to its nitrate content.

Abstract: Non-inflammable filaments having good physical characteristics are disclosed, wherein the filaments have a chlorine content of 25-40% by weight and a sticking temperature of at least 215.degree.C, and a shrinkage of less than 32% when subjected to steam at 130.degree.C in the free or unrestrained state. The filaments are formed by spinning a mixture of incompatible polymers, one polymer, used in an amount of 50-99% by weight, containing 79.5 to 58 weight percent of acrylonitrile units, 20-40 weight percent of vinylidene chloride units and 0.5 to 2 weight percent of a comonomer which enhances dyeability, and the other copolymer, used in an amount of from 1-50 weight percent, containing from 20-50 percent by weight of acrylonitrile units and 50-80 percent of vinylidene chloride units.The filaments may be used in textile applications, such as for clothing, furniture upholstery, and the like.

Abstract: Method for producing a synthetic fiber substantially comprising dissolving a composition consisting essentially of:A. 5-40 percent by weight of a copolymer consisting ofA. 20-80 percent by weight of polyvinyl alcohol, andB. 80-20 percent by weight of acrylonitrile, andB. 60-95 percent by weight of a copolymer consisting ofC. 55-95 percent by weight of styrene, andD. 5-45 percent by weight of acrylonitrile, in dimethyl sulfoxide or dimethyl acetamide as a solvent, and wet-spinningThis fiber is used for producing paper and has a potentially fibrillar texture. When beaten, it forms a synthetic pulp having stalk fibrils and micro fibrils extending from the stalk fibrils.High-tenacity synthetic paper can be made because this synthetic pulp is self-adhesive.

Abstract: An improved method for washing acrylic filaments in which the acrylic filaments are produced by wet-spinning a solution of an acrylic polymer in dimethylacetamide, and are coagulated, and if desired stretched, and are then finally washed with an aqueous wash solution containing an alkaline agent, wherein the aqueous wash solution contains acetic acid in a quantity between 0.0050% and 0.1% and dimethylamine in such a quantity that the dimethylamine/acetic acid molar ratio is greater than 0.2, and preferably between 0.4 and 0.8.

Abstract: Apparatus for manufacturing synthetic tow for stretch-cut spinning process. This synthetic tow is produced by changing the coagulation condition after delivery from the spinnerets so the weak points are distributed in individual filaments in a particular condition defined by variation of unevenness of breaking strength. The coagulation condition of each filaments in the tow is positively changed according to periodic changes in the filament's passage by contacting a deviation bar disposed in the filament's passage.

Abstract: Aqueous solutions containing at least 30% sodium thiocyanate and 2 to 25% dipropylene glycol are solvents for acrylonitrile polymers containing 55 to 80% acrylonitrile and 15 to 40% vinyl chloride, vinyl bromide, vinylidene chloride, vinylidene chlorobromide, and/or vinylidene bromide useful in forming solutions of 8 to 15% of such polymers for wet-spinning into fibers.

Abstract: Flame-retardant acrylic filaments containing a flame retardant which is the reaction product of a dibasic acid amide, an oxyacid of phosphorus and a polyhydroxy alcohol, the flame retardant being bound to the acrylic filaments by a cross-linking agent. The filaments are made flame-retardant by applying the flame retardant and cross-linking agent to the filaments and subsequently heating the filaments to chemically bind the flame retardant to the acrylic filaments.

Abstract: A method of manufacturing acrylic fibers free from delustering in boiling water, comprises the steps of forming a spinning solution by dissolving in a solvent of Aceton et al, (a) a copolymer consisting of (1) 30 - 80% acrylonitril and (2) 70 - 20% vinyl chloride or vinylidenechloride, or (b) a tripolymer consisting of (1), (2) and (3) 3.0% or less by weight of ethylenically unsaturated monomer having hydrophilic radicals, and adding one or more compound selected from the group of (1) homopolymer or copolymer of glycidyl methacrylate and (2) specific organic tin compounds, and spinning said spinning solution into a first bath consisting of 60% or less said organic solvent-water and leading said yarn in a 2nd bath consisting of 61 - 85% said organic solvent-water and then in a 3rd and more bath consisting of less than 60% said organic solvent-water and drying, drawing out and annealing said yarn by ordinary methods.