A Process For The Manufacture of Void-free and Constant Cross-Sectional-Shaped Polyacrylonitrile Fibers With High Packing_Densities

Sep 21, 2026

Uploaded by Aria

Patent text describing a spinning process to manufacture void-free, constant cross-sectional polyacrylonitrile fiber materials with high packing density. The method dissolves acrylonitrile polymer containing hydrophilic groups in dimethylformamide and uses a nozzle with a high hole number and 50–500 µm hole diameters, then draws into an aqueous coagulation medium. Coagulation proceeds stepwise in two stages with decreasing solvent concentration (first 75–85% dimethylformamide / 25–15% water, second 40–65% dimethylformamide / 60–35% water) to reduce adhesive coagulation effects.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages24

Reading Time1 h 0 min

AccessFree to download

Invention overview

Prior-art coagulation and spinning backgrounds

Problems with higher-solvent precipitation baths

Purpose of the invention

Core process steps and parameters

Eberhard,P. A process for the manufacture of void-free andconstant cross-sectional-shaped polyacrylonitrilefibers with high packing densities /byP.Eberhard and others.10 p. Patent(East German)No.78624.Filed: TRANSLATION NO.4736. n-1 EAST GERMAN PATENT NO.78624 P.Eberhard,P.Anneliese,S.Hartig # "A Process For The Manufacture of Void-free and Constant Cross- Sectional-Shaped Polyacrylonitrile Fibers With High Packing_Densities" The invention is concerned with a process for the manufacture ofvoid-free and constant cross-sectional-shaped fiber materials withhigher packing densities produced by means of their spinning frompolymerized acrylonitrile materials which contain hydrophilic groupsand which are dissolved in dimethylformamide and spun into anaqueous coagulation medium of higher solvent concentration. It is known that the polymerized acrylonitrile dissolved in theorganic solvents,such as in particular,in dimethylformamide, dimethylacetamide or in dimethyl sulfoxide,can be spun into an aqueouscoagulation medium of higher solvent concentration,whereby the structure of the fiber fixed in the coagulation process in particularwith respect to the formation of voids and the packing density inaddition to the type of polymer is dependent upon the ratio of thesolvent to the non-solvent in the coagulation bath. The percentagefraction of the solvent in the coagulation system,whereby water isused for the most part as the coagulating liquid,however,may be ashigh as is possible,in order to obtain the highest possible spinningspeed in addition to the improvements in the structure of the fibersand to spin the fine denier,which shapes the economics of therecovery of the solvent. The improvement in the structure of suchfibers obtained in precipitation process and the possibility of an Digitized by the Internet Archivein 2017 Page 2 optimal formation of the spnning technology with respect to thehigher spinning speeds and the spinning of the finest denier isreferred back to the varied coagulation mechanism. The markedcoagulation effect of the water is moderated by means of the higherportion of the solvent and a slower coagulation acts without the for-mation of a membrane for the equivalent(=more uniform)segregationover the entire cross-section of the fiber. The fiber thus producedalso may possess its plasticity after passage in the precipitationbath. These developments are extensively related to radial capil-laries and voids in the inside of the fibers. With regard to the production of the continuous fibers it isfurther known that the spinning of a polymerized acrylonitrile into anaqueous medium of coagulation having a content of from 75%up to 90号dimethylformamide,or into a percipitation medium which contains asmaller concentration of the dimethylformamide but has an addition ofan organic non-solvent,such as xylenol or ethylene glycol,ispracticed. Also,the application of a coagulation system with a compositionof from 40 up to 70%dimethylsulfoxide and 60 up to 30%water,wherebythe temperature of the precipitation medium is maintained at 35 up to80°c,is already known.Therefore,the fibers thus obtained other-wise show a more porous fiber structure so far as they are not passedafterwards into a second batch or for example stretched out on acooled metal plate. Page 3 Collectively these processes have the disadvantage that by theirapplication it is possible to apply the spinning of the polyacrylo-nitrile fibers in precipitating baths having higher solvent concen-trations without the complications with the nozzles with smaller holevalves,as they are applied in particular for the spinning of thecontinuous fibers. When also the spinning speeds achievable there-with from 200 up to 1000 m/minute are permitted in spite of an economic form of the process,then still the production of the staplefibers and fiber cables for the converter-processing assumes for anoptimally economical form of the,process the introduction o

FAQs

What material and solvent are used in the invention’s fiber-manufacturing process?

The process uses a polymerized acrylonitrile containing hydrophilic groups, dissolved in dimethylformamide, and spun into an aqueous coagulation medium.

How does the invention achieve stepwise coagulation and what are the two-stage solvent ranges?

Coagulation is accomplished stepwise with decreasing solvent concentration, preferentially in two stages: first 75–85% dimethylformamide with 25–15% water, then 40–65% dimethylformamide with 60–35% water.

Why is the invention intended to improve spinning quality compared with known higher-solvent processes?

It aims to eliminate adhesive effects arising from coagulation behavior, which otherwise can increase sticking and lead to poorer fiber quality and processing properties.

Sep 21, 2026

Uploaded by Aria