Ceskoslovenska Akademie Ved

Josef Kucera

Artur Stoy

Vladimir Stoy

Renata Urbanova

Jaroslav Prokop

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. The concentration of the coagulating bath is kept constant during the wet spinning by withdrawing a part of the bath equimolar to the amount of nitric acid introduced therein by the wet spinning, adding a neutralizing agent to the bath at a rate at which the nitric acid is introduced into the bath and replacing the water lost from the bath during the withdrawing of the portion thereof. The filament fibers are concommitantly formed by washing, stretching, heat stabilizing and drying the material as it leaves the bath, together with the formation of nitrates by treating the withdrawn portion of the bath in conventional manner to recover in solid form the nitrates found in the withdrawn bath.

Method of simultaneously manufacturing acrylic fibers and nitrates

There is disclosed a method of preparing hydrophilic copolymers of acrylonitrile by initially polymerizing acrylonitrile with about 0.01 to about 30% by weight of a monomer selected from the group consisting of acrylamide; methacrylamide; monomers of the formula CH.sub.2 =CRCONHR.sup.1 wherein R is hydrogen or methyl and R.sup.1 is hydrogen, methyl or ethyl; N,N-dialkylacrylamides and methacrylamides and N-alkylol amides, thereafter subjecting said copolymer to hydrolysis by an aqueous acidic solvent for the monomers or swelling agent for the polymer comprising at least one compound selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, formic acid, zinc chloride and zinc chloride/HCl mixtures and subsequent isolating the product thus formed by removal of the acidic hydrolytic agent therefrom. The products thereof possess such properties as high tensile strength and high swelling capacity and they are accordingly suitable for the production of fibers, membranes, tubing and the like.

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Pardubice, Czechoslovakia

Josef Kucera