Process for preparing high stength cellulosic fibers

DETAILED DESCRIPTION What is claimed is: 1.
Process for preparing high strength cellulose triacetate fibers having at least 42.
5% by weight acetyl groups by extruding a high solids, optically anisotropic solution of cellulose triacetate in a solvent mixture comprising nitric acid and another solvent having a molecular weight of less than 160 through an inert noncoagulating fluid layer into a coagulating bath wherein the cellulose triacetate has an inherent viscosity of at least 5 (0.
5 g/dl in hexafluoroisopropanol at 30.
degree.
C.
), the polymer concentration is from about 30% to about 50% by weight, and the mol ratio of nitric acid to the other solvent is from about 1 to about 3.
2.
Process of claim 1 wherein the other solvent is selected from the group consisting of water and methylene chloride.
3.
Process of claim 2 wherein the other solvent is water, the mol ratio of nitric acid to water is 1.
1 to 2.
6 and the polymer concentration is 35-40% by weight.
4.
Process of claim 2 wherein the coagulation bath is comprised of a 1-3 carbon atom alcohol or diol and water.
5.
Process of claim 4 wherein the coagulating bath is comprised of methanol and water.
6.
Process of claim 5 wherein the coagulating bath is comprised of from about 25 to about 50% methanol.




Description:
This invention concerns a new process for making cellulose triacetate fiber from optically anisotropic solutions of cellulose triacetate.
BACKGROUND OF THE INVENTION Anisotropic spinning solutions from aromatic polyamides have been described in Kwolek U.
S.
Pat.
No.
3,671,542 and U.
S.
Pat.
No.
Re.
30,352.
These solutions (dopes) are useful in making aramid fibers of very high tenacity and modulus.
Optically anisotropic solutions of cellulosic materials have been described in French Pat.
No.
2,340,344, and these too have provided high tenacity/high modulus fibers.
The ever-increasing costs of petrochemicals gives increasing impetus to the study of fibers from renewable sources, such as the cellulosics.
In particular cellulosic fibers with properties approaching the aramid properties have been sought