Spinning regenerated cellulose filaments of a denier below 0.5

摘要

Regenerated cellulose filaments of less than 0,5 denier are made by extruding viscose through spinnerets, the orifices of which do not exceed 0,002 inch in diameter, into a coagulating bath maintained at a pH above 4 and preferably above 6, applying to the extruded filaments a "jet stretch factor" of at least 4, passing the filaments through a strongly acid regenerating bath of low pH, and collecting the filaments, the strength of the coagulating bath being adjusted with respect to the salt test of the viscose used so that the filaments are only coagulated sufficiently to prevent them from adhering to each other on leaving the bath. The "jet stetch factor" is defined as the ratio of the velocity of the yarn as drawn from the coagulating bath on to the first godet to the velocity of the viscose passing through the spinneret orifices. The ratio may be up to 10 or even more, as compared to ratios of about 0,3-1,5 used in conventional viscose spinning. Low spinning speeds not exceeding about 20 metres per minute are preferably used. In an example, viscose containing 7,4% of cellulose, 6,6% of sodium hydroxide, and 36% of carbon disulphide based on cellulose, and having a sodium chloride salt test value of 4,5, is spun through a jet having 0,002-inch diameter holes into a bath containing 8% of sodium sulphate and a mixture of mono-, di- and tri-sodium phosphates in a total amount of 7,7% calculated as trivalent phosphate ion, and having a pH of 7,5 and a temperature of about 40 DEG C. The filaments pass through this bath a distance of 20 inches and thence to a godet wheel having a peripheral speed of 11,4 metres per minute. The jet stretch ratio is about 6,3 : 1. The yarn then passes through a regenerating bath at about 70 DEG C. containing about 10% of sulphuric acid, about 20% of sodium sulphate, and a small proportion of phosphoric acid. From the regenerating bath the yarn passes to a pair of godets having a peripheral speed of 20 metres per minute and is then washed and collected in a centrifugal spinning box. Its denier per filament is about 0,14. Numerous coagulating bath compositions and components are specified, the latter including formic, acetic and propionic acids, methanol, ethanol, dioxane, ethylene glycol, and acetone.