| 摘要 |
<p>A process for washing filaments obtained from polymers of acrylonitrile or from copolymers containing a major proportion of acrylonitrile units which have been produced by extruding a spinning solution consisting of the polymer or copolymer in an aqueous nitric acid solution containing at least 52% by weight of nitric acid into an aqueous precipitation bath containing less than 50% by weight of <PICT:0921483/IV(a)/1> nitric acid comprises washing the filaments leaving the precipitation bath continuously in countercurrent with a quantity of water which is at most sufficient for diluting the solvent transferred with the polymer or copolymer into the precipitation bath to the precipitation bath concentration and combining the washing liquid with the precipitation bath whereby practically all the solvent is recovered in the precipitation bath. In a preferred embodiment, a spinning solution consisting of 120 parts by weight of polyacrylonitrile and 880 parts of 59% HNO3 is fed into a precipitation bath 3 via a nozzle 4 which has 100 holes each with in diameter of 0,4 mm. 44% HNO3 circulates in the bath 3 at a temperature of -2 DEG to 6 DEG C. 10 cm. in front of the nozzle 4, the filament structure is taken up by withdrawal devices 5 and 6 at a velocity of 3,5 and 13,0 metres per second respectively, and then by washing devices 7 and 8 at a velocity of 13,5 metres per second. A controlled supply of water is fed to washing device 7 by means of a flow meter 13. The washing rollers may be made from polyvinyl chloride or may be covered with a cotton material of towel quality.</p> |
