FIBRE AND FILAMENT YARN

The continuity of the viscose jets is more likely to be disrupted when the size of the gel particles and their number per ml viscose are large and the spinneret holes small. The gel particles are easily deformed in the flow of viscose so that it is sometimes assumed that the shape of the viscose jet might be distorted if the diameter of these particles is larger by 10% than that of the spinneret holes (i.e., larger than 5-8 ~ in normal conditions of the spinning of viscose rayon and film). It has been established [2] that the gel particles in the viscose originate from primary and secondary sources. The primary sources take the form of low cellulose reactivity, uneven mercerizing and xanthation conditions, and a low degree of esterification; the secondary source is the formation of aggregations of macromolecules of cellulose xanthate in the viscose as a result of the generation of new hydrogen bonds during the separation of the xanthate groups in the ripening process of the viscose. The number of secondary gel particles increases by 8% in i0 h, i.e. during the ripening period [2]. In the spinning of staple fibre and continuous yarn it is important that the quality of the viscose be determined upstream from the spinneret. The methods of determining the clogging factor C s and the slowing down of the filtration of the viscose through a nickel screen [3, p. 143] consist of forcing the viscose through a screen with holes of about 70 and are suitable only for assessing the purity of filtered viscose. The method of determining the purity of the viscose by forcing it through a spinneret with 50 ~ holes is suitable for viscose after the first filtration stage. Gel particles larger than 30-70 ~ can pass through the filter screen in both cases so that all three methods are unsuitable for an assessment of the purity of the viscose entering the spinning process. The present writers have developed a method of determining the purity of viscose admitted to the spinning process which is based on the slowing down of the filtration of the viscose in its passage through a filter screen with pores of about 6 ~ in diameter and a retention capacity for particles 2 ; in diameter. The viscose used in the tests was obtained from the Experimental Plant of the All-Union Scientific-Research Institute of Man-Made Fibre Projects which contained 8.3% a-cellulose and 6.35-6.45% NaOH and had a viscosity of 50-60 sec (ripening time 25-30 h followed by 5-10