Viscose aging

Viscose Aging, Filtration, and Deaeration. After the dissolution step, the viscose cannot be spun into fibers because it contains many small air bubbles and particles. Furthermore, the degree of xanthation is too high, with too many of the xanthate groups in positions dictated by their accessibihty and not in the ideal positions for uniform dissolution. 

The correct viscose age or ripeness for spinning varies according to the type of fiber being made. Ripeness can be assessed by estabHshing the salt concentration necessary to just coagulate the viscose dope. The preferred test uses sodium chloride (salt figure) although ammonium chloride is the basis of the alternative method (Hottenroth number). 

Fig. 5. Viscosity aging of plastisols at 23°C where A is BBP/DIPB B, DOP C, FllO and D, 911P.

By selection of those chlorinated paraffins specifically developed for the PVC industry to match the properties of primary plasticizers, reductions in costs can be achieved without significant change in properties. However, certain aspects can be improved by the inclusion of chlorinated paraffin such as flame resistance, chemical and water resistance, low temperature performance, and the viscosity aging stabiUty in plastisols. 

Analysis of the viscosity aging data, Table III, reveals one significant trend. In general, as dryer temperatures are increased, plastisol viscosity aging decreases, Figure IX. The... 

Figure 9. Influence of dryer outlet temperature on viscosity aging (dryer conditions—inlet/outlet (%) 2 h, 180°/60°C (O) 7 day, 180°/60°C 2 h, 180°/...

Viscosity aging behavior has been shown to be dependent on exposed resin surface area and agglomerate fusion.Higher dryer temperatures will decrease the former and increase the latter, resulting in better viscosity aging stability. 

RHEOLOGY OF PYC PLASTISOL - X. VISCOSITY AGING, MECHANISMS AND RESIN TYPES... 

Dilute solution viscosity, aged polymer + soluble, - insoluble ... 

The viscose obtained from Cross and Bevan was so successful for production of lamp filaments that Steam asked Topham to try to spin it for use in textiles. The first experiments failed dismally. After several years of painstaking work, Topham made several discoveries essential to the spinning of yam from viscose aging (ripening) of the solution, filtration to remove particles, multiple-hole platinum spinnerettes, and a circular, centrifugally operated yarn collecting device that twisted the yam and packaged it in convenient cake form [117]. The Topham box, as it is still called, or variations of it are still on many of the continuous-filament rayon machines today. 

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