Paper to the Polymer Processing Society Annual Meeting, Yokohama, Japan, 8th-12th June 1998, paper 10-04.

S F Bush with C G A Clayton and S Baillie Strong

Introduction

Earlier papers (1991, (1995a, (1995b) have described factory control systems based on relating the appearance of woven or knitted assemblies of textured, dyed or pigmented polyester or nylon fibres to variables in the spinning and texturising processes. As part of this programme quantitative relationships between changes in the appearance of woven or knitted dyed fabric and changes in process variables such as windup speeds, fibre cooling rates, and polymer intrinsic viscosity have been inferred from large quantities of factory data. The appearance of carpet or fabric made up of prepigmented filaments is generally less sensitive to process variation than is fabric made from dyed fibre. However, the quality of both classes of product are very dependent on minimising variations in polymer morphology, the effects of which are often only apparent in the hands of customers.

Because dyestuffs tend to accumulate in the less ordered regions of the polyester fibre, and the rate of diffusion differs markedly in the crystalline and amorphous regions, dye uptake within a given time may be taken as a sensitive indication of morphological development. Moreover different dye molecules respond differently to different morphologies and therefore provide an additional and sensitive way of validating the models. The present paper outlines the basis of a model which has been used to predict morphological development at spinning, drawing and texturing, and combinations of these processes.

References

[1] S F Bush and C G A Clayton: “Analysis and Control of Variability in the Fibre-Making Process”, 7th Ann Mtg Poly Proc Soc, Hamilton, Canada, April 11-14 (1991)

[2] S F Bush and C G A Clayton: “Intelligent Manufacture of Polyester Fibres on the Full Scale”, 11th Ann Mtg Poly Proc Soc, Seoul, Korea, 27-30 March (1995)

[3] S F Bush: “Characterization of Pigment Distribution in Extrusion of Synthetic Fibres”, Poly Proc Soc Euro Mtg, Stuttgart, Germany, 26-28 Sept (1995) KN1-01

See also the section on Systems Design & Control.

Systems Technology Group Technical Note, ICI Europa.

S F Bush with S Baillie-Strong.

Summary and Conclusions

1. Major variations in texturised yarn dye-uptake were observed which correlate strongly with time at spinning and clearly moved in sympathy with pack pressure and Draw Tension Integrator date at spinning.
2. The most likely cause of these variations was differences in moisture content of the polymer fed to the driers causing hydrolysis and molecular weight changes in the spun yarn.
3. These variations caused about 20% of the total package-to-package variability with shifts of almost 2 dye-shades in mean level in about 36 hours. These magnitudes are for Turquoise CG dye at pressure – a typical continental customer requirement. The recommended quality control dyestuff, Navy D2G, probably underestimates these variations.
4. The cause of gross variations in polymer moisture content should be eliminated. However, since the polymer transport system (Tote Bins) cannot be hermetically sealed and since the chip moisture content is below atmospheric humidity, some variations will always be present. A drying control strategy to deal with these variations with the aid of a drying model should be developed.
5. The same magnitudes of changes in initial water content and yarn i.v. have been obtained by other investigators on 167 f30 at various times from January 1974 to the present.
6. The calculated i.v. to water content sensitivities agree closely with measured values.