YARN PRINTING (SPACE DYEING)

Although the printing of yarns for true patterned effects proved very difficult to control, the random space-dyed effects that can be more readily attained by a variety of yarn-printing methods have continued to be popular. The patent literature abounds with systems for producing coloured flecked effects on yarns but the two most successful methods entail either warp printing or colour application to a tubular knitted ‘sock’. The essential process sequence begins with dye liquor application, followed by steam fixation, washing-off and drying Various warp-printing methods have been used over the years. In most present-day systems several ends of carpet yarn are taken from wound packages on a creel and colour is applied, either by lick rollers or by some form of spray or spinning disc applicator, to the yarns. The yarns are carried past the print heads in warp form or lying on a brattice on which they have been laid down in a continuous circular or elliptical coil. Warp printing tends to give the so-called ‘long spacing’ designs in the tufted carpet produced from them. Knit–deknit applications, on the other hand, tend to give characteristically speckled ‘microspaced’ designs, because of the limited degree of penetration of dye liquor achieved by the duplex printing rollers into the yarn sock. Although the end-effects produced by the two methods are basically different, the processes can be modified so that their results are more closely comparable. Thus the long spacing effects of warp printing can be imitated by overall application of a ground colour followed by colour spotting with segmented lick rollers or oscillating jets of dye liquor. Similarly oscillating jets of liquor can be applied to knitted sock and excess liquor squeezed out before steaming.