The Application of Reactive and Direct Dyes to Rayon Staple by Continuous Methods *

The principles of continuous piece dyeing have been studied, and an investigation has been made into the possible application of these principles to viscose staple fibre, with particular reference to dyeing for the carpet trade, whoro large weights to a colour are often called for. Various machines capablo of convoying staple fibro in a continuous manner have been considered, including the nocossary machines for opening, dyeing, squeezing, steaming, and drying. Development work over the past two years has resulted in ono continuous dyoing systom based on the Fleissner revolving drum principle. This machine is now operating on a commercial scale with 15–donier crimped Fibro for use in tufted carpets. An alternative dyeing system based on the Callaghan machine for bonded non–woven fabrics is also being developed, and attention has boon given to the possibility of using scouring bowls. It has been demonstrated that reactive dyes can be applied satisfactorily in continuous systems, using the method whereby the fibre is impregnated with dye–alkali mixture and dried; only the cold–dyeing members of the Procion range have been applied commercially. Direct dyes have also been applied successfully, mainly on the Fleissner system, and in order to obtain efficient penetration and tho required fastness standards, the method has become essentially short–term dyeing followed by simultaneous steaming and drying. The application of direct dyes to Fibro in continuous systems has been studied in some detail, with main emphasis on tho measures to be taken to ensure regularity of colour over a long run. This is particularly important in view of the large proportion of dye absorbed by the fibre during immersion in the dye liquor. Soveral methods have been examined for means of arriving at tho necessary adjustments to the feed liquor; one promising method relies on spectrophotometrc estimation of tho dye romoved from a sample of fibre initially dyed to tho required colour. Wet fastness of fibre dyed in these continuous systems is in some cases lower than that obtained by normal methods of dyeing, but adding salt or increasing the tomperature of impregnation minimises the disparity. Fibro dyed on the Fleissner system has been subsequently processed to yarn on tho modified cotton and on the woollen systems of spinning. No particular difficulties have boen encountered and the fibro is more lofty than when dyed in enclosed machines. The position of dyed fibre in relation to mass–dyed fibre has been discussed. It is thought that the two methods of colouring will be complementary.