Machines winch dyeing

High pressure winch dyeing machines for polyester fabrics have been developed. As an example the one designed by Samuel Pegg is she v n in Fig. 13.25. The dyebath is essentially a normal v/inch dyeing machine and... 

It must be emphasized that these instructions only apply to winch dyeing of cotton, and the dyestuff maker s technical information must be consulted for other materials or machines. 

The method of application is basically similar to the chlorotriazinyl dyes. The dyebath is made up with SO to 100 g per litre of common salt and fixation is brought about by the addition of 30 to 40 g per litre of soda ash, 20 to 30 g per litre of trisodium phosphate or 1-5 to 7 ml of sodium hydroxide (66°Tw 23 per cent). The temperature necessary for fixation varies from 80 C (176°F) to 90°C (198°F) according to the dye and the method of application. When these dyes are applied in a winch or a package machine the dye, salt, and alkali can all be added at the commencement because there is little danger of the reactive group becoming hydrolysed before it has reacted with the cellulose. The trichloropyrimidyl dyes do not exhaust easily and padding methods are therefore preferable. 

Another extremely popular machine of this type is the jet dyeing machine which conserves energy by reducing the cloth-to-Hquor ratio to 1 10 or lower as compared to 1 20 for the winch. In this machine, the fabric which is in a rope form is transported by movement of the dye Hquor through a Venturi jet. This method provides intimate contact between the dye Hquor and each meter of material. The machine operates at 40—135°C. 

Batch Processes. In batch processes, dyeing is conducted in various circulating-goods machines (e.g., jigger, winch beck, jet, and overflow machines) and circulating-liquor machines (yam, piece, and package dyeing machines) (see Sections 4.1.1). 

Piece goods made of CA are usually dyed in a jigger, less often in a star frame or winch beck, with gentle material guidance. The piece beam is suitable for warp materials. Yam was previously dyed in hanks. Since suitable winding machines are available, CA can also be dyed on cylindrical cheeses. Woven CA fabrics are occasionally dyed semicontinuously in a pad roll system at 80-90 °C. Dyeing auxiliaries are subsequently washed out. 

A fault with winch machines is the tendency for the temperature to vary in different parts, particularly in the open type where the fabric loses heat during its passage through the air and cools the liquor at the back when it re-enters. This deficiency is remedied by the incorporation of an external calorifier and pump to give forced circulation of the dye liquor. 

The speed of the winch should be adjusted according to the nature of the material to be dyed. Naturally the greater the amount of movement the more uniform will be the dyeing. With wool fabrics, however, excessive movement can cause undesirable felting or shrinkage and a slow speed is preferred. It is under such circumstances that the forced circulation with an external pump has much in its favour. With cotton and rayon fabrics fast-running machines are used, except when the materials are so delicate that they would suffer damage. 

As the cloth or web falls into the liquor from the winch at the back of the machine, it tends to bunch up and lie in a heap for a short time. This is no disadvantage with wool or cotton materials, but tends to cause serious creases in acetate rayons and other thermoplastic fibres. To overcome this a long shallow machine with an elliptical winch has been designed (Fig. 13.24). The elliptical shape of the roller folds the material in wide layers which are free from random creases as it falls into the dye liquor. The... 

Woven woollen pieces are almost always dyed on winch machines, but for cotton and rayon goods the jig is used. This is particularly suitable for cellulosic fibres because the dyes generally do not exhaust well and the jig works with an exceedingly low liquor ratio. The machine is illustrated in... 

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