Pad steam method

Continuous dyeing of piece goods by pad—steam methods is one of the principal outiets for sulfur dyes, mostiy in prereduced Hquid form. 

It is the most stable enzyme at temperatures of 160F. to 180F. and is, therefore, considered most adaptable to the new rapid pad steam method of desizing. 

Blends of polyester with cotton (qv) or viscose are first dyed with disperse dyes, then with sulfur dyes (see Fibers, polyester Fibers, regenerated CELLULOSics). Disperse and sulfur dyes can also be appHed simultaneously in a pad—dry—thermofix/chemical reduction pad—steam sequence. In this case, the sulfur dyes cannot be used in thein reduced form because of the effect of the sodium sulfide on the disperse dye. Therefore, this method is confined to the solubilized sulfur dyes or sulfur dyes in the dispersed form. 

The most important continuous dyeing methods are the thermosol pad steam process and the thermo sol pad batch process. In all continuous processes, the sub-stantivity of the reactive dyes should be taken into account, i.e., the reactive dye can exhaust from the pad liquor or accumulate to a greater or lesser extent even at room temperature depending on the pH value and salt content. 

Disperseand Sulfur Dyes (see also Section 4.7.3). The thermosol pad steam process is the primary method for application of disperse and sulfur dyes. The sulfur dyes that are used preferentially in the ready-for-dyeing soluble form, and are especially inexpensive for muted shades, must be applied after the thermosol step because of their incompatibility with disperse dyes. 

Dyeing is performed mainly by exhaustion processes (batchwise). Another dyeing method with increased importance is the gel dyeing process. Dyeing in the gel state takes place during production of the fiber, i.e., after the fiber has been extruded and the solvent has been washed out, but before the fiber is stretched and dried (see Section 4.14.6). Continuous dyeing of stock, cable, and tops is also possible according to the pad steam process. 

The most effective method of bleaching polyester/cotton is sodium chlorite, which may be followed by peroxide bleaching. Chlorite bleaches the husk, but does not destroy them completely. Polyester/cotton blends may be bleached with sodium chlorite in long liquors and also by pad-steam process [Table 6.10]. The... 

In recent decades, simpler and more environmentally sustainable dyeing sequences such as pad-dry-steam and pad-steam have been introduced by the major machinery manufacturers in collaboration with dye suppliers. The new sequences and machinery minimize bleeding and migration problems associated with pad-dye pad-chemical methods (Bright, 1990). 

Nonstabilized foams are referred to as froths froth-bonded fabrics are similar in properties to some saturation-bonded nonwovens. Typical foams used as nonwoven binder solutions have a consistency similar to shaving cream. AppHcation methods include knife-edge layering onto a horizontal web surface followed by vacuum penetration, and saturation and penetration of a vertical web surface using a horizontal-nip pad. Drying and curing is carried out in ovens, dmm dryers, or steam cans. 

In the batchwise process the temperature can be raised to 80°C to promote levelness providing dyes not sensitive to reductive breakdown are used. In the continuous appHcation method the vat dye is padded onto fabric and dried under conditions that avoid migration, passed through a solution of sodium hydrosulfite and caustic, through a pad mangle, and then steamed in saturated steam for up to 60 s. 

Power supply, 9 from a not gas stream, 12 generation with steam, 11 Pressure control, 42,44,51,52,59,60 Pressure drop cyclone separators, 617 gas-solid flow, 119-120 granular beds, 117 heat exchanger example, 193, 194 heat exchangers, 188 non-Newtonian flow, 106-109 wire mesh pads, 616 Pressure drop, piplines, 92 chart method, 96 two-phase flow, 116 typical values, 95 Ptaskie vessel code, ASME, 625 Prilling, 361,362 equipment size, 367 flowsketch, 366 operating, data. 367 products of, 367 size distribution, 362 Prism membrane separation process, 633 643... 

Method A For white/printing Singeing cum Desizing -> Wash -> Scour on Pad-Roll (T.R.C.) Wash Dry -> Mercerize -> Bleaching on Pad-Roll (T.R.C.) —> Steaming -> Wash Dry. 

The double padding method makes it possible to work with a very stable stock solution of the dye containing no alkali whatsoever. The cloth is first padded with the dye solution and then dried, after which it is impregnated with alkali and salt. It then passes into a steaming chamber where the dyestuff is fixed, and finally washed off. The sequence of operations is illustrated diagrammatically in Fig. 22.7. There are other permutations of the sequence of events in continuous ranges but, with the exception... 

Low shear process will produce larger liquid droplets (>30 microns), and heavy/light liquids can be separated using gravity settling method. Examples of low shear process are solvent extraction, mixer settlers, steam stripping, washing process, and counter-current tower. Coalescer pad can be used to speed up the liquid/liquid separation and reduce the separator size. 

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