Bath exhaustion

Cottoa—acryHc fiber bleads are also used for high quaHty upholstery pile fabrics. Besides the oae-bath exhaust dyeiag procedure involving a very high ratio of Hquor to fabric, a coatiauous pad-steam process is used to dye these fabrics. After padding, the goods are steamed for 7—15 min at 98—100°C. The material thea must be riased warm and cold before dryiag. 

High affinity for the fiber and rapid diffusion mean short dye cycles, independence from liquor ratio, no dyeing accelerants, and good reprocibility. However it also means poor migration properties of the dyes after they have formed a het-eropolar bond with the anionic sites on the fiber, so that inequalities in the dyed material are difficult to level out. Therefore, it is very important to aim for homogeneous bath exhaustion. 

To prevent staining of the borders and highlights of prints, use Kodak SB-8 citric acid stop bath or a plain running water bath. Citric acid stop bath exhausts quickly, so discard after about ten to twelve 8X10 inch prints. 

Note that if the Carnot heat engine is operated as shown in Fig. 4.3-2 it absorbs heat from the high-temperamre bath, exhausts heat to the low-temperature bath, and produces work. However, if the engine is operated in reverse, it accepts work, absorbs heat from the low-temperature bath, and exhausts heat to the high-temperature bath. In this mode it is operating as a refrigerator, air conditioner, or heat pump. 

Table 3.6 Time of half dyeing and final bath exhaustion for chrome...

Sample Time of half dyeing (min) Final bath exhaustion (%)... 

Acid dyes are typically applied in batch processes from acidic baths (pH 3-7), with high bath exhaustion. These dyes are very water soluble, making machine cleaning fairly easy and not requiring mnch in the way of chemicals. One subclass of acid dyes that is used for navy and black shades on wool (premetallized) contain cobalt and chromium. These dyes show aquatic toxicity due to their high metal content and are therefore more damaging to the environment than nonmetallized acid dyes [64]. 

Properties of laser cotton treated (a) % weight loss, (b) tearing force, (c) % reflectance and (d) % dye bath exhaustion. Source Adapted from Chow et al., 2011.)... 

In some cases (e.g., chitosan and gelatin capsules), ionic interaction can create ample binding during bath (exhaustion) treatment Chitosan is a biocompatible, biodegradable, and nontoxic polysaccharide which, as a result of its cationic character, is able to react with polyanions and give rise to polyelectrolyte complexes. For this reason, chitosan has been adopted for use in bath treatment processes. Because of these interesting properties, chitosan has become the subject of numerous scientific reports. 

Monllor et al. (2007) investigated impregnation and bath exhaustion (in the presence of acrylic resin) of cotton fabrics using melamine formalin microcapsules loaded with a mint flavor. Fig. 5.8 shows the difference in the effect of both methods of embedding microcapsules into a cotton textile structure. Since there was no affinity between microcapsules and fabrics, impregnation resulted in a higher amount of microcapsules in the substrate. In both cases, microcapsules were sensitive to rubbing. 

Hocker et al. [137] synthesized anionic A-acylated L-amino acids, oligopeptides, and protein hydrolysates and studied the adsorption on wool. Increased bath exhaustion and a more intense coloration of wool were obtained during dying of wool by the addition of the studied amino acid surfactants. These surfactants exhibited good biodegradabilities with 68-78% BOD5/COD. 

A high level of dye exhaustion on the treated fabric can be achieve in the absence of salt and alkali at a temperature as low as 60-80°C that is used in the conventional dyeing process. Further increases in temperature may improve dye bath exhaustion, but only to a limited extent. However, higher temperatines (90-100°C) are generally recommended for dyeing modified fabrics to obtain better penetration and fixation. 

An anionic fluorinated surfactant, such as sodium 3-[3-perfluorome-thylphenoxyl]-l-propanesulfonate, has been claimed to increase the dye bath exhaustion of cationic dyes into acetate fibers [326]. 

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