Acid Leveling dyes

Acid Leveling Dyes. These are molecular dispersions at low temperatures (tme solutions) and are simple molecules. They have low affinity at neutral pH and exhibit ionic attraction at acidic pH when the wool becomes charged. They exhibit good leveling and migration behavior. Their low affinity however also results in low fastness. 

Practical Processes. With acid leveling dyes no real problems exist because the dyes show good migration, electrolyte is added from the beginning, and rather like Class A direct dyes level dyeing is achieved by prolonging the times at the boil. 

These are all good levelling dyes but of somewhat inferior wet-fastness Figure 2.55 Acid levelling dyes... 

Langmuir type absorption isotherms are observed when only a limited number of dye sites are available inside the fibre. In this case the concentration of (fye in the polymer reaches a maximum limiting level as the concentration of dye in the dyebath is increased. This behaviour is typical of acid levelling dyes on wool and silk. " ... 

These acid rhodamines are usually used for sHk and wool because they have level dyeing properties and show good fastness to alkaU however, they have poor lightfastness. An improved process for manufacturing 3,6-diaminosubstituted xanthenes is reaction of the inner salts of... 

Glasses. There are three classes of acid dyes acid leveling, acid milling, and super milling. 

These dyes are not very commercially important, and the dyeing mechanism has been described in detail elsewhere (15,25). The difficulty in applying fiber-reactive dyes to wool is the result of the same reactions already described. They are negatively charged and the wool is positively charged so ionic attraction exists. The fiber-reactive dyes are essentiaUy acid leveling or milling dyes and so this attraction can be controUed by pH. Once the dye is fixed no... 

Wool—Acrylic Fibers. This blend is being used for iadustrial and hand knitting yams. The acryHc fiber is aesthetically similar to wool, iacreases the strength of the yam, and adds bulk to the goods. Special precautions are necessary siace the two fibers are colored with dyes of opposite ionic type. Coprecipitation is prevented with the use of an antiprecipitant. Usually, level dyeing acid dyes are used for the wool portion in combination with the cationic dyes for acryHc fiber. 

Only the products associated with acid and premetallised dyes are dealt with in this section. The auxiliaries used with mordant dyes are covered in section 5.8. Anionic acid dyes, applied principally to wool and nylon, vary widely in their fastness and level-dyeing properties (section 3.2.2) in general, the higher the wet fastness of a dye the more difficult it is to apply evenly. Hence it is not surprising that the use of auxiliaries with acid dyes is related mainly to level-dyeing properties. There are two basic aspects ... 

Bilirubin effects depend on the method used for analysis. Interferences in direct serum protein methods are observed at bilirubin levels greater than 5 mg/100 ml (K7). A sample containing 20 mg of bilirubin per 100 ml increased the apparent total protein by 0.2 g/100 ml. Concentrations of bilirubin as high as 20 mg/ml do not effect albumin assays using bromocresol green binding (D12), but have a marked effect on these assays when [2-(p-hydroxyphenylazo)-benzoic acid] (HABA) dye is used (A7b). 

The effect of pH depends on the liber type. The SO j groups on libers are so strong that they are deprotonated even in neutral dyebalhs The dyebalh pH therefore has no inlluence on the availability of these sites in the liber and therefore pH cannot be used lo control the uptake and level dyeing behavior of the dye. For carboxylic acid groups the pA is about 5.5. Ai lower pH values there arc considerably fewer sites available for the dye and at higher pH values considerably more COO. ... 

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