Reaction to generate hydroxyl compound is the dye leuco acid, and dyes do not dissolve in water, but soluble in alkaline medium, sodium salt solution of leuco. Custom Checkered Flags The sodium salt of the leuco seldom showing dye the original color, it was known as leuco:
≥ C-OH NaOH-→ ≥ C-ONa H2O
Dye reductive dissolution of sodium hydrosulfite – caustic soda method, should have a good caustic soda, the amount of hydrosulfite and the reduction temperature of dye normal restore, Discount Decorative House Flags or cause dyes to produce over-restored or hydrolysis, and molecular rearrangement is not a normal reaction such as The resulting dye destruction wilt dark, color and lower color fastness.
2 Leuco dye vat dyes by the hydrosulfite, Custom Checkered Flags caustic soda to restore the dissolved into the sodium salt of the leuco that have a direct cellulose fibers, the first adsorbed on the fiber surface, and then revert to the fiber internal diffusion of fiber the dye. The dye contains a large number of electrolytes, fiber larger, so the faster the rate of dyeing fiber, dye transfer dye performance is poor, often difficult to dye evenly. Therefore, adding a small amount of slow agent in the dyeing process, such as peregal 0 glue.
Leuco dye fibers on the oxidation of 3. Leuco subject to air or oxidants into the insoluble vat dyes and regain its original color, the oxidation reaction is as follows:
≥ C-ONa – → C = O
Because different types of vat dyes have different oxidation resistance, and appropriate selection and response to oxidative conditions, such as air oxidation, or the use of hydrogen peroxide, sodium perborate oxidation.
4 soap boiled handle soap boiling can remove adsorbed on the fiber surface oxidation floating color, dyed fabrics with bright color and a good rubbing fastness. Soap boiling process, the dye molecules in the surface of the fiber aggregate, and thus the formation of micro-crystals, and further improve the fastness of the dyed fabrics. Custom Checkered Flags
(B) restore the dyeing vat dyes can be used for cotton and polyester and maintenance of cotton blended fabric dyeing. According to the different forms of dye uptake can be divided into Leuco Garden House Flags staining and suspension padding
A leuco staining leuco dyeing is to restore the dye pre Leuco fiber adsorption of the dye bath, and then oxidation, soaping a staining method. It can be divided into the dip, jigger and pad used for the dip and jigger. Leuco dip applicable to yarn dyeing jigger degree of staining through the core, white core phenomenon. Dye of a different nature, can be taken to restore.
(1) dry cylinder law: dip dyeing, and some dye reduction slow, Custom Checkered Flags must be more severe conditions to improve the reduction rate of the dye reduction method known as dry cylinder.
Dry cylinder Reduction of first dye with a small amount of water and Pacific oil or pull the powder will be transferred into a slurry, then add the right amount of warm water and the specified amount of caustic soda, Custom Advertising Feather Flags sodium hydrosulfite, at specified temperature reduction of 10 ~ 15min, until the dye to fully restore containing caustic soda, then filtered to join in the dye vat of sodium hydrosulfite solution, and dilute to the desired concentration for dyeing. Due to restore the minimal amount of water, the equivalent of the caustic soda, sodium hydrosulfite concentration, Feather Flags Wholesale speed up the reduction rate of the dye, Custom Checkered Flags so that the reduction reaction to normal completion.
(2) full bath: this restore method is applicable to a faster reduction rate of vat dyes. The method can be dyed in the dye directly into the dyeing tank, adding the required amount of caustic soda and sodium hydrosulphite, so that the dye restore, restore 10 ~ 15min. More severe reduction of such dyes, could easily lead to excessive dye hydrolysis or reduction, affect the staining quality of finished products.
Restore more dye species, the larger structural differences, Custom Checkered Flags making each dye in the leuco dyeing restore the difficulty of different, the way to restore and caustic soda, sodium hydrosulfite also vary the amount of Production in order to facilitate the application of generally leuco dyeing process conditions fall into four categories (see Table 2-4).
Table 2-4 Common vat dyes leuco dyeing conditions
Special law of the staining method A method B method C method
Dyeing temperature (° C)
Dyeing time (min)
Dye (fabric weight%)
Caustic soda 360Be (mL / L),
85% (g / L), sodium hydrosulfite
Sodium sulphate (g / L) 60 ~ 62
45 to 60
Pale 0.3 the following
20 to 30
3 to 12
– 50 to 52
45 to 60
In color 0.3 1.5
7 to 16
3 to 10
0 ~ 825 ~ 30
45 to 60
7 to 16
3 to 10
0 ~ 2465 ~ 70
30 to 45
3 to 12
These staining classification, A method of dyeing temperature is relatively high, Custom Checkered Flags sodium hydrosulfite is easy to decompose, so the more the amount of acid produced by decomposition of hydrosulfite used and the amount of alkaline agent with the increase in So, the total volume of caustic soda is greater. The staining method the classification is for the convenience of the application, but not absolute, for some dyes, the two staining methods or even three methods can be used to process conditions and the amount of caustic soda, sodium hydrosulfite may also be due to mechanical equipment, etc. a variety of different conditions.