Deficiency Of Medium Temperature Reactive Dyes

The reactive turquoise blue BGFN and reactive brilliant blue KN-R can reach 100 g/L in 40 degrees neutral bath, and 150 g/L in 80 degrees neutral bath.

But in the presence of electrolytes, the solubility will be reduced or even seriously reduced.

At 60 C, the dye solution of 15 g/L reactive turquoise blue BGFN can withstand 80 g/L of salt. If the concentration exceeds 80 g/L, the dye will produce obvious agglomeration and even flocculation (the higher the dye concentration, the lower the salt tolerance.)

However, because of the existence of reactive dyes only in the presence of 30~80 g/L, higher dye uptake can be achieved. Therefore, reactive dyes with poor salt solubility and poor stability may have a potential for agglomeration.

Especially when the alkali agent is added, the dye is alkaline.

The agglomerative tendency will be greater, such as commonly used reactive yellow 6GL and reactive brilliant blue KN-R.

Example 1

Reactive yellow 6GL 10 g/L, Huaiyan 50 g/L, 80 h, its dye solution is clear and pparent, and its solubility is good.

When 5 g/L of soda is added, the dye will immediately become cloudy due to coagulation.

For a moment, it will precipitate due to flocculation.

Example two

Reactive turquoise blue BGFN 15 g/L, Huaiyan 70 g/L, 80 h, the dye solution has good solubility.

When 20 g/L of soda was added, the dye immediately coagulate and then flocculate and precipitate.

Example three

activity

KN-R 5 g/L, Huaiyan 40 g/L, and 60 g/L in the dye solution were added with 15 g/L of soda ash.

The dye solution was clear and stable 10 min significantly condense 10 min, serious flocculation 10 min and water separation, losing dyeing ability.

The above three cases showed that the reactive stability of medium temperature reactive dyes was poor because of three reasons:

(1) reactive dyes do not exist as single molecules in water, but exist in the form of several or even hundreds of molecular complexes.

Therefore, the dye has different colloid properties and good stability.

The addition of electrolytes will destroy the stable colloid system, resulting in a decrease in solubility stability.

(2) the medium temperature reactive dye contains the beta hydroxyethyl sulfone sulfate active group.

The chemical bond between the sulfonyl group (SO2CH2CH2) and the sulfated ester in the active group is unstable. Under the conditions of application (pH 10. 5~11. 0, temperature 60~65 C), both of them will break rapidly and eliminate the reaction, so that the original hydrophilic beta hydroxyethyl sulfone sulfate will become a hydrophobic sulfonyl group, and the dye's self dissolution ability will be significantly reduced.

(3) electrolytes can dissociate large amounts of sodium ions in water, and their hydration ability is very strong. They can attract a large number of polar water molecules to form a direct and indirect hydration layer, thus reducing the hydration degree of the hydrophilic groups and decreasing the solubility of the dye molecules.

At the same time, the same ion effect produced by a large amount of sodium ions also causes the dissociation degree of the hydrophilic groups of dyes to decrease, and the solubility of dyes themselves decreases.

2, sensitive to alkali.

Many commonly used mesophilic reactive dyes have a severe dyeing at the initial stage of alkali fixation.

If the fabric absorbs 30 min in dye 2% (OWF), Huaiyan 50 g/L and 60 degrees neutral dye, adding 20 min of soda ash and 10 min at 60 degrees, the relative color absorption can be increased by 30% ~70%.

Among them, reactive dark blue M-2GE increased by 28.32%, active turquoise blue BGFN increased by 32.94%, active yellow 6GLN increased by 55.39%, reactive brilliant blue KN-R increased by 59.96%, active black KN-B increased by 68.95%.

The main reason for the sudden dyeing is that the beta hydroxyethyl sulfone sulfate in the dye will rapidly change to a highly active vinyl sulfone group under alkaline conditions.

Therefore, on the one hand, the affinity of dyes to fibers suddenly increased, resulting in the rapid absorption of dyes. On the other hand, the fast binding and fixation reaction between dyes and fibers continuously destroyed the adsorption equilibrium of dyes, which also played a significant role in promoting the rapid coloring of dyes.

The production practice has proved that there are two major defects in the medium temperature reactive dyes, which are the color spots and color differences in dyeing process.

The root causes of many dyeing quality problems such as decline and poor fastness.