No, It'S Your Loss! The Improvement Of Wet Rubbing Fastness Of Reactive Dyes.

How to improve the activity

Wet rubbing fastness?

Auxiliaries should be applied correctly.

(1) the amount of electrolyte applied.

After testing, most of the medium temperature reactive dyes are dyed dark, and the highest dosage of electrolyte is <70 g/L.

Some reactive dyes, such as active turquoise blue BGFN dye dark color, the maximum amount of electrolytes must be <60 g/L; active blue KN-R dye dark color, the highest dosage of electrolyte must be <40 g/L.

The reason is that the amount of electrolyte is too high and its color depth is not much improved, but the concentration of salt and alkali (soda is also electrolyte) is too high in the initial stage of alkali fixation, which causes the "condensation" and "sudden dyeing" to be too large, causing a negative effect on dyeing (especially the effect of leveling and dyeing wet fastness).

(2) the application of electrolytes.

When the rope dyeing (jet overflow dyeing and airflow dyeing), the electrolyte must be added first and the dye added (the order of addition is opposite to that of the dyeing).

Because the dye is added in the traditional way, the dye is dissolved in the reflux water to dye the electrolyte. The dye will instantly flocculate and precipitate in the saturated solution of the electrolyte, and then press into the cylinder to adhere to the fabric.

First, electrolytes are added, and the reflux solution containing electrolytes is used to dissolve and dilute the pre mixed dye. The dye does not occur "agglomeration" or precipitation.

After testing, the commonly used medium temperature reactive dyes have good solubility in the neutral bath of electrolyte <80 g/L.

(3) application of soda ash

After testing, the best fixation pH value of cotton dyed with medium temperature reactive dyes is 10.5~11.0 (active turquoise blue at 60 C, pH value is 12, and pH value at 80 C is 11).

Commonly used Lianyungang powdery light soda ash 5~25 g/L, pH=10.65~10.99, its pH buffer capacity is very big.

Therefore, according to the depth of dyeing, the dosage of soda 20~25 g/L is enough.

The excessive amount of color is not obvious, but it will reduce the solubility of dyes in saline bath and affect the color fastness.

(4) application of soda ash

The addition of soda must be based on the balance of color absorption and uniform absorption.

That is to say, only in neutral salt bath (color absorption bath) can the color balance be reached and the color absorption is uniform after pfer and dyeing, the alkali agent can be added.

This is because, after reaching the equilibrium of color absorption, the concentration of residual dyes is the lowest. After the addition of alkali agents, the smaller the concentration of dyes, the more moderate the two color absorption rate. The levelling effect and color fastness will be better.

After adding the alkali agent, the dye on the fiber will lose the migration ability due to the fixation, thus making the non-uniformity of the color absorption phase become permanent defect.

The application of alkali agents must be "first less, then more."

Because the faster the alkali agent (soda ash) is added, the stronger the alkalinity of the fixing bath is, the higher the concentration of salt and alkali will be. The more intense the dye's condensation behavior and color behavior, the easier the dyeing quality will be.

Practice has proved that the alkalinity of the fixing bath is weakened gradually, the concentration of salt and alkali increases from low to high, and the concentration of dye solution is thicker and thicker. It can effectively reduce the excesses caused by the addition of alkali agents, ensure that the dye is evenly coloured and fully fixed, thus effectively improving the wet fastness of dyeing.

Post treatment should be strengthened.

The fixation rate of medium temperature reactive dyes is not high, usually only 65%~75%.

Therefore, dyed fabrics (

There must be some dyes (floating colors) that do not react with fibers, including dyes that have not been hydrolyzed and not fixed with fibers, and dyes that have been hydrolyzed and lose fixation ability, and dyes that have been removed, sulfated to vinyl sulfonyl groups but not react with fibers or water.

Among them, unhydrolyzed and unbound dyes still retain the beta hydroxyethyl sulfone sulfate radical, which is less direct and water-soluble, and is most easily washed away.

However, the sulfated ester has become a vinyl sulfonyl group but has not been reacted with fiber or water. Due to its high directness and poor water solubility, it is the most difficult to wash.

The existence of these floating dyes is the main cause of low wet rubbing fastness.

Therefore, water washing and soaping must be strengthened during dyeing.

There are two purposes for washing after dyeing. One is to remove the residual alkali from the fiber, so as to prevent the dyestuff of the bonded dyes from breaking down and hydrolyzing from the fibers at high temperature and alkaline condition when the soap is washed at high temperature.

The two is to remove the remaining electrolytes and some unfixed dyes and hydrolytic dyes on the fibers, so as to prevent the high concentration of dyestuff and electrolyte in the soap solution when the soap is being washed at high temperature, and make the two staining of the fiber become heavier and reduce the soaping effect.

This is often neglected in actual production.

In particular, when jet overflow dyeing is done, usually the water draining on the side of the water inlet is discharged. After the foot water is not released, the soap is washed up and heated. The result is that the soaping solution has high dye concentration, two times of serious contamination, and the soaping effect is very poor.

The purpose of soaping is to further reduce the floating dyestuffs which remain on the fibers after washing. (because these floating dyes have certain affinity to fibers, in real conditions, it is impossible to completely remove them, only to minimize them).

In order to improve the soaping effect, 5 measures can be adopted:

It is necessary to strengthen the cleaning before dyeing and soaping, such as raising the washing temperature appropriately, prolonging the washing time appropriately, increasing the number of water changing appropriately or speeding up the flow of water properly.

Improving the cleaning effect before soaping is the foundation for improving the soaping effect.

(2) choose the soaping agent with good washing ability, dispersing ability, emulsifying ability and carrying capacity, which is very important to ensure the soap washing effect.

(3) 1~2 g/L chelating dispersant is added to the soaping solution. The chelating dispersant has good dispersion and suspension function to the impurities in the soaping liquid, and prevents contamination of equipment and fabrics.

At the same time, it has good complexing ability, can chelate the calcium and magnesium ions in water, prevent the formation of calcium and magnesium dye lake, and reduce the soaping effect.

Six sodium partial phosphate is not suitable for use in soaping. It can only be used for dyeing because it will significantly decrease the chelating ability of metal ions at high temperature.

(4) soaping must be carried out under neutral conditions (pH=6~7).

This is because the bond between reactive dyes and fibers is limited by acid and alkaline hydrolysis. Under the condition of high temperature and strong acid-base, the dyed dyestuffs may be hydrolyzed and broken into new floating dyes, which not only affect the color depth, but also affect the soaping effect.

In actual production, in order to increase production and reduce energy consumption, after dyeing, the effluent is cleaned and soaped to form "alkaline soaping"; some of them are neutralized by acid directly, often forming "acid soaping".

Both three azine dyes (type K, X type), or vinyl sulfone type dye (KN), or mixed double reactive dyes (M, ME, A, B, etc.), their dyestuff bonds are all stable at pH=6~7, pH value rises or decreases, and the stability of dyestuff bond decreases.

Alkaline soaping makes it easy to hydrolyze the fiber bonds of vinyl sulfone type dyes, and the acid soap soaps make it easy to hydrolyze and break all three azine dye fiber bonds.

The reactive dyes containing three chlorazine and two active groups of vinyl sulfone are more stable to acids and bases than those of single active bases.

It must be high temperature soaping. This is because in the soaping process, the floating color dye remaining on the fabric is affected by two forces simultaneously.

The first is the affinity between dyes and fibers, which has the tendency to adhere. Two, the water-soluble SO3Na of dyes is hydrophilic and has a tendency to dissolve.

Improving the soaping temperature can effectively improve the water solubility of floating dyes and reduce the adhesion of dyes, so that the floating dyes on the fibers can be dissolved more quickly and improve the soaping effect.

Soaping at high temperature (95 degrees Celsius) under neutral conditions, there is no need to worry that the dye dyed on the fiber will dissolve too much.

Because dyestuff chemically bonded with cellulose has become a part of cellulose molecular chain, it has good binding fastness.

Some manufacturers worry that the color will be changed due to the worry that the color of the soap will be washed off. The color fastness is not good with soap at 60~70.

If the soap is washed too much, it must be checked from the color absorbability of the semi-finished products, the leveling and dyeing of dyeing, the adequacy of dye fixation, and the acidity and basicity of the soaping solution.

Reactive dye dyestuffs, even after washing and soaping, still retain some floating dyes on the fibers, especially dyed dark colored scarlet, jujube, sauce red and turquoise blue. Their wet rubbing fastness and soaping fastness are often very poor.

At this point, fixation is usually required.

The commonly used fixative or crosslinking agent enters the fiber, and on the one hand it bonds with the dye on the fiber (fixing dye and unfixed dye). The water soluble group of the dye is sealed, so that its water solubility decreases. On the other hand, it will produce crosslinking between the fiber and dye.

Therefore, when dyestuff is treated with fixing agent, the dye is not easy to fall off when testing wet fastness. Even if it falls into the water, it will have less staining on white cloth.

Therefore, the soaping fastness and wet press fastness of the dyed fabric can be obviously improved.

However, it must be pointed out that fixation treatment often can not effectively prevent the surface of the fibers from falling off when they are rubbed, so the improvement of rubbing fastness is limited.

Good fixing effect must be done by soap and water washing.

If the color of the soap is not clear before fixing the color, the dye will fall off more when it is fixed. If it falls into the fixing bath, it will form flocculent aggregates with the fixing agent, resulting in serious fouling of the fibers and the decrease of rubbing fastness.

Color fixing also brings many problems.

For example, fixing color treatment often causes different degrees of sunshine fastness and chlorine fastness to drop; it will reduce the softening finishing effect and affect the handle of the finished products to a certain extent; it will make the color of the cloth change to varying degrees (shades, shades, and colourful), and the extent of change will vary with the dyestuffs. It will vary with the color matching ratio of the dyestuffs, and the color and light can not be accurately controlled with the change of fixation conditions.

Color fixing will also bring difficulties to "color fixing".

After fixing, whether dyed with dyestuff or paint, it will be difficult to infiltrate and diffuse into the fiber due to the blocking of fixing agent, and float on the surface of the fiber, resulting in a significant decrease in the color fastness.

If the fixing agent is first stripped and cleaned, then the color will be repaired. The comprehensive cost is too high, and it is easy to produce color flowers because of the unevenness of the fixing agent.

Therefore, the author believes that the fixation treatment after dyeing depends on the specific circumstances.

For example, dyed dark blue, navy blue, iron gray, black and so on. As long as the processing technology is reasonable and controlled properly, wet fastness can meet the requirements of export without fixing.

Dyed red, red, red sauce, turquoise blue and other color, wet fastness is poor, but the color fixative treatment of the change of color, there is a certain degree of concealment, therefore, can be treated with fixative.

However, we must conscientiously select fixative, choose a significant increase in fastness, no impact on light fastness and fastness to chlorine, and little change in color.