Dyeing Of Several Commonly Used Dyes

Dyeing with direct dyes

Direct dyes can generally be dissolved in water, and a small number of dyes need to be added with soda ash to help dissolve. It can directly dye cotton, linen, silk, wool and viscose fibers without any other auxiliaries, so it is called direct dyes.

direct

Chromatography is complete, bright color, low price, easy dyeing method, but the biggest drawback is that most of these dyes are not good enough in color fastness. For the defects of poor color fastness, many reforms have been made. For example, chemicals are used to process the dyed fabric after processing, improve the color fastness and fastness of the dyestuffs, and also adopt the new chain fixing agent to improve the post-processing fastness of dyed fabrics.

Two. Dyeing with reactive dyes

Reactive dyes can be classified into two categories according to their active genes.

1. common type (or cold dye) reactive dyes: domestic X type reactive dyes belong to this category.

The active genes of these dyes are cyanuric chloride containing two active chlorine atoms.

Its chemical properties are very active and its reaction ability is strong, but its stability is poor. It can react with fiber chemically at low temperature (20~30 degrees), and it only needs to be fixed at low temperature and weak base agent (pH =10.5).

2. thermosetting reactive dyes: domestic K type reactive dyes belong to this category.

Its active gene is also composed of cyanuric chloride, but there is only one active chlorine atom on the active group.

Its chemical activity is low, its reaction ability is poor, and the dye solution is relatively stable.

Therefore, when the reaction is carried out with fiber, the requirements are more severe, the fixing temperature is about 90 degrees, and strong alkaline agents are needed. The fixation time is longer than that of X reactive dyes.

The domestic KN type reactive dye, whose active group is beta hydroxyethylene sulfone sulfate ester, is also known as vinyl sulfone type reactive dye. Its reaction activity is between X type and K type reactive dye. The fixing temperature is 60~65 degrees.

In addition, M reactive dyes containing double active groups and reactive dyes containing other active groups are also included.

Dyeing properties of reactive dyes

When reactive dyes are dyed, dyes can be directly dyed onto the cloth. At the same time, because of its good diffusivity, dyes can easily diffuse into the fibers. However, because this fashion is not chemically reacting with fibers, it is easy to wash most of the dyes with water. Therefore, alkali must be used to make dyes and fibers react chemically and fix the dye on the fibers.

The former is called dyeing, and the latter is fixation.

(two) reactive dyeing process

1. volume dyeing: the dyeing process is suitable for small batch and multi variety production.

It is easy to dye, flexible and can be dyed shallow, medium and dark.

Because of the different dye types and the direct size of fibers, dyeing conditions, fixing temperature, alkali dosage and electrolyte dosage are also different.

2. pad dyeing: pad dyeing of reactive dyes is divided into one bath and two bath.

One bath is to put dye and alkali agent together. The caustic agent is sodium bicarbonate. After being steamed or baked, the baking soda will decompose Na2C03 and raise the pH, which is good for fixing the dyestuff. The X reactive dye is used in one bath.

The two bath method is to dip the dye solution into the dye solution and then dip the alkali fixing agent into the fixing liquid, then steaming and fixing. The alkali agent used can be soda or phosphoric acid three sodium. It can also be added with baking soda in the first bath, and soda in the second bath.

Three, vat dyeing

Vat dyes are insoluble in water. They should be reduced in alkaline strong reducing solution and dissolved into hidden dye sodium salt before dyeing. After oxidation, they are restored to insoluble dye lakes and fixed on fibers.

(1) dyeing process of vat dyes: dyeing, dyeing or pad dyeing when vat dyes are dyed.

Most of the yarn and knitted fabrics are impregnated. Most of the woven fabrics are dyed and dyed. They generally include the following four basic processes.

1. dye reduction: the reduction process of dyes, that is, the formation process of the leucophore of vat dyes, is usually carried out in alkaline medium.

2. staining on the leucosomes: the vat dyes are reduced and dissolved into sodium salt of cryptic body after the reduction of dyestuff and caustic soda, which is direct to cellulose fiber, first adsorbed on the surface of the fiber, then diffusing into the fiber to finish dyeing the fiber.

3. crypto chromophore oxidation: the chromophore of the dyed fibers needs to be oxidized by air or oxidant to convert the original insoluble vat dye to the original color.

4. soaping and processing: soaping can adsorb.

The removal of floating color on the surface has made the dyed fabrics have bright coloring and good rubbing fastness.

(two) vat dyeing method

1. the method of leucosomal staining: the staining of leucosomes is a method of dyeing the dye into a latent chromophore, adsorbed in the dye bath, and then oxidized and soaped.

(1) dry cylinder method: in the process of dyeing and dying, some dyes are reducing slowly, so we must adopt more severe conditions to increase the reduction rate of dyes. This reduction method is called dry cylinder method.

(2) full bath method: this reduction method is suitable for vat dyes with high reduction rate.

The method is to dye the dye directly into the dye bath, add the prescribed amount of caustic soda and insurance powder, so that the dye can be reduced and the dye can be dyed after 10 to 15min reduction.

2. suspension pad dyeing: the highly dispersed suspension is made by mixing the unreduced dye particles with the dispersant by grinding.

The fabric is evenly adhered to the fiber after being impregnated in the liquid, and then the dye is directly reduced to the hidden color body on the fabric and then absorbed by the fiber, and then fixed on the fiber by oxidation. This dyeing method is called suspension dyeing.

This method can solve the problem of white core.