Basic knowledge of dyes: disperse dyes

Disperse dyes are the most important and main category in the dye industry. They do not contain strong water-soluble groups and are non-ionic dyes that are dyed in a dispersed state during the dyeing process. Mainly used for the printing and dyeing of polyester and its blended fabrics. It can also be used in the printing and dyeing of synthetic fibers such as acetate fiber, nylon, polypropylene, vinyl, and acrylic.

An overview of disperse dyes

1 Introduction:
Disperse dye is a kind of dye that is slightly soluble in water and is highly dispersed in water by the action of dispersant. Disperse dyes do not contain water-soluble groups and have low molecular weight. Although they contain polar groups (such as hydroxyl, amino, hydroxyalkylamino, cyanoalkylamino, etc.), they are still non-ionic dyes. Such dyes have high post-treatment requirements, and usually need to be ground by a mill in the presence of a dispersant to become highly dispersed and crystal-stable particles before they can be used. The dye liquor of disperse dyes is a uniform and stable suspension.

2. History:
Disperse dyes were produced in Germany in 1922 and are mainly used for dyeing polyester fibers and acetate fibers. It was mainly used for dyeing acetate fibers at that time. After the 1950s, with the emergence of polyester fibers, it has developed rapidly and has become a major product in the dye industry.

Classification of disperse dyes

1. Classification by molecular structure:
According to the molecular structure, it can be divided into three types: azo type, anthraquinone type and heterocyclic type.

Azo-type chromatographic agents are complete, with yellow, orange, red, purple, blue and other colors. Azo-type disperse dyes can be produced according to the general azo dye synthesis method, the process is simple and the cost is low. (Accounting for about 75% of disperse dyes) Anthraquinone type has red, purple, blue and other colors. (Accounting for about 20% of disperse dyes) The famous dye race, anthraquinone-based dye heterocyclic type, is a newly developed type of dye, which has the characteristics of bright color. (The heterocyclic type accounts for about 5% of the disperse dyes) The production process of anthraquinone type and heterocyclic type disperse dyes is more complicated and the cost is higher.

2. Classification according to the heat resistance of the application:
It can be divided into low temperature type, medium temperature type and high temperature type.

Low temperature dyes, low sublimation fastness, good leveling performance, suitable for exhaustion dyeing, often called E-type dyes; high temperature dyes, high sublimation fastness, but poor levelness, suitable for hot melt dyeing , known as S-type dyes; medium-temperature dyes, with sublimation fastness between the above two, also known as SE-type dyes.

3. Terminology related to disperse dyes

1. Color fastness:
The color of textiles is resistant to various physical, chemical and biochemical effects in the dyeing and finishing process or in the process of use and consumption. 2. Standard depth:

A series of recognized depth standards that define medium depth as 1/1 standard depth. Colors of the same standard depth are psychologically equivalent, so that color fastness can be compared on the same basis. At present, it has developed to a total of six standard depths of 2/1, 1/1, 1/3, 1/6, 1/12 and 1/25. 3. Dyeing depth:

Expressed as the percentage of dye weight to fiber weight, the dye concentration varies according to different colors. Generally, the dyeing depth is 1%, the dyeing depth of navy blue is 2%, and the dyeing depth of black is 4%. 4. Discoloration:

The change in shade, depth or brilliance of the color of a dyed fabric after a certain treatment, or the combined result of these changes. 5. Stain:

After a certain treatment, the color of the dyed fabric is transferred to the adjacent lining fabric, and the lining fabric is stained. 6. Gray sample card for assessing discoloration:

In the color fastness test, the standard gray sample card used to evaluate the degree of discoloration of the dyed object is generally called the discoloration sample card. 7. Gray sample card for evaluating staining:

In the color fastness test, the standard gray sample card used to evaluate the degree of staining of the dyed object to the lining fabric is generally called the staining sample card. 8. Color fastness rating:

According to the color fastness test, the degree of discoloration of dyed fabrics and the degree of staining to the backing fabrics, the color fastness properties of textiles are rated. In addition to the light fastness of eight (except AATCC standard light fastness), the rest are five-level system, the higher the level, the better the fastness. 9. Lining fabric:

In the color fastness test, in order to judge the degree of staining of the dyed fabric to other fibers, the undyed white fabric is treated with the dyed fabric.

Fourth, the common color fastness of disperse dyes

1. Color fastness to light:
The ability of the color of a textile to withstand exposure to artificial light.

2. Color fastness to washing:
The resistance of the colour of textiles to the washing action of different conditions.

3. Color fastness to rubbing:
The color resistance of textiles to rubbing can be divided into dry and wet rubbing fastness.

4. Color fastness to sublimation:
The degree to which the color of a textile resists heat sublimation.

5. Color fastness to perspiration:
The resistance of the color of textiles to human sweat can be divided into acid and alkali perspiration fastness according to the acidity and alkalinity of the test sweat.

6. Color fastness to smoke and fading:
The ability of textiles to resist nitrogen oxides in smoke. Among disperse dyes, especially those with anthraquinone structure, the dyes will change color when they encounter nitric oxide and nitrogen dioxide.

7. Color fastness to heat compression:
The ability of the color of textiles to resist ironing and roller processing.

8. Color fastness to dry heat:
The ability of the color of a textile to resist dry heat treatment.

Post time: Jul-21-2022