Traditional acid dyes refer to water-soluble dyes containing acidic groups in the dye structure, and are usually dyed under acidic conditions.
1. Overview of acid dyes
1. The history of acid dyes:
In 1868, the earliest acid dye, triarylmethane acid dye, appeared, which had strong dyeing ability but poor fastness;
In 1877, the first acid dye Acid Red A used for wool dyeing was synthesized, and its basic structure was determined;
After 1890, acid dyes with anthraquinone structure were invented, and their chromatograms became more and more complete;
To date, there are nearly hundreds of acid dye varieties and are widely used. Suitable for dyeing wool, silk, nylon and other fibers.
2. Characteristics of acid dyes:
Among acid dyes The acidic groups are generally sulfonic acid groups (-SO3H), which exist on the dye molecules in the form of sulfonate sodium salt (-SO3Na). There are also some dyes with carboxylic acid sodium salt (-COONa) as the acidic group.
It is characterized by good water solubility, bright color, complete chromatography, relatively simple molecular structure compared with other dyes, lack of long conjugated coherent system in the dye molecules, and direct dyeing. Lower sex.
3. Reaction mechanism of acid dyes:
2. Classification of acid dyes
1. Classification according to the molecular structure of the dye parent:
Azos (accounting for 60%, broad chromatogram)
Anthraquinones (accounting for 20%, mainly blue and green)
Triarylmethanes (accounting for 10%, purple and green series)
Heterocycles (accounting for 10%, red and purple series)
2. Classification according to the pH of dyeing:
Strongly acidic bath, acidic Dyes: dyeing pH value 2.5-4, good light fastness, but poor wet processing fastness, bright color, good level dyeing;
Weakly acidic bath acid dyes: dyeing With a pH value of 4-5, the proportion of sulfonic acid groups in the molecular structure of the dye is slightly lower, so the water solubility is slightly worse, the wet processing fastness is better than that of strong acid bath dyes, and the leveling properties are slightly worse.
Neutral bath acid dyes: dyeing pH value is 6-7, the proportion of sulfonic acid groups in the dye molecular structure is lower, the dye solubility is low, the leveling property is poor, and the color is not bright enough , but the wet processing fastness is high.
3. Terminology related to acid dyes
1. Color fastness :
The color of a textile is related to its resistance to various physical, chemical, and biochemical effects during the dyeing and finishing process or during use and consumption.
2. Standard depth:
The recognized depth standard series defines medium depth as 1/ 1 standard depth. Colors of the same standard depth are psychologically equivalent, allowing color fastness to be compared on the same basis. At present, it has developed to a total of six standard depths: 2/1, 1/1, 1/3, 1/6, 1/12 and 1/25.
3. Dyeing depth:
Expressed by the percentage of dye quality and fiber quality (i.e. O.M.F. ), the dye concentration varies according to different colors.
4. Discoloration:
After certain treatment, the color of the dyed fabric changes in the shade, light and Changes in depth or brightness, or a combination of these changes.
5. Staining:
After certain treatment, the color of the dyed fabric will change to the same color. Transferred to adjacent lining fabrics, causing contamination of the lining fabrics.
6. Use gray sample card to evaluate discoloration:
In the color fastness test, it is used to evaluate The standard gray sample card used to measure the degree of discoloration of dyed materials is generally called a discoloration sample card.
7. Gray sample card for evaluating staining:
In the color fastness test, it is The standard gray sample card used to evaluate the staining degree of dyeing materials on adjacent fabrics is generally called a stain sample card.
8. Color fastness rating:
According to the color fastness test, the discoloration of dyed fabrics The color fastness properties of textiles are rated based on the degree of staining and staining of the backing fabric. Except for the eight-level light fastness (except AATCC standard light fastness), the rest are in the five-level system. The higher the level, the better the fastness.
9. Adjacent fabrics:
In the color fastness test, in order to judge the adhesion of dyed fabrics to Degree of staining of other fibers, undyed white fabric treated with dyed fabric.
4. Common color fastness of acid dyes
1. Sunlight fastness:
Also known as light color fastness, the ability of the color of textiles to withstand artificial light exposure. The general inspection standard is ISO105 B02;
2. Color fastness to washing (water immersion):
The color of textiles changes to different conditions. Resistance to washing, such as ISO105 C01\C03\E01, etc.;
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 chlorine water:
Also known as chlorine pool fastness, usually Simulate the concentration of chlorine in the swimming pool to test the fabric’s resistance to chlorine discoloration. For example, it is suitable for nylon swimsuits. The detection method is ISO105 E03 (effective chlorine content 50ppm);
5 , color fastness to sweat stains:
The resistance of the color of textiles to human sweat,According to the acidity and alkalinity of the test sweat, it can be divided into acid and alkali perspiration fastness. Fabrics dyed with acid dyes are generally tested for alkaline perspiration fastness. </p
