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Traditional acid dyes are water-soluble dyes that contain acidic groups in the dye structure, usually stained under acidic conditions.
First, an overview of acid dyes
1. History of acid dyes:
In 1868, the earliest acidic dye triaryl methane acid dye appeared, which had strong dyeing ability but poor fastness;
In 1877, the first acid dye for wool dyeing, Acid Red A, was synthesized, and its basic structure was determined;
After 1890, anthraquinone structure of acid dyes was invented, and its chromatography became more and more complete;
So far, there have been nearly hundreds of dye varieties of acid dyes, which are widely used in the dyeing of wool, silk, nylon and other fibers.
2. Characteristics of acid dyes:
The acid groups in acid dyes are generally based on sulfonic acid groups (-SO3H), which exist on the dye molecules in the form of sodium sulfonate salts (-SO3Na), and there are also individual dyes with sodium carboxylate salts (-COONa) as acid groups.
It is characterized by good water solubility, bright color, complete chromatography, simple molecular structure compared with other dyes, lack of longer conjugate coherent system in dye molecules, and low directness of dyes.
3. Reaction mechanism of acid dyes:
Second, the classification of acid dyes
1. Classification according to the molecular structure of the dye matrix:
Azos (60% broad chromatography)
Anthraquinones (20%, mainly blue and green)
Triaryl methane (10%, purple, green)
Heterocyclic (10%, red, purple)
2. Classification according to the pH of dyeing:
Strong acidic bath acid dye: dyeing pH 2.5-4, good sun fastness, but poor wet treatment fastness, bright color, good leveling;
Weak acid bath acid dye: staining pH 4-5, the proportion of sulfonate groups in the dye molecular structure is slightly lower, so the water solubility is slightly poor, the wet treatment fastness is better than that of the strong acid bath dye, and the leveling is slightly worse.
Neutral bath acid dyes: dyeing pH 6-7, the proportion of sulfonate groups in the dye molecular structure is lower, the dye solubility is low, the leveling is poor, the color is not bright enough, but the wet treatment fastness is high.
Third, acid dye related terms
1. Color fastness:
The color of the textile is resistant to various physical, chemical, and biochemical effects during dyeing and finishing processes, or in the process of use and taking. 2. Standard depth:
A recognized depth standard series that defines a medium depth of 1/1 standard depth. Colors of the same standard depth are psychologically equal, allowing color fastness to 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 a percentage of dye mass to fiber mass (i.e. O.M.F), dye concentration varies according to different colors. 4. Discoloration:
After a certain treatment, the color of the dyed fabric changes in color, depth or brightness, or the result of a combination of these changes. 5. Stained color:
After a certain treatment, the color of the dyed fabric is transferred to the adjacent lined fabric, and the lining fabric is stained. 6. Gray sample card for color change:
In the color fastness test, the standard gray sample card used to assess the degree of discoloration of the chromosome is generally called the color change sample card. 7. Gray sample card for grading color:
In the color fastness test, the standard gray sample card used to assess the degree of color staining of the color of the coated fabric is generally referred to as the staining sample card. 8. Color fastness rating:
According to the color fastness test, the degree of discoloration of the dyed fabric and the degree of color staining of the lined fabric are rated. Except for the light fastness of eight levels (except for the AATCC standard lightfastness), the rest is a five-stage system, and the higher the number of stages, the better the fastness. 9. Lining fabric:
In the color fastness test, the unstained white fabric is treated together with the dyed fabric to determine the degree of color staining of the dyed fabric on other fibers.
Fourth, the common color fastness of acid dyes
1. Sun fastness:
Also known as lightfast color fastness, textile color resistance to artificial light irradiation ability, general inspection standards according to ISO105 B02;
2. Washable (immersion) color fastness:
The resistance of textile color to washing under different conditions, such as ISO105 C01C03E01, etc.; 3, friction color fastness:
The resistance of textile colors to friction can be divided into dry and wet friction fastness. 4. Chlorine-resistant water color fastness:
Also known as chlorine pool fastness, generally imitate the concentration of chlorine in the pool for testing, test the degree of chlorine discoloration of the fabric, such as suitable for nylon swimwear, detection methods such as ISO105 E03 (effective chlorine content of 50ppm); 5, sweat resistance color fastness:
The color of the textile is resistant to human sweat, according to the acidity and alkalinity of the test sweat, it can be divided into acid, alkali sweat fastness, acid dye dyed fabric is generally to detect the alkaline sweat fastness.