Sulfide Dyes
Definition
Sulfide dyes are produced by the reaction of amines, phenols or nitro substances of aromatic hydrocarbons with sulfur or sodium polysulfide through sulfurization, and were first synthesized by French chemists Crucian and Bretonnier.
Dyeing mechanism
In simple terms, it is a sulfur-containing dye, a kind of sulfur-containing dye formed by certain sulfurization of organic matter, which is able to dissolve the sulfur in some way when dyeing, and finally finish dyeing.
Sulfur dyes are insoluble in water and require the use of sodium sulfide or other reducing agents to reduce the dye to a soluble cryptochrome when dyeing. It has an affinity for fibers and stains the fibers, and then reverts to its insoluble state after oxidation and color development and is fixed on the fibers. Therefore, sulfide dyes are also a kind of reducing dyes.
Commonly used dyes
Sulfide black
Vulcanized blue CV
Disperse dyes
Definition
Disperse dyes are a class of non-ionic dyes with low water solubility. They were first used for dyeing vinyl acetate fiber and were called vinyl dyes. With the development of synthetic fibers, nylon and polyester appeared one after another, especially polyester, because of its properties such as high neatness, few fiber voids and strong hydrophobicity, it is necessary to expand the fiber with a carrier or under high temperature and heat solubility in order for the dye to enter the fiber and be dyed. Therefore, new requirements for dyestuff, namely, the requirement for better hydrophobicity and certain dispersion and resistance to sublimation dyestuff, etc., printing and dyeing process for polyester fabric dyeing disperse dyestuff basically has these properties, but because of the variety, the use must also be selected according to the processing requirements line selection. These dyestuffs require a high level of post-processing and are usually ground by a mill in the presence of dispersant to become highly dispersed and crystallographically stable particles before they can be used.
Dyeing mechanism
Disperse dyes have small molecules and do not contain water-soluble groups in their structure, and they are uniformly dispersed in the dyeing solution by the action of dispersants. It can dye polyester fiber, acetate fiber and polyester amine fiber, and has become a special dye for polyester.
Main classification
One is classified by chemical structure, which can be mainly divided into azo, anthraquinone and heterocyclic types, among which the azo type is mainly used, and the azo type is divided into single azo type and double azo type.
Another kind of classification by application performance, can be divided into high temperature type, medium temperature type and low temperature type three categories, detailed classification see the following table:
Acid dyes
Definition
AcidDyes are a class of water-soluble dyes with acidic groups in their structure, which are used for dyeing in acidic media. Most acid dyes contain sodium sulfonate salts, are soluble in water, and have a bright color and complete chromatography. They are mainly used for dyeing wool, silk and nylon, but also for leather, paper, ink, etc. It has no coloring power for cellulose fiber in general.
Dyeing mechanism
The acidic group in acid dyes is generally dominated by sulfonic acid group (-SO3H), which exists on the dye molecule in the form of sodium salt of sulfonic acid (-SO3Na), and there are also individual dyes with sodium salt of carboxylic acid (-COONa) as the acidic group.
They are characterized by good water solubility, bright color, full chromatography, relatively simple molecular structure compared to other dyes, lack of a longer conjugated coherent system in the dye molecule, and low directivity of the dye.
Main classification
Classified by the molecular structure of the parent dyestuff:
1、Azo class (60% of the total, extensive chromatography)
Azo dyes (a class of organic compounds with aromatic groups attached to both ends of the azo group) is the most widely used class of synthetic dyes for textile garments in the printing and dyeing process, used in the dyeing and printing of a variety of natural and synthetic fibers, also used in the coloring of paints, plastics, rubber, etc.. Under special conditions, it can decompose and produce more than 20 kinds of carcinogenic aromatic amines, which can cause lesions and induce cancer by changing the DNA structure of human body through activation.
2, anthraquinones (accounting for 20%, mainly blue, green system)
Triarylmethane class (accounting for 10%, purple, blue, green system)
Triaryl methane dyes are substituted triaryl methane derivatives and substituted anthracenes oxide compounds, with different precipitating agents to generate dyes.
4、heterocyclic class (10%, red, purple system)
Heterocyclic pigments (heterocyclic pigments) contain heterocyclic structure in organic pigment molecules, mainly oxygen heterocyclic ring or nitrogen heterocyclic ring as the color-emitting system. Heterocyclic pigment chromatography includes yellow, orange, red, purple, a few are blue, and have molecular symmetry and planarity, many varieties show excellent heat resistance, migration resistance and weather resistance similar to phthalocyanines.
2、Classification according to the pH of dyeing:
Strong acid bath acidic dyes: dyeing pH 2.5-4, good sun fastness, but poor wet treatment fastness, bright color, good uniformity;
Weak acid bath acid dyes: dyeing pH 4-5, the proportion of sulfonic acid groups in the dye molecular structure is slightly lower, so the water solubility is slightly worse, wet treatment fastness is better than strong acid bath dyes, leveling is slightly worse.
Neutral bath acidic dyes: dyeing pH 6-7, the proportion of sulfonic acid group in the molecular structure of dyestuff is even lower, so the solubility of dyestuff is low, the leveling is poor, the color is not bright enough, but the wet treatment fastness is high.
Basic dyestuff
Definition
Basic dyes, also known as salt-based dyes, are salts generated by aromatic bases and acids (organic acids, inorganic acids), i.e. salts of colored organic bases. The basic group is usually an amino group, which becomes salt as -NH2-HCl salt group and dissolves in water to form dye cations and acid anions. Also known as cationic dyes.
Dyeing principle
Dyes that dissociate in aqueous solution to form cationic pigments, so they are classified as cationic dyes. Because of the poor light fastness and wash fastness of basic dyes after dyeing fibers, they are rarely used for dyeing fabrics, but are mainly used for coloring educational materials and paper and for manufacturing color deposits.
Common Dyes
Reduction dyes
Definition
Vatting dyes are dyes that have excellent properties. They are insoluble in water and are treated with sodium dithionite (insurance powder) in an alkaline solution to dye fibers.
Dyeing mechanism
Insoluble dyes are dyed by reducing the dyestuff into a leuco form. Firstly, it becomes soluble sodium salt of cryptophore by reduction in alkali solution and is absorbed by cellulose fiber, then it is oxidized and reverts to original insoluble dye, which generally has higher fastness to washing and sunlight. For example, Shilin blue, etc. It is mainly used for printing and dyeing of cotton and polyester-cotton blended fabrics, and can also be used for coloring of vinyls, and in the silk industry, it is used for human silk, human silk-cotton interweaving, and real silk dyeing and printing.
Reduction dyes are insoluble in water, when dyeing, they have to be reduced and dissolved in alkaline strong reducing solution to become sodium salt of cryptochromes in order to dye fibers, after oxidation, they return to insoluble dye precipitate and fix on fibers.
Main classification
Reduction dyes are dyes with excellent properties. According to their main chemical structure, they can be divided into two categories: indigo and anthraquinone.
Indigo
Anthraquinones
Phthalocyanine dyes
Definition
Phthalocyanine dyes are a kind of dyes produced by condensation of phthalocyanine on fiber and then by metal complexation.
Main classification
Phthalocyanine pigments mainly include phthalocyanine blue and phthalocyanine green. Phthalocyanine blue is widely used in ink, paint, plastic, rubber, leather and stationery coloring for its excellent heat and weather fastness and bright color; in recent years, it plays a special role in catalysis, semiconductor, electronic photography and light energy conversion.
Phthalocyanine blue
Phthalocyanine green
