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How much do you know about sulphur dyes?

Sulfide dyes are a kind of sulfur-containing dyes with complex molecular structure. It is generally made of some aromatic amines, aminophenols and other organic compounds heated with sulfur or sodium polysulfide, that is, vulcanized.

 Sulfide dyes are mostly insoluble in water, and when dyeing, they need to be dissolved in sodium sulfide or alkaline insurance powder solution to reduce to leaches, and then oxidized to show color after fiber absorption.

 Overview of sulphur dyes

Vulcanized dyes have been manufactured for cellulose fiber dyeing for the first time since 1873, and its production process is relatively simple, generally made of aromatic amines or phenolic compounds mixed with sulfur or sodium polysulfide and heated. Low cost, easy to use, no cancer control, with good washing fastness and sun fastness, is a popular dye. However, because it is a class of water-insoluble dyes, when dyeing, they are reduced to soluble lemony sodium salt in alkali sulfide solution, after dyeing human fiber, after oxidation to become insoluble state fixed on the fiber, so the dyeing process is complex, and under strong alkaline conditions can not be used for wool, silk and other protein fibers.

 Therefore, vulcanized dyes are mostly used in the dyeing of cellulose fibers, especially in the dyeing of dark products of cotton fabrics, of which the two colors of Sulfide dyes are a kind of sulfur-containing dyes with complex molecular structure. It is generally made of some aromatic amines, aminophenols and other organic compounds heated with sulfur or sodium polysulfide, that is, vulcanized.

 Sulfide dyes are mostly insoluble in water, and when dyeing, they need to be dissolved in sodium sulfide or alkaline insurance powder solution to reduce to leaches, and then oxidized to show color after fiber absorption.

 Overview of sulphur dyes

 Vulcanized dyes have been manufactured for cellulose fiber dyeing for the first time since 1873, and its production process is relatively simple, generally made of aromatic amines or phenolic compounds mixed with sulfur or sodium polysulfide and heated. Low cost, easy to use, no cancer control, with good washing fastness and sun fastness, is a popular dye. However, because it is a class of water-insoluble dyes, when dyeing, they are reduced to soluble lemony sodium salt in alkali sulfide solution, after dyeing human fiber, after oxidation to become insoluble state fixed on the fiber, so the dyeing process is complex, and under strong alkaline conditions can not be used for wool, silk and other protein fibers.

Therefore, vulcanized dyes are mostly used in the dyeing of cellulose fibers, especially in the dyeing of dark products of cotton fabrics, of which the several  colors of sulphur black and sulphur blue 

sulphur dark brown gd sulphur brown dye
sulphur red color red lgf
sulphur brown 10 yellow brown color
sulphur yellow 2 yellow powder
sulphur bordeaux 3b sulphur red powder

are the most widely used.

 Second, the dyeing mechanism of sulfide dyes

 The sulfide dye is reduced and dissolved into a dye solution, and the dye leucochroma formed is adsorbed by cellulose fibers and treated by air oxidation to make the cellulose fibers show the desired color. Its chemical reaction formula is

 D-S-SO3Na + Na2S→D-SNa + Na2S2O3

 The sulfide dye parent has no affinity for the fiber, and its structure contains sulfur bonds (1 S 1), disulfide bonds (1 s — S) or polysulfide bonds (1 Sx 1), which are reduced to a hydrogen sulfide group (1 SNa) under the action of sodium sulfide reducing agents, and become a leucochromic sodium salt soluble in water. The reason why leucochromes have a good affinity for cellulose fibers is that the molecules of dyes are larger, which in turn produces larger van der Waals forces and hydrogen bonding forces between the fibers.

 Iii. Classification of sulphur dyes

 Sulfide dyes can be divided into four categories:

 1, powder sulfide dye

 Dye structure general formula: D-S-S-D, generally need to use sodium sulfide boiling, dissolved after application.

 2, hydrolytic sulfide dyes

 Dye structure general formula: D-SSO3Na, this kind of dye is made of sodium sulfite or sodium bisulfite treatment of traditional sulfide dyes, dyes contain water-soluble groups, so water-soluble, but the dye does not contain reducing agents, no affinity for fibers, generally adopted suspension pad dyeing method applied on the fabric.

 3, liquid sulfide dye

 The general formula of dye structure is: D-SNa, containing a certain amount of reducing agent, the dye is pre-reduced into soluble leptochroma.

 Before 1936, the vulcanized dye was in powder form as its commercial form. When used, the powder vulcanized dye was co-heated to boil with the vulcanized, soda ash aqueous solution to dissolve it. In 1936, John Le Clester of the United States made a pre-reduced good, fairly stable sulfide dye concentrated solution, and obtained a patent, which is now known as liquid sulfide dye.

 4, environment-friendly sulfide dye

 In the process of production, it is refined into dye leaches, but the sulfur content and polysulfide content are much lower than that of ordinary sulfide dyes. The dye has high purity, stable reduction degree and good permeability. At the same time, the binary reducing agent of glucose and insurance powder is used in the dye bath, which can not only reduce the sulfide dye but also play a role in environmental protection.

 Fourth, the dyeing process of sulfide dyes

 The vulcanization dyeing process can be divided into the following four steps:

 1. Reduction of dyes

It is relatively easy to reduce and dissolve sulfide dyes, and sodium sulfide is commonly used as a reducing agent, which also acts as an alkali agent. In order to prevent the leucophore from being hydrolyzed, substances such as soda ash can be added appropriately, but the reduction bath alkaline can not be too strong, otherwise the dye reduction rate will be slow.

 2, the dye in the dye solution is adsorbed by the fiber

The leucophore of sulfide dye exists in the anion state in the dye solution, it has direct properties to cellulose fiber, can be adsorbed on the fiber surface and diffused into the fiber interior. The direct property of sulphur dyes to cellulose fibers is low, generally using a small bath ratio, while adding appropriate electrolytes, at higher temperature can improve the dyeing rate, levelling and permeability.

 3, oxidation treatment

After dyeing on the fiber, the sulfur dye leuco must be oxidized to show the desired color. Oxidation is an important step after the dyeing of vulcanized dyes. The easily oxidized vulcanized dye can be oxidized by air after dyeing by washing and ventilation, that is, air oxidation method; For some sulfide dyes that are not easy to oxidize, oxidizing agents are used to promote oxidation.

 4. Post-processing

Post-treatment includes cleaning, oiling, anti-embrittlement and color fixing. Sulfur dyes must be fully washed after dyeing to reduce the residual sulfur on the fabric and prevent fabric brittleness, because the sulfur in the dye and the sulfur in the alkali sulfide are easy to oxidize in the air to generate sulfuric acid, which will cause acid hydrolysis of the cellulose fiber and reduce the strength of the fiber brittleness. Therefore, it can be treated with anti-brittleness loss agents, such as: urea, trisodium phosphate, bone glue, sodium acetate, etc. In order to improve the solarization and soaping fastness of vulcanized dyes, the color can be fixed after dyeing. There are two methods of color fixing treatment: metal salt treatment (such as: potassium dichromate, copper sulfate, copper acetate and a mixture of these salts) and cationic color fixing agent treatment.

black and vulcanized blue are the most widely used.

 Second, the dyeing mechanism of sulfide dyes

The sulfide dye is reduced and dissolved into a dye solution, and the dye leucochroma formed is adsorbed by cellulose fibers and treated by air oxidation to make the cellulose fibers show the desired color. Its chemical reaction formula is

 D-S-SO3Na + Na2S→D-SNa + Na2S2O3

The sulfide dye parent has no affinity for the fiber, and its structure contains sulfur bonds (1 S 1), disulfide bonds (1 s — S) or polysulfide bonds (1 Sx 1), which are reduced to a hydrogen sulfide group (1 SNa) under the action of sodium sulfide reducing agents, and become a leucochromic sodium salt soluble in water. The reason why leucochromes have a good affinity for cellulose fibers is that the molecules of dyes are larger, which in turn produces larger van der Waals forces and hydrogen bonding forces between the fibers.

 Iii. Classification of sulphur dyes

 Sulfide dyes can be divided into four categories:

 1, powder sulfide dye

 Dye structure general formula: D-S-S-D, generally need to use sodium sulfide boiling, dissolved after application.

 2, hydrolytic sulfide dyes

 Dye structure general formula: D-SSO3Na, this kind of dye is made of sodium sulfite or sodium bisulfite treatment of traditional sulfide dyes, dyes contain water-soluble groups, so water-soluble, but the dye does not contain reducing agents, no affinity for fibers, generally adopted suspension pad dyeing method applied on the fabric.3, liquid sulfide dye

The general formula of dye structure is: D-SNa, containing a certain amount of reducing agent, the dye is pre-reduced into soluble leptochroma.

Before 1936, the vulcanized dye was in powder form as its commercial form. When used, the powder vulcanized dye was co-heated to boil with the vulcanized, soda ash aqueous solution to dissolve it. In 1936, John Le Clester of the United States made a pre-reduced good, fairly stable sulfide dye concentrated solution, and obtained a patent, which is now known as liquid sulfide dye.

4, environment-friendly sulfide dye

In the process of production, it is refined into dye leaches, but the sulfur content and polysulfide content are much lower than that of ordinary sulfide dyes. The dye has high purity, stable reduction degree and good permeability. At the same time, the binary reducing agent of glucose and insurance powder is used in the dye bath, which can not only reduce the sulfide dye but also play a role in environmental protection.

Fourth, the dyeing process of sulfide dyes

 The vulcanization dyeing process can be divided into the following four steps:

 1. Reduction of dyes

It is relatively easy to reduce and dissolve sulfide dyes, and sodium sulfide is commonly used as a reducing agent, which also acts as an alkali agent. In order to prevent the leucophore from being hydrolyzed, substances such as soda ash can be added appropriately, but the reduction bath alkaline can not be too strong, otherwise the dye reduction rate will be slow.

 2, the dye in the dye solution is adsorbed by the fiber

The leucophore of sulfide dye exists in the anion state in the dye solution, it has direct properties to cellulose fiber, can be adsorbed on the fiber surface and diffused into the fiber interior. The direct property of sulphur dyes to cellulose fibers is low, generally using a small bath ratio, while adding appropriate electrolytes, at higher temperature can improve the dyeing rate, levelling and permeability.

 3, oxidation treatment

After dyeing on the fiber, the sulfur dye leuco must be oxidized to show the desired color. Oxidation is an important step after the dyeing of vulcanized dyes. The easily oxidized vulcanized dye can be oxidized by air after dyeing by washing and ventilation, that is, air oxidation method; For some sulfide dyes that are not easy to oxidize, oxidizing agents are used to promote oxidation.

 4. Post-processing

Post-treatment includes cleaning, oiling, anti-embrittlement and color fixing. Sulfur dyes must be fully washed after dyeing to reduce the residual sulfur on the fabric and prevent fabric brittleness, because the sulfur in the dye and the sulfur in the alkali sulfide are easy to oxidize in the air to generate sulfuric acid, which will cause acid hydrolysis of the cellulose fiber and reduce the strength of the fiber brittleness. Therefore, it can be treated with anti-brittleness loss agents, such as: urea, trisodium phosphate, bone glue, sodium acetate, etc. In order to improve the solarization and soaping fastness of vulcanized dyes, the color can be fixed after dyeing. There are two methods of color fixing treatment: metal salt treatment (such as: potassium dichromate, copper sulfate, copper acetate and a mixture of these salts) and cationic color fixing agent treatment.


Post time: Dec-19-2023