Categories of sulfur dyes in dyeing

Application of sulfur dyes in dyeing of cellulosic fibers are many. It mainly used for yarns industrial fabrics and heavy fabrics. Sulfur dyes do not dissolve in water, the dyeing needs sodium sulfide or other reducing agents to revert a dye soluble leuco. It has affinity to fiber. Sulfur dyes can be used for dyeing of fiber such as cotton, linen, viscose, etc. Its manufacturing process is relatively simple, low cost, dye color or mixed colors, good light fastness, but abrasion resistant fastness is poor.

Sulfur dyes now can be divided into six main categories:


1 powdered sulfur dyes
Structure formula is D-S-S-D. These dyes are not soluble in water, alkaline reducing agents can make the dyes reduce to leuco, and dissolves in the water, leuco-sodium salts can be adsorbed by fibers.


2 water-soluble sulfur dye
Structure formula is D-SSO3Na. Such dyes molecular structure has water-soluble group, both solubility and levelling are good. Water-soluble sulfur dyes have fine excellent high temperature properties. But dyes do not contain a reducing agent and have no affinity to the fibers, so it need to add sodium sulfide when dyeing, and through Nucleophilic, reduction to make it into cellulose affinity State.


3 liquid sulfur dyes
It contains a certain amount of sodium sulfide reducing agents. When diluted, it can be directly applied. Such dyes some contain sulfur, some contain very small amounts or little sulfur.


4 environmentally friendly sulfur dyes
They are refined into dyeing leuco in the production process, but the amount of sulphur are far lower than common sulfur dyes. They are high purity, stable restoring and good permeability, also use glucose and insurance powder in the dye bath as a binary reduction agent. It not only reduce sulfur dyes, but also play a role in environmental protection.


5 curing VAT dyes
It usually is made into powder, fine, Superfine powder or liquid dyes, and it applied to the one-bath dyeing of polyester/cotton blended fabric and disperse dyes. Also it can be used for caustic alkali and hydrosulfite (thiourea) restore.


6 disperse sulfur dyes
Disperse sulfur dyes is based on sulfur dyes and VAT dyes sulfide, and made by the commodity processing methods of disperse dyes. It mainly used for disperse dyes in one bath dyeing polyester and viscose or polyester/cotton blended fabric. Read more!