Cotton is dyed with vat dyes or reactive dyes.
The vat dye is bright in color, safe in chromatography, washable and light-resistant, and is an important dye for cotton and other cellulose fibers. The vat dye is insoluble in water, and it is reduced to a soluble leuco sodium salt in an alkaline solution, adsorbed on the fabric to be dyed, and then oxidized to return to an insoluble dye, thereby being fixed on the fabric.
Reactive dyes have bright color, good dyeing, simple dyeing method, high color fastness, complete chromatogram and low cost. They are mainly used for dyeing cotton, hemp, viscose, silk, wool and other blended fabrics. And printing.
The vat dye is insoluble in water. When dyeing, it should be reduced and dissolved in a strong alkaline reducing solution to become a leuco-sodium salt to dye the fiber. After oxidation, it will be restored to an insoluble dye lake and fixed on the fiber. Generally, it is washable. Fast fastness to light. For example, Shilin Blue and so on. Mainly dyed with cotton, polyester-cotton blended fabric; vinylon can also be colored; in the silk industry, used for human silk, human silk, human cotton intertwined, silk discharge printing.
When the vat dye is dyed, it may be impregnated, dyed or padded. Generally, yarns and knitted fabrics are mostly dyed, and most of the woven fabrics are dyed and padded, and generally include the following four basic processes.
The best is vat dye, but the process is complicated, and the chromatogram is not complete, and some color vat dyes can't be dyed.
At present, there are more reactive dyes, and the color fastness is theoretically worse than that of vat dyes, but it is enough for daily use, the UV fastness is also in the middle, the chromatogram is complete, the process is relatively simple, and the cost is lower than that of vat dyes. /3, is the most suitable dye for printing and dyeing cellulose fibers.
If it is printing, the printing process of cotton cloth is more, the more common ones are: watermark printing (water slurry printing), offset printing (glue printing), reactive printing, digital printing and so on.
1, watermark printing, the main components are: water, adhesives, thickeners, emulsifiers, etc., suitable for light or white cotton fabric printing, good post-printing feel. The specific operation process is: flat screen printing machine or manual screen printing table version, easy to operate.
2, offset printing, the main component is titanium white powder, suitable for dark cotton fabric printing, the post-printing feel is slightly harder than the watermark printing, so please choose carefully when printing over-sized patterns. The specific operation process is: flat screen printing machine or manual printing table version, easy to operate.
3, reactive printing, the main components are: water, reactive dyes, sodium alginate (or starch printing paste), etc., the post-press feel is softer than watermark printing and offset printing. Suitable printing equipment: rotary screen printing machine, flat screen printing machine, manual screen printing platen. The actual operation process is slightly more complicated than watermark printing and offset printing. After printing, it must be steamed, washed, dried and fixed.
4, digital printing processing, using active digital printing process printing. Main equipment: digital printing machine. After the desired pattern is processed by computer color separation, the dye ink is directly printed on the fabric to obtain the desired pattern. Process: fabric sizing, direct spray printing, steaming, washing, drying, shaping. Advantages: soft to the touch, bright luster, good fastness. Disadvantages: high cost.