Application of PH Value in Textile Dyeing

Application of PH Value in Textile Dyeing

Vat dye dyeing

Vat dye dyeing is often used in yarn dyeing of yarn-dyed handkerchiefs and yarn-dyed towels. Vat dyes are water-insoluble dyes. The dyes themselves have no affinity for fibers and cannot be directly dyed. They must be dissolved with caustic soda and insurance powder to make leuco sodium salts for dyeing. The pH value depends on the depth of the color, and varies from light to dark colors, correspondingly in the range of 12~13.5.

Insoluble azo dye dyeing

When dyeing with insoluble azo dyes, it is very important to control the pH value of the color developing solution. If the pH value is too high, the color will develop quickly and the color will not be strong; if the pH value is too low, the color will develop slowly and the color will be light. The pH value is generally controlled at 3.5~4.5. If the pH value of Lamin Blue coloring is higher, it should be controlled at 6.5~7.0. It should be noted that although insoluble azo dyes have played an important role in the history of home textile production, they have been eliminated because their color bases contain many carcinogenic aromatic amines and the gases released by the diazotization of the color bases are harmful to the health of operators.

Cationic dye dyeing

The pH value of cationic dye dyeing should be controlled at 4.5~5, and acetic acid and sodium acetate are used to form a pH buffer solution. In the production of home textiles, cationic dyes are used for dyeing involving the use of acrylic fibers, such as dyeing and printing of acrylic carpet materials, dyeing and printing of acrylic artificial fur used for pillows, dyeing of acrylic fancy yarns used for curtains and sofa fabrics, and dyeing of electrostatic flocking acrylic fluff.

Acid dye dyeing

In acid dye dyeing, changes in the pH value of the dye bath have a great influence on the dye uptake and dyeing rate. Generally speaking, the stronger the acidity of the dye bath, the faster the dyeing, and the more the dye liquid absorbs the color in the end, but if the acidity is too strong, it is easy to cause uneven dyeing and poor hand feel. When dyeing, different pH values are used depending on whether strong acid dyes or weak acid dyes are used. The pH value of strong acid dyes is 3~4, and the pH value of weak acid dyes is 5~6. Acid dyes are used for printing and dyeing household textiles with silk, wool, and nylon as raw materials, such as silk bedding, silk headscarves, mulberry silk and tussah silk threads, wool carpet yarns, blanket yarns, cotton and brocade interwoven imitation peach skin velvet, etc.

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