Acidic dyes dye protein fibers. In addition to the direct impact of the composition, chemical properties and physical state of the fiber and dye itself on the dyeing, external conditions such as the pH value of the dye solution, temperature and the addition of electrolytes also directly affect the dyeing results. conduct.
1. pH value of dye bath
When the pH value of the solution is low, wool is positively charged, and there are more opportunities for wool to combine with inorganic anions (chloride ions or sulfate ions) and dye anions. At this time, wool Easy to dye.
So controlling the pH value of the dye bath also controls the amount and speed of dye adsorption by wool. Adding acid during the dyeing process increases the concentration of hydrogen ions in the dye bath, making the wool easier to dye. In order to achieve the purpose of leveling, it can be added in batches.
Different acids are selected according to the type of dye, such as sulfuric acid for strong acid bath dyeing, acetic acid for weak acid bath dyeing, and ammonium acetate or ammonium sulfate for neutral bath dyeing.
2. Adding electrolytes
Add electrolytes when dyeing wool The effect is related to the pH value of the dye bath. That is, when the pH value of the dye bath is below the isoelectric point of wool, wool and dyes are mostly combined with salt bonds, and the addition of electrolytes plays a dyeing retarding effect; when the pH value of the dye bath is higher than the isoelectric point of wool, wool and dyes are mostly bonded with hydrogen The bonds are combined with van der Waals forces, and electrolytes are added to promote dyeing.
3. Temperature
The relative molecular mass of acid dyes is approximately Between 300 and 800. At normal dyeing concentrations and room temperature, the dye rarely aggregates. However, acid dyes dyed in weak acid baths and neutral baths will aggregate at room temperature. Only higher temperatures or even boiling dyeing can be used to reduce the aggregation tendency of dyes.
The greater the tendency of dye aggregation, the more significant the influence of temperature. Increasing the temperature can also promote wool puffing, which is beneficial to the diffusion of dye into the fiber. When it is above 50°C, increasing the temperature has a significant effect on fiber puffing.
The scale layer of wool greatly hinders the diffusion of dyes, so dyeing requires boiling and prolonged dyeing. In order to avoid uneven dyeing, the dyeing temperature should be low when starting dyeing, and then gradually increase the temperature to boiling. Controlling temperature rise is of great significance to leveling dyeing. </p
