How to choose dyes for dyeing nylon?

Dye selection, nylon is a hydrophobic fiber, but the macromolecule contains a large number of weakly hydrophilic groups (- CONH -), and there are-NH2,-COOH hydrophilic groups at both ends of the molecule, so a variety of dyes can be used for dyeing . Such as disperse dyes, neutral dyes, weak acid dyes, reactive dyes and direct dyes, etc., can be used as dyes for nylon dyeing.

Through the size sample test, it is found that the covering ability of various dyes on the warp and rung defects of nylon fabrics are: disperse dyes> acid dyes> reactive dyes> neutral dyes> direct dyes.

Although there are a variety of dyes that can be used to dye nylon products, each has its advantages and disadvantages. At present, the dyeing of nylon is usually based on weak acid dyes, but weak acid dyes are difficult to obtain level dyed products due to fast coloring and poor migration, and they have high requirements for operation. A slight improper operation will cause stains and stains. Wait for dye defects.

Disperse dye dyeing nylon has the characteristics of good level dyeing, stable dyeing quality, good reproducibility and less dyeing defects. At the same time, disperse dyes can also be dyed in the same bath with weak acid dyes or neutral dyes to adjust shade and improve levelness. In addition, most of the disperse dyes are easy to handle when dyeing light colors, the fiber damage is small, the compatibility between the dyes is good, the color depth and the color fastness are good. The disadvantage is that the color is dim and the covering is poor, so it is not suitable for dyeing light and bright color varieties.

The isoelectric point of nylon is 5-6. When the p H value is lower than this, it is good for dyeing.

Generally, the lower the pH, the faster the dyeing speed, but the level of dyeing and the ability to cover blemishes will decrease. For this reason, the pH value of the dye solution must be controlled. If the pH value of acid and neutral dyes in the dye bath is controlled below 5-6, the dye uptake and color fastness can be improved, and the color difference between the warp willow and the crosspiece can be reduced. Disperse dyes can be dyed in neutral bath or acid bath, but the dyeing effect is better when the pH value is 5-6. Reactive dyes are dyed in a neutral bath, and the dye uptake rate is extremely poor, but under the condition of pH 3 to 5, the dye uptake rate is improved and the color fastness is good.

Nylon dyeing usually adopts two dyeing schemes, namely: light and medium colors are mainly dyed with disperse dyes; medium and dark colors are mainly dyed with neutral dyes, supplemented by weak acid and reactive dyes to make up for the incomplete chromatogram, so as to obtain more satisfaction The dyeing effect.