How to choose disperse dyes when dyeing light color for nylon ?

Nylon/cotton fabrics are dyed with light color, and their nylon components are usually dyed with disperse dyes. The reason is: disperse dyes do not contain water-soluble groups, do not ionize in water, and do not carry active groups. Therefore, disperse dyes dye nylon, there is no ionic bond and covalent bond. The dyeing is completely dependent on the molecular gravity between the two. In addition, the relative molecular weight of disperse dyes is small, the diffusing ability and dyeing ability are strong, and the difference in the inherent quality of nylon is excellent, so the effect of leveling and penetration is excellent, and it is very suitable for dyeing nylon with light color (Note: Due to the weak binding force of disperse dyes and nylon, the dye depth and color fastness are poor, so it is not suitable for dyeing nylon with deep color).

Nylon dyed with disperse dyes has the advantages of outstanding levelness and incomparable with neutral dyes and acid dyes, but not all disperse dyes are suitable.

About: Nylon dyes light colors, and the requirements for disperse dyes are "two high and four low"

(1) The requirements for the light fastness of dyes are high. There are two reasons

①Dyeing light color, the dye is highly dispersed on the fiber, and the specific surface area in contact with sunlight, air and moisture is large, and it is more likely to be damaged. Therefore, the lighter the color, the worse the light fastness.

② The light fastness of disperse dyed nylon is usually lower than or seriously lower than that of polyester, that is, most disperse dyed nylon has poor light fastness. The reason is that the microstructure of nylon is relatively loose, the moisture absorption capacity is relatively high, and sunlight, air and moisture are more likely to invade.

It is one of the keys to the quality of disperse dyes dyeing nylon light color to choose disperse dyes with good light fastness and similar light fastness.

(2) High requirements for the stability of dye shades. Compared with dyeing polyester, disperse dyed nylon has a prominent problem, that is, it has color and light variability.

① The shades of disperse dyed nylon and polyester are mostly different

②Disperse dyes dye nylon, the pH value of the dyeing bath is different, and the color and light are also different. After testing, many disperse dyes dyed nylon, and its color and light will change with the pH value of the dyeing bath.

Note: Disperse dyes have good stability at 100 °C, and almost no appreciable hydrolysis occurs. Therefore, in the slightly alkaline dyeing bath with pH=7~8, the change of the color light is not caused by the hydrolysis of the dye, which means that the disperse dye dyeing nylon, once the pH value of the dyeing bath fluctuates (usually caused by the release of alkali from water and fabrics) ), the color light may produce obvious or even serious difference. The reason is likely to be caused by the isomerism of dyes or the different existing states of dyes in the fiber.

(3) Low compatibility requirements for dye temperature type. Polyester has a tight structure and a small degree of swelling. Therefore, dyes of different temperature types have different degrees of difficulty in coloring (E-type dyes have a small molecular weight and are easy to color; S-type dyes have a large molecular weight and are more difficult to color). Once the dyes of different temperature types are mixed and dyed, it is easy to produce color difference due to the difference of dyeing time or the difference of dyeing temperature. The structure of nylon is relatively loose, and the swelling degree in water is relatively large. Therefore, whether it is a low temperature type (E type) dye or a high temperature type (S type) dye, it is easier to color at 100 °C. That is, disperse dyes of different temperature types dye nylon, and its color synchronization is much better than that of polyester. Therefore, disperse dyes dyeing nylon has a wide selection range of disperse dye temperature type, and has low requirements on the compatibility and consistency of dye temperature type.

 (4) The requirements for the hydrolytic stability of dyes are low. Under the condition of high temperature and high pressure (130℃), disperse dyes generally have the defects of easy hydrolysis, which will make the color obviously or seriously lighten. However, under the condition of normal temperature and pressure (100℃), as long as the pH value of the dye bath is less than 8, the hydrolysis of the dye is very small, and it is not enough to affect the dyeing result. Therefore, compared with dyeing polyester, dyeing nylon has lower requirements on the hydrolytic stability of disperse dyes.

(5) The requirements for the thermal migration of dyes are low. Disperse dyes dyed nylon, and the phenomenon of thermal migration also occurs after post-treatment under high temperature dry heat conditions. However, since the thermal migration of disperse dyes is proportional to the depth of color, when nylon is dyed with light color, the effect of thermal migration of disperse dyes on shade and color fastness is not obvious. Therefore, disperse dyes dye nylon with light color, and the thermal migration of dyes can be less or not considered.

(6) The requirements for the thermal cohesion of the dye are low. The degree of thermal agglomeration of commonly used disperse dyes is much smaller at boiling temperature (100°C) than at high temperature (130°C), generally not enough to affect the dyeing quality. Obviously, this is because the dyeing temperature is low, the stability of the diffusing agent is good, and the agglomeration tendency of the dye itself is relatively small.

Therefore, in terms of the cohesion of dyes, most commonly used disperse dyes can be selected. It can be seen that the use of disperse dyes on nylon with good light fastness and good color and light stability is the key to dyeing nylon with light color.