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How to choose disperse dyes when dyeing nylon light colors with disperse dyes?

Views:34     Author:Site Editor     Publish Time: 2021-05-28      Origin:Site Inquire

Nylon/cotton fabrics are dyed lightly in color, and the nylon component is usually dyed with disperse dyes. The reason is: Disperse dyes do not contain water-soluble groups, do not ionize in water, and do not have active groups. Therefore, when dyeing nylon with disperse dyes, there is no ionic bonding and covalent bonding. It is completely dependent on the molecular gravity between the two. In addition, the relative molecular weight of disperse dyes is small, the diffusion ability and migration ability are strong, and the difference in the inherent quality of nylon is excellent. Therefore, the level dyeing effect is excellent, and it is very suitable for dyeing the light color of nylon (Note: Due to the weak binding force between disperse dyes and nylon, dyeing depth and color fastness are poor, it is not suitable for dyeing nylon with deep and dense color).


Although disperse dyes dye nylon, although they have outstanding level dyeing properties, neutral dyes and acid dyes are incomparable, but not all disperse dyes are suitable.

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About: Nylon dyes light and light colors, and the requirements for disperse dyes are "two highs and four lows".


(1) High requirements for the light fastness of dyes. There are two reasons:


①Dyeing light and 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 susceptible to damage. Therefore, the lighter the color, the worse the light fastness.


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


The use of disperse dyes with good light fastness and similar light fastness is one of the keys to the quality of disperse dyes in light and light colors of nylon.


(2) High requirements for the stability of dye shade. Compared with dyeing polyester with disperse dyes, there is an outstanding problem, that is, it has color and light change.


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


②When the disperse dyes dye nylon, the pH value of the dyeing bath is different, and the color shade is also different. After testing, many disperse dyes dye nylon, the color shade will change with the pH value of the dyeing bath.


Note: Disperse dyes have good stability at 100°C and almost no detectable hydrolysis will occur. Therefore, in the slightly alkaline dyeing bath with pH=7~8, the change of the shade is not caused by the hydrolysis of the dye. This shows that when the disperse dye dyes nylon, once the pH value of the dye bath fluctuates (usually caused by water, fabric alkali release ), the color light may have obvious or even serious differences. The reason is probably caused by the isomerism of dyes or the existence of different dyes in the fiber.

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(3) Low compatibility requirements for warm dyes. Polyester has a compact structure and low swelling degree. Therefore, dyes of different temperature types have different degrees of difficulty in coloring (E-type dyes have a small relative molecular mass and are easy to color; S-type dyes have a larger molecular weight and are more difficult to color). Once dyeing with different temperature types of dyes is compatible, 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 its swelling degree in water is relatively large. Therefore, whether it is a low-temperature (E-type) dye or a high-temperature (S-type) dye, it is easier to color at 100°C. That is to say, disperse dyes of different temperature types are dyed with nylon, and the color synchronization is much better than that of polyester. Therefore, when dyeing nylon with disperse dyes, there is a wide range of options for disperse dye temperature type, and low requirements for the consistency of dye temperature type compatibility.


(4) Low requirements on the quality of dye hydrolysis stability. Under the conditions of high temperature and high pressure (130℃), disperse dyes generally have the defect that they are easy to be hydrolyzed, which will make the color obvious or severely lighten. However, under the condition of normal temperature and pressure (100℃), as long as the pH value of the dyeing bath is<8, the hydrolysis of the dye is very small, and it is not enough to affect the dyeing result. Therefore, compared with dyed polyester, dyed nylon has lower requirements for the hydrolytic stability of disperse dyes.


(5) Low requirements on the size of dye thermal migration. Disperse dyes dye nylon, after treatment under high temperature and dry heat conditions, thermal migration also occurs. However, because the thermal migration of disperse dyes is directly proportional to the depth of color, when nylon is dyed with light colors, the thermal migration phenomenon of disperse dyes has no obvious effect on the shade and color fastness. Therefore, when disperse dyes dye light colors of nylon, the thermal migration of the dyes can be little or no consideration.


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


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


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