Effect of Dyeing Process Conditions on Dyeing Quality
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The choose of dye when dyeing rayon
Procion HE produced by British ICI company is a kind of high-temperature reactive dyes, especially suitable exhaust dyeing. It has bright color, economical, leveling good leveling property, excellent color performance property. In order to prevent the nylon yarn from staining with color, we can choose to add soda first, then anhydrous sodium sulphate, running in 20min, then add the activity dye, the holding time can vary with the amount of dye.
The process of dyeing Nylon filament / modified polyester filament yarn 1. The addition sequence of dye
For the acid dyes used on dyeing nylon yarn, we should control the appropriate initial dyeing temperature, heating rate and dyeing time according to its diffusion, aggregation tendency and dye migration performance level. Only by thus, it can have good levelness and penetration effect.
Cationic dye has good affinity with modified polyester filament. Due to its quick absorption and slow diffusion property, uneven dyeing phenomenon is easy to occur.Once uneven dyeing occurs, it is difficult to correct by extending dyeing time.
Because the ion of acid and cationic dyes is on the contrary. We must pay attention to the dyeing sequence when we make process. So they need to be dissolved separately and adding anionic retarding agent M and anti-settling agent S to achieve the effect of leveling.
We use two-step dyeing in a bath generally, and take into account the different characteristics of dyes and materials in making the process. Adding acidic dyes first, and then add cationic dyes, heating up the same bath dyeing modified polyester.
Temperature is an important factor to control the leveling. The acidic dyes start to dye nylon from 40℃. The modified polyester filament yarn is dyed with cationic dyes. It’s uptaking rate is very low under temperature 70℃, when it reaches the glass transition temperature of the dyeing fiber (70-85 C), the dye uptake rate began to increase rapidly. Therefore, we selected the dyeing process, strictly control the heating rate, to ensure that the dyeing temperature subsection and reaches good leveling effect.
3. The PH value control in dyeing bath
Acid dyes and cationic dyes dyeing pH value is generally between 4-5, and we generally add the acetic acid to reach the Ph value. We also can add ammonium sulfate or sodium acetate into the dye bath, and adjust pH value in dye bath to the required range, and we also can reach the PH value using slow acid adjusting agent
4. The use of levelling agent, retarding agent, and anti-setting agent
Adding acid leveling agent AD in acid dyes, the dye uptaking of the nylon yarn will be uniform, Adding anionic retarding agent M and then cationic dye. Due to cationic dyes and anionic dyes can be used in the same dyeing bath, which creating conditions for acid dyes and cationic dyes one bath.
Adding anionic retarding agent M, which combine with cationic dye and form compound with low solubility, which will suspend in the dye bath, and no easy to attach to fiber. With less free cationic dyes, the dye uptaking rate is slow down. With the increasing of the dyeing temperature , the complex gradually decomposed, releasing free cationic dyes, and the dyeing rate increased gradually, so as to achieve the purpose of leveling.
In order to avoid precipitation of complex compounds, anti-precipitation agent S should be added at the same time as the anionic dye M is added
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