Cationic dyes can be dissolved in water and remain cationic in aqueous solution. They are mainly used for dyeing acrylic fibers. The dyed products are bright and eye-catching and have excellent fastness.
1. Issues related to dyeing:
A. Best The determination of the dyeing process mainly considers factors such as dyeing temperature, dyeing pH value and application of auxiliaries
1. Water quality
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Water quality is very important for dyeing acrylic with cationic dyes. If the water contains calcium and magnesium ions, it can combine with the anionic acid gene of acrylic and be adsorbed on the fiber, and compete with the cations for the dyeing seat, thus affecting the dyeing effect. Therefore, the water must be softened when dyeing. If the water hardness is too high, it will often cause dyeing. Especially when dyeing very light colors, it can easily cause defects such as yellow spots and spots.
2. Dissolution of materials:
Ionic dyes are generally used Make a slurry with acetic acid (60%), and then add 40-50 times the amount of boiling water to dissolve it. When the dye is made into a slurry with glacial acetic acid, it must be stirred sufficiently to prevent the dye particles from becoming lumpy.
3. Dye bath PH value:
Cationic dyes are generally It is not resistant to alkali. Adding acetic acid and sodium acetate to the dye bath as a buffer can adjust and stabilize the pH value of the dye bath. The pH value of 4-4.5 is the best range for cationic dyeing.
4. Electrolyte
Yuanming powder (Na2SO4) is commonly used The amount of inorganic retarder used for dyeing light colors can be higher, about 5-10% (heavier for fabrics), but it can be omitted for dyeing heavy colors.
5. Cationic surfactant
1227 is commonly used in acrylic dyeing The retarder has good leveling effect and can effectively slow down the dye uptake rate of cationic dyes.
The amount of 1227 generally depends on the depth of dyeing. Add more when dyeing light and dark. When dyeing acrylic fiber, too much 1227 will affect the dye solution. When absorbing the dye, in order to repair or modify the dyed product, 1227 can be used to strip the dye in an acetic acid bath.
6. Bath ratio:
Dyeing bath for cationic dye acrylic fiber There is a certain relationship between the dyeing strip and the amount of color obtained. A large bath ratio will lead to slow dyeing and a loss of color. If the bath ratio is too small, it is easy to cause color blooming.
7. Compatibility of cationic dyes
Different cationic dyes When mixed together for dyeing, they may have a different dyeing rate than when they are dyed individually, so the compatibility of dyes is a very important performance.
When two dyes are mixed for dyeing, if the dyeing rate of each dye is equal and the proportion of each dye amount in the dyed fiber remains unchanged as the dyeing time increases, then the dyeing The color tone of the object remains basically unchanged throughout the dyeing process, and the two dyes are compatible.
If the compatibility is inconsistent, not only the color concentration results will change with time during the entire dyeing process, but the hue will also change with time, making it difficult to obtain consistent color. Products are prone to color differences.
The compatibility properties of cationic dyes are generally obtained through mutual comparison. The most widely used one at present is the compatibility value, whose symbol is K.
The compatibility performance of dyes is the comprehensive effect of the affinity and diffusion performance of dyes to fibers. It is mainly determined by the affinity of the dye, the diffusion coefficient and the number of charges carried by the dye. In the case of the same charge number, a dye with high affinity and small diffusion coefficient and a dye with low affinity and large diffusion coefficient may have the same dyeing rate.
8. What is the maximum adaptable temperature for acrylic fiber dyed with cationic dyes? Why?
1), the maximum suitable temperature is 97-105℃;
2), because the dyeing temperature is too high, acrylic fiber will produce Excessive shrinkage will make the hand feel hard and the fabric deformed. If the temperature is too low, the dyeing and leveling properties will be poor
9 , in order to improve the dyeing effect of cationic dyes, what measures can be taken; the specific methods are as follows
1), control the temperature
①Below 80℃, the heating speed can be faster;
②Above 80℃, the dyeing amount increases quickly, and the heating speed should be strictly controlled;
2) Use retarder:
Leveling agents, such as 1227 or Yuanming powder, can be added during the dyeing process to improve the leveling effect;
3), control the pH value
The pH value should be controlled at 3-5
① When the color is light, the PH value should be lowered to facilitate level dyeing;
② When the color is dark, the PH value can be appropriately increased to facilitate dyeing;
B. Dyeing process analysis
1. Dyeing curve:
2. Adding sequence:
Leveling agent (Yuanming powder) → Glacial acetic acid → Dye
3. Dye liquor composition and various auxiliaries Function:
Dye
Leveling agent 1227
Glacial acetic acid ( Sodium acetate)
Yuanming powder
1), leveling agent 1227
Function: to achieve uniform dyeing effect 0.21%;
2), glacial acetic acid
Function: to adjust the PH value PH =3—5
PH↓ → Dyeing percentage ↓
Requirements:
① Light color: more acid is used, PH value = 3-4.5 is good for level dyeing;
② Dark color: less acid is used, PH value is�=4-4.5 is conducive to dyeing;
3) Yuanming powder:
Function: used as a dye retardant, Conducive to leveling dyeing
4. How to mix and add materials:
1) Chemical ingredients: (beat with cold water → dissolve in boiling water)
1/2 HAC + a small amount of water → add boiling water to dissolve and stir thoroughly
Slurry
2), Adding materials:
5. Cation What are the cooling requirements for dye dyeing?
1) Temperature rise
It is required to strictly follow the process curve to heat up, otherwise heating up too fast will cause color blooming;
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① Temperature＜80℃, dyeing is slow, and the temperature can be raised quickly;
② Temperature＞80℃, dyeing is fast, should be used Gradually raise the temperature;
③ The purpose of keeping the temperature at 80℃ for a certain period of time is to make the dye evenly adsorbed by the fiber to prevent color blooming;
2) Cooling:
After dyeing, the fabric should be slowly cooled to 50°C before washing. Otherwise, cooling too quickly will cause wrinkles on the fabric and make it rough to the touch;
C. Operation points:
1. The dye must be fully dissolved and the materials must be added. Slowly and evenly;
2. Strictly control the heating rate to prevent color blooming;
3. Sufficient heat preservation to ensure that the dyeing reaches Level dyeing effect;
4. The temperature should be cooled down slowly, and the temperature must not be dropped suddenly to prevent the fabric from wrinkles and rough feel.
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