Basic Principles And Production Process Parameters Of Cationic Dyes

Issues Related to Dyeing:

The determination of the optimal dyeing process mainly takes into account factors such as dyeing temperature, dyeing PH value and the application of auxiliaries

Water quality

When dyeing acrylic with cationic dyes, water quality is of great significance. If the water contains calcium and magnesium ions, they can combine with the anionic acidic groups of acrylic and adsorb onto the fibers, competing with cations for dyeing spots, thereby affecting the dye's upline and color vividness. Therefore, the water must be softened during dyeing. If the water hardness is too high, it often leads to uneven dyeing, especially when dyeing extremely light colors. It is very likely to cause defects such as macules and pigmentation.

Dissolution of materials:

Nowadays, ion dyes are generally made into a paste with acetic acid (60%), and then 40 to 50 times the amount of boiling water is added to dissolve them. When dyes are made into a paste with glacial acetic acid, they must be thoroughly stirred to ensure that the dye particles do not form lumps or granules.

PH value of the dye bath

Cationic dyes are generally not resistant to alkali. Adding acetic acid and sodium acetate as buffers to the dye bath can adjust and stabilize the PH value of the dye bath. The optimal PH range for cationic dyeing is 4 to 4.5.

Electrolyte

Sodium sulfate (Na2SO4) is a commonly used inorganic retarder. For light colors, the dosage can be higher, about 5-10% (depending on the weight of the fabric), but it can be omitted for dark colors.

Cationic surfactant 1227 is a commonly used retarder in the dyeing of acrylic fibers. It has a good leveling effect and can effectively slow down the dye uptake rate of cationic dyes.

The amount of 1227 is generally determined by the depth of dyeing. For light dyeing, a more amount is needed; for dark dyeing, a more can be added. When dyeing acrylic, excessive use of 1227 May affect the absorption of dye in the dyeing solution. To restore or modify the dyed product, 1227 can be used for color stripping in an acetic acid bath.

Bath ratio

The dyeing bath ratio of cationic dye acrylic has a certain relationship with the dye strip and the color yield. A large bath ratio leads to slow coloring and poor color yield. If the bath ratio is too small, it is easy to cause color streaking.

The compatibility of cationic dyes is related to the staining pattern:

The compatibility values can be 1, 2, 3, 4, or 5

Low compatibility value leads to fast dyeing rate but poor leveling property

High compatibility value → slow dyeing rate, good leveling property;

2) When matching colors with dyes, dyes with the same or similar compatibility (±0.5) should be selected to prevent color streaks.

3) When dyeing with a single dye, it is easier to achieve a uniform dyeing effect by choosing dyes with a high K value.

What is the maximum applicable temperature for dyeing acrylic fiber with cationic dyes? Why?

The maximum suitable temperature is 97 to 105 degrees Celsius.

2) Due to excessively high dyeing temperatures, acrylic fibers will undergo excessive shrinkage, making the hand feel hard and the fabric deformed. If the temperature is too low, the penetration and even dyeing properties will be poor

What measures can be taken to improve the dyeing effect of cationic dyes? The specific measures are as follows

1) Control the temperature

Below 80℃, the heating rate can be faster.

Above 80℃, the dye uptake increases rapidly, and the heating rate should be strictly controlled.

2) Select dye retarders:

Leveling agents such as 1227 or mirage can be added during the dyeing process to enhance the leveling effect.

3) Control the PH value

The PH value should be controlled between 3 and 5

When the color is light, the PH value should be reduced to facilitate even dyeing.

② When the color is dark, the PH value can be appropriately increased to facilitate staining.

Analysis of Dyeing Process

Dyeing curve

Sequence of adding materials

Leveling agent (mirabilite) → glacial acetic acid → dye

Composition of dyeing solution and functions of each auxiliary agent:

Dye

Leveling agent 1227

Glacial acetic acid (sodium acetate

"Yuanmingfen"

1) Leveling agent 1227

Function: To achieve a uniform dyeing effect of 0.21%;

2) Glacial acetic acid

Function: Regulate PH value, PH=3-5

PH↓ → Staining percentage ↓

Requirement

① Light color: A large amount of acid is used, and a PH value of 3 to 4.5 is beneficial for even dyeing.

② Dark color: Less acid is used, and a PH value of 4-4.5 is conducive to staining.

3) Mirabilite

Function: As a retarder, it is beneficial for even dyeing

How to prepare and add materials:

1) Material dissolution: (Beating with cold water → dissolving in boiling water)

1/2HAC+ a small amount of water → Dissolve in boiling water and stir thoroughly

Paste-like

2) Feeding:

What are the requirements for cooling down when dyeing with cationic dyes?

1) Heat up

The temperature rise must be carried out strictly in accordance with the process curve; otherwise, if the temperature rises too fast, it will cause the color mottling phenomenon.

① When the temperature is less than 80℃, the dyeing process is slow and can be heated up quickly.

When the temperature is above 80℃, the dyeing process is fast, and a gradual increase in temperature should be adopted.

The purpose of maintaining the temperature at 80℃ for a certain period of time is to ensure that the dye is evenly adsorbed by the fibers to prevent color bleeding.

2) Cooling:

After dyeing, the fabric should be cooled down slowly to 50℃ before being washed with water. Otherwise, if it cools down too quickly, the fabric will develop wrinkles and feel rough.

Key Points of Operation:

The dye should be fully dissolved and the material should be added slowly and evenly.

Strictly control the heating rate to prevent color bleeding.

Sufficient heat preservation is ensured to achieve uniform dyeing effect.

The cooling should be done slowly. Do not cool down suddenly to prevent the fabric from getting wrinkles and feeling rough.