After treatment of direct dyes

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After treatment of direct dyes:


After dyeing the product, all the treatments that are done to increase the fastness of the colored object such as light fastness, washing fastness, etc., are called after treatment. After dyeing by after treatment, the dye particles are insoluble inside the fiber.

After treatment of direct dyes. To achieve the purpose of dyeing, dye is converted into a complex compound or dye molecular size is increased, which increases wet fastness. After treatment is the chemical reaction between the dye and the after-treatment agent, depending on the functional group present in the molecule. Not all after treatments can be used on all direct dyes. These are used only as recommended by dye manufacturers.

After treatment of direct dyes-Purpose:

1. The fastness of Direct Dye is not good after treatment is done to increase the fastness quality.

2. Some treatments increase the dye molecular weight of the colored object.

3. Some of them make the dye insoluble in the fiber, which increases the weight fastness.

Different methods of after treatment:

The after-treatment procedure is performed differently depending on the function group and the position of the group in the dye. E.g.

1. After treatment with a different metallic salt

A) After treatment (with cu – Salt) with copper salt

B) After treatment with Chromium Salt (With cr – Salt)

2. After treatment with formaldehyde

3. After treatment with diazotization and coupling

4. After treatment by coupling with diazotized base

5. After treatment with cationic fixing agents

6. After treatment by topping with basic dyes

7. After treatment with resins

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