Cotton fabric dyeing with the basic dye:
Table of Contents
Since Cellulose does not have an acidic group, Auramine, Magenta, Methyl, Methyl violet, etc. (Lower washing fastness) have no affinity to Cellulose of other basic dyes except a few. Therefore, before dyeing cellulose fiber with a basic dye, it must be mordanted. Cotton and basic dye application can be divided into two parts. https://bdfabric.com/dyeing-of-jute-fabric-with-basic-dye/
(1) Dyeing with mordanted cotton.
(2) Topping process.
(1) Dyeing with mordanted cotton:
This method can be divided into three different parts.
(c) Aftertreatment (not required in all cases)
(a) Cotton fabric dyeing with basic dye-Mordanting:
Tannic acid → 4% (When dye 2%)
Water → 20 – 30 times
Temperature →60 – 1000C
Time → 2 hours – overnight.
Tannic acid Used as mordant. In the traditional process, with double the amount of tannic acid of dye, it is mordanted to cotton. When cotton is added to this tannic acid solution, its temperature must first be raised to boil and then to temp.
Must be lowered to 600C. The material can be kept for two hours or overnight in this Temp. To increase the affinity of Cellulose towards Tannic acid. The material is then taken out and squeezed and treated with Tartar Emetic to fix up the tannic acid.
# fixing recipe:
Tartar Emetic →2%
Water →20 – 30 times
Temperature → room temperature
Time → 30 minutes
The resulting mordanted cotton is then immersed in half the amount of tannic acid in a solution of tartar emetic for 30 minutes and stirred. As a result, tannic acid is fixed up in cotton.
Dye: Tannic acid: tartar emetic = 2: 4: 2
= 1: 2: 1
Dye (Rhodamine) → 2%
Acetic acid → 1 – 3%
Water →20 times
Dyestuff is first pasted with the same amount of acetic acid or methylated spirit. Here CH3COOH acts as retreading agent. An adequate amount of boiling water is then added and dissolved by stirring. In this way, a stock solution of dye is made. Thus the dye solution is divided into three equal parts.
In the first part, Dye solution with 1-3% CH3COOH is prepared and it is reacted with cold conditioned mordanted cellulose (Cotton) for 15 minutes. Then the second part of the dye solution is added to it and the material is kept for 20 minutes at a temperature of 30-40°C. Finally, the rest of the dye solution is mixed with the material, the temperature is raised to 70°C and it is kept for 25 minutes and after the dyeing is completed the material is lifted.
(a) The water used in Dye solution must be mild, otherwise, a water softening agent must be used.
(b) The prepared dye solution has to be thoroughly scrubbed before use, otherwise, dye particles float on top of the dye solution in an insoluble state and this causes stains on the fabric.
(c) Iron containers should not be dyed. Because dye, in contact with iron can become shade dull.
(d) Dye solution has to be added into several parts.
(2) Cotton fabric dyeing with basic dye-Topping Process:
The topping method is used to get a bright shade. In this case, fastness also increases in dye. Fabrics dyed with direct dye are topped with basic dye. Because indirect dye – there is SO3Na group, which creates anion through ionization. This anion reacts with basic cotton as follows.
D – SO3Na++ R4– N+CI– → D – SO3N = R4 + NaCl
Basic dye weighing half the weight of direct dye is treated with 1 – 3% CH3COOH in cold condition for 15-20 minutes.