Dyeing of cotton fabric with sulpher dye

Theory: Water insoluble dyes have to be converted into water soluble from (leuco from). Sulpher dye is a insoluble dye. Then lecuo from is colorless from with an alkaline liquor. This color returns after oxidation.  This conversation (insoluble soluble) is carried out by dilate aqueous solution of sodium sulphide.

Dye Type : Sulpher Dye
Fabric type :Cotton
Color : Ash

This leuco compound have affinity toward cellulosic fiber and they are sensitive to atmosphere oxygen. This reduced from of sulpher dyes absorbed by fiber substance and dyeing occurred and finally again converted into insoluble from of dye by chemical oxidation with Na/K dichromate.

Dye – S – S – Dye + 2[H] → Dye – SH + dye – SH

Dye – SH + [O] → Dye – S – S – Dye + H₂o

Recipe:

Sulpher Dyes = 8%

Na₂CO₃ = 5 g/l

Na₂S = 8 g/l

Wetting agent = 1 g/l

Sequestering agent = 1 g/l

Temp = 85°C

Time = 40 min

Sample weight =5 gm

P^h =10

Neutralization:

CH3COOH = 1 g/l

K₂Cr₂O₇  = 1 g/l

Temp = 50°C

Time = 10 min

Soaping:

Detergent = 1 g/l

Time = 10 min

Temp = 95 °C

 Friction of the chemical required:

Wetting agent: It accelerates the wettability of material in solution thus helps to easy penetration of chemicals into substrate.

Sequestering agent: it one kind of surfactants surface active agent act in solid liquid , solid gas or liquid gas interfaces and reduces the interfacial tension.

Reducing agent: The chemical compound which losses electron during chemical reaction. It reduces other substrates chemically especially by during on electron.

 Recipe calculation:

Dye: 100 gm fabric for  8 gm dye

           1     gm        “     “    8/100 “

            5   gm        “   “         8×5 / 100 “ = 0.4 gm

Water: 200 gm [ m:L = 1:40]

Na₂CO₃  = 1000 CC water, Na₂CO₃  required = 5 gm

                    1              “              “               “      =5 / 1000 “

                    200          “                “             “      = 5 × 200 / 1000    gm = 1g

Similarity,

Na₂S = 1.6 g/l

Wetting agent = 0.2 g/l

Sequestering agent = 0.2 g/l

CH₃COOH = 0.2 g/l

Detergent = 0.2 g/l

K₂Cr₂O₇  = 0.2 g/l

Curve

                         

Cotton Fabric Dyeing 101

Conclusion: Sulpher dye have been in practical commercial use in most of the countries of the world for many decades. During ability flexibility of application etc. The main characteristis of this class of dye of all sulpher dyes, block, blue and brown dyes are the most important from the standpoint of tonnage.