Black is one of the highest volume shade dyed on cotton& synthetic textile material having all time great demand especially forcasual wear (denims & garments). Amongst all the classes of dyestuffs, Sulphur black is an important class of dye for the colouration of cellulosics, being intoexistence for nearly a hundred years.

 

 

The good fastness properties, cost effectiveness & easeof applicability under different processing conditions exhaust, semi-continuousand continuous make it one of the most popular dyestuffs. Further, a widechoice of selection of various forms conventional, leuco and solubilised formis the major factor contributing to the continuous existence &ever-increasing demand for this class of dyestuff.

 

Growth scenario

Indian Textile Industry is expected to grow from Current US$ 40 bil to US $ 95 bil by 2010. India is the third largest producer of Cotton after China & the USA. While growth story is due to Exports and a rise inDomestic demand, India is also a Global alternative to China in several categories of Textile products.

 

The world textile Dyestuffs market is expected to reach US $5.9 bil in 2010, with a CAGR - 3.8 %. India s share in the world market isabout 6.8 %. In the world market, Sulphur Dyes is expected to account a shareof about 6%.

 

Textile dye classes - World market size

 

Sr. No.	DYE CLASS	%SHARE
1	Disperse	35
2	Reactive	28
3	Acid	12
4	Direct	7
5	Vat + Indigo	8
6	Azoic + Other	4
7	Sulphur	6
	총	100

 

ATUL Ltd. founded in 1947, is the only major Indian dyestuffmanufacturing organization, dedicated to manufacturing almost all classes ofdyestuffs for natural & synthetic colouration - Vat dyes, all classes ofReactive, Direct, Napthol-Bases, Sulphur, Acid, Disperse & Pigment Powder.The state of the art manufacturing plants spread over 1200 acres land, with thebiggest Sulphur Black manufacturing site in India producing more than 4500 MTper annum. All forms of Atul Sulphur Blacks are environment friendly & GOTSapproved.

 

Different forms of Sulphur Dyes

 

Basically Sulphur dyes belong to reductionoxidation-dyeingsystem. Though Sulphur Black is a leading member, demand for other colors likeGreens, Navy Blue, Browns, Bordeaux, Khakhi & Olives is also increasing.

 

The environmental pollution problems associated withconventional dyeing systems involving use of Sodium Sulphide as a reducingagent is addressed by use of a non-polluting system consisting Glucose +Dithionate resulting in ecological advantages.

 

Atul Sulphur Blacks are available in Grains, Ready to useLiquid form as well as Solubilised form & known for:

 

 

Character - high tinctorial value, good solubility & better penetration

 

Performance excellent level dyeing, high build-up & shade consistency

 

Properties high light, wash & perspiration fastness. Moderate crocking & poor Chlorine fastness (advantageous in Denim washing)

 

 

 

Product	CI Generic Name	Form	Major Applications
Atul Sulphur Black Grains OG, Grains Extra OG Exp., Grains, GXE & Grains AR.	C.I. SULPHUR BLACK 1	Water insoluble, Grains, Made substantive to cotton by Reduction process	Cotton fabric dyeing in Jigger. Knit dyeing in soft flow. Yarn dyeing by standing bath technique in handloom sector.
Atul Sulphur Black G & G H/C	C.I. LEUCO SULPHUR BLACK 1	Pre-reduced & stable liquid, Leuco form, substantive to Cellulosic as such, Low Sulphide content	Denim dyeing (warp sheet & rope ). Continuous dyeing of cotton fabric Pad- Steam. Garment dyeing in drum dyeing machine, Knit dyeing in soft flow
Tulasol Black G & G H/C	C.I. SOLUBILISED SULPHUR BLACK1	Solublised form, non - substantive to Cellulosics as such and becomes substantive by reduction	Package dyeing of cotton yarn & fibre. Continuous dyeing of cotton fabric.Pad - Dry Pad - Steam. Knit dyeing in soft flow

 

 

Some major usage & dyeing systems for Suphur Black dyeing are

 

1. Eco friendly Red-Ox systems

 

Reducing System

Polluting Sodium Sulphide

Non-polluting Glucose + Hydros + Caustic Soda,

Glucose + Caustic Soda, Alkaline Sodium Sulphoxylate Formaldhyde, Alkaline Hydros

, Thiourea Dioxide, Sodium Borhydride, Thioglycolic Acid, Hydroxy Methane Sulphinilic Acid.

 

Oxidizing System

Polluting Potassium Dichromate + Acetic Acid

Non-polluting Hydrogen Peroxide + Acetic Acid, Sodium Per Borate + Acetic Acid, Air Oxidation, Alkaline Solution Of Sodium Chlorite.

 

 

2. Topping System

 

This is an approach for getting a wide range of shades using Sulphur (major portion) and other class of dye (smaller portion).

 

The advantages are - economy & better fastness properties.

 

Suggested systems -Sulphur topped with Reactive/Direct/Vat/Azoic

Or Azoic topped with Sulphur, Vat topped with Sulphur.

 

Popular dyed shades are Greens, Olive, Navy, Maroon & Brown.

 

 

3. Denim yarn dyeing

 

Liquid Sulphur Black is extensively used for Denim yarn dyeing either by warp sheet (Slasher dyeing) or Rope dyeing system for obtaining.

 

Black Denim, Sulphur bottom with Indigo Topping, Indigo bottom with Sulphur Topping, Indigo+ Sulphur bottom and Indigo + Sulphur Topping

 

4. Standing Bath Technique Handloom Sector

 

It is a popular practice for coloring cotton yarn in handloom sector and in this approach; the spent dye bath is being replenished for subsequent dyeing. The major advantages are -water & steam conservation, reduced effluent load, High productivity & saving of dyes & chemicals. It can be defined as Continuous Exhaust dyeing.

 

5. One bath two step P/C blend dyeing using Tulasteron / Duratic Disperse dyes + Atul Sulphur Black for cost effective Jet black shade

 

The Polyester part is dyed first with Disperse dyes & without intermittent reduction clearing the cotton is dyed with Atul Sulphur Black.

 

The advantages are - time, water & energy conservation, minimum loading & unloading operations. Avoiding reduction clearing after Polyester dyeing due to the usage of Caustic Soda + Hydros during Sulphur Dyeing.

 

SOLUTION PROVIDING APPROACH

 

Difficulties Experienced	Areas of concern & remedial measures
Unlevelness during cotton woven dying on Jigger / Cotton Knit In Soft Flow.	Proper dye dissolution, uniform pretreatment of fabric. Ensuring optimum dye-reduced condition, Good over-flow rinse /sharpener wash before oxidation.
Poor dry & wet rub fastness.	Proper soaping off. Good over-flow rinse /sharpener wash before oxidation. Finishing with polymeric softener.
Dye bath stability & colour In-consistency in Denim colouration and continuous dyeing	Use of appropriate quantity of reducing agent/ anti-oxident, anionic wetting agent, sequestrant & uniform pH control.
Ending (variation from end to end fabric roll) and Listing (center to selvedge variation) in Jigger dyeing	Adding the dye in installments during different ends, Maintaining uniform dyeing temperature through out the dye bath, Use of closed Jigger.
Spotting & speckiness in knit dyeing on soft flow	Proper dye dissolution. Use of adequate sequester ant & dispersant. Controlled dye reduction.
Tailing during continuous dyeing with Pad Steam process	Maintaining uniform dye reduction during steaming. Ensuring uniform pretreatment of the substrate,
Crease marks / rope marks in Garment dyeing in drum dyeing machine	Use of adequate anticrease lubricant, Maintaining proper Material to Liquor ratio
Shade variation in knit dyeing	Maintaining uniform dyeing time & temperature.
PH variations in Padding	Check bicarbonate alkalinity of water. Use caustic soda in the pad liquor for adjusting pH.
Seeking greener or redder tone	Varying the quantity of reducing agent & anti-oxidant.

 

 

Inferior crocking and bronziness	Proper dye dissolution. Thorough overflow rinsing & sharpener wash before oxidation. Good soaping after oxidation for removing unfixed dye. Final t reatment with TRO and Ammonia.
Stripping of faulty dyeing	P artial stripping - Treatment with Sodium Sulphide + wetting agent+ sequestrant & Caustic Soda with Sodium Hydrosulphite   Total stripping -Treatment with Sodium Hypochlorite
Tendering of cotton	Strength loss of dyed goods during storage   due to liberation of acid (Sulphur present in the dyed substrate, getting oxidized to Sulphuric Acid in presence of atmospheric Oxygen & moisture)   Treatments - Soda Ash -2-3 g / l, Sodium Acetate 2-3 g / l, Resin Finishing

 

 

The major future trends are -

 

Extensive use of Sulphur Liquid Blacks & Sulphur liquid Colours for Denim Colouration

Pollution free practices - using Eco-Friendly reducing & oxidation systems

Applications on Paper & Leather colourations