Source: Atul Ltd (Colors Division), Valsad, Gujarat, India


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


The good fastness properties, cost effectiveness & ease of applicability under different processing conditions exhaust, semi-continuous and continuous make it one of the most popular dyestuffs. Further, a wide choice of selection of various forms conventional, leuco and solubilised form is 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 in Domestic 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 is about 6.8 %. In the world market, Sulphur Dyes is expected to account a share of 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


Total

100


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


Different forms of Sulphur Dyes


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


The environmental pollution problems associated with conventional dyeing systems involving use of Sodium Sulphide as a reducing agent 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 use Liquid 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


About the Source:


For further information on Individual dyestuffs & application processes, contact us at nsk@atul.co.in



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