Scouring - Definition of Scouring

Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing.. Even though these impurities are not soluble in water,

SCOURING

Name : MAZADUL HASAN SHESHIR

ID: 2010000400008

Batch: 13th Batch (Session 2009-2013) Department: Wet Processing Technology Email: mazadulhasan@yahoo.com

Blog: www Textilelab.blogspot.com

Southeast University

Department of Textile Engineering

PREPARED BY ©right

Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils Mill grease used to lubricate processing equipment mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced The process of removing these impurities is called Scouring

Even though these impurities are not soluble in water, they can be removed

by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water soluble components

Definition:

The tern scouring applies to the removal of impurities such as oil, wax gum, soluble impurities and solid dirt commonly found in textile material The process consists essentially of treatment with alkali, a good supply of water is essential

Scouring:

Types of Scouring Treatments :

1 Scouring By Chemicals Means

2 Bio scouring or scouring with Enzymes

Objects: - The main object of this process is to iron the fabric.

1 To remove natural as well as added impurities of essentially hydrophobic character as completely as possible

2 To increase absorbency of textile materials

3 To leave the fabric in a highly hydrophilic condition without undergoing

physical or chemical treatment or damage

4 Remove all natural impurities such as oil , wax , fat etc from the surface

of the fabric

5 Produce the fabric more hydrophilic

6 Increasing the absorbency and clean the fabric by use alkaline

7 To make the suitable situation for next bleaching, dyeing, printing, and

finishing process

8 Removing the natural coloring matter of the cotton fabric

Objects Of Scouring:

Scouring is the process which is removes all the natural impurities like oil wax fat etc, from the surface of the fabric and produce the fabric more hydrophilic, Scouring done by using alkali such as NaoH & Na2Co3 Natural impurities of cellulosic fabric are normally removed by boiling off in a strong alkaline solution The main object of scouring cotton fabrics is to remove natural as well as added impurities of essentially hydrophobic character as completely as possible and leave the fabric in a highly absorptive condition without undergoing chemical

or physical damage significantly

3C17 – COOH + 3NaOH= 3C17H35COONa +3H2O

Or Oil + Caustic =Soap + Glycerine

There are three types of scouring:

SCOURING BLEACHING CURVE

Chemical Use

Caustic (NaOH) Neutralize acidic materials, saponify glycerides (Waxes and

Oils), and solubilize silicate.

Sodium Silicate Penetrate and break down lignins in motes.

Surfactant Reduces surface tension and minimize interfacial tensions Detergent Emulsify oils, fats, and waxes; remove oil – borne stains;

suspend materials after they have been removed.

Chelating

(Sequestering) agent

Deactivate metal ions.

Builder (Salt) Cause detergents to become increasingly effective.

Solvent Assist emulsification by dissolving oily materials.

Chemical Used and Purpose:

Scouring process depends on:

-1 The type of cotton

2 The color of cotton

3 The cleanliness of cotton

4 The twist and count of the yarn

5 The construction of the fabric

Scouring process depends on:

- Yarns and fabrics may be dirty, contain natural waxes or oils, or have been treated

with size or lubricants used in spinning, weaving or knitting

 These can all interfere with dyeing, often leading to non-level results Scouring is a

large topic, and the process used depends on the fibre type and its condition

 “True” scouring of greige cellulosic fabrics is typically done, after desizing, at the

boil or at higher temperature in pressure vessels, with as much as 10 grams sodium hydroxide per litre of water, plus surfactants, and the process may last for several hours

 Commercial scouring of wool may use solvents, similar to dry cleaning, as part of

the process White fabrics sold at retail have normally be scoured at the mill;

“natural” fabrics usually have not (some “natural” fabrics have been scoured but not bleached)

SCOURING

 Art dyeing literature often refers to what amounts to laundering as scouring

This is inadequate for greige fabrics, but often quite acceptable for “white

goods”

 A long machine wash with the hottest water possible, about a gram of soda ash

per litre of water (about a teaspoon per gallon) and some (preferably optical brightener free) detergent, followed by two rinses is usually acceptable

 Sodium hexametaphosphate may be helpful if the water is hard Woven white

cottons often contain starch that will not be removed by such a limited

process

Theory of Scouring:

Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils Mill grease used t o lubricate processing equipment mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced The process of removing these impurities is called Scouring

Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water

Theory of Scouring

SN SCOURING AGENT CHEMICALS

1 Alkaline agents

NaOH, KOH, Na2CO3, Liquid NH3 sod metasilicate, sod silicate, sod phosphate, trisodium phosphate, tetrasodium phosphate, sodium tripolyphosphate and borax

2 Surfactants Anionic activator, non-ionic activator

3 Organic solvent

Chlorine system: Carbonate trichloride, trichloroethylene, perchloro ethylene, methyl chloroform, trichloro methane, fluorine

Hydrocarbon system: Benzene, industrial gasoline, white spirit, solvent naphtha

SCOURING AGENT

Impurities Mechanism of impurity removal

Fats and waxes

 Saponification: The saponifiable parts of waxes (fatty acid, glycerides, and esters) are converted in to soap.

 Emulsification: The non-saponifiable parts of the waxes such as alcohols and hydrocarbons are emulsified by the soap formed.

 High temperature: melts some of the waxy materials and converts some of it to a water soluble form.

 In extreme cases the use of solvent is necessary.

Pectin and related

 Partially dissolve in NaOH

 By use of sequestering or chelating agents.

 By producing more soluble salt e.g acid demineralisation

IMPURITIES OF SUBSTRATE

A typical adopted approach in past towards Enzymatic Scouring

process of cotton fabrics

An illustration of various steps identified to achieve fast and efficient

Enzymatic Cotton Scouring process.

Procedure of Scouring Process:

Procedure of Scouring Process:

The main processes occurring during scouring are:

1 Saponification of fats into water-soluble soap and water-miscible glycerin under alkaline conditions,

2 Hydrolysis of proteins into water-soluble degradation products,

3 Dissolution of hydrolysis to ammonia of simpler amino compounds,

4 Conversion of pectose and pectin into their soluble salts,

5 Dissolution of mineral matter,

6 Emulsification of unsaponifiable oils and waxes, and

7 Removal of dirt particles from the kier liquor by the detergent present therein

Alkaline Enzyme Scouring of Cotton Textiles

The invention relates to a process for treatment of cellulosic material, as for example, knitted or woven cotton fabric, comprising the steps of preparing an aqueous enzyme solution comprising pectinase, treating the cellulosic material with an effective amount of the aqueous enzyme solution under alkaline scouring conditions; e.g., pH of 9 or above and a temperature of 50° C

or above, in a low calcium or calcium-free environment, yielding a modification of the cellulosic material such that exhibits an enhanced respond to a subsequent chemical treatment

Traditionally, cotton scouring has required the use of harsh alkaline chemicals (caustic), extreme temperatures and large volumes of water Expenses include not only the cost of the caustic and energy, but also the cost of treating waste water to remove residual caustic and by- products

Today, textile producers have a new, effective alternative to chemical scouring with the advent

of the Cottonase™ enzyme This novel enzyme not only cleans better than chemical scouring, but also greatly reduces the need for extensive waste water treatment and energy consumption The Cottonase™ enzyme is a versatile, economically viable and environmentally friendly alternative to chemical scouring in cotton preparation.

Alkaline Enzyme Scouring of Cotton Textiles

1 Simply wash your fabric, this includes PFD fabric, in the washing machine in hot water with Soda Ash Do not add any fabric softeners to the wash If you must dry your fabric

do so without any fabric softener sheets

2 Using an large enamel or stainless steel pot, fill the pot at least half full and place one ounce of soda ash into the pot per pound of cotton or linen fabric/fiber.

3 Place fabric into water, swish it around using a stainless steel spoon.

4 Bring water to a boil!!!

5 Adjust heat to a low boil/hard simmer and allow to boil for two hours stir the fabric every 15 minutes or so t make sure that the fabric is being adequately scoured

6 After two hours remove from heat source, allow fabric to cool down until the fabric is

at room temperature

7 Remove the fabric from the water and rinse

How to Scouring Textile Fabric:

Scouring Treatments of Cotton, Silk, Wool and Synthetics Materials

Natural fibers contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing Synthetic fibers contain producer spin finishes, coning oils and/or knitting oils, Mill grease used to lubricate processing equipment, mill dirt, temporary fabric markings and the like may contaminate fabrics as they are being produced.

The process of removing these impurities is called Scouring Even though these impurities are not soluble in water, they can be removed by Extraction, dissolving the impurities in organic solvents, Emulsification, forming stable suspensions of the impurities in water and Saponification, Converting the contaminates into water soluble components.

Scouring is usually carried out by means of continuous or discontinuous systems, with the same machines used for downstream treatments; temperature, processing time, pH, concentration of reagents, depend on the fibre,whiteness required and on the machine used.Incomplete scouring processes usually originate dyeing and printing defects due to different degrees of wettability and to inconsistent affinity for dyes of the material.

Scouring Treatments of Cotton, Silk, Wool and Synthetics Materials

Scouring of Cotton

In the scouring process the cotton cellulose material is treated with a solution containing alkali ( soda ash and caustic soda), an anionic and/or nonionic detergent, a wetting agent, a complexing and sequestering for the removal of metal ions and polyacrylates or polyphosphonates as special surfactant free dispersing agents, at high temperature.

The scouring operation was conventionally done in kier machines and hence the process was called kier boiling , but now a days the scouring is done mostly in the dyeing machines itself as a part of combined or single operation such as scouring and bleaching.

 Saponification of fats into water soluble soap and water miscible glycerin under alkaline conditions.

 Hydrolysis of proteins into water soluble degradation products.

 Dissolution of amino compounds.

 Solubilising of pectose and pectins by converting into soluble salts

 Dissolution and extraction of mineral matter.

 Emulsification and solubilisation of natural oils and waxes.

 Removal and dispersion of dirt particles and kitty by the action of alkali and detergent The material after scouring is more absorbent , free from natural impurities and coloring matter.This treatment can be carried out on filaments, yarns and fabrics.

Scouring of Cotton

Scouring of Silk

The scouring of pure silk is a degumming process used to remove sericin (silk gum) from fibroin floss Sericin is the gummy element which keeps together the fibroin floss and gives the silk a hard hand and dull appearance It is carried out

on yarn, on dyed yarn, piece-dyed fabric or on products ready for printing The treatment, which causes a loss of weight ranging between 24 and 28%, gives the degummed silk a lustrous appearance and a soft hand; the treatment is carried out with soapy solutions or with buffer dissolving agents It is also possible to use enzymes (protease), which hydrolyses sericin

Scouring of Silk

Scouring of Wool

On wool, the scouring process removes oils and contaminants accumulated during upstream processing steps and can be carried out on slivers, yarns and fabrics with solutions containing sodium carbonate with soap or ammonia, or anionic and non-ionic surfactants, which carry out a softer washing to avoid any damage to the fibres

Scouring of Synthetics

The scouring process applied to synthetic fibres removes oils, lubricants and anti-static substances, dust, contaminants and can be carried out on yarns and fabrics (when warp yarns have been bonded, the treatment is called debonding) It is carried out by means of surfactants, detergents and emulsifying agents

Scouring of Wool- Synthetics

Scouring of Polyester/Cotton Blends:

Polyester and cotton are two different fibers obtained from natural source and made of synthetically consecutively Because of varying physical (Length, diameter, strength, elasticity, torsional rigidity, frictional properties) and chemical properties (thermal properties, density, resistance to chemical agents) of these two fibers have led to treat this blend within proper conditions.Cotton has very good resistance to alkalis but the action of aqueous alkalis may lead an adverse impact on polyester It should not be pressure kier boiled in the presence of alkalis, as these conditions favor an accelerated attack on the fiber

Scouring of Polyester/Cotton Blends: