The PresentationOnECO FRIENDLY TEXTILE PROCESSING
UNDER THE GUIDANCE OFProf. (Dr.) M.D.TELI BYOmkar S. ParmajAlemayehu Leta
A good preparatory process has several objectives
Removal of loose hairy protruding fibres from the surface of the fabric to give a smooth, even and clean looking face.
Removal of natural impurities like oils, fats, waxes, greases, natural matter, lignin and sizing material like starches.
To obtain an absorbent fabric,this is ready for dyeing or printing process.
To obtain softer and proper white fabric, depending on its application.
SingeingDesizingScouring and BleachingMerserization
PROCESS SEQUENCE FOR PRETREATMENT
The process of singeing is carried out for the purpose of removing the loose hairy fibres protruding from the surface of the cloth, thereby giving it a smooth, even and clean looking face.
Objective if singeing machineRemoving of protruding fibreImproving lusterReduce dyeing and printing problem
Types of singeing process1. Plate singeing machine2. Rotary-cylinder singeing machine3.Gas singeing machine
Material ofburner: metal replaced by ceramic.
Composition of gas fuel: air to petroleum chemical ratio
Fabric is pre heated to remove the moisture.
Water cooling system is incorporated just behind the ceramic material to control the temperature of ceramic material.
in case of power failure, both burners tilt away from the fabric simultaneously.
Fabric passing path is variable for maintaining contact angle for different kind of fabric.
ADVANCEMENT IN SINGEING
Eco friendly pre-treatmentEco friendly pretreatment carried out by enzymatic processEnzymes are a class of proteins that function as biocatalysts which are biodegradable, very specific in action and are used in small quantities. They are made up of 200-250 amino acids. They work by lowering the activation energy of the reaction making it much faster.They are produced by living organisms such as fungi or bacteria.Enzymes are complex organic, soluble bio-catalysts, formed by living organisms that catalyze chemical reaction in biological processes.Enzymes are quite specific in their action on a particular substance.
EnzymeEffectAmylaseDesizing (to decompose starches applied in sizing) CatalaseAct on H2O2 to decompose it into water & oxygenProteases, lipases and pectinasesWhen combined, act on proteins, pectin and natural waxes to effect scouringLaccasesDecomposes indigo molecules for wash-down effect on denim CellulasesBreak down cellulosic chains to remove protruding fibres by degrading &create wash-down effect by surface etching on denims etc. Cellulases and HemicellulasesBio stoning of jeans Desizing of CMC Stylish effect on cellulose fibres PectinasesBreaks down pectin in scouring ProteasesScouring of animal fibres, degumming of silk and modification of wool properties LipasesElimination of natural triglycerides (in scouring) or present in desizing (tallow compounds)
Enzymes for textile processing
E + S E S P + E (Enzyme) (Substrate) (Enzyme-Substrate) (Product) (Enzyme)
Substrate entering In active side of enzymeEnzyme substratecomplexEnzyme/substratecomplexProdcut release fromenzymeENZYME WORKING MECHANISM
The removing of size material which incorporated in pre-weaving process is known as desizing.
There are three main advanced desizing method are
Enzymatic desizingSolvant desizingAtmospheric plasma desizing
ADVANCEMENT IN DESIZING
Amylases are the enzyme that hydrolyses and reduces the molecular weight of cellulose.
hydrolyze starch molecules to give diverse products.
specific for starch, removing it without damaging to the support fabric.
optimum temperature is 30-60C, optimum pH is 5.5-6.5.
ContEnzymatic desizing and utilisation of desizing liquor for H2O2To utilize desizing baths for bleaching in which glucose oxidase enzymes generate hydrogen peroxide and gluconic acid using glucose as a substrate. Amyloglucosidases are enzymes used in desizing to degrade starch until it becomes glucose.Optimum conditions are 0.75% (o.w.f.) enzyme, pH 4.1, 62 C and a process time of 45 minutes.
Advantages:reducing the use of peroxide stabilizing agents with the help of gluconic acidsaving water and energy by using desizing liquor for bleach.
Some solvent are used for desizing of textile substrate.
Sonafab 1000). It isa unique Desizing Agent, having excellent solvent and emulsifying action on all types of stain. (Sonal Dye-ChemPvt. Ltd)Perchloroethylene -- desizing solvent
DIFFERENT SOLVENTS USE IN DESIZING
It is a very clean operation with no disposal problem, the pollution effect is negligible.The time of desizing and floor area for the machinery is far less than for conventional system.Due to quick and even solvent penetration the size removal is more uniform.The solvents are recoverable and have less or no effluent load.This method is useful since energy consumption is low, time of desizing is low.Acrylic and wool fabrics develop a lustrous, soft hand in solvent without any felting.When solvent desizing is followed by bleaching, the caustic scouring is omitted since pectin and wax ADVANTAGES OF SOLVENT DESIZING
DISADVANTAGE OF SOLVENT DESIZING
Although solvent desizing ranges are available commercially, the price of the equipment is high.
The majority of size systems used in aqueous process is not readily applicable in solvent desizing.
Cost of processing is higher than for water base process.
Plasma is four states of matterHere material having in ionized condition Plasma is produce by applying electric field on a gasPlasma is etching the fabric surfaceEtching is depend upon the voltage, type of gas, time
ATMOSPHERIC PLASMA DESIZING
Ultrasonic energy are the high frequency waves rangeing from 20Khz to 50Mhz which is nnot audiable by human In liquids, longitudinal vibrations of molecules generate compression and rarefaction, i.e., areas of high pressure and low local pressure The latter gives rise to cavities or bubbles, which expand and finally during the compression phase, collapse violently generating shock waves. The phenomena of bubble formation and collapse (known as cavitation) is generally considered responsible for most of ultrasonic physical and chemical effects observed in solid/liquid or, liquid/liquid systems.
Use of ultrasonic energy in desizing Amylase - 0.75 g/l wetting agent - o.5 g/l Temperature - 55C Time - 20 min.Desizing efficiency 7 when US is used.Desizing efficiency 2.5 when US is not used.Energy savings resulting from lower process temperatures and shorter cycle times Reduced consumption of dyes and chemicals, which allows for a 20-30% reduction in the amount of effluent Water savings of around 20% Improvement in product quality Increased productivity because of shorter cycle times
LimitationThis process requires some assistance from temperature. This process does not involve complete elimination of temperature.RecipeAdvantageADVANTAGES OF ULTRASONIC
To remove natural as well as added impurities of essential hydrophobic character(oil,fat,waxes) as completely as possible and leave the fabric in high absorptive condition without undergoing significant chemical or physical damage To make the goods suitable for removing the natural colouring matter of the cotton during the subsequent bleaching process.Conventional method: Alkali scouring.Where 3-4% caustic soda is used at high temperature (90-95oC) for long duration (2-3hours)
Disadvantages of alkali scouring:1) Damage to fibre.2) Requirement of large quantity of water for washing.3) Heavy effluent load (Salts of neutralization) SCOURING
Enzymatic Scouring or Bio-Scouring can simply be defined as the application of living organisms and their components to remove the natural and added impurities.
Enzymes used for Bio scouringPectinase (Pectins removal)Protease (Removal of proteins)Combination of 2 or 3 enzymes may be used to get synergistic effect.
Conventional scouring requires high temperatures and high consumption of chemicals. Suppliers. BIO SCOURING
ParameterBio ScouringAlkaline ScouringpH7-812-13Temperature50-600C950CResidual Pectin20-25%10-11%Weight loss Rinse --> Rinse --> Rinse --> Dye
There are two methods for bleach clean-upAfter completion of the process the bleached liquor was drained out, then the fabric was rinsed with water a number of times to remove the H2O2from the bleached fabric. use of a mild reducing agent to neutralise the bleach.
ContCatalase have been used to decompose residual hydrogen peroxide in fabric prior to dyeing
Catalase enzyme catalyzesthe decomposition ofhydrogen peroxidetowaterandoxygen. One catalase molecule can convert millions of molecules of hydrogen peroxide to water and oxygen each second
Use of Catalase enzyme made it possible to reduce the temperature and volume of the second wash after bleaching from 80-950C to 30-400C, resulting in a 9-14% saving of energy, a 17-18% saving of water and an overall cost saving of 9%
Industrial production of ozone can be accomplished by applying a plasma discharge to oxygen in air. Ozone is a natural substance and it is a strong oxidising agent and it decomposes rapidly.Process
Fabric having 24% moisture content is placed in application chamber and exposed to 100 g/m of concentration of ozone oxygen gas mixture. pH 5 with acetic acid Time 1-7 minTemperature- 30C
ADVANTAGES AND LIMITATION OF OZONE BLEACHINGAdvantages
The quality of the processed fabric is comparable.Grey preparation with ozone can be completed in one or two minute.This process has additional advantages such as savings in thermal energy, water and chemicalsLimitations
The yield of ozone generator is low (6-12% from oxygen and 4-6% from air), and ozone concentration is low as well. Ozone has to be generated on-site because its problems to be stored and transported. Energy consumption for production of O3: Based on pure oxygen, the costs will be 6 to 15 kWh/kg O3.
PER ACETIC ACID BLEACHING Per acetic acid is also known as peroxyacetic acid. It is colorless in nature. It is miscible with water and most of organic solvents. It is very powerful oxidizing agent. It is also used as germicide for protecting fruits/vegetables against spoilage. General formula is C2H4O3. It corresponds to acetic acid with additional oxygen atom per molecule. i.e. CH3COOOH (peracetic acid) It is highly unstable at pH 5-5.5. But stable at lower pH of 1.5-2. A concentration of 35% to 40% is dangerously explosive.
Mechanism of oxidation with peracetic acid, it gives extra oxygen atom and acetic acid is formed as co-product.
CH3COOH CH3COOH + [O] Procedure for bleaching with peracetic acid:
1) Peracetic acid being unstable has to be prepared before bleaching being carried out as per above procedure. 2) Bleaching is carried out with MECHANISM OF PERACETIC ACID
LIQUID AMMONIA MERCERIZATION In this technique the fabric is first passed through drying cylinders to reduce the moisture content of fabric then through a cooling station.
Afterwards it is impregnated with liquid ammonia in a closed chamber and then the fabric is passed through felt calendars in which 90-95% of ammonia is removed.Advantages over alkali mercerization:
Quick processLow shrinkage post washing Superior in the degree of improvement in strength Durability of dimension stabilitySoft handle
LIQUID AMMONIA MERCERIZATION
Rapid changes in technology a dire need to conserve water and energy have forced the textile industry to give up the old conventional processes and try out new methods All over the world, the environmental regulations are becoming more and more stringent and are forcing the shift of technology towards less polluting or non-polluting areas of technological development. To go towards the eco friendly and sustainable textile processing, New technology has to be incorporated in the textile processing