Transcript of "Eco – friendly in textile wet processing"
Eco – Friendly in Textile Wet Processing By Aravin Prince Periyasamy., M.Tech (Textiles) Lecturer, Dept of Apparel Technology, S.S.M. Institute of Textile Technology & Polytechnic College, Komarapalayam, Namakkal. Mobile #:+91-97 90 08 03 02 E-mail: firstname.lastname@example.orgABSTRACT Environmental considerations are now becoming vital factors during the selection ofconsumer goods including textiles all over the world. However due to increased awareness ofthe polluting nature of textiles effluents, social pressures are increasing on textile processingunits. Awareness about eco-friendliness in textiles is one of the important issues in recenttimes since textiles are used next to skin and is called second skin. Owing to the demand ofglobal consumer the researchers are being carried out for new eco-friendly technology.Plasma, biotechnology, ultrasonic, super critical carbon dioxide and laser is quite newtechnology for the textile industry. It offers many advantages against wet techniques. Thereare no harmful chemicals, wet processes, waste water and mechanical hazards to textiles, etc.It has specific action on the all types of fibres and textiles.INTRODUCTION: Increasing environment consciousness in textile processing has forced research anddevelopment efforts to search the safe methods for textile processing. The textile chemicalprocessing plays an important role in controlling the pollution load for environment. Becausethe textile industry has long recognized that, for a large number of process and applications,the surface properties are a key aspect of the product and often need to be quite different fromthose of the fabric bulk. New applications and improved applicability of the many fibre usedfor clothing, as industrial materials and for interior decoration requires the provisions of newproperties in such areas as dyeability, static resistance, and current control, stain resistance,water absorption, hydrophilicity, water repellency, adhesive ability and so on. There aresurface treatment methods that additionally increase the value of textile materials. The methods can be classified as chemical treatment (wet) methods and physicaltreatment (dry) methods. Chemical treatment methods are most often used in actual practice.Because of the large amount of energy involved and the high consumption of water andconsequently increase of pollution, these techniques are costly and not eco-friendly. Inaddition, these processes treat the fabric in bulk, something which is unnecessary and mayadversely affect overall product performance. Problems related to toxicity and other healthhazards have resulted in the replacement of chemical processing by more eco-friendlyphysical methods. The physical treatment processes are dry, which makes it possible topreserve certain properties intrinsic to textile materials; they are likely to affect the surface ofthe materials. Therefore the researchers are extensively studying the possibilities of physicalsurface treatments as alternatives to the chemical treatments.
At the beginning, studies initially focused on electron beam irradiation and ultravioletlight irradiation, but electron beam irradiation required too much energy and as a result,properties deteriorated and graft polymerization sometimes occurred. In the latter case it wasnecessary to find a means of reducing the efficiency of grafting. Ultraviolet light irradiationwas tried as a method of resin hardening, but never went beyond the scope of studies onmethods of treating fiber surface. In all probability, this was because it offered no specificfeatures superior to what could be obtained with chemical treatment. The industry is,therefore, strongly motivated to seek alternative surface engineering processes which couldoffer lower cost, environmentally-friendly manufacturing and routes to new products, withimproved lifetime, quality and performance. Research is going on worldwide with the focuson new quality requirements that include maintaining the intrinsic functionality of the productthrough an eco-friendly production process. Therefore, an attempt has been made to reviewthe physical methods for processing of textile materials by plasma, laser and supercriticalcarbon dioxide to enhance the specific properties.PLASMA TECHNOLOGY The physical definition of plasma (glow-discharge) is an ionized gas with anessentially equal density of positive and negatives charges. It can exist over an extremelywide range of temperature and pressure. Plasma treatment usually practiced in textile industryto enhance the functional finishing. High-pressure glow discharge plasma, modifying theactive surface characteristics of the polymer so it contains polar functional groups. A treatedfibre will comprise a hydrophobic core and a receptive pouter sheath which consists ofhydrophilic functional groups, resulting from the active species interacting with the surface ofpolymer during treatment. Fig 1 Plasma Technology Plasma technology has been shown to improve fibre surface properties withoutaffecting desirable bulk properties. It also offers environmental advantages. Therefore, thereare increasing uses of plasma treatment of synthetic fibres such as polyethylene terephthalate,nylon, and polypropylene. A general effect is in improvement in their hydrophilic properties. Fig 2: Plasma Technology in TextilesHow does the Plasma treatment affects the textile material? According to requirements the textile materials to be processed processing will betreated for seconds or some minutes with the plasma. The following are the propertiesimprovements with plasma treatment:1. The cleaning effect is mostly combined with changes in the wettability and the surface texture. This leads to an increase of quality printing, dye-uptake, adhesion and so forth.2. Increase of micro-roughness: this effect an anti-pilling finishing of wool.
3. Generation of radicals: The presence of free radicals induces secondary reactions such as cross linking. Furthermore, graft polymerisation can be carried out as well as reaction with oxygen to generate hydrophilic surfaces in hydrophobic fibres such as polyester or polypropylene.4. Plasma polymerization: It enables the deposition of solid polymeric materials with desired properties onto the substrates. The advantage of plasma treatment is that the modification is restricted to theuppermost layers of the substrate, thus not affecting the overall desirable bulk properties ofthe treated substrate. Functional groups are introduced in the treated textile materials which would playprominent role in improving the dyeability of hydrophobic fibres such as poly (tetraetylene)(PET) and polypropylene (PP). The plasma treated PP and PET could be easily dyed bywater soluble acid dye which is more environmentally friendly plasma is advantageous information of hydroxyl groups on the PET surfaces. To improve the deep colouring effect ofpolyethylene terephthalate (PET) fabrics, anti-reflective coating layers have been depositedon the surface of the fabrics with two different organo-silicon compounds such as HMDS,TTMSVS using atmospheric pressure plasma. Oxygen promoted the decomposition oforganic monomers and contributed to the enhancement of the colour intensity on the PETsurface. Plasma treatment can also be used for grafting of textile fiber with other polymer toenhance specific properties. For example, Poly (ethylene terephthalate) (PET) would beexposed to oxygen plasma glow discharge to produced peroxides on its surfaces. Theseperoxides were then used as catalysts for the polymerization of acrylic acid (AA) in order toprepare a PET introduced by a carboxylic acid group(PET-A). Chitosan and quaternizedchitosan (QC) were then coupled with the carboxyl groups and the PET-A to obtain chitosangrafted PET (PET-A-C) and QC-grafted PET (PET-A-QC), respectively. After the launderingthe inhibition of the growth of the bacteria was maintained in the range of 48 – 58%, showingthe fastness of the grafted PET textures against laundering. Not only the hydrophobic fibres but also the natural fibres treatment such as in wooldyeing, plasma could be employed. The kinetics of dyeing of wool with acid dyes aftertreatment with low temperature plasma was investigated researcher. It shown the plasmatreated wool can be dyed at 80‟c at high rates and dye fixing was improved. Modification ofthe wool with low temperature plasma enables the dyeing temperature to be reduced, thushelping to reduce fibre damage. Colour fastness of a wool fabric that was low-temperatureair-plasma treated and dyed with an acid dye has been evaluated. Colour fading of the plasmatreated fabric by carbon arc light irradiation was lesser at initial stage than that of the fabricwithout plasma treatment. The oxidized substrate through the plasma treatment may inhibitthe photo reduction reaction of the dye. The colour fastness of the plasma treated fabric tolaundering was poorer than that of untreated fabric. The phenomena may be attributed to an
enhancement of dye diffusion in wool substrate by relaxation of inter cellular material ofwool by the plasma treatment. Wool and nylon 6 fibres treated with oxygen low-temperature plasma were dyed withacid and basic dyes. Despite the increase of electro negativity of the fibre surface caused bythe plasma treatment, the rate of the dyeing of wool was increased with both dyes, while thatof nylon 6 was decreased with the acid dye and increased with the basic dye. After a lowtemperature glow discharge treatment on wool, reduced dyeing times are possible, reducedcost of maintenance and possibilities of recycling are also possible due to reduced dischargesof toxic components. The process is also more environmentally friendly and introduces costsavings by reducing the amount of dyestuffs and auxiliaries required. Marino wool can be treated with low temperature plasma based onoxygen/helium/argon/tetrafluromethane for 30 – 180 sec before dyeing with acid or directdyes. The pretreatment not only increases the dyeing rate, but also the saturation of dyeexhaustion. The barrier effect is reduced by plasma treatment. The surface of the endocuticleor the adhesive filler in the wool scales is relaxed by the plasma treatment, thereby improvingthe dyeing of wool with direct dyes. Time of half-dyeing is reduced by oxygen andtetrafluoromethane plasma treatment. Although the dyeing rate in short periods increasedindependently of dyes and plasma gases, the helium/argon, plasma was especially effective. Itwas found that there is no relationship to wettability with water and the dyeing rate of plasmatreated wool. Dye penetration is accelerated as a result of the plasma pretreatment.LASER TREATMENT: Another physical surface treatment method to create the hydrophilic groups onhydrophobic fibres and enhance the dyeing process is laser treatment. Extensive research hasbeen carried out into the possibility of surface finishing of synthetic fibre fabrics by laserirradiation. A laser type must be selected which irradiates in a strongly absorbing spectralregion of the high polymers. It is possible to obtain surface structuring without affecting thethermal and mechanical properties of the body of the fibre. Surface properties affectedinclude particle adhesion, wettability and optical properties. Poly (ethylene terephthalate)(PET)modified by a 248 nm KrF excimer laser withhigh(above ablation threshold) and low (below ablation threshold)energy irradiation .ThePET surface develops a well-oriented periodic structure of hills and grooves or a “ripplestructure” with high energy treatment. However, the ripple size can be reduced to submicronlevel by irradiation of the sample below the ablation threshold. Chemical surface changes ofthe material can be characterized by X-ray photoelectron spectroscopy (XPS) and contactangles. PET modified by high energy will normally exhibit the deposition of some yellow toblack ionized, carbon –rich debris on the treated surface, resulting in a reduction of the O/Cratio. In contrast, a PET surface modified by low energy leads to oxidation and almost noablation. The increased oxygen concentration on low energy modified surfaces is probablydue to a subsequent reaction with atmospheric O2 during irradiation. Polar oxidized groupslike carboxyl are also included .Contact angle measurements are in good agreement with
these findings .Changes in surface morphology of PET fibres were found in relation to laserenergy applied . The mean roll to roll distance increased with increasing laser energy.Merging of ripples was observed and believed to be a major reason of increased roll to rolldistance. With approximately 50 to 200 pulses, ripple almost approached parallelism. Nofurther change of PET surface was observed with more laser pulses applied since the fibrehas disintegrated into “ellipsoidal” segments. In the study of morphological modification of laser-ablated PET fabrics, it wasobserved that after laser treatment the ratio of carboxylic acid groups to ester groupsincreased, the relative size if the amorphous regions increased and the ratio of oxygen tocarbon increased. A greater depth of shade was achieved on treated fabrics compared withuntreated fabrics dyed with the same amount of disperse dye. This is due to the scattering oflight caused by ripples on the fibre surface, and greater dye uptake by the amorphous regionson the surface of laser irradiated PET fabrics. The same depth of shade can be obtained onlaser –treated fabric with less dye than is needed on untreated fabric. Polyamide (nylon 6) fabrics were irradiated with a 193nm argon fluoride excimerlaser and the effects on the dyeing properties of the fabrics were investigated. Chemicalanalysis indicated that carbonisation occurred in the laser irradiated samples. The lasertreatment breaks the long chain molecules of nylon, increasing the number of amine endgroups which change the dyeing properties with acid and disperse dyes. The results suggestedthat laser treatment could be used to improve the dyeing properties of nylon fabric with adisperse dye. Ablation products must be removed to achieve better bonding at laser treatedsurfaces. Carboxyl group formation at surface of nylon or polyester is stimulated leading tobetter dye ability. Anomalous surface structure of nylon and polyester fibres and yarns werestudied .ultraviolet laser radiation causes less damage to nylon yarn than to polyester yarn,which absorbs more radiation and heats to higher temperatures. The higher temperatures areproduced in a pulse-like action in microscopic areas, resulting in a short-time pyrolysis whichgenerates changes in the surface structure.SUPER CRITICAL CARBON DIOXIDE: Hydrophobic textile materials require creating pores, so that the non-ionic dyeparticles would be entered into the textile materials at high temperature and pressure duringdyeing process. After dyeing when the temperature of the dyed materials goes down to theroom temperature, the dye particles would entrapped by the dyed textile materials. Thereforethe hydrophobic textiles are normally dyed from aqueous dye liquors. In such dyeing, acomplete bath exhaustion never occurs, i.e. the dye does not exhaust quantitatively onto therespective substrate, with the further result that, after the dyeing process, the residual dyeliquor still contains more or less amount of dye depending on the particular dyes andsubstrates. For this reason, dyeing results in the formation of this reason, dyeing results in theformation of relatively large amount of coloured effluents which have to be purified atconsiderable trouble and expense. The process of the invention has a number of advantages as they claimed such as:
1. The supercritical carbon dioxide used in the process does not pass into the effluent, but is reused after the dyeing process. Therefore no contamination of the effluent occurs. 2. Further, compared with the aqueous system, the mass transfer reactions necessary for dyeing the textile substrate proceed substantially faster, so that in turn the textile substrate to be dyed can be penetrated particularly well and rapidly by the dye liquor. 3. When dyeing would carried out in wound packages by the process of the invention, no unlevelness would occurs with respect to penetration of the packages, which unlevelness is regarded as responsible for causing listing defects in the conventional process for the beam dyeing of flat goods. 4. Also the novel process does not give rise to the undesirable agglomeration of disperse dyes which from time to time occurs in conventional dyeing with disperse dyes. Thus the know lightening of disperse dyes and hence the spotting which may occur in the conventional dyeing processes carried out in aqueous systems are avoided by using the process of the invention. Fig 3 phase diagram of CO2 Carbon dioxide, as pressurized liquid in super critical conditions was used withsuccess as a solvent in the dyeing polyester fibres at pressures up to 30 MPa and temperatureto 423k.The solubility of the dyes is of the order 10 mg/litre of carbon dioxide at 293.15k anda pressure of 25MPa. Not only the dyeing process but also the other chemical process could be carried outby the super critical carbon dioxide. Hydrophobic textile materials are usually whitened fromaqueous liquors. This never results in complete exhaustion of the bath, i.e. the fluorescentwhitening agents do not show quantitative exhaustion onto the textile material. This in turnhas the effect that the whitening liquor remaining after whitening still contains, depending onthe particular fluorescent whitening agents and substrates, certain amounts of fluorescent
whitening agent. Their invention relates to a process for the fluorescent whitening ofhydrophobic textile material with fluorescent whitening agents, wherein the textile material istreated with a fluorescent whitening agent in super critical carbon dioxide. The processaccording to the invention has a number of advantages same as in dyeing with super criticalcarbon dioxide, such as no water pollution, much higher mass transfer rate than in aqueoussystems, no non-uniformities with respect to the flow through the wound package, nounwanted agglomerations on the fibre material. A further advantage of the process accordingto the invention is that it is possible to use disperse fluorescent whitening agents whichexclusively consist of the actual whitening agent and do not contain the customarydispersants and diluends. The fluorescent whitening agents used in the process according to the invention arewater insoluble compounds two identical or different radicals selected from the group ofconsisting styryl, stilbenyl, naphthotriazolyl, benzoxazolyl, coumarin, naphthalimide, pyrene,and trizinyl which are linked to one another directly or via a bridging member selected fromthe group consisting of vinylene, styrylene, stilbenylene, thienylene, phenylene, napthyleneand oxadiazolylene.ULTRASONIC ASSISTED WET PROCESSING Ultrasonic represents a special branch of general acoustics, the science of mechanicaloscillations of solids, liquids and gaseous media. With reference to the properties of humanear, high frequency inaudible oscillations are ultrasonic or supersonic. In other words, whilethe normal range of human hearing is in between 16Hz & 16 kHz. Ultrasonic frequencies liebetween 20 kHz and 500 MHz. Expressed in physical terms, sound produced by mechanicaloscillation of elastic media. The occurrence of sound presupposes the existence of material itcan present itself in solid, liquid or gaseous media. Wet processing of textiles uses largequantities of water, and electrical and thermal energy. Most of these processes involves theuse of chemicals for assisting, accelerating or retarding their rates and carried out at elevatedtemperatures to transfer mass from processing liquid medium across the surface of the textilematerial in a reasonable time. Scaling up from lab scale trials to pilot plant trials have beendifficult. In order for ultrasound to provide its beneficial results during dyeing, highintensities are required. Producing high intensity, uniform ultrasound in a large vessel isdifficult. Ultrasound reduces processing time and energy consumption, maintain or improveproduct quality, and reduce the use of auxiliary chemicals. In essence, the use of ultrasoundfor dyeing will use electricity to replace expensive thermal energy and chemicals, which haveto be treated in wastewaterBUBBLING PHENOMENON Ultrasound energy is sound waves with frequencies above 20,000 oscillations per second,which is above the upper limit of human hearing. In liquid, these high-frequency waves causethe formation of microscopic bubbles, or cavitations. They also cause insignificant heating ofthe liquid.” Ultrasound causes cavitational bubbles to form in liquid. When the bubbles
collapse, they generate tiny but powerful shock waves. we needed to agitate the border layerof liquid to get the liquor through the barrier more quickly, and these shock waves seemedlike the perfect stirring mechanism.BASIC PRINCIPLE In a solid both longitudinal and transverse waves can be transmitted whereas in gas andliquids only longitudinal waves can be transmitted. In liquids, longitudinal vibrations ofmolecules generate compression and refractions, i.e., areas of high pressure and low localpressure. The latter gives rise to cavities or bubbles, which expand and finally during thecompression phase, collapse violently generating shock waves. The phenomena of bubbleformation and collapse (known as cavitations) are generally responsible for most of ultrasoniceffects observed in solid/liquid or liquid/liquid systems. Here Fig below shows the wavesproduced by ultrasound . Figure 4: Representation of Some Typical Characteristics of an Ultrasonic WaveGENERATION OF ULTRASONIC WAVES The ultrasonic waves can be generated by variety of ways. Most generally known are thedifferent configurations of whistles, Hooters and sirens as well as piezo-electric andmagnatostrictive transducers. The working mechanism of sirens and whistles allow anoptimal transfer of the ultrasonic sound to the ambient air. In the case of magnatostrictive andor piezo-electric transducers of ultrasonic waves, the generators as such will only produce low oscillation amplitudes, which are difficult to transfer to gases. The occurrence ofcavities depends upon several factors such as the frequency and intensity of waves,temperature and vapor pressure of liquids.
ULTRASOUND IN TEXTILE APPLICATIONS The effect of ultrasound on textile substrates and polymers has started after theintroduction of the synthetic materials and their blends to the industry. These includeapplication in mechanical processes (weaving, finishing and making up for cutting andwelding woven, non-woven and knitted fabrics) and wet processes (sizing, scouringbleaching, dyeing, etc) .It deals with the application of ultrasound in the mechanicalprocesses of industrial as well as apparel textiles. Ultrasonic equipment for cutting andwelding has gained increase acceptance in all sectors of the international textile industry fromweaving, through finishing to the making-up operation.Mass transfer in textile materials and ultrasound waves A piece of textile is a non-homogeneous porous medium. A textile comprises of yarns,and the yarns are made up of fibers. A woven textile fabric often has dual porosity: inter-yarnporosity and intra-yarn porosity. As mentioned earlier, diffusion and convection in the inter-yarn and intra-yarn pores of the fabric form the dominant mechanisms of mass transfer in wettextile processes. The major steps in mass transfer in textile materials are: Mass transfer from intra-yarn pores to inter-yarn pores, Mass transfer from the inter-yarn pores to the liquid boundary layer between the textile and the bulk liquid, Mass transfer from the liquid boundary layer to the bulk liquid. The relative contribution of each of these steps to the overall mass transfer in the textilematerials can be determined by the hydrodynamics of the flow through the textile material.BIO-TECHNOLOGY: One of the most negative environment impacts from textile production is thetraditional process used to prepare cotton fiber, yarn, and fabric. Before cotton fabric or yarncan be dyed, it goes through a number of processes in a textile mill. One important step isscoring is the complete or partial removal of the non-cellulosic components found in nativecotton as well as impurities such as machinery and size lubricants. Traditionally it isachieved through a series of chemical treatments and subsequently rinsing in water. Thistreatment generates large amounts of salts, acids, and alkali and requires huge amount ofwater.THE GREEN ALTERNATIVE: With bio-preparation using the enzyme the cotton fibers can be treated under verymild condition. The environmental impact is reduced since there is less chemical waste anda lower volume of water is needed for the procedure. The bio preparation process decreasesboth effluent load and water usage to the extent that the new technology becomes an
economically viable alternative. Instead of using hot sodium hydroxide to remove theimpurities and damaging parts of the fiber enzymes do the same job leaving the cotton fiberintact. It is believed that the replacement of caustic scouring of cotton substrates by biopreparation with selected enzymes will result in the following quantifiable improvements:lower, BOD, COD, TDS, and Alkalinity. Process time, Cotton weight loss, and harshness ofhand. An extremely powerful alkaline pectinase recently has been isolated. This newenzyme is now being produced in volume and is being reduced to commercial use in biopreparation on a worldwide basis. The major benefit of this enzyme in bio preparation is thatthe enzyme does not destroy the cellulose of the cotton fiber. The enzyme is a pectate lyase,and as such very rapidly catalyses hydrolysis of salts of polygalacturonic acids (pectin‟s) inthe primary wall matrix. The term alkaline pectinase is used to describe the enzyme becausethe biological catalyst is used under mildly alkaline conditions which are very beneficial inpreparation process.ENZYMES: Enzyme is a Greek word „Enzymos‟ meaning „in the cell‟ or „from the cell‟. They arethe protein substances made up of more than 250 amino acids. Based on the medium fortheir preparation, they are classified as bacterial, pancreatic (blood, lever etc) malt(germinated barely) etc. their major functions are fails on hydrolysis, oxidation, reductioncoagulation and decomposition. Grouped under the following groups :ENZYME IN TEXTILES Enzymes are used to remove lubricants and sizes. Enzymatic desizing has achievedindustry-wide adoption as a particularly cost-effective treatment, with savings in bothprocessing costs and wastewater treatments. Sticky insect secretions from silk fibres can beremoved using enzymes. Wool and Cotton can be scoured effectively using enzyme ratherthan harsh chemicals. Enzymes rather than caustic chemicals can be used to fade fabricswithout the wastewater treatment cost of ordinary bleaches. Bio-stoning has been widelyadopted as the standard method of achieving “stone –washed” denim. Enzymes are used to fade the denim rather than the abrasive action of pumicestones. Substantial savings result from reduced water usage and less damage to the fabric.Enzymes has been used effectively in shrink proofing of wool, giving improved quality andsignificantly reduced effluent costs as opposed to using chemical treatments. Bio polishing involves the use of enzymes to shear off the micro fibres of cottonand other cellulose materials to produce fabrics with superior softness, drape and resistanceto pilling. This mode has been specially developed to achieve a cleaner pile on terry towels.A treatment with “ultrazyme LF conc.”- A powerful composition gives a clear look to thepile, improved softness and absorbency. Fabrics containing regenerated cellulosic fiberoften show fuzzy surface due to chafing during wet processing. A smooth and clear finishcan be achieved by bio singing.
CONCLUSIONS: Due to the increasing requirements on the dyeing and finishing of textile fibres/fabrics, the society demand for textiles that have been processed by eco-friendly soundmethods, therefore, new innovative production techniques are demanded. In this field, theplasma technology, laser treatment and supercritical fluids treatment shows distinctadvantages because, these are environmentally friendly, and even surface properties of inertmaterials can be changed easily. It is thus expected that in future, many of the physicalprocesses would help in solving the environmental problems possessed by dyeing andfinishing plant of textile industry. Therefore these physical processes need to be explored atthe bulk processing level.The result of bio-preparation with enzymes is that the cellulose isnot degraded, resulting in less weight or strength loss than occurs with either caustic scouringor cellulose treatment.REFERENCE 1. Aravin Prince Periyasamy- Application of Nano Technology In Textile Finishing – Textile Magazine Dec 2006 2. Aravin Prince Periyasamy - Bio Processing in Textile Application / Textile magazine-July 07 3. Aravin Prince Periyasamy- Ultrasonic assisted textile wet processing – Indian Textile Journal May 2009 4. Dr Bhaarathi dhurai Application of enzyme in textile processing – National Conference held in PSG Tech Coimbatore 5. www.resil.com 6. www.mapsenzyme.com 7. www.bharattextile.com