Indian Journal of Fibre & Textile Research Vol. 21, March 1996, pp. 41-49. .

New developments in process control

M DTeli Department of C hemical Techn9logy, University of Bombay, Matunga. Bombay 400 019, India

Present textile market is buyers' market. The consumer dictates the term as far as the quality, quantity and delivery schedule are concerned. To withstand such competition. the manufacturers/processors have to adopt total quality management approach so th at not only they ge t the ~ond~ processed ri ght at the first time, but quality is ensured. I ncreasing environmental polluti on a\l4areness has thrown new challenges before the textile technocrats. The present paper reviews the new developments in the field of manufactured, methods of application and machinery used . It also takes into account the impact of advent of micro fibres and specihc developments in processing of terry-towels, garments. etc. The future trend is also predicted based on all the above factors.

Keywords: Dyei ng. Di sperse dyes. Reacti ve dyes. Polyester fibre. Cellulosic fibre. Wool fibre , Silk fibre . Dyeing machinery

1 Introduction also account for a sizable production and some deve~ The globalization has widen the scope of the textile lopments in this respect need to be also summarized. business with the inevitable entry of international co­ The advancements in dyeing processes have bea ring mpetition. The challenges and opportunities are incr­ on the developments In dyes and newer easing and the appropriate response has to be evoked. applications. in terms of technological advancement and on-time The colouration and finishing are the key stages in delivery. Such "quality and quantity" supply has to imparting fa shion appeal to the textile apparels. The be done on the basis of right-first-time, right-every­ timing and positioning of colouration in the handling time, quick response approach. While this is being of textile are essential factors in ensuring that a chosen attempted, it is also incumbent to consider reduction ma rket is supplied with the right product at the right in energy and production cost. The challenges posed time and in ri ght quantities as well as at the right by this decade revolve around the conservation of pnce. environment, an issue which has aroused the attent­ The first aspect of Quick Response (QR) to consi­ ion at global level and will direct th!! future chemical der is the shortening of the traditional pipeline l by technological adva ncements predominantly. eliminating unnecessary inventories and optimiza­ The emergence of new materials such as polyester tion of process times. Learning to operate with signifi­ microfibres, increasing applications of computer tec­ cantly lower stocks of raw materials and finished go­ hnology for recipe prediction as well as for expert ods is no simple matter because so many new discipli­ systems of dyeing and fini shing, and the increasing nes must permeate the organization. One such new use of microprocessor-based process monitoring discipline is the Right-First-Time concept in wet and control equipment will stimulate the fin e tuning processing. The objective is to avoid unnecessary act­ of our production efficiency and effectiveness as well ivity and complexity- wasted time, wasted energy, ,\seconomy. The opportunities placed before us, of wasted material and correction of errors. This in posi­ course with a package of challenges, in post-GATT tive terms means quality managementz (QM). period need to be exploited and it is the technological As far as the recent trends in dyeing process contr­ advances which will be playing major role in shaping ols are concerned, they are the result of developments the destiny of this industry. in dyes, fibres, application conditions and machine­ When one talks about technological advance­ ry3. ments in dyeing process control it is natural tha t the majority of these advances are concentrated on ­ 2 Developments in Dyes ing of woven fabric. However, dyeing of garment, The technological developments in the dyestuff in­ terry-towel, microfibre and hosiery or knit goods dustry are taking place from the point of view of: 42 INDIAN 1. FIBRE TEXT. RES., MARCH 1996

(i) High-performance products It has good fastness to heat-setting/wet treatments Concentrated brands: To minimize neutral cutt· too. ing agents and to incorporate useful additives. Navy Blue··CF: It is an extension to the Palanil CF Non-dusting brands: Granulated and liquid (Controlled Fastness) series and is suitable for all dye­ brands. ing processes. The use of non-dusting grains or powders and liq­ Brilliant Blue BGM-CF: It can be readily thermo­ uid brands of dyes help in minimizing air/water pollu­ fixed and has good light fastness even at hi~hte'mpera­ tion and in application of automated dye dispensing ture. It is particularly suitable for automotive systems. textiles. • Dispersol SF (Super Fast), a new range from ICI (ii) Cost effectiveness which inCludes black, navy, rubine, yellow, blue Increased automation, advanced instrumentation and brown dyes specifically targeted for dull tern­ and controls, and computerization for the manufact­ ary shades, a very difficult area fo r most dyers. uring operations with the objectives of high quality They are alkali clearable dyes and exhibit extre­ standards help in cost reduction and increasing profi­ mely low cross-staining. tability with Quality production. • The Dispersol XF range complements the ICI Di­ spersol SF (Super Fast) dyes which are benzodifu­ (iii) Health , safety and ecology 4 ranone ba6ed . Selection of dyes is necessary from the points of view of: • A fascinating area of chemistry has been the development of high-value speciality co­ Avoiding the use of dyes which can fonn on reduc­ lours giving brilliant fluorescent dyes. These are tion carcinogenic amines, and complicated, expensive structures involving sop­ Selection of high exhaustion/fixation dyes, parti­ histicatd organic chemistry yielding brilliant sha­ cularly among reactives. des with acceptable fastness propertiess. Most of the product development has been concen­ • Zeneca (previously ICI) has introduced diester, trated in the field of disperse and reactive dyes. Some thiophene and benzod'ifuranone based high fast­ of the new dyes of these classes introduced in the mar­ ness Dispersol dyes. They obviate the need for ket in recent years are briefly reviewed here. reduction clearing and are used in both exhaust and continuous dyeing. • Marlow-Van Loan Corp. offers a new disperse 2.1 Disperse Dyes bfack which claims excellent colour yield and ex­ Disperse dyes are used to colour polyester. Anthra­ haustion properties in dyeing of polyester6 . quinone dyes have much lower colour values and are • Black ASB Extra exhibits superior sublimation, more expensive although they give valuable bright light, wash and perspiration fastness properties red, blue and turquoise shades whereas azo dyes offer and high alkaline stability, thus enabling to acco­ a full shade range and high colour values. With the mplish single bath dyeing of polyester/cellulosics advent of jet dyeing and tHermosol application, the with minimum staining. search for new chromophores has led to the develop­ ment ofbenzodifuranone dyes of high colour value, brightness of shade, good substantivity and low ther­ 2.2 Reactive O V,,'S momigration. Some of the new disperse dyes availa­ Of all the classes of dyes used for cellulose, reactive ble are: dyes account for 21 % of total consumption of dyes in • Resoline Brilliant Red F 3GS (Bayer) has good the world and show upward trend in their application fastness to dry heat fixation and high brilliance for obvious reasons. which is required for fashion polyester and poly.e- Recently, a new generation of bi- and poly­ ster/cotton sports and leisure wear. ' functional dyes have been introduced which consist • BASF has introduced a new series of Pal ani! dyes of homo or hetero reactive systems. As a result, exha­ in its Palanil disperse range- Palanil Black G, ustion, fixa tion and migration can be controlled, lea­ Red FFB, Navy Blue GN, Navy Blue-CF, Brilli­ ding to much improved dye fixation and better repro­ ant Blue BGFN and Brilliant Blue BGM-CF. ducibility. Some of the recent additions are reviewed These dyes are available as low-dusting powders/ here. liquids. • Sumifix Supra range (bifunctional) has a high de­ Palanil Bue BGFN: Suitable for polyester blend gree of exhaustion and fixation, resulting in less dyeing, it is in sensitive to dyebath pH and reduction. wl:lshi ng-off (hence less dye in the effluent), high TELl: DEVELOPMENTS IN DYEING PROCESS CONTROL 43

fa stness to li ght, perspiration, peroxide washing In Indian market too, a number of companies have and chlorinated water, and high stability to acid come out with high-exhaustion a nd medium-exhau­ hydrolysis? stion bireactive d yes which a re finding increasi ng ap­ • Kayacelon reactive dyes are high-temperature plica tions. neutral -dyeing dyes which a re especially suitable for fast processing of cotton and o ne-bath dyeing 3 Developments in Application Methods of cotton/nylon, cotton / ~crylic and cotton/poly­ ester blends. 3.1 Pol)"ester Fibres • Cibacron C rangedyes (Ciba-Geigy) are bifunct­ During the dyeing of po lyester fibre. the conventio­ ional reactive dyes which have an aliphatic vinyl nal dyeing liquor contains la rge a1Tlounts of dispers­ sulphone gro up combined with either a monoflu­ ing agents a nd surfactants which are used to get rea­ orotriazine group o r an aromatic vinylsulpho ne sona ble rates of dyeing, ensuri ng levelness. This leads group with following features: to an effluent loaded with dye and dispersing agents Suitable for pad application and exhaust d yeing which is to be treated with an ever increasing cost. One at low liquor ratios, radically new approach is to use supercritical CO2 Very good solubility a nd hi gh to ve ry high degrees medium for dyeing PET with disperse d yes9 . After the of fixation , dyeing o peratio n is conwlete, dry dye powder, which - Excellent wash-off, and has not been used up. deposits at the bottom. There is High fastness levels8 no necessit y of dispersing agent or carrier. However. The environmental benefits include: thi s dyeing requires di sperse dyes of special structural No urea needed fo r di ssolvin g the d ye, features. free from dispersing agents. Also. the cost of - Less d ye in effluent due to hi gh fixati o n, a nd equipmcnt and pipings is hi gh. Bl~t the operational - Water and energy savings due to easy \vash-ofT. costs are very low as compared to that in conventional • Zencca's H-EXLexha ust dyes (hifuncti­ dyeing method (requires only 1/ 5th of the energy). o nal) have been engineered to produce hi gh per­ There is also no requirement fo r reduction clearing formance le vel d ye ing, mi gration, diffusio n a'nd treatments, washings, dryings, etc., thereby saving exceptional build-up pro perties. time and energy and providing protectio n to environ­ Of the reactive d yes available today, new Remazol ment. This method looks to set further the cause of EF d yes significantly reduce waste in efflu ent, cla ims QR and hence QM . Hoechst. These dyes Recently, Hoechst Mitsubishi Kasei (HMK) has Require 33-70% less salt than conventional reac­ made possible the d yeing of polyester in an alkalinc tive d yes, medium. thereby making the entire wet processi ng Provide higher fix a tion under low salt conditions simple and reproducible. The quality of dyed materi­ as compared to conventional reacti ve dyes, and als is also improved. In addition, the problems due to Arc available in environrnental safe packaging the presence of polyester oligomers in acidic d yei ng (low-dust powders or liquids). conditions are also minimized 10. • Rite Industries Inc. has launched the Rite Reac­ The HMK system involves both alkali-resistant tive B se ries of d yes which a llow to reduee the dyes and a newly developed stabilizer JPH95 for dyes amount of salt to be used in the d yein g with similar fo r alkaline conditions. The stabilizer has many func­ advantages. ti o ns such as buffering the dyebath pH to around 9.0-9.5 during dyeing, stabilizing dyes. chelating me­ • BASF hilS introduced five new reactive d yes into tal io ns and dissolving oligomers. The small variation the . Basil en range. These are Basilen Blue in pH during the dyeing cycle promotes excellent re­ E-FRN. Blue E- BGF,.Red F-RM, Red F-3BM producibility. and Yell ow f~3RM . Ba silen Blue E-FRN is a double anchor type mo nQc hl o ro trizine dye free of heavy metal which produces a unique royal 3.2 Cellulosic· Fibres blue shade and can be used o n polyester/cellulosic Many ideas surround the concept of blind colorati­ blends by the BASF recommended process. Basi­ o n, ranging from a simple no addition dyeing to the len Blue E- BGF is a brilliant blue d ye free of he­ management of all those factors that affect the colora­ avy meta ls and stable under hi gh-temperature tion ofa textile, resulting in a right-first-time dyeing. dyeing conditions (e.g. polyester/cellulose blend The latter definitio n implies the total control of all d ye ing). The o ther three Ha si len FM dyes have factors (including the human ones) that can influence hi gh exhaustion and easy wash o ut propertics to coloration and cause a shade to deviate fro III the stan­ decrease water usag.e and water contamination. da rd . 44 INDIAN J. FIBRE TEXT. RES .. MARCH 1996

The beneflts of blind dyeing can be summarized as a vinyl sulphone group a nd a monochlorotriazi ne rea­ follows: cost savin g, improved planning, better quali ­ ctive group. They react with cellulose over a wide pH ty. increased productivity, customer satisfaction. range and are, therefore, suitable for use in such opti­ etc. I I. mized dyeing processes I 5 . Dyeing with monofunctional reactive dyes is Thesc dyes have bee n adapted both fo r exhaust known to be rather sensitive to changes in dyei ng con­ dyeing and semi-continuous operations. Hi gh fixati­ ditions such as temperature, liquor ratio, addition of on, low substanti vity and good diffusion, effect ing salt and alkali. A low se nsitivity to dyeing parameters rapid and efTicient rcmoval of small amounts of unfix­ using dyes with two different reactive groups is parti­ cd dye, are the salient fea tures of these dyes. To i ncre­ cularly advantageous in continuous dyeing operati­ ase the fixation of dye, the one of the most popular ons as it helps to achieve reproducibility of shades, i.e. alternative energy sources which could he used is rad­ right-first-time and every time. io-frequency (RF) energy. The key factors influencing the rates of ri ght-first­ Heating of the batch with radio-frequency energy time production are dye selection, control of raw mat­ during the batching stage grea!ly accelerated the rate erials and on-line process control. In itself, improv­ of fixa ti on. Fixa tion levels achieved usi ng opti mi zed ing the rate of right-first-time production can impr­ R F-assisted methods were approximately equival­ ove productivity by 20% and the return on sales to ent to those achieved in conventional pad-batch dye­ l6 a round 13 % (ref. 12). ing . Right-first-time production will be maximized if Dawson International, in 1978, patented a process these fundamental measures of performance within and the equipment design used for fixing dyes or che­ the compatibility matrix RCM are set micals with RF energyl6. The process involved conti­ a t: nuous conveying of treated fibres through closely co­ Substantivity 70-80% nfined tube located between flat parallel electrodes. Migration Index > 90% By generating RF energy field within the tube, a self-­ LDF > 70% sealing pressure chamber was created by the format­ Tso, a minimum of 10 min ion of steam from the wetted fibres. The advantage claimed was an increase in the reaction rate ofthe dye A comparison ofRCM of individual dyes will pro­ on the fi bre. vide a measure of the compatibility of dyes when they The semi-continuous pad-batch process using RF are used in combination. Dyes with similar performa­ energy has also been recognized as one of the most nce and with substantivity, migration index, LDF, efficient methods ofapplying reactive dyes to cellulo­ and Tso values within the target specification will offer sics with excell ent reproducibility, leading to ri ght­ robustness to small variations in processing condi­ first-time every time concept. tions, shade reproducibility and level dyeing perfor­ Laser fixation is a feasible low-heat trea tment met­ l2 hod for fine-line dye fixation . A comparison of wash mance . Newer developments controlling additional para­ fastness of ha nd-ironed and laser-treated specimens meters relati ng to the physical characteristics of the showed that the specimens treated with a n argon-i on substrate take into account the influence of me chan i­ laser at 129°C and 23YC maintained color significan­ cal and hydraulic forces exercised by the machine du­ tly bcttcr than thc specimens trcatcd with a lowcr lascr l3 heat (94°C) and hand iron ( 190°C). This was true for ring the process . The control equipment a ll ow the hydraulic and mechanical action of the dyeing mach­ 10, 20 and 30 washes. A laser tempera! ure of 129°C ine to be adjusted, not only for the entire process but was as effective in setting fibre reactive d ye in cotton as also for each period in the dyeing pcocess. This princi­ was a laser temperature of 23°C, indicating that a ple is utilized in the synchron dyeing control system, lower energy laser would be as useful in setting dye as 17 which synchronizes liquor circulation, fabric speed higher power models . l 4 and process cycle . Electromagnetic hea ti ng produces d yei ngs of si mi­ The alkali dosing process is becoming popular as a lar shades to those obtained by conventional heating 6 rationalized dyeing method for reactive dyes - s. when pressure and temperature conditions are kept Many types of reactive dye can be used, but the opti­ the same for both treatments. However, electromag­ mum pH range will depend on the nature of the dye netic heating allows smoother and more homogene­ employed. To control the rate of exhaustion, it is desi­ ous boiling than docs conventional heating and can rable to use a dye that reacts over a wide pH range so be useful industriall y 18 . that the conditions can easily be controlled during Lewis and eoworkers l 9 carried out fibre pretreat­ dyeing. The Sumifix Supra range of dyes contain both ments aimed a t dyeing with reactive dyes under neut- TEll: DEVELOPM ENTS IN DYEING PROCESS CONTROL 45 ral to sli ght Iy acid ic conditi ons in the absence of elec t­ Such amin o-containing dyes can be readily prepared 2 1 rolytes. All of th ese' treatments introduce cationic rrom all eO lllme r~ ial ranges of reactive dyes . (basic) resid ues in the form of quarternary, terti ary Prdrea tm en t or cotton wi th polye pichlorohydrin and secondary am in es. dilllethylamine prod uces a modi li ed cotton that can One of the most conveni ent pretreatments wa s to he dyed un der neutral conditions with se lected low­ apply polyamide epichl orohyd rin res in to the ce llul o­ reactivity dyes wi th out sa lt. The dyei ngs of trea ted sic fab ric usin g pad-dry system. Selection of highl y colton ex hibit improved colour yield and hi gh was h reactive dyes gave good co lour yield on thi s type or r;' lstness .. Bot h ex haust dye in g and continuous dye ing 2 2 fabric and the fixation of dyes proceeded si mpl y by l)f trea ted cotton give hi gh colour yield . appl ying them from a dyebath se t at pH 5 and raising Pretreatment of co tt on with hi gher molecu lar mass the temperature to boil. Unfortunately. rin g dye ing pol ye pi chl orohydrin dimeth ylamine could intro­ of tb e fibre and ya rn s was clearly evident and as a duce more cationic sites onto the modified cotton. result, li ght fas tness red uced by 1-2 points. These dra­ This would increase the ex tent of complexing with the wbacks, however, have bee n overcome by th e use or dye and thus improve th e dyeability with direct and low molecular we ight species and pretrea tin g the cot­ reactive dye s~3. ton fabric usin g a pad-thermollxa ti on tec hnique. Eth ylened iami ne tetra(methylene ph osph onic) Another advant age is th e need fo r short er washin g­ acid when adsorbed by cotton fibres prior to the appli­ olfprocess to remove the unfi xed dye because of hi gh ca ti on of the direc t dye Solamine I- ast Red 4BL causes level or dye -libre fixation ac hi eved. a marked in crease in rate of dyeing. It also improves 24 In eo loura ti on of ce llul osic fibres. vat dyes (includ­ the wet fastness properties of the dyed eotton . in g Indigo) and sulphur dyes hold a la rge part of th e dyestuO' mark et. Vat dyes give exce ll ent fa stness, 3.3 Wool Fibres whereas sulphur dyes arc economical with good deg­ . Due to th e increasing enviro nmenta l problems of ree of fastness properties. The red uction process emp­ dyeing with heavy metal containing dyes as we ll as loyed here req uires reducing age i1t s and it has ye t not wi th reacti ve dyes, the dyein g behaviour of pl asma­ been possi ble to regenera te th ese conven ti ona I ag­ treated wool toward s these dyes was recently in vesti­ ents, except in th e standing dyebath procedure. ga ted by Hocker and eoworkers2s. Plasma trea tment on wool have shown th at it leads to, apart from an In recent inves tigations, an elec trolyti c process was improvement in the mec hanical properties of the used to

the acti on offree radicals which might be assisting in A ut o ma tion or the d yei ng process avoiding in­ covalent fi xa ti on of the dye in addition to usua l ionic correct a ddi ti o ns of dye solutio n, auxiliaries a nd links, hydrogen bonds a nd va n der Waals' fo rces. The chemicals: mo reover, there are no idle times. use of bufTers like sod ium acetate-acetic acid has a lso Reliability of the process, because there is a lways been found to be quite promisin g as far as the fi xatio n an o ptimum reacti o n medium a vailable for the and the fastness properties of th e on silk a re d yein g process. concerned 26.27 . - Increased reproducibility by exact rcpetition of the d yeing process. 4 Developments in Machinery Optimiza tion of the leve ln ess. As the textile wet processors reali ze that they must Cost sa vings by using caustic as fixation alkali adapt to the changing needs of the ma rket, the machi­ in stead of soda (e.g. in reacti ve dyeing). nery manufacturers must take appro priate actions Cost savings by using acid (acetic o r fo rmic) in through extensive research and development to deve­ wool/po lya mide d yeing. lop a new genera tion of dyein,!! machineries that are - Simplilication of the rinsing a nd washing proces­ able to meet the changing market conditio ns. ses in reacti ve d yeing, owing to less hydrolyzate The machinery develo pments are towards achi ev- fo rmatio n during the d yei.ng process. ing o ne o r more of the following o bjectives: Orten it is possible to reduce the d yeing time. Reducing the labo ur complement, Mo re re li abl e sho rt liquor dyei ng, especially wit h Increasing the prod uctivity, dark colours. By metering-in the d ye, the concen­ Minimizing the req uirements of Iltilities, tra ti o n of d ye in the dyebath is reduced so tha t no Simplifying the machine operations, agglo meration can occur. Saving in machine space, Increasing automation in application o f dyes to the Reducing the efflu ents, thus minimizing possible fibre substrate has been o ne mo re guidin g principle in po llutio n, the d eve lo pment of the machinery as described aho­ Recovery of heat energy a nd water, and ve. One of th e typical examples in exhaust d yeing is Economizing the cost structure. ADC-200, a metering device deve lo ped by Hoechst In batch piece a nd yarn d yeing, it is essential that a nd ADCON. The process, mo re known as Ramazal- the fi nisher has machines at hi s disposal that operate automat, meters the supply o f a lkali for the li xatio n cost efTectively. At the same time, the finished product o f the reactive d yes a uto ma ticall y and progressively must meet the quality demands of the consumer. The in order to o btain the hi ghest leve ln ess in sho rtest introductio n of new technology and the modification dyeing time. of design that entails are the moves in the right directi­ The emergence or short liq uo r jets fo r d yeing cot­ on. M o re economica l d yeing processes can be achie­ to n and it s bl ends has been marked over recent years. ved in the piece and yarn dye ho use applying the short Not only d ocs this process offer the possibility of and ultni-short liquo r techno logy, liquor fl ow cont­ more econo lllical d yeing but it also reduces the load rol and finishing by the Synchron D yeing System. inflected o n the environment to the tune or 30% (rd. 29). Of course, an increase in productivity a nd qua lity is On-line controls in continuous dyein g are ro und to today inconceivable without a n electronica ll y-cont­ be elTective in improving the cost elliciency and repro­ rol led process seq uence. ducibi!ity. Forexample, on-line liquo r pi ck-up mea­ It is, therefore, important for the fini sher when inv­ surement wit h level correctio n and contro l en:lblcs esting in new equipment or improving old machine precise calculation of the volume o f li quo r Ileelled plant to get familiar with the la test advancement in and conseq ucntl y savin gs in the cost of dyes a nd auxi l­ dyeing machine ma l1Lifacture a nd the latest process iaries. On-line colourimctry orthe p;ldJed rabri c im­ tech no logy28 . proves the control over the productio n process wit h T he advent of metering techno logy has made the reliability and improved quality·'o . short liquo r dyeing a reliable process. The modern meteri ng system- M ulti-prod uct II1J ection 4, I J igg('r Dye ing (M PI)- permits contro lled dispensing of solids o r li­ Jigger is the most stable mac hine in dyeho use and quids such as dyes, salts, alkalies, acids or o ther tex tile future d yeingjiggers will have a very modern look and a uxili a ri es. will be characterized with useful aspects vvhich a re M lIlti-product injection (MPI) metering system in sUlllmarized under " Future Trend<' in this JXlpc r. conjunction with the application of sho rt and ultra­ sho rt liquo r technology has the foll owing advantag­ 4.2 J(" Dyeing es: The utility, specific applicatio n and press ure con- TEll: DEVELOPMENTS IN DYEING PROCESS.CONTROL 47 dition inside the vessel as well as the shape of the vessel The FD 45 pad-stream machine from Ramisch have been, for quite some time, under constant exami­ Kleinewefers for the continuous dyeing of cotton and nation. Some manufacturers have finalized designs its blends with viscose rayon or polyester has been for all types of materials and dyes, which claim all the reported. In addition to a Bicoflex padding arrange­ important features such as: ment, the machine has system for feeding in single Dyeing.temperatures up to 140°C when desired, doses of chemicals and storage programmable contr­ Soft flow or overflow, ol. This control system has a modem whidi permits Low liquor ratio up to 1:5, continuous dialogue between the supplier and the cu­ Automatic controls by microprocessors, stomer. It could be preferably used for vat and sulp­ 33 Suitability for light weight as well as heavy fab­ hur dyes . 2 rics, say 50-500 g/m , High fabric speeds at the lowest possible 5 Garment Dyeing pressure, . Whilst garment dyeing has an in-built lead time Tangle-free operation, advantage for producing comparatively sm'all tots, High quality dyeing results with reduced tension the com bined effect of customers wanting larger lot and surface abrasion, sizes quicker and more reprod~cibility and the adva­ Minimum operator involvement, and nces in response time made by the colouration routes Economy of energy, water and chemical auxiliary has driven development in gannent dyeing technolo­ 3 1 ingredients . gy. In other words, more air, less liquor and gentle han­ dling have been the key factors behind the develop­ ment of jet dyeing machines. 5.1 Dyes Then's Air-Flow ASF machine uses the liquor ra­ Proper selection of dyes and finishing chemicals is tio about 1:2 and it is found to give high productivity quite important for dyeing of gaments made of cott­ and low consumption of water and chemica1. The dye on, wool, nylon, polyester, acrylic and .their blends. solution is automatized with the air stream which is pro­ The range of articles include socks, sportswear, duced by the blower for application on the fabric. The shirts, T-shirts, etc. Of the dyes available in the mark· Italian machinery maker 'Laip' has brought out air­ et, reactive dyes are the most popular dyes used in water-flow Mod 800, a latest rope dyeing machine, garment dyeing. Newly introduced bireactive dyes for both knitted and woven fabrics. The air-injection are finding increasing application and are preferred 3 is not simply used to accelerate the fabric to high speed to direct dyes ,,". Subsequent treatment with dye fixing but in some cases to open the fabric. " Apollon Twin agent is also recommended to improve fastness prop­ Soft Flow" machine manufactured by a Greek mach­ erties. Other dyes used for garment include acid and inery manufacturer makes use of micro wash system, reactive dyes for woollen gannents, cationic dyes for using clean hot water which is introduced through the acrylic, and sulphur and vat dyes for cellulosic gar­ double-overflow of the machine to achieve very high men ts. The chlorine fastness of sulphur and reactive cleani ng efficiency32. dyes is poor whereas vat dyes have the best perfonna­ nce properties although they a re quite expensive. 4.3 Continuous Dyeing The component units of the contin.uous dyeing ran­ 5.2 Dyeing Methods ges are being modified from time to time to minimize Exhaust dyeing is carried out using special dyeing the possible imperfections in the final dyed product. 111achines for garments. Development work regarding these component units is still .in progress. The points which have been a nd 5.3 Machinery which will still be considered during such work inclu­ The most recent development from Gilwood (Fab­ de: ricators) Co. Ltd, a British machine maker, is an oval, Composition and formation of pad rollers, double side-paddle machine for dyeing readymade Pre-drying by infra-red radiation to avoid possi­ knitwear. Machine capacity ranges frum 150 to 6800 ble mi gration, with vertical fa bric passage, and litres. Positive dye penetration is achieved by specia­ Well-designed and evenly impinging hot flue or lly designed paddles fitted with synchronised drive high-temperature dryers for thermosol dyeing. for enhanced liquor circulation. An innovative recir­ With the advent of synthetics and blends, the ther­ culation system delivers heated liquor simultane~u­ mosol system is bound to achieve a very promising sly to the two-paddle area, significantly improving position. the overall temperature controp5. 48 INDIAN 1. FIBRE TEXT RES .. MARCf-1 1996

The recent inn ova ti on in convcntional drum dye­ used I'or 100% cellul osic fabrics. The dyeing is carried ing machine is the one with liquor circulation through out in tensionl ess form in winch and sin ce th e wi nch the drum centre. This helps imparting an extremely dyeing machine doesn' t allow uniform temperature gentle treatment to the goods even at low liquor rati­ Illaintelwnce. the reactive dyes of HE and ME cl ass os. i.e. I :6. This kind of machinery has the advantage arc increasingly being preferred. of dyeing all kinds of hosiery. The goods dyed can al so be cent,:ifuged in the same machi ne which means in ve­ 8 D)'eing of Terry-Towels stment costs ["or centrifugers a re a voided. The techni­ The dye ing of terry-t owel is more conlined to dye­ ca l advantages include: ing of ya rn s which are then subsequently used for Level dyei ng due to rapid liquor interchange. producing jacquard designs. The asr ects of dye in g Reduced water eilluent and less steam and chemi­ and the se lec tion of dyes rema in sa me as in the case of cal consumption because of operations at low liq­ hosiery. However, when no tinting of th e' gro und is lI or ratios. and e.\ pec ted , th e va t dyed ya rn s are used in manufact ure - In-built hydroex traction·". of terry-towels rather than azo, sulphur, reactive and The newer machinery for garment dyeing are based direct dyes. on the foll owin g features: (i) Low liq uor ratio, (ii) A two-s tep dyeing tec hnique is available by which Microprocessors- for improved lot-t o-I ot reprod­ cross-dyein g of 100 % colton te rry cl oth can be achie­ ucibility, (iii) Hea t exchange rs - for rapid heating ved with fibre reactive dyes. The fir st step in volves uJ1dcooling. (iv) !....int filte rs) (v) Centrifugal hydroex­ continuously dyeing of the fa bric, usi ng an auxil iary traction , (vi) Ea sy sa mpling with out droping dye that promotes colora ti on of the tips of th e terry cloth. liq uor. (vii) Tilting- for ease of loading/unl oading, Subsequent dyeing is carried out in a beck with contr­ (vi ii ) Cushi oned suspension, (ix) Variable drum asting colour fibre-reactive dye. An att racti ve tow­ speed, and (x) Automatic balancing drum. toned appearance result sJ o. What is important in garment dyein g is to achieve level dyeing, with excell en t penetration in short dye­ 9 Future Trends ing cycle. The deve lopments arc thus directed tow­ The ~ ye manufacturers wou.ld conce ntrate on re­ ards these aspects. sea rch acti viti es to deve lop new chrolllophores and dyes offering wider shade gamuts, hi gher colour fa st­ 6 M icrofibre Dyeing ness, improved environmental impact and higher ov­ The microfibres are the lates t entrant in textile mar­ erall cost elTic iency in the coloura ti on process. ke t and ha ve inherent adva ntages for which their con­ I n future, the di sperse dyes based on benzodifur an­ sumption is increasing day by day. However, because ones wilLencourage m<1re resea rch to dea l with struc­ the microlibre has increased su rface area, th e rate of tural and ph ysical fOnll modifications designed to im­ dyeing is tremendously enhanced and it becomes ess­ prove build-u p, and also encourage resea rch for new en ti al to control the dyeing of microfibres to avoid ehromogens th at are particularly suit able for polyes­ uneven dyeing. The dyeings obtained are also appare­ ler in ge neral and microfibres in particular. ntly lighter as compared to the ones with the normal The future developments in reacti ve d yes are likel y denier polyester yarn and it is difficult to ge t the dee p to be concentrated on: shades in microdenier varieties. The fastness to wa sh­ • High application flexibilit y: A broad spectrum of ing. rubbing and li ght is inferior to th at of normal ~hades ,h t) uld be dyea ble by widel y dilkringappl­ denier polyes ter. This necessita tes the selection of ica tion !/.,'lhods with a small number of dyes. proper range of disperse dyes specially suited for mic­ • Goo el reproducibility and good le ve lling proper­ rofi bres. ti es. The Foron RD dyes of Sandoz seem to be perform­ • Outstanding protecti on to environment. in g favo urabl y. To improve th e li gh t fa stness of the • Maximum productivity. dyed microllbres, use ofFadex RF liquid is recommc­ Apart from these, the dyeing process with dyes con­ nded since thi s acts as a kind of UV -absorber. A num­ taining no reactive group (in the usual sense) but cap­ ber of dyes manufacturers are making the se lection of able of being crosslinked to cellulose via a suitable dyes from the pont of view of their applica tion on reagent will find its pl ace in industrial applicatiun. micro Ii bre fa bric. For dyei ng cellulosic fibres, high-fastness direct dyes will be selected ( 0 avoid usc of corper or chrom­ 7 D)leing of Hosiery/Knits ium sa lts. In reacti ve dyeing, use of urea will be mini­ In dyeing of kn ilted fabrics. cold brand as well as mi zed . For dyeing with sulphur dyes, the hi ghl y poll­ hot brand reacti ve dyes and also the direc t dyes are uting sodiulll sulphide will be replaced by other ag- TELl: DEVELOPMENTS IN DYEING PROCESS CONTROL 49 ents such as reducing byproduct from maize starch 6 Anon. Am Dyest Rep. 83(4) ( 1994) 19. 37 38 industry or hydroxy acetone • • For oxidation of 7 Andreq Lee, Inl Dyer. 179 (April 1994) 29-30. vat and sulphur dyes, hydrogen peroxide, sodium pe­ 8 Lultdiuzer J P, Texl Chem Color. 25(5) ( 1993) 25 . 9 Saur W. Krittel D & Schollmeyer E, Inl Text Bull. Dyeing/ rborate and 1, 3-dinitrobenzene sulphonic acid wi ll Prinling/ Finishing, ( I) (1993) 20. be used in place of dichromate. 10 Imafuku H, J Soc Dyers Colour. 109 ( 1993) 350, During polyester dyeing, chlorinated or phenolic II Gordo n M Fannie, J Soc Dyers Colour, 107 (1991) 197. carriers will be avoided. Acetic acid used for pH adju­ 12 Bradbury M J, Collishaw P S & Moorhouse S, Inl Dyer , 179 stment having hi gh BOD will be replaced by other (A pril 1994) 12- 18. 13 Carbonell J, Am Dyest Rep. 76(3) (1987) 34, agents. 14 Colli shaw P S. G lover B& Bradbury M J, J Soc Dyers Colour. In case of dyeing machineries, the jiggers oftomor­ 108 ( 1992) 13-1 7. row will be characterized by the following useful as­ IS Kunihiko Imada & Naoki Harada, J Soc Dyers C% ur, 108 pects: (1 992) 210-214. • Excellent closing and opening. 16 Carlough Mark S & Perkins Warren S. J Soc Dyers Colour. 109 (1993) 65-7 1. • Heated hook for drip-proof working. 17 Kathlee Kearney & Alice Maki, Texl Chern Colour , 26( I) • One way flap-opening chimney for releasing un­ (1994) 24-28. wanted hot and wet flue . 18 Jean-Pierre Dueaz, Jean-Marie Thiebaut & Daniel Wattiez. J • Internal machine li ghting to offer a good view of .'Inc Dyer lolnur. lOR (1992) 2R4-287. the fabric under process. 19 Lewis D M, J Soc Dyers Colour , 109 (1993) 357. 20 Bachtole T, Burtscher E, Turcauu A & Bobleter 0, J Soc Dyers • Pump for recirculating the dye liquo r. Colour, 110 (1994) 14. • Safety devices and emergency switches for avoid­ 21 Lewis D M & Lei X P, J Soc Dyers Colollr . 107 (1991 ) ing damage owing to sudden breakdown. 102- 109. • Automatically controlled drain va lve. 22 Wu T S & Chen K M, J Soc Dyers Colour. 109 (1993) • Automatic reversal, delay-relay fabric direction 153- 158. 23 Wu T S & Chen K M, J Soc Dyers Colour, 109 (1993) indicator as well as speed indicato rs. 365-368. • Effective crease removing expanders and motori­ 24 Ri ad Y. EI-Nahas H M & Harnza H M. J Soc Dyers Colollr, IOT~ zed selvedge aligning and continuous centering ( 199 1) 144-147. system. 25 Hocker H. Thomas H, Kusters A & Herrhing J, Melliand Text- Developments in winch dye ing machinery with ilh!!,., 75(6) (1994) 131. 26 Jutao Luo. J Soc Drws Colollr, 107 ( 199 1) 11 7- 120. better temperature. distribution a nd liquor movem­ 27 Jutao Luo. J Soc Dyers C% ll r. 107 ( 1991) 14 1-143. ent are ex pected, mainly for dyei ng knitted fabrics. 28 Bo hrer E. Jan,- Handrik Heetjans & Caesfeld . Me/liand Texti­ Ib er. 12 ( 1990) E44 1. References 29 Kurt Bacher. J Soc Dyers Coluur , 108 ( 1992) 479-480. 30 Kurt Van Wersch. Monchngladbach. M ellialld Tex lilber. ( I) I Parto r R. J Soc DI'ers Colour. 11 0 ( 1994) 4. (1993) E23. 2 Allan H N. Quick re.ljJOI1Se ill apparel mWIl!/,acllIring (The Tex­ 31 Bhagw1it R S. Cololl/'age, (May 1994) 53. tile In stitute. Manchester). 1990. 42. 32 Anon. flit Dyer, (A ugust 1994) 29. 3 Teli M D & Ve nu G R Gudigantla. Proceedings Guldel; Texlile 33 Hulsewig H. Textilveredlung . 29(7/8) ( 1994) 196-198. Con/'erence [Textile Association (India)]. 1994, 6 1-67. 34 Gore C D & Settle H J. Am Dyw Rep. 83(5) ( 1994) 24. 4 Holme I, /nl Dyer. 178( 10) (1993) 13 . 35 Anon. /111 Dyer. 179(3) (1994) 22 . 5 Sheshadri S, Book a/papers, Scminar Oil s tat e - o f~ th c-a ,.t · alld 36 Ellers J N. Am Drest Rep , 82 (September 1993) 70-73 . .Iii/ure trellds in chem ical processing o/,I!!x liles (BTRA. Bom­ 37 Dalmia R K & Sharma M. J TeXI Assoc, 54 (1993) 32 . bay). 1994. 38 Ballmga rt e U. Prog Colour. 17 (1987) 32.