Indian Journal of Fibre & Textile Research Vol. 21, March 1996, pp. 57-63

Recent advances in wet chemical processing machinery

Sanjay Gupta Textile Design & Development Department. National Institute of Fashion Technology, Hauz Khas,

New Delhi 110 016, .lndia

Advances in textile processing machinery in past few years have been influenced by globalization of textile industry. environment and socio-economic factors. diverse finishing requirements and quality demands. Advances have taken place in process control and automated systems that provide flexibility , versatility and reproducibility. Innovations have been few. Against this backdrop, the various advances in machine design, processes and automation for pretreatment, dyeing, printing and finishing of fabrics have been discussed . It is observed that the advances in process machinery sector meet the requirements of our times, i.e. need for shorter/faster processing and maximl:lm flexibility (quick change and rapid response) as also the demand of reduced water, energy and chemical consumption.

Keywords: Automated systems, Dyeing, Finishing, Pretreatment, Printing, Textile processing machinery

1 Introduction 1 - 6

The paper is in the unenviable position of being written just before ITMA '95 and being read imme­diately afterwards. The machine suppliers are, how­ever, unlikely to have held back any major innovation for the show from the competitive market conditions existing today.

Since the last ITMA held four years back, many new challenges and changes have emerged that have influenced the direction of development in textile ma­chinery. The major influences have been of globaliza­tion of the textile industry, environment factors, ene­rgy constraints, diversity and multiplicity of colouni­tion and finishing requirements, quality demands and requirements emanating from a more discerning and selective consumer market.

In the global market, the need to produce world class product quality virtually eliminates any diffe­rentiation with regard to the degree of sophistication desired in machinery. For India, to opt for maximum automation may not be justified against low labour costs but, nevertheless, cannot be ignored in terms of the more important 'automation for quality' target­ted at export markets. Yesterdays' " we cannot afford to" has to change to present days' reality of "we can­not afford not to" (refs 3 & 4).

Against this background , global operators at the leading edge of technology must remain adept at sele­cting and investing in machinery, equipment, process control and automation systems that provide flexibi­lity and versatility in terms of range of fabrics that can be wet processed, and reproducibility to provide uni-

f;ormity. Top priorities today are economy, ecology, fast response , quality and flexibility.

With these priorities in mind, specific technologi­cal advances in machine design, processes and auto­mation are discussed in this paper.

2 Machinery for Chemical Pretreatment Chemical pretreatment sector is of vital importa­

nce to the processing industry because of the increa­sed necessity for greater uniformity and fault-free, right-first-time production in subsequent dyeing, printing and finishing4 ·6 . The general trend towards the increasing use of light-weight fabrics , particu­larly polyester/cotton blends, which crease more, re­quires open-width pretreatment using integrated pad­batch or pad-steam process. Use of hydrogen per­oxide as a predominant bleaching agent from enviro­nment point of view also supports this process route . Refined versions of high wet pick-up systems (ini­tially displayed at ITMA '9 1) for single-stage bleach­ing consume less water, caustic, energy and time, and cause minimum pollution of waste water. A number of such systems, all operating on the basic principle of maximizing the liquor pick-up while impregnating the goods before steaming, are available6 - 8

(Table I). Continuous, high-intensity, high-temperature

and counter-current flow washing is an essential part of any pretreatment sequence. New open-width wa­shers based on continuous interchange of water aro­und the fibres in the fabric with wash liquors oflower contamination have been developed. These washers

58 INDIAN J. FffiRE TEXT. RES., MARCH 1996

bascd on spray, multi-nips, vacuum extraction and ultrasonics, e.g. Jat-Vac by Farmer-Norton, Extra­cta and Impecta by Benninger, and Effecta by Goller, decrease water and ste.am consumption, give a highly concentrated effluent for recycling and have extre­mely small space requirement, investment and opera­ting costs9 - 11 .

Machine developments in mercerization include hot impregnation Lones, improved designs of clips to minimize clip marks, enhanced fabric stretching syst­ems for chainless mercerizing machines and improve­ment in recuperation of caustic soda. A development important to India, however, is that of small-size batch mercerisers (Fig. I). Occupying minimum of space, these ranges are universally applied for the processes of partial mercerizing/caustic treatment, stabilizing and rinsing to smallest of lots9 •

12.

Table I- Maximum pick-up systems for single-stage bleaching

System

Super-Sat

VAS 200

Flexnip

Optimax

Ben Bleach. Impecta

Reco Vac. Raco-Yet

Dip-Sat

Brubo-Sat

Manufacturer

Babcock

Farmer-Norton

E. Kusters Maschinenfabrik

Menzel Vertriebs

Benninger AG

Ramisch Kleinwefers

Maschinenfabric Max Goller

Brugman

Flexnip application system by Kuster (Fig. 2), mentioned above, can be effectively used in place of a saturator in a mercerizer, thus bringing down alkali content from 1000-2000 L to just 10 L. It also offers an unmatched flexibility of interchanging mercerizing with causticizing quickly, without any change in set­up. Modern open-width washers used here will give highly concentrated washings for easy recuperation of caustic l3

.

t Fig. 2-Schematic diagram 01 Flexnip applicator

Expander Elargisseur Ensanchadora

Spray Gicleur Rociadora

50 kN SQueezer Exprimeur de 50 KN Exprimidor de 50 kN

Spray Gicleur Rociadora

Expander Elargisseur Ensanchadora

Refrigeration Unit Unite de Relrig(lration Unidadde Relrigeracion

i Refrigerated Caustic Storage Tank Reservoir a Soude Caushque Refrigeree Tanque de Sosa Relrigerado

Circulating Pump Pompa de Circulation Bomba de Circulaci6n

Hoi Water Tank Reservoir it Eau Chaude Tanque de Agua Caliente

Fig. I- Schematic diagram of a batch-mercerizer by Farmer-Norton

Floor l.eYe1 Niveau it Terre Nivel del Suelo

GUPTA: ADVANCES IN WET CHEMICAL PROCESSING MACHINERY 59

Significant developments have taken place in mer­cerization machinery for knit goods. Major manufac­turers are Dornier, Sperotto Rimer and Brazzoli . Machine offered by Dornier has a patented system of stepless adjustable circular expanders, giving a selv­edge-mark and crease-free, dimentionally-stable fa­bric of extremely soft fee !I 4.

3 Machinery for Dyeing Developments here have been on several fronts,

Vi;l. vacuum application systems for dyeing; high-effi~ cl.ency padders and other application systems for con­tinuous dyeing; soft flow and air flow machines for dyeing of knits and light-weight fabrics ; automatic dye dispensing and colour kitchens; and flexible, au­tomatic yarn dyeing systems.

Dyeing industry today lacks a cost-effective, eco­logically sound system for dyeing small lots. Lot size has come down to 200-600 m which is economically unviable on a continuous dye range and for which batch dyeing machi nes like jigger, winch and jets are to be used. These exhaust machines are prone to batch to batch variations and waste generation. Vacuum dyeing systems like LVLM (low-volume low-moist­ure) systems by EVAC Corp.15 (Fig. 3) and VAS 200 by Farmer-Norton effectively surmount this prob­lem by giving an even and thorough penetration of dye on a,continual basis from a high concentration low-volume dye trough. As against a typical dye/pad bath of about 140-150 L, the capacity of these systems is less than 15 L. Vacuum also removes surplus water, giving a large saving in energy during drying9 . 16 .

Though small lots are required for sampling, bulk orders require large yardages to be dyed in a single shade. Continuous dyeing by pad-store or pad­steammethod is making a comeback. Primary requi­rement of such a range is a padding mangle giving a level, even application throughout the length and

Fabric

ChE'micol tank

OVE'rflow

Fig. 3- Schematic diagram of low-volume , low-moisture (L VLM) system for c()l1tinuous dyeing of small loIS

width of the fabric . Ordinary mangles cannot do this job. Severai speciali7,ed "Intelligent pad-rolls" aJ:e available today like Kusters swimming rolls and Bico­flex padders by Ramisch Kleinwefers l 6 . The flexnip applicator described earlier is also eminently suitable for pad-steam dyeing l 6 . All these systems have built­in cleaning down facility , minimum waste at the end of production run , and minimum downtime between production runs.

Dyeing of knitted fabrics, microfibre fabrics and fabrics· made out of blended and easily creasable mat­erial require more gentle handling. Injet dyeing mac­hine, fabric is displaced by the force exerted by a large volume ofliquor moving through a venturi, resulting in relatively high fabric speeds and causing certain degree of fabric surface abrasion . In overflow system, fabric is propelled by the overflow liquor only with­o~t dynamic pressure, providing more gentle treat­ment. In the latest generation of soft-flow machines. a part ofliquor has been replaced by air, giving a loftier fabric and a highly ecofriendly dyeing. Several Asian, British, Italian, German and American machine ma­kers have come up with different versions based on this aerodynamic principle. Variably adjustable and programmable nozzles are available now (Fig. 4). Po­Iytetrafluoroethylene coating of inner sUiface is carr­ied out to reduce frictional drag4

• Liquor ratios used are in the region of 1:4 to 1 :6, irrespective of the load .

. Technology of dyeing polyester in supercritical ca­rbon dioxide under pressure, first demonstrated in ITMA '91 , is quite well developed now. Larger mach­ines will no doubt be shown during ITMA '95 (ref. 4).

With the current interest in quick response and right-fIrst-time dyeing, practice of blind dyeing us­ing standardized dyeing cycles and automated dye dispensing and colour kitchen equipment is on the increase. Lower-cost systems with greater flexibility , versatility and ability to network with laboratory dy­eing machines are now available 17. These are comple­mented by on-line colour measurement and control systems, hand-held spectrophotometers fur quality control and colour matching softwares. Data colour, IIunterlab and Macbeth are the. pioneers in this field.

Yarn package dyeing machines have undergone a total technology upgradation in last few years. Em­phasis now is on flexible load capacity, versatility and automation/robotics options l8 . Many machine ma­kers like Gaston County, Longclose, Fong, Bellini and OBEM will be coming up with innovations cover­ing the above-mentioned aspects. OBEM's horizon­tal multiple-tube API/O dyeing systems, for example, .

60 INDIAN J. FIBRE TEXT. RES., MARCH 1996

Liquor

Liquor

Fig. 4-Vario nozzle of the new Thies soft-flow machine

has ability to handle lot sizes rangiIJ.g from 20 kg to 3000 kg per batch with almost constant liquor ratios, independent of batch size. Cubotex of Italy has come up with a multi-purpose cabinet machine with a spec­ial pump that gives a range of capacity and head requi­red to dye yam in hank, bobbin or cake form. Most machines have PLC (programmable logic controll­ers) to monitor and control process variables and ro­botic options to load and unload the machines7

•18

•

4 Machinery for Printing The technological advancements 19

-22 in the field

of printing have been dramatic, particularly where I ndia is concerned. The process of printing, consist­ing of design development, colour separation, tracing production, screen engraving, sampling, paste prep­aration and finally printing, may take anywhere bet­ween 6-18 weeks and large investments are made even

before the customer makes a decision regarding his selection. With modem technology, this time frame has been reduced to less than a week. At this point, I would like to stress that the modem technology does not replace the original designer who would continue to give the initial creative input.

CAD application starts with at least one overall coloured design which is scanned into the computer and can then be mo.dified and coloured. Various col­our combinations are tried, stored and a hard copy taken out on paper or fabric. Inkjet printers available now-a-days can print directly on fabric using react­ive dyes. In fact, there are special steamers for fixation of such prints23. Selection of design by customer can hence be made at this stage by simply looking at the printed sample or at the hard copy. Major saving in time is, however, made in the pre-print stage where the colour separation of selected design is carried out

GUPTA: ADVANCES IN WET CHEMICAL PROCESSING MACHINERY 61

by the computer and the screens directly engraved . Laser engraving systems by Stork and Zed for lacquer rotary screens and flat screens by companies such as Macchine e Sistemi are commonly available24

. These systems can prepare screens for several designs in one day. Chaper systems where, instead of engravers, plo­tters are used to prepare tracing are commonly availa­ble even in India.

Among the printing machines, the share of flat screen has remained more or less static, with rotary screen printing replacing roller printing in most cases. 61 % of the total meterage is printed using rotary prin­ting, 19% by flat screen printing and only 14% by roller printing machines. In the last two years, rotary printing machines have been modified to make them more versatile (coping with sma11 lots) , economical and ecofriendly. Modifications include providing a ring motor for individual coritrol on every single screen and synchronization between printing blanket and screen in terms of speed and repeat adjustment. Machine downtime is reduced from 60 to 12 min. Des­ign setting is now a matter of few minutes and the repeat errors, even at high printing speeds, are negli­gible. In fact, a new design can be set on the machine even when it is busy printing another. The paste cont­ent in screen, squeezee, pump and printing is recover­able, reducing system waste from 4.5 kg to 700 g per screen. Even the clearing of squeezee, etc can be carried out on-line. Using this machine, it is possible toprint non-stop any number of designs on any length of the fabric. For such an operation, however, it must be dye dispensing and paste preparing system.

Considerable improvements in adjustment and changeover functions of flat-bed screen printing un­its have also been made to get faster production spe­eds. These machines are now capable of giving over 20 m/min production rate of high definition , level and deeper colour prints. There is a provision of heating the blanket up to 50°C, continuous gluing and clean­ing of conveyor belt and tension-free transport of fabric.

Print washers have also been modified to give high energy and washing efficiency and reduced water con­sumpti on in open width . Most o f these washers use a combination of spray and vacuum attachments.

Not much advancement has taken place in the a rea of steamer designs, though a fl ash steam ager by Ari­a li promises fixati on of reactive prints on cotton with­out urea. Fabric is transported through the steamer in small loo ps. The system a llows a trea tment ti me of 60- 120 s a t a speed of 30-50 m/min and tempe ra tu re of 120T (refs 7 & 25). In addition, the machine may be used as a conventi onal steam ager for flxation in satu­rated and superheated steam and fo r polymerization of pigment prin ts with hot air.

Mechan ical moisture applicato rs, such as WEKO rolor damping system and Farmer-Norton spinning disk system, have also been available for sometime fo r conditioning the fabric and for partial replacement of urea in reactive printed fabrics by spraying water on them just before steaming6 .

5 Machinery for Finishing Mechanica l finishing, owing to being environmen­

tally most preferred , is coming back in a big way. 01d concepts are being modified and modernized using PLCs, microprocessors, servo motors , individua l drivers and the like.

Control and monitoring of running fabric , weft straightening, uncurling, opening, detwisting or even simple guidingoffabric are now carried out by some very innovative equipment developed by Bianco, Mahlo, Erhardt, Leimer and Tandematic, etc. (ref. 7).

Process control and automation are at an advanced level on the new range of stenters by Babcock, Bruec­kner and Monforts26 - 2B . Maintenance-free chains, automatic control offabric width, overfeed tempera­ture, moisture and dwell time with high energy efficie­ncy and reduced exhaust pollution are some of the features. Many other new drying machines, like shrink dryers and tumble dryers, are designed to be ~ulti-functional machines. Shrink dryer by Krantz not only dries, but also controls shrinkage, develops volume and improves feel in its tumbling zone. Fabric is fed at low tension onto a screen belt with an adjusta­ble high overfeed of up to 200%. Drying is carried out continuously by hot air in either of two modes- rebo­undjet or permeation drying (Fig. 5). This semi-dry, pre-heated fabric is then dynamically moved by a special circulating-air control system. The speed of thi s tumbler process is adjustable according to the fini sh desired 29

.

Softset tumbler by Henrikson, on the other hand, uses the same principle as the jet dyeing machine, only with hot air instead of water to transport the fabric30 .

Air velocity, adjustable from 0 to 2000 m/min, allows processing of small amount of delicate fabrics to even large amo unt of heavy fabrics. The machine not only dries the fabric and reduces the residual shrinkage to less th an 5% but a lso gives a very soft handle, breaks pigment prints, imparts fini sh to ve lvet, artificial lea­ther and fur. The softset dryer is available in both continuous a nd batch models. Another mechanical machine re-developed fo r softenin g uses breaking ro lls7

• O ther surface effects like sueding (Fig. 6), pe­ach skin , sa nd was h, fading, ra ising, cutting, press­ing, compress ive shrinkage (sa nfo ri zin g), compact­ing of weft knit fa brics and calendering are all popu lar today. New machines for all these fi ni shes are being

62 INDIAN 1. FIBRE TEXT. RES., MARCH 1996

offered by many machine makers3 ) . Farmer-Nort­on, for example, is offering a two-bowl calender to produce a wide variation of finishes (from glazed to dull) with different degrees of softness and stiffness. One of the bowl is high-temperature steel and the other a polyamide sleeved roll. Individual drives al­low finishes which were earlier possible only on frict­ion calender 7 .

Dry treatment of wool using corona discharge or plasma pretreatment machinery for producing mac­hine-washable or superwash finishes is fast replacing wet chlorination techniq ues because of environmen­tal advantage32

.

For the few chemical finishes which need to be app­lied, there are low add-on applicators like Recovac by Ramisch and high add-on applicators like Flexnip

Air circulation system

Operating mode: permeation drying

Operating mode: rebound jet drying

Fig. 5- Cross-sectio n ofa compartment in Krantz shrink-oryer showlIlg the two op.:ration modes of permeation orying and rebound jet dryi ng

I~ 2 3 4 5 6

ca. 4300

-:-J 7 /.-.-.,

/ ,\, / I i ) , -t.- e::>

\ / Lr1 r-

\ / , . ./

~. '-..._--' ,...

! /'-'-". .// "-

./ / \ ~. I .

~~~~--Tt;;:i ( -+._ ) \ I . . / \ . . / '. ./' '-..._.-'

Fig. 6- Diagram of m-tec (Menschner) sueding machine model WIS I" [I - steamer. 2- hea ting pl ate. 3- pnellmat ic roller with spreading device.4-6-guide rollers. 7- slleding ro lle r. 8- sllction. 9- ta ke-otf roller. and IO- brushin g device]

GUPTA ADVANCES IN W ET CHEM IC AL PROCESSING MAC HINERY 63

by K lister. Drying, particularly at ya rn stagc, is elTect­ive ly carri ed out using radio frequency (RF) dryer as it ensllrcs dryinga t lowest possible temperature. For fabr ic, UV and I R superheaters are ava ilable for fl ash dryirig and subsequent curin g?

6 Conclusion The ad vances ill the wet proccssing machinery sec­

tor mce t th e requirements of our times, i.e. need fo r the shorter faster processes and treatment cycles and ma ximum tl ex ibility (quick change, rapid response) as al so the dema nd for a substanti al reduction in the co nsumpti on of wa ter , energy and chemicals.

The machinery industry is ready. Que~tion is- Are we '?

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shillg) , 4 1( 1) ( 1995) 8. 4 H o lme I. A T A j Ollrlllll. 6(3) ( 1995) 3 1. :'i (;ulrajani M I.. Pri va te comll1unica tion . 6 Gupta S. C/ulheslille. (12) (1995) 8S. 7 ITMA Preview. 1111 Dl'er , (9) ( 199S) 22. g Forna lli S . Mel/ii/lltl Te."ilh('/" , 4 (1993) E 14S.

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E)S7. 20 Press release. F rit z Buser A G. June 1995. 2 1 Recent innovat io ns in tex til e print technology. 1111 Dra. (3)

(1994) 11 . 22 New and improved print techno logy. Inl D l'a, (3) ( 199S) 22. 2J New verti ca l s tudio stea mer. 1111 Drer, (9) ( 1994) 2 1. 24 F lat f creen las;r e ngrave r. 1111 Dre'r , (9) (1994) 27 . 25 Ario li . 1111 Dr('/', (9) ( 1994) 55. 26 Kaphahn W. 1111 Dr('/' , (2) ( 199:5) 10. 17 Bo llig W . Hampel R & So uren I. AT t1 j Ollrnal,4(4)( 1993) 46 . 2X Stenter makers aim for maxi mum machine efficiency. In! Drer,

(2) (1994) 15. 2') New generation of shrink-drye r. 1111 Dl'er, (2) (1995) 14. 3() Versatile dryi ng and tumbling. 1111 Dyer, (2) ( 1995) 16. 3 I Fashion . Il ex ibility and the dry fini shing machine. lnl Dyer, (7)

( 1995) 12 32 Ho lme I. 1111 Dyer, (7) (1995) 17.