Appendix A Problems With Fiber Reactive Dyeings Not Repeating - .A Look at Five Typical Cases By: Brent Smith, Keith Beck, and Tod Uadderra College of Textiles, NCSU Raleigh, NC Reprinted with permission f” American Dyestuff Reuorter (September 1990) Problems With Fiber Reactive Dyeings Not Repeating- A Look At Five Typical Cases -! By Brent Smith, Keith Beck, Tod Madderra School of Textiles, N.C.S.U. Raleigh, NC Introduction igure 1-Data acquisition system. demonstrated by our real-time data While it’s a fact that the fiber reac- acquisition system. tive dyeing of cellulosic materials is of great commercial importance, it is also one of the most difficult batch Case I: A “Normal” Dyeing with prdcesses to control. As part of a Triazines Consortium for Research in Apparel, Dyeings known to have good pro- .. Fiber and Textile Manufacturing duction history generally use dye (CRAFTM), the authors have de- combinations with similar exhaus- : I veloped a system for acquiring real- tion and substantivity characteris- time on-line data from batch dyeings. tics. A typical case is shown in Figure Actual production dyeing problems 2 for a combination of two mono- can now be diagnosed in our own chloro triazine dyes, Orange 13 and laboratory using data from this data Violet 1. The kinetics of exhaustion acquisition system. This information as well as the substantivity of the is a great asset to both laboratory dyes clearly produce similar exhaust ’. I and production dyers in establishing curves up to the time of alkali addi- dye recipes and procedures which, tion (25 minutes). Addition of alkali, due to their inherent design, repeat which in this case produces essen- consistently and resist shade varia- tially no further exhaustion of the tions. le dye procedures and recipes. bath, initiates the reaction phase of The data acquisition system is de- To control fiber reactive dyes, onc the dyeing. The overall reaction rate scribed in more detail elsewhere’.*. lust consider many important fac is controlled by several factors: con- Data from this system include infor- )rs, such as diffusion, reactivity anc centration of dye present, concentra- mation about dye concentration in Jbstantivity. In addition, there arc tion of nucleophile (i.e., cellulose or the dye bath at any time, conductiv- nportant differences between type! hydroxyl anions), and reaction rate ity, pH and temperature. In addition ‘hich must be taken in account constant. The fixation efficiency de- to diagnosis of dyeing problems, hese differences are graphicall) pends on the relative reaction rate of . -. these data can be used for other pur- .. poses such as modelling and study- .. igure 2-Dye exhaustion vs. time-Violet 1 and Orange 13. .. ing dyeing processes, and real time process control. The system consists of sensors to detect pH. conductivity, temperature, dye and chemical concentrations in the dyebath on a real time basis; sig- nal- conditioners; micro and mini computers; displays and peripherals, as shown in the block diagram in Figure 1. We have used this appa- .. ratus to examine dyeing recipes and procedures with exceptional produc- tion history (good and bad). Data from such dyeings show exactly why some dyeings “went wrong,“ and also indicate how to improve the per- formance of these shades in terms of I ~~~ The dye with cellulose compared to Case II: Triazine Dyes of Differe tive efficiency of fixation of the two water, which in turn depends on the Substantivity dyes will depend on their relative re relative amounts of dye in the fiber Figure 3 shows another combin action rates which in turn depend on and in the dyebath respectively. Note tion shade of two monochloro tri their relative concentrations in the that, at the time of alkali addition, ex- zine dyes, Yellow 135 and Blue 5. I fiber. Even with all other factors (e.g., haustion has essentially reached a in case I, exhaustion of each dye hi reactivity of the dyes) being equal, steady state, thus the timing of the reached a relatively steady state pril the fraction of blue dye in the fiber is alkali addition is not critical. Also, to alkali addition. But in this cas about half as great, giving much the exhaustion is moderate to high the yellow component is nearly 80 lower fixation efficiency and more for fiber reactive dyes-about 60% at exhausted at the time of alkali adc hydrolysis. Thus, the “hot patch” the time of alkali addition. Under tion, compared to just over 40% fl taken before washing will contain these conditions, reaction of the dye the blue. much more unfixed hydrolyzed blue with the fiber occurs reproducibly This has important practical imp dye, which will wash out and the and efficiently. cations to the dyer because the re1 shade will wash down to a more yel- low cast. The dyer will be faced with a hot patch decision requiring con- siderable judgment as to how much the shade will change on washing. Case 111: Alkali Added Too Soon Figure 4 shows a combination of !wo dichloro triazine dyes, Yellow 7 and Blue 4. Although alkali was added after the same time (25 min- Jtes) as in the two previous cases, :he data clearly indicate that, in this :ase, dye is still exhausting. There- ‘ore, the timing of the alkali add has f great effect upon the ultimate shade. If alkali is added slightly ear- ier than specified, more dye will re- nain in the bath and thus relatively ess of the dye will be fixed. Control If the alkali add must be almost Introducing.. ?xact,since any deviation in the tim- ng of alkali addition or even at the ime it takes to circulate the alkali hroughout the dyeing machine Stater by Washex :ould well produce shade variation. lther factors (e.g., fabric prepara- ion, temperaturehate of rise, salt The Features The Results :oncentration) might well advance Superior STATIC EXTRACTION Improved productivity-no straight- )r retard dye exhaustion slightly, and CAPABILITY is a reality with a ening is required; and this design hereby significantly affect shade re- unique and revolutionary design feature costs less than specialized jeatability. feature found only in Washex static dye machines. In cases I and II exhaust to a steady Textile Dyein&xtractors. tate existed prior to alkali addition. :or those processes, ultimate dye The Benefits lxhaustion depends primarily on the call toll-free outside Texas: inal conditions in the exhaust Ideal for dyeing pantyhose, knit (800) suits, lingerie, and panties. Recent 433-0933 ihase, e.g.. temperature, salt con- tests confirm that STATEX inside Texas: entration and liquor ratio. Mo- dyeing/extractors reduce picks and (817)855-3990 nentary fluctuations do not substan- tangles more than 50%. ially affect the final exhaustion. But, i this case, dye continues to ex- laust after the addition of alkali, giv- -- - -.-e*-zz ig simultaneous exhaustion and re- WASHEXe9 ction. The dyeing results then D.,..- -. ,.-~,-~~~”,.- &.,-A&:q lecome highly path dependent and IY ny fluctuation in the factors previ- Washex Machinery Company usly mentioned is likely to result in Division White Consolidated Industries, Inc. poor shade repeat or unlevel dye- 5000 Central Freeway ig. This is a higher risk situation and Wichita Falls, Texru 76306 ?quires more careful control to P132a chieve good shade repeats. Circle 24 on Reader Service Card 40 American Dyestuff Reporter 0 September 1990 a .-- Gigure &Dye exhaustion vs. time-Yellow 135 and Blue 5. Figure &-Dye exhaustion vs. time-Yellow 7 and Blue 4. 0 YOllOW 135 - Yellow 7 - BlrU.5 --- Blue4 --- 0 a-- - - - __ I 0 10 20 30 40 50 60 70 Tlm (Minuter) :igure -ye exhaustion vs. time-Blue 3R and Blue 21 Figure &Dye exhaustion vs. time-Blue 19 and Red 180. , 0 .-0 T- ElW33R - Blue19 --- Elm21 --- Red180 - I m0. 0 10 20 30 40 50 60 70 TIM (Mlnuter) :ase IV: Vinyl Sulfones of Different leactivlty Figure 5 shows the performance of combination of two sulfatoethyl ulfone dyes, Remazol Blue 3R (no .I. Number) and Blue 21. (Note- ue to pH sensitivity of the dyes in lis reme, a scale factor adjustment was made at the time of addition of ilkali.) These dyes have very compat- ble exhaustion prior to alkali addi- ion and reach a fairly steady state. 3ut, in contrast to the triazine dyes fescribed in the preceding, these fyes commence exhaustion again 42 I I ently unstable shade repeats can b identified by examination of dyebat The Textile data. Dye recipes and procedure which are high risk can be identifie1 Industry’s in advance using real time dyebatl data acquisition. Air In these studies the authors suc don similar to cases Ill and IV. Thi: cessfully identified several specifit Pollution y!, .-_-muires careful control of many fac situations leading to higher risk o tors, e.g.. temperature and alkali ad poor shade repeats in fiber reactivc Solution dition, to achieve good shade re - _--------. -- dyeing as demonstrated by thesc peats and level dyeings. - cases. A few of the most prominen problems included (a) selection o 1- Conclusions dyes of different affinity or reactivit! Fiber reactive dye formulation: and (b) addition of alkali toc and procedures vary greatly in theii soon. 0 0 0 performance. Even if dyers had es sentially perfect control over theii processes, shade variations would leferences 1 ) Madderra. Tod. Development of a Rea still result from uncontrollable fac. Time Data Acquisition System for Batct tors such as fiber maturity, ambienl Dyeing, Master’s Thesis, NCSU College conditions, water quality, dye and of Textiles, 1990. chemical variances. Therefore, it is 2) Beck. Keith, Madderra. Tod and Smith, important to devise dyeing protocols Brent. Real-Time Data Acquisition in Batch Dyeing, in press, Proceedings oi which ale highly resistant to varia- the 1990 AATCC National Technical Photo: Third precipitator on the far tions.