Appendix A Problems With Fiber Reactive

The first part of this article (Mar.8;ADR) presented some fundamenta aspects of dyeing quality control irgeneral. This part (11) present:specific details of controlling batctjye processes. Critical quality conlrol parapeters are discussed foitarious dye classes, equipmentxocesses, and substrates. AlsoYiagnostic tests and repair pro:edures are presented. The final pari)f this article will concentrate on:ontinuous dyeing. ntroductionMany different classes of dyes areapplied to various substrates bybatch methods in mill-specific situa.tions using a wide variety of equipment. It would be impossible toreview each and every commerciallyimportant combination of circum-stances in depth; therefore, informa.tion presented herein is intendedprimarily as a guide for troubleshoot-ing in a variety of bath dyeing produc-tion situations. Dyeing defectsVarious types of defects may occur during batch dyeing and par-ticular combinations of processes,equipment, dyes or substrates maybe more or less susceptible tospecific types of defects. Most pro-duction dyers cite various defects,such as those listed in Table I, astheir major problem areas. However,:here is no question that the majoriroblem which occurs in. batch dyetditor's Notes-Third in a series oflen articles to be prepared by Dr.Brent Smith on the general theme, "Troubleshooting In Wet Processing".ing i s poor shade repeats (off shadedye ings).In addition to production whichgets out of the dyehouse with anunacceptable shade, poor shaderepeats actually are the underlyingcause of a substantial portion ofphysical damages, uneven dyeings,and foreign deposits. These defectsfrequently occur when a shade doesnot repeat properly and requires cor-rective action such as dyeor chemi-cal adds, extra run time, boilingdown, stripping, redyeing, andloroverdyeing. Correctivelre pai r pro-cedures require extra time and proc-essing; hence, the risk of physicaldamage is greater. Practices such asstripping or adds increase the risk ofuneven dyeing and bath instability.Consideration of dyeing econom-ics and losses associated with dye-ing defects must take into accountthe relative value of the substrate (fre-quently several dollars per pound),versus the actual labor, overhead,dye, and chemical cost for dyeing(usually less than $0.50 per pound formost shades). Thus, a relatively largesavings in dye cost can be quicklyoffset by even a minor increase indefect level and the associatedlosses such as the loss of expensivesubstrate. For example, a 10% costreduction on a dye cost of $0.25 perpound would be offset by an increaseof only 1% off-quality on a $2.50substrate.In addition, that 1% off qualitymight be reworked or redyed by acostly procedure (causing additionaleconomic loss) which has a higherrisk and lower chance to produce acceptable product than first-run dye-ings. Thus the dyer's priority must beto avoid producing defects. To avoid defects, the first step must be to pro. duce consistent shade repeats.There is a very widespread impression that avoiding defects, and espe.cially improving shade repeats, is asimple matter of discipline. Althoughsupervision, good maintenance, andproper operation of equipment areimportant, it is also very important toput quality (not cost reduction andshort cuts) as the number one prior-ity, Management pressure to reducecost or increase production beyondreasonable limits (for example, byoverloading eq u ipmen1) is frequent-ly counterproductive. Dye selectionThe exhaust dyer has a wide vari-ety of colorants from which to selecthis dye recipe. Many considerationsenter into selection of dye class,subclass, and specific dyestuffs. Atypical selection protocol is shown inTable II. Sometimes special situa-tions such as unusual blend, sub-strates, constructions, or productionvolume arise which require completereview of the entire formulationprotocol. In these cases, it is impor-tant to make a careful evaluation and7otto treat the situation as "routine."To avoid trouble, these situationsnust be identified in advance andiandled properly in terms of equipnent, process and dye selection,quality control requirements, costanalysis, and expectations for off-quality and re-working. Using a cer-,ain set of dyes, procedures, costanalysis, etc., from habit is sure toead, sooner or later, to trouble.Examples of such situations arerot difficult to find. One examplevhich frequently occurs is the designI f difficult-to-dye blends, especiallyhree fiber blends, by stylists who dolot realize the difficulties involved.'he dyeing behavior of many binary