THE JOURNAL OF THE

Society of Dyers and Colourists FEBRUARY 1947 lamed Monthly

Proceedings of the Society SCOTTISH SECTION

Meeting held at the St. Enoch Hotel, Glasgow, on 26th October, 1946, Mr. J. A. Yoma in the chair.

“Let the Society take up the Challenge!” c. M. WIiITTAKBR

(President of the Society)

In asking the Society to take up the challenge I shall naturally be asked, “Who has issued the challenge?”

The dyeing and finishing industry is now slowly emerging from the inevitable wartime controls and directions, the purpose of which was the production, in long runs and limited shades, of textiles for war purposes end Utility fabrics. Whilst admitting that long runs in standard fabrics of a limited range of shades constitute the dyer’s “dream of paradise”, this state of the industry, although conducive to impressive production figures which reflect great credit on the industry, has not been conducive to the maintenance and improvement of those standards of quality which are necessary in a buyer’s market, because the seller’s market prevailing has enabled anything to be sold, however low its quality.

.Experience of the shortages arising from conditions in the last two world-wars has compelled countries to endeavour to reach self-sufficiency in articles previously imported by them. Textiles, of course, have been one of the major shortages, and many of the efforts made to produce them in countries without previous experience have resulted in much inefficiency, which can only persist with the aid of import quotas and tariffs.

To give an example of such conditions- I know of one company abroad where the trades union would only allow a weaver to run two Crompton t Knowles’ automatic looms on one shift. Since it is acknowledged that the use of automatic looms requires two shifts of 24/40 looms to a weaver to make them economic, it will readily be understood how uneconomic are two C. t I(. looms to one weaver on one-shift working, and that such uneconomic restridtiona can only persist under uneconomic shelter.

The result of the two world-.wars has inevitably been that exporting countries like Great Britain have suffered a severe contraction in their export markets in textiles. It is equally certain that the buyer’s market will return as soon as the shelves are filled or a buyer’s strike takes place, resulting in a slump. Therefore, the necessity for increased efficiency and more superior qualities must be realised by the British textile industry.

Meantime, our patent specifications and technical literatwe reveal the fact that chemists, physicists and engineem have been, and are. extremely active with new developments. So active are they that those who are technically responsible to their managements, for keeping a wetchful eye on 811 improvements likely to impinge on their own specific branch of the dyeing and finishing industry, carry a very heavy responsibility which is con- tinuously growing more burdensome, because we are living in a period of unparalleled scientific advancement. The dyeing and finishing industry has the task of harnessing the results of all this fundamental and applied research to commercial production.

The challenge to our industry is coming from four quarters, viz,- (1) Fundamental and applied research in chemistry. (2) Fundamental and applied research in physics. (3) Engineering research and developments in new equipment. (4) The Planners-nominated by the Government as Working Parties, or self-appointed.

I propose to confine myself to the nature of the challenge, as I see it, of the chemists, physicists, and engineers, the activities of whom overlap and cannot, therefore, always be separated for discussion of their efforts.

One of the most interesting growing challenges to our industry is that of the new synthetic fibres, the production of which requires chemistn, engineers and physicists, preferably with diplomas in common-sense!

It has been truly said that the fabric has to be made to fit the natural fibre; in contrast, the fibre can.be made to fit the fabric when using man-made fibres. Fibro (Courtaulds Ltd.) can be produced in any denier and staple length, so i t may be spun on any of the existing spinning systems. Taking the natural fibres and the existing man-made fibres, 78 different blends of two of them and 286 different blends of three of them can be made. These facts present the dyeing and finishing industry with a challenge and give those engaged in i t a glorious opportunity of displaying their art.

Nylon is now becoming available for free commercial development in the textile industry. Sincc Du I’ont L% Co. have stated that approximately 250 chemists, physicists and engineers contributed to the commercial production of nylon, it will be appreciated that nylon .is a product in which all three of our challengers have had a hand.

What is the challenge which nylon makes to the dyeing and finishing industry?

Its first challenge is the permanent and uniform setting of a nylon fabric. There is common agrcement, both in the United States and in Grgat Britain, that our present kishing equipment is unable to do that, and i t will be necessary for the industry to design and build machines to do it efficiently.

Nylon also presents many challenges to the dye-maker and the dyer. One of its most serious challenges is the production of fast shades with dyes which will cover up spinning variations in the nylon itself. Many of the newer synthetic fibres require high stretching during their manufacture, and the present nylon is stretched almost 400%, so the production of perfectly uniformly stretched nylon in bulk is a major engineering problem. Fortunately for the dyer, the dyes initially produced specifically for cellulose acetate rayon give even shades on the present commercial nylon. It will readily be appreciated by dyers, however, that these dyes have not a sufficient fastness for many textile purposes.

38 W H I T T A K E R “LET THE SOCIETY TAKE U P THE CHALLENGE I” hkb. 1817

Nylon challenges the dyer and dye-maker to explain why vat dyes, which in many cases are so outstanding in their fastness to light on cellulosic fibres, wool and silk, are not fast to light on nylon, and why dyes of other C ~ S assert their pronounced individuality and varying compatibility to an even more marked degree on nylon than on other fibres, 88 the dyer knows to his cost when he has to choose a mixture of dyes to dye a fast shade on nylon.

Another challenge from the synthetic fibres is the lack of 8 BstiEffbCtOIy method for the stabilisation of Fibro tunic shirtings. Courtaulds Ltd. we not aware of any satisfactory treatment p t present, so they do not recom- mend the manufacture of tunic shirts from Fibro. On the other hand, sports shirtings made from Fibro are satis- factory in performance.

It is well-known that the compressive shrinkage process is not setisfactory on 100% Fibro fabrics, because as often a8 not the fabric lengthens on subsequent laundering. I have made many personal wearing tests of 100% Fibro tunic shirts and have had them measured carefully after each visit to a power laundry. It is the experience, both of my COll08gu08 and myself, that sometimes the sleeve shrinks, whereas at other times it stretches, with a maxi- mum variation of 2) in. in a 26-in. length of sleeve. This variation is probably due to the personal fector of the ironer, and depends on how much pressure she exerts during ironing. I have made up my mind that, unless a shirting fabric will withstand man-handling during ironing, via. deliberate pulling and stretching, i t will not be mitable for sending to a power laundry and, therefore, should not be sold.

For the purpose of such a test I was supplied with four typical cotton poplins (2 single warp and 2,two-fold warp) and lOOyo Fibro fabrics finished in various ways with the object of obtaining a s t a b i l i i fabric. All were submitted to 60 washes in a 4% soap solution at 6 0 ” ~ . for 20 min. and measured after the firat and fiftieth wash. After each wash they were man-handled during ironing. The results showed that the maximum variation with one of the cotton poplins was S%, whilst with one of the Fibro fabrics i t was 17%. One point worth noting is that after fifty washes neither the cotton poplin nor the Fibro fabrics can be stretched during handling to the same extent as the fabric washed only once. The urea-formaldehyde finish gives a certain stability to a cloth which is crease-resisted in E strained condition, but this stability progressively diminishes as the number of power laundry treatments i ncreases .

Recently, the Cluett Peabody interests in the United States put forward their glyoxal-formaldehyde treatment aa being the solution to the problem, but i t is too early to pass judgment on this finish. The sglution of the problem must, in my opinion, come from a treatment based on the use of formaldehyde or a formddehyde resin, or from the alternetive direction of a fundamental alteration in the physical properties of Fibro.

The production of spun-dyed synthetic fibres is 8 challenge which, I think, the dyer is unable to counter, and he must seek consolation in the fact that the extent of the challengeof spun-dyed synthetic fibres is limited by practical production considerations. On the other hand, if the dyer is also a finisher, he finds that their excellent fastness to wet processing obviates many fkishing faults which arise from the bleeding of normal dyeings.

Nince i t is well-known that pigments are used in the production of spun-dyed synthetic fibres and plastic+ hence their superior fastness to wet processhg- i t is appropriate to mention the challenge coming to the piece dyer from the fixation of pigments on the flbre by means of the new resins and plasticisers, instead of by the normal method of dyeing. Great claims are made in America for the Aridye process, whilst the fabric printers have used pigments from the outset.

Those piece dyers who wish for an easy life, and there- fore close their eyes to progressive ideas, are prone to discount this challenge by saying that shadea so produced rub. Has one really to close one’s eyes to a11 the poaei- bilities of the new types of resins and plasticisem end my that, with these at the piece dyer’s disposal, this lack of fastness to rubbing cannot be overoome?

In the Droylsden laboratory, work h m been done on this problem on Fibro cloth for the peat two years and moat

encouraging results have been obtained. My own view i8 that a satisfactory commercial result will be obtained, which will be of great value for producing in bulk runs shades of high fastness to light and wet processing.

I remember the time when it was not considered possible to apply Sulphur Black to pieces, and the undisguised scepticism that the idea of applying it to pieces received in certain quarters. In point of fact, I dyed the fist Sulphur Black on pieces in more than o,ne dyehouse at that period. What is the present position of Sulphur Black in piere dyeing? Its application is, as is well-known, a routine job of the piece dyehouse. I mention this merely to lace a heavy discount on the Jeremiah8 in the dyeing m i finishing industry, of which there are far too many. Personally, I find Jeremiah8 very stimulating, because, when I hem them bemoaning the impossibility of solving a difficulty, i t always spurs me to redouble my efforts to solve that difficulty.

Formaldehyde is an increasingly important chemical which challenges the dyeing and finishing industry in many directions, because so many of its usw, in conjunc- tion with resin-forming bodies, markedly depreciate the fastness to light of many- fortunately not all- direct cotton dyes.

It is a long time since formaldehyde was first recom- mended for the aftertreatment of selected direct cotton dyes to improve their fastness to washing. It waa shown that, with direct cotton dyes which had in their end- components amino- or hydroxyl groups in m-position to each other+-phenylene and m-toluylene diamines and resorcinol are examples of such end-components-an aftertreatment with formaldehyde considerably improved their fastness to washing. Since i t w88 found necessary for the groups to be in the m-position to obtain this fastncss, it has been suggested that t,he formaldehyde linked the terminal groups to give a cloned ring-

-NH. -m, -m* - + O:CH,= -NH >OH, + H,O

It is, however, disconcerting to find that the faatness to light is always considerably reducod, despite the fact that, in place of an open ring, there now exists a closed ring- a formation which has always been assumed to increase fastness to light. This w@&~~e~s has, therefore, reduced considerably the application of the formaldehyde after- treatment.

It is well-known that, since the dimethylol urea used in the crease-resist process diminishes the fastness to light of some direct cotton dyes, the dye manufacturers were compelled to issue lists of dyes suitable for the process.

Some dyes on Rayolanda (Courtaulds Ltd.), in the manufacture of which formaldehyde is used, are not 08 fast to light 118 the same dyes when dyed on wool or Fibro. The same experience is met in the case of Fibrofix (Courtaulds L a . ) , which is made with the help of formal- dehyde. Here again, the dyes wsert their individualism, because some dyes remain unaffected in their fastness, whilst others are affected to a varying tlegreo of severity.

I have considered for a long time that this effect of formaldehyde on the light-fastness of many dyea is a problem which urgently requires solution and t,hat its solution would most probably bo of great benefit,.

A parallel -88 is provided by some of thc auxiliary products of the pyridmium group, which are recommended for improving the fastness of direct cotton dyes to water and acids. Some of those products a180 reduce the fastness to light of some direat cotton dyes.

The number of patents taken out with the object of rendering wool unshrinkable appears to indicate that the present processes used on 8 large scale are not completely satisfactory.

The papers and discussions on this subject at the Society’s recent Symposium on Fibrous Proteins were highly informative and interesting to those who, like myself, have no direct specific interest in its commercial development. One point which struck me immediately WBB that, although ohlorine hss been used since the outset for making wool unshrinkable, the results of the use of fluorine for this purpose were fh t discussed at the Symposium, which sup orb my contention that the dyeing and finishing in&stry cannot escape the charge

MI. 1047 WHITTAKER- “LET THE SOCIETY TAKE UP T m CWLE;N(XE 1 ” 38

that i t is very slow-moving. It seems 8 fairly obvious step to try alternative halogens!

Despite the numerous and distinct processes for makin wool unshrinkable, one challenge still remains unanswere2 -Why is it that a blend containing ti-lOO,/, of untreated wool and 96-90~o of wool treated by a non-shrink procees shrinks on washing, despite the fact that the Kiton Red staining technique never shows a chlorination greater than 90-95% complete treatment, yet such an incom- pletely chloiinated wool does not shrink unless blended with untreated wool? One fact does stand out crystal clear, viz. that all the suggested processes for making wool iinshrinkable call for very exact and continuous maintenance of the conditions specified in order to attain uniform treatment in long runs.

Another challenge which is coming to the forward- looking members of the piece-dyeing section of the in- dustry is the dyeing of pieces in package form. I am perfectly aware that this idea is not new and that the late John Brandwood made an appropriate machine of limited capacity, but the development at Droylsden during the war of the dyeing of narrow fabrics up to 18 in. wide in large weights (our maximum weight was 1,100 lb., representing 250,000 yd. of 4 in. tape in a pack-dyeing machine) has opened out new possibilities with regard to quantities which can be dyed in one batch.

We have a 42-spindle Longclose machine at Droylsden in which 42 pieces may be dyed together. Owing to the present difficulties and reetrictions, it has not been possible to determine its economic value, but from the technical viewpoint i t can be said definitely that i t makes possible finishes and handle which my fabric colleagues say are new and attractive and not attainable by winch, jig or pad dyeing.

The axiom of pack dyeing may be stated in very simple terms. The rate of flow of the dyeliquor through the package must be greater than the rate of absorption uf the dye by the package. If this is attained package dyeing 18 easy.

All these challenges to the dyeing and finishing industry result in one obvious conclusion, viz. that greater accuracy of control of processes is needed throughout the industry. This, in turn, demands a better standard of education of the personnel, both managerial and operative, in attaining which I hope the Society, if and when i t gets its Charter, will be able to play a prominent part. Our Society has played an important part in problems common to our industry, thanks to the self-sacrificing spirit of many members, which is such a pleasant and encouraging feature of our Society. I refer to our Fastness Tests Committee, our Committee on Education, and to our latest one on Direct Cotton Dyes. There are other problems waiting, and members should not be afraid of asking our Council to take action.

I know I am not popular when I say that the efficiency of the dyeing and finishing industry leaves much room for improvement, but I am always prepared to risk unpopu- larity in the interests of t ru th when facing the facts.

The old days, when dyeing skill was the personal prerogative of the dyer, have passed away. Servicing by the manufacturers of dyes and auxiliary products, as well as by some of the rayon producers, coupled with the lectures and communications in our own Journal and articles in the technical Press, have abolished the secrecy of the old days, and this has been aided by the good fellowship at our Society’s meetings and functions.

I a m concerned very intimately with seeing that the processing of rayon is carried out in an efficient and intelligent manner. The mishandling of rayon by the dyeing and finishing industry after so much effort has been made in the production of the rayon itself is, at times, very disheartening. In describing i t to my colleagues, I call i t “the hidden menace to the rayon producer”. The followi‘ng are a few of the many examples encountered by my colleagues and myself.

After I had given a lecture to the Society on how viscose rayon cakes should be dyed with direct cotton dyes belonging to Classes “B” and “C”, a dyer of a very large firm in its own specific line of rayon goods came up to me and said, “It is not a bit of use Mr. Whittrqker talking about adding the salt in small controlled quantities individually weighed; the only meamre we have in our dye- house is a scoop.” I know from many conversations that

the dyestuff classification and salt-sensitivity figures which have been published by Courtaulds Ltd. over a period of years have received practically no notice in many quarters, let alone been applied in practice.

After our “Adequate Shrinkage of Fibro” Exhibition in Manchoster, a firm sent to Droylsden a cutting from a 100% Fibro fabric, and said that they had been asked to shrink it 9yo, but could only shrink it 4%. On testing the sample i t was found that the cloth was fully shrunk. The dyehouse was vieited by our technicians, and only after a great deal of cross-examination under pressure was it found that the cloth had actually been shrunk 22% from its loom state. A junior member of thestaff disclosed that the piece had been run through caustic soda on a rope washer. It is a fair guess to say that that particular piece would be pulled back to as near $94 shrinkaqe as possible and delivered. The fist time the piece was wetted it would go back to the 22% shrinkage, to the very grave detriment of, the reputation of Fibro.

Two pieces of the same lOOyo Fibro fabric were sent to two firms to dye and crease-resist, with the request that one piece be shrunk 5% and the other 10%. In due course they came back, but both pieces from one 6rm were shrunk 5% and both pieces from the other firm were shrunk lo%, yet both firms had ca:efully labelled one piece ‘‘50/” and the other piece lOy,” Rhrunk-a beautiful example of lack of control!

The development of our test for crease-resisted fabrics by staining with the Brenthol’ AS+ Fast Red 3GL Salt technique has revealed an amazing variation in the appli- cation of this fmish. One of the worst examples examined revealed 8.9% resin in the selvedges and 15.4% resin in the centre of a tropical fabric. After removal of the resin the selvedge was soluble in cuprammonirim, whilst the centre of the cloth was insoluble. The variation in the swellability and so1ub;lity of crease-resistcd Fibro cloths, together with iineven distribution of the resin on the cloth itself, shows that in manyhstances the drymg and poly- merimtion are under anything but exact control. , ,

It is claimed as 6 valuable’ feature of the finish that the resin is imide the filaments. This may be so, biit in practice there is also a great deal left on the ouhside of the filaments owing to inefficient processing. It is surely evident, therefore, that the more widespread the adoption of these chemical finishes, the more necessary i t is to ensiire that the process is carried out under exact scientific control and that a new atmosphere and outlook is adopted in the dyeing and finishing industry.

There is one challenge which still remains to be answered. The dyeing industry has not yet been supplied with a levelling agent for vat dyes. One must carefully differentiate between a levelling and a restraining agent. There are many restraining agents for vat dyes on the market, from siilphite cellulose waste liquors to expensive chemicals, but all of them have two g a v e disadvantqes. Of all that I have had examined (and they have been numerous), none overcomes the pronounced individualisrp of the vat dyes and so restrains them at. the same rate and to the same degree, and none acts solely as a levelling agent. Every user of vat dyes would welcome a *his- factory levelling agent with open arms.

The ha1 challenge with which I will deal is what I term the challenge of the post-war era.

Labour, coal and many of our materials are going to remain permanently dearer, whilst the working week is going to be shorter. This means that the dyeing and finishing industry will have to economise in its proceesing time, and, again a t the risk of some unpopularity, I m y that there is scope for the saving of a great deal of time in the average dyehouse. I am always surprised at the number of master dyers who sit in their offices and Say they are too busy passing shades to walk about the dyehouse. If they did walk about they would see how much time is wasted and how many “cobblers” could be avoided. Having the shade first matched in the hhOr8- tory instead of pitching for i t saves much time, whilst a careful examination in the laboratory of the behaviour of the dyes used in compound shades enables time to be saved in dyeing through knowledge of the individualism of the dves.

The following amusing experience concerned a customer for whom I dyed viscose yarn for corset weft to be thrown

40 WHITTAKER- “LET THE SOCIETY TAKE UP THE CHALLENQE I ’I Feb. 1967

across a dyed cotton warp. I could never satisfy’him- the cloth had previously been made in America. My customer sent for the recipe used in America and it con- tained five dyes. I lost that customer for a time, but only for a short time, because I wrote to him to say that the recipe had amused us and that any dyer at Droylsden who dared to use five dyes to match any shade on a single fibre would get the “sack”. The American recipe con. tained three dyes which had evidently given too bright a shade, so the dyer had pitched some black in it, but, having overdone it, he had then to add some Chryso- phenine to brighten up the shade again.

Laboratory experiment will show the critical percentage of salt or critical temperature a t which the dye is rapidly absorbed by the fibre- these usually exist, atid they vary with individual dyes. This information obtained in the laboratory indicates where the danger lies, so that, once having passed that point on the large scale, no further precautions against unevenness are necessary and the dyeing time may be shortened considerably. For exemple. Durazol Grey VCL (ICI) dyes on much more rapidly than Chlorazol Fast Orange AO (ICI) when they are used in admixture for dyeing visrose rayon cakes, and it is difficult to get a level result and even penetrat,ion. As a result of bitter experience, we ~ I W R ~ H dye on the Durazol Grey VCL before adding the Chlorazol Fast Orange AC to the dyebath. That may seem finicky, but i t is the only way in which we can obtain a satisfactory result on viscose rayon cakes.

Finally, I do not wanb the small individual firm to be afraid to take up the challenge because of the belief that the research battalions of the big firms have so many advantages. Don’t let the small firm be discouraged by them- they frequently fail to see the wood for the trees! Let small firms remember that the first step in the nyn- thetic dyestufT industry was taken in a small laboratory in a private house by the young William Perkin.

It is a mistake tjo think that elaborate apparatus i n necessary for dyeing research- the dyeing laboratory a t Droylsden is a Very unpretentious one. The finent equipped laboratory is very handicapped if common-sense is not present. I have often been accused of just taking bottles off the laboratory shelf, and it is said that I have been lucky. 1 am never iipset by such criticism and never afraid to confess that, in tackling u problem, I give instructions to try anything sensible or silly. I seek con- solation in I’asteur’s paying, “Chtmco only favours the mind t,hat i R prepared”.

Discussion Mr. C. C3Armm-r trsked if the Society could take up the

challenge of educating the merchants. The old trouble of the pain in length froin the grey to the finished state was appearing once more.

As a typical case he instanced 15G yd. of cloth sent to bleach and/or dye to make up into 4 ends of 40 yd. With sewing losses this did not, leave an adequate margin. In these days, with Sanforised, etc., shrunk goods so prominent, this gain in length, with shortages charged es D. & K. (Damaged and Kept), was a menace.

A fiirther point was the width shrinkage allowance on spun Fibro sheetings. There was a wide difference of gr6y width for a standard finished width; it must result. in totally. different fabrics in ultinlctte use.

The Lecturer replied that he would mention this matter on an appropriate occasion at a meeting of tho Counril of the Society.

Courtadds Ltjd. had staged an Exhibition in Manchester showing the necessity for adequate shrinkage of 100% Fibro fabrics, in order to illustrate the detrimental effect of not allowing adequate shrinkage. It was only by allowing adequate shrinkage that the intrinsic merits of Fibro were revealed.,

The Chairman (Mr. J . A. YOUNG) referred to the Lecturer’s statement about the dyeing of Fibro in 10 min., and said that this might be of little use in yarn dyeing where the governing factor in production was frequently the time required t,o get the next load ready to enter the dyeing machine.

Secondly, did the Lecturer believe that, in the light of rerent knowledge concerning the level dyeing of fibres, the oontrol of the rate of Now was sufficient to ensure est,is- factory results, arid that the old method nf dyeing at, cold

or low temperatures for 8ome timo, end then gredually raieing to a high temperature, WM merely a waste of time?

Further, with reference to the successful pack dyeing of Fibro, must the machine be fully enclosed with two-way circulation, or was an open machine, with one.way circulation, suitable?

The Lecturer said that the 10 min. dyeing of Fibro was on loose staple, and he thought i t was obvious that yarn dyeing could not possibly be completed in 10 min. He had quoted the example of the saving of time in the dyeing of Fibro staple to empliasiso the desirahility of avoiding unnecessarily prolonged dyeing.

When he started dyeing viscose ribyon on tho Iwge srale he onteretl it a t 90”(:., thus eliminating dyeing a t low temperatures, which hn considered W H , ~ e conipletc wtvhm of time, except in the case of Class “C” direct cotton dyos.

He used pack-dyeing machines which were fully eu- closed with two-way circulation, and alsn open machines wit>h one-way nircultition. Whilst no innchine waR successful for all purpoxos, he preferrod tJho opeii machine with one-way circulation for the dyeing of viscose rayon cakes with direct cotton dyes.

Mr. A. E. DoOriSoN remarked that the Lecturer had stated that in liin dyohouse i t was tho practice to match all shades first in the Iaborrhtory, arid that from these mntch- ings the dyeing recipes were compiled. Further, he had stated that u dyeing recipe was mado out overy 5 min. of the working day, which would mean some 480 recipes por ,

week. Surely, a vory comprehensive record would have been accumulated over u period, and, by roferonce to this, almost any shado could be matched, and it, would only be necessary very oarasionitlly to resort to the working oiit of a “pitch” in the lahorlttory.

Had Courtaulds Ltd. rnrried out tiny work on the treatment of * 100‘xj Vihro fn.hric with dkali-soluble ethers? In processing these fttlirics for 13. standard shrinkage tolerance, a difiiciilty to he o v e r ~ o ~ n e was the variation in the relaxation &rinkaye, which was often as much RR 6% in individual piocen i n t,he same lot of good8 in the loom &ate.

Answering Mr. Doodson, the Lecturer stated that he was in complete disagreoment, with his viows. For the last 26 yea,rs all .new shades in his dyoliouse llrrd been matched in the laboratory hefore being clyctt on the lerge scale. It was not his osporienco t81itat ti recording o f ti l l patterns enabled new s11:~~les to bo pitalit4 from the old patterns. Mr. Doodson w ~ s also ignoring the fact that, as improved dyes were pit on the market, they werr adopted antl, therefore, tho old matchings with the older dyes automcitictillg tmctime useless. I-10 was convinced that matching in the laboratory was ewily the most efficient system. Repeat orders of a shade ltlretdy dycd were, or (:ours@, worked from the origincil recipe.

Mr. R. A. PEEL said thet the Lacturor htbd exhibited many interesting patterns which showed big variations in resin content, frnm different finishers. With such variations possible, would there also he similar variations in free-fomialdehyde content? The strong sinell of fonnaldelryde had often I)enn noticed wheii areitst*- resisted garments wero wnshetl antl ironed for the first t.ime.

The Lecturer naitl thnt onalysos of ovor 100 crease- resistod fabrics had sliowt~ very great vtirititinns in tho amount .of formaldehyde on tho fabric.

Forma!dehyde could only ca~tiio dermatit,is to those people who wore idiosyncratic or allergic to formaldehyde. An enormous numbor of garments mi& from toxt,iles which had been given t b forndlehyde finish had btml sold and wed wit,hout aiiy snbseyuent conipltiirits re- garding dermatitis. No CRSC had been reportod to him of dermatitis arising froin the wearing of R garment which had been processcd wit,ll formaldehyde. He apreod. howover, that the strong s i r i~ l l of fornrultleliytle was very unpleasant and usually caosetl run!iing of tho cyos.

Mr. PEIEL renierked that adequate shrinktbgo of FibIw was certainly essential, and, whilst Cowtaulds Ltd. might well think their fabrics were maltreated, there wiw another point of view, viz. that the low shrinkage had enabled large quantities of material to be placed on a fahric- starved market. In his opinion, the Utility Specification scheme, in which shrinkages were kept low so as to con- serve cloth, was tho correct, one to follow under t8he sptwie.l t-ircnmstnnces.

Could this freo forrnaldnhyde cause (lorinntitis?

k’eb I941 WlLCOCK- “PSEl’NWl’ION, DYEING ANU FlNlSHINU OF THE NEW FIBRES” 41

In answer to Mr. Peel, the Lecturer said that he did not share his view. He did not consider that even under the Utility Specification scheme there was any justification for fabrics being put on the market which would shrink on repeated washing up to 774 or 8%. There was no con- tiumer satisfaction in such fabrics.

Mr. PEEL next referred to matching in the laboratory, iurd wid thtit he did not agree that this procedure always gave a correct recipe to tlie dyer. Laboratory matching was capable of error. He agreed that i t WRE good to use t,he laboratory to match difficult shiides which were being dyed for the first time, but, in his experience, a skilled and properly trained dyer should seldom need a prior shade m~itching. If the dyer knew his job, and kcpt a proper filing system, he could easily adjust a recipe to give a close “first bit” when presented with a new shade which was i tenr one of his standard reference shades.

Thew was much to be said in favour of close litiison lwtween the la.boratory and the dyehouse. but he did riot considrr it necessary for the 1aborw.tory to cont,rol the ;:olour rriwtrhiny in the dyehouse.

The Lect.urer said that chemists i n tho laboratory were only human and, of course, could mekr mistakes like

anybody else. He referred Mr. Peel to the reply he had made to Mr. Doodson.

He had been misunderstood if Mr. Peel thought tli& he had implied that the laboratory should control colour matching in the dychoutie. Supervisory dyers in the dyehouse had the right to refiise any recipe which waR sent out from the laboratory if they thought i t unsuitable.

Illr. J. Smrcrc said that the Lcrcturer had presented the meeting with tt series of probloms sot out as a challenge to the abilities of those within the Society. It was clear that Mr. Whittaker believed that “the impossible only takes longer”, given the energetic imaginative effort which British textile technologists were well capable of providing.

He would venture t,o add two further challoiiges to those put forward during the lecture. In the first place, the Society must try to find some means of educating the Designers in the technology of colour application as regards what is possible, or feasible, in present-day practice, especially with the Itmge, arid growing, range of fibres. Secondly, there \cas the problem of obtaining dyeings on unions, e.g. wool/cotton and wool/viscose rayon, with fastness to light and washing equal to that obtainable on cellulosic fibres.

MIDLANDS SECTION Meeting held a t the Mic?litnd Hotel. Derby, on 20th Novcinber, 1946, ,Mr. W . PENN in the chaw.

Preparation, Dyeing and Finishing of the New Fibres C. C. WILCOCK

( 1 ) A summary 18 givcn of certain of the more recent trends in the methods used lor the preparation, dyeing and finishing of rayons. (2) . General information is given on the dyeing properties of rayons. Under the generic term “rayon” are included not only the older rayons, but the truly synthetic, fibres, nylon and Vinyon, as well es casein fibre, Rayolanda and alginate rayons.

Part I Yarn Dyeing

Contiiiuoiis filttment viscose rayon yarns were formerly dyed esclysively in skein form; moi’o revently dyeing in cake form has boeti achieved. In this connexion it is of interest to note that, ttlthough viscose rayon cakes were lkst produced in the Topham centrifugal spinning box in 1900, i t was not until t,he early 1930s that the dyeing of viscose rayon in this form became a practical proposition. This was a direct result of the successful work of the rayon producer in devising a satisfactory technique for desulphurising and bleaching cakes, with its attendant, improvemerit in quality due t o reduction in handling. Once this w~ls achioved the dyeing of cakes became not only feasible, but a logical development, since inany advantages over skein dyeing are srlrieved i n subsequent^ processing, viz.-

( A ) An operative can more readily be trained to wind cekes than to wind skeins, end after training can supervise t,he winding of more dyed cakes than dyed skeins.

( B ) Cake-dyed yarn is superior in quality to skein-dyetl yttrii, as there is less danger of entnnglement and broken tilanients resulting from the dyeing process. There is, t,herefore, less winding waste.

( c ) Cake-dyed yarn can be coned directly from the cnke. which is a more economical method than winding into skeins for dyeing and then coning. Moreover, there n,re fewer knots in the cones.

( D ) Cake-dyed yarn is in a better condition than skein- dyed yarn, so tho rate of production in bot,lr knitt,ing and weaving is higher thim with skein-dyed yarn.

As the application of direct cotton dyes to viscose rayon in cake form has been tlie subject of several papers, i t is riot proposed to cover the same ground cigain, upart from stating that the successful dyeing of these dyes depends essentially upon ( a ) the uniform flow of liquor t>hrough all parts of the cake, preferably at a rate greater than the rate of exhaustion of the dyes used, and ( b ) correct choicc of dyes and their intelligent application.

With vat dyes the production of level well-penetrated dyeings is undoubtedly still one of the major problems of the cake dyer. This difficulty is largely due to the great, affinity poesessed by reduced vat dyes for viscose rayon, which results in the more accessible parts of the cake

absorbing most of the dye from the dyeliquor, so t,liat only a weaker dyeliquor is available for dyeing the less accessible parts. Three methods of overcoming this tliffirulty are possible-

( 1 ) By reducing the afiinit,y oftlie lcuco-vat, dye tor the fibre, and so controlling the exhkustion of the dyeliquor by the more accessible parts of the cake.

A large number of auxiliary products are recommended for restraining the exhaustion of‘ vat, dyeliquors, includng sulphite cellulose waste liquors, Albatex P O (CAC) and Dispersol VL (ICI). With all these products one prac- tical difKculty is that all vat dyes are not equally restrained; one dye may be considerably restrained, whilat another may uot be restrained w t all. Products.of this type have only a very limitetl use in cake dyeing, and certainly do not solve the problem of applying vat dy& to cakes.

(2) By increasing the levelling properties ofthe leuco-rat dyes, so promoting more repid transfcrenre of dye from heavily dyed to lighter dyed piwts.

From a large amount of cxperinrenttd work it ha,s beell concluded that the temperature of the dyeliquor must be higher than that used in normal practice, viz. 80”-90°c. By the use of such a high dyeing temperature, coupled in some cases with the me of auxiliary products, it is possible to dye a number of vat dyes on cokes. This is almost entirely due to the increased levelling attained et YO%., as compared with 60”c., which is normally the highest temperature used in vat dyeing. A further factor is the lower viscosity of water a t YO”<,. Dyes of the Cdedon Blue RC ( ICI) type decompose under these conditions, which is particularly unfortunato as they provide such a high proportion of commercially vat-dyed shades. A possible solution to this problem is to use organic solvent solutions in which leuco-vat dyes exhibit increased lcvclling properties compared with their behaviour in water. 20-250/0 Holntion of methylated spirits in water has been suggested for the application of vat dyes to viscose rayon cakes (see B.P. 4G7,(i(i2 and 482,321). Tho use of such t~ m-thod will depend largely upou economic f‘artorj, arid SO far i t does not appear to have been used commercially.

(3) By circulating through the cakes a suspension of the inreduced vat dye containing a dispersing agent,

It is interesting to note that, the use of