The Lecturer mid that chlorinuted wool did uot require more oil than iuitreatetl wool. The surface of chlorinated wool was oxidisetl and this inareased ite polar charanter. which prolmbly lad to tho observed increased a m i t y for. dyes.

Mr. D. Heii~oii iwked if temporttture ctntl Glauber’s salt affected the dyeing of chlorinated wool.

The Lecturer Raid that when treated ant1 untreated wools were dyed together, tlie treated wool took up the dye more rapitfly, uiid therefore yavo t i darker ehade, but

by boiling, “crysta~oidal” dyes could be made to give the same shade on both wools, wherem “colloirlal” dyes did not even-up after dyeing for tho norinltl time.

Mr. C. M. Whittaker, in propotring n vote of thanks to the Lecturer, Huggested that another meeting could well be devoted to a diwiiasion on *‘lVhy doe8 iuool felt?”

Mr. H. Wilkinson, in seconding the vote of thanks, emphasisetl that increased scientific control was essential to enable wool to be.produred with a hotter und inoro consistent resistance to Hhrinkage.

COMMUNICATION

Direct Cotton Dyes, Common Salt, and Commonsense C. M. WEITTAXFIR

Knecht iiti(l Uatey’ atatfeil--”lt is well-known that many direct cotton dyes, sucll mi Benzopurpurine, Will o d y dye the cotton fibre in presence of an inorganic salt, auch as Glnuber’w salt, sodium chloride, potassium chloride, et,c.” It, would be interesting to know the earlier publication of this fact which led Knecht and Batey aa early as 1909 t.o state that this fact was “well-known”, because i t is perfectly rlear that they made no claim t.0 be the original observers. Uoulton, Delph, Pothergill and Morton2, and Hamon, Neale and Stringfellow3 have clescribed work which confirmed this fact. This is n striking example of a fart of the highest importance in the applica- tion of direct rotton dyes in the dyeing of rellrilosir fibres not having been fully apprcciat,ed over a long period of years.

The dyestuff manufacturers have continued to load their commercial standards of dyes with electrolytes and have then devoted research to the discovery of retarding agents for me with direct cotton dyes, whereas a proper appreciation of the above fact makes it obvious that a large measure of control of the rate of dyeing of direct cotton dyes on cellulosic fibres may be cheaply obtained by the sitpply of dyes aa concentrated as is commercially feasible. This presupposes always that the water used by the dyer has not a sufficiently high electrolyte content to nullify the advantage of lining a highly concentrated dye. The present author ha8 knowledge of a dyehouse where Permiitit-treated water of an original hardnem of 26“ rontained sufflcient electrolytes to nullify completely the advantage of using a more concentrated dye. Doubt.leas there are many other dyehouses working tinder similar distldvintageous conditiom.

The objectiom raised by some dyers against concentrated brands are, of course, familiar, viz. that highly con- centrated dyes are more expensive to use in that they may be accidentally spilled or surplns dye thrown away by an operative who does not scruple surreptitiously to empty dye solution down the drain rather than to look for an empty bucket. Moreover, successive batches of a dye are not exactly the same shade and must, therefore, be standardised by shading with ot,her dyes. The present author considers that them possible clisadvantages are fully outweighed by the easy control of the rate of dyeing which concentrated direct cotton dyes give the intelligent dyer by the use of commonsense in adding the electrolytes during tlie dyeing of packagm of c!elliilosic fibres, whilst possible variations in shade of successive deliveries of dye are outweighed by the obvioue atlvantccgea. The need to save containers during wartime has made it desirable for the dyestuff manufacturer to supply more concentrated brands of dyes, and i t is to be hoped that th i s practice will be continued in normal times.

In I030 the presont autlior addressed the Scottiwli 8twtion of the Society4 on ‘LComnionsenae i8 still the best dyeing mistant”, from which the following is quoted dealing with direct cotton dyes-

“The use of commonsense leads to the conclusion that the most concentrated form of dye available should be purchased, because the amount, of salt or sodium sulphate used in Atandardising the salt-sensitive dyes is enough to give rise to defective work”.

It has been appreciated for ti loiig Lime that the liquor- material ratio plays 8. very important part in the rate of dyeing, but it has not always been appreciated that the liquor-materinl rat,io i3.t the mtnal dyeing surface in pack dgeipg is not more than 3:l; it makes no difference whatsoever whether the liquor-material ratio in the whole machine is 8:l or 1OO:l so long as the material i R stationary as in park dyeing; the liquor-material ratio at the flbre nurface of stationary yarn remains not more than 3:1, which is the deciding ftwtor controlling rate of exhaustion and, therefore, penetretion.

It is, of course, imposrtible to do laboratory testa with a liquor-material ratio of 3:l and the present author has found that 1O:l is the lowest ratio which can be used conveniently and reliably in tho laboratory. Some exhaustion figures of direct cotton dyes under various conditions on viscose rayon have already been givenK. Since the publication of these figures a considerable number of additional determinations on the exhaustion of many direct cotton dyes have been carried out in much greater detail.

Experimmtnl Procedure - It was found necessary, as a first step, to establish a reliable technique and, after many comparative and repeated trials, the following technique waR adopted. The material used throughout was continuous filament viscose rayon 150 den. 27 fil., which had been wet-procestled in cake form subsequcnt to spinning, and the necessary hanks were wound from dry cakes; skeins wound from the same r:nke mnnt nlway~ be used in any one set of dyeings.

The water to be used was of primary iinportancc in view of the fact that the influence of minute amounts of electrolytes was being investigated. A Pennutit-treated water was available, made from water of initial hardness of 12-14’, but this was proved unsuitable for the purpose owing to the content of electrolytes. I t was h d l y decided to scoiu the yarn in distilled water, using 3 parts of ammonia (0.880) per 1000 parts of distilled water at 6O”o. for 20 min., and then wash off in three lots of distilled water. Dyeings were carried out in Manohester Corporation water, which was the water being used in the bulk dyeings for which these figures were required; the liquor-material ratio throughout was 10: 1.

In accurate dyeing work in 10 vol. it is ewential to maintain the volume aa nearly constant HS possible. The work now described w a ~ carried out throughout in conical shaped dyepots which are the most suitable for working in very small volumes.

After many detailed trials the following procedure was adopted for 4 -h . dyeings, and 10 g. hanks of continuous filament viscose rayon l50/27 were used throughout. ufl being first scoured as described above. The dyeliquore were prepared as follows-enough dye for 10 dyeing8 was dissolved in 600 C.C. water, from which the requisito number of dyebaths were prepered by measuring 60 C.C. of the above dye solution into each dyepot, to which were added the requiRite amount of common salt from a dilute solution, and then made up to a total volume of 100 c.c.; the dyeliquors were next raised to QOOc, . , any loss dim to evaporation being made up with water a t 90(0. After withdrawing 1 C.C. for colorimetric esti- mations, the skeins were entered and dyeing carried out

254 WHJTTAJLEIt-"DIRECT OOTTdN DYES, COMMON SALT, AND COMMONSENSE" 1942 ___--_-____ for 4 hr.; after 10 inin., 1 R 13.c. water a t ! W c . were uddetl to compensate for evttportrtion loss. Thin procedure. was repeated itfter ii further I 0 inin., then the dyeinx continlied for another 10 min., iift>or which the skeins were t,aken out, excess dyeliquor retiwiled to tho respuctive dyepots, and the volume in eacbh made up to 100 c.c., from which the sttinples for coloriniet~ric: rst,irnations wero made. In the clyeings of 2, 4, (i, and 8 min. duration, no utlilition of water to compenmte for ovtlporution was made, but tho final volume w t i s correctly adjusted before withdrawing the sample for estimation. The dyepots were heated in a bath containing calcium chloride solution. When studying the effect of small quantities of elsct,rolyte under these conditions, it is essential that no trace of calcium chloride is allowed to get into tho pots, or even on to the fingers, as it may coinpletely u p e t the results.

Colorimetric readings were made in ti Leit,z coloriinoter of t,he Duhoscq type by tho Haine Observer throughout. I t is well-known that nolutions of sonie tlyee w e much more difficult t.0 read in tho. colorimeter than others, owing to the exhaustion liquor frequently being of (I

different tone from the initial dye solution. Although every care was taken in making the readings, in no inetance must the figures be regarded ~ I H absolute, but purely as relative, one to the othor.

It has been found convenient to rla,ssify direct cot,ton dyes in three classes. This classification has beon based upon a study of the rate of exhaustion figiiren determined under varying condit,ionn and ro-ordinating these wit,h the times of half-dyeing; it has been confirmed by IIHO i n t.ho large scale dyeing of cellulosic piicke,ges.

Clam "A" Dyes have a high rate of exhaustion without added coininon salt, but have a very low time of half- dyeing, 80 that they level quickly. T ~ R H O dyes may he dyed at DO'-(-., hecause if the initial penetrittioii is bad, owing to the high rate of exhaustion, it does not matter. since their low time of hulf-dyeing enwreR thiit they level rapidly as dyeing proceeds. For tho mine rotison exrossively H I O W niilting iR not eswntitrl.

CIALIH "A' I)YP:j

___-..__

Benurnll Fmt Bordeanx4BL (Y.D.C.) ... Benmnll B a t Bordcaux 4BLN IY.D.C.1 Chloraml Fast Black BKS (1.C.I.) Chlorazol Fmt Hello BKS (I.C.1).

i 5

CNorazol Faat Bordeaux LKY (1.C.I:j' ... ...I

I:;)'! ... ... I

Blgan Blie R (C.A.C.) . . . . . . . . . 52 Rigau Sky Blue 0 (C.A.C.) ... ...I 4 5 Vlscoso Rluo Grey NB (C.N.1 . . . . . . lie Viacosn Nnvy BIIII- RB (G.N.) ...I 117

dye6 have H low initial rate of exha.i~stion, iineven peric- tnition will not be very ~nnrketl, h i t (wrefiilly reguliitetl :tdditioii of stilt is eswntial, sincse, owing t,o their relatively

. high times of half-rlyoing, very little levelling may he nnticipttccl if the ilyo in salt,etl on t,oo rnpidly, iind, therefore, unevenly.

Clctas ".-I" or "H" Dycu-- I t will he appreciated that, no absolutely rigid claseificfltion may 110 mcido, and tho following dyes may be used in either ( ' IHHX "A" nr C1o.s~ "B".

CLAW "A" OH "B" DYk;s _. . _- . .~ ~- . -

Diphenyl I Durazol Fast Blue 80

311 20 24 36 27 0

-

C ' l t ~ u ~ "B" D y v hnvc a low rate of exticiiiution and this

... 411 . 4.98 Pyrazol Orauge UH 260 (X.) ... ...I 31) I 3.7 Trlaulphou Violet B (S.) . . . . . . 2!l 0.02

I . . ~

C ' l n ~ a "L"' Dyea htrve a high rate of osltttustioii without tiildetl stilt, but tho time of half-dyoing indicates that they cannot be expected to level quickly as in the case of Cliisrr "A" dyes. With these dyes there are two methods of obtaining satisfactory penetration- (1) by the use of highly concentrated dyes HO that the initial rate of exhaustion is low and may be controlled as in Class "B". imd (2) by temperature control of the dyeing, i.e. by starting the dyeing at a lower temperature, which slow8 down the rate of exhaustioil, and gradually raising the teniperatrire to 9 0 " ~ . Carefiilly regulated salting may then be done a t 90"c., if necensciry, to obt,nin inwe complete exhaustion.

It would be desirable to discover protiiicts which, when added to the dyebath, retard their riite of exhaustion or * increase their levelling property. J n the present author'~ experienre, no such products have yet been put on tho market. They are desirable for Class "C" dyes and for those unfortunate dyehouses in which the wnter contuinx already 80 high a proportion of eleetrolyti3s t.litit t,lii* precautions now outlined do not apply.

('l~loriiui6e~Purpie lOBd (8.) . . . . . .' ('hlorazol Rlnck E 240 fI.C.1.) ... l'hlorazol Blue BY (1.C.I.) . . . . . . 1:hlorazol Bruwii BS (1.C.I.) . . . .

82 w2 IiC 44 :, b XR :ti 04 48 70 4fi U0

-I-

I ~. ~ rnte of exhaustion may be utlequately controlled I)y -~ ca.refully regulated iidditionn of comrnoii salt hawed 0 1 1 I i ~ r e - ~ ~ o t e r m i n t l t j o l l of their s,tlt 8onRiti\.ity. t~lRHO The effert, of the electrolytes in tho commeruiiil tlyc

itself, without any further addition to the dyebath, is CLASS "B" DYEb clearly shown by the following percentage exhnustion

_ _ - ~ . ___ ~ ~~ figures of two highly conceritrn.ted commerciel direct. HLulf.dyeillg cotton dyes.

~~ ~. ~ . -. ___ I

Beumuil Badt Brown YRL (Y.D.C.) ...I BenmnU Y w t Orunge ER (Y.D.C.) ... Clilorantlue Fadt Blue SULL (C.A.U.) Chlornntilit. Fa& Blue 0LN200 (O.A.U.) Chlorazol Bluo B 6% (I.C.I. Chlorazol Past Blue 40KS )I:C.I.) 1:: Uhlorazol Vaat Orange AUS (I.C.1.) . . , Chlorazol E'Wt Piuk BEY 1.C I ) D~phwyl Blue M2B 300 (&y.). . :.: l ) ip l~ t~ i~yl Vast Blue lOGL WY.) . . Dlphenvl Fast Blue 31tL ((ty.) DiphciDI Past Blue Green BL (Uy.j" Dlphenvl B u t Rubtila RL (Uy.) . . . I imnzoi violet IBS (I.c.I.) . . . . . . Ylrius Supra OUvc UL (1.U.) Sirlua Supra Bcnrlet 20 (I 0.) ... ...i Yoloplrenyl Red Brown (Uy.) ... Solar Rubinole B (Y.) Solar Yellow 2R (8.)

Solar Orange RUL (8.) Solar Red 2BL (8.)

. . . . . .

. . . . . . . . . . . .

I2

'C 1 2v

I 31; 10 LO 30 2X I 4 19

I I \ 16 24 30 12 u 20

!!

If the Itbove figure^ iiro c~xuminetl rritlcally, I t ifl wen 2804 in.:{ 9141 that Chlorazol Bliio U 526 h w 110 atfinity at I )O@(, . when i4i dyed without salt, so thiit tho U H ~ of these conventrsted

commercial dyes permits the dyer to have perfect control 159.2 38.2 354 over tho Hfflnity in package dyeing hy controlling the

100 4 tititlition of coininon sitlt with roininonmnse. If the equivalent aniount of actual dye had been used in the I:Kl.0

1 6 4 46.1 form of Chlorazol Blue BS, the dyebath would already 8.0 hive contained 1 % salt, which the above table shows

exhausts 08% of 4% Chlorazol Blue B 626. The difference 1 3 3 86.G

in salt content in the actual dye itself between 4% Diphenyl I_---

Blue M2U 500 and 4% Chlorazol Blue B €325 is yo common salt approx.: d l pergentages are calculated on the weight of matorial. Yet, the table shows that this amount OF common flult prwent in the Diphenyl Blue M2U 300 itself oaueed 30%, oxlittiistioil of the dye.

Another conclii~ion to be drawn from the above eshaustion figures is that the danger of salting on tho dye too quickly on the outside of the packages k peatot4 in the early stages of dyeing, since G8% of Chlorazol Blue B 825 k oshiiilsted when 1 yo of coinmon Halt has been added, whereas the ttddition of ii further 4% increnws the exhtlustion only 26%.

Selecting two dyes from the opposite enda of Uoulton and Reading's c~lamification of direct cotton dyes', v ~ z . Chlorwml Bast Orange GS and Chloritzol Fast Orangc ACH, the following am tho c.ompiirative exhaustion fignrea.

Fwt, Orange AQY ..., IH i 215 , :it; 4 i n:i QI 1 06

From this it \r-oultl iinliiediatdj. Iw ailid t.liitL C!lilortizol Pwt Orange US would be more dit€icult to dye thuii C!orazol Fast Orange AGS owing to the rapid exha~istion. That is not so, because Boulton and Reading showed that Clilorazol Past Orange 08 has a very low time of half- dyeing which meam that, it reaches equilibrium or levels very quickly. It does not matter, therefore, if CNorazol Fmt Orange GS does initially dye t,he outside of the package, because i t reaches equilibrium so quickly that the package ia soon penetrated evenly throughout. Thie statement has been confirmed over and over again i l l

large scale package dyeing. Commonrrem, therefore, must be uwd in deciding

which direct cotton dyes should he obtained in highly concentrated form, so that there may be proper control over their rate of dyeing when dyeing cellulosic package% becauw dyes of very low times of half-dyeing level very quickly by reaeon of that property. It is the dyes in Clws "C" which miwt be had in highly concentrated quality.

The high substantivity of some dye8, even when obtained in the highest concentration commercially available, iw illustrated by the following erhauation figures for $yu Benzopurpurinc 4B 180, which wore obtaincd by tho standard dyeing procedure already outlined.

... I ! / ' "6 Exhausti6u of t% I!hlonrml ~

'

. . ~ ~ ~- ~ ~ --

jot, BENZOPURPURINR 4B 180 -

If the exhaustion of the most concentrtitstl cominerc4Hl product is 82% a t 9O"c. without riddition of common salt, it is ohvious that temperature control as well HR salt control must tm studied. In stutlying tempertLture control, it mu&,, howcver, nlways be remembered that tho vimosity of water a t low tempertltiires in inucti highor t.htui at !lo?., so that it must be iicceptecl that the circulation of the dyeliquor at the low temperature will not be as rapid as at 9 0 " ~ .

The figures obtained by the temperature control method iming &% Benzopurpurine 4B 180 are given below. Two mta of skeins were dyed with 10"c. dierence between each. It ww preferred to dye two distinct sets with lo%,. difference. aa being more accurate than working the mme Bets of dyeings to 6%. difference. The time of dyoing was 4 hr. a t oach temperatiirc.. and the resultw aro given in the followiiig table.

3.5 45 G6 65 75 86

I U 35 16 UR 74 81

40 50 80 70

DO no

25 40 52 04 76 81

It is seen from thk ta,ble that ut 0 0 " ~ . the exhaustion without salt was 81%. but that at 3 6 " ~ . tlie exhaustion,

again without salt, wcts only 16%. which illuetrates the very wide control which may be ohtainecl by the common. wnse use of temperature.

The following set of oxhaustion figures, using i;h Chlorantine Pant Ulue GLL 200, dyed for 4 hr. in 10 vol., with different quentitiw of salt a t different temperatures, further emphaskw the wide coiitrol possible by a comnion- sense control of the rate of exlitlustion by both common sult and temperature.

47" L'HLOMIilYNl! F A ~ T BIJ'F UJJ, SIWI - - Tttuiiicrature to(!.) ... ... ..I 40 I 50 1 OU 71) 1 bU f f lJ

collllnonaalt ... 13 10 25 38 GO 5e common salt ... ?!l 44 nu 80 uu common salt ...I $ 1 i1.1 1 63 1 49 1 95 HH common salt ... .>13 157 78 01 96 1100

How necossary it is for the package dyer to have thk detailed information is illustrated by the comparutive figires of Chlorazol Bast Yellow 6aKS and Chlorazol Fast Yellow CICKS. Large scale dyeings of a pale green shade had shown that the 5GKS brand waa better than the CQCKS brand, HO that 4% shades of each dyeing were carried out without salt addition a t 9 0 " ~ . for 2, 4, 6, 8, and 50 An. , respectively, from which the following percentage exhaustion figures were obtained.

~- I I - 1 _ I - - I -

These figures show a wide variation in the rate of oxhaustion which explains the preference for the 5GKS brand fourided upon experienre in mtual large wale dyeings and confirmed by the% results.

It is necessary in ohoosing dyes for uw in compound wliades to employ the "golden rule of dyeing", viz. that dyes dyeing on at tho same rato niust be used, if available. This makes tho classification into Clams "A", "I<", and "C" of great value, since obvioiisly dyes will bo chosen from the Rame olass.

The following case illustratoe that, hi compound shades, the possible effect of electrolyte in one dye having R cletrimental effect on another dye used a t the same time must not be neglected; thk applies in particular to the ilyen in Claw "C".

A very striking example which giive great trouble on the large scale was a mixing of 1.4% Cliloramine Purple LOBC and 0.760/, Benzopurpurine 4B 180. In order to dmover tho rectson why this shade gave such bad results, it was finally decided to determine the amount of ctsh in Chloramine Piirple IOBC by hectting it in a porcelain crucible until all the dye was destroyed. It was found tliut C'liloramine Plwple lOBC contuiited rjS''/, of electrolyte and, therefore, in the above mixing there wm practically 1% of electrolyte being put into the dyebath in luring 14yu Chloramine Purple 10BC. A tempernture range tost, therefore, was made with 0.75y0 Benzopurpurine kB 180, adding to the dyebath l"/o on the weight of yam of the ash obtained from Chloramine Purple LOBC; tliiw gave the following exhaustion fipires after dyeing for

hr. _ . .. . ~ .-

The cause of tlie troublo was, of oourae, abundantly clear when it wtul shown that, under these oonditiom and a t the low temperature of 4Ooc., Uenzopurpurine 4B 180

266 EXTERNAL ADDRESS DCC. 1912

”/; Exhauntion 9 . Tot,nl lnfter each skciiil exhaustion

lo/, Chlorazol Buat Orange AU8 (1) (I.C.I.)

- ~ - - 2Ci 26 46 20 00 1 4 ti9 u 3s :I:< v2 10 89 JI 70 7 5ti 58 86 20 93 8 97 4

8 16

20 6 13 13 24 11 34 10 33 0 53 53 75 22 86 10 89 4.7 62 o:! 90 , 28 x Q8 08 35 36 55 20 69 14 76 7 33 3Y 49 18

08 1 44 44 06 21 78 13 88 S 14 14 26 If 37 11 46 S 12 12 22 10 31 R :IS 7 18 18 30 14 42 12 G3 11

H 21 d

-

61 1:

gave t I !W?” exhaustion due to tho electrolyte present in the Chloraniine Purple l0BC used along with it. This is a very Rtriking example of the necessity of having available as highly concentrated brands of direct cotton dyes of the type of Chloramine Purple 1013C an is com- mercially feasible.

.Lt is apprei:iated t.hat tho objection nuiy be ruisecl t h t r t thiN type of work is beyond t,he capavity of mauy tlyehouw Iihoratorios, but mother nietliotl of tittack mtiy be made. wliivh requires only the simplest clyeing equipment. Thits, dye n Nurcession of equiil weiglit skeim in t h e mine dyeliquor for equul intervals of t,ime in t i predetermined liquor ratio with tt pretleterminecl udclition of common sdt a,t, a predetermined temperatiire; these conditions may be viwied a t will. These results rnHy only be expet-ted to be rcproducible on t,he large H C H ~ U when tlie liquor ratio nnd temperature are the Nanio. The prerautioii must be taken that the dyeliquor from each skein, as it is taken out of the dyebath, iti squerzecl out. its completely RH possible and returned to the dyebath.

The figorcs tabulated in the preceding colnnin itre for one railgo of determinations using four ecpal-weight successive skeinsof continuous filament viscose rayon 150/27 for 1 min. dyeing time with 174 of various dyes at 00%. in 36 vol., with 4% common stilt added a t the ontmt. The exhaus- tion percentages given were determined hy colorimeter, but visual examination of the skeins will Nerve RS a very good guide to the relative affinity and rate of dyeing of t.hc dyes. This method is especitilly \duable in testing the suitability of dyes for usc in any compound shade. If tt rapid and a slow dyeing dye are used in the same compound shade, tlie Nwcessive skeins will show different tones. On tho first skein a rapid dyeing dye will predominate, whereas on tho fourth skein a slow dyeing dye will predominate.

A utudy of the results given UI the preuent paper clearly indicate8 that it is time the type of general instructions for the ilyeing of direct cotton dyes included on manil- facturer~’ pattern cards should be radically expanded on the lines jlluetratecf, so that the individualism of dyes may he reulisoil and such information intelligently used in applying tho “golden rule of dyeing”, via. t.htit dyeN chosen for use in compound ~hades must dyc on a t the same rate.

This work wtis carried o i i t untlur the *upervision of 0. C. Wilcock, whilst tho ctyaiugs and determinations in the first part of the paper were made by J. 1’. Brennan, tuid in t,ho second part by W. Armfielcl.

(Receiwd 011 281h July, 1942.)

I~EFEHENCES 1 Kiii!cht aird B h y this Juicr 1900 25 200. 2 Boultou Delph, F&hergill I I I ~ Modou,’J. Teatile Inat., 1933, 24,

3 Ha%o_u,, Nenlc and Strin~fc~llon, Tnrna. Faraduy Sw., 1936, 31,

~OUHTAULDY LTD.

122k.

EXTERNAL ADDRESS Possibilities of the Plastics Industry in India

Sir S. S. BHATNAGAR liitlia still occupies rather an insignificant position

industrially, eflpecially in connexion with plastics. So far, most attention has been paid to synthetic resins, but increasing attention will be paid to natural resins, which have a variety of uses when suitably modified. The nhief classes of synthetic resins are as follows.

(A) C!o?idensatio,i PoZyrner.9- (1) Resinox, bakelite and durez- condonsates of phenols with formalrlehyde. (2) Beetle or plaskon- condensates of urea with form- aldehyde. (3) Melamine resins- melainine condensed with formaldehyde or with shellac. ( 4 ) Nylon- hexamethylene diamine condensed with adipic or sebacic acid. (5) Beckosol, glyptal or duraplex- condensat,es of phthnlic anhydride with glycerol a,nd linoleic acid. ((I) Amberol, beckacite and inaleic resinf- intlleic anhyclricle condensed with glycerol and abietic wid. (7) Paraplex- a condensate of sebacic mid and glycerol. (8) Thiokol- ethylene dichloride condensed wit,h sodium tetrasulphide.

(R) L ~ N E U ~ polyaials-( I ) Styroii- derived from styrene, the dehydrogenated product of ethylbenzene. (2) Cmnar, picco and n e v i n d h e from the interaction of uidene with ooumarone. (3) Vistanex- derived from isobutylene, the dehydrogenation product of isobutane. (4) Acryloid-

polymerised ethylacrylate. (6) Luvite mid crystallite- polymerised methyl mothacrylate. (ti) Oelvti, vinylite A. (7) Polyvinyl alcohol. (8) Butvar, butacite, vinylite XYSG - all the vinyl rosins (ti), (7), and (8) tire obtained from vinyl acetate, derived from acetylene and acetic acid. (9) Koroseal. (10) Saran. (1 1) Neoprene- ( Q ) , (lo), and (11) are all polyvinyl chlorides. (.12) Buna SS- butane i H dehydrogenatecl tlnd the butadiene polymerised.

(6’) C‘o-poZyvm-y- (1) Vinylite V- polymerisecl mixed vinyl chloride and vinylacetate. (2) Ar,ryloid-polyinerised mixed methyl methacrylate and ethylacrylate. (3) Bum1 S-- polymerised mixed styrene and butudiene. ( 4 ) Per- hitnaii- polymerised mixed acrylonitrile and butacliene.

The above list indicates the raw niatoriah which must be made available in India, phenols and formaldehylle being perhnps thc most importmt. l’lionolx are availttble, hiit the Rupply is not yet nnficient, a1111 pilot phnts have been erected for the mtinufactnre of formaldehyde. Good yields of furfural- which coulcl be used ns u resin-forming aldehyde- have been obtninecl from rice husks, but Inany other types of available cheap cellulosic materials, c.g. water-hyacinth, jute waste, etr., could also be used as cheap sour& of furfural. The raw materials next in importance are urea, calcium carbide, ant1 acetylene.