WATER CONSERVATION-AN ALTERNATIVE TO SOLVENT DYEING 7 9

Proceedings of the Society Water Conservation-An Alternative to Solvent Dyeing ?

G. H. LISTER

Sandoz Products Ltd, Calverley Lane, Horsforth, Leeds LS18 4RP

Meetings of the Scottish Region, held in the Whitehall Restaurant., Glasgow, on I 2 October 1971, Mr W. P. Edmondson in the chair; of the West Riding Region, held at the University of Bradford, on 14 October 1971, Mr J. Furniss in the chair; of the Manchester Junior Section (presented by Mr P . Turner), held at the University of Manchester Institute of Science and Technology, on 14 October 1971, Mr R. I. Chariesworth in the chair; and of the Northern Ireland Region (presented by Mr. P. Turner), held in the Dunadry Inn,

Dunadry, on 7 December 1971, Mr H. S. Blair in the chair*

Textiles can be dyed using appreciably less water than is normal in conventional dyeing if satisfactory distribution of the dye-liquor can be obtained, e.g. by padding. Padding techniques are, however, unsuitable for many types of material, because of their construction or the economics of the process. However, by converting small volumes of water into large volumes of micro-foam in the body of the substrate, by the addition of a foaming agent to the dye-liquor, even distribution of the liquor can be obtained in a relatively short time. Subsequent heating fixes the dye to give level well-penetrated dyeings. The principle is also applicable to preparatory and finishing processes. Because of the efficiency of the distribution system, dyes can be applied by this technique (the Sancowad process) which, because of their properties, cannot be applied evenly in long liquors. The method has proved

satisfactory on garments, half-hose, and short lengths of fabric in bulk application with loads up to 50 kg.

The need to reduce the amount of water used and the effluent produced has been a problem in the dye-application industry for some time. Information on the amount of water used in wet processing, including dyeing, is given in Table 1, emphasising the part played by the textile industry in the consumption of water (I).

TABLE 1 Water Consumption in the Wet Processing of Textiles

Works’ averages Individual batches (gal/lb) (gal/lb)

Product group* Least Most Least Most Nylon hose 9.7 23.9 5 . 8 34.3 Nylon socks 12.5 15.1 5 .8 27.0 Acrylic garments 10.2 22.8 7-1 60.0 Wool garments 26.4 46.3 18.6 86.3 Wool hank 4.1 6 . 4 1.9 10.7 Synthetic-polymer fabric

(polyester and nylon) 6.6 18.9 3.0 61.9 *Batches partly wet-processed but not dyed were excluded; batches not only dyed but also scoured and/or shrink-resist treated and/or otherwise finished were included

Various attempts have been made to alleviate the problem, e.g. by designing machines requiring shorter liquor :goods ratios, continuous dyeing, using padding techniques, and the use of solvents other than water. The last approach has attracted con- siderable attention, since it offers the possibility of completely eliminating the use of water and the formation of effluent requiring discharge. However, although some solvent preparatory and finishing processes are being used commercially, solvent dyeing-although technically feasible-has made little progress. Few existing dyes can be applied satisfactorily from solvents, and no true costing of the process has yet been published. At present, pressure is not sufficiently great to direct dye research into developing dyes specially for application from solvents which have the same wide range of colour and fastness properties as those of dyes available for application by conventional methods.

Consideration was given, therefore, to the development of an application technique that would enable less water to be used than in the most efficient of existing dyeing machines, and either reduce or eliminate effluent requiring discharge, at the same time allowing existing dye ranges to be used.

Application of pad-steam and pad-thermofix techniques, as well as the experimental organic solvent-water dyeing techniques, indicates that large volumes of water are not essential to the production of satisfactory dyeings. At any particular moment in conventional dyebaths, the only effective dyeing is taking place ‘The lecture is to be presented at a meeting of the Huddersfiefd Junior Section, in the Chemistry Building, Huddersfield Polytechnic, on Wednesday, 2 February 1972.

C

at the immediate interface between the substrate and the dye- liquor, although the much larger bulk of liquor is functional in the overall process. Pad-steam and pad-thermofix techniques are applied only to fabric and loose material. With the former, the fabric must be in open width, and with loose material a blending process is required to even out irregularities. The methods are not applicable to garments, fabric in rope form, or yam.

In the more successful ‘solvent dyeing’ processes, small amounts of water (from which dyeing takes place) are emulsified or dissolved in the organic solvent. The water is carried to various parts of the substrate, where it is concentrated at the liquid-fibre interface and absorbed.

It was decided to consider whether dispersion of a small volume of water into a large bulk could be achieved by an alternative technique. The most obvious answer was to convert the water into a foam, i.e. using air as the dispersant instead of organic solvent. Early experiments consisted in boiling a small amount of aqueous dye-liquor containing an efficient foaming agent in a small specially designed laboratory winch. The head of foam was maintained by passing hot compressed air into the liquor, and the substrate in piece form was rotated on the winch only in the foam zone.

Results on various substrates indicated that it was technicaIiy possible to dye under these conditions. Certain difficulties arose which need not be recounted here, but it was decided to run trials on a larger scale using a winch capable of dyeing up to 5 m of material. Partial success followed, some of the problems of the very small-scale experiments being eliminated, but at the same time more serious ones became evident.

This new technique had the same weakness as the conventional batchwise dyeing systems, i.e. at any time dyeing was taking place only from foam at the interface, the remainder of the foam serving other useful functions in the overall process. However, it had been clearly established that it was possible to convert a small amount of water into a large volume of foam, and by this technique to ensure that the water was evenly distributed throughout the material, leading to level dyeings. It was decided to test a dyeing technique whereby the foam was formed on or in the textile substrate, thus eliminating the use and wastage of liquors away from the dyeing area.

A semi-bulk dyeing was carried out in a steam-jacketed drum normally used for the dyeing of leather. Bulked nylon 6.6 (500 g) was dyed at a 1 .5:1 1iquor:goods ratio, the liquor containing a foaming agent and conventional water-soluble dyes for nylon. The liquor was added to the drum, followed by the nylon fabric. The drum was rotated without heating for 15 min, after which

10 JSDC JANUARY 1972; LISTER

all parts of the piece were evenly coloured with dye-liquor. No excess of liquor or foam was visible in the dyeing machine, and when running the material appeared to be a 'dry dyeing'. However, foam formed on the surface of the material as soon as it was handled. As the material was carried upwards as the drum rotated, it fell at a certain point, and the mechanical action of striking the lower side of the drum generated new foam. After the 15-min treatment at room temperature, the air temperature in the drum was raised to 100°C by steaming; this temperature was maintained for 30 min. A level dyeing of good fastness properties was obtained. The experiment was repeated in the absence of the foaming agent. At the end of the cold treatment even coverage of the substrate was not obtained, and the final dyeing was grossly uneven.

Similar experiments were carried out on other substrates, viz. Trice1 (Courtaulds), Crimplene (ICI) and bulked acrylic fabric. Level results were obtained in the presence of the foaming agent.

Having shown that the technique was feasible on a semi-bulk scale, we initiated a laboratory investigation to examine a range of foaming agents, and to investigate other aspects of the technique in more detail.

Using the method of Ross and Miles (2), the foam-forming properties of a range of products were determined at different concentrations at room temperature. The results are shown in Table 2.

TABLE 2 Properties of Different Foaming Agents

Height of foam formed (cm) at concentration of foaming agent (g/l) of Foaming

agent * 1 2 5 10 20 30 40 1 15 18 20 21 22 23 24 2 5 6 10 15 18 20 22 3 4 5 9 12 15 16 17 4 5

_ _ _ _ - .. ..

4 5 9 12 14 15 15 15 20 21 22 23 23 23

6 8 9 13 14 18 19 19 7 3 4 16 7 1 1 11 1 1 8 9

3 4 I5 6 6 7 7 10 19

'The foaming agents have the following constitutions: 1 6 0 % 2 35%

paste of lauryl(0C H,),OSO,Na solution of octylpfienyldecaglycol ether

3 30% solution of stearylpentacosaglycol ether 4 45% solution of the adduct of 90 moles of ethylene oxide and 1 mole of 3-stearyl-

aminooroovlamine 5 70% solitioLof partially carhoxymethylated alkylpolyglycol ether,

e.g. C,,H,,(OC,H,),OCH,COONa r.-w.mr-u.i.nu -1.- -ID\- -z--.,v---

6 30% solution of highly sulphonated castor oil 7 the adduct of 30 moles of ethylene oxide to 1 mole of castor oil 8 the condensate of 4 moles of benzyl chloride with 1 mole o f ethylenediamine

quaternised with 2 moles of dimethyl sulphate (20% in a mixture of equal parts of water, isopropanol and the adduct of 30% moles of ethylene oxide to 1 mole of castor oil)

9 nonylphenylpentadecaglycol ether

The air-solution interfacial tension was also determined by the du Nouy method, together with that of a non-foaming compound expected to have interfacial tensions of the same order as those of the foaming agents used. The results are given in Table 3.

TABLE 3 Surface Tension Measurements on Solutions of Foaming Agents

Surface tension (dynlcm) Foaming agent (10 g/l)* 1 34.3 2 30.1 3 38.9 4 48.3 5 27.7 6 35.3

Water 66.6 35.0 15 % vol./vol. aq. n-propanol

*For constitutions of foaming agents see Table 2

Attempts to determine the relative wetting properties of the compounds under investigation by using the Draves test with various textile substrates proved impracticable, as sinking was instantaneous in all tests at the concentrations of foaming agents required for adequate distribution of dye-liquor.

It was necessary to determine whether the even distribution of dye-liquor at the short liquor:goods ratio was due to foam formation or to reduction of the surface tension of the liquor.

Nylon 6.6 garments were wetted out separately at a liquor: goods ratio of 3:l in:

(a) dye in aqueous solution only (surface tension 67 dynlcni) (b) dye in water containing 15% vol./vol. n-propanol (surl'ace

(c) dye in water containing 20 g4 of product 1 (surface tension

After even distribution of the liquors by rotation in drums, a further dry garment was added to each drum and rotation continued for a further 15 min. Both garments in each drum were then examined. The Figure shows clearly that even distribu- tion is due to foam and not to surface tension. Subsequent work on a larger scale (50-kg batches) supported this conclusion ; under conditions causing a loss of foam-forming properties of the agent, distribution of dye-liquor was adversely affected.

tension 35 dyn!cm)

34 dynlcni)

a 6 C

-Cffect of surface tension on distribution: (a) dye in water containing 20 gll of product I (surface tension 34 dynlcm), (b) dye in water containing 15 % vol./vol. n-propanol (surface tension 35 dynicm), and (c) dye in aqueous solution only (surface tension 67 dynlcm); (Top line:

garments added first; bottom line, garments added later)

The influence of 1iquor:goods ratio on time of distribution of dye-liquor was determined using a technique similar to that described above. Thus, a 10-g sample was wetted out with a quantity of dye-liquor equal to twice that finally required. After even distribution of the liquor had been achieved by rotation in a drum, a further 10 g of dry material was added. Both materials were then rotated together until the two pieces were judged visually to be level and equal in depth. The results of one typical experiment are shown in Table 4.

TABLE 4 Effect of Liquor : Goods Ratio on Distribution Time

Liquor:goods ratio 0.75:1

1 :I 1.5:1

2:l

Distribution time (min) 25 16 8 4

The influence of foam-forming capacity on distribution was next examined by a technique similar to the one described above but using a final 1iquor:goods ratio of 1:l and varying the concentration of the foaming agent. The results are given in Table 5. Tables 4 and 5 indicate that the distribution time is an inverse function of the 1iquor:goods ratio and concentration of foaming agent.

TABLE 5 Effect of Concentration of Foaming Agent on Distribution Time

Concn of foaming agent (g/l) Product 1 Product 6 Distribution time (min)*

2 7 7 . 5 10 4 4.5 30 3 3

'Using aqueous solution time=38 min Using 15% VOI./VOI. n-dropanol solution, time= I I min

Although no exact mathematical relation between the three factors-1iquor:goods ratio, concentration of foaming agent and

WATER CONSERVATION-AN ALTERNATIVE TO SOLVENT DYEING 1 11

mechanical force-has yet been established, it will most probably involve a power series, since one element will be the probability of any two pieces of material coming into contact during the rotation of the drum. As the load increases, the probability will decrease, and the results shown in Tables 4 and 5 cannot be taken as an indication of the times required for the even distribu- tion of dye-liquor with much larger loads of material.

Results obtained in small-scale experiments (0 3 kg) justified bulk trials being carried out. First, it was decided to use sub- strates manufactured in a form unsuitable for padding, i.e. garments, half-hose, and other materials dyed in the form in which they are finally marketed. Since laboratory experiments had been carried out in drum equipment, similar equipment, originally designed for solvent dyeing by Samuel Pegg, was used for semi-bulk trials (3 kg).

It was decided to use a standard time of 15 min and adjust other variables to obtain even distribution in this time.

Normally, a 1iquor:goods ratio of 1 -5: l was used. At this ratio, after even distribution is achieved, no liquor or foam appears outside the substrate. Visually, the dyeing appears to be a ‘dry’ one.

The construction of the material has some influence on the amount of liquor required, e.g. a nylon 6.6 garment of high bulk requires more liquor than one of low bulk to obtain even distribution in the standard time (the amounts of foaming agent are the same), Liquor :goods ratios appreciably higher than 1 .5 : 1 may be used, without excess of liquor or foam appearing outside the substrate.

As a result of intensive work at this level, the following requirements for the process became evident.

(1) Conditions during the initial distribution of the dye should be such that the dye has little or no substantivity for the substrate.

(2) Only one solvent phase should exist; i.e. emulsions, e.g. those of conventional carriers, should not be used, since this leads to unequal distribution of the two phases.

(3) The rules normally applied to the preparation of highly concentrated liquors for pad-thermofix and pad-steam processes and textile printing should be observed, e.g. avoid high-speed stirrers with disperse dyes, and give consideration to the solubility of water-soluble dyes, e.g. use concentrated dyes when possible. Since emulsified carriers cannot readily be used in this system,

water-soluble ones, e.g. benzyl alcohol, may be selected. Although these carriers are uneconomic when used in long liquors, they are of interest at the low 1iquor:goods ratios-employed in the foam dyeing technique.

The following are typical recipes for the production of dyeings on various substrates (garments, etc.).

The dry goods are placed in the equipment and the drum is rotated. The dye-liquor containing

x % dye 2&40 gil foaming agent water (and other auxi!iary agents if required) to give 1*5:1 liquor :goods ratio

is sprayed on to the material, and rotation is continued for 15 min, The temperature is then raised rapidly to 100°C by means of hot air or steam injection (or both). This temperature is maintained for 30 min.

It was established in bulk trials that, with appropriate dyes, 30 min at 100°C was adequate to establish equilibrium on all substrates. If complete exhaustion is not obtained, an adjustment of recipe is required by changing the pH or the electrolyte concentration, or increasing the carrier concentration.

Examples of Recipes Dyed in Bulk (25-50 kg) on Garments or Hay- hose

0.18 % Nylosan Yellow N-3RL (C.T. Acid Orange

0.70% Nylosan Orange N-RL (C.I. Acid Orange

Nylon 6.6 67)

127)

Wool

Polyester

Trice1

Courtelle

Cellulose

Nylon-Cellulose

0.42% Nylosan Blue N-5GL 200% (C.I. Acid Blue

50 g/l Product 1 liquid 2 % Ammonium hydrogen phosphate Liquor:goods ratio 1.5:1 1 % Lanasyn Yellow GLN (C.I. Acid Yellow 112) 0- 1 % Lanasyn Red 2GL (C.I. Acid Red 216) 0.03 % Lanasyn Grey BL (C.I. Acid Black 58) 50 g/l Product 1 liquid 2% Ammonium hydrogen phosphate Liquor :goods ratio 1 *5:1 12% Foron Navy E-2BL liquid (S) 50 g/l Product 1 liquid 45 g/l Benzyl alcohol pH 5 . 5 Liquor:goods ratio 2:l 0.24% Artisil Brilliant Rose 5BP gran. (C.I.

Disperse Red 11) 0.30 % Artisil Red RLN gran. 150 % ((2.1. Disperse

280)

Red- 53) 50 g/l Product 1 liquid Liquor :goods ratio 1 . 5 : 1 0.02 ”/, Sandocryl Yellow Brown B-RLE (C.I. Basic

Brown 13)

44) 0.027% Sandocryl Red B-2GLE (C.I. Basic Red

0.25% Sandocryl Blue B-2GLE (C.I. Basic Blue 33) 0.3 % Glacial acetic acid 30 g/l Product 9 liquid Liquor:goods ratio 2:l 2 % Drimarene Discharge Orange XJLG (C.I.

Reactive Orange 11) 0.7% Drimarene Blue X3LR (C.I. Reactive Blue

32) 30 g/1 Product 1 liquid 100 g/l Soda ash 2 g/l Revatol S powder (S) Liquor:goods ratio 2:l 0.10% Drimarene Brilliant Red X-2B (C.1.

Reactive Red 56) 0’05% Nylosan Red F-2BLN (C.I. Aid Red 261) 30 g/l Product 9 liquid 5 g/l Soda ash 1 g/l Revatol S powder Liquor :goods ratio 2 : 1

dyed in one bath Orlon-Nylon 0.55% Nylosan Yellow N-5GL (C.I. Acid Yellow

0.15 % Nylosan Yellow N-3RL (C.I. Acid Orange

0.34 L Nvlosan Blue N-5GL 200 ”/, (C.I. Acid Blue

127)

671

Wool-Ny Ion

280)” 0.80% Sandocryl Golden Yellow B-RLE (C.I.

Basic Orange 37) 0.105 % Sandocryl Yellow Brown B-RLE (C.I.

Basic Brown 13) 0.30% Sandocryl.Blue B-3G ((7.1. Basic Blue 3) 30 g/l Product 9 liquid pH 5.5 Liquor:goods ratio 3:l dyed in one bath 0.10% Nylosan Yellow N3RL (C.I. Acid Orange 67)

0.04/% Nylosan Orange N-RL (C.I. Acid Orange

0.18 % Nylosan Blue N-5GL 200 % (C.I. Acid Blue

1 % Ammonium hydrogen phosphate 50 g/l Product 1 liquid Liquor:goods ratio 1 *5:1

dyed in one bath

127)

280)

The following points are worth noting: Nylon-A foaming agent that does not ‘block’ the acid dyes

should be chosen. Wool-Because of the mechanical action required for foam

formation, the material must be given a shrink-resist process to at least machine-washability standards.

Polyester and Triacetate-A water-soluble carrier, e.g. benzyl alcohol, should be used.

12 JSDC JANUARY 1972; LISTER

Cellulose-To minimise substantivity during the distribution stage, the electrolyte content of the liquor should be kept to a minimum, i.e. dyes should be used in the concentrated form when possible.

Blends-In the dyeing of materials containing one type of fibre only, recipes established for pad-steam processes may be used for the micro-foam technique. In the dyeing of fibre blends, where the result obtained in conventional dyeing arises from migration of dye from one type of fibre to another, new recipes may have to be established because, except with intimate blends, migration cannot occur in the technique described.

Once fixation of dye has been achieved, migration of dye does not occur. However, addition of water to the system until liquor exists outside the substrate (normally at a 1iquor:goods ratio exceeding 4: l ) enables migration to occur if it is necessary to correct unlevelness.

Because of the excellent distribution of the micro-foam, not only in the main bulk of the material but also through seams, dyes can be applied which, because of high rate of strike or poor migration properties (or both), cannot be applied by conventional means. In addition, dyes and finishing agents of too low sub- stantivity to be of commercial interest in conventional dyeing, because of the long liquors used, may come under consideration for application in the short liquor of the micro-foam technique.

Tn the laboratory experiments (0 35-kg loads), it was observed (hat the distribution system was effective for substrates in any form other than package. However, after distribution of the dye-liquor, fixation must be carried out and this gives rise to more complex problems. The foam, containing air, is a good heat insulator and a poor heat transmitter, and development work is required to devise a suitable device for the fixation of materials in a form where even simultaneous heating of all parts of the goods is possible.

With garments, body blanks, half-hose and high-denier tights and hose, and forms of fabric of relatively small area, e.g. bath mats and rugs, bulk working has proved the system to be completely satisfactory. More detailed practical information is given elsewhere (4).

Fluorescent brighteners can also be applied by the technique. In addition, certain preparatory, e.g. scouring and S-finishing, and finishing processes, e.g. backtanning and softening, can be satisfactorily carried out.

With existing machinery, fabric of conventional length may on occasions become entangled. Despite this, level distribution of the dye-liquor occurs even in the entangled area. However, variation in heat transfer gives rise subsequently to unlevel dyeing. A solution to this problem is expected in the near future.

Loads of 30-50 kg have been processed continuously on large- scale equipment, and with the types of material mentioned above, the process has proved to be technically and commercially viable. A system has been devised which requires only 2 *5-5 % of the water required for conventional processing from long liquors.

The dyeing technique described is the subject of patent applications made in most industrial countries.

* * * I thank Mr D. K. Clough and Mr P. A. Turner, of Sandoz

Products Ltd, for assistance in the laboratory and in bulk dyeing respectively, and Miss B. Karpavicius, of Bradford University, for additional assistance with laboratory work. (MS. received 12 August 1971)

References I H.A.T.R.A. Note I1 (March 1971). 2 Ross and Miles, Oil (e Soup, 18 (May 1941) 99. 3 Draves and Clarkson, Anier. Dyestuff Rep., 20 (1931) 201 ;

4 Sandoz Ltd, Bask, Technical Informatior2 Bulletin, 'Sancowad Dyeing Draves, ibid., 28 (1939) 421.

Process', and Sancowad Dyeing Pattern Card,

Discussion WEST RIDING REGION

Mr E. YALE: (1) Is there a possibility of lack of compatibility between foaming agent and dispersing agent in a disperse dye?

(2) Is there any possibility of an anionic foaming agent affecting the substantivity of an anionic dye?

Dr L 1 s ~ ~ ~ : T h r e e foaming agents are available: one is strongly anionic, the second mildly anionic and the third non-ionic. Selection is made on the basis of compatibility with the dyes, and its relationship to the process, e.g. a strongly anionic agent would not be used for dark dyeings on nylon.

Mr J. F. DAWSON: Do the small amounts of residual foaming agent present in the fibre affect the fastness properties of the dyeings in any way, as has been found with certain carriers?

Dr LISTER: After two washes at 1 - 5 : l 1iquor:goods ratio and three hydroextractions, the concentration of foaming agent is only 1/27th that originally present, assuming no substantivity. This amount is not sufficient to cause problems.

Dr J. BUDDING: Do you experience difficulties in applying mixtures of acid and basic dyes to material containing acid- and basic-dyeable nylon at these very low liquor :goods ratios? Do you envisage the process being applicable to fabric ?

Dr LISTER: The application technique for mixtures of acid dyes and basic dyes would be similar to that in conventional dyeing, i.e. single-bath single-stage or a two-stage process.

The process itself, as far as distribution is concerned, is applic- able to fabric. The drum type of machine, however, is not interest- ing for production, because of its limited capacity and, in addition, with full-length pieces problems in dye fixation arise. The foam- dyeing technique will probably be applicable to piece goods, but it is improbable that the current type of machine will be used.

Mrs A. K. GILCHRIST: Will there not be excess of foam formed during washing-off?

Dr LISTER: Excessive quantities of foam are formed only when there is free liquor outside the substrate. If washing-off is confined, as in dyeing, to 1iquor:goods ratios of the order of 1$:2, excessive foam is not formed.

Mr B. A. O'FARRELL: What concentrations of foaming agents are required? Do the small but concentrated volumes of foaming agent pose a disposal problem?

Dr LISTER: Concentrations of foaming agent range from 20 to 50 g/l, i.e. 3-7+% on the weight of the material. It should be remembered that the agent also functions as a scouring agent, and that the higher quantity mentioned above is required only in the carrier dyeing of polyester.

Dr C. B. STEVENS: With reactive dyes on cellulosic material, what modifications, if any, of the normal washing-off procedure are required ?

Dr LISTER: Thdwashing-off of reactive dyes consists of two stages. The first is the removal of residual electrolyte, etc., plus dye remaining in the dyebath. This can be readily accomplished by two washes at short 1iquor:goods ratios, with hydroextraction between. Removal of substantive but unreacted dye is achieved by the use of longer 1iquor:goods ratios. After the two short washes, three washes (5-6:l 1iquor:material ratio) would be employed. The total amount of water required for washing-off is still only 25% of that used in washing-off following con- ventional dyeing from long liquors.

Mr B. C . BURDETT: Many dyes in aqueous solution have their own foam-forming characteristics; do these contribute to the process ?

Dr LISTER: The foam-forming characteristics of dyes are in themselves inadequate to obtain distribution. Their contribution in the presence of forming agent is so small that it need not be taken into consideration.

Mr J. V. SUMMERSGILL: It has been stated that most dyes are sufficiently soluble at room temperature for application by this process. In some cases one may wish to use dyes of insufficient

WATER CONSERVATION-AN ALTERNATIVE TO SOLVENT DYEING 7 13

solubility. Is it possible to carry out the first stage with the dyes incompletely dissolved, but finely dispersed, and rely on increased solubility at the final dyeing temperature? Alternatively, is there any product that can be used to increase solubility ?

Dr LISTER: Very few cases have been found where the solu- bility of a dye at room temperature is inadequate to obtain the colour required. We would not recommend that dyes not in com- plete solution should be used, except, of course, disperse dyes for polyester and Tricel. The normal solubilising agents such as urea or benzyl alcohol could be used, but it should be remembered that the latter is an antifoaming agent and more foam-forming compound may be required.

Mr G. LUND: Is soiling of machinery a problem? Dr LISTER: No, this has been taken care of in the design of the

machinery. SCOTTISH REGION

Dr R. J. Harwood: (1) I would expect that for the foam-dyeing system described the BOD of the effluent per pound of material processed would not be reduced and may be increased. Would Dr Lister like to comment?

(2) The solvent dyeing of polyester fabrics would appear to offer a strong alternative to foam dyeing; is this your opinion?

(3) Does the foam-dyeing process overcome the faults usually associated with tippy wools?

Dr LISTER: (1) From the point of view of treatment of the effluent, the present process neither adds to nor solves any problems. However, the small amount of effluent produced would reduce the storage capacity required at the dyehouse, enabling effluent treatment to be carried out, therefore, by the more modern systems currently being developed.

(2) The future of solvent dyeing is itself problematical. It is of most interest in the dyeing of polyester and to stand any chance of success must be capable of covering barre material. At the moment, an inadequate range of dyes is available.

(3) At present we have no experience of dyeing tippy wool by this process.

Mr M. ROBERTS: You have given the impression that the process is perfect. Would you care to point out the major problems at present?

Dr LISTER: The original difficulties were the felting of wool, which required us to determine the minimum non-shrink treat- ment required to enable the material to be dyed satisfactorily. This has now been solved and really the sole problem is the ‘handle’ of garments.

Mr J. B. SCALES: You have given low priority to the application of this system in package dyeing. Despite its inherent disadvan- tages, hank dyeing is still the preferred method in many cases. Has the dyeing of hanks in other than rotating-drum machines been considered? Possibly there may be a case for reverting to the old type of conventional hank-dyeing machine of the rotating- cylinder type, since this would help to overcome the heat-transfer problem.

Mr R. MCDONALD: In the process described it appears to be necessary to agitate the fabric to assist generation of the foam. Have you any thoughts on the application of foam dyeing to systems where agitation of the fibre would not be possible, for example in the dyeing of yarn in package form?

Dr LISTER: At present we do not anticipate extension of the use of the foam-dyeing technique to the dyeing of yarn in package form. The dyeing of yarn will probably take a completely different direction, but the same results will be achieved. Certainly it is a low priority in our development work.

Dr D. G . DUFF: (1) Why is such a high concentration of foam- ing agent required?

(2) Is the choice of foaming agent determined by the ionic charge on the dye?

(3) Is the increase in solubility of dyes brought about by foaming

agents relatively greater for non-ionic disperse dyes than for water-soluble dyes ?

Dr LISTER: ( 1 ) A high concentration is required to give uniform distribution within 15 min; in addition, the high concentration enables soil on the goods to be emulsified satisfactorily. Lower concentrations of agent could be used if the 1iquor:goods ratio were increased, but ultimately this leads to foam formation out- side the goods.

(2) The choice of foaming agent is determined by the compatibility of other products in the dyebath.

(3) The increase in solubility of disperse dyes is greater than that obtained with water-soluble dyes as a result of the presence of foaming agent. The non-ionic and mildly anionic products give the greatest increase in solubility of the disperse dyes.

Mr C. MCNEIL: In view of the apparent universal nature of this process, is it also possible to use the principle in preparatory processes such as scouring where a considerable amount of water is used.

Dr LISTER : Although considerable development work is requir- ed, we anticipate that itwill be possible to carry out anywet process by the foam-treatment technique. S finishing of Tricel has already been carried out, and scouring is a relatively simple matter.

Mr D. BYRNE: You claim that nylon is the easier fibre to dye by this process and that the application of milling acid dyes presents no problem. Does this help to overcome barrC effects?

Dr LISTER: In our present state of knowledge with regard to both nylon and polyester, a foam dyeing will present no different result with regard to barre effects than that obtained by conven- tional dyeing at 100°C.

MANCHESTER JUNIOR SECTION Mr E. D. HARVEY: (1) The Sancowad process was described

as an alternative to solvent dyeing; do you consider that this technique is applicable to beam and jet dyeing?

(2) Are the costs of Sancowad agents comparable with those of conventional auxiliaries in use?

(3) What is the effect of benzyl alcohol on foaming? (4) Is the use of benzyl alcohol sufficient to enable satisfactory

dyeing of polyester at atmospheric pressure? Mr TURNER: (1) We have not yet applied the Sancowad

principle to beam dyeing. The problem here will be to obtain even distribution of heat for dye fixation.

(2) Yes. (3) Benzyl alcohol acts as an anti-foam agent, and when the

quantity used is above its solubility limit then no foam is formed and there is no dye distribution. This is further proof that the foam is essential for dye distribution.

(4) Use of benzyl alcohol (45 g/l) will enable all depths to be dyed on polyester. However, it does have some limitations, because it is liable to steam-distil and so we are considering other carriers.

Mr W. BEAL: (1) Does one have to take special precautions in the preparatory processes to ensure that no product is carried over into the dyeing system which would adversely affect it, e.g. oils and foam depressants?

(2) What factors determine whether dyes are compatible with this process?

(3) Can the process be used for differential-dyeing fibres ? (4) Can a solid dyeing be produced on blends such as wool-

nylon with normally incompatible dye combinations, e.g. a mono- sulphonate yellow acid dye with a disulphonate blue acid dye?

Mr TURNER: (1) Spinning oils, particularly cationic products, will affect the foam level. The foaming agents act as detergents and will cope with a moderate amount of oil, etc., but it may be necessary to scour heavily soiled goods before dyeing.

(2) As mentioned in the paper, the dye must have adequate solubility at room temperature, low substantivity for the fibre at room temperature, and the same ionic activity as the foaming agent. A non-ionic foaming agent is used with basic dyes.

14 JSDC JANUARY 1972; DELMENICO AND NARSIAN

(3) There is sufficient local migration to allow differential

(4) The usual precautions must be taken with wool-nylon effects to be produced.

blends. NORTHERN IRELAND REGION

Mr R. A. M. MACKINNON: (1) Does the spray system used for impregnation ensure that all the liquor is absorbed by the goods or is liquor lost at this stage?

(2) In the dyeing of acrylic fibres by the Sancowad process is it necessary to apply heat slowly in the 8@9O0C region, which is normally critical in conventional methods of dyeing, or can the temperature be raised rapidly to boiling point ?

Mr TURNER: (1) The spray is fine and directed so that the liquor is more or less completely picked up by the goods. With bath mats or similar goods some dye may miss and then it is necessary to re-cycle this dye-liquor to give complete pick-up.

(2) At present it has not been found necessary to proceed slowly through the critical temperature range, but there may be some colours where care is necessary.

Mr N. J. MOUNT: With disperse dyes on polyester, are the rates of exhaustion of dyes affected by the short 1iquor:goods ratio? Are the washing- and rubbing-fastness properties of heavy dyeings affected?

Mr TURNER: The rate of dyeing is higher than that at high 1iquor:goods ratios, but the total exhaustion is not significantly different, since the foaming agents used tend to have a solubilising effect, so nullifying the effect of the low 1iquor:goods ratio. The rubbing fastness is often better, since the foam acts as a cleansing agent and it is possible to hydroextract and remove the unexhausted dye near the boil, so preventing crystallisation of the dye during cooling.

Mr I. W. REYNOLDS: In the Sancowad process, are soluble dyes concentrated in solution in the liquor phase? Is it difficult to level dyeings carried out with substantive dyes that have poor migration properties?

Mr TURNER: Care must be taken to reduce the substantivity of such dyes either by reducing the concentration of the electrolyte or by using cationic restraining agents.

Com mu n ica t ions Setting and Stabilisation of Crimped Wool Yarn Produced by the Knit-Deknit Method

J. DELMENICO

Division of Textile Industry, C.S.I.R.O., Geelong, Victoria, Australia

M. G. NARSIAN

Wool Research Organisation of New Zealand (Inc.), Christchurch, New Zealand

The crimp in wool yarn produced by the knit-deknit method can be made stable to release in hot water while in the extended configuration by setting the knitted fabric with bisulphite and then applying stabilising techniques previously found effective on

pleated fabric. These include oxidation, crosslinking and application of reactive polymers.

Introduction The knit-deknit method can be employed for producing bulky

yarns. The steps of this process are knitting, setting, deknitting (unravelling), and winding on to suitable packages. The crimped yarn so produced can be used in the carpet industry for producing curly-pile carpets. The degree of setting is important, because it will determine the appearance of the carpet after making-up and the stability of the crimp to shampooing or spilt liquids.

The knitted fabric can be set by autoclave steaming, but this usually causes yellowing of the wool. Setting without yellowing can be achieved by steaming in the presence of reducing agents. Under these conditions, the set is largely the result of stress relaxation via rearrangement of disulphide bonds. The set configuration is stable to soaking without movement in hot or cold water. However, when the set wool is distorted during, for example, machine-washing of garments, further stress relaxation can occur and the original set is lost (I, 2). The set can be stabilised to these dynamic conditions of release by treatments that inhibit the bond rearrangements, such as crosslinking (3), prevention of thiol-disulphide interchange (4) or the application of reactive polymers (5, 6). The set stable to immersion in water under static conditions is also enhanced by such treatments (7,8). This paper illustrates the setting and stabilisation of yarns crimped by the knit-deknit method using techniques (4, 9) previously shown to increase the stability of pleated fabric to machine-washing.

Experimental

Yarn The yarn was a commercial, scoured [aq. extract (IO), pH 7-81,

two-ply carpet yarn spun on the semi-worsted system from New

MATERIALS

Zealand crossbred wool: R560 Tex/2, 98 t/m, S twist (singles 176 t/m, Z ) .

Knitted Fabric This was prepared on a circular hose-knitting machine of

4 -5 in diameter with 44 needles, and was used without further treatment. The loop length (18 mm) remained unchanged during setting.

Reagents

the following proprietary products: Laboratory-grade reagents were used throughout except for

Surfactant Antarox C0730 (GAF)

Crosslinking agents Kaurit S (BASF) NW-Dimethylolurez Sulfix A (ICI)* Disodium (tris P-sulphoethyl) sul-

Polymers Hercosett 57 (Hercules) A polyamide-epichlorohydrin precon-

densate in aqueous solution Primal K3 (Primal) A self-curing polyacrylate in aqueous

dispersion [ = Rhoplex K3 (RH)].

Nonylphenol-ethylene oxide condensate

phonium inner salt

METHODS

Setting Unless otherwise stated, the knitted fabric was soaked in a

solution (liquor :wool, 20: 1) containing 5 % sodium bisulphite (on wt of wool) at 80°C for 30 min, rinsed, and allowed to dry under ambient conditions. 'This product is not available commercially