Jan 5, 1995 - of mordants. Effect of dyeing padding techniques as well as mordants has been visualised on the colour strength and fastness properties.
Studies on dyeing of wool with a natural dye using padding techniques A natural dye extracted from the skin of babool bark has been applied on woolen substrate in presence and absence of metallic salts (mordants). Application of the dye liquor is done using two padding techniques, namely cold pad-batch and pad-dry-steam techniques. Metamordanting technique has been employed for the application of mordants. Effect of dyeing padding techniques as well as mordants has been visualised on the colour strength and fastness properties of the dyed sample.
India has a long golden era of dyeing textiles with vegetable dyes. Documents of Mughal periods bear a testimony to the utilisation of these dyes. Today, Rajasthan and Kutch still possess a rich tradition in the use of natural colourants for textile dyeing and printing applications I. Vegetable dyes are unsophisticated and harmonised with nature. The use of natural dyes offers no pollution problem since toxic substances are not involved in their production. Sometimes, these dyes also provide a creative natural finish to the textile materials which do not cause any carcinogenic effect to the body of the wearer. Natural dyes offer several advantages over synthetic dyes from the point of view of health, safety and ecology. How~ ever, natural dyes have their own limitations, viz. limited shade range, low colour yield, reproducibility, availability, etc."". With the advent of coal-tar dyes, the use of natural dyes declined tremendously because the existing natural dyes failed to fulfill the demand of the market and also the new synthetic dyes were cheaper, more readily synthesised and exhiiJit better fastness properties to various agencies. Recently, extensive research is being carried out around the world on the application of natural dyes to textile substrates, because the traditional processes for dyeing with natural dyes have been lost due to absence of proper documentation and years of neglect. It is, therefore, necessary to develop new techniques of dyeing with the help of modern scientific inputs so that these dyes can offer themselves as an effective eco-option. From the
extensive literature survey, it has been observed that there is hardly any work reported in the field of dyeing wool with natural colourants using padding techniques. The present study has been undertaken to apply a natural dye (Acacia arabica Willd) to wool substrate using padding techniques of dyeing and to evaluate the fastness properties of the dyed substrate.
Collection of material for dyeing: The outermost skin of Acacia arabica Willd (babool) bark was utilised for dyeing wool. It was collected from various parts of South Gujarat region. Fabric : For the experimental work, woolen fabric was procured from Khadi Gramodhyog, Vadodara. The fabric was scoured using a non-ionic detergent (Lissapol N, 2 gpI) and soda ash (l gpl) at 55°C for 30 min and then bleached with hydrogen peroxide at 60°C for 45 min keeping the pH 8.5.
Mordants: Three individual mordants, namely stannous chloride, ferrous sulphate and copper sulphate as well as a mixed mordant system of ferrous sulphate and copper sulphate (in 1: 1 proportion) were selected for the present investigation. The mordants used were of L.R. grade. Experimental methods Extraction of the dye : The outermost skin of matured babool bark was removed without causing any appreciable damage to the parent plant. The skin was then cut into small chips and dried. Cold water was added to the dried chips. After
filtration, the residue was re-dissolved in hot water and charcoal was added. The solution was boiled and filtered hot. The filtrate was cooled to obtain fine crystals of the dye. Mordanting : Mordanting of wool fabric with various metallic salts was carried out at room temperature by 2-dip-2-nip technique on a two bowl padding mangle using 70% padding expression. Meta-mordanting technique was utili sed for the present work. In this technique, requisite amount of mordant (10 gpl) was added to the dye-liquor itself and subsequently padding was done. Dyeing : Pad-dry-steam and cold pad-batch dyeing techniques were utilised for the application of the dye liquor. In pad-dry-steam technique, the sample was impregnated with the dye liquor containing required amount of metallic salt (10 gpl). Glacial acetic acid was added to maintain the pH of the liquor at 4.5. The concentrations of the dye selected for the study were 5, I 0, and 15 gpl. The fabric was immersed in the above liquor at room temperature and padded on a two-bowl padding mangle by 3-dip-3-nip technique (using 70% expression). After padding, the samples were dried and then steamed at 105°C and 25 psi steam pressure for 15 min. In cold pad-batch dyeing technique, the preparation of the dye-liquor and padding procedure were identical to those mentioned in pad-dry-steam technique. After padding, the sample was carefully batched on a glass rod and then wrapped with a polythene sheet. The sample was then stored for 24 hours at room temperature. Soaping Procedure: After dyeing, all samples were rinsed, squeezed and soaped with a non-ionic detergent (Lissapol N) at 70°C for 30 min. Finally, the samples were thoroughly washed and air-dried. Testing
and Analysis
Evaluation
of colour
strength
Colour strength (K/S values) of measured on MS 2000 (Colour U.V. Spectrophotometer. These calculated from reflectance Kubelka-Munk equation'l Assessment
of fastness
a dyed samples were Eye-31 00), Macbeth values are computer data according to
properties
Washing, light and rubbing fastness properties of dyed sample were evaluated according to standard methods. Wash fastness was determined by the
appropriate ISO Test NO.3 on Launder-o-meter; light fastness on Fade-o-meter using carbon arc continuous illumination (BS 1006: I 987); and rub fastness (both dry and wet) on Crockmeter (BS 1006: No X 12; 1978)
5·li •
In the present study, woolen fabric is dyed with a natural dye extracted from babool bark in presence and absence of various metallic salts. The application of babool dye has been done by padding techniques ( pad-dry-steam and cold pad-batch techniques) using meta-mordanting process for the application of the mordant. Effect of application technique on colour strength, change in hue/tone and shade as well as fastness properties has been investigated and compared with samples dyed without mordants.
Effect of padding technique on colour strength Table 1 reveals that the colour strength (in terms of K/S value) qf the dyed woolen sample increases with an increase in the concentration of dye in the dye-liquor which indicates that the preparation of shade card can be done with ease with babool dye applied on wool substrate. From table 1, it can also. be observed that among two padding techniques utilised for the study, the pad-dry-steam technique performed better than the cold pad-batch technique, irrespective of whether a mordant is added during dyeing or not. Furthermore, among the three individual mordants used, it has been visualised that in most of the cases, ferrous sulphate mordant gave the best dyeing performance followed by copper sulphate. Only stannous chloride mordant gave some inferior results as indiTable 1 Colour strength (in terms of K/S values) of wool sample dyed with babool dye using padding techniques K/S Values Mordant
Cold pad-batch
Pad-dry-steam
10 gpl
15 gpl
5 gpl
10 gpl
IS gpl
1048
11.30
12.56
10.64
11.9(;
12.82
SnCI,
8.16
9.77
1040
8.91
12.1:~
14.85
FeSO,
22.39
25.40
27.88
29.07
32.61
37.07
CuSO.,
1.5.95
17.25
20.28
20.85
24.08
29.'11
Mixed (Cll + Fe)
19.29
22.36
25.13
26.56
28.51
:~0.59
(lO gpI)
5gpl
Control
/cated
by the lowe' coloue stcength (K/S value) of the dyed samples. However, the results are quite comparable with the control sample. The mixed mordant system of ferrous sulphate and copper sulphate gave the colour strength of dyed sample which is higher than that of copper sulphate mordant but lower than that of ferrous sulphate mordant system.
other mordants (including mixed mordant system) gave higher colour value than control (unmordnated and dyed) sample. However, higher colour yield of sample dyed along with mordant (except with stannous chloride) should not be misinterpreted since the hue and tone of the dyed samples sometimes changes much as compared to the samples dyed without mordant.
The results are also represented in Fig. 1 and 2. From these figures, it can be seen that for paddry-steam scheme, except stannous chloride, all
In case of cold pad-batch dyeing scheme, it can be clearly observed from Fig. 1 and 2 that ferrous sulphate mordant performed better than other mordants employed for mordanting in the present investigation. When two padding techniques are compared with each other, the pad-dry-steam technique gave better dyeing performance than the cold pad-batch dyeing process. However, the average steam consumption in pad-dry-steam technique is much higher than that in cold pad-batch technique of dyeing, where practically no steam is being required. From Fig. 1, it can be seen that higher colour value is obtained when pad-dry-steam techniques is employed and the colour value obtained by cold pad-batch technique of dyeing is quite comparable with unmordanted and dyed control samples.
A: Stannous chloride B: Ferrous sulphate C: Copper sulphate D: Mixed mordant system of ferrous sulphate and copper sulphate (I: I) fig.
1. Effect of metallic salts on colour strength of wool fabric dyed with 5 gpl babool bark dye using cold pad-batch and pad-dry-steam dyeing techniques.
1 20
1
en ;z
l 15-1 ! 10
1
A: Stannous chloride B: Ferrous sulphate C: Copper sulphate D: Mixed mordant system of ferrous sulphate and copper sulphate (I: I) Fig. 2. Comparison of colour strength of wool fabric dyed with 5 gpl babool bark dye using cold pad-batch and pad-dry-steam dyeing techniques.
From these results, it can be postulated that wool fabric can successfully be dyed with babool dye using padding techniques. This may be attributed to the fact that babool is rich in tannin. These tannis are phenolic compounds which can form hydrogen bond with carboxyl group of wool fibre. Other two possibilities are - (a) suitably charged anionic (phenolic) groups on tannin may form an ionic bond with cationic (amino) groups on wool substrate, and (b) covalent bond may also be formed by an interaction between any quinone or semiquinone groups present in the tannin and suitable reactive groups on wool fibre.
Effect of padding technique on colour hue/ shade Different shades obtained with various metallic salts used in the dyeing of babool dye on wool using padding techniques are represented in Table 2. Cold pad-batch dyeing produce quite wide range of shades in different hues. For instance, with ferrous sulphate, gray to chocolate brown colour is being produced, while pale brown to dark copper brown shades are obtained with stannous chloride and copper sulphate mordants respectively. The mixed mordant system of copper and ferrous
Table 2 Shades obtained on wool fabric dyed with babool dye using padding technique Mordant
Effect of dyeing technique on fastness properties Table 3 indicate the fastness properties of dyed samples towards various agencies, viz, light, washing and rubbing (both dry and wet). It can be clearly postulated that the fastness characteristics of babool dyed samples to various agencies ranges from good to very good level. The fastness ratings for sample dyed using a mordant is higher by 1-2 points in some cases than that of sample dyed without using mordants. However, in almost all cases, the wash and rub fastness declines with an increase in the dye concentration.
Shade obtained
(10 gpl)
Cold pad-batch
Pad-dry-steam
Control
Pale to medium brown
Pale to medium brown
SnCI,
Cream to pale brown
Pale to medium brown
FeSo"
Gray to chocolate brown
Gray to brownish black
CuSo,
Pale to medium copper brown
Medium to dark copper brown
Mixed (Cu + Fe)
Gray to dark copper brown
Brownish black to dark copper brown
sulphates gives gray to dark brownish black shade on woolen substrate, The colours obtained with various mordants varies in their tone. The reason for such behaviour may be attributed to the fact that when tannin combines with metal ion, a tannin-metal complex is formed and depending upon type of metal ion (metallic salt/mordant), different tones are obtained. The light and dark shades obtained further depends on the nature of the bond formed between the dye and the metal ion (mordant).
On comparing the fastness ratings of the samples dyed by two padding techniques, it can be postulated that the pad-dry-steam technique in some cases exhibits somewhat better fastness properties than the samples dyed by cold patch-batch technique of dyeing. However, an overall good to very good fastness properties, as obtained, may be attributed due to the presence of tannin which can form metal chelates with different metallic salts. A treatment with metal salts not only alter the light sorption characteristics of tannin but can also make them insoluble in water. Hence, they get fixed on the textile substrate and improve the fastTable 3 ness properties. Fastness ratings of wool fabric babool dye using padding techniques .'
Conclusions
Mordant
Dye
(lOgpI)
cone. (gpl)
Control
SnCI,
FeSo,
CuSo"
Fastness Grades Pad-Dry-Steam LF
Cold Pad-Batch RF
WF
LF
Dry
Wet
RF
WF
Dry
Wet 4
5
6-7
4-5
4-5
4
6-7
4-5
4
10
6-7
4
4
3
6-7
4-5
3-4
3
15
6
4
3-4
3
6-7
4
3-4
2-3
5
6-7
4-5
4-5
4
6-7
4-5
4-5
4
10
6
4-5
4-5
3-4
6-7
4-5
4
3-4
15
6
4
4
3
6
4
3-4
3
5
6-7
4-5
4-5
4
6-7
4-5
4
4
10
6-7
4-5
4
3-4
6-7
4-5
3-4
3
15
6
4
4
3-4
6
4-5
3-4
3
5
7
4-5
4-5
4
7
4-5
4
4
10
6-7
4-5
4
3-4
6-7
4-5
3-4
3-4
15
6-7
4-5
4
3
6-7
4-5
3
3
Mixed
5
6-7
4-5
4-5
4
6-7
4-5
4
4
(Fe+Cu)
10
6-7
4-5
4
3-4
6-7
4-5
3-4
3-4
15
6
4
3-4
3
6-7
4
3-4
3-4
Woolen fabric can be dyed successfully with a natural dye extracted from the skin of babool bark with and without metallic salts (mordants) using padding techniques. The use of various metallic salts as mordants not only improves the colour yield but also provide a wide variety of shades with different hues. The application of babool dye on woolen fabric by cold pad-batch and pad-dry-steam technique of dyeing can be considered as an affective eco-option because it gives extremely good results with substantial minimisation of processing cost. In case of pad-dry-steam tech-' nique, the average steam consumption is considerably high whereas no steam is being consumed in cold pad-batch process which leads to energy conservation. However, the time employed for the fixation of babool dye is very long in cold pad-batch technique. So, these techniques can be considered as be~' suitable for small scale industries or cottage dyeing of babool.
Fastness properties of samples dyed by padding techniques are adequate for both techniques of dyeing irrespective of whether the metallic salt (mordant) is present in the dye bath or not.
tions, Landsberg, (1992). 4. Billmeyer F.W. Jr. and Saltzman M., Principles of Colour Technology. 2nd Edition; John Wiley and Sons: New York; (1981) 140. 5. AATCC
1. Mohanty. B. C., National seminar dyes, Jaipur, NHDC, (1989).
on natural
2. Glower Brain, J. Soc. Dyers. Col., 114 (1998) 4. 3. Schweppe
Technical
Manual (1977).
6. Trotman E.R., Dyeing and Chemical Technology of Textile Fibres, 6fh Edition; B.1. Publication Pvt. Ltd.; New Delhi. (1994) 511.
H., Natural dyes, Ecomed Publica-
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