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New approach for the application of natural dye in modern textile dye houses

Abstract

The use of natural colorants will offer less effluent problems and will provide a natural finish to textiles treated with these materials. It is also noted that some limitations with natural dyes still exist such as dyeing efficiency, process complexity, availability etc. In the present investigation, cotton samples were dyed with and without using metallic salts. The main problem associated with the dyeing of natural dyes is low exhaustion so; standing dye bath study is also carried out to minimize the wastage of natural colorants. Very encouraging result are found. A new multi-dip technique is being developed to reduce the time and to improve the dye-ability of natural dyes. Much deeper shades, which could not be attained by any of the single dip (exhaust) methods. With all round fastness properties of various samples dyed using exhaust dyeing method are adequate and quite comparable with control dyed samples.

Keywords: Acasia Arabica Wild; Dyeing; Eco-preservation; Metallic salts; Natural colorant

  1. Introduction

In this new millenniums, maintenance of a safe environmental balance will become a necessary requirement. Most of the synthetic dyes are not only based on toxic raw materials and intermediates but their use in textile wet processing also produce effluent which causes environmental pollution. Natural dyes are free from such problems [1-3]. Moreover, if steps are taken to commercialize the cultivation of plants from which most natural dyes are generated, it will definitely assist in preserving the eco-balance [4-7]. These vegetable resources are not only replaceable but also bio-degradable compared to limited and irreplaceable petrochemical resources of synthetic dyes. These have also been much interest recently in the pharmacological effects and possible health benefits of the use of natural dyes. [8-11]

Recently extensive research work is being carried out around the world on application of natural dyes to textile substrates as textile colorants [12-18]. Because the earlier sources of natural colorants as well as the traditional processes of coloration have almost been lost due to the absence of documentation and years of neglecting. It therefore becomes prime necessary for the textile scientists to search new sources and to standardize the application methods of natural dyes to textile substrates to prove their effectiveness and market potential. In the present study an attempt has been made to study the effect of various metallic mordant and effect of different mordanting techniques on the colour strength and colour hue to cotton dyed with natural colouring matter extracted from skins ofAcasia Arabica Wild bark.

The chemical composition of Acasia Arabica Wild skin includes mainly tannins and colouring matter. Acasia Arabica Wild or bawal is a small tree with dark brown or black; longitudinally fissured bark. The plant is mainly found in India, Sri-lanka, Sudan and Africa. In India, it is found in Punjab, Rajasthan, Gujarat and Western ghats. The botanical name of this plant is “Acasia Arabica Wild” which belongs to the “Legominosae” family, the plant is very good source of tannin. In case of Acacia arabica wild bark the tannin found is of hydrolysable tannins. The tannins are hydrolyses by acids or enzymes quickly and the products of hydrolysis are gallic acid or ellagic acid. On distillation, gallic acid and other components get converted to pyrogallol. Fig.1 shows the chemical structure of Gallic acid, Glucogallin, Pyrogallol, Ellagic acid.

1 (2)

Fig.1: Chemical constituents of Acacia Arabica willd

Acasia Arabica Wild is widely used for medicinal purposes, because bark is astringent, demulcent and aphrodisiac, pods are expectorant; extract of gum is styptic, tonic and astringent[19].

The natural dyes being neglected for about 150 years, but currently they have again come into limelight. However, the main requirement for their successful revival is to be accepted by and large. On a commercial scale is to develop some new techniques, which are effective enough to provide maximum utilization of available natural dyes. Today in the era of eco-preservation, the natural colorants have attracted the attention of whole world and have get growing commercial potential. Hence the present study is also aimed to standardize the dyeing in terms of its reproducibility, tonal variation, and depth.

2. Materials and Experimental Methods

2.1 Material

Locally available poplin cotton fabric was selected for the present study. Before dyeing, the cotton fabric was scoured to remove the impurities. 2 g/l of soda bicarbonate and 5 g/l of nonionic detergent were used in a material to liquor ratio of 1:50. The cotton fabric was boiled in this solution for 30 min. It was then cooled and rinsed in water to remove traces of soap, and then dried in shade.

2.2 Dyes and Chemicals

As a natural dye source, Acasia Arabica Wild bark was selected. Outermost skin of the matured Acasia Arabica Wild bark was removed without causing any appreciable damage to the present plant and cuts into a small pieces or chips, which were then boiled in water for 2 hrs. So a brown coloured solution was obtained which was then filtered through fine-fabric. The filtrate was further boiled with charcoal powder and again filtered through watt man filter paper. The filtrate was then evaporated to dryness resulted in brown coloured powder which was subsequently used for a dyeing process.

Metallic mordant – stannous chloride, ferrous sulphate, copper sulphate and a mixture of copper sulphate and ferrous sulphate (1:1) were selected for the study. Two different mordanting processes viz., pre-mordanting and meta-mordanting was selected in which the concentration of mordant was kept 6% (owf). In pre-mordanting the samples were treated in mordant solution at boil for 1 hr, and then the samples were squeezed evenly and entered in the respective dye bath prepared with the dye solution without intermediate washing or drying. While in meta-mordanting process, mordanting and dyeing were carried out simultaneously.

2.3  Dyeing

The exhaust dyeing was performed on laboratory constant temperature water bath (Paramount Instrument Pvt. Ltd, India). The dye baths were prepared with the requisite amount of Acasia Arabica Wild dye viz, 10%, 20% and 30% (owf); sodium carbonate was added to the dye bath to maintain the pH of the liquor at 8.5. Mordant sample was introduced in the above dye bath at room temperature, worked for 10 min. The temperature of the bath was raised to boil gradually and the dyeing was continued for 1 hr. After dyeing the sample was rinsed thoroughly and dried.

After dyeing was completed the dye liquor left in dye bath was again used for dyeing by maintaining the material to liquor ratio 1:50 with water and dyeing were carried out as above, same process was repeated for two times.
Another method used is multi-dip technique in which mordanting bath and dye bath were prepared separately by adding required amount of mordant and dye solution. The fabric was first dipped in mordanting bath containing ferrous sulphate, copper sulphate, stannous chloride and mixed mordants (FeSO4 + CuSO4) at boil for three minutes, squeezed and then dipped in dye bath at boil for three minutes. This is defined as one dip. The process was repeated for 15 to 30 times, which is defined here as multi-dip technique.

2.4 Measurement of K/S Value

After completion of dyeing of cotton fabric with Acasia Arabica Wild dye, the dyed samples were assessed to find out K/S values by Spectra scan 5100 (RT) spectrophotometer (illuminant D65/100 observer), (Premium colorscan instruments pvt.Ltd, India).The K/Svalue is directly proportional to the concentration of colorant in the substrate.

2.5 Evaluation of fastness properties

Wash fastness of the samples dyed under the optimized conditions, was tested according to ISO 105-CO3 method. The samples were washed in standard soap solution at 60 °C for 30 min, keeping liquor to material ratio as 1:50. Dry and wet rubbing fastnesses of the dyed farbic were tested according to ISO 105-X12 method. Light fastness was tested according to ISO 105-BO2 method. The dyed samples were exposed to xenon arc lamp for 24 hrs at standard testing conditions [20].

3. Results and Discussion

Cotton fabric was mordanted with various metallic salts viz. ferrous sulphate, copper sulphate and stannous chloride using pre-mordanting (mordanting followed by dyeing) and meta-mordanting (simultaneous mordanting and dyeing) techniques. Dye extracted from acacia arabica wild bark is then applied on mordanted cotton fabric using open bath dyeing process. Colour strength, change in hue and shade as well as fastness properties of such dyed samples are compared with unmordanted and dyed (control) samples.

3.1 Effect of metallic salts on colour strength

On referring to the results given in Table 1 it is observed that the colour strength (in terms of K/S value) of control sample (i.e. without mordanting) as well as mordanted sample increases with the increase in the concentration of the dye in the bath. The observations further indicate that the colour strength value of mordanted and subsequently dyed sample is much higher than that of control sample except in case of SnCl2 using meta-mordanting technique. The variation in colour strength is further dependent on the type of mordant used and the technique involved for mordanting.

Table 1: Color strength (K/S value) of cotton fabric dyed with Acasia Arabica Wild  dye using different mordants, by Exhaust dyeing technique.

Sr. No.

Technique

Mordant 6% (owf)

K/S Value

10%

20%

30%

1.

Control

1.616

2.048

2.509

2.

Pre-mordanting

SnCl2

1.280

3.085

5.437

FeSO4

3.142

3.920

5.540

CuSO4

5.470

5.515

6.409

Mixed (FeSO4 + CuSO4)

6.198

6.912

8.858

3.

Meta – Mordanting

SnCl2

1.432

1.796

2.446

FeSO4

2.041

3.159

3.251

CuSO4

2.597

3.598

4.625

Mixed (FeSO4 + CuSO4)

2.431

3.199

4.113

In case of individual mordant maximum colour strength is observed with copper sulphate for either mordanting techniques used. However the colour strength observed with mixed mordant system [FeSO4 + CuSO4 in 1:1 proportion] for pre-mordanting technique is maximum than the other mordant used in the present study. When the two mordanting techniques are compared, preordaining technique performs better as visualized from higher color strength values, which is graphically represented in Fig – 2.

2

Fig. 2: Effect of different mordants and mordanting techniques on K/S Values of the Cotton dyed with Acacia Arabica wild dye for 10% shade

 3.2  Effect of metallic salts on colour hue

In the present study, it is observed that a variety of colours are obtained using different mordant on cotton fabric dyed with Acasia Arabica Wild dye as mentioned in Table – 2.

Table 2: Colours obtained during dyeing of Acasia Arabica Wild on cotton

Sr. No.

Process

Mordant

Color Obtained on Cotton

1.

Control

Pale to Medium Brown

2.

Pre mordanting

SnCl2

Pale to dark brunt shina

FeSO4

Pale to chocolate brown

CuSO4

Pale to medium brunt shina

Mixed (FeSO4 + CuSO4)

Pale to dark brownish black

3.

Meta Mordanting

SnCl2

Pale to medium cream

FeSO4

Grey to brownish grey

CuSO4

Dark cream to medium brown

Mixed (FeSO4 + CuSO4)

Grey to medium brown

It is clearly observed from the Table – 2 that there is a considerable change in tone for both the technique of mordanting. For 10% depth of shade using ferrous sulphate as a mordant, a pale chocolate brown colour is obtained in case of premordanting technique while grey shade is obtained in case of metamordeting technique. Thus variety of shade can be produced by using different mordant. The reason may be attributed to the fact that the main contaminant of Acasia Arabica Wild is ‘tannin’. These tannins are phenolic compounds and when it is combined with metal ion, a tannin-metal ion complex is formed and tannin combines with ferrous sulphate, dark bluish black coloured tannin-metal ion complex is produced. The light and dark colours that are obtained depend on the bond between the dye and metal-ion.

3.3 Fastness properties

Light, Washing and rubbing fastness ratings of cotton fabric dyed with Acasia Arabica Wild dye using exhaust dyeing method are shown in Table – 3.

From the Table 3 it can be seen that the Acasia Arabica Wild dye exhibits adequate fastness ratings for cotton fabric dyed by exhaust dyeing method. The control i.e. unmordanted dyed samples exhibit very good light fastness and good to very good fastness to washing. The dry rubbing fastness varies from very good to excellent while the wet rubbing fastness ranges from moderate to good. The mordanting technique alters the tone of the dyed samples but generally do not affect the fastness ratings of the dyed samples to a great extent. Only a slight increase by 1 to 2 points is observed in some cases, however the fastness properties are quite comparable with those of control samples. It can also be noted from the table 3 that the fastness grades (particularly for washing and wet rubbing) generally decreases with increase in dye concentration.

Table 3: Fastness ratings of cotton samples dyed with Acasia Arabica Wild dye by Exhaust dyeing method.

Mordanting
Technique

Mordant

Dye Conc. % (owf)

Fastness Test

LF

WF

RF

Shade change

Staining
To cotton

DRF

WRF

Without Mordanting

10
20
30

5-6
5-6
5-6

4
4
3-4

4
4
3-4

4-5
4
4

3-4
3
2-3

Pre Mordanting

SnCl2

10
20
30

6
6
5-6

4-5
4-5
4

4-5
4-5
4

4-5
4
4

3-4
3
3

FeSO4

10
20
30

6
5-6
5-6

4
4
3-4

4
4
3-4

4-5
4-5
4

3
2-3
2-3

CuSO4

10
20
30

5-6
5-6
5-6

4-5
4-5
4

4-5
4-5
4

4
4-5
3-4

3
3
3

Mixed (FeSO4 + CuSO4)

10
20
30

5-6
5
5

4
4
3-4

4
4
3-4

4
4
4

3-4
3
3

Meta
Mordanting

SnCl2

10
20
30

6
6
5-6

4
4
4

4
4
4

4-5
4
4

3
3
3

FeSO4

10
20
30

5-6
6
6

4
3-4
3-4

4
3-4
3-4

4
3-4
3-4

3
2-3
2

CuSO4

10
20
30

6
5-6
5-6

4-5
4
4

4-5
4
4

4
4
4-5

3
3
3

Mixed (FeSO4 + CuSO4)

10
20
30

6
5-6
5-6

4
4
3

4
4
3

4
4
3-4

3
2-3
2-3

In Table 3, LF= Light Fastness, WF = Wash Fastness, DRF = Dry Rubbing Fastness, WRF=Wet Rubbing Fastness

It is also seen that as far as the fastness ratings are concerned, the premordanting technique is found to be somewhat better than the metamordanting technique in case of most of the mordant selected. The higher fastness properties of the dyed samples may be due to the presence of tannin (the tannins are hydrolyses by acids or enzymes quickly and the products of hydrolysis are gallic acid or ellagic acid. On distillation, gallic acid and other components get converted to pyrogallol. They respond to ferrous sulphate solution, producing blue colours) which helps in formation of covalent bond with the fibre and thereby assist in proper fixation of the dye on the fibre material.

3.4 Standing dye bath study

One of the main problems associated with natural dyeing is that lot of dye remains in the dye bath even after dyeing. Hence here efforts had been made to reduce this problem. The results in terms of K/S values are given in Table – 4.

From the table 4 it is seen that the K/S values of 2nd and 3rd bath is slightly lowered than that of 1st original dye bath irrespective of mordant and the process of

mordanting. Standing dye baths follow similar trend as in case of exhaust dyeing.

3.5 Multi dip process

From the Table – 5 it is observed that in multi-dip technique mixed mordant (FeSO4 + CuSO4) gives higher depth of shade as compared to single dip (exhaust) method (K/S – 6.198 and 2.431) showing 5.00% and 62.73% improvement in depth over
premordanting and metamordanting method of dyeing respectively.

Table 4: Effect of standing dye bath on the colour strength on cotton dyed with Acasia Arabica Wild dye. Note – In 1st dye bath the concentration of dye was 10% (owf)

Sr. No.

Process

Mordant

K/S Value

6% (owf)

1st (exh.)

2nd

3rd

1.

Control

1.616

1.427

1.032

2.

Pre mordanting

SnCl2

1.280

1.003

0.735

FeSO4

3.142

2.843

2.463

CuSO4

5.470

5.103

4.587

Mixed (FeSO4 + CuSO4) 6.198 5.919 5.298

3.

Meta Mordanting

SnCl2

1.437

1.292

0.914

FeSO4

2.041

1.702

1.333

CuSO4

2.597

2.241

1.814

Mixed (FeSO4 + CuSO4) 2.431 2.118 1.781

Table 5 Color strength of cotton fabric dyed with Acasia Arabica Wild dye using different mordants by multi-dip technique

Sr. No.

No. of Dips

Mordant 6% (owf)

K/S value

1.

15 Dips

SnCl2

1.399

FeSO4

3.542

CuSO4

5.804

Mixed (FeSO4 + CuSO4)

6.976

2.

30 Dips

SnCl2

1.924

FeSO4

4.324

CuSO4

6.422

Mixed (FeSO4 + CuSO4)

7.211

This could possibly be due to the bathochromic shift and more rigid complex forming ability of mixed mordant. It is also studied that as the number of dips increases (15 to 30 dips) the K/S value also increases. This is illustrated in figure 2. Attributed to the fact that, in the multidip method the fabric is dipped in dye bath and mordant-bath alternately, resulting in formation of insoluble dye mordant complex inside the fibre the mechanism is similar to the ingrain dye formation.

 3

Fig. 3: Comparison of exhaust dyeing process and multidip dyeing technique in terms of K/S Values for 10% shade of Acacia Arabica wild dye

3.6 Economical Aspects in the Dyeing of acacia Arabica

The results of open bath (exhaust) dyeing are adequate. Moreover, the average steam consumption is also not very high. So, this dyeing process may satisfactorily be utilized if Acacia Arabica dyeing of cotton has to be commercialized. In case of standing dyebath and muti dip techniques of dyeing, performed well as visualized from the moderate colour value of dyed samples. Thus, whenever shade factor is not a constraint, the standing dyebath and multi dip technique can be very well utilized for dyeing cotton with full advantage of eco-conservation.

4. Conclusions

Cotton can be dyed successfully in presence and in absence of mordant in different hues and tones at various concentration levels. The increase in colour strength value of cotton dyed with Acasia Arabica Wild is possible with selection of metallic mordant and variety of shades can be produced on cotton. Shade ranging from cream to medium brown to dark brown can be readily produced on cotton without mordant. Mixed mordant system (i.e. FeSO4 + CuSO4) is found to be the best in premordanting method as far as the colour strength is concerned while copper soleplate is found to be the best in case of metamordanting technique. Thus selection of mordanting technique is equally important. Premordanting technique is found superior than the meta-mordanting technique.

Reuse of dye bath not only decreases the amount of dyeing effluent remarkably but it also saves the expenses of dyes and energy considerably. The reused dye baths show consistency in shades indicating the prospects of no effluent dyeing with natural dyes.
The most significant result of the study is that the new multidip method resulted in much deeper shades, which could not be attained by any of the single dip (exhaust) methods.

The all round fastness properties of various samples dyed using exhaust dyeing method are adequate and quite comparable with control dyed samples.

At present, Acasia Arabica Wild dyed articles fall into small niche markets fed by craft workers and small commercial firms, viz. dyeing of fishing nets. But today’s small niche market can become a larger market tomorrow as has been shown for herbal teas and natural cosmetics. There has been little attempt to define and predict the market for Acasia Arabica Wild dyed products.

References
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  2. M.L. Gulrajani, Colourage, XLVI (July, 1999), 29.
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  12. B H Patel, B J Agarwal and H M Patel,Dyeing of nylon with Acacia arabica willd bark extract, Textile Asia, 33, 9 (2002)34- 42.
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  15. Shailesh R Shah and Bharat H. Patel, Characterization and fixation of Ocimum sanctum extract on wool fabric, Bangladesh Textile Today  6, 6, (2013) 31-34.
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