**3. Using of natural dyes**

Currently, application of natural dye incorporates new technology not only to exploit traditional techniques but also to improve the rate, cost and consistency production. It therefore, requires some special measurement to ensure evenness in dyeing. The processes of natural dyes for textile dyeing are as follows:

### **3.1 Extraction**

Efficient extraction of the dyes from plant material is very important for standardization and optimization of vegetable dyes, utilizing a) soxhlet b) supercritical fluid extraction c) subcritical water extraction and d) sonicator method.

### **3.2 Dyeing**

Normally, one technique used for dyeing with natural dye; exhaustion dyeing (conventional dyeing, sonicator dyeing and microwave dyeing). Exhaustion dyeing is using lot of water as

Natural Dye from Eucalyptus Leaves and

anthraquinone disperse dye (Fig. 2).

N

N N

(a)

natural dyes, such as the indigoid and anthocyanin dyes.

**5. Ecological and economical aspects of dyeing with natural dyes** 

If we carry out the dyeing process with natural dyes in a slightly large manufacturing unit or a factory rather than in a household unit, we can surpass the limits of historic methods of dyeing and material pretreatments, which are lengthy and uneconomical procedures. The old methods (likely transmitted without facing critical evaluation), consist of various actions that do not address modern requirements, and do not take into account the new possibilities offered by the modern textile chemistry. The number and duration of baths seem to be too high (at least for European standards and customs) and are non-productive. For example,

Cl

O2N

dyes

Application for Wool Fabric Dyeing by Using Padding Techniques 61

neutral electrolytes (sodium chloride or sulfate) as substantive dyes. And bath acidifying, while having a significant effect on the so-called acid dyes (coloured sodium salts of sulfonic acids), has a negligible effect on the natural dyes.The structure of the flavonoid-colouring components of eucalyptus leaves and tannin (Fig. 1) is compared with the typical azo and

CH2CH2CN

C.I. Disperse Red 50 R = H (C.I. Disperse Blue 27)

OH

O

OH

R = CH3 (C.I. Disperse Blue 72)

NH R

O

(b)

OH

CH2CH3

Fig. 2. Chemical constitution of typical disperse dyes. (a) Azo dye and (b) anthraquinone

Assume that most natural dyes are, on the basis of modern dyeing science, the disperse dyes. But what are the dyes for wool, silk, cotton, and flax? Consider that each fiber type in dyeing has already been studied, and it has become apparent that the disperse dyes are not good dyes for the aforementioned fibers. On the contrary, the synthetic disperse dyestuffs were developed for dyeing acetyl cellulose and synthetic fibers (i.e., hydrophobic fibers), and they have a low affinity for wool, silk, cotton, and other such fibers that are mainly hydrophilic. Though low, the indispensable affinity of disperse dyes makes them very undesirable for the staining of wool or cotton component by the dyeing of fiber mixtures, namely with polyester fiber (which is dyeable only in disperse dyes). This imperfect colouration-staining must be rather difficult to remove from wool or cotton component after dyeing because of its poor wet fastness and mostly unpleasant shade, which can be different from the shade of the same dye on polyester. However, the above-mentioned majority of natural dyes are providing only inexpressive wet fastness on wool and cotton fibers, and the mordanting by salts of suitable metals is also needed to improve wet fastness (not only to deepen but also to intensify the colour). A lower affinity results in the low dye exhaustion after the dye bath on the fiber. This can also be observed in the dyeing of natural fibers with

shown in "Liquor Ratio (ratio between water and goods)". Producers immerge the goods in dye for extended periods for complete penetrate. This produces excessive waste water compared to a continuous process. The techniques used for dyeing of natural dyes, such as


#### **3.3 Mordanting**

In the actual dyeing process, there are four ways of using mordant (Bechtold & Mussak, 2009; Moeyes, 1993) as follows:


#### **4. Theoretical presuppositions of natural dyes to dyeing**

Achieving a good, or at least a relatively good, water solubility using natural dyes is rather exceptional. No chemical group is capable of electrolytic dissociation or ionization in a molecule; an interesting and important exception is the anthocyanins, for example, pelargonidine, cyanidine, and betanidine are slightly cationic dyes and, therefore, also have relatively good solubility in water (Mongkholrattanasit et al., 2009). The "conditional solubility" of indigoid natural dyes, which in their original form are entirely insoluble, presents a quite special principle. In fact, indigo has been imitated to a great extent; synthetic indigo and their derivatives were produced on an industrial scale at the end of the nineteenth century as a forerunner of the latter large group of vat dyestuffs. The alkali reductive conversion of this fully insoluble compound in a proper soluble sodium salt of leucocompound with affinity to fibers and their oxidation after dyeing with the primary insoluble vat dye, which is finely dispersed in the fiber, is well known. What do the majority of natural dyes have in common? The chemical constitution (and corresponding physical properties) of indigo and other anthocyanin dyes has remarkable similarity with the modern synthetic disperse dyes: the solubility of more or less elongated molecules of chromogen is due to the presence of several polar groups (mainly –OH) on aromatic rings. No groups are capable of electrolytic ionization (with the exception of the anthocyanin and betanin). From this follows that they only have low solubility in water. Empirically, it is known that it is impossible to strengthen dyeing of cotton with natural dyes, but it can be done by adding

shown in "Liquor Ratio (ratio between water and goods)". Producers immerge the goods in dye for extended periods for complete penetrate. This produces excessive waste water compared to a continuous process. The techniques used for dyeing of natural dyes, such as 1. Conventional dyeing : conventional dyeing is carried out by boiling the fabric in dye bath for 4-hours and often the dye uptake is still not completed. Enormous amount of

2. Sonicator dyeing: utilization of ultrasound energy to aid wet processing of fabrics. The process of increasing dye transfer from the dye-bath to fabric using ultrasound energy is a function of the acoustic impedance characteristics of the fabrics (Vankar, 2007 ;

3. Microwave dyeing : microwave dyeing take into account only the dielectric and the thermal properties. The dielectric property refers to the intrinsic electrical properties which affect dyeing by dyeing by dipolar rotation of the dye and the influence of microwave field upon dipoles. The aqueous solution of dye has two components, which are polar. In the high frequency microwave field, oscillating at 2450 MHz; it influences the vibrational energy in the water molecule and the dye molecules (Tiwari & Vankar,

In the actual dyeing process, there are four ways of using mordant (Bechtold & Mussak,

Achieving a good, or at least a relatively good, water solubility using natural dyes is rather exceptional. No chemical group is capable of electrolytic dissociation or ionization in a molecule; an interesting and important exception is the anthocyanins, for example, pelargonidine, cyanidine, and betanidine are slightly cationic dyes and, therefore, also have relatively good solubility in water (Mongkholrattanasit et al., 2009). The "conditional solubility" of indigoid natural dyes, which in their original form are entirely insoluble, presents a quite special principle. In fact, indigo has been imitated to a great extent; synthetic indigo and their derivatives were produced on an industrial scale at the end of the nineteenth century as a forerunner of the latter large group of vat dyestuffs. The alkali reductive conversion of this fully insoluble compound in a proper soluble sodium salt of leucocompound with affinity to fibers and their oxidation after dyeing with the primary insoluble vat dye, which is finely dispersed in the fiber, is well known. What do the majority of natural dyes have in common? The chemical constitution (and corresponding physical properties) of indigo and other anthocyanin dyes has remarkable similarity with the modern synthetic disperse dyes: the solubility of more or less elongated molecules of chromogen is due to the presence of several polar groups (mainly –OH) on aromatic rings. No groups are capable of electrolytic ionization (with the exception of the anthocyanin and betanin). From this follows that they only have low solubility in water. Empirically, it is known that it is impossible to strengthen dyeing of cotton with natural dyes, but it can be done by adding

b. Mordanting and dyeing at the same time, called stuffing or simultaneous; c. Mordanting after dyeing, or after-mordanting or post-mordanting;

heat is consumed in terms of heating the dye bath (Vankar, 2007).

Vankar et al., 2009 ; Tiwari & Vankar, 2001).

a. Mordanting before dyeing, or pre-mordanting;

d. A combination of pre-mordanting and after-mordanting.

**4. Theoretical presuppositions of natural dyes to dyeing** 

2001).

**3.3 Mordanting** 

2009; Moeyes, 1993) as follows:

neutral electrolytes (sodium chloride or sulfate) as substantive dyes. And bath acidifying, while having a significant effect on the so-called acid dyes (coloured sodium salts of sulfonic acids), has a negligible effect on the natural dyes.The structure of the flavonoid-colouring components of eucalyptus leaves and tannin (Fig. 1) is compared with the typical azo and anthraquinone disperse dye (Fig. 2).

Fig. 2. Chemical constitution of typical disperse dyes. (a) Azo dye and (b) anthraquinone dyes

Assume that most natural dyes are, on the basis of modern dyeing science, the disperse dyes. But what are the dyes for wool, silk, cotton, and flax? Consider that each fiber type in dyeing has already been studied, and it has become apparent that the disperse dyes are not good dyes for the aforementioned fibers. On the contrary, the synthetic disperse dyestuffs were developed for dyeing acetyl cellulose and synthetic fibers (i.e., hydrophobic fibers), and they have a low affinity for wool, silk, cotton, and other such fibers that are mainly hydrophilic. Though low, the indispensable affinity of disperse dyes makes them very undesirable for the staining of wool or cotton component by the dyeing of fiber mixtures, namely with polyester fiber (which is dyeable only in disperse dyes). This imperfect colouration-staining must be rather difficult to remove from wool or cotton component after dyeing because of its poor wet fastness and mostly unpleasant shade, which can be different from the shade of the same dye on polyester. However, the above-mentioned majority of natural dyes are providing only inexpressive wet fastness on wool and cotton fibers, and the mordanting by salts of suitable metals is also needed to improve wet fastness (not only to deepen but also to intensify the colour). A lower affinity results in the low dye exhaustion after the dye bath on the fiber. This can also be observed in the dyeing of natural fibers with natural dyes, such as the indigoid and anthocyanin dyes.

## **5. Ecological and economical aspects of dyeing with natural dyes**

If we carry out the dyeing process with natural dyes in a slightly large manufacturing unit or a factory rather than in a household unit, we can surpass the limits of historic methods of dyeing and material pretreatments, which are lengthy and uneconomical procedures. The old methods (likely transmitted without facing critical evaluation), consist of various actions that do not address modern requirements, and do not take into account the new possibilities offered by the modern textile chemistry. The number and duration of baths seem to be too high (at least for European standards and customs) and are non-productive. For example,

Natural Dye from Eucalyptus Leaves and

ABA, were supplied by Chemotex Decin, Czech Republic.

spectrophotometer in the 190 nm to2100 nm range.

**6. Experimental** 

thoroughly investigated.

at the wavelength mentioned.

Application for Wool Fabric Dyeing by Using Padding Techniques 63

The research focused on the properties of pad-dyeing techniques, we investigated the dyeing and ultraviolet (UV) protection properties of wool fabric using an aqueous extract of eucalyptus leaves as the natural dye. Different factors affecting dyeing ability were also

The following laboratory-grade mordants were used: aluminium potassium sulfate dodecahydrate (AlK(SO4)2.12H2O), ferrous (II) sulfate heptahydrate (FeSO4.7H2O), copper (II) sulfate pentahydrate (CuSO4.5H2O) and stannous chloride pentahydrate (SnCl2.5H2O). The anionic wetting agent, Altaran S8 (sodium alkylsulfate), and soaping agent, Syntapon

The mordanting and dyeing processes were carried out in a two-bowl padding mangle machine (Mathis, Typ-Nr. HVF.69805). A drying machine (Mathis Labdryer, Typ-Nr. LTE-2992) was used for the drying of the dyed fabrics. A GBC UV/VIS 916 (Australia) spectrophotometer and a Datacolor 3890 were employed for the absorbance and colour strength measurements, respectively. The transmittance and ultraviolet protection factor (UPF) values were measured by a Shimadzu UV3101 PC UV-VIS-NIR scanning

Fresh eucalyptus leaves (*E. Camaldulensis)* were dried in sunlight for one month and crumbled using a blender, and then were used as the raw material for dye extraction, which was achieved by the reflux technique: 70 g of crumbled eucalyptus leaves was mixed with one liter of distilled water and refluxed for one hour. The dye solution was filtered, evaporated, and dried under reduced pressure using a rotary evaporator. The crude dye extract of the eucalyptus leaves was then crumbled with a blender and used for obtaining the standard calibration curve. The dilution of the eucalyptus leaf extract gives a relatively clear solution with a linear dependence on the concentration absorbance, an absorption peak (λmax) at 262 nm (Yarosh et al., 2001). The concentration of 20 g/l was calculated from a standard curve between concentrations of eucalyptus leaf dye solutions versus absorbance

The pre-mordanting methods, wool fabrics were immersed in each mordant solution with anionic wetting agent and padded on a two-bowl padding mangle at 80% pick up. Next, the mordanted sample was impregnated in each eucalyptus dye concentration. After padding for 2 seconds the samples were dried at 90°C for 5 minutes for a pad-dry technique. Under the cold pad-batch dyeing technique, the padded fabric was rolled on a glass rod with a plastic sheet wrapped around the rolled fabric. Then it was kept at room temperature for 24 hours. After the dyeing step, the samples were washed in 1 g/l of a soaping agent, Syntapon ABA, at 80°C for 5 minutes, then air dried at room temperature. For the simultaneous mordanting (metamordanting) method (i.e. dyeing in the presence of mordants), the fabrics were immersed in a bath containing a mordant and the dye extract at room temperature and padded on a two-bowl padding mangle at 80% pick up. The processing of pad-dry, pad-batch and soaping were the same as above mention. In the post-mordanting method, the fabrics were immersed in each eucalyptus dye concentration and without mordant, followed by padded on a two-bowl padding mangle at 80% pick up. Then the padded samples were padded by mordanting.

The colour strength (*K/S*) and CIELAB of the dyed samples were evaluated using a spectrophotometer (Datacolor 3890). All measured sample showed the maximum absorption wavelength (λmax) value at 400 nm. The *K/S* is a function of colour depth and is

Further processing was the same as described in the pre-mordanting method.

the required 3–5 hours wetting of material with water before dyeing could be greatly reduced by wetting in a bath by specially made wetting agent, and this or another agent could also be added into the dyeing bath. The ineffective use of natural dyes was already discussed above. The majority of dyes ceases as effluents in sewer. The mordanting salts do not have affinity to the fibers and therefore only a small part of them is bounded with fibers, and after dyeing and final rinsing all the remnants are carried off by water. What about the idea of storing the mordanting baths for future use? While logical, the number and volume of stock reservoirs (and place in dye house) make it an unpractical possibility. Naturally, serious conception-questions follow from this. Should "natural dyeing" remain as something principally untouchable whose traditional originality must be safe-guarded at any costs, or are we going to consider this natural raw-material source as an ecologically favorable supplement to synthetic colourants? or, can we synthesize the methodologies of "natural dyeing" with the research and application processes of modern dyeing technology? Nevertheless, both natural dyeing and modern dyeing technology can coexist. In any case, we are trying to explore the second of the following:


All these can be assured by the padding (pad) technologies, in which the liquor ratio (weight of textiles: bath) is about one order lower (≤1:1) than the common exhaustion (bath or batch) dyeing methods. The padding technologies are particularly advantageous to dyeing with the low-affinity products, because the dye affinity to fiber by padding is unnecessary (in phase of the dye deposition on the fabric). The dye bath is cloth "padded": mechanically applied by the rapid passage through the small padding trough*,* the intensive squeezing between expression rollers follows immediately. The process of padding is continuous and very rapid. It depends on the arrangement of the following dye fixation if the total procedure is continuous or semi continuous. The dye bath by padding is about one order higher than by the common dyeing from the "long bath" (the so-called exhaustion methods), in which the dyestuff exhausts on the fiber in consequence to its affinity to the fiber. The higher padding bath concentration results in more rapid dye diffusion in fiber during the next fixation operation. Much smaller bath volume (related to the fiber unit) causes the higher dye exploitation. In the case of natural dyes, the dye fixation is based on the reaction (see also Agarwal and Patel) (Agarwal & Patel, 2001) with the salts of complexforming metals-mordants in the same or next bath-or the textile can be pre-metalized with mordant (this pre-mordanting is carried out from the long bath-the large non-effectiveness is mentioned above*.* Therefore, we also experimented with pad-dry and pad-batch principle at this operation). In semi continuous dyeing technology, several methods of dye fixation are known. The following two principles are important for our purpose:


After both dye fixation methods water rinsing follows repeatedly.
