Facility for Ecological and Analytical Testing
Indian Institute of Technology, Kanpu-208 016, India
correspondence be made, email: psv@iitk.ac.in


Abstract:

Coloring pigment from Hollyhock (Alcea rosea) flower has been extracted and used for dyeing wool yarn, silk and cotton fabrics. It is observed that the dyeing with hollyhock gives fair to good fastness properties in sonicator in1 hour and shows good dye uptake as compared with conventional dyeing. The pigment is found to contain cyanidin-3-glucoside,delphinidin-3-glucoside, and malvidin-3,5-diglucoside. The shade ranges from green to brown in the presence of 2-4% of mordants.

Keywords: Alcea rosea, Dyeing, Cotton, Silk , Wool.

Introduction

Hollyhock( Alcea rosea) grows 4 to 8 feet high, they grow best in full sun in deep, rich, well drained soils. Some varieties act as reseeding biennials. The blooms are dramatic spires of rosette, single or double flowers in a scope of colors. The single flowers have five petals. Many colors are available from pastel pinks to near black. A reddish dye is obtained from the petals[1,2]. The study reports that the flowers can used for food coloring purposes both in fresh and dry forms. The red anthocyanin constituent of the flowers is known to be used as litmus[3].

Materials and Methods

Materials

Flower color chosen


Dark pink variety of hollyhock flowers were collected from the IIT Kanpur horticulture department. The plant grows in winter and the blooming period is February-May . The pigment obtained from hollyhock has good coloring capacity. It is thermostable, thus is also suitable for conventional dyeing where the bath temperature ranges from 60-90aC.

Substrates

Bleached cotton was used for dyeing. Commercially bleached wool yarn supplied by Jaypee
(pure new wool) was used for dyeing. Pure munga khadi silk was purchased from Gandhi Ashram.

Chemicals: Alum, stannic chloride, stannous chloride were supplied by S.D.Fine. Inc and ferrous sulphate was supplied by Loba Chemie, Inc. Labolene detergent solution was supplied by Chemical and Instruments, Kanpur.

Methods

Extraction of colorant


Flowers from plant source were crushed and dissolved in distilled water and allowed to boil in a beaker kept over water bath for quick extraction for 3 hour. All the color was extracted from flowers by the end of 3 hours. The solution was filtered for immediate use. The flowers were also dried in trays, in thin layers, in a current of warm air immediately after picking. When dry, they are a deep, purplish-black. These flowers could be used as and when required. The colorant showed one major peak, max at 296.33 nm in the UV region( flavonoids) and at 547.96

nm in the visible region . Comparison of the color content in dry and fresh flowers was also carried out as shown in Fig-1 to evaluate the color depth available for dyeing from the two sources. The extract shows changes in visible graph at different pH as shown in the Fig-2 At pH-4 the max was at 525 nm, 545 nm (pH-7) and 585 nm (pH-9).

Preparation and optimization of aqueous extract of hollyhock

The flowers of hollyhock were found to give out color in hot water very easily. The flowers were frozen after collection and then dipped in hot boiling water to get the maximum color in 30 min which shows deepening of hue color. However increasing the quantity of flowers from 2gm to 20 gm per 100 ml water, boiled for 60 min is accompanied with the increase in color strength and depth in color hue.

Chemical composition of the colorant

Petals of hollyhock (0.5 kg) were extracted twice with a Me2CO-H2O (1:1) mixture (5 L) at 50-55a for 20-25 min, the extract was filtered, and Me2CO was distilled off to give dry product (60 g) containing 12-13% red pigment. Preliminary analysis showed [4,5 ] that the pigment contained cyanidin-3-glucoside, delphinidin-3-glucoside, and malvidin-3,5-diglucoside.

Scouring of Cotton, Silk and Wool

Silk and cotton fabrics and wool yarn were washed with solution containing 0.5 g/L sodium carbonate and 2 g/L non-ionic detergent (Labolene) solution at 40-45a C for 30 min, keeping the material to liquor ratio at 1:50. The scoured material was thoroughly washed with tap water and dried at room temperature. The scoured material was soaked in clean water for 30 min prior to dyeing or mordanting.

Mordanting

Accurately weighed cotton, silk or wool sample was treated with different metal salt, only premordanting with metal salts was carried out before dyeing. The mordant was dissolved in water to make liquor ratio 1:50. The wetted sample was entered into the mordant solution and then it was brought to heating. Temperature of the dye bath was raised to 60aC over a period of half an hour and left at that temperature for another 30 minutes. The mordanted material was then rinsed with water thoroughly, squeezed and dried. Mordanted cotton and wool need be used immediately for dyeing because some mordants are very sensitive to light.

Dyeing

The cotton, silk as well as wool yarn were dyed with dye extract, keeping M:L ratio as 1:40 however for cotton dyeing it was used directly while in the case of silk and wool dyeing the pH was maintained at 4 by adding buffer solution (sodium acetate and acetic acid). The dye extract was prepared by adding 4gm dye powder in 100ml water.(M:L:: 1: 40). Dyeing was done by conventional dyeing method as well as by sonicator. In each case the dyed material was washed with cold water and dried at room temperature, it was then dipped in brine for dye fixing. The color strength was determined colorimetrically using Premier Colorscan at the maximum wavelength of the natural colorant.

Sonicator Dyeing

It is well documented [6 ]the ultrasound energy gives rise to acoustic cavitation in liquid media. The acoustic cavitation occurring near a solid surface which generates microjets, this microjet effect facilitate the liquid to get agitated with a high speed resulting in increased diffusion of solute inside the pores of the fabric. This causes localized rise in temperature and pressure thus swelling in fiber takes place, this may also contribute in improved diffusion.

The stable cavitation bubbles oscillate which is responsible for the enhanced molecular motion and stirring effect of ultrasound. In case of cotton dyeing, the effects produced due to stable cavitation may be realized at the interface of leather and dye solution. Dye uptake was studied during the course of the dyeing process for a total dyeing time of 1 h with and without ultrasound. Dye uptake showed 81% and 67% respectively.

Measurement of Color Strength

The color yield of both dyed and mordanted samples were evaluated by light reflectance measurements using Premier Colorscan machine.

The color strength (K/S value) was assessed using the Kubelka-Munk equation[7,8]:
K/S= (1-R)2/2R

Where R is the decimal fraction of the reflectance of dyed yarn

Optimization of mordants with K/S and Color hue changes

Different mordants are used in 2-4% keeping in mind the toxicity factor of some mordants. Varied hues of color can be obtained from premordanting the cotton , silk fabrics and wool yarn with FeSO4, SnCl2, CuSO4, SnCl4, K2Cr2O7 and alum were dyed by aqueous extract of hollyhock as shown in the Table-1,2 and 3 the different mordants not only cause difference in hue color and significant changes in K/S values but also L* values and brightness index values. Copper and Iron exhibited the highest K/S values, due to their ability to form coordination complexes with the dye molecules. This strong coordination tendency of Fe enhances the interaction between the fibre and the dye, resulting in high dye uptake, while all other metals show similar coordination. This is clearly shown in the Fig-4.

Results and Discussion

Fastness Properties


It was observed that dyeing with hollyhock gave fair to good fastness properties[9] in conventional dyeing for one hour showed good dye uptake. The structure of the dye molecules show that presence of 3-5 hydroxyl groups makes them very good substrates for metal chelation. The Table-1,and 2 shows L*, a* and b* values and fastness properties for different mordants, some show higher value of L* showing lighter shades while lower L* values signifies deeper shades. Similarly negative a* and negative b* represents green and blue respectively. The colorfastness to washing was between 4 to 4-5 to 5, for cotton and silk respectively. For wool yarn fastness was above 4-5 in all the cases as shown in Table-3. We have compared the sonicator dyeing with conventional method. The results clearly show that sonicator dyeing is better in terms of better dye uptake, reduced dyeing time and cost effective. Overall, it could be used for commercial purpose, the dyed wool yarn attains acceptable range.



Table 1 shows different pre-mordants, color obtained, fastness properties and L*, a*, b* values for dyed cotton with hollyhock at

Table 3 shows different pre-mordants, color obtained, fastness properties and L*, a*, b* values for dyed wool yarn with hollyhock at max 545nm

Conclusion

Aqueous extract of hollyhock flowers give light green to dark green shades to cotton, silk and wool with good fastness properties both by conventional as well as by sonicator dyeing. A flavylium ring B and a 3, 4-dihydroxy group is well suited for Fe-binding and in case of aluminium ion binding, the 3-hydroxychromane groups is envisaged. The mordants used are in 2-4 % only. Although the dye extract is red in color and varies slightly with change in pH, the dye still has good scope in the commercial dyeing of cotton and silk for garment dyeing and wool yarn dyeing for carpet industry.

Acknowledgement

The authors express their sincere thanks to Khadi and Village Industries Commission (KVIC) for financial support.

References

1. Ferenczi, S., Kallay, M. and Bardi, G. (1983), Hung. Teljes 5.

2. Kasumov, M. A., (1984), Red dye from the hollyhock and its use in the food industry, Doklady-Akademiya Nauk Azerbaidzhanskoi SSR 40(6), 76-9.

3. Matula, V. H., Macek, C. B., (1936), The anthocyanins as indicators in neutralization analysis, Chemicky Obzor 11 83-4.

4. Salikhov, S. A., Idriskhodzhaev, U. M., (1978), Prospective coloring plant for the food industry, Khlebopekarnaya i Konditerskaya Promyshlennost (8), 23-4.

5. Bhattacharya, S.D, Shah, A.K, (2000), Journal of Society for Dyers and Chemists (116), 10.

6. Ghorpade,B., Darvekar,M. and Vankar,P.S., (2000), Ecofriendly cotton dyeing with Sappan wood dye using ultrasound energy, Colourage, 27-30.

7. Kubelka P (1948), New Contributions to the Optics of Intensely Light-Scattering Materials. Part I, JOSA, 38 (5), 448451.

8. Kubelka P (1954), New Contributions to the Optics of Intensely Light-Scattering Materials Part II: Nonhomogeneous Layers, JOSA, 44 (4), 330-335.

9. Indian Standards Institution(BIS), Handbook of Textile Testing,(1982), Manak Bhawan, New Delhi, 539, 550, 553, 569.