SOME STUDIES ON NATURAL DYES

by

DEEPTI BAHL

A thesis submitted in fulfilment of the requirements for the award of the degree of

DOCTOR OF PHILOSOPHY

Department of Textile Technology INDIAN INSTITUTE OF TECHNOLOGY, DELHI

December, 1994

TO MY HUSBAND ... WITH LOVE

CERTIFICATE

This is to certify that the thesis entitled Some Studies on Natural Dyes being submitted by Ms. Deepti Bahl to the Indian Institute of Technology, Delhi for the award of the degree of Doctor of Philosophy is a record of bonafide research work carried out by her under my guidance and supervision.

To the best of my knowledge this thesis has reached the required standard. The material presented in this thesis,, in part or full has not been submitted to any other University or any other Institute for the award of degree or diploma.

M.L.Gulrajani Professor Department of Textile Technology Indian Institute of Technology New Delhi - 110016

ACKNOWLEDGEMENTS

It is with a deep sense of gratitude that I thank my project supervisor Prof. M.L.Gulrajani, without whose foresight and continued guidance, this work could not have been undertaken or completed successfully.

Sincere thanks are due to Prof R.C.D Kaushik, Director TIT&S, Bhiwani for granting me leave and providing other facilities to continue with the experimental and writing work while at the Institute.

I thank Dr. Khanna, Vice President, Ranbaxy R&D Centre for allowing me full use of all facilities at their centre and Dr. J.Singh and other scientists for helping out so enthusias-tically with the chromatographic and characterization studies.

I express my thanks to Dr. Raghavan of Physics department and Dr. G.S.Kapoor, Ms Anju Khanna and all other friends, colleagues and technical staff of Chemistry Department, who helped me with small and big things all through this work.

I am grateful to Dr. Sushil Kumar, Director CIMAP and Dr. K.0 Gupta of GBPUA&T, for helping out with literature survey.

Thanks are due to the faculty members of Textile Department for providing valuable guidance, whenever required. To my colleagues Sheetal, Deepali, Shailja and Kannanji for the memorable lunch and tea sessions. Also to Mr. V.A. Passi, Mr. Rajender Prasad, Mr. Prakash Chand, Mr. Shiv Charan,, Jagdish, Suresh and Ashok of Textile Chemistry Lab; to Mr. Didarmal, Mr. Padam and Mr. Prabhu for rendering timely assistance.

Special thanks to Mr. Rajesh Arora for typing this manuscript always in time with my schedule.

I thank my parents and my mother and brother-in-law for their unwavering support and co-operation throughout. Finally, I thank my husband for believing in me, for being so patient and for everything else that helped make all these years of work so enjoyable. Last, but not the least, I thank my little daughter for sparing me the time, which was rightfully hers, to complete this manuscript.

E I

ABSTRACT

In recent years, the world has become increasingly aware of

the environmental issues. Synthetic dyestuffs, in particular,

have come under severe criticism for they are highly polluting

in their stage of manufacturing as well as application. At the

same time there has been a renewal of interest in the use of

natural colouring matters for dyeing of textiles.

Many empirical studies have been conducted on colour charac-

teristics, fastness properties and dyeing methods used for

dyeing with indigenously available natural dye materials.

Studies are also being conducted for identification, preserva-

tion and restoration of the natural dyes present on ancient

museum textiles. Systematic scientific studies in this field

are few.

This thesis is an attempt to study in detail, the mechanism of

dyeing various textile fibres with natural dyes; to standar-

dise a method for separation and purification of colouring

compounds present in a selected plant material and to charac-

terize and identify them; to comprehensively review natural

dyes and their fastness properties to test and document the

fastness properties of some prominent Indian dyes and to study

the kinetics of light fading of a particular dye.

Lawsone (2-hydroxy-1,4-naphthoquinone) is the colouring

compound found in henna leaves. The dye, possessing the char-

acteristics of a disperse dye was used to conduct thermo-

dynamic and kinetic studies on six different textile fibres

and at three different temperatures. Results showed that rate

of dyeing is directly related to the denier and diffusion

coefficient of fibres. The mechanism of dyeing on all fibres

resembled the partition mechanism corresponding to the Nernst

isotherm at 70 and 1000C. However, at 50°C isotherms were

curved, indicating the attainment of a pseudo equilibrium -

caused most probably by the aggregation of dye in solution at

that temperature. Excessive uptake of dye was observed for all

fibres. Experimental evidence showed that this was due to the

aggregation of dye molecules inside the fibre. Standard

affinity was seen to increase with increase in temperature and

heat of dyeing H was positive indicating an exothermic

reaction in all cases except wool. On wool, affinity was found

to be independent of temperature change. Mordanting with A13+

ions did not appear to affect the equilibrium dye uptake by

wool and silk fibres.

Identical studies, as for lawsone, were conducted with juglone

- the 5-hydroxy isomer of lawsone. It is the pigment extrac-

ted from the rind of green walnuts. Results of the study

were quite similar to those for lawsone. Diffusion

coefficient was directly related to the diameter of fibres.

Adsorption isotherms were linear at both 50°C and 100°C for

all fibres and the standard affinity increased with

temperature.. Juglone, in general, showed higher affinity for

hydrophobic fibres, as compared to hydophilic fibres but there

is little difference in the affinity of individual fibres in

each class.

Dye extracted from the roots of dolu or Himalayan rhubarb

gives a variety of deep and bright shades on wool and silk. A

literature survey showed that the roots contain several deri-

vatives of hydroxy anthraquinones which are responsible for

the colouring power. Thus it was decided to develop a proce-

dure to separate the pigments, purify and identify them, and

study their dyeing mechanism. TLC analysis of the extract

established the presence of five coloured species and some

colourless impurities in the extract. Two solvent systems were

standardised as mobile phases for preparative column chromato-

graphy. Flash chromatographic technique was employed to elute

the columns.

Compounds collected from columns were recrystallized for

further purification. HPLC analysis of crude extract and the

purified fractions (A,B,C,D and E) estimated the purity of the

five compounds as 100%, 97.5%, 98%, 99.44% and 91% respec-

tively.

The melting point, Ultra violet and visible spectrum, Infrared

spectrum, mass spectrum and Proton NMR spectrum of the frac-

tions were recorded, interpreted and compared with reported

data to arrive at their structure. First three compounds were

identified as - chrysophanic acid (3-methyl, 1,8-dihydroxy

anthraquinone), physcion (1,8-dihydroxy, 3-methyl, 6-methoxyl,

anthraquinone) and emodin (1,3,8-trihydroxy, 6-methyl anthra-

quinone).

Dyeing studies, similar to those conducted with lawsone and

juglone were conducted on polyester with the purified dye

chrysophanic acid separated from rhubarb extract. The dye

exhibited no affinity for silk fibres. Linear isotherm was

obtained at 130°C but at 100°C the isotherm was curved -

indicating the establishment of a pseudo-equilibrium.

Extensive light and wash fastness tests were conducted on wool

and silk fabrics dyed with some prominent yellow, red and

brown dyes of India and their fastness ratings recorded as per

ISO standards. No natural yellow dye was found to have a

fastness grade more than 4 as most yellow dyes are based on

the flavonoid molecule which is sensitive to light. Also,

several yellow shades turn brown instead of bleaching on

exposure to light. Red dyes, in comparison exhibit better

fastness, as they are mostly anthraquinone based mordant dyes.

Brown and black dyes mostly obtained from combining tannins

with ferrous salt also exhibit moderate to good light

fastness. Wash fastness of most dyes was good, ranging between

3-4 grade. But good fastness to light was not always found in

dyes having good fastness to washing.

Kinetics of light fading tests showed interesting results. On

silk samples the rate of fading curve showed an initial

darkening of shades followed by no fading. On wool samples,

the curves were near horizontal, indicating little or no

fading. The rate, or nature of fading was neither influenced

by humidity nor mordanting. The rate of change in colour (DE)

was retarded by ferrous mordanting on silk. Unmordanted and

alum mordanted wool samples showed a much higher rate of

change in colour than the other mordanted samples.

Spectral curves of silk samples showed increased absorbance in

the entire visible region after exposure. On wool samples

there were very little change in the spectral curve after

exposure. All samples in general turned redder on exposure to

light. From these results it could be concluded that the dye

is present in a highly associated form in the fibre, due to

which it is highly resistant to colour change when exposed to

light.

CONTENTS

ABSTRACT

1. INTRODUCTION TO NATURAL DYES ............................ 1

1.1 CHEMICAL CLASSIFICATION ................................. 3

1.1.1 Quinones 1.1.2 Indigoids 1.1.3 Pyridine Based Dye 1.1.4 Carotenoids 1.1.5 Diaroyl Methane Based Dye 1.1.6 Dihydropyran Based Dyes 1.1.7 Flavonoids 1.1.8 Tannins

1.2 CLASSIFICATION ON THE BASIS OF APPLICATION METHODS ...... 71

1.2.1 Mordant Dyes 1.2.2 Vat Dyes 1.2.3 Direct Dyes 1.2.4 Acid Dyes 1.2.5 Basic Dyes 1.2.6 Disperse Dyes

2. STUDIES ON DYEING WITH NAPHTHOQUINONE DYES ............... 78

2A. INTRODUCTION ............................................80 2A.1 INTRODUCTION TO PHYSICAL CHEMISTRY OF DYEING MECHANISMS . 80

2A.1.1 Kinetics of Dyeing 2A.1.2 The Dyeing System in Equilibrium

2A.2 STUDIES ON MECHANISM OF DYEING WITH NATURAL DYES ........ 88

2B. STUDIES WITH LAWSONE .....................................90 2B.1 EXPERIMENTAL ............................................91

2B.1.1 Fibres 2B.1.2 The Dye 2B.1.3 Fibre Pretreatment 2B.1.4 Test Methods 2B.1.5 Dyeing Studies 2B.1.6 Mordanting Studies

2B.2 RESULTS AND DISCUSSION ..................................95

2B.2.1 The dye

2B.2.2 Fibre Characterization

2B.2.3 Kinetic Studies

2B.2.5 Mordanting Studies

2B.2.6 Desorption Study

2C. STUDIES ON DYEING WITH JUGLONE .......................... 114 2C.1 EXPERIMENTAL ............................................. 114

2C.1.1 Fibres 2C.1.2 Dye 2C.1.3 Fibre Pretreatment 2C.1.4 Dyeing Studies

2C.2 RESULTS AND DISCUSSION .................................. 115 2C.2.1 Spectral Studies 2C.2.2 Kinetic Studies 2C.2.3 Thermodynamic Studies

2D. CONCLUSIONS .............................................. 126

3. STUDIES WITH HIMALAYAN RHUBARB (Rheum emodi) ............ 128 3A. EXTRACTION AND CHROMATOGRAPHIC SEPARATION OF

COMPONENTS OF RHUBARB EXTRACT ........................... 134 3A.1 EXPERIMENTAL ............................................ 136 3A.1.1 Dye Extraction 3A.1.2 Thin Layer Chromatographic Procedure 3A.1.3 Column Procedure 3A.1.4 HPLC Procedure

3A.2 RESULTS AND DISCUSSION .................................. 139 3A.2.1. TLC Analysis 3A.2.2 Preparative Column Chromatography 3A.2.3 Purification of the Separated Compounds 3A.2.4 HPLC Analysis

3A.3 CONCLUSIONS ............................................. 149 3B. CHARACTERIZATION DATA AND STRUCTURE ASSIGNMENT

OF COMPOUNDS ISOLATED FROM RHUBARB EXTRACT ............. 150 3B.1 EXPERIMENTAL ............................................ 153

3B.1.1 Instrumentation

3B.2 RESULTS AND DISCUSSION .................................. 154 3B.2.1 Fraction A 3B.2.2 Fraction B 3B.2.3 Fraction C 3B.2.4 Fraction D 3B.2.5 Fraction E

3B.3 CONCLUSIONS ............................................. 166 3C. DYEING OF POLYESTER WITH COMPOUND A (CHRYSOPHANIC ACID) . 169 3C.1 EXPERIMENTAL. ........................................... 169

3C.1.1 Fibre 3C.1.2 Dye 3C.1.3 Preparation of dye liquor 3C.1.4 Dyeing

3C.2 RESULTS AND DISCUSSION .................................. 170 3C.2.1 Rate of Dyeing 3C.2.2 Diffusion Coefficient 3C.2.3 Thermodynamic Studies

3C.3 CONCLUSIONS ............................................. 173

4. FASTNESS PROPERTIES OF NATURAL DYES ..................... 175 4A. INTRODUCTION TO THE CONCEPT OF COLOURFASTNESS AND

REVIEW OF LITERATURE ON FASTNESS PROPERTIES OF NATURAL DYES ............................................176

4A.1 MECHANISM OF FADING .....................................176 4A.2 LIGHT FASTNESS PROPERTIES OF DYES .......................177

4A.2.1 Chemical Structure of the Colorant 4A.2.2 Dye Concentration 4A.2.3 Nature of Incident Light 4A.2.4 Nature of Fibre 4A.2.5 Temperature and Humidity 4A.2.6 Atmospheric Contaminants 4A.2.7 Effect of Mordants 4A.2.8 Presence of Foreign Substances

4A.3 WASHFASTNESS PROPERTIES OF DYES ........................182

4A.3.1 State of Dye Inside the Fibre

4A.4 CHEMICAL STRUCTURE OF NATURAL DYES AND THEIR FASTNESS TO LIGHT ....................................... 184

4A.4.1 Yellow and Orange Dyes 4A.4.2 Red Dyes 4A.4.3 Blue Dyes 4A.4.4 Black Dyes 4A.4.5 Brown Dyes

4B. TESTING OF LIGHT AND WASHFASTNESS OF SOME PROMINENT NATURAL DYES OF INDIA ................................... 193

4B.1 DYES .................................................... 193 4B-.2 EXPERIMENTAL ............................................ 193 4B.2.1 Fabric

4B.2.2 Dyebath preparation

4B.2.3 Mordanting and dyeing

4B.2.4 Testing and Analysis

4B.3 RESULTS AND DISCUSSION .................................. 196

4B.4 CONCLUSIONS .............................................205 4C. LIGHT FADING MECHANISM OF RHUBARB DYED WOOL AND SILK ....207 4C.1 MATERIALS AND METHODS ...................................210 4C.1.1 Lightfastness tests

4C.2 RESULTS AND DISCUSSION .................................. 212

4C.2.1 Light Fading Behaviour of Rhubarb Dyed Silk 4C.2.2 Light Fading Behaviour of Rhubarb Dyed Wool

5. CONCLUSIONS ............................................. 230

REFERENCES APPENDIX PUBLICATIONS