richard blackburn 2004

8/7/2019 Richard Blackburn 2004

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NATURAL DYESOpportunities for a greener

textile and coloration industry

Dr. Richard S. BlackburnCentre for Technical TextilesUniversity of Leeds

[email protected]


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Coloration of textiles

Textiles essential to everyday lifeDyeing characterised by high environmental pollution and high healthrisk to personnel handling harmful substances (dyes, auxiliaries, etc .)*Synthetic colorants can be harmful and cause allergies in humans1856 William Perkin accidentally discovered MauveineResearch into natural dyes over last 150 years very limitedConsumer demand for 'natural' products incorporating naturalingredientsMove to find renewable resources (synthetic colorants from finiteresources, e.g. petroleum)Search for new sources of natural colorants has intensifiedInterest in natural dyes has recently increased

* Blackburn, RS, Burkinshaw, SM. Green Chem. 2002, 4 (1), 47.

Lea, AGH. In: Atsuchi, K (Ed.),HPL

C in Food Analysis , Academic Press, London.


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N atural colorants

Some experts highlight various problems(land for growth, poor technical performance)Others concentrate on advantages of technologies based onsustainable resources*Textile, coloration and agricultural industries in UK all requirerejuvenationUse of natural colorants offers a potential to link all three areasDevelopment of new alternative crops is a principal objective of theDEFRA Science and Innovation Strategy

Synergy needed between different sectors by pooling differentknowledge basesProvision of high quality raw materials linked to novel dyeing methodsapplying natural dyes

* Hill, DJ. R ev. P rog. Color . 1997, 27 , 18.; Ali, SI. J . Soc. Dyers. Color . 1993, 109 , 13.


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Current limitations of natural dyes

Traditionally yield and concentration lower than synthetic dyesLarge quantities of raw material to obtain the same depth of colour Limited success in coloration of synthetic fibres (polyester has a 45% share of

the global textile market)N early all natural dyes need application with a mordant (salts of Cr, Sn, Zn, Cu, Al, Fe) to secure sufficient wash and light fastness and to give good build-up

Effluent contains heavy metals far in excess of allowable limitsArgued that employing mordants of Al and Fe negative environmental impact islower Extremely desirable to develop new methods of fixation using non-metalmordantsSome research ongoing within EC (AIR2.CT94.0981) to determine how naturaldyes can be produced and used in sustainable and efficient processesModern cultivation methods of producing: I satis tinctoria (woad), R eseda luteola (weld), Solidago virgauria (golden rod),

R ubus tinctorum (madder)

Hancock, M. P otential for colourants from plant sources in England and Wales. 1997, ST0106.


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Examples of natural dyes

Madder produces red anthraquinone dye in its roots, mostimportant being alizarin ( 1 )

Weld produces yellow flavanoid colorants from foliage andflowers, most important being luteolin ( 2 )

1 2


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Extraction

Dyes have been extracted from plant material by a number of methods, not all entirely greenDesirable to extract using superheated water Clean solvent with minimal environmental impactRecently reported* that polyphenol dyes have been successfullyand rapidly extracted from elderberry, raspberry and blueberryusing water at 120CSuperheated water under pressure between 125 and 175C has

been shown to rapidly extract the oxygenated compoundsExtraction by superheated water could be a viable process for production of high quality natural colorants

* Lauro G J; Francis F J. Natural food colorants: science and technology, P roceedings of a symposium.I nstitute of Food Technologists , 1999, 336.

Delgado-Vargas F; Jimenez A R; Parades-Lopez O. Crit. R ev. Food Sci. Nutrit. 2000, 4 0 , 193-195 .


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Objectives of Green Chemistry Group (UoL)

and opportunities for research

Identify the key variables affecting the production of sustainable,consistent plant based dye compoundsDevelop environmentally friendly extraction and concentrationprocessesDevelop a range of natural and environmentally safe textile dyesDevelop coloration processes using natural dyes to obtain high colour depth and high fastness dyeings on natural fibresEmployment of non-metal mordants to enhance these parametersDevelop coloration processes using natural dyes to obtain high colour depth and high fastness dyeings on synthetic fibresApplication of natural dyes using scCO 2Chemically modify natural dyes to enhance fastness and to secureadditional colour gamut (range of shades) on a variety of substratesDevelop pilot-scale dyeing processes


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Objectives of Green Chemistry Group (UoL)

and opportunities for research

Important non-textile natural coloration

research opportunities: Packaging Plastics Cosmetics Personal care Food

}improve biodegradability of system?

}direct human contact/consumption


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Toxicology

Unmodified natural dyes may have a significantly lower environmental impact (broken down through biologicalprocesses)Should not assume that natural means safeToxicology of successful natural dyes needs to beresearched extensivelyWill not require new testing, as all potential naturalcompounds will have extensive testing already carried outAny chemical modification of the dyes may require newtoxicology testing


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LCA

Life Cycle Assessment of the whole textile dyeing processwill be essential to demonstrating the sustainability of thisproposed systemUniversity of Leeds researchers experienced in this type of assessmentLCA will study environmental aspects and potential impactsthroughout the products life ( i.e. cradle-to-grave) from plant material growing land use acquisition through processing application end use disposal


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Expertise @ UoL

Richard Blackburn Colour chemistry, coloration processes, dye-

fibre interactions, fastness testingChris Rayner Green chemical modification, applications in

scCO 2Tony Clifford Green extraction processes, superheated water

richard blackburn 2004

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