Post on 10-May-2015
description
New green chemical techniques in textile coloration processes
Dr. Richard S. BlackburnSenior Lecturer and Head of Green Chemistry Group
Centre for Technical TextilesUNIVERSITY OF LEEDS, LS2 9JT, UK
r.s.blackburn@leeds.ac.uk
© University of Leeds 2006
Where can Green Chemistry have an impact in Coloration?
• Dye chemistry– Alternative synthesis, sustainable source, natural platform
chemicals
• Dyes in effluent– Reduction (efficiencies of sorption) and cleaner treatment
technologies
• Auxiliary chemicals– Reduction in use and emission of harmful auxiliaries (e.g. salt,
reducing agents, carriers)
• Application processes– Reduction in energy, water usage, time
• Coloration of ‘greener’ fibres– PLA, PHAs, lyocell, etc.
© University of Leeds 2006
Sustainable platform chemicals
• Natural dyes derived from plant material represent a more sustainable source of colorants
• Natural dyes colour natural fibres (cotton, wool, silk) to a greater or lesser extent– 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• Natural dyes have found limited success in coloration of synthetic
fibres– PET has a 45% share of the global textile market
• Madder plant (Rubia tinctorum L.) is an important dye plant– produces the dye alizarin (1,2-dihydroxyanthraquinone)– also contains rubiadin (1,3-dihydroxy-2-methylanthraquinone) and
purpurin (1,2,4-trihydroxyanthraquinone)
© University of Leeds 2006
Sustainable platform chemicals
• Derivatisation of alizarin to produce more hydrophobic molecule– higher affinity for hydrophobic polyesters
• Successful synthesis of 1-hydroxy-2-ethylanthraquinone (1H2EA)– 93% yield– confirmed by FT-IR and NMR– OH at 1-position not derivatised due to intramolecular hydrogen bond
formation and lower intrinsic reactivity
O
O
OH
OHCH3CH2I
KOH, DMSO
alizarin1,2-dihydroxyanthraquinone
O
O
OH
O
1-hydroxy-2-ethylanthraquinone
+ KI, H2O
© University of Leeds 2006
Sustainable platform chemicals
• Problem with application of alizarin is pH sensitivity
• 1H2EA displays no such sensitivity due to derivatisation of 2-OH
pH Alizarin 1H2EA
4 v. sparingly solubleno colour
insolubleno colour
7 sparingly solubleorange/yellow colour
insolubleno colour
10 solublepurple colour
insolubleno colour
Table: The effect of pH on solubility and colour of alizarin and 1H2EA
O
O
O
O
H
O
O
O
O
H
© University of Leeds 2006
Sustainable platform chemicals
• Dyes applied with dispersing agent to PET and PLA• Colour strength (K/S) achieved with 1H2EA higher than alizarin• Dyeings unlevel, poor quality with alizarin• Dyeings level, bright, good quality with 1H2EA• Alizarin gives higher K/S on PET w.r.t. PLA, but opposite observed for 1H2EA
– increased interactions with PLA via alkyl chain addition
*O
O
O
O
*
PET
Table: Colour strength (K/S) values of dyed samples
Conditions of application
Alizarin 1H2EA
PET PLA PET PLA
1% omf at 90 °C 1.5 4.3
1% omf at 100 °C 3.1 2.1 4.3 5.1
1% omf at 130 °C 6.5 8.7
4% omf at 115 °C 2.2 10.6
4% omf at 130 °C 19.2 20.9
PLA
O*
O
CH3H
*
© University of Leeds 2006
Sustainable platform chemicals
• Wash fastness comparable and excellent on all dyeings• Light fastness considerably higher for 1H2EA compared to alizarin
– 2-OH susceptible to photo-oxidation, as it cannot form an intra-molecular H-bond
– In 1H2EA 2-OH derivatised, so not as susceptible to photo-oxidation
Table: Light fastness of dyed samples(1-8 scale)
Conditions of application
Alizarin 1H2EA
PET PLA PET PLA
1% omf at 90 °C 3 5
1% omf at 100 °C 3 3 6 5/6
1% omf at 130 °C 4 6
4% omf at 115 °C 3/4 6
4% omf at 130 °C 5 6
O
O
O
OH*
H
© University of Leeds 2006
Green ChemistrySulphur Dyeing
• Economical, good colour strength, good fastness dyeings on cellulosics
• Significant share of the colorants market– annual consumption of ca. 70,000 tons
• C. I. Sulphur Black 1 alone represents a substantial portion (20-25%) of dyestuff market for cotton– highest consumption of any single textile dye in the world
• Complex mixtures of reproducible, but uncertain, compositions
• Contain within their ring structure thiazole, thiazone, or thianthrene as chromophores
• All sulphur dye molecules contain disulfide linkages
© University of Leeds 2006
Mechanism ofsulphur dyeing
• Initially dye is in insoluble oxidised (pigment) form• Addition of reducing agent cleaves a proportion of the disulfide linkages to
form the partially soluble ‘leuco’ sulphur form• Further addition of reducing agent and increase in redox potential causes
reduction of the remaining disulfide linkages and quinoneimine groups• After exhaustion of the dye onto fibre, the reduced, adsorbed dye is
reformed in situ within the fibre by air or chemical oxidation
[O]dyestuff particleC.I. Sulphur Black 1
[H]
C.I. Leuco Sulphur Black 1
S
N S
S N
S
S
O
O
S
R
R
2
n
S
N S
S N
S
S
O
O
S
H
H
R
R
[H]
step A step B
e e
[O]
© University of Leeds 2006
Reducing agents insulphur dyeing
• Sulphur dyes themselves have a relatively low detrimental environmental impact– free from heavy metals and AOX
• Significant environmental problem with the dyeing process– employ sulfides as reducing agents– 90% of all sulphur dyes are reduced using sodium sulfide
• Discharge of sulfides only permissible in very small amounts (usually the legal allowance is 2 ppm)– danger to life from liberated hydrogen sulfide– corrosion of sewerage systems– damage to treatment works– high pH– aquatic life down stream significantly affected
• damage to the DNA of tadpoles– classed as micropollutants– over time the substance can reach high concentrations
© University of Leeds 2006
Alternative reducing agents
• Thiourea dioxide from both a practical and ecological point of view– dyeings comparable, but environmental effect unclear– significantly more expensive than sodium sulfides
• Indirect cathodic reduction processes– successfully reduce sulphur dyes– some reducing agent was required to prevent premature re-oxidation
of the dye– dyeing was comparable– electrolysis is an appreciably more expensive technology
• Glucose/NaOH– above 90°C has sufficient reducing potential– no current systems in commercial use– dyeings secured had lower colour strength and fastness– no fundamental work on the reducing sugar/NaOH system conducted
to understand optimum
© University of Leeds 2006
Application of various reducing D-sugars
• D-arabinose• D(-)-fructose• D(+)-galactose
• α-D-glucose
• β-D-lactose• D-maltose
• sodium polysulfide• sodium hydrosulfide
Blackburn, R. S.; Harvey, A. Env. Sci. Technol. 2004, 38 (14), 4034.
R2 = 0.9963
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
D-arabinose
R2 = 0.9845
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
D(-)-fructose
R2 = 0.9875
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
D(+)-galactose
R2 = 0.9975
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
α-D-glucose
D-maltoseβ-D-lactose
R2 = 0.9912
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
R2 = 0.9993
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
0.0
5.0
10.0
15.0
20.0
25.0
400 450 500 550 600 650 700
-mV
SU
M (
K/S
)
Sugars
Sulfide-based reducing agents0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
400 450 500 550 600 650 700
-mV
Lc
(%)
Sugars
Sulfide-based reducing agents
© University of Leeds 2006
Environmental and economical considerations
Relative theoretical COD and price of reducing agents per kg dyed cotton
Reducing agent g O2 kg-1 dyed cottona £ kg-1 dyed cottona
sodium sulfide 51.3 1.60
sodium hydrosulfide 71.3 1.18
D-arabinose 66.6 28.06
D(-)-fructose 66.6 1.65
D(+)-galactose 66.6 4.14
α-D-glucose 66.6 0.58
β-D-lactose 70.1 2.08
D-maltose 70.1 4.30a Based on 2.5 g dm-3 reducing agent (typical optimum concentration) at a liquor ratio of 25:1
© University of Leeds 2006
Greener reactive dyeingof cellulose
• Treatment of cellulose with cationic, nucleophilic polymers to enable reactive dyeing at neutral pH without electrolyte addition
• Reactive dyeing problems– High electrolyte concentrations used– High colour concentrations in effluent– High volume of water consumed
© University of Leeds 2006
Problems with high electrolyte concentration
• High levels of salt (sodium sulfate/chloride) used when dyeing cotton– Particularly reactive dyes– Fibre has negative charge in water– Repels anionic dyes – low adsorption– Electrolyte screens negative charge– Overcomes repulsion between dye anions and negative fibre
surface to allow adsorption
• Soil too alkaline to support crops• Kills aquatic life• Examples of fresh water courses turned saline
downstream from reactive dyeing operations• Difficult to remove from effluent
Mechanism of reactive dye fixation to cellulose
(Nucleophilic substitution)
6
R
NC
X
reaction withcellulose
reaction withwater
W D
OH
O Cell
W = water solubilising groupD = dye chromophoreX = leaving group (e.g. Cl)
W D
NC
X
R
6
6
R
NC
X
W D
6
R
NC
OCell
W D
W D
NC
OH
R
6
Mechanism of reactive dye fixation to cellulose(Michael Addition)
reaction withcellulose
reaction withwater
W D SO2 CH CH2H
O Cell
W D SO2 CH CH2
W D SO2 CH CH2H
OH
W D SO2 CH2 CH2 O Cell
W D SO2 CH2 CH2 OH
© University of Leeds 2006
Colour (unfixed dye)in effluent
• Reactive dyes poor fixation– 10-40% dyestuff hydrolysed– Goes down drain– Aesthetically unpleasant– Blocks sunlight
• Algae overpopulate• Reduction in O2 levels in water• Suffocation of flora and fauna in watercourses
• Clean effluent– High cost
© University of Leeds 2006
High water consumption
• High level of water used in reactive dyeing
• Incredible volume used in wash-off of hydrolysed dye– Up to 10 separate rinsings– High energy consumption– 50% total cost dyeing procedure
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Pre-treatment agents
N
H3C CH3
NH2
Cl
mn
Copolymer of diallyldimethylammonium chloride and3-aminoprop-1-ene (PT1)
N N
NH2
Cl
m n
Copolymer of4-vinylpyridine quaternised with 1-amino-2-chloroethane(PT2)
© University of Leeds 2006
High substantivity ofpre-treatments for cotton
• Both pre-treatment polymers are highly substantive to cellulosic fibre
• ion-ion interactions between cationic groups in the agent and the anionic carboxylic acid groups in the substrate– low pKa values will be ionised at the pH values of
application (pH 6-7)
• Other forces of attraction– H-bonding, van der Waals
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PT1
Conformational interaction betweenPT1 and cellulose
O
HOOH
O
OH
CH3
NCH3
cellulose
PT1
© University of Leeds 2006
PT2
(a) Ion-dipole interactions between cellulose hydroxyl groups and pyridinium residues of PT2
(b) Yoshida H-bonding between cellulose hydroxyl groups and pyridine residues in PT2
poly(4-vinylpyridine)quaternary ammoniumcompound - pyridineresidue
poly(4-vinylpyridine)quaternary ammoniumcompound - pyridiniumresidue
(a) (b)
OH
cellulose
O
H
NN
NH2
© University of Leeds 2006
Mechanism of operation (schematic)
cellulose
Nu Nu Nu NuNu Nu Nu Nu
Nu NuNu Nu Nu NuNu Nu
cellulose
DYE X
DYE XDYE X
DYE X
pre-treatment agent
Nu = pre-treatment nucleophilesX = leaving group in reactive dye
© University of Leeds 2006
Advantages ofpre-treatment system
• Polymers cationic– No requirement for salt
• Nucleophiles in polymer more reactive than hydroxyl groups in fibre– Neutral pH of application– Hydrolysis minimised– Colour fixation yield maximised– Less colour in effluent– Less wash-off requirement– Significant reduction in operation time– Significant reduction in water consumption
System comparison
Procedure Wash-off stages
Time(mins)
Water(ℓ/kg
fabric)
NaCl(g/kg
fabric)
Na2SO4
(g/kg fabric)
Na2CO3
(g/kg fabric)
Other Chemicals(g/kg fabric)
Remazol RR 6 355 145 0 1250 500acetic acid (60), detergent (20)
Procion H-EXL 4 365 105 1625 0 500 detergent (20)
Cibacron F 5 295 125 0 1500 500acetic acid (60), detergent (20)
Pre-treatment 1 195 50 0 0 0pre-treatment (10),
detergent (20)
© University of Leeds 2006
Publications
Blackburn, R. S.; Burkinshaw, S. M. Green Chemistry 2002 4 (1), 47.
Blackburn, R. S.; Burkinshaw, S. M. Green Chemistry 2002, 4 (3), 261.
Blackburn, R. S.; Burkinshaw, S. M. Journal of Applied Polymer Science, 2003, 89, 1026-1031.
• “Dye Hard”, New Scientist,1st December 2001
• “Greener Dyes”, The Alchemist,6th February 2002
• “Problem Fixed”, Chemistry in Britain, April 2002
© University of Leeds 2006
DyeCat Ltd.
• A University of Leeds Spinout Company
• Dr. Patrick McGowan– Organometallic chemistry– Novel polymerisation catalysts– Organometallic anticancer drugs
• Dr. Richard Blackburn– Coloration of natural and synthetic polymers and
fibres– Physical organic chemistry of dyeing processes– Green Chemistry in the textile and coloration
industries• Prof. Chris Rayner
– Organic synthesis (pharmaceuticals and fine chemicals)
– Supercritical carbon dioxide– Green Chemistry
©DyeCat 2006
© University of Leeds 2006
DyeCat Technology
• Patented technology for the preparation of light absorbing polymeric materials (IR, visible, UV).
• Variety of approaches; allows flexibility in – Polymer composition– Polymer molecular weights and polydispersities– Coloration strength– Range of light absorbing chromophores
• Applicable to natural and synthetic polymers (particularly polyesters such as PLA and PET).
• Superior coloration technology– Homogeneous colorant throughout cross section of polymer– Increased wash and light fastness
• Greatly improved preparative method– Significant cost reductions on comparable conventional technology– Reduced environmental impact
• Applicable to sustainable, biodegradable polymers such as PLA and PHB.
©DyeCat 2006
© University of Leeds 2006
Contacts
• Laura Bond (general inquiries)– Laura@techtrangroup.com
• Dr. Patrick McGowan– p.c.mcgowan@leeds.ac.uk
• Dr. Richard Blackburn– r.s.blackburn@leeds.ac.uk
• Prof. Chris Rayner– c.m.rayner@leeds.ac.uk
www.dyecat.com
©DyeCat 2006
© University of Leeds 2006
Acknowledgements
• Colleagues– Prof. Chris Rayner– Prof. Tony Clifford– Prof. Stephen Burkinshaw– Prof. Carl Lawrence– Prof. Paul Knox– Dr. Patrick McGowan– Dr. Steve Russell– Dr. Abbas Dehghani
• Research Assistants– Dr. Tony Blake– Dr. Nagitha Wijayathunga– Dr. Xiangfeng Zhao
• PhD Students– Iram Abdullah– Nabeel Amin– Ioannis Drivas– Parikshit Goswami– Anna Harvey– Andrew Hewitt– Nandan Kumar– Wei Zhang
• Industrial Partners– Body Shop International plc
(UK)– DyStar (Germany)– Lenzing Fibers Ltd. (Austria)– NatureWorks LLC (USA)– Reilly Industries inc. (USA)– Uniqema (UK)