Transcript Slide 1

New green chemical
techniques in textile
coloration processes
Dr. Richard S. Blackburn
Senior Lecturer and Head of Green Chemistry Group
Centre for Technical Textiles
UNIVERSITY OF LEEDS, LS2 9JT, UK
[email protected]
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
O
OH
O
OH
OH
O
CH3CH2I
+ KI, H2O
KOH, DMSO
O
alizarin
1,2-dihydroxyanthraquinone
O
1-hydroxy-2-ethylanthraquinone
• 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
© 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
O
H
O
O
O
Table: The effect of pH on solubility and
colour of alizarin and 1H2EA
pH
Alizarin
1H2EA
4
v. sparingly soluble
no colour
insoluble
no colour
7
sparingly soluble
orange/yellow colour
insoluble
no colour
soluble
purple colour
insoluble
no colour
10
© University of Leeds 2006
O
H
O
O
O
Sustainable platform
chemicals
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•
•
•
•
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
Table: Colour strength (K/S) values of dyed samples
Conditions of
application
Alizarin
PET
1% omf at 90 °C
PET
1.5
1% omf at 100 °C
3.1
1% omf at 130 °C
6.5
4% omf at 115 °C
4% omf at 130 °C
PLA
2.1
*
H
PLA
4.3
5.1
O
8.7
10.6
CH3
PLA
4.3
2.2
19.2
O *
1H2EA
*
O
O
*
20.9
© University of Leeds 2006
PET
O
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 intramolecular 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
PET
1% omf at 90 °C
PET
3
1% omf at 100 °C
3
1% omf at 130 °C
4
4% omf at 115 °C
4% omf at 130 °C
PLA
1H2EA
3
PLA
6
5/6
6
O
6
6
© University of Leeds 2006
H
O
OH*
5
3/4
5
O
Green Chemistry
Sulphur 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 of
sulphur dyeing
2
S
O
S
S
O
S
R
S
step A
[H]
e
dyestuff particle
C.I. Sulphur Black 1
[O]
N
R
step B
N
H
[H]
S
S
N
N
S
S
O
H
e
R
R
S
[O]
O
S
S
n
C.I. Leuco Sulphur Black 1
•
•
•
•
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
© University of Leeds 2006
Reducing agents in
sulphur 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
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–
–
–
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
• sodium polysulfide
• sodium hydrosulfide
• D-arabinose
• D(-)-fructose
• D(+)-galactose
• α-D-glucose
• β-D-lactose
• D-maltose
Blackburn, R. S.; Harvey, A. Env. Sci. Technol. 2004, 38 (14), 4034.
© University of Leeds 2006
25.0
25.0
D-arabinose
20.0
20.0
2
R = 0.9845
2
R = 0.9963
SUM (K/S)
SUM (K/S)
D(-)-fructose
15.0
10.0
5.0
15.0
10.0
5.0
0.0
400
450
500
550
600
650
0.0
400
700
450
500
-mV
25.0
600
650
700
650
700
-mV
25.0
D(+)-galactose
α-D-glucose
20.0
20.0
2
R = 0.9875
SUM (K/S)
SUM (K/S)
550
15.0
10.0
2
15.0
10.0
5.0
5.0
0.0
400
0.0
400
450
500
550
-mV
600
650
700
R = 0.9975
450
500
550
-mV
600
25.0
25.0
β-D-lactose
20.0
2
R = 0.9912
SUM (K/S)
SUM (K/S)
20.0
D-maltose
15.0
10.0
15.0
10.0
5.0
5.0
0.0
400
0.0
400
450
500
550
600
650
700
R2 = 0.9993
450
500
-mV
600
650
700
-mV
25.0
70.0
Sugars
60.0
20.0
Sulfide-based reducing agents
50.0
15.0
Lc (%)
SUM (K/S)
550
10.0
Sugars
Sulfide-based reducing agents
0.0
450
500
550
-mV
30.0
20.0
5.0
400
40.0
600
650
700
10.0
0.0
400
450
500
550
-mV
600
650
700
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
4.30
a 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 dyeing
of 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
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–
–
–
–
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
© University of Leeds 2006
Mechanism of reactive dye
fixation to cellulose
(Nucleophilic substitution)
R
R
O
reaction with
cellulose
R
W
D
W
D
6
W
C
N
Cell
D
6
C
X
N
Cell
O
6
C
N
X
R
R
OH
reaction with
water
W = water solubilising group
D = dye chromophore
X = leaving group (e.g. Cl)
W
D
6
W
D
6
C
N
C
X
N
OH
Mechanism of reactive dye
fixation to cellulose
(Michael Addition)
reaction with
cellulose
W
D
SO2
CH
H
CH2
O
W
D
SO2
CH
W
D
SO2 CH2 CH2 O
W
D
SO2 CH2 CH2 OH
Cell
CH2
reaction with
water
W
D
SO2
CH
CH2
H
OH
Cell
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
© University of Leeds 2006
Pre-treatment agents
NH2
m
m
n
n
N
N Cl
H3C
CH3
N Cl
NH2
Copolymer of
diallyldimethylammonium
chloride and
3-aminoprop-1-ene (PT1)
© University of Leeds 2006
Copolymer of
4-vinylpyridine quaternised
with 1-amino-2-chloroethane
(PT2)
High substantivity of
pre-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
© University of Leeds 2006
PT1
CH3
PT1
N
CH3
OH
HO
O
O
cellulose
OH
Conformational interaction between
PT1 and cellulose
© University of Leeds 2006
PT2
poly(4-vinylpyridine)
quaternary ammonium
compound - pyridinium
residue
poly(4-vinylpyridine)
quaternary ammonium
compound - pyridine
residue
NH2
N
N
 H
 O
(b)
(a)
O

H
cellulose
(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
© University of Leeds 2006
Mechanism of operation
(schematic)
pre-treatment agent
Nu
Nu
Nu
Nu
Nu
Nu
Nu
Nu
cellulose
X
DYE
DYE
Nu
Nu
X
DYE
X
DYE
Nu
Nu
Nu
cellulose
Nu = pre-treatment nucleophiles
X = leaving group in reactive dye
© University of Leeds 2006
Nu
Nu
X
Nu
Advantages of
pre-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
© University of Leeds 2006
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
500
acetic acid (60),
detergent (20)
Procion H-EXL
4
365
105
1625
0
500
detergent (20)
Cibacron F
5
295
125
0
1500
500
acetic acid (60),
detergent (20)
Pre-treatment
1
195
50
0
0
0
pre-treatment (10),
detergent (20)
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)
– [email protected]
• Dr. Patrick McGowan
– [email protected]
• Dr. Richard Blackburn
– [email protected]
• Prof. Chris Rayner
– [email protected]
www.dyecat.com
©DyeCat 2006
© University of Leeds 2006
Acknowledgements
• Colleagues
–
–
–
–
–
–
–
–
• PhD Students
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
–
–
–
–
–
–
–
–
Iram Abdullah
Nabeel Amin
Ioannis Drivas
Parikshit Goswami
Anna Harvey
Andrew Hewitt
Nandan Kumar
Wei Zhang
• Industrial Partners
– Dr. Tony Blake
– Dr. Nagitha Wijayathunga
– Dr. Xiangfeng Zhao
© University of Leeds 2006
– Body Shop International plc
(UK)
– DyStar (Germany)
– Lenzing Fibers Ltd. (Austria)
– NatureWorks LLC (USA)
– Reilly Industries inc. (USA)
– Uniqema (UK)