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Investigation of Dye-FiberReactions in SC-CO2
NSF Green Processing Summer Research Experience forUndergraduates
Faculty Mentors: Dr. David Hinks and Dr. Gerardo MonteroGraduate Student Mentor: Mr. Ahmed El-Shafei
North Carolina State University, College of Textiles
Undergraduate Student: Nneka C. Ubaka-Adams
Bennett College and North Carolina Agricultural andTechnical State University
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Background
Conventional dye-fiber reactions use water as atransport medium, and result in:
Low reaction efficiency due to the competinghydrolysis reaction with hydroxyl ions in water
(hydrolyzed dye cannot react w/fiber) Environmental problems due to residual,
unreacted/hydrolyzed dye present in effluent
Replacing water with supercritical fluids (SCF) as atransport medium can result in:
Eliminating toxic waste (no hydrolyzed by-product)
Lower costs for the entire dyeing process
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Conventional aqueous-based dye-fiber reaction
S
O
O
NC
H
C
H
H
N N
Et
Et(CH2)6NH2N
H
C
O
(CH2)4C
O
N
H
(CH2)6N
H
C
O
HOOC(CH2)4
n
H2O
100 0C, 2h
n
S
O
ONC
H
C
H
H
N N
Et
EtH
(CH2)6NN
H
C
O
(CH2)4C
O
N
H
(CH2)6N
H
C
O
HOOC(CH2)4
H
+
+
N
N N
Et
Et
S
O
O
CH2CH2HO
Polyamide (nylon 6.6.)
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Dye-Fiber Reaction in SCCO2
Polyamide (nylon 6.6.)
S
O
O
NC
H
C
H
H
N N
Et
Et(CH2)6NH2N
H
C
O
(CH2)4C
O
N
H
(CH2)6N
H
C
O
HOOC(CH2)4
n
SC CO2P,T
n
S
O
O
NC
H
C
H
H
N N
Et
Et
H
(CH2)6NN
H
C
O
(CH2)4C
O
N
H
(CH2)6N
H
C
O
HOOC(CH2)4
H
+
no hydrolyzed by-products
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Sulfonyl-azo-dyes
NN
NEt
Et S
O
O
CH2 CH3
Non-Reactive Dye
NN
NEt
Et S
O
O
CH CH2
Reactive Dye
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Dyeing Procedure
Add fiber and dye to vessel
Pressurize system (with CO2) up to 800 psi andstir at approximately 850 rpm
Heat to required temperature (100 -180 C)
Pressurize to 3500 psi; hold for 2 hours
Release pressure, remove fabric
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Testing Dye-Fiber Reaction
Measure color strength (K/S) of each dyed fiber
Wash fiber with acetone (remove surface dye)
Conduct soxhlet extraction using ethyl acetate(to remove unreacted dye)
Compare effect of vinylsulfone reactive group ondye fixation
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Results
Vinylsulfonyl-Dye Color Strength
0
2
4
6
8
10
12
14
16
18
20
22
100C 120C 140C 160C 180C
Dyeing Temperature
K/Svalue
Original VS-dyed wool
Extracted VS-dyed wool
31%
26%
6.2%
9.4%
5.9%
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Results
Ethylsulfonyl-Dye Color Strength
0
2
4
6
8
10
12
14
100C 120C 140C 160C 180C
Dyeing Temperature
K/Svalue
Original wool fibers
Extracted wool fibers
92%
91%
77.9%
72.9%
58.6%
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Comparison of Dyed Fabrics
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Initial Conclusions
Color depth improved with increasingtemperature
Strong evidence for dye-fiber bond
formation using vinylsulfone-based dye onnylon and wool
ES-dyeing on wool fibers showed extremely
low color yields after extraction (no reaction) 94% fixation at 180 oC/ 3500 psi on wool
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Acknowledgements
This research was conducted with the support of the NSF
Green Processing Undergraduate Research Program with a
grant from the National Science Foundation, Award
Number, EEC-9912339.
