Synthesis and efficient dyeing of anthraquinone derivatives on polyester fabric with supercritical carbon dioxide

Article abstract of DOI:10.1016/j.dyepig.2019.03.027

Two series of anthraquinone dye derivatives [CNU-1 to CNU-7 and CNU-8 to CNU-10] have been successfully synthesized from commercially inexpensive and readily available starting materials by using simple and convenient methods. All synthesized anthraquinon

Full text of DOI:10.1016/j.dyepig.2019.03.027

Accepted Manuscript
Synthesis and efficient dyeing of anthraquinone derivatives on polyester fabric with
supercritical carbon dioxide
Raju Penthala, Rangaraju Satish Kumar, Gisu Heo, Hyorim Kim, In Yeol Lee, Eun
Hee Ko, Young-A. Son
PII:
S0143-7208(18)32698-6
https://doi.org/10.1016/j.dyepig.2019.03.027
DYPI 7416
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 9 December 2018
Revised Date: 8 March 2019
Accepted Date: 12 March 2019
Please cite this article as: Penthala R, Kumar RS, Heo G, Kim H, Lee IY, Ko EH, Son Y-A, Synthesis
and efficient dyeing of anthraquinone derivatives on polyester fabric with supercritical carbon dioxide,
Dyes and Pigments (2019), doi: https://doi.org/10.1016/j.dyepig.2019.03.027.
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ACCEPTED MANUSCRIPT
Graphical Abstract

ACCEPTED MANUSCRIPT
Synthesis and efficient dyeing of anthraquinone derivatives on
polyester fabric with supercritical carbon dioxide
a
a
a
a
b
b
Raju Penthala , Rangaraju Satish Kumar , Gisu Heo , Hyorim Kim , In Yeol Lee , Eun Hee Ko ,
a
Young-A Son ,*
a
Department of Advanced Organic Materials Engineering, Chungnam National University, 220 Gung-
dong, Yuseong-gu, Daejeon 305-764, South Korea.
b
Korea High Tech Textile Research Institute, Yangju, 11410, South Korea.
*Corresponding author. Tel.: +82 42 821 6620; fax: +82 42 821 8870.
E-mail address: yason@cnu.ac.kr (Y.-A. Son).
1

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Abstract
Two series of anthraquinone dye derivatives [CNU-1 to CNU-7 and CNU-8 to CNU-10] have
been successfully synthesized from commercially inexpensive and readily available starting
materials by using simple and convenient methods. All synthesized anthraquinone dyes were
1
13
characterized by H NMR, C NMR, and UV-Vis spectroscopy and HRMS. The UV-Vis spectra
of the dyes indicated that the absorption wavelengths of dyes were approximately 590 - 655 nm,
which indicated that these are blue dyes. Polyester fabrics were dyed with these compounds
using supercritical carbon dioxide as a green medium. All the compounds displayed deep color
shades and excellent dye fixation even at low concentrations (0.5%). In the fastness experiments,
compounds CNU-1 to CNU-10 all exhibited excellent results in washing (4-5), sweat (4-5) and
lightfastness [CNU-1 to 7 (4-5), CNU-8 to 10 (2-3)]. Hence, our results revealed that these types
of anthraquinone dyes are commercially most acceptable, and they practically exhibited
satisfactory color uniformity.
Keywords
Anthraquinone dyes; Blue color; Supercritical carbon dioxide; polyester fabric (PET).
2

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1
. Introduction
When using conventional water-based dyeing methods, the textile industry requires more
water to dye polyester fabrics and requires several chemical additives, such as dispersing agents
and surfactants, to enhance the solubility of the dyes in water [1, 2]. This method produces
enormous quantities of polluted water, which is very expensive to purify and harmful to the
environment [3, 4]. Therefore, the textile industry seeks an ecofriendly process to replace the
conventional water-based dyeing method. To overcome the ecological and economic
disadvantages of the traditional method, supercritical fluid dyeing processes have been
introduced [5-10].
In supercritical fluid dyeing, supercritical fluids are used as the dye solvents instead of
water. A supercritical fluid can be defined as a substance above its critical temperature (Tc) and
pressure (Pc). Under these described conditions, the substance has unique properties in that it
exists as a vapor and liquid in equilibrium. Carbon dioxide is particularly attractive due to its
green properties, such as recyclability, nontoxic, and nonflammability [11, 12]. In the dyeing
process, the critical conditions required to generate supercritical carbon dioxide (Tc = 304.34 K,
Pc = 7.38 MPa) are easily attainable, and it does not require any dispersing agents or surfactants
[13]. In the traditional wet dyeing process, more energy is required in the washing and drying
steps, whereas in the supercritical fluid dyeing process, this energy can be saved, as this process
requires only one step (either washing or drying) after dyeing [6]. Furthermore, supercritical
carbon dioxide has a high diffusion rate because the dye penetrates more readily into the porous
textile fibers [14-18].
Polyester (polyethylene terephthalate or PET) fabrics have compact, nonpolar, and highly
crystalline structures. Therefore, for the dyeing of PET fabrics with supercritical carbon dioxide,
3

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nonpolar dyes are used to ensure dissolution. Due to the wide range of available hues and
excellent fastness, disperse dyes are used for the dyeing of polyester fabrics [19-23].
Anthraquinone disperse dyes play a vital role in the dyestuffs industry [24]. These molecules are
more stable under experimental conditions and in various organic solvents during calibration
studies. The molar absorption coefficients (B˜ν) of anthraquinone dyes allow their spectroscopic
determination even at very low concentrations [25]. The design and development of new
anthraquinone disperse dye derivatives has become a hot research area in modern textile
chemistry. Previously, our group synthesized various dyes and used them to dye polyester fabrics
[19, 26-30]. In a continuation of our work, we have synthesized two series of anthraquinone dyes
and used them to dye polyester fabrics with supercritical carbon dioxide as the medium.
2
. Experimental
2
.1. Materials and methods
Starting materials and commercial reagents were purchased from Sigma Aldrich and Alfa Aesar.
1
13
H and C NMR spectra were recorded using an AVANCE III spectrometer operating at 600
MHz and 150 MHZ, respectively, with CDCl as the solvent. The chemical shift (δ) values are
3
given in ppm downfield from an internal standard of tetramethyl silane. UV-visible absorption
spectra were acquired with an Agilent 8453 spectrophotometer, and reflectance spectra were
recorded using a Shimadzu UV 26000 spectrophotometer. HRMS data were recorded on a
Bruker micrOTOF-Q spectrometer. Melting points were recorded visually in a capillary tube on
Electrothermal IA9100/OA series melting point apparatus. The capillary tube was filled with the
synthesized dyes ~3 mm high and placed in melting temperature apparatus. Set the MEL-TEMP
-1
to the appropriate power level, and increased temperature is 2 ℃ min . We observed the melting
4

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process with the magnifying lens. These experiments were done in triplicate. The purity of
synthesized dyes CNU-1 to CNU-10 was determined by using Ultimate-3000 ISQ EC high
performance liquid chromatography by calculate percentage of peak area in relation to total area
of peaks under interests or in relation to main peak (small impurities determined). The HPLC
conditions in this study were mobile phase composition is 0.1% formic acid in acetonitrile
(
0.0%), flow rate (0.3 mL/min). The corresponding HPLC spectra were placed at supporting
information (Fig. S31 to Fig. S40).
.2. Synthesis
The main task of the current work was to develop the new designed anthraquinone-
2
derived blue dyes that would be commercially most accessible to supercritical carbon dioxide
application in near future. We have synthesized anthraquinone dyes from previous literature
reports with slight modifications [31, 32]. These dyes were applied to polyester fabrics using
ecofriendly supercritical carbon dioxide dyeing conditions. Herein, we planned to synthesize two
series of 10 anthraquinone dyes namely CNU-1 to CNU-10.
Scheme 1. Synthesis of CNU-1 to CNU-7 supercritical dyes.
In the case of the first series of compounds, 1,8-dihydroxy-4,5-dinitroanthracene-9,10-
dione (I) was chosen as the starting material. A condensation reaction was performed between
the starting material (I) and the appropriate aryl amines (II a-g) in the presence of 2-
5

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methoxyethanol at reflux to afford compounds CNU-1 to CNU-7 (Scheme 1). By using this
method, we synthesized 7 compounds by changing the substituents on the aryl amino moiety.
The structures of the compounds are shown in Fig. 1.
Fig. 1. Chemical structures of CNU-1 to CNU-7 supercritical dyes.
For the synthesis of the second series of compounds, 1,4-dihydroxyanthracene-9,10-dione
(
III) was chosen as the starting material. This starting material was reacted with tosyl chloride
IV) in the presence of Et N to afford compound (V). Further compound (V) was reacted with
(
3
excess of various substituted amines VI (a-c) under mild reaction conditions to give 1-amino-4-
tosyloxy)-anthraquinones VII (a-c) as red products. Reactions of intermediates VII (a-c) with
amines VIII (a-c) in the presence of pyridine at 100 °C afforded compounds CNU-8 to CNU-10
Scheme 2). Herein, we synthesized three compounds using this method by varying the amines,
(
(
and the structures of these compounds are shown in Fig. 2.
6

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O
S
R
O
Cl S
O
O HN
O
OH
OH
R-NH2
VI (a-c)
O
O
O
O
O
O
IV
DCM, RT, 24 h
Et N, ACN,
O
3
O
O
S
O
reflux, 5 h
O
S
O
VII (a-c)
III
V
1
Pyridine,
R -NH
2
reflux, 16 h VIII (a-c)
R
O HN
O
NH
R1
CNU-8 to CNU-10
Scheme 2. Synthesis of CNU-8 to CNU-10 supercritical dyes.
Fig. 2. Chemical structures of CNU-8 to CNU-10 supercritical dyes.
2
.3. General experimental procedure for the synthesis of dyes CNU-1 to CNU-7: A mixture
of 1,8-dihydroxy-4,5-dinitroanthracene-9,10-dione (I) (0.5 g, 1.514 mmol), and aryl amines (II
a-g) (3.028 mmol) in 2-methoxyethanol (10 mL) was stirred at 125 °C for 6 h. After completion
of the reaction (as monitored by TLC), the crude reaction mixture was directly absorbed onto
7

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silica (230-400 mesh) and subjected to column chromatography using 12 to 15% ethyl acetate: n-
hexane as the eluent to afford CNU-1 to CNU-7 as blue solids.
2
.3.1. 1-((4-Hexylphenyl)amino)-4,5-dihydroxy-8-nitroanthracene-9,10-dione (CNU-1):
1
Blue solid; Yield: 86% (0.43 g), mp: 115 – 117 °C; H NMR (CDCl , 600 MHz): δ 12.82 (s,
3
1
9
=
H), 12.73 (s, 1H), 11.65 (s, 1H), 7.53 (d, J = 8.8 Hz, 1H), 7.48 (d, J = 9.7 Hz, 1H), 7.20 (d, J =
.0 Hz, 1H), 7.14 (d, J = 8.0 Hz, 2H), 7.09 (d, J = 9.5 Hz, 1H), 7.05 (d, J = 8.0 Hz, 2H), 2.55 (t, J
1
3
7.9 Hz, 2H), 1.55 (qt, J = 7.1 Hz, 2H), 1.32 – 1.21 (m, 8H), 0.83 (t, J = 6.7 Hz, 3H); C NMR
(
CDCl , 150 MHz): δ 188.2, 176.4, 162.3, 157.9, 145.2, 141.0, 140.3, 134.3, 129.4, 128.6, 128.0,
3
1
4
2
27.2, 125.6, 123.8, 121.3, 114.5, 111.0, 107.3, 34.4, 30.6, 30.3, 27.9, 21.5, 13.0. HRMS:
+
59.1522 [M-H] Calcd for C H N O : 459.1556. Purity: 93%.
2
6
23
2
6
.3.2. 1,8-Dihydroxy-4-nitro-5-((4-pentylphenyl)amino)anthracene-9,10-dione (CNU-2):
1
Blue solid; Yield: 84% (0.41 g), mp: 260 – 262 °C; H NMR (CDCl , 600 MHz): δ 12.83 (s,
3
1
8
=
H), 12.74 (s, 1H), 11.66 (s, 1H), 7.54 (d, J = 9.0 Hz, 1H), 7.49 (d, J = 9.5 Hz, 1H), 7.21 (d, J =
.8 Hz, 1H), 7.15 (d, J = 8.2 Hz, 2H), 7.10 (d, J = 9.5 Hz, 1H), 7.06 (d, J = 8.2 Hz, 2H), 2.55 (t, J
1
3
7.9 Hz, 2H), 1.56 (qt, J = 7.5 Hz, 2H), 1.32 – 1.23 (m, 4H), 0.84 (t, J = 6.9 Hz, 3H); C NMR
(
CDCl , 150 MHz) δ 189.3, 177.5, 163.3, 158.9, 146.3, 142.1, 141.3, 135.3, 130.5, 129.6, 128.2,
3
+
1
26.7, 124.8, 122.3, 115.6, 112.1, 108.4, 35.4, 31.4, 31.0, 22.5, 14.0. HRMS: 447.2458 [M+H] .
Calcd for C H N O : 447.4677. Purity: 82%.
2
5
23
2
6
2
.3.3. 1-((4-Butylphenyl)amino)-4,5-dihydroxy-8-nitroanthracene-9,10-dione (CNU-3):
1
Blue solid; Yield: 83% (0.39 g), mp: 250 – 252 °C; H NMR (CDCl , 600 MHz): δ 12.83 (s,
3
1
8
=
H), 12.74 (s, 1H), 11.66 (s, 1H), 7.54 (d, J = 8.8 Hz, 1H), 7.49 (d, J = 9.7 Hz, 1H), 7.20 (d, J =
.8 Hz, 1H), 7.15 (d, J = 8.0 Hz, 2H), 7.10 (d, J = 9.7 Hz, 1H), 7.06 (d, J = 8.0 Hz, 2H), 2.56 (t, J
1
3
7.7 Hz, 2H), 1.54 (qt, J = 7.7 Hz, 2H), 1.35 – 1.26 (m, 2H), 0.88 (t, J = 7.5 Hz, 3H); C NMR
8

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(
CDCl
3
, 150 MHz): δ 188.3, 176.5, 162.3, 157.9, 145.3, 141.1, 140.3, 134.3, 129.5, 128.6, 128.1,
+
1
27.2, 125.7, 123.8, 121.3, 114.6, 107.4, 34.1, 32.5, 21.3, 12.9. HRMS: 431.1223 [M-H] . Calcd
for C H N O : 431.1243. Purity: 86%.
2
4
19
2
6
2
9
.3.4. 1,8-Dihydroxy-4-((4-(2-(2-methoxyethoxy)ethoxy)phenyl)amino)-5-nitroanthracene-
1
,10-dione (CNU-4): Blue solid; Yield: 69% (0.37 g), mp: 94 – 96 °C; H NMR (CDCl , 600
3
MHz): δ 12.90 (s, 1H), 12.79 (s, 1H), 11.46 (s, 1H), 7.31 (d, J = 9.5 Hz, 1H), 7.09 (d, J = 8.6 Hz,
2
3
1
1
H), 7.02 – 6.96 (m, 2H), 6.92 – 6.86 (m, 3H), 4.09 (t, J = 4.8 Hz, 2H), 3.81 (t, J = 5.0 Hz, 2H),
1
3
3
.69 – 3.66 (m, 2H), 3.54 – 3.52 (m, 2H), 3.33 (s, 3H); C NMR (CDCl , 150 MHz): δ 189.2,
84.0, 155.6, 155.3, 144.2, 143.6, 131.7, 129.8, 127.6, 125.1, 125.0, 124.9, 124.7, 114.5, 113.0,
+
12.8, 110.4, 110.3, 70.9, 69.7, 68.7, 66.7, 58.0. HRMS: 493.1276 [M-H] . Calcd for
C H N O : 493.1247. Purity: 85%.
25
21
2
9
2
.3.5. 1,8-Dihydroxy-4-((2-methoxy-5-methylphenyl)amino)-5-nitroanthracene-9,10-dione
1
(
CNU-5): Blue solid; Yield: 85% (0.38 g), mp: 190 – 192 °C; H NMR (CDCl , 600 MHz): δ
3
1
7
2.84 (s, 1H), 12.77 (s, 1H), 11.42 (brs, 1H), 7.55 (d, J = 9.0 Hz, 1H), 7.35 (d, J = 9.7 Hz, 1H),
.21 – 7.18 (m, 1H), 7.10 (d, J = 9.5 Hz, 1H), 7.00 – 6.98 (m, 1H), 6.97 – 6.94 (m, 1H), 6.80 (d,
13
J = 8.2 Hz, 1H), 3.72 (s, 3H), 2.23 (s, 3H); C NMR (CDCl
3
, 150 MHz): δ 189.4, 177.6, 163.3,
1
1
2
59.0, 151.2, 146.0, 130.5, 130.3, 128.9, 128.6, 127.6, 127.0, 126.2, 122.2, 115.7, 112.1, 111.7,
+
08.6, 55.7, 20.5. HRMS: 419.0891 [M-H] . Calcd for C H N O : 419.0879. Purity: 75%.
2
2
15
2
7
.3.6. 1-((4-Heptylphenyl)amino)-4,5-dihydroxy-8-nitroanthracene-9,10-dione (CNU-6):
1
Blue solid; Yield: 87% (0.45 g), mp: 90 – 92 °C; H NMR (CDCl , 600 MHz): δ 12.84 (s, 1H),
3
1
2.75 (s, 1H), 11.66 (s, 1H), 7.54 (d, J = 8.8 Hz, 1H), 7.49 (d, J = 9.5 Hz, 1H), 7.20 (d, J = 8.8
Hz, 1H), 7.15 (d, J = 8.2 Hz, 2H), 7.10 (d, J = 9.7 Hz, 1H), 7.06 (d, J = 8.2 Hz, 2H), 2.55 (t, J =
1
3
7
.9 Hz, 2H), 1.59 – 1.52 (m, 2H), 1.31 – 1.17 (m, 10H), 0.82 (t, J = 7.1 Hz, 3H); C NMR
9

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(
CDCl
3
, 150 MHz): δ 188.3, 176.5, 162.3, 157.9, 145.3, 141.1, 140.3, 134.3, 129.5, 128.6, 128.1,
1
4
2
27.2, 125.7, 123.8, 121.3, 114.6, 111.1, 107.3, 34.4, 30.7, 30.3, 28.2, 28.1, 21.6, 13.0. HRMS:
+
73.1708 [M-H] . Calcd for C H N O : 473.1713. Purity: 89%.
2
7
25
2
6
.3.7. 1,8-Dihydroxy-4-nitro-5-((4-propylphenyl)amino)anthracene-9,10-dione (CNU-7):
1
Blue solid; Yield: 86% (0.39 g), mp: 238 – 240 °C; H NMR (CDCl , 600 MHz): δ 12.81 (s,
3
1
8
=
H), 12.72 (s, 1H), 11.65 (s, 1H), 7.53 (d, J = 8.8 Hz, 1H), 7.48 (d, J = 9.5 Hz, 1H), 7.19 (d, J =
.8 Hz, 1H), 7.14 (d, J = 8.0 Hz, 2H), 7.09 (d, J = 9.5 Hz, 1H), 7.05 (d, J = 8.0 Hz, 2H), 2.53 (t, J
1
3
3
7.7 Hz, 2H), 1.63 – 1.55 (m, 2H), 0.89 (t, J = 7.3 Hz, 3H); C NMR (CDCl , 150 MHz) δ
1
1
4
89.3, 177.5, 163.3, 158.9, 146.3, 142.1, 141.0, 135.4, 130.5, 129.7, 129.1, 128.2, 126.7, 124.8,
+
22.3, 115.6, 112.1, 108.4, 37.5, 24.4, 13.7. HRMS: 417.3960 [M-H] . Calcd for C H N O :
2
3
17
2
6
17.3981. Purity: 90%.
2
.4. Synthetic procedure for the synthesis of 9,10-dioxo-9,10-dihydroanthracene-1,4-diyl
bis(4-methylbenzenesulfonate) (V): A solution of 1,4-dihydroxyanthracene-9,10-dione (III)
10 g, 41.66 mmol) in acetonitrile (300 mL) was treated with Et N (30 mL, 214 mmol) followed
(
3
by p-toluene sulfonyl chloride (IV) (19.2 g, 100 mmol), and the reaction mixture was stirred at
reflux temperature for 5 h. After completion of the reaction, acetonitrile was removed by a rotary
evaporator, and the resulting crude material was dissolved in DCM (500 mL). This mixture was
washed with water (2 x 300 mL), and the organic layer was dried over Na SO and filtered. The
2
4
resulting solution was concentrated to give (V) a yellow brown solid. This crude material was
triturated with diethyl ether and n-hexane to afford 9,10-dioxo-9,10-dihydroanthracene-1,4-diyl
1
bis(4-methylbenzenesulfonate) (V) as a bright yellow solid. Yield: 86% (19.6 g); H NMR
(
CDCl
3
, 600 MHz): δ 8.05 (dd, J = 5.6, 4.3 Hz, 2H), 7.89 – 7.84 (m, 4H), 7.75 (dd, J = 5.6, 3.3
+
Hz, 2H), 7.52 (s, 2H), 7.37 – 7.31 (m, 4H); ESI-MS: 549 [M+H] .
1
0

ACCEPTED MANUSCRIPT
2
.4.1. General experimental procedure for the synthesis compounds (VII a-c): A solution of
,10-dioxo-9,10-dihydroanthracene-1,4-diyl bis(4-methylbenzenesulfonate) (V) (2 g, 3.646
9
mmol) in DCM (100 mL) was added the appropriate alkyl amine (VIII a-c) (4.375 mmol) at
room temperature, and the reaction mixture was stirred at this temperature for 24 h. After
completion of the reaction (as monitored by TLC), the reaction mixture was concentrated under
reduced pressure to afford red solids, which were used in the next step without further
purification.
2
.4.2. General experimental procedure for the synthesis compounds (CNU-8 to CNU-10): A
solution of crude compounds (VII a-c) (1.0 mmol) in pyridine (20 mL) was added the
appropriate amine (IX a-c) (1.0 mmol) at room temperature, and the reaction mixture was
refluxed for 16 h. After completion of the reaction (as monitored by TLC), the crude reaction
mixture was directly absorbed onto silica (230-400 mesh) and subjected to column
chromatography using 4 to 7% ethyl acetate:n-hexane as the eluent to afford CNU-8 to CNU-10
as a blue solids.
2
8
–
2
.4.3. 1-(Benzylamino)-4-(heptylamino)anthracene-9,10-dione (CNU-8): Blue solid; Yield:
1
1% (1.2 g), mp: 139 – 141 °C; H NMR (600 MHz, CDCl
3
): δ 11.06 (s, 1H), 10.66 (s, 1H), 8.31
8.25 (m, 2H), 7.66 – 7.59 (m, 2H), 7.32 – 7.18 (m, 5H), 7.10 – 7.05 (m, 2H), 4.61 – 4.57 (m,
1
3
H), 3.31 – 3.24 (m, 2H), 1.70 – 1.63 (m, 2H), 1.16 – 1.14 (m, 6H), 0.80 (t, J = 7.1 Hz, 3H); C
NMR (CDCl , 150 MHz): δ 181.9, 181.3, 145.3, 144.7, 137.6, 133.5, 131.1, 127.8, 126.3, 125.8,
3
+
1
22.7, 122.4, 109.4, 108.7, 45.7, 41.8, 30.7, 28.6, 28.0, 26.1, 21.5, 13.0. HRMS: 426.2326 [M] .
Calcd for C H N O : 426.2307. Purity: 86%.
2
8
30
2
2
2
.4.4. 1-(Benzylamino)-4-(tridecylamino)anthracene-9,10-dione (CNU-9): Blue solid; Yield:
1
7
8% (1.5 g), mp: 259 – 261 °C; H NMR (600 MHz, CDCl
3
): δ 8.28 – 8.25 (m, 2H), 7.67 – 7.64
1
1

ACCEPTED MANUSCRIPT
(m, 2H), 7.32 – 7.25 (m, 5H), 7.20 – 7.18 (m, 1H), 7.15 – 7.11 (m, 1H), 4.57 (s, 2H), 3.27 (t, J =
7
3
1
1
2
.3 Hz, 2H), 1.75 – 1.68 (m, 2H), 1.42 – 1.35 (m, 2H), 1.31 – 1.15 (m, 18H), 0.80 (t, J = 7.1 Hz,
1
3
H); C NMR (CDCl , 150 MHz): δ 183.0, 182.4, 146.4, 145.7, 138.6, 134.6, 134.4, 132.1,
3
32.0, 128.8, 127.3, 126.9, 123.8, 123.4, 110.5, 109.7, 46.7, 42.9, 31.9, 29.6, 29.3, 27.1, 22.6,
+
4.1. HRMS: 510.3257 [M] . Calcd for C H N O : 510.3246. Purity: 75%.
3
4
42
2
2
.4.5. 1-((2-Ethylhexyl)amino)-4-(hexadecylamino)anthracene-9,10-dione (CNU-10):
1
Blue solid; Yield: 71% (1.4 g), mp: 139 – 141 °C; H NMR (600 MHz, CDCl
3
): δ 10.95 (brs,
1
H), 10.87 (brs, 1H), 8.29 – 8.21 (m, 2H), 7.66 – 7.59 (m, 2H), 7.20 – 7.15 (m, 2H), 3.39 – 3.22
1
3
(
m, 4H), 1.78 – 0.79 (m, 46H); C NMR (CDCl
3
, 150 MHz): δ 182.1, 182.1, 146.5, 146.2,
1
2
34.5, 134.5, 131.8, 126.0, 125.9, 123.5, 109.6, 45.9, 45.9, 42.9, 39.4, 31.9, 31.2, 29.7, 29.6,
9.6, 29.5, 29.3, 29.3, 29.0, 28.9, 27.1, 24.5, 23.0, 22.6, 14.1, 14.1, 10.9. HRMS: 573.4409 [M-
+
H] . Calcd for C H N O : 573.4420. Purity: 93%.
3
8
57
2
2
2
.5. Dyeing apparatus
Fig. 3 represents the diagram of the whole apparatus. It mainly consists of a heating bath,
a dyeing bath, temperature and pressure control units and a recycling unit. First, from the CO
2
cylinder, the CO gas was passed through a circulated cooling bath. This cooling bath has a water
2
and ethylene glycol mixture to maintain the temperature in the range of -10 to +5 ℃ . Due to this
maintaining temperature, CO gas can be converted to a liquid. A high-pressure pump was
2
equipped with a motor and had a power of 2.2 kW. The heating bath had a heating power of ~24
kW. These pressure pumps and heating baths were helped us to maintain the pressure and
temperature of the liquid to above its critical conditions (critical pressure: 7.38 MPa and critical
temperature (31.1 ℃ ). The dyeing bath was designed to be cylindrical with an autoclave with a
rotating warp beam. Polyester fabrics were dyed with our synthesized anthraquinone dyes by
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wrapping the fabrics around the rotating warp beam in a cyclic manner. The dyeing bath
temperature was maintained by a temperature control unit with a temperature range of 40-300 ℃ .
After dyeing, recycling and separation of the unfixed dye and carbon dioxide is essential. Thus,
depressurization was carried out while maintaining a suitable pressure (4 MPa) and temperature
(
25 °C) for separation. The CO gas was purified by passage through a chamber containing
2
2
molecular sieves. After purification, the CO gas was released from the separator and stored in a
recycling vessel.
Fig. 3. Schematic representation of the apparatus 1) CO cylinder, 2) Circulated cooling bath,
2
3
2
) CO pump, 4) Heating bath, 5) Temperature controller, 6) Stirrer, 7) Dye bath, 8) Pressure
regulator, and 9) Separator.
2
.6. Supercritical dyeing procedure
Polyester fabrics (10 g) were suspended in a stainless steel cylinder and placed inside an
autoclave. The synthesized anthraquinone dyes were loaded on the bottom surface of the vessel.
Herein, we used different amounts of dye (0.5%, 1% and 1.5%) with respect to polyester fabric.
The reactor was sealed and heated to the required temperature. Before heating, liquid CO was
2
pumped into the vessel via the valve. At this time, the initial pressure was 5 MPa. After 10 min,
1
3

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the pressure had reached 15 MPa. After 1 h of dyeing, the heating was shut off, and the system
cooled slowly. After reaching atmospheric pressure, the needle valve was opened to release the
CO . Then, the polyester fabric was removed from the sample vessel and washed with soap at 50
2
°
C for 15 min and then washed with water.
3
. Results and discussion
3
.1. Factors affecting dyeing properties of polyethylene terephthalate (PET) fabrics
In our experiments, we investigated the effect of dyeing parameters like concentration,
temperature and pressure on color strength values of the PET fabrics with our new synthesized
dyes CNU-1 to CNU-10 under supercritical carbon dioxide medium. The corresponding results
obtained in this experiments were shown in fig. 4 and an appropriate discussion were presented
below.
3
.1.1. Effect of dye concentration:
According to Kubelka-Munk (K/S) equation, the measurement of K/S values are given
directly correlated with the dye concentration on the dye substrate [33]. The K/S factor was first
calibrated using a series of PET fabrics dyed in supercritical carbon dioxide at various
concentrations of dye. The dye uptake in the fabric was extracted with hot acetone solution and
the concentration of the solution was measured at a maximum wavelength. In our study the color
intensities were increased with increasing the percentage of dye (0.5 to 1.5%) (Fig. 4a). This is
attributed to the degree of solubility of anthraquinone disperse dyes are increased by increasing
the percentage of dye [34, 35].
3
.1.2. Effect of dyeing temperature:
The dyeing temperature (T °C) is a key factor and plays an important role in the color
yield of the polyester fabrics. A series of dyeing experiments were carried out at constant
1
4

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concentration (0.5%) and pressure (15 MPa) with different temperatures ranging from 80 °C to
1
20 °C (Fig. 4b). The results indicated that higher temperatures could improve the dye
adsorption and liberty of the macromolecular chains of the polyester fabrics. The differences in
color strength is very minor for dyes CNU-6, CNU-8, CNU-9 and CNU-10 at 80 ℃ and 100 ℃ .
In our study, 120 °C provided the maximum equilibrium capacity of dye adsorption. Higher
temperature generally enhances the freedom of the macromolecular chains of PET and dyes.
Hence dye molecules rate of diffusion was very high and penetrated in to the polyester fabrics,
resulting in good color strength of fabrics.
3
.1.3. Effect of dyeing pressure:
The dyeing pressure also plays a crucial role in the color yield of polyester fabrics. A
series of dyeing experiments were carried out at constant concentration (0.5%) and temperature
120 °C) with different pressures ranging from 5 to 15 MPa (Fig. 4c). While increasing the
(
pressure the density of the supercritical carbon dioxide is increased at constant temperature.
Therefore, the solubility of the dye molecules was increased, and they easily diffused into the
amorphous region of the swelled polyester fabric. As a result, the color strength of the dyed
polyester fabrics increased. Fig. 5. shows photo images of the PET fabrics dyed with ten
anthraquinone dyes in supercritical carbon dioxide.
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6

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Fig. 4. (a) ꢀ⁄ꢁ values vs. amount of dye (b) Effect of dyeing temperature (80 ℃ , 100 ℃ , 120 ℃ )
on ꢀ⁄ꢁ values. (c) Effect of dyeing pressure (5, 10, 15 [MPa]) on ꢀ⁄ꢁ values.
The solubility properties of the disperse dyes are a complex process in supercritical carbon
dioxide. At low pressures the solubility of the disperse dye decreases with increasing temperature
because of the decrease in carbon dioxide density. Therefore, the color strengths decrease. At
high pressures the solubility of the disperse dyes is increases with increasing temperature
because the decrease in carbon dioxide density cannot overcome the increase in vapor pressure
[36]. The dye solubility is increases with increasing pressure at constant temperature due to
increasing the density of carbon dioxide. Hence the color strengths also increase [37,38].
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2
Fig. 5. Photo images of PET fabrics dyed with anthraquinone dyes in supercritical CO .
3
.2. Color strength and dye fixation
The color strength (K/S) values of the dyed PET fabrics were calculated from the
Kubelka–Munk equation by substituting the reflectance (R).
ꢃꢄꢅꢆꢇꢈ
ꢀ
⁄ꢁ ꢂ
ꢉꢆ
Where K is absorbance, S is the scattering and R is the minimum reflectance. Rmin can be
recorded by using Shimadz UV 26000 spectrophotometer.
1
8

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ꢜ
1
ꢀ
⁄ꢁ ꢂ ꢖꢃꢀ⁄ꢁꢇꢗ, ꢘꢙꢚꢛ
ꢕ
ꢝꢞꢄ
Where ꢀ ꢁ is the arithmetic mean of K/S values of an individual fabric. i = 1, 2, 3,…, n (n = 5
⁄
was used in this work), refers to the different sites measured of an individual colorful PET fabric.
The percentage of dye fixation (F) values were calculated from the following equation by
substituting ꢃꢀ ꢁ )extracted (after extraction) and ꢃꢀ ꢁꢇ dyed (after dyeing). Soxhlet extraction
⁄ ⁄
method was used to extract the dye molecules from the dyed fabrics by using acetone as a
solvent at 80 °C [39].
ꢃꢋ⁄ꢌꢇꢍꢎꢏꢐꢑꢒꢏꢍꢓ
ꢊ ꢂ
X 100%
⁄
ꢃꢋ ꢌꢇꢓꢔꢍꢓ
Fig. 6. ꢃꢀ ꢁꢇdyed, ꢃꢀ ꢁ )extracted values of dyed PET fabrics
⁄ ⁄
1
9

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Fig. 6 shows the ꢃꢀ ꢁꢇdyed, ꢃꢀ ꢁ )extracted values of the dyed PET fabrics. These values
⁄ ⁄
were studied by using 0.5% dye concentration at 120 °C temperature, 15 MPa pressure at 1 h
time. In the first series of compounds, all the compounds exhibited excellent color strength and
dye fixation values. The dye fixation value for CNU-5 (93%) is significantly higher than those of
the other dyes. While for CNU-4 (75%, high molecular weight PEG chain,) is lower. One
explanation for this result could be that the dye molecule having lower molecular weight
possessing high solubility in supercritical carbon dioxide medium. Therefore, high solubility
enhanced the fixation value of the dyed fabric [39]. Compounds CNU-2 (5-carbon chain), CNU-
3
(4-carbon chain) and CNU-7 (3-carbon chain) also displayed excellent percentages of dye
fixation (88%, 86% and 83%, respectively) when compared to CNU-1 (6-carbon chain, 78%)
and CNU-6 (7-carbon chain, 76%). However, by increasing the alkyl chain (–CH group) length,
2
both solubility and dye adsorption will increase due to the nonpolar nature of the alkyl chain, but
we originally observed that the solubility is decreased for longer alkyl chains (chains longer than
5
carbons). This is because, in the solutions, long alkyl chains display high flexibility around the
molecule. For these long alkyl chains, the mixing process is generally controlled by the less
favorable entropy. Therefore, the formation of inter- or intramolecular hydrogen bonds enhances
mutual solute interactions. Hence, the solubility of the dyes in supercritical carbon dioxide is
decreased [40].
Our results indicate that all the compounds in the second series [CNU-8, CNU-9 and
CNU-10] were also exhibited good to moderate color strength and dye fixation values. The
(
K/S)dyed and dye fixation values for these three dyes ranked in the following order: CNU-8 >
CNU-9 > CNU-10. This could be attribute to that dye molecule structure (long alkyl chains) and
solubilities in supercritical carbon dioxide medium. In general, molecules with lower molecular
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0

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weights and lower polarities have higher solubilities in supercritical carbon dioxide [39]. In
addition, PET fabrics have hydrophobic characteristics and close structure with high
crystallinity. Therefore, carbon dioxide molecules were breaking the dense area of PET fabric
results swelling of the PET fabric. Thus our synthesized anthraquinone molecules easily
penetrate the swelled PET fabrics. The adsorption of the dyes increased, resulting in excellent
color shades.
3
3
.3. Fastness determination
.3.1. Washing fastness
The washing fastness represents the resistance of dyed fabrics to color changes during
washings. This test was performed according to the KS K ISO 105 - C06:2014 method. Herein,
we determined the color change of our dyed PET fabrics (specimen) and along with staining of
color on the adjacent samples of white acetate, cotton, nylon, polyester, acryl and wool. The test
specimen, along with the sample fabrics, was placed in a washing machine and treated with 0.4%
detergent at 40 ℃ for 30 min. After washing, the specimen was separated from the adjacent
fabrics, rinsed in cold water, squeezed and dried in air. Color changes of the dyed fabrics and the
staining of adjacent fabrics were evaluated by using an international grayscale. All the fabrics
dyed with CNU-1 to CNU-10 displayed remarkable grades (grades 4-5, Table 1), which indicate
that our synthesized dyes have excellent penetration capacity and good affinity for PET fabrics.
3
.3.2. Light fastness
The light fastness test provides information about the color fading of dyed fabrics when
exposed to known light. Herein, we used the KS K ISO 105 – B02:2015, xenon arc method. In
2
1

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this experiment, our dyed fabrics were exposed to light for 20 h, and the color changes were
determined by comparison with unexposed samples. The changes were measured by blue scales.
According to the results, all compounds in the first series (CNU-1 to CNU-7) exhibited excellent
light fastness (more than grade 4), whereas the second series of compounds (CNU-8 to CNU-10)
exhibited weak light fastness (grades 2-3 only) (Table 1). Because, first series of compounds
having 1,8-dihydroxy-4-amino functionality and it may form 6 membered rings (3 rings) with
quinone group via intramolecular hydrogen bond. Whereas the second series of compounds
having 1,4-diamino functionality and it may form only 2 rings. Therefore, more light energy is
required to break these 3 rings for CNU-1 to CNU-7 when compared to CNU-8 to CNU-10 (Fig.
7
) [41]. On the other hand, the lowest unoccupied molecular orbital (LUMO) frontier electron
density on the oxygen atoms [free –OH group] is lower for the dyes CNU-1 to CNU-7, which
gives them higher light fastness (4-5), whereas, the LUMO frontier electron densities on their
nitrogen atoms for the dyes CNU-8 to CNU-10 is higher (electron donating alkyl groups on N
atom), giving them lower fastness (2-3) [42]. Furthermore, the samples with dark shades showed
good resistance to light. Darker shaded fabrics contain a larger number of dye molecules, and the
small proportion of dye molecules that are involved in fading relative to the remaining content of
dye molecules helps in maintaining the depth of shade. On the other hand, in the lighter shades,
fewer dye molecules were present, and all are affected by exposure to light, which results in
reduced light fastness.
2
2

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Fig. 7. Ring formation via intramolecular hydrogen bonding
3
.3.3. Sweat fastness
Fastness to perspiration was determined by using the KS K ISO 105 – E04:2015
procedure. The test samples were placed between undyed fabrics (acetate, cotton, nylon,
polyester, acryl and wool) and were immersed in acid or base solutions at room temperature.
After 30 min, the samples were removed and placed between two plastic plates under a force of
approximately 4.5 kg. These plates were placed in an oven at 37 ℃ for 4 h. The test samples were
separated from the undyed fabrics, and the color changes of the dyed fabrics and the staining of
the undyed fabrics were measured using an international grayscale. The results are listed in
Table 2. All the synthesized compounds in the first and second series reached grades 4-5. This
indicates that our synthesized anthraquinone dyes have excellent affinity for PET fabrics.
2
3

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Table 1. Wash fastness and light fastness properties of dyes CNU-1 to CNU-10 on PET fabrics
a
Dye
Wash fastness
Light
fastness
4-5
b
Acetate
4-5
Cotton
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
Nylon
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
Polyester
Acryl
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
Wool
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
CNU-1
CNU-2
CNU-3
CNU-4
CNU-5
CNU-6
CNU-7
CNU-8
CNU-9
CNU-10
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
2
4-5
4-5
4-5
4-5
4-5
4-5
2
4-5
3
a
Rate for wash fastness: 3-5 (acceptable), 1–2 (not acceptable) and
Rate for light fastness: 4–8 (acceptable), 1–3 (not acceptable).
b
2
4

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Table 2. Sweat fastness properties of dyes CNU-1 to CNU-10 on PET fabrics
a
Sweat fastness
CNU CNU CNU CNU CNU CNU CNU CNU CNU CNU
-
1
-2
-3
-4
-5
-6
-7
-8
-9
-10
4-5
Acetate 4-5
Cotton 4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5 4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
4-5
Nylon
PET
4-5
4-5
4-5
4-5
Acidic
Acryl
Wool
Acetate 4-5
Cotton 4-5
Nylon
PET
4-5
4-5
4-5
4-5
Alka-
line
Acryl
Wool
a
Rate for sweat fastness: 3–5 (acceptable); 1–2 (not acceptable).
3
.4. Color characteristics
All the synthesized anthraquinone dyes were soluble in many common organic solvents,
such as cyclohexane, hexane, toluene, dichloromethane, acetone and tetrahydrofuran. These dyes
can form deep blue colored solutions in these solvents. The UV-absorption spectra were recorded
in acetone in the range of 400-800 nm, and the spectra showed single absorbance maxima for the
first series of compounds at 610 nm for CNU-1, 612 nm for CNU-2, 613 nm for CNU-3, 609 nm
2
5

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for CNU-4, 612 nm for CNU-5, 613 nm for CNU-6 and 614 for CNU-7 and double absorbance
maxima for the second series of compounds at 595 nm and 640 nm for CNU-8, 594 nm and 642
nm for CNU-9 and 597 nm and 652 nm for CNU-10 (Fig. 8). The reflectance spectra of the dyed
PET fabrics were also recorded using BaSO as the white standard. The reflectance curve
4
minimum values were centered at approximately 630 nm for CNU-1, 631 nm for CNU-2, 630
nm for CNU-3, 631 nm for CNU-4, 632 nm for CNU-5, 629 nm for CNU-6, 633 nm for CNU-7,
6
49 nm for CNU-8, 647 nm for CNU-9 and 655 nm for CNU-10.
2
6

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Fig. 8. a) UV-Vis absorption spectra of CNU-1 to CNU-7, b) UV-Vis absorption spectra of
-4
CNU-8 to CNU-10 in acetone (1×10 M).
3
.5. Color assessment
The assessment of the color of the supercritical dyed polyester fabrics was conducted using
the CIELAB system, which is based on the parameters of lightness (L*), chroma (C*), hue (h),
a* indicates that the degree of greenness (negative) and redness (positive) and b* indicates that
the degree of blueness (negative) and yellowness (positive). The color coordinates are listed in
Table 3. These coordinates indicate that our synthetic dyes have good levelness, brightness and
depth on polyester fabric. The color lightness values (L* values) of the dyes varied from 39.41 to
5
7.91. Compound CNU-9 is lighter than the other compounds. The color hues of dyes CNU-1 to
2
7

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CNU-9 on the polyester fabric are shifted toward the greenish direction on the red-green axis
according to the negative values of a*, and for CNU-10, the color hues were shifted toward the
reddish direction on the red-green axis based on the positive value of a*. The color hues of all
the synthesized dyes [CNU-1 to CNU-10] on polyester fabric are shifted to the bluish direction
on the yellow–blue axis according to the negative values of b*. The dyes under our investigation
displayed deep and bright intense hues in the range of blue color on polyester fabrics at the given
temperature. According to the color brightness (C*) values, compounds CNU-8 and CNU-4
exhibited brighter and duller colors, respectively, than the other compounds. The color strength
(
K/S) values of the anthraquinone dyes varied from 7.40 to 10.76.
Table 3. Color coordinates and color strength (K/S) of dyed polyethylene terephthalate fabrics
Dye
L*
a*
b*
C*
h
ꢀ ꢁ
⁄
CNU-1
CNU-2
CNU-3
CNU-4
CNU-5
CNU-6
CNU-7
CNU-8
CNU-9
CNU-10
45.90
41.30
46.36
43.29
48.50
41.67
39.41
45.41
57.91
50.61
-12.69
-10.46
-12.74
-13.67
-13.21
-9.84
-33.12
-32.06
-28.51
-21.62
-25.26
-33.05
-30.70
-38.68
-31.08
-35.66
35.47
33.73
31.23
25.58
28.51
34.48
32.53
39.11
32.28
35.66
249.09
251.93
245.93
242.39
237.71
253.43
250.67
261.54
254.33
270.41
8.3±0.3
9.3±0.3
9.0±0.4
7.5±.03
10.7±0.3
8.3±0.3
8.6±0.2
7.5±0.3
7.4±0.3
7.4±0.3
-10.77
-5.76
-8.72
0.26
2
8