One-pass process for the continuous dyeing

Document Sample
One-pass process for the continuous dyeing Powered By Docstoc
					doi: 10.1111/j.1478-4408.2008.00174.x


One-pass process for the continuous dyeing
of polyester⁄unmercerised cotton blends
with disperse⁄reactive dyes. Part 1:
Investigation of limited colour depth of the
dyed blend 
Arshad Mehmood, Duncan A S Phillips,*,à John A Bone and
John A Taylor
Textiles and Paper, School of Materials, University of Manchester, Manchester M60 1QD,
UK
Email: duncan.phillips.css@btconnect.com

Received: 21 October 2008; Accepted: 14 November 2008

In the continuous dyeing of polyester ⁄ cellulose blends, the trend over the last 20 years, towards shorter
production runs and greater numbers of fashion shades, has led to the development of more productive
processes, in particular, the use of a one-pass pad–dry–thermofix process for the application of disperse
and reactive dyes. However, there are limitations to such a one-pass process, of which the most
important is the limited colour depth that can be achieved on polyester ⁄ unmercerised cotton blends. The
current study examines the reasons for this limitation, with a view to either modifying the dyeing process
or designing superior dyes.




Introduction                                                                  From the late 1970s, a move towards smaller order
Blends of polyester with cotton have shown remarkable                      sizes for fashion outlets and, therefore, short continuous
worldwide growth since their first commercial production                    dyeing production runs [13–15], dramatically reduced the
in the late 1950s and early 1960s [1–3]. Continuous                        efficiency of machinery utilisation. Thus, in the late
dyeing technology for woven polyester ⁄ cotton fabrics was                 1970s and early 1980s, as a result of advances in
developed by simply adding a thermofixation stage, for                      continuous dyeing machinery to handle short lots [14–16]
the dyeing of the polyester component with disperse                        and improvements in the fixation efficiency of the
dyes, to the classical ‘chemical pad–steam’ process, which                 reactive dyestuffs [4,17–19], ‘one-bath, one-pass’
had been developed by DuPont in the 1940s for dyeing                       production processes (Figure 2) were introduced for
100% cotton with vat dyes [1,4]. DuPont’s ‘thermosol’                      dyeing polyester ⁄ cotton blends.
process (Figure 1), introduced in 1949, used disperse and                     Two approaches were adopted:
vat dyes and was used commercially in the 1950s for the                    – The development of new reactive dyes. Procion T
dyeing of fabric for military uniforms (a blend of 65:35                       dyes [20], introduced by ICI, were fixed under the
Dacron–cotton) [5–10].                                                         same chemical conditions as the disperse dyes (i.e.
  Reactive dyes, first introduced in the mid to late 1950s                      pH 5–6) (however, these dyes had limited commercial
[11,12], were initially simply substituted for vat dyes in the                 success during the 1980s, despite providing an elegant
existing ‘chemical pad–steam’ route, but soon were                             way of dyeing polyester ⁄ cellulose blends, and were
recognised as being second best to vat dyes in both colour                     later withdrawn;
fastness and application performance. Vinyl sulphone-                      – The use of conventional reactive dyes in a one-pass
based reactive dyes, first introduced by Hoechst as Remazol                     process, using mild alkaline conditions and in the
dyes, showed better build-up in the ‘chemical pad–steam’                       presence of urea (Figure 2).
process than monochlorotriazine (MCT) dyes, the other
leading reactive dye system for cotton. MCT dyes gave                      Small order sizes were not the only challenge facing the
optimum build-up in dry heat fixation processes,                            continuous dyeing industry. At the same time, increasing
particularly in the ‘two-pass’ process for (i) ‘pad–dry–                   demands for higher quality, including more severe
thermofix’ with option reduction clear (disperse dyes) or (ii)              fastness requirements and minimum adverse impact on
‘pad–dry–wash-off’ (reactive dyes, urea and alkali, baked for              the environment, had to be satisfied.
approximately 1.5 min at 165 °C with MCT dyes).                              Various one-pass dyeing processes such as TTN [22],
                                                                           RTN [23], AT [4], and 2DA [24] were introduced by DyStar,
                                                                           ICI, Bayer and Sandoz, respectively. Improvements were
                                                                           delivered by these process, such as urea being replaced by
                                                                           non-toxic and non-hygroscopic dicyandiamide [21,25],
  For Part 2 of this study, see the next paper in this issue
                                                                           which is stable at a temperature of 200–210 °C. Alkali-
à Present address: Colour Synthesis Solutions Ltd, Hexagon                 clearable disperse dyes [3], such as Dispersol ⁄ Dianix SF
Tower, Blackley, Manchester M9 8ZS, UK                                     and XF, whose stain on cotton is removed at the same time


ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52                       43
Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



                                                    I.R. dryer,
                                                    To reduce       Chemical pad
                                                    moisture        NaOH + Na2S2O4 (hydros)
                               Padder               to 50%



                                               Drying     Thermofix               Steaming
                                Disperse/vat                                                       Washing
                                               100–110 °C 200–215 °C              100–150 °C

Figure 1 ‘Chemical pad–steam’ route for continuous dyeing of polyester ⁄ cotton blend dyeing with disperse ⁄ vat dyes




                                Disperse/reactive       Dry            Thermofix
                                                        60 s at 110 °C 60 s at 210 °C          Wash-off

Figure 2 One-pass continuous process for polyester ⁄ cotton blend dyeing



as the hydrolysed reactive dyes (during the washing                          Dye synthesis
process), satisfied the higher fastness requirements.                         The dyes synthesised in this study are shown in Table 2.
  However, despite these improvements, there were still                      Dyes 1, 2 and 3 were prepared from the dichloro-s-
limitations to such one-pass continuous dyeing processes.                    triazine (DCT) of the parent dye amino-8-hydroxy-
For example, such one-stage processes were unable to                         naphthalene-3, 6-disulphonic acid and dye 4 was
achieve heavy depths of shade on polyester ⁄ unmercerised                    prepared from Procion Red PX-4B (Figure 3).
cotton blends, although dyeing heavy shades on
polyester ⁄ mercerised cotton blends was regarded as being                   Table 2 Dyes synthesised in this study
less of a problem. The present study was therefore
conducted to determine whether it was the disperse dyes                                                                            X
or the reactive dyes (or both) that were responsible for                                             SO3H
the difficulties in achieving heavy depths of shade when                                                                       N        N
continuously dyeing polyester ⁄ unmercerised cotton                                                       H           H
                                                                                                     N         O          N        N       Y
blends in a one-pass process. This was carried out with a
                                                                                                     N
view to either modifying the process or designing
improved dyes. The TTN process, introduced by DyStar
                                                                                                 SO3H                              SO3H
to dye polyester ⁄ cotton blends, was used as the
benchmark, one-pass continuous dyeing process in this                         Dye                                 X                              Y
study.                                                                                                            +
                                                                                                                  N
                                                                              1                                                             OH
Experimental                                                                                                                –
                                                                                                                          CO2
Commercial dyes
                                                                              2                           Cl                                SCH2CO2H
The various disperse and reactive commercial dyes used
in this study, as shown in Table 1, were obtained from                                                            +
                                                                                                                  N
DyStar (Germany).                                                             3                                                             SCH2CO2H
                                                                                                                            –
                                                                                                                          CO2
                                                                                                                  +                            NH
                                                                                                                  N                                  CH3
Table 1 Commercial dyes used
                                                                              4a
                                                                                                                            –
                                                                                                                          CO2
Commercial name                 Category

                                                                             a Parent dye used in the preparation of dye 4 was Procion Red PX-4B
Dianix Rubine CC                Alkali-stable disperse dye
                                                                             with nicotinic acid
Dianix Yellow Brown CC          Alkali-stable disperse dye
Dianix Navy CC                  Alkali-stable disperse dye
Dianix Yellow Brown XF          Alkali-sensitive disperse dye                                                                 Cl
Dianix Red CBN SF               Alkali-sensitive disperse dye
                                                                                                    SO3H
Dianix Blue XF                  Alkali-sensitive disperse dye                                                             N        N
Dianix Deep Red SF              Alkali-sensitive disperse dye                                             H       H
Procion Yellow PX-R             Monofunctional (MCT) reactive dye                                   N         O       N       N        NH
Procion Red PX-4B               Monofunctional (MCT) reactive dye                                   N                                          CH3
Procion Navy PX-2R              Monofunctional (MCT) reactive dye
Levafix Yellow CA                Hetero bifunctional reactive dye
Levafix Red CA                   Hetero bifunctional reactive dye                                SO3H                          SO3H
Levafix Navy CA                  Hetero bifunctional reactive dye
                                                                             Figure 3 Structure of Procion Red PX-4B


44                          ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52
                                                                            Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



  These dyes were also converted to their equivalent                pH stabilised, the temperature was raised slowly to
hydroxyl–triazine    compounds     to aid compound                  10–15 °C and, after stirring for ca. 2 h at this temperature,
identification in the HPLC analyses.                                 the product was precipitated out by adding 20% w ⁄ v salt to
                                                                    the reaction mixture. The solid, 1-hydroxy-2-(2-sulpho-
Synthesis of the parent DCT reactive dye                            phenylazo)-8-(4-chloro-6-[carboxymethyl-thio-s-triazine-2-
A freshly prepared solution of 1-amino-8-hydroxy-                   ylamino)-naphthalene-3,6-disulphonic acid, tetrasodium
naphthalene-3, 6-disulphonic acid (H-acid, 116.82 g,                salt (2) was collected and dried under reduced pressure,
0.302 mol) at pH 5 was added, at 0–5 °C, to a freshly               over calcium chloride. Yield: 46 g, strength 52%, Mole
prepared, well-stirred, suspension of cyanuric chloride             In 1491, purity 94%, m ⁄ z 705 (M)2H)), 727 (M)H+Na))
(99%, 28.5 g, 0.153 mol) in acetone (150 ml) and ice ⁄ water        and 749 (M)H+Na)), kmax (water) 533, emax
(150 ml). The mixture was stirred for 1 h, at 0–5 °C,               29 000 dm3 mol)1 cm)1.
allowing the pH to fall. After 2 h, the reaction was complete
as indicated by a negative test with Ehrlich’s reagent.             Synthesis of dye 3
   Sodium nitrite (2 M, 78.75 ml, 0.15 mol) was added in a          Nicotinic acid (99.5%, 2.18 g, 0.0177 mol) was added, at
freshly prepared solution of 2-aminobenzenesulphonic                room temperature, to a freshly prepared solution of dye 2
acid (orthanilic acid, 80.6%, 32.23 g, 0.15 mol) in an              (strength 52%, 28.2 g, 0.0189 mol) in water (200 ml) at
aqueous solution of bicarbonate (100 ml) at pH 6 and this           pH 5 – 0.2. The reaction mixture was stirred at 50 °C for
was added to concentrated hydrochloric acid (32.75 ml,              3 h and monitored using HPLC. The solution was allowed
0.375 mol) at 0–5 °C. The mixture was stirred at this               to cool to 20 °C and the desired quaternary salt was
temperature for 1 h, after which diazotisation was                  precipitated by adding a mixture of isopropanol and
completed, as indicated by a negative test with Ehrlich’s           water (50% v ⁄ v) to the cold reaction mixture. The solid,
reagent. Excess of nitrous acid was destroyed by adding             1-hydroxy-2-(2-sulphophenylazo)-8-(4-[3-carboxypyridinium]-
sulphamic acid. The resulting diazonium salt was added to           6-[carboxymethylthio-s-triazin-2-ylamino)-naphthalene-3,6-
freshly prepared dichlorotriazinyl-H-acid at 0–5 °C, the            disulphonic acid, tetrasodium salt (3) was collected and
reaction mixture was allowed to warm to room                        dried under reduced pressure, over calcium chloride.
temperature while the pH was maintained at 6.0–6.5 using            Yield: 9.8 g, strength 77%, Mole In 1151, purity 98%, m ⁄ z
aqueous sodium carbonate (2N). The reaction mixture was             792 (M)H)) and 814 (M)H+Na)), kmax (water) 533, emax
stirred for 2 h at room temperature, then the product was           30 000 dm3 mol)1 cm)1.
precipitated out by adding salt (25% w ⁄ v, portionwise)
with stirring, over 45 min. The solid was collected, washed         Synthesis of dye 4
with acetone, buffered with solid phosphate buffer [2 parts         Nicotinic acid (99.5%, 3.1 g, 0.025 mol) was added, at
potassium phosphate (KH2PO4) + 1 part sodium                        room temperature, to a solution of Procion Red PX-4B
phosphate (Na2HPO4); 5% w ⁄ w] and dried at room                    (Figure 3) (strength 70%, 24.5 g, 0.0217 mol) in water
temperature under reduced pressure. Yield: 95.8 g,                  (200 ml). After stirring the reaction mixture for 6 h at 80–
strength 62%, Mole In (i.e. the number of grams containing          85 °C and at pH 6.0–6.5, the solution was allowed to cool
1 mole of dye [27]) 1168, purity 98%, m ⁄ z 649 (M)2H)),            to 20 °C and the desired product was precipitated out
671 (M)H+Na)) and 693 (M)H+Na)), kmax (water) 533,                  by adding 20% w ⁄ v salt to the cold reaction mixture
emax 30 000 dm3 mol)1 cm)1.                                         and stirring overnight. The solid, 1-hydroxy-2-(2-sulpho-
                                                                    phenylazo)-8-(4-[3-carboxypyridinium]-6-[N-methylphenyl-
Synthesis of dye 1                                                  amino]-s-triazin-2-ylamino)-naphthalene-3,6-disulphonic
Nicotinic acid (strength 99.5%, 10.6 g, 0.085 mol) was              acid, tetrasodium salt (4), was collected and dried under
added slowly at room temperature to a freshly prepared              reduced pressure, over calcium chloride. Yield: 38 g,
solution of the dichloro-s-triazine (DCT dye, strength              strength 39%, Mole In 1807, purity 94%, m ⁄ z 807
62%, 46 g, 0.0408 mol) in water (300 ml) at pH 6–6.5.               (M)H)), 829 (M)H+Na)), kmax (water) 533, emax
After 25 min of stirring at room temperature, the reaction          29 000 dm3 mol)1 cm)1.
mixture was warmed slowly to 35 °C with control by
HPLC. After 3 h, the mixture was cooled to room                     Hydroxy triazine dyes
temperature and the product was precipitated by adding              Hydrolysed dyes 1a, 2a ⁄ 3a and 4a (Table 3) were also
20% w ⁄ v salt (60 g) to the cold stirred reaction solution.        prepared by dissolving 1–2 g of the parent dyes (dyes 1, 2
The solid, 1-hydroxy-2-(2-sulphophenylazo)-8-(4-[3-carboxy-         and Procion Red PX-4B, respectively) in 2 N sodium
pyridinium]-6-hydroxy-s-triazin-2-yl amino)-naphthalene-            carbonate (100 ml) at 80 °C. The resultant compounds
3,6-disulphonic acid, tetrasodium salt (1) was collected            were confirmed by mass spectrometry, with molecular
and dried under reduced pressure, over calcium                      ions at m ⁄ z 613 (M)H), 635 (M)H+Na)), 657
chloride. Yield: 62 g, strength 34%, Mole In 2462,                  (M)H+Na)) for dye 1a, 687 (M)H)), 709 (M)H+Na)) for
purity 96%, m ⁄ z 718 (M)H), kmax (water) 533, emax                 dyes 2a ⁄ 3a and 703 (M)H)), 725 (M)H+Na)) for dye 4a.
30 000 dm3 mol)1 cm)1.                                              HPLC retention times of the hydrolysed species were
                                                                    noted and then used in the identification of the
Synthesis of dye 2                                                  hydrolysis products formed during the dyeing process.
Thioglycolic acid (3.2 g, 0.0028 mol) was added gradually,
at 0–5 °C, to a freshly prepared solution of the dichloro-          Fabrics and chemicals
s-triazine dye (strength 62%, 30 g, 0.0257 mol) in water            Unmercerised cotton fabric (100%) (1 ⁄ 1 plain weave)
(200 ml) while the pH was maintained at 7 Æ 0.2. Once the           and 67:33 woven polyester ⁄ unmercerised cotton blend


ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52                             45
Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends


Table 3 Hydrolysed dyes used in this study




                                                                                                                                                                                                                                                                                                                                                                              Urea (100–150 g ⁄ l)
                                                                                                                                                                                                                                                                                                                                                   Urea (50–100 g ⁄ l)



                                                                                                                                                                                                                                                                                                                                                                                                         Dicyandiamide
                                                  X




                                                                                                                                                                                                                                                                     Humectants




                                                                                                                                                                                                                                                                                                                                                                                                          (15 g ⁄ l)
                         SO3H
                                              N       N




                                                                                                                                                                                                                                                                                                 None

                                                                                                                                                                                                                                                                                                                   None
                              H       H
                         N        O       N       N       Y
                         N




                                                                                                                                                                                                                                                                                                                                                                                                         Sodium bicarbonate (10–20 g ⁄ l)
                                                                                                                                                                                                                                                                                                                                                    + sodium bicarbonate (10 g ⁄ l)
                                                                                                                                                                                                                                                                                                                                                   Sodium carbonate(10–15 g ⁄ l)
                                                                                                                                                                                                                                                                                                                                                   Sodium carbonate (0–10 g ⁄ l)
                    SO3H                          SO3H




                                                                                                                                                                                                                                                                                                                   Sodium bicarbonate (10 g ⁄ l)
                                                                              Table 4 Application conditions and dyeing auxiliaries used in both the two-bath, two-pass and one-pass (TTN) continuous dyeing processes for disperse and reactive dyesa
Dye                       X                           Y

1a                        OH                          OH

2a/3a                     OH                          SCH2CO2H




                                                                                                                                                                                                                                                                     Alkali


                                                                                                                                                                                                                                                                                                 None
                                                          NH
4a                        OH
                                                           H3C




                                                                                                                                                                                                                                                         pH of pad




                                                                                                                                                                                                                                                                                                                                                                              11.0–11.5
                                                                                                                                                                                                                                                                                                                                                   8.5–10.0
                                                                                                                                                                                                                                                                                                                   8.0–9.0




                                                                                                                                                                                                                                                                                                                                                                                                         8.0–9.0
                                                                                                                                                                                                                                                         liquor


                                                                                                                                                                                                                                                                                                 4.5
were used in this study. Eriopon R (anionic surfactant
agent; Huntsman, UK) was used as a soaping agent in

                                                                                                                                                                                                                                                         Baking ⁄ thermofixation
the washing-off process. Sodium sulphate (anhydrous,
                                                                                                                                                                                                                                                         time ⁄ temperature
99%) and sodium carbonate (anhydrous, >99%) were


                                                                                                                                                                                                                                                                                                 1 min at 210 °C

                                                                                                                                                                                                                                                                                                                   1 min at 210 °C


                                                                                                                                                                                                                                                                                                                                                   1 min at 150 °C

                                                                                                                                                                                                                                                                                                                                                                              1 min at 160 °C

                                                                                                                                                                                                                                                                                                                                                                                                         1 min at 210 °C



                                                                                                                                                                                                                                                                                                                                                                                                                                            a In addition, 10 g ⁄ l borax was added to the pad liquor of the one-pass (TTN) continuous dyeing process, as recommended by DyStar
obtained from Fisher Chemicals (UK). Sodium hydroxide
reagent ACS and nicotinic acid (99.5%) from Acros
Organics (UK), dicyandiamide (99%) from Aldrich (UK)
and borax pentahydrate was obtained from Borax Europe
Limited.
                                                                                                                                                                                                                                                                     Drying time ⁄ temperature




Dyeing procedure
Specimen fabric samples (10 · 30 cm) of the cotton and
polyester ⁄ cotton blend were padded in 50 ml of dye
                                                                                                                                                                                                                                                                                                 1 min at 110 °C

                                                                                                                                                                                                                                                                                                                   1 min at 110 °C


                                                                                                                                                                                                                                                                                                                                                   1 min at 110 °C

                                                                                                                                                                                                                                                                                                                                                                              1 min at 110 °C

                                                                                                                                                                                                                                                                                                                                                                                                         1 min at 110 °C
solution using a laboratory pad mangle (Werner Mathis,
Zurich, Switzerland) with nip-pressure set to obtain
60% wet pick-up for 67:33 polyester ⁄ unmercerised
cotton blends and 70–80% for 100% unmercerised
cotton. The padded fabrics were dried in a Werner
Mathis laboratory oven and thermofixed ⁄ baked in a
                                                                                                                                                                                                                                                                                                 67 ⁄ 33 polyester ⁄ unmercerised

                                                                                                                                                                                                                                                                                                 67 ⁄ 33 polyester ⁄ unmercerised




Benz stenter (Zurich, Switzerland) at the recommended
                                                                                                                                                                                                                                                                                                                                                   100% unmercerised cotton

                                                                                                                                                                                                                                                                                                                                                                              100% unmercerised cotton

                                                                                                                                                                                                                                                                                                                                                                                                         100% unmercerised cotton




temperature (Table 4). The conditions used in this
study were those recommended by DyStar for the one-
pass (TTN) continuous process and for the conventional
two-bath, two-pass continuous process [22]. The
                                                                                                                                                                                                                                                                                                  cotton blend

                                                                                                                                                                                                                                                                                                  cotton blend




reduction process was carried out at 70 °C for 10 min,
using 3 g ⁄ l NaOH and 3 g ⁄ l sodium hydrosulphite.
                                                                                                                                                                                                                                                                     Substrate




Batchwise washing-off processes were carried out in the
laboratory, using a through cold rinse (until essentially
no further colour washed off), a warm rinse (5 min at
70 °C), a ‘soap boil’ using 1–2 g ⁄ l soaping agent
                                                                                                                                                                                                                                                                                                  dyeing process for reactive dyes




(Eriopon R) at 100 °C for 10 min followed by a cold
                                                                                                                                                                                                                                                                                                 (Two-bath, two-pass) process

                                                                                                                                                                                                                                                                                                 (Two-bath, two-pass) process
                                                                                                                                                                                                                                                                                                  dyeing process for disperse




rinse.
                                                                                                                                                                                                                                                                                                 One-pass (TTN) continuous




                                                                                                                                                                                                                                                                                                 One-pass (TTN) continuous
                                                                                                                                                                                                                                                                                                  process for disperse dyes




Determination of the percentage fixation of the reactive
                                                                                                                                                                                                                                                                                                  for Procion PX dyes
                                                                                                                                                                                                                                                                                                 (Two-bath, two-pass)




                                                                                                                                                                                                                                                                                                  for Levafix CA dyes




dyes on cotton
A known amount of a given reactive dye was dissolved
in 70% w ⁄ w sulphuric acid solution [26]. The
absorbance was measured on Camspec M350 double-
                                                                                                                                                                                                                                                                     Process




                                                                                                                                                                                                                                                                                                  dyes




beam ultraviolet visible spectrophotometer (Camspec,
Cambridge, UK) at the wavelength of maximum


46                            ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52
                                                                              Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



absorbance (kmax), using 70% w ⁄ w of sulphuric acid                   Analytical methods
solution as reference solvent. The solution was diluted                HPLC analyses were performed with a Hewlett
successively by a factor of 2, 4 and 8 and the                         Packard1100 series instrument fitted with a quaternary
absorbance measured. In each case, the absorbance was                  pump. The column was a purospher RP-18 (5 lm) packing
proportional to the concentration of dye, indicating                   with a LiChroCart 125-4 HPLC column cartridge. The
adherence to Beer–Lambert’s law.                                       mobile phase flow rate was 2 ml ⁄ min and the injection
  Subsequently, accurately weighed samples of dyed                     volume was 5 ll. Either dicyclohexyl ammonium
cotton (0.15–0.2 g) were dissolved, over 3 h, in 70% w ⁄ w             phosphate (0.25%) or cetavlon (0.5%) was used as an ion–
sulphuric acid (50 ml) at room temperature. From the                   pair agent. Samples were analysed using a diode array
absorbance of the resulting solution of degraded, dyed                 detector. An area percentage figure obtained by the HPLC
cotton, it was possible to determine the concentration of              was taken as the percentage of organic purity of the end
dye present on the dyed cotton sample and, knowing the                 products. Other details are listed in Table 5. Gradient and
concentration of dye applied, the percentage fixation of                isocratic methods (Table 5) were used either to separate
reactive dye.                                                          different dye species or to follow reactions by HPLC.
                                                                          Mass spectra were recorded with a Micromass
Extraction of unfixed dye from the fabric                               Instruments     LCT      orthogonal     time-of-light mass
The unfixed dye species of the most reactive dyes (dye 3                spectrometer fitted with a Z-spray electrospray ion source
and dye 4) were extracted from the dyed fabric using low               operating in negative mode at 3 kV needle potential.
washing temperature in order to avoid the possibility of               Nitrogen was used as a drying and sheath gas. Infusion
hydrolysis during the extraction process.                              was at a rate of 20 ml ⁄ min with a Harvard Instruments
  For this purpose, 2 g of dyed fabric was washed at                   syringe pump for sample introduction.
40 °C with vigorous stirring in a 20-ml of 25% solution of                The colour strength of the dyed fabric was assessed
urea for 40–60 min. The pH level of the liquors was                    using a Datacolor International Spectraflash 600
maintained at 6.5 using a mixed phosphate buffer                       spectrophotometer (Datacolor, Zurich, Switzerland) under
solution (w ⁄ w) [2 parts potassium dihydrogen phosphate               D65 ⁄ 10 conditions. Four reflectance readings were taken
(KH2PO4) + 1 part disodium phosphate (Na2HPO4)]. The                   at different positions on the dyed fabric and expressed as
unfixed dye species of dye 1, dye 2 and Procion Red                     K ⁄ S values.
PX-4B were extracted from the dyed fabric by washing at                   The absorbance of the reactive dyes, in aqueous
80–90 °C for 1 h at a neutral pH using the above-                      solution, was recorded using a Camspec M350 double-
mentioned phosphate buffer solution.                                   beam ultraviolet visible spectrophotometer (Camspec).



Table 5 HPLC analysis conditions and methods


                                                                                                                                  Temperature
Reaction                                                         Method           Mobile phase                                    (oC)


Synthesis of dyes 1, 2, 3 and 4                                  Gradient         Acetonitrile ⁄ dicyclohexyl                     40
Hydrolysis of dyes 1, 2, 3 and Procion Red PX-4B                 Gradient          ammonium phosphate (0.25%)
Separation of dye species (hydrolysed and reactive form)         Gradient
 extracted from fabric dyed with dyes 1, 2, 3 and Procion
 Red PX 4B
Hydrolysis of dye 4                                              Isocratic        Cetonitrile ⁄ cetavlon (0.5%)                   30
Separation of dye species (hydrolysed and reactive form)         Isocratic
 extracted from fabric dyed with dye 4


Gradient method


                                                                                                                        % Dicyclohexyl
Time                                                   %                                                                ammonium
(min)                                                  Acetonitrile                                                     phosphate (0.25%)


0                                                      30                                                               70
5                                                      50                                                               50
6                                                      40                                                               60
7                                                      30                                                               70


Isocratic method

Time                                                    %                                                                    % Cetavlon
(min)                                                   Acetonitrile                                                         (0.5% solution)

0–7                                                     30                                                                   70



ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52                               47
Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



  The Mole In, that is, the number of grams containing                      influence on the uptake of the disperse dyes. However,
1 mole of dye [31], of the synthesised dyes was                             this small difference in colour yield remained almost
determined by elemental analyses for carbon, hydrogen,                      constant across the depths (5–40 g ⁄ l) applied. For
nitrogen and sulphur, carried out on a Carlo Erba 1108                      example, at a heavy depth of shade, the difference in
elemental analyser. Chlorine analysis was by automatic                      colour yield was 5–8% for ‘alkali-sensitive’ disperse dyes
argentometric   titration   following   oxygen    flask                      and 3–6% for ‘alkali-stable’ disperse dyes.
decomposition.
                                                                            Reactive (monofunctional and bifunctional) dyes: To
                                                                            compare the performance of a series of Procion PX and
Results and Discussion                                                      Levafix CA reactive dyes in a one-pass (TTN) continuous
                                                                            dyeing process and a conventional pad–dry–bake process,
Determination of the dye class responsible for the
                                                                            the build-up in visual colour yield (at 5,10, 20 and 40 g ⁄ l
limited colour depth on polyester/unmercerised cotton
                                                                            depth applied) of these dyes on 100% unmercerised
blends
                                                                            cotton was studied.
Comparison of the visual colour yield by conventional and                      Build-up profiles (Figures 6 and 7) indicated that
one-pass continuous dyeing process                                          reactive dyes give a lower colour yield on unmercerised
‘Alkali-stable’ and ‘alkali-sensitive’ disperse dyes: To                    cotton in the one-pass (TTN) continuous dyeing process
compare the yield from a series of disperse dyes in                         than in the conventional pad–dry–bake process. The
different continuous dyeing processes, a 67:33                              loss of colour yield increased with the concentration of
polyester ⁄ unmercerised cotton blend was dyed using a                      dye, with considerably lower colour yields (12–45%)
conventional process at pH 4.5 (adjusted using 1% w ⁄ w                     being observed at the heavier depths (40 g ⁄ l) of shade.
acetic acid) and a one-pass (TTN) continuous process (at                    This was particularly noticeable in the case of Procion
pH 8.5–9.0), adding 10 g ⁄ l bicarbonate. The cotton                        Yellow PX-R and Levafix Yellow CA (both dyes being
component of the blend was ‘burnt out’ in 70% w ⁄ w                         based on the same chromophore) and could be
sulphuric acid at room temperature [28] and colour yields                   attributable to factors such as solubility, diffusion and
obtained on the polyester ‘skeletons’ were compared.                        reactivity.
  Only a small loss in colour yield was observed                               The lowering in colour yield of the Levafix CA (hetero
(Figures 4 and 5) in the one-pass (TTN) continuous                          bifunctional) dyes, with the exception of the Levafix
process (pH 8.5–9.0) compared with that obtained from                       Yellow CA, was not as great as that for the Procion PX
the conventional process (pH 4.5) with both ‘alkali-stable’                 (monofunctional) dyes. However, the difference in colour
and ‘alkali-sensitive’ disperse dyes. Inevitably, this small                yields obtained from these two processes was sufficient to
loss in colour yield was as a result of the pH having an                    suggest that the reason for the inability of the one-pass



  (a) 16                                                                    (b) 25
      14                                                                           20
      12
      10                                                                           15
                                                                             K/S
     K/S




       8
                                                                                   10
       6
       4                                                                            5
       2
       0                                                                            0
                0      10         20           30        40            50               0     10       20         30       40       50
                                Depth applied, g/l                                                   Depth applied, g/l
            Control process     One-stage (TTN) continuous process                 Control process     One-stage (TTN) continuous process
  (c)                                                                       (d) 20
           18
                                                                                18
           16                                                                   16
           14                                                                   14
           12                                                                   12
                                                                             K/S




           10
     K/S




                                                                                10
            8                                                                    8
            6                                                                    6
            4                                                                    4
            2                                                                    2
            0                                                                    0
                0      10       20        30        40            50                    0     10       20        30       40      50
                              Depth applied, g/l                                                     Depth applied, g/l
           Control process      One-stage (TTN) continuous process                 Control process     One-stage (TTN) continuous process

Figure 4 Comparison of the build-up (visual colour yield, K ⁄ S) of ‘alkali-sensitive’ disperse dyes, (a) Dianix Yellow Brown XF, (b)
Dianix Blue XF, (c) Dianix Red CBN-SF and (d) Dianix Deep Red SF in a conventional two-pass process (pH 4.5) and one-pass (TTN)
process (pH 8.5–9.0)


48                            ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52
                                                                                                          Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



 (a)                                                                             (b)
        25

        20                                                                                25
                                                                                          20
        15
  K/S



                                                                                          15




                                                                                    K/S
        10
                                                                                          10
        5                                                                                  5
        0                                                                                  0
             0          10         20        30        40        50                             0           10         20          30      40        50
                                 Depth applied, g/l                                                                Depth applied, g/l
            Control process       One-stage (TTN) continuous process                                Control process             One-stage (TTN) continuous process
                                          (c) 25

                                                20

                                                15
                                          K/S




                                                10

                                                 5

                                                 0
                                                      0            10   20        30      40         50
                                                                      Depth applied, g/l
                                                      Control process   One-stage (TTN) continuous process

Figure 5 Comparison of the build-up (visual colour yield, K ⁄ S) of ‘alkali-stable’ disperse dyes, (a) Dianix Navy CC, (b) Dianix Rubine CC
and (c) Dianix Yellow Brown CC in a conventional two-pass process (pH 4.5) and in a one-pass (TTN) continuous process (pH 8.5–9.0)


(a) 21                                                                                    (b) 25

       18
                                                                                                20
       15
       12                                                                                       15
                                                                                          K/S
 K/S




        9                                                                                       10
        6
                                                                                                 5
        3
        0                                                                                        0
            0           10         20          30                   40         50                    0            10          20          30              40          50
                                  Depth applied, g/l                                                                         Depth applied, g/l
                 P.D.B process      One-stage (TTN) continuous process                                    P.D.B process         One-stage (TTN) continuous process

                                                (c) 25


                                                      20

                                                      15
                                                K/S




                                                      10

                                                      5

                                                      0
                                                           0            10       20                  30           40          50
                                                                               Depth applied, g/l
                                                               P.D.B process     One-stage (TTN) continuous process

Figure 6 Comparison of the build-up (visual colour yield, K ⁄ S) of monofunctional reactive dyes, (a) Procion Yellow PX-R, (b) Procion
Red PX-4B and (c) Procion Navy PX-2R applied by a pad–dry–bake (P.D.B) process and the one-pass (TTN) continuous dyeing process


(TTN) continuous dyeing process to give heavy depths,                                        The poor performance from the reactive dyes could be
economically, on polyester ⁄ unmercerised cotton was                                       as a result either of the reactivity of the dyes being too
associated with the performance of the reactive dyes and                                   low for efficient fixation at pH 8.5–9.0 or of slow
not the disperse dyes.                                                                     diffusion to a reactive site, as a result of either too high


ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52                                                           49
Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



(a) 12                                                                              (b) 25

       10                                                                                  20

        8
                                                                                           15




                                                                                     K/S
 K/S




        6
                                                                                           10
        4
                                                                                            5
        2

        0                                                                                   0
            0           10        20            30          40           50                     0           10           20       30        40        50
                                Depth applied, g/l                                                               Depth applied, g/l
                P.D.B process    One-stage (TTN) continuous process                                 P.D.B process        One-stage (TTN) continuous process


                                         (c) 25

                                                20

                                                15
                                          K/S




                                                10

                                                 5

                                                 0
                                                     0        10           20          30              40           50
                                                                         Depth applied, g/l
                                                         P.D.B process          One-stage (TTN) continuous process

Figure 7 Comparison of the build-up (visual colour yield, K ⁄ S) of hetero bifunctional reactive dyes, (a) Levafix Yellow CA, (b) Levafix
Red CA and (c) Levafix Navy CA applied by a pad–dry–bake (P.D.B) process and the one-pass (TTN) continuous dyeing process


substantivity or too low solubility. As the difference in                          methodology, rate constants, for hydrolysis, were
colour yields for the two dyeing processes was smaller in                          determined at three different temperatures (Table 6).
the case of the more reactive Levafix CA dyes (the dyes                             From these data the temperature, at which the rate
comprising a combination of a reactive system based on a                           constant for hydrolysis of each dye was a value of
fluoroheterocyclic group and a modified vinyl sulphone                               0.0006 min)1 was determined. The relative rate constants,
group [29]), it suggested that ‘reactivity’ might be the key                       and thereby the reactivities of the different reactive groups
factor in determining colour yield. Further work was                               of dyes 1–4 and Procion Red PX-4B, are listed in Table 6.
therefore carried out to determine if increasing the level                            As can be seen in Table 6, the reactivity of the novel
of reactivity of the MCT reactive dyes would improve the                           reactive dyes was very much higher (1.4–5 times) than
colour yield in the one-pass (TTN) continuous dyeing                               that of Procion Red PX-4B. However, these dyes exhibited
process. For this purpose, a series of s-triazinyl dyes,                           either equal or slightly less (%) fixation yield at the end
based on the same chromophore (Table 2), were                                      of the dyeing process (Figure 8). Compared with the least
synthesised. Their relative order of reactivity was                                reactive dye (Procion Red PX-4B), reactive dyes with
determined and their fixation yields on unmercerised                                higher reactivity fixed more rapidly but also hydrolysed
cotton, after application by the one-pass (TTN)                                    more quickly. Furthermore, the trend in fixation yield
continuous dyeing process, was compared with that of                               shown by the dyes was not consistent with their relative
commercial Procion Red PX-4B.                                                      levels of reactivity. Dye 4, which is marginally more
                                                                                   reactive than dye 2, exhibited much less fixation onto the
Comparison of the fixation yield and dye species of the                             cotton and much more hydrolysis.
dyes 1–4 and Procion Red PX-4B                                                        However, the presence of dyes 1–4 in their reactive
The fixation yield and dye species present at each stage                            form (20–30%) at the end of the dyeing process,
of the dyeing process (30 s, 60 s drying and 30 s, 60 s                            indicated that hydrolysis of such highly reactive dyes
thermofixation), when applying a heavy depth (40 g ⁄ l) of                          was not the major reason for the failure of these
shade to unmercerised cotton with dyes 1–4 and Procion                             dyes to improve the fixation yield. The reason for this
Red PX-4B (based on the same chromophore) was                                      inability could be the insufficient diffusion of the dye
assessed (Figure 8).                                                               molecules into the unmercerised cotton fibres within
  In addition, the rate constant for the hydrolysis of the                         the limited time period (the fibre becomes ‘dry’ after
reactive groups of the dyes was determined by assessing                            30–40 s). Indeed, the dyeing of cellulose with reactive
the rate of disappearance of the starting dye and the                              dyes is a true heterogeneous process, where the number
formation of the hydrolysed product, in aqueous sodium                             of cellulose hydroxyl groups, participating in the
carbonate, as previously described [30,31]. Using this                             reactive dye–cellulose reaction, is limited by dye


50                              ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52
                                                                                                                                       Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends



                                                                                                                       Dye 2
                                                                                                                      100
               Dye 1                                                                                                                                               Fixation
                                                                         Fixation
              100                                                                                                            90
                                                                                                                                                                   Hydrolysed dye
                                                                         Hydrolysed dye
              90                                                                                                             80                                    Reactive dye
                                                                         Reactive dye
               80
                                                                                                                             70
               70
                                                                                                                             60




                                                                                                         Percentage
 Percentage




               60
               50                                                                                                            50

               40                                                                                                            40
               30
                                                                                                                             30
               20
                                                                                                                             20
               10
                                                                                                                             10
                 0
                                  0s        30s      60s                 30s          60s                                     0
                                            Drying at 110 °C Thermofixation at 210 °C                                                  0s       30s       60s          30s       60s
                                                                                                                                              Drying at 110 °C       Thermofixation at 210 °C
                                                           Time                                                                                                 Time

                                                                                                                              Dye 4
                            Dye 3                                                                                            100
                            100                                                                                                                                              Fixation
                                                                                                                              90
                             90                                          Fixation                                                                                            Hydrolysed dye
                                                                                                                              80
                             80                                          Hydrolysed dye                                                                                      Reactive dye
                             70                                                                                               70
                                                                         Reactive dye
               Percentage




                                                                                                                Percentage




                             60                                                                                               60
                             50                                                                                               50
                             40                                                                                               40
                             30                                                                                               30
                             20
                                                                                                                              20
                             10
                                                                                                                              10
                              0
                                       0s     30s     60s                30s        60s                                           0
                                                                                                                                         0s       30s        60s          30s       60s
                                               Drying at                 Thermofixation at
                                                110 °C                       210 °C                                                              Drying at 110 °C       Thermofixation at 210 °C
                                                           Time                                                                                                    Time

                                                                           Procion Red PX-4B
                                                                           100                                                                    Fixation
                                                                               90                                                                 Hydrolysed dye
                                                                               80                                                                 Reactive dye
                                                                               70
                                                                               60
                                                            Percentage




                                                                               50
                                                                               40
                                                                               30
                                                                               20
                                                                               10
                                                                                0
                                                                                          0s    30s           60s                     30s       60s
                                                                                               Drying at 110 °C                       Thermofixation at 210 °C
                                                                                                                              Time

Figure 8 Variation in fixation yields and dye species (reactive and hydrolysed form) of various reactive dyes at different stages of the
one-pass (TTN) continuous dyeing process

accessibility. Hence fixation can be influenced both                                                                        As, in the case of the one-pass (TTN) continuous
by the rate of dye diffusion and chemical reactivity                                                                    dyeing process, highly reactive dyes did not improve the
[32].                                                                                                                   fixation yield on unmercerised cotton, the level of


ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52                                                                                        51
Mehmood et al. Dyeing of polyester ⁄ unmercerised cotton blends


Table 6 Temperature of equal reactivity and relative order of reactivity of dyes 1–4 and Procion Red PX-4B


                                    Temperature                   Rate constant            Temperature of                  Relative order
Dye                                 (oC)                          (min)1)                  equal reactivity (oC)           of reactivity


1                                   45                            0.0015
                                    50                            0.0025                            37                           4
                                    55                            0.0041
2                                   35                            0.0030
                                    40                            0.0048                            21                           3
                                    45                            0.0072
3                                   25                            0.0042
                                    35                            0.0134                            10                           1
                                    40                            0.0241
4                                   35                            0.005
                                    40                            0.0099                            19                           2
                                    45                            0.0169
Procion Red PX-4B                   45                            0.0003
                                    55                            0.0009                            52                           5
                                    65                            0.0025




reactivity of the dyes cannot be the sole reason for the                    7. A N Stuart, Amer. Dyestuff Rep. (Mar) (1976) 23.
poor colour yield on unmercerised cotton. Factors such as                   8. V A Shenai, Text. Dyer Printer (Apr) (1972) 31.
                                                                            9. G Lippert and M Schulze-Braucks, Textilveredlung, 24
insufficient solubility of the dyes under the dyeing                            (1989) 355.
conditions and insufficient diffusion of dye molecules to                   10. D Hildebrand and W Marschener, Textile Praxi (English
the reactive sites in the unmercerised cotton fibres could                      edition) (1976) XXIII.
be the foremost reason for the lower colour yield. Studies                 11. I D Rattee, The Procion Dyestuffs in Textile Dyeing, ICI
                                                                               (Leeds: Knight and Forster Ltd, 1962) 5.
of these factors will be reported in a later paper.                        12. P J Dolby, Am. Dyestuff Rep. (Mar) (1976) 30.
                                                                           13. R F Hyde, J.S.D.C., 109 (1993) 142.
Conclusions                                                                14. R F Hyde, Colourage (Nov) (1989) 15.
                                                                           15. H-U von der Eltz, J.S.D.C., 101 (1985) 168.
Low levels of fixation of reactive dyes are responsible for                 16. R F Hyde and G Thompson, J.S.D.C., 108 (1992) 122.
the inability to achieve heavy depths of shade in the one-                 17. P J Dolby, Am. Dyestuff Rep. (Mar) (1976) 23.
pass (TTN) continuous dyeing of polyester ⁄ unmercerised                   18. B Eden and M Schaffeld, Melliand, 5 (2000) E 99.
                                                                           19. R F Hyde, Rev. Prog. Color., 28 (1998) 26–31.
cotton blends with disperse and reactive dyes.                             20. L A Graham and Celia A Suratt, Am. Dyestuff Rep., (Jul)
   The level of reactivity of the reactive dyes is not the                     (1978) 36.
prime reason for the poor performance of the reactive                      21. J Shore, Blends dyeing (Bradford: SDC, 1998) 192.
dyes on unmercerised cotton by a one-pass continuous                       22. DyStar Technical Information, TTN process.
                                                                           23. Zenica Technical Information, RTN process.
process and factors such as the solubility of the dye and                  24. F Somm, Textileveredlung, 17 (1982) 463.
its ability to diffuse to an accessible reactive site on the               25. G Alberghina, M E Amato, S Fisichella and I D Rattee, Dyes
cotton may be much more influential.                                            Pigm., 7 (1986) 33.
                                                                           26. V Murtagh and J A Taylor, Dyes Pigm., 63 (2004) 17.
                                                                           27. E Knecht and E Hibbert, New Reduction Methods in
References                                                                     Volumetric analysis, 2nd Edn (London: Longmans, Green
 1. H D Moorhouse, Rev. Prog. Color., 26 (1996) 20–28.                         and Co., 1925) 62.
 2. J R Provost and H G Connor, J.S.D.C., 103 (1987) 437.                  28. J A Bone, T T Le, D A Phillips and J A Taylor, Color.
 3. P W Leadbetter and A T Leaver, Rev. Prog. Color., 19 (1989)                Technol., 123 (2007) 155.
    33.                                                                    29. W B Achwal, Colourage (May) (2001) 51.
 4. D P Chattopadhyay and T M Shaikh, Man-Mad Textiles in                  30. E Karapinar, D A S Phillips and J A Taylor, Dyes Pigm., 75
    India (Dec) (2002) 456.                                                    (2006) 491.
 5. E J Gorondy, The Du Pont Co, Wilmington, Del., Text Chem.              31. J D Rattee and K S Murthy, J.S.D.C., 85 (1969) 368.
    And Col., 10 (1978) 105 ⁄ 19.                                          32. I Rusnak, J Zobor and G Lavai, Dyes Pigm., 2 (1981) 285.
 6. A P Lockett, J.S.D.C., 83 (1967) 213.




52                          ª 2009 The Authors. Journal compilation ª 2009 Society of Dyers and Colourists, Color. Technol., 125, 43–52

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:97
posted:4/8/2010
language:English
pages:10
imraniqbal imraniqbal
About