Indian Journal of Fibre & Textile Research Vol. 30, September 2005, pp. 315-323 Effect of cationization of cotton on it's dyeability M Ramasamy Department of Textile Technology, PSG College of Technology, Coimbatore 641 014,1ndia and P V Kandasaamy" Department of Textile Technology, Erode Institute of Technology, Kavindapadi 638 455,1ndia Received 23 February 2004; revised received and accepted 28 October 2004 The efficiency of (3-chloro-2-hydroxypropyl)trimethylammonium chloride and polyamino chlorohydrin quaternary ammonium compound for cationization of cotton has been studied. The influence of process conditions during cationization on the colour strength (K/S) and total dye utilization has also been studied. It is observed that the cationization increases the dye utilization by 30% with no change in colour fastness and reduces the environmental pollution to a great extent. Cationized cotton dyeing is found to consume only 40 % steam and 50% time to that of normal dyeing. Cationization with (3-chloro-2-hydroxypropyl)trimethylammonium chloride is found to be a successful and commercially-viable process which ensures 17 % saving in dyeing cost. Keywords: Cationizati on, Cotton , (3- Chloro-2-hydroxypropyl)trimethylammonium chloride, Dyei ng , Polyamino chlorohydrin quaternary ammonium compound IPC Code: lnt.Cl. 7 D06Pl/38, D06M 15/00 1 Introduction The reactive dyes are known as the best for cotton as they show wide range of colours, ease of application and better fastness properties. However, all the reactive dyeing systems require huge amounts of electrolyte to exhaust and alkali to fix the dye. These electrolytes are neither exhausted nor destroyed and hence remain in the dye bath after dyeing. Only 60-65% dye utilization is attainable even with the use of salt in the normal dyeing systems. When alkalinity is introduced in the bath to facilitate the formation of covalent bond between the fibre and the functional group of reactive dye, the abundance of hydroxyl ions causes significant hydrolys is of reactive dyes. These hydrolysed dyes are called 'dead' dyes as they have no affinity towards cotton and hence remain in the dye bath. Their deposition on the fibre significantly lowers the fastness properties that causes severe wash-offs. Reactive dyeing thus pollutes the environment 1 due to the highly coloured dye bath discharge, and the discharge of high electrolyte concentration. High electrolyte concentration in the effluents causes worst effects due to the evolution of hydrogen "To whom all th e correspondence should be addressed. Ph one : 240497: Fax :+91-4256-243619 ; E-mail : karurpvk @yahoo.com sulphide gas, upsetting the balance in biochemistry of aquatic organisms, deposition of alumino-sulphato complex in the concrete pipes, etc. The salt can be reduced by molecular modification of fibre to have higher affinity and attraction towards anionic dyes which results in reduction of colourant, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS) and highly toxic chlorinated organic byproduct (AOX) in the effluent. This also reduces no. of wash-offs, eliminates neutralizing treatment, reduces effluent volume, increases productivity due to reduced dyeing time, increases dye utilization and reduces cost of dyeing and effluent treatment. This shows the possibility to have one bath dyeing of polyester/cotton blends. A number of processes 3 - 18 have been proposed from the early 1930s to improve the substantivity of anionic dyes for cellulose by introducing cationic sites in the fibre. Lewis and Lei reviewed numerous chemicals that can be used to provide cationic sites in the cotton fibre. Modification of fibre with glycidyl trimethylammonium chloride, N,N-dimethylaze- tidinium chloride, N-methylol acrylamide, chloro propionyl chloride, polymer PL, polyepichlorohydrin acrylamides and nicotinyl thioglycollate has been tried and some of them yielded encouraging results which have already been patented.
Transcript
Indian Journal of Fibre & Textile Research Vol. 30, September 2005, pp. 315-323
Effect of cationization of cotton on it's dyeability
M Ramasamy
Department of Textile Technology, PSG College of Technology, Coimbatore 641 014,1ndia
and
P V Kandasaamy"
Department of Textile Technology, Erode Institute of Technology, Kavindapadi 638 455,1ndia
Received 23 February 2004; revised received and accepted 28 October 2004
The efficiency of (3-chloro-2-hydroxypropyl)trimethylammonium chloride and polyamino chlorohydrin quaternary ammonium compound for cationization of cotton has been studied. The influence of process conditions during cationization on the colour strength (K/S) and total dye utilization has also been studied. It is observed that the cationization increases the dye utilization by 30% with no change in colour fastness and reduces the environmental pollution to a great extent. Cationized cotton dyeing is found to consume only 40% steam and 50% time to that of normal dyeing. Cationization with (3-chloro-2-hydroxypropyl)trimethylammonium chloride is found to be a successful and commercially-viable process which ensures 17% saving in dyeing cost.
1 Introduction The reactive dyes are known as the best for cotton
as they show wide range of colours, ease of application and better fastness properties. However, all the reactive dyeing systems require huge amounts of electrolyte to exhaust and alkali to fix the dye. These electrolytes are neither exhausted nor destroyed and hence remain in the dye bath after dyeing. Only 60-65% dye utilization is attainable even with the use of salt in the normal dyeing systems.
When alkalinity is introduced in the bath to facilitate the formation of covalent bond between the fibre and the functional group of reactive dye, the abundance of hydroxyl ions causes significant hydrolysis of reactive dyes. These hydrolysed dyes are called 'dead' dyes as they have no affinity towards cotton and hence remain in the dye bath. Their deposition on the fibre significantly lowers the fastness properties that causes severe wash-offs .
Reactive dyeing thus pollutes the environment1 due to the highly coloured dye bath discharge, and the discharge of high electrolyte concentration.
High electrolyte concentration in the effluents causes worst effects due to the evolution of hydrogen
"To whom all the correspondence should be addressed. Phone: 240497: Fax :+91-4256-243619; E-mail : karurpvk @yahoo.com
sulphide gas, upsetting the balance in biochemistry of aquatic organisms, deposition of alumino-sulphato complex in the concrete pipes, etc.
The salt can be reduced by molecular modification of fibre to have higher affinity and attraction towards anionic dyes which results in reduction of colourant, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS) and highly toxic chlorinated organic byproduct (AOX) in the effluent. This also reduces no. of wash-offs , eliminates neutralizing treatment, reduces effluent volume, increases productivity due to reduced dyeing time, increases dye utilization and reduces cost of dyeing and effluent treatment. This shows the possibility to have one bath dyeing of polyester/cotton blends.
A number of processes3-18 have been proposed from
the early 1930s to improve the substanti vity of anionic dyes for cellulose by introducing cationic sites in the fibre. Lewis and Lei reviewed numerous chemicals that can be used to provide cationic sites in the cotton fibre. Modification of fibre with glycidyl trimethylammonium chloride, N,N-dimethylazetidinium chloride, N-methylol acrylamide, chloro propionyl chloride, polymer PL, polyepichlorohydrin acrylamides and nicotinyl thioglycollate has been tried and some of them yielded encouraging results which have already been patented.
3!6 INDIAN J. FIBRE TEXT. RES .. SEPTEMBER 2005
In the present paper, the influence of process variables on the cationization efficiency of two cationizing agents, namely (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHPTMAC) and polyamino chlorohydrin quaternary ammonium compound (Cibafix WFF), has been studied. In addition, the techno-economic comparison of the cationized cotton dyeing with the existing method of dyeing is also dealt with .
2 Materials and Methods
2.1 Materials
The plain woven grey cotton fabric having 72 ends per inch , 52 picks per inch, 40s Ne warp and 40s Ne weft was used . Cibafix WFF of Ciba Specialty Chemicals (a cationic fixing agent), CHPTMAC (a cationizing agent), sodium hydroxide, sodium chloride, sodium carbonate, sodium silicate, acetic acid, sulphuric acid and hydrogen peroxide, all of laboratory grade, were used along with a commercial non-ionic wetting agent (Alphox 200 of IGL). Vinyl sulphone reactive dyes supplied by M/s Colourtex, Proc ion M and H dyes. and CIBA FN dyes were used for the study.
2.2 Preparation of Fabric
The grey fabric was desized using 2% enzyme under slightly acidic pH at 60-70°C for 2 h in a laboratory jigger. The enzyme was deactivated by boiling it at 95°C for 30 min and the degraded starch products were thoroughly washed out. The fabric was scoured in jigger at boiling temperature with 3% NaOH, 2% Na2C03 and 0.5 % non-ionic wetting agent for 2 h and then given a hot wash followed by cold wash. The fabric was bleached with 2 volume hydrogen peroxide at 85-95°C in jigger using pH !0.5- 10.8, buffered with sodium hydroxide and stabi lized with sodium silicate for 2 h. Finally, the fabric was given a wash, neutralized with 0.5% sulphuric acid and washed thoroughly.
2.3 Cationization
To study the influence of variables used in the pretreatment, a structured design of experiments was used to minimize the number of experiments. BoxBehnken experimental design, • nd second order rotatable response surface des ign with 3 factors and 3 levels were selected because of the obvious advantages of rotatability and analysis of all the quadratic and interaction effects. The actual values of three variables and their coded levels are shown in Table!.
Table !-Actual values of variables corresponding to coded leve ls
Variable Coded leve l -I 0 +I
CHPTMAC
Conc .of CHPTMAC (X1), gpl 40 50 60
Conc.of NaOH (X2), % of CHPTMAC 20 30 40
Batching time (X3), h 12 18 24
Cibafix WFF
Cone. (x1), % 10 20 30
Temperature (x2) , °C 30 50 70
Soda ash (x3), gpl 5 10 15
2.3.1 Pretreatment with CHPTMAC
The fabric was padded with CHPTMAC using a laboratory padding mangle with I 00% expression and then wrapped in a polyethylene cover. It was stored for the required time as given in the experimental design, after which the fabric was washed thoroughly in the Rota dyer.
2.3.2 Pretreatment with Cibaj"u: WFF
The fabric was treated with Cibafix WFF in a laboratory Rota dyer with a M:L ratio of I :20 using the concentration and the temperatu re as given in the design matrix for 1 h. Then, sodium carbonate was added and the reaction was continued for another I h after which the fabric was taken out and washed thoroughly.
2.4 Dyeing
2.4.1 Normal Dyeing
The bleached fabric was dyed with vinyl sulphone reactive dyes (Corozol Blue HR) for 2% shade. The laboratory dyeing machine Rota dyer with the M:L ratio of 1:20 was used throughout the study. The fabric was kept at room temperature. One gpl nonionic surfactant (Alphox 200), 50 gpl Glaubour salt, 2 gpl NaOH and 10 gpl soda ash were added in the bath and the dyeing was performed for 90 min at 60°C. The fabric was rinsed 3 times for 20 min each, neutralized with 2.5 gpl acetic acid for 30 min and hot soaped at 60°C for 30 min .
2.4.2 Dyeing of Cationized Cotton
The cationized fabric was dyed in Rota dyer with M:L ratio of I :20 using vinyl sulphone reactive dyes. The bath was made up to the liquor ratio with water and 1 gpl non-ionic wetting agent. The fabric was introduced, the temperature was rai sed to 60°C at the rate of 1 °C per min and the dyeing was continued for
RAMASAMY & KANDASAAMY: EFFECT OF CATIONIZATION OF COTTON ON IT'S DYEABILITY 317
further 45 min at this temperature. The fabric was then soaped with 3 gpl soap and lgpl soda ash at 60°C for 30 min. No salt and no alkali was added during dyeing.
2.5 Test Methods
2.5.1 Determination of Exhaustion The optical density of dye solution before and after
the dyeing was measured using BOUCH-LOMP UVvisible spectrophotometer at the maximum wave length of absorbance O•rnax) .The dye bath exhaustion percentage (%£) was calculated using the following equations :
(A -A) %£ = " 1 xlOO
A"
where Ao and A1 are the absorbencies at maximum wavelength (Arnax) of dye originally in the dye bath and of residual dye after dyeing respectively.
2.5.2 Measurement of Colour Strength
The colour strength (KIS) was measured on Jaypack Computer Color Matching System with spectrophotometer (x4000).
2.5.3 Determination of Fixation
The percentage of dye fixation (%F) was calculated using the following equation:
o/oF = (F IS) , xlOO (K I S)b
where (KIS)b and (KIS)a are the colour strengths before soaping and after soaping respectively.
2.5.4 Determination of Total Dye Utilization The total dye utilization percentage (%7) was
calculated using the following eq11ation:
o/oT=ExF 100
2.5.5 Assessment of Fastness Properties ISO Test No.3 (IS :764-1979) method on Launder-
0-meter was used to assess the wash fastness. The change in colour and degree of staining were evaluated using geometric grey scales. The light fastness was evaluated with MBTL light fastness tester (IS:2454-1967) and the rub fastness on crockmeter (IS :766-1956)
2.5.6 Determination of Nitrogen Content
The nitrogen content was determined using Elementar Varia EL III elemental analyzer available at Central Drug Research Institute, Lucknow.
2.5. 7 Infrared Analysis Infrared microscopic examination of treated and
untreated cottons was carried out using a Perkin Elmer Spectrum RXI FT-IR spectrophotometer. The fibres were ground to the fine powder of the size that passes through 20 mesh screen and then spectrum was recorded using KBr pallets.
2.5.8 Testing of Effluent
BOD. COD and TDS were determined using the standard procedures.
3 Results and Discussion
3.1 Effect of Variables in Cationization with CHPTMAC From the results given in Table 2 and the response
equation shown in Table 3, it can be observed that the total dye utilization is influenced by the concentrations of cationizing agent and NaOH, and batching time. The ANOV A result (Table 4) depicts that the batching time has little effect on the variation in T%.
3.1.1 Effect of Concentration ofCHPTMAC The percentage contribution of CHPTMAC is
7.75% which is the second dominant factor that
Table 2-Experimental detail s for CHPTMAC
[Dye- Corozol Blue HR, 2% and "-max -590 nmj
Experiment CHPTMAC NaOH Time KIS T o/o Combination No % % h
influences the total dye utilization (T%) . This may be due to its minimum utilization in cationizing the cellulose which is well supported by a ver6' low nitrogen content (0.19% ). From the literature 1
, it is known that the maximum theoretical nitrogen add-on on cellulose with CHPTMAC is 19.362 % owf. But only 1% of it is utilized and the remaining quaternary compound seems to be hydrolysed. In the selected range, more than sufficient quantity of cationizing agent is available hence its variation within this range does not affect the response much.
3.1.2 Effect of NaOH Concentration · Sodium hydroxide is added to the pretreatment bath
to provide the necessary alkalinity to form the epoxy derivative of CHPTMAC and consequently to bind the same with the fibre . It is the predominant factor that contributes 89 % on the To/o as it is responsible for the two primary reactions to take place. Moreover, it is rapidly consumed while converting the CHPTMAC into epoxy-PTMAC. Its quantity in the bath severely affects the efficiency of cationization of cellulose. Hence, it should be ensured to have the sufficient quantity of alkali at all the time. From the contour plot (Fig.1) between the concentrations of CHPTMAC and NaOH, it can be observed that about 53 gpl (coded value, 0.32) and 37% NaOH (coded value, 0.72) on the weight of CHPTMAC are found as optimum values.
Variable Sum of Degree of Mean F-ratio Percentage squares freedom square contribution
XI' 160.918 2 80.459 34.878 7.75
x2 1801.871 2 900.936 390.544 89.15
x3 34.705 2 17.353 7.522 1.5
Error 18.455 8 2.307
Total 2015 .949
3.2 Effect of Variables in Cationization with Cibafix WFF
3.2.1 Effect of Concentration of Cibafu: WF F
The experimental and Anova results of Cibafix WFF process are given in Tables 5 and 6 respectively. The concentration of Cibafix WFF contributes only 5.15% on the variance of response variable as only a little of it is consumed to add the nitrogen content in the cellulose. Its cationizing efficiency solely depends on the temperature rather than on its quantity in the bath. From the response equation shown in Table 3 and the contour plot in Fig.2, it can be observed that the increase in concentration up to 24% owf (coded value, 0.34) increases the To/o remarkably.
Fig. !-Effect of concentration of CHPTMAC and NaOH on To/o [· -to- 58 64. -c-62.279,. ·- 65.919,-+ 69.568, . f>-73. 198, -<r- 76 837,
• <>- 80.477,-.. 84.116, · •- 87.756, and -- 91395]'
(Graph generated using Statistica 6.0 software)
Table 5-Experimental details for Cibafix WFF [Dye-Corozol Blue HR, 2% and Amax -590 nm]
Experiment Cibafix Temperature Soda KIS combination WFF oc ash
No % %
10 30 10 6.602
2 30 30 10 8.499
3 iO 70 10 11.320
4 30 70 10 12.253
5 10 50 5 10.358
6 30 50 5 11.315
7 10 50 15 10.911
8 30 50 15 11.180
9 20 30 5 7.139
10 20 70 5 12.035
11 20 30 15 7.543
12 20 70 15 13.037
13 20 50 10 12.690
14 20 50 10 12.779
15 20 50 10 12.751
T %
45 0
59.1
80.8
87.4
72.9
80.8
76.4
79 .1
47 .1
87.1
52.4
85 .9
85.5
85.4
85 .6
RAM AS AMY & KANDASAAMY: EFFECT OF CATIONIZATION OF COTTON ON IT'S DYEABILITY 319
Table 6-Analysis of variance for Cibafix WFF process [Dependent variable. T%; N, 15; and R2
, 0.983]
Variable Sum of Degree of Mean F- ratio Percentage squares freedom square contribution
X J 185.288 2 92.644 13.267 5.15
x2 3019.852 2 1509.926 216.235 90.33
X3 65.664 2 32.832 4.702 1.55
Error 55.863 8 6.983
Total 3326.667 14
Table ?-Colour build-up of different dyeing systems [Dye-Corozol Blue HR. 2% and "-'Tlax -590 nm]
Process
Con ventional
CHPTMAC
Cibafix WFF
Ex haustion %
76
99.28
99.3 1
3.2.2 Effect of Temperature
Fixation %
85
94.64
92.26
Total dye K/S after utilization soaping
%
64.6 7.012
93 .96 13.590
91.68 12.352
From Table 6, it can be concluded that the temperature is prime factor that greatly influences the T% due to the increased rate of penetration of cationizing agent into the vicinity of substrate. As in every other molecule, the increase in temperature increases the molecular vibrations both in fibre and in the agent, thereby inducing favourable sorption kinetics . There exists a sharp increase in T% up to 65°C (coded value, 0.63) and thereafter the rate of increase is less significant (Fig . 2) . The concentration of soda ash has no significant contribution on the variation in T%.
3.3 Effect of Cationization on Colour Strength The optimized recipes were taken and the bulk
trials were carried out in laboratory winch dyeing machine with M :L ratio of 1:20. The colour build up in terms of exhaustion and fixation is given in . Table 7.
The exhaustion of Corozol Blue HR is above 99% that leaves the dye bath nearly colourless, about 23% more than that of normal dyeing. Fixation is also increased by 7-9%. The total dye utilization ratio is increased to 94 % and 91.5% in CHPTMAC and Cibafix WFF processes respectively . Hence, -30 % dye can be saved by using the cationization dyeing.
A similar trend is also observed in some other dyes (Table 8) in terms of KIS value before soaping for varying depth of shade. The increase in colour strength for a particular shade varies between the dyes
Fig. 2-Effect of concentration of CIBAFIX WFF and temperature on To/o
which may be attributed to the different dye chemistry. However, for all the dyes, there is a larger increase in light shades than in dark shades. This may probably be due to the insufficient number of cationic sites in the fibre to accommodate those larger quantity of dyes. This hypothesis is well supported by the fact that the KIS values of CHPTMAC process are greater than the corresponding KIS values of Cibafix WFF process. The nitrogen content of CHPTMAC treated fabric is 0.19 %as against 0.15% in Cibafix WFF treated fabric, because of which the CHPTMAC can provide more cationic sites to accommodate more dyes.
3.4 Effect of Cationization on Colour Fastness Table 9 shows that the wash fastness and rub
fastness are not affected significantly. This may be due to the formation of strong ionic bond between the fibre and the dye because it is equally good as the covalent bond that normally links the dye and fibre. The light fastness rating is slightly reduced in some dyes, about half to one point as reported by various researchers previously. The presence of an aliphatic molecule between dye and fibre may be disturbing the stable electronic configuration of dye that leads to the shifting of electrons to the higher energy state and subsequent disintegration of dye by the photons of light rays
3.5 Infrared Analysis Infrared spectra of untreated and CHPTMAC
treated cottons an~ shown in Fig. 3. The strong absorption bands at 1114 and 1163 cm-1 correspond to -C-0-C linkage9
•20 as obtained from the ether
320 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 2005
Table 8-Colour strength of different dyes
Dye Am ax Shade% Normal process CHPTMAC 12rocess Cibafix WFF 12rocess nm KIS KIS %of normal KIS % of normal
E ~ >< E ~ >< § >< E ~ >< E ~ >< .... t .... t .... t .... t 0 1..:: 0 1..:: 0 1..:: 0 1..:: 0 1..:: z Ol z "' z "' z Ol z "' :I: .0 :I: .0 :I: .0 :I: .0 :c .0
u a u 0 u 0 u 0 u 0 Corozol 5 5 5 4-5 4-5 4-5 5 5 5 4-5 5 5 7 7 6-7 Blue HR
RAMASAMY & KA DASAAMY: EFFECT OF CATIONIZATION OF COTTON ON IT'S DYEABILITY 321
100
I
\t> I ' I CO
c-. N . \t) . o \t)oqo\t>
,...;.n \t)
0~--,---~--~------------~--------------~~---
4000 3500 3000 2500 2000 1500 1000 500
Wave length. cm-1
Fig. 3-Combined spectra of untreated and cat ionised cotton
formed by the 2,3-epoxypropyl trimethylammonium chloride and alcohol of cellulose. The absorption band at 1637 cm- 1 clearly depicts the presence of quaternary nitrogen group (-N+-3R) in which the 'R' groups are substituted with methyl groups. A strong band at 1060 cm-1 is responsible for aliphatic Cstretching. The absorption bands at 560, 614 and 667 cm- 1 are due to the presence of -CH2 groups out of the plane bending. The inter polymer hydrogen bond linkages confirm their presence as their vibration causes a broad absorption band at 3342 cm-1
.
Such spectral analysis reveals that the epoxypropyl trimethylammonium chloride binds with the primary alcohol group of cellulose with the help of a covalent bond between them as shown in reaction scheme 1
1.12
(Fig. 4). The spectrum of Cibafix WFF treated cotton has a
very similar absorption characteristics. Additionally, at 290lcm- 1
, a small absorption band due to the C-H stretching confirms that a polymeric quaternary molecule is incorporated in the cellulose.
3.6 Mechanism of Cationized Cotton Dyeing The quaternary nitrogen site has a strong positive
potential and its inclusion in the cellulose makes the fibre to attract the nucleophilic dye anions when it is dyed with anionic dyes like direct, reactive and acid dyes. Hence, no salt is required to force the dye molecules to transfer from the solution to the fibre as in the case of normal dyeing. Moreover, theN+ group renders the fibres that could be dyed with acid dyes,
H H H CH3 H H H CH3 I I I IE) I I I I(!)
H- C-C-C- N -CHJ + NaOH-+ H- C-C-C- N- CH3 +NaCl+H20 I I I I \ I I I
H CH3 CH 0 -C- C-C-N -CH3 CH20H 2 \ I I I 2,3-Epoxypropyl 0 H CH3 trimethylammonium chloride Cellulose Reaction product
Fig . 4-Reaction sc heme of CHPTMAC
which do not have the affinity towards them in normal conditions. Acid is no longer required to make the fibre suitable to be dyed with acid dyes, as al so confirmed by the researches 16
·17
.
In normal dyeing system, the direct dyes and reactive dyes are fixed with cellulose with hydrogen bonds and covalent bonds respectively . To form the covalent bond, cellulosate ions (Cell-O-) need to be produced for which the pH should be highly alkaline (11-12). Hence, larger quantity of alkali is required to fix the reactive dye in normal dyei ng system.
In cationized cotton dyeing, the anionic n•Jcleophilic dye ions show increased substanti vity towards cationic 'dye sites' in the fibre and they readily combine to form 'dye-fibre' complex with strong ionic bond. Hence, no alkali is required for
322 INDIAN J. FIBRE TEXT. RES ., SEPTEMBER 2005
fixation. In contrast, the addition of alkali may deprotonate the cationic amino sites in the fibre, resulting in reduced colour yield.
3. 7 Effect of Cationization on Environment
3.7.1 Effect on Volume of Effluent Discharge
The fabric is in pure neutral state and contains very less quantity of unfixed dye and hydrolysed dye. Hence, the neutralizing and subsequent acid washing treatments can be eliminated. One soaping is sufficient to remove those surface deposited dyes and hence atleast three baths can be reduced. A substantial reduction in the requirement of water and treatment cost can be expected.
3. 7.2 Effect on Effluent Load There is very good scope for the reuse of dye bath
water as it contains no hydrolysed dye and no consumed or converted auxiliaries. However, it needs to be verified by further research.
The effluent analysis results (Table 1 0) clearly depict that the process with CHPTMAC produces effluent with an effluent load well below the norms prescribed by the Tamilnadu Pollution Control Board (TNPCB). Hence, the dyeing effluents need not be sent to the effluent treatment plant which reduces the needs of plant capacity and investment. It leads to a substantial reduction in the dyeing cost. However, the process with Cibafix WFF generates the effluent with more load that needs to be treated. But, the effluent of both cationized cotton dyeing methods possess less load than that of conventional dyeing. It is because of no addition of salt and alkali in the dye bath. The wash water effluent consists of negligible effluent load as the maximum fixation of dye is assured through cationization.
The most beneficial part of the cationization technique is the reduction of TDS in the effluent as this cannot be removed from the effluent easily and needs capital intensive and costly treatments like reverse osmosis, nanofiltration and ion exchange.
Parameter
BOD. mg/L
COD. mg/L
TDS, ppm
Table 10-Efnuent content
Conventional CHPTMAC Cibafix WFF
485
1408
15200
25 119.3
1803.2
68
287.6
2365
TNPCB- Tamil Nadu Pollution Control Board
TN PCB standards
30 250 2100
3.8 Cost Consideration The time of dyeing, steam consumption and
effluent discharge are shown in Fig . 5. The time of dyeing can be half reduced to t..'lat of normal dyeing. The steam consumption of CHPTMAC process is only 40% of that of normal dyeing. Hence, the capacity of boiler and corresponding investment can be reduced to a sizeable volume. It is also evident that the effluent discharged in cationic dyeing process is only half to that of normal dyeing. The water purchase cost, the effluent treatment cost and the interest on the investment on the effluent treatment plant (ETP) are greatly reduced which compensate the additional cost involved in cationizing the cotton.
120
100
'it 80
~ 60 .. ~
40
20
0
• NORMAL DYEING
.CHPTMAC
DCIBAFIX
STEAM
100 40 68
TIME EFLL.UENT COST
100 100 100
50 50 83
50 50 106
Fig. 5-Comparison of normal and cationized cotton dyeing
50 -\ 43.72 46 .28
45 -1
40 1 36.4
I
35 ·i i
<l) ::j <l) 0. ::J
0:: , _1 15-
10 J I
5 ! oL _______ - ---··· .. ·--- -----------
NORMAL CHPTMAC CIBAFIX
OOVERHEADS
DLABOUR
!!I ENERGY
0 WATER&EFFLUENT
• CHEMICAL COST
5 2.5 4
4
4 36
5.61
24.75
1 5
1 73
29.2
3
2.97
2 81
33.5
Fig . 6- Cost of dyeing per kg
RAMASA MY & KANDASAAMY: EFFECT OF CATI ONIZATION OF COTTON ON IT• S DYEAB ILITY 323
Moreover, the otherwise required huge in vestment on ETP can be substantiall y reduced. The near 90% reducti on in chemical discharge can lead to significantl y lower process cos t as well as cleaner n vers.
The cost components of the three processes (Normal dyeing, CHPTM AC process, Cibafix WFF process) are shown in Fig.6. The CHPTMAC process envisages about 17% overall sav ing. The only extra process cos t that is involved in the cationized cotton dyeing is the cost of cationic reactants. Cost reduction due to the reduction of dye, salt, alkali and energy usage is more than the cost of cationic reactant.
3.9 Limitations
The cationic cotton dyeing is reported to have the fo llowing limitations which offer considerable resistances to the wide spread commercialization :
• Light fastness of some dyes is slightly reduced. • Strict process control in the cationization
treatment is essentially required to obtain the desired uni formity of colour and fastness.
• Ammonia odour in the dye house needs to be evacuated to provide a healthy environment for worker.
• Higher cost of cationizing agent needs to be considered.
• The mai n barrier to commercialization is the psychological mind set of the dye house managers.
4 Conclusions Cotton treated with di fferent cationizing agents
provides cationic dye sites and thus can be dyed with reactive dyes without electrolyte and alkali in the bath
with excellent colour yield. The fastness for cationized dyeings is equal to that for conventional dyeing of cotton . The dyeing procedure is shorter and uses less water, chemical auxili aries and energy than the corresponding procedure of untreated cotton. The TDS in the effluent is greatl y reduced in cati onic dyeing. The limitations of cationi c cotton dyeing are the requirement of strict process control, liberation of ammonia vapour in the dye house and reduction of light fastness in some dyes .
References I Sekar N, Colourage , 46(6) (1 999) 29. 2 Cook F L, Text World, 144(8) ( 1994) 83. 3 Schlack P, US Pat 2,1 3 1, 120, September 1938;
http://www.us-patenet-search.com. 4 Hall D M, US Pat 5,330,54 1 (to American Emul sions Co.),
July I 994; http://www.us-patenet-search.com. 5 Kanic M & Hauser P J , Coloration Tee/mol, 11 8 (2002) 300. 6 Hauser P J & Tabba A H, Coloration Techno!, 11 7 (200 I)
282. 7 Hauser P J, Text Chem Color, 32(6) (2000) 44. 8 Lewi s D M, Text Chem Color, 2 1(1 989) 23. 9 Bhattacharya S D, Indian J Fibre Text Res, 26( 4) (200 I) 41 8.
10 Chen K M, J Soc Dyers Colour, 108 ( 1992) 388. II Chen K M, J Soc Dyers Colour, 109 (1 993) 153. 12 Burkinshaw S M, J Soc Dyers Colour, I 05 ( 1989) 391 . 13 Burkinshaw S M, J Soc Dyers Colour, I 06 ( 1990) 307 . 14 Lei X P & Lewis D M, J Soc Dyers Colour, 106 (1 990) 353. 15 Lei X P & Lewis D M, J Soc Dyers Colour, 107 ( 199 1) 103. 16 Lewis D M, J Soc Dyers Colour, 109 (1993) 357. 17 Lewis D M, New methods fo r improving the dyeabiliry of
cellulosic fibres with reactive dyes, paper presented at the AATCC International Conference and Exhibition, At lanta, I November 1992.
18 Palithorpe T, Text Res J, 69(6) ( 1999) 440.
19 Poonam Praful Karnik, Use of cationized colton fo r textile effluent colour reduction, MS thesis, North Caroli na Stale University, 2002, 84.
20 Dadashian F & Wielding M A, Indian J Fibre Text Res , 28 (2003) 385.
