Indian Journal of Fibre & Textile Research Vol . 3 1 , December 2006, pp. 588-590

Low temperature bleaching of cotton using T AED acti vated peroxide bath

S K Mal ik' & Manoj Das

Department of Text i le Chemistry, The Technological I nstitute of Textile & Sciences, Bhiwani 1 27 02 1 , I ndia

Received 1 7 Novell/ber 2005; revised received {{lid {{ccepted 19 lallu({fY 2006

Low temperature bleaching of cotton fabric using tetraacetylethylenediamine (TAED) in the hydrogcn peroxide (H202) bath has been studied and the most appropriate conditions for this bleaching established. In this technique, ill -situ peracetic acid formation takes place via reaction of T AED and H202 This method gives bleaching comparable to that of the conventional method at relatively low temperature (60°C). The extent of bleaching depends upon the temperature of bleaching, pH, concentration of T AED and treatment time. The loss of strength, process t ime and alkali required are also found to be less than for the samples bleached i n conventional manner.

Keywords: Cotton, Hydrogen peroxide, Low temperature bleaching, Tetraacetylethylenediamine

JPC Code: Int. Cl .8 D06B3/00

Typical peroxide-based textile bleaching systems require highly elevated temperatures (::; 85°C) to provide acceptable whi teness profiles on the treated fabrics and a high throughput due to reduced reaction time (::; 60 min). However, high temperature processing has significant drawbacks of higher energy consumption and cost, and adversely affects the useful properties of fabrics like strength and handle.

In Europe and USA, TAED (tetraacetylethylene­diamine) i s being used as an activator for hydrogen peroxide in laundry detergents and cleaning products so that these processes can be carried out efficiently at lower temperature. 1 .2

Recent research has also shown that T AED activated system has potential in bleaching of cellulosic textiles with improved effectiveness under mild conditions3 via production of the peracetatc anion at lower temperature, at which peroxide would be ineffective. TAED reacts with two moles of hydrogen peroxide in aqueous solution to produce two

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moles of peracetic acid (PAA) and one mole of diacetylethylenediamine (DAED) [Fig. l (a)] .4.6

Peracetate formed is used for bleaching of cotton by means of active oxygen produced, as shown in Fig. l (b).

In this study, T AED has been used in H202 bleaching to bring down the bleaching temperature and also to min imize damage to various fabric properties. T AED and reaction products DAED as well as peracetic acid are non-toxic and biodegradable, and give carbon dioxide, water, n itrate and ammonia as end products. Therefore, TAED provides totally environment-friendly bleaching.

Grey plain weave 1 00% cotton fabric (64 endslinch, 50 picks/inch, 30s warp count, 20s weft count, and 1 19 g/m

2) was used. Sodium chloride,

sodium hydroxide, soda ash, hydrogen peroxide (50% w/v), stabi l izer A WNI (peroxide stabi l izer, Clariant India Ltd), Bactasol AMI LlQ (desizing enzyme, Clariant India Ltd), Lisapol D (anionic wett ing agent, ICI), all of commercial grade, and T AED (LR grade) were used.

Grey cotton fabric was desized in a bath containing Bactasol AMI LlQ (2% owf), and sodium chloride (5% owf), keeping 1 :30 material-to-l iquor ratio and 5 .5-6 pH at 70°C for 2 h. This sample was washed thoroughly with hot and cold water and finally dried at ambient temperature.

(;I h-CO co-c II, HOO-> N-CI I2-CH2-N < CI i)-CO co -{; tI,

TAED

CH,-{;<Xr-O +

I'eracetate

CH,-{;O > co-c H, N-CH2-CH2-N<

CH,-{;O . H TriAED

I I CO-Cl l) CH,-{;OO-O- + > N- CH2-CH2-N <

CH,-{;O H

))cracclalc (a) DAED

H,C-C<Xr-O - + Collon -. Dlcachcd COllon + I hC-CoO Peracetic anion

(b)

Fig. I-(a) Reaction of TAED with H202, (b) Reaction of peracelate anion with cotton

SHORT COMMUNICATION 589

Desized cotton fabric was treated with an aqueous solution containing NaOH (4% owf), soda ash (2% owf) and non-ionic detergent (0.5% owf), keeping 1 :30 material-to-liquor ratio at boil for 2 h . The sample was then washed thoroughly with hot and cold water and finally dried at ambient temperature.

Three different control samples were prepared separately by bleaching i n standard hydrogen peroxide bath7.8 with 5% (owf) H202, 3% (owf) sodium si l icate, 1 % (owf) soda ash, 0 .5% (owf) NaOH, 0.5% (owf) wetting agent (anionic detergent) at 90°C for 60 min using pH 1 0.5 .

To find out the optimum temperature, bleaching was first carried out at four different temperatures (40, 50, 60 and 70°C) using TAED (2 giL) , keeping all other chemicals and condi tions same. A series of experiments was carried out to optimize other parameters. To determine the optimum amount of T AED required, optimum bleaching duration and optimum pH, four d ifferent concentrations of TAED ( 1 , 2, 3 , and 4g/L) were used separately at four different bleaching durations (20, 30, 45 and 60 min) and four different pH values (8, 9.5, 1 0.5 and 1 1 .5) respectively. The bleached sample was washed thoroughly with hot and cold water and fi nally dried 1 11 air.

Whiteness i ndex (WI) was calculated from the reflectance measurements made with a computer aided Machbeth color eye spectrophotometer using the equations of Hunter lab system ( 1 958, 1 960) (ref. 9). Yellowness index (YI) was measured according to the ASTM E3 1 3 standard method at 1 0° observer and i l luminant C.

Tensi le strength was measured as per the IS : 1 680- 1 979 standard method using Good Brand's strength tester.

60

50 x OJ 40 " ..:: til 30 til OJ c: .� 20 ..c: �

1 0

0 40 50 60 70

Temp eratul'e, °c

Fig. 2-Efrect of bleaching temperature on wh iteness index of untreatl!d cotton and treated colton using 2 giL TACO at pH 1 0.5

Table I -Whiteness and yellowness i ndices of colton bleached at di fferent pH values and TAEO concentrations at GO°C [Average WI of control sample "' 59.0GO]

pH Time I ", giL 2 ", giL 3 ", giL 4 ", giL mi n WI YI WI YI WI YI WI Y I

20 42.667 1 8.67 1 48.84 1 1 7.50 1 54. 1 99 1 3 .575 58.796 1 1 .696 30 44.420 1 6. 1 45 59.234 1 2 .088 58.093 1 1 . 1 22 62.494 1 0.3 1 4 45 44.496 1 5 .632 59.566 1 1 .793 6 1 .2 1 6 1 0. 1 03 62. 130 09.395 60 5 1 .3 1 8 1 4.27G 59.723 1 1 . 1 08 62.467 1 0.787 62.038 1 0.075

9.5 20 38.234 20.569 48.38 1 1 4.442 57.7 1 0 1 2 .089 59.06 1 10.337 30 42.965 1 9.09 1 55 .02 1 14 .043 58.338 1 1 .65 1 59.795 I 1 . 1 53 45 44.232 1 7 .809 56.935 1 3 .2 1 7 59.997 1 1 . 7 1 1 59.746 1 1 .238 60 46.76 1 1 6.069 58.508 1 1 .432 59.524 1 1 .046 60.3 1 4 1 0.25 1

1 0.5 20 48.478 15 .657 45.04 1 1 6.305 56.393 1 3.96 1 55. 1 33 1 2 .825 30 48. 1 57 1 6.2 1 5 55.287 1 4.44 1 58. 146 1 0.449 57.753 1 1 .520 45 44.44 1 1 5 .625 57.84 1 1 2 .433 60. 1 05 1 0. 1 24 58.297 1 0.8()2 60 50. 8 1 3 1 5 .223 58.238 I 1 .856 60.758 1 1 . 1 04 59.855 1 0. 1 1 6

1 1 .5 20 44.545 1 6.808 48.376 1 7 .227 55.947 1 3 . 1 9 1 55.965 1 1 .239 30 45.65 1 1 6.228 56.069 1 3 .202 60.647 1 1 .529 60.806 1 l . l 87 45 48. 175 1 6.424 57.746 1 2 .52 1 60.64 1 1 l . l 24 60. 1 88 1 1 .623 60 49.728 1 5 .244 58.6 1 5 1 1 .632 60. 1 43 1 0. 1 44 6 1 .02 1 09.368

aT AEO concentration. WI-Whiteness i ndex, and Y I-Yellowness index.

590 INDIAN J. FIBRE TEXT. RES., DECEMBER 2006

The whiteness index values (Fig . 2) show that raising the bleaching temperature from 500e to 600e results in significant i ncrease in whiteness index, whereas the i ncrease in whiteness index from 600e to 700e bleaching temperature is insignificant. The whiteness i ndex at a temperature of 600e is found to be better than that of control sample, thus the bleaching at 600e with T AED can be the optimum condition.

The increase in whiteness index with the i ncrease in temperature in case of bleaching with TAED activated peroxide bath can be associated with: (i) more release of perhydroxyl ion with the i ncrease in temperature, (ii) the reaction of T AED with peroxide to generate more PAA, which is a stronger bleachi ng agent than peroxide at lower temperature.5

It may be observed from Table 1 that the maximum whiteness index i n the bleached samples i s achieved at a pH of 8, and with the further increase in pH, the WI values decrease. Therefore, in this bleaching the pH of 8 is the optimum.

Table 1 also shows that with the i ncrease in the concentration of T AED from I giL to 2 giL, the WI of the fabric increases significantly and after that the increase in WI is not much. Therefore, the concentration of 2 giL is the optimum value.

It is also observed from Table I that the whiteness i ndex increases with the increase in bleachincr eo duration from 20 min to 30 min at 2g/L concentration of TAED at pH 8 (optimum conditions) and there is no s ignificant increase in WI when the bleaching duration is further increased. Therefore, the optimum duration in this bleaching method i s 30 min .

Table 2 shows that there is a significant loss in tensile strength of samples bleached with conventional method, whereas at low temperature bleaching when T AED was used in the bath the strength loss in the samples is less. This may be due to the less hydrolysis of cellulose occurred as a resul t of less reduction i n chain length. 1 0 The trend of loss i n

Table 2---Comparison of tensi le strength of cotton fabric after bleaching i n various conditions

Sample Tensile strength, Ib/in2

Untreated Conventionally TAED treated (at optimum sample treated sample pH & temperature)

Warp 65

Weft 50

50 47 50

39 35 37

30 min 45 min 60 min

59 57 56 58 53 54 60 54 56

47 45 44 47 43 42 49 42 44

tensile strength is similar in warp as well as weft direction; however, the difference in strength is due to the fabric specifications.

T AED can be successfully used with hydrogen peroxide for bleaching of cotton at low temperature (60°C) , which appreciably reduces the energy required. B leachi ng duration, loss of strength and alkali required are also found to be less in this new bleaching method. This bleaching can eas i ly be done with solar heating system and operating hazards at high temperature can be e l iminated.

References I 2 3 4

5 6 7

8

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