Indian Journal of Fibre & Textile Research Vol. 24,June 1999,pp. 120-125

Sequential bleaching of jute with eco-friendly peracetic acid and hydrogen peroxide

D P Chattopadhyay & J K Sharma

The Technological Institute of Textile and Sciences, Bhiwani 127 021, India

and

R B Chavan

Department of Textile Technology, Indian Institute of Technology, New Delhi 110 016, India

Received 22 August 1997; revised received and accepted 28 May 1998

An attempt has been made to investigate a two-stage eco-friendly bleaching of jute with peracetic acid-hydrogen per­oxide as a substitute for the conventional sodium hypochlorite-hydrogen peroxide bleaching. A non-silicate organic stabi­li zer has been used in place of conyentional sodium silicate in hydrogen peroxide bleaching. It is observed that peracetic acid-hyd rogen peroxide bleaching gives higher whiteness, lower loss in strength and abrasion resistance, and improved soft­ness compared to the conventional process. However, the problem of photoyellowing of the fabric on photoex.posure for long duration sti ll persists.

Keywords : Bleaching. Jute, Whiteness index, Yellowness index

1 Introduction Quite a number of substances utilized in textile

chemical processing are known to pose various envi­ronmefHal problems. Chlorine bleaching is recom­mended ! to be avoided by the environmentalists as residua l chlorine in waste water and chloro deriva­tives of organic impurities in cellulosic natural fibres lead to the problem of absorbable organic halogen (AOX) . Keep ing in mind the environmental aware­ness and hence the production of eco-friendly textiles , the natural fibres including jute are again gaining im­portance in textile manufacturing. The conventional bleaching process for jute is based on sodium hypo­chlorite fo ll owed by hydrogen peroxide bleaching. Satisfactory whiteness is obtained in this method . Hypochlorite bleaching offers some advantages like low cost, easy ava ilability and saving in energy as it works at room temperature , but the problem with hy­pochlorite bleac hing is its non-ecofriendliness. The formation of hi ghly toxic chlorinated organic byprod­ucts (AOX) , during the bl«aching process has limited its use over the last few years because these com­pounds have a potential hazard to the drinking water resources when di scharged .

In the present study, therefore, an attempt has been made to substitute sodium hypochlorite (NaOCI) by peracetic acid (CH,COO.OH) in the conventional

sequential bleaching process (sodium hypochlorite followed by hydrogen peroxide) of jute. The effects of single and double bleaching of jute with sodium hypochlorite, peracetic acid and hydrogen peroxide 00 jute properties are also compared.

2 Materials and Methods 2.1 Materials 2.1.1 Fabric

Jute fabric having the following specifications was used: weave, plain ; area density, 555 g/m2

; warp count, 8 Ib; weft count, 8 Ib; endslin., 17; and picks/in. , ] 6.

2.1.2 Chemicals

Sodium silicate, sodium hydroxide, sodium sulphite, sodium hypochlorite, tetrasodium pyrophosphate, peracetic acid (10%), Stabi lizer SIF A (a non-silicate organic stabilizer, Sandoz), Stabilizer A WNI (a silicate type stabiliser, Sandoz), all of commercial grade, were used .

2.2 Methods 2.2.1 Scouring

Scouring of fabric was carried out using 6 g/I oda ash at 95°C for 60 min at pH 8-9, keeping the material-to-liquor ratio at 1:30.

, -'

CHA ITOPADHY A Y et al.: SEQUENTIAL BLEACHING OF JUTE 121

2.2.2 Bleaching 2.2.2.1 Single Bleaching 2.2.2.1.1 Bleaching with Sodium Hypochlorite

A portion of scoured fabric was bleached with 3 gil (avai lable chlorine) NaOCI at room temperature, maintaining the pH between 9.5 and 10.5 for 90 min. After bleaching, the fabric was antichlored with 5% (owf) sodium sulphite for 20 min at 70°C.

2.2.2.1.2 Bleaching with Peracetic Acid

A portion of scoured fabric was bleached with 10 mill peracetic acid (10%). The pH of the bath was maintained at 6.5 with tetrasodium pyrophosphate as buffer. The bleaching was carried out for 1 h at 70°C, keeping the material-to-Iiquor ratio at 1:30.

2.2.2.1.3 Bleaching with Hydrogen Peroxide

Another portion of scoured fabric was subjected to hydrogen perox ide bleaching with 3% (owf) H20 2

(50% ) for 90 min at 85°C, maintaining the pH between 10 and 11 and material-to-liquor ratio at 1:30 and using I gIl sodium silicate as stabilizer.

2.2.2.2 Double Bleaching

A segment of the scoured fabric was subjected to two consecutive bleaching treatments with a particular bleaching agent under the same condition and concentrat ion of bleaching agents as used in single bleach ing.

2.2.2.3 Sequential Bleaching 2.2.2.3.1 Bleaching of NaOCI-bleached sample

A portion of single hypochlorite-bleached fabric was again bleached with 3% (owf) H20 2, keeping the materia l-to-liquor ratio at I :30 and maintaining the pH of the bath at 10- 11. Bleaching was carried out for 90 min at 85°C in the presence of 1 gil sodium silicate as stabi li zer.

2.2.2.3.2 Bleaching of CH~\COO.OH-bleached Sample

A portion of single peracetic acid-bleached sample was further bleached with hydrogen peroxide in exactly the same manner as gi ven in section 2.2.2.3.1 except that in thi s case. eco-friendly non-s ilicate type Stabilizer SIFA ( 1 g/I ) was used.

After the completion of single. double and sequential hleaching, the fabric samples were thorough ly was hed. neutralised, dried in air and conditj on~d at 65% RH and 27°C before testing.

2.3 Teslmg and Evaluat ion of Fabri 2.3.1 Whitenes:-. Index

The whi lelle:-s index of the fabric after each bleaching treatment was measured in the Hunter lab

scale employing Macbeth spectrophotometer interphased with computer colour matching system.

2.3.2 Tensile Strength The tensile strength of the samples was measured

as per the IS: 1969-1968 method using 1445 CRT Zwick universal tensile testing equipment. Test samples of 50 mm x 20 mm were used and the traverse speed and pretension level were 100 mmlmin and O.2N respectively . An average of 10 observations was taken for each sample.

2.3.3 Bending Length The bending length of the samples was measured

in both warp and weft directions as per the IS : 6490-1971 (Cantilever test 90) method using Sasmira stiffness tester with a specimen size of 200 mm x 25 mm. The average of five tests was taken for each sample.

2.3.4 Abrasion Resistance Flex abrasion test was carried out using C.S.!.

abrasion tester. Specimens (6 in . x 1 in .) from both warp and weft direct ions were clamped, one at a time, at the edges over the flex plates and a load of 4 Ib was placed to the spigot and 2 Ib weight to the bell crank lever; a 2 : I velocity ratio created a tension of 4 Ib in the specimen. When the machine was switched on, the fabric was repeatedly pulled back and forth due to the movement of the carriage and eventually ruptured. The number of cycles to cause rupture of the speci men was noted down by the counter. An average of ten observations was taken for each sample.

2.3.5 Surface Morphology Surface morphology of scoured and bleached jute

fabrics was exami ned using a scanning electron microscope (model--Stereoscan 360, Cambridge Instrument Limited, UK). The photographs were taken at a magnification of x 2000.

2.3.6 Lignin Content About 2 g of the sample was treated with 100 cc

H2S04 (72%) at about 20°C for 2 h to di ssol ve the carbohydrate fraction of j ute . The acid was then di luted to 3% with distilled water and the liquor was boiled for some time and cooled . The residual matter (lignin) was allowed to se ttle. The liqour was filtered through sintered glass cruci ble, washed with distilled water, dried and weighed. Ligni nV content wa calcu lated and expressed in percentage on the basis of the oven-dry-weight of jute.

i22 INDIAN lFIBRE TEXT. ~ .• lliNh 1999

2.3.7 PhOlOSiability

The samples were photoexposed in a Fadometer (SDL 237) for different durations (2,8,14.26,32 and 40 h) and yellowness index (ASTM E-313) of these photoexposed sampies was measured usmg reflectance spectrophotometer interpnased with computer colour matching system.

3 Results and Discussion 3.1 Effect of Single Bleaching on Fabric Properties

Table I shows that NaOCI bleaching gives the minimum whiteness index and the maximum loss in strength and abra ion resistance. The lignin content in thi s case is lowest. On the other hand, H20 2 bleaching gives the maxi mum improvement in whiteness. The loss in strength and abrasion resistance in H20 2

bleaching is lower than that in NaOCI bleaching but greater th an that in CH3COO.OH bleaching. In case of CH3COO.OH bleaching, the whiteness index lies in between the values for NaOCl and H20 2 bleaching. The loss in strength, abrasion resistance and lignin content is minimum. The minimum bending length of CH3COO.OH-bleached sample shows that this treatment has a so ftening effect also. The highest loss in strength and abrasion resistance of NaOCl­bleached sample is obvious because NaOCl dissolves lignin in the form of chloroJignin4. As the lignin acts as a cementin g material between the jute ultimates and contributes to the strength of the fibre, the loss of lignin causes loss in strength and abrasion resistance. 'n case of CH)COO.OH bleaching, the loss of lignin content is negli gible. resulting in maximum strength

;U :iiJraslOll resistance. Z\-l aximum . mprovemem in

whiteness index in case of H20 2 bleaching n ay be .:mributed to its larger effect on he colouring matter. !t appears that the extent of removal of colouring matter is in the following order: H20 2 > ,H3COO.OH > NaOCI.

3.2 Eftect 01 Double Bleaching on Fabric Properties

In c~mmercial practice, normally two I)leaching treatments are given to jute fabric to get the acceptable whiteness. The effect of double bleaching with various bleaching agents on jute fabric properties is shown in Table 2. It is observed that the double bleaching improves the whiteness over that by the single bleaching. However. the improvement in whiteness with CH)COO.OH is marginal. Here again. the maximum improvement in whiteness is found with H20 2 bleaching. NaOCl bleaching, as expected, results in the maximum loss in strength and abrasion resistance due to heavy loss of lignin content. The loss in strength and abrasion resistance of CH3COO.OH-bleached sample is lowest because of the high lignin content, whereas m case of H20 2-

bleached sample, the loss is within the acceptable limits. Here again, CH3COO.OH-bleached sample IS

quite softer.

3.3 Effect of Sequential Bleaching on Fabric Properties

In commercial practice, normally the Jute fabnc is sequentially bleached with NaOCl followed by H20 2•

It is thought that this treatment may not be appropriate from the point of view of adverse effect

Table I--Effect of ~ lngle bleaching treatment on the properties of jute fabric

Treatmcnt

Control (scoured; I aOCI i ! )Ol CH1COO.OH

Treittment

NaOCI (120 1

CH~COO .OH

Whitencss index

38. 1

52.6 58.8 54.2 ._ ---

Whiteness inuex

J2 .5 68.,; 56.3

Strength Weight Abrasion resistanc~ Li gnin content loss loss (No. of cycles) % %. % Warp Weft

486 462 12.48

14.6 3.67 231 221 7.16 8.6 2.88 341 33U 12.22 4.4 1.58 402 395 12.3

Tahle 2--Effect of double bleaching trealment on the proverties of jUle [aone

Strength Weight brasion resistance Lignin content loss loss __ -<No otj:y'c1e~t_ % % % Warp Weft

30.2 7.77 198 i1l8 5.1 14.5 4.6 .H I :. 07 12. 1 5.8 3.0 378 373 12.0

Bending len~h, cm Warp Weft

{-...1~ 5. i

~. 5 : .0 4.0 /

". 2.6

.... 00., -./

_ Belldl,:!~,!!~~ Warp Weft

2.: ., >

.... ~ .;:"\. J 1. 2 " . -'-.1

Y

,...

CHA'IT0P ADHY A Y et al. : SEQUEN11AL BLEACHING OF Jl.ITE 123

on strength and abrasion resistance because any treatment with chlorine containing bleaching agent (e.g. NaOC1) is likely to produce loss of lignin, resulting in heavy loss in strength and abrasion resistance. Moreover, the process is not eco-friendly. Therefore, in the present work, jute fabric was sequentially bleached with CH3COO.OH followed b ... H20" since both of them are non-chlorine compounds and peracetic acid particularly has only marginal effect on li !,'1lin. Table ' shows that. this treatment produced the jute fabric with high lignin content and relatively high strength and abrasion resistance. Whiteness and softness (in terms of bending length) are also better in this case compared to that in sequenti al NaOCI-H20 2 bleaching.

The SEM photomicrographs (Fig. 1) show that there is fibre surface disruption due to the removal of lignIn in the case of sequential NaOCI-H20 2 bleaching which is not evident in CHJCOO.OH-H20 2 bleaching. This suggests that sequential bleaching with CH1COO.OH-H20 1 is much milder in action on jute compared to NaOCI -H20 2 bleaching.

One of the major drawbacks of bleached jute fabric is the loss of whiteness or development of yellowness on photoexposure which is due to the absorption of UV component of light by the lignin present in the bleached jute fabric 5

.

It is assumed that sequential CH3COO.OH-H20 Z

treatment retains a substantial quantity of lignin which might lead to severe photo-yellowing on prolong photoexposure. To confirm ' the above hypothesis, jute fabrics sequentially bleached with NaOCI-H20 2 and CH3COO.OH-H202 were exposed continuously to artificial daylight for different durations (up to 40h). The yellowness indices of these two samples were measured at different time intervals and the results are shown in Table 4. It is observed that in both th treatments, yellowness index increases up to first 20 h exposure after which there appears to be a stabilisation effect. The lower values of yellowness index at all the time intervals in case of CH3COO.OH-H20 2 bleached sample is due to its initial higher whiteness index.

To eliminate the effect of initial difference in whiteness, the increase in yellowness index at each time interval was determined by subtracting the yellowness index value of unexposed sample from the yellowness index value at any particular time of exposure. The results (Table 5) show that the yellowness index values determined in this way are higher for CH3COO.OH-H202 bleached sample as compared to that for NaOCl-H20 2 bleached sample. This may be attributed to the higher lignin content of CH3COO.OH-H202 bleached sample.

Thus, the suggested sequential bleaching tr~atment of jute fabric with CH3COO,OH-H20 2 ' has the

Table 3--Effect of sequential bleaching treatment on the properties of jute fabric

Bleachi ng Whitenes~ Strength Weight Abrasion resistance Lignin content Bending leng!h. cm sequence index loss loss (No. of crcles) % Warp Weft

% % Warp+Weft

NaOCl -H2O_ 70.1 23.2 6.6 43 1 7. 11 3.05 3.17 CH3COO.OH- H10 2 76.3 10.1 4.3 59 1 12.0 2.42 2. 19

Table 4-Effect of photoexposure on yellowness index of sequeniially bleached jute fabric

Bleachlllg Duration of Yellowness index sequence el<posure, h-1 0 2 8 14 20 26 32 40

NaOCl-H 20 2 27.9 39.0 45 .5 49.5 51.2 53.1 54.4 55.0 CH)COO.OH-H2C 2 15.4 25.09 34.5 39.9 42.9 43.1 43.9 44.1

Table 5--Effect of photoexposure on yellowness index increment of sequentially bleached samples

Bleaching Duration of Increment in r ellowness index sequence exposure, h-l' 0 2 8 14 20 26 32 40

NaOCl-H20 2 0 Il.l 17.6 21.6 23.3 25.2 26.5 27.1 CH)COO.OH-H20 2 0 10.5 19.1 24.5 27.5 27.7 28.5 28 .7

124 INDIAN J.ABRE TEXT. RES. JUNE 1999

Fi g. J.........scdl1ning electron photomicrographs of jute fi bres [(a) control. (b) bleached wi th NaOCI. (c) bleacheu wi 11 CB3COO.OH, (d) bleached with NaOCI-H l 0 2• and (e) bleached with CH3COO.OH-H~02 1

CHATrOPADHYAY e! af.: SEQ JENTIAL BLE CHING OF JUTE 125

advantage of highest degree of whiteness w' h maximum re te ti on of strength and abras ion resIst; nee. T he fabric bleached through this. e uence i surprisingly softer, though the harsh e<: <; of 'ute is il.nown to oe oecause of its high lignin content and the same re illatlle aimost umtffe ted ue tG perace',c ,Lid O[ hvorogen perox ide treatment.

" Conclusions ·u Single bleaching of j ute with NaOCII}h 0 2/

CH)COO.OH does not produce adequate whitenes . Bleaching with NaOCI results in higher strength and weight loss whereas that with CH)COO.OH gives better fee l and higher abrasion resistance.

4.2 Double bleaching with H20 2 gives better whiteness, whereas double bleaching with NaOCI causes severe damage 10 the fibre and that with CH~COO .OH does not give adequate whiteness

4.3 Con ventional NaOCI-H20 2 sequential bleaching gives acceptable whiteness but other ;Jroperties are adversel y affected .

4.4 Sequentia l leachi ng wi th CH)COO.OH and H20 2 gives higher whi eness, lower loss in st rengt . and abrasion res istance . and a improved softness.

4.5 B) h con entional and suggested bleaching sequence :lave a maj or drawback 0 " photo-yellowing of bJeac;)ed !>ampies on photoex pos ure.

, ckno'"ledgemcnt The unt'lOrs ::: re than kful 0 Dr. .K. Guha Roy and

Dr. N.C. Som, Chemical f echnology Departn tent. :,1di an J te industries Re~earch Association, Calcutta, fo r providing some irnporta tliterat re on peracetIc aCid and for encouragement during this work.

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3 Sc:ngupta A B & Call1lw H J J, J Text Inst, 40 ( J 940) T 650.

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