Indian Journal o f Fibre & Textile Research Vo l. 29 , March 2004, pp. 79-84

Pseudo single-bath process for alkali treatment and bleaching of jute at ambient temperature

N C Pan, S N Chattopadhyay & A Day"

Chemical & Biochemical Processing Division, National Institute of Research o n Jute & Allied Fibre Technology, 12 Regent Park, Kolkata 700 040, Indi a

Received 26 March 200; accepled 16 Jlllle 2003

Grey jute fibre has been alkali-treated and bleached at ambient temperature using sodium hydroxide by different process sequences namely true sing le-bath process of alkali treatment and bleaching, and pseudo single-bath process of alkali treatment and bleaching and then cold dyed with Procion Red M8B and Remazol Yellow FG. The effect of process sequences on physico-chemical properties of jute fibres has been evaluated. It is observed that the alkali treatment for I h using 60 gpl sod ium hydroxide and 1:3 material-to-liquor ratio following the pseudo single-bath alkali treatment and ambient te mperature bleaching process gives the optimum dye ing results. The treated fibre samples show sufficie ntl y hi gh whiteness index and dye uptake . The increase in dye uptake is about 18% in case of Procion Red M8B and about 42% in case of Remazol Yellow FG. As all the treatments have been carried out at ambient te mperature, thi s process is highl y suitable fo r cottage and small-scale industries in rural areas.

Keywords: Alkali treatment, Bleaching, Jute fibre, Pseudo single-bath process, Reacti ve dyeing

IPC Code: Int. CI.7 D06B 1/00, D06L 3/00, DOIC 1/00.

1 Introduction Jute has now found its lise in several diversified

applications, like furnishing fabric, automobile seat cover, carpet, blanket and selective apparel textiles. Hence, the colouration of jute has now become essential to make these value-added products attractive and make jute compatible with other natural and synthetic fibres with respect to their colour in case of blending. Moreover, the harsh feel of this fibre needs improvement for its application in value-added sector. Alkali treatment of jute fabric improves its softness but the removal of res idual alkali is very tedious. Consequently , the wet processing of jute fabric although has occupied an important place in modern jute industry but still there is a scope for further improvement in it. Jute wet processing requires a lot of water, energy input for drying and more dye for a particular shade development. Therefore, a lot of research work is being carried out and more work in this regard is needed. Single-bath processing technology to reduce the requirement of water and energy, ambient temperature processing" 3 of jute textiles to make the process ecofriendly as well

"To whom all the correspondence should be addressed. Phone: 242 12115 ; Fax : +91-33-24712583: E-ma il: nirjaft @vsnl.net

as cost effective and alkali treatment 4·5 of jute fabric to improve its softness as well as dye affinity are some of the processes developed in the recent past to meet some of the requirements of wet processing in a jute industry. In the present work, an attempt has been made to carry out alkali treatment and ambient temperature bleaching of jute in sequences by true single-bath and pseudo single-bath processing techniques to get optimum bleaching effect and improved dye uptake. In this process, caustic bath can be reused, intermediate washing step can be avoided and material handling can be minimised by carrying out two processes (alkali treatment and bleaching) in the same bath. All the processes, like alkali treatment, bleaching and dyeing6

, have been done at ambient condition and hence no electrical energy input is required. This process is, therefore, ideal for rural small-scale sector. Conventional hot bleaching, ambient temperature bleaching and dyeing experi­ments have also been done to make a comparative study.

2 Materials and Methods

2.1 Materials

Grey jute fibre of TD-3 variety having fineness of 2.4 tex was used for the experiment.

80 INDIAN J. FIBRE TEXT. RES., MARCH 2004

The fo ll ow ing chemi cal s o f an alytical g rade were used for the study: hydrogen perox ide, tri sodium phosphate, sod ium hydrox ide, sod ium carbonate, sod ium persul phate, sodium s ilica te, magnes ium sulphate heptahydrate, no n-ioni c dete rgen t (Ultravon J U) and aceti c ac id .

Reacti ve dyes, viz . Procio n Red M8B (C.r. Reacti ve Red I I ) and Remazol Yellow FG (C. r. Reacti ve Yell ow 42), were used fo r dye ing o f jute fib re.

2.2 Methods

Both conventi ona l ho t b leaching and ambient temperature bleaching processes were carri ed out as per the methods reported earli e r7

.

2.2.1 Single-Bath Alkali T rea tment a nd Bleaching

For sing le-bath alka li trea tment and bleaching at ambient te mperature, the fo ll ow ing different comb in at ions were used to opti mise the process:

• Ambient temperature bl eaching of grey jute fibre (Sample Code - a ) was carri ed o ut as per the method reported earl ie ,.7 .

• Grey j ute fibre (Sample Code - b) was d ipped in water fo r I h, taken out , squeezed and immedi ate ly d ipped in bleach bath for bleaching at ambient temperature .

• True single-bath process of a lka li treatment and bleaching was carried o ut us ing the fo llowi ng th ree seq uences:

- Fibres (Sampl e Code - c) were dipped in sod ium hydrox ide solu tion (25 gpl ) at 1:3 materi a l- ta­I iq uor ratio, kep t as such for I h, sq ueezed and taken out. Rest of the chemicals apart fro m sodi um hyd rox ide were added to the bath fo r ambient temperature bleaching. T he alkal i-treated and bleached fibres were then taken o ut, squeezed, kept in the plast ic bag for 2 h, washed , soured and fin a lly dried.

- G rey j ute fib res (Sample Code - d) were dipped in sod iu m hydroxide soluti on (50 gpl) at 1:3 materi al -to-liq uor rat io, kept as such for I h, squeezed and taken out. Rest of the chem icals apart from sodium hydroxide were added to the bath for ambient temperature bl eaching. The a lkali-treated and bleached fibres were then taken out, squeezed, kept in the plastic bag for 2 h, washed, soured and fin ally dried.

- Grey j ute fibres (Sample Code - e) were dipred in sod ium hydroxide solution (50 gpl) at 1:5

materi al- to- liquor rati o, kept as such fo r I h, squeezed and taken out. Res t of the chemica ls apart fro m sodium hydroxide were added to the bath for ambient temperature bleaching. The a lkali-treated and bleached fibres were then taken out, squeezed , kept in the plastic bag for 2 h, washed, soured and finally dried .

• Pseudo sing le-bath process o f a lkali treatment and bleaching was carried out using the following fo ur sequences :

- G rey jute fibres (Sample Code - f) were dipped in sodium hydroxide solu tion (25 gpl) at 1:3 material­to-liquor ratio, kept as such fo r I h, squeezed and taken out. The alka li -treated fibres were then d ipped in a water bath (M:L rati o, I :3) for 15 min . Then a ll o ther ingredients, except sodium hydrox ide, were added to the bath and ambi ent temperature bleaching was carried out in the usual way .

- G rey jute fibres (Sample C ode - g) were d ipped in sodium hydroxide soluti on (50 gpl ) at 1:3 materi a l-to-liquor rati o, kept as such for I h, squeezed and taken o ut. The alka li -treated fi bres were then d ipped in a water bath (M:L ratio, 1: 3) fo r 15 mi n. Then a ll other ingredi ents, except sod ium hyd rox ide, were added to the bath and ambient temperature b leaching was carried out in the uSll al way.

- Grey jute fibres (Sample I::::ode - h ) were d ipped in sodium hydrox ide soluti on (50 gpl) at 1:5 mate ri al-to-liquor ratio, kept as such for I h, squeezed and taken out. The a lkali -treated fibres were dipped in a water bath (M :L ratio, I :3) for 15 min . The alkali coming o ut to the water was then titrated and the concentratio n of sod ium hydroxi de was fo und to be 2 1.6 gpl. Hence, 3 .4 g pl sodium hydroxi de was added to the bath a long with other b leaching ingredients for ambi ent temperature bleaching . The fibres were then squeezed to g ive 100% wet p ick up and kept in a p las ti c bag for 2 h. Finally, they were washed, soured and dri ed.

- Grey jute fibres (Sample Code - i) were dipped in sod ium hydroxide solutio n (60 gpl) at 1:3 material­to-liquor ratio, kept as such for 1 h, squeezed and taken out. The alkali-treated fibres were di pped in a water bath (M: L ratio, 1:3) for 15 min. The alkali coming out to the water was then titrated and the concentration of sodi um hydroxide was found to be 25 gpl. Hcnce, other bleachi ng ingredients except sodium hydroxide were added to the bath for ambient temperature bleaching. The fib res were then squeezed

PAN et al.: ALKALI TREATMENT & BLEACHING OF JUTE 8 1

to give 100% wet pick up and kept in a plastic bag for 2 h. Finally, they were washed, soured and dried.

2.2.2 Dyeing of Bleached Jute Fibres

Conventi onally bleached, ambient temperature bleached, alkal i-treated and ambi ent temperature bleached, si ngle-bath (true and pseudo) alkal i-treated and ambient temperature bleached jute fib res were dyed with two different reactive dyes using the fo llowing procedures:

Proc ioll Red M8B - Dye bath was made with dye (4%) and Glaubers' salt (60 giL), keeping the materi al-to-liquor ratio at I :20 . The bleached fibre samples were dipped into the dye bath and kept as such for I h with stirring at a temperature of 30°C. After thi s treatment, the sodi um carbonate (20 giL) was added in the same bath and kept for 45 min under the same condition. Thereafter, the samples were washed with cold water, soaped with Ultravon JU (2 giL) for 15 min followed by usual washing and drying in air.

ReJllazol Yellow FG - Dye bath was made with dye (4%) and Glaubers ' salt (80 giL ), keeping the material -to-liquor ratio at I :20. The bleached fibre samples were dipped into the dye bath and kept for 20 min with stirring at a temperature of 30°C. After this treatment, the sodium hydrox ide (4 giL) was added in the same bath and kept for 2 h under the same condition. Thereafter, the samples were washed with cold water, soaped with Ultravon JU (2 giL) for 15 min followed by usual washing and drying in air.

2.2.3 Dctcrmmination of Physico - chcmical Propcl,tics

2.2.3. 1 BI/lldle Strellgth al/d Fil/el/ess

Bundle strength of grey and processed jute fibre samples was determined as per the IS : 7032 (Part VII) - 1975 method. The fineness of grey and processed jute fibre samples was determined as per the IS : 7032 (Part VIII) - 1976 methods.

2.2.3.2 Whitel/ess, Yel/OIl'lless al/d Brightl/ess II/dices

Whiteness index in the HUNTER scale , ye ll owness index in the ASTM D 1925 scale and brightness index in the TAPPI 45 scale of grey and processed jute fibre samples were measured by the Spectrascall - 51 OO® computer colour matchi ng system usi ng relevant softwares.

2.2.3.3 KIS Vall/e, Refl ectal/ce al/d Colol/r Strel/gth

Spectrascan-5 100® computer colour matching system was used to measure KIS value, refl ectance and colour strength of diffe rent types of reacti ve dyed jute fibre samples.

2.2.3.4 Wash Fastl/ ess

All the reacti ve dyed jute fibre samples were subj ected to wash fastness tes t in a launder-O-meter as per the IS : 336 1- 1979 method9

, Wash fastness rating of all the dyed fibre samples was evaluated with the help of computer colour matching system .

3 Results and Discussion Table I reveals that the ambient temperature

bl eached samples produce higher wh iteness and brightness indices compared to the alkali-treated and

Tab le I - Effect of different process sequences on fi bre properties and bleaching behaviour

Sample Whiteness index Yellowness index Brightness index Bundle strength Air fl ow code (HUNTER) (ASTM D 1925) (TAPPI45) gtex fi neness, tex

a 79.79 19.48 59.02 23.02 3.4

b 77.61 25.32 55.67 21.98 2.85

c 74. 16 3 1.4 1 4S.0 1 19.96 3.6

d 74. 18 2S.49 48.75 20.83 3.3

e 74.27 2S.5 1 48.SI 20.S3 3. 15

f 70.63 33.04 4j. 19 2 1.69 3.4 1

g 72.05 3 1.56 45.1 () 19.52 3.35

h 72.55 33.7 1 45.26 IS .52 3.25

72.95 33. 17 45 .69 21.61 4.05

Grey jute 53.99 46.2 1 23.96 2S.2 2.4

82 INDIAN J. FIB RE TEXT. RES., MARCH 2004

bleached samples. Here, alkali treatment and bleaching have been done by true single-bath method and pseudo sing le-bath method. In order to make the comparison with alkali treatment and then bleaching, a blank test was performed where the fibre was dipped in water bath fo r I h, sq ueezed and then dipped in a bleach bath intended for ambient temperature bleaching in the usual way . In thi s case, the whiteness and brightness indices are found to be less than that produced in the case of only ambient temperature bleaching but hi gher than that produced in case of single-bath process. In true single-bath process (samples C, d and e) the whiteness index is sli ghtly lower than that in ambient temperature bleaching process. In case of sample c, the alkali treatment before bleaching consumes a portion of alkali from the bath, resulting in lower concentration of alkali during ambient temperature bleaching whereas in samples d and e, the higher alka li concentration during ambient temperature bleaching produces lower whiteness index. In order to exp loit higher benefit and reuse of costly chemicals, pseudo single-bath process was followed in single-bath alkali treatment and bleaching. Here, whiteness index produced is slightly lower but sufficient enough to get quality dyeing after bl eaching. In sample f, the alka li treatment before bleaching and lower alkali concentration during bleaching result in lower whiteness index but in samples g and h, though the bleaching has been done in a separate bath after alkali treatment , sodium hydrox ide concentration is nearly optimum in case o( sample g and equal to optimum in case of sample h. Hence, the whiteness index values of these samples are hi gher than that of sample f. In sample i, the alkali

concentration during alkali treatment has been chosen in such a way that whi le using the bath intended for ambient temperature bleaching, sodiu m hydrox ide is released which is equal to the optimum concentration for ambient temperature bleaching. It is observed that the whiteness index produced in case of sample i is suffici ent for subsequent dyeing in any particular shade. Bundle strength decreases from 28.2 g/tex to 23.0 g/tex after ambient temperature bleaching but there is marginal drop in tenacity in case of single­bath alkali treated and bleached samples compared to only ambient temperature bleached samples . There is swelling in fibres after ambient temperature bleaching and single-bath alkali treatment-ambient temperature bleaching. Swelling is found to be maxi mum in case of sample i , which is indicated by its highest air fl ow fin eness reading.

Table 2 shows the effect of single-bath alkali treatment-ambient temperature bleaching on dyeing behaviour. It is observed that both the dyes behave equally in all the samples. Single-bath processed samples show higher colour yield in all the cases compared to that produced in case of only ambient temperature bleached samples. It is clear from Table 2 that the colour yield is max imum in case of sample i. This may be due to the max imum swelling during pseudo single-bath alkali treatment and ambient temperature bleaching, which helps the reactive dyes to enter the fibres through pores and fix there.

Considering all the properties like whiteness index, brightness index and colour yield for both types of reactive dyes, it is observed that sample i has produced best results. So, pseudo single-bath alkali treatment and ambient temperature bleaching using 60

Table 2 - Effect of different process seq uences on dyei ng behav io ur

Sample Procion Red M8B Remazol Yellow FG code KIS value Colour strength, % KIS value Co lour strength , %

a 8.27 100.00 3.4 1 100.00

b 7.99 96.6 1 3. 18 93.25

c 9. 15 110.64 4.39 128.73

d 9.42 11 3.9 1 4.64 136.07

e 9.54 115.35 2.55 74.78

f 9.23 111.6 1 4.26 124.92

g 9.39 113.54 4.37 128. 15

h 9.3 1 112.57 4.4 1 129.32

9.77 11 8. 13 4 .68 142.52

PAN et 01.: ALKALI TREATMENT & BLEACHING OF JUTE 83

Table 3 - Phys ica l properties and bl eaching behaviour of different ambient temperature processed fibres

Jute fibre

Grey

Hot H]O] bl eached

Amb. temp. bleached

Amb. temp. alkali­treated and bleached

Bund le strength g/tex

28.21

25.48

23 .02

2 1.6 1

Air fl ow fi neness tex

2.41

2.14

3.40

4.05

Whiteness index Yellowness index Brightness index (HUNTER) (ASTM D 1925) (TAPPI45)

53.99 46.21 23.96

83. 17 18.82 64.59

79.79 19.48 59.02

72.95 33. 17 45.69

Table 4 - Dyeing behaviour of diffe rentl y dyed jute tibres

Jute fibre Procion Red M8B

KIS va lue Refl ec tance

Hot hydrogen perox ide 8. 11 5.51 bleached and dyed

Amb. hyd rogen perox ide 8.27 5.41 bleached and dyed

Amb. temp . alka li -treated, 9.77 4.23 bleached and dyed

gpl sodium hydroxide and 1:3 material-to-liquor ratio is the optimum process.

Table 3 shows the fibre bundle strength decreases slightly after ambient temperature bleaching as compared to conventional hot bleaching. The drop in fibre bundle strength is more in case of alkali-treated and bleached fibre. Due to swelling effect after alkali treatment, fibre becomes coarse. Whiteness and brightness indices are found to be maximum in hot conventional bleached fibre . Ambient temperature bleached jute fibres show sufficiently high whiteness and brightness indices whereas single-bath alkali­treated and bleached fibre shows whiteness which is sufficient enough for subsequent dyeing operation.

Dye uptake of ambient temperature bleached fibre is more than that of conventional bleached jute fibre (Table 4) . It is maximum in case of alkali-treated and ambient temperature bleached jute fibre . These findings are true both in case of Procion Red M8B and Remazol Yellow FG dyes. Single-bath alkali ­treated and ambient temperature bleached fibre swells maximum which he lps dye to enter the fibre through the pores and fix inside, thereby producing deep shade.

4 Conclusions 4.1 Pseudo s ingle-bath process of alkali treatment

and ambient temperature bleaching produces bleached

Re mazo l Ye llow FG

Wash KIS value Re fl ec tance Wash fastness fastness

3-4 2.61 14. 14 3-4

4 3.41 11 .47 3-4

4 4 .68 10.67 4

samples with sufficiently high whiteness and brightness indices.

4.2 The bleached fibres thus produced show very high affinity towards reactive dye, producing 18% more colour yield in case of Procion Red M8B and 42% more in case of Remazol Yellow FG dye.

4.3 Pseudo single-bath alkali treatment and ambient temperature bleaching using 60 gpl sodium hydroxide in the alkali bath and 1:3 material-to-Iiquor ratio in the bleach bath is the optimum process sequence.

4.4 This process is simple and cost effective as intermediate washing step after alkali treatment is eliminated. Moreover, the same alkali bath can be reused after correcting the concentration of alkali in the bath.

4.5 The total process of single-bath alkali treatment-bleaching and reactive dyeing is can-ied out at ambient temperature and hence is highly suitable for cottage and small-scale industries in rural areas

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84 INDIAN J . FIBRE TEXT. RES. , MARCH 2004

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