Ambient temperature bleaching of jute fibre - Its effect on yam properties and dyeing behaviour

Transcription

1 Indian Journal of Fibre & TextileResearch Vol.21, September 1996, pp Ambient temperature bleaching of jute fibre - Its effect on yam properties and dyeing behaviour G Basu & SN Chattopadhyay Jute Technological Research Laboratories, 12 Regent Park, Calcutta , India Received 26 June 1995; revised received & accepted 28 November 1995 The effect of ambient temperature bleaching of jute fibre with hydrogen peroxide on yarn properties and dyeing behaviour has been studied and compared with that produced by conventional hot bleaching technique. The optimum duration for ambient temperature bleaching of jute fibres of both white and tossa varieties has been found to be 1.5 h. Spinning process causes around 30% loss in whiteness index of bleached fibre, and carding and spinning stages are mainly responsible for it. Yarns produced from both hot and ambient temperature bleached fibres using suitable bleaching recipes give remarkably higher tenacity and higher work of rupture than that of grey yarn. Dyeing of yarn made from ambient temperature bleached fibres results in higher dye uptake and shows an upward trend in work of rupture. A suitable recipe for ambient temperature bleaching consisting of 50 gpl hydrogen peroxide, 15 gpl sodium hydroxide, 20 gpl sodium silicate and 2.5 gpl sodium persulphate is suggested to get better yarn property and dyeing behaviour. Keywords: Ambient temperaure bleaching, Dye uptake, Hydrogen peroxide, Jute, Tensile property, Whiteness index 1 Introduction The thrust on development of jute product for diversified use like wall covering, curtains, draperies, etc. started a few years back and since then a lot of products have been identified for which jute fibre has proved its excellence. Mainly, these products are value added and so the improved feel and aesthetic appeal of the final product along with the improved technical qualities have become essential. The international market for jute products too is set for a major breakthrough. Thanks to "back to the natural fibre movement" throughout the world, specially in most of the developed and developing countries, for use of natural biodegradable product that has given tremendous boost for use of jute diversified product. On the way to develop the value-added products, an in-depth study of the production techniques as well as various technical properties of the end products is needed and at the same time it is essential to find out means and ways to produce these products economically. Moreover, the alarming energy crisis all over the world and the problem of effluent disposal have burdened the scientific community with the responsibilities to evolve technologies which are eco-friendly as well as energy saving. The work on ambient tempeature bleaching of jute fibre1-3 was started a few years back consid~ ering all the above points. In the study2 on spinning performance of jute fibre bleached with sodium hypochlorite, it was reported that though bundle tenacity was decreased significantly due to bleaching but the yam produced from bleached fibre had slightly better quality index than that of the yam produced from raw jute. In another study on spinnability of bleached fibre3, where bleaching chemicals were applied along with JBO emulsion during batching stage, it was reported that both bundle tenacity and yam tenacity decreased with increase in hydrogen peroxide concentration. The probability of uneven bleaching along the fibre length was also reported. Our earlier work1 on optimization of bleaching recipe for ambient temperature bleaching of jute fibre with hydrogen peroxide using the statistical method, central composite rotatable plan, suggested a compromised recipe by considering whiteness property and bundle strength of bleached fibre. Contour diagrams showing the effect of various combinations of chemicals on whiteness property and bundle strength of bleached fibre were prepared from which several bleaching recipes can be chosen to suit various requirements. It was al-

2 ",',' '11"+' ril"'i!!"i'" Ii '" I' "'" 'I ""'I,!,' 'I' 1"" I!" INDIAN 1. FIBRE TEXT. RES., SEPTEMBER 1996 so observed that the effect of bleaching on bundle tenacity of code fibre was not much significant. silicate HBP HBY CB-6 CB-3 CB-4 CB-5 CB-2 CB-7 CBY CB-l Sample The present atsp-5 work gllmainly deals with the analysis of properties of yarn spun from ambient temperature bleached jute fibres and selection of an appropriate bleaching recipe which would give improved yarn properties. Properties of the yarn spun from conventionally hot bleached fibres and that of grey yarn bleached at yarn stage by both ambient temperature and hot bleached processes have also been compared. A lot of changes in whiteness, yellowness and redness indices were found to occur at different spinning stages when bleached jute fibres were spun into yarn. An effort has also been made to identify the stages which are mainly responsible for changes in whiteness property. The dyeing behaviour of all types of yarn and the tensile properties of dyed yarns have also been evaluated. Grey Grey 10- Table 12.5 NaOH NaPS Sod. fibre yarn fibre yarn I-Bleaching chemicals, recipesmaterial withgllsample codes For 10 gll samples and for CB-l HzOz CB-l sample - CB-7, - HBF, CB-7, the2 amount gll the amount of MgS04 of wetting is 0.5 g/l agent is 2 Materials and Methods 2.1 Materials Fibre Jute reed of TD-3 (C. olitorius) and W-2 (C. capsularis) grades were cut into 33 cm length and used for the study Chemicals Hydrogen peroxide solution (30%) was used as a bleaching agent and sodium hydroxide pellets, sodium silicate, magnesium sulphate, sodium persulphate and non-ionic wetting agent were used as bleaching bath assistants. Acetic acid was used as neutralising agent. Direct dye (CWorantine Fast Orange TGLL) obtained from Mis tiindusthan Ciba-Geigy was used for dyeing. Trisodium phosphate and sodium sulphate were used as dye bath assistants. All the chemicals used were of AR grade. Commercial jute batching oil (JBO) and nonionic emulsifier were used for application on jute,fibre as oil-in-water emulsion. 2.2 Methods Bleaching of Fibre and Yarn Ambient Temperature Bleaching The concentrations of bleaching agents and the bleaching auxiliaries, with corresponding sample codes, are given in Table 1. Each sample was dipped in the appropriate solution, squeezed to give 80% wet pick-up and kept in plastic bags for 1.5 h in case of fibre and for 6 h in case of yarn. The samples were then washed, neutralized in acetic acid and then again washed in plain water before drying at room temperatur~. Bleached fibre samples spun into yarns have been coded as CB-1 - CB- 7 and the grey yarn bleached at ambient temperature has been coded as CBY Hot Bleaching by Conventional Process Hot bleaching was carried out in ROACHES dyeing machine (2-bath Standard Model SMK II, ID) for 60 min at 90 C, keeping the material-toliquor ratio at 1:20 with the bleaching recipe given in Table 1. The ph of the bath was maintained at The hot bleached fibre processed into yarn has been coded as HBF while the grey yarn bleached by this process has been coded as HBY Preparation of Yarn Samples Each fibre sample was first sprayed with standard oil-in-water emulsion and then kept in bin for 48 h for piling. The application of batching oil (JBO) was maintained at the level of 2% on the weight of fibre. The fibres were then processed through small-scale jute carding and hybrid draw frame, developed in our laboratory, with three passages of drawing. The drawn sliver thus produced was spun into yarn of 138 tex in the Mackie's apron draft spinning frame with 217 tpm at 4200 rpm Dyeing of Yarn Samples All the yarn samples were dyed in separate bath in ROACHES dyeing machine at 95 C for 1

3 BASU & CHATIOPADHYAY: AMBIENT TEMPERATURE BLEACHING OF JUTE FffiRE 219 h, keeping the material-to-liquor ratio at 1:20. Each dye bath contained dye (2% owf), trisodium phosphate (5 gpl) and sodium sulphate (10 gpl). The ph of the dye bath was maintained at around 8.0. The dyed yarns were washed with cold water, soaped in non-ionic detergent (5 gpl) at 40 C for 15 min, again washed with water and then dried at room temperature. 65 Q\ 60 " c.. c.. L ::: 55 ~ Jutevoriety -x- C.olitorius -o-c capsularis Evaluation or Colour Strength, Whiteness Index, YelIowness Index and Redness Index Colour strength, whiteness index (WI), yellowness index (YI) and redness index (RI) were evaluated using the computer match prediction system - JAYPAK The K/S value was calculated using the following equation: K/S = (1- R)2I2R where K is the coefficient of absorption; S, the coefficient of scattering; and R, the reflectance Evaluation of Light Fastness The light fastness of all the fibre and yarn samples was evaluated by XENOTEST-150S and VARIOLUX using D-65 light source according to IS: Evaluation of Physical Properties ofvam For evaluation of breaking load and breaking extension, the Instron tensile tester was used with 50 cm gauge length and 200 mmlmin crosshead speed. The average of 60 test results was taken for each sample. Yarn mass irregularity (Um%) and thick anu thin places were measured using Uster yam evenness tester (Model-UT3) at a speed of 100 mimin for 2'.5 min. Three tests were carried out for each sample and the average result noted. 3 Results and Discussion Ambient temperature bleaching recipes (Table 1) were selected, consulting the contour diagrams 1, which would give whiteness property of fibre nearer to that produced by suggested compromised recipel. In the present paper, the compromised recipe has been coded as CB-5. A few extreme recipes involving high and low concentration of hydrogen peroxide, sodium hydroxide, sodium silicate and sodium persulphate have also been chosen. So, an endeavour has been made to search out for suitable recipe which would give better.yarn property with satisfactory level 'of whiteness. 50 o 0 5 "0 "5 Z'O Z-5 3'0 3'5 "2.4'0 Tr~tmMllim h Fig. I-Effect of treatment time on whiteness index of bleached fibre 3.1 Effect of Duration of Ambient Temperature Bleaching on Whiteness Index Both the varieties of jute fibre (TD-3 and W-2) were treated with bleaching recipe CB-5 and kept in plastic bags for different durations. Fig. 1 shows that initially the whiteness index increases with increase in treatment time and then it decreases slightly and ultimately reaches to the maximum after 24 h. But a satisfactory level of whiteness is reached at around 1.5 h for both the varieties of jute fibre and after that the treatment time up to 24 h results in only a marginal increase in whiteness. Therefore, 1.5 h may be considered as optimum treatment time for ambient temperature bleaching of jute fibre. 3.2 Whiteness, Yellowness and Redness Indices It is clear from Table 2 that CB-7, followed by CB-5, gave the highest level of W.I. among the ambient temperature bleached fibre samples and that the whiteness is comparable with that produced by conventional hot bleaching process. CB 2, CB-3 and CB-4 gave slightly lower level of whiteness. High caustic and persulphate concentration and low peroxide concentration are responsible for the poor whiteness index1 given by CB-6. Therefore, it is evident that ambient temperature bleaching with appropriate recipe can produce similar or sometimes better whiteness property than that produced by hot bleaching process. Spinning of yarn results in decrease in W.I. by 30%, on an average, in all the cases. Ambient temperature bleaching and hot bleaching at yarn stage produce higher W.I. compared to that of yam produced from bleached jute fibres. But bleaching of fibre offers some which will be discussed later. other advantages Fig. 2 shows the percentage change in whiteness, yellowness and redness indices of bleached

4 220 INDIAN 1. FffiRE TEXT. RES., SEPTEMBER 1996 Sample Table 2-Changes in whiteness, yellowness and redness indices from fibre to yarn stage Whiteness index Yellowness index Redness index (HUNTER) (ASTM) % ' decrease ; ~ , Reed Yarn fibre Reed fibre Yarn -- " -0- Whiteness index 50 r -f:r- Ye!lowness index 30 g' 10 o.c u 0.. g'-10 'Ẹ.," 1~ ~ ~ Redness index Reed Carding IS t 2 nd Spinning Drawing DraWing STAGES OF YARN FORMATION Fig.2-Effect of different stages of yarn formation on whiteness, yellowness and redness indices fibre at various stages of spinning. It is observed that W.I. decreases mainly during carding and spinning stages, while the drawing stages have little effect on \V.I. Application of batching oil before piling, rubbing between fibres and machine parts, oxidation of batching oil, accumulation of dust particles during carding and twisted configuration of the fibres in yarn are apparently responsible for decrease in whiteness and increase in yellownessand redness indices. 3.3 Effect of Bleaching on Dyeing Behaviour The colour strength, K/S and Amax values of the various samples are given in Table 3. The lower Amax value of grey yarn is due to the natural colour of grey jute along with dye. Uniformity in the Amax values of all the dyed yarns, except CB-6, Table 3- Effect of bleaching on dyeing behaviour Sample Grey yarn CB-l CB-2 CB-3 CB-4 CB-5 CB-6 CB-7 CBY (Standard) HBF HBY Colour strength, % of yarn K/Svalue All the dyed yarn samples 'showed Amax value of 450 nrn exc.ept grey yarn (430 nm) and CB-6 (440 nm) produced from bleached samples confirms the satisfactory bleaching operation in all the cases of bleaching studied. Considering the ambient temperature bleached yarn dyed with CWorantine Fast Orange TGLL as standard, it is observed that hot bleached products show poor K/S value while CB-l and CB-2 samples show much higher K/S value. The other ambient temperature bleached samples (CB-3, CB-4 and CB-7) show more or less the same dye uptake as that of standard. The higher alkalinity during ambient temperature bleaching causes opening of fibre structure, resulting in an increase in dye uptake. Use of minimum quantity of sodium persulphate during ambient temperature bleaching may have resulted in more dye uptake in case of CB-l and CB Light Fastness of Fibre and Yam Light fastness rating of all the bleached fibre I 'I I " 'I' "I,"',''II"'"' "I",~""II,H!I III I' II I II ~

5 BASU & CHATTOPADHYAY: AMBIENT TEMPERATURE BLEACHING OF JUTE FIBRE rnjltex-rn mj/tex-rn Irnperfections/250 rupture ~ Thick Breaking Work extn. Urn % of % places Tenacity Thin rn cn/tex Before Table 4- dyeingafter Physicaldyeing properties of yarns samples and yams produced from them were found to be 2 in 8-point scale. In case of dyed yams, only a marginal improvement in light fastness (3) was observed over the bleached material. Hot bleaching, either at yam or fibre stage, produced dyed yam with higher light fastness (3-4) compared to other dyed yams. 3.5 Physical Properties of Yarn Table 4 shows that the yams produced from both hot bleached fibres (HBF) and ambient temperature bleached fibres using recipes CB-1 and CB- 2 have significantly higher tenacity as well as higher work of rupture (WOR) than that of the grey yam and the yam bleached by hot bleaching (HBY). CB-3 and CB-4 samples also showed an upward trend in tenacity value but no improvement in their WOR. It may be noted from Table 4 that the regularity of yarns made out of bleached fibres, in terms of yaw imperfections and Um%,. has also been affected when compared with that of grey yam. The regularity of yams is worst affected in case of HBF, CB-4, CB-6and CB-7. Bleaching of jute reed causes partial removal of hemicellulose, pectin and, to some extent, lignin4 also, resulting in individual fibre finer and is responsible for lessening of adhering property of individual filaments. Therefore, carding of bleached reeds apparently helps in much higher degree of filamentation of their meshy structure which makes the individual entity finer and shorter. Hence, spinning of bleached jute fibres contributed higher number of fibres in the yam cross-section than that of grey yam, resulting in higher tenacity. And as more filamentation was achieved at the cost of fibre length, these short fibres contributed more number of yam imperfections and ultimately caused higher Um%. Poor spinning performance of the fibres bleached with recipes CB 5, CB-6 and CB-7 may be attributed to the fibre damage caused by the use of higher percentage of alkali and persulphate. A tendency of further improvement in WOR was observed after dyeing of yam made from ambient temperature bleached fibres due to increase in extensibility mainly. It is also worth noting that the ambient temperature bleaching at yam ~tage and then dyeing resulted in an increase in WOR as compared to that of grey yam due to an increase in its extensibility after bleaching, while hot bleached yam (HBY) failed to maintain similar trend due to loss in tenacity after dyeing. Yam made out of hot bleached fibres also showed a drastic fall in tenacity after dyeing though its WOR remained same, mainly due to an increase in extensibility after dyeing. 4 Conclusions 4.1 Ambient temperature bleaching of jute fibre for 1.5 h produces the optimum level of whiteness. 4.2 Carding and spinning stages are mainly responsible for 30% decrease in whiteness and around 35% and 60% increase in yellowness and redness in~ices respectively.

6 222 INDIAN J. FIBRE TEXT. RES., SEPTEMBER Spinning of bleached fibres results in an increase in yam tenacity and work of rupture compared to that of grey yarn. 4.4 The following bleaching recipe is suggested for ambient temperature bleaching of jute, which is expected to give improved yarn tensile property with reasonably acceptable level of whiteness and higher dye uptake : hydrogen peroxide, 50 gpl; sodium hydroxide, 15 gpl; sodium silicate, 20 gpl; and sodium persulphate, 2.5 gp1. Acknowledgement The authors are grateful to Dr C R Debnath, Director, JTRL, for providing necessary help and guidance. One of the authors (GB) is thankful to Dr S K Ghosh of JTRL for help in preparing the yam samples and to Dr U Mukhopadhyay and Mr A Muiherjee, both of the Institute of Jute Technology, Calcutta, for providing the facilities to carry out yam mass irregularity tests. References 1 Pandey S N, Chattopadhyay S N & Basu G, Indian J Fibre Text Res, 20 (1995) Sinha M K, Sanyal A K, Day A & Ghosh S K, Annual report (Jute Technological Research Laboratories, Calcutta , India), 1977, Datta D, Guha Roy T K, Chatterjee S, Ghosh D K & Sikdar B, Indian] Fibre Text Res, 12 (1987) Guha Roy T K, Mukhopadhyay A K & Mukherjee A K, Text Res], 54 (1984) 874., I I I "" I I,.! 11'1' I ~ '1"" I!" r