Characterization of grey and dyed cotton fibres as well as waste at different stages of rotor spinning process

Transcription

1 Indian Journal of Fibre & Textile Research Vol. 28, March 2003, pp Characterization of grey and dyed cotton fibres as well as waste at different stages of rotor spinning process S M Ishtiaque Department of Textile Technology, Indian Institute of Technology, New Delhi , India and A Das ' Northern India Textile Research Association, Sector 23, Raj Nagar, Ghaziabad , India Received 19 September 2001; revised received and accepted 11 December 2001 A detailed analysis of the properties of grey and dyed (reactive dyed and natural dyed) cotton fibres including the waste materials at different stages of rotor spinning process has been carried out. Significant changes in length-related parameters are observed in each mechanical processing, the effect being more prominent in case of dyed fibres where the frictional coefficient is high. The effects of opening roller speed and its type on the fibre characteristics have also been reported. Keywords: Blow room droppings, Open-end spinning, Opening roller speed, Short fibre content, Span length 1 Introduction A close monitoring of fibre characteristics at different stages of spinning is very important for its proper realization to yarn properties. Few studies 1.2 have been reported on properties of grey cotton fibres at different spinning preparatory processes. Based on the available information on fibre characteristics at a particular stage of spinning, one can do necessary changes in the process parameters and take necessary corrective action in the subsequent process. It is a very well-known fact that any mechanical process, like beating and carding, changes the fibre characteristics in terms of length-related parameters and trash content. To have more uniformity and consistency in the shade of cotton yam, particularly in open-end spinning, the present trend is to mix the dyed fibre in blow room stage instead of dyeing at yarn stage. It is very important to know the characteristics of grey as well as dyed fibres at various spinning stages to assess the quality of the ultimate yam. The efforts made in this area are insignificant. "To whom all the correspondence should be addressed. Present address: Department of Textile Technology, Indian Institute of Technology, New Delhi , India Phone: ; Fax: ; apurba_das@hotmail.com In different preparatory stages of spinning, waste is bound to generate although the technological advancement is able to reduce the waste level to some extent. In addition to the waste minimization, industries are now reusing the waste generated at different spinning stages, particularly in coarser counts for cost minimization. It is very important to know the properties of waste material for its effective reuse. No detailed information is available on characterization of grey and dyed cotton wastes in spinning. In spite of its inherent advantages in productivity, the rotor-spun yam suffers from few deficiencies, like low strength, consistent deterioration in yam quality and running performance due to the accumulation of dust particles in the rotor groove 3-5, and poor fibre length realization due to the lower spinning-in coefficient 6 The action of the opening roller during rotor spinning results in better individualization and cleaning of fibres and at the same time fibre breakage also takes paice 7-9 The present paper reports the properties of grey and dyed (natural and reactive) fibres including the waste materials at different stages of rotor spinning process. The effects of opening roller speed and its type on the characteristics of fibres and waste have also been reported. The study was carried out on a large scale under the actual running condition in industry_ As both the grey and dyed cottons were processed in the set of machinery

2 66 INDIAN 1. FIBRE TEXT. RES., MARCH 2003 available in the industry, the present study was confined with those machines only. 2 Materials and Methods Three different types of cotton (medium grade) fibres, viz. grey cotton, grey cotton dyed with reactive black dye and grey cotton dyed with natural yellow dye, were used for the study. The properties of grey and dyed cotton fibres are given in Table 1. The grey cotton fibres were first opened in a bale breaker and then opened and cleaned with the help of step cleaner before dyeing. The grey and dyed cotton fihres were processed in the same machinery line under the actual running condition in industry. 2.1 Dyeing Dyeing with Reactive Black Dye The partially opened cotton fibres from blow room were filled in the HTHP fibre dyeing machine of 200 kg capacity, scoured, washed properly, and dyed with 10% solution of Reactive Black HFGR for 20 min at room temperature with 1: 10 material-to-liquor ratio. The dyed fibres were then treated sequentially with common salt (80-90 gil) at 60 C for I h, soda ash (20 gil) at 60 C for I h, and caustic soda (2 gil) at 60 C for 30 min. Finally, the fibres were washed as per the following sequence: Cold wash Mild acid wash Cold wash Soaping at 90 C Hot wash Final cold wash Hydro extraction Drying Dyeing with Natural Yellow The same dyeing machine was used in case of natural yellow dye also. The fibres were first of all scoured, washed properly and then dyed with dye solution containing 8% of natural yellow dye and 2% of potash alum at 80 C for 45 min with material-toliquor ratio of 1: 10. After dyeing, the following washing sequence was used: Cold wash Soaping at 60 C Hot wash at 60 C Cold wash Hydro extraction Drying 2.2 Collection of Processed and Waste Materials The grey and dyed cotton fibres were opened and cleaned in Hennatex blow room line with a series of beater. The total beating points were kept at four for all the samples. The blow room droppings were collected from different points and then mixed homogeneously. The detailed analysis of fibre properties of blow room droppings was then carried out. Ten laps were selected randomly from each lot of grey and dyed cottons for measuring the fibre properties in the lap. The fibre samples were then randomly collected from different portions of the lap to have representative sample. All the fibre samples collected from different laps were then mixed homogeneously for the analysis of fibre properties. The same procedure was repeated for all the three types of cotton. The blow room laps were then processed in Whitin cards with 6 in/min flat speed, 780 rpm licker-in speed, 350 rpm cylinder speed and 20 rpm doffer speed. In the present study, only flat strip from cards has been taken for the analysis of properties. The licker-in dropping was not taken into consideration due to the very high level of waste content and very low fibre length. The flat strips collected from all the cards were mixed homogeneously and the samples were then collected for analysis. Similarly, to measure the fibre properties of card sliver, the sliver samples were collected from all the cards randomly and mixed homogeneously for the analysis. Two passages were given in the draw frame (00/6 Model). Analysis of draw frame waste was not carried out because of the very insignificant quantity. For draw frame slivers, no significant change in the fibre properties from card slivers was observed for all the three types of fibre. The finisher draw frame slivers of linear density 5.37 ktex were fed to the 0 E spinning machine (Rieter M 2/1 Model). The rotor speed was kept at 50,000 rpm for all the samples and the rotor diameter was 45 mm. The total draft of the rotors was Table 1- Properties of grey and dyed cotton fibres before spinning Fibre type Sample 2.5% Span 50% Span Short fibre Bundle Fibre Mature Trash Coefficient of code length length content strength fineness fibres content friction mm mm % cn/tex j.lg/in % % at 40 gf Grey S, Reactive black S dyed Natural yellow S l. l dyed

3 ISHTIAQUE & DAS : CHARACTE RIZATION OF GREY AND DYED COTTON FIBRES 67 so adjusted to have a yarn of 59 tex and 5.0 TM. The deposited fibres inside the rotors were collected from full machine (from 220 rotors) and then mixed homogeneously for testing the fibre characteristics. The waste deposited in the waste chamber of the open-end machine was also collected for measuring the properties of waste. The characteristics of deposited fibres in the rotor and open-end waste were studied at different levels of opening roller speed using two types of opening rollers (saw toothed type and pin type). The waste levels of blow room, carding and open-end machine are given in Table Measurement of Fibre Characteristics All the fibre characteristics were measured in low volume instruments. The fibre length and short fibre content were measured in Keisokki Classifibre (Model KCFILS-ME). The averages of 30 readings were taken as representative values. Bundle strength was measured in Stelometer with 3 mm gauge length and fibre fineness was measured by air-flow method. In both the cases, the average of 20 readings was taken. Percentage matured fibre was measured by caustic swelling method with the help of projection microscope and for each sample 1000 fibres were observed. Trash content was measured by trash analyzer. The frictional coefficient (at normal load of 40 g) of grey and dyed fibres was measured with the help of an attachment fitted with tensile tester. The details of test results are given in Tables 1, 3, 4 and 5. 3 Results and Discussion 3.1 Percentage Waste at DilTerent Stages Table 2 shows the percentage waste generated at different stages of spinning for both grey and dyed cottons. It is clear from the table that the grey cotton generates minimum waste followed by reactive dyed black cotton and then natural yellow dyed cotton in all the stages of spinning. This is due to the higher frictional coefficient in natural yellow dyed fibres which results in higher fibre breakage, thereby generating higher waste. Length and related data from Tables 3 and 4 support this phenomenon. From these tables, it is clear that in laps, card slivers and rotor deposited fibres, the grey cotton has highest 2.5% span length and lowest short fibre content followed by Table 2 - Level of waste at different stages of spinning Sample code Total waste Waste at carding Total waste at open end, % in blow room % Total Flat ST Pin waste, % strip, % 6500 rpm 7000 rpm 7500 rpm 6500 rpm 7000 rpm 7500 rpm S I LSI S S ST - Saw toothed type opening roller; and Pin - Pin type opening roller. Table 3-- Properties of processed materials and wastes of grey and dyed cottons at different spinning preparatory stages Spinning Sample 2.5% Span 50% Span Short fibre Bundle Fibre Mature Trash preparatory code length length content strength fineness fibres content stage mm mm % cn/tex ILg/in % % Blow room S I droppings S S) Lap S I S S) Flat strip S I S S) Card sliver S I S S

4 68 INDIAN J. FIBRE TEXT. RES., MARCH 2003 Table 4 - Properties of rotor deposited grey and dyed cottons fibres Sample Opening roller Type of open- 2.5% Span 50% Span Short fibre Bundle strength Fibre Mature Trash code speed ing roller length length content cn/tex fineness fibres content rpm mm mm % Ilg/in % % S ST Pin ST Pin ST Pin S ST Pin ST Pin ST Pin S ST Pin ST Pin ST Pin O.ot reactive black dyed cotton. The natural yellow dyed cotton shows the lowest 2.5% span length and the highest short fibre content. Table 2 shows that the higher card waste in case of dyed cottons is mainly due to the higher flat strips. The frictional coefficient values in Table 1 and flat strips in Table 2 show that the higher the frictional coefficient, the higher is the flat strip. This may be due to the fact that in case of higher frictional coefficient, the fibres try to get embedded with flat wires and do not easily get transferred to the cylinder wire which results in higher flat waste and thus increases the total card waste. The pin type opening roller shows little bit higher open-end waste than saw toothed type which may be due to the better release of dust particles. The opening roller speed does not show any significant trend on open-end waste of grey cotton (Table 2), but for dyed cotton fibres the open-end waste increases with the increase in opening roller speed. This may be due to the higher release of dust particles and higher fibre breakage at higher opening roller speed. Table 4 shows that with the increase in opening roller speed the reactive black and natural yellow dyed fibres show decrease in 2.5% span length and increase in short fibre content, whereas no specific trend in these parameters is observed in case of grey cotton. These above findings show that the increase in opening roller speed results in fibre breakage in case of both reactive black and natural yellow dyed cottons. 3.2 Fibre Length and Related Parameters All the length-related parameters of grey and dyed cottons, processed materials and waste are given in Tables 1, 3, 4 and 5. It is clear from these tables that in each mechanical processing the fibre length of the processed materials consistently reduces due to the fibre breakage. The drop in fibre length is found to be maximum in case of natural yellow dyed cotton followed by reactive black dyed cotton and then grey cotton. This may be due the to higher coefficient of friction (Table 1) for natural yellow dyed fibre. The short fibre content of processed materials for grey and dyed cottons (Tables 3 and 4) also shows a similar trend, i.e. with the increase in frictional coefficient the short fibre content increases due to the fibre breakage. Table 3 also shows that the short fibre contents of blow room droppings and flat strips are very high, but as the 2.5% span length is not very low, which indicates some loss in long fibres, these can be reused in some inferior mixing. The loss of long fibres in case of blow room droppings is higher than that in case of flat strip. This is evident from the higher 2.5% span length and lower short fibre content in blow room droppings for all the fibres (Table 3). It is evident from Table 4 that the opening roller speed does not have any significant effect on fibre

5 I SHTlAQUE & DAS : CHARACTE RIZATION OF GREY AND DYE D COTTON FIBRES 69 Table 5- Properties of open-end waste of grey and dyed cottons Sample Opening roller Type of 2.5% Span 50% Span code speed opening length length rpm roller mm mm S I 6500 ST Pin ST Pin ST Pin S ST Pin ST Pin ST Pin Short fibre Bundle Fibre Mature Trash content strength fineness fibres content % cnltex l1g/ m % % S ST Pin ST Pin ST Pin length parameters of grey cotton (sample S,) which indicates that it does not have much influence on fibre breakage of grey cotton. The earlier workers 7. 'o also observed the same trend. But, for dyed cotton fibres (samples S2 and S3), there is a drop in fibre length and consistent increase in short fibre content with the increase in opening roller speed. This may be due to the higher coefficient of friction of dyed cottons which causes more fibre breakage at higher opening roller speed. Fibre breakage in case of saw toothed type of opening roller is always higher than that in case of pin type opening roller for all the samples. This is clear from the values of fibre length and short fibre content given in Table 4. This is due to the more severe action of saw toothed opening rollers 7 The fibre lengthrelated parameters of open-end waste (Table 5) also show the similar trend. 3.3 Fibre Fineness and Maturity It is observed from Tables 1, 3 and 4 that there is no change in fibre micronaire and percentage matured fibres of processed materials with the variation in stage of processing from mixing to rotor deposited fibres for both grey and dyed fibres. The micronaire and matured fibre percentage in blow room droppings remain same as that in the mixing. But the analysis of flat strips shows that there is marginal drop in fibre fineness. This is due to the fact that more number of immature fibres gets separated from main stream fibres and comes out as flat strip. The low maturity values of flat strip (Table 3) reinforce this phenomenon. The same trend is observed for all the samples. Table 5 shows that the micronaire values of openend waste for all the samples are much higher than that of original fibres. This indicates that the majority of the coarser cotton fibres is separated as open-end waste. The maturity result indicates that the open-end waste contains higher number of matured fibres. Tables 3-5 show that the removal of majority immature fibres with lower average micronaire in flat strip or the removal of majority mature fibres with higher average micronaire in open-end waste do not affect the maturity and micronaire values of fibres in card sliver or rotor deposited fibres. This is due to the fact that very low proportions of both finer fibres in flat strip and coarser fibres in open-end waste are removed with respect to total qu:miity of fibre. 3.4 Trash Content Table 1 shows that the trash content of grey cotton is higher than that of dyed cotton which is due to the fact that the dyed cotton fibres were partially cleaned prior to dyeing. The trash content of natural yellow dyed cotton lap and card sliver are higher than those of grey and reactive dyed cottons (Table 3). This is due to the deposition of large undissolved dye

6 70 INDIAN.I. FIBRE TEXT. RES., MARCH 2003 particles on the surface of the fibre ll From trash content values of grey and dyed cotton fibres before spinning and in laps (Tables 1 and 3), it is clear that the cleaning efficiency in blow room for grey cotton is maximum (68.6%) followed by reactive black dyed fibre (46.9%) and then natural yellow dyed fibre (41.3%). The high cleaning efficiency in case of grey cotton is mainly due to the presence of higher quantity of heavy trash particles as in grey cotton no prior cleaning is done like that in case of dyed cottons. Also, the higher coefficient of friction and more undissolved large dye particle deposition on the fibre surface in case of natural yellow dyed fibre result in lower cleaning efficiency. In case of card cleaning efficiency, as can be observed from trash content values of laps and card slivers (Table 3), the grey cotton shows maximum cleaning efficiency (77.7%) followed by reactive black dyed cotton (73.9%) and then natural yellow dyed cotton (55.1 %). The reason behind this has already been explained. Similarly, in case of deposited fibres inside the rotor the grey cotton shows minimum trash content followed by reactive black dyed cotton and then natural yellow dyed cotton (Table 4). The residual trash content in deposited fibres with pin type opening roller is always lower than that with saw toothed type opening roller (Table 4). This is due to the fact that the pin type opening roller performs better cleaning and individualization of fibres which results in better extraction of microdust l2 The trash content of openend waste (Table 5) supports the earlier trend, i.e. the higher trash content in case of pin type opening roller is due to the more release of microdust. It is also observed that the complete cleaning of open-end waste is very difficult, even with trash separator. Very light leafy matters remain attached with lints even after repeated cleaning which restricts its reuse at least for yarn manufacturing. 3.5 Bundle Strength No specific trend in bundle strength of grey and dyed cotton fibres is observed during spinning (Tables 1, 3 and 4). Bundle strength values of flat waste and open-end waste are found to be lower than that of normal fibres. 4 Conclusions 4.1 Fibre length and related parameters consistently deteriorate in each mechanical processing stage and the effect is more prominent in case of natural dyed yellow fibres where the frictional coefficient is very high. 4.2 Pin type opening roller shows less fibre breakage and better dust separation than saw toothed type opening roller. 4.3 Opening roller speed does not have any significant effect on fibre length related parameters of grey cotton. But in case of natural yellow dyed cotton, where the fibre friction is high, the fibre length drops and short fibre content increases with the increase in opening roller speed. 4.4 The micronaire value of flat strips is marginally lower than that of normal mixing due to the presence of more number of immature fibres in the flat strip, whereas the open-end waste shows just opposite trend. 4.5 The residual trash content of rotor deposited fibres in case of pin type opening roller is always lower than that of saw toothed type opening roller. References I Billasubramanian N, Basu A & Ravindranathan A Y, Fibre properties by HVI and conventional testing at di ferent of spinlling, paper presented at the 35t h Joint Technological Conference of ATIRA, BTRA, SITRA and NITRA, lit - Delhi, February Grover 1 M, Some studies at blow room and card in relation to waste extraction and lint loss, paper presented at the 24t h.ioint Technological Conference of ATIRA, BTRA, SITRA and NITRA, SITRA, Coimbatorc, February Ishtiaque S M & Das A, Indian J Fibre Text Res, 27 (2002) Krishnan K B, Pillay K R P & Balasundram 0, The effect of trash content in draw frame slivers on open-end pinning performance and yam quality, paper presented at the 28 th loint Tcchnological Conference of ATIRA, BTRA, SITRA and NITRA, SITRA, Coimbatore, February Grafton P M, cited in Rotor Spinning - Technical Economic Aspects, edited by E Dyson (The Textile Trade Press, Stockport, England), 1975,23. 6 Ishtiaque S M & Saxena A K, Indian J Fibre Text Res, 23 (1998) Ishtiaquc S M & Bhortakke M K, J Text Inst, 90 (1999) Looney F S, Text World, 12S (1978) Salhotra K R & Chattopadhyay R, Text Res J, 52 (1982) Wang X & Johnson NAG, J Text Inst, 82 (1991) 399. II Ishtiaque S M & Das A, Indian J Fibre Text Res, 27 (2002) Harlock S C, Dutta B & Dang S K, An investigation into performance of trash extraction devices on rotor spinning machines, paper presented in Seminar on Rotor Spinning, IIT Delhi, September 1981.