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Research Scholar, Department of Chemistry, PSG College of Technology, Coimbatore-641004
Email id : lammayappan@yahoo.co.in
Introduction
Rising environment awareness promotes the development of alternative procedures and processing in many branches of industry. Also in the textile industry residual substances arrive from processing become an effluent and the cost of effluent treatment becomes much cost. Here potential operational areas exist for new technologies. In recent years utilization of enzymes for textile processing is focused to solve these problems. Enzymatic processes can carry an innovative advance out as ecological and economical alternative to existing processes. For example investigation of the scouring of cotton using pectinase enzyme called Bioscouring is one of the interesting projects. In addition modification of wool by a enzymatic pretreatment process is also a favorable process. Enzyme pretreatment on wool and woolen products has many advantages but it is not established as effective to replace the conventional process. Many research workers have worked on the effectiveness of enzyme pretreatment on wool and woolen products mainly made out of Australian/New Zealand wools and they investigated the physical and chemical properties such as softness, handle, dye ability, whiteness index etc(1,2,3). However the work on the effectiveness of enzyme pretreatment on Indian wool is not only scanty but not available. Based on this back round a work was conducted to study the effect of enzyme pretreatment on carpet woolen yarn made from Indian wool in terms of dye ability , whiteness index and tensile strength. In order to evaluate the effect of process conditions on the properties of the enzyme treated woolen yarn an experimental design based on Box-Benkhen design (4) for three factors has been used. These designs are rotatable and require three levels of each factor. A second order response surface design of three levels / three variables and utilizing 15 different conditions were chosen for the present investigations. The variables and their corresponding levels are given in Table 1.
A multiple linear regression analysis was used to determine the relationship between the variables by the quadratic polynomial equation.
Where Y is response from each experiment, Bo is a constant and Bi, Bii, Bij are the coefficients of each monomial and X is the variable.
Experimental plan
The experimental plan as per Box-Benkhen design is given in Table 2. A mild scoured woolen yarn of 4 Nm was used for this study. Swiss Soft WLL a commercial alkaline protease enzyme was obtained from Adonil Pvt. Ltd, used for this study without further purification. All other chemicals of AR grade.
Enzyme pretreatment of woolen yarn
The woolen samples were taken in a bath containing I gpl Lumipon LN 100 and various amounts of enzyme as per experimental design at pH 8.5 to 9.0 (adjusted with sodium carbonate solution). The enzyme pretreatments were carried out in Tub-liquor dyeing machine at various temperature and various time as per in experimental plan. After pretreatment the sample was treated with 0.5 gpl acetic acid for 10 minutes at 25oC in order to inactivate the enzyme, then washed, rinsed with water and dried at ambient temperature.
Dyeing
The treated samples were dyed with an acid dye (CI Acid Blue 126) in Tub-liquor dyeing machine. A dye concentration of 1% owm was used together with 10% owm sodium sulphate and 4% ammonium sulphate. The liquor to good ratio was 50:1 and the pH was adjusted to 4.0-4.5 with acetic acid. The dyeing processes were carried out on control and enzyme pretreated samples. No auxiliary product was used in these dyeing processes.
Testing
Percentage weight loss, whiteness index (Hunter), yellowness index (ASTM) , K/S value, Tensile strength and moisture regain of the control and enzyme treated samples were estimated in order to ascertain the physiochemical and mechanical properties of woolen yarn.
Weight Loss and Moisture Regain
The percentage weight loss was calculated by using the following formula
Whiteness index, Yellowness index and K/S value
Whiteness index (Hunter) and Yellowness index (ASTM) of the undyed enzyme treated and undyed control samples were estimated by exposing the samples in JAYPAK 4802 Colour matching system (of Jay Instruments Ltd, Mumbai) at D65 illuminate/ 10 Deg Observer with duplicate measurements as per standard AATCC 153-1985.
K/S Value
The adsorption of dyes on fiber was assessed by the Kulbeka Munkel equation is K/S = (I-R)2/2R and it was estimated by exposing the dyed samples (both enzyme treated and control samples) in JAYPAK 4802 Colour matching system (of Jay Instruments Ltd, Mumbai) at D65 illuminate/ 10 Deg Observer with duplicate measurements and K/S was taken at 590 Nm wavelength (max of the dye) as per standard AATCC 110 -2000.
Tensile strength
Tensile strength was measured in terms of yarn strength in Uster Dynamat Yarn strength tester with duplication of 10 samples of each sample as per standard ASTM D 2256-97.
Results and Discussion
In order to study the effect of an enzyme pretreatment on carpet woolen yarn, the effect of various variables on physiochemical and mechanical properties of the enzyme treated samples were analyzed and based on the results an economic recipe can be formulated.
Weight loss
From the table 3 it is observed , the weight loss of the control sample is 1.57% where as in enzyme pretreatment sample the minimum and maximum weight loss are 3.18% and 12.98 % respectively. Middle brook et al intimated that the reaction kinetics of an enzyme depend on the concentration of enzyme, treatment time, pH, treatment temperature and also the diffusion of the enzyme to and into the solid substrate (wool polymer ). Having diffused into the interior of the fiber matrix, enzyme hydrolyses parts of the cuticle and proteins of the cell membrane (8). Thus the weight loss of an enzyme pretreated woolen yarn is gradually increased when increases in concentration of enzyme, treatment time, and treatment temperature .The hydrolytic action of this enzyme is severe at 2% enzyme on 50oC for 45 minutes and so weight loss is high and optimum weight loss occurred at 1% enzyme at 50oC for 30-45 minutes i.e. between 5 and 8%
Moisture regain
From the table 3 it is observed that the moisture regain of the control sample is 9.08 % where as in enzyme pretreatment the minimum moisture regain is 9.36% and the maximum moisture regain is 10.06 %. Davidson et.al referred that the enzymatic treatment leads to breaking down of covalent linkages present in the wool polymer and thus the number of amorphous region and hydrogen bonding within the wool fiber was increased and finally the capacity of wool to retain moisture was also increased. (9). The percentage moisture regain is gradually increased with increase in enzyme concentration.
Whiteness index and Yellowness index
From the table 3 it is observed that the whiteness index and yellowness index of the control sample are 21.55 and 50.54 where as in enzyme pretreated samples the minimum and maximum values are 25.67, 41.36 and 33.52, 46.75 respectively. Petar Jovancic et al intimated that the protease enzyme hydrolyses cuticle at the external surface of the wool fiber, which causes improvement in the whiteness index (10). The optimum whiteness index and yellowness index occurred at 1% enzyme at 50oC for 30-45 minutes.
K/S value
Dyeing and diffusion properties of wool fibers are beloved to be governed by the lipid structure of the intercellular spaces. An enzyme treatment markedly improves dye ability without causing significant fiber damage. (9) The K/S of the control sample is 9.74 where as in enzyme pretreatment sample the minimum K/S is 11.97 and the maximum K/S is 15.85. J.Cegarra et.al stated that enzyme treated wool had more amine terminal groups than untreated wool and as a consequence there are more sites in the fiber capable of attracting the dye (11) . From the table 3 it is observed that the K/S of the enzyme pretreatment has linear relationship with enzyme concentration, treatment time and temperature which indicates that degradation of proteins within the fiber allowed greater accessibility and mobility of dye molecules.
Tensile strength
From the table 3 it is observed that the yarn strength of the control sample is 1.728 g/Tex where as in enzyme pretreated sample the maximum and minimum yarn strength are 1.595 and 0.969 g/tex respectively. It is stated that increasing in the weight loss there will be a decrease in yarn strength. The reduction in tensile strength after enzyme pretreatment was explained by K Sawada et al that protease enzyme hydrolysis mainly inside the fiber polymer rather than outer cuticle which declined the tensile strength of wool polymer (1).
Statistical analysis
Table 4 indicates the response of linear regression analysis of three factors as per the quadratic polynomial equation and it is noted that the F-values of each factor is greater d than 7.0 which indicates that the significance of the experimental design and co-efficient R values are greater than 0.95 which shows that there is a good correlation between all parameters and the experimental variables. From the table 3 , the observed values and predicted values are shown to be very closeness of fit of the experimental model. Table 5 indicates the correlation between properties of enzyme-pretreated samples and it is observed that whiteness index have negative correlation with yellowness index and positive correlation with other parameters . The K/S had positive correlation with weight loss and moisture regain of the treated samples and the tensile strength has negative correlation with K/S , weight loss and moisture regain.
Economic recipe
Based on Box-Benkhen experimental design and regression analysis of the data , many possible formulations were considered and the following recipe can be considered as an economic enzyme pretreatment for woolen yarn.
Protease Enzyme- 1.0%
pH- 8.5 9.0 (adjusted with sodium carbonate)
Treatment time- 30 minutes
Treatment Temperature- 50oC
Conclusion
The percent weight loss, whiteness index (Hunter), Yellowness index (ASTM), K/S value percentage moisture regain and tensile strength(g/tex) of the enzyme pretreated sample and control sample are 5.77%, 1.57%; 31.33, 21.55, 42.40, 50.54; 13.89, 9.74 ;9.93, 9.08 and 1.728, 1.386 respectively. From the above results it can be concluded that enzyme pretreatment leads to improvement in the aesthetic properties of carpet woolen yarn such as whiteness, moisture regain and dyeablilty. Apart from the improvement in physio-chemical properties this enzyme pretreatment causes loss in weight and tensile strength in an acceptable limit. This declination of tensile strength would be the important subjects to be solved with further studies. Thus a protease enzyme pretreatment on carpet woolen yarn is saving energy, enhances the value of end products produced from the woolen yarn fetching more value for products and is more economical than the conventional preparatory process.
References
1.Kazuya Sawada and Mitsuo Ueda, Journal of biotechnology, 89(3), 263-269(2001).
2.A.Riva, J.Cegarra and R.Prieto, Journal of the Society for Dyers and Colourists, 109(5/6), 210-213 (1993).
3.E.Heine and H.Hocker, Review of Progress in Colouration, 25, 57-63 (1995).
4.Website http://www.itl.nist.gov/div898/handbook/pri/section 3/pri3362.html.
5.Annual book of ASTM Standards, Vol. 07.01, ASTM, Philadelphia, 2000.
6.AATCC Technical Manual, Vol 76, AATCC, North Carolina (USA), 2001.
7.M.L.Gulrajani and N.Sugumar, Journal of the Society for Dyers and Colourists, 100(1), 21-27 (1984)
8.W.R.Middlebrook and H.Philips, Journal of the Society for Dyers and Colourists, 57 (4), 137 (1941)
9.A.N.Davidson and R.Prestor, Journal of Textile Institute, 47(8), 685 (1956)
10.Petar Jovancic and Dragan Jocic, Textile Research Journal, 71(11), 948-953 (2001)
11.J.Cegarra, A.Riva, J.Gacen and A.Naik, Tinctoria, 89(4), 64 (1992)
L. Ammayappan# and N. P. Gupta
Division of Wool Technology,
Central Sheep and Wool Research Institute,
Avikanagar-304501.
Abstract
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