Pad Roll Bioscouring Process for Cotton-Woven Fabrics

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1 Pad Roll Bioscouring Process for CottonWoven Fabrics By Biljana Mangovska and Igor Jordanov, Ss. Cyril and Methodius University Most traditional cotton woven fabrics are wetprocessed in an openwidth form by a pad roll process. The pad roll process usually consists of a saturator with a storage method for extended application time, followed by a washer. The treatment of cottonbased textiles includes three main operations: dcsi/ing to remove sizing materials. scouring to remove impurities such as fats, waxes, and pectins, and oxidative (bleach) treatment to destroy natural coloring matter. Traditional scouring ha.s been carried out through the combined use of alkali, surfactants, and chelating agents at high temperatures for 12 hours. This process is followed by the removal of most impurities and, sometimes, modification of the cellulosic part of the fiber, using large amounts of rinsing water resulting in wastewater with high biochemical and chemical oxygen demand (BOD and COD, re.spectively). In the past decade, however, commercially viable alternative methods for preparing cotton fabrics, based on the use of en/ymes. have emerged. The enzymes used are biological catalysts usually derived from a fungal or bacterial source. They consist of complex, threedimensional proteins composed of polypeptide chains. These enzymes primarily function hy prompting the hydrolysis of specific substrates, a process by which waterinsoluble material is converted to watersoluble products, and washed away. Different classes of enzymes were investigated for the scouring process, including pectinases. cellulases, lipases, and proteases, but the best results were obtained with pectinases.'"^ Pectin is believed to function as cement in the fiber's outmost layer since degradation of pectin by the pectinase en/yme facilitated the removal of these euticle components. Various parameters, such as enzyme concentration, temperature, ph. and chelating agent concentration for alkaline pectinase Bio Prep 3L treatment were determined in our previous work."* In general, alkaline scouring could he replaced by bioscouring. Knitted fabrics made of enzymescoured yarns as well as knitted fabrics which had been enzymescoured had better quality parameters than those which had been alkaline scoured. "^"^ This study evaluated the quality parameters of cotton woven fabrics after bioscouring and bleaching by a pad roll process. Weight, tensile strength, elongation, abrasion resistance, whiteness, and color coordinates, as well as shrinkage values, were obtained and compared to traditional alkaline scouring, before and after ten launderings. Values for water COD. cycle length, quantity of rinsing water, and energy required for the different scouring methods were also obtained and compared. SCOURING METHODS The greige polyvinyl alcoholstarched cloth used in this study is a g/m. plain woven, 1% cotton fabric, with threads/cm in the warp direction, threads/cm in the fill direction, and yarn size 34/1 in both directions. The pectinase enzyme solution used was Bio Prep 3L (Novozyme) with a standard activity of at least 3, APSU. The preparation contains the monocomponent pectate lyase, which is active in the alkaline ph range. Lavotan DSU, a wetting agent with high washing affect, Kollasol SD defoaming agent. Kemonecer NI wetting agent, Heptol dppliedtechnology EMG chelating agent, as well as Tuboblank 2B optical brightener and Tubingal softener (all from CHT) were used. All other chemicals used were analytical grade (Merck and Alkaloid.) Desizing was done by impregnating the greige fabric with the bath containing 2 g/l Lavotan DSU and 1 g/l Kolassol SD at 2C. The fabric was wound onto a perforated stainless beam and stored in the chamber for 3 min at 8C. After desizing, the material was rinsed for 2 min with hot water and 2 min with cold water. Bioscouring was performed in a bath of.2 ml/l Heptol EMG,.5 ml/l Kemonecer NI, and 2 g/kg Bio Prep 3L, with Na^P4, at ph 9 and C. The fabric was again wound onto a perforated stainless beam and stored in the ehamher for 3 min at C. After bioscouring, the material was again rinsed for 2 min with hot water and 4 gfl Heptol EMG, and 2 min with cold water. Traditional alkaline scouring was performed on the desized fabric with 3 ml/l Lavotan DSU, 5 nil/l Heptol MNG. and 8 ml/l NaOH (5%) at 6C, and storing the beam for 6 min at looc. Rinsing was performed as for the bioscouring procedure. Both the bioscoured and the alkalinescoured fabrics were bleached. This was done by impregnating the fabrics with 15 ml/l Na^SiOi. 1 ml/l NaOH (5%), and 4 ml/l H2O2 (5%), and storing in the chamber for 6 min at looc. Additional bleaching was achieved by rotating the beam for 1 min at I IOC. This was followed by hot rinsing, neutralization, and cold rinsing. An optical brightening and softening agent was applied to both fabrics by padding the fabrics before drying on an openwidth pin MARCH 2QO6 WWW AATCC.ORG 33

2 appliedtechnology tenter and stabilizing at I6C. TESTING METHODS After each step of the finishing process, the following parameters were measured: weight, threads per cm, tensile strength, ek>ngation, ahrasion resistance, bending length, shrinkage after washing at 9C, Berger whiteness, and color coordinates. Comfort characteristics of differently scoured and bleached fabrics were measured as well. These included percent water after padding (WAP)," vapor permeablilty (VP),^' and COD of alkaline and bioscouring baths by standard procedure."^ RESULTS AND DISCUSSION Cotton fibers are structurally differentiated into concentric zones with a hollow central core. The outermost layer is known as the cuticle and is a thin film of fats, pectins, and waxes. Beneath this is the primary wall, composed mainly of cellulose, in which the fibrils are arranged in a crisscross pattern. Next is the secondary wall, also composed of cellulose, which constitutes the bulk of the fiber. The secondary wall is laid down in three successive layers, visible as rings corresponding with daily growth. The central core is known as the lumen, and consists of the mineral salts and proteins derived from the drying up of the cell sap. Cotton yarns or piece goods may contain dirt, size, and machine oils in addition to cotton fibers. In the present work, polyvinyl alcohol was used as a size before weaving. Polyvinyi alcohol is soluble in water, so dissolving it with a wetting agent having a high washing TABLE 1. Time and Temperature Influence on Water Absorbencv Desizing 3 g/l Lavtan DSU Time (min) 3 Pad Roll Bioscouring 2 g/kg Bio Prep 3L effect completes the desizing process on the woven fabric. After desizing, the cotton woven fabrics were scoured. The main purpose of scouring is to remove impurities by wet treatment so that the impurities do not interfere with dyeing and finishing applications. The amounts and types of impurities present depend on the fiber source, the maturity, and other factors. In traditional scouring (with caustic soda, surfactants, and builders at looc), pectins and proteins are hydrolyzed to lower molecular weight components, while mineral and other organic components are dissolved. Waxes, fats, and other oils are also saponified during this process. Cotton contains extraneous matter such as leaves and seed coat fragments in addition to the usable fiber. The vegetable matter is swollen by the hot alkaline treatments so it can be removed or decolorized by the bleaching process, after scouring. The Temperature (C) 8 2 Water Absorbency t(sec) C, chemical concentrations, temperature, and the time required vary with the particular process being used and are well defined for the pad roll process. Optimal parameters for the bio.scouring of cotton woven fabrics were examined by varying the temperature of impregnation, as well as the time and temperature of storage. Under laboratory conditions, cotton woven fabrics were impregnated in a bath of.2 ml/l Heptol EMG. O.^'i ml/l Kemonecer NI, and 2 g/kg Bio Prep 3()()L. with Na.CO^ at ph 9. The fahric was rolled on a beam, covered with PE folio, and kept in the dryer at C for 312 min. In a separate experiment, the material was impregnated with the same bath composition, at room temperature, and kept at room temperature for 12 hr. Although the fabric wa.s wet after desizing,.2 ml/l Kemonecer NI was added to increase the interaction of the pectinase enzymes with the cotton surface and to improve TABLE II. Fabric Properties vs. Finishing Method Desized & bleached, bleached S optically brightened Aikaline scoured Aikaline scoured & bleached Weight (g/m^) Threads (cm^) Per cm (cm^) 23 2 Tensile (N) Strength (N) Elongation {%) , , Abrasion Resistance (cycles) Bend (mg«cm] Length (mg"cm) AATCC REVIEW MARCH 26

dppliedtechnology the pectin hydrolysi.s. as well as dissolving or extracting the other cotton impurities."^ The degree of scouring was determined by a water absorbency test.

3 dppliedtechnology the pectin hydrolysi.s. as well as dissolving or extracting the other cotton impurities."^ The degree of scouring was determined by a water absorbency test. The results are given in Table I. Increasing the time from 3 to 12 min at C had no influence on the scouring process (Table I). A scouring time of 3 min at C, or hr at room temperature, was enough to remove the impurities based on the water absorbency test. The industrial process was developed as 3 min scouring at C. The weight, threads per cm, tensile strength, elongation, abrasion resistance, and bending length for each step and for each finishing process, are given in Table 11. The weight of alkaline scoured, bleached, and optically brightened cotton woven fabric is 1% lower than that of the bioscoured, bleached, and optically brightened fabric (Table II). fabrics also have a higher number of threads per cm in both directions, better abrasion resistance, and higher bending length values (indicating a softer fabric) than alkaline scoured fabrics. Pectinases break down the pectin in the cuticle of the cotton and thereby assist in the removal of waxes, proteins, oils, and other impurities. During this process, part of the wax remains on the cotton surface, protecting the fiber from further damage during the subsequent stages of finishing. This may explain why bioscoured fabric has higher weight, better abrasion resistance, and improved softness. The same properties, as well as shrinkage, were tested after ten launderings. The results are given in Table III. The following conclusion can be made; bioscoured, bleached, and optically brightened fabrics have more shrinkage, a greater number of threads per cm in each direction, higher weight, and better abrasion resistance compared with alkaline scoured, bieached. and optically brightened fabrics (Table HI). The degree of whiteness and color coordinates after each step of finishing, as well as after ten launderings. are given in Table IV. cotton fabrics have lower Berger whiteness scores compared to those which have been alkaline scoured. This is due to the residual waxes and seed eoat fragments remaining on the cotton surface. and alkaline scoured fabrics that have both been bleached had almost the same whiteness, as well as similar a and b values. Greater differences were noted after the optical brightening of differently scoured fabrics. This may indicate that alkaline scoured fabrics have a higher affinity for optical brighteners than do bioscoured fabrics, ln the other experiments, however, enzyme scoured fabrics had higher affinity for direct dyes."* The whiteness increased after ten launderings for both alkaline and bioscoured fabrics. The increase in the whiteness is due to the oxidative bleaching as well as brightening TABLE III. Fabric Properties vs. Finishing Method After Ten Launderings and bleached, bleached & optically brightened Alkaline scoured and bleached Weight (g/m=) Threads (cm^) 27 Per cm Fiii (cm1 23 Tensiie Strenqth ) (N) (N) Eionqation Abrasion Resistance (cycles) Dimensionai Change , TABLE IV. Whiteness and Color Coordinates vs. Finishing Method Desized and bleached. bleached Alkaline scoured Alkaline scoured & bleached Before Laundering Berger Coior Coordinates Whiteness ,35 L' a' b* 2, ,62 127, C* h' , , After Ten Launderings Berger Coior Coordinates Whiteness L* a* b' C h' , MARCH 2OO6 ORG 35

4 appliedtechnology TABLE V. Vapor Permeability (VP) and Water after Padding (WAP) vs. Finishing Method and bleaohed, bleached Alkaline scoured Alkaline scoured & bleaohed agents in the detergent used in the experiment. Comfort characteristics of differently scoured and bleached fabrics were tested by measuring the WAP and VP. The results are given in Table V. and bleached fabrics have higher VP, but lower WAP. s of the processing baths were collected and analyzed for COD and ph. The bath had the highest value of COD (87. mg/l) after desizing. Bioscouring and alkaline scouring baths had 5,2 and 9,8 mg/l, respectively. The bioscouring bath had a ph of 7.6 when complete. while the ph of the alkaline scouring bath was 11. The rinsing process after bioscouring is easily done with half of the rinsing water required after alkaline scouring. VP CONCLUSION WAP h) The following conclusions can be made based on these comparisons of the alkaline and bioscouring processes. Pectinase enzymes used for bioscouring are liquids and can be easily dosed directly into the impregnation bath. Alkaline scouring is done in the presence of strong alkali (NaOH). When NaOH is dissolved, the reaction is exothermal, and can be very dangerous for workers. Bioscouring is done at a lower temperature and for half the time of traditional alkaline scouring. fabric is rinsed more easily than alkaline scoured fabric. Compared to alkaline scoured, bleached, and optically brightened fabric, bioscoured, bleached, and optically brightened fabric has higher weight, higher number of threads per cm. higher abrasion resistance, and satisfactory whiteness. The highest values of COD occurred after desizing for hoth processes. The COD after bioscouring was just over half of what it was after alkaline scouring. References 1. Li. Yonghua and I. Hardin. Te.itilc Research Journal. Vol. 68. No. 9. September p Li. Yonghua and I. Hardin. Textile Chemist and Colorist. Vol. 3. No. 9. September 1998, p Li, Yonghua and I. Hardin., Te.xtUe Chemist and Colorist, Vol. 29, No. 8. August p Jordanov. I. and B. Mangovska, Tekstil. Vol. 5, No. 1, October 21. p.^oi. 5. Jordanov. L and B. Mangovska. Te.xtil. Vol. 52, No. 3. March 23. plo4. 6. Jordanov. I., B. Mungovska. and A. Vlakna. Tcv///. Vol. 11. No. 2. 2(X)2. p Mangovska. B.. G. Demboski, and I. Jordanov. Bulletin of the Chemists and Teclinoloi^ists of Macedonia. Vol. 23, No.l,2(X)4. pl9. Author's Address Biljana Mangovska; Ss. Cyril and Methodius University. Faculty of Technology & Metallurgy; Ruger Boskovic 16, PO. 58, Skopje, Macedonia; telephone ; fax t ; mangova@tmf.ukim. edu.mk. WEIGHT This cylindrical weight is used in AATCC TM 13, Soil Release: Oily Stain Release Method. It is made entirely of stainless steel and has a diameter of 6.4 cm. Order No P.O. Box 115 Research Triangle Park NC 2779 Tel: Fax: WWW. aatcc. o rg 36 AATCC REVIEW MARCH 2OOB

TEXTILE INDUSTRY AND ENVIRONMENT. W.J.K.Dushyanthi Ranpatige Research Officer Industrial Technology Institute

TEXTILE INDUSTRY AND ENVIRONMENT W.J.K.Dushyanthi Ranpatige Research Officer Industrial Technology Institute The textile industry One of the major contributors to many Asian economies and one of the main