Application of Acacia nilotica spp nilotica Pods (Garad )Powder as Alternative Vegetable Retanning Material

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1 esearch Article 112 Application of Acacia nilotica spp nilotica Pods (Garad )Powder as Alternative Vegetable etanning Material A.E. Musa* 1 and G.A. Gasmelseed 2 1 Department of Leather Technology, College of Applied and Industrial Sciences, University of Bahri, Khartoum Sudan, P..Box Department of Chemical Engineering, University of Science and Technology, Khartoum- Sudan E mail: gurashigar@hotmail.com Telephone: (eceived: December 25, 2013; Accepted: February 21, 2014) Abstract- etannage is a process used to improve roundness, grain firmness and leather filling by the use of vegetable tannins, syntans and various types of resins. The aims of the process, to fill the looser and softer parts of leather in order to produce leathers of more uniform physical properties, to allow for the production of unlined footwear and to improve the chemical stability of the leather and to allow rapid finishing and delivery to the customer. Powder of Acacia nilotica spp nilotica pods (garad) widely distributed in Sudan has been evaluated for its utilization in the retanning of the leather and presented in this paper. The garad powder has been used for the retanning of wet blue leathers. The effectiveness of garad powder in retanning of wet blue leathers has been compared with wattle retanning.the organoleptic properties of the leathers viz. softness, fullness, grain smoothness, grain tightness (break), roundness, general appearance, uniformity of dyeing of garad retanned leather have been evaluated in comparison with wattle retanned leathers. Garad retanning resulted in leathers with good grain tightness. Dyeing characteristics of garad retanned leathers have been found to be better than wattle retanned leathers. Also physical strength characteristic and shrinkage temperature and were noted. Index Terms - etannage; Acacia nilotica; Wet blue, Wattle P I. INTDUCTIN osttanning operations, in general, attempt the addition of aesthetic values and improvement of intrinsic properties of leather [1]. echroming, neutralization, retanning, dyeing, and fatliquoring form the major steps of posttanning operations [2]. The term post tanning refer to the wet processing steps that follow the primary tanning reaction. This might refer to following tannage with chromium (III), as usually the case in industry, but equally it applies to vegetable tanning or indeed any other tannage used to confer the primary stabilization to pelt [3]. etanning may be a single chemical process or may be a combination of reactions applied together or more usually consecutively. The purpose is to modify the properties and performance of the leather. These changes include the handle, the chemical and hydrothermal stability or the appearance of the leather. The effects are dependent on both the primary tanning chemistry and the retanning reactions [3]. Vegetable tannins materials are widely employed for retanning side * Corresponding author E mail: ali206w@hotmail.com Telephone: leather and they are occasionally used in calf and goatskin in upper leather productions. They are also widely employed as general mordants for the production of dry crust tanned chrome leathers. They are cheap, readily, good filling agents, and make the grain hydrophilic. The condensed tannins (Fig. 1), such as mimosa or quebracho, reduce the chrome characteristics only very slightly but give leathers of poor fastness. The most widely condensed tannins are based on (-)- epicatechin and (+) - catechin. The hydrolzable tannins (Fig. 2), such as sumach, myrabolans, or chestnut, give leathers of improved light fastness and soft mellow handle. Hydrolysable tannins containing gallic acid esterified with glucose [4]. The vegetable retanning agents (tara and mimosa) inhibit the formation of free radicals so that the oxidation of unsaturated fatliquoring agents is avoided as well as chromium VI formation. The retanning agent of the polyhydroxyphenol type acts as an efficient antioxidant showing good temperature fastness [5]. Studying the antioxidant effect of several phenolic compounds in the presence of unsaturated fatty acids, [6] showed that gallic acid, tocopherol and caffeic acid were effective antioxidant compounds. Acacia nilotica, also known as Mimosa nilotica, is a member of the family Mimosaceae and is known in the Sudan as Garad. ther Acacia species such as A. seyal, Acacia arabica and A. abyssinica and are considered the most utilized and widely distributed species in eastern, southern and northern Africa and some Asian countries such as Saudi Arabia [7]. Acacia nilotica and other Acacia species are used in folk medicine by people in rural areas as a remedy for tuberculosis, leprosy, small pox, dysentery, cough, ophthalmia, toothache, skin ulcers and cancers and as astringents, antispasmodics, aphrodisiac [8,9]. Phytochemical analysis of the aerial parts of the plant demonstrated the presence of flavonoids and polyphenolic compounds in the flowers, tannins, glycosides, volatile oils, organic acids, coumarins and carbohydrates in the fruits[7]. Sudan has various indigenous tanning materials. Some of these, such as Garad pods (Acacia nilotica sub. sp. nilotica) and Talh bark (Acacia seyal) are used extensively in the Sudan by rural tanners. The tannin content of garad pods is fairly high and amounts to approximately 30% of the total weight, soluble nontans are nearly 20%, while moisture and insolubles make up the remainder. The main constituent of the garad tannin is presumably leucocyanidin gallate i.e. gallic acid esterified with

2 113 a flavanoid. Garad tannin is reported to contain chebulinic acid, gallic acid and to have a high sugar content, factors which are common in hydrolysable tanning materials. Garad tannins are therefore mixed tannins i.e. containing condensed tannins as well as hydrolysable tannins containing gallic acid esterified with glucose [10]. When garad pods are crushed, they disintegrate into three parts, the husk with about 12% pure tannins, the seeds with no tannin content and the grain powder with approximately 55% tannins. The seeds and husk form about 63.6% of the weight of the pod, the remainder being the grain powder [10]. ecently, both rural garad tanned crust leathers improved for production of semi-alum shoe upper leathers [11] and a combination tanning process based on garad powder (Acacia nilotica sub. sp. nilotica) and tetrakis hydroxymethyl phosphonium sulphate (THPS) for the production of upper leathers as a cleaner alternative, were presented[12]. Since the garad contains mixture of several compounds with varied molecular weight including polyphenols, an attempt has been made in this study to utilize them for the retanning of wet blue leathers. H = H, H H H H H H H H H N H H H Figure 1: Condensed Tannin Figure 2: Hydrolyzable tannin

3 114 II. MATEIALS AND METDS Materials Conventionally processed compact and fine wet blue cow sides were selected as raw material for this study. Garad (Acacia nilotica sub. sp. nilotica) pods were sourced from Sudan. Chemicals used for post tanning were of commercial grade. Chemicals used for the analysis of spent liquor were of analytical reagent. etanning procedure Two wet blue cow hides were taken. 2 sq. ft of leather in the official sampling portion (butt region) of the two left sides were taken for experimental retanning trails using garad pods powder. Similarly 2 sq. ft of the corresponding two right halves were taken for the retanning using wattle as a matched pair control as a comparison for the experimental leathers. The post tanning process mentioned in Table 1 is followed for both experimental and control leathers. Determination of Hydrothermal Stability The shrinkage temperature (Ts) is a useful index of the resistance of collagen to swelling in water or water solutions. The shrinkage temperature of both control and experimental leathers were determined using the Theis shrinkage tester [13]. A 2cm sample, cut out from the leather was clamped between the jaws of the clamp, which in turn was immersed in a solution of glycerol: water mixture (3:1). The solution was stirred using mechanical stirrer attached with the shrinkage tester. The temperature of the solution was gradually increased and the temperature at which the sample shrinks was noted. Triplicates were carried out for each sample and the average values are reported. Table 1 Formulation of Post-tanning process for making upper crusts aw material: Shaved wet blue leathers (cow) of thickness ~1.2 mm % chemicals for post tanning process is based on shaved weight Process % Product Duration (min) emarks Washing 200 Water 10 Drain Neutralization 100 water 1 Sodium formate 0.75 Sodium bicarbonate 3 15 ph etanning 20 Garad (Experimental)/ Wattle (Control) 1 hour Fatliquoring 5 Lipoderm liquor SAF (Syntheic fatliquor) 45 min Dyeing 3 Acid black dye 45 min Penetration of dye was checked Fatliquoring 5 Lipoderm liquor SAF (Syntheic fatliquor) 45 min Fixing 1.5 Formic acid 3 x min ph 3.5 Washing 200 Water 10 min Leathers were piled over night; Next day set, hooked to dry, staked, trimmed and buffed Hand Evaluation of the crust leather Experimental and control crust leathers were assessed for softness, fullness, roundness, grain smoothness, grain tightness (break), general appearance by hand and visual examination. Three experienced tanners rated the leathers on a scale of 0-10 points for each functional property, where higher points indicate better property. The tanners have also evaluated the dyeing characteristics viz., uniformity of dye, shade intensity and differential dyeing for both experimental and control crust leathers. Physical testing Samples for various physical tests from experimental and control crust leathers were obtained as per IULTCS methods [14]. Specimens were conditioned at 20±2 o C and 65±2%.H

4 115 over a period of 48 hrs. Physical properties such as tensile strength [16], and tear strength [17] were measured as per standard procedures. Each value reported is an average of four (1 along the backbone, 1 across the back bone from each side of the two sides) samples. Analysis of spent liquor The spent liquor from control and experimental post tanning processing were collected, filtered and analyzed for chemical oxygen demand (CD), Biochemical oxygen demand (BD 5 ), and total solids (TS) as per standard procedures [18]. strength, percentage elongation at break [15], grain crack important parameters especially for making upper leathers. The grain smoothness of garad retanned leathers has been found to be similar to that of wattle retanning. n the whole the leathers retanned with garad had been found to be better than wattle retannning. Hence use of garad for retanning appears to be a fruitful option for making leathers with good organoleptic properties. Table 2 Shrinkage temperature of crust leathers retanned with garad and wattle Chemical analysis The chemical analysis of the leathers for total ash, moisture, oils and fats, water soluble, hide substance, insoluble ash and degree of tannage were carried out as per standard procedures [19]. Analyses were carried out in triplicate for each sample and the average values are reported. Sample Wattle (Control) Garad (Experimental) Shrinkage temperature, Ts ( o C) III. ESULTS AND DISCUSSIN Shrinkage temperature Shrinkage temperature (referred to as Ts) is one of the most important parameters in characterizing the thermal stability of leather. It is the temperature at which the leather sample starts to shrink in water or other heating medium. apid and accurate determination of Ts is of great significance for the industrial leather production process as well as professionals in-depth research. The shrinkage temperature of wet blue crust leathers retanned using garad and wattle is given in Table 2. The wet blue leathers resulted in shrinkage temperature of 109 C; however the retanning with wattle and garad resulted in increase of shrinkage temperature to 121 C and 119 C respectively. It is clear that the treatment of garad enhances the shrinkage temperature significantly similar to the case of wattle; hence retanning with garad appears to be a promising option in terms of its reactivity with the leather matrix. Bulk properties of leathers hand evaluation of leathers The organoleptic properties of leathers retanned using garad and control wattle is given in Fig. 3. From the figure it is observed that retanning with garad resulted in leathers with good grain tightness and roundness compared to wattle retanned leathers. The fullness of the leathers with garad retanning had been found to be comparable to that of wattle. However, the softness of leathers with wattle retanning is found to be better than that of garad. To be an effective agent for retanning, the retanning material should improve the fullness, grain tightness and roundness of the leather, as they are the Note- Shrinkage temperature of wet blue leathers were 109±2 C Dyeing Characteristics of garad etanned Leathers The dyeing characteristics of garad and wattle retanned leathers have been evaluated by experienced tanners and the results are given in Table 3. The uniformity of dye of the garad retanned leathers has been found to be better than the wattle retanned leathers. The shade intensity of the garad retanned leathers has been found to be better than the wattle retanned leathers. No differential dyeing (between grain and flesh) has been observed for both garad and wattle retanned leathers. It is clear that the use of garad did not affect the dyeing characteristics of the leather compared to control; rather it enhances uniformity of dye and the shade intensity of the leathers, which is benevolent in obtaining leathers with brilliant shades. Physical strength characteristics of garad retanned leathers The physical strength measurements of matched pair garad retanned experimental and wattle retanned control leathers are given in Table 4. The physical strength measurements viz., tensile strength, elongation, tear strength, load at grain crack and distension at grain has been found to be comparable. The strength values of garad retanned leathers have been found to meet the BIS standards [20] for chrome retanned leathers. Table 3 Visual evaluation of the dyeing characteristics of crust leathers retanned with garad and wattle Property Garad (Experimental) Wattle (Control) Uniformity of V.Good Good dye Shade intensity V.Good Good Differential Dyeing Nil Nil

5 ating Garad (Experimental) Wattle (Control) Figure 3: Graphical 0 Fullness Grain tightness oundness Bulk properties Grain Softness smoothness General appearance Fullness Grain tightnessoundness Grain smoothnesssoftnessgeneral appearance organoleptic properties of the Experimental and control leather representation of Spent liquor Analysis The CD, BD 5 and TS of the spent liquor for both experimental and control trials were determined and are given in Table 5. From the table it is observed that the CD and BD of the spent liquor processed using garad retanning is lesser than the spent liquor from wattle retanning. However the solid content of garad retanning liquor has been observed to be higher than the wattle retanning liquor. Even though the solid content of the garad retanning liquor is higher, the degradability of the same is easier than the wattle retanning liquor. Table 4 Physical strength characteristics of crust leather retanned using garad (Exp) and wattle (Con.) Property Garad Wattle BIS norms* Tensile strength (Kg/cm2) ± ± Elongation at break (%) ± ± Tear strength (Kg/cm thickness) 40.55± ± Load at grain crack (kg) 25±6 27±4 20 Distention at grain crack (mm) 11.42± ±0.57 Min 7 *-Bureau of Indian standards (BIS) specification for chrome retanned upper leathers Table 5 Characteristic of spent liquor for control and experimental post tanning trials Parameter Wattle(Control) Garad (Experimental) CD (mg/l) 89980± ±1230 BD 5 (mg/l) 32900± ±750 Total solid (mg/l) 21980± ±850 Chemical analysis of the crust leather The chemical analysis of crust leathers are given in Table 6. The results for the experimental leathers are comparable to the control leathers. However, the water soluble matter for the control (wattle) leathers is more than the experimental leathers (garad).

6 117 Table 6 Chemical Analysis of crust leather of experimental and control Parameter Garad (control) Wattle (experimental) Moisture % Total ash content % Fats and oils % Water soluble matter % Hide substance % Insoluble ash % Degree of tannage % IV. CNCLUSINS The retanning may be a single chemical process or may be a combination of reactions applied together or more usually consecutively. The purpose is to modify the properties and performance of the leather. These changes include the handle, the chemical and hydrothermal stability or the appearance of the leather. The effects are dependent on both the primary tanning chemistry and the retanning reactions. Most organoleptic properties of the experimental leathers produced from garad pods powder are better than control leathers produced from wattle. However softness property is better in the case of wattle retanned leather and the physical strength properties are comparable with the matched pair control leathers. etanning with garad also facilitates in intense dyeing. Hence using garad appears to be a good alternative for the retanning processes. Further exploration is required to find effective utilization of garad pods powder in leather processing. EFEENCES [1]. amasami, T., ao, J.., Chandrasekaran, B., and Chandrababu, N.K., (1999c). Leather chemicals:emerging trends, Leather Age, [2]. amasami, T., and Prasad, B.G.S., (1991). Environmental aspects of leather processing, Proceedings of the LEXP XV, Calcutta, [3]. Covington, A. D., (2009). In Tanning chemistry: the Science of leather, published by the oyal Society of Chemistry, p 348. [4].Tuck, D. H.,(1981). The Manufacture of Upper Leathers. Tropical Products Institute, 56/62 Gray s Inn oad, London, WC1 8LU.verseas Development Administration, p 65. [18]. Clesceri.L.S., Greenberg, A.E., Trussel,., Eds., (1989). In standard methods for the examination of water and wastewater, 17th ed, American public health association, Washington DC. [5]. Palop,., Ballusi,., Manich, A. and Marsal, A., (2010). Leather Ageing and Hexavalent Chromium Formation as a Function of the Fatliquoring Agent. Part III: Interaction with Synthetic and Vegetable etanning Agents, J. Soc. Leather Technol. Chem., 94, [6]. Zhang, WH., Shi, B. and Shi, J., (2007). A theoretical study on autoxidation of unsaturated fatty acids and antioxidant activity of phenolic compounds. J. Amer. Leather Chem. Ass., 102(3), [7]. El-Shanawany, M.A.A., (1996).Medicinal plants used in Saudi traditional medicine. King Abdel Aziz City for Science and Technology, iyadh. [8]. Duke, J.A., (1983). Medicinal Plants of the Bible. Trado-Medic Book, werri, New York. [9].Van Wky, B., P. van Wky and B.E. van Wky., (2000). Photographic Guide to Trees of Southern Africa. Briza Publications, Pretoria, pp: 86. [10]. Gasmelseed, G. A. and Mulla, T. H. A., (1976). Simulation of Continuous Counter-current Leaching of Garad Pods., J. Chem. Biotech., Britain. [11]. Musa A.E., and Gasmelseed, G.A.,( 2012). Upgrading of rural garad-tanned crust leathers. J. Soc. Leather Technol. Chem., 96, [12]. Musa A.E., and Gasmelseed, G.A., (2012). Combination Tanning System for Manufacture of Shoe Upper Leathers: Cleaner Tanning Process. J. Soc. Leather Technol. Chem., 96(6), [13]. McLaughlin, G.D. and Thesis, E.., (1945). The chemistry of leather manufacture, einhold Publishing Corp., New York, p [14]. IUP 2, (2000).Sampling. J. Soc. Leather Technol. Chem., 84, 303. [15]. IUP 6, (2000).Measurement of tensile strength and percentage elongation. J. Soc. Leather Technol. Chem., 84, 317. [16]. SLP 9 (IUP 9), (1996). Measurement of distension and strength of grain by the ball burst, fficial methods of analysis. The Society of Leather Technologist and Chemists, Northampton,. [17]. IUP 8, (2000). Measurement of tear load double edge tear. J. Soc. Leather Technol. Chem., 84, [19]. fficial Methods of Analysis., (1965). U.K. Society of Leather Technologists and Chemists.. [20]. Bureau of Indian Standards (1964).Specification for chrome retan upper leather; IS 2961; New Delhi, India.