Transaction Effective Lac Dyeing of Cotton Fabric by Pretreating with Tannic Acid and Aluminum Acetate Yukiko Togo and Motoko Komaki Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan Abstract: Lac dyeing of cotton fabrics pretreated with tannic acid and aluminum acetate was investigated. Five treatment methods (tannic acid alone, aluminum alone, tannic acid → aluminum, aluminum → tannic acid, and tannic acid → aluminum → tannic acid) before dyeing with lac were compared for their effect on adsorption of the laccaic acid to cotton fabric. The treatment with tannic acid → aluminum was found to be the most effective for lac dyeing of cotton. It was found that tannic acid enhanced the aluminum adsorption to cotton fabric, and the affinity of aluminum to laccaic acid enhanced the dyeing effect. The adsorption of tannic acid, aluminum and laccaic acid to cotton was quantitatively determined, and the dyeing mechanism was proposed. (Received 11 November, 2009 ; Accepted 24 November, 2009) 1. Introduction pretreated with a cationic agent [3, 4], polyethyleneimine (PEI) [5] and chitosan [6, 7]. On the other hand, it was Lac color is a natural red dyestuff obtained from the proposed by an artist a method of pretreating cotton with resinous secretion, sticklac, from lac scale insects which tannic acid and aluminum acetate for dyeing with inhabit Southeast Asia. This sticklac adheres to the twigs cochineal which has the main component of carmic acid of trees, and contains a resin and colorant. This resin, of similar chemical structure to laccaic acid [8]. The shellac, is used for such purposes as varnish, a coating method described was treating the cotton fabric with agent for medical tablets and fruits, and a water-proof tannic acid solution beforehand, then with aluminum material. The colorant has been used in the past for solution and with tannic acid solution again before dyeing dyeing silk, and is presently used as a food color. with cochineal. It will be proposed in this paper that Environmental considerations are now increasing interest cotton can be dyed with lac dye after being pretreated in coloring textiles with natural dyes. It was suggested the with tannic acid and aluminum acetate, and the dyeing economical and ecological dyeing method with natural mechanism is also investigated. dyes such as grape pomace for wine or poor brew of tea were applied in Austrian textile industry [1]. The shellac 2. Experimental demand is now getting high however the residual lac dye is in a state of excess-supply in Japan. The extracted 2.1 Materials colorant from sticklac is composed of water-soluble Scoured and bleached cotton fabric (plain woven laccaic acids which are derivatives of hydroxyl- anthraquinone carboxylic acid. The relevant chemical structures are shown in Fig. 1 [2]. Laccaic acids are able to dye conveniently protein fibers such as wool and silk, but quite different on cellulose fiber, because the dye has not any “substantially” towards cellulose coming from the long chain like molecule structure. Wool or silk have been still dyed traditionally with the lac dye in Bhutan and Laos. Cotton is hardly dyed with lac color using any alum as mordant and repeating the dyeing process in Laos but it does not become deep shade. It has been recently reported that cotton could be dyed with lac after being Fig. 1 Chemical structure of laccaic acids （41） SEN’I GAKKAISHI（報文）Vol.66, No. 4 (2010) 99 #2023, Kanebo), lac dye powder (Aikuma Senryo Co.), were each dyed with lac dye at a concentration of 1% owf tannic acid (C6H7O6{C6H2(OH)3COOC6H2(OH)2CO}5, in a dyeing solution adjusted to pH 3.3, a liquor ratio of SIGMA) and soluble aluminum acetate (Al(CH3COO)3, 1:50and80℃ with 100 cpm agitation for 10 min. Each Nakarai Tesque) were used to this experiment without dyed cotton fabric sample was rinsed twice with father purification. We could not use basic aluminum deionized water and then dried at room temperature. acetate because it become aluminum hydroxide and 2.6 Quantitative analysis of aluminum in precipitated upon attempting to dissolve in water. The solution other chemicals used were of reagent grade. All reagents The quantity of aluminum in the soluble aluminum were dissolved in deionized and then millipore-filtered acetate solution was gravimetrically determined with water. 8-hydroxyquinoline (oxine, C9H7ON). An aqueous 2.2 Instruments solution of 2% 8-hydroxyquinoline in 4% acetic acid was An M-100N shaker (Taitec) was used for treating the prepared. A drop of a 2 M HCl solution, 10 ml of the 2% cotton fabric with aluminum and then with lac dye. A 8-hydroxyquinoline solution and 1 ml of 2 M ammonium UV-visible spectrophotometer (V-550 Jasco) was used to acetate were added to a solution of the aluminum acetate measure the absorbance of the liquor for qualitative and sample. The mixed solution was stirred at more than 70℃ quantitative analyses. The reflective spectra and for 30 min. After the reaction had been completed, the chromaticity values of the dyed fabrics were respectively yellow precipitate was filtered through GA100 glass fiber measured by a diffused reflectance integrating sphere paper under reduced pressure, dried at 130℃ and then attached to a UV-visible spectrophotometer (UV-240 weighed. It was confirmed that the weight of the Shimadzu) and a visible spectrophotometer (NF777 precipitate corresponded to the aluminum content with a Nippon Denshoku). linear relationship (aluminum acetate concentration of 0 - 2.3 Pre-treatment of the cotton with tannic acid 2 g/l). A tannic acid solution (0 - 5.0 g/l) was prepared by 2.7 Quantitative analysis of the adsorption of lac dissolving the required amount of tannic acid in deionized dye to cotton, calculation of K/S and the water. The cotton fabric (1 g) was immersed in 50 ml of chromaticity value of the dyed fabric from the solution at 60℃, and the bath was heated to boiling reflectance point and heating continued for 10 min. The residual The residual dye liquor contained aluminum concentration of tannic acid in the solution was calculated desorbed from the pretreated fabric. The reaction of the from the absorbance measured by spectrometry at 276 nm lac dye with aluminum in solution was in equilibrium at (UV-visible spectrophotometer V-550). Each pretreated the isosbestic point at 507 nm (Fig. 2). cotton fabric sample was rinsed twice with deionized The n value in Fig. 2 represents the ratio of water and then dried at room temperature. aluminum to lac dye ( n = [Al] / [Lac] ). The dye liquor 2.4 Pre-treatment of cotton with aluminum concentration in residual liquor was determined from the Soluble aluminum acetate was dissolved in difference of absorbance at 507 nm (UV-visible deionized water to a solution concentration of 1 g/l. spectrophotometer V-550). Kubelka-Munk function K/S Cotton fabric (1 g) was treated in 50 ml of the solution at 100 cpm and 20℃ for 30 min, then removed and rinsed three times with deionized water and then dried at room temperature. This processing method is called “Al”. The cotton fabric treated with the tannic acid solution beforehand was treated with the aluminum solution by a similar procedure. This is called “TA→Al”. The cotton fabric treated with the aluminum solution beforehand was treated with the tannic acid solution. This is called “Al→ TA”. After the TA→Al treatment, the cotton fabric was treated in the tannic acid solution, this being called “TA →Al→TA”. 2.5 Lac dying procedure Fig. 2 Spectral change of laccaic acid with soluble The cotton fabric samples pretreated by the five aluminum acetate added by the ratio Lac : Al (1 : methods (TA, Al, TA→Al, Al→TA, and TA→Al→TA) 0~1:3n=0~3) 100 SEN’I GAKKAISHI（報文）Vol.66, No. 4 (2010) （42） and L*a*b* (CIE 1976) chromaticity values were determined from the reflectance of the lac-dyed cotton fabric. The reflectance %T for K/S calculation was measured by UV-240, under the condition of λ range : 400 - 700 nm with 5 nm width. L*a* b* was determined by using NF777. 2.8 Calculation of the quantity of tannic acid, aluminum and lac dye adsorbed to the cotton The quantity of tannic acid, aluminum and lac dye adsorbed to the cotton, Q (mg/g of cotton), was estimated by using the following equation : Fig. 3 K/S spectra of lac-dyed cotton fabric pretreated with TA and Al Q =(C0-Cf) V /W (1) acid was combined with aluminum (TA→Al) for lac where C0 and Cf are the initial and final concentrations of dyeing. Adsorbed quantity Q to the cotton, and the K/S at the tannic acid, aluminum and lac dye solution (mg/l), maximum wavelength and CIE L*a*b* color system respectively, V is the volume of the dye liquor (l) and W values of the lac-dyed cotton fabric are listed in Table 1. is the weight of fiber (g). The adsorption of tannic acid to cotton by the pretreatment was 16.7 mg/g. Subsequently, as a result of 3. Results and discussion lac dyeing, the lac dye adsorbed was 0.7 mg/g and 0.8 mg/g with and without tannic acid, respectively. The K/S spectra for the lac-dyed fabric pretreated by the pretreatment of cotton with only tannic acid did not different methods are shown in Fig. 3. Each picture of the enhance the dye uptake, it being almost the same as that dyed fabric is shown in Fig.4. The effect of the of the untreated cotton.