TECHNICAL FIELD

The invention relates to dye preparation from tea waste, in particular to a natural effective tea dye powder and a method of extraction and application thereof on fabric and garments.

BACKGROUND ART

Biomass pigments have been regarded as promising alternatives to conventional synthetic dyestuffs for the development of sustainable and clean dyeing. Tea is a renewable biomass resource that is grown in many nations and regions around the world.

The issue of using tea extracts as a biomass pigment, in commercial scale is due to the limitation, that, the tea compounds which gives the colour of the tea dye such as flavan-3-ols, and their concatenated polymers, contain many phenolic groups, and are hydrophilic. Thus, these negatively charged dye molecules, are poorly adsorbed to the hydrophobic fabric and tends to come to the aqueous phase. The issue is worst in case of cotton, which has negative charge OH groups on the surface, and therefore, there is repulsion between the similarly charge polyphenolic dye of the tea, which results in poor absorption of the dye to the fabric, and does not meet the required wash and light fastness property of the dye.

There are ample literature reports, of the use of tea ( Camellia sinensis) as a good source of colorant due to the presence of colored polyphenolic compounds, but it is not an effective natural dye, due to its poor wash and light fastness properties, thus limits its commercial application.

There are a number of reports on the use of tea dye in the presence of metal mordants, to reduce the negative repulsion between the dye and the fabric molecule (CN 101956334B). The metal mordant such as Fe, Al, Cu, has been used, which adheres, to both OH groups of the fabric and the dye. However, repeatability, fastness properties, and discharge of dyed liquor with substantial amounts of metal, hinders its commercial application.

There is a report on the use of Chitosan as a cleaner and greener compound, to increase the dye uptake of hot water tea extract (CN 103451963 A). However, the degree of deacetylation, chain length, of chitosan is not provided.

Further, there are a number of reports, including Japanese patent, describing potential methods of extracting theaflavins and thearubigins (W02009119111 Al), by oxidation of tea polyphenols and subsequently extracting them to organic solvents. Due to expensive organic extraction procedure, again limits its commercial application. There is a patent for a method for the production of plant extracts having a standardized flavonoid content, in particular the luteolin content from plants of the Resedaceae family using water/ethanol extraction and for dyeing textiles or leathers. (US 20060078630A1). The extract contained luteolin, apigenin, luteolin-7-glucoside and luteolin-3,7-glucoside, with luteolin being more than 10% of extract weight.

DETAILED DESCRIPTION

The tea used for extraction of tea dye are the tea rejects namely Broken Mixed Fannings (BMF); small bits of tea that are left over after higher forms of tea leaves are gathered and generated. Approximately 30,000 MT of BMF is generated, for the 350 Million Kg of high quality, black tea exported each year from Sri Lanka. Approximately 10,000 MT of this BMF is used to generate instant tea. And rest of 20,000 MT is discarded as waste material. Further, it is interesting to note that by using, 10,000 MT of BMF, Sri Lanka has become the main sourcing unit on the world instant tea market, accounting for close to 50% of the global supply of the Ready to Drink volumes sourced from Pepsi Lipton International.

In brief the BMF is extracted to hot water at 80 - 95 °C for 20 -45 min. with Liquid to Material Ratio (L/M) varying from 10:1 to 30:1 in a counter current extraction apparatus. The tea extract (A), thus obtained, after squeezing out the spent tea leaves accounts for 25-30% w of original BMF. The tea extract (A) is further heated for 20-30 min, at 80-95°C, in presence of air, and cooled to 40-45 °C and treated with 2g/L of, hydrolysing enzymes such as viscozyme (Sigma Aldrich) which is a cellulotic enzyme mixture. The resulting mixture (B), with a solid content around 3-6%, are separated into two fractions by centrifugation and filteration namely supernatant (C) and sediment (D). The supernatant (C) is rich in soluble solids including, concatenated polymers of flavan-3-ols, such as theaflavins, thearubigins etc, whereas the sediment (D) is richer in insoluble solids which are bulkier hydrophobic comparatively non polar groups such as flavones/isoflavones glycosides, which is used for the preparation of dye. The bulkier hydrophobic non polar flavones rich sediment (D) with solid content from 15-20% is filtered through a mesh of 200- 400 mM, and sediment (E) with complexed glycosides with particle size above 400 pM are removed, while the filterate (F) with solid content of 10-14%, is further evaporated to regain the solid content up to 15-20%, and spray dried at 240 °C to obtain the powder, which is used as the tea dye. The difference in the composition of (D) with respect to (B) and (C), is illustrated in the FTIR spectra (Figure 2), and the chemical constituents of each fractions were analysed using Liquid Chromatography Mass Spectrometry Quadrapole Time of Flight (LCMS QTOF).

The supernatant (C) of extraction procedure (figure 1) can be used as a raw material for various ready to drink tea drinks, and if so, the tea dye (obtained through sediment D) could be considered as waste material of tea drink manufacturing process and results in reduction of C(¾ foot print.

LCMS-QTOF analysis of Tea dye obtained after spray drying of filterate (F) showed a higher percentage of flavones/isoflavones glycosides including but not limited to, Apigenin glycosides, Vitexin, Isovitexin, Genistein 8- C-glucoside/ Vicinin 2, Saponarin, Pelagomin, Vitexin-2-rhamnoside, Isovitexin 2"-0-Rhamnoside, 5, 7 -dihydroxy - 3 -(4-hydro xyphenyl)-6, 8-bis [3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl] chromen-4-one, 5, 7-dihydroxy-2-(4- hydroxyphenyl)-6-[3, 4, 5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]chromen-4-one,8-[4, 5-dihydroxy 6(hy droxymethyl)-3-[3, 4, 5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxyoxan-2-yl]-5, 7-dihydroxy -2- (4hydroxyphenyl)chromen-4-one,3-[(2S,3R,4S,5R,6S)-3,4-dihydr oxy-6-methyl-5-[(2S,3R,4S,5S,6R)-3,4,5- trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxyoxan-2-yl]oxy-2-(3, 4-dihydroxyphenyl)-5-hydroxy-7-[3,4,5 trihydroxy-6-(hydroxymethyl) oxan-2-yl]oxychromen-4-one,Neoeriocitrin, whereas lower in concatenated polymers, such as-theobromine and theophilin and also comparatively lower in flavonol glycosides namely but not limited to Quercetin glycosides, Isoquercetin glycosides, Kaempferol glycosides, Hyperoside, Nicotiflorin, Hirsutrin, Rutin, Myricitrin, Hespiridin, Astragalin, Spiraeoside, Datistin, Maritimein, Plantaginin, 2-(3,4- dihydroxyphenyl)-5,7-dihydroxy-3-[(2S,3R,4S,5R,6R)-3,4,5-tri hydroxy-6-(hydroxymethyl)oxan-2- yl]oxychromen-4-one, 3, 5, 7-trihydroxy -2-[3-hydroxy-4-[(2S,3R,4S, 5S,6R)-3 ,4, 5-trihydroxy -6-(hydroxymethyl) oxan-2-yl]oxyphenyl]chromen-4-one. Table 1 compares the intensities, which is proportional to concentration of these compounds in the original Broken Mixed Fannings (the starting material- with poor light and wash fastness) and the filterate (F), the extract which is an effective natural tea dye with required wash and light fastness properties.

Figure 3 and 4 gives structures of flavone glycosides and flavanol glycosides for clarification. Figure 5 is the heat map, analysis of LC-MS metabolomics. The row displays the compounds and the column represents the tea samples namely, Broken Mixed Fannings (BMF) and the tea dye (Filterate F). Compounds which significantly decreased (low intensity) are displayed in green, while compounds which significantly increased (high intensity) are displayed in red. The brightness of each color corresponded to the magnitude of the difference when compared with average value

Quantification was carried out using standard compounds, and it showed that the tea dye contained Catechin and Epicathecin concentration below 1 mg/g, ECG of below 5 mg/g, EGCG 40-45 mg/g and caffeine content of 20-25 mg/g quantity. The quercetin content of the tea dye was low as 0.05 mg/g.

Table 1 : Comparison of compound intensities as for LC-QToF data, found in BMF and Tea dye

PROCEDURE OF DYING TEXTILE USING THE TEA DYE

The invention has enabled to earn carbon credit by reducing consumption of fossil fuel (petroleum) based synthetic dyes, with reduction in dying time and water consumption More specifically, the disclosed natural dye process includes first pre-treating the fabrics in the presence of non-metallic, poly amine mordant solution including but not limited to chitosan. Chitosan is obtained through deacetylation of chitin, the exoskeleton of crustaceous. The degree of deacetylation of chitosan should be minimum 90%. Fabric is pre-treated with chitosan (0.5-2 g/L), from pH 3-6 at a temperature between 60° - 80° C for 20- 30 min. The pre-mordanted fabric are then treated with the natural dye solution, concentration ranging from 7-20% as for the fabric used for sufficient time to produce the desired colour. Unlike prior art techniques, often necessary to choose conditions which severely damage the fiber to obtain a suitably dyed fabric, the dying conditions of this invention, are compatible to the synthetic dying procedures, with no additional drastic conditions. The fabrics are then rinsed, drained and dried.

The dying time and water consumption are reduced from 15-50% depending upon the fabric (cotton, linen, nylon, wool, polyester).

As for the type of fibre/fabric (cotton, liner, nylon, wool, polyester), the dying time varies from 45 -90 min, material to liquor ratio (MLR) ranging from 15-30, dying temperature ranging from 80-130 °C.

The technology was further extravagated to obtain full palette of colours by adding minute quantities of synthetic dyes to natural dye, with synthetic dye to natural dye ratio of 4:96. That is by use of reactive dyes in case of cotton fabric, acid dyes in case of nylon fabric and disperse dyes in case of polyester fabric, in ratios ranging from 0.25 - 1.0 % as for the weight of the fabric in combination with tea dye, gave different colour pallets. In case of reactive dyes the required amount of sodium sulphate and sodium hydroxide are added for synthetic dye exhaustion and fixation to the cotton fibre.

Further, the dye process of this invention does not require the use of heavy metal salts or iron and thus produces permanently dyed fibers without producing toxic waste. The improved biodegradable poly amine mordant solution and natural dye process of this invention reduces the wastewater disposable cost which results in cleaner production, with greater social and economic benefits.

The dyed fabrics were tested for colour fastness to light, water, perspiration, laundering, crocking and bleaching using standard protocols. The dyed fabrics showed the required fastness properties, the value ranging from 3.5-4.5, depending upon the fabric and the standard protocols. The colour fastness to light was evaluated using water cooled xenon arc lamp 20 AATCC FADING UNIT (AFU), using American Association of Textile Chemists and Colorists (AATCC) 16.3-14 protocol. Colour fastness to non-CL bleach was measured using AATCC/ASTM TS-001 protocol, and color fastness to perspiration using AATCC 15-13, and colour fastness to laundering accelerated was accessed using AATCC 61 protocols.