| Naturally colored cotton (NCC) is a kind of cotton with natural color in its fiber. Theappearance of fiber color is the result of production and accumulation of the fiber pigment infiber cell. Up to now, only the brown and green NCC fiber can be used in machine spinningtextiles. NCC fibers are of interest in the textile industry because they require little dyeing andresult in less environmental pollution. NCC produces have some excellent properties, such asnatural luster, elegant, soft, and so on. But some of their shortcomings have restricted the furtherdevelopment of NCC industry, such as its monotonous color, poor fiber quality and bad colorstability. Therefore, the type and property of pigment of NCC fiber have become hot issues forthe development of NCC production. The main aim of this paper was to extract, separate andidentify the pigment of green NCC and brown NCC fiber. Also, the improvement of colorchange, the antibacterial performances and UV-visible diffuse reflectance spectral UV-VisDRS properties were analyzed preliminarily.At first, solubility of the pigment in green NCC and brown NCC fiber was researchedsystemically. Absolute ethyl alcohol and70%ethanol aqueous solution were selected as pigmentextraction solvent for green NCC and brown NCC, respectively. According to the chemicalcharacteristics and the wave spectra analysis, pigment types of two kinds NCCs are different.The pigment of green NCC is weaker polarity and alkali-soluble compound, and it may belong toflavonol with two adjacent hydroxide groups and indican replaced a hydroxide group. Thepigment of brown NCC is strong polarity and water-soluble compound, and it may belong tocondensed tannin (CT) or quinine from condensed tannin oxidation.Because of difficult extraction of green NCC pigment, this paper analyzed the optimumextraction process of green NCC pigment with ultrasonic-assisted by using orthogonal testdesign and using absolute ethyl alcohol as extractant, and built a method for the relativequantitative test of pigment in extract liquor of green NCC using an ultravioletspectrophotometer. Comparing with the ordinary extraction, effects of different processconditions with ultrasonic-assisted on pigment extraction efficiency were discussed. In the paper,the supercritical extraction method of green NCC pigment was also explored. The resultsindicated that the pigment composition extracted by ultrasonic-assisted method was as same as that extracted by ordinary extraction, while the extraction efficiency was significantly increased.At the same condition, the efficiency of ultrasonic-assisted extraction of green NCC pigment for20min was equivalent to that of ordinary extraction for5h. By orthogonal experiment, theoptimum extraction technology with ultrasonic frequency40KHz and power100W was:temperature70℃, time100min, solid-liquid ratio1陶奉125ml. At the condition of pressure30MPa,80℃,5h with right amount entainer, the green NCC pigment could be extracted bysupercritical fluid extraction method. In a certain process, supercritical fluid extraction can makegreen NCC pigment to external transfer, and deepen the color of fiber surface.This paper got a kind of pigment material in green NCC and identified its structure. Afterextraction with ultrasonic-assisted, the extracted pigments of green NCC were purified with C18reversed-phase silica gel column, and identified with UV-vis, IR, MS and NMR. Resultsindicated that green NCC pigment is multicomponent. One of the main ingredients was separated,and it has properties of flavonoid compound. After drying, this separated main component islight yellow powder, and molecular weight is592. It has intensive pH value dependence. Inalkali solution, its color darkens with the increase of pH value. This color change is consistentwith the color change rule of green NCC fiber with alkali treatment. Results indicated that thisgreen cotton pigment is a kind of flavonoid also, it has6,7–OH,5–OCH3,6–C–Glu in ring A and3’,4’–OH in ring B, in addition,3–OH is possibly being substituted. Other two separatedcomponents belong to flavonoid compounds also, and their properties are similar. Theirmolecular structure needs to separate and identify in the further.The extracted pigments of brown NCC were purified with polyamide columnchromatography, reverse-phase high-performance liquid chromatography (RP-HPLC) andpreparative liquid chromatography, and identified with UV-vis, MADLI-TOF MS and ESI-MS.Results indicated that there were many ingredients in brown NCC pigment extract, most ofwhich were in the850~1250molecular-weight (MW) region. The pigment extracts of brownNCC could be successfully separated by preparative C18-Reversed-phase chromatography, thepigment extracts consists of five components at least, including four poor reservationscompositions on reverse phase column and one cluster mixture with span bigger MW. Usingdistilled water,50%acetone, pH=9.0ammonia water and0.3%urea solution for elution agent inturn, the pigment extract could be effectively divided into four part fraction by polyamidecolumn chromatography. Two colored and two colorless compositions were isolated from thewater elusion segment by preparative C18-Reversed-phase chromatography. The two colored components didn’t belong to the same kind of substance. One belongs to another phenoliccompound in addition to the CT, the other may be the trimer or tetramer of B type CT. Thestructures of two colorless components were extremely similar. A phenyl was the only difference,and they probably belonged to lignans with multiple aromatic rings.This paper reports a novel treatment method for improving the color stability of green NCC.Pretreatment with petroleum ether can improve color thermal stability and light fastness. Ethanolextracts from green NCC were analyzed by Gas chromatography-mass spectrometry (GC-MS).Results indicated that treatment with petroleum ether can remove certain components which maybe detrimental to the color stability of green NCC. This treatment method is useful for thatneeding high-temperature finishing of green NCC products.The antibacterial property of brown NCC was discovered. The antibacterial activity ofNCCs was evaluated though improved AATCC Test Method100-2004, and the antibacterialperformance of the pigments in NCCs was analyzed with the K-B programe (Inhibition zonemethod). The experiment found that pigments in NCCs influence antibacterial properties ofNCCs. After degreasing process with petroleum ether, brown NCC shows excellent antibacterialproperties with a reduction rate of96.4%and89.1%, when contacting with Klebsiellapeneumoniae and Staphylococcus aureus, respectively. While the antibacterial effect of greenNCC and white cotton were not obvious. The darker was brown NCC, the better wasantibacterial performance. The antibacterial activity of brown NCC is relevant to its pigment.Inhibition zone methods showed that the pigment of brown NCC has good and durableantibacterial ability. The antibacterial effect of the pigment extract in brown NCC shows aninsignificant change under human body sweat conditions. General textile high temperaturecuring conditions will decrease its antibacterial activity, but the antibacterial activity still hassatisfied retention.Finally, using of the color character, UV-Vis DRS properties of NCCs were analyzedpreliminarily. It was found that UV-Vis DRS of NCC is different from dyeing cotton and whitecotton. UV-Vis DRS can identify NCC and rapidly determinate the blended ratio of NCC andwhite cotton fiber. For the investigative NCC and white cotton fiber,450nm wavelength can beused for characteristic wavelength to quantitatively predict. The relationships of reflectivity andgreen NCC content meet the equation: y=尼14.165Ln (x)+16.3, R2reaches0.9918; the relationships of reflectivity and brown NCC content meet the equation: y=尼14.799Ln (x)+6.0894, R~2reaches0.9903. |
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