Dissolution Of Naturally Colored Cotton In [BMIM]C1Ionic Liquid And Its Assistant Extraction Of The Pigment

Naturally colored cotton fabrics have the advantages such as the protection of theenvironment and comfortable to wear, so the products have wide potential uses in the markets.However its color instability, color incomplete and poor quality of the fiber restrict thedevelopment of colored cotton products. From the study of the pigment composition and structureof colored cotton fiber, we can find the probable ways to improve the color stability of fiber aswell as improve the product competition of naturally colored cotton textiles. In recent years, thestructure and properties of naturally colored cotton fiber and pigment components structure werestudied extensively, but not yet a clear conclusion. Ionic liquids are new type of cellulose solventwhich was regarded as "green chemistry," having low temperature melt, good thermal stability,designable and other advantages. In this paper, natural colored cotton fibers were studied.The swelling and dissolution behavior of naturally colored cotton in [BMIM]Cl wereinvestigated by optical methods. The effects of reaction temperature, reaction time, andpretreatments on the swelling and dissolution behaviors were studied. The results showed thatbrown cotton, green cotton and white cotton all having balloon swollen followed by completelydissolving in [BMIM]Cl ionic liquids, but their solubility was different. The pigment substance ofgreen cotton spreaded out from the fiber lumen during the balloon swelling and dissolution whilethe pigment of brown cotton did not. The alkaline and enzymatic pretreatment could increase theswelling ratio of the fiber. But the ballooning phenomenon of cotton fiber disappeared after theenzymatic pretreatment. The time required to reach maximum swelling decreased and the fiberdiameter at maximum swelling increased with the increasing of ionic liquid temperature.The change of the degree of polymerization of cotton cellulose had been studied. Thecrystalline structure of the regenerated cellulose have been analyzed by the X-ray diffractometer(XRD),the chemical structure of cellulose have been analyzed by FT-IR, the thermal stability,thermal degradation rate have been compared by TGA and DSC, the cut-section of the regenerated cellulose were observed by SEM. Results indicated that the DP of the fiber aggregate decreasedobviously. The crystal structure of the cellulose transformed without derivatization. Theamorphous region increased after dissolution and regeneration in [BMIM]Cl. At the same timethe thermal stability of the cellulose after dissolution were decreased. The regenerated celluloseshowed uniform internal structure.The investigation found that the pigment of brown cotton can be extracted effectively frombrown cotton cellulose.[BMIM]Cl ionic liquid-assisted method could extract more componentsthan common water extracting method. Ionic liquid-assisted extraction had some ingredients thatwater extracting method could not achieve.[BMIM]Cl ionic liquid have significant interactionwith brown cotton pigment, their UV spectral curves show good affinity. HPLC chromatographicpeak of ionic liquid-assisted extraction had stronger absorption at500nm, which indicate its morepronounced colored characteristic. Ionic liquid-assisted method could not extract some substancesfrom common extraction by water. Common extraction had the pigment substances at theretention of1.43min and2.33min which was differed from ionic liquid-assisted extraction. Boththe method of water extraction and ionic liquid-assisted extraction have good complementary.