The effect of different regimes for each stage of fabrication of cotton cellulose on its supermolecular structure was evaluated by electron microscopic methods. It was shown that rigorous conditions of fabrication of cotton cellulose cause destruction and loosening of the surface and inner layers of the fibre. This indicates an increase in the reactivity of the cellulose and is promising for processing # into viscose fibres.As a function of the method of separation of cellulose, its structure has special features which are manifested by different reactivity, kinetics of mechanical transformations of the cellulose, and properties of the final product [1][2][3]. There are data which suggest the dependence of the reactivity of wood cellulose on the morphological structure and degree of its breakdown [4][5][6].Cotton cellulose has lower reactivity than the wood cellulose used for fabrication of viscose fibres. For this reason, it is important to select the conditions of separation of cellulose which will maximally increase its capacity for esterification and decrease the viscosity while preserving a high concentration of o~-cellulose.Microfibrils of the primary wall of fibres based on cotton cellulose are known to form an unusual loosely packed network which virtually does not prevent penetration of reagents inside the fibre [7]. The following first layer of the secondary wall has a dense structure with rigorously parallel mutual orientation of packed microfibrils, in turn densely twisted around the axis of the fibre. This layer swells poorly, and the size changes little in delignification. We can hypothesize that the reactivity of the cellulose in this layer is lower than for the cellulose in the basic secondary wall.The effect of the basic stages of processing (preliminary cleaning of linter and cellulose, cooking, bleaching, etc.) in fabrication of cotton cellulose suitable for viscose formation on the supermolecular structure of the surface and inner layers of the fibre was investigated in the present study. Type III cotton linter with an 8% degree of contamination was the starting raw material. The cellulose was obtained by alkaline cooking with subsequent bleaching.The structure of the cellulose was investigated with a PEM-100 electron microscope using a Pt/C replica and ultrasound dispersion methods [8]. The possibility of maximum cleaning of extraneous contaminants from the cotton linter was determined first, since there are high requirements concerning ripeness, degree of contamination, and length for linter intended for chemical processing.Using multistage Centricleaner cleaning (CCC) of linter as the most efficient, it was possible to decrease the degree of contamination from 8 to 2.8%. Maximum elimination of waste contaminants was obtained after 4 cleaning stages.The purpose of cooking is the further removal of lignin from the linter and other substances associated with cellulose, as well as to decrease the viscosity. Cellulose suitable for viscose formation should have a viscosity within the limits of 17...
In order to obtain high-quality cellulose for the chemical industry, it is necessary to maximally free the linters of waste contaminants before further processing. The cleaner the linters are, the higher the yield of cellulose, the better its processing, and consequently the higher the reactivity (Re).On the other hand, the quality of cellulose esters is not only a function of the degree of purity of the starting cellulose but also of its molecular homogeneity, the morphological structure of the starting raw material, and the degree of its de~adation during fabrication of cellulose, is.e., there is a correlation between the Re of cellulose and its morphological structure [1][2][3]. The Re of cellulose also varies as a function of the character and type of treatments it undergoes [4, 5].Microscopic studies of different wood celluloses showed that the stronger the damage of the surface of the fibres, the higher the Re of the cellulose [4]. As a result of treatments of the cellulose (mechanical, chemical), its Re can increase, and in many cases, decrease.The results of the study of the qualitative and structural characteristics of samples of cotton cellulose prepared by combined boiling and bleaching as a function of the method of cleaning the linters are reported here. All samples were prepared from type one linters (III) and in the same conditions of combined boiling and bleaching: concentration of hydrogen peroxide: 4% of the weight of the linters, alkali: 5 g/liter, temperature of 135~ duration of 60 mill. The difference in them was that sample 1 was obtained from linters without cleaning, sample 2 was obtained from linters dry cleaned in a LO-4 machine to a 4.3% degree of soiling, sample 4: the linters were ground in a beater and cleaned in a central cleaning installation, sample 3 --the linters Were first treated with an alkali with a concentration of 5 (a) 10 (b), and 20 (c) g/liter at a temperature of 50~ for 30 mill. The basic characteristics of the samples are reported in Table 1.The structural and sorption characteristics of the cellulose were investigated by x-ray diffraction, microscopic, and sorption methods.For the x-ray diffraction studies, a DRON-3M diffractometer with monochromatic CuK~ radiation with current of 12 mA and voltage of 23 kV was used. The patterns were taken in the interval of 20 = 10-35 ~ The degree of crystallinity was calculated with the ratio, of the peak intensities with the Segal equation.The microscopic studies were conducted in transmitted and polarized light with a MBI-6 optical microscope. The outer appearance, shape, presence of anisotropy, defects, degree of homogeneity, and swellability of the samples in a solution of Cadoxen in a concentration at which cotton cellulose does not dissolve were determined. The size (width) of the samples before and after swelling was determined with all ocular microscope and the average size of two parallel estimations was then found with the results of 30 measurements.Sorption of vapors was determined on a McBain vacuum balance with a quar...
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