Correlation between the conditions of fabrication and structure of cotton cellulose for viscose formation

Abstract

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...

Cotton cellulose: Ecological and resource-saving raw material for production of viscose fibres. A review

“…Studies of production of cotton cellulose showed [25] that the basic characteristics which make it possible to process cellulose with the viscose method and spin viscose textile fibre with properties close to the indexes of the industrial product can be attained with the following process scheme: centricleaner washing, alkaline pulping, centricleaner washing, two-stage bleaching with sodium hypochlorite solution, acid wash, washing.…”