The dissolving ability and technological suitability of different cellulose solvent systems are compared. Based on a critical analysis of the available literature and experimental data, the dimethylformamide-dinitrogen tetroxide system is the most suitable solvent from the point of view of solution preparation and fiber production. The principal parameters of the technological process for manufacturing regenerated cellulose fibers by the "Camilon" process are compared with those for the viscose process.The Camilon process is demonstrated to have ecological and economical advantages. Composite fibers of cellulose and various synthetic polymers are considered. The special properties of cellulose solutions in zinc chloride and the regenerated cellulose fibers produced from these solutions are discussed.In the manufacture of man-made fibers, it is a paradox that one of the cleanest fiber types, i.e., regenerated cellulose fibers, is produced by one of the least environmentally acceptable methods. The viscose process compares unfavorably with other methods of synthetic fiber manufacture on the basis of air and water pollution and the use of carbon disulfide [ 9 ] . A substantial decrease in the emission of harmful pollutants into the atmosphere and hydrosphere is practically unattainable because of difficulties in recycling wash waters and recovering carbon disulfide [ 10 ] . Therefore, the development of a nonpolluting method for manufacturing regenerated cellulose fibers based on the viscose process seems highly improbable.New Solvents ' One of the possible ways of solving this problem is the development of processes based on nontraditional, less harmful solvents. In recent decades, there has been great scientific and practical interest in studies of nonaqueous cellulose solvents. We have considered these solvents on the basis of several factors that characterize their dissolving ability and technical suitability [3][4][5] .These factors include dissolution rate, temperatures and pressures required, maximum attainable cellulose concentrations at various levels of degree of polymerization (DP), solution viscosities, cellulose degradation upon storage, solvent and spinning solution stabilities, toxicity and availability of reagents, recovery of reagents, and finally the quality and processability of the spun fibers. It follows from the data shown in Table I that for the preparation of spinning dopes, temperatures in the range of 40 to 200°C are required, and for volatile substances such as ammonia and sulfur dioxide, elevated pressures must be used. Dissolving under normal temperatures and pressures is possible only for mixtures of organic liquids with dinitrogen tetroxide.A distinctive feature of nonaqueous cellulose solutions is their higher viscosity compared to that of normal viscose solutions. In contrast to viscose solutions. the time dependence of viscosity is not extreme ( Figure I ). Viscosity either increases regularly (cellulose solutions in aminoxide, ethyl acetate, and acetonitrile with N204 ), which r...

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