The rheological properties of viscoses prepared from celluloses of varying polydispersity were investigated. Decreasing the polydispersity increases the homogeneity of spinning solutions with a decrease in the concentration of carbon disulfide in them. A universal curve characterizing the change in the viscosity of viscose within wide shear rate limits is proposed and can be used for technological calculations.Studying the rheological properties of viscoses in a wide range of shear rates and stresses not only provides extensive information on the behavior of polymer systems in different types of deformation but can also be used for the necessary technological calculations in creating equipment for fabrication and spinning of viscoses.This situation becomes important in developing technologies for fabrication of fibres, thread, and films from highly concentrated viscoses or viscoses prepared from celluloses with a high degree of polymerization (DP) and simultaneously decreasing consumption of carbon disulfide. Only such an approach to preparation of viscoses and the creation of processes for high-speed spinning of viscose fibres, thread, and films will allow the viscose method to compete with "carbon diaflfidefree" processes for fabrication of these cellulose materials (cellulose carbamates, dissolution of cellulose in N-morpholine Noxide, oxypropylation and methylation of celluloses, etc.).In studying the rheological properties of viscose, special attention has been focused on such an important index as the polydispersity of the celluloses, which can significantly affect the properties of viscoses prepardd with low carbon disulfide technology. Celluloses of "high," "medium," and "low" polydispersity were investigated. The differential molecular-weightdistribution (MWD) curves of these celluloses are shown in Fig. 1. The celluloses were fractionated in cadoxen with subsequent precipitation of the fractions in 75 % propanol solution [1]. The weight-average DP w, viscosity-average DP v, and number-average DP n degrees of polymerization and the polydispersity index of the celluloses, DPw/DP n, were calculated from the data obtained. "High" polydispersity was characterized by DPw/DP n = 1.8, and "medium" and "low" polydispersity were character ized by values of 1.5 and 1.3, respectively. Viscoses with a different concentration of a-e.ellulose, sodium hydroxide, carbon disulfide, and different DP of the celluloses were prepared from celluloses of varying polydispersity on the UkrSRIF pilot installation.The effective viscosity r/e f of these viscoses was measured at 20"C in the region of low and medium shear stress (shear stress up to 103 sec-t) on a Reotest instrument and high shear stresses (shear rate up to 106 sec-t) on capillary viscometers [2][3][4][5][6][7]. The initial Newtonian viscosity r/0 was calculated from the flow curve in coordinates of log D (shear rate) -log r (shear stress). The curves characterizing t,,e effective viscosity as a function of the shear rate in logarithmic coordinates for viscoses prepa...

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The duration of preripening was determined by estimat#~g the kinetics of degradation of alkaline cellulose fabricated by bulk mercerization of cotton cellulose. Comb#wd melrerization and preripening, xanthation, and dissolution of celhdose xanthate were conducted in the conditions of the VA equipment, and the basic characteristics of the viscose were determined. It wasjbund that spinning a standard solution into a spinn#Tg bath produces viscose fibre with satisfactory physicochemical indexes.Due to the characteristics of the structure and the much higher homogeneity of the molecular weight, cotton cellulose as raw material for processing with the viscose method is of the greatest interest for production of cellulose materials used wet (viscose sausage casings, dialysis and ultrafiltration membranes), and for production of high-modulus viscose fibres. However, the possibilities of using it in viscose are not exhausted by this list, since cotton cellulose can be used in production of both industrial and textile fibres as a function of indexes primarily determined by the method of production from linters [ 1 ]. The correct selection of the parameters for the stages of manufacture of viscose and spinning fibres from it will ensure obtaining the required and even a high level of physicomechanical indexes for the finished product [2][3][4][5][6][7]. The results of a study of the possibility of manufacturing viscose fibre by processing an experimental batch of cotton cellulose* prepared by the scheme described in [8] are reported below. The basic characteristics of the cellulose are reported in Table 1.According to the data from x-ray structural analysis (Fig. 1), cotton cellulose has a crystallinity index (approximately 72%) and hygroscopicity (for relative humidity of 65%, sorption of moisture of 7 g/100 g of absolutely dry cellulose) typical of this type of cellulose. Moreover, the data on the solubility of the cellulose in solutions of NaOH indicate the comparatively high polydispersity of the sample.At Ukrainian Scientific-Research Institute of Man-Made Fibres, we proposed an equation which allows characterizing the correlation of the polydispersity index U 0 = DPw/DP with the degree of maximum swelling in NaOH solution with a concentration of 120 g/liter (Srnax), where U 0 = 3.26 -2.21-10-~. Srnax , based on mathematical processing of the data for cellulose of varied origin and methods of fabrication.The maximum degree of swelling of the experimental batch of cellulose (805%) and the calculated values of U 0 = 1.48 indicate its higher polydispersity than for industrial samples of cotton cellulose (U 0 = 1.2-1.35).Viscose was fabricated with consideration of the crystallinity of the cellulose, c~-cellulose content, and initial degree of polymerization (DP) in a Simplex experimental xanthator with a Z-shaped stirrer designed for a load of 1 kg of cellulose. Combined mercerization of the cellulose and preripening of the alkaline cellulose were conducted by treating cotton cellulose previously cut into staples 10-15 m...

Rigorous respect of the standard character and purity of the spinning solution, spinning bath parameters, and orientation draw ratio ensures obtaining a complex fibre homogeneous over the length. By varying the flow rate of viscose from the spinneret and disk rotation, it is possible to vary the fibre tension, strength, elongation, and shrinkage within wide limits and ensure a high capacity for uniform dyeing. The limits of the overall draw ratio of viscose textile fibres of varying assortment without elementary fibre breakage and formation of nap were established.Such eminent scientists as Z. A. Rogovin, E. M. Mogilevskii, A. B. Pakshver, and their many students were deeply involved in creating the first viscose textile fibre plants in the prewar years in Russia, Ukraine, and Belarus. In the first stages of creating technologies, most of the attention was focused on the study of fibre spinning and elucidating the mechanism of passage through its basic stages neutralization of free alkali, coagulation of viscose, and saponification of cellulose xanthate (CX) [1][2][3]. Interesting research on saponification of CX was conducted at the end of the 1950s under the direction of Z. A. Rogovin and A. A. Konkin, then a post-graduate student, and subsequently the first director of the Kiev branch of the All-Union Scientific-Research Institute of Man-Made Fibres D. N. Arkhangelskii [4][5][6]. His students repeatedly returned to this problem in manufacture of not only fibres and filaments but also cellophane, and cellulose films and membranes [6][7][8][9][10][11][12].The fundamental structural elements and physicomechanical properties of viscose textile fibres are formed when the spinning solution flows out of the spinneret and during orientation drawing of the spun fibre. For this reason, the composition of the spinning baths is selected to make it possible to attain the required strength and elongation of the finished fibre by establishing a defined spinneret and orientation draw ratio. Repeated attempts to assess their effect on the physicomechanical indexes of fibres both overall and individually did not produce positive results. An overall draw ratio that takes into account the effect of the longitudinal force acting on the gel and then on the fibre, which is in a plastic state, was most effective for this evaluation. The overall draw ratio λ o is the ratio of the maximum fibre takeup rate (usually the spinning speed ν s ) and the flow rate of the viscose out of the spinneret (ν f ):In consideration of the spinneret (B s , %) and orientation (B or , %) drawing used in the plants, the value of λ o can be calculated with the equationThe data on the effect of λ o on the relative breaking stress (σ, cN/tex) and elongation at break (ε, %) in production of viscose textile fibres are shown in Figs. 1 and 2. As we can see, σ increases with an increase in the draw ratio, attaining extremal values at λ o = 1.46, and then decreases. In the same region, the elongation of the fibre ε decreases sharply with an

Equations are proposed for calculating the kinetics of the change in the degree of polymerization of cellulose in basic medium; they describe the experimental data with sufficiently high accuracy. The dependence of the rate constant of degradation of cellulose in mercerization on the concentration and temperature of the alkali and the content of low-molecular-weight fractions in the reaction mass was established. It was found that degradation of cellulose in the disperse state in mercerization and preripening of alkaline cellulose obey the same rules. The effective concentration of alkali included in the liquid phase of alkaline cellulose was proposed as the criterion for evaluating the occurrence of preripening, identical to the concentration of mercerizing alkali. Using previously established degradation mechanisms and having calculated the residence time of the cellulose in basic medium in different stages of the manufacturing process, it is possible to evaluate and predict the degree of polymerization up to the finished product.Degradation of cellulose, which takes place in viscose technologies primarily in basic medium, is one of the most important stages used to regulate the viscosity of spinning solutions within wide limits and attain the required degree of polymerization (DP) to ensure the necessary strength and elasticity of viscose fibres, filaments, films, and coatings. Z. A. Rogovin also did not abandon the study of degradation of cellulose in different media, publishing the first work on this subject at the beginning of the 1930s in the journals Iskusstvennoe Volokno and Kunstseide (Germany). Studies on cellulose chemistry were subsequently reflected in the well-known seminal monographs of Z. A. Rogovin [1-3] and his many publications.Unfortunately, not all of the scientific ideas and endeavors were realized in this outstanding scientists lifetime. It was possible to theoretically substantiate and implement his idea of increasing the solubility of cellulose xanthate and decreasing the consumption of toxic carbon disulfide by activation of alkaline celluloses before xanthation with a low-concentrated alkali in industry only in the mid-1990s [4-6]. His research on alkaline degradation of cellulose was also not brought to the logical conclusion.It was historically established, so that most of the attention of researchers investigating this process was focused on comparing different hypotheses on the chemical transformations of cellulose in basic medium and developing methods of measuring the degree of polymerization and molecular-weight distribution. The studies in this direction were undoubtedly pressing and made some contribution to the science of cellulose chemistry. However, the fundamental mechanisms of degradation of cellulose in basic medium were not established, and the lack of a mathematical description does not allow controlling the process in industrial practice. And to this day, the temperature-time regime of degradation of cellulose in viscose technologies is actually not regulated, but is ...