677.4.051.261 The spinning stability and thread defectiveness are not only a function of the degree of purity of the industrial solutions, correspondence of the parameters of the viscose and spinning bath, but also the conditions of flow of the viscose through, the spinneret openings and formation of a threadlike jet.Since precipitation of the polymer and structure formation take place in the immediate vicinity of the spinneret (0.02-0.2 ram) -in the zone where the thread is subject to high tension from contact with the spinrfing bath (SB), it is necessary to create conditions which will decrease the length of this "liquid" section. It is also necessary for the elementary jet of viscose coming out of the spinneret to be uniform, for its surface to have no defects, and for the shape to be close to cylindrical. These conditions can be created not only with the material but also with the use of spinnerets of special design.As published sources indicate, the characteristics of the spinnerets which affect the spinning stability and thread defectiveness are the following: the shape of the spinneret, the angle of the input cone, the ratio of the channel length to the diameter//d, and the density of the openings on the bottom. The currently used cup-shaped spinnerets have a significant drawback -stagnant zones appear inside them along the generator of the bottom. Contaminants and air bubbles can accumulate and the viscose can coagulate in stagnant zones.In going from a cylindrical to a conical spinneret, where the openings are positioned over the entire surface of the bottom, stagnant zones are almost totally eliminated. In addition, the normal constituent (directed perpendicular to movement of the thread) of the force of the hydrodynamic resistance of the SB decreases, deforming the jet, and causing formation of splices and breaks. Due to these advantages, conical spinnerets have long been used by many foreign manufacturers of viscose textile thread.The uniformity of flow of the viscose in the channel of the spinneret opening greatly affects the stability of the spinning process. In going into the channel of the opening, the shear stress increases sharply and the input energy increases [1]. If it exceeds a certain critical value, the continuity of the jet is perturbed and it breaks. Spinnerets with conical expansion of the opening at the inlet are used to reduce the shear stress.For uniform flow of the viscose, this angle must be no less than 20* [2]. In our opinion, the angle of the input cone should be within the limits of 20-30 ~ In the platinum-palladium spinnerets manufactured by Mostochlegmash Co., the angle of the input cone, calculated with the standard channel dimensions (USSR Technical Standard TU 3-17A.4-88) is 18"; this could be a possible cause of the appearance of unstable flow of the viscose in the channel.Expansion of the viscose jet in coming out of the opening channel is an unfavorable factor in spinning. Many factors affect expansion of the jet: the viscose flow rate, density of the SB, spinneret ...
This article describes tests of nonwoven antimicrobial filter materials from viscose fibre (rayon) containing the antimicrobial preparations catamin AB and desant. Wide-ranging tests of antimicrobial filter materials have been carried out to determine the aerodynamic characteristics, dust content and dust penetrability, weather tolerance, resistance to saprophytic (mold) fungi, etc. The tests and functionbased classification of antimicrobial filter materials comply with GOST R 51251. Investigations were carried out at the microbiological laboratories of I. V. Michurin All-Russia Scientific Research Institute of Orcharding, Center of Hygiene and Epidemiology in the Moscow Region, and FGU "Mendeleevskii TsSM" to determine the efficiency of air purification from microorganisms by antimicrobial filter materials made of viscose fibre containing the preparations catamin AB and desant employing a specially designed equipment. Performance tests of various types of air filters having filter elements from filter materials containing desant and catamin AB have been carried out. The efficiency of air purification from the microorganisms Staphylococcus aureus, Micrococcus falvus, Bacillus subtilis, etc. that infect patients in medical institutions has been determined.Specialists of NITsKhV "Viskoza" (Scientific Research Center of Chemical Fibres "Viscose") have developed a nonwoven antimicrobial filter material (NAFM) from viscose fibre (rayon) containing the antimicrobial preparations catamin AB and desant for air filters whose main function is to rid air of microorganisms.Diverse conditions of use of air filters having filter elements made from antimicrobial filter material, such as differing fractional compositions of mechanical impurities in the air being filtered (particle size ranging from 0.0001 to 1000.0 μm), varying compositions of microorganisms, etc., make it necessary to conduct wide-ranging tests of the filters for determining the aerodynamic characteristics and the efficiency of air purification from dust and microorganisms.Filter materials containing antimicrobial additives, alongside high efficiency of decontamination (sterilization) of the air from microorganisms, should also help clean the air from mechanical impurities at the level of those filter materials that are proposed to be substituted by the referred filter materials.Depending upon the function of the filter, the filtration efficiency (pass-through factor) is determined in conformity with GOST (All-Russia State Standard) R 51251 [1] from the mass dust concentration (for rough and fine filters) or from the countable particle concentration using model mixtures (for high-and super-high efficiency filters).One of the basic characteristics of any filter materials used for filtering air is aerodynamic resistance, which determines to a great extent the energy consumption for filtration.Additionally determined, in general, is the aerodynamic characteristic of the filter material or of the filter, which is a graphic representation of the aerodynamic resistan...
We have studied the filter materials in the most popular foreign breathing filters. We have established that the filter set for a bacterial/viral heat and moisture exchange (HME) filter consists of a primary filtering layer which provides highly efficient removal of bacteria and viruses from the air as a result of mechanical or electrostatic filtration; barrier layers, preventing migration of fibers and moisture droplets into the primary filtering layer; and a heat and moisture exchange layer, providing the needed humidity and temperature for the air inspired by the patient.As a result of our studies, we have selected or designed de novo filter materials to make a filter set for a domestic breathing filter. We have determined the parameters of the material for the heat and moisture exchange layer: weight percent of fibers, thickness, surface and volume density, air permeability, hygroscopicity, weight percent calcium chloride.In designing domestic filter materials for breathing filters, we studied materials in the most widely used imported breathing filters: Pharma Systems (Sweden), Pall (an international company), and Venticaire (UK).As a result of our studies, we have established that there are two basic types of filter sets: -a filter set for bacterial/viral filters, consisting of a primary filtering layer ensuring efficient removal of bacteria and viruses from breathing mixtures, plus two barrier layers which are mainly intended to keep droplets of liquid from entering the primary filtering layer; -a filter set for bacterial/viral heat and moisture exchange filters, consisting of a primary filtering layer, a heat and moisture exchange layer that humidifies and warms the breathing mixtures, and two barrier layers.Furthermore, there are breathing filters in which only one type of filter material is used, designed only for humidification and warming of the breathing mixtures ("artificial nose"). Primary filtering layerThe primary filtering layer is designed for highly efficient bacterial/viral filtration. As follows from the results of analysis of filter materials in imported breathing filters providing highly efficient removal of bacteria and viruses from air, two types of materials are used:-filter materials consisting of fine glass, ceramic, or other fibers of diameter down to 1 µm and having a dense, fine-pored structure, and which accomplish mechanical filtration of the breathing mixtures;-electret (electrostatic) filter materials, consisting of polyester, polypropylene, or polyacrylonitrile fibers of diameter 20-35 µm, providing high-efficiency filtration largely due to electrostatic attraction forces between aerosol particles and the fibers of the material. These materials are most promising for breathing filters, since they have low aerodynamic resistance and significantly cheaper materials for mechanical filtration.
This articles examines the production of thin-filament cellulosic (viscose) filament fibers for making a filter-material that can efficiently remove leukocytes from blood and its components. The main requirements for the fibers were formulated on the basis of preliminary studies. Equipment was chosen, an existing AVK-0.6 unit was rebuilt, and a process was developed for producing the fibers. The process includes the stages of fiber formation, regeneration, and washing. Processes were also developed for forming tows from the filament fibers and cutting the tows into fibers 4-6 mm long. The fibers have been used to create a filter-material for filtering leukocytes from blood and its components.A process for making thin-filament cellulosic (viscose) fibers has been developed to create a Russian-made filtering material that can efficiently remove leukocytes from blood and other transfusion media.Leukocytes are known to be the principal means by which viral infections are transmitted. Agents that cause illness generally become attached to the cellular components of blood -leukocytes -or end up inside those components [1,2]. Providing patients with transfusions of leukocyte-free blood plasma, erythrocytes, or thrombocytes reduces the risk of infection by pathogens a hundred-fold.According to international requirements in the Guide to the Preparation, Use, and Quality Assurance of Blood Components (Council of Europe Press, 15th edition, 2009) and the Engineering Standard on the Safety Requirements for Blood and Its Products [3], the number of leukocytes remaining in a dose of any component of blood should not exceed 1·10 6 . Since some leukocytes have dimensions ≥ 7 μm -which is comparable to the 7-8 μm dimensions of erythrocytes -the problem of separating cells of nearly the same size in order to remove cells of one type (leukocytes) while allowing cells of another type (erythrocytes) to pass through the filter is very complex.After reviewing the patent literature, the best foreign-made blood-filtering materials, and the results of laboratory studies, we chose to a method of making filtering material that employs technology used in the production of paper. We also determined the main requirements for the fibrous components of the product. The most important requirements for the fibers used in the composition are that they be small in diameter, hydrophilic, and easily separated in an aqueous medium without forming floccules.An analysis of the properties of the chemical fibers produced in the nations of the CIS (Commonwealth of Independent States) during the period 2002-2007 showed that cellulose-hydrate fibers are the fibers best-suited for making filtering materials by the technology employed in paper production. These fibers have properties similar to those of natural cellulose fibers but absorb less water.In the process of formulating the technology, we came up with the following requirements for the cellulosehydrate fibers:-low linear density (no higher than 0.042 tex, which corresponds to a fiber diameter of 4.8 μm...
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