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Method and device for regulating the atmospheric conditions during a spinning processRelated Patent Categories: Refrigeration, Automatic Control, Refrigeration ProducerMethod and device for regulating the atmospheric conditions during a spinning process description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060144062, Method and device for regulating the atmospheric conditions during a spinning process. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention relates to a method and a device for controlling the room air conditions in a spinning process carried out in an open spinning area opposite the room, whereby endless molded articles are extruded, in the spinning area, from a spinning mass containing cellulose, water and tertiary amine oxide, and the extruded endless molded articles are air-quenched with a gas phase in an air jet prior to the immersion into a precipitating bath, and wherein the spinning plant can be inspected and maintained by operating staff in a staying area adjacent to the spinning area. [0002] Endless molded articles from a spinning mass containing water, cellulose and tertiary amine oxide are substantially produced in the three process steps extruding, drafting and precipitating. N-methyl-morpholine-N-oxide (NMMNO) is used as tertiary amine oxide. [0003] For the extrusion the heated spinning mass is passed through extrusion openings of the spinning plant and is extruded to form endless molded articles. An air gap is directly adjacent to the extrusion openings or, respectively, to the extrusion or spinning nozzles. In the air gap, a tensile force is applied to and drafts the endless molded articles. The thickness of the endless molded articles, e.g. the fiber titer of textile fibers, is adjusted by means of the tensile force. Moreover, under the influence of the tensile force, the molecules orientate themselves in the endless molded articles thereby increasing the mechanical stability thereof. Subsequently, the endless molded articles are immersed in a precipitating bath, in which the solvent still contained in the endless molded articles is precipitated. In industrial practice the spinning process takes place in a substantially closed room, mostly a hall, a spinning hall or the like. [0004] The production of endless molded articles from a spinning mass containing cellulose, water and tertiary amine oxide involves on the one hand the problem that the surface adhesiveness or tackiness of the endless molded articles directly after the extrusion is very high. For rendering the fiber production process economical, extrusion nozzles with a high spinning density, i.e. a high number of extrusion openings per surface unit have, on the other hand, to be used. This inevitably leads to a small spacing between the individual extrusion openings and the extruded endless molded articles in the air gap and, thus, to a negative influence on the thermal balance in the area of the extrusion and drafting zone. Thus, high temperatures are generated that may reduce the spinning or drafting viscosity of the extruded endless molded articles to such an extent that the fibers break. [0005] For reducing the surface adhesiveness and the temperature of the endless molded articles in the air gap, some solutions have been proposed in the prior art. [0006] Document U.S. Pat. No. 4,246,221 describes the production of cellulose fibers and filaments, which are sprayed, in the air gap, with a nonsolvent such as water after the extrusion so as to reduce the adhesiveness of the filament surfaces. [0007] As the spraying with a nonsolvent is relatively complicated, air quenching of the endless molded articles in the air gap with air or a gas mixture according to the prior art has generally been adopted. [0008] In document WO 93/19230 it was described for the first time that, for the production of cellulose fibers according to the NMMNO process, the filaments exiting the nozzle can be cooled with air or a gaseous medium directly after the exit, so as to obtain a higher productivity. [0009] According to the teaching of WO 96/21758 the spinning performance can be improved and the fibrillation tendency can be reduced, if the air humidity in two portions of the air gap is adjusted at different levels. [0010] In the two devices according to WO 95/01470 and WO 95/01473 an annular spinning nozzle is employed for the production of fibers, allowing the supply of the cooling gas stream to the filament bundles in a constantly laminar manner. [0011] Document WO 96/17118 describes a method according to which conditioned air is used for cooling the freshly spun filaments. In other words, air with a relative air humidity of up to 85% can be injected. DE 19717257 A1 describes an improvement where air between 14 and 25.degree. C. is used for the air quenching. [0012] Document WO 96/07777 describes a method for the production of cellulose fibers, whereby, for the production of fibrillation-reduced fibers, aliphatic alcohols such as methanol, ethanol, propanol and butanol are introduced in a gaseous state for air quenching the extruded filaments. [0013] All of the devices and processes according to the aforementioned prior art documents commonly describe air-quenching at a very low velocity, so that the quench air stream is substantially laminar. The laminar stream has the purpose to avoid too strong a mechanical load of the endless molded articles by the air stream. According to the devices described in documents WO 94/28218 and WO 98/18983 the air jet is sucked off through a suction nozzle in the air gap on the opposite side for stabilizing the air-quenching direction. [0014] As the cooling effects of these conventional air-quenching methods within the air gap are not sufficient to obtain high production rates of endless molded articles by simultaneously increasing the quality, which is due to the low air-quenching velocities, a turbulent gaseous substance stream is directed at the endless molded articles in the air gap in accordance with the teaching of document DE 102 00 406 filed by the applicant, the entire contents of which are included by reference in the present specification. Such a turbulent cooling gas stream effects a more efficient cooling, and a better intermixture in the area of the endless molded articles, as well as a better thermal compensation. The type of air supply described in DE 102 00 406, preferably not directly after the filaments exit the nozzle and not directly before the immersion thereof in the precipitating bath, stabilizes the spinning process. With simultaneously high hole densities a sufficient drafting tension during the extrusion can be applied on one hand. On the other hand, the endless molded articles no longer stick to each other in the air gap as soon as they touch each other, which could, otherwise, easily entail the tearing of individual endless molded articles or undrafted parts in the finished endless molded articles. If tearings occur, the extrusion process has to be stopped and restarted. Undrafted parts or thickenings result in a reduced fiber quality and increased waste. [0015] Due to the strong turbulent intermixture in such a turbulent cooling gas stream, however, solution substances and degradation products from the spinning process are entrained by the cooling gas stream to an increased extent, and are transported into the environment of the spinning plant. [0016] Due to the high velocities of the cooling gas stream, a removal by suction--as is described in WO 94/28218 or WO 98/18983--in the direct vicinity of the endless molded articles is no longer possible, as a strong suction effect would otherwise be exerted on the endless molded articles. Moreover, the turbulent cooling gas stream influences the room air conditions in the room in which the spinning process takes place, as it penetrates more easily through the endless molded articles deep into the spinning area or the staying area as a result of its high velocities. [0017] In view of the aforementioned processes and devices comprising air-quenching by means of a gaseous substance stream, it is a basic problem that the degradation products transported by the gaseous substance stream are a burden to the room air conditions in the environment of the plant, thus entailing unfavorable working conditions for the operating staff. [0018] In view of the production of Rayon fibers it is known from the prior art, e.g. from U.S. Pat. Nos. 3,924,984 and 4,477,951, to hermetically seal the spinning area and to suck off the degradation products released during the spinning process into the ambient air inside the sealed portion. The byproducts such as carbon disulfide and hydrogen sulfide are sucked out of the hermetically sealed spinning areas, as said gases are dangerous to health and must not be released into the work environment. Said documents additionally disclose that the spinning points are subjected to vapor for adjusting the spinning ambient temperature and the humidity, as the room air conditions are of great importance for the quality of the fibers. [0019] Such insulated or sealed spinning areas are, however, disadvantageous in as far as the very unfavorable operating properties of such a plant are concerned: If maintenance or repair works take place, a hermetic sealing of the spinning area under a kind of protection cover is problematical, as the operating staff inspecting the spinning plant and the spinning process from an inspection area located in the staying area cannot, or only with difficulties, notice malfunctions in the spinning process through said protection cover. Moreover, if maintenance works take place in the spinning area, it is complicated to remove the hermetic cover at first. The provision of a protection cover also negatively influences the exchange of nozzles. [0020] A solution for facilitating the maintenance and the inspection of a spinning plant is described in document DE 102 04 381 of the applicant, the entire contents of which are herewith incorporated by reference. The spinning plant according to DE 102 04 381 comprises spinning means, which are freely visible from an inspection area being a part of a staying area for the operating staff, and which are, at the same time, accessible by the operating staff--essentially out of one posture--in a maintenance area located between the inspection area and the spinning plant, which likewise forms part of the staying area. [0021] For obtaining, as a consequence, an efficient air-quenching on one hand, which increases the quality of the spun endless molded articles, and, on the other hand, an easy inspection and maintenance performance of the spinning plant, it is accordingly necessary to keep the spinning area open with respect to the room, in which the spinning area is located or, respectively, in which the spinning process takes place. [0022] If the air-quenching in the air gap takes place at high flow rates, as are commonly required for the spinning of cellulose fibers, there is the problem that the room air conditions in both the spinning area and the staying area for the operating staff deteriorate. A deterioration of the room air conditions in the spinning area, especially an increase of humidity and temperature, may require stronger air-quenching for maintaining a constant spinning quality. This, on one hand, results in the further deterioration of the room air conditions or the atmospheric environment of the room in the maintenance area and, on the other hand, in an increased mechanical stress on the endless molded article, up to filament breakage. [0023] The invention is, therefore, based on the object to provide a method and a device allowing the use of efficient air-quenching, with the simultaneous ergonomic construction of the spinning plant, and the adjustment of the room air conditions necessary under the aspect of working technique. [0024] According to the invention this object for the above-mentioned method is solved by controlling the exhaust air from and the additional air to the room, taking into account the gaseous substance stream, such that predetermined room air conditions are adjusted in the spinning area and/or maintenance area. Continue reading about Method and device for regulating the atmospheric conditions during a spinning process... 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