高分子物質の曳糸性について

Abstract

In the case of dry spinning or melt spinning, the extruded liquid-thread from the spinneret are coagulated rapidly or slowly by drying or cooling depending on the system. The spinnability of the extruded liquid-thread under such conditions are different as compared with the spinnability of ordinary means, but it has important meaning at the stand point of industrial spinning process.It has been tried to analyse the deformation process of extruded liquidthread under simple assumptions, i.e., there is no drying or cooling of liquid-thread during the deformation process. Under such special conditions, the following behavior is recognized.1. Keeping the diameter of spinneret hole and the viscosity of spinning liquid constant, a small rate of extrusion brings a small rate of deformation.2. Keeping the rate of extrusion and the viscosity of spinning liquid constant, a large diameter of spinneret hole brings a small rate of deformation.3. Keeping the rate of extrusion and the diameter of spinneret hole constant, a large viscosity of spinning liquid brings a small rate of deformation.From the behavior mentioned above, some interesting suggestions about the practical spinning process will be obtained. In the case of melt spinning, the extruded liquid-thread is cooled by heat conduction only, and the coagulating speed is rather slow as compared with the dry spinning of volatile spinning solution. Then rather large diameter of spinneret hole is suitable for melt spinning, because a small rate of deformation provides a sufficient time for coagulation. From another view point, the extruded liquid-thread will be drafted enough during the long coagulating time, so a fine denier filament is obtainable by using even a large diameter spinneret hole.A spinning of slow coagulating liquid should take a spinning condition of small rate of deformation in order to get a suitable coagulating time, but an extremly small rate of deformation brings some difficulties, that is, the position of the maximum stress in the extruded liquid-thread shifts upwards by smaller rate of deformation and uncoagulated liquid-thread receives a large stress, it becomes a cause of breaking of liquid-thread in actual spinning process.In the case of dry spinning of cellulose acetate, the spinning solution is very volatile and the coagulation of extruded liquid-thread is rapid. Then it is rather difficult to get a long drafting time, so small diameter of spinneret hole is suitable to get a fine denier filament.From above considerations, we can choose an optimum spinning condition for getting suitable coagulating time by changing the diameter of spinneret hole, the rate of extrusion, and the viscosity of spinning liquid.There are another characteristics having influence on the spinnability, for instance, the shear dependence of viscosity, the balooning of extruded liquid-thread and the surface tension of the spinning liquid.The spinning liquid having large shear dependence of viscosity will not suitable for slow coagulating spinning conditions, because a large shear dependence brings an acceleration of deformation, and it is difficult to control the spinning condition without breaking of liquid-thread. The influences of the balooning and the surface tension are not described in this paper.