Optical resin formed body manufacturing method, resin fiber manufacturing method, and resin fiber manufacturing apparatus

A resin fiber manufacturing method, comprising:

• (I) depressurizing an inside of a container holding a molten resin material;
• (II) pressurizing the inside of the container holding the molten resin material;
• and
• (III) spinning by extruding the molten resin material out of the container to shape the molten resin material into a fiber shape, wherein
• the steps (I) and (II) are sequentially performed once each or are alternately performed two or more times each,
• in the step (I), a duration t1 [min] of the depressurization of the inside of the container is set such that the duration t1 and a viscosity µ1 [Pa•s] of the molten resin material satisfy a relation µ1/t1 < 200,
• in the step (II), a duration t2 [min] of the pressurization of the inside of the container is set such that the duration t2 and a viscosity µ2 [Pa•s] of the molten resin material satisfy a relation µ2/t2 < 200,
• the viscosity µ1 is a viscosity of the resin material at a shear rate of 0.05 s-1 at a temperature in the container in the step (I), and
• the viscosity µ2 is a viscosity of the resin material at a shear rate of 0.05 s-1 at a temperature in the container in the step (II).

A resin fiber manufacturing apparatus, comprising:

• a holding portion that holds a resin material serving as a raw material of a resin fiber;
• an extrusion portion that allows the resin material held in the holding portion to be extruded out of the holding portion;
• a heating portion that heats the holding portion;
• a pressure control portion that controls a pressure in the holding portion;
• a depressurization mechanism that depressurizes an inside of the holding portion;
• and
• a pressurization mechanism that pressurizes the inside of the holding portion, wherein
• the pressure control portion controls the pressure in the holding portion such that depressurization and pressurization are alternately repeated at least once,
• the pressure control portion depressurizes the inside of the holding portion such that a duration t1 [min] of the depressurization of the inside of the holding portion and a viscosity µ1 [Pa•s] of the resin material that is molten satisfy a relation µ1/t1 < 200,
• the pressure control portion pressurizes the inside of the holding portion such that a duration t2 [min] of the pressurization of the inside of the holding portion and a viscosity µ2 [Pa•s] of the resin material that is molten satisfy a relation µ2/t2 < 200,
• the viscosity µ1 is a viscosity of the resin material at a shear rate of 0.05 s-1 at a temperature in the holding portion in the depressurization,
• the viscosity µ2 is a viscosity of the resin material at a shear rate of 0.05 s-1 at the temperature in the holding portion in the pressurization, and
• the resin material extruded through the extrusion portion is shaped into a fiber shape.