Abstract: A porous regenerated cellulose hollow fiber is obtained by a micro-phase-separation method. The hollow fiber is characterized in that the viscosity average molecular weight is at least 5.times.10.sup.4, each of the average pore diameter D.sub.1 on the inner wall surface of the hollow fiber and the average pore diameter D.sub.2 on the outer wall surface is 0.02 to 10 .mu.m, the in-plane porosity Pr on the outer wall surface is at least 10%, and the hollow fiber comprises a wall thickness portion having pores piercing therethrough between the inner wall surface and outer wall surface and a hollow portion extending continuously over the entire fiber length.

Abstract: A nylon 66 fiber capable of being uniformly dyed is made by extruding a melt of nylon 66, passing the extruded filaments through a heating zone provided at the surface of the extrusion nozzle and having a length of at least about 5 cm to about 100 cm and a temperature of about 150.degree. C. to about 260.degree. C., applying a suction with an aspirator located below the heating zone, and then winding at a winding speed of at least 6,000 m/min.

Abstract: A porous regenerated cellulose hollow fiber obtained by a micro-phase-separation method is described. The hollow fiber is characterized in that the viscosity average molecular weight is at least 5.times.10.sup.4, each of the average pore diameter D.sub.1 on the inner wall surface of the hollow fiber and the average pore diameter D.sub.2 on the outer wall surface is 0.02 to 10 .mu.m, the in-plane porosity Pr on the outer wall surface is at least 10%, and the hollow fiber comprises a wall thickness portion having pores piercing therethrough between the inner wall surface and outer wall surface and a hollow portion extending continuously over the entire fiber length.

Abstract: A porous regenerated cellulose membrane consisting essentially of cellulose molecules having a viscosity average molecular weight of at least about 5.times.10.sup.4, the crystalline region of the cellulose molecules being substantially cellulose II crystal, cellulose III-2 crystal or the mixture thereof and having a degree of crystal orientation at a face of (101) in the crystalline region in the direction of the surface of the membrane of at most about 40%, the membrane having a dynamic modulus at 30.degree. C. measured with a frequency of 110 Hz of at least about 1.5.times.10.sup.8 (100-pr.rho.) dyn/cm.sup.2 wherein Pr.rho. is a porosity by percentage, a mean pore size represented by D(.mu.m) of about 0.01 .mu.m to about 20 .mu.m and at the same time a porosity in a plane of at least one plane of at least about 30% or a number of pores in a plane per 1 cm.sup.2 of about 6.times.10.sup.5 /D to about 3.times.10.sup.7 /D; and a process for preparing the same.

Abstract: A nylon 66 fiber capable of being uniformly dyed and having an initial modulus at 20.degree. C. and a relative humidity of 60% of about 15 g/d to about 65 g/d and a relationship of a peak temperature [T.sub.max (.degree.C.)] at peak of dynamic mechanical loss tangent (tan .delta.) measured with a frequency of 110 Hz and a peak value of the dynamic mechanical loss tangent [(tan .delta.).sub.max ] represented by the equation:T.sub.max (.degree.C.).ltoreq.-320(tan .delta.).sub.max +132The fiber has such a structure that refractive indices are different between an outer layer of the fiber and an inner layer of the fiber. The fiber is made by extruding a melt of nylon 66, passing the extruded filaments through a heating zone provided at the surface of the extrusion nozzle and having a length of at least about 5 cm and a temperature of about 150.degree. C.

Abstract: A polyethylene terephthalate fiber capable of being dyed under normal pressure and having an initial modulus of more than 50 g/d, a peak temperature (T max) at peak of dynamic mechanical loss tangent (tan .delta.) measured with a frequency of 110 Hz of about 85.degree. C. to about 110.degree. C., and a peak value of the dynamic mechanical loss tangent ((tan .delta.) max) of about 0.115 to about 0.135. The fiber has a sheathcore structure such that refractive indices are different between an outer layer of the fiber and an inner layer of the fiber, and a local average refractive index distributed symmetrically around the center of the cross section of the fiber. The fiber is made by extruding a dope of polyester, passing the extruded filaments through a heating zone provided at the surface of the extrusion nozzle and having a length of at least about 5 cm and a temperature of about 150.degree. C.

Abstract: A polyethylene terephthalate fiber capable of being dyed under normal pressure and having an initial modulus of more than 50 g/d, a peak temperature (T max) at peak of dynamic mechanical loss tangent (tan .delta.) measured with a frequency of 110 Hz of about 85.degree. C. to about 110.degree. C., and a peak value of the dynamic mechanical loss tangent ((tan .delta.) max) of about 0.115 to about 0.135. The fiber has a sheath-core structure such that refractive indices are different between an outer layer of the fiber and an inner layer of the fiber, and a local average refractive index distributed symmetrically around the center of the cross section of the fiber. The fiber is made by extruding a dope of polyester, passing the extruded filaments through a heating zone provided at the surface of the extrusion nozzle and having a length of at least about 5 cm and a temperature of about 150.degree. C.