Abstract: A sea-island composite fiber includes island component fibers having a circumscribed circle diameter of 10 to 1000 nm, a circumscribed circle diameter variation of 1 to 20%, a non-circularity of 1.2 to 5.0, and a non-circularity variation of 1 to 10%.

Abstract: The fiber cross-section of an island-in-a-sea composite fiber perpendicular to the fiber axis, the island component and sea component are arranged such that the sea component surrounds the island components. The composite cross-section is very consistent, and the fiber has excellent post-processibility. The island-in-a-sea composite fiber wherein diameter of the island component is 10 to 1000 nm, variation of the island component diameter is 1.0 to 20.0%, modification ratio is 1.00 to 1.10, and variation of the modification ratio is 1.0 to 10.0%.

Abstract: A sea-island composite fiber includes island component fibers having a circumscribed circle diameter of 10 to 1000 nm, a circumscribed circle diameter variation of 1 to 20%, a non-circularity of 1.2 to 5.0, and a non-circularity variation of 1 to 10%.

Abstract: A composite spinneret for discharging a composite polymer stream consisting of at least two or more component polymers, which includes a metering plate having multiple metering holes for metering respective component polymers, a distribution plate with multiple distribution holes formed in the distribution grooves for joining the polymer streams discharged from the metering holes, and a discharge plate.

Abstract: A sea-island composite fiber has an island component which is ultrafine fibers having a noncircular cross-section, the ultrafine fibers being uniform in the degree of non-circularity and in the diameter of the circumscribed circle. The sea-island composite fiber includes an easily soluble polymer as the sea component and a sparingly soluble polymer as the island component, and the island component has a circumscribed-circle diameter of 10-1,000 nm, a dispersion in circumscribed-circle diameter of 1-20%, a degree of non-circularity of 1.2-5.0, and a dispersion in the degree of non-circularity of 1-10%.

Abstract: A method of manufacturing a polyacrylonitrile fiber includes a spinning process in which a spinning dope including polyacrylonitrile is spun; a first drawing process; a drying process; and a second hot drawing process in this order.

Abstract: The fiber cross-section of an island-in-a-sea composite fiber perpendicular to the fiber axis, the island component and sea component are arranged such that the sea component surrounds the island components. The composite cross-section is very consistent, and the fiber has excellent post-processibility. The island-in-a-sea composite fiber wherein diameter of the island component is 10 to 1000 nm, variation of the island component diameter is 1.0 to 20.0%, modification ratio is 1.00 to 1.10, and variation of the modification ratio is 1.0 to 10.0%.

Abstract: A method of manufacturing a polyacrylonitrile fiber includes a spinning process in which a spinning dope including polyacrylonitrile is spun; a first drawing process; a drying process; and a second hot drawing process in this order.

Abstract: The present invention provides an aggregate of nanofibers having less spread of single fiber fineness values that can be used in wide applications without limitation to the shape and the kind of the polymer, and a method for manufacturing the same. The present invention is an aggregate of nanofibers made of a thermoplastic polymer having single fiber fineness by number average in a range from 1×10?7 to 2×10?4 dtex and single fibers of 60% or more in fineness ratio have single fiber fineness in a range from 1×10?7 to 2×10?4 dtex.

Abstract: A sea-island composite fiber has an island component which is ultrafine fibers having a noncircular cross-section, the ultrafine fibers being uniform in the degree of non-circularity and in the diameter of the circumscribed circle. The sea-island composite fiber includes an easily soluble polymer as the sea component and a sparingly soluble polymer as the island component, and the island component has a circumscribed-circle diameter of 10-1,000 nm, a dispersion in circumscribed-circle diameter of 1-20%, a degree of non-circularity of 1.2-5.0, and a dispersion in the degree of non-circularity of 1-10%.

Abstract: A polymer alloy fiber that has an islands-in-sea structure of two or more kinds of organic polymers of different levels of solubility, wherein the island component is made of a low solubility polymer and the sea component is made of a high solubility polymer, while the diameter of the island domains by number average is in a range from 1 to 150 nm, 60% or more of the island domains in area ratio have sizes in a range from 1 to 150 nm in diameter, and the island components are dispersed in a linear configuration. A method for manufacturing the polymer alloy fiber includes melt spinning of a polymer alloy that is made by melt blending of a low solubility polymer and a high solubility polymer.

Abstract: The present invention provides a nanoporous fiber being substantially free from coarse pores and having homogeneously dispersed nanopores, unlike conventional porous fibers. A porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, and the pores are unconnected pores, or a porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, the pores are connected pores, and the fiber has a strength of 1.0 cN/dtex or more.

Abstract: The present invention provides a nanoporous fiber being substantially free from coarse pores and having homogeneously dispersed nanopores, unlike conventional porous fibers. A porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, and the pores are unconnected pores, or a porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, the pores are connected pores, and the fiber has a strength of 1.0 cN/dtex or more.

Abstract: The present invention provides a nanoporous fiber being substantially free from coarse pores and having homogeneously dispersed nanopores, unlike conventional porous fibers. A porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, and the pores are unconnected pores, or a porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, the pores are connected pores, and the fiber has a strength of 1.0 cN/dtex or more.

Abstract: The present invention provides a nanoporous fiber being substantially free from coarse pores and having homogeneously dispersed nanopores, unlike conventional porous fibers. A porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, and the pores are unconnected pores, or a porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, the pores are connected pores, and the fiber has a strength of 1.0 cN/dtex or more.

Abstract: The present invention provides an aggregate of nanofibers having less spread of single fiber fineness values that can be used in wide applications without limitation to the shape and the kind of the polymer, and a method for manufacturing the same. The present invention is an aggregate of nanofibers made of a thermoplastic polymer having single fiber fineness by number average in a range from 1×10?7 to 2×10?4 dtex and single fibers of 60% or more in fineness ratio have single fiber fineness in a range from 1×10?7 to 2×10?4 dtex.

Abstract: The present invention provides a nanoporous fiber being substantially free from coarse pores and having homogeneously dispersed nanopores, unlike conventional porous fibers. A porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, and the pores are unconnected pores, or a porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, the pores are connected pores, and the fiber has a strength of 1.0 cN/dtex or more.

Abstract: A process for preparing highly oriented undrawn core-sheath type conjugated polyester fibers including the step of spinning a polyester as the sheath polymer and a polymer having a larger gradient of elongational viscosity with the temperature than that of the sheath polymer as a core polymer at a spinning speed of about 4000 to 12000 m/min.

Abstract: A highly oriented undrawn polyester fiber which is crystalline such that the fiber is capable of exhibiting a diffraction peak observable in a wide angle X-ray diffraction image of the fiber and has a birefringence of 0.015 to 0.05.A process for preparing highly oriented undrawn core-sheath type conjugated polyester fibers including the step of spinning a polyester as the sheath polymer and a polymer having the larger gradient of elongational viscosity with the temperature than that of the sheath polymer at a spinning speed of about 4000 to 12000 m/min.A textured yarn made of said highly oriented undrawn polyester fibers and a process for preparing the textured yarn.