US 12,227,881 B2
Ultrafine fibers and liquid fiber dispersion
Kosuke Hamada, Shizuoka (JP); Norio Suzuki, Shizuoka (JP); and Masato Masuda, Shizuoka (JP)
Assigned to Toray Industries, Inc., Tokyo (JP)
Appl. No. 17/293,392
Filed by Toray Industries, Inc., Tokyo (JP)
PCT Filed Nov. 14, 2019, PCT No. PCT/JP2019/044779
§ 371(c)(1), (2) Date May 12, 2021,
PCT Pub. No. WO2020/101002, PCT Pub. Date May 22, 2020.
Claims priority of application No. 2018-215287 (JP), filed on Nov. 16, 2018.
Prior Publication US 2022/0010461 A1, Jan. 13, 2022
Int. Cl. D01F 8/14 (2006.01); D01D 5/08 (2006.01)
CPC D01F 8/14 (2013.01) [D01D 5/08 (2013.01); D10B 2331/04 (2013.01)] 6 Claims
OG exemplary drawing
 
1. An ultrafine fiber having a fiber diameter (D) of 100 to 5000 nm, a ratio (L/D) of a fiber length (L) to the fiber diameter (D) of 3000 to 6000, and a carboxyl terminal group amount of 40 eq/ton or more,
wherein at least a part of a surface layer of the ultrafine fiber is formed of polyester, when the ultrafine fiber is dispersed in an aqueous medium to obtain a fiber dispersion liquid having a solid content concentration of 0.01 to 10% by weight, a dispersion index measured by the following method is 20 or less,
method of measuring the dispersion index: a fiber dispersion liquid is prepared such that the solid content concentration is 0.01% by weight with respect to a total amount of the fiber dispersion liquid, an image of the obtained fiber dispersion liquid at a magnification of 50 times is captured with a microscope under transmitted illumination, the image is converted into a monochrome image by using an image processing software, then a luminance histogram is formed with 256 grades, and a standard deviation obtained from the luminance histogram is used as the dispersion index.