Carbon fiber precursor acrylic fiber bundle, thermal oxidation treatment method, a thermal oxidation treatment furnace, and method of producing a carbon fiber bundle some of its

摘要

Provided is a carbon-fiber-precursor acrylic fiber bundle which can smoothly pass through a flame-resistance impartation step and a carbonization step. The carbon-fiber-precursor acrylic fiber bundle has a high-density part as a portion thereof, wherein the high-density part satisfies the following requirements (A) and (B). Requirement A: The high-density part has a maximum fiber density Á max of 1.33 g/cm3 or higher. Requirement B: The portion extending between an intermediate-density point and a maximum-density-region arrival point has an increase in fiber density of 1.3×10-2 g/cm3 or less per 10 mm of the fiber bundle length. The term "intermediate-density point" means the site which has a density Á m that is intermediate between the fiber density Á 0 of the non-high-density part and the maximum fiber density Á max . The term "maximum-density-region arrival point" means the site P r at which the increase in fiber density per 10 mm of the fiber bundle length becomes 1.0×10-3 g/cm3 or less, the increase in fiber density being represented by (Á r +1-Á r )/5 determined from a measurement in which density measurement points beginning with the point where the density begins to increase and located at intervals of 50 mm are successively examined for fiber density (Á 1 , Á 2 , ···, Á r , ···, Á n ).