Abstract: A horizontal heat treatment device continuously subjects an untreated continuous flat object to heat treatment while horizontally transferring the untreated object within a heat treatment chamber. Seal chambers are interconnected to the untreated-object loading opening and treated-object unloading opening of the heat treatment chamber. A passage is connected to an opening of each of the seal chambers, the opening located on the side opposite the heat treatment chamber. The untreated-object passage loading opening interconnected to the untreated-object seal chamber loading opening and the treated-object passage unloading opening interconnected to the treated-object seal chamber unloading opening are the untreated-object loading opening and treated-object unloading opening of the heat treatment device. A pair of gas ejection nozzles are provided at upper and lower positions of the passages. The nozzles eject gas in specific directions, and the nozzle openings have a specific shape, a direction, and a length.

Abstract: 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 ?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.

Abstract: The present invention is: a horizontal heat treatment apparatus for continuously heat-treating by moving a continuous flat workpiece to be treated (carbon-fiber-precursor fiber bundles) back and forth in the horizontal direction on multiple levels inside a heat treatment chamber, the horizontal heat treatment apparatus being characterized by being provided with a sealing chamber (4) which is continuous from the entrance (6) side of the heat treatment chamber (2) in to which the workpiece to be treated is conveyed to the exit (6?) side thereof and that is vertically delimited by partition plates making a heat transfer zone in which 2 to 4 levels of the workpiece are transferred, among which the temperature of the workpiece transferred in a lower level is higher than the temperature of the workpiece transferred in a higher level. As a result, the horizontal heat treatment apparatus completely prevents leakage of poisonous gas produced in the heat treatment chamber, and effectively prevents energy loss.

Abstract: A horizontal heat treatment device continuously subjects an untreated continuous flat object to heat treatment while horizontally transferring the untreated object within a heat treatment chamber. Seal chambers are interconnected to the untreated-object loading opening and treated-object unloading opening of the heat treatment chamber. A passage is connected to an opening of each of the seal chambers, the opening located on the side opposite the heat treatment chamber. The untreated-object passage loading opening interconnected to the untreated-object seal chamber loading opening and the treated-object passage unloading opening interconnected to the treated-object seal chamber unloading opening are the untreated-object loading opening and treated-object unloading opening of the heat treatment device. A pair of gas ejection nozzles are provided at upper and lower positions of the passages. The nozzles eject gas in specific directions, and the nozzle openings have a specific shape, a direction, and a length.

Abstract: 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 ?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 ?m that is intermediate between the fiber density ?o of the non-high-density part and the maximum fiber density ?max. The term “maximum-density-region arrival point” means the site Pr at which the increase in fiber density per 10 mm of the fiber bundle length becomes 1.