Abstract: The invention provides a production method capable of reducing the amount of the chemical liquid (hydrazine and sodium carbonate, etc.) for applying a crosslinking treatment and a hydrolytic treatment, capable of shortening the treatment time, and capable of obtaining crosslinked acrylic moisture absorbing fibers having a sufficient moisture absorbing-moisture releasing performance and provides crosslinked acrylic moisture absorbing fibers. In the case of producing the crosslinked acrylic moisture absorbing fibers by applying a crosslinking treatment and a hydrolytic treatment to acrylic fibers, acrylic fibers made of a copolymer containing from 1 to 5% by weight a comonomer having an acidic group as a comonomer component are used as the raw material fibers to be treated.

Abstract: This invention relates to acrylic fiber strands suitable for use in production of carbon fibers and to a process for the production of the acrylic fiber used, in which an aminopolysiloxane and a dialkyl sulfosuccinate are coated on acrylic polymer filaments which permits the avoidance of problems such as the generation of static electricity and the deposition of an oil scum on rollers and guides. Because of such effects, excellent bundlability of fiber strands and stable operation of the carbonization process can be attained. The acrylic fiber strands thus obtained can be used for the production of high quality carbon fiber strands.

Abstract: A process for producing preoxidized fibers, which comprises preoxidizing acrylic fibers having a fluorine-containing surface active agent and at least one phosphoric surface active agent selected from the group consisting of compounds represented by the following formulae (I), (II) and (III), and preoxidizing the acrylic fibers thus-obtained: ##STR1## wherein R.sub.1 represents an aliphatic hydrocarbon group having 1 to 17 carbon atoms, R.sub.2, R.sub.3 and R.sub.4, which may be the same or different, and each represents a hydrogen atom, a lower alkyl group, a hydroxyethyl group or a hydroxyisopropyl group, ##STR2## wherein R.sub.5, R.sub.6 and R.sub.7, which may be the same or different, each represents a hydrogen atom or a hydroxyethyl group.

Abstract: A method for manufacturing carbon fiber strand from an acrylic polymer by steps of (a) wet spinning, (b) washing with water to obtain gelled fiber strand and (c) drying, wherein during the drying step the gelled fiber strand is shrunk by about 5 to 15% when the water of the gelled fiber strand is within a range of from about 100 to 20% by weight based on the weight of the dry fiber strand. An acrylic fiber strand without coalescence or entangling of filaments can consistently be obtained, from which carbon fibers with high quality and substantially no coalescence can be produced.

Abstract: Acrylic fibers suitable for producing preoxidized fibers free from coalescence which have a fluorine-containing surface active agent or further have at least one phosphoric surface active agent selected from the group consisting of compounds represented by the following formulae (I), (II) and (III): ##STR1## (wherein all the symbols are defined in the appended claims).

Abstract: A preoxidized fiber suitable for producing carbon fiber, comprising preoxidizing an acrylic fiber having thereon an ammonium salt of a fatty ester represented by formula [A] and [B] ##STR1## wherein R.sub.1 is an aliphatic hydrocarbon group having from 11 to 17 carbon atoms; R.sub.2 and R.sub.3 can each be hydrogen, a lower alkyl group, a hydroxyethyl group, or an hydroxyisopropyl group; and X.crclbar. is an anion.The preoxidized fiber produced from the acrylic fiber has very little coalescence, and therefore high-strength carbon fiber can be obtained from this preoxidized fiber.