Abstract: It is an object of the present invention to provide a package in an optimal form obtained by winding a carbon fiber bundle having a fineness of 25,000 to 35,000 deniers, which has a high wound density and is less apt to become loose, and a method for producing the same. The present invention is a carbon fiber package obtained by winding a carbon fiber bundle having a fineness of 25,000 to 35,000 deniers on a bobbin in a square-end type, wherein the width per unit fineness of the carbon fiber bundle is in the range of 0.30×10?3 to 0.63×10?3 mm/denier, the traverse angle in the beginning of winding is in the range of 13 to 14°, the traverse angle in the end of winding is 3° or larger, and the fractional portion W0 of the winding ratio W is in the range of 0.07 to 0.08.

Abstract: It is an object of the present invention to provide a package in an optimal form obtained by winding a carbon fiber bundle having a fineness of 25,000 to 35,000 deniers, which has a high wound density and is less apt to become loose, and a method for producing the same. The present invention is a carbon fiber package obtained by winding a carbon fiber bundle having a fineness of 25,000 to 35,000 deniers on a bobbin in a square-end type, wherein the width per unit fineness of the carbon fiber bundle is in the range of 0.30×10?3 to 0.63×10?3 mm/denier, the traverse angle in the beginning of winding is in the range of 13 to 14°, the traverse angle in the end of winding is 3° or larger, and the fractional portion W0 of the winding ratio W is in the range of 0.07 to 0.08.

Abstract: The present invention relates to a carbon fiber sizing agent comprised of water-soluble thermoplastic resin and amphoteric surfactant within a weight ratio range of 6/1 to 1/3, a carbon fiber sizing method comprising treating carbon fibers using a sizing liquid containing the aforementioned sizing agent, sized carbon fibers comprising adhering the aforementioned sizing agent to their surfaces, and a fabric that uses said carbon fibers. The carbon fiber sizing agent of the present invention has satisfactory solubility in water over a wide pH range, and is able to impart to carbon fibers adequate convergence for forming stable chopped carbon fibers, superior workability and satisfactory uniform tow dispersibility in water over a wide pH range. Since a fabric of the present invention demonstrates affinity to water over a wide pH range, it is suitable for applications such as immersing said fabric in an aqueous matrix in order to impregnate the fabric with that matrix.

Abstract: The present invention relates to a carbon fiber sizing agent comprised of water-soluble thermoplastic resin and amphoteric surfactant within a weight ratio range of 6/1 to 1/3, a carbon fiber sizing method comprising treating carbon fibers using a sizing liquid containing the aforementioned sizing agent, sized carbon fibers comprising adhering the aforementioned sizing agent to their surfaces, and a fabric that uses said carbon fibers. The carbon fiber sizing agent of the present invention has satisfactory solubility in water over a wide pH range, and is able to impart to carbon fibers adequate convergence for forming stable chopped carbon fibers, superior workability and satisfactory uniform tow dispersibility in water over a wide pH range. Since a fabric of the present invention demonstrates affinity to water over a wide pH range, it is suitable for applications such as immersing said fabric in an aqueous matrix in order to impregnate the fabric with that matrix.