An aqueous liquid of a carbon fiber precursor treatment agent contains a carbon fiber precursor treatment agent and water, the carbon fiber precursor treatment agent containing an amino-modified silicone and a particular nonionic surfactant having a molecular weight distribution (Mw/Mn) of from 1.05 to 1.50. The amino-modified silicone may have a kinematic viscosity at 25° C. of 50 to 4,000 mm.sup.2/s. The carbon fiber precursor treatment agent is adhered to a carbon fiber precursor.

The present invention provides a method for producing a carbon fiber bundle, the method including steps (b) to (e) described below: (b) an oil agent application step of applying a silicone oil agent to a precursor fiber bundle to produce an oil-agent-attached precursor fiber bundle; (d) a stabilization step of subjecting the oil-agent-attached precursor fiber bundle to an oxidization treatment to produce an oxidized fiber bundle; and (e) a carbonization step of carbonizing the oxidized fiber bundle, wherein the silicone oil agent has a skin over time at 250° C. of less than 40 minutes.

Carbon fiber precursor treatment agents include a nonionic surfactant, an amino-modified silicone, and a dimethyl silicone with a kinematic viscosity at 25° C. of 5 to 200 mm.sup.2/s. The mass ratio of the content of the amino-modified silicone with respect to the content of the dimethyl silicone is 99.9/0.1 to 90/10. Alternatively, when the total content of the nonionic surfactant, the amino-modified silicone, and the dimethyl silicone is taken as 100 parts by mass, the nonionic surfactant is contained at a ratio of 9 to 85 parts by mass, the amino-modified silicone is contained at a ratio of 10 to 90.9 parts by mass, and the dimethyl silicone is contained at a ratio of 0.1 to 5 parts by mass.

A method of producing a carbon fiber bundle is provided, involving performing a flame-proof treatment to a carbon-fiber-precursor acryl fiber bundle having a single-fiber fineness of 1.5 dtex or more and 5.0 dtex or less, and having a roundness of 0.7 or more and 0.9 or less in a cross-section shape perpendicular to a fiber axis of the single fiber to obtain a flame-proofed fiber bundle; and performing a carbonization treatment to the flame-proofed fiber bundle.

A method of producing a carbon fiber bundle is provided, involving performing a flame-proof treatment to a carbon-fiber-precursor acryl fiber bundle having a single-fiber fineness of 1.5 dtex or more and 5.0 dtex or less, and having a roundness of 0.7 or more and 0.9 or less in a cross-section shape perpendicular to a fiber axis of the single fiber to obtain a flame-proofed fiber bundle; and performing a carbonization treatment to the flame-proofed fiber bundle.

Carbon fiber precursor treatment agents include a nonionic surfactant, an amino-modified silicone, and a dimethyl silicone with a kinematic viscosity at 25° C. of 5 to 200 mm.sup.2/s. The mass ratio of the content of the amino-modified silicone with respect to the content of the dimethyl silicone is 99.9/0.1 to 90/10. Alternatively, when the total content of the nonionic surfactant, the amino-modified silicone, and the dimethyl silicone is taken as 100 parts by mass, the nonionic surfactant is contained at a ratio of 9 to 85 parts by mass, the amino-modified silicone is contained at a ratio of 10 to 90.9 parts by mass, and the dimethyl silicone is contained at a ratio of 0.1 to 5 parts by mass.

A method includes charging PET bottle flakes having particular characteristics as a raw material into a crystallizer to generate a crystalline version thereof, drying the crystalline version with dehumidified air at a temperature of 160-180° C. and with a dew point of −40° C. to bring down a moisture level thereof below 100 ppm, melting the dried crystalline version through an extruder configured to have a temperature therein maintained at 285-295° C., and feeding the melted raw material into a spin beam. The method also includes generating, through a spinneret, a number of filaments based on extruding, through the spinneret, the melted raw material fed into the spin beam, forming a yarn based on combining the number of filaments, and winding the formed yarn to generate a spool of Partially Oriented Yarn (POY) configured to be utilized as another raw material to generate a Draw Texturized Yarn (DTY).

A method includes charging PET bottle flakes having particular characteristics as a raw material into a crystallizer to generate a crystalline version thereof, drying the crystalline version with dehumidified air at a temperature of 160-180° C. and with a dew point of −40° C. to bring down a moisture level thereof below 100 ppm, melting the dried crystalline version through an extruder configured to have a temperature therein maintained at 285-295° C., and feeding the melted raw material into a spin beam. The method also includes generating, through a spinneret, a number of filaments based on extruding, through the spinneret, the melted raw material fed into the spin beam, forming a yarn based on combining the number of filaments, and winding the formed yarn to generate a spool of Partially Oriented Yarn (POY) configured to be utilized as another raw material to generate a Draw Texturized Yarn (DTY).

A type of high-modulus-low-shrinkage activated PET industrial yarn and preparing method thereof are disclosed. The preparing method is to manufacture filament from a modified polyester, which is the product of the esterification and the successive polycondensation reactions of evenly mixed terephthalic acid, ethylene glycol and tert-butyl branched heptanediol, through a series of processes composed of viscosity enhancing by solid state polycondensation, melting, metering, extruding, cooling, oiling, stretching, heat setting, relaxation heat-treating, oiling with activation oil, winding and pre-activation treatment. The relaxation heat-treating indicates passing the modified polyester yarns through a space with a certain temperature within 200-220° C. under a proper relaxation state; and the proper relaxation state means a 3.0-5.0% of overfeed for the winding. The improvement of activator efficiency by importing the tert-butyl branched diol into the polyester, together with the synergistic effect of heat setting temperature and high winding overfeed rate, will reduce the fiber thermal shrinkage.

A method includes charging PET bottle flakes having particular characteristics as a raw material into a crystallizer to generate a crystalline version thereof, drying the crystalline version with dehumidified air at a temperature of 160-180° C. and with a dew point of −40° C. to bring down a moisture level thereof below 100 ppm, melting the dried crystalline version through an extruder configured to have a temperature therein maintained at 285-295° C., and feeding the melted raw material into a spin beam. The method also includes generating, through a spinneret, a number of filaments based on extruding, through the spinneret, the melted raw material fed into the spin beam, forming a yarn based on combining the number of filaments, and winding the formed yarn to generate a spool of Partially Oriented Yarn (POY) configured to be utilized as another raw material to generate a Draw Texturized Yarn (DTY).