An object of the present invention is to provide a method capable of producing a protein fiber in which shrinkage at the time of first contact with moisture after production is more reliably suppressed and generation of crimp is also suppressed. A method for producing a protein fiber according to the present invention includes: a pre-shrinking step of shrinking a protein fibril in a relaxed state after drawing and before being wound; a winding step of winding the protein fibril subjected to the pre-shrinking step to obtain a wound product; and a post-shrinking step of shrinking the protein fibril subjected to the winding step in a relaxed state.

A drawing method is provided which enables a pressurized steam drawing of an acrylonitrile-based fiber bundle used as the precursor fiber of the carbon fiber bundle. In particular, a drawing method is provided which realizes a high processability when this treatment is conducted at a high draw ratio and high speed. This invention is a method for producing an acrylonitrile-based fiber bundle which includes the steps of spinning a spinning solution containing an acrylonitrile-based copolymer, and subjecting the fiber bundle to a pressurized steam drawing in a pressurized steam drawing apparatus (A) having at least two zones which are a preheating zone on the fiber bundle inlet side and a heating zone on the fiber bundle exit side, the two zones being separated by a seal member. The preheating zone is in a pressurized steam atmosphere at 0.05 to 0.35 MPa, the heating zone is in a pressurized steam atmosphere at 0.45 to 0.70 MPa, temperature difference ΔT1 in the preheating zone of the steam drawing apparatus in the fiber bundle-moving direction defined in the specification is up to 5° C., and temperature difference ΔT2 in the preheating zone of the steam drawing apparatus in the cross-sectional direction of the steam drawing apparatus defined in the specification is up to 5° C.

The present invention relates to a method for manufacturing a protein fiber, including an extension and contraction step of contracting or extending a protein raw fiber containing a protein by bringing the protein raw fiber into contact with a liquid or vapor; and a drying step of drying the protein raw fiber that has undergone the extension and contraction step while adjusting a length of the protein raw fiber to an arbitrary length.

A multi-end monofilament production apparatus includes the following sequential process units along monofilaments flow direction: a vertical spinning machine comprising a spinneret and a distribution plate below the spinneret; a water bath for quenching spun monofilaments; a vacuum jet device for transferring monofilaments from the water bath; a steam jet able to provide superheated steam at a temperature within the range between 300° C. and 380° C. and at a pressure within the range between 4 bars and 5 bars; a drawing unit; and a monofilament winder for winding monofilaments at a speed exceeding 500 m/min. The present invention further proposes a method for multi-end monofilament yarn production.

A drawing method is provided which enables a pressurized steam drawing of an acrylonitrile-based fiber bundle used as the precursor fiber of the carbon fiber bundle. In particular, a drawing method is provided which realizes a high processability when this treatment is conducted at a high draw ratio and high speed. This invention is a method for producing an acrylonitrile-based fiber bundle which includes the steps of spinning a spinning solution containing an acrylonitrile-based copolymer, and subjecting the fiber bundle to a pressurized steam drawing in a pressurized steam drawing apparatus (A) having at least two zones which are a preheating zone on the fiber bundle inlet side and a heating zone on the fiber bundle exit side, the two zones being separated by a seal member. The preheating zone is in a pressurized steam atmosphere at 0.05 to 0.35 MPa, the heating zone is in a pressurized steam atmosphere at 0.45 to 0.70 MPa, temperature difference ΔT1 in the preheating zone of the steam drawing apparatus in the fiber bundle-moving direction defined in the specification is up to 5° C., and temperature difference ΔT2 in the preheating zone of the steam drawing apparatus in the cross-sectional direction of the steam drawing apparatus defined in the specification is up to 5° C.

A polyvinyl alcohol fiber that can easily be fibrillated at a low manufacture cost is provided. The readily fibrillative polyvinyl alcohol fiber contains a polyalkylene oxide in addition to a polyvinyl alcohol. A mass ratio of the polyalkylene oxide ranges from 3 to 40% relative to the total mass of the polyvinyl alcohol and the polyalkylene oxide. A method for manufacturing the polyvinyl alcohol fiber is also provided.

A method of manufacturing an acrylonitrile fiber bundle includes drawing a fiber bundle with pressurized steam under a pressurized steam atmosphere using a pressurized steam drawing device, wherein the fiber bundle includes a yarn spun from a spinning solution containing an acrylonitrile copolymer, the pressurized steam drawing device has at least two zones of a preheating zone provided on a fiber bundle introduction side and a heating/drawing zone provided on a fiber bundle extraction side, and a sealing zone has a sealing member and separates the two zones.

An apparatus for producing ultrafine fibers is configured to produce ultrafine fibers by melting and drawing raw filaments. The apparatus for producing ultrafine fibers comprises: a plurality of raw filament passages arranged in a straight row; and a laser irradiation device for irradiating a plurality of raw filaments with a laser beam so as to melt, oscillate and vibrate the plurality of raw filaments after the plurality of raw filaments have passed through the respective raw filament passages together with airstreams. Specifically, the laser irradiation device is configured to output a focused laser beam having a diameter decreasing as distance from the laser irradiation device increases, and having a beam axis parallel to a direction of the row of the plurality of raw filament passages.

A stretching apparatus of fibre tows in a pressurized steam environment comprises a plurality of stretching chests (1) and associated supporting structures (3, 4, 6) arranged side by side, at the same level, on a holding frame. The stretching chests (1) are each formed by two opposed metallic half-chests (1b, 1t), delimiting a stretching chamber (2). The stretching chamber (2) has a generally rectangular section of a low height and opens outwards in correspondence of the two transversal edges of the stretching chest (1) through tow entry and exit openings. Inside the stretching chambers (2) the tows are treated with saturated or overheated steam at high temperature and pressure and simultaneously undergo a mechanical stretching operation.

This process for manufacturing a carbon-fiber precursor acrylic fiber bundle and this steam drawing apparatus are characterized in that the drawing of an acrylic fiber bundle with a pressured-steam drawing apparatus is conducted by: opening an acrylic fiber bundle by blowing a fluid thereto; supplying humidifying steam to the opened acrylic fiber bundle at a fiber temperature of 80 to 130 C. to adjust the water content of the fiber bundle to 3 to 7%; and thereafter drawing the resulting acrylic fiber bundle in a pressurized-steam atmosphere. Thus, the present invention can prevent the breaking of a single fiber, the fluffing of the fiber bundle, and the breaking of the whole of the fiber bundle, though such defects are susceptible to occurring in a case where an acrylic fiber bundle is drawn by steam drawing at a high draw ratio, at a higher speed, or into a fiber having a small denier.