JP2005193405A - Fluffy bamboo fiber manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluffy bamboo fiber manufacturing method capable of efficiently obtaining a fluffy bamboo fiber bundle suitable for manufacturing a fiberboard. <P>SOLUTION: A bamboo material cut so as to leave an interval in its longitudinal direction is compressed and torn to be formed into a flat plate shape under compression. The flat plate-shaped bamboo material formed under compression is steamed under a heated steam atmosphere and the steamed bamboo material is fibrillated under normal pressure at a temperature higher than the normal temperature to manufacture fluffy bamboo fibers. The bamboo fibers can be easily entangled with each other by forming the bamboo fibers into a fluffy state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing cotton-like bamboo fibers, and more particularly to a method for producing cotton-like bamboo fibers suitable for producing high-quality fiberboard.

A fiberboard, for example, a medium fiberboard (medium density fiberboard, that is, MDF (see JIS A 5905)) is made of wood or plant fibers other than wood as a raw material, and a synthetic resin adhesive is used as an adhesive for bonding the fibers together. In addition, it is a fiberboard formed by hot compression processing. The density is as light as 0.35 g / cm ² or more and less than 0.80 g / cm ² , is homogeneous and has no directionality, and has excellent workability and surface smoothness. However, since the length of the fiber used is short, the strength is inferior to the plywood in which the fibers are arranged in the horizontal direction. Moreover, many of the fibers that are the raw materials for producing such fiberboard are obtained by cutting down trees. However, because of the carbon dioxide assimilation effect, trees take in carbon dioxide in the air, synthesize organic matter, and release oxygen. In order to protect the global environment, such as reducing the concentration of carbon dioxide in the air and regenerating oxygen. It is considered valuable, and it takes a long period of time, which is several decades, until trees can be cut down, and it takes a long time to recover the forest after cutting down. It has become difficult. On the other hand, bamboo grows faster than wood, and can be easily propagated by inserting bamboo shoots. Its lifespan is said to be 60 years or 100 years. Has been.

Therefore, the bamboo fiber is produced by, for example, crushing bamboo cut into a predetermined length with a roll, and smashing the crushed bamboo with a hammer mill or the like, and crushing the bamboo. A method for producing bamboo fiber that has been defibrated to a predetermined diameter by sending it into the defibrator from the side of the defibrating machine and then defibrating the strip-shaped bamboo slab after having been made into a strip-shaped bamboo piece in a state of being in a state ( For example, refer to Japanese Unexamined Patent Publication No. 2000-71209. In addition, the bamboo is cut into a predetermined length, the cut bamboo is filled into a pressure vessel, and steam heated and pressurized is introduced into the pressure vessel to bring the bamboo into a heated and pressurized state. There has been proposed a reinforced fiber plastic molding in which pressure is reduced to a pressurized state, bamboo is crushed to produce bamboo fibers, and the bamboo fibers are used as reinforcing fibers (see, for example, Japanese Patent Application Laid-Open No. 2003-253011). ). In addition, lignocellulosic fibers such as coconut, hemp, sugar cane, bamboo, rice or kenaf can be removed by treating with hot water to dissolve and remove hot water soluble components. A method has been proposed in which fibers are mixed with an adhesive to form a fiberboard formed by applying heat and pressure to form a fiberboard (see Japanese Patent Application Laid-Open No. 2000-102910).
JP 2000-102910 A JP 2000-71209 A JP 2003-253011 A

However, when bamboo is defibrated by a hammer mill, the supply port is generally provided substantially perpendicularly to the surface of the rotating hammer blade, so that the crushed bamboo pieces to be crushed are The crushed bamboo pieces will be broken in the longitudinal direction and become mostly short fibers and powder, producing bamboo long fibers exceeding 10 mm. Difficult to do. A fiberboard made of such short fibers has a relatively short fiber length, and therefore has a problem that its strength is smaller than that of plywood. Therefore, it has been proposed to produce bamboo long fibers by supplying the crushed bamboo pieces in parallel to the rotating hammer blade of a hammer mill (see Japanese Patent Laid-Open No. 2000-71209). However, even in this case, the obtained bamboo fiber is relatively straight and easily broken, and it is difficult to obtain a long bamboo fiber exceeding 30 mm with a good yield. Therefore, a heating and pressurizing operation for heating and pressurizing bamboo cut into a predetermined length in a pressure cooker at a temperature of 100 ° C. or higher and a water vapor pressure corresponding to the temperature, and a depressurizing operation for rapidly releasing the pressure in the pressure can It is proposed that the bamboo fibers are separated from each other without damaging them to obtain bamboo fibers having a predetermined length (see Japanese Patent Application Laid-Open No. 2003-155679). However, the number of repetitions of the heating and pressurizing operation and the depressurizing operation is large, and what is obtained is a bundle of long fibers of a predetermined length obtained by tearing between the fibers, and the overall diameter is 0.1 millimeters to several tens of microns. It is difficult to obtain a relatively long bamboo fiber bundle suitable for a raw material for a fiberboard having a good entanglement condition.
An object of this invention is to solve the problem concerning the bamboo fiber used for manufacture of the conventional fiber board.

The present invention provides a method for producing bamboo fiber, which can efficiently obtain a cotton-like bamboo fiber bundle suitable for producing a fiberboard.
That is, the present invention lies in a method for producing cotton-like bamboo fibers, characterized in that bamboo is steamed in the presence of high-temperature and high-pressure steam, and the steamed bamboo is defibrated at a temperature exceeding normal temperature under normal pressure. Further, the present invention compresses bamboo material cut at intervals in the longitudinal direction, cleaves it, compresses it into a flat plate, and forms the compressed flat bamboo material under the atmosphere of heated steam. In the method for producing cotton-like bamboo fiber, characterized in that the bamboo material cooked and steamed at room temperature is defibrated under normal pressure and at a temperature higher than room temperature, and the present invention has a length of 200 cm or less. The bamboo material cut into pieces is compressed and cleaved to form a flat plate with a thickness of 20 mm or less, and the compressed flat plate-like bamboo material is cooked in a heated steam atmosphere. Take the time of 1 minute or more to lower the pressure to normal pressure. The present invention relates to a method for producing cotton-like bamboo fibers characterized by defibration at a high temperature. Furthermore, the present invention compresses and cleaves bamboo material that has been divided and cut to a length of 10 to 200 cm, The bamboo material formed into a flat plate shape of 5 to 20 mm and compressed into a flat plate shape is cooked in an atmosphere of heated steam having a temperature of 100 to 200 ° C. and a pressure of 0.1 to 1.6 MPa, There is a method for producing cotton-like bamboo fibers, characterized in that steamed bamboo is depressurized over a period of one minute or longer and then defibrated in an atmosphere having an atmospheric pressure and a temperature of 50 ° C. or higher. In addition, in the present invention, bamboo material divided and cut to a length of 10 to 200 cm is compressed and cleaved to form a flat plate having a thickness of 5 to 20 mm, and compressed into a flat plate. Bamboo wood is heated at a temperature of 100 to 200 ° C. and 0. Steamed in an atmosphere of heated steam having a pressure of 1 to 1.6 MPa for 5 to 60 minutes, and the steamed bamboo material is decompressed to normal pressure in 5 to 10 minutes to a temperature of 50 to 100 ° C. and 10 to 30% by weight. In a state having a water content of at least one of the cutting blades, a rough defibrating machine having a rotary blade is used to perform rough defibrating to form a defibrated fiber bundle having a thickness of 0.1 to 1.0 mm. Then, this coarse defibrated fiber bundle is brought into a state having a temperature of 50 to 100 ° C. and a moisture content of 10 to 30% by weight under atmospheric pressure, and at least one defibrating blade is a rotary blade. A cotton-like bamboo fiber manufacturing method characterized in that a fiber bundle having a diameter of 0.01 to 0.2 mm is manufactured by further fine disentanglement by high-speed rotation by a fiber device. The present invention is divided and cut into lengths of 10 to 200 cm. The bamboo material is compressed and cleaved to form a flat plate having a thickness of 5 to 20 mm, and the compressed bamboo material is formed into a flat plate with a temperature of 100 to 200 ° C. and 0.1 to 1.6 MPa. Steamed in an atmosphere of heated steam having a pressure of 5 to 60 minutes and reduced the steamed bamboo material to normal pressure in 5 to 10 minutes to a temperature of 50 to 100 ° C. and a moisture content of 10 to 30% by weight. In a state of having a rough defibrating fiber bundle having a thickness of 0.1 to 1.0 mm by performing rough defibrating with a rough defibrating machine in which at least one of the cutting blades is a rotary blade, A high speed by a fine defibrating apparatus in which a crude defibrated fiber bundle is brought into a state having a temperature of 50 ° C. or higher and a moisture content of 10 to 30% by weight at atmospheric pressure, and at least one of the cutting edges is a rod-shaped rotary blade Further defibration by rotation, the diameter is 0.01 to 0 In 2 mm, in the manufacturing method of the shaped bamboo fiber cotton, characterized in that the length to produce a fine fibrillated fiber bundle 1 to 100 mm. In the present invention, the steaming atmosphere is preferably an atmosphere having a temperature of 130 to 160 ° C. and a pressure of 0.28 to 0.64 MPa, and the bamboo material is defibrated in advance at a cutting angle of 50 to 80 degrees. It is preferable that rough defibration is performed and then performed at a rotational speed of 1000 to 6000 rpm. In the present invention, the bamboo fiber has a cotton shape, and preferably has a diameter of 10 to 200 microns or a diameter of 10 to 200 microns and a length of 1 to 100 mm.

  The present invention compresses bamboo material cut at intervals in the longitudinal direction, cleaves it, compresses it into a flat plate shape, and steams the compression-formed flat bamboo material in an atmosphere of heated steam. The bamboo fiber is produced by rough defibration of the cooked bamboo under normal pressure at a temperature higher than room temperature, and then finely defibrating. Fine cotton-like bamboo fibers can be produced.

  In the present invention, the bamboo fibers are formed in a cotton shape so as to be easily entangled with each other in order to increase the strength of the fiberboard. In the present invention, in order to form bamboo fibers into a cotton shape, the bamboo is cut into a length of 10 to 200 cm. The cylindrical bamboo cut into circles is crushed by pressing in the diametrical direction to form a flat bamboo material having a thickness of 5 to 20 mm. The bamboo material thus formed is steamed under high temperature and high pressure so as to be soft and contain moisture. The bamboo is steamed in an atmosphere having a steaming temperature of 100 to 200 ° C., preferably 130 to 160 ° C., and steaming steam pressure of 0.1 to 1.6 MPa, preferably 0.28 to 0.64 MPa. It is allowed to stand for 5 to 60 minutes, preferably 20 to 30 minutes, and is cooked.

  In the present invention, the flat bamboo material softened by containing moisture by steaming is roughly defibrated and then finely defibrated while maintaining flexibility. The steaming process can be performed in a single mode or a continuous mode. In the case of a single type, the inside of the cooking apparatus is opened after the steaming process, and the steaming process temperature and pressure are returned to room temperature and normal pressure. The inventor of the present invention can obtain a cotton-like bamboo fiber that is easily entangled even when fibrillated when the holding temperature of the steamed flat bamboo material is lowered to room temperature and the moisture content is reduced to less than 10%. I found no.

  Therefore, in the present invention, it is preferable that the steamed bamboo material is kept warm and moisturized in, for example, a steaming apparatus so that the moisture contained in the steamed material escapes to the outside air and does not lose flexibility. In this case, the pressure and temperature in the steaming device are lowered to normal pressure and room temperature after the steaming process, but the steamed flat bamboo material does not lose its flexibility because the contained moisture escapes to the outside air. In addition, for example, the retained moisture is kept within a range of 10% or more, preferably 10 to 30%, and the retained temperature is within a temperature range of 50 ° C. or more, preferably 50 to 100 ° C. And moisturized. For this purpose, the inside of the steaming apparatus for storing the cooked flat bamboo material is reduced to normal pressure over 1 to 20 minutes, preferably 5 to 10 minutes, allowed to cool, and then dried.

  In the present invention, the cooked flat bamboo material is coarsely defibrated by a coarse defibrating device. This rough defibrating apparatus can use a conventional defibrating apparatus. In the present invention, the flat bamboo material to be defibrated by the coarse defibrating apparatus has a moisture content of 10% or more, preferably 10 to 30%, in order to obtain cotton-like bamboo fibers. It has been found that the holding temperature needs to be in the temperature range of 50 ° C. or higher, preferably 50 to 100 ° C. there. In the present invention, the flat bamboo material to be defibrated by the coarse defibrating device has a retained water content of 10% or more, preferably 10 to 30% in the storage room or the heat and moisture retaining device, and has a retained temperature. It is kept warm and moisturized so that it is in the temperature range of 50 ° C. or higher, preferably 50 to 100 ° C. It is difficult to produce cotton-like bamboo fibers when the moisture content, ie, the moisture content is lower than 10%, and it is difficult to obtain cotton-like bamboo fibers whose moisture content, ie, the moisture content is higher than 30%. .

  The flat bamboo material that is kept warm and moisturized in this way is provided, for example, with an outer cylinder having a screen with a cutting blade formed on the inner side and a rotatable inside the outer cylinder, and with a cutting blade provided on the outer side and rotating. Rough defibrating is performed by a rough defibrating apparatus having an inner cylinder provided as possible. At the time of rough defibration of this rough defibrating apparatus, the outer cylinder can be stationary and act as a fixed blade, and the inner cylinder can be rotated to act as a rotary blade. This rough defibrating apparatus is arranged so that the fixed blade of the outer cylinder and the rotary blade of the inner cylinder have an angle of intersection (cutting angle) of their respective blade lines of 50 ° or more, preferably 50 to 80 °. It is preferable to provide a screen for passing a fiber bundle having a cutting blade thickness of 0.1 mm or more, preferably 0.1 to 1.0 mm. However, in the present invention, in the coarse defibrating apparatus, both the outer cylinder and the inner cylinder can be formed on the rotary blade.

  In the present invention, the coarsely defibrated fiber bundle is defibrated into finer bamboo fibers by a fine defibrating device. As this defibrating device, a defibrating device that can be defibrated into a conventional fine fiber bundle can be used. In the present invention, the defibrating apparatus includes, for example, a plate-shaped or thin dish-shaped rotating body that is fixed to a defibrating pin formed in a bar shape, and a screen on the outer periphery thereof. At the time of fibering, the fibers are defibrated in a cotton shape by a shearing action between defibrating pins provided in each of plate-like or thin dish-shaped rotating bodies facing each other. In this fine defibrating apparatus, one or more defibrating pins are provided on plate-shaped or thin dish-shaped rotating bodies facing each other. In this case, a plurality of defibrating pins can be provided. When a plurality of defibration pins are provided, the plurality may be provided in a row, or may be provided concentrically in a plurality of stages. In any fine defibrating apparatus, at the time of defibrating, the plate-like rotating body provided with the defibrating pins is rotated at a rotational speed of 1,000 rpm or more, preferably 1,000 to 6,000 rpm, and is roughly defibrated. The fiber bundle is, for example, a fiber bundle having a diameter of 10 to 200 μm (micron) or a diameter of 10 to 200 μ and a length of 1 to 1 due to the shearing action of the defibration pins of the opposing plate-shaped or thin dish-shaped rotating body. It is defibrated into a 100 mm fiber bundle. In the present invention, the screen of the fine fiber apparatus is formed so as to pass these fine fiber bundles that have been fine fiber. In the present invention, when fine defibrating is performed by a fine defibrating apparatus including plate-shaped or thin dish-shaped rotating bodies facing each other, one plate-shaped or thin dish-shaped rotating body is stopped and the other Only the plate-shaped or thin dish-shaped rotating body may be rotated at high speed, but both the plate-shaped or thin dish-shaped rotating bodies may be rotated in different directions.

  Hereinafter, embodiments of the present invention will be described with reference to examples, but the present invention is not limited to the following examples and explanations.

1. Divided cutting and crushing of bamboo material Cylindrical bamboo material with a thickness of about 10 mm, cut to a length of 30 cm, was divided vertically into 6 pieces to obtain 6 arc-shaped bamboo pieces per piece of bamboo material cut out. . The arc-shaped bamboo pieces were removed from the inner nodes, and crushed and crushed to produce flat bamboo pieces.

2. Steaming treatment The crushed bamboo pieces were put into a steaming apparatus, and 0.43 MPa pressurized saturated steam was supplied into the steaming apparatus. Pressure saturated steam was supplied into the steaming apparatus for about 10 minutes, and the temperature in the steaming apparatus was raised to 145 ° C. Then, the bamboo piece was steamed by maintaining the inside of the steaming apparatus at a temperature of 145 ° C. and a pressure of 0.43 MPa for about 20 minutes. When the bamboo piece steaming process was completed, the pressure in the steaming apparatus was gradually reduced and released to the atmosphere in about 5 minutes. The bamboo pieces after release to the atmosphere were kept at 70 ° C. and a moisture content of 15% by weight, and kept warm and moist.

3. Defibration treatment Bamboo pieces having a temperature of 70 ° C. and a moisture content of 15% by weight were placed in a coarse defibrating machine and defibrated. In the coarse defibration, the fixed blade and the rotary blade have a gap of about 1 mm, cut into a thin piece having a thickness of 0.5 mm or less, and cut to produce an elongated coarse defibrated fiber bundle. Next, the elongated, loosely defibrated fiber bundle that was torn was finely defibrated by a defibrating device having a pair of plate-like rotating bodies facing each other, each having a plurality of defibrating pins fixed in two stages. In this example, the fine defibrating is performed by fixing one plate-like rotating body of the fine-defining device and rotating the other plate-like rotating body at a high speed of about 3000 rpm. The coarse defibrated fiber bundle was further finely deflated by a shearing action between the defibrating pin of the rotator and the defibrating pin of the plate rotator rotating at high speed to produce cotton-like bamboo fibers. Refined cotton-like bamboo fiber was obtained through a screen provided at the end. In this example, one plate-shaped rotating body of a pair of plate-shaped rotating bodies facing each other is stopped and the other plate-shaped rotating body is rotated to perform fine defibration. Fine defibration can be performed by rotating the body in opposite directions.

Processing of fiberboard The moisture content of the cotton-like bamboo fiber produced in Example 1 was adjusted to 10% by weight. A synthetic resin adhesive of 6 to 8% by weight with respect to the bamboo fiber is added to and mixed with the cotton-like bamboo fiber whose water content is adjusted, and the synthetic resin adhesive is uniformly dispersed. The bamboo fiber in which the adhesive is dispersed is put in a mold and pre-press-molded to produce a plate-like molded body. The produced plate-like molded bodies are stacked in a mold, and are subjected to hot compression molding under a press temperature of 160 ° C., a press pressure of 50 kg / cm ² and a press time of 5 minutes, and are 300 mm wide, 300 mm long, and thick. A 10 mm fiberboard was produced.

Bending Young's modulus of fiberboard About the manufactured fiberboard having a width of 300 mm, a length of 300 mm and a thickness of 10 mm, a specimen having a width of 50 mm and a length of 200 mm was cut out to obtain a specimen for measuring a bending Young's modulus. Was used to measure the bending Young's modulus of the fiberboard. The measured bending Young's modulus of the fiberboard was 2518 N / mm ² . The measured value of the bending Young's modulus of the fiberboard satisfies the standard value of 800 to 2518 N / mm ² or more of the bending Young's modulus of the fiberboard MDF.

Peel strength of fiber board About the manufactured fiber board of width 300mm, length 300mm, and thickness 10mm, the test body for width 50mm and length 50mm was cut out, and the test body for measuring the peel strength of fiber board was used. Prepared. The measured peel strength of the fiberboard was 1.20 N / mm ² . The measured value of the peel strength of the fiberboard satisfies the reference value of 0.2 to 0.5 N / mm ² or more of the peel strength of the fiberboard MDF.

Measurement of the water absorption thickness expansion coefficient of the fiber board by cutting out a specimen having a width of 50 mm and a length of 50 mm from the manufactured fiber board having a width of 300 mm, a length of 300 mm and a thickness of 10 mm. A test specimen was prepared. The measured water absorption thickness expansion coefficient of the fiberboard was 5.3%. This measured value satisfied each reference value of 10 to 17% or less of the reference value of the water absorption thickness expansion coefficient of the fiberboard MDF.

The present invention can produce cotton-like bamboo fibers that are easily entangled with each other by cooking bamboo in the presence of high-temperature and high-pressure steam and defibrating the cooked bamboo at a temperature exceeding normal temperature under normal pressure. it can. In the present invention, the bamboo fibers are formed in a cotton shape, so that they can be entangled with each other in the molding stage, and used for the fiberboard to improve the defect related to the strength of the fiberboard using fibers with a short fiber length. can do. In order to entangle bamboo fibers with each other, the amount of the adhesive used is 6 to 8% by weight. The amount of the adhesive used is 10 to 13 of the amount of the adhesive used for the fiberboard of the wood fiber. It is remarkably small compared to the weight%, and the amount of adhesive used can be saved, resulting in excellent economic efficiency.

Claims (9)

A method for producing cotton-like bamboo fibers, characterized in that bamboo materials are steamed in the presence of high-temperature and high-pressure steam, and the steamed bamboo materials are defibrated at a temperature exceeding normal temperature under normal pressure. Bamboo material cut at intervals in the longitudinal direction was compressed, cleaved, compressed into a flat plate shape, and the flat formed bamboo material was steamed and steamed in an atmosphere of heated steam A method for producing cotton-like bamboo fibers, characterized in that bamboo material is defibrated under normal pressure and at a temperature higher than room temperature. Bamboo material cut to a length of 200 cm or less is compressed and cleaved, and compressed into a flat plate with a thickness of 20 mm or less. The compressed flat bamboo material is cooked in an atmosphere of heated steam, A method for producing cotton-like bamboo fibers, characterized in that steamed bamboo is reduced to normal pressure over a period of 1 minute or longer, and defibrated at a temperature higher than normal temperature under normal pressure. Bamboo material divided and cut into lengths of 10 to 200 cm is compressed and cleaved to form a flat plate with a thickness of 5 to 20 mm, and the bamboo formed into a flat plate with a thickness of 100 to 200 ° C. And steamed in an atmosphere of heated steam having a pressure of 0.1 to 1.6 MPa, the steamed bamboo material is depressurized over a period of 1 minute, and then an atmosphere having an atmospheric pressure and a temperature of 50 ° C. or higher Inside, a method for producing cotton-like bamboo fiber, which is defibrated. Bamboo material divided and cut into lengths of 10 to 200 cm is compressed and cleaved to form a flat plate with a thickness of 5 to 20 mm, and the bamboo formed into a flat plate with a thickness of 100 to 200 ° C. And steamed in an atmosphere of heated steam having a pressure of 0.1 to 1.6 MPa for 5 to 60 minutes, and the steamed bamboo material is decompressed to normal pressure in 5 to 10 minutes to a temperature of 50 to 100 ° C. and 10 A coarse defibrated fiber having a thickness of 0.1 to 1.0 mm by performing rough defibration using a rough defibrating machine having a moisture content of thirty to 30% by weight and at least one cutting blade being a rotary blade. A bundle is formed, and then this coarse defibrated fiber bundle is brought into a state having a temperature of 50 to 100 ° C. and a moisture content of 10 to 30% by weight at atmospheric pressure, and at least one defibrating blade is a rotary blade The high-speed rotation by Seikai fiber to method for producing a cotton-like bamboo fiber characterized by a diameter to produce a fine fibrillated fiber bundle of 0.01 to 0.2mm in. Bamboo material divided and cut into lengths of 10 to 200 cm is compressed and cleaved to form a flat plate with a thickness of 5 to 20 mm, and the bamboo formed into a flat plate with a thickness of 100 to 200 ° C. And steamed in an atmosphere of heated steam having a pressure of 0.1 to 1.6 MPa for 5 to 60 minutes, and the steamed bamboo material is decompressed to normal pressure in 5 to 10 minutes to a temperature of 50 to 100 ° C. and 10 A coarse defibrated fiber having a thickness of 0.1 to 1.0 mm by performing rough defibration using a rough defibrating machine having a moisture content of thirty to 30% by weight and at least one cutting blade being a rotary blade. A bundle is formed, and then the crude defibrated fiber bundle is brought to a state having a temperature of 50 ° C. or higher and a moisture content of 10 to 30% by weight at atmospheric pressure, and at least one of the cutting blades is a rod-shaped rotary blade The high-speed rotation by And fine defibration, a diameter of 0.01 to 0.2 mm, the manufacturing method of the cotton-like bamboo fiber, wherein a length to produce a fine fibrillated fiber bundle 1 to 100 mm. A method for producing cotton-like bamboo fibers, wherein the steaming atmosphere is an atmosphere having a temperature of 130 to 160 ° C. and a pressure of 0.28 to 0.64 MPa. The rough defibration of the bamboo material is performed at an angle of 50 to 80 degrees where one cutting edge of the rough defibrating machine and the other cutting edge intersect each other. A method for producing cotton-like bamboo fiber. The fine defibrating following the rough defibration of the bamboo material is performed by rotating the rotary blade at 1000 rpm or more by a fine defibrating device in which the pair of cutting blades are both rod-shaped and at least one of the cutting blades is a rotary blade. The manufacturing method of the cotton-like bamboo fiber as described in any one of Claims 1 thru | or 8.