Staple fiber manufacturing method, nonwoven fabric manufacturing method, staple fiber manufacturing apparatus, and nonwoven fabric manufacturing apparatus

Abstract

A method for manufacturing short fibers according to the present invention comprises: an entanglement alleviating step in which tension is applied in a predetermined conveyance direction to a tow band that is conveyed in the conveyance direction, contains crimped cellulose acetate fibers, and has moisture added thereto, thereby alleviating entanglement of the crimped cellulose acetate fibers in the tow ban; and a short fiber forming step in which the tow band with alleviated entanglement is cut to form short fibers.

Description

[Technical field]

[0001] The present disclosure relates to a method for producing staple fibers using crimped cellulose acetate fibers, a method for producing nonwoven fabric, an apparatus for producing staple fibers, and an apparatus for producing nonwoven fabric. [Background technology]

[0002] Staple fibers made from crimped cellulose acetate fibers are known. These staple fibers are used, for example, as materials for nonwoven fabrics. Nonwoven fabrics made from these staple fibers take advantage of the texture of cellulose acetate fibers and are soft and comfortable to the touch. Furthermore, bulky nonwoven fabrics can be produced by using staple fibers cut from crimped cellulose acetate fibers.

[0003] When producing short fibers from crimped cellulose acetate fibers, for example, after a tow band containing the fibers is unwound from a packaging box, the entanglement of the fibers in the tow band is alleviated to make the fibers easier to process. The tow band is then cut by a cutter to form short fibers. Known types of cutters include, for example, a guillotine type shown in Patent Document 1 and a rotary type shown in Patent Document 2. When producing a nonwoven fabric, the formed short fibers are carded in advance. This causes the short fibers to be spread out in a sheet shape and the flow direction of the fibers to be aligned. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Application No. 2000-141290 [Patent Document 2] Japanese Patent Application Publication No. 1-148818 Summary of the Invention [Problem to be solved by the invention]

[0005] The crimped cellulose acetate fibers are relatively bulky, highly elastic, and highly entangled. Therefore, the short fibers made of the crimped cellulose acetate fibers may get caught or clog the conveying path in the short fiber manufacturing device. In addition, the short fibers made of the crimped cellulose acetate fibers are unstable in length due to the variation in their position relative to the cutter. This reduces the production efficiency of the short fibers.

[0006] Therefore, an object of the present disclosure is to enable efficient production of staple fibers having uniform length dimensions when producing staple fibers using crimped cellulose acetate fibers.

[0007] The inventors of the present application have conducted research and found that a tow band containing crimped cellulose acetate fibers can be stretched by adding moisture, thereby reducing fiber entanglement. The present disclosure is based on such findings.

[0008] That is, the method for producing staple fibers according to one embodiment of the present disclosure includes an entanglement relaxation step of relaxing entanglement of the crimped cellulose acetate fibers in a tow band, which is transported in a predetermined transport direction and contains crimped cellulose acetate fibers and has moisture added thereto, by applying tension in the transport direction to the tow band, and a short fiber formation step of cutting the tow band whose entanglement has been relaxed to form short fibers.

[0009] According to the above method, in the entanglement relaxation step, the entanglement of the crimped and moisture-imparted cellulose acetate fibers is relaxed, and the elasticity of the cellulose acetate fibers is reduced when the tow band is cut. Therefore, the formed short fibers are prevented from being caught in the short fiber manufacturing device or being clogged in the conveying path. In addition, when the tow band is cut in the short fiber formation step, the attitude of the fibers relative to the cutter can be suppressed from varying. As a result, short fibers of uniform length can be formed. This allows efficient production of short fibers of stable quality by a relatively simple method.

[0010] In the entanglement alleviation step, moisture may be added to the tow band so that the moisture content of the tow band immediately before cutting in the short fiber formation step is in the range of 7% by mass or more and 80% by mass or less. This makes it easier to add an appropriate amount of moisture to the tow band to form short fibers of uniform length by stretching the tow band to alleviate fiber entanglement. Therefore, the load on the short fibers when drying the short fibers can be reduced. In addition, the manufacturing equipment can be made less susceptible to water. Therefore, the burden on equipment management can be reduced.

[0011] In the entanglement relaxation step, the tow band may be heated to promote the relaxation of the entanglement. By heating the tow band in this manner, the cellulose acetate fiber in the tow band at the time of cutting can be plasticized to a certain extent, and the elasticity of the cellulose acetate fiber can be reduced. Therefore, the entanglement of the cellulose acetate fiber in the tow band can be further relaxed.

[0012] In the entanglement reduction step, moisture may be impregnated to the tow band by contacting the tow band with a mist containing moisture. This prevents the tow band from becoming excessively wet. Therefore, the amount of water used to reduce the entanglement of the fibers of the tow band can be reduced. In addition, the labor and energy consumption required to dry the tow band after the entanglement reduction step can be reduced. In addition, the tow band impregnated with moisture can reduce excessive wetting of the short fiber manufacturing device.

[0013] The mist may contain moisture vapor. This can better prevent the tow band from being excessively wetted by moisture. In this case, in the entanglement alleviation step, the mist may be brought into contact with the tow band so that the moisture content of the tow band immediately before cutting in the short fiber formation step is in the range of 7% by mass or more and 15% by mass or less. This can obtain an appropriate amount of moisture to alleviate the entanglement of the fibers of the tow band, and can better prevent the tow band from being excessively wetted by moisture.

[0014] In the entanglement reducing step, the mist may be brought into contact with the tow band so that the moisture content of the tow band immediately before cutting in the short fiber forming step is in the range of 7% by mass to 35% by mass. In addition, a drying step of drying the moisture adhering to the short fibers after the short fiber forming step may be provided.

[0015] In the short fiber forming step, the tow band may be cut by a rotary cutter having a cutting blade arranged on a circumferential surface, which is supported by a shaft and is rotated so that the tow band contacts the cutting blade. By using a rotary cutter having such a configuration, the tow band being conveyed can be continuously cut, and short fibers can be formed more efficiently.

[0016] In addition, a method for producing a nonwoven fabric according to an embodiment of the present disclosure produces a nonwoven fabric using staple fibers formed by any of the methods for producing staple fibers described above.

[0017] In addition, a short fiber manufacturing apparatus according to one embodiment of the present disclosure includes an entanglement reduction section that reduces entanglement of the crimped cellulose acetate fibers in a tow band that is transported in a predetermined transport direction and contains crimped cellulose acetate fibers and has moisture added thereto by applying tension in the transport direction, and a short fiber forming section that cuts the tow band whose entanglement has been reduced to form short fibers.

[0018] A nonwoven fabric manufacturing apparatus according to an aspect of the present disclosure includes the staple fiber manufacturing apparatus and a nonwoven fabric forming unit that forms a nonwoven fabric using the staple fibers formed by the staple fiber forming unit. Effect of the Invention

[0019] According to each aspect of the present disclosure, when staple fibers are produced using crimped cellulose acetate fibers, staple fibers having a uniform length can be efficiently produced. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic diagram of a nonwoven fabric manufacturing apparatus according to a first embodiment. [Diagram 2] 2 is a schematic diagram showing the internal structure of a cutting mechanism of the short fiber forming section of FIG. 1. [Diagram 3] FIG. 11 is a schematic diagram of a nonwoven fabric manufacturing apparatus according to a third embodiment. [Figure 4] This is a photograph of the tow band immediately after mitigation in Example 1. [Diagram 5] This is a photograph of the tow band immediately after mitigation in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Each embodiment of the present disclosure will be described with reference to the drawings. (First embodiment) FIG. 1 is a schematic diagram of a nonwoven fabric manufacturing apparatus 1 according to the first embodiment. FIG. 2 is a schematic diagram showing the internal structure of the cutting mechanism 30 of the short fiber forming unit 3 of FIG. 1. The nonwoven fabric manufacturing apparatus 1 shown in FIG. 1 pays out a bale-shaped tow band 60 folded and packed in a packaging box B, and forms short fibers 62 using this tow band 60. That is, the nonwoven fabric manufacturing apparatus 1 of this embodiment also serves as a short fiber manufacturing apparatus. The short fibers 62 are used as a material for the nonwoven fabric 63. The nonwoven fabric referred to in this specification refers to a nonwoven fabric conforming to JIS L 0222:2001.

[0022] The tow band 60 includes crimped cellulose acetate fibers 61 (hereinafter also referred to as CA fibers 61). This makes the tow band 60 elastic. In addition, the tow band 60 is in a state where a plurality of CA fibers 61 are intertwined with each other. The CA fibers 61 in the tow band 60 unwound from the packaging box B are long fibers. The CA fibers 61 are crimped by the primary crimp, which is the smallest crimp unit, and are crimped by the secondary crimp, which is a crimp unit larger than the primary crimp. The CA fibers 61 may be further crimped by the higher crimp, which is a crimp unit larger than the secondary crimp.

[0023] Each of the TD (total denier) and FD (filament denier) of the tow band 60 can be set appropriately. As an example, the TD of the tow band 60 is a value in the millions, hundreds of thousands, tens of thousands, or thousands. In another example, the TD of the tow band 60 is a value in the range of 3 million to 5 million, and more preferably a value in the range of 1 million to 2 million. In another example, the TD of the tow band 60 is a value in the range of 100,000 to 700,000, and more preferably a value in the range of 100,000 to 300,000. In yet another example, the TD of the tow band 60 is a value in the range of 5,000 to 100,000, and more preferably a value in the range of 10,000 to 50,000.

[0024] In addition, as an example, the FD of the tow band 60 is a value in the range of 10 or less. In another example, the FD of the tow band 60 is a value in the range of 1 to 8. The tow band 60 of this embodiment is conveyed along a predetermined conveying path 50 provided in the nonwoven fabric manufacturing apparatus 1 while being given a relatively weak tension (load) in the conveying direction P of 2 mgf to 50 mgf per denier.

[0025] As shown in Figures 1 and 2, the nonwoven fabric manufacturing apparatus 1 includes a guide member 7 that guides the tow band 60 unwound from the packaging box B, and a plurality of guide rolls R1 to R4 that are arranged at a distance in a predetermined conveying direction P and guide the tow band 60. The nonwoven fabric manufacturing apparatus 1 also includes an entanglement alleviation section 2 that is arranged in the middle of the conveying path 50 of the tow band 60 to alleviate the entanglement of the CA fibers 61 in the tow band 60, and a short fiber forming section 3 that cuts the tow band 60 in which the entanglement of the CA fibers 61 has been alleviated to form short fibers 62. The nonwoven fabric manufacturing apparatus 1 also includes a drying section 4 that dries the short fibers 62 discharged from the short fiber forming section 3, and a nonwoven fabric forming section 5 that entangles the short fibers 62 that have passed through the drying section 4 to form a nonwoven fabric 63.

[0026] The entanglement reduction section 2 imparts moisture to the tow band 60, which includes the CA fibers 61 that have been conveyed in the conveying direction P and crimped, while applying tension in the conveying direction P. As an example, the entanglement reduction section 2 adjusts the tension applied to the tow band 60 by changing the rotation speed of the rotating roll 21 described later. This tension is applied to the tow band 60 from just before it is introduced into the entanglement reduction section 2 to just before it is cut by the cutting mechanism 30 of the short fiber forming section 3. As a result, the entanglement reduction section 2 stretches the CA fibers 61 and relieves the entanglement of the CA fibers 61 in the tow band 60. The entanglement reduction section 2 of this embodiment imparts moisture to the tow band 60 by bringing the mist M into contact with the tow band 60. The mist M in this specification is fine particles of a liquid that is dispersed in a gas and contains moisture. The mist M includes at least one of steam and fine droplets.

[0027] The tension applied to the tow band 60 can also be adjusted by, for example, changing the load from the rotating roll 21 to the tow band 60. For example, in this case, if the relative position of the rotating roll 21 to the tow band 60 is shifted downward, the tension applied to the tow band 60 increases. Also, for example, if the relative position of the rotating roll 21 to the tow band 60 is shifted upward, the tension applied to the tow band 60 decreases. The tension applied to the tow band 60 can also be adjusted by changing the material of the rotating roll 21 or fixing the relative position of the rotating roll 21 to the tow band 60 at a predetermined position.

[0028] The mist M of this embodiment includes steam as an example. In this embodiment, the steam is heated steam. The temperature of the heated steam can be set appropriately, but as an example, it is higher than room temperature (25 ° C). In another example, the steam is superheated steam that is superheated to the boiling point (100 ° C) or higher. As an example, the particle size of the steam is a value in the range of 0.3 nm to 40 nm. The entanglement reduction section 2 imparts moisture to the tow band 60 while heating the tow band 60 by bringing the heated steam into contact with the tow band 60.

[0029] The entanglement reduction section 2 has a housing 20 filled with mist M, at least one rotating roll 21 journaled inside the housing 20 and having a tow band 60 wound around its circumferential surface, and at least one nozzle 22 for spraying mist M onto the tow band 60 inside the housing 20. A supply pipe 23 for supplying moisture to the nozzle 22 from the outside of the entanglement reduction section 2 is connected to the rear end of the nozzle 22. For example, when the rotation speed of the rotating roll 21 is increased, the tension applied to the tow band 60 is increased. Also, when the rotation speed of the rotating roll 21 is decreased, the tension applied to the tow band 60 is decreased.

[0030] By the entanglement reduction section 2 impregnating the tow band 60 with moisture, the moisture content of the tow band 60 immediately before cutting in the short fiber forming section 3 is greater than the moisture content of the tow band 60 before the moisture is impregnated by the entanglement reduction section 2 (equilibrium moisture content according to JIS L 1013:2010). As an example, the entanglement reduction section 2 of the present embodiment adjusts the spray amount of the mist M so that the moisture content of the tow band 60 immediately before cutting in the short fiber forming section 3 is a value in the range of 7% by mass or more and 80% by mass or less. The spray amount of the mist M is adjusted by at least one of the amount of moisture supplied per unit time to the nozzle 22 and the conveying speed of the tow band 60, for example. By adjusting the spray amount of the mist M to a value in the above range, as described later, it is possible to ensure the moisture amount required for plasticizing the CA fiber 61 in the tow band 60, and to easily adjust the moisture amount so that it is not excessive. In this embodiment, the entanglement reduction section 2 further brings the mist M into contact with the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber forming section 3 is in the range of 7% by mass or more and 15% by mass or less.

[0031] The mist M may contain at least one additive selected from the group consisting of an oil agent, a softener, and an antistatic agent. By applying the additive to the CA fiber 61, the properties of the nonwoven fabric 63 can be changed by the additive. In addition, the additive can be locally applied to the CA fiber 61 in the tow band 60 by adjusting at least one of the spray amount of the mist M and the spray direction of the mist M from the nozzle 22. In order to adjust the amount of these additives applied separately from the amount of moisture applied to the tow band 60, the additive may be applied to the tow band 60 separately from the mist M.

[0032] The short fiber forming section 3 is a long fiber bundle cutting section. The short fiber forming section 3 has a cutting mechanism 30 that cuts the CA fiber 61 into a predetermined length to form short fibers 62, and a carding machine 31 that cards the formed short fibers 62. The cutting mechanism 30 has a guide roll (push roll) 32 that is rotatably supported so as to contact the tow band 60 with its circumferential surface and guide the tow band 60, and a rotary cutter 33 that cuts the tow band 60 guided by the guide roll 32. The rotary cutter 33 has a cutting blade 34 arranged on its circumferential surface and is rotatably supported. The guide roll 32 and the rotary cutter 33 are rotated so that the cutting blade 34 of the rotary cutter 33 contacts the tow band 60 transported on the circumferential surface of the guide roll 32. The structure in which the guide roll 32 and the rotary cutter 33 are combined is also called an EC cutter.

[0033] In this embodiment, the distance between the cutting edge of the cutting blade 34 and the peripheral surface of the guide roll 32 is set to a distance at which the CA fiber 61 at the outermost periphery of the tow band 60 wound around the peripheral surface of the guide roll 32 comes into contact with the cutting blade 34 and is cut. The length dimension of the short fiber 62 formed by the short fiber forming unit 3 can be set appropriately. As an example, the length dimension of the short fiber 62 in this embodiment is a value in the range of 1 mm or more and 80 mm or less. In another example, it is a value in the range of 1 mm or more and 9 mm or less. In another example, it is a value in the range of 30 mm or more and 80 mm or less. The length dimension of the short fiber 62 is not limited to this.

[0034] The drying section 4 has a conveying mechanism 40 which conveys the short fibers 62 discharged from the short fiber forming section 3, and a heating section 41 which heats and dries the short fibers 62 conveyed by the conveying mechanism 40. The nonwoven fabric forming section 5 forms a nonwoven fabric 63 by entangling the dried short fibers 62. The nonwoven fabric forming section 5 also adjusts the entanglement of the dried short fibers 62 to adjust the thickness dimension, texture, or size of the fiber gaps of the nonwoven fabric 63. When only a short fiber manufacturing device is configured, for example, the carding machine 31 and the nonwoven fabric forming section 5 are omitted.

[0035] As shown in Figures 1 and 2, when the nonwoven fabric manufacturing apparatus 1 is driven, a bale-shaped tow band 60 is unwound from a packaging box B. The tow band 60 is conveyed in a conveying direction P while being guided by a guide member 7 and guide rolls R1 to R4. The conveyed tow band 60 is introduced into the inside of the housing 20 filled with mist M in the entanglement reduction section 2. The tow band 60 is conveyed inside the housing 20 while being wound around the circumferential surface of the rotating roll 21.

[0036] At this time, the tow band 60 is applied with mist M by at least one nozzle 22 while being given a relatively weak tension (load) of 2 mgf or more and 50 mgf or less per denier in the conveying direction P. As an example, the nozzle 22 sprays mist M onto the tow band 60 from a plurality of directions including a direction perpendicular to the surface of the tow band 60. After contacting the surface of the tow band 60, the mist M penetrates into the inside of the tow band 60. The tow band 60 also has abundant fiber gaps. Therefore, the mist M directly contacts the multiple CA fibers 61 inside and outside the tow band 60 through the fiber gaps. As a result, moisture is impregnated into the multiple CA fibers 61 contained in the tow band 60. Each CA fiber 61 is plasticized by the impregnation of moisture, so that the high-order crimp of at least the secondary crimp is slowed.

[0037] Here, the nozzle 22 of this embodiment sprays heated steam onto the tow band 60. The CA fibers 61 in the tow band 60 are plasticized by both moisture and heat as the heated steam is applied to them. As a result, the elasticity of the multiple CA fibers 61 is reduced and the relaxation of entanglement is promoted. In this embodiment, the CA fibers 61 can be easily plasticized by applying moisture to the tow band 60 and heating the tow band 60. Therefore, the amount of moisture used to relax the entanglement of the CA fibers 61 can be reduced.

[0038] The tow band 60 that has passed through the entanglement alleviation section 2 is conveyed in the conveying direction P toward the short fiber forming section 3 while being subjected to the tension. In this embodiment, the amount of moisture sprayed as steam onto the tow band 60 in the entanglement alleviation section 2 is relatively small. Therefore, a process for removing excess moisture from the tow band 60 between the entanglement alleviation section 2 and the short fiber forming section 3 is not required. Therefore, the nonwoven fabric manufacturing apparatus 1 can be simplified.

[0039] The tow band 60 being conveyed is introduced into the cutting mechanism 30 in the short fiber forming section 3. As shown in FIG. 2, the tow band 60 is conveyed while being guided by the circumferential surface of the guide roll 32 which is rotated while being tensioned, and comes into contact with the cutting blade 34 of the rotary cutter 33 which is rotated. As a result, the CA fiber 61 in the tow band 60 is cut into a predetermined length dimension to form a plurality of short fibers 62.

[0040] Here, in this embodiment, the moisture content of the tow band 60 introduced into the cutting mechanism 30 is relatively small. For this reason, for example, the tow band 60 containing excessive moisture is prevented from being clogged between the guide roll 32 and the rotary cutter 33, or the CA fibers 61 in the tow band 60 before and after cutting are prevented from sticking to the guide roll 32 or the rotary cutter 33 due to moisture, making it difficult to discharge. In this embodiment, the multiple CA fibers 61 of the tow band 60 are cut by the cutting blade 34 in a state in which the intertwining is relaxed and the tension is applied. Therefore, the posture of the CA fibers 61 relative to the cutting blade 34 is stable. As a result, the tow band 60 is cut by the rotary cutter 33 with a uniform length dimension. The short fibers 62 formed thereby are continuously discharged from the short fiber forming section 3. In this embodiment, by adopting the rotary cutter 33, the short fibers 62 are formed while conveying the tow band 60. Therefore, the short fibers 62 are formed efficiently.

[0041] The formed plurality of short fibers 62 are then carded by the carding machine 31. This adjusts the thickness dimension and flow direction of the short fibers 62. In this embodiment, the short fibers 62 introduced into the carding machine 31 are plasticized by impregnating them with moisture. Therefore, the plurality of short fibers 62 are well carded while being prevented from becoming entangled in the carding machine 31 or being caught by the needles of the carding machine 31 and being unable to pass through the carding machine 31.

[0042] As shown in FIG. 1, the carded short fibers 62 are transported in the transport direction P and introduced into the drying section 4. The short fibers 62 are dried by the heating section 41 while being transported by the transport mechanism 40. As a result, the short fibers 62 are dried to a predetermined moisture content. The short fibers 62 introduced into the drying section 4 do not have a very large moisture content. Therefore, in the drying section 4, the short fibers 62 are dried relatively lightly, and the load caused by heating is reduced. The short fibers 62 that have passed through the drying section 4 are introduced into the nonwoven fabric forming section 5. In the nonwoven fabric forming section 5, the short fibers 62 are entangled, for example, based on a needle punch method. As a result, a nonwoven fabric 63 is formed.

[0043] In the entanglement reducing section 2, moisture is added to the tow band 60 and the tow band 60 is stretched, so that in the short fiber forming section 3, the elasticity of the CA fiber 61 is reduced when the tow band 60 is cut, and the crimping of the CA fiber 61 is slowed. Then, the moisture of the short fiber 62 is reduced by drying, so that in the nonwoven fabric forming section 5, the texture of the CA fiber 61 is utilized to obtain a nonwoven fabric 63 that is soft and comfortable to the touch.

[0044] The method by which the nonwoven fabric forming unit 5 forms the nonwoven fabric 63 can be any known method such as a needle punch method, a dry method, a wet method, a chemical bond method, a hydroentanglement method, etc. The nonwoven fabric 63 discharged from the nonwoven fabric forming unit 5 is cut to a predetermined length as necessary. If the moisture content of the multiple short fibers 62 when introduced into the nonwoven fabric forming unit 5 is appropriate, the drying unit 4 may be omitted.

[0045] As described above, the manufacturing method of the short fibers 62 of this embodiment includes an intertwining relaxation step in which the tow band 60, which is transported in a predetermined transport direction P and contains the crimped CA fibers 61 and is impregnated with moisture, is subjected to tension in the transport direction P to relieve the intertwining of the CA fibers 61 in the tow band 60, and a short fiber forming step in which the tow band 60 in which the intertwining of the CA fibers 61 has been relaxed is cut to form the short fibers 62. In the short fiber forming step of this embodiment, the tow band 60 in which the intertwining of the CA fibers 61 has been relaxed is cut under the tension to form the short fibers 62.

[0046] In addition, the manufacturing method of the short fibers 62 of this embodiment has, as an example, a preparation step before the entanglement reduction step, for making preparations for impregnating the tow band 60 with moisture during the entanglement reduction step (for example, in this embodiment, the setting of the entanglement reduction section 2, etc.). In addition, the manufacturing method of the short fibers 62 of this embodiment has, as an example, a drying step after the short fiber formation step, for drying the moisture attached to the short fibers 62. In addition, the manufacturing method of the nonwoven fabric 63 of this embodiment uses the manufactured short fibers 62 to manufacture the nonwoven fabric 63.

[0047] As described above, the manufacturing method of the nonwoven fabric 63 of this embodiment has an entanglement relaxation step and a short fiber formation step. According to this manufacturing method, in the entanglement relaxation step, the entanglement of the multiple CA fibers 61 that have been crimped and impregnated with moisture is relaxed, and the elasticity of the CA fibers 61 when the tow band 60 is cut is reduced. Therefore, in the nonwoven fabric manufacturing apparatus 1, the formed short fibers 62 are prevented from being caught on the nonwoven fabric manufacturing apparatus 1 or clogging the conveying path 50. In addition, when the tow band 60 is cut in the short fiber formation step, the attitude of the CA fibers 61 relative to the cutter 33 can be suppressed from varying. As a result, short fibers 62 of uniform length can be efficiently formed. This allows the short fibers 62 of stable quality to be efficiently manufactured by a relatively simple method.

[0048] According to the above manufacturing method, the CA fibers 61 are stretched by impregnating the tow band 60 with moisture and applying tension in the conveying direction P, thereby reducing the entanglement of the CA fibers 61. Therefore, for example, a fiber-opening roll that mechanically opens the tow band 60 or a gas-opening device that opens the tow band 60 with gas is not required. Therefore, the nonwoven fabric manufacturing apparatus 1 can be simplified. According to the present embodiment, even if a tow band 60 made of crimped CA fibers 61 is used to make the tow band 60 bulky, short fibers 62 having a uniform length can be efficiently formed.

[0049] According to the above manufacturing method, the entanglement relaxation step using moisture is performed, so that the short fibers 62 having uniform length can be efficiently formed. Therefore, for example, a step of modifying the tow band 60 with a chemical to reduce the number of crimps before forming the short fibers 62 is not required. Furthermore, since moisture is used in the entanglement relaxation step, the short fibers 62 can be efficiently formed in a relatively safe manner. According to the above method, the crimp of the short fibers 62 can be maintained to a certain degree even when the entanglement relaxation step is performed. Therefore, a bulky nonwoven fabric 63 can be manufactured by using the crimped short fibers 62.

[0050] In addition, in the short fiber forming step of this embodiment, the tow band 60 in which the entanglement of the CA fibers 61 is relaxed is cut under the tension to form the short fibers 62. This makes it possible to further stabilize the posture of the CA fibers 61 when cutting the tow band 60. Therefore, it is easier to form the short fibers 62 having a uniform length.

[0051] In addition, in the intertwining relaxation step of this embodiment, moisture is impregnated into the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber formation step is in the range of 7% by mass or more and 80% by mass or less. This makes it easy to impregnate the tow band 60 with an appropriate amount of moisture required to form short fibers 62 of uniform length dimensions by stretching the tow band 60 and relaxing the intertwining of the CA fibers 61. Therefore, the load on the short fibers 62 when drying the short fibers 62 can be reduced. In addition, the manufacturing equipment can be made less susceptible to water. Therefore, the burden on equipment management can be reduced.

[0052] In addition, in the intertwining relaxation step of this embodiment, the tow band 60 is heated to promote the relaxation of the intertwining of the CA fibers 61. By heating the tow band 60 in this manner, the CA fibers 61 in the tow band 60 at the time of cutting can be plasticized within a certain range, and the elasticity of the short fibers 62 can be reduced. Therefore, the intertwining of the CA fibers 61 in the tow band 60 can be further relaxed.

[0053] In the entanglement reduction step, the mist M containing water is brought into contact with the tow band 60 to impregnate the tow band 60 with water. This, for example, can prevent the tow band 60 from becoming excessively wet. Therefore, the amount of water used to relieve the entanglement of the CA fiber 61 can be reduced. In addition, the effort and energy consumption required to dry the tow band 60 after the entanglement reduction step can be reduced. In addition, the tow band 60 to which water is impregnated can reduce excessive wetting of the nonwoven fabric manufacturing apparatus 1.

[0054] The mist M also contains moisture vapor. This can more effectively prevent the tow band 60 from becoming excessively wetted by moisture. In the entanglement alleviation step, the mist M is brought into contact with the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber formation step is in the range of 7% by mass or more and 15% by mass or less. This can obtain an appropriate amount of moisture to alleviate the entanglement of the CA fibers 61 in the tow band 60, and can more effectively prevent the tow band 60 from becoming excessively wetted by moisture.

[0055] As another example, the method for producing the nonwoven fabric 63 of this embodiment includes a drying step for drying the moisture adhering to the short fibers 62 after the short fiber forming step. This makes it possible to prevent the water-containing short fibers 62 from adhering to the nonwoven fabric production apparatus 1. Also, it is possible to prevent the nonwoven fabric 63 to be formed from containing unnecessary moisture.

[0056] As an example, in the short fiber forming step, the tow band 60 is cut by a rotary cutter 33 having a cutting blade 34 arranged on the circumferential surface and supported by a shaft, which is rotated so that the tow band 60 contacts the cutting blade 34. By using the rotary cutter 33 having such a configuration, the tow band 60 being conveyed can be continuously cut, and the short fibers 62 can be formed more efficiently.

[0057] The cutting mechanism 30 may not have the rotary cutter 33, but may have a guillotine cutter as disclosed in Patent Document 1, and a feeder that supplies the tow band 60 to the guillotine cutter. The guillotine cutter may have at least one of a pair of blades (e.g., a lower blade and an upper blade) for cutting the tow band 60. When a guillotine cutter is used, the tension applied to the tow band 60 is adjusted, for example, by the feed speed of the feeder. As an example, when the feed speed of the feeder is increased, the tension increases. Also, when the feed speed of the feeder is decreased, the tension decreases. However, when the cutting mechanism 30 has a rotary cutter 33, the short fibers 62 are formed at a relatively high speed. Therefore, for example, the use of the rotary cutter 33 improves the manufacturing efficiency of the nonwoven fabric 63. In addition, when the tow band 60 is heated in the intertwining relaxation step, the process of impregnating the tow band 60 with moisture and the process of heating the tow band 60 may be performed separately. In this case, for example, by impregnating the tow band 60 with moisture and then heating the tow band 60, the temperature of the tow band 60 can be prevented from decreasing due to the impregnation of the moisture.

[0058] In addition, either one tow band 60 or a bundle of tow bands 60 including a plurality of tow bands 60 may be introduced into the entanglement reduction section 2 and the short fiber forming section 3. In this embodiment, the nonwoven fabric 63 is efficiently manufactured as described above. Therefore, even when the nonwoven fabric 63 is manufactured using a bundle of tow bands 60, the nonwoven fabric 63 can be manufactured well. Below, the other embodiments will be described, focusing on the differences from the first embodiment.

[0059] Second embodiment The entanglement reduction section 2 of the nonwoven fabric manufacturing apparatus 1 according to the second embodiment sprays the mist M onto the tow band 60 using the nozzle 22, as in the first embodiment. The mist M contains minute droplets of water. The particle size of these minute droplets is larger than the particle size of steam. As an example, the particle size of the minute droplets is in the range of 0.1 μm or more and 100 μm or less.

[0060] As in the first embodiment, the manufacturing method of the nonwoven fabric 63 of this embodiment also has, as an example, a preparation step before the entanglement relaxation step, for preparing to impregnate the tow band 60 with moisture during the entanglement relaxation step. Also, as an example, after the staple fiber formation step, a drying step for drying the moisture adhering to the staple fiber 62.

[0061] In the intertwining relaxation step, the tow band 60 is sprayed with water droplets while being applied with a relatively weak tension (load) of 2 mgf to 50 mgf per denier in the conveying direction P. The CA fibers 61 in the tow band 60 are plasticized by the water droplets to reduce their elasticity. This reduces the intertwining between the CA fibers 61. In the present embodiment, as in the first embodiment, in the intertwining relaxation step, water is added to the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber forming step is a value in the range of 7% by mass to 80% by mass. As an example, in the intertwining relaxation step, the mist M is brought into contact with the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber forming step is a value in the range of 7% by mass to 35% by mass (in another example, a value in the range of 15% by mass to 35% by mass). As in the first embodiment, the mist M may contain an additive. According to this embodiment, by using water in the form of minute droplets, a larger amount of additive can be attached to the CA fibers 61 than in the first embodiment.

[0062] In this embodiment, the mist M containing moisture can be efficiently applied to the tow band 60 using, for example, an existing spray device. Therefore, moisture can be applied to the tow band 60 at a relatively low cost. In addition, when manufacturing a nonwoven fabric 63 using the crimped CA fiber 61 (tow band 60), short fibers 62 of uniform length can be efficiently formed. Also in this embodiment, the amount of moisture applied to the tow band 60 in the entanglement reduction section 2 is relatively small. Therefore, a process of removing excess moisture contained in the tow band 60 between the entanglement reduction section 2 and the short fiber forming section 3 can be omitted.

[0063] In the intertwining relaxation step of this embodiment, the mist M is brought into contact with the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber formation step is in the range of 7% by mass or more and 35% by mass or less. This allows the moisture content of the tow band 60 to be set to an appropriate amount. In this embodiment, in the intertwining relaxation step, the mist M containing heated microdroplets may be sprayed onto the tow band 60. In this case, as in the first embodiment, the CA fiber 61 in the tow band 60 is plasticized by both moisture and heat.

[0064] Third embodiment FIG. 3 is a schematic diagram of a nonwoven fabric manufacturing apparatus 11 according to a third embodiment. The entanglement reduction section 12 of the nonwoven fabric manufacturing apparatus 11 shown in FIG. 3 impregnates the tow band 60 with water by immersing the tow band 60 in a tensioned state, thereby impregnating the tow band 60 with water and alleviating the entanglement of the CA fibers 61 in the tow band 60. The entanglement reduction section 12 has a storage section 25 for storing water and at least one rotating roll 26 that is supported inside the storage section 25 and has the tow band 60 wound around its circumferential surface. The tow band 60 is wound around the circumferential surface of the rotating roll 26, and is immersed in the water in the storage section 25 while being tensioned in the conveying direction P to impregnate the water. The water in the storage section 25 may be hotter than room temperature (25 ° C.). That is, in this embodiment, the tow band 60 may be heated in the entanglement reduction step to promote the relaxation of the entanglement of the CA fibers 61.

[0065] The manufacturing method of the nonwoven fabric 63 of this embodiment also includes, as an example, a preparation step before the entanglement reduction step, in which preparation is made to add moisture to the tow band 60 during the entanglement reduction step (for example, in this embodiment, the setting of the entanglement reduction section 12, etc.). As an example, the manufacturing method of the nonwoven fabric 63 of this embodiment also includes a drying step after the short fiber formation step, in which moisture attached to the short fiber 62 is dried.

[0066] In the intertwining relaxation step of this embodiment, as an example, moisture is added to the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber forming step is in the range of 7% by mass to 80% by mass. As another example, in the intertwining relaxation step, moisture is added to the tow band 60 so that the moisture content of the tow band 60 immediately before cutting in the short fiber forming step is in the range of 60% by mass to 80% by mass.

[0067] In the short fiber forming step, the water content of the tow band 60 immediately before cutting is preferably, for example, a value in the range of less than 100% by mass, preferably a value in the range of 80% by mass or less, such that the tow band 60 immersed in water does not drip in a natural state. In addition, the amount of water for immersing the tow band 60 in water (the amount of water in the storage section 25) is set to a degree that does not cause excessive load on the short fibers 62 when the short fibers 62 are dried. As a result, the amount of water applied to the tow band 60 is appropriately adjusted. In this embodiment, too, the CA fiber 61 can be plasticized by applying water to the tow band 60. In addition, by applying heated moisture to the tow band 60, the CA fiber 61 can be plasticized by both moisture and heat. Therefore, by forming short fibers 62 with uniform length dimensions, the nonwoven fabric 63 can be efficiently manufactured.

[0068] (Confirmation test) Next, confirmation tests will be described, but the present disclosure is not limited to the following examples. Short fibers according to Examples 1 to 3 and Comparative Examples 1 and 2 were produced according to the following procedure. [Preparation of Example 1] TD is 30,000, FD is 3A tow band 60 was used, in which the number of crimps per inch length (number of primary crimps) was set to 346. The number of crimps in the tow band 60 was counted by the following method. The sampled tow band 60 was placed on a table, one end of the tow band 60 in the direction in which the crimps extended was fixed to the table side, and the other end was hung down from the edge of the table. A constant load was applied to the other end of the tow band 60 by a weight, thereby applying a constant tension to the tow band 60 in the direction in which the crimps extended. In this state, the unevenness present on the surface of the tow band 60 was highlighted by lighting. Then, the surface of the tow band 60 was photographed by an optical sensor such as a CCD camera.

[0069] The captured image was binarized by the following method. The computer converted the pixel value (for example, brightness) of each pixel in the captured image to "1" if it was equal to or greater than a predetermined threshold, and converted it to "0" if it was less than the threshold. Next, if the computer determined that the converted image contained a pixel group in which pixels with a pixel value of "1" were consecutive in a predetermined manner in the direction in which the crimp was extended in the tow band 60, the computer determined that the pixel group was a mountain portion. If the computer determined that the converted image contained a pixel group in which pixels with a pixel value of "0" were consecutive in a predetermined manner in the direction, the computer determined that the pixel group was a valley portion. The computer also counted the total number of valleys and peaks divided by 2 as the number of crimps. This counted the number of crimps (number of primary crimps) of the tow band 60 per inch length in the direction.

[0070] The tow band 60 was introduced into the nonwoven fabric manufacturing apparatus 1, and the entanglement relaxation step and the short fiber formation step were performed by the method disclosed in the first embodiment. In the entanglement relaxation step, the tension applied to the tow band 60 in the conveying direction P was set to 0.3 kgf (10 mgf per denier) throughout the tow band 60. In addition, the tow band 60 was impregnated with moisture by spraying heated steam (100 ° C or higher) from the nozzle 22. In the entanglement relaxation step, the moisture content of the tow band 60 was adjusted so that the moisture content of the tow band 60 immediately before cutting in the short fiber formation step was 10.8 mass%. In the short fiber formation step, the tow band 60 was cut to a target dimension of 51 mm by a cutting mechanism 30 having a guillotine type cutter.

[0071] [Preparation of Example 2] The same tow band 60 as in Example 1 was introduced into the nonwoven fabric manufacturing apparatus 11, and the entanglement relaxation step and the short fiber formation step were performed by the method disclosed in the second embodiment. In the entanglement relaxation step, the tension applied to the tow band 60 in the conveying direction P was set to 0.3 kgf (10 mgf per denier) throughout the tow band 60. In the entanglement relaxation step, moisture was added to the tow band 60 by spraying moisture droplets (25 ° C.) from the nozzle 22 onto the tow band 60. In the entanglement relaxation step, the moisture content of the tow band 60 was adjusted so that the moisture content of the tow band 60 immediately before cutting in the short fiber formation step was 28 mass%. In the short fiber formation step, the tow band 60 was cut to a target dimension of 51 mm by a cutting mechanism 30 having a guillotine-type cutter.

[0072] [Preparation of Example 3] The same tow band 60 as in Example 1 was introduced into the nonwoven fabric manufacturing apparatus 11, and the entanglement relaxation step and the short fiber formation step were performed by the method disclosed in the third embodiment. In the entanglement relaxation step, the tension applied to the tow band 60 in the conveying direction P was set to 0.3 kgf (10 mgf per denier) throughout the tow band 60. In the entanglement relaxation step, the moisture content of the tow band 60 was adjusted so that the moisture content of the tow band 60 immediately before cutting in the short fiber formation step was 68.4 mass%. In the short fiber formation step, the tow band 60 was cut to a target dimension of 51 mm by a cutting mechanism 30 having a guillotine-type cutter.

[0073] [Preparation of Comparative Examples 1 and 2] The staple fibers of Comparative Examples 1 and 2 were formed in the same manner as in Example 1, except that the intertwining relaxation step was not performed, and a spreading step was performed in which the tow band transported in a predetermined transport direction was spread by applying tension in the transport direction and width direction with a plurality of spreading rolls arranged at a distance in the transport direction to the tow band. In Comparative Example 1, a tow band having a crimp number (primary crimp number) of 340 per inch length before the spreading was used. In Comparative Example 2, a tow band having a crimp number (primary crimp number) of 310 per inch length before the spreading was used.

[0074] The short fibers of Examples 1 to 3 and Comparative Examples 1 to 2 prepared as described above were evaluated for the state of carding, the presence or absence of clogging of the short fibers in the conveying path in the short fiber manufacturing device, the uniformity of the length dimension of the short fibers, and the feel of the short fibers. The evaluation results and test results are shown in Tables 1 and 2. Figure 4 is a photograph of the tow band 60 immediately after the entanglement relaxation of Example 1. Figure 5 is a photograph of the tow band 60 immediately after the entanglement relaxation of Example 2.

[0075] [Table 1]

[0076] [Table 2]

[0077] As shown in Table 2, in Comparative Examples 1 and 2, a problem occurred in which the short fibers were caught (entangled) in the carding machine during carding. The tow band of Comparative Example 1 was bulky and elastic. The tow band of Comparative Example 2 also had the same bulkiness and elasticity as Comparative Example 1. Therefore, in Comparative Examples 1 and 2, it was difficult to introduce the tow band into the short fiber forming section 3. In Comparative Examples 1 and 2, the posture of the CA fiber relative to the cutter when cutting the tow band by the cutting mechanism 30 was not stable compared to Examples 1 to 3. Therefore, in Comparative Examples 1 and 2, the length dimension of the short fibers varied relatively greatly.

[0078] As shown in Table 1, FIG. 4, and FIG. 5, in contrast, in the tow band 60 of Examples 1 to 3, the number of crimps of the tow band 60 after the moisture impregnation is slightly lower than the number of crimps of the tow band 60 before the moisture impregnation, but it was confirmed that the number of crimps of the tow band 60 is maintained within a substantially problem-free range. In addition, in Examples 1 to 3, it was confirmed that the entanglement of the CA fiber 61 in the tow band 60 is well alleviated by impregnating the tow band 60 with moisture. In addition, in Example 1, it was confirmed that the CA fiber 61 in the tow band 60 is plasticized by the heated steam, and the relaxation of the entanglement of the CA fiber 61 in the tow band 60 is promoted. In addition, in Examples 1 to 3, it was confirmed that the carding process can be well performed on the multiple short fibers 62, and that there is no trouble such as the short fiber 62 clogging the conveying path 50. In addition, it was confirmed that the length dimension of the short fiber 62 is stabilized in Examples 1 to 3 compared to Comparative Examples 1 and 2.

[0079] In addition, the tow band 60 just before cutting in Example 1 had a moisture content of 10.8% by mass, and the tow band 60 just before cutting in Example 2 had a moisture content of 28% by mass. The short fibers 62 in Examples 1 and 2 did not have a sticky feel or appearance. In Examples 1 and 2, there was no need to dry the tow band 60 that passed through the entanglement reduction section 2, 8 and the short fiber forming section 3. In Examples 1 and 2, no noticeable troubles were observed due to the addition of moisture to the tow band 60. In Example 3, the amount of moisture added to the tow band 60 before cutting was reduced to a certain extent. Therefore, the short fibers 62 in Example 3 were not sticky enough to cause water release. This confirmed the superiority of Examples 1 to 3 over Comparative Examples 1 and 2.

[0080] Each configuration and each method in each embodiment, and combinations thereof, etc. are merely examples, and addition, omission, substitution, and other modifications of the configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the claims. In addition, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification.

[0081] In the above embodiment, an example of manufacturing a nonwoven fabric 63 using the short fibers 62 has been shown, but the short fibers 62 may be used for purposes other than manufacturing a nonwoven fabric. In addition, the entanglement reduction units 2, 12 are not essential to the nonwoven fabric manufacturing apparatuses 1, 11. That is, in the nonwoven fabric manufacturing apparatuses 1, 11, for example, the entanglement reduction units 2, 12 may be omitted, and a tow band 60 containing crimped CA fibers 61 and having moisture added thereto may be brought in from the outside and introduced into the short fiber forming unit 3.

[0082] In the first and second embodiments, in the entanglement relaxation step, the mist M is sprayed from the nozzle 22 toward the tow band 60 to impart moisture to the tow band 60. However, the method of imparting moisture to the tow band 60 is not limited to this. For example, in the entanglement relaxation step, the mist M may be filled in the housing 20 and the tow band 60 may be passed through the inside of the housing 20 to impart moisture to the tow band 60.

[0083] In the drying step, the tow band 60 may be dried by a method other than heating. As a method for drying the tow band 60, for example, a method of blowing gas onto the tow band 60 to remove moisture, a method of vibrating the tow band 60 to remove moisture, a method of centrifuging the moisture of the tow band 60, a method of passing the tow band 60 between a pair of axially supported squeeze rolls (compression rolls) to squeeze the moisture of the tow band 60, or a method of pressing the tow band 60 with tension in the conveying direction P against a contact member such as a rotating roll to handle the tow band 60, etc., may be used.

[0084] In the second and third embodiments, for example, the tow band 60 impregnated with moisture in the entanglement reduction step may be dehydrated before the short fiber formation step to reduce the moisture content of the tow band 60 immediately before cutting to a certain extent. As a method for reducing the moisture content of the tow band 60, any of the drying methods for the tow band 60 listed in the drying step may be adopted. As a result, for example, when using a rotary cutter 33, the moisture content of the tow band 60 immediately before cutting may be set to a value in the range of, for example, 7% by mass or more and 10% by mass or less, thereby suppressing the occurrence of malfunctions and maintenance work of the cutting mechanism 30 due to excessive moisture in the tow band 60. Therefore, the short fibers 62 can be formed with even higher manufacturing efficiency. [Explanation of symbols]

[0085] M Mist P Transport direction 1, 11 Nonwoven fabric manufacturing equipment (short fiber manufacturing equipment) 2, 12 Intertwining relief section 3 Short fiber forming section 5 Non-woven fabric forming part 33 Rotary cutter 60 Toe Band (Toe) 61 Cellulose acetate fiber 62 Staple Fiber 63 Nonwoven fabrics

Claims

1. A tangle relaxation step of relaxing the tangle of the crimped cellulose acetate fibers in the tow band by applying tension in the conveying direction to the tow band, which is conveyed in a predetermined conveying direction and contains crimped cellulose acetate fibers and has moisture impregnated therein; A short fiber forming step of cutting the tow band whose entanglement has been alleviated to form short fibers, In the entanglement relaxation step, the tow band is heated to promote the relaxation of the entanglement.

2. 2. The method for producing staple fibers according to claim 1, wherein in the entanglement alleviation step, moisture is added to the tow band so that the moisture content of the tow band immediately before cutting in the staple fiber formation step is in the range of 7% by mass or more and 80% by mass or less.

3. The method for producing staple fibers according to claim 1 or 2, wherein in the entanglement reduction step, moisture is added to the tow band by contacting the tow band with a mist containing moisture.

4. The method for producing staple fibers according to claim 3 , wherein the mist contains water vapor.

5. An entanglement relaxation step of relaxing entanglement of the crimped cellulose acetate fibers in a tow band conveyed in a predetermined conveying direction by applying tension in the conveying direction to a tow band containing crimped cellulose acetate fibers and having moisture added thereto; A short fiber forming step of cutting the tow band whose entanglement has been alleviated to form short fibers, In the entanglement alleviation step, moisture is added to the tow band by contacting the tow band with a mist containing moisture vapor so that the moisture content of the tow band immediately before cutting in the short fiber formation step is in the range of 7% by mass or more and 15% by mass or less. A method for producing short fibers.

6. 4. The method for producing staple fibers according to claim 3, wherein in the entanglement alleviation step, the mist is brought into contact with the tow band so that the moisture content of the tow band immediately before cutting in the staple fiber formation step is in the range of 7% by mass or more and 35% by mass or less.

7. The method for producing staple fibers according to any one of claims 1 to 6, further comprising a drying step of drying moisture adhering to the staple fibers after the staple fiber forming step.

8. In the short fiber forming step, the tow band is cut by a rotary cutter having a cutting blade arranged on a circumferential surface, which is supported by a shaft and is rotated so that the tow band contacts the cutting blade. The method for producing short fibers according to any one of claims 1 to 7.

9. A method for producing a nonwoven fabric, comprising the steps of: producing a nonwoven fabric using the staple fibers formed by the method according to any one of claims 1 to 8.

10. A tow band is conveyed in a predetermined conveying direction, and the tow band contains crimped cellulose acetate fibers and is moistened and heated. The tow band is conveyed in the conveying direction, and tension is applied to the tow band to relieve the entanglement of the crimped cellulose acetate fibers in the tow band. A staple fiber manufacturing apparatus comprising: a staple fiber forming section that cuts the tow band whose entanglement has been alleviated to form staple fibers.

11. The staple fiber manufacturing apparatus according to claim 10, a nonwoven fabric forming unit that forms a nonwoven fabric using the short fibers formed by the short fiber forming unit.

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