Regenerated cellulose fiber, fiber assembly thereof, method for producing viscose rayon fiber bundle, fiber bundle for artificial hair, artificial hair, and hair accessories

Abstract

A regenerated cellulose fiber (A) has a fineness of 20-160 dtex, the fiber cross section has a plurality of arm portions (12, 13, 14) and constrictions (10, 11) formed by the arms, of the arm portions in the fiber cross section, at least two arm portions are arm portions a (12, 13, 14) having a length of 1.5 times or more and less than 2.5 times the width, and the fiber cross section has no arm portion having a length of 2.5 times or more the width.

Description

[Technical Field]

[0001] The present disclosure relates to a regenerated cellulose fiber, a fiber assembly using the same, and a method for producing a viscose rayon fiber bundle.The present disclosure also relates to a fiber bundle for artificial hair, artificial hair, and a hair accessory. [Background technology]

[0002] Regenerated cellulose fibers, obtained by coagulating and regenerating a solution of dissolved cellulose using methods such as the viscose method, the cuprammonium method, and solvent spinning, are biodegradable and are therefore being considered for use in a variety of environmentally friendly applications. Furthermore, depending on the application, it may be necessary to modify the mechanical properties and shape of the regenerated cellulose fibers.

[0003] Viscose rayon fiber, a type of regenerated cellulose fiber, is obtained by discharging viscose, an aqueous dilution of cellulose (alkaline), from a spinneret into an acidic spinning bath, coagulating and regenerating the viscose to form threads, and then treating the threads with hot water, for example, while stretching them. A so-called Mueller bath, which is a three-component bath consisting of sulfuric acid, zinc sulfate, and sodium sulfate, is generally used as the spinning bath. The contact condition between the viscose and the spinning bath during coagulation and regeneration of the viscose significantly affects the quality of the resulting viscose rayon fiber.

[0004] In the past, various viscose rayon fibers with large fineness have been proposed to improve the stiffness and other properties of viscose rayon fibers, and various uses and manufacturing methods for these fibers have also been proposed. For example, Patent Document 1 proposes an example in which viscose rayon fibers with a fineness of 55 to 167 dtex are used in cleaning tools such as mops. Furthermore, Patent Document 2 proposes a method for manufacturing viscose rayon fibers with a fineness of 11 dtex or more.

[0005] On the other hand, various methods have been proposed for producing viscose rayon fibers by forming the cross-sectional shape into various shapes in order to improve the bulkiness, etc., of the viscose rayon fibers. For example, Patent Document 3 proposes a method for producing viscose rayon fibers by changing the shape of the nozzle holes of a spinneret so that the cross-sectional shape of the resulting viscose rayon fibers is a desired shape. Also, Patent Document 4 proposes a method for producing viscose rayon fibers that expresses various cross-sectional shapes by adding a modifier called a transformation agent to viscose and controlling the coagulation and regeneration reaction.

[0006] The present applicant has also proposed a viscose rayon fiber with an irregular cross section, an arm length including a constriction that is 2.5 times or more the arm width, and a fineness of 40 to 160 dtex, with the aim of improving stiffness and bulkiness (Patent Document 5).

[0007] One application of regenerated cellulose fibers is artificial hair fibers used in hair accessories such as wigs, hairpieces, braids, and hair extensions. For example, Patent Documents 6 and 7 propose cellulose-based fibers suitable for artificial hair fibers that can be sprinkled on thinning hair areas and adhesively fixed to make the thinning hair less noticeable. Patent Document 4 also proposes the use of viscose rayon fibers having the above-mentioned specific fiber cross-sectional shape as artificial hair. Artificial hair is often provided as fiber bundles for artificial hair, consisting of multiple strands (e.g., several hundred strands) of artificial hair fibers bundled together, and is often traded in the form of fiber bundles, and evaluations of texture, etc. are often performed in the form of fiber bundles. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 7-23886 [Patent Document 2] Japanese Patent Application Publication No. 8-302520 [Patent Document 3] Japanese Patent Application Publication No. 64-45811 [Patent Document 4] Special Publication No. 44-30445 [Patent Document 5] Patent No. 4546208 [Patent Document 6] International Publication No. 2015 / 194521 Brochure [Patent Document 7] Japanese Patent Application Laid-Open No. 2001-254216 Summary of the Invention [Problem to be solved by the invention]

[0009] The stiffness (or flexibility) and texture required for viscose rayon fibers and regenerated cellulose fibers such as lyocell vary widely depending on the application, etc. For example, even when applied to cleaning tools such as mops, different stiffness may be required depending on the material of the floor to be cleaned with the cleaning tool and the type of detergent used with the cleaning tool. As mentioned above, one of the uses of viscose rayon fibers with a fineness of approximately several tens of dtex is as fibers for artificial hair, but the stiffness and texture required for artificial hair fibers also vary depending on the age and sex of the wearer, the type of the wearer's natural hair, etc.

[0010] An object of the present disclosure is to provide regenerated cellulose fibers that have stiffness and a feel different from conventional regenerated cellulose fibers. [Means for solving the problem]

[0011] The present disclosure provides regenerated cellulose fibers, The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Among the arms of the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width. Regenerated cellulose fibers are provided.

[0012] The present disclosure also provides a fiber bundle for artificial hair containing 20% ​​by volume or more of regenerated cellulose fiber bundles formed by bundling multiple regenerated cellulose fibers, wherein the regenerated cellulose fiber bundle contains 35% by volume or more of regenerated cellulose fiber A having the following configuration: (Composition of regenerated cellulose fiber A) The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Of the arms in the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width. [Effects of the Invention]

[0013] The regenerated cellulose fibers of the present disclosure have a relatively large fineness and a specific fiber cross section, which gives them suitable stiffness and flexibility. The regenerated cellulose fibers of the present disclosure can also impart bulk to fiber bundles or fiber assemblies containing the regenerated cellulose fibers.

[0014] Furthermore, the fiber bundle for artificial hair of the present disclosure has a relatively large fineness and contains a certain amount or more of regenerated cellulose fibers having a specific fiber cross section, so it is moderately stiff and has bulkiness similar to that of human hair. Furthermore, due to the high hygroscopicity of regenerated cellulose fibers, the fiber bundle for artificial hair of the present disclosure can have a texture and feel different from that of fibers made of synthetic fibers. [Brief explanation of the drawings]

[0015] [Figure 1(a)] 1 is an optical microscope photograph showing the fiber cross section of a viscose rayon fiber bundle containing the viscose rayon fiber of the present disclosure, produced in Example 1. [Figure 1(b)] 1 is an optical microscope photograph showing the fiber cross section of a viscose rayon fiber bundle produced in Comparative Example 1. [Figure 1(c)]1 is an optical microscope photograph showing the fiber cross section of a viscose rayon fiber bundle containing the viscose rayon fiber of the present disclosure, produced in Example 2. [Figure 2] FIG. 1 is a cross-sectional view schematically showing a cross section of a viscose rayon fiber according to a first embodiment. [Figure 3] 1 is a cross-sectional view schematically showing a cross section of a viscose rayon fiber A according to a first embodiment. [Figure 4] FIG. 10 is an explanatory diagram showing a method for producing a viscose rayon fiber bundle according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Background to this disclosure) As described above, the applicant proposed a viscose rayon fiber having an irregular cross section, including constrictions whose arm lengths are 2.5 times or more their widths, and a fineness of 40 to 160 dtex in Patent Document 5. This viscose rayon fiber has rigidity due to its large fineness, and the length / width ratio of the arms formed in the fiber cross section is relatively large, which can increase the bulkiness of fiber bundles and fiber assemblies containing it.

[0017] However, as mentioned above, there are various requirements for stiffness and bulkiness, and further improvements or changes in the properties of viscose rayon fibers have been desired for certain applications. For example, the viscose rayon fiber of Patent Document 5 has relatively long arms in the fiber cross section, but it has been found that such arms tend to reduce stiffness. Furthermore, in fiber assemblies containing this viscose rayon fiber, particularly fiber bundles, entanglement of fibers tends to occur due to the interlocking of arms formed in the fiber cross section, i.e., poor splitting ability. These tendencies cannot be ignored, particularly when using viscose rayon fiber bundles containing the above viscose rayon fiber as artificial hair, as they affect combing ability. Therefore, a viscose rayon fiber that has improved stiffness and can produce fiber bundles with good splitting ability has been desired.

[0018] Therefore, the inventors of the present invention considered that by controlling the length / width ratio of the arms and making it smaller than the value proposed in Patent Document 5, it would be possible to improve the stiffness and splittability. As mentioned above, viscose rayon fiber is produced using a wet spinning process in which natural cellulose, such as wood pulp, is treated with alkali (caustic soda) and then reacted with carbon disulfide to produce a cellulose derivative. This cellulose derivative is then dissolved in an alkaline solution to produce a stock solution (called viscose). This stock solution is then extruded through the nozzle holes of a spinneret into an acidic bath called a spinning bath or coagulation bath, where it undergoes a chemical reaction while forming fibers, regenerating the cellulose. In this spinning process, the cross-sectional shape of the resulting fiber tends to vary depending on how the solvent "escapes" from the fiber during spinning. For example, viscose rayon fiber, commonly used in clothing and hygiene products, does not have a circular cross section but rather has a chrysanthemum-like cross section with fine irregularities on the outer edge. The mechanism by which these fine irregularities are formed is thought to be as follows: Viscose extruded from the nozzle holes immediately coagulates to form a surface layer (also called a skin layer). Through this layer, the viscose is dehydrated, and the interior is coagulated and regenerated, solidifying. It is believed that shrinkage occurs during this process, causing minute irregularities to form as the volume decreases.

[0019] Patent Document 5 discloses that coagulation regeneration and dehydration are possible in such a way that arms having a length-to-width ratio of 2.5 or more are formed by taking up the spun yarn discharged from the spinneret holes in a direction oblique to the surface of the spinning bath. However, the inventors' investigations have shown that this method does not allow for more control of the fiber cross section, and it has not been possible to consistently obtain viscose rayon fibers having arm cross sections with short length-to-width ratios.

[0020] As described above, the cross-sectional shape of viscose rayon fibers is difficult to control because it is affected by coagulation regeneration and dehydration, making it difficult to design the cross-sectional shape of viscose rayon fibers. The inventors further investigated spinning conditions and found conditions under which viscose rayon fibers having multiple arms with a length / width ratio of 1.5 or more and less than 2.5 can be produced, resulting in the present disclosure. Furthermore, the inventors found that the cross-sectional shape of viscose rayon fibers produced by this method can also be achieved by adjusting the shape of the spinneret in methods other than the viscose method, such as regenerated cellulose fibers (lyocell) obtained by the solvent spinning method and regenerated cellulose fibers (cupra) obtained by the cuprammonium method.

[0021] The regenerated cellulose fibers of the present disclosure are The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Among the arms of the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width. These are regenerated cellulose fibers. As will be described later, these regenerated cellulose fibers are manufactured as part of a fiber bundle made of regenerated cellulose fibers, and the fiber bundle may also contain regenerated cellulose fibers other than these regenerated cellulose fibers. Therefore, in the following description, regenerated cellulose fibers having the above-mentioned specific fiber cross-sectional shape will be referred to as "regenerated cellulose fiber A" (specific types of fibers will be referred to by adding A to the type name), to distinguish them from regenerated cellulose fibers that do not have the above-mentioned specific fiber cross-sectional shape. Regenerated cellulose fiber A will be described below as embodiment 1.

[0022] [Embodiment 1: Regenerated cellulose fiber A]

[0023] The fineness of the regenerated cellulose fiber A is 20 dtex or more and 160 dtex or less, for example, 40 dtex or more and 160 dtex or less, particularly 45 dtex or more and 120 dtex or less, and more particularly 50 dtex or more and 80 dtex or less. If the fineness is less than 20 dtex, sufficient stiffness may not be obtained. On the other hand, if the fineness exceeds 160 dtex, the fiber diameter may be too large, making it difficult to handle. Furthermore, when the regenerated cellulose fiber A is used as a fiber for artificial hair, the fineness affects the feel and appearance, and if the fineness is outside this range, the feel and appearance may become unnatural.

[0024] The cross section of regenerated cellulose fiber A has multiple arms and constrictions formed by the arms, with at least two, i.e., multiple, arm sections a, each with a length 1.5 to less than 2.5 times its width. This specific cross section allows a fiber bundle containing regenerated cellulose fiber A to maintain appropriate gaps between the regenerated cellulose fibers A and / or between the regenerated cellulose fibers A and other fibers (which may be fibers other than regenerated cellulose fiber). When regenerated cellulose fiber A is used as a fiber for artificial hair, the gaps provided by the regenerated cellulose fiber A can impart a volume similar to that of human hair.

[0025] Here, an example of an embodiment of regenerated cellulose fiber A and how to determine the length and width of the arm portion will be described with reference to Figure 2. Figure 2 is a cross-sectional view showing the fiber cross section of viscose rayon fiber A as regenerated cellulose fiber A. For the sake of convenience in the description below, the fiber cross section is not hatched in Figure 2.

[0026] In FIG. 2, 10 and 11 are constrictions, the constriction 10 being formed by two arms 12 and 13, and the constriction 11 being formed by two arms 13 and 14.

[0027] The method for determining the length and width of an arm will be described using arm 14 as an example. As shown in FIG. 2, first, line segment 15 is drawn between points 14a, 14a on the curve of the two bottom portions of arm 14, where the radius of curvature is smallest. Next, line segment 16 is drawn from point 15a, which bisects the length of line segment 15, to apex 14b of arm 14. Next, line segment 17 is drawn by cutting the perpendicular bisector of line segment 16 with arm 14. Point 17a, which bisects the length of line segment 17, is then found, and line segment 18 is drawn connecting point 15a and point 17a, and line segment 19 is drawn connecting point 17a and apex 14b. The lengths of line segments 18 and 19 are then measured, and their sum is taken as the length of arm 14. Also, line segment 20 is drawn where the perpendicular bisector of line segment 18 is cut by arm 14, and line segment 21 is drawn where the perpendicular bisector of line segment 19 is cut by arm 14. Then, the lengths of line segments 15, 17, 20, and 21 are measured, and their average value is taken as the width of arm 14.

[0028] In this embodiment, the cross section of regenerated cellulose fiber A has a plurality of arms a whose length, as measured by the above method, is 1.5 to less than 2.5 times its width, as measured by the above method (i.e., the length / width ratio is 1.5 to less than 2.5). The term "arms a" is used here to distinguish it from arms whose length / width ratio is less than 1.5 or 2.5 or greater. Having a plurality of arms a in its cross section allows regenerated cellulose fiber A to impart appropriate bulkiness to a fiber assembly (e.g., a fiber bundle) when the fiber is included therein.

[0029] Regenerated cellulose fiber A may have at least two arms a, and particularly three or more. The number of arms a may be five or less. As the number of arms a increases in a regenerated cellulose fiber A of a certain fineness, the width of the arms a becomes narrower, and it tends to become more difficult to form such arms a. The number of arms, including the arms a, is also affected by the fineness of the regenerated cellulose fiber A. For example, regenerated cellulose fiber (particularly viscose rayon fiber A) with a fineness of about 50 dtex tends to have two or three arms a when produced by the method described below, and the number of arms a tends to increase as the fineness increases.

[0030] When the arm portions a having a length / width ratio of 1.5 or more but less than 2.5 are divided into arm portions a1 having a length / width ratio of 1.5 or more but less than 2 and arm portions a2 having a length / width ratio of 2 or more but less than 2.5, the ratio of the number of each of these in the regenerated cellulose fiber A (a1 / a2) is preferably 0.1 or more, more preferably 1 or more. There is no upper limit, but it is preferably 9 or less, more preferably 7 or less. When a1 / a2 is within the above range, for example, a fiber bundle containing the regenerated cellulose fiber A can be obtained with bulkiness and splittability similar to that of human hair. Alternatively, all of the arm portions a may be arm portions a1, or all of the arm portions a2.

[0031] The cross section of the regenerated cellulose fiber A may have arms other than arm a (i.e., arms with a length / width ratio of 1.5 or more and not less than 2.5). However, the cross section of the regenerated cellulose fiber A of this embodiment does not have relatively long arms with a length / width ratio of 2.5 or more. If arms with a length / width ratio of 2.5 or more are formed, the regenerated cellulose fiber A may not have sufficient rigidity, and the fibers may easily become entangled, making it unsuitable for applications where splitting is important (e.g., artificial hair).

[0032] In the regenerated cellulose fiber A of this embodiment, arms other than arm a may be formed, such as arm b (the symbol "b" is used to distinguish it from arm a), whose length is 1 to 1.5 times its width. In the regenerated cellulose fiber A of this embodiment, preferably four or fewer arms b may be formed, particularly three or fewer, and more particularly two or fewer. When arm b having a length / width ratio of 1 to 1.5 is present in the fiber cross section, adhesion between fibers tends to be more suppressed than when no arm b is present; however, if a large number of arm b are present, the number of arm a may decrease and there may not be multiple arm b. The ratio (b / a) of the number of arms b to the number of arms a is preferably 0 to 0.5, more preferably 0 to 0.4, and even more preferably 0 to 0.3.

[0033] Alternatively, the regenerated cellulose fiber A may have only arm portion a, with no arm portion other than arm portion a. Such regenerated cellulose fiber A can increase the bulkiness of the fiber assembly to a certain extent while also improving the splitting ability to an appropriate degree, and when used as artificial hair, the splitting ability can be made closer to that of human hair.

[0034] The fiber cross section shown in Figure 1 is E-shaped, with three arms 12, 13, and 14 and two constrictions 10 and 11, and all three arms 12, 13, and 14 are arm a. The fiber cross section of regenerated cellulose fiber A is not limited to that shown in the figure and may be any shape, such as Y-shaped, W-shaped, F-shaped, X-shaped, H-shaped, or n-shaped. For example, when the fiber cross section of regenerated cellulose fiber A is n-shaped, it has two arms and one constriction, and both arms are arm a.

[0035] In the regenerated cellulose fiber A of this embodiment, the arm portion a may have a "medium-thick" shape. Whether the arm portion a has a "medium-thick" shape is determined by measuring the length of line segment 17 corresponding to approximately the center of the arm in Figure 2 for an arm a having a length / width ratio of 1.5 or more but less than 2.5, and the length of line segment 15 corresponding to approximately the base or line segment 20 located approximately one-quarter of the way from the base, and calculating the length of line segment 15 or 20 when the length of line segment 17 is set to 1. If the length of line segment 15 or 20 is less than 1 when the length of line segment 17 is set to 1, the arm has a medium-thick shape.

[0036] Among the regenerated cellulose fibers A having at least two arms a, the proportion of fibers having at least two arms a with a medium-sized shape may be, for example, 25% by volume or more, particularly 40% by volume or more, and more particularly 50% by volume or more. Fibers having at least two arms a with a medium-sized shape have an appearance that is closer to a hollow shape. Therefore, fiber bundles containing such fibers tend to have greater bulkiness or tend to be more likely to confine liquids, etc., inside the fibers, i.e., tend to have improved liquid retention.

[0037] Alternatively or additionally, in the regenerated cellulose fiber A of this embodiment, the arm a may have a bent shape. Whether the arm a is bent or not can be determined by measuring the angle (acute angle, θ in FIG. 3) formed by the line segment 18 connecting point 17a that bisects line segment 17 in FIG. 3 with point 15a that bisects the length of line segment 15, and the line segment 19 connecting point 17a and the top 14b of the arm, for an arm a having a length / width ratio of 1.5 or more but less than 2.5. The method for determining the line segments 17, 18, and 19 is as explained above with reference to FIG. 2. If the angle is 45° or more, the arm is considered to have a bent shape.

[0038] Among the regenerated cellulose fibers A having at least two arms a, the proportion of fibers having at least one bent arm a may be, for example, 25% by volume or more, particularly 40% by volume or more, and more particularly 50% by volume or more. Fibers having at least two bent arms a appear more hollow, and this tendency becomes stronger the more bent the arms a there are. Therefore, fiber bundles containing such fibers tend to be bulkier, or tend to be more likely to trap liquids, etc., inside the fibers, i.e., to have improved liquid retention.

[0039] In this embodiment, the regenerated cellulose fiber A has multiple arms and therefore one or more constrictions. The constrictions are portions that can hold liquids or minute solids (including semi-solids). Therefore, when the regenerated cellulose fiber A (or a fiber assembly containing the same) is used in a cleaning tool such as a mop, the constrictions can hold fine debris, or when a liquid detergent is used, the detergent can be held. Furthermore, when the regenerated cellulose fiber A is used in fibers for artificial hair, it can hold liquid or wax-type styling agents, providing artificial hair that can be styled with styling agents.

[0040] The cross section of the regenerated cellulose fiber A may have one or more constrictions. The greater the number of constrictions, the greater the number of arms, which tends to improve the liquid retention and bulkiness. Specifically, the number of constrictions may be, for example, one to four, and particularly one to three. The number of constrictions tends to increase as the fineness of the regenerated cellulose fiber A increases.

[0041] In the cross section of the regenerated cellulose fiber A, the width of the arm a may be 5 μm or more and 50 μm or less, particularly 10 μm or more and 40 μm or less, and more particularly 15 μm or more and 30 μm or less. Attempting to obtain an arm a with a width of less than 5 μm may make it difficult to form the regenerated cellulose fiber. On the other hand, if the width of the arm a exceeds 50 μm, the neck tends to become smaller, making it difficult to form the arm a, and may also make it difficult for the fiber to retain liquids or small solids.

[0042] In the cross section of the regenerated cellulose fiber A, the length of the arm a may be 20 μm or more and 60 μm or less, particularly 22 μm or more and 50 μm or less. More particularly, it may be 25 μm or more and 45 μm or less. When attempting to obtain arm a lengths of less than 20 μm, the neck tends to become smaller, making it difficult to form arm a and making it difficult for the fiber to retain liquids or small solids. On the other hand, when the length of arm a exceeds 50 μm, the regenerated cellulose fiber A may not have sufficient rigidity and may be prone to entanglement of fibers, making it unsuitable for applications where splitting is important (e.g., artificial hair).

[0043] The regenerated cellulose fiber may be viscose rayon fiber, solvent-spun cellulose fiber (lyocell), or regenerated cellulose fiber obtained by the cuprammonium method (cupro). Viscose rayon fiber is obtained by coagulating and regenerating viscose, an aqueous solution (alkaline) of cellulose. The viscose is not particularly limited, and the composition used in the production of conventional viscose rayon fiber can be used. For example, viscose containing 8.0 to 9.5% by mass of cellulose, 5.0 to 6.5% by mass of sodium hydroxide, and 2 to 4% by mass of carbon disulfide can be used. Lyocell fiber is obtained by coagulating a spinning solution in which cellulose is dissolved using an aqueous solution of N-methyl morpholine-N-oxide (NMMO) as a solvent. Cupra fiber is obtained by wet spinning a spinning solution in which cellulose, such as cotton linters or pulp, is dissolved in a cuprammonium solution (Schweitzer solution) at a concentration of 9 to 12% by mass.

[0044] When the regenerated cellulose fiber is a viscose rayon fiber, the regenerated cellulose fiber A has an irregular fiber cross section. When the regenerated cellulose fiber is a lyocell fiber or a cupra fiber, the regenerated cellulose fiber A tends to have a relatively uniform fiber cross section due to its manufacturing method.

[0045] The regenerated cellulose fiber A may contain one or more additives selected from ultraviolet absorbers, infrared absorbers, fluorescent brighteners, release agents, lubricants, antibacterial agents, nucleating agents, heat stabilizers, antioxidants, antistatic agents, color inhibitors, conditioners, matting agents, deodorizers, antifoaming agents, color tinting agents, flame retardants, yarn friction reducers, preservatives, gelling agents, latex, fillers, inks, colorants, dyes, pigments, and fragrances. These additives may be contained in fibers other than the regenerated cellulose fiber A in the fiber assembly described below.

[0046] [Embodiment 2: Fiber assembly] The fiber assembly of the present disclosure contains the above-described regenerated cellulose fibers A. Hereinafter, this fiber assembly will be described as embodiment 2.

[0047] As will be described later, when the regenerated cellulose fiber A is viscose rayon fiber A, the viscose rayon fiber A can have the above-mentioned specific fiber cross section by selecting the wet spinning conditions. On the other hand, even fibers simultaneously extruded from a common spinneret into the same spinning bath may not have a fiber cross section with arm a due to local variations in spinning conditions. In such cases, the viscose rayon fiber A is spun together with other viscose rayon fibers (those whose fiber cross sections do not have arm a, or have only one arm a, if any) to form a fiber bundle, which is then spun and taken up. It is generally difficult to select and use only the viscose rayon fiber A from this fiber bundle. This also applies to cupra A produced by the cuprammonium method and lyocell fiber A produced by the solvent spinning method. Therefore, in this embodiment, the proportion of regenerated cellulose fiber A in a fiber aggregate (regenerated cellulose fiber aggregate) made of regenerated cellulose fibers is specified, and a fiber aggregate containing a predetermined proportion or more of the regenerated cellulose fiber aggregate is described.

[0048] More specifically, the regenerated cellulose fiber assembly of this embodiment has a proportion of regenerated cellulose fiber A of 35% by volume or more. If the proportion of regenerated cellulose fiber A is less than 35% by volume, the regenerated cellulose fiber assembly may have insufficient bulkiness, and in particular, when made into a fiber bundle, the fiber bundle may be too soft. The proportion of regenerated cellulose fiber A in the regenerated cellulose fiber assembly may be particularly 45% by volume or more, more particularly 60% by volume or more, and even more particularly 80% by volume or more. The greater the proportion of regenerated cellulose fiber A in the regenerated cellulose fiber assembly, the more the effects of including regenerated cellulose fiber A (such as improved bulkiness and rigidity) will be exerted.

[0049] The regenerated cellulose fiber assembly may be in the form of a fiber bundle (also called a "tow"), or may be an assembly of short fibers formed by cutting the fiber bundle to a certain length. The assembly of fiber bundles and short fibers can be used as materials for spun yarn, woven fabric, knitted fabric, nonwoven fabric, paper, etc. Alternatively, the fiber assembly of this embodiment may be a woven fabric, knitted fabric, nonwoven fabric, paper, etc.

[0050] The regenerated cellulose fibers A contained in the regenerated cellulose fiber assembly do not all need to be the same, as long as they are as described in embodiment 1. For example, the regenerated cellulose fibers A in the fiber assembly may each have a different shape, and may differ from one another in the dimensions and number of arms a, the number of constrictions, etc. Furthermore, the fiber assembly may contain regenerated cellulose fibers A of different finenesses.

[0051] The regenerated cellulose fiber assembly of this embodiment may contain regenerated cellulose fibers other than regenerated cellulose fiber A, so long as the regenerated cellulose fiber A is contained in a certain proportion or more of the total volume of the regenerated cellulose fibers. For example, regenerated cellulose fibers other than regenerated cellulose fiber A may have, in their fiber cross-section, no arm portion a, but only arm portion b having a length / width ratio of 1 to less than 1.5. Regenerated cellulose fibers having only arm portion b may be contained in a proportion of, for example, 65% by volume or less, particularly 55% by volume or less, and more particularly 40% by volume or less of the total volume of the regenerated cellulose fibers (the combined volume of each regenerated cellulose fiber).

[0052] The average width of the arm a of the regenerated cellulose fibers A contained in 30 regenerated cellulose fibers randomly selected from the regenerated cellulose fiber assembly of this embodiment may be 5 μm or more and 50 μm or less. The average width of the arm a may particularly be 10 μm or more and 40 μm or less, more particularly 15 μm or more and 30 μm or less. If the average width of the arm a of the regenerated cellulose fibers A in the fiber assembly is within the above range, even if the fiber assembly contains regenerated cellulose fibers A having arm a widths outside the above range, the same effect as when the width of the arm a of each regenerated cellulose fiber A is within the above range can be achieved overall.

[0053] Furthermore, the average length of the arm a of 30 regenerated cellulose fibers A randomly selected from the regenerated cellulose fiber assembly of this embodiment may be 20 μm or more and 60 μm or less. The average length of the arm a may particularly be 22 μm or more and 50 μm or less, more particularly 25 μm or more and 45 μm or less. If the average length of the arm a of the regenerated cellulose fibers A in the fiber assembly is within the above range, even if the fiber assembly contains regenerated cellulose fibers A having arm a lengths outside the above range, the same effect as when the arm a length of each regenerated cellulose fiber A is within the above range can be achieved overall.

[0054] The regenerated cellulose fiber aggregate of this embodiment may be combined with other fibers to form another fiber aggregate (hereinafter also referred to as "fiber aggregate S" to distinguish it from the regenerated cellulose fiber aggregate). In this case, the proportion of the regenerated cellulose fiber aggregate of this embodiment in the fiber aggregate S may be 20% by volume or more, particularly 40% by volume or more, and more particularly 60% by volume or more. If the proportion of the regenerated cellulose fiber aggregate of this embodiment is small, the absolute amount of regenerated cellulose fiber A will also be small, and the effects of regenerated cellulose fiber A may not be obtained in the fiber aggregate S.

[0055] The other fibers contained in the fiber assembly S may be synthetic fibers, other cellulosic fibers, or natural fibers.

[0056] When the regenerated cellulose fiber aggregate of this embodiment is an aggregate of short fibers obtained by cutting regenerated cellulose fiber bundles, for example, those having a fiber length of 1 mm or less can be used as a blasting material for deburring circuit boards. For example, those having a fiber length of 0.1 to 3 mm can be used as a resin mixing material for patterning plastic molded products. The same applies when the fiber aggregate S is an aggregate of short fibers.

[0057] When the regenerated cellulose fiber assembly of this embodiment is a regenerated cellulose fiber bundle, the fiber bundle may be cut to an appropriate length to form a mop cleaning tool. Alternatively, the fiber assembly of this embodiment may be provided as, or as a raw material for, filters, civil engineering materials (nets, cheesecloth, sandbags, and protective mats), spun yarns used in crisp clothing, bath sponges, and the like. In particular, for civil engineering materials, products that are biodegradable (i.e., decomposed by microorganisms in the soil after a certain number of years of use) are sometimes desired, and the regenerated cellulose fiber assembly of this embodiment is preferably used for this purpose. This is because regenerated cellulose fibers are biodegradable. From the perspective of environmental protection, biodegradability is increasingly required for a variety of applications other than civil engineering materials, and the fiber assembly of this embodiment is also preferably used for these applications. The same applies when the fiber assembly S is a fiber bundle.

[0058] [Embodiment 3: Fiber bundle for artificial hair] Alternatively, the regenerated cellulose fiber aggregate of this embodiment, or a fiber aggregate S containing this, may be used as a material for artificial hair in hair accessories, i.e., as a fiber bundle for artificial hair. Hereinafter, a fiber bundle for artificial hair will be described as embodiment 3. The fiber bundle for artificial hair of this embodiment is a fiber bundle for artificial hair containing 20 volume % or more of regenerated cellulose fiber bundles formed by bundling multiple regenerated cellulose fibers, and the regenerated cellulose fiber bundle contains 35 volume % or more of regenerated cellulose fiber A described in embodiment 1. The regenerated cellulose fiber bundle contained in the fiber bundle for artificial hair may contain regenerated cellulose fiber A in an amount of particularly 45 volume % or more, more particularly 60 volume % or more. The greater the proportion of regenerated cellulose fiber A in the regenerated cellulose fiber bundle, the more the effects of including regenerated cellulose fiber A (such as improved bulkiness and rigidity) will be exerted.

[0059] As in embodiment 2, the regenerated cellulose fibers A contained in the artificial hair fiber bundle of this embodiment do not all need to be the same, as long as they are as described in embodiment 1. For example, the regenerated cellulose fibers A in the artificial hair fiber bundle may each have a different shape, and may differ from one another in the dimensions and number of arm portions a, the number of constrictions, etc. Furthermore, the artificial hair fiber bundle may contain regenerated cellulose fibers A of different finenesses.

[0060] When producing the fiber bundle for artificial hair of this embodiment using the method described in embodiment 4, the fiber bundle is provided as a regenerated cellulose fiber bundle itself spun from a spinneret having multiple nozzles, or as a combination of this bundle with other fiber bundles. For example, when the regenerated cellulose fiber is a viscose rayon fiber, viscose rayon fiber A has the above-mentioned specific fiber cross-section by selecting the wet spinning conditions. On the other hand, even fibers simultaneously discharged from a common spinneret into the same spinning bath may not have a fiber cross-section having arm a due to local changes in spinning conditions. As long as the fiber bundle of this embodiment contains a certain proportion or more of regenerated cellulose fiber A, it may also contain regenerated cellulose fiber in which arm a is not formed in the fiber cross-section due to local changes in spinning conditions. For example, regenerated cellulose fibers other than regenerated cellulose fiber A contained in the regenerated cellulose fiber bundle may have arms in their fiber cross-sections that do not have arm a and have a length / width ratio of less than 1.5, for example. The regenerated cellulose fibers having such arms may be contained in the regenerated cellulose fiber bundle in a proportion of, for example, 65% by volume or less, particularly 55% by volume or less, and more particularly 40% by volume or less.

[0061] The artificial hair fiber bundle of this embodiment may contain fibers other than regenerated cellulose fibers (hereinafter referred to as "other fibers"), as long as it contains 20% by volume or more of the regenerated cellulose fiber bundle described above. The other fibers may be synthetic fibers, other cellulose-based fibers, natural fibers, or human hair. For example, acrylic fibers are preferred as synthetic fibers.

[0062] The length of the artificial hair fiber bundle is not particularly limited, and it can be a length suitable for processing the hair accessory depending on the type and design of the hair accessory to be used. Alternatively, the fiber bundle can be provided as a bundle having a length of about several meters. In this case, the fiber bundle can be cut to the desired length when the hair accessory is manufactured.

[0063] Because the fiber bundle for artificial hair contains a regenerated cellulose fiber bundle containing a predetermined percentage or more of regenerated cellulose fiber A, the inherent properties of the regenerated cellulose fiber impart excellent characteristics to hair accessories. For example, human hair is hygroscopic, and its moisture content changes depending on the surrounding environment, etc., and changes in moisture content affect its texture. However, regenerated cellulose fiber A also has water absorption or hygroscopic properties, and the cross-sectional shape and water absorption properties of the regenerated cellulose fiber A can make the texture of the fiber bundle more similar to that of human hair. Furthermore, because regenerated cellulose fiber does not melt when heated, the fiber bundle of this embodiment can be provided as one that can be styled with a hair dryer or iron. Furthermore, because regenerated cellulose fiber is not easily charged, static electricity generation in hair accessories can be suppressed.

[0064] Furthermore, since regenerated cellulose fibers are biodegradable, the artificial hair fiber bundle of this embodiment can reduce the burden on the environment when disposed of after use compared to artificial hair fiber bundles made only of synthetic fibers.

[0065] Therefore, this embodiment is suitable for use as artificial hair in hair accessories such as wigs (including partial wigs and full wigs), hair pieces, braids, and hair extensions. The hair portion of hair accessories using this artificial hair exhibits a feel, stiffness, and combability that is closer to that of human hair, making it less likely for the wearer and those who come into contact with the wearer to feel uncomfortable.

[0066] Furthermore, the artificial hair fiber bundle of this embodiment may be used to make hair for dolls (including those for toys, ornamental use, commercial use (mannequins, etc.), educational and training use, experimental use (dummy dolls, etc.), and those for explanation in museums and archives). According to this embodiment, the thickness of the regenerated cellulose fiber A constituting the artificial hair fiber bundle can be selected according to the size or scale of the doll, thereby avoiding or reducing the unnatural appearance of the doll caused by hair that is too thick or too thin.

[0067] [Embodiment 4: Method for producing fiber bundle] Next, a method for producing a fiber bundle including viscose rayon fibers A as regenerated cellulose fibers A and formed by bundling a plurality of viscose rayon fibers will be described as a fourth embodiment. The production of viscose rayon fibers involves discharging viscose into a spinning bath from a plurality of nozzle holes provided in a spinneret, coagulating and regenerating the viscose to form a fiber bundle, and taking up this fiber bundle with a take-up roller provided outside the spinning bath.The production method of this embodiment ensures that the fiber bundle contains at least a certain proportion of viscose rayon fiber A by setting predetermined spinning conditions.

[0068] The viscose used in this embodiment is not particularly limited and may have a composition used in the production of conventional viscose rayon fibers. The spinning bath is also not particularly limited, and a general acidic spinning bath can be used. For example, a Mueller bath containing 110 to 170 g / L of sulfuric acid, 10 to 30 g / L of zinc sulfate, and 150 to 350 g / L of sodium sulfate can be used. The temperature of the spinning bath may be, for example, 45°C to 65°C, and particularly 53°C to 58°C. If the spinning bath temperature is below 45°C, coagulation and regeneration of the viscose becomes difficult, and the fibers may stick together. On the other hand, if the spinning bath temperature exceeds 65°C, coagulation and regeneration may proceed excessively, and excessive force may be applied during drawing, causing the fibers to break.

[0069] In the manufacturing method of this embodiment, where V1 is the viscose discharge speed at the spinneret outlet and V2 is the fiber bundle take-up speed by the take-up roller, take-up is performed with a value of V2 / V1 (hereinafter referred to as the "Jet Draft ratio") of 0.5 to 1.5, particularly 0.8 to 1.4. By setting the Jet Draft ratio to 0.5 to 1.5, even when the angle between the fiber bundle take-up direction and the surface of the spinning bath is set to approximately perpendicular, as described below, the tension applied to the fibers is relaxed, and the speed of solvent (generally water) escaping from the interior of the fibers (dehydration) and coagulation regeneration can produce fiber cross sections with the shape described in Embodiment 1. More specifically, the relaxed tension applied to the fiber bundle causes the fibers to swell slightly immediately after spinning, increasing the perimeter of the fiber cross section. This is thought to contribute to the coagulation regeneration and dehydration of the skin layer, which differs from that of ordinary viscose rayon fiber.

[0070] If the jet draft ratio is less than 0.5, the tension applied to the yarn at the outlet of the spinneret hole becomes weak, which may cause the fibers to stick together, whereas if the jet draft ratio exceeds 1.5, the tension applied to the fiber at the outlet of the spinneret hole becomes strong, making it difficult to obtain the desired fiber cross section.

[0071] In this embodiment, spinning is carried out using a spinneret provided with multiple spinneret holes. The spinneret holes have a hole diameter of, for example, 0.15 mm to 0.5 mm, particularly 0.2 mm to 0.48 mm, and more particularly 0.3 mm to 0.45 mm. If the hole diameter is less than 0.15 mm, the viscose extrusion speed tends to be too fast and the jet draft ratio tends to be too small. On the other hand, if the hole diameter exceeds 0.5 mm, the viscose extrusion speed tends to be too slow and the jet draft ratio tends to be too large.

[0072] The radial cross section of the nozzle hole may be a perfect circle or an ellipse. When the cross section is an ellipse, the hole diameter refers to the major axis of the ellipse. When the cross section is an ellipse, the minor axis of the ellipse may be, for example, 0.1 mm or more and 0.4 mm or less.

[0073] In the production method of this embodiment, when the viscose rayon fiber bundle is taken up by the take-up roller, the take-up is performed so that the angle between the take-up direction of the spun yarn located approximately in the center of the fiber bundle in the spinning bath and the bath surface of the spinning bath is 80° or more and 110° or less. This angle range means that the take-up direction of the viscose rayon fiber bundle is approximately perpendicular to the bath surface of the spinning bath. The spun yarn located approximately in the center of the fiber bundle is a yarn spun from the approximately central nozzle hole among multiple nozzle holes formed in the spinneret. The direction of the yarn spun from the nozzle holes is determined by the positional relationship between the spinneret and the take-up roller, etc., so when carrying out the production method of this embodiment, this positional relationship is adjusted to adjust the angle between the spun yarn and the bath surface.

[0074] The take-up direction of the viscose rayon fiber bundle is generally perpendicular to the surface of the spinning bath in the production of viscose rayon, which is widely used for clothing and the like. When the viscose rayon fiber bundle is taken up substantially perpendicular to the bath surface, the removal of the viscose solvent tends to proceed relatively uniformly, resulting in a chrysanthemum-shaped fiber cross section with fine irregularities formed on the outer edge. In this embodiment, as described above, by relaxing the tension applied to the fiber by setting the jet draft ratio within a specific range, even when the take-up direction of the fiber bundle is substantially perpendicular to the surface of the spinning bath, the regeneration rate of the skin layer formed in the early stage of coagulation and the irregularities formed by dehydration shrinkage are adjusted, thereby obtaining a viscose rayon fiber A having a specific fiber cross section different from the chrysanthemum-shaped cross section of general-purpose viscose rayon fiber.

[0075] In the production method of this embodiment, the take-up speed of the yarn by the take-up roller may be 10 m / min or more and 60 m / min or less, particularly 20 m / min or more and 40 m / min or less. If the take-up speed is less than 10 m / min, productivity may decrease. On the other hand, if the take-up speed exceeds 60 m / min, the residence time of the yarn in the spinning bath becomes short, so that viscose rayon fiber A may not be obtained or the proportion of viscose rayon fiber A in the fiber bundle may become small. The residence time of the fiber bundle in the spinning bath may be, for example, 0.4 seconds or more and 2.4 seconds or less, particularly 0.6 seconds or more and 1.2 seconds or less. If the residence time is short, coagulation and regeneration may be insufficient.

[0076] To ensure a sufficient residence time in the spinning bath, in this embodiment, the length between the spinneret (more specifically, the discharge surface of the spinneret) of the spun yarn located at the center of the viscose rayon fiber bundle and the bath surface of the spinning bath may be 400 mm or more. That is, by making the spinning bath deeper and increasing the contact time between the viscose rayon fiber bundle and the spinning bath, it is possible to prevent the solvent from remaining in the fibers even when the solvent is removed more unevenly, and to ensure sufficient coagulation and regeneration of the viscose. The length of the viscose rayon fiber bundle between the spinneret and the bath surface of the spinning bath may particularly be 450 mm or more. The upper limit of the length of the fiber bundle between the spinneret and the bath surface of the spinning bath may be, for example, 550 mm, particularly 500 mm.

[0077] The manufacturing method of this embodiment may include further drawing the viscose rayon fiber bundle after it has been taken up by the take-up roller. In this case, the draw ratio of the fiber bundle from the take-up roller to the final roller may be, for example, 20% to 50%. If the draw ratio is less than 20%, the orientation of the regenerated cellulose constituting the viscose rayon fiber A may decrease, making it impossible to obtain a rigid viscose rayon fiber A. On the other hand, if the draw ratio exceeds 50%, the fibers may break during drawing. Note that when drawing the viscose rayon fiber bundle, if the take-up speed of the fiber bundle by the take-up roller is 20 m / min to 40 m / min, the take-up speed by the final roller may be, for example, 24 m / min to 60 m / min.

[0078] In the production method of this embodiment, viscose is simultaneously discharged from a spinning nozzle provided with multiple spinneret holes to produce a viscose rayon fiber bundle. Therefore, due to the influence of factors such as the position of the spinneret holes and the temperature in the spinning bath, arm portions a having a predetermined length / width ratio may not be formed in the fiber cross sections of some fibers, and the fiber bundle may contain viscose rayon fibers other than viscose rayon fiber A. Even in such cases, the production method of this embodiment produces a viscose rayon fiber bundle containing a certain proportion of viscose rayon fiber A (e.g., 35% by volume or more), and a fiber aggregate produced using this viscose rayon fiber bundle exhibits the effects of viscose rayon fiber A. Therefore, in the production method of this embodiment, the final viscose rayon fiber bundle may contain viscose rayon fibers other than viscose rayon fiber A.

[0079] An explanatory diagram schematically illustrating the method for producing a viscose rayon fiber bundle in this embodiment is shown in Figure 4. As shown in Figure 4, the production method of this embodiment is a method for producing viscose rayon fibers in which viscose is discharged into a spinning bath 30 from nozzle holes of a spinneret 31 provided in the spinning bath 30, the viscose is coagulated and regenerated to form a viscose rayon fiber bundle 32, and this fiber bundle 32 is taken up by a take-up roller 33 provided outside the spinning bath 30.

[0080] The die holes have a hole diameter of, for example, 0.15 mm or more and 0.5 mm or less. The jet draft ratio when the viscose rayon fiber bundle 32 is taken up by the take-up roller 33 is 0.5 or more and 1.5 or less. The angle θ between the spun yarn 32a of the viscose rayon fiber bundle 32 discharged from the die hole provided at approximately the center of the spinneret and the bath surface 30a of the spinning bath 30 is 80° or more and 110° or less, and the fiber bundle 32 is taken up approximately perpendicular to the bath surface 30a. In this case, the distance L1 between the approximate center of the discharge surface of the spinneret 31 and the bath surface 30a (corresponding to the length from the spinneret to the bath surface of the spun yarn located at approximately the center of the viscose rayon fiber bundle being spun) may be 400 mm or more and 600 mm or less, and the distance between the bath surface 30a and the take-up roller 33 may be 150 mm or more and 300 mm or less. The fiber bundle 32 taken up by the take-up roller 33 is stretched, for example, by a stretching roller (not shown).

[0081] The manufacturing method of this embodiment may further include subjecting the viscose rayon fiber bundle obtained by the method described above to appropriate treatments that are typically performed when manufacturing viscose rayon fibers. For example, the viscose rayon fiber bundle may be cut to a predetermined length. After spinning, the fiber bundle may be subjected to a drying treatment. The viscose rayon fiber bundle may also be subjected to a dyeing treatment.

[0082] In the production method of this embodiment, a plurality of spinnerets are placed in a spinning bath, and after viscose rayon fiber bundles are taken up and drawn from each spinneret under the above-mentioned conditions, these fiber bundles may be combined to form one viscose rayon fiber bundle.

[0083] Lyocell fiber bundles are produced by passing a spinning dope discharged from a spinning nozzle equipped with multiple spinneret holes through an air gap section and immersing it in a coagulation bath. Lyocell fiber bundles containing Lyocell fiber A are obtained by using a spinneret equipped with spinneret holes having a shape corresponding to a fiber cross-section having at least two arms a, or a shape that will result in such a fiber cross-section. The cross-sectional shape of Lyocell fibers tends to closely match the shape of the spinneret holes. Therefore, in the production of Lyocell fiber bundles, spinneret holes are selected that correspond to the desired fiber cross-sectional shape, taking into account changes in shape due to other conditions during spinning.

[0084] Cupra fiber bundles are obtained by coagulating a spinning dope discharged into a spinning funnel from a spinning nozzle equipped with multiple spinneret holes with a coagulation liquid, followed by regeneration in a sulfuric acid bath. Cupra fiber bundles containing cupra fiber A are obtained by using a spinneret equipped with spinneret holes having a shape corresponding to a fiber cross-section having at least two arm portions a, or a shape that will result in such a fiber cross-section. In the case of cupra fiber bundles, by increasing the temperature of the hot water injected into the coagulation liquid injector to promote coagulation and by increasing the jet draft ratio, the fiber cross-sectional shape can be made to more closely match the shape of the spinneret holes, making it easier to control the fiber cross-sectional shape. [Example]

[0085] Example 1 The raw material viscose was 8.5% by mass of cellulose, 5.7% by mass of sodium hydroxide, 2.7% by mass of carbon disulfide, and the remainder was water. To this viscose was added 2.6% by mass of black pigment (carbon black). A Mueller bath (60°C) containing 145 g / L of sulfuric acid, 15 g / L of zinc sulfate, and 350 g / L of sodium sulfate was used. The spinneret used to extrude the viscose had 126 nozzle holes with a diameter of 0.35 mm.

[0086] When the yarn was taken up by the take-up roller, the angle θ (see FIG. 3) formed between the line segment connecting the center of the spinneret and the take-up roller and the surface of the spinning bath was 90°. The length L1 (see FIG. 3) of the portion of the line segment within the spinning bath and the length L2 (see FIG. 3) from the intersection of the line segment with the surface of the spinning bath to the take-up roller were 500 mm and 200 mm, respectively. Other spinning conditions were set as shown in Table 1, and the viscose rayon fiber bundle of Example 1 was produced.

[0087] Example 2 The viscose rayon fiber bundle of Example 2 was produced using the same viscose and spinning bath as in Example 1 in the same manner as in Example 1 (θ, L1, and L2 were the same as those in Example 1), except that the spinneret for discharging viscose was equipped with 1,000 nozzle holes each having a hole diameter of 0.18 mm, and that the spinning conditions shown in Table 1 were used.

[0088] (Comparative Example 1) A viscose rayon fiber bundle of Comparative Example 1 was produced using the same viscose and spinning bath as in Example 1, except that L1 and L2 were set to 230 mm and 150 mm, respectively, and the spinning conditions were as shown in Table 1.

[0089] (Comparative Example 2) Spinning was carried out using the same viscose and spinning bath as in Example 1 under the following spinning conditions. When the yarn was taken up by the take-up roller, the angle θ formed between the line segment connecting the center of the spinneret and the take-up roller and the surface of the spinning bath was set to 15.3°. The length L1 of the portion of the line segment within the spinning bath and the length L2 of the portion from the intersection of the line segment with the surface of the spinning bath to the take-up roller were set to 513 mm and 549 mm, respectively. Other spinning conditions were set as shown in Table 1, and a viscose rayon fiber bundle of Comparative Example 2 was produced.

[0090] [Table 1]

[0091] The cross sections of the obtained viscose rayon fiber bundles of Example 1 and Comparative Example 1 were observed with an optical microscope. Cross-sectional photographs of the fiber bundles of Example 1 and Comparative Example 1 are shown in Fig. 1(a) and Fig. 1(b), respectively. As shown in Fig. 1(a), it was confirmed that the fiber bundle of Example 1 produced a viscose rayon fiber with an irregular cross section and multiple arms and constrictions formed by the arms. As shown in Fig. 1(b), arms and constrictions were also confirmed in the fiber bundle of Comparative Example 1, but the lengths of the arms were all relatively short, and most of the bundles had a length / width ratio of less than 1.5, as will be described later.

[0092] Thirty fibers were randomly selected from the fiber bundle of each Example and Comparative Example, and for each fiber, the percentage (%) of viscose rayon fiber in the fiber cross section having arms with length / width ratios within the ranges shown in Table 2 was determined. Note that for fibers having multiple arms that belong to two or more of the length / width ratio categories shown in Table 2, the arm with the largest length / width ratio was used as the reference. Furthermore, since the fineness of the fibers constituting the fiber bundle is all approximately the same, the percentage of the specific viscose rayon fiber determined by this method can be regarded as the volume percentage of the specific viscose rayon fiber.

[0093] Furthermore, from the fiber bundles of each Example and Comparative Example, fibers having arms a with a length / width ratio of 1.5 or more and less than 2.5 were extracted, and the percentage (%) of viscose rayon fibers with the number of arms shown in Table 2 was determined. Furthermore, among viscose rayon fibers A (fibers having at least two arms a), the percentages of fibers having one arm a with a medium-sized shape and two or more arms a, and the percentages of fibers having one arm a with a bent shape and two or more arms a were determined. The results are shown in Table 2. The widths and lengths of all the arms a of the viscose rayon A of 30 fibers extracted from the fiber bundles of Examples 1 and 2 were determined and their average values ​​were calculated. For Example 1, the average width was 23.6 μm and the average length was 40.0 μm, and for Example 2, the average width was 16.6 μm and the average length was 28.1 μm. The widths of the arms a of the fiber cross sections of the viscose rayon A contained in the fiber bundles of Examples 1 and 2 were within the ranges of 14.8 μm to 33.1 μm (Example) and 10.8 μm to 23.8 μm (Example 2), respectively. Furthermore, in Comparative Example 2, the average width of arms with a length / width ratio of 2.5 or more was 19.1 μm.

[0094] [Table 2]

[0095] Furthermore, the fiber bundles of the examples and comparative examples were measured for single fiber fineness, dry strength, wet strength, dry elongation and wet elongation in accordance with JIS L 1015. The results are shown in Table 3.

[0096] [Table 3]

[0097] As shown in Table 2, in Examples 1 and 2, many viscose rayon fibers were formed having arms with a length-to-width ratio of 1.5 or more but less than 2.5, and the proportion of fibers with two or more such arms was 84 vol % in Example 1 and 60 vol % in Example 2. In the fiber bundle of Comparative Example 1, 67 vol % of the fibers had arm length-to-width ratios of less than 1.5, which is thought to be due to the high jet draft rate in Comparative Example 1. In Comparative Example 2, most of the viscose rayon fibers had arms with a length-to-width ratio of 2.5 or more. This is thought to be due to the fact that the fiber bundle was taken up so that the spun threads were oblique to the surface of the spinning bath, which resulted in different skin layer formation and dehydration shrinkage during coagulation regeneration from those in the Examples.

[0098] The fiber bundles of Examples 1 and 2, and Comparative Examples 1 and 2 were evaluated for bulkiness / convergence / separability, stiffness, and liquid retention of the fiber bundles according to the following evaluation criteria. The results are shown in Table 4. Stiffness was compared relative to the three examples, and the one with the greatest stiffness was rated B, as shown below.

[0099] (bulk / convergence / separation) S: Bulky and easy to bundle and separate A: Bulky and easy to bundle, but difficult to separate B. Small volume

[0100] (rigidity) S: Moderately stiff and flexible A Most rigid B. Least rigid

[0101] (liquid retention) S Easy to hold liquid B. Difficult to hold liquid

[0102] [Table 4]

[0103] The present disclosure includes the following aspects. (Aspect 1) Regenerated cellulose fibers, The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Among the arms of the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width. Regenerated cellulose fiber. (Aspect 2) The regenerated cellulose fiber according to aspect 1, wherein the width of the arm portion a is 5 μm or more and 50 μm or less. (Aspect 3) 3. The regenerated cellulose fiber of embodiment 1 or 2, wherein the fiber cross section has two or three arms a. (Aspect 4) The regenerated cellulose fiber according to any one of Aspects 1 to 3, wherein at least two of the arm portions a have a medium-thickness shape. (Aspect 5) The regenerated cellulose fiber according to any one of Aspects 1 to 4, wherein at least one of the arm portions a has a bent shape. (Aspect 6) 6. The regenerated cellulose fiber of any one of aspects 1 to 5, wherein the cross section of the fiber includes, as an arm other than arm a, arm b whose length is at least 1 time but less than 1.5 times its width. (Aspect 7) The regenerated cellulose fiber according to any one of Aspects 1 to 6, wherein the regenerated cellulose fiber is a viscose rayon fiber obtained by coagulating and regenerating viscose. (Aspect 8) The regenerated cellulose fibers according to any one of Aspects 1 to 7, wherein the regenerated cellulose fibers have an irregular cross section. (Aspect 9) A regenerated cellulose fiber assembly containing 35% by volume or more of the regenerated cellulose fibers according to any one of aspects 1 to 8. (Aspect 10) A regenerated cellulose fiber assembly according to aspect 9, wherein the regenerated cellulose fiber assembly is a regenerated cellulose fiber bundle formed by bundling a plurality of regenerated cellulose fibers together, or an assembly of short fibers formed by cutting the regenerated cellulose fiber bundle to a predetermined length. (Aspect 11) A regenerated cellulose fiber aggregate as described in claim 9, wherein the average width and average length of arm portion a of regenerated cellulose fiber A contained in 30 regenerated cellulose fibers randomly selected from the regenerated cellulose fiber aggregate satisfy at least one of the following. (i) The average width of the arm portion a of the regenerated cellulose fiber A is 5 μm or more and 50 μm or less. (ii) The average length of the arm portion a of the regenerated cellulose fiber A is 20 μm or more and 60 μm or less. (Aspect 12) A fiber assembly comprising 20% ​​by volume or more of the regenerated cellulose fiber assembly according to any one of aspects 9 to 11. (Aspect 13) A method for producing a viscose rayon fiber bundle comprising a plurality of viscose rayon fibers bundled together, the method comprising the steps of discharging viscose into a spinning bath from a plurality of nozzle holes provided in a spinneret, coagulating and regenerating the viscose to form a fiber bundle, and taking up the fiber bundle with a take-up roller provided outside the spinning bath, The nozzle hole has a hole diameter of 0.15 mm or more and 0.5 mm or less, When the discharge speed of the viscose at the outlet of the spinneret hole is V1 and the take-up speed of the fiber bundle by the take-up roller is V2, the value of V2 / V1 is 0.5 to 1.5, When the fiber bundle is taken up by the take-up roller, the take-up is performed so that the angle formed between the take-up direction of the spun yarn located approximately at the center of the fiber bundle in the spinning bath and the bath surface of the spinning bath is 80° or more and 110° or less; and A method for producing a viscose rayon fiber bundle, comprising obtaining a fiber bundle containing viscose rayon fibers having a single fiber fineness of 20 dtex or more and 160 dtex or less. (Aspect 14) Aspect 14. The method for producing a viscose rayon fiber bundle according to aspect 13, wherein take-up is performed between the spinneret and the surface of the spinning bath so that the length of the spun yarn located approximately in the center of the fiber bundle is 400 mm or more. (Aspect 15) Aspect 15. The method for producing a viscose rayon fiber bundle according to aspect 13 or 14, wherein the take-up speed of the fiber bundle by the take-up roller is 10 m / min or more and 60 m / min or less. (Aspect 16) A fiber bundle for artificial hair containing 20% ​​by volume or more of regenerated cellulose fiber bundles formed by bundling multiple regenerated cellulose fibers, wherein the regenerated cellulose fiber bundle contains 35% by volume or more of regenerated cellulose fiber A having the following composition. (Composition of regenerated cellulose fiber A) The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Of the arms in the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width. (Aspect 17) A fiber bundle for artificial hair according to Aspect 16, wherein the regenerated cellulose fibers are viscose rayon fibers obtained by coagulating and regenerating viscose. (Aspect 18) Artificial hair comprising the fiber bundle for artificial hair according to embodiment 16 or 17. (Aspect 19) A hair accessory comprising the artificial hair of embodiment 18. [Industrial Applicability]

[0104] The regenerated cellulose fibers of the present disclosure have bulkiness and rigidity not previously available with regenerated cellulose fibers, and can be used as artificial hair in hair accessories, as a resin kneading material for patterning plastic molded products, as a blasting material for removing burrs from circuit boards, as filters, as civil engineering materials that require biodegradability (nets, cheesecloth, sandbags, protective mats), as spun yarn for crisp clothing, as cleaning mops, and as bath sponges. [Explanation of symbols]

[0105] A Viscose rayon A 10, 11 Waist 12, 13, 14 Arm a 30 Spinning bath 30a bath surface 31 Spinneret 32 Fiber bundle 32a A yarn spun from a nozzle hole provided at approximately the center of the spinneret 33 Pick-up roller

Claims

1. Regenerated cellulose fibers, The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Among the arms of the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width. A regenerated cellulose fiber assembly containing 35% or more by volume of regenerated cellulose fibers.

2. 2. The regenerated cellulose fiber assembly according to claim 1, wherein the width of the arm portion a is 5 μm or more and 50 μm or less.

3. 3. The regenerated cellulose fiber assembly according to claim 1, wherein the fiber cross section has two or three arms a.

4. 4. The regenerated cellulose fiber assembly according to claim 1, wherein at least two of the arm portions a have a medium-thickness shape.

5. The regenerated cellulose fiber assembly according to any one of claims 1 to 4, wherein at least one of the arm portions a has a bent shape.

6. A regenerated cellulose fiber aggregate according to any one of claims 1 to 5, wherein the fiber cross section includes arm portion b other than arm portion a, the length of which is at least 1 time but less than 1.5 times the width.

7. 7. The regenerated cellulose fiber assembly according to claim 1, wherein the regenerated cellulose fibers are viscose rayon fibers obtained by coagulating and regenerating viscose.

8. The regenerated cellulose fiber assembly according to any one of claims 1 to 7, wherein the regenerated cellulose fibers have an irregular cross section.

9. The regenerated cellulose fiber aggregate described in any one of claims 1 to 8, which is a regenerated cellulose fiber bundle formed by bundling multiple regenerated cellulose fibers together or an aggregate of short fibers formed by cutting the regenerated cellulose fiber bundle to a predetermined length.

10. A regenerated cellulose fiber aggregate described in any one of claims 1 to 8, wherein the average width and average length of arm portion a of regenerated cellulose fiber A contained in 30 regenerated cellulose fibers randomly selected from the regenerated cellulose fiber aggregate satisfy at least one of the following. (i) The average width of the arm portion a of the regenerated cellulose fiber A is 5 μm or more and 50 μm or less. (ii) The average length of the arm portion a of the regenerated cellulose fiber A is 20 m or more and 60 μm or less.

11. A fiber assembly comprising 20% ​​by volume or more of the regenerated cellulose fiber assembly according to any one of claims 1 to 10.

12. A method for producing a viscose rayon fiber bundle comprising a plurality of viscose rayon fibers bundled together, the method comprising the steps of discharging viscose into a spinning bath from a plurality of nozzle holes provided in a spinneret, coagulating and regenerating the viscose to form a fiber bundle, and taking up the fiber bundle with a take-up roller provided outside the spinning bath, The nozzle hole has a hole diameter of 0.15 mm or more and 0.5 mm or less, where V1 is the discharge speed of the viscose at the outlet of the spinneret hole and V2 is the take-up speed of the fiber bundle by the take-up roller, the value of V2 / V1 is 0.5 to 1.5, When the fiber bundle is taken up by the take-up roller, the take-up is performed so that the angle formed between the take-up direction of the spun yarn located approximately at the center of the fiber bundle in the spinning bath and the bath surface of the spinning bath is 80° or more and 110° or less; and A method for producing a viscose rayon fiber bundle, comprising obtaining a fiber bundle containing viscose rayon fibers having a single fiber fineness of 20 dtex or more and 160 dtex or less.

13. 13. The method for producing a viscose rayon fiber bundle according to claim 12, wherein take-up is carried out so that the length of the spun yarn located approximately in the center of the fiber bundle between the spinneret and the bath surface of the spinning bath is 400 mm or more.

14. The method for producing a viscose rayon fiber bundle according to claim 12 or 13, wherein the take-up speed of the fiber bundle by the take-up roller is 10 m / min or more and 60 m / min or less.

15. A fiber bundle for artificial hair containing 20% ​​by volume or more of a regenerated cellulose fiber bundle formed by bundling a plurality of regenerated cellulose fibers, wherein the regenerated cellulose fiber bundle contains 35% by volume or more of regenerated cellulose fiber A having the following structure. (Configuration of regenerated cellulose fiber A) The fineness is 20 dtex or more and 160 dtex or less, The fiber cross section has a plurality of arms and a constriction formed by the arms, Of the arms in the fiber cross section, at least two arms are arm portions a whose length is 1.5 times or more and less than 2.5 times the width, and the fiber cross section does not have any arms whose length is 2.5 times or more the width.

16. 16. The fiber bundle for artificial hair according to claim 15, wherein the regenerated cellulose fibers are viscose rayon fibers obtained by coagulating and regenerating viscose.

17. Artificial hair comprising the fiber bundle for artificial hair according to claim 15 or 16.

18. A hair accessory comprising the artificial hair according to claim 17.

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