Nonwoven fabric, and narrow tape and slit yarn of the nonwoven fabric

Abstract

The purpose of the present invention is to provide a nonwoven fabric composed of regenerated cellulose fiber derived from natural fiber rather than petroleum, and excellent in narrow-width slitting processability, and furthermore, to maintain high strength even if the thickness is low (low basis weight), enabling processing into a fine-denier slit yarn. The present invention relates to: a nonwoven fabric comprising regenerated cellulose fiber, having a fiber orientation index from 4 to 8 as calculated by small-angle X-ray scattering (SAXS) measurement, and having a surface arithmetic average height of 25 um or less; a narrow tape obtained by cutting the nonwoven fabric to a width from 0.5 mm to 10 mm; a slit yarn formed by twisting the narrow tape; a yarn obtained by twisting the narrow tape or the slit yarn with another yarn-like material or tape; a knitted fabric knitted by using the narrow tape and / or the slit yarn; and a woven fabric woven by using the narrow tape and / or the slit yarn.

Description

Nonwoven fabric, and narrow tapes and slit yarns of the nonwoven fabric.

[0001] The present invention relates to a nonwoven fabric that can be used as a processing raw material for narrow tapes and slit yarns, which are suitable as craft materials or knitting materials for making knitted or woven fabrics using tools such as knitting needles and crochet hooks or knitting machines.

[0002] Narrow tapes made of nonwoven fabric are used alone or in combination with other thread-like materials as materials for handicrafts and woven / knitted goods. Conventionally, known narrow tapes made of nonwoven fabric include tape-shaped handicraft materials with a width of 10 to 20 mm made of continuous filaments, and thread-like materials in which protrusions are formed by partially loosening an entanglement of narrow nonwoven fabric tapes and other thread-like materials. Although these narrow tapes can be processed into knitted or woven goods using crochet hooks, knitting needles, knitting machines, etc., they have the problem of being difficult to narrow and having poor gloss. Furthermore, although such thread-like materials can have design appeal, lightness, and bulkiness while maintaining the shape of nonwoven fabric produced by the spunbond method or dry process, the knitting process requires a complex process using special knitting machines, resulting in poor productivity and a lack of gloss that gives a sense of luxury.

[0003] To solve these problems, Patent Document 1 below provides a narrow tape or narrow tape-like material made of nonwoven fabric with improved properties, particularly strength and gloss, resulting in a tape with excellent gloss, colorability, and machinability, allowing for the creation of high-quality handicrafts and woven / knitted fabrics. Such a narrow tape is obtained by cutting a thermoplastic filament nonwoven fabric that has been partially heat-sealed or calendered to increase its strength. The thermoplastic filament nonwoven fabric has an average fiber diameter of 1 to 20 μm (preferably 3 to 15 μm) and a basis weight of 10 to 50 g / m². ２ (Preferably 15 to 30 g / m ２ ), average apparent density 0.25–0.7 g / cm³ ３ (Preferably 0.28 to 0.55 g / cm³) ３It has the following characteristics: a thickness of 0.2 to 0.02 mm (preferably 0.15 to 0.04 mm), and a gloss of 2.0 or higher (preferably 2.5 or higher) measured at 60 degrees. As a result, it has high strength and excellent gloss, can be used on known knitting machines such as flat knitting machines and circular knitting machines, and has excellent narrow width processing and machinability. Furthermore, by using it alone or in combination with various filament yarns, twisted yarns, spun yarns, and processed yarns, it is possible to obtain thin, lightweight knitted fabrics and handicrafts with excellent gloss and dimensional stability. However, because this narrow tape is derived from synthetic fibers, it has the problem of being inferior in environmental friendliness and dyeability compared to Japanese paper and regenerated cellulose fibers.

[0004] On the other hand, nonwoven fabric face masks impregnated with cosmetic liquid are expanding as anti-aging products, and the base material mainly uses cellulose-based short fiber nonwoven fabrics such as cotton and rayon, or cupro continuous long fiber nonwoven fabrics, due to their liquid retention performance and good liquid retention when worn. Patent Document 2 below describes a cellulose-based fiber nonwoven fabric for face masks with excellent adhesion and handling properties when wet, with a bulk density of 0.20 g / cm³. ３ 0.30g / cm or more ３ A nonwoven fabric has been proposed characterized by an initial lateral tensile strength of 0.25 N / 50 mm or more and less than 0.90 N / 50 mm when wet. This is a dense sheet with an increased number of fibers to achieve both ease of handling and adhesion for face masks. However, because this nonwoven fabric has lower strength than thermoplastic filament nonwoven fabrics, it is not suitable as a raw material for processing into narrow tapes or slit yarns used in knitted fabrics using knitting needles, crochet hooks, or knitting machines.

[0005] Furthermore, Patent Document 3 proposes a condenser separator that has tensile strength equal to or greater than conventional materials, is thin, and has low internal resistance. This is achieved by highly densifying a cellulose fiber woven or nonwoven fabric, controlling its thickness to 5-35 μm, porosity to 30-60%, and air permeability to 10 sec / 100 cc or less. However, although high tensile strength can be obtained through calendering, the thickness becomes excessively thin, making it unsuitable as a raw material for processing narrow tapes and slit yarns used in handicrafts and knitted fabrics.

[0006] Thus, while synthetic fibers are typically the dominant material for nonwoven fabrics used in slit yarn applications due to their strength, there has been a growing demand for plastic-free materials in recent years. Paper is also used as a raw material for slit yarn processing, but it suffers from poor dyeability. Therefore, the application of cellulose fiber nonwoven fabrics is sought, but these fabrics have poor strength and low processability (narrow slitting processability) when slitting into narrow widths. Furthermore, for use in a wide range of apparel products, it is desirable that the nonwoven fabric be processed into fine-denier, fine-count slit yarn. In this case, in addition to high strength, thinness is also required. However, conventional cellulose fiber nonwoven fabrics lack sufficient strength, making it difficult to process them into narrow widths with good processability. Moreover, achieving both "thinness / low basis weight" and "high strength" simultaneously has not been possible. Note that Patent Document 1 describes partial heat bonding and calendering to increase strength, but this technology is based on synthetic fibers and cannot be applied to cellulose fibers, which do not inherently melt with heat.

[0007] Japanese Patent Publication No. 4511260, Japanese Unexamined Patent Publication No. 2018-127744, Japanese Unexamined Patent Publication No. 2008-124064

[0008] In view of the level of prior art, the problem that the present invention aims to solve is to provide a nonwoven fabric composed of regenerated cellulose fibers derived from natural fibers rather than petroleum, which has excellent narrow slitting properties. Furthermore, it aims to maintain high strength even at low thickness (low basis weight) and enable processing into fine-denier slit yarn.

[0009] The present inventors conducted extensive research and experiments to solve the above problems. As a result, they discovered an unexpected effect: by adjusting the orientation of the fibers constituting the nonwoven fabric and the arithmetic mean roughness of the nonwoven fabric surface, the strength per unit basis weight increased despite the nonwoven fabric containing regenerated cellulose, resulting in excellent narrow slitting processability. This led to the completion of the present invention.

[0010] In other words, the present invention is as follows: [1] A nonwoven fabric containing regenerated cellulose fibers, wherein the fiber orientation index calculated from small-angle X-ray scattering (SAXS) measurement is 4 or more and 8 or less, and the arithmetic mean height of the surface is 25 μm or less. [2] The nonwoven fabric according to [1], wherein the longitudinal stiffness per unit basis weight is 5 mm or more and 15 mm or less. [3] The nonwoven fabric according to [1] or [2], wherein the regenerated cellulose fiber content is 50 wt% or more based on the total weight of the nonwoven fabric. [4] A fabric with a basis weight of 10 g / m ２ 30g / m or more ２ The nonwoven fabric according to any of [1] to [3] above, which is as follows: [5] The nonwoven fabric according to any of [1] to [4] above, having a thickness of 0.05 mm or more and 0.20 mm or less. [6] The nonwoven fabric according to any of [1] to [5] above, having a longitudinal breaking strength per unit basis weight of 2 N / 50 mm or more and 6 N / 50 mm or less. [7] The nonwoven fabric according to any of [1] to [6] above, wherein the cross-section of the regenerated cellulose fibers is substantially circular. [8] A narrow tape obtained by cutting the nonwoven fabric according to any of [1] to [7] above to a width of 0.5 mm or more and 10 mm or less. [9] A slit yarn formed by twisting the narrow tape according to [8] above.

[10] The slit yarn according to [9] above, having a fiber orientation index calculated from small-angle X-ray scattering (SAXS) measurement of 4 or more and 9 or less.

[11] A yarn in which the narrow tape described in [8] or the slit yarn described in [9] is twisted with other yarn-like material or tape.

[12] A knitted fabric made using the narrow tape described in [8] and / or the slit yarn described in [9].

[13] A woven fabric made using the narrow tape described in [8] and / or the slit yarn described in [9].

[0011] The nonwoven fabric of the present invention is composed of environmentally friendly, non-petroleum-derived regenerated cellulose fibers, yet possesses high strength per unit basis weight, making it excellent for narrow slitting. Furthermore, it maintains high strength even at low thickness (low basis weight), enabling processing into fine-denier slit yarn.

[0012] SEM image of the surface of the nonwoven fabric of Example 1. SEM image of a slit yarn obtained by slitting the nonwoven fabric of Example 1 to a width of 1.5 mm and twisting it at 600 T / m (left: surface, right: cross section). SEM image of the Japanese paper slit yarn used in Comparative Example 21 (left: surface, right: cross section).

[0013] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is a nonwoven fabric containing regenerated cellulose fibers, having a fiber orientation index calculated from small-angle X-ray scattering (SAXS) measurement of 4 or more and 8 or less, and an arithmetic mean height of the surface of 25 μm or less.

[0014] <Components of the nonwoven fabric> As used herein, the term "nonwoven fabric" refers to a material formed by mechanically, chemically, thermally, or by combining these methods to entangle or bond fibers into a sheet or web form, having a structure different from woven or knitted fabrics. Note that the "nonwoven fabric" in this specification may include those having a paper-like (paper-like) appearance and texture.

[0015] The nonwoven fabric of this embodiment contains regenerated cellulose fibers. Examples of regenerated cellulose fibers include cupra, viscose rayon, polynosic rayon, and lyocell (tencel). The form of the regenerated cellulose fibers may be either short fibers or long fibers, but long fibers are preferred. By using long fibers, the strength and rigidity of the nonwoven fabric are improved, and the slit processing property and texture feel are good.

[0016] The cross section of the regenerated cellulose fibers constituting the nonwoven fabric of this embodiment is preferably substantially circular. The circularity described later is preferably 1.1 to 1.2. If the cross section is substantially circular, the strength and rigidity per unit basis weight of the nonwoven fabric are improved, and the slit processing property and texture feel are good.

[0017] In this embodiment, the nonwoven fabric preferably contains 50 wt% or more of regenerated cellulose fibers based on the total weight of the nonwoven fabric. A regenerated cellulose fiber content of 50 wt% or more provides excellent environmental friendliness and dyeability. The regenerated cellulose fiber content is preferably 80 wt% or more, and more preferably 90 wt% or more. There is no particular upper limit, but it is 100% or less.

[0018] In this embodiment, the composition of the nonwoven fabric is not particularly limited and may be composed of a single type of fiber or multiple types of fibers. In addition, binders, fillers, etc. may be included in addition to fibers, and films or the like may be laminated onto the nonwoven fabric.

[0019] In this embodiment, it is preferable that adhesive points are formed between the fibers constituting the nonwoven fabric. An "adhesion point" refers to a portion where fibers are bonded and integrated using an adhesive, or a portion where fibers are directly bonded and integrated by heat, pressure, or chemical action without the use of an external adhesive. The formation of adhesive points improves the strength of the nonwoven fabric. The higher the adhesive strength at the adhesive points, and the more densely and uniformly the adhesive points are distributed, the better the processability for narrow slitting. Furthermore, anisotropy may occur in the shape and strength of the adhesive points. From the viewpoint of improving the processability for narrow slitting, it is preferable to have adhesive points that have stronger strength in the longitudinal direction. From the viewpoint of being able to form adhesive points at high density and uniformly, the wet spunbond method is preferred as a method for manufacturing the nonwoven fabric. However, it is possible to form adhesive points between fibers by other manufacturing methods, and this is not excluded.

[0020] <Physical Properties of Nonwoven Fabrics> Regardless of whether it is made of regenerated cellulose or not, nonwoven fabrics tend to have fibers that are easily oriented in the direction of machine movement (longitudinal direction) due to their manufacturing process, and therefore generally tend to have greater strength and rigidity in the longitudinal direction. On the other hand, they tend to stretch easily in the transverse direction and have a lower initial tensile strength. In this specification, "longitudinal direction of nonwoven fabric" refers to the tensile direction that shows the highest tensile strength when the maximum tensile strength is measured in a dry state. In other words, if the longitudinal and transverse directions cannot be determined, the direction with the highest strength or rigidity shall be considered the longitudinal direction.

[0021] In this embodiment, the fiber orientation index calculated from SAXS measurement of the nonwoven fabric is between 4 and 8. More preferably, it is between 4.5 and 8, and even more preferably between 5 and 7. When the fiber orientation index is within this range, the fibers are strongly oriented in the longitudinal direction, which improves the longitudinal strength of the nonwoven fabric and improves its ability to be processed into narrow slits. Here, the fiber orientation index indicates the degree of fiber orientation; a value of 1 means there is no bias in orientation, and a larger value means a stronger bias in orientation in a particular direction. To achieve the fiber orientation index within the above range, for example, when manufacturing a nonwoven fabric using the wet spunbond method, it is effective to adjust the conditions when extruding the dissolved cellulose stock from the spinneret and shaking it onto the net to form the web. Specifically, by vibrating the net perpendicular to the direction of travel while it is moving, the fibers deposited on the net are arranged to generally follow a sinusoidal curve. At this time, by appropriately controlling the vibration amplitude and vibration period of the net, the arrangement direction of the fibers can be adjusted, and the desired fiber orientation index can be obtained. As another example, when manufacturing nonwoven fabrics using the spunlace method, the orientation of fibers in a specific direction can be adjusted by controlling the wrap formation conditions before water entanglement and the water entanglement conditions. Specifically, while there are various wrap formation methods such as parallel, cross, and random, by employing the parallel method and adjusting the condensing roll and water entanglement conditions, the fiber arrangement direction can be adjusted to obtain a desired fiber orientation index. It should be noted that the method is not limited to the manufacturing method exemplified above, as long as the degree of fiber orientation can be adjusted. The degree of fiber orientation can be similarly controlled to a desired range by other manufacturing methods and conditions.

[0022] The nonwoven fabric of this embodiment has an arithmetic mean height of 25 μm or less on its surface. More preferably, it is 23 μm or less, and even more preferably, 20 μm or less. The lower limit is not particularly limited and may be 0 μm or more, 5 μm or more, or 10 μm or more. Having the arithmetic mean height within this range reduces surface irregularities of the nonwoven fabric and makes it less likely for areas with uneven thickness, especially locally thin areas, to occur. Uneven thickness negatively affects processability when slitting into narrow widths. Specifically, locally thin areas become a drawback, causing problems such as the resulting narrow tape breaking. Lowering the arithmetic mean height eliminates this drawback and improves slit processability. To achieve the above range for the arithmetic mean height of the surface, it is effective to either not perform water flow entanglement or to perform water flow entanglement at low water pressure during the manufacturing process of the nonwoven fabric. Note that it is sufficient to adjust the arithmetic mean height of the surface, and the manufacturing method is not limited to the example given above.

[0023] In the nonwoven fabric of this embodiment, the longitudinal breaking strength per unit basis weight is preferably 2 N / 50 mm or more and 6 N / 50 mm or less, more preferably 2.2 N / 50 mm or more and 5 N / 50 mm or less, and even more preferably 2.5 N / 50 mm or more and 4 N / 50 mm or more. If the longitudinal breaking strength per unit basis weight is within the above range, the processability of the nonwoven fabric when slitting will be good, and it will also be easy to reduce the fineness to 300 dtex or less after twisting.

[0024] In the non-woven fabric of this embodiment, the rigidity in the vertical direction per unit weight is preferably 5 mm or more and 15 mm or less, more preferably 6 mm or more and 13 mm or less, and even more preferably 7 mm or more and 10 mm or less. When the rigidity in the vertical direction per unit weight is within this range, appropriate tension and firmness are generated in the fabric using the slit yarn obtained by processing the non-woven fabric, and a good texture with a crispy feeling can be obtained. To make the rigidity in the vertical direction per unit weight within the above range, in the manufacturing process of the non-woven fabric, it is effective to adjust the physical properties of the raw material fibers (for example, material, rigidity, fiber diameter, fiber length, circularity, crimpability, etc.), the number of web laminations, the density and shape of the adhesion points, etc. In the case of a long fiber non-woven fabric manufactured by the wet spunbond method, the number of laminations is preferably 4 or more, and more preferably 5 or more. Note that as long as the rigidity in the vertical direction can be adjusted, it is not limited to the manufacturing methods exemplified above.

[0025] The basis weight of the non-woven fabric of this embodiment is preferably 10 g / m ２ or more and 30 g / m ２ or less, more preferably 10.2 to 24.5 g / m ２ If the basis weight is within the above range, it is possible to make the fineness after twisting 300 dtex or less while maintaining the workability during slitting of the non-woven fabric.

[0026] The thickness of the non-woven fabric of this embodiment is preferably 0.05 mm or more and 0.20 mm or less, more preferably 0.06 to 0.12 mm. If the thickness is within the above range, it is possible to make the fineness after twisting 300 dtex or less while maintaining the workability during slitting of the non-woven fabric.

[0027] <Manufacturing method of non-woven fabric> The manufacturing method of the non-woven fabric of this embodiment is not particularly limited, but for example, it can be manufactured by the following manufacturing methods.

[0028] The method for manufacturing cupro nonwoven fabric involves first preparing a stock solution by dissolving cotton linters, which have had impurities removed and whose degree of polymerization has been adjusted, in a copper ammonium solution. Next, the stock solution is extruded through a spinneret (spinning nozzle) having pores (stock solution discharge holes), and deammonia is removed by letting it fall through a funnel with water. The stock solution is then stretched while solidifying, and shaken onto a net to form a web. After drying, the resulting nonwoven fabric can be rolled or wound into a roll.

[0029] The draw ratio during spinning can range from 100 to 500 times, and this can be arbitrarily controlled by adjusting the shape of the spinning funnel and the amount of spinning water flowing through it. By changing the draw ratio, the fineness of the single filament and the strength of the nonwoven fabric can be adjusted. Furthermore, by adjusting the amount of spinning water and temperature, the content of low molecular weight cellulose, i.e., hemicellulose, that remains in trace amounts in the raw solution can be controlled. The shape of the spinning funnel is preferably rectangular, the length of the funnel is preferably 100 to 400 mm, and the slit width of the outlet is preferably 2 to 5 mm. The diameter of the raw solution discharge hole at the spinning nozzle is preferably 0.3 to 0.7 mm, and a round shape is desirable.

[0030] In this embodiment, from the viewpoint of increasing the number of bonding points between fibers, the discharge pore density is preferably 0.13 to 0.51, and more preferably 0.25 to 0.35. In the conventional art, the discharge pore density is generally about 0.13, but compared to this condition, it is possible to obtain a nonwoven fabric with more bonding points between fibers and superior strength and rigidity per unit basis weight. Discharge pore density [cm ２ / cm ２ The density of the discharge port [cm³] can be calculated using the following formula: ２ / cm ２ ]=Discharge hole density [pieces / cm ２ ] × Area per single hole [cm²] ２ / piece]

[0031] In the formation of a nonwoven web, vibrating the net perpendicular to its direction of travel causes the fibers that fall onto the net to exhibit a sine curve. To ensure uniformity of the fiber arrangement, the phase of the sine curve of the fibers falling onto the net is uniformly varied in 3 to 10 steps per layer, resulting in a 3 to 10-layer laminated web. This allows for the production of a cellulose-based nonwoven fabric with an extremely uniform fiber arrangement. Such a multilayer nonwoven fabric with a uniform fiber arrangement has uniform interfiber gaps and a consistent average pore size, and densification results in a thin, smooth surface. Furthermore, increasing the number of layers improves the longitudinal stiffness per unit basis weight. Additionally, by adjusting the net's travel speed and vibration amplitude, it is possible to control the fiber arrangement direction and the morphology, density, strength, and anisotropy of the fiber adhesion points, thereby controlling the physical properties of the nonwoven fabric, such as strength and elongation. Note that reducing the vibration amplitude or decreasing the vibration frequency tends to bias the fiber orientation towards the MD direction (longitudinal direction).

[0032] The laminated web can be regenerated or scouring in web form by methods described in, for example, Japanese Patent Publication No. 787914 or Japanese Patent Publication No. 877579, and then subjected to high-pressure water entanglement. Generally, high-pressure water entanglement is performed to form fiber entanglements, through-holes, and recesses. However, in this embodiment, it is preferable not to perform water entanglement, or to perform it at low water pressure, from the viewpoint of maintaining the adhesion points between fibers and lowering the arithmetic mean height of the surface.

[0033] By maintaining the bonding points between fibers, nonwoven fabrics possess high levels of longitudinal strength and rigidity per unit basis weight, and are excellent for narrow slitting. Therefore, even bulky nonwoven fabrics can be slit. When bulky nonwoven fabric is used as slit yarn, the yarn has a high porosity, and the fabric using it also becomes bulky. Furthermore, if the fibers constituting the nonwoven fabric are regenerated cellulose fibers, the properties of the fibers themselves combine to create a soft, light, and pleasant texture.

[0034] The above manufacturing conditions are merely examples and are not limited to those described above, as long as a nonwoven fabric with the desired physical properties and characteristics can be obtained.

[0035] <Processed Nonwoven Fabric Products> Another embodiment of the present invention is a narrow tape obtained by cutting a roll of nonwoven fabric (raw material) obtained by the above method into a width of 0.5 mm to 10 mm in the longitudinal direction. The narrow tape of this embodiment is obtained by cutting the nonwoven fabric into a width of 0.5 mm to 10 mm, but it is preferable to employ a multi-stage slitting method in which the nonwoven fabric is first slit with a slit width of 30 to 70 cm, and then slit into narrow widths of 0.5 mm to 10 mm.

[0036] Another embodiment of the present invention is a slit yarn obtained by twisting the narrow tape thus obtained with an appropriate number of twists according to the tape width, thickness, and fineness. Slit yarn twisted on its own has a soft, light, and pleasant texture, reflecting the physical properties of the nonwoven fabric and the regenerated cellulose fibers that make up the nonwoven fabric, and can be used to produce knitted fabrics and handicrafts with excellent dyeability. Slit yarn may be dyed in the yarn state (pre-dyed) or dyed after it has been made into fabric (post-dyed).

[0037] The slit yarn obtained by twisting narrow tapes preferably has a fiber orientation index of 4 to 9, more preferably 4.5 to 9, and even more preferably 5 to 8, calculated from small-angle X-ray scattering (SAXS) measurements. Having a fiber orientation index within this range results in good yarn strength, improved fabric knitting or weaving processability, and improved fabric mechanical strength.

[0038] Another embodiment of the present invention is a yarn obtained by twisting the above-mentioned narrow tape with other yarn-like material or tape. There are no particular restrictions on the other yarn-like material or tape, and various filament yarns, twisted yarns, spun yarns, processed yarns, tapes, films, etc., can be used. The yarn twisted with other yarn-like material or tape can be given properties according to the properties of the yarn-like material or tape, and for example, knitted fabrics and handicrafts that are thinner, lighter, and have excellent gloss, dimensional stability, and wash durability can be obtained. There are no particular restrictions on the twisting method, and the above-mentioned narrow tape may be twisted with other yarn-like material or tape in an untwisted state, or the above-mentioned narrow tape may be twisted beforehand and then twisted with other yarn-like material or tape.

[0039] Another embodiment of the present invention is a knitted fabric made using the above-mentioned narrow tape and / or slit yarn. The knitted fabric may be dyed or post-processed.

[0040] Another embodiment of the present invention is a fabric woven using the above-mentioned narrow tape and / or slit yarn. The fabric may be dyed or post-processed.

[0041] The nonwoven fabric of this embodiment is suitable for slit yarn applications because it possesses unprecedented thinness, high strength, and rigidity. It can also be suitably used in other applications where a thin, strong, and rigid nonwoven fabric is required, such as tea bags, wipers, and filters.

[0042] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. First, the methods for measuring various characteristics used in the examples will be explained.

[0043] All samples used in the examples and comparative examples were left in a constant temperature room at 20°C and 65% RH for at least 16 hours. Furthermore, the "longitudinal direction" refers to the tensile direction in which the nonwoven fabric exhibits the highest tensile strength when its maximum tensile strength is measured in a dry state.

[0044] (1) When the fiber orientation index sample was a nonwoven fabric, a SAXS sample was prepared by cutting it into strips 15 mm in the horizontal direction and 300 mm in the vertical direction, folding them back at 30 mm intervals, and stacking 10 of these strips. Stacking 10 strips allowed for obtaining the average structure of the nonwoven fabric. During measurement, the sample was set on the sample stage so that the vertical direction was horizontal, and SAXS measurements were performed under the following conditions by irradiating the sample surface with X-rays perpendicular to it. When the sample was a twisted yarn, the nonwoven fabric roll obtained in the example was slit to a width of 1.5 mm, and a twisted yarn was produced using the resulting 1.5 mm wide slit tape under the condition of 600 Z-twists / m. To obtain the average structure, the twisted yarn was bundled so that the total fineness was approximately 15000 dtex, the yarn length direction was considered the vertical direction, and the direction perpendicular to it was considered the horizontal direction, and the sample was set on the sample stage so that the yarn length direction was horizontal. To accurately analyze the orientation of each fiber constituting the twisted yarn, all the twisted yarns were arranged so that their length direction was aligned horizontally to the sample stage. The measurement was performed by irradiating the yarn bundle with X-rays perpendicular to the radial direction, and SAXS measurement was performed under the following conditions.

[0045] [Measurement Conditions] Measurement device: Rigaku Corporation NANOPIX Incident X-ray wavelength λ: 0.154 nm Detector: 2D detector "HyPix-6000" Measurement time: 5 minutes Camera length: 1312 mm Optical system: Point collimation 1st slit: 0.55 mmφ, guard slit: 0.35 mmφ4 High Resolution Mode Beam stopper: 2 mmφ

[0046] For the SAXS pattern I(2θ, φ) obtained by the 2D detector, the azimuth angle φ was defined clockwise, with the 12 o'clock direction being 0°. In this case, the horizontal direction of the sample corresponds to φ = 0°, and the vertical direction corresponds to φ = 90°. The average scattering intensity I(2θ) of the sector-shaped region was calculated using the following formula. {In the formula, φ ｓ、 φ ｅ : Starting and ending azimuth angles of the sector region, θ: Bragg angle.

[0047] Next, empty cell correction is performed using the following formula, and the one-dimensional scattering intensity I ｃ (2θ) was calculated. {In the formula, I ｃ (2θ): Empty cell corrected scattering intensity, I ｓａｍｐｌｅ (2θ): Scattering intensity of the sample, I ｅｍｐｔｙ (2θ): Scattering intensity of the empty cell, t ｓａｍｐｌｅ : Sample measurement time, t ｅｍｐｔｙ {: Measurement time for empty cell measurement, T: Transmittance} The angular range of the sector-shaped average is φ ± 10°, and the scattering intensity in the lateral direction is I ｃ＿ヨコ (2θ) is φs = -10°, φe = 10°, and the vertical scattering intensity is I ｃ＿タテ (2θ) was obtained with φs = 80° and φe = 100°.

[0048] Next, the obtained I ｃ The fiber orientation index was calculated from (q) using the following formula. {In the formula, A ヨコ A タテ : I ｃ＿ヨコ (q), I ｃ＿タテ The coefficient fitted to (q) by the following formula}

[0049] The analysis focused on the porodo region, where scattering originating from the specific surface area of ​​each fiber can be analyzed. In this region, the scattering intensity is q -4 It is known to be proportional to, and fitting is performed using Equation 4 based on Polod's law, A ヨコ and A タテ The following was calculated. The fitting range is 0.04 < q (nm -1 ) < 0.1 was used. For fitting, the analysis software: Wavemetrics Igor Pro 8.00 was used. Note that q is the absolute value of the scattering vector defined by the following equation. {wherein the formula, θ: Bragg angle, λ: incident X-ray wavelength} The obtained A ヨコ and A タテ The fiber orientation index was determined using Equation 3. Scattering in the porodo region is known to be due to the specific surface area of ​​the fiber and is strongly expressed in the radial direction of the fiber. Therefore, when the fibers are oriented longitudinally, the scattering intensity in the transverse direction becomes relatively higher, and the fiber orientation index becomes larger.

[0050] Furthermore, if the warp and weft directions of the nonwoven fabric cannot be determined, the direction showing the maximum intensity of the peak obtained by the following method should be considered the weft direction, its azimuth angle should be defined as φ = 0°, and the fiber orientation index should be determined using the method described above.

[0051] The azimuthal angle distribution I(φ) of the scattering intensity in the region where the scattering of interest exists (2θs < 2θ(deg) < 2θe) was calculated using the following equation 6. The region of the scattering of interest is 0.04 < q(nm). －１ ) < 0.1, and the definition of the scattering vector q is as described above. {In the formula, 2θ ｓ、 2θ ｅ : Small-angle and wide-angle scattering angles of the scattering intensity of interest, θ: Bragg angle. I(φ): Azimuthal distribution of scattering intensity, T: X-ray transmittance, t ｓａｍｐｌｅ , t ｅｍｐｔｙ : Exposure time for sample and empty cell} Next, normalize using the following equation 7 to obtain the normalized azimuth distribution I N (φ) was obtained. Normalized azimuth angle I N In (φ), the direction showing the maximum peak intensity is defined as the horizontal direction, and its azimuth angle is defined as φ = 0°. Note that, generally, the azimuth angle distribution is symmetrical, so if a peak exists at φ = 0°, a peak may also appear at φ = 180°. Either of these symmetrical peaks may be selected as the reference direction, and the difference in selection does not affect the calculation and effect of the structural parameters. Furthermore, the azimuth angle φ is defined clockwise.

[0052] (2) Arithmetic Mean Height In this specification, "arithmetic mean height (Sa)" is one of the indicators for evaluating the roughness of a surface shape, and refers to the value obtained by calculating the average of the absolute values ​​of the heights of each point in the surface area to be measured. Specifically, it is the value obtained by summing the absolute values ​​of the heights (distance from the reference plane) of each point in the measurement area and dividing by the number of measurement points, and is measured in accordance with international standards such as ISO 25178. The arithmetic mean height quantitatively indicates the degree of surface irregularity and is used for evaluating the surface properties of nonwoven fabrics, sheets, etc. The arithmetic mean height [μm] of nonwoven fabric was measured using a Keyence one-shot 3D shape measuring machine and analysis application in the following way. A test piece cut from the nonwoven fabric or slit tape to a length of 300 mm in the longitudinal direction and an arbitrary width of 0.5 mm to 10 mm was fixed to the measuring stand with a tension of 0.05 [N] per 1 mm of width applied in the longitudinal direction. The camera magnification was set to high magnification 150x and an observation image was obtained by photographing an arbitrary location. The arithmetic mean height (Sa) was measured for N=20 arbitrary regions of 1000 μm × 1000 μm within the acquired images. The average of the obtained values ​​was defined as the arithmetic mean height. The test specimens were acquired so that their longitudinal direction was the longitudinal direction of the nonwoven fabric (vertical direction, machine direction, production direction).

[0053] (3) Longitudinal breaking strength per unit basis weight The longitudinal breaking strength [N / 50 mm] was measured by the following method. A test piece cut from the nonwoven fabric to a size of 5 cm wide and 15 cm long was gripped to a gripping length of 10 cm, and then stretched using a constant-speed elongation tensile testing machine (Tensilon UCT-1t, manufactured by Orientec Co., Ltd.) at a tensile speed of 30 ± 3 cm / min, and the tensile strength at which the sample broke was measured with N=5. The average value of the obtained values ​​was taken as the breaking strength. Test pieces were obtained so that the longitudinal direction of the test piece was the longitudinal direction of the nonwoven fabric (longitudinal direction, machine direction of travel, production direction). Next, the obtained longitudinal breaking strength [N / 50 mm] was divided by the basis weight of the nonwoven fabric described later, to obtain the following formula: Longitudinal breaking strength per unit basis weight = Longitudinal breaking strength [N / 50 mm] ÷ basis weight [g / m ２ The fracture strength in the longitudinal direction per unit weight was determined by [this method].

[0054] (4) The longitudinal stiffness [mm] of the nonwoven fabric per unit basis weight was measured by the following method. A test piece cut from the nonwoven fabric to a size of 25 mm in width and 150 mm in length was placed on a 41.5° cantilever type testing machine. The short side was aligned with the baseline of the scale, and the test piece was gently slid in the direction of the slope. When one end of the test piece touched the slope, the position [mm] of the other end was read on the scale, and the distance extruded was measured. Five test pieces were obtained so that the longitudinal direction of the test piece was the longitudinal direction of the nonwoven fabric (longitudinal direction, machine direction of travel, production direction), and the average of all data was taken as the longitudinal stiffness [mm]. Next, the obtained longitudinal stiffness [mm] was divided by the basis weight of the nonwoven fabric, as described later, to obtain the following formula: Longitudinal stiffness per unit basis weight = Longitudinal stiffness [mm] ÷ basis weight [g / m ２ The vertical stiffness per unit area was determined by [this method].

[0055] (5) Basis weight After drying at 105°C for 60 minutes, the nonwoven fabric is left in a constant temperature room at 20°C and 65% RH for 16 hours or more. A piece of 5 cm x 5 cm is cut out, its mass is measured, and the mass of the nonwoven fabric is measured. ２ The mass per unit [g] was determined. The measurement was performed on 30 samples, and the average value [g / m²] was used. ２ ]

[0056] (6) Thickness The thickness of the nonwoven fabric was measured in accordance with JIS-L1096 at a load of 1.96 kPa. Measurements were taken at 30 locations, and the average value was taken as the thickness [mm].

[0057] (7) Circularity (Fiber Cross-Sectional Shape) After the fiber was sliced ​​crosswise with a razor, it was mounted on the sample stage of a scanning electron microscope (SEM) with the cross-section facing upwards. The cross-section of the fiber was then observed, and the major axis and minor axis of the cross-section were measured to determine the major axis / minor axis ratio. A major axis / minor axis ratio of 2.0 or less was defined as approximately circular.

[0058] (8) Narrow Slitting Processability Narrow slitting processability was evaluated based on the number of times the fabric broke when a 100 mm wide nonwoven fabric roll was slit into 1 mm wide strips totaling 20,000 m in length, according to the following evaluation criteria. [Evaluation Criteria] 5 points: Less than 5 fabric breaks / 20,000 m 4 points: 5 or more but less than 10 fabric breaks / 20,000 m 3 points: 10 or more but less than 15 fabric breaks / 20,000 m 2 points: 15 or more but less than 25 fabric breaks / 20,000 m 1 point: 25 or more fabric breaks / 20,000 m From the viewpoint of production efficiency and processing stability of slitting, it is desirable that the above evaluation score be 3 points or higher. Furthermore, the production and testing of twisted yarn was carried out for those that received an evaluation score of 3 points or higher.

[0059] (9) Fineness after twisting A narrow tape slit to 1 mm was twisted at 800 revolutions / m in a Z-twist pattern, and the resulting test yarn was left in a constant temperature room at 20°C and 65% humidity for at least 4 hours. Then, 20 test yarns, each 90 cm long, were taken from the measured yarn, and their weight [g] was measured. From the average weight, the fineness [dtex] after twisting was calculated using the following formula: Fineness [dtex] = 10000 × weight of test yarn [g] ÷ length of test yarn [m].

[0060] (10) KES bending characteristics Using a KES-FB2-A pure bending tester, the maximum curvature K = ±2.5 cm -1 Measurements were taken under the following conditions. The test specimens were cut from the knitted fabric to a size of 20 cm in the warp direction and 20 cm in the weft direction, set in the testing machine, and measured for curvature K = -2.5 to +2.5 cm. -1 Pure bending with constant velocity curvature was performed within the specified range, and the relationship between bending moment and curvature was obtained. The test environment was kept constant at 20°C and 65% RH. Measurements were taken in the longitudinal and latitudinal directions of three test specimens, and the average of the obtained values ​​was evaluated as bending stiffness (B) and bending recovery (bending hysteresis width 2HB).

[0061] (11) KES Surface Properties The average coefficient of friction (MIU), variation in the average coefficient of friction (MMD), and surface roughness (SMD) were measured using a KES-FB4-A surface testing machine. Test specimens were cut from the knitted fabric to a size of 20 cm in the warp direction and 20 cm in the weft direction, and set in the testing machine. MIU and MMD were calculated from data obtained by measuring the friction force while moving the sample horizontally 2 cm at a constant speed of 0.1 cm / sec with a metal contact (0.5 mm diameter piano wire, 10 strands in a row) pressed against the test specimen with a force of 50 gf. SMD was calculated from data obtained by measuring the friction force while moving the sample horizontally 2 cm at a constant speed of 0.1 cm / sec with a 0.5 mm diameter piano wire contact pressed against the test specimen with a force of 10 gf. The test environment was a constant temperature and humidity condition of 20°C and 65% RH. Measurements were taken in the warp and weft directions of three test specimens, and the average of the obtained values ​​was taken as the KES surface property value.

[0062] (12) KES Compression Characteristics Using a KES-G5 compression tester, with a maximum compression load of 50 gf / cm ２ Compression speed 50 sec / mm, compression area 2 cm² ２ Measurements were taken under the following conditions. Test specimens were cut from the knitted fabric to a size of 20 cm in the warp direction and 20 cm in the weft direction. After setting them in the testing machine, a compressive load was applied, and the relationship between compressive force and displacement was obtained. The test environment was maintained under constant temperature and humidity conditions of 20°C and 65% RH. Measurements were performed on three test specimens, and the average of the obtained values ​​was evaluated as the linearity of the compressive properties (LC), the work of compression (WC), and the compressive resilience (RC).

[0063] [Example 1] A cotton linter was dissolved in a copper ammonia solution, resulting in a discharge hole diameter of 0.6 mm and a discharge hole density of 90.6 holes / cm². ２ , discharge hole density 0.26cm ２ / cm ２ Using a spinneret, a sheet was formed by continuously spinning six layers of yarn onto a net under downward tension. The oscillation condition of the conveying net was set to A / L = 0.15. Here, A is the amplitude of the conveying net [m], and L is half the distance the sheet travels during one oscillation (reciprocating motion) [m]. After forming the web without high-pressure water entanglement, it was dried. The basis weight of the resulting nonwoven fabric was 17.4 g / m². ２A regenerated cellulose fiber nonwoven fabric was obtained with a thickness of 0.07 mm, a fiber orientation degree in the longitudinal direction of 5.46, and an arithmetic mean height of 16.9. The processability of the obtained regenerated cellulose fiber nonwoven fabric when slit into narrow widths is shown in Table 1 below.

[0064] [Examples 2-10] Regenerated cellulose fiber nonwoven fabrics were obtained in the same manner as in Example 1, except that the discharge hole diameter, discharge hole density, A / L, number of layers, and water flow entanglement conditions were as shown in Table 1 below. The properties of the obtained nonwoven fabrics and the processability when slitting to narrow widths are shown in Table 1 below.

[0065] [Example 11] Pulp was dissolved in N-methylmorpholine N-oxide, and five layers were continuously spun onto a net using a spinning nozzle under flow tension by a wet spinning method to form a sheet. After forming the web without applying high-pressure water entanglement, it was dried. The discharge hole diameter, discharge hole density, A / L, number of layers, and water entanglement conditions were as shown in Table 1 below. The properties of the obtained nonwoven fabric, processability when slitting into narrow widths, and the results of the texture evaluation are shown in Table 1 below.

[0066] [Example 12] The nonwoven fabric from Example 3, with a basis weight of 10.5 g / m². ２ Polyester spunbond nonwoven fabric was prepared and laminated. Both the upper and lower rolls were then calendered using a stainless steel calendering machine at a roll pressure of 10 kN, a processing speed of 10 m / min, and 50°C to obtain a nonwoven fabric with a thickness of 0.11 mm. The processability and texture evaluation results of the obtained regenerated cellulose fiber-containing nonwoven fabric when slit into narrow widths are shown in Table 1 below.

[0067] [Example 13] Prepared cotton made of rayon short fibers 1.4 dtex x 38 mm, and used a carding machine (Otori Kiko Co., Ltd. Fine Opener SMZR) to obtain a basis weight of 35.8 g / m². ２ The card web was then made. Next, 15.5 g / m ２ A polyester spunbond nonwoven fabric was prepared and laminated onto a 70-mesh conveyor net so that the longitudinal direction of the previously prepared card web and the longitudinal direction of the polyester spunbond nonwoven fabric were aligned. The laminated web was formed by applying a high-pressure water flow of 2.0 MPa to create a water-entangled structure, and then dried. The basis weight of the resulting nonwoven fabric was 51.3 g / m².２ A regenerated cellulose fiber mixed nonwoven fabric was obtained with a thickness of 0.14 mm, a fiber orientation degree in the longitudinal direction of 7.54, and an arithmetic mean height of 22.0. The processability and texture evaluation results of the obtained regenerated cellulose fiber mixed nonwoven fabric when slit into narrow widths are shown in Table 1 below.

[0068] [Comparative Examples 1-14] Regenerated cellulose fiber nonwoven fabrics were obtained in the same manner as in Example 1, except that the discharge hole diameter, discharge hole density, A / L, number of layers, and water flow entanglement conditions were as described in Tables 2-3 below. The characteristics of the obtained nonwoven fabrics, processability during narrow slitting, and texture evaluation results are shown in Tables 2-3 below. In Comparative Example 2, the fiber orientation index was too large, and the fibers did not entangle with each other, resulting in tearing in the width direction during nonwoven fabric production, making stable production impossible. In Comparative Examples 1, 3-14, the slitting processability was poor, and many yarn breaks occurred during twisting, making stable processing impossible.

[0069] [Comparative Examples 15 and 16] Pulp was dissolved in N-methylmorpholine N-oxide, and five layers were continuously spun onto a net using a spinning head under downward tension by a wet spinning method to form a sheet. After forming the web without applying high-pressure water entanglement, it was dried. The discharge hole diameter, discharge hole density, A / L, number of layers, and water entanglement conditions were as shown in Table 3 below. The properties of the obtained nonwoven fabric and its processability when slitting narrow widths are shown in Table 3 below. Slitting processability was poor, and many yarn breaks occurred during twisting, making stable processing impossible.

[0070] [Comparative Example 17] The oscillation frequency and layer count of the conveying net were adjusted, and the basis weight of the nonwoven fabric was set to 25.0 g / m². ２ Except for changing the thickness to 0.15 mm, a regenerated cellulose fiber nonwoven fabric A was obtained in the same manner as in Comparative Example 6. Similarly, the number of oscillations of the conveying net and the number of layers were adjusted, and the basis weight of the nonwoven fabric was 25.5 g / m². ２Except for changing the thickness to 0.16 mm, a regenerated cellulose fiber nonwoven fabric B was obtained in the same manner as in Comparative Example 6. Nonwoven fabrics A and B were laminated on a 70-mesh conveyor net, and a laminated web was formed by water entanglement with a high-pressure water flow of 2.7 MPa, after which it was dried. The properties of the obtained nonwoven fabric and its processability when slitting to a narrow width are shown in Table 3 below. The slitting processability was poor. Furthermore, many thread breaks occurred during the twisting process, making stable processing impossible.

[0071] [Comparative Example 18] Using Bemberg® short fibers (material name: Cupro) 1.4 dtex x 38 mm cotton manufactured by Asahi Kasei Corporation, a parallel card web was prepared using a spunlace manufacturing facility, subjected to high-pressure water entanglement at 2.0 MPa, and then dried. The properties of the obtained nonwoven fabric and its processability when slitting to a narrow width are shown in Table 3 below. The threads broke immediately after the start of slitting, making processing impossible.

[0072] [Comparative Example 19] Cotton with 1.4 dtex x 38 mm lyocell short fibers was prepared, and a parallel card web was fabricated using spunlace manufacturing equipment. After entanglement with a high-pressure water flow of 2.0 MPa, it was dried. The properties of the obtained nonwoven fabric and its processability when slitting to a narrow width are shown in Table 3 below. The threads broke immediately after the start of slitting, making processing impossible.

[0073] [Comparative Example 20] A cotton made of rayon short fibers 1.4 dtex x 38 mm was prepared, and a parallel card web was manufactured using spunlace manufacturing equipment. After entanglement with a high-pressure water flow of 2.0 MPa, it was dried. The properties of the obtained nonwoven fabric and its processability when slitting to a narrow width are shown in Table 3 below. The threads broke immediately after the start of slitting, making processing impossible.

[0074]

[0075]

[0076]

[0077] [Example 14] The nonwoven fabric from Example 1 was slit to a width of 1.5 mm, and the yarn, which was twisted at 800 revolutions / m with a Z twist, was knitted into a jersey knit on a circular knitting machine (14 gauge). After that, it was dyed black with a reactive dye and post-processed to obtain a knitted fabric.

[0078] [Example 15] A knitted fabric was obtained in the same manner as in Example 14, except that the nonwoven fabric from Example 9 was used.

[0079] [Comparative Example 21] A knitted fabric was obtained in the same manner as in Example 14, except that washi paper yarn (OJO 1515 Std Z500, manufactured by Oji Fiber Co., Ltd.) was used.

[0080] Table 4 below shows the physical properties of the knitted fabrics obtained in Examples 14, 15, and Comparative Example 21, as well as the KES texture evaluation results. From the KES bending characteristics, it can be seen that Examples 14 and 15 are more flexible in bending than Comparative Example 21, and from the KES surface characteristics, Examples 14 and 15 have smoother surfaces than Comparative Example 21. From the KES compression characteristics, it can be seen that Examples 14 and 15 are more easily compressed than Comparative Example 21. Furthermore, from the sensory evaluation results, Examples 14 and 15 had a soft, supple, and bulky texture, which was different from that of Comparative Example 21 and was a uniquely good texture. Comparing Examples 14 and 15, Example 14 had a stronger sense of stiffness and crispness, while Example 15 was a softer fabric with superior drape. This is thought to be due to the difference in the warp stiffness per unit basis weight of the nonwoven fabric.

[0081]

[0082] The nonwoven fabric of the present invention is composed of regenerated cellulose fibers derived from natural fibers, which are environmentally friendly, rather than petroleum-derived fibers, while achieving both "low basis weight / thinness" and "high strength." As a result, the nonwoven fabric can be easily processed, cut into thin and narrow strips (slit formation), and thereby meet the requirement for fine denier slit yarn. Therefore, the nonwoven fabric of the present invention can be used as a processing raw material for narrow tapes and slit yarns, which are suitable as handicraft materials and knitted fabric materials for making knitted fabrics using tools such as knitting needles and crochet hooks or knitting machines.

Claims

1. A nonwoven fabric containing regenerated cellulose fibers, having a fiber orientation index of 4 or more and 8 or less calculated from small-angle X-ray scattering (SAXS) measurements, and having an arithmetic mean height of 25 μm or less on the surface.

2. The nonwoven fabric according to claim 1, wherein the vertical stiffness per unit basis weight is 5 mm or more and 15 mm or less.

3. The nonwoven fabric according to claim 1 or 2, wherein the regenerated cellulose fiber content is 50 wt% or more based on the total weight of the nonwoven fabric.

4. Weight: 10 g / m ２ 30g / m or more ２ The nonwoven fabric according to claim 1 or 2, which is as follows:

5. The nonwoven fabric according to claim 1 or 2, wherein the thickness is 0.05 mm or more and 0.20 mm or less.

6. The nonwoven fabric according to claim 1 or 2, wherein the longitudinal breaking strength per unit basis weight is 2 N / 50 mm or more and 6 N / 50 mm or less.

7. The nonwoven fabric according to claim 1 or 2, wherein the cross-section of the regenerated cellulose fibers is substantially circular.

8. A narrow tape made by cutting the nonwoven fabric described in claim 1 or 2 to a width of 0.5 mm or more and 10 mm or less.

9. A slit yarn formed by twisting the narrow tape described in claim 8.

10. The slit yarn according to claim 9, wherein the fiber orientation index calculated from small-angle X-ray scattering (SAXS) measurement is 4 or more and 9 or less.

11. A yarn obtained by twisting the narrow tape described in claim 8 or the slit yarn described in claim 9 with another thread-like material or tape.

12. A knitted fabric made using the narrow tape described in claim 8 and / or the slit yarn described in claim 9.

13. A fabric woven using the narrow tape described in claim 8 and / or the slit yarn described in claim 9.

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