Stretching multifilament and method for manufacturing same, multifilament and method for manufacturing same, and staple and method for manufacturing same

Abstract

The present invention is a stretching multifilament having 30 or more single threads. The single threads contain a poly(3-hydroxyalkanoate)-based resin and a nucleating agent. The average value of the fineness of the single threads is 30 dtex or lower, and the coefficient of variation for the fineness of the single threads is 33% or lower.

Description

Multifilament for drawing and its manufacturing method, multifilament and its manufacturing method, and staple and its manufacturing method

[0001] The present invention relates to a multifilament for drawing and a method for producing the same, a multifilament and a method for producing the same, and a staple and a method for producing the same.

[0002] In recent years, plastic waste has become a major problem that causes a significant burden on the global environment, including impacts on ecosystems, the generation of harmful gases when burned, and global warming due to the large amount of heat generated by combustion. As a solution to these problems, biodegradable plastics have been actively developed.

[0003] Among these biodegradable plastics, those made from plant-derived raw materials emit carbon dioxide when burned, which was originally present in the air and does not increase the amount of carbon dioxide in the atmosphere. This is called carbon neutrality, and is considered important under the Kyoto Protocol, which imposed carbon dioxide reduction targets, and active use of such plastics is desired.

[0004] Recently, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester resins, and in particular polyhydroxyalkanoate resins, have been attracting attention as biodegradable plastics that are produced by microorganisms using plant-derived raw materials as a carbon source.

[0005] Patent Document 1 discloses a multifilament having a plurality of single yarns containing a 3-hydroxyalkanoate polymer.

[0006] Patent Document 1 also discloses that the multifilament is obtained by a melt extrusion method. Specifically, Patent Document 1 discloses a process including a step (A) of obtaining a plurality of molten yarns by discharging a melt using a spinning nozzle having four discharge holes, and a step (B) of obtaining a multifilament to be drawn by cooling the plurality of molten yarns while conveying them. The multifilament to be drawn is then drawn with a roll to obtain a multifilament.

[0007] On the other hand, with regard to modified cross-section fibers containing wholly aromatic polyamides, the coefficient of variation of single filament fineness is 9.0% or less, and there are known wholly aromatic polyamide modified cross-section fibers having a specific relationship (for example, Patent Document 2).

[0008] International Publication No. 2015 / 029316 Japanese Patent Application Laid-Open No. 2014-122448

[0009] Incidentally, with regard to multifilaments in which the single yarns contain a poly(3-hydroxyalkanoate)-based resin, there will be a demand in the future for multifilaments in which the single yarns are thin and have high strength. Here, if the draw ratio is increased when drawing a multifilament to be drawn to obtain a multifilament, the orientation of the polymer in the multifilament increases, and as a result, the strength of the obtained multifilament increases. However, the present inventors prepared multifilaments to be drawn in which the single yarns are thin using a poly(3-hydroxyalkanoate)-based resin, and attempted to draw the multifilament to be drawn at a high draw ratio, but the single yarns broke during drawing, and it was not possible to obtain a multifilament.

[0010] Therefore, the first object of the present invention is to obtain a multifilament for drawing in which single yarns contain a poly(3-hydroxyalkanoate)-based resin, and which can easily produce a multifilament with high strength even if the average single yarn fineness is small. The second object of the present invention is to obtain a multifilament in which single yarns contain a poly(3-hydroxyalkanoate)-based resin, and which can easily produce a multifilament with high strength even if the average single yarn fineness is small. The third object of the present invention is to obtain a staple from the multifilament cut.

[0011] The first aspect of the present invention relates to a multifilament for drawing having 30 or more single yarns, wherein the single yarns contain a poly(3-hydroxyalkanoate)-based resin and a crystal nucleating agent, the average fineness of the single yarns is 30 dtex or less, and the coefficient of variation of the fineness of the single yarns is 33% or less. Preferably, the poly(3-hydroxyalkanoate)-based resin contains a poly(3-hydroxybutyrate)-based resin.

[0012] A second aspect of the present invention relates to a drawn multifilament, the multifilament having 30 or more single yarns, the single yarns containing a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average fineness of the single yarns being 20 dtex or less, and the coefficient of variation of the fineness of the single yarns being 33% or less.

[0013] The third aspect of the present invention relates to a staple in which the multifilament according to claim 3 is cut and has a length of 20 cm or less.

[0014] A fourth aspect of the present invention is a method for producing a multifilament to be drawn by a melt spinning method, the method comprising: a step (A) of obtaining 30 or more molten yarns by discharging a melt by the melt spinning method using a spinning nozzle having 30 or more discharge holes; and a step (B) of obtaining a multifilament to be drawn by blowing a gas at 0°C or more and 50°C or less onto the 30 or more molten yarns to cool the 30 or more yarns, the melt containing a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent; the average fineness of the single yarns in the multifilament to be drawn is 30 dtex or less; and in the step (B), the heat transfer coefficient between the 30 or more molten yarns and the gas is 60 W / (m ２ Preferably, in the step (B), the heat transfer coefficient is 125 W / (m ２ Preferably, in the step (B), the velocity of the gas blown onto the 30 or more yarns is set to 0.1 m / s or more.

[0015] A fifth aspect of the present invention relates to a method for producing a multifilament, comprising: obtaining the multifilament to be drawn by the method for producing a multifilament to be drawn; and (C) drawing the multifilament to be drawn by 1.5 times or more in a drawing roll section to obtain a multifilament. Preferably, in the step (B), the multifilament to be drawn is obtained by blowing a gas from 0°C to 50°C onto 30 or more of the raw yarns in a molten state, thereby cooling the 30 or more raw yarns to 50°C or less, and in the step (C), the multifilament to be drawn is heated and drawn in the drawing roll section.

[0016] A sixth aspect of the present invention relates to a method for producing a staple, which comprises obtaining the multifilament by the method for producing a multifilament and cutting the multifilament to obtain staples having a length of 20 cm or less.

[0017] According to the present invention, it is possible to provide a multifilament for drawing in which single yarns contain a poly(3-hydroxyalkanoate)-based resin, and which is likely to produce a multifilament with high strength even if the average single yarn fineness is small.Furthermore, according to the present invention, it is possible to provide a multifilament in which single yarns contain a poly(3-hydroxyalkanoate)-based resin, and which is likely to produce a multifilament with high strength even if the average single yarn fineness is small.Furthermore, according to the present invention, it is possible to provide a staple in which the multifilament is cut.

[0018] 1 is a schematic diagram of an apparatus used in steps (A) and (B) of the first embodiment, a schematic diagram of an apparatus used in step (C) of the first embodiment, and a schematic diagram of an apparatus used in a second embodiment.

[0019] An embodiment of the present invention will be described below.

[0020] <Multifilament for drawing> First, the multifilament for drawing according to this embodiment will be described. The multifilament for drawing according to this embodiment has 30 or more first single yarns. The first single yarns contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent. The average fineness of the first single yarns is 30 dtex or less. The coefficient of variation of the fineness of the first single yarns is 33% or less.

[0021] The multifilament for drawing according to this embodiment is drawn to obtain a multifilament, and the multifilament is cut to obtain a staple.

[0022] As described above, with regard to fibers containing a wholly aromatic polyamide, there are known wholly aromatic polyamide fibers having a coefficient of variation of single yarn fineness of 9.0% or less (for example, Patent Document 2). However, unlike wholly aromatic polyamides, poly(3-hydroxyalkanoate)-based resins are resins that are difficult to mold. For this reason, it has been difficult to reduce the average fineness of the first single yarns while also reducing the coefficient of variation of the fineness of the first single yarns in a multifilament for drawing having first single yarns containing a poly(3-hydroxyalkanoate)-based resin. Therefore, the present inventors conducted extensive research into a multifilament for drawing having 30 or more first single yarns containing a poly(3-hydroxyalkanoate)-based resin, and have succeeded in reducing the average fineness of the first single yarns to 30 dtex or less and the coefficient of variation of the fineness of the first single yarns to 33% or less. The present inventors have further conducted extensive research into a multifilament for drawing having 30 or more first single yarns containing a poly(3-hydroxyalkanoate) resin, and have found that by setting the average fineness of the first single yarns to 30 dtex or less and the coefficient of variation of the fineness of the first single yarns to 33% or less, it is possible to provide a multifilament for drawing that is likely to produce a multifilament with high strength even if the average fineness of the single yarns is small.

[0023] The first single yarn is a polymer composition containing a polymer component formed into a thread shape.

[0024] The polymer component contains a poly(3-hydroxyalkanoate)-based resin. The polymer component may contain other polymers in addition to the poly(3-hydroxyalkanoate)-based resin. The polymer composition contains a crystal nucleating agent. The polymer composition may contain other additives in addition to the crystal nucleating agent.

[0025] The poly(3-hydroxyalkanoate) resin is a polyester containing 3-hydroxyalkanoic acid as a monomer. That is, the poly(3-hydroxyalkanoate) resin is a resin containing 3-hydroxyalkanoic acid as a structural unit. The poly(3-hydroxyalkanoate) resin is also a biodegradable polymer. In this embodiment, "biodegradability" refers to the ability to be decomposed into low-molecular-weight compounds by microorganisms in nature. Specifically, biodegradability can be determined based on tests appropriate for each environment, such as ISO 14855 (compost) and ISO 14851 (activated sludge) under aerobic conditions, and ISO 14853 (aqueous phase) and ISO 15985 (solid phase) under anaerobic conditions. Microbial decomposition in seawater can also be evaluated by measuring biochemical oxygen demand. The poly(3-hydroxyalkanoate) resin may be a homopolymer or a copolymer.

[0026] The poly(3-hydroxyalkanoate) resin preferably contains a structural unit represented by the following formula (1): [—CHR—CH ２ —CO—O—] (1) (In the formula (1), R is C ｐ H ２ｐ＋１ and p is an integer of 1 to 15.

[0027] The poly(3-hydroxyalkanoate)-based resin preferably includes a poly(3-hydroxybutyrate)-based resin. The poly(3-hydroxybutyrate)-based resin is a resin containing 3-hydroxybutyrate as a structural unit. The poly(3-hydroxybutyrate)-based resin may be a homopolymer or a copolymer.

[0028] Examples of poly(3-hydroxyalkanoate) resins containing 3-hydroxybutyrate as a structural unit include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate), and the like. Here, P3HB means poly(3-hydroxybutyrate). P3HB3HH means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). P3HB3HV means poly(3-hydroxybutyrate-co-3-hydroxyvalerate). P3HB4HB means poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0029] Since P3HB has the function of promoting the crystallization of P3HB itself and poly(3-hydroxyalkanoate) resins other than P3HB, the poly(3-hydroxyalkanoate) resin preferably contains P3HB.

[0030] From the viewpoint of achieving both excellent biodegradability and moldability, the poly(3-hydroxyalkanoate) resin is preferably, but not particularly limited to, P3HB, P3HB3HH, P3HB3HV, P3HB4HB, etc. Furthermore, from the viewpoint of increasing the strength of the multifilament obtained by drawing the multifilament to be drawn according to the present embodiment and increasing the moldability of the multifilament to be drawn and the multifilament, P3HB3HH is preferred as the poly(3-hydroxyalkanoate) resin.

[0031] The poly(3-hydroxyalkanoate) resin preferably contains 85.0 mol % to 99.5 mol %, more preferably 85.0 mol % to 97.0 mol %, of 3-hydroxybutyrate as a structural unit. When the poly(3-hydroxyalkanoate) resin contains 85.0 mol % or more of 3-hydroxybutyrate as a structural unit, the rigidity of the multifilament according to this embodiment is increased. Furthermore, when the poly(3-hydroxyalkanoate) resin contains 99.5 mol % or less of 3-hydroxybutyrate as a structural unit, the multifilament according to this embodiment is excellent in flexibility.

[0032] The polymer component may contain only one type of poly(3-hydroxyalkanoate) resin, or may contain two or more types. When the poly(3-hydroxyalkanoate) resin contains a copolymer (such as P3HB3HH), the poly(3-hydroxyalkanoate) resin may contain two or more types of copolymers having different average composition ratios of structural units.

[0033] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is preferably 50,000 to 3,000,000, more preferably 50,000 to 1,500,000. When the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 3,000,000 or less, the multifilament to be drawn according to this embodiment and the molding of the multifilament are facilitated. When the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 50,000 or more, the strength of the multifilament can be increased. Note that the weight-average molecular weight in this embodiment refers to a value measured from the polystyrene-equivalent molecular weight distribution using gel permeation chromatography (GPC) with a chloroform eluent. A column appropriate for measuring the molecular weight may be used as the column for the GPC.

[0034] The other polymer is preferably biodegradable.

[0035] Examples of other biodegradable polymers include polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, unmodified starch, modified starch, cellulose acetate, and chitosan. The polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. The polymer composition may contain one or more other polymers.

[0036] The polymer component preferably contains 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more of a poly(3-hydroxyalkanoate) resin.

[0037] The multifilament for drawing according to this embodiment contains a biodegradable polymer, and therefore even if the multifilament or staple obtained from the multifilament for drawing is discarded in the environment, the multifilament or the staple is easily decomposed in the environment, thereby reducing the burden on the environment.

[0038] The polymer composition contains a crystal nucleating agent. The crystal nucleating agent is a compound that can promote crystallization of the poly(3-hydroxyalkanoate)-based resin. The crystal nucleating agent has a higher melting point than the poly(3-hydroxyalkanoate)-based resin. Examples of the crystal nucleating agent include inorganic substances (boron nitride, titanium oxide, talc, layered silicates, calcium carbonate, sodium chloride, metal phosphates, etc.); sugar alcohol compounds derived from natural products (pentaerythritol, erythritol, galactitol, mannitol, arabitol, etc.); polyvinyl alcohol; chitin; chitosan; polyethylene oxide; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylate esters; dicarboxylic acid derivatives (dimethyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl stearate, etc.); Examples of suitable poly(3-hydroxyalkanoate) resins include cyclic compounds having C═O and a functional group selected from NH, S, and O in the molecule (such as indigo, quinacridone, and quinacridone magenta); sorbitol derivatives (such as bisbenzylidene sorbitol and bis(p-methylbenzylidene)sorbitol); compounds containing a nitrogen-containing heteroaromatic nucleus (such as a pyridine ring, triazine ring, and imidazole ring) (such as pyridine, triazine, and imidazole); phosphate ester compounds; bisamides of higher fatty acids; metal salts of higher fatty acids; and branched polylactic acid. Furthermore, the poly(3-hydroxyalkanoate) resin P3HB can also be used as a crystal nucleating agent. These may be used alone or in combination of two or more.

[0039] As the crystal nucleating agent, from the viewpoint of the effect of improving the crystallization rate of the poly(3-hydroxyalkanoate) resin and from the viewpoint of compatibility and affinity with the poly(3-hydroxyalkanoate) resin, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan are preferred. Among the sugar alcohol compounds, pentaerythritol is preferred.

[0040] The nucleating agent preferably has a crystalline structure at room temperature (25°C). The nucleating agent having a crystalline structure at room temperature (25°C) has the advantage of further accelerating the crystallization of the poly(3-hydroxyalkanoate) resin. Furthermore, the nucleating agent having a crystalline structure at room temperature (25°C) is preferably in a powder form at room temperature (25°C). Furthermore, the average particle size of the nucleating agent in a powder form at room temperature (25°C) is preferably 10 μm or less.

[0041] The content of the crystal nucleating agent in the polymer composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the poly(3-hydroxyalkanoate)-based resin. Having the content of the crystal nucleating agent in the polymer composition be 0.05 parts by mass or more, per 100 parts by mass of the poly(3-hydroxyalkanoate)-based resin, has the advantage of further promoting crystallization of the poly(3-hydroxyalkanoate)-based resin. Furthermore, the content of the crystal nucleating agent in the polymer composition is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the poly(3-hydroxyalkanoate)-based resin. By having the content of the crystal nucleating agent in the polymer composition be 10 parts by mass or less relative to 100 parts by mass of the poly(3-hydroxyalkanoate)-based resin, when a multifilament for drawing is produced from a melt of the polymer composition, the viscosity of the melt can be reduced, which has the advantage of facilitating the production of a multifilament for drawing. Note that P3HB is a poly(3-hydroxyalkanoate)-based resin and can also function as a crystal nucleating agent, so when the polymer composition contains P3HB, the amount of P3HB is included in both the amount of the poly(3-hydroxyalkanoate)-based resin and the amount of the crystal nucleating agent.

[0042] Examples of other additives include lubricants, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, flame retardants, inorganic fillers, organic fillers, antistatic agents, etc.

[0043] The polymer composition preferably contains the lubricant. When the first single yarn contains the lubricant, the lubricity of the first single yarn improves, and fusion between the first single yarns can be suppressed. Examples of the lubricant include a compound having an amide bond. The compound having an amide bond preferably contains one or more compounds selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0044] The content of the lubricant in the polymer composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the polymer component. Having the content of the lubricant in the polymer composition be 0.05 parts by mass or more, per 100 parts by mass of the polymer component, offers the advantage of excellent lubricity for the first single yarn. Furthermore, the content of the lubricant in the polymer composition is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and most preferably 5 parts by mass or less, per 100 parts by mass of the polymer component. Having the content of the lubricant in the polymer composition be 12 parts by mass or less, per 100 parts by mass of the polymer component, offers the advantage of being able to inhibit the lubricant from bleeding out onto the surface of the multifilament to be drawn, the multifilament, or the staple.

[0045] From the viewpoint of improving the molding processability of the multifilament for drawing, the plasticizer is preferably a biodegradable plasticizer. Examples of biodegradable plasticizers include polyglycerin fatty acid esters (PGFE) (e.g., "Chirabazole" manufactured by Taiyo Kagaku Co., Ltd.), mixed-group dibasic acid esters (e.g., "DAIFATTY" manufactured by Daihachi Chemical Industry Co., Ltd.), and glycerin fatty acid esters (e.g., "Rikemal" manufactured by Riken Vitamin Co., Ltd.).

[0046] From the viewpoint of improving the molding processability of the multifilament for drawing, the plasticizer is preferably a plasticizer that becomes a supercritical fluid under the temperature and pressure when the material is kneaded while being heated in the step (A) described later, and that becomes a gas at room temperature and normal pressure (25°C, 1 atmosphere).２ ), carbon dioxide, lower aliphatic hydrocarbons, etc. Examples of the lower aliphatic hydrocarbons include propane, butane, and isobutane.

[0047] The multifilament for drawing according to this embodiment has 30 or more first single yarns, preferably 30 to 500,000 first single yarns, and more preferably 50 to 300,000 first single yarns.

[0048] The cross-sectional shape of the first single yarn is, for example, a circular shape (a concept including a perfect circle, a nearly circular shape, an ellipse, and a nearly ellipse).

[0049] The average fineness of the first single yarn is 30 dtex or less. The average fineness of the first single yarn is preferably 20 dtex or less, more preferably 10 dtex or less. The average fineness of the first single yarn is preferably 1.5 dtex or more, more preferably 3.0 dtex or more.

[0050] In this embodiment, the fineness of a yarn refers to the thickness of the yarn and is defined as the mass per unit length, expressed in units of dtex (g) per 10,000 m.

[0051] In this embodiment, the average value of the fineness of the first single yarns can be determined as follows. First, the fineness (total fineness) of the multifilament for drawing is measured. Then, the number of first single yarns contained in the multifilament for drawing is determined. Then, the average value of the fineness of the first single yarns is determined using the following formula: Average value of the fineness of the first single yarns = Fineness of the multifilament for drawing / Number of first single yarns contained in the multifilament for drawing

[0052] The coefficient of variation of the fineness of the first single yarn is 33% or less. The coefficient of variation of the fineness of the first single yarn is preferably 32% or less, more preferably 30% or less, and even more preferably 28% or less. Although the coefficient of variation of the fineness of the first single yarn is preferably small, the coefficient of variation of the fineness of the first single yarn is, for example, 5% or more, more specifically 10% or more.

[0053] When the coefficient of variation of the fineness of the first single yarn is 33% or less, the stability of the doubling process (the "doubling" will be described later) and the drawing process is improved. Furthermore, when the coefficient of variation of the fineness of the first single yarn is 33% or less, the mechanical properties (strength, etc.) of the multifilament obtained by drawing are improved.

[0054] That is, by setting the coefficient of variation of the fineness of the first single yarn to 33% or less, extremely thin first single yarns and extremely thick first single yarns are less likely to be included in the draw multifilament. Since extremely thin yarns are less likely to be included in the draw multifilament, the stability of the doubling process ("doubling" will be described later) and the drawing process is improved. Specifically, the payout property of the draw multifilament and the multifilament from the winding roll section (specifically, the bobbin of the winding roll section) ("winding roll section" and "bobbin" will be described later) ("bobbin" is a concept that includes "paper tube") is improved. Furthermore, yarn breakage when drawing tension is applied to the draw multifilament is suppressed. Furthermore, winding of the draw multifilament around the drawing roll section ("drawing roll section" will be described later) is improved. Furthermore, sagging of the draw multifilament and the multifilament during transport is suppressed. Furthermore, since the multifilament for drawing is less likely to contain extremely thick yarns, drawing stress acts uniformly on the multifilament for drawing when the multifilament for drawing is drawn, thereby suppressing drawing unevenness. As a result, the fineness of the first single yarns is uniformly reduced, and the mechanical properties (strength, etc.) of the resulting multifilament are improved.

[0055] The coefficient of variation of the fineness of the first single yarn can be determined as follows. First, the multifilament for drawing is cut perpendicular to the longitudinal direction with a blade, and the cut surface is photographed under a microscope to obtain a cross-sectional photograph. Next, in the cross-sectional photograph, the cross-sectional area of ​​each of the first single yarns constituting the multifilament for drawing is measured. Alternatively, 30 or more first single yarns are randomly selected from the multifilament for drawing, and the cross-sectional area of ​​each first single yarn is measured. That is, since it may not be practical to measure the cross-sectional area of ​​each of the first single yarns constituting the multifilament for drawing, 30 or more first single yarns may be randomly selected from the multifilament for drawing, and the cross-sectional area of ​​each first single yarn may be measured. Then, from the cross-sectional area of ​​each first single yarn, the arithmetic mean value of the cross-sectional area of ​​the first single yarn and the standard deviation of the cross-sectional area of ​​the first single yarn are determined. Next, the coefficient of variation of the fineness of the first single yarn is determined using the following formula. Coefficient of variation (%) of fineness of first single yarn = (standard deviation of cross-sectional area of ​​first single yarn / arithmetic mean value of cross-sectional area of ​​first single yarn) × 100 (%). The method for measuring the cross-sectional area is also described in "8.5.3 Fineness variation rate" of JIS L 1015:2021 "Test method for chemical fiber staples".

[0056] From the viewpoint of suppressing fusion between adjacent first single yarns and suppressing separation between adjacent first single yarns due to static electricity, the multifilament for drawing according to this embodiment preferably further comprises a spinning oil on the surface of the first single yarn. Examples of the spinning oil include cationic surfactants, anionic surfactants, nonionic surfactants, refined esterified oils, mineral oils, poly(oxyethylene) alkyl ethers, silicone oils, and paraffin waxes. These may be used alone or in combination of two or more. From the viewpoint of suppressing fusion between adjacent first single yarns, silicone oil is preferred as the spinning oil. From the viewpoint of suppressing separation between adjacent first single yarns due to static electricity, an anionic surfactant or a nonionic surfactant is preferred as the spinning oil. For example, a spinning oil containing silicone oil and an anionic surfactant (e.g., "Polymax FKY" manufactured by Marubishi Chemical Co., Ltd.) can be used as the spinning oil.

[0057] <Multifilament> The multifilament according to this embodiment is a drawn multifilament. The multifilament according to this embodiment has 30 or more second single yarns. The second single yarns contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent. The average fineness of the second single yarns is 20 dtex or less. The coefficient of variation of the fineness of the second single yarns is 33% or less.

[0058] The second single yarn is formed from the polymer composition in the form of a thread.

[0059] The multifilament according to this embodiment has 30 or more second single yarns, preferably 30 to 500,000, and more preferably 50 to 300,000.

[0060] The cross-sectional shape of the second single yarn is, for example, a circular shape (a concept including a perfect circle, a nearly circular shape, an ellipse, and a nearly ellipse).

[0061] The average fineness of the second single yarns is 20 dtex or less. Furthermore, if the average fineness of the second single yarns is 20 dtex or less, the average fineness of the second single yarns may be determined based on the required quality in the application of the multifilament or the required quality of the staple obtained from the multifilament. The average fineness of the second single yarns is preferably greater than 1.0 dtex, more preferably 1.2 dtex or more, and even more preferably 1.5 dtex or more. The average fineness of the second single yarns is preferably 18 dtex or less, more preferably 16 dtex or less.

[0062] In this embodiment, the average value of the fineness of the second single yarns can be determined as follows. First, the fineness (total fineness) of the multifilament is measured. Then, the number of second single yarns contained in the multifilament is determined. Then, the average value of the fineness of the second single yarns is determined using the following formula: Average value of the fineness of the second single yarns = Fineness of the multifilament / Number of second single yarns contained in the multifilament

[0063] The coefficient of variation of the fineness of the second single yarn is 33% or less. The coefficient of variation of the fineness of the second single yarn is preferably 32% or less, more preferably 30% or less, and even more preferably 28% or less. Although the coefficient of variation of the fineness of the second single yarn is preferably small, the coefficient of variation of the fineness of the second single yarn is, for example, 5% or more, more specifically 10% or more.

[0064] The coefficient of variation of the fineness of the second single yarn can be determined as follows. First, the multifilament is cut perpendicular to the longitudinal direction with a blade, and the cut surface is photographed under a microscope to obtain a cross-sectional photograph. Next, in the cross-sectional photograph, the cross-sectional area of ​​each second single yarn is measured for all second single yarns constituting the multifilament. Alternatively, 30 or more second single yarns are randomly selected from the multifilament, and the cross-sectional area of ​​each second single yarn is measured. That is, since it may not be practical to measure the cross-sectional area of ​​each second single yarn for all second single yarns constituting the multifilament, 30 or more second single yarns may be randomly selected from the multifilament, and the cross-sectional area of ​​each second single yarn may be measured. Then, from the cross-sectional area of ​​each second single yarn, the arithmetic mean value of the cross-sectional area of ​​the second single yarn and the standard deviation of the cross-sectional area of ​​the second single yarn are determined. Next, the coefficient of variation of the fineness of the second single yarn is determined using the following formula. Coefficient of variation (%) of fineness of second single yarn = (standard deviation of cross-sectional area of ​​second single yarn / arithmetic mean value of cross-sectional area of ​​second single yarn) × 100 (%). The method for measuring the cross-sectional area is also described in "8.5.3 Fineness variation rate" of JIS L 1015:2021 "Test method for chemical fiber staples".

[0065] The average tensile strength of the second single yarn is preferably 1.5 cN / dtex or more, more preferably 1.7 cN / dtex or more, and even more preferably 2.0 cN / dtex or more. Although a larger average tensile strength of the second single yarn is preferable, the tensile strength of the second single yarn is, for example, 20 cN / dtex or less (specifically, 10 cN / dtex or less).

[0066] The average value of the tensile strength of the second single yarns can be determined as follows. First, the tensile strength of each of all second single yarns constituting the multifilament is measured. Alternatively, 10 or more second single yarns are randomly selected from the multifilament, and the tensile strength of each second single yarn is measured. That is, since it may not be practical to measure the tensile strength of each second single yarn of all second single yarns constituting the multifilament, 10 or more second single yarns may be randomly selected from the multifilament, and the tensile strength of each second single yarn may be measured. Then, the arithmetic mean value of the tensile strength of the second single yarns is determined from the tensile strengths of each second single yarn, and this value is defined as the average value of the tensile strength of the second single yarns.

[0067] The tensile strength of each second single yarn can be measured based on JIS L 1015:2021 "Test Method for Chemical Fiber Staples" at an initial length of 20 mm and a speed of 20 mm / min. For example, the tensile strength of each second single yarn can be determined as follows. First, using a tensile measuring device Autograph AG-I (manufactured by Shimadzu Corporation), the load (cN) at break of each second single yarn is measured under the following conditions: Initial length of each second single yarn: 20 mm Pulling speed: 20 mm / min Load cell: load cell with a rated capacity of 5 N Furthermore, the fineness of each second single yarn is measured. The fineness of each second single yarn can be measured, for example, by the autobibroscope method. Then, the tensile strength of each second single yarn is calculated using the following formula: Tensile strength of each second single yarn (cN / dtex) = Load at break of each second single yarn (cN) / Fineness of each second single yarn

[0068] <Staple> The staple according to this embodiment is a staple obtained by cutting the multifilament according to this embodiment. The length of the staple according to this embodiment (also referred to as "fiber length") is 20 cm or less, specifically 0.1 to 10 cm. The staple length means the "average fiber length" obtained by "c) Method C (substitution method)" of "8.4.1 Average fiber length" of "8.4 Fiber length" in JIS L1015:2021 "Test methods for synthetic fiber staples."

[0069] The staple according to the present embodiment may be a crimped yarn (crimped yarn). In other words, the staple according to the present embodiment may have a crimp. The length (fiber length) of the crimped staple can be appropriately set depending on the application, and may be, for example, 1.5 to 16 cm, 2.0 to 11 cm, or 2.5 to 7.6 cm.

[0070] From the viewpoints of improving the carding ability when obtaining a nonwoven fabric from staples, improving the texture of the obtained nonwoven fabric, and reducing the water absorption rate of the nonwoven fabric to thereby improve the quick-drying ability of the nonwoven fabric, the number of crimps of the staples is preferably 5 to 25 per 25 mm, more preferably 6 to 20 per 25 mm, even more preferably 7 to 18 per 25 mm, and particularly preferably 8 to 17 per 25 mm. The number of crimps of the staples means the number of crimps per 25 mm of staple length. Furthermore, the number of crimps of the staples means the average number of crimps of 15 staples randomly selected. When there are fewer than 15 staples, the number means the average number of crimps of all staples. The number of crimps of each staple can be determined by using a microscope to count the number of crimps within a 25 mm length of the staple. When the length of each staple is less than 25 mm, the number of crimps per 25 mm may be determined by counting the number of crimps over the entire length using a microscope.

[0071] <Method for producing a multifilament for drawing, and method for producing a multifilament> The method for producing a multifilament for drawing according to this embodiment is a method for obtaining a multifilament for drawing by a melt spinning method. The method for producing a multifilament for drawing according to this embodiment includes: a step (A) of obtaining 30 or more molten yarns by discharging a melt by the melt spinning method using a spinning nozzle having 30 or more discharge holes; and a step (B) of obtaining a multifilament for drawing by blowing a gas at 0°C or more and 50°C or less onto the 30 or more molten yarns to cool the 30 or more yarns. The melt contains a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent. The average fineness of the single yarns in the multifilament for drawing is 30 dtex or less. In the step (B), the heat transfer coefficient between the 30 or more molten yarns and the gas is set to 60 W / (m ２ ・K) or higher.

[0072] In the step (B), the velocity of the gas blown onto the 30 or more original yarns is preferably 0.3 m / s or more.

[0073] In the step (A), the melt is the polymer composition in a molten state.

[0074] The method for producing a multifilament according to the present embodiment includes obtaining the multifilament to be drawn by the method for producing a multifilament to be drawn according to the present embodiment. The method for producing a multifilament according to the present embodiment also includes a step (C) of drawing the multifilament to be drawn by 1.5 times or more in a drawing roll section to obtain a multifilament.

[0075] Preferably, in the step (B), a gas of 0°C or more and 50°C or less is blown onto 30 or more of the raw yarns in a molten state to cool the 30 or more raw yarns to 50°C or less, thereby obtaining the multifilament to be drawn, and in the step (C), the multifilament to be drawn is heated and drawn by the drawing roll section.

[0076] (First embodiment: sequential drawing method) Hereinafter, a method for producing a multifilament to be drawn and a multifilament according to the first embodiment will be described with reference to Figs. 1 and 2 , taking as an example a method for producing a multifilament to be drawn and a multifilament by the sequential drawing method (also referred to as a "second drawing method").

[0077] (Step (A)) As shown in Fig. 1 , in the step (A), first, the materials for the melt are fed into a material feed section 101. Next, the materials fed from the material feed section 101 are kneaded while being heated in a kneading extruder 102, thereby obtaining the melt. A screw extruder is preferably used as the kneading extruder 102. The kneading extruder 102 may be a single-screw extruder or a twin-screw extruder.

[0078] Then, using a spinning nozzle 104 having 30 or more discharge holes, the molten material obtained in the kneading extruder 102 is discharged from the 30 or more discharge holes to obtain 30 or more molten raw yarns 100A. The flow rate of the molten material discharged from the multiple discharge holes of the spinning nozzle 104 is adjusted by a gear pump 103.

[0079] The temperature of the spinning nozzle 104 is, for example, 140 to 180°C.

[0080] The spinning nozzle 104 has 30 or more discharge holes, preferably 30 to 10,000, and more preferably 30 to 5,000. The shape and size of each discharge hole are selected according to the properties required of the multifilament to be drawn (for example, appearance, fineness, strength, cross-sectional shape, etc.). The shape of the discharge hole is, for example, circular (a concept including perfect circle, approximately circle, ellipse, and approximately ellipse). The area of ​​each discharge hole is determined to be, for example, 10 to 5,000 times the cross-sectional area of ​​the first single yarn in the multifilament to be drawn. In this embodiment, the shapes of the discharge holes are approximately the same. Furthermore, the areas of the discharge holes are approximately the same. The area of ​​each discharge hole is preferably 1.0 x 10 －３ ~20mm ２ , more preferably 5.0 × 10 －３ ~10mm ２ is.

[0081] The speed at which the molten material is extruded from the spinning nozzle 104 (hereinafter also referred to as the "spinning nozzle flow rate") is preferably 0.02 m / min to 20 m / min, more preferably 0.05 m / min to 10 m / min, and even more preferably 0.1 m / min to 5.0 m / min.

[0082] In the first embodiment, the spinning oil may be applied to the surface of each of the 30 or more cooled raw yarns 100A.

[0083] (Step (B)) In the step (B), a gas of 0°C or more and 50°C or less is blown onto the 30 or more molten yarns obtained in the step (A) to cool the 30 or more yarns, thereby obtaining a multifilament for drawing. In the first embodiment, the yarn 100A is cooled with a gas of 0°C or more and 50°C or less in a first cooling box 105. In the first embodiment, the yarn 100A cooled in the first cooling box 105 may be further cooled with a gas of 0°C or more and 50°C or less in a second cooling box 106.

[0084] In the step (B), the temperature of the gas blown onto the plurality of molten yarns 100A obtained in the step (A) is 0 to 50°C, preferably 0 to 40°C, and more preferably 15 to 40°C. When the temperature of the gas is 0°C or higher, mutual fusion of the first single yarns of the multifilament to be drawn is suppressed. Furthermore, when the temperature of the gas is 0°C or higher, the mechanical properties (strength, etc.) of the multifilament to be drawn are improved. When the temperature of the gas is 50°C or lower, unevenness in the fineness of the first single yarns is suppressed (the coefficient of variation of the first single yarns can be reduced). Furthermore, when the temperature of the gas is 50°C or lower, yarn breakage of some of the plurality of yarns 100A can be suppressed. Furthermore, in the step (B), the temperature of the gas is preferably equal to or higher than the glass transition temperature of the polymer composition. When the temperature of the gas is equal to or higher than the glass transition temperature of the polymer composition, the polymer composition is more likely to undergo plastic deformation, and the raw yarn 100 A is less likely to break. Note that the "temperature of the gas blown onto the plurality of raw yarns 100 A in a molten state obtained in the step (A)" refers to the temperature of the gas when the gas comes into contact with the raw yarn 100 A.

[0085] In step (B), the velocity of the gas blown onto the 30 or more yarns is preferably 0.10 m / s or higher, more preferably 0.20 to 5.0 m / s, even more preferably 0.20 to 3.0 m / s, even more preferably 0.30 to 3.0 m / s, and particularly preferably 0.32 to 3.0 m / s. When the gas velocity is 0.10 m / s or higher, the cooling effect of the gas is more easily exerted. When the gas velocity is 5.0 m / s or lower, the molten yarn 100A discharged from the spinning nozzle 104 is prevented from being shaken by the gas. As a result, fusion and / or yarn breakage between the molten yarns 100A is prevented, i.e., spinning stability is improved. Note that the "velocity of the gas blown onto the molten yarns 100A obtained in step (A)" refers to the relative velocity of the gas with respect to the yarns 100A when the gas contacts the yarns 100A.

[0086] Examples of the gas include air, inert gases (nitrogen gas, argon gas, etc.), and water vapor.

[0087] The heat flow rate Q between the gas and the solid is related to the heat transfer coefficient h between the gas and the solid, the contact area A between the gas and the solid, and the temperature difference ΔT between the gas and the solid by the following formula: Q = h × A × ΔT. Therefore, by increasing the heat transfer coefficient h between the gas and the solid, the heat flow rate Q between the gas and the solid can be increased. Therefore, by increasing the heat transfer coefficient between the 30 or more yarns in a molten state and the gas, it becomes easier to sufficiently cool the 30 or more yarns in a molten state. In the step (B), the heat transfer coefficient between the 30 or more yarns in a molten state and the gas is increased to 60 W / (m ２ ·K) or more, preferably 65 W / (m ２ ·K) or more, more preferably 70 W / (m ２ ·K) or more, and even more preferably 125 W / (m ２ ·K) or more, particularly preferably 130 W / (m ２ ·K) or more, most preferably 135 W / (m ２ In the step (B), the heat transfer coefficient between the 30 or more molten yarns and the gas is set to, for example, 500 W / (m ２ ·K) or less (more specifically, 350 W / (m ２ ・K) or below.

[0088] The heat transfer coefficient can be calculated from the temperature T of the gas, the velocity u of the gas, and the cross-sectional diameter d of the raw yarn.

[0089] The cross section of the yarn refers to a cross section perpendicular to the longitudinal direction of the yarn. The value of the "diameter of the discharge hole" is used as the "diameter of the cross section of the yarn." If the shape of the discharge hole is not a perfect circle, the area of ​​the discharge hole is found, and the diameter of the discharge hole is calculated from the area of ​​the discharge hole assuming that the discharge hole is a perfect circle, and this calculated value is used as the "diameter of the cross section of the yarn."

[0090] Specifically, the heat transfer coefficient can be determined by the following steps (1) to (5).

[0091] [1] From the gas temperature T, the gas density ρ, the gas viscosity coefficient μ, and the gas specific heat C ｐ , and the thermal conductivity of the gas λ.

[0092] Gas density ρ (kg / m ３ For example, when the gas is air, the temperature ρ can be calculated from the following formula and the temperature T (K) of the gas: ρ = 351.99 / T + 344.84 / T ２

[0093] For example, if the gas is air, the viscosity coefficient μ (Pa s) of the gas can be calculated from the following formula and the gas temperature T (K): μ = (1.4592 × 10 －６ ×T ３／２ ) / (109.10 + T)

[0094] Specific heat of gas C ｐ For example, if the gas is air, the mass (J / (kg·K)) can be calculated from the following formula and the gas temperature T (K): Cp = 1030.5 - 0.19975 × T + 3.9734 × 10 －４ ×T ２

[0095] For example, when the gas is air, the thermal conductivity λ (W / (m·K)) of the gas can be calculated from the following formula and the gas temperature T (K): λ = (2.3340×10 －３ ×T ３／２ ) / (164.54 + T)

[0096] In addition, when the gas is other than air, the density ρ of the gas, the viscosity coefficient μ of the gas, and the specific heat C of the gas can be calculated from the conventionally known relational expression for the gas and the temperature T of the gas, as in the case of air. ｐ , and the thermal conductivity of the gas λ can be determined.

[0097] [2] The Reynolds number Re is calculated from the following formula, where ρ is the density of the gas, u is the velocity of the gas, d is the diameter of the cross section of the raw fiber (the diameter of the discharge hole), and μ is the viscosity coefficient of the gas: Re = ρ × u × d / μ

[0098] [3] The following formula, the viscosity coefficient μ of the gas, the specific heat C of the gas ｐThe Prandtl number Pr is calculated from the thermal conductivity λ of the gas. Pr = μ × Cp / λ

[0099] [4] The Nusselt number Nu is calculated from the following equation, the Reynolds number Re, and the Prandtl number Pr: Nu = C × Re ｍ ×Pr １／３ Note that C and m are coefficients determined by the Reynolds number Re. Table 1 below shows C and m relative to the Reynolds number Re.

[0100]

[0101] [5] The heat transfer coefficient h is calculated from the following formula, where Nusselt number Nu, diameter of the cross section of the raw yarn (diameter of the discharge hole) d, and thermal conductivity λ of the gas: h = Nu × λ / d

[0102] For the calculations of [1] to [5] above, you can use the "Science.Tools" website of CatTech Labs [searched on July 26, 2021] (URL: https: / / cattech-lab.com / science-tools / ) or the like.

[0103] As a method for blowing gas onto 30 or more molten yarns, a method of blowing gas onto the yarns from at least four directions when viewed in the longitudinal direction of the yarns (a cross-sectional view of the yarns perpendicular to the longitudinal direction of the yarns) (so-called circular quench method) is preferred. In the circular quench method, gas is blown onto the yarns from preferably eight or more directions, more preferably sixteen or more directions. The direction in which gas is blown onto the yarns is preferably between a direction perpendicular to the flow direction of the yarns and the flow direction of the yarns. The distance between the discharge hole of the spinning nozzle 104 and the position where the gas contacts the yarns discharged from the discharge hole is determined by the required properties of the multifilament to be drawn. By setting the degree of orientation and degree of crystallinity of the yarn 100A within appropriate ranges, the process for obtaining a multifilament from the multifilament to be drawn is stabilized and the mechanical properties of the multifilament are improved. In step (B), it is preferable to discharge the gas that has come into contact with the yarn to the outside of the cooling box along the direction of the yarn flow. For example, a straightening plate, a straightening fin, an ejector, a Venturi tube, a transvector manufactured by Kogi Co., Ltd., or the like can be used to discharge the gas that has come into contact with the yarn to the outside of the cooling box along the direction of the yarn flow.

[0104] In the step (B), 30 or more strands of the raw yarn 100A cooled with a gas of 0°C or higher and 50°C or lower are taken up by a first take-up roll unit 107. The first take-up roll unit 107 is composed of two rolls. The first take-up roll unit 107 may be composed of one roll or three or more rolls. In the first embodiment, the 30 or more strands of the raw yarn 100A taken up by the first take-up roll unit 107 are transported using a first transport roll unit 108, a second transport roll unit 109, a third transport roll unit 110, and a fourth transport roll unit 111, and the 30 or more strands of the raw yarn 100A transported by the transport roll units 108, 109, 110, and 111 are wound up by a first wind-up roll unit 112 to obtain a multifilament for drawing. The first wind-up roll unit 112 has a bobbin. The concept of a bobbin also includes a cardboard tube. The bobbin may or may not have a flange. Specifically, in the step (C), the raw yarn 100A is wound around the bobbin of the first winding roll unit 112 to obtain a multifilament for drawing. Each transport roll unit is composed of two rolls in FIG. 1, but may be composed of one roll or three or more rolls.

[0105] In the step (B), 30 or more of the raw yarns 100A are cooled to preferably 70°C or less, more preferably 60°C or less, even more preferably 50°C or less, and particularly preferably 40°C or less. In the step (B), 30 or more of the raw yarns 100A are cooled to, for example, 0°C or more, preferably 10°C or more. In the step (B), 30 or more of the raw yarns 100A are preferably cooled to a temperature equal to or higher than the glass transition temperature of the polymer composition. In the step (B), 30 or more of the raw yarns may be cooled to 70°C or less by blowing gas at a temperature of 0°C to 50°C. In addition, in the step (B), the 30 or more raw yarns 100A may be cooled to a certain degree by blowing gas at a temperature of 0°C or higher and 50°C or lower, and then cooled with ambient air while transporting the 30 or more raw yarns 100A from the first take-up roll section 107 to the first winding roll section 112, thereby cooling the 30 or more raw yarns 100A to 70°C or lower.

[0106] In order to draw the multifilament to be drawn in the step (C), it is preferable that in the step (B), 30 or more of the raw yarns 100A are not substantially drawn, or 30 or more of the raw yarns 100A are not drawn very much. That is, the draw ratio in the step (B) is preferably 1.5 times or less, more preferably 1.2 times or less, and even more preferably 1.1 times or less. The draw ratio in the step (B) can be calculated by the following formula: Draw ratio in the step (B) = Speed ​​(m / min) of the transport roll unit / Speed ​​(m / min) of the take-up roll unit (in the first embodiment, "first take-up roll unit 107") used in the step (B)

[0107] The speed (m / min) of the take-up roll unit used in step (B) is the length per unit time of 30 or more strands of the raw yarn 100A taken up by the take-up roll unit (in the first embodiment, the "first take-up roll unit 107") used in step (B). The speed of the transport roll unit is the length per unit time of 30 or more strands of the raw yarn 100A transported by the transport roll unit. When multiple transport roll units are used, the highest speed among the multiple transport roll units is defined as the "speed of the transport roll unit."

[0108] The following relational expression approximately holds true for the fineness of the first single yarn of the multifilament to be drawn: Fineness (dtex) of the first single yarn of the multifilament to be drawn = (((a x 1000 / 60) / b x 10000) / c) / d a: Amount (kg / h) of the molten material discharged from the spinning nozzle 104 b: Speed ​​(m / min) of the take-up roll section (in the first embodiment, "first take-up roll section 107") used in step (B) c: Number (number) of discharge holes possessed by the spinning nozzle 104 d: Draw ratio (-) in step (B) Therefore, by adjusting b, etc., it is possible to adjust the fineness of the first single yarn of the multifilament to be drawn.

[0109] In step (B) in FIG. 1 , 30 or more strands of the raw yarn 100A are wound around the first winding roll unit 112. However, in the first embodiment, 30 or more strands of the raw yarn 100A may be stored in a storage container without being wound around the first winding roll unit 112, thereby obtaining a multifilament for drawing.

[0110] When the transport roll section is not used, the stretching ratio in the step (B) is 1.0.

[0111] (Step (C)) As shown in FIG. 2, in the step (C), the multifilament to be drawn 100B is heated and drawn by the drawing roll section 114.

[0112] In the step (C), the multifilament to be drawn is taken up from the first take-up roll unit 112 by a second take-up roll unit 113. Next, in the step (C), the multifilament to be drawn 100B taken up by the second take-up roll unit 113 is drawn by the draw roll unit 114. Then, in the step (C), the multifilament to be drawn 100B drawn by the draw roll unit 114 is taken up by a second take-up roll unit 116 to obtain a multifilament. The second take-up roll unit 116 has a bobbin. The bobbin is a concept that also includes a paper tube. The bobbin may or may not have a flange. In the step (C), specifically, the drawn multifilament to be drawn 100B is taken up by the bobbin of the second take-up roll unit 116 to obtain a multifilament. 2, the multifilament to be drawn 100B drawn in the drawing roll section 114 is wound around the second winding roll section 116 to obtain a multifilament, but the multifilament to be drawn 100B drawn in the drawing roll section 114 may be obtained without being wound around the second winding roll section 116. Furthermore, in the step (C), the multifilament to be drawn 100B drawn in the drawing roll section 114 may be transported by a take-off roll section 115.

[0113] The second take-up roll section 113 is composed of two rolls. The second take-up roll section 113 may be composed of one roll or three or more rolls. In the step (C), the multifilament for drawing 100B is preferably heated in the second take-up roll section 113. In the step (C), heating the multifilament for drawing 100B in the second take-up roll section 113 facilitates adjusting the temperature of the first single yarn to be within a temperature range suitable for enhancing the orientation of the polymer component contained in the first single yarn in the multifilament for drawing 100B, thereby facilitating enhancing the orientation of the polymer component of the first single yarn. The temperature of the second take-up roll section 113 is preferably 15°C or higher and lower than 60°C, more preferably 20 to 55°C. When the temperature of the environment in which the step (C) is performed is 15°C or higher, the multifilament for drawing 100B does not need to be heated in the second take-up roll section 113.

[0114] The drawing roll section 114 is composed of two rolls. The drawing roll section 114 may be composed of one roll, or may be composed of three or more rolls. In the step (C), the multifilament to be drawn 100B may or may not be heated in the drawing roll section 114. That is, in the first embodiment, the drawing roll section 114 may also serve as a heat treatment roll section. In the step (C), by heating the multifilament to be drawn 100B in the drawing roll section 114, it is possible to promote crystallization of the polymer component contained in the first single yarn of the multifilament to be drawn 100B, or to improve the heat resistance of the polymer component contained in the first single yarn. The temperature of the drawing roll section (heat treatment roll section) 114 is preferably 30 to 100°C, more preferably 40 to 90°C.

[0115] In the first embodiment, it is preferable that the take-off roll section 115 also serves as the heat treatment roll section. The take-off roll section 115 (heat treatment roll section 115) is composed of two rolls. The take-off roll section 115 (heat treatment roll section 115) may be composed of one roll, or may be composed of three or more rolls. In the step (C), by heating the multifilament for drawing 100B in the heat treatment roll section 115, it is possible to promote crystallization of the polymer component contained in the first single yarn of the multifilament for drawing 100B, or to improve the heat resistance of the polymer component contained in the first single yarn. The temperature of the take-off roll section (heat treatment roll section) 115 is preferably 30 to 100°C, more preferably 40 to 90°C. Both or either one of the drawing roll section 114 and the take-off roll section 115 may be the heat treatment roll section.

[0116] In step (C) of the first embodiment, the first single yarn is heated in the take-up roll section 113, the drawing roll section 114, and the take-off roll section 115. However, the first single yarn may be heated as appropriate to achieve the purpose of controlling the orientation, crystallization, and heat resistance of the polymer component of the first single yarn. For example, the first single yarn may be heated in the first winding roll section 112. Alternatively, the first single yarn may be heated in the second winding roll section 116 to obtain a multifilament. The first single yarn may be heated in all of the roll sections from the first winding roll section 112 to the second winding roll section 116. Alternatively, the first single yarn may be heated in only some of the roll sections from the first winding roll section 112 to the second winding roll section 116, and the first single yarn may not be heated in the other roll sections. It is preferable that the heating of the first single yarn in the roll section is controlled in each roll section.

[0117] Furthermore, the method of heating the polymer component of the first single yarn in step (C) of the first embodiment (hereinafter also simply referred to as the "heating method") may be a method of heating the polymer component of the first single yarn by heating the rolls of the roll unit. Alternatively, the roll unit may have a container that houses the rolls and a liquid (e.g., water) that is housed in the container together with the rolls, and the heating method may be a method of heating the liquid to heat the polymer component of the first single yarn. In step (C), for example, in-bath drawing may be performed. Furthermore, the heating method may be a method of heating the polymer component of the first single yarn by blowing heated gas (e.g., air) onto or near the roll unit. These heating methods may also be used in combination.

[0118] The draw ratio in the step (C) is 1.5 times or more, preferably 1.7 times or more. The draw ratio in the step (C) is, for example, 20 times or less. When the draw ratio in the step (C) is 1.5 times or more, the orientation of the polymer component of the first single yarn in the multifilament for drawing 100B is further increased. The draw ratio in the step (C) can be calculated by the following formula: Draw ratio in the step (C) = draw roll section (m / min) / speed (m / min) of the take-up roll section used in the step (C) (in the first embodiment, "second take-up roll section 113").

[0119] In the step (C), the relaxation rate calculated by the following formula is preferably 1 to 30%, and more preferably 1 to 15%. Relaxation rate (%) = ((speed of the drawing roll unit 114 - speed of the take-up roll unit that takes up the multifilament to be drawn (in the first embodiment, the "second take-up roll unit 116")) / speed of the take-up roll unit that takes up the multifilament to be drawn) x 100

[0120] The speed (m / min) of the drawing roll section is the length per unit time of the multifilament to be drawn transported by the drawing roll section. In the first embodiment, only one drawing roll section is used, but multiple drawing roll sections may be used. When multiple drawing roll sections are used, the highest speed among the multiple drawing roll sections is defined as the "speed of the drawing roll section." The speed (m / min) of the take-up roll section used in the step (C) is the length per unit time of the multifilament to be drawn transported by the take-up roll section. The speed (m / min) of the take-up roll section that takes up the multifilament to be drawn is the length per unit time of the multifilament to be drawn taken up by the take-up roll section.

[0121] In the step (C), a multifilament may be obtained by drawing only one multifilament for drawing, or a multifilament may be obtained by doubling a plurality of multifilaments for drawing and drawing the doubling multifilaments for drawing.

[0122] (Second embodiment: spin draw method) Next, a second embodiment will be described with reference to Fig. 3. Note that the description overlapping with the first embodiment will be omitted, and the second embodiment will be the same as the first embodiment unless otherwise specified.

[0123] The method for producing a multifilament according to the second embodiment is a method for producing a multifilament to be drawn and a multifilament by a spin draw method. The spin draw method is a method in which a step of obtaining a plurality of molten yarns by discharging a melt from a plurality of discharge holes and a step of drawing the multifilament to be drawn with a drawing roll section are carried out in one step. The spin draw method is also called the "SDY method" or the "direct spinning drawing method."

[0124] In the second embodiment, in the step (B), a gas at 0°C or higher and 50°C or lower is blown onto 30 or more of the molten yarns 100A to cool the 30 or more yarns 100A, thereby obtaining a multifilament to be drawn 200B, and the multifilament to be drawn 200B obtained in the step (B) is taken up by a take-up roll unit 207. Next, in the step (C), the multifilament to be drawn 200B taken up by the take-up roll unit 207 is drawn by three draw-up roll units (a first draw-up roll unit 208, a second draw-up roll unit 209, and a third draw-up roll unit 210). Then, in the step (C), the drawn multifilament to be drawn 200B is taken up by a take-up roll unit 212 to obtain a multifilament. The take-up roll unit 212 has a bobbin. The bobbin is a concept that also includes a paper tube. The bobbin may or may not have a flange. In the step (C), specifically, the drawn multifilament to be drawn 200B is wound around a bobbin in the winding roll section 212 to obtain a multifilament. Note that in the step (C) in Fig. 3, the multifilament to be drawn 200B drawn in the drawing roll section is wound around the winding roll section 212 to obtain a multifilament, but the multifilament to be drawn 200B drawn in the drawing roll section may be obtained without being wound around the winding roll section 212. Also, in the step (C), the multifilament to be drawn 200B drawn in the drawing roll section may be transported by the take-off roll section 211.

[0125] In the step (B), 30 or more of the raw yarns 100A are cooled in a first cooling box 105 to obtain a multifilament to be drawn 200B, and in the step (C), the multifilament to be drawn 200B is taken up by a take-up roll unit 207. Note that the 30 or more raw yarns 100A cooled in the first cooling box 105 may also be cooled in a second cooling box 106 to obtain a multifilament to be drawn 200B. The take-up roll unit 207 is configured with two rolls in Fig. 1, but may be configured with one roll or three or more rolls.

[0126] In the second embodiment, each drawing roll section may also serve as a heat treatment roll section. While each drawing roll section 208, 209, 210 (each heat treatment roll section 208, 209, 210) is configured with two rolls in FIG. 1 , it may be configured with one roll or with three or more rolls. From the viewpoint of promoting crystallization of the polymer component contained in the first single yarn in the multifilament for drawing 200B or improving the heat resistance of the polymer component contained in the first single yarn, the temperature of the heat treatment roll section is preferably 30 to 100°C, more preferably 40 to 90°C. Note that when the temperature of the environment in which step (C) is performed is 30°C or higher, crystallization of the polymer component contained in the first single yarn can be promoted without using a heat treatment roll section.

[0127] In this embodiment, the spinning draft number (NDR) is preferably 50 or more, more preferably 80 or more. Furthermore, the NDR is usually 5,000 or less. The NDR can be calculated using the following formula: NDR = speed (m / min) of the take-up roll section (first take-up roll section) that initially takes up the yarn from the spinning nozzle / spinning nozzle flow rate (m / min). An NDR of 50 or more can improve the orientation of the polymer component contained in the first single yarn in the multifilament 100B, 200B to be drawn, thereby further increasing the strength of the multifilament. In the first embodiment (sequential drawing method), the first take-up roll section is the first take-up roll section 107 that takes up 30 or more of the raw yarn 100A. In the second embodiment (spin draw method), the first take-up roll section is the take-up roll section 207 that takes up the multifilament 200B to be drawn.

[0128] <Method of manufacturing staple> In the method of manufacturing a staple according to this embodiment, the multifilament is obtained by the method of manufacturing a multifilament according to this embodiment. Then, in the method of manufacturing a staple according to this embodiment, the multifilament is cut to obtain a staple having a length of 20 cm or less. Note that a plurality of multifilaments may be bundled together and the bundled plurality of multifilaments may be cut to obtain a staple having a length of 20 cm or less.

[0129] In the staple manufacturing method according to the present embodiment, a staple as a crimped yarn (crimped yarn) may be obtained by crimping the multifilament and cutting the crimped multifilament. In addition, in the aspect in which the drawn multifilament to be drawn is wound around the winding roll unit 116, 212 to obtain the multifilament in the step (C), the drawn multifilament to be drawn may be crimped before being wound around the winding roll unit 116, 212 to obtain the crimped multifilament.

[0130] That is, the drawn multifilament to be drawn may be wound around the winding roll section 116, 212 (specifically, the bobbin (paper tube or the like) of the winding roll section 116, 212) to obtain a multifilament, and then the multifilament may be subjected to crimping. Alternatively, the multifilament obtained without using the winding roll section may be subjected to crimping. Furthermore, the drawn multifilament to be drawn may be subjected to crimping while being transferred from the take-off roll section 115, 211 to the winding roll section 116, 212.

[0131] The crimping process is not particularly limited, and can be carried out by known crimping methods (e.g., gear crimping, stuffing box, etc.). The crimping process results in the staple having a crimp (specifically, mechanical crimping). If necessary, a preheating step may be carried out to preheat the yarn to be crimped (multifilament or drawn multifilament for drawing) before crimping it. In the preheating step, the surface temperature of the yarn to be crimped is measured, and appropriate conditions are determined taking into consideration the degree of orientation, crystallinity, strength, heat resistance, etc. The surface temperature is generally 40 to 140°C, preferably 40 to 120°C, and more preferably 50 to 120°C. A surface temperature of 40°C or higher provides mechanical properties suitable for crimping. By setting the temperature at 140°C or less, drawdown can be suppressed and the process stability of the crimping process can be improved. The preheating step can be, for example, a wet heat treatment or a dry heat treatment. In the wet heat treatment, for example, steam can be used. In the dry heat treatment, for example, a hot air oven or an electric heater can be used.

[0132] When crimping the multifilament by the stuffing box method after preheating the yarn to be crimped so that the surface temperature of the yarn to be crimped is 40 to 140°C, it is preferable to impart crimp to the multifilament under a stuffing box pressure of 0.001 to 0.1 MPa. The stuffing box pressure is more preferably 0.001 to 0.08 MPa, even more preferably 0.001 to 0.06 MPa, and even more preferably 0.001 to 0.04 MPa.

[0133] This embodiment is configured as described above and has the following advantages.

[0134] That is, the multifilament for drawing according to this embodiment has 30 or more first single yarns. The first single yarns contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent. The average fineness of the first single yarns is 30 dtex or less. The coefficient of variation of the fineness of the first single yarns is 33% or less.

[0135] Because the coefficient of variation of the fineness of the first single yarn in the multifilament for drawing according to this embodiment is as small as 33% or less, the multifilament for drawing according to this embodiment is less likely to contain an extremely thin second single yarn. As a result, when drawing the multifilament for drawing according to this embodiment to obtain a multifilament, the first single yarn is less likely to break even if the draw ratio is increased while the average fineness of the second single yarn is reduced. Furthermore, by increasing the draw ratio when drawing the multifilament for drawing according to this embodiment to obtain a multifilament, the orientation of the poly(3-hydroxyalkanoate)-based resin in the multifilament is improved, and as a result, the strength of the obtained multifilament is increased. Therefore, with the multifilament for drawing according to this embodiment, a multifilament with high strength can be easily obtained even if the average fineness of the second single yarn is small.

[0136] The multifilament according to this embodiment is a drawn multifilament. The multifilament according to this embodiment has 30 or more second single yarns. The second single yarns contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent. The average fineness of the second single yarns is 20 dtex or less. The coefficient of variation of the fineness of the second single yarns is 33% or less.

[0137] When the coefficient of variation of the fineness of the second single yarn in the multifilament according to this embodiment is 33% or less, the coefficient of variation of the fineness of the first single yarn in the multifilament to be drawn used to produce the multifilament is small. Furthermore, when the coefficient of variation of the fineness of the first single yarn in the multifilament to be drawn is small, the multifilament to be drawn is less likely to contain an extremely thin second single yarn. As a result, when the multifilament to be drawn is drawn to obtain a multifilament, the single yarn is less likely to break even if the draw ratio is increased to reduce the average fineness of the second single yarn. Furthermore, by increasing the draw ratio when drawing the multifilament to be drawn to obtain a multifilament, the orientation of the poly(3-hydroxyalkanoate)-based resin in the multifilament is improved, resulting in an increased strength of the resulting multifilament. Therefore, the multifilament according to this embodiment is a multifilament that can easily achieve high strength even if the average fineness of the second single yarn is small.

[0138] Furthermore, the method for producing a multifilament for drawing according to this embodiment is a method for obtaining a multifilament for drawing by a melt spinning method. The method for producing a multifilament for drawing according to this embodiment includes the steps of: (A) discharging a melt by the melt spinning method using a spinning nozzle having 30 or more discharge holes to obtain 30 or more molten yarns; and (B) blowing a gas at 0°C to 50°C onto the 30 or more molten yarns to cool the 30 or more yarns, thereby obtaining a multifilament for drawing. The melt contains a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent. The average fineness of the first single yarns in the multifilament for drawing is 30 dtex or less; and in the step (B), the heat transfer coefficient between the 30 or more molten yarns and the gas is 60 W / (m ２ ・K) or higher.

[0139] In the step (B), a gas of 0°C or more and 50°C or less is blown onto the 30 or more molten yarns to cool the 30 or more yarns, and the heat transfer coefficient between the 30 or more molten yarns and the gas is set to 60 W / (m ２By setting the temperature (K) or higher, it is possible to adjust the time during which the poly(3-hydroxyalkanoate) resin is within the crystallization temperature range within an appropriate range, and to optimize the progress of crystallization of the poly(3-hydroxyalkanoate) resin. This allows the drawability of the multifilament to be optimized. Therefore, when drawing the multifilament to be drawn to obtain a multifilament, the single yarns are less likely to break even if the draw ratio is increased. Furthermore, in the step (B), the raw yarn is drawn to some extent by taking up at the take-up roll section, but the single yarns present inside the raw yarn (hereinafter also referred to as "internal single yarns") and the single yarns present outside (hereinafter also referred to as "outer single yarns") are cooled relatively uniformly by gas at 0°C or higher and 50°C or lower, so that the internal single yarns and the outer single yarns are uniformly drawn. As a result, the coefficient of variation of the fineness of the first single yarns in the multifilament to be drawn becomes small (for example, the coefficient of variation becomes 33% or less). That is, the multifilament to be drawn is less likely to include an extremely thin first single yarn. As a result, when the multifilament to be drawn is drawn to obtain a multifilament, the first single yarn in the multifilament to be drawn is less likely to break even if the draw ratio is increased. Furthermore, by increasing the draw ratio when the multifilament to be drawn is drawn to obtain a multifilament, the orientation of the poly(3-hydroxyalkanoate)-based resin in the multifilament is improved, and as a result, the strength of the obtained multifilament is increased. Therefore, according to the manufacturing method of the multifilament to be drawn according to this embodiment, it is possible to obtain a multifilament to be drawn that makes it easy to produce a multifilament with high strength even if the average fineness of the second single yarns is small.

[0140] The method for producing a multifilament according to the present embodiment includes a step (C) of obtaining a multifilament to be drawn by the method for producing a multifilament to be drawn according to the present embodiment, and includes a step (C) of obtaining a multifilament by drawing the multifilament to be drawn by 1.5 times or more in a drawing roll section.

[0141] In the method for producing a multifilament according to this embodiment, the multifilament for drawing is obtained by the method for producing a multifilament for drawing according to this embodiment, and in step (C), the multifilament for drawing is drawn by 1.5 times or more in a drawing roll section to obtain a multifilament, thereby making it possible to obtain a multifilament having high strength even if the average fineness of the second single yarns is small.

[0142] Furthermore, in the method for producing a multifilament according to the present embodiment, in the step (B), a gas at 0°C or higher and 50°C or lower is blown onto 30 or more of the raw yarns in a molten state, thereby cooling the 30 or more raw yarns to 50°C or lower, thereby obtaining the multifilament to be drawn, and in the step (C), the multifilament to be drawn is heated and drawn by the drawing roll section.

[0143] In the step (C), the orientation of the poly(3-hydroxyalkanoate)-based resin contained in the multifilament to be drawn is increased by drawing the multifilament to be drawn, thereby increasing the strength of the multifilament. Here, in order to increase the orientation of the poly(3-hydroxyalkanoate)-based resin, it is desirable to draw the multifilament in a temperature range suitable for increasing the orientation of the poly(3-hydroxyalkanoate)-based resin. This is because if the multifilament to be drawn is drawn at a temperature higher than this temperature range, the poly(3-hydroxyalkanoate)-based resin will be in a molten state, and as a result, the orientation of the poly(3-hydroxyalkanoate)-based resin will not be very high even after drawing. Furthermore, if an attempt is made to draw the multifilament to be drawn at a temperature lower than the temperature range, the poly(3-hydroxyalkanoate) resin will harden too much, making it difficult to draw the raw yarn, and if the multifilament to be drawn is forcibly pulled in an attempt to draw the multifilament to be drawn, the multifilament to be drawn will break, making it impossible to produce the multifilament. In this embodiment, in the step (B), a gas at 0°C or higher and 50°C or lower is blown onto 30 or more of the molten yarns, thereby cooling the 30 or more yarns to 50°C or lower to obtain the multifilament to be drawn, and in the step (C), the multifilament to be drawn is heated and drawn in the drawing roll section. Compared to the SDY method (spin draw method) (a method of drawing a multifilament to be drawn while cooling it with ambient air), this makes it easier to adjust the temperature of the multifilament to be drawn so that it is within a temperature range suitable for increasing the orientation of the poly(3-hydroxyalkanoate)-based resin when drawing the multifilament to be drawn, and as a result, it becomes easier to increase the orientation of the poly(3-hydroxyalkanoate)-based resin in the multifilament to be drawn. Therefore, in this embodiment, the strength of the multifilament becomes even easier to increase.

[0144] The multifilament and staple according to the present embodiment may be used as they are in the form of thread. Furthermore, the multifilament or staple according to the present embodiment may be used to produce a textile product (fibrous body). The textile product can be formed into various shapes (for example, a nonwoven fabric). The multifilament, staple, and textile product according to the present embodiment can be suitably used in conventionally known applications. The multifilament, staple, and textile product according to the present embodiment can be suitably used in fields such as agriculture (for example, horticulture), fisheries, forestry, the medical industry, and the food industry. Examples of the textile product include clothing, curtains, carpets, bags, shoes, wiping materials, sanitary products, automotive components, building materials, and filtration materials (filters).

[0145] Disclosure Items Each of the following items is a disclosure of a preferred embodiment.

[0146] [Item 1] A multifilament for drawing having 30 or more single yarns, wherein the single yarns contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average fineness of the single yarns is 30 dtex or less, and the coefficient of variation of the fineness of the single yarns is 33% or less.

[0147] [Item 2] The multifilament for drawing according to Item 1, wherein the poly(3-hydroxyalkanoate)-based resin includes a poly(3-hydroxybutyrate)-based resin.

[0148] [Item 3] A drawn multifilament, the multifilament having 30 or more single yarns, the single yarns containing a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average fineness of the single yarns being 20 dtex or less, and the coefficient of variation of the fineness of the single yarns being 33% or less.

[0149] [Item 4] A staple in which the multifilament according to item 3 is cut and has a length of 20 cm or less.

[0150] [Item 5] A method for producing a multifilament to be drawn by a melt spinning method, the method comprising: a step (A) of discharging a melt by the melt spinning method using a spinning nozzle having 30 or more discharge holes to obtain 30 or more molten raw yarns; and a step (B) of blowing a gas at 0°C or more and 50°C or less onto the 30 or more molten raw yarns to cool the 30 or more raw yarns, thereby obtaining a multifilament to be drawn, the melt containing a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average fineness of the single yarns in the multifilament to be drawn is 30 dtex or less, and in the step (B), the heat transfer coefficient between the 30 or more molten raw yarns and the gas is 60 W / (m ２ ・K) or more.

[0151] [Item 6] In the step (B), the heat transfer coefficient is 125 W / (m ２ Item 6. The method for producing a multifilament for drawing according to Item 5, wherein the number of strands is 1 or more.

[0152] [Item 7] The method for producing a multifilament for drawing according to Item 5 or 6, wherein in the step (B), the speed of the gas blown onto 30 or more of the raw yarns is set to 0.3 m / s or more.

[0153] [Item 8] A method for producing a multifilament, comprising: obtaining a multifilament to be drawn by the method for producing a multifilament to be drawn according to any one of Items 5 to 7; and (C) drawing the multifilament to be drawn by 1.5 times or more in a drawing roll section to obtain a multifilament.

[0154] [Item 9] The method for producing a multifilament according to Item 8, wherein in the step (B), a gas at 0°C or higher and 50°C or lower is blown onto 30 or more of the raw yarns in a molten state, thereby cooling the 30 or more raw yarns to 50°C or lower, thereby obtaining the multifilament to be drawn; and in the step (C), the multifilament to be drawn is heated and drawn by the drawing roll section.

[0155] [Item 10] A method for producing a staple, comprising obtaining a multifilament by the method for producing a multifilament according to item 8 or 9, and cutting the multifilament to obtain staples having a length of 20 cm or less.

[0156] It should be noted that the present invention is not limited to the above-described embodiment. Furthermore, the present invention is not limited to the above-described effects. Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention.

[0157] For example, although the multifilament for drawing according to the present embodiment is obtained by the above-mentioned production method, the multifilament for drawing according to the present invention may also be obtained, for example, as follows: That is, the multifilament for drawing may be obtained by selecting and collecting 30 or more first single yarns so that the average fineness of the first single yarns is 30 dtex or less and the coefficient of variation of the fineness of the first single yarns is 33% or less.

[0158] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0159] Example 1 A multifilament was produced by the method of the first embodiment (sequential drawing method).

[0160] (Step (A)) First, the following materials were dry-blended in the following proportions, and the dry-blended materials were melt-kneaded at 150°C in an extruder to obtain pellets. Poly(3-hydroxyalkanoate) resin: (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (proportion of 3-hydroxyhexanoate: 6 mol%, Mw: 350,000, melt flow rate (MFR) (165°C, 5 kg): 12 g / 10 min) (P3HB3HH): 100 parts by mass; Pentaerythritol (Nippon Synthetic Chemical Industry Co., Ltd., Neurizer P): 1.0 part by mass as a crystal nucleating agent; Erucic acid amide: 0.5 parts by mass as a lubricant having an amide bond; Behenic acid amide: 0.5 parts by mass as a lubricant having an amide bond. The glass transition temperature of the pellets was 2°C. The crystallization temperature of the pellets was 100°C. The melting point of the pellets was 146°C. The pyrolysis temperature of the pellets was 180°C.

[0161] As shown in Figure 1, the pellets were melted in a kneading extruder 102 (single-screw extruder, screw diameter: 25 mm) to obtain a melt. The melt was then extruded from a spinning nozzle 104 (temperature: 175°C, number of nozzles: 368, nozzle shape: circular, nozzle diameter: 0.3 mm) to obtain 368 original yarns 100A. The flow rate of the melt was adjusted to 5.6 kg / h by a gear pump 103.

[0162] (Step (B)) In the cooling box 105, air at 20°C was blown onto 368 strands of the yarn 100A at a speed of 0.7 m / s by a circular quench method. The heat transfer coefficient between the 368 strands of the yarn 100A in a molten state and the air was calculated using the air temperature, air speed, and diameter of the discharge hole by the method described above, and the heat transfer coefficient was found to be 194 W / (m ２.K). No gas was blown into the cooling box 106. Next, the 368 yarns 100A cooled in the cooling boxes 105 and 106 were taken up by the first take-up roll section 107 (448 m / min), and the 368 yarns 100A passed through the first transport roll section 108 (471 m / min), the second transport roll section 109 (471 m / min, 70°C), the third transport roll section 110 (471 m / min), and the fourth transport roll section 111 (471 m / min) in that order, and then the 368 yarns 100A were taken up by the first take-up roll section (461 m / min) and stored at room temperature (5 to 35°C) for 18 hours to obtain a multifilament for drawing.

[0163] (Step (C)) As shown in FIG. 2 , the multifilament to be drawn was taken up from the first take-up roll section 112 by the second take-up roll section 113 (4.8 m / min, 30° C.), drawn by the drawing roll section 114 (11.5 m / min, 25° C.), transported through the take-off roll section (heat treatment roll section) 115 (10.4 m / min, 90° C.), and taken up by the second take-up roll section 116 (10.4 m / min), to obtain a multifilament. The draw ratio was 2.4 times. In the multifilament, the second single yarns were not broken. Furthermore, no fusion between the second single yarns was observed. From these facts, the appearance of the multifilament was good.

[0164] The take-up roll section and the transport roll section each used a roll section consisting of two rolls with the same speed and temperature.

[0165] Staples were produced using the obtained multifilaments as follows. First, to obtain staples of an appropriate fineness, the obtained multifilaments were doubling. Next, the doubling multifilaments were preheated with steam so that the surface temperature of the doubling multifilaments reached 65°C. The preheated multifilaments were then fed to a stuffing box at a conveying speed of 30 m / min, and further crimped under conditions of a nip pressure of 0.20 MPa and a stuffing pressure of 0.03 MPa to obtain crimped yarns. Next, the crimped yarns were cut with a tow cutter so that the staples had a length of 51 mm, thereby obtaining crimped staples. The number of crimps in the staples was 14 per 25 mm.

[0166] Examples 2 to 7 Multifilaments to be drawn, multifilaments, and staples were obtained in the same manner as in Example 1, except that the conditions of steps (A) to (C) were changed to those shown in the following Table 2. In Examples 2 to 7 as well, the number of crimps in the staples was 14 per 25 mm.

[0167] Comparative Examples 1 and 5 A multifilament to be drawn and a multifilament were obtained in the same manner as in Example 1, except that the conditions of steps (A) to (C) were changed to those shown in Table 2 below.

[0168] <Comparative Example 2> A multifilament for drawing was obtained in the same manner as in Example 1, except that the conditions for steps (A) and (C) were changed to those shown in the following Table 2. Then, using the multifilament for drawing, an attempt was made to obtain a multifilament in the same manner as in Example 1, except that the conditions for step (C) were changed to those shown in the following Table 2. However, when an attempt was made to obtain a multifilament using the multifilament for drawing in the same manner as in Example 1, a part of the first single yarn broke, and it was not possible to produce a multifilament.

[0169] Comparative Examples 3 and 4 An attempt was made to obtain a multifilament for drawing in the same manner as in Example 1, except that the conditions of steps (A) and (B) were changed to those shown in Table 2 below. However, in Comparative Example 3, adjacent first single yarns were fused together, and a multifilament for drawing could not be obtained. In Comparative Example 4, some of the raw yarns were broken between the spinning nozzle 104 and the first take-up roll section 112, and a multifilament for drawing could not be obtained.

[0170] <Average value and coefficient of variation of fineness of first single yarn in multifilament to be drawn> The average value and coefficient of variation of fineness of first single yarn in multifilament to be drawn were determined by the method described above. The average value and coefficient of variation of fineness of first single yarn in multifilament to be drawn are shown in Table 2 below.

[0171] <Average value and coefficient of variation of fineness of second single yarn in multifilament> The average value and coefficient of variation of fineness of second single yarn in multifilament were determined by the method described above. The average value and coefficient of variation of fineness of second single yarn in multifilament are shown in Table 2 below.

[0172] <Average value of tensile strength of second single yarn in multifilament> The average value of tensile strength of second single yarn in multifilament was determined by the method described above. The average value of tensile strength of second single yarn in multifilament is shown in Table 2 below.

[0173]

[0174] As shown in Table 2, in Examples 1 to 7 within the scope of the present invention, the tensile strength of the second single yarn in the multifilament was higher than in Comparative Examples 1 and 5, in which the coefficient of variation of the fineness of the first single yarn in the multifilament to be drawn was 38.1% or more. Furthermore, in Comparative Example 2, in which an attempt was made to obtain a multifilament at the same draw ratio as in Example 3 using a multifilament to be drawn in which the coefficient of variation of the fineness of the first single yarn was 38.1%, a multifilament could not be obtained. Therefore, it can be seen that the present invention can provide a multifilament to be drawn that is likely to provide a multifilament with high strength even if the average fineness of the single yarns is small.

[0175] Furthermore, as shown in Table 2, in Examples 1 to 7 within the scope of the present invention, the heat transfer coefficient was 45 W / (m ２ The coefficient of variation of the fineness of the first single yarn in the multifilament to be drawn was smaller than that in Comparative Examples 1 and 5, where the coefficient of variation was 0.0 m / s or less. In Comparative Example 3, in which no air was blown (air velocity was 0.0 m / s), and Comparative Example 4, in which the air temperature was 60° C., it was not possible to obtain a multifilament to be drawn.

[0176] 100A: raw yarn, 100B: multifilament for drawing, 101: material input section, 102: kneading extruder, 103: gear pump, 104: spinning nozzle, 105: first cooling box, 106: second cooling box, 107: first take-up roll section, 108: first conveying roll section, 109: second conveying roll section, 110: third conveying roll section, 111: fourth conveying roll section, 112: first winding roll section, 113: second take-up roll section, 114: drawing roll section (heat treatment roll section), 115: take-off roll section (heat treatment roll section), 116: second winding roll section, 200B: multifilament for drawing, 207: take-up roll section, 208: first drawing roll section (heat treatment roll section), 209: second drawing roll section (heat treatment roll section), 210: third drawing roll section (heat treatment roll section), 211: take-off roll section, 212: winding roll section

Claims

1. A multifilament for stretching, having 30 or more single filaments, wherein the single filaments contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average value of the fineness of the single filaments is 30 dtex or less, the coefficient of variation of the fineness of the single filaments is 33% or less, and the poly(3-hydroxyalkanoate) resin contains poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), a multifilament for stretching.

2. A stretched multifilament, wherein the multifilament has 30 or more single filaments, the single filaments contain a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average value of the fineness of the single filaments is 20 dtex or less, the coefficient of variation of the fineness of the single filaments is 33% or less, and the poly(3-hydroxyalkanoate) resin contains poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), a multifilament.

3. The multifilament according to claim 2 is cut, a staple having a length of 20 cm or less.

4. A method for producing a multifilament for stretching, comprising obtaining a multifilament for stretching by melt spinning, a step (A) of discharging a melt by the melt spinning method using a spinneret having 30 or more discharge holes to obtain 30 or more raw filaments in a molten state, and a step (B) of obtaining a multifilament for stretching by blowing a gas at 0°C or higher and 50°C or lower onto the 30 or more raw filaments in a molten state to cool the 30 or more raw filaments, wherein the melt contains a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent, the average value of the fineness of the single filaments in the multifilament for stretching is 30 dtex or less, In the step (B), the heat transfer coefficient between the 30 or more raw yarns in a molten state and the gas is set to 60 W / (m ２ ·K) or more, and the poly(3-hydroxyalkanoate) resin contains poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), a method for producing a multifilament for stretching.

5. In the step (B), the heat transfer coefficient is set to 125 W / (m ２ ·K) or more. The method for manufacturing a multifilament for stretching according to claim 4.

6. In the step (B), the method for producing a multifilament for stretching according to claim 4 or 5, wherein the speed of the gas blown onto the 30 or more raw filaments is 0.1 m / s or more.

7. The multifilament for stretching is obtained by the method for producing a multifilament for stretching according to claim 4 or 5, A method for manufacturing a multifilament, comprising a step (C) of obtaining a multifilament by stretching the multifilament for stretching at least 1.5 times in a stretching roll section.

8. In the step (B), a gas at 0°C or higher and 50°C or lower is blown onto 30 or more of the raw yarns in a molten state, and the 30 or more raw yarns are cooled to 50°C or lower to obtain the multifilament for stretching. In the step (C), the method for manufacturing a multifilament according to claim 7, wherein the multifilament for stretching is heated and stretched in the stretching roll section.

9. The multifilament is obtained by the method for manufacturing a multifilament according to claim 7. A method for manufacturing staples, wherein the staples having a length of 20 cm or less are obtained by cutting the multifilament.