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

Abstract

The present invention is a multifilament, etc., comprising a plurality of single threads, the single threads containing a poly(3-hydroxyalkanoate)-based resin and polycaprolactone, the fineness of the single threads being 1.0-5.0 dtex, and the tensile strength of the single threads being 2.5 cN / dtex or greater.

Description

Multifilament and its manufacturing method, and staple and its manufacturing method

[0001] The present invention relates to 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 comprising a plurality of single yarns containing a 3-hydroxyalkanoate polymer.

[0006] International Publication No. 2015 / 029316

[0007] Incidentally, there will likely be a demand for multifilaments with even higher strength in the future, but sufficient research has not been conducted on high-strength multifilaments to date.

[0008] Therefore, a first object of the present invention is to provide a multifilament having high strength, and a second object is to obtain staples by cutting the multifilament.

[0009] The first aspect of the present invention relates to a multifilament including a plurality of single yarns, wherein the single yarns contain a poly(3-hydroxyalkanoate) resin and polycaprolactone, the fineness of the single yarns is 1.0 to 5.0 dtex, and the tensile strength of the single yarns is 2.5 cN / dtex or more. Preferably, the ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is 30 / 70 to 80 / 20. Preferably, the poly(3-hydroxyalkanoate) resin 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 represents an integer of 1 to 15. Preferably, the single yarn has a matrix-domain structure including a matrix and a domain, the matrix containing the poly(3-hydroxyalkanoate) resin, and the domain containing the polycaprolactone.

[0010] A second aspect of the present invention relates to a staple in which the multifilament is cut, has a crimped structure, and has an average length of 200 mm or less.

[0011] Furthermore, the third aspect of the present invention relates to a method for producing a multifilament comprising a plurality of single yarns by a melt spinning method using a spinning nozzle having a plurality of discharge holes, the method comprising: step (A) of obtaining a plurality of molten yarns by discharging a molten material from the plurality of discharge holes; step (B) of cooling the plurality of molten yarns by blowing a gas at 3 to 15°C onto the plurality of molten yarns; and step (C) of drawing the cooled plurality of yarns in a drawing roll section to obtain the multifilament, wherein the molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone, and the single yarns have a fineness of 1.0 to 5.0 dtex. Preferably, the tensile strength of the single yarns is 2.5 cN / dtex or more. Preferably, in step (C), the multifilament is obtained by heating the drawn plurality of yarns in a heat treatment roll section. Preferably, the fineness of the yarn used in step (C) is 5.0 to 15.0 dtex. Preferably, in step (C), the plurality of yarns cooled in step (B) are heated while being taken up by a take-up roll section at 25°C or higher and lower than 50°C, the plurality of yarns heated by the take-up roll section are drawn by the drawing roll section, and the plurality of yarns drawn by the drawing roll section are heated by a heat treatment roll section at 40 to 100°C. Preferably, in step (B), the plurality of cooled yarns are taken up by a yarn take-up roll section, and in step (C), the plurality of yarns taken up by the yarn take-up roll section are drawn by the drawing roll section. Preferably, the method for producing the multifilament is a method for producing the multifilament by a spin draw method. Preferably, in the step (C), the plurality of raw yarns drawn in the drawing roll section are heated in a heat treatment roll section at 25 to 100°C.

[0012] A fourth aspect of the present invention relates to a method for producing a staple, comprising obtaining the multifilament by the method for producing a multifilament, and cutting the multifilament to obtain staples, the staples having a crimped structure, and the average length of the staples being 200 mm or less.

[0013] According to the present invention, a multifilament having high strength can be provided, and further, according to the present invention, a staple formed by cutting the multifilament can be provided.

[0014] 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.

[0015] <<Multifilament>> First, the multifilament according to this embodiment will be described.

[0016] The multifilament according to this embodiment includes a plurality of single yarns. The single yarns contain a poly(3-hydroxyalkanoate) resin and polycaprolactone (PCL). The fineness of the single yarns is 1.0 to 5.0 dtex. The tensile strength of the single yarns is 2.5 cN / dtex or more.

[0017] The single yarn is a polymer composition containing a polymer component formed into a thread shape. The polymer composition may further contain an additive.

[0018] The polymer component includes a poly(3-hydroxyalkanoate)-based resin and polycaprolactone. The polymer component may contain other polymers in addition to the poly(3-hydroxyalkanoate)-based resin and polycaprolactone.

[0019] The poly(3-hydroxyalkanoate) resin is a polyester containing 3-hydroxyalkanoic acid as a monomer. The poly(3-hydroxyalkanoate) resin is 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 be evaluated by measuring biochemical oxygen demand. The poly(3-hydroxyalkanoate) resin may be a homopolymer or a copolymer.

[0020] 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.

[0021] The poly(3-hydroxyalkanoate) resin preferably contains 3-hydroxybutyrate as a constituent unit.

[0022] 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).

[0023] 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.

[0024] As the poly(3-hydroxyalkanoate)-based resin, from the viewpoint of achieving both excellent biodegradability and moldability, P3HB, P3HB3HH, P3HB3HV, P3HB4HB, etc. are preferred, but are not particularly limited to. Furthermore, as the poly(3-hydroxyalkanoate)-based resin, from the viewpoint of increasing the strength of the multifilament according to this embodiment and improving moldability, P3HB3HH is preferred.

[0025] 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.

[0026] 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.

[0027] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,500,000. When the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 3,000,000 or less, the multifilament according to this embodiment can be easily molded. When the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 50,000 or more, the strength of the multifilament according to this embodiment 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 suitable for measuring the molecular weight may be used as the column for the GPC.

[0028] The polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. Similarly to poly(3-hydroxyalkanoate)-based resins, polycaprolactone is biodegradable. Furthermore, since the single yarn contains polycaprolactone, the multifilament according to this embodiment has high strength. The weight-average molecular weight of the polycaprolactone is preferably 5,000 to 500,000, and more preferably 10,000 to 200,000. The weight-average molecular weight of the polycaprolactone is 500,000 or less, which makes it easier to mold the multifilament according to this embodiment. The weight-average molecular weight of the polycaprolactone is 5,000 or more, which makes it possible to increase the strength of the multifilament according to this embodiment.

[0029] The other polymer is preferably biodegradable.

[0030] Examples of other biodegradable polymers include polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, unmodified starch, modified starch, cellulose acetate, chitosan, poly(4-hydroxyalkanoate)-based resins, etc. The polymer composition may contain one type of other polymer, or may contain two or more types of other polymers.

[0031] 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 the poly(3-hydroxyalkanoate) resin and polycaprolactone in total.

[0032] The ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is preferably 30 / 70 to 80 / 20, more preferably 40 / 60 to 75 / 25, and even more preferably 55 / 45 to 70 / 30. When the ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is 30 / 70 or more, the multifilament according to this embodiment has the advantage of being excellent in heat resistance. When the ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is 80 / 20 or less, the multifilament according to this embodiment has the advantage of being easily increased in strength.

[0033] Preferably, the single yarn has a matrix-domain structure including a matrix and a domain, the matrix containing the poly(3-hydroxyalkanoate) resin, and the domain containing the polycaprolactone. The multifilament according to this embodiment has the advantage of having excellent heat resistance due to the single yarn having such a structure. The reason why the multifilament according to this embodiment has such an advantage is thought to be as follows. Here, the matrix-domain structure is also called a sea-island structure. In a matrix-domain structure, the matrix is ​​a continuous phase. On the other hand, the domains are discontinuous phases like islands floating in the sea. Therefore, the properties of the matrix are mainly expressed as the properties of the single yarn. The poly(3-hydroxyalkanoate) resin has higher heat resistance than polycaprolactone. Therefore, it is thought that the multifilament according to this embodiment has excellent heat resistance due to the single yarn having such a structure.

[0034] The multifilament according to this embodiment contains a biodegradable polymer, and therefore, even if discarded in the environment, it is easily decomposed in the environment, thereby reducing the burden on the environment.

[0035] Examples of the additives include nucleating agents, lubricants, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, inorganic fillers, organic fillers, and antistatic agents.

[0036] In order to promote the crystallization of the poly(3-hydroxyalkanoate)-based resin, the polymer composition preferably contains a crystal nucleating agent. The crystal nucleating agent is a compound that has the effect of promoting the 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.

[0037] 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.

[0038] 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 per 100 parts by mass of the poly(3-hydroxyalkanoate)-based resin, when producing a multifilament from a melt of the polymer composition, the viscosity of the melt can be reduced, which has the advantage of facilitating the production of multifilaments. 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.

[0039] The polymer composition preferably contains the lubricant. The lubricant in the single yarn improves the lubricity of the single yarn, thereby preventing the single yarns from fusing together. Examples of the lubricant include compounds 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.

[0040] 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 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 prevent the lubricant from bleeding out onto the surface of the multifilament.

[0041] The fineness of the single yarn is 1.0 to 5.0 dtex. The fineness of the single yarn is preferably more than 1.0 dtex, and more preferably 1.5 dtex or more. The fineness of the single yarn is preferably 4.7 dtex or less, and more preferably 4.5 dtex or less. In this embodiment, the fineness of the single yarn refers to the thickness of the yarn and is defined as the mass per unit length. The mass (g) per 10,000 m is expressed in units (dtex). Specifically, it is measured by an autobibroscope method.

[0042] The tensile strength of the single yarn is 2.5 cN / dtex or more. The tensile strength of the single yarn is preferably 2.6 cN / dtex or more. A higher tensile strength of the single yarn is preferable, but the tensile strength of the single yarn is, for example, 10 cN / dtex or less. The tensile strength of the single yarn is not particularly limited as long as it is within a range that does not impair the flexibility and toughness required depending on the application, but may be 10 cN / dtex or less. The tensile strength of the single yarn can be measured based on JIS L 1015:2010, Test Method for Staple Man-Made Fibers, at an initial length of 20 mm and a speed of 20 mm / min.

[0043] The multifilament according to the present embodiment may be used as a single multifilament, or may be used as a braid or sheet formed from a plurality of multifilaments. The multifilament according to the present embodiment can be used in marine and terrestrial environments. The multifilament according to the present embodiment can be used, for example, for fishing nets, marine ropes, aquaculture nets, fishing lines, agricultural nets, artificial turf, sandbag nets, and waterproof sheets. Sandbag nets can be used, for example, in revetment construction.

[0044] <<Staple>> The staple according to this embodiment is a staple obtained by cutting the multifilament according to this embodiment. The staple according to this embodiment has a crimped structure. In other words, the staple according to this embodiment is a crimped yarn.

[0045] The average length of the staple according to this embodiment is 200 mm or less, and is not particularly limited as long as it is 200 mm or less, and may be appropriately set according to the application for which the staple is used. From the viewpoint of ease of use in various applications, the average length of the staple according to this embodiment is preferably 160 mm or less, more specifically 1.0 to 100 mm. The average length of the staple means the "average value of fiber length" obtained by "c) Method C (substitution method)" of "8.4 Fiber Length" of "8.4.1 Average Fiber Length" in JIS L1015:2021 "Test Methods for Chemical Fiber Staples."

[0046] The staple according to the present embodiment can be used as a dry-laid nonwoven fabric. The dry-laid nonwoven fabric can be used as a sanitary material, a medical material, a daily necessities material, a waterproof material, an interior material for an automobile, etc. Specifically, the dry-laid nonwoven fabric can be used for diapers, filters, towels, wipes, gauze, napkins, carpets, etc.

[0047] <<Method for Producing a Multifilament>> The method for producing a multifilament according to this embodiment is a method for producing a multifilament including a plurality of single yarns by a melt spinning method using a spinning nozzle having a plurality of discharge holes. The method for producing a multifilament according to this embodiment includes the steps of: (A) obtaining a plurality of molten yarns by discharging a molten material through the plurality of discharge holes; (B) cooling the plurality of molten yarns by blowing a gas at 3 to 15°C onto the plurality of molten yarns; and (C) obtaining the multifilament by drawing the cooled plurality of yarns using a drawing roll unit. The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The single yarns have a fineness of 1.0 to 5.0 dtex.

[0048] The tensile strength of the single yarn is preferably 2.5 cN / dtex or more.

[0049] In the step (A), the melt is the polymer composition in a molten state.

[0050] <First embodiment: second drawing method (sequential drawing method)> Hereinafter, a method for producing a multifilament by the second drawing method (also referred to as the "sequential drawing method") will be described as an example, with reference to Figures 1 and 2. In the method for producing a multifilament according to the first embodiment, the plurality of yarns cooled by the gas are wound by a yarn take-up roll unit, and the plurality of yarns wound by the yarn take-up roll unit are drawn by the drawing roll unit.

[0051] (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. The kneading extruder 102 is a screw extruder. The kneading extruder 102 may be a single-screw extruder or a twin-screw extruder.

[0052] Then, a spinning nozzle 104 having a plurality of discharge holes is used to discharge the molten material obtained in the kneading extruder 102 from the plurality of discharge holes, thereby obtaining a plurality of molten raw yarns 100A. The flow rate of the molten material discharged from the plurality of discharge holes of the spinning nozzle 104 is adjusted by a gear pump 103.

[0053] The temperature of the spinning nozzle 104 is, for example, 160 to 180°C.

[0054] The shape, size, and number of the ejection holes are not particularly limited. For example, when the ejection holes are circular, the diameter of the ejection holes is preferably 0.1 mm to 3.0 mm. The number of the ejection holes may vary depending on the size of the ejection holes, but may be, for example, 15 or more and 1,000 or less.

[0055] The spinning nozzle flow rate, that is, the rate at which the molten material is discharged from the spinning nozzle 104, is preferably 0.05 m / min to 20 m / min, more preferably 1.0 m / min to 10 m / min, and even more preferably 0.5 m / min to 5.0 m / min.

[0056] The rate at which the molten material is discharged from the discharge hole of the spinning nozzle 104 is preferably 0.10 g / min / hole or more, more preferably 0.15 g / min / hole or more. The rate is preferably less than 1.0 g / min / hole, more preferably 0.90 g / min / hole or less.

[0057] (Step (B)) In step (B), a gas at 3 to 15°C is blown onto the molten yarns 100A obtained in step (A), thereby cooling the yarns 100A. In step (B), cooling the yarns 100A with gas at 3 to 15°C shortens the time during which the yarns 100A are in the temperature range in which the polycaprolactone and poly(3-hydroxyalkanoate)-based resin constituting the yarns 100A crystallize, thereby suppressing the progress of crystallization of the polycaprolactone and poly(3-hydroxyalkanoate)-based resin. This prevents the yarns 100A from becoming hard. This makes it easier to draw the yarns 100A in step (C). As a result, the strength of the multifilament is easily increased. In the first embodiment, the raw yarn 100A is cooled in a first cooling box 105 with gas at 3 to 15°C, and the raw yarn 100A cooled in the first cooling box 105 is then cooled in a second cooling box 106 with gas at 3 to 15°C.

[0058] The temperature of the gas blown onto the plurality of molten yarns 100A obtained in the step (A) is 3 to 15° C., and preferably 3.0 to 6.0° C. Note that the "temperature of the gas blown onto the plurality of molten yarns 100A obtained in the step (A)" refers to the temperature of the gas when the gas comes into contact with the yarns 100A.

[0059] The speed of the gas blown onto the plurality of molten yarns 100A obtained in step (A) is not particularly limited, but is preferably 0.1 m / s or more and 5 m / s or less, and more preferably 0.1 m / s or more and 3 m / s or less. When the gas speed is 0.1 m / s or more, the cooling effect of the gas is easily exerted. When the gas speed is 5 m / s or less, the molten yarns 100A discharged from the spinning nozzle 104 are 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 "speed of the gas blown onto the plurality of molten yarns 100A obtained in step (A)" refers to the speed of the gas when the gas comes into contact with the yarns 100A.

[0060] Examples of the gas include air and inert gases (nitrogen gas, argon gas, etc.).

[0061] In the step (B), the yarn 100A cooled by gas at 3 to 15°C is 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. Then, in the step (B), the plurality of yarns 100A taken up by the first take-up roll unit 107 are wound up by a yarn take-up roll unit 112. In the first embodiment, the plurality of yarns 100A taken up by the first take-up roll unit 107 are transported to the yarn take-up roll unit 112 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. Although each transport roll unit is composed of two rolls in FIG. 1, it may be composed of one roll or three or more rolls.

[0062] In step (B), the plurality of yarns 100A are cooled to preferably 50°C or less, more preferably 40°C or less. In step (B), the plurality of yarns 100A are cooled to, for example, 0°C or more, more specifically 10°C or more. In step (B), the plurality of yarns may be cooled to 50°C or less by blowing gas at 3 to 15°C. Alternatively, in step (B), the plurality of yarns 100A may be cooled to a certain extent by blowing gas at 3 to 15°C, and then cooled with ambient air while the yarns 100A are transported from the first take-up roll unit 107 to the yarn take-up roll unit 112, thereby cooling the plurality of yarns to 50°C or less.

[0063] In order to draw the yarn 100A in step (C), it is preferable that the yarn 100A is not drawn or is drawn only slightly in step (B). That is, the draw ratio in step (B) is preferably 1.5 times or less, more preferably 1.2 times or less, even more preferably 1.1 times or less, and most preferably 1.0 times. The draw ratio in step (B) is 1.0 times or more. The draw ratio in step (B) can be calculated using the following formula: Draw ratio in step (B) = Speed ​​(m / min) of yarn take-up roll unit / Speed ​​(m / min) of take-up roll unit (in the first embodiment, "first take-up roll unit 107") used in step (B). The speed (m / min) of the yarn take-up roll unit is the length of the yarn per unit time wound around the yarn take-up roll unit. The speed (m / min) of the take-up roll unit used in the step (B) is the length per unit time of the raw yarn taken up by the take-up roll unit used in the step (B) (in the first embodiment, the "first take-up roll unit 107"). In the first embodiment, when the calculated value of the draw ratio in the step (B) is less than 1.0, the draw ratio is set to 1.0.

[0064] (Step (C)) As shown in FIG. 2 , in step (C), the plurality of yarns 100A cooled to 50°C or less in step (B) are heated and drawn by the drawing roll section 114. In step (C), the plurality of yarns 100A are drawn, thereby increasing the orientation of the polymer components contained in the yarns, thereby increasing the tensile strength of the yarns. As a result, the strength of the multifilament can be increased. Here, to increase the orientation of the polymer components, it is desirable to draw the yarns within a temperature range suitable for increasing the orientation of the polymer components. This is because if the yarns are drawn at a temperature higher than this temperature range, the polymer components are in a molten state, and as a result, the orientation of the polymer components does not increase significantly even after drawing. Furthermore, if the yarns are drawn at a temperature lower than this temperature range, the polymer components solidify too much, making the yarns difficult to draw. Furthermore, if the yarns are forcibly pulled in an attempt to draw them, the yarns will break, making it impossible to produce a multifilament. In the first embodiment, the plurality of yarns 100A cooled to 50°C or less in the step (B) are heated and drawn by the drawing roll section 114. This makes it easier to adjust the temperature of the plurality of yarns to fall within a temperature range suitable for increasing the orientation of the polymer components when drawing the plurality of yarns, compared to the spin draw method in which the plurality of yarns are drawn while being cooled by ambient air. As a result, it becomes easier to increase the orientation of the polymer components of the plurality of yarns. Therefore, in the first embodiment, it becomes easier to increase the strength of the multifilament.

[0065] The fineness of the raw yarn used in step (C) is preferably 5.0 to 15.0 dtex, more preferably 6.0 to 10 dtex. The following relationship approximately holds true for the fineness of the raw yarn used in step (C): Fineness (dtex) of raw yarn used in step (C) = (((a x 1000 / 60) / b x 10000) / c) / d, where a: Amount (kg / h) of the molten material discharged from the spinning nozzle 104, b: Speed ​​(m / min) of the take-up roll unit (in the first embodiment, "first take-up roll unit 107") used in step (B), c: Number (number) of discharge holes in the spinning nozzle 104, and d: Draw ratio (-) in step (B). Therefore, by adjusting b, etc., the fineness of the raw yarn used in step (C) can be adjusted.

[0066] In the step (C), the plurality of yarns wound by the yarn take-up roll unit 112 are taken up by a second take-up roll unit 113. Next, in the step (C), the yarns 100A taken up by the second take-up roll unit 113 are drawn by the drawing roll unit 114. Then, in the step (C), the obtained multifilament is taken up by a multifilament take-up roll unit 116. Also, in the step (C), the yarns 100A drawn by the drawing roll unit 114 may be transported by a take-off roll unit 115.

[0067] 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 step (C), it is preferable to heat the plurality of yarns 100A in the second take-up roll section 113. In step (C), heating the plurality of yarns 100A in the second take-up roll section 113 facilitates adjusting the temperature of the plurality of yarns 100A to within a temperature range suitable for enhancing the orientation of the polymer components contained in the plurality of yarns 100A. As a result, it becomes easier to enhance the orientation of the polymer components of the plurality of yarns 100A. The temperature of the second take-up roll section 113 is preferably 25°C or higher and lower than 50°C, more preferably 30 to 45°C. If the temperature of the environment in which step (C) is performed is 25°C or higher, it is not necessary to heat the plurality of yarns 100A in the second take-up roll section 113.

[0068] The stretching roll section 114 is composed of two rolls. The stretching roll section 114 may be composed of one roll, or may be composed of three or more rolls. In the step (C), the plurality of yarns 100A may or may not be heated in the stretching roll section 114. That is, in the first embodiment, the stretching roll section 114 may also serve as a heat treatment roll. In the step (C), a method of promoting crystallization of the polymer component contained in the plurality of yarns 100A by heating the plurality of yarns 100A in the stretching roll section 114 may also be used. The temperature of the stretching roll section (heat treatment roll section) 114 is preferably 40 to 100°C, more preferably 50 to 90°C.

[0069] In the first embodiment, it is preferable that the take-off roll 115 also serves as a heat treatment roll. The take-off roll 115 (heat treatment roll section 115) is composed of two rolls. The take-off roll 115 (heat treatment roll section 115) may be composed of one roll or three or more rolls. That is, in the step (C), the drawn yarns 100A are heated in the heat treatment roll section 115 to obtain the multifilament. In the step (C), the crystallization of the polymer components contained in the yarns 100A can be promoted by heating the yarns 100A in the heat treatment roll section 115. The temperature of the take-off roll (heat treatment roll section) 115 is preferably 40 to 100°C, more preferably 50 to 90°C. Both or only one of the drawing roll section 114 and the take-off roll section 115 may be a heat treatment roll section.

[0070] The draw ratio in the step (C) is preferably 2.0 times or more. The draw ratio in the step (C) is, for example, 10.0 times or less. When the draw ratio in the step (C) is 2.0 times or more, the orientation of the polymer components of the multiple raw yarns 100A is further increased. The draw ratio in the step (C) can be calculated by the following formula: Draw ratio in the step (C) = Speed ​​(m / min) of the multifilament take-up roll unit / Speed ​​(m / min) of the take-up roll unit used in the step (C) (in the first embodiment, the "second take-up roll unit 113").

[0071] In the step (C), the relaxation rate calculated by the following formula is preferably 5 to 15%: Relaxation rate (%) = ((speed of the drawing roll unit 114 - speed of the multifilament take-up roll unit 116) / speed of the multifilament take-up roll unit 116) × 100

[0072] The speed (m / min) of the multifilament take-up roll unit is the length per unit time of the multiple yarns taken up by the multifilament take-up roll unit. The speed (m / min) of the take-up roll unit used in step (C) is the length per unit time of the multiple yarns taken up by the take-up roll unit (in the first embodiment, the "second take-up roll unit 113") used in step (C). The speed (m / min) of the stretching roll unit is the length per unit time of the multiple yarns transported by the stretching roll unit. In the first embodiment, only one stretching roll unit is used, but multiple stretching roll units may be used. When multiple stretching roll units are used, the highest speed among the multiple stretching roll units is defined as the "stretching roll unit speed."

[0073] In step (B) in FIG. 1 , the raw yarn 100A taken up by the first take-up roll unit 107 is wound up by the raw yarn take-up roll unit 112. However, in the first embodiment, the raw yarn 100A taken up by the first take-up roll unit 107 may be accommodated in a storage container without being wound up by the raw yarn take-up roll unit 112. When the raw yarn 100A taken up by the first take-up roll unit 107 is transported to a storage container using a transport roll unit without being wound up by the raw yarn take-up roll unit 112, the draw ratio in step (B) can be calculated using the following formula: Draw ratio = Speed ​​of transport roll unit (m / min) / Speed ​​of first take-up roll unit (m / min) The speed of the transport roll unit (m / min) is the length of the raw yarn transported by the transport roll unit per unit time. When multiple transport roll units are used, the speed of the fastest transport roll unit is used in the formula for the draw ratio. When neither the yarn take-up roll section 112 nor the transport roll section is used, the draw ratio is 1.0.

[0074] Second Embodiment: Spin Draw Method Next, a second embodiment will be described with reference to Fig. 3. Note that descriptions that overlap with the first embodiment will be omitted, and unless otherwise specified, the second embodiment will be the same as that described in the first embodiment.

[0075] The method for producing a multifilament according to the second embodiment is a method for producing the 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 plurality of molten yarns with a drawing roll unit are carried out in a single step. The spin-draw method is also called the "SDY method" or the "direct spinning drawing method."

[0076] In the step (C) of the second embodiment, as shown in Fig. 3, the plurality of raw yarns cooled in the step (B) are taken up by a take-up roll section 207. Next, the plurality of raw yarns taken up by the take-up roll section 207 are drawn by three drawing roll sections (a first drawing roll section 208, a second drawing roll section 209, and a third drawing roll section 210). Then, in the step (C), the obtained multifilament is wound up by a multifilament winding roll section 212. Also, in the step (C), the raw yarn 100A drawn by the drawing roll section may be transported by a take-off roll section 211.

[0077] In the step (C), the plurality of raw yarns cooled in the first cooling box 105 and the second cooling box 106 are taken up by a take-up roll section 207. Although the take-up roll section 207 is configured with two rolls in FIG. 1, it may be configured with one roll or with three or more rolls.

[0078] 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 208, 209, 210) is configured with two rolls in FIG. 1 , it may be configured with one roll or three or more rolls. From the viewpoint of promoting crystallization of the polymer component contained in the multiple original yarns 100A, the temperature of the heat treatment roll section is preferably 25 to 100°C, more preferably 40 to 90°C. Note that when the temperature of the environment in which step (C) is performed is 25°C or higher, crystallization of the polymer component contained in the multiple original yarns 100A can be promoted without using a heat treatment roll.

[0079] In the multifilament manufacturing method according to this embodiment, the spinning draft number (NDR) is preferably 150 or more, more preferably 200 or more. Furthermore, the NDR is usually 1,000 or less. The NDR can be calculated using the following formula: NDR = speed (m / min) of the take-up roll section (initial take-up roll section) that initially takes up the raw yarn from the spinning nozzle / spinning nozzle flow rate (m / min). By setting the NDR to 150 or more, the raw yarn can be drawn between the spinning nozzle and the initial take-up roll section, thereby increasing the strength of the multifilament. In the first embodiment (post-drawing method), the initial take-up roll section is the first take-up roll section 107. Meanwhile, in the second embodiment (spin-draw method), the initial take-up roll section is the take-up roll section 207.

[0080] <Method for manufacturing staple> In the method for manufacturing a staple according to this embodiment, a multifilament is obtained by the method for manufacturing a multifilament according to this embodiment, and the multifilament is cut to obtain a staple. The staple has a crimped structure. The average length of the staple is 200 mm or less, preferably 160 mm or less, and more specifically 1.0 to 100 mm.

[0081] In the method for producing the staple according to this embodiment, a staple having a crimped structure can be obtained by crimping a multifilament and cutting the crimped multifilament.

[0082] The multifilament and its manufacturing method, and the staple and its manufacturing method according to the present embodiment are configured as described above, and therefore have the following advantages.

[0083] That is, the multifilament according to this embodiment includes a plurality of single yarns. The single yarns contain a poly(3-hydroxyalkanoate) resin and polycaprolactone. The fineness of the single yarns is 1.0 to 5.0 dtex. The tensile strength of the single yarns is 2.5 cN / dtex or more. Due to this configuration, the multifilament according to this embodiment has high strength.

[0084] In the future, from the viewpoint of applicability to a variety of uses, there will be a demand for multifilaments that have high strength, thin single yarns, and good biodegradability. Here, polycaprolactone, like poly(3-hydroxyalkanoate)-based resins, is biodegradable. Furthermore, the single yarns become thin by setting the fineness of the single yarns to 5.0 dtex or less. Therefore, according to this embodiment, it is possible to provide multifilaments that have high strength, thin single yarns, and good biodegradability.

[0085] The method for producing a multifilament according to this embodiment is a method for producing a multifilament having a plurality of single yarns using a spinning nozzle having a plurality of discharge holes. The method for producing a multifilament according to this embodiment includes the steps of: (A) obtaining a plurality of molten yarns by discharging a molten material through the plurality of discharge holes; (B) cooling the plurality of molten yarns by blowing a gas at 3 to 15°C onto the plurality of molten yarns; and (C) obtaining the multifilament by drawing the cooled plurality of yarns using a drawing roll unit. The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The single yarns have a fineness of 1.0 to 5.0 dtex. In the step (B), by cooling the yarn with a gas at 3 to 15°C, the time during which the polycaprolactone and poly(3-hydroxyalkanoate) resin constituting the yarn are in the temperature range in which they crystallize can be shortened, and the progress of crystallization of the polycaprolactone and poly(3-hydroxyalkanoate) resin can be suppressed. This prevents the yarn from becoming hard. This makes it easier to sufficiently draw the yarn in the step (C). As a result, it becomes easier to increase the strength of the multifilament.

[0086] In the method for producing a multifilament according to the present embodiment, the multifilament is obtained by heating the drawn raw yarns in a heat treatment roll section in the step (C). The method for producing a multifilament according to the present embodiment has such a configuration, and therefore the crystallinity of the multifilament can be increased, and as a result, the strength of the multifilament can be increased.

[0087] Furthermore, in the method for producing a multifilament according to this embodiment, in the step (B), the plurality of yarns are cooled to 50°C or below, and in the step (C), the plurality of yarns cooled to 50°C or below in the step (B) are heated and drawn in the drawing roll section. Here, to enhance the orientation of the polymer component, it is generally desirable to draw the yarn in a temperature range suitable for enhancing the orientation of the polymer component. This is because, if the yarn is drawn at a temperature higher than this temperature range, the polymer component is in a molten state, and as a result, the orientation of the polymer component is not significantly enhanced even after drawing. Furthermore, if an attempt is made to draw the yarn at a temperature lower than this temperature range, the polymer component will solidify too much, making it difficult to draw the yarn. Furthermore, if the yarn is forcibly pulled in an attempt to draw the yarn, the yarn will break, making it impossible to produce a multifilament. In this embodiment, the plurality of yarns cooled to 50°C or less in step (B) are heated and drawn in the drawing roll section, which makes it easier to adjust the temperature of the plurality of yarns to fall within a temperature range suitable for enhancing the orientation of the polymer components when drawing the plurality of yarns, compared to the spin draw method in which the plurality of yarns are drawn while being cooled in ambient air. As a result, it is easier to enhance the orientation of the polymer components of the plurality of yarns. Therefore, in this embodiment, it is easier to enhance the strength of the multifilament.

[0088] It should be noted that the multifilament and its manufacturing method, and the staple and its manufacturing method according to the present invention are not limited to the above-described embodiments. Furthermore, the multifilament and its manufacturing method, and the staple and its manufacturing method according to the present invention are not limited by the above-described effects. Furthermore, the multifilament and its manufacturing method, and the staple and its manufacturing method according to the present invention can be modified in various ways without departing from the gist of the present invention.

[0089] 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.

[0090] Example 1 A multifilament was produced by the method of the first embodiment (post-drawing method).

[0091] (Step (A)) First, as shown in FIG. 1 , a melt produced in a kneading extruder 102 was extruded through the nozzle of a spinning nozzle 104 to obtain a plurality of 100A (80) original yarns. The melt was a polymer composition containing a poly(3-hydroxyalkanoate) resin, a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (3-hydroxyhexanoate ratio = 6 mol%, Mw = 550,000) (P3HB3HH), polycaprolactone (PCL), erucic acid amide as a lubricant having an amide bond, behenic acid amide as a lubricant having an amide bond, and pentaerythritol as a crystal nucleating agent, in the blending ratios shown in Table 1 below. In Table 1 below, the "content of lubricant having an amide bond" refers to the amount (parts by mass) of lubricant having an amide bond relative to 100 parts by mass of P3HB3HH. The "content of nucleating agent" is the amount (parts by mass) of nucleating agent relative to 100 parts by mass of P3HB3HH. Furthermore, "parts by mass" is simply expressed as "parts."

[0092] (Step (B)) In cooling boxes 105 and 106, air at 7°C (quench air) was blown onto the plurality of yarns 100A. Next, the plurality of yarns 100A cooled in the cooling boxes 105 and 106 were taken up by a first take-up roll unit 107, and the plurality of yarns 100A passed through transport roll units 108, 109, 110, and 111 in order, after which the plurality of yarns 100A were taken up by a yarn take-up roll unit 112. The yarn fineness taken up by the yarn take-up roll unit 112 was 7.6 dtex. The NDR was 353, and the draw ratio was 1.1.

[0093] (Step (C)) As shown in Fig. 2 , a plurality of yarns (room temperature (25°C)) taken up by the yarn take-up roll unit 112 were taken up by a second take-up roll unit 113 (room temperature (25°C)) and drawn by a drawing roll unit (heat treatment roll unit) 114 (60°C). After the plurality of yarns passed through a take-off roll unit (heat treatment roll unit) 115 (60°C), the obtained multifilament was taken up by the multifilament take-up roll unit 116. The draw ratio was 2.2, and the relaxation rate was 10%.

[0094] Example 2 A multifilament was produced by the method of the second embodiment (SDY method). A plurality of raw yarns 100A were obtained by cooling in cooling boxes 105 and 106 in the same manner as in Example 1. Next, as shown in FIG. 3 , the plurality of raw yarns 100A cooled in the cooling boxes 105 and 106 were taken up by a take-up roll section 207 and drawn in drawing roll sections (heat treatment roll sections) 208, 209, and 210 (50°C). After the plurality of raw yarns passed through a take-off roll section 211, the obtained multifilament was wound up by a multifilament winding roll section 212. The NDR was 324, the draw ratio was 2.0, and the relaxation rate was 5%.

[0095] Examples 3, 5, and 7, Comparative Example 1 Multifilaments were obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1.

[0096] Examples 4, 6, and 8, Comparative Example 2 Multifilaments were obtained in the same manner as in Example 2, except that the conditions were changed as shown in Table 1.

[0097] (Single Yarn Fineness and Tensile Strength) For each multifilament of the Examples and Comparative Examples, the single yarn fineness and tensile strength of the single yarn in the multifilament were measured by the method described above. The single yarn fineness and tensile strength are shown in Table 1 below.

[0098] (Matrix-Domain Structure of Single Yarn) The presence or absence of a matrix-domain structure in the single yarn in the multifilaments of the Examples and Comparative Examples was confirmed using a transmission electron microscope (TEM). In addition, the single yarns in the multifilaments of the Examples and Comparative Examples were dyed with ruthenium tetroxide, and the dyed single yarns were observed using the transmission electron microscope to determine the polymers contained in the matrix and the domains based on the difference in the dyeing state. The presence or absence of a matrix-domain structure in the single yarn, the polymer contained in the matrix, and the polymer contained in the domain are shown in Table 1 below.

[0099] (Single Yarn Elongation and Single Yarn Young's Modulus) For each multifilament in the Examples and Comparative Examples, the single yarn elongation and single yarn Young's modulus in the multifilament were measured at an initial length of 20 mm and a speed of 20 mm / min according to JIS L 1015:2010, Test Method for Staple Chemical Fibers. The single yarn elongation and single yarn Young's modulus are shown in Table 1 below.

[0100] (Fusion Rate) For each multifilament in the Examples and Comparative Examples, the multifilament was cut in a plane perpendicular to the longitudinal direction of the multifilament, thereby cutting all of the single yarns contained in the multifilament. Next, the cut surface of the multifilament was observed using a scanning electron microscope (SEM), and the total number of single yarns contained in the multifilament at the cut surface and the number of single yarns fused to other single yarns at the cut surface (which is also the number obtained by subtracting the number of single yarns not fused to other single yarns from the total number of single yarns contained in the multifilament) were counted. The fusion rate was then calculated using the following formula: Fusion rate (%) = (number of single yarns fused to other single yarns at the cut surface / total number of single yarns contained in the multifilament at the cut surface) × 100. The fusion rates are shown in Table 1 below.

[0101] (Heat Resistance Test) For each of the multifilaments of the Examples and Comparative Examples, a single yarn in the multifilament was subjected to thermomechanical analysis (TMA) under the following conditions to measure the temperatures at which the shrinkage of the single yarn became 5%, 10%, and 20%: Load: 3 g Measurement atmosphere: Air Temperature range: Room temperature (25°C) to 180°C Heating rate: 5°C / min The results of the heat resistance test (temperatures at which the shrinkage became 5%, 10%, and 20%) are shown in Table 1 below.

[0102]

[0103] As shown in Table 1, in Examples 1 to 8, which are within the scope of the present invention, the tensile strength of the single yarn was higher than that of Comparative Examples 1 and 2, which did not use polycaprolactone. Therefore, it can be seen that according to the present invention, a multifilament having high strength can be obtained.

[0104] Furthermore, as shown in Table 1, in Examples 1 to 6 in which the matrix contained a poly(3-hydroxyalkanoate) resin, the temperature at which the specified heat shrinkage rate was achieved was higher than in Examples 7 and 8 in which the matrix contained polycaprolactone. Therefore, it is clear that the multifilament in which the matrix contained a poly(3-hydroxyalkanoate) resin has excellent heat resistance.

[0105] (Comparative Example 3) An attempt was made to produce a multifilament in the same manner as in Example 1, except that the quench air temperature was set to 25°C. However, the raw yarn broke between the spinning nozzle 104 and the first take-up roll 107, and it was not possible to produce a multifilament.

[0106] (Comparative Example 4) An attempt was made to produce a multifilament in the same manner as in Example 3, except that the quench air temperature was set to 25°C. However, the raw yarn broke between the spinning nozzle 104 and the first take-up roll 107, and it was not possible to produce a multifilament.

[0107] (Comparative Example 5) An attempt was made to produce a multifilament in the same manner as in Example 7, except that the quench air temperature was set to 25°C. However, the raw yarn broke between the spinning nozzle 104 and the first take-up roll 107, and it was not possible to produce a multifilament.

[0108] From the above, in Comparative Examples 3 to 5, in which the quench air temperature was set to 25°C, the yarn broke between the spinning nozzle 104 and the first take-up roll 107, making it impossible to produce a multifilament. In Comparative Examples 3 to 5, lowering the NDR may have made it possible to produce a multifilament, but doing so would have led to a certain degree of crystallization of the polymer component while suppressing drawing to single yarns. On the other hand, in Examples 1 to 8 within the scope of the present invention, by performing step (B) of blowing gas at 3 to 15°C onto multiple molten yarns, it is possible to perform drawing to a certain extent before crystallization of the polymer component progresses. As a result, it is believed that a multifilament with high strength was obtained. In other words, it can be seen that according to the present invention, a multifilament with high strength can be obtained.

[0109] 100A: raw yarn, 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: raw yarn take-up 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: multifilament take-up roll section, 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: Multifilament winding roll section

Claims

1. A multifilament having a plurality of single yarns, The single yarn contains a poly(3-hydroxyalkanoate)-based resin and polycaprolactone, The fineness of the single yarn is 1.0 to 5.0 dtex, The tensile strength of the single yarn is 2.5 cN / dtex or more, The poly(3-hydroxyalkanoate)-based resin comprises poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

2. The multifilament according to claim 1, wherein a mass ratio of the poly(3-hydroxyalkanoate) resin to the polycaprolactone is 30 / 70 to 80 / 20.

3. The single yarn has a matrix-domain structure comprising a matrix and a domain, the matrix contains the poly(3-hydroxyalkanoate)-based resin, The multifilament according to claim 1 or 2, wherein the domain contains the polycaprolactone.

4. The multifilament according to any one of claims 1 to 3 is cut, It has a crimped structure, A staple having an average length of 200 mm or less.

5. A method for producing a multifilament comprising the steps of: producing a multifilament having a plurality of single yarns by a melt spinning method using a spinning nozzle having a plurality of discharge holes; A step (A) of discharging a molten material from the plurality of discharge holes to obtain a plurality of molten yarns; A step (B) of cooling the plurality of raw yarns in a molten state by blowing gas at 3 to 15°C onto the plurality of raw yarns; and (C) a step of drawing the cooled raw yarns in a drawing roll section to obtain the multifilament, the melt contains a poly(3-hydroxyalkanoate)-based resin and polycaprolactone; The fineness of the single yarn is 1.0 to 5.0 dtex, the mass ratio of the poly(3-hydroxyalkanoate) resin to the polycaprolactone is 55 / 45 to 70 / 30; In the step (C), the raw yarns are heated at a heat treatment roll section at 40 to 100° C.

6. The method for producing a multifilament according to claim 5, wherein the single yarn has a tensile strength of 2.5 cN / dtex or more.

7. 7. The method for producing a multifilament according to claim 5 or 6, wherein in the step (C), the multifilament is obtained by heating the drawn raw yarns in a heat treatment roll section.

8. The method for producing a multifilament according to any one of claims 5 to 7, wherein the draw ratio in the step (C) is 2.0 times or more.

9. In the step (B), the plurality of raw yarns are cooled to 50° C. or less, The method for producing a multifilament according to any one of claims 5 to 8, wherein in the step (C), the plurality of raw yarns cooled to 50°C or less in the step (B) are heated and drawn by the drawing roll section.

10. The method for producing a multifilament according to claim 9, wherein the fineness of the raw yarn used in the step (C) is 5.0 to 15.0 dtex.

11. The method for producing a multifilament according to claim 9 or 10, wherein in the step (C), the plurality of raw yarns cooled in the step (B) are heated while being taken up by a take-up roll section having a temperature of 25° C. or higher and lower than 50° C., the plurality of raw yarns heated by the take-up roll section are drawn by the drawing roll section, and the plurality of raw yarns drawn by the drawing roll section are heated by a heat treatment roll section having a temperature of 40 to 100° C.

12. In the step (B), the cooled raw yarns are wound on a raw yarn winding roll section, The method for producing a multifilament according to any one of claims 5 to 11, wherein in the step (C), the plurality of raw yarns wound by the raw yarn winding roll section are drawn by the drawing roll section.

13. The method for producing a multifilament according to any one of claims 5 to 8, wherein the multifilament is produced by a spin draw method.

14. The method for producing a multifilament according to claim 13, wherein in the step (C), the plurality of raw yarns drawn in the drawing roll section are heated in a heat treatment roll section at 25 to 100°C.

15. Obtaining the multifilament by the method for producing a multifilament according to any one of claims 5 to 14, The multifilament is cut to obtain a staple, The staple has a crimped structure, A method for producing a staple, wherein the average length of the staple is 200 mm or less.