Multifilament and method for manufacturing the same, and staple and method for manufacturing the same

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

Technical Field

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

Background Art

[0002] In recent years, plastic waste has been causing problems that impose a significant burden on the global environment, such as its impact on the ecosystem, generation of harmful gases during combustion, and global warming due to a large amount of combustion heat. As a solution to this problem, the development of biodegradable plastics has been actively pursued.

[0003] Among such biodegradable plastics, carbon dioxide emitted when burning biodegradable plastics obtained using plant-derived raw materials is originally present in the air, and thus the amount of carbon dioxide in the atmosphere does not increase. This is referred to as carbon neutral, and is highly regarded under the Kyoto Protocol, which sets a target value for carbon dioxide reduction, and active use is desired.

[0004] Recently, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester-based resins, particularly polyhydroxyalkanoate-based resins, have attracted attention as biodegradable plastics produced by microorganisms using plant-derived raw materials as a carbon source.

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

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, there may be a demand for multifilaments with even higher strength in the future. However, high-strength multifilaments have not been sufficiently studied to date.

[0008] Therefore, the primary objective of the present invention is to provide a multifilament with high strength. Furthermore, a second objective is to obtain staples from which the multifilament has been cut. [Means for solving the problem]

[0009] The first aspect of the present invention is a multifilament comprising a plurality of single threads, The aforementioned single yarn contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The fineness of the aforementioned single yarn is 1.0 to 5.0 dtex. This invention relates to a multifilament in which the tensile strength of the single filament is 2.5 cN / dtex or higher. 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 constituent unit represented by the following formula (1). [-CHR-CH2-CO-O-] (1) (In the above formula (1), R is C p H 2p+1 This represents an alkyl group, where p is an integer between 1 and 15. Preferably, the monofilament has a matrix-domain structure including a matrix and domains. The matrix contains the poly(3-hydroxyalkanoate) resin, The domain contains the polycaprolactone.

[0010] Furthermore, the second aspect of the present invention is that the multifilament is cut, Having a crimped structure, This concerns staples with an average length of 200 mm or less.

[0011] Furthermore, the third aspect of the present invention is a method for manufacturing a multifilament comprising multiple single filaments, using a melt spinning method and a spinning nozzle having multiple discharge holes, A step (A) to obtain multiple molten filaments by discharging the molten material from multiple discharge holes, (B) A step of cooling the multiple filaments by blowing a gas at 3 to 15°C onto the multiple filaments in a molten state, The process includes (C) a step of obtaining the multifilament by stretching a plurality of cooled filaments in a stretching roll section, The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. This invention relates to a method for manufacturing a multifilament in which the fineness of the single filament is 1.0 to 5.0 dtex. Preferably, the tensile strength of the single yarn is 2.5 cN / dtex or higher. Preferably, in step (C), the multifilament is obtained by heating the stretched filaments 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 multiple filaments cooled in step (B) are taken up and heated in a take-up roll section at 25°C or higher and less than 50°C, the multiple filaments heated in the take-up roll section are stretched in the stretching roll section, and the multiple filaments stretched in the stretching roll section are heated in a heat treatment roll section at 40 to 100°C. Preferably, in step (B), the cooled strands of yarn are wound on a yarn winding roll section. In step (C) above, the multiple strands of yarn wound up by the yarn winding roll section are stretched by the stretching roll section. Preferably, the method for manufacturing the multifilament is a method for manufacturing the multifilament by the spindraw method. Preferably, in the step (C), the plurality of the raw yarns drawn in the drawing roll section are heated in a heat treatment roll section at 25 to 100°C.

[0012] Fourthly, the present invention obtains the multifilament by the method for producing the multifilament, and obtains staple fibers by cutting the multifilament, the staple fibers have a crimp structure, and relates to a method for producing staple fibers, wherein an average value of the length of the staple fibers is 200 mm or less.

Advantages of the Invention

[0013] According to the present invention, a multifilament having high strength can be provided. Further, according to the present invention, staple fibers obtained by cutting the multifilament can be provided.

Brief Description of the Drawings

[0014] [Figure 1] Schematic diagram of the apparatus used in the steps (A) and (B) of the first embodiment. [Figure 2] Schematic diagram of the apparatus used in the step (C) of the first embodiment. [Figure 3] Schematic diagram of the apparatus used in the second embodiment.

Modes for Carrying Out the Invention

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

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

[0017] The aforementioned single filament is formed from a polymer composition containing polymer components, which is then arranged in a thread-like form. The polymer composition may further contain additives.

[0018] The polymer component includes a poly(3-hydroxyalkanoate) resin and polycaprolactone. The polymer component may contain other polymers besides poly(3-hydroxyalkanoate) resin and polycaprolactone.

[0019] The aforementioned poly(3-hydroxyalkanoate) resin is a polyester whose monomer is 3-hydroxyalkanoic acid. Furthermore, the poly(3-hydroxyalkanoate) resin is a biodegradable polymer. In this embodiment, "biodegradability" refers to the property of being able to be broken down into low-molecular-weight compounds by microorganisms in nature. Specifically, the presence or absence of biodegradability can be determined based on tests appropriate to 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. Furthermore, the degradability by microorganisms in seawater can be evaluated by measuring the biochemical oxygen demand. The poly(3-hydroxyalkanoate) resin may be a homopolymer or a copolymer.

[0020] The poly(3-hydroxyalkanoate) resin preferably contains the constituent unit shown in the following formula (1). [-CHR-CH2-CO-O-] (1) (In the above formula (1), R is C p H 2p+1 This represents an alkyl group, where p is an integer between 1 and 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 constituent unit include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate). Here, P3HB stands for poly(3-hydroxybutyrate). P3HB3HH stands for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). P3HB3HV stands for poly(3-hydroxybutyrate-co-3-hydroxyvalerate). P3HB4HB stands for poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0023] Furthermore, since P3HB has the function of promoting the crystallization of P3HB itself and poly(3-hydroxyalkanoate) resins other than P3HB, it is preferable that the poly(3-hydroxyalkanoate) resin contains P3HB.

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

[0025] The poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate as a constituent unit, preferably in an amount of 85.0 mol% to 99.5 mol%, more preferably 85.0 mol% to 97.0 mol%. The poly(3-hydroxyalkanoate) resin contains 85.0 mol% or more of 3-hydroxybutyrate as a constituent unit, thereby increasing the rigidity of the multifilament according to this embodiment. Furthermore, the poly(3-hydroxyalkanoate) resin contains 99.5 mol% or less of 3-hydroxybutyrate as a constituent unit, which provides the multifilament of this embodiment with excellent flexibility.

[0026] The polymer component may contain only one type of poly(3-hydroxyalkanoate) resin, or it may contain two or more types. If the poly(3-hydroxyalkanoate) resin contains a copolymer (such as P3HB3HH), it may contain two or more copolymers with different average composition ratios of constituent 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. The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 3,000,000 or less, which facilitates the molding of the multifilament according to this embodiment. The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 50,000 or more, which increases the strength of the multifilament according to this embodiment. In this embodiment, the weight-average molecular weight refers to the molecular weight obtained by measuring the polystyrene-reduced molecular weight distribution using gel permeation chromatography (GPC) with chloroform eluent. Any column suitable for measuring the molecular weight can be used in the GPC.

[0028] The aforementioned polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. Furthermore, polycaprolactone, like poly(3-hydroxyalkanoate) resins, is biodegradable. Furthermore, the inclusion of polycaprolactone in the single filament results in high strength for the multifilament according to this embodiment. The weight-average molecular weight of the polycaprolactone is preferably 5,000 to 500,000, more preferably 10,000 to 200,000. The weight-average molecular weight of the polycaprolactone being 500,000 or less facilitates the molding of the multifilament according to this embodiment. The weight-average molecular weight of the polycaprolactone is 5,000 or more, which increases the strength of the multifilament according to this embodiment.

[0029] The other polymers are preferably biodegradable.

[0030] Other biodegradable polymers include, for example, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, unmodified starch, modified starch, cellulose acetate, chitosan, and poly(4-hydroxyalkanoate) resins. The polymer composition may contain one other polymer, or it may contain two or more other polymers.

[0031] The polymer component contains poly(3-hydroxyalkanoate) resin and polycaprolactone in a total amount of preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0032] The ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is preferably 30 / 70-80 / 20, more preferably 40 / 60-75 / 25, and even more preferably 55 / 45-70 / 30. The fact that the mass of the poly(3-hydroxyalkanoate) resin / the mass of the polycaprolactone is 30 / 70 or more provides the advantage that the multifilament according to this embodiment has excellent heat resistance. Having a ratio of 80 / 20 or less between the mass of the poly(3-hydroxyalkanoate) resin and the mass of the polycaprolactone has the advantage of making it easier to increase the strength of the multifilament according to this embodiment.

[0033] The monofilament preferably has a matrix-domain structure comprising a matrix and domains, wherein the matrix contains the poly(3-hydroxyalkanoate) resin and the domains contain the polycaprolactone. The multifilament according to this embodiment has the advantage of having excellent heat resistance due to the configuration of the single filament. The following are possible reasons why the multifilament according to this embodiment has such advantages. Here, the matrix-domain structure is also called the sea-island structure. In the matrix-domain structure, the matrix is ​​in a continuous phase. On the other hand, the domains are in a discontinuous phase, like islands floating in the sea. Therefore, the properties of the matrix are primarily expressed as the properties of the single filament. Poly(3-hydroxyalkanoate) resins have higher heat resistance than polycaprolactone. Therefore, it is believed that the multifilament according to this embodiment has excellent heat resistance because the single filament is constructed in this manner.

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

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

[0036] To promote the crystallization of poly(3-hydroxyalkanoate) resins, the polymer composition preferably contains a crystal nucleating agent. The aforementioned nucleating agent is a compound that has the effect of promoting the crystallization of poly(3-hydroxyalkanoate) resins. Furthermore, the nucleating agent has a higher melting point than the poly(3-hydroxyalkanoate) resin. Examples of the aforementioned nucleating agents include inorganic substances (boron nitride, titanium dioxide, talc, layered silicates, calcium carbonate, sodium chloride, and metal phosphates); sugar alcohol compounds derived from natural products (pentaerythritol, erythritol, galactitol, mannitol, and arabitol, etc.); polyvinyl alcohol; chitin; chitosan; polyethylene oxide; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylic acid esters; dicarboxylic acid derivatives (dimethyl adipate, dibutyl adipate, diisodecyl adipate, and dibutyl adipate); Examples include: baquete; cyclic compounds having C=O and functional groups selected from NH, S, and O in their molecule (such as indigo, quinacridone, and quinacridone magenta); sorbitol derivatives (such as bisbenzylidene sorbitol and bis(p-methylbenzylidene) sorbitol); compounds containing nitrogen-containing heteroaromatic nuclei (such as pyridine rings, triazine rings, and imidazole rings) (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 can be used individually, or in combination of two or more types.

[0037] From the viewpoint of improving the crystallization rate of poly(3-hydroxyalkanoate) resins, as well as from the viewpoint of compatibility and affinity with poly(3-hydroxyalkanoate) resins, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan are preferred as the crystallization nucleating agents. Furthermore, among the sugar alcohol compounds, pentaerythritol is preferred.

[0038] The content of the 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) resin. A content of 0.05 parts by mass or more of the nucleating agent in the polymer composition per 100 parts by mass of the poly(3-hydroxyalkanoate) resin has the advantage of further promoting the crystallization of the poly(3-hydroxyalkanoate) resin. Furthermore, the content of the 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) resin. Having a nucleating agent content of 10 parts by mass or less per 100 parts by mass of the poly(3-hydroxyalkanoate) resin in the polymer composition has the advantage of lowering the viscosity of the molten material when producing multifilaments from the molten polymer composition, thereby facilitating the production of multifilaments. Furthermore, since P3HB is a poly(3-hydroxyalkanoate) resin and can also function as a crystal nucleating agent, when a polymer composition contains P3HB, the amount of P3HB is included in both the amount of poly(3-hydroxyalkanoate) resin and the amount of crystal nucleating agent.

[0039] The polymer composition preferably contains the lubricant. The lubricant in the single filaments improves their lubricity and suppresses fusion between the single filaments. Examples of such lubricants include compounds having an amide bond. The compound having the amide bond preferably includes one or more selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0040] The lubricant content 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 a lubricant content of 0.05 parts by mass or more per 100 parts by mass of the polymer component in the polymer composition has the advantage of providing excellent lubricity to the single filament. Furthermore, the lubricant content 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 polymer components. Having a lubricant content of 12 parts by mass or less per 100 parts by mass of polymer components has the advantage of suppressing the bleed-out of the lubricant to the surface of the multifilament.

[0041] The fineness of the aforementioned single yarn is 1.0 to 5.0 dtex. The fineness of the single yarn is preferably greater than 1.0 dtex, and more preferably 1.5 dtex or greater. 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 a single yarn refers to the thickness of the yarn and is defined as the mass per unit length. The mass per 10,000 m (g) is expressed in units (dtex). Specifically, it is measured by the autobiscope method.

[0042] The tensile strength of the aforementioned single yarn is 2.5 cN / dtex or higher. The tensile strength of the aforementioned single yarn is preferably 2.6 cN / dtex or higher. While a high tensile strength of the single yarn is preferable, 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 does not impair the flexibility and toughness required for the application, but it may be 10 cN / dtex or less. The tensile strength of a single yarn can be measured according to JIS L 1015:2010 Chemical Fiber Staple Test Method, with an initial length of 20 mm and a speed of 20 mm / min.

[0043] The multifilament according to this embodiment may be used as a single multifilament, or it may be used as a braid or sheet formed from multiple multifilaments. Furthermore, the multifilament according to this embodiment can be used in marine environments, terrestrial environments, and other similar environments. The multifilament according to this embodiment can be used, for example, in fishing nets, marine ropes, aquaculture nets, fishing lines, agricultural nets, artificial turf, sandbag nets, waterproof sheets, and the like. The sandbag net can be used, for example, in seawall 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 staples according to this embodiment is 200 mm or less, and is not particularly limited as long as it is 200 mm or less; it can be set appropriately according to the application in which the staples are used. The average length of the staples according to this embodiment is preferably 160 mm or less, and more specifically 1.0 to 100 mm, from the viewpoint of ease of use in various applications. Note that the average value of the staple length refers to the "average value of the fiber length" obtained by "c) Method C (substitution method)" in "8.4 Fiber Length" of "8.4.1 Average Fiber Length" of JIS L1015:2021 "Test Method for Chemical Fiber Staples".

[0046] The staples according to this embodiment can be used as a dry nonwoven fabric. This dry nonwoven fabric can be used as a sanitary material, medical material, household goods, waterproofing material, automotive interior material, etc. Specifically, this dry nonwoven fabric can be used for diapers, filters, towels, wipes, gauze, napkins, carpets, etc.

[0047] <<Manufacturing method for multifilaments>> The method for manufacturing a multifilament according to this embodiment is a method for manufacturing a multifilament comprising multiple single filaments using a melt spinning method and a spinning nozzle having multiple extrusion holes. Furthermore, the method for manufacturing a multifilament according to this embodiment comprises the steps of: (A) obtaining a plurality of molten filaments by extruding a molten material from a plurality of discharge holes; (B) cooling the plurality of molten filaments by blowing a gas at 3 to 15°C onto them; and (C) obtaining the multifilament by stretching the cooled plurality of filaments with a stretching roll. The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The fineness of the aforementioned single yarn is 1.0 to 5.0 dtex.

[0048] Furthermore, it is preferable that the tensile strength of the single yarn is 2.5 cN / dtex or higher.

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

[0050] <First Embodiment: Post-Stretching Method (Sequential Stretching Method)> In the following, the method for manufacturing multifilaments according to the first embodiment will be described with reference to Figures 1 and 2, using the post-drawing method (also called the "sequential drawing method") as an example. In the method for manufacturing multifilaments according to the first embodiment, a plurality of the filaments cooled with the gas are wound on a filament winding roll section, and the plurality of filaments wound on the filament winding roll section are stretched on a stretching roll section.

[0051] (Process (A)) As shown in Figure 1, in step (A), first, the molten material is introduced into the material input section 101. Next, the material introduced from the material input section 101 is kneaded in the kneading extruder 102 while being heated to obtain the molten material. 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, using a spinning nozzle 104 having multiple discharge holes, the molten material obtained in the kneading extruder 102 is discharged from the multiple discharge holes to obtain multiple strands of molten yarn 100A. The flow rate of the molten material discharged from the multiple discharge holes of the spinning nozzle 104 is adjusted by the 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 discharge holes are not particularly limited. For example, if the shape of the discharge hole is circular, a diameter of 0.1 mm to 3.0 mm is preferred. The number of discharge holes depends on the size of the discharge holes, but may be 15 or more, or 1000 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 discharge rate of molten material from the discharge hole of the spinning nozzle 104 is preferably 0.10 g / min / hole or more, and more preferably 0.15 g / min / hole or more. Furthermore, the discharge rate is preferably less than 1.0 g / min / hole, and more preferably 0.90 g / min / hole or less.

[0057] (Process (B)) In step (B), the multiple molten filaments 100A obtained in step (A) are cooled by blowing a gas at 3 to 15°C onto them. In step (B), by cooling the filament 100A with a gas at 3 to 15°C, the time during which the polycaprolactone and poly(3-hydroxyalkanoate) resin constituting the filament 100A are within the temperature range in which they crystallize can be shortened, thereby suppressing the progression of crystallization of the polycaprolactone and poly(3-hydroxyalkanoate) resin. This prevents the filament 100A from hardening. Therefore, the stretching of the filament 100A in step (C) becomes easier. As a result, the strength of the multifilament becomes easier to increase. In the first embodiment, the yarn 100A is cooled with a gas at 3 to 15°C in a first cooling box 105, and the yarn 100A cooled in the first cooling box 105 is then cooled with a gas at 3 to 15°C in a second cooling box 106.

[0058] The temperature of the gas blown onto the multiple molten filaments 100A obtained in step (A) is 3 to 15°C, preferably 3.0 to 6.0°C. Furthermore, "the temperature of the gas blown onto the multiple molten filaments 100A obtained in step (A)" means the temperature of the gas when it comes into contact with the filaments 100A.

[0059] The velocity of the gas blown onto the multiple molten filaments 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 velocity of the gas is 0.1 m / s or higher, the cooling effect of the gas is more easily achieved. By keeping the gas velocity below 5 m / s, the molten yarn 100A discharged from the spinning nozzle 104 is suppressed from being disturbed by the gas. As a result, fusion and / or breakage of the molten yarns 100A is suppressed, which improves spinning stability. Furthermore, "the velocity of the gas blown onto the multiple molten filaments 100A obtained in step (A)" means the velocity of the gas when it comes into contact with the filaments 100A.

[0060] Examples of the aforementioned gases include air and inert gases (such as nitrogen gas and argon gas).

[0061] In step (B) above, the raw yarn 100A, cooled with a gas at 3 to 15°C, is taken up by the first take-up roll section 107. The first take-up roll section 107 is composed of two rolls. The first take-up roll section 107 may be composed of one roll or three or more rolls. Then, in step (B), the multiple strands of yarn 100A taken up by the first take-up roll section 107 are wound up by the yarn winding roll section 112. In the first embodiment, the first transport roll section 108, the second transport roll section 109, the third transport roll section 110, and the fourth transport roll section 111 are used to transport the multiple strands of yarn 100A taken up by the first take-up roll section 107 to the yarn winding roll section 112. Each conveying roll section is composed of two rolls in Figure 1, but it may also be composed of one roll or three or more rolls.

[0062] In step (B), the multiple strands of the raw yarn 100A are cooled to a temperature of preferably 50°C or lower, more preferably 40°C or lower. In step (B), the multiple strands of the raw yarn 100A are cooled to, for example, 0°C or higher, more specifically 10°C or higher. In step (B), the multiple strands of yarn may be cooled to 50°C or below by blowing a gas at 3 to 15°C. Alternatively, in step (B), the multiple strands of yarn 100A may be cooled to a certain extent by blowing a gas at 3 to 15°C, and then cooled by the surrounding air while the yarn 100A is being transported from the first take-up roll section 107 to the yarn winding roll section 112, thereby cooling the multiple strands of yarn to 50°C or below.

[0063] In order to stretch the yarn 100A in step (C), it is preferable that the yarn 100A is not stretched, or stretched only slightly, in step (B). In other words, the stretching 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. Note that the stretching ratio in step (B) is 1.0 times or more. The stretch ratio in step (B) above can be determined by the following formula. The stretching ratio in step (B) = Speed ​​of the yarn winding roll section (m / min) / Speed ​​of the take-up roll section used in step (B) (in the first embodiment, "first take-up roll section 107") (m / min) The speed (m / min) of the yarn winding roll section is the length of yarn wound onto the yarn winding roll section per unit time. Furthermore, the speed (m / min) of the take-up roll section used in step (B) is the length of the raw yarn taken up by the take-up roll section (in the first embodiment, "first take-up roll section 107") per unit time. In the first embodiment, if the calculated value of the stretching ratio in step (B) is less than 1.0, the stretching ratio is set to 1.0.

[0064] (Process (C)) As shown in Figure 2, in step (C), the multiple strands of the raw yarn 100A that were cooled to 50°C or below in step (B) are heated and stretched by the stretching roll section 114. In step (C) above, by stretching multiple filaments 100A, the orientation of the polymer components contained in the filaments can be increased, thereby increasing the tensile strength of the filaments. As a result, the strength of the multifilament can be increased. Here, in order to increase the orientation of the polymer components, it is desirable to stretch the yarn in a temperature range suitable for increasing the orientation of the polymer components. If the yarn is stretched at a temperature higher than this range, the polymer components will melt, and as a result, the orientation of the polymer components will not increase significantly even after stretching. On the other hand, if the yarn is stretched at a temperature lower than this range, the polymer components will solidify too much, making it difficult to stretch the yarn. Also, if the yarn is forcibly pulled in an attempt to stretch it, it will break, making it impossible to manufacture multifilaments. In the first embodiment, by heating the multiple filaments 100A that have been cooled to 50°C or below in step (B) and stretching them with the stretching roll section 114, it becomes easier to adjust the temperature of the multiple filaments so that they are within a temperature range suitable for increasing the orientation of the polymer components when stretching them, compared to the spindraw method in which the multiple filaments are stretched while being cooled with ambient air. As a result, it becomes easier to increase the orientation of the polymer components of the multiple filaments. Therefore, in the first embodiment, it becomes easier to increase the strength of the multifilament.

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

[0066] In step (C) above, the multiple strands of yarn wound by the yarn winding roll section 112 are taken up by the second take-up roll section 113. Next, in step (C), the yarn 100A taken up by the second take-up roll section 113 is stretched by the stretching roll section 114. Then, in step (C), the obtained multifilament is wound up by the multifilament winding roll section 116. In addition, in step (C), the yarn 100A stretched by the stretching roll section 114 may be conveyed by the take-off roll section 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 of three or more rolls. In step (C), it is preferable to heat multiple strands of the raw yarn 100A in the second take-up roll section 113. In step (C), heating the multiple filaments 100A with the second take-up roll section 113 makes it easy to adjust the temperature of the multiple filaments 100A to be within a temperature range suitable for increasing the orientation of the polymer components contained in the multiple filaments 100A. As a result, it becomes easier to increase the orientation of the polymer components of the multiple filaments 100A. The temperature of the second take-up roll section 113 is preferably 25°C or higher and less than 50°C, more preferably 30 to 45°C. Furthermore, if the temperature of the environment in which step (C) is performed is 25°C or higher, it is not necessary to heat the multiple strands of yarn 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 also be composed of one roll or three or more rolls. In step (C) above, the multiple strands of yarn 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 step (C) above, a method can also be used in which multiple strands of the yarn 100A are heated in the stretching roll section 114 to promote the crystallization of polymer components contained in the multiple strands of yarn 100A. 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 consist of one roll, or it may consist of three or more rolls. In other words, in step (C), the multifilament is obtained by heating the multiple stretched filaments 100A in the heat treatment roll section 115. In step (C), the crystallization of polymer components contained in the multiple filaments 100A can be promoted by heating the multiple filaments 100A with the heat treatment roll section 115. The temperature of the take-off roll (heat-treated roll section) 115 is preferably 40 to 100°C, more preferably 50 to 90°C. Furthermore, both or just one of the stretching roll section 114 and the take-off roll section 115 may be the heat treatment roll section.

[0070] The stretching ratio in step (C) is preferably 2.0 times or more. For example, the stretching ratio in step (C) is 10.0 times or less. By having a stretching ratio of 2.0 times or more in the above-mentioned process (C), the orientation of the polymer components of the multiple filaments 100A is further enhanced. The stretch ratio in step (C) can be determined by the following formula. The stretching ratio in step (C) = Speed ​​of the multifilament winding roll section (m / min) / Speed ​​of the take-up roll section used in step (C) (in the first embodiment, "second take-up roll section 113") (m / min)

[0071] In step (C) above, the relaxation rate calculated by the following formula is preferably 5 to 15%. Relaxation rate (%) = ((Speed ​​of the stretching roll section 114 - Speed ​​of the multifilament winding roll section 116) / Speed ​​of the multifilament winding roll section 116) × 100

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

[0073] In step (B) shown in Figure 1, the yarn 100A taken up by the first take-up roll section 107 is wound up by the yarn winding roll section 112. However, in the first embodiment, the yarn 100A taken up by the first take-up roll section 107 may be stored in a storage container without being wound up by the yarn winding roll section 112. If the yarn 100A taken up by the first take-up roll section 107 is not wound up by the yarn winding roll section 112, but is instead transported to the storage container using the transport roll section, the stretch ratio in step (B) can be calculated by the following formula. Stretch ratio = Speed ​​of the conveying roll section (m / min) / Speed ​​of the first take-up roll section (m / min) The speed of the conveying roll section (m / min) is the length of yarn conveyed by the conveying roll section per unit time. When multiple conveying rolls are used, the speed of the fastest conveying roll is used in the formula for the stretching ratio. If neither the yarn winding roll section 112 nor the conveying roll section is used, the stretching ratio becomes 1.0.

[0074] <Second Embodiment: Spindraw Method> Next, a second embodiment will be described with reference to Figure 3. Furthermore, explanations that overlap with those in the first embodiment will be omitted, and anything not specifically explained in the second embodiment will be the same as that explained in the first embodiment.

[0075] The method for manufacturing a multifilament according to the second embodiment is a method for manufacturing the multifilament by the spindraw method. The spindraw method is a method that performs two steps in a single process: obtaining multiple molten yarns by extruding molten material from multiple discharge holes, and stretching the multiple yarns using a stretching roll. The spindraw method is also called the "SDY method" or "direct spinning and stretching method."

[0076] In step (C) of the second embodiment, as shown in Figure 3, the multiple filaments cooled in step (B) are taken up by the take-up roll section 207. Next, the multiple strands of yarn taken up by the take-up roll section 207 are stretched by three stretching roll sections (the first stretching roll section 208, the second stretching roll section 209, and the third stretching roll section 210). Then, in step (C), the obtained multifilament is wound up by the multifilament winding roll section 212. In addition, in step (C), the yarn 100A stretched by the stretching roll section may be conveyed by the take-off roll section 211.

[0077] In step (C) above, the multiple strands of yarn cooled in the first cooling box 105 and the second cooling box 106 are taken up by the take-up roll section 207. In Figure 1, the take-up roll section 207 is composed of two rolls, but it may be composed of one roll, or it may be composed of three or more rolls.

[0078] In the second embodiment, each stretching roll section may also serve as a heat treatment roll section. Each stretching roll section 208, 209, 210 (each heat treatment roll 208, 209, 210) is composed of two rolls in Figure 1, but it may be composed of one roll or three or more rolls. From the viewpoint of promoting the crystallization of polymer components contained in multiple strands of yarn 100A, the temperature of the heat treatment roll section is preferably 25 to 100°C, more preferably 40 to 90°C. Furthermore, if the temperature of the environment in which process (C) is carried out is 25°C or higher, the crystallization of polymer components contained in multiple strands of yarn 100A can be promoted without using a heat treatment roll.

[0079] In the method for manufacturing multifilaments according to this embodiment, the spinning draft value (NDR) is preferably 150 or higher, more preferably 200 or higher. Furthermore, the NDR is typically 1000 or lower. The NDR can be calculated using the following formula. NDR = Speed ​​of the take-up roll (first take-up roll) that initially takes the yarn from the spinning nozzle (m / min) / Spinning nozzle flow rate (m / min) An NDR of 150 or higher allows for the stretching of the yarn between the spinning nozzle and the first take-up roll, which in turn increases the strength of the multifilament. In the first embodiment (post-stretching method), the first take-up roll section is the first take-up roll section 107. On the other hand, in the second embodiment (spindraw method), the first take-up roll section is the take-up roll section 207.

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

[0081] The method for manufacturing staples according to this embodiment involves crimping a multifilament and cutting the crimped multifilament to obtain a staple having a crimped structure.

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

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

[0084] Furthermore, in the future, from the perspective of applicability to a wide range of applications, there may be a demand for multifilaments that are high in strength, have thin single threads, and possess good biodegradability. Here, polycaprolactone, like poly(3-hydroxyalkanoate) resins, is biodegradable. Furthermore, by reducing the fineness of the single yarn to 5.0 dtex or less, the single yarn becomes thinner. Therefore, according to this embodiment, it is possible to provide a multifilament that has high strength, thin single filaments, and good biodegradability.

[0085] The method for manufacturing a multifilament according to this embodiment is a method for manufacturing a multifilament comprising multiple single filaments using a spinning nozzle having multiple extrusion holes. Furthermore, the method for manufacturing a multifilament according to this embodiment comprises the steps of: (A) obtaining a plurality of molten filaments by extruding a molten material from a plurality of discharge holes; (B) cooling the plurality of molten filaments by blowing a gas at 3 to 15°C onto them; and (C) obtaining the multifilament by stretching the cooled plurality of filaments with a stretching roll. The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The fineness of the single yarn is 1.0 to 5.0 dtex. In step (B), by cooling the filament with a gas at 3 to 15°C, the time during which the polycaprolactone and poly(3-hydroxyalkanoate) resin constituting the filament are within the temperature range in which crystallization occurs can be shortened, thereby suppressing the progression of crystallization of the polycaprolactone and poly(3-hydroxyalkanoate) resin. This prevents the filament from hardening. Therefore, it becomes easier to sufficiently stretch the filament in step (C). As a result, it becomes easier to increase the strength of the multifilament.

[0086] Furthermore, in the method for manufacturing a multifilament according to this embodiment, the multifilament is obtained by heating the multiple stretched filaments in a heat treatment roll section in step (C). The method for manufacturing multifilaments according to this embodiment, having such a configuration, can increase the degree of crystallinity of the multifilaments, and as a result, can increase the strength of the multifilaments.

[0087] Furthermore, in the method for manufacturing multifilaments according to this embodiment, in step (B), a plurality of the filaments are cooled to 50°C or below, and in step (C), the plurality of filaments cooled to 50°C or below in step (B) are heated and stretched in the stretching roll section. In order to increase the orientation of the polymer components, it is generally desirable to stretch the yarn within a temperature range suitable for increasing the orientation of the polymer components. If the yarn is stretched at a temperature higher than this range, the polymer components will melt, and as a result, the orientation of the polymer components will not increase significantly even after stretching. Conversely, if the yarn is stretched at a temperature lower than this range, the polymer components will solidify too much, making it difficult to stretch the yarn. Also, if the yarn is forcibly pulled in an attempt to stretch it, it will break, making it impossible to manufacture multifilaments. In this embodiment, by heating the multiple filaments cooled to 50°C or below in step (B) and stretching them in the stretching roll section, it becomes easier to adjust the temperature of the multiple filaments to be within a temperature range suitable for increasing the orientation of the polymer components when stretching them, compared to the spindraw method in which the multiple filaments are stretched while being cooled by the surrounding air. As a result, it becomes easier to increase the orientation of the polymer components of the multiple filaments. Therefore, in this embodiment, it becomes easier to increase the strength of the multifilament.

[0088] Furthermore, the multifilament and its manufacturing method, as well as the staple and its manufacturing method, according to the present invention are not limited to the embodiments described above. Also, the multifilament and its manufacturing method, as well as the staple and its manufacturing method, according to the present invention are not limited by the effects described above. Moreover, the multifilament and its manufacturing method, as well as the staple and its manufacturing method, according to the present invention can be modified in various ways without departing from the spirit of the present invention. [Examples]

[0089] Next, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited in any way to these examples.

[0090] <Example 1> A multifilament was fabricated using the method of the first embodiment (post-stretching method).

[0091] (Process (A)) First, as shown in Figure 1, the molten material produced by the kneading extruder 102 was discharged from the discharge hole of the spinning nozzle 104 to obtain multiple strands (80 strands) of yarn 100A. The molten material is a polymer composition containing, as a poly(3-hydroxyalkanoate) resin, (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 proportions shown in Table 1 below. Furthermore, in Table 1 below, "Content of lubricant having amide bonds" refers to the amount of lubricant having amide bonds (parts by mass) per 100 parts by mass of P3HB3HH. "Content of nucleating agent" refers to the amount of nucleating agent (parts by mass) per 100 parts by mass of P3HB3HH. In addition, "parts by mass" is simply expressed as "parts".

[0092] (Process (B)) In cooling boxes 105 and 106, 7°C air (quench air) was blown onto multiple strands of yarn 100A. Next, the multiple strands of yarn 100A, which had been cooled in the cooling boxes 105 and 106, were taken up by the first take-up roll section 107. After the multiple strands of yarn 100A passed through the conveying roll sections 108, 109, 110, and 111 in order, the multiple strands of yarn 100A were wound up by the yarn winding roll section 112. The fineness of the yarn wound on the yarn winding roll section 112 was 7.6 dtex. Furthermore, the NDR was set to 353, and the extension ratio was set to 1.1.

[0093] (Process (C)) As shown in Figure 2, multiple filaments (at room temperature (25°C)) wound on the filament winding roll section 112 are taken up by the second take-up roll section 113 (at room temperature (25°C)), stretched by the stretching roll section (heat treatment roll section) 114 (60°C), and after the multiple filaments pass through the take-off roll section (heat treatment roll section) 115 (60°C), the resulting multifilament is wound on the multifilament winding roll section 116. The extension ratio was set to 2.2, and the relaxation rate to 10%.

[0094] (Example 2) A multifilament was fabricated using the method of the second embodiment (SDY method). Multiple filaments 100A were obtained by cooling them in cooling boxes 105 and 106 in the same manner as in Example 1. Next, as shown in Figure 3, the multiple filaments 100A cooled in the cooling boxes 105 and 106 were taken up by the take-up roll section 207, stretched by the stretching roll sections (heat treatment roll sections) 208, 209, and 210 (50°C), and after the multiple filaments passed through the take-off roll section 211, the resulting multifilament was wound up by the multifilament winding roll section 212. The NDR was set at 324, the extension ratio at 2.0, and the relaxation rate at 5%.

[0095] (Examples 3, 5, 7, Comparative Example 1) A multifilament was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1.

[0096] (Examples 4, 6, 8, Comparative Example 2) A multifilament was obtained in the same manner as in Example 2, except that the conditions were changed as shown in Table 1.

[0097] (Fineness of the single yarn, and tensile strength of the single yarn) For each multifilament in the examples and comparative examples, the fineness of the single filament and the tensile strength of the single filament were measured by the method described above. The fineness and tensile strength of the single yarns are shown in Table 1 below.

[0098] (Monofibular matrix-domain structure) The presence or absence of a monofilament matrix-domain structure in the multifilaments of the examples and comparative examples was confirmed by a transmission electron microscope (TEM). Furthermore, monofilaments of the multifilaments in the examples and comparative examples were stained with ruthenium tetroxide, and the stained monofilaments were observed with the transmission electron microscope to identify the polymers contained in the matrix and domains, respectively, based on the differences in staining. Table 1 below shows the presence or absence of a matrix-domain structure in monofilaments, as well as the polymers contained in the matrix and the polymers contained in the domains.

[0099] (Elongation of a single yarn, and Young's modulus of a single yarn) For each multifilament in the examples and comparative examples, the elongation and Young's modulus of the single filament were measured according to JIS L 1015:2010 Chemical Fiber Staple Test Method, with an initial length of 20 mm and a speed of 20 mm / min. The elongation and Young's modulus of the single yarn are shown in Table 1 below.

[0100] (Fusion rate) For each multifilament in the examples and comparative examples, all single filaments contained in the multifilament were cut by cutting the multifilament with a plane perpendicular to the longitudinal direction of the multifilament. Next, a scanning electron microscope (SEM) was used to observe the cross-section of the multifilament, and the total number of single filaments contained in the multifilament at the cross-section and the number of single filaments fused to other single filaments at the cross-section (which is also the number obtained by subtracting the number of single filaments not fused to other single filaments from the total number of single filaments contained in the multifilament) were counted. The fusion rate was then calculated using the following formula. Fusion rate (%) = (Number of single filaments fused to other single filaments at the cross-section / Total number of single filaments in the multifilament at the cross-section) × 100 The fusion rate is shown in Table 1 below.

[0101] (Heat resistance test) For each multifilament in the examples and comparative examples, the single filaments were subjected to thermomechanical analysis (TMA) under the following conditions, and the temperatures at which the shrinkage rates of the single filaments reached 5%, 10%, and 20% were measured. Load: 3g 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 rate is 5%, 10%, and 20%) are shown in Table 1 below.

[0102] [Table 1]

[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 compared to Comparative Examples 1 and 2, which do not use polycaprolactone. Therefore, it can be seen that, according to the present invention, a multifilament with high strength can be obtained.

[0104] Furthermore, as shown in Table 1, in Examples 1-6, where the matrix contained a poly(3-hydroxyalkanoate) resin, the temperature at which the predetermined thermal shrinkage rate was achieved was higher compared to Examples 7 and 8, where the matrix contained polycaprolactone. Therefore, it can be seen that multifilaments containing poly(3-hydroxyalkanoate) resin in the matrix exhibit excellent heat resistance.

[0105] (Comparative Example 3) Except for setting the quench air temperature to 25°C, we attempted to produce a multifilament in the same manner as in Example 1. However, the filament broke between the spinning nozzle 104 and the first take-up roll 107, and we were unable to produce a multifilament.

[0106] (Comparative Example 4) In an attempt to produce a multifilament in the same manner as in Example 3, except that the quench air temperature was set to 25°C, the filament broke between the spinning nozzle 104 and the first take-up roll 107, making it impossible to produce a multifilament.

[0107] (Comparative Example 5) Except for setting the quench air temperature to 25°C, we attempted to produce a multifilament in the same manner as in Example 7. However, the filament broke between the spinning nozzle 104 and the first take-up roll 107, and we were unable to produce a multifilament.

[0108] Based on the above, in Comparative Examples 3 to 5, where the quench air temperature was set to 25°C, the filament broke between the spinning nozzle 104 and the first take-up roll 107, making it impossible to manufacture multifilaments. In Comparative Examples 3-5, while lowering the NDR may allow for the production of multifilaments, this results in a certain degree of crystallization of the polymer components while the stretching into monofilaments is suppressed. 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 filaments, a certain degree of stretching can be performed before the crystallization of the polymer components progresses. As a result, it is believed that a multifilament with high strength can be obtained. In other words, it can be seen that a multifilament with high strength can be obtained according to the present invention. [Explanation of symbols]

[0109] 100A: Raw yarn, 101: Material input section, 102: Mixing 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: Winding roll section for raw yarn, 113: Second take-up roll section, 114: Stretching roll section (heat treatment roll section), 115: Take-off roll section (heat treatment roll section), 116: Winding roll section for multifilament, 207: Take-up roll section, 208: First stretching roll section (heat treatment roll section), 209: Second stretching roll section (heat treatment roll section), 210: Third stretching roll section (heat treatment roll section), 211: Take-off roll section, 212: Multifilament winding roll section

Claims

1. A multifilament comprising multiple single threads, The aforementioned single yarn contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The fineness of the aforementioned single yarn is 1.0 to 5.0 dtex. The tensile strength of the aforementioned single yarn is 2.5 cN / dtex or more. The poly(3-hydroxyalkanoate) resin is a multifilament containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

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

3. The monofilament has a matrix-domain structure including a matrix and domains, The matrix contains the poly(3-hydroxyalkanoate) 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, Having a crimped structure, Staples with an average length of 200 mm or less.

5. A method for manufacturing a multifilament, comprising using a melt spinning method and a spinning nozzle having multiple extrusion holes to produce a multifilament comprising multiple single filaments, A step (A) to obtain multiple molten filaments by discharging the molten material from multiple discharge holes, (B) A step of cooling the multiple filaments by blowing a gas at 3 to 15°C onto the multiple filaments in a molten state, The process includes step (C) of obtaining the multifilament by stretching a plurality of cooled filaments in a stretching roll section, The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The fineness of the aforementioned single yarn is 1.0 to 5.0 dtex. The ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is 55 / 45 to 70 / 30. In step (C) above, multiple strands of the yarn are heated in a heat treatment roll section at 40 to 100°C. A method for producing a multifilament, wherein the poly(3-hydroxyalkanoate) resin contains poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

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

7. The method for producing a multifilament according to claim 5 or 6, wherein in step (C), the multiple stretched filaments are heated in a heat treatment roll section to obtain the multifilament.

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

9. In step (B) above, multiple strands of the yarn are cooled to 50°C or below. The method for manufacturing a multifilament according to any one of claims 5 to 8, wherein in step (C), a plurality of the filaments that were cooled to 50°C or below in step (B) are heated and stretched in the stretching roll section.

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

11. The method for manufacturing a multifilament according to claim 9 or 10, wherein in step (C), a plurality of filaments cooled in step (B) are taken up and heated in a take-up roll section at 25°C or more and less than 50°C, the plurality of filaments heated in the take-up roll section are stretched in the stretching roll section, and the plurality of filaments stretched in the stretching roll section are heated in a heat treatment roll section at 40 to 100°C.

12. In step (B) above, the cooled strands of yarn are wound onto a yarn winding roll section. The method for manufacturing a multifilament according to any one of claims 5 to 11, wherein in step (C), a plurality of the filaments wound on the filament winding roll section are stretched on the stretching roll section.

13. A method for manufacturing a multifilament according to any one of claims 5 to 8, wherein the multifilament is manufactured by the spindraw method.

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

15. The multifilament is obtained by the method for manufacturing a multifilament described in claims 5 to 14. By cutting the multifilament, staples are obtained. The staple has a crimped structure, A method for manufacturing staples, wherein the average length of the staples is 200 mm or less.

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