Monofilament and method for manufacturing the same

Abstract

To provide a monofilament having high strength and excellent heat resistance.SOLUTION: There are provided a monofilament and the like, which contain poly(3-hydroxyalkanoate)-based resin and polycaprolactone, wherein the weight ratio of the poly(3-hydroxyalkanoate)-based resin to the polycaprolactone is 15 / 85 to 85 / 15; the tensile strength is 2.5 cN / dtex or more; and the fineness is 15 to 3000 dtex.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a monofilament and a method for producing the same. [Background Art]

[0002] In recent years, plastic waste has become a problematic source of large load on the global environment, including impacts on ecosystems, generation of toxic gases during combustion, and global warming caused by a large amount of combustion heat. Development of biodegradable plastics has been actively pursued as a solution to this problem.

[0003] Among such biodegradable plastics, the carbon dioxide released when burning a biodegradable plastic obtained from plant-derived raw materials was originally present in the atmosphere, and thus does not increase the amount of carbon dioxide in the atmosphere. This property, called carbon neutrality, is regarded as important under the Kyoto Protocol that sets carbon dioxide reduction targets, and active use thereof is desired.

[0004] Recently, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester resins, particularly polyhydroxyalkanoate 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 filament containing polycaprolactone and poly(β-hydroxyalkanoate). [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Publication No. 8-228640 [Summary of the Invention] [Problem to be Solved by the Invention]

[0007] Monofilament is used as fishing line, among other things. Fishing lines may be exposed to high temperatures (e.g., 60°C) due to being stored in vehicles during the summer, so excellent heat resistance may be required. Therefore, there may be a need for monofilament fishing lines with excellent heat resistance. Furthermore, heat-resistant monofilaments may be required not only for fishing lines but also for other applications.

[0008] Furthermore, monofilaments may also be required to have high strength.

[0009] In other words, a monofilament with high strength and excellent heat resistance may be required. However, sufficient research has not yet been conducted on monofilaments that possess both high strength and excellent heat resistance.

[0010] Therefore, the object of the present invention is to provide a monofilament that has high strength and excellent heat resistance. [Means for solving the problem]

[0011] The first aspect of the present invention is a material containing a poly(3-hydroxyalkanoate) resin and polycaprolactone. The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone is 15 / 85 to 85 / 15. The tensile strength is 2.5 cN / dtex or higher. This concerns monofilaments with a fineness of 15 to 3000 dtex.

[0012] The second aspect of the present invention is a method for producing monofilaments by melt spinning, The process (A) involves extruding the molten material from a spinning nozzle and passing the resulting yarn through a water bath at 15-35°C, The process includes (B) stretching the yarn that has passed through the water bath in a stretching roll section, The melt contains a poly(3-hydroxyalkanoate)-based resin and polycaprolactone, a weight ratio of the poly(3-hydroxyalkanoate)-based resin to the polycaprolactone is 15 / 85 to 85 / 15, a total draw ratio in the step (B) is 5.0 times or more, and the monofilament has a fineness of 15 to 3000 dtex. The present invention relates to a method for producing a monofilament. [Advantageous Effects of Invention]

[0013] According to the present invention, a monofilament having high strength and excellent heat resistance can be provided. [Brief Description of Drawings]

[0014] [Figure 1] 1 is a schematic diagram of an apparatus for producing a monofilament. [Figure 2] 2 is an image of a first cross-section of Example 1 (scale bar: 5 µm). [Figure 3] 3 is an image of the first cross-section of Example 1 at a higher magnification than that in Fig. 2 (scale bar: 1 µm). [Figure 4] 4 is an image of a second cross-section of Example 1 (scale bar: 5 µm). [Figure 5] 5 is an image of the second cross-section of Example 1 at a higher magnification than that in Fig. 4 (scale bar: 1 µm). [Figure 6] 6 is an image of a first cross-section of Example 3 (scale bar: 5 µm). [Figure 7] 7 is an image of the first cross-section of Example 3 at a higher magnification than that in Fig. 6 (scale bar: 1 µm). [Figure 8] 8 is an image of a second cross-section of Example 3 (scale bar: 5 µm). [Figure 9] 9 is an image of the second cross-section of Example 3 at a higher magnification than that in Fig. 8 (scale bar: 1 µm). [Figure 10] 10 is an image of a first cross-section of Example 4 (scale bar: 5 µm). [Figure 11]An image of the first cross-section of Example 4, magnified more than in Figure 10 (scale bar: 1 μm). [Figure 12] Image of the second cross-section of Example 4 (scale bar: 5 μm). [Figure 13] An image of the second cross-section of Example 4, magnified more than Figure 12 (scale bar: 1 μm). [Modes for carrying out the invention]

[0015] The following describes one embodiment of the present invention.

[0016] First, the monofilament according to this embodiment will be described.

[0017] The monofilament according to this embodiment contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone is 15 / 85 to 85 / 15. The tensile strength of the monofilament according to this embodiment is 2.5 cN / dtex or higher. The fineness of the monofilament according to this embodiment is 15 to 3000 dtex.

[0018] The monofilament according to this embodiment is formed from a polymer composition containing polymer components in a thread-like shape. The polymer composition may further contain additives.

[0019] 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.

[0020] The aforementioned poly(3-hydroxyalkanoate) resin is a polyester whose monomer is 3-hydroxyalkanoic acid. In other words, the poly(3-hydroxyalkanoate) resin is a resin that contains 3-hydroxyalkanoic acid as a constituent unit. 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 includes homopolymers and / or copolymers.

[0021] 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.

[0022] The aforementioned poly(3-hydroxyalkanoate) resin preferably includes a poly(3-hydroxybutyrate) resin. Poly(3-hydroxybutyrate) resins are resins that contain 3-hydroxybutyrate as a constituent unit. Poly(3-hydroxybutyrate) resins may be homopolymers or copolymers.

[0023] 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 refers to the homopolymer 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).

[0024] 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.

[0025] 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, P3HB3HH is preferred as the poly(3-hydroxyalkanoate) resin from the viewpoint of improving the moldability of the monofilament according to this embodiment.

[0026] 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 monofilament according to this embodiment. Furthermore, the poly(3-hydroxyalkanoate) resin contains 99.5 mol% or less of 3-hydroxybutyrate as a constituent unit, which results in the monofilament of this embodiment having excellent processability.

[0027] 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.

[0028] 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 monofilament 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 monofilament 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.

[0029] There are no particular limitations on the method for producing poly(3-hydroxyalkanoate) resin (hereinafter also referred to as "P3HA"), but one example is a method in which P3HA is produced by microorganisms having the ability to produce P3HA. Such microorganisms are not particularly limited, but examples of P3HB-producing bacteria include Bacillus megaterium, discovered in 1925, as well as Cupriavidus necator (formerly classified as Alcaligenes eutrophus, Ralstonia eutropha), and Alcaligenes latus. Furthermore, examples of microorganisms that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HH and P3HB3HV, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, among the P3HB3HH-producing strains, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bacteriol., 179, p4821-4830 (1997)) is an example in which genes for the P3HA synthase group have been introduced to increase the productivity of P3HB3HH.

[0030] P3HA can be produced by culturing these microorganisms under appropriate conditions to accumulate P3HA within the cells and then recovering the P3HA. The culture conditions, including the type of substrate, can be optimized according to the microorganism used. In addition to the microorganisms listed above, P3HA can also be produced by culturing genetically modified microorganisms into which various P3HA synthesis-related genes have been introduced, depending on the type of P3HA to be produced.

[0031] The aforementioned polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. Furthermore, polycaprolactone, like poly(3-hydroxyalkanoate) resins, is biodegradable. The polycaprolactone may be a homopolymer and / or copolymer. From the viewpoint of increasing the strength of the monofilament according to this embodiment, the polycaprolactone preferably contains a homopolymer, and more preferably is a homopolymer. Furthermore, because the monofilament according to this embodiment contains polycaprolactone, the monofilament according to this embodiment has high strength. 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 monofilament according to this embodiment. The weight-average molecular weight of the polycaprolactone is 5,000 or more, which increases the strength of the monofilament according to this embodiment.

[0032] Other 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.

[0033] 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.

[0034] The ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is 15 / 85 to 85 / 15, preferably 20 / 80 to 80 / 20, more preferably 25 / 75 to 75 / 25, even more preferably 30 / 70 to 70 / 30, still more preferably 30 / 70 to 50 / 50, and particularly preferably 30 / 70 to 40 / 60. The fact that the ratio of the mass of the poly(3-hydroxyalkanoate) resin to the mass of the polycaprolactone is 15 / 85 or more provides the advantage that the monofilament according to this embodiment has excellent heat resistance. Having a ratio of 85 / 15 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 monofilament according to this embodiment.

[0035] The monofilament according to this embodiment has a matrix-domain structure comprising a matrix and domains, wherein the matrix preferably contains the poly(3-hydroxyalkanoate) resin and the domain preferably contains the polycaprolactone. The monofilament according to this embodiment has the advantage of having excellent heat resistance due to its configuration. The following reasons can be considered for why the monofilament 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 monofilament. Poly(3-hydroxyalkanoate) resins have higher heat resistance than polycaprolactone. Therefore, it is believed that the monofilament according to this embodiment, having such a configuration, will have even greater heat resistance.

[0036] Furthermore, the fact that "the monofilament has a matrix-domain structure including a matrix and domains, the matrix contains the poly(3-hydroxyalkanoate) resin, and the domains contain the polycaprolactone" can be confirmed by photographing a first cross-section (a cross-section perpendicular to the longitudinal direction of the monofilament) and a second cross-section (a cross-section perpendicular to the first cross-section) of the monofilament with a transmission electron microscope (TEM). In other words, ultrathin sections of the first and second cross-sections of the monofilament can be stained with ruthenium tetroxide (RuO4), and the stained ultrathin sections can be photographed with the aforementioned transmission electron microscope (TEM) for confirmation. "The matrix contains the poly(3-hydroxyalkanoate) resin" means "the poly(3-hydroxyalkanoate) resin is present in greater quantities in the matrix than in the domain." Furthermore, "the domain contains the polycaprolactone" means "the polycaprolactone is present in greater quantities in the domain than in the matrix."

[0037] Furthermore, from the viewpoint of further increasing the strength of the monofilament and further increasing the heat resistance of the monofilament, it is preferable that the poly(3-hydroxyalkanoate) resin is a poly(3-hydroxybutyrate) resin. Poly(3-hydroxybutyrate) resins have a moderate affinity for polycaprolactone. Therefore, the monofilament according to this embodiment has a sea-island structure even if the volume ratio of one of the poly(3-hydroxybutyrate) resin and polycaprolactone is greater than that of the other. Furthermore, when the volume ratio of the poly(3-hydroxybutyrate) resin and polycaprolactone is equal, the monofilament according to this embodiment has a co-continuous structure including a continuous phase of poly(3-hydroxybutyrate) resin and a continuous phase of polycaprolactone, in addition to the sea-island structure. As a result, the monofilament according to this embodiment, by containing a poly(3-hydroxybutyrate) resin and polycaprolactone, has even higher strength and even better heat resistance.

[0038] The monofilament 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 polymer component. 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 polymer component has the advantage of further promoting the crystallization of the polymer component. 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 polymer component. Having a nucleating agent content of 10 parts by mass or less per 100 parts by mass of the polymer component allows for a lower viscosity of the molten material during monofilament production, which in turn facilitates the production of monofilaments. 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.

[0043] The polymer composition preferably contains the lubricant. The presence of the lubricant in the monofilament improves its lubricity. 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.

[0044] 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 monofilament. 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 monofilament.

[0045] The fineness of the monofilament according to this embodiment is 15 to 3000 dtex. The fineness of the monofilament according to this embodiment is preferably 100 dtex or more, more preferably 200 dtex or more. The fineness of the monofilament according to this embodiment is preferably 1500 dtex or less, more preferably 1000 dtex or less. The fineness of a monofilament is defined as the mass per unit length, expressed in units of dtex (g) per 10,000 m. The fineness of a monofilament can be measured using the autobiscope method.

[0046] The tensile strength of the monofilament according to this embodiment is 2.5 cN / dtex or higher. The tensile strength of the monofilament according to this embodiment is preferably 2.6 cN / dtex or higher, more preferably 4.0 cN / dtex or higher, and even more preferably 4.5 cN / dtex or higher. In this embodiment, a higher tensile strength is preferable for the monofilament. The tensile strength of the monofilament according to this embodiment 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 the monofilament according to this embodiment refers to the tensile strength measured at an initial length of 20 mm and a speed of 20 mm / min, based on JIS L 1015:2021 "Test Method for Chemical Fiber Staples". For measuring tensile strength, for example, a tensile strength measuring device (Shimadzu Corporation, Autograph AG-1) can be used.

[0047] Examples of the cross-sectional shape (cross-section perpendicular to the longitudinal direction) of the monofilament according to this embodiment include circular (including elliptical), Y-shaped, X-shaped, H-shaped, and multi-lobed shapes.

[0048] In this embodiment, the monofilament may be a mixture of a poly(3-hydroxyalkanoate) resin and polycaprolactone.

[0049] Furthermore, the monofilament according to this embodiment may be a composite fiber. Composite fibers are specified in JIS L0204-3:1998, section 3.2.10. The composite fiber may, for example, be a core-sheath composite fiber having a core portion and a sheath portion. The core portion may contain a poly(3-hydroxyalkanoate) resin, and the sheath portion may contain polycaprolactone. Alternatively, the core portion may contain polycaprolactone, and the sheath portion may contain a poly(3-hydroxyalkanoate) resin. Furthermore, the composite fiber may have one semicircular portion in a cross-section perpendicular to the longitudinal direction containing a poly(3-hydroxyalkanoate) resin, and the other semicircular portion containing polycaprolactone.

[0050] The monofilament according to this embodiment can be used, for example, as marine materials, agricultural materials, civil engineering materials, medical materials, and the like. Specifically, the monofilament according to this embodiment can be used, for example, as fishing line, fishing net, aquaculture net, seaweed seedling thread, artificial turf material, toothbrush bristles, beverage extraction filters (tea bag fabric), insect nets, animal nets, sutures, surgical nets, stents, prosthetic materials, 3D printing filaments, tennis strings, hook-and-loop fasteners (e.g., Velcro®), tire cords, printing screens, wigs, hose reinforcements, weft knitted fabrics for clothing, grass cutting cords (wire material), screen door nets, and the like.

[0051] The monofilament according to this embodiment is configured as described above. Next, a method for manufacturing the monofilament according to this embodiment will be described.

[0052] The method for manufacturing monofilaments according to this embodiment is a method for manufacturing monofilaments by melt spinning. Furthermore, the method for manufacturing monofilament according to this embodiment includes a step (A) of passing the yarn obtained by extruding molten material from a spinning nozzle through a water bath at 15 to 35°C, and a step (B) of stretching the yarn that has passed through the water bath with a stretching roll section. The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone is 15 / 85 to 85 / 15. The total stretch ratio in the above process (B) is 5.0 times or more. The fineness of the aforementioned monofilament is 15 to 3000 dtex.

[0053] In the following section, the method for manufacturing monofilaments according to this embodiment will be explained using the monofilament manufacturing apparatus 1 shown in Figure 1 as an example.

[0054] (Process (A)) The aforementioned step (A) is a step in which the raw yarn obtained by extruding the molten material from the spinning nozzle is passed through a water bath at 15 to 35°C.

[0055] As shown in Figure 1, in step (A), first, the molten material is introduced into the material input section 2a. Next, the material introduced from the material input section 2a is kneaded in the kneading extruder 2b while being heated to obtain the molten material. The kneading extruder 2b is a screw extruder. The kneading extruder 2b may be a single-screw extruder or a twin-screw extruder.

[0056] Then, using a spinning nozzle 2d having an discharge hole, the molten material obtained in the kneading extruder 2d is discharged from the discharge hole to obtain molten yarn A. The flow rate of the molten material discharged from the discharge hole of the spinning nozzle 2d is adjusted by the gear pump 2c.

[0057] The temperature of the spinning nozzle 2d is, for example, 150 to 190°C, more specifically 160 to 180°C.

[0058] The spinning nozzle 2d may have one or more discharge holes, or multiple discharge holes. Since the spinning nozzle 2d has multiple discharge holes, multiple monofilaments can be produced simultaneously.

[0059] Examples of the shapes of the discharge holes include circular (including elliptical), Y-shaped, X-shaped, H-shaped, and multi-lobed shapes. Regarding the size of the discharge hole, for example, if the shape of the discharge hole is circular, the diameter of the discharge hole is preferably 0.5 mm to 20 mm, and more preferably 1.0 mm to 10 mm. Furthermore, if the shape of the discharge hole is circular, the ratio of the length of the discharge hole (L) to the diameter of the discharge hole (D), in other words, L / D, is preferably 1 to 10, more preferably 2 to 5.

[0060] The discharge rate of molten material discharged from a single discharge port is preferably 0.20 to 2.0 kg / hr, more preferably 0.40 to 1.2 kg / hr.

[0061] In step (A) above, the raw yarn A is cooled by passing it through a water bath at 15 to 35°C. Furthermore, in step (A), the raw yarn A, which is at a temperature higher than the solidification temperature of the raw yarn A, is passed through a water bath 3a at 15 to 35°C.

[0062] In step (A) above, by passing the raw yarn A through a water bath 3a at 35°C or lower, it is possible to suppress the raw yarn A from coming into contact with the take-up roll section 4 while still in a softened state and becoming sticky. Furthermore, in step (A), by passing the raw yarn A through a water bath 3a at 35°C or lower, the time during which the polycaprolactone and poly(3-hydroxyalkanoate) resin constituting the raw yarn A 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 raw yarn A from hardening. Therefore, it becomes easier to stretch the raw yarn A in step (B). As a result, it becomes easier to increase the strength of the monofilament.

[0063] Furthermore, by keeping the water bath 3a at 15°C or higher, it is possible to ensure a certain amount of time during which the polycaprolactone and poly(3-hydroxyalkanoate) resin constituting the yarn A are within the temperature range for crystallization. This prevents the yarn A from coming into contact with the water bath roll section 3c and becoming sticky before it has fully crystallized.

[0064] The water bath 3a is the water placed in the water tank 3b.

[0065] The monofilament manufacturing apparatus 1 includes a water bath roll section 3c that conveys the filament A so that it passes through the water bath 3a. In step (A) above, the raw yarn A is conveyed by the water bath roll section 3c, thereby passing the raw yarn A through the water bath 3a.

[0066] The temperature of the water bath 3a is 15 to 35°C, preferably 18 to 34°C.

[0067] In step (A), the raw yarn A is cooled to preferably 50°C or lower, more preferably 40°C or lower. In step (A), the raw yarn A is cooled to, for example, 0°C or higher, more specifically 10°C or higher. In step (A), the raw yarn A may be cooled to 50°C or below by passing it through a water bath at 15-35°C. Alternatively, in step (A), the raw yarn A may be cooled to a certain extent by passing it through a water bath at 15-35°C, and then cooled to 50°C or below by being cooled with ambient air before stretching.

[0068] (Process (B)) In step (B) above, the cooled raw yarn A is stretched in the stretching roll section. In step (B) above, stretching the yarn A can increase the orientation of the polymer components contained in the yarn, thereby increasing the strength of the monofilament.

[0069] In step (B) above, it is preferable to heat the cooled yarn A and stretch it in the stretching roll section. To enhance the orientation of the polymer components, it is 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. Furthermore, 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 monofilaments. In this embodiment, the cooled yarn A is heated and then stretched in the stretching roll section. Compared to the method of stretching the yarn while cooling it with ambient air, this makes it easier to adjust the temperature of the yarn to be within a temperature range suitable for increasing the orientation of the polymer components during stretching. As a result, it becomes easier to increase the orientation of the polymer components of the yarn. Therefore, in this embodiment, it becomes easier to increase the strength of the monofilament.

[0070] In step (B) above, the yarn A cooled in the water bath 3a is taken up by the take-up roll section 4. The take-up roll section 4 is a roll section for taking up the raw yarn A from the water bath 3a. Next, the yarn A taken up by the take-up roll section 4 is stretched by the first stretching roll section 6. Then, the yarn A stretched by the first stretching roll section 6 is stretched by the second stretching roll section 8. Next, the yarn A stretched by the second stretching roll section 8 is wound up by the winding roll section 9 to obtain a monofilament.

[0071] In step (B), the yarn A that has been stretched by the first stretching roll section 6 is stretched by the second stretching roll section 8. In other words, in step (B), the yarn A is stretched in two stages. In addition, step (B) may be performed in multiple stages (two or more stages), or in a single stage. In step (B) above, by stretching in multiple stages (two or more stages), it is possible to increase the total stretch ratio while suppressing breakage of the filament during stretching. As a result, it becomes easier to further increase the strength of the monofilament. Multi-stage stretching (two or more stages) means that multiple stretching rolls are used for stretching, and the speed of the later stretching rolls is faster than the speed of the earlier stretching rolls. The speed of the stretching roll section refers to the length of yarn conveyed by the stretching roll section per unit time.

[0072] The total stretch ratio in step (B) is 5.0 times or more, preferably 6.0 times or more, and more preferably 6.5 times or more. The total stretch ratio in step (B) is, for example, 13.0 times or less. In step (B) above, the total stretching ratio is 5.0 times or more, which increases the orientation of the polymer components of the monofilament, and as a result, increases the strength of the monofilament. The total stretch ratio in step (B) can be calculated using the following formula. The total stretch ratio in step (B) = Speed ​​of the winding roll section 9 (m / min) / Speed ​​of the take-up roll section 4 (m / min)

[0073] The speed of the winding roll (m / min) is the length of yarn wound onto the winding roll per unit time. Furthermore, the speed of the take-up roll section (m / min) is the length of yarn taken up by the take-up roll section per unit time.

[0074] In step (B) above, it is preferable to heat the yarn A that has passed through the take-up roll section 4 in the hot water bath 5 before stretching the yarn A in the first stretching roll section 6. In step (B) above, before the yarn A is stretched by the first stretching roll section 6, the yarn A that has passed through the take-up roll section 4 is heated in the hot water bath 5. This makes it easy to adjust the temperature of the yarn A before stretching so that it is within a temperature range suitable for increasing the orientation of the polymer components contained in the yarn A by stretching. As a result, it becomes easier to increase the orientation of the polymer components of the yarn A by stretching. The temperature of the hot water in the hot water tank 5 is preferably 25 to 65°C, more preferably 30 to 60°C.

[0075] In step (B) above, the stretched yarn A may be heated with heated air in the heat treatment tank 7. In step (B) above, the stretched yarn A is heated with heated air in the heat treatment tank 7, thereby promoting the crystallization of the polymer components contained in the yarn A. As a result, the strength of the monofilament can be increased. The temperature of the air in the heat treatment tank 7 is preferably 50 to 120°C, more preferably 60 to 110°C.

[0076] [Disclosure items] Each of the following items is a disclosure of a preferred embodiment.

[0077] [Item 1] It contains poly(3-hydroxyalkanoate) resin and polycaprolactone. The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone is 15 / 85 to 85 / 15. The tensile strength is 2.5 cN / dtex or higher. Monofilament with a fineness of 15-3000 dtex. The monofilament described in item 1, due to its configuration, exhibits high strength and excellent heat resistance.

[0078] Furthermore, in the future, there may be a need for monofilaments that possess high strength, excellent heat resistance, and good biodegradability, from the perspective of applicability to a wide range of applications. Here, polycaprolactone, like poly(3-hydroxyalkanoate) resins, is biodegradable. Therefore, according to this embodiment, it is possible to provide a monofilament that has high strength, excellent heat resistance, and good biodegradability.

[0079] [Item 2] The poly(3-hydroxyalkanoate) resin is a monofilament according to item 1, comprising at least one selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0080] [Item 3] The poly(3-hydroxyalkanoate) resin is a monofilament according to item 2, comprising the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0081] [Item 4] A method for manufacturing monofilaments by melt spinning, The process (A) involves extruding the molten material from a spinning nozzle and passing the resulting yarn through a water bath at 15-35°C, The process includes (B) stretching the yarn that has passed through the water bath in a stretching roll section, The molten material contains a poly(3-hydroxyalkanoate) resin and polycaprolactone. The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone is 15 / 85 to 85 / 15. The total stretch ratio in the above process (B) is 5.0 times or more. A method for manufacturing a monofilament, wherein the fineness of the monofilament is 15 to 3000 dtex.

[0082] [Item 5] The method for manufacturing a monofilament according to item 4, wherein step (B) involves stretching the yarn in multiple stages.

[0083] Furthermore, the present invention is not limited to the embodiments described above. Nor is it limited by the effects and advantages described above. Moreover, the present invention can be modified in various ways without departing from the spirit of the invention. [Examples]

[0084] Next, the present invention will be described in more detail with reference to examples, comparative examples, and reference examples. However, the present invention is not limited in any way to these examples.

[0085] <Example 1> (Process (A)) First, as shown in Figure 1, a molten product was prepared by mixing the following materials at 165°C in a single-screw extruder (screw diameter D: 30 mm, screw length L / screw diameter D = 24) called a kneading extruder 2b. • Poly(3-hydroxyalkanoate) resin: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (percentage of 3-hydroxyhexanoate = 6 mol%, Mw = 550,000) (P3HB3HH) • Polycaprolactone (PCL) (Ingevity's "CAPA6800") • Lubricants containing amide bonds: Behenamide • Lubricants containing amide bonds: Erucic acid amide • Nucleating agent: Pentaerythritol The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone (P3HB3HH / PCL) was set to 70 / 30. In other words, the content of P3HB3HH in the polymer component (hereinafter also referred to as the "ratio of P3HB3HH") was set to 70% by weight. Furthermore, per 100 parts by weight of polymer components (total of P3HB3HH and PCL), erucic acid amide was added in a ratio of 0.5 parts by weight, behenic acid amide in a ratio of 0.5 parts by weight, and pentaerythritol in a ratio of 1.0 part by weight.

[0086] Next, five strands of yarn A were obtained by extruding the molten material from the discharge hole of the spinning nozzle 2d. The spinning nozzle 2d had five discharge holes. All of the discharge holes were circular. The diameter (φ) of all discharge holes was 1.5 mm. Furthermore, the ratio of the length (L) of the discharge hole to the diameter (D), in other words, L / D, was 3. Furthermore, the temperature of the spinning nozzle 2d was set to 160°C. Furthermore, the total discharge volume of molten material from all discharge ports was set at 4.5 kg / hr. In other words, the discharge volume of molten material from a single discharge port was set at 0.90 kg / hr.

[0087] Then, the yarn A, which was at a temperature higher than its solidification temperature, was passed through a 35°C water bath 3a for 36 seconds to cool the yarn A.

[0088] (Process (B)) In process (B), the cooled raw yarn A was taken up by the take-up roll section 4 (speed: 5.0 m / min), heated in a hot water bath 5 (hot water temperature: 45°C) for 2.9 seconds, and then stretched by the first stretching roll section 6. Then, the yarn A, which had been stretched by the first stretching roll section 6, was heated in a heat treatment tank 7 (hot air temperature: 80°C) for 4.0 seconds, stretched by the second stretching roll section 8, and wound up by the winding roll section 9 to obtain a monofilament. The extension ratio for the first stage was set to 7.0 times, resulting in a total extension ratio of 9.0 times.

[0089] The total extension ratio was calculated using the method described above. Furthermore, the extension ratio of the first stage was calculated using the following formula. First stage stretching ratio = Speed ​​of the first stretching roll section 6 (m / min) / Speed ​​of the take-up roll section 4 (m / min) Here, the speed of the first stretching roll section is the length of the yarn A conveyed by the first stretching roll section per unit time.

[0090] (Examples 2-4, Comparative Examples 1-3) A monofilament was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1 below.

[0091] (Fineness and tensile strength of monofilament) The fineness and tensile strength (tensile strength of the monofilament before heating, described later) of the monofilament were determined by the method described above. The measured values ​​are shown in Table 1 below.

[0092] (Heat resistance test) The length of the monofilament was measured before heating. The monofilament was heated under tension at 60°C for 24 hours. Next, the length and tensile strength of the heated monofilament were measured. The dimensional retention rate was then calculated using the following formula. Dimensional retention rate (%) = [1 - (length of monofilament before heating - length of monofilament after heating) / length of monofilament before heating] × 100% Furthermore, the intensity reduction rate was calculated using the following formula. Strength reduction rate (%) = [(Tensile strength of monofilament before heating - Tensile strength of monofilament after heating) / Tensile strength of monofilament before heating] × 100% The results are shown in Table 1 below.

[0093] [Table 1]

[0094] As shown in Table 1, in Examples 1 to 4, which are within the scope of the present invention, the tensile strength of the monofilament was higher compared to Comparative Examples 1 and 2, in which the ratio of P3HB3HH was 90% by weight or more. Furthermore, in Examples 1 to 4, which fall within the scope of the present invention, the dimensional retention rate in the heat resistance test was higher compared to Comparative Example 3, where the ratio of P3HB3HH was 10% by weight. In Comparative Example 3, the monofilament was too brittle after heating to measure its tensile strength, and therefore the strength reduction rate (%) could not be determined. Therefore, it is clear that this disclosure makes it possible to provide a monofilament that is both high in strength and has excellent heat resistance.

[0095] (Comparative Example 4) In an attempt to obtain a monofilament in the same manner as in Example 1, except that the water bath temperature was set to 10°C, the raw yarn A adhered to the water bath roll section 3c, and it was not possible to obtain a monofilament. Assuming the water bath temperature is 10°C, the reason why the raw yarn A adheres to the water bath roll section 3c is thought to be that the raw yarn A was rapidly cooled in the water bath, preventing it from crystallizing sufficiently before it came into contact with the water bath roll section 3c and became sticky.

[0096] (Comparative Example 5) Except for setting the water bath temperature to 40°C, we attempted to obtain a monofilament in the same manner as in Example 1. However, the raw yarn A adhered to the take-up roll section 4, and we were unable to obtain a monofilament. If the water bath temperature is 40°C, the reason why the raw yarn A adheres to the take-up roll section 4 is thought to be that the raw yarn A is not sufficiently cooled in the water bath, causing it to come into contact with the take-up roll section 4 while still in a softened state and adhere to it.

[0097] (Reference example 1) A monofilament was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 2 below.

[0098] [Table 2]

[0099] (Reference examples 2~4) As a reference example 2, cellulose was prepared as a reference substance. As a reference example 3, we prepared cotton yarn (60 / 2: 60 count double yarn, equivalent to 200 dtex). Furthermore, as the monofilament for Reference Example 4, a high-density polyethylene (HDPE) monofilament was prepared.

[0100] (Evaluation test of biodegradability in soil) Fabrics were prepared using the monofilaments of Examples 1, 3, and 4, Comparative Example 1, and Reference Example 1. Next, the "Aerobic Biodegradation Assessment of Plastics in Soil (ISO 17556)" was performed on the textile, and the percentage of biodegradation was calculated from the theoretical carbon dioxide emissions up to day 51. Furthermore, for cellulose, the reference substance in Reference Example 2, we conducted the "Aerobic Biodegradation Evaluation of Plastics in Soil (ISO 17556)" and calculated the percentage of biodegradation from the theoretical carbon dioxide emissions up to day 51. The theoretical value was calculated as follows. First, 120 mg of monofilament was added to 120 g of soil, and carbon dioxide generated from the soil containing the monofilament was collected in a gas bag for 51 days. Next, the amount of carbon dioxide (measured value) collected in the gas bag was measured using the NDIR method. Similarly, the amount of carbon dioxide (blank value) emitted from soil without monofilaments over a 51-day period was also measured. Then, the theoretical amount of carbon dioxide emissions was calculated by subtracting the blank value from the measured value. A higher percentage of biodegradation indicates that biodegradation has progressed more rapidly in the soil. The results are shown in Table 3 below.

[0101] [Table 3]

[0102] As shown in Table 3, the biodegradability of Examples 1, 3, and 4 ranged from 6.7% to 13.2%. Furthermore, in Examples 1, 3, and 4, the degree of biodegradability was lower compared to Comparative Example 1, where the ratio of P3HB3HH was 100% by weight, and to Reference Example 2, which was cellulose. From the above, it can be seen that the monofilaments of Examples 1, 3, and 4 are biodegradable and have a long lifespan.

[0103] (Evaluation of biodegradability in seawater) The monofilaments of Examples 1, 3, and 4, Comparative Example 1, and Reference Examples 1 and 4 were immersed in seawater. Next, the tensile strength of the monofilament was measured before immersion, 4 weeks after immersion, 8 weeks after immersion, 12 weeks after immersion, and 16 weeks after immersion. The strength retention rate was then calculated using the following formula. Strength retention rate (%) = [1 - (Tensile strength of monofilament before immersion - Tensile strength of monofilament after immersion) / Tensile strength of monofilament before immersion] × 100% Furthermore, instead of monofilament, the cotton yarn from Reference Example 3 was used, and the tensile strength of the cotton yarn was measured before immersion, 4 weeks after immersion, 8 weeks after immersion, 12 weeks after immersion, and 16 weeks after immersion, and the strength retention rate was determined. The results are shown in Table 4 below. In Comparative Example 1, the monofilament was too brittle after 8 weeks of immersion to measure its tensile strength. Furthermore, in Reference Example 3, the cotton yarn disappeared after 8 weeks of immersion, making it impossible to measure the tensile strength.

[0104] [Table 4]

[0105] As shown in Table 4, in Examples 1, 3, and 4, the strength retention rate after 4 weeks from immersion was 67-72%, after 8 weeks from immersion it was 52-67%, after 12 weeks it was 52-68%, and after 20 weeks it was 41-46%. As shown in Table 4, in Reference Example 4, where the monofilament was formed from high-density polyethylene (HDPE), the strength retention rate was 100% or more. Therefore, it can be seen that the monofilaments of Examples 1, 3, and 4 are biodegradable, unlike Reference Example 4. Furthermore, as shown in Table 4, Examples 1, 3, and 4 showed higher strength retention compared to Comparative Example 1, where the P3HB3HH ratio was 100% by weight; Reference Example 1, where the P3HB3HH ratio was 0% by mass; and Reference Example 3, which was cotton yarn. Therefore, it can be seen that the monofilaments of Examples 1, 3, and 4 have a long lifespan. From the above, it can be seen that the monofilaments of Examples 1, 3, and 4 are biodegradable and have a long lifespan.

[0106] (Structure in cross-section of a monofilament) The first cross-section (a cross-section perpendicular to the longitudinal direction of the monofilament) and the second cross-section (a cross-section perpendicular to the first cross-section) of the monofilaments of Example 1 (P3HB3HH / PCL=70 / 30), Example 3 (P3HB3HH / PCL=50 / 50), and Example 4 (P3HB3HH / PCL=30 / 70) were photographed using a transmission electron microscope (TEM). Specifically, ultrathin sections of the first and second cross-sections of the monofilaments of Examples 1, 3, and 4 were stained with ruthenium tetroxide (RuO4), and the stained ultrathin sections were photographed using the transmission electron microscope (TEM).

[0107] Figure 2 shows an image of the first cross-section of Example 1 (scale bar: 5 μm). Figure 3 shows an image of the first cross-section of Example 1 with a higher magnification than Figure 2 (scale bar: 1 μm). Figure 4 shows an image of the second cross-section of Example 1 (scale bar: 5 μm). Figure 5 shows an image of the second cross-section of Example 1 with a higher magnification than Figure 4 (scale bar: 1 μm). Figure 6 shows an image of the first cross-section of Example 3 (scale bar: 5 μm). Figure 7 shows an image of the first cross-section of Example 3 with a higher magnification than Figure 6 (scale bar: 1 μm). Figure 8 shows an image of the second cross-section of Example 3 (scale bar: 5 μm). Figure 9 shows an image of the second cross-section of Example 3 with a higher magnification than Figure 8 (scale bar: 1 μm). Figure 10 shows an image of the first cross-section of Example 4 (scale bar: 5 μm). Figure 11 shows an image of the first cross-section of Example 4 (scale bar: 1 μm) with a higher magnification than Figure 10. Figure 12 shows an image of the second cross-section of Example 4 (scale bar: 5 μm). Figure 13 shows an image of the second cross-section of Example 4 (scale bar: 1 μm) with a higher magnification than Figure 12. In Figures 4, 5, 8, 9, 12, and 13, the direction of the arrows indicates the longitudinal direction of the monofilament. The lighter areas are thought to be the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH) portion, the darker areas are thought to be the polycaprolactone (PCL) portion, and the black areas are thought to be other components (bacteria, additives, etc.).

[0108] As shown in Figures 2 and 3, in the first cross-section of Example 1 (P3HB3HH / PCL=70 / 30) (a cross-section perpendicular to the longitudinal direction of the monofilament), a matrix-domain structure (sea-island structure) was observed in which the domain PCL was dispersed within the matrix P3HB3HH, and a co-continuous structure was observed in which the continuous phase of P3HB3HH and the continuous phase of PCL were present. As shown in Figures 4 and 5, in the second cross-section (a cross-section perpendicular to the first cross-section) of Example 1 (P3HB3HH / PCL=70 / 30), it was confirmed that both P3HB3HH and PCL have a phase-separated structure oriented in the longitudinal direction of the monofilament. As shown in Figures 6 and 7, in the first cross-section of Example 3 (P3HB3HH / PCL=50 / 50) (a cross-section perpendicular to the longitudinal direction of the monofilament), it was confirmed that the P3HB3HH domains were dispersed within the PCL matrix, forming a matrix-domain structure (sea-island structure). Furthermore, the domains were amorphous and approximately several hundred nanometers in size. As shown in Figures 8 and 9, in the second cross-section (a cross-section perpendicular to the first cross-section) of Example 3 (P3HB3HH / PCL=50 / 50), it was observed that the PCL domains were dispersed within the P3HB3HH matrix, forming a matrix-domain structure (sea-island structure). The domains had an elongated elliptical shape in the longitudinal direction of the monofilament. As shown in Figures 10 and 11, in the first cross-section of Example 4 (P3HB3HH / PCL=30 / 70) (a cross-section perpendicular to the longitudinal direction of the monofilament), a matrix-domain structure (sea-island structure) was observed in which the domain P3HB3HH was dispersed in the matrix PCL, and a co-continuous structure was observed in which the continuous phase of P3HB3HH and the continuous phase of PCL were present. As shown in Figures 12 and 13, in the second cross-section (a cross-section perpendicular to the first cross-section) of Example 4 (P3HB3HH / PCL=30 / 70), it was confirmed that the P3HB3HH domains were dispersed within the PCL matrix, forming a matrix-domain structure (sea-island structure). The domains were oriented along the longitudinal direction of the monofilament. [Explanation of Symbols]

[0109] 1: Monofilament manufacturing equipment, 2a: Material input section, 2b: Mixing extruder, 2c: Gear pump, 2d: Spinning nozzle, 3a: Water bath, 3b: Water tank, 3c: Water bath roll section, 4: Take-up roll section, 5: Hot water tank, 6: First stretching roll section, 7: Heat treatment tank, 8: Second stretching roll section, 9: Winding roll section

Claims

1. It contains poly(3-hydroxyalkanoate) resin and polycaprolactone. The ratio of the weight of the poly(3-hydroxyalkanoate) resin to the weight of the polycaprolactone is 15 / 85 to 85 / 15. The aforementioned poly(3-hydroxyalkanoate) resin includes the aforementioned poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), The tensile strength is 2.5 cN / dtex or higher. Monofilament with a fineness of 15 to 3000 dtex.

2. A method for producing a monofilament according to claim 1 by melt spinning, The process (A) involves extruding the molten material from a spinning nozzle and passing the resulting yarn through a water bath at 15-35°C, The process includes (B) stretching the yarn that has passed through the water bath in a stretching roll section, The molten material contains the poly(3-hydroxyalkanoate) resin and the polycaprolactone. A method for manufacturing a monofilament, wherein the total draw ratio in step (B) is 5.0 times or more.

3. The method for manufacturing a monofilament according to claim 2, wherein step (B) involves stretching the yarn in multiple stages.

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