Method for producing fiber for stretching and method for producing fiber

Abstract

To provide fiber for stretching for producing poly(3-hydroxyalkanoate)-based resin-containing fiber having high strength and low shrinkage rate.SOLUTION: The present invention is a method for producing fiber for stretching by a melt spinning method, comprising a step (A) of discharging a molten material obtained by melting a raw material composition comprising a poly(3-hydroxyalkanoate)-based resin by heating from a discharge hole to obtain an undrawn yarn, a step (B) of taking up the undrawn yarn with a take-up roll and winding the undrawn yarn on a core, and a step (C) of allowing the undrawn yarn in a state of being wound on the core to stand for 6 hours or more. In the step (B), during the winding, the temperature of the undrawn yarn is 35 to 75°C, and the tension applied to the undrawn yarn is 0 to 0.30 cN / dtex.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing fibers for drawing and a method for producing fibers. [Background technology]

[0002] Fibers are used in a variety of applications, and a known method for producing fibers is, for example, a method for obtaining fibers from polytrimethylene terephthalate using a melt spinning method (for example, Patent Document 1).

[0003] In recent years, plastic waste has become a major problem that causes a significant burden on the global environment, including impacts on ecosystems, the generation of harmful gases during combustion, and global warming due to the large amount of heat generated by combustion. As a solution to these problems, biodegradable plastics have been actively developed. Among these biodegradable plastics, those made from plant-derived raw materials emit carbon dioxide when burned, which was originally present in the air and does not increase the amount of carbon dioxide in the atmosphere. This is called carbon neutrality, and is considered important under the Kyoto Protocol, which imposed carbon dioxide reduction targets, and active use of such plastics is desired. Recently, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester resins, and in particular polyhydroxyalkanoate resins, have been attracting attention as biodegradable plastics that are produced by microorganisms using plant-derived raw materials as a carbon source.

[0004] Known methods for producing fibers containing polyhydroxyalkanoate resins include melt-extruding polyhydroxyalkanoic acid to produce melt-extruded fibers, rapidly cooling the melt-extruded fibers to a temperature below the glass transition temperature of the polyhydroxyalkanoic acid +15°C and solidifying them to produce amorphous fibers, leaving the amorphous fibers at a temperature below the glass transition temperature +15°C to produce crystallized fibers, stretching the crystallized fibers, and further subjecting them to tension heat treatment (e.g., Patent Document 2). Also known is a method comprising the steps of: (A) obtaining 30 or more molten yarns by melt spinning a melt containing a poly(3-hydroxyalkanoate) resin and a crystal nucleating agent using a spinning nozzle having 30 or more discharge holes; (B) obtaining a multifilament to be drawn by blowing a gas at a temperature of 0°C to 50°C onto the 30 or more molten yarns to cool the 30 or more yarns; and (C) obtaining a multifilament by drawing the multifilament to be drawn by 1.5 times or more in a drawing roll section (e.g., Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2003-527497 [Patent Document 2] International Publication No. 2006 / 038373 [Patent Document 3] International Publication No. 2023 / 022015 Summary of the Invention [Problem to be solved by the invention]

[0006] However, poly(3-hydroxyalkanoate) resins have a very slow crystallization rate, and even after being formed into fibers, the residual stress in the fibers relaxes, which can result in a decrease in fiber strength over time. In response to this, it has been found that after obtaining a raw yarn by a melt spinning method, the raw yarn is wound around a core (e.g., a paper tube, etc.) and the raw yarn is constrained by the core, thereby suppressing relaxation shrinkage of the fiber obtained from the raw yarn and also suppressing a decrease in the strength of the fiber. However, in this method, residual stress is not relaxed and remains in the drawing fiber and in the fiber obtained by drawing the drawing fiber, and it is known that severe shrinkage occurs when the drawing fiber or the fiber is heat-treated. Thus, in fibers containing poly(3-hydroxyalkanoate) resins, maintaining strength and suppressing shrinkage are in a trade-off relationship, and it has been difficult to achieve both.

[0007] Therefore, an object of the present invention is to provide a fiber for drawing for producing a poly(3-hydroxyalkanoate)-based resin-containing fiber having high strength and low shrinkage, and to provide a fiber obtained by drawing the fiber for drawing. [Means for solving the problem]

[0008] As a result of intensive research, the present inventors have found that in a method for producing a fiber for drawing by melt spinning from a raw material composition containing a poly(3-hydroxyalkanoate) resin, when the obtained raw yarn is wound around a core, the temperature of the raw yarn is within a predetermined range, the tension applied to the raw yarn is within a predetermined range, and further, the raw yarn in a wound state around the core is left to stand for a predetermined period of time or more, thereby making it possible to obtain a fiber for drawing for producing a poly(3-hydroxyalkanoate) resin-containing fiber having high strength and a low shrinkage rate, and have completed the present invention.

[0009] That is, the present invention provides a method for producing a fiber for drawing by a melt spinning method, a step (A) of discharging a melt obtained by heating a raw material composition containing a poly(3-hydroxyalkanoate) resin through a discharge hole to obtain a raw yarn; A step (B) of taking up the raw yarn with a take-up roll and winding it around a core; and (C) a step of leaving the yarn wound around the core for 6 hours or more, In the step (B), the temperature of the raw yarn is 35 to 75°C and the tension applied to the raw yarn is 0 to 0.30 cN / dtex during the winding.

[0010] The present invention also relates to a method for producing a fiber, which includes a step (D) of drawing the fiber to be drawn obtained by the method for producing a fiber to be drawn at a draw ratio of 1.1 to 2.5 times. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a fiber for drawing for producing a poly(3-hydroxyalkanoate)-based resin-containing fiber having high strength and low shrinkage, and also to provide a fiber obtained by drawing the fiber for drawing. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic diagram of an apparatus used in step (A) and step (B) of the present embodiment. [Figure 2] FIG. 2 is a schematic diagram of an apparatus used in step (D) of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0014] <Method of manufacturing fibers for drawing> In the method for producing fibers to be drawn according to this embodiment, fibers to be drawn are obtained by melt spinning. The method for producing a fiber for drawing according to this embodiment includes the steps of: (A) obtaining a raw yarn by discharging a melt obtained by heating a raw material composition containing a poly(3-hydroxyalkanoate) resin through a discharge hole; (B) taking up the raw yarn with a take-up roll and winding it around a core; and (C) leaving the raw yarn wound around the core for at least 6 hours to obtain a fiber for drawing. In the step (B), during the winding, the temperature of the raw yarn is 35 to 75° C., and the tension applied to the raw yarn is 0 to 0.30 cN / dtex.

[0015] The drawing fiber may contain one or more single yarns, that is, the drawing fiber may be a drawing multifilament or a drawing monofilament.

[0016] The raw material composition contains a poly(3-hydroxyalkanoate) resin.

[0017] The poly(3-hydroxyalkanoate) resin is a polyester containing 3-hydroxyalkanoic acid as a monomer. That is, the poly(3-hydroxyalkanoate) resin is a resin containing 3-hydroxyalkanoic acid as a constituent unit. The poly(3-hydroxyalkanoate) resin is a biodegradable polymer. In this embodiment, "biodegradability" refers to the property of being decomposed into low molecular weight compounds by microorganisms in nature. Specifically, the presence or absence of biodegradability can be determined based on tests suitable for each environment, such as ISO 14855 (compost) and ISO 14851 (activated sludge) under aerobic conditions, and ISO 14853 (aqueous phase) and ISO 15985 (solid phase) under anaerobic conditions. Furthermore, the decomposition ability of microorganisms in seawater can be evaluated by measuring biochemical oxygen demand. The poly(3-hydroxyalkanoate) resin includes a homopolymer and / or a copolymer.

[0018] The poly(3-hydroxyalkanoate) resin preferably contains a structural unit represented by the following formula (1). [-CHR-CH2-CO-O-] (1) (In the formula (1), R is C p H 2p+1 and p represents an integer of 1 to 15.

[0019] The poly(3-hydroxyalkanoate) resin is preferably a resin containing 3-hydroxybutyrate as a constituent unit (poly(3-hydroxybutyrate) resin). The poly(3-hydroxybutyrate) resin includes a homopolymer and / or a copolymer.

[0020] Examples of poly(3-hydroxyalkanoate) resins containing 3-hydroxybutyrate as a structural unit include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate). Here, P3HB means the homopolymer poly(3-hydroxybutyrate). P3HB3HH means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). P3HB3HV means poly(3-hydroxybutyrate-co-3-hydroxyvalerate). P3HB4HB means poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0021] Since P3HB has the function of promoting the crystallization of P3HB itself and poly(3-hydroxyalkanoate) resins other than P3HB, the poly(3-hydroxyalkanoate) resin preferably contains P3HB.

[0022] Examples of poly(3-hydroxyalkanoate) resins other than polymers containing 3-hydroxybutyrate as a structural unit include poly(3-hydroxyvalerate) and poly(3-hydroxyhexanoate).

[0023] As the poly(3-hydroxyalkanoate) resin, from the viewpoint of achieving both excellent biodegradability and moldability, P3HB, P3HB3HH, P3HB3HV, P3HB4HB, and the like are preferred, but are not particularly limited. Furthermore, the poly(3-hydroxyalkanoate) resin is preferably P3HB3HH from the viewpoint of increasing the strength of the resulting fiber and improving the molding processability.

[0024] When the poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate as a structural unit, the poly(3-hydroxyalkanoate) resin preferably contains 3-hydroxybutyrate units in an amount of 80 mol% or more, more preferably 85.0 mol% to 99.5 mol%, and even more preferably 85.0 mol% to 97.0 mol%, based on 100 mol% of all monomer structural units in the poly(3-hydroxyalkanoate) resin. When the poly(3-hydroxyalkanoate) resin contains 80 mol % or more of 3-hydroxybutyrate as a structural unit, the rigidity of the fiber increases. Furthermore, when the poly(3-hydroxyalkanoate) resin contains 99.5 mol % or less of 3-hydroxybutyrate as a structural unit, the fibers have excellent flexibility.

[0025] The content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin can be determined by the method described in the examples below.

[0026] The raw material composition may contain only one type of poly(3-hydroxyalkanoate) resin, or may contain two or more types of poly(3-hydroxyalkanoate) resin. When the poly(3-hydroxyalkanoate) resin contains a copolymer (such as P3HB3HH), it may contain two or more types of copolymers with different average composition ratios of the structural units.

[0027] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition is preferably 3.0×10 5 ~7.0×10 5 , more preferably 3.5 × 10 5 ~7.0×10 5 , and more preferably 4.0 × 10 5 ~7.0×10 5 , most preferably 4.5 x 10 5 ~6.5×10 5 is. The weight average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition is 3.0 × 10 5As a result of the above, it becomes easier to increase the weight average molecular weight of the poly(3-hydroxyalkanoate) resin in the fiber, and as a result, it becomes easier to increase the strength of the fiber. The weight average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition is 7.0 × 10 5 When the above condition is satisfied, the forming of the fiber to be drawn and the fiber becomes easy.

[0028] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition means the weight average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition before it is melted by heating.

[0029] The weight-average molecular weight in this embodiment is measured from the polystyrene equivalent molecular weight distribution using gel permeation chromatography (GPC) with a chloroform eluent. As the column for the GPC, a column appropriate for measuring the molecular weight may be used. For example, the weight-average molecular weight (Mw) can be determined by setting the column temperature to 40°C, injecting 10 μL of 3 mg of the target substance dissolved in 2 mL of chloroform, and setting the flow rate of the chloroform eluent (mobile phase) to 1.0 mL / min. A Shimadzu 20A (Shimadzu Corporation) GPC system and a Shodex K-806M (Showa Denko) column can be used.

[0030] The raw material composition contains preferably 50% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more of a poly(3-hydroxyalkanoate) resin.

[0031] The raw material composition may contain a polymer other than the poly(3-hydroxyalkanoate)-based resin (hereinafter also referred to as "other polymer"). The other polymer is preferably biodegradable. Other biodegradable polymers include, for example, polycaprolactone, 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)-based resins. The polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. The raw material composition may contain one type of other polymer, or may contain two or more types.

[0032] By including a biodegradable polymer in the raw material composition, even if the fibers to be drawn or the fibers are discarded in the environment, they are easily decomposed in the environment, thereby reducing the burden on the environment.

[0033] The raw material composition may contain additives. Examples of the additives include nucleating agents, lubricants, plasticizers, spinning oils, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), inorganic fillers, organic fillers, and antistatic agents.

[0034] From the viewpoint of promoting the crystallization of the poly(3-hydroxyalkanoate) resin, the raw material composition preferably contains a crystal nucleating agent. The nucleating agent is a compound that has the effect of promoting the crystallization of the poly(3-hydroxyalkanoate) resin, and has a melting point higher than that of the poly(3-hydroxyalkanoate) resin. Examples of the crystal nucleating agent include inorganic substances (boron nitride, titanium oxide, talc, layered silicates, calcium carbonate, sodium chloride, metal phosphates, etc.); sugar alcohol compounds derived from natural products (pentaerythritol, erythritol, galactitol, mannitol, arabitol, etc.); polyvinyl alcohol; chitin; chitosan; polyethylene oxide; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylate esters; dicarboxylic acid derivatives (dimethyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl selenide, etc.); Examples include: cyclic compounds having C═O and a functional group selected from NH, S, and O in the molecule (such as indigo, quinacridone, and quinacridone magenta); sorbitol derivatives (such as bisbenzylidene sorbitol and bis(p-methylbenzylidene) sorbitol); compounds containing a nitrogen-containing heteroaromatic nucleus (such as a pyridine ring, triazine ring, and imidazole ring) (such as pyridine, triazine, and imidazole); phosphate ester compounds; bisamides of higher fatty acids; metal salts of higher fatty acids; and branched polylactic acid. Furthermore, the poly(3-hydroxyalkanoate) resin P3HB can also be used as a crystal nucleating agent. These may be used alone or in combination of two or more.

[0035] As the crystal nucleating agent, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan are preferred from the viewpoint of improving the crystallization rate of poly(3-hydroxyalkanoate) resins and from the viewpoint of compatibility and affinity with poly(3-hydroxyalkanoate) resins. Among the sugar alcohol compounds, pentaerythritol is preferred.

[0036] The content of the crystal nucleating agent in the raw material composition is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, and even more preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. By having the content of the crystal nucleating agent in the raw material composition be 0.05 parts by weight or more per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, there is an advantage in that the crystallization of the poly(3-hydroxyalkanoate) resin can be further promoted. By having the content of the crystal nucleating agent in the raw material composition be 10 parts by weight or less per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the viscosity of the melt can be reduced when preparing fibers for drawing from the melt, which has the advantage of making it easier to prepare fibers for drawing. P3HB is a poly(3-hydroxyalkanoate) resin and can also function as a nucleating agent. Therefore, when the raw material composition contains P3HB, the amount of P3HB is included in both the amount of poly(3-hydroxyalkanoate) resin and the amount of nucleating agent.

[0037] The raw material composition may contain a lubricant. The lubricant may, for example, be a fatty acid amide. The fatty acid amide preferably includes at least one selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0038] The content of the lubricant in the raw material composition is preferably 0.05 to 12 parts by weight, more preferably 0.1 to 10 parts by weight, even more preferably 0.5 to 8 parts by weight, and most preferably 0.5 to 5 parts by weight, relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. By setting the content of the lubricant in the raw material composition to 0.05 parts by weight or more per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, there is an advantage that the lubricity of the single yarn of the fiber to be drawn is excellent. By setting the content of the lubricant in the raw material composition to 12 parts by weight or less per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, there is an advantage in that the lubricant can be prevented from bleeding out onto the surface of the fiber to be drawn.

[0039] The above steps (A) to (C) will be described below with reference to FIG.

[0040] (Process (A)) In the step (A), first, the materials are dry-blended and melt-kneaded in an extruder to obtain pellets as a raw material composition. Then, as shown in FIG. 1, the pellets are put into a raw material hopper 1. Next, the pellets fed from the raw material hopper 1 are heated and melted in the extruder 2 to obtain a melted material as a raw material composition. A screw extruder can be used as the extruder 2. The extruder 2 may be a single-screw extruder or a twin-screw extruder.

[0041] The molten material composition is then extruded from the spinning nozzle 4 to obtain a plurality of molten yarns A. The flow rate of the melt discharged from the spinning nozzle 4 is adjusted by the gear pump 3 .

[0042] The spinning nozzle 4 has one or two or more discharge holes 4a, preferably 12 or more, more preferably 30 to 10,000, more preferably 40 to 5,000, and even more preferably 50 to 3,000.

[0043] The shape and size of each discharge hole 4a are selected according to the characteristics required of the fiber to be drawn and the fiber (for example, appearance, fineness, strength, cross-sectional shape, etc.). It is preferable that the shapes of the discharge holes 4a are substantially the same, and it is also preferable that the areas (cross-sectional areas) of the discharge holes 4a are substantially the same. The shape of the discharge hole 4a may be, for example, a circle, an ellipse, a regular polygon, or a star-shaped regular polygon. The area (cross-sectional area) of each discharge hole 4a is preferably 1.0×10 -3 ~20mm 2 , more preferably 5.0 × 10 -3 ~10mm 2 is.

[0044] The flow rate of the melt discharged from the spinning nozzle 4 is preferably 1.0 to 20 kg / h, more preferably 2.0 to 15 kg / h.

[0045] The temperature of the melt immediately after being discharged from the spinning nozzle 4 is preferably 150 to 168°C, more preferably 151 to 167°C. When the temperature is 150° C. or higher, the raw material composition is sufficiently melted, and the melt can be easily discharged from the discharge hole 4a. By keeping the temperature at 168°C or less, decomposition of the poly(3-hydroxyalkanoate) resin is suppressed, and breakage of the molten yarn can be easily suppressed.

[0046] (Process (B)) In the step (B), the raw yarn A in a molten state is cooled by blowing gas onto the raw yarn A. Examples of the gas include air, inert gases (nitrogen gas, argon gas, etc.), and water vapor. In the step (B), as shown in FIG. 1, gas is blown onto the molten yarn A in a quenching section 5 . The quenching section 5 has a cooling box 5a. In the step (B), gas is blown onto the raw yarn A in the cooling box 5a. Examples of spraying methods include the circular method and the backside method. The back surface method is a method in which the gas is blown onto the yarn A from one direction within a cooling box 5a when viewed in the longitudinal direction of the yarn A (a cross-sectional view of the yarn A perpendicular to the longitudinal direction of the yarn A). The circular method is a method in which a cooling box 5a having a cylindrical side wall is used, and gas is blown into a cylindrical box 51 in a spiral shape along the inner circumferential surface of the cylindrical side wall, thereby blowing the gas onto the raw yarn A. The flow direction of the raw yarn A is approximately parallel to the imaginary axis of the cylindrical side wall. The cooling box 5a has a cylindrical perforated metal inside the cylindrical side wall, and may further have a cylindrical mesh (e.g., 80 mesh) inside the cylindrical perforated metal. The outer diameter of the cylindrical perforated metal is smaller than the inner diameter of the cylindrical side wall. The outer diameter of the cylindrical mesh is smaller than the inner diameter of the cylindrical perforated metal. In this case, in the circular method, the raw yarn A passes through the inside of a cylindrical net. The circular method is preferred as the blowing method, as the circular method can blow gas relatively uniformly onto the raw yarn A, thereby allowing the raw yarn A to be cooled more uniformly and suppressing variations in the fineness of the raw yarn A.

[0047] In the step (B), it is preferable to discharge the gas that has come into contact with the raw yarn A to the outside of the cooling box 5a along the flow direction of the raw yarn A. In order to discharge the gas that has come into contact with the raw yarn A to the outside of the cooling box 5a along the flow direction of the raw yarn A, for example, a straightening plate, a straightening fin, an ejector, a Venturi tube, a Transvector manufactured by Kogi Co., Ltd., or the like can be used.

[0048] The temperature of the gas is preferably 5 to 30° C., more preferably 10 to 25° C. The temperature of the gas means the temperature of the gas just before it hits the raw yarn A.

[0049] By keeping the temperature of the gas at 30°C or less, breakage of the raw yarn A is suppressed, and as a result, productivity of the fiber to be drawn is likely to be improved. This is thought to be because the temperature of the gas is 30°C or less, which allows the yarn A to be cooled sufficiently and shortens the time that the yarn A remains in a molten state, making the yarn A less likely to break.

[0050] Furthermore, by setting the temperature of the gas to 5°C or higher, fusion of the single yarns is suppressed, and as a result, the productivity of the fibers to be drawn is likely to be improved. This is thought to be because, when the temperature of the gas is 5°C or higher, the composition that makes up the raw yarn is more likely to crystallize after the raw yarn is taken up by the take-up roll, thereby suppressing fusion of the single yarns.

[0051] The gas velocity is preferably 0.01 m / s or more and less than 0.10 m / s, and more preferably 0.01 m / s or more and 0.09 m / s or less. The gas velocity means the gas velocity immediately before the gas hits the raw yarn A.

[0052] When the gas velocity is less than 0.10 m / s, the raw yarn A is less likely to break when taken up by the take-up roll even if the take-up roll speed is increased, and as a result, the productivity of the fiber to be drawn can be more easily improved. This is thought to be because, by setting the gas velocity to less than 0.10 m / s, the raw yarn A can be prevented from being cooled to a temperature at which the composition constituting the raw yarn is likely to crystallize before being taken up by the take-up roll, making it easier for the raw yarn A to be taken up by the take-up roll in a flexible state.

[0053] By setting the gas velocity to 0.01 m / s or more, the molten yarn A can be sufficiently cooled by the gas, which makes the molten yarn A less likely to break, and facilitates improving the productivity of the fiber to be drawn.

[0054] The distance between the discharge hole of the spinning nozzle 4 and the position where the gas comes into contact with the raw yarn A discharged from the discharge hole in step (B) is determined by the required properties of the fiber to be drawn and the fiber, but generally a shorter distance is preferable.

[0055] In the step (B), the raw yarn A cooled in the quench section 5 is taken up by the first take-up roll 8, which is the take-up roll. The take-up speed at the first take-up roll 8 is, for example, 150 to 2000 m / min, preferably 200 to 1000 m / min, and more preferably 250 to 750 m / min. When the take-up speed at the first take-up roll 8 is within the preferred range, it becomes easier to further increase the productivity of the fibers to be drawn.

[0056] In the step (B), the raw yarn A cooled in the quenching section 5 may be passed through a windshield tube 6 before being taken up by the first take-up roll 8 . Furthermore, before the raw yarn A is taken up by the first take-up roll 8, a spinning oil may be applied to the raw yarn A cooled in the quenching section 5 by an oiling roll 7. When the raw yarn A cooled in the quench section 5 is passed through a windshield tube 6, the spinning oil may be applied to the raw yarn A that has passed through the windshield tube 6 by the oil roll 7. By applying the spinning oil to the raw yarn A with the oil roll 7, it is possible to prevent the single yarns from fusing together, and also to prevent adjacent single yarns from separating due to static electricity. Examples of the spinning oil include cationic surfactants, anionic surfactants, nonionic surfactants, refined esterified oils, mineral oils, poly(oxyethylene) alkyl ethers, silicone oils, paraffin waxes, etc. These may be used alone or in combination of two or more. From the viewpoint of further suppressing fusion of the single yarns, silicone oil is preferred as the spinning oil. From the viewpoint of further preventing adjacent single yarns from separating due to static electricity, the spinning oil is preferably an anionic surfactant or a nonionic surfactant. As the spinning oil, for example, a spinning oil containing silicone oil and an anionic surfactant (for example, "Polymax FKY" manufactured by Marubishi Chemical Co., Ltd.) can be used.

[0057] In the step (B), the raw yarn A taken up by the first take-up roll 8 is wound around a core 11 by a first winder 10. The core (hereinafter also referred to as "bobbin") may be, for example, a paper tube.

[0058] The temperature of the raw yarn A during the winding is 35 to 75°C, preferably 37 to 73°C, and more preferably 40 to 70°C. The temperature range of 35 to 75°C is within the crystallization temperature range of the poly(3-hydroxyalkanoate) resin of raw yarn A and / or is close to said crystallization temperature. Therefore, by setting the temperature at 35 to 75°C, the degree of crystallization of the poly(3-hydroxyalkanoate) resin of raw yarn A is increased, resulting in a fiber with high strength. In particular, a fiber with high strength can be obtained by setting the temperature at 35°C or higher. This is thought to be because a temperature of 35°C or higher increases the crystallinity of the poly(3-hydroxyalkanoate) resin in the raw yarn A, leaving an appropriate amount of residual stress in the raw yarn A, resulting in a fiber with high strength. Furthermore, a fiber with a low shrinkage rate can be obtained by keeping the temperature at 75°C or less. This is thought to be because, when the temperature is 75°C or less, the crystallization of the poly(3-hydroxyalkanoate) resin in the raw yarn A is not excessively increased, and residual stress is alleviated, resulting in a fiber with a low shrinkage rate.

[0059] The temperature of the raw yarn A during winding means the temperature of the portion of the raw yarn A immediately before winding. The temperature was measured using a thermography camera (for example, thermography camera "E4" manufactured by FLIR Systems).

[0060] The temperature can be adjusted by adjusting the temperature of the first take-up roll 8, adjusting the ambient temperature from after the spinning nozzle discharge to the first take-up roll, or blowing temperature-controlled air onto the raw yarn A from after the spinning nozzle discharge to the first take-up roll. From the viewpoint of facilitating the temperature adjustment, it is preferable to heat the raw yarn A with the first take-up roll 8.

[0061] The tension applied to the raw yarn A during the winding is 0 to 0.30 cN / dtex, preferably 0.00 to 0.25 cN / dtex, more preferably 0.01 to 0.25 cN / dtex, and even more preferably 0.01 to 0.20 cN / dtex. By setting the tension to 0.30 cN / dtex or less, it is possible to obtain fibers with a low shrinkage rate. This is thought to be because, by setting the tension to 0.30 cN / dtex or less, the crystallization of the poly(3-hydroxyalkanoate) resin in the raw yarn A is not excessively increased, and residual stress is alleviated, resulting in fibers with a low shrinkage rate.

[0062] The tension of the raw yarn A during winding refers to the tension of the portion of the raw yarn A immediately before winding. The tension was measured directly at the portion immediately before winding using a wire tension meter (for example, wire tension meter "T-102-02" manufactured by Sodick Corporation).

[0063] In the step (B), in order to adjust the tension, the raw yarn A may be passed through a dancer roll 8 and then taken up by the first take-up roll 8, and then wound around a core 11 by a first winder 10. From the viewpoint of reducing the tension, it is preferable that the raw yarn A taken up by the first take-up roll 8 is wound around the core 11 by the first winder 10 without using a dancer roll. The tension may also be adjusted by adjusting the rotational torque of a roll (such as the first take-up roll 8) on the transport path (hereinafter also referred to as the "pass line") of the raw yarn A from the first take-up roll 8 to the first winder 10. The tension may be adjusted by arranging the rolls so that the pass line is zigzag. From the viewpoint of reducing the tension, it is preferable that the pass line is not zigzag.

[0064] (Process (C)) In the step (C), the raw yarn A wound around the core 11 is left standing for 6 hours or more to obtain a fiber to be drawn. During the standing, the raw yarn A is wound around the core 11, thereby enabling a fiber with a low shrinkage rate to be obtained. It is believed that the raw yarn A being wound around the core 11 makes it easier to maintain the tension applied to the raw yarn A in the step (B) in the step (C), thereby alleviating the residual stress in the raw yarn A, resulting in a fiber with a low shrinkage rate.

[0065] The standing time is 6 hours or more, preferably 6 to 48 hours, and more preferably 6 to 24 hours. By leaving the material for a period of 6 hours or more, it is possible to obtain a fiber with a low shrinkage rate. This is thought to be because by leaving the material for a period of 6 hours or more, there is sufficient time for the residual stress to be relaxed, and the residual stress is relaxed, resulting in the production of a fiber with a low shrinkage rate.

[0066] The raw yarn A may be left standing indoors, but if the room temperature is low, it is preferable to leave it standing in a heat-retaining cabinet. The temperature of the raw yarn A during the standing is preferably 20 to 75°C, more preferably 20 to 73°C, and even more preferably 20 to 70°C. When the temperature is 20°C or higher, fibers with even higher strength can be obtained. By setting the temperature at 75°C or less, it is possible to obtain fibers with an even lower shrinkage rate.

[0067] The temperature was measured using a thermography camera (for example, thermography camera "E4" manufactured by FLIR Systems).

[0068] <Fiber for drawing> The drawing fiber has one or more single yarns, that is, the drawing fiber may be a drawing monofilament or a drawing multifilament. The multifilament for drawing has two or more single yarns, preferably 12 or more, more preferably 30 to 10,000, more preferably 40 to 5,000, and even more preferably 50 to 3,000.

[0069] The fineness of the single yarn in the fiber to be drawn is preferably 2 to 15 dtex, more preferably 3 to 10 dtex, and more preferably 4 to 8 dtex. When the fineness is 2 dtex or more, it is easier to further reduce the shrinkage rate of the fiber. When the fineness is 2 dtex or more, it is easier to slow down the take-up speed of the first take-up roll 8 during spinning, which makes it possible to prevent excessive stress from being applied to the fiber to be drawn and sufficiently relieves residual stress during standing, which is thought to result in further reducing the shrinkage rate of the fiber. By setting the fineness to 15 dtex or less, it becomes easier to further increase the strength of the fiber. By setting the fineness to 15 dtex or less, it becomes easier to increase the take-up speed of the first take-up roll 8 during spinning, and the poly(3-hydroxyalkanoate) resin is appropriately oriented after spinning, which is thought to result in further increasing the strength of the fiber.

[0070] In this embodiment, the fineness of a yarn refers to the thickness of the yarn and is defined as the mass per unit length, expressed in units of dtex (g) per 10,000 m. In this embodiment, the fineness of the single yarn can be determined as follows. First, the fineness (total fineness) of the fiber to be drawn is measured, and the number of single yarns contained in the fiber to be drawn is also determined. Then, the fineness of the single yarn (average fineness of the single yarn) is calculated using the following formula. Single yarn fineness = Fineness of drawing fiber / Number of single yarns in drawing fiber

[0071] <Fiber manufacturing method> The method for producing a fiber according to this embodiment includes a step (D) of drawing the fiber to be drawn obtained by the method for producing a fiber to be drawn at a draw ratio of 1.1 to 2.5 to obtain a fiber. The method for producing a fiber according to this embodiment includes the method for producing a fiber to be drawn.

[0072] (Process (D)) As shown in FIG. 2, in the step (D), the drawing-use fiber B is taken up from the pay-out roll 12 by a second take-up roll 13 . Next, the drawing fiber B taken up by the second take-up roll 13 is drawn by a drawing roll 14 . The fiber to be drawn that has been drawn by the drawing roll 14 is then wound by a second winder 16 to obtain a fiber. In the step (D), the drawing fiber B drawn by the drawing roll 14 may be heated by a heat treatment roll 15 and then wound by the second winder 16 .

[0073] In the step (D), it is preferable that the drawing fiber B is heated by the second take-up roll 13 . By heating the drawing fiber B with the second take-up roll 13, it becomes easier to adjust the temperature of the poly(3-hydroxyalkanoate)-based resin contained in the drawing fiber B so that it is within a temperature range suitable for increasing the orientation of the poly(3-hydroxyalkanoate)-based resin, and as a result, it becomes easier to increase the orientation of the poly(3-hydroxyalkanoate)-based resin. The temperature of the second take-up roll 13 is preferably 15°C or higher and lower than 60°C, more preferably 20 to 55°C. When the temperature of the environment in which the step (D) is carried out is 15° C. or higher, the fibers to be drawn B do not need to be heated by the second take-up roll 13 .

[0074] In the step (D), it is preferable that the drawing fibers B are heated by the drawing rolls 14 . Heating the drawing fiber B with the drawing roll 14 promotes the crystallization of the poly(3-hydroxyalkanoate) resin in the drawing fiber B, and also improves the heat resistance of the poly(3-hydroxyalkanoate) resin. The temperature of the stretching rolls 14 is preferably 30 to 120°C, more preferably 40 to 100°C.

[0075] In the step (D), the drawing fiber B is heated by the heat treatment roll 15, thereby accelerating the crystallization of the poly(3-hydroxyalkanoate) resin in the drawing fiber B and improving the heat resistance of the poly(3-hydroxyalkanoate) resin. The temperature of the heat treatment roll 15 is preferably 30 to 120°C, more preferably 40 to 100°C.

[0076] The stretching ratio in the step (D) is 1.1 to 2.5 times, preferably 1.5 to 2.3 times, and more preferably 1.7 to 2.1 times. By setting the draw ratio in the step (D) to 1.1 times or more, the orientation of the poly(3-hydroxyalkanoate) resin in the fibers B to be drawn becomes even higher. The stretching ratio can be calculated by the following formula. Stretching ratio = Speed ​​of stretching roll (m / min) / Speed ​​of second take-up roll (m / min)

[0077] <Fiber> The average tensile strength of a single yarn in the fiber is preferably 1.0 to 10 cN / dtex, more preferably 1.1 to 10 cN / dtex, and even more preferably 1.3 to 10 cN / dtex.

[0078] The average value of the tensile strength of the single yarn of the fiber can be determined as follows. First, the tensile strength of each of all the single yarns constituting the fiber is measured. Alternatively, 10 or more single yarns are randomly selected from the fiber, and the tensile strength of each single yarn is measured. That is, since it may not be practical to measure the tensile strength of each of all the single yarns constituting the fiber, 10 or more single yarns may be randomly selected from the fiber, and the tensile strength of each single yarn may be measured. Then, the arithmetic mean value of the tensile strength of the single yarn is calculated from the tensile strength of each single yarn, and this value is used as the mean value of the tensile strength of the single yarn in the fiber. When the fiber is a monofilament, the average value of the tensile strength of a single yarn in the fiber means the average value of the tensile strength of the fiber.

[0079] The tensile strength of each single yarn can be measured based on JIS L 1015:2021 "Test method for chemical fiber staples" at an initial length of 20 mm and a speed of 20 mm / min. For example, the tensile strength of each single yarn can be determined as follows. First, the load (cN) at break of each single yarn is measured under the following conditions using a tensile measuring device Autograph AG-I (manufactured by Shimadzu Corporation). Initial length of each single thread: 20mm Tensile speed: 20 mm / min Load cell: A load cell with a rated capacity of 5N The fineness of each single yarn is also measured, which can be measured, for example, by an autobibroscope method. Then, the tensile strength of each single yarn is calculated using the following formula. Tensile strength of each single yarn (cN / dtex) = Breaking load of each single yarn (cN) / Fineness of each single yarn

[0080] The fibers may be used in the form of threads. Furthermore, the fibers may be used to produce a fiber product (fibrous body). The textile product can be in various forms (for example, in the form of a nonwoven fabric). The fibers and the fiber products can be suitably used for conventionally known applications. The fibers and textile products can be suitably used in fields such as agriculture (for example, horticulture), fisheries, forestry, the medical industry, and the food industry. Examples of the textile products include clothing, curtains, carpets, bags, shoes, wiping materials, sanitary products, automobile parts, building materials, and filtering materials (filters).

[0081] It should be noted that the present invention is not limited to the above-described embodiment. Furthermore, the present invention is not limited to the above-described effects. Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention.

[0082] [Disclosure items] Each of the following sections is a disclosure of a preferred embodiment. [Item 1] A method for producing fibers for drawing by a melt spinning method, comprising: a step (A) of discharging a melt obtained by heating a raw material composition containing a poly(3-hydroxyalkanoate) resin through a discharge hole to obtain a raw yarn; A step (B) of taking up the raw yarn with a take-up roll and winding it around a core; and (C) a step of leaving the yarn wound around the core for 6 hours or more, In the step (B), during the winding, the temperature of the raw yarn is 35 to 75°C, and the tension applied to the raw yarn is 0 to 0.30 cN / dtex. [Item 2] 2. The method for producing a fiber to be drawn according to item 1, wherein in the step (C), the temperature of the raw yarn during the standing is 20 to 75°C. [Item 3] The drawing fiber has one or more single yarns, 3. The method for producing a fiber for drawing according to item 1 or 2, wherein the single yarn has a fineness of 2 to 15 dtex. [Item 4] 4. The method for producing a fiber for drawing according to any one of items 1 to 3, wherein the fiber for drawing is a multifilament for drawing having 12 or more single yarns. [Item 5] 5. The method for producing fibers for drawing according to any one of items 1 to 4, wherein the poly(3-hydroxyalkanoate) resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). [Item 6] Item 6. A method for producing a fiber, comprising step (D) of drawing the fiber to be drawn obtained by the method for producing a fiber to be drawn according to any one of items 1 to 5 at a draw ratio of 1.1 to 2.5. [Example]

[0083] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0084] Example 1 (Process (A)) First, the following materials were dry-blended in the following proportions, and the mixture was melt-kneaded at 150° C. in an extruder to obtain a raw material composition in the form of pellets. Poly(3-hydroxyalkanoate) resin (P3HA): Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (3-hydroxybutyrate unit content: 94.0 mol%, 3-hydroxyhexanoate content: 6 mol%, weight average molecular weight (Mw): 582,936) (P3HB3HH): 100 parts by mass Lubricant erucic acid amide (EA): 0.5 parts by mass Lubricant behenamide (BA): 0.5 parts by mass Pentaerythritol (PETL) as a nucleating agent (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., Neuraizer P): 1.0 parts by mass

[0085] The weight average molecular weight of P3HA was measured by the method described above.

[0086] The content ratio of 3-hydroxybutyrate units and the content ratio of 3-hydroxyhexanoate units in P3HA were determined as follows. First, 20 mg of dried P3HA was added with 2 mL of a mixture of sulfuric acid and methanol (volume of sulfuric acid:volume of methanol=15:85) and 2 mL of chloroform to form a sample, which was then sealed. The sample was heated in a sealed state at 100°C for 140 minutes to obtain a first reaction solution containing methyl esters, which are decomposition products of P3HA. The first reaction liquid was then cooled, and 1.5 g of sodium bicarbonate was added little by little to the cooled first reaction liquid to neutralize it, and the mixture was left to stand until the evolution of carbon dioxide gas stopped, thereby obtaining a second reaction liquid. Furthermore, the second reaction solution and 4 mL of diisopropyl ether were mixed well to obtain a mixture. The mixture was then centrifuged to obtain a supernatant. The monomer unit composition of the decomposition product in the supernatant was analyzed by capillary gas chromatography under the conditions below to determine the content of 3-hydroxybutyrate units and 3-hydroxyhexanoate (3HH) units in P3HA. Gas chromatograph: Shimadzu GC-17A Capillary column: NEUTRA BOND-1 manufactured by GL Sciences (column length: 25 m, column inner diameter: 0.25 mm, liquid film thickness: 0.4 μm) Carrier gas: He Column inlet pressure: 100 kPa Sample volume: 1 μL As for the temperature conditions, the temperature was increased at a rate of 8°C / min from 100 to 200°C, and further increased at a rate of 30°C / min from 200 to 290°C.

[0087] The crystallization temperature of the raw material composition was measured in accordance with JIS K7121-1987 "Method for measuring transition temperature of plastics." Specifically, a differential scanning calorimeter (e.g., a differential scanning calorimeter DSC25 manufactured by TA Instruments) was used, and approximately 6.0 mg of the raw material composition as a sample was filled into a measurement container, and the sample was heated and cooled between −30°C and 180°C at a heating and cooling rate of 10°C / min under a nitrogen gas flow rate of 50 ml / min, and the temperature range from the rise to the fall of the exothermic peak during the second cooling was determined as the crystallization temperature. The crystallization temperature of the raw material composition was measured by this method and was found to be 50 to 80°C.

[0088] Then, as shown in FIG. 1, the pellets were melted by heating at an extrusion temperature of 170.0° C. using Extruder 2 (single-screw extruder, screw diameter: 40 mm) to obtain a melt. The melt was then discharged from the discharge hole of the spinning nozzle 4 to obtain a raw yarn A. The flow rate of the composition (melt) discharged from the spinning nozzle was adjusted to 7.0 kg / h by a gear pump 3.

[0089] (Process (B)) In the quenching section 5, the raw yarn A in a molten state was cooled by blowing gas (air) at 20°C onto the raw yarn A at a wind speed of 0.08 m / s by a circular method. The temperature of the first take-up roll 8 was adjusted to 40°C, and the cooled yarn A was taken up by the first take-up roll 8 at a speed of 650 m / min. The yarn A was then wound around a bobbin serving as a core 11 by the first winder 10. When winding by the first winder 10, the load applied to the yarn from the dancer roll 9 was adjusted so that the tension of the portion of the yarn A immediately before winding (also referred to as the "winding tension") was 0.250 cN / dtex. The temperature of the portion of the yarn A immediately before winding (also referred to as the "yarn temperature") was 40°C.

[0090] (Process (C)) The bobbin on which the raw yarn A was wound was left to stand for 6 hours in an environment controlled at 20 to 25°C, thereby obtaining a multifilament for drawing (number of single yarns: 400, average single yarn fineness: 4.5 dtex) as a fiber for drawing.

[0091] (Process (D)) After the step (C), as shown in FIG. 2, the fiber to be drawn was set on a feed roll 12, taken up by a second take-up roll (55 m / min, 30°C), drawn by a drawing roll (110 m / min, 90°C) (draw ratio: 2 times), transported by a heat treatment roll (100 m / min, 90°C), and wound up by a second winder (100 m / min) to obtain a multifilament fiber.

[0092] (Examples 2 to 11, Comparative Examples 1 to 11) Fibers to be drawn and fibers were obtained in the same manner as in Example 1, except that the production conditions for the fibers to be drawn were changed to those shown in Table 1 below. The temperature of the first take-up roll 8 was adjusted to adjust the temperature of the raw yarn. The winding tension was adjusted by adjusting the load on the raw yarn from the dancer roll 9. Furthermore, the fineness of the single yarn of the fiber to be drawn was adjusted by adjusting the take-up speed of the first take-up roll 8.

[0093] (strength) The average values ​​of the tensile strengths of the single yarns of the fibers of the Examples and Comparative Examples (also simply referred to as "strengths") were measured by the method described above.

[0094] (Dry heat shrinkage rate) The dry heat shrinkage of the fibers of the examples and comparative examples was measured as follows. The fibers were cut to a length L1 (300 mm), and the fibers of length L1 were dried in a dryer at 90°C for 30 minutes. Next, the length L2 of the dried fiber was measured with a vernier caliper, and the dry heat shrinkage was calculated using the following formula. Dry heat shrinkage rate (%) = ((L1-L2) / L1)×100(%)

[0095] [Table 1]

[0096] As shown in Table 1, Examples 1 to 7, which are within the scope of the present invention, had high strength and low dry heat shrinkage. In contrast, the dry heat shrinkage was high in Comparative Examples 1 to 3, in which the winding tension was high, in Comparative Examples 7 and 8, in which the raw yarn temperature was high, and in Comparative Examples 9 to 11, in which the standing time was short. It is believed that in Comparative Examples 1 to 3, the winding tension was too strong, which prevented the residual stress in the raw yarn from being relaxed, resulting in a high dry heat shrinkage. It is believed that in Comparative Examples 7 and 8, the raw yarn temperature was too high, which increased the crystallinity of the poly(3-hydroxyalkanoate) resin, which prevented the residual stress in the raw yarn from being relaxed significantly, resulting in a high dry heat shrinkage. It is believed that in Comparative Examples 9 to 11, the standing time was too short, which provided insufficient time for relaxing the residual stress in the raw yarn, which prevented the residual stress in the raw yarn from being relaxed significantly, resulting in a high dry heat shrinkage. Furthermore, the strength was low in Comparative Examples 4 to 6, in which the raw yarn temperature was low. In Comparative Examples 4 to 6, the raw yarn temperature was too low, which reduced the crystallinity of the poly(3-hydroxyalkanoate) resin and excessively relaxed the residual stress in the raw yarn, presumably resulting in low strength.

[0097] Therefore, it can be seen that the present invention can provide a fiber to be drawn for producing a poly(3-hydroxyalkanoate)-based resin-containing fiber having high strength and low shrinkage. [Explanation of symbols]

[0098] A: Raw yarn, B: Fiber for drawing, 1: raw material hopper, 2: extruder, 3: gear pump, 4: spinning nozzle, 4a: discharge hole, 5: quench section, 5a: cooling box, 6: windshield, 7: oil agent roll, 8: first take-up roll, 9: dancer roll, 10: first winder, 11: core, 12: pay-out roll, 13: second take-up roll, 14: stretching roll, 15: heat treatment roll, 16: second winder

Claims

1. A method for producing fibers for drawing by a melt spinning method, comprising: a step (A) of discharging a melt obtained by heating a raw material composition containing a poly(3-hydroxyalkanoate) resin through a discharge hole to obtain a raw yarn; A step (B) of taking up the raw yarn with a take-up roll and winding it around a core; and (C) a step of leaving the yarn wound around the core for 6 hours or more, In the step (B), during the winding, the temperature of the raw yarn is 35 to 75°C, and the tension applied to the raw yarn is 0 to 0.30 cN / dtex.

2. 2. The method for producing a fiber to be drawn according to claim 1, wherein in the step (C), the temperature of the raw yarn during the standing is 20 to 75°C.

3. The drawing fiber has one or more single yarns, 3. The method for producing a fiber for drawing according to claim 1, wherein the fineness of the single yarn is 2 to 15 dtex.

4. 3. The method for producing a fiber for drawing according to claim 1, wherein the fiber for drawing is a multifilament for drawing having 12 or more single yarns.

5. 3. The method for producing fibers for drawing according to claim 1, wherein the poly(3-hydroxyalkanoate)-based resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

6. A method for producing a fiber, comprising a step (D) of drawing the fiber to be drawn obtained by the method for producing a fiber to be drawn according to claim 1 or 2 at a draw ratio of 1.1 to 2.5 times.

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