Filament and method for producing same

Abstract

The present invention provides, for example, a poly(3-hydroxyalkanoate)-based resin-containing filament having excellent processability and flame retardancy. The present invention provides, for example, a method for producing a filament containing a poly(3-hydroxyalkanoate)-based resin, the method comprising: a step (A) of discharging a molten product containing the poly(3-hydroxyalkanoate)-based resin from a discharge hole to obtain a raw yarn; a step (B) of cooling the raw yarn; a step (C) of stretching the cooled raw yarn; and a step (D) of heat-treating the stretched raw yarn at a temperature of 85-130°C. The final stretching ratio is 6.0 times or more, and the stretching ratio in the step (C) is 8 times or more. The present invention also provides a filament that contains a poly(3-hydroxyalkanoate)-based resin and has a thermal shrinkage of less than 15% at 80°C and a thermal shrinkage of 15% or more at 120°C.

Description

Filament and its manufacturing method

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

[0002] A large amount of petroleum-derived plastics is discarded every year, and the resulting lack of landfill sites and environmental pollution are becoming serious issues. In recent years, microplastics have also become a major problem in the marine environment.

[0003] In particular, recent surveys have found large amounts of broken pieces of artificial turf in the form of microplastics in nearby waters, making countermeasures urgently needed. It is thought that artificial turf breaks down when people walk on it, and is washed away by rainwater and reaches the sea.

[0004] Poly(3-hydroxyalkanoate) resins have excellent seawater degradability and are a material that can solve the environmental problems caused by discarded plastics, and Patent Document 1 describes fibers made stretchable by stretching aliphatic polyesters. Also, a known method for producing fibers containing polyhydroxyalkanoic acid is a method for producing biodegradable fibers (Patent Document 2), which involves rapidly cooling a thermoplastic polymer made of polyhydroxyalkanoic acid immediately after extrusion from a melt extruder to below the glass transition point of the polymer, passing the polymer through a water bath with water at a temperature above the glass transition point, followed by stretching, and then heat treatment.

[0005] International Publication No. 2020 / 230807 Japanese Patent Application Laid-Open No. 2002-371431

[0006] Incidentally, when fibers (hereinafter also referred to as "filaments") are subjected to secondary processing (such as when processing filaments into turf yarn for artificial turf), the filaments are sometimes heated (for example, heated to 80°C), but this heating can cause the filaments to thermally shrink, making it impossible to process them into the desired shape. Furthermore, the filaments are sometimes required to have excellent flame retardancy. However, with regard to poly(3-hydroxyalkanoate)-based resin-containing filaments, filaments that are excellent in processability and flame retardancy have not yet been fully investigated.

[0007] Therefore, an object of the present invention is to provide a poly(3-hydroxyalkanoate) resin-containing filament that is excellent in processability and flame retardancy.

[0008] The present invention relates to a method for producing a filament containing a poly(3-hydroxyalkanoate)-based resin, the method comprising: a step (A) of obtaining a raw yarn by discharging a melt containing a poly(3-hydroxyalkanoate)-based resin through a discharge hole; a step (B) of cooling the raw yarn; a step (C) of drawing the cooled raw yarn; and a step (D) of heat-treating the drawn raw yarn at a temperature of 85 to 130°C, wherein the final draw ratio is 6.0 times or more, and the draw ratio in step (C) is 8 times or more. The present invention also relates to a filament containing a poly(3-hydroxyalkanoate)-based resin, the filament having a heat shrinkage rate at 80°C of less than 15% and a heat shrinkage rate at 120°C of 15% or more. The present invention also relates to turf yarn made from the filament. The present invention also relates to an artificial turf structure using the turf yarn.

[0009] According to the present invention, it is possible to provide a poly(3-hydroxyalkanoate) resin-containing filament that is excellent in processability and flame retardancy.

[0010] Schematic diagram of a filament manufacturing device.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] <Filament> The filament according to this embodiment contains a poly(3-hydroxyalkanoate) resin. The filament according to this embodiment has a heat shrinkage rate of less than 15% at 80°C and a heat shrinkage rate of 15% or more at 120°C. In this embodiment, the filament may also be referred to as a fiber.

[0013] (Poly(3-hydroxyalkanoate)-based resin) The poly(3-hydroxyalkanoate)-based resin is a biodegradable aliphatic polyester (preferably a polyester not containing an aromatic ring) and is a resin having at least one or more types of 3-hydroxyalkanoate units (also referred to as "3-hydroxyalkanoic acid units"). In the present application, the poly(3-hydroxyalkanoate)-based resin is also referred to as P3HA.

[0014] The poly(3-hydroxyalkanoate) resin preferably contains a 3-hydroxyalkanoic acid unit represented by the following formula (1): [—CHR—CH ２ —CO—O—] (1) In the formula (1), R is C ｐ H ２ｐ＋１ where p is an integer of 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl. p is preferably an integer of 1 to 10, and more preferably an integer of 1 to 8.

[0015] The poly(3-hydroxyalkanoate) resin preferably contains 3-hydroxybutyrate (hereinafter, sometimes referred to as 3HB) units, and more preferably is a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0016] The other hydroxyalkanoate units may be 3-hydroxyalkanoate units other than 3HB units, or may be hydroxyalkanoate units other than 3-hydroxyalkanoate units (for example, 4-hydroxyalkanoate units). Only one type of other hydroxyalkanoate unit may be included, or two or more types may be included.

[0017] Examples of the poly(3-hydroxyalkanoate) resin include poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH), poly(3-hydroxybutyrate- Examples of the polymerizable monomer include poly(3-hydroxybutyrate) (abbreviation: P3HB4HB), a homopolymer, poly(3-hydroxybutyrate) (abbreviation: P3HB), poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), and poly(3-hydroxybutyrate-co-3-hydroxyundecanoate). The poly(3-hydroxyalkanoate) resin is preferably at least one selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB). In particular, from the viewpoints of productivity and mechanical properties, P3HB3HH or P3HB4HB is preferred, with P3HB3HH being particularly preferred.

[0018] The filaments according to this embodiment preferably contain 3-hydroxybutyrate units and other hydroxyalkanoate units, and the average molar ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units in the filaments is preferably 80 / 20 to 95 / 5 (mol % / mol %), more preferably 85 / 15 to 95 / 5 (mol % / mol %), and even more preferably 85 / 15 to 90 / 10 (mol % / mol %).

[0019] The poly(3-hydroxyalkanoate) resin preferably contains a poly(3-hydroxybutyrate) resin having an average molar ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units of 90 / 10 to 99 / 1 (mol % / mol %). The average molar ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units in the poly(3-hydroxybutyrate) resin is more preferably 91 / 9 to 98 / 2 (mol % / mol %), and even more preferably 92 / 8 to 98 / 2 (mol % / mol %). In addition, when the poly(3-hydroxyalkanoate) resin contains a poly(3-hydroxybutyrate) resin having an average molar ratio of 3-hydroxybutyrate units / other hydroxyalkanoate units of 90 / 10 to 99 / 1 (mol % / mol %), the poly(3-hydroxyalkanoate) resin may further contain a poly(3-hydroxybutyrate) resin outside this average molar ratio range, or may not contain a poly(3-hydroxybutyrate) resin outside this average molar ratio range.

[0020] In this embodiment, the average molar ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units can be determined by the method described in the examples below.

[0021] The filament according to this embodiment is a fiber mainly composed of a poly(3-hydroxyalkanoate) resin. The proportion of the poly(3-hydroxyalkanoate) resin in the total weight of the filament may be 50 to 100% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. It may be 95% by weight or more, 98% by weight or more, or even 100% by weight.

[0022] (Other Resins) The filament according to this embodiment may contain other resins besides poly(3-hydroxyalkanoate)-based resins, as long as the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester-based resins such as polylactic acid-based resins, polybutylene succinate adipate, polybutylene succinate, and polycaprolactone, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0023] The content of the other resin is not particularly limited, but is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, and even more preferably 30 parts by weight or less, relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. It may be 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less. The lower limit of the content of the other resin is not particularly limited, and may be 0 parts by weight or more.

[0024] The filament according to this embodiment may contain additives that can be used together with the poly(3-hydroxyalkanoate) resin, as long as the effects of the invention are not impaired.

[0025] (Nucleating Agent) The filament according to this embodiment preferably further contains the nucleating agent. This further promotes crystallization of the poly(3-hydroxyalkanoate) resin, resulting in improved tensile strength, productivity, and the like. Examples of the nucleating agent include sugar alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, due to their particularly excellent effect of promoting the crystallization of poly(3-hydroxyalkanoate). These agents may be used alone or in combination of two or more.

[0026] The content of the nucleating agent is not particularly limited as long as it can promote the crystallization of the poly(3-hydroxyalkanoate) resin, but the filament according to the present embodiment preferably contains 0.1 to 10 parts by weight, and more preferably 0.5 to 8 parts by weight, of the nucleating agent (particularly pentaerythritol) per 100 parts by weight of the filament containing the poly(3-hydroxyalkanoate) resin. When the content of the nucleating agent is within the above range, the molten state and the degree of crystallization during the production of the filament are appropriately maintained, and the effect of the nucleating agent can be obtained while suppressing deterioration of the physical properties of the filament and bleed-out of the nucleating agent.

[0027] (Lubricant) The filament according to this embodiment preferably further contains the lubricant. This can improve the surface smoothness of the filament. Examples of the lubricant include a compound having an amide bond. The compound having an 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.

[0028] The content of the lubricant (when multiple lubricants are used, the total content) is not particularly limited as long as it can impart lubricity to the filaments, but is preferably 0.01 to 20 parts by weight, more preferably 0.05 to 10 parts by weight, even more preferably 0.5 to 10 parts by weight, even more preferably 0.5 to 5 parts by weight, and particularly preferably 0.7 to 4 parts by weight, relative to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. When the content of the lubricant is within the above range, it is possible to obtain the effect of the lubricant while avoiding bleeding out of the lubricant onto the filament surface.

[0029] (Other Additives) Examples of other additives include stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, inorganic fillers, organic fillers, antistatic agents, etc.

[0030] The filament according to this embodiment has a heat shrinkage rate at 80°C of less than 15%, more preferably 14.0% or less, and even more preferably 13.5% or less. The heat shrinkage rate at 80°C is, for example, 0% or more. The filament according to this embodiment has excellent processability because the heat shrinkage rate at 80°C is less than 15%. That is, the filament according to this embodiment has a heat shrinkage rate at 80°C of less than 15%, so that when the filament is heated (for example, at 80°C) for secondary processing, it is less likely to heat shrink and can be easily processed into a desired shape.

[0031] The filament according to this embodiment has a heat shrinkage rate at 120°C of 15% or more, preferably 15.3% or more, and more preferably 15.5% or more. The heat shrinkage rate at 120°C is, for example, 35% or less. The filament according to this embodiment has a heat shrinkage rate at 120°C of 15% or more, which results in excellent flame retardancy. The filament according to this embodiment has a heat shrinkage rate at 120°C of 15% or more, which is thought to result in excellent flame retardancy, as the filament is more likely to heat shrink when it catches fire.

[0032] The heat shrinkage at 80°C and 120°C can be determined by the following method. First, a filament is cut to 30 cm (fiber length before drying: 30 cm). Then, the filament is left in a hot air dryer (set temperature: 80°C or 120°C) for 10 minutes, and the length of the sample taken out (fiber length after drying) is measured, and the heat shrinkage can be calculated using the following formula: Heat shrinkage (%) = {(fiber length before drying (30 cm) - fiber length after drying (cm)) / fiber length before drying (30 cm)} x 100

[0033] The filament according to the present embodiment may be a monofilament, which is a single thread, or a multifilament having a plurality of single threads, depending on the application, but is preferably a monofilament.

[0034] When the filament according to the present embodiment is a monofilament, the fineness of a single yarn of the filament according to the present embodiment is, for example, 50 to 4,000 dtex, more specifically, 100 to 2,000 dtex. The fineness of a single yarn of the fiber can be determined, depending on the fineness range of the single yarn, by the autobibroscope method using an analytical instrument or by a gravimetric method in which the weight of the fiber over a certain measured length is measured. In the latter case, since 1 dtex = 1 g / 10,000 m, the fineness can be determined using the following formula. The total fineness of a bundle of multiple filaments may be measured and then divided by the number of filaments to calculate the average fineness per single yarn: Fineness (dtex) = (weight (g) of fiber over a certain measured length × 10,000) / measured length (m) of the certain fiber. When the filament according to the present embodiment is a multifilament, the average fineness of a single yarn of the filament according to the present embodiment is, for example, 0.5 to 15 dtex, more specifically, 1.0 to 10 dtex. When the filament is a multifilament, the fineness of each single filament may be measured as described above and the average value calculated, or the total fineness of the filament may be measured and divided by the number of single filaments in the filament to calculate the fineness.

[0035] The toughness of the filament according to this embodiment is preferably 5 (cN / dtex)·% １／２ More preferably, 10 (cN / dtex)·%１／２ More preferably, 12 (cN / dtex)·% １／２ The filament according to this embodiment has a toughness of 5 (cN / dtex)·% １／２ The higher the toughness, the better. １／２ The toughness can be determined from the tensile strength and the elongation at break, and specifically, can be determined by the method described in the examples below.

[0036] The filament according to the present embodiment can be suitably used for marine materials, agricultural materials, civil engineering materials, sports equipment materials, automotive materials, medical materials, etc. Specifically, the filament according to the present embodiment can be used as, for example, fishing lines, fishing nets, aquaculture nets, seaweed seedling threads, turf yarns, toothbrush bristles, beverage extraction filters (woven fabrics for tea bags), insect nets, animal nets, suture threads, surgical nets, stents, prosthetic materials, 3D printing filaments, tennis guts, hook-and-loop fasteners for Velcro, tire cord, printing screens, wigs, hose reinforcements, weft knitted fabrics for clothing, grass-cutting cords (wire materials), screen door nets, woven fabrics, turfline, core filaments of filament-core spun yarns, ribbons, etc.

[0037] The turf yarn according to this embodiment is made of the filament. The artificial turf structure according to this embodiment uses the turf yarn. The artificial turf structure has a base fabric and turf material planted in the base fabric and including the turf yarn. The turf material has a shape that resembles grass blades. The turf material may be cylindrical or flat. The base fabric is formed in a sheet shape. Examples of materials that make up the base fabric include thermoplastic resins, and specific examples include polypropylene and polyethylene. Plain woven fabric is preferably used as the base fabric, but other woven fabrics may also be used.

[0038] <Method for producing filaments> The method for producing filaments according to this embodiment is a method for producing filaments containing a poly(3-hydroxyalkanoate)-based resin. The method for producing filaments according to this embodiment includes the steps of: (A) obtaining a raw yarn by discharging a melt containing a poly(3-hydroxyalkanoate)-based resin from a discharge hole; (B) cooling the raw yarn; (C) drawing the cooled raw yarn; and (D) heat-treating the drawn raw yarn at a temperature of 85 to 130°C. In the method for producing filaments according to this embodiment, the final draw ratio is 6.0 times or more. The draw ratio in step (C) is 8 times or more.

[0039] In the method for producing the filament, the final draw ratio is 6.0 times or more, so that the filament has excellent flame resistance. In addition, the heat treatment temperature in step (D) is 85°C or more, so that the filament has excellent processability.

[0040] Furthermore, the filament manufacturing method can produce filaments containing a poly(3-hydroxyalkanoate) resin, which have a heat shrinkage rate at 80°C of less than 15% and a heat shrinkage rate at 120°C of 15% or more. That is, by setting the final draw ratio to 6.0 times or more, the heat shrinkage rate of the filament at 120°C can be increased. Furthermore, by setting the heat treatment temperature in step (D) to 85°C or more, the heat shrinkage rate of the filament at 80°C can be reduced. The heat shrinkage rate of the filament at 80°C can be reduced by increasing the relaxation rate after drawing, for example. The heat shrinkage rate of the filament at 120°C can be increased by performing two-stage drawing, for example.

[0041] The following describes the manufacturing method using, as an example, a method for manufacturing a monofilament using a filament manufacturing apparatus 1 shown in Fig. 1. In the manufacturing method, a filament is manufactured by a melt spinning method.

[0042] (Step (A)) In the step (A), a melt containing a poly(3-hydroxyalkanoate) resin is discharged from a discharge hole to obtain a raw yarn. As shown in FIG. 1 , in the step (A), first, the materials for the melt are charged into a kneading extruder 2a and kneaded while being heated in the kneading extruder 2a to obtain the melt. The kneading extruder 2a is a screw extruder. The kneading extruder 2a may be a single-screw extruder or a twin-screw extruder.

[0043] The temperature of the kneading extruder 2a (also referred to as "extrusion temperature") is preferably 150 to 180°C, more preferably 160 to 170°C.

[0044] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the material is preferably 200,000 to 1,400,000, more preferably 250,000 to 1,200,000, and even more preferably 300,000 to 1,000,000. Having a weight-average molecular weight of 200,000 or more facilitates the formation of filaments with high crystallinity and excellent toughness. Having a weight-average molecular weight of 1,400,000 or less further improves processability, making it easier to produce filaments. In this embodiment, the weight-average molecular weight can be determined by the method described in the examples below.

[0045] Then, using a spinning nozzle 2b having an outlet hole, the melt obtained in the kneading extruder 2a is discharged from the outlet hole to obtain a molten raw yarn A. The spinning nozzle 2b has one or more outlet holes, and may have multiple outlet holes. By having the spinning nozzle 2b have multiple outlet holes, multiple filaments can be produced simultaneously. Regarding the size of the outlet hole, for example, when the outlet hole has a circular shape, the diameter of the outlet hole is preferably 0.5 mm to 20 mm, more preferably 1.0 mm to 10 mm.

[0046] (Step (B)) In the step (B), the raw yarn A is cooled. This makes it possible to prevent the raw yarn A from coming into contact with the take-up roll 4 (the take-up roll used in the step (C) described later) in a softened state and sticking to the take-up roll 4.

[0047] In step (B), it is preferable to cool the yarn A in a liquid 3a at 60°C or lower. The temperature of the liquid 3a is preferably 60°C or lower, more preferably -10 to 50°C, -5 to 40°C, and even more preferably -2 to 30°C. By keeping the temperature of the liquid 3a at 60°C or lower, the time during which the poly(3-hydroxyalkanoate) resin constituting the yarn A is within the crystallization temperature range can be shortened, and the progress of crystallization of the poly(3-hydroxyalkanoate) resin can be suppressed. This prevents the yarn A from becoming hard. This makes it easier to draw the yarn A in step (C). As a result, the strength of the filament can be easily increased. By keeping the temperature of the liquid 3a at -10°C or higher, the time during which the poly(3-hydroxyalkanoate) resin constituting the yarn A is within the crystallization temperature range can be secured to a certain extent, thereby preventing the yarn A from coming into contact with a roll or the like and becoming stuck before it is fully crystallized.

[0048] In step (B), the cooling time in the liquid is preferably 10 to 20 seconds, more preferably 12 to 18 seconds. By setting the cooling time to 10 seconds or longer, it is possible to ensure that the poly(3-hydroxyalkanoate) resin constituting the raw yarn A is kept in the temperature range for a sufficient period of time to reach the optimum crystallinity for drawing, depending on the resin composition, and to maintain the crystallization of the poly(3-hydroxyalkanoate) resin in an optimum state. This prevents the raw yarn A from becoming too hard or remaining in a fused state. This makes it easier to draw the raw yarn A in step (C). As a result, it becomes easier to increase the strength of the filament. By setting the cooling time to 20 seconds or shorter, it is possible to prevent excessive solidification or fusion due to excessive residence time in the temperature range, and to shorten the filament production time.

[0049] The filament manufacturing apparatus 1 includes a tank 3b that contains the liquid 3a, and a tank roll 3c that transports the raw yarn A so that the raw yarn A passes through the liquid 3a. Examples of the liquid include water, ethylene glycol, and propylene glycol.

[0050] (Step (C)) In the step (C), the cooled raw yarn A is drawn. By drawing the cooled raw yarn A, the orientation of the poly(3-hydroxyalkanoate) resin constituting the raw yarn A can be increased, and as a result, the strength of the filament can be increased.

[0051] In the step (C), it is preferable that the raw yarn A is taken up by a take-up roll 4 and stretched by a stretching roll 6 .

[0052] The draw ratio in step (C) is 8 times or more, preferably 8.0 times or more, more preferably 8.2 times or more, and even more preferably 8.4 times or more. A draw ratio of 8 times or more makes it easier to further improve the flame retardancy of the filament. Furthermore, a draw ratio of 8 times or more can improve the orientation of the poly(3-hydroxyalkanoate) resin constituting raw yarn A, thereby increasing the strength of the filament. The draw ratio in step (C) is 13.0 times or less.

[0053] In an embodiment using the take-up roll 4 and the drawing roll 6, the draw ratio can be calculated by the following formula: Draw ratio = Speed ​​of drawing roll 6 (m / min) / Speed ​​of take-up roll 4 (m / min) The speed of the drawing roll (m / min) is the length per unit time of the raw yarn transported by the drawing roll. When drawing is performed using two or more drawing rolls in step (C) (when drawing is performed using multiple drawing rolls), the fastest speed is taken as the speed of the drawing roll (m / min). The speed of the take-up roll (m / min) is the length per unit time of the raw yarn taken up by the take-up roll.

[0054] In this embodiment, the yarn A may be drawn in step (C) without using both the take-up roll 4 and the drawing roll 6, or without using one of the take-up roll 4 and the drawing roll 6 and using the other. For example, the yarn A can be drawn by fixing both ends of the undrawn yarn with tenter clips in a drawing temperature atmosphere and increasing the distance between the clips (stretching the yarn A between the tenter clips). When tenter clips are used, the draw ratio in step (C) can be calculated by the following formula: Draw ratio in step (C) = Distance between tenter clips after stretching in step (C) / Distance between tenter clips before stretching

[0055] From the viewpoint of facilitating an increase in the strength of the filament, it is preferable to heat and draw the cooled yarn A in step (C). Here, in order to increase the orientation of the poly(3-hydroxyalkanoate)-based resin, it is desirable to draw the yarn A in a temperature range suitable for increasing the orientation of the poly(3-hydroxyalkanoate)-based resin. If the yarn A is drawn at a temperature higher than this temperature range, the poly(3-hydroxyalkanoate)-based resin will be in a molten state, and as a result, the orientation of the poly(3-hydroxyalkanoate)-based resin will not be very high even after drawing. Furthermore, if an attempt is made to draw the yarn A at a temperature lower than this temperature range, the yarn A will become too solid, making it difficult to draw. Furthermore, if the yarn A is forcibly pulled in an attempt to draw it, the yarn A will break, making it impossible to produce a filament. In the present embodiment, by heating and drawing the cooled yarn A, it becomes easier to adjust the temperature of the yarn A so that it falls within a temperature range suitable for increasing the orientation of the poly(3-hydroxyalkanoate) resin when drawing the yarn A, compared to a mode in which the yarn A is drawn while being cooled by ambient air, and as a result, it becomes easier to increase the orientation of the poly(3-hydroxyalkanoate) resin in the yarn A. As a result, it becomes easier to increase the strength of the filament.

[0056] In the step (C), it is preferable to heat the raw yarn A in a hot water bath 5. The temperature of the hot water in the hot water bath 5 is preferably 25°C or higher and lower than 85°C, more preferably 30 to 70°C. In the step (C), it is preferable not to heat-treat the raw yarn, or, if the raw yarn is heat-treated, to heat-treat it at a temperature lower than 85°C. Heat treatment at 85°C or higher is not preferable because rapid crystallization may prevent drawing and cause breakage, or a large amount of undrawn portions may remain after drawing, resulting in uneven fineness.

[0057] (Step (D)) In the step (D), the drawn yarn A is heat-treated at a temperature of 85 to 130°C. In the step (D), the yarn A may be heat-treated using a heated gas (for example, heated air, steam, etc.) or a heated roll. When a heated gas is used, the yarn A may be heat-treated in an oven 7 as shown in FIG. 1. In the step (D), it is preferable to heat-treat the yarn A using a heated gas from the viewpoint of maintaining a uniform heat treatment temperature, but it is also possible to use vapor (steam) from the viewpoint of production costs.

[0058] The heat treatment temperature in step (D) is 85 to 130°C, preferably 90 to 127°C, more preferably 95 to 125°C, more preferably 100 to 125°C, more preferably 105 to 125°C, and even more preferably 110 to 125°C. By using a heat treatment temperature of 85°C or higher, the heat shrinkage of the filament at 80°C can be easily reduced, resulting in excellent processability of the filament. It is believed that the heat shrinkage of the filament is due to the generation of crystals by heat. Furthermore, when the filament obtained by heat-treating the raw yarn is further heated, new crystals are generally generated at a temperature approximately 10°C higher than the heat treatment temperature of the raw yarn. By using a heat treatment temperature of 85°C or higher, further crystals are less likely to be generated even when the filament is heated to 80°C, resulting in the filament being more likely to have heat resistance capable of withstanding shrinkage and melting due to heating. This is also believed to result in a reduced heat shrinkage of the filament at 80°C. By setting the heat treatment temperature at 130° C. or less, the raw yarn is less likely to break, and as a result, filaments can be more easily obtained. This is thought to be because raw yarn A is maintained at a temperature lower than the melting point and at a temperature that is somewhat different from a temperature near the melting point, thereby performing a sufficient heat treatment while avoiding a temperature range where rapid softening or melting occurs.

[0059] In step (D), the heat treatment time is preferably 1 to 10 seconds, more preferably 2 to 9 seconds. By setting the heat treatment time to 1 second or more, the heat shrinkage rate of the filament at 80°C can be further reduced, resulting in the filament having better processability. By setting the heat treatment time to 10 seconds or less, the filament production time can be shortened.

[0060] In the method for producing a filament according to this embodiment, it is preferable to obtain a filament by winding the raw yarn A heat-treated in step (D) on a winding roll 9. In the method for producing a filament according to this embodiment, the raw yarn A heat-treated in step (D) may be transported to the winding roll 9 by a transport roll 8.

[0061] In the method for producing a filament according to this embodiment, the final draw ratio is 6.0 times or more, preferably 6.2 times or more, and more preferably 6.4 times or more. By setting the final draw ratio to 6.0 times or more, the filament has excellent flame retardancy. Furthermore, the heat shrinkage rate of the filament at 120°C can be reduced.

[0062] In an embodiment using the take-up roll 4 and the winding roll 9, the final draw ratio can be calculated by the following formula: Final draw ratio = Speed ​​of take-up roll 9 (m / min) / Speed ​​of take-up roll 4 (m / min) The speed of the winding roll (m / min) is the length of the raw yarn wound by the winding roll per unit time. Also, the speed of the take-up roll (m / min) is the length of the raw yarn taken up by the take-up roll per unit time.

[0063] In this embodiment, the filament may be produced without using both the take-up roll 4 and the winding roll 9, or without using one of the take-up roll 4 and the winding roll 9 and using the other. When neither the take-up roll 4 nor the winding roll 9 is used, or when neither the take-up roll 4 nor the winding roll 9 is used and the other is used, it is also possible to apply the drawing method using the tenter clips described above, and the final draw ratio can be calculated by the following formula: Final draw ratio = distance between tenter clips after stretching to just before the tenter clips are removed from the raw yarn / distance between tenter clips before stretching

[0064] Furthermore, in the filament manufacturing method according to this embodiment, the relaxation rate is preferably 25% or less, more preferably -10 to 24%, even more preferably 0 to 23%, even more preferably 5 to 23%, even more preferably 7 to 23%, and even more preferably 10 to 23%. A relaxation rate of 25% or less can further enhance the flame retardancy of the filament. It also facilitates enhancing the heat shrinkability of the filament at 120°C. Furthermore, a relaxation rate of -10% or more can facilitate preventing breakage of the raw yarn.

[0065] The relaxation rate can be calculated by the following formula: Relaxation rate = (length of raw yarn just before step (D) - length of filament) / length of raw yarn just before step (D) When the stretching roll 6 and the take-up roll 9 are used, the relaxation rate can be calculated by the following formula: Relaxation rate = (speed of stretching roll 6 (m / min) - speed of take-up roll 9 (m / min)) / speed of stretching roll 6 (m / min)

[0066] 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.

[0067] Disclosure Items Each of the following items is a disclosure of a preferred embodiment.

[0068] [Item 1] A method for producing a filament containing a poly(3-hydroxyalkanoate) resin, comprising: step (A) of obtaining a raw yarn by discharging a melt containing a poly(3-hydroxyalkanoate) resin from a discharge hole; step (B) of cooling the raw yarn; step (C) of drawing the cooled raw yarn; and step (D) of heat-treating the drawn raw yarn at a temperature of 85 to 130°C, wherein the final draw ratio is 6.0 times or more, and the draw ratio in step (C) is 8 times or more. [Item 2] The method for producing a filament according to item 1, wherein the heat treatment time in step (D) is 1 to 10 seconds. [Item 3] The method for producing a filament according to item 1 or 2, wherein the relaxation rate is 25% or less. [Item 4] The method for producing a filament according to any one of items 1 to 3, wherein in step (B), the raw yarn is cooled in a liquid at 60°C or less. [Item 5] The method for producing a filament according to Item 4, wherein in step (B), the cooling time in the liquid is 10 to 20 seconds. [Item 6] A filament comprising a poly(3-hydroxyalkanoate)-based resin, wherein the heat shrinkage at 80°C is less than 15% and the heat shrinkage at 120°C is 15% or more. [Item 7] The filament according to Item 6, wherein the filament comprising the poly(3-hydroxyalkanoate)-based resin comprises 3-hydroxybutyrate units and other hydroxyalkanoate units, and the average molar ratio of 3-hydroxybutyrate units / other hydroxyalkanoate units in the filament comprising the poly(3-hydroxyalkanoate)-based resin is 80 / 20 to 95 / 5 (mol % / mol %). [Item 8] The filament according to item 6 or 7, wherein the poly(3-hydroxyalkanoate)-based resin is at least one selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).[Item 9] The filament according to item 8, wherein the poly(3-hydroxyalkanoate)-based resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). [Item 10] The filament according to any one of items 6 to 9, wherein the filament contains 0.1 to 10 parts by weight of pentaerythritol per 100 parts by weight of the filament containing the poly(3-hydroxyalkanoate) resin. [Item 11] The filament according to any one of items 6 to 10, wherein the poly(3-hydroxyalkanoate)-based resin contains a poly(3-hydroxybutyrate)-based resin having an average molar ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units of 90 / 10 to 99 / 1 (mol % / mol %). [Item 12] Turf yarn comprising the filament according to any one of items 6 to 11. [Item 13] An artificial turf structure using the turf yarn of item 12.

[0069] 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.

[0070] The substances and measurement methods used in the examples and comparative examples are shown below.

[0071] <Poly(3-hydroxyalkanoate)-based resin (P3HA)> The following resin was used as the poly(3-hydroxyalkanoate)-based resin (P3HA): P3HB3HH (A-1): P3HB3HH (average molar ratio of 3HB / 3HH content = 97.2 / 2.8 (mol % / mol %), weight average molecular weight = 660,000 g / mol) The P3HB3HH (A-1) was produced in accordance with the method described in Example 2 of WO 2019 / 142845. - P3HB3HH (A-2): P3HB3HH (average molar ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight average molecular weight = 660,000 g / mol) The P3HB3HH (A-2) was produced in accordance with the method described in Example 9 of WO 2019 / 142845. - P3HB3HH (A-3): P3HB3HH (average molar ratio 3HB / 3HH = 94.0 / 6.0 (mol% / mol%), weight average molecular weight = 660,000 g / mol) The P3HB3HH (A-3) was produced in accordance with the method described in Example 1 of WO 2019 / 142845. P3HB3HH (B-1): P3HB3HH (average molar ratio 3HB / 3HH = 94.0 / 6.0 (mol% / mol%), weight average molecular weight = 900,000 g / mol) The P3HB3HH (B-1) was produced in accordance with the method described in Example 1 of WO 2019 / 142845. P3HB3HH (B-2): P3HB3HH (average molar ratio 3HB / 3HH = 89.0 / 11.0 (mol% / mol%), weight average molecular weight = 900,000 g / mol) The P3HB3HH (B-2) was produced in accordance with the method described in Example 5 of WO 2019 / 142845. P3HB3HH (C-1): P3HB3HH (average molar ratio of 3HB / 3HH = 94.0 / 6.0 (mol% / mol%), weight average molecular weight = 400,000 g / mol) The P3HB3HH (C-1) was produced in accordance with the method described in Example 1 of WO 2019 / 142845.

[0072] <Monomer Composition Ratio of P3HA> The monomer composition ratio of P3HB3HH, a P3HA having a 3-hydroxyhexanoate unit, was determined as follows. Approximately 20 mg of P3HA was added to 1 mL of a sulfuric acid-methanol mixture (15:85) and 1 mL of chloroform, sealed, and heated at 100°C for 140 minutes to obtain the methyl ester of the P3HB3HH decomposition product. After cooling, 0.5 mL of deionized water was added and mixed thoroughly, and the mixture was allowed to stand until the aqueous and organic layers separated. The monomer unit composition of the P3HA decomposition product in the separated organic layer was then analyzed by capillary gas chromatography. The average molar ratio of 3-hydroxybutyrate (3HB) to other hydroxyalkanoate units (3-hydroxyhexanoate (3HH) in the Examples and Comparative Examples) was calculated from the obtained peak areas.

[0073] <Weight-average molecular weight of P3HA> The weight-average molecular weight of P3HA was measured by first dissolving the resin to be measured in chloroform and heating it in a hot water bath at 60°C for 0.5 hours, filtering the soluble matter through a disposable PTFE filter with a 0.45 μm pore size, and then using the filtrate to perform GPC measurement under the following conditions to determine the weight-average molecular weight. GPC measurement device: High-performance liquid chromatograph 20A system manufactured by Shimadzu Corporation Column: K-G 4A (1 column), K-806M (2 columns) manufactured by Showa Denko K.K. Sample concentration: 1 mg / ml Free liquid: chloroform solution Free liquid flow rate: 1.0 ml / min Sample injection amount: 100 μL Analysis time: 30 minutes Standard sample: standard polystyrene

[0074] <Crystallization Temperature of Resin Composition> The crystallization temperature of the resin composition was measured using a differential scanning calorimeter (DSC2500) manufactured by TA Instruments. That is, approximately 4 to 10 mg of the resin composition obtained in each Example or Comparative Example was weighed, and the resin composition was heated from 30°C to 180°C at a heating rate of 10°C / min under a nitrogen stream to melt the resin composition, and then held for 1 minute. After that, the resin composition was cooled from 180°C to 0°C at a heating rate of 10°C / min. The peak top of the crystallization exotherm graph was taken as the crystallization temperature. The measured values ​​are shown in Table 1 below.

[0075] <Additives> The following substances were used as additives. Additive 1: Pentaerythritol (Neuraizer P, manufactured by Mitsubishi Chemical Corporation) Additive 2: Behenic acid amide (BNT-22H, manufactured by Nippon Fine Chemicals Co., Ltd.) Additive 3: Erucic acid amide (Neutron S, manufactured by Nippon Fine Chemicals Co., Ltd.)

[0076] <Fineness of Single Fiber Yarn> The fineness of a single fiber yarn was measured by an autobibroscopic method. The fineness of a single fiber yarn (also simply referred to as "fineness") is shown in Table 2 below. Table 2 below shows the average fineness of a single fiber yarn of five monofilaments.

[0077] <Tensile Strength and Breaking Elongation of Fiber Single Yarn> The tensile strength and breaking elongation of fiber single yarn were measured at an initial length of 20 mm and a speed of 20 mm / min in accordance with JIS L 1015:2021 "Testing Methods for Chemical Fiber Staples." The tensile strength of the single yarn was specifically determined as follows. First, using a tensile measuring device Autograph AG-I (manufactured by Shimadzu Corporation), the load (cN) at the time of breaking of the single yarn was measured under the following conditions: Initial length of each single fiber: 20 mm Pulling speed: 20 mm / min Load cell: Load cell with a rated capacity of 5 N Then, using the fineness of the single yarn measured by the autobibroscope method, the tensile strength of each single yarn was determined according to the following formula. Tensile strength of single yarn (cN / dtex) = Load at break of single yarn (cN) / Fineness of single yarn The fineness of single yarn (also simply referred to as "fineness") and the tensile strength of single yarn (also simply referred to as "tensile fineness") are shown in Table 2 below.

[0078] <Toughness> The toughness (tenacity) of a single fiber yarn was calculated using the following formula in accordance with the description of JP 2019-136348 A: Toughness = Tensile strength (unit: N / dtex) × (Elongation at break (unit: %)) １／２ The toughness is shown in Table 2 below.

[0079] <Heat shrinkage rate> The heat shrinkage rate of the fiber was determined by cutting five monofilaments to 30 cm, bundling and tying both ends, and leaving them in a hot air dryer set to 80°C and 120°C for 10 minutes, respectively, measuring the length of the removed sample, and calculating the heat shrinkage rate using the following formula. The final heat shrinkage rate was calculated using the average value (5 samples x 3) of n = 3 measurements at both 80°C and 120°C. Heat shrinkage rate (%) = {(fiber length before drying (30 cm) - fiber length after drying (cm)) / fiber length before drying (30 cm)} x 100 The heat shrinkage rates at 80°C and 120°C are shown in Table 2 below.

[0080] <Limiting oxygen index (LOI)> The limiting oxygen index of a fiber was measured according to JIS L 1019 (E-1). Fibers with a measured LOI value of 26.0 or more were judged to have flame retardancy: ◯, and fibers with a measured LOI value of less than 26.0 were judged to have flame retardancy: ×. The LOI values ​​and the judgments are shown in Table 2 below.

[0081] Example 1 Preparation of Pellet-Form Poly(3-hydroxyalkanoate)-Based Fiber Resin Composition A resin mixture was obtained by blending 100% by weight (content of all P3HA components) of P3HB3HH (A-3), 1.0 part by weight (content relative to 100 parts by weight of all P3HA components), 0.5 part by weight (content relative to 100 parts by weight of all P3HA components) of Additive 1, and 0.5 part by weight (content relative to 100 parts by weight of all P3HA components) of Additive 2. The resin mixture was fed into a 40 mm diameter co-rotating twin-screw extruder with the cylinder and extrusion nozzle temperatures set to 150°C, and strands were discharged from the extruder. The strands were passed through a water bath filled with 40°C warm water to solidify them, and then cut with a pelletizer to obtain pellet-form poly(3-hydroxyalkanoate)-based fiber resin composition. In Example 1, the average molar ratio of 3HB / 3HH contained in the resin composition was 94.0 / 6.0 (mol % / mol %).

[0082] [Production of Monofilament Fibers] In step (A), the pelletized poly(3-hydroxyalkanoate)-based fiber resin composition was introduced into a single-screw extruder (screw diameter: 30 mm) with the cylinder and spinning nozzle temperatures set to 165°C, and melted to obtain a molten material. The molten material was then extruded from a spinning nozzle having five circular nozzle holes with a diameter of 1.5 mm to obtain five original yarns. In step (B), the original yarns were cooled by passing them through a water bath at 2.0°C. The residence time in the water bath was 14.9 seconds. In step (C), the cooled original yarns were taken up with a take-up roll (speed: 5.0 m / min), and subsequently passed through a 3-m-long hot water bath filled with hot water at 60°C, and the original yarns were drawn with a drawing roll (speed: 42.5 m / min). In step (D), the raw yarn was heat-treated at a heat treatment oven temperature of 120.0°C with a residence time of 4.2 seconds. The heat-treated raw yarn was then wound on a take-up roll (speed: 42.5 m / min, relaxation rate: 0%) at a final draw ratio of 8.5 to obtain five monofilament fibers. The fineness was 315.0 dtex, the tensile strength was 2.65 cN / dtex, the elongation at break was 74.0%, and the toughness was 23.4 (cN / dtex)%. １／２ The heat shrinkage was 10.1% (80°C x 10 min) and 25.8% (120°C x 10 min), and the LOI value was 26.5.

[0083] Example 2 A pellet-shaped poly(3-hydroxyalkanoate)-based fiber resin composition was obtained in the same manner as in Example 1, except that a P3HA blend containing 90% by weight (content of all P3HA components) of P3HB3HH (A-3) and 10% by weight (content of all P3HA components) of P3HB3HH (B-1) was used. The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol% / mol%). Furthermore, a monofilament fiber was produced in the same manner as in Example 1, except that in step (C), the drawing roll (speed: 45.0 m / min) was set, and the final draw ratio on the take-up roll (speed: 45.0 m / min, relaxation rate: 0%) was set to 9.0 times. Fineness: 332.0 dtex, tensile strength: 2.91 cN / dtex, elongation at break: 171.0%, toughness: 36.9 (cN / dtex)% １／２The heat shrinkage was 13.3% (80°C x 10 min) and 29.6% (120°C x 10 min), and the LOI value was 27.0.

[0084] Example 3 A pellet-shaped poly(3-hydroxyalkanoate)-based fiber resin composition was obtained in the same manner as in Example 2, except that a P3HA blend containing 90% by weight (content of all P3HA components) of P3HB3HH (A-3) and 10% by weight (content of all P3HA components) of P3HB3HH (B-2) was used. The average molar ratio of 3HB / 3HH in the resin composition was 93.5 / 6.5 (mol% / mol%). Monofilaments were produced as fibers using the same procedures as in Example 2 for steps (A), (B), and (C). The fineness was 326.0 dtex, the tensile strength was 2.91 cN / dtex, the elongation at break was 107.0%, and the toughness was 31.3 (cN / dtex)%. １／２ The heat shrinkage was 11.4% (80°C x 10 min), 28.7% (120°C x 10 min), and the LOI value was 27.0.

[0085] Example 4 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained in the same manner as in Example 1. The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol% / mol%). Five monofilament fibers were obtained under the same conditions as in Example 1, except that in step (B), the raw yarn was passed through a 45.0°C water bath to cool it, with a residence time in the water bath of 12.5 seconds; in step (C), the cooled raw yarn was taken up with a take-up roll (speed: 6.0 m / min), and then passed through a water bath filled with 45°C warm water and drawn with a drawing roll (speed: 51.0 m / min); and in step (D), the residence time in the heat treatment oven was set to 3.5 seconds, and the final draw ratio on the take-up roll (speed: 51.0 m / min, relaxation rate: 0%) was set to 8.5 times. Fineness: 320.0 dtex, tensile strength: 2.10 cN / dtex, elongation at break: 120.0%, toughness: 23.0 (cN / dtex) / % １／２ The heat shrinkage was 5.6% (80°C x 10 min) and 18.9% (120°C x 10 min), and the LOI value was 26.5.

[0086] Example 5 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained in the same manner as in Example 2, except that pentaerythritol, the additive 1, was not used. The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol% / mol%). Five monofilament fibers were obtained in the same manner as in Example 4, except that in step (C), the raw yarn was drawn using a drawing roll (speed: 54.0 m / min), and in step (D), the heat treatment oven residence time was set to 3.3 seconds and the final draw ratio was set to 9.0 times using the subsequent take-up roll (speed: 54.0 m / min, relaxation rate: 0%). The fineness was 300.0 dtex, the tensile strength was 2.30 cN / dtex, the breaking elongation was 180.0%, and the toughness was 30.8 (cN / dtex)%. １／２ The heat shrinkage was 10.2% (80°C x 10 min) and 24.8% (120°C x 10 min), and the LOI value was 26.5.

[0087] Example 6 A poly(3-hydroxyalkanoate)-based resin composition for fibers was obtained in the same manner as in Example 1, except that a P3HA blend containing 35 wt% of P3HB3HH (A-1), 35 wt% of P3HB3HH (A-2), 20 wt% of P3HB3HH (A-3), and 10 wt% of P3HB3HH (B-2) was used. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 1, except that in step (A), the temperatures of the cylinder and the spinning nozzle were set to 162°C; in step (B), the raw yarn was passed through a water bath at 45.0°C to cool it, with a residence time in the water bath of 18.6 seconds; in step (C), the cooled raw yarn was taken up with a take-up roll (speed: 4.0 m / min), and then passed through a hot water bath at 60°C and stretched with a stretching roll (speed: 34.0 m / min); in step (D), heat treatment was performed under conditions of a heat treatment oven temperature of 120.0°C and a residence time of 5.3 seconds, and the final stretch ratio on the subsequent take-up roll (speed: 34.0 m / min, relaxation rate: 0%) was set to 8.5 times. Fineness: 785.0 dtex, tensile strength: 1.21 cN / dtex, elongation at break: 317.0%, toughness: 21.5 (cN / dtex)% １／２The heat shrinkage was 4.6% (80°C x 10 min) and 22.2% (120°C x 10 min), and the LOI value was 27.5.

[0088] Example 7 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 6. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 5, except that in step (D), the heat treatment was performed under conditions of a residence time in the heat treatment oven of 5.7 seconds and the final draw ratio on the take-up roll (speed: 31.6 m / min, relaxation rate: 7%) was set to 7.9 times. The fineness was 824.0 dtex, the tensile strength was 1.15 cN / dtex, the elongation at break was 310.0%, and the toughness was 20.2 (cN / dtex)·%. １／２ The heat shrinkage was 4.1% (80°C x 10 min), 16.0% (120°C x 10 min), and the LOI value was 27.0.

[0089] Example 8 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 6. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). In step (D), the heat treatment was performed under conditions of a residence time in the heat treatment oven of 6.8 seconds, and the final draw ratio on the take-up roll (speed: 26.5 m / min, relaxation rate: 22.0%) was set to 6.6 times. Five monofilament fibers were obtained using the same method as in Example 5. The fineness was 893.0 dtex, the tensile strength was 1.12 cN / dtex, the elongation at break was 335.0%, and the toughness was 20.5 (cN / dtex)·%. １／２ The heat shrinkage was 1.7% (80°C x 10 min) and 15.7% (120°C x 10 min), and the LOI value was 26.5.

[0090] (Example 9) A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 7. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 7, except that in step (D), the heat treatment was performed at a heat treatment oven temperature of 110.0°C. The fineness was 1025.0 dtex, the tensile strength was 1.16 cN / dtex, the elongation at break was 268.0%, and the toughness was 19.0 (cN / dtex)·%. １／２ The heat shrinkage was 5.4% (80°C x 10 min) and 19.2% (120°C x 10 min), and the LOI value was 27.0.

[0091] (Example 10) A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 7. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 7, except that in step (D), the heat treatment was performed at a heat treatment oven temperature of 100.0°C. The fineness was 1053.0 dtex, the tensile strength was 1.13 cN / dtex, the elongation at break was 377.0%, and the toughness was 21.9 (cN / dtex)·%. １／２ The heat shrinkage was 8.4% (80°C x 10 min), 26.6% (120°C x 10 min), and the LOI value was 27.5.

[0092] Example 11 A poly(3-hydroxyalkanoate)-based resin composition for fibers was obtained in the same manner as in Example 1, except that a P3HA blend containing 30 wt% of P3HB3HH (A-1), 30 wt% of P3HB3HH (A-2), 30 wt% of P3HB3HH (C-1), and 10 wt% of P3HB3HH (B-2) was used. The average molar ratio of 3HB / 3HH in the resin composition was 88.3 / 11.7 (mol% / mol%). Five monofilament fibers were obtained in the same manner as in Example 6, except that in step (A), the temperatures of the cylinder and the spinning nozzle were set to 165°C; in step (B), the raw yarn was passed through a water bath at 6.0°C to cool it, with a residence time in the water bath of 14.9 seconds; in step (C), the cooled raw yarn was taken up with a take-up roll (speed: 4.0 m / min) and then passed through a hot water bath at 60°C and drawn with a drawing roll (speed: 36.0 m / min); and in step (D), the raw yarn was heat-treated under conditions of a residence time in a heat treatment oven of 5.0 seconds, and the final draw ratio at the subsequent take-up roll (speed: 36.0 m / min, relaxation rate: 0%) was set to 9.0 times. Fineness: 1030.0 dtex, tensile strength: 1.43 cN / dtex, elongation at break: 108.0%, toughness: 14.9 (cN / dtex)% １／２ The heat shrinkage was 8.3% (80°C x 10 min) and 24.7% (120°C x 10 min), and the LOI value was 27.5.

[0093] Comparative Example 1 A poly(3-hydroxyalkanoate)-based fiber resin composition was prepared using the same method as in Example 6. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 6, except that in step (D), the heat treatment was performed under conditions of a residence time in the heat treatment oven of 8.5 seconds and the final draw ratio on the take-up roll (speed: 21.8 m / min, relaxation rate: 36.0%) was set to 5.4 times. The fineness was 958.0 dtex, the tensile strength was 1.06 cN / dtex, the elongation at break was 360.0%, and the toughness was 20.1 (cN / dtex)·%. １／２ The heat shrinkage was 1.4% (80°C x 10 min), 10.2% (120°C x 10 min), and the LOI value was 25.0.

[0094] Comparative Example 2 A poly(3-hydroxyalkanoate)-based fiber resin composition was prepared using the same method as in Example 6. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 6, except that in step (D), the heat treatment was performed under conditions of a residence time in the heat treatment oven of 9.3 seconds and the final draw ratio on the relaxation roll (speed: 19.4 m / min, relaxation rate: 47.0%) was set to 4.5 times. The fineness was 1026.0 dtex, the tensile strength was 1.01 cN / dtex, the elongation at break was 397.0%, and the toughness was 20.1 (cN / dtex)·%. １／２ The heat shrinkage was 1.6% (80°C x 10 min), 10.0% (120°C x 10 min), and the LOI value was 25.0.

[0095] Comparative Example 3 A poly(3-hydroxyalkanoate)-based fiber resin composition was prepared in the same manner as in Example 1, except that a blend of 38 wt% P3HB3HH (A-1), 38 wt% P3HB3HH (A-2), and 24 wt% P3HB3HH (A-3) was used as P3HA. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained in the same manner as in Comparative Example 1, except that in step (C), the raw yarn was stretched using a stretching roll (speed: 38.0 m / min), and in step (D), the yarn was heat-treated under conditions of a residence time in a heat treatment oven of 6.9 seconds, and the final stretch ratio was set to 5.0 times using a relaxation roll (speed: 19.1 m / min, relaxation rate: 47.0%). Fineness: 1133.0 dtex, tensile strength: 0.87 cN / dtex, elongation at break: 200.0%, toughness: 12.3 (cN / dtex)・% １／２ The heat shrinkage was 1.3% (80°C x 10 min) and 13.4% (120°C x 10 min), and the LOI value was 25.5.

[0096] Comparative Example 4 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 7. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Example 7, except that in step (D), the heat treatment was performed at a heat treatment oven temperature of 80.0°C. The fineness was 1122.0 dtex, the tensile strength was 1.18 cN / dtex, the elongation at break was 452.0%, and the toughness was 25.1 (cN / dtex)·%. １／２ The heat shrinkage was 15.8% (80°C x 10 min), 32.2.4% (120°C x 10 min), and the LOI value was 27.0.

[0097] Comparative Example 5 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 7. The average molar ratio of 3HB / 3HH in the resin composition was 86.8 / 13.2 (mol% / mol%). The same method as in Example 7 was used, except that in step (D), heat treatment was performed at a heat treatment oven temperature of 135.0°C. However, the raw yarn broke in the heat treatment oven, and monofilament fibers could not be obtained.

[0098] Comparative Example 6 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 1. The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol % / mol %). In step (B), the raw yarn was cooled by passing it through a water bath at 4.0°C, with a residence time in the water bath of 17.7 seconds. In step (C), the cooled raw yarn was taken up with a take-up roll (speed: 4.2 m / min) and then passed through a hot water bath at 45°C and drawn with a drawing roll (speed: 25.2 m / min). In step (D), the raw yarn was heat-treated at a heat treatment oven temperature of 120.0°C with a residence time of 8.0 seconds. Five monofilament fibers were obtained using the same method as in Example 1, except that the final draw ratio was set to 5.4 times on the subsequent take-up roll (speed: 22.7 m / min, relaxation rate: 10.0%). The fineness was 454.0 dtex, the tensile strength was 1.63 cN / dtex, the elongation at break was 172.3%, and the toughness was 21.4 (cN / dtex)%.１／２ The heat shrinkage was 0.2% (80°C x 10 min) and 5.8% (120°C x 10 min), and the LOI value was 25.0.

[0099] Comparative Example 7 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 1. The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Comparative Example 9, except that in step (B), the water tank residence time was set to 14.9 seconds, and in step (C), the cooled raw yarn was taken up with a take-up roll (speed: 5.0 m / min) and stretched with a stretching roll (speed: 27.5 m / min). In step (D), the raw yarn was heat-treated under conditions of a residence time of 7.2 seconds, and the final stretch ratio on the subsequent take-up roll (speed: 25.0 m / min, relaxation rate: 10.0%) was set to 5.0 times. Fineness: 725.0 dtex, tensile strength: 1.33 cN / dtex, elongation at break: 207.2%, toughness: 19.1 (cN / dtex) / % １／２ The heat shrinkage was 0.1% (80°C x 10 min) and 3.4% (120°C x 10 min), and the LOI value was 25.0.

[0100] Comparative Example 8 A poly(3-hydroxyalkanoate)-based fiber resin composition was obtained using the same method as in Example 2. The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol% / mol%). The average molar ratio of 3HB / 3HH in the resin composition was 94.0 / 6.0 (mol% / mol%). Five monofilament fibers were obtained using the same method as in Comparative Example 10, except that in step (C), the raw yarn was stretched using a stretching roll (speed: 32.5 m / min), and in step (D), the raw yarn was heat-treated under conditions of a residence time of 6.1 seconds, and the final stretch ratio was set to 5.9 times using a relaxation roll (speed: 29.5 m / min, relaxation rate: 10.0%). Fineness: 627.0 dtex, tensile strength: 1.79 cN / dtex, elongation at break: 234.5%, toughness: 27.5 (cN / dtex) / % １／２ The heat shrinkage was 0.1% (80°C x 10 min) and 3.7% (120°C x 10 min), and the LOI value was 25.5.

[0101]

[0102]

[0103] As shown in Table 2, in Examples 1 to 11, the final draw ratio was 6.0 times or more, and the filament's heat shrinkage at 120°C was 15% or more, resulting in a high LOI value and enabling high flame retardancy. Furthermore, the heat shrinkage at 80°C was suppressed to less than 15%, enabling high flame retardancy while also suppressing dimensional changes in the processed product due to heat shrinkage during secondary processing. Therefore, it is clear that the present invention makes it possible to provide poly(3-hydroxyalkanoate) resin-containing filaments that are excellent in biodegradability and flame retardancy, as well as environmentally friendly textile products that are excellent in moldability and flame retardancy.

[0104] On the other hand, in Comparative Examples 1 to 3 and 6 to 8, which had a low final draw ratio and a low heat shrinkage rate of the filament at 80°C, the LOI value was low, and it was found that the flame retardancy was inferior to that of the Examples. In Comparative Example 4, in which the heat treatment temperature was 80.0°C, the heat shrinkage rate of the filament at 80°C was high, and it was found that the processability was inferior to that of the Examples. In Comparative Example 5, in which the heat treatment temperature was 135°C, the raw yarn broke and filaments could not be obtained.

[0105] A: raw yarn, 1: filament manufacturing apparatus, 2a: kneading extruder, 2b: spinning nozzle, 3a: liquid, 3b: tank, 3c: tank roll, 4: take-up roll, 5: hot water tank, 6: drawing roll, 7: oven, 8: transfer roll, 9: winding roll

Claims

1. A method for producing a filament containing a poly(3-hydroxyalkanoate) resin, comprising: step (A) of obtaining a raw yarn by discharging a melt containing a poly(3-hydroxyalkanoate) resin from a discharge hole; step (B) of cooling the raw yarn; step (C) of drawing the cooled raw yarn; and step (D) of heat-treating the drawn raw yarn at a temperature of 85 to 130°C, wherein the final draw ratio is 6.0 times or more, and the draw ratio in step (C) is 8 times or more.

2. The method for producing a filament according to claim 1, wherein the heat treatment time in step (D) is 1 to 10 seconds.

3. A method for producing a filament according to claim 1 or 2, wherein the relaxation rate is 25% or less.

4. The method for producing a filament according to claim 1 or 2, wherein in step (B), the raw yarn is cooled in a liquid at 60°C or less.

5. The method for producing a filament according to claim 4, wherein in step (B), the cooling time in the liquid is 10 to 20 seconds.

6. Filaments containing poly(3-hydroxyalkanoate) resins, with a heat shrinkage rate of less than 15% at 80°C and a heat shrinkage rate of 15% or more at 120°C.

7. The filament according to claim 6, wherein the filament containing the poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units and other hydroxyalkanoate units, and the average molar ratio of 3-hydroxybutyrate units / other hydroxyalkanoate units in the filament containing the poly(3-hydroxyalkanoate) resin is 80 / 20 to 95 / 5 (mol % / mol %).

8. The filament according to claim 6 or 7, wherein the poly(3-hydroxyalkanoate) resin is at least one selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

9. The filament according to claim 8, wherein the poly(3-hydroxyalkanoate) resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

10. The filament according to claim 6 or 7, which contains 0.1 to 10 parts by weight of pentaerythritol per 100 parts by weight of the filament containing the poly(3-hydroxyalkanoate) resin.

11. The filament according to claim 6 or 7, wherein the poly(3-hydroxyalkanoate)-based resin contains a poly(3-hydroxybutyrate)-based resin having an average molar ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units of 90 / 10 to 99 / 1 (mol % / mol %).

12. Grass yarn made from the filaments according to claim 6 or 7.

13. An artificial turf structure using the turf yarn of claim 12.

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