Continuous long fiber of aliphatic copolymerized polyester, and method for producing same

Abstract

The present invention addresses the problem of providing a continuous long fiber that comprises an aliphatic copolymerized polyester, has excellent storage stability, and can solve a problem of unwinding defects, as well as a method for producing said continuous long fiber. This continuous long fiber comprises an aliphatic copolymerized polyester, wherein the aliphatic copolymerized polyester includes 3-hydroxybutyrate as a first monomer unit and includes 4-hydroxybutyrate or 3-hydroxyvalerate as a second monomer unit, the ratio of the second monomer unit to all monomer units is 1 mol% to 9 mol% when the second monomer unit is the 4-hydroxybutyrate unit, and the ratio of the second monomer unit to all monomer units is 1 mol% to 7.6 mol% when the second monomer unit is 3-hydroxyvalerate.

Description

Aliphatic copolymer polyester continuous long fiber and its manufacturing method

[0001] The present invention relates to an aliphatic copolyester continuous filament fiber, a multifilament yarn, a fabric, and a method for producing the fiber.

[0002] In recent years, environmental problems caused by waste plastics have come to the forefront, and there is a strong desire to realize a recycling-oriented society on a global scale. Biodegradable resins, which are decomposed by microorganisms after use, have attracted attention. Among these biodegradable resins, polyhydroxyalkanoates (hereinafter sometimes abbreviated as "PHA"), which are aliphatic copolymer polyesters and biologically derived polymers, have attracted attention from the perspective of reducing carbon dioxide emissions and immobilizing them (carbon neutrality). Because PHAs are highly biodegradable, particularly in the ocean, their use in various molded articles, such as fibers that fall off from products and end up in the ocean, and films that end up in the ocean when dumped, is being considered. For example, in the case of PHA fibers, there can be expected to be significant demand in a wide variety of fields, including clothing products such as shirts, bedding materials such as sheets, bed pads, and pillowcases, medical products such as surgical sutures, agricultural and fishery products such as bird nets, fishing lines, and fishing nets, woven products such as car seats and textiles, sanitary materials such as nonwoven fabrics and filters, building materials such as ropes, and packaging products for food and other purposes.

[0003] Among PHAs, poly-3-hydroxybutyrate (hereinafter abbreviated as P3HB) and other PHAs have been investigated for molding processing, but no resins have been found that have stable mechanical properties that meet market demands compared to general resins. P3HB has a slow crystallization rate, which requires a long cooling time for solidification after heating and melting during molding processing, resulting in very poor productivity. For example, when producing fibers, the take-up speed during melt spinning must be extremely slow. In addition, due to the slow crystallization rate, there are practical problems such as extremely poor unwinding properties after winding due to adhesion between fibers. Furthermore, P3HB has a slow crystallization rate but high crystallinity, and because its glass transition temperature is below room temperature, secondary crystallization occurs during storage, leading to deterioration over time.

[0004] Patent Document 1 below describes a method for improving mechanical properties by rapidly cooling PHA to a temperature below 15°C above the glass transition temperature of the polymer immediately after extrusion from a melt extruder to release the filaments from blocking, followed by cold drawing at a temperature below 20°C above the glass transition temperature to rapidly promote partial crystallization, and then subjecting the filaments to a tension heat treatment. Patent Document 2 below also describes a method for further drawing at a temperature above the glass transition temperature after cold drawing, followed by a tension heat treatment. These methods achieve improved mechanical properties through improvements in the manufacturing process. Meanwhile, efforts have also been made to further improve physical properties by improving the molecular design of PHA itself. Patent Document 3 below describes a fiber made of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter abbreviated as PHBH), which contains conventional 3-hydroxybutyrate as the first component and 3-hydroxyhexanoate as the second component. Furthermore, Patent Document 4 listed below describes a molded article having high elasticity that uses poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (hereinafter abbreviated as P3HB4HB) having 4-hydroxybutyrate as a second component.

[0005] Japanese Patent No. 3864187 Japanese Patent No. 3864188 Japanese Patent No. 5924623 International Publication No. 2020 / 230807

[0006] The techniques described in Patent Documents 1 to 4 are useful for producing PHA fibers having mechanical properties that meet market demands, but do not recognize the problem of storage stability. In view of the problems of the prior art, the problem that the present invention aims to solve is to provide a continuous filament fiber made of an aliphatic copolyester that has excellent storage stability, can be easily unwound after winding, and can be spun stably, and also to provide a multifilament yarn and fabric made of such a fiber, and a method for producing the fiber.

[0007] The present inventors have conducted extensive research and experiments to solve this problem, and as a result have unexpectedly found that the problem can be solved by using the following configuration, which has led to the completion of the present invention.

[0008] That is, the present invention is as follows. [1] A continuous filament made of an aliphatic copolyester, the aliphatic copolyester containing 3-hydroxybutyrate as a first monomer unit and 4-hydroxybutyrate or 3-hydroxyvalerate as a second monomer unit, wherein when the second monomer unit is a 4-hydroxybutyrate unit, the proportion of the second monomer unit to all monomer units is 1 mol % or more and 9 mol % or less, and when the second monomer unit is a 3-hydroxyvalerate unit, the proportion of the second monomer unit to all monomer units is 1 mol % or more and 7.6 mol % or less. [2] A continuous filament according to [1] above, wherein the second monomer unit is 4-hydroxybutyrate, and the proportion of the 4-hydroxybutyrate unit to all monomer units is 4 mol % or more and 6 mol % or less. [3] A continuous filament according to [1] or [2] above, wherein the degree of X-ray orientation of the α structure of the aliphatic copolyester is 90% or more. [4] The continuous continuous fiber according to any one of [1] to [3] above, having a weight-average molecular weight of 150,000 or more and a weight-average molecular weight / number-average molecular weight ratio of 10 or less. [5] The continuous continuous fiber according to any one of [1] to [4] above, having a melting point peak in DSC of 110°C or more and 200°C or less. [6] The continuous continuous fiber according to any one of [1] to [5] above, having a ratio Iβ / Iα of β crystals to α crystals of 0 or more and 0.6 or less. [7] The continuous continuous fiber according to any one of [1] to [6] above, having a ratio of the sum of the first monomer units and the second monomer units to the total monomer units of 99 mol% or more. [8] The continuous continuous fiber according to any one of [1] to [7] above, having a single filament fineness of 0.1 dtex or more and 30 dtex or less. [9] A multifilament yarn composed of the continuous continuous fiber according to any one of [1] to [7] above, having a filament count of 6 to 300.

[10] The multifilament yarn according to [9] above, having a total fineness of 1 dtex or more and 200 dtex or less.

[11] A fabric composed of the continuous filament or multifilament yarn according to any one of [1] to

[10] above.

[12] The method for producing continuous filaments according to any one of [1] to [8], comprising the following steps: a melting step of melting an aliphatic copolymer polyester, a discharge step of discharging the molten aliphatic copolymer polyester from a spinneret, and a cold drawing step of cooling the discharged aliphatic copolymer polyester in a cooling medium and simultaneously drawing it, wherein the temperature of the cooling medium is 30°C or less and the draw ratio in the cold drawing step is 4 times or more.

[13] The method according to

[12] , wherein an air gap is provided between the spinneret and the cooling medium, and the draft ratio in the air gap is 1.1 times or more.

[14] The method according to

[13] , wherein the time it takes for the aliphatic copolymer polyester discharged from the spinneret to pass through the air gap is 5 seconds or less.

[15] The method according to any one of

[12] to

[14] , wherein the residence time of the aliphatic copolymer polyester in the melting step is 900 seconds or less.

[0009] The continuous filament made of the aliphatic copolyester of the present invention has excellent storage stability. Furthermore, such continuous filament does not cause agglutination of the PHA resin during spinning, allowing for good unwinding after winding, and further allows for stable spinning without yarn breakage, thereby improving productivity.

[0010] Embodiments of the present invention will be described in detail below. One embodiment of the present invention is a continuous filament made of an aliphatic copolymer polyester, which contains 3-hydroxybutyrate as a first monomer unit and 4-hydroxybutyrate or 3-hydroxyvalerate as a second monomer unit, and the ratio of the second monomer unit to all monomer units is 1 mol % or more and 9 mol % or less for 4-hydroxybutyrate units, and 1 mol % or more and 7.6 mol % or less for 3-hydroxyvalerate units. A continuous filament refers to a fiber that is continuously spun, and the fiber length may be adjusted after spinning by processing using a cutter or the like. The fiber length is not particularly limited, but is preferably 1 cm or more, more preferably 10 m or more, even more preferably 100 m or more, and particularly preferably 1,000 m or more. Furthermore, a processing agent may be added to the fiber after spinning, such as by applying an oil.

[0011] The continuous filament fiber made of the aliphatic copolyester of the present embodiment contains a first monomer unit of [—O—CH(CH ３ )-CH ２ -CO-] as a second monomer unit, and ２ -CH ２ -CH ２ -CO-] or 4-hydroxybutyrate represented by [-O-CH(C ２ H ５ )-CH ２ The second monomer unit must contain 3-hydroxyvalerate represented by the formula [—CO—] as a monomer unit. The presence of such a second monomer unit allows for sufficient marine biodegradability, and in addition, significantly improves moldability while maintaining the mechanical strength derived from the first monomer unit, thereby achieving both strength and elongation within a desired range.

[0012] In the continuous long fiber made of the aliphatic copolyester of this embodiment, the ratio of the second monomer unit to all monomer units (hereinafter referred to as copolymerization ratio) is 9 mol % or less, preferably 8 mol % or less, more preferably 7 mol % or less, and even more preferably 6 mol % or less, when the second monomer unit is a 4-hydroxybutyrate unit. A copolymerization ratio of 9 mol % or less ensures sufficient mechanical properties. The lower limit of the copolymerization ratio is 1 mol % or more, preferably 3 mol % or more, and more preferably 4 mol % or more, from the viewpoint of ensuring excellent moldability. When the second monomer unit is 3-hydroxyvalerate, the copolymerization ratio is 7.6 mol % or less, preferably 7 mol % or less, and more preferably 6 mol % or less, from the viewpoint of ensuring excellent moldability. The lower limit of the copolymerization ratio is 1 mol % or more, preferably 2 mol % or more, and more preferably 3 mol % or more, from the viewpoint of ensuring excellent moldability. Methods for controlling the copolymerization ratio include appropriately selecting a microorganism, adjusting the composition conditions of the fermentation raw materials and culture conditions, and the like, but the control method is not particularly limited.

[0013] The copolymerization ratio referred to here can be measured by the following method. The aliphatic copolymer polyester is dissolved in deuterated chloroform (chloroform-d, 99.8%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a concentration of 1.5% by mass, and used as a measurement sample. H-NMR measurement is performed using a nuclear magnetic resonance spectrometer (Bruker BioSpin AVANCE II 400) with an observation frequency of 400 MHz, an accumulation count of 64, a chemical shift reference of chloroform (chloroform, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at 7.26 ppm, and deuterated chloroform as the lock solvent. When 4-hydroxybutyrate is contained as the second monomer unit, the integral value of the triplet peak observed at a chemical shift of 4.1 ppm ± 0.2 is designated as A, and the integral value of the quartet peak observed at a chemical shift of 5.3 ± 0.2 ppm is designated as B. The copolymerization ratio C (mol %) is calculated by the following formula: C = (A / 2) / (A / 2 + B) × 100 [mol %]. When 3-hydroxyvalerate is contained as the second monomer unit, the integral value of the triplet peak observed at a chemical shift of 0.88 ± 0.2 ppm is taken as D, and the integral value of the doublet peak observed at a chemical shift of 1.25 ppm ± 0.2 is taken as E. The copolymerization ratio F (mol %) is calculated by the following formula: F = (D / 3) / (D / 3 + E / 3) × 100 [mol %].

[0014] From the viewpoint of realizing a practically appropriate texture and feel, the continuous filament fiber made of the aliphatic copolyester of this embodiment preferably has a single filament fineness of 30 dtex or less, more preferably 20 dtex or less, and even more preferably 10 dtex or less. If the single filament fineness is 30 dtex or less, problems such as insufficient fiber strength and yarn breakage during spinning may arise, but these can be improved by adjusting the copolymerization ratio described above and the degree of X-ray orientation of the α structure described below. From the viewpoint of ensuring an acceptable frequency of yarn breakage in practical use, the lower limit of the single filament fineness is preferably 0.1 dtex or more. The single filament fineness referred to here can be measured by the following method.

[0015] The obtained continuous filament is made into a single yarn and conditioned overnight in a loosely stretched state in an atmosphere at room temperature of 23°C and humidity of 50% RH. A 1 m sample is cut out from the conditioned sample, and the weight is measured at 10 points. The number average value is multiplied by 10,000 to obtain the single yarn fineness (dtex) of the sample.

[0016] The continuous long fibers made of the aliphatic copolymer polyester of this embodiment are preferably used for multifilament yarns. The total number of filaments is preferably 6 or more, more preferably 11 or more, from the viewpoint of realizing practically adequate texture and feel while maintaining high mechanical properties. The upper limit of the total number of filaments is not particularly limited, but from the viewpoint of practically acceptable frequency of yarn breakage, 300 or less is preferred.

[0017] The multifilament yarn of this embodiment preferably has a total fineness of 200 dtex or less, more preferably 100 dtex or less, from the viewpoint of realizing a practically appropriate texture and feel while having high mechanical properties. The lower limit of the total fineness is preferably 1 dtex or more, from the viewpoint of allowing a practically acceptable frequency of yarn breakage. The total fineness referred to here can be measured by the following method.

[0018] The obtained fiber is conditioned overnight in a loosely stretched state in an atmosphere of room temperature 23°C and humidity 50% RH. A 1 m sample is cut out from the conditioned sample, and the weight is measured at 10 points. The number average value is multiplied by 10,000 to obtain the total fineness (dtex) of the sample.

[0019] In the continuous long fiber made of the aliphatic copolyester of this embodiment, the degree of X-ray orientation of the α structure is preferably 90% or more, more preferably 92% or more, and even more preferably 94% or more. The α structure referred to here refers to a lamellar crystal structure formed by folding of a helical structure, and is a higher-order structure that significantly contributes to the mechanical strength of a molded article. If the degree of X-ray orientation of the α structure is 90% or more, sufficient mechanical properties, particularly strength, are exhibited, and the molded article has excellent storage stability. Furthermore, the sticking caused by the amorphous structure on the surface of the molded article is eliminated, resulting in good unwinding properties in the form of a fiber. While there is no particular upper limit, a realistic degree of orientation is 99% or less. To achieve an X-ray orientation of the α structure of 90% or more, it is important to produce the aliphatic copolyester of this embodiment under the production conditions described below.

[0020] The degree of X-ray orientation of the α structure referred to here can be measured by the following method. Using an X-ray structure evaluation device (Rigaku, SmartLab) and a multidimensional pixel array detector (Rigaku, HiPix-3000), the X-ray source was set to Cu, the collimator diameter was 0.1 mm, the X-ray wavelength was 0.1 nm, the camera length was 27 mm, and the exposure time was 10 min. The test piece was placed perpendicular to the X-ray beam and parallel to the detector, and a two-dimensional diffraction image was obtained. In the WAXD image measured by wide-angle X-ray diffraction (WAXD), the diffraction angle range 2θ = 15 ° to 18 ° in the WAXD image was separated as the (020) plane diffraction peak, and a ring-shaped region containing the (020) plane diffraction peak was selected. All diffraction intensities with the same azimuth angle were integrated, and this intensity was plotted against the azimuth angle to create a one-dimensional azimuth angle profile. The full width at half maximum (FWHM (full width at half maximum): peak width at half the height of the peak) of the peak at the location where the diffraction point exists is measured. When the average value of the full width at half maximum of each peak is H, the degree of orientation G [%] is calculated by the following formula: G = (180 - H) / 180 × 100 [%].

[0021] The weight-average molecular weight of the continuous long fiber made of the aliphatic copolyester of this embodiment is preferably 150,000 or more, more preferably 200,000 or more, and even more preferably 250,000 or more. If the weight-average molecular weight is 150,000 or more, sufficient mechanical properties, particularly strength, are exhibited. The upper limit of the weight-average molecular weight is preferably 3,000,000 or less, from the viewpoint of enabling practically stable molding processing.

[0022] The weight-average molecular weight / number-average molecular weight ratio of the continuous long fiber made of the aliphatic copolyester of this embodiment is preferably 10 or less, more preferably 7 or less, and even more preferably 5 or less. When the weight-average molecular weight / number-average molecular weight ratio is 10 or less, molding processing is stable and mechanical properties are stable. From the viewpoint of practical synthesis, the lower limit of the weight-average molecular weight / number-average molecular weight ratio is preferably 1.1 or more.

[0023] The weight-average molecular weight and number-average molecular weight referred to here can be measured by the following method. Aliphatic copolymer polyester is dissolved in chloroform (Chloroform, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at a concentration of 0.1% by mass. A gel permeation chromatography apparatus (Tosoh HLC-8320GPC) is used, and the columns used are a guard column (Tosoh TSKgel guard column Super HZ-L) and an analytical column (Tosoh TSKgel Super HZM-M). The column temperature is 40°C, the eluent is chloroform, the flow rate is 0.35 mL / min, the injection volume is 20 μL, and the detector is RI. A polystyrene standard (Agilent Technologies EasiCal PS-1) is measured, and a calibration curve is created using data processing software (Tosoh HLC-8320GPC Ecosec-WS). A sample of an aliphatic copolyester molded article is similarly measured, and the weight average molecular weight and number average molecular weight are calculated from the calibration curve.

[0024] The melting peak of the continuous filament made of the aliphatic copolyester of this embodiment has a melting point of preferably 110° C. or higher, more preferably 130° C. or higher, from the viewpoint of ensuring practical heat resistance. The upper limit of the melting peak is preferably 200° C. or lower, more preferably 180° C. or lower, from the viewpoint of practically achieving stable spinning, because if the melting peak is too high, the difference from the thermal decomposition temperature becomes small, making stable melting difficult.

[0025] The melting point peak referred to here can be measured by the following method. The melting point peak is measured using a differential scanning calorimeter (PerkinElmer, DSC8500) equipped with an intracooler. The measurement atmosphere is nitrogen (20 ml / min), and the sample is heated from -50°C to 200°C at 20°C / min and held for 1 minute to completely melt. Next, the sample is rapidly cooled from 200°C to -50°C at 20°C / min, held for 3 minutes, and then heated again to 200°C at 20°C / min (this heating is referred to as the second run). The melting point peak is measured using the DSC curve (thermogram) measured in the second run. As the temperature continues to rise, a melting peak (endothermic peak) appears on the DSC curve, and the temperature at the apex of this peak is taken as the melting point. The sample is approximately 5 mg, and an aluminum sample pan is used. Indium is used for temperature calibration.

[0026] The X-ray diffraction intensity ratio Iβ / Iα of the β structure to the α structure of the continuous long fiber made of the aliphatic copolyester of this embodiment is preferably 0.6 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. The β structure referred to here is a β-type crystal structure formed by extended chains, which has low thermodynamic stability. If the X-ray diffraction intensity ratio Iβ / Iα of the β structure to the α structure is 0.6 or less, the less stable β structure is less likely to disappear over time, and therefore the storage stability is excellent.

[0027] The X-ray diffraction intensity ratio Iβ / Iα of the β structure to the α structure referred to here can be measured by the following method. Using an X-ray structure evaluation device (Rigaku, SmartLab) and a multidimensional pixel array detector (Rigaku, HiPix-3000), the X-ray source was set to Cu, the collimator diameter was 0.1 mm, the X-ray wavelength was 0.1 nm, the camera length was 27 mm, and the exposure time was 10 min. The test piece was placed perpendicular to the X-ray beam and parallel to the detector to obtain a two-dimensional diffraction image. When the diffraction intensity distribution in the equatorial direction of the two-dimensional diffraction image was measured, the diffraction intensity was composed of scattering due to amorphous matter and diffraction due to crystals. Crystal diffraction includes diffraction due to the α structure and diffraction due to the β structure, each of which occurs at a specific position, and the diffraction intensity is proportional to the amount of crystals. Therefore, by taking the ratio of the diffraction intensity based on the α structure to the diffraction intensity based on the β structure, an index of the amount of β structure can be obtained. However, since the intensity due to amorphous scattering interferes, in order to determine the amount of β structure in the crystal, it is necessary to remove the influence of the intensity due to amorphous scattering. Since the intensity due to amorphous scattering is observed as a broader baseline rise than the intensity due to crystalline diffraction, the line connecting 2θ = 15 ° and 21 °, which is less affected by diffraction from the crystal, is considered to be the intensity due to amorphous scattering, and this amount is subtracted from the diffraction intensity. In the subsequent diffraction intensity distribution, the maximum value between diffraction angles 2θ = 15 ° and 18 ° is considered to be the diffraction intensity from the α structure (Iα), and the maximum value between diffraction angles 18 ° and 21 ° is considered to be the diffraction intensity from the β structure (Iβ). The ratio of the two, Iβ / Iα, is considered to be the X-ray diffraction intensity ratio of the β structure to the α structure.

[0028] Although the synthesis method of the aliphatic copolymer polyester is not particularly limited, it is preferably produced by a microorganism, and an example of a microorganism that produces an aliphatic copolymer polyester is a microorganism capable of producing PHAs. For example, the first P3HB-producing bacterium was Bacillus megaterium, discovered in 1925. Other known natural microorganisms include Cupriavidus necator, (formerly classified as Alcaligenes eutrophus and Ralstonia eutropha), and Alcaligenes latus. These microorganisms accumulate PHAs within their cells. Alternatively, genetically modified microorganisms into which various PHA synthesis-related genes have been introduced may be used, or the culture conditions, including the type of substrate, may be optimized.

[0029] The continuous filaments made of the aliphatic copolyester of this embodiment can be made into fabric by secondary processing. The structure of the fabric is not particularly limited and may be appropriately selected depending on the application and purpose, and may be, for example, a knitted fabric or a woven fabric. The weight per unit area of ​​the fabric (basis weight) is not particularly limited and may be, for example, 1 to 1000 g / m ２ That's fine.

[0030] As the PHAs, granules containing PHAs may be used without purification, or purified and pelletized PHAs may be used. Furthermore, from the viewpoint of improving moldability in melt extrusion, a plasticizer, a lubricant, or a crystal nucleating agent may be contained, or other polymers may be blended. Melt extrusion of PHAs can be carried out using a conventional melting technique for plastic fibers, for example, by heating and melting the PHAs, applying a load, and extruding them from an extrusion port. The extrusion method includes syringe extrusion and screw extrusion, but screw extrusion is preferred in order to produce continuous filaments. The temperature during melt extrusion is usually equal to or higher than the melting point onset peak of the PHA measured by DSC, so that extrusion is possible and sufficient stretching can be performed after extrusion.

[0031] The molten PHA is extruded into a cooling medium, quenched, and fiberized. The quenching and fiberization temperature is preferably 30°C or lower, more preferably 20°C or lower. There is no particular lower limit, but from an economical standpoint, the process can usually be carried out at -200°C or higher. This quenching process converts the molten PHA into an amorphous fiber with excellent stretchability, and also suppresses deterioration over time during the process. The resulting fiber can be stretched and wound in a cooling solvent.

[0032] The cooling medium is not particularly limited, but examples thereof include air, water (ice water), an inert gas, and an antifreeze solution mainly composed of ethylene glycol or propylene glycol. The cooling method is not particularly limited, but examples thereof include a method of passing the PHA through a bath filled with the cooling medium, a method using a fluidized bath, a method using a cooling plate, a method using a cooling ring that can uniformly apply cold air to the fiber from all directions 360°, and a method using a blower. In the present invention, rapid cooling can be performed, for example, by extruding molten PHA into a bath filled with a cooling medium at 30°C or less, and passing it through the same solvent while winding it up on a roller in the bath.

[0033] The obtained fiber is cold-drawn in the cooling step. Cold drawing can be performed, for example, by fixing the fiber to a drawing machine or the like, and preferably by taking up the fiber with two drawing rollers or the like while applying tension by means of a speed difference. The draw ratio is preferably 4 times or more, more preferably 7 times or more, and even more preferably 10 times or more. The upper limit is not particularly limited as long as it does not cause breakage, but can be set to 50 times or less. From the viewpoint of productivity, the drawing time is preferably 1 minute or less, more preferably 30 seconds or less. There is no particular lower limit, but practically, the drawing can be performed for 0.001 seconds or more.

[0034] The draw ratio can be measured by the following method. 10 cm of the fiber is taken immediately before drawing and 10 cm of the fiber is taken immediately after drawing. The obtained fiber is conditioned overnight in a loosely stretched state in an atmosphere at room temperature of 23°C and a humidity of 50% RH. The weight of the conditioned sample is measured at 10 points, and the number average value is calculated. The value immediately before drawing is divided by the value immediately after drawing to obtain the draw ratio.

[0035] Between the cooling step and the discharge section, it is preferable to provide an air gap, which is an air layer for slowly cooling the extruded resin. The air gap may be cooled by ventilation or radiation, or the temperature may be controlled by enclosing the air gap in a housing. By providing an air gap, the resin extruded in a molten state is slowly cooled, which promotes appropriate crystallization on the surface and prevents adhesion of the fiber surface, enabling good unwinding after winding of the continuous filament. Furthermore, adjusting the crystallization and crystal growth of the fiber improves mechanical properties and productivity. The temperature of the air gap is not particularly limited, but it can usually be set in the range of 0°C to 100°C.

[0036] In the air gap, the fibers are stretched and oriented appropriately due to the difference between the linear extrusion speed and the speed of the take-up section in the subsequent process. This is called the draft ratio. The draft ratio is preferably 1.1 times or more, and more preferably 1.5 times or more. A draft ratio of 1.1 times or more promotes orientation crystallization due to moderate stretching, thereby crystallizing the fiber surface and suppressing sticking. Furthermore, yarn breakage in the subsequent cold stretching process is suppressed, allowing for sufficient stretching, resulting in the development of sufficient mechanical strength. There is no particular upper limit to the draft ratio, but it can usually be set to 100 times or less. The time for which the fibers pass through the air gap is preferably 5 seconds or less, more preferably 3 seconds or less, and even more preferably 1 second or less. A passage time of 5 seconds or less suppresses excessive crystallization of the molten resin, effectively increasing the degree of orientation of the α-structure in the cold stretching process, thereby developing sufficient mechanical strength, suppressing embrittlement due to excessive crystallization, and suppressing yarn breakage in the air gap. There is no particular lower limit to the time required for the fibers to pass through the air gap, but in reality, the time can be 0.0001 seconds or more.

[0037] When PHAs are heated, melted, and subjected to a load to be extruded through an extrusion port, the time it takes for the PHAs to pass from the inlet to the outlet is called the residence time in the extrusion port. The residence time in the extrusion port is preferably 900 seconds or less, more preferably 600 seconds or less, even more preferably 300 seconds or less, and particularly preferably 200 seconds or less. When the residence time in the extrusion port is 900 seconds or less, it is possible to suppress a decrease in molecular weight due to thermal decomposition of the resin, and sufficient mechanical strength is exhibited. The extrusion method is not particularly limited, but examples thereof include extrusion using a syringe, extrusion using a single screw, and extrusion using a twin screw.

[0038] The obtained fiber can be subjected to another process to the extent that the mechanical strength and storage stability are not affected. The other process is not particularly limited, but examples include an aligned winding process, a cross winding process, and re-stretching after winding is completed. Furthermore, by heat-treating the fiber, the crystallinity and crystalline structure of the fiber can be stabilized, thereby stabilizing the mechanical strength and enhancing the storage stability. The heat-treatment method is not particularly limited, but the heat treatment can be performed continuously by arranging a hot bath, a heated roller, a tunnel-type drying oven, or the like during the process, or the heat-treatment can be performed by placing the wound fiber in a dryer or a thermostatic oven.

[0039] The present invention will be described in detail below with reference to examples and comparative examples. Various physical property evaluations and performance evaluations were performed using the following methods. <Physical Property Evaluation> (1) [Ratio of Second Monomer Units to Total Monomer Units (Copolymerization Ratio)] An aliphatic copolymer polyester was dissolved in deuterated chloroform (chloroform-d, 99.8%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a concentration of 1.5% by mass to prepare a measurement sample. 1H-NMR measurement was performed using a nuclear magnetic resonance spectrometer (Bruker BioSpin AVANCE II 400) at an observation frequency of 400 MHz, with 64 accumulations, a chemical shift reference of chloroform at 7.26 ppm, and deuterated chloroform as the lock solvent. When 4-hydroxybutyrate was contained as the second monomer unit, the integral value of the triplet peak observed at a chemical shift of approximately 4.1 ppm was designated as A, and the integral value of the quartet peak observed at a chemical shift of approximately 5.3 ppm was designated as B, and the copolymerization ratio C (mol %) was calculated using the following formula: C = (A / 2) / (A / 2 + B) [mol %]. When 3-hydroxyvalerate was contained as the second monomer unit, the integral value of the triplet peak observed at a chemical shift of approximately 0.88 ppm was designated as D, and the integral value of the doublet peak observed at a chemical shift of approximately 1.25 ppm was designated as E, and the copolymerization ratio F (mol %) was calculated using the following formula: F = (D / 3) / (D / 3 + E / 3) [mol %].

[0040] (2) [α-structure orientation degree] Using an X-ray structure evaluation device (Rigaku, SmartLab) and a multidimensional pixel array detector (Rigaku, HiPix-3000), the X-ray source was Cu, the collimator diameter was 0.1 mm, the X-ray wavelength was 0.1 nm, the camera length was 27 mm, the exposure time was 10 min, and the test piece was placed perpendicular to the X-ray beam and parallel to the detector, and a two-dimensional diffraction image was obtained. In the WAXD image measured in the wide-angle X-ray diffraction (WAXD) measurement, the diffraction angle 2θ = 15 ° to 18 ° range in the WAXD image was separated as the (020) plane diffraction peak, and the region containing the (020) plane diffraction peak was selected in a ring shape, and all the diffraction intensities having the same azimuth angle were integrated, and this intensity was plotted against the azimuth angle to create a one-dimensional azimuth angle profile. The full width at half maximum (FWHM (full width at half maximum): peak width at half the height of the peak) of the peak at the location where the diffraction spot exists was measured. The average value of the full width at half maximum of each peak was taken as H, and the degree of orientation G [%] was calculated by the following formula: G = (180 - H) / 180 × 100 [%].

[0041] (3) [Weight-average molecular weight (Mw) and weight-average molecular weight (Mw) / number-average molecular weight (Mn)] Aliphatic copolymer polyester was dissolved in chloroform (Fujifilm Wako Pure Chemical Industries, Ltd.) at a concentration of 0.1% by mass. A gel permeation chromatography system (Tosoh HLC-8320GPC) was used, and a guard column (Tosoh TSKgel guard column Super HZ-L) and an analytical column (Tosoh TSKgel Super HZM-M) were used. A polystyrene standard (Agilent Technologies EasiCal PS-1) was measured at a column temperature of 40°C, chloroform as the eluent, a flow rate of 0.35 mL / min, an injection volume of 20 μL, and an RI detector, and a calibration curve was created using data processing software (Tosoh HLC-8320GPC Ecosec-WS). Samples of aliphatic copolymer polyester molded bodies were also measured in the same manner, and the weight-average molecular weight and number-average molecular weight were calculated from the calibration curve.

[0042] (4) [Melting Point Peak] Measurement was performed using a differential scanning calorimeter (PerkinElmer, DSC8500) equipped with an intracooler. The measurement atmosphere was nitrogen (20 ml / min), and the sample was heated from -50°C to 200°C at 20°C / min and held for 1 minute to completely melt the sample. Subsequently, the sample was rapidly cooled to -50°C at 200°C / min, held for 3 minutes, and then heated again to 200°C at 20°C / min (this heating was referred to as the second run). The melting point peak was measured using the DSC curve (thermogram) measured in the second run. As the temperature continued to rise, a melting peak (endothermic peak) appeared on the DSC curve, and the temperature at the apex of this peak was taken as the melting point. The sample was approximately 1 mg, and an aluminum sample pan was used. Indium was used for temperature calibration.

[0043] (5) [X-ray diffraction intensity ratio Iβ / Iα of β structure and α structure] X-ray structure evaluation device (Rigaku, SmartLab) and multidimensional pixel array detector (Rigaku, HiPix-3000) were used, the X-ray source was Cu, the collimator diameter was 0.1 mm, the X-ray wavelength was 0.1 nm, the camera length was 27 mm, the exposure time was 10 min, the test piece was placed perpendicular to the X-ray beam and parallel to the detector, and a two-dimensional diffraction image was obtained. A one-dimensional profile of the diffraction intensity distribution in the equatorial direction of the two-dimensional diffraction image was created, and the line connecting 2θ = 15 ° and 21 ° was considered to be the intensity based on amorphous scattering, and this amount was subtracted from the diffraction intensity. In the subsequent diffraction intensity distribution, the maximum value between the diffraction angle 2θ = 15 ° and 18 ° was taken as the diffraction intensity from the α structure (Iα), and the maximum value between the diffraction angle 18 ° and 21 ° was taken as the diffraction intensity from the β structure (Iβ). The ratio of the two, Iβ / Iα, was taken as the ratio of X-ray diffraction intensities of the β structure and the α structure.

[0044] <Performance Evaluation> (6) [Breaking Strength and Breaking Elongation] According to the method defined in JIS L 1013, a fiber was attached in a loosely tensile state to the gripping parts of a Tensilon universal testing machine (RTG-1250) manufactured by A&D Corporation, and a tensile test was performed using a 50 N load cell at a grip interval of 30 cm and a tensile speed of 30 cm / min. The load and elongation at which the sample broke were measured at 10 points, and the strength and elongation were calculated using the following formulas: Strength (cN / dtex) = Strength at Break or Strength at Maximum Load (cN) / Sample Fineness (dtex) Elongation (%) = Elongation at Break or Elongation at Maximum Load (mm) / Grip Interval (mm) × 100, and the number average values ​​were used as the strength (average strength) and elongation of the sample. Furthermore, when the breaking strength was smaller than the strength at maximum load, the strength at maximum load and the elongation at that time were measured.

[0045] (7) [Stable spinning time] The time until all filaments could no longer be wound due to filament breakage, poor discharge at the extrusion section, etc. was measured and recorded as the stable spinning time (min.). When stable spinning was possible for longer than 60 minutes, it was recorded as >60 min.

[0046] (8) [Unwinding property] After winding, the obtained sample was manually unwound, and the degree of unwinding failure due to sticking was evaluated on a three-point scale according to the following evaluation criteria: "-": No sticking was observed, and there was no unwinding failure at all. "+": Sticking was observed, and some unwinding failure occurred. "++": Sticking was observed significantly, and many unwinding failures occurred.

[0047] (9) [Storage stability] The obtained samples were stored in an atmosphere of room temperature 23°C and humidity 50% RH, and the breaking strength and breaking elongation of the samples were evaluated every week. N = 10 samples were evaluated, and when the average value of breaking strength was below 150 MPa or the average value of breaking elongation was above 150%, the number of weeks of storage up to that point was considered to be storage stability. When the storage stability exceeded 48 weeks, it was considered to be >48 weeks.

[0048] (10) [Softness of tubular knitted fabric] A fiber sample was fed into a tubular knitting machine (Eiko Sangyo single-end test tubular knitting machine NCR-ES), and a tubular knitted fabric was produced by adjusting the stitch count to 50 on the tubular knitting machine. Five subjects were asked to pass through the obtained tubular knitted fabric, and a questionnaire was given to each subject regarding softness. A knitted fabric that felt soft when passed through the hand was evaluated as having excellent softness, with 5 subjects rating it as excellent being rated as ◎, 4 subjects as ○, 3 subjects as △, and 2 or less as ×.

[0049] [Example 1] PHA pellets were produced using Cupriavidus necator H16 (ATCC 17699) as a microorganism for producing PHAs, with the raw materials and culture conditions appropriately adjusted. The PHA obtained was P3HB4HB, with a copolymerization ratio of 6.0%. The pellets were melt-extruded in a melt extruder (ALM-E005-H, manufactured by AIKI Liotech) heated to 170°C for a residence time of 600 seconds, spun using a nozzle with a 12-hole hole and a hole diameter of 0.2 mm, and passed through an air gap over 3 seconds while being subjected to a draft of 1.5 times in the air gap, cooled in a cooling step at 5°C, stretched at a draw ratio of 7 times in the cooling step, and finally wound up on a winder. The sample was placed in a blower dryer (DKM401, manufactured by Yamato Scientific) set at 60°C, allowed to stand for 30 minutes, and then removed to produce a 1000 m multifilament continuous long fiber. After production, various physical properties and performance evaluations were performed as shown in Table 1 below.

[0050] [Example 2] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 4.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0051] [Example 3] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 9.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0052] [Example 4] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 8.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0053] [Example 5] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw materials and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 7.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0054] [Example 6] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw materials and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 1.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0055] [Example 7] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 3.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0056] Example 8 A PHA fiber was produced in the same manner as in Example 1, except that the cold draw ratio was set to 10. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0057] Example 9 A PHA fiber was produced in the same manner as in Example 1, except that the air gap time was set to 1 second. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0058] Example 10 PHA fibers were produced in the same manner as in Example 1, except that the residence time in the extrusion section was set to 300 seconds. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0059] Example 11 A PHA fiber was produced in the same manner as in Example 1, except that the cold draw ratio was set to 3. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0060] Example 12 Except for changing the draft ratio to 1.0, PHA fibers were produced in the same manner as in Example 1. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0061] Example 13 A PHA fiber was produced in the same manner as in Example 1, except that the air gap time was set to 7 seconds. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0062] Example 14 A PHA fiber was produced in the same manner as in Example 1, except that the residence time was set to 1,000 seconds. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0063] Example 15 PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (hereinafter abbreviated as PHBV) with a copolymerization ratio of 6.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0064] [Example 16] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 7.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0065] [Example 17] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 7.6%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0066] [Example 18] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 1.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0067] [Example 19] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 2.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0068] [Example 20] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 3.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0069] [Comparative Example 1] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 10.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0070] [Comparative Example 2] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain P3HB4HB with a copolymerization ratio of 0.6%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0071] [Comparative Example 3] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 8.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0072] [Comparative Example 4] PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain PHBV with a copolymerization ratio of 0.6%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0073] Comparative Example 5 PHA fibers were produced in the same manner as in Example 1, except that the composition conditions of the fermentation raw material and the culture conditions were changed to obtain 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH) with a copolymerization ratio of 6.0%. After production, various physical properties and performance evaluations were carried out as shown in Table 1 below.

[0074]

[0075] [Example 21] A cylindrical knitted fabric was produced using the PHA fiber produced in Example 1. The single yarn fineness was 8 dtex, the total fineness was 96 dtex, the number of filaments was 12, and the softness was rated as "Excellent". The results are shown in Table 2 below.

[0076] [Example 22] PHA fibers were produced in the same manner as in Example 1, except that the spinning rate was adjusted so that the single yarn fineness was 5 dtex and the total fineness was 60 dtex, and a cylindrical knitted fabric was produced. The single yarn fineness was 5 dtex, the total fineness was 60 dtex, and the number of filaments was 12, and the softness was rated as "Excellent". The results are shown in Table 2 below.

[0077] [Example 23] A PHA fiber was produced in the same manner as in Example 1, and a cylindrical knitted fabric was produced, using a nozzle with a hole diameter of 0.2 mm and 36 holes, except that the spinning rate was adjusted so that the single yarn fineness was 2 dtex and the total fineness was 72 dtex. The single yarn fineness was 2 dtex, the total fineness was 72 dtex, and the number of filaments was 36, and the softness was rated "Excellent". The results are shown in Table 2 below.

[0078] [Example 24] A PHA fiber was produced in the same manner as in Example 1, and a cylindrical knitted fabric was produced using a nozzle with a hole diameter of 0.2 mm and 100 holes, except that the spinning rate was adjusted so that the single yarn fineness was 0.5 dtex and the total fineness was 50 dtex. The single yarn fineness was 0.5 dtex, the total fineness was 100 dtex, and the number of filaments was 100, and the softness was rated as "Excellent". The results are shown in Table 2 below.

[0079] [Example 25] A PHA fiber was produced in the same manner as in Example 1, and a cylindrical knitted fabric was produced, using a nozzle with a hole diameter of 0.2 mm and six holes, with the exception that the spinning rate was adjusted so that the single yarn fineness was 15 dtex and the total fineness was 90 dtex. The single yarn fineness was 15 dtex, the total fineness was 90 dtex, and the number of filaments was 6, and the softness was rated "○". The results are shown in Table 2 below.

[0080] [Example 26] PHA fibers were produced in the same manner as in Example 1, except that the spinning rate was adjusted so that the total fineness was 192 dtex, and a cylindrical knitted fabric was produced. The single yarn fineness was 16 dtex, the total fineness was 192 dtex, and the number of filaments was 12, and the softness was evaluated as "○". The results are shown in Table 2 below.

[0081] [Example 27] PHA fibers were produced in the same manner as in Example 1, except that the spinning rate was adjusted so that the total fineness was 252 dtex, and a cylindrical knitted fabric was produced. The single yarn fineness was 21 dtex, the total fineness was 250 dtex, and the number of filaments was 12. Because the total fineness was large, the softness was rated "Fair." The results are shown in Table 2 below.

[0082] [Example 28] A PHA fiber was produced in the same manner as in Example 1, and a cylindrical knitted fabric was produced, except that a nozzle with a hole diameter of 0.2 mm and four holes was used, and the spinning rate was adjusted so that the single yarn fineness was 23 dtex and the total fineness was 92 dtex. The single yarn fineness was 23 dtex, the total fineness was 92 dtex, and the number of filaments was four, and because the number of filaments was small, the softness was rated "Fair." The results are shown in Table 2 below.

[0083] [Example 29] A PHA fiber was produced in the same manner as in Example 1, and a cylindrical knitted fabric was produced, using a nozzle with a hole diameter of 0.2 mm and six holes, with the exception that the spinning rate was adjusted so that the single yarn fineness was 30 dtex and the total fineness was 180 dtex. The single yarn fineness was 30 dtex, the total fineness was 180 dtex, and the number of filaments was 6, and the softness was rated "Fair." The results are shown in Table 2 below.

[0084] [Example 30] A PHA fiber was produced in the same manner as in Example 1, and a cylindrical knitted fabric was produced, using a nozzle with a hole diameter of 0.2 mm and six holes, with the exception that the spinning rate was adjusted so that the single yarn fineness was 35 dtex and the total fineness was 210 dtex. The single yarn fineness was 35 dtex, the total fineness was 210 dtex, and the number of filaments was 6, and the softness was rated "X". The results are shown in Table 2 below.

[0085]

[0086] Example 31 The fibers produced in Example 1 were peeled off by cutting them with scissors in the width direction of the wound central tube, and then cut into 51 mm widths using a measuring cutter (Portable Cutter PC-1Z, Tokyo Ideal Co., Ltd.) to prepare staple fibers. The resulting staple fibers were ring-spun to produce a spun yarn with a British cotton count of 30 / 1 (equivalent to a total fineness of 198 dtex), and a tubular knitted fabric was produced. The softness of the resulting knitted fabric was rated "Fair."

[0087] Example 32 Using the same pellets as in Example 1, a cylinder-type melt extruder (IMC-19F8 manufactured by Imoto Machinery Co., Ltd.) was used. 5 g of pellets were filled into a 6 mm diameter cylinder and extruded through a 2 mm single-hole discharge die at an extrusion rate of 0.5 mm / sec. The pellets were wound around a roller at 23°C and allowed to stand at 23°C for 30 minutes. The fiber was then recovered and stretched 5 times while pressed against a metal pin heated to 60°C to produce a monofilament PHA fiber. The α-structure orientation degree was 89%, and the elongation at break was 190%, making it a highly stretchable yarn. Furthermore, the uniformly obtained fiber was a monofilament fiber with a fineness greater than 200 dtex, resulting in a stiff texture and feel, and the fiber length was only about 8 m at most.

[0088] The continuous filament made from the aliphatic copolymer polyester of the present invention has sufficient marine biodegradability and excellent storage stability. Furthermore, the fiber production method of the present invention enables good unwinding after winding in the form of a fiber, and further enables stable spinning without the occurrence of yarn breakage, thereby improving productivity. As described above, the continuous filament made from the aliphatic copolymer polyester of the present invention has excellent properties in terms of the environment, physical properties, and economy, and can be used in a wide variety of applications.

Claims

1. A continuous long fiber made of an aliphatic copolyester, the aliphatic copolyester containing 3-hydroxybutyrate as a first monomer unit and 4-hydroxybutyrate or 3-hydroxyvalerate as a second monomer unit, wherein when the second monomer unit is a 4-hydroxybutyrate unit, the ratio of the second monomer unit to the total monomer units is 1 mol % or more and 9 mol % or less, and when the second monomer unit is a 3-hydroxyvalerate unit, the ratio of the second monomer unit to the total monomer units is 1 mol % or more and 7.6 mol % or less.

2. The continuous filament fiber according to claim 1, wherein the second monomer unit is 4-hydroxybutyrate, and the ratio of the 4-hydroxybutyrate unit to the total monomer units is 4 mol % or more and 6 mol % or less.

3. The continuous filament fiber according to claim 1 or 2, wherein the degree of X-ray orientation of the α-structure of the aliphatic copolyester is 90% or more.

4. The continuous long fiber according to claim 1 or 2, which has a weight average molecular weight of 150,000 or more and a weight average molecular weight / number average molecular weight ratio of 10 or less.

5. The continuous long fiber according to claim 1 or 2, which has a melting point peak in DSC of 110°C or more and 200°C or less.

6. The continuous long fiber according to claim 1 or 2, wherein the ratio Iβ / Iα of β crystals to α crystals is 0 or more and 0.6 or less.

7. The continuous long fiber according to claim 1 or 2, wherein the total ratio of the first monomer unit and the second monomer unit to the total monomer units is 99 mol % or more.

8. The continuous filament according to claim 1 or 2, having a single filament fineness of 0.1 dtex or more and 30 dtex or less.

9. A multifilament yarn comprising the continuous long fiber according to claim 1 or 2 and having 6 to 300 filaments.

10. The multifilament yarn according to claim 9, having a total fineness of 1 dtex or more and 200 dtex or less.

11. A fabric comprising the continuous filament fiber according to claim 1 or the multifilament yarn according to claim 9.

12. A method for producing continuous long fibers according to claim 1 or 2, comprising the following steps: a melting step of melting an aliphatic copolyester; a discharge step of discharging the molten aliphatic copolyester from a spinneret; and a cold drawing step of cooling the discharged aliphatic copolyester in a cooling medium and drawing it at the same time, wherein the temperature of the cooling medium is 30°C or lower and the draw ratio in the cold drawing step is 4 times or more.

13. The method according to claim 12, wherein an air gap is provided between the spinneret and the cooling medium, and the draft ratio at the air gap is 1.1 or more.

14. The method according to claim 13, wherein the time it takes for the aliphatic copolyester discharged from the spinneret to pass through the air gap is 5 seconds or less.

15. The method according to claim 12, wherein the residence time of the aliphatic copolyester in the melting step is 900 seconds or less.

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