WO2025058065A1 - Continuous long fiber of aliphatic copolymerized polyester, and method for producing same - Google Patents

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

The present invention relates to aliphatic copolyester continuous filaments, multifilament yarns, fabrics, and methods for producing said fibers.

In recent years, environmental problems caused by discarded plastics have come into the spotlight, and there is a strong desire to realize a recycling-oriented society on a global scale. As a result, biodegradable resins that are decomposed by the action of microorganisms after use have attracted attention. Among these biodegradable resins, polyhydroxyalkanoates (hereinafter sometimes abbreviated as "PHA"), which are aliphatic copolymer polyesters and biological polymers, have attracted attention from the perspective of reducing and fixing carbon dioxide emissions (carbon neutrality). Since PHAs are highly biodegradable, particularly in the ocean, their use in various molded products 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 is expected to be great 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 fabrics such as car seats and textiles, sanitary materials such as nonwoven fabrics and filters, building materials such as ropes, and food and other packaging products.

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

The following Patent Document 1 describes a method in which PHA is rapidly cooled to a temperature below the glass transition temperature of the polymer +15°C immediately after being extruded from a melt extruder to release the filaments from blocking, and then cold drawing is performed at a temperature below the glass transition temperature +20°C to rapidly promote partial crystallization, and further a tension heat treatment is performed to improve the mechanical properties.
Furthermore, the following Patent Document 2 describes a method in which, after cold drawing, the film is further drawn at a temperature equal to or higher than the glass transition temperature, and then subjected to tension heat treatment.
These methods have achieved improvements in mechanical properties through improvements in the manufacturing methods.
On the other hand, efforts have been made to further improve the physical properties by improving the molecular design of PHA itself. The following Patent Document 3 describes a fiber using poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter abbreviated as PHBH) which has a conventional 3-hydroxybutyrate as the first component and 3-hydroxyhexanoate as the second component.
Furthermore, the following Patent Document 4 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.

Patent No. 3864187 Patent No. 3864188 Patent No. 5924623 International Publication No. 2020/230807

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 conventional techniques, the problem to be solved by the present invention is to provide a continuous long fiber made of an aliphatic copolyester which has excellent storage stability, can be well unwound after winding, and can be stably spun; and to provide a multifilament yarn and fabric made of such a fiber, and a method for producing the fiber.

The inventors of the present application conducted extensive research and experimentation to find a solution to this problem, and unexpectedly discovered that the problem could be solved by using the following configuration, which led to the completion of the present invention.

That is, the present invention is as follows.
[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 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 ratio of the second monomer unit to all monomer units is 1 mol % or more and 7.6 mol % or less.
[2] The continuous long fiber according to the above [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 long fiber according to the above [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 any one of [1] to [3] above, 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 any one of [1] to [4] above, having a melting point peak of 110° C. or more and 200° C. or less in DSC.
[6] The continuous long fiber according to any one of the above [1] to [5], 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 any one of the above [1] to [6], 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 long fiber according to any one of [1] to [7] above, having a single fiber fineness of 0.1 dtex or more and 30 dtex or less.
[9] A multifilament yarn composed of the continuous long fiber according to any one of [1] to [7] above, having a filament number of 6 to 300.
[10] The multifilament yarn according to [9], having a total fineness of 1 dtex or more and 200 dtex or less.
[11] A fabric composed of the continuous long fiber or multifilament yarn according to any one of [1] to [10] above.
[12] The steps of:
a melting step of melting the 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 the same 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 higher.
[13] The manufacturing method according to [12] above, wherein an air gap is provided between the spinneret and a cooling medium, and a draft ratio in the air gap is 1.1 times or more.
[14] The method according to [13] above, 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 any one of [12] to [14], wherein the residence time of the aliphatic copolyester in the melting step is 900 seconds or less.

The continuous filaments made of the aliphatic copolyester of the present invention have excellent storage stability. In addition, such continuous filaments do not cause the PHA resin to stick during spinning, allowing for good unwinding after winding, and further enabling stable spinning without yarn breakage, improving productivity.

Hereinafter, an embodiment of the present invention will be described in detail.
One embodiment of the present invention is a continuous long fiber made of an aliphatic copolyester, 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 the total monomer units is 1 mol % or more and 9 mol % or less in the case of 4-hydroxybutyrate units, and 1 mol % or more and 7.6 mol % or less in the case of 3-hydroxyvalerate.
The continuous long fiber means a fiber that is continuously spun, and the fiber length may be adjusted by processing using a cutter or the like after spinning. 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 1000 m or more. In addition, a processing agent may be added to the fiber after spinning, such as by applying an oil agent.

The continuous long fiber made of the aliphatic copolyester of this embodiment must have, as the first monomer unit, a monomer unit of 3-hydroxybutyrate represented by [-O-CH( _CH3 ) _-CH2 -CO-], and, as the second monomer unit, a monomer unit of 4-hydroxybutyrate represented by [-O- _CH2 - _CH2 - _CH2 -CO-] or a monomer unit of 3-hydroxyvalerate represented by [-O-CH( _C2H5 )-CH2 _- CO-]. The presence of such a second monomer unit allows _the fiber to have sufficient marine biodegradability, and in addition, it greatly improves moldability while maintaining the mechanical strength derived from the first monomer unit, thereby achieving both strength and elongation within a desired range.

In the continuous long fiber made of the aliphatic copolyester of this embodiment, the ratio of the second monomer unit to the total monomer units (hereinafter, abbreviated 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. By having a copolymerization ratio of 9 mol % or less, sufficient mechanical properties are exhibited. From the viewpoint of ensuring excellent moldability, the lower limit of the copolymerization ratio is 1 mol % or more, preferably 3 mol % or more, and more preferably 4 mol % or more.
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 exhibiting sufficient mechanical properties. 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 or the culture conditions, and the like, but the control method is not particularly limited.

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 to prepare a measurement sample. 1H-NMR measurement is performed using a nuclear magnetic resonance spectrometer (Bruker BioSpin AVANCE II 400) with an observation frequency of 400 MHz, an accumulation number of 64 times, a chemical shift standard of chloroform (chloroform, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 7.26 ppm, and a lock solvent of deuterated chloroform.
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 A, and the integral value of the quartet peak observed at a chemical shift of 5.3±0.2 ppm is B. The copolymerization ratio C (mol %) is calculated by the following formula:
C = (A / 2) / (A / 2 + B) × 100 [mol %]
It is calculated as follows.
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 designated as D, and the integral value of the doublet peak observed at a chemical shift of 1.25 ppm±0.2 is designated as E. The copolymerization ratio F (mol %) is calculated by the following formula:
F = (D/3)/(D/3+E/3) x 100 [mol%]
It is calculated as follows.

The continuous long fiber made of the aliphatic copolyester of this embodiment preferably has a single yarn fineness of 30 dtex or less, more preferably 20 dtex or less, and even more preferably 10 dtex or less, from the viewpoint of realizing a practically appropriate texture and feel. If the single yarn fineness is 30 dtex or less, there may be problems with insufficient fiber strength and yarn breakage during spinning, 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 an acceptable frequency of yarn breakage in practical use, the lower limit of the single yarn fineness is preferably 0.1 dtex or more. The single yarn fineness referred to here can be measured by the following method.

The obtained continuous filaments are made into single yarns and conditioned overnight in a loosely stretched state in an atmosphere of room temperature 23°C and humidity 50% RH. A conditioned sample is cut out to a length of 1m 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.

The continuous long fibers made of the aliphatic copolyester of this embodiment are preferably used for multifilament yarn. The total number of filaments is preferably 6 filaments or more, and more preferably 11 filaments or more, from the viewpoint of realizing a practically appropriate texture and feel while having high mechanical properties. There is no particular upper limit on the total number of filaments, but from the viewpoint of an acceptable frequency of yarn breakage in practical use, 300 filaments or less is preferable.

The multifilament yarn of this embodiment preferably has a total fineness of 200 dtex or less, and 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 an acceptable frequency of yarn breakage in practical use. The total fineness referred to here can be measured by the following method.

The obtained fiber is conditioned overnight in a loosely stretched state in an atmosphere of room temperature 23°C and humidity 50% RH. A conditioned sample is cut out to a length of 1m, 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.

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 here refers to a lamellar crystal structure consisting of a folded spiral structure, and is a high-order structure that greatly contributes to the mechanical strength of the molded body. If the degree of X-ray orientation of the α structure is 90% or more, sufficient mechanical properties, especially strength, are expressed, and the molded body has excellent storage stability, and the sticking caused by the amorphous structure on the surface of the molded body is also eliminated, resulting in good unwinding properties in the fiber form. There is no particular upper limit, but a realistic degree of orientation is 99% or less. In order to achieve an X-ray orientation degree of 90% or more of the α structure, it is important to manufacture the aliphatic copolyester of this embodiment under the manufacturing conditions described below.

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 is Cu, the collimator diameter is 0.1 mm, the X-ray wavelength is 0.1 nm, the camera length is 27 mm, the exposure time is 10 min, and the test piece is placed perpendicular to the X-ray beam and parallel to the detector to obtain a two-dimensional diffraction image. In the wide-angle X-ray diffraction (WAXD) measurement, the range of diffraction angles 2θ = 15 ° to 18 ° in the WAXD image measured is separated as the (020) plane diffraction peak, and the region including the (020) plane diffraction peak is selected in a ring shape, and all the diffraction intensities having the same azimuth angle are integrated, and this intensity is plotted against the azimuth angle to create an azimuth angle one-dimensional profile. The full width at half maximum (FWHM: 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[%]
It is calculated as follows.

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 practical stable molding processing.

The weight average molecular weight/number average molecular weight 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. If the weight average molecular weight/number average molecular weight 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 is preferably 1.1 or more.

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 are a guard column (Tosoh TSKgel guardcolumn SuperHZ-L) and an analytical column (Tosoh TSKgel SuperHZM-M). The column temperature is 40°C, the eluent is chloroform, the flow rate is 0.35mL/min, the injection amount is 20uL, 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.

The melting point peak of the continuous long fiber made of the aliphatic copolyester of this embodiment is preferably 110°C or higher, more preferably 130°C or higher, from the viewpoint of ensuring practical heat resistance. If the melting point peak is too high, the difference with the thermal decomposition temperature is small, making stable melting difficult, so the upper limit of the melting point peak is preferably 200°C or lower, more preferably 180°C or lower, from the viewpoint of the limit that can be obtained by practically stable spinning.

The melting point peak 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 the sample. Then, the sample is quenched from 200°C to -50°C at 20°C/min, held for 3 minutes, and heated again to 200°C at 20°C/min (this heating is called the second run). The melting point peak is measured by the DSC curve (thermogram) measured in the second run. Note that as the heating continues, a melting peak (endothermic peak) appears on the DSC curve, and the temperature at the apex of the peak is taken as the melting point. The sample is about 5 mg, and an aluminum sample pan is used. Indium is used for temperature calibration.

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 storage stability is excellent.

The X-ray diffraction intensity ratio Iβ/Iα of the β structure to the α structure 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 is Cu, the collimator diameter is 0.1 mm, the wavelength of X-rays is 0.1 nm, the camera length is 27 mm, the exposure time is 10 min, the test piece is placed perpendicular to the X-ray beam and parallel to the detector, and a two-dimensional diffraction image is obtained. When the diffraction intensity distribution in the equatorial direction of the two-dimensional diffraction image is measured, the diffraction intensity is composed of scattering due to amorphous and diffraction due to crystals. Diffraction due to crystals includes diffraction of α structure and β structure, each of which generates diffraction 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 regarding the amount of β structure can be obtained. However, since the intensity based on the scattering of amorphous interferes, in order to determine the amount of β structure in the crystal, it is necessary to remove the influence of the intensity based on the scattering of amorphous. 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°, where the influence of diffraction from crystals is small, is regarded as 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 the diffraction angles 2θ=15° and 18° is regarded as the diffraction intensity from the α structure (Iα), and the maximum value between the diffraction angles 18° and 21° is regarded as the diffraction intensity from the β structure (Iβ). The ratio of the two, Iβ/Iα, is regarded as the X-ray diffraction intensity ratio of the β structure to the α structure.

The synthesis method of the aliphatic copolymer polyester is not particularly limited, but it is preferably produced from a microorganism, and an example of a microorganism that produces an aliphatic copolymer polyester is a microorganism capable of producing PHAs.For example, as a P3HB producing bacterium, the first was Bacillus megaterium, discovered in 1925, and other natural microorganisms such as Cupriavidus necator, (old classification: Alcaligenes eutrophus, Ralstonia eutropha), and Alcaligenes latus are known, and PHA is accumulated in the bacterial body in these microorganisms.In addition, 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.

The continuous filaments made of the aliphatic copolyester of this embodiment can be made into a 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/ ^m2 .

As the PHAs, granules containing the PHAs may be used without purification, or may be purified and pelletized. In order to improve moldability in melt extrusion, the PHAs may contain a plasticizer, a lubricant, or a crystal nucleating agent, or may be blended with other polymers.
The 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 or screw extrusion, but screw extrusion is preferred in order to produce continuous long fibers.
The temperature during melt extrusion is usually equal to or higher than the melting point onset peak of the PHA measured by DSC, from the viewpoint of enabling extrusion and performing sufficient stretching after extrusion.

The molten PHA is extruded into a cooling medium, quenched, and fiberized. The temperature for quenching and fiberization is preferably 30°C or lower, more preferably 20°C or lower. There is no particular lower limit, but from an economical standpoint, it can usually be performed at -200°C or higher. This quenching process turns the molten PHA into an amorphous fiber with high extensibility, and also suppresses deterioration over time during the process. The obtained fiber can be stretched and wound up in the cooling solvent.

The cooling medium is not particularly limited, but examples thereof include air, water (ice water), inert gas, and antifreeze solutions mainly composed of ethylene glycol or propylene glycol. The cooling method is not particularly limited, but examples thereof include a method in which a bath is filled with a cooling medium and the PHA is passed through it, a method using a fluidized bath, a method using a cooling plate, a method using a cooling ring that can apply cold air uniformly to the fibers from all directions at 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 rollers in the bath.

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, and preferably by drawing the fiber with two drawing rollers while applying tension by using a speed difference. The drawing ratio is preferably 4 times or more, more preferably 7 times or more, and even more preferably 10 times or more. There is no particular upper limit as long as the fiber does not break, but it can be 50 times or less. From the viewpoint of productivity, the drawing time is preferably 1 minute or less, and more preferably 30 seconds or less. There is no particular lower limit, but in practice the drawing can be performed for 0.001 seconds or more.

The stretch ratio can be measured by the following method.
A 10 cm length of the fiber is taken just before stretching and just after stretching. The obtained fiber is conditioned overnight in a loosely stretched state in an atmosphere of room temperature 23°C and humidity 50% RH. The weight of 10 points of the conditioned sample is measured and the number average value is calculated. The value just before stretching is divided by the value just after stretching to obtain the stretch ratio.

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 blowing air 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 moderate crystallization on the surface and suppresses adhesion of the fiber surface, enabling good unwinding after winding of the continuous long fiber. In addition, adjusting the crystallization and crystal growth of the fiber improves mechanical properties and productivity. There are no particular limitations on the temperature of the air gap, but it can usually be performed in the range of 0°C to 100°C.

In the air gap, the fibers are stretched and oriented appropriately due to the difference in speed between the extrusion linear speed and the winding speed in the next 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. By setting the draft ratio at 1.1 times or more, orientation crystallization due to moderate drawing proceeds, so that the fiber surface crystallizes and sticking can be suppressed. In addition, yarn breakage in the subsequent cold drawing process can be suppressed, and sufficient drawing treatment can be performed, resulting in sufficient mechanical strength. There is no particular upper limit for the draft ratio, but it can usually be performed at 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. By setting the time for passing through to 5 seconds or less, excessive crystallization of the molten resin can be suppressed, and the degree of orientation of the α-structure can be effectively increased in the cold drawing step, sufficient mechanical strength can be achieved, and embrittlement due to excessive crystallization can be suppressed, thereby suppressing yarn breakage in the air gap. There is no particular lower limit for the time for which the fibers pass through the air gap, but in practice, the time can be set to 0.0001 seconds or more.

When PHAs are heated, melted, and pressed out of the 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. If the residence time in the extrusion port is 900 seconds or less, the molecular weight reduction caused by thermal decomposition of the resin can be suppressed, and sufficient mechanical strength is achieved. There are no particular limitations on the extrusion method, but examples include extrusion using a syringe, extrusion using a single screw, and extrusion using a twin screw.

The obtained fiber can be subjected to another process as long as it does not affect the mechanical strength or storage stability. The other process is not particularly limited, but examples include aligned winding, twill winding, and re-stretching after winding is completed. In addition, by heat treating the fiber, the crystallinity and crystal structure of the fiber can be stabilized, which stabilizes the mechanical strength and increases the storage stability. The heat treatment method is not particularly limited, but the heat treatment can be performed continuously by arranging a hot bath, heated rollers, tunnel-type drying oven, etc. during the process, or the fiber after winding can be left to stand in a dryer or thermostatic chamber and heat treated.

The present invention will be described in detail below with reference to examples and comparative examples. Various physical properties and performance evaluations were performed by the following methods.
<Physical property evaluation>
(1) [Ratio of second monomer units to total monomer units (copolymerization ratio)]
The aliphatic copolyester 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) with an observation frequency of 400 MHz, an accumulation number of 64, a chemical shift standard of chloroform at 7.26 ppm, and a lock solvent of deuterated chloroform.
In the case where 4-hydroxybutyrate is contained as the second monomer unit, the integral value of the triplet peak observed at a chemical shift of about 4.1 ppm is A, and the integral value of the quartet peak observed at a chemical shift of about 5.3 ppm is B. The copolymerization ratio C (mol %) is calculated by the following formula:
C = (A / 2) / (A / 2 + B) [mol %]
The calculation was made as follows.
In the case where 3-hydroxyvalerate is contained as the second monomer unit, the integral value of the triplet peak observed at a chemical shift of about 0.88 ppm is defined as D, the integral value of the doublet peak observed at a chemical shift of about 1.25 ppm is defined as E, and the copolymerization ratio F (mol %) is calculated by the following formula:
F = (D/3)/(D/3+E/3) [mol %]
The calculation was made as follows.

(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 to obtain a two-dimensional diffraction image. In the wide-angle X-ray diffraction (WAXD) measurement, the diffraction angle 2θ range from 15° to 18° in the WAXD image measured was separated as a (020) plane diffraction peak, and the region including 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 an azimuth angle one-dimensional profile. The full width at half maximum (FWHM: peak width at half the height of the peak) of the peak at the location where the diffraction point 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 using the following formula:
G=(180-H)/180×100[%]
The calculation was made as follows.

(3) [Weight average molecular weight (Mw) and weight average molecular weight (Mw)/number average molecular weight (Mn)]
Aliphatic copolymer polyester was 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) was used, and a guard column (Tosoh TSKgel guardcolumn SuperHZ-L) and an analytical column (Tosoh TSKgel SuperHZM-M) were used as columns. The column temperature was 40°C, the eluent was chloroform, the flow rate was 0.35mL/min, the injection amount was 20uL, and the detector was RI. A polystyrene standard (Agilent Technologies EasiCal PS-1) was measured, and a calibration curve was created using data processing software (Tosoh HLC-8320GPC Ecosec-WS). The samples of the aliphatic copolyester molded articles were also measured in the same manner, and the weight average molecular weight and the number average molecular weight were calculated from the calibration curve.

(4) [Melting point peak]
The 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. Then, the sample was quenched 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 the second run). The melting point peak was measured using the DSC curve (thermogram) measured in the second run. As the heating continued, a melting peak (endothermic peak) appeared on the DSC curve, so the temperature at the apex of the peak was taken as the melting point. The sample was about 1 mg, and an aluminum sample pan was used. Indium was used for temperature calibration.

(5) [X-ray diffraction intensity ratio Iβ/Iα of β structure and α structure]
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 to obtain a two-dimensional diffraction image. 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 angles 2θ = 15 ° and 18 ° was taken as the diffraction intensity from the α structure (Iα), and the maximum value between the diffraction angles 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 X-ray diffraction intensity ratio of the β structure and the α structure.

<Performance evaluation>
(6) [Breaking strength and breaking elongation]
According to the method defined in JIS L 1013, the fiber was loosely stretched and attached to the grip of a Tensilon universal testing machine (RTG-1250) manufactured by A&D Co., Ltd., and a tensile test was performed using a 50N load cell with 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 according to the following formulas:
Strength (cN/dtex) = Strength at break or strength at maximum load (cN) / Fineness of sample (dtex)
Elongation (%) = elongation at break or elongation at maximum load (mm) / grip interval (mm) x 100
The number average values were used as the strength (average strength) and elongation of the sample. When the breaking strength was smaller than the strength at the maximum load, the strength at the maximum load and the elongation at that time were measured.

(7) [Stable spinning time]
The time until all the filaments could not be wound due to breakage of the filaments or poor discharge from the extrusion section was measured, and this time was taken as the stable spinning time (min.). When stable spinning was possible for longer than 60 minutes, it was recorded as >60 min.

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

(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 breaking strength was below 150 MPa or the average breaking elongation was above 150%, the number of weeks of storage up to that point was regarded as the storage stability. When the storage stability exceeded 48 weeks, it was regarded as >48 weeks.

(10) [Softness of tubular knitted fabric]
A fiber sample was fed into a cylindrical knitting machine (Eiko Sangyo's single-end test cylindrical knitting machine NCR-ES), and a cylindrical knitted fabric was produced by adjusting the stitch count to 50 on the cylindrical knitting machine. Five subjects were asked to pass through the obtained cylindrical knitted fabric, and each subject answered a questionnaire about its softness. Fabrics that felt soft when passed through the hand were evaluated as having excellent softness, with 5 subjects rating it as excellent with an ⊚, 4 subjects rating it as excellent with an ◯, 3 subjects rating it as excellent with an △, and 2 or less subjects rating it as excellent with an X.

[Example 1]
As a microorganism for producing PHAs, Cupriavidus necator H16 strain (ATCC17699 strain) was used, and pellets of PHA produced by appropriately adjusting the raw material and culture conditions were used. The obtained PHA was P3HB4HB, and the copolymerization ratio was 6.0%.
The pellets were melt extruded with a residence time of 600 seconds using a melt extruder (ALM-E005-H manufactured by AIKI Liotech) heated to 170°C, spun using a nozzle with a hole diameter of 0.2 mm and 12 holes, passed through an air gap in 3 seconds while being drafted at 1.5 times in the air gap, cooled in a cooling process at 5°C, stretched at a draw ratio of 7 times in the cooling process, and finally wound up with a winder. The sample was placed in a blower dryer (DKM401 manufactured by Yamato Scientific) set at 60°C, left to stand for 30 minutes, and then taken out to produce a 1000 m long multifilament continuous long fiber. After production, various physical properties and performance evaluations were performed as shown in Table 1 below.

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

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

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

[Example 5]
Except for changing the composition conditions of the fermentation raw material and the culture conditions to obtain P3HB4HB with a copolymerization ratio of 7.0%, PHA fibers were produced in the same manner as in Example 1. After production, various physical properties and performance evaluations were performed as shown in Table 1 below.

[Example 6]
Except for changing the composition conditions of the fermentation raw material and the culture conditions to obtain P3HB4HB with a copolymerization ratio of 1.0%, PHA fibers were produced in the same manner as in Example 1. After production, various physical properties and performance evaluations were performed as shown in Table 1 below.

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

[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.

[Example 9]
Except for changing the air gap time to 1 second, 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.

[Example 10]
Except for changing the residence time in the extrusion section to 300 seconds, 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.

[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.

[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.

[Example 13]
Except for changing the air gap time to 7 seconds, 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.

[Example 14]
Except for changing the residence time to 1000 seconds, 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.

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

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

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

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

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

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

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

[Comparative Example 2]
Except for changing the composition conditions of the fermentation raw materials and the culture conditions to obtain P3HB4HB with a copolymerization ratio of 0.6%, PHA fibers were produced in the same manner as in Example 1. After production, various physical properties and performance evaluations were performed as shown in Table 1 below.

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

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

[Comparative 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 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH) with a copolymerization ratio of 6.0%. After production, various physical properties and performance evaluations were performed as shown in Table 1 below.

[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 "A". The results are shown in Table 2 below.

[Example 22]
A PHA fiber was 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, the number of filaments was 12, and the softness was "◎". The results are shown in Table 2 below.

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

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

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

[Example 26]
A PHA fiber was 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, the number of filaments was 12, and the softness was "○". The results are shown in Table 2 below.

[Example 27]
A PHA fiber was 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. Since the total fineness was large, the softness was rated as "Δ". The results are shown in Table 2 below.

[Example 28]
A PHA fiber was produced in the same manner as in Example 1, 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. A cylindrical knitted fabric was produced using the same method as in Example 1. The single yarn fineness was 23 dtex, the total fineness was 92 dtex, and the number of filaments was four, and the softness was "Δ" because the number of filaments was small. The results are shown in Table 2 below.

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

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

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

[Example 32]
Using the same pellets as in Example 1, a cylinder-type melt extrusion device (IMC-19F8 manufactured by Imoto Manufacturing Co., Ltd.) was used, 5 g of pellets were filled in a cylinder with a diameter of 6 mm, and extruded from a single-hole discharge die with a diameter of 2 mm at an extrusion speed of 0.5 mm/sec. The fibers were wound around a roller at 23°C, and left to stand at 23°C for 30 minutes in the wound state, after which the fibers were recovered and stretched 5 times while being pressed against a metal pin heated to 60°C to produce monofilament PHA fibers. The degree of α-structure orientation was 89%, and the elongation at break was 190%, making it a highly elastic yarn. In addition, the uniformly obtained fibers were monofilament fibers with a fineness of more than 200 dtex, so the texture and feel were hard, and the fiber length was at most about 8 m.

The continuous filaments made from the aliphatic copolyester of the present invention have sufficient marine biodegradability and excellent storage stability. Furthermore, the fiber manufacturing method of the present invention allows for good unwinding after winding in fiber form, and further allows for stable spinning without yarn breakage, improving productivity. From the above, the continuous filaments made from the aliphatic copolyester of the present invention have excellent characteristics in terms of the environment, physical properties, and economy, and can be used in a wide variety of applications.

Claims (15)

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, the ratio of the second monomer unit to the total monomer units being 1 mol% or more and 9 mol% or less when the second monomer unit is a 4-hydroxybutyrate unit, and the ratio of the second monomer unit to the total monomer units being 1 mol% or more and 7.6 mol% or less when the second monomer unit is a 3-hydroxyvalerate unit. The continuous long fiber according to claim 1, wherein the second monomer unit is 4-hydroxybutyrate, and the ratio of the 4-hydroxybutyrate units to the total monomer units is 4 mol% or more and 6 mol% or less. The continuous long fiber according to claim 1 or 2, in which the degree of X-ray orientation of the α-structure of the aliphatic copolyester is 90% or more. The continuous long fiber according to claim 1 or 2, 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. The continuous long fiber according to claim 1 or 2, having a DSC melting point peak of 110°C or more and 200°C or less. The continuous long fiber according to claim 1 or 2, in which the ratio Iβ/Iα of β crystals to α crystals is 0 or more and 0.6 or less. 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. The continuous filament fiber according to claim 1 or 2, having a single filament fineness of 0.1 dtex or more and 30 dtex or less. 　A multifilament yarn made of the continuous long fiber according to claim 1 or 2, the number of filaments being 6 or more and 300 or less. The multifilament yarn according to claim 9, having a total fineness of 1 dtex or more and 200 dtex or less. A fabric made of the continuous long fiber described in claim 1 or the multifilament yarn described in claim 9. The following steps:
a melting step of melting the 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 the same at the same time.
3. The method for producing continuous long fibers according to claim 1 or 2, 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. The manufacturing method according to claim 12, in which 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. The manufacturing 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. The method according to claim 12, wherein the residence time of the aliphatic copolyester in the melting step is 900 seconds or less.