Method for producing fibers

Abstract

The present invention provides a method for producing poly(3-hydroxyalkanoate)-based resin-containing fibers, the method being capable of suppressing fusion bonding while improving fiber productivity. The present invention is a method for producing poly(3-hydroxyalkanoate)-based fibers, the method comprising: a step (A) for melting a raw material composition containing a poly(3-hydroxyalkanoate)-based resin and a filler to obtain a molten composition; a step (B) for obtaining molten precursor yarn by discharging the molten composition from discharge holes; a step (C) for cooling the molten precursor yarn in an atmosphere at or below the crystallization temperature of the poly(3-hydroxyalkanoate)-based resin; and a step (D) for passing the cooled precursor yarn through an atmosphere of 120-170°C.

Description

Method for producing fibers

[0001] The present invention relates to a method for producing fibers.

[0002] In recent years, there has been a problem that plastic waste imposes a large burden on the global environment, such as impacts on ecosystems, generation of harmful gases during combustion, and global warming caused by a large amount of combustion heat. Development of biodegradable plastics has been actively pursued as a means to solve this problem.

[0003] Among such biodegradable plastics, carbon dioxide generated when a biodegradable plastic obtained using plant-derived raw materials is combusted was originally present in the air, so carbon dioxide in the atmosphere does not increase. This property is called carbon neutral, and it has been regarded as important under the Kyoto Protocol, which sets carbon dioxide reduction targets, and active use thereof is desired.

[0004] Recently, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester resins have attracted attention as biodegradable plastics produced by microorganisms using plant-derived raw materials as a carbon source, and poly(3-polyhydroxyalkanoate) resins have particularly attracted attention.

[0005] As a method for producing fibers containing a poly(3-polyhydroxyalkanoate) resin, a method for producing a multifilament, which comprises a step (A) of obtaining a melt by heating and melting a raw material composition containing a poly(3-polyhydroxyalkanoate) resin, discharging the melt from discharge holes to obtain a plurality of undrawn yarns in a molten state, and a step (B) of blowing gas to the plurality of undrawn yarns, has been disclosed, for example, in Patent Document 1.

[0006] International Publication No. WO 2024 / 090257

[0007] However, poly(3-polyhydroxyalkanoate) resins have a slow crystallization rate, and in the manufacturing process of poly(3-polyhydroxyalkanoate) resin-containing fibers, the surface of the filament may not solidify sufficiently, resulting in the filament fusing and sticking to manufacturing equipment such as rolls in a sticky state. This can reduce the filament's runability and decrease fiber productivity. Furthermore, if the fiber is a multifilament containing multiple single fibers, the single fibers may fuse together.

[0008] Therefore, the object of the present invention is to provide a method for producing poly(3-hydroxyalkanoate) resin-containing fibers that can suppress fusion while improving the productivity of the fibers.

[0009] Through diligent research, the inventors discovered that by cooling molten yarn in an atmosphere below a predetermined temperature and then passing the cooled yarn through an atmosphere within a predetermined temperature range, it is possible to improve fiber productivity while suppressing fusion, thus completing the present invention.

[0010] In other words, the present invention relates to a method for producing poly(3-hydroxyalkanoate) fibers, comprising the steps of: (A) melting a raw material composition containing a poly(3-hydroxyalkanoate) resin and a filler to obtain a molten composition; (B) discharging the molten composition from an discharge hole to obtain molten yarn; (C) cooling the molten yarn in an atmosphere below the crystallization temperature of the poly(3-hydroxyalkanoate) resin; and (D) passing the cooled yarn through an atmosphere of 120 to 170°C.

[0011] According to the present invention, a method for producing poly(3-hydroxyalkanoate) resin-containing fibers is available that can improve fiber productivity while suppressing fusion.

[0012] Schematic diagram of the apparatus used in steps (A) to (D) of this embodiment. Schematic diagram of the apparatus used in step (E) of this embodiment.

[0013] The following describes one embodiment of the present invention.

[0014] The method for producing poly(3-hydroxyalkanoate) fibers according to this embodiment includes the steps of: (A) melting a raw material composition containing a poly(3-hydroxyalkanoate) resin and a filler to obtain a molten composition; (B) extruding the molten composition from an extrusion hole (hereinafter also referred to as "hole") to obtain molten yarn; (C) cooling the molten yarn in an atmosphere below the crystallization temperature of the poly(3-hydroxyalkanoate) resin; and (D) passing the cooled yarn through an atmosphere of 120 to 170°C.

[0015] (Poly(3-hydroxyalkanoate) resin) The raw material composition contains the poly(3-hydroxyalkanoate) resin (hereinafter also referred to as "P3HA"). Examples of the poly(3-hydroxyalkanoate) resin include poly(3-hydroxybutyrate) copolymers containing 3-hydroxybutyrate units and other hydroxyalkanoate units, and poly(3-hydroxybutyrate) homopolymers (abbreviated as P3HB). Examples of the poly(3-hydroxybutyrate) copolymer include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviated as P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviated as P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviated as P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate). These may be used individually or in combination of two or more. From the viewpoint of further improving fiber productivity while further suppressing fusion, the poly(3-hydroxyalkanoate) copolymer is preferred as the poly(3-hydroxybutyrate) resin, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is more preferred.

[0016] When the poly(3-hydroxyalkanoate) resin is a poly(3-hydroxybutyrate) copolymer, from the viewpoint of further improving fiber productivity while further suppressing fusion, the poly(3-hydroxyalkanoate) resin contains 3-hydroxybutyrate units in an amount of preferably 80 mol% or more, more preferably 85.0 mol% to 99.5 mol%, and even more preferably 85.0 mol% to 97.0 mol% of 100 mol% of the total monomer constituent units. The content ratio of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin can be determined by the method described in the examples below.

[0017] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is preferably 3.0 × 10⁻¹⁴, from the viewpoint of further improving fiber productivity while further suppressing fusion. ５ ~7.0 x 10 ５ More preferably 3.5 × 10 ５ ~7.0 x 10 ５ More preferably 4.0 × 10 ５ ~7.0 x 10 ５ Most preferably 4.5 × 10 ５ ~6.5 x 10 ５ That is the case.

[0018] In this embodiment, the weight-average molecular weight refers to the molecular weight measured from the polystyrene-equivalent molecular weight distribution using gel permeation chromatography (GPC) with chloroform eluent. For the GPC column, any column suitable for measuring the molecular weight should be used. For example, the column temperature can be set to 40°C, 10 μl of a solution containing 3 mg of the target substance dissolved in 2 ml of chloroform can be injected, and the flow rate of the chloroform eluent (mobile phase) can be set to 1.0 ml / min to determine the weight-average molecular weight (Mw). A Shimadzu 20A (manufactured by Shimadzu Corporation) can be used as the GPC apparatus, and a Shodex K-806M (manufactured by Showa Denko) can be used as the column.

[0019] The raw material composition contains poly(3-hydroxyalkanoate) resin, preferably more than 50% by weight and not more than 100% by weight, more preferably 80 to 100% by weight, and even more preferably 90 to 100% by weight.

[0020] (Filler) The raw material composition contains the filler. By including the filler in the raw material composition, fiber productivity can be improved while suppressing fusion. It is believed that the filler increases the surface roughness of the yarn A and the fibers, and as a result, fusion is suppressed. Examples of the filler include carbon black and talc. These may be used individually or in combination of two or more. Carbon black and talc are preferred as the filler, and carbon black is particularly preferred.

[0021] The median diameter (D50) of the filler is preferably 10 to 500 nm, more preferably 20 to 400 nm, and even more preferably 50 to 200 nm. A median diameter of 500 nm or less makes the filament A less prone to breakage, facilitating the production of fibers. A median diameter of 10 nm or more suppresses the aggregation of carbon black, making the carbon black easier to handle. The median diameter can be determined by the method described in the examples below.

[0022] In the raw material composition, the content of the filler is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and even more preferably 0.5 to 2 parts by weight, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. When the content of the filler is 0.01 parts by weight or more, the surface of the fibers is further given an unevenness, which further improves the peelability from manufacturing equipment such as rolls, and in the case of multifilaments, the fusion of single fibers can be suppressed. When the content of the filler is 10 parts by weight or less, there is a sufficient amount of resin component per cross-sectional area of ​​the yarn, so the yarn can easily follow shape changes when stretched, and the breakage of the yarn is further suppressed.

[0023] (Additives) The raw material composition may contain additives that can be used together with the poly(3-hydroxyalkanoate) resin and filler, to the extent that they do not impair the effects of the invention. Examples of such additives include crystal nucleating agents, lubricants, plasticizers, spinning oils, stabilizers (antioxidants, UV absorbers, etc.), colorants (dyes, pigments, etc.), and antistatic agents.

[0024] To promote the crystallization of poly(3-hydroxyalkanoate) resin, the raw material composition preferably contains a crystal nucleating agent. The inclusion of a crystal nucleating agent in the raw material composition promotes the crystallization of poly(3-hydroxyalkanoate) resin, making it easier to obtain fibers. Examples of the crystal nucleating agent include sugar alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, due to their excellent effect in promoting the crystallization of poly(3-hydroxyalkanoate) resin. These may be used individually or in combination of two or more.

[0025] From the viewpoint of further promoting the crystallization of the poly(3-hydroxyalkanoate) resin and lowering the viscosity of the molten composition, thereby facilitating the production of fibers, the content of the crystal nucleating agent in the raw material composition is preferably 0.05 to 10 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. The lower limit is more preferably 0.1 parts by weight or more, and even more preferably 0.5 parts by weight or more. The upper limit is preferably 10 parts by weight or less, more preferably 8 parts by weight or less, and even more preferably 5 parts by weight or less.

[0026] The raw material composition may contain a lubricant. Examples of the lubricant include compounds having an amide bond. Preferably, the compounds having an amide bond include one or more selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0027] From the viewpoint of providing excellent lubricity for the single fibers and suppressing the bleed-out of the lubricant to the fiber surface, the lubricant content in the raw material composition is preferably 0.05 to 12 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. The lower limit is more preferably 0.1 parts by weight or more, and even more preferably 0.5 parts by weight or more. The upper limit is more preferably 10 parts by weight or less, even more preferably 8 parts by weight or less, and most preferably 5 parts by weight or less.

[0028] The above-mentioned steps (A) to (D) will be explained below with reference to Figure 1.

[0029] (Step (A)) In step (A), the raw material composition is melted to obtain a molten composition. In the embodiment shown in Figure 1, the raw material composition is put into a raw material hopper 1, and the raw material composition put into the raw material hopper 1 is melted by heating in an extruder 2 to obtain a molten product which is the molten raw material composition. When putting the raw material composition into the raw material hopper 1, materials other than the filler may be melted to obtain raw material pellets, and the raw material pellets and the filler may be put into the raw material hopper 1. Examples of the extruder 2 include a single-screw extruder and a twin-screw extruder. The melting temperature for melting the raw material composition is preferably 155 to 185°C, and more preferably 160 to 180°C. When the extrusion temperature is 155°C or higher, the poly(3-hydroxyalkanoate) resin is sufficiently melted, increasing the fluidity of the molten product and making it easier to spin. When the extrusion temperature is 180°C or lower, the decrease in molecular weight of the poly(3-hydroxyalkanoate) resin due to thermal decomposition is less likely to occur, and fusion can be further suppressed.

[0030] (Step (B)) In step (B), the molten composition is discharged from the discharge hole to obtain molten yarn. In the embodiment shown in Figure 1, the molten material is discharged from the discharge hole 4a of the spinning nozzle 4 to obtain molten yarn A. The spinning nozzle 4 has one or more discharge holes 4a, preferably 12 or more, more preferably 30 to 10,000, more preferably 40 to 5,000, and even more preferably 50 to 3,000. The flow rate of the molten material discharged from the spinning nozzle 4 is preferably 1.0 to 20 kg / h, more preferably 2.0 to 15 kg / h. The flow rate of the molten material discharged from the spinning nozzle 4 can be adjusted by the gear pump 3.

[0031] (Step (C)) In step (C), the molten yarn is cooled in an atmosphere below the crystallization temperature of the poly(3-hydroxyalkanoate) resin. In the embodiment shown in Figure 1, the molten yarn A is cooled in the first box 5a of the quench section 5 in an atmosphere below the crystallization temperature of the poly(3-hydroxyalkanoate) resin. This promotes the crystallization of the poly(3-hydroxyalkanoate) resin in the yarn A, making the yarn A less likely to break. The crystallization temperature of the poly(3-hydroxyalkanoate) resin is usually around 50 to 80°C. Furthermore, in step (C), it is preferable to cool the molten yarn A in an atmosphere of 10 to 35°C, and more preferably in an atmosphere of 15 to 25°C. By keeping the atmosphere temperature above 10°C, the productivity of the fibers is further improved, and fusion is further suppressed. By keeping the ambient temperature below 35°C, the raw yarn A becomes even more resistant to breakage.

[0032] In step (C) above, it is preferable to cool the molten yarn A by blowing a gas onto it. This allows the yarn A to be sufficiently cooled. Examples of the gas include air, inert gas (nitrogen gas, argon gas, etc.), and water vapor. Examples of blowing methods include the circular method and the back method. The back method is a method in which the gas is blown onto the yarn A from one direction within the first box 5a in a longitudinal view of the yarn A (a cross-sectional view of the yarn A perpendicular to the longitudinal direction of the yarn A). The circular method is a method in which the gas is blown onto the yarn A by using the first box 5a having a cylindrical side wall and blowing the gas spirally into the cylindrical first box 5a along the inner circumferential surface of the cylindrical side wall. The flow direction of the yarn A is approximately parallel to the virtual axis of the cylindrical side wall. The circular method is preferred as the blowing method. The circular method allows for relatively uniform application of gas to the yarn A, resulting in more uniform cooling of the yarn A and suppression of variations in the fineness of the yarn A.

[0033] The gas velocity is preferably 0.01 m / s or more and less than 0.10 m / s, and more preferably 0.01 m / s or more and 0.09 m / s or less. Note that the gas velocity refers to the gas velocity immediately before it strikes the yarn A. When the gas velocity is less than 0.10 m / s, the yarn A is less likely to break when taken up by the take-up roll even if the speed of the take-up roll is increased, and as a result, the productivity of the fibers can be further improved. When the gas velocity is 0.01 m / s or more, the molten yarn A can be sufficiently cooled by the gas. As a result, the molten yarn A is less likely to break, and the productivity of the fibers can be further improved.

[0034] (Process (D)) In process (D), the cooled yarn is passed through an atmosphere of 120 to 170°C, preferably 125 to 170°C, more preferably 135 to 170°C, even more preferably 140 to 170°C, and particularly preferably 145 to 170°C. By having an atmosphere temperature of 120°C or higher, the stickiness (tackiness) of the yarn is reduced, which can improve the productivity of the fibers while suppressing fusion. By having an atmosphere temperature of 170°C or lower, the melting of the yarn can be suppressed. In the embodiment shown in Figure 1, the cooled yarn is passed through an atmosphere of 120 to 170°C in the second box 6. The yarn is then taken up by the first take-up roll 8 and wound onto the core 11 by the first winding machine 10.

[0035] From the viewpoint of further increasing fiber productivity, the spinning draft is preferably 50 to 1500, and more preferably 100 to 1000. The spinning draft can be determined by the method described in the examples below.

[0036] (Step (E)) The method for producing poly(3-hydroxyalkanoate) fibers according to this embodiment may further include a step (E) of stretching the fibers after step (D). In step (E), in the embodiment shown in Figure 2, the fibers B are taken from the feed roll 12 by the second take roll 13, stretched between the second take roll 13 and the third take roll 14, and wound up by the second winding machine 16. The speed of the second winding machine 16 may also be lower than the speed of the third take roll 14 (a relaxation treatment may be performed).

[0037] The stretching ratio in step (E) can be set as appropriate, preferably 120 to 400%, and more preferably 160 to 330%. The stretching ratio can be calculated by the following formula: Stretching ratio (%) = Speed ​​of the third take-up roll 14 (m / min) / Speed ​​of the second take-up roll 13 (m / min) × 100 (%)

[0038] Furthermore, the final draw ratio can be appropriately set, and is preferably 110 to 380%, more preferably 150 to 300%. The final draw ratio can be obtained by the following formula. Final draw ratio (%) = Speed of second winder (m / min) / Speed of second take-up roll 13 (m / min) × 100 (%)

[0039] The speed of the second take-up roll 13 refers to the length of the fiber taken up by the second take-up roll 13 per unit time. The speed of the third take-up roll 14 refers to the length of the fiber taken up by the third take-up roll 14 per unit time. The speed of the second winder 16 refers to the length of the fiber wound by the second winder 16 per unit time.

[0040] (Fiber) The fiber may contain one or two or more single fibers (hereinafter also referred to as "monofilaments"). That is, the fiber may be a multifilament or a monofilament. The multifilament has two or more monofilaments, preferably 12 or more, more preferably 30 to 10000, further preferably 40 to 5000, and still more preferably 50 to 3000 monofilaments.

[0041] The fineness of the single fiber of the fiber is preferably 1.0 to 15 dtex, more preferably 1.5 to 15 dtex, and still more preferably 2.0 to 15 dtex. When the fineness of the single fiber is 15 dtex or less, the fiber has an advantage that it can be used for various applications. When the fineness of the single fiber is 1.0 dtex or more, the fiber becomes easy to produce. When the fiber is a multifilament, the fineness of the single fiber of the fiber means the average value of the fineness of the single fibers contained in the fiber. When the fiber is a monofilament, the fineness of the single fiber of the fiber means the fineness of the fiber itself. In addition, when the fiber is drawn, the fineness may be measured before drawing, or may be measured after drawing. The fineness of the single fiber can be measured by the method described in the Examples mentioned below.

[0042] The aforementioned fibers can be used as sewing threads or fibers in fiber aggregates. The yarn, which is a fiber aggregate, may contain multiple of the aforementioned fibers, or one or more of the aforementioned fibers and one or more other fibers. Examples of the yarn include spun yarn. Examples of the woven fabric include plain weave, twill weave, satin weave, modified plain weave, modified twill weave, modified satin weave, variegated weave, patterned weave, single-layer weave, double weave, multi-layer weave, warp pile weave, weft pile weave, leno weave, etc. Examples of the knitted fabric (also called knit) include circular knit, weft knit, warp knit, pile knit, etc., and also plain knit, jersey knit, rib knit, smooth knit (double-sided knit), rib knit, pearl knit, denby weave, cord weave, atlas weave, chain weave, and inserted weave, etc. The nonwoven fabric may be a long-fiber nonwoven fabric or a short-fiber nonwoven fabric.

[0043] From the viewpoint of enhancing biodegradability such as marine biodegradability, the fiber aggregate preferably contains 10% by weight or more of the fibers, more preferably 20% by weight or more, even more preferably 30% by weight or more, even more preferably 40% by weight or more, even more preferably 50% by weight or more, even more preferably 60% by weight or more, even more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more. The fiber aggregate may also consist of 100% by weight of the fibers.

[0044] The fiber assembly may contain other fibers in addition to the fibers. The other fibers are not particularly limited, and examples thereof include synthetic fibers, natural fibers, and regenerated fibers. From the viewpoint of biodegradability, the other fibers are preferably biodegradable fibers. Examples of biodegradable synthetic fibers include synthetic fibers containing aliphatic polyesters other than P3HA. Examples of aliphatic polyesters other than P3HA include polylactic acid, polycaprolactone, polybutylene adipate terephthalate, polybutylene succinate adipate, and polybutylene succinate. Examples of natural fibers include natural cellulose fibers and natural animal fibers. Examples of natural cellulose fibers include cotton fiber, kapok fiber, flax fiber, cannabis fiber, ramie fiber, jute fiber, manila hemp fiber, and kenaf fiber. Examples of natural animal fibers include wool fiber, mohair fiber, cashmere fiber, camel fiber, alpaca fiber, and angora fiber. Examples of regenerated fibers include regenerated cellulose fibers such as rayon, polynosic, cupra, and lyocell, and regenerated protein fibers such as regenerated collagen fiber.

[0045] The fiber assembly can be used for various fiber products. Examples of fiber products include clothing, daily necessities, and interior goods. Examples of clothing include outerwear, underwear, sweaters, vests, trousers, gloves, socks, mufflers, and hats. Examples of daily necessities include bedding, pillows, cushions, stuffed toys, and sanitary materials. Examples of interior goods include curtains and carpets.

[0046] It should be noted that the present invention is not limited to the above embodiments. Furthermore, the present invention is not limited by the above-mentioned functions and effects. In addition, various modifications can be made to the present invention without departing from the gist of the present invention.

[0047] [Disclosure Items] Each of the following items is a disclosure of preferred embodiments.

[0048] [Item 1] A method for producing poly(3-hydroxyalkanoate) fibers, comprising: (A) a step of melting a raw material composition containing a poly(3-hydroxyalkanoate) resin and a filler to obtain a molten composition; (B) a step of discharging the molten composition from an discharge hole to obtain molten yarn; (C) a step of cooling the molten yarn in an atmosphere below the crystallization temperature of the poly(3-hydroxyalkanoate) resin; and (D) a step of passing the cooled yarn through an atmosphere of 120 to 170°C. [Item 2] The method for producing fibers according to Item 1, wherein the filler includes one selected from the group consisting of carbon black and talc. [Item 3] The method for producing fibers according to Item 1 or 2, wherein in step (C), the molten yarn is cooled in an atmosphere of 10 to 35°C. [Item 4] A method for producing fibers according to any one of items 1 to 3, wherein the median diameter of the filler is 10 to 500 nm. [Item 5] A method for producing fibers according to any one of items 1 to 4, wherein the content of the filler in the raw material composition is 0.01 to 10 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. [Item 6] A method for producing fibers according to any one of items 1 to 5, wherein the fineness of the single fibers of the fiber is 1.0 to 15 dtex. [Item 7] A method for producing fibers according to any one of items 1 to 6, further comprising a step (E) of stretching the fiber after step (D). [Item 8] A method for producing fibers according to any one of items 1 to 7, wherein the poly(3-hydroxyalkanoate) resin is a poly(3-hydroxybutyrate) copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units. [Item 9] The method for producing fibers according to Item 8, wherein the poly(3-hydroxybutyrate) copolymer is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0049] The present invention will be described in detail below with reference to examples, but these examples are not intended to limit the present invention.

[0050] [Measurement Method and Evaluation Method] (Content ratio of 3-hydroxybutyrate units and 3-hydroxyhexanoate units in P3HB3HH, which is P3HA) The content ratio of 3-hydroxybutyrate units and 3-hydroxyhexanoate units in P3HB3HH, which is P3HA, was determined as follows. First, 2 mL of a mixture of sulfuric acid and methanol (volume of sulfuric acid:volume of methanol = 15:85) and 2 mL of chloroform were added to a dried 20 mg sample. The sample was then sealed and heated at 100°C for 140 minutes to obtain a first reaction solution containing methyl ester, which is a decomposition product of P3HA. The first reaction solution was then cooled, and 1.5 g of sodium bicarbonate was added little by little to the cooled first reaction solution to neutralize it. The mixture was left to stand until the generation of carbon dioxide stopped to obtain a second reaction solution. Furthermore, a mixture was obtained by thoroughly mixing the second reaction solution with 4 mL of diisopropyl ether. Next, the supernatant was obtained by centrifugation of the mixture. The monomer unit composition of the decomposition product in the supernatant was then analyzed by capillary gas chromatography under the following conditions to determine the content of 3-hydroxybutyrate units and 3-hydroxyhexanoate (3HH) units in P3HA. Gas chromatograph: GC-17A manufactured by Shimadzu Corporation Capillary column: NEUTRA BOND-1 manufactured by GL Sciences (column length: 25 m, column inner diameter: 0.25 mm, liquid film thickness: 0.4 μm) Carrier gas: He Column inlet pressure: 100 kPa Sample volume: 1 μL For the temperature conditions, the temperature was increased at a rate of 8 °C / min from 100 to 200 °C, and then at a rate of 30 °C / min from 200 to 290 °C.

[0051] (Crystallization temperature of P3HA) The crystallization temperature of P3HA was measured according to JIS K7121-1987 "Method for measuring the transition temperature of plastics". Specifically, a differential scanning calorimeter (for example, a differential scanning calorimeter DSC25 manufactured by TA Instruments) was used. Approximately 6.0 mg of the sample was placed in a measuring container, and the temperature was increased and decreased between -30°C and 180°C at a temperature increase / decrease rate of 10°C / min under a nitrogen gas flow rate of 50 ml / min. The temperature at the peak top of the exothermic peak during the second cooling was taken as the crystallization temperature. If there were two or more exothermic peaks, the temperature at the peak top of the exothermic peak with the largest peak area was taken as the crystallization temperature.

[0052] (Weight-average molecular weight of P3HA) The weight-average molecular weight of P3HA was measured by the method described above.

[0053] (Median diameter of the filler) The median diameter of the volume-based primary particles was determined by laser diffraction / scattering measurement using a Horiba Partica LA-960V2.

[0054] (Fiber Fineness) The fineness of individual fibers was measured using a DENICON DC-21 fiber fineness meter manufactured by Search Co., Ltd. The measured values ​​are shown in Table 1 below.

[0055] (Fiber Separability) The fiber separation ability of the obtained fibers was evaluated according to the following criteria: ○: Each individual fiber separates easily without any intervention. △: Some fusion is observed between the individual fibers, but they can be separated individually by hand. ×: Some fusion is observed between the individual fibers, and they cannot be separated even by hand. The results are shown in Table 1 below.

[0056] (Fusion Rate) The cross-section of the multifilament fiber was imaged using a Keyence VHX-6000, and the fusion rate was defined as the ratio of the number of fused single fibers to the total number of single fibers in the multifilament. The results are shown in Table 1 below.

[0057] (Sticking to the Roll) The sticking to the roll (also called "roll sticking") was evaluated according to the following criteria. ○: Stable running is possible without the yarn sticking to the roll. △: Slight sticking of the yarn to the roll is observed, running is unstable, and yarn breakage occurs. ×: The yarn sticks to the roll so much that it cannot be peeled off. The results are shown in Table 1 below.

[0058] (Surface Roughness) The surface roughness of the fiber (also called "surface roughness") was measured using a Keyence VK-X3000. The measured values ​​are shown in Table 1 below.

[0059] (Spinning Draft) The spinning draft was calculated using the following formula: Spinning Draft = Take-up Speed ​​ / ((Discharge Amount per Hole / Density of Molten Material) / Cross-sectional Area of ​​Hole) The take-up speed is the speed of the take-up roll (the first take-up roll 8 in Figure 1) that initially takes up the yarn discharged from the discharge hole, and is the length of yarn taken up by the take-up roll per unit time. The calculated values ​​are shown in Table 1 below.

[0060] <Method for Manufacturing Raw Material Pellets> First, the following materials were dry-blended in the following proportions, and this mixture was melt-kneaded at 150°C using an extruder to obtain raw material pellets. Poly(3-hydroxyalkanoate) resin (P3HA) poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (3-hydroxybutyrate unit content: 94 mol%, 3-hydroxyhexanoate content: 6 mol%, weight-average molecular weight (Mw): 582,936, crystallization temperature: 60°C) (P3HB3HH): 100 parts by mass Erucic acid amide (EA): 0.5 parts by mass Behenic acid amide (BA): 0.5 parts by mass Pentaerythritol (PETL) (manufactured by Nippon Synthetic Chemical Co., Ltd., Neurizer-P): 1.0 part by mass

[0061] (Example 1) The raw material pellets prepared by the above method and 1 part by weight of carbon black (median diameter 100 nm) as a filler per 100 parts by weight of poly(3-hydroxyalkanoate) resin of the raw material pellets were placed in a poly bag and hand-blended to obtain a raw material composition. The raw material composition was heated and melted at a melting temperature (also called "extrusion temperature") of 170°C using an extruder 2 (single-screw extruder, screw diameter: 40 mm) to obtain a molten material. The molten material was then discharged from 400 discharge holes of a spinning nozzle 4 to obtain yarn A. The flow rate of the composition (molten material) discharged from the spinning nozzle was adjusted to 7.0 kg / h using a gear pump 3. In the first box 5a of the quench section 5, the molten yarn A was cooled by blowing 20°C gas (air) at a wind speed of 0.08 m / s using a circular method. The temperature inside the second box 6, located between the quench section 5 and the first take-up roll 8, was adjusted to 120°C, and the raw yarn A was kept warm inside the second box 6. The temperature of the first take-up roll 8 was adjusted to 40°C, and the raw yarn A, which had been kept warm in the second box 6, was taken up by the first take-up roll 8 at a speed of 650 m / min. The raw yarn A was then wound onto a bobbin, which served as the core 11, using the first winding machine 10, to obtain a multifilament fiber (number of single filaments: 400, average fineness of single filaments: 4.5 dtex).

[0062] (Examples 2-8, Comparative Examples 1-4) Fibers were obtained in the same manner as in Example 1, except that the type of filler, the presence or absence of filler, the air temperature in the quench section 5 (also called the "quench temperature"), the temperature inside the second box 6, and the spinning draft were changed to the conditions shown in Table 1 below.

[0063]

[0064] As shown in Table 1, in Examples 1 to 9, which are within the scope of the present invention, the fusion rate was low and the roll adhesion evaluation was ○. On the other hand, in Comparative Examples 1 to 3, where the temperature inside the second box was low (80°C or less), and in Comparative Example 4, where no filler was used, the fusion rate was higher than in the examples, and the roll adhesion evaluation was △ or ×. In Comparative Example 5, where no filler was used and the temperature inside the second box was low (30°C), the roll adhesion evaluation was △. Therefore, it can be seen that the present invention provides a method for producing poly(3-hydroxyalkanoate) resin-containing fibers that can suppress fusion while improving fiber productivity.

[0065] In Examples 1 to 9, which fall within the scope of the present invention, the surface roughness of the fibers was higher compared to Comparative Examples 4 and 5, which did not use a filler. From this, it is considered that in the present invention, the filler increases the surface roughness of the yarn A and the fibers, and as a result, fusion is suppressed.

[0066] Furthermore, in Examples 1 to 9, the evaluation of fiber separation properties was also positive. Therefore, it can be seen that the fibers produced by the fiber production method according to the present invention have excellent fiber separation properties.

[0067] In a comparison of the examples (Examples 2, 8, and 9) that differed only in quench temperature, the fusion rate was lower in Examples 2 and 9, which had higher quench temperatures, compared to Example 8, which had a quench temperature of 10°C.

[0068] In a comparison of the examples (Examples 1-4) where only the temperature inside the second box differed, the higher the temperature inside the second box, the lower the fusion rate.

[0069] In a comparison of examples (Examples 2, 5, and 6) that differed only in spinning draft, the smaller the spinning draft, the lower the fusion rate.

[0070] In a comparison of Examples (2 and 7) that differed only in the type of filler used, Example 2, which used carbon black, had a lower fusion rate compared to Example 7, which used talc.

[0071] A: Raw yarn, B: Fiber, 1: Raw material hopper, 2: Extruder, 3: Gear pump, 4: Spinning nozzle, 4a: Discharge port, 5: Quench section, 5a: First box, 6: Second box, 8: First take-up roll, 9: Dancer roll, 10: First winding machine, 11: Core, 12: Feed-out roll, 13: Second take-up roll, 14: Third take-up roll, 16: Second winding machine

Claims

1. A method for producing poly(3-hydroxyalkanoate) fibers, comprising: (A) a step of melting a raw material composition containing a poly(3-hydroxyalkanoate) resin and a filler to obtain a molten composition; (B) a step of extruding the molten composition from an extrusion hole to obtain molten yarn; (C) a step of cooling the molten yarn in an atmosphere below the crystallization temperature of the poly(3-hydroxyalkanoate) resin; and (D) a step of passing the cooled yarn through an atmosphere of 120 to 170°C.

2. The method for producing fibers according to claim 1, wherein the filler comprises one selected from the group consisting of carbon black and talc.

3. The method for producing fibers according to claim 1 or 2, wherein in step (C), the molten yarn is cooled in an atmosphere of 10 to 35°C.

4. The method for producing fibers according to claim 1 or 2, wherein the median diameter of the primary particles of the filler, on a volume basis, is 10 to 500 nm.

5. The method for producing fibers according to claim 1 or 2, wherein the content of the filler in the raw material composition is 0.01 to 10 parts by weight per 100 parts by weight of the poly(3-hydroxyalkanoate) resin.

6. The method for producing the fiber according to claim 1 or 2, wherein the fineness of the single fiber of the fiber is 1.0 to 15 dtex.

7. A method for producing fibers according to claim 1 or 2, further comprising a step (E) of stretching the fibers after step (D).

8. The method for producing fibers according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) resin is a poly(3-hydroxybutyrate) copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

9. The method for producing fibers according to claim 8, wherein the poly(3-hydroxybutyrate) copolymer is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

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