Method for producing aliphatic polyester fiber

Abstract

Provided is a method for producing an aliphatic polyester fiber containing a poly(3-hydroxybutyrate)-based resin and a crystal nucleating agent, the method including: (i) a step for heating a resin composition containing the poly(3-hydroxybutyrate)-based resin and the crystal nucleating agent to a temperature of at least a melting point of the resin composition and at most the thermal decomposition temperature of the resin composition and discharging the resin composition from a spinning nozzle; (ii) a step for drawing, with a drawing roll, the resin composition discharged from the spinning nozzle; and (iii) a step for winding the drawn resin composition with a winding roll, wherein the drawing roll comprises at least two rolls including a first roll and a second roll, the total draw ratio of the resin composition is at least 250, and the speed of the winding roll is 500-1,500 m / min.

Description

Technical Field

[0001] The present invention relates to a method for producing an aliphatic polyester fiber, an aliphatic polyester fiber, and a multifilament.

Background Art

[0002] In recent years, plastic waste has been causing problems that impose a significant burden on the global environment, such as its impact on the ecosystem, generation of harmful gases during combustion, and global warming due to a large amount of combustion heat. As a solution to this problem, the development of biodegradable plastics has been actively pursued.

[0003] Among such biodegradable plastics, the carbon dioxide emitted when burning biodegradable plastics obtained using plant-derived raw materials is originally present in the air, and the carbon dioxide in the atmosphere does not increase. This is called carbon neutral, and it is highly regarded under the Kyoto Protocol, which sets a target value for carbon dioxide reduction, and its active use is desired.

[0004] Recently, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester-based resins have attracted attention as biodegradable plastics produced by microorganisms using plant-derived raw materials as a carbon source. In particular, polyhydroxyalkanoate (hereinafter sometimes referred to as PHA) -based resins, and among PHA-based resins, poly(3-hydroxybutyrate) homopolymer resin, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer resin, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (hereinafter sometimes referred to as P3HB3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer resin, and polylactic acid, etc. have attracted attention.

[0005] However, since the PHA-based resin has a slow crystallization rate and a glass transition temperature lower than room temperature (about 0 to 4°C), during the molding process, after heating and melting, it is necessary to extend the cooling time for solidification, resulting in poor productivity. In particular, when attempting to produce fibers by the melt spinning method using PHA, due to the slow solidification of the resin, adhesion between fibers and sticking to the rolls occur, making it difficult to stably produce fibers and resulting in low-quality fibers.

[0006] As a prior art example of the melt spinning technology of 3-hydroxyalkanoate polymers, Patent Document 1 describes a melt spinning method in which a polyester resin containing poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is spun at a take-up speed of 1,500 m / min to 7,000 m / min. It is also described that by this method, spinnability and productivity can be improved and the tensile strength can be increased.

[0007] As another prior art example, Patent Document 2 describes a melt spinning method for biodegradable aliphatic polyester fibers containing polyhydroxyalkanoate, a crystal nucleating agent, and a lubricant. During spinning, a melt is extruded from a spinneret at a temperature of 130°C or higher and 190°C or lower to obtain a raw yarn, which is taken up by a first take-up roll at a take-up speed of 300 m / min or higher and 4,000 m / min or lower, and continuously, the raw yarn is taken up by a second take-up roll at a take-up speed of 600 m / min or higher and 7,000 m / min or lower to perform drawn spinning. It is also described that by this method, the crystallization rate of polyhydroxyalkanoate can be improved, the suction property can be improved, the spinnability and productivity of the fibers can be improved, and the tensile strength can be increased.

[0008] Also, as another prior art example, Patent Document 3 describes that PHA is fibrillated under specific spinning conditions, and further, in the stretching process, stretching is performed in a temperature range where there is no waste of energy used during production, and further, excellent mechanical properties are exhibited by relaxation in the heat treatment process.

Prior Art Documents

Patent Documents

[0009] [Patent Document 1] International Publication No. 2015 / 029316 [Patent Document 2] International Publication No. 2017 / 122679 [Patent Document 3] International Publication No. 2012 / 133231 [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] However, in the melt spinning methods disclosed in Patent Documents 1 and 2, aliphatic polyester fibers containing a poly(3-hydroxybutyrate)-based resin having sufficient tensile strength cannot be obtained. Further, the method disclosed in Patent Document 3 requires stretching and further heat treatment after fiber formation, which takes a long time for fiber production and has poor productivity.

[0011] An object of the present invention is to improve the productivity of aliphatic polyester fibers containing a poly(3-hydroxybutyrate)-based resin and a crystal nucleating agent and to increase the tensile strength. [Means for Solving the Problems]

[0012] A first aspect of the present disclosure is a method for producing an aliphatic polyester fiber containing a poly(3-hydroxybutyrate)-based resin and a crystal nucleating agent, comprising: (i) heating a resin composition containing the poly(3-hydroxybutyrate)-based resin and the crystal nucleating agent to a temperature equal to or higher than the melting point and lower than the thermal decomposition temperature of the resin composition, and discharging it from a spinning nozzle; (ii) stretching the resin composition discharged from the spinning nozzle with a stretching roll; and (iii) winding up the stretched resin composition with a winding roll, wherein the stretching roll consists of two or more rolls including a first roll and a second roll, the total stretching ratio of the resin composition (the winding roll speed (m / min) / the spinning nozzle flow rate (m / min)) is 250 or more, and the winding roll speed is 500 to 1500 m / min.

[0013] In the method for producing an aliphatic polyester fiber, it is preferable that the ratio of the winding roll speed (m / min) to the first roll speed (m / min) is 1.5 or more.

[0014] In the method for producing an aliphatic polyester fiber, it is preferable that the ratio of the first roll speed (m / min) to the spinning nozzle flow rate (m / min) is 55 or more.

[0015] In the method for producing an aliphatic polyester fiber, before the resin composition discharged from the spinning nozzle contacts the stretching roll, it is preferable to apply an air flow at a temperature equal to or higher than the glass transition temperature and lower than the crystallization temperature of the resin composition to the resin composition.

[0016] In the method for producing an aliphatic polyester fiber, in the step (ii) of stretching, it is preferable to set the temperature of the resin composition to 40 to 100°C.

[0017] In the method for producing an aliphatic polyester fiber, it is preferable that the winding roll speed is 2 to 15% lower than the roll speed of the roll with the maximum speed among the two or more rolls constituting the stretching roll.

[0018] In the method for producing the aliphatic polyester fiber, it is preferable to convey the resin composition from the spinning nozzle to the winding roll within 1 minute.

[0019] In the method for producing the aliphatic polyester fiber, it is preferable that the spinning nozzle has 15 or more discharge holes.

[0020] In the method for producing the aliphatic polyester fiber, the poly(3-hydroxybutyrate) - based resin contains poly(3-hydroxybutyrate - co - 3-hydroxyhexanoate), and among the total monomer units constituting the poly(3-hydroxybutyrate - co - 3-hydroxyhexanoate), the proportion of 3-hydroxyhexanoate is preferably 3 to 15 mol%.

[0021] The second aspect of the present disclosure relates to an aliphatic polyester fiber containing a poly(3-hydroxybutyrate) - based resin and a crystal nucleating agent, wherein the fineness of a single fiber is 1 to 20 dtex, and the tensile strength of the single fiber is 1.5 cN / dtex or more.

[0022] In the aliphatic polyester fiber, the poly(3-hydroxybutyrate) - based resin contains poly(3-hydroxybutyrate - co - 3-hydroxyhexanoate), and among the total monomer units constituting the poly(3-hydroxybutyrate - co - 3-hydroxyhexanoate), the proportion of 3-hydroxyhexanoate is preferably 3 to 15 mol%.

[0023] The third aspect of the present disclosure relates to a multifilament containing 15 or more of the aliphatic polyester fibers.

Advantages of the Invention

[0024] According to the present invention, the productivity of the aliphatic polyester fiber containing a poly(3-hydroxybutyrate) - based resin and a crystal nucleating agent can be improved, and the tensile strength can be increased.

Brief Description of the Drawings

[0025]

Figure 1

Mode for Carrying Out the Invention

[0026] [Method for Manufacturing Aliphatic Polyester Fiber] The method for manufacturing an aliphatic polyester fiber of the present disclosure is a method for manufacturing an aliphatic polyester fiber containing a poly(3-hydroxybutyrate) - based resin and a crystal nucleating agent, (i) A step of heating a resin composition containing the poly(3-hydroxybutyrate) - based resin and the crystal nucleating agent to a temperature equal to or higher than the melting point and lower than the thermal decomposition temperature of the resin composition, and discharging it from a spinning nozzle; (ii) A step of stretching the resin composition discharged from the spinning nozzle with a stretching roll; and (iii) A step of winding up the stretched resin composition with a winding roll, The stretching roll is composed of two or more rolls including a first roll and a second roll, the total stretching ratio of the resin composition (the winding roll speed (m / min) / the spinning nozzle flow rate (m / min)) is 250 or more, and the winding roll speed is 500 to 1500 m / min.

[0027] (i) The step of heating a resin composition containing a poly(3-hydroxybutyrate) - based resin and a crystal nucleating agent to a temperature equal to or higher than the melting point and lower than the thermal decomposition temperature of the resin composition, and discharging it from a spinning nozzle will be described in detail below.

[0028] In the present disclosure, the poly(3-hydroxybutyrate) - based resin is an aliphatic polyester containing 3-hydroxybutyrate as a monomer unit constituting the resin.

[0029] Examples of the poly(3-hydroxybutyrate) - based resin include resins containing poly(3-hydroxybutyrate) such as poly(3-hydroxybutyrate); and resins containing a copolymer resin composed of 3-hydroxybutyrate and another hydroxyalkanoate.

[0030] Examples of the copolymer resin composed of 3-hydroxybutyrate and other hydroxyalkanoates include P3HB3HH [poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)], PHBV [poly(3-hydroxybutyrate-co-3-hydroxyvalerate)], P3HB4HB [poly(3-hydroxybutyrate-co-4-hydroxybutyrate)], poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate). Among these, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferred. This is because the resulting aliphatic polyester fiber is not only excellent in biodegradability but also has sufficient practical moldability and is excellent in tensile strength and flexibility.

[0031] In the resin containing the copolymer resin composed of 3-hydroxybutyrate and other hydroxyalkanoates, the proportion of 3-hydroxyhexanoate is preferably 0.5 to 15 mol%, more preferably 1.5 to 15 mol%, still more preferably 3 to 15 mol%, and most preferably 3 to 8 mol% based on the total monomer units constituting the resin. This is because the resulting aliphatic polyester fiber is excellent in tensile strength and flexibility.

[0032] The weight average molecular weight Mw of the poly(3-hydroxybutyrate) - based resin is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,500,000, and still more preferably 200,000 to 1,000,000. This is because if the weight average molecular weight Mw is too low, the tensile strength of the resulting aliphatic polyester fiber tends to decrease, and if the weight average molecular weight Mw is too high, the processability may decrease and molding may become difficult.

[0033] The weight-average molecular weight Mw is measured from the polystyrene-equivalent molecular weight distribution using gel permeation chromatography (GPC) with a chloroform eluent. As the column in the GPC, a column appropriate for measuring the molecular weight may be used.

[0034] In the present disclosure, the crystal nucleating agent is a compound that has a melting point higher than that of the poly(3-hydroxybutyrate)-based resin and has an effect of promoting the crystallization of the resin. The compound is not particularly limited. Examples of the crystal nucleating agent include inorganic substances (such as boron nitride, titanium oxide, talc, layered silicate, calcium carbonate, sodium chloride, and metal phosphate); sugar alcohol compounds derived from natural products (such as pentaerythritol, erythritol, galactitol, mannitol, and arabitol); polyvinyl alcohol; chitin; chitosan; polyethylene oxide; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylic acid esters; dicarboxylic acid derivatives (such as dimethyl adipate, dibutyl adipate, diisodecyl adipate, and dibutyl sebacate); cyclic compounds having a functional group selected from C=O and NH, S, and O in the molecule (such as indigo, quinacridone, and quinacridone magenta); sorbitol-based derivatives (such as bisbenzylidene sorbitol and bis(p-methylbenzylidene)sorbitol); compounds containing a nitrogen-containing heteroaromatic nucleus (such as a pyridine ring, a triazine ring, and an imidazole ring) (such as pyridine, triazine, and imidazole); phosphate ester compounds; bisamides of higher fatty acids; metal salts of higher fatty acids; and branched polylactic acid, etc. can be exemplified. Further, when the poly(3-hydroxybutyrate)-based resin is P3HB3HH, poly(3-hydroxybutyrate) having a melting point higher than that of P3HB3HH can also be used.

[0035] Among these, from the viewpoints of the effect of improving the crystallization rate of the poly(3-hydroxybutyrate) resin and the compatibility and affinity with the poly(3-hydroxybutyrate) resin, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan are preferable, and pentaerythritol is more preferable. These may be used alone or in combination of two or more.

[0036] In the resin composition containing the poly(3-hydroxybutyrate) resin and the crystal nucleating agent, the content of the crystal nucleating agent is preferably 0.05 part by weight or more, more preferably 0.1 part by weight or more, still more preferably 0.5 part by weight or more, based on 100 parts by weight of the poly(3-hydroxybutyrate) resin. Also, the content is preferably 12 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 8 parts by weight or less, and most preferably 5 parts by weight or less. If the content of the crystal nucleating agent is too small, the effect as a crystal nucleating agent may be insufficient, and if the content of the crystal nucleating agent is too large, the viscosity of the resin composition during heating may decrease.

[0037] Further, the resin composition may contain known additives as optional components other than the poly(3-hydroxybutyrate) resin and the crystal nucleating agent, if necessary. Examples of the known additives include stabilizers such as antioxidants and ultraviolet absorbers; colorants such as dyes and pigments; plasticizers; lubricants; inorganic fillers; organic fillers; and antistatic agents. These additives may be used alone or in combination of two or more.

[0038] The plasticizer is not particularly limited, and examples thereof include adipic acid ester plasticizers, acetylated monoglyceride plasticizers, and polyglycerin fatty acid ester plasticizers. Also, the plasticizing action of supercritical fluids such as carbon dioxide and nitrogen can be utilized.

[0039] The lubricant is not particularly limited, and examples thereof include fatty acid amides such as behenic acid amide, stearic acid amide, erucic acid amide, and oleic acid amide.

[0040] When heating the resin composition to a temperature equal to or higher than the melting point and lower than the thermal decomposition temperature of the resin composition, the heating temperature may be appropriately adjusted according to the type of the resin composition, but it is preferably +5°C or higher than the melting point of the resin composition, and more preferably +10°C or higher. Further, the heating temperature is preferably lower than the thermal decomposition temperature of the resin composition, and more preferably -5°C or lower than the thermal decomposition temperature.

[0041] In the present disclosure, the melting point is measured by a differential scanning calorimetry (DSC) method. Specifically, using a differential scanning calorimeter, it is measured at a heating rate of 10°C / min, and the obtained endothermic peak is taken as the melting point.

[0042] In the present disclosure, the thermal decomposition temperature is the starting temperature of weight loss measured by thermogravimetry (TG). Specifically, using a thermogravimeter, it is measured at a heating rate of 10°C / min, and the temperature at the start of weight loss is taken as the thermal decomposition temperature.

[0043] The resin composition containing a poly(3-hydroxybutyrate) - based resin and a crystal nucleating agent preferably has a melt flow rate (hereinafter, may be referred to as MFR) measured at 165°C and 5 kgf of 0.1 to 100 g / 10 min, more preferably 0.5 to 80 g / 10 min, and even more preferably 1.0 to 60 g / 10 min.

[0044] The measuring method of the melt flow rate is the value measured at 165°C and a load of 5 kg in accordance with JIS K7210 - 2:2014.

[0045] The spinning nozzle is provided with discharge holes through which the resin composition discharges. The shape, size, and number of the discharge holes are not particularly limited. As for the size of the discharge holes, for example, when the shape of the discharge holes is circular, the diameter Φ0.1 mm to 3.0 mm is preferable. Also, the number of the discharge holes may depend on the size of the discharge holes, and for example, it may be 15 or more and may be 1000 or less.

[0046] The flow rate of the spinning nozzle, that is, the rate at which the resin composition is discharged from the spinning nozzle, is preferably from 0.05 m / min to 6.0 m / min, more preferably from 0.1 m / min to 6.0 m / min, and even more preferably from 0.5 m / min to 6.0 m / min.

[0047] In addition, the discharge amount from the spinning nozzle is preferably 0.10 g / min / hole or more, more preferably 0.15 g / min / hole or more. Also, the discharge amount is preferably less than 1.0 g / min / hole, more preferably 0.90 g / min / hole or less.

[0048] Before the resin composition discharged from the spinning nozzle comes into contact with the drawing roll, it is preferable to apply an air flow at a temperature equal to or higher than the glass transition temperature and equal to or lower than the crystallization temperature of the resin composition to rapidly cool it. By such rapid cooling, the cooling and solidification of the resin composition can be promoted, and the drawing strain caused by the speed difference between the drawing rolls is more effectively reflected. As a result, the tensile strength of the obtained aliphatic polyester fiber can be further increased.

[0049] In the present disclosure, the glass transition temperature is measured by differential scanning calorimetry (DSC). Specifically, using a differential scanning calorimeter, it is measured at a heating rate of 10 °C / min, and the temperature of the inflection point of the obtained DSC curve is taken as the glass transition temperature.

[0050] In addition, the crystallization temperature is measured by differential scanning calorimetry (DSC). Specifically, using a differential scanning calorimeter, it is measured at a cooling rate of 10 °C / min, and the heat release peak of the obtained DSC curve is taken as the crystallization temperature.

[0051] The temperature of the air flow applied to the resin composition discharged from the spinning nozzle may be equal to or higher than the glass transition temperature and equal to or lower than the crystallization temperature of the resin composition, and may be appropriately adjusted according to the type of the resin composition. The temperature of the air flow is preferably less than the crystallization temperature of the resin composition, more preferably crystallization temperature - 20 °C or lower, and even more preferably crystallization temperature - 40 °C or lower.

[0052] The speed of the airflow is not particularly limited, but is preferably 0.1 m / s or more and 5 m / s or less, and more preferably 0.1 m / s or more and 3 m / s or less. If the speed of the airflow is less than 0.1 m / s, the resulting cooling effect becomes too small. If it exceeds 5 m / s, the resin composition discharged from the spinning nozzle sways in the airflow, which may cause fusion between the discharged resin compositions and / or yarn breakage, etc., leading to a decrease in spinning stability.

[0053] The type of the airflow is not particularly limited, but air; inert gases such as nitrogen gas and argon gas are preferable.

[0054] (ii) The step of stretching the resin composition discharged from the spinning nozzle with a stretching roll, and (iii) the step of winding the stretched resin composition with a winding roll will be described in detail below.

[0055] The resin composition discharged from the spinning nozzle is first taken up by the first roll and then stretched by two or more rolls including the first roll and the second roll.

[0056] The stretching roll only needs to include the first roll and the second roll, and the number of the stretching rolls is not particularly limited. It may be appropriately selected in consideration of the temperature control efficiency of the fiber, the stretching ratio, etc. The number of the stretching rolls may be 3 or more, 4 or more, or 5 or more. Also, within the scope of the object of the present invention, there is no particular upper limit to the number of the stretching rolls, but from the viewpoints of equipment cost and not making the manufacturing apparatus too large, it may be 10 or less.

[0057] In addition, each stretching roll among the stretching rolls may be composed not only of one roll but also of rolls in which two or more rolls with the same speed are grouped together. It is possible to make the temperature of the stretched fiber uniform and manufacture longer fibers with less space.

[0058] The ratio of the first roll speed (m / min) to the spinning nozzle flow rate (m / min) (hereinafter sometimes referred to as NDR) is preferably 55 or more, more preferably 100 or more, still more preferably 150 or more, and particularly preferably 200 or more. By increasing NDR, the alignment of the molecular chains of the resin composition can be promoted, and since the diameter of the resin composition becomes smaller, the cooling and solidification can be promoted. Also, although there is no upper limit for NDR as long as fiber breakage does not occur, it may be 1000 or less.

[0059] The ratio of the winding roll speed (m / min) to the first roll speed (m / min) is preferably 1.5 or more, more preferably 1.7 or more, and still more preferably 1.8 or more. This is because an aliphatic polyester fiber with more excellent tensile strength can be obtained. Also, although there is no upper limit for the ratio as long as fiber breakage does not occur, it may be 30 or less.

[0060] (ii) In the step of stretching the resin composition discharged from the spinning nozzle with a stretching roll, it is preferable to set the temperature of the resin composition to 40 to 100°C, and more preferably 50 to 80°C. This is because the crystallization rate of the resin composition can be increased, and the productivity and tensile strength of the aliphatic polyester fiber can be further improved. The temperature adjustment of the resin composition may be performed by adjusting the temperature of an object in contact with the resin composition, such as a solid like the stretching roll surface, a liquid like a bath and droplets, and a gas like an air current.

[0061] The stretched resin composition is wound around a winding roll. The total draw ratio of the resin composition is 250 or more. The total draw ratio is preferably 270 or more, more preferably 300 or more, still more preferably 330 or more, and even more preferably 340 or more. Also, although there is no upper limit for the total draw ratio as long as fibers with a desired fineness can be stably obtained, it may be 2000 or less.

[0062] Note that the total draw ratio is defined as the winding roll speed (m / min) / the spinning nozzle flow rate (m / min).

[0063] The winding roll speed is 500 to 1500 m / min. In this range, it may be appropriately adjusted in consideration of the flow rate of the spinning nozzles and the speeds of other rolls.

[0064] The winding roll speed is preferably 2 to 15% lower, more preferably 3 to 15% lower, and even more preferably 3 to 12% lower than the roll speed of the roll with the maximum speed among two or more rolls constituting the drawing roll. This is because residual stress is less likely to remain in the obtained aliphatic polyester fiber, and dry heat shrinkage is less likely to occur. Note that the ratio indicated by the “%”, that is, (the roll speed of the roll with the maximum speed - the winding roll speed) / the winding roll speed × 100 can be rephrased as the “relaxation rate (%)”.

[0065] The time for transporting the resin composition is preferably within 1 minute, more preferably within 50 seconds, even more preferably within 40 seconds, and even more preferably within 30 seconds from the spinning nozzles to the winding roll. Also, the time may be 1 second or more. According to the production method of the present disclosure, aliphatic polyester fibers with high tensile strength can be produced with high productivity in a short time.

[0066] [Aliphatic polyester fiber] The aliphatic polyester fiber of the present disclosure is an aliphatic polyester fiber containing a poly(3-hydroxybutyrate) - based resin and a crystal nucleating agent, wherein the fineness of a single fiber is 1 to 20 dtex, and the tensile strength of a single fiber is 1.5 cN / dtex or more.

[0067] In the aliphatic polyester fiber of the present disclosure, the content of the crystal nucleating agent is preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, and even more preferably 0.5 parts by weight or more, based on 100 parts by weight of the poly(3-hydroxybutyrate) - based resin. Also, the content is preferably 12 parts by weight or less, 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, based on 100 parts by weight of the poly(3-hydroxybutyrate) - based resin.

[0068] Further, the particle size of the crystal nucleating agent contained in the aliphatic polyester fiber is preferably 1 / 3 or less with respect to the minimum diagonal line length of the cross-section of the fiber. This is because the tensile strength of the fiber is excellent.

[0069] The particle size of the crystal nucleating agent is determined as D50 (median diameter) using the laser diffraction method.

[0070] The fineness of a single fiber of the aliphatic polyester fiber of the present disclosure may be 1.5 dtex or more, and may be 2 dtex or more. Further, the fineness may be 15 dtex or less, and may be 10 dtex or less.

[0071] The fineness of a single fiber refers to the thickness of the yarn and is defined as the mass per unit length. The mass (g) per 10,000 m is expressed in units (dtex). Specifically, it is measured by the autovibroscope method.

[0072] The tensile strength of a single fiber of the aliphatic polyester fiber of the present disclosure is preferably 1.6 cN / dtex or more, more preferably 1.7 cN / dtex or more, still more preferably 1.8 cN / dtex or more, and most preferably 1.9 cN / dtex or more. The tensile strength is not particularly limited as long as it does not impair the flexibility and toughness required depending on the application, but may be 10 cN / dtex or less. The aliphatic polyester fiber of the present disclosure is excellent in tensile strength despite being thin.

[0073] The tensile strength of a single fiber is measured based on JIS L 1015:2010 Chemical Fiber Staple Test Method at an initial length of 20 mm and a speed of 20 mm / min.

[0074] [Multifilament] The aliphatic polyester fibers of the present disclosure may form a multifilament. When forming a multifilament, the number and fineness of the aliphatic polyester fibers forming the multifilament may be determined according to the required properties, but it is preferable to include 15 or more of the aliphatic polyester fibers, more preferably 20 or more, and even more preferably 30 or more. Also, the aliphatic polyester fibers may be included up to 1000. If the total fineness of the multifilament is the same, the greater the number of fibers forming the multifilament, the higher the flexibility and softness, while the durability tends to decrease.

Examples

[0075] Hereinafter, the present invention will be specifically described by way of examples, but the technical scope of the present invention is not limited by these examples.

[0076] (Example 1) As a poly(3-hydroxybutyrate) - based resin, 100 parts by weight of a (3-hydroxybutyrate - co - 3-hydroxyhexanoate) copolymer resin (proportion of 3-hydroxyhexanoate = 6 mol%, Mw = 550,000, MFR (165 °C, 5 kg) = 3 g / 10 min), 1 part by weight of pentaerythritol "Neutralizer P" (manufactured by Nippon Synthetic Chemical Co., Ltd.) as a crystal nucleating agent, and 0.5 part by weight of erucic acid amide and 0.5 part by weight of behenic acid amide as lubricants were dry - blended, and melt - kneaded at 150 °C using an extruder and pelletized to obtain a resin composition.

[0077] The glass transition temperature of the obtained pellets (resin composition) was 2 °C, the crystallization temperature was 80 °C, the melting point was 142 °C, and the thermal decomposition temperature was 180 °C.

[0078] The process of manufacturing aliphatic polyester fibers using the obtained pellets will be described with reference to Fig. 1. The obtained pellets are melted using a single-screw extruder with a screw diameter of 25 mm (not shown), the flow rate is adjusted using a gear pump, and at a melt spinning temperature of 170°C, they are extruded from a spinning nozzle 1 (shape of the discharge hole: circular) under the conditions shown in Table 1 into a first space (first quenching firm) 2 where air (quenching air) at 14°C and 1.0 m / s is blown; then sent to a second space (second quenching firm) 3 where air (quenching air) at 13°C and 1.0 m / s is blown; taken up by a first roll 4 under the conditions shown in Table 1; passed through a second roll 5 (896 m / min, 70°C), a third roll 6 (1050 m / min, 70°C), a fourth roll 7 (1050 m / min, 70°C), and a fifth roll 8 (1010 m / min, 34°C / 36°C) in sequence, and wound up by a winding roll 9 (1000 m / min) to obtain aliphatic polyester fibers 10. The time for transporting the resin composition from the spinning nozzle to the winding roll was within 30 seconds.

[0079] At this time, the first roll 4, the second roll 5, the third roll 6, and the fourth roll 7 were each configured as a set of two rolls with the same speed and the same temperature. The fifth roll 8 was configured as a set of two rolls with the same speed. Also, NDR = first roll speed / spinning nozzle flow rate, relaxation rate (%) = (roll speed of the maximum speed - winding roll speed) / winding roll speed × 100, and total draw ratio = winding roll speed / spinning nozzle flow rate. In the present disclosure, normal temperature refers to a temperature included in the range of 5 to 35°C.

[0080] The fineness, fiber diameter, and tensile strength of the obtained aliphatic polyester fibers were measured by the following methods. The results are shown in Table 1.

[0081] (Fineness) Measured using a Search automatic vibro-type fineness measuring machine DENIER COMPUTER DC-11 with a sample length of 50 mm.

[0082] (Fiber diameter) Since the shape of the discharge holes of the spinning nozzle is circular and the cross-sectional shape of the obtained fibers is also circular, it was calculated from the cross-sectional area determined from the previously measured fineness per unit length and the specific gravity of the aliphatic polyester fiber (the cross-sectional shape was calculated as a perfect circle).

[0083] (Tensile strength) Using Shimadzu Corporation's tensile measurement device Autograph AG-I, the tensile strength was measured under the following conditions. That is, using the obtained aliphatic polyester fiber as a sample, the initial length of each sample was set to 20 mm, a load cell with a rated capacity of 5 N was used, and the measurement was performed at a speed of 20 mm / min. In addition, based on the previously measured fineness per unit length, the tensile strength per fineness per unit length (cN / dtex) was calculated.

[0084] (Examples 2 to 9, Comparative Examples 1 to 4) Except that each condition was changed as described in Table 1, aliphatic polyester fibers were obtained in the same manner as in Example 1. The time for transporting the resin composition from the spinning nozzle to the take-up roll was within 30 seconds.

[0085] The results of measuring each physical property of the obtained aliphatic polyester fiber are shown in Table 1.

[0086] [Table 1]

[0087] As shown in Table 1, the aliphatic polyester fibers of Comparative Examples 1 to 4, in which the total draw ratio is less than 250 or the take-up roll speed is less than 500 m / min, all have low tensile strength. On the other hand, the aliphatic polyester fibers of the examples have excellent tensile strength despite being manufactured using the same resin composition.

Explanation of symbols

[0088] 1 Spinning nozzle 2 First quenching firm 3 Second quenching firm 4 First roll 5 Second roll 6 Third roll 7 Fourth roll 8 Fifth roll 9 Take-up roll 10 Aliphatic polyester fiber

Claims

1. A method for producing an aliphatic polyester fiber containing a poly(3-hydroxybutyrate) resin and a crystal nucleating agent, comprising: (i) heating a resin composition containing the poly(3-hydroxybutyrate) resin and the crystal nucleating agent to a temperature equal to or higher than the melting point and lower than the thermal decomposition temperature of the resin composition, and discharging it from a spinning nozzle; (ii) a step of stretching the resin composition discharged from the spinning nozzle with a stretching roll; and (iii) a step of winding up the stretched resin composition with a winding roll, wherein the stretching roll is composed of two or more rolls including a first roll and a second roll, and the total stretching ratio of the resin composition (the winding roll speed (m / min) / the spinning nozzle flow rate (m / min)) is 250 or more, and the winding roll speed is 500 to 1500 m / min. A method for producing an aliphatic polyester fiber.

2. The method for producing an aliphatic polyester fiber according to claim 1, wherein the ratio of the winding roll speed (m / min) to the first roll speed (m / min) is 1.5 or more.

3. The method for producing an aliphatic polyester fiber according to claim 1 or 2, wherein the ratio of the first roll speed (m / min) to the spinning nozzle flow rate (m / min) is 55 or more.

4. The method for producing an aliphatic polyester fiber according to any one of claims 1 to 3, wherein, before the resin composition discharged from the spinning nozzle comes into contact with the stretching roll, an air flow at a temperature equal to or higher than the glass transition temperature and lower than the crystallization temperature of the resin composition is applied to the resin composition.

5. The method for producing an aliphatic polyester fiber according to any one of claims 1 to 4, wherein, in the step (ii) of stretching, the temperature of the resin composition is set to 40 to 100°C.

6. The method for producing an aliphatic polyester fiber according to any one of claims 1 to 5, wherein the winding roll speed is 2 to 15% lower than the roll speed of the roll having the maximum speed among the two or more rolls constituting the stretching roll.

7. The method for producing an aliphatic polyester fiber according to any one of claims 1 to 6, wherein the resin composition is conveyed from the spinning nozzle to the winding roll within 1 minute.

8. The method for producing an aliphatic polyester fiber according to any one of claims 1 to 7, wherein the spinning nozzle has 15 or more discharge holes.

9. The poly(3-hydroxybutyrate) resin contains poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), The method for producing an aliphatic polyester fiber according to any one of claims 1 to 8, wherein the proportion of 3-hydroxyhexanoate in the total monomer units constituting the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is 3 to 15 mol%.

Images