WO2021206154A1 - Method for producing aliphatic polyester fiber, aliphatic polyester fiber, and multifilament - Google Patents

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

Manufacturing method of aliphatic polyester fiber, aliphatic polyester fiber and multifilament

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

In recent years, there are problems that plastic waste has caused a great burden on the global environment, such as impact on the ecosystem, generation of harmful gas during combustion, and global warming due to a large amount of combustion heat. Biodegradable plastics are being actively developed as a solution to this problem.

Among such biodegradable plastics, the carbon dioxide emitted when burning biodegradable plastics obtained by using plant-derived raw materials was originally in the air, and the carbon dioxide in the atmosphere increased. do not. This is called carbon neutral, and it is regarded as important under the Kyoto Protocol, which imposes a carbon dioxide reduction target value, and active use is desired.

Recently, from the viewpoint of biodegradability and carbon neutrality, aliphatic polyester resins have been attracting attention as biodegradable plastics produced by microorganisms using plant-derived raw materials as carbon sources, and in particular, polyhydroxyalkanoates (hereinafter, PHA). Poly (3-hydroxybutyrate) homopolymerized resin, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer resin, poly (3-hydroxybutyrate) copolymer resin, poly (3-hydroxybutyrate) homopolymerized resin, poly (3-hydroxybutyrate) copolymer resin, poly (3-hydroxybutyrate) copolymer resin, poly (3-hydroxybutyrate) 3-Hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (hereinafter sometimes referred to as P3HB3HH), poly (3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer resin, and Attention is being paid to polylactic acid and the like.

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.), it is necessary to lengthen the cooling time for solidification after heating and melting during the molding process. There is poor productivity. In particular, when trying to produce fibers by the melt spinning method using PHA, the solidification of the resin is slow, so that the fibers stick to each other and stick to the roll, making it difficult to produce stable fibers. In addition, the quality of the obtained fiber is also low.

As a precedent example of the melt spinning technique for a 3-hydroxyalkanoate polymer, Patent Document 1 describes a polyester resin containing poly (3-hydroxybutyrate-co-3-hydroxyhexanoate). A melt spinning method for spinning at a take-up speed of 500 m / min to 7,000 m / min is described. It is also described that this method can improve spinnability and productivity and increase tensile strength.

As another precedent example, Patent Document 2 describes a melt spinning method for biodegradable aliphatic polyester fibers containing a polyhydroxy alkanoate, a crystal nucleating agent and a lubricant, at a temperature of 130 ° C. or higher and 190 ° C. or lower during spinning. The melt is extruded from the spinning die to obtain the raw yarn, and the raw yarn is taken up by the first take-up roll at a take-up speed of 300 m / min or more and 4,000 m / min or less, and continuously 600 m / min or more. A method of drawing and spinning is described in which the raw yarn is taken up by a second take-up roll at a take-up speed of 7,000 m / min or less. It is also described that this method can improve the crystallization rate of polyhydroxyalkanoates, improve the suction property, improve the spinnability and productivity of the fiber, and increase the tensile strength.

Further, as another precedent example, Patent Document 3 states that PHA is fiberized under specific spinning conditions, and further, in the drawing step, stretching is performed in a temperature range where energy used during production is not wasted, and further, heat treatment is performed. It is described that excellent mechanical properties are exhibited by relaxing in the process.

International Publication No. 2015/029316 International Publication No. 2017/122679 International Publication No. 2012/133231

However, the melt spinning method disclosed in Patent Documents 1 and 2 cannot obtain an aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin having sufficient tensile strength. Further, the method disclosed in Patent Document 3 requires fibrosis, stretching, and further heat treatment, which requires a long time for fiber production and poor productivity.

An object of the present invention is to improve the productivity of an aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent, and to increase the tensile strength.

The first of the present disclosure is a method for producing an aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent, wherein (i) the poly (3-hydroxybutyrate) resin and the poly (3-hydroxybutyrate) resin and A step of heating the resin composition containing the crystal nucleating agent to a temperature equal to or higher than the melting point of the resin composition and lowering the thermal decomposition temperature and discharging the resin composition from the spinning nozzle. It has a step of stretching and (iii) a step of winding the stretched resin composition with a take-up roll, and the stretched roll comprises two or more rolls including a first roll and a second roll, and the resin composition. The total draw ratio of the product (the take-up roll speed (m / min) / the spinning nozzle flow velocity (m / min)) is 250 or more, and the take-up roll speed is 500 to 1500 m / min. The present invention relates to a method for producing a polyester fiber.

In the method for producing an aliphatic polyester fiber, the ratio of the winding roll speed (m / min) to the first roll speed (m / min) is preferably 1.5 or more.

In the method for producing an aliphatic polyester fiber, the ratio of the first roll speed (m / min) to the spinning nozzle flow velocity (m / min) is preferably 55 or more.

In the method for producing an aliphatic polyester fiber, an air stream having a temperature equal to or higher than the glass transition temperature of the resin composition and lower than the crystallization temperature is applied to the resin composition before being discharged from the spinning nozzle and contacting the drawing roll. It is preferable to hit it.

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

In the method for producing an aliphatic polyester fiber, it is preferable that the take-up roll speed is 2 to 15% lower than the maximum roll speed of the two or more rolls constituting the stretch roll.

In the method for producing an aliphatic polyester fiber, it is preferable to transfer the resin composition from the spinning nozzle to the take-up roll within 1 minute.

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

In the method for producing an aliphatic polyester fiber, the poly (3-hydroxybutyrate) resin contains poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and the poly (3-hydroxybutyrate) is contained. The ratio of 3-hydroxyhexanoate to the total monomer unit constituting rate-co-3-hydroxyhexanoate is preferably 3 to 15 mol%.

The second of the present disclosure is an aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent, in which the fineness of the single fiber is 1 to 20 dtex and the tensile strength of the single fiber is 1. For aliphatic polyester fibers of .5 cN / dtex or higher.

In the aliphatic polyester fiber, the poly (3-hydroxybutyrate) resin contains poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), and the poly (3-hydroxybutyrate-co) is contained. The ratio of 3-hydroxyhexanoate to the total monomer unit constituting (-3-hydroxyhexanoate) is preferably 3 to 15 mol%.

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

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

It is a conceptual diagram which shows an example of the manufacturing apparatus used in the manufacturing method of the aliphatic polyester fiber of this disclosure.

[Manufacturing method of aliphatic polyester fiber]
The method for producing an aliphatic polyester fiber of the present disclosure is a method for producing an aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent.
(I) A step of 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 of the resin composition and lower than the thermal decomposition temperature and discharging the resin composition from a spinning nozzle.
(Ii) includes a step of stretching the resin composition discharged from the spinning nozzle with a drawing roll, and (iii) a step of winding the stretched resin composition with a take-up roll.
The drawing roll comprises two or more rolls including a first roll and a second roll, and the total drawing ratio of the resin composition (the take-up roll speed (m / min) / the spinning nozzle flow rate (m / min)). ) Is 250 or more, and the take-up roll speed is 500 to 1500 m / min.

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

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

The poly (3-hydroxybutyrate) -based resin includes a resin containing poly (3-hydroxybutyrate) such as poly (3-hydroxybutyrate); and 3-hydroxybutyrate and other hydroxyalkanoates. Examples thereof include resins containing copolymerized resins.

Examples of the copolymer resin composed of 3-hydroxybutyrate and other hydroxyalkanoate include P3HB3HH [poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)] and PHBV [poly (3-hydroxy). Butyrate-co-3-hydroxyvalerate)], P3HB4HB [poly (3-hydroxybutyrate-co-4-hydroxybutyrate)], poly (3-hydroxybutyrate-co-3-hydroxyvalerate-co) Examples thereof include -3-hydroxyhexanoate, poly (3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly (3-hydroxybutyrate-co-3-hydroxyoctanoate). Of these, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferable. The obtained aliphatic polyester fiber not only has excellent biodegradability, but also has sufficient molding processability for practical use. This is because it is excellent in tensile strength and flexibility.

A resin containing a copolymer resin composed of 3-hydroxybutyrate and another hydroxyalkanoate has a proportion of 3-hydroxyhexanoate of 0.5 to 15 mol% in the total monomer units constituting the resin. It is preferably 1.5 to 15 mol%, more preferably 3 to 15 mol%, and most preferably 3 to 8 mol%. This is because the obtained aliphatic polyester fiber is excellent in tensile strength and flexibility.

The weight average molecular weight Mw of the poly (3-hydroxybutyrate) resin is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,500,000, and 200,000 to 1,000, 000 is more preferable. This is because if the weight average molecular weight Mw is too low, the tensile strength of the obtained 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.

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

In the present disclosure, the crystal nucleating agent is a compound having a melting point higher than that of a poly (3-hydroxybutyrate) resin and having an effect of promoting crystallization of the resin. The compound is not particularly limited. Crystal nucleating agents include, for example, inorganic substances (boron nitride, titanium oxide, talc, layered silicates, calcium carbonate, sodium chloride, and metal phosphates, etc.); naturally occurring sugar alcohol compounds (pentaerythritol, erythritol, etc.) Galactitol, mannitol, arabitol, etc.); Polyvinyl alcohol; Chitin; Chitosan; Polyethylene oxide; aliphatic carboxylic acid salt; aliphatic alcohol; aliphatic carboxylic acid ester; Dicarboxylic acid derivatives (dimethyl adipate, dibutyl adipate, diisodecyl adipate, and Dibutyl sevacate); Cyclic compounds having C = O and a functional group selected from NH, S and O in the molecule (such as indigo, quinacridone, and quinacridone magenta); sorbitol-based derivatives (bisbenzylene sorbitol, and bis (p). -Methylbenzylidene) sorbitol, etc.); Compounds containing nitrogen-containing heteroaromatic nuclei (pyridine ring, triazine ring, imidazole ring, etc.) (pyridine, triazine, imidazole, etc.); Phosphate ester compounds; Bisamide of higher fatty acids; higher Examples thereof include metal salts of fatty acids; and branched polylactic acids. When the poly (3-hydroxybutyrate) resin is P3HB3HH, poly (3-hydroxybutyrate) having a melting point higher than that of P3HB3HH can also be used.

Of these, sugar alcohol compounds and polyvinyl alcohols, from the viewpoint of improving the crystallization rate of poly (3-hydroxybutyrate) -based resins and compatibility and affinity with poly (3-hydroxybutyrate) -based resins. , Chitin, and chitosan are preferred, and pentaerythritol is more preferred. These may be used alone or in combination of two or more.

The content of the crystal nucleating agent in the resin composition containing the poly (3-hydroxybutyrate) resin and the crystal nucleating agent is 0.05 weight by weight with respect to 100 parts by weight of the poly (3-hydroxybutyrate) resin. More than parts are preferable, 0.1 parts by weight or more is more preferable, and 0.5 parts by weight or more is further preferable. The content thereof is preferably 12 parts by weight or less, more preferably 10 parts by weight or less, further 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 the 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. There is.

Further, the resin composition may contain a known additive as an optional component other than the poly (3-hydroxybutyrate) resin and the crystal nucleating agent, if necessary. Known additives include stabilizers such as antioxidants and UV 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.

The plasticizer is not particularly limited, and examples thereof include an adipate ester-based plasticizer, an acetylated monoglyceride-based plasticizer, and a polyglycerin fatty acid ester-based plasticizer. It is also possible to utilize the plasticizing action of supercritical fluids such as carbon dioxide and nitrogen.

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

When the resin composition is heated to a temperature equal to or higher than the melting point of the resin composition and lower than the thermal decomposition temperature, the heating temperature may be appropriately adjusted depending on the type of the resin composition, but the melting point of the resin composition is + 5 ° C. or higher. It is preferable, and a melting point of + 10 ° C. or higher is more preferable. The heating temperature is preferably less than the thermal decomposition temperature of the resin composition, and more preferably the thermal decomposition temperature of −5 ° C. or lower.

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

In the present disclosure, the thermal decomposition temperature is the weight reduction start temperature measured by the thermogravimetric analysis method (TG). Specifically, it is measured at a heating rate of 10 ° C./min using a thermogravimetric analyzer, and the temperature at the start of weight reduction is defined as the thermal decomposition temperature.

The resin composition containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent 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 / g. It is preferably 10 min, more preferably 0.5 to 80 g / 10 min, and even more preferably 1.0 to 60 g / 10 min.

The method for measuring the melt flow rate is a value measured at 165 ° C. and a load of 5 kg according to JIS K7210-2: 2014.

The spinning nozzle is provided with a discharge hole for discharging the resin composition, and the shape, size, and number of the discharge holes are not particularly limited. As the size of the discharge hole, for example, when the shape of the discharge hole is circular, the diameter is preferably Φ0.1 mm to 3.0 mm. The number of discharge holes depends on the size of the discharge holes, but may be, for example, 15 or more, or 1000 or less.

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

Further, the discharge amount from the spinning nozzle is preferably 0.10 g / min / hole or more, and more preferably 0.15 g / min / hole or more. The discharge amount is preferably less than 1.0 g / min / hole, and more preferably 0.90 g / min / hole or less.

It is preferable that the resin composition is rapidly cooled by applying an air flow having a temperature equal to or higher than the glass transition temperature of the resin composition to lower than the crystallization temperature before discharging the resin composition from the spinning nozzle and contacting the drawing roll. By such quenching, the cooling and solidification of the resin composition can be promoted, and the stretching strain given by the speed difference between the stretching rolls and the like is more effectively reflected. As a result, the tensile strength of the obtained aliphatic polyester fiber can be further increased.

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

The crystallization temperature is measured by the differential scanning calorimetry (DSC) method. Specifically, it is measured at a temperature lowering rate of 10 ° C./min using a differential scanning calorimeter, and the heat dissipation peak of the obtained DSC curve is defined as the crystallization temperature.

The temperature of the air flow applied to the resin composition discharged from the spinning nozzle may be not less than the glass transition temperature of the resin composition and not more than the crystallization temperature, and may be appropriately adjusted depending on 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 the crystallization temperature of −20 ° C. or lower, and further preferably the crystallization temperature of −40 ° C. or lower.

The velocity of the air flow 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 velocity of the air flow is less than 0.1 m / s, the obtained cooling effect becomes too small, and if it exceeds 5 m / s, the resin composition discharged from the spinning nozzle sways in the air flow, so that the discharged product is discharged. This is because fusion and / or yarn breakage between the resin compositions may occur, which may lead to a decrease in spinning stability.

The type of the air flow is also not particularly limited, but air; an inert gas such as nitrogen gas and argon gas is preferable.

(Ii) A step of stretching the resin composition discharged from the spinning nozzle with a drawing roll, and (iii) a step of winding the stretched resin composition with a winding roll will be described in detail below.

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

The drawn roll may include a first roll and a second roll, and the number of the drawn rolls is not particularly limited, and may be appropriately selected in consideration of the temperature control efficiency of the fiber, the draw ratio, and the like. Just do it. The number of the stretched rolls may be 3 or more, 4 or more, and 5 or more. The number of the stretched rolls is not particularly limited as long as it is within the scope of the object of the present invention, but may be 10 or less from the viewpoint of not increasing the equipment cost and the manufacturing equipment too much.

Further, each of the stretching rolls may be composed of not only one roll but also a set of two or more rolls having the same speed. The temperature of the fibers to be drawn can be made uniform, and longer fibers can be produced in a smaller space.

The ratio of the first roll speed (m / min) to the spinning nozzle flow velocity (m / min) (hereinafter, may be referred to as NDR) is preferably 55 or more, more preferably 100 or more, still more preferably 150 or more. , 200 or more is particularly preferable. This is because increasing the NDR can promote the alignment of the molecular chains of the resin composition, and the diameter of the resin composition becomes smaller, so that cooling solidification can be promoted. The NDR has no upper limit as long as the fibers are not broken, but may be 1000 or less.

The ratio of the take-up roll speed (m / min) to the first roll speed (m / min) is preferably 1.5 or more, more preferably 1.7 or more, still more preferably 1.8 or more. This is because an aliphatic polyester fiber having a higher tensile strength can be obtained. The ratio may be 30 or less, although there is no upper limit as long as the fibers are not broken.

(Ii) In the step of stretching the resin composition discharged from the spinning nozzle with a drawing roll, the temperature of the resin composition is preferably 40 to 100 ° C, 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 of the resin composition may be adjusted by adjusting the temperature of an object in contact with the resin composition, such as a solid such as the surface of a stretched roll; a liquid such as a bathtub and droplets; and a gas such as an air flow.

When the stretched resin composition is wound up by a take-up 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, further preferably 330 or more, and even more preferably 340 or more. The total draw ratio may be 2000 or less, although there is no upper limit as long as fibers having a desired fineness can be stably obtained.

The total draw ratio is defined by the take-up roll speed (m / min) / the spinning nozzle flow velocity (m / min).

The take-up roll speed is 500 to 1500 m / min, and may be appropriately adjusted in the range in consideration of the spinning nozzle flow velocity, the speed of other rolls, and the like.

The take-up roll speed is preferably 2 to 15% lower than the maximum roll speed of the two or more rolls constituting the stretch roll, more preferably 3 to 15% lower, and 3 to 12%. It is even more preferable that it is low. 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. The ratio indicated by the "%", that is, (the roll speed of the maximum speed-the winding roll speed) / the winding roll speed x 100 can be rephrased as the "relaxation rate (%)".

The time for transporting the resin composition is preferably within 1 minute, preferably within 50 seconds, more preferably within 40 seconds, and even more preferably within 30 seconds from the spinning nozzle to the take-up roll. Moreover, the time may be 1 second or more. According to the production method of the present disclosure, an aliphatic polyester fiber having high productivity and high tensile strength can be produced in a short time.

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

The content of the crystal nucleating agent in the aliphatic polyester fiber of the present disclosure is preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, based on 100 parts by weight of the poly (3-hydroxybutyrate) resin. It is preferable, and 0.5 parts by weight or more is more preferable. The content thereof is preferably 12 parts by weight or less, more preferably 10 parts by weight or less, further preferably 8 parts by weight or less, and 5 parts by weight or less with respect to 100 parts by weight of the poly (3-hydroxybutyrate) resin. Is the most preferable.

Further, the particle size of the crystal nucleating agent contained in the aliphatic polyester fiber is preferably one-third or less of the minimum diagonal length of the cross section of the fiber. This is because it is superior in the tensile strength of the fiber.

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

The fineness of the 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.

The fineness of a single fiber is the thickness of the thread 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 motorcycle broscope method.

The tensile strength of the 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, further preferably 1.8 cN / dtex or more, and 1.9 cN / dtex or more. Is the most preferable. The tensile strength is not particularly limited as long as it does not impair the flexibility and toughness required by the application, but may be 10 cN / dtex or less. Although the aliphatic polyester fiber of the present disclosure is thin, it has excellent tensile strength.

The tensile strength of a single fiber is measured at an initial length of 20 mm and a speed of 20 mm / min based on the JIS L 1015: 2010 chemical fiber staple test method.

[Multifilament]
The aliphatic polyester fibers of the present disclosure may constitute a multifilament. When forming a multifilament, the number and fineness of the aliphatic polyester fibers constituting the multifilament may be determined according to the desired characteristics, but it is preferable that 15 or more of the aliphatic polyester fibers are contained, and 20 fibers are contained. It is more preferable to include the above, and it is further preferable to include 30 or more. Further, 1000 or less of the aliphatic polyester fibers may be contained. If the total fineness of the multifilaments is the same, as the number of fibers constituting the multifilaments increases, the flexibility and suppleness tend to increase, but the durability tends to decrease.

Hereinafter, the present invention will be specifically described with reference to Examples, but the technical scope of the present invention is not limited by these Examples.

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

The obtained pellet (resin composition) had a glass transition temperature of 2 ° C., a crystallization temperature of 80 ° C., a melting point of 142 ° C., and a thermal decomposition temperature of 180 ° C.

The process of producing an aliphatic polyester fiber using the obtained pellets will be described with reference to FIG. The obtained pellets are melted by a uniaxial extruder (not shown) having a screw diameter of 25 mm, the flow rate is adjusted by a gear pump, the melt spinning temperature is 170 ° C., and the spinning nozzle 1 (of the discharge hole) under the conditions shown in Table 1 is used. Extruded from (shape: circular) into the first space (first quenching farm) 2 where air (quenching air) at 14 ° C. and 1.0 m / s is blown; air at 13 ° C. and 1.0 m / s (quenching air). To the second space (second quenching farm) 3 to be sprayed; picked up by the first roll 4 under the conditions shown in Table 1; second roll 5 (896 m / min, 70 ° C.), third roll 6 (1050 m / min, 70 ° C.), 4th roll 7 (1050 m / min, 70 ° C.), and 5th roll 8 (1010 m / min, 34 ° C./36 ° C.) are passed in this order, and the winding roll 9 (1000 m / min / ° C.) is passed. In min), the mixture was wound to obtain an aliphatic polyester fiber 10. The time for transporting the resin composition from the spinning nozzle to the take-up roll was within 30 seconds.

At this time, the first roll 4, the second roll 5, the third roll 6, and the fourth roll 7 are all configured as a set of two rolls having the same speed and the same temperature. The fifth roll 8 is composed of two rolls having the same speed as a set. Further, NDR = first roll speed / spinning nozzle flow velocity, relaxation rate (%) = (maximum speed roll speed-winding roll speed) / winding roll speed x 100, and total draw ratio = winding roll. Velocity / spinning nozzle flow velocity. In the present disclosure, the normal temperature means a temperature included in the range of 5 to 35 ° C.

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

(Single fineness)
The sample length was 50 mm using a motorcycle bro-type fineness measuring machine DENIER COMPUTER DC-11 manufactured by Search Co., Ltd.

(Fiber diameter)
Since the shape of the discharge hole of the spinning nozzle is circular and the cross-sectional shape of the obtained fiber is also circular, it was calculated from the cross-sectional area obtained from the previously measured single fineness and the specific gravity of the aliphatic polyester fiber (the cross-sectional shape is true). Calculated as a circle).

(Tensile strength)
The tensile strength was measured under the following conditions using the Shimadzu tensile measuring device Autograph AG-I. That is, using the obtained aliphatic polyester fiber as a sample, the initial length of each sample was set to 20 mm, and the measurement was performed at a speed of 20 mm / min using a load cell having a rated capacity of 5 N. In addition, the tensile strength (cN / dtex) per single fineness was calculated based on the single fineness measured in advance.

(Examples 2 to 9, Comparative Examples 1 to 4)
Aliphatic polyester fibers were obtained in the same manner as in Example 1 except that the conditions were changed as shown in Table 1. The time for transporting the resin composition from the spinning nozzle to the take-up roll was within 30 seconds.

Table 1 shows the results of measuring the physical characteristics of the obtained aliphatic polyester fiber.

As shown in Table 1, all of the aliphatic polyester fibers of Comparative Examples 1 to 4 having a total draw ratio of less than 250 or a take-up roll speed of less than 500 m / min have low tensile strength. On the other hand, the aliphatic polyester fiber of the example has excellent tensile strength even though it is produced using the same resin composition.

1 Spinning nozzle 2 1st quenching farm 3 2nd quenching farm 4 1st roll 5 2nd roll 6 3rd roll 7 4th roll 8 5th roll 9 Winding roll 10 Aliphatic polyester fiber

Claims (12)

1. A method for producing an aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent.
   (I) A step of 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 of the resin composition and lower than the thermal decomposition temperature and discharging the resin composition from a spinning nozzle.
   (Ii) includes a step of stretching the resin composition discharged from the spinning nozzle with a drawing roll, and (iii) a step of winding the stretched resin composition with a take-up roll.
   The drawing roll comprises two or more rolls including a first roll and a second roll, and the total drawing ratio of the resin composition (the take-up roll speed (m / min) / the spinning nozzle flow rate (m / min)). ) Is 250 or more,
   A method for producing an aliphatic polyester fiber, wherein the take-up roll speed is 500 to 1500 m / min.
2. The method for producing an aliphatic polyester fiber according to claim 1, wherein the ratio of the take-up 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 velocity (m / min) is 55 or more.
4. Any of claims 1 to 3, wherein the resin composition is blown with an air flow having a temperature equal to or higher than the glass transition temperature of the resin composition and lower than the crystallization temperature before being discharged from the spinning nozzle and brought into contact with the drawing roll. The method for producing an aliphatic polyester fiber according to item 1.
5. The method for producing an aliphatic polyester fiber according to any one of claims 1 to 4, wherein the temperature of the resin composition is set to 40 to 100 ° C. in the stretching step (ii).
6. The aliphatic polyester fiber according to any one of claims 1 to 5, wherein the take-up roll speed is 2 to 15% lower than the maximum roll speed of the two or more rolls constituting the stretch roll. Manufacturing method.
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 take-up 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).
   Any of claims 1 to 8, wherein the ratio of 3-hydroxyhexanoate to the total monomer unit constituting the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) is 3 to 15 mol%. The method for producing an aliphatic polyester fiber according to the above item.
10. An aliphatic polyester fiber containing a poly (3-hydroxybutyrate) resin and a crystal nucleating agent.
    An aliphatic polyester fiber having a single fiber fineness of 1 to 20 dtex and a single fiber tensile strength of 1.5 cN / dtex or more.
11. The poly (3-hydroxybutyrate) resin contains poly (3-hydroxybutyrate-co-3-hydroxyhexanoate).
    The fat according to claim 10, wherein the ratio of 3-hydroxyhexanoate to the total monomer unit constituting the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) is 3 to 15 mol%. Group polyester fiber.
12. A multifilament containing 15 or more aliphatic polyester fibers according to claim 10 or 11.

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