Biodegradable monofilament

Abstract

To provide a monofilament with excellent biodegradability in soil.SOLUTION: The invention relates to a biodegradable monofilament containing a polymeric component, wherein: the polymeric component comprises 85 wt.% or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); and the molar ratio of hydroxycarboxylic acids constituting the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is in a range of 3-hydroxybutyrate / 3-hydroxyhexanoate=80 / 20 to 99 / 1; and the fineness thereof is in a range of 15-3,000 dtex.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a biodegradable monofilament. [Background technology]

[0002] The attractant string is used to help the growth of vines (e.g. Chinese yam, cucumber, etc.) by entangling the vines around the string. The attractant string is made of monofilament containing polyolefin material. Because the vines become entangled with the attractant string, it is sometimes impossible to separate the vines from the attractant string, and so traditionally, after the vines are harvested, the attractant string has been burned along with the vines. However, an increasing number of areas are now prohibited from burning fields by ordinance, and in these areas, the strings must be disposed of at incinerators, resulting in high disposal costs. For this reason, attractant strings made of biodegradable polylactic acid have been developed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-337116 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, polylactic acid cannot be fully decomposed by simply leaching it into fields, and therefore must be biodegraded under composting conditions. Furthermore, biodegradation during composting takes time. For these reasons, there is a demand for monofilaments that are highly biodegradable in soil.

[0005] Therefore, an object of the present invention is to provide a monofilament that is highly biodegradable in soil. [Means for solving the problem]

[0006] The present invention provides a biodegradable monofilament containing a polymer component, The polymer component contains 85% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), the molar ratio of hydroxycarboxylic acids constituting the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is in the range of 3-hydroxybutyrate / 3-hydroxyhexanoate=80 / 20 to 99 / 1; The present invention relates to a biodegradable monofilament having a fineness in the range of 15 to 3000 dtex. Effect of the Invention

[0007] According to the present invention, a monofilament having excellent biodegradability in soil can be provided. [Brief description of the drawings]

[0008] [Figure 1] Schematic diagram of a monofilament production apparatus. [Diagram 2] SEM photograph of accelerated hydrolysis test (jungle test). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of the present invention will be described.

[0010] The biodegradable monofilament according to this embodiment is a monofilament containing a polymer component. The polymer component contains at least 85% by weight of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). The molar ratio of hydroxycarboxylic acids constituting the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is in the range of 3-hydroxybutyrate / 3-hydroxyhexanoate=80 / 20 to 99 / 1. The fineness of the monofilament according to this embodiment is in the range of 15 to 3000 dtex.

[0011] The monofilament according to the present embodiment is formed into a thread-like shape from a polymer composition containing a polymer component. The polymer composition may further comprise additives.

[0012] The polymer component contains 85% by weight or more and 100% by weight or less, and preferably 90% by weight or more and 100% by weight or less, of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter, also referred to as "P3HB3HH"). When the polymer component contains 85% by weight or more of P3HB3HH, the monofilament becomes highly biodegradable in soil. The soil also includes bottom sediments at the bottom of seas, rivers, lakes and marshes.

[0013] In addition, the polymer component contains 85% by weight or more of P3HB3HH, which gives it excellent hydrolysis resistance. Like polylactic acid, P3HB3HH has ester bonds that are subject to hydrolysis, but P3HB3HH has a larger number of carbon atoms between the ester bonds than polylactic acid, which is thought to give it excellent hydrolysis resistance.

[0014] The P3HB3HH has excellent biodegradability and moldability. In this embodiment, "biodegradability" refers to a property that can be decomposed into low molecular weight compounds by microorganisms in nature. Specifically, the presence or absence of biodegradability can be determined based on tests suitable for each environment, such as ISO 14855 (compost) and ISO 14851 (activated sludge) under aerobic conditions, and ISO 14853 (aqueous phase) and ISO 15985 (solid phase) under anaerobic conditions. In addition, the decomposition by microorganisms in seawater can be evaluated by measuring biochemical oxygen demand.

[0015] The molar ratio of hydroxycarboxylic acids constituting the P3HB3HH, 3-hydroxybutyrate / 3-hydroxyhexanoate, is in the range of 80 / 20 to 99 / 1, preferably in the range of 85 / 15 to 98 / 2, and more preferably in the range of 90 / 10 to 97 / 3. When the molar ratio of 3-hydroxybutyrate to 3-hydroxyhexanoate (3-hydroxybutyrate / 3-hydroxyhexanoate) is 80 / 20 or more, the rigidity of the monofilament according to this embodiment is increased. When the molar ratio of 3-hydroxybutyrate to 3-hydroxyhexanoate (3-hydroxybutyrate / 3-hydroxyhexanoate) is 99 / 1 or less, the monofilament according to this embodiment has excellent processability.

[0016] The weight average molecular weight of the P3HB3HH is preferably 50,000 to 2.5 million, more preferably 70,000 to 1 million, and further preferably 100,000 to 400,000. When the weight average molecular weight of the P3HB3HH is 2,500,000 or less, the productivity at the time of obtaining a monofilament by spinning through nozzle extrusion can be easily improved. When the weight average molecular weight of the P3HB3HH is 50,000 or more, the physical properties (such as the strength of the monofilament) are improved. P3HB3HH with the optimum weight average molecular weight can be used according to the required "productivity" and "monofilament properties".

[0017] In the present embodiment, the weight average molecular weight is measured from the polystyrene equivalent molecular weight distribution by gel permeation chromatography (GPC) using chloroform as an eluent. As the column for the GPC, a column suitable for measuring the molecular weight may be used. For example, the weight average molecular weight (Mw) can be determined by setting the column temperature at 40°C, injecting 10 μl of 3 mg of the target substance dissolved in 2 ml of chloroform, and setting the flow rate of the chloroform eluent (mobile phase) to 1.0 ml / min. The GPC device used is an LC-10A system (manufactured by Shimadzu Corporation), and the column used is a GPCK-806M (manufactured by Showa Denko Corporation).

[0018] The method for producing P3HB3HH is not particularly limited, but examples thereof include a method in which P3HB3HH is produced by a microorganism capable of producing P3HB3HH. An example of a P3HB3HH-producing bacterium is Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bacteriol., 179, pp. 4821-4830 (1997)), into which genes encoding P3HA synthases have been introduced to increase the productivity of P3HB3HH. P3HB3HH can be produced by culturing a microorganism under appropriate conditions, allowing P3HB3HH to accumulate in the cells, and then recovering the P3HB3HH. Culture conditions, including the type of substrate, can be optimized according to the microorganism used.

[0019] The polymer component may contain other biodegradable resins other than P3HB3HH. The polymer component may contain 15% by weight or less, or 10% by weight or less, of the other biodegradable resins. The polymer component may contain 1% by weight or more, 2% by weight or more, or 5% by weight or more of the other biodegradable resins. Examples of the other biodegradable resins include polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, unmodified starch, modified starch, cellulose acetate, chitosan, and poly(4-hydroxyalkanoate)-based resins. Furthermore, the other biodegradable resins include poly(3-hydroxyalkanoate) resins other than P3HB3HH. Examples of poly(3-hydroxyalkanoate) resins other than P3HB3HH include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate), and the like. Here, P3HB means the homopolymer poly(3-hydroxybutyrate). P3HB3HH means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). P3HB3HV means poly(3-hydroxybutyrate-co-3-hydroxyvalerate). P3HB4HB means poly(3-hydroxybutyrate-co-4-hydroxybutyrate). The polymer component may contain one type of other biodegradable resin, or may contain two or more types.

[0020] From the viewpoint of increasing the strength of the monofilament according to the present embodiment, the polymer component preferably contains polycaprolactone. The polymer component may contain 15% by weight or less of polycaprolactone, and may contain 10% by weight or less. Also, from the viewpoint of increasing the strength of the monofilament, the polymer component preferably contains 1% by weight or more of polycaprolactone, more preferably 2% by weight or more, and even more preferably 5% by weight or more. The polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. Moreover, polycaprolactone is biodegradable, similar to poly(3-hydroxyalkanoate) resins. The polycaprolactone may be a homopolymer and / or a copolymer. From the viewpoint of increasing the strength of the monofilament according to the present embodiment, the polycaprolactone preferably contains a homopolymer, and more preferably is a homopolymer. Furthermore, since the monofilament according to this embodiment contains polycaprolactone, the monofilament according to this embodiment has high strength. The weight average molecular weight of the polycaprolactone is preferably 5,000 to 500,000, and more preferably 10,000 to 200,000. When the weight average molecular weight of the polycaprolactone is 500,000 or less, the monofilament according to the present embodiment can be easily molded. When the weight average molecular weight of the polycaprolactone is 5,000 or more, the strength of the monofilament according to this embodiment can be increased.

[0021] From the viewpoint of easily controlling the biodegradation rate of the monofilament and improving the strength of the monofilament, the monofilament according to the present embodiment is preferably a monofilament spun from a mixture of the P3HB3HH and the other biodegradable resin, and the other biodegradable resin preferably contains polycaprolactone.

[0022] Since the monofilament according to the present embodiment contains a biodegradable polymer, even if it is discarded in the environment, it is easily decomposed in the environment, thereby reducing the burden on the environment.

[0023] Examples of the additives include crystal nucleating agents (nucleating agents), lubricants, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, inorganic fillers, organic fillers, antistatic agents, etc.

[0024] In order to promote the crystallization of the P3HB3HH, the polymer composition preferably contains a crystal nucleating agent. The crystal nucleating agent is a compound that has the effect of promoting the crystallization of the P3HB3HH, and has a melting point higher than that of the P3HB3HH. Examples of the crystal nucleating agent include inorganic substances (boron nitride, titanium oxide, talc, layered silicates, calcium carbonate, sodium chloride, metal phosphates, etc.); sugar alcohol compounds derived from natural products (pentaerythritol, erythritol, galactitol, mannitol, arabitol, etc.); polyvinyl alcohol; chitin; chitosan; polyethylene oxide; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylate esters; dicarboxylic acid derivatives (dimethyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl selenite, etc.); Examples include cyclic compounds having C=O and a functional group selected from NH, S and O in the molecule (indigo, quinacridone, quinacridone magenta, etc.); sorbitol derivatives (bisbenzylidene sorbitol, bis(p-methylbenzylidene)sorbitol, etc.); compounds containing a nitrogen-containing heteroaromatic nucleus (pyridine ring, triazine ring, imidazole ring, etc.) (pyridine, triazine, imidazole, etc.); phosphate ester compounds; bisamides of higher fatty acids; metal salts of higher fatty acids; and branched polylactic acid. P3HB can also be used as a crystal nucleating agent. These may be used alone or in combination of two or more.

[0025] As the crystal nucleating agent, from the viewpoint of the effect of improving the crystallization rate of P3HB3HH and from the viewpoint of compatibility and affinity with P3HB3HH, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan are preferred. Among the sugar alcohol compounds, pentaerythritol is preferred.

[0026] The monofilament according to this embodiment contains a crystal nucleating agent in an amount of preferably 0.1 part by weight or more, more preferably 0.2 part by weight or more, and even more preferably 0.4 part by weight or more, based on 100 parts by weight of the P3HB3HH. The monofilament according to this embodiment contains 0.1 part by weight or more of a crystal nucleating agent based on 100 parts by weight of the P3HB3HH, thereby making it possible to promote crystallization of P3HB3HH. Moreover, the monofilament according to this embodiment contains a crystal nucleating agent in an amount of preferably 4 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 2.5 parts by weight or less, based on 100 parts by weight of the P3HB3HH. The monofilament of this embodiment contains 4 parts by weight or less of a crystal nucleating agent per 100 parts by weight of the P3HB3HH, which has the advantage that the viscosity of the molten material can be lowered when producing the monofilament, making it easier to produce the monofilament.

[0027] The monofilament according to this embodiment contains pentaerythritol in an amount of preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 0.4 parts by weight or more, based on 100 parts by weight of the P3HB3HH. The monofilament according to this embodiment contains pentaerythritol in an amount of preferably 4 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 2.5 parts by weight or less, based on 100 parts by weight of the P3HB3HH.

[0028] The polymer composition preferably contains the lubricant, which improves the lubricity of the monofilament. The lubricant may, for example, be a fatty acid amide. The fatty acid amide preferably includes at least one selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0029] The monofilament according to this embodiment contains a lubricant in an amount of preferably 0.1 part by weight or more, more preferably 0.2 part by weight or more, and even more preferably 0.4 part by weight or more, based on 100 parts by weight of the P3HB3HH. The monofilament according to this embodiment contains 0.1 part by weight or more of a lubricant per 100 parts by weight of the P3HB3HH, and thus has the advantage of providing excellent lubricity to the monofilament. Moreover, the monofilament according to this embodiment contains a lubricant in an amount of preferably 4 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 2.5 parts by weight or less, based on 100 parts by weight of the P3HB3HH. The monofilament according to this embodiment contains 4 parts by weight or less of a lubricant per 100 parts by weight of the P3HB3HH, which has the advantage that bleeding out of the lubricant onto the surface of the monofilament can be suppressed.

[0030] The monofilament according to this embodiment contains preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 0.4 parts by weight or more of fatty acid amide per 100 parts by weight of the P3HB3HH. The monofilament according to this embodiment contains preferably 4 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 2.5 parts by weight or less of fatty acid amide per 100 parts by weight of the P3HB3HH.

[0031] The weight average molecular weight (Mw) of the monofilament according to this embodiment is preferably in the range of 50,000 to 2.5 million, more preferably 70,000 to 1 million, and further preferably 100,000 to 400,000. When the weight average molecular weight is 2,500,000 or less, the productivity when obtaining monofilaments by spinning through nozzle extrusion can be easily improved. When the weight average molecular weight is 50,000 or more, the physical properties (such as the strength of the monofilament) are improved. A resin having an optimum weight average molecular weight can be used according to the required "productivity" and "physical properties of the monofilament".

[0032] The monofilament according to this embodiment has a fineness of 15 to 3000 dtex. When the fineness is 15 dtex or more, high strength of the monofilament is easily ensured. When the fineness is 3000 dtex or less, productivity in post-processing (for example, knitting and weaving) can be easily improved. The fineness of the monofilament according to this embodiment is preferably 100 dtex or more, more preferably 200 dtex or more, and even more preferably 300 dtex or more. The fineness of the monofilament according to this embodiment is preferably 1500 dtex or less, and more preferably 1000 dtex or less. The fineness of the monofilament is the mass per unit length, and is expressed in units of mass (g) per 10,000 m (dtex). The fineness of the monofilament can be measured by the autobibroscope method.

[0033] The tensile strength of the monofilament according to this embodiment is preferably 0.5 cN / dtex or more, more preferably 0.8 cN / dtex or more, and even more preferably 1.0 cN / dtex or more. The tensile strength of the monofilament according to the present embodiment is preferably high. The tensile strength of the monofilament according to this embodiment is not particularly limited as long as it is within a range that does not impair the flexibility and toughness required depending on the application, but may be 6.0 cN / dtex or less. The tensile strength of the monofilament according to this embodiment means the tensile strength measured at an initial length of 20 mm and a speed of 20 mm / min based on JIS L 1015:2021 "Test method for chemical fiber staples". The tensile strength can be measured using, for example, a tensile measuring device (Autograph AG-1, manufactured by Shimadzu Corporation).

[0034] The monofilament according to this embodiment preferably has a decomposition rate after 210 days in the ISO17556 test of 60% or more, more preferably 62% or more. Specifically, the decomposition rate can be determined by the method described below. Since the decomposition rate is 60% or more, the monofilament according to this embodiment has the advantage of being more excellent in biodegradability in soil. By increasing the content of P3HB3HH in the polymer component, the decomposition rate can be increased.

[0035] The monofilament according to this embodiment has a yarn strength ratio before and after a constant temperature and humidity test at a temperature of 80° C. and a humidity of 90%, which is calculated by the following formula, of preferably 70% or more, more preferably 73% or more. Yarn strength ratio (%) = monofilament strength after 82 hours of exposure to the constant temperature and humidity test / monofilament strength before the constant temperature and humidity test × 100% The strength in the yarn strength ratio is the tensile strength. The tensile strength can be determined in accordance with JIS L 1013:2021 "Testing method for chemical fiber filament yarn" or JIS L 1015:2021 "Testing method for chemical fiber staple". Specifically, the tensile strength of the monofilament can be measured using a tension and compression tester (INTESCO Model 201, manufactured by INTESCO) in accordance with JIS L 1015:2021. More specifically, one monofilament (single fiber) with a length of 40 mm is taken, and both ends of the monofilament are sandwiched between a paper (thin paper) with double-sided tape with adhesive applied, and air-dried overnight to prepare a sample with a length of 20 mm. The sample is then attached to a testing machine and tested at a temperature of 24°C, a relative humidity of 80% or less, a load of 0.038 gf x fineness (dtex), and a pulling speed of 20 mm / min to measure the tensile strength at break. Since the yarn strength ratio is 70% or more, the monofilament according to this embodiment has the advantage of being less susceptible to the effects of moisture such as rain. By increasing the content of P3HB3HH in the polymer component, the yarn strength ratio can be increased.

[0036] Examples of the cross-sectional shape (cross-section perpendicular to the longitudinal direction) of the monofilament according to this embodiment include a circular shape (a concept that includes an elliptical shape), a Y-shape, an X-shape, an H-shape, and a multi-lobed shape.

[0037] The monofilament according to the present embodiment may be a composite fiber. Composite fibers are specified in JIS L0204-3:1998, 3.2.10. The composite fiber may be, for example, a core-sheath composite fiber having a core and a sheath. The core may contain P3HB3HH and the sheath may contain another biodegradable resin. Alternatively, the core may contain another biodegradable resin and the sheath may contain P3HB3HH.

[0038] The monofilament according to this embodiment can be used, for example, as marine materials, agricultural materials, civil engineering materials, medical materials, and the like. Specifically, the monofilament according to this embodiment can be used as, for example, braided cord, tape, agricultural attractant net, fishing line, fishing net, aquaculture net, seaweed seedling thread, turf material for artificial turf, toothbrush bristles, beverage extraction filters (fabric for tea bags), insect net, animal net, suture thread, surgical net, stent, prosthetic material, filament for 3D printing, tennis string, hook-and-loop fastener (e.g., Velcro (registered trademark)), tire cord, printing screen, wig, hose reinforcement material, weft knitted fabric for clothing, grass cutting cord (wire material), net for screen doors, woven fabric, turbin, core filament of filament core spun yarn, ribbon, etc.

[0039] The braid according to this embodiment is a braid formed from the biodegradable monofilament. The tape according to this embodiment is a tape formed from the biodegradable monofilament. The agricultural attractant net of this embodiment is an agricultural attractant net formed from the biodegradable monofilament.

[0040] In the method for producing the monofilament according to the present embodiment, the monofilament is produced by a melt spinning method. The manufacturing method includes a step (A) of passing a raw yarn obtained by discharging a molten material from a spinning nozzle through a water bath, and a step (B) of drawing the raw yarn that has passed through the water bath with a drawing roll section.

[0041] In the following, the manufacturing method will be described by taking as an example a method for manufacturing a monofilament using the monofilament manufacturing apparatus 1 shown in FIG.

[0042] (Process (A)) The step (A) is a step in which the raw yarn obtained by discharging the molten material from a spinning nozzle is passed through a water bath.

[0043] As shown in FIG. 1, in the step (A), first, the material of the molten material is charged into a material charging section 2a. Next, the material fed through the material feed section 2a is heated and kneaded in a kneading extruder 2b to obtain the molten material. The kneading extruder 2b is a screw extruder. The kneading extruder 2b may be a single screw extruder or a twin screw extruder.

[0044] Then, the molten material obtained in the kneading extruder 2d is discharged from the discharge hole using a spinning nozzle 2d having a discharge hole, thereby obtaining a raw yarn A in a molten state. The flow rate of the molten material discharged from the discharge hole of the spinning nozzle 2d is adjusted by a gear pump 2c.

[0045] The temperature of the spinning nozzle 2d is, for example, 150 to 190°C, more specifically, 160 to 180°C.

[0046] The spinning nozzle 2d has one or more discharge holes, and may have a plurality of discharge holes. The spinning nozzle 2d has a plurality of discharge holes, so that a plurality of monofilaments can be produced simultaneously.

[0047] Examples of the shape of the discharge hole include a circular shape (including an elliptical shape), a Y-shape, an X-shape, an H-shape, and a multi-lobe shape. Regarding the size of the nozzle hole, for example, when the nozzle hole has a circular shape, the diameter of the nozzle hole is preferably 0.5 mm to 20 mm, and more preferably 1.0 mm to 10 mm. When the nozzle hole has a circular shape, the ratio of the length (L) of the nozzle hole to the diameter (D) of the nozzle hole, in other words, L / D, is preferably 1-10, and more preferably 2-5.

[0048] The rate at which the molten material is discharged from one discharge hole is preferably 0.20 to 2.0 kg / hr, and more preferably 0.40 to 1.2 kg / hr.

[0049] In the step (A), the raw yarn A is cooled by passing the raw yarn A through a water bath. In the step (A), the raw yarn A having a temperature higher than the solidification temperature of the raw yarn A is passed through a water bath 3a.

[0050] The temperature of the water bath 3a is preferably 15 to 35°C, and more preferably 18 to 34°C. In the step (A), the raw yarn A is passed through a water bath 3a at 35° C. or lower, thereby preventing the raw yarn A from coming into contact with the take-up roll section 4 in a softened state and becoming stuck thereto. In addition, in the step (A), the raw yarn A is passed through a water bath 3a at 35°C or less, thereby shortening the time during which the polymer components constituting the raw yarn A are in the temperature range in which they crystallize, and suppressing the progress of crystallization of the polymer components. This prevents the raw yarn A from becoming hard. This makes it easier to stretch the raw yarn A in the step (B). As a result, it becomes easier to increase the strength of the monofilament. In addition, since the water bath 3a is at 15°C or higher, a certain amount of time can be ensured within the temperature range in which the polymer components constituting the raw yarn A crystallize, thereby preventing the raw yarn A from coming into contact with the water bath roll section 3c without being sufficiently crystallized and sticking to it.

[0051] The water bath 3a is water placed in a water tank 3b.

[0052] The monofilament manufacturing apparatus 1 includes a water bath roll section 3c that conveys the raw yarn A so that the raw yarn A passes through the water bath 3a. In the step (A), the raw yarn A is conveyed by a water bath roll section 3c, so that the raw yarn A passes through the water bath 3a.

[0053] In the step (A), the raw yarn A is cooled to preferably 50° C. or less, more preferably 40° C. or less. In the step (A), the raw yarn A is cooled to, for example, 0° C. or more, more specifically, 10° C. or more. In the step (A), the raw yarn A may be cooled to 50° C. or less by passing the raw yarn A through a water bath at 15 to 35° C. In addition, in the step (A), the raw yarn A may be cooled to a certain degree by passing the raw yarn A through a water bath at 15 to 35° C., and then cooled with ambient air until the drawing, thereby cooling the raw yarn A to 50° C. or less.

[0054] (Process (B)) In the step (B), the cooled raw yarn A is stretched in a stretching roll section. In the step (B), the raw yarn A is stretched, whereby the orientation of the polymer component contained in the raw yarn can be increased, and thus the strength of the monofilament can be increased.

[0055] In the step (B), it is preferable that the cooled raw yarn A is heated and stretched in a stretching roll section. Here, in order to increase the orientation of the polymer component, it is desirable to stretch the yarn in a temperature range suitable for increasing the orientation of the polymer component. If the yarn is stretched at a temperature higher than this temperature range, the polymer component will be in a molten state, and as a result, the orientation of the polymer component will not be very high even if the yarn is stretched. If the yarn is stretched at a temperature lower than this temperature range, the polymer component will be too solidified, making it difficult to stretch the yarn, and if the yarn is forcibly pulled in an attempt to stretch it, the yarn will break and it will not be possible to produce a monofilament. In this embodiment, the cooled raw yarn A is heated and stretched in the stretching roll section. This makes it easier to adjust the temperature of the raw yarn so that it is within a temperature range suitable for increasing the orientation of the polymer components when stretching the raw yarn, compared to a mode in which the raw yarn is stretched while being cooled with surrounding air. As a result, it becomes easier to increase the orientation of the polymer components of the raw yarn. Therefore, in this embodiment, the strength of the monofilament can be easily increased.

[0056] In the step (B), the raw yarn A cooled in the water bath 3 a is taken up by a take-up roll section 4 . The take-up roll section 4 is a roll section for taking up the raw yarn A from the water bath 3a. Next, the raw yarn A taken up by the take-up roll section 4 is drawn by a first drawing roll section 6 . Then, the raw yarn A drawn in the first drawing roll section 6 is drawn in a second drawing roll section 8 . Next, the raw yarn A drawn in the second drawing roll section 8 is wound in a take-up roll section 9 to obtain a monofilament.

[0057] In the step (B), the raw yarn A drawn in the first drawing roll unit 6 is drawn in the second drawing roll unit 8. That is, in the step (B), the raw yarn A is drawn in two stages. In the step (B), the film may be stretched in multiple stages (two or more stages) or in one stage. In the step (B), the multi-stage (two or more) drawing can increase the total draw ratio while suppressing breakage of the raw yarn during drawing, which makes it easier to further increase the strength of the monofilament. Multistage (two or more) stretching means that a plurality of stretching roll sections are used for stretching, and the speed of the rear stretching roll section is faster than the speed of the front stretching roll section. The speed of the stretching roll section is the length of the raw yarn transported through the stretching roll section per unit time.

[0058] The total stretching ratio in the step (B) is preferably 5.0 times or more, more preferably 6.0 times or more, and further preferably 6.5 times or more. The total stretching ratio in the step (B) is, for example, 13.0 times or less. By setting the total draw ratio in the step (B) to 5.0 times or more, the orientation of the polymer components of the monofilament is increased, and as a result, the strength of the monofilament is increased. The total stretching ratio in the step (B) can be calculated by the following formula. Total stretching ratio in the step (B) = Speed ​​of the winding roll section 9 (m / min) / Speed ​​of the take-up roll section 4 (m / min)

[0059] The speed (m / min) of the winding roll section is the length of the yarn wound around the winding roll section per unit time. The speed (m / min) of the take-up roll section is the length of the raw yarn taken up by the take-up roll section per unit time.

[0060] In the step (B), it is preferable that the raw yarn A having passed through the take-up roll section 4 is heated in a hot water bath 5 before the raw yarn A is drawn in the first drawing roll section 6 . In the step (B), before the raw yarn A is drawn in the first drawing roll section 6, the raw yarn A that has passed through the take-up roll section 4 is heated in a hot water bath 5, which makes it easy to adjust the temperature of the raw yarn A before drawing so that it is within a temperature range suitable for increasing the orientation of the polymer components contained in the raw yarn A by drawing. As a result, it becomes easier to increase the orientation of the polymer components of the raw yarn A by drawing. The temperature of the hot water in the hot water tank 5 is preferably 25 to 65°C, and more preferably 30 to 60°C.

[0061] In the step (B), the drawn raw yarn A may be heated with heated air in a heat treatment tank 7. In the step (B), the drawn raw yarn A is heated with heated air in the heat treatment tank 7, thereby promoting the crystallization of the polymer component contained in the raw yarn A. As a result, the strength of the monofilament can be increased. The temperature of the air in the heat treatment tank 7 is preferably 50 to 120°C, and more preferably 60 to 110°C.

[0062] The present invention is not limited to the above-described embodiment. The present invention is also not limited to the above-described effects. Furthermore, the present invention can be modified in various ways without departing from the gist of the present invention.

[0063] [Disclosure items] Each of the following sections is a disclosure of a preferred embodiment.

[0064] [Item 1] A biodegradable monofilament containing a polymer component, The polymer component contains 85% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), The molar ratio of hydroxycarboxylic acids constituting the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is 3-hydroxybutyrate / 3-hydroxyhexanoate, which is in the range of 80 / 20 to 99 / 1; A biodegradable monofilament with a fineness in the range of 15 to 3000 dtex.

[0065] [Item 2] 2. The biodegradable monofilament according to item 1, having a tensile strength of 0.5 to 6.0 cN / dtex.

[0066] [Item 3] 3. The biodegradable monofilament according to item 1 or 2, wherein the decomposition rate after 210 days in an ISO 17556 test is in the range of 60% or more.

[0067] [Item 4] 4. The biodegradable monofilament according to any one of items 1 to 3, wherein the yarn strength ratio before and after a constant temperature and humidity test at a temperature of 80° C. and a humidity of 90%, which is calculated by the following formula, is 70% or more. Yarn strength ratio (%) = monofilament strength after 82 hours of exposure to the constant temperature and humidity test / monofilament strength before the constant temperature and humidity test × 100%

[0068] [Item 5] The polymer component further contains a biodegradable resin other than the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), 5. The biodegradable monofilament according to any one of items 1 to 4, wherein the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the other biodegradable resin are mixed and spun.

[0069] [Item 6] Item 6. The biodegradable monofilament according to item 5, wherein the other biodegradable resin contains polycaprolactone.

[0070] [Item 7] 7. The biodegradable monofilament according to any one of items 1 to 6, comprising 0.1 to 4 parts by weight of pentaerythritol and 0.1 to 4 parts by weight of a fatty acid amide relative to 100 parts by weight of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0071] [Item 8] 8. The biodegradable monofilament according to any one of items 1 to 7, having a weight average molecular weight in the range of 50,000 to 2,500,000.

[0072] [Item 9] Item 9. The biodegradable monofilament according to item 8, wherein the weight average molecular weight is in the range of 100,000 to 400,000.

[0073] [Item 10] 10. A braid formed from the biodegradable monofilament according to any one of items 1 to 9.

[0074] [Item 11] A tape formed from the biodegradable monofilament according to any one of items 1 to 9.

[0075] [Item 12] An agricultural attractant net formed from the biodegradable monofilament according to any one of items 1 to 9.

[0076] The present invention is not limited to the above-described embodiment. The present invention is also not limited to the above-described effects. Furthermore, the present invention can be modified in various ways without departing from the gist of the present invention. EXAMPLES

[0077] The present invention will now be described in more detail with reference to examples, comparative examples, and reference examples, although the present invention is not limited to these examples in any way.

[0078] <Example 1> (Process (A)) First, as shown in FIG. 1, the following materials were mixed at 165° C. in a single-screw extruder (screw diameter D: 30 mm, screw length L / screw diameter D=24) as a kneading extruder 2b to prepare a molten material. Polymer component: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (3-hydroxyhexanoate content = 6 mol%, Mw = 550,000) (P3HB3HH) Fatty acid amide lubricant: behenamide Fatty acid amide lubricant: erucic acid amide · Nucleating agent: Pentaerythritol Further, erucamide was 0.5 part by weight, behenamide was 0.5 part by weight, and pentaerythritol was 1.0 part by weight relative to 100 parts by weight of P3HB3HH.

[0079] Next, the molten material was discharged from the discharge holes of the spinning nozzle 2d to obtain five raw yarns A. The spinning nozzle 2d had five discharge holes. All of the discharge holes were circular. The diameter (φ) of all the discharge holes was 1.5 mm. Furthermore, the length (L) of the discharge hole / diameter (D) of the discharge hole, in other words, L / D, was 3. The temperature of the spinning nozzle 2d was set to 160°C. The total amount of the molten material discharged from all the discharge holes was 4.5 kg / hr. In other words, the amount of the molten material discharged from one discharge hole was 0.90 kg / hr.

[0080] Then, the raw yarn A, which had a temperature higher than the solidification temperature of the raw yarn A, was passed through a water bath 3a at 30° C. for 36 seconds to cool the raw yarn A.

[0081] (Process (B)) In step (B), the cooled raw yarn A was taken up by a take-up roll section 4 (speed: 5.0 m / min), heated in a hot water bath 5 (hot water temperature: 50° C.) for 2.9 seconds, and drawn by a first drawing roll section 6. Then, the raw yarn A stretched in the first stretching roll section 6 was heated for 4.0 seconds in a heat treatment tank 7 (hot air temperature: 100°C), stretched in the second stretching roll section 8, and wound up in the winding roll section 9 to obtain a monofilament. The stretching ratio in the first stage was 7.0 times, and the total stretching ratio was 7.0 times.

[0082] The total stretch ratio was determined by the method described above. The first-stage stretching ratio was calculated by the following formula. Stretching ratio in the first stage = speed of the first stretching roll section 6 (m / min) / speed of the take-up roll section 4 (m / min) Here, the speed of the first stretching roll section is the length per unit time of the raw yarn A transported by the first stretching roll section.

[0083] (Example 2, Comparative Examples 1 to 7) A monofilament was obtained in the same manner as in Example 1, except that the following PCL was also used as the polymer component and the conditions were changed as shown in Table 1 below. Polycaprolactone (PCL) (Ingevity's "CAPA6800") The ratio of P3HB3HH in Table 1 means the content of P3HB3HH in the polymer component. The amounts of erucamide, behenamide, and pentaerythritol were 0.5 parts by weight, 0.5 parts by weight, and 1.0 part by weight, respectively, relative to 100 parts by weight of P3HB3HH.

[0084] (Monofilament fineness, tensile strength, and weight average molecular weight) The fineness, tensile strength ("tensile strength of monofilament before heating" described later), and weight average molecular weight (Mw) of the monofilament were determined by the above-mentioned methods. The measured values ​​are shown in Table 1 below. In addition, "K" in the weight average molecular weight (Mw) in Table 1 is "× 10 3 " means.

[0085] (Heat resistance test) Before heating, the length of the monofilament was measured. The monofilaments were heated under tension at 60° C. for 24 hours. The length and tensile strength of the heated monofilament were then measured. The dimensional retention rate was then calculated using the following formula. Dimensional retention rate (%) = [1-(monofilament length before heating-monofilament length after heating) / monofilament length before heating] x 100% The strength reduction rate was calculated using the following formula. Strength reduction rate (%) = [(tensile strength of monofilament before heating - tensile strength of monofilament after heating) / tensile strength of monofilament before heating] x 100% The results are shown in Table 1 below.

[0086] [Table 1]

[0087] Comparative Example 8 An attempt was made to obtain a monofilament in the same manner as in Example 1, except that the temperature of the water bath was set to 10°C. However, the raw yarn A stuck to the water bath roll section 3c, and it was not possible to obtain a monofilament. When the temperature of the water bath is 10°C, it is believed that the reason why the raw yarn A sticks to the water bath roll section 3c is that the raw yarn A is cooled rapidly in the water bath, causing the raw yarn A to come into contact with the water bath roll section 3c without being sufficiently crystallized, resulting in the raw yarn A sticking to the water bath roll section 3c.

[0088] Comparative Example 9 An attempt was made to obtain a monofilament in the same manner as in Example 1, except that the temperature of the water bath was set to 40°C. However, raw yarn A stuck to the take-up roll section 4, and a monofilament could not be obtained. When the temperature of the water bath is 40°C, the reason why raw yarn A sticks to the take-up roll section 4 is thought to be that raw yarn A is not sufficiently cooled in the water bath, so that raw yarn A comes into contact with the take-up roll section 4 while still in a softened state, causing it to stick.

[0089] (Comparative Example 10, Reference Examples 1 to 4) As Comparative Example 10, a polylactic acid (PLA) monofilament (a monofilament produced by the method described in JP-A-2007-314899) was prepared. Also, as Reference Examples 1 to 4, hemp, polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) were prepared, respectively.

[0090] (Simple soil decomposition test) The samples were placed in a PP mesh bag with 2 mm openings, and the sample was buried in Takii Seed's hydrated cell culture soil. Before the start of the test, sufficient water was poured onto the soil to allow it to absorb water. The soil pH was 6-7, the environmental temperature was 33°C, and the humidity was 60%. During the test period, water was added to the soil when the soil surface became dry. After one month had passed since the sample was placed in the soil, the sample was removed and its condition was visually observed. The results are shown in Table 2 below. In the table, ◯ indicates complete decomposition and disappearance, △ indicates partial decomposition, and × indicates no decomposition.

[0091] [Table 2]

[0092] As shown in Table 2, Example 1 is superior in biodegradability in soil compared to Comparative Example 2, in which the polymer component contains 50% by weight of P3HB3HH, Comparative Example 10, in which the polymer component is polylactic acid, and Reference Examples 1 to 4. Therefore, it is evident that the present invention can provide a monofilament that is highly biodegradable in soil.

[0093] (Detailed soil decomposition test: ISO 17556) The monofilaments were used to make the fabric. Next, the textile was subjected to the "Aerobic biodegradation evaluation of plastics in soil (ISO 17556)" and the percentage of biodegradation (decomposition rate) was calculated from the theoretical amount of carbon dioxide generated up to the 51st and 210th days. The theoretical values ​​were determined as follows. First, 120 mg of the monofilament was added to 120 g of soil, and carbon dioxide generated from the soil containing the monofilament was collected using a gas bag for 51 days. Next, the amount of carbon dioxide captured by the gas bag (measured value) was measured using the NDIR method. In addition, the amount of carbon dioxide generated from soil without monofilaments for 51 and 210 days (blank value) was also measured in the same manner. The theoretical amount of carbon dioxide generated was then calculated by subtracting the blank value from the measured value. A higher decomposition rate indicates greater biodegradation in soil. The results are shown in Table 3 below. In addition, from the data of Example 1 (P3HB3HH ratio: 100% by weight) and Comparative Example 1 (P3HB3HH ratio: 70% by weight), an approximation equation was obtained in which the P3HB3HH ratio is x and the decomposition rate is y (y=0.8454x-7.7463). Based on this approximation formula, we calculated the estimated decomposition rates when the ratio of P3HB3HH was 90% and 85%. The calculated values ​​are shown in Table 3 below.

[0094] [Table 3]

[0095] As shown in Table 3, the higher the ratio of P3HB3HH, the higher the degradation rate in soil tended to be. In addition, the estimated decomposition rate showed that if the ratio of P3HB3HH in the polymer component was 85% by weight or more, the decomposition rate after 210 days was 60% or more. Therefore, it is evident that the present invention can provide a monofilament that is highly biodegradable in soil.

[0096] (Reference example 5) As the monofilament of Reference Example 5, a monofilament made of high density polyethylene (HDPE) was prepared.

[0097] (Evaluation of biodegradability in seawater) The monofilament was immersed in seawater. Next, the tensile strength of the monofilament was measured before immersion, 4 weeks after immersion, 8 weeks after immersion, 12 weeks after immersion, and 16 weeks after immersion. The strength retention rate was calculated using the following formula. Strength retention rate (%) = [1 - (tensile strength of monofilament before immersion - tensile strength of monofilament after immersion) / tensile strength of monofilament before immersion] x 100% The results are shown in Table 4 below. In Example 1, the monofilament was too brittle 8 weeks after immersion and the tensile strength could not be measured.

[0098] [Table 4]

[0099] As shown in Table 4, Example 1 is also excellent in biodegradability in seawater.

[0100] (Reference example 6) As Reference Example 6, a multifilament containing 100% by weight of P3HB3HH as a polymer component was prepared.

[0101] (Constant temperature and humidity test) When the filament is used in an open-field cultivation, the filament is affected by moisture such as rain. In order to confirm the effect of water on the filament, the effect of moisture was confirmed by an accelerated test. Specifically, the yarn strength ratio before and after a constant temperature and humidity test at a temperature of 80° C. and a humidity of 90% was calculated using the following formula. Yarn strength ratio (%) = filament strength after 82 hours of exposure to the constant temperature and humidity test / monofilament strength before the constant temperature and humidity test × 100% The strength was measured by the method described above. The results are shown in Table 5 below.

[0102] (Hydrolysis acceleration test (jungle test)) Filaments exposed to an accelerated hydrolysis test (jungle test) at a temperature of 70°C and a humidity of 95% for 7 and 21 days were photographed using an SEM. The filaments before the jungle test were also photographed with an SEM. The SEM photograph is shown in Figure 2.

[0103] (Light resistance test) 48W / m at 40℃ and 50% humidity 2 The strength of the filament after 60 hours of irradiation with light (strength of monofilament after irradiation) and the strength of the filament before irradiation were measured, and the rate of change in yarn strength was calculated using the following formula. Yarn strength change rate (%) = (filament strength after irradiation - filament strength before irradiation) / filament strength before irradiation × 100% The strength was determined in the same manner as in the constant temperature and humidity test. The results are shown in Table 5 below.

[0104] [Table 5]

[0105] As shown in Table 5, Reference Example 6 (P3HB3HH) had a higher strength retention rate in the constant temperature and humidity test than Comparative Example 10 (polylactic acid). Furthermore, as shown in FIG. 2, in Reference Example 6 (P3HB3HH), no deterioration was observed due to the accelerated hydrolysis test, but in Comparative Example 10 (polylactic acid), deterioration occurred due to the accelerated hydrolysis test, resulting in breakage of the thread. Therefore, it is clear that P3HB3HH is less susceptible to the effects of moisture such as rain than polylactic acid.

[0106] As shown in Table 5, in Reference Example 6, the strength change rate in the light resistance test was 19%. This indicates that P3HB3HH is less susceptible to the effects of light. [Explanation of symbols]

[0107] 1: monofilament manufacturing apparatus, 2a: material input section, 2b: kneading extruder, 2c: gear pump, 2d: spinning nozzle, 3a: water bath, 3b: water tank, 3c: water bath roll section, 4: take-up roll section, 5: hot water tank, 6: first stretching roll section, 7: heat treatment tank, 8: second stretching roll section, 9: winding roll section

Claims

1. A biodegradable monofilament containing a polymer component, the polymer component contains 85% by weight or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), the molar ratio of hydroxycarboxylic acids constituting the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), 3-hydroxybutyrate / 3-hydroxyhexanoate, is in the range of 80 / 20 to 99 / 1; A biodegradable monofilament having a fineness in the range of 15 to 3000 dtex.

2. 2. The biodegradable monofilament according to claim 1, having a tensile strength of 0.5 to 6.0 cN / dtex.

3. 3. The biodegradable monofilament according to claim 1, wherein the decomposition rate after 210 days in an ISO 17556 test is in the range of 60% or more.

4. 3. The biodegradable monofilament according to claim 1, wherein the yarn strength ratio before and after a constant temperature and humidity test at a temperature of 80°C and a humidity of 90%, which is calculated by the following formula, is 70% or more. Yarn strength ratio (%) = strength of monofilament after 82 hours of exposure to the constant temperature and humidity test / strength of monofilament before the constant temperature and humidity test × 100%

5. the polymer component further contains a biodegradable resin other than the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), 3. The biodegradable monofilament according to claim 1, wherein the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the other biodegradable resin are mixed and spun.

6. The biodegradable monofilament according to claim 5 , wherein the other biodegradable resin contains polycaprolactone.

7. The biodegradable monofilament according to claim 1 or 2, comprising 0.1 to 4 parts by weight of pentaerythritol and 0.1 to 4 parts by weight of a fatty acid amide relative to 100 parts by weight of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

8. 3. The biodegradable monofilament according to claim 1, having a weight average molecular weight in the range of 50,000 to 2,500,000.

9. The biodegradable monofilament according to claim 8, wherein the weight average molecular weight is in the range of 100,000 to 400,000.

10. A braided cord formed from the biodegradable monofilament according to claim 1 or 2.

11. A tape formed from the biodegradable monofilament according to claim 1 or 2.

12. An agricultural attractant net formed from the biodegradable monofilament according to claim 1 or 2.

13. A method for producing the biodegradable monofilament according to claim 1 or 2, comprising: a step (A) of cooling the raw yarn obtained by discharging the melt from a spinning nozzle by passing the raw yarn through a water bath; and (B) drawing the raw yarn that has passed through the water bath in a drawing roll section, The temperature of the water bath is 15 to 35°C.

14. The manufacturing method described in claim 13, wherein the biodegradable monofilament contains a nucleating agent.

15. In the step (B), the stretched raw yarn is heated with heated air, The method according to claim 13, wherein the temperature of the heated air is 80 to 120°C.

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