METHOD FOR PRODUCING MULTIFILAMENT

Abstract

A method for producing a multifilament including 50 or more single filaments by melt spinning is provided. The method includes the steps of (A) obtaining 50 or more raw filaments in a molten state by discharging a composition including a poly(3-hydroxyalkanoate) resin from a spinning nozzle, and (B) cooling the raw filaments by blowing gas onto the raw filaments in the molten state. The spinning nozzle includes a nozzle surface including 50 or more discharge holes. The nozzle surface is segmented into a central region and a peripheral region surrounding the central region. An outer edge of the central region and an outer edge of the peripheral region are similar in shape to each other and share a same area centroid. A similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1:2.

Claims

1. A method for producing a multifilament including 50 or more single filaments by melt spinning, the method comprising: obtaining 50 or more raw filaments in a molten state by discharging a composition comprising a poly(3-hydroxyalkanoate) resin from a spinning nozzle; and cooling the raw filaments by blowing gas onto the raw filaments in the molten state, wherein: the spinning nozzle includes a nozzle surface including 50 or more discharge holes; the nozzle surface is segmented into a central region and a peripheral region surrounding the central region; an outer edge of the central region and an outer edge of the peripheral region are similar in shape to each other and share a same area centroid; a similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1:2; the number of the discharge holes present in the peripheral region exceeds 75% of the number of the discharge holes present on the nozzle surface; a temperature of the gas is from (Tc-45) C. to (Tc-20) C. where Tc is a crystallization temperature of the composition comprising the poly(3-hydroxyalkanoate) resin; a speed of the gas is 0.01 m/s or greater and less than 0.10 m/s; and an average value of fineness of the single filaments is from 3.0 dtex to 15.0 dtex.

2. The method for producing the multifilament according to claim 1, wherein no discharge holes are present in the central region.

3. The method for producing the multifilament according to claim 1, wherein each of the outer edge of the central region and the outer edge of the peripheral region has a circular shape, an ellipsoidal shape, or a regular polygonal shape.

4. The method for producing the multifilament according to claim 3, wherein each of the outer edge of the central region and the outer edge of the peripheral region has the circular shape.

5. The method for producing the multifilament according to claim 1, wherein a temperature of the composition immediately after the composition is discharged from the spinning nozzle is from 150 C. to 168 C.

6. The method for producing the multifilament according to claim 1, wherein the poly(3-hydroxyalkanoate) resin comprises a poly(3-hydroxybutyrate) resin.

7. The method for producing the multifilament according to claim 2, wherein each of the outer edge of the central region and the outer edge of the peripheral region has a circular shape, an ellipsoidal shape, or a regular polygonal shape.

8. The method for producing the multifilament according to claim 7, wherein each of the outer edge of the central region and the outer edge of the peripheral region has the circular shape.

9. The method for producing the multifilament according to claim 2, wherein a temperature of the composition immediately after the composition is discharged from the spinning nozzle is from 150 C. to 168 C.

10. The method for producing the multifilament according to claim 2, wherein the poly(3-hydroxyalkanoate) resin comprises a poly(3-hydroxybutyrate) resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic diagram showing an apparatus used in a method for producing a multifilament according to one or more embodiments of the present invention.

[0014] FIG. 2 is a schematic diagram showing a nozzle surface side of a spinning nozzle according to the present embodiment.

[0015] FIG. 3 is a schematic diagram showing the nozzle surface side of the spinning nozzle according to the present embodiment.

[0016] FIG. 4 is a schematic diagram showing the nozzle surface side of the spinning nozzle according to the present embodiment.

DETAILED DESCRIPTION

[0017] Hereinafter, one or more embodiments of the present invention are described with reference to the accompanying drawings.

[0018] A method for producing a multifilament according to the present embodiment is a method for producing a multifilament including 50 or more single filaments by melt spinning.

[0019] The method for producing a multifilament according to the present embodiment includes the steps of: (A) obtaining 50 or more raw filaments in a molten state by discharging a composition including a poly(3-hydroxyalkanoate) resin (this composition is hereinafter also referred to as raw material composition) from a spinning nozzle; and (B) cooling the raw filaments by blowing gas onto the raw filaments in the molten state.

[0020] The spinning nozzle includes a nozzle surface including 50 or more discharge holes.

[0021] The nozzle surface is segmented into a central region and a peripheral region surrounding the central region.

[0022] The outer edge of the central region and the outer edge of the peripheral region are similar in shape to each other and share the same area centroid.

[0023] The similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1:2.

[0024] The number of discharge holes present in the peripheral region exceeds 75% of the number of discharge holes present on the nozzle surface.

[0025] The temperature of the gas is from (Tc-45) to (Tc-20) C. [Tc is the crystallization temperature of the composition including the poly(3-hydroxyalkanoate) resin].

[0026] The speed of the gas is 0.01 m/s or greater and less than 0.10 m/s.

[0027] The average value of the fineness of the single filaments is from 3.0 dtex to 15.0 dtex.

[0028] The method for producing a multifilament according to the present embodiment further includes the step (C) of obtaining the multifilament by hauling off, by a haul-off roll, the raw filaments that have been cooled in the step (B).

[0029] The aforementioned Patent Literature 1 (WO 2021/206154) describes that in a case where the speed of the air flow applied onto the resin composition discharged from the spinning nozzle is less than 0.1 m/s, the obtained cooling effect is too small, and for this reason, the speed of the air flow may be 0.1 m/s or greater. On the other hand, in the present embodiment, the speed of the gas in the step (B) is 0.01 m/s or greater and less than 0.10 m/s.

[0030] In a case where the discharge holes are arranged uniformly on the nozzle surface with the similarity ratio of 1:2, the ratio of the number of discharge holes present in the peripheral region to the number of discharge holes present on the nozzle surface (this ratio is hereinafter also referred to as presence ratio) is 75%. On the other hand, in the present embodiment, the presence ratio exceeds 75%, which means that the discharge holes are distributed in a non-uniform manner such that the discharge holes are present more densely in the peripheral region than in the central region.

[0031] The present embodiment makes it possible to increase the productivity of the multifilament containing the poly(3-hydroxybutyrate) resin and having a small average value (from 3.0 dtex to 15.0 dtex) of the fineness of the single filaments.

[0032] The reason for this is considered as follows.

[0033] Specifically, since the discharge holes are non-uniformly distributed such that the discharge holes are more densely present in the peripheral region, in the step (B), in a bundle of raw filaments, sufficient cooling of the raw filaments positioned at the inner side, which are cooled less easily than the raw filaments positioned at the outer side, is facilitated. Consequently, even though the speed of the gas is less than 0.10 m/s, the time during which the raw filaments are in the molten state can be shortened, and breakage of the raw filaments is less likely to occur. Moreover, in the bundle of raw filaments, cooling unevenness between the outer raw filaments and the inner raw filaments is suppressed; variation in the fineness of the raw filaments is suppressed; and the number of excessively thin raw filaments is reduced, and thereby breakage of the raw filaments is less likely to occur.

[0034] Furthermore, since the speed of the gas is less than 0.10 m/s, after the raw filaments are discharged from the spinning nozzle and before the raw filaments are hauled off by the haul-off roll, heat can be suitably removed from the raw filaments while suppressing the temperature of the raw filaments from dropping to fall within a crystallization temperature range (e.g., 50 to 80 C.). Consequently, crystallization of the raw filaments can be suppressed, and the raw filaments are rendered in a state of having excellent flexibility (i.e., easily deformable state), so that breakage of the raw filaments is less likely to occur when the raw filaments are hauled off by the haul-off roll.

[0035] Since breakage of the raw filaments is less likely to occur, the spinning speed (i.e., the speed of the haul-off roll) can be increased, which makes it possible to increase the productivity of the multifilament.

[0036] The raw material composition contains a polymer component and an additive.

[0037] The polymer component includes the poly(3-hydroxyalkanoate) resin.

[0038] The polymer component may contain another polymer in addition to the poly(3-hydroxyalkanoate) resin.

[0039] The poly(3-hydroxyalkanoate) resin is a polyester containing a 3-hydroxyalkanoic acid as a monomer.

[0040] Specifically, the poly(3-hydroxyalkanoate) resin is a resin including the 3-hydroxyalkanoic acid as a structural unit.

[0041] The poly(3-hydroxyalkanoate) resin is a biodegradable polymer.

[0042] It should be noted that being biodegradable in the present embodiment means being able to be decomposed into low molecular weight compounds by microorganisms in a natural environment. Being biodegradable or not can be determined based on tests suited for different environments. Specifically, for example, ISO 14855 (compost) and ISO 14851 (activated sludge) are suited for an aerobic condition, and ISO 14853 (aqueous phase) and ISO 15985 (solid phase) are suited for an anaerobic condition. Also, biodegradability by microorganisms in seawater can be evaluated by biochemical oxygen demand measurement.

[0043] The poly(3-hydroxyalkanoate) resin includes a homopolymer and/or a copolymer.

[0044] The poly(3-hydroxyalkanoate) resin may include a structural unit expressed by an equation (1) shown below.

##STR00001##

[0045] (In the above equation (1), R is an alkyl group represented by C.sub.pH.sub.2p+1, and p is an integer from 1 to 15. )

[0046] The poly(3-hydroxyalkanoate) resin may be a resin including 3-hydroxybutyrate as a structural unit (i.e., a poly(3-hydroxybutyrate) resin).

[0047] It should be noted that the poly(3-hydroxybutyrate) resin includes a homopolymer and/or a copolymer.

[0048] Examples of the poly(3-hydroxyalkanoate) resin including 3-hydroxybutyrate as a structural unit include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate).

[0049] P3HB herein means poly(3-hydroxybutyrate) as a homopolymer.

[0050] P3HB3HH herein means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

[0051] P3HB3HV herein means poly(3-hydroxybutyrate-co-3-hydroxyvalerate).

[0052] P3HB4HB herein means poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0053] It should be noted that P3HB has a function to facilitate crystallization of P3HB itself and crystallization of the poly(3-hydroxyalkanoate) resin other than P3HB. Accordingly, the poly(3-hydroxyalkanoate) resin may include P3HB.

[0054] In order to achieve both excellent biodegradability and excellent molding processability, the poly(3-hydroxyalkanoate) resin may be, but not particularly limited to, P3HB, P3HB3HH, P3HB3HV, or P3HB4HB.

[0055] Further, in order to increase the strength of the multifilament according to the present embodiment and to increase the molding processability thereof, the poly(3-hydroxyalkanoate) resin may be P3HB3HH.

[0056] The poly(3-hydroxyalkanoate) resin may include 80% by mole or greater of 3-hydroxybutyrate, include from 85.0% by mole to 99.5% by mole of 3-hydroxybutyrate, or include from 85.0% by mole to 97.0% by mole of 3-hydroxybutyrate, as a structural unit.

[0057] As a result of the poly(3-hydroxyalkanoate) resin including 80% by mole or greater of 3-hydroxybutyrate as a structural unit, the stiffness of the multifilament is increased.

[0058] As a result of the poly(3-hydroxyalkanoate) resin including 99.5% by mole or less of 3-hydroxybutyrate as a structural unit, the multifilament has excellent flexibility.

[0059] It should be noted that the content ratio of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin can be determined in a manner described in Examples below.

[0060] The polymer component may include only one kind of the poly(3-hydroxyalkanoate) resin, or may include two or more kinds of the poly(3-hydroxyalkanoate) resins.

[0061] In a case where the poly(3-hydroxyalkanoate) resin includes a copolymer (e.g., P3HB3HH), the poly(3-hydroxyalkanoate) resin may include two or more kinds of copolymers having different average composition ratios of the structural unit.

[0062] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition may be from 3.010.sup.5 to 7.010.sup.5, from 3.510.sup.5 to 7.010.sup.5, from 4.010.sup.5 to 7.010.sup.5, or from 4.510.sup.5 to 6.510.sup.5.

[0063] As a result of the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition being 3.010.sup.5 or greater, the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the single filaments can be readily increased, which consequently makes it possible to readily increase the strength of the multifilament.

[0064] As a result of the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition being 7.010.sup.5 or less, the forming of the multifilament can be readily performed.

[0065] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition herein means the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition before it is subjected to heat-melting.

[0066] It should be noted that the weight-average molecular weight in the present embodiment is measured based on a molecular weight distribution in terms of polystyrene by using gel permeation chromatography (GPC) using a chloroform eluent. A column used in the GPC may be any column suitable for measuring the molecular weight.

[0067] For example, the column temperature is set to 40 C.; 3 mg of a target material is dissolved into 2 ml of chloroform; 10 l of the chloroform in which the target material has been dissolved is injected; the flow rate of the chloroform eluent (mobile phase) is set to 1.0 ml/min; and thereby a weight-average molecular weight (Mw) can be determined. SHIMADZU 20A (available from Shimadzu Corporation) may be used as GPC equipment, and ShodexK-806M (available from Showa Denko K. K.) may be used as the column.

[0068] The aforementioned another polymer may be biodegradable.

[0069] Examples of this other polymer that is biodegradable 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) resin.

[0070] The polycaprolactone is a polymer obtained by ring-opening polymerization of -caprolactone.

[0071] The polymer component may include one kind of this other polymer, or two or more kinds of these other polymers.

[0072] The polymer component may contain 50% by weight or greater of the poly(3-hydroxyalkanoate) resin, 80% by weight or greater of the poly(3-hydroxyalkanoate) resin, or 90% by weight or greater of the poly(3-hydroxyalkanoate) resin.

[0073] As a result of the raw material composition including the biodegradable polymer, even if the multifilament is discarded in an environment, since the multifilament is readily decomposed in the environment, the load on the environment can be reduced.

[0074] Examples of the additive include a crystal nucleating agent, a lubricant, a plasticizer, a spinning oil, a stabilizer (such as an oxidation inhibitor or ultraviolet absorber), a colorant (such as a dye or pigment), an inorganic filler, an organic filler, and an antistatic agent.

[0075] In order to facilitate the crystallization of the poly(3-hydroxyalkanoate) resin, the raw material composition may contain a crystal nucleating agent.

[0076] The crystal nucleating agent is a compound that has an effect of facilitating the crystallization of the poly(3-hydroxyalkanoate) resin. The crystal nucleating agent has a melting point higher than that of the poly(3-hydroxyalkanoate) resin.

[0077] Examples of the crystal nucleating agent include: inorganic substances (e.g., boron nitride, titanium oxide, talc, layered silicate, calcium carbonate, sodium chloride, metal phosphate, etc.); sugar alcohol compounds derived from natural products (e.g., pentaerythritol, erythritol, galactitol, mannitol, arabitol, etc.); polyvinyl alcohol; chitin; chitosan; polyethylene oxides; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylic acid esters; dicarboxylic acid derivatives (e.g., dimethyl adipate, dibutyl adipate, di-isodecyl adipate, dibutyl sebacate, etc.); cyclic compounds having, in their molecule, CO and a functional group selected from the group consisting of NH, S, and O (e.g., indigo, quinacridone, quinacridone magenta, etc.); sorbitol derivatives (e.g., bis-benzylidene sorbitol, bis (p-methylbenzylidene) sorbitol, etc.); compounds including a nitrogen-containing heteroaromatic nucleus (e.g., pyridine ring, triazine ring, imidazole ring, etc.) (e.g., pyridine, triazine, imidazole, etc.); phosphate ester compounds; bisamides of higher fatty acids; metal salts of higher fatty acids; and branched polylactic acid.

[0078] It should be noted that P3HB, which is the poly(3-hydroxyalkanoate) resin, can be used as the crystal nucleating agent.

[0079] One of these crystal nucleating agents may be used alone, or two or more of these crystal nucleating agents may be used in combination.

[0080] As the crystal nucleating agent, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan may be preferable in light of the effect of improving the crystallization rate of the poly(3-hydroxyalkanoate) resin as well as in light of compatibility and affinity with the poly(3-hydroxyalkanoate) resin.

[0081] Among the sugar alcohol compounds, pentaerythritol may be preferable.

[0082] The crystal nucleating agent may have a crystal structure at normal temperature (25 C.).

[0083] As a result of the crystal nucleating agent having a crystal structure at normal temperature (25 C.), the crystallization of the poly(3-hydroxyalkanoate) resin is further facilitated, which is advantageous.

[0084] The crystal nucleating agent that has a crystal structure at normal temperature (25 C.) may be powdery at normal temperature (25 C.).

[0085] The crystal nucleating agent that is powdery at normal temperature (25 C.) may have a mean particle diameter of 10 um or less.

[0086] The content of the crystal nucleating agent in the raw material composition may be 0.05 parts by weight or greater, 0.1 parts by weight or greater, or 0.5 parts by weight or greater, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the crystal nucleating agent in the raw material composition being 0.05 parts by weight or greater with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the crystallization of the poly(3-hydroxyalkanoate) resin can be further facilitated, which is advantageous.

[0087] The content of the crystal nucleating agent in the raw material composition may be 10 parts by weight or less, 8 parts by weight or less, or 5 parts by weight or less, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the crystal nucleating agent in the raw material composition being 10 parts by weight or less with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the viscosity of a molten product when fabricating the multifilament from the molten product can be reduced, which consequently makes it possible to readily fabricate the multifilament, which is advantageous.

[0088] It should be noted that P3HB is the poly(3-hydroxyalkanoate) resin, and can also function as the crystal nucleating agent. Therefore, in a case where the raw material composition contains P3HB, the amount of the P3HB is included both in the amount of the poly(3-hydroxyalkanoate) resin and in the amount of the crystal nucleating agent.

[0089] The raw material composition may contain a lubricant.

[0090] The lubricant is, for example, a fatty acid amide.

[0091] The fatty acid amide may include at least one selected from the group consisting of lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0092] The content of the lubricant in the raw material composition may be 0.05 parts by weight or greater, 0.1 parts by weight or greater, or 0.5 parts by weight or greater, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the lubricant in the raw material composition being 0.05 parts by weight or greater with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the single filaments have excellent slipperiness, which is advantageous.

[0093] The content of the lubricant in the raw material composition may be 12 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, or 5 parts by weight or less, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the lubricant in the raw material composition being 12 parts by weight or less with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the lubricant can be advantageously suppressed from bleeding out on the surface of the multifilament.

[0094] Hereinafter, the aforementioned steps (A) to (C) are described with reference to FIGS. 1 and 2.

Step (A)

[0095] In the step (A), first, materials are subjected to dry blending, which are then melt-kneaded by an extruder to obtain a raw material composition in the form of pellets.

[0096] Then, as shown in FIG. 1, the pellets are put into a feeder 10.

[0097] Next, the feeder 10 feeds the pellets into an extruder 20, and the extruder 20 heat-melts the pellets to obtain a molten product, i.e., a molten raw material composition.

[0098] A screw extruder can be used as the extruder 20. The extruder 20 may be a single screw extruder, or may be a twin screw extruder.

[0099] Then, the molten product, which is the molten raw material composition, is discharged from a spinning nozzle 40 to obtain 50 or more raw filaments A in a molten state.

[0100] It should be noted that the flow rate of the molten product discharged from the spinning nozzle 40 is adjusted by a gear pump 30.

[0101] As shown in FIG. 2, the spinning nozzle 40 includes a nozzle surface 41 including 50 or more discharge holes 42. It should be noted that in a case where the spinning nozzle 40 includes an outermost edge region 43, in which no discharge holes 42 are formed, the outermost edge region 43 is not included in the nozzle surface 41.

[0102] Other than the discharge holes 42, the spinning nozzle 40 may include different holes formed therein (e.g., holes intended for fixing the spinning nozzle 40).

[0103] Alternatively, the spinning nozzle 40 may be configured as shown in FIG. 3 or FIG. 4.

[0104] The nozzle surface 41 is segmented into a central region 41a and a peripheral region 41b surrounding the central region 41a.

[0105] An outer edge 41a1 of the central region and an outer edge 41b1 of the peripheral region are similar in shape to each other and share the same area centroid. It should be noted that the area centroid herein means, assuming a thin plate whose outer edge has the same shape as that of the outer edge of each region and whose weight per unit area is uniform, the centroid of the thin plate.

[0106] The similarity ratio between the outer edge 41a1 of the central region and the outer edge 41b1 of the peripheral region is 1:2.

[0107] Since the similarity ratio is 1:2, the area ratio between the central region 41a and the peripheral region 41b is 1 (=1.sup.2): 3 (=2.sup.21.sup.2), i.e., 25:75.

[0108] A line that is drawn on the outer side of the collectively arranged discharge holes 42 on the nozzle surface 41 to connect the discharge holes 42 on the outer side serves as the outer edge 41b1 of the peripheral region. In other words, a line that is drawn to surround the collectively arranged discharge holes 42 on the nozzle surface 41 serves as the outer edge 41b1 of the peripheral region.

[0109] Further, a line that shares the area centroid with the outer edge 41b1 of the peripheral region, has a shape similar to the shape of the outer edge 41b1 of the peripheral region, and has a length that is half the length of the outer edge 41b1 of the peripheral region serves as the outer edge 41a1 of the central region.

[0110] In the peripheral region 41b, the discharge holes 42 are formed at a higher density than in the central region 41a.

[0111] The number of discharge holes 42 present in the peripheral region 41b exceeds 75% of the number of discharge holes 42 present on the nozzle surface 41, and may be from 80 to 100% of the number of discharge holes 42 present on the nozzle surface 41, from 85 to 100% of the number of discharge holes 42 present on the nozzle surface 41, from 90 to 100% of the number of discharge holes 42 present on the nozzle surface 41, or from 95 to 100% of the number of discharge holes 42 present on the nozzle surface 41.

[0112] As a result of the number of discharge holes 42 present in the peripheral region 41b exceeding 75% of the number of discharge holes 42 present on the nozzle surface 41, sufficient cooling of the inner raw filaments in the bundle of raw filaments is facilitated, which makes it possible to suppress cooling unevenness in the bundle of raw filaments between the outer raw filaments and the inner raw filaments.

[0113] Consequently, even if the speed of the haul-off roll is increased, breakage of the raw filaments is less likely to occur, which makes it possible to increase the productivity of the multifilament.

[0114] Further, variation in the fineness of the raw filaments A can be suppressed, which consequently makes it possible to suppress variation in the fineness of the single filaments in the obtained multifilament.

[0115] It should be noted that in a case where there is a particular discharge hole that straddles both the central region 41a and the peripheral region 41b, the area of the particular discharge hole in the central region 41a and the area of the particular discharge hole in the peripheral region 41b are compared with each other, and one of these two regions in which the area of the particular discharge hole is greater than in the other region is defined as the region in which the particular discharge hole is present. Based on this definition, the number of discharge holes 42 in each region is counted.

[0116] From the viewpoint of facilitating relatively uniform cooling of the raw filaments, it may be preferable that the discharge holes 42 be arranged in circumferential lines on the nozzle surface 41.

[0117] The nozzle surface 41 may include a single line of circumferentially arranged discharge holes 42 (FIG. 3). In light of ease of formation of a large number of discharge holes 42 on the nozzle surface 41, the nozzle surface 41 may include two or more lines of circumferentially arranged discharge holes 42, or include four or more lines of circumferentially arranged discharge holes 42 (five lines in FIG. 2 and eight lines in FIG. 4). Although depending on the size of the nozzle surface 41 and the size of each discharge hole 42, in a case where the nozzle surface 41 includes a line or lines of circumferentially arranged discharge holes 42, the number of lines of circumferentially arranged discharge holes 42 on the nozzle surface 41 is 20 or less, or more specifically 15 or less.

[0118] As shown in FIGS. 2 and 3, the peripheral region 41b may include, on the central region 41a side, a region in which no discharge holes 42 are present.

[0119] Alternatively, as shown in FIG. 4, the discharge holes 42 may be uniformly distributed in the entire peripheral region 41b.

[0120] As shown in FIGS. 2 to 4, from the viewpoint of further increasing the productivity of the multifilament, it may be preferable that no discharge holes 42 be present in the central region 41a. It should be noted that discharge holes 42 may be present in the central region 41a. From the viewpoint of facilitating relatively uniform cooling of the raw filaments, it may be preferable that distances between adjacent discharge holes 42 be substantially equal to each other.

[0121] From the viewpoint of facilitating relatively uniform cooling of the raw filaments, it may be preferable that the discharge holes 42 be substantially uniformly arranged in the region in which the discharge holes 42 are present on the nozzle surface 41.

[0122] From the viewpoint of facilitating relatively uniform cooling of the raw filaments, each of the outer edge 41a1 of the central region and the outer edge 41b1 of the peripheral region may have a circular shape, an ellipsoidal shape, a regular polygonal shape, or a regular star polygonal shape, may have a circular shape, an ellipsoidal shape, or a regular polygonal shape, or may have a circular shape.

[0123] The number of discharge holes 42 included in the spinning nozzle 40 may be 50 or more, from 50 to 10000, from 50 to 5000, from 50 to 3000, from 50 to 2000, or from 50 to 1000.

[0124] The spinning nozzle 40 includes 50 or more discharge holes 42, and in the present embodiment, the number of discharge holes 42 present in the peripheral region 41b exceeds 75% of the number of discharge holes 42 present on the nozzle surface 41. Consequently, sufficient cooling of the inner raw filaments A in the bundle of raw filaments is facilitated.

[0125] As a result of the spinning nozzle 40 including up to 10000 discharge holes 42, sufficient cooling of the inner raw filaments A in the bundle of raw filaments is facilitated.

[0126] The shape and the size of each discharge hole 42 are selected in accordance with required characteristics (e.g., appearance, fineness, strength, sectional shape, etc.) of the multifilament.

[0127] The discharge holes 42 may have substantially the same shape as each other. The discharge holes 42 may have substantially the same area (the same cross-sectional area) as each other.

[0128] The shape of each discharge hole 42 is, for example, a circular shape, an ellipsoidal shape, a regular polygonal shape, or a regular star polygonal shape.

[0129] The area (the cross-sectional area) of each discharge hole 42 may be from 1.010.sup.3 to 20 mm.sup.2, or from 5.010.sup.3 to 10 mm.sup.2.

[0130] The flow rate of the composition (the molten product) discharged from the spinning nozzle 40 may be from 1.0 to 20 kg/h, or from 2.0 to 15 kg/h.

[0131] The temperature of the composition (the raw material composition) immediately after being discharged from the spinning nozzle 40 may be from 150 to 168 C., or from 151 to 167 C.

[0132] As a result of the temperature being 150 C. or higher, the composition melts sufficiently, and thereby the composition can be readily discharged through the discharge holes 42.

[0133] As a result of the temperature being 168 C. or lower, decomposition of the poly(3-hydroxyalkanoate) resin is suppressed, and thereby breakage of the raw filaments in the molten state can be readily suppressed.

Step (B)

[0134] In the step (B), the gas is blown onto the 50 or more raw filaments A in the molten state to cool the raw filaments A.

[0135] Examples of the gas include air, inert gas (nitrogen gas, argon gas, etc.), and water vapor.

[0136] In the step (B), as shown in FIG. 1, in a cooler 50, the gas is blown onto the 50 or more raw filaments A in the molten state.

[0137] The cooler 50 includes a cooling box 51. In the step (B), the gas is blown onto the raw filaments A in the cooling box 51.

[0138] Examples of a gas blowing method to adopt in the step (B) includes a circular method and a back-side method.

[0139] The back-side method is a method for blowing the gas onto the 50 or more raw filaments A in the cooling box 51 from one direction when the raw filaments A are seen in their longitudinal direction (i.e., when the raw filaments A are seen in a cross-sectional view of the raw filaments A, the cross-sectional view being perpendicular to the longitudinal direction of the raw filaments A).

[0140] The circular method uses the cooling box 51, which includes a cylindrical side wall, and is a method for blowing the gas onto the 50 or more raw filaments A by blowing the gas into the cylindrical box 51 helically along the inner circumferential surface of the cylindrical side wall. It should be noted that a flow direction of the raw filaments A is substantially parallel to a virtual axis of the cylindrical side wall.

[0141] The cooling box 51 may include a cylindrical perforated metal inside the cylindrical side wall, and may further include a cylindrical mesh (e.g., 80 mesh) inside the cylindrical perforated metal. The external diameter of the cylindrical perforated metal is less than the internal diameter of the cylindrical side wall. The external diameter of the cylindrical mesh is less than the internal diameter of the cylindrical perforated metal.

[0142] In this case, in the circular method, the 50 or more raw filaments A pass through the inside of the cylindrical mesh.

[0143] The circular method may be preferable as the gas blowing method. The circular method makes it possible to blow the gas onto the 50 or more raw filaments A relatively uniformly. Consequently, the raw filaments A can be cooled more uniformly, and also, variation in the fineness of the raw filaments A can be suppressed.

[0144] In the step (B), the gas that has come into contact with the raw filaments A may be discharged from the cooling box 51 to the outside in the flow direction of the raw filaments A. In order to discharge the gas that has come into contact with the raw filaments A from the cooling box 51 to the outside in the flow direction of the raw filaments A, for example, a flow-straightening plate, a flow-straightening fin, an ejector, a venturi tube, or a Transvector available from KOGI CORPORATION Co., Ltd., can be used.

[0145] The temperature of the gas may be from (Tc-45) to (Tc-20) C. [Tc is the crystallization temperature of the composition (the raw material composition) including the poly(3-hydroxyalkanoate) resin], or may be from (Tc-40) to (Tc-25) C.

[0146] It should be noted that the temperature of the gas herein means the temperature of the gas immediately before the gas comes into contact with the raw filaments A.

[0147] As a result of the temperature of the gas being (Tc-20) C. or lower, breakage of the raw filaments A is suppressed, and consequently, the productivity of the multifilament can be readily increased.

[0148] The reason for this is considered as follows: as a result of the temperature of the gas being (Tc-20) C. or lower, the raw filaments A are sufficiently cooled, and thereby the time during which the raw filaments A are in the molten state can be shortened, and consequently, breakage of the raw filaments A is less likely to occur.

[0149] Also, as a result of the temperature of the gas being (Tc-45) C. or higher, the fusion of the single filaments to each other can be suppressed, and consequently, the productivity of the multifilament can be readily increased.

[0150] The reason for this is considered as follows: as a result of the temperature of the gas being (Tc-45) C. or higher, after the raw filaments are hauled off by the haul-off roll, the crystallization of the composition forming the raw filaments can be readily facilitated, and consequently, the fusion of the single filaments to each other is suppressed.

[0151] It should be noted that the crystallization temperature (Tc) of the raw material composition can be measured in accordance with JIS K7121-1987 Testing Methods for Transition Temperatures of Plastics.

[0152] Specifically, with use of a differential scanning calorimeter (e.g., Differential Scanning calorimeter DSC 25 available from TA Instruments), a sample of the raw material composition in an amount of about 6.0 mg put in a measurement container is subjected to both heating and cooling at a heating rate of 10 C./min and a cooling rate of 10 C./min within a temperature range from 30 C. to 180 C. while flowing nitrogen gas at a flow rate of 50 ml/min. The peak top temperature of the exothermic peak when the sample is subjected to the cooling for the second time is determined as the crystallization temperature.

[0153] In a case where there are two or more exothermic peaks, the peak top temperature of the exothermic peak having the largest peak area among the two or more exothermic peaks is determined as the crystallization temperature.

[0154] The speed of the gas may be 0.01 m/s or greater and less than 0.10 m/s, or from 0.01 m/s to 0.09 m/s.

[0155] It should be noted that the speed of the gas herein means the speed of the gas immediately before the gas comes into contact with the raw filaments A.

[0156] As a result of the speed of the gas being less than 0.10 m/s, even if the speed of the haul-off roll is increased, breakage of the raw filaments A is less likely to occur when the raw filaments A are hauled off by the haul-off roll, and consequently, the productivity of the multifilament can be readily increased.

[0157] The reason for this is considered as follows: as a result of the speed of the gas being less than 0.10 m/s, up to a point when the raw filaments A are hauled off by the haul-off roll, the raw filaments A can be suppressed from being cooled to a temperature at which the composition tends to be crystallized, and consequently, when the raw filaments A are hauled off by the haul-off roll, the raw filaments A have flexibility so that the raw filaments A can be readily hauled off by the haul-off roll.

[0158] As a result of the speed of the gas being 0.01 m/s or greater, the raw filaments A in the molten state can be sufficiently cooled by the gas. Consequently, breakage of the raw filaments A in the molten state is less likely to occur, and the productivity of the multifilament can be readily increased.

[0159] The distance from the discharge holes of the spinning nozzle 40 to a position where the gas in the step (B) comes into contact with the raw filaments A, which are obtained as a result of the discharging through the discharge holes, is set depending on required characteristics of the multifilament. However, generally speaking, this distance may be short.

Step (C)

[0160] In the step (C), the raw filaments A cooled in the step (B) are hauled off by a haul-off roll 62 of a haul-off machine 60 to obtain the multifilament B.

[0161] The haul-off speed of the haul-off roll 62 may be, for example, from 150 to 2000 m/min, from 200 to 1000 m/min, or from 250 to 750 m/min.

[0162] As a result of the haul-off speed of the haul-off roll 62 falling within any of the above ranges, the productivity of the multifilament can be further increased.

[0163] From the viewpoint of, for example, suppressing single filaments adjacent to each other from fusing to each other and suppressing single filaments adjacent to each other from separating from each other due to static electricity, in the step (C), before hauling off the raw filaments A by the haul-off roll 62, spinning oil may be applied, by an oiling roll 61 of the haul-off machine 60, onto the surface of each of the raw filaments A that have been cooled.

[0164] Examples of the spinning oil include a cationic surfactant, an anionic surfactant, a nonionic surfactant, a refined esterified oil, a mineral oil, a poly(oxyethylene) alkyl ether, a silicone oil, and a paraffin wax. One of these spinning oils may be used alone, or two or more of these spinning oils may be used in combination.

[0165] From the viewpoint of further suppressing single filaments adjacent to each other from fusing to each other, silicone oil may be preferable as the spinning oil.

[0166] From the viewpoint of further suppressing single filaments adjacent to each other from separating from each other due to static electricity, an anionic surfactant or a nonionic surfactant may be preferable as the spinning oil.

[0167] For example, as the spinning oil, one that includes a silicone oil and an anionic surfactant can be used (e.g., Polymax FKY available from Marubishi Oil Chemical Co., Ltd.).

[0168] Then, in the step (C), the multifilament B can be wound by a winding roll 71 of a winding machine 70.

[0169] It should be noted that, in the step (C) in FIG. 1, the multifilament B is wound by the winding roll 71. Alternatively, in the present embodiment, the multifilament B may be, without being wound by the winding roll 71, put into an accommodating container.

[0170] In the step (C), the multifilament B as a to-be-drawn multifilament may be subjected to drawing, and thereby a multifilament (i.e., a drawn multifilament) may be obtained.

[0171] A drawing method to be adopted is, for example, a sequential drawing process (which is also referred to as a post-drawing process) or a spin-draw process (which is also referred to as a SDY process or direct spin-draw process).

[0172] In the sequential drawing process, the to-be-drawn multifilament that has been wound by the winding roll 71 is subjected to drawing, and thereby the drawn multifilament can be obtained.

[0173] In the spin-draw process, the to-be-drawn multifilament that has been hauled off by the haul-off roll 62 is subjected to drawing to obtain the drawn multifilament, and the drawn multifilament is wound by the winding roll 71. In the spin-draw process, multiple steps from a step of obtaining the plurality of raw filaments in the molten state by discharging the molten product through the plurality of discharge holes to a step of drawing the to-be-drawn multifilament are performed as one process.

[0174] The number of single filaments included in the multifilament is 50 or more, from 50 to 10000, from 50 to 5000, or from 50 to 3000.

[0175] The average value of the fineness of the single filaments in the multifilament is from 3.0 dtex to 15.0 dtex.

[0176] As a result of the average value of the fineness of the single filaments being 15.0 dtex or less, the multifilament can be used for various applications. For example, the multifilament can be used as a material for fabricating a spun yarn.

[0177] As a result of the average value of the fineness of the single filaments being 3.0 dtex or greater, spinning is made possible.

[0178] The average value of the fineness of the single filaments may be 3.5 dtex or greater, or 4.0 dtex or greater.

[0179] The average value of the fineness of the single filaments may be 10 dtex or less, or 7.0 dtex or less.

[0180] In the present embodiment, the average value of the fineness of the single filaments can be determined in a manner described below.

[0181] First, the fineness of the multifilament (i.e., total fineness) is measured. Also, the number of single filaments included in the multifilament is determined.

[0182] Then, the average value of the fineness of the single filaments is determined by using an equation shown below.

[0183] Average value of the fineness of the single filaments =the fineness of the multifilament/the number of single filaments included in the multifilament

[0184] The multifilament may be used in the form of a yarn as it is.

[0185] The multifilament may be cut to obtain a staple having a length of 20 cm or less. The staple may be used in the form of a yarn as it is.

[0186] The multifilaments and/or the staples may be used to fabricate a fibrous product (a fibrous body).

[0187] The fibrous product can be made into various shapes (e.g., made into a nonwoven fabric).

[0188] The multifilaments, the staples, and the fibrous product can be suitably used for conventionally known use applications.

[0189] The multifilaments, the staples, and the fibrous product can be suitably used in the fields of, for example, agriculture (e.g., horticulture), fishery, forestry, medical care, and food industry.

[0190] Examples of the fibrous product include clothes, curtains, carpets, bags, shoes, wiping materials, sanitary items, automobile parts, building materials, and filtration materials (filters).

[Disclosure Items]

[0191] The following items each disclose a suitable embodiment.

[Item 1]

[0192] A method for producing a multifilament including 50 or more single filaments by melt spinning, the method including the steps of: (A) obtaining 50 or more raw filaments in a molten state by discharging a composition including a poly(3-hydroxyalkanoate) resin from a spinning nozzle; and (B) cooling the raw filaments by blowing gas onto the raw filaments in the molten state, wherein: the spinning nozzle includes a nozzle surface including 50 or more discharge holes; the nozzle surface is segmented into a central region and a peripheral region surrounding the central region; an outer edge of the central region and an outer edge of the peripheral region are similar in shape to each other and share a same area centroid; a similarity ratio between the outer edge of the central region and the outer edge of the peripheral region is 1:2; the number of discharge holes present in the peripheral region exceeds 75% of the number of discharge holes present on the nozzle surface; a temperature of the gas is from (Tc-45) to (Tc-20) C. [Tc is a crystallization temperature of the composition including the poly(3-hydroxyalkanoate) resin]; a speed of the gas is 0.01 m/s or greater and less than 0.10 m/s; and an average value of fineness of the single filaments is from 3.0 dtex to 15.0 dtex.

[Item 2]

[0193] The method for producing a multifilament according to item 1, wherein no discharge holes are present in the central region.

[Item 3]

[0194] The method for producing a multifilament according to item 1 or 2, wherein each of the outer edge of the central region and the outer edge of the peripheral region has a circular shape, an ellipsoidal shape, or a regular polygonal shape.

[Item 4]

[0195] The method for producing a multifilament according to item 3, wherein each of the outer edge of the central region and the outer edge of the peripheral region has a circular shape. [Item 5]

[0196] The method for producing a multifilament according to any one of items 1 to 4, wherein a temperature of the composition immediately after the composition is discharged from the spinning nozzle is from 150 to 168 C.

[Item 6]

[0197] The method for producing a multifilament according to any one of items 1 to 5, wherein the poly(3-hydroxyalkanoate) resin includes a poly(3-hydroxybutyrate) resin.

[0198] It should be noted that the present invention is not limited to the above-described embodiments. Also, the present invention is not limited by the above-described functional advantages. Further, various modifications can be made to the present invention without departing from the scope of the present invention.

EXAMPLES

[0199] Next, one or more embodiments of the present invention are described more specifically with Examples and Comparative Examples. It should be noted that the present invention is not limited by these Examples in any way.

Example 1

(Step (A))

[0200] First, materials listed below were subjected to dry blending at a blending ratio indicated below, and the resulting mixture was melt-kneaded at 150 C. by an extruder to obtain a raw material composition in the forms of pellets.

[0201] As a poly(3-hydroxyalkanoate) resin (P3HA), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (with a content ratio of a 3-hydroxybutyrate unit of 94.0 mol %, a content ratio of a 3-hydroxyhexanoate of 6 mol %, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH): 100 parts by mass

[0202] An erucic acid amide (EA) as a lubricant: 0.5 parts by mass

[0203] A behenic acid amide (BA) as a lubricant: 0.5 parts by mass

[0204] Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass

[0205] It should be noted that the weight-average molecular weight of the P3HA was measured in the above-described manner.

[0206] The content ratio of the 3-hydroxybutyrate unit and the content ratio of the 3-hydroxyhexanoate (3HH) unit in the P3HA were determined in a manner described below.

[0207] First, 2 mL of a mixed solution of sulfuric acid and methanol (the volume of sulfuric acid: the volume of methanol =15:85) and 2 mL of chloroform were added to 20 mg of the P3HA in a dry state. The resulting sample was placed in a container, and the container was sealed. The sample in the sealed container was heated at 100 C. for 140 minutes, and thereby a first reaction solution was obtained, the first reaction solution including a methyl ester that was a P3HA degradation product.

[0208] Then, the first reaction solution was cooled, and 1.5 g of sodium hydrogen carbonate was added to the cooled first reaction solution little by little for neutralization. The resulting mixture was left stand until generation of carbon dioxide stopped. In this manner, a second reaction solution was obtained.

[0209] Further, 4 mL of diisopropyl ether was added to and mixed well with the second reaction solution, and thereby a mixture was obtained.

[0210] Next, the mixture was subjected to centrifugal separation, and thereby a supernatant solution was obtained.

[0211] Then, the monomer unit composition of the aforementioned degradation product in the supernatant solution was analyzed by capillary gas chromatography under the conditions indicated below, and thereby the content ratio of the 3-hydroxybutyrate unit and the content ratio of the 3-hydroxyhexanoate (3HH) unit in the P3HA were determined.

[0212] Gas chromatograph: GC-17A available from Shimadzu Corporation

[0213] Capillary column: NEUTRA BOND-1 (column length: 25 m, column inner diameter: 0.25 mm, liquid film thickness: 0.4 m) available from GL Sciences Inc.

[0214] Carrier gas: He

[0215] Column inlet pressure: 100 kPa

[0216] Sample amount: 1 L

[0217] As the temperature condition, the temperature was raised from 100 C. to 200 C. at the rate of 8 C./min, and then raised from 200 C. to 290 C. at the rate of 30 C./min.

[0218] The crystallization temperature of the composition (the raw material composition) was measured in the above-described manner. The crystallization temperature of the composition (the raw material composition) was 50 C.

[0219] Then, as shown in FIG. 1, the extruder 20 (a single screw extruder with a screw diameter of 25 mm) was used to melt the pellets at an extrusion temperature of 170.0 C., and thereby a molten product was obtained.

[0220] Then, the molten product was discharged from the nozzle surface 41 of the spinning nozzle 40 of FIG. 2 (with the total number of discharge holes 42 being 400, the number of discharge holes 42 in the peripheral region 41b being 400, the number of discharge holes 42 in the central region 41a being 0, the shape of the discharge holes 42 being circular, and the diameter of the discharge holes 42 being 0.5 mm), and thereby 400 raw filaments A were obtained.

[0221] In Example 1, the ratio of the number of discharge holes 42 present in the peripheral region 41b to the number of discharge holes 42 present on the nozzle surface 41 (i.e., presence ratio) is 100%.

[0222] The temperature of the composition (the molten product) immediately after it was discharged from the spinning nozzle 40 (hereinafter, this temperature will occasionally be simply referred to as the temperature of the composition) was 161 C.

[0223] It should be noted that the flow rate of the composition (the molten product) discharged from the spinning nozzle 40 was adjusted by the gear pump 30 to 7.0 kg/h.

(Step (B))

[0224] In the cooler 50, gas (air) having a temperature of 20 C. was blown onto the 400 raw filaments A in the molten state with the circular method at a gas speed of 0.08 m/s, and thereby the 400 raw filaments A were cooled.

[0225] It should be noted that a value (Tc-T) obtained by subtracting the temperature (T) of the gas from the crystallization temperature (Tc) of the composition is shown in Table 1 below.

(Step (C))

[0226] The 400 raw filaments A were hauled off by the haul-off roll 62, and thereby a multifilament B was obtained. It should be noted that the haul-off speed of the haul-off roll 62 when hauling off the raw filaments A was set to a high speed (650 m/min).

[0227] The average value of the fineness of single filaments in the multifilament B was measured in the above-described manner. The average value of the fineness of the single filaments was 5.0 dtex.

Examples 2 to 14, Comparative Examples 1 to 7

[0228] A multifilament was produced in the same manner as in Example 1 except that the production conditions of the multifilament were changed as shown in Table 1 below.

[0229] It should be noted that the average value of the fineness of the single filaments was adjusted by adjusting one of the following: the flow rate of the composition (the molten product) discharged from the spinning nozzle 40; the total cross-sectional area of the discharge holes; and the haul-off speed of the haul-off roll 62.

[0230] It should be noted that, in Example 2, the spinning nozzle of FIG. 3 was used, whereas in Example 3, the spinning nozzle of FIG. 4 was used.

Evaluation of Productivity

[0231] The production of the multifilament was performed for one hour, and the productivity was evaluated in accordance with evaluation criteria indicated below.

[0232] Good: No trouble occurred.

[0233] Bad: A trouble described in Remarks in Table 1 below occurred at least once.

[0234] The evaluation results are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Nozzle surface Fineness Number of Number of average Total discharge discharge Pres- value of number of holes in holes in ence Gas Gas single Extrusion Composition Results discharge peripheral central ratio temp. T Tc T speed filaments temp. temp. Produc- holes region region (%) ( C.) ( C.) (m/s) (dtex) ( C.) ( C.) tivity Remarks Ex. 1 400 400 0 100 20 30 0.08 5.0 170.0 161 Good Ex. 2 50 50 0 100 20 30 0.08 5.0 170.0 160 Good Ex. 3 600 600 0 100 20 30 0.08 5.0 170.0 161 Good Ex. 4 400 400 0 100 5 45 0.08 5.0 170.0 161 Good Ex. 5 400 400 0 100 30 20 0.08 5.0 170.0 161 Good Ex. 6 400 400 0 100 20 30 0.05 5.0 170.0 161 Good Ex. 7 400 400 0 100 20 30 0.03 5.0 170.0 161 Good Ex. 8 400 400 0 100 20 30 0.01 5.0 170.0 161 Good Ex. 9 400 400 0 100 20 30 0.08 3.0 170.0 161 Good Ex. 10 400 400 0 100 20 30 0.08 10.0 170.0 161 Good Ex. 11 400 400 0 100 20 30 0.08 15.0 170.0 161 Good Ex. 12 400 400 0 100 20 30 0.08 5.0 160.0 151 Good Ex. 13 400 400 0 100 20 30 0.08 5.0 175.0 167 Good Ex. 14 1000 1000 0 100 25 25 0.09 6.5 170.0 165 Good Comp. 400 400 0 100 2 48 0.08 5.0 170.0 161 Bad Fusion of single Ex. 1 filaments to each other occurred a lot. Comp. 400 400 0 100 35 15 0.08 5.0 170.0 161 Bad Filament breakage Ex. 2 occurred a lot near spinning nozzle. Comp. 400 400 0 100 20 30 0.12 5.0 170.0 161 Bad Fusion of single Ex. 3 filaments to each other occurred a lot. Comp. 400 400 0 100 20 30 0.15 5.0 170.0 161 Bad Fusion of single Ex. 4 filaments to each other occurred a lot. Comp. 400 400 0 100 20 30 0.08 2.0 170.0 161 Bad Spinning could not Ex. 5 be performed Comp. 184 138 46 75 20 30 0.08 2.0 170.0 161 Bad Spinning could not Ex. 6 be performed. Comp. 184 138 46 75 20 30 0.08 5.0 170.0 161 Bad Filament breakage Ex. 7 occurred a lot near spinning nozzle.

[0235] As shown in Table 1, the productivity in Examples 1 to 14, which fall within the scope of the present invention, was better than the productivity in the following Comparative Examples: Comparative Example 1, in which the temperature of the gas in the step (B) was lower than (Tc-45) C.; Comparative Example 2, in which the temperature of the gas in the step (B) was higher than (Tc-20) C.; Comparative Examples 3 and 4, in which the speed of the gas in the step (B) was 0.12 m/s and 0.15 m/s, respectively; Comparative Example 5, in which the average value of the fineness of the single filaments in the multifilament was 2.0 dtex; Comparative Example 6, in which the presence ratio was 75% and the average value of the fineness of the single filaments in the multifilament was 2.0 dtex; and Comparative Example 7, in which the presence ratio was 75%.

[0236] Thus, one or more embodiments of the present invention make it possible to increase the productivity of a multifilament containing a poly(3-hydroxybutyrate) resin and having a small average value of the fineness of single filaments.

[0237] Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present disclosure. Accordingly, the scope of the invention should be limited only by the attached claims.

REFERENCE SIGNS LIST

[0238] A: raw filament, B: multifilament, [0239] 10: feeder, 20: extruder, 30: gear pump, 40: spinning nozzle, 41: nozzle surface, 41a: central region, 41a1: outer edge of the central region, 41b: peripheral region, 41b1: outer edge of the peripheral region, 42: discharge hole, 43: outermost edge region, 50: cooler, 51: cooling box, 60: haul-off machine, 61: oiling roll, 62: haul-off roll, 70: winding machine, 71: winding roll