Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D4/00—Spinnerette packs; Cleaning thereof
  • D01D4/02—Spinnerettes
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
  • D01D5/088—Cooling filaments, threads or the like, leaving the spinnerettes
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/08—Melt spinning methods
  • D01D5/088—Cooling filaments, threads or the like, leaving the spinnerettes
  • D01D5/092—Cooling filaments, threads or the like, leaving the spinnerettes in shafts or chimneys
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/24—Formation of filaments, threads, or the like with a hollow structure; Spinnerette packs therefor
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
  • D01D5/30—Conjugate filaments; Spinnerette packs therefor
  • D01D5/36—Matrix structure; Spinnerette packs therefor
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
  • D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
  • D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
  • D01F6/625—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters derived from hydroxy-carboxylic acids, e.g. lactones
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/14—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyester as constituent
• • D—TEXTILES; PAPER
  • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B2331/00—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products
  • D10B2331/04—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyesters, e.g. polyethylene terephthalate [PET]
  • D10B2331/041—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyesters, e.g. polyethylene terephthalate [PET] derived from hydroxy-carboxylic acids, e.g. lactones

Definitions

• the present invention relates to a method for producing a multifilament.
• Biodegradable plastics are the materials that can solve this problem, and the development of biodegradable plastics has been actively ongoing.
• Patent Literature 1 discloses a method for producing a multifilament containing a poly(3-hydroxybutyrate) resin.
• the production method described in Patent Literature 1 includes the steps of: heating a resin composition containing a poly(3-hydroxybutyrate) resin to a temperature that is not lower than the melting point of the resin composition and that is not higher than the thermal decomposition temperature of the resin composition and discharging the heated resin composition from a spinning nozzle; applying an air flow to the resin composition discharged from the spinning nozzle, which includes 80 holes, the air flow having a temperature that is not lower than the glass transition temperature of the resin composition and that is not higher than the crystallization temperature of the resin composition; and obtaining a multifilament by drawing, with a roll, the resin composition to which the air flow has been applied.
• Patent Literature 1 further describes that the cooling effect that is obtained in a case where the speed of the air flow is less than 0.1 m/s is too small.
• a problem to be solved by the present invention is 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.
• the present invention relates to 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.
• 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.
• An average value of fineness of the single filaments is from 3.0 dtex to 15.0 dtex.
• the present invention makes 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.
• 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.
• the method for producing a multifilament 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.
• 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.
• 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.
• the 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.
• 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].
• the speed of the gas is 0.01 m/s or greater and less than 0.10 m/s.
• the average value of the fineness of the single filaments is from 3.0 dtex to 15.0 dtex.
• 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).
• 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 is preferably 0.1 m/s or greater.”
• the speed of the gas in the step (B) is 0.01 m/s or greater and less than 0.10 m/s.
• the ratio of the number of discharge holes present in the peripheral region to the number of discharge holes present on the nozzle surface is 75%.
• 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.
• 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.
• the discharge holes are non-uniformly distributed such that the discharge holes are more densely present in the peripheral region.
• 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.
• 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.
• the speed of the gas is less than 0.10 m/s
• 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.
• the spinning speed i.e., the speed of the haul-off roll
• the spinning speed of the haul-off roll can be increased, which makes it possible to increase the productivity of the multifilament.
• the raw material composition contains a polymer component and an additive.
• the polymer component includes the poly(3-hydroxyalkanoate) resin.
• the polymer component may contain another polymer in addition to the poly(3-hydroxyalkanoate) resin.
• the poly(3-hydroxyalkanoate) resin is a polyester containing a 3-hydroxyalkanoic acid as a monomer.
• the poly(3-hydroxyalkanoate) resin is a resin including the 3-hydroxyalkanoic acid as a structural unit.
• the poly(3-hydroxyalkanoate) resin is a biodegradable polymer.
• 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.
• the poly(3-hydroxyalkanoate) resin includes a homopolymer and/or a copolymer.
• the poly(3-hydroxyalkanoate) resin includes a structural unit expressed by an equation (1) shown below.
• [-CHR-CH 2 -CO-O-] (1) (In the above equation (1), R is an alkyl group represented by C p H 2p+1 , and p is an integer from 1 to 15.)
• the poly(3-hydroxyalkanoate) resin is a resin including 3-hydroxybutyrate as a structural unit (i.e., a poly(3-hydroxybutyrate) resin).
• the poly(3-hydroxybutyrate) resin includes a homopolymer and/or a copolymer.
• poly(3-hydroxyalkanoate) resin including 3-hydroxybutyrate as a structural unit examples include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate).
• P3HB herein means poly(3-hydroxybutyrate) as a homopolymer.
• P3HB3HH herein means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).
• P3HB3HV herein means poly(3-hydroxybutyrate-co-3-hydroxyvalerate).
• P3HB4HB herein means poly(3-hydroxybutyrate-co-4-hydroxybutyrate).
• P3HB has a function to facilitate crystallization of P3HB itself and crystallization of the poly(3-hydroxyalkanoate) resin other than P3HB. Accordingly, preferably, the poly(3-hydroxyalkanoate) resin includes P3HB.
• the poly(3-hydroxyalkanoate) resin is preferably, but not particularly limited to, P3HB, P3HB3HH, P3HB3HV, or P3HB4HB.
• the poly(3-hydroxyalkanoate) resin is preferably P3HB3HH.
• the poly(3-hydroxyalkanoate) resin preferably includes 80% by mole or greater of 3-hydroxybutyrate, more preferably includes from 85.0% by mole to 99.5% by mole of 3-hydroxybutyrate, or yet more preferably includes from 85.0% by mole to 97.0% by mole of 3-hydroxybutyrate, as a structural unit.
• the stiffness of the multifilament is increased.
• the multifilament has excellent flexibility.
• the content ratio of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin can be determined in a manner described in Examples below.
• 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.
• 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.
• the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition is preferably from 3.0 ⁇ 10 5 to 7.0 ⁇ 10 5 , more preferably from 3.5 ⁇ 10 5 to 7.0 ⁇ 10 5 , yet more preferably from 4.0 ⁇ 10 5 to 7.0 ⁇ 10 5 , or most preferably from 4.5 ⁇ 10 5 to 6.5 ⁇ 10 5 .
• the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition being 3.0 ⁇ 10 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.
• the forming of the multifilament can be readily performed.
• 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.
• 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.
• GPC gel permeation chromatography
• a column used in the GPC may be any column suitable for measuring the molecular weight.
• 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
• ShodexK-806M available from Showa Denko K. K.
• the aforementioned another polymer is preferably biodegradable.
• this other polymer that is biodegradable examples 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.
• the polycaprolactone is a polymer obtained by ring-opening polymerization of ⁇ -caprolactone.
• the polymer component may include one kind of this other polymer, or two or more kinds of these other polymers.
• the polymer component preferably contains 50% by weight or greater of the poly(3-hydroxyalkanoate) resin, more preferably 80% by weight or greater of the poly(3-hydroxyalkanoate) resin, or yet more preferably 90% by weight or greater of the poly(3-hydroxyalkanoate) resin.
• 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.
• the additive examples 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.
• the raw material composition preferably contains a crystal nucleating agent.
• 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.
• P3HB which is the poly(3-hydroxyalkanoate) resin, can be used as the crystal nucleating agent.
• One of these crystal nucleating agents may be used alone, or two or more of these crystal nucleating agents may be used in combination.
• sugar alcohol compounds polyvinyl alcohol, chitin, and chitosan are 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.
• pentaerythritol is preferable.
• the crystal nucleating agent preferably has a crystal structure at normal temperature (25°C).
• the crystal nucleating agent that has a crystal structure at normal temperature (25°C) is preferably powdery at normal temperature (25°C).
• the crystal nucleating agent that is powdery at normal temperature (25°C) preferably has a mean particle diameter of 10 ⁇ m or less.
• the content of the crystal nucleating agent in the raw material composition is preferably 0.05 parts by weight or greater, more preferably 0.1 parts by weight or greater, or yet more preferably 0.5 parts by weight or greater, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin.
• 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.
• the content of the crystal nucleating agent in the raw material composition is preferably 10 parts by weight or less, more preferably 8 parts by weight or less, or yet more preferably 5 parts by weight or less, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin.
• 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.
• 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.
• the raw material composition may contain a lubricant.
• the lubricant is, for example, a fatty acid amide.
• the fatty acid amide includes 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.
• the content of the lubricant in the raw material composition is preferably 0.05 parts by weight or greater, more preferably 0.1 parts by weight or greater, or yet more preferably 0.5 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.
• the content of the lubricant in the raw material composition is preferably 12 parts by weight or less, more preferably 10 parts by weight or less, yet more preferably 8 parts by weight or less, or most preferably 5 parts by weight or less, with respect to 100 parts by weight of the poly(3-hydroxyalkanoate) resin.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• the spinning nozzle 40 may include different holes formed therein (e.g., holes intended for fixing the spinning nozzle 40).
• the spinning nozzle 40 may be configured as shown in FIG. 3 or FIG. 4 .
• the nozzle surface 41 is segmented into a central region 41a and a peripheral region 41b surrounding the central region 41a.
• 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.
• 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.
• the similarity ratio between the outer edge 41al of the central region and the outer edge 41b1 of the peripheral region is 1 : 2.
• 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.
• 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.
• 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.
• the discharge holes 42 are formed at a higher density than in the central region 41a.
• 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 is preferably from 80 to 100% of the number of discharge holes 42 present on the nozzle surface 41, more preferably from 85 to 100% of the number of discharge holes 42 present on the nozzle surface 41, yet more preferably from 90 to 100% of the number of discharge holes 42 present on the nozzle surface 41, or particularly preferably from 95 to 100% of the number of discharge holes 42 present on the nozzle surface 41.
• 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.
• the discharge holes 42 be arranged in circumferential lines on the nozzle surface 41.
• the nozzle surface 41 may include a single line of circumferentially arranged discharge holes 42 ( FIG. 3 ).
• the nozzle surface 41 preferably includes two or more lines of circumferentially arranged discharge holes 42, or more preferably includes four or more lines of circumferentially arranged discharge holes 42 (five lines in FIG. 2 and eight lines in FIG. 4 ).
• 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.
• the peripheral region 41b may include, on the central region 41a side, a region in which no discharge holes 42 are present.
• the discharge holes 42 may be uniformly distributed in the entire peripheral region 41b.
• distances between adjacent discharge holes 42 be substantially equal to each other.
• the discharge holes 42 be substantially uniformly arranged in the region in which the discharge holes 42 are present on the nozzle surface 41.
• each of the outer edge 41a1 of the central region and the outer edge 41b1 of the peripheral region preferably has a circular shape, an ellipsoidal shape, a regular polygonal shape, or a regular star polygonal shape, or more preferably has a circular shape, an ellipsoidal shape, or a regular polygonal shape, or yet more preferably has a circular shape.
• the number of discharge holes 42 included in the spinning nozzle 40 is 50 or more, preferably from 50 to 10000, more preferably from 50 to 5000, yet more preferably from 50 to 3000, even more preferably from 50 to 2000, or particularly preferably from 50 to 1000.
• 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.
• each discharge hole 42 are selected in accordance with required characteristics (e.g., appearance, fineness, strength, sectional shape, etc.) of the multifilament.
• the discharge holes 42 have substantially the same shape as each other.
• the discharge holes 42 have substantially the same area (the same cross-sectional area) as each other.
• each discharge hole 42 is, for example, a circular shape, an ellipsoidal shape, a regular polygonal shape, or a regular star polygonal shape.
• each discharge hole 42 is preferably from 1.0 ⁇ 10 -3 to 20 mm 2 , or more preferably from 5.0 ⁇ 10 -3 to 10 mm 2 .
• the flow rate of the composition (the molten product) discharged from the spinning nozzle 40 is preferably from 1.0 to 20 kg/h, or more preferably from 2.0 to 15 kg/h.
• the temperature of the composition (the raw material composition) immediately after being discharged from the spinning nozzle 40 is preferably from 150 to 168°C, or more preferably from 151 to 167°C.
• the temperature being 150°C or higher, the composition melts sufficiently, and thereby the composition can be readily discharged through the discharge holes 42.
• the gas is blown onto the 50 or more raw filaments A in the molten state to cool the raw filaments A.
• gas examples include air, inert gas (nitrogen gas, argon gas, etc.), and water vapor.
• the gas is blown onto the 50 or more raw filaments A in the molten state.
• the cooler 50 includes a cooling box 51.
• the gas is blown onto the raw filaments A in the cooling box 51.
• Examples of a gas blowing method to adopt in the step (B) includes a circular method and a back-side method.
• 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).
• 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.
• the 50 or more raw filaments A pass through the inside of the cylindrical mesh.
• the circular method is 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.
• the gas that has come into contact with the raw filaments A is discharged from the cooling box 51 to the outside in the flow direction of the raw filaments A.
• 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.
• the temperature of the gas is 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], and is preferably from (Tc - 40) to (Tc - 25)°C.
• 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.
• 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.
• 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.
• the speed of the gas herein means the speed of the gas immediately before the gas comes into contact with the raw filaments A.
• 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.
• 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.
• 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 is preferably short.
• 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.
• the haul-off speed of the haul-off roll 62 is, for example, from 150 to 2000 m/min, preferably from 200 to 1000 m/min, or more preferably from 250 to 750 m/min.
• the productivity of the multifilament can be further increased.
• 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.
• 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.
• the average value of the fineness of the single filaments in the multifilament is from 3.0 dtex to 15.0 dtex.
• the average value of the fineness of the single filaments is preferably 3.5 dtex or greater, or more preferably 4.0 dtex or greater.
• the average value of the fineness of the single filaments is preferably 10 dtex or less, or more preferably 7.0 dtex or less.
• the average value of the fineness of the single filaments can be determined in a manner described below.
• the fineness of the multifilament i.e., total fineness
• the number of single filaments included in the multifilament is determined.
• the multifilament may be used in the form of a yarn as it is.
• 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.
• the multifilaments and/or the staples may be used to fabricate a fibrous product (a fibrous body).
• the fibrous product can be made into various shapes (e.g., made into a nonwoven fabric).
• the multifilaments, the staples, and the fibrous product can be suitably used for conventionally known use applications.
• 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.
• 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.
• 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.
• 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.
• 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%.
• 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.
• 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.
• 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.
• Tc - T a value obtained by subtracting the temperature (T) of the gas from the crystallization temperature (Tc) of the composition is shown in Table 1 below.
• 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).
• 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.
• 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.
• 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.
• Example 2 the spinning nozzle of FIG. 3 was used, whereas in Example 3, the spinning nozzle of FIG. 4 was used.
• the production of the multifilament was performed for one hour, and the productivity was evaluated in accordance with evaluation criteria indicated below.
• 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%.
• the present invention makes 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.

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