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(11) | EP 4 800 166 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
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| (54) | FIBERS AND NON-WOVEN FABRIC |
| (57) The present invention provides a poly(3-hydroxyalkanoate) resin-containing fiber
in which the poly(3-hydroxyalkanoate) resin includes a 3-hydroxybutyrate unit, the
fiber being suppressed from fusing during production of the fiber and being thermally
fusible at low temperatures during thermal processing of the fiber. The present invention
is, for example, a fiber including a core-sheath structure including a core portion
and a sheath portion. Each of the core portion and the sheath portion contains a poly(3-hydroxyalkanoate)
resin including a 3-hydroxybutyrate unit. An average molar content of the 3-hydroxybutyrate
unit in the poly(3-hydroxyalkanoate) resin of the core portion is greater than an
average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate)
resin of the sheath portion. |
Technical Field
Background Art
[0002] In recent years, there has been a problem in that plastic wastes cause heavy burdens on the global environment, such as harmful effects on ecosystems, generation of harmful gas during combustion of the plastic wastes, and global warming due to a large amount of heat generated by the combustion of the plastic wastes. Biodegradable plastics are considered as materials that can solve this problem, and the development of biodegradable plastics has been actively ongoing.
[0003] Among such biodegradable plastics, carbon dioxide that is generated when a biodegradable plastic obtained using a plant-derived raw material is combusted originally exists in the air. Therefore, combusting such a biodegradable plastic does not cause an increase in carbon dioxide in the atmosphere. This is called carbon neutrality. Importance is given to carbon neutrality under the Kyoto Protocol, which specifies carbon dioxide reduction goals, and active use of biodegradable plastics obtained using plant-derived raw materials is desired.
[0004] Nowadays, from the viewpoints of biodegradability and carbon neutrality, aliphatic polyester resins are attracting attention as biodegradable plastics that are microbially produced using plant-derived raw materials as carbon sources. Attention has been directed particularly to polyhydroxyalkanoate resins.
[0005] Patent Literature 1 discloses a microorganism-degradable conjugated fiber including: a poly(β-hydroxyalkanoate) or a copolymer thereof as a core component; and poly-ε-caprolactone and/or poly-β-propiolactone as a sheath component.
[0006] Patent Literature 2 discloses a foamed fibrillated molded article including the following copolymer (A) and copolymer (B).
- (A) a copolymer including the following structural units (a1) and (a2) in a ratio
specified below (with the total of (a1) and (a2) being 100 mol%)
(a1) a 3-hydroxybutyrate structural unit
from 92 mol% to 98 mol%(a2) a structural unit represented by [-O-R1-CO-]
from 2 mol% to 8 mol%(R1 represents a straight-chain or branched-chain alkyl group having 3 to 17 carbon atoms.)
(It should be noted that the structural unit (a2) includes no 3-hydroxybutyrate structural unit.)
- (B) a copolymer including the following structural units (b1) and (b2) in a ratio
specified below (with the total of (b1) and (b2) being 100 mol%)
(b1) a 3-hydroxybutyrate structural unit
85 mol% or greater and less than 92 mol%(b2) a structural unit represented by [-O-R2-CO-]
greater than 8 mol% and less than or equal to 15 mol%(R2 represents a straight-chain or branched-chain alkyl group having 3 to 17 carbon atoms.)
(It should be noted that the structural unit (b2) includes no 3-hydroxybutyrate structural unit.)
Citation List
Patent Literature
[0007]
PTL 1: Japanese Laid-Open Patent Application Publication No. H05-93318
PTL 2: Japanese Laid-Open Patent Application Publication No. 2023-49669
Summary of Invention
Technical Problem
[0008] Incidentally, conventional fibers may undergo fusion during their production, or may fail to sufficiently fuse thermally at low temperatures during their thermal processing, making the thermal processing difficult.
[0009] In view of the above, a problem to be solved by the present invention is to provide a poly(3-hydroxyalkanoate) resin-containing fiber in which the poly(3-hydroxyalkanoate) resin includes a 3-hydroxybutyrate unit, the fiber being suppressed from fusing during production of the fiber and being thermally fusible at low temperatures during thermal processing of the fiber, and to provide a nonwoven fabric including the fiber.
Solution to Problem
[0010] The present invention relates to a fiber including a core-sheath structure including a core portion and a sheath portion, wherein: each of the core portion and the sheath portion contains a poly(3-hydroxyalkanoate) resin including a 3-hydroxybutyrate unit; and an average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the core portion is greater than an average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the sheath portion.
[0011] The present invention also relates to a method for producing a fiber, the method including melt-spinning a raw material composition for the core portion and a raw material composition for the sheath portion by using a core-sheath composite spinning nozzle to obtain the fiber.
Advantageous Effects of Invention
[0013] The present invention makes it possible to provide a poly(3-hydroxyalkanoate) resin-containing fiber in which the poly(3-hydroxyalkanoate) resin includes a 3-hydroxybutyrate unit, the fiber being suppressed from fusing during production of the fiber and being thermally fusible at low temperatures during thermal processing of the fiber, and to provide a nonwoven fabric including the fiber.
Brief Description of Drawings
[0014] FIG. 1 is a schematic diagram showing a cross section of a single filament that is a fiber according to an embodiment of the present invention.
Description of Embodiments
[0015] Hereinafter, one embodiment of the present invention is described with reference to the accompanying drawing.
<Fiber According to Present Embodiment>
[0016] A fiber according to the present embodiment includes a core-sheath structure including a core portion and a sheath portion.
[0017] Each of the core portion and the sheath portion contains a poly(3-hydroxyalkanoate) resin including a 3-hydroxybutyrate unit (which is hereinafter also referred to as "P3HA resin", "P3HA", "poly(3-hydroxybutyrate) resin", or "P3HB resin").
[0018] The average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the core portion is greater than the average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the sheath portion.
[0019] By having the above configuration, the fiber according to the present embodiment is a poly(3-hydroxyalkanoate) resin-containing fiber that is suppressed from fusing during its production and that is thermally fusible at low temperatures during its thermal processing.
[0020] The fiber according to the present embodiment may be a multifilament including a plurality of single filaments or may be a monofilament that is a single filament. However, the fiber is preferably a multifilament since a multifilament is flexible, soft, and usable for a nonwoven fabric or the like.
[0022] FIG. 1 is a schematic diagram showing a cross section of a single filament 1, which is a core-sheath conjugated fiber as the fiber according to the present embodiment (the cross section is taken perpendicularly to the longitudinal direction of the single filament).
[0023] As shown in FIG. 1, the single filament 1, which is a core-sheath conjugated fiber, includes a core portion 10 and a sheath portion 20. In the cross section of the core-sheath conjugated fiber (the cross section perpendicular to the longitudinal direction of the core-sheath conjugated fiber), preferably, the core portion is present inside the sheath portion. The core-sheath conjugated fiber may have, in the cross section (the cross section perpendicular to the longitudinal direction of the core-sheath conjugated fiber), a concentric structure in which the center position of the core portion coincides with the center position of the core-sheath conjugated fiber, or an eccentric structure in which the center position of the core portion does not coincide, i.e., eccentric, with the center position of the core-sheath conjugated fiber.
[0024] The sectional shape of the single filament 1, which is a core-sheath conjugated fiber, and that of the core portion 10 are not particularly limited. The sectional shape may be, for example, a circular shape or a non-circular shape. Examples of the non-circular shape include an ellipsoidal shape, an intersecting circular shape, a cocoon shape, a dumbbell shape, a dogbone shape, and a ribbon shape. The sectional shape of the core-sheath conjugated fiber and the sectional shape of the core portion may be the same (or similar to each other), or may be different from each other.
[0025] In the present embodiment, the major-axis direction of the cross section of the single filament and the major-axis direction of the cross section of the core portion coincide with each other.
[0026] In the embodiment shown in FIG. 1, both the sectional shape of the single filament 1, which is a core-sheath conjugated fiber, and the sectional shape of the core portion 10 are circular, and the core portion 10 is disposed concentrically with the single filament 1, which is a core-sheath conjugated fiber.
[0027] The sectional shape of the single filament, which is a core-sheath conjugated fiber, and the sectional shape of the core portion can be controlled, when fabricating the fiber with a below-described core-sheath composite spinning nozzle, by using the core-sheath composite spinning nozzle that has nozzle holes with shapes close to intended sectional shapes.
[0028] In the cross section of the fiber according to the present embodiment (the cross section perpendicular to the longitudinal direction of the fiber, i.e., the cross section perpendicular to the longitudinal direction of the single filament), the core-sheath ratio (the ratio between the core portion 10 and the sheath portion 20) is not particularly limited. From the viewpoint of achieving a complex appearance, spinning, cross-sectional stability, etc., the area ratio between the core portion 10 and the sheath portion 20 is preferably in a range from 1:9 to 9:1, more preferably from 2:8 to 8:2, and even more preferably from 3:7 to 7:3.
[0029] In other words, in the cross section of the fiber, the area ratio of the core portion 10 to the sheath portion 20 is such that preferably the core portion/the sheath portion = from 9/1 to 1/9, more preferably the core portion/the sheath portion = from 8/2 to 2/8, and even more preferably the core portion/the sheath portion = from 7/3 to 3/7.
[0032] The polymer component contains a poly(3-hydroxyalkanoate) resin including a 3-hydroxybutyrate unit.
[0033] The polymer component may contain another polymer in addition to the poly(3-hydroxyalkanoate) resin.
[0035] 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.
[0038] Examples of the poly(3-hydroxyalkanoate) resin include P3HB, P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate).
[0040] P3HB3HH herein means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), which may also be referred to as a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin.
[0043] 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, preferably, the poly(3-hydroxyalkanoate) resin includes P3HB.
[0044] From the viewpoint of achieving both excellent biodegradability and excellent molding processability, the poly(3-hydroxyalkanoate) resin is preferably, but not particularly limited to, P3HB, P3HB3HH, P3HB3HV, or P3HB4HB.
[0045] Further, from the viewpoints of increasing the strength of the fiber according to the present embodiment and increasing the molding processability, the poly(3-hydroxyalkanoate) resin is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH).
[0046] The average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the core portion is greater than the average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the sheath portion.
[0047] In the present application, the "average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin" is also referred to as the "average molar content of 3HB in the P3HA resin".
[0048] From the viewpoints of further suppressing fusion during production of the fiber and enabling thermal fusion of the fiber at lower temperatures during thermal processing of the fiber, the value of a difference between the average molar content of 3HB in the P3HA resin of the core portion and the average molar content of 3HB in the P3HA resin of the sheath portion is preferably from 0.2 to 9.0 mol%, more preferably from 0.4 to 7.0 mol%, even more preferably from 0.5 to 4.5 mol%, particularly preferably from 1.0 to 4.0 mol%, and most preferably from 1.5 to 3.5 mol%.
[0049] It should be noted that the value of the difference between the average molar content of 3HB in the P3HA resin of the core portion and the average molar content of 3HB in the P3HA resin of the sheath portion is obtained by subtracting the average molar content of 3HB in the P3HA resin of the sheath portion from the average molar content of 3HB in the P3HA resin of the core portion.
[0050] As a result of the average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the core portion being greater than the average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the sheath portion, the fiber according to the present embodiment can suppress fusion of the fiber during production of the fiber and is thermally fusible at low temperatures during thermal processing of the fiber.
[0051] From the viewpoints of further suppressing fusion during production of the fiber and enabling thermal fusion of the fiber at lower temperatures during thermal processing of the fiber, the fiber according to the present embodiment preferably includes: a copolymer (A) in which the molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of another hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 99/1 to 93/7; and a copolymer (B) in which the molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of another hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 92/8 to 76/24.
[0052] In the copolymer (A), the molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of the other hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 99/1 to 93/7, preferably from 98/2 to 93/7, and more preferably from 97/3 to 93/7.
[0053] In the copolymer (B), the molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of the other hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 92/8 to 76/24, preferably from 91/9 to 80/20, and more preferably from 90/10 to 85/15.
[0054] The average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin, and the molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of the other hydroxyalkanoate unit (the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit) in the poly(3-hydroxyalkanoate) resin, can each be determined by a method described below.
[0055] 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 are added to 20 mg of the P3HA resin in a dry state. The resulting sample is placed in a container, and the container is sealed. The sample in the sealed container is heated at 100°C for 140 minutes, and thereby a first reaction solution is obtained, the first reaction solution including a methyl ester that is a P3HA resin degradation product.
[0056] Then, the first reaction solution is cooled, and 1.5 g of sodium hydrogen carbonate is added to the cooled first reaction solution little by little for neutralization. The resulting mixture is left to stand until generation of carbon dioxide stops. In this manner, a second reaction solution is obtained.
[0057] Further, 4 mL of diisopropyl ether is added to and mixed well with the second reaction solution, and thereby a mixture is obtained.
[0058] Next, the mixture is subjected to centrifugal separation, and thereby a supernatant solution is obtained.
[0059] Then, the average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin, and the molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of the other hydroxyalkanoate unit (the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit) in the poly(3-hydroxyalkanoate) resin, can be determined by analyzing the monomer unit composition of the aforementioned degradation product in the supernatant by capillary gas chromatography under the conditions indicated below.
Gas chromatograph: GC-17A available from Shimadzu Corporation
Capillary column: NEUTRA BOND-1 (column length: 25 m, column inner diameter: 0.25 mm, liquid film thickness: 0.4 µm) available from GL Sciences Inc.
Carrier gas: He
Column inlet pressure: 100 kPa
Sample amount: 1 µL
[0060] From the viewpoints of further suppressing fusion during production of the fiber and enabling thermal fusion of the fiber at lower temperatures during thermal processing of the fiber, the content of the copolymer (B) in the fiber according to the present embodiment is preferably from 5 to 40% by weight, more preferably from 10 to 35% by weight, and even more preferably from 12 to 30% by weight, per 100% by weight of the poly(3-hydroxyalkanoate) resin.
[0061] From the viewpoint of enabling thermal fusion of the fiber at lower temperatures during thermal processing of the fiber, the sheath portion preferably includes the copolymer (B).
[0062] From the viewpoints of further suppressing fusion during production of the fiber and enabling thermal fusion of the fiber at lower temperatures during thermal processing of the fiber, the sheath portion more preferably includes the copolymer (A) and the copolymer (B).
[0063] From the viewpoint of further suppressing fusion during production of the fiber, the core portion preferably includes the copolymer (A).
[0064] The fiber according to the present embodiment contains the poly(3-hydroxyalkanoate) resin in an amount of preferably 50% by weight or greater, more preferably 80% by weight or greater, and even more preferably 90% by weight or greater.
[0065] The fiber according to the present embodiment further contains the copolymer (A) and the copolymer (B) in an amount of preferably 50% by weight or greater, more preferably 80% by weight or greater, and even more preferably 90% by weight or greater.
[0067] 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.
[0069] The polymer component may include one kind of this other polymer, or two or more kinds of these other polymers.
[0070] Since the fiber according to the present embodiment includes the biodegradable polymer(s), even if the fiber is discarded in an environment, since the fiber is readily decomposed in the environment, the load on the environment can be reduced.
[0072] 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.
[0073] In order to facilitate the crystallization of the poly(3-hydroxyalkanoate) resin, the fiber according to the present embodiment preferably contains a crystal nucleating agent.
[0074] 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.
[0075] 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 (dimethyl adipate, dibutyl adipate, di-isodecyl adipate, and dibutyl sebacate); cyclic compounds having, in their molecule, C=O 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.
[0076] It should be noted that P3HB, which is the poly(3-hydroxyalkanoate) resin, can be used as the crystal nucleating agent.
[0077] One of these crystal nucleating agents may be used alone, or two or more of these crystal nucleating agents may be used in combination.
[0078] As the crystal nucleating agent, 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.
[0080] The crystal nucleating agent preferably has a crystal structure at normal temperature (25°C).
[0081] Since the crystal nucleating agent has a crystal structure at normal temperature (25°C), the crystallization of the poly(3-hydroxyalkanoate) resin is further facilitated, which is advantageous.
[0082] The crystal nucleating agent that has a crystal structure at normal temperature (25°C) is preferably powdery at normal temperature (25°C).
[0083] The crystal nucleating agent that is powdery at normal temperature (25°C) preferably has a mean particle diameter of 10 µm or less.
[0084] The content of the crystal nucleating agent in the fiber according to the present embodiment is preferably 0.05 parts by weight or greater, more preferably 0.1 parts by weight or greater, and even more preferably 0.5 parts by weight or greater, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the crystal nucleating agent in the fiber according to the present embodiment being 0.05 parts by weight or greater per 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.
[0085] Further, the content of the crystal nucleating agent in the fiber according to the present embodiment is preferably 10 parts by weight or less, more preferably 8 parts by weight or less, and even more preferably 5 parts by weight or less, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the crystal nucleating agent in the fiber according to the present embodiment being 10 parts by weight or less per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the viscosity of a molten material when fabricating the fiber from the molten material by a below-described melt spinning technique can be reduced, which consequently makes it possible to readily fabricate the fiber, which is advantageous.
[0086] 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 fiber contains P3HB, the amount of the P3HB is included in both the amount of the poly(3-hydroxyalkanoate) resin and the amount of the crystal nucleating agent.
[0089] The compound having an amide bond preferably 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.
[0090] The content of the lubricant in the fiber according to the present embodiment is preferably 0.05 parts by weight or greater, more preferably 0.1 parts by weight or greater, and even more preferably 0.5 parts by weight or greater, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the lubricant in the fiber according to the present embodiment being 0.05 parts by weight or greater per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the single filament has excellent slipperiness, which is advantageous.
[0091] Further, the content of the lubricant in the fiber according to the present embodiment is preferably 12 parts by weight or less, more preferably 10 parts by weight or less, ever more preferably 8 parts by weight or less, and most preferably 5 parts by weight or less, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin. As a result of the content of the lubricant in the fiber according to the present embodiment being 12 parts by weight or less per 100 parts by weight of the poly(3-hydroxyalkanoate) resin, the lubricant can be advantageously suppressed from bleeding out on the surface of the fiber.
[0092] The single filament fineness of the fiber according to the present embodiment is preferably from 1 to 15 dtex, more preferably from 2 to 13 dtex, and even more preferably from 3 to 12 dtex
As a result of the single filament fineness being 15 dtex or less, the fiber according to the present embodiment has an advantage in that the fiber can be used for various applications. For example, the fiber according to the present embodiment can be used as a material for fabricating a spun yarn.
[0093] As a result of the single filament fineness being 1 dtex or greater, the fiber according to the present embodiment has an advantage of increased strength.
[0094] It should be noted that in a case where the fiber according to the present embodiment is a multifilament, the single filament fineness of the fiber means an average value of the fineness of the single filaments included in the fiber.
[0095] In a case where the fiber according to the present embodiment is a monofilament, the single filament fineness of the fiber means the fineness of the fiber itself.
[0097] In a case where the fiber according to the present embodiment is a multifilament including a plurality of single filaments, the number of single filaments included in the multifilament is preferably 30 or greater, more preferably from 30 to 300,000, and even more preferably from 50 to 300,000.
[0098] The weight-average molecular weight of the fiber according to the present embodiment is preferably from 2.0 × 105 to 6.0 × 105, and more preferably from 2.3 × 105 to 4.0 × 105, from the viewpoint of achieving excellent processability when processing the fiber to obtain a processed product.
[0099] 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.
[0100] For example, the weight-average molecular weight in the present embodiment can be measured under the conditions indicated below.
Measurement equipment: SHIMADZU 20A available from Shimadzu Corporation
Column: ShodexK-806M available from Showa Denko K. K.
Detector: RI detector
Reference material: polystyrene
Eluent: chloroform (HPLC grade)
Flow rate: 1 mL/min
Temperature: 40°C
[0102] The fiber 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.
[0105] The fiber, the staple, and the fibrous product can be suitably used for conventionally known applications.
[0106] The fiber, the staple, 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.
[0107] Examples of the fibrous product include clothes, curtains, carpets, bags, shoes, wiping materials, sanitary items, automobile parts, building materials, and filtration materials (filters).
<Nonwoven Fabric According to Present Embodiment>
[0108] A nonwoven fabric according to the present embodiment includes the fiber according to the present embodiment.
[0109] Examples of the nonwoven fabric according to the present embodiment include a thermally bonded nonwoven fabric, a needle-punched nonwoven fabric, a chemically bonded nonwoven fabric, an airlaid nonwoven fabric, and a wet-laid nonwoven fabric.
[0110] The fiber according to the present embodiment is suitably used for fabricating a thermally bonded nonwoven fabric since the fiber according to the present embodiment enables thermal fusion of the fiber at low temperatures during thermal processing of the fiber.
<Method for Producing Fiber According to Present Embodiment>
[0111] A method for producing the fiber according to the present embodiment includes melt-spinning a raw material composition for the core portion and a raw material composition for the sheath portion by using a core-sheath composite spinning nozzle to obtain the fiber.
[0112] For example, the method for producing the fiber according to the present embodiment includes: a spinning step of, by a melt spinning technique, melting the raw material compositions to obtain molten materials and spinning the molten materials to obtain undrawn filaments; and a drawing step of drawing the undrawn filaments.
[0113] The raw material compositions include the raw material composition for the core portion and the raw material composition for the sheath portion separately.
[0115] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in each raw material composition is preferably from 3.0 × 105 to 7.0 × 105, more preferably from 3.5 × 105 to 7.0 × 105, even more preferably from 4.0 × 105 to 7.0 × 105, and most preferably from 4.5 × 105 to 6.5 × 105.
[0116] As a result of the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition being 3.0 × 105 or greater, the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the fiber can be readily increased, which consequently makes it possible to readily increase the strength of the fiber.
[0117] As a result of the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin in the raw material composition being 7.0 × 105 or less, the forming of the fiber can be readily performed.
[0118] In the spinning step, the raw material composition for the core portion is fed to an extruder for the core portion, and the raw material composition for the sheath portion is fed to an extruder for the sheath portion. Then, the raw material composition for the core portion and the raw material composition for the sheath portion are melted to obtain a molten material for the core portion and a molten material for the sheath portion.
[0119] Thereafter, the molten material for the core portion and the molten material for the sheath portion are each extruded through the core-sheath composite spinning nozzle and wound onto a winding roll unit to obtain one or more undrawn filaments.
[0120] In the drawing step, the obtained one or more undrawn filaments are hauled off by a haul-off roll unit from the winding roll unit, then drawn by a drawing roll unit, and wound onto a heat treatment roll unit to obtain the fiber.
[0121] It should be noted that the present invention is not limited to the above-described embodiment. 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.
[0122] For example, in the present embodiment, one or more undrawn filaments are drawn to obtain the fiber. Alternatively, in the present invention, one or more undrawn filaments may be obtained as the fiber.
[Disclosure Items]
[Item 1]
[0124] A fiber including a core-sheath structure including a core portion and a sheath portion, wherein: each of the core portion and the sheath portion contains a poly(3-hydroxyalkanoate) resin including a 3-hydroxybutyrate unit; and an average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the core portion is greater than an average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the sheath portion.
[Item 2]
[0125] The fiber according to item 1, including: a copolymer (A) in which a molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of another hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 99/1 to 93/7; and a copolymer (B) in which a molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of another hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 92/8 to 76/24.
[Item 3]
[0126] The fiber according to item 2, wherein a content of the copolymer (B) in the fiber is from 5 to 40% by weight per 100% by weight of the poly(3-hydroxyalkanoate) resin.
[Item 4]
[Item 5]
[0128] The fiber according to item 4, wherein the sheath portion includes the copolymer (A) and the copolymer (B).
[Item 6]
[0129] The fiber according to any one of items 1 to 5, wherein in a cross section of the fiber, an area ratio of the core portion to the sheath portion is such that the core portion/the sheath portion = from 8/2 to 2/8.
[Item 7]
[0130] The fiber according to any one of items 1 to 6, wherein the poly(3-hydroxyalkanoate) resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).
[Item 8]
[0131] The fiber according to any one of items 1 to 7, wherein a single filament fineness of the fiber is from 1 to 15 dtex.
[Item 9]
[0132] A method for producing a fiber, the method comprising melt-spinning a raw material composition for the core portion and a raw material composition for the sheath portion by using a core-sheath composite spinning nozzle to obtain the fiber according to any one of items 1 to 8.
[Item 10]
Examples
[0134] Next, the present invention is 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.
[0135] Measurement and evaluation methods used in Examples and Comparative Examples are as described below.
(Example 1)
[0136] 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 for a core portion and a raw material composition for a sheath portion each in the forms of pellets.
<Raw Material Composition for Core Portion>
[0137] As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 94.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 6 mol%, a melting point of 145°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH) (copolymer (A1)): 100 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
<Raw Material Composition for Sheath Portion>
[0138]
As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 94.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 6 mol%, a melting point of 145°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH) (copolymer (A1)): 50 parts by mass
As a poly(3-hydroxyalkanoate) resin (copolymer (B)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 89.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 11.0 mol%, a melting point of 108°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH) (copolymer (B1)): 50 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
[0139] It should be noted that the molar content of the 3-hydroxybutyrate unit (3HB ratio), the molar content of the 3-hydroxyhexanoate unit (3HH ratio), and the weight-average molecular weight (Mw) were each determined by the above-described method.
[0140] On a DSC curve determined by differential scanning calorimetry (DSC), the melting point was defined as a temperature at which an endothermic energy amount was maximum (i.e., the apex of an endothermic peak).
[0141] The differential scanning calorimetry (DSC) is a method that accords with JIS K7122 (1987) "Testing Methods for Heat of Transitions of Plastics".
[0142] Specifically, measurement was performed under the following conditions.
Equipment: Differential scanning calorimeter DSC6200 available from Seiko Instruments Inc.
Sample amount: 4 to 10 mg
Measurement temperature range: 30°C to 200°C
Temperature rise rate: 10 °C/min
[0143] The crystallization temperature (Tc) was measured in accordance with JIS K7121-1987 "Testing Methods for Transition Temperatures of Plastics".
[0144] Specifically, with use of a differential scanning calorimeter (e.g., Differential Scanning Calorimeter DSC 25 available from TA Instruments), a sample of the poly(3-hydroxyalkanoate) resin in an amount of about 6.0 mg put in a measurement container was 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 of -30°C to 180°C while flowing nitrogen gas at a flow rate of 50 ml/min. The peak top temperature of an exothermic peak when the sample was subjected to the cooling for the second time was determined as the crystallization temperature.
[0145] In a case where there were 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 was determined as the crystallization temperature.
<Spinning Step>
[0146] Next, the raw material composition for the core portion in the form of pellets was fed to an extruder for the core portion, and the raw material composition for the sheath portion in the form of pellets was fed to an extruder for the sheath portion. Then, the raw material composition for the core portion and the raw material composition for the sheath portion were melted to obtain a molten material for the core portion and a molten material for the sheath portion.
[0147] Then, the molten material for the core portion and the molten material for the sheath portion were each extruded through a concentric circular core-sheath composite spinning nozzle (having 200 holes with a hole diameter of 0.5 mm) with a setting temperature of 175°C, and wound onto a winding roll unit at a speed of 250 to 300 m/min, thereby obtaining 200 undrawn filaments of a core-sheath conjugated fiber having an area ratio between the core portion and the sheath portion (core:sheath) in a cross section of 7:3 (this ratio is hereinafter also referred to as "core-sheath ratio").
<Core-Sheath Ratio>
[0148] At room temperature, the fibers were bundled together, and the fiber bundle (total fineness: 2200 dtex) was fixed with a shrinkable tube to prevent the fibers from shifting relative to each other. Thereafter, the fiber bundle was cut by a cutter into round cross sections, thereby preparing a fiber bundle for cross-sectional observation. An image of the fiber bundle was taken at a magnification of 500 times using a laser microscope ("VK-9500" available from KEYENCE CORPORATION) to obtain a fiber cross-sectional photograph, and the core-sheath ratio was determined based on the photograph.
<Drawing Step>
[0149] The obtained 200 undrawn filaments were hauled off from the winding roll unit by a haul-off roll unit (at 55.5 m/min and 30°C), drawn by a drawing roll unit (at 110 m/min and 90°C), and wound onto a heat treatment roll unit (at 100 m/min). In this manner, a fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber having the sectional shape shown in FIG. 1) (with a single filament fineness of 5.5 dtex and a core-sheath ratio of 7:3) was obtained. The draw ratio was 2.0 times, and the relaxation rate was 10%.
[0150] It should be noted that each of the haul-off roll unit, the drawing roll unit, and the heat treatment roll unit used above includes two rolls that roll at the same speed and that have the same temperature.
<Single Filament Fineness>
[0151] It should be noted that the single-filament fineness was measured using an auto-vibro type fineness measuring instrument ("DENIER COMPUTER Type DC-11" available from SEARCH CO., LTD). An average value of measurement values obtained from 10 samples was calculated and defined as the single-filament fineness.
(Example 2)
[0152] A fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber) (with a single filament fineness of 6.1 dtex and a core-sheath ratio of 5:5) was obtained in the same manner as in Example 1 except that, in Example 2, the core-sheath ratio of the undrawn filaments was set to 5:5.
(Example 3)
[0153] A fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber) (with a single filament fineness of 5.8 dtex) was obtained in the same manner as in Example 1 except that, in Example 3, the blending ratio of the raw material composition for the sheath portion was set as indicated below.
As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a content ratio of the 3-hydroxybutyrate unit of 94.0 mol%, a content ratio of the 3-hydroxyhexanoate unit of 6 mol%, a melting point of 145°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH) (copolymer (A1)): 30 parts by mass
As a poly(3-hydroxyalkanoate) resin (copolymer (B)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a content ratio of the 3-hydroxybutyrate unit of 89.0 mol%, a content ratio of the 3-hydroxyhexanoate unit of 11.0 mol%, a melting point of 108°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH) (copolymer (B1)): 70 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
(Example 4)
[0154] A fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber) was obtained in the same manner as in Example 1 except that, in Example 4, the single filament fineness was set to 11.0 dtex.
(Example 5)
[0155] A fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber) (with a single filament fineness of 4.5 dtex) was obtained in the same manner as in Example 1 except that, in Example 5, the blending ratio of the raw material composition for the core portion was set as indicated below; the blending ratio of the raw material composition for the sheath portion was set as indicated below; the core-sheath ratio of the undrawn filaments was set to 5:5; and the drawing step was not performed.
<Raw Material Composition for Core Portion>
[0156]
As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 97.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 3 mol%, a melting point of 152 °C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 390,000 (P3HB3HH) (copolymer (A2)): 100 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
<Raw Material Composition for Sheath Portion>
[0157]
As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 94.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 6 mol%, a melting point of 145°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936) (P3HB3HH) (copolymer (A1)): 50 parts by mass
As a poly(3-hydroxyalkanoate) resin (copolymer (B)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 89.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 11.0 mol%, a melting point of 108°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 220,000) (P3HB3HH) (copolymer (B2)): 50 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
(Example 6)
[0158] A fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber) (with a single filament fineness of 4.5 dtex) was obtained in the same manner as in Example 1 except that, in Example 6, the blending ratio of the raw material composition for the core portion was set as indicated below; the blending ratio of the raw material composition for the sheath portion was set the same as in Example 5; the core-sheath ratio of the undrawn filaments was set to 5:5; and the drawing step was not performed.
<Raw Material Composition for Core Portion>
[0159]
As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 97.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 3 mol%, a melting point of 152°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 390,000 (P3HB3HH) (copolymer (A2)): 50 parts by mass
As a poly(3-hydroxyalkanoate) resin (copolymer (B)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a molar content of the 3-hydroxybutyrate unit (3HB ratio) of 89.0 mol%, a molar content of the 3-hydroxyhexanoate unit (3HH ratio) of 11.0 mol%, a melting point of 108°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 310,000 (P3HB3HH) (copolymer (B3)): 5 parts by mass
As a poly(3-hydroxyalkanoate) resin, a poly(3-hydroxybutyrate) homopolymer (P3HB) (with a melting point of 180°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 310,000): 45 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
(Comparative Example 1)
[0160] A fiber (a multifilament including 200 single filaments, each being a core-sheath conjugated fiber) (with a single filament fineness of 5.6 dtex) was obtained in the same manner as in Example 1 except that, in Comparative Example 1, the blending ratio of the raw material composition for the sheath portion was set as indicated below.
As a poly(3-hydroxyalkanoate) resin (copolymer (A)), a (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (with a content ratio of the 3-hydroxybutyrate unit of 94.0 mol%, a content ratio of the 3-hydroxyhexanoate unit of 6 mol%, a melting point of 145°C, a crystallization temperature (Tc) of 60°C, and a weight-average molecular weight (Mw) of 582,936 (P3HB3HH)): 100 parts by mass
An erucic acid amide (EA) as an amide bond-containing lubricant: 0.5 parts by mass
A behenic acid amide (BA) as an amide bond-containing lubricant: 0.5 parts by mass
Pentaerythritol (PETL) as a crystal nucleating agent (Neulizer P available from The Nippon Synthetic Chemical Industry Co., Ltd.): 1.0 part by mass
(Comparative Example 2)
[0161] A fiber (a multifilament including 400 single filaments each being a single-layer fiber) (with a single-filament fineness of 5.8 dtex) was obtained in the same manner as in Example 1 except that, in Comparative Example 2, only the raw material composition for the core portion of Example 1 was used; the concentric circular core-sheath composite spinning nozzle was not used; and a spinning nozzle intended for a single layer was used.
(Comparative Example 3)
[0162] A fiber (a multifilament including 400 single filaments each being a single-layer fiber) (with a single-filament fineness of 6.0 dtex) was obtained in the same manner as in Example 1 except that, in Comparative Example 3, only the raw material composition for the sheath portion of Example 1 was used; the concentric circular core-sheath composite spinning nozzle was not used; and a spinning nozzle intended for a single layer was used.
(Fusion Rate)
[0164] First, the multifilament as the fiber was cut along a plane perpendicular to the longitudinal direction of the fiber, and thereby all the single filaments included in the fiber were cut.
[0165] Next, by using a scanning electron microscope (SEM), the cut surface of the multifilament was observed, and the total number of single filaments included in the multifilament was counted at the cut surface, and the number of single filaments fused to other single filaments at the cut surface (in other words, a number obtained by subtracting "the number of single filaments not fused to other single filaments" from "the total number of single filaments included in the multifilament") was counted.
[0166] Then, the fusion rate was determined by using an equation shown below.
Fusion rate (%) = (the number of single filaments fused to other single filaments
at the cut surface / the total number of single filaments included in the multifilament
at the cut surface) × 100
(Thermal Fusion Temperature)
[0167] Eight fiber bundles each having a length of about 3 cm were cut out, and two sets of four fiber bundles were arranged in a grid pattern. The fiber bundles thus arranged were sandwiched between iron plates heated to 60 to 120°C, left to stand for 1 minute, and then removed. The temperature at which overlapping portions of the fiber bundles arranged in the grid pattern were fused together was defined as the thermal fusion temperature.
| 3HH ratio (mol%) | 3HB ratio (mol%) | Melting point | Ex. 1 | Ex. 2 | Ex. 3 | Ex. 4 | Ex. 5 | Ex. 6 | Comp. Ex. 1 | Comp. Ex. 2 | Comp. Ex. 3 | ||
| Blending ratio of core portion (parts by weight) | Copolymer (A1) | 6 | 94 | 145°C | 100 | 100 | 100 | 100 | - | - | 100 | 100 | 0 |
| Copolymer (A2) | 3 | 97 | 152°C | - | - | - | - | 100 | 50 | - | - | - | |
| Copolymer (B3) | 11 | 89 | 108°C | 5 | |||||||||
| P3HB | 0 | 100 | 180°C | - | - | - | - | - | 45 | - | - | - | |
| Erucic acid amide | - | - | - | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | - | |
| Behenic acid amide | - | - | - | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | - | |
| Pentaerythritol | - | - | - | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | - | |
| Average molar content (mol%) of 3HB in P3HA resin of core portion | 94.0 | 94.0 | 94.0 | 94.0 | 94.0 | 93.5 | 94.0 | 94.0 | - | ||||
| Copolymer (A1) | 6 | 94 | 145°C | 50 | 50 | 30 | 50 | 50 | 50 | 100 | 0 | 50 | |
| Copolymer (B1) | 11 | 89 | 108°C | 50 | 50 | 70 | 50 | - | - | 0 | 0 | 50 | |
| Copolymer (B2) | 11 | 89 | 108°C | - | - | - | - | 50 | 50 | - | - | - | |
| Erucic acid amide | - | - | - | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | - | 0.5 | |
| Behenic acid amide | - | - | - | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | 0.5 | - | 0.5 | |
| Pentaerythritol | - | - | - | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | - | 1.0 | |
| Average molar content (mol%) of 3HB in P3HA resin of sheath portion | 91.5 | 91.5 | 90.5 | 91.5 | 91.5 | 91.5 | 94.0 | - | 91.5 | ||||
| Core-sheath ratio of fiber (core : sheath) | 7:3 | 5:5 | 7:3 | 7:3 | 5:5 | 5:5 | 7:3 | - | - | ||||
| Single filament fineness (dtex) | 5.5 | 6.1 | 5.8 | 11.0 | 4.5 | 4.5 | 5.6 | 5.8 | 6.0 | ||||
| Fusion rate (%) | 8.6 | 8.9 | 9.1 | 0.0 | 10.8 | 3.8 | 4.0 | 4.6 | 18.3 | ||||
| Thermal fusion temperature (°C) | 80 | 80 | 70 | 80 | 80 | 80 | 120 | 120 | 80 | ||||
| Copolymer (B) content (wt%) per 100 wt% of P3HA resin | 15 | 25 | 21 | 15 | 25 | 27.5 | 0 | 0 | 50 | ||||
| Difference (mol%) between average molar content of 3HB in P3HA resin of core portion and average molar content of 3HB in P3HA resin of sheath portion | 2.5 | 2.5 | 3.5 | 2.5 | 2.5 | 2.0 | 0.0 | - | - | ||||
[0168] As shown in Table 1, the thermal fusion temperatures in Examples 1 to 6, which fall within the scope of the present invention, were lower than those in Comparative Example 1 (poly(3-hydroxyalkanoate) resin: copolymer (A) only), in which the average molar content of the 3-hydroxybutyrate unit was the same in the core portion and the sheath portion, and Comparative Example 2 (poly(3-hydroxyalkanoate) resin: copolymer (A) only), in which the fiber did not have a core-sheath structure.
[0169] Further, the fusion rates in Examples 1 to 6, which fall within the scope of the present invention, were lower than the fusion rate in Comparative Example 3 (poly(3-hydroxyalkanoate) resin: copolymer (A) and copolymer (B)), in which the fiber did not have a core-sheath structure.
[0170] Therefore, it is understood that the present invention makes it possible to provide a poly(3-hydroxyalkanoate) resin-containing fiber in which the poly(3-hydroxyalkanoate) resin includes a 3-hydroxybutyrate unit, the fiber being suppressed from fusing during production of the fiber and being thermally fusible at low temperatures during thermal processing of the fiber.
Reference Signs List
1. A fiber comprising a core-sheath structure including a core portion and a sheath portion,
wherein:
each of the core portion and the sheath portion contains a poly(3-hydroxyalkanoate) resin including a 3-hydroxybutyrate unit; and
an average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the core portion is greater than an average molar content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin of the sheath portion.
2. The fiber according to claim 1, comprising:
a copolymer (A) in which a molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of another hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 99/1 to 93/7; and
a copolymer (B) in which a molar ratio of monomers of the 3-hydroxybutyrate unit to monomers of another hydroxyalkanoate unit is such that the 3-hydroxybutyrate unit/the other hydroxyalkanoate unit = from 92/8 to 76/24.
3. The fiber according to claim 2, wherein
a content of the copolymer (B) in the fiber is from 5 to 40% by weight per 100% by weight of the poly(3-hydroxyalkanoate) resin.
a content of the copolymer (B) in the fiber is from 5 to 40% by weight per 100% by weight of the poly(3-hydroxyalkanoate) resin.
4. The fiber according to claim 2 or 3, wherein
the sheath portion includes the copolymer (B).
the sheath portion includes the copolymer (B).
5. The fiber according to claim 4, wherein
the sheath portion includes the copolymer (A) and the copolymer (B).
the sheath portion includes the copolymer (A) and the copolymer (B).
6. The fiber according to any one of claims 1 to 3, wherein
in a cross section of the fiber, an area ratio of the core portion to the sheath portion is such that the core portion/the sheath portion = from 8/2 to 2/8.
in a cross section of the fiber, an area ratio of the core portion to the sheath portion is such that the core portion/the sheath portion = from 8/2 to 2/8.
7. The fiber according to any one of claims 1 to 3, wherein
the poly(3-hydroxyalkanoate) resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).
the poly(3-hydroxyalkanoate) resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).
8. The fiber according to any one of claims 1 to 3, wherein
a single filament fineness of the fiber is from 1 to 15 dtex.
a single filament fineness of the fiber is from 1 to 15 dtex.
9. A method for producing a fiber, the method comprising melt-spinning a raw material
composition for the core portion and a raw material composition for the sheath portion
by using a core-sheath composite spinning nozzle to obtain the fiber according to
any one of claims 1 to 3.
10. A nonwoven fabric comprising the fiber according to any one of claims 1 to 3.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description