Fiber and fiber structure

Abstract

To provide a poly(3-hydroxyalkanoate)-based resin-containing fiber capable of yielding a fiber structure that is hard to tear.SOLUTION: The present invention provides a fiber comprising a resin composition, the resin composition comprising a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin, wherein the content of the polylactic acid-based resin is 40-70 pts.wt. per 100 pts.wt. in total of the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin, and the weight average molecular weight of the polylactic acid-based resin is 20,000-120,000.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to fibers and fiber structures. [Background technology]

[0002] In recent years, with the increasing use of fiber structures (nonwoven fabrics, woven fabrics, knitted fabrics, etc.) such as disposable masks, environmental pollution caused by the outflow of microfibers into the ocean has become apparent. Therefore, nonwoven fabrics using plant-derived polylactic acid resins (abbreviated as PLA resins) have been proposed (for example, Patent Documents 1 and 2). Furthermore, poly(3-hydroxyalkanoate) resins (abbreviated as P3HA resins) are attracting attention due to their advantages such as home compostability and excellent marine biodegradability, and meltblown nonwoven fabrics using P3HA resins have also been proposed (e.g., Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5356960 [Patent Document 2] Patent No. 5486331 [Patent Document 3] International Publication No. 2023 / 106230 Summary of the Invention [Problem to be solved by the invention]

[0004] However, fiber structures using fibers containing poly(3-hydroxyalkanoate)-based resin or polylactic acid-based resin have the problem of being easily torn.

[0005] Therefore, an object of the present invention is to provide a poly(3-hydroxyalkanoate) resin-containing fiber that can provide a tear-resistant fiber structure, and a fiber structure containing the fiber. [Means for solving the problem]

[0006] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they discovered that by constructing a fiber structure using fibers containing a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin in a predetermined ratio and in which the weight-average molecular weight of the polylactic acid-based resin is within a predetermined range, the fiber structure becomes less likely to break, and they have completed the present invention.

[0007] That is, the present invention provides a fiber containing a resin composition, The resin composition contains a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin, and contains 40 to 70 parts by weight of the polylactic acid-based resin per 100 parts by weight of the total of the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin; The polylactic acid resin has a weight average molecular weight of 20,000 to 120,000. The present invention also relates to a fiber structure comprising the fiber. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a poly(3-hydroxyalkanoate) resin-containing fiber that can provide a tear-resistant fiber structure, and a fiber structure containing the fiber. [Brief explanation of the drawings]

[0009] [Figure 1] Schematic diagram of a fiber manufacturing device. [Figure 2] FIG. [Figure 3] FIG. 4 is a schematic cross-sectional view of a nozzle hole and a conveyor belt. [Figure 4] SEM image of the fiber structure of Example 2. [Figure 5] SEM image of the fiber structure of Comparative Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below.

[0011] <Fiber> The fiber according to this embodiment contains a resin composition. The resin composition contains a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin, and contains 40 to 70 parts by weight of the polylactic acid-based resin per 100 parts by weight of the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin combined. The weight average molecular weight of the polylactic acid resin is 20,000 to 120,000.

[0012] (Poly(3-hydroxyalkanoate) resin) The poly(3-hydroxyalkanoate) resin is a polyester containing 3-hydroxyalkanoic acid as a monomer. That is, the poly(3-hydroxyalkanoate) resin is a resin containing 3-hydroxyalkanoic acid as a constituent unit. The poly(3-hydroxyalkanoate) resin can be produced from a microorganism. The poly(3-hydroxyalkanoate) resin is a biodegradable polymer. In this embodiment, "biodegradability" refers to the property of being decomposed into low molecular weight compounds by microorganisms in nature. Specifically, the presence or absence of biodegradability can be determined based on tests suitable for each environment, such as ISO 14855 (compost) and ISO 14851 (activated sludge) under aerobic conditions, and ISO 14853 (aqueous phase) and ISO 15985 (solid phase) under anaerobic conditions. Furthermore, the decomposition ability of microorganisms in seawater can be evaluated by measuring biochemical oxygen demand.

[0013] The poly(3-hydroxyalkanoate) resin preferably contains a poly(3-hydroxybutyrate) resin (abbreviated as P3HB resin), and more preferably is a P3HB resin.

[0014] The P3HB resin is a resin containing a 3-hydroxybutyrate unit as a constituent unit. The P3HB-based resin is a concept that includes poly(3-hydroxybutyrate) (abbreviated as P3HB), which is a homopolymer, and copolymers having 3-hydroxybutyrate units. Examples of the copolymerization type of the copolymer include random copolymerization, alternating copolymerization, and graft copolymerization.

[0015] In the copolymer having a 3-hydroxybutyrate unit, examples of the monomer unit other than the 3-hydroxybutyrate unit include a hydroxyalkanoate unit other than the 3-hydroxybutyrate unit. Examples of hydroxyalkanoate units other than 3-hydroxybutyrate units include 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxyoctadecanoate, 3-hydroxyvalerate (also referred to as "3-hydroxyvalerate"), and 4-hydroxybutyrate.

[0016] Examples of the P3HB-based resins include poly(3-hydroxybutyrate) (abbreviation: P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), and poly(3-hydroxybutyrate-co- Examples of such copolymers include poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (abbreviation: P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviation: P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviation: P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HV3HH). Among these, P3HB, P3HB3HH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially. Also, P3HB3HH and / or P3HB4HB are more preferred, with P3HB3HH being particularly preferred.

[0017] The P3HB resin is preferably at least one selected from the group consisting of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate).

[0018] Examples of poly(3-hydroxyalkanoate) resins other than the P3HB resin include poly(3-hydroxyvalerate) and poly(3-hydroxyhexanoate).

[0019] The content of the 3-hydroxybutyrate unit (3HB) in the poly(3-hydroxyalkanoate) resin is preferably 40 mol% or more and 98 mol% or less, more preferably 60 mol% or more and 97 mol% or less, even more preferably 70 mol% or more and 96 mol% or less, and particularly preferably 80 mol% or more and 96 mol% or less. When the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin is 40 mol % or more, the rigidity of the fiber is increased. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin is 98 mol % or less, the fiber structure is less likely to break. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin is 92 mol % or less, the fiber structure is less likely to fluff and is even more unlikely to break. The content ratio of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin means the content ratio of the 3-hydroxybutyrate unit in the entire poly(3-hydroxyalkanoate) resin contained in the fiber.

[0020] The content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin can be determined by the method described in the examples below.

[0021] The weight average molecular weight of the poly(3-hydroxyalkanoate) resin is preferably 50,000 to 350,000, more preferably 100,000 to 350,000, and even more preferably 150,000 to 300,000. When the weight average molecular weight is 50,000 or more, the strength and elongation of the fiber are increased. By making the weight-average molecular weight 350,000 or less, the tension applied to the fibrous melt during stretching can be reduced, making it easier to thin the resulting fibers, which in turn makes it easier to increase the particle collection efficiency of the fiber structure.

[0022] In this embodiment, the weight-average molecular weight (Mw) is measured from the polystyrene equivalent molecular weight distribution by gel permeation chromatography (GPC) using chloroform as an eluent. As the column for the GPC, a column appropriate for measuring the molecular weight may be used. For example, the weight-average molecular weight (Mw) can be determined by setting the column temperature to 40°C, injecting 10 μl of 3 mg of the target substance dissolved in 2 ml of chloroform (HPLC grade), and setting the flow rate of the chloroform eluent (mobile phase) to 1.0 ml / min. The GPC system used is a Shimadzu 20A manufactured by Shimadzu Corporation, the column is a GPCK-806M (manufactured by Showa Denko), and the detector is an RI detector.

[0023] In addition, when fibers are produced by thermally melting a poly(3-hydroxyalkanoate) resin using a melt spinning method or the like, the weight average molecular weight of the poly(3-hydroxyalkanoate) resin means the weight average molecular weight of the poly(3-hydroxyalkanoate) resin before thermal melting.

[0024] (Polylactic acid resin) The polylactic acid resin is a polyester containing lactic acid as a constituent monomer.

[0025] The polylactic acid resin is preferably a homopolymer of lactic acid, but may contain other monomers in addition to lactic acid.

[0026] The lactic acid constituting the polylactic acid resin may be either the L-form or the D-form, or may contain both. In the latter case, the proportion of the D-form in the polylactic acid resin is preferably 1.0% to 99.0%, more preferably 1.5% to 98.5%, even more preferably 2.0% to 98.0%, and particularly preferably 3.0% to 97.0%. By ensuring that the proportion of D-isomer in the polylactic acid resin is 1.0% or more and 99.0% or less, the melting point of the polylactic acid resin can be lowered, and the poly(3-hydroxyalkanoate) resin can be processed at a temperature at which it is less likely to decompose. Furthermore, when the proportion of D-isomer in the polylactic acid resin is 1.0% or more, biodegradability can be improved. The polylactic acid resin may be any of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin, or may be a blend of these.

[0027] Examples of the other monomers that may be contained in the polylactic acid resin include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, and polyfunctional polysaccharides.

[0028] The polylactic acid resin may be either a crystalline polylactic acid resin or an amorphous polylactic acid resin. From the viewpoint of heat resistance, such as shrinkage upon heating, it is preferable to use a crystalline polylactic acid resin. On the other hand, from the viewpoint of enhancing biodegradability and imparting heat-weldability, it is preferable to use an amorphous polylactic acid resin.

[0029] The lactic acid raw material for producing polylactic acid resins is not particularly limited, and examples thereof include L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, or L-lactide, D-lactide, meso-lactide, or a mixture thereof. Lactic acid obtained by microbial fermentation from renewable plant-derived raw materials such as starch can be suitably used. The method for producing the polylactic acid resin is not particularly limited, and known methods such as dehydration condensation polymerization and ring-opening polymerization can be used.

[0030] The weight average molecular weight of the polylactic acid resin is 20,000 to 120,000, preferably 30,000 to 110,000, and more preferably 40,000 to 100,000. When the weight average molecular weight is 20,000 or more, the strength and elongation of the fiber are increased. By having a weight average molecular weight of 120,000 or less, one of the polylactic acid-based resin and the poly(3-hydroxyalkanoate)-based resin is more finely dispersed and mixed with the other in the fiber, making the fiber structure even more resistant to tearing. The weight average molecular weight can be measured by the method described above.

[0031] The melting point of the polylactic acid resin is preferably 100 to 185°C, more preferably 120 to 175°C, and even more preferably 140 to 165°C. The melting point of the polylactic acid resin is 100° C. or higher, which improves the heat resistance of the fiber. When the melting point of the polylactic acid resin is 185° C. or less, it can be spun at a low temperature, making it easy to produce fibers.

[0032] The melting point refers to the peak-top temperature Tm of the crystalline melting peak in a DSC curve obtained by differential scanning calorimetry (DSC measurement). The DSC curve was obtained by precisely weighing out approximately 5 mg of the measurement object and heating it from 0°C to 200°C at a heating rate of 10°C / min using a differential scanning calorimeter. When multiple crystalline melting peaks appear, the peak-top temperature Tm of the crystalline melting peak located at the highest temperature is taken as the peak-top temperature of the crystalline melting peak of the polylactic acid resin.

[0033] The melt flow rate of the polylactic acid resin at 190°C under a load of 2.16 kg (hereinafter also referred to as "MFR (190°C, 2.16 kg)") is 40 to 1500 g / 10 min, preferably 50 to 1300 g / 10 min, more preferably 60 to 1200 g / 10 min, still more preferably 80 to 1000 g / 10 min, and particularly preferably 100 to 800 g / 10 min. When the MFR (190°C, 2.16 kg) of the polylactic acid-based resin is 40 g / 10 min or more, one of the polylactic acid-based resin and the poly(3-hydroxyalkanoate)-based resin is more finely dispersed and mixed with the other in the fiber, making the fiber structure even more resistant to tearing. When the MFR (190° C., 2.16 kg) of the polylactic acid resin is 1500 g / 10 min or less, the strength and elongation of the fiber are increased.

[0034] In this embodiment, the melt mass-flow rate (MFR) at 190°C and a load of 2.16 kg is determined by calculating the melt volume-flow rate (MVR) of the object using Method B of ASTM-D1238 (ISO1133-1, JIS K7210-1:2011), and then calculating the melt mass-flow rate (MFR) of the object from the melt volume-flow rate (MVR) and density of the object. As a measuring device, a melt flow rate tester (G-02, manufactured by Toyo Seiki Seisakusho) can be used. The melt volume flow rate (MVR) of an object is measured by heating 3 to 8 g of the object at a heating temperature of 190°C for 4 minutes, and then applying a load of 2.16 kg to the heated object.

[0035] The melt flow rate of the polylactic acid resin at 210°C and a load of 2.16 kg (hereinafter also referred to as "MFR (210°C, 2.16 kg)") is preferably more than 80 g / 10 min and not more than 2000 g / 10 min, more preferably 90 to 1500 g / 10 min, even more preferably 100 to 1200 g / 10 min, and particularly preferably 150 to 1000 g / 10 min. When the MFR (210°C, 2.16 kg) of the polylactic acid-based resin exceeds 80 g / 10 min, either the polylactic acid-based resin or the poly(3-hydroxyalkanoate)-based resin is more finely dispersed and mixed with the other in the fiber, making the fiber structure more resistant to tearing. When the MFR (210° C., 2.16 kg) of the polylactic acid resin is 2000 g / 10 min or less, the strength and elongation of the fiber are increased. The MFR (210°C, 2.16 kg) can be measured by changing the heating temperature from 190°C to 210°C in the above-mentioned method for measuring the MFR (190°C, 2.16 kg).

[0036] In addition, the weight average molecular weight, melting point, MFR (190°C, 2.16 kg), and MFR (210°C, 2.16 kg) of the polylactic acid resin refer to the weight average molecular weight and melting point of the polylactic acid resin before thermal melting when fibers are produced by thermally melting the polylactic acid resin using a melt spinning method or the like. The weight average molecular weight, melting point, MFR (190°C, 2.16 kg), and MFR (210°C, 2.16 kg) of the polylactic acid resin can be adjusted by hydrolyzing the polylactic acid resin, for example.

[0037] From the viewpoint of making the fiber structure less likely to break, the resin composition contains 40 to 70 parts by weight of the polylactic acid-based resin per 100 parts by weight of the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin in total, preferably 50 to 70 parts by weight, and more preferably 55 to 65 parts by weight. The reason why the fiber structure is less likely to break when the resin composition has this configuration is thought to be that the polylactic acid-based resin is more likely to form a continuous phase within the fiber, and the poly(3-hydroxyalkanoate)-based resin phase and the polylactic acid-based resin phase form a finely intertwined phase separation structure within the fiber, which increases the interfacial layer area and allows the fiber to sufficiently absorb energy when stress is applied.

[0038] The resin composition is a resin composition mainly composed of a poly(3-hydroxyalkanoate) resin and a polylactic acid resin. The total proportion of the poly(3-hydroxyalkanoate) resin and the polylactic acid resin in the total amount of the resin composition may be 50 to 100% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. It may be 95% by weight or more, 98% by weight or more, or even 100% by weight.

[0039] (other resins) The resin composition may contain other resins in addition to the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin, provided that the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester-based resins such as polybutylene succinate adipate, polybutylene succinate, and polycaprolactone, and aliphatic aromatic polyester-based resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0040] The content of the other resin is not particularly limited, but is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, and even more preferably 30 parts by weight or less, relative to 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin and the polylactic acid resin. It may be 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less. The lower limit of the content of the other resin is not particularly limited, and may be 0 parts by weight or more.

[0041] The resin composition may contain an additive that can be used together with the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin, as long as it does not impair the effects of the invention.

[0042] Examples of additives include nucleating agents, lubricants, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, inorganic fillers, organic fillers, antistatic agents, etc.

[0043] The resin composition may contain a crystal nucleating agent. The nucleating agent is a compound that can promote the crystallization of the poly(3-hydroxyalkanoate) resin, and has a melting point higher than that of the poly(3-hydroxyalkanoate) resin. The resin composition contains a crystal nucleating agent, which promotes crystallization of the poly(3-hydroxyalkanoate) resin during fiber production, making it difficult for adjacent fibers to fuse together, making it easier to obtain a fiber structure with a homogeneous structure. Examples of the crystal nucleating agent include sugar alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, boron nitride, etc. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, because they are particularly effective in promoting the crystallization of poly(3-hydroxyalkanoate). The poly(3-hydroxyalkanoate) resin P3HB can also be used as a crystal nucleating agent. These may be used alone or in combination of two or more.

[0044] When a nucleating agent is used, its amount is not particularly limited, but is preferably 0.1 to 2.5 parts by weight, more preferably 0.3 to 2.0 parts by weight, and even more preferably 0.5 to 2.0 parts by weight, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin and the polylactic acid resin combined. The inclusion of 0.1 parts by weight or more of a nucleating agent per 100 parts by weight of the poly(3-hydroxyalkanoate) resin and polylactic acid resin combined has the advantage of further promoting the crystallization of the poly(3-hydroxyalkanoate) resin when producing fibers. When the content of the crystal nucleating agent is 2.5 parts by weight or less per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin and the polylactic acid resin, there is an advantage in that fibers can be easily obtained.

[0045] The weight average molecular weight of the resin composition is preferably 40,000 to 350,000, more preferably 50,000 to 350,000, still more preferably 70,000 to 300,000, and particularly preferably 80,000 to 250,000. The weight average molecular weight can be measured by the method described above.

[0046] When the weight average molecular weight of the resin composition is 40,000 to 350,000, the fiber according to this embodiment can be easily produced. When the weight average molecular weight of the resin composition is 40,000 or more, the strength and elongation of the fiber are increased. When the weight-average molecular weight of the resin composition is 350,000 or less, the tension applied to the fibrous melt during stretching can be reduced, making it easier to thin the resulting fibers, and as a result, it is easier to improve the particle collection efficiency of the fiber structure.

[0047] The MFR (190°C, 2.16 kg) of the resin composition is preferably 20 to 1500 g / 10 min, more preferably 30 to 1400 g / 10 min, still more preferably 50 to 1300 g / 10 min, and particularly preferably 100 to 1200 g / 10 min. The MFR (190°C, 2.16 kg) can be measured by the method described above.

[0048] When the resin composition has an MFR (190° C., 2.16 kg) of 20 to 1500 g / 10 min, the fiber according to this embodiment can be easily produced. When the MFR (190°C, 2.16 kg) of the resin composition is 1500 g / 10 min or less, the strength and elongation of the fiber are increased. When the resin composition has an MFR (190°C, 2.16 kg) of 20 g / 10 min or more, the tension applied to the fibrous melt during stretching can be reduced, making it easier to thin the resulting fibers, which in turn makes it easier to improve the particle collection efficiency of the fiber structure.

[0049] The proportion of the resin composition in the fibers may be 50 to 100% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, and may be 95% by weight or more, 98% by weight or more, or even 100% by weight.

[0050] The fibers are primarily composed of poly(3-hydroxyalkanoate) resin and polylactic acid resin. The total proportion of poly(3-hydroxyalkanoate) resin and polylactic acid resin in the total amount of fibers may be 50 to 100% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. It may be 95% by weight or more, 98% by weight or more, or even 100% by weight.

[0051] The upper limit of the average fiber diameter of the fibers is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, still more preferably 20 μm or less, particularly preferably 8 μm or less, and especially preferably 5 μm or less. The lower limit of the average fiber diameter of the fibers is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. The coefficient of variation of the fiber diameter of the fibers is preferably 0.30 or less, more preferably 0.27 or less, even more preferably 0.25 or less, and particularly preferably 0.20 or less. The coefficient of variation of the fiber diameter of the fibers is, for example, 0.05 or more.

[0052] By making the average fiber diameter of the fibers 100 μm or less, the rigidity of the fibers can be reduced. As a result, when the fibers are made into a fiber structure, the texture (e.g., feel to the skin, touch, etc.) is improved. In addition, when the fibers are made into a fiber structure, the particle collection efficiency is increased. When the average fiber diameter of the fibers is 0.5 μm or more, the strength and elongation of the fibers and the fiber structure are increased, and productivity is also increased. When the fiber diameter is within the above range (0.5 μm or more and 100 μm or less), the effect as a mask or various filters for beverages can be sufficiently obtained. When the coefficient of variation of the fiber diameter of the fibers is 0.30 or less, the fiber diameter of the fibers when made into a fiber structure is uniform with little variation, and the particle collection efficiency of the fiber structure is further improved. By setting the weight-average molecular weight of the polylactic acid resin to 120,000 or less, the polylactic acid resin and the poly(3-hydroxyalkanoate) resin are more finely dispersed and mixed with each other in the fiber, which results in less discharge unevenness and pressure fluctuations near the nozzle during spinning, and makes it easier to achieve a coefficient of variation of the fiber diameter of 0.30 or less.

[0053] The average value and coefficient of variation of the fiber diameter of the fibers can be determined as follows. When the fiber is a monofilament, the diameter (width) is measured at 20 or more randomly selected locations at intervals of 10 cm or more along the fiber axis. The diameter (width) can be measured using, for example, a scanning electron microscope. Next, the average value (arithmetic mean value) and coefficient of variation (=standard deviation / arithmetic mean value) are calculated from the arithmetic mean value and standard deviation of all the measured diameters (widths). When the fiber is a multifilament, the diameter (width) of 100 or more randomly selected single fibers is measured. The diameter (width) can be measured using, for example, a scanning electron microscope. Next, the average value (arithmetic mean value) and coefficient of variation (=standard deviation / arithmetic mean value) are calculated from the arithmetic mean value and standard deviation of all the measured diameters (widths). In the present embodiment, the "fiber diameter of the fiber" means the "fiber diameter of a single fiber of the fiber."

[0054] <Fiber structure> The fiber structure according to this embodiment contains the fibers. The fiber structure according to this embodiment is preferably in the form of a sheet. Examples of the fiber structure include fabrics (nonwoven fabrics, woven fabrics, knitted fabrics, etc.). Examples of the nonwoven fabric include chemically bonded nonwoven fabric, thermally bonded nonwoven fabric, needle-punched nonwoven fabric, water-punched nonwoven fabric, stitch-bonded nonwoven fabric, air-laid nonwoven fabric, spunlace nonwoven fabric, spunbonded nonwoven fabric, melt-blown nonwoven fabric, flash-spun nonwoven fabric, electrospun nonwoven fabric, and papermaking nonwoven fabric. The nonwoven fabric is preferably a direct-spun nonwoven fabric. The directly spun nonwoven fabric means "a nonwoven fabric obtained by entangling raw yarns obtained by melt spinning to form a sheet directly, and then solidifying the raw yarns." Note that "entangling raw yarns to form a sheet directly" means "entangling raw yarns to form a sheet before solidifying the raw yarns." Examples of the direct spun nonwoven fabric include meltblown nonwoven fabric, spunbond nonwoven fabric, flash spun nonwoven fabric, and electrospun nonwoven fabric. The meltblown nonwoven fabric is a concept that also includes nonwoven fabrics obtained by the Spunblown (registered trademark) method. The fiber structure according to this embodiment is more preferably a meltblown nonwoven fabric or a spunbonded nonwoven fabric, and even more preferably a meltblown nonwoven fabric.

[0055] The basis weight of the fiber structure according to this embodiment is preferably 10 to 150 g / m 2 , more preferably 15 to 100 g / m 2 , and more preferably 20 to 80 g / m 2 , and particularly preferably 20 to 60 g / m 2 is. The fiber structure according to this embodiment has a basis weight of 10 g / m 2 As a result, the strength and elongation are increased, and the efficiency of capturing particles (for example, blood cells, pollen, coffee powder, tea leaves, particles with viruses attached, etc.) is improved. The fiber structure according to this embodiment has a basis weight of 150 g / m 2 When the thickness is equal to or less than 100 μm, the liquid permeability (water permeability, etc.) or air permeability is high.

[0056] The basis weight of the fiber structure according to this embodiment can be determined as follows. First, a test piece is obtained from the fiber structure according to this embodiment. The size of the test piece can be, for example, 100 mm x 100 mm, 200 mm x 200 mm, etc. Next, the weight of the test piece is measured using an electronic balance or the like. The weight of the test piece is then divided by the area of ​​the test piece to calculate the basis weight.

[0057] The thickness of the fiber structure according to this embodiment is preferably 0.05 to 0.80 mm, more preferably 0.08 to 0.60 mm, still more preferably 0.10 to 0.50 mm, and particularly preferably 0.10 to 0.40 mm. When the thickness of the fiber structure according to this embodiment is 0.05 to 0.80 mm, a uniform fiber structure can be easily obtained when the fiber structure is produced. Furthermore, when the thickness of the fiber structure according to this embodiment is 0.05 mm or more, the strength and elongation of the fiber structure are increased, and the particle collection efficiency of the fiber structure is further improved. Furthermore, when the thickness of the fiber structure according to this embodiment is 0.80 mm or less, the liquid permeability (water permeability, etc.) or breathability of the fiber structure can be improved.

[0058] The thickness of the fiber structure according to this embodiment can be determined by measuring the thickness of the fiber structure at three or more locations with a thickness meter and averaging the measured values. An example of a thickness gauge is "PEACOCK" manufactured by Ozaki Seisakusho Co., Ltd.

[0059] The average fiber diameter of the fibers in the fiber structure is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, still more preferably 20 μm or less, particularly preferably 8 μm or less, and especially preferably 5 μm or less. The average fiber diameter of the fibers in the fiber structure is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and even more preferably 1.5 μm or more. The coefficient of variation of the fiber diameter of the fibers in the fiber structure is preferably 0.30 or less, more preferably 0.27 or less, even more preferably 0.25 or less, and particularly preferably 0.20 or less. The coefficient of variation of the fiber diameter of the fibers in the fiber structure is, for example, 0.05 or more.

[0060] When the average fiber diameter of the fibers in the fiber structure is 100 μm or less, the rigidity of the fibers can be reduced, the texture (e.g., feel to the skin, touch, etc.) of the fiber structure is improved, and the particle collection efficiency is increased. When the average fiber diameter of the fibers in the fiber structure is 0.5 μm or more, the strength and elongation of the fiber structure are increased. When the coefficient of variation of the fiber diameter of the fibers in the fiber structure is 0.30 or less, the fiber structure has little variation in fiber diameter and is a homogeneous fiber structure, and the particle collection efficiency of the fiber structure is further improved. By setting the weight-average molecular weight of the polylactic acid resin to 120,000 or less, the polylactic acid resin and the poly(3-hydroxyalkanoate) resin are more finely dispersed and mixed with each other in the fiber, which results in less discharge unevenness and pressure fluctuations near the nozzle during spinning, and makes it easier to achieve a coefficient of variation of the fiber diameter of 0.30 or less.

[0061] The average value and coefficient of variation of the fiber diameter of the fibers in the fiber structure can be determined as follows. First, a test specimen is obtained from the fiber structure. Next, photographs (1700x magnification) of five or more locations on the surface of the test piece are taken using a scanning electron microscope. Then, measure the diameter (width) of 20 or more randomly selected fibers per photograph. Next, the arithmetic mean value and coefficient of variation (=standard deviation / arithmetic mean value) are calculated from the diameter (width) values ​​of all the measured fibers.

[0062] The proportion of the fibers in the total amount of the fiber structure may be 50 to 100% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, and may be 95% by weight or more, 98% by weight or more, or even 100% by weight.

[0063] The fiber structure according to this embodiment can be suitably used as a substrate for various products (e.g., masks, filters, disposable diapers, sanitary napkins, taping materials, patches, bandages, gloves, clothing, etc.). The term "substrate" includes reinforcing materials. Examples of the filter include removal filters (e.g., mask filters) that remove particles (e.g., particles with viruses or the like attached, pollen, etc.), blood filters that capture blood cells, and filters for beverage extraction (e.g., coffee drip filters, tea bags, etc.).

[0064] <Method for producing fiber and method for producing fiber structure> The fiber manufacturing method according to this embodiment can manufacture the fiber. The method for producing fibers according to this embodiment is a method for producing fibers by melt spinning. In addition, the fiber manufacturing method according to this embodiment includes a step (A) of melting a raw material composition containing a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin, and a step (B) of obtaining fibers from the melt.

[0065] In the method for producing a fiber structure according to this embodiment, a fiber structure containing the fibers is produced by the fiber production method. Examples of the melt spinning method include a melt blown method, a spunbond method, a flash spinning method, and an electrospinning method. The melt spinning method is preferably a melt blown method or a spunbond method.

[0066] In the following, a method for producing fibers according to this embodiment and a method for producing a fiber structure according to this embodiment will be described, taking as a specific example a method for obtaining fibers and a fiber structure by a meltblown method. The meltblown method is a concept that also includes the spunblown (registered trademark) method.

[0067] In the fiber production method and fiber structure production method according to this embodiment, a fiber production apparatus is used to obtain a fiber structure from the raw material composition.

[0068] As shown in FIG. 1 , the fiber production apparatus 1 includes an extruder 3 that melts a raw material composition to obtain a molten material, a hopper 2 that supplies the raw material composition to the extruder 3, a kneader 6 that kneads the molten material, a nozzle 7 that discharges the kneaded molten material in a fibrous form, a collector 8 that collects and cools the fibrous molten material to obtain a fibrous structure B, and a winding device 9 that winds up the fibrous structure B.

[0069] Furthermore, the fiber production apparatus 1 may include a gear pump 4 that supplies the melt to a kneader 6, if necessary. The fiber production apparatus 1 is provided with the gear pump 4, so that the amount of the melt supplied to the kneader 6 can be prevented from fluctuating.

[0070] Furthermore, the fiber production apparatus 1 may be provided with a filter 5 for removing foreign matter from the melt on the upstream side of the kneader 6, if necessary.

[0071] In the step (A), the raw material composition is fed to an extruder 3 via a hopper 2, and the raw material composition is melted to obtain a melt.

[0072] The raw material composition supplied to the extruder 3 is preferably in a solid state, more preferably in a pellet state.

[0073] Examples of the extruder 3 include a single-screw extruder, a co-rotating intermeshing twin-screw extruder, a co-rotating non-intermeshing twin-screw extruder, a counter-rotating non-intermeshing twin-screw extruder, and a multi-screw extruder.

[0074] In the step (A), the melt is supplied to a kneader 6 via a filter 5 by a gear pump 4, and the melt is kneaded in the kneader 6.

[0075] In the step (B), the melt is discharged from the nozzle 7 in the form of fibers.

[0076] 2, the nozzle 7 has a plurality of nozzle holes 7a that discharge the molten material in a fibrous form. As shown in FIG. 2, the nozzle 7 discharges a plurality of fibrous molten material A (also referred to as "raw yarn A"). The nozzle 7 may have only one nozzle hole 7a (the "nozzle hole" may also be simply referred to as "hole"). In other words, the nozzle 7 may discharge only one yarn A.

[0077] The opening diameter of the nozzle hole 7a is appropriately selected depending on the fiber diameter of the fibers of the fiber structure. The opening diameter of the nozzle hole 7a is preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.15 mm or more. The opening diameter is preferably 1.0 mm or less, more preferably 0.5 mm or less, even more preferably 0.4 mm or less, and particularly preferably 0.3 mm or less. The opening diameter (also referred to as "pore diameter") means the arithmetic mean value of the opening diameter.

[0078] The nozzle 7 has a plurality of nozzle holes 7a arranged in a row at intervals. In FIG. 2, a plurality of nozzle holes 7a are arranged in a row. The number of rows of the nozzle holes 7a may be two or more. In other words, the meltblown method may be a spunblown (registered trademark) method. The distance between adjacent nozzle holes 7a (hereinafter also referred to as "spacing" or "hole spacing") is, for example, preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.25 mm or more. By setting the distance (spacing) between adjacent nozzle holes 7a to 0.05 mm or more, it is possible to prevent adjacent fibers from fusing together, and as a result, it is possible to reduce the coefficient of variation of the fiber diameter of the fibers. The distance (interval) between adjacent nozzle holes 7a is, for example, preferably 3.0 mm or less, more preferably 2.0 mm or less, and even more preferably 1.0 mm or less. The distance between adjacent nozzle holes 7a may or may not be uniform, but it is preferable that the distances are uniform in order to facilitate the production of a homogeneous fiber structure. The distance (interval) between adjacent nozzle holes 7a means the arithmetic mean value of the distance (interval) between adjacent nozzle holes 7a.

[0079] The collector 8 has a collecting surface for collecting the fibrous melt A. The collector 8 is a conveyor. The conveyor includes a conveyor belt 8a having the collecting surface, and a plurality of rollers 8b that drive the conveyor belt 8a. The collection surface is disposed directly below the nozzle hole 7a. The conveyor belt 8a is breathable. Specifically, the conveyor belt 8a is made of a mesh material. That is, the collection surface is mesh-like.

[0080] The distance between the nozzle hole 7a and the collection surface (hereinafter also referred to as "DCD") is preferably 20 mm or more, more preferably 50 mm or more, and even more preferably 80 mm or more. The distance (DCD) between the nozzle holes 7a and the conveyor belt 8a serving as the collecting section is preferably 300 mm or less, and more preferably 250 mm or less. The distance (DCD) between the nozzle hole 7a and the collection surface means the arithmetic mean value of the distance (DCD) between the nozzle hole 7a and the collection surface.

[0081] As shown in FIG. 3, the fiber production apparatus 1 is configured to stretch the fibrous melt A by blowing a high-temperature gas C onto the fibrous melt A.

[0082] In the step (B), a high-temperature gas C is blown onto the fibrous melt A, and the high-temperature gas C blown onto the melt A is passed through a mesh conveyor belt 8a. In the step (B), it is preferable to suck the high-temperature gas C by suction (not shown) so that the high-temperature gas C sprayed onto the molten material A can easily pass through the mesh conveyor belt 8a. This makes it easier to prevent the fibers from bouncing off the collection surface of the mesh conveyor belt 8a, and as a result, it becomes easier to form a fiber structure B in which the fibers are well fused together.

[0083] In the step (B), the drawn fibrous melt A is collected by the conveyor belt 8a and cooled while being conveyed by the conveyor belt 8a, thereby obtaining fibers. Also, a fiber structure containing the fibers is obtained.

[0084] The material constituting the mesh-like collection surface is not particularly limited as long as it has heat resistance to the temperature conditions involved in the production of the fiber structure B, does not excessively fuse with the fiber structure B, and is a material from which the fiber structure B can be peeled off.

[0085] Examples of the gas C include air and inert gases (nitrogen gas, etc.). As a method for blowing the high-temperature gas C, there is a method in which the gas C pressurized by a compressor (not shown) is heated by a heater (not shown), for example.

[0086] The flow rate of the high-temperature gas C blown onto the fibrous melt A is preferably 500 NL / min or more, more preferably 1000 NL / min or more, and even more preferably 2000 NL / min or more. The flow rate of the high-temperature gas C blown onto the fibrous melt A is preferably 12,000 NL / min or less, and more preferably 10,000 NL / min or less.

[0087] In the step (B), the temperature and flow rate of the high-temperature gas C are appropriately controlled in order to obtain a fiber structure with a high degree of crystallinity.

[0088] In the step (B), the fiber structure B is transferred to the winding device 9 by the conveyor belt 8a, and the fiber structure B is wound up in a roll by the winding device 9.

[0089] It should be noted that the present invention is not limited to the above-described embodiment. Furthermore, the present invention is not limited to the above-described effects. Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention.

[0090] The above describes the fiber manufacturing method according to this embodiment and the fiber structure according to this embodiment, using the meltblown method as an example to obtain the fibers and the fiber structure, but various modifications are possible within the scope of the present invention. For example, in the fiber manufacturing method according to this embodiment and the fiber structure manufacturing method according to this embodiment, the fiber and the fiber structure may be manufactured by a spunbonding method, a flash spinning method, or an electrospinning method. In the method for producing a fiber according to this embodiment and the method for producing a fiber structure according to this embodiment, the nonwoven fabric is preferably produced by a meltblown method or a spunbond method.

[0091] [Disclosure items] Each of the following sections is a disclosure of a preferred embodiment.

[0092] [Item 1] A fiber comprising a resin composition, The resin composition contains a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin, and contains 40 to 70 parts by weight of the polylactic acid-based resin per 100 parts by weight of the total of the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin; The polylactic acid resin has a weight average molecular weight of 20,000 to 120,000. [Item 2] Item 2. The fiber according to item 1, wherein the weight-average molecular weight of the poly(3-hydroxyalkanoate) resin is 50,000 to 350,000. [Item 3] 3. The fiber according to item 1 or 2, wherein the melting point of the polylactic acid resin is 100 to 185°C. [Item 4] 4. The fiber according to any one of items 1 to 3, wherein the poly(3-hydroxyalkanoate)-based resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). [Item 5] 5. The fiber according to any one of items 1 to 4, wherein the coefficient of variation of the fiber diameter is 0.30 or less. [Item 6] A fiber structure comprising the fiber according to any one of items 1 to 5. [Item 7] 7. The fibrous structure of item 6, which is a spunbond or meltblown nonwoven. [Example]

[0093] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0094] The following materials were prepared.

[0095] (Poly(3-hydroxyalkanoate) resin (P3HA resin)) A P3HA-based resin, P3HB3HH, was prepared according to the method described in Example 1 of WO 2019 / 142845 (melting point: 145°C, MFR (190°C, 2.16 kg): 65 g / 10 min, 3-hydroxybutyrate unit (3HB unit) content: 94.9 mol%, 3-hydroxyhexanoate unit (3HH unit) content: 5.1 mol%, weight-average molecular weight: 240,000).

[0096] <3HB unit content and 3HH unit content in poly(3-hydroxyalkanoate) resin> The content ratio of 3-hydroxybutyrate units (3HB units) and the content ratio of 3-hydroxyhexanoate units (3HH units) in the poly(3-hydroxyalkanoate) resin were measured by the following method. A sample prepared by adding 2 mL of a mixture of sulfuric acid and methanol (volume of sulfuric acid:volume of methanol = 15:85) and 2 mL of chloroform to 20 mg of poly(3-hydroxyalkanoate) resin was sealed, and the sample was heated in a sealed state at 100°C for 140 minutes to obtain a first reaction liquid containing methyl esters, which are decomposition products of the poly(3-hydroxyalkanoate) resin. Next, the first reaction liquid was cooled, and 1.5 g of sodium hydrogen carbonate was added little by little to the cooled first reaction liquid to neutralize it, and the mixture was left to stand until the evolution of carbon dioxide gas stopped, thereby obtaining a second reaction liquid. Furthermore, the second reaction solution was thoroughly mixed with 4 mL of diisopropyl ether to obtain a mixture, and the mixture was centrifuged to obtain a supernatant. The monomer unit composition of the degradation product in the supernatant was analyzed by capillary gas chromatography under the conditions below to calculate the content of 3-hydroxybutyrate units (3HB units) and 3-hydroxyhexanoate units (3HH units) in the poly(3-hydroxyalkanoate) resin. Gas chromatograph: Shimadzu GC-17A Capillary column: NEUTRA BOND-1 manufactured by GL Sciences (column length: 25 m, column inner diameter: 0.25 mm, liquid film thickness: 0.4 μm) Carrier gas: He Column inlet pressure: 100 kPa Sample volume: 1 μL As for the temperature conditions, the temperature was increased at a rate of 8°C / min from 100 to 200°C, and further increased at a rate of 30°C / min from 200 to 290°C.

[0097] The melting point, MFR (190° C., 2.16 kg), and weight average molecular weight of the poly(3-hydroxyalkanoate) resin were measured by the methods described above.

[0098] (Polylactic acid resin (PLA resin)) Using a highly accelerated life tester (ESPEC, EHS-222MD), a PLA-based resin (LX-175, Total Energies Corbion) was hydrolyzed for 3.5 hours under high temperature and humidity conditions (temperature: 105°C, humidity: 100%), and then dried overnight at 80°C to produce a PLA-based resin, PLA-1 (melting point: 152°C, MFR (190°C, 2.16 kg): 317 g / 10 min, MFR (210°C, 2.16 kg): 515 g / 10 min, weight-average molecular weight: 74,000). Using a highly accelerated life tester (ESPEC, EHS-222MD), a PLA-based resin (LX-175, Total Energies Corbion) was hydrolyzed for 1.5 hours under high temperature and humidity conditions (temperature: 105°C, humidity: 100%), followed by drying overnight at 80°C to produce a PLA-based resin, PLA-2 (melting point: 152°C, MFR (190°C, 2.16 kg): 38 g / 10 min, MFR (210°C, 2.16 kg): 85 g / 10 min, weight-average molecular weight: 128,000).

[0099] The melting point, MFR (190°C, 2.16 kg), MFR (210°C, 2.16 kg) and weight average molecular weight of the polylactic acid resin were measured by the methods described above.

[0100] (nucleating agent) PETL: Pentaerythritol (Taisei Kayaku Co., Ltd., Neuralyzer P)

[0101] (Examples 1 to 4, Comparative Examples 1 to 4) The above materials were fed to a twin-screw extruder in the formulation shown in Table 1 below, and melt-kneaded at a set temperature of 165°C to obtain pellets. The pellets were then dried overnight at 80°C to obtain a raw material composition in the form of pellets. Next, using a fiber manufacturing device, a fibrous molten material (fibrous molten kneaded material) was obtained by kneading the pellet-shaped raw material composition under the following conditions: extruder temperature 180°C, nozzle temperature 192°C, and single-hole discharge rate 0.045 g / min / hole (gear pump rotation speed 15 rpm). Then, a gas (air) set at a temperature of 185°C was blown onto the fibrous melt-kneaded material at a rate of 6140 NL / min to produce a melt-blown nonwoven fabric, which is a fiber structure containing fibers. The fiber structure was manufactured using a nozzle with a width of 600 mm, a hole diameter of 0.15 mm, a hole spacing of 0.35 mm, and 1207 holes. The distance (DCD) between the nozzle hole and the collection surface of the collector (conveyor belt) was 175 mm. The room temperature around the fiber manufacturing equipment was 22°C.

[0102] The physical properties were measured by the following methods.

[0103] (Physical properties of raw material composition) The weight average molecular weight and MFR (190°C, 2.16 kg) of the raw material composition were measured by the methods described above. The measured values ​​are shown in Table 1 below.

[0104] (Maximum load, elongation at maximum load, and elongation at break in the CD and MD directions of the fiber structure) The fiber structure was measured for maximum load, elongation at maximum load, and elongation at break in the CD and MD directions. The maximum load in the CD and MD directions, the tensile elongation at the maximum load, and the tensile elongation at break were measured using a constant-speed extension tensile testing machine in accordance with JIS B7721:2018 "Tensile testing machine / compression testing machine - Calibration and verification methods for force measurement systems." A universal testing machine (RTG-1210 manufactured by A&D Co., Ltd.) was used as the constant-speed extension type tensile testing machine. First, a test piece (width: 8 mm, length: 40 mm) was cut out from the fiber structure. Next, the test piece was attached to the tensile testing machine with an initial load and a grip distance of 20 mm. In other words, the grip distance when the initial load was applied to the test piece was 20 mm. However, during the initial load, the test piece was pulled by hand to a degree that did not cause slack. A load was applied at a tensile speed of 20 mm / min until the test piece broke, and the maximum load in the CD and MD directions was measured. In addition, the elongation at maximum load and the tensile strength at break in the CD and MD directions were calculated using the following formulas. Elongation at maximum load (%) = [(Grip spacing at maximum load - Grip spacing when initial load is applied to test piece) / Grip spacing when initial load is applied to test piece] x 100 (%) Elongation at break (%) = [(Grip spacing at break - Grip spacing when initial load is applied to test piece) / Grip spacing when initial load is applied to test piece] x 100 (%) The measured values ​​are shown in Table 1 below.

[0105] (Other physical properties) The basis weight and thickness of the fiber structure, the weight average molecular weight and MFR (190°C, 2.16 kg) of the resin composition, and the average fiber diameter and coefficient of variation of the fibers in the fiber structure were measured by the methods described above. The measured values ​​are shown in Table 1 below. 4 and 5 show SEM images of the fiber structures of Example 2 and Comparative Example 4.

[0106] The evaluation test was carried out in the following manner.

[0107] (Fiber structure's breaking energy in CD and MD: tear resistance) Using a universal testing machine (e.g., RTG-1210, manufactured by A&D) conforming to JIS B7721:2018 "Tensile testing machines and compression testing machines - Calibration and verification methods for force measurement systems," a tensile test was performed on a test piece (fiber structure) with a width of 8 mm and a length of 40 mm, with a grip spacing of 20 mm and a tensile speed of 20 mm / min, and data on the "load (N) - displacement (mm) curve" was obtained. The integral value of the data up to the fracture of the test piece was taken as the fracture energy (mJ), and the fracture energy per unit cross-sectional area (mJ / mm 2 ) was calculated. Breaking energy per unit cross-sectional area (mJ / mm 2 ) = Breaking energy (mJ) / (Width of test piece (mm) × Thickness of test piece (mm)) Hereinafter, the "breaking energy per unit cross-sectional area" will also be simply referred to as "breaking energy." The breaking energy was measured in both the CD and MD directions of the fiber structure. The measured values ​​are shown in Table 1 below.

[0108] (Virus droplet collection efficiency of fiber structures) The viral droplet collection efficiency (VFE) of the fiber structure was measured in accordance with JIS T9001:2021 "Performance requirements and test methods for medical masks and general-use masks." The virus droplet collection efficiency refers to the collection efficiency of viruses attached to particles. The measured values ​​are shown in Table 1 below.

[0109] (Pressure loss due to fiber structure) The pressure loss due to the fiber structure was measured. Pressure loss was measured in accordance with JIS T9001:2021 "Performance requirements and test methods for medical masks and general-use masks." The measured values ​​are shown in Table 1 below.

[0110] [Table 1]

[0111] As shown in Table 1, in Examples 1 to 4, which are within the scope of the present invention, the break energy of the fiber structures in both the CD and MD directions was high. On the other hand, in Comparative Example 1, which did not contain polylactic acid-based resin, Comparative Example 2, which contained a relatively small amount of polylactic acid-based resin, Comparative Example 3, which did not contain P3HA-based resin, and Comparative Example 4, in which the weight-average molecular weight of the polylactic acid-based resin exceeded 120,000, the breaking energy was smaller in both the CD and MD directions of the fiber structure than in Examples 1 to 4. Therefore, it can be seen that the present invention can provide a fiber structure that is difficult to tear.

[0112] Furthermore, as shown in Table 1, in the embodiments containing the P3HA resin, Examples 1 to 4 had a higher VFE than Comparative Examples 1, 2, and 4. Therefore, it can be seen that the present invention can provide a P3HA-based resin-containing fiber structure with high particle collection efficiency. As shown in FIG. 4, fine fibers of uniform fineness were obtained in Example 2, whereas as shown in FIG. 5, it was confirmed that there was a large variation in fiber diameter in Comparative Example 4. In the fibers according to the present invention, the poly(3-hydroxyalkanoate) resin and the polylactic acid resin are thoroughly mixed, which reduces discharge unevenness and pressure fluctuations near the nozzle during spinning, resulting in neat fibers of uniform fineness. As a result, it is believed that the fiber structure has a high particle collection efficiency.

Claims

1. A fiber comprising a resin composition, the resin composition contains a poly(3-hydroxyalkanoate)-based resin and a polylactic acid-based resin, and contains 40 to 70 parts by weight of the polylactic acid-based resin per 100 parts by weight of the poly(3-hydroxyalkanoate)-based resin and the polylactic acid-based resin combined; The polylactic acid resin has a weight average molecular weight of 20,000 to 120,000.

2. 2. The fiber according to claim 1, wherein the weight average molecular weight of the poly(3-hydroxyalkanoate) resin is 50,000 to 350,000.

3. 3. The fiber according to claim 1, wherein the melting point of the polylactic acid resin is 100 to 185°C.

4. 3. The fiber according to claim 1, wherein the poly(3-hydroxyalkanoate)-based resin is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate).

5. The fiber according to claim 1 or 2, wherein the coefficient of variation of the fiber diameter is 0.30 or less.

6. A fiber structure comprising the fiber according to claim 1 or 2.

7. The fibrous structure of claim 6, which is a spunbonded nonwoven or a meltblown nonwoven.

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