Nonwoven fabric and production method therefor

Abstract

The present invention provides a nonwoven fabric that is difficult to tear. The present invention is a nonwoven fabric comprising fibers, wherein: the fibers are formed from a resin composition containing a poly(3-hydroxyalkanoate)-based resin; the poly(3-hydroxyalkanoate)-based resin contains a copolymer that has a 3-hydroxybutyrate unit; the content ratio of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate)-based resin included in the nonwoven fabric is 70.0-92.0 mol%; the tensile elongation at break point in the MD of the nonwoven fabric is not less than 100%; and the tensile elongation at break point in the CD of the nonwoven fabric is not less than 100%.

Description

Nonwoven fabric and its manufacturing method

[0001] The present invention relates to a nonwoven fabric and a method for producing the same.

[0002] Nonwoven fabrics are used, for example, as the base material for a variety of products (e.g., masks, filters, disposable diapers, sanitary napkins, taping materials, patches, bandages, gloves, clothing, etc.) Fibers containing poly(3-hydroxyalkanoate) resins, which are biodegradable resins, are used as fibers for nonwoven fabrics from the viewpoint of reducing the burden on the global environment (e.g., Patent Document 1).

[0003] International Publication No. 2019 / 142920

[0004] Nonwoven fabrics are often required to be tear-resistant, but tear-resistant nonwoven fabrics have not been sufficiently studied to date.

[0005] Therefore, an object of the present invention is to provide a nonwoven fabric that is tear-resistant.

[0006] A first aspect of the present invention relates to a nonwoven fabric comprising fibers, wherein the fibers are formed from a resin composition containing a poly(3-hydroxyalkanoate)-based resin, and the poly(3-hydroxyalkanoate)-based resin contains a copolymer having 3-hydroxybutyrate units, and the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the nonwoven fabric is 70.0 mol % or more and 92.0 mol % or less, and the nonwoven fabric has a tensile elongation at break in the MD direction of 100% or more, and a tensile elongation at break in the CD direction of 100% or more.

[0007] A second aspect of the present invention relates to a method for producing a nonwoven fabric, using a nozzle having nozzle holes to produce a nonwoven fabric containing fibers, the method comprising: a step (A) of obtaining a raw yarn by discharging a molten material from the nozzle holes; and a step (B) of stretching the raw yarn, wherein the molten material contains a poly(3-hydroxyalkanoate)-based resin, the poly(3-hydroxyalkanoate)-based resin contains a copolymer having 3-hydroxybutyrate units, the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the molten material is 70 mol% or more and 92 mol% or less, and the ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fibers is 300 or more.

[0008] A third aspect of the present invention relates to a method for producing a nonwoven fabric, using a nozzle having nozzle holes to produce a nonwoven fabric containing fibers, the method comprising: a step (A) of obtaining a raw yarn by discharging a molten material from the nozzle holes; and a step (B) of drawing the raw yarn, wherein the raw material composition contains a poly(3-hydroxyalkanoate)-based resin, the poly(3-hydroxyalkanoate)-based resin contains a copolymer having 3-hydroxybutyrate units, the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the molten material is 70 mol % or more and 92 mol % or less, and the ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fibers is 150 or more.

[0009] According to the present invention, a tear-resistant nonwoven fabric can be provided.

[0010] 1 is a schematic diagram of a nonwoven fabric manufacturing apparatus; a schematic perspective view of a nozzle; a schematic cross-sectional view of a nozzle hole and a conveyor belt; photographs of two first test pieces; and a photograph of a mask.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] <Nonwoven Fabric> First, the nonwoven fabric according to this embodiment will be described. The nonwoven fabric according to this embodiment includes fibers. The fibers are formed from a resin composition containing a poly(3-hydroxyalkanoate)-based resin. The poly(3-hydroxyalkanoate)-based resin includes a copolymer having 3-hydroxybutyrate units. The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the nonwoven fabric is 70.0 mol % or more and 92.0 mol % or less. The tensile elongation at break of the nonwoven fabric in the MD direction is 100% or more. The tensile elongation at break of the nonwoven fabric in the CD direction is 100% or more.

[0013] The resin composition contains a polymer component. The resin composition may further contain an additive.

[0014] The polymer component contains a poly(3-hydroxyalkanoate)-based resin. The polymer component may contain other polymers in addition to the poly(3-hydroxyalkanoate)-based resin.

[0015] 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 structural unit. The poly(3-hydroxyalkanoate) resin is also a polymer having biodegradability. Note that, 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 suited to 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. The decomposition ability of microorganisms in seawater can be evaluated by measuring the biochemical oxygen demand.

[0016] The poly(3-hydroxyalkanoate) resin includes a copolymer having a 3-hydroxybutyrate unit.

[0017] 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, etc. Examples of the hydroxyalkanoate unit other than the 3-hydroxybutyrate unit include 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxyoctadecanoate, 3-hydroxyvalerate, and 4-hydroxybutyrate.

[0018] Examples of copolymers having 3-hydroxybutyrate units include P3HB3HH, P3HB3HV, P3HB4HB, poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate). Here, P3HB3HH means poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). P3HB3HV means poly(3-hydroxybutyrate-co-3-hydroxyvalerate). P3HB4HB means poly(3-hydroxybutyrate-co-4-hydroxybutyrate). The poly(3-hydroxyalkanoate) resin may contain only one copolymer having 3-hydroxybutyrate units, or may contain two or more copolymers having 3-hydroxybutyrate units. P3HB3HH is preferred as the copolymer having 3-hydroxybutyrate units.

[0019] The resin composition contains a copolymer having a 3-hydroxybutyrate unit in an amount of preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0020] The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric is 70.0 mol% or more and 92.0 mol% or less, preferably 80.0 mol% or more and 92.0 mol% or less, more preferably 82.0 mol% or more and 92.0 mol% or less, and even more preferably 85.0 mol% or more and 91.6 mol% or less. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric is 70.0 mol% or more, the rigidity of the fibers is increased. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric is 92.0 mol% or less, the nonwoven fabric according to this embodiment is less likely to tear. Furthermore, when the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the nonwoven fabric is 92.0 mol % or less, the nonwoven fabric according to this embodiment is less likely to fluff. Note that the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the nonwoven fabric refers to the content of the 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate)-based resin contained in the nonwoven fabric.

[0021] The content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric can be determined as follows. First, 20 mg of the dried poly(3-hydroxyalkanoate) resin from the nonwoven fabric is added with 2 mL of a mixed solution of sulfuric acid and methanol (volume of sulfuric acid:volume of methanol=15:85) and 2 mL of chloroform to form a sample, which is then sealed and heated at 100°C for 140 minutes in a sealed state to obtain a first reaction solution containing methyl esters, which are decomposition products of the poly(3-hydroxyalkanoate) resin. The first reaction solution is then cooled, and 1.5 g of sodium bicarbonate is gradually added to the cooled first reaction solution to neutralize it. The mixture is then left to stand until the evolution of carbon dioxide gas ceases to yield a second reaction solution. The second reaction solution is then thoroughly mixed with 4 mL of diisopropyl ether to obtain a mixture. The mixture is then centrifuged to obtain a supernatant. The monomer unit composition of the decomposition product in the supernatant is then analyzed by capillary gas chromatography under the following conditions to determine the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin: Gas chromatograph: GC-17A manufactured by Shimadzu Corporation 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 amount: 1 μL Temperature conditions include heating at a rate of 8°C / min from 100 to 200°C, and then at a rate of 30°C / min from 200 to 290°C.

[0022] Furthermore, the content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the raw material composition (the "raw material composition" will be described later) may be used as the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric. The content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the raw material composition can be determined in the same manner as the above-mentioned "content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric" using dried poly(3-hydroxyalkanoate) resin of the raw material composition.

[0023] From the viewpoint of improving the mechanical properties of the nonwoven fabric, the poly(3-hydroxyalkanoate) resin preferably contains a poly(3-hydroxyalkanoate) resin component having a 3-hydroxybutyrate unit content of 76 mol% or less. The 3-hydroxybutyrate unit content in the poly(3-hydroxyalkanoate) resin component is 0 to 76 mol%, preferably 1 to 76 mol%, and more preferably 50 to 76 mol%. Preferred examples of the poly(3-hydroxyalkanoate) resin component include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate).

[0024] (MIBK Fractionation Method) Whether the poly(3-hydroxyalkanoate) resin contains the poly(3-hydroxyalkanoate) resin component can be confirmed, for example, by using a solvent fractionation method (also referred to as the "MIBK fractionation method") that utilizes differences in solubility in methyl isobutyl ketone (MIBK). That is, by fractionating the poly(3-hydroxyalkanoate) resin into an MIBK-soluble fraction and an MIBK-insoluble fraction by the MIBK fractionation method, and finding that the content of 3-hydroxybutyrate units in either fraction is 76 mol% or less, it can be confirmed that the poly(3-hydroxyalkanoate) resin contains the poly(3-hydroxyalkanoate) resin component.

[0025] The specific fractionation procedure is described below. First, approximately 100 mg of poly(3-hydroxyalkanoate) resin is weighed into a screw-cap test tube, 10 ml of MIBK is added, and the cap is closed. The tube is then heated at 140°C for approximately 1 to 3 hours while shaking to completely dissolve the poly(3-hydroxyalkanoate) resin. After complete dissolution, the tube is left at 25°C for 1 minute to reduce the temperature below the boiling point, and all of the solution is quickly transferred to a pre-weighed centrifuge tube and the cap is closed. The capped centrifuge tube is then left at 25°C for an additional 15 minutes to precipitate a portion of the solution. The precipitate and solution are separated by centrifugation (9000 rpm, 5 minutes), and all of the solution is transferred to a pre-weighed aluminum cup. To the centrifuge tube containing the remaining precipitate, 10 ml of MIBK was added and mixed using a vortex mixer. The mixture was then centrifuged again (9,000 rpm, 5 minutes), and the solution was transferred to the aluminum cup containing the dissolving solution. The aluminum cup was heated at 120°C for 30 minutes to volatilize the MIBK and precipitate the dissolved material. The precipitate remaining in the aluminum cup and the precipitate remaining in the centrifuge tube were then vacuum-dried at 100°C for 6 hours. The precipitate remaining in the aluminum cup was weighed as the MIBK-soluble fraction, and the precipitate remaining in the centrifuge tube was weighed as the MIBK-insoluble fraction. It was confirmed that the difference between the total weight of the MIBK-soluble fraction and the MIBK-insoluble fraction and the weight of the poly(3-hydroxyalkanoate) resin measured initially was within ±3%.

[0026] The content of 3-hydroxybutyrate units in each of the MIBK-soluble fraction and the MIBK-insoluble fraction can be measured by the method described above. The content of 3-hydroxybutyrate units in either the MIBK-soluble fraction or the MIBK-insoluble fraction is preferably 0 to 76 mol %, more preferably 1 to 76 mol %, and even more preferably 50 to 76 mol %.

[0027] Examples of poly(3-hydroxyalkanoate) resins other than copolymers having 3-hydroxybutyrate units include P3HB, poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), etc. Here, P3HB refers to poly(3-hydroxybutyrate) as a homopolymer.

[0028] P3HB has the function of promoting the crystallization of P3HB itself and poly(3-hydroxyalkanoate) resins other than P3HB.

[0029] The other polymer is preferably biodegradable.

[0030] Examples of other biodegradable polymers include polycaprolactone, polylactic acid, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, unmodified starch, modified starch, cellulose acetate, and chitosan. The polycaprolactone is a polymer obtained by ring-opening polymerization of ε-caprolactone. The resin composition may contain one or more other polymers.

[0031] The nonwoven fabric according to this embodiment contains a biodegradable polymer, so that even if the nonwoven fabric is discarded in the environment, the nonwoven fabric is easily decomposed in the environment, thereby reducing the burden on the environment.

[0032] The resin composition may further contain an additive.

[0033] Examples of additives include nucleating agents, lubricants, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, inorganic fillers, organic fillers, antistatic agents, etc.

[0034] The resin composition preferably contains a nucleating agent as an additive. The nucleating agent is a compound that can promote crystallization of the poly(3-hydroxyalkanoate)-based resin. The nucleating agent has a higher melting point than the poly(3-hydroxyalkanoate)-based resin. By containing the nucleating agent in the resin composition, crystallization of the poly(3-hydroxyalkanoate)-based resin is promoted when producing a nonwoven fabric, making it difficult for adjacent fibers to fuse together. As a result, it becomes easier to reduce the coefficient of variation of the fiber diameter of the fibers. Examples of the crystal nucleating agent include inorganic substances (e.g., boron nitride, titanium oxide, talc, layered silicates, calcium carbonate, sodium chloride, metal phosphates, etc.); sugar alcohol compounds derived from natural products (e.g., pentaerythritol, erythritol, galactitol, mannitol, arabitol, etc.); polyvinyl alcohol; chitin; chitosan; polyethylene oxide; aliphatic carboxylates; aliphatic alcohols; aliphatic carboxylate esters; dicarboxylic acid derivatives (e.g., dimethyl adipate, dibutyl adipate, diisodecyl adipate, djibutyl adipate, etc.); Examples of suitable hydroxyalkanoate include sorbitol derivatives (e.g., bisbenzylidene sorbitol, bis(p-methylbenzylidene)sorbitol, etc.); cyclic compounds having C═O and a functional group selected from NH, S, and O in the molecule (e.g., indigo, quinacridone, quinacridone magenta, etc.); sorbitol derivatives (e.g., bisbenzylidene sorbitol, bis(p-methylbenzylidene)sorbitol, etc.); compounds containing 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. 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.

[0035] As the crystal nucleating agent, from the viewpoint of the effect of improving the crystallization rate of the poly(3-hydroxyalkanoate) resin and from the viewpoint of compatibility and affinity with the poly(3-hydroxyalkanoate) resin, sugar alcohol compounds, polyvinyl alcohol, chitin, and chitosan are preferred. Among the sugar alcohol compounds, pentaerythritol is preferred.

[0036] The nucleating agent preferably has a crystalline structure at room temperature (25°C). The nucleating agent having a crystalline structure at room temperature (25°C) has the advantage of further accelerating the crystallization of the poly(3-hydroxyalkanoate) resin. Furthermore, the nucleating agent having a crystalline structure at room temperature (25°C) is preferably in a powder form at room temperature (25°C). Furthermore, the average particle size of the nucleating agent in a powder form at room temperature (25°C) is preferably 10 μm or less.

[0037] The resin composition contains a nucleating agent in an amount of preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more per 100 parts by mass of poly(3-hydroxyalkanoate)-based resin. By containing 0.1 parts by mass or more of a nucleating agent per 100 parts by mass of poly(3-hydroxyalkanoate)-based resin, the resin composition has the advantage of further promoting crystallization of the poly(3-hydroxyalkanoate)-based resin when producing a nonwoven fabric. Furthermore, the resin composition contains preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less of a nucleating agent per 100 parts by mass of poly(3-hydroxyalkanoate)-based resin. By containing 2.5 parts by mass or less of a nucleating agent per 100 parts by mass of poly(3-hydroxyalkanoate)-based resin, the resin composition has the advantage of making it easier to obtain fibers when producing a nonwoven fabric. It should be noted that P3HB is a poly(3-hydroxyalkanoate)-based resin and can also function as a crystal nucleating agent. Therefore, when the resin composition contains P3HB, the amount of P3HB is included in both the amount of the poly(3-hydroxyalkanoate)-based resin and the amount of the crystal nucleating agent.

[0038] The resin composition preferably contains the lubricant. When producing a nonwoven fabric, the lubricant in the fibers improves the lubricity of the fibers, thereby preventing fusion between the fibers. On the other hand, when the resin composition does not contain a lubricant or contains a very small amount of a lubricant, there are advantages, for example, in improving the tape adhesiveness of the nonwoven fabric and making it easier to handle during the nonwoven fabric production process. The presence or absence of a lubricant and the amount of lubricant added can be determined appropriately depending on the intended use of the nonwoven fabric (e.g., meltblown nonwoven fabric). Examples of the lubricant include compounds having an amide bond. The compound having an amide bond preferably contains one or more compounds selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0039] The content of the lubricant in the resin composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the polymer component. Having a lubricant content of 0.05 parts by mass or more per 100 parts by mass of the polymer component has the advantage of further suppressing fusion between fibers when producing a nonwoven fabric. On the other hand, having a lubricant content of 0 to 0.2 parts by mass per 100 parts by mass of the polymer component has the advantage of improving the tape adhesiveness of the nonwoven fabric and making it easier to handle during the nonwoven fabric production process. Furthermore, the content of the lubricant in the resin composition is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and most preferably 5 parts by mass or less, per 100 parts by mass of the polymer component. Having a lubricant content of 12 parts by mass or less per 100 parts by mass of the polymer component has the advantage of suppressing bleeding of the lubricant onto the fiber surface.

[0040] The melt mass flow rate (MFR) of the resin composition at 165°C is preferably 20 to 1500 g / 10 min, more preferably 30 to 1500 g / 10 min, still more preferably 40 to 1300 g / 10 min, and particularly preferably 50 to 1200 g / 10 min.

[0041] When the resin composition in the fiber has a melt mass flow rate of 1500 g / 10 min or less at 165°C, the strength and elongation of the nonwoven fabric are increased. When the resin composition in the fiber has a melt mass flow rate of 20 g / 10 min or more at 165°C, the tension applied to the raw yarn (the "raw yarn" will be described later) can be reduced when the raw yarn is stretched, making it easier to reduce the fiber diameter of the fibers in the resulting nonwoven fabric. As a result, the particle collection efficiency of the nonwoven fabric is easily improved. Furthermore, when the resin composition in the fiber has a melt mass flow rate of 20 g / 10 min or more at 165°C, the generation of clumps of polymer components can be suppressed when producing a nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved. Furthermore, when the resin composition in the fiber has a melt mass flow rate of 20 g / 10 min or more at 165°C, clogging of nozzle holes (the "nozzle holes" will be described later) can be suppressed when producing a nonwoven fabric. As a result, productivity of the nonwoven fabric is improved.

[0042] The melt mass flow rate (MFR) of the resin composition at 165°C is determined by ASTM-D1238 (ISO1133-1, JIS K7210-1:2011) Method B, and the melt mass flow rate (MFR) of the resin composition at 165°C is determined from the melt volume flow rate (MVR) of the resin composition at 165°C and the density of the resin composition. The melt volume flow rate (MVR) of the resin composition at 165°C is measured by heating 5 g or more of the resin composition at 165°C for 4 minutes and then applying a load of 5 kg to the heated resin composition.

[0043] The weight average molecular weight of the resin composition is preferably 50,000 to 350,000, more preferably 70,000 to 300,000, still more preferably 80,000 to 250,000, and particularly preferably 150,000 to 250,000.

[0044] When the weight-average molecular weight of the resin composition in the fibers is 50,000 or more, the strength and elongation of the nonwoven fabric are increased. Furthermore, when the weight-average molecular weight of the resin composition in the fibers is 150,000 or more, the nonwoven fabric becomes even more tear-resistant. When the weight-average molecular weight of the resin composition in the fibers is 350,000 or less, the tension applied to the raw yarn during drawing can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting nonwoven fabric. As a result, the particle collection efficiency of the nonwoven fabric is easily improved. Furthermore, when the weight-average molecular weight of the resin composition in the fibers is 350,000 or less, the generation of clumps of polymer components can be suppressed when producing the nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved. Furthermore, when the weight-average molecular weight of the resin composition in the fibers is 350,000 or less, clogging of nozzle holes (the "nozzle holes" will be described later) can be suppressed when producing the nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved.

[0045] The weight-average molecular weight in this embodiment is measured from the polystyrene-equivalent molecular weight distribution by gel permeation chromatography (GPC) using chloroform as an eluent. As a column for the GPC, a column appropriate for measuring the molecular weight may be used.

[0046] The average fiber diameter of the fibers is preferably 30.0 μm or less, more preferably 25.0 μm or less, even more preferably 20.0 μm or less, still more preferably 0.50 to 20.0 μm, particularly preferably 0.80 to 15.0 μm, and most preferably 1.0 to 15.0 μm. The coefficient of variation of the fiber diameter of the fibers is preferably 0.40 or less, more preferably 0.36 or less, and even more preferably 0.32 or less. The coefficient of variation of the fiber diameter of the fibers is, for example, 0.10 or more.

[0047] When the average fiber diameter of the fibers is 20.0 μm or less, the particle collection efficiency of the nonwoven fabric is increased. Furthermore, when the average fiber diameter of the fibers is 20.0 μm or less, the rigidity of the fibers can be reduced, resulting in an improved texture (e.g., feel to the skin, touch, etc.) of the nonwoven fabric. When the average fiber diameter of the fibers is 0.50 μm or more, the strength and elongation of the nonwoven fabric are increased. When the fiber diameter coefficient of variation of the fibers is 0.40 or less, extremely thick fibers are reduced, resulting in an increased particle collection efficiency of the nonwoven fabric. Furthermore, when the fiber diameter coefficient of variation of the fibers is 0.40 or less, extremely thin fibers are reduced, resulting in an increased strength and elongation of the nonwoven fabric.

[0048] The average fiber diameter and coefficient of variation of the fibers can be determined as follows. First, a test piece is obtained from a nonwoven fabric. Next, photographs (1700x magnification) of five locations on the surface of the test piece are taken using a scanning electron microscope. Then, the diameters (widths) of 20 or more randomly selected fibers are measured for each photograph. Next, the arithmetic mean value and coefficient of variation (= standard deviation / arithmetic mean value) are determined from the diameter (width) values ​​of all the measured fibers.

[0049] The basis weight of the nonwoven fabric according to this embodiment is preferably 20 to 150 g / m ２ , more preferably 30 to 140 g / m ２ , more preferably 40 to 120 g / m ２ The nonwoven fabric according to this embodiment has a basis weight of 20 g / m ２ By satisfying the above conditions, the strength and elongation of the nonwoven fabric are increased. ２ By satisfying the above, the particle collection efficiency of the nonwoven fabric is improved. ２ By satisfying the condition below, liquid permeability (water permeability, etc.) or breathability can be improved.

[0050] The basis weight of the nonwoven fabric according to this embodiment can be determined as follows. First, a test piece is obtained from the nonwoven fabric 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. Then, the basis weight is calculated by dividing the weight of the test piece by the area of ​​the test piece.

[0051] Furthermore, the thickness of the nonwoven fabric according to this embodiment is preferably 0.10 to 0.80 mm, more preferably 0.15 to 0.60 mm. When the thickness of the nonwoven fabric according to this embodiment is 0.10 to 0.80 mm, it becomes easier to obtain a homogeneous nonwoven fabric when producing the nonwoven fabric. When the thickness of the nonwoven fabric according to this embodiment is 0.10 mm or more, the strength and elongation of the nonwoven fabric are increased. When the thickness of the nonwoven fabric according to this embodiment is 0.10 mm or more, the particle collection efficiency of the nonwoven fabric is increased. Furthermore, when the thickness of the nonwoven fabric according to this embodiment is 0.80 mm or less, the liquid permeability (water permeability, etc.) or breathability of the nonwoven fabric can be increased.

[0052] The thickness of the nonwoven fabric according to this embodiment can be determined by measuring the thickness of the nonwoven fabric at three or more points with a thickness meter, and taking the arithmetic mean value of the measured values. Examples of thickness meter include "PEACOCK" manufactured by Ozaki Seisakusho Co., Ltd.

[0053] Furthermore, the average pore size of the nonwoven fabric according to this embodiment is preferably 2.5 μm or more and 30.0 μm or less, more preferably 3.0 μm or more and 25.0 μm or less, and even more preferably 3.0 μm or more and 20.0 μm or less. When the average pore size of the nonwoven fabric according to this embodiment is 2.5 μm or more, the liquid permeability (water permeability, etc.) or breathability of the nonwoven fabric can be improved. When the average pore size of the nonwoven fabric according to this embodiment is 30.0 μm or less, the particle collection efficiency of the nonwoven fabric is improved.

[0054] The average pore size of the nonwoven fabric according to this embodiment is the mean flow pore size determined in accordance with JIS K3832-1990 "Bubble point test method for microfiltration membrane elements and modules." The mean flow pore size can be measured using, for example, a Perm Porometer (manufactured by PMI).

[0055] The tensile elongation at break in the MD direction (also simply referred to as "MD elongation") of the nonwoven fabric according to this embodiment is 100% or more, preferably 120% or more, and more preferably 150% or more. The MD elongation of the nonwoven fabric according to this embodiment is, for example, 800% or less. By having an MD elongation of 100% or more, the nonwoven fabric according to this embodiment is less likely to break even when pulled in the MD direction. By setting the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin to 92.0 mol% or less, the MD elongation tends to be increased.

[0056] The tensile elongation at break in the CD direction (also simply referred to as "CD elongation") of the nonwoven fabric according to this embodiment is 100% or more, preferably 120% or more, and more preferably 150% or more. The CD elongation of the nonwoven fabric according to this embodiment is, for example, 800% or less. By having a CD elongation of 100% or more, the nonwoven fabric according to this embodiment is less likely to break even when pulled in the CD direction. By setting the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin to 92.0 mol% or less, the CD elongation is likely to be increased.

[0057] Here, the MD direction is the direction in which the nonwoven fabric moves when it is produced (machine direction). The CD direction is the direction perpendicular to the MD direction. The tensile elongation at break is also called the tensile elongation at break.

[0058] The ratio of the tensile elongation at break in the CD direction of the nonwoven fabric to the tensile elongation at break in the MD direction of the nonwoven fabric (CD elongation / MD elongation) is preferably 0.50 to 2.00, more preferably 0.56 to 1.80. By having a CD elongation / MD elongation of 0.50 to 2.00, when stress is applied to the nonwoven fabric according to this embodiment, the concentration of stress in only one of the CD direction and the MD direction in the nonwoven fabric is suppressed, resulting in the nonwoven fabric being less likely to tear. By setting the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin to 92.0 mol% or less, the CD elongation / MD elongation is more likely to be within the range of 0.50 to 2.00.

[0059] The tensile elongation at break can be measured using a constant-rate extension tensile tester conforming to JIS B7721:2018 "Tensile and Compression Testers - Calibration and Verification Methods for Force Measurement Systems." A universal testing machine (RTG-1210 manufactured by A&D Co., Ltd.) or the like can be used as the constant-rate extension tensile tester. Specifically, the tensile elongation at break can be determined as follows. First, a test specimen (width: 8 mm, length: 40 mm) is cut out from the nonwoven fabric. Next, the test specimen is attached to the constant-rate extension tensile tester with a grip spacing of 20 mm under an initial load. In other words, the grip spacing when the initial load is applied to the test specimen is 20 mm. However, at the initial load, the test specimen is pulled by hand to a degree that does not cause slack. Then, a load is applied at a pulling rate of 20 mm / min until the test specimen breaks. Next, the tensile elongation at break is determined using the following formula: Tensile 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 (%)

[0060] The nonwoven fabric according to this embodiment has a 50% elongation recovery rate in the MD direction of preferably 50% or more, more preferably 55% or more. The nonwoven fabric according to this embodiment has a 50% elongation recovery rate in the MD direction of 100% or less, for example 90% or less. Since the nonwoven fabric according to this embodiment has a 50% elongation recovery rate in the MD direction of 50% or more, the nonwoven fabric according to this embodiment has excellent stretchability in the MD direction.

[0061] The nonwoven fabric according to this embodiment has a 50% elongation recovery rate in the CD direction of preferably 50% or more, more preferably 55% or more. The nonwoven fabric according to this embodiment has a 50% elongation recovery rate in the CD direction of 100% or less, for example, 90% or less. Since the nonwoven fabric according to this embodiment has a 50% elongation recovery rate in the CD direction of 50% or more, the nonwoven fabric according to this embodiment has excellent stretchability in the CD direction.

[0062] The nonwoven fabric preferably has a 50% elongation recovery rate in the MD direction of 50% or more and / or a 50% elongation recovery rate in the CD direction of 50% or more.More preferably, the nonwoven fabric has a 50% elongation recovery rate in the MD direction of 50% or more and a 50% elongation recovery rate in the CD direction of 50% or more.

[0063] The 50% elongation recovery rate is measured in accordance with JIS L1096:2010 "Testing Methods for Woven and Knit Fabrics." Specifically, the 50% elongation recovery rate can be determined as follows. First, a test piece (width: 50 mm, length: 300 mm) is cut out from the nonwoven fabric. Next, the test piece is attached to a constant-rate extension tensile tester with a grip spacing of 200 mm under an initial load. In other words, the grip spacing when the initial load is applied to the test piece is 200 mm. However, under the initial load, the test piece is pulled by hand to a degree that does not cause slack. Then, a load is applied to 50% of the grip spacing at a pulling rate of 200 mm / min, and the load is maintained for 1 minute, and the test piece is returned to its original position while unloading at the same rate. 50% elongation recovery rate (%) = [(Grip spacing at 50% elongation - Grip spacing at which the load becomes 0 during unloading) / (Grip spacing at 50% elongation - Grip spacing when the initial load is applied to the test piece)] × 100 (%)

[0064] The nonwoven fabric according to this embodiment is preferably a direct-spun nonwoven fabric. The direct-spun nonwoven fabric refers to a "nonwoven fabric obtained by entangling raw yarns obtained by melt spinning to form a sheet directly and solidifying the raw yarns." Note that "entangling raw yarns to form a sheet directly" means "entangling raw yarns to form a sheet before the raw yarns are solidified." Examples of the direct-spun nonwoven fabric include meltblown nonwoven fabrics, spunbond nonwoven fabrics, flash-spun nonwoven fabrics, and electrospun nonwoven fabrics. Note that the meltblown nonwoven fabric is a concept that also includes nonwoven fabrics obtained by the Spunblown (registered trademark) method. The nonwoven fabric according to this embodiment is more preferably a meltblown nonwoven fabric or a spunbond nonwoven fabric, and even more preferably a meltblown nonwoven fabric.

[0065] The nonwoven fabric according to this embodiment can be suitably used, for example, as a substrate for various products (e.g., masks, filters, disposable diapers, sanitary napkins, taping materials, patches, bandages, gloves, clothing, etc.). The concept of substrate also 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.). The nonwoven fabric according to this embodiment is particularly suitable for use as a substrate for the ear loops of masks or as a reinforcing material for masks.

[0066] <Method for manufacturing nonwoven fabric> The nonwoven fabric according to this embodiment is configured as described above. Next, a method for manufacturing the nonwoven fabric according to this embodiment will be described.

[0067] A method for producing a nonwoven fabric according to this embodiment uses a nozzle having nozzle holes to produce a nonwoven fabric containing fibers. The method for producing a nonwoven fabric according to this embodiment includes a step (A) of obtaining a raw yarn by discharging a molten material from the nozzle holes, and a step (B) of drawing the raw yarn. The molten material contains a poly(3-hydroxyalkanoate)-based resin. The poly(3-hydroxyalkanoate)-based resin contains a copolymer having a 3-hydroxybutyrate unit. The content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate)-based resin contained in the molten material is 70 mol% or more and 92 mol% or less. The ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fibers is 300 or more.

[0068] Hereinafter, the method for producing a nonwoven fabric according to this embodiment will be described using a method for producing a nonwoven fabric by the meltblown method as an example. Note that the meltblown method is a concept that also includes the spunblown (registered trademark) method.

[0069] The melt is obtained from a raw material composition. In the step (A), the raw material composition is melted by heating to obtain a melt, and the melt is discharged from the nozzle hole to obtain a raw yarn.

[0070] The melt mass flow rate (MFR) of the raw material composition at 165°C is preferably 1.0 to 1500 g / 10 min, more preferably 2.0 to 1000 g / 10 min, still more preferably 5.0 to 1000 g / 10 min, and particularly preferably 10 to 800 g / 10 min.

[0071] When the raw material composition has a melt mass flow rate of 1500 g / 10 min or less at 165°C, the strength and elongation of the nonwoven fabric are further increased. When the raw material composition has a melt mass flow rate of 1.0 g / 10 min or more at 165°C, the tension applied to the raw yarn during drawing can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting nonwoven fabric. As a result, the particle collection efficiency of the nonwoven fabric is improved. Furthermore, when the raw material composition has a melt mass flow rate of 1.0 g / 10 min or more at 165°C, the generation of clumps of polymer components can be suppressed when producing the nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved. Furthermore, when the raw material composition has a melt mass flow rate of 1.0 g / 10 min or more at 165°C, clogging of nozzle holes in the nozzle can be suppressed when producing the nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved.

[0072] The melt mass-flow rate (MFR) of the raw material composition at 165°C is determined by ASTM-D1238 (ISO1133-1, JIS K7210-1:2011) Method B, and the melt mass-flow rate (MFR) of the raw material composition at 165°C is determined from the melt volume-flow rate (MVR) of the raw material composition at 165°C and the density of the raw material composition. The melt volume-flow rate (MVR) of the raw material composition at 165°C is measured by heating 5 g or more of the raw material composition at 165°C for 4 minutes, and then applying a load of 5 kg to the heated resin composition.

[0073] The weight average molecular weight of the raw material composition is preferably 100,000 to 550,000, more preferably 110,000 to 500,000, even more preferably 110,000 to 450,000, and particularly preferably 200,000 to 450,000.

[0074] When the weight-average molecular weight of the raw material composition is 100,000 or more, the strength and elongation of the nonwoven fabric are increased. Furthermore, when the weight-average molecular weight of the raw material composition is 200,000 or more, the nonwoven fabric becomes even more resistant to tearing. When the weight-average molecular weight of the raw material composition is 550,000 or less, the tension applied to the raw yarn during drawing can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting nonwoven fabric. As a result, the particle collection efficiency of the nonwoven fabric is improved. Furthermore, when the weight-average molecular weight of the raw material composition is 550,000 or less, the generation of clumps of polymer components can be suppressed when producing the nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved. Furthermore, when the weight-average molecular weight of the raw material composition is 550,000 or less, clogging of nozzle holes in the nozzle can be suppressed when producing the nonwoven fabric. As a result, the productivity of the nonwoven fabric is improved.

[0075] The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten product is 70.0 mol% or more and 92.0 mol% or less, preferably 80.0 mol% or more and 92.0 mol% or less, more preferably 82.0 mol% or more and 92.0 mol% or less, and even more preferably 85.0 mol% or more and 91.6 mol% or less. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten product is 70.0 mol% or more, the rigidity of the fiber is increased. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten product is 92.0 mol% or less, the nonwoven fabric according to this embodiment is less likely to tear. Furthermore, when the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin is 92.0 mol% or less, the nonwoven fabric according to this embodiment is less likely to fluff.

[0076] The content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten material refers to the content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric. The content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the molten material can be determined in the same manner as the above-mentioned "content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric" using dried poly(3-hydroxyalkanoate) resin contained in the molten material. Furthermore, the content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in a raw material composition (the "raw material composition" will be described later) may also be used as the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten material.

[0077] In the method for producing a nonwoven fabric according to this embodiment, a nonwoven fabric is obtained from the raw material composition using a nonwoven fabric production apparatus.

[0078] As shown in FIG. 1 , the nonwoven fabric manufacturing 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 to obtain a kneaded molten material, a nozzle 7 that discharges the molten material in the form of fibers to obtain a raw yarn, a collector 8 that collects and cools the raw yarn to obtain a first nonwoven fabric B, and a winding device 9 that winds up the first nonwoven fabric B.

[0079] Furthermore, the nonwoven fabric production apparatus 1 may, if necessary, include a gear pump 4 that supplies the molten material from the extruder 3 to the kneader 6. By including the gear pump 4, the nonwoven fabric production apparatus 1 can suppress fluctuations in the amount of molten material supplied to the kneader 6.

[0080] Furthermore, the nonwoven fabric manufacturing apparatus 1 may be provided with a filter 5 upstream of the kneader 6 for removing foreign matter from the molten material, if necessary.

[0081] 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.

[0082] The raw material composition supplied to the extruder 3 is preferably in a solid state, more preferably in a pellet state. The raw material composition supplied to the extruder 3 is preferably dried by heating, from the viewpoint of suppressing hydrolysis of the resin in the raw material composition and suppressing oxidative deterioration of the resin in the raw material composition. The moisture content in the raw material composition supplied to the extruder 3 is preferably 200 ppmw or less. When drying the raw material composition, it is preferable to remove oxygen from the atmosphere or to remove oxygen from the raw material composition. The drying atmosphere is preferably an inert gas atmosphere (e.g., nitrogen gas). In the step (A), the raw material composition may be dried before being supplied to the hopper 2, or the hopper 2 may be a hopper-type dryer, and the raw material composition may be dried in the hopper 2.

[0083] 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, a multi-screw extruder, etc. As the extruder 3, a single-screw extruder is preferred from the viewpoint that thermal deterioration of the raw material composition during extrusion is easily suppressed due to a small resin retention area in the extruder, and from the viewpoint that equipment costs are low.

[0084] 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 to obtain a kneaded melt.

[0085] Examples of the filter 5 include a screen mesh, a pleated filter, and a leaf disc filter. From the viewpoints of filtration accuracy, filtration area, and pressure resistance, as well as the fact that clogging due to foreign matter is unlikely to occur, a leaf disc filter is preferred as the filter 5. As the filter material of the filter 5, for example, a sintered nonwoven fabric of metal fibers can be used.

[0086] In the step (A), the melt is discharged from the nozzle 7 in the form of fibers to obtain a raw yarn.

[0087] The nozzle 7 is a spinning die head. In Fig. 2, the nozzle 7 has a plurality of nozzle holes 7a for discharging a melt in the form of fibers to obtain the yarn A. As shown in Fig. 2, the nozzle 7 discharges a plurality of yarns A. Note that the nozzle 7 may have only one nozzle hole 7a. In other words, the nozzle 7 may discharge only one yarn A.

[0088] The plurality of nozzle holes 7a open downward. The shape of the nozzle holes 7a is, for example, circular (a concept including circular, approximately circular, elliptical, and approximately elliptical). The diameter of the nozzle holes 7a is appropriately selected depending on the fiber diameter of the fibers of the nonwoven fabric. The diameter of the nozzle holes 7a is preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.12 mm or more. The diameter of the nozzle holes 7a is preferably 1.0 mm or less, more preferably 0.50 mm or less, even more preferably less than 0.30 mm, and particularly preferably 0.25 mm or less. The opening diameter means the arithmetic mean value of the opening diameters.

[0089] The ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber is 300 or more, preferably 300 to 20,000, more preferably 400 to 20,000, and even more preferably 500 to 15,000. When the ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber is 300 or more, the tensile elongation at break in the MD direction and the tensile elongation at break in the CD direction of the nonwoven fabric can be increased. The ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber serves as an indicator of the draw ratio.

[0090] The cross-sectional area of ​​the fiber can be determined from the average fiber diameter of the fiber, assuming that the cross section of the fiber is circular.

[0091] The opening area of ​​the nozzle hole means the average value of the opening area of ​​the nozzle hole. When the opening is circular, the opening area of ​​the nozzle hole can be calculated from the arithmetic mean value of the opening diameter.

[0092] The nozzle 7 has a plurality of nozzle holes 7a arranged in a row with a gap therebetween. In FIG. 2, the plurality of nozzle holes 7a are arranged in a single row. The plurality of nozzle holes 7a may be arranged in two or more rows. 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") is, for example, preferably 0.05 mm or more, more preferably 0.1 mm or more, and even more preferably 0.25 mm or more. By having the distance (spacing) between adjacent nozzle holes 7a be 0.05 mm or more, fusion of adjacent yarns can be suppressed, and as a result, the coefficient of variation of the fiber diameter of the fiber can be reduced. Furthermore, the distance (spacing) between adjacent nozzle holes 7a is, for example, preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. The distance between adjacent nozzle holes 7a may or may not be uniform, but uniformity is preferable in terms of facilitating the production of a homogeneous nonwoven fabric. The distance (interval) between adjacent nozzle holes 7a means the arithmetic mean value of the distance (interval) between adjacent nozzle holes 7a.

[0093] The collector 8 has a collecting surface that collects the raw yarn 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 collecting surface is disposed directly below the nozzle holes 7a. The conveyor belt 8a is breathable. Specifically, the conveyor belt 8a is formed of a mesh-like material. That is, the collecting surface is mesh-like. The collector 8 only needs to have a collecting unit, and may be a collecting drum or a collecting net instead of the conveyor.

[0094] The distance (DCD) between the nozzle hole 7a and the collecting surface 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 hole 7a and the conveyor belt 8a serving as the collecting section is preferably 250 mm or less. The distance (DCD) between the nozzle hole 7a and the collecting surface refers to the arithmetic mean value of the distance (DCD) between the nozzle hole 7a and the collecting surface.

[0095] As shown in FIG. 3, the nonwoven fabric manufacturing apparatus 1 is configured to stretch the raw yarn A by blowing a gas C onto the raw yarn A.

[0096] In the step (B), gas C is blown onto the yarn A, and the gas C blown onto the yarn A is passed through a mesh conveyor belt 8a. In the step (B), the gas C is preferably sucked by suction (not shown) so that the gas C blown onto the yarn A can easily pass through the mesh conveyor belt 8a. This makes it easier to prevent the yarn A from bouncing off the collection surface of the mesh conveyor belt 8a, and as a result, it becomes easier to form a first nonwoven fabric B in which the fibers are well fused together.

[0097] The flow rate of the gas C blown onto the yarn 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 gas C blown onto the yarn A is preferably 12000 NL / min or less, and more preferably 10000 NL / min or less.

[0098] The gas C blown onto the yarn A is a high-temperature gas. The temperature of the gas C blown onto the yarn A is preferably 150°C to 195°C, more preferably 155°C to 190°C, and even more preferably 160°C to 185°C.

[0099] Examples of the gas C include air and inert gases (nitrogen gas, etc.). Examples of a method for blowing high-temperature gas C include a method in which gas C pressurized by a compressor (not shown) is heated by a heater (not shown).

[0100] In the step (B), the temperature and flow rate of the gas C are appropriately controlled in order to obtain a nonwoven fabric with a high degree of crystallinity.

[0101] In the step (B), the drawn raw yarn A is collected by a conveyor belt 8a and cooled while being conveyed by the conveyor belt 8a, thereby obtaining a first nonwoven fabric B.

[0102] 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 first nonwoven fabric B, does not excessively fuse with the first nonwoven fabric B, and is a material from which the first nonwoven fabric B can be peeled off.

[0103] The speed at which the first nonwoven fabric B is moved by the conveyor belt 8a (the speed of the conveyor belt 8a) is appropriately determined taking into consideration the discharge rate of the raw material composition and the apparent density of the resulting first nonwoven fabric B. The speed is preferably in the range of 0.2 m / min to 6.0 m / min.

[0104] In the step (B), the first nonwoven fabric B is transported by the conveyor belt 8a to the winding device 9, and the first nonwoven fabric B is wound up in a roll by the winding device 9.

[0105] In the nonwoven fabric manufacturing method according to this embodiment, the ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can be increased by increasing the volume of gas blown onto the raw yarn. Furthermore, in the nonwoven fabric manufacturing method according to this embodiment, the ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can also be increased by decreasing the amount of molten material discharged from the nozzle hole per unit time. The amount of molten material discharged from the nozzle hole per unit time can be decreased by decreasing the rotation speed of the gear pump.

[0106] The method for producing a nonwoven fabric according to this embodiment may include a step (C) of heating the first nonwoven fabric B obtained in the step (B) to obtain a second nonwoven fabric.

[0107] When the method for producing a nonwoven fabric according to this embodiment includes the step (C), the second nonwoven fabric is the nonwoven fabric. On the other hand, when the method for producing a nonwoven fabric according to this embodiment does not include the step (C), the first nonwoven fabric is the nonwoven fabric.

[0108] In the method for producing a nonwoven fabric according to this embodiment, the step (C) results in a nonwoven fabric with excellent stretchability. Furthermore, in the method for producing a nonwoven fabric according to this embodiment, the step (C) can increase the recovery rate of the nonwoven fabric after 50% elongation in the CD direction and the recovery rate of the nonwoven fabric after 50% elongation in the MD direction. Furthermore, in the method for producing a nonwoven fabric according to this embodiment, the step (C) partially fuses the fibers together, which makes it easier to suppress fuzzing of the nonwoven fabric.

[0109] The heating temperature range in step (C) is preferably 80°C to 135°C. The heating time within the preferred heating temperature range in step (C) is preferably 2 to 300 minutes, more preferably 5 to 100 minutes, and even more preferably 10 to 50 minutes. In step (C), by heating the first nonwoven fabric for 2 minutes or more within the preferred heating temperature range, the 50% elongation recovery rate in the CD direction and the 50% elongation recovery rate in the MD direction of the nonwoven fabric can be further increased. Furthermore, in step (C), by heating the first nonwoven fabric for 300 minutes or less within the preferred heating temperature range, the productivity of the second nonwoven fabric is improved.

[0110] In step (C), the first nonwoven fabric may be heated with a gas within the preferred heating temperature range. Examples of the gas include air and inert gas (nitrogen gas, etc.). Examples of a method for heating the first nonwoven fabric with a gas within the preferred heating temperature range include heating the first nonwoven fabric in a heating furnace with a gas within the preferred heating temperature range and / or heating the first nonwoven fabric by blowing a gas within the preferred heating temperature range onto the first nonwoven fabric.

[0111] In the step (C), the first nonwoven fabric may be sandwiched between a pair of heating rolls to heat the first nonwoven fabric within the preferable heating temperature range.

[0112] In the step (C), it is preferable to heat the first nonwoven fabric without contact within the preferred heating temperature range. In the step (C), if the first nonwoven fabric is heated by being sandwiched between a pair of heating rolls, there is a concern that the first nonwoven fabric may melt to the heating rolls. In the step (C), by heating the first nonwoven fabric within the preferred heating temperature range without contact with the heating rolls or the like, there is an advantage that it is possible to prevent the first nonwoven fabric from melting to the heating rolls or the like. Examples of a method for heating the first nonwoven fabric without contact within the preferred heating temperature range include a method of heating the first nonwoven fabric with a gas within the preferred heating temperature range.

[0113] In the step (C), the first nonwoven fabric may be heated in a state where the first nonwoven fabric is wound into a roll.

[0114] In the step (C), the first nonwoven fabric may be formed into a sheet without being wound around a roll, and then heated. For example, the first nonwoven fabric in a long shape may be continuously heated while being transported.

[0115] In step (C), the heated first nonwoven fabric is cooled to obtain a second nonwoven fabric. The method for cooling the heated first nonwoven fabric may be a method of naturally cooling the heated first nonwoven fabric at room temperature and normal pressure, or a method of forcibly cooling the heated first nonwoven fabric by blowing gas (e.g., room temperature gas) onto the heated first nonwoven fabric. The nonwoven fabric manufacturing method according to this embodiment may also include step (D) of pressurizing the first nonwoven fabric B obtained in step (B) for the purpose of fixing the shape of the nonwoven fabric, thinning it, and shaping it. In step (D), the first nonwoven fabric B obtained in step (B) is subjected to a pressure treatment. Examples of pressurization methods include pressurization using various rolls, such as an embossing roll, a pair of upper and lower rolls each having an engraved surface; an embossing roll consisting of a combination of a roll with one flat (smooth) surface and a roll with an engraved surface on the other; and a heat calendar roll consisting of a pair of upper and lower flat (smooth) rolls. Alternatively, an air-through method, in which hot air is passed through the nonwoven fabric in the thickness direction, can be used. Among these, pressurization using an embossing roll is preferred from the viewpoint of maintaining appropriate breathability while improving mechanical strength. The pressurization temperature in step (D), i.e., the surface temperature of the pressurization roll, is preferably 20°C to 120°C, more preferably 30°C to 100°C, and even more preferably 30°C to 80°C. Setting the pressurization temperature within this temperature range allows the shape of the nonwoven fabric containing the poly(3-hydroxyalkanoate) resin to be maintained while preventing peeling and fluffing of the sheet. On the other hand, if pressure is applied outside this temperature range, the strength and elongation will decrease due to heat, the fibers will not solidify, and the nonwoven fabric will not be able to maintain its shape, and the nonwoven fabric will tend to shrink or break. The pressure required for pressure application (pressure between rolls) is not particularly limited, but is preferably 20 to 60 kg / cm, more preferably 30 to 50 kg / cm, in terms of shape retention, etc. When the pressure of the pressure heat bonding roll is 20 kg / cm or more, it becomes easier to fully achieve effects such as shape fixation and thinning. When the pressure is 60 kg / cm or less, excessive stress is less likely to be applied to the nonwoven fabric, making it easier to suppress breakage of the nonwoven fabric.In the method for producing a nonwoven fabric of this embodiment, steps (A), (B), (C), and (D) may be carried out continuously or discontinuously, but carrying them out continuously is preferred in that the nonwoven fabric can be produced more efficiently.

[0116] 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.

[0117] For example, in the method for producing a nonwoven fabric according to the above embodiment, the nonwoven fabric is produced by a meltblown method, but in the method for producing a nonwoven fabric according to the present embodiment, the nonwoven fabric may be produced by a spunbond method, a flash spinning method, or an electrospinning method. In the method for producing a nonwoven fabric according to the present embodiment, the nonwoven fabric is preferably produced by a meltblown method or a spunbond method.

[0118] In a method for producing a nonwoven fabric using a spunbonding method (a method for producing a spunbonded nonwoven fabric), the ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber is 150 or more, preferably 150 to 15,000, more preferably 160 to 15,000, particularly preferably 165 to 12,000, and most preferably 200 to 10,000. When the ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber is 150 or more, the tensile elongation at break in the MD direction of the nonwoven fabric and the tensile elongation at break in the CD direction of the nonwoven fabric can be increased.

[0119] In the spunbonding method, the raw material composition is heated to melt the melt, and the melt is discharged from the nozzle hole to obtain the raw yarn. Next, the raw yarn is stretched by blowing gas onto the raw yarn. The temperature of the gas is preferably 2 to 40°C, more preferably 2 to 30°C, and even more preferably 5 to 25°C. A gas temperature of 2°C or higher allows sufficient solidification of the resin, making it easier to prevent fusion between the raw yarns. A gas temperature of 40°C or lower allows the resin to solidify slowly, making it easier to prevent breakage of the raw yarn during air stretching. In the spunbonding method, the ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can be increased by increasing the air volume of the gas blown onto the raw yarn. The ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can also be increased by reducing the amount of molten material discharged from the nozzle hole per unit time. In the spunbonding method, the raw yarn may be stretched using a stretching roll. In this case, the ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fiber can be increased by increasing the rotation speed of the drawing roll. The ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fiber can also be increased by decreasing the amount of molten material discharged from the nozzle holes per unit time. In step (B) of the method for producing a spunbonded nonwoven fabric, the fiber is drawn using, for example, a suction device such as an ejector. When an ejector is used, the spinning speed can be adjusted by adjusting the air drawing pressure. Increasing the volume of the blown air (increasing the air pressure) increases the spinning speed and further draws the fiber. In step (B), before the raw yarn extruded from the spinning nozzle in step (A) is drawn and attenuated, a device for applying rectifying air, such as quenching air, may be used to apply rectifying air to the raw yarn. The rectifying air, also known as quenching air, stabilizes the flow of the raw yarn (thread). It is also possible to cool the raw yarn (spun filament) using cooled gas. The quench air is preferably discharged through a net or mesh so as to be uniformly delivered to the yarn.The rectifying air may be blown from one or both sides of the entangled yarns, or may be blown circumferentially. In the method for producing a spunbonded nonwoven fabric, the temperature of the quench air is preferably 2 to 40°C, more preferably 2 to 30°C, and even more preferably 5 to 25°C. A quench air temperature of 2°C or higher ensures sufficient solidification of the resin, making it easier to suppress fusion between the yarns. A quench air temperature of 40°C or lower allows the resin to solidify slowly, making it easier to suppress yarn breakage during air drawing. The speed of the quench air is preferably 0.1 to 3 m / sec. A quench air speed of 0.1 m / sec or higher makes it easier to achieve the effect of rectifying the yarns. A quench air speed of 3 m / sec or lower makes it easier to suppress yarn disorder. In a method for producing a nonwoven fabric by the spunbond method, the temperature of the gas C blown onto the raw yarn A (for example, the gas blown onto the raw yarn when air-pulling it with an ejector) is preferably 2°C to 80°C, more preferably 5°C to 60°C, and even more preferably 10°C to 40°C.

[0120] In the flash spinning method, the raw material composition materials and a solvent are mixed under high temperature and pressure to obtain a melt under high temperature and pressure. The melt under high temperature and pressure is then extruded from the nozzle hole under normal temperature and pressure to obtain the raw yarn, and the obtained raw yarn is stretched. Examples of the solvent include alcohol (e.g., methanol, ethanol, etc.) and acetone. In the flash spinning method, the ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can be increased by increasing the pressure applied to the melt. The ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can also be increased by decreasing the amount of melt extruded from the nozzle hole per unit time.

[0121] In the electrospinning method, the raw material composition is heated and melted by irradiating it with laser light while a high voltage is applied. As a result, the molten material can be obtained. The molten material is then ejected from the nozzle hole to obtain a raw yarn. The raw yarn is then stretched by electrostatic force. In the electrospinning method, the ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can be increased by increasing the electrostatic force. In addition, the ratio of the nozzle hole opening area to the cross-sectional area of ​​the fiber can also be increased by decreasing the amount of molten material ejected from the nozzle hole per unit time.

[0122] Disclosure Items Each of the following items is a disclosure of a preferred embodiment.

[0123] [Item 1] A nonwoven fabric comprising fibers, wherein the fibers are formed from a resin composition containing a poly(3-hydroxyalkanoate)-based resin, the poly(3-hydroxyalkanoate)-based resin includes a copolymer having 3-hydroxybutyrate units, the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin contained in the nonwoven fabric is 70.0 mol % or more and 92.0 mol % or less, the nonwoven fabric has a tensile elongation at break in an MD direction of 100% or more, and the nonwoven fabric has a tensile elongation at break in a CD direction of 100% or more.

[0124] [Item 2] The nonwoven fabric according to item 1, wherein the nonwoven fabric has a 50% elongation recovery rate in the MD direction of 50% or more and / or a 50% elongation recovery rate in the CD direction of 50% or more.

[0125] [Item 3] The nonwoven fabric has a basis weight of 20 to 150 g / m ２ 3. The nonwoven fabric according to item 1 or 2,

[0126] [Item 4] The nonwoven fabric according to any one of Items 1 to 3, wherein the nonwoven fabric is a spun nonwoven fabric.

[0127] [Item 5] The nonwoven fabric according to any one of Items 1 to 4, wherein the poly(3-hydroxyalkanoate) resin contains a poly(3-hydroxyalkanoate) resin component having a 3-hydroxybutyrate unit content of 76 mol% or less.

[0128] [Item 6] A method for producing a nonwoven fabric using a nozzle having nozzle holes to produce a nonwoven fabric containing fibers, the method comprising: a step (A) of obtaining a raw yarn by discharging a molten material from the nozzle holes; and a step (B) of drawing the raw yarn, wherein the raw material composition contains a poly(3-hydroxyalkanoate)-based resin, the poly(3-hydroxyalkanoate)-based resin contains a copolymer having a 3-hydroxybutyrate unit, the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate)-based resin contained in the molten material is 70 mol% or more and 92 mol% or less, and the ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fibers is 300 or more.

[0129] [Item 7] The method for producing a meltblown nonwoven fabric according to Item 6, wherein in the step (B), the raw yarn is stretched by blowing gas at 150°C to 195°C onto the raw yarn.

[0130] [Item 8] A method for producing a nonwoven fabric using a nozzle having nozzle holes to produce a nonwoven fabric containing fibers, the method comprising: a step (A) of obtaining a raw yarn by discharging a molten material from the nozzle holes; and a step (B) of drawing the raw yarn, wherein the raw material composition contains a poly(3-hydroxyalkanoate)-based resin, the poly(3-hydroxyalkanoate)-based resin contains a copolymer having a 3-hydroxybutyrate unit, the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate)-based resin contained in the molten material is 70 mol% or more and 92 mol% or less, and the ratio of the opening area of ​​the nozzle holes to the cross-sectional area of ​​the fibers is 150 or more.

[0131] [Item 9] The method for producing a spunbonded nonwoven fabric according to Item 8, wherein in step (B), the raw yarn is stretched by blowing gas at 2°C to 40°C onto the raw yarn.

[0132] 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.

[0133] The following materials were prepared.

[0134] (Poly(3-hydroxyalkanoate) resin (P3HA)) The following P3HA-1 was produced according to the method described in Example 1 of WO 2019 / 142845. P3HA-1: P3HB3HH (3-hydroxybutyrate unit content: 94.5 mol%, 3-hydroxyhexanoate (3HH) unit content: 5.5 mol%) The following P3HA-2 was produced according to the method described in Example 6 of WO 2021 / 206155. P3HA-2: P3HB3HH (content of 3-hydroxybutyrate units: 85.0 mol%, content of 3-hydroxyhexanoate (3HH) units: 15.0 mol%) (weight percentage of MIBK soluble fraction: 54 wt%, content of 3-hydroxybutyrate units in the MIBK soluble fraction: 74.0 mol%, content of 3-hydroxyhexanoate (3HH) units in the MIBK soluble fraction: 26.0 mol%) (weight percentage of MIBK insoluble fraction: 46 wt%, content of 3-hydroxybutyrate units in the MIBK insoluble fraction: 98.0 mol%, content of 3-hydroxyhexanoate (3HH) units in the MIBK insoluble fraction: 2.0 mol%) Furthermore, if necessary, P3HA-1 and P3HA-2 were heat-treated under high temperature and humidity conditions (temperature: 120°C, humidity: 100%) using a highly accelerated life tester (ESPEC, EHS-222MD) to adjust the weight average molecular weight (Mw) and melt mass-flow rate (MFR) at 165°C of P3HA-1 and P3HA-2. That is, by extending the heat treatment time, the weight average molecular weight (Mw) was reduced and the melt mass-flow rate (MFR) at 165°C was increased.

[0135] The 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in P3HA-1 were determined as follows. First, 20 mg of dried P3HA-1 was added with 2 mL of a mixture of sulfuric acid and methanol (sulfuric acid volume:methanol volume=15:85) and 2 mL of chloroform. The resulting sample was sealed and heated at 100°C for 140 minutes in a sealed state to obtain a first reaction solution containing a methyl ester, a decomposition product of P3HA-1. The first reaction solution was then cooled, and 1.5 g of sodium bicarbonate was added little by little to neutralize the cooled first reaction solution. The mixture was then left to stand until the evolution of carbon dioxide gas ceased, to obtain a second reaction solution. The second reaction solution was then thoroughly mixed with 4 mL of diisopropyl ether to obtain a mixture. The mixture was then centrifuged to obtain a supernatant. The monomer unit composition of the decomposition product in the supernatant was then analyzed by capillary gas chromatography under the following conditions to determine the content of 3-hydroxybutyrate units and 3-hydroxyhexanoate (3HH) units in P3HA-1. Gas chromatograph: GC-17A manufactured by Shimadzu Corporation. 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. Regarding 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.

[0136] The 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in P3HA-2 were also determined in the same manner as the 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in P3HA-1. Furthermore, P3HA-2 was fractionated into an MIBK-soluble fraction and an MIBK-insoluble fraction by the MIBK fractionation method described above. The 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in each of the MIBK-soluble fraction and the MIBK-insoluble fraction were then determined in the same manner as the 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in P3HA-1.

[0137] (Lubricant) BA: behenic acid amide (also called "behenic acid amide") (manufactured by Nippon Fine Chemicals Co., Ltd., BNT-22H) EA: erucic acid amide (manufactured by Nippon Fine Chemicals Co., Ltd., Neutron S)

[0138] (Nucleating Agent) PETL: Pentaerythritol (manufactured by Taisei Kayaku Co., Ltd., Neuraizer P)

[0139] Examples 1 to 9 and Comparative Examples 1 and 2 The above materials were melt-kneaded in the blending ratios shown in Table 1 below to obtain raw material compositions.

[0140] (Content of each monomer unit in the entire poly(3-hydroxyalkanoate)-based resin) The content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate)-based resin contained in the raw material composition was calculated from the content of 3-hydroxybutyrate units in P3HA-1, the content of 3-hydroxybutyrate units in P3HA-2, and the blending ratio of P3HA-1 and P3HA-2. The content of 3-hydroxyhexanoate (3HH) units in the entire poly(3-hydroxyalkanoate)-based resin contained in the raw material composition was also calculated in the same manner. The "content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the raw material composition" means the "content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric" and also means the "content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the molten material." The "content of 3-hydroxyhexanoate (3HH) units in the entire poly(3-hydroxyalkanoate) resin contained in the raw material composition" means the "content of 3-hydroxyhexanoate (3HH) units in the entire poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric" and also means the "content of 3-hydroxyhexanoate (3HH) units in the entire poly(3-hydroxyalkanoate) resin contained in the molten material." The calculated values ​​are shown in Table 1 below.

[0141] (Measurement of physical properties of raw material composition) The weight average molecular weight (Mw) and melt mass flow rate (MFR) at 165°C of the raw material composition were measured. The measured values ​​are shown in Table 1 below. The weight average molecular weight (Mw) of the raw material composition was calculated by GPC measurement. The conditions for the GPC measurement are shown below. Measuring apparatus: Shimadzu 20A manufactured by Shimadzu Corporation Column: Shodex K-806M manufactured by Showa Denko Detector: RI detector Standard material: polystyrene Eluent: chloroform (HPLC grade) Flow rate: 1 mL / min Temperature: 40°C

[0142]

[0143] Using the nonwoven fabric manufacturing apparatus shown in Figures 1 to 3, a first nonwoven fabric was manufactured from the raw material composition by a melt-blown method under the conditions shown in Table 2. A nozzle with a width of 600 mm was used to manufacture the nonwoven fabric.

[0144] Next, the first nonwoven fabric was heated using a box-type hot air dryer (PH-202, manufactured by ESPEC Corporation) under the heating conditions shown in Table 2 below, and then naturally cooled at room temperature and normal pressure (20°C, 1 atmosphere) to obtain the second nonwoven fabrics of Examples 1 to 9 and Comparative Examples 1 and 2.

[0145] Example 10 The first nonwoven fabric of Example 4 was used as the nonwoven fabric of Example 10.

[0146] (Examples 11, 12, 15, 16, and Comparative Examples 3, 4) Nonwoven fabrics were obtained in the same manner as in Example 10, except that the spunbond method was used instead of the meltblown method, the above materials were melt-kneaded in the blending ratios shown in Table 1 below, a first nonwoven fabric was produced from the raw material composition under the conditions shown in Table 2 below, rectified air (quench air) at 12.5°C was blown onto the raw yarns discharged from the spinning nozzle from both sides of the entangled raw yarns at a wind speed of 0.5 m / s, and air at 25°C was blown onto the raw yarns using an ejector to air-pull the raw yarns, and a nonwoven fabric was produced under the conditions shown in Table 2 below.

[0147] (Examples 13 and 14) Nonwoven fabrics were obtained in the same manner as in Example 11, except that a first nonwoven fabric was produced from the raw material composition under the conditions shown in Table 2 below, and the first nonwoven fabric was subjected to a pressure treatment (embossing) using an embossing roll set to the temperature shown in Table 2 below.

[0148]

[0149] (Measurement of physical properties of nonwoven fabric) For the nonwoven fabric, the basis weight, thickness, average fiber diameter of the fibers, coefficient of variation of fiber diameter of the fibers, and weight average molecular weight (Mw) of the resin composition were measured. The measured values ​​are shown in Table 3 below. The average fiber diameter of the fibers and the coefficient of variation of fiber diameter of the fibers were determined using a JEOL JCM-6000 tabletop scanning electron microscope. The weight average molecular weight (Mw) of the resin composition was measured in the same manner as the weight average molecular weight (Mw) of the raw material composition.

[0150] (Maximum load, tensile elongation at maximum load, and tensile elongation at break in the CD and MD directions of nonwoven fabric) The maximum load, tensile elongation at maximum load, and tensile elongation at break in the CD and MD directions of the nonwoven fabric were measured. The maximum load, tensile elongation at maximum load, and tensile elongation at break in the CD and MD directions were measured using a constant-rate extension tensile tester in accordance with JIS B7721:2018 "Tensile tester / compression tester - Calibration and verification method for force measurement system." A universal testing machine (RTG-1210 manufactured by A&D Co., Ltd.) or the like was used as the constant-rate extension tensile tester. First, a test specimen (width: 8 mm, length: 40 mm) was cut from the nonwoven fabric. Next, the test specimen was attached to the tensile tester with an initial load and a grip spacing of 20 mm. In other words, the grip spacing when the initial load was applied to the test specimen was 20 mm. However, when the initial load was applied, the test specimen was pulled by hand to a degree that did not cause slack. A load was then applied at a pulling rate of 20 mm / min until the test specimen broke, and the maximum load in the CD and MD directions was measured. The tensile elongation at maximum load in the CD and MD directions and the tensile elongation at break were also calculated using the following formulas: Tensile elongation at maximum load (%) = [(Grip spacing at maximum load - Grip spacing when initial load was applied to the test specimen) / Grip spacing when initial load was applied to the test specimen) x 100 (%) Tensile elongation at break (%) = [(Grip spacing at break - Grip spacing when initial load was applied to the test specimen) / Grip spacing when initial load was applied to the test specimen] x 100 (%) The measured values ​​are shown in Table 3 below.

[0151] (CD Tensile Elongation at Break / MD Tensile Elongation at Break) The CD tensile elongation at break / MD tensile elongation at break (CD elongation / MD elongation) was calculated. The CD elongation / MD elongation is shown in Table 3 below.

[0152] (50% elongation recovery rate) The 50% elongation recovery rate of the nonwoven fabric was measured by the method described above. The measured values ​​are shown in Table 3 below. Note that for Comparative Example 1, the nonwoven fabric broke during the measurement of the 50% elongation recovery rate, making it impossible to measure the 50% elongation recovery rate.

[0153] (Nozzle hole opening area / cross-sectional area of ​​fiber) The nozzle hole opening area / cross-sectional area of ​​fiber was calculated by the method described above. The calculated values ​​are shown in Table 3 below.

[0154]

[0155] (Nonwoven fabric tear resistance, stretchability, and low fluffing) Two first test pieces were obtained by cutting the nonwoven fabric, as shown in Figure 4. Next, the first test pieces were welded together to produce a mask with the shape shown in Figure 5. Next, a professional technician wore the mask for three hours and evaluated it according to the following criteria. The results are shown in Table 4 below.

[0156] <Tear resistance> 3: No cracks occurred in the mask, and no tears occurred in the welded parts of the mask. 2: Cracks of less than 1 cm occurred in the mask, or tears of less than 1 cm occurred in the welded parts of the mask (no cracks of 1 cm or more occurred in the mask, and no tears of 1 cm or more occurred in the welded parts of the mask). 1: Cracks of 1 cm or more occurred in the mask, or tears of 1 cm or more occurred in the welded parts of the mask.

[0157] <Stretchability (adhesion)> 3: The mask's adhesion remained almost unchanged and it did not slip off the face. 2: The mask's adhesion decreased slightly and it sometimes slipped off the face, but this did not cause any problems in use. 1: The mask's adhesion decreased significantly and it became difficult to wear due to tearing or other reasons.

[0158] <Low pilling> 3: No pilling was visually observed on the mask. 2: Small amounts of pilling were observed on the mask, but the expert technician did not experience any itching due to the pilling. 1: The mask was heavily pilled, and the expert technician experienced itching due to the pilling.

[0159]

[0160] As shown in Tables 1, 3, and 4, in Examples 1, 3, 4, 6 to 8, and 10 to 16, which are within the scope of the present invention, the nonwoven fabrics were less likely to tear than Comparative Example 1, in which the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric had a 3-hydroxybutyrate unit content of 94.5% and the tensile elongation at break in the MD of the nonwoven fabric was 49%; Comparative Example 2, in which the CD of the nonwoven fabric had a tensile elongation at break of 95% and the MD of the nonwoven fabric had a tensile elongation at break of 93%; Comparative Example 3, in which the CD of the nonwoven fabric had a tensile elongation at break of 83%; and Comparative Example 4, in which the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric had a 3-hydroxybutyrate unit content of 94.7%, the CD of the nonwoven fabric had a tensile elongation at break of 66%, and the MD of the nonwoven fabric had a tensile elongation at break of 72%.

[0161] Furthermore, as shown in Tables 1, 3, and 4, in the method for producing a meltblown nonwoven fabric, in Examples 1, 3, 4, 6 to 8, and 10 within the scope of the present invention, the nonwoven fabrics were less likely to tear than Comparative Example 1, in which the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the melt was 94.5%, and Comparative Example 2, in which the ratio of the nozzle hole opening area to the fiber cross-sectional area was 238. Furthermore, as shown in Tables 1, 3, and 4, in the method for producing a spunbonded nonwoven fabric, in Examples 11 to 16 within the scope of the present invention, the nonwoven fabrics were less likely to tear than Comparative Example 3, in which the ratio of the nozzle hole opening area to the fiber cross-sectional area was 113, and Comparative Example 4, in which the poly(3-hydroxyalkanoate) resin contained in the melt contained 94.7% 3-hydroxybutyrate units.

[0162] As shown in Table 3, in Examples 1 to 10, which are within the scope of the present invention, the tensile elongation at break in the CD direction and the tensile elongation at break in the MD direction were higher than in Comparative Examples 1 and 2. Therefore, it is presumed that the nonwoven fabrics in Examples 2, 5, and 9, like Examples 1, 3, 4, 6 to 8, and 10, are less likely to tear than those in Comparative Examples 1 and 2.

[0163] Therefore, it can be seen that the present invention can provide a tear-resistant nonwoven fabric.

[0164] Furthermore, as shown in Tables 3 and 4, in Examples 1, 3, 4, and 10, in which the weight average molecular weight (Mw) of the resin composition was 150,000 or more, the nonwoven fabrics were less likely to tear than in Examples 6 and 7, in which the weight average molecular weight (Mw) of the resin composition was 147,000 or less. Therefore, it can be seen that a resin composition with a weight average molecular weight (Mw) of 150,000 or more makes the nonwoven fabric less likely to tear.

[0165] Furthermore, as shown in Tables 1 and 4, in Examples 1, 3, 4, and 10, in which the weight-average molecular weight (Mw) of the raw material composition was 200,000 or more, the nonwoven fabrics were less likely to tear than in Examples 6 and 7, in which the weight-average molecular weight (Mw) of the raw material composition was 198,000 or less. This shows that a raw material composition with a weight-average molecular weight (Mw) of 200,000 or more makes the nonwoven fabric less likely to tear.

[0166] Furthermore, as shown in Table 4, the nonwoven fabrics of Examples 1, 3, 4, and 10 were less likely to tear than Example 8.

[0167] Furthermore, as shown in Table 4, in Examples 1, 3, 4, 6 to 8, and 10 to 16, which are within the scope of the present invention, the nonwoven fabrics were superior in stretchability compared to Comparative Examples 1 to 4.

[0168] Furthermore, as shown in Table 4, in Example 4, in which the second nonwoven fabric was obtained by heating the first nonwoven fabric, which is the nonwoven fabric of Example 10, the nonwoven fabric had superior stretchability compared to Example 10. Therefore, it can be seen that heating a nonwoven fabric makes the nonwoven fabric superior in stretchability.

[0169] Furthermore, as shown in Table 3, in Example 4, in which the second nonwoven fabric was obtained by heating the first nonwoven fabric, which was the nonwoven fabric of Example 10, the recovery rate of the nonwoven fabric from 50% elongation in the CD direction and the recovery rate of the nonwoven fabric from 50% elongation in the MD direction were high. Therefore, it can be seen that heating a nonwoven fabric increases the recovery rate of the nonwoven fabric from 50% elongation in the CD direction and the recovery rate of the nonwoven fabric from 50% elongation in the MD direction.

[0170] Furthermore, as shown in Table 4, in Examples 1, 3, 4, 6 to 8, and 10 to 16, which are within the scope of the present invention, the nonwoven fabrics had less fluffing than Comparative Examples 1 and 4.

[0171] Furthermore, as shown in Table 4, in Examples 13 and 14 in which the first nonwoven fabric was pressure treated, the nonwoven fabric had little fluff.

[0172] 1: Nonwoven fabric manufacturing apparatus, 2: Hopper, 3: Extruder, 4: Gear pump, 5: Filter, 6: Kneader, 7: Nozzle, 7a: Nozzle hole, 8: Collector, 8a: Conveyor belt, 8b: Roller, 9: Winding device, A: Raw yarn, B: First nonwoven fabric, C: Gas

Claims

1. Nonwoven fabric containing fibers, The aforementioned fiber is formed from a resin composition containing a poly(3-hydroxyalkanoate) resin, The poly(3-hydroxyalkanoate) resin comprises a copolymer having 3-hydroxybutyrate units. The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric is 70.0 mol% or more and 92.0 mol% or less. The tensile elongation at the breaking point of the nonwoven fabric in the MD direction is 100% or more. The tensile elongation at the breaking point of the nonwoven fabric in the CD direction is 100% or more. The poly(3-hydroxyalkanoate) resin is a nonwoven fabric containing a poly(3-hydroxyalkanoate) resin component in which the content of 3-hydroxybutyrate units is 76 mol% or less.

2. The nonwoven fabric according to claim 1, wherein the 50% elongation recovery rate of the nonwoven fabric in the MD direction is 50% or more, and / or the 50% elongation recovery rate of the nonwoven fabric in the CD direction is 50% or more.

3. The basis weight of the aforementioned nonwoven fabric is 20 to 150 g / m². ２ The nonwoven fabric according to claim 1 or 2.

4. The nonwoven fabric according to claim 1 or 2, wherein the nonwoven fabric is a direct-spun nonwoven fabric.

5. A method for manufacturing a nonwoven fabric, comprising using a nozzle having nozzle holes to produce a nonwoven fabric containing fibers, Step (A) involves obtaining raw yarn by discharging the molten material from the nozzle hole, The process includes (B) stretching the aforementioned yarn, The aforementioned raw material composition contains a poly(3-hydroxyalkanoate) resin, The poly(3-hydroxyalkanoate) resin comprises a copolymer having 3-hydroxybutyrate units. The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten material is 70 mol% or more and 92 mol% or less. The ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber is 300 or more. The method for producing a meltblown nonwoven fabric comprises a poly(3-hydroxyalkanoate) resin component having a 3-hydroxybutyrate unit content of 76 mol% or less.

6. The method for producing a meltblown nonwoven fabric according to claim 5, wherein in step (B), the yarn is stretched by blowing a gas at 150°C to 195°C onto the yarn.

7. A method for manufacturing a nonwoven fabric, comprising using a nozzle having nozzle holes to produce a nonwoven fabric containing fibers, Step (A) involves obtaining raw yarn by discharging the molten material from the nozzle hole, The process includes (B) stretching the aforementioned yarn, The aforementioned raw material composition contains a poly(3-hydroxyalkanoate) resin, The poly(3-hydroxyalkanoate) resin comprises a copolymer having 3-hydroxybutyrate units. The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin contained in the molten material is 70 mol% or more and 92 mol% or less. The ratio of the opening area of ​​the nozzle hole to the cross-sectional area of ​​the fiber is 150 or more. The method for producing a spunbond nonwoven fabric includes a poly(3-hydroxyalkanoate) resin component having a 3-hydroxybutyrate unit content of 76 mol% or less.

8. The method for producing a spunbond nonwoven fabric according to claim 7, wherein in step (B), the yarn is stretched by blowing a gas at 2°C to 40°C onto the yarn.