Melt-blown nonwoven fabric, laminate, filter for mask, and mask

Abstract

The present invention provides a melt-blown nonwoven fabric which is hard to tear and has high particle collection efficiency. The present invention is a melt-blown nonwoven fabric containing a fiber, wherein: the fiber is formed of a resin composition containing a poly(3-hydroxyalkanoate)-based resin; the poly(3-hydroxyalkanoate)-based resin contains a copolymer having a 3-hydroxybutyrate unit; the content ratio of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate)-based resin is 80.0-93.5 mol%; and the average fiber diameter in the fiber is at most 8.0 μm.

Description

Meltblown nonwoven fabric, laminate, mask filter, and mask

[0001] The present invention relates to a meltblown nonwoven fabric, a laminate, a mask filter, and a mask.

[0002] Meltblown nonwoven fabrics are nonwoven fabrics obtained by a meltblowing method in which a polymer and hot air are extruded together from a spinneret. Meltblown nonwoven fabrics have a microporous structure. Meltblown nonwoven fabrics are used, for example, as materials for constituting removal filters (a concept that also includes mask filters, filtration filters, etc.) that remove particles (e.g., particles with viruses or the like attached, pollen, etc.), blood filters that capture blood cells, and beverage extraction filters (e.g., coffee drip filters, tea bags, etc.) (see, for example, Patent Document 1).

[0003] As fibers constituting nonwoven fabrics, fibers containing poly(3-hydroxyalkanoate) resin, which is a biodegradable resin, are used from the viewpoint of reducing the burden on the global environment (for example, Patent Document 2).

[0004] JP 2022-505070 A, WO 2019 / 142920

[0005] Incidentally, meltblown nonwoven fabrics are required to have high particle collection efficiency (e.g., particles with blood cells, pollen, coffee grounds, tea leaves, viruses, etc.). For this reason, the particle collection efficiency of meltblown nonwoven fabrics has been improved by charging the nonwoven fabric with corona discharge. However, techniques other than charging have not been fully investigated to improve the particle collection efficiency of meltblown nonwoven fabrics.

[0006] Meltblown nonwoven fabrics may also be required to be tear-resistant.

[0007] Therefore, an object of the present invention is to provide a meltblown nonwoven fabric that is tear-resistant and has high particle collection efficiency. Another object of the present invention is to provide a laminate including the meltblown nonwoven fabric, a mask filter formed from the meltblown nonwoven fabric or the laminate, and a mask including the mask filter.

[0008] The first aspect of the present invention relates to a meltblown nonwoven fabric containing 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 having 3-hydroxybutyrate units, the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin is 80.0 mol % or more and 93.5 mol % or less, and the average fiber diameter of the fibers is 8.0 μm or less.

[0009] A second aspect of the present invention relates to a laminate comprising a first nonwoven fabric and a second nonwoven fabric laminated on at least one side of the first nonwoven fabric, wherein the first nonwoven fabric is the meltblown nonwoven fabric, and the second nonwoven fabric is a nonwoven fabric containing cellulosic fibers.

[0010] A third aspect of the present invention relates to a mask filter formed from the meltblown nonwoven fabric or the laminate.

[0011] A fourth aspect of the present invention relates to a mask comprising a mask body and the mask filter.

[0012] According to the present invention, it is possible to provide a meltblown nonwoven fabric that is tear-resistant and has high particle collection efficiency. Furthermore, according to the present invention, it is possible to provide a laminate including the meltblown nonwoven fabric, a mask filter formed from the meltblown nonwoven fabric or the laminate, and a mask including the mask filter.

[0013] 1 is a schematic diagram of a meltblown nonwoven fabric manufacturing apparatus; a schematic perspective view of a nozzle; a schematic cross-sectional view of a nozzle hole and a conveyor belt; a photograph of a first test piece; a photograph of a second test piece; and a photograph of a mask body.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0015] <Meltblown Nonwoven Fabric> First, the meltblown nonwoven fabric according to this embodiment will be described. The meltblown 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 is 80.0 mol% or more and 93.5 mol% or less. The average fiber diameter of the fibers is 8.0 μm or less.

[0016] The meltblown nonwoven fabric according to the present embodiment is a nonwoven fabric obtained by the meltblown method. Note that the meltblown nonwoven fabric according to the present embodiment is a concept that also includes nonwoven fabrics obtained by the spunblown (registered trademark) method.

[0017] The resin composition contains a polymer component. The resin composition may further contain an additive.

[0018] 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.

[0019] 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.

[0020] The poly(3-hydroxyalkanoate) resin includes a copolymer having a 3-hydroxybutyrate unit.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin is 80.0 mol% or more and 93.5 mol% or less, preferably 82.0 mol% or more and 93.0 mol% or less, and 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 is 80.0 mol% or more, the rigidity of the fibers is increased. When the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin is 93.5 mol% or less, the meltblown 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 93.5 mol% or less, the meltblown nonwoven fabric according to this embodiment is less likely to fluff. The content ratio of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin means the content ratio of the 3-hydroxybutyrate unit in the entire poly(3-hydroxyalkanoate) resin contained in the nonwoven fabric.

[0025] The content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin can be determined as follows. First, 20 mg of the dried poly(3-hydroxyalkanoate) resin from the meltblown nonwoven fabric is added with 2 mL of a mixture of sulfuric acid and methanol (volume of sulfuric acid:volume of methanol=15:85) and 2 mL of chloroform. The resulting sample is 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.

[0026] 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 be used as the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin of the meltblown nonwoven fabric.

[0027] From the viewpoint of improving the mechanical properties of the meltblown 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).

[0028] (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.

[0029] 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%. 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.

[0030] 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 %.

[0031] 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.

[0032] P3HB has the function of promoting the crystallization of P3HB itself and poly(3-hydroxyalkanoate) resins other than P3HB.

[0033] The other polymer is preferably biodegradable.

[0034] 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.

[0035] The meltblown nonwoven fabric according to this embodiment contains a biodegradable polymer, so that even if the meltblown nonwoven fabric is discarded in the environment, the meltblown nonwoven fabric is easily decomposed in the environment, thereby reducing the burden on the environment.

[0036] The resin composition may further contain an additive.

[0037] Examples of additives include nucleating agents, lubricants, stabilizers (antioxidants, ultraviolet absorbers, etc.), colorants (dyes, pigments, etc.), plasticizers, inorganic fillers, organic fillers, antistatic agents, etc.

[0038] 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) resin. The nucleating agent has a higher melting point than the poly(3-hydroxyalkanoate) resin. By containing the nucleating agent in the resin composition, crystallization of the poly(3-hydroxyalkanoate) resin is promoted when producing a meltblown nonwoven fabric by the meltblown method, 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.

[0039] 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.

[0040] 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.

[0041] 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 meltblown nonwoven fabric by the meltblown method. 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 easily obtaining fibers when producing a meltblown nonwoven fabric by the meltblown method. 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.

[0042] The resin composition preferably contains the lubricant. When producing a meltblown nonwoven fabric by the meltblown method, 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 manufacturing 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 meltblown nonwoven fabric. Examples of the lubricant include compounds having an amide bond. The compound having an amide bond preferably contains one or more selected from lauric acid amide, myristic acid amide, stearic acid amide, behenic acid amide, and erucic acid amide.

[0043] 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 meltblown nonwoven fabric by the meltblown method. 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. By setting the content of the lubricant in the resin composition to 12 parts by mass or less per 100 parts by mass of the polymer component, there is an advantage in that bleeding out of the lubricant onto the surface of the fiber can be suppressed.

[0044] The melt mass flow rate (MFR) of the resin composition at 165°C is preferably 50 to 1500 g / 10 min, more preferably 70 to 1500 g / 10 min, still more preferably 80 to 1300 g / 10 min, and particularly preferably 80 to 1200 g / 10 min.

[0045] When the resin composition in the fibers has a melt mass flow rate of 1500 g / 10 min or less at 165°C, the strength and elongation of the meltblown nonwoven fabric are increased. When the resin composition in the fibers has a melt mass flow rate of 50 g / 10 min or more at 165°C, the tension applied to the fibrous melt during stretching can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting meltblown nonwoven fabric. As a result, the particle collection efficiency of the meltblown nonwoven fabric can be easily improved.

[0046] 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.

[0047] The weight average molecular weight of the resin composition is preferably 100,000 to 250,000, more preferably 110,000 to 200,000, and even more preferably 110,000 to 180,000.

[0048] When the weight-average molecular weight of the resin composition in the fibers is 100,000 or more, the strength and elongation of the meltblown nonwoven fabric are increased. When the weight-average molecular weight of the resin composition in the fibers is 250,000 or less, the tension applied to the fibrous molten material during stretching can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting meltblown nonwoven fabric. As a result, it is easier to improve the particle collection efficiency of the meltblown nonwoven fabric.

[0049] 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.

[0050] The average fiber diameter of the fibers is 8.0 μm or less, preferably 5.0 μm or less, more preferably 3.3 μm or less, and even more preferably 3.0 μm or less. The average fiber diameter of the fibers is preferably 0.50 to 8.0 μm, more preferably 0.50 to 5.0 μm, even more preferably 0.50 to 3.3 μm, even more preferably 0.50 to 3.0 μm, particularly preferably 0.80 to 2.8 μm, and especially preferably 1.0 to 2.6 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.

[0051] When the average fiber diameter of the fibers is 8.0 μm or less, the particle collection efficiency of the meltblown nonwoven fabric is improved. When the average fiber diameter of the fibers is 0.50 μm or more, the strength and elongation of the meltblown nonwoven fabric are improved. When the fiber diameter coefficient of variation of the fibers is 0.40 or less, extremely thick fibers are reduced, resulting in a further improvement in the particle collection efficiency of the meltblown 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 improvement in the strength and elongation of the meltblown nonwoven fabric.

[0052] The average fiber diameter and coefficient of variation of the fibers can be determined as follows. First, a test piece is obtained from a meltblown 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.

[0053] The basis weight of the meltblown nonwoven fabric according to this embodiment is preferably 20 to 80 g / m ２ , more preferably 25 to 77 g / m ２ , more preferably 30 to 75 g / m ２ The meltblown nonwoven fabric according to this embodiment has a basis weight of 20 g / m ２ By satisfying the above, the strength and elongation of the meltblown nonwoven fabric are increased, and the particle collection efficiency of the meltblown nonwoven fabric is further improved. ２ By satisfying the condition below, liquid permeability (water permeability, etc.) or breathability can be improved.

[0054] The basis weight of the meltblown nonwoven fabric according to this embodiment can be determined as follows. First, a test piece is obtained from the meltblown 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.

[0055] The thickness of the meltblown nonwoven fabric according to this embodiment is preferably 0.10 to 0.40 mm, more preferably 0.15 to 0.35 mm. Having a thickness of 0.10 to 0.40 mm makes it easier to obtain a homogeneous meltblown nonwoven fabric when producing the meltblown nonwoven fabric. Having a thickness of 0.10 mm or more increases the strength and elongation of the meltblown nonwoven fabric, and further enhances the particle collection efficiency of the meltblown nonwoven fabric. Furthermore, having a thickness of 0.40 mm or less makes it possible to improve the liquid permeability (e.g., water permeability) or breathability of the meltblown nonwoven fabric.

[0056] The thickness of the meltblown nonwoven fabric according to this embodiment can be determined by measuring the thickness of the meltblown nonwoven fabric at three or more points with a thickness meter, and taking the arithmetic mean value of the measured thicknesses. Examples of thickness meter include "PEACOCK" manufactured by Ozaki Seisakusho Co., Ltd.

[0057] Furthermore, the average pore size of the meltblown nonwoven fabric according to this embodiment is preferably 2.5 μm or more and 10.0 μm or less, more preferably 3.0 μm or more and 7.0 μm or less. When the average pore size of the meltblown nonwoven fabric according to this embodiment is 2.5 μm or more, the liquid permeability (water permeability, etc.) or breathability of the meltblown nonwoven fabric can be improved. When the average pore size of the meltblown nonwoven fabric according to this embodiment is 10.0 μm or less, the particle collection efficiency of the meltblown nonwoven fabric is further improved.

[0058] The average pore size of the meltblown 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, for example, using a Perm Porometer (manufactured by PMI).

[0059] The tensile elongation at break in the MD direction (also simply referred to as "MD elongation") of the meltblown nonwoven fabric according to this embodiment is preferably 50% or more, more preferably 100% or more, even more preferably 120% or more, and particularly preferably 150% or more. The MD elongation of the meltblown nonwoven fabric according to this embodiment is, for example, 500% or less. By having an MD elongation of 50% or more, the meltblown 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 93.5 mol% or less, the MD elongation is likely to be increased.

[0060] The tensile elongation at break in the CD direction (also simply referred to as "CD elongation") of the meltblown nonwoven fabric according to this embodiment is preferably 50% or more, more preferably 100% or more, even more preferably 120% or more, and particularly preferably 150% or more. The CD elongation of the meltblown nonwoven fabric according to this embodiment is, for example, 500% or less. By having a CD elongation of 50% or more, the meltblown nonwoven fabric according to this embodiment is less likely to tear even when pulled in the CD direction. By setting the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin to 93.5 mol% or less, the CD elongation is likely to be increased.

[0061] When the tensile elongation at break in the MD direction of the meltblown nonwoven fabric is 120% or more and the tensile elongation at break in the CD direction of the meltblown nonwoven fabric is 120% or more, the meltblown nonwoven fabric becomes even more resistant to tearing.

[0062] Here, the MD direction is the direction in which the meltblown 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.

[0063] The ratio of the tensile elongation at break in the CD direction of the meltblown nonwoven fabric to the tensile elongation at break in the MD direction of the meltblown 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 meltblown nonwoven fabric according to this embodiment, stress concentration in only one of the CD direction and the MD direction in the meltblown nonwoven fabric is suppressed, resulting in the meltblown nonwoven fabric being less likely to tear. By setting the content of the 3-hydroxybutyrate unit in the poly(3-hydroxyalkanoate) resin to 93.5 mol% or less, the CD elongation / MD elongation is more likely to be within the range of 0.50 to 2.00.

[0064] The tensile elongation at break can be measured using a constant-rate extension tensile tester in accordance with 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 meltblown 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 (%)

[0065] The meltblown nonwoven fabric according to this embodiment can be suitably used, for example, as a material for a filter, etc. 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.).

[0066] Furthermore, two or more sheets of the meltblown nonwoven fabric according to this embodiment may be laminated together and used as a material for a filter, etc.

[0067] <Laminate> The laminate according to this embodiment includes a first nonwoven fabric and a second nonwoven fabric laminated on at least one side of the first nonwoven fabric. The first nonwoven fabric is the meltblown nonwoven fabric according to this embodiment. The second nonwoven fabric contains cellulosic fibers.

[0068] Examples of the cellulosic fibers include cotton fibers, rayon (a concept that also includes cupra (also called "cuprammonium rayon")), and acetate fibers. Such a laminate has high particle collection efficiency due to the first nonwoven fabric, and the strength of the laminate is further increased due to the second nonwoven fabric. Examples of the second nonwoven fabric include spunlace nonwoven fabric.

[0069] <Mask Filter> The mask filter according to this embodiment is formed from the meltblown nonwoven fabric according to this embodiment or the laminate according to this embodiment.

[0070] <Mask> The mask according to this embodiment may include a mask body and the mask filter according to this embodiment.

[0071] The mask body includes a pair of ear loops and a holder for holding the mask filter. The mask according to this embodiment may be configured so that the mask filter is detachable from the holder.

[0072] Furthermore, the mask according to this embodiment may be configured such that the mask body and the mask filter are integrated into one body.

[0073] Furthermore, the mask according to this embodiment may be a disposable mask.

[0074] The mask according to the present embodiment may have a two-layer or more structure in which the meltblown nonwoven fabric according to the present embodiment and a base sheet are laminated together. Specifically, the mask according to the present embodiment may have a three-layer structure in which a base sheet, the meltblown nonwoven fabric according to the present embodiment, and a base sheet are laminated together in this order.

[0075] The base sheet includes fibers, and examples of the base sheet include nonwoven fabrics and woven fabrics.

[0076] Examples of the fiber material of the base sheet include cellulose-based fibers, polypropylene-based fibers (PP-based fibers), polyethylene terephthalate-based fibers (PET-based fibers), polybutylene terephthalate-based fibers (PBT-based fibers), etc. Examples of the cellulose-based fibers that are the fibers of the base sheet include cotton fibers, rayon (a concept that also includes cupra (also called "cuprammonium rayon")), acetate fibers, etc. The fibers of the base sheet may be long fibers or short fibers.

[0077] Examples of nonwoven fabrics that can be used as the substrate sheet include spunbond nonwoven fabrics and spunlace nonwoven fabrics.

[0078] An example of a woven fabric that can serve as a base sheet is gauze, which contains cotton fibers.

[0079] Examples of nonwoven fabrics that serve as substrate sheets containing cellulosic fibers include nonwoven fabrics manufactured by a wet staple fiber spunbonding method. Examples of nonwoven fabrics manufactured by the wet staple fiber spunbonding method include TCF (registered trademark) series nonwoven fabrics (manufactured by Futamura Chemical Co., Ltd.). TCF (registered trademark) series nonwoven fabrics are nonwoven fabrics manufactured by the TCF (registered trademark) method.

[0080] Examples of fibers constituting the spunlace nonwoven fabric include cellulosic fibers, and specifically, rayon fibers.

[0081] Examples of fibers that make up the spunbond nonwoven fabric include polypropylene fibers (PP fibers), polyethylene terephthalate fibers (PET fibers), and polybutylene terephthalate fibers (PBT fibers).

[0082] The mask according to the present embodiment has a three-layer structure in which a spunbond nonwoven fabric, a meltblown nonwoven fabric according to the present embodiment, and a spunbond nonwoven fabric are laminated in this order, i.e., has an SMS three-layer structure. In other words, the mask may be an SMS mask.

[0083] The mask according to the present embodiment may include the second nonwoven fabric and / or woven fabric. The mask according to the present embodiment may have a three-layer structure in which the second nonwoven fabric or woven fabric, the meltblown nonwoven fabric according to the present embodiment, and the second nonwoven fabric or woven fabric are laminated in this order. In other words, the mask according to the present embodiment may use a second nonwoven fabric and / or woven fabric instead of the spunbond nonwoven fabric in the SMS mask.

[0084] <Method for producing meltblown nonwoven fabric> The method for producing a meltblown nonwoven fabric according to this embodiment is a method for obtaining the meltblown nonwoven fabric by a meltblown method. The method for producing a meltblown nonwoven fabric according to this embodiment includes a step (A) of melting a raw material composition by heating to obtain a molten material, and a step (B) of obtaining a meltblown nonwoven fabric from the molten material. The meltblown method is a concept that also includes the Spunblown (registered trademark) method.

[0085] The melt mass flow rate (MFR) of the raw material composition at 165°C is preferably 30 to 1500 g / 10 min, more preferably 30 to 1000 g / 10 min, still more preferably 50 to 1000 g / 10 min, and particularly preferably 50 to 800 g / 10 min.

[0086] 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 meltblown nonwoven fabric are further increased. When the raw material composition has a melt mass flow rate of 30 g / 10 min or more at 165°C, the tension applied to the fibrous molten material during stretching can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting meltblown nonwoven fabric. As a result, the particle collection efficiency of the meltblown nonwoven fabric is further improved.

[0087] 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.

[0088] The weight average molecular weight of the raw material composition is preferably 100,000 to 350,000, more preferably 110,000 to 300,000, and even more preferably 110,000 to 250,000.

[0089] When the weight-average molecular weight of the raw material composition is 100,000 or more, the strength and elongation of the meltblown nonwoven fabric are further increased. When the weight-average molecular weight of the raw material composition is 350,000 or less, the tension applied to the fibrous molten material during stretching can be reduced, making it easier to reduce the fiber diameter of the fibers in the resulting meltblown nonwoven fabric. As a result, the particle collection efficiency of the meltblown nonwoven fabric is further improved.

[0090] In the method for producing a meltblown nonwoven fabric according to this embodiment, a meltblown nonwoven fabric is obtained from the raw material composition using a meltblown nonwoven fabric production apparatus.

[0091] As shown in FIG. 1 , the meltblown 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 (hereinafter also referred to as a "kneaded molten material"), a nozzle 7 that discharges the molten kneaded material in a fibrous form, a collector 8 that collects and cools the fibrous molten kneaded material to obtain a first meltblown nonwoven fabric B, and a winding device 9 that winds up the first meltblown nonwoven fabric B.

[0092] Furthermore, the meltblown nonwoven fabric manufacturing apparatus 1 may, if necessary, be provided with a gear pump 4 that supplies the molten material to the kneader 6. By providing the gear pump 4, the meltblown nonwoven fabric manufacturing apparatus 1 can suppress fluctuations in the amount of molten material supplied to the kneader 6.

[0093] Furthermore, the meltblown nonwoven fabric manufacturing apparatus 1 may be provided with a filter 5 upstream of the kneader 6 to remove foreign matter from the molten material, if necessary.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] In the step (B), the melted and kneaded material is discharged from the nozzle 7 in the form of fibers.

[0100] The nozzle 7 is a spinning die head. In Fig. 2, the nozzle 7 has a plurality of nozzle holes 7a that discharge the molten kneaded material in a fibrous form. As shown in Fig. 2, the nozzle 7 discharges a plurality of fibrous molten kneaded materials A. Note that the nozzle 7 may have only one nozzle hole 7a. In other words, the nozzle 7 may discharge only one raw yarn A.

[0101] 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 opening diameter of the nozzle holes 7a is appropriately selected depending on the fiber diameter of the fibers of the meltblown nonwoven fabric. The opening 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 opening diameter 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 average value of the opening diameter.

[0102] In the nozzle 7, a plurality of nozzle holes 7a are arranged in a row with a gap therebetween. In FIG. 2, a 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 making the distance (spacing) between adjacent nozzle holes 7a 0.05 mm or more, it is possible to suppress fusion of adjacent fibers, and as a result, it is possible to reduce the coefficient of variation of the fiber diameter of the fibers. 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 is preferably uniform in that it facilitates the production of a homogeneous meltblown nonwoven fabric. The distance (spacing) between adjacent nozzle holes 7a means the arithmetic mean value of the distance (spacing) between adjacent nozzle holes 7a.

[0103] The collector 8 has a collecting surface that collects the fibrous kneaded material 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.

[0104] 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.

[0105] As shown in FIG. 3, the meltblown nonwoven fabric manufacturing apparatus 1 is configured to stretch the fibrous melt-kneaded material A by blowing a high-temperature gas C onto the fibrous melt-kneaded material A.

[0106] In the step (B), a high-temperature gas C is blown onto the fibrous melt-kneaded material A, and the high-temperature gas C blown onto the melt-kneaded material A is passed through a mesh conveyor belt 8a. In the step (B), the high-temperature gas C is preferably sucked by suction (not shown) so that the high-temperature gas C blown onto the melt-kneaded material A can easily pass through the mesh conveyor belt 8a. This makes it easier to prevent the fibers from bouncing off the collection surface of the mesh conveyor belt 8a, and as a result, it becomes easier to form a first meltblown nonwoven fabric B in which the fibers are well fused together.

[0107] In the step (B), the stretched fibrous melt-kneaded product A is collected by the conveyor belt 8a and cooled while being conveyed by the conveyor belt 8a, thereby obtaining a first melt-blown nonwoven fabric.

[0108] 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 meltblown nonwoven fabric B, does not excessively fuse with the first meltblown nonwoven fabric B, and is a material from which the first meltblown nonwoven fabric B can be peeled off.

[0109] 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).

[0110] The flow rate of the high-temperature gas C blown onto the fibrous melt-kneaded material A is preferably 500 NL / min or more, more preferably 1000 NL / min or more, and even more preferably 2000 NL / min or more. The flow rate of the high-temperature gas C blown onto the fibrous melt-kneaded material A is preferably 12000 NL / min or less, and more preferably 10000 NL / min or less.

[0111] In the step (B), the temperature and flow rate of the high-temperature gas C are appropriately controlled in order to obtain a meltblown nonwoven fabric having a high degree of crystallinity.

[0112] The speed at which the first meltblown 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 amount of the raw material composition and the apparent density of the resulting meltblown nonwoven fabric B. The speed is preferably in the range of 1.0 m / min to 6.0 m / min.

[0113] In the step (B), the first meltblown nonwoven fabric B is transported by the conveyor belt 8a to the winding device 9, and the first meltblown nonwoven fabric B is wound up in a roll by the winding device 9.

[0114] The method for producing a meltblown nonwoven fabric according to this embodiment may include a step (C) of heating the first meltblown nonwoven fabric B obtained in the step (B) to obtain a second meltblown nonwoven fabric.

[0115] When the method for producing a meltblown nonwoven fabric according to this embodiment includes the step (C), the second meltblown nonwoven fabric becomes the meltblown nonwoven fabric. On the other hand, when the method for producing a meltblown nonwoven fabric according to this embodiment does not include the step (C), the first meltblown nonwoven fabric becomes the meltblown nonwoven fabric.

[0116] In the method for producing a meltblown nonwoven fabric according to this embodiment, the step (C) makes the nonwoven fabric less likely to tear. Furthermore, in the method for producing a meltblown nonwoven fabric according to this embodiment, the step (C) can increase the tensile elongation at break in the CD direction and the tensile elongation at break in the MD direction of the meltblown nonwoven fabric. Furthermore, in the method for producing a meltblown nonwoven fabric according to this embodiment, the step (C) partially fuses the fibers together, which makes it easier to suppress fuzzing of the meltblown nonwoven fabric.

[0117] The heating temperature range in step (C) is preferably 80°C to 135°C. The heating time range 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 meltblown nonwoven fabric for 2 minutes or more within the preferred heating temperature range, the tensile elongation at break in the CD direction and the tensile elongation at break in the MD direction of the meltblown nonwoven fabric can be further increased. Furthermore, in step (C), by heating the first meltblown nonwoven fabric for 300 minutes or less within the preferred heating temperature range, the productivity of the second meltblown nonwoven fabric is improved.

[0118] In step (C), the first meltblown 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.). Methods for heating the first meltblown nonwoven fabric with a gas within the preferred heating temperature range include heating the first meltblown nonwoven fabric in a heating furnace with a gas within the preferred heating temperature range, and / or heating the first meltblown nonwoven fabric by blowing a gas within the preferred heating temperature range onto the first meltblown nonwoven fabric.

[0119] In the step (C), the first meltblown nonwoven fabric may be sandwiched between a pair of heating rolls to heat the first meltblown nonwoven fabric within the preferred heating temperature range.

[0120] In the step (C), it is preferable to heat the first meltblown nonwoven fabric without contact within the preferred heating temperature range. In the step (C), if the first meltblown nonwoven fabric is heated by being sandwiched between a pair of heating rolls, there is a concern that the first meltblown nonwoven fabric may be welded to the heating rolls. In the step (C), by heating the first meltblown 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 meltblown nonwoven fabric from being welded to the heating rolls or the like. Examples of methods for heating the first meltblown nonwoven fabric without contact within the preferred heating temperature range include a method of heating the first meltblown nonwoven fabric with a gas within the preferred heating temperature range.

[0121] In the step (C), the first meltblown nonwoven fabric may be heated in a state where the first meltblown nonwoven fabric is wound around a roll.

[0122] In the step (C), the first meltblown nonwoven fabric may be formed into a sheet without being wound around a roll, and then the first meltblown nonwoven fabric may be heated. For example, the first meltblown nonwoven fabric in a long shape may be continuously heated while being transported.

[0123] In step (C), the heated first meltblown nonwoven fabric is cooled to obtain a second meltblown nonwoven fabric. The method for cooling the heated first meltblown nonwoven fabric may be a method in which the heated first meltblown nonwoven fabric is naturally cooled at room temperature and normal pressure, or the heated first meltblown nonwoven fabric may be forcibly cooled by blowing gas (e.g., gas at room temperature) onto the heated first meltblown nonwoven fabric.

[0124] Disclosure Items Each of the following items is a disclosure of a preferred embodiment.

[0125] [Item 1] A meltblown nonwoven fabric containing 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 having 3-hydroxybutyrate units, the content of the 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate)-based resin is 80.0 mol% or more and 93.5 mol% or less, and the fibers have an average fiber diameter of 8.0 μm or less.

[0126] [Item 2] The meltblown nonwoven fabric according to item 1, wherein the average fiber diameter is 5.0 μm or less.

[0127] [Item 3] The meltblown nonwoven fabric according to item 2, wherein the average fiber diameter is 3.0 μm or less.

[0128] [Item 4] The meltblown nonwoven fabric has a basis weight of 20 to 80 g / m ２ 4. The meltblown nonwoven fabric according to any one of items 1 to 3, wherein

[0129] [Item 5] The meltblown nonwoven fabric according to any one of Items 1 to 4, wherein the resin composition has a weight average molecular weight of 100,000 to 250,000.

[0130] [Item 6] The meltblown nonwoven fabric has a tensile elongation at break in the MD direction of 50% or more, and a tensile elongation at break in the CD direction of 50% or more. The meltblown nonwoven fabric according to any one of items 1 to 5.

[0131] [Item 7] The ratio of the tensile elongation at break in the CD direction of the meltblown nonwoven fabric to the tensile elongation at break in the MD direction of the meltblown nonwoven fabric is 0.50 to 2.00. The meltblown nonwoven fabric according to any one of items 1 to 6.

[0132] [Item 8] The meltblown nonwoven fabric according to any one of Items 1 to 7, wherein the poly(3-hydroxyalkanoate) resin contains a poly(3-hydroxyalkanoate) resin component having a 3-hydroxybutyrate unit content of 76 mol% or less.

[0133] [Item 9] A laminate comprising a first nonwoven fabric and a second nonwoven fabric laminated on at least one side of the first nonwoven fabric, wherein the first nonwoven fabric is the meltblown nonwoven fabric according to any one of items 1 to 8, and the second nonwoven fabric is a nonwoven fabric containing cellulosic fibers.

[0134] [Item 10] A mask filter formed from the meltblown nonwoven fabric according to any one of items 1 to 8 or the laminate according to item 9.

[0135] [Item 11] A mask comprising a mask body and the mask filter according to Item 10.

[0136] 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.

[0137] 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.

[0138] The following materials were prepared.

[0139] (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%, weight average molecular weight: 390,000) 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 average molecular weight: 530,000) (weight proportion 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 proportion 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%) Using a highly accelerated life tester (ESPEC, EHS-222MD), the P3HA-1 was treated under high temperature and humidity (temperature: 120°C, humidity: 100%) for 5.9 hours to obtain the following P3HA-3: P3HB3HH (3-hydroxybutyrate unit content: 94.5 mol%, 3-hydroxyhexanoate (3HH) unit content: 5.5 mol%, weight average molecular weight: 200,000). Using a highly accelerated life tester (ESPEC, EHS-222MD), the P3HA-2 was treated under high temperature and humidity (temperature: 120°C, humidity: 100%) for 5.5 hours to obtain the following P3HA-4. P3HA-4: P3HB3HH (content of 3-hydroxybutyrate units: 85.0 mol%, content of 3-hydroxyhexanoate (3HH) units: 15.0 mol%, weight average molecular weight: 220,000)

[0140] 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.

[0141] The 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in P3HA-2, P3HA-3, and P3HA-4 were determined in the same manner as for the 3-hydroxybutyrate unit content and 3-hydroxyhexanoate (3HH) unit content in P3HA-1. P3HA-2 was fractionated into an MIBK-soluble fraction and an MIBK-insoluble fraction by the MIBK fractionation method described above. The content ratios of 3-hydroxybutyrate units and 3-hydroxyhexanoate (3HH) units in the MIBK-soluble fraction and the MIBK-insoluble fraction were determined in the same manner as for the content ratios of 3-hydroxybutyrate units and 3-hydroxyhexanoate (3HH) units in P3HA-1.

[0142] (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)

[0143] (Nucleating Agent) PETL: Pentaerythritol (manufactured by Taisei Kayaku Co., Ltd., Neuraizer P)

[0144] Examples 1 to 16, 19, and 20, and Comparative Examples 1 to 3 and 5 The above materials were melt-kneaded in the blending ratios shown in Table 1 below to obtain raw material compositions.

[0145] (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, the content of 3-hydroxybutyrate units in P3HA-3, the content of 3-hydroxybutyrate units in P3HA-4, and the blending ratios of P3HA-1, P3HA-2, P3HA-3, and P3HA-4. 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 also means the content of 3-hydroxybutyrate units in the entire poly(3-hydroxyalkanoate) resin contained in the meltblown nonwoven fabric. Furthermore, the content of 3-hydroxyhexanoate (3HH) units in the entire poly(3-hydroxyalkanoate) resin contained in the raw material composition also means the content of 3-hydroxyhexanoate (3HH) units in the entire poly(3-hydroxyalkanoate) resin contained in the meltblown nonwoven fabric. The calculated values ​​are shown in Table 1 below.

[0146] (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

[0147]

[0148] Using the meltblown nonwoven fabric manufacturing apparatus shown in Figures 1 to 3, a first meltblown nonwoven fabric was produced from the raw material composition under the conditions shown in Table 2. A nozzle with a width of 600 mm was used to produce the first meltblown nonwoven fabric.

[0149] Next, the first meltblown nonwoven fabric was heated using a box-type hot air dryer (PH-202, manufactured by ESPEC Corporation) under the heating conditions in Table 2 below, and then naturally cooled at room temperature and normal pressure (20°C, 1 atmosphere) to obtain the second meltblown nonwoven fabrics of Examples 1 to 16, 19, and 20, and Comparative Examples 1 to 3, and 5.

[0150] Examples 17 and 18 and Comparative Example 4 The first meltblown nonwoven fabrics of Examples 1 and 4 and Comparative Example 1 were used as meltblown nonwoven fabrics of Examples 17, 18 and Comparative Example 4, respectively.

[0151]

[0152] (Measurement of physical properties of meltblown nonwoven fabric) For the meltblown 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.

[0153] (Maximum load, tensile elongation at maximum load, and tensile elongation at break in the CD and MD directions of meltblown nonwoven fabric) The maximum load, tensile elongation at maximum load, and tensile elongation at break in the CD and MD directions of the meltblown 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." As a constant-rate extension tensile tester, a universal testing machine (RTG-1210 manufactured by A&D Co., Ltd.) or the like was used. First, a test piece (width: 8 mm, length: 40 mm) was cut from the meltblown nonwoven fabric. Next, the test piece 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 piece was 20 mm. However, during the initial load, the test piece was pulled by hand to a degree that did not cause slack. Then, a load was applied at a pulling rate of 20 mm / min until the test piece broke, and the maximum load in the CD and MD directions was measured. In addition, the tensile elongation at maximum load in the CD and MD directions and the tensile elongation at break were 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 piece) / Grip spacing when initial load was applied to the test piece] x 100 (%) Tensile elongation at break (%) = [(Grip spacing at break - Grip spacing when initial load was applied to the test piece) / Grip spacing when initial load was applied to the test piece] x 100 (%) The measured values ​​are shown in Table 3 below.

[0154] (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.

[0155] (Virus droplet collection efficiency, fine particle collection efficiency, and pollen collection efficiency of meltblown nonwoven fabric) The virus droplet collection efficiency (VFE), fine particle collection efficiency (PFE), and pollen collection efficiency of the meltblown nonwoven fabric were measured. The virus droplet collection efficiency (VFE), fine particle collection efficiency (PFE), and pollen collection efficiency were measured in accordance with JIS T9001:2021 "Performance requirements and test methods for medical masks and general masks." The virus droplet collection efficiency means the collection efficiency of viruses attached to particles. The measured values ​​are shown in Table 3 below.

[0156] (Pressure loss due to meltblown nonwoven fabric) The pressure loss due to the meltblown nonwoven fabric was measured. The pressure loss was measured in accordance with JIS T9001:2021 "Performance requirements and test methods for medical masks and general masks." The measured values ​​are shown in Table 3 below.

[0157]

[0158] (Resistance to tearing of meltblown nonwoven fabric and low fuzzing of meltblown nonwoven fabric) A first test piece having the shape shown in Figure 4 was obtained by cutting the meltblown nonwoven fabric. Next, the first test piece was folded in half and the overlapping portions were welded together to obtain a second test piece having the shape shown in Figure 5. In addition, a mask body having a pair of ear loops and a retaining portion capable of holding a mask filter was prepared. Then, a mask was produced by inserting the second test piece, which was the mask filter, into the retaining portion of the mask body. 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.

[0159] <Tear resistance> 3: No cracks occurred in the second test piece, and no tears occurred in the welded portion of the second test piece. 2: Cracks of less than 1 cm occurred in the second test piece, or tears of less than 1 cm occurred in the welded portion of the second test piece (no cracks of 1 cm or more occurred in the second test piece, and no tears of 1 cm or more occurred in the welded portion of the second test piece). 1: Cracks of 1 cm or more occurred in the second test piece, or tears of 1 cm or more occurred in the welded portion of the second test piece.

[0160] <Low fuzzing> 3: No fuzzing was visually observed on the second test piece. 2: Small fuzzing occurred on the second test piece, but adhesion of the fuzz to the mask body was not visually observed. 1: Large fuzzing occurred on the second test piece, and adhesion of the fuzz to the mask body was visually observed.

[0161]

[0162] As shown in Table 3, Examples 16, 19, and 20, which are within the scope of the present invention, had higher viral droplet collection efficiencies (VFE), fine particle collection efficiencies (PFE), and pollen collection efficiencies than Comparative Example 5, in which the average fiber diameter of the fibers was 9.6 μm. Also, as shown in Table 3, Examples 1, 2, 5-15, 17, and 18, which are within the scope of the present invention, had higher viral droplet collection efficiencies (VFE) and fine particle collection efficiencies (PFE) than Comparative Example 5, in which the average fiber diameter of the fibers was 9.6 μm. Note that pollen collection efficiencies were not measured for Examples 1, 2, 5-15, 17, and 18. Furthermore, as shown in Table 3, Examples 3 and 4, which are within the scope of the present invention, had higher viral droplet collection efficiencies (VFE) than Comparative Example 5, in which the average fiber diameter of the fibers was 9.6 μm. Note that fine particle collection efficiencies (PFE) and pollen collection efficiencies were not measured for Examples 3 and 4.

[0163] As shown in Tables 1 and 4, in Examples 1, 4, 10, and 13, which are within the scope of the present invention, the meltblown nonwoven fabrics were less likely to tear than in Comparative Example 1, in which the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin was 94.5 mol %.

[0164] As shown in Table 3, in Examples 1 to 18, 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 Example 1, and the CD elongation / MD elongation ratio was closer to 1.00. Therefore, it is presumed that the meltblown nonwoven fabrics of Examples 2, 3, 5 to 9, 11, 12, and 14 to 18 are less likely to tear than Comparative Example 1, similar to Examples 1, 4, 10, and 13.

[0165] Therefore, it can be seen that the present invention can provide a meltblown nonwoven fabric that is tear-resistant and has a high particle collection efficiency.

[0166] Furthermore, as shown in Table 3, Examples 1, 2, 5 to 15, 17, and 18, in which the average fiber diameter of the fibers was 5.0 μm or less, had higher viral droplet collection efficiencies (VFE) and fine particle collection efficiencies (PFE) than Example 20, in which the average fiber diameter of the fibers was 6.1 μm. Note that pollen collection efficiencies were not measured in Examples 1, 2, 5 to 15, 17, and 18. Also, as shown in Table 3, Examples 3 and 4, in which the average fiber diameter of the fibers was 5.0 μm or less, had higher viral droplet collection efficiencies (VFE) than Example 20, in which the average fiber diameter of the fibers was 6.1 μm. Note that the fine particle collection efficiencies (PFE) and pollen collection efficiencies were not measured in Examples 3 and 4. Furthermore, as shown in Table 3, Examples 16 and 19, in which the average fiber diameter of the fibers was 5.0 μm or less, had similar pollen collection efficiencies to Example 20, in which the average fiber diameter of the fibers was 6.1 μm, but had higher viral droplet collection efficiencies (VFE) and fine particle collection efficiencies (PFE) than Example 20. Therefore, it can be seen that by making the average fiber diameter of the fibers of a meltblown nonwoven fabric 5.0 μm or less, a meltblown nonwoven fabric with even higher particle collection efficiency can be provided.

[0167] Furthermore, as shown in Table 3, Examples 1, 2, 6 to 15, 17, and 18, in which the average fiber diameter of the fibers was 3.0 μm or less, had higher viral droplet collection efficiencies (VFE) and fine particle collection efficiencies (PFE) than Example 19, in which the average fiber diameter of the fibers was 3.3 μm. Note that pollen collection efficiencies were not measured in Examples 1, 2, 6 to 15, 17, and 18. Also, as shown in Table 3, Examples 3 and 4, in which the average fiber diameter of the fibers was 3.0 μm or less, had higher viral droplet collection efficiencies (VFE) than Example 19, in which the average fiber diameter of the fibers was 3.3 μm. Note that the fine particle collection efficiencies (PFE) and pollen collection efficiencies were not measured in Examples 3 and 4. Furthermore, as shown in Table 3, Example 5, in which the average fiber diameter of the fibers was 3.0 μm or less, had a similar fine particle collection efficiency (PFE) to Example 19, in which the average fiber diameter of the fibers was 3.3 μm, but had a higher viral droplet collection efficiency (VFE) than Example 19. Note that the pollen collection efficiency was not measured in Example 5. Also, as shown in Table 3, Example 16, in which the average fiber diameter of the fibers was 3.0 μm or less, had similar fine particle collection efficiency (PFE) and pollen collection efficiency to Example 19, in which the average fiber diameter of the fibers was 3.3 μm, but had a higher viral droplet collection efficiency (VFE) than Example 19. Therefore, it can be seen that by having the average fiber diameter of the fibers of the meltblown nonwoven fabric be 3.0 μm or less, a meltblown nonwoven fabric with even higher particle collection efficiency can be provided.

[0168] Furthermore, as shown in Tables 3 and 4, in Examples 1, 2, and 6 to 15, in which the meltblown nonwoven fabrics had a tensile elongation at break in the MD direction of 120% or more and a tensile elongation at break in the CD direction of 120% or more, the meltblown nonwoven fabrics were less likely to break than in Examples 17 and 18, in which the meltblown nonwoven fabrics had a tensile elongation at break in the MD direction of 115% or less. Therefore, it can be seen that by having a meltblown nonwoven fabric with a tensile elongation at break in the MD direction of 120% or more and a tensile elongation at break in the CD direction of 120% or more, the meltblown nonwoven fabric becomes even more resistant to break.

[0169] Furthermore, as shown in Table 4, in Example 1, in which a second meltblown nonwoven fabric was obtained by heating the first meltblown nonwoven fabric, which is the nonwoven fabric of Example 17, the meltblown nonwoven fabric was less likely to tear than in Example 17. Also, as shown in Table 4, in Example 4, in which a second meltblown nonwoven fabric was obtained by heating the first meltblown nonwoven fabric, which is the nonwoven fabric of Example 18, the meltblown nonwoven fabric was less likely to tear than in Example 18. Therefore, it can be seen that heating a meltblown nonwoven fabric makes the meltblown nonwoven fabric even more resistant to tearing.

[0170] Furthermore, as shown in Table 3, in Example 1, in which a second meltblown nonwoven fabric was obtained by heating the first meltblown nonwoven fabric, which was the nonwoven fabric of Example 17, the tensile elongation at break in the MD direction of the meltblown nonwoven fabric and the tensile elongation at break in the CD direction of the meltblown nonwoven fabric were higher than in Example 17. Furthermore, as shown in Table 3, in Example 4, in which a second meltblown nonwoven fabric was obtained by heating the first meltblown nonwoven fabric, which was the nonwoven fabric of Example 18, the tensile elongation at break in the MD direction of the meltblown nonwoven fabric and the tensile elongation at break in the CD direction of the meltblown nonwoven fabric were higher than in Example 18. Therefore, it can be seen that by heating the meltblown nonwoven fabric, the tensile elongation at break in the MD direction of the meltblown nonwoven fabric and the tensile elongation at break in the CD direction of the meltblown nonwoven fabric are increased.

[0171] Furthermore, as shown in Table 3, in Example 1, in which a second meltblown nonwoven fabric was obtained by heating the first meltblown nonwoven fabric, which was the nonwoven fabric of Example 17, the tensile elongation at break in the CD direction and the tensile elongation at break in the MD direction were higher than in Example 17. Furthermore, as shown in Table 3, in Example 4, in which a second meltblown nonwoven fabric was obtained by heating the first meltblown nonwoven fabric, which was the nonwoven fabric of Example 18, the tensile elongation at break in the CD direction and the tensile elongation at break in the MD direction were higher than in Example 18. Therefore, it can be seen that by heating a meltblown nonwoven fabric, the tensile elongation at break in the CD direction and the tensile elongation at break in the MD direction of the meltblown nonwoven fabric can be increased.

[0172] Furthermore, as shown in Tables 1 and 4, in Examples 1, 4, 10, 13, 17, and 18, which are within the scope of the present invention, the meltblown nonwoven fabrics had less fuzz than Comparative Example 1, in which the content of 3-hydroxybutyrate units in the poly(3-hydroxyalkanoate) resin was 94.5 mol %.

[0173] 1: meltblown 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: kneaded material, B: first meltblown nonwoven fabric, C: gas

Claims

1. A meltblown 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 is 80.0 mol% or more and 93.5 mol% or less. The average fiber diameter of the aforementioned fiber is 8.0 μm or less. The coefficient of variation of the fiber diameter in the aforementioned fiber is 0.40 or less. A meltblown nonwoven fabric having a weight-average molecular weight of 100,000 to 250,000 of the resin composition.

2. The meltblown nonwoven fabric according to claim 1, wherein the average value of the fiber diameter is 5.0 μm or less.

3. The meltblown nonwoven fabric according to claim 2, wherein the average value of the fiber diameter is 3.0 μm or less.

4. The basis weight of the meltblown nonwoven fabric is 20 to 80 g / m². ２ The meltblown nonwoven fabric according to any one of claims 1 to 3.

5. The tensile elongation at the breaking point in the MD direction of the meltblown nonwoven fabric is 50% or more. The meltblown nonwoven fabric according to any one of claims 1 to 3, wherein the tensile elongation at the breaking point in the CD direction of the meltblown nonwoven fabric is 50% or more.

6. A meltblown nonwoven fabric according to any one of claims 1 to 3, wherein the ratio of the tensile elongation at the breaking point of the meltblown nonwoven fabric in the CD direction to the tensile elongation at the breaking point of the meltblown nonwoven fabric in the MD direction is 0.50 to 2.

00.

7. The meltblown nonwoven fabric according to any one of claims 1 to 3, wherein the poly(3-hydroxyalkanoate) resin comprises a poly(3-hydroxyalkanoate) resin component having a content of 76 mol% or less of 3-hydroxybutyrate units.

8. A laminate comprising a first nonwoven fabric and a second nonwoven fabric laminated on at least one side of the first nonwoven fabric, The first nonwoven fabric is the meltblown nonwoven fabric described in claim 1, A laminate in which the second nonwoven fabric is a nonwoven fabric containing cellulose fibers.

9. A mask filter formed from a meltblown nonwoven fabric according to any one of claims 1 to 3, or a laminate according to claim 8.

10. A mask comprising a mask body and a mask filter as described in claim 9.