Base material for face mask excellent in adhesion to skin

Abstract

To provide a biodegradable nonwoven fabric for face mask base material, excellent in flexibility and elasticity.SOLUTION: A biodegradable nonwoven fabric for face masks, which includes a biodegradable thermoplastic resin-containing fiber, having an extensibility of 50% or more and an elongation recovery rate of 50% or more for 20% elongation.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric suitable as a substrate for face masks, which has excellent adhesion to the skin. [Background technology]

[0002] In recent years, the use of cosmetic and medical products worn on the skin, such as face masks, has been increasing. In the cosmetic field, face masks are used to improve facial beauty by delivering moisturizers, emulsions, etc. to the facial skin. They are often worn on the skin during use, removed from the skin after use, and discarded. For this reason, relatively inexpensive nonwoven fabrics tend to be used as face mask materials.

[0003] For example, Patent Document 1 describes a beauty pack sheet (face mask) made of nonwoven fabric, which has a partially three-dimensional shape and multiple cuts to make it a pack sheet that adheres well to the face, under the chin, and around the neck.

[0004] Patent Document 2 discloses a cosmetic face mask that uses a stretchable nonwoven fabric for the ear loops so that it can fit snugly against the contours and curves of the face. As a highly stretchable nonwoven fabric, a nonwoven fabric containing a blend or composite fiber of two types of polyolefin and polyurethane is proposed.

[0005] Biodegradable nonwoven fabrics are made from various biodegradable resins, including polylactic acid, and in recent years, with growing awareness of promoting sustainability, they have been widely deployed in various fields and applications, resulting in high demand. Cosmetic face masks, in particular, are expected to be disposable, and the use of biodegradable nonwoven fabrics is expected to contribute to reducing environmental impact. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-172732 [Patent Document 2] Japanese Patent Application Publication No. 2019-047910 Summary of the Invention [Problem to be solved by the invention]

[0007] However, biodegradable resins are generally hard, and their applications are often limited to those in which flexibility and stretchability are not required as application characteristics. Furthermore, when selecting raw materials to impart flexibility, if soft resins are used to make nonwoven fabrics, the thread strength tends to be low and thread breakage is likely to occur during the thread drawing process, which can lead to productivity problems.

[0008] An object of the present invention is to provide a nonwoven fabric using a biodegradable resin, which has excellent conformability to the skin, is soft and pleasant to the touch, and is suitable as a base material for face masks.

[0009] The problem to be solved by the present invention is to provide a biodegradable nonwoven fabric for face masks that is biodegradable and has excellent flexibility and stretchability. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems, and as a result have found that a novel production method can be used to stably produce biodegradable nonwoven fabrics that are biodegradable and have excellent flexibility and stretchability, thereby completing the present invention.

[0011] That is, the present invention provides the following. (1) A biodegradable nonwoven fabric for face masks, which is made of fibers containing a biodegradable thermoplastic resin and has an elongation of 50% or more and a recovery rate at 20% elongation of 50% or more.

[0012] (2) In the configuration (1) above, the biodegradable thermoplastic resin is preferably an aromatic-containing polyester.

[0013] (3) In the configuration of (1), it is desirable that the melt flow rate of the biodegradable thermoplastic resin is 0.3 g / 10 min or more and 50 g / 10 min or less.

[0014] (4) In the configuration of (1) above, it is desirable that the melting point of the biodegradable thermoplastic resin be 70°C or higher and 200°C or lower.

[0015] (5) The biodegradable thermoplastic resin preferably contains adipic acid components, terephthalic acid components, and butanediol components in a total amount of 70 mol % or more, based on 100 mol % of all components.

[0016] (6) It is desirable that the biodegradable thermoplastic resin contains polybutylene adipate terephthalate.

[0017] (7) It is desirable that the biodegradable nonwoven fabric of (1) above is not subjected to a mechanical entanglement treatment.

[0018] (8) A face mask made of a biodegradable nonwoven fabric that is made of fibers containing a biodegradable thermoplastic resin and has an elongation of 50% or more and an elongation recovery rate of 50% or more at 20% elongation.

[0019] (9) A method for producing a biodegradable nonwoven fabric according to (1), comprising: step A of discharging a molten biodegradable thermoplastic resin from a spinneret, cooling and solidifying the resin, and then pulling and stretching the resin with an ejector to form long fibers; step B of collecting the long fibers obtained in step A to form a long-fiber web; and step C of thermocompression bonding the long-fiber web. [Effects of the Invention]

[0020] The present invention provides a biodegradable nonwoven fabric with excellent flexibility and stretchability. Because the elongation is 50% or more, when used as a base material for a face mask, it does not tear even when lightly pulled and easily deforms, providing sufficient conformability for its intended use. Furthermore, because the recovery rate at 20% elongation is 50% or more, the fabric has excellent stretchability and provides a comfortable feel when used as a base material for a face mask. Hereinafter, embodiments of the present invention will be described in detail.

[0021] The biodegradable thermoplastic resin preferably has a crystalline melting enthalpy of 9 J / g or more. Having a crystalline melting enthalpy of 9 J / g or more can improve the recovery properties of the biodegradable nonwoven fabric during stretching. The crystalline melting enthalpy is more preferably 14 J / g or more, even more preferably 18 J / g or more, even more preferably 19 J / g or more, still more preferably 20 J / g or more, and particularly preferably 21 J / g or more. On the other hand, the crystalline melting enthalpy is preferably 50 J / g or less. This improves the flexibility of the biodegradable nonwoven fabric and reduces the generation of noise during compression and recovery. The crystalline melting enthalpy can be more preferably 28 J / g or less, even more preferably 26 J / g or less.

[0022] The crystalline melting enthalpy (J / g) of the biodegradable thermoplastic resin can be determined from the integral of the endothermic peak (melting peak) of the endothermic curve measured using a differential scanning calorimeter with a sample mass of 2.0 mg±0.1 mg at a heating rate of 20°C / min under a nitrogen atmosphere. The integral can be determined by setting the point at which the curve relating to the endothermic peak (melting peak) begins to deviate from the baseline on the low temperature side as the starting point and the point at which it begins to touch the baseline on the high temperature side as the end point, drawing a straight line connecting the starting point and the end point, and integrating the area enclosed by the straight line and the curve.

[0023] The weight-average molecular weight (g / mol) of the biodegradable thermoplastic resin is preferably 35,000 or more. This can improve recovery upon elongation after compression. The weight-average molecular weight is more preferably 37,000 or more, and even more preferably 40,000 or more. Also, it is preferably 150,000 or less. When it is 150,000 or less, flexibility can be improved. Furthermore, when the weight-average molecular weight is 120,000 or less, the polymer melt viscosity can be reduced. The weight-average molecular weight is more preferably 120,000 or less. The weight-average molecular weight can be determined by gel permeation chromatography (GPC) or the like.

[0024] The melt flow rate (MFR) of the biodegradable thermoplastic resin can be in the range of 0.3 g / 10 min to 50 g / 10 min at 190°C, preferably 0.4 g / 10 min to 20 g / 10 min, and more preferably 0.5 g / 10 min to 15 g / 10 min. It is even more preferably 3 g / 10 min to 13 g / 10 min, even more preferably 6 g / 10 min to 12 g / 10 min, and even more preferably 8 g / 10 min to 10 g / 10 min. When fiberizing thermoplastic resins using methods such as spunbonding, thermoplastic resins with a melt flow rate (MFR) of around 100 g / 10 min are often used because of the ease of thread formation during melting. However, with such an MFR, the fiber strength of the biodegradable thermoplastic resin is often weak, making the fiber prone to breakage during the drawing process. Therefore, when the MFR is 15 g / 10 min or less, the strength of the single yarn constituting the nonwoven fabric is improved and yarn breakage during the drawing process tends to be prevented. When the MFR is 10 g / 10 min or less, yarn breakage resistance tends to be better. Furthermore, when the MFR is 0.3 g / 10 min or more, the viscosity when melted is not too high, making it easy to mold into yarn. The MFR of the biodegradable thermoplastic resin can be measured by the method described in the examples below.

[0025] The melting point of the biodegradable thermoplastic resin is preferably 70°C to 200°C, more preferably 100°C to 170°C, and even more preferably 110°C to 130°C. If the melting point is below 70°C, the strength of the single fibers constituting the nonwoven fabric will decrease, making it more likely for thread breakage to occur during the stretching process. On the other hand, if the melting point is above 200°C, the ratio of hard segments in the intramolecular structure will be too high, making the nonwoven fabric more likely to lose its flexibility and stretchability.

[0026] Preferred biodegradable thermoplastic resins include polylactic acid, polylactic acid / polycaprolactone copolymer, polylactic acid / polyether copolymer, polyethylene terephthalate succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyglycolic acid, polycaprolactone, polyvinyl alcohol, and cellulose acetate. Aromatic-containing polyesters such as polyethylene terephthalate succinate and polybutylene adipate terephthalate are even more preferred, with polybutylene adipate terephthalate-based resins being particularly preferred. Aromatic-containing polyesters provide superior stretchability. When polybutylene adipate terephthalate-based resins are used as biodegradable thermoplastic resins, they may also contain other biodegradable thermoplastic resins as described above. For details, please refer to the positive list for GreenPla (biodegradable plastics) classification number A-1 of the Japan BioPlastics Association. The fibers constituting the biodegradable nonwoven fabric may contain resins other than biodegradable thermoplastic resins, such as polyurethane and polyester. The Japan Bioplastics Association's GreenPla (biodegradable plastic) Classification Number A-1 Positive List (Ver. 2023.4 (Sep.)) lists the following: hydroxyl-modified starch manufactured by Kuraray, starch polyesters Mater-Bi (registered trademark) NF01U and Mater-Bi (registered trademark) ZF03U / A manufactured by GSI Creos (Novamont), cellulose acetate (cellulose acetate (diacetate) manufactured by Daicel), and polylactic acid products manufactured by NatureWorks Japan: NatureWorks 2000 series, 3000 series, 4000 series, 6000 series, 7000 series, 8000 series, Ingeo (registered trademark) 5061A, and Ingeo (registered trademark) 5061B.Further examples of polylactic acid include Kanepearl (registered trademark) B100 manufactured by Kaneka, Viroecole (registered trademark) BE-400, BE-410, and HYD-006 manufactured by Toyobo MC, REVODE (registered trademark) 100 series and 200 series manufactured by Daishin Pharmaceutical (Zhejiang Haizheng Biomaterials), PLA manufactured by Chori (Pliith Biotechnology), Luminy L-series, Luminy LX-series, and Luminy manufactured by Total Energies Corbion. Examples of suitable polylactic acid / polycaprolactone copolymers include Viroecole (registered trademark) BE-450, HYD-306, and BE-910 manufactured by Toyobo MC, AONILEX (registered trademark) manufactured by Kaneka as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), Cressage (registered trademark) and Credax (registered trademark) manufactured by Kureha as polyglycolic acid, Ecodia (registered trademark) L4E6 series manufactured by Toray as polylactic acid / polyether copolymer, Placcel (registered trademark) H1P, H5C, and H8C manufactured by Daicel, and Capa 6500, Capa 6500D, and Capa manufactured by Ingevity Japan as polycaprolactone. 6800, Capa 6800D, Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) manufactured by CJ CHEIL JEDANG. TM A1000P, PHACT TMExamples include S1000P, Mater-Bi (registered trademark) CS series manufactured by GSI Creos (Novamont) which is a butanediol / long-chain dicarboxylic acid copolymer, Ecoflex (registered trademark) manufactured by BASF Japan which is a polybutylene adipate / terephthalate, Ecoflex (registered trademark) FS manufactured by BASF Japan as an aliphatic aromatic polyester, Origo-Bi ES01G and Eastar Bio Ultra manufactured by GSI Creos (Novamont) as polytetramethylene adipate-co-terephthalate, BioPBS FZ71, BioPBS FZ91, and BioPBS FZ78 manufactured by PTT MCC as polybutylene succinate, TUNHE PBS manufactured by BLUERIDGE, and ECO-B manufactured by Changchun Japan. Polybutylene succinate adipate includes BioPBS FD92 manufactured by PTT MCC, and polybutylene adipate terephthalate includes A400 (ECOPOND KD 1024) manufactured by KINGFA, TUNHE PBAT manufactured by BLUERIDGE, CKBP-PBAT-01 manufactured by Mitoku Harness, ECO-A manufactured by Changchun Japan, HF101 manufactured by HighChem (Zhejiang Huafeng Environmental Protection Materials), Ecoworld Biodegradable Polymer manufactured by JinHui ZhaoLong High Tech, and Biodegradable Resin manufactured by Kanghui New Material Technology. Examples of polyvinyl alcohol include KHB21, HF901 manufactured by Chori, Gohsenol (registered trademark), Gohsenex (registered trademark) T, Gohsenex (registered trademark) WO, and Nichigo (registered trademark) G Polymer manufactured by Mitsubishi Chemical, and Kuraray Poval (registered trademark) fully saponified product, Kuraray Poval (registered trademark) intermediate saponified product, Kuraray Poval (registered trademark) partially saponified product, Kuraray Poval (registered trademark) low saponified product, and Kuraray Exeval (registered trademark).

[0027] Although petroleum-derived monomers may be used as monomers for synthesizing biodegradable thermoplastic resins, it is preferable to use biomass-derived monomers because they can reduce the environmental impact. For biomass-derived monomers, see, for example, the monomers listed in the positive list for classification number A (biomass plastics) of the Japan Bioplastics Association.

[0028] Of 100 mol% of all components constituting the biodegradable thermoplastic resin, the total content of the adipic acid component, the terephthalic acid component, and the butanediol component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 99 mol% or more. Of 100 mol% of all components constituting the biodegradable thermoplastic resin, it is even more preferable that they account for 100 mol%. Furthermore, it is preferable that the fibers constituting the biodegradable nonwoven fabric are made solely of biodegradable thermoplastic resin, from the viewpoint of biodegradability and environmental friendliness.

[0029] Polybutylene adipate terephthalate resin is a biodegradable resin, a copolymer of adipic acid, terephthalic acid, and butanediol. Because polybutylene adipate terephthalate resin is a biodegradable resin, it is expected to be a solution to waste disposal problems and microplastic problems. Adipic acid, terephthalic acid, and butanediol do not need to be copolymerized simultaneously; they may be copolymerized in multiple stages.

[0030] When synthesizing polybutylene adipate terephthalate resins, in addition to adipic acid, terephthalic acid, and butanediol, trace amounts of other copolymerization components may be added. Examples of other copolymerization components include dicarboxylic acids other than terephthalic acid and adipic acid, and modifiers for the purposes of chain extension and terminal blocking. These may be used alone or in combination of two or more. That's fine.

[0031] Other dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, etc. These may be used alone or in combination of two or more.

[0032] Examples of modifiers include polyisocyanate compounds and glycol compounds. Examples of polyisocyanate compounds include diisocyanate compounds. Examples of diisocyanate compounds include hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, carbodiimide-modified MDI, and polymethylenephenyl polyisocyanate. These compounds may be used alone or in combination of two or more. Examples of glycol compounds include diols other than butanediol and polyalkylene glycols. Examples of other diols include methanediol, ethanediol, propanediol, pentanediol, and hexanediol. Examples of polyalkylene glycols include polymethylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol (polytetramethylene glycol). These may be used alone or in combination of two or more.

[0033] Examples of polybutylene adipate terephthalate resins include biodegradable synthetic polymer compounds listed on the positive list of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1. Specific examples include Ecoflex (registered trademark) manufactured by BASF Japan Ltd., EastarBio GP and EastarBio Ultra manufactured by GSI Creos Co., Ltd. (Novmont), A40 (ECP ONDKD1024) manufactured by KINGFA Co., Ltd., and TUNHEPBATTH-801T manufactured by XINJIANG BLUE RIDGET UNHE CHEMICAL INDUSTRY JOINTSTOCK CO., LTD.

[0034] The biodegradable nonwoven fabric is composed of fibers containing a biodegradable thermoplastic resin. The fibers constituting the biodegradable nonwoven fabric preferably contain 80% by mass or more of the biodegradable thermoplastic resin, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass.

[0035] The shape of the fibers constituting the biodegradable nonwoven fabric is not particularly limited, but may have a circular, flat, C-shaped, Y-shaped, V-shaped or other irregular cross section, preferably a circular cross section, and may also have a sea-island structure, a sheath-core structure, or a split fiber structure.

[0036] The fibers constituting the biodegradable nonwoven fabric may further contain one or more other resins, flame retardants, inorganic fillers, softeners, plasticizers, pigments, antistatic agents, etc., depending on the purpose.

[0037] The fiber diameter of the fibers constituting the biodegradable nonwoven fabric is preferably 5 to 60 μm, more preferably 10 to 50 μm, and even more preferably 12 to 40 μm. When the fiber diameter is 5 μm or more, spinnability in the spunbonding method is improved, enabling stable production. Furthermore, when the fiber diameter is 60 μm or less, unevenness of the nonwoven fabric is less likely to occur, which is desirable.

[0038] The basis weight and thickness of the biodegradable nonwoven fabric are not particularly limited, but the basis weight is 10 to 200 g / m 2 and the thickness can be in the range of 0.05 to 6.0 mm.

[0039] The biodegradable nonwoven fabric preferably has an apparent density of 0.1 g / cc or more, more preferably 0.11 g / cc or more, and even more preferably 0.13 g / cc or more. The higher the apparent density, the better, but it can be, for example, 0.3 g / cc or less, 0.28 g / cc or less, etc. Because the apparent density is 0.1 g / cc or more, when used as a base material for a face mask, curling during use can be prevented.

[0040] It is preferable that the biodegradable nonwoven fabric has not been subjected to a mechanical entanglement treatment. Examples of mechanical entanglement treatment include entanglement treatments by needle punching and water punching. Not being subjected to a mechanical entanglement treatment is preferable because it can be produced at low cost. It is also preferable because it can avoid the risk of needle contamination that can occur when using a needle punching method. In addition, the water punching method uses a large amount of water and requires a huge amount of energy. Therefore, from the perspective of environmental conservation and energy conservation, it is preferable that the biodegradable nonwoven fabric has not been subjected to the mechanical entanglement treatment.

[0041] The biodegradable nonwoven fabric can have a stress at 5% elongation of 0.1 to 100 (N / 2.5 cm), preferably 0.3 to 15.0 (N / 2.5 cm). A stress of 10 (N / 2.5 cm) or less provides a less tight feeling and a soft feel when touched by the skin, resulting in a good feel and texture when used as a base material for face masks. In this specification, "a stress at 5% elongation of 0.1 (N / 2.5 cm) or more" means that the stress at 5% elongation in the MD (machine direction) is 0.1 (N / 2.5 cm) or more and the stress at 5% elongation in the CD (cross direction) is 0.1 (N / 2.5 cm) or more.

[0042] The biodegradable nonwoven fabric can have a mechanical strength of 1 to 200 (N / 2.5cm), preferably 5 to 100 (N / 2.5cm). In particular, a mechanical strength of 8 (N / 2.5cm) or more can prevent easy breakage when used as a base fabric for a face mask. In this specification, "a mechanical strength of 1 (N / 2.5cm) or more" means that the mechanical strength in the MD (machine direction) is 1 (N / 2.5cm) or more and the mechanical strength in the CD (cross direction) is 1 (N / 2.5cm) or more.

[0043] The biodegradable nonwoven fabric has an elongation of 50% or more. An elongation of 60% or more is preferred, more preferably 70% or more, and even more preferably 100% or more. When the elongation is 50% or more, when used as a face mask, it does not tear even when lightly pulled and can easily deform, providing sufficient conformability for its intended use. Furthermore, the elongation is preferably 500% or less, more preferably 300% or less. In this specification, "an elongation of 50% or more" means that the elongation in the MD (machine direction) is 50% or more and the elongation in the CD (cross direction) is 50% or more.

[0044] The biodegradable nonwoven fabric has a stretch recovery rate of 50% or more at 20% elongation, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. The higher the stretch recovery rate at 20% elongation, the better, and it can be, for example, 99.5% or less, 99.0% or less, etc. Because the stretch recovery rate at 20% elongation is 50% or more, the fabric has excellent stretchability and provides a comfortable feel when used as a face mask. For example, when applied to the face, the fabric can follow the movement of the skin at bent portions and suppress the formation of wrinkles. As a result, peeling caused by wrinkles is prevented, ensuring close contact with the skin. Furthermore, the fabric has good elasticity, resulting in a comfortable feel. In this specification, "a stretch recovery rate of 50% or more at 20% elongation" means that the stretch recovery rate at 20% elongation in the MD (machine direction) is 50% or more, and the stretch recovery rate at 20% elongation in the CD (cross direction) is 50% or more.

[0045] The biodegradable nonwoven fabric preferably has a ratio of elongation recovery in the MD (machine direction) to the CD (cross direction) (CD / MD) at 20% elongation of 1.0 or more and preferably less than 1.9. It is more preferably 1.7 or less, even more preferably 1.5 or less, and particularly preferably 1.2 or less. A ratio of 1.5 or less tends to allow the fabric to smoothly conform to bends and adhere well to the skin.

[0046] The biodegradable nonwoven fabric can have a bending resistance of 5 to 150, preferably 10 to 100, more preferably 12 to 80, and even more preferably 13 to 50. In particular, when the bending resistance is 50 or less, the fabric does not feel tight when used as a base fabric for a face mask, and it can provide a soft feel when touched by the skin, resulting in a good feel in use and a good texture.

[0047] The method for producing the biodegradable nonwoven fabric is not limited, and known methods such as spunbonding, meltblowing, airlaid, carding, and papermaking can be used. The biodegradable nonwoven fabric of this embodiment is preferably integrated by bonding, and bonding methods such as embossing and thermal bonding can be used. A long-fiber nonwoven fabric is preferred, and production by the spunbonding method is more preferred, as it can be produced efficiently and can suppress fluffing after molding.

[0048] When using the spunbonding method, a resin is heated and melted and extruded from a spinneret. The resulting spun yarn is cooled using a known cooling device and pulled and attenuated using a suction device such as an air sucker. The yarn group discharged from the suction device is then opened and deposited on a conveyor to form a web. The web formed on the conveyor is then partially thermocompressed using a partial thermocompression device such as a heated embossing roll, thereby obtaining a spunbonded nonwoven fabric. Nonwoven fabrics obtained by the spunbonding method have characteristic physical properties such as high fabric strength and no shedding of short fibers due to breakage of bonded portions, and are also low-cost and highly productive.

[0049] A biodegradable nonwoven fabric can be produced, for example, by a production method including the following steps A to C. A nonwoven fabric is obtained through step A, in which a molten thermoplastic resin is extruded from a spinneret, cooled and solidified, and then pulled and stretched by an ejector to form fibers, step B, in which the long fibers obtained in step A are collected to form a long-fiber web, and step C, in which the long-fiber web is thermocompression-bonded.

[0050] <Process A> In the method for producing a biodegradable nonwoven fabric according to this embodiment, first, a molten thermoplastic resin is extruded from a spinneret, cooled and solidified, and then pulled and stretched by an ejector to form fibers.

[0051] This step A can be carried out using a spinning machine such as a conventionally known spunbond spinning machine.

[0052] In the step A, the mixture is spun from a spinneret having an orifice diameter of 0.1 to 0.5 mm and fed to an ejector at a pressure of 0.5 to 4.0 kg / cm 2 It is preferable to supply dry air at a pressure (jet pressure) of 0.15 to 0.5 mm and perform drawing. The orifice diameter of the spinneret is more preferably 0.15 to 0.5 mm, and even more preferably 0.18 to 0.45 mm. By controlling the orifice diameter within the above range, it becomes easier to control the fiber diameter. Furthermore, by controlling the supply pressure (jet pressure) of the dry air within the above range, it becomes easier to control the spinning speed to a constant value and it is possible to dry the fiber appropriately.

[0053] <Process B> Next, the long fibers obtained in step A are collected to form a long-fiber web (step B). For example, the long fibers may be spread and collected on a lower conveyor to form a long-fiber web.

[0054] <Process C> Next, the long-fiber web obtained in step B is thermocompression-bonded (step C). The thermocompression-bonding is carried out within a temperature range in which the long-fiber web does not shrink. This allows for suitable transport. The thermocompression-bonding temperature is preferably at least 10°C lower than the melting point of the resin of the nonwoven fabric, the linear pressure is preferably 5 to 100 N / mm, more preferably 20 to 80 N / mm, and the compression-bonded area ratio is preferably 3 to 50%, more preferably 6 to 40%. By carrying out thermocompression-bonding within an appropriate range, it is possible to achieve both flexibility and stretchability of the nonwoven fabric and compression-bonding. [Example]

[0055] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0056] The following Examples 1 and 2 and Comparative Examples 1 to 4 were measured according to the following methods.

[0057] (intrinsic viscosity) 0.1 g of the resin was weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane (60 / 40 (weight ratio)), and the viscosity was measured three times at 30° C. using an Ostwald viscometer to calculate the average value.

[0058] (specific gravity) A density gradient solution was prepared using calcium nitrate tetrahydrate in a density gradient tube. The density gradient ranged from 1.20 to 1.5 g / cm. 3 Using the specific gravity float range, the fiber after jet drawing was put into a density gradient tube, and after stabilizing for 4 hours or more, the scale of the floating position was read, and the specific gravity was calculated from the float calibration curve.

[0059] (crystal melting enthalpy) 2.0 mg ± 0.1 mg of resin was weighed, and the endothermic curve was measured using a TA Instruments Discovery DSC25 differential scanning calorimeter at a heating rate of 20 °C / min under a nitrogen atmosphere. The crystalline melting enthalpy (J / g) was determined from the integrated value of the endothermic peak (melting peak). Specifically, the integrated value of the endothermic peak (melting peak) was determined by taking the point where the curve relating to the endothermic peak (melting peak) begins to deviate from the low-temperature baseline as the starting point and the point where it begins to contact the high-temperature baseline as the end point. A line was drawn connecting the start point and the end point, and integrating the area enclosed by the line and the curve. This procedure was performed three times to determine the average crystalline melting enthalpy (n = 3). The starting point was also designated as the melting onset temperature (°C).

[0060] (Melting Point) The resin was weighed to a mass of 2.0 mg ± 0.1 mg. Next, a differential scanning calorimeter (TA Instruments, Discovery DSC25) was used to measure the DSC curve under a nitrogen atmosphere at a heating rate of 20°C / min, and the endothermic peak (melting peak) temperature was determined from the DSC curve. The above procedure was repeated three times, and the average melting point (n = 3) was calculated.

[0061] (Melt Flow Rate (MFR)) After the resin was vacuum dried at 80°C for at least 2 hours, the melt flow rate (MFR) was measured quickly so as to minimize the amount of moisture in the air. The melt flow rate was measured in accordance with ISO 1133 using a Melt Indexer F-F01 machine manufactured by Toyo Seiki Seisakusho Co., Ltd. The measurement temperature was 190°C and the load was 2.16 kg. This operation was performed three times, and the average melt flow rate (n = 3) was calculated.

[0062] (Weight average molecular weight) The resin was dissolved in a small amount of chloroform to prepare a sample solution. The sample solution was further diluted with chloroform to a concentration of 0.05% by mass. The solution was filtered through a 0.2 μm membrane filter, and GPC analysis of the resulting solution was performed under the following conditions. The molecular weight was calculated in terms of standard polystyrene. Equipment: TOSOH HLC - 8320GPC Column: TSKgelSuper HM-H x 2 + TSKgelSuperH 2000 (TOSOH) Solvent: Chloroform

[0063] (Metsuke) The mass per unit area was measured according to JIS L1913(2010)6.2.

[0064] (Apparent density (bulk density)) 1cm from the above basis weight and thickness calculated in accordance with JIS-L1913(2010)6.2 and 6.1 3 The weight was converted into the weight per unit of the sample and used as the bulk density. 2 The thickness was measured using a terminal, and the bulk density was calculated by dividing the basis weight by the thickness.

[0065] (fiber diameter) Five randomly selected points on the sample (long fiber web before thermocompression bonding) were used to measure the diameter of the single fiber (n=20) using an optical microscope, and the average value was calculated.

[0066] (Fineness (dtex)) Five randomly selected locations on the sample (long fiber web before thermocompression bonding) were used to measure the single fiber diameter (n = 20) using an optical microscope to determine the average single fiber diameter. Fibers from the same five locations were taken out, and the specific gravity of the fibers (n = 5) was measured using a density gradient tube to determine the average specific gravity. Next, the fiber fineness (dtex), which is the fiber weight per 10,000 m, was calculated from the single fiber cross-sectional area and average specific gravity calculated from the average single fiber diameter.

[0067] (Spinning speed (m / min)) The spinning speed V (m / min) was calculated from the above-mentioned fineness T (dtex) and the set single-hole output Q (g / min) according to the following formula. V=(10000×Q) / T

[0068] (5% elongation stress) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-speed extension tensile tester with a self-recording device, the sample was attached to a grip gap of 50 mm while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The sample was then stretched to 5% of the grip gap at a tensile speed of 10 mm / min. The load value at this point was calculated as the stress at 5% elongation. Measurements were performed on n=5 samples in both the longitudinal and transverse directions, and the average value was rounded to the nearest tenth.

[0069] (mechanical strength) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-speed extension tensile tester with a self-recording device, the sample was attached to a grip with a 50 mm gap while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The sample was then stretched at a tensile speed of 10 mm / min until it broke. The maximum load value at this point was calculated as the mechanical strength. Measurements were performed on 5 samples in each of the machine direction and the cross direction, and the average value was rounded to the nearest tenth.

[0070] (Elongation) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-speed extension tensile tester with a self-recording device, the sample was attached to a grip with a 50 mm gap while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The sample was then stretched at a tensile speed of 10 mm / min until it broke. The maximum elongation value at this point was calculated as the average elongation. Measurements were performed on 5 samples in each of the machine and cross directions, and the average value was rounded to the nearest tenth.

[0071] (20% elongation recovery rate) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-speed extension tensile tester with a self-recording device, the sample was attached to a grip gap of 50 mm while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The value of "(grip gap) + (length stretched when the initial load was applied)" at this time was defined as L0. The sample was then stretched to 20% of the grip gap at a tensile speed of 25 mm / min. This length was defined as L1. The sample was then immediately unloaded at the same speed until it reached the initial load, and the resulting length was defined as L2. The 20% elongation recovery was calculated using the following formula. Measurements were performed on 5 samples in each of the machine and cross directions, and the average values ​​were rounded to the nearest tenth. 20% elongation recovery rate (%)=[(L1-L2) / (L1-L0)]×100

[0072] (bending resistance) The bending resistance per unit area was measured according to JIS L1913 (2000) 6.7.3 (cantilever method).

[0073] (Texture) Nine subjects conducted a sensory test by pinching the sample between the thumb and index finger of their right hand so that the cross direction (CD) of the sample was perpendicular to the fingers, and rubbing it back and forth with light pressure five times. They then judged the feel of the sample when touched with the skin using the following three levels (good, fair, bad), and evaluated it based on the total score. 〇 (5 points): Very soft and elastic to the touch △ (2 points): Feels slightly hard to the touch and has little elasticity × (0 points): Hard to the touch and lacking elasticity

[0074] (Thread breakage) In step A, the state of the yarn during drawing was visually checked, and the number of yarn breakages per 5 minutes was judged as follows to evaluate the yarn breakage resistance. 〇: 1 bottle / 5 min or less △: 2 / 5min to 9 / 5min or less ×: 10 bottles / 5 min or more

[0075] (stretchability) The nonwoven fabric sheet that had passed through step C was measured for recovery at 20% elongation in both the longitudinal and transverse directions, and the stretchability was evaluated by judging the recovery rate as follows. 〇: Recovery rate after 20% elongation in both the vertical and horizontal directions is 60% or more △: Either the recovery rate at 20% elongation in the vertical or horizontal direction is 60% or more ×: Recovery rate after 20% elongation in both the longitudinal and transverse directions is less than 60%

[0076] (biodegradable) It was determined whether the resin that constitutes the nonwoven fabric sheet retains biodegradable properties. 〇: The substance name (resin name) is listed on the positive list of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1. ×: The substance name (resin name) is not listed on the positive list of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1.

[0077] (comprehensive evaluation) Based on the above various evaluations, the fabric was evaluated as a biodegradable nonwoven fabric for face masks. Good: The balance of stretchability, flexibility, conformability and texture is good, and the material can be used effectively as a biodegradable adhesive material. ×: The balance of stretchability, flexibility, conformability and feel to the skin is poor, making it difficult to use as a biodegradable nonwoven fabric for face masks.

[0078] Example 1 Polybutylene adipate terephthalate (PBAT) (MFR: 4 g / min, melting point: 120°C, crystalline melting enthalpy: 14 J / g) shown in Table 1 was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 230°C. Filaments were pulled using a high-speed air jet pulling device (Step A), and these were deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section) (Step B). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the laminate was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 80°C for both rolls, and a roll linear pressure of 40 N / mm (step C), resulting in a basis weight of 70 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0079] Example 2 The PBAT (MFR: 9 g / min, melting point: 120°C, crystalline melting enthalpy: 27 J / g) shown in Table 1 was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 220°C. The filaments were pulled using a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 110°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a basis weight of 70 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0080] (Comparative Example 1) Polylactic acid (MFR: 65 g / min, melting point: 170°C) (abbreviated as PLA) was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 210°C. Filaments were pulled using a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 130°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a fabric weight of 70 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0081] (Comparative Example 2) Using a side-by-side nozzle on a two-component spunbond spinning system, polyethylene terephthalate (intrinsic viscosity (iv value): 0.63) and copolymer polyester (a copolymer in which the dicarboxylic acid component is terephthalic acid and the glycol component is 70 mol % of ethylene glycol and 30 mol % of neopentyl glycol, intrinsic viscosity (iv value): 0.75, Tg: 75°C) were spun in a mass ratio of 5.5 (polyethylene terephthalate): 4.5 (copolymer polyester). Spinning was carried out from a spinneret with an orifice diameter of 0.36 mm at a single-hole discharge rate of 1.0 g / min. Then, a pressure of 3.5 kg / cm was applied to the ejector. 2 Dry air was supplied at a pressure (jet pressure) of 1000 kJ / s, and the web was stretched in one step, and the fibers were spread and collected on a conveyor below to obtain a long-fiber web. The long-fiber web was then thermocompressed. The thermocompression conditions were a thermocompression roll temperature of 60°C and a linear pressure of 5 kg / cm. As a result, a basis weight of 25 g / m was obtained. 2 A long fiber web of 1000 .mu.m was obtained.

[0082] Next, the obtained continuous fiber web was subjected to crimping while being transported between six heated rolls. The nonwoven fabric sheet obtained had a basis weight of 100 g / m. 2 , thickness 0.8 mm, apparent density 0.13 g / cc.

[0083] (Comparative Example 3) Thermoplastic polyurethane elastomer (TPU) (MFR: 100 g / min, melting point: 270°C) was melted and kneaded in a single-screw extruder, and extruded by the spunbond method at a throughput rate of 1.0 g / min·Hole and a spinning temperature of 220°C. The filaments were pulled by a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed at a pressure of 12%, with both rolls at a temperature of 80°C and a roll linear pressure of 30 N / mm, to obtain a fabric with a basis weight of 85 g / m 2 A nonwoven fabric sheet of 1000g was obtained.

[0084] Comparative Example 4 Polyethylene terephthalate (PET) (intrinsic viscosity (iv value): 0.63) was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 280°C. The filaments were pulled using a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed at a pressure-bonding area ratio of 12%, a temperature of 240°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a fabric with a basis weight of 70 g / m 2 A nonwoven fabric sheet of 1000g was obtained.

[0085] [Table 1]

Claims

1. A biodegradable nonwoven fabric for face masks, which is made of fibers containing a biodegradable thermoplastic resin, and which has an elongation of 50% or more and an elongation recovery rate at 20% elongation of 50% or more.

2. The biodegradable nonwoven fabric for face masks according to claim 1, wherein the biodegradable thermoplastic resin is an aromatic-containing polyester.

3. The biodegradable nonwoven fabric for face masks according to claim 1 or 2, characterized in that the biodegradable thermoplastic resin has a melting point in the range of 70°C or higher and 200°C or lower.

4. The biodegradable nonwoven fabric for face masks according to claim 1 or 2, characterized in that the melt flow rate of the biodegradable thermoplastic resin is in the range of 0.3 g / 10 min or more and 50.0 g / 10 min or less.

5. The biodegradable nonwoven fabric for face masks according to claim 1 or 2, characterized in that the biodegradable thermoplastic resin contains adipic acid components, terephthalic acid components, and butanediol components in a total amount of 70 mol% or more, based on 100 mol% of all components.

6. The biodegradable nonwoven fabric for face masks according to claim 1 or 2, characterized in that the biodegradable thermoplastic resin contains polybutylene adipate terephthalate.

7. The biodegradable nonwoven fabric for face masks according to claim 1 or 2, characterized in that it has not been subjected to a mechanical entanglement treatment.

8. A face mask using a biodegradable nonwoven fabric that is made of fibers containing a biodegradable thermoplastic resin and has an elongation of 50% or more and an elongation recovery rate of 50% or more when stretched by 20%.

9. 3. The method for producing a biodegradable nonwoven fabric for face masks according to claim 1, further comprising: step A: discharging a molten biodegradable thermoplastic resin from a spinneret, cooling and solidifying it, and then pulling and stretching it with an ejector to form long fibers; step B: collecting the long fibers obtained in step A to form a long-fiber web; and step C: thermocompression bonding the long-fiber web.

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