Biodegradable nonwoven fabric and method for manufacturing same

Abstract

The problem to be solved by the present invention is to provide a biodegradable nonwoven fabric having biodegradability as well as excellent flexibility and stretchability, and a method for manufacturing the same. The biodegradable nonwoven fabric according to the present invention is a nonwoven fabric constituted by fibers containing a biodegradable thermoplastic resin and is characterized in that the elongation is 50% or more and the elongation recovery rate at 20% elongation is 60% or more.

Description

Biodegradable nonwoven fabric and its manufacturing method

[0001] The present invention relates to a biodegradable nonwoven fabric containing a biodegradable thermoplastic resin, and a method for producing the same.

[0002] Patches and bandages used in medical applications must be able to follow the movement of the skin caused by movement of joints, etc. They also need to have a high bulk density to prevent curling at the edges during use and to ensure sufficient medicinal efficacy.

[0003] As a nonwoven fabric that can be used for such purposes, Patent Document 1 discloses a long-fiber nonwoven fabric that is composed of long fibers obtained by bicomponent conjugation spinning of polyethylene terephthalate and a copolymer polyester, and that is characterized by having an apparent density of 0.1 g / cc or more and a 10% elongation recovery rate of 65% or more.

[0004] Furthermore, biodegradable nonwoven fabrics are made of various biodegradable resins such as polylactic acid, and in recent years, due to the growing awareness of promoting sustainability, they have been widely used in various fields and applications, and are therefore in high demand. Patent Document 2 discloses a biodegradable nonwoven fabric that has an excellent texture and good moldability by controlling the shear viscosity at a specific shear rate at high temperature to a certain level or less.

[0005] JP 2022-55016 A, WO 2023-032763 Pamphlet

[0006] 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, if soft resins are used to create nonwoven fabrics in order to impart flexibility, the yarn strength tends to be low and yarn breakage is likely to occur during yarn stretching in the production process, which can lead to productivity problems.

[0007] Furthermore, the nonwoven fabric disclosed in Patent Document 2 uses a biodegradable resin with a relatively low melt viscosity, which has favorable melting properties for enhancing moldability. However, in this case, the recovery rate upon stretching, which is in a trade-off relationship with moldability, is poor, and there is room for improvement in stretchability for use in, for example, patches. Furthermore, when a biodegradable resin with a relatively low melt viscosity is used, thread breakage is likely to occur during stretching, and further adjustment of manufacturing conditions was necessary from the viewpoint of productivity, etc.

[0008] As mentioned above, nonwoven fabrics that have conformability and an excellent recovery rate when stretched have been known in the past, but they were not biodegradable nonwoven fabrics (Patent Document 1). Also, while nonwoven fabrics that are obtained using biodegradable resins and have good moldability are known (Patent Document 2), biodegradable nonwoven fabrics that are excellent in flexibility and stretchability have not been known in the past.

[0009] The problem to be solved by the present invention is to provide a biodegradable nonwoven fabric that is biodegradable and has excellent flexibility and stretchability, and a method for producing the same.

[0010] The present inventors have conducted extensive research to solve the above problems, and as a result have found that by using a biodegradable thermoplastic resin with a relatively high melt viscosity and adopting production conditions suitable for the melting properties of the resin, it is possible to stably obtain a biodegradable nonwoven fabric that is not only biodegradable but also has excellent flexibility and stretchability, thereby completing the present invention.

[0011] That is, the present invention provides the following.

[0012] [1] A biodegradable nonwoven fabric comprising fibers containing a biodegradable thermoplastic resin, characterized in that the nonwoven fabric has an elongation of 50% or more and an elongation recovery rate of 60% or more before and after elongation at a 20% elongation of the nonwoven fabric.

[0013] [2] The biodegradable nonwoven fabric according to [1], characterized in that the biodegradable thermoplastic resin is an aromatic-containing polyester.

[0014] [3] The biodegradable nonwoven fabric according to [1] or [2], characterized in that the crystalline melting enthalpy of the biodegradable thermoplastic resin is in the range of 9 J / g or more and 50 J / g or less.

[0015] [4] The biodegradable nonwoven fabric according to any one of [1] to [3], 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 under conditions of a temperature of 190 ° C and a load of 2.16 kg.

[0016] [5] The biodegradable nonwoven fabric according to any one of [1] to [4], wherein the biodegradable thermoplastic resin has a melting point in the range of 70°C or higher and 200°C or lower.

[0017] [6] The biodegradable nonwoven fabric according to any one of [1] to [5], 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.

[0018] [7] The biodegradable nonwoven fabric according to any one of [1] to [6], wherein the biodegradable thermoplastic resin contains polybutylene adipate terephthalate.

[0019] [8] The biodegradable nonwoven fabric according to any one of [1] to [7], which is not subjected to a mechanical entanglement treatment.

[0020] [9] A method for producing the biodegradable nonwoven fabric according to any one of [1] to [8], 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.

[0021] According to the present invention, a nonwoven fabric having biodegradability and excellent flexibility and stretchability can be provided. Since the elongation is 50% or more, when used as a patch, bandage, etc., it does not tear even when lightly pulled and can easily deform, providing sufficient conformability for the intended use. Furthermore, since the recovery rate at 20% elongation is 60% or more, the fabric has excellent stretchability and provides a good feel when used as a patch, bandage, etc.

[0022] In order to obtain a nonwoven fabric with excellent flexibility and stretchability, it is effective to use a biodegradable thermoplastic resin with a relatively high melt viscosity and to adopt manufacturing conditions that are suitable for its melting properties. Although the details of why this is the case are unclear, it is presumed that the use of a biodegradable thermoplastic resin with a higher molecular weight than conventionally used results in an appropriate degree of crystal orientation during the spinning, stretching, and other processes.

[0023] Hereinafter, embodiments of the present invention will be described in detail.

[0024] The biodegradable nonwoven fabric of the present invention is composed of fibers containing a biodegradable thermoplastic resin. 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 improves 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 noise generation 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.

[0025] 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 where 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 where it begins to contact the baseline on the high temperature side as the end point, drawing a straight line connecting the start point and the end point, and integrating the area enclosed by the straight line and the curve.

[0026] The weight-average molecular weight (g / mol) of the biodegradable thermoplastic resin is preferably 35,000 or more. This can improve recovery during elongation after compression. The weight-average molecular weight is more preferably 37,000 or more, and even more preferably 40,000 or more. Also, 150,000 or less is preferable. 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.

[0027] 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 under conditions of a temperature of 190°C and a load of 2.16 kg, 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 due to the ease of thread formation during melting. However, with such an MFR, the fiber strength of the biodegradable thermoplastic resin is often weak, making it prone to thread 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 does not become too high, making it easier to mold into yarn. The MFR of the biodegradable thermoplastic resin can be measured by the method described in the examples below. The MFR of the biodegradable thermoplastic resin can be adjusted by the type, copolymer composition, molecular weight, melting point, etc. of the biodegradable thermoplastic resin.

[0028] 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 single yarn strength of the fibers constituting the nonwoven fabric will decrease, and yarn breakage will be more likely to occur during the drawing process. On the other hand, if the melting point exceeds 200°C, the ratio of hard segments in the intramolecular structure will be too high, and the flexibility and stretchability of the nonwoven fabric will be easily lost.

[0029] Preferred biodegradable thermoplastic resins include polylactic acid, polylactic acid / polycaprolactone copolymers, polylactic acid / polyether copolymers, 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. When the biodegradable thermoplastic resin is an aromatic-containing polyester, better stretchability is obtained, and when the biodegradable thermoplastic resin is a copolymer polyester containing structural units derived from an aromatic carboxylic component and an aliphatic carboxylic component, even better stretchability is obtained. When the biodegradable thermoplastic resin contains a polybutylene adipate terephthalate-based resin, it may also contain other biodegradable thermoplastic resins as described above. For details, please refer to the positive list of GreenPla (biodegradable plastic) classification number A-1 of the Japan BioPlastics Association. The fibers that make up the biodegradable nonwoven fabric may contain resins other than biodegradable thermoplastic resins. Examples of such resins include thermoplastic resins such as polyurethane and polyester.

[0030] The positive list (Ver. 2023.4 (Sep.)) of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1 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 (diacetate) manufactured by Daicel, and polylactic acid products manufactured by NatureWorks Japan, including 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 Yaoka (Zhejiang Haizheng Biomaterials), PLA manufactured by Chori (PliithBiotechnology), LuminyL-series, LuminyLX-series, and LuminyD-series manufactured by Total Energies Corbion, CKBP-PLLA-F01 manufactured by Mitoku Harness, and FY200 series, FY400 series, and FY600 series manufactured by HighChem (Anhui Fengyuan Futairai Lactic Acid). Examples of polylactic acid / polycaprolactone copolymers include Viroecole (registered trademark) BE-450, HYD-306, and BE-910 manufactured by Toyobo MC; poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is AONILEX (registered trademark) manufactured by Kaneka; polyglycolic acid is CRESAGE (registered trademark) and CREDAX (registered trademark) manufactured by Kureha; polylactic acid / polyether copolymers are Ecodia (registered trademark) L4E6 series manufactured by Toray; polycaprolactone is Plaxel (registered trademark) H1P, H5C, and H8C manufactured by Daicel; Capa6500, Capa6500D, Capa6800, and Capa6800D manufactured by Ingevity Japan; and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is PHACT manufactured by CJCHEIL JEDANG. TMA1000P, PHACT TM Examples of such polybutylene adipate / terephthalate 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, Ecoflex (registered trademark) FS manufactured by BASF Japan as an aliphatic aromatic polyester, Origo-BiES01G, EastarBio, and Ultra manufactured by GSI Creos (Novamont) as polytetramethylene adipate-co-terephthalate, BioPBSFZ71, BioPBSFZ91, and BioPBSFZ78 manufactured by PTTMCC, TUNHEPBS manufactured by BLUERIDGE, and ECO-B manufactured by Changchun Japan as polybutylene succinate. Polybutylene succinate adipate includes BioPBSFD92 manufactured by PTTMCC, A400 (ECOPONDKD1024) manufactured by KINGFA as polybutylene adipate terephthalate, TUNHEPBAT 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 JinHuiZhaoLongHighTech, and KanghuiNewMaterialTechno Examples of polyvinyl alcohol include Biodegradable Resin KHB21 manufactured by logy, HF901 manufactured by Chori as polypropylene carbonate, 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) manufactured by Kuraray.

[0031] 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.

[0032] Of all 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 all 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, in terms of biodegradability and environmental friendliness.

[0033] 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.

[0034] The molar ratio of the adipic acid component to the terephthalic acid component (adipic acid component / terephthalic acid component) in the polybutylene adipate terephthalate resin is preferably 35 / 65 or more and 60 / 40 or less, and more preferably 40 / 60 or more and 55 / 45 or less, from the viewpoint of improving the elongation recovery rate at 20% elongation of the nonwoven fabric while exhibiting biodegradability.

[0035] 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, terminal blocking, etc. These may be used alone or in combination of two or more.

[0036] 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.

[0037] 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, polybutylene glycol (polytetramethylene glycol), etc. These may be used alone or in combination of two or more.

[0038] 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 ECO-A20 manufactured by CHANG CHUN PLASTICS CO., LTD., Ecoflex (registered trademark) manufactured by BASF Japan Ltd., EastarBio GP and EastrBo Ultra manufactured by GSI Creos Co., Ltd. (Novmont), A40 (ECPONDKD1024) manufactured by KINGFA Co., Ltd., and TUNHEP BATTH-801T manufactured by XINJIANG BLUE RIDGETUNHE CHEMICAL INDUSTRY JOINT STOCK CO., LTD.

[0039] 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.

[0040] 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, and is preferably a circular cross section. Furthermore, the fibers may have a sea-island structure, a sheath-core structure, or a split fiber structure.

[0041] 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.

[0042] 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, the uniformity of the nonwoven fabric is less likely to decrease, and bleeding of medicinal ingredients can be suppressed when used as a patch.

[0043] 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 range from 0.05 to 6.0 mm.

[0044] 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, and it can be, for example, 0.3 g / cc or less, 0.28 g / cc or less, etc. Since the apparent density is 0.1 g / cc or more, when used as a patch or bandage, even if friction occurs with clothing, etc., it is less susceptible to friction, and curling during use can be prevented.

[0045] 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.

[0046] The biodegradable nonwoven fabric can have a stress at 5% elongation of 0.1 to 100 (N / 2.5 cm), preferably 0.3 to 2.0 (N / 2.5 cm). In particular, a stress of 1.0 (N / 2.5 cm) or less results in less tightness and a good feel when used as a base fabric for a patch. 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) direction is 0.1 (N / 2.5 cm) or more and the stress at 5% elongation in the CD (cross direction) direction is 0.1 (N / 2.5 cm) or more.

[0047] The biodegradable nonwoven fabric can have a mechanical strength of 1 to 200 (N / 2.5 cm), preferably 5 to 100 (N / 2.5 cm). In particular, a mechanical strength of 8 (N / 2.5 cm) or more can prevent easy breakage when used as a base fabric for a patch. In this specification, "a mechanical strength of 1 (N / 2.5 cm) or more" means that the mechanical strength in the MD (machine direction) direction is 1 (N / 2.5 cm) or more and the mechanical strength in the CD (cross direction) direction is 1 (N / 2.5 cm) or more.

[0048] The biodegradable nonwoven fabric has an elongation of 50% or more. The elongation is preferably 60% or more, more preferably 70% or more, and even more preferably 100% or more. When the elongation is 50% or more, when used as a patch, bandage, or the like, it will not tear even when gently pulled and will easily deform, providing sufficient conformability for the intended use. Furthermore, the elongation is preferably 500% or less, more preferably 300% or less. In this specification, "an elongation of 50% or more" refers to an elongation of 50% or more in the MD (machine direction) direction and an elongation of 50% or more in the CD (cross direction). To improve the elongation of a biodegradable nonwoven fabric, it is effective to use a biodegradable thermoplastic resin with a relatively small melt flow rate (MFR) and to adopt preferred manufacturing conditions according to its melting characteristics.

[0049] The biodegradable nonwoven fabric has a stretch recovery rate before and after 20% elongation of 60% or more, preferably 70% or more, and more preferably 80% or more. The higher the stretch recovery rate at 20% elongation, the more preferable it is, and it can be, for example, 99.5% or less, 99.0% or less, etc. Because the 20% stretch recovery rate is 60% or more, it has excellent elasticity and provides a good feel when used as a patch or bandage. For example, when applied to a joint such as an elbow, it can follow the movement of the skin at the bent part and suppress the occurrence of wrinkles. As a result, peeling caused by wrinkles can be prevented. In this specification, "a 20% stretch recovery rate of 60% or more" means that the 20% stretch recovery rate in the machine direction (MD) is 60% or more and the 20% stretch recovery rate in the cross direction (CD) is 60% or more. In order to improve the elongation recovery rate of a biodegradable nonwoven fabric at 20% elongation, it is effective to use a biodegradable thermoplastic resin with a relatively small melt flow rate (MFR) and to adopt preferred manufacturing conditions according to its melting characteristics.

[0050] 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, there is little tightness when used as a base fabric for a patch, and the feel when used as a base fabric for a patch is good.

[0051] 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.

[0052] 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.

[0053] 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 discharged 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.

[0054] <Step 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 (Step A).

[0055] In this case, it is preferable to adjust the spinning temperature and spinning speed when discharging the molten biodegradable thermoplastic resin from the spinneret depending on the MFR (melting property) of the biodegradable thermoplastic resin. For example, when using a biodegradable thermoplastic resin with a lower MFR value than conventional ones, it is effective to increase the spinning temperature or reduce the spinning speed.

[0056] This step A can be carried out using a spinning machine such as a conventionally known spunbond spinning machine.

[0057] 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 ２It 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.

[0058] <Step 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 collected while being spread on a lower conveyor to form a long-fiber web.

[0059] <Step 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 the flexibility and stretchability of the nonwoven fabric and compression bonding.

[0060] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0061] The following Examples 1 to 5 and Comparative Examples 1 to 5 were measured based on the following methods. The physical properties and other characteristics in this specification are specifically measured by the following methods.

[0062] (Intrinsic Viscosity) 0.1 g of resin was weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane (60 / 40 (weight ratio)). The viscosity was measured three times at 30° C. using an Ostwald viscometer, and the average value was calculated.

[0063] (Specific gravity) A density gradient solution was prepared using calcium nitrate tetrahydrate in a density gradient tube. ３Using a specific gravity float range of 100%, the fiber after jet drawing was put into a density gradient tube, and after stabilizing for 4 hours or more, the scale at the floating position was read, and the specific gravity was calculated from the float calibration curve.

[0064] (Crystalline 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). In detail, 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 depart 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, drawing a straight line connecting the starting point and the end point, and integrating the area enclosed by the straight line and the curve. This operation was performed three times to determine the average value (n = 3) of the crystalline melting enthalpy. The starting point was also designated as the melting onset temperature (° C.).

[0065] (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. The endothermic peak (melting peak) temperature was determined from the DSC curve. The above operation was repeated three times, and the average melting point (n = 3) was calculated.

[0066] (Melt Flow Rate (MFR)) After the resin was vacuum dried at 80°C for 2 hours or more, the melt flow rate (MFR) was quickly measured so as to minimize the incorporation of moisture from the air. The melt flow rate was measured in accordance with ISO 1133 using a Melt Indexer F-F01 machine manufactured by Toyo Seiki Seisaku-sho, Ltd. The measurement temperature was 190°C and the load was 2.16 kg. This operation was performed three times to determine the average melt flow rate (n = 3).

[0067] (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 prepare a sample solution concentration of 0.05% by mass. The solution was filtered through a 0.2 μm membrane filter, and GPC analysis of the obtained solution was performed under the following conditions. The molecular weight was calculated in terms of standard polystyrene.

[0068] Apparatus: TOSOH HLC-8320 GPC Column: TSKgel Super HM-H x 2 + TSKgel Super H2000 (TOSOH) Solvent: Chloroform

[0069] (Basis Weight) The mass per unit area was measured in accordance with JIS L1913 (2010) 6.2.

[0070] (Thickness, apparent density (bulk density)) 1 cm from the above basis weight and thickness obtained in accordance with JIS-L1913 (2010) 6.2 and 6.1 ３ The weight per unit was converted to 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.

[0071] (Fiber Diameter) Five randomly selected points on the sample (long fiber web before thermocompression bonding) were used to measure the diameter of single fibers (n=20) using an optical microscope, and the average value was calculated.

[0072] (Fineness (dtex)) Five randomly selected points 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 were taken out from the same five points, and the specific gravity of the fibers (n = 5) was measured using a density gradient tube to determine the average specific gravity. Next, the 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.

[0073] (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 rate Q (g / min) according to the following formula: V = (10000 x Q) / T

[0074] (Stress at 5% 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 spacing of 50 mm while being pulled by hand to the extent that it would not loosen, and an initial load of 0.02 N / 25 mm was applied. The sample was then stretched to 5% of the grip spacing at a tensile speed of 10 mm / min. The load value at this time was determined as the stress at 5% elongation. Measurements were performed with n = 5 in each of the longitudinal and transverse directions, and the average value was rounded to the nearest tenth.

[0075] (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 with a grip spacing of 50 mm while being pulled by hand to the extent that it would not loosen, 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 time was determined as the mechanical strength. Measurements were performed with n = 5 in each of the longitudinal and transverse directions, and the average value was rounded to the nearest tenth.

[0076] (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 with a grip distance of 50 mm while being pulled by hand to the extent that it would not loosen, and the initial load was set to 0.02 N / 25 mm. The sample was then stretched at a tensile speed of 10 mm / min until it broke. The maximum elongation value at this time was calculated as the average elongation. Measurements were performed with n = 5 in each of the longitudinal and transverse directions, and the average value was rounded to the nearest tenth.

[0077] (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 to the extent that it would not loosen, and an initial load of 0.02 N / 25 mm was applied. At this time, "(grip gap) + (length stretched when the initial load was applied)" was defined as L0. The sample was then stretched to 20% of the grip gap at a tensile speed of 25 mm / min. The length at this time was defined as L1. Immediately thereafter, the sample length was unloaded at the same speed to the initial load, and defined as L2. The 20% elongation recovery rate was calculated using the following formula. Measurements were performed with n = 5 in each of the longitudinal and transverse directions, and the average value was rounded to the nearest tenth. 20% elongation recovery rate (%) = [(L1 - L2) / (L1 - L0)] x 100

[0078] (Bending Resistance) The bending resistance per unit area was measured according to JIS L1913 (2000) 6.7.3 (cantilever method).

[0079] (Yarn Breakage) In step A, the yarn condition during drawing was visually checked, and the yarn breakage was evaluated by judging the number of yarn breaks per 5 minutes as follows: ◯: 1 yarn / 5 min or less, △: 2 to 9 yarns / 5 min or less, ×: 10 yarns / 5 min or more

[0080] (Stretchability) The nonwoven fabric sheet that had passed through step C was measured for recovery rates at 20% elongation in both the longitudinal and transverse directions, and the stretchability was evaluated by judging the recovery rates as follows: ◯: Recovery rates at 20% elongation in both the longitudinal and transverse directions were 60% or more; △: Recovery rates at 20% elongation in either the longitudinal or transverse direction were 60% or more; ×: Recovery rates at 20% elongation in both the longitudinal and transverse directions were less than 60%.

[0081] (Biodegradability) It was determined whether the resin that makes up the nonwoven fabric sheet retained biodegradable properties. ◯: The substance name (resin name) is listed on the Japan Bioplastics Association's positive list for GreenPla (biodegradable plastic) classification number A-1. ×: The substance name (resin name) is not listed on the Japan Bioplastics Association's positive list for GreenPla (biodegradable plastic) classification number A-1.

[0082] Example 1 Polybutylene adipate terephthalate (MFR: 4 g / min, melting point: 120°C, crystalline melting enthalpy: 14 J / g, molar ratio (adipic acid component / terephthalic acid component) = 52.5 / 47.5) (abbreviated as PBAT) shown in Table 1 was melted and kneaded in a single-screw extruder, and extruded by the spunbond method at a throughput rate of 0.5 g / min / Hole and a spinning temperature of 230°C. Filaments were pulled with a high-speed airflow pulling device using an air jet (Step A), and these were deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section) (Step B).

[0083] Next, using a pair of embossing rolls consisting of a roll having a concave-convex pattern on its surface and a roll having a smooth surface, the laminate was heat-pressed at a pressure of 12%, with both rolls at a temperature of 80°C 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.

[0084] Example 2 PBAT shown in Table 1 (MFR: 6 g / min, melting point: 150°C, crystalline melting enthalpy: 27 J / g, molar ratio (adipic acid component / terephthalic acid component) = 52.5 / 47.5) was melted and kneaded in a single-screw extruder and extruded by the spunbond method at a throughput rate of 0.5 g / min / hole and a spinning temperature of 220°C. A group of filaments was pulled with a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section).

[0085] Next, using a pair of embossing rolls consisting of a roll having a concave-convex pattern on the surface and a roll having 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.

[0086] Example 3 A biodegradable nonwoven fabric sheet was produced in the same manner as in Example 1, except that PBAT shown in Table 1 (MFR: 9 g / min, melting point: 120°C, molar ratio (adipic acid component / terephthalic acid component) = 52.5 / 47.5) was used.

[0087] Example 4 A biodegradable nonwoven fabric sheet was produced in the same manner as in Example 1, except that PBAT shown in Table 1 (CHANG CHUN PLASTICS CO., LTD., product number (MFR20): ECO-A20, MFR: 20 g / min, melting point: 120°C, molar ratio (adipic acid component / terephthalic acid component) = 52.5 / 47.5) was used.

[0088] Example 5 A biodegradable nonwoven fabric sheet was produced in the same manner as in Example 1, except that PBAT shown in Table 1 (MFR: 42 g / min, melting point: 120°C, molar ratio (adipic acid component / terephthalic acid component) = 52.5 / 47.5) was used.

[0089] 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 by the spunbond method at a throughput rate of 0.5 g / min / hole and a spinning temperature of 210°C. A group of filaments was 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).

[0090] Next, using a pair of embossing rolls consisting of a roll having a concave-convex pattern on its surface and a roll having a smooth surface, the fabric was heat-pressed at 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 with a basis weight of 70 g / m. 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0091] (Comparative Example 2) Using a side-by-side nozzle in a two-component spunbond spinning facility, polyethylene terephthalate (intrinsic viscosity (iv value): 0.63) and a copolymer polyester (a copolymer in which the dicarboxylic acid component is terephthalic acid and the glycol components are 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. Thereafter, 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.

[0092] Next, the obtained continuous fiber web was subjected to crimping while being conveyed between six heated rolls. Pressurization was carried out using rubber nip rolls. The obtained nonwoven fabric sheet had a basis weight of 100 g / m. ２ The thickness was 0.8 mm and the apparent density was 0.13 g / cc.

[0093] Comparative Example 3 Polyethylene terephthalate (intrinsic viscosity (iv value): 0.63) (abbreviated as PET) was melted and kneaded in a single-screw extruder, and extruded by the spunbond method at a throughput rate of 0.5 g / min / Hole and a spinning temperature of 280°C. A group of filaments was 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).

[0094] Next, using a pair of embossing rolls consisting of a roll having a concave-convex pattern on its surface and a roll having a smooth surface, the laminate 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 basis weight of 70 g / m. 2 A nonwoven fabric sheet of 1000g was obtained.

[0095] Comparative Example 4 Nylon (Ny) 66 (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 0.5 g / min / hole and a spinning temperature of 280°C. A group of filaments was 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).

[0096] Next, using a pair of embossing rolls consisting of a roll having a concave-convex pattern on its surface and a roll having a smooth surface, the laminate 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 basis weight of 71 g / m. 2 A nonwoven fabric sheet of 1000g was obtained.

[0097] Comparative Example 5 Polybutylene terephthalate (MFR: 100 g / min, melting point: 223°C) (PBT) was melted and kneaded in a single-screw extruder, and extruded by the spunbond method at a throughput rate of 0.5 g / min / hole and a spinning temperature of 240°C. A group of filaments was 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).

[0098] Next, using a pair of embossing rolls consisting of a roll having a concave-convex pattern on its surface and a roll having a smooth surface, the fabric was heat-pressed at a pressure-bonding area ratio of 12%, a temperature of 180°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a fabric with a basis weight of 76 g / m.2 A nonwoven fabric sheet of 1000g was obtained.

[0099] The results are shown in Table 1 together with the production conditions.

[0100]

Claims

1. A biodegradable nonwoven fabric comprising fibers containing a biodegradable thermoplastic resin, the nonwoven fabric having an elongation of 50% or more and an elongation recovery rate of 60% or more before and after elongation at 20% elongation of the nonwoven fabric.

2. The biodegradable nonwoven fabric according to claim 1, characterized in that the biodegradable thermoplastic resin is an aromatic-containing polyester.

3. The biodegradable nonwoven fabric according to claim 1, characterized in that the crystalline melting enthalpy of the biodegradable thermoplastic resin is in the range of 9 J / g or more and 50 J / g or less.

4. The biodegradable nonwoven fabric according to claim 1, 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 under conditions of a temperature of 190°C and a load of 2.16 kg.

5. The biodegradable nonwoven fabric according to claim 1, characterized in that the melting point of the biodegradable thermoplastic resin is in the range of 70°C or higher and 200°C or lower.

6. The biodegradable nonwoven fabric according to claim 1, 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.

7. The biodegradable nonwoven fabric according to claim 1, characterized in that the biodegradable thermoplastic resin comprises polybutylene adipate terephthalate.

8. The biodegradable nonwoven fabric according to claim 1, which has not been subjected to a mechanical entanglement treatment.

9. A method for producing a biodegradable nonwoven fabric according to any one of claims 1 to 8, 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.

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