Biodegradable nonwoven fabric and its uses

Abstract

The present invention provides a biodegradable nonwoven fabric which has biodegradability, while having extremely excellent texture, or having good formability and being suppressed in fluffing in an embossed part during forming. One embodiment of the present invention provides: a biodegradable nonwoven fabric which is configured from fibers that contain a biodegradable thermoplastic resin, and is characterized in that the shear viscosity thereof is more than 0 Pa∙s but not more than -41.4 × ln(x) + 500.84 Pa∙s at a shear rate x (x is from 20 / s to 10,000 / s) at 230°C, or is characterized in that the biodegradable nonwoven fabric has an embossed part and a non-embossed part, and the embossed part thickness index that is obtained by dividing the thickness of the embossed part by the square root of weight is 2.75 to 4.36 mm / (g / m2)0.5; or a food filter such as a coffee filter or a filter for tea bags, a mask, a diaper, an agricultural material or a lightweight packaging material, each of which comprises this biodegradable nonwoven fabric.

Description

[Technical Field]

[0001] The present invention relates to a biodegradable nonwoven fabric and its uses. [Background technology]

[0002] Traditionally, biodegradable nonwoven fabrics have been made from various biodegradable resins, including polylactic acid, and in recent years, due to growing awareness of promoting sustainability, they have been widely deployed in various fields and applications. However, biodegradable resins are generally hard, and it is difficult to achieve excellent texture (the texture that people feel when they touch something, such as the feel, texture, and comfort of wearing) as a nonwoven fabric.

[0003] Furthermore, molded articles made of biodegradable nonwoven fabrics have been known and are used in a variety of fields and have a wide range of applications. Molded articles can be obtained by thermoforming nonwoven fabrics.

[0004] Patent Document 1 below discloses a biodegradable nonwoven fabric that is bulky and has excellent bending flexibility by forming a nonwoven web from crimped fibers made from modified yarns and further setting the embossing interval to a certain level or more.

[0005] Patent Document 2 below describes a fabric made of polylactic acid polymer fibers with a basis weight of 20 to 350 g / m 2 The document discloses that the biodegradable nonwoven fabric for thermoforming is free from tearing and has little uneven stretching during thermoforming, and allows for the production of a molded product with a beautiful shape in a shorter time, and that the handleability during thermoforming is good. Furthermore, since the nonwoven fabric can conform to complex molded shapes during thermoforming, it is possible to produce a molded product with excellent design. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2021 / 054465 [Patent Document 2] International Publication No. 2018 / 070490 Summary of the Invention [Problem to be solved by the invention]

[0007] However, there is a demand for a biodegradable nonwoven fabric that has a better feel than the biodegradable nonwoven fabric described in Patent Document 1.

[0008] Furthermore, there is a demand for a biodegradable nonwoven fabric for thermoforming that is less susceptible to fluffing at the embossed portion during molding than the biodegradable nonwoven fabric described in Patent Document 2.

[0009] In view of the above-mentioned problems of the prior art, the first problem to be solved by the present invention is to provide a biodegradable nonwoven fabric that is biodegradable and has an extremely excellent feel.

[0010] The second problem to be solved by the present invention is to provide a biodegradable nonwoven fabric for thermoforming that is biodegradable, has good formability, and suppresses fuzzing of the embossed portions during molding. [Means for solving the problem]

[0011] The present inventors conducted extensive research and experiments to achieve the first object. As a result, they focused on the properties of nonwoven fabrics and unexpectedly discovered that a biodegradable nonwoven fabric composed of fibers containing a biodegradable thermoplastic resin and having a shear viscosity of more than 0 Pa s and less than or equal to -41.4 × ln(x) + 500.84 Pa s (where ln(x) is the natural logarithm; for ease of reading, an "x" is placed before the natural logarithm) at 230°C and a shear rate of x (where x is 20 / s to 10,000 / s) has an extremely good texture. Furthermore, as a result of extensive research and experiments conducted by the present inventors to achieve the second object, it has been discovered that a biodegradable nonwoven fabric is made of fibers containing a biodegradable thermoplastic resin, has an embossed portion and a non-embossed portion, and has an embossed portion thickness index, obtained by dividing the thickness of the embossed portion by the square root of the basis weight, of 2.75 to 4.36 mm / (g / m 2 ) 0.5It has been unexpectedly discovered that a biodegradable nonwoven fabric characterized by the formula (I) has good moldability and inhibits fluffing of the embossed portion during molding.

[0012] That is, one aspect of the present invention is as follows. [1] A biodegradable nonwoven fabric made of fibers containing a biodegradable thermoplastic resin, characterized in that at 230°C and a shear rate x (where x is 20 / s to 10,000 / s), the shear viscosity is greater than 0 Pa s and not greater than -41.4 × ln(x) + 500.84 Pa s. [2] The biodegradable nonwoven fabric according to [1] above, which has a shear viscosity of -5.45 × ln(x) + 50.759 Pa s or more at a shear rate of x (where x is 20 / s to 10,000 / s) at 230°C. [3] The biodegradable nonwoven fabric according to [1] or [2], which has a shear viscosity of -36.8 × ln(x) + 366.03 Pa s or less at a shear rate of x (where x is 20 / s to 10,000 / s) at 230°C. [4] The biodegradable nonwoven fabric according to any one of [1] to [3] above, which has a shear viscosity of -25.46 × ln(x) + 257.11 Pa s or less at a shear rate of x (where x is 20 / s to 10,000 / s) at 230°C. [5] The biodegradable nonwoven fabric according to any one of [1] to [4] above, which has a glass transition temperature of 25°C or lower when heated at a rate of 10°C / min using a differential scanning calorimeter. [6] The biodegradable nonwoven fabric according to any one of [1] to [5], wherein the biodegradable thermoplastic resin is at least one selected from the group consisting of polybutylene succinate adipate, polybutylene adipate terephthalate, polyhydroxybutyrate valerate, and polyhydroxybutyrate butyrate. [7] The biodegradable nonwoven fabric according to [6], wherein the biodegradable thermoplastic resin is polybutylene adipate terephthalate. [8] An embossed portion has an embossed portion and a non-embossed portion, and the embossed portion thickness index obtained by dividing the thickness of the embossed portion by the square root of the basis weight is 2.75 to 4.36 mm / (g / m 2 ) 0.5 The biodegradable nonwoven fabric according to any one of [1] to [7] above, [9] The Raman spectrum of the fibers constituting the biodegradable nonwoven fabric measured by polarized Raman spectroscopy with polarized light perpendicular to the fiber axis is 1612 cm -1 The peak intensity I⊥ at 1612 cm in the Raman spectrum measured with polarization parallel to the fiber axis -1 The biodegradable nonwoven fabric according to any one of the above [1] to [8], wherein the ratio I / / / I⊥ of the peak intensity I / / in the

[10] The biodegradable nonwoven fabric according to any one of [1] to [9] above, which is for thermoforming.

[11] A food filter comprising the biodegradable nonwoven fabric according to any one of [1] to

[10] above.

[12] The food filter according to

[11] , which is a coffee filter or a tea bag filter.

[13] A mask comprising the biodegradable nonwoven fabric according to any one of [1] to

[10] .

[14] A diaper comprising the biodegradable nonwoven fabric according to any one of [1] to

[10] above.

[15] An agricultural material comprising the biodegradable nonwoven fabric according to any one of [1] to

[10] above.

[16] A lightweight packaging material comprising the biodegradable nonwoven fabric according to any one of [1] to

[10] .

[0013] Another aspect of the present invention is as follows. <1> A biodegradable nonwoven fabric made of fibers containing a biodegradable thermoplastic resin, having an embossed portion and a non-embossed portion, and an embossed portion thickness index obtained by dividing the thickness of the embossed portion by the square root of the basis weight is 2.75 to 4.36 mm / (g / m 2 ) 0.5 A biodegradable nonwoven fabric characterized by: <2> The thickness index of the embossed portion is 2.75 to 4.05 mm / (g / m 2 ) 0.5The aforementioned <1> The biodegradable nonwoven fabric according to claim 1. <3> The glass transition temperature when heated at a rate of 10°C / min using a differential scanning calorimeter is 25°C or less. <1> or <2> The biodegradable nonwoven fabric according to claim 1. <4> The biodegradable thermoplastic resin is at least one selected from the group consisting of polybutylene succinate adipate, polybutylene adipate terephthalate, polyhydroxybutyrate valerate, and polyhydroxybutyrate butyrate. <1> ~ <3> 1. The biodegradable nonwoven fabric according to any one of the preceding claims. <5> The biodegradable thermoplastic resin is polybutylene adipate terephthalate. <4> The biodegradable nonwoven fabric according to claim 1. <6> The Raman spectrum of the fibers constituting the biodegradable nonwoven fabric measured by polarized Raman spectroscopy with polarized light perpendicular to the fiber axis is 1612 cm -1 The peak intensity I⊥ at 1612 cm in the Raman spectrum measured with polarization parallel to the fiber axis -1 The ratio value I / / / I⊥ of the peak intensities I / / in the <1> ~ <5> 1. The biodegradable nonwoven fabric according to any one of the preceding claims. <7> The above-mentioned is for thermoforming. <1> ~ <6> 1. The biodegradable nonwoven fabric according to any one of the preceding claims. <8> The aforementioned <1> ~ <7> A method for producing a molded article, comprising a step of thermoforming the biodegradable nonwoven fabric according to any one of the above items. <9> The molded body is a food filter. <8> The method described below. <10> The molded article is a coffee filter or a tea bag filter. <9> The method described below. <11> The molded body is a mask. <8> The method described below. <12> The molded body is an agricultural material. <8> The method described below. [Effects of the Invention]

[0014] The biodegradable nonwoven fabric of one embodiment of the present invention is biodegradable and has an extremely excellent feel. Furthermore, the biodegradable nonwoven fabric according to another embodiment of the present invention is biodegradable, has good moldability, and is suppressed from fuzzing at the embossed portions during molding. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is a biodegradable nonwoven fabric made from fibers containing a biodegradable thermoplastic resin, characterized in that the biodegradable nonwoven fabric has a shear viscosity of more than 0 Pa s and less than or equal to -41.4 × ln(x) + 500.84 Pa s at 230°C and a shear rate of x (where x is 20 / s to 10,000 / s). Another embodiment of the present invention is a biodegradable nonwoven fabric made of fibers containing a biodegradable thermoplastic resin, which has an embossed portion and a non-embossed portion, and has an embossed portion thickness index, obtained by dividing the thickness of the embossed portion by the square root of the basis weight, of 2.75 to 4.36 mm / (g / m 2 ) 0.5 The biodegradable nonwoven fabric is characterized by:

[0016] The biodegradable nonwoven fabric of this embodiment is composed of fibers containing a biodegradable thermoplastic resin. Examples of biodegradable thermoplastic resins include polyhydroxybutyrate valerate, polyhydroxybutyrate butyrate, nylon 4, polyglycolic acid, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene terephthalate succinate, polybutylene succinate carbonate, polybutylene adipate terephthalate, polyethylene succinate, polyethylene terephthalate succinate, and polyvinyl alcohol. From the viewpoints of biodegradability and texture, polyhydroxybutyrate valerate, polyhydroxybutyrate butyrate, and polybutylene adipate terephthalate are preferred. Furthermore, from the viewpoint of readily exhibiting home compostability and soil compostability, polycaprolactone, nylon 4, polybutylene succinate adipate, and polybutylene adipate terephthalate are preferred, and from the viewpoint of readily exhibiting marine compostability, polyhydroxybutyrate valerate, polycaprolactone, and nylon 4 are preferred. Details of home compostability, soil compostability, and marine compostability will be described later. Furthermore, from the viewpoint of ease of separation as a component of the final product, polycaprolactone and polybutylene succinate adipate are preferred, as they can be melted with the heat of boiling water.

[0017] The method for producing the biodegradable nonwoven fabric of this embodiment 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 that can be used include embossing, thermal bonding, columnar flow entanglement, mechanical entanglement, and needle punching. 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 fuzzing after molding.

[0018] 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.

[0019] The biodegradable nonwoven fabric of this embodiment may have a laminated structure, such as a laminated structure of SS, SMS, SMMS, or SMSM. Here, S means a spunbonded long-fiber nonwoven fabric, and M means a meltblown ultrafine nonwoven fabric. Alternatively, a short-fiber nonwoven fabric layer may be laminated on a biodegradable nonwoven fabric substrate.

[0020] The shape of the fibers constituting the biodegradable nonwoven fabric of the present embodiment is not particularly limited, and may have a circular, flat, C-shaped, Y-shaped, V-shaped or other irregular cross section, with a circular cross section being preferred. Furthermore, the fibers may have a sea-island structure, a sheath-core structure, or a split fiber structure.

[0021] The fibers constituting the biodegradable nonwoven fabric of this embodiment may further contain one or more other resins, flame retardants, inorganic fillers, softeners, plasticizers, pigments, antistatic agents, etc., depending on the purpose.

[0022] The fibers constituting the biodegradable nonwoven fabric of this embodiment may contain a secondary thermoplastic resin (hereinafter also referred to as "secondary resin") other than the biodegradable thermoplastic resin. The content of the secondary resin is preferably 0.5% by mass or more and 50% by mass or less, more preferably 2 to 50% by mass, even more preferably 5 to 30% by mass, and most preferably 5 to 25% by mass, when the total mass of the nonwoven fabric is taken as 100% by mass. If the amount added is 0.5% by mass or more, the crystallinity of the nonwoven fabric can be controlled, and therefore the texture of the nonwoven fabric can be easily controlled.

[0023] Examples of resins that can be used as minor components include polyhydroxybutyrate valerate, polyhydroxybutyrate butyrate, nylon 4, polycaprolactone, polybutylene succinate, polybutylene succinate adipate, polybutylene terephthalate succinate, polybutylene succinate carbonate, polybutylene adipate terephthalate, polyethylene succinate, polyethylene terephthalate succinate, polyglycolic acid, polyvinyl alcohol, polypropylene, polyethylene terephthalate, and polyethylene. From the viewpoints of biodegradability and texture, polyhydroxybutyrate valerate, polyhydroxybutyrate butyrate, and polybutylene adipate terephthalate are desirable, and from the viewpoint of ease of separation as a component of the final product, polycaprolactone and polybutylene succinate adipate are desirable, as they can be melted with the heat of boiling water. The secondary component resin may also contain non-biodegradable resins such as polypropylene, polyethylene terephthalate, and polyethylene, but from the viewpoint of satisfying the various biodegradability requirements described below, it is preferable that the content of the non-biodegradable resin is less than 10% by mass.

[0024] When the fibers constituting the biodegradable nonwoven fabric of this embodiment are sea-island fibers in which the biodegradable thermoplastic resin as the main component forms the sea and the resin as the secondary component forms the islands, the crystallinity can be controlled with a smaller addition rate, and the texture of the nonwoven fabric can also be easily controlled.

[0025] The spunbonding method typically uses a high-speed airflow traction device using an air jet, and the traction force can be adjusted by adjusting the amount of air introduced into the traction device. This traction force was measured by inserting two 0.235 mm diameter fishing lines (Toray Industries, Inc. nylon fishing line "Ginrin (No. 2 / natural / 50 m roll)" in this specification) into the traction device, measuring the stress using a spring scale connected to the fishing lines, and dividing the stress by the length of the fishing lines inserted to determine the traction force (mN / m). The traction force is preferably 27 to 125 mN / m, more preferably 38 to 75 mN / m, and most preferably 46 to 63 mN / m. A traction force of 125 mN / m or less sufficiently prevents yarn breakage during spinning and prevents excessive crystallization by preventing excessive orientation and crystallization, thereby preventing an excessive increase in birefringence Δn after thermocompression bonding or fixed-length heat treatment. If the strength is 27 mN / m or more, oriented crystallization can be promoted to a suitable degree, making it possible to perform thermocompression bonding, thereby obtaining a nonwoven fabric with sufficient strength.

[0026] The method of thermocompression bonding in the production of the biodegradable nonwoven fabric of this embodiment is not limited, and may be a combination of an embossed roll with a textured surface and a flat roll without texture, or a pair of embossed rolls with textured surfaces. The material of the roll surface is also not limited, and may be metal, rubber, resin, or the like. When an embossed roll with a textured surface is used, thermocompression bonding can be performed at a roll temperature preferably 10°C or more lower than the melting point of the resin of the nonwoven fabric, at a linear pressure of preferably 5 to 100 N / mm, more preferably 20 to 80 N / mm, and at a compression area ratio of preferably 3 to 50%, more preferably 6 to 40%. By performing thermocompression bonding within an appropriate range, it is possible to achieve both the texture of the nonwoven fabric and compression bonding.

[0027] In the production of the biodegradable nonwoven fabric of this embodiment, a fixed-length heat treatment may be performed regardless of whether or not the thermocompression bonding step is performed. The fixed-length heat treatment is performed under conditions in which the dimensions of the nonwoven fabric in the length and width directions are regulated so as not to change during the heat treatment. The nonwoven fabric obtained by thermocompressing a nonwoven fabric web immediately after spinning and then performing a fixed-length heat treatment has good surface smoothness and excellent stretchability in a thermal environment, making it less likely to tear during molding and easier to obtain a molded product with a clean shape. The fixed-length heat treatment may be performed using a conventional method, such as hot air drying, pin tenter drying, hot plate drying, calendering, felt calendering, air-through processing, or heat pressing. The temperature range during fixed-length heat setting may be any temperature that ensures that the resin constituting the nonwoven fabric does not adhere to the equipment and that the fibers of the nonwoven fabric are adequately bonded.

[0028] In the production of the biodegradable nonwoven fabric of this embodiment, bonding may be performed by a method other than thermocompression bonding. For example, in the case of hydroentanglement or needle punching, bonding of the nonwoven fabric is possible without applying heat, improving the texture of the nonwoven fabric. Note that these bonding methods may be performed after embossing.

[0029] The biodegradable nonwoven fabric of this embodiment can improve crystallinity and suppress thermal shrinkage of the nonwoven fabric by specific aging conditions. Specific aging conditions include storage at 40°C for 10 days or more, which can easily achieve the above-mentioned effects.

[0030] The biodegradable nonwoven fabric of this embodiment may contain a surfactant to enhance antistatic properties and water absorption. The surfactant may be any of nonionic, anionic, or cationic surfactants, including carboxylic acid, sulfonic acid, sulfate, phosphate, ester, ether, ester ether, alkanolamide, alkylamine, and quaternary ammonium types. Ester types are preferred, and among the ester types, sorbitan fatty acid esters, polyglycerin fatty acid esters, and polyoxyalkylene alkyl esters are particularly preferred. These surfactants may be used alone or in combination.

[0031] The surfactant adhesion rate is preferably 0.1 wt% or more, and more preferably 2.0 wt% or less, relative to the mass of the nonwoven fabric, from the viewpoint of sufficient antistatic properties and water absorption. If the surfactant adhesion rate is 0.1 wt% or more and 2.0 wt% or less, sufficient performance can be obtained.

[0032] The surfactant can be applied by any of the existing methods such as the kiss method, gravure method, spray method, etc., and can be appropriately selected depending on the purpose. Specifically, if it is desired to express performance on only one side, a transfer method such as the kiss method or gravure method is preferred, and if it is desired to obtain the same performance on both sides, application by the spray method is preferred.

[0033] The basis weight of the biodegradable nonwoven fabric of this embodiment is preferably 10 g / m 2 More than 450g / m 2 or less, more preferably 10 to 250 g / m 2 and more preferably 12 to 100 g / m 2 The basis weight is 10g / m 2 If it is more than 450g / m, the strength is sufficient. 2 If it is below this, a sufficient texture can be maintained.

[0034] The biodegradable nonwoven fabric of this embodiment preferably has a shear viscosity of more than 0 Pa·s and not more than −41.4×ln(x)+500.84 Pa·s, more preferably not more than −41.4×ln(x)+500.84 Pa·s, and even more preferably not more than −36.8×ln(x)+366.03 Pa·s, at 230°C, where x is a shear rate (where x is 20 / s to 10,000 / s). Here, the shear viscosity is most preferably -25.46 × ln(x) + 257.11 or less, and preferably -5.45 × ln(x) + 50.759 Pa·s or more, more preferably -10.17 × ln(x) + 98.781 or more, and most preferably -10.95 × ln(x) + 109.1 or more (where ln(x) is the natural logarithm. For ease of reading, an "x" is placed before the natural logarithm). If the shear viscosity is -41.4 × ln(x) + 500.84 Pa·s or less, excellent texture is achieved. On the other hand, if the shear viscosity is -5.45 × ln(x) + 50.759 Pa·s or more, a nonwoven fabric with good dispersion uniformity is easily obtained. If the dispersion uniformity of the nonwoven fabric is good, it is easy to obtain a nonwoven fabric with a good texture regardless of the sampling position, and the nonwoven fabric will have excellent filtering performance required for food filters and mask applications, or excellent resistance to powder leakage required for food filter applications such as coffee filters and tea bag filters.

[0035] The shear viscosity of the biodegradable nonwoven fabric of this embodiment can be controlled by the molecular structure, molecular weight, and viscosity of the resin, the extrusion temperature, residence time, various additives including water, and the crystallinity and orientation of the nonwoven fabric during nonwoven fabric production. For example, it is preferable to use polybutylene terephthalate adipate or polybutylene succinate adipate as the resin type. When nonwoven fabric is produced by the spunbonding method, for example, the shear viscosity of the final nonwoven fabric is often about 1 to 30% lower than that of the raw resin, depending on the thermal decomposition rate of the resin, the water content of the resin, the thermal history before extrusion, and the shear rate.

[0036] The glass transition temperature of the biodegradable nonwoven fabric of this embodiment is preferably 25° C. or lower, more preferably 10° C. or lower, and even more preferably 0° C. or lower. When the glass transition temperature is 25° C. or lower, the mobility of molecular chains is improved in a room temperature environment, and the texture is improved.

[0037] The biodegradable nonwoven fabric of the present invention has both biodegradability and excellent texture, and is suitable for a wide range of applications, including medical and sanitary materials, industrial materials, vehicle interior and exterior materials, soundproofing and absorbing materials, part transport trays, fruit and vegetable trays, food containers, agricultural materials such as seedling pods and mulch sheets, light packaging materials, and filters. It is particularly suitable for food filters such as coffee filters and tea bag filters, diapers, masks, agricultural materials, and light packaging materials.

[0038] When the biodegradable nonwoven fabric of the present invention is made of a biodegradable thermoplastic resin with a melting point of 100°C or less, its property of melting and shrinking in hot water can be utilized to facilitate the separation and recovery of the nonwoven fabric from products that contain multiple materials, such as diapers.

[0039] Hereinafter, a biodegradable nonwoven fabric suitable for thermoforming, which is one embodiment of the present invention, will be described. The glass transition temperature of the biodegradable nonwoven fabric of this embodiment is preferably 25°C or lower, more preferably 10°C or lower, and even more preferably 0°C or lower. When the glass transition temperature is 25°C or lower, embossing is performed at low temperature and high pressure in the thermocompression bonding step, which allows sufficient compression bonding between the fibers in the embossed areas while increasing the amount of residual amorphous material during thermoforming, making it easier to achieve both reduced fuzzing and good moldability. From the perspective of achieving a glass transition temperature within the above range, the biodegradable nonwoven fabric of this embodiment preferably contains a biodegradable thermoplastic resin such as polyhydroxybutyrate valerate, polyhydroxybutyrate butyrate, polybutylene adipate terephthalate, polycaprolactone, or polybutylene succinate adipate.

[0040] When the glass transition temperature of the biodegradable nonwoven fabric of this embodiment is 25°C or lower, the structure after thermoforming is not easily solidified, and shrinkage (shrinkage back) is likely to occur immediately after the thermoforming mold is released. This shrinkage can be suppressed by providing a shape-retaining process to rapidly cool and solidify the molded body after molding, or by optimizing the crystalline structure of the nonwoven fabric by adjusting the spinning speed in the spinning process and the conditions for thermocompression bonding and fixed-length heat treatment. Furthermore, this shrinkage can also be suppressed by performing inter-fiber compression bonding of the embossed portion at low temperature and high pressure with minimal heat application during thermocompression bonding by embossing. This further enhances both thermoformability and reduced fuzzing. When using an embossing roll with a textured surface for the embossing process, the roll temperature is preferably at least 10°C, more preferably at least 40°C, lower than the melting point of the resin of the nonwoven fabric, and the line pressure is preferably 5 to 100 N / mm, more preferably 20 to 80 N / mm.

[0041] When the biodegradable nonwoven fabric of this embodiment has an embossed portion and a non-embossed portion, the thickness index (mm / (g / m)) of the embossed portion is calculated by dividing the thickness of the embossed portion by the square root of the basis weight of the biodegradable nonwoven fabric. 2 ) 0.5 ) is greater than 0, preferably 2.75 or greater, 3.08 or greater, and preferably 4.36 or less, 4.05 or less, 3.63 or less, 3.51 or less, 3.43 or less, or 3.24 or less. If the thickness index of the embossed portion is 2.75 or greater, the embossed portion is less likely to break and formability is improved, while if it is 4.36 or less, inter-fiber compression bonding in the embossed portion is stronger and fluffing is suppressed. In particular, when the glass transition temperature is 25°C or less, the effect of having a thickness index of the embossed portion of 2.75 or greater and 4.36 or less is enhanced.

[0042] The polarized Raman spectroscopy of the fibers constituting the biodegradable nonwoven fabric of this embodiment measures the peak at 1612 cm in the Raman spectrum measured with polarized light perpendicular to the fiber axis. -1 The peak intensity I⊥ at 1612 cm in the Raman spectrum measured with polarization parallel to the fiber axis -1The ratio I / / / I⊥ of the peak intensity I / / at is preferably 2.9 or less, more preferably 2.7 or less, and even more preferably 1.2 to 2.5. When I / / / I⊥ is 2.9 or less, excessive orientation is prevented, allowing molecular chains to maintain their elongation during molding, and moldability is likely to be improved. From the viewpoint of pleat retention, the lower I / / / I⊥ is preferable, but for biodegradable fibers, it is generally greater than 1.08. A detailed method for measuring I / / / I⊥ will be described later.

[0043] The biodegradable nonwoven fabric of this embodiment preferably has a yield point in the displacement range of 0 to 40 mm in an SS curve obtained by stretching the biodegradable nonwoven fabric at 70°C, and the SS curve approximation equation for this range is preferably y=-2.6×10 -6 ×x 4 +0.0003x 3 -0.0112x 2 +0.2474x-0.0059~y=-3.5×10 -5 ×x 4 +0.0032x 3 -0.1146x 2 + 2.1105x+0.3381, more preferably y=-2.6×10 -6 ×x 4 +0.0003x 3 -0.0112x 2 +0.2474x-0.0059~y=-2.9×10 -5 ×x 4 +0.0026x 3 -0.0947x 2 +1.7434x+0.2793, or more preferably y=-2.6×10 -6 ×x 4 +0.0003x 3 -0.0112x 2 +0.2474x-0.0059~y=-8×10 -6 ×x 4 +0.0007x 3 -0.0282x 2 +0.8017x+0.2779, most preferably y=-5×10 -6 ×x 4 +0.0006x 3 -0.022x2 +0.4841x-0.0115~y=-7×10 -6 ×x 4 +0.0006x 3 -0.0256x 2 +0.7511x+0.211. The yield point is in the displacement range of 0 to 40 mm at 70°C, and the SS curve approximation formula for the same range is y=-2.6E×10 -6 ×x 4 +0.0003x 3 -0.0112x 2 If the value is +0.2474x-0.0059 or more, tearing during molding is unlikely to occur, and y=-3.5×10 -5 ×x 4 +0.0032x 3 -0.1146x 2 If it is +2.1105x+0.3381 or less, it is easy to suppress shrinkage immediately after molding.

[0044] The biodegradable nonwoven fabric of this embodiment can be processed by thermoforming to form a molded body. There are no particular limitations on the shape of the molded body, and it can be selected depending on the intended use, such as semicircular, cylindrical, elliptical, triangular, or rectangular. If it is desired to obtain a molded body with a larger area (surface area) than the area of ​​the nonwoven fabric before molding, it is sufficient to appropriately select a molding die that will increase the area of ​​the nonwoven fabric before and after molding.

[0045] The thermoforming method for the biodegradable nonwoven fabric of this embodiment is not particularly limited as long as it includes a thermoforming step, but may also include a preheating step before thermoforming and a shape-retaining step for maintaining the volume after thermoforming. By including a preheating step before thermoforming, the temperature of the nonwoven fabric immediately before molding can be controlled, allowing the nonwoven fabric's properties, such as storage modulus, to be adjusted to values ​​suitable for molding. The temperature of the nonwoven fabric immediately before molding is preferably 30 to 70°C, more preferably 40 to 60°C, and even more preferably 40 to 50°C. If the nonwoven fabric temperature immediately before molding is 30°C or higher, the nonwoven fabric becomes sufficiently soft and has good conformability to the mold during molding, reducing the likelihood of molding defects such as bag breakage and molding irregularities. Furthermore, if the temperature immediately before molding is 70°C or lower, the nonwoven fabric does not heat shrink and is easy to mold. The thermoforming temperature range is preferably 30 to 150°C, more preferably 50 to 90°C, and even more preferably 60 to 80°C. If the thermoforming temperature is 30°C or higher, the nonwoven fabric is sufficiently stretched.

[0046] The biodegradable nonwoven fabric for thermoforming of this embodiment is suitable for food filters such as coffee filters and tea bag filters, masks, and agricultural materials. [Example]

[0047] The present invention will be specifically described below with reference to examples. First, the measurement methods and evaluation methods used in the examples and comparative examples will be explained.

[0048] (1) Weight (g / m 2 ) According to JIS L-1913, the total area is 1500cm 2 The nonwoven fabric samples were cut into 3 pieces (20 cm wide x 25 cm long) and converted into mass per unit.

[0049] (2) Average fiber diameter (μm) A 500x magnified photograph was taken using a Keyence VHX-700F microscope, and the average value of 10 fibers in focus within the observation field was calculated.

[0050] (3) Bulk density (g / cm 3 ) The thickness (mm) of the nonwoven fabric sample was measured under a load of 100 g using a thickness gauge manufactured by Mitsutoyo Co., Ltd., and calculated using the following formula: Bulk density (g / cm 3 ) = basis weight (g / m 2 ) / Thickness (mm) / 1000 was calculated.

[0051] (4) Glass transition temperature (℃) Using a PerkinElmer DSC6000 differential scanning calorimeter, approximately 5.0 mg of nonwoven fabric was heated in a nitrogen atmosphere at a heating rate of 10°C / min from -50°C to a temperature near the melting point (Tm) + 60°C. The starting temperature of the second-order transition in heat quantity in the second-order transition region corresponding to the transition region from a glassy state to a rubbery state, detected during the heating process, was taken as the glass transition point (Tg).

[0052] (5) Melting point (°C) Using a PerkinElmer DSC6000 differential scanning calorimeter, 5.0 mg of nonwoven fabric was heated in a nitrogen atmosphere at a rate of 10°C / min from -50°C to a temperature near the melting point (Tm) + 60°C. The endothermic peak detected during the temperature rise process was taken as the melting peak, and the apex of this peak was taken as the melting point. Note that depending on the type and number of resins constituting the nonwoven fabric, multiple melting peaks may be observed.

[0053] (6) Shear viscosity (Pa s) Using a ROSAND capillary rheometer RH7-D, a volumetric flow rate (Q) of 0.118 cm was measured at 230°C through an orifice with a diameter (D) of 0.1 cm and a capillary length (L) of 1.6 cm connected to the end of a barrel with a radius of 1.5 cm. 3 / min, 0.588cm 3 / min, 2.946cm 3 / min, 5.885cm 3 / min, 11.778cm 3 / min, 58.904cm 3The program was set to change the shear rate stepwise from 1 / min to 20 / s, 100 / s, 500 / s, 1000 / s, 2000 / s, and 10000 / s, and the molten nonwoven fabric sample was extruded at shear rates (γ) of 20 / s, 100 / s, 500 / s, 1000 / s, 2000 / s, and 10000 / s, and the pressure (P: Pa) applied to the die was measured using the following formula:

number

[0054] (7) Biodegradable The following four types of biodegradation tests were conducted, and if a substance passed at least one of the tests, it was determined to be biodegradable. <Industrial compostability> In accordance with ISO 14855-1 (58±2°C) and JIS K 6953-1, biodegradation tests were conducted under conditions simulating industrial composting (composting plants) using organic components of municipal solid waste as compost at 58±2°C, and the degree of biodegradation was calculated as the ratio of the amount of carbon dioxide generated to the theoretical amount of carbon dioxide generated. If the degree of biodegradation reached 90% or more within six months, it was considered a pass (O), and if it failed, it was considered an fail (X). <Home compostability> Biodegradation tests were conducted at 28±2°C in accordance with ISO 14855-1 (28±2°C) and JIS K 6953-1, and the degree of biodegradation was calculated as the ratio of the amount of carbon dioxide generated to the theoretical amount of carbon dioxide generated. If the degree of biodegradation reached 90% or more within six months, it was marked as a pass (◯), and if it failed, it was marked as an x.

[0055] <Soil compostability> Biodegradation tests were conducted at 25±2°C in accordance with ISO 17556 (25±2°C), and the degree of biodegradation was calculated as the ratio of the amount of carbon dioxide generated to the theoretical amount of carbon dioxide generated. If the degree of biodegradation reached 90% or more within six months, it was marked as a pass (◯), and if it failed, it was marked as an x. <Marine compostability> Biodegradation tests were conducted at 30±1°C in accordance with ASTM D6691 (30±1°C), and the degree of biodegradation was calculated as the ratio of the amount of carbon dioxide generated to the theoretical amount of carbon dioxide generated. If the degree of biodegradation reached 90% or more within 6 months, it was marked as a pass (◯), and if it failed, it was marked as an x.

[0056] (8) Texture A 10 cm square sample of the nonwoven fabric was taken, and 10 randomly selected people picked it up and touched it for 30 seconds, and the sensation was scored according to the following criteria, and the average value was used. [Evaluation criteria] 5: Very good texture 4: Good texture 3: Relatively good texture 2: Poor texture 1: The texture is extremely poor.

[0057] (9) Dispersion uniformity A 1 m square sample of the nonwoven fabric was taken, and ten randomly selected people visually inspected it for 30 seconds to determine the uniformity of dispersion, which was scored according to the following criteria, and the average value was used. [Evaluation criteria] 4: The dispersion uniformity was extremely good. 3: The dispersion uniformity was good. 2: The dispersion uniformity was relatively good. 1: The dispersion uniformity was poor.

[0058] [Example 1] Polybutylene adipate terephthalate (abbreviated as PBAT in Tables 1 and 3) was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.9 g / min·Hole and a spinning temperature of 210°C. The filaments were pulled with a pulling force of 93 mN / m 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 11%, a temperature of 95°C for both rolls, and a roll linear pressure of 20 N / mm, to obtain a basis weight of 20 g / m 2 A biodegradable nonwoven fabric was obtained.

[0059] [Examples 2 to 6, 14 to 18] Biodegradable nonwoven fabrics were produced in the same manner as in Example 1, except that polybutylene adipate terephthalates with different shear viscosities were used.

[0060] [Examples 7 to 13] Biodegradable nonwoven fabrics were produced in the same manner as in Example 6, except that the line speed was changed so as to obtain the basis weights shown in Tables 1 and 2 below.

[0061] [Example 19] A biodegradable nonwoven fabric was produced in the same manner as in Example 6, except that the extrusion was carried out using the spunbond method at a spinning temperature of 220°C, the extruded filaments were stretched in the traction zone using the suction force of the moving collection surface, and then passed through a diffuser and deposited on the moving collection surface.

[0062] [Example 20] Polybutylene succinate adipate (abbreviated as PBSA in Table 3) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 190°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 65°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A biodegradable nonwoven fabric was obtained.

[0063] [Examples 21 and 22] Biodegradable nonwoven fabrics were produced in the same manner as in Example 20, except that polybutylene succinate adipates with different shear viscosities were used.

[0064] [Example 23] Polyglycolic acid (abbreviated as PGA in Table 3) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 260°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 190°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A biodegradable nonwoven fabric was obtained.

[0065] [Example 24] Polybutylene succinate (abbreviated as PBS in Table 3) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 210°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 95°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A biodegradable nonwoven fabric was obtained.

[0066] [Example 25] Polyamide 4 (abbreviated as PA4 in Table 3) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 210°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 185°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A biodegradable nonwoven fabric was obtained.

[0067] [Example 26] Polycaprolactone (abbreviated as PCL in Table 3) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 100°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 45°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A biodegradable nonwoven fabric was obtained.

[0068] [Comparative Examples 1 and 2] Biodegradable nonwoven fabrics were produced in the same manner as in Example 1, except that polybutylene adipate terephthalates with different shear viscosities were used.

[0069] Comparative Example 3 Polyethylene terephthalate (abbreviated as PET in Table 4) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 290°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 220°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A nonwoven fabric of 1000 g was obtained.

[0070] Comparative Example 4 Polypropylene (abbreviated as PP in Table 4) was melted and kneaded in a single-screw extruder, and filaments were extruded toward a moving collection surface using the spunbonding method at a throughput rate of 0.9 g / min·Hole, a spinning temperature of 230°C, and a traction force of 93 mN / m to prepare a biodegradable long-fiber web (circular cross section). Next, the web was thermally bonded using a pair of embossing rolls, one with a textured surface and the other with a smooth surface, under conditions of a bonded area ratio of 11%, both rolls at a temperature of 135°C, and a roll linear pressure of 20 N / mm, resulting in a basis weight of 20 g / m. 2 A nonwoven fabric of 1000 g was obtained.

[0071] The physical properties and evaluation results of the nonwoven fabrics of Examples 1 to 26 and Comparative Examples 1 to 4 are shown in Tables 1 to 4.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] The invention relating to a biodegradable nonwoven fabric for thermoforming will be specifically explained below with reference to examples. In addition to the above evaluations, the biodegradable nonwoven fabric for thermoforming was also evaluated as follows.

[0077] (10) Thickness index of embossed part The nonwoven fabric sample was freeze-fractured in the cross-sectional direction, and the thickness of the embossed portion was observed using a Keyence VE-8800 scanning electron microscope. The magnification was ×200, and the thickness of the central portion of the embossed portion was The thickness was measured at five points, 20 μm from the center on both sides and another 20 μm outward. Of the five points, the maximum and minimum values ​​were omitted, leaving three points as the data for one embossment, and the average value of the thicknesses for the five embossments, i.e., a total of 15 points, was taken as the thickness of the embossed area. This value was then divided by the square root of the basis weight of the nonwoven fabric to give the thickness index. In principle, the basis weight is measured using the method described in (1), but if a sufficient sample size cannot be obtained, it may be measured at any size, such as a 5 cm square.

[0078] (11) 1612 cm in the Raman spectrum measured with polarized light perpendicular to the fiber axis -1 The peak intensity (I⊥) at 1612 cm in the Raman spectrum measured with polarization parallel to the fiber axis -1 Ratio of peak intensities (I / / ) at (I / / / I⊥) Using a Renishaw Raman spectrophotometer InViaReflex, the polarized Raman spectrum of one arbitrary fiber in the fiber layer (I) in the sample was measured by placing the sample so that the polarization plane of the excitation light was parallel to the fiber axis. -1 Next, the sample was rotated by 90°, and the polarized Raman spectrum was measured with the polarization plane of the excitation light perpendicular to the fiber axis. -1 The peak intensity (I⊥) at this point was measured. The ratio of (I / / ) to (I⊥), (I / / / I⊥), was calculated as the average value for 10 fibers. The larger the value of (I / / / I⊥), the higher the orientation of the molecular chains relative to the fiber axis. Note that the measurement was performed so that the optical axis of the polarizer on the detection side of the polarized Raman spectrum was parallel to the optical axis of the excitation light. The measurement conditions using the Raman spectrophotometer are as follows: (Measurement conditions) Laser wavelength: 532nm Excitation light intensity at measurement position: 1.5 mW Objective lens: 20x (NA 0.40) Diffraction grating: 1800gr / mm Exposure time: 2 seconds Number of times accumulated: 4 times

[0079] (12) Approximation formula for the SS curve obtained by stretching a biodegradable nonwoven fabric at 70°C in the displacement range of 0 mm to 40 mm Using a Shimadzu Corporation Autograph AG-X plus (load cell: 1 kN), a 30 mm wide sample was held at an ambient temperature of 70°C for 1 minute, and stretched at an elongation origin of 0.1% FS, a grip length of 20 mm, and a tensile speed of 200 mm / min. The SS curve obtained was plotted in Microsoft Excel up to a displacement of 40 mm. For this graph, the "Add Approximate Curve" tool in Excel was used, selecting "Polynomial Approximation: Degree 4" and using a quartic function approximation. Ten measurements were taken in the machine direction of the nonwoven fabric, and the SS curve with the breaking stress closest to the average value was used.

[0080] (13) Moldability Two types of cylindrical molded metal were used, one with a diameter of 4.4 cm and a height of 1.5 cm (15 mm), and the other with a diameter of 4.4 cm and a height of 3.0 cm (30 mm). The press temperature was set to 70°C and the press time was set to 1.0 second. The appearance of the molded body was observed and evaluated according to the following evaluation criteria. The number of surface fluffs was determined by counting the number of fluffs on the surface of the molded body and calculating the average value for N=10. [Evaluation criteria] ⊚: Out of 100 molded products, the number of broken bags was 1 or less and the number of surface fluffs was 3 or less. ◯: Out of 100 molded products, the number of broken bags is 2 or more and 5 or less, or the number of surface fluffs is 4 or more and 9 or less. △: There are at least one problem among the following: spots on the surface of the molded product, spots due to stretching, and 10 or more pieces of fluff on the surface. ×: The molded article was torn and no molded article was obtained.

[0081] (14) Shrinkage of molded body (dimensional change immediately after release from mold) The change rate of height of the molded body actually obtained relative to the theoretical height of the molded body produced by the method (13) above was calculated as an average value of N=5. The change rate of height was evaluated according to the following criteria. [Evaluation criteria] 5: Height change of molded body is within ±20% 4: Height change of molded body is more than ±20% and less than ±30% 3: Height change of molded body is more than ±30% and less than ±40% 2: Height change of molded body is more than ±40% and within ±50% 1: The height change of the molded body exceeds ±50%.

[0082] [Examples 27 to 41] Biodegradable nonwoven fabrics were produced in the same manner as in Example 15, except that the traction force, roll temperature, and roll pressure were changed.

[0083] [Examples 42 and 43] A biodegradable nonwoven fabric was produced in the same manner as in Example 39, except that polybutylene succinate and polycaprolactone were added as accessory components.

[0084] [Example 44] As the short fibers, raw cotton of polybutylene adipate terephthalate with a single fiber diameter of 30 μm was used, and this was passed through a carding machine to obtain a basis weight of 150 g / m 2 The web was then placed on a 100-mesh wire net and subjected to high-pressure liquid jet treatment using a high-pressure liquid jet treatment system with 0.08 mm diameter jet holes spaced 0.7 mm apart to integrate the web. The liquid jet conditions were 60 kg / cm 2 120kg / cm water pressure 2 The water pressure was 120 kg / cm from the opposite side. 2 The web was then dried at 70°C in a hot air dryer to remove excess moisture. Subsequently, a pair of embossing rolls, one of which had a concave-convex pattern on its surface, was used to heat-press the web under the following conditions: a pressed area ratio of 14%, a temperature of 55°C for both the upper and lower rolls, and a roll linear pressure of 60 N / mm, resulting in a basis weight of 150 g / m. 2 A biodegradable nonwoven fabric was obtained.

[0085] [Example 45] Weight is 68.0g / m 2 A web (basis weight 68.0 g / m) was produced in the same manner as in Example 39, except that the line speed was adjusted so that 2PBAT (melting point 110°C, shear viscosity 13 Pa·s at a shear rate of 1000 / sec at 230°C) was melt-blown onto the fiber at a spinning temperature of 210°C and heated air temperature of 230°C at a speed of 1000 Nm 3 / hr, meltblown web (basis weight 14.0 g / m 2 The resulting laminated web was heat-pressed in the same manner as in Example 39 to form a spunbond web of polylactic acid with a total weight of 150.0 g / m2. 2 A nonwoven fabric of 1000 g was obtained.

[0086] [Example 46] A biodegradable nonwoven fabric was produced in the same manner as in Example 45, except that for the first spunbond layer, the cross-sectional shape of the single yarn was sheath-core with a sheath-core ratio of 50 / 50 wt%, and PBAT was used on the core side and PBSA on the sheath side.

[0087] The physical properties and evaluation results of the nonwoven fabrics of Examples 27 to 36 are shown in Tables 5 to 7 below. In the table, the SS curve obtained by stretching the biodegradable nonwoven fabric at 70°C has an approximate equation of y = -2.6 x 10 for the SS curve in the displacement range of 0 to 40 mm. -6 ×x 4 +0.0003x 3 -0.0112x 2 +0.2474x-0.0059~y=-3.5×10 -5 ×x 4 +0.0032x 3 -0.1146x 2 + 2.1105x+0.3381 is "Condition A", y=-2.6×10 -6 ×x 4 +0.0003x 3 -0.0112x 2 +0.2474x-0.0059~y=-2.9×10 -5 ×x 4 +0.0026x3 -0.0947x 2 +1.7434x+0.2793 is "Condition B", y=-2.6×10 -6 ×x 4 +0.0003x 3 -0.0112x 2 +0.2474x-0.0059~y=-8×10 -6 ×x 4 +0.0007x 3 -0.0282x 2 +0.8017x+0.2779 is "Condition C", and y=-5×10 -6 ×x 4 +0.0006x 3 -0.022x 2 +0.4841x-0.0115~y=-7×10 -6 ×x 4 +0.0006x 3 -0.0256x 2 The case where the equation is +0.7511x+0.211 is referred to as "Condition D."

[0088] [Table 5]

[0089] [Table 6]

[0090] [Table 7] [Industrial Applicability]

[0091] The biodegradable nonwoven fabric of the present invention has excellent texture as well as biodegradability, and therefore can be suitably used in a wide range of fields, such as medical and sanitary materials, industrial materials, vehicle interior and exterior materials, soundproofing materials, sound-absorbing materials, parts transport trays, fruit and vegetable trays, food containers, agricultural materials such as seedling raising pods and mulch sheets, light packaging materials, and filters.

Claims

[Claim 1] A biodegradable nonwoven fabric for thermoforming, composed of fibers containing 80% to 100% by weight of a biodegradable thermoplastic resin that is polybutylene adipate terephthalate (PBAT), wherein the nonwoven fabric has a shear viscosity of -10.95 x ln(x) + 109.1 Pa s or more at 230°C and a shear rate of x (where x is 20 / s to 10,000 / s), and at 230°C: The shear viscosity is −25.46×ln(x)+257.11 Pa s or less at a shear rate of x (where x is 20 / s to 10,000 / s), and the glass transition temperature when heated at a rate of 10° C. / min using a differential scanning calorimeter is 0° C. or less. Furthermore, the Raman spectrum of the fibers constituting the nonwoven fabric measured by polarized Raman spectroscopy using polarized light perpendicular to the fiber axis has a peak at 1612 cm a ratio I / / / I⊥ of the peak intensity I / / at 1612 cm -1 in a Raman spectrum measured with polarized light parallel to the fiber axis to the peak intensity I⊥ at 1612 cm -1 is greater than 1.08 and not greater than 2.9, and the nonwoven fabric has embossed portions and non-embossed portions, and an embossed portion thickness index, obtained by dividing the thickness of the embossed portion by the square root of the basis weight, is 2.75 to 3.63 μm / (g / m 2 ) 0.5 .

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