Biodegradable nonwoven fabric for protecting farm product

Abstract

To provide a nonwoven fabric for protecting farm product, which is used in agricultural field, easily disposed of after use, hardly broken by wind, and has excellent installation workability and biodegradability.SOLUTION: A biodegradable nonwoven fabric for protecting farm products is a nonwoven fabric consisting of fibers including biodegradable thermoplastic resin, and has 40% or more of elongation recovery percentage at 20% elongation, 5 N or more of tear strength, and 20 mm or less of bending resistance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a biodegradable nonwoven fabric for protecting agricultural crops that is less likely to damage crops when protecting them from frost, dew, etc. during cultivation, is less likely to tear after laying, and can provide efficient protection. [Background technology]

[0002] The present invention relates to a nonwoven fabric for protecting agricultural crops that can be easily disposed of after use in the agricultural field, has excellent laying workability, and is biodegradable so that it is less likely to tear due to wind, etc.

[0003] Biodegradable nonwoven fabrics are 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, resulting in high demand. In particular, biodegradable nonwoven fabrics for protecting agricultural crops are expected to contribute to reducing environmental impact, and for example, Patent Document 1 proposes a nonwoven fabric made from polylactic acid-based long fibers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-333542 Summary of the Invention [Problem to be solved by the invention]

[0005] However, biodegradable resins are generally hard, and their applications are often limited to those where flexibility and stretchability are not required as application characteristics. In Patent Document 1, although the sheet biodegrades after a certain period of use, the inherent hardness and brittleness of the resin make it difficult to conform to the unevenness of agricultural crops and prone to tearing in a short period of time. Furthermore, when selecting raw materials to impart flexibility, using soft resins to create nonwoven fabrics tends to result in low thread strength, which can easily break during thread stretching in the production process, creating productivity issues.

[0006] The present invention aims to provide a biodegradable nonwoven fabric suitable for protecting agricultural crops, which is less likely to damage the crops when protecting them from frost, dew, etc. during cultivation, is less likely to tear after laying, and can provide efficient protection. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems, and as a result have found that a novel production method can be used to stably obtain a biodegradable nonwoven fabric suitable for protecting agricultural crops, which is biodegradable, does not damage crops when protecting them from frost, dew, etc. during cultivation, and is less likely to tear after installation, and has thus completed the present invention.

[0008] That is, the present invention provides the following. (1) A biodegradable nonwoven fabric for protecting agricultural crops, which is made of fibers containing a biodegradable thermoplastic resin, and which has an elongation recovery rate of 40% or more at 20% elongation, a tear strength of 5N or more, and a bending resistance of 20mm or less.

[0009] (2) In the configuration of (1) above, it is preferable that the elongation is 60% or more and the 5% elongation load is 10 N or less.

[0010] (3) In the configuration of (1) or (2), the biodegradable thermoplastic resin is preferably an aromatic-containing polyester.

[0011] (4) In the configuration of (1) or (2), it is desirable that the melt flow rate of the biodegradable thermoplastic resin be 0.3 g / 10 min or more and 50 g / 10 min or less.

[0012] (5) In the configuration of (1) or (2) above, it is desirable that the biodegradable thermoplastic resin of the biodegradable thermoplastic resin has a melting point of 70°C or higher and 200°C or lower.

[0013] (6) The biodegradable thermoplastic resin preferably contains adipic acid components, terephthalic acid components, and butanediol components in a total amount of 70 mol % or more, based on 100 mol % of all components.

[0014] (7) It is desirable that the biodegradable thermoplastic resin contains polybutylene adipate terephthalate.

[0015] (8) It is desirable that the biodegradable nonwoven fabric of (1) or (2) above is not subjected to a mechanical entanglement treatment.

[0016] (9) A method for producing a biodegradable nonwoven fabric according to (1) or (2), comprising: step A of discharging a molten biodegradable thermoplastic resin from a spinneret, cooling and solidifying the resin, and then pulling and stretching the resin with an ejector to form long fibers; step B of collecting the long fibers obtained in step A to form a long-fiber web; and step C of thermocompression bonding the long-fiber web. [Effects of the Invention]

[0017] The present invention provides a biodegradable nonwoven fabric that is both flexible and stretchable. Its elongation recovery at 20% elongation is 40% or more, its tear strength is 5N or more, and its bending resistance is 20mm or less. Therefore, when used as a substrate for protecting agricultural crops, it does not tear even when pulled lightly and easily deforms, providing sufficient conformability for its intended use. Hereinafter, embodiments of the present invention will be described in detail.

[0018] The biodegradable thermoplastic resin preferably has a crystalline melting enthalpy of 9 J / g or more. Having a crystalline melting enthalpy of 9 J / g or more can improve the recovery properties of the biodegradable nonwoven fabric during stretching. The crystalline melting enthalpy is more preferably 14 J / g or more, even more preferably 18 J / g or more, even more preferably 19 J / g or more, still more preferably 20 J / g or more, and particularly preferably 21 J / g or more. On the other hand, the crystalline melting enthalpy is preferably 50 J / g or less. This improves the flexibility of the biodegradable nonwoven fabric and reduces the generation of noise during compression and recovery. The crystalline melting enthalpy can be more preferably 28 J / g or less, even more preferably 26 J / g or less.

[0019] The crystalline melting enthalpy (J / g) of the biodegradable thermoplastic resin can be determined from the integral of the endothermic peak (melting peak) of the endothermic curve measured using a differential scanning calorimeter with a sample mass of 2.0 mg±0.1 mg at a heating rate of 20°C / min under a nitrogen atmosphere. The integral can be determined by setting the point at which the curve relating to the endothermic peak (melting peak) begins to deviate from the baseline on the low temperature side as the starting point and the point at which it begins to touch the baseline on the high temperature side as the end point, drawing a straight line connecting the starting point and the end point, and integrating the area enclosed by the straight line and the curve.

[0020] The weight-average molecular weight (g / mol) of the biodegradable thermoplastic resin is preferably 35,000 or more. This can improve recovery upon elongation after compression. The weight-average molecular weight is more preferably 37,000 or more, and even more preferably 40,000 or more. Also, it is preferably 150,000 or less. When it is 150,000 or less, flexibility can be improved. Furthermore, when the weight-average molecular weight is 120,000 or less, the polymer melt viscosity can be reduced. The weight-average molecular weight is more preferably 120,000 or less. The weight-average molecular weight can be determined by gel permeation chromatography (GPC) or the like.

[0021] The melt flow rate (MFR) of the biodegradable thermoplastic resin can be in the range of 0.3 g / 10 min to 50 g / 10 min at 190°C, preferably 0.4 g / 10 min to 20 g / 10 min, and more preferably 0.5 g / 10 min to 15 g / 10 min. It is even more preferably 3 g / 10 min to 13 g / 10 min, even more preferably 6 g / 10 min to 12 g / 10 min, and even more preferably 8 g / 10 min to 10 g / 10 min. When fiberizing thermoplastic resins using methods such as spunbonding, thermoplastic resins with a melt flow rate (MFR) of around 100 g / 10 min are often used 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 the fiber prone to breakage during the drawing process. Therefore, when the MFR is 15 g / 10 min or less, the strength of the single yarn constituting the nonwoven fabric is improved, and yarn breakage during the stretching process tends to be prevented. When the MFR is 10 g / 10 min or less, the yarn breakage resistance is improved, the sheet is less likely to tear when used as a crop protection sheet, and damage due to frictional contact between the sheet and crops tends to be less likely to occur. Furthermore, when the MFR is 0.3 g / 10 min or more, the viscosity when melted is not 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.

[0022] The melting point of the biodegradable thermoplastic resin is preferably 70°C to 200°C, more preferably 100°C to 170°C, and even more preferably 110°C to 130°C. If the melting point is below 70°C, the strength of the single fibers constituting the nonwoven fabric will decrease, making it more likely for thread breakage to occur during the stretching process. On the other hand, if the melting point is above 200°C, the ratio of hard segments in the intramolecular structure will be too high, making the nonwoven fabric more likely to lose its flexibility and stretchability.

[0023] Preferred biodegradable thermoplastic resins include polylactic acid, polylactic acid / polycaprolactone copolymer, polylactic acid / polyether copolymer, polyethylene terephthalate succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene adipate terephthalate, polyglycolic acid, polycaprolactone, polyvinyl alcohol, and cellulose acetate. Aromatic-containing polyesters such as polyethylene terephthalate succinate and polybutylene adipate terephthalate are even more preferred, with polybutylene adipate terephthalate-based resins being particularly preferred. Aromatic-containing polyesters provide superior stretchability. When polybutylene adipate terephthalate-based resins are used as biodegradable thermoplastic resins, other biodegradable thermoplastic resins may also be included. For details, see the positive list for GreenPla (biodegradable plastics) classification number A-1 of the Japan BioPlastics Association. The fibers constituting the biodegradable nonwoven fabric may contain resins other than biodegradable thermoplastic resins. Examples of such resins include thermoplastic resins such as polyurethane and polyester. The Japan Bioplastics Association's GreenPla (biodegradable plastic) Classification Number A-1 Positive List (Ver. 2023.4 (Sep.)) lists the following: hydroxyl-modified starch manufactured by Kuraray, starch polyesters Mater-Bi (registered trademark) NF01U and Mater-Bi (registered trademark) ZF03U / A manufactured by GSI Creos (Novamont), cellulose acetate (cellulose acetate (diacetate) manufactured by Daicel), and polylactic acid products manufactured by NatureWorks Japan: NatureWorks 2000 series, 3000 series, 4000 series, 6000 series, 7000 series, 8000 series, Ingeo (registered trademark) 5061A, and Ingeo (registered trademark) 5061B.Further examples of polylactic acid include Kanepearl (registered trademark) B100 manufactured by Kaneka, Viroecole (registered trademark) BE-400, BE-410, and HYD-006 manufactured by Toyobo MC, REVODE (registered trademark) 100 series and 200 series manufactured by Daishin Pharmaceutical (Zhejiang Haizheng Biomaterials), PLA manufactured by Chori (Pliith Biotechnology), Luminy L-series, Luminy LX-series, and Luminy manufactured by Total Energies Corbion. Examples of suitable polylactic acid / polycaprolactone copolymers include Viroecole (registered trademark) BE-450, HYD-306, and BE-910 manufactured by Toyobo MC, AONILEX (registered trademark) manufactured by Kaneka as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), Cressage (registered trademark) and Credax (registered trademark) manufactured by Kureha as polyglycolic acid, Ecodia (registered trademark) L4E6 series manufactured by Toray as polylactic acid / polyether copolymer, Placcel (registered trademark) H1P, H5C, and H8C manufactured by Daicel, and Capa 6500, Capa 6500D, and Capa manufactured by Ingevity Japan as polycaprolactone. 6800, Capa 6800D, Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) manufactured by CJ CHEIL JEDANG. TM A1000P, PHACT TMExamples include S1000P, Mater-Bi (registered trademark) CS series manufactured by GSI Creos (Novamont) which is a butanediol / long-chain dicarboxylic acid copolymer, Ecoflex (registered trademark) manufactured by BASF Japan which is a polybutylene adipate / terephthalate, Ecoflex (registered trademark) FS manufactured by BASF Japan as an aliphatic aromatic polyester, Origo-Bi ES01G and Eastar Bio Ultra manufactured by GSI Creos (Novamont) as polytetramethylene adipate-co-terephthalate, BioPBS FZ71, BioPBS FZ91, and BioPBS FZ78 manufactured by PTT MCC as polybutylene succinate, TUNHE PBS manufactured by BLUERIDGE, and ECO-B manufactured by Changchun Japan. Polybutylene succinate adipate includes BioPBS FD92 manufactured by PTT MCC, and polybutylene adipate terephthalate includes A400 (ECOPOND KD 1024) manufactured by KINGFA, TUNHE PBAT manufactured by BLUERIDGE, CKBP-PBAT-01 manufactured by Mitoku Harness, ECO-A manufactured by Changchun Japan, HF101 manufactured by HighChem (Zhejiang Huafeng Environmental Protection Materials), Ecoworld Biodegradable Polymer manufactured by JinHui ZhaoLong High Tech, and Biodegradable Resin manufactured by Kanghui New Material Technology. Examples of polyvinyl alcohol include KHB21, HF901 manufactured by Chori, Gohsenol (registered trademark), Gohsenex (registered trademark) T, Gohsenex (registered trademark) WO, and Nichigo (registered trademark) G Polymer manufactured by Mitsubishi Chemical, and Kuraray Poval (registered trademark) fully saponified product, Kuraray Poval (registered trademark) intermediate saponified product, Kuraray Poval (registered trademark) partially saponified product, Kuraray Poval (registered trademark) low saponified product, and Kuraray Exeval (registered trademark).

[0024] 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.

[0025] Of 100 mol% of all components constituting the biodegradable thermoplastic resin, the total content of the adipic acid component, the terephthalic acid component, and the butanediol component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 99 mol% or more. Of 100 mol% of all components constituting the biodegradable thermoplastic resin, it is even more preferable that they account for 100 mol%. Furthermore, it is preferable that the fibers constituting the biodegradable nonwoven fabric are made solely of biodegradable thermoplastic resin, from the viewpoint of biodegradability and environmental friendliness.

[0026] 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.

[0027] 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 types.

[0028] 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.

[0029] Examples of modifiers include polyisocyanate compounds and glycol compounds. Examples of polyisocyanate compounds include diisocyanate compounds. Examples of diisocyanate compounds include hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylene diisocyanate, carbodiimide-modified MDI, and polymethylenephenyl polyisocyanate. These compounds may be used alone or in combination of two or more. Examples of glycol compounds include diols other than butanediol and polyalkylene glycols. Examples of other diols include methanediol, ethanediol, propanediol, pentanediol, and hexanediol. Examples of polyalkylene glycols include polymethylene glycol, polyethylene glycol, polypropylene glycol, and polybutylene glycol (polytetramethylene glycol). These may be used alone or in combination of two or more.

[0030] Examples of polybutylene adipate terephthalate resins include biodegradable synthetic polymer compounds listed on the positive list of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1. Specific examples include Ecoflex (registered trademark) manufactured by BASF Japan Ltd., EastarBio GP and EastarBio Ultra manufactured by GSI Creos Co., Ltd. (Novmont), A40 (ECP ONDKD1024) manufactured by KINGFA Co., Ltd., and TUNHEPBATTH-801T manufactured by XINJIANG BLUE RIDGET UNHE CHEMICAL INDUSTRY JOINTSTOCK CO., LTD.

[0031] 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.

[0032] The shape of the fibers constituting the biodegradable nonwoven fabric is not particularly limited, but may have a circular, flat, C-shaped, Y-shaped, V-shaped or other irregular cross section, preferably a circular cross section, and may also have a sea-island structure, a sheath-core structure, or a split fiber structure.

[0033] 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.

[0034] The fiber diameter of the fibers constituting the biodegradable nonwoven fabric is preferably 5 to 60 μm, more preferably 10 to 50 μm, and even more preferably 12 to 40 μm. When the fiber diameter is 5 μm or more, spinnability in the spunbonding method is improved, enabling stable production. Furthermore, when the fiber diameter is 60 μm or less, unevenness of the nonwoven fabric is less likely to occur, which is desirable.

[0035] The basis weight and thickness of the biodegradable nonwoven fabric are not particularly limited, but the basis weight is 10 to 200 g / m 2 and the thickness can be in the range of 0.05 to 6.0 mm.

[0036] The biodegradable nonwoven fabric preferably has an apparent density of 0.1 g / cc or more, more preferably 0.11 g / cc or more, and even more preferably 0.13 g / cc or more. The higher the apparent density, the better, but it can be, for example, 0.3 g / cc or less, 0.28 g / cc or less, etc. Because the apparent density is 0.1 g / cc or more, when used as a biodegradable nonwoven fabric for protecting agricultural crops, curling during use can be prevented.

[0037] 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.

[0038] The biodegradable nonwoven fabric can have a stress at 5% elongation of 0.1 to 20 (N / 2.5 cm), preferably 0.1 to 10.0 (N / 2.5 cm). A stress of 5 (N / 2.5 cm) or less provides good conformability to uneven surfaces when laid, and provides excellent protection from frost and dew when used as a crop protection material. 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 machine direction (MD) is 0.1 (N / 2.5 cm) or more, and the stress at 5% elongation in the cross direction (CD) is 0.1 (N / 2.5 cm) or more.

[0039] The biodegradable nonwoven fabric can have a mechanical strength of 1 to 50 (N / 2.5cm), preferably 5 to 25 (N / 2.5cm). In particular, a mechanical strength of 5 (N / 2.5cm) or more can prevent easy breakage when used as a crop protection material. In this specification, "a mechanical strength of 1 (N / 2.5cm) or more" means that the mechanical strength in the MD (machine direction) is 1 (N / 2.5cm) or more and the mechanical strength in the CD (cross direction) is 1 (N / 2.5cm) or more.

[0040] The biodegradable nonwoven fabric preferably has an elongation of 60% or more, more preferably 70% or more, and even more preferably 100% or more. If the elongation is 60% or more, when used as a crop protection material, it will not tear even when lightly pulled and will easily deform, providing sufficient conformability for the intended use. The elongation is preferably 500% or less, more preferably 300% or less. In this specification, "elongation of 50% or more" means that the elongation in the MD (machine direction) is 50% or more and the elongation in the CD (cross direction) is 50% or more.

[0041] The biodegradable nonwoven fabric has a stretch recovery rate at 20% elongation of 40% or more, preferably 45% or more, and more preferably 50% or more. The higher the stretch recovery rate at 20% elongation, the better, and it can be, for example, 99.5% or less, 99.0% or less, etc. A 20% stretch recovery rate of 40% or more provides excellent stretchability and a good feel when used as a crop protection material. For example, when laid on an uneven surface, it can restore to some degree its original shape even when blown by wind, thereby maintaining its shape. As a result, it is possible to prevent peeling caused by wind and reduce damage to crops by contact. In this specification, "a 20% stretch recovery rate of 40% or more" means that the 20% stretch recovery rate in the machine direction (MD) is 40% or more and the 20% stretch recovery rate in the cross direction (CD) is 40% or more.

[0042] The biodegradable nonwoven fabric has a bending resistance of 20 mm or less. It can be 1 to 18 mm, preferably 3 to 16 mm, and more preferably 5 to 15 mm. When the bending resistance is 20 mm or less, the fabric maintains a good laying shape when used as a crop protection material, and the fabric softly overlaps with the crops, resulting in less friction and less damage.

[0043] The biodegradable nonwoven fabric has a tear strength of 5 N or more, preferably 5.5 N or more, and more preferably 6.0 N or more. It can also have a tear strength of 50 N or less, and preferably 30 N or less. If the tear strength is 5 N or more, the fabric is less likely to tear during installation or due to the effects of wind.

[0044] The biodegradable nonwoven fabric preferably has a 5% elongation load of 10 N or less. It is more preferably 6 N or less, even more preferably 5.0 N or less, and particularly preferably 1.5 N or less. Furthermore, a load of 0.05 N or more is preferable, as this makes the nonwoven fabric prone to deformation during laying and reduces laying workability. When the load is 10 N or less, it is moderately easy to stretch, resulting in good laying workability and moderate flexibility.

[0045] 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.

[0046] 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.

[0047] A biodegradable nonwoven fabric can be produced, for example, by a production method including the following steps A to C. A nonwoven fabric is obtained through step A, in which a molten thermoplastic resin is extruded from a spinneret, cooled and solidified, and then pulled and stretched by an ejector to form fibers, step B, in which the long fibers obtained in step A are collected to form a long-fiber web, and step C, in which the long-fiber web is thermocompression-bonded.

[0048] <Process A> In the method for producing a biodegradable nonwoven fabric according to this embodiment, first, a molten thermoplastic resin is extruded from a spinneret, cooled and solidified, and then pulled and stretched by an ejector to form fibers.

[0049] This step A can be carried out using a spinning machine such as a conventionally known spunbond spinning machine.

[0050] In the step A, the mixture is spun from a spinneret having an orifice diameter of 0.1 to 0.5 mm and fed to an ejector at a pressure of 0.5 to 4.0 kg / cm 2 It is preferable to supply dry air at a pressure (jet pressure) of 0.15 to 0.5 mm and perform drawing. The orifice diameter of the spinneret is more preferably 0.15 to 0.5 mm, and even more preferably 0.18 to 0.45 mm. By controlling the orifice diameter within the above range, it becomes easier to control the fiber diameter. Furthermore, by controlling the supply pressure (jet pressure) of the dry air within the above range, it becomes easier to control the spinning speed to a constant value and it is possible to dry the fiber appropriately.

[0051] <Process B> Next, the long fibers obtained in step A are collected to form a long-fiber web (step B). For example, the long fibers may be spread and collected on a lower conveyor to form a long-fiber web.

[0052] <Process C> Next, the long-fiber web obtained in step B is thermocompression-bonded (step C). The thermocompression-bonding is carried out within a temperature range in which the long-fiber web does not shrink. This allows for suitable transport. The thermocompression-bonding temperature is preferably at least 10°C lower than the melting point of the resin of the nonwoven fabric, the linear pressure is preferably 5 to 100 N / mm, more preferably 20 to 80 N / mm, and the compression-bonded area ratio is preferably 3 to 50%, more preferably 6 to 40%. By carrying out thermocompression-bonding within an appropriate range, it is possible to achieve both flexibility and stretchability of the nonwoven fabric and compression-bonding. [Example]

[0053] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0054] The following Examples 1 and 2 and Comparative Examples 1 to 4 were measured according to the following methods. Various properties are shown in Table 1.

[0055] (intrinsic viscosity) 0.1 g of the resin was weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane (60 / 40 (weight ratio)), and the viscosity was measured three times at 30° C. using an Ostwald viscometer to calculate the average value.

[0056] (specific gravity) A density gradient solution was prepared using calcium nitrate tetrahydrate in a density gradient tube. The density gradient ranged from 1.20 to 1.5 g / cm. 3 Using the specific gravity float range, the fiber after jet drawing was put into a density gradient tube, and after stabilizing for 4 hours or more, the scale of the floating position was read, and the specific gravity was calculated from the float calibration curve.

[0057] (crystal melting enthalpy) 2.0 mg ± 0.1 mg of resin was weighed, and the endothermic curve was measured using a TA Instruments Discovery DSC25 differential scanning calorimeter at a heating rate of 20 °C / min under a nitrogen atmosphere. The crystalline melting enthalpy (J / g) was determined from the integral of the endothermic peak (melting peak). Specifically, the integral of the endothermic peak (melting peak) was determined by taking the point where the curve corresponding to the endothermic peak (melting peak) begins to deviate from the low-temperature baseline as the starting point and the point where it begins to contact the high-temperature baseline as the end point. A line was drawn connecting the starting point and the end point, and integrating the area enclosed by the line and the curve. This procedure was performed three times to determine the average crystalline melting enthalpy (n = 3). The starting point was also designated as the melting onset temperature (°C).

[0058] (Melting Point) The resin was weighed to a mass of 2.0 mg ± 0.1 mg. Next, a differential scanning calorimeter (TA Instruments, Discovery DSC25) was used to measure the DSC curve under a nitrogen atmosphere at a heating rate of 20°C / min, and the endothermic peak (melting peak) temperature was determined from the DSC curve. The above procedure was repeated three times, and the average melting point (n = 3) was calculated.

[0059] (Melt flow rate (MFR)) After vacuum drying the resin at 80°C for at least 2 hours, the melt flow rate (MFR) was quickly measured so as to minimize the amount of moisture in the air. The melt flow rate was measured in accordance with ISO 1133 using a Melt Indexer F-F01 machine manufactured by Toyo Seiki Seisakusho Co., Ltd. The measurement temperature was 190°C and the load was 2.16 kg. This procedure was performed three times, and the average melt flow rate (n = 3) was calculated.

[0060] (Weight average molecular weight) The resin was dissolved in a small amount of chloroform to prepare a sample solution. The sample solution was further diluted with chloroform to a concentration of 0.05% by mass. The solution was filtered through a 0.2 μm membrane filter, and GPC analysis of the resulting solution was performed under the following conditions. The molecular weight was calculated in terms of standard polystyrene. Equipment: TOSOH HLC-8320GPC Column: TSKgelSuper HM-H × 2 + TSKgelSuperH 2000 (TOSOH) Solvent: Chloroform

[0061] (Metsuke) The mass per unit area was measured according to JIS L1913(2010)6.2.

[0062] (Apparent density (bulk density)) 1cm from the above basis weight and thickness calculated in accordance with JIS-L1913(2010)6.2 and 6.1 3 The weight was converted into the weight per unit of the sample and used as the bulk density. 2 The thickness was measured using a terminal, and the bulk density was calculated by dividing the basis weight by the thickness.

[0063] (fiber diameter) Five randomly selected points on the sample (long fiber web before thermocompression bonding) were used to measure the diameter of the single fiber (n=20) using an optical microscope, and the average value was calculated.

[0064] (Fineness (dtex)) Five randomly selected locations on the sample (long fiber web before thermocompression bonding) were used to measure the single fiber diameter (n = 20) using an optical microscope to determine the average single fiber diameter. Fibers from the same five locations were taken out, and the specific gravity of the fibers (n = 5) was measured using a density gradient tube to determine the average specific gravity. Next, the fiber fineness (dtex), which is the fiber weight per 10,000 m, was calculated from the single fiber cross-sectional area and average specific gravity calculated from the average single fiber diameter.

[0065] (Spinning speed (m / min)) The spinning speed V (m / min) was calculated from the above-mentioned fineness T (dtex) and the set single-hole output Q (g / min) according to the following formula. V=(10000×Q) / T

[0066] (mechanical strength) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-speed extension tensile tester with a self-recording device, the sample was attached to a grip with a 50 mm gap while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The sample was then stretched at a tensile speed of 10 mm / min until it broke. The maximum load value at this point was calculated as the mechanical strength. Measurements were performed on 5 samples in each of the machine direction (MD) and cross direction (CD), and the average was rounded to the nearest tenth.

[0067] (Elongation) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-rate extension tensile tester with a self-recording device, the sample was attached to a grip with a 50 mm gap while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The sample was then stretched at a tensile speed of 10 mm / min until it broke. The maximum elongation value at this point was calculated as the average elongation. Measurements were performed with n=5 in each of the machine direction (MD) and cross direction (CD), and the average value was rounded to the nearest tenth.

[0068] (20% elongation recovery rate) A 25 x 100 mm sample (nonwoven fabric) was prepared. Using a constant-rate extension tensile tester with a self-recording device, the sample was attached to a 50 mm grip gap while being pulled by hand until it no longer loosened, and an initial load of 0.02 N / 25 mm was applied. The "(grip gap) + (length stretched when the initial load was applied)" at this time was defined as L0. The sample was then stretched to 20% of the grip gap at a tensile speed of 25 mm / min. This length was defined as L1. The sample was then immediately unloaded at the same speed until it reached the initial load, and this length was defined as L2. The 20% elongation recovery was calculated using the following formula. Measurements were performed on 5 samples in each of the machine direction (MD) and cross direction (CD), and the average was rounded to the nearest tenth. 20% elongation recovery rate (%)=[(L1-L2) / (L1-L0)]×100

[0069] (Tear strength) According to the single tongue method (JIS method) described in JIS L-1913:2010 6.4.3 Tear Strength, b) using a constant speed extension tensile tester with a self-recording device, 20 test pieces, 50 mm wide and 250 mm long, were cut in the center of the short side of the test piece at right angles to the short side using a constant speed extension tensile tester with a self-recording device. The test piece was gripped at both ends of the cut with a gripping distance of 100 mm, and the average tear strength obtained at a pulling speed of 200 mm / min was taken as the tear strength (N).

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

[0071] (bending resistance) The bending resistance was measured according to JIS L1096:2020 8.21.1 Method A (45° cantilever method).

[0072] (The sheet broke one month after installation) A mound of soil 50cm wide, 200cm long and 30cm high was created in the farmland, and a nonwoven fabric 80cm wide and 230cm long was placed over it. All edges were secured with U-shaped pins at 30cm intervals, and the material was left for one month before being observed for tears.

[0073] (Unevenness tracking ability) The nonwoven fabric sheet that had passed through step C was measured, and the recovery rate at 20% elongation in both the machine direction (MD) and the cross direction (CD) was evaluated for stretchability (unevenness-following ability) by judging it as follows. A: The recovery rate at 20% elongation in both the longitudinal and transverse directions is 40% or more, and it has excellent conformability to uneven surfaces. B: Either the recovery rate at 20% elongation in the machine direction or the cross direction is 40% or more, and the conformability to unevenness is good. C: The recovery rate at 20% elongation in both the longitudinal and transverse directions is less than 40%, and the conformability to unevenness is insufficient.

[0074] (biodegradable) It was determined whether the resin that constitutes the nonwoven fabric sheet retains biodegradable properties. 〇: The substance name (resin name) is listed on the positive list of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1. ×: The substance name (resin name) is not listed on the positive list of the Japan Bioplastics Association's GreenPla (biodegradable plastic) classification number A-1.

[0075] (comprehensive evaluation) Based on the above evaluations, an overall evaluation was made. Good: The balance of flexibility, stretchability, and sheet tear resistance one month after installation is good, and the fabric can be used effectively as a biodegradable nonwoven fabric for protecting agricultural crops. ×: The balance between flexibility, stretchability, and sheet tear resistance one month after laying is poor, and the fabric is not practical as a biodegradable nonwoven fabric for protecting agricultural crops.

[0076] Example 1 Polybutylene adipate terephthalate (PBAT) (MFR: 4 g / min, melting point: 120°C, crystalline melting enthalpy: 14 J / g) shown in Table 1 was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 230°C. Filaments were pulled using a high-speed air jet pulling device (Step A), and these were deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section) (Step B). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the laminate was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 80°C for both rolls, and a roll linear pressure of 30 N / mm (step C), resulting in a basis weight of 15 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0077] Example 2 The PBAT (MFR: 9 g / min, melting point: 120°C, crystalline melting enthalpy: 9 J / g) shown in Table 1 was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 220°C. The filaments were pulled using a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 110°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a basis weight of 15 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0078] (Comparative Example 1) Polylactic acid (MFR: 65 g / min, melting point: 170°C) (abbreviated as PLA) was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 210°C. Filaments were pulled using a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 130°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a basis weight of 15 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0079] (Comparative Example 2) Polyethylene terephthalate (PET) (intrinsic viscosity (iv value): 0.63) was melted and kneaded in a single-screw extruder, and extruded using the spunbond method at a throughput rate of 0.5 g / min·Hole and a spinning temperature of 280°C. Filaments were pulled using a high-speed air jet pulling device, and these were deposited on a moving collecting surface to prepare a long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed at a pressure-bonding area ratio of 12%, a temperature of 240°C for both rolls, and a roll linear pressure of 30 N / mm, to give a basis weight of 15 g / m 2 A nonwoven fabric sheet of 1000g was obtained.

[0080] (Comparative Example 3) Polypropylene (PP) (MFR: 10 g / min, melting point: 160°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 260°C. The filaments were pulled by a high-speed air jet pulling device and deposited on a moving collecting surface to prepare a long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 150°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a fabric weight of 15 g / m 2 A nonwoven fabric sheet of 1000g was obtained.

[0081] Comparative Example 4 Polybutylene succinate (MFR: 10 g / min, melting point: 110°C) (abbreviated as PBS) 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. The filaments were pulled by a high-speed air jet pulling device and deposited on a moving collection surface to prepare a biodegradable long-fiber web (circular cross section). Next, using a pair of embossing rolls consisting of a roll with a concave-convex pattern on the surface and a roll with a smooth surface, the fabric was heat-pressed under the conditions of a pressure-bonding area ratio of 12%, a temperature of 70°C for both rolls, and a roll linear pressure of 30 N / mm, to obtain a basis weight of 15 g / m 2 A biodegradable nonwoven fabric sheet of 100g was obtained.

[0082] [Table 1]

Claims

1. A biodegradable nonwoven fabric for protecting agricultural crops, which is made of fibers containing a biodegradable thermoplastic resin, has an elongation recovery rate of 40% or more at 20% elongation, a tear strength of 5N or more, and a bending resistance of 20mm or less.

2. 2. The biodegradable nonwoven fabric for protecting agricultural crops according to claim 1, which has an elongation of 60% or more and a 5% elongation load of 10 N or less.

3. 3. The biodegradable nonwoven fabric for protecting agricultural crops according to claim 1, wherein the biodegradable thermoplastic resin is an aromatic polyester.

4. 3. The biodegradable nonwoven fabric for protecting agricultural crops according to claim 1, wherein the melt flow rate of the biodegradable thermoplastic resin is in the range of 0.3 g / 10 min to 50.0 g / 10 min.

5. 3. The biodegradable nonwoven fabric for protecting agricultural crops according to claim 1, wherein the biodegradable thermoplastic resin has a melting point in the range of 70°C or higher and 200°C or lower.

6. 3. The biodegradable nonwoven fabric for protecting agricultural crops according to claim 1, wherein 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. 3. The biodegradable nonwoven fabric for protecting agricultural crops according to claim 1, wherein the biodegradable thermoplastic resin contains polybutylene adipate terephthalate.

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

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

Images