Aliphatic polyester film, package, material for agricultural, forestry and fishery uses, and raw material for agricultural, forestry and fishery uses

Abstract

This aliphatic polyester film contains at least a polyhydroxy alkanoic acid and has a property such that the half width Hh of a height distribution histogram as determined by AFM measurement of a film cross section obtained with a rotary microtome is 5 nm to 60 nm inclusive. Provided is an aliphatic polyester film of which the disintegration start timing during biodegradation is shortened, thereby enhancing the treatment efficiency of composting at home (hereinafter, referred to as "home composting"), and which can also be suppressed from undergoing deterioration in quality, such as formation of wrinkles, when processed into a packaging material or a material for agricultural, forestry and fishery uses.

Description

Aliphatic polyester film, packaging, agricultural, forestry and fishery materials, and agricultural, forestry and fishery ingredients

[0001] The present invention relates to an aliphatic polyester film, a packaging material, an agricultural, forestry and fisheries material, and an agricultural, forestry and fisheries ingredient.

[0002] Various efforts are being made around the world to curb global warming. Plastic products, in particular, emit a lot of CO during their manufacture and disposal. ２ There is a need to reduce the amount of plastic used and disposed of, as it generates a lot of waste. Of all the plastic products, packaging plastic is used in particularly large quantities, and since much of it is disposable, efforts are underway to replace it with biodegradable plastics that can be composted after use.

[0003] In recent years, the environmental pollution problem of plastics entering the ocean has also been attracting attention. For example, there have been known cases of fish, seabirds, and marine mammals accidentally ingesting plastic products that have drifted into the ocean, resulting in deaths. Furthermore, microplastics, which are broken down by waves and ultraviolet rays, bioaccumulate in the marine food chain, and the impact of microplastics on the human body through consumption of fish and other marine life has been noted. These issues are caused by improperly disposed packaging plastics, plastic materials used in agriculture that flow into the ocean via rivers, and plastic materials dumped after use in fishing and aquaculture that drift in the ocean. Therefore, there is a demand for biodegradable plastics used in agriculture, forestry, and fisheries.

[0004] Therefore, the following have been proposed: a high-strength biaxially stretched film (Patent Document 1) that is mainly composed of polylactic acid, which is biodegradable in the natural environment, and is suitable for processing into packaging material; a manufacturing method in which a sheet mainly composed of polyhydroxyalkanoic acid, which is biodegradable in the ocean, is continuously biaxially stretched at a stretch ratio of 1.1 or more in the flow direction (longitudinal direction) and the direction perpendicular to it (width direction) in the film manufacturing process without rolling (Patent Document 2); and a film made of a resin composition containing an aliphatic polyester resin containing, as main constituent units, repeating units derived from an aliphatic diol and repeating units derived from an aliphatic dicarboxylic acid, and polyhydroxyalkanoic acid (Patent Document 3).

[0005] JP 2001-122289 A JP 2022-062759 A JP 2022-031161 A

[0006] However, because the film described in Patent Document 1 is primarily composed of polylactic acid, efficient composting requires the use of industrial high-temperature composting equipment. Patent Document 2 describes a method for biaxially stretching a highly biodegradable polyhydroxyalkanoic acid that can be composted at home. However, this method results in insufficient molecular chain orientation due to stretching, making it difficult to process into packaging materials or agricultural, forestry, and fisheries materials. Patent Document 3 describes that a film containing an aliphatic polyester resin containing, as its main structural units, repeating units derived from an aliphatic diol and repeating units derived from an aliphatic dicarboxylic acid and a polyhydroxyalkanoic acid can be composted at home. However, this film is difficult to biaxially stretch, and there is also room for improvement in its processability into packaging materials and agricultural, forestry, and fisheries materials. Furthermore, the film may exhibit insufficient disintegration properties during composting.

[0007] Therefore, an object of the present invention is to provide an aliphatic polyester film that has excellent biodegradability and begins to break down earlier when composted at home (hereinafter referred to as home composting), thereby improving the efficiency of home composting, while suppressing deterioration in quality, such as the occurrence of wrinkles, when the film is processed into packaging materials or agricultural, forestry, and fisheries materials.

[0008] The present inventors have conducted extensive research to solve the above problems and have arrived at the following invention. That is, a preferred embodiment of the present invention is as follows.

[0009] 1. An aliphatic polyester film comprising at least a polyhydroxyalkanoic acid, wherein the half-width Hh of a height distribution histogram obtained by AFM measurement of a film cross section obtained with a rotary microtome is 5 nm or more and 60 nm or less. 2. The aliphatic polyester film according to 1., which contains more than 50 mass % and 75 mass % or less of polyhydroxyalkanoic acid, relative to 100 mass % of the total mass of the film. 3. An aliphatic polyester film comprising at least a polyhydroxyalkanoic acid, wherein the half-width Hm of a modulus distribution histogram obtained by AFM measurement of a film cross section obtained with a rotary microtome is 0.08 GPa or more and 0.80 GPa or less. 4. An aliphatic polyester film according to any one of 1. to 3., further comprising an aliphatic polyester other than polyhydroxyalkanoic acid, wherein the aliphatic polyester is polylactic acid. 5. The intensity ratio (I ８７５ / I １７７０ ) and the orientation parameters in the longitudinal and transverse directions in the plane are defined as P ＭＴ , the orientation parameters in the plane direction and thickness direction are P Ｚ When this is done, P Ｚ and P ＭＴ The difference (P Ｚ -P ＭＴ 6. The aliphatic polyester film according to any one of 1. to 4., wherein the molecular weight distribution curve has the logarithm logM of the molecular weight M on the horizontal axis and the weight fraction dW / dlogM per unit logM on the vertical axis, and when the maximum value on the vertical axis is Wm, the molecular weight M on the lowest molecular weight side among the molecular weights that become Wm / 2 on the vertical axis is Wm / 2. Ｌ 7. The aliphatic polyester film according to any one of 1. to 5., wherein the molecular weight M is 30,000 or more and 100,000 or less. 8. In a molecular weight distribution curve in which the horizontal axis is the logarithm logM of the molecular weight M and the vertical axis is the weight fraction dW / dlogM per unit logM, when the maximum value on the vertical axis is Wm, the molecular weight M on the highest molecular weight side among the molecular weights that become Wm / 2 on the vertical axis is ＨThe aliphatic polyester film according to any one of 1. to 6., wherein the aspect ratio of pores is 3 or more in a cross section of the film after home composting at 28°C for 14 days according to the aerobic disintegration test method described in ISO 20200 (2023). 9. The aliphatic polyester film according to any one of 1. to 8., wherein, when the 120°C heat shrinkage rate in the longitudinal direction is S1 (%) and the 120°C heat shrinkage rate in the width direction is S2 (%), both S1 and S2 are 0% to 20%. 10. The aliphatic polyester film according to any one of 1. to 9., wherein the aliphatic polyester is contained in an amount of 70% by mass or more relative to the total mass of the film (100% by mass). 11. The aliphatic polyester film according to any one of 1. to 10., which has a collapsed area ratio of 10% or more when home composted for 60 days at a test temperature of 28°C according to a method based on the aerobic collapse test described in ISO 20200 (2023). 12. The aliphatic polyester film according to any one of 1. to 11., which has a half-width Hm of 0.10 GPa or more and 0.70 GPa or less in an elastic modulus distribution histogram obtained by AFM measurement of a film cross section obtained with a rotary microtome using a force curve method. 13. The aliphatic polyester film according to any one of 1. to 12., which has a moisture regain of 700 ppm or more and 9000 ppm or less after conditioning at 28°C and 90% RH for 48 hours. 14. The AR measured by the following method Ｌ and A.R. Ｈ The difference between (AR Ｌ -AR Ｈ 13. The aliphatic polyester film according to any one of 1. to 13., wherein the ratio of the number of concave portions to the total area of ​​the measurement range is 0.2% or more and 10% or less: (1) The film is frozen and cut using a rotary microtome to obtain a film cross-section sample; (2) The obtained cross-section sample is immersed in pure water for 12 hours; (3) The cross-section sample after immersion in pure water in (2) is subjected to AFM measurement to obtain a height distribution histogram of the cross section; (4) In the obtained height distribution histogram, portions having heights smaller than the maximum peak value are defined as concave portions, and portions having heights larger than the maximum peak value are defined as convex portions, and the ratio of the number of concave portions to the total area of ​​the measurement range is calculated as AR. Ｌ (%), the ratio of the convex portions is ARＨ (%). 15. The aliphatic polyester film according to any one of 1. to 14., containing a water-soluble resin in an amount of 0.4% by mass or more and 15% by mass or less, relative to 100% by mass of the total mass of the film. 16. The aliphatic polyester film according to 15., wherein the water-soluble resin is at least one selected from polyvinyl alcohol, polyethylene glycol, polypropylene glycol, and polyvinylpyrrolidone. 17. The aliphatic polyester film according to 15. or 16., wherein the water-soluble resin has a weight-average molecular weight of 2,000 to 9,500. 18. The aliphatic polyester film according to any one of 1. to 17., further comprising a functional layer on at least one surface. 19. A package in which contents are packaged in a packaging material comprising the aliphatic polyester film according to any one of 1. to 18. 20. An agricultural, forestry, and fishery material comprising the aliphatic polyester film according to any one of 1. to 18. 21. A coated agricultural, forestry, and fishery material in which an agricultural, forestry, and fishery material is coated with the aliphatic polyester film according to any one of 1. to 18.

[0010] The aliphatic polyester film of the present invention has excellent biodegradability and begins to disintegrate quickly when composted at home (hereinafter referred to as home composting), thereby improving the efficiency of home composting. It also facilitates orientation control by stretching, and can suppress deterioration in quality, such as wrinkles, when the film is processed into packaging materials or agricultural, forestry, and fisheries materials (hereinafter referred to as processability). In a further preferred embodiment, the aliphatic polyester film contains a water-soluble resin, which suppresses variation in disintegration time (hereinafter referred to as disintegration uniformity), thereby further improving the above-mentioned properties.

[0011] Wm, M in the molecular weight distribution curve Ｌ , M Ｈ FIG.

[0012] The aliphatic polyester film of the present invention will be described in detail below. When the upper and lower limits of the preferred ranges are separately stated below, the combination of the upper and lower limits can be selected arbitrarily. In this specification, the aliphatic polyester film may be simply referred to as a film. In the aliphatic polyester film of the present invention, the "thickness direction" refers to the direction perpendicular to the film surface. The "longitudinal direction" refers to the direction corresponding to the flow direction in the film production process (hereinafter sometimes referred to as "MD"), and the "width direction" refers to the direction perpendicular to the flow direction in the film production process within the film surface (hereinafter sometimes referred to as "TD"). When a film sample is in the form of a reel or roll, the film winding direction can be considered the longitudinal direction. If the longitudinal and width directions are unknown, the breaking strength at break can be measured in the mechanical property evaluation described below, and the direction of the main orientation axis with the largest measured value can be considered the longitudinal direction in this invention, and the direction perpendicular to the main orientation axis can be considered the width direction. Details will be described later.

[0013] It is important that the aliphatic polyester film of the present invention preferably contains at least a polyhydroxyalkanoic acid. Here, the polyhydroxyalkanoic acid is a polymer containing repeating units derived from a hydroxyalkanoic acid as a constituent. Examples of polyhydroxyalkanoic acids include [—CHR—CH ２ 3-hydroxyalkanoate repeating units represented by the general formula: —CO—O— (wherein R is C ｎ H ２ｎ＋１ where n is an integer of 1 to 15.) and poly(3-hydroxyalkanoates) (hereinafter also referred to as "P3HA") containing the alkyl group represented by the formula:

[0014] Examples of P3HA include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxyvalerate) (P3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (P3HB3HV3HH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (P3HB3HO), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (P3HB3HD). Note that "-co-" means copolymerization.

[0015] P3HA may be either chemically synthesized (for example, obtained by ring-opening polymerization of the corresponding lactone) or produced by a microorganism. From the viewpoint of ease of production using biomass raw materials such as vegetable oil, P3HA produced by a microorganism is preferred. Among P3HA produced by a microorganism, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, P3HB4HB, etc. are preferably used from the viewpoint of ease of industrial production.

[0016] The content of polyhydroxyalkanoic acid contained in the aliphatic polyester film of the present invention is preferably more than 50% by mass but not more than 75% by mass, more preferably 55% by mass or more but not more than 72% by mass, and particularly preferably 60% by mass or more but not more than 70% by mass, when the total mass of the film is taken as 100% by mass. By controlling the content of polyhydroxyalkanoic acid within the above range and controlling the film structure as described below, sufficient biodegradability and processability can be achieved at the same time.

[0017] It is preferable to select a biodegradable resin as the aliphatic polyester other than polyhydroxyalkanoic acid contained in the aliphatic polyester film of the present invention. Examples of biodegradable resins include, but are not limited to, polyglycolic acid, polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, and polycaprolactone. Here, the biodegradable resin is preferably either a naturally degradable resin or an enzymatically degradable resin. Even if a resin does not decompose sufficiently by itself in home composting, the residual indegradable material can be reduced by combining it with polyhydroxyalkanoic acid.

[0018] Furthermore, from the viewpoint of enabling melt extrusion at a temperature close to that of polyhydroxyalkanoic acid, the melting point of the aliphatic polyester other than polyhydroxyalkanoic acid is preferably 50°C or higher and 180°C or lower, more preferably 80°C or higher and 175°C or lower, and even more preferably 100°C or higher and 170°C or lower. By setting the melting point of the aliphatic polyester other than polyhydroxyalkanoic acid to 50°C or higher, it is possible to prevent the mixed state from becoming uneven when the raw materials are supplied for melt extrusion. Furthermore, by setting the melting point of the aliphatic polyester other than polyhydroxyalkanoic acid to 180°C or lower, it is possible to prevent thermal decomposition of the polyhydroxyalkanoic acid during melt extrusion, thereby reducing the uneven mixed state and breakage during film formation. Specific preferred examples of such aliphatic polyester other than polyhydroxyalkanoic acid include one or more selected from polylactic acid, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, and polycaprolactone.

[0019] From the viewpoint of achieving both film-forming properties and processability, the glass transition temperature of the aliphatic polyester other than polyhydroxyalkanoic acid is preferably 30°C or higher and 100°C or lower, more preferably 40°C or higher and 90°C or lower, and even more preferably 50°C or higher and 80°C or lower. By setting the glass transition temperature of the aliphatic polyester other than polyhydroxyalkanoic acid to 30°C or higher, the strength of the aliphatic polyester film can be sufficiently achieved, thereby achieving both biodegradability and processability. Furthermore, by setting the glass transition temperature of the aliphatic polyester other than polyhydroxyalkanoic acid to 100°C or lower, the difference in thermal properties with polyhydroxyalkanoic acid can be minimized, thereby preventing uneven stretching and tearing during film formation. Specific examples of preferred aliphatic polyesters other than polyhydroxyalkanoic acid include one or more selected from polyglycolic acid and polylactic acid. Polylactic acid is particularly preferred from the viewpoints of biodegradability, melting point, and glass transition temperature.

[0020] That is, the aliphatic polyester film of the present invention contains polyhydroxyalkanoic acid and polylactic acid, and preferably contains more than 50% by mass and not more than 75% by mass of polyhydroxyalkanoic acid, and 25% by mass or more and less than 50% by mass of polylactic acid, more preferably contains 55% by mass or more and not more than 72% by mass of polyhydroxyalkanoic acid, and 28% by mass or more and not more than 45% by mass of polylactic acid, and particularly preferably contains 60% by mass or more and not more than 71% by mass of polyhydroxyalkanoic acid, and 29% by mass or more and not more than 40% by mass of polylactic acid.

[0021] The aliphatic polyester film of the present invention may also contain components other than the polyhydroxyalkanoic acid and the aliphatic polyester other than polyhydroxyalkanoic acid (collectively referred to as aliphatic polyester). Examples of such components include resin components other than aliphatic polyesters, additives, organic particles, inorganic particles, antioxidants, heat stabilizers, slipping agents, antistatic agents, antiblocking agents, fillers, viscosity modifiers, color inhibitors, and chain extenders. To avoid impairing the effects of the present invention, the content of the aliphatic polyester is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total mass of the film being 100% by mass.

[0022] The resin component other than the aliphatic polyester preferably contains a water-soluble resin. Here, water-soluble resin refers to a resin that dissolves in water at room temperature at 0.005 g / ml or more. Specifically, natural polymers, semi-synthetic polymers, or synthetic polymers having hydrophilic functional groups in their molecular structure are preferred. Examples of natural polymers include alginate, hyaluronate, and corn starch. Examples of semi-synthetic polymers include cellulose-based compounds. Examples of synthetic polymers include resins having polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polybutylene glycol, polyvinylpyrrolidone, polyacrylic acid, and styrene sulfonate as the main skeleton. Synthetic polymers are preferred from the viewpoint of suitability for melt extrusion processing, and resins selected from polyvinyl alcohol, polyethylene glycol, polypropylene glycol, and polyvinylpyrrolidone are more preferred from the viewpoint of improving biodegradability, with polyethylene glycol being particularly preferred.

[0023] Biodegradable aliphatic polyesters such as polyhydroxyalkanoates and polylactic acids are less polar than aromatic polyesters such as polyethylene terephthalate, and therefore less likely to retain moisture. Biodegradable aliphatic polyesters undergo biodegradation by microorganisms that prefer moist environments, but the state of biodegradation tends to depend on the external environment, resulting in uneven degradation. Therefore, by incorporating a water-soluble resin into the film to give it the appropriate hydrophilicity to facilitate the incorporation of microorganisms, it is possible to achieve not only excellent biodegradability but also more uniform biodegradation.

[0024] The content of the water-soluble resin contained in the aliphatic polyester film of the present invention is preferably 0.4% by mass or more and 15% by mass or less, even more preferably 2% by mass or more and 10% by mass or less, and particularly preferably 4% by mass or more and 6% by mass or less, relative to the total mass of the film (100% by mass). If the content of the water-soluble resin is less than 0.4%, the effect of enhancing microbial activity is low, which may result in poor disintegration uniformity. If the content of the water-soluble resin is more than 15%, the film may absorb excessive water and swell, which may result in poor processability and film-forming ability.

[0025] The weight-average molecular weight of the water-soluble resin contained in the aliphatic polyester film of the present invention is preferably 2,000 to 9,500, more preferably 3,000 to 5,000. If the weight-average molecular weight of the water-soluble resin is less than 2,000, the film may swell excessively, resulting in reduced processability. If the weight-average molecular weight of the water-soluble resin is 9,500 or more, the molecular chain of the water-soluble resin may become long, which may result in reduced biodegradability because it takes longer for microorganisms to biodegrade it.

[0026] Furthermore, the aliphatic polyester film of the present invention is preferably a stretched oriented film, more preferably a biaxially oriented film. Orientation can increase film strength. Here, an oriented film refers to one that exhibits an orientation pattern in wide-angle X-ray diffraction or Raman spectroscopy polarization analysis. An oriented film can be suitably obtained by stretching at least uniaxially during the production process. Because the aliphatic polyester film of the present invention is a stretched oriented film, it can achieve both excellent biodegradability and processability.

[0027] In a preferred embodiment of the aliphatic polyester film of the present invention, the half-width Hh of the height distribution histogram obtained by AFM measurement of the film cross section obtained with a rotary microtome is 5 nm to 60 nm. Here, Hh indicates the degree of uniformity of the unevenness when the film cross section is measured. The more uniform the structure of the inside of the aliphatic polyester film, the flatter the cross section obtained by microtome cutting becomes, and the smaller Hh becomes. Conversely, if the internal structure is non-uniform due to a phase separation structure between resins with different properties, subtle unevenness will be formed on the cross section at the resin interface during microtome cutting, and Hh will be large. Hh is measured by the method described in the examples.

[0028] Although the polyhydroxyalkanoic acid used in the aliphatic polyester film of the present invention has excellent biodegradability, its low glass transition temperature makes it difficult to strengthen and fix the structure of a film made solely of polyhydroxyalkanoic acid by extrusion molding and biaxial stretching. Therefore, it was inferred that a method of adding an aliphatic polyester other than polyhydroxyalkanoic acid to an aliphatic polyester film and dispersing it in the polyhydroxyalkanoic acid would be effective.

[0029] As described above, a small Hh indicates a uniform internal structure of the film, while a large Hh indicates a non-uniform internal structure. The inventors have surprisingly discovered that by dispersing an aliphatic polyester other than polyhydroxyalkanoic acid in polyhydroxyalkanoic acid while maintaining a moderate degree of uniformity, it is possible to produce an aliphatic polyester film that has excellent biodegradability, which is beneficial for improving the efficiency of home composting, and that is easy to control orientation by stretching and has excellent processability for packaging and agricultural, forestry, and fishery materials. According to the inventors' investigations, as described below, neither an excessively uniform nor an excessively non-uniform dispersion state can achieve these effects.

[0030] When Hh is less than 5 nm, it is thought that the dispersion state of polyhydroxyalkanoic acid and aliphatic polyesters other than polyhydroxyalkanoic acid is extremely uniform. Aliphatic polyesters other than polyhydroxyalkanoic acid are unlikely to undergo sufficient biodegradation under home composting conditions. In such cases, it is difficult to form starting points for mechanical disintegration of the film in the early stages of home composting, and the biodegradability of the polyhydroxyalkanoic acid itself is reduced, leading to a delay in the onset of disintegration. As a result, it was found that when aliphatic polyester film is composted at home, the film is difficult to break down into fine particles due to external forces such as stirring, which can reduce the operating efficiency of the treatment device.

[0031] On the other hand, when Hh exceeds 60 nm, the dispersion state is excessively non-uniform, which causes the film to start to disintegrate earlier, but also makes it difficult to control the orientation by stretching, and the aliphatic polyester film may lack stiffness and cause wrinkles when processed into packaging materials or agricultural, forestry, and fishery materials.

[0032] From the viewpoint of improving biodegradability while maintaining sufficient film-formability, the Hh of the aliphatic polyester film of the present invention becomes increasingly preferable in the order of 6 nm or more, 7 nm or more, 8 nm or more, 9 nm or more, 10 nm or more, 11 nm or more, and 12 nm or more. From the viewpoint of improving film-formability while maintaining sufficient biodegradability, the Hh of the aliphatic polyester film of the present invention becomes increasingly preferable in the order of 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, 30 nm or less, 27 nm or less, and 25 nm or less.

[0033] Another preferred embodiment of the aliphatic polyester film of the present invention is that the half-width Hm of the elastic modulus distribution histogram obtained by AFM measurement using the force curve method on a film cross-section obtained with a rotary microtome is 0.08 GPa or more and 0.80 GPa or less. Here, Hm indicates the degree of uniformity of hardness when measuring the film cross-section. Hm becomes smaller when the internal structure of the aliphatic polyester film approaches a uniform structure or when resins with similar mechanical properties are dispersed, while Hm becomes larger when resins with different mechanical properties are dispersed or when a large amount of inorganic substances other than resins are present. Hm is measured by the method described in the examples.

[0034] As described above, the inventors have discovered that by dispersing an aliphatic polyester other than polyhydroxyalkanoic acid in polyhydroxyalkanoic acid while maintaining a moderate degree of uniformity, an aliphatic polyester film having excellent biodegradability and excellent processability can be realized. When Hm is less than 0.08 GPa, the dispersion state is thought to be an extremely uniform structure, resulting in reduced biodegradability. On the other hand, when Hm exceeds 0.80 GPa, the dispersion state is excessively non-uniform, resulting in reduced processability.

[0035] From the viewpoint of improving biodegradability while maintaining sufficient processability, the Hm of the aliphatic polyester film of the present invention becomes increasingly preferable in the order of 0.09 GPa or more, 0.10 GPa or more, 0.11 GPa or more, 0.12 GPa or more, 0.13 GPa or more, 0.14 GPa or more, and 0.16 GPa or more. From the viewpoint of improving film formability while maintaining sufficient biodegradability, the Hm of the aliphatic polyester film of the present invention becomes increasingly preferable in the order of 0.70 GPa or less, 0.60 GPa or less, 0.50 GPa or less, 0.45 GPa or less, 0.40 GPa or less, 0.35 GPa or less, 0.30 GPa or less, and 0.25 GPa or less.

[0036] Methods for controlling Hh and Hm within the above ranges include, for example, selecting a resin raw material with melt viscosity characteristics as described below when adding and dispersing an aliphatic polyester other than polyhydroxyalkanoic acid into an aliphatic polyester film, adjusting the kneading temperature and residence time during melt extrusion, and adjusting the draft ratio and stretch ratio during cast sheet molding.

[0037] The aliphatic polyester film of the present invention has a Raman spectrum intensity ratio (I ８７５ / I １７７０ ) and the orientation parameters in the longitudinal and transverse directions in the plane are defined as P ＭＴ , the orientation parameters in the plane direction and thickness direction are P Ｚ When this is done, P Ｚ and P ＭＴ The difference (P Ｚ -P ＭＴ ) is preferably 0.2 or more and 5.0 or less, more preferably 0.5 or more and 3.0 or less, and even more preferably 0.7 or more and 2.0 or less.

[0038] The intensity ratio of the Raman spectrum (I ８７５ / I １７７０ ) indicates the degree of molecular orientation derived from the resin components such as polylactic acid contained in the aliphatic polyester film. ＭＴ The more uniform the orientation in the longitudinal and transverse directions, the closer to 1 it approaches, and the greater the difference in orientation, the greater it becomes. Ｚ The closer the orientation in the plane direction to the thickness direction, the closer it approaches 1, and the stronger the orientation in the plane direction to the thickness direction, the larger it becomes. (P Ｚ -P ＭＴ When the value of P is less than 0.2, the plane orientation due to stretching is insufficient. Ｚ is too small, or the orientation in the longitudinal and transverse directions is uneven, resulting in P ＭＴ In either case, the above-mentioned Hh and Hm become excessively large, which may impair processability and film-forming properties.

[0039] Also (P Ｚ -P ＭＴ) exceeds 5.0, it means that the planar orientation due to stretching is too large. In this case, the structure is too finely refined by stretching, and the above-mentioned Hh and Hm become excessively small, which may reduce the biodegradability of the film.

[0040] In the above range (P Ｚ -P ＭＴ As a method for controlling the above, for example, an aliphatic polyester other than polyhydroxyalkanoic acid is added to an aliphatic polyester film in a preferred mode, and the draft ratio and stretch ratio during cast sheet molding as described below are adjusted.

[0041] The aliphatic polyester film of the present invention preferably has the following characteristics in terms of molecular weight distribution measured by the evaluation method described below: As shown in Fig. 1, in a molecular weight distribution curve in which the horizontal axis represents the logarithm of molecular weight M (logM) and the vertical axis represents the weight fraction per unit logM (dW / dlogM), when the maximum value on the vertical axis is Wm, the molecular weight on the lowest molecular weight side among the molecular weights that become Wm / 2 on the vertical axis is defined as molecular weight M Ｌ , the molecular weight of the highest molecular weight side is the molecular weight M Ｈ Let's say.

[0042] Molecular weight M Ｌ is preferably 30,000 or more and 100,000 or less, more preferably 40,000 or more and 80,000 or less, and even more preferably 60,000 or more and 70,000 or less. Ｈ is preferably 300,000 or more and 1,000,000 or less, more preferably 450,000 or more and 800,000 or less, and even more preferably 600,000 or more and 700,000 or less.

[0043] Here, M Ｌ If M is less than 30,000 ＨWhen the molecular weight of the polyhydroxyalkanoic acid in the aliphatic polyester film of the present invention exceeds 1,000,000, the difference between the molecular weight of the polyhydroxyalkanoic acid and the molecular weight of the aliphatic polyester other than the polyhydroxyalkanoic acid becomes large after being affected by the kneading temperature and residence time during melt extrusion. In this case, the dispersion state becomes excessively non-uniform, which may result in excessively large Hh and Hm, thereby impairing processability and film-forming properties.

[0044] Also M Ｌ If M exceeds 100,000 Ｈ When the molecular weight of the polyhydroxyalkanoic acid contained in the aliphatic polyester film of the present invention is less than 300,000, this indicates that the difference in molecular weight between the polyhydroxyalkanoic acid and the aliphatic polyester other than the polyhydroxyalkanoic acid becomes small after being affected by the kneading temperature and residence time during melt extrusion. In this case, the dispersion state becomes too fine, which may result in excessively small Hh and Hm, thereby reducing biodegradability.

[0045] In the above range, Ｌ and M Ｈ Examples of methods for controlling this include a method of adding an aliphatic polyester other than polyhydroxyalkanoic acid or a resin component other than aliphatic polyester to an aliphatic polyester film in a preferred mode, selecting a resin raw material with melt viscosity characteristics as described below, and a method of adjusting the kneading temperature and residence time during melt extrusion.

[0046] The aliphatic polyester film of the present invention preferably has a pore aspect ratio of 3 or more in a cross section of the film after home composting at a test temperature of 28°C for 14 days according to the aerobic disintegration test method described in ISO 20200 (2023).

[0047] The above-mentioned pores are derived from the morphology of the polyhydroxyalkanoic acid moiety, which biodegrades first during short-term home composting. Aliphatic polyester films with a pore aspect ratio of 3 or more do not have an excessively uniform dispersion structure, indicating that the polyhydroxyalkanoic acid forms a dispersion structure with moderate continuity with the aliphatic polyester other than the polyhydroxyalkanoic acid. From the viewpoint of achieving both biodegradability and film-forming properties, the pore aspect ratio is more preferably 4 or more, and even more preferably 5 or more. The upper limit of the pore aspect ratio is not particularly limited, but is preferably 60 or less. The method conforming to the aerobic disintegration test described in ISO 20200 (2023) refers to the method described in the Examples. The pore aspect ratio is determined using the method described in the Examples.

[0048] Furthermore, the aliphatic polyester film of the present invention preferably has a collapse area ratio of 10% or more when subjected to home composting at a test temperature of 28°C for 60 days according to the aerobic disintegration test method described in ISO 20200 (2023).

[0049] The above-mentioned collapsed area ratio indicates the shape retention of the aliphatic polyester film in the early stage of home composting. Aliphatic polyester films with a collapsed area ratio of 10% or more after 60 days of home composting are easily broken down into fine particles by external forces such as stirring during home composting, indicating that the film is in a form suitable for improving the operating efficiency of the treatment device. The collapsed area ratio is determined by the method described in the examples.

[0050] From the viewpoint of biodegradability, the collapsed area ratio is more preferably 20% or more, and even more preferably 40% or more.

[0051] In the aliphatic polyester film of the present invention, when the heat shrinkage rate at 120°C in the longitudinal direction is S1 (%) and the heat shrinkage rate in the transverse direction is S2 (%), it is preferable that both S1 and S2 are 0% to 20%. An aliphatic polyester film having S1 and S2 of 0% to 20% can suppress the occurrence of wrinkles and sagging that cause tears and defects during processing at high temperatures and high speeds, and can therefore sufficiently improve processability when processed into packaging materials and agricultural, forestry and fishery materials.

[0052] From the above viewpoints, S1 and S2 are each more preferably 0.1% or more and 15% or less, and even more preferably 0.3% or more and 10% or less. The lower limits of S1 and S2 are not particularly limited, but from the viewpoint of preventing wrinkles and slack due to thermal expansion during high-temperature and high-speed processing, it is preferable that S1 and S2 are both 0% or more. In this specification, the 120°C heat shrinkage is determined as the percentage change in film length before and after heat-treating a film in a predetermined direction at 120°C for 15 minutes, and is specifically determined by the method described in the examples.

[0053] The aliphatic polyester film of the present invention preferably has a moisture content of 700 ppm to 9000 ppm, more preferably 1000 ppm to 6000 ppm, and even more preferably 2000 ppm to 3000 ppm after conditioning at 28°C and 90% RH for 48 hours. If the moisture content is less than 700 ppm, the initiation points of microbial degradation are unlikely to occur uniformly, which may result in reduced uniformity of biodegradation. If the moisture content is more than 9000 ppm, the film may swell excessively, resulting in reduced processability.

[0054] The aliphatic polyester film of the present invention has an AR determined by the following method. Ｌ and A.R. Ｈ The difference between (AR Ｌ -AR Ｈ ) is preferably 0.2% or more and 10% or less, more preferably 0.5% or more and 5.0% or less, and even more preferably 1.0% or more and 3.0% or less. Ｌ and A.R. Ｈ(1) A film is frozen and cut using a rotary microtome to obtain a film cross-section sample. (2) The obtained cross-section sample is immersed in pure water for 12 hours. (3) The cross-section sample after immersion in pure water in (2) is subjected to AFM measurement to obtain a height distribution histogram of the cross section. (4) In the obtained height distribution histogram, portions with heights smaller than the maximum peak value are defined as recesses, and portions with heights larger than the maximum peak value are defined as protrusions, and the ratio of the presence of recesses to the area of ​​the entire measurement range is calculated as AR. Ｌ (%), the ratio of the convex portions is AR Ｈ (%).

[0055] Here (AR Ｌ -AR Ｈ The value of AR indicates the state of the water-soluble resin dissolved in the pure water from the cross section. Ｌ -AR Ｈ If the content of the water-soluble resin is less than 0.2%, this means that the amount of the water-soluble resin is insufficient, or that the water-soluble resin is completely compatible with the aliphatic polyester resin component, or that the water-soluble resin is finer than the size of the microorganisms. In this case, the effect of improving the uniformity of disintegration during biodegradation by microorganisms may be reduced.

[0056] Also (AR Ｌ -AR Ｈ If the ratio (%) exceeds 10%, it means that the film is swollen due to an excessive amount of the water-soluble resin, or that the water-soluble resin is dispersed in the aliphatic polyester film in a coarse structure. In this case, it becomes difficult to control the orientation by stretching, and there is a possibility that the processability and film-forming ability will be deteriorated.

[0057] The moisture content and AR are within the above range. Ｌ , A.R. Ｈ Examples of methods for controlling this include a method of incorporating a water-soluble resin as a resin component other than the aliphatic polyester in a preferred form using the production method described below, selecting a resin raw material with melt viscosity characteristics as described below, adjusting the kneading temperature and residence time during melt extrusion, and adjusting the draft ratio and stretch ratio during cast sheet molding.

[0058] The thickness of the aliphatic polyester film of the present invention can be set depending on the application, but for example, in applications where the film is used in sheet form, such as general packaging applications, release applications, and agricultural, forestry, and fisheries applications, it is preferably 6 μm to 200 μm, more preferably 8 μm to 100 μm, and even more preferably 10 μm to 50 μm, from the viewpoint of handling during processing and use. Furthermore, in applications including a molding process such as tray molding or applications requiring self-supporting properties, it is preferably 10 μm to 300 μm from the viewpoint of processability and handling, and more preferably 30 μm to 250 μm, and even more preferably 50 μm to 220 μm, from the viewpoint of cost and film formability.

[0059] The aliphatic polyester film of the present invention can be widely used for packaging, release agents, etc. Specifically, it can be used for various purposes such as packaging materials, packing materials, sanitary products, agricultural, forestry, and fishery products, construction supplies, medical supplies, and process films for manufacturing various products. In particular, it can be suitably used as a packaging material suitable for home composting and a film to be processed into agricultural, forestry, and fishery materials that can be decomposed in soil at room temperature.

[0060] <Aliphatic polyester film having a functional layer> The aliphatic polyester film of the present invention is preferably further provided with a functional layer depending on the application, and preferably has a functional layer on at least one side. Hereinafter, an aliphatic polyester film having a functional layer will be described. The aliphatic polyester film of the present invention provided with a functional layer may be simply referred to as a "laminate".

[0061] Examples of functional layers that can be laminated on the aliphatic polyester film include a gas barrier layer, an adhesive layer, a heat seal layer, an easy-adhesion layer, a colored layer, a printed layer, an easy-peel layer, a release layer, an easy-slip layer, a porous layer, and a nonwoven fabric.

[0062] The method for laminating the functional layer may be selected depending on the functional layer, but for example, the functional layer can be laminated by vapor deposition, sputtering, coating, various printing methods such as gravure printing and offset printing, thermal bonding, lamination via an adhesive layer, etc.

[0063] In addition, from the viewpoint of not impairing the effects of the present invention, it is preferable that the functional layer is biodegradable or has low toxicity. As a preferred functional layer that can be laminated, for example, when used for packaging applications or agricultural, forestry, and fisheries applications, it is preferable to provide a gas barrier coating layer or a vapor deposition layer from the viewpoint of imparting gas barrier properties. A vapor deposition layer is more preferable from the viewpoint of exhibiting high gas barrier performance. Furthermore, it is preferable to provide a heat-sealable resin layer or an adhesive coating layer from the viewpoint of imparting lamination processability. When multiple films are laminated, a coating layer is more preferable from the viewpoint of reducing the thickness of the final product. When the aliphatic polyester film of the present invention is used to cover agricultural, forestry, and fisheries materials such as fertilizers, feeds, seeds and seedlings, and pharmaceuticals, a heat-sealable resin layer (hereinafter sometimes referred to as a "heat-seal layer") that imparts thermocompression bonding properties is preferred as a functional layer that imparts adhesiveness.

[0064] When a vapor-deposited layer is laminated as a functional layer on the aliphatic polyester film of the present invention, the vapor-deposited layer is preferably laminated on at least one side of the film. Furthermore, from the viewpoint of gas barrier property, the vapor-deposited layer is preferably a layer containing more than 50% by mass but not more than 100% by mass of a metal and an inorganic compound (hereinafter, sometimes referred to as a "D layer"). Here, "a layer containing more than 50% by mass but not more than 100% by mass of a metal and an inorganic compound" refers to a layer containing more than 50% by mass of a metal alone, a layer containing more than 50% by mass of an inorganic compound alone, or a layer containing both a metal and an inorganic compound in a total amount exceeding 50% by mass, where the total amount of all components constituting the vapor-deposited layer is taken as 100% by mass. As the metal and / or inorganic compound that can be used in the D layer, from the viewpoints of improving adhesion to the film, improving gas barrier property when laminated on the film, and reducing environmental impact, for example, aluminum, aluminum oxide, silicon oxide, germanium oxide, magnesium oxide, cerium oxide, calcium oxide, diamond-like carbon film, or a mixture thereof is preferably used. From the viewpoint of visibility of the contents, it is more preferable to use inorganic compounds, particularly aluminum oxide, silicon oxide, or mixtures containing these.

[0065] The thickness of the D layer in the laminate is preferably 200 nm or less from the viewpoints of recyclability when the laminate is reused as a resin or film, suppressing deterioration of gas barrier properties due to cracks, and ensuring visibility of contents when used as a packaging material. From the above viewpoints, the thickness of the D layer is more preferably 110 nm or less, even more preferably 50 nm or less, and even more preferably 30 nm or less. The lower limit is not particularly limited, but is set to 1 nm from the viewpoint of exhibiting barrier properties.

[0066] In the laminate of the present invention, from the viewpoint of improving the gas barrier property and suppressing a decrease in the gas barrier property due to deposition defects or cracks in the D layer, an overcoat layer may be provided on the surface of the D layer opposite to the aliphatic polyester film.

[0067] When a heat seal layer is laminated as a functional layer on the aliphatic polyester film of the present invention, it is preferable to laminate the heat seal layer on at least one side of the film. Furthermore, from the viewpoint of achieving both the quality and heat sealability of the aliphatic polyester film, it is preferable for the heat seal layer to be a layer that fuses at a temperature of 100°C or higher and 20°C or lower than the melting point of the aliphatic polyester film of the present invention (hereinafter, sometimes referred to as "Layer E"). Here, "a layer that fuses at a temperature of 100°C or higher and 20°C or lower than the melting point of the aliphatic polyester film of the present invention" refers to a resin component that accounts for more than 50% by mass of the total mass of Layer E and has a softening point or melting point of 100°C or higher and 20°C or lower than the melting point of the aliphatic polyester film of the present invention. Resin components that can be used in Layer E, from the viewpoint of high heat seal strength, are preferably, for example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-propylene random copolymer, ethylene-propylene block copolymer, ethylene-methacrylic acid copolymer, etc., or mixtures thereof. When multiple films are laminated, from the viewpoint of reducing the thickness of the final product, for example, ethylene-vinyl acetate copolymer (EVA)-based hot melt adhesives, olefin-based hot melt adhesives, rubber-based hot melt adhesives, polyester-based hot melt adhesives, polyamide-based hot melt adhesives, polyurethane-based hot melt adhesives, etc., or mixtures thereof are preferably used. From the viewpoint of increasing the biodegradability of the entire laminate, for example, resin components containing the constituent elements of the polyhydroxyalkanoic acids exemplified above as copolymerization components, biodegradable resins having a softening point or melting point 20°C or more lower than that of the aliphatic polyester film of the present invention, such as polylactic acid, polyglycolic acid, and polybutylene succinate, or mixtures thereof are preferably used.

[0068] The thickness of Layer E in the laminate is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 3 μm or more, from the viewpoint of exhibiting high heat seal strength. Furthermore, from the viewpoint of suppressing a decrease in the biodegradability of the laminate and suppressing the thickness of the final product when multiple films are laminated, the thickness of Layer E is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less.

[0069] In the laminate of the present invention, a resin layer having a thickness of 1 μm or less may be provided by coating or the like between a functional layer such as a D layer or an E layer and the surface of the aliphatic polyester film. The provision of such a resin layer may provide an effect such as improving the adhesion between the functional layer and the aliphatic polyester film. However, from the viewpoint of production costs, an embodiment without such a resin layer is preferred, and an embodiment in which the functional layer is directly on the surface of the aliphatic polyester film is more preferred.

[0070] The method for forming functional layers such as layer D and layer E on the aliphatic polyester film of the present invention to form a laminate can be selected from known techniques such as coating, vapor deposition, lamination, and coextrusion. For example, vapor deposition is more preferable for layer D because it is independent of humidity and can exhibit excellent gas barrier properties even in a thin film. Vacuum deposition methods include physical vapor deposition (e.g., vacuum deposition, EB vapor deposition, sputtering, and ion plating), and various chemical vapor deposition methods (e.g., plasma CVD). From the viewpoint of productivity, vacuum deposition is more preferred. For layer E, coating and lamination are particularly preferred because they can exhibit high heat seal strength in a thin film. Examples of coating methods that can be used include bar coating, gravure coating, calendar coating, and die coating. Examples of lamination methods that can be used include dry lamination, solventless lamination, extrusion lamination, and coextrusion. From the viewpoint of productivity, gravure coating, die coating, extrusion lamination, and coextrusion are more preferred.

[0071] <Packaging Material, Package> The packaging material and package of the present invention are described below. The packaging material of the present invention is characterized by including the aliphatic polyester film of the present invention. The packaging material of the present invention is preferably a packaging material in which a functional layer is laminated on the aliphatic polyester film of the present invention, and more preferably a packaging material in which a gas barrier layer and / or a heat seal layer is laminated as the functional layer. The aliphatic polyester film of the present invention does not break or deform even under the conveying tension of the vapor deposition process of the vapor deposition layer provided as a gas barrier layer. Therefore, the packaging material of the present invention has good gas barrier properties and can be suitably used for packaging items that are susceptible to deterioration by water vapor or oxygen. Furthermore, the aliphatic polyester film of the present invention has good sealing quality due to the uniform fusion of the resin layer provided as a heat seal layer. Therefore, the packaging material of the present invention can be suitably used for packaging in which multiple sheets are stacked and sealed, such as snack packaging.

[0072] The package of the present invention is a package in which contents are packed using the packaging material of the present invention. The contents are not particularly limited, but since the packaging material of the present invention has excellent transparency, gas barrier properties, and heat sealability, it is preferable that the contents be visible from the outside and be easily deteriorated by water vapor or oxygen. The package of the present invention can be produced by covering the contents with the packaging material of the present invention, and the form is not particularly limited. For example, a package can be produced by processing the packaging material of the present invention into a bag shape by heat sealing and placing the contents inside, or a package can be produced by filling or placing the contents in a tray-shaped container and then sealing it with the packaging material of the present invention.

[0073] <Agricultural, forestry and fishery materials> The agricultural, forestry and fishery materials of the present invention are described below. The agricultural, forestry and fishery materials of the present invention are characterized by including the aliphatic polyester film of the present invention. The aliphatic polyester film may be a laminate provided with a functional layer. Because the agricultural, forestry and fishery materials of the present invention are biodegradable, they are suitably used for materials that preferably have the function of biodegrading after use, such as soil mulch films, vegetation films, fumigation films, water retention films, fertilizer covering materials, feed covering materials, seed and seedling covering materials, pesticide covering materials, aquaculture support films, films for inhibiting the adhesion of marine organisms, and environmental conservation materials.

[0074] <Coating Film for Agricultural, Forestry, and Fishery Materials> By using the aliphatic polyester film of the present invention to coat agricultural, forestry, and fishery materials, the coated agricultural, forestry, and fishery materials can be protected, preventing quality deterioration due to degradation and environmental pollution due to leakage. Meanwhile, the aliphatic polyester film of the present invention is biodegradable in soil or the ocean, allowing coated agricultural, forestry, and fishery materials, such as fertilizers, feed, and chemicals, to be dispersed or dispersed at the appropriate time. Furthermore, after protecting the seedlings until they settle and become established, the aliphatic polyester film biodegrades, preventing interference with the growth of the seedlings. Here, agricultural, forestry, and fishery materials refer to materials or components contained in agricultural, forestry, and fishery materials. These materials are not particularly limited as long as they do not impair the effects of the present invention, and a wide variety of known materials can be used. The agricultural, forestry, and fishery materials are preferably one or more selected from fertilizers, feeds, seeds, and chemicals.

[0075] The aliphatic polyester film of the present invention has excellent biodegradability, high-temperature and high-speed processability, and heat-sealing processability. Its use in coating agricultural, forestry, and fishery materials can prevent uneven diffusion of the agricultural, forestry, and fishery materials contained therein due to uneven coating thickness or heat-pressing. Specifically, controlling the thickness of the aliphatic polyester film of the present invention makes it possible to control the diffusion and dispersion rate of the coated agricultural, forestry, and fishery materials in soil or the ocean. In addition, two or more agricultural, forestry, and fishery materials selected from fertilizers, feeds, seeds, and chemicals can be coated together with the aliphatic polyester film of the present invention. For example, coating seeds and the desired fertilizer or chemical together with the aliphatic polyester film of the present invention is preferable because it can enhance crop growth simultaneously with germination.

[0076] From the above viewpoints, the thickness of the aliphatic polyester film of the present invention is preferably selected within the above-mentioned preferred range in accordance with the diffusion and scattering rate in soil or ocean. If the thickness of the aliphatic polyester film is excessively thin, the strength may be insufficient, resulting in reduced protection of the contents or tearing during processing. Furthermore, if the thickness of the aliphatic polyester film is excessively thick, the flexibility may be insufficient, making it difficult to process into the desired shape described below. For example, when producing a fast-acting fertilizer, a thin aliphatic polyester film may be selected to ensure rapid diffusion and scattering after biodegradation. When producing a slow-acting fertilizer, a thick aliphatic polyester film may be selected to ensure slow diffusion and scattering after biodegradation. Spreading fast-acting and slow-acting fertilizers together can reduce the workload of agricultural workers.

[0077] Furthermore, by taking advantage of the characteristics of the aliphatic polyester film of the present invention, the coating can be made into a multilayer structure. Specifically, by coating a fertilizer with the aliphatic polyester film of the present invention to prepare a slow-release fertilizer, and then further coating the slow-release fertilizer and a fast-release fertilizer with the aliphatic polyester film of the present invention, it is possible to prepare a fertilizer in which the slow-release fertilizer and the fast-release fertilizer are coated in multiple layers with multiple aliphatic polyester films of the present invention. In addition, by using a similar method, it is possible to coat seeds and seedlings with multiple layers of the aliphatic polyester films of the present invention, and the effect of applying the fertilizer, feed, or chemical to the grown agricultural and marine products at the appropriate time can be expected.

[0078] As described above, agricultural, forestry, and fishery materials coated with the aliphatic polyester film of the present invention can be dispersed and dispersed in soil or the ocean at an appropriate time while preventing environmental pollution due to unintended leakage, thereby improving efficacy and reducing the workload of workers, making them particularly suitable for use in the fields of agriculture, forestry, and fisheries, particularly in agricultural, forestry, and fishery products, such as fertilizers, feeds, seeds and seedlings, and pharmaceuticals.

[0079] The form of the coated agricultural, forestry and fishery material coated with the aliphatic polyester film of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and various forms such as pellets, granules, capsules, blocks, pouches, ropes, sheets, etc. Specifically, for coated fertilizers for agricultural use, a form selected from block, pellets, granules and capsules that are compatible with spreaders is preferred, and for coated seeds and seedlings, a rope or sheet form that is expected to reduce work is preferred.

[0080] <Production Method> A preferred embodiment of the method for producing the aliphatic polyester film of the present invention will now be described.

[0081] The method for producing the aliphatic polyester film of the present invention involves the following steps in this order: a melt extrusion step in which raw material pellets are introduced into an extruder, melted, and extruded into a sheet form through a die; a casting step in which the extruded resin sheet is cooled and solidified on a support to obtain an unstretched aliphatic polyester film; a stretching step in which the unstretched film obtained in the casting step is stretched in two perpendicular directions; and a heat treatment step in which the film obtained in the stretching step is subjected to a heat treatment and relaxation treatment. The layer structure of the aliphatic polyester film of the present invention is not particularly limited. For example, it may have a single-layer structure containing only a layer containing the polyhydroxyalkanoic acid exemplified above (hereinafter sometimes referred to as "layer A"), or a two-layer structure (layer A / layer B) or a two-layer structure (layer A / layer B / layer A) containing a layer of a different composition from layer A (hereinafter sometimes referred to as "layer B"). As long as the effects of the present invention are not impaired, a three-layer structure such as a layer A / layer B / layer C structure including a layer (hereinafter sometimes referred to as a "layer C") having a different composition from the layers A and B can be adopted so that the content of polyhydroxyalkanoic acid and the content of aliphatic polyester relative to the total mass of the film are within the preferred ranges as exemplified above. Hereinafter, the production method thereof will be described in more detail using an aliphatic polyester film having a single layer A structure made from two raw materials, a polyhydroxyalkanoic acid and an aliphatic polyester other than a polyhydroxyalkanoic acid, as an example, but the aliphatic polyester film of the present invention and its production method should not be construed as necessarily being limited thereto.

[0082] First, raw material pellets of polyhydroxyalkanoic acid and raw material pellets of aliphatic polyester other than polyhydroxyalkanoic acid are prepared. Since the melting point and thermal decomposition onset temperature of polyhydroxyalkanoic acid are close, a decrease in viscosity due to thermal decomposition during the melt extrusion process is unavoidable. Taking this into consideration, it is important to adjust the melt state of the two types of aliphatic polyesters to an optimal range when they are melted and kneaded in the extruder.

[0083] Specifically, when the melt viscosity of the polyhydroxyalkanoic acid raw material measured by the method described below is M1, and the melt viscosity of the aliphatic polyester raw material other than polyhydroxyalkanoic acid is M2, the difference between M2 and M1, |M2-M1|, is preferably 40 Pa·s or more and 1000 Pa·s or less. If the viscosity difference between M2 and M1, |M2-M1|, is less than 40 Pa·s, the dispersion structure of the two types of aliphatic polyesters may become excessively fine, or the structure may become too uniform due to transesterification or compatibilization. On the other hand, if |M2-M1| exceeds 1000 Pa·s, the dispersion structure of the two types of aliphatic polyesters may become excessively large. From the above viewpoint, |M2-M1| is more preferably 100 Pa·s or more and 700 Pa·s or less, and even more preferably 200 Pa·s or more and 500 Pa·s or less.

[0084] Furthermore, when adding a resin component other than aliphatic polyester, such as a water-soluble resin, it is preferable to form a masterbatch with a resin other than polyhydroxyalkanoic acid. When the water-soluble resin is formed into a masterbatch with a polyhydroxyalkanoic acid resin that is easily thermally decomposed, or when the water-soluble resin is directly added to the melt extrusion process, the molecular weight of the polyhydroxyalkanoic acid or the aliphatic polyester resin other than polyhydroxyalkanoic acid decreases during melt extrusion, resulting in insufficient entanglement of molecular chains, making it difficult to crystallize the orientation when the film is stretched, which may impair processability or make film formation difficult.

[0085] Next, in the melt extrusion process, the above-mentioned raw materials are fed into an extruder heated to above the melting point of the polyhydroxyalkanoic acid and melted while kneading with the screw. When the heating temperature in the compression section of the screw is taken as the melt-kneading temperature, the melt-kneading temperature is preferably 160°C or higher and 185°C or lower. If the melt-kneading temperature is lower than 160°C, the dispersion structure of the two types of aliphatic polyesters may become too fine, or the structure may become too uniform due to transesterification or compatibilization. In addition, the raw material pellets may not melt sufficiently into the extruder, resulting in a large load. On the other hand, if the melt-kneading temperature exceeds 185°C, the viscosity of the polyhydroxyalkanoic acid may decrease too much, causing the dispersion structure of the two types of aliphatic polyesters to become excessively large. From the above viewpoint, the melt-kneading temperature is more preferably 165°C or higher and 180°C or lower, and even more preferably 168°C or higher and 175°C or lower.

[0086] Next, the molten resin discharged from the extruder is passed through a pipe equipped with a filtration filter to remove foreign matter, and then extruded into a sheet form from a slit-shaped die. When the melt residence time is defined as the time from when the molten resin is discharged from the extruder until when it is extruded from the die, the melt residence time is preferably 2 minutes or more and 15 minutes or less. If the melt residence time is less than 2 minutes, the dispersion structure of the two types of aliphatic polyesters may become excessively fine. On the other hand, if the melt residence time exceeds 15 minutes, excessive re-agglomeration may occur, causing the dispersion structure of the two types of aliphatic polyesters to become excessively large. From the above viewpoint, the melt residence time is more preferably 3 minutes or more and 10 minutes or less, and even more preferably 4 minutes or more and 7 minutes or less.

[0087] Subsequently, the molten resin extruded from the slit die is cooled and solidified on a casting drum whose surface temperature is controlled to 10° C. to 40° C. to obtain an unstretched film. The method for adhering the resin to the casting drum may be any of an electrostatic application method, an adhering method utilizing the surface tension of water, an air knife method, a press roll method, an underwater casting method, an air chamber method, or the like, or a combination of two or more methods may be used.

[0088] Here, when the ratio (Td / Tn) of the discharge thickness width Td of the slit-shaped spinneret to the thickness Tn of the unstretched film is defined as the draft ratio, the draft ratio is preferably 2 or more and 30 or less. By setting the draft ratio within this range, when the dispersion structure of two types of aliphatic polyesters is discharged from the slit-shaped spinneret, the dispersion structure is elongated in the take-up direction, thereby making it possible to make the dispersion structure appropriately fine. From the above viewpoint, the draft ratio is more preferably 4 or more and 15 or less, and even more preferably 5 or more and 10 or less.

[0089] Next, the unstretched film is stretched in two perpendicular directions. The stretching method may be sequential biaxial stretching, in which stretching is performed separately in the longitudinal direction and the width direction, or simultaneous biaxial stretching, in which stretching is performed simultaneously in the longitudinal direction and the width direction. Furthermore, additional stretching may be performed after stretching. Stretching may be performed continuously or batchwise. A specific explanation will be given below using sequential biaxial stretching as an example.

[0090] First, an unstretched film is longitudinally stretched to obtain a uniaxially oriented film. In the longitudinal stretching process, the unstretched film is introduced between a group of heated rolls, preheated, and then stretched in the machine direction at a magnification of 1.5 to 10 times by using the speed difference between the rolls to obtain a uniaxially stretched (longitudinal stretched) film.

[0091] Next, the film uniaxially stretched in the longitudinal direction is introduced into a tenter while the ends of the film are held with clips, and stretched (transversely stretched) in the width direction by 1.5 times or more and 10 times or less while the ends of the film are held with clips, thereby obtaining a biaxially stretched film.

[0092] Thereafter, the heat shrinkage rate can be controlled by applying a heat treatment and a relaxation treatment. Specifically, it is preferable to apply a relaxation treatment of 1% to 30% in the width direction by narrowing the width of the tenter rails while heating the biaxially stretched film to 100°C or higher and lower than the melting point of the polyhydroxyalkanoic acid.

[0093] The heat treatment and relaxation treatment may be carried out continuously or batchwise, and the relaxation treatment may be carried out simultaneously or continuously in both the longitudinal and transverse directions.

[0094] The aliphatic polyester film of the present invention can be obtained by the stretching method exemplified above. Here, the areal stretching ratio relative to the unstretched film is preferably 4 to 25 times. When the aliphatic polyester film of the present invention has a dispersed structure consisting of polyhydroxyalkanoic acid and an aliphatic polyester other than polyhydroxyalkanoic acid, if the areal stretching ratio is within the above range, the dispersed structure can be elongated by stretching, thereby making the structure appropriately finer. From the above viewpoint, the areal stretching ratio is more preferably 6 to 20 times, and even more preferably 8 to 16 times.

[0095] Then, the edges on both sides of the film width direction are slit in a winding process. When a functional layer is subsequently laminated on the aliphatic polyester film of the present invention, it is preferable to apply an in-line surface modification treatment or an easy-adhesion coating to the surface in contact with the functional layer in order to increase the peel strength. The film thus obtained is wound into a roll to obtain the aliphatic polyester film of the present invention.

[0096] The aliphatic polyester film obtained by this production method has a dispersion structure of polyhydroxyalkanoic acid and aliphatic polyester other than polyhydroxyalkanoic acid that is finely controlled within an appropriate range, and while it has excellent biodegradability, it can also be made high in strength and can be easily processed into packaging materials and agricultural, forestry and fishery materials.

[0097] Next, the method for producing agricultural, forestry and fishery materials coated with the aliphatic polyester film of the present invention will be explained in more detail using a fertilizer as an example, but it should not be construed as being necessarily limited to this.

[0098] In the method for producing the fertilizer coated with the aliphatic polyester film of the present invention, the aliphatic polyester film obtained by the above method is introduced into upper and lower molds each having a pellet-shaped depression, and the film is then adhered to the upper and lower molds by suction. Next, the fertilizer to be coated is spread on the film in the lower mold, and the upper mold is lowered and heated to bond the upper and lower films together.

[0099] The fertilizer to be coated with the aliphatic polyester film of the present invention may be in any of the following forms: pellets, granules, powder, paste, and liquid. Among these, from the viewpoints of ease of protection with the film and conformability to the shape of a mold, the form of the fertilizer is preferably any of the following forms: granules, powder, paste, and liquid.

[0100] In this case, from the viewpoint of adhesiveness, it is preferable to provide the aliphatic polyester film of the present invention with the aforementioned heat seal layer as an adhesive layer. In this case, it is more preferable to place the film in a mold so that the adhesive layer is located on at least one side of the surfaces where the films contact each other. Next, the film-coated fertilizer is removed from the mold, and the excess film-bonded portion is cut and removed to obtain a pelletized coated fertilizer. Here, the cutting method preferably uses a cutter equipped with a blade. Examples of the cutting method include a batch-type sheet processing method using a mold equipped with a blade, a method in which the fertilizer is continuously cut in one direction using a rotary blade to form a rope-like shape and then periodically cut in the perpendicular direction, and a method in which the above-mentioned mold is equipped with a blade to perform heat-compression bonding and cutting simultaneously.

[0101] Other methods for covering agricultural, forestry and fishery materials include a method in which two rolls of the aliphatic polyester film of the present invention are prepared, and while unwinding the two films from the rolls, the agricultural, forestry and fishery material is inserted between the films at regular intervals to laminate them; a method in which the agricultural, forestry and fishery material is held on the film and heated to heat-shrink the film, or a method in which the film is shrunk by reducing pressure to cover the agricultural, forestry and fishery material with the film.

[0102] By using this production method of the present invention, agricultural, forestry and fishery materials can be obtained that are coated with the aliphatic polyester film of the present invention, which has excellent biodegradability and processability.

[0103] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the embodiments shown below. Each item was evaluated by the following methods.

[0104] <Methods for Measuring Characteristic Values ​​and Methods for Evaluating Effects> The methods for measuring characteristic values ​​and evaluating effects in the present invention are as follows.

[0105] (1) Evaluation of the composition of aliphatic polyester films: Accurately weighed film samples and appropriate reference substances of known purity are dissolved in solvents such as chloroform, hexafluoroisopropanol (HFIP), and dimethyl sulfoxide (DMSO). １ H-NMR and １３ By measuring with C-NMR, the aliphatic polyester and polyhydroxyalkanoic acid components can be qualitatively and quantitatively determined. In the examples and comparative examples, the composition was calculated from the resin content during film production.

[0106] (2) Film Thickness Evaluation The thickness (unit: μm) of the aliphatic polyester film was measured in an atmosphere of 23° C. and 65% RH using a contact-type high-precision digital length measuring instrument "Litematic VL50B" manufactured by Mitutoyo Corporation.

[0107] (3) Evaluation of melt viscosity of raw material: Using a capillary rheometer ("Capillograph" 1D, manufactured by Toyo Seiki Seisakusho, Ltd.), raw material pellets dried at 50°C for 24 hours in a dehumidifying dryer were measured under the following conditions, and the melt viscosity (unit: Pa s) was calculated when the load stabilized. Measurements were performed three times for each raw material pellet, and the average value was used. Cylinder diameter: 9.55 mm, Capillary die diameter: 1 mm, Capillary die length: 10 mm, Set temperature: 180°C, Preheating time: 10 minutes, Test speed: 10 mm / min.

[0108] (4) Determination of Samples with Unknown Orientation For films with an unknown orientation, a rectangular sample measuring 150 mm in length and 10 mm in width was cut out with an arbitrary direction facing upward, and designated sample <1>. The direction of the long side of sample <1> was defined as 0°. Next, sample <2> of the same size was taken so that the long side direction was rotated 15° to the right from the 0° direction. Similarly, the long side direction of the rectangular sample was rotated 15° at a time, and samples <3> to <12> were taken in the same manner. Next, each rectangular sample was set in a tensile tester (Orientec Co., Ltd. "Tensilon (registered trademark)" universal testing machine RTG-1210) with an initial chuck distance of 30 mm so that the long side direction was the tensile direction, and a tensile test was performed at a temperature and humidity of 25±5°C and 65±10% RH at a tensile speed of 300 mm / min. The maximum load at which the sample broke was read and divided by the cross-sectional area of ​​the sample before the test to calculate the breaking strength (unit: MPa). The cross-sectional area of ​​the sample was calculated by multiplying the film thickness obtained in (2) by the film width.

[0109] The longitudinal direction of the sample having the highest breaking strength among samples <1> to <12> was defined as the machine direction in the present invention, and the direction perpendicular to the main orientation axis was defined as the width direction. In the examples and comparative examples, the machine direction or the width direction was determined based on the stretching direction during film production.

[0110] (5) Film Cross-Section Exposure The aliphatic polyester film was embedded in UV-curable resin, and a rotary microtome (RMS type manufactured by Nippon Miktrom Laboratories) was used to extrude the film cross-section under the following conditions in an atmosphere of 25±5°C and 65±10% RH: Knife: HISTO-Wet 6 mm manufactured by Diatome Knife angle: 6° Cutting thickness: 2 graduations (1 μm) Cutting speed: 1 mm / sec. The knife board was filled with pure water, and the cutting was performed while checking the cutting state under a microscope with the cutting edge wet.

[0111] (6) Evaluation of the half-width Hh of the height distribution histogram and the half-width Hm of the elastic modulus distribution histogram obtained by AFM measurement of the film cross section (6-1) Calibration and measurement of AFM The sample with the cross section exposed in the embedding resin prepared in (5) was fixed vertically to a pedestal so that the cross section was horizontal, and measurements were performed using an AFM (DimensionIcon atomic force microscope manufactured by Bruker Corporation) under the following conditions in an atmosphere of 25 ° C and 65% RH. The cantilever warpage sensitivity, spring constant, and tip curvature were calibrated according to the PeakForceQNM mode manual. At this time, the spring constant and tip curvature vary depending on the individual cantilever, but cantilevers that satisfy the conditions of a spring constant of 150 (N / m) to 250 (N / m) and a tip curvature radius of 100 (nm) or less were used, as ranges that do not affect the measurement. The measurement was performed by specifying a range so that the center point in the thickness direction of the film cross section was the center. Measurement mode: PeakForceQNM (force curve method) Cantilever: BRUKER model RTESPA-525 Analysis software: NanoScopeAnalysis V1.40 Measurement range: 10 (μm) square Samples / Line x Lines: 512 x 512 Aspect Ratio: 1 Scan Rate: 0.900 to 1.000 Hz Scan Asyst Noise Threshold: 0.5

[0112] (6-2) Calculation of the half-width Hh of the height distribution histogram The data of the height sensor channel obtained in (6-1) was output using the analysis software "NanoScopeAnalysis V1.40", and after image processing using Planefit processing (XY, 3rd), a height distribution histogram was obtained. Next, the numerical data of the histogram was output, and the half-width of the peak fitted with a Gaussian distribution was taken as Hh (unit: nm). Note that when the peak was divided into two or more, the result of the largest peak was adopted. In addition, a total of five different locations on the film cross section were arbitrarily selected in the same manner, and the average value of the images of a total of 10 locations in the longitudinal and transverse directions of the film was adopted.

[0113] (6-3) Calculation of the half-width Hm of the elastic modulus distribution histogram The data of the DMT Modulus channel obtained in (6-1) was output using the analysis software "NanoScopeAnalysis V1.40" to obtain a histogram of the elastic modulus distribution. Next, the numerical data of the histogram was output, and the half-width of the peak fitted with a Gaussian distribution was taken as Hm (unit: GPa). Note that if the peak was divided into two or more, the result of the largest peak was adopted. In addition, a total of five different locations on the film cross section were arbitrarily selected, and the average value of a total of 10 images in the longitudinal and transverse directions of the film was adopted.

[0114] (7) Aspect ratio of pores in the cross section of a home-composted film: 40 parts by weight of sawdust, 30 parts by weight of rabbit feed, 10 parts by weight of matured compost, 10 parts by weight of cornstarch, 5 parts by weight of sucrose, 4 parts by weight of corn oil, and 1 part by weight of urea were mixed together in accordance with the aerobic disintegration test described in ISO 20200 (2023), and the moisture content was adjusted to 50% to prepare 1 L of wet synthetic compost, which was then placed in a 10 L polypropylene container. Next, the sample with its cross section exposed was embedded in the embedding resin prepared in (5) so that it was in contact with the compost, and then composted in an oven controlled at 28 ° C for 14 days, with stirring and moisture content adjustment at specified intervals.

[0115] The buried film sample was then recovered, the compost adhering to the surface was washed away with pure water, and the sample was dried. The cut surface was then fixed vertically to a base and pretreated using a sputtering device (JEOL "Auto Fine Coater" JFC-1600) under the following conditions: Target: Platinum (purity 99.99%), Current: 30 mA, Treatment time: 20 seconds, Number of treatments: 2

[0116] Thereafter, the cut cross section of the sample was observed using a scanning electron microscope (SEM) (JEOL Ltd., field emission scanning electron microscope "JSM-6700F") under the following conditions: Acceleration voltage: 3 kV, Detection mode: LEI, with the area designated so that the center point in the film thickness direction was the center.

[0117] The observation magnification was adjusted so that 20 to 100 pores were included in the observation field of view using the above method, and an observation image was obtained. Then, using image analysis software, the ratio (LL / SL) of the longest distance (LL) to the shortest distance (SL) for each pore in the observation field was measured, and the average aspect ratio of the pores in the observation image was calculated. The same operation was performed on five different locations on the film cross section, and the average value of a total of 10 images obtained by cutting the film cross section in the longitudinal and width directions of the film was used.

[0118] (8) Evaluation of 120°C heat shrinkage rates S1 and S2 The film was cut into rectangles of 150 mm length x 10 mm width in the longitudinal and transverse directions, and a mark was made in the center of the film within 100 mm using an oil-based marker. The length was measured using a universal projector to determine the initial length I ０ The measured sample was then hung in a gear-type hot air oven adjusted to a temperature of 120°C, and a 2.1 g load was attached to the bottom of the hanging film, and the film was heat-treated for 15 minutes while rotating the gear. The film was then taken out and cooled to room temperature, and the length between the marks was measured with a universal projector to determine the length after heat treatment, I. Ｈ The measured length I ０ and I Ｈ The 120°C heat shrinkage (unit: %) was calculated from the following formula. The same measurements were performed five times in the longitudinal direction and width direction of each sample, and the average value in the longitudinal direction was taken as S1 (%), and the average value in the width direction was taken as S2 (%). 120°C heat shrinkage (%) = (I ０ -I Ｈ ) / I ０ ×100.

[0119] (9) Orientation parameter P calculated from the intensity ratio of the Raman spectrum ＭＴ and P Ｚ(9-1) Measurement of Polarized Raman Spectra Three types of samples were prepared from the same film specimen: (A) a film cut to a size suitable for measurement, (B) a cross-section cut in the longitudinal direction with a microtome using the method described in (5), and (C) a cross-section cut in the width direction with a microtome. Next, under the following conditions, sample (A) was irradiated with a laser having a polarization axis in the longitudinal and width directions onto an arbitrary surface, while samples (B) and (C) were fixed to a cross-section observation stage, and lasers having a polarization axis in the surface direction and thickness direction were irradiated onto the cut cross-section, thereby measuring the Raman spectrum in two directions of polarization axes for each sample. Apparatus: Renishaw InVia Conditions: Microscopic Raman measurement mode Objective lens: 50x Beam diameter: 2 μm Light source: Semiconductor laser 532 nm Laser power: 300 mW Diffraction grating: Single 3000, -3000 gr / mm Detector: Renishaw CCD 1024×256.

[0120] (9-2) Orientation parameter P ＭＴ and P Ｚ Calculation of the C═O stretching band (1770 cm ) in the Raman spectrum obtained in (9-1) －１ Nearby) and CC elastic band (875 cm －１ The peak intensity ratio (I ８７５ / I １７７０ ) to the orientation parameter P ＭＴ , P Ｚ was calculated from the following formula. Three samples of each type were prepared in advance, and measurements were carried out for each sample. The average value of the three measurements was used. ８７５ / I １７７０ ): I ＭＤ The spectral intensity ratio (I ８７５ / I １７７０ ): I ＴＤ The spectral intensity ratio (I ８７５ / I １７７０ ): I ＭＺ The spectral intensity ratio of the thickness direction polarization axis of sample (B) (I ８７５ / I １７７０ ): I ＺＭThe spectral intensity ratio (I ８７５ / I １７７０ ): I ＴＺ The spectral intensity ratio of the thickness direction polarization axis of sample (C) (I ８７５ / I １７７０ ): I ＺＴ Orientation parameter P ＭＴ =I ＭＤ / I ＴＤ Orientation parameter P Ｚ = (I ＭＺ / I ＺＭ +I ＴＺ / I ＺＴ ) / 2

[0121] (10) Moisture Content Evaluation Films were prepared by conditioning for 48 hours in a thermo-hygrostat (LHL-113 manufactured by ESPEC) set at 28°C and 90% RH, and the moisture content (ppm) was measured using a Karl Fischer moisture content meter under the following conditions. The average value of three measurements was used. Moisture content meter: AQUACOUNTER "AQ-7" manufactured by HIRANUMA Moisture vaporizer: EVAPORATOR UNIT "EV-6" manufactured by HIRANUMA Counter electrode: AQUALIGHT CN manufactured by HIRANUMA Generator liquid: AQUALIGHT RS-A manufactured by HIRANUMA Baking conditions: 130°C for 15 minutes Moisture content measurement conditions: 130°C for 15 minutes

[0122] (11) The ratio AR of recesses on the frozen cut cross section after immersion in pure water Ｌ and the abundance ratio AR of the convex portions Ｈ (11-1) Film cross-section extraction by freezing cutting method An aliphatic polyester film was embedded in a UV-curable resin, and cross-sections were extracted under the following conditions using an automatic rotary microtome (Leica RM2265) whose chamber was cooled to -70°C by supplying liquid nitrogen using a freezing control device (Leica LN22). Knife: Diatome HISTO cryo dry 6.0 mm, knife angle: 45°, cutting thickness: 0.25 μm, cutting speed: 0.5 mm / sec

[0123] (11-2) AFM Measurement The cross-section cut sample prepared in (11-1) was immersed in pure water for 12 hours in a temperature and humidity atmosphere of 25°C and 65% RH, and then air-dried. Next, AFM measurement and analysis were performed in the same manner as in (6-1) and (6-2), and the numerical data of the height distribution histogram in the cross section was output. Parts with heights smaller than the maximum peak value (the height corresponding to the most frequent point) of the obtained height distribution histogram were designated as recesses, and parts with heights larger than the maximum peak value were designated as protrusions. The ratio of the total area of ​​recesses to the area of ​​the entire measurement range was determined as the presence ratio AR of recesses. Ｌ (%), and similarly, the ratio of the total area of ​​the convex portions is the convex portion presence ratio AR. Ｈ (%). When the histogram had two or more peaks, the largest peak was used. The same procedure was repeated at five different locations on the film cross section, and the average value of the images from a total of 10 locations in the longitudinal and transverse directions of the film was used.

[0124] (12) Evaluation of Molecular Weight (12-1) Obtaining Molecular Weight Distribution Curve 5 mL of a measurement solvent was added to 10 mg of a raw material or film sample, and the mixture was stirred at room temperature until the sample was dissolved. Then, gel permeation chromatography (GPC) was performed under the following conditions to obtain a molecular weight distribution curve in which the horizontal axis represents the logarithm of the molecular weight M (log M) and the vertical axis represents the weight fraction dW / dlog M per unit log M. Detector: Differential refractive index detector RI (RI-8020, Tosoh, sensitivity 32) Column: TSKgel GMHHR-M (φ7.8 mm × 30 cm, Tosoh), 2 Filters: (Millex Syringe Filter, Hydrophilic PTFE, Non-sterile, model number SLCR033NS) Solvent: Chloroform Flow rate: 1.0 mL / min Column temperature: 40°C Injection volume: 0.200 mL Standard sample: Monodisperse polystyrene, Tosoh Data processing: GPC data processing system, Toray Research Center

[0125] (12-2) M Ｌ and M ＨIn the molecular weight distribution curve obtained in (12-1), as shown in FIG. 1, when the maximum value on the vertical axis is Wm, the molecular weight at Wm / 2 on the vertical axis is read, and the molecular weight on the lowest molecular weight side is M Ｌ , the molecular weight of the highest molecular weight side is M Ｈ The same measurement was performed three times and the average value was used.

[0126] (12-3) Measurement of weight-average molecular weight (Mw) The weight-average molecular weight (Mw) was calculated from the molecular weight distribution curve obtained in (12-1). The average value of three similar measurements was used.

[0127] (13) Biodegradability: A 5 cm x 5 cm piece of the evaluation film was placed in a polyethylene holder with a 2 cm square cutout on the inside, leaving the film inside the holder exposed. Next, a wet synthetic compost was prepared in accordance with the aerobic disintegration test described in ISO 20200 (2023) using the same method as in (7), and the film sample fixed in the holder was buried in the compost. The sample was then treated for 60 days in an oven controlled at 28°C, with stirring and moisture content adjustment at specified intervals.

[0128] After 60 days, the film sample was removed from the container and photographed with a digital camera. The pixel count of the photograph was 1200 dpi (2 million pixels) or more. From the photograph, the area of ​​the film sample remaining within a 2 cm square frame inside the holder was determined, and the collapsed area ratio (%) was calculated using the formula: (initial area of ​​the sample within the holder - remaining area of ​​the sample within the holder) / (initial area of ​​the sample within the holder) x 100. A total of three holders were evaluated in the same compost, and the arithmetic mean value of the three measurements was taken as the collapsed area ratio (%) of the film sample. The biodegradability in the present invention was evaluated according to the following criteria: A: Collapsed area ratio of 40% or more; B: Collapsed area ratio of 20% or more but less than 40%; C: Collapsed area ratio of 10% or more but less than 20%; D: Collapsed area ratio less than 10%; E: No collapse occurred. The biodegradability of a film is preferably D or higher.

[0129] (14) Uniformity of Disintegration A total of 10 holders were evaluated in the same compost using the same method as in (13), and the collapse area ratio (%) of each was measured. The degree of variation in the state of disintegration during biodegradation was calculated using the following formula from the maximum and minimum values ​​of the collapse area ratio (%), and the uniformity of disintegration in the present invention was judged according to the following criteria: Variation in disintegration state (%) = (maximum value of collapse area ratio) - (minimum value of collapse area ratio) A: The degree of variation in the state of disintegration is less than 25% B: The degree of variation in the state of disintegration is 25% or more but less than 40% C: The degree of variation in the state of disintegration is 40% or more It is preferable that the uniformity of disintegration of the film is C or higher.

[0130] (15) Processability (15-1) Heat-sealing layer lamination to film The surface of the aliphatic polyester film that had been in contact with the casting drum in the film-forming process was gravure coated with a heat-sealing agent "Seikadyne" (registered trademark) BP-1910W manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. in an amount of 3.0 g / m ２ The coating was carried out so that the coating amount was 100%.

[0131] (15-2) Evaluation of film seal quality The laminated body with the heat seal layer laminated in (15-1) was cut into a width of 10 cm and a length of 20 cm. Next, a plurality of the cut-out laminated bodies were stacked, and the film was subjected to a heat seal test using a heat seal tester manufactured by Tester Sangyo Co., Ltd., with a seal width of 10 mm, a heater temperature of 120°C, and a seal pressure of 2 kg / cm. ２ The film was heat-sealed widthwise for a sealing time of 1 sec. Starting with two sheets, the number of sheets to be heat-sealed was increased by one each time. The film's sealing quality was evaluated based on the number of stacked sheets at which visually noticeable deterioration in quality, such as wrinkles or bubbles, occurred in the heat-sealed area. Heat sealing was performed at five locations 3 cm apart in the longitudinal direction, and the number of sheets at which deterioration in quality was observed in at least one of the five locations was recorded. A: No deterioration in quality with five or fewer sheets. B: No deterioration in quality with four or fewer sheets, but deterioration in quality with five sheets. C: No deterioration in quality with three or fewer sheets, but deterioration in quality with four sheets. D: No deterioration in quality with two sheets, but deterioration in quality with three sheets. E: Deterioration in quality with two sheets. Film processability of D or higher is preferred.

[0132] (16) Film Formability In the examples and comparative examples of the present invention, the film formability in the present invention was judged according to the following criteria based on the frequency of stretching breakage when produced by the described method: A: No breakage occurred within a length of 300 m B: Only one breakage occurred within a length of 300 m C: Two or more but less than five breakages occurred within a length of 300 m D: Five or more but less than 10 breakages occurred within a length of 300 m E: A film with 10 or more breakages within a length of 300 m preferably has a film formability of D or higher.

[0133] [Resin Raw Materials, etc.] The following resins were used to produce the aliphatic polyester films in each Example and Comparative Example. PHA-1: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) BP350-05 (melting point: 130°C, glass transition temperature: -3°C) manufactured by Blue Crystal Microorganisms was used. The melt viscosity was 630 Pa·s. PHA-2: PHA-1 was melt-extruded (residence time: 5 minutes) using a twin-screw extruder maintained at 170°C to prepare raw material pellets for use. The melt viscosity was 295 Pa·s. PHA-3: PHA-1 was melt-extruded (residence time: 5 minutes) using a twin-screw extruder maintained at 185°C to prepare raw material pellets for use. The melt viscosity was 44 Pa·s. PLA-1: Polylactic acid LX175 (melting point: 155°C, glass transition temperature: 60°C) manufactured by Total Energy Corbion was used. The melt viscosity was 954 Pa·s. PLA-2: Polylactic acid LX530 (melting point: 165°C, glass transition temperature: 60°C) manufactured by Total Energy Corbion was used. The melt viscosity was 679 Pa·s. PCL: Polycaprolactone Capa 6800D (melting point: 60°C, glass transition temperature: -60°C) manufactured by Ingevity was used. The melt viscosity was 1351 Pa·s. PEG-1: Polyethylene glycol PEG-4000N manufactured by Sanyo Chemical Industries, Ltd. was used. The weight average molecular weight was 4010. PEG-2: Polyethylene glycol PEG-1000 manufactured by Sanyo Chemical Industries, Ltd. was used. The weight average molecular weight was 1000. PEG-3: Polyethylene glycol PEG-6000S manufactured by Sanyo Chemical Industries, Ltd. was used. The weight average molecular weight was 8000. PVP: Polyvinylpyrrolidone K-15 manufactured by Nippon Shokubai Co., Ltd. was used. The weight average molecular weight was 9900.

[0134] Example 1 As resin raw materials for an aliphatic polyester film, PHA-1 and PLA-1, which had been dried at 50°C for 24 hours in a dehumidifying dryer, were blended in the ratios shown in Table 1 and supplied to a single-screw melt extruder. The temperature in the compression section of the screw was set to 170°C, and the mixture was discharged from the extruder. While maintaining the temperature at 170°C, the mixture was passed through a pipe equipped with a 250-mesh filtration filter to remove foreign matter, and then introduced into a T-die and discharged from a die in the form of a sheet. The time from discharge from the extruder until the molten resin was extruded from the die was 5 minutes.

[0135] The extruded molten resin sheet was then taken up onto a casting drum maintained at 25°C, and cooled and solidified while being adhered by electrostatic application to obtain an unstretched film. At this time, the extrusion thickness width of the T-die was 1.5 mm, while the central thickness of the unstretched film was 200 µm, and the draft ratio was 7.5.

[0136] The unstretched film was then continuously introduced into a longitudinal stretching machine consisting of multiple roll groups, preheated with a group of rolls preheated to 70 ° C, and stretched 3.0 times in the longitudinal direction by applying a peripheral speed difference with a roll maintained at 30 ° C. The resulting film was then continuously introduced into a tenter-type width stretching machine, preheated to 70 ° C while holding both widthwise ends with clips, stretched 4.0 times in the width direction at 75 ° C, and then heat-treated at 130 ° C while applying 10% relaxation in the width direction. Subsequently, while continuing to tensely hold both widthwise ends with clips, the film was cooled to 50 ° C and introduced to the outside of the tenter, the clips at both widthwise ends were released, and a 20 μm thick film containing an aliphatic polyester was wound into a roll using a winding machine. The evaluation results are shown in Table 1. The resulting aliphatic polyester film was found to have excellent biodegradability, processability, and film-forming properties.

[0137] (Examples 2 to 11, Comparative Example 1) Aliphatic polyester films were obtained in the same manner as in Example 1, except that the production conditions were changed as shown in the table. The evaluation results are shown in the table. Comparative Example 1 was found to be inferior in biodegradability.

[0138] (Examples 12 to 18, Comparative Example 2) Aliphatic polyester films were obtained in the same manner as in Example 1, except that the resin composition and production conditions were changed as shown in the table. The evaluation results are shown in the table. Comparative Example 2 was found to be inferior in processability and film-forming ability.

[0139] (Comparative Example 3) As shown in the resin composition in the table, an aliphatic polyester film was obtained in the same manner as in Example 1, except that no polyhydroxyalkanoic acid was contained. The evaluation results are shown in the table. It was found that Comparative Example 3 had poor biodegradability.

[0140] (Examples 19 to 24) Aliphatic polyester films were obtained in the same manner as in Example 1, except that PLA-1 and the water-soluble resins listed in the table were melt-kneaded in a vented twin-screw extruder at 190°C. The water-soluble resins were supplied as polylactic acid-based master batches (PLA-MB) so as to obtain the resin compositions listed in the table. The evaluation results are shown in the table. All of the films were found to have superior disintegration uniformity compared to Example 1.

[0141] Example 25 An aliphatic polyester film was obtained in the same manner as in Example 20, except that the resin raw materials shown in the table were directly fed to the single-screw extruder so as to obtain the resin composition shown. The evaluation results are shown in the table. It was found that the processability and film-forming ability were inferior to those of Example 20.

[0142] Examples 26 and 27 Aliphatic polyester films were obtained in the same manner as in Example 20, except that the production conditions were as shown in the table. The evaluation results are shown in the table.

[0143]

[0144]

[0145]

[0146]

[0147]

[0148] The present invention can provide an aliphatic polyester film that has high strength and excellent processability into packaging materials and agricultural, forestry and fishery materials while being biodegradable enough for home composting.

Claims

1. An aliphatic polyester film containing at least a polyhydroxyalkanoic acid, in which the half-width Hh of a height distribution histogram obtained by AFM measurement of a film cross section obtained with a rotary microtome is 5 nm or more and 60 nm or less.

2. The aliphatic polyester film according to claim 1, which contains more than 50% by mass and not more than 75% by mass of polyhydroxyalkanoic acid, based on 100% by mass of the total mass of the film.

3. An aliphatic polyester film containing at least a polyhydroxyalkanoic acid, in which the half-width Hm of the elastic modulus distribution histogram obtained by AFM measurement using the force curve method on a film cross-section obtained using a rotary microtome is 0.08 GPa or more and 0.80 GPa or less.

4. The aliphatic polyester film according to any one of claims 1 to 3, further comprising an aliphatic polyester other than polyhydroxyalkanoic acid, wherein the aliphatic polyester is polylactic acid.

5. Raman spectrum intensity ratio (I ８７５ / I １７７０ ) and the orientation parameters in the longitudinal and transverse directions in the plane are defined as P ＭＴ , the orientation parameters in the plane direction and thickness direction are P Ｚ When this is done, P Ｚ and P ＭＴ The difference (P Ｚ -P ＭＴ 4. The aliphatic polyester film according to claim 1, wherein the value of (a) is 0.2 or more and 5.0 or less.

6. In a molecular weight distribution curve with the horizontal axis representing the logarithm of molecular weight M (logM) and the vertical axis representing the weight fraction per unit logM (dW / dlogM), when the maximum value on the vertical axis is Wm, the molecular weight M on the lowest molecular weight side among the molecular weights that are Wm / 2 on the vertical axis is Ｌ 4. The aliphatic polyester film according to claim 1, wherein the molecular weight is 30,000 or more and 100,000 or less.

7. In a molecular weight distribution curve with the horizontal axis representing the logarithm of molecular weight M (logM) and the vertical axis representing the weight fraction per unit logM (dW / dlogM), when the maximum value on the vertical axis is Wm, the molecular weight M on the highest molecular weight side among the molecular weights that are Wm / 2 on the vertical axis is Ｈ 4. The aliphatic polyester film according to claim 1, wherein the molecular weight is 300,000 or more and 1,000,000 or less.

8. The aliphatic polyester film according to any one of claims 1 to 3, wherein the aspect ratio of pores in the cross section of the film after home composting at a test temperature of 28°C for 14 days in accordance with the aerobic disintegration test method described in ISO 20200 (2023) is 3 or more.

9. An aliphatic polyester film according to any one of claims 1 to 3, wherein, when the thermal shrinkage rate at 120°C in the longitudinal direction is S1 (%) and the thermal shrinkage rate at 120°C in the transverse direction is S2 (%), both S1 and S2 are 0% or more and 20% or less.

10. The aliphatic polyester film according to any one of claims 1 to 3, which contains 70% by mass or more of aliphatic polyester relative to 100% by mass of the total mass of the film.

11. The aliphatic polyester film according to any one of claims 1 to 3, which has a collapsed area ratio of 10% or more when home composted at a test temperature of 28°C for 60 days using a method conforming to the aerobic disintegration test described in ISO 20200 (2023).

12. An aliphatic polyester film according to any one of claims 1 to 3, wherein the half-value width Hm of the elastic modulus distribution histogram obtained by AFM measurement of a film cross section obtained with a rotary microtome using the force curve method is 0.10 GPa or more and 0.70 GPa or less.

13. The aliphatic polyester film according to any one of claims 1 to 3, which has a moisture content of 700 ppm or more and 9,000 ppm or less after conditioning at 28°C and 90% RH for 48 hours.

14. AR calculated by the following method Ｌ and A.R. Ｈ The difference between (AR Ｌ -AR Ｈ 4. The aliphatic polyester film according to claim 1, wherein the ratio of the height of the recesses to the area of ​​the entire measurement range is 0.2% or more and 10% or less. (1) The film is frozen and cut using a rotary microtome to obtain a film cross-section sample; (2) The obtained cross-section sample is immersed in pure water for 12 hours; (3) The cross-section sample after immersion in pure water in (2) is subjected to AFM measurement to obtain a height distribution histogram of the cross section; (4) In the obtained height distribution histogram, portions having heights smaller than the maximum peak value are defined as recesses, and portions having heights larger than the maximum peak value are defined as protrusions, and the ratio of the recesses to the area of ​​the entire measurement range is calculated as AR. Ｌ (%), the ratio of the convex portions is AR Ｈ (%).

15. An aliphatic polyester film according to any one of claims 1 to 3, which contains a water-soluble resin in an amount of 0.4% by mass to 15% by mass relative to 100% by mass of the total mass of the film.

16. The aliphatic polyester film according to claim 15, wherein the water-soluble resin is at least one selected from the group consisting of polyvinyl alcohol, polyethylene glycol, polypropylene glycol, and polyvinylpyrrolidone.

17. The aliphatic polyester film according to claim 16, wherein the water-soluble resin has a weight-average molecular weight of 2,000 or more and 9,500 or less.

18. The aliphatic polyester film according to any one of claims 1 to 3, further comprising a functional layer on at least one surface thereof.

19. A package in which contents are packed in a packaging material comprising the aliphatic polyester film according to any one of claims 1 to 3.

20. A material for agriculture, forestry and fisheries, comprising the aliphatic polyester film according to any one of claims 1 to 3.

21. A coated agricultural, forestry and fishery material, which is coated with the aliphatic polyester film according to any one of claims 1 to 3.

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