Aliphatic polyester film, package, material for agriculture, forestry and fisheries industries, and material for agriculture, forestry and fisheries

Abstract

To provide an aliphatic polyester film excellent in piercing resistance and capable of suppressing the generation of pinholes or the like at the time of processing into a packaging material or an agricultural, forestry and fishery industrial material while enhancing fertilizer capacity by shortening the disintegration completion time at the time of composting treatment at home due to excellent biodegradability.SOLUTION: The aliphatic polyester contains at least polyhydroxyalkanoic acid and has a half-width Hh of 20nm or more and 300nm or less in a height histogram obtained by AFM measurement of a film cross section obtained by a rotary microtome.SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

[0002] From the perspective of curbing global warming, various efforts are underway around the world to achieve carbon neutral goals, and there is a particular need to reduce the amount of plastic products used and disposed of, as they emit a large amount of CO2 during their manufacture and disposal.Plastic packaging is used in particularly large quantities among various plastic products, 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, fish, seabirds, and marine mammals have died after accidentally ingesting plastic products that have drifted into the ocean. Microplastics, which have been broken down by waves and ultraviolet light, are bioaccumulated in the marine food chain, posing a risk to humans who consume fish and other marine life. 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 primarily composed of polylactic acid, which is biodegradable in the natural environment, and is suitable for processing into packaging materials; a manufacturing method in which a sheet primarily composed of polyhydroxyalkanoic acid, which is biodegradable in the ocean, is continuously biaxially stretched at a stretching ratio of 1.1 or more in both the flow direction (longitudinal direction) and the direction perpendicular to it (width direction) in the film manufacturing process without roll-rolling (Patent Document 2); and a film made of a resin composition containing an aliphatic polyester resin that contains, 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). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-122289 [Patent Document 2] Japanese Patent Publication No. 2022-062759 [Patent Document 3] Japanese Patent Publication No. 2022-031161 Summary of the Invention [Problem to be solved by the invention]

[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, but 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 a film that contains 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 polyhydroxyalkanoic acid, and is described as being compostable at home, but biaxial stretching is difficult, and similarly, there is room for improvement in processability into packaging materials or agricultural, forestry, and fisheries materials, and disintegration properties during composting may be insufficient.

[0007] Therefore, an object of the present invention is to provide an aliphatic polyester film that has excellent biodegradability, which allows for a faster completion time for disintegration when composted at home (hereinafter referred to as home composting), thereby improving fertilizer performance, and also has excellent puncture resistance, which prevents pinholes from forming when processed into packaging materials or agricultural, forestry, and fisheries materials. Preferably, the object is to provide an aliphatic polyester film that has improved properties by reducing the variation in disintegration time. [Means for solving the problem]

[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. 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 20 nm or more and 300 nm or less. 2. The aliphatic polyester film according to 1., which contains more than 50% by mass and not more than 75% by mass of polyhydroxyalkanoic acid, relative to 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 with a rotary microtome is 0.20 GPa or more and 4.00 GPa or less. 4. The aliphatic polyester film according to any one of 1. to 3., which contains an aliphatic polyester other than polyhydroxyalkanoic acid, and the aliphatic polyester is polylactic acid. 5. Raman Spectral 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 Difference (P Z -P MT 5. The aliphatic polyester film according to any one of 1. to 4., 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 being the logarithm of molecular weight M, logM, and the vertical axis being 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 where the vertical axis is Wm / 2 is L 6. The aliphatic polyester film according to any one of 1. to 5., wherein the molecular weight is 20,000 or more and 90,000 or less. 7. In a molecular weight distribution curve with the logarithm of molecular weight M on the horizontal axis and the weight fraction per unit logM on the vertical axis, 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 at which the vertical axis is Wm / 2 is H 7. The aliphatic polyester film according to any one of 1. to 6., wherein the molecular weight is 200,000 or more and 900,000 or less. 8. An aliphatic polyester film according to any one of 1. to 7., 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 according to the aerobic disintegration test method described in ISO 20200 (2023) is 1.2 or more. 9. The aliphatic polyester film according to any one of 1. to 8., 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 width direction is S2 (%), S1 and S2 are both 0% or more and 20% or less. 10. The aliphatic polyester film according to any one of 1. to 9., which contains 70% by mass or more of aliphatic polyester relative to 100% by mass of the total mass of the film. 11. An aliphatic polyester film according to any one of 1. to 10., which has a quantitative disintegration rate of 70% or more when home composted at a test temperature of 28°C for 180 days according to the aerobic disintegration test method described in ISO 20200 (2023). 12. An aliphatic polyester film according to any one of 1. to 11., wherein 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 0.30 GPa or more and 2.50 GPa or less. 13. The aliphatic polyester film according to any one of 1. to 12., which has a moisture content of 700 ppm or more and 9000 ppm or less after conditioning at 28°C and 90% RH for 48 hours. 14. AR calculated by the following method L and AR H Difference (AR L -AR H 14. The aliphatic polyester film according to any one of 1. to 13., wherein the ratio of the total mass of the aliphatic polyester to the total mass of the polyester is 0.2% or more and 10% or less. [AR L and AR H How to measure the difference -Cryosectioning of film cross-section samples using a rotary microtome -Immerse the cross-section sample in pure water for 12 hours. Obtain a height distribution histogram of the cross section after immersion by AFM measurement The ratio of the number of recesses whose height is smaller than the maximum peak value of the histogram is calculated as AR. L (%) The ratio of peaks with heights greater than the maximum peak value of the histogram is calculated as AR H (%) 15. The aliphatic polyester film according to any one of 1. to 14., which contains 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 the group consisting of 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 or more and 9,500 or less. 18. The aliphatic polyester film according to any one of 1. to 17., further comprising a functional layer on at least one surface thereof. 19. Packaging containing an aliphatic polyester film in any of 1. to 17. 20. Agricultural, forestry and fishery materials containing aliphatic polyester film in any of 1. to 17. 21. An aliphatic polyester film according to any one of 1. to 17., which is a film used to cover agricultural, forestry and fishery materials, wherein the agricultural, forestry and fishery materials include one or more selected from fertilizers, feeds, seeds and seedlings, and chemicals. 22. An agricultural, forestry and fishery material coated with the aliphatic polyester film according to any one of 1. to 17. [Effects of the Invention]

[0009] The aliphatic polyester film of the present invention has excellent biodegradability, which allows it to complete disintegration quickly when composted at home (hereinafter referred to as home composting), thereby enhancing fertilizer performance (hereinafter referred to as biodegradability). Furthermore, the film has excellent puncture resistance, which prevents pinholes from forming when processed into packaging materials or agricultural, forestry, and fisheries materials (hereinafter referred to as processability). In a more preferred embodiment, the above properties can be further improved by reducing the variation in disintegration time (hereinafter referred to as disintegration uniformity). [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the positional relationship between Wm, ML, and MH in a molecular weight distribution curve. DETAILED DESCRIPTION OF THE INVENTION

[0011] The aliphatic polyester film of the present invention will be described in detail below. When the upper and lower limits of a preferred range are separately stated below, they may be combined 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 also 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 also 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. When the stretching direction (longitudinal direction and width direction) is 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.

[0012] In a preferred embodiment of the aliphatic polyester film of the present invention, it is important to contain at least a polyhydroxyalkanoic acid. Here, the polyhydroxyalkanoic acid is a polymer containing a hydroxyalkanoic acid as a constituent component, for example, a 3-hydroxyalkanoate repeating unit represented by the general formula [—CHR—CH—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:

[0013] 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 copolymerized.

[0014] P3HA may be either chemically synthesized (for example, obtained by ring-opening polymerization of the corresponding lactone) or produced by a microorganism, but P3HA produced by a microorganism is preferred from the viewpoint of ease of production using biomass raw materials such as vegetable oil. Among P3HA produced by a microorganism, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferably used from the viewpoint of ease of industrial production.

[0015] The content of polyhydroxyalkanoic acid 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.

[0016] As the aliphatic polyester component other than polyhydroxyalkanoic acid contained in the aliphatic polyester film of the present invention, it is preferable to select a biodegradable resin, and although not particularly limited, examples include polyglycolic acid, polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, polycaprolactone, etc. Here, the biodegradable resin is preferably either a naturally degradable resin or an enzymatically degradable resin, and even if the resin does not sufficiently decompose by itself in home composting, by combining it with polyhydroxyalkanoic acid in an embodiment of the present invention, the remaining indegradable material can be suppressed.

[0017] Furthermore, from the viewpoint of enabling melt extrusion at a temperature close to that of polyhydroxyalkanoic acid, the melting point of the aliphatic polyester component 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 component 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 shared in melt extrusion. Furthermore, by setting the melting point of the aliphatic polyester component 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 examples include one or more of polylactic acid, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, and polycaprolactone.

[0018] From the viewpoint of achieving both film-forming and processability, the glass transition temperature of the aliphatic polyester component 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 component 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 component 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 include one or more of polyglycolic acid and polylactic acid, with polylactic acid being particularly preferred from the viewpoints of biodegradability, melting point, and glass transition temperature.

[0019] That is, the aliphatic polyester film of the present invention contains polyhydroxyalkanoic acid and polylactic acid, and when the total mass of the film is taken as 100 mass%, it preferably contains more than 50 mass% to 75 mass% of polyhydroxyalkanoic acid and 25 mass% to less than 50 mass% of polylactic acid, more preferably 55 mass% to 72 mass% of polyhydroxyalkanoic acid and 28 mass% to 45 mass% of polylactic acid, and particularly preferably 60 mass% to 71 mass% of polyhydroxyalkanoic acid and 29 mass% to 40 mass% of polylactic acid.

[0020] The aliphatic polyester film of the present invention may also contain components other than those described above, such as resin components other than the aliphatic polyester, additives, organic particles, inorganic particles, antioxidants, heat stabilizers, slipping agents, antistatic agents, antiblocking agents, fillers, viscosity modifiers, color inhibitors, chain extenders, etc. Here, from the viewpoint of not 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, when the total mass of the film is 100% by mass.

[0021] The resin component other than the aliphatic polyester preferably contains a water-soluble resin. Here, the term "water-soluble resin" refers to a resin that dissolves in water at room temperature at a concentration of 0.005 g / mL or more. Specifically, natural polymers, semi-synthetic polymers, or synthetic polymers having hydrophilic functional groups within their molecular structure are preferred. Examples of natural polymers include alginates, hyaluronates, 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.

[0022] 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.

[0023] The content of the water-soluble resin in the aliphatic polyester film of the present invention is preferably 0.4% by mass to 15% by mass, more preferably 2% by mass to 10% by mass, and particularly preferably 4% by mass to 6% by mass, based on 100% by mass of the total mass of the film. 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 exceeds 15%, the film may absorb too much water and swell, which may result in poor processability and film-forming ability.

[0024] The weight-average molecular weight of the water-soluble resin contained in the aliphatic polyester film of the present invention is preferably 2000 or more and 9500 or less, more preferably 3000 or more and 5000 or less. If the weight-average molecular weight of the water-soluble resin is less than 2000, the film may swell excessively, resulting in reduced processability. If the weight-average molecular weight of the water-soluble resin is 9500 or more, the molecular chain of the water-soluble resin may become longer, which may result in reduced biodegradability because it takes longer for microorganisms to biodegrade it.

[0025] 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 a film 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.

[0026] A preferred embodiment of the aliphatic polyester film of the present invention is one in which the half-width Hh of a height distribution histogram obtained by atomic force microscopy (AFM) measurement of a film cross-section obtained using a rotary microtome is 20 nm to 300 nm. Here, Hh indicates the degree of uniformity of the unevenness in the film cross-section. The more uniform the internal structure of the aliphatic polyester film, the flatter the cross-section after microtome cutting and the smaller Hh. If the internal structure is non-uniform due to a phase separation structure between resins with different properties, subtle unevenness will form on the cross-section at the resin interface during microtome cutting, resulting in a larger Hh. Hh is measured using the method described in the Examples.

[0027] The polyhydroxyalkanoic acid used in the aliphatic polyester film of the present invention is highly biodegradable, but its low glass transition temperature makes it difficult to strengthen and fix the structure through sheet extrusion and biaxial stretching. Therefore, adding and dispersing aliphatic polyester components other than polyhydroxyalkanoic acid into the aliphatic polyester film was considered effective. However, when the Hh is less than 20 nm, the dispersion state is excessively fine, and the aliphatic polyester components other than polyhydroxyalkanoic acid, which are unlikely to undergo sufficient biodegradation under home composting conditions, are thought to have a continuous and / or fine, dense structure. This behavior leads to mechanical resistance of the film shape as biodegradation progresses, and increased contact between the resistant components and microorganisms leads to inactivation, delaying the completion of degradation. As a result, it was found that many large, insufficiently disintegrated film fragments remain in the fertilizer obtained by composting the aliphatic polyester film, which can impede the circulation of water and air in the compost and reduce the performance of the resulting fertilizer. On the other hand, if Hh exceeds 300 nm, the dispersion state becomes excessively large and non-uniform, and although the time to complete disintegration is shortened, the puncture strength of the film may be insufficient when the aliphatic polyester film is processed into packaging materials or agricultural, forestry, and fisheries materials, which may result in the formation of pinholes, etc. Furthermore, even after disintegration is complete, the aliphatic polyester components other than polyhydroxyalkanoic acid may remain as extremely large lumps, which may actually reduce fertilizer performance.

[0028] Based on this, the inventors have surprisingly discovered that by dispersing an aliphatic polyester component, which is less biodegradable than polyhydroxyalkanoic acid, in polyhydroxyalkanoic acid while maintaining a moderate degree of heterogeneity, it is possible to realize an aliphatic polyester film that has excellent biodegradability from the perspective of improving the fertilizer performance obtained by home composting, while also making it easy to homogenize the components that make up the film, and that has excellent processability for packaging materials and agricultural, forestry, and fisheries materials.

[0029] 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 23 nm or more, 25 nm or more, 28 nm or more, 30 nm or more, 32 nm or more, 34 nm or more, and 35 nm or more. Also, 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 250 nm or less, 200 nm or less, 160 nm or less, 130 nm or less, 100 nm or less, 80 nm or less, 70 nm or less, and 60 nm or less.

[0030] In addition, a 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 0.20 GPa to 4.00 GPa. Here, Hm indicates the degree of uniformity of hardness in the film cross-section. Hm becomes smaller when the aliphatic polyester film approaches a uniform structure or when resins with similar mechanical properties are dispersed, and 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 using the method described in the examples.

[0031] From the viewpoint of improving biodegradability while maintaining sufficient film-forming properties, the Hm of the aliphatic polyester film of the present invention becomes increasingly preferable in the order of 0.25 GPa or more, 0.30 GPa or more, 0.35 GPa or more, 0.40 GPa or more, 0.44 GPa or more, 0.47 GPa or more, and 0.50 GPa or more. From the viewpoint of improving film-forming properties while maintaining sufficient biodegradability, the Hm of the aliphatic polyester film of the present invention becomes increasingly preferable in the order of 3.20 GPa or less, 2.50 GPa or less, 1.80 GPa or less, 1.40 GPa or less, 1.20 GPa or less, 1.00 GPa or less, 0.90 GPa or less, and 0.80 GPa or less.

[0032] 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 component 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.

[0033] 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 Difference (P Z -P MT ) is preferably 0.2 or more and 5.0 or less, more preferably 0.4 or more and 2.4 or less, and even more preferably 0.6 or more and 2.0 or less.

[0034] The intensity ratio of the Raman spectrum measured by the evaluation method described below (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, and P MT The more uniform the orientation in the longitudinal and transverse directions, the closer to 1, and P Z The stronger the orientation in the plane direction relative to the thickness direction, the larger the value becomes. (P Z -P MT ) is less than 0.2, the planar orientation due to stretching is insufficient, or the orientation in the longitudinal direction and the width direction is non-uniform, which may result in excessively large Hh and Hm, impairing processability and film-forming properties.

[0035] Also (P Z -P MT ) exceeds 5.0, the structure becomes too fine due to stretching, the above-mentioned Hh and Hm become too small, and biodegradability may decrease.

[0036] In the above range (PZ -P MT ) can be controlled, for example, by adding an aliphatic polyester component other than polyhydroxyalkanoic acid to an aliphatic polyester film in a preferred mode and adjusting the draft ratio or stretch ratio during cast sheet molding as described below.

[0037] 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: 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 lowest molecular weight side among the molecular weights at which the vertical axis corresponds to Wm / 2 is L is preferably 20,000 or more and 90,000 or less, more preferably 30,000 or more and 70,000 or less, and even more preferably 50,000 or more and 60,000 or less. In addition, 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 at which the vertical axis is Wm / 2 is H is preferably 200,000 or more and 900,000 or less, more preferably 500,000 or more and 800,000 or less, and even more preferably 540,000 or more and 700,000 or less.

[0038] Here, M L If M is less than 30,000 H If 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.

[0039] Also M L If M exceeds 100,000 HIf 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 is 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 values, thereby reducing biodegradability.

[0040] 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.

[0041] The aliphatic polyester film of the present invention preferably has a pore aspect ratio of 1.2 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).

[0042] The 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 2 or greater exhibit a less uniform structure and a dispersed structure with adequate continuity with the aliphatic polyester components other than polyhydroxyalkanoic acid. From the perspective of achieving both biodegradability and film-forming properties, the pore aspect ratio is preferably 2.0 or greater, and even more preferably 2.5 or greater. While there is no particular upper limit for the pore aspect ratio, a pore aspect ratio of 60 or less is preferred. The "method conforming to the aerobic disintegration test" described in ISO 20200 (2023) refers to the method described in the Examples. The pore aspect is determined using the method described in the Examples.

[0043] Furthermore, the aliphatic polyester film of the present invention preferably has a quantitative disintegration rate of 70% or more when subjected to home composting at a test temperature of 28°C for 180 days according to the aerobic disintegration test method described in ISO 20200 (2023).

[0044] The quantitative disintegration degree indicates the amount of large, insufficiently disintegrated film fragments remaining in the fertilizer obtained by composting the aliphatic polyester film of the present invention. A fertilizer obtained by composting an aliphatic polyester film having a disintegrated area ratio of 70% or more after 180 days of home composting indicates that the fertilizer is suitable as a fertilizer with excellent action efficiency due to sufficient circulation of moisture and air in the compost. The quantitative disintegration degree is determined by the method described in the Examples.

[0045] From the viewpoint of biodegradability, the quantitative disintegration degree is more preferably 75% or more, and even more preferably 80% or more.

[0046] 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 both 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, thereby enabling sufficiently improved processability into packaging materials and agricultural, forestry and fishery materials.

[0047] From the above viewpoints, S1 and S2 are each more preferably 0.1% or more and 12% or less, and even more preferably 0.3% or more and 8% or less. While there are no particular limitations on the lower limits of S1 and S2, from the viewpoint of preventing wrinkling and loosening due to thermal expansion during high-temperature, 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.

[0048] The aliphatic polyester film of the present invention preferably has a moisture content of 700 ppm to 9000 ppm after conditioning at 28°C and 90% RH for 48 hours, more preferably 1000 ppm to 6000 ppm, and even more preferably 2000 ppm to 3000 ppm. 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, which may reduce processability.

[0049] The aliphatic polyester film of the present invention has an AR determined by the following method. L and AR H Difference (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. [AR L and AR H How to measure the difference -Cryosectioning of film cross-section samples using a rotary microtome -Immerse the cross-section sample in pure water for 12 hours. Obtain a height distribution histogram of the cross section after immersion by AFM measurement The ratio of the number of recesses whose height is smaller than the maximum peak value of the histogram is calculated as AR. L (%) The ratio of peaks with heights greater than the maximum peak value of the histogram is calculated as AR H (%) 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 ratio is less than 0.2%, this means that the amount of 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 too fine for the size of the microorganisms. In this case, the effect of improving the uniformity of disintegration during biodegradation by microorganisms may be reduced.

[0050] Also (AR L -AR H If the ratio (%) exceeds 10%, it means that the film is swollen due to an excessive amount of water-soluble resin, or that the water-soluble resin is dispersed in a coarse structure in the aliphatic polyester film. In this case, it becomes difficult to control the orientation by stretching, and there is a possibility that processability and film-forming ability will be reduced.

[0051] 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.

[0052] The thickness of the aliphatic polyester film of the present invention can be set depending on the application, but for example, for general packaging, release agents, agricultural, forestry, and fishery applications in which it is used in sheet form, 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, for 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.

[0053] The aliphatic polyester film of the present invention can be used for a wide variety of purposes, including packaging applications, release applications, and processing films for the production of packaging materials, packaging materials, sanitary products, agricultural, forestry and fishery products, construction supplies, medical supplies, and various other products. In particular, the film can be suitably used as a packaging material suitable for home composting, or as a film to be processed into agricultural, forestry and fishery materials that can be decomposed in soil at room temperature.

[0054] <Aliphatic polyester film with functional layer> The aliphatic polyester film of the present invention preferably has 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 having a functional layer may be simply referred to as a "laminate." Examples of functional layers that can be laminated on the aliphatic polyester film include a gas barrier layer, an adhesive layer, a heat-sealing 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. The lamination method for the functional layer may be selected depending on the functional layer. For example, deposition, sputtering, coating, various printing methods such as gravure printing and offset printing, thermal adhesion, lamination via an adhesive layer, etc. may be used. From the viewpoint of not impairing the effects of the present invention, it is preferable that the functional layer be biodegradable or have low toxicity. For example, when used for packaging applications or agriculture, forestry, and fisheries, a gas barrier coating layer or a vapor deposition layer is preferably provided from the viewpoint of imparting gas barrier properties, and a vapor deposition layer is more preferable from the viewpoint of exhibiting high gas barrier performance. In addition, from the viewpoint of providing lamination processability, it is preferable to provide a heat-sealable resin layer or an adhesive coating layer, and 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 fishery materials such as fertilizers, feeds, seeds and seedlings, and medicines, a heat-sealable resin layer (hereinafter sometimes referred to as a "heat-sealing layer") that provides thermocompression bonding is preferred as a functional layer that provides adhesiveness.

[0055] 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 "Layer D"). 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, the total of which exceeds 50% by mass, where the total 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 Layer D, 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. Furthermore, from the viewpoint of the visibility of the contents, it is more preferable to use an inorganic compound, particularly aluminum oxide, silicon oxide, or a mixture containing these. 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 obtaining visibility of the contents when used as a packaging material. From the above viewpoints, it 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.

[0056] Furthermore, in the laminate of the present invention, a resin layer having a thickness of 1 μm or less may be provided between the D layer and the surface of the aliphatic polyester film by coating or the like. The provision of such a resin layer may have the effect of improving the adhesion between the D 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 with the D layer on the surface of the aliphatic polyester film is more preferred.

[0057] The method for forming the D layer on the aliphatic polyester film of the present invention to form a laminate includes vapor deposition, coating, lamination, etc., but vapor deposition is particularly preferred because it is independent of humidity and can exhibit excellent gas barrier properties even in a thin film. Vacuum deposition, physical vapor deposition such as EB vapor deposition, sputtering, and ion plating, and various chemical vapor deposition methods such as plasma CVD can be used as the vapor deposition method, but vacuum deposition is particularly preferred from the viewpoint of productivity.

[0058] In the laminate of the present invention, an overcoat layer may be provided on the surface of Layer D facing the aliphatic polyester film, 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 Layer D.

[0059] When a heat-sealable layer is laminated as a functional layer on the aliphatic polyester film of the present invention, it is preferable that the heat-sealable layer be laminated 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 that the heat-sealable layer 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" means that the main component of layer E is a resin component that 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 include, for example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-propylene random copolymer, ethylene-propylene block copolymer, ethylene-methacrylic acid copolymer, etc., or mixtures thereof, which provide high heat seal strength. When multiple films are laminated, 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, which provide reduced thickness of the final product. Resin components that can be used in Layer E include, for example, resin components containing the polyhydroxyalkanoic acid copolymer components exemplified above, biodegradable resins such as polylactic acid, polyglycolic acid, and polybutylene succinate, which have a softening point or melting point 20°C or more lower than that of the aliphatic polyester film of the present invention, or mixtures thereof, which provide increased biodegradability of the entire laminate.

[0060] 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 achieving high heat seal strength, and is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less, from the viewpoint of preventing a decrease in the biodegradability of the laminate and of reducing the thickness of the final product when multiple films are laminated.

[0061] 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 the functional layer (Layer D or Layer E) and the surface of the aliphatic polyester film. Providing such a resin layer may provide effects 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 with a functional layer on the surface of the aliphatic polyester film is more preferred.

[0062] 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 preferred for Layer D because it is independent of humidity and can exhibit excellent gas barrier properties even in a thin film. Vapor deposition methods include physical vapor deposition (e.g., vacuum vapor deposition, EB vapor deposition, sputtering, and ion plating), and various chemical vapor deposition methods (e.g., plasma CVD). From the viewpoint of productivity, vacuum vapor 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.

[0063] <Packaging materials, packaging> The packaging material and package of the present invention are described below. The packaging material of the present invention is characterized by using at least one of the aliphatic polyester film of the present invention and the laminate of the present invention. The packaging material of the present invention has good gas barrier properties and 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, making it suitable for use in packaging of items that are susceptible to deterioration by water vapor or oxygen. Furthermore, the resin layer provided as a heat seal layer is uniformly fused, providing good sealing quality, making it suitable for use in packaging where multiple sheets are stacked and sealed, such as snack packaging.

[0064] The package of the present invention is characterized in that the contents are packaged in 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 obtained by covering the contents with the packaging material of the present invention, and the form thereof is not particularly limited. For example, a package obtained by processing the packaging material of the present invention into a bag by heat sealing and placing the contents inside, or a package obtained by filling or placing the contents in a tray-shaped container and then sealing it with the packaging material of the present invention, etc., can be mentioned.

[0065] <Agriculture, forestry and fisheries materials> The agricultural, forestry, and fishery material of the present invention will be described below. The agricultural, forestry, and fishery material of the present invention is characterized by using at least one of the aliphatic polyester film of the present invention and the laminate of the present invention. The agricultural, forestry, and fishery material of the present invention is characterized by being biodegradable, and is suitable for use as a material that biodegrades after use, such as soil mulch film, vegetation film, fumigation film, water retention film, fertilizer coating material, feed coating material, seed and seedling coating material, pesticide coating material, aquaculture support film, marine organism adhesion prevention film, and environmental conservation material.

[0066] <Covering film for agricultural, forestry and fishery materials> The aliphatic polyester film of the present invention can be used to cover agricultural, forestry, and fishery materials containing one or more selected from fertilizers, feed, seeds, and chemicals, protecting the covered agricultural, forestry, and fishery materials and preventing quality deterioration due to degradation and environmental pollution due to leakage, while biodegrading in soil or the ocean, allowing the fertilizer, feed, or chemical to diffuse and disperse at an appropriate time, protecting the seeds and seedlings from settling and settling in bed, and then biodegrading to prevent interference with their growth. The agricultural, forestry, and fishery materials referred to here refer to materials and components contained in agricultural, forestry, and fishery materials, and are not particularly limited as long as they do not impair the effects of the present invention, but a wide variety of known materials can be used.

[0067] As described above, the aliphatic polyester film of the present invention, which has excellent biodegradability, high-temperature and high-speed processability, and heat-sealing properties, can be used for this purpose to prevent uneven diffusion of the agricultural, forestry, and fishery materials contained therein due to uneven coating thickness or heat-compression bonding. The thickness of the aliphatic polyester film of the present invention also makes it possible to control the diffusion and dispersion rate in soil and ocean. In addition, two or more agricultural, forestry, and fishery materials, such as fertilizers, feeds, seeds, and chemicals, can be coated together. For example, coating seeds and seedlings with the desired fertilizers or chemicals together is preferable because it can enhance crop growth simultaneously with germination.

[0068] From the above viewpoint, the thickness of the aliphatic polyester film is preferably selected within the above-mentioned preferred range according to the diffusion and scattering speed in the soil or ocean. If the thickness of the aliphatic polyester film is too thin, the strength may be insufficient, which may reduce the protection of the contents or cause tearing during processing. Furthermore, if the thickness of the aliphatic polyester film is too thick, the flexibility may be insufficient, which may make it difficult to process into the desired shape described below. For example, by selecting a thin film for fast-acting fertilizers that will diffuse and scatter quickly after biodegradation and a thick film for slow-acting fertilizers that will diffuse and scatter slowly after biodegradation, and spreading these coated fertilizers together, the work of farmers can be reduced.

[0069] 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 slow-release fertilizer with the aliphatic polyester film of the present invention and then coating the surrounding area with a fast-release fertilizer and the aliphatic polyester film of the present invention, it is possible to produce a fertilizer in which the slow-release fertilizer and the fast-release fertilizer are sequentially coated with the aliphatic polyester film of the present invention. Furthermore, by coating seeds and seedlings with fertilizer, feed, and chemicals in that order in a similar manner, it is expected that the fertilizer, feed, and chemicals will be applied to the grown agricultural and marine products at the appropriate time.

[0070] As described above, agricultural, forestry, and fishery materials coated with the aliphatic polyester film of the present invention can enhance the effectiveness of agricultural, forestry, and fishery materials selected from fertilizers, feeds, seeds and seedlings, and chemicals, while preventing environmental pollution due to unintended leakage. By diffusing and scattering in the soil or ocean at the appropriate time, the efficacy can be improved and the workload of workers can be reduced, making the film particularly suitable for use in the agriculture, forestry, and fishery fields.

[0071] The form of the fertilizer, feed, seeds and medicines 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, block, pellet, granule or capsule forms that are compatible with spreaders are preferred, while for coated seeds and medicines, rope or sheet forms that are expected to reduce work are preferred.

[0072] <Manufacturing method> A preferred embodiment of the method for producing an aliphatic polyester film of the present invention will be described below.

[0073] The method for producing the aliphatic polyester film of the present invention includes the following steps in this order: a melt-extrusion step in which raw material pellets are fed into an extruder; a casting step in which the melted pellets are extruded into a sheet form from a die and cooled and solidified on a support to obtain an unstretched aliphatic polyester film; a stretching step in which the unstretched film 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 a relaxation treatment. The layer structure of the aliphatic polyester film of the present invention is not particularly limited. For example, the film may be a single layer containing only the polyhydroxyalkanoic acid-containing layer (hereinafter sometimes referred to as "layer A") exemplified above, or may have a two-type two-layer structure (layer A / layer B) including a layer of a different composition from layer A (hereinafter sometimes referred to as "layer B"), or a two-type three-layer structure (layer A / layer B / layer A) including a layer of a different composition from layer A or layer B (hereinafter sometimes referred to as "layer C"), as long as it does not impair the effects of the present invention. A three-type three-layer structure (layer A / layer B / layer C) including a layer of a different composition from layer A or layer B (hereinafter sometimes referred to as "layer C") can also be used, so long as the polyhydroxyalkanoic acid content and the aliphatic polyester content relative to the total mass of the film are within preferred ranges. Hereinafter, a method for producing the aliphatic polyester film will be described in more detail using an aliphatic polyester film of a single layer structure consisting of layer A as an example, but the aliphatic polyester film and its production method of the present invention should not be construed as being necessarily limited thereto.

[0074] First, raw material pellets of polyhydroxyalkanoic acid and aliphatic polyester other than polyhydroxyalkanoic acid are prepared. Since polyhydroxyalkanoic acid has a melting point close to the temperature at which thermal decomposition begins, a decrease in viscosity due to thermal decomposition is unavoidable during the melt extrusion process. Therefore, it is important to adjust the two melt states within the optimum range when the raw materials are melted and kneaded in the extruder.

[0075] Specifically, if 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 200 Pa·s or more and 1300 Pa·s or less. If the viscosity difference between M2 and M1, |M2-M1|, is less than 200 Pa·s, the dispersion structure of the two types of aliphatic polyesters may become excessively fine, or the structure may become homogenized due to transesterification or compatibilization. On the other hand, if |M2-M1| exceeds 1300 Pa·s, the dispersion structure of the two types of aliphatic polyesters may become excessively large. From the above perspective, |M2-M1| is more preferably 400 Pa·s or more and 950 Pa·s or less, and even more preferably 500 Pa·s or more and 750 Pa·s or less. Preferred methods for adjusting the viscosity difference of the raw materials within the above range include selecting raw materials with different molecular weights, solid-state polymerization, adding a viscosity modifier such as a chain extender or a plasticizer in advance, and feeding the resin into an extruder and applying a thermal history to cause moderate thermal decomposition.

[0076] 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.

[0077] Next, in the melt extrusion step, 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 a 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 170°C or higher and 195°C or lower. If the melt-kneading temperature is lower than 170°C, the dispersion structure of the two types of aliphatic polyesters may become too fine, or the structure may become uniform due to transesterification or compatibilization. On the other hand, if the melt-kneading temperature exceeds 195°C, the viscosity of the polyhydroxyalkanoic acid may be reduced 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 175°C or higher and 190°C or lower, and even more preferably 180°C or higher and 187°C or lower.

[0078] The molten resin discharged from the extruder is then passed through a pipe equipped with a filtration filter to remove foreign matter, and then extruded through a slit-shaped die. 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 3 minutes or more and 118 minutes or less. If the melt residence time is less than 3 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, resulting in the dispersion structure of the two types of aliphatic polyesters becoming excessively large. From the above viewpoints, the melt residence time is more preferably 5 minutes or more and 13 minutes or less, and even more preferably 7 minutes or more and 10 minutes or less.

[0079] The molten resin extruded from the slit die is then 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 the following: electrostatic application, adhesion using the surface tension of water, air knife, press roll, underwater casting, air chamber, etc., or a combination of several methods may be used.

[0080] 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. When the dispersion structure of two types of aliphatic polyesters is discharged from the slit-shaped spinneret, the dispersion structure elongates while melting in the take-up direction, allowing the structure to be 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.

[0081] Next, the unstretched film is stretched in two perpendicular directions. The stretching method is preferably sequential biaxial stretching, in which stretching in the longitudinal direction and the width direction is performed separately, simultaneous biaxial stretching, in which stretching is performed simultaneously, or a step of additional stretching after stretching, and these may be performed continuously or individually in a batch system. A specific description will be given below using sequential biaxial stretching as an example.

[0082] First, a uniaxially oriented film is obtained in the longitudinal stretching process. In this process, the unstretched film is first guided between a group of heated rolls, preheated, and then stretched in the machine direction at a ratio of 1.5 to 10 times, using the speed difference between the rolls, to obtain a uniaxially stretched (longitudinal stretched) film.

[0083] Next, the film is guided into a tenter while the edges of the film that has been uniaxially stretched in the longitudinal direction are held by clips, and is stretched in the width direction (transverse stretching) by 1.5 to 10 times while the edges of the film are held by clips.

[0084] The heat yield can be controlled by subsequent heat treatment and relaxation treatment. Specifically, it is preferable to heat the sequentially biaxially stretched film that has been stretched in the longitudinal and width directions to 100°C or higher and below the melting point of the polyhydroxyalkanoic acid while narrowing the width of the tenter rails to relax the film by 1% or more and 30% or less in the width direction.

[0085] The heat treatment and relaxation treatment may be carried out continuously or separately in a batch system. The relaxation treatment may be carried out simultaneously or continuously in both the longitudinal and transverse directions.

[0086] The aliphatic polyester film of the present invention can be obtained by the stretching method exemplified above. Here, the area stretching ratio, which is the sum of the longitudinal and transverse stretching ratios and the relaxation treatment, is preferably 3 to 20 times. When the aliphatic polyester film of the present invention has a dispersed structure composed of polyhydroxyalkanoic acid and aliphatic polyester other than polyhydroxyalkanoic acid, the dispersed structure can be elongated by stretching, thereby further reducing the structure. From the above viewpoint, the area stretching ratio is more preferably 4 to 16 times, and even more preferably 6 to 10 times.

[0087] 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.

[0088] The aliphatic polyester film obtained by this production method allows the dispersion structure of polyhydroxyalkanoic acid and aliphatic polyester other than polyhydroxyalkanoic acid to be precisely controlled within an appropriate range, and while having excellent biodegradability, it can also be made strong by stretching, making it easy to process into packaging materials and agricultural, forestry and fisheries materials.

[0089] Next, the method for producing fertilizers, feeds, seeds and seedlings, and drugs coated with the aliphatic polyester film of the present invention will be described in more detail using examples, but the present invention is not necessarily limited to these.

[0090] 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 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.

[0091] The fertilizer to be coated with the aliphatic polyester film of the present invention may be in the form of pellets, granules, powder, paste, or 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 granules, powder, paste, and liquid.

[0092] Furthermore, 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 arrange the film in a mold so that the adhesive layer is located on at least one of the surfaces where the films contact each other. Next, the fertilizer-coated film is removed from the mold, and the excess film-bonded portion is cut and removed to obtain coated fertilizer processed into pellets. Here, the cutting method preferably uses a cutter equipped with a blade. Examples of the cutting method include a batch-type sheet-by-sheet processing method using a mold equipped with a blade, a method in which the film is continuously cut in one direction using a rotary blade to form a rope 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.

[0093] Other methods for coating agricultural, forestry, and fishery materials include a method in which two rolls of the aliphatic polyester film of the present invention are prepared and the agricultural, forestry, and fishery material is inserted between them at regular intervals while laminating them; a method in which the agricultural, forestry, and fishery material is held on the film and heated to cause thermal shrinkage, thereby coating; and a method in which the film is reduced pressure to cause shrinkage and coating.

[0094] By using the production method of the present invention, it is possible to obtain fertilizers, feeds, seeds and seedlings, and medicines coated with the aliphatic polyester film of the present invention, which has excellent biodegradability and processability. [Example]

[0095] 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.

[0096] <Methods for measuring characteristic values ​​and evaluating effects> The methods for measuring the characteristic values ​​and evaluating the effects in the present invention are as follows.

[0097] (1) Composition evaluation of aliphatic polyester film An accurately weighed film sample and a suitable reference material of known purity are dissolved in a solvent such as chloroform, hexafluoroisopropanol (HFIP), or dimethyl sulfoxide (DMSO). 1 H-NMR and 13 By measuring 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.

[0098] (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.

[0099] (3) Evaluation of melt viscosity of raw materials Using a capillary rheometer (Toyo Seiki Seisakusho's "Capilograph" 1D), raw material pellets dried in a dehumidifying dryer at 50°C for 24 hours 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: 9.55mm Capillary die diameter: 1 mm Capillary die length: 10 mm Set temperature: 180℃ Preheat time: 10 minutes Test speed: 10mm / min.

[0100] (4) Identifying samples with unknown orientation For films with an unknown orientation, cut them into a rectangular sample measuring 150 mm long x 10 mm wide with any direction facing up. <1> Then, the sample <1> The direction of the long side of the sample was defined as 0°. Next, a sample of the same size was placed so that the long side direction was rotated 15° to the right from the 0° direction. <2> Similarly, the rectangular sample was rotated 15° in the long side direction, and the sample was taken in the same way. <3> ~ <12> 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 tension speed of 300 mm / min in an atmosphere of 25±5°C and 65±10% RH. The maximum load at which the sample broke was read, and the value divided by the cross-sectional area of ​​the sample before the test (film thickness x width obtained in (2)) was calculated as the breaking strength (unit: MPa). Sample <1> ~ <12> The longitudinal direction (main orientation axis direction) of the sample with the highest breaking strength was defined as the machine direction in the present invention, and the direction perpendicular to the main orientation axis direction 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.

[0101] (5) Film cross section The aliphatic polyester film was embedded in UV-curable resin and cross-sectioned using a rotary microtome (RMS model, manufactured by Nippon Miktrom Laboratories) under the following conditions in an atmosphere of temperature and humidity of 25±5°C and 65±10% RH. Knife: Diatome HISTO-Wet 6mm Knife angle: 6° Cutting thickness: Scale 2 (1 μm) Cutting speed: 1mm / sec The board part of the knife was filled with pure water, and the cutting edge was wet while the cutting was performed while checking the cutting state under a microscope.

[0102] (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) AFM calibration and measurement The sample with its cross section exposed in the embedding resin prepared in (5) was fixed vertically to a base so that the cross section was horizontal. Measurements were performed using an AFM (DimensionIcon atomic force microscope, Burker Corporation) at 25°C and 65% RH under the following conditions. The cantilever's warpage sensitivity, spring constant, and tip curvature were calibrated according to the PeakForceQNM mode manual. While the spring constant and tip curvature varied among individual cantilevers, cantilevers with a spring constant of 150 (N / m) to 250 (N / m) and a tip curvature radius of 100 (nm) or less were selected to ensure that the measurement was not affected. The measurement was performed within a specified range, centered on the center point of the film cross section in the thickness direction. Measurement mode: PeakForceQNM (force curve method) Cantilever: BRUKER Model No. RTESPA-525 Analysis software: NanoScopeAnalysis V1.40 Measurement range: 10 (μm) square Samples / Line×Lines:512×512 Aspect Ratio:1 Scan Rate: 0.900 to 1.000 Hz ScanAsyst Noise Threshold:0.5.

[0103] (6-2) Calculation of the half-width Hh of the height distribution histogram The height sensor channel data obtained in (6-1) was output using the analysis software "NanoScopeAnalysis V1.40" and image processing was performed using Planefit processing (XY, 3rd) to obtain a histogram of the height distribution. The numerical data of the histogram was then output, and the half-width of the peak fitted with a Gaussian distribution was taken as Hh (unit: nm). If the peak was divided into two or more, the result of the largest peak was used. The same operation was also performed at five different locations on the film cross section, and the average value of the images of a total of 10 locations in the longitudinal and transverse directions of the film was used.

[0104] (6-3) Calculation of the half-width Hm of the elastic modulus distribution histogram The DMT Modulus channel data obtained in (6-1) was output using the analysis software "NanoScopeAnalysis V1.40" to obtain a histogram of the elastic modulus distribution. The numerical data of the histogram was then output, and the half-width of the peak fitted with a Gaussian distribution was taken as Hm (unit: GPa). If the peak was divided into two or more, the result of the largest peak was used. The same procedure was also performed at five different locations on the film cross section, and the average value of a total of 10 images in the longitudinal and transverse directions of the film was used.

[0105] (7) Aspect ratio of pores on the cross section of home-composted film Using a method conforming to the aerobic disintegration test described in ISO 20200 (2023), 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 (cane sugar), 4 parts by weight of corn oil, and 1 part by weight of urea were mixed, and 1 L of wet synthetic compost adjusted to a moisture content of 50% was prepared. This was then placed in a 10 L polypropylene container. Next, the sample with its cross section exposed was buried in the embedding resin prepared in (5) so that it was touching the compost, and it was stored in an oven controlled at 28°C for 14 days, with stirring and moisture content adjustment at specified intervals.

[0106] The buried film sample was then recovered, the compost adhering to the surface was washed away with pure water, and the sample was allowed to dry. The cut cross section 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 value: 30mA Processing time: 20 seconds Number of times processed: 2 Then, using a scanning electron microscope (SEM) (JEOL Ltd. field emission scanning electron microscope "JSM-6700F"), the cut cross section of the sample was observed under the following conditions, with the area specified so that the center point in the film thickness direction was the center. Accelerating voltage: 3 kV Detection mode: LEI The observation magnification was adjusted so that 20 to 100 pores observed using the above method were included in the observation field, 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 procedure was repeated at five different locations on the film cross section, and the average value of 10 images taken by cutting the film cross section in the longitudinal and transverse directions was used.

[0107] (8) 120℃ heat shrinkage rates S1 and S2 The film is cut into a rectangle of 150 mm length x 10 mm width in the longitudinal and transverse directions, and a mark is made in the center 100 mm with an oil-based marker. The length is measured using a universal projector to determine the initial length I0. The measured sample is then placed in a gear-type hot air oven adjusted to 120°C, and a 2.1 g load is attached to the bottom of the hanging film. The gear is rotated while the oven is heated for 15 minutes. The film is then removed and cooled to room temperature, and the length between the marks is measured using a universal projector to determine the thermal contraction length I0. H Measured I0 and I HThe 120°C heat shrinkage (unit: %) was calculated from the following formula. Similar measurements were performed five times in the longitudinal and transverse directions of each sample, and the average value in the longitudinal direction was taken as S1 (%), and the average value in the transverse direction was taken as S2 (%).

[0108] 120℃ heat shrinkage rate (%) = (I0 - I H ) / I0×100.

[0109] (9) Orientation parameter P calculated from the intensity ratio of the Raman spectrum MT and P Z Rating (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 longitudinally using a microtome as described in (5), and (C) a cross-section cut widthwise using a microtome. Next, under the following conditions, sample (A) was irradiated with a laser with a polarization axis in the longitudinal and width directions on an arbitrary surface, while samples (B) and (C) were fixed to a cross-section observation stage, and lasers with polarization axes in the surface and thickness directions were irradiated on the cut cross-section, thereby measuring the Raman spectrum in two polarization axes for each sample. Equipment: Renishaw InVia Conditions: Microscopic Raman measurement mode Objective lens: 50x Beam diameter: 2 μm Light source: Semiconductor laser 532nm Laser power: 300mW Diffraction grating: Single 3000, -3000gr / mm Detector: Renishaw CCD 1024x256.

[0110] (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 stretch band (875cm -1 The peak intensity ratio (I875 / 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 on each sample, and the average value of the three measurements was used. The spectral intensity ratio (I 875 / I 1770 ):I MD The spectral intensity ratio of the width direction polarization axis of sample (A) (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 ZM The 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 (10) Moisture content evaluation Films were prepared by conditioning them for 48 hours in a thermo-hygrostat (ESPEC LHL-113) set at 28°C and 90% RH, and the moisture content (ppm) was measured using a Karl Fischer moisture meter under the following conditions: The average value of three measurements was used. Moisture meter: HIRANUMA AQUACOUNTER “AQ-7” Moisture evaporator: Hiranuma Evaporator Unit "EV-6" Counterelectrode: Aqualite CN manufactured by Hiranuma Generated liquid: HIRANAUMA Aqualight RS-A Baking conditions: 130°C for 15 minutes Moisture content measurement conditions: 130°C for 15 minutes (11) The ratio of recesses in the frozen cut cross section after immersion in pure water (AR) L and the ratio of convex parts present, AR H Rating (11-1) Film cross section extraction by freezing cutting method The aliphatic polyester film was embedded in UV-curable resin, and cross-sections were taken under the following conditions using an automatic rotary microtome (Leica RM2265) with the chamber cooled to -70°C by supplying liquid nitrogen using a freezing control device (Leica LN22). Knife: Diatome HISTO cryo dry 6.0mm Knife angle: 45° Cutting thickness: 0.25 μm Cutting speed: 0.5mm / sec (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 using the same methods as in (6-1) and (6-2), and the numerical data of the height distribution histogram on the cross section was output. Areas with heights smaller than the maximum peak value (the height corresponding to the most frequent point) of the obtained height distribution histogram were defined as recesses, and areas with heights larger than the maximum peak value were defined as protrusions. The ratio of the total area of ​​recesses to the area of ​​the entire measurement range was defined as the recess abundance ratio AR. L (%), and similarly, the ratio of the total area of ​​the convex parts is the convex part presence ratio AR H (%). If the histogram had two or more peaks, the largest peak was used. The same procedure was also performed 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.

[0111] (12) Molecular weight evaluation (12-1) Obtaining molecular weight distribution curve 5 mL of the measurement solvent was added to 10 mg of the raw material or film sample, and the mixture was stirred at room temperature until the sample dissolved. Then, gel permeation chromatography (GPC) was performed under the following conditions to obtain a molecular weight distribution curve, with the horizontal axis representing the logarithm of the molecular weight M (logM) and the vertical axis representing the weight fraction dW / dlogM per unit logM. Detector: Differential refractive index detector RI (Tosoh RI-8020, sensitivity 32) Column: TSKgel GMHHR-M (φ7.8 mm x 30 cm, Tosoh), 2 columns Filter: (Millex Syringe Filter, Hydrophilic PTFE, Non-sterile, Model No. SLCR033NS) Solvent: Chloroform Flow rate: 1.0mL / min Column temperature: 40℃ Injection volume: 0.200mL Standard sample: Tosoh monodisperse polystyrene Data processing: GPC data processing system manufactured by Toray Research Center (12-2)M L and M H Measurement of In the molecular weight distribution curve obtained in (12-1), when the maximum value of the vertical axis is Wm, the molecular weight at which the vertical axis becomes Wm / 2 is read, and the molecular weight at the intersection point on the low molecular weight side is M L , the molecular weight at the intersection point on the high molecular weight side is M H The average value of three similar measurements was used.

[0112] (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.

[0113] (13) Biodegradable Quantitative disintegration was determined using a method conforming to the aerobic disintegration test described in ISO 20200 (2023). Specifically, 1 kg of wet synthetic compost was prepared using the same method as in (8). Next, film samples were cut into 15 mm x 15 mm squares with a total weight of 10 g. These were then vacuum dried at 40°C to a constant weight and immersed in distilled water for 30 seconds. The wet synthetic compost was then placed in a 10 L polypropylene container with two 5 mm diameter holes on each side for gas exchange. The film samples were then buried in the container and stored in an oven controlled at 28°C for 180 days, with stirring and moisture content adjustments at specified intervals. After 180 days, the mixture in the container was passed through a 2 mm stainless steel sieve, and the weight of the film sample that did not pass through the sieve was measured by vacuum drying at 40°C. The weight of the film sample measured before treatment was taken as m2, and the weight of the film sample measured before treatment was taken as m1. The proportion of the sample that passed through the sieve ((m1-m2) / mL x 100) was taken as the quantitative disintegration degree. The biodegradability in the present invention was judged according to the following criteria. A: Quantitative decay rate is 80% or more B: Quantitative disintegration rate is 75% or more but less than 80% C: Quantitative disintegration rate is 70% or more but less than 75% D: Quantitative disintegration rate is 50% or more but less than 70% E: Quantitative decay rate is less than 50% The biodegradability of the film is preferably D or higher.

[0114] (14) Uniformity of Collapse The quantitative disintegration degree was determined from the passing rate through a 4 mm stainless steel sieve and a 1 mm stainless steel sieve in the same manner as in (13), and the disintegration uniformity in the present invention was evaluated according to the following criteria.

[0115] Variation in disintegration state (%) = (quantitative disintegration degree of 1 mm sieve) - (quantitative disintegration degree of 4 mm sieve) A: The degree of variation in the collapse state is less than 20% B: Variation in collapse state is 20% or more but less than 30% C: Variability of collapse state is 30% or more The film disintegration uniformity is preferably C or higher.

[0116] (15) Processability (15-1) Puncture test The puncture strength (Force) of the film was measured under the following conditions in accordance with JIS Z1707 (2019). The measurement was performed five times, and the average value was used.

[0117] Equipment: KATOTECH HANDY-TYPE COMPRESSION TESTER KES-G5 SENS:10 SPEED:0.20cm / sec STROKE:20mm / 10V Needle diameter: 1.0 mm Hole diameter: 10.0mmφ.

[0118] (15-2) Film processability The puncture strength was calculated based on the thickness of the film used in (15-1) and the puncture strength measured in the test, converted into a 20 μm thickness (gf / 20 μm), and the processability in the present invention was evaluated according to the following criteria. A:Piercing strength is 500 gf / 20μm or more B: Puncture strength is 400 gf / 20μm or more, less than 500 gf / 20μm C: Puncture strength is 300 gf / 20μm or more, less than 400 gf / 20μm D:Piercing strength is 250 gf / 20μm or more, less than 300 gf / 20μm E: Puncture strength less than 250 gf / 20 μm The processability of the film is preferably D or higher.

[0119] (16) Film forming properties 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 breakage due to stretching when the film was produced by the method described above. A: No tear occurred within the 50m length B: Only one tear occurred within a 50m length C: Breaks occurred 2 or more times but less than 5 times within a 50m length D: Breaks occurred 5 to 10 times within a 50m length E: More than 10 tears occurred within a 50m length The film formability of the film is preferably D or higher.

[0120] [Resin raw materials, etc.] The following resins were used in producing the aliphatic polyester films in the Examples and Comparative Examples. PHA-1: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) BP350-05 (melting point: 130°C, glass transition temperature: -3°C) manufactured by Blue Crystal Microorganisms Co., Ltd. The melt viscosity was 630 Pa·s. PHA-2: PHA-1 was melt-extruded (residence time: 5 minutes) in a twin-screw extruder maintained at 170°C to produce raw material pellets. The melt viscosity was 295 Pa·s. PHA-3: PHA-1 was melt-extruded (residence time: 5 minutes) in a twin-screw extruder maintained at 185°C to produce raw material pellets. 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. 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. The weight-average molecular weight was 4010. PEG-2: Polyethylene glycol PEG-1000 manufactured by Sanyo Chemical Industries, Ltd. The weight-average molecular weight was 1,000. PEG-3: Polyethylene glycol PEG-6000S manufactured by Sanyo Chemical Industries, Ltd. The weight-average molecular weight was 8000. PVP: Polyvinylpyrrolidone K-15 manufactured by Nippon Shokubai Co., Ltd. The weight-average molecular weight was 9,900.

[0121] Example 1 PHA-2 and PLA-1, which were used as resin raw materials for aliphatic polyester film and dried for 24 hours at 50°C in a dehumidifying dryer, were blended in the ratios shown in Table 1 and fed to a single-screw melt extruder. The temperature in the compression section of the screw was set to 185°C, and the mixture was discharged from the extruder. While maintaining the temperature at 185°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 into sheet form. At this time, it took 9 minutes from the time the molten resin was discharged from the extruder until it was extruded from the die.

[0122] 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 width of the T-die was 1.0 mm, while the central thickness of the unstretched film was 140 µm, and the draft ratio was 7.2.

[0123] The unstretched film was then continuously fed into a longitudinal stretching machine consisting of multiple roll groups. After preheating with a group of rolls preheated to 70°C, it was stretched 2.5 times in the longitudinal direction by applying a peripheral speed difference with a roll maintained at 30°C. The resulting film was then continuously fed into a tenter-type width stretching machine, preheated to 70°C while holding both widthwise ends with clips, stretched 3.0 times in the widthwise direction at 75°C, and then heat-treated at 130°C while applying 10% relaxation in the widthwise direction. The film was then cooled to 50°C while still tensely holding both widthwise ends with clips, and fed outside 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 on a winding machine. The resulting aliphatic polyester film was found to have excellent biodegradability, processability, and film-forming properties.

[0124] (Examples 2 to 11, Comparative Example 1) Except for changing the production conditions as shown in the table, an aliphatic polyester film was obtained in the same manner as in Example 1. The evaluation results are shown in the table. It was found that Comparative Example 1 was poor in biodegradability.

[0125] (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. It was found that Comparative Example 2 was inferior in processability and film-forming ability.

[0126] (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. Comparative Example 3 was found to be poor in biodegradability.

[0127] (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) to achieve the resin compositions listed in the table. The evaluation results are shown in the table. All films were found to have superior disintegration uniformity compared to Example 1.

[0128] 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.

[0129] (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.

[0130] [Table 1]

[0131] [Table 2]

[0132] [Table 3]

[0133] [Table 4]

[0134] [Table 5] [Industrial Applicability]

[0135] 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, wherein the half-width Hh of a height distribution histogram obtained by AFM measurement of a film cross section obtained by a rotary microtome is 20 nm or more and 300 nm or less.

2. The aliphatic polyester film according to claim 1 , comprising 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 comprising at least a polyhydroxyalkanoic acid, wherein the half-width Hm of an elastic modulus distribution histogram obtained by AFM measurement using a force curve method on a film cross section obtained using a rotary microtome is 0.20 GPa or more and 4.00 GPa or less.

4. 4. The aliphatic polyester film according to claim 1, further comprising an aliphatic polyester other than polyhydroxyalkanoic acid, wherein the aliphatic polyester is polylactic acid.

5. The intensity ratio of the Raman spectrum (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 in which the horizontal axis is the logarithm of the molecular weight M (logM) and the vertical axis is 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 at which the vertical axis is Wm / 2 is Ｌ The aliphatic polyester film according to claim 1 , wherein the molecular weight is 20,000 or more and 90,000 or less.

7. In a molecular weight distribution curve in which the horizontal axis is the logarithm of the molecular weight M (logM) and the vertical axis is 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 at which the vertical axis is Wm / 2 is Ｈ The aliphatic polyester film according to claim 1 , wherein the molecular weight is 200,000 or more and 900,000 or less.

8. 4. The aliphatic polyester film according to claim 1, wherein the aspect ratio of pores 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) is 1.2 or more.

9. 4. The aliphatic polyester film according to claim 1, wherein, when a heat shrinkage rate at 120°C in the longitudinal direction is S1 (%) and a heat shrinkage rate at 120°C in the width direction is S2 (%), both S1 and S2 are 0% or more and 20% or less.

10. The aliphatic polyester film according to claim 1 , comprising 70% by mass or more of the aliphatic polyester relative to 100% by mass of the total mass of the film.

11. 4. The aliphatic polyester film according to claim 1, wherein the aliphatic polyester film has a quantitative disintegration rate of 70% or more when subjected to home composting at a test temperature of 28°C for 180 days according to the aerobic disintegration test method described in ISO 20200 (2023).

12. 4. The aliphatic polyester film according to claim 1, 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 a force curve method is 0.30 GPa or more and 2.50 GPa or less.

13. 4. The aliphatic polyester film according to claim 1, 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 determined 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 saturation ratio (Sr) is 0.2% or more and 10% or less. [A.R. Ｌ and A.R. Ｈ Method for measuring the difference - Obtain a cross-sectional film sample by freezing and cutting with a rotary microtome - Immerse the cross-section sample in pure water for 12 hours - Obtain a height distribution histogram of the cross section after immersion by AFM measurement The ratio of the number of recesses whose height is smaller than the maximum peak value of the histogram is calculated as AR. Ｌ (%) The ratio of convex parts with heights greater than the maximum peak value of the histogram is calculated as AR. Ｈ (%)

15. The aliphatic polyester film according to claim 1 , comprising a water-soluble resin in an amount of 0.4% by mass to 15% by mass, based on 100% by mass of the total mass of the film.

16. 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. 4. The aliphatic polyester film according to claim 1, further comprising a functional layer on at least one surface thereof.

19. A packaging material comprising the aliphatic polyester film according to any one of claims 1 to 3.

20. 4. A material for agriculture, forestry and fisheries, comprising the aliphatic polyester film according to claim 1.

21. 4. The aliphatic polyester film according to claim 1, which is used to cover agricultural, forestry, and fishery materials, wherein the agricultural, forestry, and fishery materials include at least one selected from the group consisting of fertilizers, feeds, seeds and seedlings, and chemicals.

22. 4. An agricultural, forestry and fishery material coated with the aliphatic polyester film according to claim 1.

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