Aliphatic polyester films, packaging materials, agricultural, forestry, and fisheries materials, and agricultural, forestry, and fisheries raw materials.

Abstract

To provide a film that offers excellent biodegradability while simultaneously providing long-term storage and processability. [Solution] An aliphatic polyester film containing 40% by mass or more of polyhydroxyalkanoic acid per 100% by mass of the total film mass, having a moisture content of 700 ppm to 9000 ppm after 48 hours of humidity control at 28°C and 90% RH, and having a weight-average molecular weight of 150,000 or more.

Description

Technical Field

[0001] The present invention relates to an aliphatic polyester film, particularly an aliphatic polyester film used for packaging applications and agricultural, forestry, and fishery applications.

Background Art

[0002] In recent years, various studies have been conducted on the separation and recycling of food waste and composting. Polyethylene terephthalate, which is a common packaging film, has a problem of poor biodegradability, so biodegradable plastic products and packaging materials that can be composted together with food waste are desired. Among biodegradable plastics, aliphatic polyester resins have attracted attention because of their high biodegradability, and application studies have been conducted for use in packaging materials and the like. However, polylactic acid, which is generally considered to be easy to form into a film and excellent in strength, has a slow progress of biodegradation in soil under low-temperature environments. On the other hand, polyhydroxyalkanoic acid, which has excellent biodegradability, is a resin that is difficult to stretch, and there is a problem that post-processing of the film becomes difficult due to its inferior mechanical strength and thermal dimensional stability (hereinafter referred to as processability).

[0003] As an improvement measure, Patent Document 1 proposes a method of obtaining a biodegradable card that suppresses material deterioration during storage and has excellent collapsibility at the time of disposal by copolymerizing a high water-absorbing resin with polylactic acid. Patent Document 2 proposes a method of obtaining a film excellent in biodegradability and strength by mixing polyhydroxyalkanoic acid and polylactic acid at a specific ratio.

Prior Art Documents

Patent Documents

[0004] ​​​​​​​​​​​​​​​

[0005] However, the technology described in Patent Document 1 has the problem that the film swells due to excessive water absorption, causing wrinkles during long-term storage (hereinafter referred to as "long-term storage capability"), and that its very high polylactic acid content makes biodegradation difficult under home composting conditions. The technology described in Patent Document 2 has the problem that the disintegration is uneven and the biodegradability is insufficient. Therefore, the present invention aims to provide an aliphatic polyester film that exhibits minimal unevenness in disintegration during biodegradation, does not wrinkle during long-term storage, and has excellent thermal dimensional stability. [Means for solving the problem]

[0006] The inventors of the present invention have conducted extensive research to solve the above problems and have arrived at the present invention as follows. That is, a preferred embodiment of the present invention is as follows. (1) An aliphatic polyester film containing 40% by mass or more of polyhydroxyalkanoic acid per 100% by mass of the total film mass, having a moisture content of 700 ppm to 9000 ppm after 48 hours of humidity control at 28°C and 90% RH, and having a weight-average molecular weight of 150,000 or more. (2) An aliphatic polyester film containing 40% by mass or more of polyhydroxyalkanoic acid and 0.4% by mass or more and 15% by mass or less of water-soluble resin, based on 100% by mass of the total film mass. (3) The aliphatic polyester film according to (1) or (2), which contains 10% to 60% by mass of polylactic acid based on 100% by mass of the total film mass. (4) An aliphatic polyester film according to any of (1) to (3), wherein the rate of change in Young's modulus after conditioning from a dry state at 28°C and 90%RH for 48 hours is -10% or more and 2% or less. (5) An aliphatic polyester film according to any of (1) to (4), wherein the expansion rate when conditioned from a dry state at 28°C and 90%RH for 48 hours is 700 ppm or less. (6) An aliphatic polyester film according to any one of (1) to (5), wherein the heat of fusion ΔHm of the crystals in the heating step in differential scanning calorimetry is 20 J / g or more and 50 J / g or less. (7) An aliphatic polyester film according to any of (1) to (6), wherein when the heat shrinkage rate at 120°C in the direction of the main orientation axis is S1 (%) and the heat shrinkage rate at 120°C in the direction perpendicular to the direction of the main orientation axis is S2 (%), both S1 and S2 are 15% or less. (8) An aliphatic polyester film according to any of (1) to (7), wherein the weight loss rate after washing is 0.4% or more and 8.0% or less. (9) An aliphatic polyester film according to any one of (1) to (8), comprising 0.4% to 15.0% by mass of a water-soluble resin based on 100% by mass of the total film mass. (10) An aliphatic polyester film according to any one of (1) to (9), comprising a water-soluble resin, wherein the water-soluble resin consists of one or more of the following: polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinylpyrrolidone, and polypropylene glycol. (11) An aliphatic polyester film according to any of (1) to (10), comprising a water-soluble resin, wherein the weight-average molecular weight of the water-soluble resin is 2000 or more and 11000 or less. (12) An aliphatic polyester film according to any one of (1) to (11), comprising an A1 layer and a B1 layer whose layer thickness t is related by formula 1, wherein at least the B1 layer is a layer containing a water-soluble resin, and satisfying formula 2 when the water-soluble resin content of the A1 layer is 1% by mass Wa and the water-soluble resin content of the B1 layer is 1% by mass Wb relative to 100% by mass of the B1 layer. t(B1) / t(A1)>1.2...Equation 1 Wb1>Wa1...Formula 2 (However, t(A1) represents the thickness of layer A1, and t(B1) represents the thickness of layer B1.) (13) An aliphatic polyester film according to any one of (1) to (12), comprising at least an A1 layer constituting the outermost layer of one of the films, an A2 layer constituting the outermost layer of the other, and a B1 layer constituting an intermediate layer, wherein at least the B1 layer is a layer containing a water-soluble resin, and when the water-soluble resin content in the A1 layer is 1% by mass per 100% by mass, the water-soluble resin content in the A2 layer is 2% by mass per 100% by mass, and the water-soluble resin content in the B1 layer is 1% by mass per 100% by mass of the B1 layer, the film satisfies formulas 3 and 4. Wb1>Wa1...Formula 3 Wb1>Wa2...Formula 4 (14) An aliphatic polyester film according to any of (1) to (13), wherein the weight-average molecular weight of the water-soluble resin contained in the B1 layer is 2000 or more and 11000 or less. (15) A laminate comprising a functional layer laminated on at least one side of an aliphatic polyester film according to claim 1 or 2. (16) A packaging body containing an aliphatic polyester film as described in any of (1) to (14). (17) Agricultural, forestry, and fisheries materials containing an aliphatic polyester film as described in any of (1) to (14). (18) An aliphatic polyester film according to any one of (1) to (14), which is used for covering agricultural, forestry, and fishery materials, wherein the agricultural, forestry, and fishery materials include one or more selected from fertilizers, feed, seeds and seedlings, and chemicals. Agricultural, forestry, and fishery material characterized by being coated with an aliphatic polyester film as described in any of (19)(1) to (14). [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an aliphatic polyester film that exhibits minimal unevenness in disintegration during biodegradation, does not wrinkle during long-term storage, and has excellent thermal dimensional stability. [Modes for carrying out the invention]

[0008] The aliphatic polyester film of the present invention will be described in detail below. When upper and lower limits are described separately for preferred ranges, the combination thereof is arbitrary. In this specification, the aliphatic polyester film may be simply referred to as "film". In the aliphatic polyester film of the present invention, "longitudinal direction" refers to the direction corresponding to the flow direction in the film manufacturing process (hereinafter sometimes referred to as "MD"), and "width direction" refers to the direction perpendicular to the flow direction in the film manufacturing process within the film surface (hereinafter sometimes referred to as "TD"). If the film sample is in the shape of a reel, roll, etc., the film winding direction can be said to be the longitudinal direction. In addition, the principal orientation axis direction in the present invention is defined by the following method. First, with an arbitrary direction facing upwards, cut out a rectangle with a length of 150 mm and a width of 10 mm to form a sample. <1> Sample <1> Define the direction of the longer side as 0°. Next, create a sample of the same size such that the direction of the longer side is rotated 15° to the right from the 0° direction. <2> Collect the sample. Similarly, rotate the rectangular sample by 15° along its longer side, and collect the sample. <3> ~ <12> A sample is taken. Next, each rectangular sample is set on a tensile testing machine (A&D Company, Limited "Tensilon® Universal Testing Machine" RTG-1210) with an initial chuck distance of 30 mm so that the longer side is the tensile direction, and a tensile test is performed at a tensile speed of 300 mm / min in an atmosphere of temperature and humidity of 25±5℃ and 65±10%RH. At this time, the value obtained by dividing the load at which the sample broke by the cross-sectional area of ​​the sample before the test (thickness × width of the film sample) is the breaking strength (unit: MPa), and the strain at the time of breakage is calculated as the breaking elongation (unit: %). The same measurement is performed five times for each sample and the average value is adopted. In this invention, the measurement direction in which the breaking strength obtained by this method was the maximum is defined as the principal orientation axis direction, and the direction perpendicular to this is defined as the direction perpendicular to the principal orientation axis direction.

[0009] A preferred embodiment of the aliphatic polyester film of the present invention contains 40% by mass or more of polyhydroxyalkanoic acid per 100% by mass of the total film mass, has a moisture content of 700 ppm to 9000 ppm after 48 hours of humidity control at 28°C and 90% RH, and has a weight-average molecular weight of 150,000 or more. The moisture content is based on mass.

[0010] As described above, using an aliphatic polyester film results in a film with excellent biodegradability, long-term storage properties, and processability.

[0011] From the viewpoint of improving biodegradability and processability, the ratio of polyhydroxyalkanoic acid to 100% by mass of the total film mass is more preferably 55% by mass or more and 75% by mass or less, and even more preferably 60% by mass or more and 70% by mass or less. If it is less than 40% by mass, the content of polyhydroxyalkanoic acid, which has excellent biodegradability, decreases, which may impair biodegradability.

[0012] From the viewpoint of improving biodegradability and long-term storage, the moisture content after 48 hours of humidity control at 28°C and 90% RH is more preferably 1000 ppm to 6000 ppm, and even more preferably 2000 ppm to 3000 ppm. Setting the moisture content to 700 ppm or higher promotes moisture absorption by the film, and the penetration of microorganisms into the film via the absorbed moisture promotes good biodegradability. Setting the moisture content to 9000 ppm or lower suppresses the expansion and wrinkle formation of the film due to excessively high moisture content. Furthermore, by keeping the moisture content within the above range, precipitates on the film surface can be suppressed, improving printability.

[0013] Biodegradable aliphatic polyester resins such as polyhydroxyalkanoic acid are less polar than aromatic polyester resins such as polyethylene terephthalate and thus have difficulty retaining moisture. On the other hand, biodegradable aliphatic polyester resins undergo biodegradation by microorganisms that prefer a moist environment, but this state is highly dependent on the external environment and uneven disintegration is likely to occur. Therefore, by controlling the amount and method of adding a water-soluble resin and the molecular weight of the aliphatic polyester resin within a range suitable for the film manufacturing method, it is important to impart appropriate hydrophilicity to the film so that microorganisms can easily intervene while orienting and crystallizing the aliphatic polyester resin to fix the structure.

[0014] Specifically, as methods for setting the moisture content within the above range, there are methods for controlling the addition amount and molecular weight of the water-soluble resin within a preferable range, and methods for controlling the draw ratio in the manufacturing process within a preferable range.

[0015] From the viewpoint of improving processability, the weight-average molecular weight of the film is more preferably 180,000 or more, and even more preferably 200,000 or more. The upper limit is not particularly limited, but it may be 500,000 or less. If it is less than 150,000, the entanglement of molecular chains is insufficient, making it difficult to achieve orientation crystallization when the film is drawn and potentially impairing the film strength.

[0016] Here, polyhydroxyalkanoic acid is a polymer containing hydroxyalkanoic acid as a constituent component. For example, it is represented by the general formula [-CHR-CH2-CO-O-] of 3-hydroxyalkanate repeating units (where R is C n H 2n+1An alkyl group represented by , where n is an integer from 1 to 15. Examples include poly(3-hydroxyalkanoate) (hereinafter sometimes referred to as "P3HA") containing ). It is preferable that the number of carbon atoms between ester bonds in the main chain of the polyhydroxyalkanoic acid is 2 or more, and more preferably 2. The polymer may be a homopolymer of hydroxyalkanoic acid alone, or a copolymer of two or more types of hydroxyalkanoic acid. Furthermore, the polyhydroxyalkanoic acid may be a mixture of multiple polyhydroxyalkanoic acids.

[0017] Examples of P3HA include poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxyhexanoate) (P3HH), 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) (P3HBP3HD).

[0018] P3HA can be either chemically synthesized (for example, obtained by ring-opening polymerization of the corresponding lactone) or produced by microorganisms. However, from the viewpoint of ease of production using biomass raw materials such as vegetable oil, P3HA produced by microorganisms is preferred. Among the P3HAs produced by microorganisms, P3HB, P3HB3HH, P3HB3HV, P3HB3HV3HH, and P3HB4HB are preferred from the viewpoint of ease of industrial production.

[0019] Polyhydroxyalkanoates, including P3HA, can have their melting point and crystallinity adjusted by changing the composition ratio of repeating units. Although polyhydroxyalkanoates are generally known to be easily thermally decomposed, by designing a copolymer structure of two or more hydroxyalkanoates to have a low melting point, it is possible to create a sufficient temperature difference between the temperature range where melt extrusion is possible and the thermal decomposition temperature range.

[0020] A preferred embodiment of the aliphatic polyester film of the present invention contains 40% by mass or more of polyhydroxyalkanoic acid and 0.4% by mass or more and 15.0% by mass or less of water-soluble resin, based on 100% by mass of the total film mass.

[0021] By composing the material as described above, a film with excellent biodegradability, long-term storage properties, and processability is obtained.

[0022] From the viewpoint of improving biodegradability and long-term storage, the ratio of water-soluble resin to 100% by mass of the total film mass is preferably 2.0% by mass or more and 10.0% by mass or less, more preferably 4.0% by mass or more and 6.0% by mass or less. By including a specific ratio of water-soluble resin in the film, after being exposed to moisture for a long time in a high-humidity composting environment, the water-soluble resin flows out of the film, and fine cavities are formed where the water-soluble resin was present. These fine cavities thus formed act as a disintegration starting point, making it possible to improve biodegradability (especially disintegration after composting). If the ratio of water-soluble resin contained in the film to 100% by mass of the total film mass is less than 0.4% by mass, the formation of disintegration starting points after composting may be insufficient, potentially impairing biodegradability. If it exceeds 15.0% by mass, hydrolysis may proceed during melt extrusion processing, potentially reducing the molecular weight of the film, or the film may absorb too much moisture, causing it to swell and become prone to wrinkles.

[0023] Here, water-soluble resins refer to resins that dissolve in water at room temperature at a concentration of 0.005 g / ml or more. Specifically, natural polymers, semi-synthetic polymers, and synthetic polymers having hydrophilic functional groups in their molecular structure are preferred. Examples of natural polymers include alginates, hyaluronic acid salts, and corn starch. Examples of semi-synthetic polymers include cellulose compounds. Examples of synthetic polymers include resins having polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polypropylene glycol, polybutylene glycol, polyvinylpyrrolidone, polyacrylic acid, and styrene sulfonate as the main backbone. Among these, synthetic polymers are preferred from the viewpoint of suitability for melt extrusion processing, and polyvinyl alcohol and polyethylene glycol are more preferred from the viewpoint of improving long-term storage and processability.

[0024] The aliphatic polyester film of the present invention preferably contains a biodegradable resin other than polyhydroxyalkanoic acid, from the viewpoint of improving biodegradability and processability. Examples include polyglycolic acid, polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, and polycaprolactone. Here, the biodegradable resin can be either a naturally decomposing resin or an enzymatically decomposing resin. Even resins that do not decompose sufficiently by home composting on their own can have the remaining undecomposed material suppressed by combining them with polyhydroxyalkanoic acid according to the embodiment of the present invention.

[0025] In particular, from the viewpoint of enabling extrusion at temperatures close to those of polyhydroxyalkanoic acid, it is preferable that the film contains a total of 10% to 60% by mass of one or more selected from polyglycolic acid, polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, and polycaprolactone per 100% by mass of the total film mass, more preferably 20% to 45% by mass, and even more preferably 25% to 35% by mass. Furthermore, from the viewpoint of enabling extrusion at temperatures close to those of polyhydroxyalkanoic acid, it is preferable that the film contains a total of 10% to 60% by mass of one or more selected from polylactic acid and polybutylene succinate adipate per 100% by mass of the total film mass, more preferably 20% to 45% by mass, and even more preferably 25% to 35% by mass. Preferably, from the viewpoint of enabling extrusion at a temperature close to that of polyhydroxyalkanoic acid, the total amount of polylactic acid is preferably 10% to 60% by mass per 100% by mass of the total film mass, more preferably 20% to 45% by mass, and even more preferably 25% to 35% by mass. When the amount is 10% by mass or more, it is possible to suppress the deterioration of processability due to a decrease in film strength and dimensional stability, and when the amount is 60% by mass or less, it is possible to suppress the occurrence of uneven collapse and a decrease in collapse uniformity.

[0026] From the viewpoint of improving biodegradability and processability, the aliphatic polyester film of the present invention preferably has a Young's modulus change rate of -10% to 2% after conditioning from a dry state at 28°C and 90% RH for 48 hours, more preferably -7% to 0%, and even more preferably -4% to -2%. Setting it to -10% or more suppresses the deterioration of processability due to a decrease in film strength and dimensional stability, while setting it to 2% or more suppresses the deterioration of biodegradability because the film strength is improved and it takes time for microorganisms to break down the molecular chains. Methods for setting the Young's modulus change rate within the above range include controlling the amount of biodegradable resin added other than polyhydroxyalkanoic acid within a preferred range, and controlling the stretching ratio in the manufacturing process within a preferred range.

[0027] From the viewpoint of improving long-term storage properties, the aliphatic polyester film of the present invention preferably has an expansion rate of 700 ppm or less, more preferably 500 ppm or less, and even more preferably 300 ppm or less when humidified at 28°C and 90% RH for 48 hours from a dry state. By setting the expansion rate to 700 ppm or less, the film swells, which suppresses the formation of wrinkles during long-term storage.

[0028] From the viewpoint of improving long-term storage and processability, the aliphatic polyester film of the present invention preferably has a crystal melting heat ΔHm in the heating step of differential scanning calorimetry of 20 J / g or more and 50 J / g or less, more preferably 21 J / g or more and 45 J / g or less, and even more preferably 22 J / g or more and 40 J / g or less. By keeping it within the above range, orientation crystallization proceeds appropriately, suppressing swelling of the film and resulting in a film with excellent film strength.

[0029] From the viewpoint of improving processability, the aliphatic polyester film of the present invention preferably has a thermal shrinkage rate of 120°C of 15% or less in the longitudinal direction, more preferably 10% or less, and even more preferably 7% or less, when S1 (%) is the thermal shrinkage rate of 120°C in the width direction and S2 (%) is the thermal shrinkage rate of 120°C in the width direction. If the thermal shrinkage rate exceeds 15%, it may shrink significantly due to heating during processing, which may impair processability. Methods for achieving the thermal shrinkage rate within the above range include controlling the amount and molecular weight of biodegradable resins other than polyhydroxyalkanoic acid within a preferred range, and controlling the stretching ratio and heat-fixing temperature in the manufacturing process within a preferred range.

[0030] The aliphatic polyester film of the present invention preferably has a weight loss rate after washing of 0.4% to 8.0%, more preferably 1.0% to 5.0%, and even more preferably 2.0% to 4.0%, as determined by the measurement method described later, from the viewpoint of improving biodegradability and long-term storageability. Setting it to 0.4% or more suppresses the impairment of biodegradability by stabilizing microbial activity, making hydrolysis less likely to progress and reducing the occurrence of disintegration starting points. Setting it to 8.0% or less suppresses the tendency for wrinkles to form due to excessive moisture absorption and swelling of the film.

[0031] The aliphatic polyester film of the present invention preferably contains 0.4% to 15.0% by mass of water-soluble resin per 100% by mass of the total film mass, more preferably 2.0% to 10.0% by mass, and even more preferably 4.0% to 6.0% by mass, from the viewpoint of biodegradability, long-term storage, and improved printability. By having 0.4% by mass or more, microbial activity is stunted, hydrolysis is less likely to progress, and a point of disintegration is less likely to occur, thereby suppressing the impairment of biodegradability. By having 15.0% by mass or less, it is possible to suppress the film from excessively absorbing moisture and swelling, which can easily cause wrinkles and increase precipitates on the film surface, thus suppressing the impairment of printability.

[0032] The aliphatic polyester film of the present invention preferably has a weight-average molecular weight of 2,000 to 11,000 of the water-soluble resin, and more preferably 3,000 to 9,500, from the viewpoint of biodegradability, long-term storage, and improved printability. If the molecular weight is less than 2,000, the short molecular chains of the water-soluble resin make it easier for the film to absorb moisture and swell, which may impair long-term storage, and the increase in precipitates on the film surface may impair printability. If the molecular weight is 11,000 or more, the long molecular chain difference of the water-soluble resin improves the film strength, which may impair biodegradability because it takes time for microorganisms to break down the molecular chains.

[0033] The aliphatic polyester film of the present invention, from the viewpoint of improving biodegradability and printability, comprises an A1 layer and a B1 layer whose layer thickness t is related by formula 1, and at least the B1 layer is a layer containing a water-soluble resin, and preferably satisfies formula 2 when the water-soluble resin content of the A1 layer relative to 100% by mass of the A1 layer is Wa 1% by mass, and the water-soluble resin content of the B1 layer relative to 100% by mass of the B1 layer is Wb 1% by mass. (However, t(A1) represents the thickness of the A1 layer, and t(B1) represents the thickness of the B1 layer.) t(B1) / t(A1)>1.2...Equation 1 Wb1>Wa1...Formula 2 A film satisfying the above formulas 1 and 2 maintains biodegradability due to the thickness of the B1 layer containing water-soluble resin, while the presence of the A1 layer suppresses deposition on the film surface and improves printability. Furthermore, if the A1 layer contains water-soluble resin, an even greater improvement in biodegradability can be obtained. It is more preferable that the film satisfies the following formula 1'. 20.0>t(B1) / t(A1)>5.0...Equation 1'

[0034] The aliphatic polyester film of the present invention, from the viewpoint of biodegradability and improved printability, preferably satisfies formulas 3 and 4 when the water-soluble resin content of the water-soluble resin in the A1 layer relative to 100% by mass of the A1 layer is Wa1% by mass, the water-soluble resin content of the A2 layer relative to 100% by mass of the A2 layer is Wa2% by mass, and the water-soluble resin content of the B1 layer relative to 100% by mass of the B1 layer is Wb1% by mass. Wb1>Wa1...Formula 3 Wb1>Wa2...Formula 4 A film satisfying the above equations 3 and 4 maintains biodegradability due to the thickness of the B1 layer containing water-soluble resin, while the presence of A1 and A2 layers further enhances the suppression of precipitates on the film surface and results in a film with superior printability. Furthermore, if the A1 and A2 layers also contain water-soluble resin, an even greater improvement in biodegradability can be obtained.

[0035] The aliphatic polyester film of the present invention preferably has a weight-average molecular weight of 2,000 to 11,000 of the water-soluble resin contained in the B1 layer, more preferably 3,000 to 9,500. If the molecular weight is less than 2,000, the short molecular chains of the water-soluble resin make it easier for the film to absorb moisture and swell, which may impair its long-term storage properties, and the increase in precipitates on the film surface may impair its printability. If the molecular weight is 11,000 or more, the long molecular chain difference of the water-soluble resin improves the film strength, which may impair biodegradability because it takes time for microorganisms to break down the molecular chains.

[0036] The aliphatic polyester film of the present invention may be provided with a functional layer depending on the application, and it is preferable to have a functional layer on at least one side. The aliphatic polyester film having a functional layer will be described below. The aliphatic polyester film of the present invention provided with a functional layer may be simply referred to as a "laminated body". Examples of functional layers that can be laminated to the aliphatic polyester film include a gas barrier layer, an adhesive layer, a heat seal layer, an easy-to-adhere layer, a colored layer, a printed layer, an easy-to-peel layer, a release layer, an easy-to-slip layer, a porous layer, a nonwoven fabric, etc. The method of laminating the functional layer may be selected according to the functional layer, but for example, it can be laminated by vapor deposition, sputtering, coating, various printing methods such as gravure printing and offset printing, heat bonding, lamination via an adhesive layer, etc. 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. As for functional layers that can be preferably laminated, for example, when used for packaging or agricultural, forestry, and fishery purposes, it is preferable to provide a gas barrier coating layer or a vapor-deposited layer from the viewpoint of providing gas barrier properties, and a vapor-deposited layer is more preferable from the viewpoint of exhibiting high gas barrier performance. Furthermore, from the viewpoint of providing lamination processability, it is preferable to provide a heat-sealable resin layer or an adhesive coating layer, and when laminating multiple films, the 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 coat agricultural, forestry, and fishery materials such as fertilizers, feed, seeds, and pharmaceuticals, a heat-sealable resin layer that provides heat-sealing properties (hereinafter sometimes referred to as the "heat-seal layer") is preferred as a functional layer that provides adhesion.

[0037] When a vapor-deposited layer is laminated as a functional layer to the aliphatic polyester film of the present invention, it is preferable that the vapor-deposited layer be laminated on at least one side of the film. Furthermore, from the viewpoint of gas barrier properties, it is preferable that the vapor-deposited layer be a layer containing a total of more than 50% by mass and 100% by mass of metal and inorganic compounds (hereinafter sometimes referred to as "layer A"). Here, "a layer containing a total of more than 50% by mass and 100% by mass of metal and inorganic compounds" refers to a layer containing more than 50% by mass of metal only, a layer containing more than 50% by mass of inorganic compounds only, or a layer containing both metal and inorganic compounds, with their total exceeding 50% by mass, when the total components constituting the vapor-deposited layer are taken as 100% by mass. From the viewpoint of improving adhesion to the film, improving gas barrier properties when laminated to the film, and reducing environmental impact, suitable metals and / or inorganic compounds that can be used for layer A include, for example, aluminum, aluminum oxide, silicon oxide, germanium oxide, magnesium oxide, cerium oxide, calcium oxide, diamond-like carbon film, or mixtures thereof. Furthermore, from the viewpoint of visibility of the contents, it is more preferable to use inorganic compounds, particularly aluminum oxide, silicon oxide, or mixtures containing these. The thickness of layer A in the laminate is preferably 200 nm or less from the viewpoint of recyclability when the laminate is reused as a resin or film, suppression of the decrease in gas barrier properties due to cracking, and obtaining visibility of the contents when used as packaging material. From the above viewpoint, 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 it is set to 1 nm from the viewpoint of barrier property development.

[0038] Furthermore, in the laminate of the present invention, a resin layer with a thickness of 1 μm or less may be provided between layer A and the surface of the aliphatic polyester film by coating or the like. Providing such a resin layer may improve the adhesion between layer A and the aliphatic polyester film. However, from the viewpoint of manufacturing cost, an embodiment without the resin layer is preferred.

[0039] Methods for forming a laminate by creating an A layer on the aliphatic polyester film of the present invention include vapor deposition, coating, lamination, etc. However, vapor deposition is particularly preferred because it is humidity-independent and can exhibit excellent gas barrier properties in a thin film. As vapor deposition methods, physical vapor deposition methods such as vacuum deposition, EB deposition, sputtering, and ion plating, and various chemical vapor deposition methods such as plasma CVD can be used, but from the viewpoint of productivity, vacuum deposition is particularly preferred.

[0040] Furthermore, in the laminate of the present invention, an overcoat layer may be provided on the surface facing the aliphatic polyester film of layer A, from the viewpoint of improving gas barrier properties and suppressing a decrease in gas barrier properties due to deposition defects or cracks in layer A.

[0041] When a heat-seal layer is laminated as a functional layer to the aliphatic polyester film of the present invention, it is preferable that the heat-seal layer be laminated to at least one side of the film. Furthermore, it is preferable that the heat-seal layer be a layer that fuses at a temperature of 100°C or higher and below the melting point of the aliphatic polyester film of the present invention -20°C (hereinafter sometimes referred to as "layer C"), from the viewpoint of achieving both the quality of the aliphatic polyester film and heat-sealability. Here, "a layer that fuses at a temperature of 100°C or higher and below the melting point of the aliphatic polyester film of the present invention -20°C" means that the main component of layer C is a resin component having a softening point or melting point of 100°C or higher and below the melting point of the aliphatic polyester film of the present invention -20°C. From the viewpoint of having high heat seal strength, suitable resin components for the C layer include, for example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-propylene random copolymer, ethylene-propylene block copolymer, ethylene-methacrylic acid copolymer, or any mixture thereof. When laminating multiple films, from the viewpoint of reducing the thickness of the final product, suitable adhesives include, for example, ethylene-vinyl acetate copolymer (EVA)-based hot melt adhesive, olefin-based hot melt adhesive, rubber-based hot melt adhesive, polyester-based hot melt adhesive, polyamide-based hot melt adhesive, polyurethane-based hot melt adhesive, or any mixture thereof. From the viewpoint of improving the biodegradability of the entire laminate, suitable adhesives include, for example, resin components containing the copolymer components of polyhydroxyalkanoic acid exemplified above, or 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 the aliphatic polyester film of the present invention, or any mixture thereof.

[0042] The thickness of the C layer 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. Furthermore, from the viewpoint of suppressing a decrease in the biodegradability of the laminate and from the viewpoint of suppressing the thickness of the final product when multiple films are laminated, it is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less.

[0043] In the laminate of the present invention, a resin layer with a thickness of 1 μm or less may be provided between the functional layers A and C and the surface of the aliphatic polyester film by coating or the like. Providing such a resin layer may improve the adhesion between the functional layer and the aliphatic polyester film. However, from the viewpoint of manufacturing cost, an embodiment without the resin layer is preferred, and an embodiment having the functional layer on the surface of the aliphatic polyester film is more preferred.

[0044] As a method for forming functional layers A and C on the aliphatic polyester film of the present invention to form a laminate, known methods such as coating, vapor deposition, lamination, and co-extrusion can be selected. For example, for layer A, vapor deposition is more preferable because it is humidity-independent and can exhibit excellent gas barrier properties in a thin film. As vapor deposition methods, physical vapor deposition methods such as vacuum vapor deposition, EB vapor deposition, sputtering, and ion plating, and various chemical vapor deposition methods such as plasma CVD can be used, but from the viewpoint of productivity, vacuum vapor deposition is even more preferable. For layer C, coating and lamination are particularly preferable because it can exhibit high heat seal strength in a thin film. As coating methods, bar coating, gravure coating, calendering, and die coating can be used, and as lamination methods, dry lamination, solvent-free lamination, extrusion lamination, and co-extrusion can be used. From the viewpoint of productivity, gravure coating, die coating, extrusion lamination, and co-extrusion are even more preferable.

[0045] The aliphatic polyester film of the present invention can be widely used for various applications, including packaging, release, packaging materials, hygiene products, agricultural products, agricultural and forestry products, construction products, medical products, and process films used in the manufacture of various products. In particular, when used in packaging and agricultural and forestry materials, it can be suitably used as an aliphatic polyester film that has excellent biodegradability and can be used without deformation during long-term storage or post-processing.

[0046] The aliphatic polyester film according to the embodiments of the present invention is preferably used for packaging applications due to its excellent biodegradability, long-term storage properties, and various processability. A package containing the aliphatic polyester film according to the embodiments of the present invention can protect various contents, including food, but the form is not particularly limited. For example, one method is to process the film or laminate of the present invention into a bag shape by heat sealing and place the contents inside, or to fill or place the contents into a tray-shaped container and then seal it using the film or laminate of the present invention.

[0047] The aliphatic polyester film according to the embodiment of the present invention exhibits good biodegradability in various environments, including the ocean, and has minimal unevenness during disintegration and excellent processability, making it suitable for use as an agricultural, forestry, and fisheries material. For example, it is suitable for use in materials where biodegradability after use is desirable, such as soil mulch films, vegetation films, fumigation films, water retention films, fertilizer coatings, feed coatings, aquaculture support films, marine organism fouling inhibition films, and environmental conservation materials.

[0048] This invention relates to an aliphatic polyester film. Here, an aliphatic polyester is a polymer compound without an aromatic ring structure, classified as one of the following: a polyhydroxy acid, a polyhydroxyalkano acid, or a polyalkylenedicarboxylic acid. The aliphatic polyester film of this invention contains 50% by mass or more of aliphatic polyester, preferably 95% by mass or more. In addition to polylactic acid and polyhydroxyalkano acid, the aliphatic polyester of this invention may include polyhydroxy acids such as polyglycolic acid, and polyalkylenedicarboxylic acids such as polyethylene succinate, polybutylene succinate, and polybutylene succinate adipate. However, it is not limited to these aliphatic polyesters.

[0049] The aliphatic polyester film of the present invention may contain various additives, such as organic particles, inorganic particles, antioxidants, heat stabilizers, lubricants, antistatic agents, antiblocking agents, fillers, viscosity modifiers, colorants, color inhibitors, and crystal nucleating agents, as long as they do not impair the objectives of the present invention.

[0050] <Packaging materials, packaging> The packaging material and packaging body of the present invention will be 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 is less prone to wrinkling during long-term storage, does not break or deform even under the transport tension of post-processing such as printing or the vapor deposition process of the vapor deposition layer provided as a gas barrier layer, and has excellent handling properties, making it suitable for use as a packaging material. Furthermore, since it can suppress the reduction in gas barrier properties due to cracking of the vapor deposition layer, it can be suitable for packaging items that are easily degraded by water vapor and oxygen.

[0051] The packaging of the present invention is characterized in that the contents are packaged using the packaging material of the present invention. The form is not particularly limited. For example, examples include packaging obtained by processing the packaging material of the present invention into a bag shape by heat sealing and placing the contents inside, and packaging obtained by filling or placing the contents into a tray-shaped container and then sealing it using the packaging material of the present invention.

[0052] <Agricultural, Forestry, and Fisheries Supplies> The agricultural, forestry, and fisheries materials of the present invention will be described below. The agricultural, forestry, and fisheries materials of the present invention are 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 fisheries materials of the present invention are characterized by their excellent biodegradability, long-term storage properties, and processability, and are suitably used in applications where biodegradability after use is advantageous, such as soil mulch films, vegetation films, fumigation films, water retention films, fertilizer coatings, feed coatings, seedling coatings, chemical coatings, aquaculture support films, marine organism fouling suppression films, and environmental conservation materials.

[0053] <Coating 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. By protecting the covered agricultural, forestry, and fishery materials, it prevents quality deterioration due to degradation and environmental pollution due to leakage, while biodegrading in soil and ocean allows for the appropriate diffusion and dispersion of fertilizers, feed, and chemicals, and protects seeds and seedlings until they are established and laid down, preventing them from being hindered by biodegradation. The agricultural, forestry, and fishery materials referred to here are materials and components contained within 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 range of known materials can be used. As mentioned above, the aliphatic polyester film of the present invention, which has excellent biodegradability, long-term storage properties, and processability, and exhibits minimal disintegration, can be used for this application to prevent leakage of agricultural, forestry, and fishery materials from pinholes, cracks, and areas with uneven coating thickness. In addition, it is possible to prevent leakage of fragments of the aliphatic film caused by uneven disintegration. The thickness of the aliphatic polyester film of the present invention allows for control of diffusion and scattering rates in soil and ocean. Furthermore, it is possible to coat two or more types of agricultural, forestry, and fishery materials, such as fertilizers, feed, seeds, and chemicals, together. For example, coating seeds together with fertilizers and chemicals to be applied is preferable because it is possible to enhance crop growth simultaneously with germination.

[0054] From the above perspective, it is preferable to select the thickness of the aliphatic polyester film within the aforementioned preferred range, according to the diffusion and dispersal speed in soil and ocean. If the aliphatic polyester film is excessively thin, it may lack sufficient strength, reducing the protective effect on the contents or causing tearing during processing. Conversely, if the aliphatic polyester film is excessively thick, it may not be biodegradable enough. For example, a thin film that allows for rapid diffusion and dispersal after biodegradation can be selected for fast-acting fertilizers, and a thick film that allows for slow diffusion and dispersal after biodegradation can be selected for slow-acting fertilizers. By applying these coated fertilizers together, the workload of agricultural workers can be reduced.

[0055] 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-acting fertilizer and the aliphatic polyester film of the present invention, it becomes possible to produce a fertilizer in which slow-release and fast-acting fertilizers are sequentially coated with the aliphatic polyester film of the present invention. Also, by sequentially coating seedlings with fertilizers, feed, and pesticides in the same manner, it is expected that fertilizers, feed, and pesticides can be applied to grown agricultural and marine products at the appropriate timing.

[0056] The agricultural, forestry, and fishery materials, characterized by being coated with the aliphatic polyester film of the present invention, as described above, can enhance the effectiveness of agricultural, forestry, and fishery materials selected from fertilizers, feed, seeds, and chemicals, while preventing environmental pollution due to unintended leakage. By diffusing and scattering in soil and oceans at appropriate times, they can improve efficacy and reduce the workload of workers, making them particularly suitable for use in the fields of agriculture, forestry, and fisheries.

[0057] The fertilizers, feeds, seedlings, and pharmaceuticals characterized by being coated with the aliphatic polyester film of the present invention are not particularly limited in form as long as they do not impair the effects of the present invention, but can be used in various forms such as pellets, granules, blocks, pouches, ropes, and sheets. Specifically, for coated fertilizers for agricultural use, block, pellet, or granular forms that can be used with a spreader are preferred, and for coated seedlings, ropes or sheets that can be expected to reduce work are preferred.

[0058] <Manufacturing method> The method for producing the aliphatic polyester film of the present invention will be described below.

[0059] A preferred embodiment of the method for producing an aliphatic polyester film of the present invention involves performing, in this order, a melting step of melting a resin raw material mainly composed of aliphatic polyester, a casting step of extruding the melted resin raw material in the form of a film from a die and cooling and solidifying it on a support, a stretching step of stretching the obtained film in two orthogonal directions, and a heat treatment step of subjecting the film obtained in the stretching step to heat treatment and relaxation treatment.

[0060] The manufacturing method will be described in more detail below, but the aliphatic polyester film and its manufacturing method of the present invention are not necessarily limited to this, and the film structure can be either single-layer or laminated.

[0061] First, a single film is described as an example. The resin is melted in a single-screw extruder, and then extruded from the extrusion temperature set to 150°C to 220°C. The resulting material is then passed through a filtration filter to remove foreign matter and other impurities.

[0062] Next, the molten resin is extruded through a slit-shaped die to form a molten resin film. At this time, it is preferable to control the oxygen concentration in the raw material input hopper to 0.10 volume% or less, from the viewpoint of preventing resin degradation and increasing the strength of the film.

[0063] Regarding the method of adding water-soluble resin, from the viewpoint of improving processability, direct addition to the hopper during manufacturing or masterbatching with a resin other than polyhydroxyalkanoic acid is preferred, with the latter being more preferable. When masterbatching with a polyhydroxyalkanoic acid resin that is easily decomposed by heat is performed, the weight-average molecular weight of the film decreases.

[0064] Next, the molten resin film extruded from the slit-shaped die is cooled and solidified on a casting drum with a surface temperature controlled to 10°C to 40°C to obtain an unstretched film. Any of the following methods can be used to adhere the molten film to the casting drum: electrostatic application, adhesion using the surface tension of water, air knife method, press roll method, underwater casting method, air chamber method, etc., or a combination of multiple methods may be used.

[0065] In the present invention, it is preferable to impart orientation to the unstretched film obtained by the above method by sequentially biaxially stretching or simultaneously biaxially stretching it in the longitudinal and width directions.

[0066] First, when performing sequential or simultaneous biaxial stretching, the unstretched film is preheated to a temperature between (melting point of aliphatic polyester - 100°C) and (melting point of aliphatic polyester - 10°C) by guiding it into multiple roll groups or a continuous oven before stretching.

[0067] Next, the preheated unstretched film is guided to a group of rolls or a continuous oven, which is maintained at a temperature below the melting point of aliphatic polyester, without cooling, and subjected to uniaxial stretching in the longitudinal direction, or simultaneous biaxial stretching in the longitudinal and width directions. From the viewpoint of improving processability, it is preferable that the uniaxial stretching ratio in the longitudinal direction, or the stretching ratios in the longitudinal and width directions in simultaneous biaxial stretching, be between 2.3 and 5 times. The passage time through the stretching section in uniaxial stretching in the longitudinal direction or simultaneous biaxial stretching is preferably between 0.1 seconds and 100 seconds.

[0068] When uniaxial stretching is performed in the longitudinal direction as described above, it is preferable to then grip the ends of the resulting stretched film with clips and guide it into a continuous oven controlled to a temperature below the melting point of aliphatic polyester, where it is stretched in the width direction. From the viewpoint of improving processability, it is preferable that the stretching ratio in the width direction be 2.3 times or more and 5 times or less. The process time in the width direction stretching step is preferably 1 second or more and 1000 seconds or less in the preheating section and 0.1 seconds or more and 100 seconds or less in the stretching section.

[0069] Furthermore, from the viewpoint of improving processability, the surface magnification of the film is preferably 5.3 times or more and 25 times or less.

[0070] Next, while holding the ends of the obtained stretched film with clips, it is preferable to guide it into a continuous oven and subject it to heat treatment and relaxation treatment at a temperature of (melting point of aliphatic polyester - 100°C) to (melting point of aliphatic polyester - 5°C). The process time in the heat treatment and relaxation treatment steps is preferably 0.1 seconds or more and 100 seconds or less.

[0071] Furthermore, in terms of controlling the thermal shrinkage rate of the aliphatic polyester film to a desirable range, it is preferable to apply heat treatment and relaxation treatment in accordance with the treatment temperature. Specifically, the heat treatment and relaxation treatment are preferably performed at a temperature of 50°C to 150°C for 1 second or more.

[0072] Next, the clips supported in a room temperature atmosphere are released, and the ends on both sides in the film width direction are slit to obtain an aliphatic polyester film. The above processes of unstretched film formation, stretching, heat treatment, and relaxation may be carried out in a continuous process or individually in a batch process. In addition, additional stretching, heat treatment, relaxation, surface treatment, coating, etc. may be performed as long as they do not impair the objective of the present invention.

[0073] Next, we will describe lamination as an example. Let the raw resin constituting layer A1 be "raw material A," and the raw resin constituting layer B1 be "raw material B." (If layer A2 is to be laminated, let the raw resin constituting layer A2 be "raw material C.") Raw materials A and B are melted in separate single-screw extruders. (If layer A2 is to be laminated, raw material C is also fed into a separate single-screw extruder.) The materials are melted and extruded from each single-screw extruder set to an extrusion temperature of 150°C to 220°C, and then passed through a filtration filter to remove foreign matter, etc.

[0074] Next, the molten resins were combined using a lamination device so that they were arranged alternately in the thickness direction, and then extruded through a slit-shaped die to form a molten resin film laminated in two or more layers. From there, the film was obtained using the same manufacturing method as for a single film.

[0075] The present invention makes it possible to obtain an aliphatic polyester film that has excellent biodegradability, long-term storage properties, processability, and printability by controlling the orientation and crystallization state and thermal shrinkage rate through the manufacturing method described above.

[0076] Next, we will describe in more detail, with examples, the methods for producing fertilizers, feed, seeds, and pharmaceuticals coated with the aliphatic polyester film of the present invention, but this description is not necessarily limited to these examples.

[0077] The present invention provides a method for producing fertilizer coated with an aliphatic polyester film. This method involves guiding the aliphatic polyester film obtained by the above method into upper and lower molds that have been molded into pellet-shaped depressions, and then using suction to make the film adhere to the molds. Next, the fertilizer to be coated is spread onto the film in the lower mold, and the upper mold is lowered and heated to bond the upper and lower films together.

[0078] The fertilizer coated with the aliphatic polyester film of the present invention may be in pellet form, granular form, powder form, paste form, or liquid form. Among these, the fertilizer is preferably in granular, powder, paste form, or liquid form from the viewpoint of ease of protection by the film and conformability to the mold shape.

[0079] Furthermore, from the viewpoint of adhesion, it is preferable to provide the aforementioned heat-seal layer as an adhesive layer on the aliphatic polyester film of the present invention, and in that case, it is more preferable to position the adhesive layer in the mold so that it is located on at least one side of the surfaces where the films come into contact with each other. Next, the film coated with fertilizer is removed from the mold, and the excess pressed portions between the films are cut and removed to obtain coated fertilizer processed into pellets. Here, it is preferable to use a cutting machine equipped with blades as the cutting method, and examples include a batch processing method using a mold with blades already positioned, a method of processing into a rope shape by continuously cutting in one direction using a rotary blade and then periodically cutting in a perpendicular direction, and a method of mounting blades on the above-mentioned mold and performing heat sealing and cutting simultaneously.

[0080] Other methods for coating agricultural, forestry, and fishery materials include preparing two rolls of the aliphatic polyester film of the present invention and laminating them while inserting the agricultural, forestry, and fishery materials between them at regular intervals; coating by heating the film while holding the agricultural, forestry, and fishery materials on it to cause thermal shrinkage; and coating by shrinking the film under reduced pressure.

[0081] By this manufacturing method, the present invention makes it possible to obtain fertilizers, feed, seeds, and pharmaceuticals coated with the aliphatic polyester film of the present invention, which has excellent biodegradability, long-term storage properties, and processability.

[0082] <Biodegradation method> The aliphatic polyester film of the present invention, and the packaging and agricultural / forestry / fishery materials containing the aliphatic polyester film of the present invention, can be biodegraded using composting equipment. Known composting equipment can be used, including industrial compost systems that enhance biodegradability by heating or maintaining a temperature of around 60°C, simple compost systems made by digging holes in the soil, small compost systems such as compost containers and compost bags that are partially or completely buried in the soil, and biological compost systems such as worm compost and zoo compost using flies. If the aliphatic polyester film of the present invention, and the packaging and agricultural / forestry / fishery materials containing the aliphatic polyester film of the present invention do not have a functional layer, or if the functional layer is a biodegradable or low-toxicity vapor-deposited layer, they can be decomposed by placing them in composting equipment and subjecting them to general treatments such as mixing with soil or microbial fermentation accelerators. Furthermore, when using functional layers or other layers that are not biodegradable, the functional layers may be peeled off before being added to the composting equipment. Alternatively, if the layers have low toxicity, such as environmental toxicity or human toxicity, they may be added to the composting equipment even if they are not biodegradable, and the residue may be recovered after the aliphatic polyester film of the present invention has decomposed. The purposes of composting include waste reduction through volume reduction, composting, and biogas production, but the aliphatic polyester film, packaging, and agricultural, forestry, and fishery materials of the present invention are suitable for composting equipment for any of these purposes. [Examples]

[0083] 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. The evaluation of each item was carried out by the following method.

[0084] <Film evaluation, method for determining the effects of the present invention> The method for evaluating the film and determining the effects of the present invention are as follows. The film used for evaluation shall be one that has been left standing for 24 hours in a temperature and humidity environment of 25°C and 65%RH.

[0085] (1) Film thickness The thickness of the film was measured at five arbitrary points using a contact-type high-precision digital length measuring instrument manufactured by Mitutoyo Corporation, "Lightmatic" (registered trademark) VL50B. The arithmetic mean of these five thicknesses was defined as the film thickness (unit: μm).

[0086] (2) Moisture content of the film The moisture content was measured using a moisture meter (HIRANUMA AQUACOUNTER “AQ-7”) and a moisture vaporizer (HIRANUMA EVAPORATOR UNIT “EV-6”), with HIRANUMA Aqualight CN as the counter electrode and HIRANUMA Aqualight RS-A as the generating solution. After pre-heating the glass tube of the apparatus at 130°C for 15 minutes to remove moisture, the film was conditioned for 48 hours in a constant temperature and humidity chamber (ESPEC LHL-113) set to 28°C and 90%RH, and then placed into the apparatus tube to measure the moisture content of the film. The measurement conditions were 130°C for 15 minutes.

[0087] (2-1) Expansion rate of the film A film dried for 24 hours under reduced pressure of 200 Pa or less in a vacuum dryer (ADVANTEC DRV420DA) set to 40°C was cut into a rectangle measuring 150 mm in length and 10 mm in width. A mark was made in the center 100 mm apart with an oil-based marker, and the length was measured using a universal projector to determine the initial length E0. Next, the measured sample was conditioned for 48 hours in a constant temperature and humidity chamber set to 28°C and 90% RH. After that, to remove any moisture adhering to the surface, it was left to stand for 1 hour at 25°C and 65% RH, and the length between the marks was measured using a universal projector to determine the length after expansion EH. The expansion rate (in ppm) was calculated from the measured lengths E0 and EH using the following formula. The same measurement was performed 5 times, and the average value was taken as the expansion rate (ppm). Expansion rate (ppm) = (EH - E0) / E0 × 1,000,000

[0088] (3) Determination of the principal orientation axis direction and the direction perpendicular to the principal orientation axis direction In the film manufacturing process, the flow direction (MD) was defined as the direction perpendicular to the main orientation axis, and the direction perpendicular to the flow direction within the film plane (TD) was defined as the direction perpendicular to the main orientation axis. For films where the flow direction was unknown, the direction of the main orientation axis was determined by the following method. First, a rectangle with a length of 150 mm and a width of 10 mm was cut out with an arbitrary direction as the longer side to form a sample. <1> Sample <1> Define the direction of the longer side as 0°. Next, create a sample of the same size such that the direction of the longer side is rotated 15° to the right from the 0° direction. <2> A sample was taken. Similarly, the rectangular sample was rotated by 15° in the direction of its longer side, and the sample was taken. <3> ~ <12> A sample was taken. Next, each rectangular sample was set on a tensile testing machine (A&D Company, Limited's "Tensilon" (registered trademark) universal testing machine RTG-1210) with an initial chuck distance of 30 mm so that the long side was the tensile direction, and a tensile test was performed at a tensile speed of 300 mm / min in a temperature and humidity atmosphere of 25°C and 65% RH. The breaking strength (unit: MPa) was calculated by dividing the load at which the sample broke by the cross-sectional area of ​​the sample before the test (film thickness × width obtained in (1)). The strain at which the sample broke was calculated as the elongation at break (unit: %). The same measurement was performed five times for each sample, and the average value was adopted. In this invention, the principal orientation axis direction was defined as the measurement direction in which the breaking strength obtained by this method was maximum, and the direction perpendicular to this was defined as the direction perpendicular to the principal orientation axis direction.

[0089] (4) Rate of change of Young's modulus The film, dried for 24 hours under reduced pressure of 200 Pa or less in a vacuum dryer set to 40°C, was cut into a rectangle measuring 150 mm in length and 10 mm in width. The initial Young's modulus Y0 was determined by measuring it using the tensile testing machine described in (3). The measured sample was then conditioned for 48 hours in a constant temperature and humidity chamber set to 28°C and 90% RH. After that, to remove any moisture adhering to the surface, it was left to stand for 1 hour at 25°C and 65% RH, and then measured again to determine the Young's modulus YH after expansion. The rate of change of Young's modulus (in %) was calculated from the measured Y0 and YH using the following formula. The same measurement was performed 5 times, and the average value was taken as the rate of change of Young's modulus (%). The rate of change of Young's modulus (%) = (YH - Y0) / Y0 × 100.

[0090] (5) Melting point, heat of fusion Measurements and analyses were performed using a differential scanning calorimeter (Rigaku Thermo plus EVO2 DSC vesta) in accordance with JIS K7121-1987 and JIS K7122-1987. A 5.0 mg sample was weighed, and the DSC curve was measured when the temperature was raised from -50°C to 200°C at a rate of 20°C / min. The maximum peak temperature on the endothermic side was defined as the melting point of the resin or film. If multiple endothermic peaks were present, the peak temperature with the largest endothermic value was adopted as the melting point. The heat of crystalline fusion was determined from the peak area of ​​the endothermic peak due to crystalline fusion at the melting point.

[0091] (6) Thermal shrinkage The thermal shrinkage rates (S1, S2) obtained by heat treatment at 120°C for 15 minutes were determined by cutting a rectangle of 150 mm in length and 10 mm in width from the film in the direction of the principal orientation axis and in the direction perpendicular to the principal orientation axis. Marks were made with an oil-based marker 100 mm apart in the center, and the length was measured using a universal projector to determine the initial length I0. Next, the measured sample was placed in a gear-type hot air oven adjusted to 120°C, a 2.1 g load was attached to the bottom of the suspended film, and the heat treatment was performed for 15 minutes while rotating the gear. After that, the film was removed and cooled to room temperature, and the length between the marks was measured using a universal projector to determine the heat-recovered length IH. From the measured lengths I0 and IH, the 120°C thermal shrinkage rate (unit: %) was calculated using the following formula. The same measurement was performed 5 times each in the direction of the principal orientation axis and in the direction perpendicular to the principal orientation axis for each sample, and the average value in the direction of the principal orientation axis was taken as S1 (%), and the average value in the direction perpendicular to the principal orientation axis was taken as S2 (%). Heat shrinkage rate at 120°C (%) = (I0 - IH) / I0 × 100 The obtained thermal shrinkage rate was evaluated according to the following criteria. A: Heat shrinkage rate is less than 8% B: Thermal shrinkage rate of 8% or more and less than 11% C: Heat shrinkage rate of 11% or more and less than 16% D: Thermal shrinkage rate of 16% or more.

[0092] (7) Weight reduction rate after washing The weight of the film, dried for 24 hours in a vacuum dryer set to 40°C under reduced pressure of 200 Pa or less, was weighed using a precision balance (A&D HR-202i) to determine the weight before washing. Subsequently, the same sample was immersed in 40°C hot water for 24 hours, and then left to stand at 25°C 65% RH for 1 hour to remove any moisture adhering to the surface. The weight was then weighed again to determine the weight after washing. For each weight, the percentage of weight loss after washing was calculated using the formula {(weight before washing) - (weight after washing)} / (weight before washing) × 100.

[0093] (8) Biodegradability of the film A 1L wet-compost mixture was prepared in accordance with JIS K6954 (2008) and placed in a 10L polypropylene container. Next, a 5cm x 5cm evaluation film was sandwiched between polyethylene holders with a 2cm square cutout on the inside, leaving the film inside the holders exposed to the outside.

[0094] Subsequently, the film sample, fixed with a holder, was added to a moist synthetic compost in a polypropylene container, and a 60-day culture test was conducted in an oven controlled at 28°C according to the method of JIS K6954 (2008). When adding the film sample, it was ensured that the entire 2cm square exposed portion of the film in the holder was covered with the moist synthetic compost. After the initial addition, the film sample was removed every two days, the moist synthetic compost was stirred with a shovel, and then the film sample was added again, and this process was repeated.

[0095] To determine the collapse area ratio, a total of 10 holders were evaluated in the same compost, and the arithmetic mean of the 10 measurements was taken as the collapse area ratio (%) of the film sample. After 60 days from the initial introduction, the film sample was removed from the container, and a photograph was taken with a digital camera at a resolution of 1200 dpi (2 million pixels) or higher. From the photographic image, the collapse area ratio (%) was calculated using the formula (initial sample area in the holder - remaining sample area in the holder) / (initial sample area in the holder) × 100 for the area of ​​the sample remaining within a 2 cm square frame inside the holder. The biodegradability of the film was determined based on the following criteria. A: Collapse area ratio is 80% or more B: Collapse area ratio is 60% or more but less than 80% C: Collapse area ratio is between 25% and less than 60% D: The disintegration area ratio is less than 25%. The biodegradability of the film is preferably C or higher, more preferably B, and even more preferably A.

[0096] (9) Uniformity of film disintegration A total of 10 holders were evaluated in the same compost in the same manner as in (8), and the percentage of collapsed area for each was measured. The degree of variation in the collapse state during biodegradation was calculated from the maximum and minimum values ​​of the percentage of collapsed area using the following formula, and the uniformity of collapse in the present invention was judged according to the following criteria. Variation in collapse state (%) = (Maximum value of collapse area ratio) - (Minimum value of collapse area ratio) A: The degree of variation in the collapse state is less than 20%. B: The degree of variation in the collapse state is between 20% and 40%. C: The degree of variation in the collapse state is between 40% and 50%. D: The degree of variation in the collapse state is 50% or more. The uniformity of film disintegration is preferably C or higher, more preferably B, and even more preferably A.

[0097] (10) Long-term storage properties of film A 300mm wide, 200m long film was prepared, wound onto a 6-inch, 350mm long core, and the wrinkles were visually inspected after being stored for one week at 28°C and 90% RH. The long-term storage capabilities obtained were evaluated according to the following criteria. A: Wrinkles do not form during long-term storage. B: One wrinkle may appear during long-term storage. C: Wrinkles may appear in 2 to 4 places during long-term storage. D: More than 5 wrinkles appear during long-term storage. The long-term storage properties of the film are preferably C or higher, more preferably B, and even more preferably A.

[0098] (11) Printability of the film Film cut to A5 size (210cm x 148cm) using a cutter was coated with DIC XS-903R607 blue ink using a No. 4 wire bar, and then dried in a hot air oven at 100°C for 1 minute to prepare ink-coated samples. A cross-cut evaluation was performed on the ink-coated surface of each sample in accordance with JIS K5600-5-6, and the results were confirmed by counting the number of squares where the ink was peeled out of 100 cuts. The printability obtained was evaluated according to the following criteria. A: Less than 5 delamination squares during crosscutting. B: There are 5 to 10 peeling masses during cross-cutting. C: There are 10 or more but less than 20 peeling squares during cross-cutting. D: More than 20 delamination squares during cross-cutting. The printability of the film is preferably C or higher, more preferably B, and even more preferably A.

[0099] (12) Content of polyhydroxyalkanoic acid and resin components other than polyhydroxyalkanoic acid Dissolve the aliphatic polyester film in hexafluoroisopropanol (HFIP), 1 H-NMR and 13The polyhydroxyalkanoic acid content (mass%) was measured using 1C-NMR. The resin components other than polyhydroxyalkanoic acid were determined by subtracting the polyhydroxyalkanoic acid content (mass%) from the total film content (100% mass%). In the case of laminated films, the components constituting each layer were collected and evaluated by scraping off each layer of the film according to the laminate thickness. In the examples and comparative examples, the composition was calculated from the raw material mixing ratio during film manufacturing.

[0100] (13) Weight average molecular weight 10 mg of the sample was mixed with 5 mL of the measurement solvent described below, stirred at room temperature until the sample dissolved, filtered, and measured using gel permeation chromatography (GPC). The same measurement was performed three times for each sample, and the average of the peak area values ​​obtained was taken as the weight-average molecular weight (Mw). If multiple peak areas were obtained after measurement, the value with the largest peak area was adopted. Aliphatic polyester films and aliphatic polyester resins were measured using chloroform solvent, while water was used as the solvent for water-soluble resins because elution into chloroform solvent may be insufficient. • Detector: Differential refractive index detector RI (Tosoh RI-8020, sensitivity 32) • Columns: TSKgel GMHHR-M (φ7.8mm x 30cm, manufactured by Tosoh), 2 pieces • Filter: (Millex Syringe Filter, Hydrophilic PTFE, Non-sterile, Model No. SLCR033NS) • Solvent: Chloroform or water ·Flow rate: 1.0mL / min Column temperature: 40°C ·Injection volume: 0.200mL • Standard sample: Monodisperse polystyrene manufactured by Tosoh Corporation • Data processing: GPC data processing system manufactured by Toray Research Center.

[0101] (14) Processability A 300mm wide, 200m long film was prepared by winding it onto a 6-inch, 350mm long core. After passing it through an infrared continuous oven with one chamber (1m long) maintained at 120°C and two chambers (1m long) maintained at 40°C, at a transport tension of 50N / m, the film was rewinded onto a 6-inch, 350mm long core of the same configuration. The processability of the film was determined as follows based on the transport speed at which tearing occurred. A: No tearing occurred even when rewinding at a conveying speed of 8 m / min. B: No tearing occurred when rewinding at a conveying speed of 6 m / min, but tearing occurred when the conveying speed was changed to 8 m / min. C: No tearing occurred when rewinding at a conveying speed of 4 m / min, but tearing occurred when the conveying speed was changed to 6 m / min. D: When rewinding at a conveying speed of 4 m / min, tearing occurred. The processability of the film is preferably C or higher, more preferably B, and even more preferably A.

[0102] The following resins were used to produce the aliphatic polyester films and aromatic polyester films in each example and comparative example. Note that polyhydroxyalkanoic acid may be abbreviated as "PHA," polylactic acid as "PLA," polyethylene glycol as "PEG," polybutylene succinate adipate as "PBSA," polyvinylpyrrolidone as "PVP," and polyethylene terephthalate as "PET." The weight-average molecular weight is the value measured using the evaluation method described above.

[0103] [Aliphatic polyester resins, aromatic polyester resins] PHA: Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) BP350-05 (Mw 300,000) manufactured by Aosho Microbial Co., Ltd. PLA: Polylactic acid LX175 (Mw 150,000) manufactured by TotalEnergiesCorbion. PBSA: Polybutylene succinate adipate FD92PM (Mw 140,000) manufactured by Mitsubishi Chemical Corporation. PET: Polyethylene terephthalate (Mw 220,000) exhibiting an intrinsic viscosity of 0.65 dl / g, a glass transition temperature of 78°C, and a melting point of 255°C.

[0104] [Hydrophilic resin] PEG1: Polyethylene glycol PEG-4000N (Mw2900) manufactured by Sanyo Chemical Industries. PEG2: Polyethylene glycol PEG-1000 (Mw700) manufactured by Sanyo Chemical Industries. PEG3: Polyethylene glycol PEG-11000 (Mw8000) manufactured by Sanyo Chemical Industries. PEG4: Polyethylene glycol PEG-9500 (Mw9500) manufactured by Kahka Chemical Co., Ltd. PEG5: Polyethylene glycol PEG-20000 (Mw14500) manufactured by Sanyo Chemical Industries. PVP: Polyvinylpyrrolidone K-15 (Mw10000) manufactured by Nippon Shokubai Co., Ltd.

[0105] (Example 1) PLA and PEG1 were melt-kneaded in a vented twin-screw extruder at 190°C to prepare a PLA and PEG1 masterbatch. Then, the raw material, which was a blend of PHA and the aforementioned masterbatch, was supplied to a single-screw extruder so that the weight ratios of PHA, PLA, and PEG1 were as shown in the table. Here, the oxygen concentration in the extruder supply hopper was controlled to 0.05 volume%, and melt extrusion was performed in the extruder at a temperature of 170°C. After that, foreign matter was removed from the extruded molten resin using a 250 μm cut mesh filter. Subsequently, the extruded molten film was cooled and solidified on a casting drum maintained at 30°C to obtain an unstretched film.

[0106] Next, the unstretched film was guided into a longitudinal stretcher with roll group 1 held at 30°C, roll groups 2 and 3 held at 65°C, and roll group 4 held at 30°C in a continuous sequence, and uniaxially stretched 3.0 times in the longitudinal direction, with a passage time of 0.5 seconds from roll group 3 to roll group 4.

[0107] Next, the film that had passed through roll group 4 was guided to a tenter, and while both ends in the width direction were held with clips, it was preheated and stretched to 3.0 times its original width in an oven controlled to 70°C, and then heat-treated at 120°C while allowing 10% relaxation in the width direction. The passing times during this process were 3 seconds for the preheating section, 3 seconds for the stretching section, and 10 seconds for the heat treatment section.

[0108] Subsequently, the film was guided to the outside of the tenter after a cooling process at 30°C while the ends in the width direction were still held taut with clips. The clips at both ends in the width direction were then released, and an aliphatic polyester film with a thickness of 20 μm was obtained using a winding machine.

[0109] The obtained film evaluation results and the properties of the aliphatic polyester film are shown in the table. It was found that the polyhydroxyalkanoic acid and water-soluble resin have excellent biodegradability, and the polylactic acid has excellent long-term storage and processability.

[0110] (Examples 2-9) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the weight ratios of PHA, PLA, and PEG were changed as shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0111] (Example 10) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the PEG1 addition method was changed to direct addition to the hopper during the manufacturing process, without using a masterbatch, to achieve the weight ratio shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0112] (Example 11) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that a PBSA and PEG1 masterbatch was used instead of a PLA and PEG1 masterbatch. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0113] (Example 12) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the water-soluble resin was changed from PEG1 to PVP. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0114] (Example 13) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the stretching ratio was changed as shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0115] (Example 14) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the method of adding PEG1 was changed to adding it directly to the hopper during the manufacturing process instead of using a masterbatch. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0116] (Examples 15, 16) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the water-soluble resin was changed as shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0117] (Example 17) PLA and PEG4 were melt-kneaded in a vented twin-screw extruder at 190°C to prepare a masterbatch of PLA and PEG4. A raw material blend of PHA and the aforementioned masterbatch was supplied to a single-screw extruder so that PHA, PLA, and PEG4 were in the weight ratios shown in the table (layer B1). In addition, a raw material blend of PBSA and PLA was supplied to another single-screw extruder (layer A1). Here, the oxygen concentration in the extruder supply hopper was controlled to 0.05 volume%, and melt extrusion was performed at a temperature of 170°C in each extruder. After that, foreign matter was removed from the extruded molten resin using a 250 μm cut mesh filter. The layers were merged in a lamination device designed with two slits so that the outermost layer thickness was 8% of the film thickness, resulting in a laminate with two layers stacked in the thickness direction.

[0118] Subsequently, the extruded molten film was cooled and solidified on a casting drum maintained at 30°C to obtain an unstretched film.

[0119] Next, the unstretched film was guided into a longitudinal stretcher with roll group 1 held at 30°C, roll groups 2 and 3 held at 65°C, and roll group 4 held at 30°C in a continuous sequence, and uniaxially stretched 3.0 times in the longitudinal direction, with a passage time of 0.5 seconds from roll group 3 to roll group 4.

[0120] Next, the film that had passed through roll group 4 was guided to a tenter, and while both ends in the width direction were held with clips, it was preheated and stretched to 3.0 times its original width in an oven controlled to 70°C, and then heat-treated at 120°C while allowing 10% relaxation in the width direction. The passing times during this process were 3 seconds for the preheating section, 3 seconds for the stretching section, and 10 seconds for the heat treatment section.

[0121] Subsequently, with both ends in the width direction still held taut by clips, the film was guided to the outside of the tenter after a 30°C cooling process, the clips at both ends in the width direction were released, and an aliphatic polyester film with a thickness of 25 μm was obtained using a winding machine.

[0122] The obtained film evaluation results and the properties of the aliphatic polyester film are shown in the table. It was found that the film exhibits excellent biodegradability derived from polyhydroxyalkanoic acid and water-soluble resin, as well as excellent long-term storage and processability derived from polylactic acid. Furthermore, it was found that lamination suppresses precipitates on the film surface and improves printability.

[0123] (Example 18) PLA and PEG4 were melt-kneaded in a vented twin-screw extruder at 190°C to prepare a masterbatch of PLA and PEG4. A raw material blend of PHA and the aforementioned masterbatch was supplied to a single-screw extruder so that PHA, PLA, and PEG4 were in the weight ratios shown in the table (layer B1). A raw material blend of PBSA and PLA was supplied to another single-screw extruder (layer A1). Furthermore, a raw material blend of PBSA, PLA, and PCL was supplied to yet another single-screw extruder (layer A2). At this point, the oxygen concentration in the extruder supply hopper was controlled to 0.05 volume%, and melt extrusion was performed at a temperature of 170°C in each extruder. After that, foreign matter was removed from the extruded molten resin using a 250 μm cut mesh filter. An aliphatic polyester film was obtained using the same procedure as in Example 17, except that the layers were merged in a lamination device designed with 3 slits so that the thickness of the outermost layer on both sides was 8% of the film thickness, resulting in a laminate with 3 layers stacked in the thickness direction.

[0124] The obtained film evaluation results and the properties of the aliphatic polyester film are shown in the table. It was found that the film exhibits excellent biodegradability derived from polyhydroxyalkanoic acid and water-soluble resin, as well as excellent long-term storage and processability derived from polylactic acid. Furthermore, it was found that lamination suppresses precipitates on the film surface and improves printability.

[0125] (Examples 19, 21) An aliphatic polyester film was obtained using the same procedure as in Example 17, except that the molecular weight of PEG was changed as shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0126] (Examples 20, 22) An aliphatic polyester film was obtained using the same procedure as in Example 18, except that the molecular weight of PEG was changed as shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0127] (Example 23) An aliphatic polyester film was obtained using the same procedure as in Example 17, except that PEG was added to the A1 layer in the proportions shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0128] (Examples 24, 25) An aliphatic polyester film was obtained using the same procedure as in Example 18, except that PEG was added to the A1 layer or to the A1 and A2 layers in the ratios shown in the table. The evaluation results of the obtained film and the properties of the aliphatic polyester film are shown in the table.

[0129] (Comparative Example 1) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the raw material composition was as shown in the table, and PHA and PLA were added directly to the hopper in the manufacturing process without using a masterbatch. From the evaluation results of the obtained film, it was found that although it had excellent long-term storage properties and processability, the film did not absorb moisture easily and its biodegradability was poor.

[0130] (Comparative Example 2) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the raw material composition was changed as shown in the table. From the evaluation results of the obtained film, it was found that although it had excellent biodegradability, its long-term storage and processability deteriorated.

[0131] (Comparative Example 3) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that the raw material composition was as shown in the table, and only the PLA and PEG1 masterbatches were added to the hopper in the manufacturing process. From the evaluation results of the obtained film, it was found that although the processability was excellent, the biodegradability deteriorated due to the decrease in the polyhydroxyalkanoic acid ratio. In addition, the increased polylactic acid ratio made the film more susceptible to moisture absorption, worsening its long-term storage properties.

[0132] (Comparative Example 4) An aliphatic polyester film was obtained using the same procedure as in Example 1, except that 95% by mass of PET and 5% by mass of PEG1 were directly added to the hopper in the manufacturing process in the weight ratios shown in the table, and the melt-kneading temperature of the twin-screw extruder was changed to 280°C, the temperature of roll group 1 to 60°C, the temperatures of roll groups 2 and 3 to 90°C, and the temperature of the tenter to 110°C.

[0133] The film evaluation results showed that while it had excellent processability, its strong orientation and poor moisture absorption resulted in poor biodegradability and long-term storage capabilities.

[0134] (Comparative Example 5) An aliphatic polyester film was obtained using the same procedure as in Example 17, except that the raw material composition and the layer thicknesses of layers A1 and B1 were changed as shown in the table. From the evaluation results of the obtained film, it was found that although it had excellent long-term storage properties, processability, and printability, its biodegradability deteriorated.

[0135] (Comparative Example 6) An aliphatic polyester film was obtained using the same procedure as in Example 17, except that the raw material composition and the PEG content ratio of the B1 layer were changed as shown in the table. From the evaluation results of the obtained film, it was found that although it had excellent biodegradability, its long-term storage, processability, and printability deteriorated.

[0136] [Table 1]

[0137] [Table 2]

[0138] [Table 3]

[0139] [Table 4]

[0140] [Table 5]

[0141] [Table 6]

[0142] [Table 7]

[0143] [Table 8]

[0144] [Table 9] [Industrial applicability]

[0145] The present invention provides an aliphatic polyester film that has excellent biodegradability, does not wrinkle during long-term storage, and has excellent processability. Because the aliphatic polyester film of the present invention possesses the above characteristics, it can be suitably used in packaging applications and agricultural, forestry, and fisheries applications that require biodegradability and strength during processing and use.

Claims

1. An aliphatic polyester film containing 40% or more polyhydroxyalkanoic acid per 100% of the total film mass, having a moisture content of 700 ppm to 9000 ppm after 48 hours of humidity control at 28°C and 90% RH, and having a weight-average molecular weight of 150,000 or more.

2. An aliphatic polyester film containing 40% or more by mass of polyhydroxyalkanoic acid and 0.4% to 15.0% by mass of water-soluble resin, based on 100% by mass of the total film mass.

3. An aliphatic polyester film according to claim 1 or 2, comprising 10% to 60% by mass of polylactic acid based on 100% by mass of the total film mass.

4. The aliphatic polyester film according to claim 1 or 2, wherein the rate of change in Young's modulus after conditioning from a dry state at 28°C and 90% RH for 48 hours is -10% or more and 2% or less.

5. The aliphatic polyester film according to claim 1 or 2, wherein the expansion rate when humidified from a dry state at 28°C and 90% RH for 48 hours is 700 ppm or less.

6. The aliphatic polyester film according to claim 1 or 2, wherein the heat of fusion ΔHm of the crystals during the heating step in differential scanning calorimetry is 20 J / g or more and 50 J / g or less.

7. The aliphatic polyester film according to claim 1 or 2, wherein when the 120°C heat shrinkage rate in the direction of the main orientation axis is S1 (%) and the 120°C heat shrinkage rate in the direction perpendicular to the direction of the main orientation axis is S2 (%), both S1 and S2 are 15% or less.

8. The aliphatic polyester film according to claim 1 or 2, wherein the weight loss rate after washing is 0.4% or more and 8.0% or less.

9. The aliphatic polyester film according to claim 1, comprising 0.4% to 15.0% by mass of a water-soluble resin based on 100% by mass of the total film mass.

10. The aliphatic polyester film according to claim 1 or 2, comprising a water-soluble resin, wherein the water-soluble resin consists of one or more of the following: polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinylpyrrolidone, and polypropylene glycol.

11. An aliphatic polyester film according to claim 1 or 2, comprising a water-soluble resin, wherein the weight-average molecular weight of the water-soluble resin is 2,000 or more and 11,000 or less.

12. An aliphatic polyester film according to claim 1 or 2, comprising an A1 layer and a B1 layer having a layer thickness t related to the relationship in formula 1, wherein at least the B1 layer is a layer containing a water-soluble resin, and satisfying formula 2 when the water-soluble resin content in the A1 layer is 1% by mass Wa relative to 100% by mass of the A1 layer, and the water-soluble resin content in the B1 layer is 1% by mass Wb relative to 100% by mass of the B1 layer. t(B1) / t(A1)>1.2...Formula 1 Wb1>Wa1...Formula 2 (However, t(A1) represents the thickness of layer A1, and t(B1) represents the thickness of layer B1.)

13. An aliphatic polyester film according to claim 1 or 2, comprising at least an A1 layer constituting one outermost layer of the film, an A2 layer constituting the other outermost layer, and a B1 layer constituting an intermediate layer, wherein at least the B1 layer is a layer containing a water-soluble resin, and satisfying formulas 3 and 4 when the water-soluble resin content in the A1 layer is 1% by mass, the water-soluble resin content in the A2 layer is 2% by mass, and the water-soluble resin content in the B1 layer is 1% by mass relative to 100% by mass of the B1 layer. Wb1>Wa1...Formula 3 Wb1>Wa2...Formula 4

14. The aliphatic polyester film according to claim 12 or 13, wherein the weight-average molecular weight of the water-soluble resin contained in the B1 layer is 2,000 or more and 11,000 or less.

15. A laminate comprising a functional layer laminated on at least one side of an aliphatic polyester film according to claim 1 or 2.

16. A packaging comprising the aliphatic polyester film according to claim 1 or 2.

17. Agricultural, forestry, and fisheries material comprising the aliphatic polyester film according to claim 1 or 2.

18. An aliphatic polyester film according to claim 1 or 2, which is used for covering agricultural, forestry, and fishery materials, wherein the agricultural, forestry, and fishery materials include one or more selected from fertilizers, feed, seeds and seedlings, and pharmaceuticals.

19. Agricultural, forestry, and fishery material characterized by being coated with an aliphatic polyester film as described in claim 1 or 2.

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