Film

Abstract

A film according to the present invention contains a poly(3-hydroxyalkanoate)-based resin (A) and a polylactic acid-based resin (B). The poly(3-hydroxyalkanoate)-based resin (A) contains a poly(3-hydroxyalkanoate)-based copolymer (A-1), and the content of the poly(3-hydroxyalkanoate)-based copolymer (A-1) is from 55-85 wt% with respect to the total weight of the poly(3-hydroxyalkanoate)-based resin (A) and the polylactic acid-based resin (B). The polylactic acid-based resin (B) contains a polylactic acid-based resin (B-1) having no melting point peak in differential scanning calorimetry, and the content of the polylactic acid-based resin (B-1) is from 15-45 wt% with respect to the total weight of the poly(3-hydroxyalkanoate)-based resin (A) and the polylactic acid-based resin (B).

Description

Film

[0001] The present invention relates to a film containing a poly(3-hydroxyalkanoate) resin, which can be suitably used as a film for heat sealing.

[0002] In recent years, the separate collection and composting of food waste have been promoted mainly in Europe, and plastic products that can be composted together with food waste are desired. In addition, in order to solve the problem of marine pollution caused by plastics, plastics with marine degradability are expected.

[0003] As such a plastic material having compost degradability and marine degradability, poly(3-hydroxyalkanoate) resins typified by poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) have attracted attention.

[0004] It has been studied to use such a poly(3-hydroxyalkanoate) resin as a resin constituting a film or layer for heat sealing. For example, in Patent Document 1, in a laminate including a base material layer, a gas barrier layer, and a sealant layer, it is disclosed that the sealant layer contains poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and has a top temperature in the range of 130 to 160°C in the crystal melting curve.

[0005] Further, in Patent Document 2, in a multilayer film including a first resin layer corresponding to a base material layer and a second resin layer corresponding to a heat seal layer, each resin layer contains a poly(3-hydroxyalkanoate) resin, and it is described that the heat of fusion in the range of 130 to 190°C of each resin layer is set in a specific range.

[0006] Furthermore, although poly(3-hydroxyalkanoate) resins have not been studied, Patent Document 3 describes a biodegradable film being constructed from a biodegradable resin composition containing starch, a biodegradable resin other than a polylactic acid polymer, and an amorphous polylactic acid polymer in specific amounts. It is stated that this biodegradable film has improved moldability and mechanical properties, and excellent heat-seal properties. In this document, the amorphous polylactic acid polymer is disclosed as a component related to the biodegradation rate and the Young's modulus of the film.

[0007] International Publication No. 2022 / 244712, International Publication No. 2022 / 075233, International Publication No. 2013 / 073402

[0008] Poly(3-hydroxyalkanoate) resins are materials that crystallize more slowly than general thermoplastic resins, and require time to solidify after heating and melting, which tends to result in lower productivity in molding processes such as film forming.

[0009] On the other hand, heat sealing is a process in which films are melted and bonded under heat and pressure, and generally, higher heating temperatures result in better heat sealability. However, when a stretched resin film is used as the substrate laminated to the heat-seal layer, the substrate may shrink due to heat during heat sealing. To avoid this, it is desirable to lower the heating temperature during heat sealing (for example, to 125°C or below). Therefore, it is required that sufficient seal strength be achieved even when heat sealing is performed at such low temperatures.

[0010] The formulations used in the heat-seal layers described in Patent Documents 1 and 2 resulted in a long solidification time after heating and melting during film molding, making it difficult to sufficiently increase film productivity. Furthermore, attempts to increase productivity sometimes resulted in insufficient heat-sealability at low temperatures, making it difficult to achieve both film productivity and low-temperature heat-sealability simultaneously.

[0011] In view of the above situation, the present invention aims to provide a poly(3-hydroxyalkanoate) resin-containing film that exhibits both good film productivity and good heat sealability at low temperatures.

[0012] As a result of diligent research to solve the above problems, the inventors of the present invention have found that by blending a poly(3-hydroxyalkanoate) copolymer and a polylactic acid resin exhibiting specific physical properties in specific amounts, it is possible to achieve both the productivity of the film and heat sealability at low temperatures, thus completing the present invention.

[0013] That is, the present invention relates to a film containing a poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), wherein the poly(3-hydroxyalkanoate) resin (A) contains a poly(3-hydroxyalkanoate) copolymer (A-1), and the content of the poly(3-hydroxyalkanoate) copolymer (A-1) is 55% by weight or more and 85% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), and the polylactic acid resin (B) contains a polylactic acid resin (B-1) that does not have a melting point peak in differential scanning calorimetry, and the content of the polylactic acid resin (B-1) is 15% by weight or more and 45% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). The present invention also relates to a laminate comprising the film and a layer containing a poly(3-hydroxyalkanoate) resin (C) laminated on at least one side of the film.

[0014] According to the present invention, it is possible to provide a poly(3-hydroxyalkanoate) resin-containing film that exhibits both good film productivity and good heat sealability at low temperatures. According to the present invention, it is possible to provide a poly(3-hydroxyalkanoate) resin-containing film that can increase the production speed during film molding and exhibit sufficient seal strength even when heat-sealed at relatively low temperatures. Furthermore, according to the present invention, it is possible to provide a resin film with good biodegradability.

[0015] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below. This embodiment relates to a film containing a poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B).

[0016] [Poly(3-hydroxyalkanoate) resin (A)] Poly(3-hydroxyalkanoate) resin (A) may be a single poly(3-hydroxyalkanoate) resin or a mixture of two or more poly(3-hydroxyalkanoate) resins. However, in order to easily achieve both film strength and productivity, it is preferable that it be a mixture of at least two poly(3-hydroxyalkanoate) resins in which the types of constituent monomers and / or the content ratios of constituent monomers differ from each other.

[0017] The poly(3-hydroxyalkanoate) resin (A) is preferably a polymer having a 3-hydroxyalkanoate unit, specifically a polymer containing the unit shown in the following general formula (1): [-CHR-CH ２ -CO-O-] (1)

[0018] In general formula (1), R is C ｐ H ２ｐ＋１ R represents an alkyl group, where p is an integer from 1 to 15. Examples of R include linear or branched alkyl groups such as methyl, ethyl, propyl, methylpropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl groups. p is preferably 1 to 10, and more preferably 1 to 8.

[0019] As the poly(3-hydroxyalkanoate) resin (A), poly(3-hydroxyalkanoate) resins produced from microorganisms are particularly preferred. In poly(3-hydroxyalkanoate) resins produced from microorganisms, all 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0020] The poly(3-hydroxyalkanoate) resin (A) preferably contains 50 mol% or more of 3-hydroxyalkanoate units (particularly units represented by general formula (1)) of the total constituent units, more preferably 60 mol% or more, and even more preferably 70 mol% or more. The poly(3-hydroxyalkanoate) resin (A) may contain only one or more types of 3-hydroxyalkanoate units as constituent units of the polymer, or it may contain one or more types of 3-hydroxyalkanoate units in addition to other units (for example, 4-hydroxyalkanoate units).

[0021] The poly(3-hydroxyalkanoate) resin (A) is a concept that includes either a homopolymer or a copolymer, but the film according to this embodiment includes at least a poly(3-hydroxyalkanoate) copolymer (A-1). The film according to this embodiment may contain only the copolymer (A-1) as resin (A), or it may contain both the copolymer (A-1) and a homopolymer.

[0022] In the film according to this embodiment, the content of the poly(3-hydroxyalkanoate) copolymer (A-1) is 55% by weight or more and 85% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). By blending the copolymer (A-1) in this weight ratio, it is possible to achieve both film productivity and heat sealability at low temperatures, as well as impart good biodegradability (particularly biodegradability in compost and marine biodegradability) to the film.

[0023] From the viewpoint of improving the productivity of the film, it is preferable that the copolymer (A-1) content be low, specifically 80% by weight or less. It may also be 75% by weight or less, or 70% by weight or less. On the other hand, from the viewpoint of improving the biodegradability of the film (especially biodegradability in compost and marine biodegradability), it is preferable that the copolymer (A-1) content be high, specifically 60% by weight or more. It may also be 65% by weight or more, or 70% by weight or more.

[0024] The poly(3-hydroxyalkanoate) resin (A) is preferably a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units. In particular, it is preferable that all 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units. Furthermore, it is preferable that the poly(3-hydroxyalkanoate) resin (A) contains copolymers of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0025] Specific examples of poly(3-hydroxyalkanoate) resins (A) include, for example, poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3H Examples include poly(3-hydroxybutyrate-co-3-hydroxyheptanoate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxynonanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxybutyrate-co-3-hydroxyundecanoate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviated as P3HB4HB). In particular, from the viewpoint of film productivity and mechanical properties, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) are preferred.

[0026] Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred from the viewpoint that by changing the composition ratio of repeating units, the melting point and degree of crystallinity can be changed, thereby altering physical properties such as Young's modulus and heat resistance, and that it is possible to impart physical properties between those of polypropylene and polyethylene. Furthermore, it is easy to produce industrially and is a plastic with useful physical properties. In particular, among poly(3-hydroxyalkanoate) resins that have the property of being easily thermally decomposed when heated at 180°C or higher, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferred from the viewpoint that its melting point can be lowered, enabling molding and processing at low temperatures.

[0027] Examples of commercially available poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) include Kaneka Corporation's "Kaneka Biodegradable Polymer Green Planet" (registered trademark).

[0028] When the poly(3-hydroxyalkanoate) copolymer (A-1) contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, the average content ratio of 3-hydroxybutyrate units to other hydroxyalkanoate units in the total monomer units constituting the poly(3-hydroxyalkanoate) resin (A) is preferably 3-hydroxybutyrate units / other hydroxyalkanoate units = 99 / 1 to 80 / 20 (mol% / mol%), more preferably 97 / 3 to 82 / 18 (mol% / mol%), and even more preferably 95 / 5 to 85 / 15 (mol% / mol%), from the viewpoint of achieving both film strength and productivity.

[0029] The average content ratio of each monomer unit to the total monomer units constituting the poly(3-hydroxyalkanoate) resin (A) can be determined by a method known to those skilled in the art, for example, the method described in paragraph

[0047] of International Publication 2013 / 147139. The average content ratio means the molar ratio of each monomer unit to the total monomer units constituting the poly(3-hydroxyalkanoate) resin (A), and if the poly(3-hydroxyalkanoate) resin (A) is a mixture of two or more poly(3-hydroxyalkanoate) resins, it means the molar ratio of each monomer unit contained in the whole mixture.

[0030] As described above, the poly(3-hydroxyalkanoate) resin (A) may be a mixture of at least two poly(3-hydroxyalkanoate) resins having different types of constituent monomers and / or different content ratios of constituent monomers. In this case, at least one highly crystalline poly(3-hydroxyalkanoate) resin and at least one low-crystalline poly(3-hydroxyalkanoate) resin can be used in combination.

[0031] Generally, highly crystalline poly(3-hydroxyalkanoate) resins have excellent productivity but poor mechanical strength, while low-crystalline poly(3-hydroxyalkanoate) resins have poor productivity but excellent mechanical properties. By using both resins in combination, the strength and productivity of the film can be further improved.

[0032] The content of 3-hydroxybutyrate units in highly crystalline poly(3-hydroxyalkanoate) resins is preferably higher than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin (A). On the other hand, the content of 3-hydroxybutyrate units in low-crystalline poly(3-hydroxyalkanoate) resins is preferably lower than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin (A).

[0033] In this embodiment, the poly(3-hydroxyalkanoate) copolymer (A-1) preferably contains a copolymer (A-1-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content of other hydroxyalkanoate units is 10 mol% or more and less than 24 mol%. By using a copolymer (A-1-1) with moderate crystallinity in this way, it becomes easier to improve the heat sealability of the poly(3-hydroxyalkanoate) resin-containing film at low temperatures. Furthermore, it becomes easier to control the heat of fusion ΔH of the film at 120°C or below to a value of 2.0 J / g or more in differential scanning calorimetry.

[0034] In copolymer (A-1-1), the content of other hydroxyalkanoate units is 10 mol% or more and less than 24 mol%, but is preferably 10 to 20 mol%, more preferably 10 to 17 mol%, and even more preferably 10 to 14 mol%.

[0035] The copolymer (A-1-1) is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate), with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) being particularly preferred.

[0036] The weight-average molecular weight of the copolymer (A-1-1) is not particularly limited, but from the viewpoint of film productivity and heat sealability, it is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,500,000, and even more preferably 400,000 to 1,000,000.

[0037] The weight-average molecular weight of poly(3-hydroxyalkanoate) resins or copolymers can be measured in polystyrene equivalents using gel permeation chromatography with chloroform solution (Shimadzu HPLC GPC system). Any column suitable for measuring weight-average molecular weight should be used in the gel permeation chromatography. The same applies to the following descriptions.

[0038] In the film according to this embodiment, the content of copolymer (A-1-1) is preferably 30% by weight or more and 100% by weight or less of the total amount of poly(3-hydroxyalkanoate) resin (A) from the viewpoint of heat sealability. Within this range, the heat sealability of the poly(3-hydroxyalkanoate) resin-containing film at low temperatures can be improved. Furthermore, it becomes easier to control the heat of fusion ΔH of the film at 120°C or below in differential scanning calorimetry to a value of 2.0 J / g or more. The lower limit is preferably 40% by weight or more, and more preferably 50% by weight or more, from the viewpoint of heat sealability. The upper limit is preferably 90% by weight or less, more preferably 80% by weight or less, more preferably 70% by weight or less, and even more preferably 60% by weight or less, from the viewpoint of improving the productivity of the film and suppressing blocking between films.

[0039] In one embodiment of this product, the poly(3-hydroxyalkanoate) copolymer (A-1) may further contain, together with copolymer (A-1-1), a copolymer (A-1-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content of other hydroxyalkanoate units is 1 mol% or more and less than 10 mol%. By using such a highly crystalline copolymer (A-1-2), the productivity of the film can be further increased. It also contributes to suppressing blocking between films. This makes it possible to adopt a composition that substantially does not contain sugar alcohols, which are crystal nucleating agents.

[0040] In the copolymer (A-1-2), the content of other hydroxyalkanoate units is preferably 3 to 9 mol%, more preferably 4 to 8 mol%, and even more preferably 5 to 7 mol%.

[0041] The copolymer (A-1-2) is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate), with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) being particularly preferred.

[0042] The weight-average molecular weight of the copolymer (A-1-2) is not particularly limited, but from the viewpoints of film productivity, heat-sealability, and blocking suppression, it is preferably from 200,000 to 2,000,000, more preferably from 300,000 to 1,500,000, and still more preferably from 400,000 to 1,000,000.

[0043] When the copolymer (A-1) contains the copolymer (A-1-1) and the copolymer (A-1-2), the weight ratio (A-1-1 / A-1-2) of the copolymer (A-1-1) to the copolymer (A-1-2) is preferably from 20 / 80 to 90 / 10, more preferably from 30 / 70 to 80 / 20, and still more preferably from 40 / 60 to 70 / 30 from the viewpoints of film productivity, heat-sealability, and blocking suppression.

[0044] Further, the poly(3-hydroxyalkanoate) - based copolymer (A-1) may contain no copolymer (A-1-1) and contain only the copolymer (A-1-2). Alternatively, the poly(3-hydroxyalkanoate) - based copolymer (A-1) may contain, together with the copolymer (A-1-!) and / or the copolymer (A-1-2), a poly(3-hydroxyalkanoate) - based copolymer that does not conform to any of the definitions of the copolymer (A-1-1) and the copolymer (A-1-2).

[0045] In another aspect of this embodiment, the film may further contain a poly(3-hydroxybutyrate) resin (A-2) as the poly(3-hydroxyalkanoate) - based resin (A) in addition to the copolymer (A-1). By using the resin (A-2), the film productivity can be further increased. It also contributes to suppressing blocking between films. As a result, it becomes possible to adopt a composition in which sugar alcohols as a nucleating agent are not substantially blended and the blending amount of the polylactic acid - based resin (B) is reduced to enhance biodegradability.

[0046] The poly(3-hydroxybutyrate) resin (A-2) refers to a homopolymer of 3-hydroxybutyrate or a polymer that contains a small amount of hydroxyalkanoate units other than 3-hydroxybutyrate units in addition to 3-hydroxybutyrate units. Specifically, in the poly(3-hydroxybutyrate) resin (A-2), the content ratio of 3-hydroxybutyrate units in the total constituent monomers is preferably more than 99 mol% and 100 mol% or less.

[0047] The hydroxyalkanoate units other than 3-hydroxybutyrate units that can be contained in the poly(3-hydroxybutyrate) resin (A-2) are not particularly limited as long as they can copolymerize with 3-hydroxybutyrate units. For example, 3-hydroxyalkanoate units other than 3-hydroxybutyrate units and hydroxyalkanoate units other than 3-hydroxyalkanoate units (e.g., 4-hydroxyalkanoate units) can be mentioned. Particularly, 3-hydroxyhexanoate units are preferred.

[0048] The weight average molecular weight of the resin (A-2) is not particularly limited, but from the viewpoints of film productivity, heat sealability, and blocking suppression, it is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,500,000, and still more preferably 400,000 to 1,000,000.

[0049] From the viewpoint of improving the heat sealability of the film at low temperatures, the content of the resin (A-2) is preferably 40% by weight or less, more preferably 30% by weight or less, and still more preferably 20% by weight or less, based on the total amount of the poly(3-hydroxyalkanoate) - based resin (A). The lower limit may be 0% by weight, but from the viewpoints of improving the film productivity and suppressing blocking in a composition in which sugar alcohols as a crystal nucleating agent are not substantially blended and the blending amount of the polylactic acid - based resin (B) is reduced to enhance biodegradability, it is preferably 1% by weight or more, more preferably 3% by weight or more, still more preferably 5% by weight or more, and even more preferably 10% by weight or more.

[0050] Furthermore, from the same viewpoint as above, the content of resin (A-2) is preferably 30% by weight or less, more preferably 20% by weight or less, of the total weight of poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B). The lower limit may be 0% by weight, but is preferably 1% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, and even more preferably 10% by weight or more.

[0051] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited and may be by microbial production or by chemical synthesis. Alternatively, the blend may be obtained by melt-kneading the two or more resins using an extruder, kneader, Banbury mixer, rolls, etc., or by dissolving the two or more resins in a solvent, mixing and drying them.

[0052] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin (A) is not particularly limited, but from the viewpoint of film productivity and heat sealability, it is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,500,000, and even more preferably 400,000 to 1,000,000.

[0053] The method for producing poly(3-hydroxyalkanoate) resins is not particularly limited and may be by chemical synthesis or by microbial production. Among these, microbial production is preferred. Known methods can be applied to microbial production. For example, known microorganisms that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutropus, which produces P3HB4HB. In particular, with respect to P3HB3HH, to increase the productivity of P3HB3HH, strains such as Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)), into which genes for the P3HA synthase group have been introduced, are more preferable, and microbial cells that have accumulated P3HB3HH in their cells by culturing these microorganisms under appropriate conditions are used. In addition to the above, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes may be introduced according to the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0054] As the poly(3-hydroxyalkanoate) resin (A), an unmodified poly(3-hydroxyalkanoate) resin can be used. However, a resin obtained by modifying an unmodified poly(3-hydroxyalkanoate) resin using a raw material that reacts with the resin, such as a peroxide (hereinafter referred to as "modification raw material"), may also be used.

[0055] When using a modified resin as a film material, the modified resin obtained by reacting the resin with the modifying material beforehand may be formed into a film, or the modifying material may be mixed with the resin and reacted during film formation. Furthermore, when reacting the resin with the modifying material, the entire resin may be reacted with the modifying material, or a portion of the resin may be reacted with the modifying material to obtain a modified resin, and then the remaining unmodified resin may be added to the modified resin.

[0056] The aforementioned modification raw material is not particularly limited as long as it is a compound that can react with poly(3-hydroxyalkanoate) resins, but organic peroxides are preferably used because of their ease of handling and ease of controlling the reaction with poly(3-hydroxyalkanoate) resins. Known compounds may be used as the organic compound.

[0057] In the film according to this embodiment, the content of the poly(3-hydroxyalkanoate) resin (A) is preferably 55% to 85% by weight of the total weight of the poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B), in order to achieve both the productivity and heat sealability of the film, as well as good biodegradability (particularly biodegradability in compost and marine biodegradability). The lower limit is more preferably 60% by weight or more from the viewpoint of improving the biodegradability of the film. It may also be 65% by weight or more, or 70% by weight or more. The upper limit is preferably 80% by weight or less from the viewpoint of improving the productivity of the film. It may also be 75% by weight or less, or 70% by weight or less.

[0058] [Polylactic acid resin (B)] Polylactic acid resin (B) includes at least amorphous polylactic acid resin (B-1). Amorphous polylactic acid resin refers to one that does not have a melting point peak in the DSC curve obtained by differential scanning calorimetry. On the other hand, polylactic acid resins that have a melting point peak in differential scanning calorimetry are called crystalline polylactic acid resins. Differential scanning calorimetry can be performed by heating a differential scanning calorimeter from 0°C to 200°C at a heating rate of 10°C / min.

[0059] By blending polylactic acid resin (B) with poly(3-hydroxyalkanoate) resin (A), the molten resin material becomes less likely to adhere to the cast roll, thereby improving film productivity. However, if only crystalline polylactic acid resin is used as the polylactic acid resin, the heat sealability at low temperatures will decrease. However, by using at least amorphous polylactic acid resin (B-1) as the polylactic acid resin, it is possible to achieve both film productivity and heat sealability at low temperatures.

[0060] Polylactic acid resin (B) is a polyester having lactic acid as a constituent monomer. While polylactic acid resin (B) is preferably a homopolymer of lactic acid, it may also contain trace amounts of other monomers in addition to lactic acid.

[0061] The amorphous polylactic acid resin (B-1) is preferably a copolymer containing both L-lactic acid and D-lactic acid as repeating units, and the content of L-lactic acid and D-lactic acid is preferably less than 90 mol% each. Within this range, a polylactic acid resin without a melting point peak can be suitably constructed.

[0062] Other monomers that may be included in the polylactic acid resin (B) include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polyhydric acids, and polyfunctional polysaccharides. When the polylactic acid resin (B) is a copolymer of lactic acid and other monomers, the content of the other monomers is preferably about 0 to 3 mol%, and more preferably 0 to 2 mol%, relative to the total monomers contained in the polylactic acid resin (B).

[0063] The molecular weight of the polylactic acid resin (B) is not particularly limited and may be set as appropriate, but it is preferably 1,000 to 700,000 in number-average molecular weight, and more preferably 10,000 to 300,000 in number-average molecular weight.

[0064] The lactic acid raw material for producing polylactic acid resin (B) is not particularly limited, and L-lactic acid, D-lactic acid, DL-lactic acid, or mixtures thereof, or L-lactide, D-lactide, meso-lactide, or mixtures thereof can be used. Lactic acid obtained by microbial fermentation from plant-derived renewable raw materials such as starch can be suitably utilized. The method for producing polylactic acid resin (B) is not particularly limited and can be any known method such as dehydration condensation polymerization or ring-opening polymerization.

[0065] The film according to this embodiment may contain both amorphous polylactic acid resin (B-1) and crystalline polylactic acid resin (B-2) as the polylactic acid resin (B), or it may contain only amorphous polylactic acid resin (B-1). From the viewpoint of heat sealability, it is preferable that the proportion of amorphous polylactic acid resin (B-1) to the total polylactic acid resin (B) is high, specifically, 50% by weight or more is preferable, 70% by weight or more is more preferable, and 90% by weight or more is even preferable. It may also be 100% by weight.

[0066] In the film according to this embodiment, the content of the polylactic acid resin (B) is preferably 15% by weight or more and 45% by weight or less of the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). By blending the polylactic acid resin (B) in such a weight ratio, it is possible to achieve both the productivity of the film and heat sealability at low temperatures, as well as to impart good biodegradability (particularly biodegradability in compost and marine biodegradability) to the film.

[0067] From the viewpoint of improving the productivity of the film, a higher content of polylactic acid resin (B) is preferable, specifically 20% by weight or more. It may also be 25% by weight or more, or 30% by weight or more. On the other hand, from the viewpoint of improving the biodegradability of the film (especially biodegradability in compost and marine biodegradability), a lower content of polylactic acid resin (B) is preferable, specifically 40% by weight or less. It may also be 35% by weight or less, or 30% by weight or less.

[0068] In the film according to this embodiment, the content of amorphous polylactic acid resin (B-1) is 15% by weight or more and 45% by weight or less, relative to the total weight of poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B). By blending polylactic acid resin (B-1) in this weight ratio, it is possible to achieve both film productivity and heat sealability at low temperatures, as well as impart good biodegradability (particularly biodegradability in compost and marine biodegradability) to the film.

[0069] From the viewpoint of improving the productivity of the film and its heat-sealability at low temperatures, it is preferable that the content of amorphous polylactic acid resin (B-1) be high, specifically 20% by weight or more. It may also be 25% by weight or more, or even 30% by weight or more. On the other hand, from the viewpoint of improving the biodegradability of the film (especially biodegradability in compost and marine biodegradability), it is preferable that the content of amorphous polylactic acid resin (B-1) be low, specifically 40% by weight or less. It may also be 35% by weight or less, or even 30% by weight or less.

[0070] The film according to this embodiment is a resin film mainly composed of a poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B). The total proportion of the poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B) in the total amount of film may be 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more. It may also be 95% by weight or more, or 98% by weight or more.

[0071] (Other Resins) The film according to this embodiment may contain other resins besides the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), to the extent that the effects of the invention are not impaired. Examples of such other resins include aliphatic polyester resins such as polybutylene succinate adipate, polybutylene succinate, and polycaprolactone, and aliphatic aromatic polyester resins such as polybutylene adipate terephthalate, polybutylene sebatate terephthalate, and polybutylene azelate terephthalate. The other resin may consist of only one type or two or more types.

[0072] The content of the other resins is not particularly limited, but is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, and even more preferably 30 parts by weight or less, relative to 100 parts by weight of the total of poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B). It may also be 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less. The lower limit of the content of the other resins is not particularly limited and may be 0 parts by weight or more.

[0073] The film according to this embodiment may contain additives that can be used together with the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), to the extent that they do not impair the effects of the invention. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolites, fragrances such as vanillin and dextrin, fillers, plasticizers, antioxidants, weather-resistant modifiers, ultraviolet absorbers, crystal nucleating agents, lubricants, mold release agents, water repellents, antibacterial agents, and sliding properties modifiers. Only one type of additive may be included, or two or more types may be included. The content of these additives can be appropriately determined by those skilled in the art depending on the intended use. The crystal nucleating agents, lubricants, fillers, and plasticizers will be described in more detail below.

[0074] (Crystal Nucleating Agent) The film according to this embodiment may contain a crystal nucleating agent. Examples of crystal nucleating agents include sugar alcohols such as pentaerythritol, galactitol, and mannitol; talc; fatty acid amides; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, sugar alcohols are preferred, and pentaerythritol is particularly preferred, as they are especially effective in promoting the crystallization of the poly(3-hydroxyalkanoate) resin (A). One type of crystal nucleating agent may be used, or two or more types may be used, and the ratio of use can be appropriately adjusted depending on the purpose.

[0075] When using a nucleating agent, the amount is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.7 to 1.5 parts by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).

[0076] However, the film according to this embodiment does not need to substantially contain sugar alcohols such as pentaerythritol. Substantially not containing sugar alcohols means that the amount of sugar alcohols is less than 0.1 parts by weight per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). It may even be less than 0.01 parts by weight. In the embodiment where sugar alcohols are not substantially contained, the problem of contamination of the cast roll surface due to the bleed-out of sugar alcohols can be avoided.

[0077] When sugar alcohols are substantially omitted, it is preferable to include talc and / or fatty acid amide as crystal nucleating agents, and it is particularly preferable to include both talc and fatty acid amide. This allows for good film productivity even when sugar alcohols are substantially omitted, and further suppresses the problem of blocking, where the films stick together after being wound up. Specific examples of fatty acid amides are described in detail below as lubricants. The fatty acid amide incorporated into the film according to this embodiment can function as both a crystal nucleating agent and a lubricant.

[0078] (Lubricant) The film according to this embodiment may contain a lubricant. Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearate, ethylenebisoleamide, ethylenebiserucamide, ethylenebislaurylamide, ethylenebiscaprate, p-phenylenebisstearate, polycondensate of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide or erucamide is preferred because it has a particularly excellent lubricating effect on the poly(3-hydroxyalkanoate) resin (A). One type of lubricant may be used, or two or more types may be used, and the ratio of use can be appropriately adjusted depending on the purpose.

[0079] When a lubricant is used, the amount used is not particularly limited, but preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 1.5 parts by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). The film according to this embodiment preferably contains a lubricant, but may not contain one.

[0080] (Filler) The film according to this embodiment may contain a filler. Including a filler can result in a film with higher strength. The filler may be either an inorganic filler or an organic filler, or both may be used in combination. The inorganic filler is not particularly limited, but examples include silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, carbon black, etc. Only one type of inorganic filler may be used, or two or more types may be used in combination.

[0081] When the filler is used, its content is not particularly limited, but is preferably 1 to 100 parts by weight, more preferably 3 to 80 parts by weight, even more preferably 5 to 70 parts by weight, and still more preferably 10 to 60 parts by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). However, the film according to this embodiment may not contain the filler substantially. Substantially not containing the filler means that the amount of filler added is less than 1 part by weight per 100 parts by weight of the total of the resin (A) and the resin (B). It may even be less than 0.1 parts by weight.

[0082] (Plasticizer) The film according to this embodiment may contain a plasticizer. Examples of plasticizers include glycerin ester compounds, citrate ester compounds, sebacate ester compounds, adipate ester compounds, polyether ester compounds, benzoate ester compounds, phthalate ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds. Among these, glycerin ester compounds, citrate ester compounds, sebacate ester compounds, and dibasic acid ester compounds are preferred because they have a particularly excellent plasticizing effect on the poly(3-hydroxyalkanoate) resin (A). Examples of glycerin ester compounds include glycerin diacetomolaurate. Examples of citrate ester compounds include tributyl acetylcitrate. Examples of sebacate ester compounds include dibutyl sebacate. Examples of dibasic acid ester compounds include benzylmethyldiethylene glycol adipate. One type of plasticizer may be used, or two or more types may be used, and the ratio of use can be adjusted as appropriate depending on the purpose.

[0083] When a plasticizer is used, the amount used is not particularly limited, but preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 10 parts by weight, per 100 parts by weight of the total of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). However, the film according to this embodiment may not contain a plasticizer substantially. Substantially not containing a plasticizer means that the amount of plasticizer added is less than 1 part by weight per 100 parts by weight of the total of the resin (A) and the resin (B). It may even be less than 0.1 parts by weight.

[0084] [Film] The film according to this embodiment may be an unstretched film that has not undergone stretching treatment, or a stretched film that has undergone stretching treatment in the MD direction and / or TD direction after film formation. The term "film" as used in this application may include both unstretched films and stretched films. From the viewpoint of strength, a stretched film is preferred.

[0085] In this embodiment, it is preferable that the film has a melting heat ΔH of 2.0 J / g or more at 120°C or below, as measured by differential scanning calorimetry. This makes it possible to achieve sufficient seal strength even when heat sealing is performed at relatively low temperatures (for example, 125°C or below).

[0086] The heat of fusion ΔH of the film at 120°C or below is more preferably 2.5 J / g or more, even more preferably 3.0 J / g or more, and even more preferably 3.5 J / g or more. There is no particular upper limit, but from the viewpoint of film productivity, it is preferably 15 J / g or less, more preferably 10 J / g or less, and even more preferably 5 J / g or less.

[0087] A film exhibiting a melting heat ΔH of 2.0 J / g or more below 120°C can be obtained by adjusting the composition of the resin components contained in the film, particularly the poly(3-hydroxyalkanoate) resin (A). In particular, by using the copolymer (A-1-1) described above and adjusting its blending amount, it becomes easy to control the melting heat ΔH of the film below 120°C to a value of 2.0 J / g or more.

[0088] Furthermore, it is preferable that the film according to this embodiment satisfies the condition that the ratio of the heat of fusion ΔH at 120°C or below to the total heat of fusion ΔH (total) measured in differential scanning calorimetry for the film is 8% or more and 50% or less. Within this range, it is easier to achieve both the productivity of the film and heat sealability at low temperatures. The upper limit of the ratio is more preferably 40% or less, even more preferably 30% or less, and particularly preferably 25% or less. The lower limit is preferably 10% or more, more preferably 12% or more, and even more preferably 14% or more.

[0089] Differential scanning calorimetry (DSC) analysis of a film can be performed by heating the film from 0°C to 200°C at a heating rate of 10°C / min using a differential scanning calorimeter. In the DSC curve obtained, a straight line is drawn connecting the baseline before the start of melting and the baseline after the end of melting. The area of ​​the region below 120°C within the region enclosed by this line and the DSC curve is calculated as the heat of fusion ΔH of the film below 120°C. Furthermore, the area of ​​the region enclosed by the line and the DSC curve is calculated as the total heat of fusion ΔH (overall) of the film.

[0090] The thickness of the film (especially the stretched film) according to this embodiment is preferably 10 to 200 μm, more preferably 15 to 150 μm, and even more preferably 20 to 100 μm, from the viewpoint of uniform film thickness, appearance, strength, and lightness.

[0091] Furthermore, the film according to this embodiment is preferably a long film produced industrially, and is particularly preferably a strip-shaped film wound into a roll. The length of such a film is not particularly limited, but for example, it may be 50 m or more, or 100 m or more. In this embodiment, such a long film can be manufactured continuously and stably.

[0092] [Method for Manufacturing Film] Next, an example of a method for manufacturing the film according to this embodiment will be described, but the present invention is not limited to the following description. First, a film raw material containing a poly(3-hydroxyalkanoate) resin (A), a polylactic acid resin (B), and other components as needed is melted.

[0093] The method of melting is not particularly limited, but it is preferable to extrude the molten film material from a T-die, i.e., to perform an extrusion molding method. Using the extrusion molding method, a film with a uniform thickness can be easily manufactured. For extrusion molding, a single-screw extruder, a twin-screw extruder, or the like can be used as appropriate.

[0094] The conditions for melting the film raw materials are as long as they allow the poly(3-hydroxyalkanoate) resin (A) and polylactic acid resin (B) to melt, but the temperature of the molten film raw materials should be, for example, around 140 to 210°C.

[0095] Next, the molten film material is extruded onto a cast roll to form a film. The molten film material comes into contact with the cast roll and moves along its surface, where it cools and solidifies.

[0096] The process may involve extruding the molten material onto one or more cast rolls, or it may involve placing a touch roll opposite the cast rolls and sandwiching the molten material extruded onto the cast rolls between the touch rolls. Furthermore, an air knife or air chamber may be used to ensure stable contact between the molten material and the cast rolls. To efficiently cool the opposite side of the contact surface with the cast rolls, the cast rolls may be placed in a water tank or an air chamber may be used.

[0097] The lower limit of the set temperature for the cast roll is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher, in order to suppress the tackiness of the poly(3-hydroxyalkanoate) resin (A) and improve its release from the cast roll. Furthermore, it is preferable that the temperature exceeds the glass transition temperature (Tg) of the poly(3-hydroxyalkanoate) resin (A) + 10°C.

[0098] The upper limit of the set temperature for the cast roll is not particularly limited, but from the viewpoint of promoting the solidification of the poly(3-hydroxyalkanoate) resin (A), it is preferably 80°C or lower, and more preferably 60°C or lower.

[0099] Next, the film cooled on the cast roll is peeled off the cast roll by transporting it while the cast roll rotates. This allows an unstretched film to be obtained.

[0100] Next, by stretching the obtained film in the MD direction, a uniaxially oriented film with high strength in the MD direction can be obtained. The MD direction is also called the machine direction, flow direction, or length direction. The TD direction, which will be described later, is the direction perpendicular to the MD direction, and is also called the vertical direction or width direction.

[0101] The stretching process in the MD direction can be carried out continuously from peeling off the cast rolls within a single production line. This process is not particularly limited, but can be carried out, for example, by using a roll longitudinal stretcher and varying the rotational speed of the rolls that transport the film.

[0102] The stretching process in the MD direction is preferably carried out while heating the film. The heating method is not particularly limited, but examples include applying an airflow adjusted to a predetermined temperature to the film, controlling the film temperature by setting a roll to a predetermined temperature, using an auxiliary heating means such as an IR heater to heat the film and control the film temperature to a predetermined temperature, and passing the film through an oven that has been temperature-controlled to a predetermined temperature. These may be used individually or in combination.

[0103] In the production of the film according to this embodiment, the temperature during stretching in the MD direction is preferably 35°C or higher, more preferably 45°C or higher, and even more preferably 55°C or higher. Since the film according to this embodiment contains amorphous polylactic acid resin (B-1), it softens easily even at temperatures below the melting point of poly(3-hydroxyalkanoate) resin, enabling good stretching. Furthermore, the temperature is easy to control and stabilize. Therefore, the film can be stretched continuously and stably, and long stretched films can be produced stably.

[0104] Furthermore, while there is no particular upper limit to the temperature during stretching in the MD direction, from the viewpoint of avoiding film breakage during stretching, it is preferably 110°C or lower, preferably 100°C or lower, and more preferably 90°C or lower.

[0105] The stretching ratio in the MD direction is not particularly limited, but is preferably 2 times or more. More preferably 2.5 times or more, and even more preferably 3 times or more. According to the composition of the film raw material in this embodiment, such a high stretching ratio can be achieved. The upper limit of the stretching ratio is not particularly limited and can be determined as appropriate, but for example, it may be 8 times or less.

[0106] Next, by stretching in the MD direction followed by stretching in the TD direction, a biaxially oriented film with high strength in both the MD and TD directions can be obtained. The stretching process in the TD direction can be carried out continuously from the stretching process in the MD direction within a single production line. This process is not particularly limited, but for example, it can be carried out by clamping both ends of the film in the width direction using a transverse stretching machine such as a clip-type tenter and pulling it in the TD direction.

[0107] The stretching process in the TD direction is also preferably carried out while heating the film. The heating method is not particularly limited, and the method described above for the stretching process in the MD direction is an example.

[0108] The temperature during stretching in the TD direction may be the same as the temperature during stretching in the MD direction described above, preferably 35 to 110°C, preferably 45 to 100°C, and more preferably 55 to 90°C.

[0109] The stretching ratio in the TD direction is not particularly limited, but is preferably 2 times or more. More preferably 3 times or more, and even more preferably 4 times or more. According to the composition of the film raw material in this embodiment, such a high stretching ratio can be achieved. The upper limit of the stretching ratio is not particularly limited and can be determined as appropriate, but for example, it may be 8 times or less.

[0110] After the stretching process in the MD direction or the TD direction, it is preferable to perform a heat setting process in which the stretched film is heated to a temperature at which high-melting-point crystals grow. This increases the degree of crystallinity of the stretched film, enhances its strength, and stabilizes its physical properties.

[0111] The heating temperature during heat setting is preferably 80 to 150°C, more preferably 90 to 135°C, and most preferably 100 to 130°C. If the heating temperature is 80°C or higher, the degree of crystallinity of the stretched film increases, and the formed crystals may have a high melting point. If the heating temperature is 150°C or lower, breakage due to melting of the film can be avoided.

[0112] This heating can be carried out, for example, by stretching the material in the TD direction using a transverse stretcher such as a clip-type tenter, and then heating it while maintaining the stretched state. At this time, thermal shrinkage occurs in the opposite direction to the stretching direction, so it is preferable to relieve the tension to prevent breakage. Relief is the operation of releasing the tension in the opposite direction to the stretching direction, and it is preferable to adjust the amount of relief appropriately between 5% and 30%.

[0113] After this, a cooling step of the film may be carried out as appropriate. After this, it is preferable to carry out a step of winding the film onto a winding roll.

[0114] In this embodiment, the film manufacturing method is preferably carried out while continuously transporting the film from melt extrusion to the final process. This makes it possible to manufacture the film with high productivity using an industrially simple process. The manufacturing method in this embodiment can be carried out while continuously winding the manufactured film on a winding roll.

[0115] When continuously transporting film, the transport speed is not particularly limited, but from the viewpoint of film productivity, it is preferable that it be 5 m / min or more before the start of stretching. Also, from the viewpoint of production stability, it is preferable that it be 50 m / min or less before the start of stretching.

[0116] [Laminate] The film according to this embodiment may be a resin film composed of independent single layers, but it can also be a laminate formed by laminating other layers on one or both sides of the film. Such a laminate also constitutes one aspect of the present invention. Examples of the other layers include resin layers, inorganic layers, metal layers, metal oxide layers, and printed layers. These other layers may be laminate layers, coating layers, or vapor-deposited layers.

[0117] The resin layer, which is one form of another layer in the laminate, is not particularly limited, but from the viewpoint of improving the biodegradability of the entire laminate, it is preferable that the layer contains a poly(3-hydroxyalkanoate) resin (C). As the poly(3-hydroxyalkanoate) resin (C), the above-mentioned poly(3-hydroxyalkanoate) resin (A) can be used as appropriate, but is not particularly limited. The components other than the poly(3-hydroxyalkanoate) resin (C) are not particularly limited, and known components can be used as appropriate as additives to the resin layer.

[0118] Such a resin layer can function as a base layer for the film according to this embodiment. Furthermore, it is preferable that the resin layer is a stretched layer in order to ensure strength.

[0119] When a laminate comprising the film according to this embodiment and a base layer composed of a stretched film containing a poly(3-hydroxyalkanoate) resin (C) is heat-sealed at a relatively high temperature (e.g., 130°C or higher), the base layer is prone to thermal shrinkage. However, since the film according to this embodiment exhibits good heat-sealability even at relatively low temperatures (e.g., 125°C or lower), thermal shrinkage of the base layer due to heat sealing can be avoided by performing the heat-sealing at such low temperatures.

[0120] [Applications of the film] The film according to this embodiment can be suitably used as a heat-sealing film. In particular, it can be suitably used as a packaging material for applications in which heat sealing is performed. Furthermore, the film may be in the form of a molded body (for example, various bags) that includes a portion fused by heat sealing.

[0121] Such molded products are not particularly limited, but examples include side-seal packaging, three-side-seal packaging, pillow packaging, standing pouches, and other packaging bags. More specifically, examples include shopping bags, various types of bags, food and confectionery packaging materials, cups, trays, cartons, and other various packaging container materials.

[0122] The heating temperature during heat sealing is not particularly limited and may be, for example, in the range of 100 to 200°C. However, since the film according to this embodiment exhibits good heat sealability even at relatively low temperatures, heat sealing can be performed at temperatures such as 125°C or lower, preferably 120°C or lower, and more preferably 115°C or lower.

[0123] The heat sealing described above is preferably performed between the films according to this embodiment, but may also be performed between the film according to this embodiment and other layers.

[0124] The following sections list preferred embodiments of this disclosure, but the present invention is not limited to these sections. [Item 1] A film containing a poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), wherein the poly(3-hydroxyalkanoate) resin (A) contains a poly(3-hydroxyalkanoate) copolymer (A-1), and the content of the poly(3-hydroxyalkanoate) copolymer (A-1) is 55% by weight or more and 85% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), and the polylactic acid resin (B) contains a polylactic acid resin (B-1) that does not have a melting point peak in differential scanning calorimetry, and the content of the polylactic acid resin (B-1) is 15% by weight or more and 45% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). [Item 2] The film according to Item 1, wherein the heat of fusion ΔH at 120°C or below in differential scanning calorimetry of the film is 2.0 J / g or more. [Item 3] The film according to Item 1 or 2, wherein the poly(3-hydroxyalkanoate) copolymer (A-1) comprises a copolymer (A-1-1) of 3-hydrokybtyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 10 mol% or more and less than 24 mol%. [Item 4] The film according to any one of Items 1 to 3, wherein the poly(3-hydroxyalkanoate) copolymer (A-1) comprises a copolymer (A-1-2) of 3-hydrokybtyrate units and other hydroxyalkanoate units, in which the content of other hydroxyalkanoate units is 1 mol% or more and less than 10 mol%. [Item 5] A film according to any one of Items 1 to 4, wherein the poly(3-hydroxyalkanoate) resin (A) further comprises a poly(3-hydroxybutyrate) resin (A-2). [Item 6] A film according to any one of Items 3 to 5, wherein the other hydroxyalkanoate units include 3-hydroxyhexanoate units. [Item 7] A film according to any one of Items 1 to 6, which is substantially free of sugar alcohols. [Item 8] A film according to any one of Items 1 to 7, which further comprises talc and / or fatty acid amide.[Item 9] A film according to any one of Items 1 to 8, wherein the film is a heat-sealable film. [Item 10] A film according to any one of Items 1 to 9, wherein the film is a stretched film. [Item 11] A laminate comprising a film according to any one of Items 1 to 10 and a layer containing a poly(3-hydroxyalkanoate) resin (C) laminated on at least one side of the film.

[0125] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way to these examples.

[0126] In each example and comparative example, the following raw materials were used. (Poly(3-hydroxyalkanoate) resin (A)) As the P3HA copolymer (A-1), the following poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH) resins PHBH-1 to PHBH-4 were used. In addition, as the P3HB resin (A-2), poly(3-hydroxybutyrate) (P3HB) resin was used. 3HB represents the 3-hydroxybutyrate repeating unit, and 3HH represents the 3-hydroxyhexanoate repeating unit. PHBH-1: P3HB3HH (average content ratio 3HB / 3HH = 94 / 11 (mol% / mol%, weight-average molecular weight is 790,000 g / mol)) Manufactured according to the method described in Example (Raw Material A-3) of International Publication No. 2013 / 147139. PHBH-2: P3HB3HH (average content ratio 3HB / 3HH = 97.2 / 2.8 (mol% / mol%), weight-average molecular weight is 660,000 g / mol) Manufactured according to the method described in Example 2 of International Publication No. 2019 / 142845. PHBH-3: P3HB3HH (average content ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight-average molecular weight is 600,000 g / mol) Manufactured according to the method described in Example 1 of International Publication No. 2019 / 142845. PHBH-4: P3HB3HH (average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight-average molecular weight is 660,000 g / mol) Manufactured according to the method described in Example 9 of International Publication No. 2019 / 142845. PHBH-5: P3HB3HH (average content ratio 3HB / 3HH = 91 / 9 (mol% / mol%), weight-average molecular weight is 660,000 g / mol) Manufactured according to the method described in Example 5 of International Publication No. 2019 / 142845. PHB: Poly(3-hydroxybutyrate) (weight-average molecular weight is 300,000 g / mol) Manufactured according to the method described in Comparative Example 1 of International Publication No. 2004 / 041936.

[0127] (Polylactic acid resin) B-1: PLA (4060D grade, manufactured by Natureworks, no melting point peak) B-2: PLA (LX175 grade, manufactured by Total Corbion PLA, melting point peak temperature is 155°C)

[0128] (Crystal nucleating agent) C-1: Pentaerythritol (manufactured by Mitsubishi Chemical Corporation, Neulizer P)

[0129] (Lubricants) D-1: Behenamide (manufactured by Nippon Seika Co., Ltd.: BNT-22H) D-2: Erucamide (manufactured by Nippon Seika Co., Ltd.: Neutron-S)

[0130] (Inorganic filler) E-1: Talc [Manufactured by Nippon Talc, Microace® K-1]

[0131] The following evaluations were performed in each example and comparative example. [Measurement of Melting Point Peak Temperature (Crystal Melting Temperature: Tm) of Polylactic Acid Resin] The melting point peak temperature of the polylactic acid resin was measured by differential scanning calorimetry (DSC measurement). For differential scanning calorimetry, approximately 5 mg of the polylactic acid resin to be measured was accurately weighed, and the temperature was increased from 0°C to 200°C at a heating rate of 10°C / min using a differential scanning calorimeter (SSC5200, manufactured by Seiko Electronics Industries, Ltd.) to obtain a DSC curve. From the obtained DSC curve, the peak top temperature of the crystal melting peak was defined as the melting point peak temperature (Tm).

[0132] [Measurement of the heat of fusion of the film] Differential scanning calorimetry was performed on the films obtained in each example or comparative example as samples, in the same manner as described above, to obtain DSC curves. In the DSC curve, a straight line was drawn connecting the baseline before the start of melting and the baseline after the end of melting. The area of ​​the region enclosed by this straight line and the DSC curve was defined as the total heat of fusion of the film ΔH (total) (J / g), and the area of ​​the portion within the region below 120°C was defined as the heat of fusion of the film below 120°C ΔH (below 120°C) (J / g).

[0133] [T-die film moldability] (Roll contamination) Each resin composition was melted at 165°C in a single-screw extruder with a screw diameter of 20 mm, and the T-die film was obtained by taking the film from a die with a lip width of 250 μm at a cast roll (CR) temperature of 40 to 60°C at the molding speeds listed in Table 1. At that time, the roll contamination was evaluated according to the following evaluation criteria.

[0134] <Evaluation Criteria> ○: Visual inspection of the cast roll surface after 1 hour of continuous operation did not reveal the boundary between the film contact area and the non-contact area. ×: Visual inspection of the cast roll surface after 1 hour of continuous operation revealed the boundary between the film contact area and the non-contact area.

[0135] [Blocking properties] After winding the obtained T-die film into a roll, the condition of the film when unwinding it after 30 minutes was observed, and the blocking properties were evaluated according to the following evaluation criteria.

[0136] <Evaluation Criteria> ○: Can be peeled off without resistance △: Can be peeled off with some resistance ×: The films are stuck together and cannot be peeled off

[0137] [Heat sealability] Two strips 25 mm wide were cut from the obtained film, and the films were brought into contact with each other and pressed at a pressure of 2 kgf / cm². ２ The specimens were heat-sealed under pressure for 0.5 seconds at a temperature of 90°C. This process was repeated at temperatures ranging from 90°C to 140°C in 5°C increments. To measure the heat-seal strength of each specimen, an autograph was used to grasp both sides of the film with a chuck, and the peeled area was visually observed after 180° peeling to confirm whether the film had peeled with fracture. The SIT (Seal Integrity Test) value, obtained by subtracting 5°C from the lowest temperature at which the film peeled with fracture, is shown in Table 1. Furthermore, the heat-sealability was evaluated based on the following evaluation criteria using the SIT.

[0138] <Evaluation Criteria> ○: SIT is 120°C or lower △: SIT is 125°C or lower ×: SIT is 130°C or higher

[0139] [Biodegradability] The degree of biodegradability was calculated as the ratio of biological oxygen demand (BOD) to theoretical oxygen demand (ThOD) and evaluated according to the following evaluation criteria. Specifically, regarding home compostability, biodegradation tests were conducted at 28±2℃ in accordance with ISO 14855-1 (28±2℃) and JIS K 6953-1, and the degree of biodegradability was determined as the ratio of carbon dioxide generated to theoretically generated carbon dioxide.

[0140] <Evaluation Criteria> ○○○: BOD 75% or higher ○○: BOD 70% or higher but less than 75% ○: BOD 65% or higher but less than 70% △: Less than 65%

[0141] (Example 1) (Method for producing the resin composition) 100 parts by weight of poly(3-hydroxyalkanoate) resin PHBH-1 was dry-blended with 1.0 part by weight of C-1 as a crystal nucleating agent, and 0.5 parts by weight of D-1 and 0.5 parts by weight of D-2 as lubricants. The obtained resin material was put into a φ26 mm co-screw extruder hopper with the cylinder temperature and die temperature set to 150°C, melt-kneaded, extruded in strand form from the die, passed through a water bath filled with 45°C water to solidify the strand, and cut with a pelletizer to obtain resin pellets P-1.

[0142] (Manufacturing of biaxially oriented film in MD and TD directions) Furthermore, the resin pellets P-1 and B-1 were fed into a single-screw extruder in a weight ratio of 60:40 and extruded into a film shape using a T-die. The formed film was cooled on a cooling roll at a set temperature of 50°C, then taken up by a take-up roll, and continuously stretched three times in the MD direction at 60-70°C using a roll longitudinal stretcher. Then, continuously stretched five times in the TD direction at a stretching temperature of 70-80°C using a clip-type tenter transverse stretcher, and subsequently heated to 130°C while gradually reducing the stretch by 15% to heat-set the film. The biaxially oriented film was cooled to 50°C, and the widthwise ends were slit to obtain a biaxially oriented film with a width of 1200 mm and a thickness of 20 μm. The above process was carried out continuously. Roll contamination was evaluated after 1 hour of continuous operation from the start of T-die film production. Furthermore, the ΔH of the obtained stretched film was measured, and its blocking properties, heat sealability, and biodegradability were evaluated. The evaluation results are shown in Table 1.

[0143] (Examples 2-9) Biaxially oriented films were manufactured in the same manner as in Example 1, except that the formulation was changed as shown in Table 1. ΔH was measured, and roll contamination, blocking properties, heat sealability, and biodegradability were evaluated. The evaluation results are shown in Table 1.

[0144] (Comparative Examples 1-6) Biaxially oriented films were manufactured in the same manner as in Example 1, except that the formulation was changed as shown in Table 1. ΔH was measured, and roll contamination, blocking properties, heat sealability, and biodegradability were evaluated. The evaluation results are shown in Table 1.

[0145] In Examples 1-9 and Comparative Examples 1, 3-5, film molding could be performed even at a molding speed of 18.5 m / min without the resin material adhering to the cast roll. However, in Comparative Examples 2 and 6, the molten resin material tended to adhere to the cast roll, and the molding speed could only be increased to 2 m / min or 8 m / min.

[0146]

[0147] Table 1 shows that the films obtained in Examples 1 to 9 allowed for a molding speed of up to 18.5 m / min, demonstrating good productivity, as well as low SIT (Stock Integrity) and good heat sealability at low temperatures.

[0148] On the other hand, in Comparative Examples 1, 4, and 5, the content of poly(3-hydroxyalkanoate) copolymer (A-1) was low, resulting in high SIT and insufficient heat sealability at low temperatures. In Comparative Examples 2 and 6, the molding speed could not be sufficiently increased because the polylactic acid resin (B) was not included, or the content of amorphous polylactic acid (B-1) was low, resulting in insufficient film productivity. In Comparative Example 3, amorphous polylactic acid (B-1) was not used as the polylactic acid resin (B), but instead crystalline polylactic acid (LX175) with a melting point peak was used, resulting in high SIT and insufficient heat sealability at low temperatures.

Claims

1. A film containing a poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), wherein the poly(3-hydroxyalkanoate) resin (A) contains a poly(3-hydroxyalkanoate) copolymer (A-1), and the content of the poly(3-hydroxyalkanoate) copolymer (A-1) is 55% by weight or more and 85% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), and the polylactic acid resin (B) contains a polylactic acid resin (B-1) that does not have a melting point peak in differential scanning calorimetry, and the content of the polylactic acid resin (B-1) is 15% by weight or more and 45% by weight or less based on the total weight of the poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).

2. The film according to claim 1, wherein the heat of fusion ΔH of the film at 120°C or below, as determined by differential scanning calorimetry, is 2.0 J / g or more.

3. The film according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) copolymer (A-1) comprises a copolymer (A-1-1) of a 3-hydrokybtyrate unit and other hydroxyalkanoate units, wherein the content of other hydroxyalkanoate units is 10 mol% or more and less than 24 mol%.

4. The film according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) copolymer (A-1) comprises a copolymer (A-1-2) of a 3-hydrokibutyrate unit and other hydroxyalkanoate units, wherein the content of other hydroxyalkanoate units is 1 mol% or more and less than 10 mol%.

5. The film according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) resin (A) further comprises a poly(3-hydroxybutyrate) resin (A-2).

6. The film according to claim 3, wherein the other hydroxyalkanoate unit includes a 3-hydroxyhexanoate unit.

7. The film according to claim 1 or 2, which is substantially free of sugar alcohols.

8. The film according to claim 1 or 2, further comprising talc and / or a fatty acid amide.

9. The film according to claim 1 or 2, wherein the film is a heat-sealable film.

10. The film according to claim 1 or 2, wherein the film is a stretched film.

11. A laminate comprising a film according to claim 1 or 2, and a layer containing a poly(3-hydroxyalkanoate) resin (C) laminated on at least one side of the film.

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