Film

Abstract

A film according to the present invention contains a modified poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), wherein the modified poly(3-hydroxyalkanoate) resin (A) is the reaction product of a poly(3-hydroxyalkanoate) resin (a) and an organic peroxide. The polylactic acid resin (B) content is preferably 10-50 wt% with respect to the total weight of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).

Description

film

[0001] The present invention relates to a film containing a poly(3-hydroxyalkanoate)-based resin.

[0002] In recent years, the separate collection and composting of food waste has been promoted, particularly in Europe, and there is a demand for plastic products that can be composted together with food waste. Furthermore, there are hopes for marine-degradable plastics to solve the problem of marine pollution caused by plastics.

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

[0004]

[0003] Meanwhile, a method of stretching a film is known as a technique for producing a thin, high-strength film. For example, to produce a stretched film from a general-purpose resin such as polypropylene, a molten resin is cooled and solidified using a cast roll to form a raw sheet, and the raw sheet is then preheated to a temperature at which it can be stretched, and then stretched, thereby enabling continuous production of a stretched film with good productivity.

[0005] However, poly(3-hydroxyalkanoate) resins are known to be difficult to stretch due to their properties, and therefore various techniques have been investigated for producing stretched films containing poly(3-hydroxyalkanoate) resins with good productivity.

[0006] For example, Patent Document 1 describes a method for efficiently producing a biaxially stretched film by melting a film raw material containing a poly(3-hydroxybutyrate) resin in an extruder, forming the film into a film, and then continuously stretching the film in both the MD and TD directions at a stretching ratio of 1.1 or more.

[0007] Furthermore, Patent Document 2 describes a method for producing a stretched film by melting a film raw material containing a poly(3-hydroxybutyrate) resin, extruding it onto a casting roll, peeling the film from the casting roll under conditions where the film temperature is 0 to 50° C., and then stretching the film in the MD direction under conditions where the film temperature is 10 to 65° C. This method controls the crystallinity of the poly(3-hydroxybutyrate) resin to a relatively low level by controlling the film temperature to a relatively low temperature, thereby realizing stretching at a high ratio.

[0008] JP 2022-62759 A JP 2023-73820 A

[0009] According to the method described in Patent Document 1, a biaxially stretched film containing a poly(3-hydroxybutyrate)-based resin can be produced, but the stretching ratio achieved in the examples was limited to about 1.5 to 1.6 times.

[0010] Furthermore, according to the method described in Patent Document 2, a high stretch ratio is achieved by controlling the temperature conditions during the production of the stretched film, but the film temperature during production needs to be controlled to a relatively low temperature around room temperature, and it is difficult to stabilize the production environment in such a temperature range, which makes it difficult to stably carry out continuous production of the stretched film.

[0011] As described above, Patent Documents 1 and 2 describe stretching a film containing a poly(3-hydroxyalkanoate) resin by controlling the production conditions of the stretched film, but have not fully investigated how to improve stretchability by changing the composition of the film raw material containing the poly(3-hydroxyalkanoate) resin.

[0012] In view of the above-mentioned current situation, an object of the present invention is to provide a poly(3-hydroxyalkanoate) resin-containing film having improved stretchability.

[0013] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors discovered that the stretchability of a film can be greatly improved by blending a polylactic acid resin with a modified resin obtained by reacting a poly(3-hydroxyalkanoate) resin with an organic peroxide, and thereby completing the present invention.

[0014] Specifically, the present invention relates to a film containing a modified poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), wherein the modified poly(3-hydroxyalkanoate) resin (A) is a reaction product of the poly(3-hydroxyalkanoate) resin (a) and an organic peroxide. 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.

[0015] According to the present invention, it is possible to provide a poly(3-hydroxyalkanoate)-based resin-containing film with improved stretchability. According to the present invention, stretchability can be improved by adjusting the composition of the film raw materials. Therefore, there is no need to employ the specific temperature conditions described in Patent Document 2, and film stretching can be carried out even under temperature conditions that are easier to control and stabilize than the temperature conditions described in Patent Document 2. Therefore, it is possible to continuously and stably stretch a poly(3-hydroxyalkanoate)-based resin-containing film. As a result, the quality of the stretched film can be stabilized, and in particular, long stretched films can be stably produced. Furthermore, a high stretching ratio can be achieved. According to a preferred embodiment of the present invention, a uniaxially stretched film stretched in the MD direction or a biaxially stretched film stretched in both the MD and TD directions can be produced, and a high stretching ratio can be achieved in each direction.

[0016] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment. The present embodiment relates to a film containing a modified poly(3-hydroxyalkanoate)-based resin (A) and a polylactic acid-based resin (B).

[0017] [Modified Poly(3-hydroxyalkanoate) Resin (A)] The modified poly(3-hydroxyalkanoate) resin (A) refers to a reaction product of the poly(3-hydroxyalkanoate) resin (a) and an organic peroxide. The reaction product is a modified resin in which a crosslinked structure has been introduced into the poly(3-hydroxyalkanoate) resin by the reaction with the organic peroxide. The stretchability of the poly(3-hydroxyalkanoate) resin-containing film can be improved by using a modified poly(3-hydroxyalkanoate) resin having a crosslinked structure in combination with the polylactic acid resin (B).

[0018] [Poly(3-hydroxyalkanoate)-based resin (a)] The poly(3-hydroxyalkanoate)-based resin (a) refers to a poly(3-hydroxyalkanoate)-based resin before being reacted with an organic peroxide. The poly(3-hydroxyalkanoate)-based resin (a) may be a single poly(3-hydroxyalkanoate)-based resin or a mixture of two or more poly(3-hydroxyalkanoate)-based resins. However, in order to easily achieve both film strength and stretchability, a mixture of at least two poly(3-hydroxyalkanoate)-based resins that differ from each other in the type of constituent monomer and / or the content ratio of the constituent monomer is preferred.

[0019] The poly(3-hydroxyalkanoate) resin (a) is preferably a polymer having a 3-hydroxyalkanoate unit, specifically a polymer containing a unit represented by the following general formula (1): [—CHR—CH ２ -CO-O-] (1)

[0020] In the general formula (1), R is C ｐ H ２ｐ＋１ where p is an integer of 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. p is preferably an integer of 1 to 10, and more preferably an integer of 1 to 8.

[0021] As the poly(3-hydroxyalkanoate) resin (a), a poly(3-hydroxyalkanoate) resin produced by a microorganism is particularly preferred. In the poly(3-hydroxyalkanoate) resin produced by a microorganism, all of the 3-hydroxyalkanoate units are contained as (R)-3-hydroxyalkanoate units.

[0022] The poly(3-hydroxyalkanoate) resin (a) preferably contains 3-hydroxyalkanoate units (particularly units represented by general formula (1)) in an amount of 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more of the total structural units. The poly(3-hydroxyalkanoate) resin (a) may contain only one or more types of 3-hydroxyalkanoate units as structural units of the polymer, or may contain one or more types of 3-hydroxyalkanoate units as well as other units (e.g., 4-hydroxyalkanoate units).

[0023] The poly(3-hydroxyalkanoate) resin (a) is preferably a homopolymer or copolymer containing 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) units (hereinafter, both polymers are collectively referred to as "poly(3-hydroxybutyrate) resin"). In particular, it is preferable that all of the 3-hydroxybutyrate units are (R)-3-hydroxybutyrate units. Furthermore, the poly(3-hydroxyalkanoate) resin (a) preferably contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0024] Specific examples of poly(3-hydroxybutyrate)-based resins include 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), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: P3HB3HH), Examples of such polyhydroxybutyrate 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) (abbreviation: P3HB4HB). In particular, from the viewpoints of film stretchability and mechanical properties, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred.

[0025] Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred from the viewpoints that changing the composition ratio of the repeating units can change the melting point, degree of crystallinity, and physical properties such as Young's modulus and heat resistance, making it possible to impart physical properties between those of polypropylene and polyethylene, and that it is easy to produce industrially and is a physically useful plastic. In particular, among poly(3-hydroxybutyrate)-based resins that tend to be thermally decomposed when heated to 180°C or higher, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is preferred from the viewpoints that it can lower the melting point and enable molding and processing at low temperatures.

[0026] Commercially available poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) products include Kaneka Biodegradable Polymer Green Planet (registered trademark) manufactured by Kaneka Corporation.

[0027] When the poly(3-hydroxyalkanoate) resin (a) contains a copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, the average content ratio of the 3-hydroxybutyrate units and other hydroxyalkanoate units to all 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 strength and stretchability of the film.

[0028] The average content ratio of each monomer unit in all 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 WO 2013 / 147139. The average content ratio means the molar ratio of each monomer unit in all monomer units constituting the poly(3-hydroxyalkanoate) resin (a), and when 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 entire mixture.

[0029] As described above, the poly(3-hydroxyalkanoate) resin (a) may be a mixture of at least two poly(3-hydroxyalkanoate) resins that differ from each other in the type and / or content ratio of the 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.

[0030] 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.

[0031] The content of 3-hydroxybutyrate units in the highly crystalline poly(3-hydroxyalkanoate) resin 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 the low-crystalline poly(3-hydroxyalkanoate) resin is preferably lower than the average content of 3-hydroxybutyrate units in all monomer units constituting the poly(3-hydroxyalkanoate) resin (a).

[0032] In this embodiment, the poly(3-hydroxyalkanoate)-based resin (a) preferably contains at least a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 24 mol % or more. By modifying the copolymer (a-1) having a high content of other hydroxyalkanoate units and exhibiting low crystallinity, and using it in combination with the polylactic acid-based resin (B), the stretchability of the poly(3-hydroxyalkanoate)-based resin-containing film can be improved.

[0033] The poly(3-hydroxyalkanoate) resin (a) preferably further contains, in addition to the copolymer (a-1), a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, the content of which is 1 mol % or more and 9 mol % or less of the other hydroxyalkanoate units. This improves the film's stretchability as well as its productivity and strength.

[0034] In copolymer (a-1), the content of other hydroxyalkanoate units is preferably 24 to 99 mol%, more preferably 24 to 50 mol%, even more preferably 24 to 35 mol%, and particularly preferably 24 to 30 mol%. In copolymer (a-2), the content of other hydroxyalkanoate units is preferably 2 to 8 mol%, more preferably 2 to 7 mol%.

[0035] As the copolymer (a-1) and the copolymer (a-2), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred.

[0036] In the film according to this embodiment, the amount of copolymer (a-1) used is preferably more than 5% by weight and less than 20% by weight, and more preferably 6% by weight or more and 18% by weight or less, based on the total weight of the poly(3-hydroxyalkanoate) resin (a) and the polylactic acid resin (B), from the viewpoint of the balance between the stretchability of the film, productivity, and strength. The upper limit is preferably 16% by weight or less, and more preferably 15% by weight or less. The lower limit is preferably 8% by weight or more, and more preferably 10% by weight or less.

[0037] When the resin (a) contains the copolymer (a-1) and the copolymer (a-2), the weight ratio (a-1 / a-2) of the copolymer (a-1) to the copolymer (a-2) is preferably 5 / 95 to 30 / 70, more preferably 10 / 90 to 25 / 75, and even more preferably 15 / 85 to 20 / 80, from the viewpoint of achieving both strength and stretchability of the film.

[0038] Copolymer (a-2) may be a mixture of at least two types of copolymers having different content ratios of constituent monomers. Specifically, it preferably contains the following copolymer (a-2-1) and copolymer (a-2-2). According to this embodiment, it is easier to achieve both strength and stretchability of the film. Copolymer (a-2-1): A copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content ratio of other hydroxyalkanoate units is 1 mol % or more and less than 4 mol %. Copolymer (a-2-2): A copolymer of 3-hydroxybutyrate units and other hydroxyalkanoate units, in which the content ratio of other hydroxyalkanoate units is 4 mol % or more and 9 mol % or less.

[0039] In the copolymer (a-2-1), the content of the other hydroxyalkanoate units is preferably 1 to 3 mol %, more preferably 2 to 3 mol %. In the copolymer (a-2-2), the content of the other hydroxyalkanoate units is preferably 5 to 8 mol %, more preferably 6 to 7 mol %.

[0040] As the copolymers (a-2-1) and (a-2-2), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3-hydroxybutyrate-co-4-hydroxybutyrate) is preferred, and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is particularly preferred.

[0041] When the resin (a) contains the copolymer (a-2-2), the weight proportion of the copolymer (a-2-2) in the entire resin (a) is preferably 10 to 90% by weight, more preferably 40 to 90% by weight, even more preferably 50 to 80% by weight, and particularly preferably 60 to 75% by weight, from the viewpoint of achieving both strength and stretchability of the film.

[0042] The method for obtaining a blend of two or more poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a method for obtaining a blend by microbial production or a method for obtaining a blend by chemical synthesis. Alternatively, a blend may be obtained by melt-kneading two or more resins using an extruder, kneader, Banbury mixer, roll, or the like, or by dissolving two or more resins in a solvent, mixing, and drying the resins.

[0043] The weight average molecular weight of the entire poly(3-hydroxyalkanoate) resin (a) is not particularly limited, but from the viewpoint of achieving both strength and stretchability of the film, 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.

[0044] Furthermore, when the poly(3-hydroxyalkanoate) resin (a) is a mixture of two or more poly(3-hydroxyalkanoate) resins, the weight-average molecular weight of each poly(3-hydroxyalkanoate) resin constituting the mixture is not particularly limited. However, from the viewpoint of achieving both film strength and stretchability, the weight-average molecular weight of the copolymer (a-1) is preferably 200,000 to 1,000,000, more preferably 220,000 to 800,000, and even more preferably 250,000 to 600,000. On the other hand, from the viewpoint of achieving both film strength and stretchability, the weight-average molecular weight of the copolymer (a-2) is preferably 200,000 to 2,500,000, more preferably 250,000 to 2,300,000, and even more preferably 300,000 to 2,000,000. Furthermore, from the viewpoint of achieving both film strength and stretchability, the weight-average molecular weight of the copolymer (a-2-2) is preferably 200,000 to 2,500,000, more preferably 250,000 to 2,300,000, and even more preferably 300,000 to 2,000,000.

[0045] The weight-average molecular weight of the poly(3-hydroxyalkanoate) resin can be measured in terms of polystyrene using gel permeation chromatography (HPLC GPC system manufactured by Shimadzu Corporation) using a chloroform solution. As the column for the gel permeation chromatography, a column appropriate for measuring the weight-average molecular weight may be used.

[0046] The method for producing poly(3-hydroxyalkanoate) resins is not particularly limited, and may be a production method using chemical synthesis or a production method using a microorganism. Among these, a production method using a microorganism is preferred. Known methods can be applied to the production method using a microorganism. For example, known bacteria that produce copolymers of 3-hydroxybutyrate and other hydroxyalkanoates include Aeromonas caviae, which produces P3HB3HV and P3HB3HH, and Alcaligenes eutrophus, which produces P3HB4HB. In particular, with regard to P3HB3HH, in order to increase the productivity of P3HB3HH, Alcaligenes eutrophus AC32 strain (FERM BP-6038) (T. Fukui, Y. Doi, J. Bateriol., 179, pp. 4821-4830 (1997)) or the like into which genes encoding P3HA synthases have been introduced is more preferred, and microbial cells obtained by culturing these microorganisms under appropriate conditions and allowing P3HB3HH to accumulate within the cells can be used. In addition to the above, genetically modified microorganisms into which various poly(3-hydroxyalkanoate) resin synthesis-related genes have been introduced may be used depending on the poly(3-hydroxyalkanoate) resin to be produced, or the culture conditions, including the type of substrate, may be optimized.

[0047] [Organic Peroxide] The organic peroxide to be reacted with the poly(3-hydroxyalkanoate) resin (a) is not particularly limited, and examples thereof include diisobutyl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, bis(4-t-butylcyclohexyl)peroxydicarbonate, bis(2-ethylhexyl)peroxydicarbonate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, 1,1,3 , 3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxy-2-ethylhexyl carbonate, t-butylperoxy isopropyl carbonate, 1,6-bis(t-butylperoxycarbonyloxy)hexane, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxyacetate, t-butylperoxybenzoate, t-amylperoxy, 3,5,5-trimethylhexanoate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-di-t-butylperoxybutane, and the like. Among these, dibenzoyl peroxide, t-butylperoxy 2-ethylhexyl carbonate, and t-butylperoxy isopropyl carbonate are preferred. One organic peroxide may be used alone, or two or more organic peroxides may be used in combination.

[0048] The organic peroxide may be used in various forms such as solid or liquid, and may be in liquid form diluted with a diluent, etc. Among these, an organic peroxide in a form that can be mixed with the poly(3-hydroxyalkanoate) resin (a) (particularly an organic peroxide that is liquid at room temperature (25°C)) is preferred because it can be uniformly dispersed in the poly(3-hydroxyalkanoate) resin (a) and makes it easier to suppress local modification reactions.

[0049] From the viewpoint of improving the stretchability of the film, the amount of the organic peroxide used is preferably 0.01 to 1 part by weight, more preferably 0.03 to 0.5 parts by weight, and even more preferably 0.05 to 0.3 parts by weight, per 100 parts by weight of the poly(3-hydroxyalkanoate) resin (a).

[0050] The modified poly(3-hydroxyalkanoate) resin (A) can be preferably obtained by adding the poly(3-hydroxyalkanoate) resin (a) and an organic peroxide to an extruder and melt-kneading them. This allows the poly(3-hydroxyalkanoate) resin (a) to be uniformly crosslinked. Furthermore, in addition to the poly(3-hydroxyalkanoate) resin (a) and the organic peroxide, other components such as a crystal nucleating agent and a lubricant, as described below, may also be added to the extruder and melt-kneaded.

[0051] The melt-kneading can be carried out according to a known or conventional method, and can be carried out using, for example, an extruder (single-screw extruder or twin-screw extruder), a kneader, or the like. The conditions for melt-kneading are not particularly limited and can be set appropriately, but it is preferable to set a resin temperature and residence time that can complete the reaction with the organic peroxide during melt-kneading. Specifically, it is preferable to melt-knead at a resin temperature measured with a die thermometer in the range of 130°C to 175°C. It is also preferable to melt-knead so that the residence time in the extruder is 60 seconds to 300 seconds.

[0052] After melt-kneading, the resin material can be extruded into strands and cut to obtain pellets having particle shapes such as cylindrical, elliptical, spherical, cubic, and rectangular parallelepiped shapes. The produced pellets are preferably used after being thoroughly dried at 40 to 80°C to remove moisture. However, the pelletizing step may be omitted, and the polylactic acid resin (B) may be mixed in and formed into a film following the melt-kneading.

[0053] In the film according to this embodiment, the content of the modified poly(3-hydroxyalkanoate) resin (A) is preferably 40% by weight or more and 90% by weight or less, based on the total weight of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), from the viewpoint of achieving both stretchability and biodegradability (particularly biodegradability in compost and marine degradability) of the film. From the viewpoint of enhancing biodegradability, the lower limit is more preferably 50% by weight or more, even more preferably 60% by weight or more, even more preferably 70% by weight or more, and particularly preferably 80% by weight or more. From the viewpoint of enhancing stretchability, the upper limit is more preferably 85% by weight or less, even more preferably 80% by weight or less.

[0054] [Polylactic Acid Resin (B)] Polylactic acid resin (B) is a polyester containing lactic acid as a constituent monomer. Polylactic acid resins typically have a glass transition temperature of around 60°C and are difficult to crystallize when rapidly cooled from a molten state, resulting in an amorphous state. Therefore, the incorporation of polylactic acid resin (B) facilitates the softening of the film. Therefore, by using polylactic acid resin (B) in combination with modified poly(3-hydroxyalkanoate) resin (A), the stretchability of the poly(3-hydroxyalkanoate) resin-containing film can be improved. This allows for the production of a high-quality stretched film without breakage during stretching and without uneven stretching. Furthermore, film stretching can be performed continuously and stably even under temperature conditions other than the specific temperature described in Patent Document 2. Furthermore, a high stretch ratio can also be achieved.

[0055] The polylactic acid resin (B) is preferably a homopolymer of lactic acid, but may contain a small amount of other monomer in addition to lactic acid.

[0056] The lactic acid constituting the polylactic acid-based resin (B) may be either the L- or D-form, or may contain both. In the latter case, the ratio of the L- and D-forms is not particularly limited. The polylactic acid-based resin (B) may be any of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin. It may also be a blend of these.

[0057] Examples of the other monomer that may be contained in the polylactic acid-based resin (B) include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, aliphatic polycarboxylic acids, polyfunctional polysaccharides, etc. When the polylactic acid-based resin (B) is a copolymer of lactic acid and other monomers, from the viewpoint of crystallinity, the content of the other monomers is preferably about 0 to 3 mol %, more preferably 0 to 2 mol %, based on the total monomers contained in the polylactic acid-based resin (B).

[0058] The polylactic acid resin (B) may be either a crystalline polylactic acid resin or an amorphous polylactic acid resin, but it is preferable to use a crystalline polylactic acid resin from the viewpoint of heat resistance, such as shrinkage during heating in subsequent processes such as printing and vapor deposition. Among crystalline polylactic acid resins, polylactic acid resins having a melting point peak of less than 170°C in differential scanning calorimetry are particularly preferable.

[0059] The peak temperature of the melting point peak of the polylactic acid resin (B) (hereinafter also referred to as "melting point peak temperature") is preferably 165° C. or lower, more preferably 160° C. or lower, from the viewpoint of enhancing the stretchability and strength of the film. The lower limit of the peak temperature is preferably 120° C. or higher, more preferably 130° C. or higher, and even more preferably 140° C. or higher, from the viewpoint of enhancing the stretchability of the film.

[0060] The melting point peak temperature refers to the peak top temperature Tm of the crystalline melting peak in a DSC curve obtained by differential scanning calorimetry (DSC measurement). The DSC curve was obtained by precisely weighing about 5 mg of the resin to be measured and heating it from 0°C to 200°C at a heating rate of 10°C / min using a differential scanning calorimeter.

[0061] The polylactic acid-based resin (B) exhibiting the above-described melting point peak temperature is not particularly limited, and commercially available products can be used. Specific examples include polylactic acid-based resins having an L-isomer purity of lactic acid units of 88% or more and 98% or less.

[0062] From the viewpoint of enhancing the stretchability of the film, the melting peak temperature of the polylactic acid resin (B) is preferably close to the melting peak temperature of the poly(3-hydroxyalkanoate) resin (a). Specifically, the absolute value of the difference between the melting peak temperatures of the polylactic acid resin (B) and the poly(3-hydroxyalkanoate) resin (a) is preferably 40°C or less, more preferably 30°C or less, and even more preferably 20°C or less.

[0063] The melting peak temperature of the poly(3-hydroxyalkanoate) resin (a) is measured in the same manner as the melting peak temperature of the polylactic acid resin (B). When multiple melting peaks appear in the DSC curve measured for the poly(3-hydroxyalkanoate) resin (a), the peak temperature of the melting peak on the highest temperature side is taken as the melting peak temperature of the poly(3-hydroxyalkanoate) resin (a).

[0064] The molecular weight of the polylactic acid resin (B) is not particularly limited and may be set appropriately, but the number average molecular weight is preferably 1,000 to 700,000, and more preferably 10,000 to 300,000.

[0065] The lactic acid raw material for producing the polylactic acid resin (B) is not particularly limited, and examples thereof include L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof, or L-lactide, D-lactide, meso-lactide, or a mixture thereof. Lactic acid obtained by microbial fermentation from renewable plant-derived raw materials such as starch is preferably used. The method for producing the polylactic acid resin (B) is not particularly limited, and known methods such as dehydration condensation polymerization and ring-opening polymerization can be used.

[0066] In the film according to this embodiment, the content of the polylactic acid resin (B) is preferably 10% by weight or more and 50% by weight or less, based on the total weight of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), from the viewpoint of achieving both stretchability and biodegradability (particularly biodegradability in compost and marine degradability) of the film. From the viewpoint of stretchability, the lower limit is more preferably 15% by weight or more, and even more preferably 20% by weight or more. From the viewpoint of biodegradability, the upper limit is more preferably 40% by weight or less, even more preferably 30% by weight or less, even more preferably 25% by weight or less, and particularly preferably 20% by weight or less.

[0067] The film according to this embodiment is a resin film mainly composed of a modified poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B). The total proportion of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) in the total amount of the 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.

[0068] (Other Resins) The film according to this embodiment may contain other resins in addition to the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), provided 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 sebate terephthalate, and polybutylene azelate terephthalate. Only one type of other resin may be contained, or two or more types may be contained.

[0069] The content of the other resin 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 the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). It may 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 resin is not particularly limited, and may be 0 parts by weight or more.

[0070] The film according to this embodiment may contain additives that can be used together with the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B), provided that the effects of the invention are not impaired. Examples of such additives include colorants such as pigments and dyes, odor absorbers such as activated carbon and zeolite, fragrances such as vanillin and dextrin, fillers, plasticizers, antioxidants, weather resistance improvers, UV absorbers, crystal nucleating agents, lubricants, release agents, water repellents, antibacterial agents, and sliding properties improvers. Only one type of additive may be contained, or two or more types may be contained. The content of these additives can be appropriately determined by those skilled in the art depending on the intended use. Crystal nucleating agents, lubricants, fillers, and plasticizers are described in more detail below.

[0071] (Crystal Nucleating Agent) The film according to this embodiment may contain a crystal nucleating agent. Examples of crystal nucleating agents include polyhydric alcohols such as pentaerythritol, galactitol, and mannitol; orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, pentaerythritol is preferred because of its particularly excellent effect of promoting the crystallization of the modified 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.

[0072] When a nucleating agent is used, its 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 modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).

[0073] However, the film according to the present embodiment can achieve good productivity even without substantially blending a nucleating agent such as pentaerythritol. "Substantially no nucleating agent" means that the amount of nucleating agent blended is less than 0.1 parts by weight per 100 parts by weight of the total of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). It may also be less than 0.01 parts by weight. In an embodiment in which pentaerythritol is substantially not blended, the problem of contamination of the cast roll surface due to bleed-out of pentaerythritol can be avoided.

[0074] (Lubricant) The film according to this embodiment may contain a lubricant. Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislauricamide, ethylenebiscapricamide, p-phenylenebisstearamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide or erucamide is preferred because of its particularly excellent lubricating effect on the modified poly(3-hydroxyalkanoate) resin (A). One or more lubricants may be used, and the ratio of use can be adjusted appropriately depending on the purpose.

[0075] When a lubricant is used, the amount thereof is not particularly limited, but is 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, relative to 100 parts by weight of the total of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). The film according to this embodiment preferably contains a lubricant, but does not necessarily contain one.

[0076] (Filler) The film according to this embodiment may contain a filler. By including a filler, the film can have 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 thereof include silicates, carbonates, sulfates, phosphates, oxides, hydroxides, nitrides, and carbon black. Only one type of inorganic filler may be used, or two or more types may be used in combination.

[0077] 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 even more preferably 10 to 60 parts by weight, per 100 parts by weight of the combined total of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). However, the film according to this embodiment may be substantially free of filler. "Substantially no filler" means that the amount of filler is less than 1 part by weight per 100 parts by weight of the combined total of the resins (A) and (B). It may also be less than 0.1 parts by weight.

[0078] (Plasticizer) The film according to this embodiment may contain a plasticizer. Examples of plasticizers include glycerin ester compounds, citrate ester compounds, sebacic ester compounds, adipate ester compounds, polyether ester compounds, benzoic ester compounds, phthalic ester compounds, isosorbide ester compounds, polycaprolactone compounds, and dibasic acid ester compounds. Among these, glycerin ester compounds, citrate ester compounds, sebacic ester compounds, and dibasic acid ester compounds are preferred because of their particularly excellent plasticizing effect on the modified poly(3-hydroxyalkanoate) resin (A). Examples of glycerin ester compounds include glycerin diacetomonolaurate. Examples of citrate ester compounds include acetyl tributyl citrate. Examples of sebacic ester compounds include dibutyl sebacate. Examples of dibasic acid ester compounds include benzyl methyl diethylene 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 appropriately depending on the purpose.

[0079] When a plasticizer is used, the amount used is not particularly limited, but is 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 combined total of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). However, the film according to this embodiment may be substantially free of plasticizer. "Substantially free of plasticizer" means that the amount of plasticizer blended is less than 1 part by weight per 100 parts by weight of the combined total of the resins (A) and (B). It may also be less than 0.1 part by weight.

[0080] [Film] The film according to the present embodiment may be an unstretched film that has not been subjected to a stretching treatment, or may be a stretched film that has been stretched in the MD direction and / or TD direction after film formation. The term "film" as used herein may include both an unstretched film and a stretched film. From the viewpoint of strength, a stretched film is preferred.

[0081] The thickness of the film (particularly 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 viewpoints of uniform thickness, appearance, strength, lightness, and the like of the film.

[0082] The film according to the present embodiment is preferably an industrially produced long film, and more preferably a strip-shaped film wound into a roll. The length of such a film is not particularly limited, but may be, for example, 50 m or more, or 100 m or more. In the present embodiment, such a long film can be continuously and stably produced.

[0083] According to a preferred aspect, the stretched film according to one embodiment can exhibit an elastic modulus of 1500 MPa or more and a breaking strength of 40 MPa or more in at least the MD direction. It may also be a biaxially stretched film exhibiting an elastic modulus of 1500 MPa or more and a breaking strength of 40 MPa or more in both the MD and TD directions. The elastic modulus is preferably 2000 MPa or more, more preferably 2500 MPa or more. The breaking strength is preferably 60 MPa or more, more preferably 70 MPa or more. The elastic modulus and breaking strength are values ​​measured by the methods described in detail in the Examples section.

[0084] [Film Manufacturing Method] Next, an example of a method for manufacturing the film according to the present embodiment will be described, but the present invention is not limited to the following description. First, a film raw material containing the modified poly(3-hydroxyalkanoate) resin (A), the polylactic acid resin (B), and, if necessary, other components, is melted.

[0085] Although the melting method is not particularly limited, it is preferable to extrude the molten film raw material through a T-die, i.e., to carry out extrusion molding. By extrusion molding, a film with a uniform thickness can be easily produced. In extrusion molding, a single-screw extruder, a twin-screw extruder, etc. can be appropriately used.

[0086] The conditions for melting the film raw materials may be any conditions under which the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B) melt, and the temperature of the molten film raw materials may be, for example, about 140 to 210°C.

[0087] The molten film material is then extruded onto a casting roll to form a film. The molten film material comes into contact with the casting roll and moves along the surface of the casting roll, where it cools and solidifies.

[0088] This step may involve extruding the melt onto one or more casting rolls, or may involve placing a touch roll opposite the casting roll and sandwiching the melt extruded onto the casting roll between the touch rolls. An air knife or air chamber may be used to ensure stable contact of the melt with the casting roll. To efficiently cool the side opposite the contact surface with the casting roll, the casting roll may be placed in a water tank or an air chamber may be used.

[0089] The lower limit of the set temperature of the casting 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 adhesiveness of the modified poly(3-hydroxyalkanoate) resin (A) and improve its releasability from the casting roll. The temperature is preferably a temperature exceeding the glass transition temperature (Tg) of the poly(3-hydroxyalkanoate) resin (a) + 10° C.

[0090] The upper limit of the temperature setting of the cast roll is not particularly limited, but from the viewpoint of promoting solidification of the modified poly(3-hydroxyalkanoate) resin (A), it is preferably 80°C or lower, more preferably 60°C or lower.

[0091] Next, the film cooled on the casting roll is transported while the casting roll is rotated, and the film is peeled off from the casting roll, thereby obtaining an unstretched film.

[0092] The resulting film is then stretched in the MD direction to obtain a uniaxially stretched film with high strength in the MD direction. The MD direction is also called the machine direction, flow direction, or longitudinal direction. The TD direction, which will be described later, is the direction perpendicular to the MD direction and is also called the perpendicular direction or width direction.

[0093] The stretching step in the MD direction can be carried out continuously in one production line from the time of peeling from the casting roll. This step is not particularly limited, but can be carried out, for example, by using a roll longitudinal stretching machine and varying the rotation speed of multiple rolls that transport the film.

[0094] The MD stretching step is preferably carried out while heating the film. The heating method is not particularly limited, but examples thereof include a method of exposing the film to an air current adjusted to a predetermined temperature, a method of controlling the film temperature by setting a roll to a predetermined temperature, a method of heating the film using auxiliary heating means such as an IR heater to control the film temperature to a predetermined temperature, and a method of passing the film through an oven adjusted to a predetermined temperature. These methods may be used alone or in combination.

[0095] In Patent Document 2, in order to achieve film stretching by suppressing crystallization of the resin in the MD stretching step, a relatively low film temperature of 20° C. or 30° C. is employed in the examples. In contrast, in the present embodiment, the stretchability of the film is improved by the composition of the film raw materials, so there is no need to control the film temperature as described above, and MD stretching can be achieved even at a temperature higher than the aforementioned temperature.

[0096] Specifically, 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. Polylactic acid-based resins typically have a glass transition temperature of around 60°C, and are less likely to crystallize when rapidly cooled from a molten state, resulting in an amorphous state. Therefore, even if the temperature is below the melting point of the poly(3-hydroxyalkanoate)-based resin, the film according to this embodiment is likely to soften in this temperature range, enabling good stretching. Furthermore, this temperature is easy to control and stabilize. Therefore, film stretching can be carried out continuously and stably, enabling the stable production of long stretched films.

[0097] The upper limit of the temperature during stretching in the MD direction is not particularly limited, but from the viewpoint of avoiding breakage of the film during stretching, it is preferably 110°C or less, more preferably 100°C or less, and more preferably 90°C or less.

[0098] 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. The composition of the film raw material according to this embodiment makes it possible to achieve such a high stretching ratio. The upper limit of the stretching ratio is not particularly limited and may be determined appropriately, but may be, for example, 8 times or less.

[0099] Next, by stretching in the MD direction followed by stretching in the TD direction, a biaxially stretched film with high strength in both the MD and TD directions can be obtained. The TD stretching step can be carried out continuously from the MD stretching step in a single production line. This step is not particularly limited, but can be carried out, for example, by clamping both widthwise ends of the film using a transverse stretching machine such as a clip-type tenter and pulling it in the TD direction.

[0100] The stretching step in the TD direction is also preferably carried out while heating the film. The heating method is not particularly limited, and examples thereof include those described above for the stretching step in the MD direction.

[0101] The temperature conditions in the TD stretching step do not need to be controlled to the specific temperature disclosed in Patent Document 2. Specifically, the temperature during TD stretching may be the same as the temperature during MD stretching described above, and is preferably 35 to 110°C, more preferably 45 to 100°C, and more preferably 55 to 90°C.

[0102] 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. The composition of the film raw material according to this embodiment makes it possible to achieve such a high stretching ratio. The upper limit of the stretching ratio is not particularly limited and may be determined appropriately, but may be, for example, 8 times or less.

[0103] After the MD stretching step or the TD stretching step, it is preferable to carry out a heat setting step in which the stretched film is heated to a temperature at which high-melting-point crystals grow, thereby increasing the crystallinity of the stretched film, increasing its strength, and stabilizing its physical properties.

[0104] 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 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.

[0105] This heating can be carried out, for example, by stretching the film in the TD direction using a transverse stretching machine such as a clip-type tenter, and then heating the film while maintaining the stretched state. At this time, since heat shrinkage occurs in the direction opposite to the stretching direction, it is preferable to relax the film to prevent breakage. Relaxation is an operation of releasing tension in the direction opposite to the stretching direction, and the amount of relaxation is preferably adjusted appropriately between 5 and 30%.

[0106] Thereafter, a step of cooling the film may be carried out as appropriate, and then, a step of winding the stretched film on a winding roll is preferably carried out.

[0107] The film manufacturing method according to this embodiment is preferably carried out while continuously transporting the film from melt extrusion to the final step. This makes it possible to produce the film with high productivity through an industrially simple process. The manufacturing method according to this embodiment can be carried out while continuously winding up the produced film on a winding roll.

[0108] When the film is continuously transported, the transport speed is not particularly limited, but from the viewpoint of film productivity, it is preferably 5 m / min or more at the stage before the start of stretching, and from the viewpoint of production stability, it is preferably 50 m / min or less at the stage before the start of stretching.

[0109] [Laminate] The film according to this embodiment may be a resin film composed of an independent single layer, or may 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 such other layers include a resin layer, an inorganic layer, a metal layer, a metal oxide layer, a printed layer, etc. These other layers may be laminate layers, coating layers, or vapor-deposited layers.

[0110] The resin layer, which is one of the other layers in the laminate, is not particularly limited, but from the viewpoint of enhancing the biodegradability of the entire laminate, it is preferably a layer containing a poly(3-hydroxyalkanoate)-based resin (C). As the poly(3-hydroxyalkanoate)-based resin (C), those described above for the poly(3-hydroxyalkanoate)-based resin (a) can be used as appropriate, but are not particularly limited. The components other than the poly(3-hydroxyalkanoate)-based resin (C) are also not particularly limited, and known components as additives to resin layers can be used as appropriate. This resin layer may function as a heat seal layer.

[0111] [Applications of Film] The film according to this embodiment can be suitably used as a packaging film, a heat-sealable film, a twist film, or the like.

[0112] The following items list preferred embodiments of the present disclosure, but the present invention is not limited to each of them. [Item 1] A film containing a modified poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), wherein the modified poly(3-hydroxyalkanoate) resin (A) is a reaction product of poly(3-hydroxyalkanoate) resin (a) and an organic peroxide. [Item 2] The film according to Item 1, wherein the content of the polylactic acid resin (B) is 10% by weight or more and 50% by weight or less, based on the total weight of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B). [Item 3] The film according to Item 1 or 2, wherein the poly(3-hydroxyalkanoate) resin (a) contains a copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content of the other hydroxyalkanoate units is 24 mol % or more. [Item 4] The film according to Item 3, wherein the amount of the copolymer (a-1) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content of the other hydroxyalkanoate units is 24 mol% or more, is more than 5 wt% and less than 20 wt% relative to the total weight of the poly(3-hydroxyalkanoate) resin (a) and the polylactic acid resin (B). [Item 5] The film according to Item 3 or 4, wherein the poly(3-hydroxyalkanoate) resin (a) further contains a copolymer (a-2) of 3-hydroxybutyrate units and other hydroxyalkanoate units, wherein the content of the other hydroxyalkanoate units is 1 mol% or more and 9 mol% or less. [Item 6] The film according to any of Items 3 to 5, wherein the other hydroxyalkanoate units include 3-hydroxyhexanoate units. [Item 7] The film according to any of Items 1 to 6, wherein the film is a uniaxially or biaxially stretched film. [Item 8] The film according to item 7, wherein the uniaxially or biaxially stretched film exhibits an elastic modulus of 1500 MPa or more and a breaking strength of 40 MPa or more, at least in the MD direction. [Item 9] A laminate comprising the film according to any one of items 1 to 8, and a layer containing a poly(3-hydroxyalkanoate) resin (C) laminated on at least one surface of the film.

[0113] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0114] In the examples, the following raw materials were used. (Poly(3-hydroxyalkanoate)-based resin (a)) As the P3HA-based resin (a), the following poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HB3HH) resins PHBH-1 to PHBH-3 were used. Below, 3HB represents a 3-hydroxybutyrate repeating unit, and 3HH represents a 3-hydroxyhexanoate repeating unit. PHBH-1:P3HB3HH (average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight average molecular weight 660,000 g / mol) These resins were produced in accordance with the method described in Example 9 of WO 2019 / 142845. PHBH-2: P3HB3HH (average content ratio 3HB / 3HH = 97.2 / 2.8 (mol% / mol%), weight average molecular weight is 660,000 g / mol) Produced in accordance with the method described in Example 2 of WO 2019 / 142845. PHBH-3: P3HB3HH (average content ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight average molecular weight is 600,000 g / mol) Produced in accordance with the method described in Example 1 of WO 2019 / 142845.

[0115] (Polylactic acid resin (B)) B-1: PLA (LX175 grade, manufactured by Total Corbion PLA, melting point peak temperature 155°C)

[0116] (Lubricant) D-1: Behenic acid amide (manufactured by Nippon Fine Chemical Co., Ltd.: BNT-22H)

[0117] (Organic Peroxide) E-1: Perbutyl I (t-butylperoxyisopropyl carbonate, 1-minute half-life temperature: 159°C) manufactured by NOF Corporation

[0118] The following evaluations were carried out for each example and comparative example. [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 taken up through a die with a lip width of 250 µm at a casting roll (CR) temperature of 40 to 60°C at the molding speed shown in Table 1 to obtain a T-die film. At this time, roll contamination was evaluated according to the following evaluation criteria.

[0119] <Evaluation criteria> ◯: The cast roll surface after 1 hour of continuous operation was visually observed, and the boundary between the film contact area and the non-contact area could not be detected. ×: The cast roll surface after 1 hour of continuous operation was visually observed, and the boundary between the film contact area and the non-contact area could be detected.

[0120] [Film stretchability] A film was produced from each resin composition using a T-die and continuously stretched 3 times in the MD direction (the flow direction of T-die film production) using a roll stretching machine at a temperature range of 60°C to 70°C, and the stretchable range (stretching ratio) was evaluated according to the following evaluation criteria. In addition, the film stretched in the MD direction was fixed at both MD end portions and stretched 5 times in the TD direction (direction perpendicular to the MD direction) at a temperature range of 70°C to 80°C, and the stretchable range (stretching ratio) was evaluated according to the following evaluation criteria.

[0121] <Evaluation criteria> ◯: The stretched film was obtained without breaking during stretching, and no stretching unevenness (uneven stretching portions such as uneven film thickness) was observed visually in the obtained stretched film. △: The stretched film was obtained without breaking during stretching, and no stretching unevenness (uneven stretching portions such as uneven film thickness) was observed visually in the obtained stretched film, but the thickness variation was slightly larger than in ◯, but TD stretching was successful without stretching unevenness. ×: The film broke during stretching, or the obtained stretched film had stretching unevenness (uneven stretching portions such as uneven film thickness) observed visually.

[0122] [Film Properties] <Elastic Modulus, Breaking Strength, and Breaking Elongation of Film> The stretched film was stored for one week in an atmosphere of 23°C and 50% humidity, and then ten dumbbells (small test pieces, size 2(1 / 3)) in the MD and / or TD directions were punched out in accordance with JIS K7113. The elastic modulus, breaking strength, and breaking elongation were measured and calculated five times using a tensile tester ("AUTOGRAPH AG2000A" manufactured by Shimadzu Corporation) at a test speed of 100 mm / min. The average values ​​were then reported in Table 1 as the elastic modulus, breaking strength, and breaking elongation.

[0123] <Film Tear Strength> After storing the stretched film in an atmosphere of 23°C and 50% humidity for one week, the tear strength was measured using the Elmendorf tear method based on JIS K 1281. The measurement was carried out five times, and the average value was recorded as the tear strength in Table 1.

[0124] (Example 1) (Method for producing resin composition) Poly(3-hydroxyalkanoate) resin (a): 17.5 parts by weight of PHBH-1, 17.5 parts by weight of PHBH-2, 65 parts by weight of PHBH-3, 0.5 parts by weight of D-1 as a lubricant, 0.15 parts by weight of E-1 as an organic peroxide were dry blended. The resulting resin material was charged into a φ26 mm co-rotating twin-screw extruder hopper with the cylinder temperature and die temperature set to 150 ° C., melt-kneaded, extruded into strands from the die, passed through a water tank filled with hot water at 45 ° C. to solidify the strands, and cut with a pelletizer to obtain resin pellets P-1. Note that during the melt-kneading process, the reaction between P3HA and the organic peroxide proceeded to form a modified resin (A).

[0125] (Production of biaxially stretched film in MD and TD directions) Furthermore, the resin pellets P-1 and B-1 were charged into a single-screw extruder in a weight ratio of 80:20 and extruded into a film using a T-die. The formed film was cooled with a cooling roll set at 50 ° C., then taken up with a take-up roll. Continuously, the film was stretched 3 times in the MD direction at 60-70 ° C. using a roll longitudinal stretching machine, and then continuously stretched in the TD direction at a stretching temperature of 70-80 ° C. using a clip-type tenter transverse stretching machine to a stretching ratio of 5 times. The film was then heated to 130 ° C. while relaxing the stretching by 15% and heat-set. The biaxially stretched film was cooled to 50 ° C., and the widthwise end was slit to obtain a biaxially stretched film having a width of 1200 mm and a thickness of 20 μm. The above process was carried out continuously.

[0126] After one hour of continuous operation from the start of T-die film production, roll contamination was evaluated. The film was also observed after MD stretching and TD stretching to evaluate the film's stretchability. The resulting stretched film was also evaluated for its elastic modulus, breaking strength, breaking elongation, tear strength, and biodegradability. The evaluation results are shown in Table 1.

[0127] Examples 2 and 3 Resin pellets P-2 and P-3 were produced in the same manner as in Example 1, except that the formulation was changed as shown in Table 1. Furthermore, a film was produced in the same manner as in Example 1, and the stretchability of the film, the elastic modulus of the stretched film, tensile strength, breaking strength, breaking elongation, breaking strength, and biodegradability were evaluated. The evaluation results are shown in Table 1.

[0128] Comparative Example 1 Resin pellet P-4 was produced in the same manner as in Example 1, except that no organic peroxide was used. An attempt was made to produce a film in the same manner as in Example 1. Although the roll contamination resistance was good, the film broke during stretching, and a stretched film could not be obtained.

[0129] Comparative Example 2 An attempt was made to produce a film in the same manner as in Example 1, except that B-1 was not used. Although the roll contamination resistance was good, the maximum molding speed at which film molding could be carried out without the resin material sticking to the casting roll was as slow as 3 m / min. In addition, the film broke during stretching, making it impossible to obtain a stretched film.

[0130]

[0131] As can be seen from Table 1, in Examples 1 to 3, in which a modified poly(3-hydroxyalkanoate) resin (A) obtained by reacting a poly(3-hydroxyalkanoate) resin (a) with an organic peroxide was blended with a polylactic acid resin (B), biaxially stretched films stretched at high ratios in both the MD and TD directions could be obtained. On the other hand, in Comparative Example 1, which contained unmodified poly(3-hydroxyalkanoate) resin (a) and polylactic acid resin (B) without modification with an organic peroxide, and Comparative Example 2, which was modified with an organic peroxide but did not blend polylactic acid resin (B), the film broke during the stretching process, and a stretched film could not be obtained.

Claims

1. It contains a modified poly(3-hydroxyalkanoate) resin (A) and a polylactic acid resin (B), The modified poly(3-hydroxyalkanoate) resin (A) is a reaction product of poly(3-hydroxyalkanoate) resin (a) and an organic peroxide. The poly(3-hydroxyalkanoate) resin (a) comprises a copolymer (a-1) of a 3-hydrokibutyrate unit and other hydroxyalkanoate units, wherein the content of other hydroxyalkanoate units is 24 mol% or more. A film in which the amount of the copolymer (a-1) is greater than 5% by weight and less than 20% by weight relative to 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 content of the polylactic acid resin (B) is 10% by weight or more and 50% by weight or less with respect to the total weight of the modified poly(3-hydroxyalkanoate) resin (A) and the polylactic acid resin (B).

3. The film according to claim 1 or 2, wherein the poly(3-hydroxyalkanoate) resin (a) further comprises a copolymer (a-2) of a 3-hydrokybtyrate unit and other hydroxyalkanoate units, wherein the content of other hydroxyalkanoate units is 1 mol% or more and 9 mol% or less.

4. The film according to claim 1 or 2, wherein the other hydroxyalkanoate unit includes a 3-hydroxyhexanoate unit.

5. The film according to claim 1 or 2, wherein the film is a uniaxially or biaxially oriented film.

6. The film according to claim 5, wherein the uniaxial or biaxially oriented film exhibits an elastic modulus of 1500 MPa or more and a breaking strength of 40 MPa or more in at least the MD direction.

7. 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.