Film, method for producing film, and molded body

Abstract

This film comprises a polylactic acid-based resin and a biodegradable block copolymer, wherein the biodegradable block copolymer contains a block structural unit (A) and a block structural unit (B); the block structural unit (A) contains a polylactic acid unit as a main component; the block structural unit (B) has a glass transition temperature of 55°C or lower; the content of the polylactic acid-based resin is 80% by mass or more; and the elongation at break measured in accordance with JIS K 7127:1999 is 100% or more at 23°C.

Description

Film, film manufacturing method and molded product

[0001] The present invention relates to a film that is inhibited from decreasing in transparency and rigidity, has a large effect of reducing environmental load, and is excellent in low-temperature formability, a method for producing the film, and a molded article containing the film.

[0002] From the perspective of environmental protection, active development of bioplastics and biodegradable plastics is underway. Polylactic acid is a biodegradable plastic with a high biomass content that has high transparency and tensile modulus. Replacing existing molded products with polylactic acid is expected to reduce fossil resource consumption and the generation of microplastics. However, films containing polylactic acid have lower breaking elongation than films containing other resins. As a result, polylactic acid films have difficulty conforming to molds of a certain depth or greater, which can limit the shapes of molded products that can be produced. To address this issue, a method is commonly used in which polylactic acid films are heated to conform to a mold. However, this method requires time to heat the film, which reduces production speed and requires additional film heating equipment, thereby increasing greenhouse gas emissions during the production process. Against this background, there is a need for polylactic acid films that can conform to molds of a certain depth or greater at lower temperatures, i.e., have excellent low-temperature formability.

[0003] As a method for producing a film containing polylactic acid and exhibiting high breaking elongation at low temperatures, a method has been proposed in which the proportion of polylactic acid in the film is reduced and an inorganic material or the like is added instead to adjust the physical properties of the film (e.g., Patent Documents 1 and 2).Furthermore, a method has been proposed in which the proportion of polylactic acid in the film is reduced and a non-biodegradable block copolymer is added instead (e.g., Patent Document 3).

[0004] Japanese Patent Application Laid-Open No. 2004-250697 Japanese Patent Application Laid-Open No. 2005-330318 International Publication No. 2007 / 060930

[0005] The methods described in Patent Documents 1 and 2 have the problem that the inherent advantages of polylactic acid, such as transparency and rigidity, are not easily reflected in the film, and the biodegradability, biomass content, etc. are also reduced, resulting in a decrease in the effect of reducing the environmental load.Furthermore, the method described in Patent Document 3 has the problem that the biodegradability and biomass content of the film are reduced, resulting in a decrease in the effect of reducing the environmental load.

[0006] In view of the above problems, the present invention aims to provide a film that suppresses the decrease in transparency and rigidity, has a large effect of reducing the environmental load, and has excellent low-temperature formability, a method for producing the film, and a molded article containing the film.

[0007] As a result of intensive research to solve the above problems, the present inventors have conceived the following invention and found that the above problems can be solved.

[0008] [1] A film comprising a polylactic acid resin and a biodegradable block copolymer, wherein the biodegradable block copolymer comprises a block structural unit (A) mainly composed of a polylactic acid unit and a block structural unit (B) having a glass transition temperature of 55°C or lower, the polylactic acid resin content being 80% by mass or higher, and the film having a breaking elongation at 23°C measured in accordance with JIS K 7127:1999 of 100% or higher. [2] The film according to [1] above, having a haze of 15% or lower measured in accordance with JIS K 7136:2000. [3] The film according to [1] or [2] above, having a 50% breaking impact energy of 1.0 J or higher measured in accordance with JIS K 7211-1:2006. [4] The film according to any one of [1] to [3] above, having a tensile modulus of elasticity of 2.0 GPa or higher measured in accordance with JIS K 7127:1999. [5] The film according to any one of [1] to [4] above, wherein the difference between the heat of fusion and the heat of crystallization measured in accordance with JIS K 7122: 2012 is 8 J / g or less. [6] The film according to any one of [1] to [5] above, wherein, in a cross section cut parallel to the machine direction and in the thickness direction of the film, a phase-separated structure is formed in which the biodegradable block copolymer exists as dispersed particles (X), and the number ratio (%) of dispersed particles (x) having a maximum Feret diameter of 0.3 μm or more and a value obtained by dividing the maximum Feret diameter by the minimum Feret diameter of 1.5 or more is 35% or more. [7] A method for producing the film according to any one of [1] to [6] above, comprising the following steps (1) to (3): Step (1): A step of melt-kneading a polylactic acid-based resin and a biodegradable block copolymer using a twin-screw kneading extruder. Step (2): A step of melt-extruding the melt into a film using a T-die. Step (3): A step of cooling and solidifying the melt extruded into a film using a cooling roll at a temperature of 20 to 75°C. [8] A molded product comprising the film according to any one of [1] to [6] above.

[0009] According to the present invention, it is possible to provide a film that suppresses decreases in transparency and rigidity, has a large effect of reducing environmental load, and is excellent in low-temperature formability, a method for producing the film, and a molded article containing the film.

[0010] 1 is an explanatory view for explaining the evaluation of low-temperature formability in Examples. FIG. 2 is an explanatory view of a pin used in the evaluation of low-temperature formability in Examples.

[0011] The following describes an embodiment of the present invention (hereinafter, sometimes referred to as "this embodiment"). However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. Although preferred embodiments are described herein, combinations of two or more of the individual preferred embodiments are also preferred. For matters indicated as numerical ranges, when there are several numerical ranges, the lower and upper limits can be selectively combined to form preferred embodiments. Furthermore, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." In this specification, the term "unit" (where "~" indicates a monomer) means "a structural unit derived from ~." For example, "dicarboxylic acid unit" means "a structural unit derived from dicarboxylic acid," and "diamine unit" means "a structural unit derived from diamine." In this specification, "biodegradable" means that the decomposition rate after 15 days, as measured in accordance with ISO 14855-2:2018, is 10% by mass or more.

[0012] [Film] The film according to this embodiment is a film containing a polylactic acid resin and a biodegradable block copolymer, wherein the biodegradable block copolymer contains a block structural unit (A) mainly composed of a polylactic acid unit and a block structural unit (B) having a glass transition temperature of 55°C or lower, the content of the polylactic acid resin is 80% by mass or higher, and the elongation at break at 23°C measured in accordance with JIS K 7127: 1999 is 100% or higher. In this specification, the term "biodegradable block copolymer" refers to a block copolymer having biodegradability.

[0013] Polylactic acid has high transparency and biodegradability. The film according to the present embodiment has a polylactic acid-based resin content of 80% by mass or more, which prevents deterioration in transparency, rigidity, and biodegradability, and has a significant effect in reducing environmental impact. Furthermore, the film contains a predetermined biodegradable block copolymer, which results in excellent low-temperature formability.

[0014] From the viewpoint of formability, the thickness of the film in this embodiment is preferably 0.02 to 20 mm, more preferably 0.03 to 5 mm, and even more preferably 0.05 to 1 mm.

[0015] In the film of this embodiment, in a cross section cut parallel to the flow direction and in the thickness direction, the biodegradable block copolymer preferably forms a phase-separated structure (macrophase-separated structure) in which the biodegradable block copolymer exists as dispersed particles (X) in the polylactic acid resin. Such a structure of the film results in superior low-temperature formability. In a cross section cut parallel to the flow direction and in the thickness direction of the film, the shape of the dispersed particles of the biodegradable block copolymer (also referred to as dispersed particles (X)) is preferably elliptical from the viewpoint of low-temperature formability, and more preferably the major axis of the ellipse is oriented in the flow direction of the film. The ellipse refers to a shape in which at least a portion of the periphery is curved and the maximum and minimum values ​​of the Feret diameter of the periphery differ. The major axis of the ellipse refers to the maximum value of the Feret diameter. The Feret diameter refers to the length of the line perpendicular to two parallel lines when the dispersed particles (X) are sandwiched between them in one direction. In this specification, the term "machine direction" refers to the direction in which a machine runs when continuously producing a film, and refers to the MD direction (machine direction).

[0016] In a cross section of the film cut parallel to the machine direction and in the thickness direction, the maximum Feret diameter is preferably 0.3 μm or more, more preferably 0.8 μm or more, and even more preferably 1.2 μm or more. When the maximum Feret diameter is within the above range, a film with even better low-temperature formability can be obtained. Furthermore, the maximum Feret diameter is preferably 35 μm or less, more preferably 6.0 μm or less. When the maximum Feret diameter is within the above range, a film with even better low-temperature formability can be obtained. That is, the maximum Feret diameter is preferably 0.3 to 35 μm, more preferably 0.8 to 35 μm, and even more preferably 1.2 to 6.0 μm.

[0017] In a cross section of the film cut parallel to the machine direction and in the thickness direction, the minimum Feret diameter is preferably 0.05 μm or more. When the minimum Feret diameter is within the above range, the film can have even better impact resistance. Furthermore, the minimum Feret diameter is preferably 1.8 μm or less, more preferably 0.9 μm or less. When the minimum Feret diameter is within the above range, the film can have even better transparency. That is, the minimum Feret diameter is preferably 0.05 to 1.8 μm, more preferably 0.05 to 0.9 μm.

[0018] In a cross section of the film cut parallel to the machine direction and in the thickness direction, the number ratio of dispersed particles (x) having a maximum Feret diameter of 0.3 μm or more, where the value obtained by dividing the maximum value by the minimum value of the Feret diameter is 1.5 or more, is preferably 35% or more, more preferably 50% or more, even more preferably 60% or more, even more preferably 70% or more, and even more preferably 80% or more. When the number ratio of dispersed particles (x) is within the above range, a film with even better low-temperature formability can be obtained. Furthermore, the number ratio of dispersed particles (x) among dispersed particles (X) having a maximum Feret diameter of 0.3 μm or more may be 100% or less. That is, the number ratio of dispersed particles (x) among dispersed particles (X) is preferably 35 to 100%, more preferably 50 to 100%, even more preferably 60 to 100%, even more preferably 70 to 100%, and even more preferably 80 to 100%. In this embodiment, a phase-separated structure is formed in a cross section of the film cut parallel to the flow direction and in the thickness direction, in which the biodegradable block copolymer exists as dispersed particles (X). Among the dispersed particles (X) having a maximum Feret diameter of 0.3 μm or more, the percentage (%) of dispersed particles (x) having a maximum Feret diameter divided by the minimum Feret diameter of 1.5 or more is preferably 35% or more. In this specification, the shape, size, and number of dispersed particles (X) in the film are evaluated and measured based on images of a cross section cut parallel to the flow direction and in the thickness direction of the film, photographed at 1000x magnification using a transmission electron microscope (TEM). Specifically, the evaluation and measurement are performed using the following steps (1) to (3). (1) The film is stained for 15 minutes using a 10% by mass aqueous solution of phosphotungstic acid, embedded in epoxy resin, and then cut parallel to the flow direction and in the thickness direction of the film using an ultramicrotome to prepare ultrathin sections. (2) Using a transmission electron microscope, an ultrathin section is photographed at 1000x magnification at an acceleration voltage of 100 kV and an emission current of 10 μA. (3) A 35 μm square is set as a measurement point in the obtained image (film cross-sectional image), and the shape, size, and number of dispersed particles (X) are evaluated and measured.More specifically, it can be evaluated and measured by the methods described in the Examples.

[0019] <Polylactic Acid Resin> The polylactic acid resin according to this embodiment refers to a resin containing polylactic acid units. Examples of polylactic acid resins include at least one selected from the group consisting of homopolymers of L-lactic acid, homopolymers of D-lactic acid, copolymers of L-lactic acid and D-lactic acid, homopolymers of DL-lactic acid, copolymers of DL-lactic acid and L-lactic acid, copolymers of DL-lactic acid and D-lactic acid, and polymers of lactide, a cyclic dimer of lactic acid. Furthermore, the polylactic acid resin may be, for example, a copolymer of lactic acid with an aliphatic hydroxycarboxylic acid other than lactic acid, an aliphatic dicarboxylic acid, an aliphatic diol, an aromatic dicarboxylic acid, or the like. The copolymer is preferably biodegradable. Furthermore, the copolymer preferably contains structural units derived from lactic acid in an amount of 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. Furthermore, the amount of aromatic dicarboxylic acid units contained in the polylactic acid resin is preferably as low as possible, more preferably 10 mol% or less, and even more preferably 5 mol% or less. The polylactic acid resin is preferably a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, or a copolymer of L-lactic acid and D-lactic acid, and more preferably a homopolymer of L-lactic acid. One type of polylactic acid resin may be used alone, or two or more types may be used in combination.

[0020] Commercially available polylactic acid resins may be used, such as the "INGEO series" manufactured by NatureWorks, Inc., the "Luminy series" manufactured by Total Corbion, the "Revode" series manufactured by Zhejiang Hisun Biomaterials Co., Ltd., and the "SUPLA" series manufactured by SUPLA Material Technology Co., Ltd.

[0021] <Weight-Average Molecular Weight of Polylactic Acid Resin> The weight-average molecular weight of the polylactic acid resin is preferably 50,000 to 600,000, more preferably 100,000 to 550,000, and even more preferably 150,000 to 500,000, from the viewpoint of obtaining a film with superior rigidity and improved elongation at break. The weight-average molecular weight of the polylactic acid resin can be determined in terms of standard polystyrene by gel permeation chromatography (GPC). When using a commercially available product, the catalog value may be used.

[0022] <Glass Transition Temperature of Polylactic Acid Resin> The glass transition temperature of the polylactic acid resin is preferably 110°C or lower, more preferably 65°C or lower, from the viewpoint of sufficiently melting the polylactic acid resin when melt-kneaded with the biodegradable block copolymer and facilitating the production of a film having the desired morphology. Furthermore, from the viewpoint of rigidity, the glass transition temperature of the polylactic acid resin is preferably −35°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher. That is, the glass transition temperature of the polylactic acid resin is preferably −35 to 110°C, more preferably 50 to 65°C, and even more preferably 55 to 65°C. The glass transition temperature of the polylactic acid resin can be determined using a differential scanning calorimeter, and specifically, can be measured by the method described in the Examples.

[0023] <<Melt Flow Rate (MFR) of Polylactic Acid Resin>> From the viewpoint of widening the suitable temperature range during film molding and from the viewpoint of film formation stability, the melt flow rate (MFR) of the polylactic acid resin is preferably 25 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 10 g / 10 min or less, and even more preferably 7 g / 10 min or less. Furthermore, from the viewpoint of film formation stability, the melt flow rate (MFR) of the polylactic acid resin is preferably 0.4 g / 10 min or more. That is, the melt flow rate (MFR) of the polylactic acid resin is preferably 0.4 to 25 g / 10 min, more preferably 0.4 to 20 g / 10 min, even more preferably 0.4 to 10 g / 10 min, and even more preferably 0.4 to 7 g / 10 min. The melt flow rate (MFR) of the polylactic acid resin is a value measured in accordance with ASTM D1238 under conditions of a temperature of 210° C. and a load of 2.16 kgf.

[0024] <<Melting Point of Polylactic Acid Resin>> The melting point of the polylactic acid resin is preferably less than 180°C, more preferably 170°C or less, and even more preferably 160°C or less, from the viewpoint of sufficiently melting the polylactic acid resin when melt-kneaded with the biodegradable block copolymer and facilitating the production of a film having the desired morphology. Furthermore, from the viewpoint of film formation stability, the melting point of the polylactic acid resin is preferably 110°C or higher, more preferably 130°C or higher. That is, the melting point of the polylactic acid resin is preferably 110°C or higher but lower than 180°C, more preferably 110 to 170°C, and even more preferably 130 to 160°C. The melting point of the polylactic acid resin can be determined using a differential scanning calorimeter, and specifically, can be measured by the method described in the Examples.

[0025] <Biodegradable Block Copolymer> The biodegradable block copolymer according to this embodiment contains a block structural unit (A) mainly composed of a polylactic acid unit and a block structural unit (B) having a glass transition temperature of 55°C or lower.

[0026] <Block structural unit (A)> The block structural unit (A) according to this embodiment is primarily composed of polylactic acid units. The term "primary component" refers to the unit that is most abundant among the units constituting the block structural unit (A). The content of polylactic acid units in the block structural unit (A) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, and may even be 100% by mass. There is no upper limit to the amount of polylactic acid units contained in the block structural unit (A), and it may be, for example, 100% by mass or less.

[0027] The polylactic acid constituting the block structural unit (A) may be prepared by direct condensation of lactic acid or by ring-opening polymerization of lactide. The lactic acid may be, for example, at least one selected from the group consisting of L-lactic acid, D-lactic acid, and DL-lactic acid. The lactide may be, for example, at least one selected from the group consisting of L-lactide, D-lactide, DL-lactide, and meso-lactide. Furthermore, the polylactic acid may be poly-L-lactic acid, poly-D-lactic acid, poly-DL-lactic acid, or a stereocomplex polylactic acid obtained by mixing poly-L-lactic acid and poly-D-lactic acid. However, from the viewpoints of synthesis cost, complexity, and processability of the biodegradable block copolymer, it is preferable that the polylactic acid is not a stereocomplex polylactic acid. From the viewpoints of cost and availability of raw materials, the polylactic acid is preferably at least one selected from the group consisting of poly-L-lactic acid, poly-D-lactic acid, and poly-DL-lactic acid, and more preferably at least one selected from the group consisting of poly-L-lactic acid and poly-D-lactic acid.

[0028] <Number-Average Molecular Weight of Block Structural Unit (A)> The number-average molecular weight of the block structural unit (A) is not limited as long as it does not impair the effects of the present invention. In one embodiment of the present invention, from the viewpoint of productivity, the number-average molecular weight of the block structural unit (A) is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and preferably 200,000 or less, more preferably 100,000 or less, and even more preferably 50,000 or less. That is, the number-average molecular weight of the block structural unit (A) is preferably 1,000 to 200,000, more preferably 2,000 to 100,000, and even more preferably 3,000 to 50,000. When a biodegradable block copolymer has multiple block structural units (A), the number-average molecular weight of the block structural unit (A) refers to the sum of all blocks. The number-average molecular weight of the block structural unit (A) can be determined from the number-average molecular weight of the biodegradable block copolymer and the mass content of the block structural unit (A).

[0029] <Block Structural Unit (B)> From the viewpoint of obtaining a film having excellent biodegradability and impact resistance, the block structural unit (B) preferably contains polyester units (b). From the viewpoint of obtaining a film having excellent biodegradability and impact resistance, the content of polyester units (b) in the block structural unit (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more, and may even be 100% by mass. Furthermore, there is no upper limit for the amount of polyester units (b) contained in the block structural unit (B), and it may be, for example, 100% by mass or less. From the viewpoint of obtaining a film having excellent biodegradability and impact resistance, the polyester units (b) preferably contain units derived from an aliphatic diol (b1) and an aliphatic dicarboxylic acid (b2). Specifically, the polyester units (b) preferably contain units derived from a polyester obtained by reacting an aliphatic diol (b1) with an aliphatic dicarboxylic acid (b2). The polyester unit (b) may or may not contain units derived from monomers other than the aliphatic diol (b1) and the aliphatic dicarboxylic acid (b2). The monomers other than the aliphatic diol (b1) and the aliphatic dicarboxylic acid (b2) are not particularly limited as long as they do not impair the effects of the present invention. The total amount of the aliphatic diol (b1) and the aliphatic dicarboxylic acid (b2) in the polyester unit (b) is preferably 90 mol% or more, more preferably 95 mol% or more, even more preferably 99 mol% or more, and may be 100 mol%.

[0030] <Aliphatic Diol (b1)> From the viewpoints of biodegradability and impact resistance, it is preferable that the aliphatic diol (b1) has an alkyl group as a branched chain and does not have a quaternary carbon. From the same viewpoint, it is preferable that the two hydroxyl groups in the aliphatic diol (b1) are primary hydroxyl groups. Here, the "branched chain" in the aliphatic diol (b1) refers to a partial structure branched from the "main chain" in the aliphatic diol (b1), and no hydroxyl groups are bonded to its terminals. The "main chain" in the aliphatic diol (b1) refers to a partial structure that is a molecular chain composed of two primary hydroxyl groups in the molecule at both terminals and multiple atoms, preferably carbon atoms, connecting the two primary hydroxyl groups. Therefore, the two primary hydroxyl groups in the aliphatic diol (b1) are located at both terminals of the "main chain" in the aliphatic diol (b1).

[0031] When the aliphatic diol (b1) has a branched chain that is an alkyl group, the block structural unit (B) is less likely to crystallize and has good hydrolysis resistance, so that a biodegradable block copolymer containing the block structural unit (B) has better biodegradability and hydrolysis resistance. As a result, a film containing the biodegradable block copolymer also has good biodegradability and good hydrolysis resistance. Furthermore, since the block structural unit (B) is less likely to crystallize, the block structural unit (B) has an amorphous structure that is highly flexible, resulting in good impact resistance of the film. The aliphatic diol (b1) preferably has one or two branched chains, more preferably one. The branched chain is preferably a methyl group, an ethyl group, or a propyl group, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. When the aliphatic diol (b1) has multiple branched chains, the branched chains may be the same or different.

[0032] When the aliphatic diol (b1) does not have a quaternary carbon, the biodegradability of the biodegradable block copolymer is improved, and the biodegradability of a film containing the biodegradable block copolymer is also improved. Furthermore, the aliphatic diol (b1) readily reacts with the aliphatic dicarboxylic acid (b2), facilitating the production of the biodegradable block copolymer. When the two hydroxyl groups in the aliphatic diol (b1) are primary hydroxyl groups, the glass transition temperature of the biodegradable block copolymer tends to decrease, further improving the impact resistance of the film at low temperatures (-40°C to 10°C). Furthermore, the aliphatic diol (b1) readily reacts with the aliphatic dicarboxylic acid (b2), facilitating the production of the biodegradable block copolymer.

[0033] The number of carbon atoms in the aliphatic diol (b1) is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more from the viewpoint of hydrolysis resistance and impact resistance, and is preferably 30 or less, more preferably 18 or less, and even more preferably 9 or less from the viewpoint of biodegradability. That is, the number of carbon atoms in the aliphatic diol (b1) is preferably 4 to 30, more preferably 5 to 18, and even more preferably 6 to 9.

[0034] Examples of the aliphatic diol (b1) include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 1,4-pentanediol, 2-methyl-1,5-pentanediol, and 3-methyl-1 ,5-pentanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 2-ethyl-1,6-hexanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 2-methyl-1,9-nonanediol, etc. The aliphatic diol (b1) is preferably at least one selected from the group consisting of 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,4-diethyl-1,5-pentanediol, and more preferably 3-methyl-1,5-pentanediol. The aliphatic diol (b1) may be used alone or in combination of two or more kinds.

[0035] <<Aliphatic Dicarboxylic Acid (b2)>> The number of carbon atoms in the aliphatic dicarboxylic acid (b2) is not limited as long as the effects of the present invention are not impaired, but from the viewpoint of impact resistance, it is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more, and from the viewpoint of biodegradability, it is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. That is, the number of carbon atoms in the aliphatic dicarboxylic acid (b2) is preferably 4 to 12, more preferably 5 to 10, and even more preferably 6 to 8.

[0036] From the viewpoint of hydrolysis resistance and impact resistance, the aliphatic dicarboxylic acid (b2) is preferably an acyclic aliphatic dicarboxylic acid. Examples of the aliphatic dicarboxylic acid (b2) include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, and decanedicarboxylic acid. Preferably, it is at least one selected from the group consisting of succinic acid, adipic acid, and sebacic acid, more preferably at least one selected from succinic acid and adipic acid, and even more preferably adipic acid. The aliphatic dicarboxylic acid (b2) may be used alone or in combination of two or more.

[0037] <Preferred Combinations of Aliphatic Diol (b1) and Aliphatic Dicarboxylic Acid (b2)> From the viewpoint of exhibiting even better biodegradability, hydrolysis resistance, and impact resistance, the combinations of the aliphatic diol (b1) and the aliphatic dicarboxylic acid (b2) are, for example, a combination of 3-methyl-1,5-pentanediol and adipic acid, a combination of 3-methyl-1,5-pentanediol and succinic acid, a combination of 2-methyl-1,3-propanediol and adipic acid, a combination of 2-methyl-1,3-propanediol and succinic acid, and a combination of 2,4-diethyl-1,5-pentanediol and adipic acid, and a more preferred embodiment is a combination of 3-methyl-1,5-pentanediol and adipic acid.

[0038] <Ratio of Aliphatic Diol (b1) and Aliphatic Dicarboxylic Acid (b2)> The molar ratio of the aliphatic diol (b1) and the aliphatic dicarboxylic acid (b2) charged when reacting them [aliphatic diol (b1) / aliphatic dicarboxylic acid (b2)] is preferably 1.4 / 1 to 1 / 1.4, more preferably 1.2 / 1 to 1 / 1.2.

[0039] <Number Average Molecular Weight of Block Structural Unit (B)> From the viewpoint of ease of production, the number average molecular weight of the block structural unit (B) is preferably 1,000 to 300,000, more preferably 5,000 to 200,000, even more preferably 7,000 to 150,000, and may be 9,000 to 100,000. Furthermore, from the viewpoints of heat resistance and impact resistance, the number average molecular weight of the block structural unit (B) is preferably 10,000 or more, more preferably 15,000 or more, even more preferably 20,000 or more, and even more preferably 25,000 or more. That is, from the viewpoints of heat resistance and impact resistance, the number average molecular weight of the block structural unit (B) is preferably 10,000 to 300,000, more preferably 15,000 to 200,000, even more preferably 20,000 to 150,000, and even more preferably 25,000 to 100,000. The number average molecular weight of the block structural unit (B) can be determined from the number average molecular weight of the biodegradable block copolymer and the mass content of the block structural unit (B), and specifically, can be measured by the method described in the Examples.

[0040] <Glass Transition Temperature of Block Structural Unit (B)> From the viewpoint of low-temperature (-40°C to 55°C) moldability, the glass transition temperature of the block structural unit (B) is 55°C or lower, preferably 0°C or lower, more preferably -15°C or lower, even more preferably -20°C or lower, and may be -25°C or lower, -30°C or lower, -35°C or lower, or -45°C or lower. There is no lower limit for the glass transition temperature of the block structural unit (B), and a lower temperature is preferable. However, the glass transition temperature may be -100°C or higher, -80°C or higher, -70°C or higher, or -65°C or higher. That is, the glass transition temperature of the block structural unit (B) is preferably -80 to 55°C, more preferably -80 to 0°C, even more preferably -80 to -15°C, even more preferably -70 to -20°C, and even more preferably -65 to -25°C. The glass transition temperature of the block structural unit (B) can be determined by differential scanning calorimetry.

[0041] <Structural Unit Proportion of Biodegradable Block Copolymer> The biodegradable block copolymer preferably contains 0.5 to 70 mass%, more preferably 5 to 60 mass%, even more preferably 10 to 55 mass%, even more preferably 15 to 50 mass%, and even more preferably 20 to 50 mass% of the block structural unit (A) relative to 100 mass% of the total of the block structural unit (A) and the block structural unit (B). The above content ratios make it easier to obtain a film with excellent impact resistance. The proportion of the block structural unit (A) is: １ It can be determined by H-NMR, specifically by the method described in the Examples.

[0042] The biodegradable block copolymer preferably contains 30 to 99.5% by mass of the block structural unit (B), more preferably 40 to 95% by mass, even more preferably 45 to 90% by mass, even more preferably 50 to 85% by mass, and even more preferably 50 to 80% by mass, relative to 100% by mass of the total of the block structural unit (A) and the block structural unit (B). The above content ratios facilitate the production of films with excellent impact resistance. The proportion of the block structural unit (B) is as follows: １ It can be determined by H-NMR, specifically by the method described in the Examples.

[0043] The total content of the block structural unit (A) and the block structural unit (B) in the biodegradable block copolymer is preferably 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass. There is no upper limit to the total content of the block structural unit (A) and the block structural unit (B) in the biodegradable block copolymer, and it may be, for example, 100% by mass or less.

[0044] The biodegradable block copolymer may or may not contain units other than the block structural unit (A) and the block structural unit (B). The units other than the block structural unit (A) and the block structural unit (B) are not particularly limited as long as they do not impair the effects of the present invention. In order to further exert the effects of the present invention, the content of units other than the block structural unit (A) and the block structural unit (B) in the biodegradable block copolymer is preferably 10% by mass or less, more preferably 5% by mass or less.

[0045] <<Bonding Form of Biodegradable Block Copolymer>> The bonding form of the biodegradable block copolymer is preferably a triblock type or a diblock type, and more preferably a triblock type. The biodegradable block copolymer may be a mixture of a triblock type and a diblock type. Specifically, the bonding form is preferably [block structural unit (A)]-[block structural unit (B)]-[block structural unit (A)].

[0046] <Number-Average Molecular Weight of Biodegradable Block Copolymer> In one aspect of the present invention, the number-average molecular weight of the biodegradable block copolymer is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 15,000 or more, from the viewpoints of hydrolysis resistance, impact resistance, and heat resistance, and is preferably 400,000 or less, more preferably 200,000 or less, and even more preferably 100,000 or less, from the viewpoints of ease of production and processability. That is, the number-average molecular weight of the biodegradable block copolymer is preferably 5,000 to 400,000, more preferably 10,000 to 200,000, and even more preferably 15,000 to 100,000. In another aspect of the present invention, the number-average molecular weight of the biodegradable block copolymer is preferably 20,000 or more, more preferably 25,000 or more, even more preferably 30,000 or more, and even more preferably 35,000 or more, from the viewpoints of heat resistance and impact resistance, and is preferably 400,000 or less, more preferably 200,000 or less, and even more preferably 100,000 or less, from the viewpoints of ease of production and processability. That is, the number-average molecular weight of the biodegradable block copolymer is preferably 20,000 to 400,000, more preferably 25,000 to 200,000, even more preferably 30,000 to 100,000, and even more preferably 35,000 to 100,000. The number-average molecular weight of the biodegradable block copolymer can be determined by gel permeation chromatography (GPC), specifically, by the method described in the Examples.

[0047] <Melting Point of Biodegradable Block Copolymer> From the viewpoint of processability, such as ease of melt processing, the melting point of the biodegradable block copolymer is preferably less than 180°C, more preferably 175°C or less, even more preferably 170°C or less, and even more preferably 160°C or less. From the viewpoint of practical heat resistance, the melting point of the biodegradable block copolymer is preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 125°C or higher. From the viewpoint of good processability and heat resistance, the melting point of the biodegradable block copolymer is preferably 110°C or higher but lower than 180°C, more preferably 120°C or higher but 175°C or lower, even more preferably 120°C or higher but 170°C or lower, and even more preferably 125°C or higher but 160°C or lower. The melting point of the biodegradable block copolymer can be determined using a differential scanning calorimeter, and specifically, can be measured by the method described in the examples.

[0048] <Method for Producing Biodegradable Block Copolymer> Known production methods can be used to produce the biodegradable block copolymer. When the block structural unit (B) is a polyester unit (b), a known method for producing a biodegradable block copolymer may be a method in which a polyester constituting the polyester unit (b) is synthesized and the polyester is polymerized with lactide. The polyester can be synthesized by a known method. For example, a polyester can be synthesized by reacting an aliphatic diol (b1) with an aliphatic dicarboxylic acid (b2) using an esterification catalyst (e.g., tin octoate, tin chloride, tin oxide). When polymerizing a polyester with lactide, it is preferable to use a ring-opening polymerization catalyst (e.g., tin octoate, tin chloride, tin oxide). The polymerization reaction can be performed using solution polymerization, melt polymerization, interfacial polycondensation, etc., and known polymerization reaction conditions can be set for each method.

[0049] Furthermore, when the block structural unit (B) is a polyester unit (b), another known method for producing a biodegradable block copolymer may be, for example, a method in which a block structural unit (A) mainly composed of a polylactic acid unit and a polyester constituting the polyester unit (b) are separately synthesized, and the block structural unit (A) is reacted with the polyester. The block structural unit (A) can be synthesized by a known method. For example, the structural unit (A) may be synthesized by reacting lactide by a ring-opening polymerization method. When polymerizing the structural unit (A) with the polyester, it is preferable to use an esterification catalyst (e.g., tin octoate, tin chloride, tin oxide). The polymerization reaction may be solution polymerization, melt polymerization, interfacial polycondensation, or the like, and known polymerization reaction conditions can be set for each.

[0050] <Other Components> The film of this embodiment may contain other resins, plasticizers, additives, and the like in addition to the polylactic acid resin and the biodegradable block copolymer.

[0051] <Other Resins> The other resins are not particularly limited, but from the viewpoint of ensuring the biodegradability of the film, resins that are biodegradable in any of industrial compost, household compost, soil, and marine environments are preferred. Suitable examples of other resins include polyvinyl alcohol, cellulose resins such as cellulose acetate, starch and its esters, aliphatic polyesters, and 4-nylon. These may be used alone, or two or more may be used in combination. The content of other resins in the film is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less.

[0052] <Plasticizer> A plasticizer may be added to the film to adjust its viscosity to a level suitable for molding or to obtain a molded product with the desired hardness. There are no particular limitations on the plasticizer, but plasticizers that are biodegradable in industrial compost, household compost, soil, or marine environments are preferred. Suitable examples include vegetable esters such as rapeseed oil and castor oil, synthetic esters such as triacetin, diethyl phthalate, and triethyl citrate, polyols and derivatives thereof such as ethylene glycol and trimethylolpropane, and sugars such as sorbitol. These may be used alone or in combination of two or more. When using the above plasticizer, the content of the plasticizer in the film can be determined appropriately depending on the desired physical properties of the film.

[0053] Additives The film of this embodiment may contain additives other than plasticizers. Examples of additives include inorganic fillers, softeners, heat aging inhibitors, antioxidants, hydrolysis inhibitors, light stabilizers, antistatic agents, release agents, flame retardants, foaming agents, pigments, dyes, brighteners, UV absorbers, and lubricants. These may be used alone or in combination of two or more. When using the above additives, the content of the additives in the film may be determined appropriately depending on the desired physical properties of the film.

[0054] <Content of Each Component in the Film> The film according to this embodiment has a polylactic acid resin content of 80% by mass or more. The polylactic acid resin content in the film is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 91% by mass or more, and preferably 99.5% by mass or less, more preferably 99% by mass or less, even more preferably 98.5% by mass or less, and even more preferably 98% by mass or less. That is, the polylactic acid resin content in the film is preferably 80 to 99.5% by mass, more preferably 85 to 99% by mass, even more preferably 90 to 98.5% by mass, and even more preferably 91 to 98% by mass. The above content ratios allow for a film with even better transparency, rigidity, environmental impact reduction, and low-temperature formability.

[0055] In the film of this embodiment, from the viewpoints of transparency, rigidity, and environmental load reduction, the total content of the polylactic acid resin and the block structural unit (A) is preferably 90% by mass or more. From the viewpoints of transparency, rigidity, and environmental load reduction, the total content of the polylactic acid resin and the block structural unit (A) is more preferably 92% by mass or more, even more preferably 94% by mass or more, and even more preferably 95% by mass or more. From the viewpoint of impact resistance, the total content of the polylactic acid resin and the block structural unit (A) is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. That is, the total content of the polylactic acid resin and the block structural unit (A) in the film is preferably 90 to 99% by mass, more preferably 92 to 98% by mass, even more preferably 94 to 97% by mass, and even more preferably 95 to 97% by mass.

[0056] The film of this embodiment has a biodegradable block copolymer content of preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, still more preferably 2% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 9% by mass or less. That is, the film has a biodegradable block copolymer content of preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, even more preferably 1.5 to 10% by mass, and even more preferably 2 to 9% by mass. The above content ratios allow for a film with even better low-temperature formability.

[0057] In the film of this embodiment, the total content of the polylactic acid resin and the biodegradable block copolymer is preferably 80.5% by mass or more, more preferably 86% by mass or more, even more preferably 91.5% by mass or more, even more preferably 93% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass or less. That is, the total content of the polylactic acid resin and the biodegradable block copolymer in the film is preferably 80.5 to 100% by mass, more preferably 86 to 100% by mass, even more preferably 91.5 to 100% by mass, even more preferably 93 to 100% by mass, and even more preferably 95 to 100% by mass. With the above content ratios, the effects of the present invention are more pronounced.

[0058] The biomass ratio of the film of this embodiment is preferably 90% by mass or more, more preferably 92% by mass or more, even more preferably 94% by mass or more, and even more preferably 95% by mass or more from the viewpoint of environmental load reduction effect, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less from the viewpoint of low-temperature formability. That is, the biomass ratio of the film is preferably 90 to 99% by mass, more preferably 92 to 98% by mass, even more preferably 94 to 97% by mass, and even more preferably 95 to 97% by mass. In this specification, "biomass ratio" means "the ratio of renewable, biologically derived organic resources excluding fossil resources," and includes polylactic acid resins, block structural units (A) mainly composed of polylactic acid units, and the like.

[0059] <Film Physical Properties> <Break Elongation> When the film according to this embodiment has a film thickness of 0.4 mm, the break elongation at 23°C measured in accordance with JIS K 7127:1999 is 100% or more. From the viewpoint of low-temperature formability, the break elongation is preferably 150% or more, more preferably 200% or more, even more preferably 220% or more, and preferably 1000% or less. That is, the break elongation is preferably 100 to 1000%, more preferably 150 to 1000%, even more preferably 200 to 1000%, and still more preferably 220 to 1000%.

[0060] <Crystallization> From the viewpoint of low-temperature formability, the film of this embodiment preferably has a small difference between the heat of fusion and the heat of crystallization. The smaller the difference between the heat of fusion and the heat of crystallization, the lower the crystallization of the film. From the viewpoint of low-temperature formability, the difference between the heat of fusion and the heat of crystallization of the film is preferably 8 J / g or less, more preferably 3 J / g or less, and even more preferably 2 J / g or less. There is no particular lower limit for the difference between the heat of fusion and the heat of crystallization of the film, and it may be 0 J / g or 0.001 J / g or more. That is, the difference between the heat of fusion and the heat of crystallization of the film is preferably 0 to 8 J / g, more preferably 0.001 to 3 J / g, and even more preferably 0.001 to 2 J / g. The melting point of the film can be determined using a differential scanning calorimeter, specifically, by the method described in the Examples.

[0061] <Haze> When the film thickness is 0.4 mm, the haze of the film of this embodiment is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. Within this range, a highly transparent molded article can be produced, thereby expanding the practical applicability. Furthermore, when the film thickness is 0.4 mm, the haze of the film of this embodiment is not particularly limited in terms of its lower limit, and may be 0%, 0.5% or more, 1% or more, or 3% or more. That is, when the film thickness is 0.4 mm, the haze of the film of this embodiment is preferably 0 to 20%, more preferably 0.5 to 15%, even more preferably 1 to 10%, and even more preferably 3 to 10%. The haze of the film can be determined by the method described in JIS K7136:2000, and specifically, can be measured by the method described in the Examples.

[0062] <50% Breakdown Impact Energy> When the film thickness is 0.4 mm, the 50% breakage impact energy of the film of this embodiment is preferably 1.0 J or more, more preferably 1.1 J or more, and even more preferably 1.2 J or more. Within the above range, breakage due to dropping during transportation can be suppressed, and the environmental impact caused by loss due to breakage can be reduced. Furthermore, the 50% breakage impact energy of the film of this embodiment is not particularly limited in upper limit, and may be 9.8 J or less. That is, the 50% breakage impact energy of the film of this embodiment is preferably 1.0 to 9.8 J, more preferably 1.1 to 9.8 J, and even more preferably 1.2 to 9.8 J. The 50% breakage impact energy of the film of this embodiment can be determined according to JIS K7211-1:2006, and specifically, can be measured by the method described in the Examples.

[0063] <Tensile Modulus> When the film thickness is 0.4 mm, the tensile modulus of the film of this embodiment is preferably 2.0 GPa or more, more preferably 3.0 GPa or more, even more preferably 3.5 GPa or more, and even more preferably 4.0 GPa. Within the above range, a film with even better low-temperature formability can be obtained. Furthermore, the tensile modulus of the film of this embodiment is not particularly limited in upper limit, and may be 9.7 GPa or less. That is, the tensile modulus of the film of this embodiment is preferably 2.0 to 9.7 GPa, more preferably 3.0 to 9.7 GPa, even more preferably 3.5 to 9.7 GPa, and even more preferably 4.0 to 9.7 GPa. The tensile modulus of the film can be specifically measured by the method described in the Examples.

[0064] <Film Manufacturing Method> Although known manufacturing methods can be used to manufacture the film of this embodiment, from the viewpoint of further demonstrating the effects of the present invention, it is preferable to manufacture the film by extrusion molding using a twin-screw kneading extruder and a T-die, and more preferably, to include the following steps (1) to (3). Step (1): Melt-kneading a polylactic acid-based resin and a biodegradable block copolymer using a twin-screw kneading extruder. Step (2): Melt-extruding the melt into a film using a T-die. Step (3): Cooling and solidifying the melt-extruded film using a cooling roll at a temperature of 20 to 75°C. When a film is manufactured by extrusion molding using a twin-screw kneading extruder and a T-die, not only is it easy to increase the film production rate, but it is also easy to adjust the ratio of each component to obtain the desired physical properties. Furthermore, it is possible to obtain a film with even better low-temperature formability.

[0065] <<Step (1)>> Step (1) is a step of melt-kneading a polylactic acid-based resin and a biodegradable block copolymer using a twin-screw kneading extruder. In step (1), if necessary, other resins, additives, etc., besides the polylactic acid-based resin and the biodegradable block copolymer may be added and melt-kneaded. Alternatively, pre-blending may be performed before melt-kneading. Examples of pre-blending methods include methods using a mixer such as a Henschel mixer, a high-speed mixer, a V-blender, a ribbon blender, a tumbler blender, or a conical blender.

[0066] The temperature of the twin-screw kneading extruder (kneading section temperature) during melt-kneading can be any known condition, but is preferably 150 to 250°C, more preferably 170 to 230°C, and even more preferably 190 to 225°C. If the temperature of the twin-screw kneading extruder is 250°C or less, thermal decomposition of the biodegradable block copolymer can be suppressed, and the generation of foreign matter can be suppressed. Furthermore, if the temperature of the twin-screw kneading extruder is 150°C or higher, the melt viscosity of the polylactic acid resin can be reduced, allowing for sufficient kneading, and making it easier to adjust the morphology (how the polylactic acid resin and the biodegradable block copolymer are mixed).

[0067] The temperature near the raw material inlet of the twin-screw kneading extruder is preferably 190°C or lower, more preferably 170°C or lower, even more preferably 150°C or lower, and even more preferably 140°C or lower, from the viewpoint of preventing the biodegradable block copolymer from melting and adhering at the raw material inlet, thereby causing instability in the amount of raw material introduced. Furthermore, the temperature near the raw material inlet of the twin-screw kneading extruder may be 100°C or higher, 105°C or higher, or 110°C or higher. That is, the temperature near the raw material inlet of the twin-screw kneading extruder is preferably 100 to 190°C, more preferably 100 to 170°C, even more preferably 105 to 150°C, and even more preferably 110 to 140°C.

[0068] <<Step (2)>> Step (2) is a step of melt-extruding the molten material into a film using a T-die. The T-die is not particularly limited, and known die types can be used, such as a manifold die, a fishtail die, or a coat hanger die. The T-die temperature is preferably 180°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, and even more preferably 205°C or higher, from the viewpoint of suppressing the occurrence of melt fracture due to the addition of the biodegradable block copolymer and obtaining a film with higher transparency. Furthermore, the T-die temperature is preferably 250°C or lower, more preferably 240°C or lower, and even more preferably 225°C or lower, from the viewpoint of suppressing the generation of foreign matter associated with thermal decomposition of the biodegradable block copolymer and obtaining a film with excellent low-temperature formability. That is, the T-die temperature is preferably 180 to 250°C, more preferably 190 to 240°C, even more preferably 200 to 225°C, and even more preferably 205 to 225°C.

[0069] <<Step (3)>> Step (3) is a step of cooling and solidifying the melt extruded into a film using a chill roll at a temperature of 20 to 75°C. The melt extruded into a film through a T-die can be cooled using known methods such as an air knife, chill roll, or nip roll, but it is preferable to use a chill roll. From the viewpoint of obtaining a film with higher transparency, the temperature of the chill roll is preferably 30 to 70°C, more preferably 40 to 65°C, and even more preferably 50 to 60°C. The surface of the chill roll is not particularly limited, and known surfaces can be used, but from the viewpoint of obtaining a film with higher transparency, a mirror finish is preferred.

[0070] The film of this embodiment may be laminated with other films as needed. Any known lamination method can be used as the lamination method, and there is no particular limitation. Examples of lamination methods include coextrusion, lamination, and coating. The other films to be laminated may be single-layer or multi-layer.

[0071] The film of this embodiment may be subjected to any secondary processing. Examples of secondary processing include embossing, painting, adhesion, printing, metallizing (plating, etc.), machining, heat treatment, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, lamination, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.). These may be used alone or in combination of two or more. The secondary processing may be performed before or after the production of a molded body.

[0072] <Applications of the Film> Applications of the film of this embodiment are listed below, but are not limited to these. Examples of applications of the film of this embodiment include various molded products, packaging materials, sanitary materials, medical materials, clothing materials, agricultural materials, gardening materials, fishing materials, foamed resin materials, civil engineering and construction materials, automotive parts, and electrical and electronic components. Packaging materials include shrink films, shrink labels, vapor-deposited films, cling films, food packaging, clamshell packages, garbage bags, shopping bags, standard-sized bags, heavy-duty bags, eco-friendly bags, tube containers, container stoppers, cap liners, blister packs, food trays, foam trays, conductive trays, glasses, mugs, paper cups, paper cup lids, tableware, lining films for paper containers, sealant films, adhesive films, plates, various container bottles, oil containers, printing films, ink binders, and other general packaging. Sanitary materials include disposable diapers, sanitary products, and protective gloves. Examples of clothing materials include waterproof films, breathable films, hat top buttons, clothing buttons, zippers, footwear such as fashion sandals, and raincoats. Examples of agricultural materials include agricultural mulch films, protective films, seedling pots, mulch films, labels, water conduits, and tree protection sheets. Examples of automotive parts include trim parts, mats, coatings, skins, protective layers, transparent automotive parts, tubes, connectors, airbag covers, interior parts, exterior parts, and decorative films. Examples of electrical and electronic parts include home appliance components, multi-function machine components, protective films, insulated cables, casings for optical fiber cables, and piezoelectric elements. Other applications include cable ties, prepaid cards, balloons, umbrellas, plastic gloves, cushioning materials, heat insulating materials, packaging materials, hoses, rulers, straws, buoys, aquaculture tubes, underground pipes, fishing tackle, slope sheets, drug transport tubes, and catheters.

[0073] [Molded body] The molded body of this embodiment includes the film of this embodiment. The molded body of this embodiment is molded using the film of this embodiment. The molding method can be a known molding method, and is not particularly limited, but examples thereof include vacuum molding, pressure molding, vacuum pressure molding, and molding using a bag making machine.

[0074] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0075] The compounds used in the examples and comparative examples are as follows: Polylactic acid "INGEO 2003D" (manufactured by NatureWorks Inc.) 3-methyl-1,5-pentanediol (manufactured by Kuraray Co., Ltd.) 2-methyl-1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) Adipic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) Tin octoate (manufactured by Tokyo Chemical Industry Co., Ltd.) Toluene (manufactured by Kishida Chemical Co., Ltd.) L-lactide (manufactured by Tokyo Chemical Industry Co., Ltd.) Methanol (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.)

[0076] The physical properties of the block copolymers, polymers, and resin compositions in the examples and comparative examples were measured or evaluated by the following methods. (1) Number-average molecular weight (Mn) The number-average molecular weight (Mn) of the biodegradable block copolymer was determined in terms of standard polystyrene by gel permeation chromatography (GPC). The Mn of the block structural unit (B) was calculated from the Mn of the biodegradable block copolymer and the mass content of the block structural unit (B). <GPC measurement conditions> Apparatus: GPC apparatus "HLC-8220" manufactured by Tosoh Corporation Separation column: "TSKgel SuperMultiporeHZ-M (column diameter = 4.6 mm, column length = 15 cm)" manufactured by Tosoh Corporation (two columns connected in series) Eluent: tetrahydrofuran (THF) Eluent flow rate: 0.35 mL / min Column temperature: 40°C Detection method: refractive index (RI) Injection volume: 10 μL Concentration: 1 mg / 1 mL (block copolymer / THF)

[0077] (2) Hard ratio (mass content of block structural unit (A))１ The hard ratios (% by mass) of the biodegradable block copolymer and polymer were calculated by H-NMR. The molar ratio of the block structural unit (A) to the block structural unit (B) was calculated from the area ratio of the signal at around 5.2 ppm attributable to the polylactic acid unit in the obtained spectrum to the signal at around 0.9 ppm attributable to the structural unit (B). The molar ratio was multiplied by the molecular weight of the block structural unit to obtain a mass ratio, and the mass ratio of the block structural unit (A) when adjusted so that the sum of the mass ratios became 100 was taken as the hard ratio. １ H-NMR measurement conditions> Apparatus: Nuclear magnetic resonance apparatus "JNM-ECX400" manufactured by JEOL Ltd. Solvent: deuterated chloroform Measurement temperature: 50°C Number of accumulations: 1024 Temperature rise rate: 10°C / min

[0078] (3) Glass Transition Temperature, Melting Point, Heat of Fusion, and Heat of Crystallization The glass transition temperatures of the polylactic acid resin and the block structural unit (B), the melting points of the polylactic acid resin, and the melting points of the biodegradable block copolymer were measured using a differential scanning calorimeter DSC25 (manufactured by TA Instruments) according to the method described in JIS K7121: 2012, and the heat of fusion and heat of crystallization of the film were measured according to the method described in JIS K7122: 2012. Specifically, the measurement sample (polylactic acid resin, block structural unit (B), biodegradable block copolymer, or film) was heated from 30°C to 220°C at a heating rate of 10°C / min (1st run), held at 220°C for 5 minutes, then cooled from 220°C to -70°C at a cooling rate of 10°C / min, and held at -70°C for 5 minutes. Subsequently, the sample was heated from -70 ° C. to 220 ° C. at a heating rate of 10 ° C. / min and held at 220 ° C. for 5 minutes (2nd run). Finally, the sample was cooled from 220 ° C. to 30 ° C. at a cooling rate of 10 ° C. / min. In the 2nd run, the midpoint glass transition temperature in JIS K7121:2012 was taken as the glass transition temperature, the endothermic peak temperature in the melting curve was taken as the melting temperature (melting point), and the exothermic peak temperature was taken as the crystallization temperature. In addition, the heat of fusion in the melting curve during the 2nd run and the heat of crystallization in the crystallization curve were measured. Note that, when multiple melting peaks were observed, the peak on the highest temperature side was taken as the melting temperature (melting point). Similarly, when multiple crystallization peaks were observed, the crystallization peak temperature on the highest temperature side was taken as the crystallization temperature. The glass transition temperature of the block structural unit (B) was determined to be the lowest glass transition temperature appearing in the melting curve of the biodegradable block copolymer.

[0079] (4) Melt Flow Rate (MFR) The melt flow rate (MFR) of the polylactic acid resin was measured in accordance with ASTM D1238 at 210° C. under a load of 2.16 kgf.

[0080] (5) Shape of Dispersed Particles (X) and Number Proportion of Dispersed Particles (x) The shape of dispersed particles (X) and the number proportion of dispersed particles (x) were measured using a transmission electron microscope (TEM). A film was stained for 15 minutes using a 10% by mass aqueous solution of phosphotungstic acid, embedded in epoxy resin, and then cut using an ultramicrotome parallel to the flow direction of the film and perpendicular to the film surface to prepare ultrathin sections. Using a transmission electron microscope "HT7700" (manufactured by Hitachi High-Tech Corporation), ultrathin sections were photographed at 1000x magnification with an acceleration voltage of 100 kV and an emission current of 10 μA. Of the obtained images (film cross-sectional images), a 35 μm square was set as the measurement point, and the number (I) of dispersed particles (X) with a maximum Feret diameter of 0.3 μm or more and the maximum and minimum Feret diameters of the dispersed particles (X) were measured. Next, the maximum value of the Feret diameter of each dispersed particle (X) was divided by the minimum value, and the number (i) of dispersed particles (x) whose value exceeded 1.5 was measured. From the obtained number (I) of dispersed particles (X) and the number (i) of dispersed particles (x), the number ratio of dispersed particles (x) among dispersed particles (X) whose maximum Feret diameter was 0.3 μm or more was calculated. However, for the film obtained in Comparative Example 2, the number ratio of dispersed particles (x) among dispersed particles (X) whose maximum Feret diameter was 0.3 μm or more was calculated in the same manner as above, except that the film was cut in a direction parallel to one side of the film and in the thickness direction to prepare ultrathin slices. In addition, the shape of the dispersed particles (X) in the obtained image (film cross-sectional image) was evaluated. Note that a shape in which at least a portion of the periphery was constituted by a curve and in which there was a difference between the maximum and minimum values ​​of the Feret diameter of the periphery was determined to be elliptical.

[0081] (6) Breaking Elongation and Tensile Modulus Dumbbell-shaped No. 3 test pieces according to JIS K6251:2017 were punched out from 0.4 mm thick films and left to stand for at least 88 hours in a 23°C, 50% RH environment to obtain test pieces. The breaking elongation and tensile modulus were measured at a tensile speed of 5 mm / min using an INSTRON 5900R-5666 (manufactured by Instron Corporation) in a 23°C, 50% RH environment according to JIS K 7127:1999. For the films obtained in Examples 1 to 4 and Comparative Example 1, the tensile direction was perpendicular to the machine direction of the film, and for the film obtained in Comparative Example 2, the tensile direction was parallel to one side of the film, with a gauge length of 10 mm.

[0082] (7) Haze A 50 x 50 mm square piece was cut out from a 0.4 mm thick film and attached to a smooth acrylic plate with tape to prepare a test piece. Using a HAZE METER NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the haze of the test piece was measured according to a method in accordance with JIS K7136:2000. In addition, the haze of the acrylic plate without the film attached was measured, and the haze of the film was calculated by subtracting the haze of the acrylic plate without the film attached from the haze of the test piece.

[0083] (8) 50% Breakdown Impact Energy A 10 x 10 cm square piece was cut out from a 0.4 mm thick film to prepare a test specimen. The obtained test specimen was left standing at 23°C and 49% humidity for 88 hours or more, and the 50% breakdown impact energy was measured using a DuPont impact resistance tester (manufactured by Taiyu Kizai Co., Ltd.) in accordance with the staircase method of JIS K7211-1:2006. A 0.3 kg weight and a hemispherical striker with a diameter of 20 mm were used. The test was conducted so that the striker was in contact with the center of the test specimen.

[0084] (9) Evaluation of Low-Temperature Formability Two iron plates with a 7 x 7 cm hole in the center were sandwiched between the iron plates so that a 0.4 mm thick film was stretched over the hole. The thickness of the upper iron plate was 5 mm, and the thickness of the lower iron plate was 3 mm. As shown in Figure 1 (low-temperature formability evaluation device), the iron plate with the film sandwiched between them was hung between two 16 cm high scaffolds. The scaffolds and iron plates were secured with clips so that the hole in the iron plate was positioned between the scaffolds, and four 2 kg weights were placed on the iron plate. Next, a lab jack with a pin as shown in Figure 2 was placed directly below the hole in the iron plate (see Figure 1), and the height of the lab jack was raised until the tip of the pin contacted the film. The height of the lab jack was raised at a rate of 5 mm / min or less until the tip of the pin pierced the film by 4 mm. After the above steps were completed, the pins were removed, and films in which no breakage was observed were evaluated as "A" (good low-temperature formability), and films in which breakage was observed were evaluated as "B" (poor low-temperature formability).

[0085] (10) Biomass Ratio Among the components constituting the film, components derived from polylactic acid and L-lactide were used as biomass materials, and the ratio of components derived from polylactic acid and L-lactide in the film was calculated to obtain the biomass ratio.

[0086] [Production Example 1] A flask equipped with a vacuum pump and an apparatus capable of distilling off the generated liquid was charged with 3-methyl-1,5-pentanediol and adipic acid in a molar ratio of 3-methyl-1,5-pentanediol / adipic acid = 1.1 / 1, and tin octoate was added in an amount of 0.1% by mass based on the total weight of 3-methyl-1,5-pentanediol and adipic acid. The mixture was heated under a nitrogen atmosphere at normal pressure at 160°C for 3 hours and then at 220°C for 3 hours, while distilling off water, to carry out a reaction. The pressure was then reduced to 2,000 Pa and the reaction was continued for 3 hours. The pressure was then reduced to 80 Pa and the reaction was continued while appropriately checking until the number average molecular weight reached 26,600, thereby synthesizing a polymer composed of block structural units (B) incompatible with polylactic acid resins. After the reaction was completed, the pressure was returned to normal and the temperature was cooled to 80°C. Toluene was then added to dilute the solids concentration to 40% by mass, and the toluene solution was then added to methanol in an amount (by mass) twice the total volume of the solution. The supernatant was discarded, and an equal amount of methanol was added again to wash the solution. The supernatant was discarded, and the recovered insoluble matter was dried in a vacuum dryer at 40°C to remove organic volatiles, thereby obtaining a polymer comprising block structural units (B). Toluene was again added to the purified polymer comprising block structural units (B), and the polymer was diluted to a solids concentration of 33% by mass. The temperature was then raised to 140°C, and 10% by mass of the added toluene was distilled off to dehydrate the system. The system was then cooled to 80°C, and the polymer comprising block structural units (B) and L-lactide were added in a mass ratio of polymer comprising block structural units (B) / L-lactide = 80 / 20. Toluene was then added in an amount equal to the weight of the distilled off toluene, adjusting the solids concentration to 50% by mass. The temperature was then raised to 100°C, and 0.1% by mass of tin octoate was added to the polymer consisting of block structural units (B). The reaction was allowed to proceed for 4 hours, yielding a toluene solution of a biodegradable block copolymer consisting of block structural units (A) and block structural units (B), each of which mainly consisted of polylactic acid units. Toluene was added to this solution to dilute the solids concentration to 40% by mass, and the toluene solution was then poured into a volume (by mass) of methanol twice the total volume of the solution to precipitate a solid. The supernatant methanol was discarded, and the same amount of methanol as the toluene solution added was added again for washing.The methanol was discarded, and the recovered solid was dried in a vacuum dryer at 40°C to remove organic volatiles, yielding a biodegradable block copolymer (I-1) composed of block structural units (A) mainly composed of polylactic acid units and block structural units (B). The obtained block copolymer (I-1) was subjected to the above measurements. The results are shown in Table 1.

[0087] [Production Example 2] A biodegradable block copolymer (I-2) was obtained in the same manner as in Production Example 1, except that the charging ratio of the polymer composed of block structural units (B) to L-lactide was changed to 70 / 30 by mass. The obtained biodegradable block copolymer was subjected to the above measurements. The results are shown in Table 1.

[0088] [Production Example 3] A biodegradable block copolymer (I-3) was obtained in the same manner as in Production Example 2, except that 3-methyl-1,5-pentanediol was changed to 2-methyl-1,3-propanediol. The obtained biodegradable block copolymer was subjected to the above measurements. The results are shown in Table 1.

[0089] [Examples 1 and 3] The biodegradable block copolymer obtained in the Production Examples and polylactic acid "INGEO 2003D" (manufactured by NatureWorks) were charged into a twin-screw kneading extruder (manufactured by Technovel Corporation, product name "KZW15TW") in the formulation shown in Table 1, and kneaded at a temperature of 130°C near the raw material inlet, a kneading section temperature of 200°C, a strand die temperature of 190°C, and a screw rotation speed of 350 rpm. The water-cooled strands were cut with a strand cutter, thereby obtaining kneaded pellets of the polylactic acid resin and the biodegradable block copolymer. The resulting kneaded pellets were fed into a twin-screw kneading extruder (manufactured by Technovel Corporation, product name "KZW15TW") and kneaded at a temperature of 160°C near the raw material inlet, a kneading section temperature of 200°C, and a screw rotation speed of 300 rpm. The molten material was melt-extruded onto a film at a T-die temperature of 215°C, and then cooled and solidified using a cooling roll at a temperature of 55°C to obtain a 0.4 mm thick film. The resulting film was subjected to the above measurements and evaluations. The results are shown in Table 1.

[0090] [Example 2] A film having a thickness of 0.4 mm was obtained in the same manner as in Example 1, except that the T-die temperature was set to 190°C. The obtained film was subjected to the above measurements and evaluations. The results are shown in Table 1.

[0091] Example 4 A film having a thickness of 0.4 mm was obtained in the same manner as in Example 1, except that the T-die temperature was set to 220°C and the block copolymer (I-1) was changed to (I-3). The obtained film was subjected to the above measurements and evaluations. The results are shown in Table 1.

[0092] Comparative Example 1 A film having a thickness of 0.4 mm was obtained in the same manner as in Example 1, except that the biodegradable block copolymer was not used. The obtained film was subjected to the above measurements and evaluations. The results are shown in Table 1.

[0093] Comparative Example 2 The biodegradable block copolymer obtained in the Production Example and polylactic acid "INGEO 2003D" (NatureWorks) were charged into a kneading machine Labo Plastomill (Toyo Seiki Seisaku-sho, product name "3S150", roller mixer model "R60") in the formulation shown in Table 1, and melt-kneaded for 5 minutes at a cylinder temperature of 210°C and a screw rotation speed of 50 rpm to obtain a resin composition. The obtained resin composition was reduced in pressure to -0.1 MPaG using an oil rotary pump in a vacuum heat press machine (Imoto Machinery Works, Ltd., "IMC-183B"), preheated at 200°C for 5 minutes, and pressed at 50 kN for 3 minutes. Thereafter, the resin composition was subjected to a pressure of 70 kgf / cm using a cooling press machine equipped with water flow cooling. ２ The film was pressed at 100°C for 3 minutes to obtain a film having a thickness of 0.4 mm. The obtained film was subjected to the above measurements and evaluations. The results are shown in Table 1.

[0094]

[0095] As shown in Examples 1 to 4, films containing a biodegradable block copolymer including a block structural unit (A) primarily composed of polylactic acid units and a block structural unit (B) having a glass transition temperature of 55°C or lower, and having a breaking elongation of 100% or higher, were confirmed to suppress a decrease in transparency and rigidity and to have excellent low-temperature formability. Furthermore, the films obtained in Examples 1 to 4 had high impact resistance and biomass ratios, and exhibited a significant environmental load reduction effect. On the other hand, the film obtained in Comparative Example 1 did not contain a biodegradable block copolymer including a block structural unit (A) primarily composed of polylactic acid units and a block structural unit (B) having a glass transition temperature of 55°C or lower, and therefore exhibited poor low-temperature formability. Furthermore, the film obtained in Comparative Example 2 exhibited a breaking elongation of less than 100%, and therefore exhibited poor low-temperature formability. As shown in the results of Examples 1 to 4 above, the films according to the present invention exhibited suppressed decreases in transparency and rigidity, exhibited a significant environmental load reduction effect, and exhibited excellent low-temperature formability. Therefore, the films according to the present invention are highly useful industrially.

Claims

1. A film comprising a polylactic acid resin and a biodegradable block copolymer, wherein the biodegradable block copolymer comprises a block structural unit (A) primarily composed of polylactic acid units and a block structural unit (B) having a glass transition temperature of 55°C or lower, the polylactic acid resin content is 80% by mass or higher, and the film has a breaking elongation at 23°C of 100% or higher as measured in accordance with JIS K 7127:1999.

2. The film according to claim 1, having a haze of 15% or less as measured in accordance with JIS K 7136:2000.

3. The film according to claim 1 or 2, having a 50% breaking impact energy of 1.0 J or more as measured in accordance with JIS K 7211-1:2006.

4. The film according to claim 1 or 2, having a tensile modulus of elasticity of 2.0 GPa or more as measured in accordance with JIS K 7127:1999.

5. A film according to claim 1 or 2, in which the difference between the heat of fusion and the heat of crystallization measured in accordance with JIS K 7122:2012 is 8 J / g or less.

6. The film according to claim 1 or 2, wherein in a cross section of the film cut parallel to the machine direction and in the thickness direction, the biodegradable block copolymer forms a phase-separated structure in which it exists as dispersed particles (X), and the proportion (%) of dispersed particles (x) having a maximum Feret diameter of 0.3 μm or more and having a value obtained by dividing the maximum Feret diameter by the minimum Feret diameter of 1.5 or more is 35% or more.

7. A method for producing a film according to claim 1 or 2, comprising the following steps (1) to (3): Step (1): Melt-kneading a polylactic acid resin and a biodegradable block copolymer using a twin-screw kneading extruder; Step (2): Melt-extruding the melt into a film using a T-die; and Step (3): Cooling and solidifying the melt extruded into a film using a cooling roll at a temperature of 20 to 75°C.

8. A molded article comprising the film according to claim 1 or 2.

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