Method for manufacturing resin films

Abstract

To provide a method for manufacturing a resin film containing a poly (3-hydroxybutyrate)-based resin component by the inflation molding method, which can stably achieve good blocking-resistance.SOLUTION: A method for manufacturing a resin film containing a poly (3-hydroxybutyrate)-based resin component, comprises the following steps (i) to (iii), in sequence. (i) Extruding a resin composition containing a poly (3-hydroxybutyrate)-based resin component from a cylindrical die in a molten state to form a tubular resin film. (ii) Controlling the tubular resin film to maintain a temperature of 30°C or higher. (iii) Sandwiching the tubular resin film between a pair of rolls.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a resin film containing a poly(3-hydroxybutyrate)-based resin component. [Background Art]

[0002] Large amounts of petroleum-derived plastics are discarded every year, and environmental pollution caused by these massive amounts of waste has been addressed as a serious problem. In recent years, microplastics have also become a major problem in the marine environment.

[0003] Poly(3-hydroxybutyrate)-based resins have excellent seawater degradability and are materials that can solve environmental problems caused by discarded plastics. For example, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), which is a type of poly(3-hydroxybutyrate)-based resin, allows flexible control of mechanical properties by changing the composition ratio of 3-hydroxyhexanoate.

[0004] Meanwhile, inflation molding is known as a method for molding bag-shaped resin films. Inflation molding is a type of extrusion molding, which is a method in which molten resin is extruded as a tubular resin film from a cylindrical die, and at the same time, air is fed into the inside of the tube to expand the tube to a predetermined size.

[0005] Patent Document 1 discloses production of a resin film containing a poly(3-hydroxybutyrate)-based resin using inflation molding. [Prior Art Literature] [Patent Literature]

[0006] [Patent Document 1] Japanese Unexamined Patent Publication No. 2022-37396 [Summary of the Invention] [Problem to be Solved by the Invention]

[0007] When resin films containing poly(3-hydroxybutyrate) resin are manufactured by inflation molding, their blocking resistance may be low, which can result in poor opening of the bag when processed into a bag, for example.

[0008] In view of the above situation, the present invention aims to provide a method for producing a resin film containing a poly(3-hydroxybutyrate) resin component by inflation molding, which can stably achieve good blocking resistance. [Means for solving the problem]

[0009] As a result of diligent research, the inventors of the present invention have found that the above problem can be solved by controlling the temperature of the tube film to be above a specific temperature before the expanded tube film is sandwiched between a pair of pinch rolls and folded over in the inflation molding method, and have completed the present invention.

[0010] In other words, the present invention relates to a method for producing a resin film containing a poly(3-hydroxybutyrate) resin component, comprising the following steps (i) to (iii) in sequence. (i) A process of extruding a resin composition containing a poly(3-hydroxybutyrate) resin component in a molten state from a cylindrical die to form a tubular resin film. (ii) A step of controlling the tubular resin film to maintain a temperature of 30°C or higher. (iii) The process of sandwiching the tubular resin film between a pair of rolls. [Effects of the Invention]

[0011] According to the present invention, a method for producing a resin film containing a poly(3-hydroxybutyrate) resin component by inflation molding is provided, which can stably achieve good blocking resistance. The resin film produced by the present invention has good opening properties and can be suitably used in the form of bags, bags for gloves, shower caps, aprons, straw packaging bags and other bag containers, protective materials in the form of bags for equipment, storage bags for various documents such as instruction manuals, and other items. [Brief explanation of the drawing]

[0012] [Figure 1] Schematic diagram showing the configuration of inflation molding according to the embodiment. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below.

[0014] This embodiment relates to a method for producing a resin film containing a poly(3-hydroxybutyrate) resin component.

[0015] (Poly(3-hydroxybutyrate) resin component) The aforementioned resin film contains at least a poly(3-hydroxybutyrate) resin component as a resin component. The resin component contained in the resin film may consist solely of a poly(3-hydroxybutyrate) resin, or it may also contain another resin. A biodegradable resin, as described later, can be used as the other resin.

[0016] The resin film preferably contains 50% by weight or more of poly(3-hydroxybutyrate) resin (hereinafter sometimes abbreviated as P3HB), more preferably 70% by weight or more, even more preferably 80% by weight or more, and even more preferably 90% by weight or more. By having poly(3-hydroxybutyrate) resin as the main component, the resin film can exhibit biodegradability, particularly seawater biodegradability.

[0017] P3HB refers to a homopolymer having 3-hydroxybutyrate units, and / or a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units. From the viewpoint of seawater degradability, it is preferable to include a copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

[0018] The hydroxyalkanoic acid constituting the copolymer is not particularly limited, and in addition to 3-hydroxybutanoic acid, examples include 4-hydroxybutanoic acid, 3-hydroxypropionic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, and 3-hydroxyoctanoic acid.

[0019] Specific examples of P3HB include poly(3-hydroxybutyrate) (abbreviation: PHB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (abbreviation: PHBH), poly(3-hydroxybutyrate-co-3-hydroxyvalate) (abbreviation: P3HB3HV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (abbreviation: P3HB4HB), and poly(3-hydroxybutyrate-co-3-hydroxy Examples include hydroxyoctanoate (abbreviated as P3HB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (abbreviated as P3HB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (abbreviated as P3HB3HD), and poly(3-hydroxybutyrate-co-3-hydroxyvalate-co-3-hydroxyhexanoate) (abbreviated as P3HB3HV3HH). Among these, PHB, PHBH, P3HB3HV, and P3HB4HB are preferred because they are easy to produce industrially.

[0020] Among these, PHBH is particularly preferred because, by changing the composition ratio of repeating units, its melting point and degree of crystallinity can be altered, thereby adjusting physical properties such as Young's modulus and heat resistance, and it can be given properties between those of polypropylene and polyethylene. Furthermore, it is easy to produce industrially and is a physically useful plastic.

[0021] The resin film preferably contains 50% by weight or more of PHBH, more preferably 70% by weight or more, still more preferably 80% by weight or more, and even more preferably 90% by weight or more. The resin component contained in the resin film may be only PHBH, or may further contain another resin.

[0022] Examples of resins other than PHBH include P3HB other than PHBH. Biodegradable resins other than P3HB are also mentioned, including aliphatic polyester resins such as polycaprolactone, polybutylene succinate adipate, polybutylene succinate and polylactic acid, and aliphatic-aromatic polyester resins such as polybutylene adipate terephthalate and polybutylene azelate terephthalate.

[0023] A specific method for producing PHBH is described, for example, in International Publication No. WO 2010 / 013483. Examples of commercially available PHBH products include "Kaneka Biodegradable Polymer Green Planet" (registered trademark) manufactured by Kaneka Corporation.

[0024] The average content ratio of each constituent monomer in PHBH is preferably 3HB / 3HH = 97 to 75 / 3 to 25 (mol% / mol%), and more preferably 3HB / 3HH = 94 to 82 / 6 to 18 (mol% / mol%). When the average content ratio of 3HH in PHBH is 3 mol% or more, good adhesiveness can be obtained by heat sealing. Further, PHBH having an average content ratio of 3HH of 25 mol% or less does not have an excessively slow crystallization rate and is relatively easy to produce.

[0025] PHBH having an average content ratio of 3 to 25 mol% of 3HH may be composed of one type of PHBH, or may be composed of a mixture of at least two types of PHBH having different content ratios of constituent monomers from each other, or may be composed of a mixture of at least one type of PHBH and PHB.

[0026] Examples of mixtures of at least two types of PHBH having different proportions of constituent monomers include a mixture of PHBH having a 3HH content of 1 mol% or more and less than 5 mol%, and PHBH having a 3HH content of 24 mol% or more, or a mixture of these two types plus PHBH having a 3HH content of 5 mol% or more and less than 24 mol%.

[0027] The average content ratio of each constituent monomer in PHBH can be determined by methods known to those skilled in the art, for example, by the method described in paragraph

[0047] of International Publication 2013 / 147139 or by NMR measurement. The average content ratio refers to the molar ratio of 3HB to 3HH in the total PHBH contained in the resin film, and if the PHBH is a mixture containing at least two types of PHBH, or a mixture containing at least one type of PHBH and PHB, it refers to the molar ratio of each monomer contained in the total mixture.

[0028] The weight-average molecular weight of P3HB contained in the resin film can be selected as appropriate, but from the viewpoint of balancing the strength and productivity of the resin film, it is preferably 200,000 to 2,000,000, more preferably 250,000 to 1,500,000, and even more preferably 300,000 to 1,000,000.

[0029] The weight-average molecular weight of P3HB can be measured using gel permeation chromatography with chloroform solution (HPLC GPC system manufactured by Shimadzu Corporation) and converted to polystyrene equivalent. For the gel permeation chromatography, any column suitable for measuring weight-average molecular weight should be used.

[0030] The inflation-molded article according to this embodiment may contain a plasticizer in addition to the poly(3-hydroxybutyrate) resin component. By incorporating a plasticizer, the productivity of inflation molding can be improved and the resistance to blocking can be enhanced.

[0031] The aforementioned plasticizer is not particularly limited, but from the viewpoint of compatibility with poly(3-hydroxybutyrate) resin components, it is preferable to use an ester compound having an ester bond in the molecule.

[0032] Examples of ester compounds that can be used as plasticizers include modified glycerin compounds, dibasic acid ester compounds, adipic acid ester compounds, polyether ester compounds, benzoic acid ester compounds, citrate ester compounds, isosorbide ester compounds, and polycaprolactone compounds. Among these, modified glycerin compounds, dibasic acid ester compounds, adipic acid ester compounds, polyether ester compounds, or isosorbide ester compounds are preferred, and modified glycerin compounds are particularly preferred. Furthermore, one of the ester compounds can be used alone, or two or more can be used in combination. When two or more are used in combination, the mixing ratio of the ester compounds can be adjusted as appropriate.

[0033] As the modified glycerin-based compound, glycerin ester compounds are preferred. As the glycerin ester compound, any of glycerin monoester, diester, or triester can be used, but from the viewpoint of compatibility with poly(3-hydroxybutyrate) resin components, glycerin triesters are preferred. Among glycerin triesters, glycerin diacetone monoester is particularly preferred. Specific examples of glycerin diacetone monoesters include glycerin diacetone monolaurate, glycerin diacetone monooleate, glycerin diacetone monostearate, glycerin diacetone monocaprylate, and glycerin diacetone monodecanoate. Examples of the modified glycerin-based compound include Riken Vitamin Co., Ltd.'s "Rikemar" PL series and "BIOCIZER".

[0034] Specific examples of dibasic acid ester compounds include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl) azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, diethyl succinate, and mixed dibasic acid ester compounds.

[0035] Examples of adipic acid ester compounds include diethylhexyl adipate, dioctyl adipate, and diisononyl adipate.

[0036] Examples of polyether ester compounds include polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate.

[0037] As for the ester compounds, modified glycerin compounds are preferred due to their cost-effectiveness, versatility, and high biomass content. Glycerin triesters are more preferred, glycerin diacetone monoesters are even more preferred, and glycerin diacetone monolaurates are particularly preferred from the viewpoint of food contact.

[0038] The amount of plasticizer added is not particularly limited, but for example, it may be about 0.1 to 20 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxybutyrate) resin component.

[0039] (silica) The inflation-molded article according to this embodiment may further contain silica in order to obtain an improvement in its mechanical properties.

[0040] The type of silica is not particularly limited, but from the viewpoint of versatility, synthetic amorphous silica produced by a dry or wet method is preferred. Furthermore, silica that has been treated with either hydrophobic or non-hydrophobic methods can be used, and one type can be used alone, or two or more types can be used in combination.

[0041] The silica is preferably one with an adsorbed water content of 0.5% by weight or more and 7% by weight or less. The adsorbed water content can be measured, for example, using an electromagnetic scale MX-50 manufactured by Kensei Kogyo Co., Ltd., and the volatile content at 160°C is taken as the adsorbed water content. If the adsorbed water content is greater than 7% by weight, the cohesive force of the water adsorbed on the silica surface and between particles makes dispersion difficult, which can result in fisheyes and other appearance defects during inflation molding. Conversely, if it is less than 0.5% by weight, this small amount of remaining water between particles forms a cross-linking liquid film, creating a large bonding force due to surface tension, which tends to make separation and dispersion extremely difficult.

[0042] The average primary particle diameter of the silica is not particularly limited as long as it can improve the mechanical properties of the inflation molded body, is less likely to cause cosmetic defects such as fisheyes, and does not significantly impair transparency. However, it is preferably 0.001 to 0.1 μm, and particularly preferably 0.005 to 0.05 μm, as this provides an easy way to improve mechanical properties and maintains excellent transparency. The average primary particle diameter is determined by arithmetic mean of the diameters of 50 or more arbitrary primary particles observed using a transmission electron microscope (TEM).

[0043] The amount of silica added is not particularly limited, but may be, for example, about 1 to 12 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxybutyrate) resin component.

[0044] To improve the dispersibility of the silica, it is preferable to use the silica in combination with a dispersion aid.

[0045] Examples of the aforementioned dispersing aids include glycerin ester compounds, adipic acid ester compounds, polyether ester compounds, phthalate ester compounds, isosorbide ester compounds, and polycaprolactone compounds. Of these, modified glycerin compounds such as glycerin diacetomonolaurate, glycerin diacetomonocaprylate, and glycerin diacetomonodecanoate are preferred because they have excellent affinity for resin components and do not bleed easily; adipic acid ester compounds such as diethylhexyl adipate, dioctyl adipate, and diisononyl adipate; and polyether ester compounds such as polyethylene glycol dibenzoate, polyethylene glycol dicaprylate, and polyethylene glycol diisostearate are preferred. Furthermore, those containing a large amount of biomass-derived components are particularly preferred because they can increase the overall biomass content of the composition. Examples of such dispersing aids include Riken Vitamin Co., Ltd.'s acetylated monoglyceride BIOCIZER and PL series, and ROQUETTE's Polysorb series. Dispersing agents can be used individually or in combination of two or more types.

[0046] The amount of the dispersion aid is not particularly limited, but may be, for example, about 0.1 to 20 parts by weight per 100 parts by weight of the total amount of the poly(3-hydroxybutyrate) resin component.

[0047] (Additives) The inflation-molded article according to this embodiment may contain additives to the extent that they do not impair the effects of the invention. Examples of additives that can be used, depending on the purpose, include crystallization nucleating agents, lubricants, antistatic agents, flame retardants, conductive agents, heat insulating agents, crosslinking agents, antioxidants, ultraviolet absorbers, colorants, inorganic fillers, organic fillers, hydrolysis inhibitors, and the like. Biodegradable additives are particularly preferred.

[0048] Examples of crystallization nucleating agents include pentaerythritol, orotic acid, aspartame, cyanuric acid, glycine, zinc phenylphosphonate, and boron nitride. Among these, pentaerythritol is preferred because it is particularly effective in promoting the crystallization of poly(3-hydroxybutyrate) resin components. The amount of crystallization nucleating agent used 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 amount of poly(3-hydroxybutyrate) resin components. Furthermore, one type of crystallization nucleating agent may be used, or two or more types may be used, and the usage ratio can be appropriately adjusted depending on the purpose.

[0049] Examples of lubricants include behenamide, oleamide, erucamide, stearamide, palmitamide, N-stearylbehenamide, N-stearylerucamide, ethylenebisstearateamide, ethylenebisoleamide, ethylenebiserucamide, ethylenebislaurylamide, ethylenebiscaprateamide, p-phenylenebisstearateamide, and polycondensates of ethylenediamine, stearic acid, and sebacic acid. Among these, behenamide and erucamide are preferred because they have particularly excellent lubricating effects on poly(3-hydroxybutyrate) resin components. The amount of lubricant used 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, per 100 parts by weight of the total amount of poly(3-hydroxybutyrate) resin components. Furthermore, one type of lubricant may be used, or two or more types may be used, and the ratio of use can be adjusted as appropriate depending on the purpose.

[0050] (Thickness of the inflated molded body) The thickness of the inflation molded article is not particularly limited, but is preferably 10 μm or more and 100 μm or less, more preferably 10 μm or more and 80 μm or less, and even more preferably 15 μm or more and 60 μm or less.

[0051] (Method for manufacturing an inflated molded body) The method for manufacturing a resin film according to this embodiment can be carried out by melt-kneading resin components and various additives to obtain a resin composition, and then subjecting the resin composition to an inflation molding method.

[0052] The aforementioned inflation molding refers to a molding method in which a molten resin composition is extruded in a tubular shape from an extruder equipped with a cylindrical die (also called an annular die or circular die) at its tip, and immediately afterward, gas is blown into the tube to inflate it into a balloon shape, thereby forming a tubular single-layer or multi-layer film.

[0053] The inflation molding described is not particularly limited, but can be carried out using, for example, a general inflation molding machine used for film molding of thermoplastic resins. A general inflation molding machine, in the case of single-layer film molding, refers to a machine in which one cylindrical die is attached to one single-screw extruder. In the case of multi-layer film molding, it refers to a machine in which molten resin is poured from multiple extruders according to the type of resin used into one cylindrical die, and each resin can be laminated within the die.

[0054] The aforementioned single-screw extruder should be capable of melting and kneading the raw resin material, maintaining a desired temperature, and obtaining a constant discharge rate. The screw shape of the single-screw extruder is not particularly limited, but one equipped with a mixing element is preferable from the viewpoint of kneading performance.

[0055] The structure of the cylindrical die is also designed appropriately to match the single-layer or laminated film and is not particularly limited, but among them, a spiral mandrel die is preferred because it produces less weld and makes it easier to obtain uniform thickness.

[0056] The manufacturing method according to this embodiment will be described in detail below with reference to Figure 1. First, a resin composition containing a poly(3-hydroxybutyrate) resin component is put into an extruder 11 and melted. The molten resin composition is then extruded from a cylindrical die 12 to form a tubular resin film 13. Simultaneously, gas is blown into the tube from the center of the cylindrical die 12 to expand the tube and create a bubble 15.

[0057] The temperature at which the resin composition is melted in the extruder 11 is not particularly limited as long as it is a temperature at which the resin can be properly melted, but for example, 135 to 200°C is preferred. The temperature referred to here is the resin temperature from the extruder to the point where it is discharged from the die. The resin temperature can generally be measured by a thermometer installed in an adapter, for example.

[0058] It is preferable to cool and solidify the discharged molten resin by blowing gas from an air ring (cooling ring) 14 toward the outside of the tubular resin film 13 and / or bubble 15 extruded from the cylindrical die 12, thereby stabilizing the tubular resin film and / or bubble. The temperature of the blown gas is not particularly limited and can be set as appropriate, but it is preferable to set it to 40°C or lower to achieve sufficient cooling.

[0059] One type of air ring blowing structure features multiple annular slits from which gas is blown, with chambers located between each slit to promote balloon stabilization.

[0060] The expanded bubble 15 then comes into contact with the guide plate 16, narrowing its diameter as it is guided to a pair of pinch rolls 17. The resin film is then folded and squeezed between the pair of pinch rolls 17, trapping the air inside the bubble and forming a double resin film 18. The resin film 18 is then wound up by a winding roll 19. In this way, inflation molding can be performed.

[0061] The take-up rate in inflation molding is determined by the film thickness, width, and resin discharge rate of the molded body, but it can be adjusted within a range that maintains balloon stability. Generally, 1 to 50 m / min is preferred.

[0062] Generally, the tubular resin film 13 extruded from the cylindrical die 12 is rapidly cooled and solidified by the air ring 14, and then its temperature gradually decreases until it is sandwiched between a pair of clamping rolls 17.

[0063] In this embodiment, the temperature of the resin film before being sandwiched between the pair of sandwiching rolls 17 is suppressed to prevent it from dropping too low, and the resin film is controlled to maintain a temperature of 30°C or higher. By sandwiching the resin film, which maintains a temperature of 30°C or higher, between the pair of sandwiching rolls 17, it becomes possible to stably manufacture a resin film with good blocking resistance.

[0064] Conventional inflation molding methods did not involve controlling the temperature of the resin film before it was sandwiched between the clamping rolls. As a result, the temperature of the resin film was greatly affected by the ambient temperature, and it is presumed that it could drop to as low as 10°C, especially in winter when the temperature was low. Crystallization of poly(3-hydroxybutyrate) resins proceeds easily at around 40-70°C, but if the temperature of the resin film drops below 30°C, the crystallization process may become insufficient. If the resin film is folded while crystallization has not progressed sufficiently, fusion will occur between the films, and as a result, it is presumed that the blocking resistance will decrease.

[0065] In this embodiment, it is preferable to control the temperature of the resin film measured immediately before being sandwiched by the sandwiching roll 17 so that it does not drop below 30°C. By allowing the crystallization of the poly(3-hydroxybutyrate) resin to proceed in a temperature range of 30°C or higher, a resin film with good blocking resistance can be stably manufactured without being affected by the ambient temperature.

[0066] The upper limit of the temperature is not particularly limited, but if the temperature becomes too high, creases and wrinkles are likely to form in the resin film. Since these creases and wrinkles can cause problems when printing on the film surface, from the viewpoint of reducing creases and wrinkles, the temperature of the resin film is preferably 55°C or lower, more preferably 50°C or lower, and even more preferably 45°C or lower. It may also be 40°C or lower, or 35°C or lower.

[0067] There are no particular limitations on the specific method for controlling the resin film to maintain a temperature of 30°C or higher. This can be achieved, for example, by installing the inflation molding machine in a room where the room temperature is maintained at 30°C or higher, or by surrounding the bubbles 15 with an insulating wall 21 to block out the outside air and maintaining the temperature inside the insulating wall 21 at 30°C or higher. In particular, it is preferable to maintain the temperature of the resin film by introducing warm air into the insulating wall 21 at a wind speed that does not affect the shape of the bubbles. This warm air is intended to suppress the temperature drop of the resin film and is different from the blowing of gas by the air ring described above.

[0068] After inflation molding, to easily separate the folded molded film after winding, a process of blowing air into the interface of the folded film with a pinch roll, or a process of cutting the film according to its intended use during the take-up process, may be performed. Cutting methods include cutting both ends of the folded tubular molded film in the width direction to form two films, and forming a bag-shaped film by hot cutting the tubular molded film in the width direction and then fusing the ends together by heat sealing. Additionally, a step of blowing air into the interface of the folded films just before cutting may be included to facilitate cutting.

[0069] Alternatively, a process known as gusset folding may be performed, in which both ends of the folded tubular film are folded inward. Furthermore, after folding the film with pinch rolls, a printing process may be performed on the film surface before winding. To further improve print adhesion, corona treatment may be performed on the film surface before printing. The printing method is not particularly limited, but examples include gravure printing and flexographic printing.

[0070] The inflation molded body obtained by this embodiment has excellent biodegradability and can therefore be suitably used in agriculture, fisheries, forestry, horticulture, medicine, hygiene products, food industry, clothing, non-clothing products, packaging, automobiles, building materials, and other fields. For example, it can be used for garbage bags, shopping bags, vegetable and fruit packaging bags, pillow packaging, delivery bags, gloves, shower caps, aprons, straw packaging bags and other bag containers, bag-shaped protective materials for equipment, storage bags for various documents such as instruction manuals, agricultural mulch films, forestry fumigation sheets, binding tapes including flat yarn, root wrapping films for plants, diaper backsheets, packaging sheets, shopping bags, drainer bags, and other compost bags.

[0071] The following sections list preferred embodiments of this disclosure, but the present invention is not limited to these sections. [Item 1] A method for producing a resin film containing a poly(3-hydroxybutyrate) resin component, comprising the following steps (i) to (iii) in sequence. (i) A process of extruding a resin composition containing a poly(3-hydroxybutyrate) resin component in a molten state from a cylindrical die to form a tubular resin film. (ii) A step of controlling the tubular resin film to maintain a temperature of 30°C or higher. (iii) The process of sandwiching the tubular resin film between a pair of rolls. [Item 2] The method for manufacturing a resin film according to item 1, wherein in step (ii) above, the tubular resin film is controlled to maintain a temperature of 30°C or higher and 55°C or lower. [Item 3] The method for manufacturing a resin film according to item 1 or 2, wherein step (ii) is carried out by introducing heated gas around the tubular resin film. [Item 4] A method for producing a resin film according to any one of items 1 to 3, wherein the poly(3-hydroxybutyrate) resin component comprises a poly(3-hydroxybutyrate) copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units. [Item 5] The method for producing a resin film according to item 4, wherein the other hydroxyalkanoate unit is 3-hydroxyhexanoate. [Examples]

[0072] The present invention will be specifically described below with reference to examples, but the technical scope of the present invention is not limited by these examples.

[0073] The following raw materials were used in the examples and comparative examples. P3HB3HH: P3HB3HH-1:P3HB3HH (Average content ratio 3HB / 3HH = 97.2 / 2.8 (mol% / mol%), weight-average molecular weight is 620,000 g / mol) It was manufactured in accordance with the method described in Example 2 of International Publication No. 2019 / 142845. P3HB3HH-2: P3HB3HH (Average content ratio 3HB / 3HH = 71.8 / 28.2 (mol% / mol%), weight-average molecular weight is 620,000 g / mol) It was manufactured in accordance with the method described in Example 9 of International Publication No. 2019 / 142845. P3HB3HH-3:P3HB3HH[X131A (Kaneka Biodegradable Polymer GreenPlanet®, Average Content Ratio 3HB / 3HH = 94 / 6 (mol% / mol%), Weight-Average Molecular Weight is 550,000 g / mol)] P3HB3HH-4:P3HB3HH (Average content ratio 3HB / 3HH = 94 / 6 (mol% / mol%), weight-average molecular weight is 400,000 g / mol) It was manufactured in accordance with the method described in Example 1 of International Publication No. 2019 / 142845.

[0074] (Crystallizing agent) Pentaerythritol (manufactured by Mitsubishi Chemical Corporation, Neurizer P)

[0075] (Lubricant) Erucic acid amide, behenic acid amide

[0076] The following evaluations were performed for each example and comparative example. (Blocking resistance) Assuming bag applications, the film was manufactured using inflation molding as described below, maintaining an average thickness of 30 μm. From the rolled-up tubular inflation film, a long sample of double-layered film measuring 5 cm wide x 15 cm long was cut out. The blocking resistance of this double-layered film was evaluated by rubbing it between the thumb and index finger to see if it would open or close. 〇: Open ×: Do not open

[0077] (Film appearance) In the inflation molding process described later, the inflation film was visually observed for 5 minutes at a linear speed of 11 m / min, and the number of wrinkles that formed was measured.

[0078] (Examples 1-3) Method for manufacturing resin film P3HB3HH, a nucleating agent, and a lubricant were dry-blended in the proportions shown in Table 1. The mixture was then melt-kneaded using a co-meshing twin-screw extruder (Toshiba Machine Co., Ltd.: TEM26ss) at a set temperature of 120°C to 170°C and a screw rotation speed of 100 rpm, and the resulting molten mixture was obtained by strand cutting. Subsequently, an inflation film was produced using an inflation molding machine (Hokushin Sangyo Co., Ltd.) equipped with a die fitted with a 100 mm diameter cylindrical die slip, connected to an extruder with a single-screw L / D=32. The ambient temperature during inflation molding was 15°C. The glass transition temperature of the P3HB3HH used was measured using a DSC (DSC 214 Polyma, NETZSCH). To control the resin film temperature in the bubble (tube film before being sandwiched between pinch rolls) during inflation molding, the bubble was enclosed to block some of the outside air, and warm air was introduced into the enclosure to control the resin film temperature of the bubble to the temperatures shown in Table 1. The resin film temperature was measured using a non-contact thermometer (THERMO-HUNTER PT-7LD, manufactured by OPTEX FA) just before being sandwiched between pinch rolls. The evaluation results are shown in Table 1.

[0079] (Example 4) A molten compound was prepared using the same formulation as in Example 3. Then, an inflation film was prepared in the same manner as in Example 1, except that the ambient temperature during inflation molding was as described in Table 1, and the temperature of the warm air blown into the enclosure was changed to control the temperature of the bubble resin film to the temperature described in Table 1. Each evaluation was then performed. The evaluation results are shown in Table 1.

[0080] (Comparative Example 1) An inflation film was prepared in the same manner as in Example 1, except that the temperature of the warm air blown into the enclosure was changed to control the temperature of the bubble resin film to the temperatures listed in Table 1, and each evaluation was performed. The evaluation results are shown in Table 1.

[0081] (Comparative Example 2) An inflation film was prepared in the same manner as in Example 1, except that bubble containment was not performed and the resin film temperature was not controlled, and each evaluation was carried out. The evaluation results are shown in Table 1.

[0082] (Comparative Example 3) An inflation film was prepared in the same manner as in Example 1, except that an external lubricant was added to the formulation of Example 1, bubble containment was not performed, and the resin film temperature was not controlled. Each evaluation was then performed. The evaluation results are shown in Table 1.

[0083] [Table 1]

[0084] The following can be seen from Table 1. In Examples 1 to 4, the temperature of the resin film before being sandwiched between pinch rolls was controlled to 30°C or higher, resulting in good blocking resistance of the resulting resin film. In addition, in Examples 1 to 3, no wrinkles were observed in the resulting resin film, and the appearance was good. On the other hand, in Comparative Examples 1-3, the resin film temperature before being sandwiched between pinch rolls was less than 30°C, and good results were not obtained in terms of blocking resistance. [Explanation of symbols]

[0085] 11 Extruder 12 Cylindrical dies 13. Tubular resin film 14 Air Ring 15. Bubble (Balloon-shaped molded film) 16 Guide plate 17 Pair of clamping rolls 18. Double-layered resin film 19. Winding Roll 21 Warming room

Claims

1. A method for producing a resin film containing a poly(3-hydroxybutyrate) resin component, comprising the following steps (i) to (iii) in sequence. (i) A process of extruding a resin composition containing a poly(3-hydroxybutyrate) resin component from a cylindrical die in a molten state to form a tubular resin film. (ii) A step of controlling the tubular resin film to maintain a temperature of 30°C to 57°C. (iii) The process of sandwiching the tubular resin film between a pair of rolls.

2. The method for manufacturing a resin film according to claim 1, wherein in step (ii) above, the tubular resin film is controlled to maintain a temperature of 30°C or higher and 55°C or lower.

3. The method for manufacturing a resin film according to claim 1 or 2, wherein step (ii) is carried out by introducing heated gas around the tubular resin film.

4. A method for producing a resin film according to claim 1 or 2, wherein the poly(3-hydroxybutyrate) resin component comprises a poly(3-hydroxybutyrate) copolymer containing 3-hydroxybutyrate units and other hydroxyalkanoate units.

5. The method for producing a resin film according to claim 4, wherein the other hydroxyalkanoate unit is 3-hydroxyhexanoate.

6. The method for manufacturing a resin film according to claim 1 or 2, wherein step (ii) is carried out by installing an inflation molding machine in a room where the room temperature is maintained at 30°C or higher.

7. The method for manufacturing a resin film according to claim 1 or 2, wherein step (ii) is carried out by surrounding the tubular resin film with an insulating wall to block out the outside air and maintaining the temperature inside the insulating wall at 30°C or higher.

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