Compost bag and method for processing organic waste

Abstract

To provide a compost bag that can be broken in a waste processing machine, collapsed finely without getting wound around a rotary shaft, and further completely biodegraded in a subsequent composting process when organic waste is processed by the waste processing machine, and a method for processing organic waste that uses the compost bag.SOLUTION: A compost bag is made of a biodegradable film that is 400 MPa or larger in tensile modulus in a film MD direction measured by JIS K7127 (1999) and 400% or less in breaking elongation in the film MD direction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a compost bag and a method for treating organic waste. [Background technology]

[0002] In recent years, efforts to reuse large amounts of food waste generated by food manufacturers, markets, etc. as a resource by fermenting and decomposing it into compost have been attracting attention. In composting, a composting machine that uses the power of microorganisms to ferment and decompose food waste can be used to efficiently ferment large amounts of food waste. Because composting machines are typically installed away from kitchens and other facilities that produce food waste, food waste is first placed in bags made of plastic film such as polyethylene, transported to the machine, and then dumped into the machine. Since the bags are not fermented and decomposed, the food waste must be removed from the bags. This results in foul odors and dirt being dispersed around the machine, and the used bags must be washed or disposed of. As a solution to these problems, the use of bags made from biodegradable plastic film is being considered. Biodegradable bags can be put into a composting machine along with food waste, without the need for sorting or washing.

[0003] Patent Document 1 discloses a method for treating organic waste, which comprises placing organic waste in biodegradable plastic bags, placing the biodegradable plastic bags in a fermentation tank equipped with a crusher / agitator, operating the crusher / agitator to crush the biodegradable plastic bags while stirring the organic waste, and fermenting the biodegradable plastic bags and organic waste with microorganisms.

[0004] Furthermore, Patent Document 2 discloses that by specifying the tensile breaking strength and tensile breaking elongation of the film constituting the biodegradable bag within specific ranges, it is possible to provide a biodegradable bag that can be used in composting plants, blocking the bad odors that are generated during the fermentation stage of livestock manure, food waste, etc., and biodegrading after fermentation has progressed and the generation of bad odors has ceased. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-362080 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-043892 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to collect organic waste and put it in a garbage disposal machine such as a composting machine in its bag form for composting, it is necessary that the bags do not tear when collecting the organic waste, and that after being put into the garbage disposal machine, the bags tear when they hit the agitating blades of the machine and either break down into small pieces or completely decompose without getting wrapped around the rotating shaft. Although the biodegradable plastic bags described in Patent Document 1 are described as being fermented by microorganisms, the degree of decomposition of the bags is not indicated, and if a large number of bags are put into the device, there is a possibility that problems such as the bags becoming tangled in the crushing mixer may occur. Furthermore, the biodegradable bags described in Patent Document 2 are easily stretched, and their modulus of elasticity is not specified. Therefore, if the bag is placed in the device, there is a concern that the bag may wrap around the rotating shaft of the device, causing the device to stop due to overload, or that the bag may not tear easily even when it hits the agitating blades, preventing the contents, such as food waste, from coming out of the bag.

[0007] In view of the above problems, the present invention provides a food waste processor that can be used to treat organic waste. To provide a compost bag which can be broken in a composting device, can be broken into small pieces without being wound around a rotating shaft, and can be completely biodegraded in the subsequent composting process, and a method for treating organic waste using the compost bag. [Means for solving the problem]

[0008] As a result of their investigations, the inventors discovered that the above problems can be solved by setting the tensile modulus in the MD direction and the elongation at break of the biodegradable film used in compost bags within specific ranges, and thus completed the present invention.

[0009] That is, the gist of the present invention resides in the following items. [1] A compost bag made of biodegradable film with a tensile modulus of elasticity in the MD direction of the film of 400 MPa or more and a breaking elongation in the MD direction of the film of 400% or less, as measured according to JIS K7127 (1999). [2] The compost bag according to [1], wherein the film has a breaking elongation in the TD direction of 300% or more as measured according to JIS K7127 (1999). [3] A compost bag according to [1] or [2], wherein the tensile modulus of elasticity in the MD direction of the film measured according to JIS K7127 (1999) is 2000 MPa or less. [4] The compost bag according to any one of [1] to [3], wherein the rupture elongation in the MD direction of the film measured according to JIS K7127 (1999) is 100% or more. [5] The compost bag according to any one of [1] to [4], wherein the film has a breaking elongation in the TD direction of 1500% or less as measured according to JIS K7127 (1999). [6] The compost bag according to any one of [1] to [5], wherein the biodegradable film contains an aliphatic polyester (A) and an inorganic filler (B). [7] The compost bag according to [6], wherein the biodegradable film further contains another biodegradable resin (C). [8] The compost bag according to [7], wherein the inorganic filler (B) is contained in an amount of 15% by mass or more and less than 60% by mass relative to the total amount of the aliphatic polyester (A), the inorganic filler (B), and the other biodegradable resin (C). [9] The compost bag according to any one of [6] to [8], wherein the inorganic filler (B) is a basic inorganic filler.

[10] The compost bag according to any one of [6] to [8], wherein the inorganic filler (B) is basic magnesium sulfate.

[11] The compost bag according to any one of [6] to [8], wherein the inorganic filler (B) is surface-treated calcium carbonate.

[12] The compost bag according to any one of [6] to

[11] , wherein the aliphatic polyester (A) contains at least one kind of aliphatic diol unit and at least one kind of aliphatic dicarboxylic acid unit as constituent units.

[13] The compost bag according to

[12] , wherein the aliphatic polyester (A) contains succinic acid as the aliphatic dicarboxylic acid unit.

[14] A method for treating organic waste, comprising the step of placing the compost bag according to any one of [1] to

[13] containing organic waste into a food waste processor and performing primary composting.

[15] The method for treating organic waste according to

[14] , further comprising a step of carrying out secondary composting, or secondary composting and tertiary composting, in a composting site to completely eliminate the compost bags.

[16] A method for treating organic waste according to

[14] or

[15] , characterized in that in the step of primary composting, the bag breaks when it is hit by an agitator blade installed in the food waste processor tank, and the organic waste is scraped out.

[17] A method for treating organic waste according to any one of

[14] to

[16] , characterized in that in the step of primary composting, the bag is decomposed to 30% or less of the weight of the original bag within 48 hours after being put into a food waste processor. [Effects of the Invention]

[0010] The present invention provides a compost bag that maintains usability, has good bag-breaking properties, is less likely to wrap around a rotating shaft, and is easily decomposable, as well as a method for treating organic waste using the compost. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following description and can be modified and implemented as desired within the scope that does not deviate from the gist of the present invention. In this specification, when "~" is used to express a numerical value or a physical property value, the values ​​before and after the "~" are included. In addition, in this specification, the expression "A or B" can be read as "at least one selected from the group consisting of A and B." Furthermore, although a number of embodiments are described in this specification, various conditions in each embodiment may be applied to each other to the extent that they are applicable.

[0012] In this specification, an aliphatic polyester is a polymer having repeating structural units, and each repeating structural unit is also referred to as a compound unit corresponding to the compound from which the repeating structural unit is derived. For example, a repeating structural unit derived from an aliphatic diol is also referred to as an "aliphatic diol unit (or diol unit)," a repeating structural unit derived from an aliphatic dicarboxylic acid is also referred to as an "aliphatic dicarboxylic acid unit (or dicarboxylic unit)," and a repeating structural unit derived from an aliphatic oxycarboxylic acid is also referred to as an "aliphatic oxycarboxylic acid unit (or oxycarboxylic unit)."

[0013] <Film composition> The compost bag according to one embodiment of the present invention (hereinafter simply referred to as "compost bag") is made of a biodegradable film having a tensile modulus in the MD direction of the film of 400 MPa or more and a breaking elongation in the MD direction of the film of 400% or less, as measured according to JIS K7127 (1999).

[0014] The biodegradable film according to one embodiment of the present invention is not limited to a specific type as long as it is biodegradable. It is typically a biodegradable polyester, and preferably contains an aliphatic polyester (A) and an inorganic filler (B). By including the aliphatic polyester (A), the compost bag has excellent impact resistance, tear resistance, and other properties when in use, and can be quickly disintegrated after being placed in a food waste processor. By including the inorganic filler (B), the rigidity of the film is increased, improving its shape stability during use. Furthermore, when the film is struck by the agitator blades installed in the food waste processor, the bag is more likely to tear, making it easier for organic waste to be scraped out of the bag. Furthermore, when the decomposition of the film is accelerated in the food waste processor or composting process, the inorganic filler falls off, increasing the contact area between the film and enzymes produced by microorganisms, thereby enhancing the biodegradation rate of the film. Furthermore, the biodegradable film according to one embodiment of the present invention may contain, in addition to the aliphatic polyester (A) and the inorganic filler (B), another biodegradable resin (C). By including the other biodegradable resin (C), it is possible to adjust the rigidity and tear resistance of the film. Each component contained in the biodegradable film will be described in detail below.

[0015] [Aliphatic polyester (A)] The aliphatic polyester (A) according to one embodiment of the present invention (hereinafter referred to as "aliphatic polyester (A)") is a biodegradable polyester containing at least one kind of aliphatic diol unit and at least one kind of aliphatic dicarboxylic acid unit as constituent units, or It is preferable that the biodegradable polyester contains at least one type of aliphatic hydroxycarboxylic acid unit as a main constituent unit.

[0016] (Biodegradable polyester containing aliphatic diol units and aliphatic dicarboxylic acid units as structural units) In this specification, the term "aliphatic diol" refers to an aliphatic hydrocarbon group to which two hydroxyl groups are bonded, and may be a derivative of an aliphatic diol. The aliphatic hydrocarbon group is usually a linear aliphatic hydrocarbon group, but may have a branched structure, a cyclic structure, or a plurality of such structures. Furthermore, the term "aliphatic dicarboxylic acid" refers to an aliphatic hydrocarbon group to which two carboxyl groups are bonded, and is a general term for aliphatic dicarboxylic acids such as aliphatic dicarboxylic acid and aliphatic dicarboxylic acid derivatives such as aliphatic dicarboxylic acid alkyl esters. As the aliphatic hydrocarbon group, a straight-chain aliphatic hydrocarbon group is usually used, but it may have a branched structure, a cyclic structure, or a plurality of these.

[0017] The aliphatic diol unit and the aliphatic dicarboxylic acid unit may be, for example, an aliphatic diol unit represented by the following formula (1) and an aliphatic dicarboxylic acid unit represented by the following formula (2), respectively. -OR 1 -O- (1) (In formula (1), R 1 represents a divalent aliphatic hydrocarbon group. -OC-R 2 -CO- (2) (In formula (2), R 2 represents a divalent aliphatic hydrocarbon group.

[0018] R 1 and R 2 The type of the substituent that may be present in R is not particularly limited as long as the effects of the present invention can be obtained, and examples thereof include halogen, cyano group, amino group, ester group, alkylcarbonyl group, acetyl group, silyl group, boryl group, nitrile group, thio group, and seleno group. These substituents may be of one type or of two or more types. 1 and R 2 The hydrocarbon group in may not have a substituent.

[0019] Each of the structural units contained in the aliphatic polyester (A) will be described in detail below.

[0020] (aliphatic diol unit) The diol that provides the aliphatic diol unit may be any diol that is commonly used as a raw material for polyesters, without any particular limitation. The structure of the diol may be a linear structure, a branched chain structure, or a cyclic structure.

[0021] The number of carbon atoms in the aliphatic diol is not particularly limited, but is usually 2 to 20. From the viewpoints of moldability, mechanical strength, and controlling the content of ester groups within a desired range, the number of carbon atoms is preferably 2 to 12, more preferably 2 to 6, and particularly preferably 2 to 4.

[0022] Examples of aliphatic diols include alkylene diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and neopentyl glycol; oxyalkylene diols such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol; and cycloalkylene diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. Among these, ethylene glycol, 1,3-propanediol, and 1,4-butanediol are preferred from the viewpoint of biodegradability.

[0033] These aliphatic diols are preferably used, more preferably ethylene glycol or 1,4-butanediol, and particularly preferably 1,4-butanediol, because they are easily crystallized and provide excellent strength and moldability. These aliphatic diols may or may not be derivatives thereof. The aliphatic diol unit may have a structure in which one or more types of the aliphatic diol unit are mutually dehydration-condensed. Two or more types of the aliphatic diol units may be used.

[0023] The total content of aliphatic diol units in the aliphatic polyester (A) is not particularly limited, but from the viewpoint of the mechanical properties of the film, it is usually 10 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, relative to 100 mol% of all structural units constituting the aliphatic polyester (A), and is usually 60 mol% or less, preferably 55 mol% or less.

[0024] The diol that provides the aliphatic diol unit may be derived from a compound derived from a fossil fuel or a compound derived from a plant material, but is preferably derived from a compound derived from a plant material. For example, ethylene glycol, 1,3-propanediol, or 1,4-butanediol derived from a plant material can be used.

[0025] (aliphatic dicarboxylic acid unit) As the dicarboxylic acid that provides the aliphatic dicarboxylic acid unit, any dicarboxylic acid that is usually used as a raw material for polyesters can be used without any particular limitation. The structure of the aliphatic dicarboxylic acid may be a linear structure, a branched chain structure, or a cyclic structure.

[0026] The carbon number of the aliphatic dicarboxylic acid is not particularly limited, but is usually 2 to 36, preferably 3 to 12, more preferably 3 to 10, even more preferably 3 to 6, and particularly preferably 4. When the carbon number of the aliphatic dicarboxylic acid is equal to or greater than the lower limit of the above range, good moldability can be obtained. On the other hand, when the carbon number of the aliphatic dicarboxylic acid is equal to or less than the upper limit of the above range, mechanical properties can be further improved.

[0027] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, brassylic acid, maleic acid, fumaric acid, and dimer acid. Among these, from the viewpoint of thermal stability and crystallinity, it is preferable to include succinic acid, succinic anhydride, adipic acid, sebacic acid, or azelaic acid, more preferably succinic acid, adipic acid, or sebacic acid, and particularly preferable to include succinic acid. The aliphatic dicarboxylic acid units may have a structure in which one or more types are dehydrated and condensed with each other. Two or more types of the aliphatic dicarboxylic acid units may be used. When two or more types of aliphatic dicarboxylic acids are used, the total amount of succinic acid units, adipic acid units, and sebacic acid units in the total aliphatic dicarboxylic acid units is preferably 50 mol % or more, more preferably 60 mol % or more, and particularly preferably 70 mol % or more. When two or more kinds of aliphatic dicarboxylic acids are used, the succinic acid units are 5 mol% or more, preferably 20 mol% or more, particularly preferably 40 mol% or more, and particularly preferably 50 mol% or more of the total aliphatic dicarboxylic acid units, and are less than 100 mol%, preferably 97 mol% or less, more preferably 95 mol% or less, and particularly preferably 89% or less. When the content of succinic acid units, adipic acid units, and sebacic acid units relative to the total aliphatic dicarboxylic acid units is within the above range, it is possible to obtain a film that has improved formability and is also excellent in tear resistance, impact resistance, and biodegradability.

[0028] The total content of aliphatic dicarboxylic acid units in the aliphatic polyester (A) is not particularly limited, but from the viewpoint of obtaining appropriate flexibility and biodegradability, it is usually 10 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, relative to 100 mol% of all structural units constituting the aliphatic polyester (A); and from the viewpoint of obtaining good crystallinity, strength, and moldability, it is usually 70 mol% or less, preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 55 mol% or less.

[0029] The dicarboxylic acid that provides the aliphatic dicarboxylic acid unit may be derived from a compound derived from a fossil fuel or a compound derived from a plant material, but is preferably derived from a compound derived from a plant material. For example, succinic acid or sebacic acid derived from a plant material can be used.

[0030] (Other copolymer components) In producing the aliphatic polyester (A), the following components may be copolymerized as constituent components (other copolymerization components) other than the above-mentioned aliphatic diol and aliphatic dicarboxylic acid.

[0031] The aliphatic polyester (A) may have a repeating unit (aliphatic oxycarboxylic acid unit) derived from an aliphatic oxycarboxylic acid. Specific examples of the aliphatic oxycarboxylic acid component that provides the aliphatic oxycarboxylic acid unit include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, and the like, as well as derivatives thereof, such as lower alkyl esters or intramolecular esters. When optical isomers exist, they may be in the D-form, L-form, or racemic form, and may be in the form of a solid, liquid, or aqueous solution. Among these, lactic acid, glycolic acid, or derivatives thereof are particularly preferred. These aliphatic oxycarboxylic acids may be used alone or in a mixture of two or more.

[0032] When the aliphatic polyester (A) contains an aliphatic oxycarboxylic acid unit, the content thereof is preferably 10 mol % or less, more preferably 5 mol % or less, even more preferably 2 mol % or less, and most preferably 0 mol % (not included), based on 100 mol % of all structural units constituting the aliphatic polyester (A), from the viewpoint of moldability.

[0033] From the viewpoint of film formability, it is preferable that the aliphatic polyester (A) has an increased melt viscosity by copolymerizing a trifunctional or higher aliphatic polyhydric alcohol, a trifunctional or higher aliphatic polycarboxylic acid or its acid anhydride, or a trifunctional or higher aliphatic polyoxycarboxylic acid component.

[0034] Specific examples of trifunctional aliphatic polyhydric alcohols include trimethylolpropane and glycerin, and specific examples of tetrafunctional aliphatic polyhydric alcohols include pentaerythritol. These may be used alone or in combination of two or more. Among these, trimethylolpropane and glycerin are preferred, and trimethylolpropane is more preferred.

[0035] A specific example of a trifunctional aliphatic polycarboxylic acid or its acid anhydride is propanetricarboxylic acid or its acid anhydride, and a specific example of a tetrafunctional polycarboxylic acid or its acid anhydride is cyclopentanetetracarboxylic acid or its acid anhydride, etc. These may be used alone or in combination of two or more.

[0036] In addition, trifunctional aliphatic hydroxycarboxylic acids have (i) two carboxyl groups and one hydroxyl group. (ii) types having one carboxyl group and two hydroxyl groups in the same molecule, and either type can be used. However, from the viewpoint of moldability, mechanical strength, and the appearance of molded products, (i) types having two carboxyl groups and one hydroxyl group in the same molecule, such as malic acid, are preferred. More specifically, malic acid is preferred. Furthermore, tetrafunctional aliphatic oxycarboxylic acid components can be divided into (i) types having three carboxyl groups and one hydroxyl group in the same molecule, (ii) types having two carboxyl groups and two hydroxyl groups in the same molecule, and (iii) types having three hydroxyl groups and one carboxyl group in the same molecule. Either type can be used, but those having multiple carboxyl groups are preferred. More specifically, citric acid, tartaric acid, etc. can be mentioned. These can be used alone or in combination.

[0037] (Biodegradable polyester containing aliphatic hydroxycarboxylic acid units as main structural units) In this specification, the term "aliphatic oxycarboxylic acid" refers to an aliphatic hydrocarbon group to which at least one hydroxyl group and one carboxyl group are bonded, and may be a derivative of an aliphatic oxycarboxylic acid. The aliphatic hydrocarbon group is usually a linear aliphatic hydrocarbon group, but may have a branched structure, a cyclic structure, or a plurality of these.

[0038] Specific examples of aliphatic hydroxycarboxylic acid components that provide aliphatic hydroxycarboxylic acid units include lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, 2-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, caproic acid, 2-hydroxyisocaproic acid, and the like, as well as derivatives thereof, such as lower alkyl esters or intramolecular esters. When optical isomers exist, they may be D-, L-, or racemic, and may be in the form of a solid, liquid, or aqueous solution. Among these, lactic acid or 3-hydroxybutyric acid or derivatives thereof are particularly preferred. These aliphatic hydroxycarboxylic acids can be used alone or in a mixture of two or more.

[0039] Examples of aliphatic polyesters (A) containing aliphatic diol units and aliphatic dicarboxylic acid units include polybutylene succinate (PBS) and polybutylene succinate adipate (PBSA). Examples of aliphatic polyesters (A) containing aliphatic oxycarboxylic acid units include polylactic acid (PLA), poly(3-hydroxybutyrate) (P3HB), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), and polycaprolactone (PCL). Among these, polybutylene succinate (PBS) and polybutylene succinate adipate (PBSA) are preferred from the viewpoints of moldability and the mechanical properties of the film. These can be used alone or in combination.

[0040] The content of the aliphatic polyester (A) in the biodegradable film is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more, based on the total amount of the aliphatic polyester (A), inorganic filler (B), and other biodegradable resin (C), and is preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. By having the content of the aliphatic polyester (A) in the biodegradable film within the above range, both the mechanical properties of the film and rapid decomposition in a food waste processor can be achieved.

[0041] [Characteristics of Aliphatic Polyester (A)] (molecular weight) The molecular weight of the aliphatic polyester (A) is not particularly limited, but can be measured by gel permeation chromatography (GPC). The weight average molecular weight (Mw) using monodisperse polystyrene as the standard substance is usually 10,000 or more and 1,000,000 or less. However, because this is advantageous in terms of moldability and mechanical strength, it is preferably 20,000 or more and 500,000 or less, more preferably 50,000 or more and 400,000 or less, and even more preferably 100,000 or more and 300,000 or less.

[0042] (Melt Flow Rate) The melt flow rate (MFR) of the aliphatic polyester (A) is not particularly limited, but is usually 0.1 g / 10 min or more and 100 g / 10 min or less, as measured at 190 ° C. and a load of 2.16 kg according to JIS K7210 (1999). From the viewpoint of moldability and mechanical strength, it is preferably 40 g / 10 min or less, more preferably 20 g / 10 min or less, and particularly preferably 10 g / 10 min or less. On the other hand, it is preferably 1.0 g / 10 min or more, more preferably 2.0 g / 10 min or more. The MFR of the aliphatic polyester resin (A) can be adjusted by the molecular weight.

[0043] (Melting Point) The melting point of the aliphatic polyester (A) is not particularly limited, but in the case of a biodegradable polyester containing an aliphatic diol unit and an aliphatic dicarboxylic acid unit, it is usually 50°C or higher, preferably 70°C or higher, more preferably 75°C or higher, and even more preferably 80°C or higher, and is usually 180°C or lower, preferably 160°C or lower, more preferably 140°C or lower, and even more preferably 120°C or lower. In the case of biodegradable polyesters containing aliphatic oxycarboxylic acid units, the temperature is usually 50°C or higher, preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, and is usually 200°C or lower, preferably 190°C or lower, more preferably 180°C or lower, and even more preferably 170°C or lower.

[0044] [Method for producing aliphatic polyester (A)] (Biodegradable polyester containing aliphatic diol units and aliphatic dicarboxylic acid units as structural units) The method for producing the aliphatic polyester (A) is not particularly limited, and known methods can be used. The method for producing the aliphatic polyester (A) will be described below, but it is merely an example, and the method for producing the aliphatic polyester (A) is not limited to this embodiment. The polycondensation reaction in this case can be carried out under suitable conditions that have been conventionally employed, and is not particularly limited. Usually, a method is employed in which the degree of polymerization is further increased by carrying out a reduced pressure operation after the esterification and / or transesterification reaction has proceeded.

[0045] During the production of the aliphatic polyester (A), the amounts of the diol component, the dicarboxylic acid component, and any other copolymerization components used are determined so that the aliphatic polyester (A) produced has the desired composition. Usually, the diol component and the dicarboxylic acid component react in substantially equimolar amounts, but the diol component is usually used in a 1 to 20 mol % excess over the dicarboxylic acid component because it is distilled off during the esterification or transesterification reaction.

[0046] The reaction temperature for the esterification or transesterification reaction is not particularly limited as long as it is a temperature at which the esterification reaction can be carried out. However, in order to increase the reaction rate, the reaction temperature is preferably 200°C or higher, and more preferably 210°C or higher. In order to prevent discoloration of the polyester, the reaction temperature is preferably 270°C or lower, more preferably 260°C or lower, and particularly preferably 250°C or lower.

[0047] The reaction time for the esterification or transesterification reaction is not particularly limited, but is preferably 1 hour or more, and is preferably 10 hours or less, and more preferably 4 hours or less.

[0048] The reaction vessel is then evacuated to increase the degree of polymerization.

[0049] The reaction pressure for the polymerization reaction is not particularly limited, but is usually 0.01 kPa or more, preferably 0.03 kPa or more, and is usually 1.4 kPa or less, preferably 0.4 kPa or less. If the pressure during the polycondensation reaction is too high, the polycondensation time becomes long, which leads to thermal decomposition of the polyester, resulting in a decrease in molecular weight and coloration, and tends to make it difficult to produce a polyester that exhibits sufficient properties for practical use.

[0050] The reaction temperature for the polymerization reaction is not particularly limited, but is usually 215°C or higher, preferably 220°C or higher, and usually 270°C or lower, preferably 260°C or lower. If the reaction temperature is below the lower limit of the above range, the polycondensation reaction rate is slow, not only does it take a long time to produce a polyester with a high degree of polymerization, but also a high-power stirrer is required, which is economically disadvantageous. On the other hand, if the reaction temperature exceeds the upper limit of the above range, thermal decomposition of the polyester during production tends to occur, making it difficult to produce a polyester with a high degree of polymerization.

[0051] The reaction time for the polymerization reaction is not particularly limited, but is usually 1 hour or more and usually 15 hours or less, preferably 10 hours or less, and more preferably 8 hours or less. If the reaction time is too short, the reaction is insufficient, making it difficult to obtain a polyester with a high degree of polymerization, and the mechanical properties of the molded article tend to be poor. On the other hand, if the reaction time is too long, the molecular weight reduction due to thermal decomposition of the polyester becomes significant, and not only does the mechanical properties of the molded article tend to be poor, but the amount of carboxyl group terminals, which has an adverse effect on the durability of the polyester, may increase due to thermal decomposition.

[0052] By controlling the temperature, time and reaction pressure of the polycondensation reaction within the above ranges, a polyester having a desired intrinsic viscosity can be obtained.

[0053] (reaction catalyst) The aliphatic polyester (A) is usually produced in the presence of a catalyst, which can be selected from known catalysts that can be used in the production of polyesters, as long as the effects of the present invention are not significantly impaired.

[0054] The catalyst generally used is a compound containing at least one metal element selected from Groups 1 to 14 of the periodic table. To reduce the polyester terminal concentration, which affects the thermal stability of polyester, a metal element selected from Groups 3 to 6 of the periodic table that exhibits Lewis acidity is more preferred. Specific examples of the metal element include scandium, titanium, zirconium, vanadium, molybdenum, and tungsten. Titanium and zirconium are particularly preferred due to their availability, and titanium is even more preferred due to its reactivity.

[0055] In the present embodiment, as the catalyst, a compound containing an organic group, such as a carboxylate, alkoxy salt, organic sulfonate, or β-diketonate salt containing the above-mentioned metal element; or an inorganic compound, such as an oxide or halide of the above-mentioned metal element, or a mixture thereof, is preferably used.

[0056] In this embodiment, the catalyst is in a molten or dissolved state during polymerization, which increases the polymerization rate. For these reasons, compounds that are liquid during polymerization or that dissolve in ester oligomers or polyesters are preferred. Furthermore, while polycondensation is preferably performed without a solvent, a small amount of solvent may be used separately to dissolve the catalyst. Examples of solvents for dissolving the catalyst include alcohols such as methanol, ethanol, isopropanol, or butanol; the aforementioned diols such as ethylene glycol, butanediol, or pentanediol; ethers such as diethyl ether or tetrahydrofuran; nitriles such as acetonitrile; hydrocarbon compounds such as heptane or toluene; water; or mixtures thereof. To dissolve the catalyst, the catalyst can be diluted with a diol such as 1,4-butanediol or ethylene glycol. In this case, the diol can also function as a raw material for polyester.

[0057] The titanium compound is preferably a tetraalkyl titanate or a hydrolyzate thereof, and specific examples thereof include tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, tetracyclohexyl titanate, tetrabenzyl titanate, mixed titanates thereof, and hydrolyzates thereof.

[0058] In addition, titanium compounds include alcohols, long-form periodic table (Nomenclature of Inorganic Chemistry IUPAC Recommendation A liquid obtained by mixing a Group 2 metal compound in the long-form periodic table (hereinafter sometimes referred to as a Group 2 metal compound in the long-form periodic table), a phosphate ester compound, or a titanium compound can also be used.

[0059] The amount of catalyst added is not particularly limited, but the lower limit of the metal content relative to the polyester produced is usually 0.1 ppm by mass or more, preferably 0.5 ppm by mass or more, and more preferably 1 ppm by mass or more, and the upper limit is usually 3000 ppm by mass or less, preferably 1000 ppm by mass or less, more preferably 250 ppm by mass or less, and particularly preferably 130 ppm by mass or less. This range is particularly applicable when a metal compound is used as a polycondensation catalyst. Using too much catalyst is not only economically disadvantageous, but can also increase the carboxyl group terminal concentration of the polyester. This increase in the carboxyl group terminal content and residual catalyst concentration can reduce the thermal stability and hydrolysis resistance of the polyester. Conversely, using too little catalyst reduces polymerization activity, which can induce thermal decomposition of the polyester during polyester production, making it difficult to obtain a polyester with practically useful properties.

[0060] Commercially available aliphatic polyesters (A) can be used. Commercially available aliphatic polyester resins (A) containing aliphatic diol units and aliphatic dicarboxylic acid units as constituent units include "BioPBS (registered trademark) FZ91PB," "BioPBS (registered trademark) FZ91PM," "BioPBS (registered trademark) FD92PB," and "BioPBS (registered trademark) FD92PM" manufactured by PTTMCC Biochem. Commercially available aliphatic polyester resins (A) containing aliphatic oxycarboxylic acid units as constituent units include "Ingeo (registered trademark) 2003D," "Ingeo (registered trademark) 4032D," and "Ingeo (registered trademark) 4060D" manufactured by NatureWorks, and "PHBH (registered trademark) X331N," "PHBH (registered trademark) X131A," "PHBH (registered trademark) 151A," and "PHBH (registered trademark) 151C" manufactured by Kaneka Corporation.

[0061] [Inorganic filler (B)] Examples of the inorganic filler (B) include at least one metal oxide selected from metals such as magnesium, calcium, barium, boron aluminum, silicon, titanium, zirconium, and hafnium, and further, hydroxides, carbonates, sulfates, or silicates of these metals. Among these, basic inorganic fillers are preferred, and examples of basic inorganic fillers that can be used include basic magnesium sulfate, calcium carbonate, talc, clay, magnesium oxide, and magnesium carbonate. In particular, basic magnesium sulfate and calcium carbonate are preferred from the viewpoints of improving mechanical properties (particularly rigidity), good appearance of molded articles, and dimensional stability. Specific examples of basic magnesium sulfate include MOS HIGE manufactured by Ube Material Industries, Ltd.; examples of calcium carbonate include SOFTON C1200 and SOFTON C2200 manufactured by Bihoku Funka Kogyo Co., Ltd.; NITOREX 30P, NITOREX 23P, and NS#100 manufactured by Nitto Funka Kogyo Co., Ltd.; NITOREX 30PS, NCC#2310, NCC#1010, NCC-V2300, and NCC-V1000 of the NCC series; and WISCAL A manufactured by Maruo Calcium Co., Ltd.; and examples of talc include LMS100, LMR100, PKP80, PKP53S, FFH105, and MG115 manufactured by Fuji Talc Kogyo Co., Ltd.; and MicroAce SG-95 and K-1 manufactured by Nippon Talc Co., Ltd.

[0062] The inorganic filler (B) may be surface-treated, which may improve the dispersibility of the filler, the flowability of the resin composition, and the smoothness and opening properties of the film. Furthermore, surface treatment can be expected to reduce the amounts of fillers, plasticizers, and other additives required in the resin composition. The surface treatment of the filler can be carried out by a commonly known method, and the method of surface treatment is not particularly limited. Examples of the surface treatment agent include linear fatty acids having 6 to 40 carbon atoms, branched fatty acids, and ester compounds thereof. An example of a surface-treated filler is surface-treated calcium carbonate, and the use of surface-treated calcium carbonate as the inorganic filler (B) is preferred from the viewpoint of improving dispersibility, reinforcing properties, processability, and weather resistance. Specifically, an example of the surface-treated calcium carbonate is Ryton BS manufactured by Bihoku Funka Kogyo Co., Ltd.

[0063] The average particle size of the inorganic filler (B) used is not particularly limited, but from the viewpoint of improving film properties and handling, the average particle size is preferably 0.5 μm or more, more preferably 0.6 μm or more, and even more preferably 0.7 μm or more. Furthermore, from the viewpoint of preventing poor appearance and tearing of the film, the average particle size is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

[0064] These inorganic fillers (B) may be used alone or in combination of two or more different types, which differ in material, physical properties, whether or not they have been surface treated, etc.

[0065] The content of the inorganic filler (B) in the biodegradable film is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, particularly preferably 15% by mass or more, and particularly preferably 17% by mass or more, based on the total amount of the aliphatic polyester (A), the inorganic filler (B), and the other biodegradable resin (C) described below. It is also preferably 65% ​​by mass or less, more preferably 60% by mass or less, and even more preferably 55% by mass or less. By having the content of the inorganic filler (B) in the biodegradable film within the above range, the film has excellent rigidity, elongation at break, and decomposability.

[0066] [Other biodegradable resins (C)] The biodegradable film according to one embodiment of the present invention may contain other biodegradable resins (C) in addition to the aliphatic polyester (A) and the inorganic filler (B). The other biodegradable resin (C) is a biodegradable resin other than the above-mentioned aliphatic polyester (A), for example, polybutylene succinate terephthalate (PBST), polybutylene Examples of such cellulose esters include aliphatic-aromatic polyesters such as poly(ethylene adipate terephthalate) (PBAT), polyethylene succinate terephthalate (PEST), and poly(butylene sebacate terephthalate) (PBSeT), and cellulose esters such as cellulose acetate (CA), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB). Among these, aliphatic-aromatic polyesters are preferred, and poly(butylene adipate terephthalate) (PBAT) is more preferred, from the viewpoints of melting point and film formability.

[0067] When the biodegradable film contains other biodegradable resins (C), the content of the other biodegradable resins (C) in the biodegradable film is preferably greater than 0% by mass, more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the total amount of the aliphatic polyester (A), the inorganic filler (B), and the other biodegradable resins (C). By keeping the content of the other biodegradable resins (C) in the biodegradable film within the above range, a film with a good balance between tear resistance and degradability can be obtained.

[0068] [Other ingredients] The biodegradable film may contain other ingredients, such as various additives such as lubricants, plasticizers, antistatic agents, antioxidants, light stabilizers, UV absorbers, dyes, pigments, hydrolysis inhibitors, known surface wetting improvers, flame retardants, release agents, incineration aids, pigments, dispersing aids, surfactants, nucleating agents, or compatibilizers; fine powders of animal or plant substances such as starch, cellulose, paper, wood flour, chitin / chitosan, coconut shell powder, or walnut shell powder; or mixtures thereof. Other components can be used as desired within the scope of not impairing the effects of the present invention. These may be used alone or in combination of two or more. The total content of other components in the biodegradable film is usually preferably 0.01% by mass or more and 10% by mass or less so as not to impair the physical properties of the biodegradable film.

[0069] (lubricant) The resin composition may contain a lubricant. When the resin composition contains a lubricant, the opening properties of the film made of the resin composition can be improved, and the processability when the film is molded into a bag can be improved.

[0070] Known lubricants can be used without any particular limitation. Specific examples include paraffins such as paraffin oil or solid paraffin; higher fatty acids such as stearic acid or palmitic acid; higher alcohols such as palmityl alcohol or stearyl alcohol; metal salts of fatty acids such as calcium stearate, zinc stearate, barium stearate, aluminum stearate, magnesium stearate, or sodium palmitate; fatty acid esters such as butyl stearate, glycerin monostearate, or diethylene glycol monostearate; fatty acid amides such as stearamide, methylene bis-stearamide, ethylene bis-stearamide, ethylenediamide of oxystearic acid, methylolamide, oleylamide, stearamide, or erucamide; and waxes such as carnauba wax or montan wax. The lubricants may be used alone or in any combination and ratio. Among these, erucamide is particularly preferred. When the resin composition contains a lubricant, it is generally used in an amount of 0.01 mass % or more, preferably 0.05 mass % or more, and 2.5 mass % or less, preferably 1.0 mass % or less in the resin composition. If the content of the lubricant is equal to or greater than the above lower limit, the effect of the lubricant can be sufficiently obtained, and If it is equal to or less than the upper limit, excessive slippage of the film can be prevented, and the film will have excellent secondary processability.

[0071] (plasticizer) The resin composition may contain a plasticizer. When the resin composition contains a plasticizer, the viscosity of the resin composition before molding increases, which makes it easier to improve the deterioration of the flowability of the resin composition.

[0072] The plasticizer may be any known plasticizer without any particular limitation. For example, fatty acid esters such as methyl adipate, diethyl adipate, diisopropyl adipate, di-n-propyl adipate, di-2-ethylhexyl adipate, diisobutyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl diglycol adipate, di-2-ethylhexyl azelate, dibutyl sebacate, di-2-ethylhexyl sebacate, methyl acetyl lysylate, or epoxidized soybean oil; glycerin esters such as triacetin; maleic acid and fumaric acid esters such as diethyl maleate, dibutyl maleate, dioctyl maleate, dibutyl fumarate, or dioctyl fumarate; polyesters such as adipate-1,3-butylene glycol; epoxidized esters; trioctyl triacetate; Examples of suitable plasticizers include trimellitic acid esters such as mellitate; triethylene glycol diacetate; citric acid esters such as acetyl tributyl citrate or triethyl citrate; acetylated monoglycerides such as glycerin diacetomonopropionate, glycerin diacetomonocaprylate, glycerin diacetomonocaprate, glycerin diacetomonolaurate, glycerin diacetomonooleate, glycerin monoacetomonobehenate, or glycerin monoacetomonostearate; polyglycerin fatty acid esters such as diglycerin acetate, decaglycerin propionate, tetraglycerin caprylate, decaglycerin laurate, decaglycerin oleate, or decaglycerin behenate; and rosin derivatives. These plasticizers may be used alone or in combination of two or more.

[0073] When the resin composition contains a plasticizer, the plasticizer is typically used in the range of 0.05 to 10% by mass in the resin composition. If the content of the plasticizer is equal to or greater than the lower limit, the effect of improving fluidity due to the plasticizer can be sufficiently obtained, and if the content is equal to or less than the upper limit, the fluidity can be improved without problems such as bleeding out of the plasticizer.

[0074] (antistatic agent) The resin composition may contain an antistatic agent. When an antistatic agent is contained in the resin composition, the formability when a film made of the resin composition is formed into a bag can be improved in some cases.

[0075] Any antistatic agent can be used as long as it does not significantly impair the effects of the present invention. Specific examples of preferred antistatic agents include nonionic, cationic, and anionic surfactants.

[0076] Examples of nonionic antistatic agents include glycerin fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, alkyldiethanolamines, hydroxyalkylmonoethanolamines, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, and alkyldiethanolamides. Among these, alkyldiethanolamines are preferred. Examples of cationic antistatic agents include tetraalkylammonium salts and trialkylbenzylammonium salts. Examples of anionic antistatic agents include alkyl sulfonates, alkyl benzene sulfonates, and alkyl phosphates. Among these, those that have good kneadability with resins and have low antistatic properties are Alkylbenzene sulfonates are preferred because they have a high prevention effect.

[0077] When the resin composition contains an antistatic agent, the amount used is arbitrary as long as it does not significantly impair the effects of the present invention, but it is usually 0.5% by mass or more, preferably 1% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less in the resin composition. If the amount exceeds the above range, the surface of the film made of the resin composition tends to become sticky, reducing the product value. If the amount is below the above range, the antistatic effect tends to be reduced.

[0078] (starch) The resin composition may contain starch. When the resin composition contains starch, the biodegradability and bio-based carbon content of the resin composition can be improved. Specific examples of starch include corn starch, waxy corn starch, high-amylose corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch, sago starch, bracken starch, or pea starch, or derivatives thereof. These starches may be used alone or in combination of two or more. These may be unmodified or modified. Here, "modification" includes any modification method, including chemical, physical, and biological. Chemical modification refers to modifying part or all of the structural units of carbohydrates (polysaccharides) through chemical reactions such as esterification, etherification, oxidation, reduction, coupling, dehydration, hydrolysis, dehydrogenation, or halogenation, and particularly refers to etherifying or esterifying hydroxyl groups. Physical modification refers to changing physical properties, such as imparting plasticity with glycerin, water, or inorganic salts. Biological modification refers to changing the chemical structure, etc., using living organisms.

[0079] When the resin composition contains starch, the starch is used in the range of 1 to 60 mass % in the resin composition. When the starch content is equal to or greater than the lower limit, the effect of including starch can be sufficiently obtained, and when the content is equal to or less than the upper limit, the effect of the present invention can be efficiently exhibited without causing an extreme increase in viscosity.

[0080] (light stabilizer) The resin composition may contain a light stabilizer. Lightfastness agents include decanedioic acid bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl) ester, reaction products of 1,1-dimethylethyl hydroperoxide with octane, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl 1,2,2,6,6-pentamethyl-4-piperidylsebacate, and bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate. Examples of suitable stabilizers include hindered amine stabilizers such as bacate, 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, and poly[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}]. The lightfastener is preferably used in combination with an ultraviolet absorber, and a combination of a hindered amine stabilizer and an ultraviolet absorber is effective.

[0081] When the resin composition contains a light stabilizer, the amount of the light stabilizer used is usually 100 ppm by mass or more, preferably 200 ppm by mass or more, based on the mass of the resin composition, and usually 5% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less. If the amount is less than this range, the effect of the light stabilizer tends to be reduced. On the other hand, if the amount is more than this range, the rigidity and tear resistance tend to be reduced. Furthermore, the heat resistance of the resin composition tends to be poor and bleeding out of the light stabilizer tends to occur.

[0082] (ultraviolet absorber) The resin composition may contain an ultraviolet absorber. Examples of the ultraviolet absorber include 2-(2H-benzotriazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol, etc. It is particularly preferable to use two or more different types of ultraviolet absorbers in combination.

[0083] When the resin composition contains an ultraviolet absorber, the amount of ultraviolet absorber used is optional as long as it does not significantly impair the effects of the present invention, but is usually 100 ppm by mass or more, preferably 200 ppm by mass or more, and usually 5% by mass or less, preferably 2% by mass or less, and more preferably 0.5% by mass or less, based on the mass of the resin composition. If the amount is below this range, the effect of the ultraviolet absorber tends to be reduced. On the other hand, if the amount is above this range, the production cost tends to be too high, the heat resistance of the resin composition tends to be poor, and the ultraviolet absorber tends to bleed out.

[0084] (heat stabilizer) The resin composition may contain a heat stabilizer. Heat stabilizers include dibutylhydroxytoluene (BHT; 2,6-di-t-butyl-4-methylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3,3',3",5,5',5"-hexa-tert-butyl-a,a',a"-(mesitylene-2,4,6-triyl)tri-p-cresol, and octadecyl-3-(3,5-di-tert-butyl) -4-hydroxyphenyl)propionate, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, calcium diethyl bis[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, bis( Hindered phenolic heat stabilizers such as 2,2'-dihydroxy-3,3'-di-tert-butyl-5,5'-dimethylphenyl)ethane or N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide]; tridecyl phosphite, diphenyldecyl phosphite, tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphonite, bis[2,4-bis(1,1-dimethylethyl Examples of suitable heat stabilizers include phosphorus-based heat stabilizers such as bis(2,4-di-tert-butylphenyl)pentaerythritol diphasphite, lactone-based heat stabilizers such as the reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and xylene, and sulfur-based antioxidants such as dilauryl thiodipropionate and distearyl thiodipropionate. These heat stabilizers may be used alone or in combination of two or more.

[0085] When the resin composition contains a heat stabilizer, the amount of the heat stabilizer used is typically 100 ppm by mass or more, preferably 200 ppm by mass or more, and typically 5% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less, based on the mass of the resin composition. Below this range, the effect of the heat stabilizer tends to be reduced. On the other hand, above this range, the production cost tends to increase, and the heat stabilizer may bleed out.

[0086] (end-capping agent) The resin composition may contain an end-capping agent mainly for the purpose of suppressing hydrolysis due to moisture in the atmosphere. Examples of the terminal blocking agent include carbodiimide compounds, epoxy compounds, and oxazoline compounds. Among the carbodiimide compounds, examples of monocarbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and di-β-naphthylcarbodiimide. Among these, dicyclohexylcarbodiimide and diisopropylcarbodiimide are preferred. Furthermore, polycarbodiimide compounds that can be used include those produced by the methods described in, for example, U.S. Pat. No. 2,941,956, Japanese Patent Publication No. 47-33279, J. Org. Chem., Vol. 28, pp. 2069-2075 (1963), and Chemical Review 1981, Vol. 81, No. 4, pp. 619-621. However, when using a compound that undergoes crosslinking or chain extension, such as polycarbodiimide, it is necessary to use it within a range that does not impair moldability due to an increase in viscosity. These end-capping agents may be used alone or in combination of two or more.

[0087] When the resin composition contains a terminal-capping agent, the amount of the terminal-capping agent used is usually 0.1 to 5% by mass of the resin composition. If the amount is less than this range, the effect of the terminal-capping agent cannot be fully obtained, while if the amount is more than this range, the crosslinking reaction may proceed excessively, causing gelation.

[0088] <Film characteristics> (tensile modulus) A biodegradable film according to one embodiment of the present invention (hereinafter sometimes simply referred to as "film") has a tensile modulus in the MD direction of the film of 400 MPa or more, as measured in accordance with JIS K7127 (1999). When the tensile modulus in the MD direction of the film is within the above range, the film's bag tearability is improved, allowing the compost bag to be broken down into small pieces in a food waste processor. From the same perspective, the tensile modulus in the MD direction of the film is preferably 410 MPa or more, more preferably 430 MPa or more, even more preferably 440 MPa or more, and particularly preferably 450 MPa or more. Furthermore, from the perspective of handleability when tying the opening of the film after putting organic waste into the bag, the tensile modulus in the MD direction of the film is preferably 2000 MPa or less, more preferably 1800 MPa or less, even more preferably 1600 MPa or less, and particularly preferably 1500 MPa or less. The tensile modulus of elasticity in the TD direction of the film is not particularly limited, but for the same reasons as in the MD direction of the film, it is preferably 300 MPa or more, more preferably 350 MPa or more, and is preferably 2000 MPa or less, more preferably 1800 MPa or less. (breaking elongation) A biodegradable film according to one embodiment of the present invention has a breaking elongation in the MD direction of the film measured according to JIS K7127 (1999) of 400% or less. Having a breaking elongation in the MD direction of the film within the above range can prevent the film from wrapping around the rotating shaft of a food waste processor. From the same perspective, the breaking elongation in the MD direction of the film is preferably 390% or less, more preferably 380% or less, even more preferably 370% or less, and particularly preferably 360% or less. Furthermore, from the perspective of preventing compost bags from breaking during use, the breaking elongation in the MD direction of the film is preferably 100% or more, more preferably 150% or more, even more preferably 200% or more, and particularly preferably 250% or more. In addition, in order to improve the durability of the compost bag during use, the film's breaking elongation in the TD direction measured based on JIS K7127 (1999) is 300% or more. Preferably, the elongation at break in the TD direction of the film is 350% or more, more preferably 400% or more, and particularly preferably 450% or more. In order to prevent deformation of the compost bag after organic waste is placed inside, the upper limit of the elongation at break in the TD direction of the film is more preferably 2000% or less, even more preferably 1800% or less, and particularly preferably 1500% or less.

[0089] To obtain a film having the desired tensile modulus, it is preferable to use the aliphatic polyester (A) and the inorganic filler (B) in the above-mentioned ratio. To obtain a film having the desired breaking elongation, it is preferable to use the aliphatic polyester (A) and the inorganic filler (B) in the above-mentioned ratio.

[0090] <Film manufacturing method> Examples of methods for producing biodegradable films include injection molding, extrusion molding, co-extrusion molding (film molding by inflation method or T-die method), lamination molding, heat press molding, blow molding (various blow moldings), thermoforming (vacuum forming, pressure forming), plastic processing, powder molding (rotational molding), etc. Among these, inflation molding is particularly preferred because the effects of the present invention are most pronounced.

[0091] In the case of inflation molding, the conditions such as bubble internal pressure, heating temperature, bubble diameter, cooling rate, and take-up rate can be selected from ordinary known conditions. As for molding conditions, for example, the blow ratio is usually set to 1.1 to 10 times, preferably 2 to 5 times, so that the tear strength of the film can be adjusted. Suitability for inflation molding can be determined by visually inspecting bubble stability or frost line height, for example. For example, the more stable the bubble, the better, and the more symmetrical the bubble shape. It is preferable that the frost line height is not too high. If the frost line is too high, the tubular film will be difficult to solidify, which may result in film blocking and poor opening. If the frost line is too low, the bubble may come into contact with the air ring or die, making molding impossible. Therefore, the frost line height must be appropriate for the equipment, raw materials used, and processing conditions.

[0092] The die temperature is not particularly limited and can be set appropriately depending on the composition of the resin composition, but is usually 100°C or higher so that the melt viscosity does not become too high and the extrusion rate per power of the extruder is appropriate. On the other hand, it is usually 280°C or lower so that resin deterioration does not adhere to the die and get mixed into the obtained film. The resin temperature inside the die is preferably 110 to 250°C, more preferably in the range of 120 to 200°C.

[0093] The film obtained by such inflation molding may have a single layer structure or a laminated structure. The thickness of the film produced by inflation molding is usually 20 to 150 μm, and preferably 30 to 100 μm.

[0094] The tubular film obtained by inflation molding is processed into a desired shape such as a bag through processes such as cutting and heat sealing.

[0095] <Application> The biodegradable film according to one embodiment of the present invention can be suitably used for compost bags. The method for treating organic waste using the compost bag of the present invention will now be described.

[0096] <Organic waste disposal method> One embodiment of the present invention relates to a method for treating organic waste, which involves placing a compost bag containing organic waste into a food waste processor and performing primary composting. Primary composting, as used herein, refers to fermenting and decomposing the compost bag and organic waste within the processor using microorganisms. By using the compost bag of the present invention as the bag for containing the organic waste, the bag can be easily broken down within the processor and broken down into small pieces without wrapping around the rotating shaft when the compost bag and organic waste are decomposed in the food waste processor. Furthermore, the primary composting process preferably has a feature in which the bags are broken when they hit the agitator blades installed in the food waste processor tank, and the organic waste is scraped out. This feature allows the organic waste to be quickly scraped out of the bags, shortening the time it takes for the organic waste to decompose.

[0097] Any food waste processor can be used as long as it can decompose organic waste through fermentation using microorganisms. For example, it is preferable to use FOURSTARS (decomposition bacteria: Bacillus subtilis) manufactured by Well Create Co., Ltd. or Biocomposter YC100 (decomposition bacteria: Bacillus nouveau) manufactured by Yanmar e-Star. Organic waste placed in the food waste processor is typically fermented and decomposed over a period of 12 to 48 hours. The temperature inside the food waste processor tank is typically about 20 to 70°C, and the relative humidity is typically about 30 to 80% RH. When organic waste is fed into the food waste processor, a fungal bed or a compost accelerator may be added. Examples of fungal beds include rice husks, sawdust, wood flour, wheat straw, and rice straw, with rice husks being particularly preferred. Examples of compost accelerators include soil microorganisms, fungi, rice bran, and leaf mold, with the use of Cerberix (registered trademark), which is derived from microorganisms, being particularly preferred. During the primary composting process, the weight of the organic waste and compost bags usually gradually decreases as they are fermented and decomposed. However, it is preferable for the compost bags to decompose to 30% or less of their original weight within 48 hours of being placed in the food waste processor, more preferably 20% or less, and particularly preferably 10% or less.

[0098] In the organic waste treatment method, the above-mentioned primary composting may be carried out alone, but it is preferable to further include a step of carrying out secondary composting, or secondary and tertiary composting, in a composting area to completely eliminate the compost bags. By carrying out secondary and tertiary composting in a composting area, fully matured compost can be obtained, and the resulting fully matured compost can be used to grow vegetables, etc. [Example]

[0099] Specific embodiments of the present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded. Note that the values ​​of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values ​​in the embodiments of the present invention, and preferred ranges may be defined by a combination of the above-mentioned upper or lower limit values ​​and the values ​​in the following examples or values ​​between the examples.

[0100] [Melt flow rate (MFR) measurement of resin used] Measurement was carried out using a melt indexer at 190°C under a load of 2.16 kg in accordance with JIS K7210 (1999). The unit is g / 10 min.

[0101] [Raw materials used] Details of the resins and inorganic fillers used in the examples and comparative examples are as follows. In the following, "PBS" stands for "polybutylene succinate," "PBSA" stands for "polybutylene succinate adipate," "PLA" stands for "polylactic acid," "PHBH" stands for "poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)," "PCL" stands for "polycaprolactone," and "PBAT" stands for "polybutylene adipate terephthalate." .

[0102] <Aliphatic polyester (A)> PBS (BioPBS® FZ91PM manufactured by PTTMC BioChem, succinic acid unit content in total dicarboxylic acid units: 100 mol%, adipic acid unit content: 0 mol%, MFR: 5 g / 10 min, melting point: 113°C) PBSA (BioPBS (registered trademark) FD92PM manufactured by PTTMCC Biochem, succinic acid unit content in total dicarboxylic acid units: 74 mol%, adipic acid unit content: 26 mol%, MFR: 5 g / 10 min, melting point: 89°C) PLA (Natureworks Ingeo® 4032D, MFR: 4 g / 10 min, melting point: 165°C) PHBH (Kaneka Biodegradable Biopolymer Green Planet® X131A manufactured by Kaneka Corporation, 3-hydroxybutyrate / 3-hydroxyhexanoate molar ratio: 94 / 6, MFR: 6 g / 10 min, melting point: 140°C) PCL: (Ingevity Capa® 6800, MFR: 7 g / 10 min, melting point: 60° C.)

[0103] <Other biodegradable resins (C)> PBAT: (BASF Ecoflex® F Blend C1200, adipic acid unit content in total dicarboxylic acid units: 53 mol%, terephthalic acid unit content: 47 mol%, MFR: 5 g / 10 min, melting point: 118° C.)

[0104] <Inorganic filler (B)> Talc (Micro Ace SG-95, manufactured by Nippon Talc Co., Ltd., average particle size: 3 μm) Surface-treated calcium carbonate (Ryton BS, manufactured by Bihoku Powder Chemical Industry Co., Ltd., average particle size: 2 μm) Basic magnesium sulfate (Mos High-Z, manufactured by Ube Materials Co., Ltd.)

[0105] <Amide erucate> Diamid L-200, manufactured by Mitsubishi Chemical Corporation

[0106] [Evaluation method] The evaluation methods for various physical properties and characteristics of the films in the examples and comparative examples are as follows.

[0107] <Tensile modulus> Based on JIS K7127 (1999), the tensile modulus in the MD direction and TD direction was measured and evaluated according to the following criteria. The higher the tensile modulus, the better the bag breakage resistance in the food waste processor, which is preferable. ○: Tensile modulus is 400 MPa or more ×: Tensile modulus is less than 400 MPa

[0108] <Elongation at break in the MD direction> Based on JIS K7127 (1999), the elongation at break in the MD direction was measured and evaluated according to the following criteria. If the elongation at break in the MD direction is too high, troubles such as winding around the rotating shaft of the food waste processor are likely to occur. ○: Elongation at break is 400% or less ×: Elongation at break is higher than 400%

[0109] <Elongation at break in the TD direction> Based on JIS K7127 (1999), the elongation at break in the TD direction was measured and evaluated according to the following criteria. A higher elongation at break in the TD direction is preferable because the durability during bag use increases. ○: Elongation at break is 300% or more ×: Elongation at break is less than 300% <Usability of the bag> The feel of using the bag when lifting a bag with 3 kg of cabbage in the compost bag was evaluated according to the following criteria. ○: The bag can be used without any problems ×: The bag is torn or ripped, or the heat-sealed part is torn, making it impossible to use as a bag. <Bag breakability> Ten compost bags containing cabbage were placed into the food waste processor, and the condition of the compost bags inside the device was checked one hour later and evaluated according to the following criteria. 〇: More than 8 compost bags were torn and the cabbage inside had come out of the bag. ×: 1 to 8 bags: The compost bag was torn and the cabbage inside fell out, or the bag was not torn at all and the cabbage remained inside. <Winding around the rotating shaft> The compost bag containing the cabbage was placed into the food waste processor, and after 48 hours the condition of the rotating shaft inside the device was checked and evaluated according to the following criteria. ○: No bag wrapped around the rotating shaft ×: The bag is wrapped around the rotating shaft <Degradability> The compost bag containing the cabbage was placed in a food waste processor, and the film remaining in the processor was collected after 48 hours. The weight loss rate was then calculated, and decomposition was evaluated according to the following criteria. The weight loss rate was calculated by the following method. (1-(weight of film collected after testing) ÷ (weight of 10 compost bags)) x 100 〇: Weight loss rate is 80% or more ×: Weight loss rate is less than 80%

[0110] [Examples 1 to 4, Comparative Examples 1 to 5] The raw materials shown in Table 1 were blended in the proportions shown in Table 1. The blend was extruded into strands at 160°C using a twin-screw extruder with a screw diameter of 30 mm and pelletized using a pelletizer. The resulting resin pellets were then extruded using an inflation molding machine at a temperature of 160°C and a blow ratio of 2.5 to produce an inflation film measuring 650 mm wide and 35 μm thick. The tensile modulus and elongation at break of this film were evaluated. Compost bags were also created by cutting the film into 800 mm lengths and heat-sealing the bottoms. Each compost bag contained 3 kg of cabbage. Ten of these bags were prepared and placed in a food waste processor (Well Create Co., Ltd.) called "FOURSTARS," which contained 8 kg of rice husks, 20 kg of water, and 10 g of the decomposing bacteria Servelicus. After thorough agitation, the 10 compost bags containing the cabbage were placed in the compost bag. The bags were then evaluated for usability, bag tearing, winding around the rotating shaft, and decomposition in a composting test.

[0111] [Table 1]

[0112] From Table 1, it can be seen that the biodegradable film of the present invention is less prone to tearing and less prone to wrapping around the shaft of a composting machine than conventional films, and is therefore more easily degradable.

Claims

1. A compost bag made of a biodegradable film having a tensile modulus of elasticity in the MD direction of the film of 400 MPa or more and a breaking elongation in the MD direction of the film of 400% or less, as measured in accordance with JIS K7127 (1999).

2. 2. The compost bag according to claim 1, wherein the film has a breaking elongation in the transverse direction of 300% or more as measured in accordance with JIS K7127 (1999).

3. 2. The compost bag according to claim 1, wherein the tensile modulus of elasticity in the machine direction of the film measured in accordance with JIS K7127 (1999) is 2000 MPa or less.

4. 2. The compost bag according to claim 1, wherein the film has a breaking elongation in the machine direction of 100% or more as measured in accordance with JIS K7127 (1999).

5. 2. The compost bag according to claim 1, wherein the film has a breaking elongation in the transverse direction of 1500% or less as measured in accordance with JIS K7127 (1999).

6. 2. The compost bag according to claim 1, wherein the biodegradable film comprises an aliphatic polyester (A) and an inorganic filler (B).

7. 7. The compost bag according to claim 6, wherein the biodegradable film further contains another biodegradable resin (C).

8. 8. The compost bag according to claim 7, wherein the inorganic filler (B) is contained in an amount of 15% by mass or more and less than 60% by mass relative to the total amount of the aliphatic polyester (A), the inorganic filler (B), and the other biodegradable resin (C).

9. 7. The compost bag according to claim 6, wherein the inorganic filler (B) is a basic inorganic filler.

10. 7. The compost bag according to claim 6, wherein the inorganic filler (B) is basic magnesium sulfate.

11. 7. The compost bag according to claim 6, wherein the inorganic filler (B) is surface-treated calcium carbonate.

12. 7. The compost bag according to claim 6, wherein the aliphatic polyester (A) contains at least one kind of aliphatic diol unit and at least one kind of aliphatic dicarboxylic acid unit as constituent units.

13. 13. The compost bag according to claim 12, wherein the aliphatic polyester (A) contains at least succinic acid as the aliphatic dicarboxylic acid unit.

14. A method for treating organic waste, comprising the step of putting the compost bag according to any one of claims 1 to 13 containing organic waste into a food waste processor to perform primary composting.

15. 15. The method for treating organic waste according to claim 14, further comprising a step of carrying out secondary composting, or secondary composting and tertiary composting, in a composting site to completely eliminate the compost bags.

16. In the primary composting process, the stirring blades installed in the food waste processing tank hit the bags.

15. The method for treating organic waste according to claim 14, wherein the bag is broken by the action of the pressure applied to the bag, and the organic waste is scraped out.

17. 15. The organic waste treatment method according to claim 14, wherein in the step of primary composting, the bag is decomposed to 30% or less of the weight of the original bag within 48 hours after being put into the food waste treatment machine.

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