Method for producing aliphatic polyester resin composition, aliphatic polyester resin composition, and marine degradation promoter

Abstract

Provided is a method for producing an aliphatic polyester resin composition by heating and kneading an aliphatic polyester resin and a nitrogen compound, wherein the solubility of the nitrogen compound in water at 20℃ is 50 g / 100 mL or less. Also provided are: a method for producing an aliphatic polyester resin composition that makes it possible to obtain an aliphatic polyester resin composition having marine degradability and excellent durability to moisture; an aliphatic polyester resin composition; and a marine degradation accelerator.

Description

Method for producing aliphatic polyester resin composition, aliphatic polyester resin composition, and marine degradation accelerator

[0001] The present invention relates to a method for producing an aliphatic polyester resin composition, an aliphatic polyester resin composition, and a marine degradation accelerator.

[0002] Plastics are widely used in packaging, daily necessities, electrical appliances, machine parts, toys, and more. However, there are concerns that plastic products and waste that end up in the ocean for some reason, remaining on or in the ocean as so-called plastic waste, could become a cause of marine pollution. To prevent marine pollution caused by such plastic waste, there are hopes for the use of marine biodegradable plastics, which have the ability to decompose in the ocean.

[0003] For example, Patent Document 1 discloses a marine biodegradation-promoting additive characterized by containing a nitrogen compound and a phosphorus compound as active ingredients, and a marine biodegradable resin composition in which the nitrogen and phosphorus contents are specified relative to the carbon weight. Also, Patent Document 2 discloses a biodegradable resin composition containing a polyester resin and a compound having a specific amino group, with the aim of accelerating the biodegradation rate and increasing the degree of biodegradation, particularly in the ocean.

[0004] JP 2022-142016 A International Publication No. 2023 / 058708

[0005] However, while adding an additive that promotes marine biodegradation to a biodegradable resin, as in the resin compositions described in Patent Documents 1 and 2, improves marine degradability, it also reduces the durability of the resin composition. For example, depending on the application of molded articles obtained by molding a resin composition, such as packaging containers and daily necessities, they may come into contact with water or be used under high humidity. Therefore, molded articles that are resistant to deformation and deterioration of physical properties, even in moisture-rich environments, are required to have a certain level of durability. However, molded articles molded using resin compositions containing such additives are prone to deformation and deterioration of resin properties when placed in moisture-rich environments, making it difficult to achieve both high marine degradability and excellent durability when used in moisture-rich environments. Therefore, there has been a need for a resin composition that has high marine degradability and excellent durability when used in moisture-rich environments. An objective of the present invention is to provide a method for producing an aliphatic polyester resin composition that can yield an aliphatic polyester resin composition that is both marine degradable and highly water-resistant. Another objective of the present invention is to provide an aliphatic polyester resin composition having marine degradability and a marine degradation accelerator.

[0006] After extensive research, the present inventors have found that a method for producing an aliphatic polyester resin composition by heat-kneading an aliphatic polyester resin and a specific nitrogen compound can solve the above-mentioned problems. Specifically, one aspect of the present invention is the following method for producing an aliphatic polyester resin composition, an aliphatic polyester resin composition, and a marine degradation accelerator. [1] A method for producing an aliphatic polyester resin composition by heat-kneading an aliphatic polyester resin and a nitrogen compound, wherein the nitrogen compound has a water solubility of 50 g / 100 mL or less at 20°C. [2] A method for producing an aliphatic polyester resin composition according to [1], wherein the nitrogen compound has a 10% weight loss temperature of 210°C or higher as determined by thermogravimetric analysis. [3] A method for producing an aliphatic polyester resin composition according to [1] or [2], wherein the nitrogen compound is blended in an amount of 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the aliphatic polyester resin. [4] A method for producing an aliphatic polyester resin composition according to [1] or [2], wherein the resin composition further comprises a phosphorus compound, and the sum of the amount of the nitrogen compound and the amount of the phosphorus compound per 100 parts by mass of the aliphatic polyester resin is 2 parts by mass or more and 50 parts by mass or less. [5] A method for producing an aliphatic polyester resin composition according to [4], wherein the ratio of the amount of the phosphorus compound to the amount of the nitrogen compound is 1 to 1,000. [6] A method for producing an aliphatic polyester resin composition according to [4] or [5], wherein the solubility of the phosphorus compound in water at 20°C is 50 mg / 100 mL or less. [7] A method for producing an aliphatic polyester resin composition according to any of [1] to [6], wherein the nitrogen compound comprises oxamide. [8] A method for producing an aliphatic polyester resin composition according to any of [4] to [7], wherein the phosphorus compound comprises at least one compound selected from the group consisting of triphenyl phosphate and tricalcium phosphate.[9] An aliphatic polyester resin composition comprising an aliphatic polyester resin and a nitrogen compound, wherein the aliphatic polyester resin composition is immersed in water at 23°C for 72 hours at a ratio of 4 to 6 g of the aliphatic polyester resin composition per 100 mL of water, and the total amount of nitrogen contained per mL of water is 0.01 μg to 20 μg per g of the aliphatic polyester resin composition.

[10] The aliphatic polyester resin composition according to [9], wherein the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

[11] The aliphatic polyester resin composition according to [9] or

[10] , wherein the content of the nitrogen compound in the resin composition is 1 part by mass to 50 parts by mass per 100 parts by mass of the aliphatic polyester resin.

[12] The aliphatic polyester resin composition according to [9] or

[10] , wherein the aliphatic polyester resin composition further comprises a phosphorus compound, and the total content of the nitrogen compound and the phosphorus compound in the aliphatic polyester resin composition is 2 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the aliphatic polyester resin.

[13] The aliphatic polyester resin composition according to any one of [9] to

[12] , wherein the aliphatic polyester resin composition has a biodegradability of 1% or more after being kept in seawater having a COD of 1 mg / L or less for 28 days.

[14] An aliphatic polyester resin composition comprising an aliphatic polyester resin and oxamide.

[15] The aliphatic polyester resin composition according to

[14] , wherein the aliphatic polyester resin composition further comprises a phosphorus compound.

[16] A marine degradation accelerator used to obtain the aliphatic polyester resin composition according to any one of [9] to

[15] , wherein the marine degradation accelerator contains the nitrogen compound, and the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

[0007] According to the present invention, there is provided a method for producing an aliphatic polyester resin composition that can produce an aliphatic polyester resin composition that is marine degradable and has excellent water resistance. Furthermore, there is provided an aliphatic polyester resin composition having marine degradability and a marine degradation accelerator.

[0008] [Method for producing an aliphatic polyester-based resin composition] The method for producing an aliphatic polyester-based resin composition of the present invention is a method for producing an aliphatic polyester-based resin composition by heat-kneading an aliphatic polyester-based resin and a nitrogen compound, in which the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

[0009] <Aliphatic polyester resin> In the method for producing an aliphatic polyester resin composition of the present invention, an aliphatic polyester resin is used as the main raw material constituting the composition. Examples of the aliphatic polyester resin include a copolymer of a polyvalent fatty acid and an aliphatic polyol, a polymer of a fatty acid having a hydroxyl group, and a polymer of a lactone. At least one selected from the group consisting of a copolymer of a polyvalent fatty acid and an aliphatic polyol, a polymer of a fatty acid having a hydroxyl group, and a polymer of a lactone is preferred, and at least one selected from the group consisting of a copolymer of a divalent fatty acid and an aliphatic diol, and a polymer of a fatty acid having a hydroxyl group is more preferred, and a polymer of a fatty acid having a hydroxyl group is even more preferred. As the aliphatic polyester resin, a biodegradable aliphatic polyester resin having biodegradability is preferred.

[0010] The weight-average molecular weight (Mw) of the aliphatic polyester resin is preferably 10,000 or more, more preferably 50,000 to 1,000,000, even more preferably 50,000 to 500,000, even more preferably 50,000 to 400,000, even more preferably 50,000 to 300,000, even more preferably 100,000 to 300,000, and even more preferably 150,000 to 300,000. By having the weight-average molecular weight (Mw) of the aliphatic polyester resin within the above range, a resin composition having excellent marine degradability and good mechanical properties such as tensile strength can be consistently obtained. The weight-average molecular weight (Mw) of the aliphatic polyester resin can be measured by gel permeation chromatography analysis using the aliphatic polyester resin dissolved in chloroform as an analytical sample. Specifically, it can be measured by the method described in the Examples. The weight-average molecular weight (Mw) of the aliphatic polyester resin is the weight-average molecular weight in terms of polystyrene.

[0011] The aliphatic polyester resin preferably includes at least one selected from the group consisting of polylactic acid (PLA) resin, which is a polymer of lactic acid; polybutylene succinate (PBS) resin, which is a polymer of a dicarboxylic acid including succinic acid and a diol including butanediol; polybutylene adipate resin, which is a polymer of a dicarboxylic acid including adipic acid and a diol including butanediol; polyhydroxybutyrate resin, which is a polymer of 3-hydroxybutyric acid; polyglycolic acid (PGA) resin, which is a polymer of glycolic acid; and poly-ε-caprolactone (PCL) resin, which is a polymer of ε-caprolactone. The aliphatic polyester resin may contain copolymer components derived from other compounds in addition to the main components constituting each resin, as long as the object of the present application can be achieved. For example, polybutylene adipate-based resins include polybutylene adipate terephthalate (PBAT), which is a copolymer of butanediol, adipic acid, and terephthalic acid, and polyhydroxybutyrate-based resins include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid. The aliphatic polyester-based resin more preferably includes at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate-based resins, polybutylene adipate-based resins, and polyhydroxybutyrate-based resins. Furthermore, from the viewpoints of large market supply and excellent mechanical properties such as tensile properties, the aliphatic polyester-based resin more preferably includes at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate-based resins, and polybutylene adipate-based resins, and even more preferably includes polylactic acid-based resin (PLA). Aliphatic polyester resins such as polylactic acid resins, polybutylene succinate resins, and polybutylene adipate resins exhibit good mechanical properties such as good tensile properties, but are difficult to biodegrade in seawater with low COD. In the present invention, however, by blending a nitrogen compound described below with an aliphatic polyester resin to form a resin composition, it is possible to obtain a resin composition with good marine degradability without deteriorating the physical properties of the resin.In addition, when a nitrogen compound described below is blended with an aliphatic polyester-based resin, which is relatively easily biodegradable, to form a resin composition, the marine degradability of the resin can be further improved while maintaining the physical properties of the resin.

[0012] From this viewpoint, the aliphatic polyester resin is more preferably at least one selected from the group consisting of polylactic acid resin, polybutylene succinate resin, and polybutylene adipate resin, and even more preferably polylactic acid resin.

[0013] In addition, resins other than aliphatic polyester-based resins may be used in this production method as long as the object of the present invention can be achieved and the effects of the present invention are not impaired. However, from the viewpoint of improving marine degradability, it is preferable to keep the amount of non-biodegradable resins as small as possible.

[0014] Furthermore, from the viewpoint of easily obtaining molded articles having excellent rigidity, the glass transition temperature of the aliphatic polyester resin is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher. The upper limit of the glass transition temperature is generally 120°C, and may be 100°C or higher, or may be 80°C. The glass transition temperature of the aliphatic polyester resin is measured by differential scanning calorimetry (DSC) based on JIS K7121:1987. The glass transition temperature means the midpoint glass transition temperature of the DSC curve. The condition adjustment of the test specimen is performed as described in "(3) Measuring the glass transition temperature after a certain heat treatment."

[0015] <Nitrogen Compound> The nitrogen compound used in the method for producing an aliphatic polyester resin composition of the present invention has a water solubility of 50 g / 100 mL or less at 20°C. As described in Patent Documents 1 and 2, conventionally used marine degradation accelerators have preferred nitrogen compounds that are easily eluted in seawater, i.e., nitrogen compounds with relatively high solubility in water, from the viewpoint of accelerating resin degradation. However, when such nitrogen compounds are incorporated, excessive elution of the nitrogen compounds from the resulting resin composition tends to occur. Therefore, when a molded article made of the resin composition is placed in contact with water, even for a relatively short period of contact, deformation of the molded article or deterioration of the physical properties of the resin composition is likely to occur. This tendency is particularly pronounced when a relatively large amount of nitrogen compound is incorporated to accelerate resin decomposition. Furthermore, such moisture effects can occur even when the resin composition does not directly come into contact with water, for example, when the resin composition is placed in a high-humidity environment. For these reasons, resin compositions obtained using conventional marine degradation accelerators have poor durability and may not be able to maintain the required high mechanical properties for a long period of time when used in various applications. In addition, since nitrogen compounds tend to be eluted from the resin composition in large amounts early on, there is a risk that the resin will not be sufficiently decomposed when the resin composition is discharged into a sea with less pollution and less organic matter, such as the open ocean. In the method for producing an aliphatic polyester resin composition of the present invention, it is believed that by using a nitrogen compound that has relatively low solubility in water and is not easily eluted in water, a resin composition that is marine degradable and has excellent durability against moisture can be obtained.

[0016] The nitrogen compound has a solubility in water of 50 g / 100 mL or less at 20° C., and the solubility in water of the nitrogen compound at 20° C. is preferably 30 g / 100 mL or less, more preferably 10 g / 100 mL or less, even more preferably 5 g / 100 mL or less, still more preferably 1 g / 100 mL or less, still more preferably 0.5 g / 100 mL or less, still more preferably 0.1 g / 100 mL or less, still more preferably 0.09 g / 100 mL or less, still more preferably 0.08 g / 100 mL or less, and still more preferably 0.05 g / 100 mL or less. When the solubility in water of the nitrogen compound at 20° C. is in the above range, a resin composition can be obtained that is marine degradable and is resistant to deformation and deterioration in physical properties even when used under high humidity conditions or when immersed in water. The water solubility of the nitrogen compound is preferably 0.001 g / 100 mL or more, more preferably 0.01 g / 100 mL or more. When the water solubility of the nitrogen compound at 20°C is within the above range, the resin composition can stably exhibit marine degradability even in seawater with low COD. The water solubility at 20°C can be measured based on "Test No. 105: Water Solubility" in the "OECD GUIDELINE FOR THE TESTING OF CHEMICALS." To measure the water solubility, the following preliminary test is conducted, and then the water solubility of the nitrogen compound is measured using either the column elution method or the flask method selected based on the results. In the preliminary test, first, 0.1 g of the sample (nitrogen compound) and 10 mL of pure water are placed in a 10 mL measuring cylinder with a glass stopper, and the mixture is shaken for 10 minutes. If no undissolved sample is found in the measuring cylinder as a result of this operation, select the flask method to measure the solubility of the nitrogen compound. On the other hand, if undissolved sample is found in the measuring cylinder, transfer the mixture to a 100 mL measuring cylinder, add an additional 90 mL of pure water, and let stand for 96 hours.If, as a result of this operation, no undissolved sample is found in the measuring cylinder, the flask method is selected to measure the solubility of the nitrogen compound, and if undissolved sample is found in the measuring cylinder, the column elution method is selected to measure the solubility of the nitrogen compound.

[0017] The nitrogen compound preferably has a 10% weight loss temperature by thermogravimetric analysis of 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, even more preferably 230°C or higher, and even more preferably 240°C or higher. A method for efficiently producing an aliphatic polyester-based resin composition containing a biodegradable resin such as an aliphatic polyester-based resin and a nitrogen compound includes a method of forming an aliphatic polyester-based resin composition by heating and kneading the resin and the nitrogen compound using an extruder or the like. If the nitrogen compound is prone to excessive decomposition by heat, depending on the temperature during heating and kneading, the decomposition of the resin may be accelerated due to the influence of nitrogen oxides produced by thermal decomposition of the nitrogen compound, which may result in a decrease in the physical properties of the resin constituting the resin composition. Furthermore, even when such a resin composition is thermoformed to form a molded body, the physical properties of the resin constituting the molded body tend to be easily impaired by the heat during thermoforming. On the other hand, by having the 10% weight loss temperature by thermogravimetric analysis within the above range, deterioration of the physical properties of the resin composition due to heat during heating and kneading, etc., can be stably suppressed. Furthermore, a resin composition can be obtained that can stably thermoform a molded article having the required physical properties. The upper limit of the 10% weight loss temperature by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, but it is preferably 400°C or less, more preferably 350°C or less, and even more preferably 300°C or less. The 10% weight loss temperature by thermogravimetric analysis is determined by heating a test sample made of a nitrogen compound in an air atmosphere at a heating rate of 10 / min and measuring the temperature at which the weight of the test sample decreases by 10%, assuming the weight of the test sample at the start of the measurement to be 100%. Specifically, it can be measured by the method described in the Examples.

[0018] The nitrogen compound is a compound containing nitrogen atoms. From the viewpoint of easily and stably increasing the marine degradability of the resin composition, the proportion of nitrogen atoms contained in the compound is preferably 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 25 to 40 mass%. The molecular weight of the nitrogen compound is preferably 50 to 1,000, more preferably 60 to 500, and even more preferably 60 to 150. The nitrogen compound can serve as a nutrient source for microorganisms that decompose aliphatic polyester-based resins in the ocean. By blending a nitrogen compound with an aliphatic polyester-based resin, when a resin composition containing a nitrogen compound is released into the ocean, components derived from the nitrogen compound eluted from the resin composition can serve as a nutrient source for microorganisms. This facilitates biodegradation of the resin even in the ocean, where there are few nitrogen sources that serve as nutrient sources for microorganisms.

[0019] As the nitrogen compound, an organic nitrogen compound can be preferably used, and more preferably, an organic nitrogen compound without a hydroxyl group can be used. The organic nitrogen compound is an organic compound containing a nitrogen atom. Examples of the organic nitrogen compound include an organic compound having an amide bond (-N-(C=O)-) and an organic compound having an amino group. The organic nitrogen compound is preferably at least one selected from the group consisting of an organic compound having an amide bond (-N-(C=O)-) and an organic compound having an amino group, and more preferably, an organic compound having an amide bond. The compound having an amide bond may have an amino group. The organic compound having an amide bond is preferably at least one selected from the group consisting of oxamide shown in the following formula (1), 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU, acetaldehyde condensed urea) shown in the following formula (2), and isobutylidenediurea (IBDU), more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU, acetaldehyde condensed urea), and even more preferably oxamide. The nitrogen compound preferably comprises at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and isobutylidenediurea (IBDU), more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), even more preferably oxamide. The total proportion of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU) in the nitrogen compound is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. The proportion of oxamide in the nitrogen compound is more preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. The method for producing an aliphatic polyester resin composition of the present invention includes the following aspects.A method for producing an aliphatic polyester resin composition by heat-kneading an aliphatic polyester resin and a nitrogen compound, wherein the nitrogen compound is at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine, and isobutylidenediurea.

[0020]

[0021] The oxamide represented by formula (1) has a solubility in water of 0.02 g / 100 mL at 20°C and a 10% weight loss temperature of 254°C as determined by thermogravimetric analysis. 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU) represented by formula (2) has a solubility in water of 0.08 g / 100 mL at 20°C and a 10% weight loss temperature of 215°C as determined by thermogravimetric analysis. Isobutylidenediurea (IBDU) has a solubility in water of 0.09 g / 100 mL at 20°C and a 10% weight loss temperature of 206°C as determined by thermogravimetric analysis. By using the compound having an amide bond, it is possible to suppress deterioration of physical properties due to heat kneading, and to stably obtain a resin composition that is excellent in marine degradability and durability to moisture.

[0022] The amount of the nitrogen compound used in this production method is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 1 part by mass or more and 40 parts by mass or less, even more preferably 1 part by mass or more and 30 parts by mass or less, and even more preferably 2 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the aliphatic polyester-based resin. By having the amount of the nitrogen compound in the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing deterioration in the physical properties of the resin composition due to the addition of the nitrogen compound, and a particularly excellent balance of these factors is achieved.

[0023] <Phosphorus Compound> The aliphatic polyester resin composition in the production method of the present invention preferably further contains a phosphorus compound. Examples of methods for obtaining an aliphatic polyester resin composition containing a phosphorus compound include: a method in which the aliphatic polyester resin and the nitrogen compound are heated and kneaded together using an extruder or the like, and the phosphorus compound is added at the same time; a method in which the nitrogen compound and the aliphatic polyester resin are heated and kneaded to form a kneaded mixture, and then the mixture is heated and kneaded with the phosphorus compound; and a method in which the phosphorus compound and the aliphatic polyester resin are heated and kneaded to form a kneaded mixture, and then the kneaded mixture is heated and kneaded with the nitrogen compound. From the viewpoint of increasing productivity, it is preferable to supply the aliphatic polyester resin, the nitrogen compound, and the phosphorus compound to an extruder, and heat and knead them to produce the aliphatic polyester resin composition.

[0024] By further including a phosphorus compound in the aliphatic polyester resin composition, the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound can be increased. Therefore, by using a nitrogen compound and a phosphorus compound in combination, when the total amount of the nitrogen compound and the phosphorus compound is the same as that of the nitrogen compound alone, the marine degradability of the resin composition can be further improved compared to when the nitrogen compound is blended alone. Furthermore, even when the total amount of the nitrogen compound and the phosphorus compound blended is relatively small, the marine degradability of the resin composition can be improved, so that a resin composition having both marine degradability and good physical properties can be obtained.

[0025] Some phosphorus compounds contain nitrogen atoms, and in the present invention, phosphorus compounds containing nitrogen atoms are considered to be nitrogen compounds. In other words, in the present invention, nitrogen compounds containing phosphorus atoms are included in the nitrogen compounds. Furthermore, the molecular weight of the phosphorus compound is preferably 60 to 1,000, more preferably 80 to 500, even more preferably 100 to 450, still more preferably 150 to 400, and even more preferably 200 to 400. Phosphorus compounds can serve as a nutrient source for microorganisms that decompose aliphatic polyester resins in the ocean. By blending a phosphorus compound with an aliphatic polyester resin, when a resin composition containing a phosphorus compound is released into the ocean, components derived from the phosphorus compound eluted from the resin composition can serve as a nutrient source for microorganisms. This facilitates biodegradation of the resin, even in the ocean, where there are few phosphorus sources that serve as a nutrient source for microorganisms.

[0026] The phosphorus compound may be a phosphorus compound having a solubility in water at 20°C of 100 g / 100 mL or less, preferably a phosphorus compound having a solubility in water at 20°C of 30 g / 100 mL or less. The solubility of the phosphorus compound in water at 20°C is preferably 50 mg / 100 mL or less, more preferably 20 mg / 100 mL or less, even more preferably 10 mg / 100 mL or less, still more preferably 5 mg / 100 mL or less, and even more preferably 3 mg / 100 mL or less. By having the solubility of the phosphorus compound in water at 20°C within this range, the marine degradability of the resin composition is improved, and a resin composition that is less likely to experience deterioration in physical properties even when used under high humidity conditions or immersed in water is easily obtained. Furthermore, the solubility of the phosphorus compound in water at 20°C is preferably 0.01 mg / 100 mL or more, more preferably 0.1 mg / 100 mL or more. When the solubility of the phosphorus compound in water at 20° C. is within the above range, the resin composition can stably exhibit marine degradability even in seawater with a low COD. The solubility of the phosphorus compound in water at 20° C. can be measured based on "Test No. 105: Water Solubility" of the "OECD GUIDELINE FOR THE TESTING OF CHEMICALS," similar to the solubility of nitrogen compounds in water at 20° C.

[0027] The phosphorus compound may be an organic phosphorus compound or an inorganic phosphorus compound. The organic phosphorus compound is preferably a phosphoric acid ester, more preferably a phenolic ester of phosphoric acid, and even more preferably triphenyl phosphate. The inorganic phosphorus compound is preferably a phosphate, more preferably a calcium salt of phosphoric acid, and even more preferably tricalcium phosphate. That is, the phosphorus compound preferably includes at least one selected from the group consisting of a phosphoric acid ester and a phosphate. The phosphorus compound is more preferably at least one selected from the group consisting of a phosphoric acid ester and a phosphate. The phosphorus compound is more preferably at least one selected from the group consisting of a phenolic ester of phosphoric acid and a calcium salt of phosphoric acid. The phosphorus compound is even more preferably at least one selected from the group consisting of a phenolic ester of phosphoric acid and a calcium salt of phosphoric acid. The phosphorus compound is even more preferably at least one selected from the group consisting of triphenyl phosphate and tricalcium phosphate. The sum of the proportion of triphenyl phosphate and the proportion of tricalcium phosphate in the phosphorus compound is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. Triphenyl phosphate has a solubility in water of 1.1 mg / 100 mL at 20°C. Tricalcium phosphate has a solubility in water of 2.2 mg / 100 mL at 20°C. By using a phosphate ester and / or a phosphate, the efficiency of resin decomposition by nitrogen compounds and phosphorus compounds can be increased, and a resin composition having good physical properties and good marine degradability can be stably obtained. Furthermore, from the viewpoint of easily increasing the marine degradability of the resin composition, the phosphorus compound is preferably an inorganic phosphorus compound, and more preferably a phosphate. Examples of inorganic phosphorus compounds include inorganic phosphorus compounds containing at least one selected from the group consisting of tricalcium phosphate, calcium pyrophosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate, calcium hypophosphite, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate.These inorganic phosphorus compounds include hydrates of each compound.

[0028] The total amount of the nitrogen compound and the phosphorus compound used in this production method is preferably 2 parts by mass or more and 60 parts by mass or less, more preferably 2 parts by mass or more and 50 parts by mass or less, even more preferably 5 parts by mass or more and 45 parts by mass or less, and still more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the aliphatic polyester-based resin. When the total amount of the nitrogen compound and the content of the phosphorus compound is within the above range, a resin composition that is excellent in marine degradability can be obtained while suppressing deterioration in the physical properties of the resin composition due to the addition of the nitrogen compound and the phosphorus compound, and a resin composition that is excellent in marine degradability can be obtained, with a particularly excellent balance between these.

[0029] The ratio of the blending amount of the phosphorus compound to the blending amount of the nitrogen compound used in the present production method is preferably 0.5 to 1000, more preferably 1 to 1000, even more preferably 1 to 100, still more preferably 1 to 15, and even more preferably 1 to 5. When the ratio of the blending amount of the phosphorus compound to the blending amount of the nitrogen compound is within the above range, the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound can be easily increased, and a resin composition that exhibits good marine degradability even in seawater with low COD can be stably obtained.

[0030] Furthermore, from the viewpoint of easily increasing the resin decomposition efficiency by the nitrogen compound and the phosphorus compound in the aliphatic polyester resin composition obtained by this production method, the mass ratio of phosphorus atoms to nitrogen atoms in the aliphatic polyester resin composition is preferably 0.01 or more and 5 or less, more preferably 0.05 or more and 2 or less, and even more preferably 0.1 or more and 1 or less. Here, the nitrogen atoms are nitrogen atoms substantially derived from the nitrogen compound, and the phosphorus atoms are phosphorus atoms substantially derived from the nitrogen compound and / or the phosphorus compound. The mass ratio can be calculated, for example, from the relationship between the proportion of nitrogen atoms in the compounds, the proportion of phosphorus atoms in the compounds, and the amount of each compound blended when producing the resin composition, or by measuring the amount of nitrogen atoms and the amount of phosphorus atoms contained in the resin composition and determining the ratio thereof.

[0031] <Production Conditions> The method for producing the aliphatic polyester resin composition of the present invention is a method of heat-kneading an aliphatic polyester resin and a nitrogen compound, preferably a method of heat-kneading an aliphatic polyester resin, a nitrogen compound, and a phosphorus compound. The heat-kneading of the aliphatic polyester resin, the nitrogen compound, and optionally a phosphorus compound can be carried out using a kneader or an extruder, and is preferably carried out using an extruder. In particular, heat-kneading using an extruder can efficiently disperse the nitrogen compound and phosphorus compound in the aliphatic polyester resin, resulting in excellent productivity. The extruder is not particularly limited, and known extruders can be used. The aliphatic polyester resin composition can be produced, for example, as follows. First, the aliphatic polyester resin, the nitrogen compound, and optionally other phosphorus compounds are fed into an extruder, and heated in the extruder to melt the aliphatic polyester resin and knead them to form a molten mixture. The heat-kneading temperature is preferably 130°C or higher and 220°C or lower, more preferably 150°C or higher and 210°C or lower. Next, the melt-kneaded product is extruded from the downstream side of the extruder into a string-like (strand-like) shape, and the string-like melt-kneaded product is cooled (for example, water-cooled) and cut to a desired length using a pelletizer or the like to obtain an aliphatic polyester-based resin composition. In this case, the aliphatic polyester-based resin composition is preferably granulated into pellets. The obtained pellet-like aliphatic polyester-based resin composition can be used as a resin raw material for producing a molded product having a desired shape, for example, by thermoforming or the like.

[0032] <Characteristics of Aliphatic Polyester Resin Composition Obtained by the Production Method> The aliphatic polyester resin composition obtained by the production method for an aliphatic polyester resin composition of the present invention contains the nitrogen compound because it is obtained by the above-mentioned method, and further has the following characteristics.

[0033] The weight-average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition is preferably 10,000 or more, more preferably 50,000 to 1,000,000, even more preferably 50,000 to 500,000, even more preferably 50,000 to 400,000, even more preferably 50,000 to 300,000, even more preferably 100,000 to 300,000, and even more preferably 150,000 to 300,000. By having the weight-average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition within the above range, a resin composition can be obtained that is excellent in marine degradability and has good mechanical properties such as tensile strength. The weight-average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition can be measured by gel permeation chromatography analysis using the aliphatic polyester resin composition dissolved in chloroform as an analytical sample. Specifically, it can be measured by the method described in the Examples. The weight-average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition is the weight-average molecular weight in terms of polystyrene.

[0034] The aliphatic polyester resin composition preferably has a biodegradability of 1% or more, more preferably 2% or more, even more preferably 3% or more, and even more preferably 5% or more after being stored for 28 days in seawater with a COD of 1 mg / L or less. Here, COD (chemical oxygen demand) indicates the amount of oxygen (mg / L) required to oxidize oxidizable substances in a water sample under certain conditions, and serves as an indicator of water quality. Furthermore, the more organic matter there is in the water and the worse the water quality, the higher the COD tends to be. By maintaining the biodegradability of the aliphatic polyester resin composition in seawater with a COD of 1 mg / L or less for 28 days within this range, the resin composition can be sufficiently biodegraded even in seawater with little pollution and little organic matter that serves as a nutrient source for microorganisms that decompose aliphatic polyester resins.

[0035] As long as the object of the present invention can be achieved, the upper limit of the biodegradability of the aliphatic polyester resin composition after being kept in seawater having a COD of 1 mg / L or less for 28 days is not particularly limited, but from the viewpoint of improving the durability of molded articles formed from the resin composition when used in various applications, it is preferably 90%, more preferably 70%, even more preferably 50%, still more preferably 40%, and even more preferably 30%. The biodegradability of the aliphatic polyester resin composition after being kept in seawater having a COD of 1 mg / L or less for 28 days can be measured by the method described in the Examples.

[0036] The aliphatic polyester resin composition has a total nitrogen content per mL of water when the aliphatic polyester resin composition is allowed to stand in water at 23° C. for 72 hours of preferably 0.01 μg to 20 μg, more preferably 0.05 μg to 10 μg, even more preferably 0.1 μg to 5 μg, and still more preferably 0.1 μg to 2 μg, per gram of the aliphatic polyester resin composition. When the aliphatic polyester resin composition is allowed to stand in water at 23° C. for 72 hours of the total nitrogen content per mL of water is within the above range, a resin composition that is less susceptible to excessive deterioration in physical properties due to moisture and has excellent marine degradability can be obtained. The total amount of nitrogen contained per mL of water when an aliphatic polyester resin composition is allowed to stand in water at 23°C for 72 hours can be calculated by measuring the total amount of nitrogen contained in the aqueous solution after allowing an aliphatic polyester resin composition (test piece) to stand in pure water at 23°C for 72 hours, based on JIS K 0102:2019 Section 45.6 (flow analysis method), and converting the amount into units. ３It is preferable to use a film-like aliphatic polyester resin composition having a molecular weight of 4 to 6 g or more per 100 mL of water. Measurement is performed by adding 4 to 6 g of test pieces per 100 mL of water to the water. As the test piece, a single film or multiple film pieces may be used as long as they have the above dimensions. Specifically, the measurement can be performed by the method described in the Examples. The total nitrogen amount can also be said to be the total nitrogen amount contained per mL of water when the aliphatic polyester resin composition is immersed in water at 23°C for 72 hours at a ratio of 4 to 6 g of the aliphatic polyester resin composition per 100 mL of water.

[0037] The aliphatic polyester resin composition has a 10% weight loss temperature measured by thermogravimetric analysis of preferably 170°C or higher, more preferably 220°C or higher, even more preferably 240°C or higher, still more preferably 250°C or higher, and even more preferably 270°C or higher. When the 10% weight loss temperature measured by thermogravimetric analysis of the resin composition is within the above range, deterioration of the physical properties of the resin composition due to thermoforming or the like can be stably suppressed. Furthermore, a resin composition can be obtained that can be stably thermoformed into a molded product having the required physical properties. While the upper limit of the 10% weight loss temperature measured by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, it is preferably 400°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower. The 10% weight loss temperature measured by thermogravimetric analysis is determined by heating a test sample made of an aliphatic polyester resin composition in an air atmosphere at a heating rate of 10 / min, and measuring the temperature at which the weight of the test sample decreases by 10%, assuming the weight of the test sample at the start of the measurement to be 100%. Specifically, it can be measured by the method described in the Examples.

[0038] [First Aliphatic Polyester Resin Composition] The first aliphatic polyester resin composition is an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, wherein the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less. Therefore, the first aliphatic polyester resin composition is an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, wherein the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less. There are no limitations on the method for producing the first aliphatic polyester resin composition, but it is preferable to obtain it by the above-mentioned production method. The first aliphatic polyester resin composition will be described below.

[0039] <Aliphatic polyester resin> The first aliphatic polyester resin composition contains an aliphatic polyester resin as the main raw material constituting the composition. Examples of the aliphatic polyester resin include a copolymer of a polyvalent fatty acid and an aliphatic polyol, a polymer of a fatty acid having a hydroxy group, and a polymer of a lactone, among others. A copolymer of a divalent fatty acid and an aliphatic diol and a polymer of a fatty acid having a hydroxy group are preferred, and a polymer of a fatty acid having a hydroxy group is more preferred. As the aliphatic polyester resin, a biodegradable aliphatic polyester resin having biodegradability is preferred.

[0040] For the aliphatic polyester-based resin, the description of the aliphatic polyester-based resin described in [Method for producing an aliphatic polyester-based resin composition] can be referred to as appropriate. The aliphatic polyester-based resin is preferably at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate-based resins, polybutylene adipate-based resins, and polyhydroxybutyrate-based resins. From the viewpoints of large supply to the market and excellent mechanical properties such as tensile properties, the aliphatic polyester-based resin is more preferably at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate-based resins, and polybutylene adipate-based resins, and even more preferably polylactic acid-based resins.

[0041] For the weight-average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition, reference can be made as appropriate to the description of the aliphatic polyester resin described in <Properties of the Aliphatic Polyester Resin Composition Obtained by the Production Method>. The weight-average molecular weight of the aliphatic polyester resin is preferably 10,000 or more, more preferably 50,000 to 1,000,000, even more preferably 50,000 to 500,000, still more preferably 50,000 to 400,000, still more preferably 50,000 to 300,000, still more preferably 100,000 to 300,000, and still more preferably 150,000 to 300,000.

[0042] <Nitrogen Compound> The nitrogen compound contained in the first aliphatic polyester resin composition has a solubility in water of 50 g / 100 mL or less at 20° C. Note that for properties of the nitrogen compound such as the solubility in water at 20° C. and the 10% weight loss temperature determined by thermogravimetric analysis, the description of the nitrogen compound described in [Method for producing an aliphatic polyester resin composition] can be referred to as appropriate.

[0043] The nitrogen compound has a water solubility of 50 g / 100 mL or less at 20°C, preferably 30 g / 100 mL or less, more preferably 10 g / 100 mL or less, even more preferably 5 g / 100 mL or less, even more preferably 1 g / 100 mL or less, and even more preferably 0.5 g / 100 mL or less. By having the water solubility of the nitrogen compound at 20°C within this range, a resin composition can be obtained that is marine degradable and is resistant to deformation and deterioration in physical properties even when used under high humidity conditions or immersed in water. Furthermore, the water solubility of the nitrogen compound is preferably 0.001 g / 100 mL or more, more preferably 0.01 g / 100 mL or more. By having the water solubility of the nitrogen compound at 20°C within this range, the resin composition can stably exhibit marine degradability even in seawater with a low COD.

[0044] The nitrogen compound has a 10% weight loss temperature measured by thermogravimetric analysis of preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, still more preferably 230°C or higher, and even more preferably 240°C or higher. When the 10% weight loss temperature measured by thermogravimetric analysis is within the above range, deterioration of the physical properties of the resin composition due to heat during heating and kneading, etc., can be stably suppressed. Note that the upper limit of the 10% weight loss temperature measured by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, but is preferably 400°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower.

[0045] From the viewpoint of easily and stably increasing the marine degradability of the resin composition, the nitrogen compound preferably contains nitrogen atoms in an amount of 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 25 to 40 mass%. The molecular weight of the nitrogen compound is preferably 50 to 1,000, more preferably 60 to 500.

[0046] The nitrogen compound is preferably an organic nitrogen compound. The nitrogen compound is preferably at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and isobutylidenediurea (IBDU), more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and even more preferably oxamide. The nitrogen compound is more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and even more preferably oxamide. That is, the first aliphatic polyester resin composition is preferably an aliphatic polyester resin composition containing an aliphatic polyester resin and oxamide. An aliphatic polyester resin composition containing an aliphatic polyester resin and oxamide is also included in the present invention. By using the nitrogen compound, it is possible to suppress deterioration of physical properties due to heat kneading, and to stably obtain a resin composition that is excellent in marine degradability and durability against moisture. The first aliphatic polyester resin composition of the present invention includes the following aspects. The aliphatic polyester resin composition is an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, wherein the nitrogen compound is at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine, and isobutylidenediurea.

[0047] The content of the nitrogen compound contained in the aliphatic polyester resin composition is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 1 part by mass or more and 40 parts by mass or less, even more preferably 1 part by mass or more and 30 parts by mass or less, and even more preferably 2 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the aliphatic polyester resin. By having the nitrogen compound content within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing deterioration of the physical properties of the resin composition due to the addition of the nitrogen compound, and the balance between these properties is particularly excellent.

[0048] <Phosphorus Compound> The first aliphatic polyester resin composition preferably further contains a phosphorus compound. By further containing a phosphorus compound in the first aliphatic polyester resin composition, the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound can be increased. Therefore, by using a nitrogen compound and a phosphorus compound in combination, when the total amount of the nitrogen compound and the phosphorus compound contained is the same as that of the nitrogen compound alone, the marine degradability of the resin composition can be further improved compared to when the nitrogen compound is contained alone. Furthermore, even when the total content of the nitrogen compound and the phosphorus compound is relatively low, the marine degradability of the resin composition can be improved, thereby obtaining a resin composition that has both marine degradability and good physical properties. As described above, oxamide is preferred as the nitrogen compound contained in the first aliphatic polyester resin composition. That is, the aliphatic polyester resin composition of the present invention preferably contains an aliphatic polyester resin, oxamide, and further contains a phosphorus compound. Note that for properties of the phosphorus compound, such as its solubility in water at 20°C, please refer to the explanation of the phosphorus compound described in [Method for producing an aliphatic polyester resin composition] as appropriate.

[0049] The phosphorus compound may be a phosphorus compound having a solubility in water at 20°C of 100 g / 100 mL or less, preferably a phosphorus compound having a solubility in water at 20°C of 30 g / 100 mL or less. The solubility of the phosphorus compound in water at 20°C is preferably 50 mg / 100 mL or less, more preferably 20 mg / 100 mL or less, even more preferably 10 mg / 100 mL or less, still more preferably 5 mg / 100 mL or less, and even more preferably 3 mg / 100 mL or less. By having the solubility of the phosphorus compound in water at 20°C within this range, the marine degradability of the resin composition is improved, and a resin composition that is less likely to experience deterioration in physical properties even when used under high humidity conditions or immersed in water is easily obtained. Furthermore, the solubility of the phosphorus compound in water at 20°C is preferably 0.01 mg / 100 mL or more, more preferably 0.1 mg / 100 mL or more. When the solubility of the phosphorus compound in water at 20° C. is within the above range, the resin composition can stably exhibit marine degradability even in seawater with a low COD. The molecular weight of the phosphorus compound is preferably 60 to 1,000, more preferably 80 to 500, even more preferably 100 to 450, still more preferably 150 to 400, and still more preferably 200 to 400.

[0050] Examples of the phosphorus compound include organic phosphorus compounds and inorganic phosphorus compounds. The organic phosphorus compound is preferably a phosphate ester, more preferably a phenolic ester of phosphoric acid, and even more preferably triphenyl phosphate. The inorganic phosphorus compound is preferably a phosphate, more preferably a calcium salt of phosphoric acid, and even more preferably tricalcium phosphate. The use of the phosphate ester and / or phosphate can enhance the resin decomposition efficiency of nitrogen compounds and phosphorus compounds, thereby stably producing a resin composition with good physical properties and good marine degradability. Furthermore, from the viewpoint of easily enhancing the marine degradability of the resin composition, the phosphorus compound is preferably an inorganic phosphorus compound, and more preferably a phosphate. Examples of inorganic phosphorus compounds include inorganic phosphorus compounds containing at least one selected from the group consisting of tricalcium phosphate, calcium pyrophosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate, calcium hypophosphite, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. These inorganic phosphorus compounds include hydrates of each compound.

[0051] The total content of the nitrogen compound and the phosphorus compound contained in the first aliphatic polyester resin composition is preferably 2 parts by mass or more and 60 parts by mass or less, more preferably 2 parts by mass or more and 50 parts by mass or less, even more preferably 5 parts by mass or more and 45 parts by mass or less, and still more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the aliphatic polyester resin. When the total content of the nitrogen compound and the content of the phosphorus compound is within the above range, a resin composition having excellent marine degradability can be obtained while suppressing deterioration in the physical properties of the resin composition due to the inclusion of the nitrogen compound or the phosphorus compound, and a resin composition having an excellent balance of these properties can be obtained.

[0052] The ratio of the content of the phosphorus compound to the content of the nitrogen compound contained in the first aliphatic polyester resin composition is preferably 0.5 to 1000, more preferably 1 to 1000, even more preferably 1 to 100, still more preferably 1 to 10, and still more preferably 1 to 5. When the ratio of the content of the phosphorus compound to the content of the nitrogen compound is within the above range, the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound can be easily increased, and a resin composition that exhibits good marine degradability even in seawater with low COD can be stably obtained.

[0053] Furthermore, from the viewpoint of easily increasing the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound, the mass ratio of phosphorus atoms to nitrogen atoms in the aliphatic polyester resin composition is preferably 0.01 or more and 5 or less, more preferably 0.05 or more and 2 or less, and even more preferably 0.1 or more and 1 or less. Here, the nitrogen atoms are nitrogen atoms substantially derived from the nitrogen compound, and the phosphorus atoms are phosphorus atoms substantially derived from the nitrogen compound and / or the phosphorus compound. The mass ratio can be calculated, for example, from the relationship between the proportion of nitrogen atoms in the compounds, the proportion of phosphorus atoms in the compounds, and the amount of each compound blended when producing the resin composition, or by measuring the amount of nitrogen atoms and the amount of phosphorus atoms contained in the resin composition and determining the ratio thereof.

[0054] <Characteristics of Aliphatic Polyester Resin Composition> For the characteristics of the first aliphatic polyester resin composition, the description of <Characteristics of Aliphatic Polyester Resin Composition Obtained by the Production Method> can be referred to as appropriate.

[0055] The first aliphatic polyester resin composition has a biodegradability of preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and even more preferably 5% or more after being kept in seawater having a COD of 1 mg / L or less for 28 days. The upper limit of the biodegradability of the aliphatic polyester resin composition after being kept in seawater having a COD of 1 mg / L or less for 28 days is not particularly limited, as long as the object of the present invention can be achieved. However, from the viewpoint of improving the durability when a molded article formed from the resin composition is used in various applications, it is preferably 90%, more preferably 70%, even more preferably 50%, even more preferably 40%, and even more preferably 30%.

[0056] In the first aliphatic polyester resin composition, the total amount of nitrogen contained per mL of water when the aliphatic polyester resin composition is allowed to stand in water at 23° C. for 72 hours is preferably from 0.01 μg to 20 μg, more preferably from 0.05 μg to 10 μg, even more preferably from 0.1 μg to 5 μg, and even more preferably from 0.1 μg to 2 μg, per gram of the aliphatic polyester resin composition. When the total amount of nitrogen contained per mL of water when the aliphatic polyester resin composition is allowed to stand in water at 23° C. for 72 hours is within the above range, the resin composition is less likely to suffer excessive deterioration in physical properties due to heat such as that caused by heating and kneading, or moisture, and is also excellent in marine degradability.

[0057] The aliphatic polyester resin composition has a 10% weight loss temperature measured by thermogravimetric analysis of preferably 170°C or higher, more preferably 220°C or higher, even more preferably 240°C or higher, even more preferably 250°C or higher, and even more preferably 270°C or higher. When the 10% weight loss temperature measured by thermogravimetric analysis of the resin composition is within the above range, deterioration of the physical properties of the resin composition due to thermoforming or the like can be stably suppressed. Furthermore, a resin composition can be obtained that can be stably thermoformed into molded articles having the required physical properties. While the upper limit of the 10% weight loss temperature measured by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, it is preferably 400°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower.

[0058] [Second Aliphatic Polyester Resin Composition] The present invention also includes an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, wherein the total amount of nitrogen contained per mL of water when the aliphatic polyester resin composition is left standing in water at 23°C for 72 hours is 0.01 μg or more and 20 μg or less per gram of the aliphatic polyester resin composition. Therefore, the aliphatic polyester resin composition of the present invention is an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, wherein the total amount of nitrogen contained per mL of water when the aliphatic polyester resin composition is left standing in water at 23°C for 72 hours is 0.01 μg or more and 20 μg or less per gram of the aliphatic polyester resin composition. There are no limitations on the manufacturing method of the aliphatic polyester resin composition of the present invention, but it is preferably obtained by the above manufacturing method. The aliphatic polyester resin composition is referred to as the second aliphatic polyester resin composition, and the second aliphatic polyester resin composition will be described below.

[0059] <Aliphatic polyester resin> The second aliphatic polyester resin composition contains an aliphatic polyester resin as the main raw material constituting the composition. Examples of the aliphatic polyester resin include a copolymer of a polyvalent fatty acid and an aliphatic polyol, a polymer of a fatty acid having a hydroxy group, and a polymer of a lactone, among others. A copolymer of a divalent fatty acid and an aliphatic diol and a polymer of a fatty acid having a hydroxy group are preferred, and a polymer of a fatty acid having a hydroxy group is more preferred. As the aliphatic polyester resin, a biodegradable aliphatic polyester resin having biodegradability is preferred.

[0060] For the aliphatic polyester-based resin, the description of the aliphatic polyester-based resin described in [Method for producing an aliphatic polyester-based resin composition] can be referred to as appropriate. The aliphatic polyester-based resin is preferably at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate-based resins, polybutylene adipate-based resins, and polyhydroxybutyrate-based resins. From the viewpoints of large supply to the market and excellent mechanical properties such as tensile properties, the aliphatic polyester-based resin is more preferably at least one selected from the group consisting of polylactic acid-based resins, polybutylene succinate-based resins, and polybutylene adipate-based resins, and even more preferably polylactic acid-based resins.

[0061] For the weight-average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition, reference can be made as appropriate to the description of the aliphatic polyester resin described in <Properties of the Aliphatic Polyester Resin Composition Obtained by the Production Method>. The weight-average molecular weight of the aliphatic polyester resin is preferably 10,000 or more, more preferably 50,000 to 1,000,000, even more preferably 50,000 to 500,000, still more preferably 50,000 to 400,000, still more preferably 50,000 to 300,000, still more preferably 100,000 to 300,000, and still more preferably 150,000 to 300,000.

[0062] <Nitrogen Compound> The second aliphatic polyester resin composition contains a nitrogen compound. The nitrogen compound contained in the second aliphatic polyester resin composition is preferably a nitrogen compound having a solubility in water at 20°C of 50 g / 100 mL or less. Also, it is preferably a nitrogen compound having a 10% weight loss temperature by thermogravimetric analysis of 200°C or higher. Note that for properties of the nitrogen compound such as the solubility in water at 20°C and the 10% weight loss temperature by thermogravimetric analysis, the explanation of the nitrogen compound described in [Method for producing an aliphatic polyester resin composition] can be appropriately referenced.

[0063] The solubility of the nitrogen compound in water at 20°C is preferably 50 g / 100 mL or less, more preferably 30 g / 100 mL or less, even more preferably 10 g / 100 mL or less, even more preferably 5 g / 100 mL or less, even more preferably 1 g / 100 mL or less, and even more preferably 0.5 g / 100 mL or less. By having the solubility of the nitrogen compound in water at 20°C within this range, a resin composition can be obtained that is marine degradable and is resistant to deformation and deterioration in physical properties even when used under high humidity conditions or immersed in water. Furthermore, the solubility of the nitrogen compound in water is preferably 0.001 g / 100 mL or more, more preferably 0.01 g / 100 mL or more. By having the solubility of the nitrogen compound in water at 20°C within this range, the resin composition can stably exhibit marine degradability even in seawater with a low COD.

[0064] The 10% weight loss temperature of the nitrogen compound as determined by thermogravimetric analysis is preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, still more preferably 230°C or higher, and even more preferably 240°C or higher. When the 10% weight loss temperature as determined by thermogravimetric analysis is within the above range, deterioration of the physical properties of the resin composition due to heat during heating and kneading, etc., can be stably suppressed. Note that the upper limit of the 10% weight loss temperature as determined by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, but is preferably 400°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower.

[0065] From the viewpoint of easily and stably increasing the marine degradability of the resin composition, the nitrogen compound preferably contains nitrogen atoms in an amount of 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 25 to 40 mass%. The molecular weight of the nitrogen compound is preferably 50 to 1,000, more preferably 60 to 500.

[0066] The nitrogen compound is preferably an organic nitrogen compound. The nitrogen compound is preferably at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU, acetaldehyde condensed urea), and isobutylidenediurea (IBDU), more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and even more preferably oxamide. The nitrogen compound is more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and even more preferably oxamide. The use of the nitrogen compound can suppress deterioration of physical properties due to heat kneading, and can stably produce a resin composition that is excellent in marine degradability and moisture resistance.

[0067] The content of the nitrogen compound contained in the aliphatic polyester resin composition is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 1 part by mass or more and 40 parts by mass or less, even more preferably 1 part by mass or more and 30 parts by mass or less, and even more preferably 2 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the aliphatic polyester resin. By having the nitrogen compound content within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing deterioration in the physical properties of the resin composition due to the addition of the nitrogen compound, and the balance between these properties is particularly excellent.

[0068] <Phosphorus Compound> The second aliphatic polyester resin composition preferably further contains a phosphorus compound. By further containing a phosphorus compound in the second aliphatic polyester resin composition, the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound can be increased. Therefore, by using a nitrogen compound and a phosphorus compound in combination, when the total amount of the nitrogen compound and the phosphorus compound contained is the same as that of the nitrogen compound alone, the marine degradability of the resin composition can be further improved compared to when the nitrogen compound is contained alone. Furthermore, even when the total content of the nitrogen compound and the phosphorus compound is relatively low, the marine degradability of the resin composition can be improved, thereby obtaining a resin composition that has good physical properties while maintaining marine degradability. Regarding the properties of the phosphorus compound, such as its solubility in water at 20°C, please refer to the explanation of the phosphorus compound described in [Method for producing an aliphatic polyester resin composition] as appropriate.

[0069] The phosphorus compound may be a phosphorus compound having a solubility in water at 20°C of 100 g / 100 mL or less, preferably a phosphorus compound having a solubility in water at 20°C of 30 g / 100 mL or less. The solubility of the phosphorus compound in water at 20°C is preferably 50 mg / 100 mL or less, more preferably 20 mg / 100 mL or less, even more preferably 10 mg / 100 mL or less, still more preferably 5 mg / 100 mL or less, and even more preferably 3 mg / 100 mL or less. By having the solubility of the phosphorus compound in water at 20°C within this range, it is possible to obtain a resin composition that is not susceptible to deterioration in physical properties even when used under high humidity conditions or immersed in water. The solubility of the phosphorus compound in water at 20°C is preferably 0.01 mg / 100 mL or more, more preferably 0.1 mg / 100 mL or more. When the solubility of the phosphorus compound in water at 20° C. is within the above range, the resin composition can stably exhibit marine degradability even in seawater with a low COD. The molecular weight of the phosphorus compound is preferably 60 to 1,000, more preferably 80 to 500, even more preferably 100 to 450, still more preferably 150 to 400, and still more preferably 200 to 400.

[0070] Examples of the phosphorus compound include organic phosphorus compounds and inorganic phosphorus compounds. The organic phosphorus compound is preferably a phosphate ester, more preferably a phenolic ester of phosphoric acid, and even more preferably triphenyl phosphate. The inorganic phosphorus compound is preferably a phosphate, more preferably a calcium salt of phosphoric acid, and even more preferably tricalcium phosphate. The use of the phosphate ester and / or phosphate can enhance the resin decomposition efficiency of nitrogen compounds and phosphorus compounds, thereby stably producing a resin composition with good physical properties and good marine degradability. Furthermore, from the viewpoint of easily enhancing the marine degradability of the resin composition, the phosphorus compound is preferably an inorganic phosphorus compound, and more preferably a phosphate. Examples of inorganic phosphorus compounds include inorganic phosphorus compounds containing at least one selected from the group consisting of tricalcium phosphate, calcium pyrophosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate, calcium hypophosphite, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. These inorganic phosphorus compounds include hydrates of each compound.

[0071] The total content of the nitrogen compound and the phosphorus compound contained in the second aliphatic polyester resin composition is preferably 2 parts by mass or more and 60 parts by mass or less, more preferably 2 parts by mass or more and 50 parts by mass or less, even more preferably 5 parts by mass or more and 45 parts by mass or less, and still more preferably 10 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the aliphatic polyester resin. When the total content of the nitrogen compound and the content of the phosphorus compound is within the above range, a resin composition having excellent marine degradability can be obtained while suppressing deterioration in the physical properties of the resin composition due to the inclusion of the nitrogen compound or the phosphorus compound, and a resin composition having an excellent balance of these properties can be obtained.

[0072] The ratio of the content of the phosphorus compound to the content of the nitrogen compound contained in the second aliphatic polyester resin composition is preferably 0.5 to 1000, more preferably 1 to 1000, even more preferably 1 to 100, still more preferably 1 to 10, and still more preferably 1 to 5. When the ratio of the content of the phosphorus compound to the content of the nitrogen compound is within the above range, the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound can be easily increased, and a resin composition that exhibits good marine degradability even in seawater with low COD can be stably obtained.

[0073] Furthermore, from the viewpoint of easily increasing the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound, the mass ratio of phosphorus atoms to nitrogen atoms in the aliphatic polyester resin composition is preferably 0.01 or more and 5 or less, more preferably 0.05 or more and 2 or less, and even more preferably 0.1 or more and 1 or less. Here, the nitrogen atoms are nitrogen atoms substantially derived from the nitrogen compound, and the phosphorus atoms are phosphorus atoms substantially derived from the nitrogen compound and / or the phosphorus compound. The mass ratio can be calculated, for example, from the relationship between the proportion of nitrogen atoms in the compounds, the proportion of phosphorus atoms in the compounds, and the amount of each compound blended when producing the resin composition, or by measuring the amount of nitrogen atoms and the amount of phosphorus atoms contained in the resin composition and determining the ratio thereof.

[0074] <Characteristics of Aliphatic Polyester Resin Composition> For the characteristics of the second aliphatic polyester resin composition, the explanation of <Characteristics of Aliphatic Polyester Resin Composition Obtained by the Production Method> can be referred to as appropriate.

[0075] In the second aliphatic polyester resin composition, when the aliphatic polyester resin composition is allowed to stand in water at 23° C. for 72 hours, the total amount of nitrogen contained per mL of water is 0.01 μg to 20 μg, preferably 0.05 μg to 10 μg, more preferably 0.1 μg to 5 μg, and even more preferably 0.1 μg to 2 μg, per gram of the aliphatic polyester resin composition. When the aliphatic polyester resin composition is allowed to stand in water at 23° C. for 72 hours, the total amount of nitrogen contained per mL of water is within the above range, making it possible to obtain a resin composition that is less susceptible to excessive deterioration in physical properties due to heat such as that caused by heating and kneading, or moisture, and that has excellent marine degradability.

[0076] The second aliphatic polyester resin composition has a biodegradability of preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and even more preferably 5% or more after being kept in seawater having a COD of 1 mg / L or less for 28 days. The upper limit of the biodegradability of the aliphatic polyester resin composition after being kept in seawater having a COD of 1 mg / L or less for 28 days is not particularly limited, as long as the object of the present invention can be achieved. However, from the viewpoint of improving the durability of molded articles formed from the resin composition when used in various applications, it is preferably 90%, more preferably 70%, even more preferably 50%, even more preferably 40%, and even more preferably 30%.

[0077] The second aliphatic polyester resin composition has a 10% weight loss temperature measured by thermogravimetric analysis of preferably 170°C or higher, more preferably 220°C or higher, even more preferably 240°C or higher, even more preferably 250°C or higher, and even more preferably 270°C or higher. When the 10% weight loss temperature measured by thermogravimetric analysis of the resin composition is within the above range, deterioration of the physical properties of the resin composition due to thermoforming or the like can be stably suppressed. Furthermore, a resin composition can be obtained that can be stably thermoformed into molded articles having the required physical properties. While the upper limit of the 10% weight loss temperature measured by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, it is preferably 400°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower.

[0078] [Marine Decomposition Accelerator] In order to obtain the aliphatic polyester resin composition of the present invention, a marine degradation accelerator for an aliphatic polyester resin can be used, which contains the nitrogen compound and has a solubility in water of 50 g / 100 mL or less at 20° C. That is, the marine degradation accelerator of the present invention is a marine degradation accelerator used to obtain an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, and the marine degradation accelerator contains the nitrogen compound and has a solubility in water of 50 g / 100 mL or less at 20° C.

[0079] <Nitrogen Compound> The nitrogen compound contained in the marine degradation accelerator of the present invention has a solubility in water of 50 g / 100 mL or less at 20° C. Note that for properties of the nitrogen compound such as the solubility in water at 20° C. and the 10% weight loss temperature determined by thermogravimetric analysis, the explanation of the nitrogen compound described in [Method for producing an aliphatic polyester-based resin composition] can be referred to as appropriate.

[0080] The nitrogen compound has a water solubility of 50 g / 100 mL or less at 20°C, preferably 30 g / 100 mL or less, more preferably 10 g / 100 mL or less, even more preferably 5 g / 100 mL or less, even more preferably 1 g / 100 mL or less, and even more preferably 0.5 g / 100 mL or less. By having the water solubility of the nitrogen compound at 20°C within this range, a resin composition can be obtained that is marine degradable and is resistant to deformation and deterioration in physical properties even when used under high humidity conditions or immersed in water. Furthermore, the water solubility of the nitrogen compound is preferably 0.001 g / 100 mL or more, more preferably 0.01 g / 100 mL or more. By having the water solubility of the nitrogen compound at 20°C within this range, the resin composition can stably exhibit marine degradability even in seawater with a low COD. The solubility in water at 20°C can be measured based on "Test No. 105: Water Solubility" of "OECD GUIDELINE FOR THE TESTING OF CHEMICALS."

[0081] The nitrogen compound has a 10% weight loss temperature measured by thermogravimetric analysis of preferably 200°C or higher, more preferably 210°C or higher, even more preferably 220°C or higher, still more preferably 230°C or higher, and even more preferably 240°C or higher. When the 10% weight loss temperature measured by thermogravimetric analysis is within the above range, deterioration of the physical properties of the resin composition due to heat during heating and kneading, etc., can be stably suppressed. Note that the upper limit of the 10% weight loss temperature measured by thermogravimetric analysis is not particularly limited as long as the object of the present invention can be achieved, but is preferably 400°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower.

[0082] From the viewpoint of easily and stably increasing the marine degradability of the resin composition, the nitrogen compound preferably contains nitrogen atoms in an amount of 10 to 60 mass%, more preferably 20 to 50 mass%, and even more preferably 25 to 40 mass%. The molecular weight of the nitrogen compound is preferably 50 to 1,000, more preferably 60 to 500.

[0083] The nitrogen compound is preferably an organic nitrogen compound. The nitrogen compound is more preferably at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and even more preferably oxamide. That is, the marine degradation accelerator of the present invention preferably contains oxamide as the nitrogen compound. When the marine degradation accelerator contains oxamide, the proportion of oxamide in the nitrogen compounds is 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. The marine degradation accelerator of the present invention includes the following aspects: A marine degradation accelerator used to obtain an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin and a nitrogen compound, the marine degradation accelerator contains the nitrogen compound, and the nitrogen compound is at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine, and isobutylidenediurea.

[0084] <Phosphorus Compound> The marine degradation accelerator of the present invention preferably further contains a phosphorus compound. By further containing a phosphorus compound, the resin decomposition efficiency of the marine degradation accelerator can be increased. Therefore, the marine decomposition ability of the resin composition can be further improved compared to when the same amount of a nitrogen compound is used alone as the marine degradation accelerator. Furthermore, even when the total amount of marine degradation accelerator is relatively small, the marine decomposition ability of the resin composition can be improved, thereby enabling the production of a resin composition that has both marine decomposition ability and good physical properties. As described above, oxamide is a preferred nitrogen compound contained in the marine degradation accelerator of the present invention. That is, the marine degradation accelerator of the present invention preferably contains oxamide as the nitrogen compound and further contains a phosphorus compound. For information on the type of phosphorus compound and properties of the phosphorus compound, such as its solubility in water at 20°C, please refer to the explanation of the phosphorus compound described in [Method for producing an aliphatic polyester resin composition].

[0085] The phosphorus compound may be a phosphorus compound having a solubility in water at 20°C of 100 g / 100 mL or less, preferably a phosphorus compound having a solubility in water at 20°C of 30 g / 100 mL or less. The solubility of the phosphorus compound in water at 20°C is preferably 50 mg / 100 mL or less, more preferably 20 mg / 100 mL or less, even more preferably 10 mg / 100 mL or less, still more preferably 5 mg / 100 mL or less, and even more preferably 3 mg / 100 mL or less. By having the solubility of the phosphorus compound in water at 20°C within this range, the marine degradability of the resin composition is improved, and a resin composition that is less likely to experience deterioration in physical properties even when used under high humidity conditions or immersed in water is easily obtained. Furthermore, the solubility of the phosphorus compound in water at 20°C is preferably 0.01 mg / 100 mL or more, more preferably 0.1 mg / 100 mL or more. When the solubility of the phosphorus compound in water at 20° C. is within the above range, the resin composition can stably exhibit marine degradability even in seawater with a low COD.

[0086] Examples of the phosphorus compound include organic phosphorus compounds and inorganic phosphorus compounds. The molecular weight of the phosphorus compound is preferably 60 to 1,000, more preferably 80 to 500. The organic phosphorus compound is preferably a phosphate ester, more preferably a phenolic ester of phosphoric acid, and even more preferably triphenyl phosphate. The inorganic phosphorus compound is preferably a phosphate, more preferably a calcium salt of phosphoric acid, and even more preferably tricalcium phosphate. The phosphorus compound preferably includes at least one selected from the group consisting of triphenyl phosphate and tricalcium phosphate. In this case, the proportion of the at least one selected from the group consisting of triphenyl phosphate and tricalcium phosphate in the phosphorus compound is 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more. The use of the phosphate ester and / or phosphate can increase the resin decomposition efficiency of the marine degradation accelerator, thereby enabling the stable production of a resin composition having good physical properties and good marine decomposition potential. Furthermore, from the viewpoint of easily increasing the marine decomposition potential of the resin composition, the phosphorus compound is preferably an inorganic phosphorus compound, and more preferably a phosphate. Examples of inorganic phosphorus compounds include inorganic phosphorus compounds containing at least one selected from the group consisting of calcium triphosphate, calcium pyrophosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate, calcium hypophosphite, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate. These inorganic phosphorus compounds also include hydrates of the respective compounds.

[0087] The ratio of the content of the phosphorus compound to the content of the nitrogen compound contained in the marine degradation accelerator of the present invention is preferably 0.5 to 1000, more preferably 1 to 1000, even more preferably 1 to 100, still more preferably 1 to 10, and even more preferably 1 to 5. When the ratio of the content of the phosphorus compound to the content of the nitrogen compound is within the above range, the efficiency of resin decomposition by the marine degradation accelerator can be easily increased, and a resin composition that exhibits good marine decomposition properties even in seawater with a low COD can be stably obtained.

[0088] Furthermore, from the viewpoint of easily increasing the resin decomposition efficiency of the marine degradation accelerator, the mass ratio of phosphorus atoms to nitrogen atoms in the marine degradation accelerator is preferably 0.01 or more and 5 or less, more preferably 0.05 or more and 2 or less, and even more preferably 0.1 or more and 1 or less. Here, the nitrogen atoms are nitrogen atoms contained in a nitrogen compound, and the phosphorus atoms are phosphorus atoms contained in a nitrogen compound and / or a phosphorus compound. The mass ratio can be calculated from the relationship between the proportion of nitrogen atoms in the compound, the proportion of phosphorus atoms in the compound, and the blending amount (content) of each compound. For example, when a nitrogen compound containing a phosphorus atom is blended, the mass ratio can be determined by dividing the total mass of phosphorus atoms in the nitrogen compound by the total mass of nitrogen atoms in the nitrogen compound. Furthermore, when a nitrogen compound and a phosphorus compound are used in combination, the mass ratio can be determined by dividing the sum of the product of the proportion of phosphorus atoms in the phosphorus compound and the blending amount of the phosphorus compound and the product of the proportion of phosphorus atoms in the nitrogen compound and the blending amount of the nitrogen compound by the product of the proportion of nitrogen atoms in the nitrogen compound and the blending amount of the nitrogen compound.

[0089] <Characteristics of Marine Decomposition Accelerator> The marine decomposition accelerator of the present invention is not particularly limited in shape, as long as it contains the nitrogen compound and can be kneaded with an aliphatic polyester resin to form an aliphatic polyester resin composition. From the viewpoint of improving handleability, the marine decomposition accelerator is preferably granular. Furthermore, when the marine decomposition accelerator is granular, its average diameter is preferably 0.1 mm or more and 10 mm or less, more preferably 0.2 mm or more and 5 mm or less. The average diameter refers to the particle size at 50% of the volumetric integrated value (D50) in the measured particle size distribution measured using a particle size distribution analyzer. For example, a "Militrack JPA" manufactured by Nikkiso Co., Ltd. can be used as the particle size distribution analyzer.

[0090] Furthermore, the marine degradation accelerator of the present invention may be composed solely of the nitrogen compound, or may be composed of a mixture of a nitrogen compound and a phosphorus compound. Furthermore, the marine degradation accelerator may contain, in addition to the nitrogen compound and the phosphorus compound, an excipient or binder for maintaining the shape. Such a marine degradation accelerator can also be used as a masterbatch used to accelerate the marine degradation of resins. From the viewpoint of improving the resin decomposition efficiency, the total content of the nitrogen compound and the phosphorus compound in the marine degradation accelerator is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0091] <Method for Obtaining an Aliphatic Polyester Resin Composition> The marine degradation accelerator of the present invention can be used as a marine degradation accelerator for an aliphatic polyester resin. Specifically, by blending the marine degradation accelerator of the present invention with an aliphatic polyester resin, an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound can be obtained. As a method for obtaining an aliphatic polyester resin composition using the marine degradation accelerator of the present invention, for example, the method for producing an aliphatic polyester resin composition described in the <Production Conditions> section of [Method for Producing an Aliphatic Polyester Resin Composition] can be employed. Alternatively, the aliphatic polyester resin may be formed into a fibrous or film-like material, and then impregnated with the marine degradation accelerator to form the aliphatic polyester resin composition. Regarding the aliphatic polyester resin used to obtain the aliphatic polyester resin composition and the amount of nitrogen compound blended into the aliphatic polyester resin, various explanations given in [Method for Producing an Aliphatic Polyester Resin Composition] can be referenced as appropriate.

[0092] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0093] [Measurement and Evaluation] <Solubility of Nitrogen Compounds and Phosphorus Compounds in Water at 20°C> The solubility of nitrogen compounds and phosphorus compounds in water at 20°C was measured based on "Test No. 105: Water Solubility" in "OECD GUIDELINE FOR THE TESTING OF CHEMICALS," and values ​​were adopted.

[0094] <10% Weight Loss Temperature by Thermogravimetric Analysis> The 10% weight loss temperature of the nitrogen compound or the polyester-based resin composition by thermogravimetric analysis was measured as follows. A TMA7100 manufactured by Hitachi High-Tech Science Corporation was prepared as a measuring device. 10 mg of a measurement sample consisting of a nitrogen compound or a polyester-based resin composition was placed in the measuring device, and the measurement sample was heated from 25°C to 600°C in an air atmosphere at a heating rate of 10 / min. The weight of the measurement sample at the start of the measurement was defined as 100%, and the temperature at which the weight of the measurement sample decreased by 10% was determined and defined as the 10% weight loss temperature.

[0095] <Biodegradability> A BOD (biochemical oxygen demand) test was conducted at 27°C for 28 days using the aliphatic polyester resin compositions or aliphatic polyester resins obtained in the Examples and Comparative Examples. The BOD test was performed as follows. First, a BOD sensor manufactured by VELP SCIENTIFICA was prepared as a measuring device. Seawater from Nakagusuku Bay, Uruma City, Okinawa Prefecture, was prepared as seawater with a COD of 1 mg / L or less. Note that the average COD of seawater in Nakagusuku Bay is 0.6 mg / L according to the "2023 Bathing Beach (Pre-Opening) Water Quality Survey Results" published by the Water and Environment Bureau of the Ministry of the Environment. 40 mg of a powdered test sample, prepared by freeze-pulverizing an aliphatic polyester resin composition or aliphatic polyester resin to a maximum particle size of 250 μm or less, and 250 mg of seawater were placed in a culture bottle (transparent glass bottle). The culture bottle was incubated in a constant temperature bath (27°C), and BOD measurements were performed for 28 days with stirring. Using the measured BOD and other values, the degree of biodegradability was calculated according to the following formula: Biodegradability (%) = BOD / Theoretical oxygen demand (ThOD) × 100 A higher biodegradability value means that biodegradation is more likely to occur even in the ocean, which has a low COD.

[0096] The term "BOD" (biochemical oxygen demand) refers to the mass concentration of dissolved oxygen consumed by aerobic biological oxidation of chemical substances or organic substances in water under specific conditions. In the method using the above-mentioned measuring device, the BOD can be calculated by measuring the pressure change in the culture bottle caused by the absorption of carbon dioxide released as microorganisms in seawater consume oxygen with an absorbent (NaOH) using a pressure sensor. Theoretical oxygen demand (ThOD) refers to the maximum theoretical oxygen demand calculated from the molecular formula required for the complete oxidation of a chemical substance. For example, when the composition ratio of the monomer units of an aliphatic polyester resin is C a H b O c When these C and H are CO ２ and H ２ ThOD is the amount of oxygen when completely converted to O and can be calculated using the following formula: ThOD (mL) = 32 / M x (4a + b + 4d - 2c) / 4 x w x 4 w: Weight of chemical substance (mg) M: Molecular weight of chemical substance a: Number of carbon atoms in chemical substance b: Number of hydrogen atoms in chemical substance c: Number of oxygen atoms in chemical substance d: Number of nitrogen atoms in chemical substance

[0097] In addition, for aliphatic polyester resin compositions containing nitrogen compounds, etc., the ThOD of the aliphatic polyester resin composition was calculated from the relationship between the ThOD of the aliphatic polyester resin and its blending amount and the ThOD of the nitrogen compounds, etc., calculated similarly by the above formula and their blending amounts. In the test resin (aliphatic polyester resin composition) of Example 1, the ThOD of 100 parts by mass of PLA was 186 mg / kg. ２ and 15 parts by mass of oxamide has a ThOD of 2 mg / kg. ２ Therefore, the ThOD of the test resin in Example 1 was 188 mg / L. ２ The same calculation was carried out for the test resins (aliphatic polyester resin compositions) of the other examples and comparative examples.

[0098] <Total nitrogen amount per 1 g of aliphatic polyester resin composition contained per mL of water when the aliphatic polyester resin composition was left standing in water at 23 °C for 72 hours> The aliphatic polyester resin compositions or aliphatic polyester resins obtained in the examples and comparative examples were molded to obtain 1 mm thick films. The obtained films were cut into 10 mm length x 10 mm width to obtain test pieces for measuring the total nitrogen amount. A total of approximately 13 g of the test pieces was placed in 300 mL of pure water and left standing at 23 °C for 72 hours. The mixture was then filtered to remove the test pieces, and the resulting 300 mL of test liquid (water) was subjected to total nitrogen measurement based on JIS K 0102:2019 Section 45.6 (flow analysis method). From the measurement results, the total nitrogen amount (μg) per 1 g of test piece (aliphatic polyester resin composition) contained per mL of test liquid (water) was calculated. In Tables 3 and 4, the "total nitrogen amount (μg)" refers to "the total nitrogen amount (μg) per 1 g of the aliphatic polyester resin composition contained per mL of water when the aliphatic polyester resin composition is allowed to stand in water at 23°C for 72 hours," that is, "the total nitrogen amount (μg) per 1 g of the aliphatic polyester resin composition contained per mL of water when the aliphatic polyester resin composition is immersed in water at 23°C for 72 hours at a ratio of 4 to 6 g of the aliphatic polyester resin composition per 100 mL of water."

[0099] <Weight Average Molecular Weight (Mw)> The weight average molecular weight (Mw) of the aliphatic polyester resin constituting the aliphatic polyester resin composition obtained in the Examples and Comparative Examples and the weight average molecular weight (Mw) of the aliphatic polyester resin used as a raw material resin were measured as follows. As a pretreatment, 30 mg of the aliphatic polyester resin composition or the aliphatic polyester resin was dissolved in 20 mL of chloroform to obtain a solution. The solution was filtered through a syringe filter with a pore size of 0.45 μm, and the obtained filtrate was used as an analytical sample. Gel permeation chromatography analysis of the analytical sample was performed under the following conditions to measure the weight average molecular weight (Mw) of the aliphatic polyester resin constituting the aliphatic polyester resin composition and the weight average molecular weight (Mw) of the aliphatic polyester resin used as a raw material resin. In Tables 3 and 4, "Mw of raw resin" refers to "weight average molecular weight (Mw) of the aliphatic polyester resin used as the raw resin," and "Mw of resin composition" refers to "weight average molecular weight (Mw) of the polyester resin constituting the aliphatic polyester resin composition obtained in the Examples and Comparative Examples."

[0100] Measurement apparatus: 2695 manufactured by Nihon Waters Co., Ltd. Column: TSK Gel G5000HHR manufactured by Tosoh Corporation and G3000HHR manufactured by Tosoh Corporation connected in series in this order Column temperature: 40°C Solvent: chloroform Flow rate: 1.0 mL / min Concentration: 0.4 w / v% Injection volume: 100 μl Detector: 2414 manufactured by Nihon Waters Co., Ltd. Molecular weight conversion: polystyrene (PS) conversion Molecular weight range of the calibration curve used to calculate the molecular weight distribution: 500 to 3,787,000

[0101] <Maximum Stress After Water Immersion / Maximum Stress Before Water Immersion> The aliphatic polyester resin compositions or aliphatic polyester resins obtained in the Examples and Comparative Examples were hot-pressed to obtain films having thicknesses of 0.4 to 0.6 mm. The obtained films were cut into 150 mm long x 15 mm wide specimens for tensile testing. Multiple specimens were prepared from the same aliphatic polyester resin composition or aliphatic polyester resin. Some specimens were completely immersed in pure water at 23°C. Using the specimens removed from the water, a film tensile test was performed in accordance with JIS K 7127:1999. The test speed was 5 mm / min. The maximum stress was measured and recorded as the maximum stress after water immersion. Meanwhile, a film tensile test in accordance with JIS K 7127:1999 was also performed on the specimens that were not immersed in water. The test speed was 5 mm / min. The maximum stress was measured and recorded as the maximum stress before water immersion. The maximum stress after immersion in water relative to the maximum stress before immersion in water was defined as the value of maximum stress after immersion in water / maximum stress before immersion in water. The larger the value of maximum stress after immersion in water / maximum stress before immersion in water (closer to 1), the less deterioration in physical properties due to immersion in water and the better. Table 1 lists the maximum stress (maximum tensile stress) of the aliphatic polyester resin used as the raw material, measured by the above-mentioned method. From the viewpoint of easily obtaining a molded product having excellent mechanical properties such as tensile properties, the maximum tensile stress of the aliphatic polyester resin measured at a test speed of 5 mm / min according to JIS K 7127:1999 is preferably 10 MPa or more, more preferably 20 MPa or more, and even more preferably 30 MPa or more.

[0102] <Shape Maintenance When Left in a High-Humidity Environment> The aliphatic polyester resin compositions obtained in the Examples and Comparative Examples, or the aliphatic polyester resins of the Comparative Examples, were hot-pressed to obtain films having a thickness of 0.4 to 0.6 mm. The obtained films were cut into 150 mm long x 15 mm wide pieces to obtain test pieces for shape observation. The test pieces were left in an environment of 27°C and 95% RH for 3 days, and the change in shape was observed. If the test piece was not deformed after leaving the test piece and there was no significant change in shape compared to before leaving the test piece, the shape was maintained when left in a high-humidity environment, and the test piece was evaluated as "A (Good)." If the test piece was deformed, such as bent, after leaving the test piece and there was a significant change in shape compared to before leaving the test piece, the shape was not maintained when left in a high-humidity environment, and the test piece was evaluated as "B (Poor)." If the above evaluation was "A (Good)," the aliphatic polyester resin composition had excellent durability to moisture, and was preferable.

[0103] [Raw Materials] The raw materials used in the Examples and Comparative Examples are shown in Tables 1 and 2. In Table 1, the polylactic acid is "Ingeo4060D" manufactured by NatureWorks, the polybutylene succinate is "BioPBS" manufactured by Mitsubishi Chemical Corporation, and the polybutylene adipate succinate is "TH801T" manufactured by TUNHE. Furthermore, triphenyl phosphate and tricalcium phosphate were prepared as phosphorus compounds. The solubility of triphenyl phosphate in water at 20°C is 1.1 mg / 100 mL, and the molecular weight is 326. The solubility of tricalcium phosphate in water at 20°C is 2.2 mg / 100 mL, and the molecular weight is 310.

[0104]

[0105]

[0106] [Production of Aliphatic Polyester Resin Composition] Example 1 100 parts by mass of PLA as an aliphatic polyester resin and 15 parts by mass of oxamide as a nitrogen compound were fed to an extruder with an inner diameter of 50 mm and melt-kneaded at a maximum set temperature of 180°C to form a melt-kneaded mixture. The melt-kneaded mixture was then extruded into strands from a strand-forming die installed downstream of the extruder. The extruded strands were water-cooled and cut with a pelletizer to obtain a granular aliphatic polyester resin composition. The evaluation results of the obtained aliphatic polyester resin composition are shown in Table 3.

[0107] Examples 2 to 14 and Comparative Examples 2 and 3 Aliphatic polyester resin compositions were obtained in the same manner as in Example 1, except that the types and amounts of the aliphatic polyester resin and the nitrogen compound were changed as shown in Table 3, and in Examples 7 to 10, 12, and 14, the phosphorus compound was added as shown in Table 3. The phosphorus compound was fed to the extruder together with the nitrogen compound. The evaluation results of the obtained aliphatic polyester resin compositions are shown in Table 3. The amounts of the nitrogen compound and the phosphorus compound are shown in parts by mass relative to 100 parts by mass of the aliphatic polyester resin.

[0108] The 10% weight loss temperature of the oxamide-containing aliphatic polyester resin composition obtained in Example 3 was 286° C., the 10% weight loss temperature of the CDU-containing aliphatic polyester resin composition obtained in Example 5 was 256° C., and the 10% weight loss temperature of the IBDU-containing aliphatic polyester resin composition obtained in Example 6 was 228° C. Furthermore, the maximum tensile stress before immersion in water of the oxamide-containing aliphatic polyester resin composition obtained in Example 3 was 29.4 MPa, the CDU-containing aliphatic polyester resin composition obtained in Example 5 was 17.8 MPa, and the IBDU-containing aliphatic polyester resin composition obtained in Example 6 was 14.4 MPa.

[0109] Comparative Examples 1 and 4 Evaluations were carried out in the same manner as for the aliphatic polyester resin composition, using PLA as Comparative Example 1 and PBS as Comparative Example 4. The evaluation results are shown in Table 3.

[0110] The aliphatic polyester resin composition containing tetramethylenediamine dihydrochloride obtained in Comparative Example 2 had a maximum tensile stress of 18.5 MPa before immersion in water, and the aliphatic polyester resin composition containing ammonium sulfate obtained in Comparative Example 3 had a maximum tensile stress of 21.0 MPa before immersion in water.

[0111]

[0112] Example 15 A granular aliphatic polyester resin composition was obtained in the same manner as in Example 1, except that 100 parts by mass of PHBH was used as the aliphatic polyester resin and 30 parts by mass of oxamide was used as the nitrogen compound. The evaluation results of the obtained aliphatic polyester resin composition are shown in Table 4. The maximum tensile stress of the oxamide-containing aliphatic polyester resin composition obtained in Example 15 before immersion in water was 13.7 MPa.

[0113] Example 16 A granular aliphatic polyester resin composition was obtained in the same manner as in Example 15, except that the amount of oxamide was changed as shown in Table 4 and the phosphorus compound was added as shown in Table 4. The phosphorus compound was fed to the extruder together with the nitrogen compound. The evaluation results of the obtained aliphatic polyester resin composition are shown in Table 4. The amounts of the nitrogen compound and phosphorus compound are shown in parts by mass relative to 100 parts by mass of the aliphatic polyester resin.

[0114] Comparative Example 5 In Comparative Example 5, PHBH was used and evaluation was carried out in the same manner as in the aliphatic polyester resin composition. The evaluation results are shown in Table 4.

[0115]

[0116] The results shown in Tables 3 and 4 indicate that the aliphatic polyester resin compositions of the Examples have high biodegradability and large film tensile test values ​​after water immersion. Furthermore, they are able to maintain their shape when stored under high humidity. Thus, it is clear that the aliphatic polyester resin compositions of the present invention are marine degradable and have excellent water resistance. It is believed that the aliphatic polyester resin compositions of the Comparative Examples suffered from a decrease in tensile properties and deformation of the compositions due to the large amount of nitrogen compounds eluted when stored under water immersion or high humidity.

Claims

1. A method for producing an aliphatic polyester resin composition by heating and kneading an aliphatic polyester resin and a nitrogen compound, wherein the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

2. The method for producing an aliphatic polyester resin composition according to claim 1, wherein the temperature at which the nitrogen compound loses 10% of its weight as determined by thermogravimetric analysis is 210°C or higher.

3. A method for producing an aliphatic polyester resin composition according to claim 1 or 2, wherein the amount of the nitrogen compound blended is 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the aliphatic polyester resin.

4. A method for producing an aliphatic polyester resin composition according to claim 1 or 2, wherein the resin composition further contains a phosphorus compound, and the total amount of the nitrogen compound and the phosphorus compound per 100 parts by mass of the aliphatic polyester resin is 2 parts by mass or more and 50 parts by mass or less.

5. The method for producing an aliphatic polyester resin composition according to claim 4, wherein the ratio of the amount of the phosphorus compound to the amount of the nitrogen compound is 1 to 1,000.

6. The method for producing an aliphatic polyester resin composition according to claim 4, wherein the solubility of the phosphorus compound in water at 20°C is 50 mg / 100 mL or less.

7. The method for producing an aliphatic polyester resin composition according to claim 1 or 2, wherein the nitrogen compound includes oxamide.

8. The method for producing an aliphatic polyester resin composition according to claim 4, wherein the phosphorus compound comprises at least one selected from the group consisting of triphenyl phosphate and tricalcium phosphate.

9. An aliphatic polyester resin composition comprising an aliphatic polyester resin and a nitrogen compound, wherein the aliphatic polyester resin composition is immersed in water at a ratio of 4 to 6 g per 100 mL of water at 23°C for 72 hours, and the total amount of nitrogen contained per mL of water is 0.01 μg or more and 20 μg or less per 1 g of the aliphatic polyester resin composition.

10. The aliphatic polyester resin composition according to claim 9, wherein the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

11. An aliphatic polyester resin composition according to claim 9 or 10, wherein the content of the nitrogen compound in the aliphatic polyester resin composition is 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the aliphatic polyester resin.

12. The aliphatic polyester resin composition according to claim 9 or 10, wherein the aliphatic polyester resin composition further contains a phosphorus compound, and the total content of the nitrogen compound and the phosphorus compound in the aliphatic polyester resin composition is 2 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the aliphatic polyester resin.

13. An aliphatic polyester resin composition according to claim 9 or 10, wherein the biodegradability of the aliphatic polyester resin composition is 1% or more after the aliphatic polyester resin composition is kept in seawater having a COD of 1 mg / L or less for 28 days.

14. An aliphatic polyester resin composition comprising an aliphatic polyester resin and oxamide.

15. The aliphatic polyester resin composition according to claim 14, further comprising a phosphorus compound.

16. A marine degradation accelerator used to obtain the aliphatic polyester resin composition described in claim 9, wherein the marine degradation accelerator contains the nitrogen compound, and the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

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