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

Abstract

To provide a method for producing an aliphatic polyester resin composition that makes it possible to yield the aliphatic polyester resin composition having marine degradability and excellent durability to moisture, the aliphatic polyester resin composition, and a marine degradation promoter.SOLUTION: 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°C is 50 g / 100 mL or less.SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

[0002] Plastics are widely used as materials for packaging, daily necessities, electrical appliances, machine parts, play equipment, etc. However, there are concerns that plastic products and waste that end up in the ocean for some reason, remaining on or in the sea as so-called plastic waste, can become a cause of marine pollution. In order to curb marine pollution caused by such plastic waste, it is hoped that marine biodegradable plastics, which have the property of decomposing in the ocean, will be used.

[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 specific amounts relative to the carbon weight. Furthermore, 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 rate and increasing the degree of biodegradation, particularly in the ocean. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-142016 [Patent Document 2] International Publication No. 2023 / 058708 Summary of the Invention [Problem to be solved by the invention]

[0005] However, as in the resin compositions described in Patent Documents 1 and 2, by adding an additive that promotes marine biodegradation to a biodegradable resin, the marine degradability can be increased, but there is a problem in that the durability of the resin composition is reduced. 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, even in a moisture-containing environment, molded articles are required to have a certain level of durability, with little deformation or deterioration in physical properties. However, molded articles molded using a resin composition containing the additive are prone to deformation and deterioration in resin physical properties when placed in a moisture-rich environment, and achieving compatibility with degradability in the ocean has been an issue. Therefore, there has been a demand for a resin composition that has high marine degradability and yet is excellent in durability when used in a water-containing environment. An object of the present invention is to provide 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. Another object of the present invention is to provide an aliphatic polyester resin composition having marine degradability and a marine degradation accelerator. [Means for solving the problem]

[0006] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by a method for producing an aliphatic polyester resin composition, in which an aliphatic polyester resin and a specific nitrogen compound are heated and kneaded. That is, one aspect of the present invention is a method for producing an aliphatic polyester resin composition, an aliphatic polyester resin composition, and a marine degradation accelerator, which are shown below. [1] A method for producing an aliphatic polyester resin composition by heat-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 [1], wherein the nitrogen compound has a 10% weight loss temperature of 210°C or higher as determined by thermogravimetric analysis. [3] The method for producing an aliphatic polyester-based resin composition according to [1] or [2], wherein the amount of the nitrogen compound to be blended is 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the aliphatic polyester-based resin. [4] The method for producing an aliphatic polyester-based resin composition according to any one of [1] to [3], 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-based 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 [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 [4] or [5], 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 any one of [1] to [6], wherein the nitrogen compound contains oxamide. [8] The method for producing an aliphatic polyester resin composition according to any one of [4] to [7], wherein the phosphorus compound includes 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 [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 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 any one of [9] to

[11] , 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] 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] , further comprising 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. [Effects of the Invention]

[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. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Method of producing an aliphatic polyester 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 hydroxy group, and a polymer of a lactone. Of these, 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. The aliphatic polyester resin is preferably a biodegradable aliphatic polyester resin.

[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, 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. When the weight average molecular weight (Mw) of the aliphatic polyester resin is within the above range, a resin composition that is excellent in marine degradability and has good mechanical properties such as tensile properties can be stably obtained. The weight average molecular weight (Mw) of the aliphatic polyester resin can be measured by gel permeation chromatography using an 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 a weight average molecular weight converted into polystyrene.

[0011] The aliphatic polyester-based resin preferably includes at least one selected from the group consisting of polylactic acid (PLA)-based resin, which is a polymer of lactic acid; polybutylene succinate (PBS)-based resin, which is a polymer of dicarboxylic acid including succinic acid and diol including butanediol; polybutylene adipate-based resin, which is a polymer of dicarboxylic acid including adipic acid and diol including butanediol; polyhydroxybutyrate-based resin, which is a polymer of 3-hydroxybutyric acid; polyglycolic acid (PGA)-based resin, which is a polymer of glycolic acid; and poly-ε-caprolactone (PCL)-based resin, which is a polymer of ε-caprolactone. The aliphatic polyester resins 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 resins include polybutylene adipate terephthalate (PBAT), which is a copolymer of butanediol, adipic acid, and terephthalic acid, and polyhydroxybutyrate resins include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyhexanoic acid. The aliphatic polyester resin more preferably includes at least one selected from the group consisting of polylactic acid resin, polybutylene succinate resin, polybutylene adipate resin, and polyhydroxybutyrate resin. Furthermore, from the viewpoints of being supplied in large quantities to the market and having 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, including favorable tensile strength, but are difficult to biodegrade in seawater with low COD. On the other hand, in the present invention, by blending a nitrogen compound described later with an aliphatic polyester resin to form a resin composition, it is possible to obtain a resin composition having good marine degradability without deteriorating the physical properties of the resin. Note that when a nitrogen compound described later is blended with an aliphatic polyester resin that is relatively easily biodegradable to form a resin composition, it is possible to further enhance the marine degradability of the resin 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] In order to facilitate the production of molded articles having excellent rigidity, the aliphatic polyester resin preferably has a glass transition temperature of 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 aliphatic polyester resins is measured by differential scanning calorimetry (DSC) based on JIS K7121:1987. The glass transition temperature is the midpoint glass transition temperature of the DSC curve. The test specimen conditioning method used is "(3) Measuring the glass transition temperature after a certain heat treatment."

[0015] <Nitrogen compounds> The nitrogen compound used in the method for producing the aliphatic polyester resin composition of the present invention has a solubility in water at 20°C of 50 g / 100 mL or less. As shown in Patent Documents 1 and 2, conventional marine decomposition accelerators have been considered to favor nitrogen compounds that are easily eluted in seawater, i.e., nitrogen compounds with relatively high solubility in water, in order to accelerate resin decomposition. However, when such nitrogen compounds are incorporated into the resulting resin composition, excessive elution of the nitrogen compounds is likely to occur from the resulting resin composition. Therefore, even when a molded article made from the resin composition is placed in contact with water, even a relatively short period of contact can easily cause deformation of the molded article or deterioration of the physical properties of the resin composition. This tendency is particularly pronounced when a relatively large amount of nitrogen compounds 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, such as when the resin composition is placed under high humidity. For these reasons, resin compositions obtained using conventional marine decomposition accelerators have poor durability and may not be able to maintain the required high mechanical properties for long periods of time when used in various applications. In addition, since nitrogen compounds tend to be eluted from the resin composition in large quantities early on, there is a risk that the resin will not be sufficiently decomposed when the resin composition is discharged into the open ocean or other oceans that are less polluted and contain less organic matter. 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 at 20°C of 50 g / 100 mL or less, and the solubility in water at 20°C of the nitrogen compound 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, 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 the above range, it is possible to obtain a resin composition 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 solubility of the nitrogen compound in water is preferably 0.001 g / 100 mL or more, and more preferably 0.01 g / 100 mL or more. When the solubility of the nitrogen 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. 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 water solubility, the following preliminary test is carried out, and then the solubility of the nitrogen compound in water is measured by either the column elution method or the flask method, selected based on the results. For the preliminary test, first, 0.1 g of sample (nitrogen compound) and 10 mL of pure water are placed in a 10 mL measuring cylinder with a glass stopper and shaken for 10 minutes. If this procedure reveals no undissolved sample in the measuring cylinder, the flask method is selected to measure the solubility of the nitrogen compound. On the other hand, if undissolved sample is found in the measuring cylinder, the mixture is transferred to a 100 mL measuring cylinder, an additional 90 mL of pure water is added, and the mixture is left to stand for 96 hours. If this procedure reveals no undissolved sample in the measuring cylinder, the flask method is selected to measure the solubility of the nitrogen compound. 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 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. 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 heating and kneading the resin and the nitrogen compound in an extruder or the like to form the aliphatic polyester-based resin composition. If the nitrogen compound is prone to excessive thermal decomposition, 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 deterioration in the physical properties of the resin constituting the resin composition. Furthermore, even when such a resin composition is thermoformed to form a molded product, the physical properties of the resin constituting the molded product tend to be easily impaired by the heat during thermoforming. On the other hand, by having the 10% weight loss temperature determined by thermogravimetric analysis within the above range, it is possible to stably suppress deterioration of the physical properties of the resin composition due to heat during heating and kneading, etc. Furthermore, it is possible to obtain a resin composition that can be stably thermoformed into a molded article having required physical properties. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, but 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 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 or more and 1,000 or less, and more preferably 60 or more and 500 or less. Nitrogen compounds can serve as a nutrient source for microorganisms that decompose aliphatic polyester resins in the sea. By blending nitrogen compounds with aliphatic polyester resins, when a resin composition containing nitrogen compounds is released into the ocean, components derived from the nitrogen compounds eluted from the resin composition can serve as a nutrient source for microorganisms. This makes it easier for the resin to biodegrade even in the sea, 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 includes at least one selected from the group consisting of oxamide, 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and isobutylidenediurea (IBDU), more preferably includes at least one selected from the group consisting of oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU), and even more preferably includes oxamide. The nitrogen compound preferably contains oxamide and 2-oxo-4-methyl-6-ureidohexahydropyrimidine (CDU) in an amount of 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 nitrogen compound preferably contains oxamide in an amount of 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] [ka]

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

[0023] <Phosphorus compounds> 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-based resin composition containing a phosphorus compound include a method in which the aliphatic polyester-based 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-based resin are heated and kneaded to form a kneaded product, and then the mixture is heated and kneaded with the phosphorus compound; a method in which the phosphorus compound and the aliphatic polyester-based resin are heated and kneaded to form a kneaded product, and then the kneaded product is heated and kneaded with the nitrogen compound. From the viewpoint of increasing productivity, it is preferable to supply the aliphatic polyester-based resin, the nitrogen compound, and the phosphorus compound to an extruder, and heat and knead them to produce an aliphatic polyester-based 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 amounts of the nitrogen compound and the phosphorus compound are the same, the marine degradability of the resin composition can be further increased compared to when the nitrogen compound is blended alone. Furthermore, even when the total amount of the nitrogen compound and the phosphorus compound is relatively small, the marine degradability of the resin composition can be increased, so that a resin composition having both marine degradability and good physical properties can be obtained.

[0025] It should be noted that some phosphorus compounds contain nitrogen atoms, but in the present invention, phosphorus compounds containing nitrogen atoms are treated as the nitrogen compounds, i.e., in the present invention, nitrogen compounds containing phosphorus atoms are included in the nitrogen compounds. The molecular weight of the phosphorus compound is preferably 60 or more and 1,000 or less, and more preferably 80 or more and 500 or less. 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 makes it easier for the resin to biodegrade even in the ocean, where there are few phosphorus sources that serve as a nutrient source for microorganisms.

[0026] As the phosphorus compound, 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, can be used. 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. When the solubility of the phosphorus compound in water at 20°C is within the above range, it is possible to obtain a resin composition that is less likely to experience a decrease in physical properties even when used under high humidity conditions or when immersed in water, while increasing the marine degradability of the resin composition. The solubility of the phosphorus compound in water at 20° C. is preferably 0.01 mg / 100 mL or more, and 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 phosphorus compounds in water at 20°C can be measured in accordance with "Test No. 105: Water Solubility" of the "OECD GUIDELINE FOR THE TESTING OF CHEMICALS," in the same manner as the solubility of nitrogen compounds in water at 20°C.

[0027] The phosphorus compounds include organic phosphorus compounds and inorganic phosphorus compounds. 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 phosphate esters and phosphate salts, and more preferably at least one selected from the group consisting of phosphate esters and phosphate salts. The phosphorus compound more preferably includes at least one selected from the group consisting of a phenolic ester of phosphoric acid and a calcium salt of phosphoric acid, and further preferably is 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 further preferably contains at least one selected from the group consisting of triphenyl phosphate and tricalcium phosphate, and the total proportion of triphenyl phosphate and 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 still more preferably 90% by mass or more. Triphenyl phosphate has a solubility of 1.1 mg / 100 mL in water at 20° C. Tribasic calcium phosphate has a solubility of 2.2 mg / 100 mL in water at 20° C. By using a phosphoric acid ester and / or a phosphoric acid salt, 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. 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 calcium triphosphate, 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. By setting the total amount of the nitrogen compound and the content of the phosphorus compound within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing the deterioration of the physical properties of the resin composition due to the addition of the nitrogen compound and the phosphorus compound, and the balance between these factors is particularly excellent.

[0029] The ratio of the amount of the phosphorus compound to the 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. By setting the ratio of the amount of the phosphorus compound to the amount of the nitrogen compound within the above range, it becomes easier to increase the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound, and it is possible to stably obtain a resin composition that exhibits good marine degradability even in seawater with a low COD.

[0030] Furthermore, from the viewpoint of facilitating an improvement in 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 to 5, more preferably 0.05 to 2, and even more preferably 0.1 to 1. 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] <Manufacturing conditions> The method for producing the aliphatic polyester resin composition of the present invention is a method for heat-kneading an aliphatic polyester resin and a nitrogen compound, and preferably a method for 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 the phosphorus compound can be carried out using a kneader, an extruder, etc., and is preferably carried out using an extruder. In particular, heat-kneading using an extruder can efficiently disperse the nitrogen compound and the phosphorus compound in the aliphatic polyester resin, resulting in excellent productivity. The extruder is not particularly limited, and any known extruder can be used. The aliphatic polyester resin composition can be produced, for example, as follows. First, an aliphatic polyester resin, a nitrogen compound, and optionally other additives such as a phosphorus compound are fed into an extruder, and the mixture is heated in the extruder to melt the aliphatic polyester resin and knead it to form a molten mixture. The heating and 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) form, 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 the Aliphatic Polyester Resin Composition Obtained by the Production Method> The aliphatic polyester resin composition obtained by the method for producing 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 properties.

[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, 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. When the weight average molecular weight of the aliphatic polyester resin constituting the aliphatic polyester resin composition is within the above range, a resin composition can be obtained that is excellent in marine degradability and has good mechanical properties such as tensile properties. 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 a weight average molecular weight converted into polystyrene.

[0034] The aliphatic polyester resin composition has a biodegradability of preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and still more preferably 5% or more after being kept in seawater having a COD of 1 mg / L or less for 28 days. Here, COD (chemical oxygen demand) indicates the amount of oxygen (mg / L) required to oxidize oxidizable substances in sample water under certain conditions, and is an indicator of water quality. The more organic matter there is in the water, the worse the water quality tends to be, so the higher the COD tends to be. When the aliphatic polyester resin composition has a biodegradability within the above range after being kept in seawater with a COD of 1 mg / L or less for 28 days, 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, there is no particular limitation on the upper limit of the biodegradability of the aliphatic polyester resin composition after it has been kept in seawater having a COD of 1 mg / L or less for 28 days. However, from the viewpoint of improving the durability of molded articles formed from the resin composition when used in various applications, the upper limit 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 it has been kept in seawater with 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 amount contained per mL of water when the aliphatic polyester resin composition is allowed to stand in water at 23°C for 72 hours, which is preferably 0.01 μg or more and 20 μg or less, more preferably 0.05 μg or more and 10 μg or less, even more preferably 0.1 μg or more and 5 μg or less, and even more preferably 0.1 μg or more and 2 μg or less, per 1 g of the aliphatic polyester resin composition. By ensuring that the 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 is within the above range, it is possible to obtain a resin composition that is less susceptible to excessive deterioration in physical properties due to moisture and that has excellent marine degradability. 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 according to JIS K 0102:2019 Section 45.6 (flow analysis method) and converting the amount into units. 3 It is preferable to use a film-like aliphatic polyester resin composition having the above-mentioned properties. Measurement is carried out by adding 4 to 6 g of a test piece per 100 mL of water to water. Note that the test piece may be a single film or multiple film pieces as long as they have the above-mentioned dimensions. Specifically, the measurement can be carried out 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 still more preferably 270°C or higher. When the 10% weight loss temperature of the resin composition determined by thermogravimetric analysis is within the above range, it is possible to stably suppress deterioration of the physical properties of the resin composition due to thermoforming, etc. Furthermore, it is possible to obtain a resin composition that can be stably thermoformed into a molded article having required physical properties. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, but 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 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, and 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 now be described.

[0039] <Aliphatic polyester resin> The first aliphatic polyester resin composition contains an aliphatic polyester resin as a 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. Of these, 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. The aliphatic polyester resin is preferably a biodegradable aliphatic polyester resin.

[0040] For the aliphatic polyester resin, the explanation of the aliphatic polyester resin explained in [Method for producing an aliphatic polyester resin composition] can be referred to as appropriate. The aliphatic polyester resin is preferably at least one selected from the group consisting of polylactic acid resins, polybutylene succinate resins, polybutylene adipate resins, and polyhydroxybutyrate resins. From the viewpoints of being supplied in large quantities to the market and having 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, the description of the aliphatic polyester resin described in <Properties of the aliphatic polyester resin composition obtained by the production method> can be referred to as appropriate. 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, even more preferably 50,000 to 300,000, even more preferably 100,000 to 300,000, and still more preferably 150,000 to 300,000.

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

[0043] The nitrogen compound has a solubility in water at 20°C of 50 g / 100 mL or less, 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 solubility of the nitrogen compound in water at 20°C within the above range, it is possible to obtain a resin composition 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 solubility of the nitrogen compound in water is preferably 0.001 g / 100 mL or more, and more preferably 0.01 g / 100 mL or more. When the solubility of the nitrogen 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.

[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 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 can be stably suppressed. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, 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 the deterioration of physical properties due to heat kneading, and to stably obtain a resin composition that is excellent in marine degradability and has good 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 ensuring that the nitrogen compound content is within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing the deterioration of the physical properties of the resin composition due to the addition of the nitrogen compound, and this results in a resin composition that is particularly well-balanced.

[0048] <Phosphorus compounds> 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, the marine degradability of the resin composition can be further increased 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 increased, so that a resin composition having both marine degradability and good physical properties can be obtained. As described above, the nitrogen compound contained in the first aliphatic polyester resin composition is preferably oxamide. That is, the aliphatic polyester resin composition of the present invention preferably contains an aliphatic polyester resin, oxamide, and further contains a phosphorus compound. Regarding the properties of phosphorus compounds, such as solubility in water at 20°C, the explanation of phosphorus compounds given in [Method for producing aliphatic polyester resin composition] can be referred to as appropriate.

[0049] As the phosphorus compound, 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, can be used. 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 still more preferably 3 mg / 100 mL or less. When the solubility of the phosphorus compound in water at 20° C. is within the above range, it is possible to improve the marine degradability of the resin composition, and it is also possible to obtain a resin composition that is less susceptible to deterioration in physical properties even when used under high humidity conditions or when immersed in water. The solubility of the phosphorus compound in water at 20° C. is preferably 0.01 mg / 100 mL or more, and 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.

[0050] The phosphorus compounds include organic phosphorus compounds and inorganic phosphorus compounds. 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. By using the phosphoric acid ester and / or the phosphoric acid salt, 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. 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 calcium triphosphate, 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. By ensuring that the total content of the nitrogen compound and the phosphorus compound is within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing the deterioration of the physical properties of the resin composition due to the inclusion of the nitrogen compound or the phosphorus compound, and the resin composition has a particularly excellent balance of these.

[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. By setting the ratio of the content of the phosphorus compound to the content of the nitrogen compound within the above range, it becomes easier to increase the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound, and it is possible to stably obtain a resin composition that exhibits good marine degradability even in seawater with a low COD.

[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 to 5, more preferably 0.05 to 2, and even more preferably 0.1 to 1. 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 properties of the first aliphatic polyester resin composition, the description of <Properties of the aliphatic polyester resin composition obtained by the above-described 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 still more preferably 5% or more after being kept in seawater having a COD of 1 mg / L or less for 28 days. As long as the object of the present invention can be achieved, the upper limit of the content 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. However, from the viewpoint of improving the durability of molded articles formed from the resin composition when used in various applications, the upper limit is preferably 90%, more preferably 70%, even more preferably 50%, still more preferably 40%, and even more preferably 30%.

[0056] In the first 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 preferably 0.01 μg or more and 20 μg or less, more preferably 0.05 μg or more and 10 μg or less, even more preferably 0.1 μg or more and 5 μg or less, and even more preferably 0.1 μg or more and 2 μg or less, per 1 g 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 nitrogen content per mL of water falls 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 from heating and kneading, etc., or moisture, and that has excellent 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, still more preferably 250°C or higher, and still more preferably 270°C or higher. When the 10% weight loss temperature of the resin composition determined by thermogravimetric analysis is within the above range, it is possible to stably suppress deterioration of the physical properties of the resin composition due to thermoforming, etc. Furthermore, it is possible to obtain a resin composition that can be stably thermoformed into a molded article having required physical properties. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, but 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-based resin composition containing an aliphatic polyester-based resin and a nitrogen compound, wherein the total amount of nitrogen contained per mL of water when the aliphatic polyester-based resin composition is allowed to stand in water at 23°C for 72 hours is 0.01 μg or more and 20 μg or less per 1 g of the aliphatic polyester-based 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, and 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 or more and 20 μg or less per g of the aliphatic polyester resin composition. There are no limitations on the method for producing the aliphatic polyester resin composition of the present invention, but it is preferably obtained by the above-mentioned production method. The aliphatic polyester resin composition is referred to as a 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 a 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. Of these, 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. The aliphatic polyester resin is preferably a biodegradable aliphatic polyester resin.

[0060] For the aliphatic polyester resin, the explanation of the aliphatic polyester resin explained in [Method for producing an aliphatic polyester resin composition] can be referred to as appropriate. The aliphatic polyester resin is preferably at least one selected from the group consisting of polylactic acid resins, polybutylene succinate resins, polybutylene adipate resins, and polyhydroxybutyrate resins. From the viewpoints of being supplied in large quantities to the market and having 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, the description of the aliphatic polyester resin described in <Properties of the aliphatic polyester resin composition obtained by the production method> can be referred to as appropriate. 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, even more preferably 50,000 to 300,000, even more preferably 100,000 to 300,000, and still more preferably 150,000 to 300,000.

[0062] <Nitrogen compounds> 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, the nitrogen compound is preferably a nitrogen compound having a 10% weight loss temperature of 200°C or higher as determined by thermogravimetric analysis. Regarding the properties of the nitrogen compounds, such as the solubility in water at 20°C and the 10% weight loss temperature determined by thermogravimetric analysis, the explanation of the nitrogen compounds described in [Method for producing an aliphatic polyester resin composition] can be referred to as appropriate.

[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, still more preferably 5 g / 100 mL or less, still more preferably 1 g / 100 mL or less, and still more preferably 0.5 g / 100 mL or less. By having the solubility of the nitrogen compound in water at 20°C within the above range, it is possible to obtain a resin composition 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 solubility of the nitrogen compound in water is preferably 0.001 g / 100 mL or more, and more preferably 0.01 g / 100 mL or more. When the solubility of the nitrogen 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.

[0064] The 10% weight loss temperature of the nitrogen compound 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 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 can be stably suppressed. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, 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. By using the nitrogen compound, it is possible to suppress the deterioration of physical properties due to heat kneading, and to stably obtain a resin composition that is excellent in marine degradability and has good durability against moisture.

[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 still 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 ensuring that the nitrogen compound content is within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing the deterioration of the physical properties of the resin composition due to the addition of the nitrogen compound, and this results in a resin composition that is particularly well-balanced.

[0068] <Phosphorus compounds> 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, the marine degradability of the resin composition can be further increased 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 small, the marine degradability of the resin composition can be increased, so that a resin composition having both marine degradability and good physical properties can be obtained. Regarding the properties of phosphorus compounds, such as solubility in water at 20°C, the explanation of phosphorus compounds given in [Method for producing aliphatic polyester resin composition] can be referred to as appropriate.

[0069] As the phosphorus compound, 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, can be used. 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. When the solubility of the phosphorus compound in water at 20°C is within the above range, it is possible to obtain a resin composition that is less likely to experience a decrease in physical properties even when used under high humidity conditions or when immersed in water, while increasing the marine degradability of the resin composition. The solubility of the phosphorus compound in water at 20° C. is preferably 0.01 mg / 100 mL or more, and 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.

[0070] The phosphorus compounds include organic phosphorus compounds and inorganic phosphorus compounds. 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. By using the phosphoric acid ester and / or the phosphoric acid salt, 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. 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 calcium triphosphate, 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. By ensuring that the total content of the nitrogen compound and the phosphorus compound is within the above range, it is possible to obtain a resin composition that is excellent in marine degradability while suppressing the deterioration of the physical properties of the resin composition due to the inclusion of the nitrogen compound or the phosphorus compound, and the resin composition has a particularly excellent balance of these.

[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. By setting the ratio of the content of the phosphorus compound to the content of the nitrogen compound within the above range, it becomes easier to increase the efficiency of resin decomposition by the nitrogen compound and the phosphorus compound, and it is possible to stably obtain a resin composition that exhibits good marine degradability even in seawater with a low COD.

[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 to 5, more preferably 0.05 to 2, and even more preferably 0.1 to 1. 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 properties of the second aliphatic polyester resin composition, the description of <Properties of the aliphatic polyester resin composition obtained by the above-described 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 or more and 20 μg or less, preferably 0.05 μg or more and 10 μg or less, more preferably 0.1 μg or more and 5 μg or less, and even more preferably 0.1 μg or more and 2 μg or less, per 1 g 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 nitrogen content per mL of water falls 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 from heating and kneading, etc., 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 still more preferably 5% or more after being kept in seawater having a COD of 1 mg / L or less for 28 days. As long as the object of the present invention can be achieved, the upper limit of the content 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. However, from the viewpoint of improving the durability of molded articles formed from the resin composition when used in various applications, the upper limit is preferably 90%, more preferably 70%, even more preferably 50%, still 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, still more preferably 250°C or higher, and still more preferably 270°C or higher. When the 10% weight loss temperature of the resin composition determined by thermogravimetric analysis is within the above range, it is possible to stably suppress deterioration of the physical properties of the resin composition due to thermoforming, etc. Furthermore, it is possible to obtain a resin composition that can be stably thermoformed into a molded article having required physical properties. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, but 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 at 20°C of 50 g / 100 mL or less. That is, the marine decomposition accelerator of the present invention is a marine decomposition accelerator used to obtain an aliphatic polyester resin composition containing an aliphatic polyester resin and a nitrogen compound, and the marine decomposition accelerator contains the nitrogen compound, and the solubility of the nitrogen compound in water at 20°C is 50 g / 100 mL or less.

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

[0080] The nitrogen compound has a solubility in water at 20°C of 50 g / 100 mL or less, 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. When the solubility of the nitrogen compound in water at 20°C is within the above range, it is possible to obtain a resin composition that is marine degradable and is resistant to deformation and deterioration in physical properties even when used under high humidity conditions, immersed in water, etc. The solubility of the nitrogen compound in water is preferably 0.001 g / 100 mL or more, and more preferably 0.01 g / 100 mL or more. When the solubility of the nitrogen 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 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 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 can be stably suppressed. As long as the object of the present invention can be achieved, the upper limit of the 10% weight loss temperature determined by thermogravimetric analysis is not particularly limited, 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, 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 decomposition 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 resin composition containing an aliphatic polyester resin and a nitrogen compound, the marine degradation accelerator containing the 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.

[0084] <Phosphorus compounds> The marine degradation accelerator of the present invention preferably further contains a phosphorus compound. By further including a phosphorus compound in the marine degradation accelerator of the present invention, 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 the marine degradation accelerator is relatively small, the marine decomposition ability of the resin composition can be improved, so that a resin composition having both marine decomposition ability and good physical properties can be obtained. As described above, the nitrogen compound contained in the marine degradation accelerator of the present invention is preferably oxamide. That is, the marine degradation accelerator of the present invention preferably contains oxamide as the nitrogen compound and further contains a phosphorus compound. For the types of phosphorus compounds and properties of phosphorus compounds such as solubility in water at 20°C, the explanation of phosphorus compounds described in [Method for producing an aliphatic polyester resin composition] can be referred to as appropriate.

[0085] As the phosphorus compound, 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, can be used. 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 still more preferably 3 mg / 100 mL or less. When the solubility of the phosphorus compound in water at 20° C. is within the above range, it is possible to improve the marine degradability of the resin composition, and it is also possible to obtain a resin composition that is less susceptible to deterioration in physical properties even when used under high humidity conditions or when immersed in water. The solubility of the phosphorus compound in water at 20° C. is preferably 0.01 mg / 100 mL or more, and 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] The phosphorus compound may be an organic phosphorus compound or an inorganic phosphorus compound, and the molecular weight of the phosphorus compound is preferably 60 or more and 1,000 or less, and more preferably 80 or more and 500 or less. 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. The phosphorus compound more preferably includes at least one selected from the group consisting of triphenyl phosphate and tricalcium phosphate, in which 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 still more preferably 90% by mass or more. By using the phosphoric acid ester and / or phosphate, the resin decomposition efficiency by the marine degradation accelerator can be increased, and a resin composition having good physical properties and good marine decomposition properties can be stably obtained. 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 calcium triphosphate, 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.

[0087] The ratio of the content of the phosphorus compounds to the content of the nitrogen compounds 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. By setting the ratio of the phosphorus compound content to the nitrogen compound content within the above range, it becomes easier to increase the resin decomposition efficiency by the marine degradation accelerator, 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 by the marine decomposition accelerator, the mass ratio of phosphorus atoms to nitrogen atoms in the marine decomposition 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 the nitrogen compound, and the phosphorus atoms are phosphorus atoms contained in the nitrogen compound and / or 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 amount (content) of each compound. For example, when a nitrogen compound containing a phosphorus atom is used, 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 amount of the phosphorus compound and the product of the proportion of phosphorus atoms in the nitrogen compound and the amount of the nitrogen compound by the product of the proportion of nitrogen atoms in the nitrogen compound and the amount of the nitrogen compound.

[0089] <Characteristics of marine decomposition accelerators> The marine degradation accelerator of the present invention is not particularly limited in shape, etc., 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 degradation accelerator is preferably granular. Furthermore, when the marine degradation 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 (D50) at 50% of the volume accumulated value in the particle size distribution measured by measuring the particle size distribution of the particulate matter using a particle size distribution measuring device. As the particle size distribution measuring device, for example, "Militrack JPA" manufactured by Nikkiso Co., Ltd. can be used.

[0090] The marine degradation accelerator of the present invention may be composed of the nitrogen compound or a mixture of a nitrogen compound and a phosphorus compound. The marine degradation accelerator may also 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 for accelerating the marine degradation of resins. From the viewpoint of increasing the resin decomposition efficiency, the total content of the nitrogen compound and the phosphorus compound in the marine decomposition 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 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 <Production conditions> of [Production method for an aliphatic polyester resin composition] can be employed. Alternatively, the aliphatic polyester resin composition may be formed by forming an aliphatic polyester resin into a fibrous or film-like material and then impregnating the material with the marine degradation accelerator. For the aliphatic polyester resin used to obtain the aliphatic polyester resin composition, the amount of the nitrogen compound to be blended in the aliphatic polyester resin, and the like, various explanations given in [Method for producing an aliphatic polyester resin composition] can be referred to as appropriate. [Example]

[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 water solubility of nitrogen compounds and phosphorus compounds at 20°C was determined based on "Test No. 105: Water Solubility" in the "OECD GUIDELINE FOR THE TESTING OF CHEMICALS."

[0094] <10% weight loss temperature by thermogravimetric analysis> The 10% weight loss temperature of the nitrogen compound or the polyester resin composition was measured by thermogravimetric analysis 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 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 taken as 100%, and the temperature at which the weight of the measurement sample decreased by 10% was determined, and this was taken as the 10% weight loss temperature.

[0095] <Biodegradability> Using the aliphatic polyester resin compositions or aliphatic polyester resins obtained in the Examples and Comparative Examples, a BOD (biochemical oxygen demand) test was carried out at 27° C. for 28 days. The BOD test was conducted as follows. First, a BOD sensor manufactured by VELP SCIENTIFICA was prepared as the measuring device. Seawater from Nakagusuku Bay in Uruma City, Okinawa Prefecture was prepared as seawater with a COD of 1 mg / L or less. According to the "2023 Bathing Beach (Pre-Opening) Water Quality Survey Results" published by the Ministry of the Environment's Water and Environment Bureau, the average COD of seawater in Nakagusuku Bay is 0.6 mg / L. A 40 mg powdered test sample, prepared by freeze-pulverizing an aliphatic polyester resin composition or an 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 thermostatic chamber (27°C), and BOD measurements were carried out for 28 days while stirring. Using the measured BOD and other values, the degree of biodegradation was calculated using the following formula. Biodegradability (%) = BOD / Theoretical oxygen demand (ThOD) x 100 The higher the biodegradability value, the easier it is for biodegradation to occur even in the ocean, where COD is low.

[0096] BOD (biochemical oxygen demand) refers to the mass concentration of dissolved oxygen consumed by aerobic biological oxidation of chemical or organic matter in water under specific conditions. In the method using the above-mentioned measuring device, BOD can be calculated by measuring the pressure change inside the culture bottle caused by the absorbent (NaOH) absorbing carbon dioxide released as microorganisms in seawater consume oxygen. Theoretical oxygen demand (ThOD) refers to the maximum theoretical oxygen demand calculated from the molecular formula required for a chemical substance to be completely oxidized. For example, if the composition ratio of the monomer units of an aliphatic polyester resin is C a H b O c When C and H are completely converted into CO2 and H2O, the amount of oxygen is calculated using the following formula: ThOD(mL)=32 / M×(4a+b+4d-2c) / 4×w×4 w: weight of chemical substance (mg) M: molecular weight of chemical substance a: number of carbon atoms in the chemical b: number of hydrogen atoms in the chemical c: number of oxygen atoms in the chemical substance d: Number of nitrogen atoms in the chemical substance

[0097] For aliphatic polyester resin compositions containing nitrogen compounds, 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 using the above formula, and their blending amounts. For the test resin (aliphatic polyester resin composition) of Example 1, the ThOD for 100 parts by mass of PLA was 186 mg O2, and the ThOD for 15 parts by mass of oxamide was 2 mg O2, so the ThOD for the test resin of Example 1 was 188 mg O2. Similar calculations were performed for the test resins (aliphatic polyester resin compositions) of the other Examples and Comparative Examples.

[0098] <Total amount of nitrogen per 1 g of aliphatic polyester resin composition contained in 1 mL of water when the aliphatic polyester resin composition is left to stand 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 into films with a thickness of 1 mm, which were then cut into 10 mm length x 10 mm width specimens for measuring the total nitrogen content. A total of approximately 13 g of the test pieces was placed in 300 mL of pure water and allowed to stand at 23°C for 72 hours. The test pieces were then removed by filtration, and the resulting 300 mL of test liquid (water) was subjected to total nitrogen measurement according to 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 amount of nitrogen (μg) per 1 g of aliphatic polyester resin composition contained in 1 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 amount of nitrogen (μg) per 1 g of aliphatic polyester resin composition contained in 1 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 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 the 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 the "weight average molecular weight (Mw) of the aliphatic polyester resin used as the raw resin," and "Mw of resin composition" refers to the "weight average molecular weight (Mw) of the polyester resin constituting the aliphatic polyester resin composition obtained in the examples and comparative examples."

[0100] Measurement equipment: 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℃ Solvent: Chloroform Flow rate: 1.0mL / min Concentration: 0.4w / v% Injection volume: 100μl Detector: Nihon Waters 2414 Molecular weight conversion: Polystyrene (PS) conversion Molecular weight range of the calibration curve used to calculate molecular weight distribution: 500 to 3,787,000

[0101] <Maximum stress after immersion in water / Maximum stress before immersion in water> The aliphatic polyester resin compositions or aliphatic polyester resins obtained in the examples and comparative examples were hot-pressed to obtain films with thicknesses of 0.4 to 0.6 mm. The obtained films were cut into pieces 150 mm long and 15 mm wide to obtain test pieces for tensile tests. Note that multiple test pieces were prepared from the same aliphatic polyester resin composition or aliphatic polyester resin. Some of the test pieces were completely immersed in pure water at 23°C. The test piece was taken out of the water and subjected to a film tensile test in accordance with JIS K 7127:1999. The test speed was 5 mm / min. The maximum stress was measured and used as the maximum stress after immersion in water. On the other hand, the test pieces that were not immersed in water were also subjected to a film tensile test in accordance with JIS K 7127:1999. The test speed was 5 mm / min. The maximum stress was measured and used as the maximum stress before immersion in water. 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 the material. Table 1 shows the maximum stress (maximum tensile stress) measured by the above-mentioned method for the aliphatic polyester resin, which is the raw material. From the viewpoint of facilitating the production of molded articles 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] <Maintaining shape when placed 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 with thicknesses of 0.4 to 0.6 mm. The obtained films were cut into a length of 150 mm and a width of 15 mm to obtain test pieces for shape observation. The test piece was left standing in an environment of 27°C and 95% RH for 3 days, and the change in shape was observed. If the test piece did not deform after being left standing and there was no significant change in shape compared to before being left standing, it was evaluated as "Good (◯)" and the shape was maintained when left standing in a high humidity environment. If the test piece deformed, such as bending, after being left standing and there was a significant change in shape compared to before being left standing, it was evaluated as "Poor (×)" and the shape was not maintained when left standing in a high humidity environment. If the above evaluation is "good (good)", the aliphatic polyester resin composition is preferable because it has excellent durability against moisture.

[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. Triphenyl phosphate and tricalcium phosphate were also prepared as phosphorus compounds. The solubility of triphenyl phosphate in water at 20°C is 1.1 mg / 100 mL, and its molecular weight is 326. The solubility of tricalcium phosphate in water at 20°C is 2.2 mg / 100 mL, and its molecular weight is 310.

[0104] [Table 1]

[0105] [Table 2]

[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 into an extruder with an inner diameter of 50 mm and melt-kneaded at a maximum 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 resulting 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 supplied 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 aliphatic polyester resin composition containing oxamide obtained in Example 3 had a 10% weight loss temperature of 286°C, the aliphatic polyester resin composition containing CDU obtained in Example 5 had a 10% weight loss temperature of 256°C, and the aliphatic polyester resin composition containing IBDU obtained in Example 6 had a 10% weight loss temperature of 228°C. The aliphatic polyester resin composition containing oxamide obtained in Example 3 had a maximum tensile stress of 29.4 MPa before immersion in water, the aliphatic polyester resin composition containing CDU obtained in Example 5 had a maximum tensile stress of 17.8 MPa before immersion in water, and the aliphatic polyester resin composition containing IBDU obtained in Example 6 had a maximum tensile stress of 14.4 MPa before immersion in water.

[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] [Table 3]

[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 As Comparative Example 5, PHBH was used and evaluated in the same manner as the aliphatic polyester resin composition. The evaluation results are shown in Table 4.

[0115] [Table 4]

[0116] The results shown in Tables 3 and 4 indicate that the aliphatic polyester resin compositions of the examples have high biodegradability and high film tensile test values after water immersion. Furthermore, they are able to maintain their shape when stored under high humidity. Thus, 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 exhibited a significant amount of nitrogen compound elution when stored under water immersion or high humidity, resulting in a decrease in tensile properties and deformation of the compositions.

Claims

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

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

3. The method for producing an aliphatic polyester-based 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 relative to 100 parts by mass of the aliphatic polyester-based resin.

4. the resin composition further contains a phosphorus compound, 3. The method for producing an aliphatic polyester-based resin composition according to claim 1, wherein the total amount of the nitrogen compound and the phosphorus compound is 2 parts by mass or more and 50 parts by mass or less relative to 100 parts by mass of the aliphatic polyester-based resin.

5. 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 comprises 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-based resin composition comprising an aliphatic polyester-based resin and a nitrogen compound, An aliphatic polyester resin composition, wherein 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, 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. 10. The aliphatic polyester resin composition according to claim 9, wherein the nitrogen compound has a solubility in water at 20°C of 50 g / 100 mL or less.

11. 11. The aliphatic polyester resin composition according to claim 9, 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 further contains a phosphorus compound, 11. The aliphatic polyester resin composition according to claim 9, wherein 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. 11. The aliphatic polyester resin composition according to claim 9, 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 claim 14, further comprising a phosphorus compound.

16. A marine degradation accelerator used to obtain the aliphatic polyester resin composition according to claim 9, The marine decomposition 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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