Degradation accelerator for biodegradable resin, biodegradable resin composition, biodegradable resin molded product, and method for producing degradation accelerator for biodegradable resin

Abstract

To provide a degradation accelerator suitable for biodegradable resins, which can increase and freely control the biodegradation rate and biodegradability of biodegradable resins such as aliphatic polyester-based resins, aliphatic-aromatic polyester-based resins, and aliphatic oxycarboxylic acid-based resins, and to provide a biodegradable resin composition containing the degradation accelerator.SOLUTION: A degradation accelerator for biodegradable resins comprising cellulose, hemicellulose, and lignin, wherein a mass ratio of nitrogen to carbon in the degradation accelerator for biodegradable resins is 0.04 or more, and a mass ratio of the content of hemicellulose to the total content of cellulose and lignin is 0.2 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a degradation accelerator capable of accelerating the biodegradation of biodegradable resins and a method for producing the same. The present invention also relates to a biodegradable resin composition containing the degradation accelerator for biodegradable resins, and a biodegradable resin molded article obtained by extrusion molding or injection molding the biodegradable resin composition. [Background technology]

[0002] In recent years, concerns about ecosystem and environmental pollution caused by marine disposal of plastic products have become apparent. Various regulations are being enacted around the world, with a view to preventing environmental pollution. For example, Europe is currently enacting regulations and laws banning the use of disposable plastic shopping bags and disposable plastic containers such as cups and plates in retail. To be exempt from the use bans imposed by this law, products must be made from biomass with a minimum biomass content specified and be compostable in ordinary households (home compostable products). Recently, there has also been a demand for marine biodegradable plastic products, which decompose in the ocean if plastic products are discharged into the ocean.

[0003] Conventionally, biodegradable plastics (resins) include aliphatic polyesters such as polybutylene terephthalate / adipate (hereinafter abbreviated as PBAT), polylactic acid (hereinafter abbreviated as PLA), polybutylene succinate (hereinafter abbreviated as PBS), and polybutylene succinate / adipate (hereinafter abbreviated as PBSA), as well as polyhydroxyalkanols (hereinafter abbreviated as PHA). PHAs include poly(3-hydroxybutyrate) (hereinafter abbreviated as PHB), poly(3-hydroxybutyrate / 3-hydroxyvalerate) (hereinafter abbreviated as PHBV), poly(3-hydroxybutyrate / 3-hydroxyhexanoate) (hereinafter abbreviated as PHBH), and poly(3-hydroxybutyrate / 4-hydroxybutyrate).

[0004] These resins not only differ in their biodegradation speed and decomposition rate, but also in their mechanical properties such as tensile elongation at break and flexural modulus. For this reason, they are generally used in combination with other resins or mixed with other secondary materials and additives to improve physical properties such as mechanical strength, depending on the application and location of use.

[0005] Patent Document 1 takes into consideration final disposal treatment after the end of product use, and discloses a method for producing a composite resin composition that has excellent moldability and strength properties, by, for example, heating and kneading a composition containing 5 to 95% by weight of an aliphatic aromatic polyester (component A), 95 to 5% by weight of a cellulose, lignocellulose, or starch-based substance (component B), an unsaturated carboxylic acid or a derivative thereof, and an organic peroxide (component C), as a molding material made from biodegradable resin and biomass material that decomposes when landfilled and does not remain in the environment, and that does not emit harmful substances such as dioxins when incinerated.

[0006] Patent Document 2 discloses a resin composition and a molded product obtained by blending a high-molecular-weight aliphatic polyester with a plant material containing cellulose, such as a plant epidermis or cortex, or a seed coat material, a nut peel material, sawdust, milling waste, or bagasse from sugarcane stalks. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-221423 [Patent Document 2] Special Publication No. 2004-503415 Summary of the Invention [Problem to be solved by the invention]

[0008] For home-compostable plastic products and marine-biodegradable plastic products, their biodegradation speed and decomposition rate must be faster than the biodegradation rate of conventional biodegradable resins such as PBAT, PBS, PBSA, PLA, and PHBH under conditions that are more severe than the conventional conditions generally considered to be biodegradable (for example, low temperatures and environments with few decomposing bacteria), and they must decompose more in the same amount of time.

[0009] The resin compositions and molded articles made thereof described in Patent Documents 1 and 2 have improved mechanical strength to a certain extent, but they do not focus on the biodegradation rate or decomposition rate, and it is unclear how much higher the biodegradation rate or decomposition rate is compared to conventional biodegradable resins. Furthermore, depending on the additives and secondary materials used, the decomposition rate may be reduced and the mechanical strength may not be improved. [Means for solving the problem]

[0010] An object of the present invention is to provide a degradation accelerator suitable for biodegradable resins, which can increase and optionally control the biodegradation rate and decomposition rate of biodegradable resins such as aliphatic polyester resins, aliphatic-aromatic polyester resins, and aliphatic oxycarboxylic acid resins, and a method for producing the same, as well as a biodegradable resin composition containing the degradation accelerator and a molded article thereof.

[0011] The present inventors focused on three components: nitrogen, carbon, and cellulose, hemicellulose, and lignin, or three components: soluble nitrogen-free substances, cellulose, and lignin, and believed that these components contribute to or are involved in promoting the decomposition of biodegradable resins. Based on this belief, they discovered that by adjusting the blending ratios of these components, when blended with a biodegradable resin, the biodegradation rate and decomposition rate can be increased beyond the inherent biodegradation rate and decomposition rate of the biodegradable resin.

[0012] The gist of the present invention lies in the following [1] to

[12] .

[0013] [1] A decomposition accelerator for biodegradable resins containing cellulose, hemicellulose, and lignin, wherein the mass ratio of nitrogen to carbon in the decomposition accelerator for biodegradable resins is 0.04 or more, and the mass ratio of the hemicellulose content to the total content of cellulose and lignin is 0.2 or more.

[0014] [2] A decomposition accelerator for biodegradable resins, containing 20% by mass or more of soluble nitrogen-free substances and having a total content of cellulose and lignin of 50% by mass or less.

[0015] [3] The decomposition accelerator for biodegradable resins according to [1] or [2], which has a moisture content of less than 5% by mass.

[0016] [4] A biodegradable resin composition comprising 2 parts by mass or more and 250 parts by mass or less of the degradation accelerator for biodegradable resins according to any one of [1] to [3] and 100 parts by mass of a biodegradable resin.

[0017] [5] The biodegradable resin composition according to [4], wherein the biodegradable resin is at least one selected from the group consisting of an aliphatic polyester resin (A), an aliphatic-aromatic polyester resin (B), and an aliphatic oxycarboxylic acid resin (C).

[0018] [6] The biodegradable resin composition according to [5], wherein the aliphatic polyester resin (A) contains, as main structural units, a repeating unit derived from an aliphatic diol and a repeating unit derived from an aliphatic dicarboxylic acid.

[0019] [7] The biodegradable resin composition according to [5] or [6], wherein the aliphatic-aromatic polyester resin (B) contains, as main structural units, a repeating unit derived from an aliphatic diol, a repeating unit derived from an aliphatic dicarboxylic acid, and a repeating unit derived from an aromatic dicarboxylic acid.

[0020] [8] A biodegradable resin molded article which is an extrusion molded or injection molded article of the biodegradable resin composition according to any one of [4] to [7].

[0021] [9] A method for producing a decomposition accelerator for biodegradable resins, comprising crushing raw materials and then selecting powders of a predetermined particle size from the resulting powder to obtain the decomposition accelerator for biodegradable resins.

[0022]

[10] A method for producing the decomposition accelerator for biodegradable resins according to [9], further comprising a drying step.

[0023]

[11] A method for producing a decomposition accelerator for biodegradable resins according to [9] or

[10] , wherein the decomposition accelerator for biodegradable resins contains cellulose, hemicellulose and lignin, the mass ratio of nitrogen to carbon in the decomposition accelerator for biodegradable resins is 0.04 or more, and the mass ratio of the hemicellulose content to the total content of cellulose and lignin is 0.2 or more.

[0024]

[12] The method for producing a decomposition accelerator for biodegradable resins according to any one of [9] to

[11] , wherein the decomposition accelerator for biodegradable resins contains 20% by mass or more of soluble nitrogen-free substances and the total content of cellulose and lignin is 50% by mass or less. [Effects of the Invention]

[0025] According to the degradation accelerator for biodegradable resins of the present invention, the biodegradation rate and decomposition rate of biodegradable resins such as aliphatic polyester resins, aliphatic-aromatic polyester resins, and aliphatic oxycarboxylic acid resins can be increased to be higher than the inherent biodegradation rate and decomposition rate of the biodegradable resins.

[0026] According to the biodegradable resin composition of the present invention containing the degradation accelerator for biodegradable resins of the present invention, a biodegradable resin molded article having excellent biodegradability can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, an embodiment of the present invention will be described in detail.

[0028] The present invention is not limited to the following description, and can be practiced with any modifications within the scope of the gist of the present invention. In this specification, when "~" is used to express a numerical value or a physical property value, the values before and after the "~" are included.

[0029] [Decomposition accelerator for biodegradable resins] The decomposition accelerator for biodegradable resins according to a first aspect of the present invention (hereinafter sometimes referred to as "decomposition accelerator I of the present invention") contains cellulose, hemicellulose, and lignin as essential components, and is characterized in that the mass ratio of nitrogen (nitrogen element) to carbon (carbon element) in the decomposition accelerator for biodegradable resins (hereinafter sometimes referred to as "nitrogen / carbon ratio") is 0.04 or more, and the mass proportion of the hemicellulose content to the total content of cellulose and lignin (hereinafter sometimes referred to as "hemicellulose / (cellulose + lignin) ratio") is 0.2 or more.

[0030] The decomposition accelerator for biodegradable resins according to a second aspect of the present invention (hereinafter sometimes referred to as "decomposition accelerator II of the present invention") is characterized by containing 20% by mass or more of soluble nitrogen-free substances and having a total content of cellulose and lignin of 50% by mass or less.

[0031] Hereinafter, the decomposition accelerator I of the present invention and the decomposition accelerator II of the present invention will be collectively referred to as the "decomposition accelerator of the present invention."

[0032] <Decomposition accelerator I> The decomposition accelerator I of the present invention has a nitrogen / carbon ratio of 0.04 or more. The reason why the decomposition of biodegradable resins is accelerated by the decomposition accelerator I having a nitrogen / carbon ratio that satisfies this range is presumed to be as follows. Microorganisms such as bacteria and fungi that decompose biodegradable resins require carbon and nitrogen as nutrients. However, biodegradable resins are primarily composed of carbon, oxygen, and hydrogen, with a low nitrogen content. Therefore, when microorganisms decompose biodegradable resins, a lack of nitrogen inhibits their growth and secretion of decomposing enzymes, resulting in an insufficient biodegradation rate. Since the decomposition accelerator I of the present invention contains a certain amount of nitrogen or more relative to carbon, it is presumed that it promotes the growth of microorganisms and the secretion of decomposing enzymes, thereby accelerating the decomposition of biodegradable resins.

[0033] The nitrogen / carbon ratio of the decomposition accelerator I of the present invention is preferably 0.05 or more, more preferably 0.06 or more. The upper limit of the nitrogen / carbon ratio is not particularly limited, but is preferably 5 or less. If the nitrogen / carbon ratio exceeds 5, the carbon content will be insufficient and the effect may not be sufficiently exhibited.

[0034] The decomposition accelerator I of the present invention has a mass ratio of the hemicellulose content to the total content of cellulose and lignin (hemicellulose / (cellulose + lignin) ratio) of 0.2 or more. The reason why the decomposition of biodegradable resins is accelerated by decomposition accelerator I having a hemicellulose / (cellulose + lignin) ratio that satisfies this range is presumed to be as follows. Hemicellulose tends to be decomposed and absorbed by microorganisms more quickly than cellulose or lignin. It is presumed that the use of the decomposition accelerator I of the present invention, which has a hemicellulose / (cellulose + lignin) ratio of 0.2 or more, promotes the growth of microorganisms and increases the surface area, particularly in the early stages, when the resin composition is released into the natural environment, thereby accelerating the decomposition of the biodegradable resin.

[0035] The hemicellulose / (cellulose + lignin) ratio of the decomposition accelerator I of the present invention is preferably 0.6 or more, more preferably 1.0 or more. The upper limit of the hemicellulose / (cellulose + lignin) ratio is not particularly limited, but is usually 10 or less. This is because in order to increase this ratio to more than 10, it is necessary to remove cellulose and / or lignin contained in the raw material, which increases production costs.

[0036] The decomposition accelerator I of the present invention preferably contains cellulose, hemicellulose and lignin in a total amount of about 5 to 50 mass %, particularly about 10 to 45 mass %, based on 100 mass % of the decomposition accelerator I.

[0037] When the decomposition accelerator I of the present invention contains moisture, it is preferable to dry it to a moisture content of less than 5% by mass. If the moisture content is 5% by mass or more, when it is mixed with a biodegradable resin, the biodegradable resin may undergo hydrolysis, resulting in a decrease in molecular weight and insufficient mechanical strength.

[0038] The contents of nitrogen, carbon, cellulose, hemicellulose and lignin in the decomposition accelerator I of the present invention can be measured and calculated by the methods described in the Examples below. In the case of decomposition accelerator I using two or more raw materials, the nitrogen, carbon, cellulose, hemicellulose, and lignin contents can be calculated as the sum of the nitrogen, carbon, cellulose, hemicellulose, and lignin contents of each raw material multiplied by the ratio, depending on the blending ratio of the raw materials.

[0039] <Decomposition accelerator II> The decomposition accelerator II of the present invention contains 20 mass % or more of soluble nitrogen-free substances. The reason why a decomposition accelerator having a soluble nitrogen-free substance content within this range accelerates the decomposition of biodegradable resins is presumed to be as follows. Soluble non-nitrogenous matter is an analytical value commonly used in the ingredient labeling of feed, etc., and ingredients including soluble non-nitrogenous matter have the property of being easily decomposed and absorbed by microorganisms. On the other hand, natural soil and mature compost usually contain little easily decomposable organic matter that can be used by microorganisms such as bacteria and fungi, so the number of microorganisms and the activity of decomposing enzymes are low. It is presumed that the decomposition accelerator II of the present invention, which contains a certain amount or more of soluble nitrogen-free substances, promotes the growth of microorganisms and the activation of decomposing enzymes, thereby accelerating the decomposition of biodegradable resins.

[0040] The content of the soluble nitrogen-free substance in the decomposition accelerator II of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more. Although there is no particular upper limit to the content of the soluble nitrogen-free substance, it is usually 99% by mass or less because the purification cost increases in order to make it 100% by mass.

[0041] The decomposition accelerator II of the present invention has a total cellulose and lignin content of 50% by mass or less. Cellulose and lignin have the property of being decomposed and absorbed by microorganisms later than soluble nitrogen-free substances. If the total cellulose and lignin content in the decomposition accelerator II of the present invention exceeds 50% by mass, the rate of biodegradation may decrease. The total cellulose and lignin content in the decomposition accelerator II of the present invention is preferably 30% by mass or less, more preferably 20% by mass or less. There is no particular lower limit for the total cellulose and lignin content, but it is usually 5% by mass or more.

[0042] When the decomposition accelerator II of the present invention contains moisture, it is preferable to dry it to a moisture content of less than 5% by mass. If the moisture content is 5% by mass or more, when it is mixed with a biodegradable resin, the biodegradable resin may undergo hydrolysis, resulting in a decrease in molecular weight and insufficient mechanical strength.

[0043] The contents of nitrogen-free soluble matter, cellulose and lignin in the decomposition accelerator II of the present invention can be measured and calculated by the methods described in the Examples below. In addition, in the case of decomposition accelerator II using two or more types of raw materials, the contents of soluble nitrogen-free substances, cellulose, and lignin can be calculated as the sum of the contents of soluble nitrogen-free substances, cellulose, and lignin of each raw material multiplied by the ratio, depending on the blending ratio of the raw materials.

[0044] The decomposition accelerator II of the present invention contains 20% by mass or more of soluble nitrogen-free substances, and the total content of cellulose and lignin is 50% by mass or less, but it is preferable that the mass ratio of nitrogen to carbon is 0.04 or more, and the mass ratio of the hemicellulose content to the total content of cellulose and lignin is 0.2 or more.

[0045] <Method of manufacturing the decomposition accelerator> The decomposition accelerator I of the present invention can be obtained by adjusting the concentration and ratio of raw materials containing cellulose, hemicellulose, and lignin. Examples of raw materials that can be used include the residues from squeezing plant seeds or fruits, the removed husks, bran, bran, and lees generated during the oil refining and brewing processes. Specific examples include peanuts, rice, wheat, barley, oil palm, cotton, soybeans, rapeseed, and corn.

[0046] Nitrogen-containing organic or inorganic substances may be added to the decomposition accelerator I of the present invention in order to adjust the nitrogen / carbon ratio within a predetermined range.

[0047] The decomposition accelerator II of the present invention can be obtained by adjusting the concentration and ratio of soluble nitrogen-free substances from raw materials. Examples of raw materials that can be used include the residues from squeezing plant seeds or fruits, the removed husks, bran, bran, and lees generated during the oil refining and brewing processes. Specific examples include pistachios, walnuts, chestnuts, peanuts, rice, wheat, barley, oil palm, bagasse, cotton, soybeans, rapeseed, and corn.

[0048] The decomposition accelerator of the present invention can be obtained by pulverizing the above-mentioned raw materials to a certain particle size. When two or more raw materials are used, the raw materials may be pulverized separately or a mixture of the raw materials may be pulverized in advance.

[0049] In producing the decomposition accelerator I of the present invention, it is preferable to pulverize each raw material in advance and then mix them together, since this makes it easier to control the nitrogen / carbon ratio and the hemicellulose / (cellulose+lignin) ratio within the above ranges.

[0050] In producing the decomposition accelerator II of the present invention, it is preferable to pulverize each raw material in advance and then mix them together, from the viewpoint that it is easier to control the proportions and ratios of the above-mentioned soluble nitrogen-free substances, cellulose, and lignin within the above-mentioned ranges.

[0051] The raw material can be pulverized using, for example, a pulverizer. As the pulverizer, various pulverizers can be used, such as a cutter mill, a stone mill, a crusher, a jet mill, a ball mill, a pin mill, etc. Among them, in order to obtain a decomposition accelerator having a predetermined particle size, a jet mill, a ball mill, and a pin mill are preferred, and a jet mill is particularly preferred because it allows continuous and efficient pulverization.

[0052] The grinding method is roughly divided into wet grinding using a medium such as water, and dry grinding without using a medium. Dry grinding is preferred because it is necessary to dry the material to a predetermined moisture content.

[0053] The particle size after grinding is usually 500 μm or less, preferably 300 μm or less, and more preferably 100 μm or less, from the viewpoint that when used with biodegradable resins, it is easier to mix with the biodegradable resin and it is easier to obtain the effect as a decomposition accelerator. The decomposition accelerator of the present invention preferably has a 50% mass cumulative particle size of 60 μm or less, more preferably 40 μm or less, and particularly preferably 20 μm or less. The lower the value of the 50% mass cumulative particle size of this decomposition accelerator, the better the appearance of the biodegradable resin composition obtained by mixing it with a biodegradable resin and the biodegradable resin molded article obtained by molding it (for example, the sheet surface will be smooth and transparency will be improved), and the mechanical properties of the biodegradable resin molded article, such as yield stress, stress at break, Elmendorf tear strength, puncture impact strength, and stress at break, will be improved, which is preferable. Although there is no particular limitation on the lower limit of the 50% mass cumulative particle size, it is preferably 1 μm or more. If the 50% mass cumulative particle size is less than 1 μm, the particles tend to scatter, and problems such as blocking and classification may occur when mixed with a biodegradable resin, making handling difficult.

[0054] The 50% mass cumulative particle size of the decomposition accelerator of the present invention is measured by the method described in the Examples section below. To achieve the above-mentioned preferred particle size and 50% mass cumulative particle size, it is preferable to select particles of the desired particle size using a mesh sieve or screen with openings of the desired particle size, or a centrifugal classifier, etc. Alternatively, crushing and sorting may be carried out simultaneously using a crusher equipped with a sorting mechanism.

[0055] The powders obtained by pulverizing each raw material are sorted in this way, and those having a predetermined particle size are mixed in a specific ratio as needed to obtain the decomposition accelerator of the present invention. The powders preferably used in this case are not particularly limited as long as they are powders of the above raw materials, but examples thereof include flours of rice bran, wheat bran, soybean meal, and rapeseed meal.

[0056] When mixing the decomposition accelerator of the present invention with a biodegradable resin, it is preferable to dry it beforehand. The reason for this is that moisture in the atmosphere (air) in the storage environment is adsorbed during storage, making it difficult to mix with the biodegradable resin due to the humidity. Furthermore, as mentioned above, if the decomposition accelerator contains moisture, the biodegradable resin will undergo hydrolysis, resulting in a decrease in molecular weight and a loss of mechanical strength. Therefore, it is preferable to dry the decomposition accelerator.

[0057] For this reason, when the decomposition accelerator of the present invention is produced and / or used, it is preferable to further carry out drying after the above-mentioned pulverization and particle size adjustment. For drying, a general dryer may be used and the mixture may be heated at a temperature of about 40 to 200°C. By carrying out such a drying treatment, it is preferable to make the moisture content of the decomposition accelerator less than 5% by mass, particularly 0 to 3% by mass. The moisture content of the decomposition accelerator is the mass W of the decomposition accelerator. x and the mass W of this decomposition accelerator after drying it to an absolutely dry state according to the method for measuring the water content described in the Examples section below. y It is calculated from the following formula: Moisture content (mass%)={(W x -W y ) / W x}×100

[0058] [Biodegradable resin composition] The biodegradable resin composition of the present invention contains 2 to 250 parts by mass of the decomposition accelerator of the present invention and 100 parts by mass of a biodegradable resin. If the content of the decomposition accelerator of the present invention per 100 parts by mass of the biodegradable resin in the biodegradable resin composition of the present invention is less than 2 parts by mass, the effect of improving biodegradability due to the inclusion of the decomposition accelerator of the present invention cannot be fully obtained. If the content of the decomposition accelerator of the present invention exceeds 250 parts by mass, the mechanical properties of the resulting molded article will be impaired. The biodegradable resin composition of the present invention preferably contains 10 to 100 parts by mass, more preferably 15 to 80 parts by mass, of the decomposition accelerator of the present invention per 100 parts by mass of biodegradable resin.

[0059] The biodegradable resin contained in the biodegradable resin composition of the present invention is not particularly limited as long as it is biodegradable, but examples thereof include aliphatic polyester resins (A), aliphatic-aromatic polyester resins (B), and aliphatic oxycarboxylic acid resins (C). Two or more of the aliphatic polyester resin (A), the aliphatic-aromatic polyester resin (B), and the aliphatic oxycarboxylic acid resin (C) may be mixed and used.

[0060] Each biodegradable resin will be explained below.

[0061] The aliphatic polyester resin (A), the aliphatic-aromatic polyester resin (B), and the aliphatic oxycarboxylic acid resin (C) are each polymers having repeating units, and each repeating unit is also called a compound unit corresponding to the compound from which the repeating unit is derived. For example, a repeating unit derived from an aliphatic diol is also called an "aliphatic diol unit," a repeating unit derived from an aliphatic dicarboxylic acid is also called an "aliphatic dicarboxylic acid unit," and a repeating unit derived from an aromatic dicarboxylic acid is also called an "aromatic dicarboxylic acid unit."

[0062] The "main structural unit" in the aliphatic polyester resin (A), the aliphatic-aromatic polyester resin (B), and the aliphatic oxycarboxylic acid resin (C) generally refers to a structural unit that accounts for 80 mass% or more of the polyester resin, and there are cases in which no structural units other than the main structural unit are contained.

[0063] <Aliphatic polyester resin (A)> The aliphatic polyester resin (A) is preferably an aliphatic polyester resin containing an aliphatic diol unit and an aliphatic dicarboxylic acid unit as main constituent units.

[0064] The aliphatic polyester resin (A) preferably has a proportion of succinic acid units of 5 mol % or more and 100 mol % or less of all dicarboxylic acid units. The aliphatic polyester resin (A) may be a mixture of aliphatic polyester resins having different amounts of succinic acid units. For example, an aliphatic polyester resin that does not contain aliphatic dicarboxylic acid units other than succinic acid (containing only succinic acid units as aliphatic dicarboxylic acid units) may be blended with an aliphatic polyester resin that contains aliphatic dicarboxylic acid units other than succinic acid, and the amount of succinic acid units in the aliphatic polyester resin (A) may be adjusted to fall within the above-mentioned preferred range.

[0065] More specifically, the aliphatic polyester resin (A) is an aliphatic polyester represented by the following formula (1): A polyester containing a diol unit and an aliphatic dicarboxylic acid unit represented by the following formula (2): It is a rubber-based resin. -OR 1 -O- (1) -OC-R 2 -CO- (2)

[0066] In formula (1), R 1 represents a divalent aliphatic hydrocarbon group. 2 represents a divalent aliphatic hydrocarbon group. The aliphatic diol unit and the aliphatic dicarboxylic acid unit represented by formula (1) and (2) may be derived from a compound derived from petroleum or a compound derived from a plant raw material, but are preferably derived from a compound derived from a plant raw material.

[0067] When the aliphatic polyester resin (A) is a copolymer, the aliphatic polyester resin (A) may contain two or more aliphatic diol units represented by formula (1), and the aliphatic polyester resin (A) may contain two or more aliphatic dicarboxylic acid units represented by formula (2).

[0068] As mentioned above, the aliphatic dicarboxylic acid units represented by formula (2) preferably contain succinic acid units in an amount of 5 mol % to 100 mol % based on the total dicarboxylic acid units. By setting the amount of succinic acid constituent units in the aliphatic polyester resin (A) within the above-mentioned range, it is possible to obtain a biodegradable resin composition that has improved moldability and excellent heat resistance and decomposability. For the same reason, the amount of succinic acid units in the aliphatic polyester resin (A) is preferably 10 mol % or more, more preferably 50 mol % or more, even more preferably 64 mol % or more, and particularly preferably 68 mol % or more based on the total dicarboxylic acid units. Hereinafter, the ratio of succinic acid units to all dicarboxylic acid units in the aliphatic polyester resin (A) may be referred to as the "succinic acid unit amount."

[0069] It is more preferable that the aliphatic dicarboxylic acid units represented by formula (2) contain one or more types of aliphatic dicarboxylic acid units other than succinic acid in an amount of 5 mol % to 50 mol % based on the total dicarboxylic acid units. By copolymerizing aliphatic dicarboxylic acid units other than succinic acid within the above-mentioned specified range, the crystallinity of the aliphatic polyester resin (A) can be reduced, and the biodegradation rate can be increased. For the same reason, the amount of aliphatic dicarboxylic acid units other than succinic acid in the aliphatic polyester resin (A) is preferably 10 mol % to 45 mol %, more preferably 15 mol % to 40 mol %, based on the total dicarboxylic acid units.

[0070] The aliphatic diol that provides the diol unit represented by formula (1) is not particularly limited, but from the viewpoint of moldability and mechanical strength, an aliphatic diol having 2 to 10 carbon atoms is preferred, and an aliphatic diol having 4 to 6 carbon atoms is particularly preferred. Examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol, with 1,4-butanediol being particularly preferred. Two or more of the above aliphatic diols can also be used.

[0071] The aliphatic dicarboxylic acid component that provides the aliphatic dicarboxylic acid unit represented by formula (2) is not particularly limited, but is preferably an aliphatic dicarboxylic acid having 2 to 40 carbon atoms and its derivatives such as alkyl esters, and particularly preferably an aliphatic dicarboxylic acid having 4 to 10 carbon atoms and its derivatives such as alkyl esters. Examples of aliphatic dicarboxylic acids having 4 to 10 carbon atoms other than succinic acid and their derivatives such as alkyl esters include adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, etc., and their alkyl esters. Among these, adipic acid and sebacic acid are preferred, and adipic acid is particularly preferred. Two or more types of the aliphatic dicarboxylic acid components can be used, and in this case, a combination of succinic acid and adipic acid is preferred.

[0072] The aliphatic polyester resin (A) may have a repeating unit (aliphatic oxycarboxylic acid unit) derived from an aliphatic oxycarboxylic acid. Specific examples of the aliphatic oxycarboxylic acid component that provides the aliphatic oxycarboxylic acid unit include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, and the like, as well as derivatives thereof, such as lower alkyl esters or intramolecular esters. When optical isomers exist, they may be in the D-form, L-form, or racemic form, and may be in the form of a solid, liquid, or aqueous solution. Among these, lactic acid, glycolic acid, or derivatives thereof are particularly preferred. These aliphatic oxycarboxylic acids can be used alone or in a mixture of two or more.

[0073] When the aliphatic polyester resin (A) contains these aliphatic oxycarboxylic acid units, from the viewpoint of moldability, the content thereof is preferably 20 mol % or less, more preferably 10 mol % or less, even more preferably 5 mol % or less, and most preferably 0 mol % (not included), based on 100 mol % of all structural units constituting the aliphatic polyester resin (A).

[0074] The melt viscosity of the aliphatic polyester resin (A) may be increased by copolymerizing a trifunctional or higher aliphatic polyhydric alcohol, a trifunctional or higher aliphatic polycarboxylic acid or its acid anhydride, or a trifunctional or higher aliphatic polyoxycarboxylic acid component.

[0075] Specific examples of trifunctional aliphatic polyhydric alcohols include trimethylolpropane and glycerin. Specific examples of tetrafunctional aliphatic polyhydric alcohols include pentaerythritol. These may be used alone or in combination of two or more.

[0076] Specific examples of trifunctional aliphatic polycarboxylic acids or acid anhydrides thereof include propanetricarboxylic acid or acid anhydrides thereof. Specific examples of tetrafunctional polycarboxylic acids or acid anhydrides thereof include cyclopentanetetracarboxylic acid or acid anhydrides thereof. These may be used alone or in combination of two or more.

[0077] Trifunctional aliphatic oxycarboxylic acids are divided into (i) types having two carboxyl groups and one hydroxyl group in the same molecule, and (ii) types having one carboxyl group and two hydroxyl groups, and either type can be used. From the viewpoints of moldability, mechanical strength, and appearance of molded products, (i) types having two carboxyl groups and one hydroxyl group in the same molecule, such as malic acid, are preferred, and more specifically, malic acid is preferably used. The tetrafunctional aliphatic hydroxycarboxylic acid component is divided into (i) a type in which three carboxyl groups and one hydroxyl group are shared in the same molecule, (ii) a type in which two carboxyl groups and two hydroxyl groups are shared in the same molecule, and (iii) a type in which three hydroxyl groups and one carboxyl group are shared in the same molecule, and any of these types can be used. The tetrafunctional aliphatic hydroxycarboxylic acid component is preferably one having multiple carboxyl groups, and more specific examples include citric acid, tartaric acid, etc. These may be used alone or in combination of two or more.

[0078] When the aliphatic polyester resin (A) contains such structural units derived from trifunctional or higher functional components, the content thereof, with all structural units constituting the aliphatic polyester resin (A) being 100 mol %, is generally 0 mol % or more in lower limit, preferably 0.01 mol % or more in upper limit, and generally 5 mol % or less, preferably 2.5 mol % or less in upper limit.

[0079] The aliphatic polyester resin (A) can be produced by a known method for producing polyesters. The polycondensation reaction can be carried out under suitable conditions that have been conventionally used, and is not particularly limited. Usually, the degree of polymerization is further increased by carrying out a reduced pressure operation after the esterification reaction has proceeded.

[0080] When a diol component forming a diol unit and a dicarboxylic acid component forming a dicarboxylic acid unit are reacted during the production of the aliphatic polyester resin (A), the amounts of the diol component and the dicarboxylic acid component used are set so that the aliphatic polyester resin (A) produced has the desired composition. Usually, the diol component and the dicarboxylic acid component react in substantially equimolar amounts, but the diol component is usually used in a 1 to 20 mol % excess over the dicarboxylic acid component because it is distilled off during the esterification reaction.

[0081] When the aliphatic polyester resin (A) contains components (optional components) other than the essential components such as aliphatic hydroxycarboxylic acid units and polyfunctional component units, the corresponding compounds (monomers and oligomers) are reacted so that the aliphatic hydroxycarboxylic acid units and polyfunctional component units have the desired compositions. In this case, there are no limitations on the timing and method of introducing the optional components into the reaction system, and they are optional as long as the aliphatic polyester resin (A) suitable for the present invention can be produced.

[0082] For example, the timing and method of introducing the aliphatic oxycarboxylic acid into the reaction system are not particularly limited as long as it is before the polycondensation reaction between the diol component and the dicarboxylic acid component, and examples thereof include the following (1) and (2). (1) A method in which the catalyst is dissolved in an aliphatic hydroxycarboxylic acid solution in advance and mixed. (2) A method in which the catalyst is introduced into the reaction system and mixed at the same time as the raw materials are charged.

[0083] The timing of introducing the compound that forms the polyfunctional component unit may be simultaneous with the other monomers or oligomers at the initial stage of polymerization, or may be simultaneous with the other monomers or oligomers after the transesterification reaction and before the pressure is reduced. It is preferable to simultaneously introduce the compound that forms the polyfunctional component unit with the other monomers or oligomers in terms of simplifying the process.

[0084] The aliphatic polyester resin (A) is usually produced in the presence of a catalyst. Any catalyst that can be used in the production of known polyester resins can be selected as the catalyst as long as it does not significantly impair the effects of the present invention. Examples of suitable catalysts include metal compounds such as germanium, titanium, zirconium, hafnium, antimony, tin, magnesium, calcium, and zinc. Among these, germanium compounds and titanium compounds are preferred.

[0085] Examples of germanium compounds that can be used as catalysts include organic germanium compounds such as tetraalkoxygermanium, and inorganic germanium compounds such as germanium oxide and germanium chloride. Among these, germanium oxide, tetraethoxygermanium, and tetrabutoxygermanium are preferred in terms of cost and availability, with germanium oxide being particularly preferred.

[0086] Examples of titanium compounds that can be used as catalysts include organic titanium compounds such as tetraalkoxytitanium compounds such as tetrapropyl titanate, tetrabutyl titanate, and tetraphenyl titanate. Among these, tetrapropyl titanate, tetrabutyl titanate, and the like are preferred in terms of price and availability.

[0087] Other catalysts may be used in combination as long as the object of the present invention is not impaired. The catalyst may be used alone or as a mixture of two or more kinds in any combination and ratio.

[0088] The amount of catalyst used may be any amount as long as it does not significantly impair the effects of the present invention, but is usually 0.0005% by mass or more, more preferably 0.001% by mass or more, and usually 3% by mass or less, preferably 1.5% by mass or less, based on the amount of monomer used. If the amount is below the lower limit of this range, the effect of the catalyst may not be achieved. If the amount is above the upper limit of this range, the production cost may increase, the resulting polymer may become significantly discolored, or the hydrolysis resistance may decrease.

[0089] The timing of introducing the catalyst is not particularly limited as long as it is before the polycondensation reaction, and it may be introduced when the raw materials are charged or when pressure reduction is started. When introducing an aliphatic oxycarboxylic acid unit, it is preferable to introduce it simultaneously with a monomer or oligomer that forms an aliphatic oxycarboxylic acid unit, such as lactic acid or glycolic acid, when the raw materials are charged, or to dissolve the catalyst in an aqueous aliphatic oxycarboxylic acid solution and introduce it. In particular, the method of dissolving the catalyst in an aqueous aliphatic oxycarboxylic acid solution and introducing it is preferable because it increases the polymerization rate.

[0090] The reaction conditions such as temperature, polymerization time, and pressure when producing the aliphatic polyester resin (A) are arbitrary as long as they do not significantly impair the effects of the present invention. The reaction temperature for the esterification reaction and / or transesterification reaction between the dicarboxylic acid component and the diol component is usually 150°C or higher, preferably 180°C or higher, and usually 260°C or lower, preferably 250°C or lower. The reaction atmosphere is usually an inert atmosphere such as nitrogen or argon. The reaction pressure is usually from atmospheric pressure to 10 kPa, with atmospheric pressure being preferred. The reaction time is usually 1 hour or longer and usually 10 hours or shorter, preferably 6 hours or shorter, more preferably 4 hours or shorter. If the reaction temperature is too high, excessive unsaturated bonds are generated, which can cause gelation due to the unsaturated bonds, making it difficult to control the polymerization.

[0091] The conditions for the polycondensation reaction after the esterification and / or transesterification reaction between the dicarboxylic acid component and the diol component are as follows. The pressure is typically 0.01 x 10 3 Pa or more, preferably 0.03 x 10 3 Pa or higher, typically 1.4 x 10 3 Pa or less, preferably 0.4×10 3 It is desirable to carry out the process under a vacuum of 100 Pa or less. The reaction temperature is usually 150°C or higher, preferably 180°C or higher, and usually 260°C or lower, preferably 250°C or lower. The reaction time is usually 2 hours or more and usually 15 hours or less, preferably 10 hours or less. If the reaction temperature is too high, excessive generation of unsaturated bonds may cause gelation due to the unsaturated bonds, making it difficult to control the polymerization.

[0092] When producing the aliphatic polyester resin (A), a chain extender such as a carbonate compound or a diisocyanate compound can also be used. In this case, the amount of the chain extender is usually 10 mol % or less, preferably 5 mol % or less, and more preferably 3 mol % or less, in terms of the proportion of carbonate bonds or urethane bonds in the aliphatic polyester resin (A) when all structural units constituting the aliphatic polyester resin are taken as 100 mol %.

[0093] Since the presence of urethane bonds or carbonate bonds in the aliphatic polyester resin (A) may inhibit biodegradability, in the present invention, the carbonate bond content is less than 1 mol%, preferably 0.5 mol% or less, more preferably 0.1 mol% or less, and the urethane bond content is 0.55 mol% or less, preferably 0.3 mol% or less, more preferably 0.12 mol% or less, and even more preferably 0.05 mol% or less, relative to the total structural units constituting the aliphatic polyester resin (A). This amount is 0.9 parts by mass or less, preferably 0.5 parts by mass or less, more preferably 0.2 parts by mass or less, and even more preferably 0.1 parts by mass or less, calculated per 100 parts by mass of the aliphatic polyester resin (A). In particular, if the urethane bond content exceeds the upper limit, decomposition of the urethane bonds may cause problems such as smoke and odor from the molten film exiting the die during the film formation process, and foaming may occur in the molten film, preventing stable molding.

[0094] The carbonate bond amount and urethane bond amount in the aliphatic polyester resin (A) are 1 It can be calculated from the results of NMR measurements such as H-NMR and C-NMR.

[0095] Specific examples of carbonate compounds as chain extenders include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, diamyl carbonate, dicyclohexyl carbonate, etc. In addition, carbonate compounds composed of the same or different hydroxy compounds derived from hydroxy compounds such as phenols and alcohols can also be used.

[0096] Specific examples of the diisocyanate compound include known diisocyanates such as 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, 2,4,6-triisopropylphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, and tolidine diisocyanate.

[0097] Other chain extenders that may be used include dioxazoline and silicate esters. Specific examples of silicate esters include tetramethoxysilane, dimethoxydiphenylsilane, dimethoxydimethylsilane, and diphenyldihydroxysilane.

[0098] High molecular weight polyester resins using these chain extenders (coupling agents) can also be produced using conventional techniques. After polycondensation is complete, the chain extender is added to the reaction system in a homogeneous molten state without a solvent, and reacted with the polyester obtained by polycondensation.

[0099] More specifically, a polyester resin with a higher molecular weight can be obtained by reacting the above-mentioned chain extender with a polyester obtained by catalytically reacting a diol component with a dicarboxylic acid component, which has terminal groups substantially containing hydroxyl groups and has a weight-average molecular weight (Mw) of 20,000 or more, preferably 40,000 or more. A prepolymer with a weight-average molecular weight of 20,000 or more is not affected by residual catalyst even under severe conditions, such as a molten state, and can be used with a small amount of chain extender to produce a high-molecular-weight polyester resin without forming a gel during the reaction.

[0100] The weight average molecular weight (Mw) of a polyester resin is determined as a value converted into monodisperse polystyrene from a measurement value obtained by gel permeation chromatography (GPC) at a measurement temperature of 40°C using chloroform as a solvent.

[0101] Therefore, when further increasing the molecular weight of a polyester resin using, for example, the above-mentioned diisocyanate compound as a chain extender, it is preferable to use a prepolymer having a weight-average molecular weight of 20,000 or more, preferably 40,000 or more. If the weight-average molecular weight is less than 20,000, the amount of diisocyanate compound used to increase the molecular weight may increase, resulting in a decrease in heat resistance. Using such a prepolymer, a polyester resin having urethane bonds with a linear structure linked via urethane bonds derived from the diisocyanate compound is produced.

[0102] The pressure during chain extension is usually 0.01 MPa or more and 1 MPa or less, preferably 0.05 MPa or more and 0.5 MPa or less, more preferably 0.07 MPa or more and 0.3 MPa or less, and most preferably normal pressure.

[0103] The reaction temperature during chain extension is usually 100°C or higher, preferably 150°C or higher, more preferably 190°C or higher, and most preferably 200°C or higher, and usually 250°C or lower, preferably 240°C or lower, and more preferably 230°C or lower. If the reaction temperature is too low, the viscosity will be high, making it difficult to achieve a uniform reaction, and high stirring power will also be required. If the reaction temperature is too high, gelation and decomposition of the polyester resin will tend to occur.

[0104] The reaction time during chain extension is usually 0.1 minutes or more, preferably 1 minute or more, more preferably 5 minutes or more, and usually 5 hours or less, preferably 1 hour or less, more preferably 30 minutes or less, and most preferably 15 minutes or less. If the reaction time is too short, the effect of adding the chain extender tends not to be exerted. If the reaction time is too long, gelation or decomposition of the polyester resin tends to occur concomitantly.

[0105] The molecular weight of the aliphatic polyester resin (A) is typically 10,000 to 1,000,000 in weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard substance. This Mw is advantageous in terms of moldability and mechanical strength, and is therefore preferably 20,000 to 500,000, more preferably 50,000 to 400,000.

[0106] The melt flow rate (MFR) of the aliphatic polyester resin (A) is measured at 190°C under a load of 2.16 kg according to JIS K7210 (1999), and is usually 0.1 g / 10 min or more and 100 g / 10 min or less. From the viewpoint of moldability and mechanical strength, this MFR is preferably 50 g / 10 min or less, particularly preferably 40 g / 10 min or less. The MFR of the aliphatic polyester resin (A) can be adjusted by the molecular weight.

[0107] The melting point of the aliphatic polyester resin (A) is preferably 70° C. or higher, more preferably 75° C. or higher, and is preferably 170° C. or lower, more preferably 150° C. or lower, and particularly preferably lower than 130° C. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range. If the melting point is outside the above range, moldability will be poor. The elastic modulus of the aliphatic polyester resin (A) is preferably 180 to 1000 MPa. If the modulus of elasticity is less than 180 MPa, problems with molding processability are likely to occur, and if the modulus of elasticity is more than 1000 MPa, impact strength tends to deteriorate.

[0108] The method for adjusting the melting point and elastic modulus of the aliphatic polyester resin (A) is not particularly limited. For example, the melting point and elastic modulus can be adjusted by selecting the type of copolymerization component of the aliphatic dicarboxylic acid component other than succinic acid, adjusting the copolymerization ratio of each, or combining them.

[0109] The aliphatic polyester resin (A) is not limited to one type, and two or more types of aliphatic polyester resins (A) differing in the type and ratio of constituent units, production method, physical properties, etc. may be blended and used.

[0110] <Aliphatic-aromatic polyester resin (B)> Examples of the aliphatic-aromatic polyester resin (B) include those in which at least a portion of the repeating units of the above-mentioned aliphatic polyester resin (A) have been replaced with aromatic compound units, preferably polyester resins containing aliphatic diol units, aliphatic dicarboxylic acid units, and aromatic dicarboxylic acid units as main constituent units, in which a portion of the aliphatic dicarboxylic acid units of the above-mentioned aliphatic polyester resin (A) have been replaced with aromatic dicarboxylic acid units.

[0111] Examples of aromatic compound units include aromatic diol units having an aromatic hydrocarbon group which may have a substituent, aromatic dicarboxylic acid units having an aromatic hydrocarbon group which may have a substituent, aromatic dicarboxylic acid units having an aromatic heterocyclic group which may have a substituent, and aromatic oxycarboxylic acid units having an aromatic hydrocarbon group which may have a substituent. The aromatic hydrocarbon group and aromatic heterocyclic group may be monocyclic or may have multiple rings bonded or condensed together. Specific examples of aromatic hydrocarbon groups include 1,2-phenylene groups, 1,3-phenylene groups, 1,4-phenylene groups, dinaphthylene groups, and diphenylene groups. Specific examples of aromatic heterocyclic groups include 2,5-furandiyl groups.

[0112] Specific examples of aromatic dicarboxylic acid components that provide aromatic dicarboxylic acid units include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, 2,5-furandicarboxylic acid, etc. Among these, terephthalic acid is preferred.

[0113] The aromatic dicarboxylic acid component may be a derivative of an aromatic dicarboxylic acid compound. For example, derivatives of the aromatic dicarboxylic acid components exemplified above are preferred, and among these, lower alkyl esters having 1 to 4 carbon atoms and acid anhydrides are mentioned. Specific examples of derivatives of aromatic dicarboxylic acid compounds include lower alkyl esters such as methyl esters, ethyl esters, propyl esters, and butyl esters of the aromatic dicarboxylic acid components exemplified above; and cyclic acid anhydrides of the aromatic dicarboxylic acid components exemplified above, such as succinic anhydride. Among these, dimethyl terephthalate is preferred.

[0114] Specific examples of aromatic diol components that provide aromatic diol units include xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and bis(4-β-hydroxyethoxyphenyl)sulfonic acid. The aromatic diol component may be a derivative of an aromatic diol compound. Alternatively, the aromatic diol component may be a compound having a structure in which a plurality of aliphatic diol compounds and / or aromatic diol compounds are dehydrated and condensed with each other.

[0115] Specific examples of aromatic oxycarboxylic acid components that provide aromatic oxycarboxylic acid units include p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid. The aromatic oxycarboxylic acid component may be a derivative of an aromatic oxycarboxylic acid compound. Alternatively, it may be a compound (oligomer) having a structure in which a plurality of aliphatic oxycarboxylic acid compounds and / or aromatic oxycarboxylic acid compounds are dehydrated and condensed with each other. That is, an oligomer may be used as a raw material.

[0116] When the aromatic compound component that provides these aromatic compound units has optical isomers, any of the D-form, L-form and racemic isomer may be used. The aromatic compound component is not limited to the above examples, as long as it can provide an aromatic compound unit. The aromatic compound component may be used alone or in any combination of two or more in any ratio.

[0117] For the aliphatic-aromatic polyester resin (B), it is preferable to use an aromatic dicarboxylic acid component as the component that provides the aromatic compound unit. In this case, the content of the aromatic dicarboxylic acid unit is preferably 10 mol % or more and 80 mol % or less, based on the total amount of the aliphatic dicarboxylic acid unit and the aromatic dicarboxylic acid unit (100 mol %). The aromatic dicarboxylic acid component is preferably terephthalic acid or 2,5-furandicarboxylic acid. In this case, the aliphatic-aromatic polyester resin (B) is preferably polybutylene terephthalate adipate and / or polybutylene terephthalate succinate. The aliphatic-aromatic polyester resin (B) is also preferably polybutylene-2,5-furandicarboxylate.

[0118] The aliphatic-aromatic polyester resin (B) can be produced in the same manner as the aliphatic polyester resin (A) described above, using at least an aromatic compound component as a raw material.

[0119] The molecular weight of the aliphatic-aromatic polyester resin (B) is typically 10,000 to 1,000,000 in weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard substance. This Mw is advantageous in terms of moldability and mechanical strength, and is therefore preferably 30,000 to 800,000, more preferably 50,000 to 600,000.

[0120] The melt flow rate (MFR) of the aliphatic-aromatic polyester resin (B) is measured at 190°C under a load of 2.16 kg according to JIS K7210 (1999), and is usually 0.1 g / 10 min or more and 100 g / 10 min or less. From the viewpoint of moldability and mechanical strength, this MFR is preferably 50 g / 10 min or less, and particularly preferably 30 g / 10 min or less. The MFR of the aliphatic-aromatic polyester resin (B) can be adjusted by the molecular weight.

[0121] The melting point of the aliphatic-aromatic polyester resin (B) is usually 60°C or higher, preferably 70°C or higher, more preferably 80°C or higher, and 150°C or lower, more preferably 140°C or lower, and particularly preferably 120°C or lower. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range. If the melting point is outside the above range, moldability will be poor. The elastic modulus of the aliphatic-aromatic polyester resin (B) is preferably 180 to 1000 MPa. If the modulus of elasticity is less than 180 MPa, problems with molding processability are likely to occur, and if the modulus of elasticity is more than 1000 MPa, impact strength tends to deteriorate.

[0122] The method for adjusting the melting point and elastic modulus of the aliphatic-aromatic polyester resin (B) is not particularly limited. For example, the melting point and elastic modulus can be adjusted by selecting the type of copolymerization component of the aliphatic dicarboxylic acid component other than the aromatic dicarboxylic acid component, adjusting the copolymerization ratio of each, or combining them.

[0123] The aliphatic-aromatic polyester resin (B) is not limited to one type, and two or more types of aliphatic-aromatic polyester resins (B) differing in the type and ratio of constituent units, production method, physical properties, etc. can be blended and used.

[0124] <Aliphatic hydroxycarboxylic acid resin (C)> The aliphatic oxycarboxylic acid resin (C) has an aliphatic oxycarboxylic acid unit as a main constituent unit, and the aliphatic oxycarboxylic acid unit is preferably represented by the following formula (3). -OR 3 -CO- (3) In formula (3), R 3 represents a divalent aliphatic hydrocarbon group or a divalent alicyclic hydrocarbon group.

[0125] Specific examples of the aliphatic oxycarboxylic acid component that provides the aliphatic oxycarboxylic acid unit of formula (3) include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, and mixtures thereof. When optical isomers exist in these, either the D-form or the L-form may be used. Among these, lactic acid or glycolic acid is preferred. Two or more of these aliphatic oxycarboxylic acid components may also be used in combination.

[0126] As the aliphatic oxycarboxylic acid resin (C), polylactic acid (PLA) is particularly preferred.

[0127] To the extent that biodegradability is not affected, a urethane bond, an amide bond, a carbonate bond, an ether bond, etc. can be introduced into the aliphatic oxycarboxylic acid resin (C).

[0128] The method for producing the aliphatic hydroxycarboxylic acid resin (C) is not particularly limited, and it can be produced by known methods such as direct polymerization of hydroxycarboxylic acid or ring-opening polymerization of cyclic compounds.

[0129] The molecular weight of the aliphatic oxycarboxylic acid resin (C) is typically 10,000 to 1,000,000 in weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard substance. This Mw is advantageous in terms of moldability and mechanical strength, and is therefore preferably 20,000 to 500,000, more preferably 50,000 to 400,000.

[0130] The melt flow rate (MFR) of the aliphatic hydroxycarboxylic acid resin (C) is measured at 190°C under a load of 2.16 kg according to JIS K7210 (1999), and is usually 0.1 g / 10 min or more and 100 g / 10 min or less. From the viewpoint of moldability and mechanical strength, this MFR is preferably 50 g / 10 min or less, particularly preferably 40 g / 10 min or less. The MFR of the aliphatic hydroxycarboxylic acid resin (C) can be adjusted by the molecular weight.

[0131] The melting point of the aliphatic hydroxycarboxylic acid resin (C) is preferably 70° C. or higher, more preferably 75° C. or higher, and is preferably 170° C. or lower, more preferably 150° C. or lower, and particularly preferably lower than 130° C. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range. If the melting point is outside the above range, moldability will be poor. The elastic modulus of the aliphatic oxycarboxylic acid resin (C) is preferably 180 to 1000 MPa. If the modulus of elasticity is less than 180 MPa, problems with molding processability are likely to occur, and if the modulus of elasticity is more than 1000 MPa, impact strength tends to deteriorate.

[0132] The melting point and elastic modulus of the aliphatic hydroxycarboxylic acid resin (C) may be adjusted by any method, including, for example, selecting the type of copolymerization component other than the aliphatic hydroxycarboxylic acid, adjusting the copolymerization ratio of each component, or combining these components.

[0133] As the aliphatic oxycarboxylic acid resin (C), polyhydroxyalkanoates (D) described below can also be preferably used.

[0134] The polyhydroxyalkanoate (hereinafter sometimes referred to as PHA) (D) preferably used in the present invention is an aliphatic polyester containing repeating units represented by the general formula: [-CHR-CH2-CO-O-] (wherein R is an alkyl group having 1 to 15 carbon atoms), and is a copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units as main structural units.

[0135] From the viewpoints of moldability and thermal stability, the polyhydroxyalkanoate (D) preferably contains 80 mol % or more, more preferably 85 mol % or more, of 3-hydroxybutyrate units as a constituent component, and is preferably produced by a microorganism.

[0136] Specific examples of the polyhydroxyalkanoate (D) include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin, poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) copolymer resin, and the like. In particular, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin, ie, PHBH, is preferred from the viewpoint of molding processability and the physical properties of the resulting molded article.

[0137] In the polyhydroxyalkanoate (D), the ratio of 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) to the copolymerized comonomer, such as 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH), i.e., the monomer ratio in the copolymer resin, is preferably 3-hydroxybutyrate / comonomer = 97 / 3 to 80 / 20 (mol % / mol %), more preferably 95 / 5 to 85 / 15 (mol % / mol %), from the viewpoints of molding processability and molded product quality. If this comonomer ratio is less than 3 mol %, molding may be difficult because the molding temperature and thermal decomposition temperature are close to each other. If the comonomer ratio exceeds 20 mol %, the crystallization of the polyhydroxyalkanoate (D) may be slow, which may reduce productivity.

[0138] The ratio of each monomer in the polyhydroxyalkanoate (D) can be measured by gas chromatography as follows.

[0139] Approximately 20 mg of dried PHA is added to 2 ml of a sulfuric acid / methanol mixture (15 / 85 by mass) and 2 ml of chloroform, sealed, and heated at 100°C for 140 minutes to obtain the methyl ester of the PHA decomposition product. After cooling, 1.5 g of sodium bicarbonate is added little by little to neutralize the mixture, and the mixture is left to stand until the evolution of carbon dioxide gas stops. 4 ml of diisopropyl ether is added and mixed well, and the monomer unit composition of the PHA decomposition product in the supernatant is analyzed by capillary gas chromatography to determine the ratio of each monomer in the copolymer resin.

[0140] The molecular weight of the polyhydroxyalkanoate (D), as measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard, is typically 200,000 or more and 2,500,000 or less in weight-average molecular weight (Mw). Because this Mw is advantageous in terms of moldability and mechanical strength, it is preferably 250,000 or more and 2,000,000 or less, more preferably 300,000 or more and 1,000,000 or less. If Mw is less than 200,000, mechanical properties may be poor. If Mw exceeds 2,500,000, molding processing may be difficult.

[0141] The melt flow rate (MFR) of the polyhydroxyalkanoate (D), as measured at 190°C under a load of 2.16 kg according to JIS K7210 (1999), is preferably 1 g / 10 min or more and 100 g / 10 min or less. From the viewpoint of moldability and mechanical strength, this MFR is more preferably 80 g / 10 min or less, and particularly preferably 50 g / 10 min or less. The MFR of the polyhydroxyalkanoate (D) can be adjusted by the molecular weight.

[0142] The melting point of the polyhydroxyalkanoate (D) is preferably 100° C. or higher, more preferably 120° C. or higher, and is preferably 180° C. or lower, more preferably 170° C. or lower, and particularly preferably lower than 160° C. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range.

[0143] Polyhydroxyalkanoate (D) can be produced by, for example, a microorganism such as Alcaligenes eutrophus AC32 strain, which is obtained by introducing a PHA synthase gene derived from Aeromonas caviae into Alcaligenes eutrophus (international deposit under the Budapest Treaty, international depository authority: National Institute of Advanced Industrial Science and Technology International Patent Organism Depositary (6-1 Central, 1-1 Higashi, Tsukuba, Ibaraki Prefecture, Japan), original deposit date: August 12, 1996, transferred on August 7, 1997, deposit number FERM BP-6038 (transferred from original deposit FERM P-15786)) (J. Bacteriol., 179, 4821 (1997)).

[0144] Commercially available polyhydroxyalkanoates (D) containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units as main structural units include "PHBH X331N," "PHBH X131A," and "PHBH X151A" manufactured by Kaneka Corporation.

[0145] In the present invention, the aliphatic hydroxycarboxylic acid resin (C), including the polyhydroxyalkanoate (D), is not limited to one type, and two or more types of aliphatic hydroxycarboxylic acid resins (C) differing in the type of constituent units, the ratio of constituent units, the production method, the physical properties, etc., can be blended and used.

[0146] <Other ingredients> In addition to the decomposition accelerator of the present invention, the biodegradable resin composition of the present invention may contain, as "other components," one or more of various additives such as fillers, plasticizers, antistatic agents, antioxidants, light stabilizers, ultraviolet absorbers, dyes, pigments, hydrolysis inhibitors, crystal nucleating agents, antiblocking agents, weathering agents, heat stabilizers, flame retardants, release agents, antifogging agents, surface wetting improvers, incineration aids, dispersing aids, various surfactants, and slip agents. The biodegradable resin composition of the present invention may also contain functional additives such as a freshness-preserving agent and an antibacterial agent.

[0147] These other components can be blended as desired within the range that does not impair the effects of the present invention, and one type may be used alone, or two or more types may be used in combination.

[0148] The content of these other components in the biodegradable resin composition of the present invention is usually preferably such that the total amount of the other components is 0.01% by mass or more and 40% by mass or less relative to the total amount of the biodegradable resin composition of the present invention so as not to impair the physical properties of the biodegradable resin composition of the present invention.

[0149] <Method for producing biodegradable resin composition> The biodegradable resin composition of the present invention is produced by kneading the decomposition accelerator of the present invention with the decomposition accelerator in a kneader to disperse the decomposition accelerator in the biodegradable resin. In addition, other resins and other components used as needed may be mixed in the kneader together with the decomposition accelerator and the biodegradable resin.

[0150] This mixing step is carried out by mixing the decomposition accelerator and biodegradable resin of the present invention with other resins and other components used as needed in a predetermined ratio simultaneously or in any order using a mixer such as a tumbler, V-type blender, Nauta mixer, Banbury mixer, kneading roll, or extruder, and preferably further melt-kneading the mixture.

[0151] The kneader used in the mixing step may be a melt kneader. The extruder may be either a twin-screw extruder or a single-screw extruder, with a twin-screw extruder being more preferred.

[0152] The temperature during melt-kneading is preferably 140 to 220°C. This temperature range makes it possible to shorten the time required for the melting reaction, prevent deterioration of the resin and deterioration of color tone due to carbonization of the decomposition accelerator, and further improve practical physical properties such as impact resistance and moist heat resistance. From the same viewpoint, the melt-kneading temperature is more preferably 150 to 210°C.

[0153] As mentioned above, the melt-kneading time should not be unnecessarily long in order to more reliably avoid resin deterioration, etc., and is preferably 20 seconds or more and 20 minutes or less, more preferably 30 seconds or more and 15 minutes or less. Therefore, it is preferable to set the melt-kneading temperature and time conditions so as to satisfy these melt-kneading conditions.

[0154] [Molded body] The biodegradable resin composition of the present invention can be molded by various molding methods applicable to general-purpose plastics. Examples of such molding methods include compression molding (compression molding, laminate molding, stampable molding), injection molding, extrusion molding, coextrusion molding (film molding by inflation molding or T-die molding, laminate molding, pipe molding, wire / cable molding, molding of profiled materials), heat press molding, blow molding (various blow moldings), calendar molding, solid molding (uniaxial stretch molding, biaxial stretch molding, roll molding, stretch-oriented nonwoven fabric molding, thermoforming (vacuum forming, pressure forming), plastic processing, powder molding (rotational molding), and various nonwoven fabric moldings (dry method, adhesive method, entanglement method, spunbonding method, etc.). Among these, injection molding, extrusion molding, compression molding, and heat press molding are preferred. Specific shapes of molded articles that are preferred are sheets, films, and containers.

[0155] The biodegradable resin molded article of the present invention, which is obtained by molding the decomposition accelerator of the present invention, can be subjected to various secondary processing steps in order to impart surface functions such as chemical functions, electrical functions, magnetic functions, mechanical functions, friction / wear / lubrication functions, optical functions, thermal functions, and biocompatibility. Examples of secondary processing include embossing, painting, adhesive, printing, metallizing (plating, etc.), machining, and surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.).

[0156] [Application] The biodegradable resin molded article of the present invention, which is made from the biodegradable resin composition of the present invention, is suitable for a wide range of uses, such as packaging materials for packaging liquid, powdered, and solid materials, such as various foods, medicines, and miscellaneous goods, agricultural materials, and construction materials. Specific uses include injection-molded articles (e.g., trays for fresh food, fast-food containers, coffee capsule containers, cutlery, outdoor leisure products, etc.), extrusion-molded articles (e.g., films, sheets, fishing lines, fishing nets, vegetation nets, sheets for secondary processing, water-retaining sheets, etc.), and blown-molded articles (e.g., bottles). Further examples include agricultural films, coating materials, fertilizer coating materials, seedling pots, laminated films, plates, stretched sheets, monofilaments, nonwoven fabrics, flat yarns, staples, crimped fibers, creased tape, split yarns, composite fibers, blown bottles, shopping bags, garbage bags, compost bags, cosmetic containers, detergent containers, bleach containers, ropes, binding materials, sanitary cover stock materials, cooler boxes, cushioning films, multifilaments, synthetic paper, and medical applications such as surgical thread, sutures, artificial bones, artificial skin, DDS such as microcapsules, and wound dressings.

[0157] The biodegradable resin molded article of the present invention is particularly suitable for food containers such as food packaging films, trays for fresh food, fast food containers, and lunch boxes. [Example]

[0158] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. The values of various production conditions and evaluation results in the following examples represent preferred upper or lower limit values in the embodiments of the present invention, and preferred ranges may be defined by combining the above-mentioned upper or lower limit values with the values of the following examples or values between the examples.

[0159] [Measurement of decomposition accelerators] <Measurement and calculation of nitrogen and carbon content> The nitrogen and carbon contents were measured using a commercially available combustion method automatic analyzer capable of simultaneously analyzing nitrogen and carbon. The nitrogen content can be measured separately using a total nitrogen measurement method or nitrogen measuring device conforming to JIS K0102, JIS K6451-1, JIS M8819, JIS Z7302-8, etc., and the carbon content can be measured separately using a carbon measuring device conforming to JIS K0102, JIS M8819, JIS Z7302-8, etc.

[0160] <Measurement and calculation of cellulose, lignin, and hemicellulose content> The contents of cellulose, lignin, and hemicellulose in decomposition accelerator I were calculated using the following formula from the values of heat-resistant α-amylase-treated neutral detergent fiber (aNDFom), acid detergent fiber (ADFom), and acid detergent lignin (ADL). Cellulose (%) = ADFom (%) - ADL (%) Lignin (%) = ADL (%) Hemicellulose (%) = aNDFom (%) - ADFom (%) aNDFom, ADFom, and ADL were measured according to standard methods (see, for example, "Feed Analysis Methods and Commentary 2009" published by the Japan Scientific Feed Association, "Feed Analysis Standards" published by the National Agriculture and Food Research Center (http: / / www.famic.go.jp / ffis / feed / bunseki / bunsekikijun.html), and "Recent Research Trends in the Nutritional Evaluation of Feed Crops" published by the National Agriculture and Food Research Organization (http: / / www.naro.affrc.go.jp / nilgs-neo / kenkyukai / files / jikyushiryoriyo2016_koen07.pdf)). The measurement method is outlined below.

[0161] 《aNDFom》 Sodium sulfite and a neutral detergent solution are added to a sample (mass W1) and boiled, followed by the addition of heat-resistant α-amylase and boiling. The insoluble matter is filtered through a glass filter or similar, washed, dried, and weighed (W2). This insoluble matter is then ashed by heating and weighed (W3). Calculate aNDFom (%) using the following formula. aNDFom(%)=100×(W2-W3) / W1

[0162] ADFom and ADL After adding an acid detergent solution to the sample (mass W4) and boiling, the insoluble matter is filtered using a glass filter or similar, washed, dried, and weighed (W5). Next, this insoluble matter is treated with 72% sulfuric acid, after which the insoluble matter is washed, dried, and weighed (W6). Finally, the insoluble matter is heated to ashed and weighed (W7). Calculate ADFom (%) and ADL (%) using the following formula. ADFom(%)=100×(W5-W7) / W4 ADL(%)=100×(W6-W7) / W4

[0163] The cellulose and lignin contents in decomposition accelerator II were also measured and calculated in the same manner as above from the values of acid detergent fiber (ADFom) and acid detergent lignin (ADL).

[0164] <Measurement and calculation of soluble nitrogen-free matter content> The nitrogen-free soluble matter was calculated using the following formula based on the official feed specifications (Ministry of Agriculture and Forestry Notification No. 756, July 24, 1976). Nitrogen-free soluble matter (%) = 100 - (moisture (%) + crude protein (%) + crude fat (%) + crude fiber (%) + crude ash (%)) The values of moisture, crude protein, crude fat, crude fiber, and crude ash were determined as follows using the official standards for feed or other known methods.

[0165] "moisture" The moisture content was determined by the loss on heating method. In this method, an automatic moisture measuring device is used to dry the sample at 135°C until the rate of weight change falls below a certain level, and the moisture content is determined from the change in weight before and after that. Alternatively, a weighed sample can be dried at 135°C for 2 hours, allowed to cool in a desiccator, and then weighed, and the weight loss can be calculated as the moisture content. In addition, the Karl Fischer method can also be used to quantify the moisture content.

[0166] Crude protein The crude protein was determined by the Kjeldahl method. In this method, sulfuric acid and a decomposition accelerator are first added to the sample and heated to convert the nitrogen in the sample to ammonium salts. Sodium hydroxide is then added and heated, and the ammonia generated is captured with sulfuric acid of a known concentration. The nitrogen content is measured by titrating this solution with an aqueous sodium hydroxide solution of a known concentration. The crude protein content is calculated by multiplying the resulting nitrogen content (mass%) by the nitrogen-to-protein conversion factor (6.25). In addition, an automatic analyzer using the combustion method (Dumas method) can also be used to measure the amount of nitrogen.

[0167] 《crude fat》 The crude fat content was determined using the diethyl ether extraction method. In this method, fat in a sample is extracted with diethyl ether using a Soxhlet extractor, and the extract obtained by volatilizing the diethyl ether is weighed as crude fat. Other methods for quantifying crude fat include acid decomposition and diethyl ether extraction.

[0168] Crude fiber The crude fiber content was determined by filtration. In this method, sulfuric acid is first added to the sample, boiled, and filtered. Next, aqueous sodium hydroxide solution is added to the insoluble matter, boiled, and filtered, and the resulting residue is dried and weighed. Next, the residue is heated to 550-600°C and incinerated, and its weight is measured. The crude fiber content is calculated from the difference in weight before and after heating and incineration.

[0169] 《Coarse ash content》 The crude ash content was determined by direct ashing. In this method, the sample is heated to 550-600°C, incinerated, and weighed to determine the amount of crude ash.

[0170] <Particle size measurement> The particle size distribution of the decomposition accelerator was measured using a laser diffraction particle size distribution measuring device ("SALD-2300" manufactured by Shimadzu Corporation). In this method, particles of the decomposition accelerator dispersed in a dispersion medium such as water are irradiated with laser light, and the observed diffracted / scattered light pattern is compared with the diffracted / scattered light pattern estimated by calculation when the decomposition accelerator is considered to be an aggregate of many spherical particles with different diameters, and the particle size and frequency distribution that match are calculated. As a representative value of particle size, the particle diameter that accounts for 50% of the total mass when the masses of particles are integrated in order from the smallest diameter (referred to as the 50% particle diameter or median diameter) is taken as the 50% mass cumulative particle size.

[0171] [Evaluation of biodegradable resin compositions and molded articles] <Biodegradability test> The resulting resin composition was formed into a 200 μm thick film using a heat press at 170°C. This was then cut into dumbbell shapes conforming to ISO 527-3 and embedded in a polyethylene Tupperware container containing a 1:1 mixture of horticultural soil (Iris Ohyama Corporation's "Flower and Vegetable Culture Soil") and compost (Yawata Bussan Corporation's "Inoculum for Biodegradation Tests") with a moisture content of 20%RH. The container was then closed and allowed to stand in an incubator at 28°C for two weeks. The weight change before and after standing was measured, and the rate of change (the ratio of the mass loss to the mass before standing) was calculated. The calculated rate of change was calculated as a ratio to the rate of change in Comparative Example I-1 or II-1 when only the aliphatic polyester resin (A) was used, and this was defined as the biodegradability improvement rate.

[0172] <Tensile properties> The film-like molded product was measured for yield stress and stress at break in accordance with JIS K7127 (1999). The larger these values, the better.

[0173] <Tear strength> The film-like molded product was measured for Elmendorf tear strength in accordance with ISO 6383-2 (1983). The higher this value, the better.

[0174] <Puncture impact strength> A film-like molded product having a width of 110 mm and a length of 1300 mm was punched with a punching impact tester manufactured by Toyo Seiki Co., Ltd. using an arm with a hemispherical tip having a diameter of 25 mm to punch 12 holes of 50 mm in order to measure the puncture impact strength. The higher this value, the better.

[0175] [Biodegradable resin] In the following examples and comparative examples, the following aliphatic polyester resin (A) was used as the biodegradable resin. Aliphatic polyester resin (A): Polybutylene succinate adipate (PBSA) manufactured by PTTMCCBiochem, product name: BioPBS TM FD92PB Melting point: 89℃

[0176] [Production of Decomposition Accelerator I and Comparative Decomposition Accelerator] Each raw material was crushed using a Crush Mill (IFM-C20G, manufactured by Iwatani Corporation), passed through a 100 mesh (openings 150 μm) sieve, and then dried in a dryer at 80° C. for 8 hours.

[0177] Table 1 shows the nitrogen, carbon, cellulose, lignin, and hemicellulose contents (mass%), as well as the nitrogen / carbon ratio and hemicellulose / (cellulose + lignin) ratio determined for each raw material.

[0178] [Table 1]

[0179] [Examples I-1 to I-3, Comparative Examples I-1 to I-5] Aliphatic polyester resin (A) and decomposition accelerator were blended in the ratios shown in Table 2, and melt-kneaded for 4 minutes at 170°C under a nitrogen atmosphere using a small twin-screw kneader (DSM's "Xplore Micro 15cc Twin Screw Compounder").

[0180] The resin composition obtained was subjected to the biodegradability test described above, and the results are shown in Table 2.

[0181] [Table 2]

[0182] Table 2 shows that by using the decomposition accelerator I of the present invention, which has a nitrogen / carbon ratio and a hemicellulose / (cellulose + lignin) ratio within a specified range, the biodegradability of biodegradable resins can be greatly improved.

[0183] [Production of Decomposition Accelerator II and Comparative Decomposition Accelerator] Each raw material was crushed using a Crush Mill (IFM-C20G, manufactured by Iwatani Corporation), passed through a 100 mesh (openings 150 μm) sieve, and then dried in a dryer at 80° C. for 8 hours.

[0184] Table 3 shows the nitrogen-free soluble matter, cellulose and lignin contents, and the total (mass%) determined for each raw material.

[0185] [Table 3]

[0186] [Examples II-1 to II-3, Comparative Examples II-1 to II-4] Aliphatic polyester resin (A) and decomposition accelerator were blended in the ratios shown in Table 4, and melt-kneaded for 4 minutes at 170°C under a nitrogen atmosphere using a small twin-screw kneader (DSM's "Xplore Micro 15cc Twin Screw Compounder").

[0187] The resin composition obtained was subjected to the biodegradability test described above, and the results are shown in Table 4.

[0188] [Table 4]

[0189] Table 4 shows that the biodegradability of biodegradable resins can be greatly improved by using the decomposition accelerator II of the present invention, which has a nitrogen-free soluble matter and cellulose and lignin content within a specified range.

[0190] [Production of decomposition accelerator] <50% mass cumulative particle size of 56 μm wheat bran> Coarsely ground wheat bran (manufactured by Showa Sangyo Co., Ltd.) was dried at 80°C for 8 hours to produce wheat bran with a 50% mass cumulative particle size of 56 μm. <50% mass cumulative particle size 35μm wheat bran> Coarsely ground wheat bran (manufactured by Showa Sangyo Co., Ltd.) was dried at 80°C for 8 hours to produce wheat bran with a 50% mass cumulative particle size of 35 μm. <50% mass cumulative particle size 9μm wheat bran> Unground wheat bran (manufactured by Showa Sangyo Co., Ltd.) was pre-ground using a cutter mill until it passed through a sieve with 500 μm openings, and then finely ground using a jet mill grinder ("Nano Jetmizer NJ-50" manufactured by Aisin Nano Technologies Co., Ltd.) at an air pressure of 1.4 MPa and a processing rate of 60 g / h. The bran was then dried at 80°C for 8 hours to produce wheat bran with a 50% mass cumulative particle size of 9 μm.

[0191] The moisture content of all the wheat bran samples with 50% mass cumulative particle sizes of 56 μm, 35 μm, and 9 μm before drying was 8.2% by mass, and the moisture content after drying was 2.3% by mass.

[0192] [Examples III-1 to III-3] As a decomposition accelerator, wheat bran having a 50% mass cumulative particle size of 56 μm, 35 μm, or 9 μm obtained as described above was blended in a ratio of 11.1 parts by mass per 100 parts by mass of the aliphatic polyester resin (A), and the mixture was melt-kneaded at 170°C for 4 minutes in a nitrogen atmosphere using a small twin-screw kneader (DSM's "Xplore Micro 15cc Twin Screw Compounder").

[0193] The resulting resin composition was molded into a film approximately 120 μm thick using a hot press at 170°C, and test specimens were cut out to the shapes specified in the respective test standards. The yield stress, stress at break, Elmendorf tear strength, and puncture impact strength were evaluated as described above. The results are shown in Table 5.

[0194] [Table 5]

[0195] From Table 5, it can be seen that the smaller the 50% mass cumulative particle size, the more improved the mechanical properties of the biodegradable resin molded article.

[0196] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application Nos. 2019-238580 and 2019-238581, filed on December 27, 2019, and is incorporated by reference in its entirety.

Claims

1. A decomposition accelerator for biodegradable resins, comprising cellulose, hemicellulose, and lignin, wherein the mass ratio of nitrogen to carbon in the decomposition accelerator for biodegradable resins is 0.04 or more, and the mass ratio of the hemicellulose content to the total content of cellulose and lignin is 0.2 or more.

2. A decomposition accelerator for biodegradable resins, which contains 20% by mass or more of soluble nitrogen-free substances and has a total content of cellulose and lignin of 50% by mass or less.

3. The decomposition accelerator for biodegradable resins according to claim 1 or 2, which has a moisture content of less than 5% by mass.

4. A biodegradable resin composition comprising 2 parts by mass or more and 250 parts by mass or less of the decomposition accelerator for biodegradable resins according to any one of claims 1 to 3 and 100 parts by mass of a biodegradable resin.

5. The biodegradable resin according to claim 4, wherein the biodegradable resin is at least one selected from the group consisting of an aliphatic polyester resin (A), an aliphatic-aromatic polyester resin (B), and an aliphatic oxycarboxylic acid resin (C). The biodegradable resin composition according to claim 4.

6. 6. The biodegradable resin composition according to claim 5, wherein the aliphatic polyester resin (A) contains, as main structural units, a repeating unit derived from an aliphatic diol and a repeating unit derived from an aliphatic dicarboxylic acid.

7. The biodegradable resin composition according to claim 5 or 6, wherein the aliphatic-aromatic polyester resin (B) contains, as main structural units, a repeating unit derived from an aliphatic diol, a repeating unit derived from an aliphatic dicarboxylic acid, and a repeating unit derived from an aromatic dicarboxylic acid.

8. A biodegradable resin molded article which is an extrusion molded or injection molded article of the biodegradable resin composition according to any one of claims 4 to 7.

9. A method for producing a decomposition accelerator for biodegradable resins, comprising crushing raw materials and then selecting powders of a predetermined particle size from the resulting powder to obtain the decomposition accelerator for biodegradable resins.

10. The method for producing the decomposition accelerator for biodegradable resins according to claim 9, further comprising a drying step.

11. 11. The method for producing a decomposition accelerator for biodegradable resins according to claim 9 or 10, wherein the decomposition accelerator for biodegradable resins contains cellulose, hemicellulose, and lignin, the mass ratio of nitrogen to carbon in the decomposition accelerator for biodegradable resins is 0.04 or more, and the mass ratio of the hemicellulose content to the total content of cellulose and lignin is 0.2 or more.

12. The decomposition accelerator for biodegradable resins according to any one of claims 9 to 11, wherein the decomposition accelerator for biodegradable resins contains 20% by mass or more of soluble nitrogen-free substances and the total content of cellulose and lignin is 50% by mass or less. A method for producing a decomposition accelerator for biodegradable resins according to any one of claims 9 to 11.

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