Biodegradable resin composition for agricultural materials, and agricultural materials

Abstract

To provide a biodegradable resin composition for an agricultural material which achieves both moldability and strength while being biodegradable, and enables manufacture of even a deep type molding with high difficulty, and an agricultural material which is formed from the biodegradable resin composition for the agricultural material or a biodegradable resin.SOLUTION: A biodegradable resin composition for an agricultural material contains a biodegradable resin (A), and has a loss tangent (tan δ) determined by expression 1 of 0.8 to 1.6. The biodegradable resin composition for the agricultural material is formed from a biodegradable resin having a loss tangent (tan δ) determined by expression 1 of 0.8 to 1.6.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a biodegradable resin composition for agricultural materials and an agricultural material. [Background technology]

[0002] Plastic molded products are easy to process and are used in a wide range of fields, including electrical and electronic equipment parts, automobile parts, medical parts, and food containers, and are given physical properties such as strength or mechanical properties depending on the application.In the agricultural materials field, they are used in applications that require water resistance and strength.

[0003] Examples of agricultural materials include mulch films used for purposes such as increasing or maintaining soil temperature and controlling pests, and seedling pots, which are a type of dedicated container for growing seedlings.

[0004] As a solution to the current waste problem and to reduce the work required to collect agricultural materials, there are agricultural materials made from biodegradable materials, which do not need to be collected and can be decomposed underground (in the soil) after use. For farmers, many of whom are elderly, there is an increasing need for biodegradable agricultural materials that do not require the seedlings to be removed from the nursery pots and transplanted after they have grown.

[0005] In addition, there has been a recent demand for the development of biodegradable resin compositions that take moldability into consideration and can be adapted to various shapes, such as deep agricultural materials such as seedling pots.

[0006] As an example of a biodegradable resin agricultural material, Patent Document 1 describes a mulch film that has enhanced biodegradability by containing a biodegradable resin selected from polylactic acid, polybutylene succinate, and polybutylene succinate adipate and a basic filler such as calcium oxide, calcium hydroxide, and calcium carbonate in a specific mass ratio.

[0007] Furthermore, Patent Document 2 discloses an agricultural film that is made of a resin composition in which a biodegradable plasticizer is blended with an aliphatic polyester and has excellent spreading workability.

[0008] Thus, in recent years, in addition to imparting biodegradability to materials, there has been a need for improved flexibility that allows for satisfactory moldability so that materials can be made into various shapes, and studies are being conducted to address this need. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-237764 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-191805 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the resin composition described in Patent Document 1 contains a basic filler that promotes hydrolysis during molding, which affects the moldability of the resin composition, making it difficult to form deep molded objects with a high stretch ratio, such as seedling pots.

[0011] The agricultural film described in Patent Document 2 contains a plasticizer that improves the flexibility of the biodegradable resin and improves formability, but the strength is insufficient and there is a risk of the film tearing when installed.

[0012] As described above, with conventional resin compositions for agricultural materials, it is difficult to produce agricultural materials that use biodegradable resins as the raw materials and that have moldability and sufficient strength. This is a particularly noticeable problem in deep molded articles such as seedling pots.

[0013] The present invention has been made in consideration of the above circumstances, and aims to provide a biodegradable resin composition for agricultural materials that is biodegradable yet has both moldability and strength, and that can even be used to manufacture deep molded objects, which are difficult to manufacture, and an agricultural material formed from the biodegradable resin composition for agricultural materials or a biodegradable resin. [Means for solving the problem]

[0014] In order to solve the above problems, the inventors of the present invention have conducted extensive research and have found that by focusing on the rheological properties of materials and using a resin composition or biodegradable resin whose loss tangent (tanδ) calculated from the storage modulus (G') and loss modulus (G'') measured by dynamic viscoelasticity measurement falls within a specific range, it is possible to obtain agricultural materials that are not only biodegradable but also have good moldability and strength, and have thus completed the present invention.

[0015] That is, one embodiment of the present invention is as follows. <1> A biodegradable resin composition comprising a biodegradable resin (A), The loss tangent (tanδ) calculated by the following formula 1 is 0.8 to 1.6. Biodegradable resin composition for agricultural materials. [Formula 1] Loss tangent (tanδ)=G'' / G' (In Equation 1, G' and G'' are The storage modulus (G') and loss modulus (G'') were measured by dynamic viscoelasticity measurement using a 0.45 mm thick biodegradable sheet formed from the biodegradable resin composition at a temperature [Ta-10] (°C) 10°C lower than the flow initiation temperature [Ta] (°C) of the biodegradable resin (A), a frequency of 1 Hz, and a strain of 5%. <2> The storage modulus (G') is 0.06 to 3.5 MPa. <1> The biodegradable resin composition for agricultural materials described above. <3> The loss modulus (G'') is 2.0 MPa or less. <1> or <2> The biodegradable resin composition for agricultural materials described above. <4> The tensile modulus of elasticity measured on a No. 5 dumbbell specimen prepared in accordance with JIS K6251 at a tension speed of 50 mm / min and a temperature of 23°C was 200 to 1300 MPa. <1> ~ <3> The biodegradable resin composition for agricultural materials according to any one of claims 1 to 4. <5> The tensile strength of a No. 5 dumbbell specimen prepared in accordance with JIS K6251 was measured at a tension speed of 50 mm / min and a temperature of 23°C, and was found to be 20 to 45 MPa. <1> ~ <4> The biodegradable resin composition for agricultural materials according to any one of claims 1 to 4. <6> <1> ~ <5> An agricultural material formed from any one of the biodegradable resin compositions for agricultural materials. <7> An agricultural material formed from a biodegradable resin (Ax), The biodegradable resin (Ax) has a loss tangent (tanδ) calculated by the following formula 1 of 0.8 to 1.6: Agricultural materials. [Formula 1] Loss tangent (tanδ)=G'' / G' (In Equation 1, G' and G'' are The storage modulus (G') and loss modulus (G'') were measured by dynamic viscoelasticity measurement using a 0.45 mm thick biodegradable sheet formed from biodegradable resin (Ax) at a temperature [Ta-10] (°C) 10°C lower than the flow temperature [Ta] (°C) of biodegradable resin (Ax), a frequency of 1 Hz, and a strain of 5%. [Effects of the Invention]

[0016] According to one embodiment of the present invention, it is possible to provide a biodegradable resin composition for agricultural materials that is biodegradable and has both moldability and strength, and an agricultural material.Furthermore, it is possible to provide a biodegradable resin composition for agricultural materials and an agricultural material formed from the biodegradable resin composition for agricultural materials or biodegradable resin, which can be manufactured even into deep molded articles that are difficult to manufacture. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below. Needless to say, other embodiments are also included within the scope of the present invention as long as they are consistent with the spirit of the present invention. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the lower and upper limit values ​​of the range. Furthermore, in this specification, "sheet" and "film" are not distinguished by thickness. In other words, in this specification, "sheet" includes thin film-like materials, and "film" includes thick sheet-like materials. In the present disclosure, the "biodegradable resin composition for agricultural materials" may also be referred to as a "biodegradable resin composition" or a "resin composition." Unless otherwise noted, the various components appearing in this specification may be used independently either alone or in combination of two or more. The numerical values ​​specified in this specification are values ​​determined by the methods disclosed in the embodiments or examples.

[0018] <Biodegradable resin composition> The biodegradable resin composition according to this embodiment is used to form agricultural materials, contains at least a biodegradable resin (A), and has a loss tangent (tan δ) calculated by the following formula 1 of 0.8 to 1.6. [Formula 1] Loss tangent (tanδ)=G'' / G' (In Equation 1, G' and G'' are The storage modulus (G') and loss modulus (G'') were measured by dynamic viscoelasticity measurement using a 0.45 mm thick biodegradable sheet formed from the biodegradable resin composition at a temperature [Ta-10] (°C) 10°C lower than the flow initiation temperature [Ta] (°C) of the biodegradable resin (A), a frequency of 1 Hz, and a strain of 5%.

[0019] Such a resin composition has biodegradability and can achieve both moldability and strength. In terms of formability, it has excellent formability in direct blow molding, such as blow molding and deep pot processability, and also excellent formability of sheets in vacuum molding due to reduced deflection during molding.Furthermore, it can be made to have excellent releasability from a mold.

[0020] The biodegradable resin composition is not particularly limited as long as it contains at least a biodegradable resin (A) and has a loss tangent (tanδ) of 0.8 to 1.6. The biodegradable resin composition may contain, for example, the biodegradable resin (A) and the following components: a flowability modifier (B), starch (C), a plasticizer (D), a basic filler (E), a lubricant (F), an antioxidant (G), and other components. Among these, from the viewpoint of moldability, it is preferable to contain the flowability modifier (B).

[0021] The loss tangent (tanδ) of the biodegradable resin composition is the ratio of the loss modulus (G″) of the biodegradable resin composition to the storage modulus (G′) of the biodegradable resin composition. In other words, when the loss modulus of the biodegradable resin composition is greater than the storage modulus of the biodegradable resin composition, the loss tangent (tanδ) of the biodegradable resin composition expressed by the above formula 1 exceeds 1.

[0022] The biodegradable resin composition of the present invention has a loss tangent (tan δ) of 0.8 to 1.6, preferably 1.0 to 1.3, and more preferably 1.05 to 1.14. When the loss tangent (tan δ) is within this range, it is possible to provide a biodegradable resin composition that can be used to form a molded article having good moldability and strength.

[0023] The loss tangent (tanδ) of the biodegradable resin composition can be determined from the storage modulus (G') and loss modulus (G'') measured by dynamic viscoelasticity measurement using a 0.45 mm thick biodegradable sheet formed from the biodegradable resin composition at a temperature [Ta-10] (°C) 10°C lower than the flow initiation temperature [Ta] (°C) of the biodegradable resin (A), a frequency of 1 Hz, and a strain of 5%. When the biodegradable resin (A) is a mixture of two or more resins, the flow starting temperature [Ta] (°C) of the biodegradable resin (A) after mixing is used as the reference temperature. For the dynamic viscoelasticity measurement, for example, a dynamic viscoelasticity tester, MCR (Modular Compact Rheometer, Anton Paar), can be used.

[0024] For the measurement, a biodegradable sheet having a thickness of 0.45 mm formed from the biodegradable resin composition for agricultural materials is used. For example, a biodegradable sheet having a thickness of 0.45 mm can be obtained by forming the sheet at 200°C using a T-die molding machine.

[0025] From the viewpoints of blow moldability and suppressing deflection during molding, the storage modulus (G') is preferably 0.005 MPa or more, more preferably 0.06 MPa or more, even more preferably 0.07 MPa or more, and particularly preferably 0.10 MPa or more. Also, it is preferably 5.0 MPa or less, more preferably 3.5 MPa or less, even more preferably 2.0 MPa or less, particularly preferably 1.0 MPa or less, and most preferably 0.60 MPa or less.

[0026] From the viewpoint of mold releasability, the loss modulus (G'') is preferably 5.0 MPa or less, more preferably 2.0 MPa or less, even more preferably 1.1 MPa or less, and particularly preferably 0.66 MPa or less. Also, it is preferably 0.01 MPa or more, more preferably 0.06 MPa or more, and even more preferably 0.11 MPa or more.

[0027] When the storage modulus (G') and loss modulus (G'') measured by dynamic viscoelasticity measurement using a 0.45 mm thick biodegradable sheet formed from the biodegradable resin composition at a temperature [Ta-10] (°C) 10°C lower than the flow initiation temperature [Ta] (°C) of the biodegradable resin (A), at a frequency of 1 Hz, and at a strain of 5% each satisfy the above-mentioned ranges, not only is the formability excellent, but the degree of film deflection during molding and releasability from the mold are improved, making it possible to provide a resin composition that can be used to form molded articles with excellent appearance. Preferably, both the storage modulus (G') and the loss modulus (G'') satisfy their respective preferred ranges.

[0028] In this embodiment, the loss tangent in the temperature dependency evaluation of dynamic viscoelasticity is focused on as an evaluation of the thermal properties of the biodegradable resin composition, and by optimizing this parameter, it has been possible to achieve both good moldability and strength as a biodegradable resin composition.

[0029] The loss tangent (tan δ) can be controlled to fall within the above range by adjusting the composition, blending amounts, kneading conditions, etc. during production of the biodegradable resin composition. For example, the kneading conditions can be controlled by carrying out the processing temperature in the range of 100 to 300°C, more preferably 150 to 250°C. The MFR value of the biodegradable resin used is also effective in controlling the loss tangent (tan δ). In the present invention, the MFR value of the biodegradable resin (A) used at 190°C under a load of 2.16 kg is preferably within the range of 0.5 to 20, more preferably 0.5 to 10.

[0030] The biodegradable resin composition preferably has a tensile modulus of 200 to 1300 MPa, more preferably 200 to 1000 MPa, and even more preferably 300 to 1000 MPa, in a No. 5 dumbbell piece prepared in accordance with JIS K6251. When the tensile modulus satisfies the above range, not only is excellent formability achieved, but the degree of deflection of the film during vacuum forming and the tear resistance of the formed seedling pot are improved, making it possible to provide a resin composition that has good processability and strength even in deep seedling pots, which are difficult to form.

[0031] The biodegradable resin composition preferably has a tensile strength of 20 to 45 MPa, more preferably 20 to 39 MPa, and even more preferably 20 to 32 MPa, measured using a No. 5 dumbbell piece prepared in accordance with JIS K6251. If the tensile strength satisfies the above range, not only will the impact resistance of the molded article be excellent, but the resin composition can also provide molded seedling pots with good tear resistance.

[0032] The tensile modulus and tensile strength can be determined, for example, by preparing a No. 5 dumbbell specimen (thickness: 2 mm) using a press in accordance with JIS K6251 using the biodegradable resin composition, and measuring the strength at a tensile speed of 50 mm / min using a universal testing machine (Strograph VE10D) manufactured by Toyo Seiki Seisaku-sho, Ltd. If the tensile modulus and tensile strength satisfy the above ranges, a resin composition with better moldability and strength can be provided.

[0033] The resin composition of the present invention will be described below, but the composition described below is merely an example, and the biodegradable resin composition is not limited to the composition described in this embodiment as long as it satisfies the parameter ranges described in the claims.

[0034] (Biodegradable resin (A)) Biodegradable resins are resins that are decomposed by the action of various microorganisms present in soil or water. The biodegradable resin (A) is not particularly limited, and any commonly available biodegradable resin can be used. Examples include biodegradable polyester resins and other biodegradable resins such as polycaprolactone. Examples of biodegradable polyester resins include aliphatic polyester resins and aliphatic aromatic polyester resins. From the viewpoint of moldability of the resin composition, it is preferable that the resin composition contains an aliphatic polyester resin, and more preferably contains an aliphatic polyester resin and an aliphatic aromatic polyester resin. In this case, the respective contents are preferably 50 to 85 mass% of the aliphatic polyester resin and 15 to 50 mass% of the aliphatic aromatic polyester resin, based on 100 mass% of the total amount of the resin composition. When the blending ratio of the aliphatic polyester resin to the aliphatic aromatic polyester resin is within this range, significant sagging of the biodegradable sheet due to heating is suppressed, and the moldability of the seedling pot is improved. The biodegradable resin (A) may be used either alone or in combination of two or more.

[0035] The flow starting temperature [Ta] (°C) of the biodegradable resin (A) is preferably within the range of 60 to 170°C, more preferably 110 to 150°C. A temperature of 60°C or higher shortens the cooling time required for the molded body to solidify, resulting in superior productivity. A temperature of 170°C or lower provides good fluidity during molding, making it easy to produce deep molded bodies, which is preferable from the standpoint of moldability. When a mixture of multiple biodegradable resins (A) is used, the flow initiation temperature of the mixed biodegradable resins is used as the reference temperature.

[0036] The biodegradable resin (A) preferably has a melt flow rate (MFR) value within the range of 0.5 to 20 at 190°C under a load of 2.16 kg, more preferably 0.5 to 10. When the ratio is 20 or less, drawdown during molding can be suppressed and the occurrence of molding defects can be further reduced. When the ratio is 0.5 or more, the flowability during molding is high and the flexibility is excellent, making it easier to form deep molded bodies. When the biodegradable resin (A) contains two or more kinds of biodegradable resins, the MFR value of the mixture is preferably within the above range.

[0037] [Biodegradable polyester resin] Examples of biodegradable polyester resins include biodegradable aliphatic polyester resins and biodegradable aliphatic aromatic polyester resins.

[0038] "Biodegradable aliphatic polyester resin" Examples of biodegradable aliphatic polyester resins include aliphatic polyesters obtained by polycondensation of aliphatic diols and aliphatic dicarboxylic acids, and polylactic acids obtained by polycondensation of lactic acid. Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. These may be used alone or in mixtures. Of these, 1,4-butanediol is preferred. Examples of aliphatic dicarboxylic acids include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, and dodecanedioic acid, and acid anhydrides derived from these may also be used. Of these, succinic acid or succinic anhydride, or a mixture of these with adipic acid, is preferred.

[0039] Specific examples include polybutylene succinate (PBS) obtained from 1,4-butanediol and succinic acid (for example, "BioPBS" (trade name) manufactured by PPT MCC Biochem), polybutylene succinate adipate (PBSA) obtained by copolymerizing PBS with adipic acid (for example, "BioPBS" (trade name) manufactured by PPT MCC Biochem), polycaprolactone (PCL) obtained by ring-opening polymerization of ε-caprolactone obtained by oxidizing cyclohexane with an oxidizing agent such as peracetic acid (for example, "Placcel H Series" (trade name) manufactured by Daicel Corporation), polylactic acid (PLA) (for example, "Lacia" (trade name) manufactured by Mitsui Toatsu Chemicals Inc.), and polyglycolic acid (PGA) (for example, "Kuredux" (trade name) manufactured by Kureha Corporation).

[0040] "Biodegradable aliphatic aromatic polyester resin" Examples of biodegradable aliphatic-aromatic polyester resins include copolymers containing aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and linear aliphatic and / or alicyclic diol units. The diol component that provides the diol unit usually has 2 to 10 carbon atoms, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, etc. Among these, diols having 2 to 4 carbon atoms are preferred, ethylene glycol and 1,4-butanediol are more preferred, and 1,4-butanediol is even more preferred. The dicarboxylic acid component that provides the dicarboxylic acid unit typically has 2 to 10 carbon atoms, and examples thereof include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Of these, succinic acid or adipic acid is preferred. Examples of aromatic dicarboxylic acid components that provide the aromatic dicarboxylic acid unit include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Of these, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is more preferred.

[0041] Specific examples include polybutylene adipate terephthalate (PBAT), which is a copolymer of 1,4-butanediol, adipic acid, and terephthalic acid (for example, "Ecoflex" (trade name) manufactured by BASF Co., Ltd.).

[0042] [Other biodegradable resins] Other biodegradable resins include aliphatic polyamides and polyamino acids.

[0043] (Flow improver (B)) The biodegradable resin composition of the present invention may contain a flowability modifier (B). The flowability modifier (B) is a viscosity adjuster that adjusts the viscosity of the biodegradable resin composition to improve moldability, and has the function of increasing the melt tension of the biodegradable resin composition, which is an indicator of moldability. The flowability modifier (B) is preferably selected as needed from the group consisting of carbodiimide compounds, oxazoline compounds, epoxy compounds, acid anhydride compounds, cellulose fibers, and fillers such as silica-based fillers.

[0044] When the flowability modifier (B) is contained, its content is preferably more than 0% by mass and not more than 5% by mass, more preferably not more than 2% by mass, even more preferably not more than 1.4% by mass, and particularly preferably not more than 0.8% by mass, based on 100% by mass of the biodegradable resin composition.

[0045] When the flowability modifier (B) is a polyfunctional compound, it can form a crosslinked structure with the biodegradable resin (A) to increase the melt tension of the resin composition, thereby further improving moldability. Examples of polyfunctional compounds include polyfunctional carbodiimide compounds, polyfunctional oxazoline compounds, epoxy compounds, and acid anhydride compounds. The polyfunctional carbodiimide compound may be a monomer or polymer having two or more carbodiimide groups, but a polymer having two or more carbodiimide groups is preferred.

[0046] When the flowability modifier (B) is a reactive compound, a reactive group can be introduced into the biodegradable resin (A), and a crosslinking structure can be formed from this reactive group, thereby increasing the melt tension of the resin composition. Examples of the reactive compound include carbodiimide compounds, oxazoline compounds, epoxy compounds, and acid anhydride compounds. It is preferable to use a cyclic carbodiimide as the carbodiimide compound. A cyclic carbodiimide compound is a compound having a carbodiimide group on an aliphatic or aromatic ring.

[0047] When a filler is used as the flowability modifier (B), the solid content of the resin composition is increased to improve the flowability, thereby increasing the melt tension of the resin composition. This improves the moldability. The filler may be either an organic filler or an inorganic filler, such as cellulose fiber or silica-based filler.

[0048] In one embodiment, compounds listed on the positive list of biodegradable plastics can be used, such as cellulose microfiber (CMF), which is a cellulose fiber, and carbodiimide compounds (CDI). Cellulose microfiber refers to relatively large cellulose fibers obtained by treating pulp with hot water or the like, hydrolyzing and weakening it, and then reducing the number of defibration steps in the cellulose defibrated by a pulverization method such as a high-pressure homogenizer. The inclusion of cellulose microfiber and a carbodiimide compound increases the viscosity of the resin composition and ensures strength.

[0049] That is, when a resin composition contains cellulose microfibers, the strength of the resin composition is increased due to the filler effect of the cellulose microfibers. Furthermore, since the silica-based filler has the same filler effect as the cellulose microfibers, it also increases the strength of the resin composition in the same way as the cellulose microfibers.

[0050] When a carbodiimide compound is contained in a resin composition, the resin reacts with the carbodiimide compound, increasing the molecular weight of the resin. Therefore, in the case of agricultural materials where strength is required of the resin composition, it is preferable to contain a carbodiimide compound as the flowability modifier (B). In addition, oxazoline compounds, epoxy compounds, and acid anhydride compounds also have reactivity with resins similar to that of carbodiimide compounds, and therefore can also improve the strength of the resin composition.

[0051] Examples of carbodiimide compounds include polycarbodiimide compounds such as "Carbodilite HMV-15CA (trade name)" manufactured by Nisshinbo Chemical Inc.; monocarbodiimides such as dicyclohexylcarbodiimide, diphenylcarbodiimide, di-β-naphthylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, and di-t-butylcarbodiimide; and cyclic carbodiimide compounds such as "Carbodista TCC-NP" (trade name) manufactured by Teijin Limited. These compounds may be used alone or in combination.

[0052] Examples of oxazoline compounds include "Epocross RA-45" (trade name) and "Epocross RPS-1005" (trade name) manufactured by Nippon Shokubai Co., Ltd. These compounds may be used alone or in combination. Examples of epoxy compounds include epoxy-acrylic compounds ("JONCRYL ADR-4468" (trade name), "JONCRYL ADR-4400" (trade name), manufactured by BASF, "ALFON UG-4040" (trade name), manufactured by Toagosei Co., Ltd., and "ALFON UG-4070" (trade name), manufactured by Toagosei Co., Ltd.). These compounds may be used alone or in combination of two or more.

[0053] Examples of acid anhydride compounds include styrene-maleic anhydride compounds ("XIBOND series" (trade name) manufactured by Palmer Holland) and "XIRAN series" (trade name) manufactured by Tomoe Engineering Co., Ltd. These compounds may be used alone or in combination of two or more. Examples of silica-based fillers include silica fillers ("Aerosil Series" (trade name) manufactured by Nippon Aerosil Co., Ltd.) and "Nipsil Series" (trade name) manufactured by Tosoh Silica Corporation. These may be used alone or in combination of two or more types.

[0054] (starch) The biodegradable resin composition of the present invention may contain starch. Starch has the function of promoting the activity (biodegradability) of various microorganisms present in soil or water. The starch is not particularly limited, and commonly available starches can be used, such as corn starch, wheat starch, rice starch, potato starch, sweet potato starch, and tapioca starch.

[0055] When starch is contained, the content is preferably more than 0% by mass and not more than 30% by mass, more preferably not more than 20% by mass, and even more preferably not more than 15% by mass, based on 100% by mass of the biodegradable resin composition. By keeping the content at 15% by mass or less, biodegradability can be promoted while maintaining good deflection during molding and good releasability from a mold.

[0056] (plasticizer) The biodegradable resin composition of the present invention may contain a plasticizer. The plasticizer has the function of suppressing stickiness on the surface of the resulting molded article while ensuring good moldability. Examples of plasticizers include alcohols, which are organic compounds having a hydroxyl group, such as glycerin, glycerin monoester, ethylene glycol, and diethylene glycol.

[0057] When a plasticizer is contained, the content thereof is preferably more than 0% by mass and not more than 20% by mass, more preferably not more than 15% by mass, and even more preferably not more than 10% by mass, based on 100% by mass of the biodegradable resin composition. By having the content be 10% by mass or less, significant sagging of the biodegradable sheet is suppressed, and better moldability can be ensured while maintaining the strength of the molded product.

[0058] (basic filler) The biodegradable resin composition of the present invention may contain a basic filler. The basic filler has the function of promoting the hydrolysis of the biodegradable resin. Examples of basic fillers include basic compounds containing alkali metals or alkaline earth metals. Specific examples include calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, and magnesium hydroxide. Other examples include talc, which is made of hydrated magnesium silicate. From the viewpoint of the balance between biodegradability and moldability, the pH is preferably 9.0 to 11.0.

[0059] When a basic filler is contained, its content is preferably more than 0% by mass and not more than 30% by mass, more preferably not more than 20% by mass, and even more preferably not more than 15% by mass, based on 100% by mass of the biodegradable resin composition. A content of not more than 15% by mass is preferred because it promotes biodegradability without impairing the formability of a biodegradable sheet made from the biodegradable resin composition.

[0060] (lubricant) The biodegradable resin composition of the present invention may contain a lubricant. The lubricant has the function of improving the releasability from the mold and ensuring good moldability. Examples of lubricants include magnesium stearate (e.g., "Magnesium Stearate NP-1500" (trade name) manufactured by Tannan Chemical Industry Co., Ltd.), polyethylene wax (e.g., "Fatty Acid Amide Series" (trade name) manufactured by Kao Corporation), paraffin wax (e.g., "Paraffin Wax Series" (trade name) manufactured by Nippon Seiro Co., Ltd.), and fatty acid ester (e.g., "Likestar Series" (trade name) manufactured by Riken Vitamin Co., Ltd.). These may be used alone or in combination of two or more.

[0061] When a lubricant is contained, the content thereof is preferably more than 0% by mass and not more than 5% by mass, more preferably not more than 1% by mass, and even more preferably not more than 0.5% by mass, based on 100% by mass of the biodegradable resin composition. By having the content not more than 0.5% by mass, it is possible to further improve the releasability from the mold while suppressing poor adhesion of the biodegradable resin composition to the molding machine.

[0062] (antioxidant) The biodegradable resin composition of the present invention may contain an antioxidant. The antioxidant has the function of suppressing deterioration of the biodegradable resin during processing. Examples of antioxidants include phenol-based antioxidants (for example, "Sumilizer GA-80" (trade name) manufactured by Sumitomo Chemical Co., Ltd.), and phosphorus-based antioxidants (for example, "ADEKA STAB PEP series" (trade name) manufactured by ADEKA Corporation).

[0063] When an antioxidant is contained, the content thereof is preferably more than 0% by mass and not more than 5% by mass, more preferably not more than 3% by mass, and even more preferably not more than 1% by mass, based on 100% by mass of the biodegradable resin composition. By having the content be not more than 1% by mass, it is possible to prevent significant sagging of the biodegradable sheet while further suppressing deterioration of the biodegradable resin.

[0064] (Other ingredients) The resin composition may optionally contain other components such as additives as needed. Examples of additives include dispersants, hydrotalcites, surfactants, antistatic agents, flame retardants, UV absorbers, fillers, and pigments. The selection and amount of other optional components are not particularly limited as long as they are within a range that can solve the problems of one embodiment of the present invention. Multiple additives may be used in combination. Furthermore, the resin composition may partially contain a resin other than the biodegradable resin (A) within a range that does not impair the effects of one embodiment of the present invention.

[0065] (Method of producing resin composition) The resin composition of this embodiment can be produced, for example, by kneading the biodegradable resin (A) with other optional components at a temperature at which the biodegradable resin (A) melts. Specifically, for example, the biodegradable resin (A) is mixed with various additives, such as a flowability modifier (B), if necessary, and melt-kneaded using a kneader, roll mill, supermixer, high-speed mixer, ball mill, sand mill, attritor, or a batch mixer such as a Banbury mixer, a single-screw extruder, a twin-screw extruder, or a rotor-type twin-screw kneader to produce a pellet-shaped, powder-shaped, granular, or bead-shaped resin composition. Because of its strong kneading power and ease of subsequent molding, pelletization using a single-screw or twin-screw extruder is preferred.

[0066] The biodegradable resin composition can be used as a compound to produce agricultural materials by the method described below. The biodegradable resin composition may be directly compounded. Alternatively, after producing a masterbatch, the same biodegradable resin (A) as used in producing the masterbatch may be blended with the masterbatch as a diluent resin, serving as the main component of the agricultural material, to produce a resin composition. If the loss tangent (tanδ) of the resin composition calculated by Equation 1 is 0.8 to 1.6, the biodegradable resin (A) used as the diluent may be the same as or different from that used in producing the masterbatch. Using the same biodegradable resin is preferred because it provides excellent compatibility between biodegradable resins.

[0067] <Agricultural materials> The agricultural material of this embodiment is a molded article obtained by molding the above-mentioned biodegradable resin composition.

[0068] The agricultural material of this embodiment can be obtained by molding a biodegradable resin (Ax) having a loss tangent (tanδ) of 0.8 to 1.6, as expressed in Formula 1. As long as the biodegradable resin (Ax) has a loss tangent (tanδ) of 0.8 to 1.6, the biodegradable resin (A) may be a single biodegradable resin (A) or a mixture of two or more biodegradable resins (A) such that the loss tangent (tanδ) falls within the above range. In this case, the agricultural material can be formed solely from a biodegradable resin (Ax) having a loss tangent (tan δ) expressed by formula 1 of 0.8 to 1.6. The loss tangent (tan δ) of the biodegradable resin (Ax) is preferably 1.0 to 1.3, more preferably 1.05 to 1.14. When the loss tangent (tan δ) is within this range, it is possible to provide agricultural materials that have both moldability and strength. When one type of biodegradable resin (A) is used, the biodegradable resin (A) corresponds to the biodegradable resin (Ax).

[0069] In addition, the storage modulus (G'), loss modulus (G''), tensile modulus, and tensile strength of the biodegradable resin (Ax) are preferably within the same ranges as those described above for the biodegradable resin composition.

[0070] When an agricultural material is molded from a biodegradable resin composition having a loss tangent (tanδ) represented by formula 1 of 0.8 to 1.6, the loss tangent (tanδ) of the biodegradable resin (A) may or may not be 0.8 to 1.6.

[0071] Examples of agricultural materials include seedling pots, mulch films, containers, and agricultural nets. The agricultural material of this embodiment can achieve both moldability and strength in addition to biodegradability, even in the case of deep molded articles with a high stretch ratio, such as seedling pots and plug trays. The deep molded body referred to here is a molded body whose depth is longer than its width.

[0072] (seedling pot) Seedling pots are pots used to grow seedlings in containers until they reach a certain stage of maturity, rather than sowing seeds directly in a field. The agricultural material of this embodiment biodegrades appropriately in soil, so there is no need to remove the seedlings from the seedling pots and transplant them after they have grown; they can be transplanted into soil in their seedling pots.

[0073] The seedling pots biodegrade after being buried in the soil, so they do not harm the natural environment and reduce the labor required to remove the seedlings from the pots and sow them. The seedling pots allow the seeds to grow well without decomposing for the approximately 2-4 months that they are grown in before being buried in the soil. Furthermore, because the seedling pots have the strength required for seedling raising, they are easy to handle and can maintain their proper shape throughout the seedling raising period.

[0074] The method for molding and processing the seedling pots is not particularly limited, but suitable methods include blow molding, in which a heated and plasticized resin composition or biodegradable resin (Ax) is extruded and then placed directly into a mold without being cooled and solidified, and air is blown into it, and vacuum molding, in which a sheet or film of a heated and plasticized resin composition is placed on a mold and vacuum-suctioned from the inside of the mold to form the resin.

[0075] (Multi-film) A mulch film (mulching film) is a film for covering the base of a crop. The method for molding the resin composition or biodegradable resin (Ax) into a film is not particularly limited, but suitable methods include extrusion molding in which a film extruded through a T-die using an extruder is cooled and solidified with a cast roll, or molding using an inflation molding machine.

[0076] (Method of manufacturing a molded body) The agricultural material of this embodiment can be obtained by molding the above-mentioned biodegradable resin composition for agricultural materials or the biodegradable resin (Ax) by blow molding, vacuum molding, injection molding, or the like. Both moldability and strength can be achieved by using a biodegradable resin composition for agricultural materials or an agricultural material formed from a biodegradable resin (Ax) whose loss tangent (tanδ) calculated by Equation 1 is 0.8 to 1.6. This also makes it possible to suppress deflection during molding of the biodegradable sheet (the phenomenon in which a preformed resin cannot withstand its own weight and sags in the direction of gravity).

[0077] The biodegradable resin composition or biodegradable resin (Ax) of this embodiment can be blow molded, and in the case of blow molding, it is possible to prevent the molded article from becoming thin and light. For the blow molding, for example, a direct blow molding machine can be used.

[0078] For example, when three sets of two seedling pots are produced in succession using a direct blow molding machine, the difference in weight between the first set and the third set can be less than 30% of the weight of the first set of seedling pots. Furthermore, the weight of each seedling pot is preferably 0.7 g or more but less than 0.8 g, more preferably 0.8 g or more but less than 0.9 g, and even more preferably 0.9 g or more. By using the biodegradable resin composition or biodegradable resin (Ax) described above, excellent blow moldability can be achieved.

[0079] The agricultural material of the present invention is biodegradable and combines moldability and strength, making it possible to produce even deep molded bodies that are difficult to produce, such as those with an aspect ratio (height / diameter) of 0.70 or more. [Example]

[0080] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples. In the examples and comparative examples, "parts" and "%" represent "parts by mass" and "mass%" respectively, unless otherwise specified. In addition, the compounding amounts in the table are shown in parts by mass. The blanks in the table indicate that they are not compounded. In addition, each measurement method is as follows.

[0081] <MFR Measurement> The melt flow rate (MFR) of the biodegradable resin produced in the synthesis example was measured at 190 °C and a load of 2.16 kg using a melt indexer (F-B01) manufactured by Toyo Seiki Co., Ltd.

[0082] <Flow Initiation Temperature Measurement> In accordance with JIS K721, the flow initiation temperature was measured using a flow tester. Specifically, using a thermal fluidity evaluation apparatus CFT-500D (manufactured by Shimadzu Corporation), the temperature at which the melt viscosity of the biodegradable resin becomes 4800 Pa·s or less when passing through a capillary with a die hole diameter of φ1 mm and a die length of 1 mm under a pressure of 9.8 MPa was defined as the flow initiation temperature [Ta] (°C).

[0083] <Dynamic Viscoelasticity Measurement> Using a dynamic viscoelasticity tester MCR (Modular Compact Rheometer, Anton Paar), the storage modulus (G') and loss modulus (G'') were measured respectively.

[0084] In addition, using the values of the storage modulus and loss modulus, the loss tangent (tanδ) represented by the following formula 1 was calculated. [Formula 1] ​​​​​The storage modulus (G') and loss modulus (G'') were measured by dynamic viscoelasticity measurement using a 450 μm thick biodegradable sheet formed from the biodegradable resin composition or biodegradable resin (Ax) at a temperature [Ta-10] (°C) 10°C lower than the flow initiation temperature [Ta] (°C) of the biodegradable resin (A) or biodegradable resin (Ax), at a frequency of 1 Hz, and at a strain of 5%.

[0085] <Tensile modulus measurement> No. 5 dumbbell specimens were prepared using the biodegradable resin composition or the biodegradable resin (Ax) in accordance with JIS K6251, and the tensile modulus was measured using a universal testing machine (Strograph VE10D) manufactured by Toyo Seiki Seisaku-sho, Ltd., at a temperature of 23°C, a relative humidity of 50%, and a pulling speed of 50 mm / min.

[0086] The materials used are listed below. (Flow improver (B)) B-1: ARBOCEL BE600-30 (Rettenmeyer, cellulose microfiber, average fiber length: 30 μm) B-2: Epocross RA-45 (Nippon Shokubai Co., Ltd., oxazoline compound)

[0087] (starch) C-1: Chemistar 420 (Glico Nutrition Foods Co., Ltd., corn-derived starch, average particle size: 15 μm) (plasticizer) D-1:DG (NOF Corporation, polyhydric alcohol, glycerin) (basic filler) E-1: KS-1300 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0) (lubricant) F-1: Fatty acid amide S (Kao Corporation) (antioxidant) G-1: Sumilizer GA-80 (phenolic antioxidant, manufactured by Sumitomo Chemical Co., Ltd.)

[0088] <Production of biodegradable resin> [Synthesis Example 1: Production of PBS resin (biodegradable resin (A-1))] (Esterification reaction) A 2-liter SUS304 reactor equipped with a condenser, a stirrer, and a nitrogen inlet was charged with 460 parts by mass of 1,4-butanediol (BDO), 100 parts by mass of succinic acid (SA), 1.0 part by mass of glycerol (GC), 1.0 part by mass of tetra-n-butyl titanate (TBT), and 0.1 part by mass of phosphorous acid (PPA), and the contents were stirred to produce a composition for producing a biodegradable polyester resin. The composition for producing a biodegradable polyester resin was heated to 200°C and reacted for 1.5 hours with stirring in a nitrogen atmosphere. (Condensation polymerization reaction) Next, the reaction vessel was heated to 240°C under a vacuum of 1 torr or less, and the reaction was allowed to proceed for 3 hours. The contents of the reaction vessel were then discharged, cooled to 5°C, and cut with a pellet cutter to obtain pellets of biodegradable resin (A-1). The biodegradable resin (A-1) was polybutylene succinate (PBS), and had an MFR of 5.0 g / 10 min at 190°C under a load of 2.16 kg, and a flow-initiation temperature of 115°C.

[0089] [Synthesis Example 2: Production of PBS resin (biodegradable resin (A-2))] (Esterification reaction) A 2 L SUS304 reactor equipped with a condenser, stirrer, and nitrogen inlet was charged with 370 parts by mass of 1,4-butanediol (BDO), 100 parts by mass of succinic acid (SA), 1.0 part by mass of glycerol (GC), 1.0 part by mass of tetra-n-butyl titanate (TBT), and 0.1 part by mass of phosphorous acid (PPA), and the contents were stirred to produce a composition for producing a biodegradable polyester resin. The composition for producing a biodegradable polyester resin was heated to 200°C and reacted for 1.5 hours with stirring in a nitrogen atmosphere. (Condensation polymerization reaction) Next, the reaction vessel was heated to 240°C under a vacuum of 1 torr or less, and the reaction was allowed to proceed for 8 hours. After that, the contents of the reaction vessel were discharged, cooled to 5°C, and cut with a pellet cutter to obtain pellets of biodegradable resin (A-2). The biodegradable resin (A-2) was polybutylene succinate (PBS), and had an MFR of 0.5 g / 10 min at 190°C under a load of 2.16 kg, and a flow-initiation temperature of 150°C.

[0090] [Synthesis Example 3: Production of PBAT resin (biodegradable resin (A-3))] (Esterification reaction) A 2 L SUS304 reactor equipped with a condenser, a stirrer, and a nitrogen inlet was charged with 190 parts by mass of 1,4-butanediol (BDO), 100 parts by mass of adipic acid (AA), and 6.0 x 10 parts of glycerol (GC). -3 Parts by mass of tetra-n-butyl titanate (TBT) 2.0 x 10 -3 Parts by mass and phosphorous acid (PPA) 5.0 x 10 -4 A mixture was prepared by adding 230 parts by weight of terephthalic acid (TPA) to the reactor. The mixture was then heated to 230°C and reacted under stirring in a nitrogen atmosphere until 95% or more of the theoretical amount of water was released. The water produced was then completely discharged outside the system via a condenser. Next, 230 parts by weight of terephthalic acid (TPA) was added to the reactor, and the mixture was reacted at 230°C for 2 hours under stirring. (Condensation polymerization reaction) Next, the reaction vessel was heated to 250°C under a vacuum of 2 torr or less, and the reaction was allowed to proceed for 6 hours. After that, the contents of the reaction vessel were discharged, cooled to 5°C, and cut with a pellet cutter to obtain pellets of biodegradable resin (A-3). The biodegradable resin (A-3) was polybutylene adipate terephthalate (PBAT), and had an MFR of 2.9 g / 10 min at 190°C under a load of 2.16 kg, and a flow-initiation temperature of 120°C.

[0091] [Synthesis Example 4: Production of PLA resin (biodegradable resin (A-4))] (Production of poly-L-lactic acid) 100 parts by mass of L-lactide was added to a 2 L SUS304 reactor equipped with a stirrer, a thermometer, and a nitrogen inlet. The system was purged with nitrogen, and then 2.8 x 10 parts of ethylene glycol was added. -4 parts by mass, 1.0 x 10 stannous octylate as catalyst -4Parts by mass were added, and polymerization was carried out for 3 hours at 190° C. to produce poly-L-lactic acid. The weight-average molecular weight of the obtained poly-L-lactic acid was 400,000. (Production of poly-D-lactic acid) 100 parts by mass of D-lactide was added to a 2 L SUS304 reactor equipped with a stirrer, a thermometer, and a nitrogen inlet. The system was purged with nitrogen, and then 2.8 x 10 parts of ethylene glycol was added. -4 parts by mass, 1.0 x 10 stannous octylate as catalyst -4 Parts by mass were added and polymerization was carried out for 2 hours at 190° C. Poly-D-lactic acid was produced. The weight-average molecular weight of the resulting poly-D-lactic acid was 400,000. (Production of polylactic acid) Equal amounts of poly-L-lactic acid and poly-D-lactic acid were mixed in a reactor, and after replacing the atmosphere with nitrogen, the contents of the reactor were heated to 260°C and stirred for 1 hour. The contents were then discharged, cooled to 5°C, and cut with a pellet cutter to obtain pellets of biodegradable resin (A-4). The biodegradable resin (A-4) was polylactic acid (PLA), and had a MFR of 3.0 g / 10 min at 190°C and a load of 2.16 kg, and a flow-initiation temperature of 170°C.

[0092] [Example 1] As the biodegradable resin (A), 73.6 parts by mass of biodegradable resin (A-1), 25 parts by mass of biodegradable resin (A-3), and 1.4 parts by mass of flowability modifier (B-1) were mixed, extruded at 210°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain a pellet-shaped biodegradable resin composition (P-1). The flow starting temperature of the biodegradable resin (A) was 115°C. Using the obtained biodegradable resin composition (P-1), five sets of two seedling pots 1 (diameter 9 cm, height 8 cm) were continuously produced at 150°C using a direct blow molding machine (manufactured by Nippon Placon Co., Ltd.). Separately, using the biodegradable resin composition (P-1) obtained separately, seedling pots 2 (diameter 9 cm, height 8 cm) were made at 150°C in a vacuum forming machine (manufactured by Fuse Vacuum Co., Ltd.).

[0093] [Examples 2 to 7, Comparative Examples 1 to 3] Biodegradable resin compositions (P-2 to 7, P'-1 to 3) were obtained in the same manner as in Example 1, except that the compositions and blending amounts (parts by mass) were changed to those shown in Table 1. Next, using the obtained biodegradable resin composition, seedling raising pot 1 was obtained by blow molding and seedling raising pot 2 by vacuum molding in the same manner as in Example 1.

[0094] [Example 8] 56 parts by mass of biodegradable resin (A-1), 20 parts by mass of biodegradable resin (A-2), and 24 parts by mass of biodegradable resin (A-3) were mixed, extruded at 210°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain pelletized biodegradable resin (Ax-1). The flow starting temperature of the biodegradable resin (Ax-1) was 120°C. Using the obtained biodegradable resin (Ax-1), five sets of two seedling pots 1 (diameter 9 cm, height 8 cm) were continuously produced at 150°C using a direct blow molding machine (manufactured by Nippon Placon Co., Ltd.). Separately, using the biodegradable resin (Ax-1) obtained separately, seedling pots 2 (diameter 9 cm, height 8 cm) were made at 150°C in a vacuum forming machine (manufactured by Fuse Vacuum Co., Ltd.).

[0095] [Examples 9 to 19, Comparative Example 4] Biodegradable resins (Ax-2 to 12, Ax'-1) were obtained in the same manner as in Example 8, except that the compositions and blending amounts (parts by mass) were changed to those shown in Table 2. Next, using the obtained biodegradable resin (Ax) and the like, seedling raising pot 1 was obtained by blow molding and seedling raising pot 2 by vacuum molding in the same manner as in Example 8.

[0096] [Example 20] Using biodegradable resin (A-2) as biodegradable resin (Ax-13), five sets of two seedling pots 1 (diameter 9 cm, height 8 cm) were continuously produced at 150°C using a direct blow molding machine (manufactured by Nippon Placon Co., Ltd.). Separately, using the biodegradable resin (A-2) as the biodegradable resin (Ax-12), seedling pot 2 (diameter 9 cm, height 8 cm) was produced at 150°C in a vacuum forming machine (manufactured by Fuse Vacuum Co., Ltd.).

[0097] <<Measurement and evaluation of physical properties of biodegradable resin compositions and agricultural materials>> Measurement and evaluation of the physical properties of the biodegradable resin composition and agricultural materials of the present invention were carried out by the following methods. The results are shown in Tables 1 and 2. The more + marks in the evaluation criteria, the better the results. The flow starting temperature (°C) in Tables 1 and 2 is the flow starting temperature [Ta] (°C) of the biodegradable resin (A) or the biodegradable resin (Ax).

[0098] (Preparation of biodegradable sheets) Using the biodegradable resin composition, biodegradable resin (Ax), or biodegradable resin (Ax'), a biodegradable sheet having a length of 30 cm, a width of 30 cm, and a thickness of 0.45 mm was obtained at 200°C in a T-die molding machine.

[0099] (Preparation of test specimens for measuring physical properties) Using the biodegradable resin composition, the biodegradable resin (Ax), or the biodegradable resin (Ax'), a No. 5 dumbbell piece was prepared in accordance with JIS K6251. Specifically, the material was pressed into a sheet having a thickness of 2 mm at 200° C. and 10.5 MPa using a press molding machine (manufactured by Iwaki Kogyo Co., Ltd.), and then cut out to obtain a dumbbell-shaped test piece.

[0100] <Blow molding> The blow moldability was evaluated based on the weight of each of 10 seedling pots 1 produced by direct blow molding. The heavier the seedling pots that could be blow molded, the less likely they were to break, and the better the blow moldability of the resin composition. The evaluation criteria were as follows, with +++, ++ and + being considered usable. [Evaluation criteria] +++: In 6 or more seedling pots out of 10, Each piece weighs 0.9g or more ++: In 6 or more seedling pots out of 10, Each piece weighs between 0.7g and 0.9g +: In 6 or more seedling pots out of 10, Each piece weighs between 0.5g and 0.7g NG: In 5 or more seedling pots out of 10, Each piece weighs less than 0.5g

[0101] <Deep pot workability evaluation> Using the biodegradable resin composition, biodegradable resin (Ax), or biodegradable resin (Ax'), seedling pots with different aspect ratios (height / diameter) were fabricated at 150°C using one of three molds of different sizes in a vacuum forming machine (manufactured by Fuse Vacuum Co., Ltd.). The aspect ratio of the pot shape obtained without any molding defects such as breakage during molding was used to evaluate the deep pot processability. The larger the aspect ratio (height / diameter), the better the deep pot processability. In this evaluation, "deep" refers to a seedling pot with an aspect ratio of 0.70 or greater after molding. The mold sizes used were mold 1 (10 cm diameter, 8.5 cm height), mold 2 (10 cm diameter, 7.5 cm height), and mold 3 (10 cm diameter, 7.0 cm height). The evaluation criteria were as follows, with +++, ++ and + being considered usable. [Evaluation criteria] +++: Molding was possible using mold 1 (aspect ratio 0.85). ++: Poor molding was achieved with mold 1, but molding was possible with mold 2 (aspect ratio 0.75). +: Molding was poor with mold 2, but molding was possible with mold 3 (aspect ratio 0.70). NG: Unable to mold even with mold 3.

[0102] <Releaseability evaluation> Ten seedling pots 2 were produced by vacuum molding, and the releasability of the molded bodies from the mold was evaluated. The more easily the molded bodies could be peeled off, the better the releasability. The evaluation criteria were as follows, with +++, ++ and + being considered usable. [Evaluation criteria] +++: All 10 pieces can be easily removed from the mold. ++: 1 to 2 out of 10 pots adhere to the mold, and the shape of the seedling pot is distorted when peeled off. +: 3 to 4 out of 10 pots adhered to the mold, and the shape of the seedling pots was distorted when they were peeled off. NG: Five or more out of ten pieces adhere to the mold, and the shape of the seedling pot is distorted when peeled off.

[0103] <Evaluation of deflection during molding> The formability of the biodegradable sheet during vacuum forming was evaluated based on the deflection during forming. First, a biodegradable sheet produced using a T-die molding machine was placed on the stage of a vacuum molding machine. Then, during heat molding, the contact surface of the biodegradable sheet was used as the reference plane, and the sagging distance from the reference plane was evaluated. If the sagging distance was too small, the biodegradable sheet would not stretch well and the shape of the mold could not be transferred. On the other hand, if the sagging distance was too large, wrinkles would occur due to drawdown, resulting in a defective molded product. The evaluation criteria were as follows, with +++, ++ and + being considered usable. [Evaluation criteria] +++: The hanging distance of the biodegradable sheet from the reference plane is 5 mm or more but less than 10 mm ++: The hanging distance of the biodegradable sheet from the reference plane is 4 mm or more but less than 5 mm, or 10 mm or more but less than 25 mm +: The hanging distance from the reference plane of the biodegradable sheet is 3 mm or more but less than 4 mm, or 25 mm or more but less than 40 mm NG: The hanging distance of the biodegradable sheet from the reference plane is less than 3 mm or 40 mm or more

[0104] <Brittleness of molded body> Ten seedling pots 1 were made using a direct blow molding machine, and 1 kg of soil was placed in each of the ten seedling pots. The fragility of the seedling pots was evaluated by dropping them from a height of 3 m. The fewer pots that broke, the better the strength of the pots. The evaluation criteria were as follows, with +++, ++ and + being considered usable. [Evaluation criteria] +++: Not one seedling pot in 10 is destroyed. ++: 1 or 2 out of 10 destructions occur. +: 3 or 4 out of 10 destructions occur. NG: Destruction occurs in 5 or more out of 10.

[0105] <Tear resistance evaluation> Ten seedling pots 1 were produced using a direct blow molding machine, and tear resistance was evaluated based on how difficult it was to tear each seedling pot by hand. The fewer seedling pots that were torn, the better the tear resistance. The evaluation criteria were as follows, with +++, ++ and + being considered usable. [Evaluation criteria] +++: I couldn't tear all 10. ++: 7-9 out of 10 could not be torn. +: 5 or 6 out of 10 failed to tear. NG: Fewer than 5 out of 10 could not be torn.

[0106] [Table 1]

[0107] [Table 2-1]

[0108] [Table 2-2]

[0109] As shown in Tables 1 and 2, agricultural materials formed from a biodegradable resin composition for agricultural materials having a loss tangent (tanδ) of 0.8 to 1.6, or agricultural materials formed from a biodegradable resin (Ax) having a loss tangent (tanδ) of 0.8 to 1.6, were confirmed to be not only biodegradable but also moldable and strong. In particular, because they have excellent processability, they can be suitably used for deep molded objects such as seedling pots, which are difficult to mold.

Claims

1. A biodegradable resin composition comprising a biodegradable resin (A), Based on the biodegradable resin composition, the composition contains 15 to 30% by mass of an aliphatic-aromatic polyester and 55 to 85% by mass of an aliphatic polyester; The aliphatic polyester is a fatty acid polyester obtained by a polycondensation reaction between an aliphatic diol and an aliphatic dicarboxylic acid, The starch content is 15% by mass or less, The loss tangent (tanδ) calculated by the following formula 1 is 0.8 to 1.

6. Biodegradable resin composition for agricultural materials. [Formula 1] Loss tangent (tanδ) = G'' / G' (In Equation 1, G' and G'' are The storage modulus (G') and loss modulus (G'') are measured by dynamic viscoelasticity measurement using a 0.45 mm thick biodegradable sheet formed from the biodegradable resin composition at a temperature [Ta-10] (°C) that is 10°C lower than the flow initiation temperature [Ta] (°C) of the biodegradable resin (A), a frequency of 1 Hz, and a strain of 5%.

2. 2. The biodegradable resin composition for agricultural materials according to claim 1, wherein the storage modulus (G') is 0.06 to 3.5 MPa.

3. 2. The biodegradable resin composition for agricultural materials according to claim 1, wherein the loss modulus (G'') is 2.0 MPa or less.

4. 2. The biodegradable resin composition for agricultural materials according to claim 1, wherein the tensile modulus of elasticity is 200 to 1300 MPa when measured using a No. 5 dumbbell specimen prepared in accordance with JIS K6251 at a tensile speed of 50 mm / min and a temperature of 23°C.

5. 2. The biodegradable resin composition for agricultural materials according to claim 1, wherein the tensile strength of a No. 5 dumbbell specimen prepared in accordance with JIS K6251 is measured at a tensile speed of 50 mm / min and a temperature of 23°C, and is 20 to 45 MPa.

6. An agricultural material formed from the biodegradable resin composition for agricultural materials according to any one of claims 1 to 5.

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