Thermoplastic resin composition for agricultural material and agricultural material

Abstract

The present invention provides a thermoplastic resin composition for agricultural materials, the thermoplastic resin composition comprising an alkaline filler (A), a biodegradable resin (B), and a thickening agent (C), the alkaline filler (A) having a pH in water of 8.5-12.5, the biodegradable resin (B) comprising an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2), and the thickening agent (C) comprising an aliphatic aromatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2). The thickening agent (C) contains at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and silica-based fillers, and the content of the alkaline filler (A) is 5-30 mass% and the content of the thickening agent (C) is 0.5-3 mass% based on 100 mass% of the thermoplastic resin composition.

Description

Technical Field

[0001] The present disclosure relates to a thermoplastic resin composition for agricultural materials and agricultural materials. Background Art

[0002] Plastics are used in a wide range of fields such as electrical / electronic device parts, automotive parts, medical parts, and food containers because of their easy formability. Physical properties or functions such as strength are imparted to plastic molded products according to their uses. In the field of agricultural materials, they are used for applications that require ensuring water resistance and strength.

[0003] Examples of agricultural materials include agricultural mulch films used for purposes such as raising or maintaining soil temperature and pest control; and seedling-raising pots, which are a type of special container for cultivating seedlings.

[0004] As a solution to alleviate recent waste problems and the recycling operations of agricultural materials, there are agricultural materials using biodegradable materials, which do not require recycling and can be degraded underground (in the soil) after use.

[0005] In Patent Document 1, there is described an agricultural mulch film that promotes biodegradability by containing a biodegradable resin selected from polylactic acid, polybutylene succinate, and polybutylene adipate succinate and an alkaline filler such as calcium oxide, calcium hydroxide, and calcium carbonate in a specific mass ratio.

[0006] In Patent Document 2, there is described the following technique: biodegradability is further promoted by containing a hardly hydrolyzable biodegradable resin such as polylactic acid, an ester degradation promoter containing an easily hydrolyzable polymer, and an ester degradation promoting auxiliary agent containing inorganic particles that promotes the hydrolysis of the ester degradation promoter in a specific mass ratio.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Laid-Open No. 2013-237764

[0010] Patent Document 2: Japanese Patent Laid-Open No. 2012-077246 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] Alkaline fillers promote the biodegradability of the molded body when buried in the soil. However, since they promote hydrolysis during molding, they affect the moldability of the resin composition, and molding defects such as uneven wall thickness become problems in inflation molding applications such as agricultural mulch films for agriculture. In particular, molded bodies with high draw ratios such as seedling-raising pots or plug trays that are deeply drawn may have problems with smooth molding.

[0013] In addition, leafy vegetables such as green onions or leeks have a short time from sowing to planting, and it is expected to be degraded within 1 to 2 months after being buried in the soil, and it is required to be degraded in a shorter time than before.

[0014] The present disclosure has been completed in view of the above circumstances, and an object thereof is to provide a thermoplastic resin composition for agricultural materials that can achieve both high biodegradability and formability, and an agricultural material containing the thermoplastic resin composition for agricultural materials, which can produce a formed body with high-difficulty deep drawing.

[0015] Technical means for solving the problem

[0016] To solve the above problems, the inventors of the present invention have made intensive studies, and as a result, they have found a thermoplastic resin composition for agricultural materials having the following structure, and thus completed the present invention.

[0017] That is, several embodiments of the present disclosure are as follows.

[0018] <1> A thermoplastic resin composition for agricultural materials, which is a thermoplastic resin composition containing an alkaline filler (A), a biodegradable resin (B), and a thickener (C), wherein the pH of the alkaline filler (A) in water is 8.5 to 12.5, the biodegradable resin (B) contains an aliphatic polyester resin (B1) and an aliphatic-aromatic polyester resin (B2), the thickener (C) contains at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and silica-based fillers, and based on 100% by mass of the thermoplastic resin composition, the content of the alkaline filler (A) is 5% to 30% by mass and the content of the thickener (C) is 0.5% to 3% by mass.

[0019] <2> The thermoplastic resin composition for agricultural materials according to <1>, wherein the alkaline filler (A) contains at least one selected from the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, and magnesium hydroxide.

[0020] <3> The thermoplastic resin composition for agricultural materials according to <1> or <2>, wherein the pH of the alkaline filler (A) in water is 10.0 to 12.5.

[0021] <4> The thermoplastic resin composition for agricultural materials according to any one of <1> to <3>, wherein the average particle diameter of the alkaline filler (A) is 1 μm to 10 μm.

[0022] <5> The thermoplastic resin composition for agricultural materials according to any one of <1> to <4>, wherein the thickener (C) contains at least one of a carbodiimide compound and cellulose fiber.

[0023] <6> The thermoplastic resin composition for agricultural materials according to any one of <1> to <5>, wherein the content of the aliphatic polyester resin (B1) is 100 parts by mass to 300 parts by mass with respect to 100 parts by mass of the aliphatic aromatic polyester resin (B2).

[0024] <7> The thermoplastic resin composition for agricultural materials according to any one of <1> to <6>, wherein the content of the aliphatic polyester resin (B1) is 130 parts by mass to 300 parts by mass with respect to 100 parts by mass of the aliphatic aromatic polyester resin (B2).

[0025] <8> The thermoplastic resin composition for agricultural materials according to any one of <1> to <7>, wherein the melt viscosity at a shear rate of 243 s -1 is 1000 Pa·s or more and less than 5000 Pa·s at a temperature above the melting point of the biodegradable resin (B) and below the melting point + 40°C.

[0026] <9> The thermoplastic resin composition for agricultural materials according to any one of <1> to <8> is used for blow molding or vacuum molding.

[0027] <10> The thermoplastic resin composition for agricultural materials according to any one of <1> to <9> is used for a seedling raising container.

[0028] <11> An agricultural material is formed by using the thermoplastic resin composition for agricultural materials according to any one of <1> to <10> described above.

[0029] <12> The agricultural material according to <11> is a seedling raising container.

[0030] <13> The agricultural material according to <11> is a seedling raising container for cultivating seedlings in the seedling raising container before being buried in the soil and burying the seedling raising container in the soil after the seedling raising period to cultivate plants.

[0031] Effects of the Invention

[0032] According to an embodiment of the present disclosure, a thermoplastic resin composition for agricultural materials having biodegradability and good formability and an agricultural material containing the thermoplastic resin composition for agricultural materials can be provided.

[0033] Furthermore, there can be provided a thermoplastic resin composition for agricultural materials that can manufacture a formed body with high-difficulty deep drawing and exhibits high biodegradability, and an agricultural material containing the thermoplastic resin composition for agricultural materials. Detailed Embodiments

[0034] Hereinafter, the present disclosure will be described in detail. In addition, as long as it conforms to the gist of the present invention, other embodiments are of course included in the scope of the present invention. In addition, in this specification, the numerical range specifically designated by "~" includes the numerical values described before and after "~" as the lower limit value and the upper limit value range. In addition, in this specification, "film" or "sheet" is not distinguished according to thickness. In other words, the "sheet" in this specification also includes a film-like object with a thin thickness, and the "film" in this specification also includes a sheet-like object with a thickness.

[0035] In the present disclosure, the "thermoplastic resin composition for agricultural materials" may sometimes be referred to as the "resin composition".

[0036] As long as there is no special note for the various components appearing in this specification, each can be used independently alone or in combination of two or more.

[0037] In addition, the numerical values specifically designated in this specification are values obtained by the methods disclosed in the embodiments or examples.

[0038] <Thermoplastic Resin Composition for Agricultural Materials>

[0039] The thermoplastic resin composition for agricultural materials of this embodiment is a thermoplastic resin composition containing an alkaline filler (A), a biodegradable resin (B), and a thickener (C), wherein the pH of the alkaline filler (A) in water is 8.5 to 12.5, the biodegradable resin (B) includes an aliphatic polyester resin (B1) and an aliphatic-aromatic polyester resin (B2), and the thickener (C) includes at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, epoxy compounds, acid anhydride compounds, and silica-based fillers.

[0040] Based on 100% by mass of the thermoplastic resin composition, the content of the alkaline filler (A) is 3% to 30% by mass, and the content of the thickener (C) is 0.01% to 3% by mass.

[0041] With such a resin composition, high biodegradability and formability can be achieved at the same time.

[0042] Furthermore, even a formed body with high-difficulty deep drawing can be manufactured, and high biodegradability can be exhibited.

[0043] The degradation process of the resin composition generally includes two stages.

[0044] The first stage is to reduce the molecular weight of the resin that constitutes the agricultural materials (such as seedling trays or agricultural mulch films) of the molded article of the resin composition through hydrolysis or oxidative degradation.

[0045] Subsequently, in the second stage, microorganisms in the soil degrade the single piece of agricultural material containing the resin with reduced molecular weight.

[0046] Since the molecular weight reduction of the resin also occurs during the storage period or the use period of the agricultural material, the control of hydrolysis in the first stage becomes important. As factors of hydrolysis, the crystallinity of the resin can be cited. Compared with the crystalline region, the amorphous region is more likely to undergo hydrolysis, so hydrolysis can be suppressed by increasing the crystallinity.

[0047] Generally speaking, if additives or the like are added to the thermoplastic resin composition, its particles become crystal nuclei, and since the generation of crystals (nucleation effect) can be promoted, the crystallinity is increased, and thus a hydrolysis inhibition effect can be obtained.

[0048] The thermoplastic resin composition for agricultural materials of the present embodiment can adjust the biodegradation rate of the agricultural material containing the resin composition by containing specific alkaline fillers (A) and thickeners (C) in specific amounts respectively. For example, it is desirable to suppress the degradation of the agricultural material and maintain its shape for at least about four months during the cultivation period of the seedlings, and after about one year beyond the cultivation period of the seedlings, the agricultural material is degraded by microorganisms in the soil and can penetrate into the soil.

[0049] The present embodiment will be described in detail below.

[0050] (Alkaline filler (A))

[0051] The alkaline filler (A) is an alkaline filler with a pH of 8.5 to 12.5 in water. The alkaline filler (A) has the function of promoting the hydrolysis of the biodegradable resin (B).

[0052] The alkaline filler (A) is not particularly limited as long as it is an alkaline filler with a pH of 8.5 to 12.5 in water, and generally available alkaline fillers can be used. When the agricultural material formed using the resin composition is buried in the soil and the moisture becomes abundant, the alkaline filler (A) can appropriately promote the hydrolysis of the biodegradable resin (B) under alkaline conditions. As the alkaline filler (A), for example, alkaline compounds containing alkali metals or alkaline earth metals, zeolites that release alkali metals or alkaline earth metal ions, or ion-releasing fillers, hydrotalcite, etc. can be cited.

[0053] By using these basic fillers (A), hydrolysis, which is the first stage of the degradation process of the resin composition, is promoted, and the biodegradable resin (B) is depolymerized, thereby enabling a rapid transition to the degradation process by microorganisms in the soil in the second stage. On the other hand, when the pH of the basic filler (A) becomes higher, the degradation of the biodegradable resin (B) during the kneading of the resin composition is aggravated, and due to the decrease in the melt viscosity, the moldability of the resin composition may sometimes be affected.

[0054] From the viewpoint of the balance between biodegradability and moldability, the pH is preferably 9.0 to 11.0.

[0055] From the viewpoint of biodegradability, the pH is more preferably 9.0 to 12.5, 10.0 to 12.5, 10.5 to 12.5, 11.0 to 12.5, or 12.0 to 12.5.

[0056] From the viewpoint of moldability, the pH is more preferably 8.5 to 12.0, 8.5 to 11.0, 8.5 to 10.0, 8.5 to 9.5, or 8.5 to 9.0.

[0057] In the present disclosure, the pH of the basic filler is the pH value measured at 23°C using a pH meter. As the pH meter, a pH meter HM-30P manufactured by Toa DKK Corporation can be used.

[0058] In addition, when the basic filler is soluble in water, an aqueous solution can be used for measurement. Alternatively, when it is insoluble in water, the supernatant of the dispersion can be used to measure the pH.

[0059] Specifically, for example, 0.5 g of the basic filler can be weighed and placed in a plastic container, 50 ml of deionized water is added, after vibrating for 30 minutes using a shaker, solid-liquid separation is performed using a centrifuge, and after stabilizing the temperature of the water in the supernatant in a constant temperature bath at 23°C, the pH is measured using a pH meter (pH meter HM-30P manufactured by Toa DKK Corporation), and the obtained value is taken as the pH of the basic filler.

[0060] Examples of basic compounds containing an alkali metal or an alkaline earth metal include carbonates, bicarbonates, silicates, phosphates, oxides, hydroxides, etc. Specific examples include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, potassium silicate, calcium silicate, magnesium silicate, sodium phosphate, calcium oxide, calcium hydroxide, magnesium hydroxide, etc.

[0061] As the zeolite that releases ions of an alkali metal or an alkaline earth metal, various natural or synthetic zeolites containing an alkali metal or an alkaline earth metal ion as an exchangeable ion can be used.

[0062] Examples of the ion-releasing filler include oxide glasses such as aluminosilicate glass, borosilicate glass, and soda-lime glass containing an alkali metal or an alkaline earth metal, and fluoride glasses such as zirconium fluoride glass.

[0063] Among them, from the viewpoints of both moldability and biodegradability, an alkaline compound containing an alkali metal or an alkaline earth metal is preferable, and a carbonate, an oxide, or a hydroxide of an alkali metal or an alkaline earth metal is more preferable, and calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, and magnesium hydroxide are further preferable. Further, since the alkaline filler remains in the soil after biodegradation, when the alkalinity in the soil is too high, it will affect the growth of plants. In this regard, calcium carbonate, magnesium carbonate, etc. are particularly preferable. On the other hand, when the agricultural material formed using the resin composition is buried in the soil and the moisture becomes abundant, the alkalinity in the soil can be increased in a shorter period, and the hydrolysis of the biodegradable resin (B) can be further promoted. In this regard, an alkaline compound containing an alkali metal or an alkaline earth metal with a pH of 10.0 to 12.5, 10.5 to 12.5, 11.0 to 12.5, or 12.0 to 12.5 can be used, and an oxide or a hydroxide of an alkaline compound containing an alkali metal or an alkaline earth metal is more preferable, and calcium oxide and calcium hydroxide are further preferable. Even in the case of using such a strong base, the resin composition according to the present disclosure can suppress the diffusion of excess alkali into the soil. The alkaline filler (A) can be used alone or in combination of two or more.

[0064] In addition, from the viewpoint of moldability, the average particle diameter of the alkaline filler (A) is preferably 1 μm to 20 μm, more preferably 1 μm to 10 μm. By the average particle diameter of the alkaline filler (A) being in the above range, the dispersibility of the alkaline filler (A) in the biodegradable resin (B) and the smoothness of the surface of the molded product can be taken into account.

[0065] In particular, in blow molding in which the resin is directly put into a mold and air is supplied, in order for the average particle diameter of the alkaline filler (A) in the resin composition to contribute to moldability, the average particle diameter of the alkaline filler (A) is preferably in the above range.

[0066] The average particle diameter of the alkaline filler (A) can be determined by the laser diffraction method.

[0067] For example, the laser diffraction method can be used to irradiate a laser to a dispersion liquid of the alkaline filler (A) that has been dispersion-treated, measure the angular change of the intensity of the light scattered when this laser passes through the solution, thereby obtaining a particle size distribution, and calculating the average particle diameter in the form of the median value at which the cumulative value based on volume reaches 50%.

[0068] As a particle size distribution meter, for example, a particle size distribution meter Microtrac HRA manufactured by Nikkiso Co., Ltd. can be used. A measurement sample is prepared by dispersing the basic filler (A) using isopropyl alcohol.

[0069] Based on 100% by mass of the resin composition, the content of the basic filler (A) can be 3% to 30% by mass. This content can be 3% by mass or more, 4% by mass or more, 5% by mass or more, 8% or 10% by mass or more. This content can be 30% by mass or less, 25% by mass or less, 20% by mass or less, 18% by mass or less, or 15% by mass or less within the range of these lower limit values. Within the range of these contents, the pH of the basic filler (A) in water is 8.5 to 12.5. Therefore, when the agricultural material is buried in the soil and the moisture becomes abundant, it becomes an appropriate alkaline environment, and the hydrolysis of the biodegradable resin (B) can be promoted.

[0070] (Biodegradable resin (B))

[0071] The biodegradable resin (B) is a substance that is degraded by the action of various microorganisms present in the soil or water. In the resin composition of the present disclosure, as the biodegradable resin (B), an aliphatic polyester resin (B1) and an aliphatic-aromatic polyester resin (B2) are included. Thereby, a resin composition excellent in biodegradability and moldability can be produced.

[0072] As the biodegradable resin (B), generally available biodegradable resins can be further used. These biodegradable resins can be used alone or in combination of two or more.

[0073] The content of the aliphatic polyester resin (B1) is preferably equal to or more than the content of the aliphatic-aromatic polyester resin (B2). By mixing the aliphatic polyester resin (B1) as the base resin and the aliphatic-aromatic polyester resin (B2) having ductility and excellent moldability, the moldability of the resin composition and the strength of the agricultural material as its molded product can be ensured.

[0074] Therefore, the content of the aliphatic polyester resin (B1) relative to 100 parts by mass of the aliphatic-aromatic polyester resin (B2) is preferably 100 parts by mass or more, more preferably 110% by mass or more, 120 parts by mass or more, 130 parts by mass or more, or 140 parts by mass or more, and from the viewpoint of improving biodegradability, it is further preferably 150 parts by mass or more. In addition, it is preferably 300 parts by mass or less, more preferably 280 parts by mass or less, 250 parts by mass or less, 230 parts by mass or less, or 200 parts by mass or less, and from the viewpoint of improving moldability, it is further preferably 150 parts by mass or less. For example, the content of the aliphatic polyester resin (B1) relative to 100 parts by mass of the aliphatic-aromatic polyester resin (B2) can be 100 parts by mass to 300 parts by mass, 110 parts by mass to 280 parts by mass, 120 parts by mass to 250 parts by mass, 130 parts by mass to 230 parts by mass, or 140 parts by mass to 200 parts by mass.

[0075] [Aliphatic polyester resin (B1)]

[0076] Examples of the aliphatic polyester resin (B1) include aliphatic polyesters obtained by polycondensation of aliphatic diols and aliphatic dicarboxylic acids and polylactic acid obtained by polycondensation of lactic acid. Examples of the aliphatic diol include: ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol. These can be used alone or as a mixture thereof. Among them, 1,4-butanediol is preferably used. Examples of the aliphatic dicarboxylic acid include: oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, dodecanedioic acid, and acid anhydrides which are derivatives thereof can also be used. Among them, succinic acid or succinic anhydride, or a mixture of these and adipic acid is preferred.

[0077] Specifically, examples include: polybutylene succinate (PBS) obtained from 1,4-butanediol and succinic acid (e.g., "BioPBS" (trade name) manufactured by the Petroleum Authority of Thailand (PPT), Mitsubishi Chemical Corporation (MCC), and Biochem Co., Ltd.), polybutylene succinate adipate (PBSA) obtained by copolymerizing adipic acid with PBS, and the like. In addition, as polylactic acid (PLA), examples include "REVODE" (trade name) manufactured by Hisun Biomaterials Co., Ltd., "Ingeo" (trade name) manufactured by NatureWorks LLC, and the like.

[0078] As the aliphatic polyester resin (B1), from the viewpoint of the moldability of the resin composition, it is preferably an aliphatic polyester obtained by the polycondensation reaction of an aliphatic diol and an aliphatic dicarboxylic acid and contained in the largest amount in the overall composition. For example, based on 100% by mass of the aliphatic polyester resin (B1), it is preferably an aliphatic polyester obtained by the polycondensation reaction of an aliphatic diol and an aliphatic dicarboxylic acid and containing 20% by mass or more, 50% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass. In this case, the aliphatic polyester is more preferably a copolymer containing units derived from an aliphatic diol and units derived from an aliphatic dicarboxylic acid.

[0079] [Aliphatic-aromatic polyester resin (B2)]

[0080] As the aliphatic-aromatic polyester resin (B2), examples include copolymers containing aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and linear aliphatic and / or alicyclic diol units. The diol component providing the diol units is usually a component having 2 to 10 carbon atoms, and examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. Among them, 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 providing the dicarboxylic acid units is usually a component having 2 to 10 carbon atoms, and examples include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and the like. Among them, succinic acid or adipic acid is preferred. As the aromatic dicarboxylic acid component providing the aromatic dicarboxylic acid units, examples include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and the like. Among them, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is more preferred.

[0081] Specifically, 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 Corporation), etc.

[0082] In addition, the biodegradable resin (B) can also be in a form of a blend of an aliphatic polyester resin (B1), an aliphatic-aromatic polyester resin (B2), and other biodegradable resins. In addition, as the aliphatic polyester resin (B1), in addition to the substances exemplified above, for example, poly(3-hydroxyalkanoate) which is an aliphatic polyester copolymer obtained from hydroxyalkanoic acid and polycarboxylic acid can also be used (wherein, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

[0083] (poly-3-hydroxybutyrate-co-3-hydroxyhexanoate, PHBH) (for example, "AONILEX" (trade name) manufactured by Kaneka Corporation), polycaprolactone, etc.

[0084] Based on the resin composition (100% by mass), the content of the biodegradable resin (B) can be 35% by mass to 95% by mass, more preferably 35% by mass to 94.99% by mass, still more preferably 35% by mass to 94.5% by mass, and even more preferably 39% by mass to 90% by mass. By having the content of the biodegradable resin (B) within the above range, the processability and formability of the resin composition can be balanced, so it is preferred. In addition, based on the biodegradable resin (B) (100% by mass), the total content of the aliphatic polyester resin (B1) and the aliphatic-aromatic polyester resin (B2) can be 100% by mass, preferably 80% by mass or more, more preferably 90% by mass or more.

[0085] (Thickener (C))

[0086] The thickener (C) is a viscosity modifier that adjusts the viscosity of the resin composition to improve formability, and has a function of increasing the melt tension of the resin composition which is an index of forming processability.

[0087] In addition, the thickener (C) contains at least one selected from the group consisting of carbodiimide compounds, oxazoline compounds, acid anhydride compounds, cellulose fibers, and silica-based fillers. The thickener (C) can also additionally contain an epoxy compound. Since the epoxy compound can act as a phase solvent for the polyester resin, its use can be restricted in order to obtain the strength of agricultural materials. Alternatively, the epoxy compound can be used in combination with other thickeners (C).

[0088] When the thickener (C) is a polyfunctional compound, the melt tension of the resin composition can be increased by forming a crosslinked structure with the biodegradable resin (B). Examples of the polyfunctional compound include polyfunctional carbodiimide compounds, polyfunctional oxazoline compounds, epoxy compounds, acid anhydride compounds, etc. The polyfunctional carbodiimide compound can be a monomer or polymer having two or more carbodiimide groups, but a polymer having two or more carbodiimide groups is preferred.

[0089] When the thickener (C) is a reactive compound, a reactive group can be introduced into the biodegradable resin (B), and a crosslinked structure can be formed starting from the reactive group, thereby increasing the melt tension of the resin composition. Examples of the reactive compound include carbodiimide compounds, oxazoline compounds, epoxy compounds, acid anhydride compounds, etc. It is preferred to use cyclic carbodiimide as the carbodiimide compound. The cyclic carbodiimide compound is a compound having a carbodiimide group on the ring of an aliphatic ring or an aromatic ring.

[0090] When using a silica-based filler as the thickener (C), the melt tension of the resin composition can be increased by increasing the solid content of the resin composition and thickening it. The filler can be either an organic filler or an inorganic filler, and examples include cellulose fibers, silica-based fillers, etc.

[0091] In a preferred embodiment, compounds described in the positive list of green plastics can be used. For example, cellulose microfibril (CMF) as a cellulose fiber and carbodiimide (CDI) etc. can be used. The so-called cellulose microfibril refers to cellulose fibers of a relatively large size obtained by reducing the defibrillation process, which are obtained by treating pulp with hot water etc. to make it brittle by hydrolysis and then defibrillating it by a pulverization method such as a high-pressure homogenizer. By including cellulose microfibrils and carbodiimide compounds, the viscosity of the resin composition is increased, and strength can be ensured.

[0092] That is, if the resin composition contains cellulose microfibrils, the strength of the resin composition will increase due to the filler effect of the cellulose microfibrils. In addition, the silica-based filler has the same filler effect as the cellulose microfibrils, so the strength of the resin composition is increased in the same way as the cellulose microfibrils. In the molding of a resin composition containing at least one of cellulose microfibrils and silica-based fillers as the thickener (C), for example, blow molding etc. can be used.

[0093] If the resin composition contains a carbodiimide compound, the resin reacts with the carbodiimide compound to increase the molecular weight of the resin. Therefore, it takes time for the resin to be hydrolyzed until the molecular weight decreases, and the biodegradation rate slows down. Therefore, in the case of agricultural materials that require the strength of the resin composition, it is preferably to contain a carbodiimide compound as a thickener (C). In addition, since oxazoline compounds, epoxy compounds, and acid anhydride compounds also have reactivity with the resin in the same way as the carbodiimide compound, these compounds can also increase the strength of the resin composition respectively. The resin composition containing at least one of a carbodiimide compound, an oxazoline compound, an epoxy compound, and an acid anhydride compound can be formed, for example, by vacuum forming.

[0094] Examples of the carbodiimide compound include polycarbodiimide compounds such as "Carbodilite HMV-15CA (trade name)" manufactured by Nisshinbo Chemical Inc.; monocarbo diimides such as dicyclohexylcarbodiimide, diphenylcarbodiimide, di-β-naphthylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tert-butylisopropylcarbodiimide, di-tert-butylcarbodiimide; and cyclic carbodiimide compounds such as "Carbosista TCC-NP" (trade name) manufactured by Teijin Limited. These compounds can be used alone or in combination of multiple kinds.

[0095] Examples of the cellulose fiber include "C-1: KCflockW-50" (trade name) manufactured by Nippon Paper Industries Co., Ltd.

[0096] Examples of the oxazoline compound include "Epocros RA-45" (trade name), "Epocros RPS-1005" (trade name), etc. manufactured by Nippon Catalyst Co., Ltd. These compounds can be used alone or in combination of multiple kinds.

[0097] Examples of the epoxy compound include epoxy-acrylic compounds (such as "Joncryl ADR-4468" (trade name) manufactured by BASF SE, "Joncryl ADR-4400" (trade name) manufactured by BASF SE, "Arufon UG-4040" (trade name) manufactured by Toagosei Co., Ltd., "Arufon UG-4070" (trade name) manufactured by Toagosei Co., Ltd.). These compounds can be used alone or in combination of multiple kinds.

[0098] As the acid anhydride compound, for example, there may be mentioned: styrene maleic anhydride compounds ("XIBOND 120" (trade name), "XIBOND 140" (trade name), "XIBOND 160" (trade name), "XIBOND 180" (trade name), "XIBOND 200" (trade name), "XIBOND 220" (trade name), "XIBOND 250" (trade name), "XIBOND 280" (trade name) manufactured by PALMERHOLLAND Inc.), ("XIRAN 1000" (trade name), "XIRAN 2000" (trade name), "XIRAN 2500" (trade name), "XIRAN 3000" (trade name), "XIRAN 4000" (trade name), "XIRAN 6000" (trade name), "XIRAN 9000" (trade name), "XIRAN 3500" (trade name), "XIRAN 3600" (trade name) manufactured by B Industrial Co., Ltd.), etc. These compounds can be used alone or in combination of multiple kinds.

[0099] As the silica-based filler, for example, there may be mentioned: silica fillers ("Aerosil 130" (trade name), "Aerosil 150" (trade name), "Aerosil 200" (trade name), "Aerosil 300" (trade name), "Aerosil RX200" (trade name), "Aerosil RY200" (trade name) manufactured by Aerosil Co., Ltd. of Japan), ("Nipsil SS-50" (trade name), "Nipsil SS-50B" (trade name), "Nipsil SS-50F" (trade name), "Nipsil K-500" (trade name), "Nipsil G-300" (trade name) manufactured by Tosoh Silica Corporation, etc. These compounds can be used alone or in combination of multiple kinds.

[0100] In order to make the viscosity of the resin composition appropriate, the content of the thickener (C) is preferably 0.01 part by mass to 3 parts by mass, more preferably 0.01 part by mass to 2 parts by mass, and may also be 0.01 part by mass to 1 part by mass or 0.1 part by mass to 0.8 part by mass in 100 parts by mass of the resin composition.

[0101] When the thickener (C) is in excess, it becomes difficult for moisture to reach the alkaline filler (A) and the biodegradable resin (B) after the agricultural material is buried in the soil, which may reduce the hydrolysis rate of the biodegradable resin (B). In terms of the above view, the content of the thickener (C) may be 0.01 to 3 parts by mass, 0.01 to 2.5 parts by mass, 0.01 to 2 parts by mass, 0.01 to 1.5 parts by mass, 0.01 to 1 part by mass, or 0.01 to 0.5 parts by mass in 100 parts by mass of the resin composition.

[0102] In terms of the moldability of the resin composition, the content of the thickener (C) may also be 0.01 to 3 parts by mass, 0.1 to 3 parts by mass, 0.2 to 3 parts by mass, 0.3 to 3 parts by mass, 0.5 to 3 parts by mass, 1 to 3 parts by mass, or 2 to 3 parts by mass in 100 parts by mass of the resin composition. If this content is 0.5 parts by mass or more, deep drawing molding such as blow molding and vacuum molding can also be used. Furthermore, if this content is in the range of 1.5 parts by mass or more, the moldability can be further improved, and even in the case of using vacuum molding, appearance defects and strength reduction can be suppressed.

[0103] In some embodiments, based on 100% by mass of the thermoplastic resin composition, the content rate of the alkaline filler (A) is preferably 8% to 25% or 10% to 20%, and the content rate of the thickener (C) is preferably 0.5% to 3% by mass. More preferably, based on 100% by mass of the thermoplastic resin composition, the content rate of the alkaline filler (A) is preferably 5% to 30%, and the content rate of the thickener (C) is preferably 1 to 3 parts by mass or 2 to 3 parts by mass. By specifying the content in this way, the biodegradability of the agricultural material and the moldability of the resin composition can be further improved.

[0104] (Starch (D))

[0105] In some embodiments, the resin composition may also contain starch. By using starch, the degradation process by microorganisms in the soil in the second process can also be promoted, and thus a further promotion effect can be obtained, so it is preferred.

[0106] Starch (D) promotes the action of various microorganisms present in soil or water (biodegradability). Starch (D) is not particularly limited, and generally available starches can be used. For example, corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch, etc. can be cited. Among them, if corn starch with a uniform particle size of about 20 μm is used, the thickness of the agricultural material containing the resin composition can be made uniform (the surface unevenness can be reduced), so that the generation of thin parts can be suppressed, and as a result, the breakage of the agricultural material can be suppressed. Therefore, it is preferred. These can be used alone or in combination of two or more.

[0107] In the case of containing starch (D), the content rate of starch (D) is a component that can adjust the biodegradation rate, and its content is preferably 5% by mass to 60% by mass in 100% by mass of the resin composition, and can also be 10% by mass to 50% by mass, 10% by mass to 40% by mass, or 10% by mass to 30% by mass. When the content of starch (D) is 5% by mass or more, biodegradation can be promoted, and when it is 60% by mass or less, the content of the biodegradable resin (B) can be ensured to guarantee the formability. On the other hand, according to the present disclosure, by specifically specifying the contents of the alkaline filler (A) and the thickener (C), the hydrolysis of the biodegradable resin (B) in the soil can be promoted, so the biodegradation rate in the soil is increased, and the formability of the resin composition can be further improved. Therefore, in some embodiments, the biodegradability of the agricultural material can be obtained without relying on the promoting effect of the biodegradability brought by starch (D). In terms of the above view, the content rate of starch (D) in 100% by mass of the resin composition can be 0% by mass to 20% by mass, 0% by mass to 15% by mass, 0% by mass to 10% by mass, or 0% by mass to 5% by mass, and the resin composition may also substantially not contain starch (D).

[0108] In addition, from the viewpoint of formability, the average particle size of starch (D) is preferably 5 μm to 50 μm, and can also be 10 μm to 50 μm. By the average particle size of starch (D) being in the above range, the dispersibility of starch (D) in the biodegradable resin (B) and the smoothness of the surface of the molded product can be taken into account.

[0109] The average particle size of starch (D) can be obtained, for example, by observing the starch (A) particles using a scanning electron microscope, randomly observing 100 particles, measuring the distance between the two farthest points of the outer shape of each particle according to the length of the micron mark on the screen, and averaging.

[0110] The mass ratio of starch (D) to the alkaline filler (A) is preferably alkaline filler (A) / starch (D) = 80 / 20 to 20 / 80, and more preferably 50 / 50 to 25 / 75.

[0111] Thus, through further promotion effects, agricultural materials with more excellent biodegradability can be produced, which is therefore preferred.

[0112] (Other components)

[0113] The resin composition may optionally contain other components such as additives as needed. As additives, for example, the following can be cited: dispersants, lubricants (metal salts of higher fatty acids, waxes, etc.), surfactants, antistatic agents, flame retardants, antioxidants, ultraviolet absorbers, fillers, pigments, etc. The selection of other optional components and their usage amounts are not particularly limited as long as they are within the range that can solve the problems of one embodiment of the present invention. Multiple additives can also be used in combination. In addition, the resin composition may also contain a part of a resin other than the biodegradable resin within the range that does not hinder the effects of one embodiment of the present invention.

[0114] The resin composition contains the biodegradable resin (B), but from the perspective of adjusting the biodegradation rate, a plasticizer may not be contained. By not containing a plasticizer, the biodegradability of the agricultural materials formed using the resin composition before being buried in the soil can be further suppressed. In addition, the moldability of the resin composition can also be improved. For example, relative to 100 parts by mass of the biodegradable resin (B), the plasticizer may be 5 parts by mass or less, 1 part by mass or less, or 0.1 part by mass or less.

[0115] The resin composition can be used to manufacture a molded article with excellent heat insulation effect or an easily recognizable molded article by coloring with a pigment. The pigment is not particularly limited, and generally available pigments can be used, but from the perspective of the natural environment, pigments substantially free of cadmium, lead, chromium, arsenic, mercury, copper, selenium, nickel, molybdenum, and fluorine are preferred.

[0116] For example, when the resin composition contains a pigment, it is preferably used in combination with a dispersant for dispersing the pigment. As the dispersant, a metal salt of a fatty acid can be cited. As the fatty acid component of the metal salt of a fatty acid, a linear carboxylic acid having 6 to 30 carbon atoms is preferred, which can be linear or branched, and can have only saturated bonds or unsaturated bonds.

[0117] As examples of the fatty acid, for example, the following can be cited: caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, behenic acid, oleic acid, erucic acid, linoleic acid, montanic acid, etc.

[0118] As the metal, elements of Group 1, Group 2, Group 12, and Group 13 are preferred, and elements of Group 1 or Group 2 are more preferred. As specific examples, sodium, potassium, calcium, magnesium, barium, etc. can be cited.

[0119] Examples of the fatty acid metal salts include calcium stearate, magnesium stearate, barium stearate, calcium laurate, magnesium laurate, sodium lignite, etc. One of these may be used, or two or more thereof may be used in combination. Among them, calcium stearate, magnesium stearate, calcium laurate, and magnesium laurate are preferred.

[0120] (Processability)

[0121] In the thermoplastic resin composition for agricultural materials, regarding the processability during extrusion, the occurrence of strand breakage during continuous production for 1 hour is 5 times or less, may be 1 to 5 times, and preferably no strand breakage occurs.

[0122] (Melt viscosity)

[0123] In the thermoplastic resin composition for agricultural materials, from the viewpoints of the strength of the obtained molded article, the fluidity of the resin composition, and the moldability, the melt viscosity at a shear rate of 243 s in Japanese Industrial Standards (JIS) K7199:1999 -1 is preferably 1000 Pa·s or more and less than 5000 Pa·s, more preferably 1500 Pa·s or more and less than 4500 Pa·s at a temperature above the melting point of the biodegradable resin (B) and below the melting point + 40°C.

[0124] (Use)

[0125] The thermoplastic resin composition for agricultural materials of this embodiment can be used for various agricultural materials. In particular, the resin composition is suitably used for nursery container applications. A nursery container is a container for cultivating seedlings in a container until they grow to a certain extent, rather than directly sowing and cultivating in the field. The molded article using the resin composition of this embodiment is appropriately biodegradable in the soil, so there is no need to take out the seedlings from the nursery container for transplantation after the seedlings grow, and they can be directly transplanted into the soil in the nursery container. Examples of the nursery container include nursery pots, plug trays, etc.

[0126] 《Manufacturing method》

[0127] The resin composition of the present embodiment can be produced by kneading the basic filler (A) and the thickener (C) at the temperature at which the biodegradable resin (B) is molten. Specifically, for example, the biodegradable resin (B), the basic filler (A), and the thickener (C) can be added, and various additives can be added as needed, and a batch kneader such as a kneader, a roll mill, a super mixer, a high-speed mixer, a ball mill, a sand mill, a grinder, or a Banbury mixer, a single-screw extruder, a twin-screw extruder, a rotor-type twin-screw kneader, etc. are used for mixing and melt-kneading to produce a resin composition in the form of granules, powders, particles, or beads. From the viewpoint of strong kneading force and easy subsequent forming process, it is preferably granulated using a single-screw extruder or a twin-screw extruder.

[0128] The resin composition can be used in either the form of a masterbatch or a composite.

[0129] In the case of a masterbatch, after producing the masterbatch, for example, the same biodegradable resin (B) as the substance used in the production of the masterbatch can be used as a diluent resin to formulate the masterbatch as the main resin of the agricultural material, thereby producing the agricultural material. As the content of the masterbatch, relative to 100 parts by mass of the biodegradable resin (B) as the main resin, it is preferably to contain 1 part by mass to 50 parts by mass of the masterbatch, and more preferably to contain 1 part by mass to 20 parts by mass of the masterbatch.

[0130] The biodegradable resin (B) used as the diluent resin at this time can be the same as or different from the substance used in the production of the masterbatch. When it is the same biodegradable resin, the compatibility of the thermoplastic resin composition and the resin is more excellent, so it is preferred.

[0131] In the case of a composite, after producing the composite, the composite can be directly used to produce the agricultural material by the above method.

[0132] <Agricultural material>

[0133] The agricultural material of the present embodiment can be obtained by forming the above agricultural material with a thermoplastic resin composition. As the agricultural material, for example, seedling raising containers such as seedling trays and plug trays, agricultural mulch films, containers, and agricultural nets can be cited.

[0134] Since it is the agricultural material of the present embodiment, even for a deep-drawn molded article with a high draw ratio such as a seedling tray or a plug tray, biodegradability and formability can be taken into account. The deep-drawn molded article referred to here means a molded article in which the depth direction is longer than the width of the molded article.

[0135] The agricultural material of the present embodiment is more preferably a seedling raising container for cultivating seedlings in the seedling raising container before burying in the soil and burying the seedling raising container in the soil after the seedling raising period to cultivate plants.

[0136] (Seedling-raising pot)

[0137] The seedling-raising pot is a container used for the aforesaid purpose. The method for forming and processing the seedling-raising pot is not particularly limited. For example, blow molding, in which a resin composition that has been heated and plasticized is extruded, not cooled and solidified, but directly added into a mold and air is conveyed, and vacuum forming, in which a sheet or film of the resin composition that has been heated and plasticized is placed on a mold and vacuum suction is performed from the inside of the mold, are suitable.

[0138] The seedling-raising pot containing the aforesaid resin composition will biodegrade after being buried in the soil, so it will not damage the natural environment and can reduce the effort of taking out seedlings from the seedling-raising pot and sowing and planting the seedlings. The seedling-raising pot will not degrade during the seedling cultivation period before being buried in the soil, that is, during a period of about 2 to 4 months, and can be cultivated well. In addition, the seedling-raising pot has a strength suitable for seedling-raising use, so it is easy to operate and can maintain an appropriate shape during the seedling-raising period.

[0139] (Agricultural mulching film)

[0140] The agricultural mulching film (mulching film) is a film that covers the roots of crops. The method for forming and processing the film from the aforesaid resin composition is not particularly limited. Suitable methods include extrusion molding in which the film extruded by a T-die using an extruder is cooled and solidified by a casting roll, or a method in which it is formed using an inflation molding machine.

[0141] "Blow molding, vacuum forming"

[0142] The aforesaid resin composition increases the melt tension through the thickener (C), so it can suppress sagging (a phenomenon in which the resin after preforming cannot withstand its own weight and sags in the direction of gravity).

[0143] In the case of blow molding, thinning and lightening of the molded product can be suppressed. The resin composition of the present embodiment can be blow molded. For example, when continuously producing 3 groups of two seedling-raising pots at a time using a direct blow molding machine, the difference between the weight of each seedling-raising pot in the first group and the weight of each seedling-raising pot in the third group can be set to be less than 30% relative to the weight of each seedling-raising pot in the first group. In addition, as long as the weight of each seedling-raising pot is 0.7 g or more and less than 0.8 g, preferably 0.8 g or more and less than 0.9 g, and more preferably 0.9 g or more. By using the aforesaid resin composition, blow moldability can be obtained.

[0144] For example, in the case where the molded product is a seedling-raising pot, as long as the seedling-raising pot has a strength to stand on its own, it is preferably that the seedling-raising pot does not bend. By using the aforesaid resin composition, a seedling-raising pot with ensured strength can be obtained.

[0145] In the case of vacuum forming, the generation of defective appearance parts caused by drooping such as wrinkles due to the flexure of the sheet can be suppressed. For example, even if there are defective appearance parts caused by drooping in the formed article, it is sufficient to perform vacuum forming using the resin composition. If there are only a few defective appearance parts, it is preferable, and more preferably, there are no defective appearance parts. By using the resin composition, a vacuum-formed article can be obtained.

[0146] For example, in the case where the formed article is a seedling-raising pot, regarding the brittleness of the seedling-raising pot, when 1 kg of soil is put into the seedling-raising pot and dropped from a height of 5 m, the number of damaged seedling-raising pots should be 3 or less out of 10, and it can also be 1 to 3 out of 10. Preferably, none of them is damaged. By using the resin composition, a seedling-raising pot with ensured strength can be obtained.

[0147] (Biodegradation rate)

[0148] When the formed article formed using the resin composition is buried in the ground for 6 months, it is sufficient that the formed article degrades and perforates everywhere. Preferably, the formed article degrades and becomes scattered. By using the resin composition, a formed article with appropriately adjusted biodegradation rate can be obtained.

[0149] According to the present embodiment, the thermoplastic resin composition for agricultural materials contains a specific amount of an alkaline filler (A) that promotes biodegradability and a thickener (C) that increases the melt tension. Therefore, an agricultural material with excellent biodegradability and formability can be obtained.

[0150] Several embodiments of the present disclosure are listed below. In addition, the present invention is not limited to the following embodiments.

[0151] <1> A thermoplastic resin composition for agricultural materials, which is a thermoplastic resin composition containing an alkaline filler (A), a biodegradable resin (B), and a thickener (C), wherein

[0152] The pH of the alkaline filler (A) in water is 8.5 to 12.5.

[0153] The biodegradable resin (B) contains an aliphatic polyester resin (B1) and an aliphatic-aromatic polyester resin (B2).

[0154] The thickener (C) contains at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, epoxy compounds, acid anhydride compounds, and silica-based fillers. Preferably, the thickener (C) contains at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and silica-based fillers.

[0155] Based on 100% by mass of the thermoplastic resin composition, the content rate of the basic filler (A) is 3% to 30% by mass, preferably 5% to 30% by mass, and the content rate of the thickener (C) is 0.01% to 3% by mass, preferably 0.5% to 3% by mass.

[0156] In the above <1>, the thickener (C) preferably contains at least one of a carbodiimide compound and cellulose fiber. In the above <1>, based on 100 parts by mass of the aliphatic-aromatic polyester resin (B2), the content of the aliphatic polyester resin (B1) is 100 parts by mass to 300 parts by mass, preferably 130 parts by mass to 300 parts by mass.

[0157] Examples

[0158] 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.

[0159] In addition, the blending amounts in the tables are expressed in parts by mass. In addition, the blank columns in the tables indicate non-blending.

[0160] In addition, the measurement methods of the pH and average particle diameter of the basic filler are as described below.

[0161] <pH Measurement>

[0162] Weigh 0.5 g of the basic filler and put it into a plastic container, add 50 ml of deionized water, vibrate it for 30 minutes using a vibrator, then separate the solid and liquid by a centrifuge. After stabilizing the temperature of the supernatant water in a constant temperature bath at 23°C, measure the pH using a pH meter (pH meter HM-30P manufactured by Toa DKK Corporation).

[0163] In addition, the measurement methods of the average particle diameter of the basic filler (A) and starch (D) are as described below.

[0164] <Measurement Method of Average Particle Diameter of Basic Filler (A)>

[0165] Prepare a sample by dispersing the basic filler with isopropanol. Use a particle size distribution meter Microtrac HRA manufactured by Nikkiso Co., Ltd. to irradiate the obtained dispersion liquid with laser, measure the distribution pattern of the intensity of the light scattered when this laser passes through the dispersion liquid, and thereby obtain the particle size distribution. Furthermore, based on the values of the particle size distribution, calculate the median diameter (50% diameter) on a volume basis as the average particle diameter.

[0166] <Measurement Method of Average Particle Diameter of Starch (D)>

[0167] The starch particles were observed using a scanning electron microscope (SEM) manufactured by Hitachi, Ltd. at a field magnification of 100 times. 100 particles were randomly observed, and the distance between the two farthest points on the outer shape of each particle was measured based on the length of the micron markings on the screen, and the average was calculated.

[0168] Next, the materials used in the thermoplastic resin composition for agricultural materials are listed below.

[0169] (Alkaline filler (A))

[0170] A-1: KS-1300 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0, average particle size: 1.8 μm)

[0171] A-2: KS-500 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0, average particle size: 4.4 μm)

[0172] A-3: KS-300 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0, average particle size: 8.9 μm)

[0173] A-4: magnesium carbonate (Venus) (manufactured by Kojima Chemical Industry Co., Ltd., pH 10.0, average particle size: 10 μm)

[0174] A-5: F lime-1300K (calcium oxide, manufactured by Calfine Co., Ltd., pH 12.4, average particle size: 5.0 μm)

[0175] A-6: M-300 (calcium hydroxide, manufactured by Mitsuyoshi Inoue Store Co., Ltd., pH 12.4, average particle size: 4.9 μm)

[0176] A-7: magnesium hydroxide (manufactured by Kojima Chemical Industry Co., Ltd., pH 10.5, average particle size: 6 μm)

[0177] A-8: magnesium hydroxide (manufactured by Kojima Chemical Industry Co., Ltd., pH 10.5, average particle size 15 μm)

[0178] A-9: IXE-700F (hydrotalcite, manufactured by Toagosei Co., Ltd., pH 8.5, average particle size 1.5 μm)

[0179] (Other alkaline fillers)

[0180] A'-1: sodium hydroxide (pH 14.0, average particle size: 20 μm)

[0181] (Biodegradable resin (B))

[0182] [Aliphatic polyester resin (B1)]

[0183] B1-1: BioPBS FZ91 (an aliphatic polyester resin manufactured by Petroleum Authority of Thailand (PTT), Mitsubishi Chemical Corporation (MCC), Biochem: PBS resin)

[0184] B1-2: Ingeo Biopolymer 6252D (an aliphatic polyester resin manufactured by NatureWorks: PLA resin)

[0185] [Aliphatic-aromatic polyester resin (B2)]

[0186] B2-1: Ecoflex C1200 (an aliphatic-aromatic polyester resin manufactured by BASF: PBAT resin)

[0187] [Thickener (C)]

[0188] C-1: KC Flock W-50 (manufactured by Nippon Paper Industries Co., Ltd., cellulose microfibrils, average fiber length: 50 μm)

[0189] C-2: Carbodilite HMV-15CA (manufactured by Nisshinbo Chemical Inc., polycarbodiimide compound)

[0190] C-3: Carbosista TCC-NP (manufactured by Teijin Limited, cyclic carbodiimide compound)

[0191] C-4: Joncryl ADR-4468 (manufactured by BASF, epoxy-acrylic compound)

[0192] C-5: XIBOND 220 (manufactured by PALMER HOLLAND, styrene maleic anhydride compound)

[0193] C-6: Epocros RA-45 (manufactured by Nippon Catalyst Co., Ltd., oxazoline compound)

[0194] C-7: Aerosil 200 (manufactured by Aerosil Co., Ltd. Japan, silica filler)

[0195] C-8: Nipsil SS-50 (manufactured by Tosoh Silica Corporation, silica filler)

[0196] (Other thickeners)

[0197] C'-1: Sumecton - SWF (manufactured by Kunimine Industries Co., Ltd., synthetic lithium montmorillonite)

[0198] (Starch (D))

[0199] D-1: Chemistar 420 (manufactured by Glico Nutrition Foods Co., Ltd., average particle size: 15 μm)

[0200] <Manufacture of thermoplastic resin composition for agricultural materials>

[0201] [Example 1]

[0202] (Manufacture of thermoplastic resin composition (composite) for agricultural materials)

[0203] Mix 5 parts by mass of (A-1) as the basic filler (A), 64.5 parts by mass of (B1-1) and 30 parts of (B2-1) as the biodegradable resin (B), and 0.5 parts by mass of (C-1) as the thickener (C), and extrude and pelletize at 190 °C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) to obtain a thermoplastic resin composition for agricultural materials.

[0204] (Manufacture of seedling trays)

[0205] Use the obtained thermoplastic resin composition for agricultural materials and perform forming by blow molding and vacuum forming to obtain a seedling tray.

[0206] [Examples 2 to 14, Reference Example 15, Examples 16 to 35, Comparative Examples 1 to 5]

[0207] Respectively change to the materials and blending amounts (parts by mass) shown in Table 1. Except for this, use the same method as in Example 1 to respectively obtain a thermoplastic resin composition for agricultural materials and a seedling tray.

[0208] In addition, due to poor formability, the thermoplastic resin compositions for agricultural materials in Comparative Examples 3, 4, 7 to 9 cannot be used to manufacture seedling trays, so the strength evaluation, brittleness evaluation, and biodegradability rate evaluation of the formed products cannot be performed.

[0209] Evaluate the thermoplastic resin compositions for agricultural materials and the seedling trays obtained in the examples, reference examples, and comparative examples according to the following criteria. The evaluation results are shown in Table 1.

[0210] <Processability Evaluation>

[0211] Evaluate the processability during extrusion of the thermoplastic resin composition for agricultural materials. The evaluation criteria are as follows, and ○ and △ are considered practical.

[0212] [Evaluation Criteria]

[0213] 〇: No strand breakage occurs during continuous production for 1 hour.

[0214] △: Strand breakage occurs 1 to 5 times during continuous production for 1 hour.

[0215] ×: Strand breakage occurs more than 6 times during continuous production for 1 hour.

[0216] <Melt Viscosity Evaluation>

[0217] According to JIS K7199:1999, measure the melt viscosity of the thermoplastic resin composition for agricultural materials at a temperature of 150 °C, which is above the melting point and below the melting point + 40 °C of the thermoplastic resin (B) used in the examples, reference examples, and comparative examples, at a shear rate of 243 s -1 The evaluation criteria are as follows, and ○ and △ are considered practical.

[0218] [Evaluation Criteria]

[0219] ○: The melt viscosity is 1500 Pa·s or more

[0220] △: The melt viscosity is 1000 or more and less than 1500 Pa·s

[0221] ×: The melt viscosity is less than 1000 Pa·s

[0222] <Blow Molding Processability Evaluation>

[0223] Using a direct blow molding machine (manufactured by Placon Co., Ltd., Japan), continuously produce 3 sets of two-piece seedling trays (diameter 9 cm, height 7 cm) at 150 °C. Evaluate the formability during production based on the difference in weight (weight difference) between each seedling tray in the first set and each seedling tray in the third set, as well as the weight of each seedling tray. In addition, in this evaluation, "blow moldable" means that the weight difference is less than 30% relative to the weight of each seedling tray in the first set. The evaluation criteria are as follows, and ○ and △ are considered practical.

[0224] [Evaluation Criteria]

[0225] ○: Blow moldable, and the weight of each seedling tray is 0.9 g or more

[0226] △: Can be blow - molded, the weight of each seedling - raising pot is more than 0.7 g and less than 0.8 g

[0227] ×: Cannot be blow - molded

[0228] <Vacuum formability evaluation>

[0229] Use a T - die forming machine to form a sheet with a length of 30 cm, a width of 30 cm, and a thickness of 0.45 mm at 180°C. Heat the formed sheet to 110°C, and use a vacuum forming machine to form a seedling - raising pot (diameter 6 cm, height 7 cm), and evaluate the formability during production. The evaluation criteria are as follows, and ○ and △ are considered practical.

[0230] [Evaluation criteria]

[0231] ○: Can be vacuum - formed, and there is no defective appearance part caused by sagging in the seedling - raising pot.

[0232] △: Can be vacuum - formed, and a defective appearance part caused by sagging can be confirmed in the seedling - raising pot.

[0233] ×: Cannot be vacuum - formed.

[0234] <Formed product strength evaluation>

[0235] Evaluate the strength of the seedling - raising pots made during the blow - mold formability evaluation. The evaluation criteria are as follows, and ○ and △ are considered practical.

[0236] [Evaluation criteria]

[0237] ○: The seedling - raising pot stands upright without deflection.

[0238] △: The seedling - raising pot deflects but stands upright.

[0239] ×: The seedling - raising pot cannot withstand its own weight and cannot stand upright.

[0240] -: Cannot make a seedling - raising pot and cannot conduct an evaluation.

[0241] <Formed product brittleness evaluation>

[0242] Put 1 kg of soil into each of the 10 seedling - raising pots made during the vacuum formability evaluation and drop them from a height of 5 m to evaluate the brittleness of the seedling - raising pots. The evaluation criteria are as follows, and ○ and △ are considered practical.

[0243] [Evaluation criteria]

[0244] ○: None of the 10 seedling - raising pots are damaged.

[0245] △: 1 - 3 out of 10 are damaged.

[0246] ×: 4 or more out of 10 are damaged.

[0247] -: Unable to fabricate the seedling-raising pot, thus unable to conduct the evaluation.

[0248] <Biodegradation rate evaluation>

[0249] Put 1 kg of soil into the seedling-raising pot fabricated during the blow molding formability evaluation. After 4 months, confirm the shape of the seedling-raising pot to evaluate the biodegradability. The evaluation criteria are as follows. Consider ○ and △ as practical.

[0250] [Evaluation criteria]

[0251] ○: The seedling-raising pot retains its original shape.

[0252] △: The seedling-raising pot degrades and has perforations everywhere.

[0253] ×: The seedling-raising pot degrades and becomes scattered.

[0254] -: Unable to fabricate the seedling-raising pot, thus unable to conduct the evaluation.

[0255] <Biodegradation rate evaluation in soil>

[0256] Bury the seedling-raising pot fabricated during the blow molding formability evaluation underground. Dig it out after 2 weeks, 1 month, and 3 months to evaluate the biodegradability. The evaluation criteria are as follows. Consider ○ and △ as practical.

[0257] [Evaluation criteria]

[0258] ○: The seedling-raising pot degrades and becomes scattered.

[0259] △: The seedling-raising pot degrades and has perforations everywhere.

[0260] ×: The seedling-raising pot retains its original shape.

[0261] -: Unable to fabricate the seedling-raising pot, thus unable to conduct the evaluation.

[0262] [Table 1]

[0263] Table 1.

[0264]

[0265] [Table 2]

[0266] Table 2.

[0267]

[0268] [Table 3]

[0269] Table 3.

[0270]

[0271] [Table 4]

[0272] Table 4.

[0273]

[0274] Based on the above results, it can be confirmed that the resin composition and the seedling-raising pot of the embodiment are environmentally responsive types, which can not only significantly promote biodegradation but also have excellent formability.

[0275] As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above content. Various modifications understandable by those skilled in the art can be made to the structure or details of the present invention within the scope of the invention.

[0276] The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2023-027480 filed with the Japan Patent Office on February 24, 2023, and the entire disclosure of the said application is incorporated herein by reference.

Claims

1. A thermoplastic resin composition for agricultural materials, which is a thermoplastic resin composition containing an alkaline filler (A), a biodegradable resin (B), and a thickener (C), wherein, The pH of the alkaline filler (A) in water is 8.5 to 12.5, The biodegradable resin (B) contains an aliphatic polyester resin (B1) and an aliphatic-aromatic polyester resin (B2), The thickener (C) contains at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and silica-based fillers, Based on 100% by mass of the thermoplastic resin composition, the content of the alkaline filler (A) is 5% to 30% by mass and the content of the thickener (C) is 0.5% to 3% by mass.

2. The thermoplastic resin composition for agricultural materials according to claim 1, wherein, The alkaline filler (A) contains at least one selected from the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, and magnesium hydroxide.

3. The thermoplastic resin composition for agricultural materials according to claim 1, wherein, The pH of the alkaline filler (A) in water is 10.0 to 12.

5.

4. The thermoplastic resin composition for agricultural materials according to claim 1, wherein, The average particle size of the alkaline filler (A) is 1 μm to 10 μm.

5. The thermoplastic resin composition for agricultural materials according to claim 1, wherein, The thickener (C) contains at least any one of carbodiimide compounds and cellulose fibers.

6. The thermoplastic resin composition for agricultural materials according to claim 1, wherein, Based on 100 parts by mass of the aliphatic-aromatic polyester resin (B2), the content of the aliphatic polyester resin (B1) is 100 parts by mass to 300 parts by mass.

7. The thermoplastic resin composition for agricultural materials according to claim 1, wherein Based on 100 parts by mass of the aliphatic-aromatic polyester resin (B2), the content of the aliphatic polyester resin (B1) is 130 parts by mass to 300 parts by mass.

8. The thermoplastic resin composition for agricultural materials according to claim 1, wherein, Shearing speed: 243 s -1 The melt viscosity under -1 is 1000 Pa·s or more and less than 5000 Pa·s at a temperature above the melting point of the biodegradable resin (B) and below the melting point + 40°C.

9. The thermoplastic resin composition for agricultural materials according to claim 1, which is used for blow molding or vacuum molding.

10. The thermoplastic resin composition for agricultural materials according to claim 1, which is used for seedling raising containers.

11. An agricultural material formed by using the thermoplastic resin composition for agricultural materials according to any one of claims 1 to 10.

12. The agricultural material according to claim 11, which is a seedling raising container.

13. The agricultural material according to claim 11, which is a seedling raising container for cultivating seedlings in the seedling raising container before being buried in the soil and burying the seedling raising container in the soil after the seedling raising period to cultivate plants.

Images