Thermoplastic resin composition for agricultural materials, and agricultural material

Abstract

Disclosed are: a thermoplastic resin composition which is for agricultural materials, which contains starch, biodegradable resins, and a viscosity modifier, and in which the contained amount of a plasticizing agent is 0-5 parts by mass with respect to 100 parts by mass of the thermoplastic resin composition for agricultural materials, and the biodegradable resins include an aliphatic polyester based resin and an aliphatic aromatic polyester based resin; and an agricultural material formed by using said thermoplastic resin composition for agricultural materials.

Description

Thermoplastic resin composition for agricultural materials and agricultural materials

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

[0002] Plastics are easy to mold and 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 or functionality such as strength depending on the application.In the agricultural materials field, plastics 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 of collecting 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.

[0005] Patent Document 1 describes a film that contains an aliphatic polyester resin, an aromatic aliphatic polyester resin, starch, and a polyhydric alcohol in a specific mass ratio, and thereby has high tear strength, good biodegradability, formability, heat shrinkability, and transparency, a high elastic modulus, and is wrinkle-resistant.

[0006] In this film, aliphatic polyester resins and aromatic aliphatic polyester resins are used as biodegradable materials, and by adjusting the content of polyhydric alcohol, the plasticization of starch is promoted while the physical properties of the resin composition, such as tear strength and tensile modulus, are improved.

[0007] JP 2011-26538 A

[0008] Starch is not thermoplastic and has a low thermal decomposition temperature, so that the resin composition can be modified by adding a plasticizer such as a polyhydric alcohol. However, if a plasticizer is contained in the resin composition, the surface of the resulting molded article becomes sticky, and the releasability between the mold of the molding machine and the resin composition during molding and the slipperiness for separating the molded articles individually are reduced, which may affect the molding of the resin composition.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a thermoplastic resin composition for agricultural materials that can be used to produce molded articles with reduced surface stickiness, that has biodegradability and good moldability, and an agricultural material made from the thermoplastic resin composition for agricultural materials.

[0010] In order to solve the above problems, the present inventors have conducted extensive research and have found a thermoplastic resin composition for agricultural materials having the following constitution, thereby completing the present invention.

[0011] That is, one embodiment of the present invention is as follows: <1> A thermoplastic resin composition for agricultural use, comprising starch, a biodegradable resin, and a viscosity modifier, wherein the content of a plasticizer is 0 to 5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use, the biodegradable resin comprises an aliphatic polyester resin and an aliphatic-aromatic polyester resin, the total content of the aliphatic polyester resin and the aliphatic-aromatic polyester resin is 80 parts by mass or more per 100 parts by mass of the biodegradable resin, the content of the starch is 5 to 60 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use, the content of the biodegradable resin is 35 to 94.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use, The thermoplastic resin composition for agricultural materials, wherein the viscosity modifier is a viscosity modifier that increases the melt tension of the thermoplastic resin composition for agricultural materials, and the viscosity modifier comprises at least one selected from the group consisting of a carbodiimide compound, an oxazoline compound, an epoxy compound, an acid anhydride compound, a cellulose fiber, and a silica-based filler, the content of the viscosity modifier is 0.01 to 3 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the cellulose fiber is 0 to 1.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, and the content of the aliphatic polyester-based resin is equal to or greater than the content of the aliphatic aromatic polyester-based resin.<2> The thermoplastic resin composition for agricultural materials according to <1>, wherein the content of the starch is 10 to 30 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials.<3> The thermoplastic resin composition for agricultural materials according to <1> or <2>, wherein the average particle size of the starch is 5 to 50 μm. <4> The thermoplastic resin composition for agricultural use according to any one of <1> to <3>, wherein the viscosity modifier comprises at least one selected from the group consisting of cellulose fiber and a carbodiimide compound. <5> The thermoplastic resin composition for agricultural use according to any one of <1> to <4>, wherein the content ratio (parts by mass) of the aliphatic polyester resin to the aliphatic aromatic polyester resin is 1 to 3:1. <6> A shear rate of 243 s －１The thermoplastic resin composition for agricultural materials according to any one of <1> to <5>, having a melt viscosity of 1,000 Pa s or more and less than 5,000 Pa s at a temperature of not less than the melting point of the biodegradable resin (B) and not more than the melting point + 40°C. <7> The thermoplastic resin composition for agricultural materials according to any one of <1> to <6>, which is used for blow molding or vacuum molding. <8> The thermoplastic resin composition for agricultural materials according to any one of <1> to <7>, which is used for a seedling pot. <9> An agricultural material formed using the thermoplastic resin composition for agricultural materials according to any one of <1> to <8> above. <10> The agricultural material according to <9>, which is a seedling pot.

[0012] According to one embodiment of the present invention, it is possible to provide a thermoplastic resin composition for agricultural materials that is biodegradable and has good moldability, and that can produce molded articles with reduced surface stickiness, and an agricultural material made from the thermoplastic resin composition for agricultural materials.

[0013] <Thermoplastic resin composition for agricultural materials> The thermoplastic resin composition for agricultural materials according to this embodiment is characterized by containing starch, a biodegradable resin, and a viscosity modifier, but not containing a plasticizer. By adjusting the starch and viscosity modifier contents to specific levels and not containing a plasticizer, the resulting resin composition has good moldability, is biodegradable, and can suppress stickiness on the surface of molded products.

[0014] In this disclosure, the "thermoplastic resin composition for agricultural materials" may also be referred to as the "resin composition," "starch" may also be referred to as the "starch (A)," "biodegradable resin" may also be referred to as the "biodegradable resin (B)," "viscosity modifier" may also be referred to as the "viscosity modifier (C)," and "plasticizer" may also be referred to as the "plasticizer (D)."

[0015] The decomposition process of resin compositions can be broadly divided into two stages. In the first stage, the resin that constitutes agricultural materials (such as seedling pots and mulch films) molded from the resin composition is degraded by hydrolysis or oxidative decomposition. In the second stage, individual pieces of the agricultural material made of the degraded resin are decomposed by microorganisms in the soil. Because the degrading of the resin continues even during storage or use of the agricultural materials, controlling hydrolysis in the first stage is important. Resin crystallinity is one factor in hydrolysis. Because hydrolysis is more likely to occur in amorphous regions than in crystalline regions, increasing crystallinity can suppress hydrolysis. Generally, when additives are added to a thermoplastic resin composition, their particles act as crystal nuclei, promoting crystal formation (nucleation effect), improving crystallinity and suppressing hydrolysis.

[0016] The thermoplastic resin composition for agricultural materials of this embodiment contains specific amounts of starch (A) that promotes biodegradability and viscosity modifier (C) that increases melt tension, and therefore the biodegradation rate of the agricultural material made of the resin composition can be adjusted. For example, it is desirable that the decomposition of the agricultural material is suppressed and its shape can be maintained for at least about four months, which is the period during which the seeds and seedlings are grown, and that the agricultural material has been decomposed by microorganisms in the soil about one year after the period has passed, and can be incorporated into the soil.

[0017] This embodiment will be described in detail below.

[0018] (Starch (A)) Starch (A) promotes the activity (biodegradability) of various microorganisms present in soil or water. There are no particular limitations on the starch (A), and commonly available starches can be used. Examples include corn starch, wheat starch, rice starch, potato starch, sweet potato starch, and tapioca starch. Among these, the use of corn starch with a uniform particle size of about 20 μm is preferred because it makes it possible to make the thickness of agricultural materials made of a resin composition uniform (reducing surface irregularities), suppressing the occurrence of thin portions, and consequently suppressing damage to the agricultural materials. These may be used alone or in combination of two or more.

[0019] Starch (A) is a component that can adjust the biodegradation rate, and its content is preferably 5 to 60 parts by mass, and may be 10 to 50 parts by mass, 10 to 40 parts by mass, or 10 to 30 parts by mass, per 100 parts by mass of the resin composition. When the content of starch (A) is 5 parts by mass or more, biodegradation is promoted, and when it is 60 parts by mass or less, the content of biodegradable resin (B) is ensured, and moldability can be ensured.

[0020] From the viewpoint of moldability, the average particle size of the starch (A) is preferably 5 to 50 μm, and may be 10 to 50 μm. When the average particle size of the starch (A) is within the above range, both the dispersibility of the starch (A) in the biodegradable resin (B) and the smoothness of the surface of the molded article can be achieved.

[0021] In particular, in blow molding in which a resin is directly placed in a mold and air is blown into it, the average particle size of the starch (A) in the resin composition contributes to moldability, and therefore it is preferable that the average particle size of the starch (A) be in the above-mentioned range.

[0022] The average particle size of the starch (A) can be determined, for example, by observing particles of the starch (A) with a scanning electron microscope, randomly observing 100 particles, measuring the distance between the two most distant points on the outer shape of each particle based on the length of a micron marker on the screen, and averaging the measured values.

[0023] (Biodegradable Resin (B)) The biodegradable resin (B) is decomposed by the action of various microorganisms present in soil or water. The biodegradable resin (B) is not particularly limited, and any commonly available biodegradable resin can be used. Examples include polycaprolactone, aliphatic polyester resins, and aliphatic aromatic polyester resins. These biodegradable resins may be used alone or in combination of two or more.

[0024] Among these, aliphatic polyester resins or aliphatic aromatic polyester resins are preferred from the viewpoints of biodegradability and moldability. Furthermore, when an aliphatic polyester resin and an aliphatic aromatic polyester resin are used in combination as a biodegradable resin, the content of the aliphatic polyester resin is preferably equal to or greater than the content of the aliphatic aromatic polyester resin. By mixing the aliphatic polyester resin as the base resin with an aliphatic aromatic polyester resin that is malleable and highly moldable, the moldability of the resin composition and the strength of the agricultural materials molded therefrom can be ensured. The content ratio (parts by mass) of the aliphatic polyester resin to the aliphatic aromatic polyester resin is, for example, preferably 1 to 4:1, more preferably 1 to 3:1, even more preferably 1 to 2:1, particularly preferably 1 to 1.65:1, even more preferably 1 to 1.57:1, and may be 1.5 to 2:1.

[0025] Examples of aliphatic polyester resins include aliphatic polyesters obtained by polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid, and polylactic acid 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 mixtures of these with adipic acid, are preferred. Specific examples include polybutylene succinate (PBS) obtained from 1,4-butanediol and succinic acid (for example, "BioPBS" (trade name) manufactured by PPT MCC Biochem Co., Ltd.), and polybutylene succinate adipate (PBSA) obtained by copolymerizing PBS with adipic acid.

[0026] Examples of 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 units typically has 2 to 10 carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Of these, diols with 2 to 4 carbon atoms are preferred, with ethylene glycol and 1,4-butanediol being more preferred, and 1,4-butanediol being even more preferred. The dicarboxylic acid component that provides the dicarboxylic acid units typically has 2 to 10 carbon atoms, such as 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 units include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Among these, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is more preferred.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.).

[0027] The biodegradable resin (B) may be a combination of the above-mentioned aliphatic polyester resin and / or aliphatic aromatic polyester resin with other biodegradable resins. Examples of other biodegradable resins include poly(3-hydroxyalkanoates), which are aliphatic polyester copolymers obtained from hydroxyalkanoic acids and polycarboxylic acids (particularly, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) (e.g., "Aonilex" (trade name) manufactured by Kaneka Corporation), and polylactic acid (PLA) (e.g., "REVODE" (trade name) manufactured by Kaisei Biomaterials Co., Ltd., and "Ingeo" (trade name) manufactured by NatureWorks).

[0028] The content of the biodegradable resin (B) may be 35 to 95 parts by mass, more preferably 35 to 94.99 parts by mass, even more preferably 35 to 94.5 parts by mass, and even more preferably 39 to 90 parts by mass, per 100 parts by mass of the resin composition. By ensuring that the content of the biodegradable resin (B) is within the above range, the resin composition can achieve both good processability and moldability. Furthermore, the total content of the aliphatic polyester resin and / or the aliphatic aromatic polyester resin is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, per 100 parts by mass of the biodegradable resin (B).

[0029] (Viscosity modifier (C)) The viscosity modifier (C) adjusts the viscosity of the resin composition to improve moldability, and increases the melt tension of the resin composition, which is an indicator of moldability. The viscosity modifier (C) is not particularly limited, and commonly available ones can be used. Examples include carbodiimide compounds, oxazoline compounds, epoxy compounds, acid anhydride compounds, cellulose fibers, and silica-based fillers.

[0030] The viscosity modifier (C) can be a polyfunctional compound, which forms a crosslinked structure with the biodegradable resin (B), thereby increasing the melt tension of the resin composition. Examples of the polyfunctional compound include polyfunctional carbodiimide compounds, polyfunctional oxazoline compounds, epoxy compounds, acid anhydride compounds, etc. 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.

[0031] A reactive compound is used as the viscosity modifier (C) to introduce a reactive group into the biodegradable resin (B), and a crosslinking structure is formed starting 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. The cyclic carbodiimide compound is a compound having a carbodiimide group on an aliphatic ring or an aromatic ring.

[0032] The viscosity modifier (C) can be a filler, which can increase the solid content of the resin composition and thereby increase the viscosity, thereby increasing the melt tension of the resin composition. The filler can be either an organic filler or an inorganic filler, such as cellulose fiber or silica-based filler.

[0033] In a preferred embodiment, compounds listed on the positive list for green plastics can be used, such as cellulose microfiber (CMF), which is a cellulose fiber, and carbodiimide compound (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 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 its strength.

[0034] 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, the silica-based filler has the same filler effect as the cellulose microfibers, and therefore increases the strength of the resin composition in the same way as the cellulose microfibers. For example, blow molding or the like can be used to mold a resin composition containing at least one of cellulose microfibers and silica-based fillers as the viscosity modifier (C).

[0035] When a carbodiimide compound is contained in a resin composition, the resin reacts with the carbodiimide compound, increasing the molecular weight of the resin. This increases the time it takes for the resin to be hydrolyzed and its molecular weight to decrease, slowing the rate of biodegradation. Therefore, in agricultural materials where strength is required for the resin composition, it is preferable to include a carbodiimide compound as the viscosity modifier (C). Furthermore, oxazoline compounds, epoxy compounds, and acid anhydride compounds each have the same reactivity with resins as carbodiimide compounds, and therefore these compounds can also improve the strength of the resin composition. Resin compositions containing at least one of a carbodiimide compound, an oxazoline compound, an epoxy compound, and an acid anhydride compound can be molded, for example, using vacuum molding.

[0036] Examples of the carbodiimide compound 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 of two or more.

[0037] Examples of oxazoline compounds include "EPOCROS RA-45" (trade name) and "EPOCROS RPS-1005" (trade name) manufactured by Nippon Shokubai Co., Ltd. These compounds may be used alone or in combination of two or more types. Examples of epoxy compounds include epoxy-acrylic compounds ("JONCRYL ADR-4468" (trade name) manufactured by BASF Corporation, "JONCRYL ADR-4400" (trade name) manufactured by BASF Corporation, "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 types. Examples of acid anhydride compounds include styrene maleic anhydride compounds (PALMER Examples include "XIBOND120" (trade name), "XIBOND140" (trade name), "XIBOND160" (trade name), "XIBOND180" (trade name), "XIBOND200" (trade name), "XIBOND220" (trade name), "XIBOND250" (trade name), and "XIBOND280" (trade name) manufactured by Holland Corporation, and "XIRAN1000" (trade name), "XIRAN2000" (trade name), "XIRAN2500" (trade name), "XIRAN3000" (trade name), "XIRAN4000" (trade name), "XIRAN6000" (trade name), "XIRAN9000" (trade name), "XIRAN3500" (trade name), and "XIRAN3600" (trade name) manufactured by Tomoe Engineering Co., Ltd. These compounds may be used alone or in combination of multiple types. Examples of silica-based fillers include silica fillers (manufactured by Nippon Aerosil Co., Ltd., such as "Aerosil 130" (trade name), "Aerosil 150" (trade name), "Aerosil 200" (trade name), "Aerosil 300" (trade name), "Aerosil RX200" (trade name), and "Aerosil RY200" (trade name), and Tosoh Silica Corporation, such as "Nipsil SS-50" (trade name), "Nipsil SS-50B" (trade name), "Nipsil SS-50F" (trade name), "Nipsil K-500" (trade name), and "Nipsil G-300" (trade name). These may be used alone or in combination of multiple types.

[0038] In order to make the viscosity of the resin composition appropriate, the content of the viscosity modifier (C) is preferably 0.01 to 3 parts by mass, more preferably 0.01 to 2 parts by mass, or may be 0.01 to 1 part by mass, or 0.1 to 0.8 parts by mass, per 100 parts by mass of the resin composition.

[0039] Furthermore, because cellulose fibers contribute to the high viscosity and strength of a resin composition, a high content of cellulose fibers in a resin composition may result in a decrease in the fluidity and processability of the resin composition, and a decrease in the moldability of the resin composition. Therefore, when cellulose fibers are contained in a resin composition, the content of cellulose fibers is preferably 0 parts by mass or more and less than 1.5 parts by mass, preferably 0.01 to 1.4 parts by mass, more preferably 0.01 to 1.2 parts by mass, and even more preferably 0.01 to 1 part by mass, per 100 parts by mass of the resin composition. By ensuring that the content of cellulose fibers is within the above range, the fluidity and processability of the resin composition can be ensured, and a decrease in the moldability of the resin composition can be suppressed.

[0040] (Plasticizer (D)) The thermoplastic resin composition for agricultural materials of this embodiment does not contain a plasticizer (D) that is usually used to plasticize starch (A). In this specification, "not containing a plasticizer (D)" means that the plasticizer (D) is substantially not contained, and specifically means that the content of the plasticizer (D) is 0 to 5 parts by mass per 100 parts by mass of the resin composition.

[0041] Examples of the plasticizer (D) include alcohols, which are organic compounds having a hydroxyl group, such as glycerin, glycerin monoester, ethylene glycol, and diethylene glycol.

[0042] When the amount of the plasticizer (D) is 5 parts by mass or less relative to 100 parts by mass of the resin composition, the surface stickiness of the obtained molded article can be suppressed while maintaining good moldability. From the viewpoints of suppressing stickiness and moldability, the content of the plasticizer (D) is preferably 0 to 2 parts by mass, more preferably 0 to 1 part by mass, and even more preferably 0 part by mass (not included) relative to 100 parts by mass of the resin composition.

[0043] (Other Components) The resin composition may optionally contain other additives and other components (excluding the plasticizer (D)) as needed. Examples of other additives include dispersants, lubricants (higher fatty acid metal salts, waxes, etc.), hydrotalcite, surfactants, antistatic agents, flame retardants, antioxidants, UV absorbers, fillers, pigments, etc. The selection of other optional components and their amounts to be used 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 as long as the effects of one embodiment of the present invention are not impaired.

[0044] By coloring the resin composition with a pigment, it is possible to produce a molded article with excellent heat-shielding effect or an easily identifiable molded article. The pigment is not particularly limited, and a commonly available pigment can be used, but from the viewpoint of the natural environment, it is preferable that the resin composition is substantially free of pigments containing cadmium, lead, chromium, arsenic, mercury, copper, selenium, nickel, molybdenum, or fluorine.

[0045] For example, when the resin composition contains a pigment, it is preferable to use a dispersant to disperse the pigment, and examples of such dispersants include fatty acid metal salts. The fatty acid component of the fatty acid metal salt is preferably a chain carboxylic acid having 6 to 30 carbon atoms, which may be linear or branched, and may contain only saturated or unsaturated bonds. Examples of fatty acids include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, behenic acid, oleic acid, erucic acid, linoleic acid, and montanic acid. As the metal, elements of Groups 1, 2, 12, and 13 are preferred, with elements of Groups 1 and 2 being more preferred. Specific examples include sodium, potassium, calcium, magnesium, and barium.

[0046] Examples of fatty acid metal salts include calcium stearate, magnesium stearate, barium stearate, calcium laurate, magnesium laurate, and sodium montanate. These may be used alone or in combination of two or more. Of these, calcium stearate, magnesium stearate, calcium laurate, and magnesium laurate are preferred.

[0047] (Processability) In the above-described thermoplastic resin composition for agricultural materials, the processability during extrusion is such that strand breakage occurs 5 times or less during continuous production for 1 hour, and may occur 1 to 5 times, and it is preferable that strand breakage does not occur.

[0048] (Melt Viscosity) In the above-mentioned thermoplastic resin composition for agricultural materials, the melt viscosity is －１ The melt viscosity at a temperature of not less than the melting point of the biodegradable resin (B) and not more than the melting point + 40°C is preferably 1000 Pa s or more and less than 5000 Pa s, and more preferably 1500 Pa s or more and less than 4500 Pa s, from the viewpoints of the strength of the obtained molded article and the fluidity and moldability of the resin composition.

[0049] (Uses) The thermoplastic resin composition for agricultural materials according to this embodiment can be used for a variety of agricultural materials. In particular, this resin composition can be suitably used for seedling raising pots. Seedling raising pots are pots used to raise seeds in containers until they have grown to a certain extent, rather than sowing the seeds directly in a field. Since molded articles using the resin composition according to this embodiment are suitably biodegradable in soil, there is no need to remove the seeds from the seedling raising pots and transplant them after they have grown; they can be transplanted into soil in their seedling raising pots.

[0050] <<Production Method>> The resin composition of this embodiment can be produced by kneading starch (A) and viscosity modifier (C) at a temperature at which the biodegradable resin (B) melts. Specifically, for example, the biodegradable resin (B), starch (A), viscosity modifier (C), and, if necessary, various additives are added, and the mixture is mixed and melt-kneaded using a kneader, roll mill, super mixer, 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 resin composition in the form of pellets, powder, granules, or beads. Because of their strong kneading power and ease of subsequent molding, pelletization using a single-screw or twin-screw extruder is preferred.

[0051] The resin composition may be used in the form of either a masterbatch or a compound. In the case of a masterbatch, after the masterbatch is produced, the agricultural material can be manufactured by blending the masterbatch with, for example, the same biodegradable resin (B) used in the production of the masterbatch as the base resin of the agricultural material, using the same biodegradable resin (B) as the diluent resin. The masterbatch preferably contains 1 to 50 parts by mass, more preferably 1 to 20 parts by mass, of the masterbatch per 100 parts by mass of the biodegradable resin (B) as the base resin. The biodegradable resin (B) used as the diluent resin in this case may be the same as or different from that used in the production of the masterbatch. However, using the same biodegradable resin is preferred because it provides superior compatibility between the thermoplastic resin composition and the resin. In the case of a compound, after the compound is produced, the compound can be used as is to manufacture the agricultural material using the method described above.

[0052] <Agricultural Material> The agricultural material of this embodiment can be obtained by molding the above-mentioned thermoplastic resin composition for agricultural materials. Examples of the agricultural material include seedling pots, mulch films, containers, and agricultural nets.

[0053] (Seedling Pot) The seedling pot is a container used for the above-mentioned purpose. The method of molding the seedling pot is not particularly limited, but suitable methods include, for example, blow molding, in which a heated and plasticized resin composition is extruded and then directly placed in a mold without being cooled and solidified, and air is blown into the mold, and vacuum molding, in which a sheet or film of the heated and plasticized resin composition is placed on a mold and vacuum-suctioned from the inside of the mold to form the pot.

[0054] Seedling pots made from the resin composition described above biodegrade after being buried in soil, thereby not damaging the natural environment and reducing the labor required to remove seedlings from the seedling pots and sow them. The seedling pots allow seeds to grow well without decomposing for the approximately four-month seedling growing period. Furthermore, because the seedling pots have strength suitable for seedling raising, they are easy to handle and maintain their proper shape throughout the seedling raising period.

[0055] (Mulch film) A mulch film (mulching film) is a film that covers the base of a crop. The method for molding the resin composition 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.

[0056] <Blow Molding, Vacuum Molding> The melt tension of the resin composition described above is increased by the viscosity modifier (C), and therefore drawdown (a phenomenon in which a preformed resin cannot withstand its own weight and sags in the direction of gravity) can be suppressed.

[0057] In the case of blow molding, it is possible to prevent the molded product from becoming thinner and lighter. The resin composition of this embodiment can be blow molded. For example, when three sets of two seedling pots are continuously produced using a direct blow molding machine, the difference in weight between the first set of seedling pots and the third set of seedling pots can be made less than 30% of the weight of the first set of seedling pots. Furthermore, the weight per seedling pot may be 0.7 g or more but less than 0.8 g, preferably 0.8 g or more but less than 0.9 g, and more preferably 0.9 g or more. Blow moldability can be achieved by using the above-mentioned resin composition.

[0058] For example, when the molded product is a seedling pot, it is sufficient that the seedling pot has a strength sufficient to stand on its own, and it is preferable that the seedling pot does not warp. By using the above-mentioned resin composition, a seedling pot with ensured strength can be obtained.

[0059] In the case of vacuum molding, the occurrence of defective appearances due to sagging such as wrinkles caused by deflection of the sheet can be suppressed. For example, even if the molded product has defective appearances due to sagging, it is sufficient as long as vacuum molding can be performed using the resin composition, and it is preferable that the defective appearances are slight, and more preferably that there are no defective appearances. By using the above-mentioned resin composition, a vacuum molded product can be obtained.

[0060] For example, when the molded product is a seedling pot, the brittleness of the seedling pot is such that when 1 kg of soil is placed in the seedling pot and dropped from a height of 5 m, 3 or less of the seedling pots break out of 10, or 1 to 3 or less of the 10, and preferably none of the seedling pots break out. By using the above-mentioned resin composition, a seedling pot with sufficient strength can be obtained.

[0061] (Stickyness of molded article) The dynamic friction coefficient μD of the surface of a molded article molded using the above-mentioned resin composition according to JIS K7125 may be less than 0.5, may be 0.3 or more and less than 0.5, and is preferably less than 0.3. By using the above-mentioned resin composition, a molded article with reduced stickiness can be obtained.

[0062] (Biodegradation Rate) When a molded article made using the above-mentioned resin composition is buried in the ground for six months, it is sufficient that the molded article has decomposed to the point where holes are formed in places, and it is preferable that the molded article has decomposed and fallen into pieces. By using the above-mentioned resin composition, a molded article with an appropriately adjusted biodegradation rate can be obtained.

[0063] According to this embodiment, the thermoplastic resin composition for agricultural materials contains specific amounts of starch (A) that promotes biodegradability and viscosity modifier (C) that increases melt tension, and does not contain plasticizer (D), so it is possible to obtain agricultural materials that are excellent in biodegradability and moldability and have reduced surface stickiness.

[0064] Furthermore, the embodiments of the present invention include various embodiments not described herein. For example, the embodiments include the following.

[0065] [1] A thermoplastic resin composition for agricultural use comprising starch (A), a biodegradable resin (B), and a viscosity modifier (C), but not containing a plasticizer (D), wherein the content of the starch (A) is 5 to 60 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use, and the content of the viscosity modifier (C) is 0.01 to 1 part by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use. [2] The thermoplastic resin composition for agricultural use according to [1], wherein the content of the starch (A) is 10 to 30 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use. [3] The thermoplastic resin composition for agricultural use according to [1] or [2], wherein the average particle size of the starch (A) is 5 to 50 μm. [4] The thermoplastic resin composition for agricultural use according to any one of [1] to [3], wherein the viscosity modifier (C) comprises at least one selected from the group consisting of cellulose fiber and carbodiimide. [5] The thermoplastic resin composition for agricultural materials according to any one of claims [1] to [4], wherein the biodegradable resin (B) comprises an aliphatic polyester resin and an aliphatic-aromatic polyester resin, and the content of the aliphatic polyester resin is equal to or greater than the content of the aliphatic-aromatic polyester resin. [6] Shear rate: 243 s －１The thermoplastic resin composition for agricultural materials according to any one of [1] to [5], wherein the melt viscosity at a temperature of not less than the melting point of the biodegradable resin (B) and not more than the melting point + 40°C is 1,000 Pa s or more and less than 5,000 Pa s. [7] The thermoplastic resin composition for agricultural materials according to any one of [1] to [6], which is used for blow molding or vacuum molding. [8] The thermoplastic resin composition for agricultural materials according to any one of [1] to [7], which is used for seedling pots. [9] An agricultural material comprising the thermoplastic resin composition for agricultural materials according to the above [1] to [7].

[10] The agricultural material according to [9], which is a seedling pot.

[0066] In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range in one stage can be arbitrarily combined with the upper limit or lower limit of a numerical range in another stage.

[0067] The present invention is related to the subject matter of Japanese Patent Application No. 2022-053396, filed on March 29, 2022, the entire disclosure of which is incorporated herein by reference.

[0068] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" represent "parts by mass" and "% by mass", respectively, unless otherwise specified. In addition, the blending amounts in the tables are shown in parts by mass. Note that blank spaces in the tables indicate that no blending was performed. Note that the average particle size of starch was measured as follows.

[0069] <Measurement of average particle size> Starch particles were observed using a scanning electron microscope (SEM) manufactured by Hitachi, Ltd. at a magnification of 100x. 100 particles were randomly selected and the distance between the two most distant points on the outer shape of each particle was measured based on the length of a micron marker on the screen, and the average particle size was calculated.

[0070] Next, the materials used in the thermoplastic resin compositions for agricultural materials are listed below. (Starches (A)) A-1: ​​Chemistar 420 (manufactured by Glico Nutrition Foods Co., Ltd., corn-derived starch, average particle size: 15 μm) A-2: Chemistar 310 (manufactured by Glico Nutrition Foods Co., Ltd., cassava-derived starch, average particle size: 50 μm) A-3: FP (manufactured by Glico Nutrition Foods Co., Ltd., potato-derived starch, average particle size: 100 μm)

[0071] (Biodegradable resin (B)) B-1: BioPBS FZ91 (aliphatic polyester resin: PBS resin, manufactured by PTT MCC Biochem) B-2: Ecoflex C1200 (aliphatic aromatic polyester resin: PBAT resin, manufactured by B.A.S.F.) B-3: Ingeo Biopolymer 6252D (aliphatic polyester resin: PLA resin, manufactured by NatureWorks)

[0072] (Viscosity modifier (C)) C-1: KC Flock W-50 (cellulose microfiber, average fiber length: 50 μm) C-2: Carbodilite HMV-15CA (manufactured by Nisshinbo Chemical Inc., polycarbodiimide compound) C-3: Carbodista TCC-NP (manufactured by Teijin Limited, cyclic carbodiimide compound) C-4: Joncryl ADR-4468 (manufactured by BASF, epoxy-acrylic compound) C-5: XIBOND220 (manufactured by PALMER HOLLAND, styrene-maleic anhydride compound) C-6: EPOCROS RA-45 (manufactured by Nippon Shokubai Co., Ltd., oxazoline compound) C-7: Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd., silica filler) C-8: Nipsil SS-50 (manufactured by Tosoh Silica Corporation, silica filler)

[0073] (Plasticizer (D)) D: DG (manufactured by NOF Corporation, polyhydric alcohol, glycerin)

[0074] <Production of Thermoplastic Resin Composition for Agricultural Materials> [Experimental Example 1] (Production of Thermoplastic Resin Composition (Compound) for Agricultural Materials) 5 parts by mass of (A-1) as starch (A), 94.5 parts by mass of (B-1) as biodegradable resin (B), and 0.5 parts by mass of (C-1) as viscosity modifier (C) were mixed, extruded at 190°C using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.), and granulated to obtain a thermoplastic resin composition for agricultural materials.

[0075] (Production of seedling raising pot) The obtained thermoplastic resin composition for agricultural materials was subjected to blow molding or vacuum molding to obtain a seedling raising pot.

[0076] [Experimental Examples 2 to 35, Comparative Examples 1 to 5] Thermoplastic resin compositions for agricultural materials and seedling pots were obtained in the same manner as in Experimental Example 1, except that the materials and blending amounts (parts by mass) were changed to those shown in Table 1. Experimental Examples 1 to 13 contain only one of the aliphatic polyester resin (B-1 or B-3) and the aliphatic aromatic polyester resin (B-2) as the biodegradable resin, and can be treated as reference examples to distinguish them from the experimental examples in which the aliphatic polyester resin (B-1 or B-3) and the aliphatic aromatic polyester resin (B-2) are used in combination as biodegradable resins.

[0077]

[0078] The thermoplastic resin compositions for agricultural materials and the seedling pots obtained in the Experimental Examples and Comparative Examples were evaluated according to the following criteria. The evaluation results are shown in Table 1.

[0079] <Processability evaluation> The processability of the thermoplastic resin composition for agricultural materials during extrusion was evaluated. The evaluation criteria were as follows, with ◯ and △ being practical. [Evaluation criteria] ◯: No strand breakage occurred during one hour of continuous production. △: Strand breakage occurred 1 to 5 times during one hour of continuous production. ×: Strand breakage occurred 6 or more times during one hour of continuous production.

[0080] <Melt viscosity evaluation> According to JIS K7199:1999, at 150°C and a shear rate of 243 s －１ The melt viscosity of the thermoplastic resin composition for agricultural materials was measured. The evaluation criteria were as follows, with ◯ and △ being considered practical. [Evaluation criteria] ◯: Melt viscosity of 1500 Pa·s or more △: Melt viscosity of 1000 to less than 1500 Pa·s ×: Melt viscosity of less than 1000 Pa·s

[0081] <Evaluation of Blow Moldability> Three sets of two seedling pots were continuously produced at 150°C using a direct blow molding machine (manufactured by Nippon Placon Co., Ltd.), and the difference in weight per seedling pot between the first set and the third set (weight difference) and the weight per seedling pot were evaluated as moldability during production. In this evaluation, "blow moldable" means that the weight difference is less than 30% of the weight per seedling pot in the first set. The evaluation criteria are as follows, with ◎, ◯, and △ being considered practical. [Evaluation criteria] ◎: Blow moldable, weight per seedling pot is 0.9 g or more ○: Blow moldable, weight per seedling pot is 0.8 g or more but less than 0.9 g △: Blow moldable, weight per seedling pot is 0.7 g or more but less than 0.8 g ×: Blow moldable

[0082] <Evaluation of vacuum formability> A sheet measuring 30 cm long x 30 cm wide x 0.45 mm thick was formed at 180°C using a T-die forming machine. The formed sheet was heated to 110°C and formed into seedling pots using a vacuum forming machine, and the formability during production was evaluated. The evaluation criteria were as follows, with ⊚, ◯, and △ being considered practical. [Evaluation criteria] ⊚: Vacuum forming was possible, and the seedling pot had no external defects due to sagging. ◯: Vacuum forming was possible, and the seedling pot had slight external defects due to sagging. △: Vacuum forming was possible, and external defects due to sagging were confirmed in the seedling pot. ×: Vacuum forming was not possible.

[0083] <Evaluation of molded product strength> The seedling pots produced during the blow moldability evaluation were evaluated for strength. The evaluation criteria were as follows, with ◯ and △ being considered practical. [Evaluation criteria] ◯: The seedling pot stands on its own without bending. △: The seedling pot bends but stands on its own. ×: The seedling pot cannot stand on its own weight and cannot stand on its own.

[0084] <Evaluation of Molded Product Brittleness> 1 kg of soil was placed in each of 10 seedling pots produced during the vacuum formability evaluation, and the seedling pots were dropped from a height of 5 m to evaluate their brittleness. The evaluation criteria were as follows, with ◯ and △ being considered usable. [Evaluation Criteria] ◯: None of the seedling pots broke out of 10. △: Breakage occurred in 1 to 3 of the 10 pots. ×: Breakage occurred in 4 or more of the 10 pots.

[0085] <Evaluation of stickiness of molded articles> The coefficient of dynamic friction of the side surface of the seedling pots produced during the evaluation of blow moldability was measured in accordance with JIS K7125 to evaluate the stickiness of the seedling pots. The evaluation criteria were as follows, with ◯ and △ being considered practical. [Evaluation criteria] ◯: Dynamic friction coefficient μD is less than 0.3 △: Dynamic friction coefficient μD is 0.3 or more but less than 0.5 ×: Dynamic friction coefficient μD is 0.5 or more

[0086] <Biodegradability evaluation> The seedling pots produced for the evaluation of blow moldability were buried in the ground and dug up after 6 months to evaluate biodegradability. The evaluation criteria were as follows, with ◯ and △ being considered practical. [Evaluation criteria] ◯: The seedling pot has decomposed and fallen apart △: The seedling pot has decomposed to the point where holes have appeared in places ×: The seedling pot retains its original shape

[0087] From the above results, it was confirmed that the resin compositions and seedling pots in Experimental Examples 1 to 35 are not only environmentally friendly and biodegradable, but also have reduced surface stickiness and excellent moldability.

Claims

1. A thermoplastic resin composition for agricultural use, comprising starch, a biodegradable resin, and a viscosity modifier, wherein the content of a plasticizer is 0 to 5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use; the biodegradable resin comprises an aliphatic polyester resin and an aliphatic-aromatic polyester resin, and the total content of the aliphatic polyester resin and the aliphatic-aromatic polyester resin is 80 parts by mass or more per 100 parts by mass of the biodegradable resin; the content of the starch is 5 to 60 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the biodegradable resin is 35 to 94.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the viscosity modifier is a viscosity modifier that increases the melt tension of the thermoplastic resin composition for agricultural materials, the viscosity modifier includes at least one selected from the group consisting of a carbodiimide compound, an oxazoline compound, an epoxy compound, a cellulose fiber, and a silica-based filler; the content of the viscosity modifier is 0.01 to 3 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the cellulose fiber is 0 parts by mass or more and less than 1.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, A thermoplastic resin composition for agricultural materials, wherein the content of the aliphatic polyester resin is equal to or greater than the content of the aliphatic aromatic polyester resin.

2. A thermoplastic resin composition for agricultural use, comprising starch, a biodegradable resin, and a viscosity modifier, wherein the content of the plasticizer is 0 to 5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use; the biodegradable resin comprises an aliphatic polyester resin and an aliphatic-aromatic polyester resin, and the total content of the aliphatic polyester resin and the aliphatic-aromatic polyester resin is 80 parts by mass or more per 100 parts by mass of the biodegradable resin; the content of the starch is 10 to 50 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the biodegradable resin is 35 to 94.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the viscosity modifier is a viscosity modifier that increases the melt tension of the thermoplastic resin composition for agricultural materials, the viscosity modifier includes at least one selected from the group consisting of a carbodiimide compound, an oxazoline compound, an epoxy compound, an acid anhydride compound, a cellulose fiber, and a silica-based filler; the content of the viscosity modifier is 0.01 to 3 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the cellulose fiber is 0 parts by mass or more and less than 1.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, A thermoplastic resin composition for agricultural materials, wherein the content of the aliphatic polyester resin is equal to or greater than the content of the aliphatic aromatic polyester resin.

3. A thermoplastic resin composition for agricultural use, comprising starch, a biodegradable resin, and a viscosity modifier, wherein the content of the plasticizer is 0 to 5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural use; the biodegradable resin comprises an aliphatic polyester resin and an aliphatic-aromatic polyester resin, and the total content of the aliphatic polyester resin and the aliphatic-aromatic polyester resin is 80 parts by mass or more per 100 parts by mass of the biodegradable resin; the content of the starch is 5 to 60 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the biodegradable resin is 39 to 90 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the viscosity modifier is a viscosity modifier that increases the melt tension of the thermoplastic resin composition for agricultural materials, the viscosity modifier includes at least one selected from the group consisting of a carbodiimide compound, an oxazoline compound, an epoxy compound, an acid anhydride compound, a cellulose fiber, and a silica-based filler; the content of the viscosity modifier is 0.01 to 3 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, the content of the cellulose fiber is 0 parts by mass or more and less than 1.5 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials, A thermoplastic resin composition for agricultural materials, wherein the content of the aliphatic polyester resin is equal to or greater than the content of the aliphatic aromatic polyester resin.

4. 4. The thermoplastic resin composition for agricultural materials according to claim 1, wherein the content of the starch is 10 to 30 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials.

5. 4. The thermoplastic resin composition for agricultural materials according to claim 1, wherein the starch has an average particle size of 5 to 50 μm.

6. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 3, wherein the viscosity modifier comprises at least one selected from the group consisting of cellulose fibers and carbodiimide compounds.

7. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 3, wherein the content ratio (parts by mass) of the aliphatic polyester resin to the aliphatic aromatic polyester resin is 1 to 3:

1.

8. Shear rate 243 s －１ 4. The thermoplastic resin composition for agricultural materials according to claim 1, wherein the melt viscosity at a temperature of not less than the melting point of the biodegradable resin and not more than the melting point + 40°C is 1000 Pa s or more and less than 5000 Pa s.

9. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 3, which is used for blow molding or vacuum molding.

10. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 3, which is for use in seedling pots.

11. An agricultural material formed using the thermoplastic resin composition for agricultural materials according to any one of claims 1 to 3.

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