Biodegradable resin composition and agricultural materials

Abstract

To provide a biodegradable resin composition that suppresses hydrolysis before planting and forms agricultural materials with excellent biodegradability after being buried in the soil. Furthermore, to provide a biodegradable resin composition with excellent moldability that can be manufactured as thin-walled or thick-walled molded articles and can form products with reduced stickiness, as well as agricultural materials formed from said biodegradable resin composition. [Solution] The problem is solved by a thermoplastic resin composition comprising a neutral inorganic filler (A), a biodegradable resin (B), and a thickener (C), wherein the neutral inorganic filler (A) has a pH of 6.0 to 8.0 in water, the biodegradable resin (B) comprises an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2), and the thickener (C) is at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and epoxy compounds.

Description

Technical Field

[0001] The present disclosure relates to a biodegradable resin composition and agricultural materials.

Background Art

[0002] Plastics are used in a wide range of fields such as electrical and electronic equipment parts, automotive parts, medical parts, food containers, and agricultural materials because of their easy molding process, and physical properties or functionality such as strength are imparted to plastic molded bodies according to their applications. In the field of agricultural materials, they are used in applications that require ensuring water resistance and strength.

[0003] Examples of agricultural materials include a mulch film used for the purpose of raising the ground temperature or keeping warm and controlling pests, and a seedling raising container which is a kind of dedicated container for growing seedlings.

[0004] Recently, as a solution to reduce waste problems and the collection work of agricultural materials, there are agricultural materials using biodegradable materials, which do not need to be collected and can be decomposed in the ground (soil) after use.

[0005] Patent Document 1 describes a resin composition in which biodegradability is promoted by including a biodegradable polymer composition composed of a thermoplastic polymer composition mainly composed of polylactic acid or a copolymer of lactic acid and hydroxycarboxylic acid and a mixture of starch and / or modified starch.

[0006] Patent Document 2 describes a technique for providing a molded body having a high specific gravity and excellent moldability by including an aliphatic polyester-based resin, an inorganic filler having a specific gravity of 2.5 or more, and a plasticizer such as glycerin in a specific mass ratio.

[0007] Thus, in agricultural materials using biodegradable resins, techniques for improving biodegradability after being buried in soil have been studied. Among them, agricultural materials for vegetables have a short growth period, so decomposition in a shorter period is required, and biodegradable resin products with improved biodegradability have been developed by each company. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 5-39381 [Patent Document 2] Japanese Patent Publication No. 2014-077061 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, if the biodegradability is too high, decomposition by the soil in the container will occur before the seedlings are planted in the soil, leading to problems such as the container breaking or collapsing. In particular, while the period from sowing seeds to transplanting is typically 1 to 3 months for common vegetables, it can take 6 months or more for flowers and trees. Therefore, there is a need for products that do not decompose even during a longer seedling cultivation period than conventional products, and that decompose when buried in the soil. This is expected to further broaden the applications of biodegradable resin compositions.

[0010] Furthermore, in the case of mulch film, there is a need for agricultural materials that can be widely applied regardless of the type of crop, without the mulch film collapsing during the period from laying the film until harvesting the crop.

[0011] Furthermore, when organic fillers such as starch or basic fillers such as calcium carbonate are used as fillers, decomposition during molding is accelerated, making it difficult to produce thin-walled or thick-walled molded bodies.

[0012] Generally, a known method for suppressing the decomposition of resin compositions during molding is to add thickeners such as carbodiimide. However, using such thickeners can cause stickiness on the surface of the molded product, and can also reduce the release properties between the mold and the resin composition during molding, as well as the slipperiness for separating the molded products individually, which can affect the molding of biodegradable resin compositions.

[0013] This disclosure has been made in view of the circumstances described above, and aims to provide a biodegradable resin composition that can form agricultural materials that suppress decomposition before planting seedlings in containers and when laying mulch film, and that have excellent biodegradability after being buried in the soil after planting. Furthermore, it aims to provide a biodegradable resin composition with excellent moldability that can be manufactured even in thin-walled and thick-walled molded articles, and that can form products with reduced stickiness, as well as agricultural materials formed from said biodegradable resin composition. [Means for solving the problem]

[0014] In order to solve the above problems, the inventors diligently conducted research and, as a result, discovered a biodegradable resin composition having the following structure, and completed the present invention.

[0015] In other words, some embodiments of this disclosure are as follows: <1> A thermoplastic resin composition comprising a neutral inorganic filler (A), a biodegradable resin (B), and a thickener (C), Neutral inorganic filler (A) has a pH of 6.0 to 8.0 in water. The biodegradable resin (B) includes an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2). The thickening agent (C) is at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and epoxy compounds. Biodegradable resin composition. <2>The biodegradable resin composition according to <1>, wherein the neutral inorganic filler (A) contains at least one selected from the group consisting of barium sulfate, calcium sulfate, silica, silica-alumina composite oxide, and calcium carbonate. <3>The biodegradable resin composition according to either <1> or <2>, wherein the content of the neutral inorganic filler (A) is 1 to 30% by mass based on 100% by mass of the biodegradable resin composition. <4>The biodegradable resin composition according to any one of <1> to <3>, wherein the average particle diameter of the neutral inorganic filler (A) is 20 μm or less. <5>The biodegradable resin composition according to any one of <1> to <4>, wherein the thickener (C) is at least one of a carbodiimide compound and cellulose fiber. <6>The biodegradable resin composition according to any one of <1> to <5>, wherein the content of the viscosity modifier (C) is 0.1 to 3% by mass based on 100% by mass of the thermoplastic resin composition. <7>The biodegradable resin composition according to any one of <1> to <6>, wherein the content of the aliphatic polyester resin (B1) is 100 to 2000 parts by mass with respect to 100 parts by mass of the aliphatic aromatic polyester resin (B2). <8>The biodegradable resin composition according to any one of <1> to <7>, which is used for blow molding or vacuum molding. <9>The biodegradable resin composition according to any one of <1> to <8>, which is for a seedling raising container. <10>The biodegradable resin composition according to <9>, which is for a seedling raising container for flowers or trees. <11>The agricultural material formed using the biodegradable resin composition according to any one of <1> to <8>. <12>The agricultural material according to <11>, which is a seedling raising container for flowers or trees.

Advantages of the Invention

[0016] According to one embodiment of the present disclosure, it is possible to provide a biodegradable resin composition having excellent biodegradability and an agricultural material made of the biodegradable resin composition, which suppresses the decomposition of the agricultural material during the seedling raising period and has excellent biodegradability after being buried in the ground after transplantation. Furthermore, it is possible to provide a biodegradable resin composition that has good moldability and suppressed surface stickiness and can be used to produce molded articles with thin or thick walls, as well as agricultural materials made from such a biodegradable resin composition.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present disclosure will be described in detail. Needless to say, other embodiments are also included in the scope of the present invention as long as they are consistent with the gist of the present invention. In addition, in this specification, the numerical range specified using "~" includes the numerical values described before and after "~" as the lower limit value and the upper limit value range. Also, in this specification, "film" and "sheet" are not distinguished by thickness. In other words, the "sheet" in this specification includes those in the form of a thin film, and the "film" in this specification includes those in the form of a thick sheet. In the present disclosure, the "biodegradable resin composition" may also be referred to as the "resin composition". Unless otherwise noted, each of the various components appearing in this specification may be used alone or in combination of two or more. The numerical values specified in this specification are values obtained by the methods disclosed in the embodiments or examples.

[0018] <Biodegradable Resin Composition> The biodegradable resin composition according to this embodiment is a thermoplastic resin composition containing a neutral inorganic filler (A), a biodegradable resin (B), and a thickener (C). The neutral inorganic filler (A) has a pH in water of 6.0 to 8.0. The biodegradable resin (B) includes an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2). The thickener (C) is at least one selected from the group consisting of a carbodiimide compound, cellulose fiber, oxazoline compound, acid anhydride compound, and epoxy compound. Such a resin composition can be used to create a biodegradable resin composition and agricultural materials made from the biodegradable resin composition that suppresses decomposition during the seedling stage before transplanting in seedling containers and when laying mulch film, and that exhibits excellent biodegradability after being buried in the ground after transplanting. Furthermore, it becomes possible to provide a biodegradable resin composition that exhibits good moldability and suppresses the reduction of surface stickiness, and that can be manufactured even in thin-walled and thick-walled molded articles, as well as agricultural materials made from the biodegradable resin composition.

[0019] The decomposition process of the resin composition consists of two main stages. The first step involves reducing the molecular weight of the resin that makes up the molded resin composition of agricultural materials (such as seedling containers and mulch films) through hydrolysis or oxidative decomposition. Next, in the second stage, microorganisms in the soil decompose individual pieces of agricultural material made from low-molecular-weight resin. Since the molecular weight of resins decreases while agricultural materials are being stored or used, inhibiting hydrolysis in the first stage is crucial for seedling containers used for flowers, trees, and other plants that require longer-than-usual seedling growing periods. The biodegradable resin composition of this embodiment suppresses hydrolysis of the resin composition by using a specific combination of a neutral inorganic filler (A) and a thickener (C). For example, it can suppress the decomposition of agricultural materials and maintain their shape for at least six months, which is the growing period for flower and tree seedlings. After that, when planted in the soil, the agricultural materials are decomposed by microorganisms in the soil within a few months, making it possible to incorporate them into the soil. Therefore, it can be suitably used not only for vegetables, but also for agricultural materials used for flowers, fruit trees, and other trees, which require longer seedling periods.

[0020] Furthermore, while it is known that hydrolysis can be suppressed to some extent by using a thickening agent, the thickening agent can cause stickiness on the surface of the molded product, and may also reduce the release properties between the mold and the resin composition during molding, as well as the slipperiness that allows for the individual separation of the molded products, which can affect the molding of biodegradable resin compositions. If a thickening agent is not used, the viscosity of the resin composition decreases during the manufacturing of the molded body, making it difficult to form a thick-walled molded body. In the case of a thin-walled molded body, holes are more likely to occur due to foaming, making it difficult to form thick-walled or thin-walled molded bodies. However, by using a specific combination of a neutral inorganic filler (A) and a thickener (C), the biodegradable resin composition of the present invention exhibits good moldability and suppresses surface stickiness, allowing for the production of both thin-walled and thick-walled molded articles.

[0021] This embodiment will be described in detail below.

[0022] (Neutral inorganic filler (A)) The neutral inorganic filler (A) is not particularly limited as long as it is an inorganic filler with a pH of 6.0 to 8.0 in water; any commonly available inorganic filler can be used.

[0023] Examples of neutral inorganic fillers (A) include alkali metals, alkaline earth metals, and silicon-aluminum carbonates. Examples of oxides include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, sodium sulfate, calcium sulfate, calcium oxide, silica, alumina, and silica-alumina composite oxides. Among these, barium sulfate, calcium sulfate, silica, silica-alumina composite oxides, and calcium carbonate are preferred in terms of solubility in water and specific gravity, with barium sulfate, silica, silica-alumina composite oxides, or calcium carbonate being more preferred. This makes it possible to suppress the decomposition of agricultural materials during the seedling stage and to achieve excellent biodegradability after burying them in the soil after planting. The neutral inorganic filler (A) may be used alone or in combination of two or more types.

[0024] By using a neutral inorganic filler (A), a biodegradable resin composition with higher heat resistance and less discoloration during molding can be obtained compared to when using an organic filler. Furthermore, the neutral inorganic filler (A) suppresses the hydrolysis of the biodegradable resin composition and agricultural materials before planting during molding, making it easier to adjust the thickness during molding and resulting in good moldability.

[0025] The neutral inorganic filler (A) has a pH of 6.0 to 8.0 in water, and since it suppresses hydrolysis and has superior processability, a pH of 6.5 to 7.5 is preferred.

[0026] In this disclosure, the pH of the neutral inorganic filler (A) is the pH value measured at 23°C using a pH meter. A pH meter such as the HM-30P manufactured by Toa DKK Corporation can be used. Furthermore, if the neutral inorganic filler (A) is soluble in water, the pH can be measured using an aqueous solution; if it is not soluble in water, the pH can be measured using the supernatant of the dispersion. Specifically, for example, 0.5 g of neutral inorganic filler (A) is weighed and placed in a plastic container, 50 ml of deionized water is added, and the mixture is vibrated with a vibrator for 30 minutes. After separating the solid and liquid using a centrifuge, the supernatant water is stabilized in a 23°C constant temperature bath, and the pH is measured with a pH meter (HM-30P pH meter manufactured by Toa DKK Co., Ltd.) and this value can be used as the pH of inorganic filler (A).

[0027] The neutral inorganic filler (A) may be an inorganic filler whose pH in water becomes 6.0 to 8.0 after surface treatment. Even if an inorganic filler has a pH outside the range of 6.0 to 8.0 in water, it can be used as a neutral inorganic filler (A) if surface treatment brings its pH to 6.0 to 8.0 in water. Examples of inorganic compounds used in surface treatment include silicon, aluminum, zirconium, tin, antimony, titanium compounds, and their hydrated oxides. Examples of organic compounds include polyhydric alcohols, alkanolamines and their derivatives, higher fatty acids and their metal salts, and organometallic compounds.

[0028] The neutral inorganic filler (A) is preferable to have low solubility in water, from the viewpoint of not promoting hydrolysis. Specifically, it is preferable that the solubility in water at 20°C is 0.5 g / 100 ml or less, more preferably 0.1 g / 100 ml, and most preferably 0.05 g / 100 ml.

[0029] From the standpoint of moldability, a lower specific gravity is preferable. Specifically, 4 g / cm³ 3 The following is preferable: 3 g / cm³ 3 The following are preferable.

[0030] Furthermore, from the viewpoint of moldability, the average particle size of the neutral inorganic filler (A) is preferably 20 μm or less, more preferably 0.1 to 20 μm, and even more preferably 0.3 to 15 μm. Having the average particle size of the neutral inorganic filler (A) within the above range makes it possible to achieve both dispersibility and moldability of the neutral inorganic filler (A) in the biodegradable resin (B). In particular, in blow molding, where the resin composition is directly placed into the mold and air is blown in, the average particle size of the neutral inorganic filler (A) in the resin composition contributes to the moldability, so it is preferable that the average particle size of the neutral inorganic filler (A) is within the range described above. This makes it possible to obtain a resin composition with even better moldability.

[0031] The average particle size of the neutral inorganic filler (A) can be determined by laser diffraction. For example, by using laser diffraction, a dispersion of a neutral inorganic filler (A) that has been dispersed is irradiated with laser light, and the angular change in the intensity of the scattered light as the laser light passes through the solution is measured to obtain the particle size distribution. The average particle size can then be calculated as the median value where the cumulative value based on volume is 50%. As a particle size distribution analyzer, for example, a particle size distribution analyzer such as the Microtrac HRA manufactured by Nikkiso Co., Ltd. can be used. The sample to be measured is prepared by dispersing an inorganic filler (A) with isopropyl alcohol.

[0032] From the viewpoint of moldability, suppression of surface stickiness, and shape retention, the content of neutral inorganic filler (A) is preferably 1 to 40% by mass, and more preferably 1 to 30% by mass, based on 100% by mass of the resin composition.

[0033] Furthermore, the present invention may contain other fillers such as acidic or basic inorganic fillers or organic fillers, as long as they do not impair the effects of the present invention. In that case, the content of the other fillers is preferably 5% by mass or less, more preferably 3% by mass or less, and most preferably 1% by mass or less, based on 100% by mass of the resin composition.

[0034] (Biodegradable resin (B)) Biodegradable resins (B) are decomposed not only by hydrolysis during molding and storage, but also by the action of various microorganisms present in soil or water. The resin composition of this disclosure includes an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2) as the biodegradable resin (B). This makes it possible to obtain a resin composition with excellent biodegradability and moldability. Biodegradable resin (B) can be any biodegradable resin that is generally available. Other biodegradable resins include, for example, polycaprolactone. These biodegradable resins may be used individually or in combination of two or more.

[0035] The content of aliphatic polyester resin (B1) is preferably equal to or greater than the content of aliphatic aromatic polyester resin (B2). By mixing the aliphatic polyester resin (B1), which is the base resin, with the aliphatic aromatic polyester resin (B2), which has ductility and excellent moldability, the moldability of the resin composition and the strength of the molded agricultural material can be ensured. Therefore, the content of aliphatic polyester resin (B1) per 100 parts by mass of aliphatic aromatic polyester resin (B2) is preferably 100 parts by mass or more, more preferably 110 parts by mass or more, 120 parts by mass or more, 130 parts by mass or more, or 140 parts by mass or more, and even more preferably 150 parts by mass or more from the viewpoint of improving moldability. Furthermore, it is preferably 2000 parts by mass or less, more preferably 1900 parts by mass or less, 1800 parts by mass or less, 1700 parts by mass or less, or 1600 parts by mass or less, and even more preferably 1500 parts by mass or less from the viewpoint of improving moldability.

[0036] [Aliphatic polyester resin (B1)] Examples of aliphatic polyester resins (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 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 individually or in mixtures thereof. Among these, 1,4-butanediol is preferred. Examples of aliphatic dicarboxylic acids include oxalic acid, succinic acid, glutanoic acid, adipic acid, sebacic acid, suberic acid, and dodecanedioic acid, and acid anhydrides which are derivatives thereof may also be used. Among these, succinic acid or succinic anhydride, or a mixture of these and adipic acid is preferred. Specifically, examples include polybutylene succinate (PBS) obtained from 1,4-butanediol and succinic acid (e.g., "BioPBS" (trade name) from PPT MCC Biochem), and polybutylene succinate adipate (PBSA) obtained by copolymerizing PBS with adipic acid. In addition, examples of polylactic acid (PLA) include "REVODE" (trade name) from Kaisei Biomaterials Co., Ltd. and "Ingeo" (trade name) from NatureWorks Inc.

[0037] As for the aliphatic polyester resin (B1), from the viewpoint of moldability of the resin composition, it is preferable that it contains the maximum amount of aliphatic polyester obtained by a polycondensation reaction between an aliphatic diol and an aliphatic dicarboxylic acid among all components. For example, based on 100% by mass of the aliphatic polyester resin (B1), it is preferable that it contains 20% or more by mass, 50% or more by mass, 80% or more by mass, 90% or more by mass, 95% or more by mass, or 100% by mass of aliphatic polyester obtained by a polycondensation reaction between an aliphatic diol and an aliphatic dicarboxylic acid. In this case, it is even preferable that the aliphatic polyester is a copolymer consisting of units derived from an aliphatic diol and units derived from an aliphatic dicarboxylic acid.

[0038] [Aliphatic aromatic polyester resin (B2)] Examples of aliphatic aromatic polyester resins (B2) 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 usually has 2 to 10 carbon atoms, and examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Among these, diols with 2 to 4 carbon atoms are preferred, ethylene glycol and 1,4-butanediol are more preferred, and 1,4-butanediol is even more preferred. The dicarboxylic acid component that provides the dicarboxylic acid units usually has 2 to 10 carbon atoms, and examples include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Among these, succinic acid or adipic acid is preferred. Examples of aromatic dicarboxylic acid components that provide aromatic dicarboxylic acid units include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Among these, terephthalic acid and isophthalic acid are preferred, with terephthalic acid being more preferred. Specifically, examples include polybutylene adipate terephthalate (PBAT), which is a copolymer of 1,4-butanediol, adipic acid, and terephthalic acid (for example, "Ecoflex" (product name) manufactured by B.A.S.F.).

[0039] Furthermore, the biodegradable resin (B) may be in a form in which an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2) are used in combination with other biodegradable resins. Examples of other biodegradable resins include poly(3-hydroxyalkanoate), an aliphatic polyester copolymer obtained from hydroxyalkanoic acid and polycarboxylic acid (in particular, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) (for example, "Aonirex" (trade name) manufactured by Kaneka Corporation).

[0040] The content of biodegradable resin (B) may be 40 to 99.8% by mass, more preferably 45 to 99.5% by mass, even more preferably 50 to 99.0% by mass, and even more preferably 55 to 98.5% by mass, based on 100% by mass of the resin composition. A biodegradable resin (B) content within the above range is preferable because it allows for both processability and moldability of the resin composition. Furthermore, based on biodegradable resin (B) as the standard (100% by mass), the total content of aliphatic polyester resin (B1) and aliphatic aromatic polyester resin (B2) may be 100% by mass, more preferably 80% by mass or more, and more preferably 90% by mass or more.

[0041] (Thickening agent (C)) Thickening agents have the function of adjusting the viscosity of the resin composition to improve its moldability and increase the melt tension of the resin composition, which is an indicator of moldability. The thickening agent (C) is at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and epoxy compounds. In particular, carbodiimide compounds or cellulose fibers are preferred because they can increase the viscosity of the resin composition while ensuring its strength.

[0042] The thickener (C) can be one that is generally available. In one preferred embodiment, compounds listed on the positive list of green plastics can be used, such as cellulose microfiber (CMF) and carbodiimide compounds (CDI). Cellulose microfiber refers to relatively large-sized cellulose fibers obtained by reducing the defibration step in cellulose obtained by treating pulp with hot water or the like to hydrolyze and weaken it, and then defibrating it by a grinding method such as a high-pressure homogenizer.

[0043] Furthermore, carbodiimide compounds, oxazoline compounds, acid anhydride compounds, and epoxy compounds are preferred because they react with the biodegradable resin, increasing the molecular weight of the biodegradable resin. This slows down the biodegradation rate, as it takes time for the biodegradable resin composition to hydrolyze and decrease in molecular weight, thus allowing the agricultural material to maintain its form before planting. In particular, it is preferable that the compound contains a carbodiimide compound.

[0044] Examples of carbodiimide compounds include polycarbodiimide compounds and cyclic carbodiimides, such as dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and di-β-naphthylcarbodiimide. These compounds may be used individually or in combination.

[0045] Examples of acid anhydride compounds include styrene maleic anhydride compounds, and examples of epoxy compounds include epoxy-acrylic compounds.

[0046] Examples of these commercially available products include oxazoline compounds such as "Epocross RA-45" (product name) and "Epocross RPS-1005" (product name) manufactured by Nippon Shokubai Co., Ltd. Examples of acid anhydride compounds include styrene maleic anhydride compounds (PALMER HOLLAND's "XIBOND120" (product name), "XIBOND140" (product name), "XIBOND160" (product name), "XIBOND180" (product name), "XIBOND200" (product name), "XIBOND220" (product name), "XIBOND250" (product name), "XIBOND280" (product name), and Tomoe Engineering Co., Ltd.'s "XIRAN1000" (product name), "XIRAN2000" (product name), "XIRAN2500" (product name), "XIRAN3000" (product name), "XIRAN4000" (product name), "XIRAN6000" (product name), "XIRAN9000" (product name), "XIRAN3500" (product name), "XIRAN3600" (product name)). Examples of epoxy compounds include epoxy-acrylic compounds (such as "Joncryl ADR-4468" (product name) and "Joncryl ADR-4400" (product name) manufactured by BASF, "Alphon UG-4040" (product name) and "Alphon UG-4070" (product name) manufactured by Toagosei Co., Ltd.).

[0047] The content of the thickener (C) is preferably 0.01 to 5% by mass, more preferably 0.1 to 4% by mass, even more preferably 0.1 to 3% by mass, and particularly preferably 0.3 to 3% by mass, based on 100% by mass of the resin composition. This allows the viscosity of the resin composition to be appropriate, resulting in superior moldability. Furthermore, it allows for better biodegradability in soil.

[0048] (Plasticizer (D)) The thermoplastic resin composition of this embodiment is preferably free of plasticizer (D). In this specification, "free of plasticizer (D)" means substantially free of plasticizer (D), and specifically, the content of plasticizer (D) is 0 to 5% by mass based on 100% by mass of the resin composition.

[0049] A plasticizer (D) content of 0 to 5% by mass is preferable because it suppresses stickiness on the surface of the resulting molded article while maintaining good moldability. From the viewpoint of suppressing stickiness and moldability, the content of plasticizer (D) is preferably 0 to 2% by mass, more preferably 0 to 1% by mass, and even more preferably 0% by mass (not included), based on 100% by mass of the resin composition.

[0050] Examples of plasticizers (D) include alcohols, which are organic compounds having a hydroxyl group. Specifically, examples include glycerin, glycerin monoester, ethylene glycol, and diethylene glycol.

[0051] (Other ingredients) The resin composition may optionally contain other additives and other components as needed. Examples of other additives include fillers other than neutral filler (A), thickeners other than thickener (C), dispersants, lubricants (higher fatty acid metal salts, waxes, etc.), hydrotalcite, surfactants, antistatic agents, flame retardants, antioxidants, UV absorbers, fillers, and colorants such as organic pigments. The selection and amount of other optional components are not particularly limited as long as they 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 resins other than biodegradable resins, as long as they do not hinder the effects of one embodiment of the present invention.

[0052] By coloring the resin composition with a coloring agent, it is possible to produce molded articles with excellent heat-shielding properties or easily identifiable molded articles. The coloring agent is not particularly limited, and commonly available pigments can be used, but from the viewpoint of the natural environment, it is preferable that the coloring agent is substantially free of cadmium, lead, chromium, arsenic, mercury, copper, selenium, nickel, molybdenum, and fluorine.

[0053] For example, when a resin composition contains a pigment, it is preferable to use a dispersant to disperse the pigment, and examples of dispersants include fatty acid metal salts. The fatty acid component of the fatty acid metal salt is preferably a chain-like carboxylic acid having 6 to 30 carbon atoms, and may be linear or branched, and may have only saturated bonds or only 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. Preferably, the metals are elements from Group 1, Group 2, Group 12, and Group 13, with elements from Group 1 or Group 2 being more preferred. Specific examples include sodium, potassium, calcium, magnesium, and barium.

[0054] Examples of fatty acid metal salts include calcium stearate, magnesium stearate, barium stearate, calcium laurate, magnesium laurate, and sodium montantate. These may be used individually or in combination of two or more. Among these, calcium stearate, magnesium stearate, calcium laurate, and magnesium laurate are preferred.

[0055] (Extrusion processability) In the biodegradable resin composition described above, the processability during extrusion is such that strand breakage occurs 5 times or less when production is carried out continuously for 1 hour, although it may be 1 to 5 times, and preferably no strand breakage occurs.

[0056] (Melting viscosity) In the above-mentioned biodegradable resin composition, the shear rate according to JIS K7199:1999 is 243 s². -1 The melt viscosity in this mixture 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 viewpoint of the strength of the resulting molded article and the fluidity and moldability of the resin composition, at a temperature above the melting point of the biodegradable resin (B) and below the melting point + 40°C.

[0057] ≪Method for manufacturing resin compositions≫ The resin composition of this embodiment can be produced by kneading a neutral inorganic filler (A) and a thickener (C) at the temperature at which a biodegradable resin (B) melts. Specifically, for example, a biodegradable resin (B), a neutral inorganic filler (A), a thickener (C), and various additives as needed are mixed and melt-kneaded using a batch-type kneader such as a kneader, roll mill, super mixer, high-speed mixer, ball mill, sand mill, attritor, or Banbury mixer, or a single-screw extruder, twin-screw extruder, rotor-type twin-screw kneader, etc., to obtain a resin composition in the form of pellets, powders, granules, or beads. It is preferable to form the composition into pellets using a single-screw or twin-screw extruder because it has strong kneading power and facilitates subsequent molding.

[0058] The resin composition may be used in either masterbatch or compound form. In the case of a masterbatch, after manufacturing the masterbatch, the agricultural material can be manufactured by blending it with the masterbatch, using, for example, the same biodegradable resin (B) used in the manufacture of the masterbatch as a diluent resin, which is the main resin of the agricultural material. Preferably, the masterbatch content is 1 to 50 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the biodegradable resin (B), which is the main resin. The biodegradable resin (B) used as the diluent at this time may be the same as the one used in the production of the masterbatch, or it may be a different one. However, it is preferable to use the same biodegradable resin because it provides better compatibility between the thermoplastic resin composition and the resin. In the case of compounds, after manufacturing the compound, agricultural materials can be manufactured using the compound as is, in the manner described above.

[0059] <Agricultural materials> The agricultural material of this embodiment can be obtained by molding the biodegradable resin composition described above. Examples of agricultural materials include seedling containers such as seedling pots and plug trays, mulch film, and agricultural nets. By using the biodegradable resin composition of this embodiment, it is possible to achieve both biodegradability and moldability even in deep-drawn molded articles with high stretch ratios, such as seedling pots and plug trays, as well as thin-walled and thick-walled molded articles, enabling the formation of a wide variety of molded articles to suit different applications. A deep-drawn molded article, as used here, is a molded article in which the depth direction is longer than the width direction.

[0060] (Seedling container) Seedling containers are used to grow seedlings in a container until they reach a certain size, rather than sowing seeds directly in the field. Because they biodegrade properly in the soil, they do not harm the natural environment, and they reduce the effort of removing seedlings from the container and sowing them after they have grown. It is possible to transplant them directly into the soil while still in the seedling container.

[0061] The molded article using the resin composition of this embodiment can suppress the decomposition of agricultural materials during the seedling stage and maintain its shape. Subsequently, when planted in the soil, the agricultural materials are properly decomposed by microorganisms in the soil and can be incorporated into the soil. Therefore, it can be suitably used as a seedling container, and among these, a seedling pot is preferred. Furthermore, because it is highly effective in suppressing decomposition during the seedling stage before burying it in the soil, it can be suitably used not only for vegetables but also as a seedling container for flowers or trees, which require a longer seedling stage. Furthermore, it is possible to form both thin-walled and thick-walled molded bodies, which possess strength suitable for seedling cultivation and can maintain an appropriate shape during the seedling cultivation period.

[0062] The method for molding the seedling container is not particularly limited, but suitable methods include blow molding, in which a heated and plasticized resin composition is extruded and placed directly into a mold without cooling and solidifying, and air is blown into it; and vacuum molding, in which a sheet or film of a heated and plasticized resin composition is placed on a mold and molded by vacuum suction from the inside of the mold.

[0063] (Multifilm) Mulching film is a film used to cover the base of crop plants. The method for forming the film from the resin composition described above is not particularly limited, but suitable methods include extrusion molding, in which the film is extruded using a T-die in an extruder and then cooled and solidified on a cast roll, or molding using an inflation molding machine.

[0064] In the case of mulch film, the first stage of biodegradation occurs when the mulch film is laid, and the second stage of biodegradation occurs when it is incorporated into the soil after use. Therefore, the mulch film of the present invention suppresses hydrolysis during installation, maintains its shape, and is properly biodegraded after being buried in the soil.

[0065] <<Blow molding, vacuum forming>> The aforementioned resin composition has increased melt tension due to the thickener (C) and suppresses hydrolysis, thus preventing drawdown (the phenomenon where pre-molded resin sags in the direction of gravity because it cannot withstand its own weight). Furthermore, it is possible to manufacture both thin-walled and thick-walled molded articles.

[0066] In blow molding, drawdown can be suppressed, which can cause the molded body to become thinner and lighter. The resin composition of this embodiment can be blow molded, and for example, when three sets of two seedling pots are produced consecutively using a direct blow molding machine, the difference between the weight of one seedling pot in the first set and the weight of one seedling pot in the third set can be made to less than 30% of the weight of one seedling pot in the first set. Furthermore, the weight of one seedling pot should be 0.7g or more and less than 0.8g, preferably 0.8g or more and less than 0.9g, and more preferably 0.9g or more. By using the above-described resin composition, blow moldability can be obtained.

[0067] For example, if the molded product is a seedling pot, it is sufficient that the pot has enough strength to stand on its own, and it is preferable that the seedling pot does not bend. By using the above-mentioned resin composition, hydrolysis during molding can be suppressed, and a seedling pot with sufficient strength can be obtained.

[0068] In the case of vacuum forming, it is possible to suppress the occurrence of surface defects caused by sagging, such as wrinkles, resulting from the bending of the sheet due to drawdown. For example, even if the molded body has surface defects caused by sagging, it is sufficient if vacuum forming can be performed using the resin composition, and it is preferable if the surface defects are minimal, and more preferable if there are no surface defects. By using the above-mentioned resin composition, a vacuum-formed body can be obtained.

[0069] For example, if the molded body 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 it is dropped from a height of 5 m, 3 or fewer out of 10 seedling pots break, or 1 to 3 or fewer out of 10, but preferably none break. By using the above-mentioned resin composition, a seedling pot with sufficient strength can be obtained.

[0070] (Sticky) The surface of a molded article formed using the above-mentioned resin composition, according to JIS K7125, The friction coefficient μD is preferably less than 0.5, more preferably less than 0.3. By using the above resin composition, a molded article with suppressed stickiness can be obtained.

[0071] (Shape retention) When the molded article formed using the above resin composition is left standing on the ground, it is sufficient to maintain the shape of the molded article during the 6-month seedling raising period of flowers and trees. It is preferable that the molded article such as with holes is not decomposed. By using the above resin composition, a molded article that maintains its shape during the seedling raising period of flowers and trees can be obtained.

[0072] (Biodegradability in soil) When the molded article formed using the above resin composition is buried in the ground for 6 months, it is sufficient that the molded article has progressed in decomposition and has holes here and there. It is preferable that the molded article is decomposed and scattered. By using the above resin composition, a molded article with an appropriately adjusted biodegradation rate can be obtained.

[0073] According to the present embodiment, since the biodegradable resin composition contains the neutral inorganic filler (A) and the thickener (C) that increases the melt tension, it does not decompose even during a longer seedling raising period than before, and has excellent biodegradability and moldability that decomposes when buried in the ground, suppresses stickiness on the surface, and can produce even thin and thick molded articles. An agricultural material can be obtained.

Examples

[0074] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the examples. In the examples and comparative examples, "parts" and "%" represent "parts by mass" and "mass%" respectively, unless otherwise specified. In addition, the blending amounts in the table are shown in parts by mass. The blanks in the table indicate that nothing is blended. The measurement methods for the pH and average particle diameter of the inorganic filler (A) and the like are as follows.

[0075] <pH measurement> 0.5 g of inorganic filler was weighed and placed in a plastic container. 50 ml of deionized water was added, and the mixture was vibrated for 30 minutes using a vibrator. After separating the solid and liquid using a centrifuge, the supernatant water was stabilized in a 23°C constant temperature bath, and the pH was measured using a pH meter (HM-30P pH meter manufactured by Toa DKK).

[0076] <Average particle size measurement method> Samples were prepared by dispersing fillers with isopropyl alcohol. The filler concentration during sample preparation was 3% by mass, and ultrasonic treatment was performed for 5 minutes using an ultrasonic disperser "VCX500" (Sonics & Materials, Inc., 20kHz, 500W). Laser light was irradiated onto the resulting dispersion using a particle size analyzer Microtrac HRA manufactured by Nikkiso Co., Ltd., and the distribution pattern of the intensity of the light scattered as the laser light passed through the dispersion was measured. The measured light scattering pattern was analyzed using "Microtrac FLEX" software (Nikkiso Co., Ltd.) to obtain the particle size distribution. Furthermore, the median diameter (50% diameter) based on volume was calculated from the above particle size distribution values, and this was taken as the average particle size of the sample.

[0077] Next, the materials used in the biodegradable resin composition are listed below. (Neutral inorganic filler (A), etc.) A-1: Precipitating barium sulfate 100 (barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd., pH 7.0, average particle size: 0.6 μm) A-2: Precipitating barium sulfate 200 (barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd., pH 7.0, average particle size: 0.8 μm) A-3: Special Barium Sulfate BMH-40 (Barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd., pH 7.0, average particle size: 5 μm) A-4: Special Barium Sulfate BMH-100 (Barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd., pH 7.0, average particle size: 12 μm) A-5: Japanese Pharmacopoeia Barium Sulfate BAX-150 (Barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd., pH 7.0, average particle size: 21 μm) A-6: Rheoroseal HM30S (Silica, manufactured by Tokuyama Corporation, pH 6.6, average particle size: 7.0 μm) A-7: CALUCEO P015S0 (Calcium carbonate, manufactured by Shiraishi Kogyo Co., Ltd., pH 7.0, average particle size: 0.15 μm) A-8: OS Clay (Silica-alumina composite oxide, manufactured by Sanyo Clay Industry Co., Ltd., pH 6.0, average particle size: 8 μm) A-9: Calcium sulfate (pH 7.0, average particle size: 0.5 μm) A-10: Sodium sulfate (pH 7.0, average particle size: 0.5 μm) (Other fillers) A'-1: KS-1300 (Calcium carbonate, pH 9.0, average particle size: 1.8 μm) A'-2: Sodium hydroxide (pH 14.0, average particle size: 20 μm) A'-3: Kaolin Clay RC-1 (Silica-alumina composite oxide, manufactured by Takehara Chemical Industry Co., Ltd., pH 5.0, average particle size: 0.4 μm)

[0078] (Biodegradable resin (B)) [Aliphatic polyester resin (B1)] B1-1: BioPBS FZ91 (Aliphatic polyester resin: PBS resin, manufactured by PTT MCC Biochem Co., Ltd.) B1-2: Ingeo Biopolymer 6252D (Aliphatic polyester resin: PLA resin, manufactured by NatureWorks Co., Ltd.) [Aliphatic aromatic polyester resin (B2)] B2-1: Ecoflex C1200 (Aliphatic aromatic polyester resin: PBAT resin, manufactured by B.A.S.F. Co., Ltd.)

[0079] (Thickening agent (C)) C-1: KC Floc W-50 (cellulose fiber) (manufactured by Nippon Paper Industries Co., Ltd., cellulose microfiber, average fiber length: 50 μm) C-2: Carbodilite HMV-15CA (carbodiimide compound) (manufactured by Nisshinbo Chemical Co., Ltd., polycarbodiimide compound) C-3: Carbodista TCC-NP (carbodiimide compound) (manufactured by Teijin Limited, cyclic carbodiimide compound) C-4: Joncryl ADR-4468 (epoxy compound) (manufactured by BASF, epoxy-acrylic compound) C-5: XIBOND220 (acid anhydride compound) (manufactured by Palmer Holland, styrene maleic anhydride compound) C-6: Epocross RA-45 (Oxazoline compound) (Manufactured by Nippon Shokubai Co., Ltd., Oxazoline compound) (That viscosity modifier) C'-1: Smecton-SWF (manufactured by Kunimine Industries Co., Ltd., synthetic hectorite)

[0080] (Starch (D)) D-1; Chemister 420 (starch, manufactured by Glico Nutrition Foods Co., Ltd., average particle size: 15 μm)

[0081] <Manufacturing of biodegradable resin compositions> [Example 1] (Manufacturing of biodegradable resin compositions (compounds)) A mixture of 10 parts by mass of (A-1) as a neutral inorganic filler (A), 79.5 parts by mass of (B1-1) and 10 parts by mass of (B2-1) as biodegradable resins (B), and 0.5 parts by mass of (C-1) as a thickener (C) was prepared and extruded at 190°C using a twin-screw extruder (manufactured by Japan Steel Works, Ltd.) to obtain a biodegradable resin composition.

[0082] (Manufacturing of seedling pots) The obtained biodegradable resin composition was used to produce seedling pots by blow molding and vacuum molding.

[0083] [Examples 2-39, Comparative Examples 1-8] Biodegradable resin compositions and seedling pots were obtained in the same manner as in Example 1, except that the materials and their respective proportions (parts by mass) were changed as shown in Table 1. Furthermore, the biodegradable resin compositions of Comparative Examples 3, 6, 7, and 8 had poor moldability and could not be used to manufacture seedling pots. Therefore, the stickiness, shape retention, and soil biodegradability of the molded products could not be evaluated.

[0084] Evaluation of biodegradable resin compositions and seedling pots The biodegradable resin compositions and seedling pots obtained in the examples and comparative examples were evaluated according to the following criteria. The evaluation results are shown in Tables 1 to 5.

[0085] <Extrusion processability> The processability of biodegradable resin compositions during extrusion was evaluated. The evaluation criteria were as follows, with ○ and △ indicating practical usability. [Evaluation Criteria] ○: No strand breakage occurs during continuous production for one hour. △: Strand breakage occurs 1 to 5 times when producing continuously for 1 hour. ×: Strand breakage occurs 6 or more times during continuous production for 1 hour.

[0086] <Moldability> The moldability was evaluated based on the melt viscosity. Using the obtained biodegradable resin composition, a shearing test was conducted at 150°C, a temperature above the melting point of the biodegradable resin (B) used in the examples and comparative examples, and below the melting point + 40°C, in accordance with JIS K7199:1999, at a shearing rate of 243 s². -1 The melt viscosity of biodegradable resin compositions was measured. Higher melt viscosity indicates better moldability. The evaluation criteria were as follows, with ○ and △ indicating practical usability. [Evaluation Criteria] ○: Melt viscosity of 1500 Pa·s or higher △: Melt viscosity is between 1000 and 1500 Pa·s. ×: Melt viscosity is less than 1000 Pa·s

[0087] <Blow moldability> Using the obtained biodegradable resin composition, three sets of seedling pots (9 cm in diameter, 7 cm in height), each consisting of two pots, were continuously produced at 150°C using a direct blow molding machine (manufactured by Nippon Placon Co., Ltd.). The difference in weight between the first set of seedling pots and the third set of seedling pots (weight difference), as well as the weight of each seedling pot, were used to evaluate the moldability during production. In this evaluation, "blow molding possible" means that the weight difference is less than 30% of the weight of each seedling pot in the first set. The evaluation criteria were as follows, with ○ and △ indicating practical usability. [Evaluation Criteria] ○: Can be blow-molded, and each seedling pot weighs 0.9g or more. △: Can be blow-molded, and the weight of each seedling pot is between 0.7g and 0.9g. ×: Cannot be blow-molded.

[0088] <Vacuum formability> Using the obtained biodegradable resin composition, sheets measuring 30 cm in length x 30 cm in width and thicknesses of 0.3 mm, 0.45 mm, and 1 mm were molded at 180°C using a T-die molding machine. The molded sheets were heated to 110°C and seedling pots (6 cm in diameter, 7 cm in height) were molded using a vacuum forming machine, and the moldability during production was evaluated. The evaluation criteria were as follows, with ○ and △ indicating practical usability. [Evaluation Criteria] ○: Vacuum forming is possible, and there are no cosmetic defects in the seedling pots due to dripping. △: Vacuum forming is possible, and cosmetic defects originating from dripping can be observed in the seedling pot. ×: Cannot be vacuum formed.

[0089] <Sticky> The stickiness of the seedling pots was evaluated by measuring the coefficient of dynamic friction on the sides of the seedling pots fabricated during the blow molding evaluation, in accordance with JIS K7125. The evaluation criteria were as follows, with ○ and △ indicating usable. [Evaluation Criteria] ○: Dynamic friction coefficient μD is less than 0.3 △: Dynamic friction coefficient μD is 0.3 or greater and less than 0.5 ×: The coefficient of kinetic friction μD is 0.5 or higher.

[0090] <Shape retention> The seedling pots prepared during the blow molding evaluation were placed on the ground with soil inside and their shape was evaluated after 6 months. The evaluation criteria were as follows, with ○ and △ indicating usable. [Evaluation Criteria] ○: The seedling pots retain their original shape. △: The seedling pot does not have holes, but it is deformed. ×: The seedling pots are decomposing and have holes in several places. -: We were unable to produce seedling pots, and therefore could not perform the evaluation.

[0091] <Biodegradability in soil> The seedling pots prepared during the blow molding evaluation were buried in the ground and excavated after 6 months to evaluate biodegradability based on the rate of biodegradation in the soil. The evaluation criteria were as follows, with ○ and △ indicating practical usability. [Evaluation Criteria] ○: The seedling pots have fallen apart and are in pieces. △: The seedling pots are decomposing and have holes in several places. ×: The seedling pots retain their original shape. -: We were unable to produce seedling pots, and therefore could not perform the evaluation.

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] [Table 4]

[0096] [Table 5]

[0097] Based on the above results, it was confirmed that the resin composition of the present invention suppresses the decomposition of agricultural materials during the seedling stage, has high shape retention, and exhibits good biodegradability in soil after being buried in the ground after planting, making it excellent for use as an agricultural material. Furthermore, it was confirmed that the material exhibits high moldability and processability, suppresses surface stickiness, and allows for the manufacture of both thin-walled and thick-walled molded articles.

[0098] Although the present invention has been described above with reference to embodiments, the present invention is not limited thereto. Various modifications to the structure and details of the present invention can be made that can be understood by those skilled in the art within the scope of the invention.

Claims

1. A thermoplastic resin composition comprising a neutral inorganic filler (A), a biodegradable resin (B), and a thickener (C), The neutral inorganic filler (A) has a pH of 6.0 to 8.0 in water. The biodegradable resin (B) includes an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2). The thickening agent (C) is at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, oxazoline compounds, acid anhydride compounds, and epoxy compounds. Biodegradable resin composition.

2. The biodegradable resin composition according to claim 1, wherein the neutral inorganic filler (A) comprises at least one selected from the group consisting of barium sulfate, calcium sulfate, silica, silica-alumina composite oxide, and calcium carbonate.

3. The biodegradable resin composition according to claim 1, wherein the content of neutral inorganic filler (A) is 1 to 30% by mass, based on 100% by mass of the biodegradable resin composition.

4. The biodegradable resin composition according to claim 1, wherein the average particle size of the neutral inorganic filler (A) is 20 μm or less.

5. The biodegradable resin composition according to claim 1, wherein the thickening agent (C) is at least one of a carbodiimide compound and cellulose fibers.

6. The biodegradable resin composition according to claim 1, wherein the content of the thickener (C) is 0.1 to 3% by mass, based on 100% by mass of the biodegradable resin composition.

7. The biodegradable resin composition according to claim 1, wherein the content of aliphatic polyester resin (B1) is 100 to 2000 parts by mass per 100 parts by mass of aliphatic aromatic polyester resin (B2).

8. A biodegradable resin composition according to any one of claims 1 to 7, used for blow molding or vacuum molding.

9. A biodegradable resin composition according to any one of claims 1 to 7, for use in seedling containers.

10. The biodegradable resin composition according to claim 9, for use as a container for raising seedlings of flowers or trees.

11. An agricultural material molded using the biodegradable resin composition described in any one of claims 1 to 7.

12. The agricultural material according to claim 11, which is a container for raising flower or tree seedlings.

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