Thermoplastic resin composition for agricultural materials, and agricultural material

Abstract

To provide: a thermoplastic resin composition for agricultural materials that can achieve both high biodegradability and moldability, and that can even form a molding by highly difficult deep-drawing; and an agricultural material made of the thermoplastic resin composition for agricultural materials.SOLUTION: A thermoplastic resin composition for agricultural materials contains: a basic filler (A) having a pH in water of 8.5 to 12.5; an aliphatic polyester resin (B1) and an aliphatic aromatic polyester resin (B2); and a thickening agent (C) containing at least one selected from the group consisting of a carbodiimide compound, cellulose fiber, an oxazoline compound, an epoxy compound, an acid anhydride compound and a silica-based filler. Based on 100 mass% of the thermoplastic resin composition, the content of the basic filler (A) is 3-30 mass% and the content of the thickening agent (C) is 0.01-3 mass%.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Plastics are easy to mold and process, so they 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 that use biodegradable materials, which do not need to be collected and can decompose underground (in the soil) after use.

[0005] Patent Document 1 describes a mulch film that has enhanced biodegradability by containing a biodegradable resin selected from polylactic acid, polybutylene succinate, and polybutylene succinate adipate and a basic filler such as calcium oxide, calcium hydroxide, and calcium carbonate in a specific mass ratio.

[0006] Patent Document 2 describes a technology in which biodegradability is further enhanced by containing, in a specific mass ratio, a hardly hydrolyzable biodegradable resin such as polylactic acid, an ester decomposition promoter consisting of an easily hydrolyzable polymer, and an ester decomposition promoter consisting of inorganic particles that accelerate the hydrolysis of the ester decomposition promoter. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-237764 A [Patent Document 2] JP 2012-077246 A Summary of the Invention [Problem to be solved by the invention]

[0008] The basic filler promotes the biodegradability of the molded body when buried in soil. However, it promotes hydrolysis during molding, which affects the moldability of the resin composition, and molding defects such as uneven thickness become a problem in inflation molding applications such as agricultural mulch films. In particular, deep-draw moldings with high stretch ratios such as seedling pots and plug trays cannot be molded well.

[0009] In addition, leafy vegetables such as green onions and chives have a short period from sowing to planting, and it is expected that they will decompose in 1-2 months after being buried in the soil, so there is a demand for them to decompose in an even shorter period of time than before.

[0010] The present invention has been made in consideration of the above circumstances, and provides a thermoplastic resin composition for agricultural materials that can achieve both high biodegradability and moldability, and can be used to produce even deep-drawn molded articles, which is difficult to produce, and an agricultural material made of the thermoplastic resin composition for agricultural materials. The purpose is to [Means for solving the problem]

[0011] Means of the Invention In order to solve the above problems, the present inventors have conducted intensive research and have found a thermoplastic resin composition for agricultural materials having the following configuration, thereby completing the present invention.

[0012] That is, one embodiment of the present invention is as follows. <1> A thermoplastic resin composition comprising a basic filler (A), a biodegradable resin (B), and a thickener (C), The basic filler (A) has a pH in water of 8.5 to 12.5; The biodegradable resin (B) includes an aliphatic polyester-based resin (B1) and an aliphatic-aromatic polyester-based resin (B2), The thickener (C) contains at least one selected from the group consisting of a carbodiimide compound, a cellulose fiber, an oxazoline compound, an epoxy compound, an acid anhydride compound, and a silica-based filler; The content of the basic filler (A) is 3 to 30 mass% and the content of the thickener (C) is 0.01 to 3 mass% based on 100 mass% of the thermoplastic resin composition. Thermoplastic resin composition for agricultural materials. <2> The basic filler (A) includes at least one selected from the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, and magnesium hydroxide. <1> The thermoplastic resin composition for agricultural materials described above. <3> The basic filler (A) has an average particle size of 1 to 10 μm. <1> or <2> The thermoplastic resin composition for agricultural materials described above. <4> The thickener (C) contains at least one of a carbodiimide compound and cellulose fiber. <1> ~ <3> The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 4. <5> The content of the aliphatic polyester resin (B1) is 100 to 300 parts by mass relative to 100 parts by mass of the aliphatic-aromatic polyester resin (B2). <1> ~ <4> The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 4. <6> Shear rate 243s -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 not more than 1000 Pa s and not more than 5000 Pa s. <1> ~ <5> The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 4. <7> Used for blow molding or vacuum molding, <1> ~ <6> The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 4. <8> For use in seedling pots. <1> ~ <7> The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 4. <9> the above <1> ~ <8> An agricultural material formed using any one of the thermoplastic resin compositions for agricultural materials. <10> Seedling pots, <9> Agricultural materials as described. Effect of the Invention

[0013] According to one embodiment of the present invention, it is possible to provide a thermoplastic resin composition for agricultural materials which has biodegradability and good moldability, and an agricultural material made of the thermoplastic resin composition for agricultural materials. Furthermore, it is possible to produce even deep-drawn molded articles, which is highly difficult to produce, and it is possible to provide a thermoplastic resin composition for agricultural materials that exhibits high biodegradability, and agricultural materials made of the thermoplastic resin composition for agricultural materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below. 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, a numerical range specified using "~" is a range between the lower limit and the upper limit of the numerical values ​​written before and after "~". In the present specification, the terms "film" and "sheet" are not distinguished by thickness. In other words, the term "sheet" in the present specification includes thin film-like objects, and the term "film" in the present specification includes thick sheet-like objects. In this disclosure, the "thermoplastic resin composition for agricultural materials" may also be referred to as a "resin composition." Unless otherwise noted, the various components appearing in this specification may be used independently as a single type or as a mixture of two or more types. The numerical values ​​specified in this specification are values ​​determined by the methods disclosed in the embodiments or examples.

[0015] <Thermoplastic resin composition for agricultural materials> The thermoplastic resin composition for agricultural materials according to the present embodiment is a thermoplastic resin composition comprising a basic filler (A), a biodegradable resin (B), and a thickener (C), wherein the basic filler (A) has a pH in water of 8.5 to 12.5, the biodegradable resin (B) comprises an aliphatic polyester-based resin (B1) and an aliphatic aromatic polyester-based resin (B2), and the thickener (C) comprises at least one selected from the group consisting of a carbodiimide compound, a cellulose fiber, an oxazoline compound, an epoxy compound, an acid anhydride compound, and a silica-based filler, Based on 100% by mass of the thermoplastic resin composition, the content of the basic filler (A) is 3 to 30% by mass, and the content of the thickener (C) is 0.01 to 3% by mass. Such a resin composition makes it possible to achieve both high biodegradability and moldability. Furthermore, it is possible to produce even deep-drawn molded articles, which is highly difficult to produce, and the material exhibits high biodegradability.

[0016] The decomposition process of the resin composition mainly comprises two stages. In the first stage, the molecular weight of the resin that constitutes the agricultural materials (such as seedling pots and mulch films) that are molded products of the resin composition is reduced by hydrolysis or oxidative decomposition. In the second stage, microorganisms in the soil decompose the individual pieces of agricultural materials made of low molecular weight resin. Since the molecular weight of resins continues to decrease while agricultural materials are stored or used, it is important to control hydrolysis in the first stage. One factor in hydrolysis is the crystallinity of the resin. Hydrolysis is more likely to progress in the amorphous region than in the crystalline region, so it is possible to suppress hydrolysis by increasing the crystallinity. In general, when additives are added to a thermoplastic resin composition, the particles act as crystal nuclei and promote the formation of crystals (nucleating effect), improving crystallinity and providing an effect of inhibiting hydrolysis.

[0017] The thermoplastic resin composition for agricultural materials of this embodiment contains specific amounts of a specific basic filler (A) and a specific thickener (C), so that 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 at least for about four months, which is the seedling growth period, so that the shape can be maintained, and that the agricultural material is decomposed by microorganisms in the soil about one year after the seedling growth period has passed, so that it can be incorporated into the soil.

[0018] This embodiment will be described in detail below.

[0019] (Basic filler (A)) The basic filler (A) of the present invention is a basic filler having a pH of 8.5 to 12.5 in water, and has the function of promoting the hydrolysis of the biodegradable resin (B). The basic filler (A) is not particularly limited as long as it is a basic filler having a pH of 8.5 to 12.5 in water, and any commonly available basic filler can be used. For example, there may be mentioned basic compounds containing alkali metals or alkaline earth metals, zeolites that release ions of alkali metals or alkaline earth metals, ion-releasing fillers, hydrotalcites, and the like. The use of these basic fillers (A) can promote hydrolysis, which is the first stage of the decomposition process of the resin composition, and reduce the molecular weight, thereby enabling a rapid transition to the second stage, the decomposition process by microorganisms in the soil. From the viewpoint of the balance between biodegradability and moldability, the pH is preferably 9.0 to 11.0.

[0020] The pH of the basic filler of the present invention is a pH value measured with a pH meter at 23° C. As the pH meter, a pH meter HM-30P manufactured by Toa DKK Co., Ltd. or the like can be used. do. When the basic filler is soluble in water, the pH can be measured using an aqueous solution, and when the basic filler is not soluble in water, the pH can be measured using the supernatant of the dispersion. Specifically, for example, 0.5 g of the basic filler is weighed out and placed in a plastic container, 50 ml of deionized water is added, and the container is shaken for 30 minutes with a shaker. Then, the container is centrifuged to separate the solid and liquid. The supernatant water is placed in a thermostatic bath at 23°C to stabilize the temperature, and the pH value is measured with a pH meter (PH meter HM-30P manufactured by Toa DKK Co., Ltd.). This value can be regarded as the pH of the basic filler. Cut.

[0021] Examples of basic compounds containing an alkali metal or an alkaline earth metal include sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium silicate, potassium silicate, calcium silicate, magnesium silicate, sodium phosphate, calcium oxide, calcium hydroxide, magnesium hydroxide, and the like.

[0022] As the zeolite that releases ions of an alkali metal or alkaline earth metal, various natural or synthetic zeolites that contain alkali metal or alkaline earth metal ions as exchangeable ions can be used.

[0023] Examples of the ion-releasing filler include oxide glasses such as aluminosilicate glass, borosilicate glass, and soda-lime glass containing alkali metals or alkaline earth metals, and fluoride glasses such as zirconium fluoride glass.

[0024] Among these, from the viewpoint of achieving both moldability and biodegradability, basic compounds containing alkali metals or alkaline earth metals are preferred, calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, and magnesium hydroxide are more preferred, and furthermore, carbonates such as calcium carbonate and magnesium carbonate are particularly preferred, since the basic filler remains in the soil even after biodegradation and if the basicity in the soil becomes too high, it will affect the growth of plants. These may be used alone or in combination of two or more.

[0025] From the viewpoint of moldability, the average particle size of the basic filler (A) is preferably 1 to 20 μm, more preferably 1 to 10 μm. When the average particle size of the basic filler (A) is within the above range, it is possible to achieve both the dispersibility of the basic filler (A) in the biodegradable resin (B) and the smoothness of the surface of the molded article.

[0026] 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 basic filler (A) in the resin composition contributes to moldability, so it is preferable that the average particle size of the basic filler (A) be in the above-mentioned range.

[0027] The average particle size of the basic filler (A) can be determined by a laser diffraction method. For example, by using a laser diffraction method, a dispersion of the dispersed basic filler (A) is irradiated with laser light, and the angular change in intensity of the light scattered when the laser light passes through the solution is measured to obtain a particle size distribution, from which the average particle size can be calculated. As the particle size distribution meter, for example, a particle size distribution meter Microtrack HRA manufactured by Nikkiso Co., Ltd. can be used.

[0028] (Biodegradable resin (B)) The biodegradable resin (B) is decomposed by the action of various microorganisms present in soil or water. The resin composition of the present invention contains 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. The biodegradable resin (B) may further be a commonly available biodegradable resin. Other biodegradable resins include, for example, polycaprolactone. These biodegradable resins may be used alone or in combination of two or more.

[0029] The content of the aliphatic polyester resin (B1) is preferably equal to or greater than the content of the aliphatic aromatic polyester resin (B2). By mixing the aliphatic polyester resin (B1) as the base resin with the aliphatic aromatic polyester resin (B2) having ductility and excellent moldability, the moldability of the resin composition and the strength of the agricultural material molded from the resin composition can be ensured. Therefore, the content of the aliphatic polyester resin (B1) relative to 100 parts by mass of the aliphatic aromatic polyester resin (B2) is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, and even more preferably 150 parts by mass or less.

[0030] [Aliphatic polyester resin (B1)] Examples of the aliphatic polyester resin (B1) include aliphatic polyesters obtained by polycondensation reaction of aliphatic diols and aliphatic dicarboxylic acids, and polylactic acids obtained by polycondensation of lactic acid. Examples of the 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, it is preferable to use 1,4-butanediol. Examples of the aliphatic dicarboxylic acids include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, and dodecanedioic acid, and acid anhydrides that are derivatives of these may also be used. Of these, succinic acid or succinic anhydride, or a mixture of these with adipic acid, is preferable. Specific examples include polybutylene succinate (PBS) obtained from 1,4-butanediol and succinic acid (for example, "BioPBS" (product name) manufactured by PPT MCC Biochem), and polybutylene succinate adipate (PBSA) obtained by copolymerizing PBS with adipic acid.

[0031] [Aliphatic polyester resin (B2)] Examples of the aliphatic aromatic polyester resin (B2) include copolymers containing an aliphatic dicarboxylic acid unit, an aromatic dicarboxylic acid unit, and a chain aliphatic and / or alicyclic diol unit. The diol component that gives the diol unit usually has 2 to 10 carbon atoms, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. Among these, diols having 2 to 4 carbon atoms are preferred, and ethylene glycol and 1,4-butanediol are more preferred, and 1,4-butanediol is even more preferred. The dicarboxylic acid component that gives the dicarboxylic acid unit is The aromatic dicarboxylic acid component that provides the aromatic dicarboxylic acid unit typically has a carbon number of 2 to 10, and examples of the aromatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Of these, succinic acid or adipic acid is preferred. Of these, examples of the aromatic dicarboxylic acid component that provides the aromatic dicarboxylic acid unit include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Of these, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is more preferred. Specifically, examples include polybutylene adipate terephthalate (PBAT) (for example, "Ecoflex" (product name) manufactured by BASF), which is a copolymer of 1,4-butanediol, adipic acid, and terephthalic acid.

[0032] The biodegradable resin (B) may be a combination of the aliphatic polyester resin (B1) and the aliphatic aromatic polyester resin (B2) with other biodegradable resins. Examples of other biodegradable resins include poly(3-hydroxyalkanoates) (especially poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) (e.g., "Aonilex" (trade name) manufactured by Kaneka Corporation) which are aliphatic polyester copolymers obtained from hydroxyalkanoic acid and polycarboxylic acid), and polylactic acid (PLA) (e.g., "REVODE" (trade name) manufactured by Kaisei Biomaterials, and "Ingeo" (trade name) manufactured by Natureworks).

[0033] The content of the biodegradable resin (B) may be 35 to 95% by mass, more preferably 35 to 94.99% by mass, even more preferably 35 to 94.5% by mass, and even more preferably 39 to 90% by mass, based on the resin composition (100% by mass). The content of the biodegradable resin (B) within the above range is preferable because it is possible to achieve both processability and moldability of the resin composition. In addition, the total content of the aliphatic polyester resin and the aliphatic aromatic polyester resin may be 100% by mass, and is preferably 80% by mass or more, more preferably 90% by mass or more, based on the biodegradable resin (B) (100% by mass).

[0034] (Thickener (C)) The thickener (C) is a viscosity modifier that adjusts the viscosity of the resin composition to improve moldability, and has the function of increasing the melt tension of the resin composition, which is an index of moldability. The thickener (C) contains at least one selected from the group consisting of a carbodiimide compound, an oxazoline compound, an epoxy compound, an acid anhydride compound, cellulose fiber, and a silica-based filler.

[0035] When the thickener (C) is a polyfunctional compound, it can increase the melt tension of the resin composition by forming a crosslinked structure with the biodegradable resin (B). Examples of the polyfunctional compound include polyfunctional carbodiimide compounds, polyfunctional oxazoline compounds, epoxy compounds, and acid anhydride compounds. The polyfunctional carbodiimide compound may be a monomer or polymer having two or more carbodiimide groups, but is preferably a polymer having two or more carbodiimide groups.

[0036] When the thickener (C) is a reactive compound, a reactive group is introduced into the biodegradable resin (B), and a crosslinking structure is formed from the reactive group, thereby increasing the melt tension of the resin composition. Examples of the reactive compound include carbodiimide compounds, oxazoline compounds, epoxy compounds, 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.

[0037] When a silica-based filler is used as the thickener (C), the solid content of the resin composition is increased to thicken the resin composition, thereby increasing the melt tension of the resin composition. The filler may be either an organic filler or an inorganic filler, and examples of the filler include cellulose fiber and silica-based filler.

[0038] In a preferred embodiment, a compound listed in the positive list of green plastics can be used, for example, cellulose microfiber (CMF) which is a cellulose fiber, a carbodiimide compound (CDI), etc. can be used. The cellulose microfiber refers to a relatively large-sized cellulose fiber 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. By including the cellulose microfiber and the carbodiimide compound, the viscosity of the resin composition can be increased and strength can be ensured.

[0039] That is, when a resin composition contains cellulose microfiber, the strength of the resin composition is increased due to the filler effect of the cellulose microfiber. Also, the silica-based filler has a filler effect similar to that of the cellulose microfiber, and therefore increases the strength of the resin composition in the same manner as the cellulose microfiber. For example, blow molding can be used to mold a resin composition containing at least one of the cellulose microfiber and the silica-based filler as the thickener (C).

[0040] When a carbodiimide compound is contained in a resin composition, the resin reacts with the carbodiimide compound to increase the molecular weight of the resin, so it takes time for the resin to be hydrolyzed to reduce the molecular weight, and the biodegradation rate slows down. For this reason, in the case of agricultural materials that require strength of the resin composition, it is preferable that a carbodiimide compound is contained as a thickener (C). In addition, oxazoline compounds, epoxy compounds, and acid anhydride compounds each have reactivity with resins like carbodiimide compounds, so that these compounds can also improve the strength of the resin composition. A resin composition 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.

[0041] Examples of the carbodiimide compound include polycarbodiimide compounds such as "Carbodilite HMV-15CA (trade name)" manufactured by Nisshinbo Chemical Co., Ltd.; 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 Ltd. These compounds may be used alone or in combination of two or more kinds.

[0042] Examples of oxazoline compounds include "Epocross RA-45" (trade name) and "Epocross RPS-1005" (trade name) manufactured by Nippon Shokubai Co., Ltd. These compounds may be used alone or in combination of two or more kinds. Examples of epoxy compounds include epoxy-acrylic compounds ("Joncryl ADR-4468" (trade name) manufactured by BASF, "Joncryl ADR-4400" (trade name) manufactured by BASF, "Alphon UG-4040" (trade name) manufactured by Toa Gosei Co., Ltd., and "Alphon UG-4070" (trade name) manufactured by Toa Gosei Co., Ltd.). These compounds may be used alone or in combination of two or more kinds. Examples of the acid anhydride compound include styrene-maleic anhydride compounds (manufactured by PALMER HOLLAND: "XIBOND120" (trade name), "XIBOND140" (trade name), "XIBOND160" (trade name), "XIBOND180" (trade name), "XIBOND200" (trade name), "XIBOND220" (trade name), and "XIBOND250" (trade name)). (trade name), "XIBOND280" (trade name), and Tomoe Engineering Co., Ltd.'s "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). These compounds may be used alone or in combination of two or more kinds. Examples of silica-based fillers include silica fillers (manufactured by Nippon Aerosil Co., Ltd.: "Aerosil 130" (trade name), "Aerosil 150" (trade name), "Aerosil 200" (trade name), "Aerosil 300" (trade name), "Aerosil RX200" (trade name), "Aerosil RY200" (trade name), and Tosoh Silica Corporation: "Nipseal SS-50" (trade name), "Nipseal SS-50B" (trade name), "Nipseal SS-50F" (trade name), "Nipseal K-500" (trade name), "Nipseal G-300" (trade name), and the like. These may be used alone or in combination of two or more types.

[0043] In order to make the viscosity of the resin composition appropriate, the content of the thickener (C) is preferably 0.01 to 3 parts by mass, more preferably 0.01 to 2 parts by mass, and 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.

[0044] (Starch (D)) The resin composition of the present invention may also contain starch. The use of starch is preferable because it accelerates the second step, that is, the decomposition step by microorganisms in the soil, thereby providing a further acceleration effect. Starch (D) promotes the activity (biodegradability) of various microorganisms present in soil or water. Starch (D) is not particularly limited, and commonly available starch can be used. Examples include corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch, and the like. Among them, corn starch having a uniform particle size of about 20 μm is preferably used because it can make the thickness of the agricultural material made of the resin composition uniform (reduce surface unevenness), suppress the occurrence of thin parts, and as a result, suppress damage to the agricultural material. These may be used alone or in combination of two or more.

[0045] When starch (D) is contained, the content of starch (D) is a component that can adjust the biodegradation rate, and the content is preferably 5 to 60 mass% in 100 mass% of the resin composition, and may be 10 to 50 mass%, 10 to 40 mass%, or 10 to 30 mass%. When the content of starch (D) is 5 mass% or more, biodegradation is promoted, and when it is 60 mass% or less, the content of biodegradable resin (B) is secured, and moldability can be ensured.

[0046] From the viewpoint of moldability, the average particle size of the starch (D) is preferably 5 to 50 μm, and may be 10 to 50 μm. When the average particle size of the starch (D) is within the above range, it is possible to achieve both the dispersibility of the starch (D) in the biodegradable resin (B) and the smoothness of the surface of the molded article.

[0047] The average particle size of starch (D) can be determined, for example, by observing particles of starch (A) with a scanning electron microscope, randomly observing 100 particles, measuring the distance between the two most distant points on the outline of each particle based on the length of a micron marker on the screen, and averaging the distances.

[0048] The mass ratio of the starch (D) to the basic filler (A), basic filler (A) / starch (D), is preferably 80 / 20 to 20 / 80, and more preferably 50 / 50 to 25 / 75. This will have a further promoting effect, making it possible to make agricultural materials with better biodegradability. This is preferable.

[0049] (Other ingredients) The resin composition may optionally contain other components such as additives as necessary. Examples of 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 the amount of use thereof are not particularly limited as long as they are within a range that can solve the problem of one embodiment of the present invention. A combination of multiple additives may be used. In addition, the resin composition may partially contain a resin other than the biodegradable resin within a range that does not inhibit the effect of one embodiment of the present invention.

[0050] By coloring the resin composition with a pigment, a molded article having excellent heat shielding effect or an easily identifiable molded article can be produced. The pigment is not particularly limited, and any commonly available pigment can be used, but from the viewpoint of the natural environment, it is preferable that the pigment does not substantially contain pigments containing cadmium, lead, chromium, arsenic, mercury, copper, selenium, nickel, molybdenum, or fluorine.

[0051] For example, when the resin composition contains a pigment, it is preferable to use a dispersant for dispersing the pigment, and examples of the dispersant 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 have only saturated bonds 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. The metal is preferably an element of Group 1, Group 2, Group 12, or Group 13, and more preferably an element of Group 1 or Group 2. Specific examples include sodium, potassium, calcium, magnesium, and barium.

[0052] 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. Among these, calcium stearate, magnesium stearate, calcium laurate, and magnesium laurate are preferred.

[0053] (processability) In the above-mentioned 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, may be 1 to 5 times, and preferably no strand breakage occurs.

[0054] (Melt Viscosity) In the above-mentioned thermoplastic resin composition for agricultural materials, the shear rate of 243 s according to JIS K7199:1999 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.

[0055] (Application) The thermoplastic resin composition for agricultural materials according to the present embodiment can be used for various agricultural materials. In particular, this resin composition can be suitably used for seedling pots. Seedling pots are containers for growing seedlings until they grow to a certain extent, rather than sowing seeds directly in a field. Since the molded product using the resin composition of the present embodiment is appropriately biodegradable in soil, it is not necessary to remove the seedlings from the seedling pots after they have grown and then transplant them, and they can be transplanted in soil in the seedling pots as they are.

[0056] ≪Manufacturing method≫ The resin composition of this embodiment can be produced by kneading the basic filler (A) and the thickener (C) at a temperature at which the biodegradable resin (B) melts. Specifically, for example, the biodegradable resin (B), the basic filler (A), the thickener (C), and various additives are added as necessary, and mixed and melt-kneaded with a batch kneader such as a kneader, roll mill, super mixer, high-speed mixer, ball mill, sand mill, attritor, or Banbury mixer, a single-screw extruder, a twin-screw extruder, a rotor-type twin-screw kneader, or the like to form a pellet-shaped, powder-shaped, granular, or bead-shaped resin composition. It is preferable to form the pellets with a single-screw extruder or twin-screw extruder because of its strong kneading power and easy subsequent molding processing.

[0057] The resin composition may be used in the form of either a master batch or a compound. In the case of a masterbatch, after the masterbatch is produced, the agricultural material can be produced by mixing the masterbatch with, for example, the same biodegradable resin (B) as that used in the production of the masterbatch as a diluting resin, which is the main resin of the agricultural material. The content of the masterbatch is preferably 1 to 50 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the biodegradable resin (B) which is the main resin. In this case, the biodegradable resin (B) used as the diluting resin may be the same as that used in the production of the master batch, or it may be different. However, it is preferable to use the same biodegradable resin, since this provides excellent 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 it is to produce agricultural materials by the above-mentioned method.

[0058] <Agricultural materials> The agricultural material of the present 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. The agricultural material of this embodiment makes it possible to achieve both biodegradability and moldability even in the case of deep-drawn molded articles with a high stretch ratio, such as seedling pots and plug trays. The deep-drawn molded body referred to here is a molded body whose depth is longer than its width.

[0059] (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 directly placed in a mold without cooling and solidifying it, and air is blown into the mold, and vacuum molding in which a sheet or film of a heated and plasticized resin composition is placed on a mold and vacuum-suctioned from the inside of the mold to mold the pot.

[0060] The seedling pot made of the above-mentioned resin composition is biodegradable after being buried in soil, so it does not damage the natural environment and reduces the labor required to remove the seedling from the seedling pot and sow the seedling. The seedling pot grows well without decomposing for about 2-4 months, which is the growth period of the seedling before being buried in soil. In addition, the seedling pot has a strength suitable for seedling growth, so it is easy to handle and can maintain an appropriate shape during the seedling growth period.

[0061] (Multi-film) Mulch film (mulching film) is a film that covers the base of crops. 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 using a cast roll, or molding using an inflation molding machine.

[0062] <Blow molding, vacuum molding> The above-mentioned resin composition has an increased melt tension due to the thickener (C), and therefore drawdown (the phenomenon in which a preformed resin cannot withstand its own weight and sags in the direction of gravity) can be suppressed.

[0063] In the case of blow molding, it is possible to suppress the molded product from becoming thin and light. The resin composition of the present embodiment can be blow molded, and for example, when three sets of two seedling pots are continuously produced using a direct blow molding machine, the difference between the weight of each seedling pot in the first set and the weight of each seedling pot in the third set can be made less than 30% of the weight of each seedling pot in the first set. In addition, the weight of each seedling pot may be 0.7 g or more and less than 0.8 g, preferably 0.8 g or more and less than 0.9 g, and more preferably 0.9 g or more. By using the above-mentioned resin composition, blow moldability can be obtained.

[0064] 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 bend. By using the above-mentioned resin composition, a seedling pot having sufficient strength can be obtained.

[0065] In the case of vacuum molding, the occurrence of defective appearance due to sagging such as wrinkles caused by bending of the sheet can be suppressed. For example, even if the molded product has defective appearance due to sagging, it is sufficient as long as the resin composition can be vacuum molded, and it is preferable that the defective appearance is slight, and more preferably that there is no defective appearance. By using the above-mentioned resin composition, a vacuum molded product can be obtained.

[0066] 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 put into the seedling pot and it is 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 it is preferable that none of the seedling pots break out. By using the above-mentioned resin composition, a seedling pot with sufficient strength can be obtained.

[0067] (biodegradation rate) When a molded article made from the above-mentioned resin composition is buried in the ground for six months, it is sufficient that the molded article is decomposed and has holes in places, and it is preferable that the molded article is decomposed and falls into pieces. By using the above-mentioned resin composition, a molded article with an appropriately adjusted biodegradation rate can be obtained.

[0068] According to this embodiment, the thermoplastic resin composition for agricultural materials contains specific amounts of the basic filler (A) that promotes biodegradability and the thickener (C) that increases melt tension, so that agricultural materials with excellent biodegradability and moldability can be obtained.

[0069] In addition, the embodiment of the present invention includes various embodiments not described herein. For example, the embodiment includes the following embodiments.

[0070] In this specification, a numerical range indicated using "~" indicates a range including the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage. EXAMPLES

[0071] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" respectively represent "parts by mass" and "% by mass" unless otherwise specified. The amounts in the table are shown in parts by mass. Note that blank spaces in the table indicate that no ingredient was added. The measurement methods for the pH and average particle size of the basic filler are as follows.

[0072] <pH measurement> Weighed 0.5 g of the basic filler, placed it in a plastic container, added 50 ml of deionized water, vibrated it with a vibrator for 30 minutes, then separated the solid and liquid by a centrifuge. After stabilizing the temperature of the supernatant water in a thermostatic bath at 23°C, the pH was measured with a pH meter (pH meter HM-30P manufactured by Toa DKK Corporation). -30P).

[0073] The measurement methods for the average particle sizes of the basic filler (A) and starch (D) are as follows. <Measurement method for the average particle size of the basic filler (A)> A sample was prepared by dispersing the basic filler with isopropyl alcohol. Using a particle size distribution meter Microtrac HRA manufactured by Nikkiso Co., Ltd., the obtained dispersion was irradiated with laser light, and the particle size distribution was obtained by measuring the distribution pattern of the intensity of the light scattered when the laser light passed through the dispersion. Furthermore, from the values of the above particle size distribution, the median diameter (50% diameter) on a volume basis was determined and taken as the average particle size.

[0074] <Measurement method for the average particle size of starch (D)> Using a scanning electron microscope (SEM) manufactured by Hitachi, Ltd., the starch particles were observed at a field magnification of 100 times. Randomly observed 100 particles, measured the distance between the two farthest points on the outer shape of each particle based on the length of the micron marker on the screen, and averaged them to obtain the result.

[0075] Next, the materials used in the thermoplastic resin composition for agricultural materials are listed below. (Basic filler (A)) A-1: KS-1300 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0, average particle size: 1.8 μm) A-2: KS-500 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0, average particle size: 4.4 μm) A-3: KS-300 (calcium carbonate, manufactured by Calfine Co., Ltd., pH 9.0, average particle size: 8.9 μm) A-4: Magnesium carbonate (Kinsei) (Kojima Chemical Co., Ltd., pH 10.0, average particle size: 10 μm) A-5: F-Lime-1300K (calcium oxide, manufactured by Calfine Co., Ltd., pH 12.4, average particle size: 5.0 μm) A-6:M-300 (calcium hydroxide, manufactured by Inoue Mitsukichi Shoten Co., Ltd., pH 12.4, average particle size: 4.9 μm) A-7: Magnesium hydroxide (Kojima Chemical Co., Ltd., pH 10.5, average particle size: 6 μm) A-8: Magnesium hydroxide (Kojima Chemical Co., Ltd., pH 10.5, average particle size 15 μm) A-9: IXE-700F (hydrotalcite, manufactured by Toa Gosei Co., Ltd., pH 8.5, average particle size: 1.5 μm) (Other basic fillers) A'-1: Sodium hydroxide (pH 14.0, average particle size: 20 μm)

[0076] (Biodegradable resin (B)) [Aliphatic polyester resin (B1)] B1-1: BioPBS FZ91 (PTT MCC Biochem aliphatic polyester resin: PBS resin) B1-2: Ingeо Biopolymer 6252D (NatureWorks aliphatic polyester resin: PLA resin) [Aliphatic aromatic polyester resin (B2)] B2-1: Ecoflex C1200 (Aliphatic aromatic polyester resin: PBAT resin, manufactured by BASF)

[0077] (Thickener (C)) C-1: KC Flock W-50 (cellulose microfiber, average fiber length: 50 μm) C-2: Carbodilite HMV-15CA (Nisshinbo Chemical Co., Ltd., polycarbodiimide compound) C-3: Carbodista TCC-NP (Teijin Limited, cyclic carbodiimide compound) C-4: Joncryl ADR-4468 (BASF, epoxy-acrylic compound) C-5: XIBOND220 (styrene maleic anhydride compound, manufactured by Palmer Holland) C-6: Epocross 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) (The thickener) C'-1: Sumecton-SWF (Kunimine Industries Co., Ltd., synthetic hectorite)

[0078] (Starch (D)) D-1: Chemister 420 (Glico Nutrition Foods Co., Ltd., average particle size: 15 μm)

[0079] <Production of Thermoplastic Resin Composition for Agricultural Materials> [Example 1] (Manufacture of thermoplastic resin compositions (compounds) for agricultural materials) 5 parts by mass of (A-1) as a basic filler (A), 64.5 parts by mass of (B1-1) and 30 parts by mass of (B2-1) as biodegradable resins (B), and 0.5 parts by mass of (C-1) as a thickener (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.

[0080] (Manufacturing of seedling pots) The obtained thermoplastic resin composition for agricultural materials was molded by blow molding and vacuum molding to obtain a seedling pot.

[0081] [Examples 2 to 35, Comparative Examples 1 to 5] A thermoplastic resin composition for agricultural materials and a seedling pot were obtained in the same manner as in Example 1, except that the materials and the blending amounts (parts by mass) were changed to those shown in Table 1. The thermoplastic resin compositions for agricultural materials of Comparative Examples 3, 4, and 7 to 9 had poor moldability and could not be used to manufacture seedling pots, so that evaluation of the strength, brittleness, and biodegradability rate of the molded products could not be performed.

[0082] The thermoplastic resin compositions for agricultural materials and the seedling pots obtained in the Examples and Comparative Examples were The evaluation results are shown in Table 1.

[0083] <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 occurs during continuous production for 1 hour. △: Strand breakage occurs 1 to 5 times during continuous production for 1 hour. ×: Strand breakage occurs 6 or more times during continuous production for 1 hour.

[0084] <Melt viscosity evaluation> According to JIS K7199:1999, the thermoplastic resin (B) used in the examples and comparative examples was melted at a temperature of 150°C, which is equal to or higher than the melting point and 40°C higher than the melting point, at a shear rate of 243 s -1 The melt viscosity of the thermoplastic resin composition for agricultural materials was measured at 100°C. The evaluation criteria were as follows, with ◯ and △ being considered practical. [Evaluation Criteria] ○: Melt viscosity is 1500 Pa s or more △: Melt viscosity is 1000 or more and less than 1500 Pa·s ×: Melt viscosity is less than 1000 Pa s

[0085] <Blow moldability evaluation> Three sets of two seedling pots (diameter 9 cm, height 7 cm) were made in succession at 150°C using a direct blow molding machine (manufactured by Nippon Placon Co., Ltd.), and the difference in weight between each seedling pot in the first set and each seedling pot in the third set (weight difference) and the weight of each seedling pot were evaluated as moldability during production. In this evaluation, "capable of blow molding" means that the weight difference is less than 30% of the weight of each seedling pot in the first set. The evaluation criteria are as follows, with ◯ and △ being practical. [Evaluation Criteria] 〇: Can be blow molded, and each seedling pot weighs 0.9g or more △: Blow molding is possible, and the weight of each seedling pot is 0.7 to less than 0.9g ×: Cannot be blow molded

[0086] <Vacuum forming evaluation> A sheet of 30 cm length x 30 cm width x 0.45 mm thickness is made at 180℃ using a T-die molding machine. The molded sheet was heated to 110°C and molded into a seedling pot (diameter 6 cm, height 7 cm) using a vacuum molding machine, and the moldability during production was evaluated. The evaluation criteria were as follows, with ◯ and △ being practical. [Evaluation Criteria] ◯: Vacuum molding was possible, and the seedling pot had no defective appearance due to dripping. △: Vacuum forming was possible, and defective parts in appearance due to dripping were observed in the seedling pot. ×: Cannot be vacuum molded.

[0087] <Evaluation of molded product strength> The strength of the seedling pots produced during the blow moldability evaluation was evaluated. The evaluation criteria were as follows, with ◯ and △ being deemed usable. [Evaluation Criteria] ○: The seedling pot is free-standing without bending. △: The seedling pot is bent but can stand on its own. ×: The seedling pot cannot stand upright because it cannot support its own weight. -: Seedling pots could not be made, and evaluation was not possible.

[0088] <Evaluation of molded product brittleness> The ten seedling pots made for the vacuum moldability evaluation were each filled with 1 kg of soil and dropped from a height of 5 m to evaluate the fragility of the seedling pots. The evaluation criteria were as follows, with ◯ and △ being considered usable. [Evaluation Criteria] ○: Not one seedling pot out of 10 was destroyed. △: 1 to 3 out of 10 will be destroyed. ×: 4 or more out of 10 are destroyed. -: Seedling pots could not be made, and evaluation was not possible.

[0089] <Biodegradation rate evaluation> The seedling pots made for the evaluation of blow moldability were buried in the ground and dug up after 2 weeks, 1 month, and 3 months to evaluate biodegradability. The evaluation criteria were as follows, with ◯ and △ being practical. [Evaluation Criteria] ○: The seedling pot has decomposed and fallen apart. △: The seedling pot has decomposed and has holes in it. ×: The seedling pot retains its original shape. -: Seedling pots could not be made, and evaluation was not possible.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Table 3]

[0093] [Table 4]

[0094] From the above results, it was confirmed that the resin compositions and seedling pots of the examples are environmentally friendly and capable of significantly promoting biodegradation, as well as having excellent moldability.

Claims

1. A thermoplastic resin composition comprising a basic filler (A), a biodegradable resin (B), and a thickener (C), The basic filler (A) has a pH in water of 8.5 to 12.5, The biodegradable resin (B) includes an aliphatic polyester-based resin (B1) and an aliphatic-aromatic polyester-based resin (B2), The aliphatic polyester resin (B1) contains an aliphatic polyester obtained by a polycondensation reaction of an aliphatic diol and an aliphatic dicarboxylic acid, The thickener (C) contains at least one of a carbodiimide compound and cellulose fiber, the content of the basic filler (A) is 3 to 30 mass% and the content of the thickener (C) is 0.01 to 3 mass% based on 100 mass% of the thermoplastic resin composition; Thermoplastic resin composition for agricultural materials.

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

3. 2. The thermoplastic resin composition for agricultural materials according to claim 1, wherein the basic filler (A) has an average particle size of 1 to 10 μm.

4. A thermoplastic resin composition for agricultural materials as described in claim 1, further containing starch (D).

5. A thermoplastic resin composition for agricultural materials according to claim 1, wherein the basic filler (A) has a pH in water of 10.5 to 12.

5.

6. Shear rate 243 s －１ 2. 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 (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. 2. The thermoplastic resin composition for agricultural materials according to claim 1, which is used for blow molding or vacuum molding.

8. 2. The thermoplastic resin composition for agricultural materials according to claim 1, which is for use in seedling pots.

9. An agricultural material formed using the thermoplastic resin composition for agricultural materials according to any one of claims 1 to 8.

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