JP7232367B1 - Thermoplastic resin composition for agricultural materials and agricultural materials - Google Patents

Abstract

Kind Code: A1 A thermoplastic resin composition for agricultural materials, which is biodegradable and has good moldability, and which enables the production of molded articles with reduced stickiness on the surface, and the thermoplastic resin composition for industrial materials. provide agricultural materials.
The thermoplastic resin composition for agricultural materials contains starch (A), biodegradable resin (B) and viscosity modifier (C), and does not contain plasticizer (D). The content of starch (A) is 5 to 60 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials, and the content of the viscosity modifier (C) is 100 parts by mass of the thermoplastic resin composition for agricultural materials. 0.01 to 1 part by mass.
[Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a thermoplastic resin composition for agricultural materials and agricultural materials.

Because plastics are easy to mold, they are used in a wide range of fields, including electrical and electronic equipment parts, automotive parts, medical parts, and food containers. has been given to In the field of agricultural materials, it is used in applications that require water resistance and strength.

Agricultural materials include, for example, mulch films used for applications aimed at raising soil temperature or heat retention, pest control, and seedling pots, which are a type of dedicated container for raising seedlings.

Agricultural materials that use biodegradable materials are available as a solution to the recent waste problem and to reduce the collection work of agricultural materials, which do not need to be collected and decompose in the ground (in the soil) after use. It is possible.

In Patent Document 1, tear strength is strong by containing aliphatic polyester resin, aromatic aliphatic polyester resin, starch and polyhydric alcohol in a specific mass ratio, biodegradability, moldability, heat shrinkability, Films with good transparency, high modulus and resistance to wrinkling are described.

In the film, an aliphatic polyester resin and an aromatic aliphatic polyester resin are used as biodegradable materials, and by adjusting the content of polyhydric alcohol, tear strength and tensile elasticity are improved while plasticizing the starch. It improves the physical properties of the resin composition such as the modulus.

Japanese Unexamined Patent Application Publication No. 2011-26538

Since starch does not have thermoplasticity and has a low thermal decomposition temperature, the resin composition can be modified by adding a plasticizer such as a polyhydric alcohol. , The surface of the resulting molded product becomes sticky, and the peelability between the mold of the molding machine and the resin composition during molding and the slipperiness for separating the molded products individually are reduced, and the molding of the resin composition is affected. may affect

The present invention has been made in view of the circumstances as described above. An object of the present invention is to provide a plastic resin composition and agricultural materials comprising the thermoplastic resin composition for agricultural materials.

In order to solve the above problems, the present inventors have made intensive studies, and as a result, have found a thermoplastic resin composition for agricultural materials having the following constitution, and completed the present invention.

That is, one embodiment of the present invention contains starch (A), biodegradable resin (B) and viscosity modifier (C), and does not contain plasticizer (D). A plastic resin composition in which the content of starch (A) is 5 to 60 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials, and the content of the viscosity modifier (C) is the heat for agricultural materials. It relates to a thermoplastic resin composition for agricultural materials, which is 0.01 to 1 part by mass in 100 parts by mass of the plastic resin composition.

Another embodiment relates to the thermoplastic resin composition for agricultural materials, wherein the content of starch (A) is 10 to 30 parts by mass per 100 parts by mass of the thermoplastic resin composition for agricultural materials.

Another embodiment relates to the thermoplastic resin composition for agricultural materials, wherein the starch (A) has an average particle size of 5 to 50 μm.

Another embodiment relates to the thermoplastic resin composition for agricultural materials, wherein the viscosity modifier (C) contains at least one selected from the group consisting of cellulose fibers and carbodiimide.

In another embodiment, the biodegradable resin (B) contains an aliphatic polyester-based resin and an aliphatic-aromatic polyester-based resin, and the content of the aliphatic polyester-based resin is the aliphatic-aromatic polyester The present invention relates to the above thermoplastic resin composition for agricultural materials, which is equal to or greater than the content of the system resin.

In another embodiment, the agricultural material has a melt viscosity at a shear rate of 243 s ⁻¹ of 1000 Pa s or more and less than 5000 Pa s at a temperature of the melting point of the biodegradable resin (B) or higher and the melting point +40 ° C. or lower. It relates to a thermoplastic resin composition for

Another embodiment relates to the thermoplastic resin composition for agricultural materials, which is used for blow molding or vacuum molding.

Another embodiment relates to the above thermoplastic resin composition for agricultural materials, which is for raising seedling pots.

Another embodiment relates to an agricultural material comprising the thermoplastic resin composition for agricultural materials.

Another embodiment relates to the above agricultural material, which is a nursery pot.

INDUSTRIAL APPLICABILITY According to one embodiment of the present invention, a thermoplastic resin composition for agricultural materials that can produce a molded article with suppressed surface stickiness, has biodegradability, and has good moldability, and the agricultural material It is possible to provide an agricultural material comprising a thermoplastic resin composition for

<Thermoplastic resin composition for agricultural materials>
The thermoplastic resin composition for agricultural materials according to the present embodiment (hereinafter also simply referred to as "resin composition") comprises starch (A), a biodegradable resin (B), and a viscosity modifier (C). , and does not contain a plasticizer (D). By adjusting the starch (A) and the viscosity modifier (C) to specific contents and not including the plasticizer (D), the resulting resin composition has good moldability and is biodegradable. In addition, it is possible to suppress stickiness of the surface of the molded product.

The decomposition process of the resin composition is roughly divided into two.
The first step is to reduce the molecular weight of the resin that constitutes the agricultural material (raising seedling pot, mulch film, etc.), which is a molded product of the resin composition, by hydrolysis or oxidative decomposition.
In the second step, microorganisms in the soil decompose the individual pieces of the agricultural material made of the low-molecular-weight resin.
Hydrolysis control in the first stage is important because the molecular weight reduction of the resin progresses while the agricultural material is stored or used. A factor of hydrolysis is the crystallinity of the resin. Hydrolysis proceeds more easily in the amorphous region than in the crystalline region, so that hydrolysis can be suppressed by increasing the crystallinity.
In general, when an additive is added to a thermoplastic resin composition, the particles become crystal nuclei, promoting the formation of crystals (nucleating effect), improving crystallinity, and obtaining an effect of suppressing hydrolysis.

The thermoplastic resin composition for agricultural materials of the present embodiment contains specific amounts of starch (A) that promotes biodegradability and viscosity modifier (C) that increases melt tension. can regulate the biodegradation rate of For example, at least for about 4 months, which is the growing period of seeds and seedlings, the decomposition of agricultural materials can be suppressed and their shape can be maintained, and about one year after the growing period of seeds and seedlings, the agricultural materials become contaminated with microorganisms in the soil. It is desirable that it is decomposed by

This embodiment will be described in detail below.

(Starch (A))
Starch (A) promotes the action (biodegradability) of various microorganisms present in soil or water. Starch (A) is not particularly limited, and commonly available starches can be used. Examples include corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch and the like. Among them, cornstarch with a uniform particle size of about 20 μm can make the thickness of the agricultural material made of the resin composition uniform (reduce unevenness on the surface) and suppress the occurrence of thin portions. , is preferable because damage to agricultural materials can be suppressed as a result. These may be used individually by 1 type, or may be used in combination of 2 or more types.

Starch (A) is a component that can adjust the biodegradation rate, and its content is preferably 5 to 60 parts by mass, 10 to 50 parts by mass, and 10 to 40 parts by mass in 100 parts by mass of the resin composition. parts, or 10 to 30 parts by mass. When the content of starch (A) is 5 parts by mass or more, biodegradation is promoted. can.

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

In particular, in blow molding where resin is directly put into a mold and air is blown, the average particle size of starch (A) in the resin composition contributes to the moldability, so the average particle size of starch (A) is as described above. A range is preferred.

The average particle diameter of starch (A) is determined, for example, by observing the particles of starch (A) with a scanning electron microscope, observing 100 particles at random, and measuring the two most distant points on the outer shape of each particle. The distance between them can be obtained by measuring and averaging the lengths of the micron markers on the screen.

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

Among these, aliphatic polyester-based resins or aliphatic-aromatic polyester-based resins are preferable from the viewpoint of biodegradability and moldability.
In addition, when an aliphatic polyester resin and an aliphatic aromatic polyester resin are used together as a biodegradable resin, the content of the aliphatic polyester resin is at least the content of the aliphatic aromatic polyester resin. preferable. Moldability of the resin composition and strength of the agricultural material that is the molded product by mixing the aliphatic polyester resin as the base resin with the ductile and highly moldable aliphatic aromatic polyester resin. can be ensured. The content ratio (parts by mass) of the aliphatic polyester-based resin and the aliphatic-aromatic polyester-based resin is, for example, preferably 1 to 3:1, more preferably 1.5 to 2:1. .

Examples of aliphatic polyester-based resins include aliphatic polyesters obtained by polycondensation reaction 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, 1,4- Cyclohexanedimethanol is mentioned. These may be used alone or as a mixture thereof. Among them, it is preferable to use 1,4-butanediol. Examples of aliphatic dicarboxylic acids include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, and dodecanedioic acid, and acid anhydrides, which are derivatives thereof, may be used. Among them, succinic acid, succinic anhydride, or a mixture of these and adipic acid is preferred.
Specifically, polybutylene succinate (PBS) obtained from 1,4-butanediol and succinic acid (for example, "BioPBS" (trade name) manufactured by PPT MCC Biochem Co., Ltd.), polybutylene obtained by copolymerizing PBS with adipic acid succinate adipate (PBSA) and the like.

Examples of aliphatic-aromatic polyester-based resins include copolymers containing aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and chain aliphatic and/or alicyclic diol units. The diol component that provides the diol unit usually has 2 to 10 carbon atoms, and examples thereof include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. . Among them, diols having 2 to 4 carbon atoms are preferred, ethylene glycol and 1,4-butanediol are more preferred, and 1,4-butanediol is still more preferred. The dicarboxylic acid component that provides the dicarboxylic acid unit usually has 2 to 10 carbon atoms, and examples thereof include succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid. Among them, succinic acid or adipic acid is preferred. Examples of aromatic dicarboxylic acid components that give aromatic dicarboxylic acid units include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Among them, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is more preferred.
Specifically, polybutylene adipate terephthalate (PBAT), which is a copolymer of 1,4-butanediol, adipic acid, and terephthalic acid (for example, "Ecoflex" (trade name) manufactured by BAS F Co., Ltd. )) and the like.

In addition, the biodegradable resin (B) may be in a form in which the above-mentioned aliphatic polyester resin and/or aliphatic aromatic polyester resin is used in combination with other biodegradable resin. Other biodegradable resins include, for example, poly(3-hydroxyalkanoates) of aliphatic polyester copolymers obtained from hydroxyalkanoic acid and polycarboxylic acid (especially poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) (PHBH) (e.g., Kaneka Corporation "Aonylex" (trade name)), polylactic acid (PLA) (e.g., Haisho Biomaterials Co., Ltd. "REVODE" (trade name), "Ingeo" (trade name) manufactured by Nature Works.

The content of the biodegradable resin (B) is preferably 35 to 95 parts by mass, more preferably 39 to 90 parts by mass, based on 100 parts by mass of the resin composition. When the content of the biodegradable resin (B) is within the above range, both processability and moldability of the resin composition can be achieved. Further, the total content of the aliphatic polyester-based resin and / or the aliphatic-aromatic polyester-based resin is preferably 80 parts by mass or more in 100 parts by mass of the biodegradable resin (B), and 90 parts by mass. It is more preferable to be above.

(Viscosity modifier (C))
The viscosity modifier (C) adjusts the viscosity of the resin composition to improve moldability, and increases the melt tension of the resin composition, which is an index of moldability. Viscosity modifier (C) is not particularly limited, and commonly available ones can be used. Examples include carbodiimide compounds, oxazoline compounds, epoxy compounds, acid anhydride compounds, cellulose fibers, silica-based fillers, and the like. In one preferred embodiment, compounds on the positive list of green plastics can be used, for example cellulose microfibers (CMF) and carbodiimide compounds (CDI). Cellulose microfiber is a relatively large size obtained by treating pulp with hot water, etc., hydrolyzing it and making it brittle, and then defibrating the cellulose by pulverization using a high-pressure homogenizer or the like, thereby reducing the fibrillation process. refers to the cellulose fibers of By containing the cellulose microfiber and the carbodiimide compound, the viscosity of the resin composition can be increased and strength can be ensured.

That is, when cellulose microfibers are contained in the resin composition, the strength of the resin composition increases due to the filler effect of the cellulose microfibers. Blow molding, for example, can be used for molding the resin composition containing cellulose microfibers as the viscosity modifier (C).

When a carbodiimide compound is contained in the resin composition, the resin reacts with the carbodiimide compound to increase the molecular weight of the resin. Therefore, it takes time for the resin to be hydrolyzed to decrease the molecular weight, resulting in a slow biodegradation rate. Become. 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 the viscosity modifier (C). A resin composition containing a carbodiimide compound can be molded, for example, using vacuum molding.

Carbodiimide compounds include, for example, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and the like. . These compounds may be used singly or in combination.

The content of the viscosity modifier is preferably 0.01 to 1 part by mass, preferably 0.1 to 0.8 parts per 100 parts by mass of the resin composition, in order to make the viscosity of the resin composition appropriate. It may be parts by mass.

(Plasticizer (D))
The thermoplastic resin composition for agricultural materials of the present embodiment does not contain a plasticizer (D) that is commonly used for plasticizing starch (A). As used herein, "free of plasticizer (D)" means that the plasticizer (D) is not substantially included, specifically, the content of the plasticizer (D) is the resin It means 0 to 5 parts by weight per 100 parts by weight of the composition.

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

When the amount of the plasticizer (D) is 5 parts by mass or less with respect to 100 parts by mass of the resin composition, the obtained molded product can have good moldability while suppressing surface stickiness. From the viewpoint of suppressing stickiness and moldability, the content of the plasticizer (D) is preferably 0 to 2 parts by mass, more preferably 0 to 1 part by mass with respect to 100 parts by mass of the resin composition. , 0 parts by mass (not included).

(other ingredients)
The resin composition can optionally contain components such as other additives (excluding the plasticizer (D)) as needed. Other additives include, for example, dispersants, lubricants (higher fatty acid metal salts, waxes, etc.), hydrotalcite, surfactants, antistatic agents, flame retardants, antioxidants, ultraviolet absorbers, fillers, pigments and the like. The selection and amount of other optional components are not particularly limited as long as they are within the range where the problem of one embodiment of the present invention can be solved. A plurality of additives may be used in combination. Moreover, the resin composition may partially contain a resin other than the biodegradable resin within a range that does not impair the effects of one embodiment of the present invention.

By coloring the resin composition with a pigment, it is possible to produce a molded article with excellent heat shielding effect or an easily identifiable molded article. Pigments are not particularly limited, and commonly available pigments can be used. It is preferred that substantially no pigments containing

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. .
As metals, elements of Groups 1, 2, 12, and 13 are preferred, and elements of Groups 1 and 2 are more preferred. Specific examples include sodium, potassium, calcium, magnesium and barium.

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 them, calcium stearate, magnesium stearate, calcium laurate, and magnesium laurate are preferred.

(workability)
In the above-described thermoplastic resin composition for agricultural materials, the processability during extrusion is such that strand breakage occurs 5 times or less when continuously produced for 1 hour, and may be 1 to 5 times. It is preferable that cuts do not occur.

(melt viscosity)
In the above-mentioned thermoplastic resin composition for agricultural materials, the melt viscosity at a shear rate of 243 s ^-1 in JIS K7199: 1999 is the melting point of the biodegradable resin (B) or higher, and the melting point + 40 ° C. or lower. From the viewpoint of strength and fluidity and moldability of the resin composition, it 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.

(Application)
The thermoplastic resin composition for agricultural materials according to this embodiment can be used for various agricultural materials. In particular, this resin composition can be suitably used for raising seedling pots. Raising seedling pots are pots used for growing seedlings until they grow to some extent in a container, rather than directly sowing seeds in a field. Since the molded article using the resin composition of the present embodiment is appropriately biodegraded in the soil, it is not necessary to remove the seedlings from the seedling pot and transplant them after the seedlings have grown, and the seedlings are placed in the soil as they are in the seedling pot. Portable.

≪Manufacturing method≫
The resin composition of the present embodiment can be produced by kneading the starch (A) and the viscosity modifier (C) at a temperature at which the biodegradable resin (B) melts. Specifically, for example, a biodegradable resin (B), a starch (A), a viscosity modifier (C), and if necessary, various additives are added, and kneader, roll mill, super mixer, high speed Mixing and melt-kneading with a batch kneader such as a mixer, ball mill, sand mill, attritor, or Banbury mixer, single-screw extruder, twin-screw extruder, rotor-type twin-screw kneader, etc. , granular or bead-like resin compositions. It is preferable to use a single-screw extruder or a twin-screw extruder to form pellets, since the kneading force is strong and the subsequent molding process is easy.

The resin composition may be used in either masterbatch or compound form.
In the case of a masterbatch, after producing the masterbatch, as the main resin of the agricultural material, for example, the same biodegradable resin (B) as used for producing the masterbatch is used as a diluent resin, and the masterbatch is blended for agriculture. Materials can be manufactured. The content of the masterbatch is preferably 1 to 50 parts by mass, more preferably 1 to 20 parts by mass, relative to 100 parts by mass of the biodegradable resin (B), which is the main resin. .
The biodegradable resin (B) used as the diluent resin at this time may be the same as that used in the production of the masterbatch, or may be different. It is preferable because the compatibility between the thermoplastic resin composition and the resin is excellent.
In the case of a compound, after the compound is produced, the compound can be used as it is to produce an agricultural material by the method described above.

<Agricultural materials>
The agricultural material of the present embodiment can be obtained by molding the above thermoplastic resin composition for agricultural materials. Examples of agricultural materials include seedling pots, mulch films, containers, and agricultural nets.

(Raising seedling pot)
A seedling pot is a container used for the purpose described above. The method of molding and processing the seedling pot is not particularly limited, but for example, blow molding in which a heated and plasticized resin composition is extruded, and air is sent directly into a mold without cooling and solidifying, and heating Also suitable is vacuum forming, in which a sheet or film of a plasticized resin composition is placed on a mold and vacuum is sucked from the inside of the mold for molding.

The seedling pot made of the resin composition described above is biodegradable after being buried in the soil, so that it does not damage the natural environment and reduces the trouble of removing the seedlings from the seedling pot and planting the seedlings. can. The raising seedling pot does not decompose for about 4 months, which is the seedling growing period, and the seedlings grow well. In addition, since this seedling-raising pot has strength suitable for seedling-raising applications, it is easy to handle and can maintain an appropriate shape during the seedling-raising period.

(multi film)
A mulch film (mulching film) is a film that covers the base of a crop plant. The method of forming a film from the above-mentioned resin composition is not particularly limited, but a method of extrusion molding in which a film extruded with a T-die using an extruder is cooled and solidified with a cast roll, or a method of molding with an inflation molding machine. is suitable.

≪Blow molding, vacuum molding≫
Since the melt tension of the above-mentioned resin composition is increased by the viscosity modifier (C), drawdown (a phenomenon in which the preformed resin cannot withstand its own weight and hangs down in the direction of gravity) can be suppressed.

In the case of blow molding, it is possible to suppress thinning and lightening of the molded product. The resin composition of the present embodiment can be blow-molded. For example, when three sets of two seedling pots are continuously produced with a direct blow molding machine, one seedling pot of the first set is produced. The difference between the weight per seedling pot and the weight per seedling pot in the third set can be less than 30% of the weight per seedling pot in the first set. Also, the weight per seedling pot may be 0.7 to less than 0.8 g, preferably 0.8 to less than 0.9 g, and more preferably 0.9 g or more. Blow moldability can be obtained by using the resin composition described above.

For example, when the molded article is a seedling pot, it is sufficient that the strength is such that the seedling pot can stand on its own, and it is preferable that the seedling pot does not bend. By using the resin composition described above, it is possible to obtain a seedling-raising pot with secured strength.

In the case of vacuum forming, it is possible to suppress the occurrence of portions with poor appearance due to sagging such as wrinkles due to bending of the sheet. For example, even if the molded article has a defective appearance due to dripping, it is sufficient if vacuum molding can be performed using the resin composition. A vacuum molded product can be obtained by using the resin composition described above.

For example, when the molded product is a seedling pot, the brittleness of the seedling pot is measured if 3 out of 10 seedling pots are broken when 1 kg of soil is placed in the seedling pot and dropped from a height of 5 m. It may be 1 to 3 or less out of 10, and it is preferable not to destroy even one. By using the resin composition described above, it is possible to obtain a seedling-raising pot with secured strength.

(Molded product is sticky)
The surface of the molded article molded using the above-mentioned resin composition has a dynamic friction coefficient μD according to JIS K7125, as long as it is less than 0.5, may be less than 0.3 to 0.5, and is less than 0.3. is preferred. By using the resin composition described above, a molded article with reduced stickiness can be obtained.

(biodegradation rate)
When a molded article molded using the resin composition described above is buried in the ground for 6 months, the molded article should be decomposed and have holes here and there. preferable. By using the resin composition described above, it is possible to obtain a molded article having an appropriately adjusted biodegradation rate.

According to this embodiment, the thermoplastic resin composition for agricultural materials contains a specific amount of starch (A) that promotes biodegradability and a viscosity modifier (C) that increases melt tension, and a plasticizer (D ), it is possible to obtain an agricultural material with excellent biodegradability and moldability and with a suppressed surface stickiness.

In this specification, a numerical range indicated using "to" indicates a range including the numerical values before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or lower limit value of the numerical range in one step can be arbitrarily combined with the upper limit value or lower limit of the numerical range in another step.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to the examples. In Examples and Comparative Examples, "parts" and "%" represent "mass parts" and "mass%", respectively, unless otherwise specified.
In addition, the blending amounts in the table are shown in parts by mass. A blank column in the table indicates that it was not blended.
In addition, the measuring method of the average particle diameter of starch is as follows.

<Average particle size measurement>
Using a scanning electron microscope (SEM) manufactured by Hitachi, Ltd., the starch particles were observed at a field magnification of 100 times, and 100 particles were observed at random. The distance between points was measured based on the length of micron markers on the screen and averaged.

Next, the materials used for the thermoplastic resin composition for agricultural materials are listed below.
(Starch (A))
A-1: Chemister 420 (manufactured by Glico Nutrition Foods, starch derived from corn, average particle size: 15 μm)
A-2: Chemister 310 (manufactured by Glico Nutrition Foods, cassava-derived starch, average particle size: 50 μm)
A-3: FP (manufactured by Glico Nutrition Foods, potato-derived starch, average particle size: 100 μm)

(Biodegradable resin (B))
B-1: BioPBS FZ91 (aliphatic polyester resin manufactured by PTT MCC Biochem: PBS resin)
B-2: Ecoflex C1200 (Aliphatic aromatic polyester resin manufactured by BASF: PBAT resin)
B-3: Inge® Biopolymer 6252D (manufactured by Nature Works, aliphatic polyester resin: PLA resin)

(Viscosity modifier (C))
C-1: KC Flock W-50 (cellulose microfiber, average fiber length: 50 μm)
C-2: Carbodilite HMV-15CA (manufactured by Nisshinbo Chemical Co., Ltd., carbodiimide compound)

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

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

(Manufacturing seedling pots)
The obtained thermoplastic resin composition for agricultural materials was subjected to blow molding or vacuum molding to obtain a raising seedling pot.

[Examples 2 to 19, Comparative Examples 1 to 4]
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 amounts (parts by mass) shown in Table 1 were changed.

The thermoplastic resin compositions for agricultural materials and seedling pots obtained in Examples and Comparative Examples were evaluated according to the following criteria. Table 1 shows the evaluation results.

<Processability evaluation>
The processability at the time of extrusion of the thermoplastic resin composition for agricultural materials was evaluated. The evaluation criteria were as follows, and ◯ and △ were regarded as practicable.
[Evaluation criteria]
◯: Strand breakage does not occur during continuous production for 1 hour.
Δ: Strand breakage occurred 1 to 5 times during continuous production for 1 hour.
x: Strand breakage occurred 6 times or more during continuous production for 1 hour.

<Melt viscosity evaluation>
The melt viscosity of the thermoplastic resin composition for agricultural materials was measured at 150° C. and a shear rate of 243 s ⁻¹ according to JIS K7199:1999. The evaluation criteria were as follows, and ◯ and △ were regarded as practicable.
[Evaluation criteria]
○: Melt viscosity is 1500 Pa s or more △: Melt viscosity is 1000 to less than 1500 Pa s ×: Melt viscosity is less than 1000 Pa s

<Blow moldability evaluation>
A direct blow molding machine (manufactured by Nippon Placon Co., Ltd.) was used to continuously produce 3 sets of 2 seedling pots at 150 ° C. The weight per 1 seedling pot of the 1st set and the 3rd set of seedling pots The difference in weight per seedling pot (weight difference) and the weight per seedling pot were evaluated as moldability at the time of production. In this evaluation, "blow molding is possible" means that the difference in weight is less than 30% with respect to the weight of each seedling pot in the first set. The evaluation criteria are as follows, and ⊚, ∘ and △ are regarded as practicable.
[Evaluation criteria]
◎: Blow molding is possible, weight per raising seedling pot is 0.9 g or more ○: Blow molding is possible, weight per raising seedling pot is 0.8 to less than 0.9 g △: Blow molding is possible, raising seedling Weight per pot is less than 0.7 to 0.8 g ×: blow molding is not possible

<Vacuum formability evaluation>
A sheet of 30 cm long×30 cm wide×0.45 mm thick was formed at 180° C. using a T-die forming machine. The formed sheet was heated to 110° C. and a seedling pot was formed using a vacuum forming machine, and the formability at the time of production was evaluated. The evaluation criteria are as follows, and ⊚, ∘ and △ are regarded as practicable.
[Evaluation criteria]
⊚: Vacuum forming is possible, and there is no defective appearance due to sagging in the seedling pot.
◯: Vacuum forming is possible, and the seedling pot has a slightly defective appearance due to dripping.
Δ: Vacuum molding can be performed, and an appearance defect caused by dripping can be confirmed in the seedling pot.
x: Cannot be vacuum-molded.

<Molded product strength evaluation>
The strength of the raised seedling pots produced during blow moldability evaluation was evaluated. The evaluation criteria were as follows, and ◯ and △ were regarded as practicable.
[Evaluation criteria]
◯: The seedling pot is self-supporting without bending.
Δ: The seedling pot is self-supporting, although the seedling pot is bent.
x: The raising seedling pot cannot bear its own weight and cannot stand on its own.

<Evaluation of molded product brittleness>
1 kg of soil was placed in each of 10 seedling pots prepared for evaluation of vacuum formability, and the brittleness of the seedling pots was evaluated by dropping them from a height of 5 m. The evaluation criteria were as follows, and ◯ and △ were regarded as practicable.
[Evaluation criteria]
◯: None of the 10 raising seedling pots were destroyed.
Δ: 1 to 3 out of 10 pieces are destroyed.
x: Breakage occurs in 4 or more out of 10 pieces.

<Molded article stickiness evaluation>
The stickiness of the raised seedling pot was evaluated by measuring the dynamic friction coefficient of the side surface of the raised seedling pot during blow moldability evaluation according to JIS K7125. The evaluation criteria were as follows, and ◯ and △ were regarded as practicable.
[Evaluation criteria]
○: dynamic friction coefficient μD is less than 0.3 △: dynamic friction coefficient μD is 0.3 or more and less than 0.5 ×: dynamic friction coefficient μD is 0.5 or more

<Biodegradation rate evaluation>
The seedling pots prepared for evaluation of blow moldability were buried in the ground and dug up after 6 months to evaluate biodegradability. The evaluation criteria were as follows, and ◯ and △ were regarded as practicable.
[Evaluation criteria]
○: The seedling pot is disassembled and separated △: The disassembly of the seedling pot is progressing and there are holes in places ×: The seedling pot retains its original shape

From the above results, it was confirmed that the resin compositions and seedling pots in Examples are not only environmentally friendly and biodegradable, but also have suppressed surface stickiness and excellent moldability.

Claims (10)

A thermoplastic resin composition for agricultural materials containing starch (A), a biodegradable resin (B), and a viscosity modifier (C), wherein the content of the plasticizer (D) is 0 to 5 parts by mass in 100 parts by mass of the thermoplastic resin composition,
The biodegradable resin (B) contains an aliphatic polyester-based resin and an aliphatic-aromatic polyester-based resin, and the total content of the aliphatic polyester-based resin and the aliphatic-aromatic polyester-based resin is the biodegradable resin. 80 parts by mass or more in 100 parts by mass of the decomposable resin (B),
The content of the starch (A) is 5 to 60 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials,
The content of the biodegradable resin (B) is 35 to 94.5 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials,
The viscosity modifier (C) is a viscosity modifier that increases the melt tension of the thermoplastic resin composition for agricultural materials,
The viscosity modifier (C) contains at least one selected from the group consisting of carbodiimide compounds, cellulose fibers, and silica-based fillers,
The content of the viscosity modifier (C) is 0.01 to 1 part by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials,
A thermoplastic resin composition for agricultural materials , wherein the content of the aliphatic polyester-based resin is equal to or greater than the content of the aliphatic-aromatic polyester-based resin . The thermoplastic resin composition for agricultural materials according to claim 1, wherein the content of said starch (A) is 10 to 30 parts by mass in 100 parts by mass of said thermoplastic resin composition for agricultural materials. The thermoplastic resin composition for agricultural materials according to claim 1 or 2, wherein the starch (A) has an average particle size of 5 to 50 µm. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 3, wherein the viscosity modifier (C) contains at least one selected from the group consisting of cellulose microfibers and carbodiimide compounds. The thermoplastic for agricultural materials according to any one of claims 1 to 4 , wherein the content ratio (parts by mass) of the aliphatic polyester-based resin and the aliphatic-aromatic polyester-based resin is 1 to 3: 1 . Resin composition. Any one of claims 1 to 5, wherein the melt viscosity at a shear rate of 243 s ⁻¹ is 1000 Pa s or more and less than 5000 Pa s at a temperature above the melting point of the biodegradable resin (B) and below the melting point +40 ° C. The thermoplastic resin composition for agricultural materials according to . The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 6, which is used for blow molding or vacuum molding. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 7, which is used for raising seedling pots. An agricultural material comprising the thermoplastic resin composition for an agricultural material according to any one of claims 1 to 8. The agricultural material according to claim 9, which is a nursery pot.