CN118591591A - Thermoplastic resin composition for agricultural materials and agricultural materials - Google Patents

Abstract

The invention discloses a thermoplastic resin composition for agricultural materials and an agricultural material formed by using the thermoplastic resin composition for agricultural materials, wherein the thermoplastic resin composition for agricultural materials comprises starch, biodegradable resin and viscosity regulator, the content of plasticizer in the thermoplastic resin composition for agricultural materials is 0to 5 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials, and the biodegradable resin comprises aliphatic polyester resin and aliphatic aromatic polyester resin.

Description

Thermoplastic resin composition for agricultural materials and agricultural materials

Technical Field

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

Background Art

Plastics are used in a wide range of fields, such as electrical and electronic equipment parts, automobile parts, medical parts, and food containers, because they are easy to mold. Physical properties such as strength and functionality are given to plastic molded products according to their use. In the field of agricultural materials, they are used for applications that require water resistance and strength.

Examples of agricultural materials include agricultural mulch films used for purposes of raising or retaining ground temperature or controlling pests, and seedling raising pots that are a type of dedicated container for raising seedlings.

As a solution to alleviate the recent waste problem and the recycling of agricultural materials, there is the use of agricultural materials made of biodegradable materials, which do not need to be recycled and can be degraded underground (in the soil) after use.

Patent document 1 describes a film that contains aliphatic polyester resin, aromatic aliphatic polyester resin, starch and polyol in a specific mass ratio, thereby having high tear strength, good biodegradability, formability, heat shrinkage and transparency, high elastic modulus and being less prone to wrinkling.

In the film, aliphatic polyester resin and aromatic aliphatic polyester resin are used as biodegradable materials and the content of polyol is adjusted, thereby plasticizing starch and improving the physical properties of the resin composition such as tear strength and tensile elastic modulus.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Publication No. 2011-26538

Summary of the invention

Problems to be solved by the invention

Since starch is not thermoplastic and has a low thermal degradation temperature, the resin composition is modified by adding a plasticizer such as a polyol. However, if the plasticizer is contained in the resin composition, there is a possibility that the surface of the obtained molded product will stick together, and the releasability of the mold of the molding machine and the resin composition during molding and the lubricity for separating the molded products will be reduced, which will affect the molding of the resin composition.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermoplastic resin composition for agricultural materials which can produce a molded product with suppressed surface blocking and has biodegradability and good moldability, and an agricultural material comprising the thermoplastic resin composition for agricultural materials.

Technical means of solving problems

The present inventors have conducted intensive studies to solve the above problems and, as a result, have found a thermoplastic resin composition for agricultural materials having the structure shown below, thereby completing the present invention.

That is, one embodiment of the present invention is as follows.

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

<2> The thermoplastic resin composition for agricultural materials according to <1>, wherein the content of the starch is 10 to 30 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials.

<3> The thermoplastic resin composition for agricultural materials according to <1> or <2>, wherein the average particle size of the starch is 5 μm to 50 μm.

<4> The thermoplastic resin composition for agricultural materials according to any one of <1> to <3>, wherein the viscosity modifier includes at least one selected from the group consisting of cellulose fibers and carbodiimide compounds.

<5> The thermoplastic resin composition for agricultural materials according to any one of <1> to <4>, wherein the content ratio (parts by mass) of the aliphatic polyester-based resin to the aliphatic aromatic polyester-based resin is 1 to 3:1.

<6> The thermoplastic resin composition for agricultural materials according to any one of <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 of at least the melting point of the biodegradable resin (B) and at most the melting point + 40°C.

<7> The thermoplastic resin composition for agricultural materials according to any one of <1> to <6>, which is used for blow molding or vacuum molding.

<8> The thermoplastic resin composition for agricultural materials according to any one of <1> to <7>, which is used in a seedling raising pot.

<9> An agricultural material formed using the thermoplastic resin composition for an agricultural material according to any one of <1> to <8>.

<10> The agricultural material according to <9>, which is a seedling raising pot.

Effects of the Invention

According to one embodiment of the present invention, there can be provided a thermoplastic resin composition for agricultural materials which can produce a molded product with suppressed surface blocking and has good biodegradability and moldability, and an agricultural material including the thermoplastic resin composition for agricultural materials.

DETAILED DESCRIPTION

＜Thermoplastic resin composition for agricultural materials＞

The thermoplastic resin composition for agricultural materials of the present embodiment is characterized in that it contains starch, a biodegradable resin and a viscosity modifier, and does not contain a plasticizer. By adjusting the starch and the viscosity modifier to specific contents and not containing a plasticizer, the obtained resin composition has good moldability, is biodegradable, and can suppress adhesion on the surface of the molded product.

In the present disclosure, a “thermoplastic resin composition for agricultural materials” may be described as a “resin composition”, “starch” may be described as “starch (A)”, “biodegradable resin” may be described as “biodegradable resin (B)”, “viscosity modifier” may be described as “viscosity modifier (C)”, and “plasticizer” may be described as “plasticizer (D)”.

The degradation process of the resin composition is roughly divided into two parts.

The first stage is to reduce the molecular weight of the resin constituting the agricultural material (seedling raising pot, agricultural mulch film, etc.) which is a molded product of the resin composition by hydrolysis or oxidative degradation.

Then, in the second stage, microorganisms in the soil degrade individual pieces of agricultural materials including the resin having a low molecular weight.

Since the molecular weight of the resin will also be reduced during the storage or use of agricultural materials, the first stage of hydrolysis control becomes important. The factors of hydrolysis include the crystallinity of the resin. Compared with the crystalline region, the amorphous region is more susceptible to hydrolysis, so hydrolysis can be suppressed by improving the crystallinity.

Generally, when additives or the like are added to a thermoplastic resin composition, the particles thereof serve as crystal nuclei, and since the formation of crystals is promoted (nucleation effect), the crystallinity is improved, and a hydrolysis inhibition effect is obtained.

Since the thermoplastic resin composition for agricultural materials of the present embodiment contains a specific amount of starch (A) that promotes biodegradability and a viscosity modifier (C) that increases melt tension, the biodegradation rate of the agricultural materials containing the resin composition can be adjusted. For example, it is desirable that the degradation of the agricultural materials can be suppressed and their shape can be maintained at least during the seedling cultivation period of about four months, and after about one year of the seedling cultivation period, the agricultural materials are degraded by microorganisms in the soil and can penetrate into the soil.

This embodiment will be described in detail below.

(Starch (A))

Starch (A) is a substance that promotes the action (biodegradability) of various microorganisms present in soil or water. Starch (A) is not particularly limited, and generally available starch can be used. For example, corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch, etc. can be mentioned. Among them, if corn starch with a consistent particle size of about 20 μm is used, the thickness of the agricultural material containing the resin composition can be uniformed (the surface unevenness can be reduced), thereby suppressing the generation of thin thickness parts, and as a result, the damage of the agricultural material can be suppressed, so it is preferred. These can be used alone or in combination of two or more.

Starch (A) is a component that can adjust the biodegradation rate, and its content is preferably 5 to 60 parts by mass in 100 parts by mass of the resin composition, and can also be 10 to 50 parts by mass, 10 to 40 parts by mass, or 10 to 30 parts by mass. If the content of starch (A) is 5 parts by mass or more, biodegradation can be promoted, and if it is 60 parts by mass or less, the content of the biodegradable resin (B) can be ensured, thereby ensuring formability.

In addition, from the viewpoint of formability, the average particle size of starch (A) is preferably 5 μm to 50 μm, and may also be 10 μm to 50 μm. When the average particle size of starch (A) is within the above range, the dispersibility of starch (A) in biodegradable resin (B) and the smoothness of the surface of the molded product can coexist.

In particular, in blow molding in which a resin is directly placed in a mold and air is fed, the average particle size of the starch (A) in the resin composition contributes to moldability, and the average particle size of the starch (A) is preferably within the above range.

The average particle size of starch (A) can be obtained, for example, by observing the particles of starch (A) using a scanning electron microscope, observing 100 particles at random, measuring the distance between the two farthest points of the outer shape of each particle based on the length of the micrometer mark on the screen, and averaging the distances to obtain the average particle size.

(Biodegradable resin (B))

The biodegradable resin (B) is a substance that is degraded 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. For example, polycaprolactone, aliphatic polyester resins, or aliphatic aromatic polyester resins can be listed. These biodegradable resins can be used alone or in combination of two or more.

Among these, from the viewpoint of biodegradability and moldability, aliphatic polyester-based resins or aliphatic aromatic polyester-based resins are preferred.

In addition, when an aliphatic polyester resin and an aliphatic aromatic polyester resin are used together as the biodegradable resin, the content of the aliphatic polyester resin is preferably greater than the content of the aliphatic aromatic polyester resin. By mixing an aliphatic polyester resin as a base resin and an aliphatic aromatic polyester resin having ductility and good formability, the formability of the resin composition and the strength of the agricultural material as its molded product can be ensured. The content ratio (mass parts) of the aliphatic polyester resin and the aliphatic aromatic polyester resin is, for example, preferably 1 to 4:1, more preferably 1 to 3:1, further preferably 1 to 2:1, particularly preferably 1 to 1.65:1, more preferably 1 to 1.57:1, and may also be 1.5 to 2:1.

As aliphatic polyester resins, for example, aliphatic polyesters obtained by polycondensation of aliphatic diols and aliphatic dicarboxylic acids and polylactic acid obtained by polycondensation of lactic acid can be cited. As aliphatic diols, for example, ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol can be cited. These can be used alone or as a mixture of these. Among them, 1,4-butanediol is preferably used. As aliphatic dicarboxylic acids, for example, oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, dodecanedioic acid can be cited, and derivatives thereof, i.e., anhydrides, can also be used. Among them, succinic acid or 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 Biochem Co., Ltd. of Mitsubishi Chemical Corporation (MCC) of the Petroleum Authority of Thailand (PPT)), polybutylene succinate adipate (PBSA) obtained by copolymerizing adipic acid with PBS, etc. can be mentioned.

As the aliphatic aromatic polyester resin, for example, copolymers containing aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and chain aliphatic and/or alicyclic diol units can be cited. The diol component providing the diol unit is a component having a carbon number of usually 2 to 10, and for example, ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, etc. can be cited. Among them, diols having a carbon number of 2 to 4 are preferred, ethylene glycol and 1,4-butanediol are more preferred, and 1,4-butanediol is further preferred. The dicarboxylic acid component providing the dicarboxylic acid unit is a component having a carbon number of usually 2 to 10, and for example, succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, etc. can be cited. Among them, succinic acid or adipic acid is preferred. As aromatic dicarboxylic acid components providing aromatic dicarboxylic acid units, for example, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, etc. can be cited. Among them, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is more preferred.

Specific examples thereof include polybutylene adipate terephthalate (PBAT) which is a copolymer of 1,4-butanediol, adipic acid, and terephthalic acid (for example, "Ecoflex" (trade name) manufactured by BASF).

In addition, the biodegradable resin (B) may also be in the form of the aliphatic polyester resin and/or aliphatic aromatic polyester resin and other biodegradable resins. As other biodegradable resins, for example, poly(3-hydroxyalkanoate) (wherein, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate, PHBH) of aliphatic polyester copolymers obtained from hydroxyalkanoic acid and polycarboxylic acid (for example, "AONILEX" (trade name) manufactured by Kaneka Co., Ltd.), polylactic acid (PLA) (for example, "REVODE" (trade name) manufactured by Hisun Biomaterials Co., Ltd., "Ingeo" (trade name) manufactured by NatureWorks Co., Ltd.).

The content of biodegradable resin (B) can be 35 to 95 parts by mass in 100 parts by mass of the resin composition, more preferably 35 to 94.99 parts by mass, and further preferably 35 to 94.5 parts by mass, and more preferably 39 to 90 parts by mass. The content of biodegradable resin (B) is the range, and the processability and formability of the resin composition can coexist. In addition, the total content of aliphatic polyester resin and/or aliphatic aromatic polyester resin is preferably 80 parts by mass or more in 100 parts by mass of the biodegradable resin (B), more preferably 90 parts by mass or more.

(Viscosity modifier (C))

The viscosity modifier (C) is a substance that adjusts the viscosity of the resin composition to improve the formability, so that the melt tension of the resin composition, which is an indicator of the formability, increases. The viscosity modifier (C) is not particularly limited, and generally available substances can be used. For example, carbodiimide compounds, oxazoline compounds, epoxy compounds, acid anhydride compounds, cellulose fibers, silica-based fillers, etc. can be listed.

The melt tension of the resin composition can be increased by using a multifunctional compound as a viscosity modifier (C) and forming a crosslinked structure with the biodegradable resin (B). As the multifunctional compound, multifunctional carbodiimide compounds, multifunctional oxazoline compounds, epoxy compounds, anhydride compounds, etc. can be listed. The multifunctional carbodiimide compound can be a monomer or polymer having two or more carbodiimide groups, but is preferably a polymer having two or more carbodiimide groups.

Reactive compounds can be used as viscosity modifiers (C), reactive groups are introduced into biodegradable resins (B), and cross-linked structures are formed with the reactive groups as starting points, thereby increasing the melt tension of the resin composition. As reactive compounds, carbodiimide compounds, oxazoline compounds, epoxy compounds, anhydride compounds, etc. can be listed. Preferably, cyclic carbodiimide is used as the carbodiimide compound. Cyclic carbodiimide compounds are compounds having carbodiimide groups on the rings of aliphatic rings or aromatic rings.

By using a filler as a viscosity modifier (C), the solid content of the resin composition is increased and the thickening is performed, thereby increasing the melt tension of the resin composition. The filler may be any of an organic filler and an inorganic filler, and examples thereof include cellulose fibers, silica-based fillers, and the like.

In a preferred embodiment, compounds listed in the positive list of green plastics can be used, for example, cellulose microfibrils (CMF) and carbodiimide compounds (CDI) as cellulose fibers can be used. Cellulose microfibrils refer to cellulose fibers of larger size obtained by reducing the fiberizing process after pulp is treated with hot water or the like and hydrolyzed to become brittle and then fiberized by a crushing method such as a high-pressure homogenizer. By including cellulose microfibrils and carbodiimide compounds, the viscosity of the resin composition is increased and the strength can be ensured.

That is, if the resin composition contains cellulose microfibrils, the strength of the resin composition will increase due to the filler effect of the cellulose microfibrils. In addition, the silica filler has the same filler effect as the cellulose microfibrils, and thus increases the strength of the resin composition in the same manner as the cellulose microfibrils. In the molding of the resin composition containing at least one of the cellulose microfibrils and the silica filler as the viscosity modifier (C), for example, blow molding can be used.

If resin combination contains carbodiimide compound, then resin reacts with carbodiimide compound and the molecular weight of resin becomes large, therefore described resin is hydrolyzed until molecular weight needs time before becoming small, and biodegradation rate slows down.Therefore, in the case of the agricultural materials requiring the intensity of resin combination, preferably comprise carbodiimide compound as viscosity modifier (C).In addition, because oxazoline compound, epoxy compound and anhydride compound also possess respectively the reactivity with resin similarly to carbodiimide compound, therefore these compounds also can improve respectively the intensity of resin combination.The resin combination comprising at least one of carbodiimide compound, oxazoline compound, epoxy compound and anhydride compound, for example, can be shaped using vacuum forming.

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, tert-butylisopropylcarbodiimide, and di-tert-butylcarbodiimide; and cyclic carbodiimide compounds such as "Carbosista TCC-NP (trade name)" manufactured by Teijin Co., Ltd. These compounds may be used alone or in combination of a plurality of them.

Examples of the oxazoline compound include "Epocros RA-45" (trade name) and "Epocros RPS-1005" (trade name) manufactured by Nippon Catalyst Co., Ltd. These compounds may be used alone or in combination of two or more.

Examples of epoxy compounds include epoxy-acrylic compounds ("Joncryl ADR-4468" (trade name) manufactured by BASF, "Joncryl ADR-4400" (trade name) manufactured by BASF, "Arufon UG-4040" (trade name) manufactured by Toagosei Co., Ltd., "Arufon UG-4070" (trade name) manufactured by Toagosei Co., Ltd.), etc. These compounds may be used alone or in combination of two or more.

Examples of the acid anhydride compound include styrene maleic anhydride compounds ("XIBOND 120" (trade name), "XIBOND 140" (trade name), "XIBOND 160" (trade name), "XIBOND 180" (trade name), "XIBOND 200" (trade name), "XIBOND 220" (trade name), "XIBOND 250" (trade name), "XIBOND 260" (trade name), "XIBOND 270" (trade name), "XIBOND 280" (trade name), "XIBOND 290" (trade name), "XIBOND 300" (trade name), "XIBOND 310" (trade name), "XIBOND 320" (trade name), "XIBOND 330" (trade name), "XIBOND 340" (trade name), "XIBOND 350" (trade name), "XIBOND 360" (trade name), "XIBOND 370" (trade name), "XIBOND 380" (trade name), "XIBOND 390" (trade name), "XIBOND 400" (trade name), "XIBOND 410" (trade name), "XIBOND 420" (trade name), "XIBOND 430" (trade name), "XIBOND 440" (trade name), "XIBOND 450" (trade name), "XIBOND 460" (trade name), "XIBOND 470" (trade name), "XIBOND 480" (trade name), "XIBOND 490" (trade name), "XIBOND 500" (trade name), "XIBOND 510" (trade name), "XIBOND 520" (trade name), "XIBOND 530" (trade name), D)280" (trade name), "XIRAN 1000" (trade name), "XIRAN 2000" (trade name), "XIRAN 2500" (trade name), "XIRAN 3000" (trade name), "XIRAN 4000" (trade name), "XIRAN 6000" (trade name), "XIRAN 9000" (trade name), "XIRAN 3500" (trade name), "XIRAN 3600" (trade name) manufactured by Pakistan Industries Co., Ltd. These compounds may be used alone or in combination of two or more.

Examples of the silica filler include silica fillers (“Aerosil 130” (trade name), “Aerosil 150” (trade name), “Aerosil 200” (trade name), “Aerosil 300” (trade name), “Aerosil RX200” (trade name), and “Aerosil RY200” (trade name) manufactured by Japan Aerosil Co., Ltd.; and “Nipsil SS-50” (trade name), “Nipsil SS-50B” (trade name), “Nipsil SS-50F” (trade name), “Nipsil K-500” (trade name), and “Nipsil G-300” (trade name) manufactured by Tosoh Silica Co., Ltd.). These compounds may be used alone or in combination of two or more.

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

In addition, cellulose fiber contributes to the high viscosity and high strength of resin composition, so if the content of cellulose fiber contained in resin composition is many, the fluidity and processability of resin composition are reduced, and sometimes the formability of resin composition is reduced. Therefore, when cellulose fiber is included in resin composition, the content of cellulose fiber is preferably more than 0 mass parts and less than 1.5 mass parts in 100 mass parts of resin composition, preferably 0.01 mass parts to 1.4 mass parts, more preferably 0.01 mass parts to 1.2 mass parts, and then preferably 0.01 mass parts to 1 mass parts. The content of cellulose fiber is the range, and the fluidity and processability of resin composition can be ensured, thereby suppressing the reduction of the formability of resin composition.

(Plasticizer (D))

The thermoplastic resin composition for agricultural materials of the present embodiment does not contain a plasticizer (D) commonly used for plasticizing starch (A). In this specification, "does not contain a plasticizer (D)" means that the plasticizer (D) is substantially not contained, and specifically, the content of the plasticizer (D) is 0 to 5 parts by mass relative to 100 parts by mass of the resin composition.

As a plasticizer (D), alcohol which is an organic compound which has a hydroxyl group is mentioned, For example, glycerin, glycerol monoester, ethylene glycol, and diethylene glycol are mentioned specifically, for example.

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

(Other ingredients)

The resin composition may contain other additives and other components (except plasticizer (D)) as needed. As other additives, for example, dispersants, lubricants (higher fatty acid metal salts, waxes, etc.), hydrotalcite, surfactants, antistatic agents, flame retardants, antioxidants, ultraviolet absorbers, fillers, pigments, etc. are listed. The selection of other arbitrary components and their usage are not particularly limited as long as they are within the scope of the problem that can solve one embodiment of the present invention. A variety of additives may also be used in combination. In addition, the resin composition may also include a part of a resin other than the biodegradable resin within the scope of not hindering the effect of one embodiment of the present invention.

The resin composition can be colored with a pigment to produce a molded product with excellent heat insulation effect or an easily identifiable molded product. The pigment is not particularly limited, and generally available pigments can be used, but from the viewpoint of the natural environment, a pigment substantially free of cadmium, lead, chromium, arsenic, mercury, copper, selenium, nickel, molybdenum, and fluorine is preferred.

For example, when the resin composition contains a pigment, it is preferred 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 straight-chain or branched, and may have only saturated bonds or unsaturated bonds.

Examples of the fatty acid 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, and Group 13, and more preferably an element of Group 1 or Group 2. 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, sodium montanate, etc. 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.

(Processability)

In the thermoplastic resin composition for agricultural materials, regarding processability during extrusion, strand breakage occurs 5 times or less, 1 to 5 times, and preferably no strand breakage occurs during continuous production for 1 hour.

(Melt viscosity)

In the thermoplastic resin composition for agricultural materials, from the viewpoint of the strength of the obtained molded product and the fluidity and moldability of the resin composition, the melt viscosity at a shear rate of 243 s ^-1 in Japanese Industrial Standards (JIS) K7199:1999 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 at a temperature above the melting point of the biodegradable resin (B) and below the melting point + 40°C.

(use)

The thermoplastic resin composition for agricultural materials of the present embodiment can be used for various agricultural materials. In particular, the resin composition can be suitable for use as a seedling pot. The so-called seedling pot is a pot used to cultivate seedlings in a container until they grow to a certain extent, rather than directly sowing and cultivating in the field. The molded product using the resin composition of the present embodiment is appropriately biodegraded in the soil, so there is no need to remove the seedlings from the seedling pot after the seedlings grow and transplant them, and they can be directly transplanted into the soil in the seedling pot.

《Manufacturing method》

The resin composition of the present embodiment can be manufactured by mixing starch (A) and viscosity modifier (C) at a temperature at which biodegradable resin (B) is melted. Specifically, for example, biodegradable resin (B), starch (A) and viscosity modifier (C) can be added, and then various additives are added as required, and batch mixers such as kneader, roller mill, super mixer, high-speed mixer, ball mill, sand mill, attritor or Banbury mixer (Banbury mixer) are used, uniaxial extruder, biaxial extruder, rotor type biaxial mixer etc. are mixed and melt-mixed, so as to make granular, powdery, granular or beaded resin composition. With regard to the viewpoint that mixing power is strong and the molding process is easy afterwards, it is preferably granularized using uniaxial extruder or biaxial extruder.

The resin composition may be used in the form of either a masterbatch or a compound.

In the case of a masterbatch, after the masterbatch is manufactured, the masterbatch can be prepared as a main resin of agricultural materials using, for example, the same biodegradable resin (B) as that used in the manufacture of the masterbatch as a diluent resin. 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) as the main resin.

The biodegradable resin (B) used as the diluent resin may be the same as or different from that used in the production of the masterbatch, but is preferably the same biodegradable resin because the thermoplastic resin composition has excellent compatibility with the resin.

In the case of a composite, after the composite is produced, the composite can be used directly to produce an agricultural material by the above method.

＜Agricultural materials＞

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

(Seedling Pot)

The seedling raising pot is a container used for the above purpose. The forming processing method of the seedling raising pot is not particularly limited, and for example, blow molding in which the heated and plasticized resin composition is extruded and directly added into a mold without cooling and solidifying it and air is conveyed, and vacuum forming in which a sheet or film of the heated and plasticized resin composition is arranged on a mold and vacuum suction is performed from the inside of the mold to form it, etc. are suitable.

The seedling raising pot containing the resin composition is biodegradable after being buried in the soil, so it does not damage the natural environment, and the work of taking out the seedlings from the seedling raising pot and sowing and planting the seedlings can be reduced. The seedling raising pot does not degrade during the seedling cultivation period, that is, a period of about 4 months, and can be cultivated well. In addition, the seedling raising pot has a strength suitable for seedling cultivation, so it is easy to handle and can maintain an appropriate shape during the seedling cultivation period.

(Agricultural mulch)

Agricultural mulching film is a film that covers the roots of crops. The method of forming the film from the resin composition is not particularly limited, and suitable methods include extrusion molding in which a film extruded from a T-die using an extruder is cooled and solidified using a casting roll, or molding using an inflation molding machine.

《Blow molding, vacuum forming》

The viscosity modifier (C) increases the melt tension of the resin composition, thereby suppressing pull-down (a phenomenon in which a preformed resin cannot withstand its own weight and sags in the direction of gravity).

In the case of blow molding, the molded product can be suppressed from becoming thinner and lighter. The resin composition of the present embodiment can be blow molded. For example, the weight of each seedling raising basin in the first group when 3 groups of seedling raising basins in a group of 2 can be continuously manufactured by a direct blow molding machine and the difference in the weight of each seedling raising basin in the third group can be set to be less than 30% relative to the weight of each seedling raising basin in the first group. In addition, as long as the weight of each seedling raising basin is more than 0.7g and less than 0.8g, it is preferably more than 0.8g and less than 0.9g, and more preferably more than 0.9g. By using the resin composition, blow molding properties can be obtained.

For example, when the molded product is a seedling raising pot, the seedling raising pot only needs to have strength enough to be self-supporting, and preferably the seedling raising pot does not bend. By using the resin composition, a seedling raising pot having secured strength can be obtained.

In the case of vacuum forming, the generation of poor appearance caused by sagging such as wrinkles due to the deflection of the sheet can be suppressed. For example, even if there are poor appearance parts caused by sagging in the molded product, as long as the resin composition is used for vacuum forming, it is preferred that the poor appearance part is small, and it is more preferred that there is no poor appearance part. By using the resin composition, a vacuum formed product can be obtained.

For example, when the molded product is a seedling raising pot, regarding the fragility of the seedling raising pot, when 1 kg of soil is put into the seedling raising pot and dropped from a height of 5 m, it is sufficient that 3 or less of 10 seedling raising pots are damaged, or 1 to 3 of 10, preferably not even 1 is damaged. By using the resin composition, a seedling raising pot having ensured strength can be obtained.

(Molding product adhesion)

The dynamic friction coefficient μD of the surface of a molded article molded using the resin composition in JIS K7125 may be less than 0.5, and may be 0.3 or more and less than 0.5, and preferably less than 0.3. By using the resin composition, a molded article with suppressed blocking can be obtained.

(Biodegradation Rate)

When a molded article formed using the resin composition is buried underground for 6 months, the molded article may be degraded and have holes everywhere, and preferably the molded article is degraded and becomes scattered. By using the resin composition, a molded article with a properly adjusted biodegradation rate can be obtained.

According to the present 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 does not contain a plasticizer (D). Therefore, an agricultural material having excellent biodegradability and moldability and suppressed surface blocking can be obtained.

In addition, the embodiments of the present invention include various embodiments not described here, etc. For example, the following related aspects are included.

[1] A thermoplastic resin composition for agricultural materials, comprising starch (A), a biodegradable resin (B) and a viscosity modifier (C) and no plasticizer (D), wherein the content of the starch (A) is 5 to 60 parts by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials, and the content of the viscosity modifier (C) is 0.01 to 1 part by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials.

[2] The thermoplastic resin composition for agricultural materials according to [1], wherein the content of the starch (A) is 10 to 30 parts by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials.

[3] The thermoplastic resin composition for agricultural materials according to [1] or [2], wherein the average particle size of the starch (A) is 5 μm to 50 μm.

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

[5] The thermoplastic resin composition for agricultural materials according to any one of claims [1] to [4], wherein the biodegradable resin (B) comprises an aliphatic polyester resin and an aliphatic aromatic polyester resin, and the content of the aliphatic polyester resin is greater than or equal to the content of the aliphatic aromatic polyester resin.

[6] The thermoplastic resin composition for agricultural materials according to any one of [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.

[7] The thermoplastic resin composition for agricultural materials according to any one of [1] to [6], which is used for blow molding or vacuum molding.

[8] The thermoplastic resin composition for agricultural materials according to any one of [1] to [7], which is used in a seedling raising pot.

[9] An agricultural material comprising the thermoplastic resin composition for an agricultural material according to [1] to [7].

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

In this specification, the numerical range expressed by "to" indicates a range that includes the numerical values recorded before and after "to" as the minimum and maximum values, respectively. In the numerical ranges recorded in stages in this specification, the upper limit or lower limit of the numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of the numerical range of other stages.

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

Example

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the Experimental Examples. In the Experimental Examples and Comparative Examples, "parts" and "%" respectively represent "parts by mass" and "mass %" unless otherwise specified.

In addition, the blending amount in the table is shown in parts by mass. In addition, a blank column in the table indicates that no blending is performed.

In addition, the method for measuring the average particle size of starch is as follows.

<Average particle size measurement>

Starch particles were observed using a scanning electron microscope (SEM) manufactured by Hitachi, Ltd. at a field magnification of 100 times. 100 particles were randomly observed, and the distance between the two farthest points of the outer shape of each particle was measured based on the length of the micrometer mark on the screen and averaged to obtain the value.

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

(Starch (A))

A-1: Chemistar 420 (Glico Nutrition Foods, corn starch, average particle size: 15 μm)

A-2: Chemistar 310 (manufactured by GLICO Nutrition Foods, cassava-derived starch, average particle size: 50 μm)

A-3: FP (Glico Nutrition Foods, potato starch, average particle size: 100 μm)

(Biodegradable resin (B))

B-1: BioPBS FZ91 (aliphatic polyester resin manufactured by Petroleum Authority of Thailand (PTT) Mitsubishi Chemical Corporation (MCC) Biochem: PBS resin)

B-2: Ecoflex C1200 (aliphatic aromatic polyester resin manufactured by BASF: PBAT resin)

B-3: Ingeo Biopolymer 6252D (aliphatic polyester resin manufactured by NatureWorks: PLA resin)

(Viscosity modifier (C))

C-1: KC Flock W-50 (cellulose microfibrils, average fiber length: 50 μm)

C-2: Carbodilite HMV-15CA (manufactured by Nisshinbo Chemical Co., Ltd., polycarbodiimide compound)

C-3: Carbosista TCC-NP (manufactured by Teijin Co., Ltd., cyclic carbodiimide compound)

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

C-5: XIBOND 220 (manufactured by Palmer Holland, Inc., styrene maleic anhydride compound)

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

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

C-8: Nipsil SS-50 (manufactured by Tosoh Silica Co., Ltd., silica filler)

(Plasticizer (D))

D: DG (manufactured by NOF Corporation, polyol, glycerin)

<Production of thermoplastic resin composition for agricultural materials>

[Experimental Example 1]

(Manufacture of thermoplastic resin composition (compound) for agricultural materials)

5 parts by mass of (A-1) as starch (A), 94.5 parts by mass of (B-1) as biodegradable resin (B), and 0.5 parts by mass of (C-1) as viscosity modifier (C) were mixed, and pelletized by extrusion at 190° C. using a twin-screw extruder (manufactured by The Japan Steel Works, Ltd.) to obtain a thermoplastic resin composition for agricultural materials.

(Manufacture of seedling pots)

The obtained thermoplastic resin composition for agricultural materials is blow molded or vacuum molded to obtain a seedling raising pot.

[Experimental Examples 2 to 35, Comparative Examples 1 to 5]

Thermoplastic resin compositions for agricultural materials and seedling raising pots were obtained by the same method as in Experimental Example 1 except that the materials and blending amounts (parts by mass) were changed to those shown in Table 1. Experimental Examples 1 to 13 are structures containing only one of the aliphatic polyester resin (B-1 or B-3) and the aliphatic aromatic polyester resin (B-2) as the biodegradable resin, and can be distinguished from the experimental examples in which both the aliphatic polyester resin (B-1 or B-3) and the aliphatic aromatic polyester resin (B-2) are used as biodegradable resins and are regarded as reference examples.

[Table 1]

The thermoplastic resin compositions for agricultural materials and the seedling raising pots obtained in the experimental examples and comparative examples were evaluated according to the following criteria.

＜Processability Evaluation＞

The processability of the thermoplastic resin composition for agricultural materials during extrusion was evaluated. The evaluation criteria are as follows, and ○ and △ were regarded as practical.

[Evaluation criteria]

○: No strand breakage occurs during continuous production for 1 hour.

△: During continuous production for 1 hour, strand breakage occurred 1 to 5 times.

×: Strand breakage occurred 6 or more times during continuous production for 1 hour.

<Evaluation of melt viscosity>

The melt viscosity of the thermoplastic resin composition for agricultural materials at a shear rate of 243 s ^-1 was measured at 150° C. in accordance with JIS K7199: 1999. The evaluation criteria are as follows, and ○ and △ were regarded as practical.

[Evaluation criteria]

○: Melt viscosity is 1500 Pa·s or more

△: Melt viscosity is 1000Pa·s to less than 1500Pa·s

×: Melt viscosity is less than 1000 Pa·s

＜Blow molding evaluation＞

A direct blow molding machine (manufactured by Placon Co., Ltd., Japan) was used to continuously produce 3 groups of seedling pots of 2 groups at 150°C, and the difference (weight difference) between the weight of each seedling pot of the first group and the weight of each seedling pot of the third group and the weight of each seedling pot were evaluated as the formability during production. In addition, in this evaluation, the so-called "blow molding" means that the weight difference is less than 30% relative to the weight of each seedling pot of the first group. The evaluation criteria are as follows, and ◎, ○ and △ are set as practical.

[Evaluation criteria]

◎: Can be blow molded, each seedling pot weighs more than 0.9g

○: Can be blow molded, the weight of each seedling pot is more than 0.8g and less than 0.9g

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

×: Cannot be blow molded

＜Evaluation of vacuum formability＞

A sheet of 30 cm in length × 30 cm in width × 0.45 mm in thickness was formed at 180°C using a T-die forming machine. The formed sheet was heated to 110°C and formed into a seedling pot using a vacuum forming machine, and the formability during production was evaluated. The evaluation criteria are as follows, and ◎, ○, and △ are set as practical.

[Evaluation criteria]

◎: Vacuum forming is possible, and there is no appearance defect caused by sagging in the seedling pot.

○: Vacuum forming is possible, but the seedling pot has a small amount of poor appearance due to sagging.

△: Vacuum forming is possible, and appearance defects caused by sagging can be confirmed in the seedling pot.

×: Vacuum forming is not possible.

＜Evaluation of molded product strength＞

The strength of the seedling raising pots produced during blow moldability evaluation was evaluated. The evaluation criteria were as follows, and ○ and △ were considered practical.

[Evaluation criteria]

○: The seedling pot was not bent and stood on its own.

△: The seedling pot is bent but self-supporting.

×: The seedling pot cannot bear its own weight and cannot stand on its own.

<Evaluation of the brittleness of molded products>

1 kg of soil was placed in each of 10 seedling raising pots produced during the vacuum formability evaluation and dropped from a height of 5 m to evaluate the fragility of the seedling raising pots. The evaluation criteria were as follows, and ○ and △ were considered practical.

[Evaluation criteria]

○: One of the 10 seedling pots was not damaged.

△: 1 to 3 out of 10 were damaged.

×: 4 or more out of 10 samples were damaged.

<Evaluation of adhesion of molded products>

The sticking of the seedling raising pot was evaluated by measuring the dynamic friction coefficient of the side surface of the seedling raising pot produced during the blow moldability evaluation in accordance with JIS K7125. The evaluation criteria were as follows, and ○ and △ were set as practical.

[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 produced during the blow moldability evaluation were buried in the ground and dug up 6 months later to evaluate biodegradability. The evaluation criteria were as follows, and ○ and △ were considered practical.

[Evaluation criteria]

○: The seedling pots degraded and became scattered

△: The seedling pot is degraded and has holes everywhere

×: The original seedling pot is preserved

From the above results, it was confirmed that the resin compositions and seedling raising pots in Experimental Examples 1 to 35 were environmentally friendly, biodegradable, and had suppressed surface adhesion and excellent moldability.

Claims (10)

1. A thermoplastic resin composition for agricultural materials, comprising starch, a biodegradable resin and a viscosity modifier, wherein the content of the plasticizer in the thermoplastic resin composition for agricultural materials is 0 to 5 parts by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials,

The biodegradable resin comprises an aliphatic polyester resin and an aliphatic aromatic polyester resin, wherein the total content of the aliphatic polyester resin and the aliphatic aromatic polyester resin is 80 parts by mass or more based on 100 parts by mass of the biodegradable resin,

The starch content is 5 to 60 parts by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials,

The content of the biodegradable resin is 35 to 94.5 parts by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials,

The viscosity modifier is a viscosity modifier for increasing the melt tension of the thermoplastic resin composition for agricultural materials,

The viscosity modifier comprises at least one selected from the group consisting of carbodiimide compounds, oxazoline compounds, epoxy compounds, acid anhydride compounds, cellulose fibers and silica-based fillers,

The content of the viscosity modifier is 0.01 to 3 parts by mass based on 100 parts by mass of the thermoplastic resin composition for agricultural materials,

The content of the cellulose fiber is 0 parts by mass or more and less than 1.5 parts by mass in 100 parts by mass of the thermoplastic resin composition for agricultural materials,

The content of the aliphatic polyester resin is not less than the content of the aliphatic aromatic polyester resin.

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

3. The thermoplastic resin composition for agricultural materials according to claim 1 or 2, wherein the average particle diameter of the starch is 5 μm to 50 μm.

4. The thermoplastic resin composition for an agricultural material according to any one of claims 1 to 3, wherein the viscosity modifier comprises at least one selected from the group consisting of cellulose fibers and a carbodiimide compound.

5. The thermoplastic resin composition 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 to the aliphatic aromatic polyester-based resin is 1 to 3:1.

6. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 5, wherein a melt viscosity at a shear rate 243s ^-1 is 1000 Pa-s or more and less than 5000 Pa-s at a temperature of a melting point of the biodegradable resin or more and a melting point +40 ℃ or less.

7. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 6, which is used for blow molding or vacuum forming.

8. The thermoplastic resin composition for agricultural materials according to any one of claims 1 to 7, which is used for a nursery pot.

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

10. The agricultural material of claim 9, which is a nursery pot.