JP2024017472A - Plasticizer for biodegradable resin and resin composition and molded product containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasticizer for a biodegradable resin which can exhibit sufficient flexibility and good moldability even in a biodegradable resin composition blended with a large amount of an inorganic filler, hardly causes bleeding and suppresses degradation of mechanical properties and appearance and to provide a resin composition and a molded product containing such a plasticizer for a biodegradable resin.

SOLUTION: There is provided a plasticizer for a biodegradable resin which contains a biodegradable resin component and inorganic substance powder in a mass ratio of 50:50 to 10:90 and contains carbon black in an amount of 1 mass% or more and 20 mass% or less of the total mass, wherein the carbon black has an iodine adsorption amount of 40 mg/g or more and 65 mg/g or more, a DBP absorption amount of 100 ml/100 g or more and 180 ml/100 g or less and an average particle diameter of 30 nm or more and 60 nm or less. The biodegradable resin component preferably has a glass transition temperature of 60°C or less, especially 40°C or less.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a plasticizer for biodegradable resins, and a resin composition and molded article containing the plasticizer for biodegradable resins.

Biodegradable resins are attracting attention as environmentally friendly resins because they are decomposed into substances that originally exist in nature through the action of microorganisms and hydrolysis. It has also been proposed to add various components such as calcium carbonate to these biodegradable resins, such as polylactic acid, in order to impart good properties without sacrificing their small environmental impact (for example, Patent Documents 1, 2).

Biodegradable resins such as polylactic acid have the disadvantage of lacking flexibility. This disadvantage becomes particularly noticeable when an inorganic filler such as calcium carbonate is added. In order to improve these points, studies have been made to incorporate various plasticizers into biodegradable resins (Patent Documents 2 to 6, etc.).

For example, Patent Document 3 discloses a polyalkylene oxide plasticizer, and Patent Document 4 discloses a plasticizer having polyalkylene oxide units and glyceryl ether units. Further, Patent Document 5 discloses a benzoate plasticizer, and Patent Document 6 discloses a plasticizer consisting of an oligomer of 3-hydroxyalkanoic acid having a terminal carboxyl group or alkoxycarbonyl group. In the invention described in Patent Document 2, polybutylene adipate terephthalate or polybutylene succinate adipate is used as a plasticizer for the purpose of softening a biodegradable resin composition containing a high calcium carbonate content.

Japanese Patent Application Publication No. 2017-119850 Patent No. 6919571 Japanese Patent Application Publication No. 2005-336448 Japanese Patent Application Publication No. 2006-22268 Special Publication No. 2015-512466 JP2019-131720A

However, plasticizers such as polyalkylene oxide, benzoate, and adipate have low compatibility with biodegradable resins such as polylactic acid, making uniform dispersion difficult. Therefore, even if it is blended into a biodegradable resin, sufficient flexibility may not be obtained. In particular, in a biodegradable resin composition containing a large amount of inorganic filler such as calcium carbonate, it is difficult to impart flexibility and improve moldability using these plasticizers. General-purpose plasticizers such as polyalkylene oxide type plasticizers also have the disadvantage that they bleed out of the resin composition during storage and use, deteriorating the mechanical properties and appearance of the resin composition. For example, in automobiles during the summer, the plasticizer released from the resin composition of the interior material evaporates and adheres to the inner surface of the window glass, resulting in a phenomenon called fogging, which obstructs visibility.

The present invention has been made in view of the above circumstances, and has excellent compatibility with biodegradable resins, and even a biodegradable resin composition containing a large amount of inorganic filler has sufficient flexibility and good properties. A plasticizer for a biodegradable resin that can exhibit excellent moldability, is difficult to cause bleeding, and suppresses deterioration of mechanical properties and appearance, and a resin composition containing such a plasticizer for a biodegradable resin. The purpose is to provide molded products.

The present inventors have discovered that the above problems can be solved by further containing a specific amount of specific carbon black in a biodegradable resin composition containing an inorganic filler, and have completed the present invention. More specifically, the invention provides:

(1) Contains a biodegradable resin component and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
Contains carbon black in an amount of 1% by mass or more and 20% by mass or less of the total mass,
The carbon black is biodegradable, having an iodine adsorption amount of 40 mg/g or more and 65 mg/g or less, a DBP absorption amount of 100 ml/100 g or more and 180 ml/100 g or less, and an average particle size of 30 nm or more and 60 nm or less. Plasticizer for resin.

(2) The plasticizer for biodegradable resins according to (1) above, wherein the biodegradable resin component has a glass transition temperature of 60° C. or lower.

(3) The plasticizer for biodegradable resins according to (1) or (2) above, which contains the biodegradable resin component and the inorganic substance powder in a mass ratio of 50:50 to 30:70.

(4) The biodegradable resin component is polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polycaprolactone, polybutylene succinate, polyethylene succinate, polyapple. One or more biodegradable resin components selected from the group consisting of acid, polyglycolic acid, polydioxanone, poly(2-oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA). A plasticizer for biodegradable resins according to any one of (1) to (3) above.

(5) The plasticizer for biodegradable resins according to any one of (1) to (4) above, wherein the inorganic substance powder is heavy calcium carbonate powder.

(6) The plasticizer for biodegradable resins according to (5) above, wherein the average particle diameter of the heavy calcium carbonate powder measured by an air permeation method according to JIS M-8511 is 0.7 μm or more and 6.0 μm or less. .

(7) The plasticizer for biodegradable resins according to any one of (1) to (6) above, further containing 5% by mass or more and 20% by mass or less of acetyltributyl citrate.

(8) Polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polycaprolactone, polybutylene succinate, polyethylene succinate, polymalic acid, polyglycolic acid, polydioxanone, The above (1) to (7) are added to one or more biodegradable resins selected from the group consisting of poly(2-oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA). A biodegradable resin composition containing any one of the following plasticizers for biodegradable resin in an amount of 0.1% by mass or more and 50% by mass or less based on the total mass.

(9) A molded article formed from the biodegradable resin composition of (8) above.

(10) The molded product according to (9) above, wherein the molded product is an extruded sheet.

According to the present invention, even a biodegradable resin composition that has excellent compatibility with biodegradable resins and contains a large amount of inorganic filler can exhibit sufficient flexibility and good moldability. Provided are plasticizers for biodegradable resins that can be used for biodegradable resins, are less likely to bleed, and are prevented from deteriorating mechanical properties and appearance, and resin compositions and molded articles containing such plasticizers for biodegradable resins.

Embodiments of the present invention will be described below, but the present invention is not limited thereto.

≪Plasticizer for biodegradable resin≫
The present invention contains a biodegradable resin component and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
Contains carbon black in an amount of 1% by mass or more and 20% by mass or less of the total mass,
For biodegradable resin, characterized in that carbon black has an iodine adsorption amount of 40 mg/g or more and 65 mg/g or less, a DBP absorption amount of 100 ml/100 g or more and 180 ml/100 g or less, and an average particle size of 30 nm or more and 60 nm or less. It is a plasticizer.

<Summary of components in plasticizers for biodegradable resins>
The present invention is characterized in that it contains a biodegradable resin component together with an inorganic substance powder and a specific carbon black. Although the present invention is not limited by any particular theory, it is conceivable that the molecular weight of the biodegradable resin component is lowered by blending the inorganic substance powder and carbon black, resulting in a plasticizing effect. Since biodegradable resins generally have hydrolyzable sites, they may be hydrolyzed in the presence of inorganic powder, particularly basic inorganic powder such as calcium carbonate, to produce low molecular weight components. Furthermore, the carbon black blended in the present invention can function as a microwave absorber. Therefore, when irradiated with microwaves, the entire biodegradable resin plasticizer is heated, and the biodegradable resin component has a lower molecular weight. As an effect of these, it is thought that it becomes possible to plasticize the biodegradable resin (base material) that is the partner material to be blended.

In addition to the above, it is also conceivable that the crystallinity of the biodegradable resin of the base material is reduced by blending the biodegradable resin component contained in the plasticizer, thereby imparting flexibility. The biodegradable resin matrix may also be compatible with the biodegradable resin plasticizer through interaction between the hydrolyzable sites. As a result, the plasticizer for biodegradable resins of the present invention is more uniformly dispersed in the mating material than general-purpose plasticizers such as polyalkylene oxide, exhibits flexibility, and suppresses the occurrence of bleeding. There is a possibility that there are.

Although the components in the plasticizer for biodegradable resin of the present invention will be described in detail later, there is no particular restriction on the type of biodegradable resin component. Typical examples include polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polycaprolactone, polybutylene succinate, polyethylene succinate, polymalic acid, and polyglycolic acid. , polydioxanone, poly(2-oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA), but are not limited thereto. It is also possible to use two or more types of biodegradable resins in combination.

Here, the biodegradable resin component constituting the plasticizer for biodegradable resin of the present invention preferably has the same or similar chemical structure as the biodegradable resin that is the target base material in which the plasticizer is blended. . For example, when polylactic acid is the base material, polylactic acid is produced, and when polyhydroxybutyrate or poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is the base material, polyhydroxybutyrate is produced. It can be a degradable resin component. By including a resin having the same or similar chemical structure as the biodegradable resin that is the base material to be blended, the plasticizer for biodegradable resins of the present invention is more uniformly distributed in the biodegradable resin base material. It is dispersed, exhibits good flexibility, and bleed becomes less likely to occur, making it easier to suppress deterioration of mechanical properties and appearance.

There is no particular restriction on the type of inorganic substance powder contained in the plasticizer for biodegradable resins of the present invention, but calcium carbonate powder and even heavy calcium carbonate powder are particularly suitable for air permeation according to JIS M-8511. A heavy calcium carbonate powder having an average particle diameter of 0.7 μm or more and 6.0 μm or less according to the method is preferable. Due to the coexistence of inorganic powder such as calcium carbonate, the biodegradable resin component in the plasticizer may have a low molecular weight. The inorganic substance powder is blended in a ratio of 50 to 90 parts by mass to 50 to 10 parts by mass of the above-mentioned biodegradable resin. The mass ratio of the biodegradable resin to the inorganic substance powder is preferably 50:50 to 30:70. When inorganic substance powder, especially heavy calcium carbonate powder, is contained in the above ratio, even if the biodegradable resin component is liquid or semi-liquid at room temperature, the plasticizer will remain solid or semi-solid. As a result, the handleability is improved, and there is also a low possibility that the plasticizing effect will be inhibited by the addition of a large amount of inorganic filler.

One of the characteristics of the plasticizer for biodegradable resins of the present invention is that carbon black (sometimes abbreviated as "CB" below) has an iodine adsorption amount of 40 mg/g or more and 65 mg/g or less, and a DBP absorption amount of 40 mg/g or more and 65 mg/g or less. The point is that the amount is 100 ml/100 g or more and 180 ml/100 g or less, and the average particle diameter is 30 nm or more and 60 nm or less. These are carbons with a relatively high structure, and correspond to CB mainly classified as HAF, MAF, FEF, GPF, etc. by the old ASTM etc., but carbon blacks other than FEF-CB etc. can also be used. By containing these CBs in an amount of 1 to 20% by mass based on the total mass, the biodegradable resin component has a lower molecular weight after microwave irradiation and exhibits a plasticizing effect. Moreover, even if the biodegradable resin component becomes liquid, the plasticizer becomes a solid or semi-solid material, making it easy to handle. On the other hand, it is also possible to suppress the possibility that the plasticizing effect will be inhibited by the addition of a large amount of reinforcing carbon.

In the plasticizer for biodegradable resins of the present invention, it is preferable that the biodegradable resin component has a low molecular weight, for example, a glass transition temperature of 60°C or less, in order to exhibit an excellent plasticizing effect. Here, as mentioned above, since the highly structured CB used in the present invention can function as a microwave absorber, the temperature rise of the entire plasticizer for biodegradable resin due to microwave irradiation and the resulting biodegradation Contributes to lowering the molecular weight of the resin component. In this way, for example, the plasticizer of the embodiment containing the biodegradable resin component having a low glass transition temperature can exhibit even more excellent plasticizing effects. Therefore, as one embodiment of the present invention, a plasticizer for biodegradable resins obtained by irradiating microwaves to a plasticizer for biodegradable resins containing the above-mentioned components can also be mentioned. Below, some embodiments of the plasticizer for biodegradable resins of the present invention will be outlined.

<Embodiments of the present invention>
As mentioned above, the present invention also includes a plasticizer for biodegradable resins obtained by irradiating a plasticizer for biodegradable resins containing the above-mentioned components with microwaves. In the biodegradable resin plasticizer of this embodiment, the glass transition temperature of the biodegradable resin component is lowered in most cases, and a good plasticizing effect is exhibited. For example, even if the biodegradable resin component is a general polylactic acid with a glass transition temperature of around 50-60°C or a biodegradable copolymer with a glass transition temperature of around 60-70°C, the glass transition temperature will be lowered by microwave irradiation. The plasticizing effect becomes even more pronounced as it becomes liquid or semi-liquid depending on the case. Yet another embodiment of the present invention provides that the biodegradable resin component has a glass transition temperature of 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, even more preferably 30°C or lower, particularly preferably 20°C or lower. The above-mentioned plasticizer for biodegradable resin has a temperature of 0.degree.

The molecular weight of the biodegradable resin component and its related glass transition temperature can also be lowered by thermal decomposition or hydrolysis during the preparation of the plasticizer. In particular, when calcium carbonate powder or the like is used as the inorganic substance powder, the entire mixture with the biodegradable resin component becomes weakly alkaline, making it easy for the molecular weight of the resin component to decrease due to hydrolysis. In this way, the molecular weight and glass transition temperature of the biodegradable resin component may be lowered by using both microwave irradiation and the decomposition reaction during mixing, but it is preferable to mainly reduce the molecular weight and glass transition temperature by microwave irradiation. . If the glass transition temperature of the biodegradable resin component is lowered by decomposition during mixing, the regularity of both the composition distribution and the molecular weight distribution may decrease. On the other hand, with microwave irradiation, even if the biodegradable resin component is at a level that liquefies, it can become a plasticizer containing a resin with a narrow composition and molecular weight distribution.

Yet another embodiment of the invention is:
biodegradable resin component,
Inorganic substance powder, and carbon black with an iodine adsorption amount of 40 mg/g or more and 65 mg/g or less, a DBP absorption amount of 100 ml/100 g or more and 180 ml/100 g or less, and an average particle size of 30 nm or more and 60 nm or less,
The biodegradable resin component and the inorganic substance powder are mixed in a mass ratio of 50:50 to 10:90, and the carbon black is mixed in a content of 1% by mass or more and 20% by mass or less based on the total mass. process, and
This is a method for producing a plasticizer for biodegradable resin, including a microwave irradiation step.

Yet another embodiment of the present invention is a method for producing a plasticizer for a biodegradable resin, in which the glass transition temperature of the biodegradable resin component is set to 60° C. or lower by the microwave irradiation step.

<Details of ingredients in plasticizer for biodegradable resin>
Below, each main component constituting the plasticizer for biodegradable resins of the present invention will be described in detail.

[Biodegradable resin]
Examples of biodegradable resin components that can be contained in the plasticizer for biodegradable resins of the present invention include polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and polycaprolactone. , polybutylene succinate, polyethylene succinate, polymalic acid, polyglycolic acid, polydioxanone, poly(2-oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA). Examples include one or more resins. Below, some of these biodegradable resins will be described in detail.

(polylactic acid)
From the viewpoint of further enhancing the plasticizing effect of the plasticizer for biodegradable resin of the present invention, the biodegradable resin component is preferably polylactic acid. In the present invention, "polylactic acid" refers to a polylactic acid homopolymer obtained by condensation polymerization of only a lactic acid component as a raw material monomer, and a polylactic acid homopolymer obtained by condensation polymerization of only a lactic acid component as a raw material monomer, and a polylactic acid component obtained by condensation polymerization of a lactic acid component as a raw material monomer and other monomer components copolymerizable with the lactic acid component. It includes polylactic acid copolymers obtained by condensation polymerization. Any polymer known as polylactic acid can be used in the present invention.

Furthermore, since polylactic acid has an asymmetric carbon in its main chain, even if it is a homopolymer consisting only of lactic acid units, crystalline poly-L-lactic acid and poly-D-lactic acid with optical purity of 100%, non-crystalline poly-D-lactic acid with optical purity of 0%, etc. Crystalline poly-DL lactic acid and polylactic acid with optical purity intermediate thereto exist. Furthermore, it is also known that stereocomplex polylactic acid can be formed by mixing poly-L-lactic acid and poly-D-lactic acid in a solution or molten state. Block copolymers consisting of poly-L-lactic acid blocks and poly-D-lactic acid blocks are also known.

Poly-L-lactic acid or poly-D-lactic acid can be produced by a direct melt polymerization method, a solid phase polymerization method, a direct condensation polymerization method of lactic acid, a melt ring-opening polymerization method of lactide, or the like. Among these, melt ring-opening polymerization of lactide is economically preferred. When poly L-lactic acid or poly D-lactic acid is produced by a melt ring-opening polymerization method, L-lactide and D-lactide are used to introduce the L-form and D-form of lactic acid. In addition, D-lactide or D-lactic acid has limited supply sources, has a small distribution volume, and has a higher market price than L-lactide or L-lactic acid, which is the raw material for poly-L-lactic acid units. From an economic point of view, it is desirable to use poly-L-lactic acid.

Poly DL lactic acid is a random copolymer consisting of L-lactic acid units and D-lactic acid units. The ratio of L lactic acid units to D lactic acid units is not particularly limited, and for example, L lactic acid units/D lactic acid units = about 60/40 to 40/60, more preferably about 55/45 to 45/55. can do. From an economical point of view, it is preferable that the amount of L-lactic acid units blended is larger than the amount of D-lactic acid units blended.

Since poly-L-lactic acid and poly-D-lactic acid have different stereoregularities, when they are mixed and melted and then crystallized, a so-called stereo complex is formed. Generally, stereocomplexes of polylactic acid are made from poly-L-lactic acid and poly-D-lactic acid, but in addition to or in place of one of these, the DL block of polylactic acid is used. It is also possible to make a stereocomplex using a copolymer as a raw material.

Polylactic acid block copolymers are stereoblock copolymers each containing one or more L-lactic acid segments and one or more D-lactic acid segments. L-lactic acid segment and D-lactic acid segment mean a polymer of two or more L-lactic acid or D-lactic acid. The weight average molecular weight (Mw) is not particularly limited, but is preferably 500 or more and 300,000 or less, more preferably 5,000 or more and 100,000 or less. When the molecular weight is less than 500, it is difficult for the L-lactic acid segment and the D-lactic acid segment to form an adjacent structure, which may result in a liquid or amorphous state. On the other hand, if it exceeds 300,000, fluidity decreases, making it difficult to form adjacent structures.

Furthermore, there is no particular limitation on the blending ratio of L-lactic acid segments and D-lactic acid segments in the polylactic acid stereoblock copolymer, as long as at least one or more segments of each are copolymerized, and the total number of segments is , preferably about 2 to 2,000.

In the polylactic acid copolymer, other monomer components copolymerizable with lactic acid are not particularly limited, but include, for example, oxyacids, dihydric alcohols, polyhydric alcohols of trihydric or higher hydric, aromatic hydroxy compounds, dihydric Examples include carboxylic acids, trivalent or higher polyhydric carboxylic acids, and lactones.

Examples of the oxyacid include oxyacids such as glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxybenzoic acid, and hydroxyheptanoic acid.

Examples of dihydric alcohols include ethylene glycol, propylene glycol, propanediol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, Examples include triethylene glycol, polyethylene glycol, polytetramethylene glycol, and the like.

Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, pentaerythritol, and the like.

Examples of aromatic hydroxy compounds include hydroquinone, resorcinol, bisphenol A, and the like.

Examples of divalent carboxylic acids include oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid. acid, bis(4-carboxyphenyl)methane, anthracene dicarboxylic acid, bis(4-carboxyphenyl)ether, sodium 5-sulfoisophthalate and the like.

Examples of the trivalent or higher polyvalent carboxylic acid include trimellitic acid, pyromellitic acid, and the like.

Examples of the lactones include caprolactone, valerolactone, propiolactone, undecalactone, and 1,5-oxepan-2-one.

(Other biodegradable resin components)
Biodegradable resin components other than lactic acid may also be homopolymers or copolymers. For example, lactic acid-glycolic acid copolymer, glycolic acid-caprolactone copolymer, glycolic acid-trimethylene carbonate copolymer, etc. can be used as the biodegradable resin component.

[Inorganic substance powder]
The inorganic substance powder that can be contained in the plasticizer for biodegradable resins of the present invention is not particularly limited, and examples include carbonates, sulfates, silicates, phosphorus, etc. of calcium, magnesium, aluminum, titanium, iron, zinc, etc. Examples include powdered salts, borates, oxides, and hydrates thereof, such as calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, Talc, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, Examples include calcium sulfite, sodium sulfate, potassium titanate, bentonite, graphite, and carbon black having properties other than those listed above. These may be synthetic or derived from natural minerals, and may be used alone or in combination of two or more.

Further, the shape of the inorganic substance powder is not particularly limited, and may be any of particles, flakes, granules, fibers, etc. Furthermore, the particles may be spherical as generally obtained by synthetic methods, or irregularly shaped as obtained by pulverizing natural minerals.

Preferred inorganic powders include calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, and magnesium hydroxide, with calcium carbonate powder being particularly preferred. Furthermore, calcium carbonate can be either one prepared by a synthetic method, so-called light calcium carbonate, or so-called heavy calcium carbonate, which is obtained by mechanically crushing and classifying natural raw materials mainly composed of CaCO ₃ such as limestone. Although it is possible to use a combination of these, from the viewpoint of economy, preferably heavy calcium carbonate is used.

Here, heavy calcium carbonate is obtained by mechanically crushing and processing natural limestone, etc., and is clearly distinguished from synthetic calcium carbonate produced by chemical precipitation reactions and the like. Incidentally, there are two types of pulverization method: a dry method and a wet method, and from the viewpoint of economic efficiency, the dry method is preferable.

Further, in order to improve the dispersibility or reactivity of the inorganic substance powder, the surface of the inorganic substance powder may be surface-modified in advance according to a conventional method. Examples of surface modification methods include physical methods such as plasma treatment, and methods in which the surface is chemically treated with a coupling agent or a surfactant. Examples of the coupling agent include a silane coupling agent and a titanium coupling agent. The surfactant may be anionic, cationic, nonionic, or amphoteric, and includes, for example, higher fatty acids, higher fatty acid esters, higher fatty acid amides, higher fatty acid salts, and the like.

Preferably, the inorganic powder is in the form of particles. Further, the inorganic substance powder, especially the heavy calcium carbonate powder, preferably has an average particle diameter of 0.7 μm or more and 6.0 μm or less, and 1.0 μm or more and 5.0 μm or more, as measured by an air permeation method according to JIS M-8511. It is more preferably 0 μm or less, and even more preferably 1.5 μm or more and 3.0 μm or less. As a device for measuring the average particle diameter, for example, a specific surface area measuring device model SS-100 manufactured by Shimadzu Corporation can be preferably used. In particular, it is preferable that the particle size distribution does not contain particles with a particle size exceeding 45 μm. On the other hand, if the particles become too fine, the viscosity will increase significantly when kneaded with the above-mentioned biodegradable resin, which may make production difficult.

[Carbon black]
The carbon black (CB) that can be included in the plasticizer for biodegradable resins of the present invention has an iodine adsorption amount of 40 mg/g or more and 65 mg/g or less, a DBP absorption amount of 100 ml/100 g or more and 180 ml/100 g or less, and an average particle size of It has a characteristic of having a diameter of 30 nm or more and 60 nm or less. Carbon black is generally produced by incomplete combustion or thermal decomposition of natural gas, petroleum, petroleum-based heavy oil, etc. Although CB is classified into channel black, furnace black, thermal black, etc. depending on the manufacturing method, any CB can be used in the present invention as long as it has the above characteristics. It is also possible to use two or more types of CB in combination. As mentioned above, CB with these characteristics has a relatively high structure and good microwave absorption ability, but on the other hand, it is difficult to increase the hardness of the polymer (composite material) to be blended. Therefore, it is suitable as a component in the present invention.

Most commercially available CB products are furnace black, and generally have a hydrogen content of about 0.2 to 0.4%. Further, depending on the atmosphere to which the particles are exposed after production in a furnace, the particles have various functional groups such as carbonyl groups on their surfaces, but the CB used in the present invention is not limited to these. CB having an average particle diameter of 30 to 60 nm is mainly classified into HAF, MAF, FEF, GPF, etc. as described above. In the present invention, CBs such as HAF, MAF, FEF, and GPF, particularly MAF-CB and FEF-CB, can be used, but are not limited thereto. However, from the viewpoint of particularly enhancing the plasticizing effect after microwave irradiation, the iodine adsorption amount is 40 to 50 mg/g, especially 40 to 45 mg/g, and the DBP absorption amount is 100 to 150 ml/100 g, especially 100 to 130 ml/g. It is preferable to use CB with a weight of 100 g and an average particle size of 35 to 55 nm, particularly 40 to 48 nm.

[Acetyltributyl citrate]
The plasticizer for biodegradable resins of the present invention may further contain a general-purpose plasticizer as a plasticizing component. Examples of general-purpose plasticizers include acetyltributyl citrate, triethyl citrate, acetyltriethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, Examples include, but are not limited to, o-benzoylbenzoic acid ester, diacetin, epoxidized soybean oil, and the like.

More preferably, among the above plasticizers, acetyltributyl citrate is used in an amount of 5% by mass or more and 20% by mass or less, particularly 8% by mass or more and 15% by mass or less, based on the total mass of the plasticizer for biodegradable resin. Contains Acetyl tributyl citrate has the advantage that, in combination with ground calcium carbonate, it does not impair the biodegradability of the biodegradable resin or the mechanical properties of the base material after adding a plasticizer.

[Other additives]
The plasticizer for biodegradable resins of the present invention can also contain other additives as adjuvants, if necessary. Other additives include, for example, colorants, coupling agents, fluidity modifiers, crosslinking agents, dispersants, ultraviolet absorbers, flame retardants, foaming agents, antistatic agents, and other additives other than those listed above. Antioxidants, stabilizers, etc. may be added. These additives may be used alone or in combination of two or more. Moreover, these may be blended in the below-mentioned kneading step, or may be blended into the raw material components in advance before the kneading step. In the resin composition filled with inorganic substance powder according to the present invention, the amount of these other additives added is not particularly limited as long as it does not impede the desired physical properties and moldability. When the mass of the entire resin composition is taken as 100%, each of these other additives is present in a proportion of about 0 to 10% by mass, particularly about 0.04 to 5% by mass, and based on the total amount of other additives. It is desirable that the content be 10% by mass or less.

[Composition of plasticizer for biodegradable resin]
The plasticizer for biodegradable resins of the present invention contains the biodegradable resin component and the inorganic substance powder in a mass ratio of 50:50 to 10:90, preferably in a mass ratio of 50:50 to 30:70. contains. The plasticizer for biodegradable resins of the present invention also contains carbon black having the above characteristics in an amount of 1 to 20% by mass, preferably 2 to 15% by mass, more preferably 3 to 12% by mass, particularly preferably 5% by mass of the total mass. Contains ~10% by mass. With such a composition, it is easy to adjust the glass transition temperature of the biodegradable resin component by microwave irradiation, and even if the biodegradable resin component becomes liquefied, it will not easily deteriorate in handling, and the hardness will increase due to filling in large quantities. can also be suppressed.

In a preferred embodiment of the invention, the biodegradable resin plasticizer comprises 10-50% by weight, especially 30-45% by weight of the biodegradable resin component; 45-89% by weight, especially 50-70% by weight of the biodegradable resin component; Inorganic substance powder; 1 to 20% by weight, such as 3 to 15% by weight, especially 5 to 12% by weight of the above carbon black; up to 20% by weight, especially 5 to 15% by weight of optional acetyltributyl citrate; and 10 Optional other additives of about 0.04 to 5% by mass or less; the entire plasticizer for biodegradable resin is 100% by mass, and the mass ratio of biodegradable resin component: inorganic substance powder is It is contained in an amount of 50:50 to 10:90.

<Method for producing plasticizer for biodegradable resin>
The plasticizer for biodegradable resins of the present invention can be produced by mixing the above components, for example, by melt-kneading them. In melt-kneading, it is preferable to uniformly disperse each component and to apply high shear stress to the mixture. Various types of mixing devices can be used, such as a general extruder, kneader, Banbury mixer, etc., but it is preferable to use a twin-screw kneader, for example.

The plasticizer for biodegradable resins of the present invention may be processed into pellets of any size and shape after kneading. The shape of the pellet is not particularly limited, and may be, for example, cylindrical, spherical, ellipsoidal, or the like. The size of the pellets is not particularly limited. For example, spherical pellets may have a diameter of 1 to 10 mm. In the case of oval spherical pellets, the aspect ratio may be 0.1 to 1.0 and the length and width may be 1 to 10 mm. In the case of cylindrical pellets, the diameter may be 1-10 mm and the length may be 1-10 mm.

The plasticizer for biodegradable resin of the present invention produced in this way can be blended into the biodegradable resin base material as it is, but the glass transition temperature of the biodegradable resin component in the plasticizer can be lowered to 60°C or less. It is preferable to blend the biodegradable resin into the biodegradable resin base material. As mentioned above, if the glass transition temperature of the biodegradable resin component is 60°C or less, especially 50°C or less, particularly 40°C or less, a better plasticizing effect will be exhibited. In order to reduce the glass transition temperature of the biodegradable resin component, it is preferable to irradiate the kneaded product or molded product produced as described above with microwaves.

[Microwave irradiation]
There are no particular limitations on the method of microwave irradiation. Note that microwaves are electromagnetic waves with a frequency of 300 MHz to 300 GHz (wavelength of 1 m to 1 mm). Industrial, scientific, and medical devices (ISM devices) have a center frequency of 13.560 MHz (frequency range 13.553 to 13.567 MHz), a center frequency of 27.120 MHz (frequency range 26.957 to 27.283 MHz), Frequency bands such as a frequency of 40.680 MHz (frequency range 40.66 to 40.70 MHz), a center frequency of 2450 MHz (frequency range 2400 to 2500 MHz), and a center frequency of 5800 MHz (frequency range 5725 to 5875 MHz) are defined. In the present invention, microwaves in any frequency band can be used. Among these, the microwave in the 2450 MHz band has the advantage that the cost of the irradiation device can be reduced because low-cost oscillation tubes are commercially available.

There is no particular restriction on the heating method using microwave irradiation, and various known methods such as a box oven method, a waveguide method, a microwave antenna method, a resonator method, etc. can be adopted. It is also possible to use multiple types of heating methods together. If the production volume is small, a microwave oven for food business or home use can be used. The above-mentioned kneaded material in the form of pellets, sheets, or films is placed in a commercially available microwave irradiation device, and irradiated with microwaves in the 2450 MHz band for 1 to 3 minutes, particularly 1 to 2 minutes , to remove the oxidation of the plasticizer. By lowering the molecular weight of the biodegradable resin component, it is possible to adjust the glass transition temperature, for example, to 60°C or lower, particularly 50°C or lower. It is also possible to make the biodegradable resin component liquid or semi-liquid.

≪Biodegradable resin composition≫
By blending the plasticizer for biodegradable resins of the present invention with various biodegradable resins, it is possible to improve the flexibility of the biodegradable resin to be blended (base material). The biodegradable resin composition containing the plasticizer for biodegradable resins of the present invention has excellent flexibility, good moldability, is less likely to cause bleeding, and deterioration of mechanical properties and appearance is suppressed. ing. The biodegradable resin to be blended (base material) is not particularly limited, and the same resin as the biodegradable resin component contained in the plasticizer for biodegradable resins of the present invention can be used.

The present invention also relates to polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polycaprolactone, polybutylene succinate, polyethylene succinate, polymalic acid, polyglycolic acid, The above biodegradable resin of the present invention is added to one or more biodegradable resins selected from the group consisting of polydioxanone, poly(2-oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA). A biodegradable resin composition containing a degradable resin plasticizer in an amount of 0.1% by mass or more and 50% by mass or less based on the total mass.

The biodegradable resin composition of the present invention can be prepared by adding the plasticizer for biodegradable resin of the present invention to the biodegradable resin base material, for example, by the method described in the explanation of <Method for producing plasticizer for biodegradable resin>. It can be manufactured by a method such as mixing, specifically, melting and kneading. There is no particular restriction on the melt-kneading method, and the method described in <Method for producing plasticizer for biodegradable resin> can be used.

Here, the partner material to which the plasticizer for biodegradable resin of the present invention is blended is a composite material (hereinafter referred to as "biodegradable resin composite material") containing an inorganic substance powder, in addition to the above-mentioned biodegradable resin. ” to distinguish it from the “base material” of the biodegradable resin.) The plasticizer for biodegradable resins of the present invention can impart excellent flexibility and improve moldability even in biodegradable resin composite materials containing a large amount of inorganic fillers such as calcium carbonate. can.

There are no particular restrictions on the composition of the biodegradable resin composite material used as the mating material, but the biodegradable resin and inorganic powder may be mixed in a mass ratio of 50:50 to 10:90, particularly in a mass ratio of 50:50 to 30: The content is preferably 70%. Such biodegradable resin composite materials are often brittle and have poor moldability, but by incorporating the plasticizer for biodegradable resins of the present invention, excellent flexibility and good moldability can be imparted. There are no particular restrictions on the types of inorganic substance powder and other additives that may be optionally blended, and those similar to those blended in the plasticizer for biodegradable resins of the present invention can be used. For example, 10 to 50% by mass, especially 30 to 45% by mass of biodegradable resin component; 45 to 90% by mass, especially 50 to 70% by mass of inorganic powder; and about 10% by mass or less, especially 0.04 to 5% by mass. It may also be a biodegradable resin composite material containing optional other additives in an amount of about % by mass.

The above biodegradable resin composite material may also contain the following resins in addition to the biodegradable resin:
Polyolefin resins such as polyethylene resins, polypropylene resins, polymethyl-1-pentene, and ethylene-cyclic olefin copolymers;
Ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid copolymer metal salt (ionomer), ethylene-acrylic acid alkyl ester copolymer, ethylene- Functional group-containing polyolefin resins such as methacrylic acid alkyl ester copolymers, maleic acid-modified polyethylene, and maleic acid-modified polypropylene;
Polyamide resins such as nylon-6, nylon-6,6, nylon-6,10, nylon-6,12;
Aromatic polyester resins such as polyethylene terephthalate and its copolymers, polyethylene naphthalate, and polybutylene terephthalate;
Polystyrene resins such as atactic polystyrene, syndiotactic polystyrene, acrylonitrile-styrene (AS) copolymer, acrylonitrile-butadiene-styrene (ABS) copolymer;
Polyvinyl chloride resins such as polyvinyl chloride and polyvinylidene chloride;
Polyphenylene sulfide;
Examples include polyether resins such as polyether sulfone, polyether ketone, and polyether ether ketone.
However, from the viewpoint of easy biodegradability, biodegradable resin composites do not contain resins other than biodegradable resins, or even if they contain a small amount (for example, 1.0% compared to biodegradable resin composites). 0% by mass or less).

There is no particular restriction on the method of blending the plasticizer for biodegradable resin of the present invention into the biodegradable resin composite material, and the method and apparatus described above for <Production method of plasticizer for biodegradable resin> The biodegradable resin plasticizer of the present invention may be mixed, for example, melt-kneaded, with the biodegradable resin composite material. Here, if the compositions of the biodegradable resin composite material and the plasticizer for biodegradable resin are similar, melt-kneading will proceed smoothly and the dispersion of the plasticizer for biodegradable resin will be made more homogeneous. It becomes easier. For example, if a biodegradable resin composite material and a plasticizer for biodegradable resins contain the same polylactic acid and the same amount of heavy calcium carbonate, the melt viscosities of the two will be similar, so the kneader will It can be mixed smoothly inside.

≪Molded products≫
The biodegradable resin composition of the present invention described above can be molded into various shapes. The present invention also includes molded articles molded from the above biodegradable resin composition. The molded product of the present invention is flexible and has good moldability, so it can be molded into various shapes by various known processing methods. In addition, since it does not easily cause bleeding and has good mechanical properties and appearance, it can be used as articles of various shapes for various purposes.

The molded products of the present invention include, for example, sheets, films, containers (food containers, etc.), daily necessities (various disposable products, etc.), automotive parts, electrical and electronic components, and various consumables (such as those in the fields of building materials, etc.) etc.

Since the resin composition of the present invention has good moldability, it is particularly suitable for extrusion molding and inflation molding. The molded articles of the invention are therefore preferably extruded articles, such as films, sheets, hollow articles, etc., especially extruded sheets.

Examples of inflation molded products include films, sheets, and bags (plastic bags, etc.).
The wall thickness of the inflation molded product is not particularly limited, but is preferably 10 μm to 200 μm, more preferably 30 μm to 100 μm.

<Method for manufacturing molded products>
The method for producing the molded article of the present invention can be appropriately selected depending on the molded article to be obtained. In addition to the extrusion molding method and inflation molding method described above, various methods such as injection molding method, foam injection molding method, injection compression molding method, blow molding method, press molding method, calendar molding method, vacuum molding method, etc. are adopted. be able to. The molding conditions can be appropriately set depending on the composition of the biodegradable resin composition, the type of molded product, etc.

In addition, when the molded product is a sheet, a film, etc., it may or may not be stretched uniaxially, biaxially, or multiaxially during or after molding.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

In the following examples, various plasticizers for biodegradable resins and biodegradable resin composites were prepared using the following raw materials, and both were kneaded to prepare biodegradable resin compositions.
・Resin component (P)
P-1: Poly L-lactic acid (weight average molecular weight Mw: 130,000, melting point: 172°C)
P-2: Mixed resin consisting of 70% by mass of polybutylene adipate terephthalate and 30% by mass of poly-L-lactic acid (P-1)

・Inorganic substance powder (I)
I-1: Heavy calcium carbonate particles (average particle size: 2.2 μm, BET specific surface area: 1.0 m ² /g, circularity: 0.85)
I-2: Silica

・Carbon black (CB)
CB-1: FEF-CB (Iodine adsorption amount 45 mg/g, DBP absorption amount 121 ml/100 g, average particle size 44 nm)
CB-2: MAF-CB (Iodine adsorption amount 58 mg/g, DBP absorption amount 158 ml/100 g, average particle size 38 nm)
CB-3: ISAF-CB (Iodine adsorption amount 118 mg/g, DBP absorption amount 91 ml/100 g, average particle size 22 nm)
CB-4: SRF-CB (Iodine adsorption amount 26 mg/g, DBP absorption amount 68 ml/100 g, average particle size 66 nm)

・Additive (A)
A-1: Acetyltributyl citrate A-2: Antistatic agent containing lauryl diethanolamide and diethanolamine

[Examples 1 to 4, Comparative Examples 1 to 4]
<Preparation of plasticizer for biodegradable resin>
The above-mentioned raw materials were put into a co-rotating twin-screw kneading extruder HK-25D (φ25 mm, L/D=41) manufactured by Parker Corporation in the amounts shown in Table 1 below. This was strand extruded at a cylinder temperature of 190 to 200°C, cooled, and cut to produce pellets of plasticizer for biodegradable resins of various compositions.

<Microwave irradiation>
A portion of the pellets prepared above was irradiated with microwaves in the 2450 MHz band using a microwave irradiation device. In addition, the glass transition temperature (Tg: equivalent to the Tg of the biodegradable resin component) of the plasticizer for biodegradable resin before and after irradiation was measured using a DSC manufactured by Shimadzu Corporation.

<Preparation of biodegradable resin composite material>
40 parts by mass of P-1, 60 parts by mass of I-1, and 1 part by mass of A-2 were added to a co-rotating twin-screw kneading extruder HK-25D (φ25 mm, L/D= 41), and in the same manner as the above plasticizer for biodegradable resin, a pellet-shaped biodegradable resin composite-1 was produced.

<Preparation and molding of biodegradable resin composition>
33 parts by mass of the pellets of each plasticizer for biodegradable resin obtained above were melt-kneaded into 67 parts by mass of biodegradable resin composite material-1. Melt-kneading was carried out in the same manner as above using a co-rotating twin-screw kneading extruder HK-25D manufactured by Parker Corporation. The obtained pellets were put into an injection molding machine to mold a dumbbell-shaped test piece.

<Testing of biodegradable resin composition sample>
For each biodegradable resin composition sample, the moldability during injection molding as an index of plasticization effect, the flexibility of the sample after molding, and the bleed resistance were measured as follows using the dumbbell-shaped test piece. It was evaluated. The evaluation results are shown in Table 1 along with the composition of the plasticizer for biodegradable resin.

(Moldability)
・〇: A dumbbell-shaped test piece with no appearance defects such as chips could be easily obtained.
・△: By repeatedly examining the molding conditions, a test piece with no appearance defects was obtained.
- ×: Even when the molding conditions were changed, only test pieces with poor appearance such as chipping were obtained.

(Flexibility)
The above test piece was bent by hand as shown in FIG. 1, and its flexibility was evaluated according to the following criteria.
・◎: The test piece was bent three times to around 160°, but it did not break.
・○: No breakage occurred unless the test piece was bent 2 to 3 times to around 160°.
・△: When the test piece was bent by about 120 to 160 degrees, it broke at one time.
・×: When the test piece was bent by about 90 to 120 degrees, it broke at one time.

(Bleed resistance)
The above test piece was stored in an oven at 80°C, and its appearance was observed at regular intervals to visually observe the presence or absence of bleed, and evaluated based on the following criteria.
・◎: Even when the test piece was held at 80° C. for 24 hours, almost no bleeding was observed.
・○: Bleeding was observed when the test piece was held at 80°C for 24 hours.
- Δ: When the test piece was held at 80° C. for 6 hours, slight bleeding was observed, and after 24 hours, significant bleeding was observed.
*×: Significant bleeding was observed even after the test piece was held at 80° C. for 6 hours.

The biodegradable resin compositions of Examples 1 to 4 in which the plasticizer for biodegradable resin according to the present invention was blended were different from the biodegradable resin composition of Comparative Example 1 in which the plasticizer for biodegradable resin was not blended. In comparison, it was easier to mold into dumbbell-shaped specimens, the flexibility was improved, and the bleed resistance was also good. In particular, in Examples 2 to 4 in which the glass transition temperature of the biodegradable resin component was lowered by irradiation with microwaves, the biodegradable resin composition was flexible and exhibited an excellent plasticizing effect. On the other hand, when CB-3, which has an extremely large amount of iodine adsorption, was used, it became impossible to produce the plasticizer itself for biodegradable resins (Comparative Example 2). Furthermore, even if the plasticizer for biodegradable resin of Comparative Example 3, which contains CB-4 with a relatively low structure, or the plasticizer for biodegradable resin, of Comparative Example 4, which does not contain carbon black, is not satisfactory. No plasticizing effect was obtained.

[Comparative example 5]
70 parts by mass of the biodegradable resin composite-1 obtained in Example 1 was put into a co-rotating twin-screw kneading extruder HK-25D manufactured by Parker Corporation, and after melting, it was mixed with a general-purpose plasticizer. A test piece was prepared in the same manner as in Example 1 by adding 30 parts by mass of polyoxyethylene sorbitan fatty acid monoester. When the obtained test piece was kept in an oven at 80° C. for 6 hours, significant bleeding was observed. Only molded products with poor moldability and poor appearance were obtained, and no particularly superior effects were observed compared to the plasticizer for biodegradable resins of the present invention.

[Examples 5 to 10, Comparative Examples 6 to 7]
<Preparation of plasticizer for biodegradable resin>
Pellets of various plasticizers for biodegradable resins having the formulations shown in Table 2 were prepared in the same manner as in Example 1. Separately, pellet-shaped biodegradable resin composite-2 was prepared in the same manner as in Example 1 using 30 parts by mass of P-2, 70 parts by mass of I-1, and 1 part by mass of A-2. was created. Next, 15 parts by mass of various plasticizers for biodegradable resins and 85 parts by mass of biodegradable resin composite-2 were kneaded and molded in the same manner as in Example 1 to create dumbbell-shaped test pieces. , conducted an evaluation test. The evaluation results are shown in Table 2.

The biodegradable resin compositions of Examples 5 to 10 in which the plasticizer for biodegradable resin according to the present invention was blended were different from the biodegradable resin composition of Comparative Example 6 in which the plasticizer for biodegradable resin was not blended. In comparison, it was easier to form into dumbbell-shaped specimens, the flexibility was greatly improved, and the bleed resistance was also good. In particular, Examples 8 to 10 in which acetyltributyl citrate was blended exhibited excellent plasticizing effects. In Example 7, in which silica was blended instead of heavy calcium carbonate, the plasticizing effect was not as great as in the other Examples. It is suggested that heavy calcium carbonate powder is preferable as the inorganic substance powder. Furthermore, the biodegradable resin plasticizer of Comparative Example 7, which had a small amount of biodegradable resin components, could not be produced by melt-kneading.

As described above, according to the present invention, even a biodegradable resin composition containing a large amount of inorganic filler can exhibit sufficient flexibility and good moldability, and is less likely to cause bleeding. It has become clear that it is possible to provide a plasticizer for biodegradable resins in which deterioration in mechanical properties and appearance is suppressed, as well as resin compositions and molded articles containing such plasticizers for biodegradable resins.

Claims (10)

Contains a biodegradable resin component and an inorganic substance powder in a mass ratio of 50:50 to 10:90,
Contains carbon black in an amount of 1% by mass or more and 20% by mass or less of the total mass,
The carbon black is biodegradable, having an iodine adsorption amount of 40 mg/g or more and 65 mg/g or less, a DBP absorption amount of 100 ml/100 g or more and 180 ml/100 g or less, and an average particle size of 30 nm or more and 60 nm or less. Plasticizer for resin. The plasticizer for biodegradable resins according to claim 1, wherein the biodegradable resin component has a glass transition temperature of 60°C or less. The plasticizer for biodegradable resin according to claim 1, which contains the biodegradable resin component and the inorganic substance powder in a mass ratio of 50:50 to 30:70. The biodegradable resin component may include polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polycaprolactone, polybutylene succinate, polyethylene succinate, polymalic acid, poly Claimed to be one or more biodegradable resin components selected from the group consisting of glycolic acid, polydioxanone, poly(2-oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA). Item 1. The plasticizer for biodegradable resins according to item 1. The plasticizer for biodegradable resins according to claim 1, wherein the inorganic substance powder is heavy calcium carbonate powder. The plasticizer for biodegradable resins according to claim 5, wherein the average particle diameter of the heavy calcium carbonate powder as measured by an air permeation method according to JIS M-8511 is 0.7 μm or more and 6.0 μm or less. The plasticizer for biodegradable resins according to claim 1, further comprising 5% by mass or more and 20% by mass or less of acetyltributyl citrate. Polylactic acid, polyhydroxybutyrate, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polycaprolactone, polybutylene succinate, polyethylene succinate, polymalic acid, polyglycolic acid, polydioxanone, poly(2 -oxetanone), polybutylene adipate terephthalate (PBAT), and polybutylene succinate adipate (PBSA). A biodegradable resin composition containing the biodegradable resin plasticizer described above in an amount of 0.1% by mass or more and 50% by mass or less based on the total mass. A molded article molded from the biodegradable resin composition according to claim 8. The molded article according to claim 9, wherein the molded article is an extruded sheet.