JP2022157778A - Biodegradable resin composition and molding - Google Patents

Abstract

To provide a biodegradable resin composition that exhibits a high degree of biodegradation at a high biodegradation speed.SOLUTION: A biodegradable resin composition contains a polyester resin and a nitrogen-containing inorganic salt. A content of the nitrogen-containing inorganic salt is 0.01 wt.% or more and 30 wt.% or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a biodegradable resin composition and a molded article containing the biodegradable resin composition.

In modern society, plastics are used in a wide range of everyday applications, such as packaging materials, home appliance materials, and construction materials, due to their lightness, electrical insulation, moldability, and durability. Plastics used for these applications include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, and the like. However, since these plastic molded articles are difficult to decompose in the natural environment, they tend to remain in the ground even if they are buried after use. In addition, even if incinerated, harmful gases may be generated that may damage the incinerator. ) are required.

As a means of solving the above problems, research has been conducted on biodegradable materials that are broken down into carbon dioxide and water by microorganisms in compost. Representative examples of biodegradable materials include polylactic acid (hereinafter sometimes abbreviated as “PLA”) and the like (Non-Patent Document 1).

Polymer Degradation and Stability 98 (2013) 1089-1096

An object of the present invention is to provide a biodegradable resin composition having a high biodegradation rate and a high degree of biodegradation. Another object of the present invention is to provide a biodegradable resin composition having a high biodegradation rate and a high degree of biodegradation, particularly in the sea.

The inventors of the present invention conducted extensive studies in view of the above circumstances. Specifically, we focused on inorganic salts that can become nitrogen-containing ions when dissolved in the environment, and the nitrogen-containing ions generated by blending nitrogen-containing inorganic salts into resins are expected to promote the growth and decomposition of microorganisms. thought to contribute. As a result of investigations, the present inventors have found that the addition of a nitrogen-containing inorganic salt to a polyester resin produces a significant biodegradation-promoting effect, thereby solving the above-described problems, and completed the present invention. That is, the gist of the present invention is as follows.

[1] A biodegradable resin composition containing a polyester resin and a nitrogen-containing inorganic salt, wherein the content of the nitrogen-containing inorganic salt is 0.01% by weight or more and 30% by weight or less.
[2] The biodegradable resin composition according to [1] above, wherein the nitrogen-containing inorganic salt contains at least one of an ammonium salt, a nitrate, and a nitrite.
[3] The biodegradable resin composition according to [1] or [2] above, wherein the polyester resin has a glass transition temperature of 40° C. or lower.
[4] The biodegradable resin composition according to any one of [1] to [3] above, wherein the polyester resin has a dicarboxylic acid unit having 4 to 22 carbon atoms.
[5] The biodegradable resin composition according to any one of [1] to [4] above, wherein the polyester resin has two or more dicarboxylic units.
[6] The biodegradable resin composition according to any one of [1] to [5] above, wherein the polyester resin has a linear aliphatic diol unit having 4 to 10 carbon atoms.
[7] The biodegradable resin composition according to any one of [1] to [6] above, wherein the polyester resin is an aliphatic polyester resin.
[8] A molded article containing the biodegradable resin composition according to any one of [1] to [7] above.
[9] A method for biodegrading a polyester resin, comprising biodegrading a polyester resin having a glass transition temperature of 40°C or less in seawater in the presence of a nitrogen-containing inorganic salt.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a biodegradable resin composition having a high biodegradation rate and a high degree of biodegradation, which greatly contributes to solving environmental problems such as marine pollution.

Embodiments of the present invention will be described in detail below.
The present invention is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present invention. In this specification, when a numerical value or a physical property value is sandwiched before and after the "~", it is used to include the values before and after it.

Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents. Various modifications can be made within the scope of the gist.

One embodiment of the present invention is a biodegradable resin composition containing a polyester resin and a nitrogen-containing inorganic salt (hereinafter referred to as "the biodegradable resin composition according to the present embodiment" or "the resin composition of the present invention"). There are cases.).
As used herein, the term "biodegradability" refers to the property that the resin is decomposed into low molecular weight molecules such as oligomers and monomers by hydrolysis or the like due to the action of microorganisms, which are further decomposed into water, carbon dioxide, and the like. do. The resin composition of the present invention may be biodegraded in any environment as long as the resin is biodegraded. In particular, the amount and types of microorganisms in seawater are small, and the resin is difficult to biodegrade. However, the resin composition of the present invention can exhibit effects in such an environment where biodegradation is difficult. Therefore, the resin composition of the present invention is preferably highly biodegradable in seawater (marine biodegradable resin composition).
The constituent components, characteristics, manufacturing method and use of the biodegradable resin composition according to the present embodiment will be described below.

[Nitrogen-containing inorganic salt]
The biodegradable resin composition according to this embodiment is characterized by containing a nitrogen-containing inorganic salt. The nitrogen-containing inorganic salt is not particularly limited as long as it exhibits the effects of the present invention, but ammonium salts, nitrates, or nitrites are preferable because they have the effect of imparting a high level of biodegradation to resins.

Ammonium salts are those in which ammonia has been protonated to the ammonium ion. Specific examples include ammonium chloride, ammonium carbonate, ammonium nitrate, ammonium bromide, ammonium iodide, ammonium acetate, ammonium vanadate, ammonium hydrogen carbonate, ammonium carbamate, ammonium succinate, and diammonium adipate. Among these, ammonium chloride, ammonium carbonate, ammonium nitrate, ammonium bromide, and ammonium iodide are preferred as ammonium salts.

Nitrate is the protonated nitrate ion (NO ³⁻ ) of nitric acid. Specifically, magnesium nitrate hexahydrate, potassium nitrate, calcium nitrate tetrahydrate, cobalt nitrate hexahydrate, sodium nitrate, aluminum nitrate nonahydrate, barium nitrate, strontium nitrate, ammonium nitrate, manganese nitrate hexahydrate hydrate, iron nitrate nonahydrate, copper nitrate trihydrate, cesium nitrate, guanidine nitrate and the like. Among these nitrates, magnesium nitrate hexahydrate, potassium nitrate, calcium nitrate tetrahydrate, cobalt nitrate hexahydrate, sodium nitrate, aluminum nitrate nonahydrate, barium nitrate, strontium nitrate, ammonium nitrate, nitric acid Copper trihydrate is preferred. Magnesium nitrate hexahydrate, potassium nitrate, calcium nitrate tetrahydrate, sodium nitrate, and the like are inorganic salts composed of elements contained in seawater, and are therefore considered preferable because microorganisms in seawater easily propagate.

Nitrite is a compound of nitrite ion (NO ²⁻ ). Specific examples include sodium nitrite, potassium nitrite, calcium nitrite, barium nitrite, and silver nitrite.
It is preferable that the nitrogen-containing inorganic salt does not easily inhibit the growth of microorganisms. Moreover, from the viewpoint of safety, it is preferable that the material is not a hazardous substance, an insecticide, or an agricultural chemical such as a herbicide.

The nitrogen-containing inorganic salt is contained in the biodegradable resin composition in an amount of 0.01% by weight or more and 30% by weight or less. The amount of nitrogen-containing inorganic salt contained in the biodegradable resin composition may be appropriately adjusted according to the type of resin, the type of nitrogen-containing inorganic salt, the application of the biodegradable resin composition, and the like. The content of the nitrogen-containing inorganic salt is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, still more preferably 1% by weight or more, and particularly preferably 5% by weight or more. On the other hand, the content is preferably 25% by weight or less, more preferably 20% by weight or less.
By setting the content of the nitrogen-containing inorganic salt in the biodegradable resin composition within the above range, the composition tends to have both biodegradability and mechanical properties when processed into a molded article.

[Polyester resin]
The biodegradable resin composition according to this embodiment contains a polyester resin. The polyester resin contained in the biodegradable resin composition according to the present embodiment is not particularly limited as long as the biodegradability is improved by making the resin composition with the nitrogen-containing inorganic salt described above. The polyester resin contained in the biodegradable resin composition according to the embodiment is preferably a biodegradable polyester resin. The biodegradability of resins and resin compositions will be described later. As for the polyester resin contained in the biodegradable resin composition according to the present embodiment, one type may be used alone, or two or more types of polyester resin may be used in any combination and ratio.
Polyester resins include polyhydroxyalkanoate (PHA), polycaprolactone, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polybutylene sebacate terephthalate (PBSeT), etc. of biodegradable polyester resins are preferred. The polyester resin may be used alone or in combination of two or more resins having different types and numbers of structural units, ratios of structural units, manufacturing methods, physical properties, and the like. Moreover, you may use resins other than polyester together. When resins other than polyester are used together, biodegradable resins such as polyvinyl alcohol, polyamide, and polyethylene glycol are preferred.

The polyester resin contained in the biodegradable resin composition according to this embodiment will be described in detail below. Each repeating unit in the polyester resin is also referred to as a compound unit for the compound from which each repeating unit is derived. For example, a repeating unit derived from an aliphatic diol is an "aliphatic diol unit", a repeating unit derived from an aliphatic dicarboxylic acid is an "aliphatic dicarboxylic acid unit", and a repeating unit derived from an aromatic dicarboxylic acid is an "aromatic dicarboxylic acid unit". Also called "acid unit". In addition, the "main structural unit" in the polyester resin is usually a structural unit that contains 80% by weight or more of the structural unit in the polyester resin, and does not contain structural units other than the main structural unit. is also included.
As the polyester resin contained in the biodegradable resin composition according to the present embodiment, the biodegradability is easily improved by forming a resin composition with a nitrogen-containing inorganic salt. A polyester resin and an aliphatic oxycarboxylic acid resin having a diol unit and a dicarboxylic acid unit are more preferable.

The polyester resin may be an aliphatic polyester resin, an aromatic polyester resin, or an aliphatic-aromatic polyester resin. Aliphatic polyester resins or aliphatic-aromatic polyester resins are preferable from the viewpoint of high flexibility, and aliphatic polyester resins are more preferable from the viewpoint of biodegradability. In addition, in this specification, heteroaromatics are also included in aromatics.
The polyester resin contained in the biodegradable resin composition according to the present embodiment is believed to be easily biodegradable due to the decrease in the crystallinity of the polyester resin and the increase in the amorphous portion. It preferably has two or more types of structural units, and more preferably has two or more types of dicarboxylic acid units.

<Diol unit>
The diol unit that the polyester resin has may be aliphatic or aromatic. In addition, the polyester resin may have one type of diol unit or two or more types of units in any combination and ratio, and may have an aliphatic diol unit and an aromatic diol unit. From the viewpoint of easy biodegradation, it preferably has an aliphatic diol unit, and more preferably has a linear aliphatic diol unit.
Further, the diol unit is particularly preferably a diol unit represented by the following general formula (1).
-OR ¹ -O- (1)
In formula (1), R ¹ represents an aliphatic hydrocarbon group having 2 to 20 carbon atoms.

The number of carbon atoms in the aliphatic hydrocarbon group represented by R ¹ is usually 2 or more, preferably 4 or more, and usually 20 or less, preferably 16 or less, more preferably 13, from the viewpoint of moldability, mechanical strength, etc. , more preferably 10 or less, particularly preferably 6 or less. A particularly preferred group as the aliphatic hydrocarbon group is an aliphatic hydrocarbon group having 4 carbon atoms.
Preferred examples of the aliphatic diol that gives the aliphatic diol unit represented by formula (1) include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol. More preferred are 1,4-butanediol, 1,3-propanediol and ethylene glycol, with 1,4-butanediol being particularly preferred.

The diol unit contained in the polyester resin may have an aromatic diol unit. Specific examples of aromatic diol components that provide aromatic diol units include xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis(4′-hydroxyphenyl)propane, 2,2-bis( 4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, bis(4-β-hydroxyethoxyphenyl)sulfonic acid and the like. The aromatic diol component, which is the starting material for the aromatic diol unit, may be a derivative of an aromatic diol compound. A compound having a structure in which a plurality of aliphatic diol compounds and/or aromatic diol compounds are dehydrated and condensed with each other may also be used.
The diol units of the polyester resin preferably contain 30 mol % or more, more preferably 50 mol % or more, of the above preferred diol units based on the total diol units. Moreover, an upper limit is 100 mol%.

<Dicarboxylic acid unit>
The dicarboxylic acid unit of the polyester resin may be aliphatic or aromatic. In addition, the dicarboxylic acid unit that the polyester resin has may be one type, or may have two or more types of units in any combination and ratio, and has an aliphatic dicarboxylic acid unit and an aromatic dicarboxylic acid unit. good too. From the viewpoint of easy biodegradation, it preferably has an aliphatic dicarboxylic acid unit.
From the viewpoint of biodegradability, moldability, and mechanical strength, the number of carbon atoms in the dicarboxylic acid unit is more preferably 2 or more, more preferably 4 or more, and on the other hand, 22 or less. is preferred, 16 or less is more preferred, and 13 or less is even more preferred.
The dicarboxylic acid unit is preferably a dicarboxylic acid unit represented by the following general formula (2).
-OC-R ² -CO- (2)
In formula (2), R ² represents a single bond, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, or an aromatic hydrocarbon group or heteroaromatic group having 4 to 8 carbon atoms.

The number of carbon atoms in the aliphatic hydrocarbon group represented by R ² is usually 1 or more, preferably 2 or more, more preferably 4 or more, and on the other hand, preferably 20 or less, more preferably 16 or less. , more preferably 12 or less, particularly preferably 8 or less. When the polyester resin contains two or more types of aliphatic dicarboxylic acid units, the combination of the aliphatic hydrocarbon groups includes an aliphatic hydrocarbon group having 2 carbon atoms and an aliphatic hydrocarbon group having 4 to 10 carbon atoms. A combination is preferred.

The aliphatic dicarboxylic acid component that provides the aliphatic dicarboxylic acid unit represented by formula (2) is not particularly limited, but an aliphatic dicarboxylic acid or A derivative thereof such as an alkyl ester is preferable, and an aliphatic carboxylic acid having 4 to 10 carbon atoms or a derivative thereof such as an alkyl ester is more preferable.
Preferred aliphatic dicarboxylic units include, for example, oxalic acid units, malonic acid units, succinic acid units, glutaric acid units, adipic acid units, pimelic acid units, suberic acid units, azelaic acid units, sebacic acid units, and undecanedioic acid units. , dodecanedioic acid units. Among these, adipic acid units, azelaic acid units, succinic acid units and sebacic acid units are preferred, succinic acid units and sebacic acid units are more preferred, and succinic acid units are particularly preferred.

In the polyester resin, the ratio of the above-described preferred dicarboxylic acid units in all dicarboxylic acid units is preferably 5 mol% or more, more preferably 10 mol% or more, and further preferably 50 mol% or more. It is preferably 64 mol % or more, particularly preferably 68 mol % or more, and most preferably 68 mol % or more. In addition, an upper limit is 100 mol%. By setting the ratio of the dicarboxylic acid in the polyester resin within the above range, it is possible to obtain a biodegradable resin composition having improved moldability and excellent heat resistance and biodegradability.
Further, when the polyester resin contains an aliphatic dicarboxylic acid unit, the aliphatic dicarboxylic acid unit preferably contains 30 mol% or more of the total dicarboxylic acid unit, and 40 mol% or more. more preferably. Moreover, an upper limit is 100 mol%.
Further, when the polyester resin contains aromatic dicarboxylic acid units, the aromatic dicarboxylic acid units are preferably 70 mol% or less, more preferably 60 mol% or less, relative to the total dicarboxylic acid units. .

The polyester preferably contains two or more types of aliphatic dicarboxylic acid components, and more preferably contains two or more types of the preferred aliphatic dicarboxylic acid components described above. In this case, the combination of the aliphatic dicarboxylic acid units is preferably a combination of an aliphatic dicarboxylic acid unit having 4 carbon atoms and an aliphatic dicarboxylic acid unit having 6 to 13 carbon atoms, and an aliphatic dicarboxylic acid unit having 4 carbon atoms. and an aliphatic dicarboxylic acid unit having 6 to 10 carbon atoms is more preferable. Specifically, the combination of aliphatic dicarboxylic acid units preferably includes at least one of succinic acid units, adipic acid units, azelaic acid units, sebacic acid units, and brassylic acid units. More preferably, two or more dicarboxylic acid units from are combined.

The dicarboxylic acid unit to be combined with the succinic acid unit is preferably a pimelic acid unit, a suberic acid unit, an azelaic acid unit, an adipic acid unit, a sebacic acid unit, an undecanedioic acid unit, a brassylic acid unit or a dodecanedioic acid unit, and an adipic acid unit. Alternatively, a combination with a sebacic acid unit is more preferred, and a combination with a sebacic acid unit is even more preferred.
Specifically, the following polyester resins are preferred. Preferred polyester resins having succinic acid units include polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene succinate sebacate (PBSSe) and polybutylene succinate azelate (PBSAz). Polyesters having two or more dicarboxylic acid units such as polybutylene succinate adipate (PBSA), polybutylene succinate sebacate (PBSSe) and polybutylene succinate azelate (PBSAz), polybutylene succinate brazilate (PBSBr) Resin is more preferred. Polybutylene succinate sebacate (PBSSe), polybutylene sebacate terephthalate (PBSeT) and polybutylene sebacate furanoate (PBSeF) are preferred as polyester resins having sebacic acid units. As polyester resins having azelaic acid units, polybutylene succinate azelate (PBSAz), polybutylene azelate terephthalate (PBAzT) and the like are preferable. Polybutylene succinate adipate (PBSA) and polybutylene adipate terephthalate (PBAT) are preferred as polyester resins having adipic acid units. Polybutylene succinate brassylate (PBSBr) and polybutylene brassylate terephthalate (PBBrT) are preferred as polyester resins having brassylic acid units.

The dicarboxylic acid unit combined with the succinic acid unit is preferably contained in an amount of 5 mol% or more, more preferably 10 mol% or more, and 15 mol% or more of the total dicarboxylic acid units. On the other hand, the content is more preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 40 mol% or less. By copolymerizing an aliphatic dicarboxylic acid unit other than the succinic acid unit within the above range, the crystallinity of the polyester resin can be lowered and the biodegradation rate can be increased.

The number of carbon atoms in the aromatic dicarboxylic acid unit represented by formula (2) is usually 4 or more and 8 or less, preferably 6 or more. Specific examples include 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group, 2,5-furandyl group and the like.

The aromatic dicarboxylic acid component that provides the aromatic dicarboxylic acid unit represented by formula (2) is not particularly limited, but is usually the aromatic dicarboxylic acid having the preferred carbon number described above or a derivative thereof. Specific examples include phthalic acid, isophthalic acid, terephthalic acid, 2,5-furandicarboxylic acid, and derivatives thereof. - Furandicarboxylic acid or derivatives thereof are further preferred.

The derivatives of aromatic dicarboxylic acids include lower alkyl esters of aromatic dicarboxylic acids having 1 to 4 carbon atoms, acid anhydrides, and the like. Specific examples of derivatives of aromatic dicarboxylic acids include lower alkyl esters such as methyl esters, ethyl esters, propyl esters and butyl esters of the above aromatic dicarboxylic acids; cyclic acid anhydrides of aromatic dicarboxylic acids; . Among them, dimethyl terephthalate is preferred.
As the polyester resin having dicarboxylic acid units, polyester resins having different amounts of dicarboxylic acid units may be used. It is also possible to adjust the ratio of dicarboxylic acid units in the polyester resin within the above range by blending with the polyester resin containing the dicarboxylic acid unit.

<Oxycarboxylic acid unit>
The polyester resin may be a resin containing oxycarboxylic acid units.
The oxycarboxylic acid unit contained in the polyester resin is preferably an aliphatic oxycarboxylic acid unit represented by the following general formula (3).
-OR ³ -CO- (3)
In formula (3), R ³ represents an aliphatic hydrocarbon group having 1 to 20 carbon atoms.

The number of carbon atoms in the aliphatic hydrocarbon group represented by R3 is preferably 16 or less ^, more preferably 12 or less, still more preferably 8 or less.

The aliphatic oxycarboxylic acid unit represented by formula (3) is not particularly limited, and examples include lactic acid units, glycolic acid units, 3-hydroxybutyric acid units, 2-hydroxy-n-butyric acid units, and 2-hydroxycaproic acid. unit, 6-hydroxycaproic acid unit, 2-hydroxy-3,3-dimethylbutyric acid unit, 2-hydroxy-3-methylbutyric acid unit, 2-hydroxyisocaproic acid unit, 3-hydroxypropionic acid unit, 4-hydroxybutyric acid , 5-hydroxyvaleric acid units, and hydroxy acid units such as 6-hydroxycaproic acid. For these aliphatic oxycarboxylic acid units, derivatives such as lower alkyl esters or intramolecular esters thereof may be used as raw materials. Moreover, when optical isomers exist in these units, they may be D-isomers or L-isomers. Preferred among these are glycolic acid units and 3-hydroxybutyric acid units.

When the polyester resin contains these aliphatic oxycarboxylic acid units, the content is preferably 20 mol% or less, more preferably 20 mol% or less, based on the total structural units constituting the polyester resin, from the viewpoint of moldability. is 10 mol % or less, more preferably 5 mol % or less. In addition, the polyester resin may not contain an aliphatic oxycarboxylic acid unit.

The oxycarboxylic acid unit contained in the polyester resin may contain an aromatic oxycarboxylic acid unit.
Specific examples of aromatic oxycarboxylic acid units include p-hydroxybenzoic acid units and p-β-hydroxyethoxybenzoic acid units. A derivative of an aromatic oxycarboxylic acid compound may be used as the raw material that provides the aromatic oxycarboxylic acid unit. It may also be a compound (oligomer) having a structure in which a plurality of aromatic oxycarboxylic acid compounds and/or aromatic oxycarboxylic acid compounds are dehydrated and condensed with each other. That is, an oligomer may be used as the raw material.

When optical isomers exist in the aromatic compound components that provide these aromatic compound units, any of the D-, L-, and racemic isomers may be used. Further, the aromatic compound component is not limited to the above examples as long as it can provide aromatic compound units.

<Trifunctional or higher units>
The polyester resin is obtained by copolymerizing a trifunctional or higher aliphatic polyhydric alcohol and a trifunctional or higher aliphatic polycarboxylic acid or its acid anhydride or a trifunctional or higher aliphatic polyhydroxycarboxylic acid component, A resin having an increased melt viscosity may be used. When these copolymer components are used, one type may be used alone, or two or more types may be used in any combination and ratio.

Specific examples of trifunctional aliphatic polyhydric alcohols include trimethylolpropane and glycerin. Specific examples of the tetrafunctional aliphatic polyhydric alcohol include pentaerythritol and the like.
Specific examples of the trifunctional aliphatic polycarboxylic acid or its acid anhydride include propanetricarboxylic acid and its acid anhydride. Specific examples of the tetrafunctional polyvalent carboxylic acid or its acid anhydride include cyclopentanetetracarboxylic acid and its acid anhydride.

In addition, the trifunctional aliphatic oxycarboxylic acid includes (i) a type having two carboxyl groups and one hydroxyl group in the same molecule, and (ii) a type having one carboxyl group and two hydroxyl groups. broadly classified into types. Any type can be used, but (i) a type having two carboxyl groups and one hydroxyl group in the same molecule, such as malic acid, is preferable from the viewpoint of moldability, mechanical strength, molded product appearance, etc. , more preferably malic acid.
In addition, the tetrafunctional aliphatic oxycarboxylic acid component has (i) a type in which three carboxyl groups and one hydroxyl group are shared in the same molecule, (ii) two carboxyl groups and two hydroxyl groups. and (iii) a type in which three hydroxyl groups and one carboxyl group are shared in the same molecule. Any type can be used, but those having a plurality of carboxyl groups are preferred, and citric acid and tartaric acid are more preferred. One of these may be used alone, or two or more of them may be used in any combination and ratio.

When the polyester resin contains structural units derived from the trifunctional or higher functional component described above, the content thereof is preferably 0.01 mol% or more as the amount contained in the total structural units constituting the polyester resin. , preferably 5 mol % or less, more preferably 2.5 mol % or less. In addition, the polyester resin does not need to contain structural units derived from the tri- or higher-functional components described above.

<Types of polyester resin>
As the polyester resin contained in the biodegradable resin composition according to the present embodiment, an aliphatic polyester resin containing an aliphatic diol unit and an aliphatic dicarboxylic acid unit as main structural units (hereinafter referred to as "aliphatic polyester resin (A )”.), an aliphatic-aromatic polyester resin (B), which is a resin in which at least part of the repeating units of the aliphatic polyester resin (A) is replaced with an aromatic compound unit, an aliphatic An aromatic polyester resin (polyarylate) (C), which is a resin in which the repeating unit of the polyester resin (A) is replaced with an aromatic compound unit, is preferable, and in terms of high biodegradability, the aliphatic polyester resin (A) is more preferred.

<Aliphatic polyester resin (A)>
As the aliphatic polyester resin (A), an aliphatic diol unit represented by the above formula (1) and an aliphatic dicarboxylic acid unit represented by the above formula (2) in which R ² is an aliphatic hydrocarbon group an aliphatic polyester resin containing; an aliphatic diol unit represented by the above formula (1) and an aliphatic dicarboxylic acid unit represented by the above formula (2) in which R ² is an aliphatic hydrocarbon group and the above An aliphatic polyester resin containing an aliphatic oxycarboxylic acid unit represented by formula (3) is preferred.
In addition, the aliphatic diol unit represented by the formula (1), the aliphatic dicarboxylic acid unit represented by the formula (2) in which R ² is an aliphatic hydrocarbon group, and the aliphatic oxy group represented by the formula (3) The carboxylic acid unit is as described above. Further, an aliphatic polyester resin preferable as the aliphatic polyester (A), the aliphatic polyester resin (A) is a trifunctional or higher aliphatic polyhydric alcohol and a trifunctional or higher aliphatic polycarboxylic acid or an acid anhydride thereof, or The case of copolymerization with a functional or higher aliphatic polyhydric oxycarboxylic acid component is also as described above.

As the aliphatic polyester resin (A), since it is highly biodegradable, polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene succinate sebacate (PBSSe), polybutylene succinatease Polybutylene succinate resins such as polybutylene succinate (PBSAz) and polybutylene brassylate terephthalate (PBSBr) are particularly preferred.

<Aliphatic-aromatic polyester resin (B)>
The aliphatic-aromatic polyester resin (B) is a resin in which at least part of the repeating units of the above-described aliphatic polyester resin (A) are replaced with aromatic compound units. As the aliphatic-aromatic polyester resin (B), the aliphatic diol unit represented by the above formula (1) and the aromatic dicarboxylic acid represented by the above formula (2) in which R ² is an aromatic group an aliphatic-aromatic polyester resin comprising units; an aliphatic diol unit represented by formula (1), an aromatic dicarboxylic acid unit represented by the above formula (2) in which R ² is an aromatic hydrocarbon group and an aliphatic-aromatic polyester resin containing an aliphatic oxycarboxylic acid unit represented by formula (3).

In addition, the aliphatic diol unit represented by the formula (1), the aromatic dicarboxylic acid unit represented by the formula (2) in which R ² is an aromatic hydrocarbon group, and the aliphatic oxy group represented by the formula (3) The carboxylic acid unit is as described above. In addition, for the aliphatic polyester preferable as the aliphatic-aromatic polyester (B), the aliphatic-aromatic polyester resin (B) is a trifunctional or higher aliphatic polyhydric alcohol and a trifunctional or higher aliphatic polyhydric carboxylic acid. It is as described above, including the case where an acid or its acid anhydride or a trifunctional or higher aliphatic polyhydric oxycarboxylic acid component is copolymerized.

The aliphatic-aromatic polyester resin (B) may contain aromatic diol units. That is, the aliphatic-aromatic polyester resin (B) comprises an aromatic diol unit and an aliphatic dicarboxylic acid unit; an aromatic diol unit, an aliphatic dicarboxylic acid unit and an aromatic dicarboxylic acid unit; an aliphatic diol unit and an aromatic It may be a polyester resin having a diol unit and an aromatic dicarboxylic acid unit; an aliphatic diol unit, an aromatic diol unit, an aliphatic dicarboxylic acid unit and an aromatic dicarboxylic acid unit. Here, specific examples of the aromatic diol component are as described above.

The aliphatic-aromatic polyester resin (B) may contain aromatic oxycarboxylic acid units. Specific examples of the aromatic oxycarboxylic acid component that provides the aromatic oxycarboxylic acid unit are as described above.

The aliphatic-aromatic polyester resin (B) preferably has an aromatic dicarboxylic acid unit as an aromatic unit, and the content of the aromatic dicarboxylic acid unit in this case is the aliphatic dicarboxylic acid unit and the aromatic It is preferably 10 mol % or more and 80 mol % or less based on the total amount of dicarboxylic acid units (100 mol %).

A terephthalic acid unit or a 2,5-furandicarboxylic acid unit is preferably used as the aromatic dicarboxylic acid unit. Specifically, the aliphatic-aromatic polyester resin (B) includes polybutylene adipate terephthalate (PBAT), polybutylene succinate terephthalate (PBST), polybutylene sebacate terephthalate (PBSeT), polybutylene azelate terephthalate ( PBAzT), polybutylene terephthalate-based resins such as polybutylene brassylate terephthalate (PBBrT), and polybutylene adipate furanoate (PBAF), polybutylene succinate furanoate (PBSF), polybutylene sebacate furanoate (PBSeF), poly Polyfurandicarboxylate resins such as butylene succinate sebacate furanoate (PBSSeF) are preferred.

As the aliphatic-aromatic polyester resin (B), resins having succinic acid units, adipic acid units and sebacic acid units as dicarboxylic acid units are preferred. Therefore, the aliphatic-aromatic polyester resin (B) includes polybutylene succinate resins such as PBST, PBSF and PBSSeF; polybutylene adibate resins such as PBAT, PBAF and PBASeF; Butylene sebacate-based resins; PBAzT (polybutylene azelate terephthalate) and PBAzF (polybutylene azelate furanoate) are preferred, and polybutylene succinate-aromatic dicarboxylic acid-based resins such as PBST, PBSF and PBSSeF are more preferred.

<Aromatic polyester resin (C)>
The aromatic polyester resin (polyarylate) (C) is a resin in which the repeating units of the above aliphatic polyester resin (A) are replaced with aromatic compound units.
As the aromatic polyester resin (C), the aromatic diol unit that may be contained in the above-mentioned aliphatic-aromatic polyester resin (B) and the above-mentioned formula (2) in which R ² is an aromatic hydrocarbon group an aromatic diol unit that may be contained in the aliphatic-aromatic polyester resin (B); R ² is an aromatic hydrocarbon group; An aromatic polyester resin containing an aromatic dicarboxylic acid unit represented by 2) and an aromatic oxycarboxylic acid unit that may be contained in the aliphatic-aromatic polyester resin (B) is preferred.

Each unit contained in the aromatic polyester resin (C) is as described above.

<Method for producing polyester resin>
As a method for producing the polyester resin, a known method for producing polyester can be adopted. Moreover, the polycondensation reaction at this time is not particularly limited, as it is possible to set appropriate conditions that have been conventionally employed. A method for producing a polyester resin containing a diol unit and a dicarboxylic acid unit will be described in detail below as an example.
For a polyester resin containing a diol unit and a dicarboxylic acid unit, a method of further increasing the degree of polymerization by carrying out an esterification reaction and then reducing the pressure is usually adopted.

When the diol component forming the diol unit and the dicarboxylic acid component forming the dicarboxylic acid unit are reacted during the production of the polyester resin, the diol component and the dicarboxylic acid are mixed so that the produced polyester resin has the desired composition. Adjust the amount of acid component used. Usually, the diol component and the dicarboxylic acid component are reacted in substantially equimolar amounts. % excess.

When the polyester resin is copolymerized with components such as oxycarboxylic acid units and polyfunctional component units, the oxycarboxylic acid units and polyfunctional component units are also mixed with corresponding compounds so as to achieve the desired composition. (monomer or oligomer) may be subjected to the reaction. At this time, there are no restrictions on the timing and method of introducing these components into the reaction system, and they are optional as long as the polyester resin can be produced.

For example, when oxycarboxylic acid is copolymerized with a polyester resin, the timing of introducing the oxycarboxylic acid component is not particularly limited as long as it is before the polycondensation reaction between the diol component and the dicarboxylic acid component, and a catalyst is added in advance. Examples include a method of mixing the catalyst in a dissolved state in an oxycarboxylic acid solution, and a method of simultaneously introducing the catalyst into the reaction system at the time of charging the raw materials and mixing the catalyst.

The timing of introduction of the compound that forms the polyfunctional component unit may be such that it is charged at the same time as other monomers or oligomers in the initial stage of polymerization, or after the transesterification reaction and before pressure reduction is started. It is preferable to charge simultaneously with the oligomer from the viewpoint of simplification of the process.

Polyester resins are usually produced in the presence of a catalyst. As the catalyst, any catalyst that can be used in the production of known polyester resins can be arbitrarily selected as long as it does not significantly impair the effects of the present invention. Metal compounds such as germanium, titanium, zirconium, hafnium, antimony, tin, magnesium, calcium, and zinc are suitable. Among them, germanium compounds and titanium compounds are preferred.

Germanium compounds that can be used as catalysts include, for example, organic germanium compounds such as tetraalkoxygermanium, and inorganic germanium compounds such as germanium oxide and germanium chloride. Among them, germanium oxide, tetraethoxygermanium, tetrabutoxygermanium, and the like are preferable in terms of price and availability, and germanium oxide is particularly preferable.

Titanium compounds that can be used as catalysts include, for example, organic titanium compounds such as tetraalkoxy titanium such as tetrapropyl titanate, tetrabutyl titanate, tetraphenyl titanate and the like. Among them, tetrapropyl titanate, tetrabutyl titanate, and the like are preferable in terms of price and availability.

In addition, other catalysts may be used in combination as long as the object of the present invention is not impaired. In addition, one type of catalyst may be used alone, or two or more types may be used together in an arbitrary combination and ratio.

The amount of the catalyst used is arbitrary as long as it does not significantly impair the effects of the present invention. % by weight or less, preferably 1.5% by weight or less. By setting the amount of the catalyst within the above range, it is possible to obtain a sufficient catalytic effect while suppressing the production cost, and to suppress the coloring of the obtained polymer or the deterioration of the hydrolysis resistance.

The introduction timing of the catalyst is not particularly limited as long as it is before the polycondensation reaction, and it may be introduced at the time of charging the raw materials or at the start of depressurization. When introducing an aliphatic oxycarboxylic acid unit, either introduce it at the same time as a monomer or oligomer forming an aliphatic oxycarboxylic acid unit such as lactic acid or glycolic acid at the time of raw material charging, or dissolve the catalyst in an aqueous aliphatic oxycarboxylic acid solution. A method of dissolving the catalyst in an aqueous aliphatic oxycarboxylic acid solution and introducing the catalyst is particularly preferable because the rate of polymerization increases.

Reaction conditions such as temperature, polymerization time, and pressure in the esterification reaction and/or transesterification reaction between the dicarboxylic acid component and the diol component are arbitrary as long as they do not significantly impair the effects of the present invention. However, the reaction temperature for the esterification reaction and/or the transesterification reaction between the dicarboxylic acid component and the diol component is usually 150°C or higher, preferably 180°C or higher, and is usually 260°C or lower, preferably 250°C. ℃ or less. Moreover, the reaction atmosphere is generally an inert atmosphere such as nitrogen or argon. The reaction pressure is usually from normal pressure to 10 kPa, with normal pressure being preferred. The reaction time is generally 1 hour or longer, and is generally 10 hours or shorter, preferably 6 hours or shorter, and more preferably 4 hours or shorter. By setting the reaction conditions within the above range, gelation due to excessive formation of unsaturated bonds can be suppressed, and the degree of polymerization can be controlled.

In addition, the pressure in the esterification reaction and/or the polycondensation reaction after the transesterification reaction between the dicarboxylic acid component and the diol component is usually 0.01×10 ³ Pa or more, preferably 0.03×10 ³ Pa or more. On the other hand, it is desirable to carry out under a degree of vacuum of usually 1.4×10 ³ Pa or less, preferably 0.4×10 ³ Pa or less. The reaction temperature at this time is generally 150° C. or higher, preferably 180° C. or higher, and is generally 260° C. or lower, preferably 250° C. or lower. The reaction time is usually 2 hours or more, and on the other hand, it is usually 15 hours or less, preferably 10 hours or less. By setting the reaction conditions within the above range, gelation due to excessive formation of unsaturated bonds can be suppressed, and the degree of polymerization can be controlled.

A chain extender such as a carbonate compound or a diisocyanate compound may be used during the production of the polyester resin. In this case, the amount of the chain extender is usually 10 mol% or less, preferably 5 mol% or less, more preferably 3 mol% or less, as a ratio of carbonate bonds or urethane bonds to all structural units constituting the polyester resin. be. From the viewpoint of biodegradability of the biodegradable resin composition according to the present embodiment, the carbonate bond is preferably less than 1 mol%, and not more than 0.5 mol%, with respect to all structural units constituting the polyester resin. It is more preferable that the content is 0.1 mol % or less. The urethane bond is preferably 0.5 mol% or less, more preferably 0.3 mol% or less, still more preferably 0.12 mol% or less, and 0.05 mol% or less. is particularly preferred. When this amount is converted to % by weight with respect to the polyester resin composition, it is preferably 0.9% by weight or less, more preferably 0.5% by weight or less, further preferably 0.2% by weight or less, and 0.1% by weight or less. is particularly preferred. In particular, by setting the amount of urethane bonds within the above range, the generation of smoke and odor caused by the decomposition of urethane bonds is suppressed in the film forming process, etc., and film breakage due to foaming in the molten film is suppressed, resulting in stable molding. can ensure the integrity of the The amount of carbonate bond or urethane bond in the polyester resin can be calculated from the results of measurement by NMR (nuclear magnetic resonance spectrometer) such as ¹ H-NMR and ¹³ C-NMR.

Specific examples of carbonate compounds as chain extenders include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, Diamyl carbonate, dicyclohexyl carbonate and the like are exemplified. In addition, carbonate compounds derived from hydroxy compounds such as phenols and alcohols can also be used.

Specific examples of diisocyanate compounds include 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, 2,4,6-triisopropylphenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, tolidine diisocyanate, etc. are exemplified by the known diisocyanates of

Other chain extenders such as dioxazolines and silicate esters may also be used.
Specific examples of silicate esters include tetramethoxysilane, dimethoxydiphenylsilane, dimethoxydimethylsilane, and diphenyldihydroxysilane.

High-molecular-weight polyester resins using these chain extenders (coupling agents) can also be produced using conventionally known techniques. After completion of the polycondensation, the chain extender is usually added to the reaction system in a uniform molten state without a solvent, and reacted with the polyester obtained by the polycondensation.

More specifically, a polyester resin having a terminal group substantially having a hydroxyl group, which is obtained by catalytically reacting a diol component and a dicarboxylic acid component, is reacted with a chain extender to obtain a polyester having a higher molecular weight. resin can be obtained. A prepolymer having a weight-average molecular weight of 20,000 or more is not affected by the residual catalyst even under severe conditions such as a molten state by using a small amount of a chain extender, so that it does not form a gel during the reaction. of polyester resin can be produced. Here, the weight-average molecular weight (Mw) of the polyester resin is obtained as a conversion value by monodisperse polystyrene from the value measured by gel permeation chromatography (GPC) at a measurement temperature of 40° C. using chloroform as a solvent.

Therefore, the weight average molecular weight of the prepolymer is preferably 20,000 or more, more preferably 40,000 or more when the polyester resin is further increased in molecular weight by using the diisocyanate compound described above as a chain extender, for example. When the weight-average molecular weight is high, the amount of the diisocyanate compound used for increasing the molecular weight is small, so the heat resistance is less likely to decrease. Thus, a polyester resin having a urethane bond having a linear structure linked via a urethane bond derived from a diisocyanate compound is produced.

The pressure during chain extension is preferably 0.01 MPa or higher, more preferably 0.05 MPa or higher, and even more preferably 0.07 MPa or higher. On the other hand, the pressure during chain extension is preferably 1 MPa or less, more preferably 0.5 MPa or less, and even more preferably 0.3 MPa or less. The pressure during chain extension is most preferably normal pressure.

The reaction temperature during chain extension is preferably 100° C. or higher, more preferably 150° C. or higher, still more preferably 190° C. or higher, and particularly preferably 200° C. or higher. On the other hand, the reaction temperature during chain extension is preferably 250° C. or lower, more preferably 240° C. or lower, and even more preferably 230° C. or lower. By setting the reaction temperature within the above range, the reaction solution can be maintained at an appropriate viscosity, so that a uniform reaction is possible, and the reaction solution can be sufficiently stirred without requiring high stirring power. Simultaneous occurrence of gelation or decomposition of the polyester resin can be suppressed.

The time for the chain extension reaction is preferably 0.1 minute or longer, more preferably 1 minute or longer, and still more preferably 5 minutes or longer. On the other hand, the chain extension reaction time is preferably 5 hours or less, more preferably 1 hour or less, still more preferably 30 minutes or less, and particularly preferably 15 minutes or less. By setting the chain extension time within the above range, the chain can be extended to a desired molecular weight, and concurrent gelation or decomposition of the polyester resin can be suppressed.

<Aliphatic oxycarboxylic acid resin (D)>
Aliphatic oxycarboxylic acid resins are also preferably used as resins contained in the biodegradable resin composition according to the present embodiment. The aliphatic oxycarboxylic acid resin (D) has aliphatic oxycarboxylic acid units as main structural units. Examples of the aliphatic oxycarboxylic acid resin (D) include aliphatic oxycarboxylic acid resins containing an aliphatic oxycarboxylic acid unit represented by the above formula (3).

In the aliphatic oxycarboxylic acid resin (D), the aliphatic oxycarboxylic acid unit and the component providing the unit are the same as the aliphatic oxycarboxylic acid unit and the aliphatic oxycarboxylic acid component in the above-described aliphatic polyester resin (A) and preferred embodiments are also the same.

Specifically, the aliphatic oxycarboxylic acid resin (D) is preferably poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) or polycaprolactone (PCL), more preferably polycaprolactone. preferable.

A urethane bond, an amide bond, a carbonate bond, an ether bond, or the like may be introduced into the aliphatic oxycarboxylic acid resin (D) as long as it does not affect biodegradability.

The method for producing the aliphatic oxycarboxylic acid resin (D) is not particularly limited, and it can be produced by a known method such as a direct polymerization method of oxycarboxylic acid or a ring-opening polymerization method of a cyclic body.

As the aliphatic oxycarboxylic acid resin (D), polyhydroxyalkanoate (E) described below is preferred.
<Polyhydroxyalkanoate (E)>
Polyhydroxyalkanoate (E) preferably used in the present embodiment has the general formula: [--CHR--CH ₂ --CO--O--] (wherein R is an alkyl group having 1 to 15 carbon atoms. ) and is a copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units as main structural units.

Polyhydroxyalkanoate (E) preferably contains 80 mol % or more, more preferably 85 mol % or more, of 3-hydroxybutyrate units as a constituent component from the viewpoint of moldability and thermal stability. Moreover, the polyhydroxyalkanoate (E) is preferably produced by microorganisms. Specific examples of polyhydroxyalkanoate (E) include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin, poly(3-hydroxybutyrate-co-3-hydroxyvalerate- co-3-hydroxyhexanoate) copolymer resin and the like.
Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin, ie, PHBH, is particularly preferred from the viewpoint of moldability and physical properties of the resulting molded product.

In the polyhydroxyalkanoate (E), 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) and comonomers such as 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH) copolymerized , that is, the molar ratio of the monomers in the copolymer resin, 3-hydroxybutyrate/comonomer is preferably 97/3 or more from the viewpoint of molding processability and molded product quality, and 95 /5 or more is more preferable, and on the other hand, it is preferably 80/20 or less, and more preferably 85/15 or less. By setting the monomer ratio within the above range, the difference between the molding processing temperature and the thermal decomposition temperature becomes large, so that molding becomes easy, and the crystallization rate falls within an appropriate range, ensuring productivity. can.

Each monomer ratio in the polyhydroxyalkanoate (E) can be measured by gas chromatography as follows.
20 mg of dried polyhydroxyalkanoate was placed in a sample container, and 2 ml of sulfuric acid/methanol mixed solution (15/85 (mass ratio)) and 2 ml of chloroform were added to the sample container, sealed, and heated at 100°C for 140 minutes. The methyl ester is obtained by decomposing the polyhydroxyalkanoate. After cooling, 1.5 g of sodium bicarbonate is added little by little to neutralize and allowed to stand until the evolution of carbon dioxide ceases. After adding 4 ml of diisopropyl ether and mixing well, the ratio of each monomer in the copolymer resin can be determined by analyzing the monomer unit composition of the sample decomposition product in the supernatant by capillary gas chromatography. can.

Polyhydroxyalkanoate (E) is, for example, Alcaligenes eutrophus AC32 strain introduced with a polyhydroxyalkanoate synthase gene derived from Aeromonas caviae into Alcaligenes eutrophus (international deposit based on the Budapest Treaty, international depositary authority: Independent Administrative Agency Industrial Technology General Institute Patent Organism Depositary Center (1-1-1 Higashi, Tsukuba, Ibaraki, Japan), original deposit date: August 12, 1996, transferred on August 7, 1997, deposit number FERM BP- 6038 (transferred from original deposit FERM P-15786)) (J. Bacteriol., 179, 4821 (1997)).

A commercial item can also be used as polyhydroxyalkanoate (E). Commercial products of polyhydroxyalkanoate (E) containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units as main structural units include Kaneka's "PHBH X331N", "PHBH X131A" and "PHBH X151A". , “PHBH 151C” and the like can be used.

In the present embodiment, the aliphatic oxycarboxylic acid resin (D), including the above-mentioned polyhydroxyalkanoate (E), is not limited to one type. Two or more kinds of aliphatic oxycarboxylic acid resins (D) can be blended and used.

As for the polyester resin contained in the biodegradable resin composition according to the present embodiment, one type may be used alone as each structural unit, or two or more types may be used in any combination and ratio. In addition, the diol unit, the dicarboxylic acid unit and the aliphatic oxycarboxylic acid unit may be derived from a compound derived from petroleum or a compound derived from a plant material. It is desirable that it is derived from a compound such as the above because it is possible to consider environmental issues.

In addition, when optical isomers are present in the aromatic compound components that provide these aromatic compound units, any of the D-, L- and racemic isomers may be used. Further, the aromatic compound component is not limited to the above examples as long as it can provide aromatic compound units. One type of the aromatic compound component may be used alone, or two or more types may be used together in any combination and ratio.

(Other resins)
The biodegradable resin composition according to this embodiment may contain resins other than the polyester resin.
Other resins are not particularly limited, and known resins can be used. For example, polyurethane resin; polyimide resin; polyacrylic resin; acrylonitrile - butadiene - styrene resin; acrylonitrile - styrene resin; polycarbonate resin; Polyolefin resins such as propylene copolymers and ethylene-butylene copolymers; polyvinyl acetate resins; polyvinyl chloride resins; polyvinylidene chloride resins; polystyrene resins; 12, nylon 610, nylon 6T, and other polyamide resins. These resins may be of one type or two or more types.

When the biodegradable resin composition according to the present embodiment contains other resins, the biodegradable resin composition is excellent in biodegradability, so it is preferable that the above-mentioned preferable resin is 5% by weight or more. , more preferably 10% by weight or more. It is preferable that the resin contained in the biodegradable resin composition according to the present embodiment is only the preferred resin described above. However, as described above, the resin contained in the biodegradable resin composition according to the present embodiment is particularly limited if the biodegradability is improved by making the resin composition with the nitrogen-containing inorganic salt described above. A resin other than the preferred resins described above may also be used.

<Physical properties of resin>
The reduced viscosity η _sp /c at 30° C. of the polyester resin may be appropriately selected according to the application, processing method, and the like. Specifically, the reduced viscosity of the resin at 30° C. is preferably 0.5 dL/g or more, more preferably 0.8 dL/g or more, and further preferably 1.0 dL/g or more. preferably 1.2 dL/g or more, particularly preferably 1.2 dL/g or more, and on the other hand, preferably 4.0 dL/g or less, more preferably 3.0 dL/g or less, and 2.5 dL/g It is more preferably 2.3 dL/g or less, particularly preferably 2.3 dL/g or less.
By setting the reduced viscosity of the polyester resin within the above range, it is possible to ensure mechanical properties when processed into a molded body, and the melt viscosity of the biodegradable resin composition during molding processing is reduced by extruder, It becomes a grade which does not put excessive load on molding machines, such as an injection machine, and can ensure productivity.

The reduced viscosity of the resin can usually be measured by the following method. First, a resin is dissolved in a solvent to prepare a resin solution having a concentration of c (g/dL). Then, using a capillary viscometer (Ubbelohde viscometer), the passage time t of the solvent and the passage time t of the resin solution were measured at a temperature of 30.0 ° C. _± 0.1 ° C., and the following formula (i) was obtained. Based on this, the relative viscosity η _rel is calculated. Then, from the relative viscosity η _rel , the specific viscosity η _sp is calculated based on the following equation (ii).
η _rel =t/t ₀ (i)
η _sp = η _rel −1 (ii)
The reduced viscosity η _sp /c can be obtained by dividing the obtained specific viscosity η _sp by the concentration c (g/dL). In general, the higher the value, the larger the molecular weight.

The molecular weight of the polyester resin is usually measured by gel permeation chromatography (GPC). From the viewpoint of moldability and mechanical strength, the resin contained in the biodegradable resin composition according to the present embodiment preferably has a weight-average molecular weight (Mw) of monodisperse polystyrene as a standard substance in the following range. . That is, the molecular weight of the polyester resin is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 30,000 or more, and particularly preferably 50,000 or more. . On the other hand, it is preferably 2,500,000 or less, more preferably 1,000,000 or less, even more preferably 800,000 or less, and particularly preferably 600,000 or less. It is preferably 500,000 or less, most preferably 400,000 or less.

In particular, the weight average molecular weight (Mw) of the polyhydroxyalkanoate resin is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 300,000 or more. . On the other hand, the weight average molecular weight (Mw) of the polyhydroxyalkanoate resin is preferably 2,500,000 or less, more preferably 2,000,000 or less, and 1,000,000 or less. is more preferable.

The melt flow rate (MFR) of a polyester resin can be evaluated based on JIS K 7210 (1999) with a value measured at 190° C. and a load of 2.16 kg. From the viewpoint of moldability and mechanical strength, the MFR of the polyester resin contained in the biodegradable resin composition according to the present embodiment is preferably within the following ranges. That is, it is preferably 0.1 g/10 minutes or more, more preferably 1 g/10 minutes or more. On the other hand, the MFR of the resin is preferably 100 g/10 min or less, more preferably 80 g/10 min or less, even more preferably 50 g/10 min or less, and 40 g/10 min or less. is particularly preferred, and 30 g/10 minutes or less is most preferred. Incidentally, the MFR of the resin can be adjusted by the molecular weight and the like.

Favorable moldability can be ensured by setting the melting point of the polyester resin within the following range. That is, the melting point of the polyester resin is preferably 50° C. or higher, more preferably 70° C. or higher, still more preferably 75° C. or higher, and particularly preferably 80° C. or higher. It is more preferably 160° C. or lower, particularly preferably 150° C. or lower, particularly preferably 140° C. or lower, and most preferably 130° C. or lower. In addition, when the polyester resin has a plurality of melting points, it is preferable that at least one melting point is within the above range.

In particular, the melting point of the polyhydroxyalkanoate resin is preferably 100° C. or higher, more preferably 110° C. or higher, and is preferably 180° C. or lower, more preferably 170° C. or lower, and particularly less than 160° C. preferable.

The tensile modulus of the polyester resin is preferably 50 MPa or more, more preferably 100 MPa or more, since good molding processability and impact strength can be secured, and on the other hand, it is preferably 2000 MPa or less. It is preferably 500 MPa or less, and more preferably 500 MPa or less. A tensile modulus can be measured by the following method.
A heat-pressed resin sheet is prepared and punched into a No. 8 dumbbell shape to prepare a test piece. Specifically, a metal frame (SUS304, outer diameter 110 mm, inner diameter 70 mm, thickness 0.2 mm) that has been subjected to surface release treatment is placed on a 150 mm × 150 mm PTFE tape, and resin is applied to the inside of this metal frame. Weigh out .6g and put a 150mm x 150mm PTFE tape on it. The resin sandwiched between the PTFE tapes is sandwiched between two iron plates (160 mm x 160 mm, thickness 3 mm), and then hot pressed using a hot press, followed by cold pressing using a cooling press. to obtain a heat-pressed sheet of 70 mm×70 mm×0.2 mm in thickness. The hot-pressing temperature is 180° C., and the hot-pressing time is 2 minutes for preheating and 2 minutes for pressing. The cooling press temperature is 20° C., and the cooling press time is 2 minutes. This hot-pressed sheet is uniaxially stretched at a rate of 50 mm/min, and the initial gradient of the resulting stress-strain curve is determined as the tensile modulus.
The method for adjusting the melting point and tensile modulus of the polyester resin is not particularly limited. It can be adjusted by the type of copolymerization component, the copolymerization ratio thereof, and the like.

The molecular chains of the resin tend to move when the temperature is higher than the glass transition temperature. Therefore, when biodegrading resin, the glass transition temperature is lower than the temperature of the environment in which the resin is placed, such as in the ocean. It is thought that biodegradation progresses easily. Therefore, it is presumed that resins with a low glass transition temperature are easily biodegraded. In particular, when the glass transition temperature of the resin is 40° C. or less, it is considered that the resin is more likely to be biodegraded by nitrogen-containing inorganic salts in seawater. Accordingly, the glass transition temperature (Tg) of the polyester resin is preferably 40° C. or lower, more preferably 30° C. or lower, still more preferably 25° C. or lower, and particularly preferably 20° C. or lower. In addition, the measurement of the glass transition temperature can be performed by the following method.
10 mg of resin is placed in an aluminum sample container to obtain a measurement sample. Next, using a DSC, the temperature is raised at a rate of 10° C./min under a nitrogen atmosphere to obtain a DSC chart. The glass transition temperature is obtained from the baseline shift existing on the lower temperature side than the peak indicating the melting point in this chart. Specifically, the intersection point of the baseline on the low temperature side and the contact point of the inflection point is taken as the glass transition temperature.

The acid value of the polyester resin is preferably low from the viewpoint of less hydrolysis and excellent storage stability. Therefore, specifically, it is preferably 250 eq/t or less, more preferably 150 eq/t or less, even more preferably 100 eq/t or less, and particularly preferably 50 eq/t or less. Incidentally, the acid value can be measured by the following method.
0.4 g of resin is precisely weighed, 25 mL of benzyl alcohol is added thereto, and dissolved by heating to 195° C. and stirring. Once the resin has dissolved, the vessel containing the resin solution is cooled in an ice bath and 2 mL of ethanol is added to the vessel. Titration is performed using a 0.01N sodium hydroxide benzyl alcohol solution (the titration amount is A (ml)).
Next, the same measurement was performed using only benzyl alcohol, and this was taken as a blank value (B (ml)). Acid value is calculated from the following formula.
Terminal acid value (μeq/g) = (AB) x F x 10/W
A (ml): measured titer B (ml): blank titer F: 0.01N NaOH benzyl alcohol your period factor W (g): sample weight

[Other ingredients]
The biodegradable resin composition according to the present embodiment contains a filler (filler), a plasticizer, an antistatic agent, an antioxidant, a light stabilizer, an ultraviolet absorber, as long as the effects of the present invention are not significantly impaired. Dyes, pigments, hydrolysis inhibitors, crystal nucleating agents, anti-blocking agents, weathering agents, heat stabilizers, flame retardants, release agents, anti-fogging agents, surface wetting agents, combustion aids, dispersing aids, various interfaces Other ingredients such as various additives such as activators, slip agents, freshness-keeping agents, and antibacterial agents may also be included. When these components are included, the component may include only one type or two or more types.

When the biodegradable resin composition contains other components, the content is 40% by weight or less with respect to the total amount of the biodegradable resin composition, from the viewpoint of not impairing the properties of the biodegradable resin composition. It is preferably 20% by weight or less, more preferably 10% by weight or less, and particularly preferably 5% by weight or less. In addition, the lower limit of the content of other components is not particularly limited.

[Method for producing biodegradable resin composition]
The method for producing the biodegradable resin composition according to this embodiment is not particularly limited. The biodegradable resin composition according to this embodiment is obtained by blending a polyester resin, a nitrogen-containing inorganic salt, and, if necessary, other resins and other components. For the production of a biodegradable resin composition, for example, each component is blended in a predetermined ratio at the same time or in an arbitrary order, and mixed with a tumbler, a V-type blender, a Nauta mixer, a Banbury mixer, a kneading roll, an extruder, etc. It can be carried out by mixing or kneading with a machine, preferably by melt-kneading. Alternatively, it can also be produced by dissolving or dispersing the polyester resin and the nitrogen-containing inorganic salt in a solvent and removing the solvent.

From the viewpoint of improving the biodegradability and biodegradation rate of the biodegradable resin composition, particularly the initial biodegradation rate, it is preferable that the nitrogen-containing inorganic salt is uniformly dispersed in the biodegradable resin composition. Therefore, the biodegradable resin composition is preferably produced by kneading, and more preferably produced by melt kneading.

The kneader used for kneading may be a melt kneader. The extruder may be either a twin-screw extruder or a single-screw extruder, but a twin-screw extruder is more preferred.

When melt kneading is performed, the melt kneading temperature is preferably 80° C. or higher, more preferably 100° C. or higher, and is preferably 220° C. or lower, more preferably 210° C. or lower. Within this temperature range, melt-kneading can be performed in a short time, resin deterioration and deterioration of color tone are unlikely to occur, and the resin has better practical physical properties such as impact resistance and moist heat resistance. It tends to be a composition.
The melt-kneading time is not particularly limited as long as the nitrogen-containing inorganic salt can be uniformly dispersed in the biodegradable resin. Specifically, the melt-kneading time is preferably 10 seconds or longer, more preferably 30 seconds or longer, and is preferably 20 minutes or shorter, more preferably 15 minutes or shorter.

[Biodegradability of biodegradable resin composition]
The biodegradable resin composition according to this embodiment has biodegradability. It is particularly preferable that the resin composition of the present invention has biodegradability in seawater where the resin is considered to be difficult to biodegrade (marine biodegradable resin composition). The reason why the resin composition of the present invention exhibits biodegradability even in seawater is presumed as follows. In seawater, the amount and types of microorganisms are usually small. For this reason, it is presumed that the formation of biofilms is important for biodegradation in seawater because fungi and the like are difficult to propagate in seawater. Furthermore, seawater is in an environment lacking in nitrogen, which is an essential element for life support. Therefore, it is speculated that the presence of nitrogen-containing inorganic salts promotes cell growth and activation of microorganisms in seawater, promotes biofilm formation, and promotes biodegradability.
As used herein, biodegradability is calculated as the ratio of biological oxygen demand (BOD) to theoretical oxygen demand (ThOD).
For example, biodegradation in seawater is measured in accordance with ISO 14851:1999 (Plastics - Determination of ultimate aerobic biodegradation in aqueous culture medium - Method by measuring the amount of carbon dioxide generated); Concerning biodegradation in soil, comply with ISO 17556:2003 (Plastics - Determination of ultimate aerobic biodegradation in soil by measuring oxygen consumption or carbon dioxide generated using a respirometer). measured.

The biodegradable resin composition according to the present embodiment has a biodegradability at any time after the start of the biodegradability test, which is a composition obtained by removing the nitrogen-containing inorganic salt from the biodegradable resin composition according to the present embodiment. (hereinafter sometimes referred to as the “reference composition”) preferably exceeds 1.0 times the biodegradability of the substance (hereinafter, the rate of increase in biodegradability with respect to the biodegradability of the reference composition is sometimes referred to as "resolution improvement"). Specifically, on the 28th day after the start of the biodegradability test based on the above standards, the biodegradation improvement degree of the biodegradable resin composition according to the present embodiment is more preferably 1.1 times or more. , more preferably 1.2 times or more, particularly preferably 2.0 times or more, and most preferably 2.5 times or more.
In the present specification, the high degree of biodegradation means that the degree of improvement in biodegradation of the biodegradable resin composition at an arbitrary point after the start of the biodegradability test is the above-mentioned preferable degree of improvement.

[Biodegradation method of polyester resin]
As described above, the nitrogen-containing inorganic salt can promote the biodegradation of the polyester resin, so the biodegradable resin composition according to the present embodiment can be applied to the biodegradation method of the polyester resin. In addition, the biodegradable resin composition according to the present embodiment can be applied to a method for biodegrading a polyester resin because it can promote the biodegradation of the polyester resin in seawater. That is, it can be applied to a method of biodegrading a polyester resin in seawater in the presence of a nitrogen-containing inorganic salt. Here, polyester resins, nitrogen-containing inorganic salts and the like suitable for this method are as described above.

[Molded body]
The biodegradable resin composition according to this embodiment can be molded by various molding methods applied to general-purpose plastics. Examples of molding methods include compression molding (compression molding, laminate molding, stampable molding), injection molding, extrusion molding, co-extrusion molding (film molding by inflation method or T-die method, laminate molding, pipe molding, wire/cable molding , profiled material molding), hot press molding, blow molding (various blow molding), calendar molding, solid molding (uniaxial stretching molding, biaxial stretching molding, roll rolling molding, stretch orientation non-woven fabric molding), thermoforming (vacuum molding, pneumatic molding), plastic working, powder molding (rotational molding), various non-woven fabric moldings (dry method, adhesion method, entanglement method, spunbond method, etc.), and the like. Among them, injection molding, extrusion molding, compression molding or hot press molding is preferably applied, and injection molding or extrusion molding is more preferably applied. As specific shapes, application to sheets, films, and containers is preferred.

In addition, the molded body obtained by molding the biodegradable resin composition according to the present embodiment has a chemical function, an electrical function, a magnetic function, a mechanical function, a friction/wear/lubricating function, an optical function, For the purpose of imparting surface functions such as thermal functions and biocompatibility, it is also possible to apply various types of secondary processing. Examples of secondary processing include embossing, painting, adhesion, printing, metallizing (plating, etc.), machining, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.).

[Use]
The biodegradable resin composition according to the present embodiment can be used in a wide range of applications such as packaging materials for packaging liquids such as various foods, medicines, miscellaneous goods, powders and solids, agricultural materials, and construction materials. It is preferably used. Specific applications include injection molded products (e.g., fresh food trays, fast food containers, coffee capsule containers, cutlery, outdoor leisure products, etc.), extrusion molded products (e.g., films, sheets, fishing lines, fishing nets, vegetation). nets, secondary processing sheets, water-retaining sheets, etc.), hollow moldings (bottles, etc.), and the like. In addition, other agricultural films, coating materials, fertilizer coating materials, nursery pots, laminated films, boards, stretched sheets, monofilaments, nonwoven fabrics, flat yarns, staples, crimped fibers, creased tapes, split yarns, composite fibers, Blown bottles, shopping bags, garbage bags, compost bags, cosmetic containers, detergent containers, bleach containers, ropes, binding materials, sanitary coverstock materials, cooler boxes, cushioning films, multifilament, synthetic paper, medical surgeries Threads, sutures, artificial bones, artificial skins, DDS such as microcapsules, wound dressings, and the like. The molded article is particularly suitable as food packaging films, fresh food trays, fast food containers, lunch boxes, and other food containers.

EXAMPLES The content of the present invention will be more specifically described below using examples and comparative examples. The present invention is not limited by the following examples as long as the gist thereof is not exceeded. Various production conditions or values of evaluation results in the following examples have meanings as preferred values of the upper limit or lower limit in the embodiments of the present invention, and the preferred range is the above-mentioned upper limit or lower limit value, and the following It may be a range defined by the value of the example or a combination of the values of the examples.

<Synthesis of Resin>
(Synthesis of PBSSe)
1,4-butanediol (100.1 g), succinic acid (75.0 g), sebacic acid (32.1 g), trimethylolpropane (0.34 g) and titanium tetrabutoxide (0.50 g) under nitrogen. It was heated with stirring at 200° C. for 2 hours. Subsequently, the temperature was raised to 250° C. while reducing the pressure, and the polymer obtained by reacting for 5 hours and 15 minutes was drawn out into water in the form of strands and cut to obtain pellets of PBSSe.
The molar ratio of succinic acid-derived units/sebacic acid-derived units of PBSSe determined by ¹ H-NMR (nuclear magnetic resonance spectroscopy) was 80/20. PBSSe had a reduced viscosity of 1.8 dL/g, a glass transition temperature of −50° C., a tensile modulus of elasticity of 280 MPa, and an acid value of 28 μeq/g, which were measured according to the following measurement method.

<Nitrogen-containing inorganic salt>
The following nitrogen-containing inorganic salts were used.
Ammonium chloride (molecular weight 53.49)
Ammonium carbonate (molecular weight 96.09)
Magnesium nitrate hexahydrate (molecular weight 256.41)
Sodium nitrite (molecular weight 69.00)

<Other compounds>
The following compounds were used as other compounds.
Sodium dihydrogen pyrophosphate (molecular weight 221.94)
Boron nitride (molecular weight 24.82)

<Method for measuring reduced viscosity>
A resin solution was prepared by dissolving a resin in a 1:1 (weight ratio) mixed solvent of phenol and tetrachloroethane so as to have a concentration of 0.5 g/dL. Then, using an Ubbelohde viscosity tube, the solution viscosity of the resin solution at 30° C. was measured, and the reduced viscosity was calculated based on the result.

<Method for measuring glass transition temperature>
10 mg of each resin was placed in an aluminum sample container to prepare a measurement sample. Then, using "DSC6220" manufactured by Hitachi High-Tech Science Co., Ltd., the temperature was raised from -100°C to 160°C at a rate of 10°C/min under a nitrogen atmosphere to obtain a DSC chart. The glass transition temperature was obtained from the baseline shift present on the lower temperature side than the peak indicating the melting point in this chart. Specifically, the intersection point of the base line on the low temperature side and the point of contact of the inflection point was taken as the glass transition temperature.

<Method for measuring tensile modulus>
A heat-pressed resin sheet was prepared and punched into a No. 8 dumbbell shape to prepare a test piece. Specifically, a metal frame (SUS304, outer diameter 110 mm, inner diameter 70 mm, thickness 0.2 mm) was placed, 1.6 g of each resin was measured inside the metal frame, and a 150 mm×150 mm PTFE tape was further placed thereon. With each resin sandwiched by this PTFE tape sandwiched between two iron plates (160 mm × 160 mm, thickness 3 mm), a heat press ("IMC-180C type" manufactured by Imoto Seisakusho Co., Ltd.) was used. It was hot-pressed and then cold-pressed using a cooling press (“IMC-181B type” manufactured by Imoto Seisakusho Co., Ltd.) to obtain a hot-pressed sheet of 70 mm×70 mm×thickness 0.2 mm. The hot-pressing temperature was 180° C., and the hot-pressing time was 2 minutes for preheating and 2 minutes for pressing. The cooling press temperature was 20° C., and the cooling press time was 2 minutes. This hot-pressed sheet was uniaxially stretched at a speed of 50 mm/min using "STB-1225L" manufactured by Orientec Co., Ltd., and the initial gradient of the resulting stress-strain curve was determined as the tensile modulus.

<Method for measuring acid value>
0.4 g of resin was precisely weighed, 25 mL of benzyl alcohol was added thereto, and dissolved by heating to 195° C. and stirring. Once the resin was dissolved, the vessel containing the resin solution was cooled in an ice bath and 2 mL of ethanol was added to the vessel. Titration was performed using a 0.01 N sodium hydroxide benzyl alcohol solution using an automatic low-pressure device "GT100" manufactured by Mitsubishi Chemical Corporation (the titration amount is A (ml)).
Next, the same measurement was performed using only benzyl alcohol, and this was taken as a blank value (B (ml)). Acid value was calculated from the following formula.
Terminal acid value (μeq/g) = (AB) x F x 10/W
A (ml): measured titer B (ml): blank titer F: 0.01N NaOH benzyl alcohol your period factor W (g): sample weight

<Examples 1 to 4, Comparative Examples 1 to 3>
A pulverized resin was obtained by pulverizing PBSSe so that the particle size (by sieving method) was 250 μm or less (Comparative Example 1). The pulverized resin and the nitrogen-containing inorganic salt or other compound were mixed at the ratio shown in Table 1 so that the total amount was 30 mg (Examples 1 to 4, Comparative Examples 1 to 3).

<Biodegradability test>
The biodegradability of the resins or resin compositions of Examples 1-4 and Comparative Examples 1-3 was measured according to ISO 14851 as follows.
To a 510 mL amber bottle containing 30 mg of the sample was added 100 mL of a mixture of standard test culture medium and seawater prepared according to ISO 14851. Attach a pressure sensor (manufactured by WTW, OxiTop (registered trademark)-C type) to a brown bottle, stir the test solution with a stirrer for 28 days in a constant temperature environment of 25 ° C., and measure biodegradation (%) based on BOD measurement. was calculated. Table 1 shows the results.

<Example 5>
PBSSe and ammonium chloride were mixed at a ratio of 95:5 (parts by mass) and pressed at 180° C. for 3 minutes to prepare a film.

A comparison between Examples 1 to 4 and Comparative Examples 1 to 3 proves that the nitrogen-containing inorganic salt significantly improves the biodegradability of the polyester resin. Since the sodium dihydrogen pyrophosphate of Comparative Example 2 does not contain a nitrogen atom, no effect was obtained. Since the boron nitride of Comparative Example 3 is not an inorganic salt, it is presumed that no nitrogen-containing ions were generated in seawater and that it did not promote biodegradation.

Claims (9)

A biodegradable resin composition comprising a polyester resin and a nitrogen-containing inorganic salt, wherein the content of the nitrogen-containing inorganic salt is 0.01% by weight or more and 30% by weight or less. 2. The biodegradable resin composition according to claim 1, wherein said nitrogen-containing inorganic salt contains at least one of ammonium salt, nitrate and nitrite. The biodegradable resin composition according to claim 1 or 2, wherein the polyester resin has a glass transition temperature of 40°C or lower. The biodegradable resin composition according to any one of claims 1 to 3, wherein the polyester resin has a dicarboxylic acid unit having 4 to 22 carbon atoms. The biodegradable resin composition according to any one of claims 1 to 4, wherein the polyester resin has two or more dicarboxylic units. The biodegradable resin composition according to any one of claims 1 to 5, wherein the polyester resin has a linear aliphatic diol unit having 4 to 10 carbon atoms. The biodegradable resin composition according to any one of claims 1 to 6, wherein the polyester resin is an aliphatic polyester resin. A molded article comprising the biodegradable resin composition according to any one of claims 1 to 7. A method for biodegrading a polyester resin, comprising biodegrading a polyester resin having a glass transition temperature of 40° C. or lower in seawater in the presence of a nitrogen-containing inorganic salt.