Marine biodegradable polymer blend

Abstract

The purpose of the present invention is to provide a polymer blend exhibiting excellent marine biodegradability even when containing a biodegradable resin having poor biodegradability in a marine environment. The present invention provides a marine biodegradable polymer blend comprising: a polyester-based polymer A having a structural unit (A) derived from a succinic acid, a structural unit (B) derived from a C7 or higher dicarboxylic acid, and a structural unit (C) derived from an aliphatic diol; and a biodegradable polymer B, wherein the polyester-based polymer A and the biodegradable polymer B are in a compatible or incompatible state.

Description

Marine biodegradable polymer blend

[0001] The present invention relates to marine biodegradable polymer blends.

[0002] Plastics are highly durable and used in a wide range of fields, but because they are difficult to decompose in the natural environment, environmental pollution caused by plastic waste has become a problem. To reduce the environmental impact of plastic waste, efforts have been made to develop biodegradable plastics that are ultimately decomposed into water and carbon dioxide by the action of microorganisms, and known examples include polylactic acid (PLA), polybutylene succinate (PBS), and polyethylene succinate (PES). However, as described in Non-Patent Document 1, while polyethylene succinate and polybutylene succinate are decomposed by microorganisms in the soil, only about 2-3% of them are biodegraded when they are discharged into the ocean, and marine pollution caused by biodegradable plastic waste discharged into the ocean has become a problem.

[0003] In recent years, research has been conducted into plastics that are highly biodegradable in the ocean (hereinafter referred to as "marine biodegradable plastics" or "marine biodegradable resins"). For example, Patent Document 1 discloses a biodegradable resin composition that has excellent biodegradability and moldability in the ocean by blending a specific amount of protein with a specific polyester resin. However, no means have yet been shown to solve the problem of marine pollution caused by biodegradable plastics that have low biodegradability in the ocean, such as polylactic acid (PLA), polybutylene succinate (PBS), and polyethylene succinate (PES).

[0004] International Publication No. 2021 / 241712 Pamphlet

[0005] Ken-ichi Kasuya et al., “Biodegradabilities of various aliphatic polyesters in natural waters”, Elsevier Science Limited, Polymer Degradation and Stability. 59 (1998) 327-332

[0006] The present invention has been made in light of the above-mentioned circumstances, and aims to provide a polyester-based polymer blend that exhibits excellent marine biodegradability even when it contains biodegradable polymers that have poor biodegradability in marine environments, such as polylactic acid (PLA), polybutylene succinate (PBS), and polyethylene succinate (PES).

[0007] The marine biodegradable polymer blend of the present invention, which has solved the above-mentioned problems, has the following configuration: [1] A marine biodegradable polymer blend comprising: a polyester polymer A having a structural unit (A) derived from succinic acid, a structural unit (B) derived from a dicarboxylic acid having 7 or more carbon atoms, and a structural unit (C) derived from an aliphatic diol; and a biodegradable polymer B, wherein the polyester polymer A and the biodegradable polymer B are in a compatible or incompatible state.

[0008] [2] The marine biodegradable polymer blend according to [1], wherein the polyester polymer A further contains a structural unit (D) derived from an amino acid.

[0009] [3] The marine biodegradable polymer blend according to [1] or [2], wherein the dicarboxylic acid having 7 or more carbon atoms is at least one selected from the group consisting of suberic acid, sebacic acid, and dodecanedioic acid.

[0010] [4] The marine biodegradable polymer blend according to any one of [1] to [3], wherein the aliphatic diol is at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.

[0011] [5] The marine biodegradable polymer blend according to any one of [1] to [4], wherein the molar ratio [(C-1) / (C)] of the ethylene glycol-derived structural unit (C-1) among the aliphatic diol units (C) is 90 / 100 or more.

[0012] [6] The marine biodegradable polymer blend according to any one of [1] to [5], wherein the amino acid is an α-amino acid.

[0013] [7] The marine biodegradable polymer blend according to any one of [2] to [6], wherein the molar ratio of the amino acid unit (D) to the sum of the succinic acid unit (A) and the dicarboxylic acid (B) having 7 or more carbon atoms [(D) / ((A)+(B))] is 1 / 100 to 90 / 100.

[0014] [8] The marine biodegradable polymer blend according to any one of [1] to [7], wherein the total amount of the succinic acid-derived structural unit (A) and the dicarboxylic acid unit (B) having 7 or more carbon atoms is 80 parts by mass or more per 100 parts by mass of dicarboxylic acid units contained in the polyester polymer A.

[0015] [9] The marine biodegradable polymer blend according to any one of [1] to [7], wherein in the polyester polymer A, the molar ratio of the structural unit (B) derived from a dicarboxylic acid having 7 or more carbon atoms [(B) / polyester polymer A] is 2 / 100 to 50 / 100.

[0016]

[10] The marine biodegradable polymer blend according to any one of [1] to [9], wherein the biodegradable polymer B is at least one selected from the group consisting of polylactic acid, polyglycolic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, polyhydroxyalkanoic acid, cellulose, hemicellulose, and cellulose acetate.

[0017]

[11] The marine biodegradable polymer blend according to any one of [1] to [9], wherein the biodegradable polymer B is at least one selected from the group consisting of polylactic acid, polyglycolic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, polyhydroxyalkanoic acid, and cellulose acetate.

[0018]

[12] The marine biodegradable polymer blend according to any one of [1] to

[11] , wherein the mass ratio (A / B) of the polyester polymer A to the biodegradable polymer B is 10 / 90 to 90 / 10.

[0019]

[13] The marine biodegradable polymer blend according to any one of [1] to

[12] , wherein the total amount of the succinic acid units (A), the dicarboxylic acid (B) having 7 or more carbon atoms, and the aliphatic diol units (C) is 90% by mass or more in 100% by mass of the polyester polymer A.

[0020]

[14] The marine biodegradable polymer blend according to any one of [1] to

[13] , wherein the total amount of the succinic acid units (A), the dicarboxylic acid (B) having 7 or more carbon atoms, the aliphatic diol units (C), and the amino acid units (D) is 90% by mass or more in 100% by mass of the polyester polymer A.

[0021]

[15] The marine biodegradable polymer blend according to any one of [1] to

[14] , wherein the incompatible state is a phase-separated state in which, when observed under an atomic force microscope, the polyester polymer A and the biodegradable polymer B form one of a sea-island structure, a striped structure, a fibrous structure, a co-continuous structure, or a composite structure thereof.

[0022]

[16] A composition comprising the marine biodegradable polymer blend according to any one of [1] to

[15] .

[0023] According to the present invention, it is possible to provide a polymer blend that exhibits excellent marine biodegradability even when it contains biodegradable polymers that have poor biodegradability in marine environments, such as polylactic acid (PLA), polybutylene succinate (PBS), and polyethylene succinate (PES).

[0024] Figure 1 is an AFM image (5 μm square) of Example 7 (island structure). Figure 2 is an AFM image (5 μm square) of Example 9 (striped structure). Figure 3 is an AFM image (5 μm square) of Example 15 (miscible). Figure 4 is an AFM image (5 μm square) of Example 16 (irregular).

[0025] As a result of extensive research, the present inventors have found that in a polymer blend containing a polyester polymer A obtained by copolymerizing succinic acid, an aliphatic diol, and a dicarboxylic acid having 7 or more carbon atoms, and a biodegradable polymer B having low marine biodegradability, not only the polyester polymer A but also the biodegradable polymer B are biodegraded in a marine environment when the polyester polymer A and the biodegradable polymer B are in a compatible or imcompatible state, and as a result, the marine biodegradability of the polymer blend is significantly improved, thereby completing the present invention.

[0026] The marine biodegradable polymer blend of the present invention comprises a polyester polymer A having excellent marine biodegradability and a biodegradable polymer B (hereinafter sometimes referred to as biodegradable polymer B) having poor marine biodegradability, and the polyester polymer A is composed of dicarboxylic acid units and structural units derived from an aliphatic diol (hereinafter sometimes referred to as aliphatic diol units (C)). The dicarboxylic acid units include structural units derived from succinic acid (hereinafter sometimes referred to as succinic acid units (A)) and structural units derived from dicarboxylic acids having 7 or more carbon atoms (hereinafter sometimes referred to as dicarboxylic acid units (B) having 7 or more carbon atoms). In the present invention, biodegradability refers to the property of ultimately being decomposed into water and carbon dioxide by the action of microorganisms or the like.

[0027] The polyester polymer A and biodegradable polymer B constituting the marine biodegradable polymer blend of the present invention are in a compatible or incompatible state. Simply mixing polyester polymer A and biodegradable polymer B did not improve the marine biodegradability of biodegradable polymer B, but a compatible or incompatible polymer blend exhibits excellent marine biodegradability. A compatible polymer blend means that polyester polymer A and biodegradable polymer B are compatible to form a single phase, and no clear interface due to the multi-component system is observed in AFM observation. A non-compatible polymer blend means a resin mixture having a phase-separated structure in which polyester polymer A and biodegradable polymer B are dispersed and mixed as fine domains. Preferably, the phase-separated state forms one of a sea-island structure, a striped structure, a fibrous structure, a cocontinuous structure, or a composite structure thereof, as observed with AFM (atomic force microscopy) as described in the examples. In the sea-island structure, either the polyester polymer A or the biodegradable polymer B may be the islands, and more preferably, the island size is 10 μm or less. In the striped structure, the stripe spacing is, for example, 5 μm or less. The fibrous structure is a structure in which one of the polymers has a fibrous structure and the other resin is present between the fibers, with the fiber spacing being, for example, 5 μm or less. The co-continuous structure is a structure in which the phase-separated polyester polymer A and biodegradable polymer B constitute a continuous phase, with the spacing between the polyester polymer A and the biodegradable polymer B being, for example, 5 μm or less. These composite structures refer to any combination of two or more structures. Composite structures also include irregular structures. In the above-mentioned immiscible state, the smaller the polyester polymer A and / or biodegradable polymer B, the greater the contact area between the polyester polymer A and the biodegradable polymer B, which is effective in improving marine biodegradability.

[0028] The structure of the polyester polymer A constituting the marine biodegradable polymer blend of the present invention will be described below. [Polyester polymer A] The polyester polymer A of the present invention is specifically a polyester polymer A1 in which a dicarboxylic acid unit (B) having 7 or more carbon atoms is incorporated into a polyester skeleton consisting of succinic acid units (A) and aliphatic diol units (C); or a polyester polymer A2 which, in addition to the units (A) to (C), contains a structural unit derived from an amino acid (hereinafter, referred to as amino acid unit (D)).

[0029] [Polyester-based polymer A1] <Dicarboxylic acid unit> The dicarboxylic acid unit contains a succinic acid unit (A) and a dicarboxylic acid unit (B) having 7 or more carbon atoms. Succinic acid unit (A) The succinic acid unit (A) forms a polyalkylene succinate skeleton together with the aliphatic diol unit (C), and exhibits biodegradability. From the viewpoint of exhibiting excellent marine biodegradability while maintaining sufficient durability, the molar ratio of the succinic acid units (A) [(A) / [(A)+(C)]] in the total [(A)+(C)] of the succinic acid units (A) and the aliphatic diol units (C) contained in the polyester polymer A1 (the molar ratio of the units (A) when the total of the units (A) and (C) in the polymer is taken as 100 moles) is preferably 2.5 / 100 or more, more preferably 5 / 100 or more, even more preferably 7.5 / 100 or more, and is preferably 97.5 / 100 or less, more preferably 95 / 100 or less, even more preferably 92.5 / 100 or less.

[0030] Dicarboxylic acid unit (B) having 7 or more carbon atoms The presence of the dicarboxylic acid unit (B) having 7 or more carbon atoms reduces the degree of crystallinity and increases the amorphous phase, thereby promoting biodegradation in seawater. The number of carbon atoms in the dicarboxylic acid unit (B) having 7 or more carbon atoms is preferably 8 or more and 12 or less. The dicarboxylic acid having 7 or more carbon atoms is preferably an aliphatic dicarboxylic acid (including saturated and unsaturated), more preferably a chain aliphatic dicarboxylic acid. Specifically, suberic acid, sebacic acid, and dodecanedioic acid are preferred. The dicarboxylic acid having 7 or more carbon atoms may be used alone or in combination of two or more.

[0031] In the polyester polymer A1, the dicarboxylic acid units (B) having 7 or more carbon atoms may be introduced randomly, or may be introduced in a block, alternating, graft, etc. It is preferable that the dicarboxylic acid units (B) having 7 or more carbon atoms are introduced randomly, as this improves marine biodegradability.

[0032] The more dicarboxylic acid units (B) having 7 or more carbon atoms there are, the more improved the marine biodegradability becomes. However, if there are too many, the strength of the marine biodegradable polymer blend decreases, and molding processability may not be maintained.

[0033] When the total amount of dicarboxylic acid units contained in the polyester polymer A1 is taken as 100 parts by mass, the total amount of the succinic acid units (A) and the dicarboxylic acid units (B) having 7 or more carbon atoms is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and even more preferably 100 parts by mass. The larger the amount of the succinic acid units (A) and the dicarboxylic acid units (B) having 7 or more carbon atoms, the better the marine biodegradability.

[0034] From the viewpoint of improving biodegradability, the molar ratio of the dicarboxylic acid units (B) having 7 or more carbon atoms, [(B) / [(A)+(B)]], of the total of the succinic acid units (A) and the dicarboxylic acid units (B) having 7 or more carbon atoms contained in the polyester polymer A1, is preferably 5 / 100 or more, more preferably 10 / 100 or more, even more preferably 15 / 100 or more, and is preferably 95 / 100 or less, more preferably 90 / 100 or less, even more preferably 85 / 100 or less.

[0035] From the viewpoint of improving productivity, the molar ratio of the structural unit (B) derived from a dicarboxylic acid having 7 or more carbon atoms in the polyester polymer A [(B) / polyester polymer A] is preferably 2 / 100 to 50 / 100, more preferably 5 / 100 to 45 / 100, and even more preferably 10 / 100 to 40 / 100.

[0036] The remainder of 100 parts by mass of dicarboxylic acid units contained in polyester polymer A1 may be dicarboxylic acid units other than succinic acid units (A) and dicarboxylic acid units (B) having 7 or more carbon atoms (hereinafter, sometimes referred to as other dicarboxylic acid units (E)). Examples of other dicarboxylic acid units (E) include structural units derived from chain aliphatic dicarboxylic acids such as oxalic acid, malonic acid, and glutaric acid, structural units derived from cyclic aliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid, and structural units derived from aromatic dicarboxylic acids such as terephthalic acid and furandicarboxylic acid. Preferably, the other dicarboxylic acid units contain structural units derived from aliphatic dicarboxylic acids, more preferably structural units derived from chain aliphatic dicarboxylic acids.

[0037] <Diol Units> Aliphatic Diol Units (C) The aliphatic diol is preferably an aliphatic diol having 4 or less carbon atoms, more preferably 3 or less carbon atoms, and even more preferably 2 carbon atoms. Preferably, it is at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol (hereinafter, sometimes referred to as ethylene glycol / 1,3-propanediol / 1,4-butanediol), and even more preferably ethylene glycol. Of the aliphatic diol units (C), the molar ratio of the ethylene glycol-derived structural unit (C-1) [(C-1) / (C)] is preferably 90 / 100 or more, more preferably 95 / 100 or more, and even more preferably 100 / 100. When the total amount of diol units contained in the polyester polymer A1 is taken as 100 parts by mass, the amount of structural units derived from aliphatic diol units (C), preferably ethylene glycol / 1,3-propanediol / 1,4-butanediol (total amount when used in combination), is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 100 parts by mass. The more structural units derived from ethylene glycol / 1,3-propanediol / 1,4-butanediol, preferably ethylene glycol, the better the marine biodegradability.

[0038] The polyester polymer A1 of the present invention may contain other diol units (hereinafter referred to as other diol units (F)) other than those mentioned above as the remainder of 100 parts by mass of the aliphatic diol units (C). Examples of the other diol units (F) include structural units derived from diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-propanediol, and hexanediol.

[0039] In the polyester polymer A1, the amount of the diol units is substantially balanced with the amount of the dicarboxylic acid units, and is, for example, 70 to 130 mol %, preferably 80 to 120 mol %, and more preferably 90 to 110 mol %, assuming that the total amount of the dicarboxylic acid units is 100 mol %.

[0040] Furthermore, in the polyester polymer A1 (100% by mass), the total proportion of the dicarboxylic acid units of the present invention (i.e., succinic acid units (A) and dicarboxylic acid units (B) having 7 or more carbon atoms) and the aliphatic diol units (C) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass. Other structural units (G) may be contained as the remainder. Examples of other units (G) include, but are not limited to, the other dicarboxylic acid units (E) and other diol units (F), as well as structural units derived from trivalent or higher carboxylic acids (e.g., aconitic acid) and trivalent or higher alcohols (e.g., glycerin). The higher the proportion of the units (A) to (C) relative to the other units (G), the better the marine biodegradability obtained.

[0041] [Polyester Polymer A2] In a preferred embodiment, the polyester polymer A further contains an amino acid unit (D) in addition to the units (A) to (C) (the polyester polymer A may be referred to as a polyester polymer A2 or a polyesteramide polymer when it contains an amino acid unit (D)). The polyester polymer A2 is a polyester skeleton consisting of a dicarboxylic acid unit (succinic acid unit (A), a dicarboxylic acid unit (B) having 7 or more carbon atoms), and an aliphatic diol unit (C), to which an amino acid is incorporated as an amide component. In the present invention, two units, a dicarboxylic acid having 7 or more carbon atoms and an amino acid, are copolymerized with the original polyester skeleton consisting of succinic acid and an aliphatic diol, thereby reducing the number of units used for modification. As a result, biodegradability can be improved while maintaining the excellent properties of the polyester skeleton consisting of succinic acid and an aliphatic diol.

[0042] <Dicarboxylic acid units> In the polyester polymer A2, the succinic acid units (A) form a polyalkylene succinate skeleton together with the aliphatic diol units (C), thereby exhibiting biodegradability. Succinic acid units (A) In consideration of biodegradability, the molar ratio of the succinic acid units (A) to the total dicarboxylic acid units contained in the polyester polymer A2 [(A) / dicarboxylic acid units] is preferably 5 / 100 or more, more preferably 10 / 100 or more, even more preferably 15 / 100 or more, and is preferably 95 / 100 or less, more preferably 90 / 100 or less, even more preferably 85 / 100 or less.

[0043] Dicarboxylic acid unit (B) having 7 or more carbon atoms The dicarboxylic acid unit (B) having 7 or more carbon atoms is bonded to the amino acid unit (D) and effectively acts to suppress the formation of a succinimide structure resulting from the bond between the succinic acid unit (A) and the amino acid unit (D). The appropriate number of carbon atoms for the dicarboxylic acid unit (B) having 7 or more carbon atoms is the same as that for the polyester polymer A1.

[0044] From the viewpoint of improving biodegradability, the molar ratio of the dicarboxylic acid units (B) having 7 or more carbon atoms, [(B) / [(A)+(B)]], of the total of the succinic acid units (A) and the dicarboxylic acid units (B) having 7 or more carbon atoms contained in the polyester polymer A2 is preferably 5 / 100 or more, more preferably 10 / 100 or more, even more preferably 15 / 100 or more, and is preferably 95 / 100 or less, more preferably 90 / 100 or less, even more preferably 85 / 100 or less.

[0045] From the viewpoint of improving productivity, the molar ratio of the structural unit (B) derived from a dicarboxylic acid having 7 or more carbon atoms in the polyester polymer A [(B) / polyester polymer A] is preferably 2 / 100 to 50 / 100, more preferably 5 / 100 to 45 / 100, and even more preferably 10 / 100 to 40 / 100.

[0046] The molar ratio of the dicarboxylic acid units (B) having 7 or more carbon atoms to the amino acid units (D) described below contained in the polyester polymer A2 [(B) / (D)] is preferably 50 / 100 or more, more preferably 100 / 100 or more, and even more preferably 200 / 100 or more. By incorporating a sufficient amount of the dicarboxylic acid units (B) having 7 or more carbon atoms relative to the amino acid units (D), it is possible to prevent the amino acid units (D) from bonding to the succinic acid units (A), thereby increasing the degree of polymerization.

[0047] In 100 parts by mass of the dicarboxylic acid units contained in the polyester polymer A2, the total amount of the succinic acid units (A) and the dicarboxylic acid units (B) having 7 or more carbon atoms is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, and even more preferably 100 parts by mass.

[0048] The other dicarboxylic acid units (E) are the same as those in the polyester polymer A1.

[0049] <Diol Units> Aliphatic Diol Unit (C) The preferred carbon number and preferred examples of the aliphatic diol, the molar ratio [(C-1) / (C)] of the ethylene glycol-derived structural unit (C-1), the aliphatic diol unit (C), preferably the structural unit derived from ethylene glycol / 1,3-propanediol / 1,4-butanediol (total when used in combination), and the other diol unit (F) that may be contained as the balance, per 100 parts by mass of the diol units contained in the polyester polymer A2, are the same as those for the polyester polymer A1.

[0050] <Amino Acid Unit (D)> The amino acid constituting the amino acid unit (D) may be one having one amino group and one carboxylic acid group, and the rest being carbon atoms and hydrogen atoms (monoaminomonocarboxylic acid), or may be one having a group containing atoms other than carbon atoms and hydrogen atoms (so-called functional group), such as an OH group, a COOH group, an NH group (C(=O)NH ２ It may also be an amino acid containing a functional group such as an OH group, a COOH group, or an NH group (functionalized amino acid). ２ Group (C(=O)NH ２Groups), SH groups, guanidino groups, and the like increase the amount of hydrogen bonds within or between polymers, contributing to improved gas barrier properties. Furthermore, when the functionalized amino acid is an α-amino acid, the functional group is contained in the side chain. Preferred amino acids include α-amino acids, β-amino acids, γ-amino acids, and ω-amino acids, with α-amino acids being more preferred and naturally occurring α-amino acids being particularly preferred. When an α-amino acid has the functional group, the functional group is contained in the side chain. Examples of the amino acid include amino acids consisting of one amino group, one carboxyl group, and a hydrocarbon group, such as glycine, alanine, valine, leucine, and isoleucine; amino acids having a hydroxy group, such as serine and threonine; dicarboxylic acid amino acids such as aspartic acid and glutamic acid; diaminomonocarboxylic acids such as lysine and glutamine; amino acids having an amide group, such as asparagine and glutamine; amino acids having a guanidino group, such as arginine; sulfur-containing amino acids such as cysteine ​​and methionine; and aromatic ring-containing amino acids such as histidine, phenylalanine, tyrosine, and tryptophan. These may be used alone or in combination of two or more. A structural unit derived from an amino acid is not included in the dicarboxylic acid unit even if it has two carboxyl groups, and is not included in the diol unit even if it has two hydroxyl groups. As long as it has an amino group and a carboxyl group, it is counted as an amino acid unit (D).

[0051] The molar ratio of the amino acid unit (D) to the sum of the succinic acid unit (A) and the dicarboxylic acid unit (B) having 7 or more carbon atoms [(D) / [(A)+(B)]] is preferably 1 / 100 or more, more preferably 3 / 100 or more, even more preferably 5 / 100 or more, and is preferably 90 / 100 or less, more preferably 70 / 100 or less, even more preferably 50 / 100 or less.

[0052] From the viewpoint of suppressing the formation of succinimide groups, it is desirable that, for example, preferably 90 mol % or more, more preferably 95 mol % or more of the amino acid units (D) form amide bonds with the dicarboxylic acid units (B).

[0053] In the polyester polymer A2 (polyesteramide polymer) containing the amino acid unit (D), the molar ratio of ester bonds to amide bonds in the total of ester bonds and amide bonds [amide bonds / (ester bonds+amide bonds)] is preferably 0.5 / 100 to 45 / 100, more preferably 1.5 / 100 to 35 / 100, and even more preferably 2.5 / 100 to 25 / 100, taking biodegradability into consideration.

[0054] In the polyester polymer A2 (100% by mass) of the present invention, the total proportion of succinic acid units (A), dicarboxylic acid units (B) having 7 or more carbon atoms, aliphatic diol units (C), and amino acid units (D) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass. The remainder may be, but is not limited to, other dicarboxylic acid units (E), other diol units (F), structural units derived from trivalent or higher carboxylic acids (e.g., aconitic acid), trivalent or higher alcohols (e.g., glycerin), or structural units derived from chain extenders such as diisocyanate compounds. The higher the total proportion of the above units (A) to (D), the better the biodegradability.

[0055] In the production stage of the polyester polymer A (A1 and A2) of the present invention, for example, a chain extender can be appropriately added as needed. Therefore, the polyester polymer A may contain structural units derived from the chain extender. Examples of the chain extender include the following compounds. Aliphatic diisocyanate compounds: ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, lysine diisocyanate. Alicyclic diisocyanate compounds: 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate, norbornane diisocyanate. Aromatic diisocyanate compounds: 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, toluene diisocyanate, naphthalene diisocyanate. These compounds can be used alone or in combination of two or more.

[0056] The amount of the chain extender is preferably 10% by mass or less, more preferably 5% by mass or less, based on the polyester polymer A (100% by mass).

[0057] Weight-Average Molecular Weight (Mw) In a preferred embodiment, the polyester polymer A of the present invention has a weight-average molecular weight (Mw) within a predetermined range, taking physical properties into consideration. The higher the weight-average molecular weight (Mw), the more improved the mechanical strength of the marine biodegradable polymer blend containing the polyester polymer A of the present invention. The weight-average molecular weight of the polyester polymer A of the present invention may be increased by a chain extension reaction using an isocyanate compound such as hexamethylene diisocyanate. The weight-average molecular weight (Mw) is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more, and even more preferably 40,000 or more. Furthermore, the weight-average molecular weight of the polyester polymer A of the present invention can be increased to 1,000,000 or more, and further increase in molecular weight can be considered. The upper limit of the weight-average molecular weight is not particularly limited, but is 10,000,000 or less.

[0058] [Biodegradable Polymer B] The biodegradable polymer B constituting the marine biodegradable polymer blend of the present invention will now be described. Biodegradable polymer B is a polymer that biodegrades in compost, soil, and river environments, but has poor biodegradability in marine environments. Examples of biodegradable polymer B include polylactic acid (PLA), polyethylene succinate (PES), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoic acids (PHAs), cellulose, hemicellulose, cellulose acetate (CA), polyvinyl alcohol (PVA), polyglycolic acid (PGA), polycaprolactone (PCL), polyamide 4 (PA4), polybutylene succinate adipate (PBSA), and polybutylene succinate lactate (PBSL). Preferred are polylactic acid, polyglycolic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, polyhydroxyalkanoic acid, cellulose, hemicellulose, and cellulose acetate. These may be used alone or in combination of two or more.

[0059] The higher the proportion of polyester polymer A in the marine biodegradable polymer blend, the better the marine biodegradability. If the blending ratio of polyester polymer A is extremely low, the contact area required for achieving high biodegradability in seawater cannot be sufficiently secured, and the effect of improving biodegradability is likely to be limited. On the other hand, if polyester polymer A is contained in a certain proportion or more, a suitable compatibility or immiscibility with biodegradable polymer B is likely to be formed, and both polymers are effectively degraded by microorganisms and enzymes in the marine, thereby improving biodegradability. The polyester polymer A is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and most preferably 20% by mass or more, of the marine biodegradable polymer blend (total of polyester polymer A and biodegradable polymer B). The biodegradable polymer B is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and most preferably 80% by mass or less.

[0060] [Other Components] (Additional Components) The marine biodegradable polymer blend may contain other components in addition to the polyester polymer A and the biodegradable polymer B, as necessary. Examples of other components include the following substances: biodegradable polymers (other than the polyester polymer A and the biodegradable polymer B), pigments, dyes, heat stabilizers, antioxidants, weather resistance agents, lubricants, antistatic agents, fillers, reinforcing agents, flame retardants, plasticizers, clay and other additives.

[0061] [Marine biodegradability] In the present invention, the term "marine biodegradability" refers to the polymer blend being decomposed into low molecular weight molecules in a seawater environment, and ultimately decomposed into water and carbon dioxide. Excellent marine biodegradability refers to a biodegradability of preferably 1% or more, more preferably 20% or more, even more preferably 25% or more, and even more preferably 30% or more within 50 days in a marine environment. Detailed test conditions are described in the Examples.

[0062] A method for producing the polyester polymer A of the present invention is described below. The polyester polymer A of the present invention can be produced by polycondensation of raw material monomers. The raw material monomers are succinic acid (a), a dicarboxylic acid (b) having 7 or more carbon atoms (hereinafter collectively referred to as dicarboxylic acid components), and an aliphatic diol component (c), and preferably an amino acid (d). The succinic acid (a) may be succinic acid or a derivative of succinic acid. Examples of succinic acid derivatives include succinic acid esters such as dimethyl succinate and diethyl succinate, and succinic anhydride. These may be used alone or in combination of two or more. The dicarboxylic acid (b) having 7 or more carbon atoms may be an aliphatic dicarboxylic acid, a chain dicarboxylic acid, or a derivative thereof having 7 or more carbon atoms, preferably 8 to 12 carbon atoms, and is preferably at least one selected from the group consisting of suberic acid, sebacic acid, and dodecanedioic acid. The aliphatic diol component (c) is preferably at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol, and is preferably ethylene glycol. The amino acid (d) can be any of the monomers exemplified for the amino acid unit (D), and is preferably an α-amino acid.

[0063] The succinic acid (a), the dicarboxylic acid (b) having 7 or more carbon atoms, the aliphatic diol (c), and the amino acid (d) may be derived from fossil fuels, but are preferably derived from plants. They may also be mixed in any ratio, and it is preferable that one or more of the above, more preferably two or more, and even more preferably all of them are derived from natural products, particularly plants.

[0064] [Suitable Method for Producing Polyester Polymer A1] In the raw material monomers, the molar ratio [(c) / ((a)+(b))] of the aliphatic diol component (c) (total when two or more types are used in combination) to the total of the succinic acid (a) and the dicarboxylic acid (b) having 7 or more carbon atoms is preferably 80 / 100 to 120 / 100, more preferably 90 / 100 to 110 / 100. The amount of the aliphatic diol component may be increased in consideration of the distillation of the aliphatic diol component during the reaction. However, if the amount of the aliphatic diol component is too large, the amount of the aliphatic diol component recovered will increase.

[0065] The molar ratio of the dicarboxylic acid (b) having 7 or more carbon atoms to the succinic acid (a) (total amount when two or more types are used in combination) [(a):(b)] is preferably 0.85:0.15 to 0.15:0.85. In order to improve marine biodegradability, it is desirable to increase the amount of the dicarboxylic acid (b) having 7 or more carbon atoms, but if it is too much, the physical properties such as strength of the polymer blend of the present invention may decrease.

[0066] In the present invention, the above-mentioned raw material monomers may be used alone as raw materials, but other components may be added as necessary to achieve the desired composition. The amount of other components is preferably within a range that does not inhibit marine biodegradability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 0 parts by mass per 100 parts by mass of the above-mentioned raw material monomers. In consideration of marine biodegradability, other components do not need to be added. Examples of other components include those described above for the marine biodegradable polymer. Although not explained below, other components can be added at an appropriate time.

[0067] The polyester polymer A1 of the present invention is obtained by mixing the dicarboxylic acid component and the aliphatic diol component, which are raw material monomers, and polycondensing the mixture. In the present invention, in order to increase the molecular weight of the polyester polymer A1, it is preferable to prepare a prepolymer by esterifying the dicarboxylic acid component and the aliphatic diol component, and then heat the prepolymer under reduced pressure to further promote the esterification reaction and increase the degree of polymerization. The melting point, heat of fusion, weight-average molecular weight, etc. of the polyester polymer A1 can be adjusted by changing the ratio of the raw material monomers or the polycondensation conditions.

[0068] The esterification reaction of the raw material monomers produces a prepolymer having a terminal hydroxy group. The prepolymer is preferably reacted under the following conditions. The reaction temperature for the prepolymer synthesis reaction should be set to a temperature sufficient for the esterification reaction to proceed, for example, preferably 150°C or higher, more preferably 180°C or higher, and preferably 300°C or lower, more preferably 250°C or lower. Too low a reaction temperature lengthens the reaction time, which can lead to undesirable side reactions. Too high a reaction temperature can lead to decomposition of raw material monomers such as aliphatic diols and the resulting prepolymer. The reaction time should be determined based on the reaction temperature and other factors, and is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, for example. The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon, more preferably a nitrogen atmosphere. Alternatively, the reaction may be initiated at atmospheric pressure and then reduced pressure. To prevent volatilization of low-molecular-weight raw material monomers, it is preferable to start the reaction at atmospheric pressure, followed by reducing the pressure to prevent the monomers from scattering due to high temperatures. The pressure may be reduced stepwise or continuously, and is preferably reduced to 1.0 kPa or less, more preferably 0.1 kPa or less.

[0069] In the present invention, after mixing the raw material monomers, the mixture is heated to a predetermined temperature under normal pressure and stirred for a predetermined time until the esterification rate (= dehydration rate = actual amount of dehydration / theoretical amount of dehydration) reaches about 30 to 70%, after which pressure reduction may be initiated. It is also preferable to gradually reduce the pressure in the system as the esterification rate increases. Esterification occurs at the above temperature, yielding a prepolymer.

[0070] In the present invention, various known catalysts can be used in the esterification reaction. Examples of catalysts include organometallic compounds, organic acid salts, organic alkoxides, metal oxides, metal hydroxides, carbonates, phosphates, sulfates, nitrates, and chlorides containing at least one selected from the group consisting of titanium, germanium, zinc, iron, manganese, cobalt, zirconium, hafnium, vanadium, iridium, lanthanum, cerium, lithium, calcium, magnesium, tin, barium, nickel, and antimony. These catalysts can be used alone or in appropriate combinations of two or more. Preferred are titanium(IV) isopropoxide, manganese diacetate, antimony oxide, dibutyltin diacetate, zinc chloride, or a combination thereof, and more preferred is titanium(IV) isopropoxide.

[0071] The catalyst may be added in the required amount, for example, preferably 10 ppm or more, more preferably 50 ppm or more, and preferably 5,000 ppm or less, more preferably 1,000 ppm or less, based on the total amount of charged monomers. Increasing the amount of catalyst promotes the esterification of the raw material monomers. On the other hand, if the amount of catalyst is too large, the color tone of the resulting marine biodegradable polymer may deteriorate or the heat resistance may decrease.

[0072] After the esterification reaction is completed, the resulting prepolymers are further subjected to a transesterification reaction to promote molecular weight increase, thereby obtaining a marine biodegradable polymer having the above weight-average molecular weight. The conditions for this transesterification reaction may be set to those sufficient for the progression of molecular weight increase. The reaction temperature is, for example, preferably 180°C or higher, more preferably 200°C or higher, and preferably 300°C or lower, more preferably 250°C or lower. The reaction time is, for example, preferably 1 to 10 hours, more preferably 2 to 7 hours. The reaction atmosphere is, for example, preferably an inert gas atmosphere, more preferably a nitrogen atmosphere. The reaction is preferably carried out under reduced pressure, and the pressure may be adjusted depending on the progress of the reaction. The pressure is, for example, preferably 0.5 kPa or lower, more preferably 0.1 kPa or lower. The above-mentioned catalyst may be used during the transesterification reaction. The amount of catalyst used is also exemplified by the above-mentioned ranges.

[0073] The polyester polymer A1 of the present invention may be subjected to a chain extension reaction using an isocyanate compound such as hexamethylene diisocyanate to further increase the molecular weight.

[0074] [Preferred Production Method for Polyester Polymer A2] In the present invention, it is preferable to first prepare a prepolymer by subjecting a dicarboxylic acid (b) having 7 or more carbon atoms, an aliphatic diol (c), and an amino acid (d) to an ester-amidation reaction in the first step, and then react the prepolymer with succinic acid (a) and an aliphatic diol (c) in the second step to produce polyester polymer A2. The amino acid (d) bonds with both succinic acid (a) and the dicarboxylic acid (b) having 7 or more carbon atoms, but the amide bond between the amino acid (d) and succinic acid (a) is easily decomposed by succinimide formation. Therefore, by first reacting the amino acid (d) with the dicarboxylic acid (b) having 7 or more carbon atoms to form an amide bond between the amino acid (d) and the dicarboxylic acid (b) having 7 or more carbon atoms, and then copolymerizing the polyalkylene succinate component (succinic acid (a) and aliphatic diol (c)), the amide bond between the amino acid (d) and succinic acid (a), which causes degradation, can be suppressed.

[0075] [Step 1] A prepolymer is obtained by subjecting a dicarboxylic acid (b) having 7 or more carbon atoms, an aliphatic diol (c), and an amino acid (d) to an ester-amidation reaction. The molar ratio of the aliphatic diol (c) (or the total when two or more types are used) to the total of the dicarboxylic acid (b) having 7 or more carbon atoms and the amino acid (d), [(c) / ((b)+(d))], is preferably 80 / 100 to 120 / 100, more preferably 90 / 100 to 110 / 100. Taking into account the distillation of the aliphatic diol (c) during the reaction, the amount of the aliphatic diol (c) may be increased. However, if the amount of the aliphatic diol (c) is too large, the amount of unreacted aliphatic diol (c) increases, requiring a recovery process.

[0076] In addition, in consideration of biodegradability, the molar ratio of the dicarboxylic acid (b) having 7 or more carbon atoms to the amino acid (d) (total when two or more kinds are used in combination) [(b):(d)] is preferably 1:5 to 5:1, more preferably 1:3 to 3:1.

[0077] [Reaction Conditions for Step 1] The temperature of the prepolymer synthesis reaction may be set to a temperature sufficient for the esterification reaction to proceed, for example, preferably 160°C or higher, more preferably 180°C or higher, and preferably 250°C or lower, more preferably 230°C or lower. If the reaction temperature is too low, the reaction time will be long, which may result in undesirable side reactions. Furthermore, if the reaction temperature is too high, raw material monomers such as the specified aliphatic diol component (c) and the resulting prepolymer may decompose. The reaction time may be set to the time required to produce the prepolymer, taking into account factors such as the reaction temperature, and is preferably 0.5 to 10 hours, more preferably 1 to 5 hours. The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon, more preferably a nitrogen atmosphere. Alternatively, the reaction may be initiated at atmospheric pressure and then reduced pressure. From the viewpoint of suppressing volatilization of low-molecular-weight raw material monomers, it is preferable to start the reaction at atmospheric pressure, and then reduce the pressure to prevent the monomers from scattering due to high temperatures. The pressure reduction may be carried out stepwise or continuously. The reduced pressure is preferably 1 kPa or less, more preferably 0.1 kPa or less.

[0078] In the present invention, after mixing a dicarboxylic acid (b) having 7 or more carbon atoms, an aliphatic diol (c), and an amino acid (d), the mixture is heated to a predetermined temperature under normal pressure and stirred for a predetermined time until the condensation rate (= dehydration rate = actual amount of dehydration / theoretical amount of dehydration) reaches about 30 to 70%, and then pressure reduction may be initiated. It is also preferable to reduce the pressure in the system as the ester-amidation rate increases. At the above temperature, ester-amidation occurs to obtain a prepolymer.

[0079] In the present invention, various known catalysts can be used in the esterification reaction. Examples of catalysts include organometallic compounds, organic acid salts, organic alkoxides, metal oxides, metal hydroxides, carbonates, phosphates, sulfates, nitrates, and chlorides containing at least one selected from the group consisting of titanium, germanium, zinc, iron, manganese, cobalt, zirconium, hafnium, vanadium, iridium, lanthanum, cerium, lithium, calcium, magnesium, tin, barium, nickel, and antimony. These catalysts can be used alone or in appropriate combinations of two or more. Preferred are titanium(IV) isopropoxide, manganese diacetate, antimony oxide, dibutyltin diacetate, zinc chloride, or a combination thereof, and more preferred is titanium(IV) isopropoxide.

[0080] The catalyst may be added in a required amount, for example, preferably 10 ppm or more, more preferably 50 ppm or more, and preferably 5,000 ppm or less, more preferably 1,000 ppm or less, based on the total amount of charged monomers. Increasing the amount of catalyst promotes the esterification of the raw material monomers. On the other hand, if the amount of catalyst is too large, the color tone of the resulting polyester polymer A2 may deteriorate or the heat resistance may decrease.

[0081] The weight average molecular weight (Mw) of the prepolymer is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,500 or more.

[0082] [Second Step] After the esterification reaction of the first step is completed, the resulting prepolymer is polycondensed with succinic acid (a) and an aliphatic diol (c).

[0083] In consideration of biodegradability, the molar ratio of succinic acid (a) to dicarboxylic acid (b) having 7 or more carbon atoms added in the first step [(a) / (b)] is preferably 1000 / 100 to 10 / 100, more preferably 600 / 100 to 15 / 100.

[0084] The molar ratio of the aliphatic diol (c) (total when two or more kinds are used in combination) to the succinic acid (a) [(c) / (a)] is preferably 80 / 100 to 120 / 100, more preferably 90 / 100 to 110 / 100. Taking into consideration the distillation and recovery of the aliphatic diol (c) during the reaction, it is preferable to appropriately adjust the amount of the aliphatic diol (c).

[0085] [Reaction Conditions for Step 2] The reaction temperature is, for example, preferably 160°C or higher, more preferably 180°C or higher, and even more preferably 200°C or higher, and preferably 250°C or lower, more preferably 230°C or lower. The reaction time is, for example, preferably 1 to 10 hours, more preferably 2 to 7 hours. The atmosphere during the reaction is, for example, preferably an inert gas atmosphere, more preferably a nitrogen atmosphere. The reaction is also preferably carried out under reduced pressure, and the pressure can be appropriately adjusted depending on the progress of the reaction. The pressure is, for example, preferably 0.5 kPa or lower, more preferably 0.1 kPa or lower. The catalyst used in Step 1 may be used in the transesterification reaction of Step 2. The amount of catalyst used also conforms to the above-mentioned range.

[0086] In the present invention, the reaction conditions and the like may be appropriately adjusted so that the weight average molecular weight (Mw) of the polymer becomes a desired value, preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 40,000 or more.

[0087] Other components may be added to the obtained polyester polymer A2. The other components follow the examples given above. Although not explained further, the other components may be added at an appropriate time. If necessary, the other components may be added to achieve the desired composition, and it is desirable that the other components are present in an amount that does not inhibit biodegradability. In the polyester polymer A2 (100 parts by mass), the other components are preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 0 parts by mass, and it is desirable that no other components are present.

[0088] [Suitable Method for Producing Biodegradable Polymer B] The method for producing biodegradable polymer B is not particularly limited, and various known raw material monomers may be polymerized. The raw material monomers may be those required for preparing biodegradable polymer B. Examples of such raw material monomers include diol components such as 1,4-butanediol and ethylene glycol; dicarboxylic acid components such as succinic acid, adipic acid, and terephthalic acid; hydroxy acids such as lactic acid, or lactides, which are dehydration condensates thereof. Other monomers may also be used as needed. Two or more types of raw material monomers for each component may be used in combination, and various additives may be added as needed. Biodegradable polymer B may be a known biodegradable polymer available commercially. For example, suitable examples such as polylactic acid (PLA), polyglycolic acid (PGA), polyethylene succinate (PES), polybutylene succinate (PBS), polybutylene adipate terephthalate, polyhydroxyalkanoic acid, cellulose, hemicellulose, and cellulose acetate may be prepared by various known methods.

[0089] [Suitable Method for Producing Marine Biodegradable Polymer Blend] In the present invention, a marine biodegradable polymer blend is prepared by melt-kneading a polyester polymer A and a biodegradable polymer B. The mass ratio of the polyester polymer A to the biodegradable polymer B (polyester polymer A / biodegradable polymer B) is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 to 90 / 10, and even more preferably 15 / 85 to 85 / 15.

[0090] When polyester polymer A and biodegradable polymer B are melt-kneaded, a marine biodegradable polymer blend in a compatible or incompatible state is obtained. The heating temperature during melt-kneading may be set to a temperature at which each polymer melts, for example, 150 to 250°C. The kneading time is not particularly limited, for example, about 1 to 60 minutes. The kneading method is not particularly limited, and a kneader such as a mixer or a single-screw or multi-screw extruder may be used.

[0091] Other components may be added to the obtained marine biodegradable polymer blend as needed, examples of which are as described above.

[0092] A composition containing the marine biodegradable polymer blend of the present invention is also a preferred embodiment. The marine biodegradable polymer blend of the present invention may be added to a known composition. Examples of compositions include nucleating agents, fillers, plasticizers, pigments, paints, and antistatic agents. The composition of the present invention also includes mixed raw materials in which the marine biodegradable polymer blend of the present invention is added to the raw materials of various molded products described below, and molded products made using such mixed raw materials.

[0093] Examples of molded articles using the marine biodegradable polymer blend of the present invention include films, sheets, fibers, foams, and microparticles. The marine biodegradable polymer blend of the present invention is suitable for various industrial applications, such as garbage bags, agricultural films, containers for cosmetics and detergents, fishing lines, fishing nets, ropes, food packaging materials, nonwoven fabrics, agricultural materials (coating materials for seeds and fertilizers), scrubbing agents, and cosmetic additives. The above molded articles can be manufactured by various known manufacturing methods.

[0094] The marine biodegradable polymer blend of the present invention is not only marine biodegradable but also biodegradable by microorganisms in general soil environments. Therefore, the marine biodegradable polymer blend of the present invention can be buried in soil as household waste or industrial waste.

[0095] This application claims the benefit of priority based on Japanese Patent Application No. 2024-053759, filed on March 28, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-053759, filed on March 28, 2024, are incorporated herein by reference.

[0096] The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is of course possible to carry out the invention by making appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention.

[0097] [Polyester Polymer A] Synthesis Example 1 (Examples 1 to 4, 9, 10, 15, 17 to 19) A separable flask reaction vessel (volume: 0.2 L) equipped with a fractional distillation condenser, a stirrer, a nitrogen inlet, a sampling port, a heater, and a pressure-reducing exhaust port was charged with 30.11 g of succinic acid (SA), 9.10 g of sebacic acid (SebA), and 19.55 g of ethylene glycol (EG) as raw material monomers. A mechanical stirrer was then installed, and the system was then purged with nitrogen. Next, the system was stirred under a nitrogen stream at normal pressure, and the temperature was raised to 200°C using an aluminum block heater, and the system was stirred at that temperature for 1 hour. The temperature was then further raised to 230°C, and the system was stirred at that temperature for 1 hour. After that, the pressure was gradually reduced to 0.1 kPa or less while the pressure was gradually reduced, and the system was stirred at 230°C for 1 hour. Next, Ti(OiPr) was added to the reaction vessel. ４ 42.6 mg of a catalyst was added, and the reaction was continued at 230° C. for 5 hours at 0.1 kPa or less to obtain a polyester polymer (yield: 78%). The weight average molecular weight (Mw) of the obtained polyester polymer was 62,500.

[0098] Synthesis Example 2 (Examples 5 to 8) A separable flask reaction vessel (volume: 0.2 L) equipped with a fractional distillation condenser, a stirrer, a nitrogen inlet, a sampling port, a heater, and a pressure-reducing exhaust port was charged with raw material monomers: 10.11 g of sebacic acid (SebA), 1.95 g of L-valine (L-Val), and 4.34 g of ethylene glycol (EG). A mechanical stirrer was then installed, and the system was then purged with nitrogen. Next, the system was stirred under normal pressure under a nitrogen stream, and the system was heated to 200°C using an aluminum block heater and stirred at that temperature for 1 hour. Thereafter, the system was gradually reduced in pressure to 0.1 kPa or less, and stirred at 200°C for 1 hour. Next, Ti(OiPr) was added to the reaction vessel. ４ 47.4 mg of catalyst was added, and the reaction was continued for 1 hour at 200°C under 0.1 kPa or less to obtain a prepolymer. The weight average molecular weight (Mw) of the prepolymer was 9,000. 33.46 g of succinic acid (SA) and 18.47 g of ethylene glycol (EG) were added to the obtained prepolymer as raw material monomers, and the mixture was stirred at 200°C for 1 hour. The pressure in the system was then reduced to 0.1 kPa or less, and the mixture was stirred at 200°C for 5 hours. The weight average molecular weight (Mw) of the obtained polyester polymer (polyesteramide polymer) (yield 79%) was 52,400.

[0099] Synthesis Example 3 (Examples 11 to 13, 21 to 23) A polyester polymer (yield 83%, weight average molecular weight Mw 62,400) was produced in the same manner as in Synthesis Example 1, except that the amount of succinic acid (SA) was changed to 24.80 g and the amount of sebacic acid (SebA) was changed to 18.20 g.

[0100] Synthesis Example 4 (Example 14) A polyester polymer (yield 79%, weight average molecular weight Mw 67,700) was produced in the same manner as in Synthesis Example 3, except that 20.73 g of dodecanedioic acid (DDDA) was used instead of sebacic acid (SebA).

[0101] Synthesis Example 5 (Example 16) A polyester polymer (yield 85%, weight average molecular weight Mw 55,800) was produced in the same manner as in Synthesis Example 1, except that the amounts of succinic acid (SA), sebacic acid (SebA), and ethylene glycol (EG) were changed to 12.60 g, 32.36 g, and 17.38 g, respectively.

[0102] [Polymer B] PLA (Polylactic Acid) Commercially available standard / general-purpose grade PLA (manufactured by Standard Test Piece Co., Ltd.) was used.

[0103] PES (polyethylene succinate) raw material monomers: succinic acid (SA): 35.43 g, ethylene glycol (EG): 19.55 g, Ti(OiPr) ４ Polyethylene succinate was produced in the same manner as in Synthesis Example 1 for Polyester Polymer A, except that the amount of catalyst was changed to 4.3 mg.

[0104] PBS (polybutylene succinate) raw material monomers: succinic acid (SA): 35.43 g, 1,4-butanediol: 28.39 g, Ti(OiPr) ４ Polybutylene succinate was prepared in the same manner as in Synthesis Example 1 of Polyester Polymer A, except that the amount of catalyst was changed to 4.3 mg.

[0105] Examples 1 to 4, 9, 10, 15, 17 to 19 Using a commercially available kneader, a kneader equipped with a small segment mixer KF6V was used. Synthesis Example 1 (Examples 1 to 4, 9, 10, 15, 17 to 19) was used as the polyester polymer A, and PLA (Examples 1 to 4, 17 to 19), PES (Examples 9 and 10), or PBS (Example 15) was used as the biodegradable polymer B. A polymer blend sample was prepared by adding the material in the proportions shown in Table 1, and mixing for a predetermined time at a rotation speed of 30 rpm under the kneading temperature shown in Table 1. For the polyester polymer A and the biodegradable polymer B, PBS and PES were prepared by adding 500 ppm of Irganox-1010 to the resin, heating to 180 ° C. under a nitrogen flow, dissolving the resin, and then adding hexamethylene diisocyanate (HDI) to a concentration of 2% by mass. The mixture was stirred for 2 hours under this environment to cause a thickening reaction, and then added.

[0106] Examples 5 to 8 Polymer blend samples were prepared by melt kneading in the same manner as in Example 1, except that the polyester polymer A of Synthesis Example 2 was used in the proportions shown in Table 1.

[0107] Examples 11 to 13 Polymer blend samples were prepared in the same manner as in Example 10, except that the polyester polymer A prepared in Synthesis Example 3 was used in the proportions shown in Table 1.

[0108] Example 14 A polymer blend sample was prepared in the same manner as in Example 10, except that the polyester polymer A prepared in Synthesis Example 4 was used in the proportions shown in Table 1.

[0109] Example 16 A polymer blend sample was prepared in the same manner as in Example 10, except that the polyester polymer A prepared in Synthesis Example 5 was used in the proportions shown in Table 1.

[0110] Examples 20 to 23 Polymer blend samples were prepared in the same manner as in Example 1, except that the polyester polymer A prepared in Synthesis Example 3 was used in the proportions shown in Table 1.

[0111] Comparative Examples 1 to 4 In Comparative Examples 1 to 4, polymer samples were prepared in the same manner as in Example 1, except that polyester polymer A was not used and only biodegradable polymer B was used. As biodegradable polymer B, PLA was used in Comparative Example 1, PES in Comparative Example 2, PBS in Comparative Example 3, and PES / PLA (blending ratio 50 / 50) in Comparative Example 4.

[0112] Weight-average molecular weight Mw The weight-average molecular weight was determined by GPC (gel permeation chromatography) measurement under the following measurement conditions. The obtained polymer was dissolved in chloroform to a solid content of approximately 0.5% by mass, and the solution was filtered through a filter with a pore size of 0.45 μm to be used as a measurement sample. Apparatus: GPC system (manufactured by Agilent) Elution solvent: chloroform Standard substance: standard polystyrene (manufactured by Shodex) Separation column: GPC K-802, GPC K-806M (manufactured by Shodex)

[0113] First, a cross section of the sample was taken using a cryomicrotome at -75 to -80°C. Next, an atomic force microscope (AFM) (Dimension Icon, manufactured by BRUKER) in Peak Force Tapping mode was used to observe the elastic modulus image of the sample cross section. A RTESPA-150 probe was used, with a spring constant of 7 N / m, in air. The island size and fringe spacing in the phase-separated state were confirmed using image analysis software (ImageJ) based on the acquired AFM elastic modulus image.

[0114] Marine Biodegradation Test Samples The samples prepared in the above Examples and Comparative Examples were freeze-pulverized using liquid nitrogen, and then classified. The powder that passed through a sieve with 300 μm openings was used as a test sample.

[0115] Marine biodegradability test: Test seawater: Seawater collected from Hojo Beach, Tateyama City, Chiba Prefecture (34°59'49.794"N, 139°51'23.724"E) was filtered to remove impurities. Mineral stock solutions: In accordance with ISO 14851:2019, solution A (potassium dihydrogen phosphate 8.5 g / L; dipotassium hydrogen phosphate 21.75 g / L; disodium hydrogen phosphate dihydrate 33.4 g / L; ammonium chloride 0.5 g / L), solution B (magnesium sulfate heptahydrate 22.5 g / L), solution C (calcium chloride dihydrate 36.4 g / L), and solution D (iron (III) chloride hexahydrate 0.25 g / L) were each prepared using purified water. The biochemical oxygen demand (BOD) biodegradation rate by aerobic microorganisms in seawater was calculated by measuring oxygen consumption using a BOD meter (OxiTop IDS, manufactured by WTW) in accordance with ISO 14851:2019. Specifically, an appropriate amount of test seawater was added to the medium bottle (0.25 L capacity) containing the biodegradation test sample, and 2 mL of solution A and 0.2 mL each of solutions B, C, and D were added to bring the final volume to 0.20 L. A solution containing no biodegradation test sample was used as a blank. Five granular sodium hydroxide grains were added to the carbon dioxide absorbent container and cultured for 50 days in an incubator set at 25°C under an aerobic environment. The seawater in the medium bottle was stirred at 180 to 450 rpm, and the biodegradation rate (%) was calculated based on the BOD measurement 50 days after the start of the test. The results are shown in Tables 1 and 2.

[0116] As a reference example, the marine biodegradability test was also conducted using cellulose (Whatman quantitative filter paper No. 42, manufactured by Cytiva). The biodegradability of the test samples of each Example and Comparative Example was evaluated relative to the biodegradability of cellulose (in the table, BOD biodegradability vs. cellulose). In the marine biodegradability test results for cellulose, the BOD biodegradability (seawater: 50 days) was 61%.

[0117]

[0118]

Claims

1. A marine biodegradable polymer blend comprising: a polyester polymer A having a structural unit (A) derived from succinic acid; a structural unit (B) derived from a dicarboxylic acid having 7 or more carbon atoms; and a structural unit (C) derived from an aliphatic diol; and a biodegradable polymer B, wherein the polyester polymer A and the biodegradable polymer B are in a compatible or incompatible state.

2. The marine biodegradable polymer blend according to claim 1, wherein the polyester polymer A further contains a structural unit (D) derived from an amino acid.

3. The marine biodegradable polymer blend according to claim 1, wherein the dicarboxylic acid having 7 or more carbon atoms is at least one selected from the group consisting of suberic acid, sebacic acid, and dodecanedioic acid.

4. The marine biodegradable polymer blend according to claim 1, wherein the aliphatic diol is at least one selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,4-butanediol.

5. A marine biodegradable polymer blend according to claim 1, wherein the molar ratio [(C-1) / (C)] of the ethylene glycol-derived structural unit (C-1) among the aliphatic diol units (C) is 90 / 100 or more.

6. The marine biodegradable polymer blend according to claim 2, wherein the amino acid is an α-amino acid.

7. The marine biodegradable polymer blend according to claim 2, wherein the molar ratio of the amino acid units (D) to the sum of the succinic acid units (A) and the dicarboxylic acid (B) having 7 or more carbon atoms [(D) / ((A)+(B))] is 1 / 100 to 90 / 100.

8. A marine biodegradable polymer blend as described in claim 1, wherein the total of the succinic acid-derived structural unit (A) and the dicarboxylic acid unit (B) having 7 or more carbon atoms is 80 parts by mass or more out of 100 parts by mass of dicarboxylic acid units contained in the polyester polymer A.

9. A marine biodegradable polymer blend according to claim 1, wherein in the polyester polymer A, the molar ratio of the structural unit (B) derived from a dicarboxylic acid having 7 or more carbon atoms [(B) / polyester polymer A] is 2 / 100 to 50 / 100.

10. The marine biodegradable polymer blend according to claim 1, wherein the biodegradable polymer B is at least one selected from the group consisting of polylactic acid, polyglycolic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, polyhydroxyalkanoic acid, cellulose, hemicellulose, and cellulose acetate.

11. The marine biodegradable polymer blend according to claim 1, wherein the biodegradable polymer B is at least one selected from the group consisting of polylactic acid, polyglycolic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate terephthalate, polybutylene succinate adipate, polyhydroxyalkanoic acid, and cellulose acetate.

12. The marine biodegradable polymer blend according to claim 1, wherein the mass ratio (A / B) of the polyester polymer A to the biodegradable polymer B is 10 / 90 to 90 / 10.

13. A marine biodegradable polymer blend as described in claim 1, wherein the total of the succinic acid units (A), the dicarboxylic acid (B) having 7 or more carbon atoms, and the aliphatic diol units (C) is 90% by mass or more of the polyester polymer A (100% by mass).

14. A marine biodegradable polymer blend as described in claim 2, wherein the total of the succinic acid units (A), the dicarboxylic acid (B) having 7 or more carbon atoms, the aliphatic diol units (C), and the amino acid units (D) is 90% by mass or more of the polyester polymer A (100% by mass).

15. The marine biodegradable polymer blend described in claim 1, wherein the incompatible state is a phase-separated state in which, when observed under an atomic force microscope, the polyester polymer A and the biodegradable polymer B form one of an island-in-the-sea structure, a striped structure, a fibrous structure, a co-continuous structure, or a composite structure thereof.

16. A composition comprising the marine biodegradable polymer blend of any one of claims 1 to 15.

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