Aliphatic-aromatic polyester resin and its molded products

Abstract

The present invention provides an aliphatic-aromatic polyester resin in which the main constituent units are aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and / or alicyclic diol units, the abundance ratio (molar ratio) between the aliphatic dicarboxylic acid units and the aromatic dicarboxylic acid units being 15:85 to 85:15, the aliphatic-aromatic polyester resin having a glass transition temperature of -25°C or above, and the aliphatic-aromatic polyester resin having a branched structure represented by the following formulas (1) to (4). (In formulas (1) to (4), Ar1, Ar2, and Ar3 independently represent a C4-12 divalent aromatic hydrocarbon ring group or an aromatic heterocyclic group that may have a substituent. R represents a hydrogen atom or a C1-4 alkyl group, and n, m, and r independently represent an integer of 2 to 10).

Description

[Technical Field]

[0001] The present invention relates to an aliphatic-aromatic polyester resin which has a high molecular weight, is excellent in formability, and provides a film with excellent mechanical properties such as tensile elongation at break, and to a molded article and film thereof. [Background technology]

[0002] In recent years, packaging materials and agricultural materials made from petroleum-derived resins have been released into the environment, where they remain without decomposing and pollute the environment as plastic waste and microplastics, which has become a social problem.

[0003] As a means of solving this problem, biodegradable polymeric materials (biodegradable plastics) have been developed, some of which have been commercialized as biodegradable packaging materials and biodegradable agricultural materials. Representative examples of biodegradable plastics include aliphatic polyester resins such as polylactic acid (hereinafter sometimes abbreviated as "PLA"), polybutylene succinate (hereinafter sometimes abbreviated as "PBS"), and polybutylene succinate adipate (hereinafter sometimes abbreviated as "PBSA"), and aliphatic-aromatic polyester resins such as polybutylene adipate terephthalate (hereinafter sometimes abbreviated as "PBAT"), polybutylene succinate terephthalate (hereinafter sometimes abbreviated as "PBST"), polybutylene sebacate terephthalate (hereinafter sometimes abbreviated as "PBSeT"), polybutylene succinate furanoate (hereinafter sometimes abbreviated as "PBSF"), and polybutylene azelate terephthalate (hereinafter sometimes abbreviated as "PBAzT").

[0004] However, compared to aromatic polyester resins such as polyethylene terephthalate and polybutylene terephthalate, the above biodegradable plastics do not have sufficient thermal stability during polymerization when attempting to obtain high molecular weight materials, and it has sometimes been impossible to increase the molecular weight.

[0005] To obtain high molecular weight materials, for example, polyesters obtained from a mixture of adipic acid or its derivatives or a mixture thereof, terephthalic acid or its ester-forming derivatives or a mixture thereof, and a sulfonate compound, a dihydroxy compound selected from an alkanediol having 2 to 6 carbon atoms and a cycloalkanediol having 5 to 10 carbon atoms, and a compound having at least three groups capable of forming an ester, or polyesters obtained by further reacting with a diisocyanate have been disclosed (Patent Document 1). Also disclosed is an aliphatic-aromatic polyester resin consisting of an aliphatic dicarboxylic acid unit, an aromatic dicarboxylic acid unit, an aliphatic and / or alicyclic diol unit, and a structural unit having a trifunctional or higher functional ester-forming group (Patent Document 2).

[0006] [Patent Document 1] Special Publication No. 10-508640 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-031457

[0007] The aliphatic-aromatic polyester disclosed in Patent Document 1 uses adipic acid or its derivatives as an essential component of the aliphatic dicarboxylic acid structural unit, resulting in poor thermal stability during polymerization and a low thermal decomposition temperature for the resulting polymer. Furthermore, since it is difficult to obtain a polyester with a sufficiently high molecular weight in a single reaction step, it is necessary to first polymerize a low-molecular-weight polyester and then increase the molecular weight by a chain extension reaction using a diisocyanate in a second reaction step.

[0008] In Patent Document 2, the presence of a predetermined proportion of malic acid as a tri- or higher functional component acting as a branching agent in a polymerization reaction system enables high molecular weight production in one step, resulting in improved productivity, impact resistance, flexibility, and tear resistance. However, the inventors' investigations have revealed that, as shown in Comparative Example 1 below, polymers containing branched structures derived from malic acid undergo crosslinking reactions under high-temperature conditions in the kneading and molding processes, resulting in unintended thickening, which leads to a decrease in molding process stability. Summary of the Invention

[0009] An object of the present invention is to provide an aliphatic-aromatic polyester resin that has a high molecular weight and high thermal stability when heated, and as a result, has excellent molding process stability and the mechanical properties of the resulting film, such as tensile elongation at break, are also excellent.

[0010] The present inventors focused on the molar ratio of aliphatic dicarboxylic acid units to aromatic dicarboxylic acid units, the glass transition temperature, and the branched structure skeleton introduced to increase the molecular weight of high-molecular-weight aliphatic-aromatic polyester resins. They found that a molar ratio of aliphatic dicarboxylic acid units to aromatic dicarboxylic acid units within a predetermined range, a glass transition temperature equal to or higher than a predetermined value, and the presence of a specific branched structure correlate with stability during molding and mechanical properties of the molded product. They also found that controlling the branched structure and its ratio results in high thermal stability during heat melting, excellent moldability, and excellent mechanical properties such as film breaking elongation.

[0011] The gist of the present invention lies in the following [1] to [6].

[0012] [1] An aliphatic-aromatic polyester resin whose main constituent units are aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and / or alicyclic diol units, wherein the ratio (molar ratio) of the aliphatic dicarboxylic acid units to the aromatic dicarboxylic acid units is 15:85 to 85:15, the glass transition temperature is -25°C or higher, and the aliphatic-aromatic polyester resin has a branched structure represented by the following formulas (1) to (4):

[0013] [ka]

[0014] (In formulas (1) to (4), Ar 1 , Ar 2 , Ar 3each independently represents a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group having 4 to 12 carbon atoms, which may have a substituent. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n, m, and r each independently represent an integer of 2 to 10.

[0015] [2] The aliphatic-aromatic polyester resin according to [1], wherein the total proportion of the branched structures represented by the formulas (1) to (4) is 0.00001 mol % or more and less than 4.0 mol % relative to 100 mol % of the total of all structural units.

[0016] [3] The aliphatic-aromatic polyester resin according to [1] or [2], wherein the aliphatic dicarboxylic acid units are linear aliphatic dicarboxylic acid units having 4 to 10 carbon atoms, the aromatic dicarboxylic acid units are aromatic dicarboxylic acid units having 6 to 8 carbon atoms, and the aliphatic diol units are linear diol units having 2 to 4 carbon atoms.

[0017] [4] The aliphatic-aromatic polyester resin according to any one of [1] to [3], wherein the aliphatic dicarboxylic acid units are succinic acid units, the aromatic dicarboxylic acid units are terephthalic acid units, and the aliphatic diol units are 1,4-butanediol units.

[0018] [5] A molded article obtained by molding the aliphatic-aromatic polyester resin according to any one of [1] to [4].

[0019] [6] A film obtained by molding the aliphatic-aromatic polyester resin according to any one of [1] to [4]. [Effects of the Invention]

[0020] According to the present invention, there are provided an aliphatic-aromatic polyester resin having a high molecular weight and high thermal stability when heated, and therefore excellent molding process stability, and the resulting film also has excellent mechanical properties such as tensile elongation at break, as well as a molded article and a film made therefrom. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a reaction flow diagram showing the process of producing the branched structures represented by formulas (1) to (4) in the production process of the aliphatic-aromatic polyester resin of the present invention. [Figure 2] FIG. 2 is a graph showing the change over time in torque during melting of the aliphatic-aromatic polyester resins obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following description, and can be implemented by any modifications within the scope of the gist of the present invention. In this specification, when a numerical value or physical property value is enclosed by "~", the values ​​before and after the "~" are used to include the values ​​before and after the "~"

[0023] [Aliphatic-aromatic polyester resin] The aliphatic-aromatic polyester resin of the present invention is an aliphatic-aromatic polyester resin whose main constituent units are aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and / or alicyclic diol units, characterized in that the abundance ratio (molar ratio) of the aliphatic dicarboxylic acid units to the aromatic dicarboxylic acid units is 15:85 to 85:15, the glass transition temperature is −25° C. or higher, and the resin has a branched structure represented by the following formulas (1) to (4):

[0024] [ka]

[0025] (In formulas (1) to (4), Ar 1 , Ar 2 , Ar 3 each independently represents a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group having 4 to 12 carbon atoms, which may have a substituent. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n, m, and r each independently represent an integer of 2 to 10.

[0026] In the present invention, the "aliphatic dicarboxylic acid unit" refers to a repeating unit derived from an aliphatic dicarboxylic acid and / or a derivative thereof (hereinafter, sometimes referred to as an "aliphatic dicarboxylic acid component") and introduced into the aliphatic-aromatic polyester resin. The "aromatic dicarboxylic acid unit" is a repeating unit derived from an aromatic dicarboxylic acid and / or a derivative thereof (hereinafter, sometimes referred to as an "aromatic dicarboxylic acid component") and introduced into an aliphatic-aromatic polyester resin. In the present invention, the aromatic dicarboxylic acid refers to a broad aromatic dicarboxylic acid including heteroaromatic dicarboxylic acids. The "aliphatic diol unit" is a repeating unit derived from an aliphatic diol and introduced into an aliphatic-aromatic polyester resin. The "alicyclic diol unit" is a repeating unit derived from an alicyclic diol and introduced into an aliphatic-aromatic polyester resin. The main structural unit is a unit that accounts for 55 mol % or more, preferably 75 mol % or more, and more preferably 85 to 100 mol % of all structural units that constitute the aliphatic-aromatic polyester resin (100 mol %).

[0027] <Branching structure (1) to (4) ratio> In the aliphatic-aromatic polyester resin of the present invention, the total proportion of the branched structures represented by the above formulas (1) to (4) relative to 100 mol % of all structural units constituting the aliphatic-aromatic polyester resin (hereinafter, this proportion may be simply referred to as the "proportion of branched structures (1) to (4)") is not particularly limited, but is preferably 0.00001 mol % or more and less than 4 mol %. When the proportion of branched structures (1) to (4) is less than 4.0 mol %, excessive crosslinking of the polymer does not proceed during polymer production, allowing stable strand extraction, and problems such as gelation during molding, which deteriorates moldability, and impairment of various physical properties do not occur. When the proportion of branched structures (1) to (4) is 0.00001 mol % or more, the reactivity of the polymerization reaction does not decrease, bubbles during inflation molding are stabilized, and molding can be easily performed. Thus, controlling the proportion of branched structures (1) to (4) within the above range not only improves productivity during polymer production, but also improves the mechanical properties of the resulting molded product (specifically, film).

[0028] The proportion of the branched structures (1) to (4) in the aliphatic-aromatic polyester resin of the present invention is more preferably 0.001 mol % or more and 2.0 mol % or less, even more preferably 0.005 mol % or more and 1.0 mol % or less, particularly preferably 0.01 mol % or more and 0.5 mol % or less, and most preferably 0.015 mol % or more and 0.4 mol % or less.

[0029] The proportion of the branched structure represented by the above formula (1) relative to the total of all structural units constituting the aliphatic-aromatic polyester resin of the present invention (hereinafter, sometimes referred to as the "branched structure (1) proportion") is not particularly limited, but is preferably less than 1.0 mol%, more preferably 0.1 mol% or less, even more preferably 0.05 mol% or less, and particularly preferably 0.04 mol% or less.

[0030] The proportion of the branched structure represented by the above formula (2) relative to the total of all structural units constituting the aliphatic-aromatic polyester resin of the present invention (hereinafter, sometimes referred to as the "branched structure (2) proportion") is not particularly limited, but is preferably less than 1.0 mol%, more preferably 0.5 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0.08 mol% or less.

[0031] The proportion of the branched structure represented by the above formula (3) relative to the total of all structural units constituting the aliphatic-aromatic polyester resin of the present invention (hereinafter, sometimes referred to as the "branched structure (3) proportion") is not particularly limited, but is preferably less than 1.0 mol%, more preferably 0.5 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0.07 mol% or less.

[0032] The proportion of the branched structure represented by the above formula (4) (hereinafter, sometimes referred to as "branched structure (4) proportion") relative to the total of 100 mol% of all structural units constituting the aliphatic-aromatic polyester resin of the present invention is not particularly limited, but is preferably less than 1.0 mol%, more preferably 0.1 mol% or less, even more preferably 0.05 mol% or less, and particularly preferably 0.04 mol% or less.

[0033] The proportions (mol %) of the branched structures represented by the above formulas (1) to (4) may be the same or different.

[0034] The proportion of branched structure (1), the proportion of branched structure (2), the proportion of branched structure (3), the proportion of branched structure (4), and the proportions of branched structures (1) to (4) are as described in the Examples section below. 1 It can be determined by mole fraction measurement using H-NMR.

[0035] <Branched structure represented by formulas (1) to (4)> In the formulas (1) to (4), Ar 1 , Ar 2 , Ar 3are each independently a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group having 4 to 12 carbon atoms, which may have a substituent. 1 , Ar 2 , Ar 3 are each independently a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group having 4 to 6 carbon atoms, which may have a substituent. The divalent aromatic hydrocarbon ring group is preferably a p-phenylene group or an m-phenylene group. The divalent aromatic heterocyclic group is preferably a 2,5-furandiyl group. These can be introduced into an aliphatic-aromatic polyester resin by using terephthalic acid and / or a derivative thereof, isophthalic acid and / or a derivative thereof, or furandicarboxylic acid and / or a derivative thereof, respectively, as the raw material dicarboxylic acid and / or a derivative thereof (hereinafter sometimes referred to as "dicarboxylic acid component") of the aliphatic-aromatic polyester resin.

[0036] Ar 1 , Ar 2 , Ar 3 may have a substituent. Specific examples of the substituent include a sulfonic acid group, a sulfonate salt group, an alkyl group, an alkoxy group, a halogen atom, a nitro group, and an aromatic group.

[0037] R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, and an n-butyl group.

[0038] n, m, and r each independently represent an integer of 2 to 10, and preferably an integer of 2 to 8.

[0039] The branched structures represented by the formulae (1) to (4) can be introduced into the aliphatic-aromatic polyester resin of the present invention by using compounds capable of introducing the branched structures represented by the formulae (1) to (4) by an ester formation reaction and / or an ester exchange reaction as the raw dicarboxylic acid component and raw diol component of the aliphatic-aromatic polyester resin of the present invention described below, preferably in a predetermined ratio so as to achieve the above-mentioned ratio of the branched structures (1) to (4).

[0040] <Aliphatic dicarboxylic acid component> The aliphatic dicarboxylic acid component constituting the aliphatic dicarboxylic acid unit constituting the aliphatic-aromatic polyester resin of the present invention is not particularly limited. In terms of the balance between cost, mechanical properties, thermal properties, and biodegradability, the aliphatic dicarboxylic acid component is preferably an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms, particularly 4 to 10 carbon atoms, with a linear aliphatic dicarboxylic acid component having 4 to 10 carbon atoms being particularly preferred. Specific examples include succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, azelaic acid, dodecanedioic acid, and derivatives thereof such as alkyl esters. Among these, succinic acid, sebacic acid, adipic acid, azelaic acid, and derivatives thereof such as alkyl esters are preferred, with succinic acid or a derivative thereof being particularly preferred. The derivative may be an acid anhydride thereof. These aliphatic dicarboxylic acid components may be used alone or in combination of two or more.

[0041] <Aromatic dicarboxylic acid component> The aromatic dicarboxylic acid component constituting the aromatic dicarboxylic acid unit, which is the dicarboxylic acid unit constituting the aliphatic-aromatic polyester resin of the present invention, is not particularly limited. From the perspective of a balance between cost, mechanical properties, thermal properties, and biodegradability, the aromatic dicarboxylic acid component is preferably an aromatic dicarboxylic acid component having 4 to 14 carbon atoms, particularly 4 to 12 carbon atoms, and particularly 4 to 8 carbon atoms, and of these, 4 to 6 carbon atoms. Specific examples include terephthalic acid, isophthalic acid, furandicarboxylic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and lower alkyl esters thereof. These may also be acid anhydrides. Among these, terephthalic acid, isophthalic acid, furandicarboxylic acid, or lower alkyl esters thereof (e.g., alkyls having 1 to 4 carbon atoms) are preferred, with terephthalic acid or its lower alkyl ester (e.g., alkyls having 1 to 4 carbon atoms) being particularly preferred. These aromatic dicarboxylic acid components may be used alone or in combination of two or more.

[0042] <Ratio of Aliphatic Dicarboxylic Acid Units to Aromatic Dicarboxylic Acid Units> The ratio (abundance ratio (molar ratio)) of aliphatic dicarboxylic acid units to aromatic dicarboxylic acid units constituting the dicarboxylic acid units of the aliphatic-aromatic polyester resin of the present invention is 15:85 to 85:15, preferably 30:70 to 70:30, and more preferably 40:60 to 60:40. If the ratio of aliphatic dicarboxylic acid units is less than the above lower limit and the ratio of aromatic dicarboxylic acid units is greater than the above upper limit, the biodegradability of the aliphatic-aromatic polyester resin tends to be impaired and flexibility tends to be insufficient. If the ratio of aliphatic dicarboxylic acid units is greater than the above upper limit and the ratio of aromatic dicarboxylic acid units is less than the above lower limit, the thermal decomposition temperature decreases, and the elongation at break when formed into a film tends to be small, resulting in insufficient flexibility. When the aliphatic-aromatic polyester resin of the present invention has the above-mentioned specific molar ratio of aliphatic dicarboxylic acid units to aromatic dicarboxylic acid units, it exhibits excellent properties such as biodegradability, heat resistance, and flexibility.

[0043] This ratio (molar ratio) can be controlled by the amounts (ratio) of the aliphatic dicarboxylic acid component and aromatic dicarboxylic acid component used as raw materials in the method for producing the aliphatic-aromatic polyester resin described below. This abundance ratio (molar ratio) is the same as that described in the Examples section below. 1 It can be determined by mole fraction measurement using H-NMR.

[0044] <Aliphatic and / or alicyclic diol> Examples of diol components constituting the aliphatic and / or alicyclic diol units constituting the diol units of the aliphatic-aromatic polyester resin of the present invention include aliphatic diols having 2 to 10 carbon atoms, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol, and alicyclic diols having 3 to 12 carbon atoms, such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol. Among these, from the viewpoint of the physical properties of the resulting aliphatic-aromatic polyester resin, preferred are linear diols having 2 to 4 carbon atoms, such as 1,4-butanediol, ethylene glycol, and 1,3-propanediol, with 1,4-butanediol and ethylene glycol being particularly preferred, and 1,4-butanediol being especially preferred. These may be used alone or in combination of two or more.

[0045] <Trifunctional polyhydric alcohol> In the aliphatic-aromatic polyester resin of the present invention, in order to form the branched structures represented by the formulae (1) to (4), it is preferable to use a trifunctional polyhydric alcohol in addition to the above components when producing the aliphatic-aromatic polyester resin. Examples of trifunctional polyhydric alcohols used to introduce the branched structures represented by formulas (1) to (4) include trimethylol alkanes, specifically trimethylol methane (introducing a branched structure of R=H in the formulas (1) to (4)), trimethylol ethane (introducing a branched structure of R=CH in the formulas (1) to (4)), trimethylol propane (introducing a branched structure of R=C2H5 in the formulas (1) to (4)), trimethylol butane (introducing a branched structure of R=n-C3H7 in the formulas (1) to (4)), trimethylol isobutane (introducing a branched structure of R=i-C3H7 in the formulas (1) to (4)), and trimethylol pentane (introducing a branched structure of R=C4H9 in the formulas (1) to (4)). Furthermore, glycerin, pentaerythritol, etc. may be used in combination. These may be used alone or in combination of two or more.

[0046] <Introduction of branched structures represented by formulas (1) to (4) and control of the proportion of branched structures> The aliphatic-aromatic polyester resin of the present invention containing the branched structure represented by the formulas (1) to (4) can be produced using, as raw materials, at least the aliphatic dicarboxylic acid component, aromatic dicarboxylic acid component, aliphatic and / or alicyclic diol, and the trifunctional polyhydric alcohol, through an esterification and / or transesterification reaction step and a subsequent polycondensation reaction step, as described below.

[0047] The aliphatic dicarboxylic acid component, aromatic dicarboxylic acid component, aliphatic and / or alicyclic diol, and trifunctional polyhydric alcohol used in producing the aliphatic-aromatic polyester resin of the present invention may be derived from either petroleum raw materials or biomass resources. It is preferable to use components derived from biomass resources as these components, as this leads to the suppression of the generation of petroleum-derived carbon dioxide that is generated during biodegradation and combustion.

[0048] In the present invention, when an aliphatic-aromatic polyester resin is produced by an esterification and / or transesterification reaction step and a subsequent polycondensation reaction step using an aliphatic and / or alicyclic diol, an aliphatic dicarboxylic acid component, and an aromatic dicarboxylic acid component in the presence of a catalyst, the branched structures represented by the formulas (1) to (4) can be produced by using the above-mentioned trifunctional polyhydric alcohol together with these raw materials. The process of producing the branched structure in this case can be thought of as shown in Figure 1. In FIG. 1, "trifunctional polyhydric alcohol" is written as "trifunctional alcohol," "aliphatic dicarboxylic acid component" is written as "aliphatic carboxylic acid," and "aromatic dicarboxylic acid component" is written as "aromatic dicarboxylic acid."

[0049] Each reaction pathway shown in Figure 1 is an equilibrium reaction, and both the difference in reactivity of the aromatic dicarboxylic acid component and the aliphatic dicarboxylic acid component toward the trifunctional polyhydric alcohol (kinetic control) and the difference in stability of the products in the equilibrium reaction (thermodynamic control) contribute to the reaction. The present inventors have found that the reaction product can be controlled thermodynamically by controlling the blending ratio of each component, the reaction temperature and the reaction time.

[0050] For example, by specifying the molar ratio of the aromatic dicarboxylic acid component to the aliphatic dicarboxylic acid component, specifying the amount of trifunctional polyhydric alcohol to be fed, and then raising the temperature to 170°C to 200°C with stirring in the initial esterification and / or transesterification reaction step and carrying out the reaction for 45 minutes to 1 hour, it is possible to control the abundance ratio (molar ratio) of the aliphatic dicarboxylic acid unit to the aromatic dicarboxylic acid unit, as well as the content and proportion of the branched structures represented by the formulas (1) to (4).In this case, the intermediate dialcohols and monoalcohols react completely, and the reaction converges to form the branched structures represented by the formulas (1) to (4) in just the right amount, so the abundance ratio of each branched structure can be easily controlled to a desired value.

[0051] In addition to this specific embodiment, the proportion of each of the branched structures of the formulas (1) to (4) can be controlled by controlling the temperature, reaction time, etc. in the raw material charging and reaction steps.

[0052] <Other constituent units, etc.> The aliphatic-aromatic polyester resin of the present invention may have a repeating unit (aliphatic oxycarboxylic acid unit) derived from an aliphatic oxycarboxylic acid. Specific examples of the aliphatic oxycarboxylic acid component that provides the aliphatic oxycarboxylic acid unit include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 6-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, etc., or derivatives thereof, such as lower alkyl esters or intramolecular esters. When optical isomers exist, they may be in the D-form, L-form, or racemic form, and may be in the form of a solid, liquid, or aqueous solution. Among these, lactic acid, glycolic acid, or derivatives thereof are particularly preferred. These aliphatic oxycarboxylic acids may be used alone or in combination of two or more.

[0053] When the aliphatic-aromatic polyester resin of the present invention contains these aliphatic oxycarboxylic acid units, the content thereof is preferably 20 mol % or less, more preferably 10 mol % or less, even more preferably 5 mol % or less, and most preferably 0 mol % (not included), based on 100 mol % of all structural units constituting the aliphatic-aromatic polyester resin, from the viewpoint of moldability.

[0054] In producing the aliphatic-aromatic polyester resin of the present invention, chain extenders such as diisocyanates, diphenyl carbonate, dioxazoline, and silicate esters may be used. Specific examples of diisocyanates include known diisocyanates such as 2,4-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Specific examples of silicate esters include tetramethoxysilane, dimethoxydiphenylsilane, dimethoxydimethylsilane, and diphenyldihydroxysilane. These may be used alone or in combination of two or more.

[0055] During the production of the aliphatic-aromatic polyester resin of the present invention, the polyester end groups may be capped with a carbodiimide, an epoxy compound, a monofunctional alcohol, or a carboxylic acid. Capping the polyester end groups is expected to improve the hydrolysis resistance of the aliphatic-aromatic polyester resin.

[0056] [Method of producing aliphatic-aromatic polyester resin] As described above, the method for producing the aliphatic-aromatic polyester resin of the present invention can employ a known method for producing polyesters, except that a trifunctional polyhydric alcohol is used to control the reaction in order to introduce the branched structure represented by the formulas (1) to (4). The polycondensation reaction in this case can be carried out under suitable conditions that have been conventionally employed, and is not particularly limited. Usually, a method is employed in which the degree of polymerization is further increased by carrying out a reduced pressure operation after the esterification and / or transesterification reaction has proceeded.

[0057] When a diol component forming a diol unit, a dicarboxylic acid component forming a dicarboxylic acid unit, and a trifunctional polyhydric alcohol for forming a branched structure represented by the formulas (1) to (4) are reacted during the production of the aliphatic-aromatic polyester resin of the present invention, the amounts of the diol component, dicarboxylic acid component, and trifunctional polyhydric alcohol used are determined so that the aliphatic-aromatic polyester resin produced has the desired composition. The diol component and the dicarboxylic acid component are usually reacted in substantially equimolar amounts, but the diol component is usually used in a 1 to 20 mol % excess over the dicarboxylic acid component because it is distilled off during the esterification or transesterification reaction.

[0058] The method for producing the aliphatic-aromatic polyester resin of the present invention will be described below using a continuous production method as an example. In the following, an example will be given of a method for producing an aliphatic-aromatic polyester resin by an esterification reaction step using an aliphatic diol and a trifunctional polyhydric alcohol with an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid, followed by a polycondensation reaction step, but the esterification reaction step may be a transesterification reaction step, or a step in which both the esterification reaction and the transesterification reaction are carried out. The aliphatic diol may be an alicyclic diol.

[0059] In the continuous production method, for example, an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid, an aliphatic diol and a trifunctional polyhydric alcohol are reacted in a plurality of continuous reaction vessels, and polyester pellets are continuously obtained through an esterification reaction step and a melt polycondensation reaction step. As long as the effects of the present invention are not impaired, the method for producing the aliphatic-aromatic polyester resin of the present invention is not limited to the continuous method, and conventionally known methods for producing polyesters can be adopted.

[0060] <Esterification reaction step> The esterification reaction step in which at least a dicarboxylic acid component, a diol component, and a trifunctional polyhydric alcohol are reacted, and the subsequent polycondensation reaction step can be carried out in a plurality of continuous reaction tanks or in a single reaction tank. In order to reduce variations in the physical properties of the resulting polyester, it is preferable to carry out the reaction in a plurality of continuous reaction tanks.

[0061] The reaction temperature in the esterification reaction step is not particularly limited as long as it is a temperature at which the esterification reaction can be carried out. To increase the reaction rate, the reaction temperature is preferably 200°C or higher, more preferably 210°C or higher. To prevent discoloration of the polyester, the reaction temperature is preferably 270°C or lower, more preferably 260°C or lower, and particularly preferably 250°C or lower. If the reaction temperature is too low, the esterification reaction rate will be slow, requiring a long reaction time, and undesirable reactions such as dehydration decomposition of the aliphatic diol will increase. If the reaction temperature is too high, decomposition of the aliphatic diol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, and trifunctional polyhydric alcohol will increase, and the amount of scattered material in the reaction vessel will increase, which can easily cause the generation of foreign matter and the reaction product will become hazy. It is preferable that the esterification reaction temperature be constant. A constant temperature stabilizes the esterification rate. The constant temperature is within ±5°C of the set temperature, preferably ±2°C.

[0062] In this esterification reaction step, as described above, in the initial stage of the reaction, the temperature is raised to 170° C. to 200° C. and the reaction is carried out for 45 minutes to 1 hour in order to control the proportion of branched structures.

[0063] The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon.

[0064] The reaction pressure is preferably 50 KPa to 200 KPa, more preferably 60 KPa or more, even more preferably 70 KPa or more, more preferably 130 KPa or less, and even more preferably 110 KPa or less. If the reaction pressure is below the lower limit, the amount of flying material in the reaction vessel increases, the haze of the reaction product increases, and this is likely to cause an increase in foreign matter. In addition, more aliphatic diol is distilled out of the reaction system, which is likely to result in a decrease in the polycondensation reaction rate. If the reaction pressure exceeds the upper limit, the dehydration decomposition of the aliphatic diol increases, which is likely to result in a decrease in the polycondensation reaction rate.

[0065] The reaction time is preferably 1 hour or longer, and the upper limit is preferably 10 hours or shorter, more preferably 4 hours or shorter.

[0066] The reaction molar ratio of the aliphatic diol to the total of the aliphatic dicarboxylic acids and aromatic dicarboxylic acids undergoing the esterification reaction represents the molar ratio of the aliphatic diol and the esterified aliphatic diol to the aliphatic dicarboxylic acids and aromatic dicarboxylic acids and the esterified aliphatic dicarboxylic acids present in the gas phase and the reaction liquid phase of the esterification reaction vessel, and does not include the aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aliphatic diols, and their decomposition products that are decomposed in the reaction system and do not contribute to the esterification reaction. Examples of products that are decomposed and do not contribute to the esterification reaction include the decomposition of the aliphatic diol 1,4-butanediol to tetrahydrofuran, and tetrahydrofuran is not included in this molar ratio.

[0067] In the present invention, the lower limit of the reaction molar ratio is usually 1.10 or more, preferably 1.12 or more, more preferably 1.15 or more, and particularly preferably 1.20 or more. The upper limit is usually 3.00 or less, preferably 2.50 or less, more preferably 2.30 or less, and particularly preferably 2.00 or less. If the reaction molar ratio is below the lower limit, the esterification reaction is likely to be insufficient, and the subsequent polycondensation reaction does not proceed smoothly, making it difficult to obtain a polyester with a high degree of polymerization. If the reaction molar ratio exceeds the upper limit, the amounts of decomposition of the aliphatic diol, aliphatic dicarboxylic acid, and aromatic dicarboxylic acid tend to increase. To maintain this reaction molar ratio within the preferred range, it is preferable to appropriately supply aliphatic diol to the esterification reaction system.

[0068] In the aliphatic-aromatic polyester resin of the present invention, in order to form the branched structure represented by the formulas (1) to (4), it is preferable to use the above-mentioned trifunctional polyhydric alcohol in addition to the above components when producing the aliphatic-aromatic polyester resin.

[0069] In order to form the branched structures represented by the formulas (1) to (4) in the above-mentioned preferred branched structure (1) to (4) ratios, the amount of trifunctional polyhydric alcohol used is preferably 0.00002 mol % or more and less than 8.0 mol %, more preferably 0.002 mol % or more and 4.0 mol % or less, even more preferably 0.01 mol % or more and 2.0 mol % or less, particularly preferably 0.02 mol % or more and 1.0 mol % or less, and especially preferably 0.03 mol % or more and 0.8 mol % or less, relative to 100 mol % of the total dicarboxylic acid components in the raw material.

[0070] In the present invention, it is preferable that the terminal acid value of the ester oligomer obtained in the esterification reaction step and supplied to the subsequent polycondensation reaction be 30 to 1000 eq. / ton. To reduce the terminal acid value of the ester oligomer below 30 eq. / ton, it is necessary to prolong the esterification reaction or increase the reaction molar ratio, which results in an increase in the amount of by-product decomposition products such as tetrahydrofuran. Furthermore, coloration due to a deterioration in the terminal balance also becomes significant. Conversely, if the terminal acid value of the ester oligomer is increased above 1000 eq. / ton, polymerization is inactivated due to catalyst precipitation and the amount of by-product decomposition products such as tetrahydrofuran is increased due to the acid. The effects of the present invention can be fully achieved if the terminal acid value supplied to the polycondensation reaction is 30 eq. / ton to 1000 eq. / ton.

[0071] In the present invention, an ester oligomer having a terminal acid value of 30 to 1,000 eq. / ton is obtained in the esterification reaction step, and the ester oligomer having a terminal acid value of 30 to 1,000 eq. / ton may be contacted with a phosphorus compound before being supplied to the polycondensation reaction step. Supplying the resulting ester oligomer to the polycondensation reaction step subsequently suppresses the production of decomposition products such as tetrahydrofuran, reduces the purification load on the plant, and produces an aliphatic-aromatic polyester resin with a good color tone. To more reliably achieve the effects of the present invention, the terminal acid value of the ester oligomer is preferably 50 to 800 eq. / ton, and even more preferably 100 to 500 eq. / ton.

[0072] To control the terminal acid value of the ester oligomer within the above range, reaction conditions such as the reaction molar ratio of the diol component to the dicarboxylic acid component, the reaction temperature, and the reaction pressure can be controlled. In other words, increasing the reaction molar ratio of the diol component to the dicarboxylic acid component tends to decrease the terminal acid value of the resulting ester oligomer, while decreasing the reaction molar ratio tends to increase the terminal acid value of the resulting ester oligomer. Furthermore, increasing the reaction temperature and lengthening the reaction time tends to decrease the terminal acid value of the resulting ester oligomer. Conversely, decreasing the reaction temperature and shortening the reaction time tends to increase the terminal acid value of the resulting ester oligomer. Therefore, by appropriately adjusting these conditions within the aforementioned preferred ranges, it is possible to obtain an ester oligomer with a terminal acid value of 30 to 1,000 eq. / ton. In addition, the terminal acid value of the ester oligomer can be controlled by appropriately selecting the type and amount of the catalyst used in the esterification reaction step described below. The terminal acid value of the ester oligomer is measured by the method described in the Examples section below.

[0073] <Polycondensation reaction step> Following the esterification reaction step, a polycondensation reaction is carried out in a polycondensation reaction step. The ester oligomer obtained in the esterification reaction step may be contacted with a phosphorus compound before being supplied to the polycondensation reaction step. In this case, the phosphorus compound is contacted with the ester oligomer having a terminal acid value of 30 to 1000 eq. / ton obtained in the esterification reaction step, and it is important that no phosphorus compound is present in the esterification reaction step. The phosphorus compound is preferably contacted with the ester oligomer together with an alkaline earth metal compound.

[0074] The polycondensation reaction can be carried out under reduced pressure using a plurality of continuous reaction vessels. Therefore, contacting the phosphorus compound with the ester oligomer before the polycondensation reaction step corresponds to contacting the phosphorus compound with the ester oligomer before the reduced pressure condition is applied.

[0075] The reaction pressure in the final polycondensation reaction tank in the polycondensation reaction step is usually 0.01 KPa or higher, preferably 0.03 KPa or higher, with the upper limit usually being 1.4 KPa or lower, preferably 0.4 kPa or lower. If the pressure during the polycondensation reaction is too high, the polycondensation time becomes longer, which can lead to thermal decomposition of the polyester, resulting in a decrease in molecular weight and coloration, making it difficult to produce a polyester with sufficient properties for practical use. A production method using ultra-high vacuum polycondensation equipment that sets the reaction pressure at less than 0.01 KPa is a preferred embodiment from the perspective of improving the polycondensation reaction rate, but requires extremely expensive capital investment, making it economically disadvantageous.

[0076] The lower limit of the reaction temperature is usually 215°C, preferably 220°C, and the upper limit is usually 270°C, preferably 260°C. If the reaction temperature is below the lower limit, the polycondensation reaction rate is slow, and production of a polyester with a high degree of polymerization takes a long time, and a high-power stirrer is also required, which is economically disadvantageous. If the reaction temperature exceeds the upper limit, thermal decomposition of the polyester during production tends to occur, making it difficult to produce a polyester with a high degree of polymerization.

[0077] The lower limit of the reaction time is usually 1 hour, and the upper limit is usually 15 hours, preferably 10 hours, and more preferably 8 hours. If the reaction time is too short, the reaction is insufficient, making it difficult to obtain a polyester with a high degree of polymerization, and the mechanical properties of the molded product tend to be poor. If the reaction time is too long, the molecular weight of the polyester decreases significantly due to thermal decomposition, and the mechanical properties of the molded product tend to be poor. In addition, the amount of carboxyl group terminals, which adversely affect the durability of the polyester, may increase due to thermal decomposition.

[0078] By controlling the polycondensation reaction temperature, time and reaction pressure, a polyester having a desired intrinsic viscosity can be obtained.

[0079] <Catalyst> The aliphatic-aromatic polyester resin of the present invention is usually produced in the presence of a catalyst. The catalyst can be arbitrarily selected from catalysts that can be used in the production of known polyester resins, as long as the effects of the present invention are not significantly impaired.

[0080] In the polycondensation reaction, the reaction does not proceed easily without a catalyst, so it is preferable to use a catalyst. The polycondensation reaction catalyst may be added at any stage between the esterification reaction step and the polycondensation reaction step. Furthermore, the polycondensation reaction catalyst may be added in multiple batches between the esterification reaction step and the polycondensation reaction step.

[0081] The polycondensation reaction catalyst generally uses a compound containing at least one metal element selected from Groups 1 to 14 of the periodic table. Specific examples of metal elements include scandium, yttrium, samarium, titanium, zirconium, vanadium, chromium, molybdenum, tungsten, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, strontium, sodium, and potassium. Among these, scandium, yttrium, titanium, zirconium, vanadium, molybdenum, tungsten, zinc, iron, and germanium are preferred, with titanium, zirconium, tungsten, iron, and germanium being particularly preferred. Furthermore, to reduce the polyester end concentration, which affects the thermal stability of polyester, among the above metals, metal elements selected from Groups 3 to 6 of the periodic table that exhibit Lewis acidity are preferred. Specifically, scandium, titanium, zirconium, vanadium, molybdenum, and tungsten are included, and titanium and zirconium are particularly preferred because of their availability, with titanium being even more preferred in terms of reaction activity. Here, the periodic table refers to the long-form periodic table (Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005).

[0082] In the present invention, a titanium compound is preferably used as a catalyst in the esterification reaction step.

[0083] The titanium compound is preferably a tetraalkyl titanate or a hydrolyzate thereof, and specific examples thereof include tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-t-butyl titanate, tetraphenyl titanate, tetracyclohexyl titanate, tetrabenzyl titanate, mixed titanates thereof, and hydrolyzates thereof.

[0084] Also suitable for use are titanium (oxy)acetylacetonate, titanium tetraacetylacetonate, titanium (diisoproxide)acetylacetonate, titanium bis(ammonium lactate)dihydroxide, titanium bis(ethylacetoacetate)diisopropoxide, titanium (triethanolaminate)isopropoxide, polyhydroxytitanium stearate, titanium lactate, titanium triethanolaminate, and butyl titanate dimer.

[0085] Among these, tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, titanium(oxy)acetylacetonate, titanium tetraacetylacetonate, titanium bis(ammonium lactate) dihydroxide, polyhydroxytitanium stearate, titanium lactate, and butyl titanate dimer are preferred, and tetra-n-butyl titanate, titanium(oxy)acetylacetonate, titanium tetraacetylacetonate, polyhydroxytitanium stearate, titanium lactate, and butyl titanate dimer are more preferred, with tetra-n-butyl titanate, polyhydroxytitanium stearate, titanium(oxy)acetylacetonate, and titanium tetraacetylacetonate being particularly preferred.

[0086] These titanium compounds are supplied to the esterification reaction step as a catalyst solution prepared using a catalyst dissolving solvent such as alcohols such as methanol, ethanol, isopropanol, butanol, diols such as ethylene glycol, butanediol, pentanediol, ethers such as diethyl ether, tetrahydrofuran, nitriles such as acetonitrile, hydrocarbon compounds such as heptane, toluene, water, and mixtures thereof, so that the titanium compound concentration is usually 0.05 to 5% by weight.

[0087] <Phosphorus compounds and alkaline earth metal compounds> Examples of the phosphorus compound to be contacted with the ester oligomer having a terminal acid value of 30 to 1000 eq. / ton obtained in the esterification reaction step include orthophosphoric acid, polyphosphoric acid, pentavalent phosphorus compounds such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(triethylene glycol) phosphate, ethyl diethylphosphonoacetate, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and triethylene glycol acid phosphate, and trivalent phosphorus compounds such as phosphorous acid, hypophosphorous acid, diethyl phosphite, trisdodecyl phosphite, trisnonyldecyl phosphite, and triphenyl phosphite. Among these, acidic phosphate ester compounds are preferred, and as the acidic phosphate ester compound, those having an ester structure of phosphoric acid having at least one hydroxyl group, represented by the following general formula (I) and / or (II), are preferably used.

[0088] [ka]

[0089] (In the formula, R a , R b , R crepresents an alkyl group having 1 to 6 carbon atoms, a cyclohexyl group, an aryl group, or a 2-hydroxyethyl group. a and R b may be the same or different.)

[0090] Specific examples of such acidic phosphate ester compounds include methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, and octyl acid phosphate, with ethyl acid phosphate and butyl acid phosphate being preferred. These acidic phosphate ester compounds may be used alone or in combination of two or more.

[0091] Acidic phosphate ester compounds include monoesters (II) and diesters (I), and it is preferable to use monoesters or mixtures of monoesters and diesters because they provide catalysts with high catalytic activity. The weight ratio of monoesters to diesters (monoesters:diesters) is preferably 80:20 or more, more preferably 70:30 or more, and particularly preferably 60:40 or more, and also preferably 20:80 or more, more preferably 30:70 or more, and particularly preferably 40:60 or less. In the present invention, these phosphorus compounds may be used arbitrarily.

[0092] It is also preferable to contact an alkaline earth metal compound with the ester oligomer. Examples of alkaline earth metal compounds include various compounds of beryllium, magnesium, calcium, strontium, and barium. From the viewpoints of ease of handling and availability, and catalytic effect, magnesium and calcium compounds are preferred, and among them, magnesium compounds with excellent catalytic effect are preferred. Specific examples of magnesium compounds include magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium alkoxide, magnesium hydrogen phosphate, etc., and among these, magnesium acetate is preferred.

[0093] When these phosphorus compounds and alkaline earth metal compounds are used, they may be added to the ester oligomer supplied to the polycondensation reaction step as a catalyst solution prepared using a solvent exemplified as a catalyst dissolving solvent used in preparing the above-mentioned titanium compound catalyst solution so that the phosphorus compound has a concentration of 0.01 to 7.6 wt % and the alkaline earth metal compound has a concentration of 0.02 to 9.7 wt %.

[0094] There are no particular restrictions on the amounts and ratios of the titanium compound used in the esterification reaction step and the phosphorus compound and alkaline earth metal compound used in the polycondensation reaction step. For example, the titanium compound is preferably used so that the amount added in terms of Ti relative to the polymer produced is 5 to 100 ppm by weight. The phosphorus compound is preferably used so that the molar ratio of the added amount of the titanium compound in terms of P to the added amount of the titanium compound in terms of Ti (P / Ti molar ratio) is 0.5 to 2.5. The alkaline earth metal compound is preferably used so that the molar ratio of the added amount of the alkaline earth metal relative to the added amount of the titanium compound in terms of Ti (alkaline earth metal / Ti molar ratio) is 0.5 to 3.0. Using too much of either catalyst compound is economically disadvantageous. Furthermore, for reasons that are not yet clear, too much catalyst compound can increase the terminal acid value of the final polyester, which can lead to reduced thermal stability and hydrolysis resistance due to increased terminal acid value and residual catalyst concentration. Using too little catalyst compound reduces the reaction activity, which can induce thermal decomposition of the polyester during polyester production, making it difficult to obtain polyesters with practically useful properties.

[0095] <Reaction tank> Known esterification reactors can be used in the present invention. The esterification reactor may be any type, such as a vertical agitated complete mixing tank, a vertical thermal convection mixing tank, or a tower-type continuous reactor. It may be a single tank or multiple tanks of the same or different types connected in series. Among these, a reactor equipped with an agitator is preferred. The agitator may be a conventional type consisting of a power unit, a bearing shaft, and an agitator blade, or a high-speed rotating type such as a turbine stator type high-speed rotating agitator, a disk mill type agitator, or a rotor mill type agitator.

[0096] There are no limitations on the form of stirring. In addition to the usual stirring method of directly stirring the reaction liquid in the reaction tank from the top, bottom, side, etc. of the reaction tank, a method can also be used in which a portion of the reaction liquid is taken out of the reaction tank via piping or the like and stirred with a line mixer or the like to circulate the reaction liquid. The type of stirring blade can be selected from known types, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, Pfaudle blades, full zone blades, and max blend blades.

[0097] There are no particular limitations on the type of polycondensation reaction tank used in the present invention. Examples include a vertical agitation polymerization tank, a horizontal agitation polymerization tank, and a thin-film evaporation polymerization tank. The polycondensation reaction tank can be a single tank, or a multiple tank of the same or different types connected in series. In the later stages of polycondensation when the viscosity of the reaction liquid increases, it is preferable to select a horizontal agitation polymerization tank as the polycondensation reaction tank, as it has a thin-film evaporation function that is excellent in interface renewal, plug flow properties, and self-cleaning properties.

[0098] [Physical properties of aliphatic-aromatic polyester resin] The molecular weight of the aliphatic-aromatic polyester resin of the present invention is typically 10,000 to 1,000,000 in terms of weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using monodisperse polystyrene as the standard. Because of advantages in terms of moldability and mechanical strength, the Mw of the aliphatic-aromatic polyester resin of the present invention is preferably 20,000 to 500,000, more preferably 50,000 to 400,000, and even more preferably 100,000 to 300,000.

[0099] The melt flow rate (MFR) of the aliphatic-aromatic polyester resin of the present invention is typically 0.1 g / 10 min or more and 100 g / 10 min or less, as measured at 190°C under a load of 2.16 kg according to JIS K7210 (2014). From the viewpoint of moldability and mechanical strength, the MFR of the aliphatic-aromatic polyester resin of the present invention is preferably 40 g / 10 min or less, more preferably 20 g / 10 min or less, and particularly preferably 10 g / 10 min or less, and is preferably 1.0 g / 10 min or more, more preferably 2.0 g / 10 min or more. The MFR of the aliphatic-aromatic polyester resin can be adjusted by the molecular weight.

[0100] The melting point of the aliphatic-aromatic polyester resin of the present invention is preferably 80°C or higher, more preferably 100°C or higher, and is preferably 180°C or lower, more preferably 160°C or lower, and particularly preferably lower than 140°C. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range. If the melting point is within the above range, the moldability tends to be excellent.

[0101] The glass transition temperature (Tg) of the aliphatic-aromatic polyester resin of the present invention is -25°C or higher, preferably -20°C or higher, and more preferably -15°C or higher. The Tg of the aliphatic-aromatic polyester resin of the present invention is preferably 5°C or lower, and more preferably 0°C or lower. If the glass transition temperature is lower than -25°C, the crystallization rate may decrease, which may lead to deterioration of moldability. The higher the glass transition temperature, the lower the impact strength tends to be.

[0102] The melting point and glass transition temperature of the aliphatic-aromatic polyester resin can be adjusted by any method, including, for example, selecting the types of copolymerization components, such as aliphatic dicarboxylic acids and aromatic dicarboxylic acids, adjusting the copolymerization ratios of each, or combining these.

[0103] The melting point and glass transition temperature of the aliphatic-aromatic polyester resin are measured by the method described in the Examples section below.

[0104] [Additives] Various additives, such as heat stabilizers, antioxidants, hydrolysis inhibitors, crystal nucleating agents, flame retardants, antistatic agents, release agents, and ultraviolet absorbers, may be added to the aliphatic-aromatic polyester resin of the present invention, as long as the properties of the resin are not impaired.

[0105] These additives may be added to the reactor before the polymerization reaction, to the conveying device during the period from the start of the polymerization reaction to before the end of the polymerization reaction, or before the product is discharged after the end of the polymerization reaction. Alternatively, they may be added to the polyester after the product is discharged.

[0106] [Aliphatic-aromatic polyester resin molded products] The aliphatic-aromatic polyester resin of the present invention can be molded by various molding methods applicable to thermoplastic resins.

[0107] Examples of the molding method include compression molding (compression molding, laminate molding, stampable molding), injection molding, extrusion molding and co-extrusion molding (film molding by inflation method or T-die method, laminate molding, pipe molding, electric wire / cable molding, molding of profiled materials), hollow molding (various blow moldings), calendar molding, foam molding (melt foam molding, solid phase foam molding), solid molding (uniaxial stretch molding, biaxial stretch molding, roll rolling molding, stretch-oriented nonwoven fabric molding, thermoforming (vacuum forming, pressure forming), plastic processing), powder molding (rotational molding), various nonwoven fabric moldings (dry method, adhesive method, entanglement method, spunbond method, etc.), etc.

[0108] Molded articles made from the aliphatic-aromatic polyester resin of the present invention are suitable for a wide range of applications, including packaging materials for packaging liquid, powdered, and solid materials such as various foods, pharmaceuticals, and miscellaneous goods, as well as agricultural and construction materials. Specific applications include injection-molded articles (e.g., fresh food trays, fast-food containers, and outdoor leisure products), extrusion-molded articles (e.g., films, fishing lines, fishing nets, vegetation nets, and water-retaining sheets), and blown-molded articles (e.g., bottles). Other applications include agricultural films, coating materials, fertilizer coating materials, laminated films, plates, stretched sheets, monofilaments, nonwoven fabrics, flat yarns, staples, crimped fibers, creased tape, split yarns, composite fibers, blown bottles, shopping bags, garbage bags, compost bags, cosmetic containers, detergent containers, bleach containers, ropes, binding materials, sanitary cover stock, insulated boxes, cushioning films, multifilaments, and synthetic paper. In addition, examples of medical applications include surgical threads, sutures, artificial bones, artificial skin, DDS such as microcapsules, wound dressings, and the like.

[0109] Further examples include electronic information materials such as toner binders and thermal transfer ink binders, packaging materials such as packaging films, fruit and vegetable bags, shopping bags, compost bags, bags, trays, bottles, cushioning foams, fish boxes, and agricultural materials such as mulching films, tunnel films, greenhouse films, sunshades, weed control sheets, ridge sheets, germination sheets, vegetation mats, seedling beds, flower pots, and the like.

[0110] The molded article of the present invention is excellent in mechanical properties such as impact resistance, tear strength and tensile elongation at break, biodegradability, etc., and is particularly preferably used for film applications among the above-mentioned applications.

[0111] The thickness of the film of the present invention obtained by molding the aliphatic-aromatic polyester resin of the present invention is appropriately designed depending on the application and is not particularly limited. The thickness of the film of the present invention is usually about 5 μm to 1 mm. [Example]

[0112] The specific embodiments of the present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. The values ​​of various production conditions and evaluation results in the following examples are meant as preferred upper or lower limit values ​​in the embodiments of the present invention, and a preferred range may be defined by a combination of the above-mentioned upper or lower limit value and the values ​​of the following examples or values ​​of the examples themselves.

[0113] [Analysis, measurement and evaluation methods] The analytical methods and methods for measuring and evaluating various physical properties in the present invention are as follows.

[0114] (1) Molar fraction measurement of aliphatic-aromatic polyester resin The mole fraction of each structural unit of the aliphatic-aromatic polyester resin was measured using a Bruker NMR "AVANCE 400". 1 H-NMR was measured, and the ratio of integral values ​​of the chemical shifts corresponding to each structural unit was determined. If the aliphatic dicarboxylic acid units and the aromatic dicarboxylic acid units are succinic acid units and terephthalic acid units, respectively, the molar ratio of succinic acid units / terephthalic acid units, i.e., aliphatic dicarboxylic acid units / aromatic dicarboxylic acid units, can be determined from the integral ratio of 2.63 ppm and 8.10 ppm. When trimethylolpropane is used as the trifunctional polyhydric alcohol, the proportion of each branched structure and the proportions (mol %) of the branched structures (1) to (4) can be determined from the integral ratios of the branched structure represented by formula (1): 1.09 ppm, the branched structure represented by formula (2): 1.02 ppm, the branched structure represented by formula (3): 0.95 ppm, and the branched structure represented by formula (4): 0.88 ppm. When the aliphatic dicarboxylic acid unit and the aromatic dicarboxylic acid unit are succinic acid unit and furan dicarboxylic acid unit, respectively, the molar ratio of the aliphatic dicarboxylic acid unit / aromatic dicarboxylic acid unit (succinic acid unit / furan dicarboxylic acid unit) can be determined from the integral ratios of 2.62 ppm and 7.20 ppm. When trimethylolpropane is used as the trifunctional polyhydric alcohol, the proportion of each branched structure and the proportions (mol%) of branched structures (1) to (4) can be determined from the integral ratios of the branched structure represented by formula (1): 1.04 ppm, the branched structure represented by formula (2): 0.98 ppm, the branched structure represented by formula (3): 0.93 ppm, and the branched structure represented by formula (4): 0.88 ppm.

[0115] (2) Measurement method for MFR of aliphatic-aromatic polyester resin The melt flow rate (MFR) was measured at 190°C and a load of 2.16 kg according to JIS K7210 (2014).

[0116] (3) Measurement methods for glass transition temperature, crystallization peak temperature, crystallization peak area, and melting point of aliphatic-aromatic polyester resin Measurements were made using a differential scanning calorimeter (Seiko Corporation, product name: DSC220). Approximately 5 mg of sample was precisely weighed and heated to 200°C in a nitrogen stream at a flow rate of 40 mL / min to melt it. The crystallization peak temperature and area were determined from the exothermic peak when the sample was cooled at a rate of 10°C / min. The glass transition temperature and melting point were then measured when the temperature was subsequently increased at a rate of 10°C / min.

[0117] (4) Method for measuring weight-average molecular weight (Mw) of aliphatic-aromatic polyester resin The weight average molecular weight (Mw) of the aliphatic-aromatic polyester resin was measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0118] (5) Measurement method for tensile elongation at break of aliphatic-aromatic polyester resin film 5 to 6 g of aliphatic-aromatic polyester resin was preheated to 100 to 230°C using a heat press molding machine to melt it, and press molded using a spacer to produce a pressed film with a thickness of 250 μm. The above-mentioned press-molded film having a thickness of 250 μm was preheated in an environment of 80 to 170°C for 5 minutes and then simultaneously biaxially stretched 4.5 times at a speed of 30 mm / s to produce a biaxially stretched film having a thickness of approximately 25 μm. This biaxially stretched film was punched to prepare film test pieces, which were then tested in accordance with ISO 527-2 (2012). The long axis is designated as MD, and the short axis is designated as TD. The elongation at break in MD (%) and the elongation at break in TD (%) were measured, and the average value (average of the elongations at break in MD and TD) was calculated.

[0119] (6) Change in stirring torque during melting of aliphatic-aromatic polyester resin 13g of aliphatic-aromatic polyester resin was mixed for 5 minutes at 190℃ using a Leo Labs "Micro 15cc Twin Screw Compounder." The change in the torque (N) of the mixing blades over time was measured, and the rate of torque increase after 5 minutes was calculated.

[0120] [Example 1] A reactor equipped with a stirrer, nitrogen inlet, heater, thermometer, and pressure regulator was charged with 100 parts by weight of succinic acid, 141 parts by weight of terephthalic acid, 168 parts by weight of 1,4-butanediol, and 0.73 parts by weight of trimethylolpropane as raw materials, 4 parts by weight of a 1,4-butanediol solution in which 5% by weight of tetra-n-butyl titanate had been dissolved, and 6.6 parts by weight of a 1,4-butanediol solution in which 2% by weight of magnesium acetate tetrahydrate had been dissolved. The molar ratio of succinic acid to terephthalic acid was 50:50, the molar ratio of 1,4-butanediol to the total molar amount of succinic acid and terephthalic acid was 1.1, and the amount of trimethylolpropane was 0.16 mol% of the total structural units of the polymer to be produced.

[0121] While stirring the contents of the vessel, nitrogen gas was introduced into the vessel, and the system was purged with vacuum to create a nitrogen atmosphere. Next, the system was heated to 185°C while stirring, and the reaction was carried out at this temperature for 45 minutes to 1 hour. The temperature was then raised to 220°C over 1 hour and 30 minutes. Thereafter, the temperature was raised to 230°C over 1 hour, and simultaneously the pressure was reduced to 0.07 KPa or less over 1 hour and 30 minutes. Polymerization was continued while maintaining the heated and reduced pressure state, and polymerization was terminated when the desired viscosity was reached, yielding an aliphatic-aromatic polyester resin.

[0122] The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, the crystallization peak temperature (°C), the crystallization peak area (J / g), the melting point (°C), the glass transition temperature (°C), the weight-average molecular weight, MFR (g / 10 min), the elongation at break (MD) (%), the elongation at break (TD) (%), the average of the elongations at break (MD and TD) (%), and the rate of torque increase during melting (after 5 minutes) (%) were measured. The measurement results are shown in Table 1. The change in stirring torque over time during melting is shown in Figure 2.

[0123] [Comparative Example 1] The same procedures were carried out as in Example 1, except that 0.73 parts by weight of malic acid was used instead of 0.73 parts by weight of trimethylolpropane. The results are shown in Table 1. The change in stirring torque over time during melting is shown in Figure 2.

[0124] Comparative Example 2 An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that 0.50 parts by weight of glycerol was used instead of 0.73 parts by weight of trimethylolpropane. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, the crystallization peak temperature (°C), the crystallization peak area (J / g), the melting point (°C), the glass transition temperature (°C), the weight-average molecular weight, MFR (g / 10 min), the elongation at break MD (%), the elongation at break TD (%), and the average of the elongations at break MD and TD (%) were measured. The measurement results are shown in Table 1.

[0125] [Example 2] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the amount of trimethylolpropane was 0.46 parts by weight, which was 0.101 mol % based on the total structural units of the polymer produced. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 2.

[0126] [Example 3] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the amount of trimethylolpropane was 0.17 parts by weight, which was 0.037 mol % based on the total structural units of the polymer produced. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 2.

[0127] [Example 4] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the amount of trimethylolpropane was 0.068 parts by weight, which was 0.015 mol % based on the total structural units of the polymer produced. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 2.

[0128] [Example 5] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the succinic acid, terephthalic acid, and trimethylolpropane were 80 parts by weight, 169 parts by weight, and 0.75 parts by weight, respectively, the molar ratio of succinic acid to terephthalic acid was 40:60, and the amount of trimethylolpropane was 0.164 mol% relative to the total structural units of the resulting polymer. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 2.

[0129] [Example 6] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the succinic acid, terephthalic acid, and trimethylolpropane were 110 parts by weight, 127 parts by weight, and 0.46 parts by weight, respectively, the molar ratio of succinic acid to terephthalic acid was 55:45, and the amount of trimethylolpropane was 0.100 mol % relative to the total structural units of the resulting polymer. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 3.

[0130] [Example 7] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the succinic acid, terephthalic acid, and trimethylolpropane were 120 parts by weight, 113 parts by weight, and 0.71 parts by weight, respectively, the molar ratio of succinic acid to terephthalic acid was 60:40, and the amount of trimethylolpropane was 0.156 mol % relative to the total structural units of the resulting polymer. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 3.

[0131] Comparative Example 3 An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that trimethylolpropane was used in an amount of 0 part by weight, ie, 0.00 mol % relative to all structural units of the polymer produced. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 2.

[0132] Comparative Example 4 An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the succinic acid, terephthalic acid, and trimethylolpropane were 180 parts by weight, 28 parts by weight, and 0.75 parts by weight, respectively, the molar ratio of succinic acid to terephthalic acid was 90:10, and the amount of trimethylolpropane was 0.164 mol% relative to the total structural units of the resulting polymer. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 3.

[0133] Comparative Example 5 An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that the succinic acid, terephthalic acid, and trimethylolpropane were 20 parts by weight, 253 parts by weight, and 0.75 parts by weight, respectively, the molar ratio of succinic acid to terephthalic acid was 10:90, and the amount of trimethylolpropane was 0.164 mol% relative to the total structural units of the resulting polymer. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, the melting point (°C), the glass transition temperature (°C), and the weight-average molecular weight were measured. This aliphatic-aromatic polyester resin had a high melting point, making it impossible to measure MFR, and it was not moldable, so MFR and tensile elongation at break could not be measured. The results are shown in Table 3.

[0134] [Example 8] An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 1, except that 80 parts by weight of succinic acid and 159 parts by weight of furandicarboxylic acid were used instead of terephthalic acid, 0.75 parts by weight of trimethylolpropane was used, the molar ratio of succinic acid to furandicarboxylic acid was 40:60, and the amount of trimethylolpropane was 0.164 mol % relative to the total structural units of the resulting polymer. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 3.

[0135] Comparative Example 6 An aliphatic-aromatic polyester resin was obtained under the same conditions as in Example 8, except that trimethylolpropane was used in an amount of 0 part by weight, ie, 0.00 mol % relative to all structural units of the polymer produced. The proportions (mol%) of branched structures (1) to (4) in the resulting aliphatic-aromatic polyester, the proportions (mol%) of each branched structure, melting point (°C), glass transition temperature (°C), weight-average molecular weight, MFR (g / 10 min), elongation at break MD (%), elongation at break TD (%), and the average value (%) of elongation at break MD and TD were measured. The results are shown in Table 3.

[0136] [Table 1]

[0137] [Table 2]

[0138] [Table 3]

[0139] From Table 1 and Figure 2, the following can be seen: In the aliphatic-aromatic polyester resin of Comparative Example 1, a crosslinking reaction proceeds during kneading and molding at high temperatures. This is presumably due to the use of malic acid as a branching agent. As a result, the melt viscosity changes, leading to molding defects. Furthermore, gelation causes defects in the film appearance, such as fish eyes. On the other hand, the aliphatic-aromatic polyester resin of Example 1 containing the branched structures (1) to (4) has higher thermal stability during heating than Comparative Example 1 containing no branched structures (1) to (4), can be molded without crosslinking reaction, and has excellent molding process stability.

[0140] The aliphatic-aromatic polyester resin of Comparative Example 2 exhibited a decrease in crystallization peak temperature and a smaller crystallization peak area compared to the aliphatic-aromatic polyester resin of Example 1 containing branched structures (1) to (4), indicating a significant decrease in crystallinity. This is presumably due to the use of glycerol as a branching agent. As a result, this may lead to a decrease in molding stability and molding speed, which may cause problems such as film fusion after molding. Compared with Comparative Example 2, which does not contain the branched structures (1) to (4), the aliphatic-aromatic polyester resin of Example 1, which contains the branched structures (1) to (4), has sufficient crystallinity and is excellent in molding process stability.

[0141] The following can be seen from Tables 2 and 3. As shown in Comparative Examples 3 and 6, the aliphatic-aromatic polyester resins without the branched structures (1) to (4) have low elongation at break of the film and poor mechanical properties.

[0142] As shown in Examples 1 to 8, the presence of branched structures (1) to (4) in the aliphatic-aromatic polyester resin increases the melt viscosity of the aliphatic-aromatic polyester resin in the low shear region, achieving an MFR of 10 g / 10 min or less, which is generally considered to be good for film or sheet molding. Furthermore, as shown in Examples 1 to 8, films with excellent elongation at break, which is particularly important as a mechanical property of the film, can be obtained.

[0143] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-122966 filed on July 17, 2020, the entire contents of which are incorporated by reference.

Claims

1. An aliphatic-aromatic polyester resin whose main constituent units are aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and / or alicyclic diol units, wherein the ratio (molar ratio) of the aliphatic dicarboxylic acid units to the aromatic dicarboxylic acid units is 15:85 to 85:15, and the glass transition temperature is -25°C or higher and 0°C or lower, The aliphatic-aromatic polyester resin has a branched structure represented by any of the following formulas (1) to (4), wherein the aliphatic dicarboxylic acid units are succinic acid units, the aromatic dicarboxylic acid units are terephthalic acid units, and the aliphatic diol units are 1,4-butanediol units: 【Chemistry 1】 (In formulas (1) to (4), Ar １ , Ar ２ , Ar ３ each independently represents a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group having 4 to 12 carbon atoms, which may have a substituent; R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and n, m, and r each independently represent an integer of 2 to 10.

2. An aliphatic-aromatic polyester resin whose main constituent units are aliphatic dicarboxylic acid units, aromatic dicarboxylic acid units, and aliphatic diol units and / or alicyclic diol units, wherein the ratio (molar ratio) of the aliphatic dicarboxylic acid units to the aromatic dicarboxylic acid units is 15:85 to 85:15, and the glass transition temperature is −25° C. or higher; The aliphatic-aromatic polyester resin has a branched structure represented by any of the following formulas (1) to (4), wherein the aliphatic dicarboxylic acid unit is a succinic acid unit, the aromatic dicarboxylic acid unit is a furandicarboxylic acid unit, and the aliphatic diol unit is a 1,4-butanediol unit: 【Chemistry 2】 (In formulas (1) to (4), Ar １ , Ar ２ , Ar ３ each independently has a substituent. R represents a divalent aromatic hydrocarbon ring group or aromatic heterocyclic group having 4 to 12 carbon atoms, which may be optionally substituted. represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; n, m, and r each independently represent 2 to 1 is an integer equal to 0.)

3. The total proportion of the branched structures represented by the formulas (1) to (4) is 0.00001 mol% or more and less than 4.0 mol% with respect to 100 mol% of the total of all structural units. The aliphatic-aromatic polyester resin according to claim 1 or 2.

4. A molded article obtained by molding the aliphatic-aromatic polyester resin according to any one of claims 1 to 3.

5. A film obtained by molding the aliphatic-aromatic polyester resin according to any one of claims 1 to 3.

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