JP2024091692A - Tubular body, straw, cotton swab, and baloon stick - Google Patents

Abstract

To provide a tubular body having high biodegradability at a room temperature compared to a conventional tubular molded product using a biodegradable resin, excellent in marine biodegradability, excellent in moldability when obtaining a tubular molded product, and also excellent in mechanical characteristics such as piercing strength, and characteristics such as heat resistance.SOLUTION: A tubular body comprises an aliphatic polyester resin composition which contains an aliphatic polyester resin (A) including a repeating unit derived from aliphatic diol, and a repeating unit derived from aliphatic dicarboxylic acid as the main constitutional units, polyhydroxyalkanoate (B) and an inorganic filler (C). The polyhydroxyalkanoate (B) is a copolymer which includes a 3-hydroxybutyrate unit and a 3-hydroxyhexanoate unit as the main constitutional units. A content ratio of the inorganic filler (C) to the total amount of the aliphatic polyester resin (A), the polyhydroxyalkanoate (B) and the inorganic filler (C) is 5-50 mass%.SELECTED DRAWING: None

Description

The present invention relates to a tubular body formed from an aliphatic polyester resin composition, and to straws, cotton swabs, and balloon sticks that use this tubular body.

In recent years, there has been active development of biodegradable plastics as a solution to problems caused by plastic waste, such as its impact on the ecosystem, the generation of harmful gases during combustion, and global warming due to the large amount of heat generated by combustion, which are major burdens on the global environment.
In particular, the carbon dioxide emitted when biodegradable plastics derived from plants are burned is originally from the air, and does not increase the amount of carbon dioxide in the atmosphere. This is called carbon neutrality, and is considered important under the Kyoto Protocol, which imposed carbon dioxide reduction targets, and active use of biodegradable plastics is desired.

Recently, from the viewpoint of biodegradability and carbon neutrality, aliphatic polyester resins have been attracting attention as plant-derived plastics, and in particular polyhydroxyalkanoate (hereinafter sometimes referred to as PHA) resins, and among PHA resins, poly(3-hydroxybutyrate) homopolymer resin (hereinafter sometimes referred to as PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer resin (hereinafter sometimes referred to as PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin (hereinafter sometimes referred to as PHBH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer resin, and polylactic acid have been attracting attention.

For example, Patent Document 1 discloses a molded article made of an aliphatic polyester resin composition containing a compound having an amide bond in a polyhydroxyalkanoate and pentaerythritol, and describes that the moldability in molding processes such as injection molding and sheet processing is improved.
Meanwhile, in recent years, the use of biodegradable resins has been considered for tubular molded products, such as straws, tubes, hoses, etc. For example, Patent Document 2 discloses a straw that contains polylactic acid as an essential component and also contains polybutylene succinate adipate, which is an aliphatic polyester, or polybutylene adipate terephthalate, which is an aliphatic/aromatic polyester, and Patent Document 3 discloses a straw molded from a resin that contains polylactic acid, polybutylene adipate terephthalate, and an inorganic filler.

International Publication No. 2014/068943 JP 2005-350530 A JP 2011-208040 A

In recent years, the social trend towards stronger environmental protection, especially environmental pollution caused by the disposal of used plastic products (especially the impact of microplastics caused by the disposal of used plastic products in the ocean), has led to a demand for resins that are completely biodegradable rather than only partially biodegradable. In addition, in terms of the biodegradation environment, not only is biodegradability required in a relatively high-temperature (58°C or higher) aerobic compost environment (in soil), but also in aerobic compost environment (in soil) at room temperature (28°C) and in the ocean. If a product shows not only room-temperature biodegradability but also in the ocean (marine biodegradability), for example, straws, tubes, hoses, etc. made of biodegradable resins can be treated as home compost after use, and furthermore, by biodegrading in the ocean, it is possible to eliminate the adverse impact of microplastics on marine life.

The above Patent Documents 2 and 3 disclose the use of biodegradable resins such as polylactic acid and polybutylene succinate adipate or polybutylene adipate terephthalate, an aliphatic-aromatic polyester, in the straws, but the biodegradable resins proposed therein have low biodegradability at room temperature and in the sea, and do not satisfy the rapidly increasing demand for reducing environmental impact today. In addition, Patent Document 1 discloses a molded body using PHBH, but this molded body is hard and brittle, so it has poor impact resistance and puncture resistance, and also has the problem of poor stability during molding.

The present invention has been made in view of this background, and aims to provide a tubular body that has a higher degree of biodegradability at room temperature and excellent marine biodegradability compared to tubular molded products made from conventional biodegradable resins, and also has excellent moldability when obtaining tubular molded products, as well as excellent mechanical properties such as puncture strength and properties such as heat resistance.

As a result of intensive research conducted by the present inventors to solve the above problems, they discovered that a tubular body molded from an aliphatic polyester resin composition containing an aliphatic polyester resin (A) containing as main structural units a repeating unit derived from an aliphatic diol and a repeating unit derived from an aliphatic dicarboxylic acid, a polyhydroxyalkanoate (B), and further containing an inorganic filler (C) in a predetermined ratio has excellent moldability, a high degree of biodegradability at room temperature, excellent marine biodegradability, and excellent mechanical properties such as puncture strength and heat resistance, thereby arriving at the present invention.

[1] A tubular body using an aliphatic polyester resin composition comprising an aliphatic polyester resin (A) containing, as main structural units, repeating units derived from an aliphatic diol and repeating units derived from an aliphatic dicarboxylic acid, a polyhydroxyalkanoate (B), and an inorganic filler (C), wherein the polyhydroxyalkanoate (B) is a copolymer containing, as main structural units, 3-hydroxybutyrate units and 3-hydroxyhexanoate units, and the content of the inorganic filler (C) relative to the total amount of the aliphatic polyester resin (A), the polyhydroxyalkanoate (B), and the inorganic filler (C) is 5 to 50 mass%.

[2] The tubular body according to [1], wherein the inorganic filler (C) is one or more selected from the group consisting of anhydrous silica, calcium carbonate, talc, and zeolite.

[3] The tubular body according to [1] or [2], in which the proportion of repeating units derived from succinic acid in all repeating units derived from dicarboxylic acids contained in the aliphatic polyester resin (A) is 5 mol% or more and 100 mol% or less.

[4] A tubular body according to any one of [1] to [3], which is an extrusion molded body.

[5] A straw made of a tubular body according to any one of [1] to [4].

[6] A cotton swab comprising a tubular body according to any one of [1] to [4].

[7] A balloon stick comprising a tubular body according to any one of [1] to [4].

[8] A tubular body that has an absolute or relative biodegradability of 60% or more after 100 days in a marine biodegradability test (ASTM D6691) at a seawater temperature of 30°C ± 2°C.

[9] A straw made of the tubular body described in [8].

According to the present invention, a tubular body is provided that has a high degree of biodegradability at room temperature, a high degree of biodegradability in the sea (marine biodegradability), excellent moldability, and excellent mechanical properties such as puncture strength and properties such as heat resistance. The tubular body of the present invention has a high degree of biodegradability even at room temperature and has even higher marine biodegradability, so that even if it is used for disposable straws, cotton swabs, balloon sticks, etc., it is expected that the impact on marine life will be significantly reduced compared to conventional plastic products.

The following describes in detail the embodiments of the present invention; however, the present invention is not limited to the following description, and can be modified in any manner without departing from the gist of the present invention.
In this specification, when "~" is used to express a value with a numerical value or physical property value before and after it, the value before and after it is included in the expression.
In this specification, "mass %" and "parts by mass" have the same meaning as "weight %" and "parts by weight", respectively.

The tubular body of the present invention is an aliphatic polyester resin composition containing an aliphatic polyester resin (A) containing, as main structural units, repeating units derived from an aliphatic diol and repeating units derived from an aliphatic dicarboxylic acid, a polyhydroxyalkanoate (B), and an inorganic filler (C), in which the polyhydroxyalkanoate (B) is a copolymer containing, as main structural units, 3-hydroxybutyrate units and 3-hydroxyhexanoate units, and the content of the inorganic filler (C) relative to the total amount of the aliphatic polyester resin (A), the polyhydroxyalkanoate (B), and the inorganic filler (C) is 5 to 50 mass% (hereinafter, sometimes referred to as the "aliphatic polyester resin composition of the present invention").

The tubular body of the present invention is preferably a tubular body having an absolute or relative biodegradability of 60% or more after 100 days in a seawater temperature of 30°C ± 2°C in a marine biodegradability test (ASTM D6691), and is preferably a tubular body molded from the aliphatic polyester resin composition of the present invention. The tubular body can also be suitably used for straws, and when used for straws, is extremely useful as a marine biodegradable straw. The higher the biodegradability, the better, and there is no particular upper limit.

In the present invention, an aliphatic diol refers to an aliphatic hydrocarbon group to which two hydroxyl groups are bonded. As the aliphatic hydrocarbon group, a straight-chain aliphatic hydrocarbon group is usually used, but it may have a branched structure or a cyclic structure, or may have a plurality of these structures.
Furthermore, an aliphatic dicarboxylic acid refers to an aliphatic hydrocarbon group to which two carboxyl groups are bonded. As the aliphatic hydrocarbon group, a straight-chain aliphatic hydrocarbon group is usually used, but it may have a branched structure or a cyclic structure, or may have a plurality of these.

The aliphatic polyester resin (A) contained in the aliphatic polyester resin composition of the present invention is a polymer having repeating units, and each repeating unit is also called a compound unit corresponding to the compound from which the repeating unit is derived. For example, a repeating unit derived from an aliphatic diol is also called an "aliphatic diol unit", and a repeating unit derived from an aliphatic dicarboxylic acid is also called an "aliphatic dicarboxylic acid unit".
The "main structural unit" in the aliphatic polyester resin (A) usually means a structural unit that is contained in the aliphatic polyester resin (A) at 80% by mass or more, and there are cases where no structural unit other than the main structural unit is contained at all. The same applies to the "main structural unit" in the polyhydroxyalkanoate (B).

[mechanism]
Since the aliphatic polyester resin (A) and polyhydroxyalkanoate (B) contained in the aliphatic polyester resin composition of the present invention have high biodegradability at room temperature and in the sea, the tubular body of the present invention made of the aliphatic polyester resin composition of the present invention containing the aliphatic polyester resin (A) and polyhydroxyalkanoate (B) as resin components has excellent biodegradability at room temperature and in the sea. In addition, by using the aliphatic polyester resin (A) and polyhydroxyalkanoate (B) in combination, it is possible to improve moldability and to obtain excellent heat resistance.
The aliphatic polyester resin composition of the present invention contains an inorganic filler (C) in a predetermined ratio in addition to the aliphatic polyester resin (A) and the polyhydroxyalkanoate (B), and can be imparted with appropriate rigidity and have excellent pierceability.
In addition, the addition of the inorganic filler (C) increases the surface area of the molded article, and further increases the contact area with the decomposition enzymes produced by the microorganisms as the inorganic filler falls off when decomposition is accelerated, thereby accelerating the biodegradation rate of the aliphatic polyester resin (A) and the polyhydroxyalkanoate (B). In addition, the inorganic filler (C) also acts as a nucleating agent, which effectively improves moldability, so that by containing the inorganic filler (C) in a specified ratio, it becomes possible to provide a tubular body with even better room temperature biodegradability and marine biodegradability with good moldability and productivity.

[Aliphatic polyester resin composition]
The aliphatic polyester resin composition of the present invention, which contains an aliphatic polyester resin (A), a polyhydroxyalkanoate (B), and preferably further contains an inorganic filler (C), will be described below.

<Aliphatic polyester resin (A)>
The aliphatic polyester resin (A) used in the present invention (hereinafter sometimes referred to as "polyester resin (A)") is an aliphatic polyester resin containing aliphatic diol units and aliphatic dicarboxylic acid units as main constituent units.

The polyester resin (A) used in the present invention preferably has a ratio of succinic acid units in all dicarboxylic acid units of 5 mol% or more and 100 mol% or less. The polyester resin (A) may be a mixture of aliphatic polyester resins having different amounts of succinic acid units. For example, an aliphatic polyester resin that does not contain aliphatic dicarboxylic acid units other than succinic acid (containing only succinic acid units as aliphatic dicarboxylic acid units) and an aliphatic polyester resin that contains aliphatic dicarboxylic acid units other than succinic acid may be blended to adjust the amount of succinic acid units in the polyester resin (A) to within the above-mentioned preferred range.

More specifically, the polyester resin (A) is a polyester resin containing an aliphatic diol unit represented by the following formula (1) and an aliphatic dicarboxylic acid unit represented by the following formula (2).
-O-R ¹ -O- (1)
-OC- ^R2 -CO- (2)

In formula (1), ^R1 represents a divalent aliphatic hydrocarbon group. In formula (2), ^R2 represents a divalent aliphatic hydrocarbon group. The aliphatic diol units and aliphatic dicarboxylic acid units represented by formulas (1) and (2) may be derived from a compound derived from petroleum or a compound derived from a plant raw material, but are preferably derived from a compound derived from a plant raw material.

When the polyester resin (A) is a copolymer, the polyester resin (A) may contain two or more aliphatic diol units represented by formula (1), and the polyester resin (A) may contain two or more aliphatic dicarboxylic acid units represented by formula (2).

As mentioned above, the aliphatic dicarboxylic acid unit represented by formula (2) preferably contains succinic acid units in an amount of 5 mol% or more and 100 mol% or less based on the total dicarboxylic acid units. By setting the amount of succinic acid constitutional units in the polyester resin (A) within the above-mentioned predetermined range, it is possible to obtain a biodegradable resin composition that has improved moldability and excellent heat resistance and decomposability. For the same reason, the amount of succinic acid units in the polyester resin (A) is preferably 10 mol% or more, more preferably 50 mol% or more, even more preferably 64 mol% or more, and particularly preferably 68 mol% or more based on the total dicarboxylic acid units.
Hereinafter, the ratio of succinic acid units to all dicarboxylic acid units in the polyester resin (A) may be referred to as the "succinic acid unit amount".
In addition, it is more preferable that the aliphatic dicarboxylic acid unit represented by formula (2) contains one or more kinds of aliphatic dicarboxylic acid units other than succinic acid in an amount of 5 mol% to 50 mol% based on the total dicarboxylic acid units. By copolymerizing the aliphatic dicarboxylic acid units other than succinic acid within the above-mentioned predetermined range, the crystallization degree of the polyester resin (A) can be reduced, and biodegradability can be increased. For the same reason, the amount of the aliphatic dicarboxylic acid units other than succinic acid in the polyester resin (A) is preferably 10 mol% to 45 mol%, more preferably 15 mol% to 40 mol%, based on the total dicarboxylic acid units.

The aliphatic diol that gives the diol unit represented by formula (1) is not particularly limited, but from the viewpoint of moldability and mechanical strength, an aliphatic diol having 2 to 10 carbon atoms is preferred, and an aliphatic diol having 4 to 6 carbon atoms is particularly preferred. Examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,4-cyclohexanedimethanol, and among these, 1,4-butanediol is particularly preferred. Note that two or more of the above aliphatic diols can be used.

The aliphatic dicarboxylic acid component that gives the aliphatic dicarboxylic acid unit represented by formula (2) is not particularly limited, but is preferably an aliphatic dicarboxylic acid having 2 to 40 carbon atoms or a derivative such as an alkyl ester thereof, and particularly preferably an aliphatic dicarboxylic acid having 4 to 10 carbon atoms or a derivative such as an alkyl ester thereof. Examples of aliphatic dicarboxylic acids having 4 to 10 carbon atoms other than succinic acid or derivatives such as an alkyl ester thereof include adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, etc., and derivatives such as alkyl esters thereof. Among these, adipic acid and sebacic acid are preferred, and adipic acid is particularly preferred. The above aliphatic dicarboxylic acid components can be used in combination of two or more kinds, and in this case, a combination of succinic acid and adipic acid is preferred.

The polyester resin (A) may have a repeating unit (aliphatic oxycarboxylic acid unit) derived from an aliphatic oxycarboxylic acid. Specific examples of the aliphatic oxycarboxylic acid component that gives the aliphatic oxycarboxylic acid unit include, for example, 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, and the like, or derivatives thereof such as lower alkyl esters or intramolecular esters. When optical isomers exist in these, they may be in any of the D-form, L-form, or racemic form, and may be in any of the forms of solid, liquid, or aqueous solution. Among these, lactic acid or glycolic acid or derivatives thereof are particularly preferred. These aliphatic oxycarboxylic acids may be used alone or as a mixture of two or more.

When polyester resin (A) contains these aliphatic oxycarboxylic acid units, the content 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), from the viewpoint of moldability, assuming that all constituent units constituting polyester resin (A) are 100 mol %.

The polyester resin (A) may have an increased melt viscosity by copolymerizing a trifunctional or higher aliphatic polyhydric alcohol, a trifunctional or higher aliphatic polycarboxylic acid or its anhydride, or a trifunctional or higher aliphatic polyoxycarboxylic acid component.

Specific examples of trifunctional aliphatic polyhydric alcohols include trimethylolpropane, glycerin, etc., and specific examples of tetrafunctional aliphatic polyhydric alcohols include pentaerythritol, etc. These may be used alone or in combination of two or more.
A specific example of a trifunctional aliphatic polycarboxylic acid or its anhydride is propanetricarboxylic acid or its anhydride, and a specific example of a tetrafunctional polycarboxylic acid or its anhydride is cyclopentanetetracarboxylic acid or its anhydride, etc. These may be used alone or in combination of two or more.

In addition, trifunctional aliphatic oxycarboxylic acids are divided into (i) a type having two carboxyl groups and one hydroxyl group in the same molecule, and (ii) a type having one carboxyl group and two hydroxyl groups. Either type can be used, but from the viewpoint of moldability, mechanical strength, and the appearance of the molded product, (i) a type having two carboxyl groups and one hydroxyl group in the same molecule, such as malic acid, is preferred, and more specifically, malic acid is preferably used. In addition, tetrafunctional aliphatic oxycarboxylic acid components are divided into (i) a type having three carboxyl groups and one hydroxyl group in the same molecule, (ii) a type having two carboxyl groups and two hydroxyl groups in the same molecule, and (iii) a type having three hydroxyl groups and one carboxyl group in the same molecule. Either type can be used, but those having multiple carboxyl groups are preferred, and more specifically, citric acid, tartaric acid, etc. can be mentioned. These can be used alone or in combination of two or more types.

When the polyester resin (A) contains such structural units derived from trifunctional or higher functional components, the content thereof, with respect to all structural units constituting the aliphatic polyester resin (A) being taken as 100 mol %, is generally 0 mol % or more in lower limit, preferably 0.01 mol % or more in upper limit, and generally 5 mol % or less, preferably 2.5 mol % or less in upper limit.

The method for producing the aliphatic polyester resin (A) according to the present invention can employ a known method for producing polyesters. In addition, the polycondensation reaction can be carried out under suitable conditions that have been conventionally used, and is not particularly limited. Usually, a method is employed in which the degree of polymerization is further increased by carrying out a decompression operation after the esterification reaction has progressed.

When reacting a diol component forming a diol unit with a dicarboxylic acid component forming a dicarboxylic acid unit during the production of aliphatic polyester resin (A), the amounts of the diol component and the dicarboxylic acid component used are set so that the aliphatic polyester resin (A) produced has the desired composition. Usually, the diol component and the dicarboxylic acid component react in substantially equimolar amounts, but since the diol component is distilled off during the esterification reaction, it is usually used in a 1 to 20 mol % excess over the dicarboxylic acid component.

When the aliphatic polyester resin (A) contains components (optional components) other than the essential components such as aliphatic oxycarboxylic acid units and polyfunctional component units, the corresponding compounds (monomers and oligomers) are reacted so that the aliphatic oxycarboxylic acid units and polyfunctional component units each have the desired composition. In this case, there is no restriction on the timing and method of introducing the optional components into the reaction system, and they can be any as long as they can produce the aliphatic polyester resin (A) suitable for the present invention.

For example, the timing and method of introducing the aliphatic oxycarboxylic acid into the reaction system is not particularly limited as long as it is before the polycondensation reaction between the diol component and the dicarboxylic acid component, and examples of such methods include (1) a method in which the catalyst is dissolved in the aliphatic oxycarboxylic acid solution in advance and mixed, and (2) a method in which the catalyst is introduced into the reaction system and mixed at the same time when the raw materials are charged.

The compound that forms the multifunctional component unit may be introduced at the same time as other monomers or oligomers at the beginning of the polymerization, or may be introduced after the ester exchange reaction and before the pressure reduction is started. However, it is preferable to introduce the compound at the same time as other monomers or oligomers in terms of simplifying the process.

Aliphatic polyester resin (A) is usually produced in the presence of a catalyst. Any catalyst that can be used in the production of known polyester resins can be selected as the catalyst as long as it does not significantly impair the effects of the present invention. Examples of suitable catalysts include metal compounds of germanium, titanium, zirconium, hafnium, antimony, tin, magnesium, calcium, zinc, etc. Among these, germanium compounds and titanium compounds are suitable.

Examples of germanium compounds that can be used as catalysts include organic germanium compounds such as tetraalkoxygermanium, and inorganic germanium compounds such as germanium oxide and germanium chloride. Among these, germanium oxide, tetraethoxygermanium, and tetrabutoxygermanium are preferred in terms of cost and availability, with germanium oxide being particularly preferred.

Examples of titanium compounds that can be used as catalysts include organic titanium compounds such as tetraalkoxytitanium compounds, such as tetrapropyl titanate, tetrabutyl titanate, and tetraphenyl titanate. Among these, tetrapropyl titanate and tetrabutyl titanate are preferred because of their price and availability.

In addition, other catalysts may be used in combination as long as the purpose of the present invention is not impaired. Note that one catalyst may be used alone, or two or more catalysts may be used in any combination and ratio.

The amount of catalyst used may be any amount as long as it does not significantly impair the effects of the present invention, but is usually at least 0.0005% by mass, more preferably at least 0.001% by mass, and usually at most 3% by mass, preferably at most 1.5% by mass, based on the amount of monomer used. Below the lower limit of this range, the effect of the catalyst may not be apparent, and above the upper limit, the production cost may increase, the resulting polymer may become significantly discolored, or the hydrolysis resistance may decrease.

The timing of introducing the catalyst is not particularly limited as long as it is before the polycondensation reaction, and it may be introduced when the raw materials are charged, or when the pressure reduction starts. When introducing an aliphatic oxycarboxylic acid unit, it is preferable to introduce it simultaneously with a monomer or oligomer that forms an aliphatic oxycarboxylic acid unit, such as lactic acid or glycolic acid, when the raw materials are charged, or to dissolve the catalyst in an aqueous aliphatic oxycarboxylic acid solution and introduce it. In particular, the method of dissolving the catalyst in an aqueous aliphatic oxycarboxylic acid solution and introducing it is preferable because it increases the polymerization rate.

The reaction conditions such as temperature, polymerization time, and pressure when producing the aliphatic polyester resin (A) are arbitrary as long as they do not significantly impair the effects of the present invention. However, the reaction temperature of the esterification reaction and/or transesterification reaction between the dicarboxylic acid component and the diol component has a lower limit of usually 150°C or more, preferably 180°C or more, and an upper limit of usually 260°C or less, preferably 250°C or less. The reaction atmosphere is usually an inert atmosphere such as nitrogen or argon. Furthermore, the reaction pressure is usually normal pressure to 10 kPa, and normal pressure is preferable. The reaction time has a lower limit of usually 1 hour or more, and an upper limit of usually 10 hours or less, preferably 6 hours or less, and more preferably 4 hours or less. If the reaction temperature is too high, excessive production of unsaturated bonds occurs, gelation caused by the unsaturated bonds occurs, and control of the polymerization may become difficult.

In addition, the polycondensation reaction after the esterification reaction and/or transesterification reaction between the dicarboxylic acid component and the diol component is desirably carried out under a vacuum pressure of usually 0.01×10 ³ Pa or more, preferably 0.03×10 ³ Pa or more, and usually 1.4×10 ³ Pa or less, preferably 0.4×10 ³ Pa or less. In addition, the lower limit of the reaction temperature at this time is usually 150° C. or more, preferably 180° C. or more, and the upper limit is usually 260° C. or less, preferably 250° C. or less. Furthermore, the lower limit of the reaction time is usually 2 hours or more, and the upper limit is usually 15 hours or less, preferably 10 hours or less. If the reaction temperature is too high, gelation caused by the unsaturated bonds due to excessive production of unsaturated bonds may occur, making it difficult to control the polymerization.

When producing the aliphatic polyester resin (A), a chain extender such as a carbonate compound or a diisocyanate compound can also be used. In this case, the amount of the chain extender is usually 10 mol% or less, preferably 5 mol% or less, more preferably 3 mol% or less, as the ratio of carbonate bond or urethane bond in the polyester resin (A) when the total structural units constituting the aliphatic polyester resin are 100 mol%. However, if urethane bond or carbonate bond exists in the aliphatic polyester resin (A), biodegradability may be inhibited, so in the present invention, the carbonate bond is less than 1 mol%, preferably 0.5 mol% or less, more preferably 0.1 mol% or less, and the urethane bond is 0.55 mol% or less, preferably 0.3 mol% or less, more preferably 0.12 mol% or less, and even more preferably 0.05 mol% or less, relative to the total structural units constituting the aliphatic polyester resin (A). This amount is 0.9 parts by mass or less, preferably 0.5 parts by mass or less, more preferably 0.2 parts by mass or less, and even more preferably 0.1 parts by mass or less, calculated per 100 parts by mass of the aliphatic polyester resin (A). In particular, if the amount of urethane bonds exceeds the upper limit, the decomposition of the urethane bonds may cause problems in the film formation process, such as smoke or odor from the molten film exiting the die outlet, and film breakage due to foaming may occur in the molten film, making it impossible to mold stably.
The carbonate bond amount and urethane bond amount in the aliphatic polyester resin (A) can be determined by calculation from the results of NMR measurements such as ¹ H-NMR and ¹³ C-NMR.

Specific examples of carbonate compounds that can be used as the chain extender include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, ethylene carbonate, diamyl carbonate, and dicyclohexyl carbonate. In addition, carbonate compounds that are derived from hydroxy compounds such as phenols and alcohols and are made of the same or different hydroxy compounds can also be used.

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

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

It is also possible to produce high molecular weight polyester resins using these chain extenders (coupling agents) using conventional techniques. After polycondensation is complete, the chain extender is added to the reaction system in a homogeneous molten state without a solvent, and is reacted with the polyester obtained by polycondensation.

More specifically, a polyester resin having a higher molecular weight can be obtained by reacting the chain extender with a polyester having a terminal group substantially containing a hydroxyl group and a weight average molecular weight (Mw) of 20,000 or more, preferably 40,000 or more, obtained by catalytically reacting a diol component with a dicarboxylic acid component. A prepolymer having a weight average molecular weight of 20,000 or more can be produced by using a small amount of chain extender without forming a gel during the reaction, because it is not affected by the remaining catalyst even under harsh conditions such as a molten state. Here, the weight average molecular weight (Mw) of the polyester resin is calculated as a monodisperse polystyrene conversion value from the measured value by gel permeation chromatography (GPC) at a measurement temperature of 40°C using chloroform as a solvent.

Therefore, for example, when the polyester resin is further increased in molecular weight using the above-mentioned diisocyanate compound as a chain extender, it is preferable to use a prepolymer having a weight average molecular weight of 20,000 or more, preferably 40,000 or more. If the weight average molecular weight is less than 20,000, the amount of diisocyanate compound used to increase the molecular weight may increase, resulting in a decrease in heat resistance. Using such a prepolymer, a polyester resin having urethane bonds with a linear structure linked via urethane bonds derived from the diisocyanate compound is produced.

The pressure during chain extension is usually 0.01 MPa or more and 1 MPa or less, preferably 0.05 MPa or more and 0.5 MPa or less, more preferably 0.07 MPa or more and 0.3 MPa or less, but normal pressure is most preferred.

The reaction temperature during chain extension has a lower limit of usually 100°C or higher, preferably 150°C or higher, more preferably 190°C or higher, and most preferably 200°C or higher, and an upper limit of usually 250°C or lower, preferably 240°C or lower, and more preferably 230°C or lower. If the reaction temperature is too low, the viscosity will be high, making it difficult to achieve a uniform reaction, and high stirring power will tend to be required, while if the reaction temperature is too high, gelation and decomposition of the polyester resin will tend to occur at the same time.

The time for chain extension is usually 0.1 minutes or more, preferably 1 minute or more, and more preferably 5 minutes or more, and the upper limit is usually 5 hours or less, preferably 1 hour or less, more preferably 30 minutes or less, and most preferably 15 minutes or less. If the time for chain extension is too short, the effect of adding the chain extender tends not to be realized, and if it is too long, gelation or decomposition of the polyester resin tends to occur.

The molecular weight of the aliphatic polyester resin (A) used in the present invention can be measured by gel permeation chromatography (GPC). The weight average molecular weight (Mw) using monodisperse polystyrene as the standard is usually 10,000 to 1,000,000, but is preferably 20,000 to 500,000, more preferably 50,000 to 400,000, because this is advantageous in terms of moldability and mechanical strength.

The melt flow rate (MFR) of the aliphatic polyester resin (A) is a value measured at 190°C and a load of 2.16 kg according to JIS K7210 (1999), and is usually 0.1 g/10 min to 100 g/10 min, but from the viewpoint of moldability and mechanical strength, it is preferably 50 g/10 min or less, and particularly preferably 30 g/10 min or less. The MFR of the aliphatic polyester resin (A) can be adjusted by the molecular weight.

The melting point of the aliphatic polyester resin (A) is preferably 70° C. or higher, more preferably 75° C. or higher, and is preferably 170° C. or lower, more preferably 150° C. or lower, particularly preferably lower than 130° C. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range.
The elastic modulus of the aliphatic polyester resin (A) is preferably 180 to 1000 MPa.
If the melting point is outside the above range, moldability is poor, if the elastic modulus is less than 180 MPa, problems are likely to occur in moldability, and if the elastic modulus exceeds 1000 MPa, the obtained tubular body tends to be easily cracked.

The method for adjusting the melting point and elastic modulus of the aliphatic polyester resin (A) is not particularly limited. For example, the melting point and elastic modulus can be adjusted by selecting the type of copolymerization component of the aliphatic dicarboxylic acid component other than succinic acid, adjusting the copolymerization ratio of each, or combining them.
As the aliphatic polyester resin (A), commercially available products can be used, and examples of the products that can be used include "BioPBS (registered trademark) FZ71PB", "BioPBS (registered trademark) FZ71PM", "BioPBS (registered trademark) FZ91PB", "BioPBS (registered trademark) FZ91PM", "BioPBS (registered trademark) FD92PB", and "BioPBS (registered trademark) FD92PM" manufactured by PTTMCC Biochem.

In the present invention, the aliphatic polyester resin (A) is not limited to one type, and a blend of two or more types of aliphatic polyester resins (A) differing in the types of constituent units, the ratio of constituent units, the manufacturing method, the physical properties, etc., can be used.

<Polyhydroxyalkanoate (B)>
The polyhydroxyalkanoate (hereinafter sometimes referred to as PHA) (B) used in the present invention is an aliphatic polyester containing repeating units represented by the general formula: [-CHR-CH ₂ -CO-O-] (wherein R is an alkyl group having 1 to 15 carbon atoms), and is a copolymer containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units as main constituent units.

From the viewpoints of moldability and thermal stability, the polyhydroxyalkanoate (B) used in the present invention preferably contains 80 mol % or more, and more preferably 85 mol % or more, of 3-hydroxybutyrate units as a constituent component. Also, those produced by microorganisms are preferred. Specific examples of polyhydroxyalkanoate (B) include poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resins, poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) copolymer resins, and the like.
In particular, from the viewpoints of molding processability and physical properties of the resulting molded article, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer resin, ie, PHBH, is preferred.

In the polyhydroxyalkanoate (B), the composition ratio of 3-hydroxybutyrate (hereinafter sometimes referred to as 3HB) to the copolymerized comonomer such as 3-hydroxyhexanoate (hereinafter sometimes referred to as 3HH), i.e., the monomer ratio in the copolymer resin, is preferably 3-hydroxybutyrate/comonomer = 97/3 to 80/20 (mol %/mol %), more preferably 95/5 to 85/15 (mol %/mol %), from the viewpoint of molding processability and molded product quality. If this comonomer ratio is less than 3 mol%, molding may be difficult because the molding temperature and the thermal decomposition temperature are close to each other. If the comonomer ratio exceeds 20 mol%, the crystallization of the polyhydroxyalkanoate (B) becomes slow, and productivity may deteriorate.

The ratio of each monomer in the polyhydroxyalkanoate (B) can be measured by gas chromatography as follows.
To approximately 20 mg of dried PHA, 2 ml of a sulfuric acid/methanol mixture (15/85 (mass ratio)) and 2 ml of chloroform are added, the container is sealed, and heated at 100°C for 140 minutes to obtain the methyl ester of the PHA decomposition product. After cooling, 1.5 g of sodium bicarbonate is gradually added to neutralize the mixture, and the mixture is left to stand until the evolution of carbon dioxide gas stops. After adding 4 ml of diisopropyl ether and mixing well, the monomer unit composition of the PHA decomposition product in the supernatant is analyzed by capillary gas chromatography to determine the ratio of each monomer in the copolymer resin.

The weight average molecular weight (hereinafter sometimes referred to as Mw) of the polyhydroxyalkanoate (B) used in the present invention can be measured by the above-mentioned gel permeation chromatography (GPC). The weight average molecular weight (Mw) using monodisperse polystyrene as the standard substance is usually 200,000 or more and 2,500,000 or less, but is preferably 250,000 or more and 2,000,000 or less, more preferably 300,000 or more and 1,000,000 or less, because it is advantageous in terms of moldability and mechanical strength. If the weight average molecular weight is less than 200,000, the mechanical properties may be poor, and if it exceeds 2,500,000, molding processing may be difficult.

The melt flow rate (MFR) of polyhydroxyalkanoate (B) is a value measured at 190°C under a load of 2.16 kg according to JIS K7210 (1999), and is preferably 1 g/10 min to 100 g/10 min, but from the viewpoint of moldability and mechanical strength, it is more preferably 80 g/10 min or less, and particularly preferably 50 g/10 min or less. The MFR of polyhydroxyalkanoate (B) can be adjusted by the molecular weight.

The melting point of polyhydroxyalkanoate (B) is preferably 100°C or higher, more preferably 120°C or higher, and is preferably 180°C or lower, more preferably 170°C or lower, and particularly preferably less than 160°C. When there are multiple melting points, it is preferable that at least one of the melting points is within the above range.

Polyhydroxyalkanoate (B) is produced by, for example, a microorganism such as Alcaligenes eutrophus AC32 strain (international deposit under the Budapest Treaty, international depositary authority: National Institute of Advanced Industrial Science and Technology Patent Organism Depositary Center (1-1-1 Central 6, Higashi 1-chome, Tsukuba-shi, Ibaraki-ken, Japan), original deposit date: August 12, 1996, transferred on August 7, 1997, deposit number FERM BP-6038 (transferred from original deposit FERM P-15786)) (J. Bacteriol., 179, 4821 (1997)), which is an Alcaligenes eutrophus into which the PHA synthase gene derived from Aeromonas caviae has been introduced.

As the polyhydroxyalkanoate (B), commercially available products can be used. Commercially available polyhydroxyalkanoates (B) containing 3-hydroxybutyrate units and 3-hydroxyhexanoate units as main constituent units include Kaneka Corporation's "Aonilex (registered trademark) X131N", "Aonilex (registered trademark) X131A", "Aonilex (registered trademark) 151A", "Aonilex (registered trademark) 151C", "PHBH (registered trademark) X331N", "PHBH (registered trademark) X131A", "PHBH (registered trademark) 151A", and "PHBH (registered trademark) 151C".

In the present invention, the polyhydroxyalkanoate (B) is not limited to one type, and a blend of two or more types of polyhydroxyalkanoates (B) differing in the types of constituent units, the ratio of constituent units, the production method, the physical properties, etc., can be used.

<Inorganic Filler (C)>
The aliphatic polyester resin composition of the present invention further contains an inorganic filler (C) in addition to the polyester resin (A) and the polyhydroxyalkanoate (B).

The inorganic filler (C) used in the present invention includes anhydrous silica, mica, talc, titanium oxide, calcium carbonate, diatomaceous earth, allophane, bentonite, potassium titanate, zeolite, sepiolite, smectite, kaolin, kaolinite, glass, limestone, carbon, wollastonite, calcined perlite, silicates such as calcium silicate and sodium silicate, hydroxides such as aluminum oxide, magnesium carbonate and calcium hydroxide, salts such as ferric carbonate, zinc oxide, iron oxide, aluminum phosphate and barium sulfate, and the like, with talc, calcium carbonate and zeolite being preferred.

Some inorganic fillers, such as calcium carbonate and limestone, have soil conditioner properties. If a tubular body made of an aliphatic polyester resin composition containing a biomass-derived aliphatic polyester resin (A) and polyhydroxyalkanoate (B), which contains a particularly large amount of these inorganic fillers, is dumped into the soil, the inorganic filler (C) remains after biodegradation and functions as a soil conditioner, thereby enhancing its usefulness as a biodegradable resin.

In addition, inorganic fillers (C) can be classified according to their shape, and include fibrous, spherical, plate-like, and needle-like fillers, with spherical or plate-like fillers being preferred. Examples of spherical fillers include calcium carbonate, spherical silica, spherical glass beads, and graphite. Examples of plate-like fillers include talc, kaolin, mica, clay, sericite, glass flakes, synthetic hydrotalcite, various metal foils, graphite, molybdenum disulfide, tungsten disulfide, boron nitride, plate-like iron oxide, plate-like calcium carbonate, plate-like aluminum hydroxide, and zeolite. From the viewpoints of ease of blending, rigidity, moldability, decomposability, and enhanced deodorizing effect, it is preferable to use talc, mica, or clay, calcium carbonate, and zeolite.

The particle size of the inorganic filler (C) used in the present invention is preferably 0.5 μm or more, more preferably 0.6 μm or more, even more preferably 0.7 μm or more, and particularly preferably 1.0 μm or more, for the reason of handling. On the other hand, the average particle size is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.
Here, the method for measuring the average particle size of the inorganic filler (C) is not particularly limited, but a specific example of the measuring method includes a method in which the specific surface area per 1 g of powder is measured using a Shimadzu Corporation powder specific surface area measuring device SS-100 (constant pressure air permeability method), and the average particle size of the filler is calculated from the measurement result of the specific surface area by the air permeability method in accordance with JIS M8511 using the following formula:
Average particle size (μm)=10,000×{6/(specific gravity of filler×specific surface area)}

The inorganic filler (C) may be used alone or in any combination of two or more in any ratio.

Specific examples of talc that can be used as a suitable inorganic filler (C) include Microace manufactured by Nippon Talc Co., Ltd., and MG113 and MG115 manufactured by Fuji Talc Kogyo Co., Ltd. Specific examples of calcium carbonate that can be used as a suitable inorganic filler (C) include Softon 1200 and 2200 manufactured by Bihoku Funka Kogyo Co., Ltd.

<Mixing ratio of aliphatic polyester resin (A), polyhydroxyalkanoate (B) and inorganic filler (C)>
The mass ratio of the aliphatic polyester resin (A) and the polyhydroxyalkanoate (B) contained in the aliphatic polyester resin composition of the present invention is preferably aliphatic polyester resin (A)/polyhydroxyalkanoate (B)=40/60 to 10/90, more preferably 45/55 to 15/85, and even more preferably 50/50 to 20/80, from the viewpoint of improving rigidity and ease of molding process. On the other hand, from the viewpoint of reducing the odor felt when used in food packaging materials, aliphatic polyester resin (A)/polyhydroxyalkanoate (B)=50/50 to 90/10, more preferably 51/49 to 85/15, and even more preferably 52/48 to 80/20.

The content of the inorganic filler (C) in the aliphatic polyester resin composition of the present invention is 5 to 50% by mass, preferably 10 to 45% by mass, and more preferably 15 to 40% by mass, based on the total of the aliphatic polyester resin (A), the polyhydroxyalkanoate (B), and the inorganic filler (C). If the content of the inorganic filler (C) is less than the above lower limit, the above-mentioned effects of blending the inorganic filler (C) cannot be fully obtained, and the effects of improving room temperature biodegradability, marine biodegradability, and moldability cannot be obtained. On the other hand, if the content of the inorganic filler (C) is more than the above upper limit, mechanical strength such as impact resistance decreases.

<Other resins>
The aliphatic polyester resin composition of the present invention may contain one or more resins other than the aliphatic polyester resin (A) and the polyhydroxyalkanoate (B), for example, synthetic resins such as aromatic polyester resins, polycarbonate, polyamide, polystyrene, polyolefin, acrylic resin, amorphous polyolefin, ABS, AS (acrylonitrile styrene), polycaprolactone, polyvinyl alcohol, and cellulose ester, and biodegradable resins such as polylactic acid and polybutylene adipate terephthalate (PBAT), which is an aliphatic aromatic polyester, within a range that does not impair the effects of the present invention.

When the aliphatic polyester resin composition of the present invention contains these other resins, in order to effectively obtain the effects of the present invention by including the aliphatic polyester resin (A) and the polyhydroxyalkanoate (B) as the resin components, it is preferable that the content of the other resins is 70 parts by mass or less, particularly 50 parts by mass or less, per 100 parts by mass of the total of the aliphatic polyester resin (A), the polyhydroxyalkanoate (B), and the other resins.

<Other ingredients>
The aliphatic polyester resin composition of the present invention may contain, as "other components", various additives such as lubricants, plasticizers, antistatic agents, antioxidants, light stabilizers, ultraviolet absorbers, dyes, pigments, hydrolysis inhibitors, crystal nucleating agents, antiblocking agents, light resistance agents, plasticizers, heat stabilizers, flame retardants, release agents, antifogging agents, surface wetting improvers, incineration aids, dispersing aids, various surfactants, and slip agents, as well as fine powders of animal/plant substances such as starch, cellulose, paper, wood flour, chitin/chitosan, coconut shell powder, and walnut shell powder, or mixtures thereof.
The aliphatic polyester resin composition of the present invention may also contain functional additives such as a freshness-preserving agent and an antibacterial agent.
These may be blended in any amount within the range that does not impair the effects of the present invention, and one type may be used alone, or two or more types may be mixed and used.

The content of these other components is usually preferably such that the total amount of the components to be mixed is 0.01% by mass or more and 40% by mass or less relative to the total amount of the aliphatic polyester resin composition of the present invention so as not to impair the physical properties of the aliphatic polyester resin composition of the present invention.

Among the other components, the antifogging agent may be kneaded into the aliphatic polyester resin composition beforehand, or may be applied to the surface of the molded product after molding. Specifically, the antifogging agent preferably used is an ester surfactant of a saturated or unsaturated aliphatic carboxylic acid having 4 to 20 carbon atoms and a polyhydric alcohol.

Examples of slip agents include unsaturated and saturated fatty acid amides and unsaturated and saturated fatty acid bisamides made of unsaturated and saturated fatty acids having 6 to 30 carbon atoms, with erucic acid amide, oleic acid amide, stearic acid amide and their bisamides being the most preferred. These can be blended in any amount within the range that does not impair the effects of the present invention, and one type may be used alone, or two or more types may be mixed and used.

Antiblocking agents include saturated fatty acid amides having 6 to 30 carbon atoms, saturated fatty acid bisamides, methylol amide, ethanol amide, natural silica, synthetic silica, synthetic zeolite, talc, etc.

Specific examples of light-resistant agents include bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl)sebacate, 2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-n-butyl-bis(2,2,6,6-tetramethyl-4-piperidyl)malonate, 2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-n-butyl-bis(1,2,2,6,6-pentamethyl-4-piperidyl)malonate, 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butyl-bis(2,2,6,6-tetramethyl-4 -piperidyl)malonate, 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butyl-bis(1,2,2,6,6-pentamethyl-4-piperidyl)malonate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate, mixed(2,2,6,6-tetramethyl-4-piperidyl/tridecyl)-1,2,3,4-butane tetracarboxylate, mixed(1,2,2,6,6-pentamethyl-4-piperidyl/tridecyl)-1,2,3,4-butane tetracarboxylate, mixed{2, 2,6,6-tetramethyl-4-piperidyl/β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro[5.5]undecane]diethyl}-1,2,3,4-butane tetracarboxylate, mixed {1,2,2,6,6-pentamethyl-4-piperidyl/β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro[5.5]undecane]diethyl}-1,2,3,4-butane tetracarboxylate, 1,2-bis(3-oxo-2,2,6,6-tetramethyl-4-piperidyl)ethane, 1-(3,5-di-t-butyl-4-hydroxyphenyl)-1,1-bis(2,2,6,6-tetramethyl-4-piperidyloxycarbonyl)pentamethyl Examples of such compounds include poly[1-oxyethylene(2,2,6,6-tetramethyl-1,4-piperidyl)oxysuccinyl], poly[2-(1,1,4-trimethylbutylimino)-4,6-triazinediyl-(2,2,6,6-tetramethyl-4-piperidyl)iminohexamethylene-(2,2,6,6-tetramethyl-4-piperidyl)imino], N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(2,2,6,6-tetramethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate and its N-methyl compound, and polycondensate of succinic acid and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine.

Among these, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate and 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butyl-bis(1,2,2,6,6-pentamethyl-4-piperidyl)malonate are particularly preferred.

Among ultraviolet absorbents such as benzophenone-based, benzotriazole-based, salicylic acid-based, and cyanoacrylate-based ultraviolet absorbents, benzotriazole-based ultraviolet absorbents are preferred, and specific examples include 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxy-phenol.

Antioxidants include BHT (dibutylhydroxytoluene), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3,3',3",5,5',5"-hexa-tert-butyl-α,α',α"-(mesitylene-2,4,6-triyl)tri-p-cresol, and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, calcium diethyl bis[{3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl}methyl]phosphonate, bis(2,2'-dihyd hindered phenol-based antioxidants such as N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl)-4-hydroxyphenyl]propionamide, tridecyl phosphite, diphenyl decyl phosphite, tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4'-diylbisphosphonite, bis[2,4-bis(1,1-dimethylethyl)- Examples of antioxidants include phosphorus-based antioxidants such as bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, lactone-based antioxidants such as the reaction product of 3-hydroxy-5,7-di-tert-butyl-furan-2-one and xylene, sulfur-based antioxidants such as dilauryl thiodipropionate and distearyl thiodipropionate, and mixtures of two or more of these. Among these, hindered phenol-based antioxidants are preferably used.

Preferred hindered phenol-based antioxidants include Irganox 3790, Irganox 1330, Irganox 1010, Irganox 1076, Irganox 3114, Irganox 1425WL, Irganox 1098, Irganox HP2225FL, Irganox HP2341, Irgafos XP-30 (all manufactured by BASF), and Sumilizer BBM-S (manufactured by Sumitomo Chemical). The most preferred antioxidants are Irganox 1010 (pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and Irganox 1330 (3,3',3",5,5',5"-hexa-tert-butyl-α,α',α"-(mesitylene-2,4,6-triyl)tri-p-cresol).

<Method of producing aliphatic polyester resin composition>
The aliphatic polyester resin composition of the present invention is produced by mixing the aliphatic polyester resin (A), the polyalkanoate (B), and the inorganic filler (C) with other resins and other components that are used as necessary.

This mixing step is carried out by mixing the aliphatic polyester resin (A), polyhydroxyalkanoate (B), and inorganic filler (C) with other resins and other components used as necessary in a predetermined ratio simultaneously or in any order using a mixer such as a tumbler, V-type blender, Nauter mixer, Banbury mixer, kneading roll, or extruder, and preferably melt-kneading the mixture.

The kneader used in the mixing step may be a melt kneader. There is no limitation on the type of twin-screw extruder or single-screw extruder, but a twin-screw extruder is more preferable for the purpose of achieving melt kneading according to the properties of the aliphatic polyester resin (A), polyhydroxyalkanoate (B), and inorganic filler (C) used.

The temperature during melt kneading is preferably 120 to 220° C., and more preferably 130 to 160° C. Within this temperature range, it is possible to shorten the time required for the melting reaction, prevent deterioration of color tone due to deterioration of the resin, and further improve practical physical properties such as impact resistance and moist heat resistance.
With regard to the melt-kneading time, from the viewpoint of more reliably avoiding the same resin deterioration as described above, unnecessary lengthening should be avoided, and the time is preferably from 20 seconds to 20 minutes, more preferably from 30 seconds to 15 minutes, and it is preferable to set the melt-kneading temperature and time conditions so as to satisfy this.

[Molded body]
The tubular body of the present invention is obtained by molding the aliphatic polyester resin composition of the present invention. Examples of the molding method include injection molding, extrusion molding, co-extrusion molding (film molding by inflation method or T-die method, laminate molding, pipe molding, electric wire/cable molding, molding of profile material), heat press molding, hollow molding (various blow moldings), thermoforming (vacuum molding, compressed air molding), plastic processing, powder molding (rotational molding), various nonwoven fabric moldings (dry method, adhesion method, entanglement method, spunbond method, etc.), etc. Among them, extrusion molding is preferably applied.

In addition, the tubular body of the present invention formed by molding the aliphatic polyester resin composition of the present invention can be subjected to various secondary processing steps in order to impart surface functions such as chemical functions, electrical functions, magnetic functions, mechanical functions, friction/wear/lubrication functions, optical functions, thermal functions, and biocompatibility. Examples of secondary processing steps include bellows processing, embossing, painting, bonding, printing, metallizing (plating, etc.), machining, and surface treatments (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, coating, etc.).

[Application]
The tubular body of the present invention can be suitably used for such purposes as straws, tubes, hoses, cotton bud shafts, film or sheet cylinders, balloon sticks (holding rods), etc., particularly for disposable applications.

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 it does not exceed the gist of the invention. Note that the various manufacturing conditions and evaluation result values in the following examples are meant as preferred upper or lower limit values in the embodiments of the present invention, and the preferred range may be a range defined by a combination of the above-mentioned upper or lower limit values and the values of the following examples or values between the examples.

[Measurement of Melt Flow Rate (MFR) of Resin Used]
Based on JIS K7210 (1999), the measurement was performed using a melt indexer at 190° C. and a load of 2.16 kg. The unit is g/10 min.

[Ingredients used]
Details of the resins and inorganic fillers used in the examples and comparative examples are as follows.
In the following, "PBS" stands for "polybutylene succinate,""PBSA" stands for "polybutylene succinate adipate,""PLA" stands for "polylactic acid,""PHBH" stands for "poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)," and "PBAT" stands for "polybutylene adipate terephthalate."

<Aliphatic polyester resin (A)>
PBS (BioPBS FZ91PM manufactured by PTTMCC BioChem, MFR: 5.0 g/10 min, melting point: 113° C.)
PBSA (BioPBS FD92PM manufactured by PTTMCC Biochem, succinic acid unit amount in total dicarboxylic acid unit amount: 74 mol%, MFR: 5.0 g/10 min, melting point: 89° C.)

<Polyhydroxyalkanoate (B)>
PHBH-1 (PHBH (registered trademark) X131A, manufactured by Kaneka Corporation, 3HB/3HH molar ratio: 94/6, MFR: 6 g/10 min, melting point: 140° C.)
PHBH-2 (Aonilex (registered trademark) X151A, manufactured by Kaneka Corporation, 3HB/3HH molar ratio: 89/11, MFR: 6 g/10 min, melting point: 131° C.)

<Polylactic acid>
PLA (NatureWorks 4032D, MFR: 3.5 g/10 min, melting point: 170° C.)

<Aliphatic/aromatic polyester>
PBAT (Ecoflex C1200, manufactured by BASF, MFR: 4 g/10 min, melting point: 110° C.)

<Inorganic Filler (C)>
Talc (MG-115, manufactured by Fuji Talc Industries Co., Ltd., average particle size: 14 μm)
Talc (Microace K-1, manufactured by Nippon Talc Co., Ltd., average particle size: 8 μm)
_CaCO3 (Softon 1200, manufactured by Bihoku Funka Kogyo Co., Ltd., average particle size: 2 μm)

[Evaluation method]
The methods for evaluating various physical properties and characteristics in the examples and comparative examples are as follows.

<Moldability evaluation>
The moldability when obtaining straws using a tubular circular die was evaluated according to the following criteria.
◯: No surging or cutting defects occurred, and a good sample was obtained.
×: Surging or cutting failure occurred.

<Puncture test>
The tips of ten straws were cut at a 45° angle using general-purpose scissors. The tip of the straw was pierced by hand from 3.5 cm above a 40 μm-thick polyethylene film attached to a cup, and the condition was evaluated according to the following criteria.
A: All ten straws penetrated the polyethylene film without breaking.
Δ: 5 to 9 out of 10 fibers penetrate the polyethylene film.
x: None of the ten pieces penetrated the polyethylene film.

<Odor test>
Ten people were asked to evaluate whether they could detect an odor when drinking mineral water using the molded straws. The evaluation criteria are shown below.
◎: 2 or fewer people noticed the odor. ○: 3 or 4 people noticed the odor. ×: 5 or more people noticed the odor.

<Elmendorf tear test>
The measurement was performed based on JIS K7128-2 (2007). The higher the tear strength, the better the tear resistance, and thus the more preferable.

<Soil biodegradation test>
The sheets were stored in soil (moisture content 30%) collected from a farm in Mie Prefecture for 3 months at 28±2°C, after which the weight was measured and the biodegradability was evaluated according to the following criteria. The decomposition rate was calculated using the following formula.
Decomposition rate (%) = 100 - (sample weight after 3 months/sample weight before test) x 100
○: Decomposition rate is 90% or more △: Decomposition rate is 30% or more but less than 90% ×: Decomposition rate is less than 30%

<Biodegradation test in seawater>
The sheets were stored in seawater collected from Yokkaichi Port in Yokkaichi City, Mie Prefecture at 28±2°C for six months, after which their weights were measured and their biodegradability was evaluated according to the following criteria. The degree of decomposition was calculated using the following formula:
Degradation rate (%) = 100 - (sample weight after 6 months/sample weight before test) x 100
○: Decomposition rate is 50% or more △: Decomposition rate is 10% or more and less than 50% ×: Decomposition rate is less than 10%

<Marine biodegradability test (ASTM D6691)>
The amount of _CO2 generated 100 days after the start of the test was measured based on the test method of ASTM D6691, and the degree of biodegradation was calculated using a calculation method in accordance with ASTM D6691. The test was performed using seawater from the sea near Belgium, the measurement temperature was 30±2°C, and the evaluation sample was 60 mg of powder with an average particle size of 250 μm or less.

[Examples 1 to 6, Comparative Examples 1 and 2]
The raw materials shown in Table 1 were blended in the ratios shown in Table 1, extruded into strands using a twin-screw extruder with a screw diameter of φ30 mm at a kneading temperature of 140° C., and pelletized using a pelletizer. The resulting resin pellets were extruded into a tube shape with a diameter of 7 mm and a wall thickness of 0.2 mm using a tubular circular die to obtain straws, after which a piercing test and an odor test were performed. The odor test was performed only for Examples 1, 3, 4, and 6 and Comparative Examples 1 and 2.
Furthermore, the obtained pellets were pressed into sheets having a thickness of 100 μm, and biodegradation tests in soil and seawater were carried out.
The obtained pellets were powdered to an average particle size of 250 μm or less, and 60 mg of the powder was used to evaluate the marine biodegradability in accordance with the marine biodegradability test according to ASTM D6691.
The results are shown in Table 1.
In addition, "Talc" in Table 1 means "Talc (MG-115, manufactured by Fuji Talc Industries Co., Ltd., average particle size: 14 μm)" in Examples 1 to 3, and means "Talc (Micro Ace K-1, manufactured by Nippon Talc Co., Ltd., average particle size: 8 μm)" in Example 6.

[Comparative Example 3]
The raw materials shown in Table 1 were blended in the ratios shown in Table 1 and kneaded at 180°C, and the mixture was molded and evaluated in the same manner as in Example 1.

[Examples 7 and 8, Comparative Example 4]
The raw materials shown in Table 2 were blended in the ratios shown in Table 2, extruded into strands using a twin-screw extruder with a screw diameter of φ30 mm at a kneading temperature of 140°C, and pelletized using a pelletizer. The resulting resin pellets were molded using an inflation film molding machine with a screw diameter of φ40 mm at a molding temperature of 160°C and a blow ratio of 2.5 to obtain a tubular film with a wall thickness of 30 μm. A tear test was conducted on this film. In addition, a soil biodegradation test and a seawater biodegradation test were conducted on the resulting film.
The results are shown in Table 2.
In addition, "Talc" in Table 2 is "Talc (Microace K-1, manufactured by Nippon Talc Co., Ltd., average particle size: 8 μm)."

From Table 1, it can be seen that the tubular body of the present invention has higher biodegradability at room temperature and excellent biodegradability in seawater compared to molded bodies made from conventional biodegradable resins, and also has excellent moldability when obtaining molded bodies, as well as excellent mechanical properties such as puncture strength.
From Table 2, it can be seen that the tubular body of the present invention has high biodegradability at room temperature, excellent biodegradability in seawater, and also has high tear strength, so that it is difficult to tear even when used as a cylindrical body made of a film.

Claims (9)

A tubular body using an aliphatic polyester resin composition comprising an aliphatic polyester resin (A) containing, as main structural units, repeating units derived from an aliphatic diol and repeating units derived from an aliphatic dicarboxylic acid, a polyhydroxyalkanoate (B) and an inorganic filler (C), the polyhydroxyalkanoate (B) being a copolymer containing, as main structural units, 3-hydroxybutyrate units and 3-hydroxyhexanoate units, and the content of the inorganic filler (C) relative to the total amount of the aliphatic polyester resin (A), the polyhydroxyalkanoate (B) and the inorganic filler (C) being 5 to 50% by mass. The tubular body according to claim 1, wherein the inorganic filler (C) is one or more selected from the group consisting of anhydrous silica, calcium carbonate, talc, and zeolite. The tubular body according to claim 1 or 2, wherein the proportion of repeating units derived from succinic acid in all repeating units derived from dicarboxylic acids contained in the aliphatic polyester resin (A) is 5 mol % or more and 100 mol % or less. The tubular body according to any one of claims 1 to 3, which is an extrusion molded body. A straw made of a tubular body according to any one of claims 1 to 4. A cotton swab comprising the tubular body according to any one of claims 1 to 4. A balloon stick made of a tubular body according to any one of claims 1 to 4. A tubular body that has an absolute or relative biodegradability of 60% or more after 100 days in a marine biodegradability test (ASTM D6691) at a seawater temperature of 30°C ± 2°C. A straw made of the tubular body according to claim 8.