Method for producing modified aliphatic or aliphatic-aromatic thermoplastic polyester resin

Abstract

A method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin is provided, which method has excellent peroxide reaction efficiency. [Solution] A method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin, comprising: (A) a step of holding an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin and a specific peroxide at a predetermined temperature for 65 minutes or more; and (B) a step of maintaining the aqueous dispersion obtained in step (A) at a constant temperature.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin. [Background technology]

[0002] In recent years, due to consideration of the global environment, biodegradable plastics such as aliphatic or aliphatic-aromatic thermoplastic polyester resins have been actively developed. Among these biodegradable plastics, aliphatic or aliphatic-aromatic thermoplastic polyester resins, such as poly(3-hydroxyalkanoate) resins, which are biodegradable plastics produced by microorganisms using plant-derived raw materials as a carbon source, have attracted attention from the viewpoints of biodegradability and carbon neutrality.

[0003] In general, aliphatic or aliphatic-aromatic thermoplastic polyester resins have a problem of poor processability during melt molding. To address this problem, a technology has been disclosed in which molecules of an aliphatic or aliphatic-aromatic thermoplastic polyester resin are bonded (modified) to obtain a (modified) aliphatic or aliphatic-aromatic thermoplastic polyester resin having a branched structure.

[0004] For example, Patent Document 1 discloses a method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin by reacting a peroxide in an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2023 / 140097 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the above-mentioned conventional techniques are excellent, there is room for improvement in terms of the reaction efficiency of peroxides.

[0007] In view of the above-mentioned circumstances, one aspect of the present invention aims to provide a method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin, which has excellent reaction efficiency with a peroxide. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they have found that when reacting a peroxide in an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin, the reaction efficiency of the peroxide during the reaction can be improved by maintaining the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin and a peroxide at a relatively low temperature prior to the reaction, and impregnating the aliphatic or aliphatic-aromatic thermoplastic polyester resin with the peroxide, thereby completing the present invention.

[0009] That is, one aspect of the present invention includes the following configuration. [1] A method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin, comprising: (A) a step of holding an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin and a peroxide having a one-minute half-life temperature of 140°C or less at a temperature of 0°C or higher and lower than (the one-minute half-life temperature of the peroxide minus 50°C) for 65 minutes or longer; and (B) a step of maintaining the aqueous dispersion obtained in step (A) at a temperature of (the one-minute half-life temperature of the peroxide minus 50°C) or higher and lower than the one-minute half-life temperature of the peroxide, and 100°C or lower. [2] The manufacturing method according to [1], wherein the aliphatic or aliphatic-aromatic thermoplastic polyester resin is at least one selected from the group consisting of poly(3-hydroxyalkanoate) resins, polybutylene adipate terephthalate, polybutylene succinate adipate, polybutylene succinate, polybutylene sebacate terephthalate, polybutylene succinate adipate terephthalate, polycaprolactone, and polylactic acid. [3] The manufacturing method according to [1] or [2], wherein the aliphatic or aliphatic-aromatic thermoplastic polyester resin is a poly(3-hydroxyalkanoate) resin. [4] The manufacturing method according to [3], wherein the poly(3-hydroxyalkanoate)-based resin is at least one selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate). [5] The method according to any one of [1] to [4], wherein the amount of the peroxide used is 0.001 to 10 parts by weight per 100 parts by weight of the aliphatic or aliphatic-aromatic thermoplastic polyester resin. [6] The method according to any one of claims [1] to [5], wherein the peroxide is at least one selected from the group consisting of di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, bis(2-ethylhexyl)peroxydicarbonate, t-butylperoxy 2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, and 1,1,3,3-tetramethylbutylperoxyneodecanoate. [7] The manufacturing method according to any one of [1] to [6], wherein the step (A) comprises: (a1) an addition step of adding the peroxide to an aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin; and (a2) a stirring step of stirring the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin and the peroxide for 50 minutes or more. [8] The method according to any one of [1] to [7], wherein the maintenance time in the step (B) is 10 to 1,200 minutes. [9] The method according to any one of [1] to [8], wherein the temperature equal to or lower than the one-minute half-life temperature of the peroxide is 0 to 100°C. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to provide a method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin, which is excellent in peroxide reaction efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0011] One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, the term "A to B" representing a numerical range means "greater than or equal to A (including and greater than A) and less than or equal to B (including and less than B)."

[0012] 1. Method for producing modified aliphatic or aliphatic-aromatic thermoplastic polyester resin A method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin according to one embodiment of the present invention (hereinafter, sometimes referred to as "the production method") comprises: (A) a step of maintaining an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin and a peroxide having a one-minute half-life temperature of 140°C or less at a temperature of 0°C or higher and lower than (the one-minute half-life temperature of the peroxide minus 50°C) for 65 minutes or longer; and (B) a step of maintaining the aqueous dispersion obtained in step (A) at a temperature of (the one-minute half-life temperature of the peroxide minus 50°C) or higher and lower than the one-minute half-life temperature of the peroxide, and 100°C or lower.

[0013] Each step that may be included in this production method will be described in detail below.

[0014] <Process (A)> The present production method includes a step (sometimes simply referred to as "step (A)") of maintaining an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin and a peroxide having a one-minute half-life temperature of 140°C or less at a temperature of 0°C or higher and lower than the one-minute half-life temperature of the peroxide minus 50°C for 65 minutes or longer.

[0015] In step (A), an aliphatic or aliphatic-aromatic thermoplastic polyester resin and a peroxide having a one-minute half-life temperature of 140°C or less (sometimes simply referred to as "peroxide") are maintained in an aqueous dispersion at a temperature above 0°C and below the one-minute half-life temperature of the peroxide minus 50°C, thereby enabling the peroxide to be distributed (impregnated) within or near the aliphatic or aliphatic-aromatic thermoplastic polyester resin. Therefore, step (A) can also be considered a process of impregnating the aliphatic or aliphatic-aromatic thermoplastic polyester resin in the aqueous dispersion. The "maintenance" step in step (A) may include adding the aliphatic or aliphatic-aromatic thermoplastic polyester resin and / or the peroxide to the aqueous dispersion. The "maintenance" step in step (A) preferably includes a stirring step to uniformly disperse the aliphatic or aliphatic-aromatic thermoplastic polyester resin and / or the peroxide in the aqueous dispersion.

[0016] In step (A), the aliphatic or aliphatic-aromatic thermoplastic polyester resin to be modified is impregnated with a peroxide, which makes it possible to efficiently proceed with the modification reaction between the aliphatic or aliphatic-aromatic thermoplastic polyester resin and the peroxide in the subsequent step (B). This in turn makes it possible to provide a method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin that is excellent in peroxide reaction efficiency.

[0017] First, each material used in step (A) will be described in detail.

[0018] (Aliphatic or aliphatic-aromatic thermoplastic polyester resin) The aliphatic or aliphatic-aromatic thermoplastic polyester resin used in step (A) is an unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin, and can also be said to be an aliphatic or aliphatic-aromatic thermoplastic polyester resin to be modified.

[0019] In this specification, an aliphatic thermoplastic polyester resin refers to a thermoplastic polyester resin containing only aliphatic hydrocarbon groups as hydrocarbon groups, and an aliphatic-aromatic thermoplastic polyester resin refers to a thermoplastic polyester resin containing both aliphatic hydrocarbon groups and aromatic hydrocarbon groups as hydrocarbon groups.

[0020] Examples of aliphatic thermoplastic polyester resins include homopolymers or copolymers of hydroxyalkanoic acids or lactones, polymers of aliphatic diols and aliphatic dicarboxylic acids, etc. Examples of aliphatic-aromatic thermoplastic polyester resins include polymers of aliphatic diols and aromatic dicarboxylic acids and / or aliphatic dicarboxylic acids, etc.

[0021] More specifically, examples of the polymer or copolymer of hydroxyalkanoic acid or lactone include polyglycolic acid, polylactic acid, poly(3-hydroxyalkanoate) resin, polycaprolactone, poly(ethylene succinic acid), poly(1,4-butylene succinic acid), poly(ethylene sebacic acid), poly(1,4-butylene sebacic acid), poly(ethylene carbonate), and poly(propylene carbonate).

[0022] Examples of the aliphatic diol include alkylene diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and neopentyl glycol; oxyalkylene diols such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol; and cycloalkylene diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0023] Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, dimer acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, etc. These aliphatic dicarboxylic acids may also be their ester-forming derivatives.

[0024] Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, furandicarboxylic acid, and derivatives thereof such as alkyl esters.

[0025] From the viewpoint of environmental protection, the aliphatic or aliphatic-aromatic thermoplastic polyester resin used in step (A) is preferably a biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin.

[0026] Specific examples of biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resins include poly(3-hydroxyalkanoate)-based resins (hereinafter sometimes referred to as "P3HA"), polybutylene adipate terephthalate, polybutylene succinate adipate, polybutylene succinate, polybutylene sebacate terephthalate, polybutylene succinate adipate terephthalate, polycaprolactone, and polylactic acid. Among these, poly(3-hydroxyalkanoate)-based resins are particularly preferred because they can be produced by microorganisms using plant raw materials and have excellent environmental protection effects.

[0027] Poly(3-hydroxyalkanoate) resin P3HA is a 3-hydroxyalkanoate repeating unit of the formula: [—CHR—CH—CO—O—] (wherein R is C n H 2n+1 where n is an integer of 1 to 15.) as an essential repeating unit. The P3HA preferably contains 3-hydroxyalkanoate acid repeating units in an amount of 50 mol % or more, and more preferably 70 mol % or more, of all monomer repeating units (100 mol %).

[0028] Specific examples of P3HA include poly(3-hydroxybutyrate) (hereinafter sometimes referred to as "P3HB"), which is a homopolymer of 3HB, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (hereinafter sometimes referred to as "P3HB3HH"), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (hereinafter sometimes referred to as "P3HB4HB"), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), poly(3-hydroxybutyrate-co-3-hydroxydecanoate), poly(3-hydroxypropionate), etc. Among these, P3HB, P3HB3HH and P3HB4HB are preferred, with P3HB3HH being more preferred, in view of ease of industrial production using microorganisms.

[0029] In this specification, "poly(X-co-Y)" refers to a copolymer containing X repeating units and Y repeating units, and is intended to mean a copolymer obtained by copolymerizing a monomer from which the X repeating unit is derived and a monomer from which the Y repeating unit is derived. As described above, the name of a P3HA is determined by the repeating units contained in the P3HA. However, a very small amount (about 1 mol % or less) of a monomer contained in a P3HA may not be reflected in the name of the P3HA, provided that such a monomer does not significantly affect the physical properties of the P3HA. In other words, a P3HA may contain, in addition to the repeating units corresponding to its name, very small amounts of other repeating units.

[0030] When P3HA contains 3HB repeating units, from the viewpoint of the balance between flexibility and strength, the composition ratio of 3HB repeating units to repeating units other than 3HB repeating units (other repeating units) in the total monomer repeating units (100 mol%) in the P3HA (3HB repeating units / other repeating units) is preferably 99 / 1 (mol% / mol%) to 60 / 40 (mol% / mol%), more preferably 97 / 3 (mol% / mol%) to 70 / 30 (mol% / mol%), and even more preferably 95 / 5 (mol% / mol%) to 80 / 20 (mol% / mol%). When the composition ratio of 3HB repeating units in P3HA is 60 mol% or more, it is advantageous in that a resin product with superior rigidity can be provided. On the other hand, when the composition ratio of 3HB repeating units in P3HA is 99 mol% or less, it is advantageous in that a resin product with superior flexibility can be provided. The monomer composition ratio of P3HA can be measured by gas chromatography or the like (see, for example, WO 2014 / 020838).

[0031] P3HA can be produced by microorganisms. Examples of microorganisms capable of producing P3HA include Bacillus megaterium, a P3HB-producing bacterium discovered in 1925, as well as other naturally occurring microorganisms such as Cupriavidus necator (formerly Alcaligenes eutrophus and Ralstonia eutropha) and Alcaligenes latus. These microorganisms accumulate P3HB within their cells.

[0032] Known microorganisms that produce P3HA, a copolymer of 3HB and other hydroxyalkanoic acids, include Aeromonas caviae, which produces P3HB3HH, and Alcaligenes eutrophus, which produces poly(3-hydroxybutyrate-co-4-hydroxybutyrate). To increase P3HB3HH productivity, Alcaligenes eutrophus AC32 (FERM BP-6038) (T. Fukui, Y. Doi, J. Bacteriol., 179, pp. 4821-4830 (1997)) is particularly preferred. In addition to the above, genetically modified microorganisms containing various P3HA synthesis-related genes can also be used depending on the desired physical properties of P3HA.

[0033] The molecular weight of the P3HA used in the present production method is not particularly limited as long as it exhibits substantially sufficient physical properties for the intended application. For example, the weight-average molecular weight of P3HA is preferably 50,000 to 3,000,000, more preferably 100,000 to 1,000,000, and even more preferably 300,000 to 700,000. When the weight-average molecular weight of P3HA is 50,000 or more, the strength of the molded article tends to be improved. Furthermore, when the weight-average molecular weight of P3HA is 3,000,000 or less, the processability tends to be improved and molding tends to be easier. Note that the weight-average molecular weight of P3HA used herein is the value measured before the P3HA is modified.

[0034] In this specification, the weight-average molecular weight of P3HA can be determined as the molecular weight converted into polystyrene using gel permeation chromatography (GPC) (Shimadzu Corporation's "High-Performance Liquid Chromatograph 20A System"), a polystyrene gel column (Showa Denko KK's "KG 4A" and "K-806M"), and chloroform as the mobile phase. In this case, a calibration curve is prepared using polystyrenes with weight-average molecular weights of 31,400, 197,000, 668,000, and 1,920,000.

[0035] Polybutylene adipate terephthalate In this production method, polybutylene adipate terephthalate (PBAT) can be used as the biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin. It is intended to be a random copolymer of 1,4-butanediol, adipic acid, and terephthalic acid. Among these, PBAT obtained by reacting a mixture of (a) 35 to 95 mol% adipic acid or its ester-forming derivative, or a mixture thereof, and 5 to 65 mol% terephthalic acid or its ester-forming derivative, or a mixture thereof (the sum of these values ​​is 100 mol%) with a mixture containing (b) 1,4-butanediol is preferred, as described in JP-A-10-508640. The molar ratio of component (a) to component (b) is preferably 0.4:1 to 1.5:1. Furthermore, PBAT obtained by reacting a glycol compound such as ethylene glycol, propylene glycol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, bisphenol A, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol with the above-mentioned component (a) may be used instead of the 1,4-butanediol. Furthermore, PBAT obtained by reacting a dicarboxylic acid such as oxalic acid, succinic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis(p-carboxyphenyl)methane, anthracenedicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, or 5-tetrabutylphosphoniumisophthalic acid with the above-mentioned component (b) may be used instead of the adipic acid. Commercially available PBAT products include, for example, "Ecoflex C1200" manufactured by BASF.

[0036] Polybutylene succinate adipate In this production method, polybutylene succinate adipate (hereinafter also referred to as "PBSA"), which can be used as a biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin, refers to an aliphatic polyester copolymer synthesized by esterification and condensation polymerization of adipic acid with an aliphatic diol component primarily composed of 1,4-butanediol and an aliphatic dicarboxylic acid component primarily composed of succinic acid, such as succinic acid and / or its derivatives. Commercially available PBSA products include "BioPBS FD72" and "BioPBS FD92" manufactured by Mitsubishi Chemical Corporation.

[0037] Polybutylene succinate In this production method, the polybutylene succinate (hereinafter also referred to as "PBS") that can be used as the biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin refers to an aliphatic polyester copolymer synthesized by an esterification reaction and / or transesterification reaction, and a condensation polymerization reaction, between an aliphatic diol component primarily composed of 1,4-butanediol and an aliphatic dicarboxylic acid component primarily composed of succinic acid and / or its derivatives. Commercially available PBS products include "BioPBS FZ71" and "BioPBS FZ91" manufactured by Mitsubishi Chemical Corporation.

[0038] Polybutylene sebacate terephthalate In this production method, polybutylene sebacate terephthalate (hereinafter also referred to as "PBST"), which can be used as the biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin, is intended to be a random copolymer of 1,4-butanediol, sebacic acid, and terephthalic acid. Commercially available PBST products include "Ecoflex FS blend B1100" (registered trademark) manufactured by BASF.

[0039] Polybutylene succinate adipate terephthalate In this production method, polybutylene succinate adipate terephthalate (hereinafter also referred to as "PBSAT"), which can be used as the biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin, is intended to be a random copolymer of 1,4-butanediol, succinic acid, adipic acid, and terephthalic acid. PBSAT is preferably a copolymer containing succinic acid, adipic acid, and phthalic acid residues in a ratio of 70-90:5-15:5-15 mol %. Examples of methods for producing PBSAT include esterification using the above-mentioned dicarboxylic acid and 1,4-butanediol in a molar ratio of 1:1.2-2.0, followed by condensation polymerization.

[0040] Polycaprolactone In the present production method, polycaprolactone (hereinafter referred to as "PCL") that can be used as the biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin is represented by the following formula: [-(CH2)5-CO-O-] The present invention contemplates a polymer having a monomer unit represented by the formula: PCL can usually be obtained by ring-opening polymerization of ε-caprolactone using a cationic or anionic initiator, for example, an active hydrogen compound such as an alcohol, as an initiator, but the production method is not limited thereto. An organometallic catalyst can also be used to promote the polymerization of PCL. Furthermore, the end-capping structure of PCL is not particularly limited. The physical properties of PCL are not particularly limited, but it is preferable that it has, for example, a melting point of 50 to 65°C, a crystallization temperature of 10 to 30°C, and a glass transition point of -50 to -60°C. The weight-average molecular weight of PCL is not particularly limited, but is preferably 30,000 to 500,000, more preferably 100,000 to 400,000, from the viewpoint of achieving both mechanical properties and processability.

[0041] Commercially available PCL products include, for example, Ingevity's "Capa 6506" (powder, Mw = 130,000), "Capa 6500" (pellet, Mw = 130,000), "Capa 6806" (powder, Mw = 230,000), "Capa 6800" (pellet, Mw = 230,000), and "FB100" (pellet, Mw = 300,000, contains PCL crosslinks).

[0042] Polylactic acid In this production method, the polylactic acid that can be used as the biodegradable aliphatic or aliphatic-aromatic thermoplastic polyester resin may be a homopolymer of lactic acid or a copolymer of lactic acid with another monomer. Examples of such other monomers include aliphatic hydroxycarboxylic acids other than lactic acid, aliphatic polyhydric alcohols, and aliphatic polycarboxylic acids. Furthermore, the lactic acid constituting the copolymer may be either the L- or D-form, or may contain both. That is, the homopolymer of lactic acid may be any of poly(L-lactic acid) resin, poly(D-lactic acid) resin, and poly(DL-lactic acid) resin.

[0043] (peroxide) In step (A), a peroxide having a one-minute half-life temperature of 140° C. or less is used. The peroxide used in step (A) is not particularly limited as long as its one-minute half-life temperature is 140° C. or less, and may be an organic peroxide or an inorganic peroxide. However, organic peroxides are preferred because they can improve processability during melt molding.

[0044] Examples of organic peroxides having a 1-minute half-life temperature of 140°C or less that can be used in step (A) include di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, bis(2-ethylhexyl)peroxydicarbonate, t-butylperoxy 2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, and 1,1,3,3-tetramethylbutylperoxyneodecanoate. In step (A), these organic peroxides may be used alone or in combination of two or more.

[0045] Examples of inorganic peroxides having a 1-minute half-life temperature of 140°C or less that can be used in step (A) include hydrogen peroxide, potassium peroxide, calcium peroxide, sodium peroxide, magnesium peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate. Among these, hydrogen peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate are preferred because they are easy to handle and have decomposition temperatures that are suitable for the heating temperature during modification. In step (A), only one of these inorganic peroxides may be used, or two or more may be used in combination. Furthermore, the above organic peroxides may be used in combination with inorganic peroxides.

[0046] The one-minute half-life temperature of the peroxide used in step (A) is not particularly limited as long as it is 140° C. or less, but is preferably 135° C. or less, and more preferably 130° C. or less. The lower limit of the one-minute half-life temperature of the peroxide is also not particularly limited, but is, for example, 60° C. or more, and preferably 70° C. or more.

[0047] (Aqueous dispersion) The aqueous dispersion used in step (A) refers to a dispersion in which the aliphatic or aliphatic-aromatic thermoplastic polyester resin, the peroxide, and other optional components are dispersed in water. The water is not particularly limited and may be deionized water, distilled water, tap water, industrial water, or the like.

[0048] (Other ingredients) The aqueous dispersion used in step (A) may optionally contain other components in addition to the aliphatic or aliphatic-aromatic thermoplastic polyester resin and peroxide. Examples of such other components include, but are not limited to, surfactants and thickeners. These other components may be used singly or in combination of two or more.

[0049] Reducing agent The reducing agent as another component is not particularly limited, but examples thereof include compounds containing reduced metal ions such as ferrous sulfate and cuprous naphthenate; chelating agents such as sodium ethylenediaminetetraacetate and sodium ferric hexamethylenediaminetetraacetate; ascorbic acid (salts) such as ascorbic acid, sodium ascorbate, and potassium ascorbate; erythorbic acid (salts) such as erythorbic acid, sodium erythorbate, and potassium erythorbate; sugars; sulfinates such as sodium hydroxymethanesulfinate; sodium sulfite, potassium sulfite, sodium hydrogen sulfite, etc. pyrosulfites such as sodium pyrosulfite, potassium pyrosulfite, sodium pyrosulfite, and potassium hydrogen pyrosulfite; thiosulfates such as sodium thiosulfate and potassium thiosulfate; phosphorous acid (salts) such as phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, and potassium hydrogen phosphite; pyrophosphite (salts) such as pyrophosphite, sodium pyrophosphite, potassium pyrophosphite, sodium hydrogen pyrophosphite, and potassium hydrogen pyrophosphite; and sodium formaldehyde sulfoxylate.

[0050] The aqueous dispersion used in step (A) preferably contains a surfactant and a thickener as other components. When the aqueous dispersion used in step (A) contains a surfactant and a thickener, the peroxide is more likely to be uniformly dispersed in the aqueous dispersion, the peroxide is more uniformly impregnated into the aliphatic or aliphatic-aromatic thermoplastic polyester resin, and the reaction between the aliphatic or aliphatic-aromatic thermoplastic polyester resin and the peroxide in the subsequent step (B) can proceed more uniformly.

[0051] Dispersant The dispersant as another component is not particularly limited, but examples thereof include water-soluble polymers such as polyvinyl alcohol (PVA), methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, sodium polyacrylate, potassium polyacrylate, polymethacrylic acid, sodium polymethacrylate, and polyethylene glycol-polypropylene glycol block copolymers.

[0052] Next, more specific implementation conditions for step (A) will be described in detail.

[0053] (Conditions) In step (A), the temperature at which the aqueous dispersion is maintained (hereinafter also referred to as the "maintenance temperature") is 0°C or higher and lower than the one-minute half-life temperature of the peroxide minus 50°C. By controlling the temperature of the aqueous dispersion within this temperature range, it becomes possible to impregnate the aliphatic or aliphatic-aromatic thermoplastic polyester resin with the peroxide while suppressing decomposition of the peroxide (suppressing the reaction of the peroxide). Note that the "one-minute half-life temperature of the peroxide minus 50°C" temperature is the temperature obtained by subtracting 50 from the one-minute half-life temperature of the peroxide used. For example, when di-sec-butyl peroxydicarbonate (one-minute half-life temperature: 107°C) is used as the peroxide, the "one-minute half-life temperature of the peroxide minus 50°C" temperature is 57°C, and the maintenance temperature is any temperature between 0 and 57°C.

[0054] The holding temperature in step (A) is not particularly limited as long as it is within the above temperature range, and can be appropriately adjusted according to the one-minute half-life temperature of the peroxide used. For example, the holding temperature may be any temperature between 10°C and the one-minute half-life temperature of the peroxide minus 50°C, or may be any temperature between 20°C and the one-minute half-life temperature of the peroxide minus 55°C.

[0055] In step (A), the time for which the aqueous dispersion is held (hereinafter also referred to as "holding time") is 65 minutes or longer. By holding the aqueous dispersion at the holding temperature for 65 minutes or longer, it becomes possible to impregnate a sufficient amount of peroxide into the aliphatic or aliphatic-aromatic thermoplastic polyester resin.

[0056] The retention time in step (A) is not particularly limited as long as it is 65 minutes or more, and may be, for example, 70 minutes or more, 80 minutes or more, or 90 minutes or more. The upper limit of the retention time is not particularly limited, but from the viewpoint of suppressing unintended decomposition of peroxide, it is preferably 180 minutes or less, more preferably 150 minutes or less, and even more preferably 120 minutes or less.

[0057] The amount of peroxide used in step (A) is not particularly limited, but is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, and even more preferably 0.1 to 3 parts by weight, per 100 parts by weight of the aliphatic or aliphatic-aromatic thermoplastic polyester resin. By setting the amount of peroxide used within the above range, there is an advantage in terms of efficiency.

[0058] As described above, the "holding" operation in step (A) may include a step of adding an aliphatic or aliphatic-aromatic thermoplastic polyester resin and / or a peroxide to the aqueous dispersion, and may further include a step of stirring the aqueous dispersion to uniformly disperse the aliphatic or aliphatic-aromatic thermoplastic polyester resin and / or the peroxide in the aqueous dispersion. In other words, step (A) in the present production method preferably includes (a1) an addition step of adding a peroxide to the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin, and (a2) a stirring step of stirring the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin and the peroxide for 50 minutes or more.

[0059] ·Addition process In the addition step that may be included in step (A), the method for adding the peroxide to the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin is not particularly limited. The entire amount of peroxide to be used may be added at once, or the peroxide may be added gradually over a certain period of time (addition time). Since this has the advantage of allowing the peroxide to be more efficiently impregnated into the aliphatic or aliphatic-aromatic thermoplastic polyester resin, it is preferable to add the peroxide gradually over a certain period of time in the addition step. Furthermore, in order to prevent a rapid reaction, it is preferable to add the peroxide while stirring the aqueous dispersion.

[0060] The addition time in the addition step is not particularly limited, but is preferably 10 minutes or more, more preferably 20 minutes or more, and even more preferably 30 minutes or more, for example. The upper limit of the addition time is not particularly limited, but may be, for example, 60 minutes or less.

[0061] The amount of peroxide added in the adding step is the amount of peroxide used in step (A). Therefore, the above description of the amount of peroxide used is used to refer to the specific amount of peroxide added in the adding step.

[0062] Mixing process In the stirring step that may be included in step (A), the method for stirring the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin and the peroxide is not particularly limited, and any known stirring method can be used.

[0063] In the stirring step, the time for stirring the aqueous dispersion (stirring time) is preferably 50 minutes or more. Stirring the aqueous dispersion for 50 minutes or more allows the aliphatic or aliphatic-aromatic thermoplastic polyester resin to be uniformly and sufficiently impregnated with the peroxide. The stirring time is not particularly limited as long as it is 50 minutes or more, but is preferably, for example, 60 minutes or more, and more preferably 90 minutes or more. The upper limit of the stirring time is also not particularly limited, but can be, for example, 180 minutes or less.

[0064] The stirring operation in the stirring step refers to stirring the aqueous dispersion after the entire amount of peroxide used in step (A) has been added, and the stirring time refers to the time required to stir the aqueous dispersion containing the entire amount of peroxide used. Therefore, when the addition step is carried out while stirring the target aqueous dispersion, the time required to stir the aqueous dispersion in the addition step is not included in the stirring time.

[0065] When step (A) includes an adding step and a stirring step, the series of operations of the adding step and the stirring step is considered to be the holding operation in step (A). Therefore, when step (A) includes an adding step and a stirring step, the holding time in step (A) is the sum of the adding time and the stirring time. For example, when the adding time is 30 minutes and the stirring time is 60 minutes, the holding time is 90 minutes. Therefore, it is preferable to adjust the adding time and the stirring time so that their sum matches the preferred holding time.

[0066] <Process (B)> The present production method includes (B) a step (sometimes simply referred to as "step (B)") of maintaining the aqueous dispersion obtained in step (A) at a temperature (sometimes referred to as the "maintenance temperature") that is equal to or higher than (the one-minute half-life temperature of the peroxide minus 50°C) and equal to or lower than the one-minute half-life temperature of the peroxide and equal to or lower than 100°C.

[0067] In step (B), the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin obtained in step (A) and a peroxide, in which the aliphatic or aliphatic-aromatic thermoplastic polyester resin is impregnated with the peroxide, is maintained at the above-mentioned temperature, thereby allowing the aliphatic or aliphatic-aromatic thermoplastic polyester resin to react (modify) with the peroxide, thereby obtaining a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin. Therefore, step (B) can also be said to be a step of reacting (modifying) the aliphatic or aliphatic-aromatic thermoplastic polyester resin with the peroxide.

[0068] First, the specific conditions for carrying out step (B) will be described in detail.

[0069] (Conditions) The temperature maintained in step (B) is a temperature that is at least 50°C below the one-minute half-life temperature of the peroxide used in step (A) and is equal to or lower than the one-minute half-life temperature of the peroxide, and is equal to or lower than 100°C. In step (B), if the one-minute half-life temperature of the peroxide used in step (A) is higher than 100°C, 100°C is used as the upper limit of the temperature maintained. In this case, the temperature maintained is any temperature within the range of "from the one-minute half-life temperature of the peroxide used in step (A) -50°C to 100°C." On the other hand, if the one-minute half-life temperature of the peroxide used in step (A) is equal to or lower than 100°C, the temperature of the peroxide used in step (A) is used as the upper limit of the temperature maintained. In this case, the temperature maintained is any temperature within the range of "from the one-minute half-life temperature of the peroxide used in step (A) -50°C to the one-minute half-life temperature of the peroxide used in step (A)." As an example, if di-sec-butyl peroxydicarbonate (1-minute half-life temperature: 107°C) is used as the peroxide, the temperature of "1-minute half-life temperature of the peroxide - 50°C" is 57°C, and the maintenance temperature is any temperature between 57°C and 100°C.

[0070] In this production method, by impregnating the aliphatic or aliphatic-aromatic thermoplastic polyester resin with a peroxide in step (A), the modification reaction can proceed efficiently even at the relatively low maintenance temperature (basically 100°C or lower) as described above. This makes it possible to save energy consumed in the modification process and to suppress deterioration of the resin (thermal modification) during the modification process.

[0071] The above-mentioned "temperature equal to or lower than the one-minute half-life temperature of the peroxide used in step (A)" is not particularly limited as long as it is literally equal to or lower than the one-minute half-life temperature of the peroxide used in step (A). However, since the reaction can be carried out at normal pressure, the temperature is preferably 0 to 100°C, more preferably 50 to 100°C, and even more preferably 75 to 100°C. In step (B), the time for which the aqueous dispersion obtained in step (A) is maintained at the maintenance temperature (hereinafter, may be referred to as "maintenance time") is not particularly limited, but from the viewpoint of more efficiently impregnating the aliphatic or aliphatic-aromatic thermoplastic polyester resin with peroxide, it is preferably 10 to 1,200 minutes, more preferably 30 to 600 minutes, and even more preferably 60 to 360 minutes.

[0072] ·Separation process Step (B) preferably includes a step of separating the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin from the aqueous dispersion after the completion of the modification reaction. In the separation step, the method for separating the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin from the aqueous dispersion is not particularly limited, and for example, filtration, centrifugation, heat drying, spray drying, etc. can be used. Among these, spray drying is preferred because it allows the direct production of a powdery modified aliphatic or aliphatic-aromatic thermoplastic polyester resin that is easy to handle.

[0073] <Modified aliphatic or aliphatic-aromatic thermoplastic polyester resin> The modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by this production method is described below. The term "modified" in the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin refers to the formation of a branched structure in the molecules of the normally linear aliphatic or aliphatic-aromatic thermoplastic polyester resin. Such a branched structure can be formed in step (B) when radicals generated by decomposition of the peroxide abstract hydrogen atoms bonded to aliphatic hydrocarbon groups in the aliphatic or aliphatic-aromatic thermoplastic polyester resin, thereby directly bonding the molecules of the aliphatic or aliphatic-aromatic thermoplastic polyester resin together. The "modification reaction" in this production method refers to this series of reactions. This production method can efficiently advance the above reaction, thereby stably introducing a branched structure into the molecules of the aliphatic or aliphatic-aromatic thermoplastic polyester resin in a short period of time.

[0074] The detailed aspects of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin are the same as those of the (unmodified) aliphatic or aliphatic-aromatic thermoplastic polyester resin used as the raw material, except that a branched structure is formed, and the above description can be used as appropriate.

[0075] The modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by this production method has a branched structure, and therefore can be applied over a wide range of temperature conditions, can be stably molded under practical processing conditions, and can suppress the generation of foreign matter in the resulting molded article.

[0076] In this production method, whether the modification reaction (peroxide-mediated reaction) has proceeded efficiently can be evaluated by the Z-average molecular weight / weight-average molecular weight ratio (Mz / Mw) of the produced modified aliphatic or aliphatic-aromatic thermoplastic polyester resin. Specifically, when the produced modified aliphatic or aliphatic-aromatic thermoplastic polyester resin has an Mz / Mw ratio of 2.0 or more, it can be evaluated that the modification reaction (peroxide-mediated reaction) has proceeded efficiently.

[0077] In this specification, the Mz / Mw of a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin is a value calculated by dividing the Z-average molecular weight of the resin by the weight-average molecular weight of the resin. Here, the Z-average molecular weight (Mz) and weight-average molecular weight (Mw) of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin to be measured are both values ​​determined by GPC measurement, more specifically, values ​​measured under the conditions described in the Examples.

[0078] The Mw of a resin is a weighted average calculated using the molecular weight of the resin as the weight, and the Mz of a resin is a weighted average calculated using the square of the molecular weight of the resin as the weight. Therefore, Mz is more susceptible to the presence of high molecular weight components than Mw, and the higher the content of high molecular weight components, the larger the Mz value. In this production method, the more efficiently the modification reaction proceeds and the more branched structures are introduced into the aliphatic or aliphatic-aromatic thermoplastic polyester resin, the larger Mz becomes relative to Mw, i.e., the larger the Mz / Mw value becomes.

[0079] From the above viewpoints, the Mz / Mw of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by the present production method is preferably 2.0 or more, more preferably 2.1 or more, and even more preferably 2.2 or more. The larger the Mz / Mw value, the more efficiently the modification reaction (reaction by peroxide) can be evaluated to have progressed. There is no particular upper limit to Mz / Mw, and it can be, for example, 10 or less, 5 or less, 3 or less, or 2.5 or less.

[0080] 2. Resin composition containing modified aliphatic or aliphatic-aromatic thermoplastic polyester resin In one embodiment of the present invention, there is provided a resin composition (hereinafter sometimes referred to as "the present resin composition") containing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by the present production method. Because the present resin composition contains a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by the present production method, it has a wide range of applicable temperature conditions, can be stably molded under practical processing conditions, and can suppress the generation of foreign matter in the resulting molded article.

[0081] Each component that may be contained in the resin composition will be described in detail below.

[0082] (Modified aliphatic or aliphatic-aromatic thermoplastic polyester resin) The resin composition contains a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin. Specific embodiments of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin are described in the above section [1. Method for producing modified aliphatic or aliphatic-aromatic thermoplastic polyester resin].

[0083] (Unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin) The resin composition may optionally contain an unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin in addition to the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by the present production method. The modified aliphatic or aliphatic-aromatic thermoplastic polyester resin produced by the present production method itself has a wide range of applicable temperature conditions, can be stably molded under practical processing conditions, and can suppress the generation of foreign matter in the resulting molded article. Therefore, the resin composition containing the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin can achieve the above-mentioned effects even when it contains an unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin, which does not normally have the above-mentioned effects. For specific embodiments of the unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin, the description in the above section [1. Method for producing modified aliphatic or aliphatic-aromatic thermoplastic polyester resin] is incorporated herein by reference.

[0084] When the resin composition contains an unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin, the ratio of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin to the unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin in the resin composition is not particularly limited. For example, the ratio of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin to the unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin in a total of 100% by weight of both components is preferably 0.1 / 99.9 (wt% / wt%) to 99.9 / 0.1 (wt% / wt%), more preferably 1 / 99 (wt% / wt%) to 99 / 1 (wt% / wt%), and even more preferably 5 / 95 (wt% / wt%) to 95 / 5 (wt% / wt%).

[0085] The content of the resin components in the present resin composition (the total amount of the modified aliphatic or aliphatic-aromatic thermoplastic polyester resin and the unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin) is not particularly limited, but from the viewpoint of improving the biodegradability of the present resin composition and, in turn, of the molded article obtained by molding the present resin composition, it is preferably 20 to 100% by weight, more preferably 40 to 95% by weight, even more preferably 60 to 92% by weight, and even more preferably 80 to 90% by weight, of the total amount (100% by weight) of the present resin composition.

[0086] (Other ingredients) The present resin composition may contain components other than the resin components (other components) to the extent that the functionality of the resulting molded article is not impaired. Examples of other components that may be contained in the present resin composition include, but are not limited to, lubricants, crystal nucleating agents, plasticizers, inorganic fillers, antioxidants, ultraviolet absorbers, colorants such as dyes and pigments, and antistatic agents. The specific types and contents of the other components are not particularly limited as long as they do not impair the effects of the present invention and can be appropriately determined by those skilled in the art. For example, the types and contents described in Prior Art 1 can be applied.

[0087] (Method of producing the present resin composition) The present resin composition can be produced by a known method. Specifically, the present resin composition can be produced by melt-kneading a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin, and optionally an unmodified aliphatic or aliphatic-aromatic thermoplastic polyester resin and other components using an extruder, kneader, Banbury mixer, kneading roll, or the like.

[0088] (Uses of the Resin Composition) The resin composition can be molded into a molded article by a known molding method, such as inflation film molding, extrusion blow molding, injection blow molding, extrusion molding, calendar molding, vacuum molding, or injection molding. The resin composition can also be foamed and molded into a foamed article by a known method. These molded articles and foamed articles made from the resin composition can be used for a variety of purposes, such as paper, film, sheet, tube, plate, rod, container (e.g., bottle container), bag, and parts, and are suitable for use in fields such as agriculture, fisheries, forestry, horticulture, medicine, sanitary products, the food industry, clothing, non-clothing, packaging, automobiles, and building materials. [Example]

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are by weight.

[0090] 〔material〕 The materials used in the examples and comparative examples were as follows:

[0091] <Aliphatic thermoplastic polyester resin> As the aliphatic thermoplastic polyester resin, the following poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) resin was used. P3HB3HH-1: Powdered P3HB3HH with (3-hydroxybutyrate) / (3-hydroxyhexanoate)=94.4 / 5.6 (mol / mol) and a weight-average molecular weight Mw of 550,000 as measured by GPC. P3HB3HH-2: Powdered P3HB3HH with (3-hydroxybutyrate) / (3-hydroxyhexanoate)=84.3 / 15.7 (mol / mol) and a weight-average molecular weight Mw of 600,000 as measured by GPC. P3HB3HH-3: Powdered P3HB3HH with a (3-hydroxybutyrate) / (3-hydroxyhexanoate) ratio of 94.5 / 5.5 (mol / mol) and a weight-average molecular weight Mw of 400,000 as measured by GPC.

[0092] The aliphatic thermoplastic polyester resins used as materials were all unmodified aliphatic thermoplastic polyester resins having a linear molecular structure.

[0093] The monomer composition ratio of each P3HB3HH was determined as follows. Approximately 20 mg of P3HB3HH was added to 1 mL of a sulfuric acid-methanol mixture (15:85) and 1 mL of chloroform, sealed, and heated at 100°C for 140 minutes to obtain the methyl ester of the P3HB3HH decomposition product. After cooling, 0.5 mL of deionized water was added, mixed thoroughly, and allowed to stand until the aqueous and organic layers separated. The monomer unit composition of the P3HB3HH decomposition product in the separated organic layer was then analyzed by capillary gas chromatography. The ratio of 3-hydroxyhexanoate units was calculated from the peak areas obtained.

[0094] <Peroxide> The following organic peroxides were used as peroxides: PO-1: di-sec-butyl peroxydicarbonate ("Luperox 225" manufactured by Arkema Yoshitomi Co., Ltd., 1-minute half-life temperature: 107°C). PO-2: t-butylperoxy 2-ethylhexanoate (NOF Corporation, "Perbutyl O", 1-minute half-life temperature: 130°C).

[0095] <Lubricant> The following lubricants were used: Behenamide ("BNT22H" manufactured by Nippon Fine Chemical Co., Ltd., hereinafter referred to as "BA"). Erucamide ("Neutron S" manufactured by Nippon Fine Chemical Co., Ltd., hereinafter referred to as "EA").

[0096] [Measurement method] The methods for measuring the parameters in the examples and comparative examples were as follows.

[0097] <Measurement of weight-average molecular weight (Mw) and Z-average molecular weight (Mz), and calculation of Mz / Mw> The weight-average molecular weight and Z-average molecular weight of modified or unmodified aliphatic polyester resins in each example and comparative example were measured as follows: First, the resin was dissolved in chloroform and heated in a 60°C hot water bath for 0.5 hours. The chloroform-soluble fraction was filtered through a PTFE disposable filter with a 0.45 μm pore size. After filtration, the filtrate was used as a sample and subjected to GPC measurement under the following conditions to determine the Z-average molecular weight and weight-average molecular weight of the resin. GPC measurement device: Shimadzu High Performance Liquid Chromatograph 20A System Column: Showa Denko KG 4A (1 column), K-806M (2 columns) Sample concentration: 1 mg / ml Free solution: Chloroform solution Free liquid flow rate: 1.0ml / min Sample injection volume: 100 μL Analysis time: 30 minutes Standard sample: standard polystyrene.

[0098] The measured Z-average molecular weight was divided by the weight-average molecular weight to calculate Mz / Mw.

[0099] <Blow-up ratio evaluation> The film extruded from the circular die lip was blown up into a cylindrical shape with a diameter larger than that of the die lip. This ratio of the diameters is called the blow-up ratio and is expressed by the following formula: Blow-up ratio = film diameter / die lip diameter.

[0100] The film was gradually inflated within a range where increasing the amount of air used to inflate the film would not cause changes in film width or tearing, and the blow-up ratio was calculated at the point where the film diameter reached its maximum. A higher blow-up ratio indicates that the film has better forming stability.

[0101] <Evaluation of foreign matter in film> A 50 mm x 50 mm sample was cut out from a 60 μm thick film, and the number of foreign particles with a major axis size of 10 μm or more present in the sample was counted using a Peak Scale Loupe (magnification: 20) manufactured by Tokai Sangyo Co., Ltd. The number of foreign particles measured was compared with a control (Comparative Example 5) containing no modified resin, and evaluated according to the following criteria. + (Good): No increase in the number of foreign bodies was observed compared to the control. - (Poor): Increased number of foreign bodies compared to the control.

[0102] Example 1 A six-neck flask equipped with a stirrer, baffle, reflux condenser, nitrogen inlet, peroxide addition port, and thermometer was charged with 100 parts by weight of an aliphatic thermoplastic polyester resin (P3HB3HH-1) and 200 parts by weight of water (total amount of water including various dilutions) to obtain an aqueous dispersion. The temperature was then raised to 50°C, and nitrogen substitution was performed when the liquid temperature reached 50°C. Next, 1.0 parts by weight of di-sec-butyl peroxydicarbonate (PO-1) as peroxide was added to the aqueous dispersion over 30 minutes while stirring (addition step), and the aqueous dispersion was further stirred for another 60 minutes while maintaining the temperature at 50°C (stirring step). The total holding time was 90 minutes. After the stirring step, the aqueous dispersion was heated to 75°C and maintained at this temperature for 5.5 hours while stirring, allowing the aliphatic thermoplastic polyester resin and the peroxide to react (maintenance step). The aqueous dispersion after the reaction was spray-dried to obtain particles of modified aliphatic thermoplastic polyester resin. The weight-average molecular weight, Z-average molecular weight, and Mz / Mw of the obtained modified aliphatic thermoplastic polyester resin were evaluated. The results are shown in Table 1.

[0103] Examples 2 to 9 Modified aliphatic thermoplastic polyester resins were obtained in the same manner as in Example 1, except that the type of aliphatic thermoplastic polyester resin, the type and amount of peroxide, and the temperature and / or time of each step were changed as shown in Table 1. The weight-average molecular weight, Z-average molecular weight, and Mz / Mw of the obtained modified aliphatic thermoplastic polyester resins were evaluated. The results are shown in Table 1.

[0104] [Table 1]

[0105] Comparative Example 1 A six-neck flask equipped with a stirrer, baffle, reflux condenser, nitrogen inlet, peroxide addition port, and thermometer was charged with 100 parts by weight of an aliphatic thermoplastic polyester resin (P3HB3HH-1) and 200 parts by weight of water (total amount of water, including various dilutions). An aqueous dispersion was obtained. The temperature was then raised to 50°C, and nitrogen substitution was performed when the liquid temperature reached 50°C. Next, 1.0 parts by weight of di-sec-butyl peroxydicarbonate (PO-1) as peroxide was added to the aqueous dispersion over 30 minutes, and stirring was continued for another 30 minutes while maintaining the aqueous dispersion at 50°C. After stirring, the aqueous dispersion was heated to 75°C and maintained at this temperature for 5.5 hours while stirring, allowing the aliphatic thermoplastic polyester resin and the peroxide to react. The aqueous dispersion after the reaction was spray-dried to obtain particles of a modified aliphatic thermoplastic polyester resin. The weight average molecular weight, Z average molecular weight and Mz / Mw of the resulting modified aliphatic thermoplastic polyester resin were evaluated. The results are shown in Table 2.

[0106] (Comparative Examples 2 to 4) A modified aliphatic thermoplastic polyester resin was obtained in the same manner as in Comparative Example 1, except that the type of aliphatic thermoplastic polyester resin, the type and amount of peroxide, and the temperature and / or time of each step were changed as shown in Table 2. The weight-average molecular weight, Z-average molecular weight, and Mz / Mw of the obtained modified aliphatic thermoplastic polyester resin were evaluated. The results are shown in Table 2.

[0107] (Reference example 1) The weight average molecular weight, Z average molecular weight, and Mz / Mw of the unmodified aliphatic thermoplastic polyester resin (P3HB3HH-1) were evaluated. The results are shown in Table 2.

[0108] [Table 2]

[0109] Tables 1 and 2 show that the modified aliphatic thermoplastic polyester resins of Examples 1 to 9, in which the holding time was 65 minutes or more, all had an Mz / Mw of 2.0 or more, indicating that the modification reaction proceeded efficiently. On the other hand, the modified aliphatic thermoplastic polyester resins of Comparative Examples 1 to 4, in which the holding time was less than 60 minutes, all had an Mz / Mw of less than 2.0, indicating that the efficiency of the modification reaction was low. Comparison of Examples 1 to 9 and Comparative Examples 1 to 4 shows that by performing a holding step of 65 minutes or more before modification, the aliphatic thermoplastic polyester resin can be reacted with peroxide efficiently.

[0110] Example 10 A resin composition was prepared by mixing 10 parts by weight of the modified aliphatic thermoplastic polyester resin obtained in Example 1, 90 parts by weight of unmodified polyester resin (P3HB3HH-1), 0.5 parts by weight of lubricant (BA), and 0.5 parts by weight of lubricant (EA). The resulting resin composition was subjected to inflation film molding to obtain a film-shaped molded article. The resulting molded article was evaluated for blow-up ratio and foreign matter in the film. The evaluation results are shown in Table 3.

[0111] Example 11 A resin composition and a film-shaped molded article were obtained in the same manner as in Example 10, except that the modified aliphatic thermoplastic polyester resin obtained in Example 6 was used instead of the modified aliphatic thermoplastic polyester resin obtained in Example 1, and P3HB3HH-2 was used instead of P3HB3HH-1 as the unmodified polyester resin. The obtained molded article was evaluated for blow-up ratio and foreign matter in the film. The evaluation results are shown in Table 2.

[0112] (Comparative Example 5) A resin composition and a film-shaped molded article were obtained in the same manner as in Example 10, except that the modified polyester resin was not used and instead, the amount of unmodified polyester resin (P3HB3HH-1) was changed to 100 parts by weight. The obtained molded article was evaluated for blow-up ratio and foreign matter in the film. The evaluation results are shown in Table 3.

[0113] [Table 3]

[0114] As is clear from Table 3, the resin compositions of Examples 10 and 11, which contained the modified aliphatic thermoplastic polyester resin produced by this production method, had a high blow-up ratio of 3.0 times, exhibited good stability during molding, and also suppressed the generation of foreign matter, with the number of foreign matter found in the film being at the same level as in Comparative Example 5. On the other hand, the resin composition of Comparative Example 5, which did not contain the modified aliphatic thermoplastic polyester resin, exhibited a low blow-up ratio of 1.5 times, exhibiting poor stability during molding. [Industrial Applicability]

[0115] According to this production method, modified aliphatic or aliphatic-aromatic thermoplastic polyester resins can be provided with excellent reaction efficiency. Molded articles using the modified aliphatic or aliphatic-aromatic thermoplastic polyester resins produced by this production method can be suitably used in agriculture, fisheries, forestry, horticulture, medicine, hygiene products, clothing, non-clothing, packaging, automobiles, building materials, and other fields.

Claims

1. A method for producing a modified aliphatic or aliphatic-aromatic thermoplastic polyester resin, comprising: (A) a step of maintaining an aqueous dispersion containing an aliphatic or aliphatic-aromatic thermoplastic polyester resin and a peroxide having a one-minute half-life temperature of 140°C or less at a temperature of 0°C or higher and lower than (the one-minute half-life temperature of the peroxide - 50°C) for 65 minutes or longer; and (B) maintaining the aqueous dispersion obtained in the step (A) at a temperature equal to or higher than (the one-minute half-life temperature of the peroxide - 50°C) and equal to or lower than the one-minute half-life temperature of the peroxide, and equal to or lower than 100°C.

2. 2. The method according to claim 1, wherein the aliphatic or aliphatic-aromatic thermoplastic polyester resin is at least one selected from the group consisting of poly(3-hydroxyalkanoate) resins, polybutylene adipate terephthalate, polybutylene succinate adipate, polybutylene succinate, polybutylene sebacate terephthalate, polybutylene succinate adipate terephthalate, polycaprolactone, and polylactic acid.

3. 2. The method according to claim 1, wherein the aliphatic or aliphatic-aromatic thermoplastic polyester resin is a poly(3-hydroxyalkanoate) resin.

4. The production method according to claim 3, wherein the poly(3-hydroxyalkanoate)-based resin is at least one selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyoctanoate), and poly(3-hydroxybutyrate-co-3-hydroxydecanoate).

5. 2. The method according to claim 1, wherein the amount of the peroxide used is 0.001 to 10 parts by weight per 100 parts by weight of the aliphatic or aliphatic-aromatic thermoplastic polyester resin.

6. The method according to claim 1, wherein the peroxide is at least one selected from the group consisting of di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, bis(2-ethylhexyl)peroxydicarbonate, t-butylperoxy 2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, and 1,1,3,3-tetramethylbutylperoxyneodecanoate.

7. The step (A) (a1) adding the peroxide to the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin; (a2) a stirring step of stirring the aqueous dispersion containing the aliphatic or aliphatic-aromatic thermoplastic polyester resin and the peroxide for 50 minutes or more.

8. The method according to claim 1, wherein the maintenance time in step (B) is 10 to 1,200 minutes.

9. 2. The method according to claim 1, wherein the temperature equal to or lower than the one-minute half-life temperature of the peroxide is 0 to 100°C.

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