Hydrolysis inhibitor and use thereof

Abstract

To provide a hydrolysis inhibitor for a polylactic acid-based resin.SOLUTION: As a hydrolysis inhibitor for inhibiting hydrolysis of a polylactic acid-based resin, a hydrolysis inhibitor containing a polyhydroxyalkanoic acid-based resin is prepared. The polyhydroxyalkanoic acid-based resin may contain at least one selected from the group consisting of a 3-hydroxybutyric acid component and a 3-hydroxyvaleric acid component as a polymerization component. A polylactic acid-based resin composition containing the polylactic acid-based resin and the hydrolysis inhibitor may be prepared. When the ratio of the hydrolysis inhibitor is 0.5 to 10 parts by mass with respect to 100 parts by mass of the polylactic acid-based resin, hydrolysis can be suppressed and elongation at break can be improved without lowering transparency and tensile modulus of the polylactic acid-based resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydrolysis inhibitor capable of inhibiting the hydrolysis of polylactic acid resins and uses thereof. [Background technology]

[0002] There is a strong demand for efforts to realize a "low-carbon society" by reducing greenhouse gas emissions and an environmentally friendly "resource-circulating society," and the spread of new materials called "bioplastics" is accelerating in order to realize these societies.

[0003] Among these, polylactic acid is used as a plant-derived, biodegradable resin, but it is a hard resin and lacks flexibility for use as a film, making it difficult to produce films that use polylactic acid as the main component.

[0004] Furthermore, other plant-derived biodegradable resins such as polyhydroxyalkanoates are also hard like polylactic acid, making them difficult to use as resins for films.

[0005] In response to this, a method is known in which an additive (plasticizer) for increasing flexibility is added to a polymer in order to impart flexibility suitable for film formation.

[0006] Japanese Patent Laid-Open Publication No. 2011-52149 (Patent Document 1) discloses a polylactic acid resin composition composed of polylactic acid, a plasticizer for plasticizing the polylactic acid, and a polymer having a thickening effect.

[0007] Japanese Patent Application Laid-Open Publication No. 2015-193750 (Patent Document 2) discloses a resin composition containing a hard biodegradable resin such as a polylactic acid-based resin, a soft biodegradable resin, a plasticizer, and at least one compound selected from the group consisting of a fatty acid amide compound, an aliphatic monoepoxy compound, and an aliphatic monocarboxylic acid compound. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-52149 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-193750 Summary of the Invention [Problem to be solved by the invention]

[0009] However, when a plasticizer is used to impart flexibility to a resin, as in the resin compositions of Patent Documents 1 and 2, the plasticizer activates the movement of the resin's molecular chains, making the film more susceptible to hydrolysis. To avoid this problem, it is necessary to select a method that reduces the amount of plasticizer used or a method that does not use plasticizer, and conventional techniques have not been able to achieve both hydrolysis inhibition and flexibility. Furthermore, the incorporation of additives such as plasticizers also causes the problem of a decrease in the transparency and elastic modulus of polylactic acid.

[0010] Therefore, an object of the present invention is to provide a hydrolysis inhibitor capable of inhibiting the hydrolysis of polylactic acid resins and uses thereof.

[0011] Another object of the present invention is to provide a hydrolysis inhibitor that can inhibit the hydrolysis of polylactic acid resins and also impart flexibility, and uses thereof.

[0012] A further object of the present invention is to provide a hydrolysis inhibitor that can inhibit hydrolysis and impart flexibility to polylactic acid resins without impairing their transparency, and to provide uses thereof.

[0013] Another object of the present invention is to provide a hydrolysis inhibitor that can inhibit hydrolysis and significantly improve the elongation at break without reducing the transparency and tensile modulus of elasticity of polylactic acid resins, and uses thereof. [Means for solving the problem]

[0014] As a result of intensive research to solve the above-mentioned problems, the inventors discovered that blending a polyhydroxyalkanoic acid-based resin with a polylactic acid-based resin can suppress hydrolysis of the polylactic acid-based resin and also impart flexibility, thereby completing the present invention.

[0015] That is, the present invention includes the following aspects.

[0016] Aspect [1]: A hydrolysis inhibitor for inhibiting the hydrolysis of a polylactic acid-based resin, the hydrolysis inhibitor comprising a polyhydroxyalkanoic acid-based resin (excluding the polylactic acid-based resin).

[0017] Aspect [2]: The polyhydroxyalkanoic acid resin is hydroxy C 4-10 The hydrolysis inhibitor according to embodiment [1], which contains an alkanoic acid component as a polymerization component.

[0018] Aspect [3]: The polyhydroxyalkanoic acid resin is hydroxy C 4-6 The hydrolysis inhibitor according to embodiment [1] or [2], which contains an alkanoic acid component as a polymer component.

[0019] Aspect [4]: ​​The hydrolysis inhibitor according to any one of Aspects [1] to [3], wherein the polyhydroxyalkanoic acid resin contains at least one polymer component selected from the group consisting of a 3-hydroxybutyric acid component and a 3-hydroxyvaleric acid component.

[0020] Aspect [5]: The hydrolysis inhibitor according to any one of Aspects [1] to [4], wherein the polyhydroxyalkanoic acid resin contains a 3-hydroxybutyric acid component as a polymerization component.

[0021] Aspect [6]: A polylactic acid resin composition comprising a polylactic acid resin and the hydrolysis inhibitor according to any one of aspects [1] to [5].

[0022] Aspect [7]: The polylactic acid-based resin composition according to aspect [6], wherein the proportion of the hydrolysis inhibitor is 0.1 to 50 parts by mass per 100 parts by mass of the polylactic acid-based resin.

[0023] Aspect [8]: The polylactic acid resin composition according to aspect [6] or [7], wherein the proportion of the hydrolysis inhibitor is 0.5 to 15 parts by mass per 100 parts by mass of the polylactic acid resin.

[0024] Aspect [9]: The polylactic acid resin composition according to any one of aspects [6] to [8], further comprising a plasticizer.

[0025] Aspect

[10] : A method for inhibiting hydrolysis of a polylactic acid resin by adding the hydrolysis inhibitor according to any one of aspects [1] to [5] to the polylactic acid resin.

[0026] Aspect

[11] : A method for improving the flexibility of a polylactic acid resin by adding the hydrolysis inhibitor according to any one of aspects [1] to [5] to the polylactic acid resin.

[0027] Aspect

[12] : A method for improving flexibility while suppressing hydrolysis of a polylactic acid-based resin by adding the hydrolysis inhibitor according to any one of aspects [1] to [5] to the polylactic acid-based resin.

[0028] Aspect

[13] : A method for suppressing hydrolysis and improving breaking elongation without reducing the transparency and tensile modulus of the polylactic acid-based resin by adding 0.5 to 10 parts by mass of the hydrolysis inhibitor according to any one of aspects [1] to [5] to 100 parts by mass of the polylactic acid-based resin.

[0029] In this specification and claims, the number of carbon atoms in a substituent is represented by C1, C6, C 10 For example, "C1 alkyl group" means an alkyl group with 1 carbon atom, and "C 6-10 The term "aryl group" refers to an aryl group having 6 to 10 carbon atoms.

[0030] In this specification and claims, 2-10 "Alkanoic acid" means that the total number of carbon atoms in the alkanoic acid, including the number of carbon atoms in the carboxyl group, is 2 to 10. 3-10The term "alkanedicarboxylic acid" also means that the total number of carbon atoms in the alkanedicarboxylic acid, including the number of carbon atoms in the carboxyl group, is 3 to 10.

[0031] In this specification and claims, when a numerical range is indicated using "X to Y," it means that the numerical values ​​X and Y at both ends are included.

[0032] In this specification and claims, the terms "carboxylic acid component," "dicarboxylic acid component," and "hydroxycarboxylic acid component" are used to mean not only carboxylic acids, dicarboxylic acids, and hydroxycarboxylic acids, but also their reactive derivatives (lower alkyl esters, acid anhydrides, or acid halides).

[0033] In this specification and claims, polyhydroxyalkanoic acid resin is also referred to as polyhydroxyalkanoate resin or PHA resin, and means a resin that does not contain polylactic acid resin. [Effects of the Invention]

[0034] The hydrolysis inhibitor of the present invention contains a polyhydroxyalkanoic acid resin, and therefore can inhibit the hydrolysis of polylactic acid resins. In particular, the hydrolysis inhibitor of the present invention can inhibit the hydrolysis of polylactic acid resins and also impart flexibility.

[0035] Furthermore, by blending the hydrolysis inhibitor in a predetermined ratio with the polylactic acid resin, hydrolysis can be inhibited without impairing the transparency of the polylactic acid resin, and flexibility can also be imparted.

[0036] Furthermore, when the hydrolysis inhibitor is blended in a predetermined ratio with the polylactic acid resin and combined with a plasticizer, hydrolysis can be suppressed without reducing the transparency and tensile modulus of the polylactic acid resin, and the elongation at break can also be greatly improved. DETAILED DESCRIPTION OF THE INVENTION

[0037] [Hydrolysis inhibitor] The hydrolysis inhibitor of the present invention can be used as a hydrolysis inhibitor for inhibiting the hydrolysis of polylactic acid resins (hydrolysis inhibitor for polylactic acid resins), and is characterized by containing a polyhydroxyalkanoic acid resin.

[0038] The polyhydroxyalkanoic acid resin may be a resin classified into the polyhydroxyalkanoate (PHA) group, which is a representative biodegradable resin, along with polylactic acid (PLA). Examples of polyhydroxyalkanoic acid resins include resins (excluding polylactic acid resins described below) containing a hydroxyalkanoic acid component (excluding a lactic acid component) as a polymer component. The polyhydroxyalkanoic acid resin may be a resin in which the proportion of a lactic acid component, which is a polymer component (monomer), is less than 50 mol% of the total constituent monomers, or a resin that does not contain a lactic acid component as a polymer component.

[0039] The hydroxyalkanoic acid component may be a hydroxyalkanoic acid or a reactive derivative of a hydroxyalkanoic acid.

[0040] Examples of hydroxyalkanoic acids include hydroxy C acids such as glycolic acid, 3-hydroxypropanoic acid (3HP), 2-hydroxybutyric acid (2-hydroxybutanoic acid), 3-hydroxybutyric acid (3HB or BHB), 4-hydroxybutyric acid (4HB), 3-hydroxy-3-methyl-butyric acid, 2-hydroxyvaleric acid (2-hydroxypentanoic acid), 3-hydroxyvaleric acid (3HV), 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxy-2-methyl-valeric acid, 3-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 7-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 8-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 9-hydroxynonanoic acid, 3-hydroxydecanoic acid, and 10-hydroxydecanoic acid. 2-15 Alkanoic acids are included.

[0041] Reactive derivatives of hydroxyalkanoic acids include C anhydrides, methyl esters, etc. 1-3Examples include alkyl esters, acid halides such as acid chlorides, and corresponding lactones.

[0042] Lactones include glycolide, β-propiolactone, β-dimethylpropiolactone, γ-butyrolactone, γ-dimethylbutyrolactone, δ-valerolactone, and ε-caprolactone. 1-6 C optionally having an alkyl group 3-15 These lactones can be used alone or in combination of two or more. Among these lactones, C 3-10 Lactones are preferred, and C hydroxy groups such as glycolide, propiolactone, and caprolactone are preferred. 4-8 Lactones are particularly preferred.

[0043] These hydroxyalkanoic acid components can be used alone or in combination of two or more.

[0044] Among these hydroxyalkanoic acid components, hydroxy C 2-12 Alkanoic acid component [C 2-12 When the alkanoic acid component is a derivative of a lower alkyl ester, the number of carbon atoms of the lower alkyl ester is not included (hereinafter the same)). 2-10 Alkanoic acid moieties are particularly preferred. 2-10 Among the alkanoic acid components, hydroxy C 3-10 Alkanoic acid moieties are preferred, and hydroxy C 4-10 Alkanoic acid moieties are more preferred, and hydroxy C 4-8 Alkanoic acid moieties are more preferred, and hydroxy C 4-6 Alkanoic acid moieties are most preferred. 4-6 Among the alkanoic acid components, 3-hydroxy C 4-6 Alkanoic acid moieties are preferred, 3-hydroxybutyric acid moieties and / or 3-hydroxyvaleric acid moieties are more preferred, and 3-hydroxybutyric acid moieties are even more preferred.

[0045] 3-Hydroxy C 4-6The alkanoic acid component may be an optical isomer (R or S), or may be an S or racemic isomer. However, from the viewpoint of biodegradability, it is preferable that the alkanoic acid component contains at least the R isomer (particularly, an (R)-3-hydroxybutyric acid component or an (R)3HB component).

[0046] 3-Hydroxy C 4-6 The proportion of R-isomers in the alkanoic acid component, particularly the optical purity (enantiomer or optical isomer excess), is, for example, 50% ee or more (e.g., 80% ee or more), preferably 90% ee or more (e.g., 95 to 100% ee), and more preferably 98 to 100% ee (e.g., 99 to 100% ee, particularly substantially 100% ee). If the optical purity is too low, biodegradability may decrease.

[0047] 3-Hydroxy C 4-6 The mass proportion of the R-isomer in the alkanoic acid component is preferably 10% by mass or more, more preferably 50% by mass or more, even more preferably 90% by mass or more, and most preferably 100% by mass.

[0048] Hydroxy C 4-6 Alkanoic acid components (especially hydroxy C 4-5 The proportion of the hydroxyalkanoic acid component may be 50 mol% or more, preferably 70 mol% or more, further preferably 80 mol% or more, even more preferably 90 mol% or more, and most preferably 100 mol% of the hydroxyalkanoic acid component. 4-6 If the proportion of the alkanoic acid component is too low, flexibility and biodegradability may decrease.

[0049] Hydroxyalkanoic acid components (especially hydroxy C 2-10 The proportion of the hydroxy C (alkanoic acid component) may be the maximum proportion among all constituent monomers, for example, 50 mol % or more of all constituent monomers, preferably 70 mol % or more, further preferably 80 mol % or more, even more preferably 90 mol % or more, and most preferably 100 mol %. 2-10 If the proportion of the alkanoic acid component is too low, the flexibility of the polylactic acid-based resin composition may decrease.

[0050] The polyhydroxyalkanoic acid resin may further contain, as a polymerization component, a copolymerizable component copolymerizable with the hydroxyalkanoic acid component, in addition to the hydroxyalkanoic acid component, such as a diol, a dicarboxylic acid component, a lactic acid component, or a hydroxycarboxylic acid component other than the hydroxyalkanoic acid component.

[0051] The diol is not particularly limited and may be any of aliphatic diols, alicyclic diols, and aromatic diols, but aliphatic diols are preferred from the viewpoint of biodegradability, etc. Examples of aliphatic diols include C 1 diols such as ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, hexanediol, and octamethylene glycol. 2-10 Alkanediols, etc. These diols can be used alone or in combination of two or more.

[0052] Of these diols, C 2-8 Alkanediols are preferred, and C alkanediols such as ethylene glycol, 1,4-butanediol, and neopentyl glycol are preferred. 2-6 Alkanediols are particularly preferred.

[0053] The dicarboxylic acid component is not particularly limited and may be any of an aliphatic dicarboxylic acid component, an alicyclic dicarboxylic acid component, and an aromatic dicarboxylic acid component, but from the viewpoint of biodegradability and the like, an aliphatic dicarboxylic acid component is preferred.

[0054] The aliphatic dicarboxylic acid component may be an aliphatic dicarboxylic acid or a reactive derivative of an aliphatic dicarboxylic acid. Examples of the aliphatic dicarboxylic acid include C carboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. 2-10 Examples of reactive derivatives of aliphatic dicarboxylic acids include C anhydrides, methyl esters, etc. 1-3Examples of the dicarboxylic acid component include alkyl esters, acid halides such as acid chlorides, etc. These dicarboxylic acid components can be used alone or in combination of two or more.

[0055] Of these dicarboxylic acid components, C 2-8 Aliphatic dicarboxylic acids or their reactive derivatives are preferred, and C carboxylic acids such as oxalic acid, succinic acid, and adipic acid are preferred. 3-6 Alkanedicarboxylic acids or reactive derivatives thereof are particularly preferred.

[0056] Examples of the hydroxycarboxylic acid component other than the hydroxyalkanoic acid component include a hydroxyalicyclic carboxylic acid component, a hydroxyaromatic carboxylic acid component, etc. These hydroxycarboxylic acid components can be used alone or in combination of two or more.

[0057] These copolymerization components can be used alone or in combination of two or more. The proportion of these copolymerization components in the total constituent monomers may be less than 50 mol%, preferably 30 mol% or less, further preferably 20 mol% or less, even more preferably 10 mol% or less, and most preferably 1 mol% or less.

[0058] Polyhydroxyalkanoic acid resin is a type of hydroxy C 4-6 Polyhydroxy C with alkanoic acid as the main polymerization component 4-6 It may be an alkanoic acid resin, and hydroxy C 4-5 Polyhydroxy C with alkanoic acid as the main polymerization component 4-5 Alkanoic acid resins are preferred. The polyhydroxyalkanoic acid resin may also be a poly(3-hydroxybutyric acid) resin (poly(3HB) resin) containing a 3-hydroxybutyric acid component (3HB component) as a main polymerization component, with poly(R)3HB resin being preferred.

[0059] Preferred examples of polyhydroxyalkanoic acid resins include homopolymers of an (R)-3-hydroxybutyric acid component, and copolymers of an (R)-3-hydroxybutyric acid component and a copolymer component.

[0060] Copolymerizable components that can be copolymerized with the (R)-3-hydroxybutyric acid component include hydroxy C components such as 3HP components, 4HB components, 3HV components, and 3-hydroxyhexanoic acid components. 2-10 Alkanoic acid components are also included. These copolymerization components can be used alone or in combination of two or more. Among these copolymerization components, 3- or 4-hydroxy C components such as 4HB component, (R)3HV component, and (R)-3-hydroxyhexanoic acid component are preferred because of their excellent biodegradability. 4-8 Alkanoic acid components are preferred, and 3-hydroxy C components such as (R)3HV components and (R)-3-hydroxyhexanoic acid components are preferred because they can improve the flexibility of polylactic acid-based resins. 5-7 Alkanoic acid components are particularly preferred.

[0061] In a copolymer of an (R)-3-hydroxybutyric acid component and a copolymerization component, the molar ratio of the two components, (R)-3-hydroxybutyric acid component / copolymerization component, is 99.99 / 0.01 to 50 / 50, preferably 99.95 / 0.05 to 70 / 30, further preferably 99.9 / 0.1 to 90 / 10, even more preferably 99.8 / 0.2 to 95 / 5, and most preferably 99.7 / 0.3 to 97 / 3.

[0062] The polyhydroxyalkanoic acid resin may be a single polyhydroxyalkanoic acid resin of the same type, or may be an alloy resin in which two or more poly(3-hydroxybutyric acid) resins of different types (or polymerization compositions) are combined.

[0063] The weight average molecular weight of the polyhydroxyalkanoic acid resin can be selected from the range of 1,000 to 3,000,000, for example, 10,000 to 2,500,000, preferably 50,000 to 2,000,000, further preferably 100,000 to 1,500,000, even more preferably 200,000 to 1,000,000, and most preferably 300,000 to 800,000.

[0064] In this specification and claims, the weight average molecular weight of the polyhydroxyalkanoic acid resin can be measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0065] The polyhydroxyalkanoic acid resin may be a crystalline resin.

[0066] The glass transition temperature (Tg) of the polyhydroxyalkanoic acid resin is, for example, −50° C. to 50° C., preferably −30° C. to 30° C., further preferably −20° C. to 20° C., even more preferably −10° C. to 10° C., and most preferably −5° C. to 5° C. If the glass transition temperature is too low, the heat resistance and mechanical properties of the polylactic acid resin composition may be reduced, and conversely, if it is too high, the biodegradability and moldability of the polylactic acid resin composition may be reduced.

[0067] Polyhydroxyalkanoic acid resin (especially polyhydroxy C 4-6 The melting point of the alkanoic acid resin is, for example, 60 to 250°C, preferably 70 to 200°C, further preferably 80 to 180°C, even more preferably 90 to 170°C, and most preferably 100 to 160°C.

[0068] In this specification and claims, the glass transition temperature and melting point of the polyhydroxyalkanoic acid resin can be measured using a differential scanning calorimeter (DSC).

[0069] Polyhydroxyalkanoic acid resin (especially polyhydroxy C 4-6 The proportion of the polyhydroxyalkanoic acid resin in the hydrolysis inhibitor may be 50% by mass or more, preferably 80% by mass or more, further preferably 90% by mass or more, even more preferably 95% by mass or more, and most preferably 99% by mass or more. If the proportion of the polyhydroxyalkanoic acid resin is too low, hydrolysis may not be inhibited. The hydrolysis inhibitor of the present invention may be a hydrolysis inhibitor consisting solely of a polyhydroxyalkanoic acid resin.

[0070] The hydrolysis inhibitor of the present invention can also improve the flexibility of polylactic acid-based resins. Therefore, the hydrolysis inhibitor of the present invention can also be used as a softener (or plasticizer) for polylactic acid-based resins. That is, the present invention also includes softeners for polylactic acid-based resins that contain polyhydroxyalkanoic acid-based resins.

[0071] [Polylactic acid resin composition] The hydrolysis inhibitor of the present invention is blended with a polylactic acid resin to inhibit hydrolysis of the polylactic acid resin. The present invention also includes a polylactic acid resin composition containing a polylactic acid resin and the hydrolysis inhibitor.

[0072] (Polylactic acid resin) Polylactic acid resins are resins (polymers) that contain lactic acid as a polymerization component. The lactic acid component may be lactic acid (2-hydroxypropanoic acid or 2-hydroxypropionic acid) or a reactive derivative of lactic acid.

[0073] Lactic acid may be an optical isomer (D-form, L-form) or a racemic form (DL-form), but it is preferable to include the L-form (L-lactic acid) in terms of mechanical properties and the like.

[0074] When lactic acid contains an L-isomer, the proportion of the L-isomer in the lactic acid is preferably 10 mol % or more, more preferably 50 mol % or more, even more preferably 70 mol % or more, and most preferably 90 mol % or more.

[0075] When the lactic acid is a combination of L- and D-forms (D-lactic acid), the molar ratio of the L- and D-forms (L- / D-form) may be 99.9 / 0.1 to 10 / 90, for example, 99.5 / 0.5 to 50 / 50, preferably 99 / 1 to 70 / 30, even more preferably 98 / 2 to 80 / 20, even more preferably 97 / 3 to 90 / 10, and most preferably 96 / 4 to 93 / 7.

[0076] Reactive derivatives of lactic acid include lactide (lactic acid dimer), acid anhydride, methyl ester, and other C 1-3 Examples thereof include alkyl esters, acid halides such as acid chlorides, and the like.

[0077] These lactic acid components can be used alone or in combination of two or more. Among these lactic acid components, a lactic acid component containing L-lactic acid [(S)-2-hydroxypropanoic acid] or a reactive derivative thereof is preferred, and a combination of L-lactic acid and D-lactic acid [(R)-2-hydroxypropanoic acid] is particularly preferred.

[0078] The polylactic acid resin is preferably a polymer having a lactic acid component as the main polymerization component, and may be a homopolymer of a lactic acid component (e.g., poly D-lactic acid, poly L-lactic acid, poly D,L-lactic acid, etc.) or a copolymer of a lactic acid component and a copolymer component.

[0079] Examples of copolymerizable components copolymerizable with the lactic acid component include diols, dicarboxylic acid components, and hydroxycarboxylic acid components.

[0080] The diol is not particularly limited, and can be selected from the diols exemplified as diols for polyhydroxyalkanoic acid resins in the section on hydrolysis inhibitors, including preferred embodiments.

[0081] The dicarboxylic acid component is not particularly limited, and can be selected from the dicarboxylic acid components exemplified as the dicarboxylic acid component of the polyhydroxyalkanoic acid resin in the section on hydrolysis inhibitors, including preferred embodiments.

[0082] The hydroxycarboxylic acid component may be any of a hydroxyaliphatic carboxylic acid component, a hydroxyalicyclic carboxylic acid component, and a hydroxyaromatic carboxylic acid component, but from the viewpoint of biodegradability and the like, a hydroxyaliphatic carboxylic acid component is preferred.

[0083] The hydroxyaliphatic carboxylic acid component may be a hydroxyaliphatic carboxylic acid or a reactive derivative of a hydroxyaliphatic carboxylic acid.

[0084] Hydroxyaliphatic carboxylic acids include glycolic acid, 3HP, 2-hydroxybutyric acid, 3HB, 4HB, 3-hydroxy-3-methyl-butyric acid, 2-hydroxyvaleric acid, 3HV, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxy-2-methyl-valeric acid, 3-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 7-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 8-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 9-hydroxynonanoic acid, 3-hydroxydecanoic acid, and 10-hydroxydecanoic acid. 1-6 Hydroxy C optionally having an alkyl group 2-15 Alkanoic acids are included.

[0085] Reactive derivatives of hydroxyaliphatic carboxylic acids include C anhydrides, methyl esters, etc. 1-3 Examples include alkyl esters, acid halides such as acid chlorides, and lactones corresponding to hydroxyaliphatic carboxylic acids.

[0086] The lactone is not particularly limited, and can be selected from the lactones exemplified as reactive derivatives of the hydroxyalkanoic acid component of the polyhydroxyalkanoic acid resin in the section on hydrolysis inhibitors, including preferred embodiments.

[0087] These hydroxycarboxylic acid components can be used alone or in combination of two or more.

[0088] Among these hydroxycarboxylic acid components, hydroxy C 2-10 Alkanoic acids or reactive derivatives thereof are preferred, and hydroxy C 2-8 Alkanoic acids or their reactive derivatives are more preferred, and hydroxy C such as glycolic acid and 3-hydroxypropanoic acid. 2-6 Alkanoic acids or reactive derivatives thereof are more preferred.

[0089] These copolymerization components can be used alone or in combination of two or more. Among these copolymerization components, C ethylene glycol and the like are preferred. 2-4C such as alkanediols and adipic acid 2-6 Alkanedicarboxylic acid components, hydroxy C such as glycolic acid 2-4 Alkanoic acid components, C such as glycolide and caprolactone 4-6 Lactone is preferred. The copolymerization component may be any copolymerization component other than the 3-hydroxybutyric acid component.

[0090] In a polylactic acid resin, the proportion of the lactic acid component as a monomer may be the maximum proportion of all constituent monomers, for example, 50 mol % or more (e.g., about 50 to 99.5 mol %) of all constituent monomers, preferably 70 mol % or more (e.g., about 70 to 99 mol %), more preferably 80 mol % or more (e.g., about 80 to 98 mol %), even more preferably 90 mol % or more, and most preferably 95 mol % or more. The polylactic acid resin may be a resin consisting only of a lactic acid component. If the proportion of the lactic acid component is too low, the biodegradability of the polylactic acid resin composition may be reduced.

[0091] The polylactic acid resin may be an alloy resin made by combining two or more polylactic acid resins of different types (or polymerization compositions), but from the viewpoint of transparency, a single type of polylactic acid resin is preferred.

[0092] The melt flow rate (MFR) of the polylactic acid resin is, for example, 1 to 30 g / 10 min, preferably 2 to 20 g / 10 min, further preferably 2.5 to 15 g / 10 min, further preferably 3 to 10 g / 10 min, and most preferably 3.5 to 7 g / 10 min, under conditions of a temperature of 190°C and a load of 2.16 kgf. If the MFR is too small, the moldability of the polylactic acid resin composition may decrease, whereas if the MFR is too large, the mechanical properties of the polylactic acid resin composition may decrease.

[0093] The weight average molecular weight of the polylactic acid resin can be selected from the range of 1,000 to 1,000,000, for example, 5,000 to 1,000,000, preferably 10,000 to 800,000, further preferably 20,000 to 700,000, even more preferably 30,000 to 600,000, and most preferably 50,000 to 500,000.

[0094] In this specification and claims, the weight average molecular weight of the polylactic acid resin can be measured by GPC in terms of standard polystyrene.

[0095] The glass transition temperature (Tg) of the polylactic acid resin is, for example, 40 to 80° C., preferably 45 to 75° C., further preferably 50 to 70° C., even more preferably 55 to 65° C., and most preferably 57 to 62° C. If the glass transition temperature is too low, the heat resistance and mechanical properties of the polylactic acid resin composition may be reduced, and conversely, if it is too high, the biodegradability and moldability of the polylactic acid resin composition may be reduced.

[0096] The polylactic acid resin may be a crystalline resin. The melting point of the polylactic acid resin is, for example, 80 to 250°C, preferably 100 to 200°C, further preferably 130 to 180°C, further preferably 140 to 170°C, and most preferably 150 to 160°C.

[0097] In this specification and claims, the glass transition temperature and melting point of the polylactic acid resin can be measured using a differential scanning calorimeter (DSC).

[0098] The acid value of the polylactic acid resin may be, for example, 0 to 100 mgKOH / g (e.g., 0.1 to 80 mgKOH / g), preferably 0.2 to 80 mgKOH / g, more preferably 0.3 to 60 mgKOH / g, and particularly preferably 0.5 to 30 mgKOH / g. If the acid value is too high, hydrolysis may occur easily. The hydroxyl value of the polylactic acid resin can also be selected from the same range as the acid value.

[0099] The polylactic acid resin may account for 50% by mass or more (for example, 50 to 99.5% by mass) of the polylactic acid resin composition, for example, 50 to 99% by mass, preferably 80 to 98% by mass, even more preferably 85 to 97% by mass, even more preferably 88 to 96% by mass, and most preferably 90 to 95% by mass.

[0100] (Ratio of hydrolysis inhibitor) The proportion of the hydrolysis inhibitor is, for example, 0.1 to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, more preferably 3 to 15 parts by mass, and most preferably 5 to 10 parts by mass, per 100 parts by mass of the polylactic acid-based resin. Furthermore, in applications where transparency is important, the proportion of the hydrolysis inhibitor is, for example, 0.1 to 30 parts by mass, preferably 0.2 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, and most preferably 1 to 9 parts by mass, per 100 parts by mass of the polylactic acid-based resin. If the proportion of the hydrolysis inhibitor is too low, hydrolysis of the polylactic acid-based resin may not be suppressed and flexibility may not be improved. If the proportion is too high, transparency and flexibility may decrease, or phase separation may occur, resulting in reduced moldability (productivity and handleability).

[0101] (plasticizer) The polylactic acid resin composition of the present invention may further contain a plasticizer, since this allows high levels of transparency and flexibility to be achieved.

[0102] The plasticizer may be a conventional plasticizer utilized as a plasticizer for polyester-based resins.

[0103] Examples of conventional plasticizers include ester-based plasticizers such as aliphatic dicarboxylic acid esters, aromatic dicarboxylic acid esters, oxycarboxylic acid esters, and polyhydric alcohol fatty acid esters; phosphate-based plasticizers such as aliphatic phosphate esters, aromatic phosphate esters, and condensed phosphate esters; epoxy-based plasticizers such as alkyl epoxy stearates; amide-based plasticizers such as sulfonamides; and oligomer-based plasticizers such as ester oligomers and amide oligomers. These plasticizers can be used alone or in combination of two or more.

[0104] Among these plasticizers, ester-based plasticizers and oligomer-based plasticizers such as ester oligomers are preferred from the viewpoint of compatibility with polylactic acid-based resins, with ester-based plasticizers being particularly preferred.

[0105] Preferred ester-based plasticizers include polycarboxylic acid esters and polyhydric alcohol esters.

[0106] The polycarboxylic acid ester may be a dicarboxylic acid ester or a polycarboxylic acid ester having three or more carboxyl groups.

[0107] Examples of the dicarboxylic acid ester include aliphatic dicarboxylic acid esters and aromatic dicarboxylic acid esters.

[0108] Examples of the aliphatic dicarboxylic acid ester include dialkyl aliphatic dicarboxylic acids, diesters of aliphatic dicarboxylic acids with glycol ethers, and diesters of aliphatic dicarboxylic acids with aralkyl alcohols and (poly)alkylene glycol monoalkyl ethers.

[0109] Examples of aliphatic dicarboxylic acid dialkyl include dibutyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, isononyl adipate, diisodecyl adipate, dibutyl sebacate, dioctyl sebacate, diethyl azelate, dibutyl azelate, and di-2-ethylhexyl azelate. 2-10 Aliphatic dicarboxylic acid di-C 1-18 Alkyl (especially C 4-10 Alkanedicarboxylic acid di-C 4-14 alkyl esters).

[0110] Examples of diesters of aliphatic dicarboxylic acids and glycol ethers include diesters of aliphatic dicarboxylic acids and (poly)alkylene glycol monoalkyl ethers, such as bis(methyldiethylene glycol) adipate [or adipic acid di(methoxyethoxyethyl) ester], bis(butyldiethylene glycol) adipate, bis(methyldiethylene glycol) succinate, methyldiethylene glycol ethyl diethylene glycol adipate (or adipic acid methoxyethoxyethyl ethoxyethoxyethyl ester), and methyldiethylene glycol butyl diethylene glycol adipate. 2-10 Aliphatic dicarboxylic acids and di- or tetra-C 2-4 Alkylene glycol mono C 1-4 Diesters with alkyl ethers are also included.

[0111] Diesters of aliphatic dicarboxylic acids with aralkyl alcohols and (poly)alkylene glycol monoalkyl ethers include C esters such as benzyl methyl diethylene glycol adipate (or adipic acid methoxyethoxyethyl benzyl ester), benzyl ethyl diethylene glycol adipate, benzyl butyl diethylene glycol adipate, benzyl methyl diglycol succinate, and benzyl butyl diglycol succinate. 2-10 Aliphatic dicarboxylic acids and C 6-10 Aryl C 1-4 Alkyl alcohols and C 2-4 Alkylene glycol mono C 1-4 Diesters with alkyl ethers are also included.

[0112] Examples of aromatic dicarboxylic acid esters include dialkyl aromatic dicarboxylic acids, alkyl-aralkyl aromatic dicarboxylic acid esters, and diesters of aromatic dicarboxylic acids and glycol ethers.

[0113] Examples of aromatic dicarboxylic acid dialkyl include C phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, and diisodecyl phthalate. 8-14 Arenedicarboxylic acid diC 1-12 Alkyl esters (especially benzenedicarboxylic acid C 4-8 alkyl esters).

[0114] Aromatic dicarboxylic acid alkyl and aralkyl esters include C butyl benzyl phthalate and other 8-14 Arenedicarboxylic acid C 1-12 Alkyl C 6-10 Aryl C 1-4 Alkyl esters and the like.

[0115] Examples of the diesters of aromatic dicarboxylic acids and glycol ethers include diesters of aromatic dicarboxylic acids and (poly)alkylene glycol monoalkyl ethers, such as C bis(methyldiethylene glycol) phthalate (or di(methoxyethyl) phthalate). 8-14 Arenedicarboxylic acids (especially C 8-12 arenedicarboxylic acids) and di- or tetra-C 2-4 Alkylene glycol mono C 1-4 Diesters with alkyl ethers are also included.

[0116] The polycarboxylic acid ester having three or more carboxyl groups may be an ester of an aliphatic or aromatic carboxylic acid having about 3 to 8 (particularly 3 to 6) carboxyl groups. Examples of such polycarboxylic acid esters include citric acid esters such as tributyl citrate, acetyl tributyl citrate, and tri-2-ethylhexyl acetyl citrate; trimellitic acid esters such as trimethyl trimellitate, triethyl trimellitate, trioctyl trimellitate, and tri-2-ethylhexyl trimellitate; and pyromellitic acid esters such as tetraoctyl pyromellitate.

[0117] The polyhydric alcohol ester may be an ester of a polyhydric alcohol having three or more hydroxyl groups and a fatty acid. Examples of the polyhydric alcohol include alcohols having about 3 to 6 hydroxyl groups, such as sucrose, glycerin, diglycerin, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitol. Examples of the polyhydric alcohol fatty acid ester include glycerin diacetate mono-C 8-10 (Poly)C such as alkyl esters, triacetin, and diglycerin tetraacetate 3-10 Alkane polyol mono- or hexa-C 2-10 Alkanoates and the like.

[0118] These ester-based plasticizers can be used alone or in combination of two or more. Among these ester-based plasticizers, aliphatic dicarboxylic acid esters are preferred from the viewpoint of biodegradability. Furthermore, among the aliphatic dicarboxylic acid esters, C esters such as adipic acid esters are preferred. 4-8 Alkanedicarboxylic acid esters are preferred, and C is preferred because it is easy to achieve both the flexibility and hydrolysis resistance of polylactic acid. 4-8 Alkanedicarboxylic acids and C 6-10 Aryl C 1-4 Alkyl alcohols and mono- or tri-C 2-4 Alkylene glycol mono C 1-4 Diesters with alkyl ethers are more preferred, C 5-7 Alkanedicarboxylic acids and phenyl C 1-3 Alkyl alcohol and mono or di C 2-3 Alkylene glycol mono C 1-3 Diesters with alkyl ethers are more preferred, C 5-7 Alkanedicarboxylic acids and phenyl C 1-2 Alkyl alcohol and diethylene glycol mono C 1-2 Diesters with alkyl ethers are most preferred.

[0119] The proportion of the plasticizer may be 50 parts by mass or less (e.g., 0.1 to 50 parts by mass) relative to 100 parts by mass of the polylactic acid resin, and is, for example, 1 to 30 parts by mass, preferably 3 to 25 parts by mass, further preferably 5 to 20 parts by mass, even more preferably 10 to 15 parts by mass, and most preferably 11 to 13 parts by mass. If the proportion of the plasticizer is too low, there is a risk that the effect of improving the flexibility of the polylactic acid resin composition will not be achieved, whereas if it is too high, there is a risk that the polylactic acid resin will be prone to hydrolysis and that the tensile modulus and transparency will also decrease.

[0120] The proportion of the plasticizer may be 1,000 parts by mass or less relative to 100 parts by mass of the hydrolysis inhibitor, for example, 1 to 500 parts by mass, preferably 10 to 300 parts by mass, further preferably 30 to 200 parts by mass, even more preferably 50 to 150 parts by mass, and most preferably 80 to 120 parts by mass. If the proportion of the plasticizer is too low, there is a risk that the effect of improving the flexibility of the polylactic acid resin composition will not be achieved, whereas if it is too high, there is a risk that the polylactic acid resin will be more susceptible to hydrolysis and that the tensile modulus and transparency will also decrease.

[0121] (Other ingredients) The polylactic acid resin composition of the present invention may further contain other components, which may be other resins or conventional additives that are blended into resins.

[0122] Examples of the other resins include other aliphatic polyester resins, aliphatic polyamide resins, cellulose-based resins, polyvinyl alcohol-based resins, etc. These other resins can be used alone or in combination of two or more.

[0123] Commonly used additives include antiblocking agents, slip agents (or anti-scratch agents), stabilizers (antiaging agents, antioxidants, antiozonants, ultraviolet absorbers, light stabilizers, heat stabilizers, etc.), flame retardants, compatibilizers, softeners, lubricants, antistatic agents, crystal nucleating agents, colorants, preservatives, antifungal agents, etc. These additives can be used alone or in combination of two or more.

[0124] The total proportion of the other components can be selected from the range of about 0.1 to 100 parts by mass relative to 100 parts by mass of the polylactic acid resin, for example, 0.5 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably 2 to 20 parts by mass.

[0125] [Characteristics and preparation method of polylactic acid resin composition] The polylactic acid resin composition of the present invention has excellent flexibility. The breaking elongation of the polylactic acid resin composition of the present invention (test speed 10 mm / min) may be 5% or more (particularly 8% or more), for example, 10 to 1000%, preferably 30 to 800%, more preferably 50 to 700%, more preferably 100 to 600%, and most preferably 150 to 500%. In applications where flexibility is important, the breaking elongation is, for example, 100 to 1000%, preferably 150 to 800%, more preferably 200 to 700%, more preferably 300 to 600%, and most preferably 400 to 500%.

[0126] In this specification and claims, the elongation at break (elongation at break or elongation at break) of a polylactic acid resin composition can be measured in accordance with JIS K 7161, and more specifically, by the method described in the examples below.

[0127] The tensile modulus of the polylactic acid resin composition of the present invention (test speed: 10 mm / min) may be 2000 MPa or less (particularly 1700 MPa or less), for example, 500 to 2000 MPa, preferably 1000 to 1700 MPa, more preferably 1200 to 1650 MPa, more preferably 1300 to 1600 MPa, and most preferably 1400 to 1550 MPa. In applications where flexibility is important, the tensile modulus is, for example, 500 to 1700 MPa, preferably 550 to 1500 MPa, more preferably 600 to 1200 MPa, more preferably 650 to 1000 MPa, and most preferably 700 to 800 MPa. If the tensile modulus is too low, the mechanical properties of the polylactic acid resin composition may be reduced, while if it is too high, the flexibility of the polylactic acid resin composition may be reduced.

[0128] In this specification and claims, the tensile modulus of elasticity of the polylactic acid resin composition can be measured in accordance with JIS K 7161, and more specifically, by the method described in the examples below.

[0129] The polylactic acid resin composition of the present invention has excellent melt fluidity and high moldability. The MFR (melt flow rate or melt flow index (MFI)) of the polylactic acid resin composition of the present invention (temperature: 190°C, load: 2.16 kgf) may be 1 g / 10 min or more, for example, 1 to 30 g / 10 min, preferably 2 to 20 g / 10 min, more preferably 3 to 10 g / 10 min, more preferably 4 to 9 g / 10 min, and most preferably 5 to 8 g / 10 min. For applications where flexibility is important, the MFR is, for example, 3 to 30 g / 10 min, preferably 5 to 20 g / 10 min, and more preferably 10 to 18 g / 10 min. If the MFR is too low, the moldability of the polylactic acid resin composition may be reduced, while if the MFR is too high, the mechanical properties of the polylactic acid resin composition may be reduced.

[0130] In this specification and claims, the MFR of a polylactic acid resin composition can be measured in accordance with ISO 1133, and more specifically, by the method described in the examples below.

[0131] The polylactic acid resin composition of the present invention has excellent hydrolysis resistance. In the present invention, hydrolysis resistance can be evaluated by comparing the MFR of the polylactic acid resin composition before and after treatment under high-temperature and high-humidity conditions. The MFR of the polylactic acid resin composition of the present invention after treatment under high-temperature and high-humidity conditions may be 30 times or less, preferably 20 times or less, more preferably 10 times or less, more preferably 5 times or less, and most preferably 3 times or less (e.g., 1.1 to 3 times) the MFR before treatment (initial MFR).

[0132] In this specification and claims, the term "high temperature and humidity conditions" refers to conditions where the temperature is 70°C and 95% RH for 6 hours.

[0133] The polylactic acid resin composition of the present invention also has excellent transparency, and when molded into a sheet having a thickness of 2 mm, it is preferable that the resin composition has transparency that is almost completely transparent or slightly cloudy.

[0134] The polylactic acid resin composition of the present invention can be prepared by mixing a polylactic acid resin, a hydrolysis inhibitor, and, if necessary, other components such as a plasticizer, by a conventional method such as dry mixing or melt kneading, and the polylactic acid resin composition may be in the form of pellets, etc. When melt kneading, the kneading temperature is, for example, 100 to 250°C, preferably 130 to 230°C, more preferably 150 to 220°C, even more preferably 160 to 200°C, and most preferably 170 to 190°C. Conventional methods can be used for melt kneading, and for example, a twin-screw extrusion kneader may be used.

[0135] [Molded body] The molded article of the present invention is formed from the polylactic acid-based resin composition. The shape of the molded article of the present invention is not particularly limited and can be selected depending on the application, and examples thereof include one-dimensional structures such as wires or threads, two-dimensional structures such as films, sheets, and plates, and three-dimensional structures such as blocks, rods, pipes, tubes, and hollow structures.

[0136] The molded article of the present invention can be produced by molding the polylactic acid resin composition using a conventional molding method, such as compression molding, injection molding, injection compression molding, extrusion molding, transfer molding, blow molding, pressure molding, and casting molding.

[0137] When the molded article of the present invention is a two-dimensional film-like or sheet-like structure, the molded article of the present invention can be produced by forming (or molding) the polylactic acid-based resin composition into a film using a conventional film-forming method, such as an inflation molding method, a casting method (solvent casting method), a melt extrusion method, or a calendar method.

[0138] When the molded article of the present invention is produced by injection molding, the cylinder temperature is, for example, 130 to 250°C, preferably 150 to 230°C, further preferably 180 to 210°C, even more preferably 185 to 205°C, and most preferably 190 to 200°C. [Example]

[0139] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The raw materials used are as follows, and the properties and evaluation of the obtained polylactic acid resin composition and test specimens were measured and evaluated as follows.

[0140] [Ingredients used] PLA (polylactic acid): manufactured by Anhui Fengyuan Group Co., Ltd.; FY804, melting point 150-160°C, L-isomer content 95.5 mol%, D-isomer content 4.5 mol%, MFR (temperature 190°C, load 2.16 kgf) 4 g / 10 min, glass transition temperature 60°C PHB (Poly(R)-3-hydroxybutyrate): Ningbo Tainan Biologic Material Co., Ltd.; ENMAT Y3000, glass transition temperature 4°C PHBV ((R)-3-hydroxybutyric acid-(R)-3-hydroxyvaleric acid copolymer): manufactured by Ningbo Tainan Biologic Material Co., Ltd.; ENMAT Y1000, glass transition temperature -1°C Adipic acid ester: "DAIFATTY-101" manufactured by Daihachi Chemical Industry Co., Ltd.

[0141] [MFR] The pellets (polylactic acid resin compositions) obtained in the examples and comparative examples were measured in accordance with ISO 1133 under conditions of a holding time of 5 minutes, a temperature of 190°C, and a test load of 2.16 kgf. To evaluate the hydrolysis resistance of the polylactic acid resin compositions, the MFR of the initial pellets (initial MFR) and the MFR of the pellets after holding for 6 hours at 70°C and 95% RH (post-treatment MFR) were measured, and the hydrolysis resistance was evaluated. As hydrolysis progresses, fluidity increases, and the ratio of the post-treatment MFR to the initial MFR increases.

[0142] [Tensile test (elongation at break and tensile modulus)] The pellets (polylactic acid resin compositions) obtained in the examples and comparative examples were injection molded at 195°C to produce test specimens for tensile tests, and the tensile modulus and elongation at break were measured using a small tabletop testing machine ("EZ-Graph" manufactured by Shimadzu Corporation) in accordance with JIS K 7161. The test conditions were a crosshead speed of 10 mm / min, and test specimens of 75 mm length, 10 mm width, and 2 mm thickness. A 100 N load cell was used.

[0143] [Transparency] The pellets (polylactic acid resin compositions) obtained in the examples and comparative examples were injection molded at 195°C to prepare test pieces with a thickness of 2 mm. The transparency of the test pieces was visually observed and evaluated according to the following criteria.

[0144] 1...Almost completely transparent 2...slightly cloudy 3...cloudy but clear 4...Highly turbid 5...completely opaque

[0145] Example 1 297 g of PLA and 3 g of PHB were mixed (PHB content: 1% by mass), and the mixture was melt-kneaded at 180° C. using a twin-screw extruder kneader to produce pellets.

[0146] Example 2 An experiment was carried out in the same manner as in Example 1, except that 291 g of PLA and 9 g of PHB (PHB content: 3% by mass) were used.

[0147] Example 3 An experiment was carried out in the same manner as in Example 1, except that 276 g of PLA and 24 g of PHB (PHB content: 8% by mass) were used.

[0148] Example 4 An experiment was carried out in the same manner as in Example 1, except that 258 g of PLA and 42 g of PHB (PHB content: 14% by mass) were used.

[0149] Example 5 An experiment was carried out in the same manner as in Example 1, except that 240 g of PLA and 60 g of PHB (PHB content: 20% by mass) were used.

[0150] Example 6 An experiment was carried out in the same manner as in Example 1, except that 297 g of PLA and 3 g of PHBV (PHBV content: 1% by mass) were used.

[0151] Example 7 An experiment was carried out in the same manner as in Example 1, except that 291 g of PLA and 9 g of PHBV (PHBV content: 3% by mass) were used.

[0152] Example 8 An experiment was carried out in the same manner as in Example 1, except that 276 g of PLA and 24 g of PHBV (PHBV content: 8% by mass) were used.

[0153] Example 9 An experiment was carried out in the same manner as in Example 1, except that 258 g of PLA and 42 g of PHBV (PHBV content: 14% by mass) were used.

[0154] Example 10 An experiment was carried out in the same manner as in Example 1, except that 240 g of PLA and 60 g of PHBV (PHBV content: 20% by mass) were used.

[0155] Example 11 An experiment was carried out in the same manner as in Example 1, except that 270 g of PLA, 30 g of PHBV, and 30 g of adipic acid ester (PHBV content and adipic acid ester content each 9.1% by mass) were used.

[0156] Comparative Example 1 The experiment was carried out in the same manner as in Example 1, except that 300 g of PLA was used.

[0157] Comparative Example 2 An experiment was carried out in the same manner as in Example 1, except that 258 g of PLA and 42 g of adipic acid ester (adipic acid ester content: 14% by mass) were used.

[0158] The pellets obtained in Examples 1 to 11 and Comparative Examples 1 and 2 were used to measure MFR, subjected to a tensile test, and evaluated for transparency. The results are shown in Table 1.

[0159] [Table 1]

[0160] As is clear from the results in Table 1, the resin compositions of Examples 1 to 11 showed a smaller increase in MFR after treatment relative to the initial MFR than the resin compositions of Comparative Examples 1 and 2, and thus exhibited hydrolysis resistance.

[0161] Furthermore, the resin compositions of Examples 1 to 10 not only exhibit hydrolysis resistance, but also have improved elongation at break, despite the tensile modulus being equivalent to that of Comparative Example 1. Therefore, in Examples 1 to 10, the hydrolysis inhibitor not only inhibited the hydrolysis of polylactic acid, but also imparted flexibility to polylactic acid, thereby functioning as a plasticizer. In particular, the resin composition of Example 11 had a lower tensile modulus than Comparative Example 1, but a better elongation at break than Comparative Example 2, demonstrating excellent flexibility.

[0162] Furthermore, the resin compositions of Examples 1 to 11 were also excellent in transparency, and in particular, when the proportion of the hydrolysis inhibitor for the polyhydroxyalkanoic acid resin was adjusted to 10 mass % or less, a high degree of transparency was achieved. [Industrial Applicability]

[0163] The hydrolysis inhibitor of the present invention can be used to inhibit the hydrolysis of polylactic acid resins.

[0164] The polylactic acid-based resin composition of the present invention may be highly biodegradable and can be used in a variety of fields, such as paints, antistatic agents, inks, adhesives, pressure-sensitive adhesives, electrical and electronic materials (e.g., carrier transport agents, light emitters, organic photoreceptors, etc.), electrical and electronic components or devices (e.g., optical lenses, optical films, optical disks, inkjet printers, digital paper, organic semiconductor lasers, dye-sensitized solar cells, etc.), and mechanical parts or devices (e.g., automobiles, aerospace materials, sensors, etc.). In particular, due to its high mechanical properties, it can be easily molded by extrusion molding, injection molding, etc., and is suitable for use in various molded components (e.g., molded articles such as casings and housings), containers (containers for food, daily necessities, electrical and electronic devices and parts, etc.), packaging materials such as films and sheets, and bags such as garbage bags. Due to its excellent transparency, it is particularly suitable as an optical material, container, and packaging material. Furthermore, its high biodegradability can also be used to solve the problem of microplastics, which has become a new issue in recent years.

Claims

1. A hydrolysis inhibitor for inhibiting the hydrolysis of a polylactic acid-based resin, the hydrolysis inhibitor comprising a polyhydroxyalkanoic acid-based resin (excluding the polylactic acid-based resin).

2. The polyhydroxyalkanoic acid resin is a hydroxy C ４－１０ The hydrolysis inhibitor according to claim 1, which comprises an alkanoic acid component as a polymer component.

3. The polyhydroxyalkanoic acid resin is a hydroxy C ４－６ The hydrolysis inhibitor according to claim 1 or 2, which contains an alkanoic acid component as a polymer component.

4. 3. The hydrolysis inhibitor according to claim 1, wherein the polyhydroxyalkanoic acid resin contains at least one polymer component selected from the group consisting of a 3-hydroxybutyric acid component and a 3-hydroxyvaleric acid component.

5. 3. The hydrolysis inhibitor according to claim 1, wherein the polyhydroxyalkanoic acid resin contains a 3-hydroxybutyric acid component as a polymer component.

6. A polylactic acid resin composition comprising a polylactic acid resin and the hydrolysis inhibitor according to claim 1 or 2.

7. 7. The polylactic acid resin composition according to claim 6, wherein the proportion of the hydrolysis inhibitor is 0.1 to 50 parts by mass per 100 parts by mass of the polylactic acid resin.

8. 7. The polylactic acid resin composition according to claim 6, wherein the proportion of the hydrolysis inhibitor is 0.5 to 15 parts by mass per 100 parts by mass of the polylactic acid resin.

9. The polylactic acid resin composition according to claim 6, further comprising a plasticizer.

10. A method for inhibiting hydrolysis of a polylactic acid resin, comprising adding the hydrolysis inhibitor according to claim 1 or 2 to the polylactic acid resin.

11. 3. A method for improving the flexibility of a polylactic acid resin, comprising adding the hydrolysis inhibitor according to claim 1 to said polylactic acid resin.

12. 3. A method for improving flexibility of a polylactic acid resin while suppressing hydrolysis of the polylactic acid resin, by adding the hydrolysis inhibitor according to claim 1 or 2 to the polylactic acid resin.

13. A method for suppressing hydrolysis and improving breaking elongation of a polylactic acid-based resin without reducing the transparency and tensile modulus of the polylactic acid-based resin, by adding 0.5 to 10 parts by mass of the hydrolysis inhibitor according to claim 1 or 2 to 100 parts by mass of the polylactic acid-based resin.

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