Plasticizers for polyester resins and their applications

Abstract

To provide a biomass-derived plasticizer for polyester resins with excellent plasticization efficiency. [Solution] A plasticizer containing 3-hydroxybutyrate ester is prepared as a plasticizer for plasticizing polyester resins. The 3-hydroxybutyrate ester may also contain R-3-hydroxybutyrate ester. The 3-hydroxybutyrate ester may also contain 3-hydroxybutyrate alkyl ester. The 3-hydroxybutyrate alkyl ester may contain 3-hydroxybutyrate C 1-24 Alkyl esters (especially 3-hydroxybutyrate C) 1-6 It may also contain alkyl esters. A polyester resin composition comprising a polyester resin and the plasticizer may be prepared. The polyester resin may include a biodegradable polyester resin such as polylactic acid. The mass ratio of the polyester resin to the plasticizer may be 99 / 1 to 80 / 20. A molded article containing the polyester resin composition may be prepared.

Description

[Technical Field]

[0001] This invention relates to a plasticizer for polyester resins and its applications. [Background technology]

[0002] There is a strong demand for efforts to realize a "low-carbon society" through the reduction of greenhouse gas emissions and a "resource-recycling society" that is in harmony with the environment. To achieve these societies, the spread of the new material "bioplastics" is accelerating.

[0003] Among these, polylactic acid (PLA) is used as a plant-derived, biodegradable resin. However, PLA is a rigid resin and lacks the flexibility to be used as a film. Therefore, it has been difficult to produce flexible films with PLA as the main component. For this reason, the development of plasticizers to make PLA more flexible is underway.

[0004] For example, Japanese Patent Publication No. 2015-512466 (Patent Document 1) discloses a biodegradable resin composition comprising a biodegradable resin and a plasticizer, wherein the plasticizer comprises a benzoate-based plasticizer.

[0005] Japanese Patent Publication No. 2019-131720 (Patent Document 2) discloses a plasticizer formed from 3-hydroxyalkanoic acid alone or copolymerized oligomers, having a carboxyl group or alkoxycarbonyl group at its terminus.

[0006] Japanese Patent Publication No. 2005-336448 (Patent Document 3) contains the general formula (1): R 1 O(AO) n R 2 [In the formula, R 1 R is a linear or branched alkyl group, alkenyl group, or alkylphenyl group with 1 to 15 carbon atoms. 2 R is an acyl group, alkyl group, or alkenyl group having 2 to 15 carbon atoms, and 1 and R 2The total carbon number is 4 to 18. A is an alkylene group having 2 to 4 carbon atoms, n is a number from 1 to 20 indicating the average number of moles of alkylene oxide added, and the n A's may be the same or different]. A plasticizer for biodegradable resins containing the compound represented by is disclosed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, none of the plasticizers had sufficient plasticization efficiency for polyester resins and were not sufficient as plasticizers for biomass-derived PLA. In addition, the plasticizers of Patent Documents 1 and 3 were derived from petroleum, and there was also a problem that the biomass degree decreased when used in mixture with PLA.

[0009] Therefore, an object of the present invention is to provide a plasticizer having excellent plasticization efficiency for polyester resins and its use.

[0010] Another object of the present invention is to provide a biomass-derived plasticizer having excellent plasticization efficiency for polyester resins and its use.

[0011] Still another object of the present invention is to provide a biomass-derived plasticizer capable of suppressing bleed-out and its use.

[0012] Another object of the present invention is to provide a biomass-derived plasticizer capable of improving the flexibility and mechanical properties of polyester resins and its use.

Means for Solving the Problem

[0013] As a result of intensive studies to solve the above problems, the present inventors have found that by including a 3-hydroxybutyrate ester as a plasticizer for a polyester resin, a plasticizer for a biomass-derived polyester resin excellent in plasticization efficiency can be provided, and thus the present invention (or the present disclosure) has been completed.

[0014] That is, the present invention includes the following aspects.

[0015] Aspect [1]: A plasticizer for plasticizing a polyester resin, the plasticizer containing a 3-hydroxybutyrate ester.

[0016] Aspect [2]: The plasticizer according to Aspect [1], wherein the 3-hydroxybutyrate ester contains an R-3-hydroxybutyrate ester.

[0017] Aspect [3]: The plasticizer according to Aspect [1] or [2], wherein the 3-hydroxybutyrate ester contains a 3-hydroxybutyrate alkyl ester (particularly, an R-3-hydroxybutyrate alkyl ester).

[0018] ​​​​​​​​​​​​​​​​​​​​​

[0021] Embodiment [7]: The polyester resin composition according to Embodiment [6], wherein the polyester resin comprises a biodegradable polyester resin.

[0022] Embodiment [8]: The polyester resin composition according to Embodiment [6] or [7], wherein the polyester resin comprises a polylactic acid resin.

[0023] Embodiment [9]: A polyester resin composition according to any of Embodiments [6] to [8], wherein the mass ratio of the polyester resin to the plasticizer is former / latter = 99 / 1 to 80 / 20.

[0024] Embodiment

[10] : A molded article comprising the polyester resin composition described in any of Embodiments [6] to [9].

[0025] Embodiment

[11] : A method for plasticizing a polyester resin by adding a plasticizer according to any of Embodiments [1] to [5] above.

[0026] In this specification and in the claims, the number of carbon atoms in substituents, etc., is defined as C1, C6, C 10 It is sometimes indicated in these ways. 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 with 6 to 10 carbon atoms.

[0027] Furthermore, when "X~Y" is used to indicate a numerical range in this specification and the claims, it may include the end numbers X and Y. [Effects of the Invention]

[0028] In this invention, since the plasticizer for the polyester resin contains 3-hydroxybutyrate ester, the plasticization efficiency of the polyester resin can be improved. Furthermore, by using a plasticizer containing R-3-hydroxybutyrate ester, a biomass-derived plasticizer for polyester resins can be provided. Therefore, when this plasticizer is added to a biodegradable polyester resin, flexibility can be imparted to the polyester resin without reducing its biodegradability. Moreover, because the plasticizer of this invention can impart flexibility to polyester resins with only a small amount of addition, it can suppress the decrease in the mechanical properties (such as tensile strength) of the polyester resin, as well as suppress bleed-out, thus preventing deterioration of the working environment due to odor generation, etc. [Modes for carrying out the invention]

[0029] [Plasticizer] The plasticizer of the present invention (first plasticizer) can be used as a plasticizer for plasticizing polyester resins (a plasticizer as an additive to polyester resins), and is characterized by containing 3-hydroxybutyrate ester (3HB ester). The 3HB ester may be a 3HB ester represented by the following formula (1).

[0030] [ka]

[0031] (In the formula, R 1 (This indicates a hydrocarbon group.)

[0032] In the above equation (1), R 1 Examples of hydrocarbon groups represented by include alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups. These hydrocarbon groups can be used individually or in combination of two or more. Of these hydrocarbon groups, alkyl groups are preferred due to their excellent biodegradability.

[0033] Examples of alkyl groups (linear or branched alkyl groups) include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, hexyl, isohexyl, octyl, decyl, dodecyl (lauryl), isododecyl (isolauryl), tetradecyl (myristyl), isotetradecyl (isomyristyl), hexadecyl (cetyl or palmityl), isohexadecyl (isocetyl), octadecyl (stearyl), isooctadecyl (isostearyl), eicosyl, and other C groups. 1-28 Examples include alkyl groups. These alkyl groups can be used individually or in combination of two or more.

[0034] Among these alkyl groups, C is chosen because of its high plasticization efficiency. 1-24 Alkyl alkyl groups are preferred, C 1-16 Alkyl alkyl groups are more preferred, C 1-12 Alkyl alkyl groups are more preferred, C 1-6 Alkyl alkyl groups are most preferred. Furthermore, when plasticizing a polylactic acid resin as a polyester resin, the affinity between 3HB ester and the polylactic acid resin is improved, which improves the plasticization efficiency, and among the alkyl groups, C 2-4 Alkyl groups are preferred, and ethyl groups are particularly preferred.

[0035] 3HB ester is obtained by a general method, for example, in formula (1) above, R 1 In the case of a 3HB alkyl ester in which is an alkyl group, 3-hydroxybutyric acid is converted into an alcohol [group R of formula (1) above] in accordance with the method described in Japanese Patent Publication No. 6979918. 1 The corresponding alcohol (R 1 It may also be produced by esterification with -OH).

[0036] The 3HB ester may be an optical isomer (R-isomer or S-isomer) or a racemic mixture, but it is preferable that it contains at least the R-isomer of 3HB ester [R-3-hydroxybutyrate ester or D-β-hydroxybutyrate, (R)3HB ester] due to its biomass origin and excellent biodegradability.

[0037] The proportion of the R-isomer in the 3HB ester, particularly the optical purity (enantiomer or optical isomer excess), may be, for example, 50% ee or higher, preferably in the following increments: 80-100% ee, 90-100% ee, 95-100% ee, 98-100% ee, 99-100% ee, and especially preferably substantially 100% ee. When the optical purity is above the lower limit, it is easier to improve biodegradability.

[0038] Furthermore, the R-isomer [(R)3HB ester] and the S-isomer [(S)3HB ester] and / or racemic mixture may be used in combination, but the proportion of the S-isomer is preferably small, and particularly preferably in a proportion that is unavoidable. The mass proportion of the R-isomer in the 3HB ester is preferably 10% by mass or more, more preferably 50% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. A higher proportion of the R-isomer can improve biodegradability.

[0039] The plasticizer of the present invention (plasticizer for polyester resins) may contain other components in addition to 3HB ester. Examples of other components include 3-hydroxybutyric acid (3HB or BHB), salts of 3HB, and oligomers of 3HB.

[0040] 3HB may be 3HB that was inevitably introduced during the manufacturing process of 3HB ester, etc.

[0041] Examples of salts of 3HB include alkali metal salts such as sodium salt, potassium salt, and lithium salt; alkaline earth metal salts such as magnesium salt and calcium salt; transition metal salts such as zinc salt; ammonium salt; amine salts such as trimethylamine salt, triethylamine salt, ethanolamine salt, and diethanolamine salt; and salts with basic amino acids such as lysine salt and arginine salt.

[0042] The average degree of polymerization of the 3HB oligomers should be 2 or higher, for example, 2 to 10, preferably 2 to 5, more preferably 2 to 4, more preferably 2 to 3, and most preferably 2. The 3HB oligomers may also be oligomers that are inevitably mixed in during the manufacturing process of 3HB esters.

[0043] The proportion of other components may be 10 parts by mass or less per 100 parts by mass of 3HB ester, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 1 part by mass or less. If the proportion of other components is too high, the plasticization efficiency may decrease.

[0044] The proportion of 3HB ester may be 50% by mass or more in the plasticizer, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, more preferably 97% by mass or more, most preferably 99% by mass or more, and may even be 100% by mass.

[0045] [Polyester resin composition] The polyester resin composition of the present invention comprises the plasticizer and the polyester resin. Conventional polyester resins can be used as the polyester resin. Examples of conventional polyester resins include aromatic polyester resins, aliphatic polyester resins, and polycarbonate ester resins.

[0046] Aromatic polyester resins include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and other poly-C 2-10 Alkilen C8-16 Arylate; poly-1,4-cyclohexanedimethylene terephthalate and other poly-C 5-10 Cycloalcane-C 1-4 Alkylene-C 8-16 Examples include arylate; polyarylate resins, and liquid crystalline polyester (LCP).

[0047] Examples of aliphatic polyester resins include polylactic acid (PLA), poly-3-hydroxybutyrate (PHB), 3-hydroxybutyrate-3-hydroxyhexanoate copolymer (PHBH), and polyhydroxyvaleric acid (PHA); polymers of aliphatic dicarboxylic acids and aliphatic diols such as polyethylene adipate, polybutylene succinate (PBS), and polybutylene succinate adipate (PBSA); lactone ring-opening polymers such as polycaprolactone (PCL); and aromatically modified aliphatic polyester resins such as polybutylene adipate terephthalate.

[0048] Examples of polycarbonate ester resins include bisphenol-type polycarbonate resins such as bisphenol A type polycarbonate resins, and polyester carbonate resins.

[0049] These polyester resins can be used individually or in combination of two or more. Of these, biodegradable polyester resins (especially aliphatic polyester resins) are preferred, and polylactic acid resins such as PLA are particularly preferred. When a biodegradable polyester resin is combined with the plasticizer, biodegradability can be improved, and when R-3HB ester is used as the plasticizer, both the resin and the plasticizer can be formed from biomass-derived resources, achieving a high degree of biodegradability.

[0050] A polylactic acid-based resin can be any resin (polymer) that contains a lactic acid component 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.

[0051] Lactic acid may be in the form of optical isomers (D-form, L-form) or a racemic mixture (DL-form), but from the viewpoint of the mechanical properties of the resin composition, it is preferable that either the L-form (L-lactic acid) or the D-form (D-lactic acid) be present in an amount of 90 mol% or more, preferably 93 mol% or more, and more preferably 95 mol% or more of lactic acid (lactic acid component).

[0052] Reactive derivatives of lactic acid include lactide (lactic acid dimer), acid anhydride, methyl ester, etc. 1-3 Examples include alkyl esters and acid halides such as acid chlorides.

[0053] These lactic acid components can be used individually or in combination of two or more. Of these lactic acid components, those containing L-lactic acid [(S)-2-hydroxypropanoic acid] or its reactive derivatives are preferred.

[0054] The polylactic acid resin is preferably a polymer in which lactic acid is the main polymerization component, and may be a homopolymer of lactic acid (e.g., poly-D-lactic acid, poly-L-lactic acid, poly-D,L-lactic acid, etc.), or a copolymer of lactic acid and copolymer components.

[0055] Examples of copolymerizable components with lactic acid components include diols, dicarboxylic acid components, and hydroxycarboxylic acid components.

[0056] The diol is not particularly limited and may be an aliphatic diol, alicyclic diol, or aromatic diol, but an aliphatic diol is preferred from the viewpoint of the biodegradability of the resin composition. Examples of aliphatic diols include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,3-butanediol, neopentyl glycol, hexanediol, octamethylene glycol, etc. 2-10 Examples include aliphatic diols. These diols can be used individually or in combination of two or more.

[0057] Of these diols, C 2-8Aliphatic diols are preferred, such as ethylene glycol, 1,4-butanediol, and neopentyl glycol. 2-6 Aliphatic diols are particularly preferred.

[0058] The dicarboxylic acid component is not particularly limited and includes aliphatic dicarboxylic acid components, alicyclic dicarboxylic acid components, aromatic dicarboxylic acid components, etc.

[0059] Examples of aliphatic dicarboxylic acids include oxalic acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. 2-12 Examples include aliphatic dicarboxylic acids.

[0060] Examples of alicyclic dicarboxylic acids include C15, such as cyclohexanedicarboxylic acid. 5-10 Examples include cycloalkane-dicarboxylic acids, such as decalindicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid, as well as di or tricycloalkanedicarboxylic acids.

[0061] Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, anthracenedicarboxylic acid, phenantradicarboxylic acid, etc. 6-14 Examples include arene-dicarboxylic acids.

[0062] Reactive derivatives of these dicarboxylic acids include acid anhydrides, methyl esters, and other C compounds. 1-3 Examples include alkyl esters and acid halides such as acid chlorides. These dicarboxylic acid components can be used individually or in combination of two or more.

[0063] Among these dicarboxylic acid components, aliphatic dicarboxylic acid components are preferred because they are easier to improve biodegradability, and C 2-8 Aliphatic dicarboxylic acid components are more preferred, such as oxalic acid, succinic acid, and adipic acid. 2-6 Aliphatic dicarboxylic acid components are more preferred.

[0064] The hydroxycarboxylic acid component may be any of the following: a hydroxyaliphatic carboxylic acid component, a hydroxyalicyclic carboxylic acid component, or a hydroxyaromatic carboxylic acid component. However, from the viewpoint of biodegradability and other factors, a hydroxyaliphatic carboxylic acid component is preferred.

[0065] The hydroxyaliphatic carboxylic acid component may be a hydroxyaliphatic carboxylic acid itself, or a reactive derivative of a hydroxyaliphatic carboxylic acid.

[0066] Examples of hydroxyaliphatic carboxylic acids include glycolic acid, 3-hydroxypropanoic acid (3HP), 2-hydroxybutyric acid (2-hydroxybutanoic acid or 2HB), 3-hydroxybutyric acid (3HB), 4-hydroxybutyric acid (4HB), 3-hydroxy-3-methylbutyric acid, 2-hydroxyvaleric acid (2-hydroxypentanoic acid), 3-hydroxyvaleric acid (3HV), 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxy-2-methylvaleric acid, 3-hydroxyhexanoic acid, 6-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 7-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 8-hydroxyoctanoic acid, 3-hydroxynanoneic acid, 9-hydroxynanoneic acid, 3-hydroxydecanoic acid, 10-hydroxydecanoic acid, etc. 1-6 Hydroxy C which may have an alkyl group 2-15 Examples include alkanic acids.

[0067] Reactive derivatives of hydroxyaliphatic carboxylic acids include acid anhydrides, methyl esters, etc. 1-3 Examples include alkyl esters, acid halides such as acid chlorides, and lactones corresponding to hydroxyaliphatic carboxylic acids.

[0068] Examples of lactones include diC14, glycoside, β-propiolactone, β-dimethylpropiolactone, γ-butyrolactone, γ-dimethylbutyrolactone, δ-valerolactone, ε-caprolactone, etc. 1-6 C may have an alkyl group 3-15Lactones are an example. These lactones can be used alone or in combination of two or more. Of these lactones, C 3-10 Lactones are preferred, such as glycosides, propiolactones, and caprolactones. 3-8 Lactones are particularly preferred.

[0069] These hydroxycarboxylic acid components can be used individually or in combination of two or more.

[0070] Of these hydroxycarboxylic acid components, hydroxyC 2-10 Alkanic acid components are preferred, and hydroxy C 2-8 Alkanic acid components are even more preferred, such as glycolic acid and 3-hydroxypropanoic acid. 2-6 Alkanic acid components are more preferable.

[0071] These copolymer components can be used individually or in combination of two or more. Among these copolymer components, C such as ethylene glycol... 2-4 Alkanediols, adipic acid, etc. 2-6 Alkanedicarboxylic acid components, glycolic acid, and other hydroxy C 2-4 Alkanic acid components, such as glycosides and caprolactone. 4-6 Lactones are preferred.

[0072] In polylactic acid resins, the proportion of lactic acid components, which are monomers, may be the largest proportion among all constituent monomers, for example, 50 mol% or more of all constituent monomers (e.g., about 50 to 99.5 mol%), 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%), more preferably 90 mol% or more, and most preferably 95 mol% or more. Polylactic acid resins may also be resins consisting only of lactic acid components. When the proportion of lactic acid components is above the lower limit, the biodegradability of the resin composition tends to improve.

[0073] Furthermore, the polylactic acid resin may be a single type of polylactic acid resin, or it may be an alloy resin formed by combining two or more different types (or polymerization compositions) of polylactic acid resins.

[0074] The melt flow rate (MFR) of polylactic acid resins is, for example, 1 to 30 g / 10 min, preferably 2 to 20 g / 10 min, more preferably 2.5 to 10 g / 10 min, more preferably 3 to 8 g / 10 min, and most preferably 4 to 6 g / 10 min, under conditions of a temperature of 190°C and a load of 2.16 kgf. When the MFR is above the lower limit, the fluidity of the resin composition tends to improve, while conversely, when it is below the upper limit, the mechanical properties of the resin composition tend to improve.

[0075] 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, more preferably 20,000 to 700,000, more preferably 30,000 to 600,000, and most preferably 50,000 to 500,000.

[0076] In this specification and in the claims, the weight-average molecular weight of the polylactic acid resin can be measured by GPC on a standard polystyrene basis.

[0077] The glass transition temperature (Tg) of polylactic acid resins is, for example, 40 to 80°C, preferably 45 to 75°C, more preferably 50 to 70°C, more preferably 55 to 65°C, and most preferably 57 to 62°C. When the glass transition temperature is above the lower limit, the heat resistance and mechanical properties of the resin composition tend to improve, while when it is below the upper limit, the biodegradability and moldability of the resin composition tend to improve.

[0078] The melting point of polylactic acid resins is, for example, 80 to 250°C, preferably 100 to 200°C, more preferably 130 to 180°C, even more preferably 140 to 170°C, and most preferably 150 to 160°C.

[0079] In this specification and within the claims, the glass transition temperature and melting point of polylactic acid resins can be measured using a differential scanning calorimetry (DSC).

[0080] The acid value of the polylactic acid resin may be, for example, 0 to 100 mg KOH / g (e.g., 0.1 to 80 mg KOH / g), preferably 0.2 to 80 mg KOH / g, more preferably 0.3 to 60 mg KOH / g, and particularly around 0.5 to 30 mg KOH / g. When the acid value is below the upper limit, hydrolysis resistance tends to improve. The hydroxyl value of the polylactic acid resin can also be selected from a range similar to that of the acid value.

[0081] Polylactic acid resins may be crystalline or amorphous.

[0082] The proportion of polyester resin (especially polylactic acid resin) may be 10% by mass or more, preferably 50% by mass, more preferably 80% by mass or more, and more preferably 85% by mass or more, in the polyester resin composition. Furthermore, the proportion of polyester resin (especially polylactic acid resin) can be selected from a range of about 10 to 99% by mass, for example, 50 to 98% by mass, preferably 80 to 97% by mass, more preferably 85 to 95% by mass, more preferably 88 to 92% by mass, and most preferably 89 to 91% by mass. When the proportion of polyester resin is above the lower limit, the mechanical properties of the resin composition tend to improve.

[0083] The ratio (mass ratio) of polyester resin (especially polylactic acid resin) to plasticizer (first plasticizer) can be selected from a range of approximately polyester resin / plasticizer = 99.9 / 0.1 to 50 / 50, for example, 99.5 / 0.5 to 70 / 30, preferably 99 / 1 to 75 / 25, more preferably 97 / 3 to 80 / 20, more preferably 95 / 5 to 85 / 15, even more preferably 92 / 8 to 88 / 12, and most preferably 91 / 9 to 89 / 11. If the proportion of plasticizer is above the lower limit, the plasticization efficiency of the polyester resin tends to improve, and if it is below the upper limit, the mechanical properties of the polyester resin composition tend to be maintained.

[0084] When using a polyester resin composition as a masterbatch, the ratio (mass ratio) of polyester resin to plasticizer can be selected from a range of approximately 10 / 90 to 99 / 1, preferably 20 / 80 to 93 / 7, more preferably 30 / 70 to 95 / 5, and more preferably 40 / 60 to 90 / 10.

[0085] The polyester resin composition of the present invention may further contain other plasticizers (plasticizers other than the first plasticizer) in addition to the first plasticizer. The other plasticizer (second plasticizer) may include, for example, plasticizers conventionally used as plasticizers for polyester resins. The proportion of the second plasticizer may be 5 parts by mass or less per 100 parts by mass of polyester resin, preferably 3 parts by mass or less, more preferably 1 part by mass or less, and more preferably 0.1 parts by mass or less. Because the polyester resin composition of the present invention contains a plasticizer containing 3HB ester, it has high flexibility, and therefore, it is particularly preferable that it does not contain a second plasticizer. Furthermore, in the present invention, by not including petroleum-derived plasticizers as the second plasticizer, biodegradability can be improved.

[0086] The polyester resin composition of the present invention may further contain various additives as needed. These additives may include resin reinforcing materials such as granular (non-fibrous) reinforcing materials and fibrous reinforcing materials, coloring agents such as dyes and pigments, conductive agents, flame retardants, lubricants, stabilizers, mold release agents, antistatic agents, dispersants, flow regulators, leveling agents, defoaming agents, surface modifiers, stress reducers, carbon materials, and the like. Examples of stabilizers include antioxidants, ultraviolet absorbers, and heat stabilizers. These additives may be used individually or in combination of two or more. The proportion of these additives may be 100 parts by mass or less (particularly 10 parts by mass or less) per 100 parts by mass of polyester resin, for example, 0.01 to 100 parts by mass, preferably 0.1 to 50 parts by mass, and more preferably 1 to 10 parts by mass.

[0087] [Method and properties of polyester resin compositions] The polyester resin composition of the present invention can be prepared by mixing a polyester resin, a plasticizer, and various additives as needed using conventional methods such as dry mixing or melt kneading, and the polyester resin composition may be in the form of pellets or the like.

[0088] The polyester resin composition of the present invention has excellent flexibility because it contains a plasticizer containing 3HB. The elongation at break of the polyester resin composition of the present invention (test speed 10 mm / min) may be 10% or more (particularly 100% or more), for example, 10 to 1000%, preferably 100 to 800%, more preferably 300 to 600%, more preferably 350 to 550%, and most preferably 400 to 500%. When the elongation at break is above the lower limit, the flexibility of the polyester resin composition tends to improve.

[0089] In this specification and in the claims, the elongation at break (elongation rate at break or elongation at break) of the polyester resin composition can be measured in accordance with JIS K 7161, and in detail, it can be measured by the method described in the examples below.

[0090] The tensile modulus of the present invention (test speed 10 mm / min) may be 2000 MPa or less (particularly 1500 MPa or less), for example, 10 to 2000 MPa, preferably 100 to 1500 MPa, more preferably 200 to 1000 MPa, more preferably 300 to 800 MPa, and most preferably 350 to 600 MPa. When the tensile modulus is below the upper limit, the flexibility of the polyester resin composition tends to improve.

[0091] In this specification and in the claims, the tensile modulus of the polyester resin composition can be measured in accordance with JIS K 7161, and more specifically, it can be measured by the method described in the examples below.

[0092] The tensile strength (test speed 10 mm / min) of the polyester resin composition of the present invention is, for example, 1 to 60 MPa, preferably 10 to 55 MPa, more preferably 15 to 50 MPa, more preferably 20 to 45 MPa, and most preferably 25 to 30 MPa. When the tensile strength is above the lower limit, the mechanical properties of the polyester resin composition tend to improve, and when it is below the upper limit, the flexibility tends to improve.

[0093] In this specification and in the claims, the tensile strength of the polyester resin composition can be measured in accordance with JIS K 7161, and more specifically, it can be measured by the method described in the examples below.

[0094] The Izod impact strength (with notch) of the polyester resin composition of the present invention is 1 kJ / m². 2 It may be greater than or equal to, for example, 1 to 30 kJ / m³ 2 Preferably 1.5 to 10 kJ / m³ 2 More preferably 2-5 kJ / m³ 2 , more preferably 2.3~4 kJ / m 2 Most preferably 2.5 to 3.5 kJ / m³ 2 When the impact strength is above the lower limit, the mechanical properties of the polyester resin composition tend to improve, and when it is below the upper limit, the flexibility tends to improve.

[0095] In this specification and in the claims, the Izod impact strength of the polyester resin composition can be measured in accordance with ISO 180, and more specifically, it can be measured by the method described in the examples below.

[0096] [Molded body] The polyester resin composition of the present invention maintains excellent mechanical properties while exhibiting superior flexibility, enabling the formation of molded articles with high moldability (or productivity) and excellent mechanical properties. The shape of the molded article is not particularly limited and can be selected according to the application. It may be a one-dimensional structure such as a linear, thread-like, or fibrous structure; a two-dimensional structure such as a film-like, sheet-like, or plate-like structure; or a three-dimensional structure such as a block-like, rod-like, tubular, or hollow structure.

[0097] Molded articles can be manufactured using conventional molding methods such as injection molding, injection compression molding, extrusion molding, transfer molding, blow molding, pressure molding, and casting molding. [Examples]

[0098] 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, equipment used in the examples, and evaluation methods for the polylactic acid resin compositions prepared in the examples are as follows.

[0099] [Raw materials] (Synthesis method of the plasticizer used in the examples) R-3-Hydroxybutyric Acid: In the following method for synthesizing plasticizers, the R-3-hydroxybutyric acid used as a raw material was obtained by concentrating R-3-hydroxybutyric acid (Osaka Gas Co., Ltd.'s "OKETOA® D-BHB Acid") in an evaporator set to 70°C, then adding ethyl acetate in a ratio of 30 parts by mass per 100 parts by mass of R-3-hydroxybutyric acid, and further adding seed crystals of R-3-hydroxybutyric acid and cooling to crystallize.

[0100] 3HB ethyl (3HB ethyl ester): Synthesized by the following method.

[0101] 700 g of R-3-hydroxybutyric acid, 2100 g of ethanol, and 70 g of strong acid ion exchange resin (DIAION® SK104H, manufactured by Mitsubishi Chemical Corporation) were placed in a four-necked flask fitted with a Dean-Stark tube and subjected to nitrogen flow. The mixture after nitrogen flow was heated under reflux conditions using a mantle heater, and the reaction was carried out for 12 hours while removing the mixture of water and ethanol produced by the reaction and adding the same amount of ethanol. The ethanol contained in the resulting reaction solution was removed using an evaporator set to 70°C. The residue after removal was obtained by vacuum distillation at an oil bath temperature of 122°C to obtain 3HB ethyl ester.

[0102] 3HB butyl: Synthesized by the following method.

[0103] 60 g of R-3-hydroxybutyric acid, 240 g of 1-butanol, and 6 g of strong acid ion exchange resin (DIAION® SK104H, manufactured by Mitsubishi Chemical Corporation) were placed in a three-necked flask fitted with a Dean-Stark tube filled with 1-butanol, and nitrogen was flowed over it. The mixture after nitrogen flow was heated under reflux in an oil bath set to 140°C and reacted for 14 hours while removing the water produced by the reaction. The 1-butanol contained in the resulting reaction solution was removed using an evaporator set to 85°C. The residue after removal was obtained by vacuum distillation at an oil bath temperature of 158°C to obtain 3HB butyl ester.

[0104] 3HB cetyl: Synthesized by the following method.

[0105] First, 57.7 g of cetyl alcohol was placed in a flask and purged with nitrogen. Then, 500 mL of dichloromethane and 38.5 mL of pyridine were added and stirred to dissolve. Next, 68.1 g of p-toluenesulfonyl chloride was added in 10-minute increments, and the mixture was stirred at room temperature for 24.5 hours. 250 mL of 2N hydrochloric acid was added to the reaction mixture and stirred for 30 minutes. After liquid-liquid extraction, the aqueous layer was extracted three times with 100 mL of dichloromethane and dried over magnesium sulfate. The magnesium sulfate was filtered off, and the mixture was concentrated to dryness using an evaporator to obtain 110 g of a translucent viscous liquid. The obtained translucent viscous liquid was dissolved and dispersed in 500 mL of tetrahydrofuran, and 14.3 g of sodium hydroxide was added and stirred and dispersed for 19 hours. After removing tetrahydrofuran by evaporation, 750 mL of diethyl ether was added and the mixture was stirred for 30 minutes. The insoluble portion was then filtered off and the mixture was concentrated to dryness using an evaporator to obtain the intermediate (p-toluenesulfonate cetyl ester; 78.3 g of a light brown solid).

[0106] Next, 1.98 g of the obtained intermediate, p-toluenesulfonate cetyl ester, and 1.43 g of R-3-hydroxybutyric acid were charged into the reactor, and after nitrogen purging, 17 mL of dimethylformamide was added and stirred to dissolve, then 2.07 g of potassium carbonate was added and the reaction was stirred at room temperature for 17 hours. The reaction mixture was stirred at 45°C for 4 hours. The reaction mixture was returned to room temperature, 40 mL of purified water and 40 mL of ethyl acetate were added and stirred for 30 minutes, then liquid-liquid was separated and the aqueous layer was extracted four times with 10 mL of ethyl acetate, and the organic layer was washed five times with 20 mL of purified water and dried over magnesium sulfate. Magnesium sulfate was filtered off and the mixture was concentrated in an evaporator to obtain 1.58 g of a waxy solid. The product was purified by column chromatography with hexane / ethyl acetate as the mobile phase to obtain 1.43 g of 3HB cetyl ester as a waxy solid.

[0107] (Plasticizer used in the comparative example) Ethyl lactate: L-ethyl lactate, manufactured by Tokyo Chemical Industry Co., Ltd. PHB (Poly(R)-Hydroxybutyrate): Manufactured by Ningbo Tainan Biologic Material; ENMAT Y3000 Petroleum-based plasticizer: "DAIFATTY-101" manufactured by Daihachi Chemical Industry Co., Ltd.

[0108] (resin) Polylactic acid (PLA): NatureWorks "2003D"

[0109] [Equipment used] Compact desktop testing machine: Shimadzu Corporation's "EZ-Graph" Twin-screw compounding extruder: Technovel Co., Ltd. "KZW15TW-30MG-NH", L / D=30 Injection molding machine: "NEX140IV" manufactured by Nissei Plastic Industrial Co., Ltd.

[0110] [Tensile test] For polyester resin compositions, the tensile modulus, tensile strength (maximum tensile strength), and elongation at break were measured in accordance with JIS K 7161 using a small benchtop testing machine (Shimadzu Corporation's "EZ-Graph"). The test conditions were a crosshead speed of 10 mm / min, with a specimen length of 75 mm, width of 10 mm, and thickness of 2 mm. A 100 N load cell was used. The dumbbell test specimens were molded using an injection molding machine at a mold temperature of 25°C and a cylinder temperature of 185-195°C. However, in Example 6, which used 3HB cetyl ester as a plasticizer, the dumbbell test specimens were prepared by punching out a 0.5 mm thick film obtained by melt-kneading at 180°C and a rotation speed of 50 rpm for 5 minutes using a laproplast mill, and then press-molding at 170°C.

[0111] [Examples 1-9 and Comparative Examples 1-7] Polylactic acid and plasticizer were melt-kneaded using a twin-screw extruder at a temperature of 180°C, a screw rotation speed of 400 rpm, and a discharge rate of 2 kg / h, according to the mass ratio (proportion of plasticizer in the resin composition) shown in Table 1, to prepare the resin composition. The results of tensile tests performed on the obtained resin composition are shown in Table 1.

[0112] [Table 1]

[0113] As is clear from the results in Table 1, the flexibility of the resin composition was improved by adding a plasticizer in the examples. Furthermore, as is clear from the comparison between Example 2 and Comparative Example 2, the effect of improving flexibility was greater in Examples 1 to 5 than in Comparative Examples 1 to 5, which also contained petroleum-based plasticizers.

[0114] Furthermore, a comparison of Examples 1 to 5 showed that adding 8% or more of plasticizer significantly improved the flexibility of the resin composition, while adding around 8-12% suppressed the decrease in tensile strength.

[0115] Furthermore, as is clear from the comparison between Example 5 and Comparative Example 6, Comparative Example 6, in which PHB was added as a plasticizer, had a smaller elongation at break compared to Example 5, indicating that the plasticization efficiency was insufficient.

[0116] In Comparative Example 7, in which ethyl lactate was added as a plasticizer, the plasticization efficiency was high, but the odor due to bleed-out was strong, and the working environment was significantly deteriorated. [Industrial applicability]

[0117] The plasticizer of the present invention can be used as a plasticizer for plasticizing polyester resins, and is particularly suitable as a plasticizer for plasticizing biodegradable polyester resins such as polylactic acid.

[0118] The polyester resin composition of the present invention may have high biodegradability and can be used in various fields, such as paints, antistatic agents, inks, adhesives, sealants, electrical and electronic materials (e.g., carrier transport agents, light emitters, organic photoreceptors, etc.), electrical and electronic components or equipment (e.g., optical lenses, optical films, optical discs, inkjet printers, digital paper, organic semiconductor lasers, dye-sensitized solar cells, etc.), and mechanical parts or equipment (e.g., automobiles, aerospace materials, sensors, etc.). In particular, because it can be easily molded by extrusion molding, injection molding, etc., it can be suitably used for molded members in various fields (e.g., molded bodies such as casings and housings), containers (containers for food, daily necessities, electrical and electronic equipment and components, etc.), tableware (plates, spoons, forks, straws, etc.), packaging materials such as films and sheets, and bags such as garbage bags. Polylactic acid resin compositions are particularly suitable as optical materials, containers, and packaging materials because they also have excellent transparency. Furthermore, the problem of microplastics, which has become a new problem in recent years, can be solved by taking advantage of its high biodegradability.

Claims

1. A plasticizer for plasticizing polyester resins, comprising a 3-hydroxybutyrate ester.

2. The plasticizer according to claim 1, wherein the 3-hydroxybutyrate ester comprises R-3-hydroxybutyrate ester.

3. The plasticizer according to claim 1 or 2, wherein the 3-hydroxybutyrate ester comprises an alkyl 3-hydroxybutyrate ester.

4. The alkyl 3-hydroxybutyrate ester is C 3-hydroxybutyrate １－２４ The plasticizer according to claim 3, comprising an alkyl ester.

5. The aforementioned 3-hydroxybutyrate C １－２４ Alkyl esters are 3-hydroxybutyrate C １－６ The plasticizer according to claim 4, comprising an alkyl ester.

6. A polyester resin composition comprising a polyester resin and a plasticizer according to claim 1 or 2.

7. The polyester resin composition according to claim 6, wherein the polyester resin comprises a biodegradable polyester resin.

8. The polyester resin composition according to claim 6, wherein the polyester resin comprises a polylactic acid resin.

9. The polyester resin composition according to claim 6, wherein the mass ratio of the polyester resin to the plasticizer is former / latter = 99 / 1 to 80 / 20.

10. A molded article comprising the polyester resin composition described in claim 6.

11. A method for plasticizing a polyester resin by adding the plasticizer described in claim 1 or 2 to the polyester resin.

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