Branched biodegradable polyester and its use

Abstract

To provide a novel branched biodegradable polyester that excels in flexibility and breaking strength.SOLUTION: A branched biodegradable polyester comprises a block structure comprising a random copolymer segment of lactide and caprolactone and a homopolymer segment of lactide. The block structure has an end having an ester bond with a tri- or higher valent polyhydric alcohol.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a branched biodegradable polyester and its use. [Background technology]

[0002] Biodegradable resins have long been attracting attention as alternatives to petroleum-derived plastics from the perspective of reducing environmental impact. Among them, polylactic acid is a biodegradable resin that is produced in large quantities, and there is a demand for its widespread use in various applications.

[0003] For example, Patent Document 1 describes a stereocomplex multiblock copolymer comprising a block of polylactic acid and a block of polycaprolactone, in which the block of polylactic acid is stereocomplexed with a chiral polymer composed of a chiral monomer that is enantiomeric with the lactic acid constituting the polylactic acid.

[0004] Furthermore, for example, Patent Document 2 describes a branched biodegradable polyester having polyglycerin as a main chain and polyester chains as side chains via hydroxyl groups of the polyglycerin.

[0005] Furthermore, for example, Patent Document 3 describes a branched polymer having at least three arms made of a lactic acid-ε-caprolactone copolymer and having a weight-average molecular weight of 150,000 or more. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-210894 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-222768 [Patent Document 3] WO2014-061341 publication Summary of the Invention [Problem to be solved by the invention]

[0007] For example, Patent Document 1 discloses a stereocomplex multiblock copolymer of polylactic acid and polycaprolactone. Although the formation of a stereocomplex improves heat resistance, it has the problem of impairing flexibility.

[0008] Furthermore, Patent Document 2 discloses a branched biodegradable polyester that uses polyglycerin as the main chain, but there is a problem that polyesters with rigid branched chain skeletons, such as polylactic acid, do not have sufficient flexibility.

[0009] Patent Document 3 discloses a branched polymer having at least three arms made of a lactic acid-ε-caprolactone copolymer. However, the branched polymer itself has low breaking strength, and there is a problem in that sufficient breaking strength cannot be imparted even when blended with polylactic acid.

[0010] An object of the present invention is to provide a novel branched biodegradable polyester that exhibits high flexibility and high breaking strength, and related technologies. [Means for solving the problem]

[0011] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that by using a trivalent or higher polyhydric alcohol as the main chain and a compound obtained by extending polyester chains to the multiple hydroxyl groups of this alcohol (hereinafter also referred to as "branched polyester"), it is possible to improve the problem of polylactic acid, namely its poor flexibility, and to impart sufficient flexibility.

[0012] That is, the branched biodegradable polyester according to one embodiment of the present invention has a block structure including a random copolymer segment of lactide and caprolactone and a homopolymer segment of lactide, and a trihydric or higher polyhydric alcohol is bonded to the end of the block structure. [Effects of the Invention]

[0013] According to one aspect of the present invention, it is possible to provide a novel branched biodegradable polyester that exhibits high flexibility and high breaking strength, and related techniques thereof. DETAILED DESCRIPTION OF THE INVENTION

[0014] <Branched biodegradable polyester> The branched biodegradable polyester according to one embodiment of the present invention will be described in detail below.

[0015] A branched biodegradable polyester according to one embodiment of the present invention is a branched biodegradable polyester (hereinafter sometimes simply referred to as "branched biodegradable polyester according to one embodiment") that has a block structure containing a random copolymer segment of lactide and caprolactone and a homopolymer segment of lactide, with a trivalent or higher polyhydric alcohol bonded to the end of the block structure. The branched biodegradable polyester according to one embodiment has an ester bond derived from a hydroxyl group of the trivalent or higher polyhydric alcohol and a carboxyl group at the end of the block structure.

[0016] High-melting biodegradable polyesters, such as polylactic acid, have the disadvantage of being hard and brittle due to the rigidity of their molecular structure. On the other hand, low-melting biodegradable polyesters, such as polycaprolactone, are flexible but have a low melting point, which makes them unsuitable for practical use as molded articles, for example. The branched biodegradable polyester according to one embodiment of the present invention comprises both a random copolymer segment of lactide and caprolactone and a homopolymer segment of lactide, and has a crosslinked structure with a trihydric or higher polyhydric alcohol, so that the branched biodegradable polyester itself has physical properties that allow it to be used as a molded article material.

[0017] (Trivalent or higher polyhydric alcohol) The trihydric or higher polyhydric alcohol is not particularly limited, but examples thereof include polyhydric alcohols such as polyglycerin, cyclic polyols, and polysaccharides, as well as polyhydric alcohols such as glycerin, sorbitol, and xylitol. An example of a cyclic polyol is quebrachitol, and an example of a polysaccharide is dextran. Among these, the trihydric or higher polyhydric alcohol is most preferably polyglycerin, since it is easy to adjust the number of hydroxyl groups. Polyglycerin is represented by the following general formula (A): [ka] In the general formula (A), n represents an integer of 1 to 30.

[0018] In general formula (A), the degree of polymerization n of polyglycerin is preferably 1 to 30, more preferably 2 to 20, and most preferably 4 to 10. When the degree of polymerization n of polyglycerin is greater than 1, the flexibility of the branched biodegradable polyester itself can be increased. Furthermore, when the degree of polymerization n of polyglycerin is less than 30, the breaking strength of the branched biodegradable polyester itself can be maintained. Furthermore, as will be described later, flexibility can be imparted to a resin composition containing the branched biodegradable polyester, and high breaking strength can be imparted to a resin composition containing the branched biodegradable polyester.

[0019] (Block structure) The block structure of the branched biodegradable polyester according to one embodiment is a block structure including a random copolymer segment and a homopolymer segment.

[0020] The random copolymer segment contains a copolymer of a monomer unit derived from one type of lactide (L-lactide, D-lactide, or DL-lactide) and a monomer unit derived from caprolactone. The random copolymer segment is formed by ring-opening polymerization of lactide and caprolactone, and the monomer unit derived from lactide is sometimes referred to as a "polylactic acid unit," and the monomer unit derived from caprolactone is sometimes referred to as a "caprolactone unit." The random copolymer segment can function as a so-called soft segment in the block structure.

[0021] The degree of polymerization (P1) of the polylactic acid units contained in the random copolymer segments is preferably 5 or more and 200 or less, more preferably 10 or more and 150 or less, and even more preferably 15 or more and 100 or less. By increasing the degree of polymerization (P1) of the polylactic acid units contained in the random copolymer segments to 5 or more, the breaking strength of the branched biodegradable polyester itself can be increased. Furthermore, high flexibility can be imparted to a resin composition containing the branched biodegradable polyester. Furthermore, by ensuring that the degree of polymerization (P1) of the polylactic acid units contained in the random copolymer segments is 200 or less, the flexibility of the branched biodegradable polyester itself can be prevented from being impaired.

[0022] The degree of polymerization (P2) of the caprolactone units contained in the random copolymer segment is preferably 5 or more and 200 or less, more preferably 10 or more and 150 or less, and even more preferably 15 or more and 100 or less. When the degree of polymerization (P2) of the caprolactone units contained in the random copolymer segment is 5 or more, the flexibility of the branched biodegradable polyester itself can be increased. Furthermore, when the degree of polymerization (P2) of the caprolactone units contained in the random copolymer segment is 200 or less, the breaking strength of the branched biodegradable polyester itself can be prevented from being impaired.

[0023] In addition, in the branched biodegradable polyester, the ratio (P2 / P1) of the degree of polymerization of caprolactone units (P2) to the degree of polymerization of polylactic acid units (P1) is preferably 0.5 or more and 3 or less. If the ratio (P2 / P1) is too small, the flexibility of the branched biodegradable polyester itself may decrease, and if it is too large, the breaking strength of the branched biodegradable polyester itself may decrease.

[0024] The homopolymer segment is preferably a lactide homopolymer segment, and includes, but is not limited to, a monomer derived from a homopolymer of any one of L-lactide, D-lactide, and DL-lactide. The homopolymer segment can function as a so-called hard segment in the block structure.

[0025] The degree of polymerization (P3) of the lactide homopolymer segment is preferably 5 or more and 200 or less, more preferably 10 or more and 150 or less, and even more preferably 15 or more and 100 or less. When the degree of polymerization (P3) of the lactide homopolymer segment is 5 or more, the breaking strength of the branched biodegradable polyester itself can be increased. Furthermore, when the degree of polymerization (P3) of the lactide homopolymer segment is 200 or less, the flexibility of the branched biodegradable polyester itself can be prevented from decreasing.

[0026] The block structure consisting of a random copolymer segment of lactide and caprolactone and a lactide homopolymer segment is represented by the following general formula (B): [ka] (In the general formula (B), m, l and k each independently represent an integer of 5 to 200.) is preferred.

[0027] The number average molecular weight (Mn) of the block structure comprising the random copolymer segment and the homopolymer segment may be, for example, 3,000 to 500,000, preferably 10,000 to 300,000, and more preferably 20,000 to 200,000.

[0028] The branched biodegradable polyester according to one aspect of the present invention is represented by the following general formula (C): [ka] (In general formula (C), each R is independently a hydrogen atom or the general formula (B) above, and n is an integer of 1 to 30.)

[0029] The block structure is not limited to that of general formula (B), and may have at least one block structure exemplified by an XYX block structure and a YXY block structure, where X is a random copolymer segment and Y is a homopolymer segment.

[0030] The number average molecular weight (Mn) of the branched biodegradable polyester of the present invention may be, for example, 5,000 to 1,000,000, preferably 10,000 to 500,000, and most preferably 30,000 to 200,000. By having a number average molecular weight of 5,000 to 1,000,000, it is possible to obtain rigidity sufficient for use as a molded article.

[0031] Furthermore, the molecular weight distribution of the branched biodegradable polyester, i.e., the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn), is, for example, 1.00 to 3.00, preferably 1.00 to 2.50, and most preferably 1.00 to 2.00. By having an Mw / Mn ratio of 1.00 to 3.00, mechanical properties such as tensile strength and impact resistance can be improved. Here, the number-average molecular weight and weight-average molecular weight can be measured using known methods such as GPC (eluent: chloroform, standard: polystyrene).

[0032] The branched biodegradable polyester according to one embodiment has high flexibility. The flexibility can be confirmed by the breaking stress and breaking strain of a molded article of the branched biodegradable polyester. The branched biodegradable polyester preferably has a breaking stress of 5 to 100 MPa, more preferably 10 to 50 MPa. The branched biodegradable polyester also preferably has a breaking strain of 50 to 1000%, more preferably 100 to 1000%.

[0033] As described above, the branched biodegradable polyester according to one embodiment has high flexibility and high breaking strength. That is, the branched biodegradable polyester according to one embodiment is a novel branched biodegradable polyester in which the brittleness characteristic of biodegradable polyesters has been improved and which has high breaking strength. For this reason, the branched biodegradable polyester according to one embodiment is expected to be used as a biodegradable polyester material for molding molded articles. Therefore, molded articles obtained by molding the branched biodegradable polyester according to one embodiment also fall within the scope of the present invention.

[0034] The molded article obtained by molding the branched biodegradable polyester according to one embodiment can be blended with known additives, for example, as described below, in the same manner as the molded article of the resin composition according to one embodiment.

[0035] <Resin composition> The branched biodegradable polyester according to one embodiment comprises both a random copolymer segment and a lactide homopolymer segment, and has a crosslinked structure with a trihydric or higher polyhydric alcohol, thereby improving compatibility with polyester resins such as biodegradable polyesters. Therefore, the branched biodegradable polyester according to one embodiment can be suitably used as a modifier for biodegradable polyester resins. Therefore, a modifier containing the branched biodegradable polyester according to one embodiment and a resin composition containing the branched biodegradable polyester according to one embodiment also fall within the scope of the present invention.

[0036] A resin composition containing a branched biodegradable polyester according to one embodiment can typically be blended with polylactic acid, a biodegradable resin. Here, the resin composition preferably contains 1 to 50% by weight, and more preferably 5 to 40% by weight, of the total content of the branched biodegradable polyester and polylactic acid taken as 100% by weight. By containing 1 to 50% by weight of the branched biodegradable polyester, a molded article of the resin composition can be imparted with high flexibility and high breaking strength.

[0037] In the branched biodegradable polyester contained in the resin composition, the degree of polymerization n of the polyglycerin is preferably 1 to 30, more preferably 2 to 20, and most preferably 4 to 10. When the degree of polymerization n of the polyglycerin is greater than 1, the flexibility of the resin composition can be increased. On the other hand, when the degree of polymerization n of the polyglycerin is less than 30, the resin composition can be imparted with high flexibility and high breaking strength.

[0038] Furthermore, in the branched biodegradable polyester contained in the resin composition, the degree of polymerization (P1) of the polylactic acid units contained in the random copolymer segment is greater than or equal to 5 and less than or equal to 200, thereby imparting high breaking strength to the resin composition containing the branched biodegradable polyester.

[0039] Furthermore, in the branched biodegradable polyester contained in the resin composition, the degree of polymerization (P2) of the caprolactone units contained in the random copolymer segments is greater than or equal to 5 and less than or equal to 200, thereby imparting high flexibility to the resin composition containing the branched biodegradable polyester. Furthermore, the degree of polymerization (P2) of the caprolactone units contained in the random copolymer segments is smaller than or equal to 200, thereby preventing the breaking strength of the resin composition from decreasing.

[0040] Furthermore, in the branched biodegradable polyester contained in the resin composition, the ratio (P2 / P1) of the degree of polymerization (P2) of the caprolactone unit to the degree of polymerization (P1) of the polylactic acid unit is preferably 0.5 or more and 3 or less. If the ratio (P2 / P1) is too small, the flexibility of the resin composition may decrease, and if it is too large, the breaking strength of the resin composition may decrease.

[0041] Furthermore, in the branched biodegradable polyester contained in the resin composition, the degree of polymerization (P3) of the lactide homopolymer segment is greater when it is 5 or more and 200 or less, thereby increasing the compatibility with polylactic acid and increasing the breaking strength of the resin composition.

[0042] (Stereo Complex) In the resin composition, the branched biodegradable polyester and the base polylactic acid preferably form a stereocomplex. This can enhance the modifying effect on the resin composition. The stereocomplex refers to an interaction between the D-lactide homopolymer portion of the branched biodegradable polyester of the present invention when the base polylactic acid is poly-L-lactic acid, and an interaction between the L-lactide homopolymer portion of the branched biodegradable polyester of the present invention when the base polylactic acid is poly-D-lactic acid.

[0043] Whether or not the resin composition forms a stereocomplex can be confirmed by the presence or absence of a peak at a specific diffraction angle by X-ray diffraction.

[0044] A resin composition containing a branched biodegradable polyester according to one embodiment has both high breaking strain as a result of high flexibility and high breaking strength. For example, when the amount of branched biodegradable polyester added relative to linear PLA is 5 to 15%, the breaking strain of the branched biodegradable polyester may be 4% or more, preferably 10% or more. For example, when the amount of branched biodegradable polyester added relative to linear PLA is 5 to 15%, the breaking stress of the resin composition may be 30 MPa or more, preferably 40 MPa or more. For example, when the amount of branched biodegradable polyester added relative to linear PLA is 25 to 35%, the elastic modulus of the resin composition may be 1000 to 2200 MPa, preferably 1000 to 2000 MPa. The flexibility, breaking stress, and elastic modulus of the resin composition can be adjusted by the compounding ratio of the branched biodegradable polyester to polylactic acid, depending on the physical properties required for the molded article formed from the resin composition.

[0045] The resin composition may contain additives such as antistatic agents, light stabilizers, ultraviolet absorbers, nucleating agents, lubricants, antioxidants, antiblocking agents, flow improvers, mold release agents, flame retardants, colorants, inorganic neutralizing agents, hydrochloric acid absorbers, filler conductive agents, chain extenders, and hydrolysis inhibitors, as long as the effects of the present invention are not impaired.

[0046] [Method for producing branched biodegradable polyester] A method for producing a branched biodegradable polyester according to one embodiment will be described in detail below. The branched biodegradable polyester of the present invention can be produced by using a trivalent or higher polyhydric alcohol as an initiator and reacting a monomer that constitutes a polyester chain with all or part of the hydroxyl groups of the trivalent or higher polyhydric alcohol to extend the polyester chain.

[0047] An example of a synthesis method when the trihydric or higher polyhydric alcohol is a polyglycerol represented by general formula (A) is as follows: General formula (A): [ka] (In general formula (A), n is an integer of 1 to 30.) For polyglycerol represented by the following general formula (D): [ka] and a compound represented by the following general formula (E): [ka] After polymerizing the compound represented by the general formula (D), the compound represented by the general formula (D) may be polymerized to produce the branched biodegradable polyesters represented by the following general formulas (B) and (C).

[0048] [ka] General formula (B) represents a polyester chain having a block structure formed from the compounds of the above-mentioned general formulae (E) and (D), and in general formula (B), m, l, and k each independently represent an integer of 5 to 200. [ka] In the general formula (C), R each independently represents a hydrogen atom or the following general formula (B), and n represents an integer of 1 to 30.

[0049] More specifically, the branched biodegradable polyester according to one embodiment can be produced by polymerizing a polyglycerol represented by the general formula (A) with a compound represented by the formula (D) and a compound represented by the formula (E) in the presence of a catalyst, and then further polymerizing the compound represented by the formula (D), thereby producing the compounds represented by the general formulas (B) and (C).

[0050] Examples of the compound represented by general formula (D) include cyclic dimers of lactic acid (e.g., D-lactide, L-lactide, DL-lactide), etc. The amount of the compound represented by general formula (D) used is 5 to 200 mol, preferably 15 to 100 mol, per mol of hydroxyl groups in the polyglycerin represented by general formula (C).

[0051] The amount of the compound represented by general formula (E) used is 5 to 200 mol, preferably 15 to 100 mol, per 1 mol of hydroxyl groups in the polyglycerol represented by general formula (A).

[0052] Examples of the catalyst include known transesterification catalysts, such as organotin catalysts exemplified by tin(II) 2-ethylhexanoate, potassium / naphthalene, etc. The amount of catalyst used is 0.005 to 0.5 mol, preferably 0.01 to 0.1 mol, per mol of hydroxyl groups in the polyglycerol represented by general formula (A).

[0053] The reaction is not particularly limited, but may be carried out by first polymerizing (bulk polymerization, etc.) a polyglycerol represented by general formula (A), a compound represented by general formula (D), a compound represented by general formula (E), and a catalyst under an inert gas atmosphere (e.g., argon, etc.) to polymerize the compounds represented by general formulas (G) and (H). More preferably, the polyglycerol represented by general formula (A), a compound represented by general formula (D), a compound represented by general formula (E), and a catalyst under an inert gas atmosphere (e.g., argon, etc.) to produce branched polyesters represented by the following general formulas (G) and (H). [ka] In general formula (G), R is independently selected from a hydrogen atom or a polyester chain represented by the following general formula (H), 50% or more of R are polyester chains of general formula (H), and n is an integer of 1 to 30. [ka] In the general formula (H), m and l each independently represent an integer of 5 to 200. Thereafter, it is preferable to isolate and purify the compounds represented by general formulas (G) and (H). Next, the compounds represented by general formulas (G) and (H), the compound represented by general formula (D), and the catalyst are polymerized (bulk polymerization, etc.) in an inert gas atmosphere (e.g., argon, etc.). This preferably produces the branched biodegradable polyester represented by the above general formula (B).

[0054] The reaction temperature and reaction time may be, for example, 80 to 180°C (preferably 100 to 160°C) for about 2 minutes to 24 hours. After the reaction, the target product may be obtained by dissolving the reactant in a soluble solvent and adding a poor solvent to precipitate the target product.

[0055] [Method for producing resin composition] The resin composition of the present invention can be mixed by pre-blending the polylactic acid and the branched biodegradable polyester of the present invention in a mixer such as a Henschel mixer or a tumbler, and then kneading them together in a kneading device.

[0056] The kneading device is not particularly limited as long as it can uniformly disperse each component, and production can be carried out using a commonly used resin kneading device. Examples of kneading devices include single-screw extruders, multi-screw extruders, Banbury mixers, pressure kneaders, rotating rolls, and internal mixers. The kneading temperature is not limited, but is preferably from the melting point of polylactic acid to about 300°C.

[0057] [Method for producing molded body] The branched biodegradable polyester according to one embodiment and its resin composition can be suitably molded by various molding methods such as film molding, blow molding, foam molding, and extrusion molding. [Example]

[0058] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0059] Branched PCLA-b-PLA was synthesized in Examples 1 to 6, and molded articles thereof and molded articles of resin compositions containing these branched PCLA-b-PLA were prepared. Linear PCLA-b-PLA was also synthesized in Comparative Examples 1 and 2, and the branched PCLA in Comparative Example 3, and molded articles thereof and molded articles of resin compositions containing these were prepared. The physical properties of the molded articles thus obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated.

[0060] Example 1 (1) Synthesis of branched PCLA (polycaprolactone lactide) Add oligoglycerin (0.564 g, 1.23 × 10 mL) to a 200 mL eggplant flask. -3 The oligoglycerin was weighed (0.500 g, 1.07 × 10 mol, 8-branch, manufactured by Sakamoto Pharmaceutical Co., Ltd.). The oil bath was then heated to 120°C, and the oligoglycerin was dried under reduced pressure for 6 hours to dehydrate it. The weight of the oligoglycerin after dehydration (0.500 g, 1.07 × 10 mol) was then weighed. -3 mol) was measured, and L-lactide (12.7 g, 8.79 × 10 -2 mol, Musashino Chemical Laboratory Co., Ltd.), ε-caprolactone (10.0 g, 8.79 × 10 -2 mol, manufactured by Tokyo Chemical Industry Co., Ltd.), tin(II) 2-ethylhexanoate (0.0682 g, 1.68 × 10 -4 A reaction solution was prepared by adding 1000 mol of ethanol (manufactured by Tokyo Chemical Industry Co., Ltd.) to a recovery flask. A polymerization tube was then attached to the recovery flask, and the reaction solution was frozen with liquid nitrogen and then dried under reduced pressure overnight. The oil bath was then heated to 120°C, and the polymerization reaction was carried out for 12 hours. This resulted in a crude branched PCLA product. The crude branched PCLA product was then purified by reprecipitation. Chloroform (134 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the good solvent, and methanol (2000 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the poor solvent. The precipitate was collected and then dried under reduced pressure to obtain branched PCLA (yield: 86%) as a colorless, transparent, viscous liquid.

[0061] The identification of the branched PCLA obtained as the product was 1 H-NMR and GPC were used. 1 H-NMR measurement: Deuterated solvent; deuterated chloroform Measurement equipment: JNM-ECS400 or JNM-AL400 (both manufactured by JEOL) 1 In the identification by H-NMR, the number average molecular weight (Mn) was also measured. GPC measurement: Eluent: chloroform Standard material: polystyrene Flow rate; 1.0mL / min Measuring device: GPC-8020 series (manufactured by Tosoh Corporation) Column: TSKgel G4000HHR, 7.8 mm x 300 mm, 1 piece (manufactured by Tosoh Corporation) In the GPC measurement, the number average molecular weight (Mn) and the weight average molecular weight (Mw) were measured, and the weight average molecular weight (Mw) / number average molecular weight (Mn) was calculated.

[0062] (2) Synthesis of branched PCLA-b-PLA The branched PCLA (2.00 g, 6.05 × 10 -5 mol) and D-lactide (1.39 g, 9.62 × 10 -3 mol, manufactured by Musashino Chemical Laboratory Co., Ltd.) was weighed into a 100 mL three-necked eggplant flask. A reflux condenser was then attached to the eggplant flask, and the flask was dried under reduced pressure overnight. The atmosphere inside the flask was then replaced with nitrogen, and toluene (3 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was added. Next, the flask, which had been replaced with a nitrogen atmosphere, was heated in an oil bath at 130°C, whereby the branched PCLA and D-lactide were uniformly dissolved in the toluene. After that, tin(II) 2-ethylhexanoate (0.0043 g, 1.06 × 10 -5 A solution of 1000 mol of PEG-1000 and toluene (0.5 mL) was added to obtain a reaction solution, which was then polymerized at 130°C for 8 hours to obtain a crude product of branched PCLA-b-PLA.

[0063] The crude branched PCLA-b-PLA product obtained by polymerization was purified by reprecipitation. Chloroform (27 mL) was used as a good solvent, and diethyl ether (300 mL, Wako Pure Chemical Industries, Ltd.) was used as a poor solvent. The reprecipitated precipitate was collected and dried under reduced pressure to obtain the branched PCLA-b-PLA of Example 1 (yield: 84%) as a white solid.

[0064] Identification of branched PCLA-b-PLA 1 H-NMR and GPC were used. 1 H-NMR measurement: Deuterated solvent; deuterated chloroform Measurement equipment: JNM-ECS400 or JNM-AL400 (both manufactured by JEOL) GPC measurement: Eluent: chloroform Standard material: polystyrene Flow rate; 1.0mL / min Measuring device: GPC-8020 series (manufactured by Tosoh Corporation) Column: TSKgel G4000HHR, 7.8 mm x 300 mm, 1 piece (manufactured by Tosoh Corporation) Table 1 below shows the composition of the branched PCLA-b-PLA of Example 1, 1 The number average molecular weight (Mn) and weight average molecular weight (Mw) determined by H-NMR and GPC identification were measured, and the weight average molecular weight (Mw) / number average molecular weight (Mn) is shown.

[0065] Examples 2 to 6 As shown in Table 1, the branched PCLA-b-PLA of Examples 2 to 4 was synthesized under the same conditions as in Example 1, except that D-lactide was replaced with L-lactide or the amount of these lactides was changed in the synthesis of branched PCLA-b-PLA.

[0066] As shown in Table 1, the branched PCLA-b-PLA of Examples 5 and 6 was synthesized under the same conditions as in Example 1, except that the amounts of oligoglycerin, L-lactide, and ε-caprolactone were changed in the synthesis of branched PCLA, and the amount of D-lactide or L-lactide was changed in the synthesis of branched PCLA-b-PLA.

[0067] Table 1 below shows the branched PCLA-b-PLA of Examples 2 to 6. 1 The number average molecular weight (Mn) and weight average molecular weight (Mw) determined by H-NMR and GPC identification were measured, and the weight average molecular weight (Mw) / number average molecular weight (Mn) is shown.

[0068] Comparative Example 1 (1) Synthesis of linear PCLA Add 1,12-dodecanediol (0.0647 g, 3.20 × 10 mL) to a 200 mL flask. -4 mol, manufactured by Tokyo Chemical Industry Co., Ltd.), L-lactide (5.52 g, 3.83 × 10 -2 mol, Musashino Chemical Laboratory Co., Ltd.), ε-caprolactone (4.38 g, 3.83 × 10 -2 mol, Tokyo Chemical Industry Co., Ltd.), tin(II) 2-ethylhexanoate (0.0315 g, 7.78 × 10 -5 mol) was weighed out to prepare a reaction solution. Then, a polymerization tube was attached to an eggplant flask, and the reaction solution was frozen with liquid nitrogen and then dried under reduced pressure overnight.

[0069] The polymerization reaction was then carried out in an oil bath at 120°C for 12 hours, yielding a crude linear PCLA product. The crude product was then purified by reprecipitation. Chloroform (60 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the good solvent, and methanol (700 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was used as the poor solvent. The precipitate was collected and then dried under reduced pressure to obtain linear dodecanediol-PCLA (yield: 85%) in the form of a colorless, transparent, viscous liquid.

[0070] Identification of dodecanediol-PCLA was carried out under the same conditions as in Examples 1 to 6. 1 1 H-NMR and GPC were used.

[0071] (2) Synthesis of linear PCLA-b-PLA In a 100 mL three-necked flask, add the synthesized dodecanediol-PCLA (2.51 g, 7.75 × 10 -5 mol), and D-lactide (0.45 g, 3.10 × 10 -3 mol, manufactured by Musashino Chemical Laboratory Co., Ltd.) was weighed. Then, a reflux condenser was attached to the recovery flask, and the flask was dried under reduced pressure overnight. After drying, the atmosphere inside the flask was replaced with nitrogen, and toluene (5 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was added. Next, the recovery flask with the nitrogen atmosphere replaced was heated to 130 °C in an oil bath, and dodecanediol-PCLA (2.51 g, 7.75 × 10 -5 mol) and D-lactide were uniformly dissolved in toluene, and then tin(II) 2-ethylhexanoate (0.0104 g, 2.57 × 10 -5 A solution of 1000 mol of PEG-1000 and toluene (0.5 mL) was added to the mixture, followed by polymerization reaction at 130° C. for 8 hours, thereby obtaining a crude product of linear PCLA-b-PLA of Comparative Example 1.

[0072] The crude linear PCLA-b-PLA product obtained by polymerization was purified by reprecipitation. Chloroform (18 mL) was used as a good solvent, and diethyl ether (200 mL, Wako Pure Chemical Industries, Ltd.) was used as a poor solvent. The reprecipitated precipitate was collected and dried under reduced pressure to obtain linear PCLA-b-PLA of Comparative Example 1 as a white solid (yield: 91%).

[0073] Linear PCLA-b-PLA was identified under the same conditions as in Examples 1 to 6. 1 H-NMR and GPC were used.

[0074] Comparative Example 2 As shown in Table 1, linear PCLA-b-PLA of Comparative Example 2 was synthesized under the same conditions as in Comparative Example 1, except that D-lactide was changed to L-lactide when synthesizing linear PCLA-b-PLA.

[0075] Comparative Example 3 As shown in Table 1, branched PCLA of Comparative Example 3 was synthesized under the same conditions as in Examples 5 and 6, except that branched PCLA-b-PLA was not synthesized.

[0076] Table 1 shows the compositions of the branched biodegradable polyesters of Examples 1 to 5 and the biodegradable polyesters of Comparative Examples 1 to 3.

[0077] [Table 1]

[0078] [Evaluation of physical properties] (1) Preparation of test specimens Linear PLA (Nature Works Ingeo® Biopolymer 4032D, L-form) (hereinafter referred to as "linear PLLA") and the branched PCLA-b-PLA of Example 1 were weighed into a sample tube at a weight ratio of 9:1. Dichloromethane (15 mL) was then added and stirred for 2 hours to prepare a 2 wt% solution. The solution was cast into a Teflon® Petri dish (6 cm diameter) and allowed to stand in a desiccator to dry overnight. After drying, the solution was dried at 60°C for 4 hours using a vacuum oven (Yamato Scientific Co., Ltd., Vacuum Oven ADP200) and then at 80°C for 4 hours. This yielded a film of the resin composition containing the branched PCLA-b-PLA of Example 1. The resulting film was punched into dumbbell shapes using a test piece punching blade (No. 7 dumbbell type) to prepare test pieces for tensile testing.

[0079] The film other than the punched portion was cut with a razor into pieces of approximately 2 cm square, and used for X-ray diffraction measurement.

[0080] Following the same procedure as when the weight ratio of linear PLLA to branched PCLA-b-PLA of Example 1 was 9:1, molded articles of linear PLLA and Example 1 were obtained in the following weight ratios. Linear PLLA only Linear PLLA:branched PCLA-b-PLA=8:2 Linear PLLA:branched PCLA-b-PLA=7:3 Branched PCLA-b-PLA only (single unit)

[0081] Following the same procedure as in Example 1, films of the resin compositions including Examples 2 to 6 and Comparative Examples 1 to 3 were produced.

[0082] (2) Tensile test The mechanical properties of each of the films of Examples 1 to 6 and Comparative Examples 1 to 3 were determined using a tensile tester (AGS-J manufactured by Shimadzu Corporation). Measurement conditions: Sample shape: dumbbell type (size 7), test piece width: 2 mm, film thickness: 80 μm Jig distance: 15 mm, tension speed: 30 mm / min The test was carried out at room temperature, with n=3, 4 or 5. Table 2 shows the average values ​​of modulus of elasticity, stress at break and strain at break for each of the films of Examples 1 to 6 and Comparative Examples 1 to 3 obtained by the tensile test.

[0083] (3) X-ray diffraction measurement Using an X-ray diffractometer (Rigaku R-AXIS RAPID GN2), it was confirmed whether each film of Examples 1 to 6 and Comparative Examples 1 to 3 exhibited diffraction peaks (12°, 21°, 24°) specific to stereocomplex crystals. The measurement was performed under the conditions of a Cu source, 40 kV, 130 mA, and room temperature.

[0084] The evaluation results are shown in Table 2. [Table 2]

[0085] The following was confirmed from the evaluation results of films formed from each of the branched PCLA-b-PLA monomers in Examples 1 to 6, each of the linear PCLA-b-PLA monomers in Comparative Examples 1 and 2, and the branched PCLA monomer in Comparative Example 3.

[0086] The films molded from the branched PCLA-b-PLA monolayers of Examples 1 to 6 exhibited both a high breaking stress and a high breaking strain compared with films molded from linear PCLA-b-PLA monolayers and films molded from branched PCLA. In particular, the films molded from the branched PCLA-b-PLA monolayers of Examples 5 and 6 exhibited high breaking strains of 385% or more compared with the films molded from linear PCLA-b-PLA monolayers of Comparative Examples 1 and 2, in which the M / OH (degree of polymerization of caprolactone units and polylactic acid units per hydroxyl group) during PCLA synthesis was similar to the M / OH (degree of polymerization of lactide per hydroxyl group) during PCLA synthesis. These results confirmed that the films molded from the branched PCLA-b-PLA monolayers of Examples 1 to 6 possess high breaking strength and flexibility.

[0087] Furthermore, evaluation of films formed from linear PLLA containing branched PCLA-b-PLA in Examples 5 and 6, linear PLLA containing linear PCLA-b-PLA in Comparative Examples 1 and 2, and linear PLLA containing branched PCLA in Comparative Example 3 also showed that the films formed from linear PLLA containing branched PCLA-b-PLA in Examples 5 and 6 exhibited higher breaking strains than those in Comparative Examples 1 to 3. Furthermore, it was confirmed that the linear PLLA films containing branched PCLA-b-PLA in Examples 1 to 4, particularly when the ratio of linear PLLA:branched PCLA-b-PLA was 9:1, had higher breaking stresses and breaking strains than films made only of linear PLLA. [Industrial Applicability]

[0088] The branched biodegradable polyester of the present invention and a molded article made from the resin composition of the present invention are suitable for use as general packaging materials, food packaging, containers, industrial materials, etc. in the fields of daily necessities, civil engineering and construction, electronics and electrical equipment, automotive vehicle parts, packaging, etc.

Claims

1. A branched biodegradable polyester having a block structure including a random copolymer segment of lactide and caprolactone and a homopolymer segment of lactide, wherein a trihydric or higher polyhydric alcohol is bonded to an end of the block structure, The branched biodegradable polyester, wherein the trihydric or higher polyhydric alcohol is polyglycerin having a degree of polymerization of 2 to 30.

2. The branched biodegradable polyester according to claim 1 , wherein a trivalent or higher polyhydric alcohol is bonded to an end of the random copolymer segment of the block structure.

3. 3. The branched biodegradable polyester according to claim 1, wherein the random copolymer segment is a random copolymer segment of any one of L-lactide, D-lactide, and DL-lactide with ε-caprolactone.

4. The branched biodegradable polyester according to any one of claims 1 to 3, wherein the lactide homopolymer segment is an L-lactide homopolymer segment or a D-lactide homopolymer segment.

5. A molded article obtained by molding the branched biodegradable polyester according to any one of claims 1 to 4.

6. A modifier comprising the branched biodegradable polyester according to any one of claims 1 to 4.

7. The total content of the branched biodegradable polyester according to any one of claims 1 to 4 and polylactic acid is taken as 100% by weight, A resin composition comprising the branched biodegradable polyester in an amount of 1% by weight or more and 50% by weight or less, and the polylactic acid in an amount of 50% by weight or more and 99% by weight or less.

8. The resin composition according to claim 7 , wherein a lactide homopolymer segment contained in the branched biodegradable polyester and the polylactic acid form a stereocomplex.

9. A molded article obtained by molding the resin composition according to claim 7 or 8.

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