Resin composition and molded article

Abstract

This invention provides technology relating to resin compositions with excellent heat resistance. [Solution] The resin composition is a copolymer polyester comprising polylactic acid, lactic acid, and another hydroxycarboxylic acid, wherein the lactic acid monomer constituting the copolymer polyester contains 75 mol% or more of one optical isomer of the L-form and the D-form, the lactic acid monomer constituting the polylactic acid contains 75 mol% or more of the other optical isomer of the L-form and the D-form, and the average chain length of the lactic acid monomer constituting the copolymer polyester is 2.0 or more.

Description

[Technical Field]

[0001] This invention relates to a resin composition. [Background technology]

[0002] Polylactic acid (PLA) is a type of biodegradable plastic, a polymer synthesized from lactic acid obtained from plant resources such as corn and sugarcane. For this reason, the use of PLA is attracting attention from the perspective of mitigating climate change caused by increasing carbon dioxide emissions.

[0003] However, because polylactic acid is a very hard resin, its applications are limited. For this reason, for example, Patent Document 1 discloses a technique for blending polylactic acid with a copolymer polyester of lactic acid and other hydroxycarboxylic acids. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2020 / 066679 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the inventors discovered that the resin composition described in Patent Document 1 has room for improvement in heat resistance. Therefore, there is a need for a resin composition that has excellent heat resistance, even if it is a blend of polylactic acid with a copolymer polyester of lactic acid and other hydroxycarboxylic acids. [Means for solving the problem]

[0006] This disclosure can be implemented in the following forms:

[0007] (1) According to one embodiment of the present disclosure, a resin composition is provided. This resin composition comprises a copolymer polyester of polylactic acid, lactic acid, and another hydroxycarboxylic acid, wherein the lactic acid monomer constituting the polylactic acid contains 75 mol% or more of one optical isomer of either the L-form or the D-form, the lactic acid monomer constituting the copolymer polyester contains 75 mol% or more of the other optical isomer of either the L-form or the D-form, and the average chain length of the lactic acid monomer constituting the copolymer polyester is 2.0 or more. According to this embodiment of the resin composition, excellent heat resistance is provided.

[0008] (2) In the resin composition described in (1) above, one optical isomer may be the L-isomer, and the other optical isomer may be the D-isomer. According to this form of resin composition, copolymer polyester can be produced by microorganisms.

[0009] (3) In the resin composition described in (1) or (2) above, the amount of polylactic acid may be 10% by mass or more and 90% by mass or less relative to the total amount of polylactic acid and the copolymerized polyester. This form of resin composition provides excellent heat resistance.

[0010] (4) In the resin composition described in any one of the above items (1) to (3), the proportion of lactic acid monomer in the copolymerized polyester may be 20 mol% or more and 80 mol% or less. This form of resin composition provides excellent heat resistance.

[0011] (5) In the resin composition described in any one of the above items (1) to (4), the other hydroxycarboxylic acid may be at least one selected from the group consisting of 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxydodecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxypentadecanoic acid, and 3-hydroxyhexadecanoic acid. This form of resin composition provides excellent heat resistance.

[0012] (6) In the resin composition according to any one of (1) to (5) above, the peak area of the stereocomplex may be 9.0 cps·° or more. According to the resin composition of this form, it is excellent in heat resistance.

[0013] (7) According to another form of the present disclosure, a molded body obtained by molding the resin composition according to any one of (1) to (6) above is provided.

[0014] Note that the present disclosure can be realized in various forms, for example, in the form of a method for producing a resin composition or a method for producing a molded body.

Brief Description of Drawings

[0015] [Figure 1] It is a diagram for explaining the assignment of peaks. [Figure 2] It is a diagram showing the obtained diffraction pattern. [Figure 3] It is a diagram showing the differential scanning calorimetry result of the sample of Example 1. [Figure 4] It is a diagram showing the differential scanning calorimetry result of the sample of Comparative Example 1.

Mode for Carrying Out the Invention

[0016] According to one form of the present disclosure, a resin composition containing (i) polylactic acid, (ii) lactic acid, and a copolyester of lactic acid and another hydroxycarboxylic acid is provided. The lactic acid monomer constituting the polylactic acid has 75 mol% or more of one of the optical isomers of the L-form and the D-form, and the lactic acid monomer constituting the copolyester has 75 mol% or more of one of the optical isomers of the L-form and the D-form. Further, the average chain length of the lactic acid monomer constituting the copolyester is 2.0 or more. According to the resin composition of this form, since the polylactic acid and the copolyester form a stereocomplex, it is excellent in heat resistance.

[0017] (Polylactic acid) The polylactic acid of the present disclosure is a polyester having lactic acid as a constituent monomer. The lactic acid monomer constituting the polylactic acid has one of the L-form and the D-form in an amount of 75 mol% or more. That is, the lactic acid monomer constituting the polylactic acid has the other optical isomer of the L-form and the D-form in an amount of 25 mol% or less. From the viewpoint of improving the heat resistance of the resin composition, the lactic acid monomer constituting the polylactic acid preferably has one of the L-form and the D-form in an amount of 80 mol% or more and 100 mol% or less, more preferably 85 mol% or more and 100 mol% or less, and even more preferably 88 mol% or more and 100 mol% or less. The lactic acid monomer constituting the polylactic acid preferably has the L-form in an amount of 75 mol% or more. The ratio of the L-form to the D-form in the lactic acid monomer constituting the polylactic acid can be calculated, for example, from the peak areas obtained by analysis with HPLC after hydrolyzing the polylactic acid.

[0018] Known polylactic acid can be used as the polylactic acid, which may be a homopolymer of L-lactic acid, a homopolymer of D-lactic acid, or a copolymer of L-lactic acid and D-lactic acid.

[0019] The raw material for producing the polylactic acid is not particularly limited, and L-lactic acid, D-lactic acid, or a mixture thereof, L-lactide, D-lactide, meso-lactide, or a mixture thereof can be used. As a method for producing the polylactic acid, known methods such as a dehydration polycondensation method and a ring-opening polymerization method can be applied, and it is not particularly limited.

[0020] The molecular weight of the polylactic acid is not particularly limited. For example, the number average molecular weight may be 0.1×10^4 or more and 70×10^4 or less, preferably 1×10^4 or more and 30×10^4 or less.

[0021] (Copolyester) The copolyester of the present disclosure is a copolyester of lactic acid and another hydroxycarboxylic acid. The copolyester of the present embodiment is a polymer material exhibiting biodegradability.

[0022] The lactic acid monomer constituting the copolymerized polyester contains 75 mol% or more of the other optical isomer of the L-isomer and the D-isomer. In other words, the lactic acid monomer constituting the copolymerized polyester contains 25 mol% or less of one optical isomer of the L-isomer and the D-isomer. From the viewpoint of improving the heat resistance of the resin composition, it is preferable that the lactic acid monomer constituting the copolymerized polyester contains 80 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, even more preferably 95 mol% to 100 mol%, and even more preferably 98% to 100 mol%. The lactic acid monomer constituting the copolymerized polyester is preferably the D-isomer. A copolymerized polyester in which the lactic acid monomer constituting the copolymerized polyester is 100% D-isomer can be produced by microorganisms. The ratio of L-isomer to D-isomer in the lactic acid monomer constituting the copolymerized polyester can be calculated, for example, from the peak areas obtained by analyzing the copolymerized polyester by HPLC after hydrolysis. Furthermore, the average molecular weight, monomer fraction, and monomer sequence, which are indicators of the primary structure of copolymerized polyesters, can be determined, for example, by gel permeation chromatography and solution chromatography. 1 This can be determined by 1H-NMR spectroscopy.

[0023] The average chain length of the lactic acid monomers constituting the copolymerized polyester is 2.0 or greater. The method for calculating the average chain length of the lactic acid monomers constituting the copolymerized polyester will be described later. The upper limit of the average chain length of the lactic acid monomers constituting the copolymerized polyester is 3.0. From the viewpoint of improving the heat resistance of the resin composition, the average chain length of the lactic acid monomers constituting the copolymerized polyester is preferably 2.1 to 3.0, more preferably 2.2 to 3.0, and even more preferably 2.3 to 3.0. By adjusting to this preferred range, the lactic acid monomers tend to bond continuously, thus further promoting the formation of stereocomplexes.

[0024] Other hydroxycarboxylic acids are not particularly limited, but from the viewpoint of improving the heat resistance of the resin composition, for example, 3-hydroxyalkanoic acid is preferred. Examples of 3-hydroxyalkanoic acid are not particularly limited, but include 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxydodecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxypentadecanoic acid, 3-hydroxyhexadecanoic acid, etc. These may be used individually or in combination of two or more. Among the other hydroxycarboxylic acids, 3-hydroxybutanoic acid is preferred.

[0025] The ratio of lactic acid to other hydroxycarboxylic acids constituting the copolymerized polyester is not particularly limited. However, from the viewpoint of improving the heat resistance of the resin composition, the proportion of lactic acid monomer in the copolymerized polyester (moles of lactic acid relative to the total number of moles of lactic acid and other hydroxycarboxylic acids constituting the copolymerized polyester) is preferably 20 mol% or more and 80 mol% or less, more preferably 25 mol% or more and 65 mol% or less, and even more preferably 25 mol% or more and 60 mol% or less. The proportion of lactic acid monomer in the copolymerized polyester can be determined by hydrolysis-HPLC or 1 This can be determined by 1H-NMR spectroscopy.

[0026] There are no particular restrictions on the molecular weight of the copolymerized polyester, but from the viewpoint of improving the heat resistance of the resin composition, the number-average molecular weight of the copolymerized polyester is preferably between 10,000 and 500,000, and more preferably between 15,000 and 80,000. Furthermore, from the viewpoint of improving the heat resistance of the resin composition, the weight-average molecular weight of the copolymerized polyester is preferably between 10,000 and 1,000,000, and more preferably between 30,000 and 350,000. The methods for measuring the number-average molecular weight and weight-average molecular weight will be described later.

[0027] The method for producing copolymer polyesters of lactic acid and other hydroxycarboxylic acids is not particularly limited and may be a known method. For example, there are methods using recombinant microorganisms, as described in International Publication No. 2009 / 131186 and International Publication No. 2006 / 126796. In addition, there are chemical polymerization methods, such as the method described in Polymer Degradation and Stability, Vol. 98, pp. 1796-1803 (2013) and Macromolecules, Vol. 53, pp. 10773-10784 (2020).

[0028] (Resin composition) The mass ratio of polylactic acid to copolymerized polyester in the resin composition of this disclosure is not particularly limited as long as the polylactic acid and copolymerized polyester can form a stereocomplex. For example, from the viewpoint of improving the heat resistance of the resin composition, the amount of polylactic acid is preferably 10% to 90% by mass, more preferably 30% to 88% by mass, and even more preferably 40% to 85% by mass, relative to the total amount of polylactic acid and copolymerized polyester.

[0029] The resin composition of this disclosure has polylactic acid and copolymerized polyester forming a stereocomplex. The presence or absence of stereocomplex formation can be evaluated by X-ray diffraction measurement. A peak area of ​​the stereocomplex in the resin composition greater than 0 cps·° indicates the formation of a stereocomplex. The peak area of ​​the stereocomplex in the resin composition is preferably 9.0 cps·° or greater, more preferably 10.0 cps·° or greater, and even more preferably 20.0 cps·° or greater. The method for calculating the peak area of ​​the stereocomplex will be described later.

[0030] (Other ingredients) The resin composition of this disclosure may also include a thermoplastic resin other than polylactic acid and copolymerized polyester. Such resins are not particularly limited, and known resins can be used, specifically, biodegradable aliphatic polyesters other than polylactic acid and copolymerized polyesters, aromatic polyesters, and the like.

[0031] The resin compositions of this disclosure may contain other additives as appropriate, as long as they do not impair the effects of the present invention. Such additives are not particularly limited, but examples include plasticizers, hydrolysis inhibitors, compatibilizers, antioxidants, ultraviolet absorbers, processing aids, antistatic agents, colorants, crystal nucleating agents, inorganic or organic particles, lubricants, mold release agents, water repellents, inorganic fillers, antifungal agents, antibacterial agents, foaming agents, flame retardants, and the like. The content of each additive can be appropriately determined according to its purpose. Furthermore, only one type of additive may be included, or two or more types may be included.

[0032] As plasticizers, those commonly used as polymer plasticizers can be used. Specifically, examples include polyester-based plasticizers, glycerin-based plasticizers, polycarboxylic acid ester-based plasticizers, polyalkylene glycol-based plasticizers, epoxy-based plasticizers, and so on.

[0033] The resin composition of this disclosure can be obtained, for example, by melt-kneading each component, extruding the molten resin into strands, and then cutting them to form pellets. After drying the obtained pellets to remove moisture, any molded article can be obtained by molding using a known molding method. The molding method is not particularly limited, but examples include film molding, sheet molding, injection molding, blow molding, fiber spinning, extrusion foaming, bead foaming, and the like.

[0034] The method for manufacturing the film molded article is not particularly limited, but examples include T-die extrusion molding, calendering, roll molding, and inflation molding. However, the film molding method is not limited to these. Furthermore, the film obtained from the resin composition of this disclosure can be subjected to, for example, thermoforming by heating, vacuum forming, and press molding.

[0035] The method for manufacturing injection-molded articles is not particularly limited, but for example, injection molding methods commonly used when molding thermoplastic resins, such as injection molding, gas-assisted molding, and injection compression molding, can be employed. In addition, methods such as in-mold molding, gas press molding, two-color molding, sandwich molding, push-pull, and SCORIM can also be employed. However, the injection molding method is not limited to these.

[0036] The resin composition of this disclosure may be processed into molded articles such as pellets, films, sheets, or fibers using an extrusion molding machine, or it may be processed into molded articles of a predetermined shape by injection molding.

[0037] Furthermore, if the resin composition of this disclosure contains a foaming agent, the molded article of this disclosure may be a foamed molded article, or it may be a molded foam by foaming after processing.

[0038] Furthermore, the resin composition of this disclosure may undergo further post-treatment processes such as heat treatment, uniaxial stretching, biaxial stretching, aging, and atmospheric exposure after being processed into a molded article.

[0039] The resin composition of this disclosure can be processed into molded articles of various shapes. The molded articles are not particularly limited, but examples include paper, film, sheet, tube, plate, rod, container, bag, and parts. Furthermore, the molded articles of this disclosure can be compounded with molded articles made from materials different from the resin composition of this disclosure (e.g., fibers, yarn, rope, woven fabric, knitted fabric, nonwoven fabric, paper, film, sheet, tube, plate, rod, container, bag, parts, foam, etc.) to improve their physical properties. The applications of the molded articles of this disclosure are not particularly limited and can be suitably used in agriculture, fisheries, forestry, horticulture, medicine, hygiene products, clothing, non-clothing products, packaging, automobiles, building materials, and other fields.

[0040] (Explanation of effects) As described above, the resin composition of the above form is a resin composition containing (i) polylactic acid and (ii) a copolymer polyester of lactic acid and another hydroxycarboxylic acid. Furthermore, in the resin composition of the above form, the lactic acid monomer constituting the polylactic acid contains 75 mol% or more of one optical isomer of either the L-form or the D-form, and the lactic acid monomer constituting the copolymerized polyester contains 75 mol% or more of the other optical isomer of either the L-form or the D-form. In other words, 75 mol% or more of the lactic acid monomer constituting the polylactic acid is one optical isomer, and 75 mol% or more of the lactic acid monomer constituting the copolymerized polyester is the other optical isomer. In addition, the average chain length of the lactic acid monomers constituting the copolymerized polyester is 2.0 or more. For this reason, the copolymerized polyester has a relatively high proportion of adjacent lactic acid monomers. It was previously known that a stereocomplex could be formed by comprising polylactic acid composed of L-form lactic acid monomers and polylactic acid composed of D-form lactic acid monomers. However, the present inventors have discovered that polylactic acid and copolymerized polyester can form a stereocomplex by adjusting the properties of the lactic acid monomers constituting the polylactic acid and the properties of the lactic acid monomers constituting the copolymerized polyester. Furthermore, by forming a stereocomplex, a resin composition with excellent heat resistance can be provided.

[0041] Examples are described below, but the present invention is not limited to these examples.

[0042] (raw materials) (Polylactic acid raw material) Polylactic acid raw materials are generally copolymers of L-lactic acid monomer and D-lactic acid monomer, which are optical isomers. The polylactic acid used was BiopolymerIngeo6202D, BiopolymerIngeo6752D, and BiopolymerIngeo10361D, all manufactured by NatureWorks. Hereafter, "BiopolymerIngeo6202D" will be abbreviated as "PLA01," "BiopolymerIngeo6752D" as "PLA02," and "BiopolymerIngeo10361D" as "PLA03." Also, in the following explanation, "polylactic acid" will be referred to as "PLA." The L-lactic acid monomer fractions of each polylactic acid raw material, determined by hydrolysis-HPLC, were 98 mol% for PLA01, 95.8 mol% for PLA02, and 89.1 mol% for PLA03.

[0043] (Synthesis of copolymer polyesters) To control the lactic acid monomer fraction and the average chain length of lactic acid monomers, eight types of copolymer polyesters were synthesized by changing the E. coli strain, plasmid, carbon source, and polymer synthesis culture conditions used. These sample codes were designated "LAHB01" through "LAHB08". In the following description, "copolymer polyester" will also be referred to as "LAHB". The E. coli strain, plasmid, carbon source, and culture conditions used for the synthesis of each copolymer polyester are summarized in Table 1 below.

[0044] [Table 1]

[0045] Specifically, the E. coli strains used in the examples were (i) BW25113, which is widely used in LAHB production; (ii) JW3175, an mtgA-deficient strain derived from BW25113; and (iii) JW1228, an adhE-deficient strain derived from BW25113. Furthermore, the plasmids used were the expression vector pTV118NpctphaC1Ps (ST / QK)AB, described in the non-patent document Proc.Natl.Acad.Sci.USA, Vol. 105, No. 45, pp. 17323-27327 (2008), which is widely used in LAHB synthesis; and pTV118Npct-Pgad-phaC1Ps (ST / QK)AB and pTV118Npct-PyliH-phaC1Ps (ST / QK)AB, which have modified promoter sequences upstream of the LAHB synthesis gene, as described in the non-patent document Microb. Cell Fact., Vol. 22, No. 131 (2023).

[0046] For LAHB production, cultures were performed in 2L container jar fermenters (air permeability 0.5-1.0 vvm, stirring 300-500 rpm, constant temperature 30°C) using LB medium supplemented with 30 g / L glucose or 30 g / L xylose as a carbon source. The biosynthesized copolymer polyester was extracted from the bacterial cells with chloroform. The average molecular weight, monomer fraction, and monomer sequence, which are indicators of the primary structure of the obtained copolymer polyester, were determined by gel permeation chromatography and solution analysis described later. 1 The determination was made by 1H-NMR. The results are summarized in Table 2 below.

[0047] (Determination of the primary structure of copolymerized polyesters) (Molecular weight measurement by gel permeation chromatography) Molecular weight was measured using a gel permeation chromatography system manufactured by JASCO Corporation. Two Shodex KF-805L size exclusion chromatography columns manufactured by Shoko Science Co., Ltd. were connected in series as the analytical column. Chloroform was used as the eluent. The analysis was performed at a temperature of 40°C and a flow rate of 1.0 mL / min. The weight-average molecular weight and number-average molecular weight were determined using a calibration curve created from the analytical values ​​of a standard polystyrene sample (Shodex STANDARD SL-105, Shoko Science Co., Ltd.) under the same conditions.

[0048] (solution 1 (Measurement of monomer fraction and monomer sequence by H-NMR method) Using the Avance III 600 MHz nuclear magnetic resonance spectrometer manufactured by Bruker Corporation, solution 1 ¹H-NMR spectra were measured. Deuterated chloroform was used as the solvent, and the residual chloroform peak was used as the internal standard at 7.26 ppm. The measurements were performed at room temperature (25°C) and accumulated eight times.

[0049] Figure 1 is a diagram illustrating the assignment of peaks. Note that Figure 1 shows data for LAHB01. The ratio of lactic acid monomer units (LA) and 3-hydroxybutanoic acid monomer units (HB) constituting the copolymerized polyester was determined as follows: The signal appearing at 4.92–5.20 ppm is attributed to the proton of the methine group of the LA unit. The signal appearing at 5.20–5.39 ppm is attributed to the proton of the methine group of the HB unit. The area of ​​these regions was measured, and each was assigned to A LA and A HB Therefore, the mole fraction of each monomer unit can be calculated using the following formula.

[0050]

number

[0051]

number

[0052] The average chain length of each monomer, which is an index indicating the arrangement state of the LA unit and the HB unit, was determined as follows. The signal region attributed to the proton of the methine group of the LA unit is divided into three regions according to the arrangement (triplet) of three monomers centered on the LA unit: the region of 4.92 to 5.01 ppm is attributed to HB-LA-HB, the region of 5.01 to 5.13 ppm is attributed to LA-LA-HB, and the region of 5.13 to 5.20 ppm is attributed to LA-LA-LA. The areas of these regions are denoted as A HB-LA-HB 、A LA-LA-HB 、A LA-LA-LA respectively. Also, the signal region attributed to the proton of the methyl group of the HB unit is divided into three regions according to the triplet centered on the HB unit: the region of 1.25 to 1.29 ppm is attributed to HB-HB-HB, the region of 1.29 to 1.32 ppm is attributed to HB-HB-LA, and the region of 1.32 to 1.36 ppm is attributed to LA-HB-LA. The areas of these regions are denoted as A HB-HB-HB 、A HB-HB-LA 、A LA-HB-LA respectively. From these areas, the molar fraction of each triplet with respect to the total number of all triplets is calculated by the following formulas respectively.

[0053]

Number

[0054]

Number

[0055]

Number

[0056]

Number

Number

[0058]

number

[0059] From the mole fraction of each triplets, the mole fraction of the sequence of LA units and HB units in the two monomer sequences (two-tlets) relative to the total two-tlets can be calculated using the following formula.

[0060]

number

[0061] Average chain length n of LA monomer units LA and the average chain length n of the HB monomer units LB These are calculated using the following formulas. Note that the "average chain length of LA monomer units" is also called the "average chain length of lactic acid monomers constituting the copolymerized polyester," and the "average chain length of HB monomer units" is also called the "average chain length of other hydroxycarboxylic acid monomers constituting the copolymerized polyester."

[0062]

number

[0063]

number

[0064] <Example 1> 0.70 g of LAHB01 and 0.70 g of PLA01 were uniformly dissolved in 14 mL of chloroform, and the chloroform was then volatilized to obtain a polymer blend composition. Subsequently, using a vacuum heating press (IMC-11FD model, manufactured by Imoto Seisakusho), the mixture was pressurized at 180°C in a vacuum to form a film with a thickness of 0.2 mm, and the film sample was rapidly cooled between cold plates at room temperature. The film sample was kept in a constant temperature bath (DKN402 forced-air constant temperature incubator, manufactured by Yamato Scientific) at 100°C for 30 minutes to undergo crystallization treatment.

[0065] <Example 2> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.28 g of LAHB01 and 1.12 g of PLA01 were used instead of 0.70 g of LAHB01 and 0.70 g of PLA01.

[0066] <Example 3> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB01 and 0.70g of PLA02 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0067] <Example 4> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.28 g of LAHB01 and 1.12 g of PLA02 were used instead of 0.70 g of LAHB01 and 0.70 g of PLA01.

[0068] <Example 5> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB01 and 0.70g of PLA03 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0069] <Example 6> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB02 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0070] <Example 7> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB03 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0071] <Example 8> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.28 g of LAHB03 and 1.12 g of PLA01 were used instead of 0.70 g of LAHB01 and 0.70 g of PLA01.

[0072] <Example 9> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB03 and 0.70g of PLA02 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0073] <Example 10> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.28 g of LAHB03 and 1.12 g of PLA02 were used instead of 0.70 g of LAHB01 and 0.70 g of PLA01.

[0074] <Example 11> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB03 and 0.70g of PLA03 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0075] <Comparative Example 1> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB04 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0076] <Comparative Example 2> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB05 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0077] <Comparative Example 3> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB06 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0078] <Comparative Example 4> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB07 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0079] <Comparative Example 5> Polymer blend compositions and film samples were prepared and crystallized in the same manner as in Example 1, except that 0.70g of LAHB08 and 0.70g of PLA01 were used instead of 0.70g of LAHB01 and 0.70g of PLA01.

[0080] Table 2 shows the test results. In the table, "Mn" represents the number-average molecular weight, and "Mw" represents the weight-average molecular weight. "fDLA" represents the percentage [mol%] of D-isomer lactic acid monomers in LAHB. Here, all lactic acid monomers in LAHB are D-isomers. Therefore, the percentage [mol%] of other hydroxycarboxylic acid monomers in LAHB is the value obtained by subtracting the value of fDLA from 100 mol%. "nLA" represents the average chain length of lactic acid monomers, and "nHB" represents the average chain length of other hydroxycarboxylic acid monomers. "fLLA" represents the percentage [mol%] of L-isomer lactic acid monomers in polylactic acid.

[0081] (Analysis of the crystalline structure of polymer blends) The crystalline structure of polymer blend films was evaluated by X-ray diffraction measurement. Using a fully automated multi-purpose X-ray diffractometer SmartLabSE manufactured by Rigaku Corporation, X-ray diffraction intensity in the diffraction angle range of 2θ = 10° to 18° was obtained by symmetric transmission. A Cu tube was used as the X-ray source, with a tube voltage of 50kV and a tube current of 40mA, and CuKα rays (wavelength 1.54186Å) passed through a Ni filter were used in a point-focus optical system (collimator diameter 0.5mmφ). A high-speed one-dimensional X-ray detector D / teX Ultra250 was used as the detector. Measurements were performed under conditions of a scan speed of 0.1° / min and a scan step of 0.05°.

[0082] Figure 2 shows the obtained diffraction patterns. PLA shows a homocrystalline peak (PLA homocrystalline) around a diffraction angle of 16.6°. LAHB also shows a homocrystalline peak (LAHB crystal) around a diffraction angle of 13.5°. When a stereocomplex is formed between LAHB and PLA, a new crystal peak (SC crystal) appears at a diffraction angle of 11.9°. In Examples 1 to 11, the formation of a stereocomplex can be confirmed in Figure 2. On the other hand, in Comparative Examples 1 to 5, no crystal peak appears at this position, indicating that a stereocomplex was not formed. The area of ​​the stereocomplex peak [cps·°] is summarized in Table 2. Note that the "area of ​​the stereocomplex peak" is also called the "SC peak area".

[0083] [Table 2]

[0084] (Analysis of the crystallization behavior of polymer blends) Differential scanning calorimetry was performed using a high-sensitivity differential scanning calorimeter DSC7000X manufactured by Hitachi High-Tech Corporation. The sample was heated from room temperature (25°C) to 210°C at a rate of 5°C / min, held for 2 minutes to completely melt the crystals, and then cooled back to room temperature at a rate of -5°C / min. The heat was then measured. The measurements were performed under a nitrogen stream of 30 mL / min.

[0085] Figure 3 shows the differential scanning calorimetry results for the sample from Example 1. Figure 4 shows the differential scanning calorimetry results for the sample from Comparative Example 1. Generally, PLA is a polymer that does not crystallize easily, and when cooled from a molten state at -5°C / min by differential scanning calorimetry, no crystallization peak is observed. On the other hand, in the sample from Example 1, as shown in Figure 3, an exothermic peak indicating crystallization was observed during cooling. Two crystallization peaks with peaks around 150°C and 118°C are visible. The peak appearing on the high-temperature side indicates that LAHB and PLA form a stereocomplex. The formation of the stereocomplex induces the formation of PLA crystals on the low-temperature side, leading to overall promotion of crystallization. On the other hand, in the sample from Comparative Example 1, as shown in Figure 4, no crystallization peak was observed, indicating that crystallization was not promoted.

[0086] As shown in Table 2, a stereocomplex peak was observed in all examples. This indicates that a stereocomplex of LAHB and PLA was formed in the resin compositions of the examples. Furthermore, generally, heat resistance is improved when a stereocomplex is formed compared to when it is not. Therefore, the resin compositions of these examples exhibit excellent heat resistance.

[0087] The present invention is not limited to the embodiments described above, and can be realized in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Industrial applicability]

[0088] The resin composition of the present invention has industrial applicability, as it can be used in applications such as paper, film, sheets, tubes, plates, rods, containers, bags, and parts. Furthermore, the applications of the molded articles of this disclosure are not particularly limited and can be suitably used in agriculture, fisheries, forestry, horticulture, medicine, hygiene products, clothing, non-clothing products, packaging, automobiles, building materials, and other fields, thus possessing industrial applicability.

Claims

1. Polylactic acid and, A copolymer polyester of lactic acid and other hydroxycarboxylic acids, A resin composition containing, The lactic acid monomer constituting the polylactic acid is such that one of the optical isomers, L-isomer or D-isomer, accounts for 75 mol% or more. The lactic acid monomer constituting the copolymerized polyester is such that the other optical isomer of the L-isomer and the D-isomer accounts for 75 mol% or more. The average chain length of the lactic acid monomers constituting the copolymerized polyester is 2.0 or greater. Resin composition.

2. In the resin composition according to claim 1, The aforementioned optical isomer is the L-isomer, The other optical isomer is the D-isomer. Resin composition.

3. In the resin composition according to claim 1, The amount of polylactic acid is 10% by mass or more and 90% by mass or less relative to the total amount of the polylactic acid and the copolymerized polyester. Resin composition.

4. In the resin composition according to claim 1, The proportion of lactic acid monomer in the copolymerized polyester is 20 mol% or more and 80 mol% or less. Resin composition.

5. In the resin composition according to claim 1, The other hydroxycarboxylic acid is at least one selected from the group consisting of 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxynonanoic acid, 3-hydroxydecanoic acid, 3-hydroxydodecanoic acid, 3-hydroxytetradecanoic acid, 3-hydroxypentadecanoic acid, and 3-hydroxyhexadecanoic acid. Resin composition.

6. In the resin composition according to claim 1, The peak area of ​​the stereo complex is 9.0 cps·° or greater. Resin composition.

7. A molded article obtained by molding the resin composition according to any one of claims 1 to 6.

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