Pellets, injection molded products, and extruded products

Abstract

To provide pellets containing PBSA with good blocking resistance. [Solution] A pellet containing PBSA having a first constituent unit derived from succinic acid, a second constituent unit derived from adipic acid, and a third constituent unit derived from 1,4-butanediol as its main constituent units, wherein the Raman spectrum measured from the pellet is 1680-1780 cm⁻¹ -1 The spectrum in the wavenumber range is 1718±5cm². -1 The first wavenumber range, and 1732±5cm -1 In a Raman spectrum fitted using a Lorentz function with two peaks each having a peak top in the second wavenumber range, the intensity of the peak in the first wavenumber range I 01 And the peak intensity I in the second wavenumber range 02 The intensity ratio (I 01 / I 02 Pellets in which the ratio is 1.1 or higher.

Description

[Technical Field]

[0001] This invention relates to pellets containing polybutylene succinate adipate (sometimes referred to as "PBSA"), and injection-molded and extruded articles obtained using these pellets. More specifically, it relates to pellets containing PBSA that are suitable for injection molding and extrusion molding, and injection-molded and extruded articles obtained using resin pellets containing these pellets. [Background technology]

[0002] In modern society, paper, plastics, aluminum foil, and other materials are used in a wide range of applications, including packaging materials for various foods, pharmaceuticals, general merchandise, liquids, powders, and solids, as well as agricultural and construction materials. Plastics, in particular, excel in strength, water resistance, moldability, transparency, and cost, and are widely used as bags and containers. Plastics currently used in these applications include polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. However, molded products made from the above-mentioned plastics do not biodegrade or hydrolyze in the natural environment, or their decomposition rate is extremely slow. As a result, if buried after use, they may remain in the soil, or if dumped, they may spoil the landscape. Furthermore, even when incinerated, they have problems such as generating harmful gases and damaging incinerators.

[0003] To address these challenges, numerous studies and developments have been conducted on biodegradable resins that are broken down into carbon dioxide and water by microorganisms in soil or water. Representative examples of biodegradable resins include aliphatic polyester resins such as polylactic acid, PBS, and polybutylene succinate adipate (PBSA), and aromatic-aliphatic copolymer polyester resins such as polybutylene adipate terephthalate (PBAT).

[0004] In particular, PBSA is a material that can achieve a high level of both biodegradability and mechanical properties and moldability, and has therefore been proposed for use in various components and resin compositions that require biodegradability. Patent Document 1 proposes the use of PBSA as the biodegradable resin in an agricultural film compounded with a biodegradable resin and coal ash, in order to accelerate the decomposition rate in the soil. Patent Document 2 discloses a biodegradable resin composition in which the biodegradation rate can be adjusted by compounding a specific amount of borate hydrate with the biodegradable resin, and discloses that it is preferable to use an aliphatic polyester resin such as PBSA, which contains aliphatic diol units and aliphatic dicarboxylic acid units as the main constituent units, as the biodegradable resin. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-83494 [Patent Document 2] Japanese Patent Publication No. 2023-110156 [Patent Document 3] Japanese Patent Publication No. 2024-049583 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, when manufacturing molded products using pellets containing PBSA, a phenomenon sometimes occurs where the pellet particles fuse together and aggregate (hereinafter referred to as "blocking") when heat and / or load is applied to the pellets during the drying process or the supply process to the molding machine. This is thought to be due to the low melting point of PBSA, which is around 80-105°C. Blocking can hinder the stable supply of pellets to the molding machine. One aspect of the present invention aims to solve the above-mentioned problems and provides pellets containing PBSA that have good blocking resistance and can be stably supplied to a molding machine as a feed material for injection molding, extrusion molding, etc. Another aspect of the present invention aims to provide biodegradable injection molded or extruded articles that can be stably manufactured. [Means for solving the problem]

[0007] The gist of this invention is as follows: [1] A constituent unit derived from succinic acid, a constituent unit derived from adipic acid, and 1,4-br A pellet comprising a polybutylene succinate adipate having a tandiol-derived constituent unit as its main constituent unit, The Raman spectrum measured from the aforementioned pellets shows values ​​between 1680 and 1780 cm⁻¹. -1 The spectrum in the wavenumber range is 1718±5cm². -1 The first wavenumber range, and 1732±5cm -1 In a Raman spectrum fitted using a Lorentz function with two peaks each having a peak top in the second wavenumber range, the intensity of the peak in the first wavenumber range I 01 And the peak intensity I in the second wavenumber range 02 The intensity ratio (I 01 / I 02 Pellets in which the ratio is 1.1 or higher. [2] The pellet according to [1], wherein the strength ratio is 2.3 or less. [3] The pellet according to [1] or [2], wherein the strength ratio is 1.4 or greater. [4] The pellet according to any one of [1] to [3], wherein the content of a cyclic dimer consisting of succinic acid and 1,4-butanediol in the pellet is 4000 ppm by mass or less. [5] The pellet according to any one of [1] to [4], wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less. [6] A pellet according to any one of [1] to [5], wherein the molar ratio of constituent units derived from succinic acid to constituent units derived from adipic acid (constituent units derived from succinic acid / constituent units derived from adipic acid) is 70 / 30 to 90 / 10. [7] The pellet according to [6], wherein the molar ratio is 70 / 30 to 80 / 20. [8] The pellet according to any one of [1] to [7], wherein the total number of moles of the constituent units derived from succinic acid, the constituent units derived from adipic acid, and the constituent units derived from 1,4-butanediol in the polybutylene succinate adipate is 80 mol% or more of the total number of moles of the constituent units constituting the polybutylene succinate adipate. [9] The pellet according to any one of [1] to [8], wherein the content of the polybutylene succinate adipate in the pellet is 80% by mass or more.

[10] An injection-molded resin pellet containing at least one of the pellets described in [1] to [9].

[11] An extruded resin pellet product comprising at least one of the pellets described in [1] to [9]. [Effects of the Invention]

[0008] According to one aspect of the present invention, pellets containing PBSA can be obtained that have good blocking resistance and can be stably supplied to a molding machine, etc., as a feed material for injection molding, extrusion molding, etc. Furthermore, according to another aspect of the present invention, biodegradable injection-molded or extruded articles containing PBSA can be obtained that can be manufactured more stably. [Brief explanation of the drawing]

[0009] [Figure 1] This is a Raman chart (Lorentz-fitted Raman Spectrum) showing the results obtained by fitting the Raman spectrum measured from the pellet according to Example 1 using the Lorentz function. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist thereof and implemented. In this specification, “mass %” and “weight %” are synonymous, “mass ppm” and “weight ppm” are synonymous, and “parts by mass” and “parts by weight” are synonymous. Also, in this specification, expressions representing numerical ranges, such as descriptions like “XX or more”, “YY or less”, and “XX to YY”, mean numerical ranges including the endpoints XX and YY unless otherwise specified. Also, when numerical ranges are described stepwise, any combination of the upper and lower limits of each numerical range is also disclosed. Furthermore, in this specification, descriptions such as “at least one selected from the group consisting of XX, YY, and ZZ” mean any one of XX, YY, ZZ, the combination of XX and YY, the combination of XX and ZZ, the combination of YY and ZZ, or the combination of XX, YY, and ZZ.

[0011] The present inventors have further studied to solve the problem of improving the blocking resistance of pellets containing PBSA. In the process, the present inventors found that the Raman spectrum measured from the pellets of PBSA changes depending on the production conditions of the pellets. Specifically, the peak intensity I attributed to the C=O stretching of the succinic acid unit of PBSA that appears in the wavenumber range of 1732 ± 5 cm -1 (hereinafter also referred to as the “second wavenumber range”) of the Raman spectrum, with respect to the peak intensity I 02 attributed to the C=O stretching of the succinic acid unit of PBSA that appears in the wavenumber range of 1718 ± 5 cm -1 (hereinafter also referred to as the “first wavenumber range”) of the Raman spectrum, the ratio I 01 / I 01 / I 02We discovered that the strength ratio (hereinafter also simply referred to as "strength ratio") of pellets manufactured through a slow cooling process is significantly higher than that of pellets manufactured without a slow cooling process, and that pellets with a strength ratio of 1.1 or higher can have excellent blocking resistance, leading to the present invention.

[0012] In other words, a pellet according to one aspect of the present invention mainly comprises a constituent unit derived from succinic acid, a constituent unit derived from adipic acid, and a constituent unit derived from 1,4-butanediol. It contains polybutylene succinate adipate as a component. And, in the Raman spectrum measured from the pellet, 1680-1780 cm⁻¹ -1 The spectrum in the wavenumber range is 1718±5cm². -1 The first wavenumber range, and 1732±5cm -1 In a Raman spectrum fitted using a Lorentz function with two peaks each having a peak top in the second wavenumber range, the intensity of the peak in the first wavenumber range I 01 And the peak intensity I in the second wavenumber range 02 The intensity ratio (I 01 / I 02 The intensity ratio is 1.1 or higher, preferably 1.3 or higher, more preferably 1.4 or higher, and also preferably 2.3 or lower. The range of the intensity ratio is preferably 1.1 or higher and 2.3 or lower, more preferably 1.3 or higher and 2.3 or lower, particularly preferably 1.3 or higher and 1.9 or lower, and even more preferably 1.4 or higher and 1.9 or lower. The inventors speculate that the reason the pellets according to this embodiment exhibit excellent blocking resistance is because the strength ratio is 1.1 or higher. In the course of further investigation, the inventors observed the changes in the intensity of the peaks in the first wavenumber range and the second wavenumber range in the Raman spectrum when PBSA was heated to transition from a crystalline state to an amorphous state. As a result, they found that as the temperature increased, the intensity of the peaks in the first wavenumber range decreased, and the intensity of the peaks in the second wavenumber range increased. Furthermore, in the Raman spectrum of PBSA, the peaks appearing in the first wavenumber range and the second wavenumber range are attributed to the C=O in the succinic acid units of PBSA. From this, it is presumed that the peaks observed in the first wavenumber range are attributed to the C=O expansion and contraction in the succinic acid units of PBSA in the crystalline state, and the peaks observed in the second wavenumber range are attributed to the C=O expansion and contraction in the succinic acid units of PBSA in the amorphous state. Therefore, I 01 / I 02 This refers to the division of crystalline and amorphous PBSA in pellets containing PBSA. It is considered an indicator of compatibility. And, I 01 / I 02 However, pellets with a ratio of 1.1 or higher are thought to have an optimized balance between the crystalline and amorphous states of PBSA within the pellet, making them less prone to blocking even when heated or pressurized. As a result, pellets containing PBSA according to the present invention are thought to exhibit excellent blocking resistance. Consequently, these pellets can be stably used in injection molding and extrusion molding, contributing to the even more stable production of injection-molded and extruded products. Furthermore, pellets with a strength ratio of 1.1 to 2.3 exhibit excellent blocking resistance and more reliably prevent the generation of fine powder. In other words, pellets containing PBSA may chip during transport or molding due to friction between the pellets themselves or between the pellets and the walls of the molding equipment, resulting in the generation of fine powder. Such fine powder can lead to problems such as clogging of the pellet inlet of the extruder or molding machine, variations in the amount of pellets supplied, and a decrease in the production cycle due to the need for cleaning as the extruder or molding machine becomes contaminated. However, pellets containing PBSA with a strength ratio of 1.1 to 2.3 exhibit excellent blocking resistance and suppress the generation of fine powder. As a result, these pellets can be stably used for injection molding and extrusion molding, and because they do not easily contaminate the extruder or molding machine, they contribute to the more stable and efficient production of injection molded and extruded products.

[0013] The reason why pellets with a strength ratio of 1.1 to 2.3 can achieve a high level of both blocking resistance and prevention of fine powder generation is, as mentioned above, the strength ratio (I 01 / I 02 ) is considered to be an indicator that shows the ratio of crystalline PBSA to amorphous PBSA in a pellet containing PBSA, 01 / I 02 However, pellets within the aforementioned specific numerical range are thought to have a more optimized balance between the crystalline and amorphous states of PBSA within the pellet, making them less prone to blocking even when heated or pressurized, and also suppressing surface embrittlement of the pellets. As a result, it is thought that fine powder is less likely to be generated due to friction between pellets or between pellets and molding equipment, etc. Consequently, pellets containing PBSA according to the present invention are thought to achieve a high level of both blocking resistance and prevention of fine powder generation.

[0014] The method for measuring the spectrum of a pellet containing PBSA according to this embodiment by Raman spectroscopy is not particularly limited, but it is preferable to measure it in accordance with, for example, Japanese Industrial Standard (JIS) K0317:2010 (General Rules for Raman Spectroscopic Analysis). More specifically, for example, the Raman spectrum of the pellet according to this disclosure can be measured using a Raman spectrometer like the one described below and under the following conditions. Raman spectrometer: "RAMAN touch" (product name, manufactured by Nanophoton Corporation) Measurement conditions • Measurement mode: Point • Laser wavelength: 532nm • Laser output: 20mW (Neutral-reducing filter opening: 210 / 255) • Diffraction grating: 1200 gr / mm • Pinhole: 50 μm • Exposure time: 10 seconds • Number of times accumulated: 5 • Objective lens: 100x ·Measurement temperature: 25℃

[0015] The Raman spectrum obtained using the above Raman spectrometer and measurement conditions shows a value of 1718±5 cm², which is attributed to the C=O stretching in the succinic acid unit of PBSA. -1 In the first wavenumber range A peak in Raman scattering intensity with a peak top and 1732±5cm² -1 The Raman scattering intensity peak, which has its peak top in the second wavenumber range, and its two components are fitted using the Lorentz function shown in equation (1) below. In equation (1) below, A represents the peak intensity and w represents the full width at half maximum of the peak. X0 represents the peak position, which in this disclosure is 1718 ± 5 cm. -1 , and 1732±5cm -1 This is the result.

[0016]

number

[0017] Then, in the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity I in the first wavenumber range 01 and the peak intensity I in the second wavenumber range 02 The intensity ratio (I 01 / I 02 Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X0 = 1718 ± 5 cm) is determined. -1 The ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A1") obtained by the above formula (1) relating to the second wavenumber range, and the intensity A (hereinafter also referred to as "A2") obtained by the above formula (1) relating to the peak in the second wavenumber range, is I 01 / I 02 It corresponds to this.

[0018] <Polybutylene succinate adipate (PBSA)> The PBSA according to the present invention is a polyester having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from adipic acid, and a constituent unit derived from 1,4-butanediol. Specifically, for example, the PBSA according to one aspect of the present invention has as its main constituent units a constituent unit derived from succinic acid represented by the following structural formula (1), a constituent unit derived from adipic acid represented by the following structural formula (2), and a constituent unit derived from 1,4-butanediol represented by the following structural formula (3). -OC-CH2-CH2-CO- (1) -OC-(CH2)4-CO- (2) -O-(CH2)4-O- (3)

[0019] Furthermore, "constituent units derived from succinic acid" refers to the constituent units corresponding to succinic acid, that is, the constituent units formed by the reaction of the two carboxyl groups present in succinic acid. Similarly, "constituent units derived from adipic acid" refers to the constituent units corresponding to adipic acid, that is, the constituent units formed by the reaction of the two carboxyl groups present in adipic acid. Moreover, "constituent units derived from 1,4-butanediol" refers to the constituent units corresponding to 1,4-butanediol, that is, the constituent units formed by the reaction of the two hydroxyl groups present in 1,4-butanediol. Furthermore, in this specification, the constituent units of PBSA may be referred to as compound units for the compounds from which each constituent unit is derived. Specifically, for example, a constituent unit derived from succinic acid may be referred to as a "succinic acid unit," a constituent unit derived from adipic acid as an "adipic acid unit," a constituent unit derived from 1,4-butanediol as a "1,4-butanediol unit," a constituent unit derived from a carboxylic acid as a "carboxylic acid unit," and a constituent unit derived from a diol as a "diol unit."

[0020] Furthermore, the term "main constituent unit" usually means that the constituent unit accounts for 80 mol% or more of the total number of moles of constituent units of PBSA. Specifically, in the PBSA according to this embodiment, the total number of moles of succinic acid units, adipic acid units, and 1,4-butanediol units is 80 mol% or more of the total number of moles of constituent units of PBSA. Furthermore, the PBSA according to this embodiment may be a polyester in which the total number of moles of succinic acid units, adipic acid units, and 1,4-butanediol units is 90% or more of the total number of moles of constituent units constituting the PBSA, and may be 95% or more of the total number of moles of constituent units constituting the PBSA, and moreover, in which no constituent units other than succinic acid units, adipic acid units, and 1,4-butanediol units are included at all, that is, consisting only of succinic acid units, adipic acid units, and 1,4-butanediol units, and the total number of moles of succinic acid units, adipic acid units, and 1,4-butanediol units is 100 mol% of the total number of moles of constituent units constituting the PBSA. In this specification, when counting the number of moles of constituent units in PBSA, the smallest ester unit constituting PBSA is defined as 1 mole.

[0021] The total ratio of succinic acid units to adipic acid units in PBSA is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and may also be 100 mol% relative to the total number of dicarboxylic acid units in PBSA. That is, based on the total number of moles of dicarboxylic acid units in PBSA, the ratio of the total number of moles of succinic acid units and adipic acid units is preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%. By having the ratio of the total number of moles of succinic acid units and adipic acid units relative to the total number of moles of dicarboxylic acid units in PBSA within the above range, it is possible to obtain PBSA with superior biodegradability and mechanical properties.

[0022] The ratio of succinic acid units to adipic acid units in PBSA is preferably such that the proportion of succinic acid units is 70 mol% or more, preferably 90 mol% or less, and particularly preferably 80 mol% or less, based on the total number of moles of succinic acid units and adipic acid units. In other words, the molar ratio of succinic acid units to adipic acid units in PBSA is preferably succinic acid units / adipic acid units = 70 / 30 to 90 / 10, and particularly preferably 70 / 30 to 80 / 20. By keeping the molar ratio of succinic acid units to adipic acid units within the above range, it is possible to produce PBSA with superior biodegradability and mechanical properties.

[0023] Other dicarboxylic acids that can constitute the dicarboxylic acid unit in PBSA, besides succinic acid and adipic acid, are not particularly limited, but include, for example, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic anhydride, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, and dimer acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. These can be used individually or as a mixture of two or more in addition to the above succinic acid. Furthermore, succinic acid, adipic acid, and sebacic acid can be derived from plant materials.

[0024] The proportion of 1,4-butanediol units in PBSA is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and may also be 100 mol%, based on the total number of diol units in PBSA. In other words, the proportion of 1,4-butanediol units based on the total number of moles of diol units in PBSA is preferably 80 to 100 mol%, more preferably 85 to 100 mol%, even more preferably 90 to 100 mol%, and particularly preferably 95 to 100 mol%. Since the proportion of 1,4-butanediol units is within the above range, a PBSA with superior heat resistance and mechanical properties can be obtained.

[0025] Examples of diols other than 1,4-butaneol that can constitute the diol unit in PBSA include alkylenediols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and neopentyl glycol; oxyalkylenediols such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol; and cycloalkylenediols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol. These can be used individually or as a mixture of two or more in addition to the above-mentioned 1,4-butaneol. Furthermore, ethylene glycol, 1,3-propanediol, and 1,4-butanediol can be derived from plant materials.

[0026] PBSA may have other constituent units other than the dicarboxylic acid unit and the diol unit (hereinafter also referred to as "other constituent units"). Examples of copolymer components that can constitute other constituent units include at least one component selected from the group consisting of oxycarboxylic acids (e.g., lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, malic acid, maleic acid, citric acid, fumaric acid, etc.), esters or lactones of the oxycarboxylic acids, polymers of the oxycarboxylic acids, etc., trifunctional or more polyhydric alcohols (e.g., glycerin, trimethylolpropane, pentaerythritol, etc.), and trifunctional or more polyhydric acids or their anhydrides (e.g., propanetricarboxylic acid, pyromellitic acid, trimellitic acid benzophenonetetracarboxylic acid and their anhydrides, etc.).

[0027] Among them, by introducing a structural unit derived from at least one polyfunctional compound having three or more functional groups selected from the group consisting of oxycarboxylic acids having three or more functional groups, alcohols having three or more functional groups, and carboxylic acids having three or more functional groups into PBSA, it is possible to adjust it in the direction of increasing the intrinsic viscosity of PBSA described later. As the polyfunctional compound having three or more functional groups, oxycarboxylic acids such as malic acid, citric acid, and fumaric acid, and polyhydric alcohols having three or more functional groups such as glycerin and trimethylolpropane are preferable, and malic acid and trimethylolpropane are particularly preferably used.

[0028] Based on the number of moles of all dicarboxylic acid units in PBSA, the ratio of the polyfunctional compound units having three or more functional groups is preferably 0.001 to 5 mol%, and particularly preferably 0.05 to 0.5 mol%. By setting the ratio of the polyfunctional compound units having three or more functional groups in PBSA within the above range, it is possible to more reliably prevent the formation of gels (unmelted substances) in the polyester and more easily adjust the intrinsic viscosity of PBSA within a preferable range as follows.

[0029] <Physical properties of PBSA> The intrinsic viscosity (IV) of PBSA is preferably 1.2 dL / g or more, and particularly preferably 1.4 dL / g. Also, it is preferably 2.2 dL / g or less, and particularly preferably 2.0 dL / g or less. That is, the intrinsic viscosity of PBSA is preferably 1.2 dL / g or more and 2.2 dL / g or less, and particularly preferably 1.4 dL / g or more and 2.0 dL / g or less. By setting the intrinsic viscosity of PBSA within the above range, the mechanical strength can be further increased when formed into a molded product, and the viscosity during melting can be adjusted to an appropriate range. As a result, high-quality injection-molded products and extrusion-molded products can be manufactured more easily. The intrinsic viscosity depends on the molecular weight of PBSA, and the larger the molecular weight, the larger the intrinsic viscosity can be.

[0030] The intrinsic viscosity can be measured, for example, in accordance with JIS K7367-1:2002 (ISO 1628-1:1998). Specifically, for example, an Ubbelohde viscometer is used, and as the solvent, a mixed solvent of phenol / tetrachloroethane (mass ratio 1:1) is used. At a temperature of 30 °C, the dropping seconds of a PBSA solution with a concentration of 0.5 g / dL and only the mixed solvent are measured, and the intrinsic viscosity can be determined from the following formula (2). IV = ((1 + 4K H η sp ) 0.5 -1) / (2K H C) ··· (2) However, in formula (2), η SP = η / η0 - 1, where η is the dropping seconds of the sample solution, η0 is the dropping seconds of the solvent, C is the sample solution concentration (g / dL), and K H is the Huggins constant. K H adopts 0.33.

[0031] <Pellet containing PBSA> There are no particular restrictions on the shape and size of the pellet containing PBSA. It is preferably shaped and sized to be suitable for being subjected to known plastic processing methods such as injection molding and extrusion molding. Specifically, examples of the shape include, for example, cylindrical, elliptical cylindrical, prismatic, disc-shaped, spherical, etc. Also, as for the size, the size of the pellet may be the generally used size. Specifically, for example, those with a diameter or one side of about 0.7 to 12 mm can be mentioned. Further, when the pellet containing PBSA is subjected to the solvent contact step described later, it is preferable that the mass of one particle of the pellet is 1 to 50 mg, particularly preferably 3 to 40 mg, and even more preferably 5 to 30 mg, from the viewpoint of the extraction efficiency of the cyclic dimer by the solvent contact step.

[0032] <Cyclic dimer in the pellet containing PBSA> In pellets containing PBSA, the content of cyclic dimers is preferably 4,000 ppm by mass or less, particularly preferably 3,500 ppm by mass or less, more preferably 3,000 ppm by mass or less, even more preferably 2,500 ppm by mass or less, and even more preferably 2,000 ppm by mass or less. By limiting the content of cyclic dimers in the pellets to the above-mentioned specific amounts or less, the blocking resistance of the pellets can be further improved. Here, a cyclic dimer is a compound produced as a by-product when a portion of the polyester obtained by reacting a dicarboxylic acid component mainly composed of succinic acid with a diol component mainly composed of 1,4-butanediol undergoes cyclization, and refers to a cyclic dimer composed of succinic acid and 1,4-butanediol. Such a cyclic dimer can be represented, for example, by the following structural formula (4).

[0033] [ka]

[0034] There is no particular lower limit to the cyclic dimer content in pellets containing PBSA, and it can be 0 ppm by mass. However, reducing the cyclic dimer content to 0 ppm by mass may lead to an increase in the labor required to remove the cyclic dimer from synthesized PBSA, and the need for larger equipment for such removal. From the perspective of reducing environmental impact, it is preferable to have a content of 1 ppm by mass or more. Furthermore, it is particularly preferable that the content be 50 ppm by mass or more, and even more preferable that it be 100 ppm by mass or more. Therefore, the content of cyclic dimers in pellets containing PBSA is preferably 1 to 4000 ppm by mass, particularly preferably 50 to 3500 ppm by mass, even more preferably 100 to 3000 ppm by mass, more preferably 100 to 2500 ppm by mass, and even more preferably 100 to 2000 ppm by mass. The method for quantifying cyclic dimers in pellets containing PBSA is not particularly limited, but for example, the absolute calibration curve method can be used. Specific methods will be explained in the examples. The method for adjusting the content of cyclic dimers in pellets containing PBSA will be described later.

[0035] The pellets containing PBSA can contain other components in addition to PBSA. One of the other components is, for example, a release agent. Examples of the release agent include those commonly used in injection molding and extrusion molding. Specifically, for example, ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid and ethylene glycol, glycerin, or pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid or montanic acid, etc.) and stearylamine or ethylenediamine, silicone compounds, etc. are included. As the blending ratio of the release agent, in order to prevent blocking of the pellets due to excessive bleeding of the release agent onto the pellet surface and improve the releasability of the molded product, based on the pellets containing PBSA, 0.001 to 1% by mass is preferable, and 0.005 to 0.8% by mass is particularly preferable. Also, within a range not impairing the object of the present invention, additives can also be contained as other components. Examples of the additives include reinforcing materials such as talc, kaolin, mica, clay, bentonite, sericite, basic magnesium carbonate, aluminum hydroxide, glass flakes, glass fibers, carbon fibers, asbestos fibers, rock wool, calcium carbonate, silica sand, wollastonite, barium sulfate, glass beads, titanium oxide, non-plate-shaped fillers, or antioxidants (phosphorus-based, sulfur-based, etc.), ultraviolet absorbers, heat stabilizers (hindered phenol-based, etc.), transesterification reaction inhibitors, lubricants, antistatic agents, colorants including dyes and pigments, flame retardants (halogen-based, phosphorus-based, etc.), flame retardant aids (antimony compounds represented by antimony trioxide, zirconium oxide, molybdenum oxide, etc.), antibacterial agents, etc. Furthermore, as one of the other components, other resins other than PBSA may be included. In this case, as the content ratio of the other resin in the pellets, 20% by mass or less is preferable, 10% by mass or less is more preferable, 5% by mass or less is particularly preferable with respect to PBSA in the pellets, and also 0% by mass, that is, the resin component in the pellets can be only PBSA.

[0036] <Method for producing pellets containing PBSA> Pellets containing PBSA can be manufactured, for example, by following steps 1 to 4 below, or steps 1 to 5 below. (Step 1) A dicarboxylic acid component comprising at least one selected from the group consisting of succinic acid and its ester-forming derivatives, and at least one selected from the group consisting of adipic acid and its ester-forming derivatives, and a diol component comprising at least 1,4-butanediol are mixed in a predetermined proportion under stirring to obtain a raw material slurry. (Step 2) Following Step 1 above, the raw material slurry is heated under normal pressure or under pressure to undergo an esterification reaction to obtain a PBSA low polymer. (Step 3) Following Step 2 above, the obtained low polymer is gradually subjected to reduced pressure and heated to carry out a melt polycondensation reaction under a polycondensation catalyst. (Step 4) Following Step 3 above, the molten PBSA is extruded into strands and cut into pellets to obtain pellets containing PBSA. (Step 5) If necessary, the pellets obtained in Step 4 above are used 01 / I 02 Processing is performed to control the content of the cyclic dimer and the cyclic dimer. Furthermore, a process of air separation and sieving of pellets may be performed between step 4 and step 5, and / or after step 5.

[0037] An example of the above step 2 for obtaining a PBSA low polymer is a method using a single esterification reactor or a multi-stage reactor in which multiple esterification reactors are connected in series, in which the esterification reaction rate (the percentage of all carboxyl groups of the starting material dicarboxylic acid that react with the diol component and are esterified) is carried out until it reaches 90% or more, while removing the water and excess diol components produced in the reaction from the system, thereby obtaining a PBSA low polymer.

[0038] An example of step 3, in which a melt polycondensation reaction is carried out, is a multi-stage reactor consisting of, for example, a single melt polycondensation tank or multiple melt polycondensation tanks connected in series, with the first stage being a fully mixed reactor equipped with stirring blades, and the second and third stages being horizontal plug-flow reactors equipped with stirring blades, while distilling the diol produced out of the system under reduced pressure.

[0039] The PBSA polycondensation catalyst may be added to the reaction system at any stage of the mixing and preparation of the dicarboxylic acid and diol components, at any stage of the process of forming the PBSA low polymer, or at an early stage of the melt polycondensation process. In this case, one or more conventionally known metal compounds such as antimony, germanium, and titanium can be used as the PBSA polycondensation catalyst.

[0040] Furthermore, in steps 1 and 2 above, which involve forming a low polymer of PBSA, and in step 3 above, which involves melt polycondensation, antioxidants and basic compounds can be added to suppress side reactions such as thermal decomposition and dimerization of diols.Specific examples of antioxidants include, for example, Irganox 1330 (manufactured by BASF) and Irganox 1010 (manufactured by BASF), and examples of basic compounds include, for example, tertiary amines such as triethylamine, tri-n-butylamine, and benzyldimethylamine, quaternary ammonium hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, and trimethylbenzylammonium hydroxide, lithium carbonate, sodium carbonate, sodium hydroxide, potassium carbonate, and sodium acetate.

[0041] Examples of the above step 4, which involves cutting the synthesized PBSA into pellets, include the strand cutting method, in which molten PBSA is extruded from the nozzle hole of a die head using a gear pump or extruder and then cut with a cutter while being cooled with water or the cooled and solidified strand; and the underwater hot cutting method, in which molten PBSA is extruded into water from the nozzle hole and immediately cut.

[0042] <Intensity ratio (I 01 / I02 ) How to adjust > I of pellets containing PBSA related to this disclosure 01 / I 02 For example, this can be adjusted by adjusting the temperature and time added to the pellet containing PBSA in a step in which the PBSA synthesized by solution polycondensation in step 3 above is extruded in strand form from a die into a cooling liquid and held at a predetermined temperature for a predetermined time (hereinafter also referred to as the "slow cooling step"), or in a step that combines the slow cooling step with a step of immersing in a solvent adjusted to a predetermined temperature for a predetermined time (hereinafter also referred to as the "solvent contact step").

[0043] <Slow cooling process> The slow cooling process can be carried out before or during step 4. Specifically, the PBSA extruded in strand form from the die into a cooling liquid adjusted to a predetermined temperature is held in the cooling liquid in strand form for a predetermined time. After that, it is cut to form pellets. Alternatively, the PBSA extruded in strand form from the die into a cooling liquid adjusted to a predetermined temperature is cut in the cooling liquid to form pellets (step 4), and the pellets are held in the cooling liquid for a predetermined time. By slowly cooling fused PBSA, the arrangement of molecules within the fused PBSA is improved. By promoting orientation, it becomes possible to appropriately develop the crystalline structure of PBSA. Here, if molten PBSA is extruded into, for example, a room temperature (25°C) environment, the PBSA will be rapidly cooled, and the PBSA molecules will be fixed in a randomly oriented state, I 01 / I 02 It becomes difficult to set it to 1.1 or higher.

[0044] Here, the temperature of the cooling liquid used to extrude the molten PBSA into strands is preferably 35 to 55°C, particularly preferably 35 to 50°C, and even more preferably 40 to 50°C. The time for holding the PBSA within the above temperature range is I 01 / I 02While there are no particular restrictions as long as it can be 1.1 or higher, it is preferable to set it to, for example, 0.1 to 10 minutes, more preferably 0.5 to 5 minutes, and even more preferably 1 to 3 minutes. When the holding time is extended within the above temperature range of the pellet containing PBSA, I 01 / I 02 The value of is generally large. Note that if the temperature of the cooling liquid is set higher within the above range, adjustments such as shortening the holding time may be necessary to achieve the desired I 01 / I 02 This can be done as appropriate depending on the value.

[0045] Furthermore, the type of cooling liquid is not particularly limited as long as it does not react with or dissolve PBSA during the above temperature range and holding time. Examples of such cooling liquids include water.

[0046] Furthermore, pellets that have undergone a process of being kept in water (hot water) at a temperature exceeding the above temperature range for a predetermined time as a cooling liquid, for reasons that are not clear, 01 / I 02 The value may exceed 2.3. This means that the proportion of crystalline PBSA in the pellet becomes too high. As a result, such pellets, with their excessive crystalline content, have a brittle surface and can easily generate fine powder due to friction between pellets or with the molding equipment.

[0047] <Solvent Contact Process> It is preferable to carry out a solvent contact step as step 5 following the slow cooling step described above. This step reduces the content of cyclic dimers in the pellets and 01 / I 02 This process contributes to further adjustment of the value, and by going through this process, the content of cyclic dimers in the pellet can be adjusted to a smaller value within the aforementioned range, and I 01 / I 02 It is possible to adjust this to a higher value, preferably within the range of 1.1 to 2.3, which is 1.1 or greater. This step involves contacting the pellets obtained through the slow cooling step with a solvent capable of dissolving the cyclic dimer, which has been adjusted to a predetermined temperature, for a predetermined time. By going through this step, at least a portion of the cyclic dimer in the pellets can be removed, and the content of the cyclic dimer in the pellets can be adjusted to 4000 ppm by mass or less. In other words, the inventors hypothesize that the cyclic dimer in the pellet is a component that inhibits the crystallization of PBSA. By forming a macroscopic crystalline structure of PBSA in the slow cooling step, I 01 / I 02 However, pellets with a ratio of 1.1 or higher can be obtained. Furthermore, by subjecting these pellets to the solvent contact step described above, the cyclic dimers can be removed from the pellets, and the cyclic dimer content can be reduced to 4000 ppm by mass or less, and it is presumed that the microcrystalline structure of PBSA will be more easily formed in the pellets. Here, in the solvent contact step, the pellets are held at a predetermined temperature for a predetermined time, so in a state where the crystallization inhibiting component (cyclic dimer) is low, the orientation of PBSA molecules in the pellets will further advance, and I 01 / I 02 However, it is considered possible to obtain pellets with a higher value, preferably within the range of 1.1 or higher, and more preferably within the range of 1.1 or higher and 2.3 or lower. Furthermore, even if only the solvent contact process is performed without the slow cooling process, 01 / I 02 It is difficult to make it 1.1 or higher. In other words, by removing the cyclic dimer in the solvent contact process P In order to develop the microcrystalline structure of BSA, it is considered necessary to perform a slow cooling process prior to the solvent contact process to form the macrocrystalline structure of PBSA in the pellet.

[0048] The solvent used in this process is preferably one that does not substantially dissolve PBSA even after contact with the pellets at a predetermined temperature and for a predetermined time, while on the other hand, it can dissolve the cyclic dimer well. Examples of such solvents include C1 to C4 alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, etc.). Alternatively, it may be an aqueous solution of at least one alcohol selected from the group consisting of these alcohols. The concentration of the alcohol in such an aqueous alcohol solution is not particularly limited, but for example, from the viewpoint of good solubility of the cyclic dimer, it is preferably 10% by mass or more and less than 100% by mass based on the aqueous alcohol solution.

[0049] Furthermore, the solvent temperature in the solvent contact step is preferably 55°C or lower, and particularly preferably 50°C or lower, so as not to excessively increase the crystallinity of PBSA. As a lower limit, from the viewpoint of better extracting the cyclic dimer and appropriately oriented the PBSA molecules, it is preferably 35°C or higher, particularly preferably 40°C or higher, and even more preferably 45°C or higher. In other words, the solvent temperature range in the solvent contact step is preferably 35 to 55°C, particularly preferably 40 to 50°C, and even more preferably 45 to 50°C. Furthermore, as for the processing time, from the viewpoint of better extracting the cyclic dimer and appropriately oriented the PBSA molecules, it is preferably 0.1 to 10 hours, particularly preferably 0.5 to 8 hours, and even more preferably 1 to 5 hours.

[0050] Specific methods for the solvent contact process described above include, for example, the methods described in i) and ii) below. i) A method in which pellets obtained through a slow cooling process and a solvent are placed in a processing tank, and after contacting them at the predetermined temperature range and for the predetermined time, the pellets are recovered from the processing tank; ii) A method of continuously supplying pellets obtained through a slow cooling process to a processing tank, while flowing a solvent adjusted to the above-mentioned predetermined temperature range in parallel or countercurrent flow relative to the flow of pellets, allowing the pellets to be processed and the solvent to come into contact for a predetermined time, and then continuously recovering the processed pellets.

[0051] The specific methods and apparatus used in this process are not particularly limited, but the method and apparatus described in Patent Document 3, which can continuously adjust the content of cyclic dimers in pellets, can be suitably used.

[0052] <Application> As described above, I 01 / I 02 However, pellets containing PBSA with a ratio of at least 1.1 and preferably with a cyclic dimer content of 4000 ppm by mass or less are less prone to pellet blocking when subjected to injection molding or extrusion molding. As a result, the supply stability to the molding machine during molding is not hindered. Therefore, molded products (injection molded products, extruded products, etc.) can be manufactured stably. 01 / I 02 However, pellets containing PBSA, which have a concentration of at least 1.1 to 2.3 and preferably a cyclic dimer content of 4000 ppm by mass or less, are less prone to blocking among pellets when subjected to injection molding or extrusion molding, and can better prevent the generation of fine powder through contact between pellets or between pellets and molding equipment. As a result, the supply stability to the molding machine during molding is not hindered, and contamination of the molding machine and extruder by fine powder is also prevented. Therefore, molded products (injection molded products, extruded products, etc.) can be manufactured stably and productively. Thus, the pellets according to this disclosure are extremely suitable as pellets for injection molding and extrusion molding to obtain biodegradable molded products. It is useful.

[0053] <Molded products (injection molded products, extruded products)> Resin pellets for obtaining injection-molded or extruded articles may consist solely of pellets containing PBSA. Alternatively, two or more types of PBSA pellets with different molar ratios of succinic acid units, adipic acid units, and 1,4-butanediol units may be mixed to form the resin pellets.

[0054] The injection-molded products and extrusion-molded products of resin pellets containing pellets containing PBSA according to the present disclosure can be obtained by molding using the injection molding method or the extrusion molding method with resin pellets containing pellets containing PBSA according to the present disclosure.

[0055] The molded shape can be any shape as long as it can be molded by the injection molding method or the extrusion molding method. The uses of the injection-molded product or the extrusion-molded product are not limited in any way. Examples of the injection-molded product include cutlery and various containers (cups, cosmetic containers, food containers, detergent containers, bleach containers, etc.). Examples of the extrusion-molded product include packaging materials (packaging films), agricultural films (agricultural mulch films), etc.

Examples

[0056] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measurement methods of the physical properties and evaluation items adopted in the following examples are as follows.

[0057] < Intrinsic viscosity (IV) dL / g > It was determined using an Ubbelohde viscometer as follows. That is, using a mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1), at a temperature of 30 °C, the dropping seconds of the polymer solution with a concentration of 0.5 g / dL and only the solvent were measured, and it was determined from the following formula (3). IV = ((1 + 4K H η sp ) 0.5 -1) / (2K H C) ··· (3) However, in formula (3), η SP = η / η0 - 1, where η is the dropping seconds of the sample solution, η0 is the dropping seconds of the solvent, C is the sample solution concentration (g / dL), and K H is the Huggins constant. K H adopted 0.33.

[0058] < Content of cyclic dimer of PBSA > 0.5 g of pellets were accurately weighed, 10 mL of chloroform was added, and the mixture was dissolved at room temperature. Then, 30 mL of ethanol / water mixture (volume ratio 4 / 1) was slowly added dropwise while stirring to precipitate the polymer components. After 15 minutes, stirring was stopped, and the mixture was allowed to stand for 90 minutes for separation. Next, 2 mL of the supernatant was taken, evaporated to dryness, and then 2 mL of acetonitrile was added to dissolve it. After filtering through a 0.45 μm filter, the mixture was eluted using high-performance liquid chromatography (product name: Prominence, Shimadzu Corporation) by starting the mobile phase with acetonitrile / water (volume ratio = 4 / 6) and continuously changing the composition up to acetonitrile / water (volume ratio = 9 / 1) using a high-pressure gradient method. The analysis was performed using an octadecylsilylated silica gel (ODS) column (product name "CAPCELL PAK C-18 TYPE MGII" (silica gel particle size: 5 μm, inner diameter: 4.6 mm, length: 150 mm; manufactured by Osaka Soda Co., Ltd.)). A UV detector was used, with detection wavelengths of 210 nm and 254 nm. The obtained results were quantified using an absolute calibration curve method with cyclic dimer pure products, and expressed as mass ppm relative to the pellet.

[0059] The cyclic dimer pure product was obtained as follows: A PBS pellet obtained by polymerizing succinic acid and 1,4-butanediol was stirred in acetone at 50°C for 12 hours to extract the oligomer component. After extraction, the pellet was filtered off to extract the oligomer component. From the acetone solution from which the substance was extracted, the acetone was evaporated to obtain a solid. This solid was dissolved in acetone at a temperature of 50°C to form a saturated solution, and then slowly cooled to room temperature (25°C) to precipitate needle-shaped precipitates (crystals) in a recrystallization operation. Next, the supernatant was discarded and the crystals were... The crystals were recovered. The obtained crystals were purified by subjecting them to the above recrystallization procedure several more times. These crystals were analyzed by 1H-NMR and high-performance liquid chromatography to confirm that they were cyclic dimers formed from succinic acid and 1,4-butanediol.

[0060] <Raman band intensity ratio (I 01 / I 02 )> Using "RAMAN touch" (trade name, manufactured by Nanophoton) as a Raman spectrometer, the Raman spectrum of the pellet was measured. The measurement conditions were as follows. The measurement conditions were as follows. <Measurement Conditions> · Measurement mode: Point · Laser wavelength: 532 nm · Laser output: 20 mW (opening degree of the attenuation filter: 210 / 255) · Diffraction grating: 1200 gr / mm · Pinhole: 50 μm · Exposure time: 10 seconds · Number of integrations: 5 times · Objective lens: 100x · Measurement temperature: 25 °C

[0061] Regarding the obtained Raman spectrum, a peak of the Raman scattering intensity having a peak top in the first wavenumber range of 1718 ± 5 cm -1 and a peak of the Raman scattering intensity having a peak top in the second wavenumber range of 1732 ± 5 cm -1 were fitted using the Lorentz function shown in the above formula (1). In the obtained Lorentz-fitted Raman spectrum, the peak intensity I 01 in the first wavenumber range and the peak intensity I 02 in the second wavenumber range, the intensity ratio (I 01 / I 02 ) was determined. Specifically, from the ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A1") in the above formula (1) corresponding to the peak in the first wavenumber range obtained by fitting (i.e., X0 = 1718 ± 5 cm -1 ) and the intensity A (hereinafter also referred to as "A2") in the above formula (1) corresponding to the peak in the second wavenumber range (i.e., X0 = 1732 ± 5 cm ), I -1 ) and the intensity A (hereinafter also referred to as "A2") in the above formula (1) corresponding to the peak in the second wavenumber range (i.e., X0 = 1732 ± 5 cm ), the ratio (A1 / A2) of the intensity A in the above formula (1) corresponding to the peak in the second wavenumber range (hereinafter also referred to as "A2"), I 01 / I 02was calculated. In this embodiment, the average value of three measurements was calculated. Specifically, three measurement samples were taken from the pellets to be measured, and for each measurement sample, the above Raman spectrum measurement, fitting, and I 01 / I 02 were calculated. For each measurement sample, the average value of I 01 / I 02 was calculated, and the I 01 / I 02 of each example and each comparative example was obtained.

[0062] <Melting Point> Using a thermal analysis system (trade name: DSC3; manufactured by Mettler Toledo), the endothermic peak temperature when heating from room temperature to 200 °C at a rate of 10 °C / min was measured and taken as the melting point of the pellets.

[0063] <Heat Fusion Test> 20 g of pellets were placed in a cylindrical container made of stainless steel (SUS) with an inner diameter of 20 mm, and a weight was placed on the surface of the pellet layer in the cylindrical container so that a pressure of 180 g per square centimeter was evenly applied. This cylindrical container was heated to a temperature of the melting point of the pellets - 15 °C and placed in an inert oven with nitrogen flowing at a flow rate of 20 liters / min for 30 minutes, then taken out and returned to room temperature (25 °C). Then, the pellets were taken out from the cylindrical container, and the fusion condition of the pellets was visually observed. The evaluation criteria were as follows, and a rank of B or above was considered qualified. Rank A: There was no fusion between the pellets, and no blocking occurred, which was the best state. Rank B: There were 5 - 10 small lumps, but they easily crumbled when gently prodded with a finger, and no blocking occurred. Rank C: The pellets were fused together and there were 10 or more lumps, and blocking occurred.

[0064] <Measurement of Fine Powder Amount> ​100g of pellets were sieved through a 0.71mm mesh sieve to remove fine powder, and the mass of the remaining pellets was measured. Next, the remaining pellets were placed in a stainless steel (SUS) cylindrical container with an inner diameter of 100mm and a height of 200mm, and shaken for 10 minutes at a shaking speed of 100 times / min and an amplitude of 40mm using a small shaker (product name: NR-3, manufactured by TAITEC). After that, all the contents of the cylindrical container were collected and sieved through a 0.71mm mesh sieve to separate the fine powder generated by the shaking, and the mass of the obtained fine powder was measured. The amount of fine powder generated (ppm) was then calculated from the mass of the total pellets before shaking and the mass of the generated fine powder. The smaller this value, the less fine powder is generated, and the fewer problems such as clogging and variations in supply volume there are. The evaluation criteria were as follows, and rank B or higher was considered acceptable. Rank A: 500 ppm or less. Rank B: Over 500 ppm and under 1000 ppm. Rank C: Over 1000 ppm.

[0065] (Example 1) [Preparation of catalyst for polycondensation] 100 parts by mass of magnesium acetate tetrahydrate were placed in a glass pear-shaped flask equipped with a stirrer, and 1500 parts by mass of anhydrous ethanol (purity 99% or higher) were added. Then, 65.3 parts by mass of ethyl acid phosphate (mixture mass ratio of monoester and diester: 45:55) was added, and the mixture was stirred at 23°C. After 15 minutes, it was confirmed that the magnesium acetate was completely dissolved, and then 122 parts by mass of tetra-n-butyl titanate was added. Stirring was continued for another 10 minutes to obtain a homogeneous mixed solution. This mixed solution was transferred to a pear-shaped flask and concentrated under reduced pressure using an evaporator in an oil bath at 60°C. After 1 hour, most of the ethanol had evaporated, yielding a translucent, viscous liquid. The oil bath temperature was further increased to 80°C, and the solution was further concentrated under reduced pressure of 5 Torr to obtain a viscous liquid. This liquid catalyst was dissolved in 1,4-butanediol to prepare a catalyst solution with a titanium atom content of 1.0% by mass.

[0066] [Manufacturing of pellets containing PBSA] A slurry was prepared by continuously supplying 48.6 parts by mass of succinic acid, 21.2 parts by mass of adipic acid, 65.1 parts by mass of 1,4-butanediol, and 0.239 parts by mass of malic acid to a slurry preparation tank, stirring, and mixing. The slurry was then continuously supplied to an esterification reaction tank, and the esterification reaction was carried out continuously at an internal temperature of 230°C and a pressure of 101 kPa to obtain a low polymer of PBSA with an esterification rate of 92%.

[0067] The obtained PBSA low polymer was continuously supplied to the first stage polycondensation reactor, and 0.50 parts by mass of the previously prepared catalyst solution was continuously added to the PBSA low polymer. The reaction was carried out continuously under reduced pressure of 2.0 kPa at a temperature of 240°C with an average residence time of 2 hours. Next, the obtained reactant was continuously supplied to the second stage polycondensation reactor, and a melt polycondensation reaction was carried out under reduced pressure of 0.4 kPa at a temperature of 240°C with an average residence time of 2 hours. Subsequently, the reaction was carried out in the third stage polycondensation reactor at a temperature of 240°C and a pressure of 0.13 kPa with an average residence time of 2 hours. After that, the molten PBSA was extruded in strand form into warm water adjusted to a temperature of 35°C from an outlet provided at the bottom of the polycondensation reactor, and immediately cut in its molten state to form individual grains. The pellets were formed into flat, cocoon-shaped pellets with a mass of approximately 15 mg, and then held in the hot water for 1 minute while applying a linear velocity to the hot water. After that, the pellets were recovered from the hot water and dried. In this way, pellets containing PBSA according to Example 1 were obtained. The molar ratio of constituent units derived from succinic acid to constituent units derived from adipic acid (constituent units derived from succinic acid / constituent units derived from adipic acid) of the obtained pellets was 74 / 26. The obtained pellets containing PBSA were subjected to the following methods: intrinsic viscosity, strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above. Figure 1 shows the Raman spectrum measured from the pellet according to this embodiment, as well as the fitted Raman spectrum obtained by fitting with two peaks having peak tops in the first and second wavenumber ranges. In Figure 1, P is the Raman spectrum measured from the pellet, P01 and P02 are Raman spectra obtained by curve fitting using the Lorentz function to the peaks in the first and second wavenumber ranges, respectively, and PS is the spectrum obtained by combining the waveforms related to P01 and P02.

[0068] (Example 2) 25 parts by mass of pellets containing PBSA prepared in Example 1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 45°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried under a nitrogen atmosphere at a temperature of 60°C. The pellets thus obtained were subjected to the method described above to determine their intrinsic viscosity and strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0069] (Example 3) 25 parts by mass of pellets containing PBSA prepared in Example 1 and a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 45°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried under a nitrogen atmosphere at a temperature of 60°C. The pellets thus obtained were subjected to the method described above to determine their intrinsic viscosity and strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0070] (Example 4) Pellets containing PBSA were prepared in the same manner as in Example 1, except that the raw materials continuously supplied to the slurry preparation tank were changed to 53.1 parts by mass of succinic acid, 16.4 parts by mass of adipic acid, 65.9 parts by mass of 1,4-butanediol, and 0.293 parts by mass of malic acid. The molar ratio of constituent units derived from succinic acid to constituent units derived from adipic acid (constituent units derived from succinic acid / constituent units derived from adipic acid) of the obtained pellets was 80 / 20. The intrinsic viscosity and strength ratio (I) of the obtained PBSA-containing pellets were determined according to the method described above. 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0071] (Example 5) 25 parts by mass of pellets containing PBSA prepared in Example 4 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 45°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried under a nitrogen atmosphere at a temperature of 60°C. The PBSA-containing pellets thus obtained were subjected to the intrinsic viscosity and strength ratio (I) according to the method described above. 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0072] (Example 6) 25 parts by mass of pellets containing PBSA prepared in Example 4 and a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 45°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried under a nitrogen atmosphere at a temperature of 60°C. The PBSA-containing pellets thus obtained were subjected to the method described above to determine their intrinsic viscosity and strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0073] (Example 7) 25 parts by mass of pellets containing PBSA prepared in Example 1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 60°C for 4 hours (hot water contact step). The pellets that underwent this hot water contact step were dried under a nitrogen atmosphere at a temperature of 60°C. The PBSA-containing pellets thus obtained were subjected to the intrinsic viscosity and strength ratio (I) according to the method described above. 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0074] (Comparative Example 1) In Example 1, after polymerization of PBSA, the molten PBSA was extracted in strand form from an outlet at the bottom of the polycondensation reaction vessel, rapidly cooled with water at 20°C, and the solidified strands were cut to form pellets. These pellets were dried in a nitrogen atmosphere at 60°C. The PBSA-containing pellets thus obtained were subjected to the method described above, and their intrinsic viscosity and strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above.

[0075] (Comparative Example 2) 25 parts by mass of pellets containing PBSA prepared in Comparative Example 1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 60°C for 4 hours (hot water contact step). The pellets that underwent this hot water contact step were dried under a nitrogen atmosphere at a temperature of 60°C. The PBSA-containing pellets thus obtained were subjected to the method described above to determine their intrinsic viscosity and strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the amount of fine powder generated were measured according to the method described above. Table 1 shows the measurement results of pellets containing PBSA for Examples 1-7 and Comparative Examples 1-2.

[0076] [Table 1]

[0077] From Table 1, I 01 / I 02 Pellets containing PBSA with a value of 1.1 or higher exhibit excellent blocking resistance, and also, I 01 / I 02 However, pellets containing PBSA with a numerical value between 1.1 and 2.3 exhibit excellent blocking resistance and significantly suppress the generation of fine powder. Furthermore, this allows for stable supply to injection molding machines and extrusion molding machines, enabling the stable production of injection-molded and extruded products. Thus, according to one aspect of the present invention, pellets containing PBSA that have good blocking resistance and can be stably supplied to a molding machine can be obtained as a feed material for injection molding, extrusion molding, etc. Furthermore, biodegradable injection molded or extruded molded articles that can be manufactured more stably can be obtained. Furthermore, according to another aspect of the present invention, pellets containing PBSA can be obtained as a feed material for injection molding, extrusion molding, etc., which have excellent blocking resistance and suppress the generation of fine powder. In addition, since such pellets are less prone to blocking and do not generate fine powder, they can be stably supplied to the molding machine, and contamination of the extruder and molding machine by fine powder can be prevented, thus enabling the production of biodegradable injection-molded or extruded articles that can be manufactured stably and productively.

Claims

1. A constituent unit derived from succinic acid, a constituent unit derived from adipic acid, and 1,4-butanedi A pellet containing polybutylene succinate adipate having oar-derived constituent units as its main constituent units, The Raman spectrum measured from the aforementioned pellets shows values ​​of 1680–1780 cm⁻¹. －１ The spectrum in the wavenumber range is 1718±5 cm⁻¹. －１ The first wavenumber range, and 1732±5 cm －１ In a Raman spectrum fitted using a Lorentz function with two peaks each having a peak top in the second wavenumber range, the intensity of the peak in the first wavenumber range I ０１ And the peak intensity I in the second wavenumber range ０２ The intensity ratio (I ０１ / I ０２ Pellets in which the ratio is 1.1 or higher.

2. The pellet according to claim 1, wherein the strength ratio is 2.3 or less.

3. The pellet according to claim 1, wherein the strength ratio is 1.4 or more.

4. The pellet according to claim 1, wherein the content of a cyclic dimer consisting of succinic acid and 1,4-butanediol in the pellet is 4,000 ppm by mass or less.

5. The pellet according to claim 1, wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less.

6. The pellet according to claim 1, wherein the molar ratio of constituent units derived from succinic acid to constituent units derived from adipic acid (constituent units derived from succinic acid / constituent units derived from adipic acid) is 70 / 30 to 90 / 10.

7. The pellet according to claim 6, wherein the molar ratio is 70 / 30 to 80 / 20.

8. The pellet according to claim 1, wherein the total number of moles of the constituent units derived from succinic acid, the constituent units derived from adipic acid, and the constituent units derived from 1,4-butanediol in the polybutylene succinate adipate is 80 mol% or more of the total number of moles of the constituent units constituting the polybutylene succinate adipate.

9. The pellet according to claim 1, wherein the content of the polybutylene succinate adipate in the pellet is 80% by mass or more.

10. An injection-molded resin pellet article comprising at least one of the pellets described in any one of claims 1 to 9.

11. An extruded resin pellet article comprising at least one of the pellets described in any one of claims 1 to 9.

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