Pellet, injection molded article, and extrusion molded article

Abstract

Provided is a pellet containing a biodegradable polyester, the pellet exhibiting good blocking resistance and being able to be stably supplied to a molding machine.　The pellet contains PBS having a constituent unit derived from succinic acid and a constituent unit derived from 1,4-butane diol as primary constituent units. In a fitted Raman spectrum obtained by fitting a spectrum having a frequency range of 1680-1780 cm-1 in a Raman spectrum measured using said pellet using a Lorentz function with two peaks having peak tops within a first frequency range of 1718±5 cm-1 and a second frequency range of 1732±5 cm-1, the intensity ratio of the intensity I01 of a peak in the first frequency range and the intensity I02 of a peak in the second frequency range (I01 / I02) is 2.0 or more.

Description

Pellets, injection molded products, and extruded products

[0001] This invention relates to pellets containing polybutylene succinate (hereinafter sometimes referred to as "PBS"), as well as injection-molded articles and extruded articles. More specifically, it relates to pellets containing PBS suitable for injection molding and extrusion molding, and injection-molded articles and extruded articles obtained by using resin pellets containing these pellets. This invention also relates to pellets containing polybutylene succinate adipate (hereinafter sometimes referred to as "PBSA"), as well as injection-molded articles and extruded articles obtained using these pellets. More specifically, it relates to pellets containing PBSA suitable for injection molding and extrusion molding, and injection-molded articles and extruded articles obtained using resin pellets containing these pellets. Furthermore, this invention relates to pellets containing polybutylene succinate sebacate (hereinafter sometimes referred to as "PBSSe"), as well as injection-molded articles and extruded articles obtained using these pellets. More specifically, it relates to pellets containing PBSSe suitable for injection molding and extrusion molding, and injection-molded articles and extruded articles obtained using resin pellets containing these pellets. Furthermore, the present invention relates to pellets containing polybutylene succinate terephthalate (hereinafter sometimes referred to as "PBST"), and injection-molded and extruded articles obtained using these pellets. More specifically, the present invention relates to pellets containing PBST that are suitable for injection molding and extrusion molding, and to injection-molded and extruded articles obtained using resin pellets containing these pellets.

[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 the aforementioned challenges, numerous studies have been conducted on biodegradable materials that are broken down into carbon dioxide and water by microorganisms in soil or water. Representative examples of biodegradable materials 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) and polybutylene succinate terephthalate (PBST).

[0004] In particular, PBS is expected to have a wide range of applications in agricultural materials, civil engineering materials, vegetation materials, packaging materials, and other products, due to its ability to use all of its raw materials from plant resources, and its combination of good physical properties and biodegradability, and numerous studies are being conducted on it.

[0005] Patent Document 1 discloses that by using PBS as a base resin and selecting and blending a specific crystal nucleating agent, a highly transparent film can be obtained that reduces roll contamination, odor and smoke during processing. Patent Document 2 discloses that by setting the zirconium compound content in a biodegradable resin composition containing PBS to a specific value, a biodegradable film with sufficient elongation during the mid-stage of cultivation can be obtained.

[0006] Furthermore, among the biodegradable materials mentioned above, PBSA is a material that can achieve a high level of balance between biodegradability and mechanical properties and moldability, and therefore it has been proposed to be used in various components and resin compositions that require biodegradability. Patent Document 4 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 5 also 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.

[0007] Furthermore, Patent Documents 6 and 7 disclose polybutylene succinate sebacate (PBSSe), obtained from an aliphatic diol such as 1,4-butanediol, succinic acid, and sebacic acid, as an example of a polyester resin used as a biodegradable resin to constitute a biodegradable resin composition.

[0008] Furthermore, among the biodegradable materials mentioned above, PBST has been the subject of various studies because it is a material that can achieve a high level of both biodegradability and mechanical strength and moldability. Patent Document 8 discloses a method for producing aliphatic aromatic polyester with improved crystallinity, addressing the problem of blocking caused by insufficient crystallinity that conventional aliphatic aromatic polyesters such as PBST had. Specifically, it discloses that when producing aliphatic aromatic polyester by polycondensation reaction via esterification and / or transesterification, aliphatic aromatic polyester with a high degree of crystallinity can be obtained by presenting a specific nucleating agent in the reaction system. In addition, Patent Document 9 discloses a method for producing polyester in which THF and oligomers produced as by-products in the manufacturing process of aliphatic aromatic polyester affect the quality of the polyester, and in order to reduce this, a contact treatment step is disclosed in which aliphatic aromatic polyester pellets are brought into contact with a mixed liquid containing ethanol and water.

[0009] Japanese Patent Publication No. 2018-162428, Japanese Patent Publication No. 2018-139560, Japanese Patent Publication No. 2024-049583, Japanese Patent Publication No. 2000-83494, Japanese Patent Publication No. 2023-110156, Japanese Patent Publication No. 2022-157778, Japanese Patent Publication No. 2023-55686, International Publication No. 2021 / 161846, Japanese Patent Publication No. 2018-145221

[0010] Incidentally, when manufacturing molded products using pellets containing PBS, a phenomenon sometimes occurred in which the pellet particles fused together and aggregated (hereinafter referred to as "blocking") when heat and / or load was applied to the pellets during the drying process or the process of supplying the pellets to the molding machine. This is thought to be due to the low melting point of PBS, which is about 114°C. Blocking could hinder the stable supply of pellets to the molding machine. One aspect of the first invention aims to solve the above problem and to provide pellets containing PBS that have good blocking resistance and can be stably supplied to a molding machine as a supply material for injection molding, extrusion molding, etc. Another aspect of the first invention aims to provide biodegradable injection molded or extruded molded products that can be stably manufactured.

[0011] Furthermore, when manufacturing molded products using pellets containing PBSA, a phenomenon sometimes occurs in which 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 of the pellets or the supply process of the pellets to the molding machine. This is thought to be due to the low melting point of PBSA, which is around 80 to 105°C. Blocking can hinder the stable supply of pellets to the molding machine. One aspect of the second invention aims to solve the above problems and provides pellets containing PBSA that have good blocking resistance and can be stably supplied to the molding machine as a supply material for injection molding, extrusion molding, etc. Another aspect of the second invention aims to provide biodegradable injection molded or extruded molded products that can be stably manufactured.

[0012] Furthermore, among the biodegradable resins mentioned above, the inventors focused on PBSSe as a resin that can achieve both excellent biodegradability and excellent mechanical properties and moldability at a high level. However, according to the inventors' studies, when manufacturing molded products using pellets containing PBSSe, a phenomenon sometimes occurs in which 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 of the pellets or the supply process of the pellets to the molding machine. This is thought to be due to the relatively low melting point of PBSSe, which is about 80 to 105°C. Blocking can hinder the stable supply of pellets to the molding machine. One aspect of the third invention aims to solve the above problems and provides pellets containing PBSSe that have good blocking resistance and can be stably supplied to the molding machine as a supply material for injection molding, extrusion molding, etc. Furthermore, another aspect of the third invention aims to provide a biodegradable injection-molded or extruded article that can be manufactured stably.

[0013] Furthermore, regarding PBST, the inventors have found that even pellets containing PBST manufactured by the method described in Patent Document 8 may have a problem where, under harsher conditions, specifically, when heat or load is applied to the pellets during drying or supply to a molding machine, the pellet particles fuse together and aggregate, resulting in so-called blocking. This problem is presumed to be due to the fact that PBST has a larger amorphous portion compared to PBS, and blocking can occur even at low temperatures such as 50-60°C. One aspect of the fourth invention aims to solve the above problem and provides pellets containing PBST that are less prone to blocking even when heat and / or pressure is applied, and that can be stably supplied to a molding machine as a feed material for injection molding or extrusion molding. Another aspect of the fourth invention aims to provide biodegradable injection molded or extruded articles that can be stably manufactured.

[0014] The gist of the present invention is as follows: [1-1] A pellet containing polybutylene succinate having as its main constituent units a constituent unit derived from succinic acid and a constituent unit derived from 1,4-butanediol, wherein the Raman spectrum measured from the pellet has a range of 1680 to 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 the fitted Raman spectrum obtained by fitting with a Lorentz function using 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 ０２A pellet having an intensity ratio of 2.0 or more. [1-2] The pellet according to [1-1], wherein the intensity ratio is 3.2 or less. [1-3] The pellet according to [1-1] or [1-2], wherein the intensity ratio is 2.2 or more. [1-4] The pellet according to any one of [1-1] to [1-3], wherein the intensity ratio is 2.5 or more. [1-5] In the polybutylene succinate, the total number of moles of the structural units derived from succinic acid and the structural units derived from 1,4-butanediol is 80 mol% or more based on the total number of moles of the structural units constituting the polybutylene succinate. The pellet according to any one of [1-1] to [1-4]. [1-6] The pellet according to any one of [1-1] to [1-5], wherein the content of polybutylene succinate contained in the pellet is 80% by mass or more. [1-7] The pellet according to any one of [1-1] to [1-6], wherein the content of the cyclic dimer composed of succinic acid and 1,4-butanediol in the pellet is 4000 mass ppm or less. [1-8] The pellet according to any one of [1-1] to [1-7], wherein the content of the cyclic dimer composed of succinic acid and 1,4-butanediol in the pellet is 2000 mass ppm or less. [1-9] The pellet according to any one of [1-1] to [1-8], wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less. [1-10] An injection molded product of a resin pellet containing at least the pellet according to any one of [1-1] to [1-9]. [1-11] An extrusion molded product of a resin pellet containing at least the pellet according to any one of [1-1] to [1-9].

[0015] [2-1] A pellet containing polybutylene succinate adipate having, as main structural units, a structural unit derived from succinic acid, a structural unit derived from adipic acid, and a structural unit derived from 1,4-butanediol. In the Raman spectrum measured from the pellet, the spectrum in the wave number range of 1680 to 1780 cm －１ is in the first wave number range of 1718 ± 5 cm －１ and in the second wave number range of 1732 ± 5 cm －１In 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 [2-2] A pellet having a strength ratio of 1.1 or more. [2-3] A pellet according to [2-1], wherein the strength ratio is 2.3 or less. [2-4] A pellet according to any one of [2-1] to [2-3], wherein the strength ratio is 1.4 or more. [2-5] A pellet according to any one of [2-1] to [2-4], 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. [2-6] A pellet according to any one of [2-1] to [2-5], wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less. [2-6] A pellet according to any one of [2-1] to [2-5], 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. [2-7] The pellet according to [2-6], wherein the molar ratio is 70 / 30 to 80 / 20. [2-8] The pellet according to any one of [2-1] to [2-7], 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. [2-9] The pellet according to any one of [2-1] to [2-8], wherein the content of the polybutylene succinate adipate in the pellet is 80% by mass or more. [2-10] An injection-molded resin pellet containing at least the pellet according to any one of [2-1] to [2-9]. [2-11] An extruded resin pellet containing at least the pellet according to any one of [2-1] to [2-9].

[0016] [3-1] A pellet containing polybutylene succinate sebacate having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from sebacic acid, and a constituent unit derived from 1,4-butanediol, wherein the Raman spectrum measured from the pellet is 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[3-2] A pellet having a strength ratio of 1.7 or more. [3-3] The pellet according to [3-1], wherein the strength ratio is 3.4 or less. [3-4] The pellet according to any one of [3-1] to [3-3], 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. [3-5] The pellet according to any one of [3-1] to [3-4], wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less. [3-6] The pellet according to any one of [3-1] to [3-5], wherein the molar ratio of constituent units derived from succinic acid to constituent units derived from sebacic acid (constituent units derived from succinic acid / constituent units derived from sebacic acid) is 70 / 30 to 95 / 5. [3-7] The pellet according to [3-6], wherein the molar ratio is 80 / 20 to 90 / 10. [3-8] The pellet according to any one of [3-1] to [3-7], wherein the total number of moles of the constituent units derived from succinic acid, the constituent units derived from sebaciic acid, and the constituent units derived from 1,4-butanediol in the polybutylene succinate sebacate is 80 mol% or more of the total number of moles of the constituent units constituting the polybutylene succinate sebacate. [3-9] The pellet according to any one of [3-1] to [3-8], wherein the content of the polybutylene succinate sebacate in the pellet is 80% by mass or more. [3-10] An injection-molded resin pellet containing at least the pellet according to any one of [3-1] to [3-9]. [3-11] An extruded resin pellet containing at least the pellet according to any one of [3-1] to [3-9].

[0017] [4-1] A pellet containing polybutylene succinate terephthalate having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from terephthalic acid, and a constituent unit derived from 1,4-butanediol, wherein the Raman spectrum measured from the pellet is 1680–1780 cm⁻¹ －１ The spectrum in the wavenumber range is 1711±5 cm⁻¹. －１The first wavenumber range, and 1722±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 [4-2] A pellet having a strength ratio of 1.00 or more. [4-3] The pellet according to [4-1], wherein the strength ratio is 1.00 or more and 2.50 or less. [4-4] The pellet according to [4-1] or [4-2], wherein the content of a cyclic dimer consisting of succinic acid and 1,4-butanediol in the pellet is 2500 ppm by mass or less. [4-5] The pellet according to any one of [4-1] to [4-4], wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less. [4-6] The pellet according to any one of [4-5], wherein the molar ratio of constituent units derived from succinic acid to constituent units derived from terephthalic acid (constituent units derived from succinic acid / constituent units derived from terephthalic acid) is 10 / 90 to 90 / 10. [4-6] The pellet according to [4-5], wherein the molar ratio is 40 / 60 to 60 / 40. [4-7] An injection-molded resin pellet product containing at least one of the pellets described in any of [4-1] to [4-6]. [4-8] An extruded resin pellet product containing at least one of the pellets described in any of [4-1] to [4-6].

[0018] According to one aspect of the first invention, pellets containing PBS 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 first invention, biodegradable injection molded articles or extruded articles that can be stably manufactured can be obtained.

[0019] According to one aspect of the second invention, pellets containing PBSA can be obtained that have good blocking resistance and can be stably supplied to a molding machine as a feed material for injection molding, extrusion molding, etc. Furthermore, according to another aspect of the second invention, biodegradable injection-molded or extruded articles containing PBSA can be obtained that can be manufactured more stably.

[0020] According to one aspect of the third invention, pellets containing PBSSe, which 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, according to another aspect of the third invention, biodegradable injection-molded or extruded articles containing PBSSe, which can be manufactured more stably, can be obtained.

[0021] According to one aspect of the fourth invention, pellets containing PBST that are less prone to blocking even when heat and / or pressure are applied can be obtained. According to another aspect of the fourth invention, biodegradable injection-molded or extruded articles that can be manufactured stably can be obtained.

[0022] 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 1-1. 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 2-1 using the Lorentz function. This is a Raman chart (Lorentz-fitted Raman Spectrum) showing the results obtained by fitting the Raman spectrum measured from the pellet containing PBSSe according to Example 3-1 using the Lorentz function. 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 4-1 using the Lorentz function. This is a schematic diagram illustrating one aspect of a part of the manufacturing process (esterification reaction step) of the pellet containing PBST according to this disclosure. This is a schematic diagram illustrating one aspect of a part of the manufacturing process (polycondensation step) of the pellet containing PBST according to this disclosure. This is a schematic diagram illustrating one aspect of a part of the manufacturing process for pellets containing PBST (solvent contact step / cyclic dimer separation step) according to this disclosure. This is a schematic diagram illustrating one aspect of a part of the manufacturing process for pellets containing PBST (drying step) according to this disclosure.

[0023] The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below and can be implemented in various modifications within the scope of its gist. 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. In this specification, expressions representing numerical ranges, such as "XX or more," "YY or less," and "XX to YY," mean numerical ranges including the endpoints XX and YY, unless otherwise specified. When numerical ranges are described in steps, any combination of the upper and lower limits of each numerical range is also disclosed. Furthermore, in this specification, for example, "at least one selected from the group consisting of XX, YY, and ZZ" means any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0024] <First Invention> The inventors conducted further studies to solve two seemingly contradictory problems: improving the blocking resistance of PBS-containing pellets and preventing the occurrence of fisheyes in molded products formed using such pellets due to poor melting of the pellets. In the process, the inventors discovered that the Raman spectrum measured from PBS pellets changes depending on the manufacturing conditions of the pellets. Specifically, the Raman spectrum at 1732 ± 5 cm⁻¹ －１ Peak intensity I, which is attributed to the C=O stretching of succinic acid units in PBS, occurring in the wavenumber range (hereinafter also referred to as the "second wavenumber range") ０２ For the Raman spectrum of 1718±5 cm⁻¹, －１ Peak intensity I, which is attributed to the C=O stretching of succinic acid units of PBS, occurring in the wavenumber range (hereinafter also referred to as the "first wavenumber range") ０１ Ratio I ０１ / I ０２We discovered that the strength ratio (hereinafter also referred to as the "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 above a certain value exhibit excellent blocking resistance, leading to the present invention.

[0025] In other words, a pellet according to one aspect of the present invention contains polybutylene succinate having as its main constituent units a constituent unit derived from succinic acid and a constituent unit derived from 1,4-butanediol. The Raman spectrum measured from the pellet is 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 the fitted Raman spectrum obtained by fitting with a Lorentz function using 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 ０２The strength ratio is preferably 2.0 or higher, more preferably 2.1 or higher, more preferably 2.2 or higher, even more preferably 2.4 or higher, even more preferably 2.5 or higher, and also preferably 3.2 or lower. The range of the strength ratio is preferably 2.0 or higher and 3.2 or lower, more preferably 2.1 or higher and 3.2 or lower, particularly preferably 2.2 or higher and 3.2 or lower, even more preferably 2.3 or higher and 3.2 or lower, even more preferably 2.4 or higher and 3.2 or lower, and especially preferably 2.5 or higher and 3.2 or lower. The strength ratio being 2.0 or higher results in the pellets according to this embodiment having excellent blocking resistance. The inventors speculate that the reason such pellets exhibit excellent blocking resistance is as follows. In the course of further investigation, the inventors observed the changes in the intensity of the peaks observed in the first wavenumber range and the peaks observed in the second wavenumber range in the Raman spectrum when PBS 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 observed in the first wavenumber range decreased, while the intensity of the peaks observed in the second wavenumber range increased. From these findings, 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 crystalline PBS, and the peaks observed in the second wavenumber range are attributed to the C=O expansion and contraction in the succinic acid units of amorphous PBS. Therefore, the intensity ratio (I ０１ / I ０２ ) is considered to be an indicator that shows the ratio of crystalline PBS to amorphous PBS in a pellet containing PBS. And, I ０１ / I ０２However, pellets with a strength ratio of 2.0 or higher are thought to exhibit excellent blocking resistance because the balance between the crystalline and amorphous states of PBS in the pellet is optimized. As a result, these pellets can be stably used in injection molding and extrusion molding, contributing to the more stable production of injection molded and extruded products. Furthermore, a strength ratio of 2.0 to 3.2 can better prevent the occurrence of fish eyes caused by insufficient melting of the pellets in injection molded and extruded products. In other words, since PBS begins to decompose at around 170°C, it is preferable to mold products at a relatively low temperature when obtaining molded products using pellets containing PBS. However, if the molding temperature is lowered, the melting of the pellets may be insufficient, and fish eyes may occur in the resulting molded product due to insufficient melting of the pellets, resulting in a molded product with a problematic appearance. However, by setting the strength ratio to 3.2 or lower, the occurrence of fish eyes in molded products molded at low temperatures is better suppressed, and molded products with a superior appearance can be obtained.

[0026] The reason why pellets with a strength ratio of 2.0 to 3.2 can achieve a high level of both blocking resistance and prevention of fish eye formation is, as mentioned above, the strength ratio (I ０１ / I ０２ ) is considered to be an indicator that shows the ratio of crystalline PBS to amorphous PBS in a pellet containing PBS, ０１ / I ０２ However, pellets within the aforementioned specific numerical range are thought to achieve a high level of both blockage prevention and fish-eye prevention because the balance between the crystalline and amorphous states of PBS in the pellet is more optimized.

[0027] The method for measuring the spectrum of a pellet containing PBS 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 the following Raman spectrometer and under the following conditions: Raman spectrometer: "RAMAN touch" (product name, manufactured by Nanophoton Inc.) Measurement conditions / measurement mode: Point Laser wavelength: 532 nm Laser output: 12 mW (opening of light-reducing filter: 200 / 255) Diffraction grating: 1200 gr / mm Pinhole: 50 μm Exposure time: 10 seconds Number of integrations: 3 Objective lens: 100x Measurement temperature: 25°C

[0028] 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 units of PBS. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range and is 1732 ± 5 cm. －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. Also, X ０ The peak position is represented by 1718 ± 5 cm in this disclosure. －１ , and 1732±5cm －１ This is the result.

[0029]

[0030] 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., X) is determined. ０ = 1718 ± 5 cm－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 peak, and the intensity A (hereinafter also referred to as "A2") obtained by the above formula (1) relating to the second wavenumber range, is I ０１ / I ０２ It corresponds to this.

[0031] <Polybutylene succinate (PBS)> The PBS contained in the pellets according to the present invention is a polyester having as its main constituent units a constituent unit derived from succinic acid and a constituent unit derived from 1,4-butanediol. Specifically, for example, the PBS 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), and a constituent unit derived from 1,4-butanediol, represented by the following structural formula (2). -OC-CH ２ -CH ２ -CO- (1) -O-(CH ２ ) ４ -O- (2)

[0032] 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 of succinic acid. Similarly, "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 of 1,4-butanediol. In this specification, the constituent units of PBS may also be referred to as compound units corresponding to 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 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."

[0033] Furthermore, "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 PBS. Specifically, in the PBS according to this embodiment, the total number of moles of succinic acid units and 1,4-butanediol units is 80 mol% or more of the total number of moles of constituent units constituting PBS. In addition, the PBS according to this embodiment may have a total number of moles of succinic acid units and 1,4-butanediol units that accounts for 90% or more of the total number of moles of constituent units constituting PBS, or 95% or more of the total number of moles of constituent units constituting PBS, and may also be a polyester that does not contain any constituent units other than succinic acid units and 1,4-butanediol units, that is, consists only of succinic acid units and 1,4-butanediol units, and the total number of moles of succinic acid units and 1,4-butanediol units is 100 mol% of the total number of moles of constituent units constituting PBS. By keeping the total number of moles of succinic acid units and 1,4-butanediol units within the above range, a PBS with superior blocking resistance can be obtained. In this specification, when counting the number of moles of constituent units in PBS, the smallest ester unit constituting the PBS is considered to be 1 mole.

[0034] The proportion of succinic acid units in PBS 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 PBS. That is, based on the total number of moles of dicarboxylic acid units in PBS, the proportion of succinic acid units is preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, even more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%. By having the proportion of succinic acid units within the above range, it is possible to obtain PBS with superior heat resistance and mechanical properties.

[0035] Examples of dicarboxylic acids other than succinic acid that can constitute dicarboxylic acid units in PBS include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic anhydride, glutaric acid, adipic 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, sebacic acid, etc., can be derived from plant materials.

[0036] The proportion of 1,4-butanediol units in PBS 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 diol units in PBS. That is, based on the total number of moles of diol units in PBS, the proportion of 1,4-butanediol units is preferably 80 to 100 mol%, more preferably 85 to 100 mol%, even more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%. Since the proportion of 1,4-butanediol units is within the above range, PBS with superior heat resistance and mechanical properties can be obtained.

[0037] Diols other than 1,4-butaneol that can constitute the diol unit in PBS 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.

[0038] PBS 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 acid, polymers of the oxycarboxylic acid, 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.). In particular, by introducing a constituent unit derived from at least one trifunctional polyfunctional compound selected from the group consisting of trifunctional or more oxycarboxylic acids, trifunctional or more alcohols, and trifunctional or more carboxylic acids into the PBS, the intrinsic viscosity of the PBS, as described later, can be increased. Preferred trifunctional or more polyfunctional compounds include oxycarboxylic acids such as malic acid, citric acid, and fumaric acid, and trifunctional or more polyhydric alcohols such as glycerin and trimethylolpropane, with malic acid and trimethylolpropane being particularly preferred.

[0039] The polyfunctional compound units with three or more functions are preferably in an amount of 0.001 to 5 mol%, and particularly preferably 0.05 to 0.5 mol%, relative to the total dicarboxylic acid units in the PBS. By keeping the proportion of polyfunctional compound units with three or more functions in the PBS within the above range, the intrinsic viscosity of the PBS can be adjusted to the following preferred range while more reliably preventing the formation of gel (unmelted material) in the polyester.

[0040] <Physical Properties of Polybutylene Succinate (PBS)> The intrinsic viscosity (IV) of the PBS according to this embodiment is preferably 1.2 dL / g or more, and particularly preferably 1.4 dL / g. It is also preferably 2.2 dL / g or less, and particularly preferably 2.0 dL / g or less. In other words, the intrinsic viscosity of the PBS 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 the PBS within the above range, the mechanical strength of the molded product can be further increased, and the viscosity at the time of melting can be adjusted to an appropriate range. As a result, high-quality injection molded products and extruded products can be manufactured more easily. Note that the intrinsic viscosity depends on the molecular weight of the PBS, and the intrinsic viscosity can be increased as the molecular weight increases.

[0041] The intrinsic viscosity can be measured, for example, in accordance with JIS K7367-1:2002 (ISO 1628-1:1998). Specifically, for example, using an Ubbelohde viscometer and a phenol / tetrachloroethane (mass ratio 1:1) mixed solvent, the intrinsic viscosity can be determined from the following formula (2) by measuring the number of seconds it takes for a 0.5 g / dL PBS solution and the mixed solvent alone to fall at a temperature of 30°C: IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) ... (2) However, in formula (2), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ We will use 0.33.

[0042] <PBS-containing pellets> There are no particular restrictions on the shape or size of the PBS-containing pellets, but it is preferable that they be shaped and sized in a way that is suitable for use in known plastic deformation methods such as injection molding and extrusion molding. Specifically, examples of shapes include cylindrical, elliptical, prismatic, disc-shaped, and spherical shapes. In terms of size, the pellets should be of a size that is generally used. Specifically, examples include those with a diameter or side length of about 0.7 to 12 mm. Furthermore, when the PBS-containing pellets are subjected to the solvent contact process described later, it is preferable, from the viewpoint of extraction efficiency of cyclic dimers by the solvent contact process, that the mass of one pellet particle be 1 to 50 mg, particularly preferably 3 to 40 mg, and even more preferably 5 to 30 mg.

[0043] <Cyclic Dimers of PBS in PBS-Containing Pellets> In pellets containing PBS, the content of cyclic dimers of PBS (hereinafter also simply referred to as "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 2,000 ppm by mass or less, and even more preferably 1,000 ppm by mass or less. By setting 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, cyclic dimers of PBS are compounds produced as by-products 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 refer to cyclic dimers consisting of succinic acid and 1,4-butanediol. Such cyclic dimers can be represented, for example, by the following structural formula (3).

[0044]

[0045] There is no particular lower limit to the cyclic dimer content in pellets containing PBS, and it may be 0 ppm by mass. However, setting the cyclic dimer content to 0 ppm by mass may lead to an increase in the number of steps required to remove the cyclic dimer from the synthesized PBS, and the need for larger equipment for such removal. From the viewpoint of reducing environmental impact, it is preferable to set the content to 1 ppm by mass or more, particularly preferably 50 ppm by mass or more, and even more preferably 100 ppm by mass or more. Therefore, the cyclic dimer content in pellets containing PBS 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, even more preferably 100 to 2000 ppm by mass, and even more preferably 100 to 1000 ppm by mass. The method for quantifying the cyclic dimer in pellets containing PBS is not particularly limited, but for example, the absolute calibration curve method can be used. Specific methods will be explained in the examples. Furthermore, methods for adjusting the content of cyclic dimers in pellets containing PBS will be described later.

[0046] Pellets containing PBS may contain other components besides PBS. One example of such a component is a mold release agent. Examples of mold release agents include those commonly used in injection molding and extrusion molding. Specifically, examples include ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid with ethylene glycol, glycerin, or pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid or montanic acid, etc.) with stearylamine or ethylenediamine, and silicone compounds. The mixing ratio of the mold release agent is preferably 0.001 to 1% by mass, and particularly preferably 0.005 to 0.8% by mass, based on the pellets containing PBS, in order to prevent pellet blocking due to excessive bleeding of the mold release agent onto the pellet surface while improving the release properties of the molded product. Furthermore, additives may be included as other components, as long as they do not impair the objectives of the present invention. Examples of 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, and titanium dioxide; non-plate-shaped fillers; 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.); and antibacterial agents. Furthermore, other resins other than PBS may be included as one of the other components. In this case, the content ratio of other resins in the pellet is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, and may also be 0% by mass, i.e., the resin component in the pellet may be only PBS.

[0047] <Method for Manufacturing PBS-Containing Pellets> PBS-containing pellets can be manufactured, for example, by following steps 1 to 4 below, or steps 1 to 5 below. (Step 1) A dicarboxylic acid component containing at least succinic acid or its ester-forming derivative and a diol component containing at least 1,4-butanediol are mixed in a predetermined ratio under stirring to obtain a raw material slurry. (Step 2) Following step 1, the raw material slurry is heated under normal pressure or under pressure to undergo an esterification reaction to obtain a low-polymer PBS. (Step 3) Following step 2, the obtained low-polymer is gradually depressurized and heated to undergo a melt polycondensation reaction under a polycondensation catalyst. (Step 4) After step 3, the molten PBS is extruded into strands and cut into pellets to obtain pellets containing PBS. (Step 5) If necessary, the pellets obtained in step 4 are processed into a 1 ０１ / I ０２ The process is carried out to control the content of cyclic dimers. Note that a process of air separation and sieving of pellets may be performed between step 4 and step 5, and / or after step 5.

[0048] An example of the above step 2 for obtaining a PBS 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 proportion 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 PBS low polymer.

[0049] An example of the above step 3, in which a melt polycondensation reaction is carried out, is a method using 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.

[0050] The PBS polycondensation catalyst may be added to the reaction system at any stage of the mixing and preparation of the dicarboxylic acid component and the diol component, at any stage of the process of forming the PBS 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 PBS polycondensation catalyst.

[0051] Furthermore, in steps 1 and 2 above, which involve forming a low-polymer PBS, 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. Specifically, examples of antioxidants include Irganox 1330 (manufactured by BASF) and Irganox 1010 (manufactured by BASF), and examples of basic compounds include 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.

[0052] Examples of the above step 4, which involves cutting the synthesized PBS into pellets, include the strand cutting method, in which molten PBS 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 PBS is extruded into water from the nozzle hole and immediately cut.

[0053] <Intensity ratio (I ０１ / I ０２ ) Adjustment method > Pellet containing PBS related to this disclosure ０１ / I ０２This can be adjusted, for example, by adjusting the temperature and time applied to the pellets containing PBS in a step in which the PBS 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").

[0054] <Slow Cooling Process> The slow cooling process can be performed before or during the above process 4. Specifically, the PBS extruded in strand form from the die into a cooling liquid adjusted to a predetermined temperature is held in the cooling liquid in a strand form for a predetermined time. After that, it is cut to form pellets. Alternatively, the PBS 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 (process 4), and the pellets are held in the cooling liquid for a predetermined time. By slowly cooling the molten PBS, the orientation of the molecules of the molten PBS is promoted, making it possible to appropriately develop the crystalline structure of the PBS. Here, if the molten PBS is extruded into, for example, a room temperature (25°C) environment, the PBS will be rapidly cooled, and the PBS molecules will be fixed in a randomly oriented state, so I ０１ / I ０２ It is difficult to make it 2.0 or higher.

[0055] Here, the temperature of the cooling liquid used to extrude the molten PBS into strands is preferably 35 to 70°C, particularly preferably 40 to 65°C, and even more preferably 45 to 60°C. The time for holding the PBS within the above temperature range is I ０１ / I ０２ While there are no particular restrictions as long as it can be set to 2.0 or higher, it is preferable to set it to 0.1 to 10 minutes, more preferably to 0.5 to 5 minutes, and even more preferably to 1 to 3 minutes. If the temperature of the cooling liquid is set higher within the above range, adjustments such as shortening the holding time may be made as desired. ０１ / I ０２It can be appropriately adjusted according to the value of

[0056] In addition, the type of the cooling liquid is not particularly limited as long as it does not react with PBS or dissolve PBS during the above temperature range and the above holding time. Examples of such cooling liquids include, for example, water and the like.

[0057] Note that as the cooling liquid, pellets that have undergone a step of being maintained in water (hot water) at a temperature exceeding the above temperature range, for example, at a temperature of 90°C for a predetermined time, although the reason is not clear, I ０１ / I ０２ The value of may exceed 3.2. That is, the proportion of the crystalline component of PBS in the pellet becomes too large. And, in the molded product obtained using this pellet, many fish eyes may occur due to poor melting of the pellet.

[0058] <Solvent contact step> Following the above slow cooling step, it is preferable to perform a solvent contact step as step 5. This step contributes to reducing the content of the cyclic dimer in the pellet and further adjusting the value of I ０１ / I ０２ By passing through this step, the content of the cyclic dimer in the pellet can be adjusted to a smaller value within the above-mentioned range, and I ０１ / I ０２ can be adjusted to a higher value within the range of 2.0 or more, preferably 2.0 to 3.,2. This step includes a step of contacting the pellet obtained through the above slow cooling step with a solvent capable of dissolving the cyclic dimer adjusted to a predetermined temperature for a predetermined time. By passing through this step, at least a part of the cyclic dimer in the pellet can be removed. That is, the inventors of the present invention presume that the cyclic dimer in the pellet is a component that inhibits the crystallization of PBS. By forming a macroscopic crystal structure of PBS in the above slow cooling step, I ０１ / I ０２Pellets with a value of 2.0 or more can be obtained. Moreover, by subjecting the pellets to the solvent contact step, cyclic dimers can be removed from the pellets, and the content of the cyclic dimers can be made 4000 mass ppm or less. It is presumed that in the pellets, a microscopic crystal structure of PBS is likely to be formed. Here, in the solvent contact step, since the pellets are held at a predetermined temperature for a predetermined time, in a state where the crystallization inhibiting component (cyclic dimer) is less, the orientation of the PBS molecules in the pellets further proceeds, and I ０１ / I ０２ is considered to be able to obtain pellets having a higher value within the range of 2.0 or more and 3.2 or less. Even if only the solvent contact step is performed without going through the slow cooling step, it is difficult to make I ０１ / I ０２ 2.0 or more. That is, in order to develop a microscopic crystal structure of PBS by removing cyclic dimers in the solvent contact step, it is considered necessary to perform a slow cooling step prior to the solvent contact step to form a macroscopic crystal structure of PBS in the pellets.

[0059] As the solvent used in this step, it is preferable that it does not substantially dissolve PBS even by contact with the pellets at a predetermined temperature and for a predetermined time, while being able to dissolve cyclic dimers well. Examples of such solvents include, for example, C1-C4 alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, etc.). Also, it can 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 alcohol aqueous solution is not particularly limited. For example, from the viewpoint of good solubility of the cyclic dimer, it is preferably 10 mass% or more and less than 100 mass% based on the alcohol aqueous solution.

[0060] Furthermore, the solvent temperature in the solvent contact step is preferably 80°C or lower, particularly preferably 75°C or lower, and even more preferably 70°C or lower, so as not to excessively increase the crystallinity of PBS. As a lower limit, from the viewpoint of better extracting the cyclic dimer and appropriately oriented the PBS molecules, it is preferably 30°C or higher, particularly preferably 40°C or higher, and even more preferably 50°C or higher. In other words, the solvent temperature range in the solvent contact step is preferably 30 to 80°C, particularly preferably 40 to 75°C, and even more preferably 50 to 70°C. Furthermore, as for the processing time, from the viewpoint of better extracting the cyclic dimer and appropriately oriented the PBS molecules, it is preferably 0.1 to 10 hours, particularly preferably 0.5 to 8 hours, and even more preferably 1 to 5 hours.

[0061] Specific methods for the solvent contact process described above include, for example, the methods i) and ii) below: i) A method in which pellets obtained through the slow cooling process and a solvent are placed in a processing tank, and after contacting them at the predetermined temperature range for the predetermined time, the pellets are recovered from the processing tank; ii) A method in which pellets obtained through the slow cooling process are continuously supplied to the processing tank, and the solvent, adjusted to the predetermined temperature range, is flowed in parallel or countercurrent to the flow of pellets, and after contacting the pellets to be processed with the solvent for the predetermined time, the processed pellets are continuously recovered. The specific methods and apparatus used in such processing are not particularly limited, but the method and apparatus described in Patent Document 3, which allows for continuous adjustment of the cyclic dimer content of the pellets, can be suitably used.

[0062] <Uses> The I obtained as described above ０１ / I ０２ However, pellets containing PBS having a ratio of at least 2.0 and preferably 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, they do not hinder the supply stability to the molding machine during molding, making them extremely useful as pellets for injection molding and extrusion molding. ０１ / I ０２However, pellets containing PBS having a ratio of at least 2.0 to 3.2, and preferably 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, and can prevent the occurrence of fish eyes caused by poor melting of the pellets. As a result, molded products with excellent appearance can be manufactured without hindering the supply stability to the molding machine during molding, making them extremely useful as pellets for injection molding and extrusion molding.

[0063] <Molded Products (Injection Molded Products, Extruded Products)> Resin pellets for obtaining injection molded products or extruded products may consist only of pellets containing PBS. Here, two types of pellets containing PBS with different molar ratios of succinic acid units and 1,4-butanediol units may also be mixed to form resin pellets.

[0064] Injection molded and extruded articles of resin pellets containing PBS as described in this disclosure are obtained by molding using resin pellets containing PBS as described in this disclosure by injection molding or extrusion molding. Any shape is possible as long as it can be molded by injection molding or extrusion molding. The applications of injection molded or extruded articles are not limited in any way. Examples of injection molded articles include cutlery and various containers (cups, cosmetic containers, food containers, detergent containers, bleach containers, etc.). Examples of extruded articles include packaging materials (packaging films) and agricultural films (agricultural mulch films).

[0065] <Second Invention; PBSA> The inventors conducted further studies to solve the problem of improving the blocking resistance of pellets containing PBSA. In the process, the inventors found that the Raman spectrum measured from PBSA pellets changes depending on the manufacturing conditions of the pellets. Specifically, the Raman spectrum at 1732 ± 5 cm⁻¹ －１ Peak intensity I, which is attributed to the C=O stretching of succinic acid units of PBSA, occurring in the wavenumber range (hereinafter also referred to as the "second wavenumber range") ０２ For the Raman spectrum of 1718±5 cm⁻¹,－１ Peak intensity I, which is attributed to the C=O stretching of succinic acid units of PBSA, occurring in the wavenumber range (hereinafter also referred to as the "first wavenumber range") ０１ Ratio I ０１ / I ０２ We 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.

[0066] In other words, a pellet according to one aspect of the present invention contains a polybutylene succinate adipate 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. The Raman spectrum measured from the pellet is 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 ０２The 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 why the pellets according to this embodiment exhibit excellent blocking resistance is that the intensity ratio is 1.1 or higher. In the course of further investigation described above, the inventors observed the changes in the intensity of the peaks observed in the first wavenumber range and the peaks observed in 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 increases, the intensity of the peaks observed in the first wavenumber range decreases, and the intensity of the peaks observed in the second wavenumber range increases. Furthermore, in the Raman spectrum of PBSA, the peaks appearing in the first and second wavenumber ranges are attributed to the C=O in the succinic acid units of PBSA. From this, it is presumed that the peak observed in the first wavenumber range is attributed to the C=O expansion and contraction in the succinic acid units of crystalline PBSA, and the peak observed in the second wavenumber range is attributed to the C=O expansion and contraction in the succinic acid units of amorphous PBSA. Therefore, I ０１ / I ０２ This is considered to be an indicator showing the ratio of crystalline PBSA to amorphous PBSA in a pellet containing PBSA. ０１ / I ０２However, pellets with a strength 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 more stable production of injection-molded and extruded products. Furthermore, pellets with a strength ratio of 1.1 to 2.3 not only exhibit excellent blocking resistance but also more reliably prevent the generation of fine powder. In other words, during transportation and molding, friction between pellets or between pellets and the walls of molding equipment can cause some of the pellets to chip, generating 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 pellet 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 in injection molding and extrusion molding, and are less likely to contaminate extruders and molding machines, thus contributing to the more stable and efficient production of injection-molded and extruded products.

[0067] 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 showing the ratio of crystalline PBSA to amorphous PBSA in a pellet containing PBSA, ０１ / I ０２However, 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.

[0068] 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 the following Raman spectrometer and under the following conditions: Raman spectrometer: "RAMAN touch" (product name, manufactured by Nanophoton Inc.) Measurement conditions / measurement mode: Point Laser wavelength: 532 nm Laser output: 20 mW (opening of light-reducing filter: 210 / 255) Diffraction grating: 1200 gr / mm Pinhole: 50 μm Exposure time: 10 seconds Number of integrations: 5 Objective lens: 100x Measurement temperature: 25°C

[0069] 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 The peak of the Raman scattering intensity has its peak top in the first wavenumber range and is 1732 ± 5 cm. －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. Also, X ０ The peak position is represented by 1718 ± 5 cm in this disclosure. －１ , and 1732±5cm －１ This is the result.

[0070]

[0071] 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., X) is determined. ０ = 1718 ± 5 cm －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 peak, and the intensity A (hereinafter also referred to as "A2") obtained by the above formula (1) relating to the second wavenumber range, is I ０１ / I ０２ It corresponds to this.

[0072] <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-CH ２ -CH ２ -CO- (1) -OC-(CH ２ ) ４ -CO- (2) -O-(CH ２ ) ４ -O- (3)

[0073] 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 of 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 of 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 of 1,4-butanediol. In this specification, the constituent units of PBSA may also be referred to as compound units corresponding to the compounds from which each constituent unit is derived. Specifically, for example, a constituent unit derived from succinic acid may be called a "succinic acid unit," a constituent unit derived from adipic acid may be called an "adipic acid unit," a constituent unit derived from 1,4-butanediol may be called a "1,4-butanediol unit," a constituent unit derived from a carboxylic acid may be called a "carboxylic acid unit," and a constituent unit derived from a diol may be called a "diol unit."

[0074] 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 that make up 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 furthermore, 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 the PBSA is considered to be 1 mole.

[0075] 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.

[0076] 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 having 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.

[0077] 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.

[0078] 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. That is, based on the total number of moles of diol units in PBSA, the proportion of 1,4-butanediol units 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, PBSA with superior heat resistance and mechanical properties can be obtained.

[0079] 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.

[0080] 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 acid, polymers of the oxycarboxylic acid, 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.).

[0081] In particular, by introducing constituent units derived from at least one trifunctional polyfunctional compound selected from the group consisting of trifunctional or more oxycarboxylic acids, trifunctional or more alcohols, and trifunctional or more carboxylic acids into PBSA, the intrinsic viscosity of PBSA, as described later, can be increased. Preferred trifunctional or more polyfunctional compounds include oxycarboxylic acids such as malic acid, citric acid, and fumaric acid, and trifunctional or more polyhydric alcohols such as glycerin and trimethylolpropane, with malic acid and trimethylolpropane being particularly preferred.

[0082] Based on the total number of moles of dicarboxylic acid units in PBSA, the proportion of the three- or more-function polyfunctional compound units is preferably 0.001 to 5 mol%, and particularly preferably 0.05 to 0.5 mol%. By keeping the proportion of three- or more-function polyfunctional compound units in PBSA within the above range, the intrinsic viscosity of PBSA can be more easily adjusted within the following preferred range while more reliably preventing the formation of gel (unmelted material) in the polyester.

[0083] <Physical Properties of PBSA> The intrinsic viscosity (IV) of PBSA is preferably 1.2 dL / g or higher, and particularly preferably 1.4 dL / g. It is also preferably 2.2 dL / g or lower, and particularly preferably 2.0 dL / g or lower. In other words, the intrinsic viscosity of PBSA is preferably 1.2 dL / g or higher and 2.2 dL / g or lower, and particularly preferably 1.4 dL / g or higher and 2.0 dL / g or lower. By setting the intrinsic viscosity of PBSA within the above range, the mechanical strength of the molded product can be further increased, and the viscosity during melting can be adjusted to an appropriate range. As a result, high-quality injection molded products and extruded products can be manufactured more easily. Note that the intrinsic viscosity depends on the molecular weight of PBSA, and the higher the molecular weight, the higher the intrinsic viscosity can be.

[0084] The intrinsic viscosity can be measured, for example, in accordance with JIS K7367-1:2002 (ISO 1628-1:1998). Specifically, for example, using an Ubbelohde viscometer and a phenol / tetrachloroethane (mass ratio 1:1) mixed solvent, the intrinsic viscosity can be determined from the following formula (2) by measuring the number of seconds it takes for a 0.5 g / dL PBSA solution and the mixed solvent alone to fall at a temperature of 30°C: IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) ... (2) However, in formula (2), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ We will use 0.33.

[0085] <PBSA-containing pellets> There are no particular restrictions on the shape or size of the PBSA-containing pellets, but it is preferable that they be shaped and sized in a way that is suitable for use in known plastic deformation methods such as injection molding and extrusion molding. Specifically, examples of shapes include cylindrical, elliptical, prismatic, disc-shaped, and spherical shapes. In terms of size, the pellets should be of a size that is generally used. Specifically, examples include those with a diameter or side length of about 0.7 to 12 mm. Furthermore, when the PBSA-containing pellets are subjected to the solvent contact process described later, it is preferable, from the viewpoint of extraction efficiency of cyclic dimers by the solvent contact process, that the mass of one pellet particle be 1 to 50 mg, particularly preferably 3 to 40 mg, and even more preferably 5 to 30 mg.

[0086] <Cyclic Dimers in PBSA-Containing Pellets> 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 setting 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 consisting of succinic acid and 1,4-butanediol. Such a cyclic dimer can be represented, for example, by the following structural formula (4).

[0087]

[0088] There is no particular lower limit to the content of cyclic dimers in pellets containing PBSA, and it may be 0 ppm by mass. However, setting the cyclic dimer content to 0 ppm by mass may lead to an increase in the number of steps required to remove cyclic dimers from synthesized PBSA, and the need for larger equipment for such removal. From the viewpoint of reducing environmental impact, it is preferable to set the content to 1 ppm by mass or more, particularly preferably 50 ppm by mass or more, and even more preferably 100 ppm by mass or more. Therefore, the cyclic dimer content 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. Furthermore, the method for adjusting the content of cyclic dimers in pellets containing PBSA will be described later.

[0089] Pellets containing PBSA may contain other components besides PBSA. One example of such a component is a mold release agent. Examples of mold release agents include those commonly used in injection molding and extrusion molding. Specifically, examples include ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid with ethylene glycol, glycerin, or pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid or montanic acid, etc.) with stearylamine or ethylenediamine, and silicone compounds. The mixing ratio of the mold release agent is preferably 0.001 to 1% by mass, and particularly preferably 0.005 to 0.8% by mass, based on the pellets containing PBSA, in order to prevent pellet blocking due to excessive bleeding of the mold release agent onto the pellet surface while improving the release properties of the molded product. Furthermore, additives may be included as other components, as long as they do not impair the objectives of the present invention. Examples of 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, and titanium dioxide; non-plate-like fillers; 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.); and antibacterial agents. Furthermore, other resins other than PBSA may be included as one of the other components. In this case, the content of other resins in the pellet is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, and may also be 0% by mass, i.e., the resin component in the pellet may be only PBSA.

[0090] <Method for producing pellets containing PBSA> Pellets containing PBSA can be produced, for example, by following steps 1 to 4 or steps 1 to 5 below. (Step 1) A dicarboxylic acid component containing 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 containing at least 1,4-butanediol are mixed in a predetermined proportion under stirring to obtain a raw material slurry. (Step 2) Following step 1, the raw material slurry is heated under normal pressure or under pressure to undergo an esterification reaction to obtain a low PBSA polymer. (Step 3) Following step 2, the obtained low polymer is gradually reduced in pressure and heated to undergo a melt polycondensation reaction under a polycondensation catalyst. (Step 4) Following step 3, 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 are processed into an I ０１ / I ０２ Processing is performed to control the content of cyclic dimers. Note that a process of air separation and sieving of pellets may be performed between step 4 and step 5, and / or after step 5.

[0091] An example of the above step 2 for obtaining a low PBSA 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 proportion 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 low PBSA polymer.

[0092] An example of the above step 3, in which a melt polycondensation reaction is carried out, is a method using 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.

[0093] The PBSA polycondensation catalyst may be added to the reaction system at any stage of the mixing and preparation of the dicarboxylic acid component and the diol component, 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 may be used as the PBSA polycondensation catalyst.

[0094] 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. Specifically, examples of antioxidants include Irganox 1330 (manufactured by BASF) and Irganox 1010 (manufactured by BASF), and examples of basic compounds include 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.

[0095] 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.

[0096] <Intensity ratio (I ０１ / I ０２ ) Adjustment method > Pellet containing PBSA related to this disclosure ０１ / I ０２For example, this can be adjusted by adjusting the temperature and time applied to the pellets 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 the pellets in a solvent adjusted to a predetermined temperature for a predetermined time (hereinafter also referred to as the "solvent contact step").

[0097] <Slow Cooling Process> The slow cooling process can be performed before or during the above process 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 a 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 (process 4), and the pellets are held in the cooling liquid for a predetermined time. By slowly cooling the molten PBSA, the orientation of the molecules of the molten PBSA is promoted, making it possible to appropriately develop the crystalline structure of the PBSA. Here, if the 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, so I ０１ / I ０２ It becomes difficult to set it to 1.1 or higher.

[0098] 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 ０２ While 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 pellets containing PBSA, I ０１ / I ０２The 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.

[0099] 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.

[0100] 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 example, at a temperature of 60°C, are subject to the following conditions, although the reason is unclear. 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 the pellets themselves or with the molding equipment.

[0101] <Solvent Contact Process> It is preferable to carry out a solvent contact process as step 5 following the slow cooling process described above. This process 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 ０２It is possible to adjust this to a higher value, preferably within the range of 1.1 to 2.3, which is 1.1 or higher. This step includes bringing the pellet obtained through the slow cooling step into contact 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 pellet can be removed, and the content of the cyclic dimer in the pellet can be adjusted to 4000 ppm by mass or less. That is, the inventors surmise that the cyclic dimer in the pellet is a component that inhibits the crystallization of PBSA. In the slow cooling step, by forming a macroscopic crystalline structure of PBSA, 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 a microcrystalline structure of PBSA can 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 there are few crystallization-inhibiting components (cyclic dimers), the orientation of PBSA molecules in the pellets progresses further, and I ０１ / I ０２ However, it is considered that pellets with a higher value, preferably within the range of 1.1 or more, and preferably between 1.1 and 2.3, can be obtained. Note that even if only the solvent contact step is performed without the slow cooling step, ０１ / I ０２ It is difficult to make the ratio 1.1 or higher. In other words, in order to develop the microcrystalline structure of PBSA by removing the cyclic dimer in the solvent contact process, 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.

[0102] The solvent used in this process is preferably one that does not substantially dissolve the PBSA even when in 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.

[0103] 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.

[0104] Specific methods for the solvent contact process described above include, for example, the methods i) and ii) below: i) A method in which pellets obtained through the slow cooling process and a solvent are placed in a processing tank, and after contacting them at the predetermined temperature range for the predetermined time, the pellets are collected from the processing tank; ii) A method in which pellets obtained through the slow cooling process are continuously supplied to the processing tank, and the solvent, adjusted to the predetermined temperature range, is flowed in parallel or countercurrent to the flow of pellets, and after contacting the pellets to be processed with the solvent for the predetermined time, the processed pellets are continuously collected.

[0105] The specific methods and apparatus used in the processing of such methods 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.

[0106] <Uses> The I obtained as described above 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 contain cyclic dimers at a concentration 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 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 useful as pellets for injection molding and extrusion molding to obtain biodegradable molded products.

[0107] <Molded Products (Injection Molded Products, Extruded Products)> Resin pellets for obtaining injection molded products or extruded products may consist solely of pellets containing PBSA. Here, two or more types of PBSA pellets with different molar ratios of succinic acid units, adipic acid units, and 1,4-butanediol units may also be mixed to form resin pellets.

[0108] Injection molded articles and extruded articles of resin pellets containing PBSA as described in this disclosure are obtained by molding using resin pellets containing PBSA as described in this disclosure by injection molding or extrusion molding.

[0109] The molded shape can be any shape that can be molded by injection molding or extrusion molding. There are no limitations on the use of injection-molded or extruded products. Examples of injection-molded products include cutlery and various containers (cups, cosmetic containers, food containers, detergent containers, bleach containers, etc.). Examples of extruded products include packaging materials (packaging films) and agricultural films (agricultural mulch films).

[0110] <Third Invention> The inventors conducted further studies to solve the problem of improving the blocking resistance of pellets containing PBSSe. In the process, the inventors found that the Raman spectrum measured from PBSSe pellets changes depending on the manufacturing conditions of the pellets. Specifically, the Raman spectrum at 1732 ± 5 cm⁻¹ －１ The Raman spectrum at 1718±5 cm⁻¹ corresponds to the peak intensity attributable to the C=O stretching of succinic acid units of PBSSe that occurs in the wavenumber range (hereinafter also referred to as the "second wavenumber range"), －１ We discovered that the peak intensity attributable to the C=O stretching of succinic acid units of PBSSe that appears in the wavenumber range (hereinafter also referred to as the "first wavenumber range") is significantly greater in pellets manufactured through a slow cooling process than in pellets manufactured without a slow cooling process, and that pellets with this intensity ratio of 1.7 or higher can have excellent blocking resistance, leading to the present invention.

[0111] In other words, a pellet according to one aspect of the present invention contains polybutylene succinate sebacate having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from sebacic acid, and a constituent unit derived from 1,4-butanediol. The Raman spectrum measured from the pellet is 1680 to 1780 cm⁻¹. －１ The spectrum in the wavenumber range is 1718±5 cm⁻¹. －１The 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 The intensity ratio is 1.7 or higher, preferably 1.9 or higher, more preferably 2.2 or higher, and also preferably 3.4 or lower. The range of the intensity ratio is preferably 1.7 or higher and 3.4 or lower, more preferably 1.9 or higher and 3.4 or lower, and particularly preferably 2.2 or higher and 3.2 or lower. The inventors speculate that the reason the pellets according to this embodiment exhibit excellent blocking resistance is that the intensity ratio is 1.7 or higher. In the course of further investigation, the inventors observed the changes in the intensity of the peaks observed in the first wavenumber range and the peaks observed in the second wavenumber range in the Raman spectrum when PBSSe was heated to transition PBSSe from a crystalline state to an amorphous state. As a result, they found that as the temperature increases, the intensity of the peaks observed in the first wavenumber range decreases, while the intensity of the peaks observed in the second wavenumber range increases. Furthermore, in the Raman spectrum of PBSSe, the peaks appearing in the first and second wavenumber ranges are attributed to the C=O in the succinic acid units of PBSSe. From this, it is presumed that the peak observed in the first wavenumber range is attributed to the C=O expansion and contraction in the succinic acid units of crystalline PBSSe, and the peak observed in the second wavenumber range is attributed to the C=O expansion and contraction in the succinic acid units of amorphous PBSSe. Therefore, the intensity ratio (I ０１ / I ０２ ) is considered to be an index that indicates the ratio of crystalline PBSSe and amorphous PBSSe in a pellet containing PBSSe. And, I ０１ / I ０２However, pellets with a strength ratio of 1.7 or higher are thought to have an optimized balance between the crystalline and amorphous states of PBSSe in the pellet, making them less prone to blocking even when heated or pressurized. As a result, pellets containing PBSSe 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 more stable production of injection molded and extruded products. Furthermore, pellets with a strength ratio of 1.7 to 3.4 not only exhibit excellent blocking resistance but also more reliably prevent the generation of fine powder. In other words, during transportation and molding, friction between pellets or between pellets and the walls of molding equipment can cause some of the pellets to chip, generating 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 pellet supplied, and a decrease in the production cycle due to the need for cleaning of equipment such as extruders and molding machines. However, pellets containing PBSSe with a strength ratio of 1.7 to 3.4 exhibit excellent blocking resistance and suppress the generation of fine powder. As a result, these pellets can be stably used in injection molding and extrusion molding, and are less likely to contaminate extruders and molding machines, thus contributing to the more stable and efficient production of injection-molded and extruded products.

[0112] The reason why pellets with a strength ratio of 1.7 to 3.4 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 index that shows the ratio of crystalline PBSSe and amorphous PBSSe in a pellet containing PBSSe, ０１ / I ０２However, pellets within the aforementioned specific numerical range are thought to have a more optimized balance between the crystalline and amorphous states of PBSSe within the pellet. As a result, blocking is less likely to occur even when heated or pressurized, and the embrittlement of the pellet surface is suppressed, making it less likely for fine powder to be generated due to friction between pellets or between pellets and the molding device. Consequently, pellets containing PBSSe according to the present invention are thought to achieve a high level of both blocking resistance and prevention of fine powder generation.

[0113] The method for measuring the spectrum of a pellet containing PBSSe 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 the following Raman spectrometer and under the following conditions: Raman spectrometer: "RAMAN touch" (product name, manufactured by Nanophoton Inc.) Measurement conditions / measurement mode: Point Laser wavelength: 532 nm Laser output: 20 mW (opening of light-reducing filter: 210 / 255) Diffraction grating: 1200 gr / mm Pinhole: 50 μm Exposure time: 10 seconds Number of integrations: 3 Objective lens: 100x Measurement temperature: 25°C

[0114] 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 PBSSe. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range and is 1732 ± 5 cm. －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. Also, X ０ The peak position is represented by 1718 ± 5 cm in this disclosure. －１ , and 1732±5cm －１ This is the result.

[0115]

[0116] 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., X) is determined. ０ = 1718 ± 5 cm －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 peak, and the intensity A (hereinafter also referred to as "A2") obtained by the above formula (1) relating to the second wavenumber range, is I ０１ / I ０２ It corresponds to this.

[0117] <Polybutylene succinate sebacate (PBSSe)> The PBSSe 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 sebacic acid, and a constituent unit derived from 1,4-butanediol. Specifically, for example, the PBSSe 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 sebacic 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-CH ２ -CH ２ -CO- (1) -OC-(CH ２ ) ８ -CO- (2) -O-(CH ２ ) ４ -O- (3)

[0118] 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 of succinic acid. Similarly, "constituent units derived from sebacic acid" refers to the constituent units corresponding to sebacic acid, that is, the constituent units formed by the reaction of the two carboxyl groups of sebacic 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 of 1,4-butanediol. In this specification, the constituent units of PBSSe may also 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 called a "succinic acid unit," a constituent unit derived from sebacic acid may be called a "sebacic acid unit," a constituent unit derived from 1,4-butanediol may be called a "1,4-butanediol unit," a constituent unit derived from a carboxylic acid may be called a "carboxylic acid unit," and a constituent unit derived from a diol may be called a "diol unit."

[0119] 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 PBSSe. Specifically, in the PBSSe according to this embodiment, the total number of moles of succinic acid units, sebacic acid units, and 1,4-butanediol units is 80 mol% or more of the total number of moles of constituent units that make up PBSSe. Furthermore, the PBSSe according to this embodiment may be a polyester in which the total number of moles of succinic acid units, sebacic acid units, and 1,4-butanediol units is 90% or more of the total number of moles of constituent units constituting PBSSe, and may be 95% or more of the total number of moles of constituent units constituting PBSSe, and furthermore, in which no constituent units other than succinic acid units, sebacic acid units, and 1,4-butanediol units are included at all, that is, consisting only of succinic acid units, sebacic acid units, and 1,4-butanediol units, and the total number of moles of succinic acid units, sebacic acid units, and 1,4-butanediol units is 100 mol% of the total number of moles of constituent units constituting PBSSe.In this specification, when counting the number of moles of constituent units in PBSSe, the smallest ester unit constituting PBSSe is considered to be 1 mole.

[0120] The total ratio of succinic acid units and sebacic acid units in PBSSe is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and may be 100 mol% relative to the total dicarboxylic acid units of PBSSe. That is, based on the total number of moles of dicarboxylic acid units in PBSSe, the ratio of the total number of moles of succinic acid units and sebacic acid units is preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, and more preferably 90 to 100 mol%. By having the ratio of the total number of moles of succinic acid units and sebacic acid units relative to the total number of moles of dicarboxylic acid units in PBSSe within the above range, it is possible to obtain PBSSe with superior biodegradability and mechanical properties.

[0121] The ratio of succinic acid units to sebacic acid units in PBSSe is preferably such that the proportion of moles of succinic acid units is 70 mol% or more, particularly preferably 80 mol% or more, and may be 95 mol% or less, preferably 90 mol% or less, and even more preferably 89 mol% or less, based on the total number of moles of succinic acid units and sebacic acid units. In other words, the molar ratio of succinic acid units to sebacic acid units in PBSSe is preferably succinic acid units / sebacic acid units = 70 / 30 to 95 / 5, particularly preferably 70 / 30 to 90 / 10, more preferably 80 / 20 to 90 / 10, and especially preferably 80 / 20 to 89 / 11. By having the molar ratio of succinic acid units to sebacic acid units within the above range, PBSSe with superior biodegradability and mechanical properties can be obtained.

[0122] Other dicarboxylic acids that can constitute the dicarboxylic acid unit in PBSSe are not particularly limited, but include, for example, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic 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.

[0123] The proportion of 1,4-butanediol units in PBSSe 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 diol units in PBSSe. That is, based on the total number of moles of diol units in PBSSe, the proportion of 1,4-butanediol units is preferably 80 to 100 mol%, more preferably 85 to 100 mol%, even more preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%. Since the proportion of 1,4-butanediol units is within the above range, PBSSe with superior heat resistance and mechanical properties can be obtained.

[0124] Diols other than 1,4-butaneol that can constitute the diol unit in PBSSe 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 1,4-butaneol. Furthermore, ethylene glycol, 1,3-propanediol, and 1,4-butanediol can be derived from plant materials.

[0125] PBSSe 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 acid, polymers of the oxycarboxylic acid, 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.).

[0126] In particular, by introducing a constituent unit derived from at least one trifunctional polyfunctional compound selected from the group consisting of trifunctional or more oxycarboxylic acids, trifunctional or more alcohols, and trifunctional or more carboxylic acids into PBSSe, the intrinsic viscosity of PBSSe, as described later, can be increased. Preferred trifunctional or more polyfunctional compounds include oxycarboxylic acids such as malic acid, citric acid, and fumaric acid, and trifunctional or more polyhydric alcohols such as glycerin and trimethylolpropane, with malic acid and trimethylolpropane being particularly preferred.

[0127] The polyfunctional compound units with three or more functions are preferably in an amount of 0.001 to 5 mol%, and particularly preferably 0.05 to 0.5 mol%, relative to the total dicarboxylic acid units in PBSSe. By keeping the proportion of polyfunctional compound units with three or more functions in PBSSe within the above range, the intrinsic viscosity of PBSSe can be adjusted to the following preferred range while more reliably preventing the formation of gel (unmelted material) in the polyester.

[0128] <Physical Properties of PBSSe> The intrinsic viscosity (IV) of PBSSe is preferably 1.2 dL / g or higher, and particularly preferably 1.4 dL / g. It is also preferably 2.2 dL / g or lower, and particularly preferably 2.0 dL / g or lower. In other words, the intrinsic viscosity of PBSSe is preferably 1.2 dL / g or higher and 2.2 dL / g or lower, and particularly preferably 1.4 dL / g or higher and 2.0 dL / g or lower. By setting the intrinsic viscosity of PBSSe within the above range, the mechanical strength of the molded product can be further increased, and the viscosity during melting can be adjusted to an appropriate range. As a result, high-quality injection molded products and extruded products can be manufactured more easily. Note that the intrinsic viscosity depends on the molecular weight of PBSSe, and the higher the molecular weight, the higher the intrinsic viscosity can be.

[0129] The intrinsic viscosity can be measured, for example, in accordance with JIS K7367-1:2002 (ISO 1628-1:1998). Specifically, for example, using an Ubbelohde viscometer and a phenol / tetrachloroethane (mass ratio 1:1) mixed solvent, the intrinsic viscosity can be determined from the following formula (2) by measuring the number of seconds it takes for a 0.5 g / dL PBSSe solution and the mixed solvent alone to fall at a temperature of 30°C: IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) ... (2) However, in formula (2), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ We will use 0.33.

[0130] <PBSSe-containing pellets> There are no particular restrictions on the shape or size of the PBSSe-containing pellets, but it is preferable that they be shaped and sized in a way that is suitable for use in known plastic deformation methods such as injection molding and extrusion molding. Specifically, examples of shapes include cylindrical, elliptical, prismatic, disc-shaped, and spherical shapes. In terms of size, the size of the pellets should be a size that is generally used. Specifically, examples include a diameter or side length of about 0.7 to 12 mm. Furthermore, when the PBSSe-containing pellets are subjected to the solvent contact process described later, it is preferable, from the viewpoint of extraction efficiency of cyclic dimers by the solvent contact process, that the mass of one pellet particle be 1 to 50 mg, particularly preferably 3 to 40 mg, and even more preferably 5 to 30 mg.

[0131] <Cyclic Dimers in Pellets Containing PBSSe> In pellets containing PBSSe, 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 2,000 ppm by mass or less, and even more preferably 1,500 ppm by mass or less. By setting 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 consisting of succinic acid and 1,4-butanediol. Such a cyclic dimer can be represented, for example, by the following structural formula (4).

[0132]

[0133] There is no particular lower limit to the content of cyclic dimers in pellets containing PBSSe, and it may be 0 ppm by mass. However, setting the cyclic dimer content to 0 ppm by mass may lead to an increase in the number of steps required to remove cyclic dimers from synthesized PBSSe, and the need for larger equipment for such removal. From the viewpoint of reducing environmental impact, it is preferable to set the content to 1 ppm by mass or more, particularly preferably 50 ppm by mass or more, and even more preferably 100 ppm by mass or more. Therefore, the cyclic dimer content in pellets containing PBSSe 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, even more preferably 100 to 2000 ppm by mass, and even more preferably 100 to 1500 ppm by mass. The method for quantifying cyclic dimers in pellets containing PBSSe is not particularly limited, but for example, the absolute calibration curve method can be used. The specific method will be explained in the examples. Furthermore, the method for adjusting the cyclic dimer content in pellets containing PBSSe will be described later.

[0134] Pellets containing PBSSe may contain other components besides PBSSe. One example of such a component is a mold release agent. Examples of mold release agents include those commonly used in injection molding and extrusion molding. Specifically, examples include ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid with ethylene glycol, glycerin, or pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid or montanic acid, etc.) with stearylamine or ethylenediamine, and silicone compounds. The mixing ratio of the mold release agent is preferably 0.001 to 1% by mass, and particularly preferably 0.005 to 0.8% by mass, based on the pellets containing PBSSe, in order to prevent pellet blocking due to excessive bleeding of the mold release agent onto the pellet surface while improving the release properties of the molded product. Furthermore, additives may be included as other components, as long as they do not impair the objectives of the present invention. Examples of 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, and titanium dioxide; non-plate-like fillers; 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.); and antibacterial agents. Furthermore, other resins other than PBSSe may be included as one of the other components. In this case, the content of other resins in the pellet is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, and may also be 0% by mass, i.e., the resin component in the pellet may be only PBSSe.

[0135] <Method for producing pellets containing PBSSe> Pellets containing PBSSe can be produced, for example, by following steps 1 to 4 or steps 1 to 5 below. (Step 1) A dicarboxylic acid component containing 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 sebacic acid and its ester-forming derivatives, and a diol component containing at least 1,4-butanediol are mixed in a predetermined proportion under stirring to obtain a raw material slurry. (Step 2) Following step 1, the raw material slurry is heated under normal pressure or under pressure to undergo an esterification reaction to obtain a PBSSe low polymer. (Step 3) Following step 2, the obtained low polymer is gradually reduced in pressure and heated to undergo a melt polycondensation reaction under a polycondensation catalyst. (Step 4) Following step 3, the molten PBSSe is extruded into strands and cut into pellets to obtain pellets containing PBSSe. (Step 5) If necessary, ０１ / I ０２ Control, or I ０１ / I ０２ Processing is performed to control the content of cyclic dimers. Note that a process of air separation and sieving of pellets may be performed between step 4 and step 5, and / or after step 5.

[0136] An example of the above step 2 for obtaining a PBSSe 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 proportion 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 PBSSe low polymer.

[0137] An example of the above step 3, in which a melt polycondensation reaction is carried out, is a method using 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.

[0138] The PBSSe polycondensation catalyst may be added to the reaction system at any stage of the mixing and preparation of the dicarboxylic acid component and the diol component, at any stage of the process of forming the PBSSe 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 may be used as the PBSSe polycondensation catalyst.

[0139] Furthermore, in steps 1 and 2 above, which involve forming a low polymer of PBSSe, 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. Specifically, examples of antioxidants include Irganox 1330 (manufactured by BASF) and Irganox 1010 (manufactured by BASF), and examples of basic compounds include 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.

[0140] Examples of the above step 4, which involves cutting the synthesized PBSSe into pellets, include the strand cutting method, in which molten PBSSe 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 is cut; and the underwater hot cutting method, in which the molten PBSSe is extruded into water from the nozzle hole and immediately cut.

[0141] <Intensity ratio (I ０１ / I ０２ ) Adjustment method > I related to step 5０１ / I ０２ This section explains the adjustment (control) of the pellet containing PBSSe. ０１ / I ０２ For example, this can be adjusted by adjusting the temperature and time applied to the pellets containing PBSSe in a process that combines the slow cooling process with a process that involves extruding the PBSSe synthesized by solution polycondensation in step 3 from a die into a cooling liquid in a strand shape and holding it at a predetermined temperature for a predetermined time (hereinafter also referred to as the "slow cooling process").

[0142] <Slow Cooling Process> The slow cooling process can be carried out before or during the above process 4. Specifically, the PBSSe extruded from the die into a cooling liquid adjusted to a predetermined temperature in a strand form and held in the cooling liquid in the strand form for a predetermined time. After that, it is cut to form pellets. Alternatively, the PBSSe extruded from the die into a cooling liquid adjusted to a predetermined temperature in a strand form and cut in the cooling liquid to form pellets (process 4), and the pellets are held in the cooling liquid for a predetermined time.

[0143] By slowly cooling PBSSe in a molten state, the orientation of the molecules of PBSSe in the molten state is promoted, making it possible to appropriately develop the crystal structure of PBSSe. However, if PBSSe in a molten state is extruded into, for example, a room temperature (25°C) environment, the PBSSe will cool rapidly, and the molecules of PBSSe will be fixed in a randomly oriented state, so I ０１ / I ０２ It becomes difficult to set it to 1.7 or higher.

[0144] Here, the temperature of the cooling liquid used to extrude the molten PBSSe into strands is preferably 35 to 65°C, particularly preferably 40 to 60°C, and even more preferably 45 to 55°C. The time for holding the PBSSe 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 pellets containing PBSSe, 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.

[0145] Furthermore, the type of cooling liquid is not particularly limited as long as it does not react with or dissolve PBSSe during the above temperature range and holding time. Examples of such cooling liquids include water.

[0146] 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 3.4. This means that the proportion of crystalline PBSSe in the pellet becomes too high. As a result, such pellets, with their excessive crystalline content, have a brittle surface and are prone to generating fine powder through friction between pellets or with the molding equipment.

[0147] <Solvent Contact Process> It is preferable to carry out a solvent contact process following the slow cooling process described above. This process 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 ０２It is possible to adjust this to a higher value, preferably within the range of 1.7 to 3.4. This step includes bringing the pellet obtained through the slow cooling step into contact 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 pellet can be removed, and the content of the cyclic dimer in the pellet can be adjusted to 4000 ppm by mass or less, and I ０１ / I ０２ This can be adjusted to a higher value within the range of 1.7 to 3.4. In other words, the inventors hypothesize that the cyclic dimer in the pellet is a component that inhibits the crystallization of PBSSe. In the slow cooling step, by forming a macroscopic crystalline structure of PBSSe, ０１ / I ０２ Pellets with a ratio of 1.7 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 or less, and it is presumed that the microcrystalline structure of PBSSe can 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 PBSSe molecules in the pellets progresses further, and I ０１ / I ０２ It is considered that pellets with a higher value of 1.7 or more, preferably within the range of 1.7 to 3.4, can be obtained. Furthermore, even if only the solvent contact step is performed without the slow cooling step, ０１ / I ０２ It is difficult to achieve a value of 1.7 or higher. In other words, in order to develop the microcrystalline structure of PBSSe by removing the cyclic dimer in the solvent contact process, it is considered necessary to perform a slow cooling process prior to the solvent contact process to form the macrocrystalline structure of PBSSe in the pellet.

[0148] The solvent used in this process is preferably one that does not substantially dissolve PBSSe even when in contact with the pellets at a predetermined temperature and for a predetermined time, while on the other hand, 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 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.

[0149] Furthermore, the solvent temperature in the solvent contact step is preferably 65°C or lower, particularly preferably 60°C or lower, and even more preferably 55°C or lower, so as not to excessively increase the crystallinity of PBSSe. As a lower limit, from the viewpoint of better extracting the cyclic dimer and appropriately oriented the PBSSe 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 65°C, particularly preferably 40 to 60°C, and even more preferably 45 to 55°C. Furthermore, as for the processing time, from the viewpoint of better extracting the cyclic dimer and appropriately oriented the PBS molecules, it is preferably 0.1 to 10 hours, particularly preferably 0.5 to 8 hours, and even more preferably 1 to 5 hours.

[0150] Specific methods for the solvent contact process described above include, for example, the methods i) and ii) below: i) A method in which pellets obtained through the slow cooling process and a solvent are placed in a processing tank, and after contacting them at the predetermined temperature range for the predetermined time, the pellets are recovered from the processing tank; ii) A method in which pellets obtained through the slow cooling process are continuously supplied to the processing tank, and the solvent, adjusted to the predetermined temperature range, is flowed in parallel or countercurrent to the flow of pellets, and after contacting the pellets to be processed with the solvent for the predetermined time, the processed pellets are continuously recovered. The specific methods and apparatus used in such processing are not particularly limited, but the method and apparatus described in Patent Document 3, which allows for continuous adjustment of the cyclic dimer content of the pellets, can be suitably used.

[0151] <Uses> The I obtained as described above ０１ / I ０２ However, pellets containing PBSSe, which have a ratio of at least 1.7 and preferably 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, and molded products can be manufactured stably. ０１ / I ０２However, pellets containing PBSSe, which have a ratio of at least 1.7 to 3.4 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 useful as pellets for injection molding and extrusion molding to obtain biodegradable molded products. <Molded products (injection molded products, extruded products)> Resin pellets for obtaining injection molded products or extruded products may consist only of pellets containing PBSSe. In this case, resin pellets can also be made by mixing two or more types of PBSSe pellets with different molar ratios of succinic acid units, sebacic acid units, and 1,4-butanediol units.

[0152] Injection molded and extruded articles of resin pellets containing PBSSe as described in this disclosure are obtained by molding using resin pellets containing PBSSe as described in this disclosure by injection molding or extrusion molding. Any shape is possible as long as it can be molded by injection molding or extrusion molding. The applications of injection molded or extruded articles are not limited in any way. Examples of injection molded articles include cutlery and various containers (cups, cosmetic containers, food containers, detergent containers, bleach containers, etc.). Examples of extruded articles include packaging materials (packaging films) and agricultural films (agricultural mulch films).

[0153] <Fourth Invention> The inventors conducted further studies to solve the problems related to PBST described above. In the process, they heated and melted PBST prepared by the method described in Patent Document 8 to transition it from a crystalline state to an amorphous state, and observed the change in the Raman spectrum of PBST before and after heating and melting. As a result, the Raman spectrum of PBST before heating and melting was 1711 ± 5 cm⁻¹. －１ A single peak with a peak top in the wavenumber range (first wavenumber range) was observed, but in the Raman spectrum of PBST after heating and melting, the Raman peak was 1722 ± 5 cm⁻¹. －１ We confirmed that it shifts to the wavenumber range (second wavenumber range). In the PBST Raman spectrum, the above-mentioned 1711±5 cm⁻¹ was observed. －１ and 1722±5cm －１ The peak appearing in the wavenumber range is attributed to the C=O expansion in the succinic acid units of PBST. From this, it is presumed that the peak observed in the first wavenumber range is attributed to the C=O expansion in the succinic acid units of crystalline PBST, and the peak observed in the second wavenumber range is attributed to the C=O expansion in the succinic acid units of amorphous PBST. Furthermore, the Raman peak observed in the Raman spectrum of PBST before heating and melting, which has its peak top in the first wavenumber range, is thought to be a peak attributed to the C=O expansion in the succinic acid units of crystalline PBST superimposed with a peak attributed to the C=O expansion in the succinic acid units of amorphous PBST. Furthermore, the present inventors have subjected the PBST pellets produced by the method described in Patent Document 8 to a specific treatment, specifically, a solvent contact step described later, or both the solvent contact step and the slow cooling step described later, thereby increasing the Raman spectrum measured from the pellets between 1680 and 1780 cm⁻¹. －１ The spectrum in the wavenumber range is 1711±5 cm⁻¹. －１ The first wavenumber range, and 1722±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 second wavenumber range (1722 ± 5 cm) －１The intensity of the peak I, which is attributed to the C=O stretching of succinate units in PBST expressed in ) ０２ For the first wavenumber range (1711±5 cm) －１ The intensity of the peak I, which is attributed to the C=O stretching of succinate units in PBST expressed in ) ０１ Ratio I ０１ / I ０２ We found that the intensity ratio (hereinafter also simply referred to as "intensity ratio") changes. Specifically, we found that the intensity ratio of pellets that have undergone a specific processing step is significantly higher than the intensity ratio of pellets that have not undergone the specific processing step, and that pellets with an intensity ratio above a certain value are less likely to block when heated and / or pressurized. This invention is based on these new findings.

[0154] In other words, a pellet according to one aspect of the present invention contains polybutylene succinate terephthalate (PBST) having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from terephthalic acid, and a constituent unit derived from 1,4-butanediol. The Raman spectrum measured from the pellet is 1680–1780 cm⁻¹. －１ The spectrum in the wavenumber range is 1711±5 cm⁻¹. －１ The first wavenumber range, and 1722±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 ) is 1.00 or higher.

[0155] The inventors speculate that the reason such pellets exhibit excellent blocking resistance even when heat / pressure is applied is as follows: As mentioned above, in the Raman chart of PBST pellets, the peaks appearing in the first wavenumber range and the second wavenumber range are attributed to the C=O stretching in the succinic acid units of PBST, and the Raman peak with a peak top in the first wavenumber range is considered to be a peak attributed to the C=O stretching in the succinic acid units of amorphous PBST superimposed on the peak attributed to the C=O stretching in the succinic acid units of crystalline PBST. ０１ And the peak intensity I in the second wavenumber range ０２ The intensity ratio (I ０１ / I ０２ ) is considered to be an indicator of the degree of balance between crystalline PBST and amorphous PBST in a pellet containing PBST. And, I ０１ / I ０２ However, PBST pellets with a value of 1.00 or higher are thought to have a higher crystalline state compared to PBST obtained by the method described in Patent Document 8, and are therefore less prone to blocking even when heated or pressurized.

[0156] The strength ratio of the PBST according to the present invention is 1.00 or higher, but more preferably 1.10 or higher. The upper limit of the strength ratio is not particularly limited, but is preferably 2.50 or lower, more preferably 1.40 or lower, and particularly preferably 1.35 or lower. That is, the strength ratio of the pellets containing PBST according to the present invention is preferably 1.00 or higher and 2.50 or lower, more preferably 1.10 or higher and 1.40 or lower, and particularly preferably 1.10 or higher and 1.35 or lower. Pellets with a strength ratio within the above range have a high crystallinity of PBST in the pellet, so blocking can be more reliably prevented when heat or pressure is applied to the pellet.

[0157] The method for measuring the spectrum of a pellet containing PBST 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 the following Raman spectrometer and under the following conditions: Raman spectrometer: "RAMAN touch" (product name, manufactured by Nanophoton Inc.) Measurement conditions / measurement mode: Point Laser wavelength: 532 nm Laser output: 12 mW (opening of light-reducing filter: 200 / 255) Diffraction grating: 1200 gr / mm Pinhole: 20 μm Exposure time: 100 seconds Number of integrations: 10 times Objective lens: 100x Measurement temperature: 25°C

[0158] The Raman spectrum obtained using the above Raman spectrometer and measurement conditions shows a value of 1711 ± 5 cm², which is attributed to the C=O stretching in the succinic acid unit of PBST. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range and is 1722 ± 5 cm. －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 the following formula (1). In formula (1) below, A represents the peak intensity and w represents the full width at half maximum of the peak. Also, X ０ The peak position is represented by 1711 ± 5 cm in this disclosure. －１ , and 1722±5cm －１ This is the result.

[0159]

[0160] Then, in the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), 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 Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X) is determined. ０= 1711 ± 5 cm －１ The intensity A (hereinafter also referred to as "A1") obtained by the above formula (1) relating to ), and the peak of the second wavenumber range (i.e., X ０ = 1722 ± 5 cm －１ The ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A2") obtained by the above formula (1) relating to ) is I ０１ / I ０２ It corresponds to this.

[0161] <Polybutylene succinate terephthalate (PBST)> PBST is an aliphatic aromatic polyester having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from terephthalic acid, and a constituent unit derived from 1,4-butanediol. Specifically, for example, PBST 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 terephthalic 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-CH ２ -CH ２ -CO- (1) -OC-C ６ H ４ -CO- (2) -O-(CH ２ ) ４ -O- (3)

[0162] 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 of succinic acid. Similarly, "constituent units derived from terephthalic acid" refers to the constituent units corresponding to terephthalic acid, that is, the constituent units formed by the reaction of the two carboxyl groups of terephthalic 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 of 1,4-butanediol. In this specification, the constituent units of PBST may also be referred to as compound units corresponding to the compounds from which each constituent unit is derived. Specifically, for example, a constituent unit derived from succinic acid may be called a "succinic acid unit," a constituent unit derived from terephthalic acid may be called a "terephthalic acid unit," a constituent unit derived from 1,4-butanediol may be called a "1,4-butanediol unit," a constituent unit derived from a carboxylic acid may be called a "carboxylic acid unit," and a constituent unit derived from a diol may be called a "diol unit."

[0163] 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 in PBST. Specifically, in the PBST according to this embodiment, the total number of moles of succinic acid units, terephthalic acid units, and 1,4-butanediol units is 80 mol% or more of the total number of moles of constituent units that make up PBST. Furthermore, the PBST according to this embodiment may be an aliphatic aromatic polyester in which the total number of moles of succinic acid units, terephthalic acid units, and 1,4-butanediol units is 90% or more of the total number of moles of constituent units constituting the PBST, and may be 95% or more of the total number of moles of constituent units constituting the PBST, and furthermore, in which no constituent units other than succinic acid units, terephthalic acid units, and 1,4-butanediol units are included at all, that is, it consists only of succinic acid units, terephthalic acid units, and 1,4-butanediol units, and the total number of moles of succinic acid units, terephthalic acid units, and 1,4-butanediol units is 100 mol% of the total number of moles of constituent units constituting the PBST.In this specification, when counting the number of moles of constituent units in PBST, the smallest ester unit constituting the PBST is considered to be 1 mole.

[0164] The total ratio of succinic acid units to terephthalic acid units in PBST is preferably 80 mol% or more, more preferably 85 mol% or more, particularly preferably 90 mol% or more, even more preferably 95 mol% or more, and may also be 100 mol% relative to the total dicarboxylic acid units in PBST. That is, based on the total number of moles of dicarboxylic acid units in PBST, the ratio of the total number of moles of succinic acid units and terephthalic acid units is preferably 80 to 100 mol%, more preferably 85 to 100 mol%, particularly preferably 90 to 100 mol%, and particularly preferably 95 to 100 mol%. By having the ratio of the total number of moles of succinic acid units and terephthalic acid units relative to the total number of moles of dicarboxylic acid units in PBST within the above range, it is possible to obtain PBST with superior biodegradability and mechanical properties.

[0165] The ratio of succinic acid units to terephthalic acid units in PBST is preferably such that the proportion of succinic acid units is 10 mol% or more, more preferably 40 mol% or more, particularly preferably 50 mol% or more, and preferably 90 mol% or less, and more preferably 60 mol% or less, based on the total number of moles of succinic acid units and terephthalic acid units. In other words, the molar ratio of succinic acid units to terephthalic acid units in PBST is preferably 10 / 90 to 90 / 10, more preferably 40 / 60 to 60 / 40, and particularly preferably 50 / 50 to 60 / 40. By keeping the ratio of succinic acid units to terephthalic acid units within the above range, PBST with excellent biodegradability and mechanical properties can be obtained.

[0166] Other dicarboxylic acids that can constitute the dicarboxylic acid unit in PBST are not particularly limited, but include, for example, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, and dimer acid; aromatic dicarboxylic acids such as 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 and terephthalic acid. Furthermore, succinic acid, sebacic acid, and adipic acid can be derived from plant materials.

[0167] The proportion of 1,4-butanediol units in PBST is preferably 80 mol% or more, more preferably 85 mol% or more, particularly 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 PBST. That is, based on the total number of moles of diol units in PBST, the proportion of 1,4-butanediol units is preferably 80 to 100 mol%, more preferably 85 to 100 mol%, particularly preferably 90 to 100 mol%, and even more preferably 95 to 100 mol%. By having the proportion of 1,4-diol units within the above range, PBST with excellent heat resistance and mechanical properties can be obtained.

[0168] Examples of diols other than 1,4-butaneol that can constitute the diol unit in PBST 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.

[0169] PBST may have other constitutional units (hereinafter also referred to as "other constitutional units") in addition to the dicarboxylic acid units and the diol units. Examples of copolymerization components that can constitute other constitutional units include oxycarboxylic acids (such as 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 and lactones of the oxycarboxylic acids, polymers of the oxycarboxylic acids, etc., polyhydric alcohols having three or more functional groups (such as glycerin, trimethylolpropane, pentaerythritol, etc.), and at least one component selected from the group consisting of polycarboxylic acids having three or more functional groups or their anhydrides (such as propanetricarboxylic acid, pyromellitic acid, trimellitic acid, benzophenone tetracarboxylic acid, and their anhydrides, etc.).

[0170] Among them, by introducing a constitutional 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 as other constitutional units into PBST, it is possible to adjust in the direction of increasing the intrinsic viscosity of PBST described later.The above polyfunctional compounds having three or more functional groups are preferably oxycarboxylic acids such as malic acid, citric acid, fumaric acid, and polyhydric alcohols having three or more functional groups such as glycerin and trimethylolpropane, and particularly preferably malic acid and trimethylolpropane are preferably used.

[0171] The ratio of the above polyfunctional compound units having three or more functional groups to the number of moles of all dicarboxylic acid units of PBST is preferably 0.001 to 5 mol%, and more preferably 0.05 to <0.5> mol%. By setting the ratio of the polyfunctional compound units having three or more functional groups in PBST 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 PBST within a preferable range as described below.

[0172] <Physical Properties of PBST> The intrinsic viscosity (IV) of PBST is preferably 1.2 dL / g or higher, more preferably 1.4 dL / g. It is also preferably 2.2 dL / g or lower, and more preferably 2.0 dL / g or lower. In other words, the intrinsic viscosity of PBST is preferably 1.2 dL / g or higher and 2.2 dL / g or lower, and more preferably 1.4 dL / g or higher and 2.0 dL / g or lower. By setting the intrinsic viscosity of PBST within the above range, the mechanical strength of the molded product can be increased, and the viscosity during melting can be adjusted to an appropriate range. As a result, high-quality injection molded and extruded products can be manufactured more easily. Note that the intrinsic viscosity depends on the molecular weight of PBST, and the higher the molecular weight, the higher the intrinsic viscosity can be.

[0173] The intrinsic viscosity can be measured, for example, in accordance with JIS K7367-1:2002 (ISO 1628-1:1998). Specifically, for example, using an Ubbelohde viscometer and a phenol / tetrachloroethane (mass ratio 1:1) mixed solvent, the intrinsic viscosity can be determined by measuring the number of seconds for dropping a 0.5 g / dL PBST solution and the mixed solvent alone at a temperature of 30°C, and using the following formula (2): IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) ... (2) However, in formula (2), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ We will use 0.33.

[0174] <Pellets Containing PBST> There are no particular restrictions on the shape and size of the pellets containing PBST, and it is preferable that they have a shape and size suitable for being subjected to known plastic processing methods such as injection molding and extrusion molding. Specific examples of the shape include, for example, cylindrical, elliptical cylindrical, prismatic, disk-shaped, spherical, and the like. Also, as for the size, the size of the pellets may be the generally used size. Specifically, for example, those having a diameter or one side of about 0.7 to 12 mm can be mentioned. Further, when the pellets containing PBST are subjected to the solvent contact step described later, it is preferable that the mass of one particle of the pellets is 1 to 50 mg, more preferably 3 to 40 mg, and particularly preferably 5 to 30 mg, from the viewpoint of the extraction efficiency of the cyclic dimer by the solvent contact step and the like.

[0175] <Cyclic Dimer in Pellets Containing PBST> In the pellets containing PBST, it is preferable that the content of the cyclic dimer is 2,500 mass ppm or less, more preferably 2,000 mass ppm or less, and particularly preferably 1,500 mass ppm or less. By setting the content of the cyclic dimer in the pellets to the above specific amount or less, the blocking resistance when heat / pressure is applied to the pellets can be further improved. Here, the cyclic dimer is a compound that is by-produced when a part of the polyester obtained by reacting a dicarboxylic acid component mainly composed of succinic acid and a diol component mainly composed of 1,4-butanediol is cyclized, 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).

[0176]

[0177] Regarding the present invention, I ０１ / I ０２However, in order to obtain pellets containing PBST with a ratio of 1.00 or higher, it is important to adjust the content of the cyclic dimer to 2500 ppm or less in the solvent contact step described later. That is, the PBST obtained by the method described in Patent Document 8 also achieves a certain degree of crystallization. However, according to the inventors' studies, when the PBST contains a certain amount or more of the cyclic dimer, the cyclic dimer inhibits the crystallization of PBST, making it difficult to achieve the high crystallization that is considered necessary to prevent blocking when heat / pressure is applied to the pellets containing PBST. Based on these considerations, the inventors' studies have shown that by reducing the content of the cyclic dimer in the solvent contact step described later, I ０１ / I ０２ This study found that it is possible to obtain pellets with a value of 1.00 or higher.

[0178] There is no particular lower limit to the content of cyclic dimers in pellets containing PBST, and it may be 0 ppm by mass. However, limiting the cyclic dimer content to 0 ppm by mass may lead to an increase in the number of steps required to remove the cyclic dimers from the synthesized PBST, and the need for larger equipment for such removal. From the viewpoint of reducing environmental impact, the inclusion of cyclic dimers in pellets is permissible as long as it does not significantly affect the crystallization of PBST. Specifically, the cyclic dimer content in the pellets can be 1 ppm by mass or more, preferably 50 ppm by mass or more, and more preferably 100 ppm by mass or more. Therefore, from the viewpoint of high crystallization of PBST and reduction of environmental impact, the cyclic dimer content in pellets containing PBST is preferably 1 to 2500 ppm by mass, more preferably 50 to 2000 ppm by mass, and particularly preferably 100 to 1500 ppm by mass. By keeping the content of cyclic dimers in pellets containing PBST within the above range, the I in pellets containing PBST can be reduced. ０１ / I ０２ This makes it easier to set it to 1.00 or higher.

[0179] The method for quantifying cyclic dimers in pellets containing PBST is not particularly limited, but one example is the use of an absolute calibration curve. Specific methods will be explained in the examples. Furthermore, specific methods for adjusting the cyclic dimer content in pellets containing PBST will be described later.

[0180] Pellets containing PBST may contain other components besides PBST. One example of such a component is a mold release agent. Examples of mold release agents include those commonly used in injection molding and extrusion molding. Specifically, examples include ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid with ethylene glycol, glycerin, or pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid or montanic acid, etc.) with stearylamine or ethylenediamine, and silicone compounds. The mixing ratio of the mold release agent is preferably 0.001 to 1% by mass, and more preferably 0.005 to 0.8% by mass, based on the pellets containing PBST, in order to prevent pellet blocking due to excessive bleeding of the mold release agent onto the pellet surface while improving the release properties of the molded product. Furthermore, additives may be included as other components, as long as they do not impair the objectives of the present invention. Examples of 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, and titanium dioxide; non-plate-like fillers; antioxidants (phosphorus-based, sulfur-based, etc.); ultraviolet absorbers; heat stabilizers (hindered phenol-based, etc.); transesterification inhibitors; lubricants; antistatic agents; colorants including dyes and pigments; flame retardants (halogen-based, phosphorus-based, etc.); flame retardant enhancers (antimony compounds represented by antimony trioxide, zirconium oxide, molybdenum oxide, etc.); and antibacterial agents. Furthermore, other resins other than PBST may be included as one of the other components. In this case, the content of other resins in the pellet is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, and may also be 0% by mass, i.e., the resin component in the pellet may be only PBST.

[0181] <Method for producing pellets containing PBST> The pellets containing PBST according to the present invention can be produced, for example, by following steps 1 to 5 below. (Step 1) A dicarboxylic acid component containing 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 terephthalic acid and its ester-forming derivatives, and a diol component containing at least 1,4-butanediol are mixed in a predetermined proportion under stirring to obtain a raw material slurry. (Step 2) Following step 1, the raw material slurry is heated under normal pressure or under pressure to undergo an esterification reaction to obtain a PBST low polymer. (Step 3) Following step 2, the obtained low polymer is gradually reduced in pressure and heated to undergo a melt polycondensation reaction under a polycondensation catalyst. (Step 4) Following step 3, the molten PBST is extruded into strands and cut into pellets to obtain pellets containing PBST. (Step 5) The I in the pellets obtained in step 4 ０１ / I ０２ Processing is performed to control this. Note that a process of air separation and sieving of pellets may be performed between step 4 and step 5, and / or after step 5.

[0182] An example of the above step 2 for obtaining a PBST 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 is carried out until the esterification rate reaches 85% or more, while removing the water and excess diol components produced in the reaction from the system, thereby obtaining a PBST low polymer. The esterification rate is the proportion of the total carboxyl groups of the raw material dicarboxylic acid component that react with the diol component and are esterified, and is expressed by the following formula (3). Esterification rate (%) = (Saponification value - Acid value) / Saponification value × 100 (3) The reaction temperature in step 2 (esterification reaction step) is not particularly limited as long as it is a temperature at which the esterification reaction can be carried out, but in order to increase the reaction rate, it is preferably 200°C or higher, more preferably 210°C or higher, and to prevent discoloration of the polyester, it is preferably 250°C or lower, more preferably 245°C or lower, and particularly preferably 240°C or lower. In other words, the reaction temperature is preferably 200 to 250°C, more preferably 210 to 245°C, and particularly preferably 210 to 240°C. By keeping the reaction temperature within the above range, the esterification reaction rate slows down, and the occurrence of dehydration decomposition of the diol component due to the longer reaction time can be more reliably prevented. In addition, the generation of foreign matter caused by the increase in scattered material in the reaction vessel due to the decomposition of the diol component and dicarboxylic acid component can be more reliably prevented. From the viewpoint of stabilizing the esterification rate, the reaction temperature is preferably kept as constant as possible, for example, preferably within ±5°C of the set temperature, and more preferably within ±2°C of the set temperature. The reaction atmosphere in step 2 is preferably an inert gas atmosphere such as nitrogen or argon. The reaction pressure is preferably 50 kPa to 200 kPa, more preferably 60 kPa or more, particularly preferably 70 kPa or more, and more preferably 130 kPa or less, and particularly preferably 110 kPa or less. In other words, the reaction pressure is preferably 50 to 200 kPa, more preferably 60 to 130 kPa, and particularly preferably 70 to 110 kPa. If the reaction pressure is within the above range, it is possible to more reliably prevent an increase in scattered material in the reaction vessel, a rise in the haze of the reactants, and an increase in foreign matter.Furthermore, a decrease in the polycondensation reaction rate due to increased distillation of the diol component outside the reaction system can be more reliably prevented. Moreover, a decrease in the polycondensation rate due to dehydration decomposition of the diol component can be more reliably prevented. The reaction time is not particularly limited, but for example, 1 to 10 hours is preferred, and 1 to 4 hours is particularly preferred. In this step, it is preferable that the esterification rate of the esterified product be 85% or more. In this disclosure, the polycondensation reaction refers to the high molecular weight conversion reaction of polyester carried out at a reaction pressure of 50 kPa or less, particularly 10 kPa or less, and the esterification reaction refers to the reaction carried out at 50 to 200 kPa. The esterification rate of the esterified product is preferably 85% or more, more preferably 88% or more, and more preferably 90% or more. The upper limit is better if it is higher for the polycondensation reaction in the subsequent step, but it is usually 99%. That is, the esterification rate is preferably 85 to 99%, more preferably 88 to 99%, and particularly preferably 90 to 99%. By keeping the esterification rate within the above range, the polycondensation reactivity in the subsequent polycondensation step can be improved, and scattering during the polycondensation reaction can be suppressed, more reliably preventing haze deterioration (foreign matter generation).

[0183] An example of the above step 3, in which a melt polycondensation reaction is carried out, is a method using 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.

[0184] The PBST polycondensation catalyst may be added to the reaction system at any stage of the mixing and preparation of the dicarboxylic acid component and the diol component, at any stage of the process of forming the PBST 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 may be used as the PBST polycondensation catalyst.

[0185] Furthermore, in order to promote the crystallization of PBST, a nucleating agent may be added in step 1, for example. Examples of nucleating agents include hydrocarbon-based nucleating agents such as polyethylene wax and polypropylene wax, aliphatic amide-based nucleating agents, phosphate ester metal salt-based nucleating agents, and inorganic nucleating agents such as anhydrous silica, talc, titanium dioxide, and calcium carbonate. From the viewpoint of the effect on the color tone and polymerizability of the obtained PBST, hydrocarbon-based nucleating agents and inorganic nucleating agents are preferred, more preferably polyethylene wax, polypropylene wax, and talc, and even more preferably polyethylene wax and talc. Only one type of nucleating agent may be used, or two or more types may be mixed and used. The nucleating agent is preferably added in an amount of 100 to 10,000 ppm by mass relative to the PBST, more preferably in an amount of 200 to 5,000 ppm by mass, and particularly preferably in an amount of 500 to 3,000 ppm by mass. By using the amount of nucleating agent within the above range, the effect of promoting the crystallization of PBST can be obtained more reliably, and it is also advantageous in terms of cost.

[0186] Furthermore, in steps 1 and 2 above, which involve the formation of a PBST low polymer, 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. Specifically, examples of antioxidants include "Irganox 1330" (trade name, manufactured by BASF) and "Irganox 1010" (trade name, manufactured by BASF), and examples of basic compounds include 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.

[0187] Examples of the above step 4, which involves cutting the synthesized PBST into pellets, include the strand cutting method, in which molten PBST is extruded from the nozzle hole of a die head using a gear pump or extruder and cooled with water, or the cooled and solidified strand is cut with a cutter; and the underwater hot cutting method, in which molten PBST is extruded into water from the nozzle hole and immediately cut.

[0188] <Intensity ratio (I ０１ / I ０２ ) Adjustment method > Pellets containing PBST ０１ / I ０２ For example, the PBST synthesized by solution polycondensation in step 3 above can be prepared by, in step 4, extruding the PBST from a die into a cooling liquid in a strand shape, cutting it into pellets, and then subjecting it to a step described later, in which it is immersed in a solvent adjusted to a predetermined temperature for a predetermined time (hereinafter also referred to as the "solvent contact step"), or in which it is held at a predetermined temperature for a predetermined time (hereinafter also referred to as the "slow cooling step") and the "solvent contact step".

[0189] <Solvent Contact Process> The solvent contact process is a process to reduce the content of cyclic dimers in the pellets, and also I ０１ / I ０２ This process may also be for adjusting the value of to 1.00 or higher. In other words, by going through this process, the content of the cyclic dimer is adjusted to 2500 ppm or less, and I ０１ / I ０２ A pellet containing PBST with an I ratio adjusted to 1.00 or higher can be obtained. This step includes, for example, contacting the pellet obtained in step 4 with a solvent capable of dissolving the cyclic dimer, adjusted to a predetermined temperature, for a predetermined time. By going through this step, at least a portion of the cyclic dimer in the pellet can be removed, making it easier to adjust the cyclic dimer content in the pellet to 2500 ppm by mass or less. Furthermore, by going through this step, the amount of cyclic dimer in the pellet that is thought to inhibit the orientation of PBST molecules is reduced, and as a result, by holding the pellet at a predetermined temperature for a predetermined time, the PBST molecules in the pellet can be oriented better, thus improving the I ratio of the pellet.０１ / I ０２ It can be controlled to be 1.00 or higher.

[0190] The solvent used in this process is preferably one that does not substantially dissolve the PBST even when in 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.

[0191] Furthermore, the solvent temperature in the solvent contact step is preferably 70°C or lower, more preferably 65°C or lower, and particularly preferably 60°C or lower. As a lower limit, from the viewpoint of better extracting the cyclic dimer and orienting the PBST molecules, it is preferably 30°C or higher, more preferably 35°C or higher, and particularly preferably 40°C or higher. That is, the solvent temperature range in the solvent contact step is preferably 30 to 70°C, more preferably 35 to 65°C, and particularly preferably 40 to 60°C. Furthermore, as for the processing time, from the viewpoint of better extracting the cyclic dimer and orienting the PBST molecules, it is preferably 0.1 to 10 hours, more preferably 0.5 to 8 hours, and particularly preferably 1 to 5 hours. Furthermore, the mass ratio of the polyester pellets to the solvent (solvent / pellets) to be in contact is preferably 1.0 or higher, particularly preferably 1.5 or higher, and even more preferably 2.0 or higher. Furthermore, this mass ratio is preferably 50.0 or lower, more preferably 30.0 or lower, and particularly preferably 20.0 or lower. Specifically, the mass ratio is preferably 1.0 to 50.0, more preferably 1.5 to 30.0, and particularly preferably 2.0 to 20.0. Having the mass ratio within this range prevents the concentration of cyclic dimers in the solvent from becoming too high, allowing for more stable removal of cyclic dimers from the pellets. Furthermore, it prevents an excessive amount of solvent relative to the pellets, thus preventing cost increases associated with larger processing equipment.

[0192] Specific methods for the solvent contact process described above include, for example, the methods i) and ii) below: i) A method in which pellets obtained through the slow cooling process and a solvent are placed in a processing tank, and after contacting them at the predetermined temperature range for the predetermined time, the pellets are recovered from the processing tank (hereinafter also referred to as the "batch method" or "palindrome method"); ii) A method in which pellets obtained through the slow cooling process are continuously supplied to a processing tank, and the solvent, adjusted to the predetermined temperature range, is flowed in parallel or countercurrent to the flow of pellets, and after contacting the pellets to be processed with the solvent for the predetermined time, the processed pellets are recovered continuously (hereinafter also referred to as the "continuous method"). The specific methods and apparatus used for the palindrome method and continuous method are not particularly limited, but as a method and apparatus related to the continuous method that can continuously adjust the content of cyclic dimers in the pellets, for example, the method and apparatus described in Patent Document 3 can be suitably used.

[0193] In the solvent contact process, it is preferable to use a fresh solvent from the viewpoint of reducing the concentration of cyclic dimers in the pellets. However, from the viewpoint of reducing environmental impact and effectively utilizing resources, it is preferable to reuse the solvent used in the solvent contact process. In this case, since the solvent that comes into contact with the pellets in the solvent contact process contains cyclic dimers, it is preferable to separate the cyclic dimers according to their concentration and control the concentration of cyclic dimers in the solvent to be low. In particular, when the solvent contact process is continuous and the solvent that has been treated in contact with the pellets is circulated and reused, it is preferable to control the concentration of cyclic dimers in the entire solvent used in the solvent contact process to be low. Since controlling the concentration of cyclic dimers in the entire solvent that comes into contact with the pellets in the solvent contact process makes it easier to reduce the amount of cyclic dimers contained in the resulting pellets, it is preferable to separate the cyclic dimers in the separation process. The method / apparatus (separation apparatus) for separating cyclic dimers from a solution containing cyclic dimers is not particularly limited, and examples include distillation columns, crystallizers, thin-film evaporators, and centrifuges. For example, when the solvent used in the solvent contact process is to be recycled, at least a portion of the solvent containing cyclic dimers can be separated by the above-mentioned separation device, and after adjusting (reducing) the concentration of cyclic dimers in the solvent, it can be used again in the solvent contact process. When the solvent contact process is carried out continuously, as shown in Figure 7 described later, the solvent that has come into contact with the pellets in the contact treatment tank (III) in Figure 7 is recovered via the solvent recovery line (106), and the proportion of the recovered solution supplied to the separator (XI) by the solvent supply line (111) is defined as the separation rate, it is preferable to set it to 20% by mass or more from the viewpoint of achieving a higher level of compatibility between the recyclability of the solvent and the quality of the pellets (low content of cyclic dimers). In particular, it is preferable to set it to 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, and even 55% by mass or more, and especially preferable to set it to 90% by mass or more. The upper limit of the separation rate is 100% by mass. A separation rate of 100% means that all of the solvent that comes into contact with the pellet is separated through the separator, and at least a portion of the cyclic dimer contained within it is separated.By achieving a separation rate of 20% by mass or more, the accumulation of cyclic dimers in the solvent can be suppressed, making it easier to obtain pellets of the desired quality. Furthermore, the separated cyclic dimers can be supplied to the esterification reaction process or the polycondensation reaction process and used as raw materials for polyester. It is a preferred method to return the separated cyclic dimers to the esterification reaction tank in the esterification reaction process or to the slurry tank of the dicarboxylic acid component and the diol component. The solvent from which the cyclic dimers have been separated may be used as is in the solvent contact process, or if the solvent is lost due to the separation of the cyclic dimers, fresh solvent can be replenished in the required amount as needed before being used in the solvent contact process.

[0194] <Slow Cooling Process> The slow cooling process can be performed before or during the above process 4. Specifically, for example, when the slow cooling process is performed during process 4, the molten PBST obtained in process 3 is extruded from the die into a cooling liquid adjusted to a predetermined temperature in a strand form, and the PBST is held in the cooling liquid in a strand form for a predetermined time. After that, it is cut to form pellets. Alternatively, the PBST extruded from the die into a cooling liquid adjusted to a predetermined temperature in a strand form is cut into pellets in the cooling liquid, and the pellets are held in the cooling liquid for a predetermined time. By slowly cooling the molten PBST, the orientation of the molecules of the molten PBST is promoted, making it possible to develop the crystalline structure of the PBST to a certain extent. Here, if the molten PBST is extruded into, for example, a room temperature (25°C) environment, the PBST will be rapidly cooled, and the molecules of the PBST will be fixed in a randomly oriented state, so I ０１ / I ０２ It becomes difficult to make it 1.00 or higher. Note that the step of contacting the pellets with water at 30°C for a few seconds as described in the example of Patent Document 8 does not fall under this slow cooling step, and unless the pellets obtained in the example of Patent Document 8 are subjected to the solvent contact step, or both this slow cooling step and the solvent contact step, I ０１ / I ０２ It is difficult to set it to 1.00 or higher.

[0195] Here, the temperature of the cooling liquid used to extrude the molten PBST into strands is preferably 30 to 60°C, particularly preferably 35 to 55°C, and even more preferably 40 to 50°C. The time for holding the PBST within the above temperature range is I ０１ / I ０２ While there are no particular restrictions as long as it can be 1.00 or higher, it is preferable to set it to, for example, 1 to 10 minutes, more preferably 1.5 to 5 minutes, and even more preferably 2 to 3 minutes. When the holding time is extended within the above temperature range of pellets containing PBST, 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.

[0196] Furthermore, the type of cooling liquid is not particularly limited as long as it does not react with or dissolve PBST during the above temperature range and holding time. Examples of such cooling liquids include, for example, water. ０１ / I ０２ In obtaining pellets containing PBST having a ratio of 1.00 or higher, it is particularly preferable to subject the pellets to both the "solvent contact step" and the "slow cooling step." When both the solvent contact step and the slow cooling step are performed, the order is not particularly limited, but it is particularly preferable to subject the pellets obtained in step 4 to the slow cooling step to improve their crystallinity to a certain extent, and then to perform the solvent contact step to extract the cyclic dimer and further develop the crystallinity of PBST.

[0197] As an example of a method for producing pellets according to this disclosure, an example in which the "continuous" method (apparatus) is used in the solvent contact step (cyclic dimer removal step) will be explained with reference to Figures 5 to 8. In the following example, a preferred embodiment of a method for producing polyester pellets using succinic acid as the aliphatic dicarboxylic acid component, terephthalic acid as the aromatic dicarboxylic acid component, 1,4-butanediol as the diol component, and trimethylolpropane as an optional polyfunctional compound as raw materials will be described, but this disclosure is not limited to this embodiment.

[0198] Figure 5 is a schematic diagram illustrating one aspect of a part of the pellet manufacturing process (esterification reaction step) according to this disclosure, and Figure 6 is a diagram illustrating one aspect of a part of the pellet manufacturing process (polycondensation step) according to this disclosure.

[0199] In Figure 5, the raw materials succinic acid and terephthalic acid, and optional components (e.g., trimethylolpropane) are typically mixed with 1,4-butanediol in a raw material mixing tank (not shown) and supplied to the esterification reactor (A) from the raw material supply line (1) in the form of a slurry or liquid. If a catalyst is added during the esterification reaction, the catalyst solution is prepared in a catalyst preparation tank (not shown) to form a solution of 1,4-butanediol, and then supplied to the catalyst supply line (3). Figure 5 shows a configuration in which the catalyst supply line (3) is connected to the 1,4-butanediol recirculation line (2), the two are mixed, and then supplied to the liquid phase of the esterification reactor (A).

[0200] The gas distilled from the esterification reactor (A) is separated into high-boiling and low-boiling components in the rectification column (C) via the distillation line (5). Typically, the main component of the high-boiling component is 1,4-butanediol, and the main components of the low-boiling component are water and tetrahydrofuran (hereinafter sometimes abbreviated as THF), which is a decomposition product of 1,4-butanediol.

[0201] The high-boiling components separated in the rectification column (C) are extracted through the extraction line (6), and via the pump (D), some are recirculated to the esterification reactor (A) via the recirculation line (2), and some are returned to the rectification column (C) via the circulation line (7). The excess is extracted to the outside via the extraction line (8). Meanwhile, the low-boiling components separated in the rectification column (C) are extracted through the gas extraction line (9), condensed in the condenser (G), and temporarily stored in the tank (F) via the condensate line (10). Some of the low-boiling components collected in the tank (F) are returned to the rectification column (C) via the extraction line (11), pump (E), and circulation line (12), and the remainder is extracted to the outside via the extraction line (13). The condenser (G) is connected to an exhaust system (not shown) via the vent line (14). The esterified product (low polymer of PBST) generated in the esterification reactor (A) is supplied to the first polycondensation reactor (a) shown in Figure 6 via the extraction pump (B) and the extraction line (4) for the esterified product.

[0202] In the process shown in Figure 5, the catalyst supply line (3) is connected to the recirculation line (2), but the two may be independent. Also, the raw material supply line (1) may be connected to the liquid phase of the esterification reactor (A).

[0203] When adding a catalyst to the esterification reaction product before polycondensation, the catalyst is first prepared to a predetermined concentration in a catalyst preparation tank (not shown), then connected to the raw material supply line (L8) via the catalyst supply line (L7) in Figure 6, further diluted with BG, and then supplied to the esterification reaction product extraction line (4).

[0204] Next, the esterification reactant supplied from the extraction line (4) of the esterification reactant to the first polycondensation reaction tank (a) via the filter (p) is polycondensed under reduced pressure and then supplied to the second polycondensation reaction tank (d) via the extraction gear pump (c), the extraction line (L1), and the filter (q). In the second polycondensation reaction tank (d), the polycondensation reaction usually proceeds at a lower pressure than in the first polycondensation reaction tank (a). The obtained polycondensate is supplied to the third polycondensation tank (k) via the extraction gear pump (e), the extraction line (L3) which is the outlet flow path, and the filter (r). The third polycondensation reaction tank (k) is a horizontal reaction tank composed of a plurality of stirring blade blocks and equipped with a two-shaft self-cleaning type stirring blade. The polycondensation reactant introduced from the second polycondensation reaction tank (d) to the third polycondensation reaction tank (k) through the extraction line (L3) is further polycondensed here and then transferred to the pelletization step.

[0205] In the pelletization step, the molten polyester is extracted from the die head (g) in the form of a molten strand through the extraction gear pump (m), the filter (s) which is the outlet flow path, and the extraction line (L5) and then cooled with water or the like, and then cut by the rotary cutter (h) to become polyester pellets. Also, it can be extracted in the form of a strand into water without being extracted into the atmosphere and cut with a rotary underwater cutter to form pellets.

[0206] The reference numerals (L2), (L4), and (L6) in FIG. 6 are the vent lines of the first polycondensation reaction tank (a), the second polycondensation reaction tank (d), and the third polycondensation reaction tank (k), respectively. The filters (p), (q), (r), and (s) do not necessarily have to be all installed, and can be appropriately installed in consideration of the foreign matter removal effect and the operation stability.

[0207] Figure 7 is a schematic diagram illustrating one aspect of the solvent contact process for pellets and the separation process of cyclic dimers from the solvent that has come into contact with the pellets. The solvent is supplied from a circulation tank (I) to a processing tank (III) via a solvent supply line (101) after being temperature-controlled by a pump (IX) through a heat exchanger (II). In the processing tank (III), the solvent comes into contact with the pellets (for example, in countercurrent contact), and is then extracted through a solvent extraction line (102) and introduced into a fine particle remover (IV). At least a portion of the solvent introduced into the fine particle remover (IV) is recovered to the circulation tank (I) via a separator (XI), and the remainder is recovered to the circulation tank (I) via an extraction line (110). In the separator (XI), the cyclic oligomer containing the cyclic dimer is separated from the solvent supplied to the separator (XI), and the solution is recovered to the circulation tank (I) via a solution extraction line (113). The cyclic oligomer containing the separated cyclic dimer is extracted to the outside through the cyclic oligomer extraction line (112). From the supply line (108), an amount of solvent equivalent to the solvent extracted from the extraction line (112) along with the separated cyclic dimer is supplied.

[0208] The pellets to be subjected to contact treatment with the solvent are continuously supplied from the pellet supply line (103), and after being subjected to contact treatment with the solvent for a predetermined time, they are continuously extracted from the pellet extraction line (104) while adjusting the extraction amount with a rotary valve (V). The solvent extracted along with the pellets is separated in the preliminary solid-liquid separator (VI), and after passing through the recovery tank (VII), is returned to the recovery line (106) via the solvent supply line (105) by a pump (X). The continuously extracted pellets are separated from the accompanying solvent in the preliminary solid-liquid separator (VI), and then continuously supplied to the drying process located downstream of the main separation process via the pellet extraction line 109, after passing through the solid-liquid separator (VIII).

[0209] Figure 8 is a schematic diagram illustrating one aspect of a part of the pellet manufacturing process (drying process) according to this disclosure. Here, an apparatus equipped with two drying towers (first drying tower (I) and second drying tower (K)) is described as an example. After the solvent contact process, pellets are continuously supplied to the first drying tower (I) via a pellet supply line (201) connected to the extraction line 109 in Figure 8. Heated and dried dry gas (e.g., nitrogen gas) is continuously introduced into the first drying tower (I) from a supply line (208) and discharged from a gas recovery line (207). The discharged nitrogen gas is heated in a heat exchanger (N) via a condenser (L), circulated back to the first drying tower (I) via the supply line (208), and reused. The solvent condensed in the condenser (L) and heat exchanger (M) is extracted from the extraction line (210). New dry gas is supplied from a new dry gas supply line (209). The pellets are continuously supplied from the first drying tower (I) through a rotary valve (O) to the cooling tower (J). Dry air is introduced into the cooling tower (J) from the cooling gas supply line (212) and discharged from the cooling gas extraction line (211).

[0210] Pellets cooled to a temperature lower than the drying temperature of the first drying tower (I) are supplied to the second drying tower (K) via a pellet extraction line (204), a rotary valve (P), and a pellet supply line (205). Drying gas (usually, for example, air) is supplied to the second drying tower (K) via a heat exchanger (S) and a drying gas supply line (214), and is also discharged from an extraction line (213).

[0211] The dried pellets are continuously or intermittently extracted via a rotary valve (Q) and a pellet extraction line (206), and then processed through a storage tank, a fine powder removal machine, a packaging machine, etc., to become the final product. In Figure 8, the components after the storage tank are not shown, but the second drying tower (K) can also be used as a storage tank.

[0212] <Uses> The I obtained as described above ０１ / I ０２However, pellets containing PBST having a ratio of at least 1.00 and preferably a cyclic dimer content of 2500 ppm by mass or less are less prone to pellet blocking when subjected to injection molding or extrusion molding. As a result, molded products can be manufactured stably without hindering the supply stability to the molding machine during molding, making them extremely useful as pellets for injection molding and extrusion molding to obtain biodegradable molded products.

[0213] <Molded Products (Injection Molded Products, Extruded Products)> Resin pellets for obtaining injection molded products or extruded products may consist solely of pellets containing PBST. Here, resin pellets can also be made by mixing two or more types of PBST pellets with different molar ratios of succinic acid units, terephthalic acid units, and 1,4-butanediol units.

[0214] Injection molded and extruded articles of resin pellets containing PBST as disclosed herein are obtained by molding using resin pellets containing PBST as disclosed herein by injection molding or extrusion molding. Any shape is possible as long as it can be molded by injection molding or extrusion molding. The applications of injection molded or extruded articles are not limited in any way. Examples of injection molded articles include cutlery and various containers (cups, cosmetic containers, food containers, detergent containers, bleach containers, etc.). Examples of extruded articles include packaging materials (packaging films) and agricultural films (agricultural mulch films).

[0215] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples unless it exceeds the gist of the invention.

[0216] <First Invention> The measurement methods for the physical properties and evaluation items adopted in the following embodiment relating to the first invention of PBS are as follows: <Intrinsic Viscosity (IV) dL / g> An Ubbelohde viscometer was used to determine this in the following manner. Specifically, a mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1) was used, and at a temperature of 30°C, the number of seconds for dropping the polymer solution with a concentration of 0.5 g / dL and the solvent alone was measured, and the intrinsic viscosity 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 / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ 0.33 was adopted.

[0217] <Cyclic Dimer Content> 0.5 g of pellet was accurately weighed, 10 mL of chloroform was added, and after dissolving at room temperature, 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 separation was performed by standing for 90 minutes. 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, elution was performed using a Shimadzu High Performance Liquid Chromatography "Prominence," starting with acetonitrile / water (volume ratio = 4 / 6) as the mobile phase 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.

[0218] The pure cyclic dimer was obtained as follows: A pellet of PBS obtained by polymerizing succinic acid and 1,4-butanediol was stirred in acetone at 50°C for 12 hours to extract the oligomeric components. After extraction, the pellet was filtered off, and the acetone was evaporated from the acetone solution containing the extracted oligomeric components to obtain a solid. This solid was dissolved in acetone at 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 needle-shaped precipitates were collected. The obtained needle-shaped precipitates were purified by subjecting them to the above recrystallization operation several more times. These needle-shaped precipitates were then analyzed by 1H-NMR and high-performance liquid chromatography to confirm that they were cyclic dimers of succinic acid and 1,4-butanediol.

[0219] <Raman band intensity ratio (I １７２０ / I １７3０ )> The Raman spectrum of the pellet was measured using the "RAMAN touch" (product name, manufactured by Nanophoton Corporation) as a Raman spectrometer. The measurement conditions were as follows: <Measurement conditions> ・Measurement mode: Point ・Laser wavelength: 532 nm ・Laser output: 12 mW (Natural density filter opening: 200 / 255) ・Diffraction grating: 1200 gr / mm ・Pinhole: 50 μm ・Exposure time: 10 seconds ・Number of integrations: 3 ・Objective lens: 100x ・Measurement temperature: 25℃

[0220] The obtained Raman spectrum was 1718 ± 5 cm⁻¹. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range, and 1732 ± 5 cm. －１ The two components of the Raman scattering intensity peak having a peak top in the second wavenumber range were fitted using the Lorentz function shown in equation (1) above. In the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity in the first wavenumber range I ０１ and the peak intensity I in the second wavenumber range ０２ The intensity ratio (I ０１ / I ０２Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X) was determined. ０ = 1718 ± 5 cm －１ The intensity A (hereinafter also referred to as "A1") in the above formula (1) relating to ) and the peak of the second wavenumber range (i.e., X ０ = 1732 ± 5 cm －１ From the ratio of the strength A (hereinafter also referred to as "A2") in the above formula (1) relating to ), I ０１ / I ０２ The following was calculated. In Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-4, the average value of three measurements was calculated. Specifically, three samples were taken from the pellet to be measured, and for each sample, the above Raman spectral measurement, fitting, and I were performed. ０１ / I ０２ The calculation is performed, and I for each measurement sample. ０１ / I ０２ The average value is calculated for each example and each comparative example. ０１ / I ０２ That's what I decided.

[0221] <Heat Fusion Test> 20g of pellets were placed in a cylindrical container made of stainless steel (SUS) with an inner diameter of 20mm, and weights were placed on the surface of the pellet layer inside the cylindrical container so that a uniform pressure of 180g per square centimeter was applied. This cylindrical container was heated to 100°C and placed in an inert oven with nitrogen flowing at a flow rate of 20 liters / minute for 30 minutes, then removed and allowed to return to room temperature (25°C). Next, the pellets were removed from the cylindrical container and the degree of pellet fusion was observed visually. The evaluation criteria were as follows, with rank B or higher being considered a pass. Rank A: There was no fusion between the pellets at all, and no blocking occurred, which was the best condition. Rank B: There were small clumps of 5 to 10 pellets, but they crumbled easily when lightly poked with a finger, and no blocking occurred. Rank C: The pellets were fused together and there were clumps of 10 or more pellets, indicating that blocking had occurred.

[0222] <Measurement of Fish Eye Count> Pellets containing PBS were dried in a nitrogen atmosphere at a temperature of 60°C for 8 hours. These pellets were extruded using a continuous extrusion film molding machine (product name: "ME-20 / 2800V4&MFA-BET&FSA-100", manufactured by OCS Corporation) under the following molding conditions to produce an extruded film. The number of fish eyes (pieces / m) caused by incomplete melting of the pellets was measured for this film. ２ The number of fisheyes was measured using the CCD camera attached to the device while the film was being formed, at 1m. ２ The number of fisheyes with a major axis of 200 μm or larger present in the area was automatically counted and measured. A smaller value indicates better molded appearance. The evaluation criteria were as follows, with rank B or higher being considered acceptable. The reason for evaluating the number of fisheyes on extruded film is that the presence of fisheyes can be easily confirmed on thin films. Rank A: 100 fisheyes / m ２ The following (particularly preferred): Rank B: 101-500 pieces / m ２ (Preferred). Rank C: 501 pieces / m ２ That's all. <Molding conditions> Cylinder temperature (temperature at 5 points between the nozzle and the bottom of the hopper): 190°C - 200°C - 195°C - 190°C - 175°C Screw rotation speed: 35 rpm Resin discharge pressure: 5 MPa Chill roll temperature: 30°C Film thickness: 50 μm

[0223] (Example 1-1) [Preparation of Catalyst for Polycondensation] 100 parts by mass of magnesium acetate tetrahydrate was placed in a glass pear-shaped flask equipped with a stirrer, and 1500 parts by mass of anhydrous ethanol (purity of 99% by mass or higher) was added. 65.3 parts by mass of ethyl acid phosphate (mixture mass ratio of monoester and diester is 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 was removed by distillation, and a translucent, viscous liquid was obtained. The temperature of the oil bath was further increased to 80°C, and the mixture 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.

[0224] [Production of pellets containing PBS] Succinic acid (68.3 parts by mass), 1,4-butanediol (66.8 parts by mass), and malic acid (0.257 parts by mass) were continuously supplied to a slurry preparation tank, stirred, and mixed to prepare a slurry. The slurry was 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 with an esterification rate of 92%.

[0225] The 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. The reaction was carried out continuously under a reduced pressure of 2.0 kPa at a temperature of 240°C for an average residence time of 2 hours. Next, the resulting reactant was continuously supplied to the second stage polycondensation reactor, and a melt polycondensation reaction was carried out under a reduced pressure of 0.4 kPa at a temperature of 240°C for 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 at 0.13 kPa for an average residence time of 2 hours. After that, the molten PBS was extruded in strand form from an outlet at the bottom of the polycondensation reactor into hot water adjusted to a temperature of 35°C. The molten PBS was immediately cut to form flat, cocoon-shaped pellets with a mass of approximately 15 mg per pellet. The pellets were then held in the hot water for 1 minute while applying a linear velocity to the hot water (slow cooling step). Subsequently, the pellets were recovered from the hot water and dried. The pellets thus obtained were then subjected to the method described above, and their intrinsic viscosity and strength ratio (I ０１ / I ０２ The content of cyclic dimers was measured. Furthermore, a heat fusion test and the measurement of the fisheye number were performed according to the method described above. The Raman spectrum measured from the pellet according to this embodiment and the fitted Raman spectrum obtained by fitting with two peaks having peak tops in the first wavenumber range and the second wavenumber range are shown together in Figure 1. 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 wavenumber range and the second wavenumber range, respectively, and PS is the spectrum obtained by combining the waveform related to P01 and the waveform related to P02.

[0226] (Example 1-2) 25 parts by mass of pellets containing PBS obtained in Example 1-1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a processing tank and contacted at a temperature of 70°C for 4 hours (solvent contact step). The pellets that have undergone the solvent contact step were dried in a nitrogen atmosphere at a temperature of 80°C. The pellets thus obtained were subjected to the intrinsic viscosity and strength ratio (I) according to the method described above. ０１ / I ０２The content of cyclic dimers was measured. In addition, a heat fusion test and the number of fish eyes were measured according to the method described above.

[0227] (Examples 1-3) 25 parts by mass of pellets containing PBS obtained in Example 1-1 and a mixture of 99.5 parts by mass of ethanol and 0.5 parts by mass of water were continuously supplied to a processing tank and contacted at a temperature of 70°C for 4 hours (solvent contact step). The pellets that have undergone the solvent contact step were dried in a nitrogen atmosphere at a temperature of 80°C. The pellets thus obtained were subjected to the method described above to determine the intrinsic viscosity and strength ratio (I ０１ / I ０２ The content of cyclic dimers was measured. In addition, a heat fusion test and the number of fish eyes were measured according to the method described above.

[0228] (Example 1-4) 25 parts by mass of pellets containing PBS obtained in Example 1-1 and 100 parts by mass of water were continuously supplied to a treatment tank and immersed at a temperature of 90°C for 4 hours (hot water treatment step). The pellets that underwent the hot water treatment step were dried in a nitrogen atmosphere at a temperature of 80°C. The 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 number of fish eyes were measured according to the method described above.

[0229] (Comparative Example 1-1) In Example 1-1, after polymerization of PBS, the molten PBS was extracted in strand form from an outlet at the bottom of the polycondensation reaction vessel, water-cooled (rapidly cooled) at a temperature of 20°C, and the solidified strands were cut to form pellets. These pellets were dried in a nitrogen atmosphere at a temperature of 80°C. The pellets thus obtained were subjected to the method described above to determine the intrinsic viscosity and strength ratio (I ０１ / I ０２ The content of cyclic dimers was measured. In addition, a heat fusion test and the number of fish eyes were measured according to the method described above.

[0230] (Comparative Example 1-2) 25 parts by mass of pellets containing PBS obtained in Comparative Example 1-1 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 subjected to contact treatment at a temperature of 70°C for 4 hours. The obtained pellets were dried in a nitrogen atmosphere at a temperature of 80°C. The intrinsic viscosity and strength ratio (I) of the pellets thus obtained 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 number of fish eyes were measured according to the method described above.

[0231] (Comparative Example 1-3) 25 parts by mass of the pellets obtained in Comparative Example 1-1 and 100 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 90°C for 4 hours. These pellets were recovered from the treatment tank and dried in a nitrogen atmosphere at a temperature of 80°C. The obtained pellets 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 number of fish eyes were measured according to the method described above.

[0232] (Comparative Example 1-4) In Example 1-1, after polymerization of PBS, the molten PBS was extruded into water at 20°C from an outlet at the bottom of the polycondensation reaction tank, and immediately cut into pellets while still molten. The pellets were then held in water at 20°C for 1 minute while a linear velocity was applied. After that, the pellets were recovered from the water and dried to obtain pellets containing PBS. 25 parts by mass of these pellets 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 subjected to contact treatment at 70°C for 4 hours. These pellets were recovered from the treatment tank and dried under a nitrogen atmosphere at 80°C. The obtained pellets 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 number of fish eyes were measured according to the method described above.

[0233] Table 1-1 shows the measurement results for each pellet related to Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-4, as well as the results of the heat fusion test and the measurement of the number of fish eyes.

[0234]

[0235] From Table 1-1, I ０１ / I ０２ However, pellets containing PBS adjusted to 2.0 or higher have good blocking resistance, and I ０１ / I ０２ However, pellets containing PBS adjusted to a range of 2.0 to 3.2 have good blocking resistance and, even when molded at low temperatures, produce molded products with excellent appearance and fewer fish eyes. Furthermore, it is found that by using such pellets, it is possible to obtain extruded or injection-molded products with excellent appearance in which the occurrence of fish eyes caused by insufficient melting of the pellets is suppressed. Thus, according to one aspect of the present invention, pellets containing PBS 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., and biodegradable injection-molded or extruded products that can be stably manufactured can be obtained. Furthermore, according to another aspect of the present invention, pellets containing PBS 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., and can produce molded products with excellent appearance, and biodegradable injection-molded or extruded products that do not have appearance defects such as fish eyes and can be stably manufactured can be obtained.

[0236] <Second Invention> The measurement methods for the physical properties and evaluation items adopted in the following embodiment relating to the second invention concerning PBSA are as follows.

[0237] <Intrinsic Viscosity (IV) dL / g> This was determined using an Ubbelohde viscometer in the following manner. Specifically, using a mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1), the number of seconds for dropping a 0.5 g / dL polymer solution and the solvent alone was measured at a temperature of 30°C, and the intrinsic viscosity was calculated using the following formula (3): IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K ＨC) ... (3) However, in formula (3), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ 0.33 was adopted.

[0238] <Content of PBSA cyclic dimers> 0.5 g of pellets was accurately weighed, 10 mL of chloroform was added, and after dissolution at room temperature, 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 separation was performed by standing for 90 minutes. Next, 2 mL of the supernatant was taken, evaporated to dryness, and then 2 mL of acetonitrile was added to dissolve it. After filtration through a 0.45 μm filter, elution was performed using high-performance liquid chromatography (product name: Prominence, manufactured by Shimadzu Corporation), starting with acetonitrile / water (volume ratio = 4 / 6) as the mobile phase 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.

[0239] The pure cyclic dimer was obtained as follows: PBS pellets obtained by polymerizing succinic acid and 1,4-butanediol were stirred in acetone at 50°C for 12 hours to extract the oligomeric components. After extraction, the pellets were filtered off, and the acetone was evaporated from the acetone solution containing the extracted oligomeric components to obtain a solid. This solid was dissolved in acetone at 50°C to form a saturated solution, and then slowly cooled to room temperature (25°C) to precipitate needle-shaped precipitates (crystals). Recrystallization was then performed, discarding the supernatant and collecting the crystals. The obtained crystals were further purified by repeating the above recrystallization procedure several 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.

[0240] <Raman band intensity ratio (I ０１ / I ０２ )> The Raman spectrum of the pellet was measured using the "RAMAN touch" (product name, manufactured by Nanophoton Corporation) as a Raman spectrometer. The measurement conditions were as follows: <Measurement conditions> ・Measurement mode: Point ・Laser wavelength: 532 nm ・Laser output: 20 mW (Natural density filter opening: 210 / 255) ・Diffraction grating: 1200 gr / mm ・Pinhole: 50 μm ・Exposure time: 10 seconds ・Number of integrations: 5 ・Objective lens: 100x ・Measurement temperature: 25℃

[0241] The obtained Raman spectrum was 1718 ± 5 cm⁻¹. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range, and 1732 ± 5 cm. －１ The two components of the Raman scattering intensity peak having a peak top in the second wavenumber range were fitted using the Lorentz function shown in equation (1) above. In the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity in the first wavenumber range I ０１ and the peak intensity I in the second wavenumber range ０２ The intensity ratio (I ０１ / I ０２Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X) was determined. ０ = 1718 ± 5 cm －１ The intensity A (hereinafter also referred to as "A1") in the above formula (1) relating to ), and the peak of the second wavenumber range (i.e., X ０ = 1732 ± 5 cm －１ From the ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A2") in the aforementioned formula (1) relating to ), ０１ / I ０２ The following was calculated. In Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-2, the average value of three measurements was calculated. Specifically, three samples were taken from the pellet to be measured, and for each sample, the above Raman spectral measurement, fitting, and I were performed. ０１ / I ０２ The calculation is performed, and I for each measurement sample. ０１ / I ０２ The average value is calculated for each example and each comparative example. ０１ / I ０２ That's what I decided.

[0242] <Melting Point> The melting point of the pellet was determined by measuring the endothermic peak temperature when the temperature was raised from room temperature to 200°C at a rate of 10°C / min using a thermal analysis system (product name: DSC3; manufactured by Mettler-Toledo).

[0243] <Heat Fusion Test> 20g of pellets were placed in a cylindrical container made of stainless steel (SUS) with an inner diameter of 20mm, and weights were placed on the surface of the pellet layer inside the cylindrical container so that a uniform pressure of 180g per square centimeter was applied. This cylindrical container was heated to the melting point of the pellets -15°C and placed in an inert oven with nitrogen flowing at a flow rate of 20 liters / minute for 30 minutes, then removed and allowed to return to room temperature (25°C). Next, the pellets were removed from the cylindrical container and the degree of pellet fusion was observed visually. The evaluation criteria were as follows, with rank B or higher being considered a pass. Rank A: There was no fusion between the pellets at all, and no blocking occurred, which was the best condition. Rank B: There were small clumps of 5 to 10 pellets, but they crumbled easily when lightly poked with a finger, and no blocking occurred. Rank C: The pellets were fused together and clumps of 10 or more pellets existed, indicating that blocking had occurred.

[0244] <Measurement of Fine Powder Amount> 100g of pellets was sieved through a sieve with a mesh size of 0.71mm to remove fine powder, and the mass of the remaining pellets was measured. Next, the remaining pellets were placed in a cylindrical container made of stainless steel (SUS) 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 sieve with a mesh size of 0.71mm 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 will be. The evaluation criteria were as follows, and rank B or higher was considered a pass. Rank A: 500 ppm or less. Rank B: Over 500 ppm and 1000 ppm or less. Rank C: Over 1000 ppm.

[0245] (Example 2-1) [Preparation of Catalyst for Polycondensation] 100 parts by mass of magnesium acetate tetrahydrate was placed in a glass pear-shaped flask equipped with a stirrer, and 1500 parts by mass of anhydrous ethanol (purity of 99% by mass or higher) was added. 65.3 parts by mass of ethyl acid phosphate (mixture mass ratio of monoester and diester is 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 was distilled off, and a translucent, viscous liquid was obtained. The temperature of the oil bath was further increased to 80°C, and the mixture 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.

[0246] [Production of pellets containing PBSA] Succinic acid (48.6 parts by mass), adipic acid (21.2 parts by mass), 1,4-butanediol (65.1 parts by mass), and malic acid (0.239 parts by mass) were continuously supplied to a slurry preparation tank, stirred, and mixed to prepare a slurry. The slurry was 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%.

[0247] 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 a 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 a 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. Subsequently, the molten PBSA was extruded in strand form into hot water adjusted to a temperature of 35°C through an outlet at the bottom of the polycondensation reaction vessel. The molten PBSA was immediately cut to form flat, cocoon-shaped pellets with a mass of approximately 15 mg per pellet. The pellets were then held in the hot water for 1 minute while applying a linear velocity to the water. After that, the pellets were recovered from the hot water and dried. Thus, pellets containing PBSA according to Example 2-1 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 intrinsic viscosity and strength ratio (I) of the obtained pellets containing PBSA were determined according to the method described above. ０１ / I ０２ The content of cyclic dimers was measured. Furthermore, a heat fusion test and the amount of fine powder generated were measured according to the method described above. The Raman spectrum measured from the pellet according to this embodiment and the fitted Raman spectrum obtained by fitting with two peaks having peak tops in the first wavenumber range and the second wavenumber range are shown together in Figure 2. In Figure 2, 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 wavenumber range and the second wavenumber range, respectively, and PS is the spectrum obtained by combining the waveform related to P01 and the waveform related to P02.

[0248] (Example 2-2) 25 parts by mass of pellets containing PBSA prepared in Example 2-1 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 in a nitrogen atmosphere at a temperature of 60°C. The 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.

[0249] (Example 2-3) 25 parts by mass of pellets containing PBSA prepared in Example 2-1 and a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to a processing 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 in a nitrogen atmosphere at a temperature of 60°C. The 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.

[0250] (Example 2-4) Pellets containing PBSA were prepared in the same manner as in Example 2-1, 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.

[0251] (Example 2-5) 25 parts by mass of PBSA-containing pellets prepared in Example 2-4 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 in 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.

[0252] (Example 2-6) 25 parts by mass of pellets containing PBSA prepared in Example 2-4 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 in 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.

[0253] (Example 2-7) 25 parts by mass of pellets containing PBSA prepared in Example 2-1 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 in 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.

[0254] (Comparative Example 2-1) In Example 2-1, after polymerization of PBSA, the molten PBSA was extracted in strand form from an outlet at the bottom of the polycondensation reaction vessel, water-cooled (rapidly cooled) at a temperature of 20°C, and the solidified strands were cut to form pellets. These pellets were dried in a nitrogen atmosphere at a temperature of 60°C. The PBSA-containing pellets thus obtained were subjected to the method described above, and the 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.

[0255] (Comparative Example 2-2) 25 parts by mass of PBSA-containing pellets prepared in Comparative Example 2-1 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 in 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. The measurement results of pellets containing PBSA for Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-2 are shown in Table 2-1.

[0256]

[0257] From Table 2-1, I ０１ / I ０２ Pellets containing PBSA with a ratio of 1.1 or higher exhibit excellent blocking resistance, and also, I ０１ / I ０２However, it can be seen that pellets containing PBSA with a numerical value within the range of 1.1 to 2.3 exhibit excellent blocking resistance and significantly suppress the generation of fine powder. Furthermore, it can be seen that this allows for stable supply to injection molding machines and extrusion molding machines, and provides PBSA-containing pellets that enable 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 molding machines can be obtained as a feed material for injection molding and extrusion molding. Furthermore, biodegradable injection-molded or extruded products that can be manufactured more stably can be obtained. In addition, according to another aspect of the present invention, pellets containing PBSA that have excellent blocking resistance and suppress the generation of fine powder can be obtained as a feed material for injection molding and extrusion molding. Furthermore, because such pellets are less prone to blocking and do not generate fine powder, they can be supplied stably to the molding machine, and contamination of the extruder and molding machine by fine powder can be prevented. As a result, biodegradable injection-molded or extruded products can be produced stably and productively.

[0258] <Third Invention> The measurement methods for the physical properties and evaluation items adopted in the following embodiment relating to the third invention concerning PBSSe are as follows.

[0259] <Intrinsic Viscosity (IV) dL / g> This was determined using an Ubbelohde viscometer in the following manner. Specifically, using a mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1), the number of seconds for dropping a 0.5 g / dL polymer solution and the solvent alone was measured at a temperature of 30°C, and the intrinsic viscosity was calculated using the following formula (3): IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) ... (3) However, in formula (3), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０ is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ0.33 was adopted.

[0260] <Content of PBSSe cyclic dimers> 0.5 g of pellet was accurately weighed, 10 mL of chloroform was added, and it 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, high-performance liquid chromatography (product name: Prominence, manufactured by Shimadzu Corporation) was used to elute the mixture by continuously changing the composition of the mobile phase from acetonitrile / water (volume ratio = 4 / 6) 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.

[0261] The pure cyclic dimer was obtained as follows: PBS pellets obtained by polymerizing succinic acid and 1,4-butanediol were stirred in acetone at 50°C for 12 hours to extract the oligomeric components. After extraction, the pellets were filtered off, and the acetone was evaporated from the acetone solution containing the extracted oligomeric components to obtain a solid. This solid was dissolved in acetone at 50°C to form a saturated solution, and then slowly cooled to room temperature (25°C) to precipitate needle-shaped precipitates (crystals). This was followed by a recrystallization procedure. The supernatant was discarded, and the crystals were collected. The obtained crystals were further purified by repeating the recrystallization procedure several 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.

[0262] <Raman band intensity ratio (I ０１ / I ０２)> The Raman spectrum of the pellet was measured using the "RAMAN touch" (product name, manufactured by Nanophoton Corporation) as a Raman spectrometer. The measurement conditions were as follows: <Measurement conditions> ・Measurement mode: Point ・Laser wavelength: 532 nm ・Laser output: 20 mW (Natural density filter opening: 210 / 255) ・Diffraction grating: 1200 gr / mm ・Pinhole: 50 μm ・Exposure time: 10 seconds ・Number of integrations: 3 ・Objective lens: 100x ・Measurement temperature: 25℃

[0263] The obtained Raman spectrum was 1718 ± 5 cm⁻¹. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range, and 1732 ± 5 cm. －１ The two components of the Raman scattering intensity peak having a peak top in the second wavenumber range were fitted using the Lorentz function shown in equation (1) above. In the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity 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 Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X) was determined. ０ = 1718 ± 5 cm －１ The intensity A (hereinafter also referred to as "A1") in the above formula (1) relating to ), and the peak of the second wavenumber range (i.e., X ０ = 1732 ± 5 cm －１ From the ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A2") in the aforementioned formula (1) relating to ), ０１ / I ０２ The following was calculated. In Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-2, the average value of three measurements was calculated. Specifically, three samples were taken from the pellet to be measured, and for each sample, the above Raman spectral measurement, fitting, and I were performed. ０１ / I ０２ The calculation is performed, and I for each measurement sample. ０１ / I ０２The average value is calculated for each example and each comparative example. ０１ / I ０２ That's what I decided.

[0264] <Melting Point> The melting point of the pellet was determined by measuring the endothermic peak temperature when the temperature was raised from room temperature to 200°C at a rate of 10°C / min using a thermal analysis system (product name: DSC3; manufactured by Mettler-Toledo).

[0265] <Heat Fusion Test> 20g of pellets were placed in a cylindrical container made of stainless steel (SUS) with an inner diameter of 20mm, and weights were placed on the surface of the pellet layer inside the cylindrical container so that a uniform pressure of 180g per square centimeter was applied. This cylindrical container was heated to the melting point of the pellets -15°C and placed in an inert oven with nitrogen flowing at a flow rate of 20 liters / minute for 30 minutes, then removed and allowed to return to room temperature (25°C). Next, the pellets were removed from the cylindrical container and the degree of pellet fusion was observed visually. The evaluation criteria were as follows, with rank B or higher being considered a pass. Rank A: There was no fusion between the pellets at all, and no blocking occurred, which was the best condition. Rank B: There were small clumps of 5 to 10 pellets, but they crumbled easily when lightly poked with a finger, and no blocking occurred. Rank C: The pellets were fused together and clumps of 10 or more pellets existed, indicating that blocking had occurred.

[0266] <Measurement of Fine Powder Amount> 100g of pellets was sieved through a sieve with a mesh size of 0.71mm to remove fine powder, and the mass of the remaining pellets was measured. Next, the remaining pellets were placed in a cylindrical container made of stainless steel (SUS) 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 sieve with a mesh size of 0.71mm to separate the fine powder generated by the shaking. 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 will be. 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 1000 ppm or less. Rank C: Over 1000 ppm.

[0267] (Example 3-1) [Preparation of Catalyst for Polycondensation] 100 parts by mass of magnesium acetate tetrahydrate was placed in a glass pear-shaped flask equipped with a stirrer, and 1500 parts by mass of anhydrous ethanol (purity of 99% by mass or higher) was added. 65.3 parts by mass of ethyl acid phosphate (mixture mass ratio of monoester and diester is 45:55) was added, and the mixture was stirred at a temperature of 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 concentrated under reduced pressure using an evaporator in an oil bath at a temperature of 60°C. After 1 hour, most of the ethanol was distilled off, and a translucent, viscous liquid was obtained. The temperature of the oil bath was further increased to 80°C, and the mixture 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.

[0268] [Production of pellets containing PBSSe] 57.8 parts by mass of succinic acid, 12.3 parts by mass of sebacic acid, 64.4 parts by mass of 1,4-butanediol, and 0.125 parts by mass of trimethylolpropane were continuously supplied to a slurry preparation tank, stirred, and mixed to prepare a slurry. The slurry was 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 PBSSe with an esterification rate of 92%.

[0269] The obtained PBSSe low polymer was continuously supplied to the first stage polycondensation reactor, and 0.60 parts by mass of the previously prepared catalyst solution was continuously added to the PBSSe low polymer. The reaction was carried out continuously under a 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 a 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. Subsequently, the molten PBSSe was extruded in strand form into hot water adjusted to a temperature of 35°C through an outlet at the bottom of the polycondensation reaction vessel, forming flat, cocoon-shaped pellets with a mass of approximately 15 mg per pellet. The pellets were then held in the hot water for 1 minute while applying a linear velocity to the water. After that, the pellets were recovered from the hot water and dried. In this way, pellets containing PBSSe according to Example 3-1 were obtained. The molar ratio of constituent units derived from succinic acid to constituent units derived from sebacic acid (constituent units derived from succinic acid / constituent units derived from sebacic acid) of the obtained pellets was 89 / 11. The intrinsic viscosity and strength ratio (I) of the obtained PBSSe-containing pellets were determined according to the method described above. ０１ / I ０２The content of cyclic dimers was measured. Furthermore, a heat fusion test and the amount of fine powder generated were measured according to the method described above. The Raman spectrum measured from the pellet according to this embodiment and the fitted Raman spectrum obtained by fitting with two peaks having peak tops in the first wavenumber range and the second wavenumber range are shown together in Figure 3. In Figure 3, 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 wavenumber range and the second wavenumber range, respectively, and PS is the spectrum obtained by combining the waveform related to P01 and the waveform related to P02.

[0270] (Example 3-2) 25 parts by mass of pellets containing PBSSe prepared in Example 3-1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a processing tank and contacted at a temperature of 60°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried in a nitrogen atmosphere at a temperature of 70°C. The 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.

[0271] (Example 3-3) 25 parts by mass of pellets containing PBSSe prepared in Example 3-1 and a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to a processing tank and contacted at a temperature of 60°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried in a nitrogen atmosphere at a temperature of 70°C. The 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.

[0272] (Example 3-4) Pellets containing PBSSe were prepared in the same manner as in Example 3-1, except that the raw materials continuously supplied to the slurry preparation tank were changed to 50.0 parts by mass of succinic acid, 21.4 parts by mass of sebacic acid, 62.0 parts by mass of 1,4-butanediol, and 0.125 parts by mass of trimethylolpropane. The molar ratio of constituent units derived from succinic acid to constituent units derived from sebacic acid (constituent units derived from succinic acid / constituent units derived from sebacic acid) of the obtained pellets was 80 / 20. The intrinsic viscosity and strength ratio (I) of the pellets thus obtained 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.

[0273] (Example 3-5) 25 parts by mass of pellets containing PBSSe prepared in Example 3-4 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a processing tank and contacted at a temperature of 60°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried in a nitrogen atmosphere at a temperature of 70°C. The 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.

[0274] (Example 3-6) 25 parts by mass of pellets containing PBSSe prepared in Example 3-4 and a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to a processing tank and contacted at a temperature of 60°C for 4 hours (solvent contact step). The pellets that underwent this solvent contact step were dried in a nitrogen atmosphere at a temperature of 70°C. The 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.

[0275] (Example 3-7) 25 parts by mass of pellets containing PBSSe prepared in Example 3-1 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 70°C for 4 hours (hot water contact step). The pellets that underwent this hot water contact step were dried in a nitrogen atmosphere at a temperature of 70°C. The 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.

[0276] (Comparative Example 3-1) In Example 3-1, after polymerization of PBSSe, the molten PBSSe was extracted in strand form from an outlet at the bottom of the polycondensation reaction vessel, and the solidified strands were cut and pelletized while being water-cooled (rapidly cooled) at a temperature of 20°C. These pellets were dried in a nitrogen atmosphere at a temperature of 70°C. The intrinsic viscosity and strength ratio (I) of the pellets thus obtained 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.

[0277] (Comparative Example 3-2) 25 parts by mass of pellets containing PBSSe prepared in Comparative Example 3-1 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 brought into contact at a temperature of 70°C for 4 hours (hot water contact step). The pellets that underwent this hot water contact step were dried in a nitrogen atmosphere at a temperature of 70°C. The 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. The measurement results of PBSSe pellets for Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-2 are shown in Table 3-1.

[0278]

[0279] From Table 3-1, the intensity ratio of the Raman band (I ０１ / I ０２Pellets containing PBSSe with a ratio of 1.7 or higher exhibit excellent blocking resistance, and I ０１ / I ０２ However, it can be seen that pellets containing PBSSe with a numerical value within the range of 1.7 to 3.4 exhibit excellent blocking resistance and suppress the generation of fine powder. Furthermore, it can be seen that this allows for stable supply to injection molding machines and extrusion molding machines, and provides pellets containing PBSSe that enable the stable production of injection molded and extruded products. Thus, according to one aspect of the present invention, pellets containing PBSSe that have good blocking resistance and can be stably supplied to molding machines can be obtained as a feed material for injection molding and extrusion molding. Furthermore, biodegradable injection molded or extruded products that can be manufactured more stably can be obtained. In addition, according to another aspect of the present invention, pellets containing PBSSe that have excellent blocking resistance and suppress the generation of fine powder can be obtained as a feed material for injection molding and extrusion molding. Furthermore, because such pellets are less prone to blocking and do not generate fine powder, they can be supplied stably to the molding machine, and contamination of the extruder and molding machine by fine powder can be prevented. As a result, biodegradable injection-molded or extruded products can be produced stably and productively.

[0280] <Fourth Invention> The measurement methods for the physical properties and evaluation items adopted in the following embodiment relating to the fourth invention concerning PBST are as follows.

[0281] <Intrinsic Viscosity (IV) dL / g> This was determined using an Ubbelohde viscometer in the following manner. Specifically, using a mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1), the number of seconds for dropping a 0.5 g / dL polymer solution and the solvent alone was measured at a temperature of 30°C, and the intrinsic viscosity was calculated using the following formula (4): IV = ((1 + 4K Ｈ η ｓｐ ) ０．５ -1) / (2K Ｈ C) ... (4) However, in formula (4), η ＳＰ =η / η ０ -1, where η is the number of seconds the sample solution falls. ０is the number of seconds the solvent falls, C is the sample solution concentration (g / dL), and K is the number of seconds the solvent falls. Ｈ K is Huggins' constant. Ｈ 0.33 was adopted.

[0282] <Content of cyclic dimers in PBST> 0.5 g of pellet was accurately weighed, 10 mL of chloroform was added, and it 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, high-performance liquid chromatography (product name: Prominence, manufactured by Shimadzu Corporation) was used to elute the mixture by continuously changing the composition of the mobile phase from acetonitrile / water (volume ratio = 4 / 6) 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.

[0283] The pure cyclic dimer was obtained as follows: A polymer 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, and the acetone was evaporated from the acetone solution containing the extracted oligomer component to obtain a solid. This solid was dissolved in acetone at 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. The supernatant was then discarded, and the crystals were collected. The obtained crystals were further purified by the above recrystallization operation several times. These crystals were analyzed by 1H-NMR and high-performance liquid chromatography, confirming that they were cyclic dimers formed from succinic acid and 1,4-butanediol.

[0284] <Raman band intensity ratio ((I ０１ / I ０２ ))> The Raman spectrum of the pellet was measured using the "RAMAN touch" (product name, manufactured by Nanophoton Corporation) as a Raman spectrometer. The measurement conditions were as follows: <Measurement conditions> ・Measurement mode: Point ・Laser wavelength: 532 nm ・Laser output: 12 mW (Natural density filter opening: 200 / 255) ・Diffraction grating: 1200 gr / mm ・Pinhole: 20 μm ・Exposure time: 100 seconds ・Number of integrations: 10 ・Objective lens: 100x ・Measurement temperature: 25℃

[0285] The obtained Raman spectrum is 1711 ± 5 cm⁻¹. －１ The peak of the Raman scattering intensity has its peak top in the first wavenumber range, and 1722 ± 5 cm －１ The two components of the Raman scattering intensity peak having a peak top in the second wavenumber range were fitted using the Lorentz function shown in equation (1) above. In the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity 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 Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X) was determined. ０ = 1711 ± 5 cm －１ The intensity A (hereinafter also referred to as "A1") in the above formula (1) relating to ), and the peak of the second wavenumber range (i.e., X ０ = 1722 ± 5 cm －１ From the ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A2") in the aforementioned formula (1) relating to ), ０１ / I ０２ The following was calculated. In Examples 4-1 to 4-3, Reference Example, and Comparative Examples 4-1 to 4-3, the average value of three measurements was calculated. Specifically, three samples for measurement were taken from the pellet to be measured, and for each sample, the above Raman spectral measurement, fitting, and I were performed. ０１ / I０２ The calculation is performed, and I for each measurement sample. ０１ / I ０２ The average value is calculated for each example, reference example, and comparative example. ０１ / I ０２ That's what I decided.

[0286] <Heat Fusion Test> 20g of pellets were placed in a cylindrical container made of stainless steel (SUS) with an inner diameter of 20mm, and weights were placed on the surface of the pellet layer inside the cylindrical container so that a uniform pressure of 180g per square centimeter was applied. This cylindrical container was heated to 60°C and placed in an inert oven with nitrogen flowing at a flow rate of 20 liters / minute for 30 minutes, then removed and allowed to return to room temperature (25°C). Next, the pellets were removed from the cylindrical container and the degree of pellet fusion was observed visually. The evaluation criteria were as follows, with rank B or higher being considered a pass. Rank A: There was no fusion between the pellets at all, and no blocking occurred, which was the best condition. Rank B: There were small clumps of 5 to 10 pellets, but they crumbled easily when lightly poked with a finger, and no blocking occurred. Rank C: The pellets were fused together and clumps of 10 or more pellets existed, indicating that blocking had occurred.

[0287] <Esterification Rate (%)> The esterification rate was calculated from the sample acid value and saponification value using the following formula (5). The acid value was determined by heating 0.3 g of the esterification reaction product sample in 40 mL of benzyl alcohol at 180°C for 20 minutes, cooling for 10 minutes, and then titrating with a 0.1 mol / L potassium hydroxide / methanol solution. The saponification value was determined by hydrolyzing the oligomer with a 0.5 mol / L potassium hydroxide / ethanol solution and then titrating with 0.5 mol / L hydrochloric acid. Esterification rate (%) = (Saponification value - Acid value) / Saponification value × 100 ... (5)

[0288] (Example 4-1) This example shows a batch-type solvent contact process. [Preparation of the Catalyst for Polycondensation] 343.5 parts by mass of magnesium acetate tetrahydrate were placed in a reactor equipped with a stirrer, and then 1434 parts by mass of anhydrous ethanol (purity of 99% by weight or more) was added. 218.3 parts by mass of ethyl acid phosphate (mixture weight ratio of monoester and diester is 45:55) was added, and the mixture was stirred at a temperature of 23°C. After confirming that the magnesium acetate was completely dissolved, 410.0 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 concentrated under reduced pressure at a controlled temperature of 60°C or lower. Approximately half the amount of ethanol was distilled off relative to the added ethanol, leaving a translucent, viscous liquid in the reactor. To this, 1108 parts by mass of 1,4-butanediol was added, and the mixture was further concentrated under reduced pressure while maintaining a temperature of 80°C or lower to obtain a catalyst solution with a titanium atom content of 3.5% by weight.

[0289] [Production of pellets containing PBST] In a reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and vacuum port, 33.6 parts by mass of succinic acid, 38.6 parts by mass of terephthalic acid, 69.7 parts by mass of 1,4-butanediol, 0.138 parts by mass of trimethylolpropane, 0.10 parts by mass of polyethylene wax (trade name: ACumist B6, manufactured by Honeywell, melting point: 124°C), and 0.0017 parts by mass of sodium hydroxide (NaOH) were added as raw materials. Tetra-n-butyl titanate was then added so that the titanium atoms amounted to 30 ppm by mass per unit of PBST obtained. The contents of the reaction vessel were stirred, nitrogen gas was introduced into the reaction vessel, and the system was subjected to a nitrogen atmosphere by vacuum displacement. Next, while stirring the contents of the reaction vessel, the temperature was raised from 160°C to 230°C over 1 hour, and the reaction was carried out at 230°C for 3 hours to obtain an ester oligomer (low polymer of PBST).

[0290] To the obtained ester oligomer, the previously prepared catalyst solution is added in an amount equal to 70 ppm by mass of titanium atoms per polyester obtained, and the temperature is raised to 250°C over 45 minutes, while simultaneously, 0.07 × 10⁻¹⁶ is added over 1 hour and 20 minutes. ３The pressure was reduced to below Pa. Then, polycondensation was continued while maintaining the heated and reduced pressure state, and polymerization was terminated when the desired viscosity was reached. The resulting polyester copolymer was cut into pellets using an underwater cutter (product name: EUP10, manufactured by ECON, cooling water temperature: 14-28°C), and the pellets immediately after cutting were cooled in 30°C hot water for about 1 minute (slow cooling step). After that, the pellets were recovered by centrifugal dewatering. The content of cyclic dimers in the pellets at this point (before the solvent contact step) is shown in Table 4-1.

[0291] In a container equipped with a stirring device, a nitrogen inlet, a heating device, and a thermometer, 25 parts by mass of the pellets obtained above and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were placed. While stirring the contents of the container, nitrogen gas was introduced into the container, and the pellets were brought into contact with the solvent at a temperature of 60°C for 2 hours (solvent contact step). The pellets that had undergone this solvent contact step were dried in a nitrogen atmosphere at a temperature of 50°C to obtain pellets. The molar ratio of constituent units derived from succinic acid to constituent units derived from terephthalic acid in the obtained pellets (constituent units derived from succinic acid / constituent units derived from terephthalic acid) was 55 / 45. The intrinsic viscosity and strength ratio (I) of the pellets thus obtained (final product) were determined according to the method described above. ０１ / I ０２ The content of ), and cyclic dimers was measured. The pellets were also subjected to the heat fusion test described above. The Raman spectrum measured from the pellets according to this embodiment, and the fitted Raman spectrum obtained by fitting with two peaks having peak tops in the first wavenumber range and the second wavenumber range are shown together in Figure 4. In Figure 4, P is the Raman spectrum measured from the pellets, P01 and P02 are Raman spectra obtained by curve fitting using the Lorentz function to the peaks in the first wavenumber range and the second wavenumber range, respectively, and PS is the spectrum obtained by combining the waveform related to P01 and the waveform related to P02.

[0292] (Example 4-2) Pellets were prepared in the same manner as in Example 4-1, except that the solvent contact process time was changed from 2 hours to 4 hours. The pellets obtained in this manner were then subjected to the same method as in Example 4-1, determining the intrinsic viscosity and strength ratio (I ０１ / I ０２ The content of ), and cyclic dimers was measured, and the samples were subjected to a heat fusion test.

[0293] (Comparative Example 4-1) Pellets were obtained in the same manner as in Example 4-1, except that the solvent contact step was omitted. The intrinsic viscosity and strength ratio (I) of the pellets obtained in this manner were determined in the same manner as in Example 4-1. ０１ / I ０２ The content of ), and cyclic dimers was measured, and the pellets were subjected to a heat fusion test. (Comparative Example 4-2) Pellets were obtained in the same manner as in Comparative Example 4-1, except that the pellets immediately after cutting were cooled in hot water at 30°C for a few seconds. The pellets obtained in this manner were subjected to the same tests as in Example 4-1, measuring the intrinsic viscosity and strength ratio (I ０１ / I ０２ The content of ), and cyclic dimers was measured, and the samples were subjected to a heat fusion test.

[0294] Table 4-1 shows the measurement results for each pellet related to Examples 4-1 to 4-2 and Comparative Examples 4-1 to 4-2, as well as the results of the heat fusion test. Note that for Comparative Examples 4-1 to 4-2, since the solvent contact process was not performed in these comparative examples, the cyclic dimer content of the final product pellets obtained in Comparative Examples 4-1 to 4-2 is equivalent to the cyclic dimer content of the pellets before the solvent contact process. Therefore, the column for the cyclic dimer content of the pellets before the solvent contact process in Table 4-1 is left blank.

[0295]

[0296] From Table 4-1, the intensity ratio of the Raman band (I ０１ / I ０２It was found that pellets containing PBST with a PBST ratio of 1.00 or higher exhibit good blocking resistance even under heating and pressurization. This indicates that pellets containing PBST can be supplied stably to injection molding machines and extrusion molding machines, enabling the stable production of injection molded and extruded products.

[0297] (Example 4-3) This example shows a continuous process of solvent contact and separation of the cyclic dimer from the solvent to which the pellets were contacted. [Preparation of the catalyst for polycondensation] 100 parts by mass of magnesium acetate tetrahydrate was placed in a glass pear-shaped flask equipped with a stirring device, and 1500 parts by mass of anhydrous ethanol (purity of 99% by mass or higher) was added. 65.3 parts by mass of ethyl acid phosphate (mixture mass ratio of monoester and diester is 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 was distilled off, and a translucent, viscous liquid was obtained. 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 solution with a titanium atom content of 3.36% by mass. The storage stability of this catalyst solution in 1,4-butanediol was good, and no precipitate formation was observed in the catalyst solution stored at 40°C under a nitrogen atmosphere for at least 40 days. The pH of this catalyst solution was 6.3.

[0298] [Production of PBST] PBST was produced as follows by the esterification process shown in Figure 5 and the polycondensation process shown in Figure 6. First, a slurry at 50°C, prepared by mixing succinic acid and terephthalic acid in amounts of 55 mol% and 45 mol% respectively, with 0.20 mol% trimethylolpropane, 1.5 times the molar amount of 1,4-butanediol, and tetra-n-butyl titanate containing 0.012 mol% Ti, was continuously supplied at a rate of 45.5 kg / hour from a slurry preparation tank (not shown) through a raw material supply line (1) to an esterification reaction tank (A) equipped with a stirrer that had been pre-filled with a low molecular weight product (esterification reaction product) with an esterification rate of 99% by mass under a nitrogen atmosphere.

[0299] The esterification reactor (A) was set to an internal temperature of 230°C and a pressure of 101 kPa. The resulting water, tetrahydrofuran, and excess 1,4-butanediol were distilled off through the distillation line (5) and separated into high-boiling and low-boiling components in the rectification column (C). After the system stabilized, a portion of the high-boiling component at the bottom of the column was extracted to the outside through the extraction line (8) to maintain a constant liquid level in the rectification column (C). Meanwhile, the low-boiling component, mainly water and tetrahydrofuran, was extracted in gaseous form from the top of the column, condensed in a condenser (G), and then extracted to the outside through the extraction line (13) to maintain a constant liquid level in the tank (F). Simultaneously, the entire amount of the bottom component of the rectification column (C) at a temperature of 100°C (98% by mass or more being 1,4-butanediol) was supplied from the recirculation line (2), and tetrahydrofuran generated in the esterification reactor and an equimolar amount of 1,4-butanediol were supplied from the raw material supply line (1), adjusting the molar ratio of 1,4-butanediol to succinic acid and terephthalic acid in the esterification reactor to 1.50.

[0300] The esterified product generated in the esterification reactor (A) was continuously withdrawn from the esterification product withdrawal line (4) using a pump (B), and the liquid level was controlled so that the average residence time of the liquid in the esterification reactor (A) was 3 hours. The esterified product withdrawn from the withdrawal line (4) was continuously supplied to the first polycondensation reactor (a) in Figure 6. After the system stabilized, the esterification rate of the esterified product collected at the outlet of the esterification reactor (A) was 96.5%.

[0301] The previously prepared catalyst solution was diluted with 1,4-butanediol in a catalyst preparation tank to a titanium atom concentration of 0.10% by mass. This catalyst solution was then continuously supplied at a rate of 2.1 kg / h to the esterification product extraction line (4) via the supply line (L8) (the catalyst was added to the liquid phase of the reaction solution). The supply rate remained stable throughout the operation.

[0302] The internal temperature of the first polycondensation reactor (a) was set to 240°C and the pressure to 2.0 kPa, and the liquid level was controlled to ensure a residence time of 120 minutes. The initial polycondensation reaction was carried out while water, tetrahydrofuran, and 1,4-butanediol were withdrawn through a vent line (L2) connected to a vacuum pump (not shown). The withdrawn reaction solution was continuously supplied to the second polycondensation reactor (d). The internal temperature of the second polycondensation reactor (d) was set to 240°C and the pressure to 450 Pa, and the liquid level was controlled to ensure a residence time of 120 minutes. The polycondensation reaction was further carried out while water, tetrahydrofuran, and 1,4-butanediol were withdrawn through a vent line (L4) connected to a vacuum pump (not shown). The resulting polyester was continuously supplied to the third polycondensation reactor (k) via an extraction line (L3) using an extraction gear pump (e). The third polycondensation reactor (k) was maintained at an internal temperature of 240°C, a pressure of 200 Pa, and a residence time of 120 minutes, and the polycondensation reaction was further carried out. The obtained polyester was continuously drawn out in strand form from the die head (g), cooled in water, and cut with a rotary cutter (h) to form pellets. The esterification and polycondensation reactions were carried out continuously for 7 days, and samples were taken every 8 hours starting 16 hours after the start of the reaction, and the properties of the obtained polyester were measured. The average value and range of each sample are shown. The intrinsic viscosity was 1.50 ± 0.05 dL / g, and the pellets contained stable quality PBST with a pellet weight of 15 ± 1 mg / pellet. The cyclic dimer content of the pellets at this point is shown in Table 4-2 as the pellet properties before contact treatment.

[0303] [Contact Treatment of Pellets with Solvent] The obtained pellets were subjected to solvent-based extraction of cyclic dimers using the solvent contact process shown in Figure 7. The mixture of ethanol and water used as the solvent in the solvent contact process was controlled to 70°C via a heat exchanger (II) by a pump (IX) from a circulation tank (I) and supplied to the treatment tank (III) via a supply line (101). The ratio of ethanol (hereinafter sometimes abbreviated as EtOH) to water in the solvent was 60% by mass of water relative to the total solvent. The mass ratio of solvent to pellets in the treatment tank was 5 (treatment liquid / pellet ratio).

[0304] The solvent was brought into countercurrent contact with pellets (not shown) in a processing tank (III), and then withdrawn from the withdrawal line (102). The entire amount (100% by mass) of the withdrawn solvent was supplied to the separator (XI) via a fine particle remover (IV). The pellets to be used in the solvent contact process were continuously supplied from the supply line (103), and after being in contact with the solvent for 4 hours, they were continuously withdrawn from the withdrawal line (104) by a rotary valve (V). The solvent withdrawn along with the pellets was separated in a preliminary solid-liquid separator (VI), and after passing through a recovery tank (VII), was returned to the recovery line (106) via the supply line (105) by a pump (X).

[0305] The solvent supplied to the separator (XI) separated the cyclic dimers in the circulating tank (I) so that the concentration of cyclic dimers in the solvent in the circulating tank (I) was 0 ppm by mass, and the cyclic dimers were withdrawn to the outside through the withdrawal line (112). A distillation column was used for the separator (XI). From the solvent supply line (108), a new solvent (ethanol aqueous solution) equivalent to the amount of solvent withdrawn from the withdrawal line (112) along with the cyclic dimers was supplied to the circulating tank (I). The continuously withdrawn pellets were separated from the accompanying solvent in the preliminary solid-liquid separator (IV), and then continuously supplied to the drying process via the withdrawal line (109) from the solid-liquid separator (VIII).

[0306] [Drying of Pellet] The pellets that had undergone the solvent contact process were dried by the drying process shown in Figure 8. For the first drying tower (I), nitrogen gas with a purity of 99% or higher (dew point minus 40°C) was used as the drying gas, with a gas temperature of 50°C, a gas (empty tower) velocity of 0.125 m / sec, and a pellet residence time of 24 hours. For the second drying tower, air (dew point minus 40°C) was used as the drying gas, with a temperature of 50°C, a gas (empty tower) velocity of 0.125 m / sec, and a pellet residence time of 48 hours. The PBST pellets obtained in this way were used as the final product pellets, and the cyclic dimer content was measured according to the method described above, and the Raman band intensity ratio was calculated. Furthermore, these pellets were subjected to the heat fusion test described above. The cyclic dimer content, Raman band intensity ratio, and evaluation rank from the heat fusion test of the final product are shown in Table 4-2.

[0307] (Reference Example) 21% by mass (separation rate: 21% by mass) of the solvent that was in countercurrent contact with the pellets, which was withdrawn from the processing tank (III), was supplied to the separator (XI) via the fine particle removal machine (IV), and the remainder was recovered into the circulation tank (I). The solvent supplied to the separator (XI) separated the cyclic dimers in the separator (XI), and the cyclic dimers were withdrawn to the outside through the withdrawal line (112). In this way, the concentration of cyclic dimers in the solvent in the circulation tank (I) was adjusted as shown in Table 4-2. Otherwise, pellets as the final product were manufactured in the same manner as in Example 4-3. The cyclic dimer content of the obtained pellets was measured according to the method described above. The measurement results are shown in Table 4-2.

[0308] (Comparative Example 4-3) Of the solvent extracted from the processing tank (III) and brought into countercurrent contact with the pellets, 1% (1% separation rate) of the solvent was supplied to the separator (XI), and the remainder was recovered into the circulation tank (I). In this way, the concentration of the cyclic dimer in the solvent in the circulation tank (I) was adjusted as shown in Table 4-2. Otherwise, the pellets as the final product were manufactured in the same manner as in Example 4-3. The cyclic dimer content of the obtained pellets was measured according to the method described above, and the Raman band intensity ratio was calculated. Furthermore, these pellets were subjected to the heat fusion test described above. The cyclic dimer content, Raman band intensity ratio, and evaluation rank from the heat fusion test of the final product are shown in Table 4-2.

[0309]

[0310] As shown in Table 4-2, when the solvent contact process is carried out continuously, and the cyclic dimer content of the solvent used to extract the cyclic dimer contained in the pellets is set to 3000 ppm by mass (Comparative Example 4-3), the cyclic dimer content in the obtained pellets becomes high, resulting in poor pellet quality. On the other hand, from Example 4-3, by setting the concentration of cyclic dimer in the solvent used in the continuous solvent contact process to zero, the cyclic dimer content is low, and as a result, the Raman band intensity ratio (I ０１ / I ０２ This allowed for the more efficient production of pellets containing PBST adjusted to a value of 1.00 or higher.

[0311] 1: Raw material supply line 2: Recirculation line 3: Catalyst supply line 4: Esterification product extraction line 5: Distillation line 6: Extraction line 7: Circulation line 8: Extraction line 9: Gas extraction line 10: Condenser line 11: Extraction line 12: Circulation line 13: Extraction line 14: Vent line 15: Supply line A: Esterification reactor B: Extraction pump C: Rectification column D: Pump E: Pump F: Tank G: Condenser L1, L3, L5: Polycondensation product extraction lines L2, L4, L6: Vent lines L7: Catalyst supply line L8: Raw material supply line a: First polycondensation reactor d: Second polycondensation reactor Q: Rotary valve R: Blower S: Heat exchanger 101, 105, 108: Solvent supply line 102, 110, 113: Solvent extraction line 103: Pellet supply line 104, 109: Pellet extraction line 106: Solvent recovery line 111: Solvent supply line 112: Circular oligomer extraction line I: Circulation tank II: Heat exchanger III: Treatment tank IV: Fine particle remover V: Rotary valve VI: Pre-solid-liquid separator VII: Recovery tank VIII: Solid-liquid separator IX, X: Pump XI: Separator 201: Pellet supply line 202: Pellet extraction line 203: Pellet supply line 204: Pellet extraction line 205: Pellet supply line 206: Pellet extraction line 207: Dry gas recovery line 208: Dry gas supply line 209: New dry gas supply line 210: Condensate extraction line 211: Cooling gas extraction line 212: Cooling gas supply line 213: Dry gas extraction line 214: Dry gas supply line

Claims

1. A pellet containing polybutylene succinate having as its main constituent units a constituent unit derived from succinic acid and a constituent unit derived from 1,4-butanediol, wherein the Raman spectrum measured from the pellet is 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 the fitted Raman spectrum obtained by fitting with a Lorentz function using 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 2.0 or higher.

2. The pellet according to claim 1, wherein the strength ratio is 3.2 or less.

3. The pellet according to claim 1, wherein the strength ratio is 2.2 or greater.

4. The pellet according to claim 1, wherein the strength ratio is 2.5 or greater.

5. 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.

6. 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 2,000 ppm by mass or less.

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

8. The pellet according to claim 1, wherein the content of polybutylene succinate contained in the pellet is 80% by weight or more.

9. A pellet containing polybutylene succinate adipate having a constituent unit derived from succinic acid, a constituent unit derived from adipic acid, and a constituent unit derived from 1,4-butanediol as main constituent units, wherein in the Raman spectrum measured from the pellet, the spectrum in the wavenumber range of 1680 to 1780 cm －１ is fitted using a Lorentz function with two peaks each having a peak top in a first wavenumber range of 1718 ± 5 cm －１ and a second wavenumber range of 1732 ± 5 cm －１ In the Raman spectrum, the intensity I of the peak in the first wavenumber range ０１ and the intensity I of the peak in the second wavenumber range ０２ The intensity ratio (I ０１ / I ０２ ) is 1.1 or more.

10. The pellet according to claim 9, wherein the strength ratio is 2.3 or less.

11. The pellet according to claim 9, wherein the strength ratio is 1.4 or greater.

12. The pellet according to claim 9, 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.

13. The pellet according to claim 9, wherein the molar ratio is 70 / 30 to 80 / 20.

14. The pellet according to claim 9, 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.

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

16. A pellet containing polybutylene succinate sebacate having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from sebacic acid, and a constituent unit derived from 1,4-butanediol, wherein the Raman spectrum measured from the pellet is 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 1.7 or higher.

17. The pellet according to claim 16, wherein the strength ratio is 3.4 or less.

18. The pellet according to claim 16, wherein the strength ratio is 1.9 or greater.

19. The pellet according to claim 16, wherein the molar ratio of constituent units derived from succinic acid to constituent units derived from sebacic acid (constituent units derived from succinic acid / constituent units derived from sebacic acid) is 70 / 30 to 95 / 5.

20. The pellet according to claim 16, wherein the molar ratio is 80 / 20 to 90 / 10.

21. The pellet according to claim 16, wherein the total number of moles of the constituent units derived from succinic acid, the constituent units derived from sebacic acid, and the constituent units derived from 1,4-butanediol in the polybutylene succinate sebacate is 80 mol% or more of the total number of moles of the constituent units constituting the polybutylene succinate sebacate.

22. The pellet according to claim 16, wherein the content of the polybutylene succinate sebacate contained in the pellet is 80% by weight or more.

23. The pellet according to claim 9 or 16, 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.

24. A pellet containing polybutylene succinate terephthalate having as its main constituent units a constituent unit derived from succinic acid, a constituent unit derived from terephthalic acid, and a constituent unit derived from 1,4-butanediol, wherein the Raman spectrum measured from the pellet is 1680–1780 cm⁻¹ －１ The spectrum in the wavenumber range is 1711±5 cm⁻¹. －１ The first wavenumber range, and 1722±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 1.00 or higher.

25. The pellet according to claim 24, wherein the strength ratio is 1.00 or more and 2.50 or less.

26. The pellet according to claim 24, wherein the molar ratio of constituent units derived from succinic acid to constituent units derived from terephthalic acid (constituent units derived from succinic acid / constituent units derived from terephthalic acid) is 10 / 90 to 90 / 10.

27. The pellet according to claim 24, wherein the molar ratio is 40 / 60 to 60 / 40.

28. The pellet according to claim 24, wherein the content of a cyclic dimer consisting of succinic acid and 1,4-butanediol in the pellet is 2,500 ppm by mass or less.

29. The pellet according to claim 24, wherein the total number of moles of the constituent units derived from succinic acid, the constituent units derived from terephthalic acid, and the constituent units derived from 1,4-butanediol in the polybutylene succinate terephthalate is 80 mol% or more of the total number of moles of the constituent units constituting the polybutylene succinate terephthalate.

30. The pellet according to claim 24, wherein the content of polybutylene succinate terephthalate contained in the pellet is 80% by weight or more.

31. The pellet according to claim 1, 9, 16, or 24, wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less.

32. An injection-molded article of resin pellets comprising at least the pellets described in claim 1, 9, 16, or 24.

33. An extruded resin pellet article comprising at least the pellets described in claim 1, 9, 16, or 24.

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